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Search Results: 1 - 10 of 104226 matches for " ZHANG Qingmiao "
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Key generation protocol based on optical OFDM bipolar real number sampling

XIONG Liting
,ZHANG Qingmiao,SHEN Keyong

- , 2018,
Abstract: 针对光信道特性生成密钥十分困难的问题,提出一种室内环境中光正交频分复用(orthogonal frequency division multiplexing, OFDM)的密钥生成协议,以提升室内可见光通信(visible light communication, VLC)网络的保密性.该方法从光OFDM所产生的双极OFDM样本中生成密钥,分配一部分循环前缀样本并将其放置在信道影响较小的区域中,以在整个会话期间进行密钥提取.为了提供较高的物理层安全性,每个OFDM信号帧均由不同的密钥加密.蒙特卡洛仿真实验表明,所提方法在密钥生成过程中,平均电信噪比更高,端到端性能更优,适合于低复杂度、低失配率密钥提取的情形.
The Explanation of the Selection of Settlement and Environment in the Western Liaohe River Valley during the Middle Holocene Epoch

HAN Maoli,LIU Xiaoquan,FANG Chen,ZHANG Yi,LI Qingmiao,ZHAO Yuhui,

地理学报 , 2007,
Abstract: The paper focuses on the environmental explanation of the selection of settlement sites belonging to different types of archaeological culture in the middle Holocene Epoch, Western Liaohe River Valley. Through Chi-square Test, the authors point out that the settlements in the target region were mainly distributed in the sloping field of 400-500 m above sea level and the distribution presents spatial and temporal changes. The settlements in 8000-6000 a BP concentrated on the sloping field of 400-500 m above sea level. The settlements in 6000-3000 a BP were extending from the core area of 400-500 m above sea level to the higher and lower directions. While showing the preference of the height of 400-500 m above sea level, the settlements in the Western Liaohe River Valley in the middle Holocene Epoch demonstrated a horizontal amassment in the sloping field 10-40 m away from the riverbed. From the environmental explanation of the selection of settlement sites belonging to different types of archaeological culture, the paper gets three main findings:1) the Western Liaohe River Valley could be divided into two parts, the woodland and the grassland, according to the style of living of the people. The periphery of the woodland is the living space of the people 8000-6000 a BP, when gathering, fishing and hunting were the main life style. The grassland is the main distribution area of primitive agriculture. 6000-3000 a BP is the vital period for the development of primitive agriculture, during which the settlements had a trend expanding from the periphery of woodland to the grassland. The sequence of the settlement sites defines the spatial and regional features of environment. 2) Though the Holocene Epoch experienced a prominent warming period, the animal and vegetation resources were far from abundant, restricted by the zonality constraints of the Western Liaohe River Valley. The living resources reserves could only afford the living of the people in 8000-6000 a BP when the population density was very low. In 6000-3000 a BP, the growth of population had exceeded the environmental capacity of this area. To fulfill the survival requirement, primitive agriculture was developing gradually and new man-land relationship was established. 3) Using thickness of the cultural sediments to analyze the continuance of the settlements in the middle Holocene Epoch, the paper points out that the population density then was much sparser than modern times. Considering the environmental capacity and population density, agriculture cultivation in the middle Holocene Epoch did not cause significant environmental disturbance.
A Comparative Study of Elastic Constants of NiTi and NiAl Alloys from First-Principle Calculations

Jianmin Lu,Qingmiao Hu,Rui Yang,

材料科学技术学报 , 2009,
Abstract: To investigate the origin of the strong dependence of martensitic transformation temperature on composition,the elastic properties of high temperature B2 phases of both NiTi and NiAl were calculated by a first-principle method, the exact-muffin orbital method within coherent potential approximation. In the composition range of 50-56 at. pct Ni of NiTi and 60-70 at. pct Ni of NiAI in which martensitic transformation occurs, non-basalplane shear modulus c44 increases with increasing Ni content, while basal-plane shear modulus c' decreases.In the above composition ranges however the transformation temperature of NiAI increases with increasing Ni content while that of NiTi decreases from experimental observation. The softening of c' is experimentally observed only in NiAl, and the decrease of c' with increasing Ni content is responsible for the increase of transformation temperature. The result of the present work demonstrates that, besides c', c44 also influences the martensitic transformation of NiTi and plays quite important a role.
Analysis on Energy Conversion of Screw Centrifugal Pump in Impeller Domain Based on Profile Lines
Hui Quan,Rennian Li,Qingmiao Su,Wei Han,Pengcheng Wang
Advances in Mechanical Engineering , 2013, DOI: 10.1155/2013/512523
Abstract: In order to study the power capability of impeller and energy conversion mechanism of screw centrifugal pump, the methods of theoretical analysis and numerical simulation by computational fluid dynamics theory (CFD) were adopted, specifically discussing the conditions of internal flow such as velocity, pressure, and concentration. When the medium is sand-water two-phase flow and dividing the rim of the lines and wheel lines of screw centrifugal pump to segments to analyze energy conversion capabilities which along the impeller profile lines with the dynamic head and hydrostatic head changer, the results show that the energy of fluid of the screw centrifugal pump is provided by helical segment, and the helical segment of the front of the impeller has played the role of multilevel increasing energy; the sand-water two phases move at different speeds because the different force field and the impeller propeller and centrifugal effect. As liquid phase is the primary phase, the energy conversion is mainly up to the change of liquid energy, the solid phase flows under the wrapped action of liquid, and solid energy is carried out through liquid indirectly. 1. Introduction As a new kind of impurity pump, screw centrifugal pump combines the advantages of screw pump and centrifugal pump, and the special structure can bring into play their advantages, sufficiently (Figure 1). Comparing with the traditional impurity pump, screw centrifugal pump has a series of strong advantages, such as without clogging, suction performance, adjustment of the performance, and cavitation resistance, and with no load, high efficiency, and high efficiency zone width [1, 2]. Figure 1: Picture of the impeller. Screw centrifugal pump internal flow apparently shows mixed spiral movement because of the unique structure of impeller, comparing with ordinary centrifugal pumps; there is still much room for efficiency improvement for screw centrifugal pump. Screw centrifugal pump is a typical sand-water two-phase flow pump, due to the different density of the solid and liquid phases, resulting in the slip velocity, which does not only affect the hydraulic performance of the pump, but also makes it easy for the solid particles and over-current surface conflicts caused by the wear of the pump flow parts and other problems [3–5]. Therefore, the study of mechanism of energy conversion and the analysis of factors that impact the conversion have a great significance for the improvement of efficiency. It is also the primary problem that optimizes the design methods of established impurity pump and
First-principles Study of Structure of Ammonia Borane

LIU Chaoren HU Qingmiao WANG Ping,

材料研究学报 , 2011,
Abstract: Two kinds of crystal structures (Pmn21 and P42cm) of (ammonia borane) are studied using first–principles plane wave pseudopotential method based on density functional theory in this paper. It was found that the Pmn21 structure is energetically more stable than the P42cm structure at 0 K. This agrees well with the experimental observation, that lower temperature phase is the Pmn21 structure whereas the room temperature phase is P42cm structure. The structure difference between Pmn21 and P42cm phases manifests itself mainly by the variation of intermolecular bond length whereas the intramolecular bond length remains almost unchanged. Electronic state of density was calculated to identify the bonding nature of ammonia borane. The XRD and FTIR patterns of the P42cm structure were calculated, results agree well with the experimental results of AB at room temperature.
Mixed-pixel clumping index calculation and scale analysis

MA Qingmiao,LI Jing,LIU Qiang,LIU Qinhuo,

遥感学报 , 2012,
Abstract: A new algorithm for mixed-pixel clumping index (MPCI) calculation is proposed, which is based on the directional gap fraction and linear mixture model from the high-resolution remote sensing data. In this algorithm, the scale difference caused by the spatial heterogeneity of the fraction of vegetation cover (FVC), end-member clumping index (EMCI) and leaf inclination angle distribution (LAD) within the mixed pixel is well considered. The preliminary sensitivity analysis with the simulated data shows that the impact factors in a descending order are the special heterogeneity of EMCI, FVC and LAD (expressed as G function). The maximum values of the relative variation ratio caused by the heterogeneities are about 55%, 43% and 12%, correspondingly. The results also demonstrate that it is very necessary and signif icant to correct the scale difference in the mixed pixel with high special heterogeneity. It is potential to improve the accuracy of coarse leaf area index retrieval by employing the MPCI algorithm presented in this paper.
An Efficient and Concise Algorithm for Convex Quadratic Programming and Its Application to Markowitz’s Portfolio Selection Model  [PDF]
Zhongzhen Zhang, Huayu Zhang
Technology and Investment (TI) , 2011, DOI: 10.4236/ti.2011.24024
Abstract: This paper presents a pivoting-based method for solving convex quadratic programming and then shows how to use it together with a parameter technique to solve mean-variance portfolio selection problems.
Investigation and Analysis of Sexual Harassment in Corporate Workplace of China  [PDF]
Xiaobing Zhang, Zewei Zhang
Sociology Mind (SM) , 2012, DOI: 10.4236/sm.2012.23038
Abstract: At present, sexual harassment in domestic workplace has a high probability of occurrence, which causes more and more attention. In this paper, the form of sexual harassment in workplace, and how to solve the sexual harassment were investigated and analyzed through questionnaires; and countermeasures and management suggestions were put forward from three aspects of corporate, employees and family.
Chaos Control in a Discrete Ecological System  [PDF]
Limin Zhang, Chaofeng Zhang
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2012, DOI: 10.4236/ijmnta.2012.13011
Abstract: In research [1], the authors investigate the dynamic behaviors of a discrete ecological system. The period-double bifurcations and chaos are found in the system. But no strategy is proposed to control the chaos. It is well known that chaos control is the first step of utilizing chaos. In this paper, a controller is designed to stabilize the chaotic orbits and enable them to be an ideal target one. After that, numerical simulations are presented to show the correctness of theoretical analysis.
Crystallization and Characterization of a New Fluorescent Molecule Based on Schiff Base  [PDF]
Dehua Zhang, Xiaoyan Zhang
Journal of Crystallization Process and Technology (JCPT) , 2013, DOI: 10.4236/jcpt.2013.31004

In this analysis, the single crystal of schiff base has been synthesized and the purity of material has been increased by repeated recrystallization process. Single crystal was grown by adopting the method growing in a slow evaporation solution using ethanol as solvent at room temperature. A new fluorescent molecule based on Schiff base has been synthesised and its binding properties investigated by fluorescence spectroscopy to show that it can selectively bind Cu2+ with fluorescence quenching.

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