基于单片机的超声波测距设计与研究

基于单片机的超声波测距仪。借助压电式陶瓷传感器TCT40-10F/S(1),其适用范围:家用电器和其他电子设备的遥控装置;超声测距,车辆倒车防撞报警装置。     

地形和湍流交换非均匀对边界层Ekman抽吸的影响

利用地转动量近似理论,讨论地形和湍流交换系数K存在水平不均匀的条件下,获得了边界 层顶Ekman抽吸的解析结果和动力特征.研究表明:在不考虑地形强迫情况下,湍流交换系数的水平变化对Ekman抽吸有明显的影响,而且这种影响的强弱与Rossby数大小有关.而在地形与湍流交换系数的共同作用下,地形的影响是边界层顶的垂直速度分布的主导性因素.     

浅析低压供电设计计算

根据低压供电系统的整定计算原则,分析了低压供电设计计算中遇到的问题,提出了利用新设备和新技术的优势,解决供电设计中的难题。     

Meteorological observations on Mount Everest in 2005

Mount Everest,the highest point on the Earth is often referred to as the earth's third pole as such the place is relatively inaccessible and little is known about its meteorology.In April 2005,an automatic weather station was installed at the mountain's North Col(6523 m a.s.l.).According to the observational 10-minute mean and daily records,the meteorological characteristics were analyzed. All the meteorological elements displayed obvious diurnal variations during May 1 to July 22,2005.The monthly variation of daily meteo- rological elements on Mount Everest coincided with that on Dingri,the closest routine meteorological station,with the high correlation co- efficients of 0.928,0.877,0.682,0.755,0.826 and 0.676(n=83,p<0.001)for mean temperature,minimum temperature,max- imum temperature,relative humidity,pressure and wind speed,respectively.Furthermore,the vertical mean gradient of temperature was above 0.6℃/100 m,especially for the daily maximum temperature.Most weather events on Mount Everest prominently appeared on the same day as those on Dingri,especially those from daily mean pressure,temperature and relative humidity with the cross-correlation coeffi- cients of 0.673,0.485 and 0.487(n=83,p<0.001),respectively.Some other weather events on Mount Everest lagged one-day be- hind those on Dingri.Furthermore,forecasting of the weather events on Mount Everest from pressure on Dingri was more reliable than those from the other meteorological elements.The conclusions are much important for research on meteorology and climate changes in the region.     

Scanning for sisnatures of geosraphically restricted selection based on population genomics analysis

Natural selection, as the driving force of human evolution, has direct impact on population differentiation. However, it is still unclear to what extent the genetic differentiation has been caused by natural selection. To explore this question, we performed a genome-wide scan with single nucleotide polymorphism （SNP） data from the International HapMap Project. Single locus FsTanalysis was applied to assess the frequency difference among populations in autosomes. Based on the empirical distribution of FsT, we identified 12669 SNPs correlating to population differentiation and 1853 candidate genes subjected to geographic restricted natural selection. Further interpretation of gene ontogeny revealed 121 categories of biological process with the enrichments of candidate genes. Our results suggest that natural selection may play an important role in human population differentiation. In addition, our analysis provides new clues as well as research methods for our understanding of population differentiation and natural selection.     

Linear and third-order nonlinear optical properties for the heptamethine cyanine chromophore H-aggregates thin film

The thin film of a heptamethine cyanine chromophore HC was prepared by spin-coating technique. Its surface morphology and linear optical property were characterized by atomic force microscopy (AFM) and UV-visible absorption spectroscopy. The results show that HC molecules are arranged in a well-ordered H-aggregate type. The third-order nonlinear optical properties of the spin-coating film were also measured by degenerate four-wave mixing (DFWM) measurement. Enhanced third-order nonlinear susceptibility can be attributed to molecular aggregation effects, and the corresponding mechanism was dealt with by collective electronic oscillator (CEO) approach.     

Density functional theory study on the insertion reaction mechanism of dibromocarbene with formaldehyde

The insertion reaction mechanism of CBr2 with CH3CH2O has been studied by using the B3LYP/6-311G(d) and CCSD(T)/6-311G(d) at single point. The geometries of reactions,transition state and products were completely optimized. All the transition state is verified by the vibrational analysis and the internal re-action coordinate (IRC) calculations. The results show that reaction (1) is the dominant reaction path,which proceeds via two steps: i) two reactants form an intermediate (IM1),which is an exothermal re-action of 8.62 kJ·mol?1 without energy barrier; ii) P1 is obtained via the TS1 and the H-shift,in which the energy barrier is 44.53 kJ·mol?1. The statistical thermodynamics and Eyring transition state theory with Wigner correction are used to study the thermodynamic and kinetic characters of this reaction in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature ranges from 200 to 1900 K at 1.0 atm,in which the reaction has a bigger spontaneity capability,equi-librium constant (K) and higher rate constant (k).     

Learning multivariate time series causal graphs based on conditional mutual information

Detection and clarification of cause-effect relationships among variables is an important problem in time series analysis.This paper provides a method that employs both mutual information and conditional mutual information to identify the causal structure of multivariate time series causal graphical models.A three-step procedure is developed to learn the contemporaneous and the lagged causal relationships of time series causal graphs.Contrary to conventional constraint-based algorithm, the proposed algorithm does not involve any special kinds of distribution and is nonparametric.These properties are especially appealing for inference of time series causal graphs when the prior knowledge about the data model is not available.Simulations and case analysis demonstrate the effectiveness of the method.     

一种快速高精度测频方法

介绍了用８０３１进行快速，宽频带，高精度的测频方法，分析了测频的基本原理，并给出了硬件框图及系统流程图。     

Cloning of aminopeptidase N promoter and its activity in hematopoietic cell and different tumor cell lines

Aminopeptidase N (APN) promoter region was cloned and sequenced from peripheral blood mononuclear cells. The recombinant reporter construct containing the promoter and luciferase gene, designated pXP1-APNLuc, was introduced into myeloblastic cell line, T lymphocyte cell line and various tumor cell lines. Luciferase assay showed that APN upstream promoter is myeloid-specific for high expression in myeloblastic cell line and much lower expression in T lymphocyte cell line. The promoter activity was relatively high in lung adenoma cell line compared with other tumor cell lines including hepatoma cell line, tong cancer cell line and esophageal cancer cell line in which the promoter activity significantly diminished or was almost undetectable. The characteristics of APN promoter may provide a new strategy for specific myeloprotection while tumor patients are being treated with chemotherapy and/or radiotherapy.