WO1998057851A2 - Systems and methods for modifying ice adhesion strength - Google Patents
Systems and methods for modifying ice adhesion strength Download PDFInfo
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- WO1998057851A2 WO1998057851A2 PCT/US1998/012421 US9812421W WO9857851A2 WO 1998057851 A2 WO1998057851 A2 WO 1998057851A2 US 9812421 W US9812421 W US 9812421W WO 9857851 A2 WO9857851 A2 WO 9857851A2
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- ice
- bias
- electrode
- interface
- adhesion
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G7/00—Overhead installations of electric lines or cables
- H02G7/16—Devices for removing snow or ice from lines or cables
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- B64D15/00—De-icing or preventing icing on exterior surfaces of aircraft
- B64D15/12—De-icing or preventing icing on exterior surfaces of aircraft by electric heating
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2214/00—Aspects relating to resistive heating, induction heating and heating using microwaves, covered by groups H05B3/00, H05B6/00
- H05B2214/02—Heaters specially designed for de-icing or protection against icing
Definitions
- the invention relates to methods and apparatus for modifying ice adhesion strength between ice and selected materials. More particularly, the invention relates to systems and methods which apply electrical energy to the interface between ice and such materials so as to either increase or decrease the ice adhesion strength to facilitate desired results.
- Ice adhesion to certain surfaces causes many problems. For example, excessive ice accumulation on aircraft wings endangers the plane and its passengers. Ice on ship hulls creates navigational difficulties, the expenditure of additional power to navigate through water and ice, and certain unsafe conditions. The need to scrape ice that forms on automobile windshields is regarded by most adults as a bothersome and recurring chore; and any residual ice risks driver visibility and safety. Icing and ice adhesion also causes problems with helicopter blades, and with public roads. Billions of dollars are spent on ice and snow removal and control. Ice also adheres to metals, plastics, glasses and ceramics, creating other day-to-day difficulties.
- Icing on power lines is also problematic. Icing adds weight to the power lines which causes power outages, costing billions of dollars in direct and indirect costs.
- a further object of the invention is to provide systems for reducing ice adhesion on vehicle surfaces such as aircraft wings, ship hulls and windshields to facilitate ice removal.
- Still another object of the invention is to provide systems for increasing the coefficient of friction between ice-clad roads and automobile tires, and between ice and other objects such as shoe soles and cross-country skis.
- Ice has certain physical properties which allow the present invention to selectively modify the adhesion of ice to conductive (and semi-conductive) surfaces.
- ice is a protonic semiconductor, a small class of semiconductors whose charge carriers are protons rather than electrons. This phenomenon results from hydrogen bonding within the ice. Hydrogen bonding occurs because the hydrogen atoms of water molecules in ice share their electrons with an oxygen atom. Thus, the nucleus of the water molecule - uniquely a single proton - remains available to bond with adjacent water molecules.
- ice is electrically conductive. While this electrical conductivity is generally weak, the conductivity can be altered by adding chemical agents that donate or accept extra charge-carrying particles, i.e., protons in the case of ice.
- ice Another physical property of ice is its evaporability. Evaporability of a substance is a function of vapor pressure at the substance surface. In most materials, vapor pressure drops rapidly at the liquid-to-solid interface. In ice, however, there is virtually no change in vapor pressure at the liquid-to-solid interface. The reason for this is that the surface of ice is covered with a liquid-like layer ("LLL").
- LLL liquid-like layer
- the LLL has important physical characteristics. First, the LLL is only nanometers thick. Second, it ranges in viscosity from almost water-like, at temperatures at or near to freezing, to very viscous at lower temperatures. Further, the LLL exists at temperatures as low as -100 ° C, and thus practically exists for most temperatures around the planet.
- the LLL is also a major factor of ice adhesion strength. For example, if one brings the smooth surface of ice in contact with the smooth surface of an airplane wing, the actual area of contact between the two surfaces is on the order of one-thousandth of the total interface area between the two surfaces.
- the LLL functions as a wetting substance between the surfaces - the principal behind almost all adhesives - and substantially increases the effective contact area between the surfaces. This increase in contact area strongly affects ice adhesion.
- the combination of the semiconductive properties of ice and the LLL allows -one to selectively manipulate ice adhesion strength between ice and other surfaces.
- water molecules within a piece of ice are randomly oriented. On the surface, however, the molecules are substantially oriented in the same direction, either outward or inward. As a result, all their protons, and hence the positive charges, either face outward or inward.
- the invention provides a power source connected to apply a DC voltage across the interface between ice and the surface upon which the ice forms.
- the conductive surface can be an aircraft wing or a ship's hull (or even the paint applied to the structure).
- a first electrode connects with the surface; a nonconductive or electrically insulating material is applied as a grid over the surface; and a second electrode is formed by applying a conductive material, for example conductive paint, over the insulating material, but without contacting the surface.
- the surface area of the second electrode should be small as compared to the overall surface area protected by the system.
- the surface area under protection i.e., that area sought to be "ice-free" should be at least about ten times larger than the surface area of the second electrode.
- One or more wires connect the second electrode to the power source; while one or more wires connect the first electrode to the power source. Ice forming over the surface and the conductive grid second electrode completes the circuit. A voltage is then applied to the circuit, selectively, which controllably modifies the ice adhesion strength of the ice with the surface.
- a voltage regulator subsystem also preferably connects with the circuit so as to adjustably control the voltage applied across the interface and so as to achieve control over the ice adhesion strength.
- ice made from different concentrations of ions can modify the optimum voltage for which the ice adhesion strength is at a minimum; and the voltage regulator subsystem thereby provides a mechanism by which the minimum can be changed selectively.
- the power source is a DC supply (e.g., a battery) which provides voltage to the circuit and which connects to the deicing electrodes.
- a DC ammeter connects with the circuit to measure the DC conductivity of the ice (i.e., the semi-conductive layer which "shorts" the two electrodes when formed over the surface and any part of the grid second electrode).
- an AC supply connects with the circuit to generate AC voltages between about 10kHz and 100kHz, selectively.
- an AC ammeter also connects with the circuit to measure the AC conductivity of the ice at frequencies within the 10-lOOkHz range.
- a current comparator compares the AC and DC conductivities.
- circuitry which can, for example, distinguish whether the semi-conductive layer formed over the surface is ice, which might be dangerous, or surface water.
- the AC conductivity (in the above-mentioned range) and DC conductivity of water are substantially the same. With respect to ice, however, the AC conductivity and DC conductivity differ by two to three orders of magnitude. This difference in conductivity is measured by the respective ammeters and is compared in the current comparator. When the difference in conductivity is greater than a predetermined set point, the current comparator signals an icing alarm.
- the voltage regulator subsystem can operate to apply a DC bias to the circuit - and thus to the interface - at a desired field strength which sufficiently reduces the ice adhesion strength.
- the icing alarm when ice is detected on an aircraft wing, the icing alarm initiates a feedback loop within the system which (a) measures ice conductivities, (b) determines appropriate bias voltages to reach minimum (or near minimum) ice adhesion conditions, and (c) applies a bias voltage to the ice-wing interface to facilitate ice removal.
- the above described system and circuit are .-also applicable to situations where it is desirable to increase the ice adhesion strength.
- the system activates the feedback loop to regulate applied DC voltages to the interface so as to increase ice adhesion.
- Situations and surfaces which can benefit from this system include, for example, the bottom soles of a person's shoe (or shoes) and car tires on icy roads.
- the invention can include a variable ice adhesion/voltage control subsystem which increases and then decreases ice adhesion strength between ice and a surface, selectively.
- a variable ice adhesion/voltage control subsystem which increases and then decreases ice adhesion strength between ice and a surface, selectively.
- cross country skis or telemarking skis
- the ice adhesion system and circuit described herein is attached in circuit with the skis and the operator can adjustably control ski friction selectively.
- the invention provides methodology for reducing the adhesion strength between an automobile windshield (or any window) so that ice is easily removed.
- the window or windshield is doped so as to make the window a semi- conductor (i.e., so that the window is conductive to electricity).
- a first electrode is attached to the window; and a second grid electrode is suspended over the windshield and without contacting the windshield.
- the second electrode can be applied to an electrically insulating grid between the grid electrode and the windshield.
- the insulator and second electrode are preferably transparent so users can see through the window. As ice forms on the windshield, a current path is created from the second electrode and the window (and hence the first electrode).
- Ice thus "shorts" the circuit when formed over the window and any part of the grid.
- a voltage is then applied across the electrodes so that the ice adhesion strength is reduced, as discussed herein.
- the area of the electrodes is preferably much less than the overall area of the interface between the ice and the windshield.
- a method for increasing the coefficient of friction between an automobile tire and an icy road.
- An AC, high voltage power source is connected with an automobile such that a voltage potential is imparted to the interface between the road and the tire.
- the AC has a frequency of between about 1kHz and 1000kHz.
- the tire is manufactured with a conductive material disposed therein, such as carbon, or doped such as with iodine, so that current flows through the tire.
- a voltage potential is then selected and applied to increase the adhesion strength of the ice relative to the tire, increasing the tire's traction on the icy road.
- Petrenko 77ze Effect of Static Fields on Ice Friction, J. Appl. Phys. 76(2), 1216-1219 (1994); Petrenko, Generation of Electric Fields by Ice and Snow Friction, J. Appl. Phys. 77(9), 4518-4521 (1995); Khusnatdinov et al., Electrical Properties of the Ice/Solid Interface, J. Phys. Chem. B, 101, 6212-6214 (1997); Petrenko, Study of the Surface of Ice, Ice/Solid and Ice/Liquid Interfaces with Scanning Force Microscopy, J. Phys. Chem.
- FIGs. 1 A - ID graphically show spatial distributions of electrical charge densities p(x) near ice-air and ice-metal interfaces
- FIGs. 2A-2C illustrate effects of DC bias on ice adhesion to a liquid metal (Mercury), smaller contact angles ⁇ indicating stronger adhesion;
- FIG. 3 schematically illustrates an ice manometer used in measurements of ice- mercury interfacial energy such as illustrated in FIG.2;
- FIG. 6 shows a graph illustrating adhesive energy of an ice-metal interface per surface unit, W a , as a function of distance, z, curves 1, 2, and 3 corresponding to perfect occupancy by D defects, H ⁇ + ions, and protons, respectively (fixed occupancy curves)
- FIG. 8 schematically shows an evaluation system constructed according to the invention and used to measure effects of DC bias on ice adhesion to stainless steel
- FIG. 9 graphically illustrates shear stress vs. time for an ice-stainless steel interface measured with the system of FIG. 8 with no voltage applied to the mobile steel electrode, the ice samples grown from 0.5% solution of NaCl in distilled water and tested at - 10°C under constant strain rate of 1 OO ⁇ m/min;
- FIG. 10 graphically illustrates shear stress vs. time for an ice-stainless steel interface measured with the system of FIG. 8 with +6.6 V applied to the mobile steel electrode, the ice sample grown from 0.5%> solution of NaCl in distilled water and tested at - 10°C under constant strain rate of 1 OO ⁇ m/min;
- FIG. 11 graphically illustrates shear stress vs. time for an ice-stainless steel interface measured with the system of FIG. 8 with -1.8 V applied to the mobile steel electrode, the ice sample grown from 0.5%> solution of NaCl in distilled water and tested at - 10°C under constant strain rate of 1 OO ⁇ m/min;
- FIG. 12 graphically illustrates the effect of +6.6 V on the interfacial strength using data of FIGs. 9 and 10;
- FIGs. 12A and 12B graphically illustrate experimental data of - 10°C ice doped with 0.5% NaCl to assess relative strength of an ice/steel interface;
- FIG. 12C illustrates how production of gas bubbles at an ice/metal interface functions as an interfacial crack to reduce interfacial strength;
- FIG. 13 shows a graph of experimental results including ⁇ W A - ⁇ (Wj /a - Wj /Hg )
- FIG. 17 illustrates one system constructed according to the invention for modifying ice adhesion to a generic conductive (or semiconductor) material
- FIG. 17A shows a cross-sectional view (not to scale) of the system of FIG. 17;
- FIG. 18 illustrates one system of the invention for decreasing the ice adhesion strength of ice that forms on an aircraft wing
- FIG. 19 illustrates a conductive paint/insulating lacquer grid constructed according to the invention and for forming over an aircraft wing
- FIG. 20 illustrates one other embodiment of the invention for modifying ⁇ ice adhesion strength of ice adhered to an aircraft wing
- FIG. 21 schematically illustrates a system constructed according to the invention for modifying ice adhesion strength between an automobile tire and an icy road;
- FIG. 22 shows one other system constructed according to the invention for imparting a voltage to the interface between an automobile tire and an icy surface for increasing the coefficient of friction therebetween;
- FIG. 23 illustrates a system for modifying ice adhered to a car windshield; and FIG. 23A shows an alternative embodiment
- FIG. 24 shows one embodiment of the invention for reducing ice adhesion to power lines; and FIG. 24A illustrates a cross-sectional view (not to scale) of a power line constructed according to the invention;
- FIG. 25 shows an embodiment of the invention for altering the ice adhesion, selectively, to a ski so as to increase or decrease friction to snow and/or ice;
- FIG. 26 illustrates a shoe heel and sole constructed according to the invention for increasing ice/snow adhesion to the sole and/or heel to increase shoe traction;
- FIG. 27 illustrates one system of the invention for removing ice and snow from power lines through application of a coating on the power line; and
- FIG. 28 illustrates application of a ferroelectric coating onto a non-active surface, in accord with the invention, to remove ice therefrom.
- the invention includes systems and methods which modify ice adhesion strength to materials such as metals and semiconductors by application of a DC bias to the interface between the ice and the materials.
- the invention can thus be used to reduce and in some cases eliminate the adhesion of ice onto such materials.
- the invention modifies the electrostatic interactions which form the bonding between ice and metals. These interactions are effectively changed (either reduced or enhanced) by application of a small DC (direct current) bias between the ice and the metals.
- FIGs. 1A-1D illustrate a relationship between molecular polarization P and space charge density p as a function of distance from an ice-air interface (FIGs. 1A-1C) or an ice-metal interface (FIG. ID).
- FIG. ID an electrical charge induced in a metal is equal in magnitude and opposite in sign to the charge in ice.
- the horizontal axes 10 of FIG. 1 refers to distance x relative to "L" as the screening length.
- FIG. 1C illustrates charge density p (along the vertical axis 12c) of the polarization P but with additional screening by minority charge carriers.
- FIG. ID graphs charge density p (relative to the vertical axis 12d) within ice near the ice-metal interface (data 14a) and within metal or dielectric material (data 14b) near the same interface.
- equation (1) provides that P « 3.3 Mpa, a magnitude comparable with, but exceeding, the macroscopic tensile strength of ice at 1.5 MPa. See, Schulson et al., A Brittle to Ductile Transition in Ice Under Tension. Phil. Mag., 49, 353- 63 (1984), which is hereby incorporated by reference.
- the adhesion strength between ice and a conductive material is changed by an external DC bias applied across the ice-material interface.
- FIG. 2B illustrates the resultant adhesion strength ⁇ i which occurs with the application of -1.75V supplied by a DC voltage source 22.
- the source 22 can be, for example, a battery or other voltage source known in the art.
- Wiring 24 connects the source 22 to the Mercury 18 and to the ice 20 to complete the circuit.
- FIG. 2C illustrates another adhesion strength ⁇ 2 which results from an applied voltage of -5 V
- Adhesion strength ⁇ 2 is relatively “strong” as compared to
- an ice manometer 26 (schematically shown in FIG. 3) was used.
- the DC power supply 22' was used for the source 22 of FIG. 2.
- a DC ammeter 28 was placed in the manometer circuit 26 to measure current flow.
- the source 22' connects in circuit to the Mercury 18' and to a mesh electrode 30 connected with the ice 20'. Accordingly, the circuit 26 is completed by the current flow through the Mercury 18' and the ice 20'.
- the Mercury 18' is in fluid communication with the ice 20' through a small capillary 32 of selected diameter.
- the equilibrium position h of the Mercury 18' in the capillary 32 is:
- Equation (2) is used to calculate Wj /Hg , and, thereby, the adhesion strength of ice to the liquid metal (Mercury).
- the capillary's radius r was 0.25 or 0.5 mm during testing.
- the bias can reduce or enhance adhesion of ice to Mercury: at approximately -1.75V, a minimum adhesion strength was reached; while the adhesion strength increased from -2V to -6V. The effect of interfacial energy is more pronounced for NaCl concentrations above 0.05%).
- the model gives an order of magnitude for the adhesive energy which is significantly greater than both chemical bonding energy and van der Waals forces. It also provides an understanding of the time- and temperature- dependent phenomena that explain the difference between adhesive properties of ice and water, the physical mechanisms of bonding between ice and other solids, and the nature and strength of molecular bonding between ice and various solids.
- bonding mechanisms into one of three groups: a covalent or chemical bonding mechanism, a dispersion of or fluctuation in electromagnetic interaction (van der Waals forces), or a direct electrostatic interaction.
- the first mechanism corresponds to chemical reactions and the formation of interfacial compounds.
- the adhesive energy results from lowering of the quantum-mechanical energy of the system due to overlap of the wave functions of the interacting solids. Such an interaction is essential only at a distance on the order of 0.1-0.2nm.
- the chemical bonding mechanism can provide adhesive energy of ⁇ 0.5 J/m 2 , a value considered the lowest value of adhesion energy for the chemical bonding mechanism.
- van der Waals forces are long-range and act between all substances. These forces are defined only by the macroscopic characteristics of a solid (dielectric function at different frequencies), and for this reason they are rather insensitive to experimental conditions. See, e.g., Mahanty et al., Dispersion Forces. Academic Press, London, Chapter 9 (1976); Barash et al., The Dielectric Function of Condensed Systems. Eds. Keldysh, et al., Elsiever Science, Amsterdam, Chapter 9 (1989), each of which is incorporated by reference.
- a model is next developed to describe the electrical properties of the surface of ice.
- the model reveals a connection between ice adhesion and other properties of ice.
- the model is compared with van der Waals forces, the chemical bonding mechanism, and with experimental results.
- Ice includes polar water molecules that strongly interact with any solid substrate which has dielectric permittivity different from that of ice.
- surface charge can also interact with the substrate.
- the surface charge originates from the capture of protonic charge carriers by the ice surface. The captured defects are
- ⁇ and ⁇ 0 are, respectively, the dielectric permittivities of ice ( « 3.2) and of
- V in equation (8) is the surface potential of ice, which has to be found from minimization of the energy for each value of distance d.
- Surface charge density can be considered a constant, which ideally corresponds to a non-equilibrium occupancy of the surface states.
- F then becomes a function of only one parameter, either V or ⁇ . It is somewhat easier to perform the final minimization over V, but the results can also be recalculated as a function of ⁇ .
- the occupancy coefficient of the surface states with D defects plotted versus surface state energy is shown in FIG. 7. The surface state energy level is measured with respect to the chemical potential of D defects in the bulk.
- Time-dependent phenomena can also be associated with ice adhesion, and are inherent in the above-described model. In order to enter or leave the surface state, defects have to overcome some electrostatic barrier, and this leads to non-equilibrium situations and time-dependent phenomena.
- ⁇ is a dielectric permittivity of the insulator. In most solid dielectrics, ⁇ is much larger than one and the induced charges are comparable with charges induced in metals. A smaller ⁇ results in smaller electrostatic related adhesion.
- Teflon has
- the above-described electrostatic model of ice adhesion shows a relationship between the electrical properties of the surface of ice and ice adhesion.
- the model gives a correct order of magnitude for the adhesive energy.
- the electrostatic interaction between ice and metals supplies energy which is significantly higher than chemical bonding energy and the van der Waals forces at distances greater than intermolecular ones.
- the model also provides an intuitive way to understand the time- and temperature-dependent phenomena that help explain the difference in adhesive properties of ice and water.
- FIG. 9 shows results of a typical load versus time diagram when an ice-steel interface is tested under zero DC bias. As one can see, the load reaches its maximum value and then drops down when the interface is broken. The residual resistance of the sample to the constant strain rate is due to viscous sliding of the steel on the salted ice. Still, application of a DC bias can significantly change both the maximum strength of the interface and the residual resistance of ice-steel specimens.
- FIG. 10 shows results of a typical mechanical test performed on an ice-steel interface when +6.6 V is applied to the inner (mobile) tube 52a.
- FIG. 11 shows results similar to that of FIG. 10 when -1.0 V is applied to the mobile electrode.
- FIGs. 9 and 10 are combined in FIG. 12 to illustrate the effect of DC bias on interfacial strength. The results of such tests are summarized in Table 1 below, which illustrates that for voltages
- FIGs. 1 and 2 show a strong and reversible effect of a small DC bias (-6V to +6V) on ice adhesion to Mercury.
- the effect was observed in ices doped with KOH, HF, and NaCl and was absent in very pure ice grown from deionized water.
- AC voltage of up to 40V did not cause any noticeable changes in ice adhesion.
- This section reports further on the effect of a low DC bias applied across an ice-Hg interface on the interfacial energy and on the work of adhesion. This section also reports the fraction of ice-metal interfacial energy that is due to long-range electrostatic interactions.
- the first technique was a conventional contact- angle method with a drop of mercury on a flat, smooth ice surface, schematically shown in FIG. 2.
- the ice surface was smoothed by a microtome machine and polished on an optically smooth quartz plate.
- the second technique used the manometer system of FIG. 3, which is more precise and reproducible in the case of the ice-Mercury interface.
- the quartz tube 31 had an internal diameter of 10mm and contained a stainless-steel cylindrical mesh electrode 30 and a thin stainless-steel wire stretched along the tube's axis. After the water was frozen, the wire was carefully pulled out, producing a thin circular capillary 33 with very smooth walls.
- the capillary's radius, r was either 0.5 or 0.25mm. Prior to the surface tension measurements, the capillary was filled with liquid mercury from the mercury tank 19.
- Equation 2 In equilibrium, the mercury level difference h is given (again) by equation (2).
- equation 2 When h is measured, equation 2 is also used to calculate Wj/ a - Wj / ⁇ g , and hence the work W A of ice adhesion to a liquid metal:
- W Hg/a is the energy of the Hg/air interface.
- W Hg/a 493 mJ ' m at -10°C.
- Table 2 Contact angle ⁇ of mercury on ice grown from water containing different dopants and under different DC biases applied between the mercury and the mesh electrode, positive voltage corresponding to a positive potential on mercury.
- FIGs. 14 and 15 show the effect of a DC bias on ⁇ W A of ice doped with HF and
- the measured DC current is a sum of the bulk, surface, and grain-boundary currents.
- FIGs. 13 and 14 In the case of ice doped with 0.2%> KOH, there was also no noticeable color change of ice/Hg interfaces associated with electro-corrosion. Other possibilities exist for anomalies in the data. For example, a stainless-steel- doped ice-mercury sandwich behaves as a weak battery, generating a small electromotive force (EMF) with a negative potential on the mercury. This EMF was -0.18V for ice doped with 0.5% NaCl and -0.3V for ice doped with 0.2% KOH .
- EMF electromotive force
- V c Due to redox reactions, there are always potential differences, V c , between a metal
- C(V) is an "apparent" interfacial capacitance that itself depends on V c .
- R is the resistance of a steel/ice/mercury sandwich
- R « lV/50 ⁇ A 2-10 ⁇
- S is the area of the ice-Hg interface. The two factor appears due to the presence of the stainless-steel/ice interface, which is assumed to be identical to the ice-Hg interface. This provides an order-of-magnitude rough estimate.
- Equation (17) calculates C at an approximate value of 0.4F/m , which is quite typical for electrode capacitance when metals are immersed in concentrated electrolytes. 2 Substitution of C « 0.4F/m and the mercury standard potential V c « 0.8V into equation
- FIG. 17 illustrate a system 100 constructed according to the invention.
- System 100 operates to reduce the adhesion of ice 102 formed onto the surface 104a of a material 104.
- the system 100 forms a circuit that includes the material 104, a conductive grid 106 (including illustrative points "A" - “F” on the grid), and a power supply 109.
- the grid 106 is suspended above the surface 104a so that it remains electrically insulated from the material 104.
- the suspension of the grid 106 over the surface 104a is obtained through use of an insulating grid 108 disposed between the grid 106 and the surface 104a.
- FIG. 17A illustrates the grid 108 in greater detail.
- the cross- sectional view of FIG. 17A is not to scale so as to illustrate the relationship of the insulating grid 108 and the conducting grid 106.
- the thickness (in the dimension of FIG. 17A) of the grids 106, 108 can be much smaller than an inch (even as low as 0.010 to 0.020 inch); and can be considered as "coatings".
- the grid 108 can be made from a thin coating of electrically insulating paint; while the grid 106 can be made from a thin coating of electrically conductive paint.
- the grid 106 is connected so as to function as a single electrode.
- the material 104 thus becomes a first electrode of the system 100; and the grid 106 becomes the second electrode in the circuit.
- Grids 106, 108 can also be pliant and formable over the surface 104a, which can represent any shape even though a flat surface 104a is shown.
- the material 104 can represent an aircraft wing or a car windshield; and the grids 106, 108 are conformal to the structure material 104.
- the circuit of system 100 is completed as the ice 102 operates as a semiconductor (as discussed above).
- the power supply 109 provides a DC bias to the interface between the ice 102 and the material 104.
- the bias is typically less than a few volts; and thus a battery can function as the supply 109.
- the magnitude of the bias depends upon the desired application. In the case of a car windshield or an ai ⁇ lane wing, the bias is selected so that a minimum (or near- minimum) ice adhesion results, thereby facilitating the removal of the ice 102 from the material 104.
- the ice 102 represents ice beneath the heel; and the bias is selected so as to increase the normal ice adhesion strength between the ice and the heel, thereby increasing friction between the shoe and possibly preventing a slip on the ice.
- a voltage regulator subsystem 112 is also preferably connected in circuit with the system 100. As described in more detail below, the voltage regulator subsystem 112 operates in feedback with the circuit and the supply 109 so as to decrease or increase the DC bias in an optimum fashion.
- the subsystem can include circuitry and a microprocessor 112a to measure data from the circuit and to determine the conductivity (and/or temperature) of the ice 102. Such measurements are used in turn by the subsystem 112 to generate a signal which effectively changes the amount of the DC bias applied to the circuit.
- the power supply 109 is responsive to the signal to generate the right voltage at the ice-material interface.
- the value of the DC bias can be stored in memory 112b within the subsystem 112 such as through a look-up table and based upon experimental data. For example, ice with a conductivity of "X" (as measured by the subsystem, in real time preferably) in contact with a material 104 of conductivity "Y" (known a priori, as the system 100 is installed with the material 104 for a given application) will be used through the look-up table in memory 112b to determine which voltage to apply to the ice-material interface.
- the grid electrode 106 is preferably spaced so as to ensure (as best as possible) that ice 102 formed onto the surface 104a will contact at least some portion of the grid 106.
- the ice 102 comes in contact with several areas of the grid 106, including at points "C" - "E". Accordingly, the circuit of system 100 will be completed as the ice 102 "shorts" at least one part of the grid to material electrodes 106, 104, respectively.
- the actual size of the spacing between conductive areas of the grid 106 - for example, the area 114 of FIG. 17 - should be sized for the specific application.
- the spacing can be relatively large, e.g., greater than one square foot.
- area 114 should be smaller, if desired, so that smaller ice deposits on the windshield (such as in the corners of the windshield) are likely to short to the grid 106.
- FIG. 18 illustrates a system 130 constructed according to the invention.
- One electrode of the subsystem 130 is the aircraft wing 132.
- the aircraft wing 132 is electrically coupled to ground 134.
- a DC power supply 136 is electrically coupled to a DC ammeter 138.
- the DC ammeter 138 is electrically coupled to an inductor 140.
- the inductor 140 is electrically coupled through wiring 141 to a conductive paint 142 (or other wing-conformal, conductive equivalent) which is applied to the insulating layer 144 fixed on the aircraft wing 132.
- the insulating layer 144 and paint 142 are preferably arranged as a grid pattern, such as described in connection with FIG. 17 and shown further in FIG. 19.
- the conductive layer 142' on the wing 132' and the insulating layer 144' (shown here as an insulating lacquer) form a grid pattern 145.
- the power supply 136' connects to the conductive paint 142' and to ground through the wing electrode 132'.
- the circuit is shorted by the ice and a DC bias is applied at the ice- wing interface so as to reduce ice adhesion and to facilitate ice removal.
- the total area covered by the insulating lacquer 144' does not exceed about 1%) of the front edge 132a' of the wing 132'.
- the grid pattern 145 can be sized and arranged over the front 132a', as shown, or over the entire wing 132', or over some other area as a matter of design choice. A wing or aircraft manufacturer who has historical or other data on typical ice deposits for the particular wing or aircraft can thus apply the grid 145 over that particular region only, if desired.
- the voltage applied between the wing 132 and 132' of FIGs. 18 and 19, respectively, is generally adjusted to between one and six volts, with a corresponding current below 1A per m 2 of the grid area.
- the DC ammeter 138 can additionally couple to a feedback subsystem 150.
- the feedback subsystem 150 in turn electrically couples to the DC power supply 136 to "control" the DC bias applied to the wing-ice interface, depending upon characteristics such as ice conductivity and temperature.
- a temperature sensor 152 thus also preferably connects with the circuit 130 to measure the temperature ofthe ice l54.
- FIG. 130 Further features of the system 130 can include an AC power supply 156 (operating between about 10kHz and 100kHz) electrically coupled to an AC ammeter 158, which in turn electrically couples to the conductive paint 142.
- a current comparator 160 is electrically coupled to both the AC ammeter 158 and the DC ammeter 138.
- An icing alarm subsystem 162 can also be included with the system 130.
- the current comparator 160 can for example couple to the icing alarm subsystem 144 and to the feedback subsystem 150 so as to initiate certain events, such as discussed below.
- the DC ammeter can be used to measure the DC conductivity of the circuit 130.
- the DC conductivity signal measurement is provided to the feedback subsystem 150, which in turn regulates the current supplied by the DC power supply 136, and to the current comparator 160.
- the AC ammeter can be used to measure the AC conductivity of the circuit 130 within the applied frequency range of 10-lOOkHz, for example.
- the AC conductivity signal measurement is provided to the current comparator 160 (and optionally to the feedback 150 for A/D and data processing).
- a comparison between the AC and DC conductivities is used by the system 130 to distinguish between water and ice, both of which "short" and complete the circuit.
- the ratio of the AC to DC conductivity is 2-3 orders of magnitude greater in the case of ice as compared to water, providing a signal measurement which readily distinguishes ice over water.
- the current comparator 160 signals the feedback subsystem 150 which in turn commands the DC power supply 136 to increase or decrease the DC bias at the ice-wing interface.
- the DC bias is selected at a magnitude (generally between one and six volts) so as to minimize ice adhesion strength of the ice 154 on the wing 132.
- the signal differential received by the current comparator 160 drops below a preset value; and the current comparator 160 deactivates the icing alarm 162. Simultaneously, the current comparator 160 signals the feedback subsystem 150 which in turn commands the DC power supply 136 to decrease the bias to the initial level.
- the ammeters 138 and 158 are used to determine conductivity of the material which shorts between the grid electrode 142 and the wing 132. As shown, that material is ice 154.
- the system 130 thus distinguishes between ice and water in an automatic manner.
- the inductor 140 prevents AC voltage from entering the "DC" parts of the circuit, which should be accurately controlled to modify the ice adhesion strength.
- the feedback subsystem 150 can and preferably does include a microprocessor and memory to command and control the power supply 136 at a near-optimum DC bias based upon feedback data such as ice temperature and ice conductivity (and/or ice purity).
- the feedback circuitry preferably increases or decreases DC bias voltages at a level that provides a density of about O.lmA/cm (or about ImA in current density at the ice- wing interface) after receiving an ice alarm signal from the subsystem 162. Accordingly, for a current of about 10-30A, a total energy consumption of about 100-500 watts is required for a typical large ai ⁇ lane.
- the "DC” parts of the circuit of FIG. 18 thus primarily operate to provide DC bias to the ice-wing interface, and, secondarily (if desired) to measure the DC conductivity of the ice 154.
- the "AC” parts of the circuit of FIG. 18 thus primarily operate to measure the AC conductivity.
- the remaining portions of the circuit of FIG. 18 thus provide: (a) an inductor to prevent signal coupling between the DC and AC parts; (b) feedback and measurement and control circuitry to control the applied DC bias based upon detection of ice (as compared to water) and/or measured feedback parameters such as ice temperature and conductivity.
- FIG. 20 illustrates one other system 200 used to de-ice an aircraft wing 202.
- a DC power source 201 supplies a DC bias to the wing 202, acting as the first electrode (the wing 202 is either conductive or coated with metal foil or conductive paint), and to a conductive grid 204 that is electrically insulated from the wing 202.
- the grid 204 is insulated from the wing 202 by an insulating film 206 disposed between the wing 202 and the grid 204.
- the grid 204 acts as the second electrode in the circuit of FIG. 20.
- FIG. 21 illustrates a system 250 used to increase friction between an automobile tire 252 and ice 254 on the road 256.
- the tire 252 includes a plurality of strips 252a that are conductively doped (such as with iodine) to transmit a current.
- a DC power supply 258 connects to the strips 252a through cabling 260 and generates a DC bias relative to ground 262.
- the DC voltage differential generated by the supply 258 is between about 5V and 1000V (and is usually in the range 10V to 100V).
- the DC supply can also include voltage regulation circuitry and feedback subsystems (as discussed above) to determine the conductivity of the ice 254 (or snow) and to adjust the DC bias accordingly.
- a non-contact temperature sensor (not shown) can also be used to remotely sample the ice temperature, as known to those in the art, so that temperature can also be used as a feedback parameter.
- Voltage is applied to the strips 252a by way of a electrical control lever 266. Alternating strips 252a can be driven with plus or minus potential through the supply 258, if desired, to acquire the highest adhesion for a given voltage range.
- the lever 266 can be moved up and out of the way when the system 250 is not in use (such as by an electro- mechanical controller). By connecting the supply 258 to the wheel axle 270, a constant distance is maintained between the lever 266 and the current source.
- the strips 252a can be welded onto existing tires (or tire material) and that fewer or more strips 252a can be used. Indeed, the tire 252 can be entirely doped so as to become conductive wherein no strips are required.
- circuitry such as presented in FIG. 18 can also be used in the tire system of FIG. 21.
- the DC and AC voltages in such an embodiment are applied to neighboring strips 252a (shown as + and - respectively) so as to decouple the two signals.
- the DC voltage applied between the strips 252a is small (about 10V) before an ice alarm is received; but is switched to high voltage of 100V to 1000 V after the signal.
- FIG. 22 shows a system 300 that increases the friction between an automobile tire 302 and an icy road 304.
- the tire 302 is doped or manufactured so that current can flow through the rubber of the tire 302.
- An AC power source 306 is housed within the car 308 and is connected to the tire 302 through appropriate wiring 309 (the wiring is non- interfering with the wheel rotation, such by connection through the axle).
- the AC source 306 applies a high frequency (10-1000kHz), high voltage signal to the tire 302; and that signal imparts a substantially DC voltage between the tire 302 and the road 304. That voltage is preferably of a magnitude which increases the friction between the ice 310 and the tire 302.
- FIG. 23 shows a system 400 which includes a car window 402 connected in circuit with a DC source 404.
- the window material is doped (such as with ITO or fluoride doped SjO 2 ) to become one conducting electrode of the system 400.
- the other electrode is a grid 406 formed by transparent conducting strips placed on the window 402 and electrically insulated by a insulating grid (not shown) between the grid 406 and the window 402.
- a voltage regulator subsystem 408 monitors factors such as ice conductivity and temperature so as to determine when ice bridges the gap between the grid 406 and the window 402 (as compared to water) and further to bias the DC voltage applied to the interface between the ice and the window to a point of near- minimum ice adhesion. See, e.g., FIG. 4.
- the insulating grid beneath grid 406 is similar to the layer 144' of FIG. 19.
- the grid 406 is connected together such that each point on the grid 406 resides at a constant potential, preferably.
- FIG. 23 A An alternative window grid and electrode pattern is shown in FIG. 23 A, which includes a DC source 450 connected to a first electrode 452 (coupled to a first grid) and to a second electrode 454 coupled to a second grid interleaved with the first grid.
- the system of FIG. 23A is an alternative embodiment as compared to FIG. 23; and can include additional circuitry and control such as described herein.
- the anti-icing grid of FIGs. 23 and 23A is preferably made of conductive transparent coatings which are common in LCD and solar-cell technologies. DC voltages of 1-2V are typically applied to the comb-like grids of transparent conductive electrodes on the window. The desired bias can depend upon the electrode material and the manufacturer. The electrodes can be either painted or vapor-deposited on the windshield.
- car windshields can be doped with either ITO or fluoride doped SjO 2 , for example, to become an acceptable semiconductor (including transparency).
- Alternative transparent coatings include doped polyaniline. Lithium ion conductive glass might also be used. For automobile tires, copolymer-carbon deposits can be used within the rubber so as to conduct electricity. Iodine might also be used. Thin rubber films developed by CSIRO in Australia might also be used with the invention.
- FIG. 24 illustrates a power line ice control system 500 constructed according to the invention.
- the system includes a power control module 502 (including functionality such as DC power supply, and preferably voltage regulation and DC and AC ice detection and measurement as described herein) that is connected by wiring 504 to doped power line wiring 506.
- the wiring 506 is shown in an illustrative cross-sectional view (and not to scale) in FIG. 24A.
- the wiring 506 thus includes a main power line 508 and an insulating layer 510 , both of which are known to those skilled in the art.
- a doped outer layer 512 surrounds the insulating layer 510 to provide ice control DC bias in circuit with the module 502.
- a conductive grid 514 axially extends (with optional circumferential winding) along the length of the wiring 506 and is electrically insulated from the layer 512 by an insulating grid 516 (also axially disposed) between the grid 514 and the layer 512.
- an insulating grid 516 also axially disposed between the grid 514 and the layer 512.
- System 600 is shown with a view of the bottom 602a of the ski 602.
- a grid 604 (shown illustratively and including an electrically conducting grid spaced from the bottom 602a by an insulating grid, such as described herein) is provided on the bottom 602a as part of the circuit of system 600.
- a battery 606 connects to the grid 604 and to the bottom 602a and provides the DC bias to the circuit.
- a controller 608 senses ice conductivity (and optionally temperature) and regulates the bias generated by the battery 606.
- the ski bottom 602a is made from semiconductor material or is doped or lacquered with conductive strips. In contact with snow or ice, the controller controls the applied voltage and, thereby, the friction between the ski 602 and snow and ice.
- controller (and/or battery) are shown illustratively in FIG. 25 as dotted lines. Their physical location is a matter of design choice and may be on the top surface of the ski or in a boot pack or binding.
- the controller can be made responsive to user input to alter the friction in real time. For example, skiers climbing up an incline (such as in cross-country) can select “increased friction” and the system 600 will respond to do so. The user can also select "decreased friction" and the controller commands a bias that minimizes the ice adhesion strength of ice/snow to the bottom 602a.
- FIG. 26 shows yet another embodiment of the invention for modifying ice adhesion strength for ice/snow in contact with a sole of a shoe 699.
- FIG. 26 shows a system 700 including a battery 702.
- the battery 702a connects to a conductive grid 704 such as described herein (and spaced from the conductive heel 699a).
- the snow or ice bridges the circuit and a DC bias is applied to the ice-heel interface to increase friction.
- FIG. 26 The other design of FIG. 26 is shown illustratively in that a grid electrode is not really required for a small surface such as a shoe 699. Rather, a single electrode 706 may be sufficient (note that as above the electrode 706 is spaced from the sole by an insulating layer 706a.
- the sole of the shoe is conductive (or made conductive through doping) so that when snow or ice contact the electrode 706, the circuit is completed and the optimum DC bias is applied from the battery 702b so as to increase shoe traction.
- FIG. 27 shows one preferred embodiment of the invention suitable to reduce or remove ice from power lines 700.
- the inset to FIG. 27 shows a cross-sectional view of the power line 700 constructed according to the invention.
- the normal power line 702 generates power at 60Hz but with very high E-fields such as 10,000 volts per inch.
- a coating 704 is applied over the line 702 at a thickness of "t".
- the coating 704 is a ferroelectric material, as known in the art.
- Ferroelectric materials are essentially ceramics that exhibit a very high dielectric constant (e.g., 10,000) and very high dielectric loss (e.g., tan ⁇ s 10) at certain conditions, and a relatively low dielectric constant (3-5) and small dielectric loss at other conditions.
- One condition that can change the constant is temperature.
- the material is selected so that above freezing, the dielectric constant is low, and below freezing temperatures, the constant is high. When ambient temperature drops below the freezing point, the coating is intensively heated by the AC electric field due to the high dielectric constant and dielectric loss.
- the above-described embodiment £an be self-regulating in keeping the coating temperature close to (or slightly above) the melting point. If the coating is overheated by the power line's electric field, it automatically undergoes a phase transformation from the ferroelectric to the normal state, at which point the coating stops absorbing the electric field energy. By choosing a phase transition temperature, therefore, the coating temperature can be adjusted per user needs and per the environmental conditions of the local area.
- the coating 704 generates heat in the presence of an AC field such as generated by the line 702. Specifically, it exhibits hysteresis that generates heat over the AC cycle; and the coating thus generates heat due to the oscillating E-field of the line 702.
- the thickness "t” is typically on the order of 1/100 of an inch, though other thicknesses can be applied depending upon coating materials and desired heating. By changing the thickness, for example, temperatures at the surface 704a can be increased by 1-10 degrees, or more.
- the thickness "t” is chosen so that a desired amount of heat is generated (i.e., heat sufficient to generally melt ice and snow on the surface 704a of the line 700).
- the coating 704 can also be constructed by ferromagnetic materials with the same or similar effect. In this case, the coating absorbs the energy of the magnetic field generated by a power line.
- the heating power per cubic meter is:
- ⁇ ' is a relative dielectric permittivity (usually ⁇ ' is approximately IO 4 for typical
- tan ⁇ is the tangent of dielectric loss
- Ferroelectrics are characterized with very large values of ⁇ ' and tan ⁇ below the so-
- T c Curie Temperature
- T c Curie Temperature
- IO 6 IO 6
- the ferroelectric material maintains a constant temperature which is close to T c and just above T m
- This self-adjusting mechanism to prevent icing is very economic: the maximum heating power per one meter of the power line, or per m 2 at any surface to be protected, can be increased or decreased by changing the coating thickness and/or by adding a neutral (not ferroelectric) insulating paint or plastic to the coating.
- suitable ferroelectric materials according to the invention include:
- the electric field strength on the wire surface is: V
- a 1mm thick film, for example, thus generates 450 watt/m 2 , which is more than sufficient for typical melting of ice.
- ⁇ is the coating's dielectric constant
- ⁇ 0 is that of free space.
- FIG. 28 illustrates an embodiment of the invention utilizing such coatings to de-ice non-active surfaces (i.e., those surfaces without internal AC e-fields).
- a ferroelectric coating 800 is applied to a structure 802 (e.g., an aircraft wing).
- Foil electrodes 804a, 804b provide for application of AC power to the structure 802.
- the AC power derives from a standard AC power supply 806.
- An ice detection system 808 e.g., the detection system of FIG. 18
- the AC frequency and coating thickness are chosen to generate heat at the desired quantities (e.g., so as to keep icing from forming on an aircraft wing).
- grid electrodes such as described in connection with FIG. 17 can also be applied to surfaces including the roof of a house, oil pipelines, driveways, and other areas prone to ice collection.
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- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
- Battery Electrode And Active Subsutance (AREA)
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Abstract
Description
Claims
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
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AU80729/98A AU8072998A (en) | 1997-06-16 | 1998-06-15 | Systems and methods for modifying ice adhesion strength |
EP98929077A EP0988229A4 (en) | 1997-06-16 | 1998-06-15 | Systems and methods for modifying ice adhesion strength |
BR9810527-2A BR9810527A (en) | 1997-06-16 | 1998-06-15 | Systems and methods to modify resistance to ice adhesion |
JP11504644A JP2000514756A (en) | 1997-06-16 | 1998-06-15 | System and method for changing ice adhesion strength |
CA002293399A CA2293399C (en) | 1997-06-16 | 1998-06-15 | Systems and methods for modifying ice adhesion strength |
IL13330298A IL133302A (en) | 1997-06-16 | 1998-06-15 | Systems and methods for modifying ice adhesion strength |
HK01100451A HK1029557A1 (en) | 1997-06-16 | 2001-01-18 | Systems for modifying ice adhesion strength |
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US4979097P | 1997-06-16 | 1997-06-16 | |
US60/049,790 | 1997-06-16 | ||
US7962398P | 1998-03-27 | 1998-03-27 | |
US60/079,623 | 1998-03-27 | ||
US7991598P | 1998-03-30 | 1998-03-30 | |
US60/079,915 | 1998-03-30 |
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EP (1) | EP0988229A4 (en) |
JP (2) | JP2000514756A (en) |
CN (2) | CN1240081C (en) |
AU (1) | AU8072998A (en) |
BR (1) | BR9810527A (en) |
CA (1) | CA2293399C (en) |
HK (1) | HK1029557A1 (en) |
IL (1) | IL133302A (en) |
WO (1) | WO1998057851A2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1242280A1 (en) * | 1999-12-30 | 2002-09-25 | Trustees of Dartmouth College | System and method for an electrical de-icing coating |
CN111685576A (en) * | 2019-03-13 | 2020-09-22 | 广东美的白色家电技术创新中心有限公司 | Pot for electromagnetic heating, preparation method thereof and temperature measuring method |
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US8124423B2 (en) * | 2003-09-30 | 2012-02-28 | Alcatel Lucent | Method and apparatus for controlling the flow resistance of a fluid on nanostructured or microstructured surfaces |
US7928345B2 (en) * | 2004-10-22 | 2011-04-19 | Ppg Industries Ohio, Inc. | Aircraft windshield defogging/deicing system and method of use thereof |
JP4644807B2 (en) * | 2005-08-11 | 2011-03-09 | 国立大学法人 千葉大学 | Ice heat storage device |
CN102214901B (en) * | 2010-04-04 | 2015-11-25 | 江苏天南电力器材有限公司 | A kind of anti-icing equipment |
GB2483672B (en) * | 2010-09-15 | 2017-01-18 | Ge Aviat Systems Ltd | Propeller blades having icephobic coating |
US10351248B2 (en) * | 2015-06-25 | 2019-07-16 | Gulfstream Aerospace Corporation | Aircraft and aircraft windshield heating systems |
GB2546976B (en) * | 2016-01-29 | 2020-01-08 | Ge Aviat Systems Ltd | Propeller blades having icephobic coating with separate substrate portions defining different colours |
CN106970021A (en) * | 2017-04-27 | 2017-07-21 | 国网山西省电力公司经济技术研究院 | It is a kind of to test ice covering on transmission lines and the apparatus and method of the tangential bond strength in power transmission line interface |
CN109193538B (en) * | 2018-09-30 | 2020-11-10 | 国网河南省电力公司社旗县供电公司 | Overhead line regular cleaning equipment |
CN111549599B (en) * | 2020-04-30 | 2021-11-26 | 中国一冶集团有限公司 | Construction structure and method suitable for roadbed filling and pavement restoration under complex conditions |
CN111770594B (en) * | 2020-06-17 | 2022-04-19 | 陕西飞机工业(集团)有限公司 | Portable multipurpose glass system of heating debugging circuit |
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GB2252285B (en) * | 1991-01-29 | 1994-07-06 | British Aerospace | Method and apparatus for separating a frozen deposit from a substrate |
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1998
- 1998-06-15 AU AU80729/98A patent/AU8072998A/en not_active Abandoned
- 1998-06-15 CA CA002293399A patent/CA2293399C/en not_active Expired - Fee Related
- 1998-06-15 WO PCT/US1998/012421 patent/WO1998057851A2/en not_active Application Discontinuation
- 1998-06-15 IL IL13330298A patent/IL133302A/en not_active IP Right Cessation
- 1998-06-15 EP EP98929077A patent/EP0988229A4/en not_active Withdrawn
- 1998-06-15 CN CN01115767.4A patent/CN1240081C/en not_active Expired - Fee Related
- 1998-06-15 JP JP11504644A patent/JP2000514756A/en not_active Withdrawn
- 1998-06-15 BR BR9810527-2A patent/BR9810527A/en not_active Application Discontinuation
- 1998-06-15 CN CN98806257A patent/CN1077062C/en not_active Expired - Fee Related
-
2001
- 2001-01-18 HK HK01100451A patent/HK1029557A1/en not_active IP Right Cessation
-
2005
- 2005-07-13 JP JP2005205006A patent/JP2006029774A/en active Pending
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US4979097A (en) | 1987-09-04 | 1990-12-18 | Digital Equipment Corporation | Method and apparatus for interconnecting busses in a multibus computer system |
US5973010A (en) | 1998-05-15 | 1999-10-26 | Crawford; Robert L. | Composition for healing skin wounds |
US7991598B1 (en) | 2005-08-01 | 2011-08-02 | The Mathworks, Inc. | Method and system for modeling a mechanical system |
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See also references of EP0988229A4 |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1242280A1 (en) * | 1999-12-30 | 2002-09-25 | Trustees of Dartmouth College | System and method for an electrical de-icing coating |
JP2004501015A (en) * | 1999-12-30 | 2004-01-15 | トラスティーズ・オブ・ダートマウス・カレッジ | System and method for electrical deicing coating |
EP1242280A4 (en) * | 1999-12-30 | 2006-02-22 | Dartmouth College | System and method for an electrical de-icing coating |
CN111685576A (en) * | 2019-03-13 | 2020-09-22 | 广东美的白色家电技术创新中心有限公司 | Pot for electromagnetic heating, preparation method thereof and temperature measuring method |
Also Published As
Publication number | Publication date |
---|---|
JP2006029774A (en) | 2006-02-02 |
IL133302A0 (en) | 2001-04-30 |
CA2293399A1 (en) | 1998-12-23 |
CN1077062C (en) | 2002-01-02 |
CN1240081C (en) | 2006-02-01 |
IL133302A (en) | 2003-12-10 |
CA2293399C (en) | 2007-08-21 |
CN1260755A (en) | 2000-07-19 |
EP0988229A2 (en) | 2000-03-29 |
BR9810527A (en) | 2000-12-19 |
AU8072998A (en) | 1999-01-04 |
HK1029557A1 (en) | 2001-04-06 |
JP2000514756A (en) | 2000-11-07 |
EP0988229A4 (en) | 2002-02-27 |
CN1352457A (en) | 2002-06-05 |
WO1998057851A3 (en) | 1999-04-15 |
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