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Search Results: 1 - 10 of 163624 matches for " ZHANG Wei-feng "
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Spectral Reflectance Estimation by Support Vector Regression

ZHANG Wei-feng,

计算机科学 , 2010,
Abstract: A spectral reflectance estimation method using support vector regression and framclet kernel was proposed.Spectral reflectance estimation is an important subject in optical research. The aim is to convert device-dependent RGB values to device-and illuminant independent reflectance spectra. Regression methods are widely used to estimate spectral reflectance of surface colors given their camera responses, such as regularized least squares method with polynomial models,kernel based regularized least squares method, etc. In this paper, we introduced a novel estimating approach based on the support vector regression method. The proposed approach utilizes a framelet based kernel, which has the ability to approximate functions with multiscale structure and can reduce the influence of noise in data. Experimental resups show that the technicaue can improve the recovery accuracy and stability.
Group Ranking Sequence Decision for Recommendation of Messaging APP  [PDF]
Wei-Feng Tung
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.27002

This research is to develop a novel recommendation service using a unique group ranking sequence technique “Mining Maximum Consensus Sequences from all Users’ Partial Ranking Lists (MCSP)”. MCSP is capable of determining the product’s sequence recommendations based on k-item candidate sequences and maximum consensus sequences. This paper also illustrates the complete decision procedures of group ranking sequences. In terms of popular information products, we select “messaging app” to reveal the MCSP’s group ranking sequence decision. The recommendation service provides that query users search for the product’s recommendation (i.e., messaging app) according to the preference sequences from query users themselves and a great deal of preference sequences from the other users. This paper consists of the definitions, procedures, implementation, and experiment analysis, as well as system demonstrations of MCSP respectively. This research contributes to a kind of systematic service innovation.

Sedimentation of short cylindrical pollutants with mechanical contacts
LIN Jian-zhong,WANG Ye-long,ZHANG Wei-feng,
LIN Jian-zhong
,WANG Ye-long,ZHANG Wei-feng

环境科学学报(英文版) , 2005,
Abstract: Lattice Boltzmann method and elastic particle collision model were used to investigate the sedimentation of short cylindrical pollutant particles with mechanical contacts for varying bulk number density epsilon and terminal Reynolds number ReT. The corresponding experiments were performed as a comparison. The clusters of pollutant particles with an inverted "T" structure were observed, the pollutant particles for high epsilon and large ReT scattered wider than that for low epsilon and small ReT. The sedimentation velocities increased suddenly at the initial stage, then decreased drastically, after that swayed around and approached to a steady value. The time to steady state did not depend on epsilon and ReT. The effect of particle interactions was to hinder the average sedimentation velocity, and hindrance was directly proportional to epsilon. The orientation distributions of pollutant particles depended on ReT and epsilon, especially on the former. Both the standard deviations of vertical and horizontal velocity, the former was larger than the latter, were nearly independent on epsilon and ReT.
Nano-LiNiO2 as cathode material for lithium ion battery synthesized by molten salt method

Bai Ying,Wang Bei,Zhang Wei-Feng,

物理学报 , 2011,
Abstract: Molten salt method is applied to synthesis stoichiometric nano-LiNiO2 in rather low temperature and short time. Our results indicate that in the process of preheating the better-crystallized LiNiO2 powder with better electrochemical performances can be produced. The final samples before and after preheating exhibit the initial discharge capacities of 151 and 148 mAh ·g-1 respectively. After 100 cycles, they decay to only 55 and 118 mAh ·g-1, with capacity retentions being 36.4% and 79.7% respectively. The lowered cation disordering is thought to be favorable for the diffusion of lithium ions, by which the enhanced electrochemial properties can be explained.
Stress responses of Canna indica to Cd and its accumulation of Cd

ZHANG Cheng-Xiang,CHEN Wei-Feng,

植物生态学报 , 2012,
Abstract: Aims The valuable ornamental plant Canna indica is widely distributed in city gardens and on roadsides in China. Our objective was to study the stress responses of C. indica to cadmium (Cd) and its accumulation of Cd. Methods With pot culture experiments, C. indica was cultured with different Cd concentrations. Morphological, ecological, physiological indexes were observed during the growth of C. indica. The distribution of Cd in C. indica plants was determined after harvest. Important findings The Cd treatment of <1 mg·kg–1 had no obvious effect on growth of C. indica; however, Cd concentration of >5 mg·kg–1 inhibited growth. The flowering period was prolonged with <5 mg·kg–1 Cd concentration. With increasing Cd concentration, root activity, chlorophyll and water content all decreased, soluble sugar content initially increased and then decreased, and free proline content and permeability of cell membrane increased gradually. The distribution of Cd in C. indica was root > shoot. With increasing Cd concentration of the medium, Cd concentration in shoots and roots increased; however, the accumulator and translocation factors decreased gradually. The maximum accumulation of Cd in C. indica was 5.89 mg·plant–1 with the treatment of 20 mg·kg–1 . It is concluded that C. indica is suitable for landscaping use when the Cd concentration in soil is <1 mg·kg–1 .
A Time Domain and Trustworthiness-Based Distributed Credential Chain Discocery Algoritnm

HAO Xiao-Xiao,ZHANG Wei-Feng,

计算机系统应用 , 2010,
Abstract: In the distributed environment, the goal-directed, distributed chain discovery algorithm finds and retrieves credentials needed. However, the exiting trust management systems have some flaws as follows: (1) delegation depth is not controlled effectively. (2) the validity of the certificate has not been reflected. To address the problems above, this paper proposes a time domain and trustworthiness-based distributed credential chain discovery algorithm, and gives a specific example of the algorithm.
Endoscopic submucosal dissection for foregut neuroendocrine tumors: An initial study
Quan-Lin Li,Yi-Qun Zhang,Wei-Feng Chen,Mei-Dong Xu
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i40.5799
Abstract: AIM: To evaluate the feasibility and efficacy of endoscopic submucosal dissection (ESD) for foregut neuroendocrine tumors (NETs). METHODS: From April 2008 to December 2010, patients with confirmed histological diagnosis of foregut NETs were included. None had regional lymph node enlargement or distant metastases to the liver or lung on preoperative computerized tomography scanning or endoscopic ultrasonography (EUS). ESD was attempted under general anesthesia. After making several marking dots around the lesion, a mixture solution was injected into the submucosa. The mucosa was incised outside the marking dots. Dissection of the submucosal layer beneath the tumor was performed under direct vision to achieve complete en bloc resection of the specimen. Tumor features, clinicopathological characteristics, complete resection rate, and complications were evaluated. Foregut NETs were graded as G1, G2, or G3 on the basis of proliferative activity by mitotic count or Ki-67 index. All patients underwent regular follow-up to evaluate for any local recurrence or distant metastasis. RESULTS: Those treated by ESD included 24 patients with 29 foregut NETs. The locations of the 29 lesions are as follows: esophagus (n = 1), cardia (n = 1), stomach (n = 23), and duodenal bulb (n = 4). All lesions were found incidentally during routine upper gastrointestinal endoscopy for other indications, and none had symptoms of carcinoid syndrome. Preoperative EUS showed that all tumors were confined to the submucosa. Among the 24 gastric lesions, 16 lesions in 11 patients were type I gastric NETs arising in chronic atrophic gastritis with hypergastrinemia, while the other 8 solitary lesions were type III because of absence of atrophic gastritis in these cases. All of the tumors were removed in an en bloc fashion. The average maximum diameter of the lesions was 9.4 mm (range: 2-30 mm), and the procedure time was 20.3 min (range: 10-45 min). According to the World Health Organization 2010 classification, histological evaluation determined that 26 lesions were NET-G1, 2 gastric lesions were NET-G2, and 1 esophageal lesion was neuroendocrine carcinoma (NEC). Complete resection was achieved in 28 lesions (28/29, 96.6%), and all of them were confined to the submucosa in histopathologic assessment with no lymphovascular invasion. The remaining patient with NEC underwent additional surgery because the resected specimens revealed angiolymphatic and muscularis invasion, as well as incomplete resection. Delayed bleeding occurred in 1 case 3 d after ESD, which was managed by endoscopic treatmen
Impurity-induced bound states in iron-based superconductors with s-wave cos(kx)cos(ky) pairing symmetry
Wei-Feng Tsai,Yan-Yang Zhang,Chen Fang,Jiangping Hu
Physics , 2009, DOI: 10.1103/PhysRevB.80.064513
Abstract: Using both the self-consistent Bogoliubov-de Gennes formulation and non-self-consistent T-matrix approach, we perform a comprehensive investigation of the in-gap bound states induced by a localized single impurity in iron-based superconductors. We focus on studying signatures associated with the unconventional sign-changed s-wave pairing symmetry. For a non-magnetic impurity, we find that there are two in-gap bounds, symmetric with respect to zero energy, only in the sign changed s-wave pairing state, not in the sign-unchanged s-wave state, due to the existence of non-trivial Andreev bound states caused by the sign change. For a magnetic impurity, we find that due to the breakdown of the local time-reversal symmetry, there exist only bound state solutions (with orbital degeneracy) carrying one of the electron-spin polarizations around the impurity. As increasing the scattering strength, the system undergoes a quantum phase transition (level crossing) from a spin-unpolarized ground state to a spin-polarized one. While the results for the magnetic impurity are qualitatively similar in both the sign-changed and sign-unchanged s-wave superconducting states, the bound states in the first case are more robust and there is no $\pi$ phase shift of the SC gap near the impurity in the strong scattering regime.
Investigation of electrochemical performances of ZnFe2O4 prepared by solid state and hydrothermal method

Bai Ying,Ding Ling-Hong,Zhang Wei-Feng,

物理学报 , 2011,
Abstract: Spinel structure ZnFe2O4 were prepared by solid state reaction and hydrothermal method. Investigations on X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific area measuements indicate that the samples are well-crystallized cubic spinel structre with average particle sizes of 500 nm and 200 nm and specific areas of 136.7 m2 g-1 and 382.5 m2 g-1 for solid state reaction and hydrothermal method, respectively. The ZnFe2O4 samples show high lithium-storage capacity and good reversibility. Compared with the sample prepared by solid state reaction, ZnFe2O4 prepared by hydrothermal method demonstrate better electrochemical performances. Its specific charge capacity decays from 750 mAh g-1 to 702 mAh g-1 after 30 cycles, with capacity retention of 93.6 %. ZnFe2O4 is a very promising anode material for lithium ion battery for its easy preparation, low coat and good electrochemical performances.
Study on the Cytology of Rosa multiflora Thunb. var. cathayensis

LUO Yu-Lan,ZHANG Dong-Mei,CHEN Wei-Feng,

植物科学学报 , 2008,
Abstract: 以野蔷薇的-变种红刺攻(Rosa multiflora Thunb.vat.cathayensis Rehd.)为材料,对其染色体数和花粉母细胞的减数分裂进程进行了研究.结果表明:红刺玫染色体数目为2n=3x=21,为三倍体;减数分裂始于4月上旬,此时花苞开始膨大、但未开裂,花瓣由绿变成黄色;在同一花药中,花粉母细胞的减数分裂并不同步,可以观察到前期到末期Ⅱ之间各个时期的分裂相;在其减数分裂过程中存在诸如单价体、染色体桥、落后染色体等一系列异常现象.实验还从细胞遗传学上分析了红刺玫育性与花粉母细胞减数分裂异常的关系,部分可育花粉的存在为红刺玫育种实践提供了有用的材料.
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