一种基于车载MP3播放机的倒车雷达设计

提出了一种基于车载MP3播放机-SH252的倒车雷达设计方案,并介绍了系统的软硬件设计思路。系统采用EM78P153单片机作为倒车雷达数据采集部分,采用超声波探测方式测距。在倒车时,倒车雷达会自动启动,并在EM78P153的控制下,由装置于车尾保险杠上的探头发送超声波信号,当遇到障碍物时,产生回波信号,探头接收到回波信号后经控制器进行数据处理并计算出车体与障碍物之间的实际距离,然后将数据发送到车载MP3播放机上进行距离显示和语音同步提示,为驾驶员提供报警提示,提高驾驶的安全性。     

甘氨酸与水分子间相互作用的理论研究

在密度泛函(DFT)B3LYP/6_311++G(3d,3p)水平,对中性甘氨酸的最小点结构Ip和H2O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了三个氢键极小结构A、C和E,其中结构A为最稳定结构,它是H2O与甘氨酸的羧基(-COOH)形成两个氢键的结构,具有C1对称性.分别采用密度泛函理论(DFT)和MP2方法,在6-311++G(3d,3p)水平,对结构A的结构和结合能进行了比较计算,得到结合能ΔEDFT为-41.88 kJ/mol,ΔEMP2为-40.34 kJ/mol.     

基于Zigbee和GPRS的远程水质监控系统

为了满足远程水质监控的需求,设计了一种基于Zigbee和GPRS的远程水质监控系统。该系统采用CC2530模块构建无线水质数据采集网络,通过双串口单片机STC12C5A60S2实现数据汇聚和对GPRS模块的控制,利用GPRS模块接入Internet,通过TCP/IP协议将水质数据发送到数据管理中心,实现对水质的远程监控。实验结果表明,该系统组网简单,系统稳定性高,成本较低,达到了设计要求,有广阔的应用市场。     

铝-钨丝混编阵的Z-箍缩实验研究

利用铝丝和钨丝混合编制的丝阵作为Z箍缩的负载，在俄罗斯Kurchatov研究所的S300强流装置上对其Z箍缩过程进行了实验研究，并与纯铝丝阵和纯钨丝阵的实验结果进行了比较.不同材料组成的丝阵的Z箍缩x射线能谱之间有明显差异，混编丝阵的铝K壳层的x射线辐射强度比纯铝丝阵的弱，在纯钨丝阵Z箍缩中没有发现波长小于1.6nm的线辐射.混编丝阵Z箍缩的x射线发光区域比纯铝丝阵的小，但比纯钨丝阵的大,混编丝阵的x射线产额比纯铝丝阵的大，但比纯钨丝阵的略低.在驱动电流为2.5—2.8MA条件下，Z箍缩的径向收缩比为4—5，x射线辐射脉冲脉宽为25ns左右，峰值为0.3—0.5TW，总能量为10—20kJ.激光探针的阴影像显示了丝阵等离子体形成的细致过程，还表明了等离子体的边界面不够清晰，其不稳定性有明显的发展，内部有丰富的结构. 关键词： Z箍缩 混编丝阵 S300强流装置     

Study of conformations and hydrogen bonds in the configurational isomers of pyrrole‐2‐carbaldehyde oxime by 1H, 13C and 15N NMR spectroscopy combined with MP2 and DFT calculations and NBO analysis

The ¹H, ¹³C and ¹⁵N NMR studies have shown that the E and Z isomers of pyrrole‐2‐carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole‐2‐carbaldehyde oxime is stabilized by the N? H···N and N? H···O intramolecular hydrogen bonds, respectively. The N? H···N hydrogen bond in the E isomer causes the high‐frequency shift of the bridge proton signal by about 1 ppm and increase the ¹J(N, H) coupling by ～3 Hz. The bridge proton shows further deshielding and higher increase of the ¹J(N, H) coupling constant due to the strengthening of the N? H···O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by ～3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of ¹H shielding and ¹J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the N? H···N and N? H···O hydrogen bondings to be estimated. The NBO analysis suggests that the N? H···N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the N? H bond through the N? H···O hydrogen bond occurs in the Z isomer. Copyright © 2010 John Wiley & Sons, Ltd.     

Computational study of reaction pathways in the course of interaction of deactivated silylenes with buta-1,3-diene

The PESs of systems including deactivated silylenes (SiHHal, SiHal₂, Hal = F, Cl, and 2-silaimidazol-2-ylidene, SiN₂H₂C₂H₂) and buta-1,3-diene have been studied using G3(MP2)//B3LYP method. Two major reaction channels, (2 + 1) and (4 + 1) cycloaddition reactions, leading to 2-vinylsiliranes and silacyclopent-3-enes, respectively, as well as [1,3]-sigmatropic rearrangements between 2-vinylsiliranes and the corresponding silacyclopent-3-enes, have been considered in detail. Reactivity of silylenes toward buta-1,3-diene decreases in the following series: SiHHal > SiHal₂ > SiN₂H₂C₂H₂, which is reflected in increase of the reaction barriers for both cycloaddition reactions and in decrease of exothermicity of the formation of the corresponding products. The (4 + 1) cycloaddition is preferable for SiHal₂ and SiN₂H₂C₂H₂ and can compete with (2 + 1) cycloaddition for SiHHal. [1,3]-Sigmatropic rearrangement is important for isomerization of 2-vinylsiliranes to the corresponding silacyclopent-3-enes for all systems studied, except the SiCl₂ system.     

A theoretical study of topomerization of imine systems: Inversion,rotation or mixed mechanisms?

The different mechanisms, rotation, inversion, or intermediate mechanism, by which occur the topomerization of imine systems R₂ CN X have been studied by applying ab initio, B3LYP, and MP2 methods. The effect of a wide variety of substituents R and X on the isomerization pathway have been examined by computing fully optimized structures of the ground and transition states (136 isomers belonging to different imine families were studied and more than 300 transition structures were determined at various levels of theory). Energy barriers have been also obtained and it was found that the groups R and X have a strong influence on the type of mechanism involved and the activation energies. Thus, and depending on the type of substituents, transition state structures related to the following kinds of processes were found: pure inversion, intermediate mechanisms, rotation, and enhanced rotation (hyper‐rotation). In turn, the corresponding activation energies range between very low (<10 kcal/mol) and extremely high (> 70 kcal/mol) values. A simple index that allows us to quantify the percentage of inversion or rotation mechanism is proposed. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Rapid and accurate assessment of GPCR–ligand interactions Using the fragment molecular orbital‐based density‐functional tight‐binding method

The reliable and precise evaluation of receptor–ligand interactions and pair‐interaction energy is an essential element of rational drug design. While quantum mechanical (QM) methods have been a promising means by which to achieve this, traditional QM is not applicable for large biological systems due to its high computational cost. Here, the fragment molecular orbital (FMO) method has been used to accelerate QM calculations, and by combining FMO with the density‐functional tight‐binding (DFTB) method we are able to decrease computational cost 1000 times, achieving results in seconds, instead of hours. We have applied FMO‐DFTB to three different GPCR–ligand systems. Our results correlate well with site directed mutagenesis data and findings presented in the published literature, demonstrating that FMO‐DFTB is a rapid and accurate means of GPCR–ligand interactions. © 2017 Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.     

Theoretical study of the structural,spectroscopic and energetic properties of difluoro(germylthio)phosphine and difluoro(germylseleno)phosphine in the gas phase

Theoretical methods have been employed to investigate the structural, spectroscopic and energetic properties of difluoro(germylthio)phosphine in the C_s symmetry in the gas phase. The levels of theory used are MP2 and DFT/B3LYP and the basis set used for all atoms is 6-311G(d,p). The computed structural parameters, namely, bond lengths and bond angles and spectroscopic parameters, namely, infrared frequencies, Raman activities and NMR chemical shifts have been compared with experimental data reported in literature. The structure of this compound has been analysed using natural bond orbital approach. Both the ab initio methods perform satisfactorily when the predicted and experimental parameters are compared. We have extended this study, using the same methods and basis set, to the selenium analogue, namely, difluoro(germylseleno)phosphine for which literature is elusive. The MP2/6-311G(d,p) geometrical parameters for difluoro(germylseleno)phosphine are: r(P–Se) = 2.270, r(Ge-Se) = 2.386, r(P–F) = 1.604, r(Ge–H) = 1.530 Å, ∠(Ge–Se–P) = 91.4, ∠(F–P–F) = 96.7, ∠(Se–P–F) = 99.9 and ∠(Se–Ge–H) = 109.5°. Apart from these, we have also studied the energetic parameters for their synthesis. The results indicate that formation of the sulphur-containing compound is favoured thermodynamically.     

A survey of wave function effects on theoretical calculation of gas phase F NMR chemical shifts using factorial design

The wave functions for calculating gas phase ¹⁹F chemical shifts were optimally selected using the factorial design as a multivariate technique. The effects of electron correlation, triple-ξ valance shell, diffuse function, and polarization function on calculated ¹⁹F chemical shifts were discussed. It is shown that of the four factors, electron correlation and the polarization functions affect the results significantly. B3LYP/6-31 + G(df,p) wave functions have been proposed as the best and the most efficient level of theory for calculating ¹⁹F chemical shifts. An additional series of fluoro compounds were used as a test set and their predicted ¹⁹F chemical shifts values confirmed the validity of the approaches.