Phase transition of polycarbonate in blends with liquid crystal

Phase transition temperatures of polycarbonate film consisting of micron-sized liquid crystalline droplets were investigated using differential scanning calorimetry (DSC) and thermo-optical analysis (TOA) methods. Both a decrease in (T _g ) and (T _m ) of the polycarbonate with an increase of liquid crystal (LC) content in the sample were observed. The decrease ofT _g is related to the plastifying effect of a low molecular weight LC substance remaining soluble in the polycarbonate matrix. A fraction of the liquid crystal contained in the droplets was estimated on the basis of theT _g decrease.     

On-line testing of gas chromatographic columns with a programmable computing integrator

Summary A program is described which calculates the number of effective plates and the coating efficiency over the entire range of a test chromatogram. The peak widths at half height are derived by assuming a Gaussian peak shape. The interpolated peak width at k=4 is used for computing a standardized number of effective plates. Plate height, column permeability, overall performance and a novel parameter called sampling efficiency are calculated from 5 other figures — i. e. carrier gas code, pressure drop, column length, column temperature and particle size.Dedicated to Dr. Leslie S. Ettre for his 60th birthday.     

Functional electronics with discrete integrators based on superionic conductors

The possibilities for developing devices on the basis of superionic conductors for measuring and providing advance electric energy consumption and determining the integral index of luminous energy are considered. It is experimentally shown that the consumed charge and the illumination intensity in a certain time interval can be measured without feeding power to the devices. The measuring transducers are easy to design and realize. The reliability and reproducibility of results are supported.     

Rigid-body dynamics in the isothermal-isobaric ensemble: a test on the accuracy and computational efficiency

We have developed a time-reversible rigid-body (rRB) molecular dynamics algorithm in the isothermal-isobaric (NPT) ensemble. The algorithm is an extension of rigid-body dynamics [Matubayasi and Nakahara, J Chem Phys 1999, 110, 3291] to the NPT ensemble on the basis of non-Hamiltonian statistical mechanics [Martyna, G. J. et al., J Chem Phys 1994, 101, 4177]. A series of MD simulations of water as well as fully hydrated lipid bilayer systems have been undertaken to investigate the accuracy and efficiency of the algorithm. The rRB algorithm was shown to be superior to the state-of-the-art constraint-dynamics algorithm SHAKE/RATTLE/ROLL, with respect to computational efficiency. However, it was revealed that both algorithms produced accurate trajectories of molecules in the NPT as well as NVT ensembles, as long as a reasonably short time step was used. A couple of multiple time-step (MTS) integration schemes were also examined. The advantage of the rRB algorithm for computational efficiency increased when the MD simulation was carried out using MTS on parallel processing computer systems; total computer time for MTS-MD of a lipid bilayer using 64 processors was reduced by about 40% using rRB instead of SHAKE/RATTLE/ROLL.     

Rules for selecting the parameters of Oustaloup recursive approximation for the simulation of linear feedback systems containing PID controller

Oustaloup recursive approximation (ORA) is widely used to find a rational integer-order approximation for fractional-order integrators and differentiators of the form s^v, v ∈ (−1, 1). In this method the lower bound, the upper bound and the order of approximation should be determined beforehand, which is currently performed by trial and error and may be inefficient in some cases. The aim of this paper is to provide efficient rules for determining the suitable value of these parameters when a fractional-order PID controller is used in a stable linear feedback system. Two numerical examples are also presented to confirm the effectiveness of the proposed formulas.     

A low‐complexity single‐carrier frequency‐division multiple access transmitter

A framework for a computationally efficient single‐carrier frequency‐division multiple access (SC‐FDMA) transmitter is proposed in this paper. Compared with a wide system bandwidth, the uplink allocation for each user is supposed to be relatively small because of multiple user access, which makes each user's signal vector to be sparse. When the localized subcarrier allocation is used for SC‐FDMA, the inverse fast fourier transform can take advantage of the sparse user input vector to reduce its complexity. The analytical and simulation results show that the proposed framework can provide a significant complexity reduction compared with the conventional SC‐FDMA transmitter. Copyright © 2011 John Wiley & Sons, Ltd.     

Photonic crystal fibers for supercontinuum generation

Photonic crystal fibers (PCFs) present a wavelength-scale periodic microstructure along their length.Their core and two-dimensional photonic crystal might be based on varied geometries and materials,al...     

采用 DWA技术的多位Σ-Δ调制器的设计

设计一个内部采用2位量化器的二阶单环Σ‐Δ调制器．为解决反馈回路中多位DAC元件失配导致的信号谐波失真问题,该调制器采用了数据加权平均（Data Weighted Averaging ,DWA ）技术来提高多位DAC的线性度．Σ‐Δ调制器信号带宽为50 kHz ,过采样率（OSR）为64,采用MXIC公司的0．35μm混合信号CMOS工艺实现,工作电压为12 V ．后仿真结果显示,在电容随机失配5％的情况下,该调制器可以达到55．8 dB的信噪比（SNR）和60.4 dB的无杂散动态范围（SFDR）．打开DWA电路比关闭DWA电路的情况下,SNR和SFDR分别提高8 dB和13 dB ．整个调制器功耗为48 mW ,面积仅为0.6mm2．     

Synthesis,experimental and in silico studies of N‐fluorenylmethoxycarbonyl‐O‐tert‐butyl‐N‐methyltyrosine,coupled with CSD data: a survey of interactions in the crystal structures of Fmoc–amino acids

Recently, fluorenylmethoxycarbonyl (Fmoc) amino acids (e.g. Fmoc–tyrosine or Fmoc–phenylalanine) have attracted growing interest in biomedical research and industry, with special emphasis directed towards the design and development of novel effective hydrogelators, biomaterials or therapeutics. With this in mind, a systematic knowledge of the structural and supramolecular features in recognition of those properties is essential. This work is the first comprehensive summary of noncovalent interactions combined with a library of supramolecular synthon patterns in all crystal structures of amino acids with the Fmoc moiety reported so far. Moreover, a new Fmoc‐protected amino acid, namely, 2‐{[(9H‐fluoren‐9‐ylmethoxy)carbonyl](methyl)amino}‐3‐{4‐[(2‐hydroxypropan‐2‐yl)oxy]phenyl}propanoic acid or N‐fluorenylmethoxycarbonyl‐O‐tert‐butyl‐N‐methyltyrosine, Fmoc‐N‐Me‐Tyr(t‐Bu)‐OH, C₂₉H₃₁NO₅, was successfully synthesized and the structure of its unsolvated form was determined by single‐crystal X‐ray diffraction. The structural, conformational and energy landscape was investigated in detail by combined experimental and in silico approaches, and further compared to N‐Fmoc‐phenylalanine [Draper et al. (2015). CrystEngComm, 42 , 8047–8057]. Geometries were optimized by the density functional theory (DFT) method either in vacuo or in solutio. The polarizable conductor calculation model was exploited for the evaluation of the hydration effect. Hirshfeld surface analysis revealed that H…H, C…H/H…C and O…H/H…O interactions constitute the major contributions to the total Hirshfeld surface area in all the investigated systems. The molecular electrostatic potentials mapped over the surfaces identified the electrostatic complementarities in the crystal packing. The prediction of weak hydrogen‐bonded patterns via Full Interaction Maps was computed. Supramolecular motifs formed via C—H…O, C—H…π, (fluorenyl)C—H…Cl(I), C—Br…π(fluorenyl) and C—I…π(fluorenyl) interactions are observed. Basic synthons, in combination with the Long‐Range Synthon Aufbau Modules, further supported by energy‐framework calculations, are discussed. Furthermore, the relevance of Fmoc‐based supramolecular hydrogen‐bonding patterns in biocomplexes are emphasized, for the first time.     

基于CIC的数字正交锁相放大器的甲烷检测实验研究

针对甲烷在大气中背景气体成分复杂、检测难度大、稳定性差等问题,本文基于可调谐二极管激光吸收光谱技术和波长调制光谱技术,将积分梳状滤波器与有限脉冲响应滤波器相结合应用于数字正交锁相放大器,开展大气中甲烷气体的痕量检测实验研究.实验表明,与传统的数字正交锁相放大器相比较,改进的数字正交锁相放大器提取的二次谐波信号的信噪比从...