Lipase‐catalyzed dynamic kinetic resolution of (R,S)‐fenoprofen thioester in isooctane

A lipase‐catalyzed enantioselective hydrolysis process under in situ racemization of the remaining (R)‐thioetser substrate with trioctylamine as the catalyst was developed for the production of (S)‐fenoprofen from (R,S)‐fenoprofen 2,2,2‐trifluoroethyl thioester in isooctane. Detailed investigations of trioctylamine concentration on the enzyme activation and the kinetic behavior of the thioester in racemization and enzymatic reactions were conducted, in which good agreement between the experimental data and theoretical results was observed. © 2002 Society of Chemical Industry     

一种基于fiat-shamir方法的信息交换协议

本文对无签名的fiat-shamir信息认证协议进行了研究,针对其财政的缺陷进行了分析,提出了一种改进的fiat-shamir协议。通过引入hash函数,改进协议的认证与信息的摘要内容相关联,避免了原有协议的缺陷。经分析新协议安全可靠。     

New initial position detection technique for three-phase brushless DC motor without position and current sensors

This paper presents a new detection technique of initial position for a three-phase brushless DC motor which does not require any current and position sensors, and thereby significantly reduces the cost. The fundamental principle of the technique is to determine the initial position of the permanent magnet by the time periods of discharge of stator windings, which are excited before discharge. As compared to previous approaches, the presented technique does not cause any rotation during detection, and it is therefore very promising for particular kinds of applications, which do not allow the motor to rotate potentially in the wrong direction during initial position detection, e.g., electrical vehicles. As compared to earlier techniques, the presented technique dramatically simplifies the detection procedures and cost. Experimental results derived from a field-programmable gate-array-based control system are presented to demonstrate the feasibility of the presented technique.     

Measurement of binocular disparity in polarized based stereoscopic display by using digital camera

This work presents an image displacement measurement by using a box pattern and the edge spread function analysis in the polarized based stereoscopic displays. The measurement determines to identify three factors (i.e., box size, image displacement, and spatial frequency response (SFR)) from the box patterns. The polarized based stereoscopic displays might sacrifice pixels for producing 3D images, which might produce errors in the image displacement and then affect the depth perception indirectly. Based on the measurement, the errors can be quantified by using the three factors. Owing to the light leakage distorting the edge spread function to obtain an inferior SFR, exactly how light leakage affects the edge spread function can be resolved on the basis of the SFR results, especially at a frequency (1/display pixel) of 1.9 in the case of the horizontal displacement. Light leakage also induces the error of the box height in even and odd intervals of the vertical displacements more than 2 pixels and 0.5 pixels, respectively. The image displacement measurement provides a simple and comprehensive means of evaluating the optical characteristics, disparity, and sharpness of the stereoscopic displays, via the three factors.     

Low-threshold InGaAlAs/lnP vertical-cavity surface-emitting laserdiodes for 1.8 μm wavelength range

The buried tunnel junction (BTJ) technique has successfully been used to realise the first electrically pumped 1.83 μm vertical-cavity surface-emitting lasers. Excellent CW performance with submilliamp threshold currents, differential quantum efficiencies up to 26% and single-mode operation has been achieved     

Long-wavelength monolithic VCSEL arrays with high optical output power

Two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays at 1.55 /spl mu/m wavelength with parallel operation of single- or multimode devices are presented. 3/spl times/3 VCSEL arrays show maximum output powers beyond 30 mW and conversion efficiencies as high as 22%.     

Submilliamp long-wavelength InP-based vertical-cavitysurface-emitting laser with stable linear polarisation

A 1.5 μm vertical-cavity surface-emitting laser operating with high efficiency under continuous wave conditions at room temperature is demonstrated with threshold current and voltage below 1 mA and 1 V, respectively. The singlemode emission spectrum exhibits stable linear polarisation with a sidemode suppression ratio of 30 dB     

Micro-mechanically tunable long wavelength VCSEL with buried tunnel junction

A novel two-chip concept for an electrically pumped and micro-electro-mechanically tunable vertical-cavity surface-emitting laser, with an emission wavelength in the 1.5 /spl mu/m range, is presented. Continuous tuning over 30 nm in singlemode operation has been shown.     

Lipase‐catalyzed dynamic hydrolytic resolution of (R,S)‐2,2,2‐trifluoroethyl α‐chlorophenyl acetate in water‐saturated isooctane

The hydrolytic resolution of (R,S)‐2,2,2‐trifluoroethyl α‐chlorophenylacetate in water‐saturated isooctane containing Lipase MY(I) at 35 °C is selected as the best reaction condition for producing (R)‐α‐chlorophenyl acetic acid. The kinetic constants, and hence an enantiomeric ratio of 33.6, are estimated and employed for the modeling of time‐course conversions of both substrates by considering product inhibition and enzyme deactivation effects. A successful dynamic kinetic resolution is also achieved, giving the desired (R)‐α‐chlorophenylacetic acid of 93.0% yield and ee_P = 89.5% when 80 mmol dm^?3 trioctylamine acting as the racemization catalyst and enzyme activator is initially added. Copyright © 2006 Society of Chemical Industry     

Properties of novel polyimides containing bismaleimide and cyclic phosphine oxide

New polyimide polymers with phosphorus in the main chain were obtained from synthesized bismaleimide (EPBMI) cured with three types of curing agents: 4,4′-bismaleimidodiphenylmethane (BDM), 4,4′-bismaleimidodiphenyl- ether (BDE), and 4,4′-bismaleimidodiphenylsulfone (BDS). In addition, the compositions of the new polymers synthesized with these three curing agents (BDM, BDE, and BDS) were used to compare the curing reactivity and thermal properties of EPBMI to conventional bismaleimide (EBMI). The reactivities were measured by differential scanning calorimetry. Thermogravimetric analysis revealed the polymers, obtained through the curing reactions between EPBMI and the three curing agents mentioned also demonstrated excellent thermal properties and a high char yield compared to the EPBMI homopolymer.