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Search Results: 1 - 10 of 31883 matches for " Lei Han "
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Fuzzy Complex Index in Water Quality Assessment of Municipalities  [PDF]
Lei Zhu, Han Hu
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.29095
Abstract: Donghu Lake in Wuhan is a multipurpose complex water body. However, its eutrophication phenomenon becomes increasingly serious. By making use of detailed and accurate contamination monitoring data and several mathematics models, we probe into the dynamic state of water quality. The year’s average value of major contamination index in Donghu Lake from 2001 to 2008 and fuzzy complex index are used to assess its short-term state of water quality. The results show that its water quality is basically stable in the 4th class of water quality standard GB3838-2002.
Retrieving Soil Moisture in Hebei by Using Temperature Vegetation Dryness Index  [PDF]
Fei Mao, Lei Han
Journal of Geoscience and Environment Protection (GEP) , 2017, DOI: 10.4236/gep.2017.58002
Abstract: The temperature-vegetation index space coupled with information of surface temperature and vegetation, is an important method to realize soil moisture estimation and agricultural drought monitoring. In order to estimate the soil moisture in the study area, we collected soil relative humidity of Agricultural meteorological station and downloaded Moderate Resolution Imaging Spectrometer (MODIS) image data. Then, the temperature vegetation dryness index was calculated based on the MODIS Normalized difference vegetation index (NDVI) and land surface temperature (LST). A correlation analysis of TVDI and soil relative humidity at depth of 10 cm was carried out and an empirical model of moisture estimation was established. Finally, another set of data was used to validate the accuracy of model. The results show that the TVDI method can be used to achieve the soil moisture in the study area. The empirical model has certain universality in the study area, and obtains a high accuracy of soil moisture estimation with an R2 of 0.374 and RMSE of 11.73%.
The Application of Deep Learning in Airport Visibility Forecast  [PDF]
Lei Zhu, Guodong Zhu, Lei Han, Nan Wang
Atmospheric and Climate Sciences (ACS) , 2017, DOI: 10.4236/acs.2017.73023
Abstract: This paper uses Urumqi International Airport’s hourly observation from 2007 to 2016 and builds regression prediction model for airport visibility with deep learning method. From the results we can see: the absolute error of hourly visibility is 706 m. When the visibility ≤ 1000 m, the absolute error is 325 m, and this method can predict visibility’s trend. So we can use this method to provide the airport visibility’s objective forecast guidance products for aviation meteorological services in the future. In this paper, the Urumqi area is as the research object, to explore the depth of learning in the field of weather forecasting applications, providing a new visibility return forecast for weather forecast personnel so as to improve the visibility of the level of visibility to ensure the safe and stable operation of the airport.
Classification of Synoptic Circulation Patterns for Fog in the Urumqi Airport  [PDF]
Nan Wang, Lei Zhu, Hongru Yang, Lei Han
Atmospheric and Climate Sciences (ACS) , 2017, DOI: 10.4236/acs.2017.73026
Abstract: The purpose of this study is to investigate the Classification of Synoptic Circulation Patterns for Fog in the Urumqi Airport in Xinjiang, China. By using relevant climate statistical method, the hourly ground observation data and four times per day and NCEP/NCAR reanalysis data (1° × 1°) from 1985 to 2014 were analyzed. The results showed that: 1) The occurrence of fog significantly increased during 1985 and 2014; There are two stages of the airport fog in the 30 years, less-fog period (1985-2002) and more-fog period (2002-2014), the fog focused occurred in November to March of the following year, most in December and least in March; 2) Based on Lamb-Jenkinson method, the dominant types of fog in Urumqi Airport are C, E, SE, W, A types (Among them, A, C, E, W, SE are the circulation types. C is Cyclone, A is Anti-cyclone, E is East, W is West, SE is Southeast), and the international distribution of each type is also different; 3) The dominant types of persistence fog are A, C, E, SE types, A type appears in the afternoon to the nighttime, in the morning less frequent, on the other hand, C type is just the opposite; 4) Atmospheric circulation characteristics for persistence fog profile can be divided into four series: A, C, E, SE series, and climatic characteristics in different series are different.
The Empirical Research of Factors Influencing Share of Wallet in the B2B Market  [PDF]
Aiwu Cheng, Lei Han, Cheng Cao
Journal of Service Science and Management (JSSM) , 2011, DOI: 10.4236/jssm.2011.42020
Abstract: Share of wallet is a key factor in Customer relationship management system (CRM) which is an important application of E-business. Research has found that share of wallet is an important indicator to measure customer loyalty and cus-tomer potential value. On the basis of the existent marketing literatures, this study analyzes the variables influencing share of wallet according the traits of the B2B market. This paper brings forward interrelated hypotheses and concep-tual model,then test the hypotheses with enterprises survey in the B2B market. Finally we use path analysis to find the principal factors influencing share of wallet and the relationships in them. The results of this research provide theo-retical foundation to upgrade CRM management level of the B2B enterprises, and there is a certain reference value to predict share of wallet in customer lifetime value’s (CLV) measurement.
Retrievable Inferior Vena Cava Filters for Venous Thromboembolism
Han Ni,Lei Lei Win
ISRN Radiology , 2013, DOI: 10.5402/2013/959452
Abstract: Inferior vena cava (IVC) filters are used as an alternative to anticoagulants for prevention of fatal pulmonary embolism (PE) in venous thromboembolic disorders. Retrievable IVC filters have become an increasingly attractive option due to the long-term risks of permanent filter placement. These devices are shown to be technically feasible in insertion and retrieval percutaneously while providing protection from PE. Nevertheless, there are complications and failed retrievals with these retrievable filters. The aim of the paper is to review the retrievable filters and their efficacy, safety, and retrievability. 1. Introduction Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is a cause of significant morbidity and mortality in both hospitalized and nonhospitalized patients. Approximately 400,000 to 650,000 patients develop PE annually with 50,000 to 240,000 deaths in the United States [1]. Standard therapy is parenteral anticoagulants (full-dose unfractionated heparin, low-molecular-weight heparin, or fondaparinux) followed by oral vitamin K antagonists (warfarin). However, in cases of contraindications to anticoagulants, bleeding complications, or recurrent VTE despite optimal anticoagulation, interruption of inferior vena cava (IVC) with a filter is necessary to prevent life-threatening PE [2]. 2. Types of IVC Filters The characteristics of an ideal IVC filter include high filtering efficiency without impedance of flow, secure fixation within IVC, rapid percutaneous insertion (small calibre, amenable to repositioning), MRI compatibility, low cost, and retrievability. Moreover, the ideal filter should be made of nonthrombogenic, biocompatible long-lasting material [3, 4]. Nevertheless, none of the currently available IVC filters meet all these criteria. IVC filters are implanted as permanent or nonpermanent. Mobin-Uddin filter was first introduced in 1967. However, due to high incidence of thrombosis and occlusion, Greenfield filter quickly became the preferred choice, which was first described in 1973 [5–7]. This Greenfield stainless steel filter and another permanent Bird’s Nest filter are MRI incompatible. Other permanent IVC filters available are Simon Nitinol, TrapEase, and VenaTech, which are all MRI compatible [3, 8]. Subsequent studies demonstrated the increased incidence of complications associated with permanent IVC filters [9]. One of the significant long-term risks of permanent filters is thrombotic occlusion of the IVC, which is seen in 6% to 30% of cases; other important complications include
Different patterns of agonist-induced modulation of α1B-adrenoceptor density at different initial expression levels
Beilei Lei,Qide Han
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02886215
Abstract: We compared the norepinephrine (NE) induced α1B-adrenoceptor (α1B-AR) expression modulation between two transfected human embryonic kidney (MEK) 293 cell lines in which α1B-AR densities were (6 336 ± 913) and (773 ± 164) fmol mg1, respectively. Treatment of cells with NE (10 μmol L1) for 48 h decreased high-level expressed α1B-AR density, but increased low-level expressed α1B-AR density. The protein kinase C inhibitor Calphostin C or Ro-31-8220 reversed, and its activator PMA mimicked the NE-induced down-regulation of high-level expressed α1B-AR. Moreover, PMA induced a down-regulation of low-level expressed α1B-AR. The endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (CPA) and the calcium chelator BAPTA/AM did not affect the down-regulation of high-level expressed α1B-AR, but inhibited the up-regulation of low-level expression α1B-AR induced by NE. These results suggest that α1B-adrenoceptor densities at different initial expression levels are differentially regulated by NE and their signal transduction pathways are different.
A micromachined inline type microwave power sensor with working state transfer switches
一种具有工作状态转换开关结构的微机械在线式微波功率传感器

Han Lei,
韩磊

半导体学报 , 2011,
Abstract: 提出了一种具有工作和不工作两种状态的8GHz-12GHz宽带在线式微波功率传感器结构,该功率传感器通过测量由MEMS膜从共面波导线耦合出的一小部分微波功率实现功率的测量。为了降低功率传感器在不工作状态的微波损耗,提出了一种能够实现两种工作状态的新型的状态转换开关结构。该结构制作工艺与GaAs MMIC工艺完全兼容。测量结果显示,在10GHz中心频率处,该结构功率传感器在不工作状态下的插入损耗为0.18dB,而在工作状态下的插入损耗为0.24dB,这意味着在不工作状态下没有微波功率被耦合出来。
Gauge glass in two dimensions
Lei-Han Tang
Physics , 2009, DOI: 10.1143/PTPS.184.429
Abstract: The gauge glass model offers an interesting example of a randomly frustrated system with a continuous O(2) symmetry. In two dimensions, the existence of a glass phase at low temperatures has long been disputed among numerical studies. To resolve this controversy, we examine the behavior of vortices whose movement generates phase slips that destroy phase rigidity at large distances. Detailed analytical and numerical studies of the corresponding Coulomb gas problem in a random potential establish that the ground state, with a finite density of vortices, is polarizable with a scale-dependent dielectric susceptibility. Screening by vortex/antivortex pairs of arbitrarily large size is present to eliminate the logarithmic divergence of the Coulomb energy of a single vortex. The observed power-law decay of the Coulomb interaction between vortices with distance in the ground state leads to a power-law divergence of the glass correlation length with temperature $T$. It is argued that free vortices possess a bound excitation energy and a nonzero diffusion constant at any $T>0$.
Vortex statistics in a disordered two-dimensional XY model
Lei-Han Tang
Physics , 1996, DOI: 10.1103/PhysRevB.54.3350
Abstract: The equilibrium behavior of vortices in the classical two-dimensional (2D) XY model with uncorrelated random phase shifts is investigated. The model describes Josephson-Junction arrays with positional disorder, and has ramifications in a number of other bond-disordered 2D systems. The vortex Hamiltonian is that of a Coulomb gas in a background of quenched random dipoles, which is capable of forming either a dielectric insulator or a plasma. We confirm a recent suggestion by Nattermann, Scheidl, Korshunov, and Li [J. Phys. I (France) {\bf 5}, 565 (1995)], and by Cha and Fertig [Phys. Rev. Lett. {\bf 74}, 4867 (1995)] that, when the variance $\sigma$ of random phase shifts is smaller than a critical value $\sigma_c$, the system is in a phase with quasi-long-range order at low temperatures, without a reentrance transition. This conclusion is reached through a nearly exact calculation of the single-vortex free energy, and a Kosterlitz-type renormalization group analysis of screening and random polarization effects from vortex-antivortex pairs. The critical strength of disorder $\sigma_c$ is found not to be universal, but generally lies in the range $0<\sigma_c<\pi/8$. Argument is presented to suggest that the system at $\sigma>\sigma_c$ does not possess long-range glassy order at any finite temperature. In the ordered phase, vortex pairs undergo a series of spatial and angular localization processes as the temperature is lowered. This behavior, which is common to many glass-forming systems, can be quantified through approximate mappings to the random energy model and to the directed polymer on the Cayley tree. Various critical properties at the order-disorder transition are calculated.
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