1. A bipolar plate for PEM fuel cells comprising a plastic structure having a surface zone including gas-transport channels, the plastic structure comprising a polymer blend which is filled with conductivity-enhancing carbon fillers and which includes at least two mutually nonmiscible blend polymers,
wherein the polymer blend includes at least one polyamide and at least one polyether ketone or polyether sulfone as blend polymers,
wherein the at least two blend polymers form a co-continuous structure and the carbon fillers are at a higher concentration in one of the blend polymers or in the phase between the blend polymers, or wherein a blend polymer in which the carbon fillers are at a higher concentration forms a continuously conductive matrix in which the at least one further blend polymer is intercalated,
wherein the polymer blend comprises from 45 to 85 wt % of blend polymers and from 15 to 65 wt % of carbon fillers, and
wherein the polymer blend contains as carbon fillers
from 1 to 30 wt % of conductive black,
from 5 to 60 wt % of carbon fibers, and
from 1 to 25 wt % of carbon nanotubes,
in each case based on the total weight of the polymer blend, and
the weight ratio, in the polymer blend, of polyamide to polyether ketonepolyether sulfone is from 1:1.6 to 4:1.
2. The bipolar plate as claimed in claim 1, wherein the carbon fillers are selected from conductive black, graphite, carbon fibers, carbon nanotubes and mixtures thereof.
3. A method of fabricating bipolar plates as claimed in claim 1 by preparing and shaping the polymer blend filled with conductivity-enhancing carbon fillers.
4. A PEM fuel cell comprising bipolar plates as claimed in claim 1.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A memory device comprising:
a substrate;
a data storage medium on the substrate; and
machine readable data stored in the data storage medium, the machine readable data having a first readability, the readability of at least a portion of the machine readable data modifiable by a limited expected lifetime so that following modification of readability, the modified portion of machine readable data has a second readability; and
wherein data having the first readability is readable by a first type of data read system and wherein data having the second readability is not readable by the first type of data read system.
2. The memory device of claim 1, wherein data having the second readability is readable by a second type of data read system.
3. (canceled)
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9. The memory device of claim 1, wherein readability of at least one first portion of the machine readable data is modifiable by the limited expected lifetime, wherein readability of at least one second portion of the machine readable data is not modifiable by the limited expected lifetime, and wherein the at least one first portion contains read-support information needed for reading data of interest in the at least one second portion.
10. (canceled)
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16. The memory device of claim 9, wherein machine readable data in the at least one first portion having the second readability is substantially unreadable, and wherein additional read-support information is stored in the at least one second portion and retrievable with a special purpose read system.
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45. A memory device comprising:
a data storage medium; and
machine readable data stored in the data storage medium, at least at least one first portion of the machine readable data having a limited expected lifetime after an initial read of data, during which the machine readable data can be read from the data storage medium by a first type of data read system, and following which the readability of the at least one first portion of the machine readable data is modified so that it is unreadable by the first type of data read system.
46. The memory device of claim 45, wherein following the limited expected lifetime, the at least one first portion of the machine readable data is readable by a second type of data read system
47. (canceled)
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53. The memory device of claim 45, wherein the at least one first portion of the machine readable data contains read-support information necessary for reading data of interest in at least one second portion of machine readable data.
54. The memory device of claim 53, wherein the read-support information includes at least a portion of a decryption key.
55. (canceled)
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58. The memory device of claim 53, wherein the at least one second portion includes additional read-support information needed for reading data of interest in the at least one second portion.
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69. A data storage device comprising:
a data storage medium capable of having machine readable data stored therein, the data storage medium capable of producing a data signal in a data read device in response to an interrogation activity by the data read device, the data storage medium including:
at least one modifiable portion capable of producing a data signal within a first signal range at the start of a limited read period characterized by a limited expected lifetime or limited temporal duration, and modifiable to produce a read signal falling within a second signal range subsequent to the limited read period.
70. The data storage device of claim 69, wherein a data signal within the first signal range is readable by a general purpose read device and wherein a data signal within the second signal range is readable by a special purpose read device but not by a general purpose read device.
71. (canceled)
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75. The memory device of claim 1, wherein machine readable data having the second readability has at least one of a reduced signal-to-noise ratio relative, an increased bit error rate, or a reduced redundancy relative to machine readable data having the first readability.
76. The memory device of claim 1, wherein the limited expected lifetime is defined by at least one of a limited number of readings of the machine readable data from the memory device, a limited number of uses of the memory device, or a limited time interval following an initial use of the device.
77. The memory device of claim 9, wherein machine readable data in the at least one first portion having the second readability has at least one of a reduced signal-to-noise ratio, an increased bit error rate or a reduced redundancy relative to machine readable data having the first readability.
78. The memory device of claim 9, wherein the read-support information includes at least one of a decryption key or index information.
79. The memory device of claim 16, wherein the data storage medium is an optical data storage medium, and wherein the additional read-support information is stored in at least one of the optical data storage medium at a different optical wavelength than the data of interest, the optical data storage medium at a different spatial frequency than the data of interest, a magnetic data storage medium included in the memory device, at least one resonant circuit included in the memory device, at least one RFID included in the memory device, or a bar code on the memory device.
80. The memory device of claim 16, wherein the data storage medium is a magnetic data storage medium, and wherein the additional read-support information is stored at least one of in the magnetic data storage medium at a different spatial frequency than the data of interest, an optical data storage medium included in the memory device, at least one resonant circuit included in the memory device, at least one RFID included in the memory device, or a bar code on the memory device.
81. The memory device of claim 16, wherein the additional read-support information is retrievable by a special purpose read system including one or more of special purpose software or special purpose hardware.
82. The memory device of claim 16, wherein the additional read-support information includes at least one copy of at least a portion of the read-support information in the at least one first portion.
83. The memory device of claim 16, wherein the additional read-support information is stored in the at least one second portion in encrypted form or distributed among multiple locations in the at least one second portion.
84. The memory device of claim 83, wherein the additional read-support information is encrypted by at least one of public key encryption method, a private key encryption method, a Diff-Hellman encryption method, an RSA encryption method, an EIGaml encryption method, a DSS encryption method, an Elliptic curve encryption method, a Paillier cryptosystem encryption method, a Password-authenticated Key agreement encryption method, or a DES encryption method.
85. The memory device of claim 1, wherein readability of the machine readable data is modifiable through one or more of degradation of the data storage medium, degradation of the substrate, or erasure or writing over of at least a portion of the machine readable data.
86. The memory device of claim 46, wherein during the limited expected lifetime, the at least one first portion of the machine readable data is readable by an optical data read system or a magnetic data read system.
87. The memory device of claim 86, wherein following the limited expected lifetime, the at least one first portion of the machine readable data is readable by an optical data read system operating at a reduced scan speed relative to a general purpose optical data read system or an optical data read system performing signal averaging on the data signal.
88. The memory device of claim 86, wherein following the limited expected lifetime, the at least one first portion of the machine readable data is readable by a magnetic data read system operating at a reduced scan speed relative to a general purpose magnetic data read system or a magnetic data read system performing signal averaging on the data signal.
89. The memory device of claim 54, wherein the decryption key is a private key or a public key.
90. The memory device of claim 53, wherein one or more copies of the read-support information are stored on the memory device in a form retrievable from the at least one first portion through the use of special purpose software or special purpose hardware.
91. The memory device of claim 90, wherein the special purpose software includes a function, a HASH function, a table lookup function, or a decryption algorithm.
92. The data storage device of claim 69, wherein data signals within the first signal range are characterized by a first signal-to-noise ratio or first bit data error rate and data signals within the second signal range are characterized by a second signal-to-noise ratio or second bit data error rate.
93. The data storage device of claim 69, including a data storage medium capable of producing a data signal in at least one of an optical data read device or a magnetic data read device.