NUCLEATION AND GROWTH DURING FACETING OF THE PLATINUM-COVERED W(111) SURFACE

Low energy electron microscopy (LEEM) and scanning tunneling microscopy (STM) have been used to investigate the faceting of W(111) as induced by Pt. The atomically rough W(111) surface, when fully covered with a monolayer film of Pt and annealed to temperatures higher than {approximately}750 K, experiences a significant morphological restructuring: the initially planar surface undergoes a faceting transition and forms three-sided pyramids with {l_brace}211{r_brace} faces. When Pt is dosed onto the heated surface, the transition from planar to faceted structure proceeds through the nucleation and growth of spatially separated faceted regions, as shown by LEEM. STM reveals the atomic structure of the partially faceted surface, with large planar regions, dotted by clusters of pyramids of various sizes

Development of a new vacuum-based photovoltaic/thermal collector, thermal and exergy analyses

Photovoltaic-thermal (PV/T) solar collectors convert solar radiation into electrical power and heat. A considerable amount of received solar energy can be lost to the ambient from the top surface of the PV/T module, especially in windy regions. Thus, in this study, a new vacuum based photovoltaic thermal (VPV/T) collector is designed and comparatively analyzed with the conventional PV/T collector. The new design differs from the conventional PV/T design by including vacuum layer above the silicon wafer. Besides, to enhance the heat dissipation from the silicon wafer in the VPV/T design to the thermal absorber, the thicknesses of ethylene-vinyl acetate and tedlar polyester tedlar layers underneath the silicon wafer are decreased. A comprehensive 3D conjugate thermal model is developed and validated. The comparison is conducted at steady and transient conditions. The effect of Reynolds number (Re), wind speed, glass emissivity, and vacuum pressure are investigated. And finally, the exergy analysis for both designs are compared. The results showed that the new VPV/T collector has accomplished a 26.6% increase in the thermal power without changing the electrical power gain at Re of 50 and solar irradiance of 1000Wm-2. In addition, the vacuum pressure degradation from 0.01 Pa to 10 Pa slightly decreases the gained thermal power of the new VPV/T. A further increase in the vacuum pressure from 10 Pa to 1.013×105 Pa significantly decreases the gained thermal power with a slight increase in the electrical power. Furthermore, the total predicted VPV/T and the conventional PV/T exergy efficiency are 40% and 32%, respectively

Indirect 3D-Space Vector Modulation for Matrix Converter

This paper discusses the indirect space vector modulation for four-leg matrix converter. Four-leg matrix converter has been proven to be a reliable, cost-effective, and compact power electronic interface to supply unbalanced or nonlinear loads. However, the added fourth leg has shifted the inverter side modulation from simple two-dimension SVM into complex three-dimension. This paper employs a new technique to implement indirect 3D SVM in digital controllers with further simplification in the modulation process. Moreover, Simulink simulation using repetitive controller has been performed to regulate the output voltage for 400 Hz Power supplies

Comparison between the efficacy of underwater treadmill and over-ground treadmill training program on knee joint during gait cycle of stroke patients

Introduction: Gait disorder is a common clinical problem for stroke survivors that impacts performance of activities of daily living.&nbsp;Objective: This study was conducted to compare between the efficacy of underwater Treadmill Training Program (TTP) and over-ground (TTP) in improving knee joint Range of Motion (ROM) during the gait cycle of stroke patients.&nbsp;Study design: Randomized control trial.&nbsp;Methods: Forty male patients suffering from post-stroke gait deficits were assigned randomly into two equal groups: study group (A): Received underwater treadmill training program. Control group (B) received over-ground treadmill training program. Patients of both groups were assessed for knee Range of Motion (ROM) during gait cycle using slow motion video and goniometer iPad application. Assessment was done before and after four weeks of treatment for both groups.&nbsp;Results: The comparison between groups post treatment showed a significant increase in knee flexion ROM in initial contact and pre-swing phase and increase in knee extension ROM in mid stance phase of the study group (A) compared with that of control group (B).&nbsp;Conclusion: Under water TTP is more effective than over-ground TTP on improving knee joint ROM during the gait cycle of stroke patients.</p