K. Joel Berry

Stretch-associated injury in cervical spondylotic myelopathy: new concept and review.

THE SIMPLE PATHOANATOMIC concept that a narrowed spinal canal causes compression of the enclosed cord, leading to local tissue ischemia, injury, and neurological impairment, fails to explain the entire spectrum of clinical findings observed in cervical spondylotic myelopathy. A growing body of evidence indicates that spondylotic narrowing of the spinal canal and abnormal or excessive motion of the cervical spine results in increased strain and shear forces that cause localized axonal injury within the spinal cord.During normal motion, significant axial strains occur in the cervical spinal cord. At the cervicothoracic junction, where flexion is greatest, the spinal cord stretches 24% of its length. This causes local spinal cord strain. In the presence of pathological displacement, strain can exceed the material properties of the spinal cord and cause transient or permanent neurological injury.Stretch-associated injury is now widely accepted as the principal etiological factor of myelopathy in experimental models of neural injury, tethered cord syndrome, and diffuse axonal injury. Axonal injury reproducibly occurs at sites of maximal tensile loading in a well-defined sequence of intracellular events: myelin stretch injury, altered axolemmal permeability, calcium entry, cytoskeletal collapse, compaction of neurofilaments and microtubules, disruption of anterograde axonal transport, accumulation of organelles, axon retraction bulb formation, and secondary axotomy. Stretch and shear forces generated within the spinal cord seem to be important factors in the pathogenesis of cervical spondylotic myelopathy.

Experimental Performance Evaluation of a Rechargeable Lithium-Air Battery Operating at Room Temperature

The effects of electrolyte, catalyst, and the process of preparation of the air-cathode on the performance of Li-air batteries were investigated. An ether based electrolyte was the best choice for Ketjen Black carbon based air cathodes and delivered high specific capacity (1050 mAh/gC) under dry air with cobalt oxide as catalyst. The introduction of an ultrasonication step in the air-cathode fabrication process improved the air-cathode microstructure. BET analyses revealed that the cathode has a higher surface area and mesopore volume when ultrasonication was used compared to those for the cathode fabricated without the ultrasonication step. With the optimized electrolyte and air-cathode, a high capacity of 2620 mAh/gC was obtained for Li-air batteries tested in dry air with a 0.1 mA/cm2 current density.Copyright

21st Century Renewable Fuels, Energy, and Materials

The objectives of this project were multi-fold: (i) conduct fundamental studies to develop a new class of high temperature PEM fuel cell material capable of conducting protons at elevated temperature (180°C), (ii) develop and fabricate a 5k We novel catalytic flat plate steam reforming process for extracting hydrogen from multi-fuels and integrate with high-temperature PEM fuel cell systems, (iii) research and develop improved oxygen permeable membranes for high power density lithium air battery with simple control systems and reduced cost, (iv) research on high energy yield agriculture bio-crop (Miscanthus) suitable for reformate fuel/alternative fuel with minimum impact on human food chain and develop a cost analysis and production model, and (v) develop math and science alternative energy educator program to include bio-energy and power.

Performance of a 1kW (16-Cell) High Temperature PEM Fuel Cell Stack Prototype: An Experimental Evaluation

In this study, we designed and built a 1 kW (16-cells) stack prototype of high temperature PEM fuel cell with 440cm2 active area of each individual cell. The purpose of this research is to experimentally study the performance of our newly built high temperature PEM fuel cell stack at different operating conditions and to judge the performance for possible commercialization aspects. The performance of the fuel cell stack in terms of current-voltage characteristics has been experimentally measured for each of the cells in the 16-cell stack (1kW). Experimental data of this type is required to develop and validate the fuel cell models to understand and optimize the operation of the stack and further stack design improvements. The fuel cell stack is fed with industry-grade (99.999%) pure hydrogen. The fuel cell stack was extensively tested at 145°C and the current-voltage characteristics were determined by varying the current loads. The results will be very helpful to understand the cell performance in terms of current-voltage characteristics of 1kW PEM fuel cell stack.Copyright

Experimental Evaluation of a Control Strategy for Real-Time Optimization of Low Temperature PEM Fuel Cell Stack

A robust control strategy which ensures optimum performance is crucial to proton exchange membrane (PEM) fuel cell development. In a PEM fuel cell stack, the primary control variables are the reactant’s stochiometric ratio, membrane’s relative humidity and operating pressure of the anode and cathode. In this study, a 5 kW (25-cell) PEM fuel cell stack is experimentally evaluated under various operating conditions. Using the extensive experimental data of voltage-current characteristics, a feed forward control strategy based on a 3D surface map of cathode pressure, current density and membrane humidity at different operating voltages is developed. The effectiveness of the feed forward control strategy is tested on the Green-light testing facility. To reduce the dependence on predetermined system parameters, real-time optimization based on extremum seeking algorithm is proposed to control the air flow rate into the cathode of the PEM fuel cell stack. The quantitative results obtained from the experiments show good potential towards achieving effective control of PEM fuel cell stack.Copyright

Modeling of a Fuel Cell Hybrid Electric Vehicle

This paper explains the method by which a small “Neighborhood” fuel cell hybrid electric vehicle (FCHEV) was modeled using Matlab/Simulink and validated using National Instruments Data Acquisition equipment and a chassis dynamometer. The vehicle is a modified four-passenger Global Electric Motorcar (GEM), which was designed for city or neighborhood operation where maximum speed limits do not exceed 35 mph. The stock 72-Volt shunt wound GE motor is powered by six 12-Volt Trojan lead-acid batteries. The vehicle was converted to a FCHEV by integrating a Ballard Nexa™ fuel cell module and a Spectrodyne Systems DC-DC converter. These devices act as a constant current range extending supplemental power source. The goals of the creation of the model include predicting motor and battery performance while driving under transient conditions and predicting the range of the vehicle while using one or several fuel cell stacks.Copyright