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In this paper, a highly efficient isolated resonant converter with a novel modulation method is proposed for delivering power from photovoltaic (PV) modules to the dc microgrid. The proposed modulation method allows the converter to boost low input voltages and regulate a wide input voltage range. The converter design is based on a series resonant converter (SRC) that operates at the resonant frequency to achieve highest efficiency under nominal input voltage condition. Under shadowed or low irradiance conditions of PV panels, the converter will operate with the proposed “double-pulse duty cycle” modulation method to step up the voltage for the dc microgrid connection. With the proposed modulation method, the output switches serve for both synchronous rectification and voltage boost function. This method enables a higher voltage boost ratio than the SRC without adding additional switches while operating at the resonant frequency. A 300-W hardware prototype with gallium-nitride devices is built to verify the performance of the proposed converter and modulation method. The converter achieved a peak efficiency of 98.9% and a California Energy Commission weighted efficiency of 98.7% under nominal input voltage condition. [ABSTRACT FROM AUTHOR]

Brown v. USA Taekwondo grapples with the problems that have dogged California law governing the determination of duty in negligence for more than fifty years now. The great California duty decisions of the late 1960s—Rowland v. Christian and Dillon v. Legg—were the bookends to an age of American tort law inaugurated by MacPherson v. Buick and Palsgraf v. Long Island Railroad. MacPherson and Palsgraf altered both the internal structure of negligence law and tort law's relation to contract and property by making reasonable foreseeability of harm the master principle of responsibility in tort. Rowland and Dillon brought the age of reasonable foreseeability to a close. As their implications unfolded over time, we learned that making reasonable foreseeability of harm the fundamental test for both the existence of obligation and the extent of liability imposes more responsibility than we can bear. Reaching the limits of reasonable foreseeability as the master principle of duty doctrine left courts hard-pressed to say when fundamental responsibilities of care should be expanded and when they should be contracted. Ever since, California courts have been muddling their way through duty cases. They have been uncertain both about when an actor bears some responsibility for reducing a risk or mitigating a harm and about how they should go about making such determinations. USA Taekwondo's efforts to recast Rowland's laundry list of relevant factors as a two-step test shows us how we might begin to bring our own age of confusion to a close. [ABSTRACT FROM AUTHOR]