Author: claimsbot

1. A DCAC power converter for transforming a DC input source to an AC output source, comprising: a transformer having a primary and a secondary windings; a switch network having a first switch electrically connected between said DC input source and said primary winding; a two-way current-transmitting module electrically connected between said secondary winding and said AC output source; and a controllable conducting circuit electrically connected to said secondary winding, wherein said controllable conducting circuit is conducting to cause a short circuit to the secondary winding when said two-way current-transmitting module transmits an electrical energy from said primary winding to said secondary winding and a current flowing through said primary winding is decreasing so as to lower down a voltage stress of said first switch of said switch network.
2. The converter according to claim 1, wherein said switch network is one of a flyback circuit and a dual flyback circuit.
3. The converter according to claim 2, wherein said secondary winding of said transformer comprises a first winding having a first and a second terminals and a second winding having a first and a second terminals, said two-way current-transmitting module comprises a second switch, a third switch, a fourth switch, a fifth switch, a capacitor and a resistor, said second switch is electrically connected to said third switch in series at a first node, said second switch is electrically connected to said first terminal of said first winding, said third switch is electrically connected to said first terminal of said second winding, said fourth switch is electrically connected to said fifth switch in series at a second node, said fourth switch is electrically connected to said second terminal of said second winding, said fifth switch is electrically connected to said second terminal of said first winding, said capacitor is electrically connected to said resistor in parallel, both said capacitor and said resistor are electrically connected to said first node and said second node, and said controllable conducting circuit is electrically connected to said first and said second terminals of said first winding in parallel.
4. The converter according to claim 3, wherein said transformer has a discharging time with a fixed value and a dynamic response of said AC output source versus said DC input source is a direct proportion of a conducting time of said first switch.
5. The converter according to claim 4, wherein said controllable conducting circuit comprises a monostable circuit having a diode and a sixth switch electrically connected to each other in series, said diode and said sixth switch are conducting simultaneously to make said two-way current-transmitting module short-circuit so as to decrease said voltage stress of said first switch when said voltage stress of said first switch equals to a voltage of said DC input source.
6. The converter according to claim 5, wherein each of said first to said sixth switches is one of a MOSFET and an IGBT.
7. The converter according to claim 1, wherein said switch network is one selected from a group consisting of a full-bridge circuit, a half-bridge circuit and a push-pull circuit.
8. The converter according to claim 7, wherein said secondary winding of said transformer comprises a winding having a first and a second terminals, said two-way current-transmitting module comprises a second switch, a third switch, a capacitor and a resistor, said capacitor is electrically connected to said resistor in parallel, both said capacitor and said resistor are electrically connected between said second switch and said third switch in series, said second and said third switches are electrically connected to said first and said second terminals of said winding respectively, and said controllable conducting circuit is electrically connected to said first and said second terminals of said winding in parallel.
9. The converter according to claim 8, wherein said controllable conducting circuit comprises two monostable circuits electrically connected to each other in reverse parallel, and each of said two monostable circuits comprises a diode and a fourth switch electrically connected to each other in series.
10. The converter according to claim 8, wherein said controllable conducting circuit comprises a fourth switch and a fifth switch electrically connected to each other in reverse series.
11. The converter according to claim 1, wherein said controllable conducting circuit is electrically connected between said secondary winding and said two-way current-transmitting module.
12. The converter according to claim 1, wherein said AC output source operates at a line-frequency.
13. A method for controlling a DCAC power converter, wherein said converter comprises a transformer having a primary and a secondary windings, a switch network having a first switch electrically connected between a DC input source and said primary winding, a two-way current-transmitting module electrically connected between said secondary winding and an AC output source and a controllable conducting circuit electrically connected to said secondary winding, comprising the steps of: (a) transmitting an electrical energy from said primary winding to said secondary winding by said two-way current-transmitting module such that said controllable conducting circuit is conducting to cause a short circuit to the secondary winding when a current flowing through said primary winding is decreasing so as to lower down a voltage stress of said first switch of said switch network; and (b) fixing a discharging time of said transformer such that a dynamic response of said AC output source versus said DC input source is a direct proportion of a conducting time of said first switch.
14. The method according to claim 13, wherein said controllable conducting circuit comprises a monostable circuit having a diode and a second switch electrically connected to each other in series.
15. The method according to claim 14, wherein said step (a) further comprises a step of: (a1) transmitting said electrical energy from said primary winding to said secondary winding by said two-way current-transmitting module such that said diode and said second switch are conducting simultaneously to make said two-way current-transmitting module short-circuit so as to decrease said voltage stress of said first switch when said voltage stress of said first switch equals to a voltage of said DC input source.
16. The method according to claim 13, wherein said controllable conducting circuit comprises two monostable circuits electrically connected to each other in reverse parallel, and each of said two monostable circuits comprises a diode and a second switch electrically connected to each other in series.
17. The method according to claim 16, wherein said step (a) further comprises a step of: (a1) transmitting said electrical energy from said primary winding to said secondary winding by said two-way current-transmitting module such that one of said two monostable circuits is conducting to make said two-way current-transmitting module short-circuit so as to decrease said voltage stress of said first switch when said voltage stress of said first switch equals to a voltage of said DC input source.
18. The method according to claim 13, wherein said controllable conducting circuit comprises a second switch and a third switch electrically connected to each other in reverse series.
19. The method according to claim 18, wherein said step (a) further comprises a step of: (a1) transmitting said electrical energy from said primary winding to said secondary winding by said two-way current-transmitting module such that one of said second and said third switches is conducting to make said two-way current-transmitting module short-circuit so as to decrease said voltage stress of said first switch when said voltage stress of said first switch equals to a voltage of said DC input source.

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 cover for a computing device, the cover comprising:
a base segment to support the computing device;
a first panel that is pivotably coupled to a top end of the base segment to at least partially overlay a portion of a front surface of the computing device; and
a pair of side segments, each side segment pair extending outward from a corresponding lateral side of the base segment and being pivotably coupled to extend into a raised position that extends vertically from the base segment relative to a perpendicular axis to the base segment, each side segment of the pair being dimensioned to occlude a display of the computing device from a corresponding peripheral direction.
2. The cover of claim 1, wherein the first panel is extendable into a raised position that extends vertically from the base segment along the perpendicular axis, and wherein at least one of the first panel and each of the side segments of the pair are formed from magnetic material to magnetically couple when each of the first panel and the pair of side segments are in the raised position so that the first panel and the pair of side segments form a three-sided enclosure about the base segment.
3. The cover of claim 2, wherein at least the first panel is magnetized.
4. The cover of claim 3, wherein the first panel includes one or more side members that are magnetized.
5. The cover of claim 4, wherein the first panel is formed from flexible material that overlays and extends between the one or more side members.
6. The cover of claim 1, further comprising a second panel that is pivotably coupled to the first panel, wherein each of the first panel and the second panel is magnetized.
7. The cover of claim 1, wherein each of the first panel and second panel include one or more side members that are magnetized, and wherein each of the first panel and second panel is formed from flexible material that overlays and extends between the one or more side members.
8. The cover of claim 6, wherein a polarity of the first panel is different than a polarity of the second panel.
9. The cover of claim 6, further comprising one or more additional panels, each of the one or more additional panels being pivotably coupled to another one of the additional panels.
10. The cover of claim 9, wherein each of the one or more additional panels is magnetized.
11. The cover of claim 10, wherein a polarity of the first panel is opposite a polarity of the second panel, and wherein the polarity of the second panel is opposite to a polarity of an adjacent panel of the one or more adjacent panels.
12. The cover of claim 1, wherein each of the side segments are triangular.
13. The cover of claim 1, wherein a dimension of each of the side segments is greatest when extended from the base segment at closest proximity to the first panel.
14. A cover for a computing device, the cover comprising:
a base segment to support the computing device; and
multiple panels that extend from a bottom end of the base segment, each panel being pivotably coupled to at least one other panel of the multiple panels in order to pivot between at least an extended position and a raised position; and
wherein at least some of the multiple panels each include one or more magnetized perimeter edges that support a position of the panel relative to another one of the multiple panels.
15. The cover of claim 14, wherein a polarity of the one or more magnetized perimeter edges of individual panels alternates as between adjacent pairs of panels.
16. The cover of claim 14, wherein each of the multiple panels includes one or more side members that are magnetized, and wherein each of the multiple panels is formed from flexible material that overlays and extends between the one or more side members.
17. The cover of claim 14, wherein the multiple panels are pivotable so that the multiple panels collectively overlay a front surface of the computing device.
18. The cover of claim 14, further comprising:
a pair of side segments, each side segment pair extending outward from a corresponding lateral side of the base segment and being pivotably coupled to extend into a raised position that extends vertically from the base segment relative to a perpendicular axis to the base segment, each side segment of the pair being dimensioned to occlude a display of the computing device from a corresponding peripheral direction.
19. The cover of claim 18, wherein the pair of side segments include material that is magnetically attracted to a most proximate panel of the multiple panels.
20. The cover of claim 19, wherein the pair of side segments are triangular and pivotably coupled to the base segment.

1. A fuel cell system comprising:
a fuel cell assembly comprising a plurality of individual fuel cells, each fuel cell having an electrolyte medium, a cathode and an anode; and,
at least one centrifugal blower system for providing a flow of gaseous medium to the fuel cell assembly, the at least one centrifugal blower system comprising:
a series of blower units, each blower unit in the series comprising a casing having an axial inlet and a radial outlet, an impeller disposed within the casing for drawing a gaseous medium at a first pressure in the axial inlet and expelling gaseous medium at a second higher pressure through the radial outlet, and a motor for driving the impeller; and,
a duct connecting the radial outlet of at least one blower unit in the series of blower units with the axial inlet of at least one successive blower unit in the series of blower units.
2. The fuel cell system of claim 1 wherein the fuel cell assembly is a solid oxide fuel cell assembly.
3. The fuel cell system of claim 2 wherein the solid oxide fuel cell assembly comprises tubular solid oxide fuel cells.
4. The fuel cell system of claim 3 comprising at least two centrifugal blower systems, a first centrifugal blower system for providing a flow of gaseous medium to the anodes of the solid oxide fuel cell assembly and a second centrifugal blower system for providing a flow of gaseous medium comprising an oxidizer gas to the cathodes of the solid oxide fuel cell assembly.
5. The fuel cell system of claim 1 wherein in the at least one centrifugal blower system further comprises:
at least one gaseous medium-directing structure selected from the group consisting of interior walls of the duct configured to be substantially parallel to the trajectory of the gaseous medium expelled from the radial outlet of a blower unit to which the duct is connected, and a gas stream housing for receiving the gas stream from the radial outlet of the last blower unit in the series of blower units, the interior walls of the gas stream housing being configured to be substantially parallel to the trajectory of the gaseous medium expelled from the radial outlet of the last blower unit.
6. The fuel cell system of claim 1 wherein in the at least one centrifugal blower system, the orientation of the radial outlet of one blower unit in the series of blower units to the axial inlet of a successive blower unit in the series of blower units is approximately 0\xb0, 90\xb0, 180\xb0 or 270\xb0.
7. The fuel cell system of claim 1 wherein in the at least one centrifugal blower system, the angle of pitch of the radial outlet of one blower unit in the series of blower units to the axial inlet of a successive blower unit in the series of blower units is approximately 0\xb0, 30\xb0, 60\xb0 or 90\xb0.
8. The fuel cell system of claim 6 wherein in the at least one centrifugal blower system, the angle of pitch of the radial outlet of one blower unit in the series of blower units to the axial inlet of a successive blower unit in the series of blower units is approximately 0\xb0, 30\xb0, 60\xb0 or 90\xb0.
10. The fuel cell system of claim 1 wherein in the at least one centrifugal blower system, at least one blower unit in the series of blower units has greater gas pressure and gas flow capability than another blower unit in the at least one centrifugal blower system.
11. The fuel cell system of claim 1 wherein in the at least one centrifugal blower system, at least one blower unit in the series of blower units is separated from at least one other blower in the at least one centrifugal blower system.
12. The fuel cell system of claim 1 wherein the at least one centrifugal blower system comprises a microprocessor configured to control independently the operation of the blower units in the series of blower units.
13. The fuel cell system of claim 5 wherein the interior walls of the gas stream housing are at an angle \u03b1 of from 12\xb0 to 20\xb0 relative to the radial outlets of the blower units in the series of blower units.
14. The fuel cell system of claim 13 wherein the angle of pitch of the radial outlet of a blower unit in the series of blower units to the axial inlet of the successive blower unit in the series of blower units is approximately 0\xb0.
15. The fuel cell system of claim 1 comprising at least two centrifugal blower systems, a first centrifugal blower system for providing a flow of gaseous medium to the anodes of the fuel cell assembly and a second centrifugal blower system for providing a flow of gaseous medium comprising air to the cathodes of the fuel cell assembly.
16. The fuel cell system of claim 1 wherein the at least one centrifugal blower system comprises a microprocessor configured to control the operation of the series of blower units.
17. The fuel cell system of claim 12 wherein the microprocessor is configured to control independently the operation of the blower units in the series of blower units such that operation of at least one blower unit in the series of blower units of the at least one centrifugal blower system provides from 50% to 90% of the flow of gaseous medium and the operation of at least one other blower unit in the series of blower units of the at least one centrifugal blower system provides the balance of the flow of gaseous medium.
18. The fuel cell system of claim 15 comprising a microprocessor configured to control independently each blower unit in the first centrifugal blower system and the second centrifugal blower system.
19. The fuel cell system of claim 18, wherein the microprocessor is configured to control independently the first centrifugal blower system such that at least one blower unit in the first centrifugal blower system provides from 50% to 90% of the flow of gaseous medium of the first centrifugal blower system and at least one other blower unit in the first centrifugal blower system provides the balance of the flow of gaseous medium of the first centrifugal blower system, and to control the operation of the second centrifugal blower system such that at least one blower unit in the second centrifugal blower system provides from 50% to 90% of the flow of gaseous medium comprising air of the second centrifugal blower system and at least one other blower unit in the second centrifugal blower system provides the balance of the flow of gaseous medium comprising air of the second centrifugal blower system.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

We claim:

1. A method of inducing immunity to pneumonic pasteurellosis in ruminants, comprising the step of:
administering a P. haemolytica bacterium to a ruminant, wherein the P. haemolytica bacterium (a) expresses no biologically active leukotoxin, (b) expresses a form of leukotoxin molecule which is a deletion mutant of about 66 kDa which lacks amino acids 34 to 378 and which induces antibodies which specifically bind to and neutralize biologically active leukotoxin; and (c) contains no foreign DNA, whereby immunity is induced.
2. The method of claim 1 wherein the step of administering is via the oral route.
3. The method of claim 1 wherein the bacterium is top-dressed on the feed of the ruminant.
4. The method of claim 1 wherein the step of administering comprises injecting the bacterium subcutaneously.
5. The method of claim 1 wherein the step of administering comprises injecting the bacterium intradermally.
6. The method of claim 1 wherein the step of administering comprises injecting the bacterium intramuscularly.
7. The method of claim 19 wherein the step of administering is via the nose.
8. A feed for ruminants which comprises a P. haemolytica bacterium to a ruminant, wherein the P. haemolytica bacterium (a) expresses no biologically active leukotoxin, (b) expresses a form of leukotoxin molecule which is a deletion mutant of about 66 kDa which lacks amino acids 34 to 378 and which induces antibodies which specifically bind to and neutralize biologically active leukotoxin; and (c) contains no foreign DNA.
9. A vaccine for reducing morbidity in ruminants, comprising:
a P. haemolytica bacterium (a) expresses no biologically active leukotoxin, (b) expresses a form of leukotoxin molecule which is a deletion mutant of about 66 kDa which lacks amino acids 34 to 378 and which induces antibodies which specifically bind to and neutralize biologically active leukotoxin; and (c) contains no foreign DNA.