A semi-synchronous SAR ADC

A semi-synchronous clocking scheme is proposed for successive approximation register (SAR) analog-to-digital converters (ADCs). The conversion time is dynamically allocated to the comparator decision and to the DAC settling in every bit cycle. This significantly improves the conversion speed.     

Extremely-low-frequency magnetic field exposure of children at schools near high voltage transmission lines

Many epidemiological studies have investigated residential exposure to extremely-low-frequency magnetic field (ELF-MF) for children, but exposure at schools where children may stay up to 8 h every weekday was rarely considered. Between March and June 2004, we carried out a field study in Taipei City and County of northern Taiwan to explore ELF-MF exposure pattern among children at schools with high voltage transmission lines (HVTL) running through the campuses. One hundred and one children attending 14 schools with nearby HVTL (exposed group) and 123 children of 18 schools at least 100 m away from HVTL (unexposed group) were monitored for 24-hour personal ELF-MF exposure. Selected classrooms and playgrounds within the buffer regions (i.e., within 30 m of HVTL) and those away from the buffer regions were also assessed, using spot measurements, to determine the extent to which HVTL may contribute to the environmental exposure on campuses. Results show that the two groups didn't differ significantly for both mean exposure and proportion of exposure greater than 0.4 micro-Tesla (microT) estimated for 24 h. However, we noted that 17.8% of the exposed children had a personal mean exposure greater than 0.4 microT during school hours, significantly (p=0.011) higher than that (6.5%) estimated for the unexposed children. An even higher percentage (27.3%) was observed for 11 students with their classrooms intersecting the buffer regions. Playgrounds near buffer regions showed a significantly higher ELF-MF than the other areas of the exposed schools (0.70 vs 0.18 microT, p=0.043). The study demonstrates a wide range of exposures to ELF-MF among school children at campuses adjacent to HVTL. Children attending the exposed schools may have a higher chance of experiencing a mean exposure greater than 0.4 microT during school hours.     

Perspective on High-efficiency Cu(In,Ga)Se2-based Thin-film Solar Cells Fabricated by Simple,Scalable Processes

We have fabricated high-efficiency Cu(In, Ga)Se₂(CIGS)-based photovoltaic (PV) devices by four different processes. Each process may be characterized as cither sequential or concurrent deposition of the metals with or without an activity of selenium. A world-record, total-area efficiency of 17.1% has been achieved by the concurrent delivery of the metals in the presence of selenium. Gallium has been introduced into the device in such a manner as to produce homogeneous, normal profiling and double-profiling graded bandgap structures. This has resulted in an open-circuit voltage (V_oc) parameter of 680 mV and a fill factor of over 78%. A growth model has been developed allowing for simple translation of these processes to a manufacturing environment for the large-scale production of modules.     

Accelerated publication 16.4% total-area conversion efficiency thin-film polycrystalline MgF2/ZnO/CdS/Cu(In,Ga)Se2/Mo solar cell

This communication reports an MgF₂/ZnO/CdS/Cu(In,Ga)Se₂/Mo/glass polycrystalline solar cell with a confirmed total-area conversion efficiency of 16.4%. the thin-film Cu(In,Ga)Se₂ absorber was fabricated by computer-controlled physical vapor deposition (PVD) from the elemental sources. the resulting absorber has a Gal/In compositional grading that we refer to as a notch. Capacitance-voltage (C-V) measurements also reveal a graded doping profile in the region near the electronic p-n junction. the enhanced device performance is characterized by an open-circuit voltage (V_oc) of 660 mV and a particularly high fill factor (FF) of 78.7%.     

A novel efficient approach to the Synthesis of 6-Oxo Ethinylestradiol and its 3-isopropanesulfonate

Ethinylestradiol ( 1 ) was converted into the corresponding 6-oxo derivative 7 by a short and simple procedure involving acetate 10 and ketone 11 . Phase transfer catalyzed esterification of compound 7 with propane-2-sulfonyl chloride gave sulfonate 12 .     

Accelerated publication 17.1% efficient Cu(In,Ga)Se2-based thin-film solar cell

We report a world-record, total-area efficiency of 17.1% for a polycrystalline thin-film Cu(In,Ga)Se₂-based photovoltaic solar cell. the incorporation of Ga to raise the absorber bandgap has been accomplished successfully and in such a manner that an open-circuit voltage of 654 mV and a fill factor of greater than 77% have been achieved. We describe briefly the deposition process, the device structure, and the device performance characteristics.