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      • Research on the Wood Cell Contour Extraction Method Based on Image Texture and Gray-scale Information

        Zhao Lei,Wang Jianhua,Li Xiaofeng 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.6

        The traditional Snake model and GVF-Snake model set high requirements on noise and initial contour in wood cell contour extraction. To solve this problem, on the premise of considering the image texture and gray-scale information, the area information is directly introduced into the active contour extraction model through force equilibrium equation. Experiments show that the contour extracted with this method is not only more close to real cell contour, but also improved in anti-noise property. In particular, in the convergence of high noise and deep sunken areas, it has some advantages not found in other traditional methods.

      • Diagnostic Accuracy of 18F-FDG-PET in Patients with Testicular Cancer: a Meta-analysis

        Zhao, Jing-Yi,Ma, Xue-Lei,Li, Yan-Yan,Zhang, Bing-Lan,Li, Min-Min,Ma, Xue-Lei,Liu, Lei Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.8

        Objective: Fluorine-18-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) is a new technique for identifying different malignant tumors using different uptake values between tumor cells and normal tissues. Here we assessed the diagnostic accuracy of 18F-FDG-PET in patients with testicular cancer by pooling data of existing trials in a meta-analysis. Methods: PubMed/MEDLINE, Embase and Cochrane Central Trials databases were searched and studies published in English relating to the diagnostic value of FDG-PET for testicular cancer were collected. The summary receiver operating characteristic (SROC) curve was used to examine the FDG-PET accuracy. Results: A total of 16 studies which included 957 examinations in 807 patients (median age, 31.1 years) were analyzed. A meta-analysis was performed to combine the sensitivity and specificity and their 95% confidence intervals (CIs), from diagnostic odds ratio (DOR), positive likelihood ratios (PLR), negative likelihood ratio (NLR). SROC were derived to demonstrate the diagnostic accuracy of FDG-PET for testicular cancer. The pooled sensitivity and specificity were 0.75 (95% confidence interval (CI), 0.70-0.80) and 0.87 (95% CI, 0.84-0.89), respectively. The pooled DOR was 35.6 (95% CI, 12.9-98.3). The area under the curve (AUC) was 0.88. The pooled PLR and pooled NLR were 7.80 (95% CI, 3.73-16.3) and 0.31 (95% CI, 0.23-0.43), respectively. Conclusion: In patients with testicular cancer, 18F-FDG-PET demonstrated a high SROC area, and could be a potentially useful tool if combined with other imaging methods such as MRI and CT. Nevertheless, the literature focusing on the use of 18F-FDG-PET in this setting still remains limited.

      • KCI등재

        CFD-DEM modeling of snowdrifts on stepped flat roofs

        Lei Zhao,Zhixiang Yu,Fu Zhu,Xin Qi,Shichun Zhao 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

        Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

      • SCIESCOPUSKCI등재

        Two Maternal Lineages Revealed by Mitochondrial DNA D-loop Sequences in Chinese Native Water Buffaloes (Bubalus bubalis)

        Lei, Chu-Zhao,Zhang, Wei,Chen, Hong,Lu, Fan,Ge, Qing-Lan,Liu, Ruo-Yu,Dang, Rui-Hua,Yao, Yun-Yi,Yao, Li-Bo,Lu, Zi-Fan,Zhao, Zhong-liang Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.4

        Little is known about the origin and genetic diversity of swamp buffaloes in China. To obtain more knowledge on genetics of the water buffalo in China, the complete mitochondrial D-loop sequences of 30 samples from 6 native types were investigated. The results revealed 12 mitochondrial haplotypes with 50 polymorphic sites. Among these polymorphic sites, there were 49 transitions and 1 transversion. The average nucleotide diversity and haplotype diversity estimated from mtDNA D-loop region in 6 Chinese water buffalo types were 0.00684 and 0.798, respectively, showing rather abundant mitochondrial genetic diversity. The Neighbor-Joining (NJ) tree of mtDNA of Chinese water buffaloes was constructed according to the 12 haplotypes. The NJ tree indicated two lineages being designated lineage A and lineage B, in which lineage A was predominant, and lineage B was at low frequency. The new lineage B was first discovered and defined in 6 Chinese water buffalo types. These results showed that two different maternal lineages were involved in the origin of domestic swamp buffaloes in China and the lineage B was probably an introgression from Southeast Asian buffaloes.

      • Size control of Co-doped ZnO rods by changing the solvent

        Zhao, Jing,Yan, Xiaoqin,Lei, Yang,Zhao, Yanguang,Huang, Yunhua,Zhang, Yue Techno-Press 2012 Advances in materials research Vol.1 No.1

        In this work, the Co-doped ZnO rods were prepared by the hydrothermal method. The size of these rods can be changed from micro-size to nano-size by using different solutions during the preparation. The results of transmission electron microscopy (TEM) and selected area electron diffraction (SAED) showed that the as-prepared nano-sized Co-doped rods have single-crystal structure. The polarized Raman experiments were presented on an individual micro-sized Co-doped ZnO rod in the $X(YY)\vec{X}$, $X(ZY)\vec{X}$ and $X(ZZ)\vec{X}$ configurations, the results of polarized Raman indicated that these rods are crystallized and their growth direction is parallel to c-axis.

      • SCIESCOPUS

        An approach for failure analysis of composite bridge deck systems with openings

        Zhao, Lei,Karbhari, Vistasp M. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.1

        Design details pertaining to the connection between some recently developed fiber reinforced polymer (FRP) composite deck systems and the supporting girders require openings through cells of the deck. This significantly changes the stress distribution in these components. As a result, the conventional assumptions that deck designs are controlled by their stiffness, and not strength, needs a closer examination. This paper proposes an analytical method to investigate the stress states and failure mechanisms using a type of "global-local" modeling perspective, incorporating classical lamination theory and first ply failure criterion with use of appropriate stress concentration factors around the cutouts. The use of a "smeared-stress" approach is presented as a potential means of simplifying certain FRP specific complexities, while still enabling prediction of overall failure.

      • KCI등재

        Dynamics, Stability, and Cooperative Formation Control of Magnetic Sail-Based Planetary Displaced Orbits

        Lei Zhao,Changqing Yuan,Ling Gao,Chengxi Zhang 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2

        The aim of this paper is to analyze dynamic characteristics and stability of magnetic sail-based planetary displaced orbits, and the feasibility of using a magnetic sail as an advanced propellantless control technology for formation flying around elliptic planetary displaced orbits (EPDOs). The thrust can be obtained from the momentum exchange between solar wind and an artificial magnetic field. First, the requirements of a magnetic sail for generating and maintaining a planetary circular displaced orbit is discussed including the value of attitude angles and characteristic acceleration. Based on different orbital periods, the circular displaced orbits are divided into three types and their linear stability is analyzed. For elliptical orbits, the conditions required to maintain an EPDO are investigated and the dynamical models of magnetic sail formation system are established. A finite time coordinated control algorithms relying on the protocols formulated on an undirected communication graph is proposed to achieve synchronized formation tracking rapidly while enhancing the robustness of formation system due to information interaction between spacecraft. Several numerical simulations are conducted to demonstrate that spacecraft formation can be effectively controlled by the proposed propellantless propulsion system.

      • SCIESCOPUS

        CFD-DEM modeling of snowdrifts on stepped flat roofs

        Zhao, Lei,Yu, Zhixiang,Zhu, Fu,Qi, Xin,Zhao, Shichun Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

        Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

      • Research on Wood Cell Shape Analysis Methods based on Fourier Descriptors

        Lei Zhao,Jian Hua Wang 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.2

        The shape parameter of wood microscopic cell is one of the important parameters in the identification of wood species. Fourier Descriptors is often used to describe the boundaries of closed areas. The paper analyzes the slice images of five kinds of common wood cells, extracting the mathematical parameters of the cells, obtaining the average value and simulating the benchmark cell shape of the five wood species to provide data support for subsequent recognition experiments.

      • KCI등재

        Modeling and Analyzing Per-flow Throughput in IEEE 802.11 Multi-hop Ad Hoc Networks

        ( Lei Lei ),( Xinru Zhao ),( Shengsuo Cai ),( Xiaoqin Song ),( Ting Zhang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.10

        In this paper, we focus on the per-flow throughput analysis of IEEE 802.11 multi-hop ad hoc networks. The importance of an accurate saturation throughput model lies in establishing the theoretical foundation for effective protocol performance improvements. We argue that the challenge in modeling the per-flow throughput in IEEE 802.11 multi-hop ad hoc networks lies in the analysis of the freezing process and probability of collisions. We first classify collisions occurring in the whole transmission process into instantaneous collisions and persistent collisions. Then we present a four-dimensional Markov chain model based on the notion of the fixed length channel slot to model the Binary Exponential Backoff (BEB) algorithm performed by a tagged node. We further adopt a continuous time Markov model to analyze the freezing process. Through an iterative way, we derive the per-flow throughput of the network. Finally, we validate the accuracy of our model by comparing the analytical results with that obtained by simulations.

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