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        • SCOPUS

          Bounding Worst-Case Performance for Multi-Core Processors with Shared L2 Instruction Caches

          Yan, Jun,Zhang, Wei Korean Institute of Information Scientists and Eng 2011 Journal of Computing Science and Engineering Vol.5 No.1

          As the first step toward real-time multi-core computing, this paper presents a novel approach to bounding the worst-case performance for threads running on multi-core processors with shared L2 instruction caches. The idea of our approach is to compute the worst-case instruction access interferences between different threads based on the program control flow information of each thread, which can be statically analyzed. Our experiments indicate that the proposed approach can reasonably estimate the worst-case shared L2 instruction cache misses by considering the inter-thread instruction conflicts. Also, the worst-case execution time (WCET) of applications running on multi-core processors estimated by our approach is much better than the estimation by simply assuming all L2 instruction accesses are misses.

        • SCISCIESCOPUS

          Evaluation of Pp/Clay Composites as Soundproofing Material

          Yan, Jun,Kim, Myung-Sub,Kang, Kyung-Min,Joo, Kyung-Hoon,Kang, Yeon-June,Ahn, Sung-Hoon RAPRA 2014 POLYMERS AND POLYMER COMPOSITES Vol.22 No.1

          Noise should be disappeared or reduced by using soundproofing materials in our daily life. Polypropylene (PP)/Clay composites are interesting because of their physical and mechanical properties dramatically increased by small quantity of clay filled in PP matrix. In this paper, different types of specimens were made at 0.9, 2.9, 4.8, 6.5, 8.2 and 9.9 wt.% of organically modified clay reinforced PP (100 gram) by solvent based techniques. A heating press and laser cutting process were used to create specimens with thickness 3 mm, diameter 29 mm and 100 mm for high and low sound frequency test, respectively. The soundproofing property was measured by sound transmission loss (TL) through impedance tube method. The measured results showed that about 7 similar to 14.8 dB sound TL was increased for 29 mm diameter PP/Clay (6.5 wt.%) composite specimens compared with pure PP at 3200 similar to 6400Hz. And about 3.3 similar to 5.3 dB sound TL was increased for 100 mm diameter PP/Clay (6.5 wt.%) composite specimens compared with pure PP at 520 similar to 640Hz. In addition, mechanical properties of this composite were measured, and TEM images were taken in order to observe the micro-structure for research on relationship between soundproofing property and micromechanism.

        • SCIESCOPUSKCI등재

          Attack-Resistant Received Signal Strength based Compressive Sensing Wireless Localization

          Yan, Jun,Yu, Kegen,Cao, Yangqin,Chen, Liang Korean Society for Internet Information 2017 KSII Transactions on Internet and Information Syst Vol.11 No.9

          In this paper a three-phase secure compressive sensing (CS) and received signal strength (RSS) based target localization approach is proposed to mitigate the effect of malicious node attack. RSS measurements are first arranged into a group of subsets where the same measurement can be included in multiple subsets. Intermediate target position estimates are then produced using individual subsets of RSS measurements and the CS technique. From the intermediate position estimates, the residual error vector and residual error square vector are formed. The least median of residual error square is utilized to define a verifier parameter. The selected residual error vector is utilized along with a threshold to determine whether a node or measurement is under attack. The final target positions are estimated by using only the attack-free measurements and the CS technique. Further, theoretical analysis is performed for parameter selection and computational complexity evaluation. Extensive simulation studies are carried out to demonstrate the advantage of the proposed CS-based secure localization approach over the existing algorithms.

        • SCOPUS

          Computing and Reducing Transient Error Propagation in Registers

          Yan, Jun,Zhang, Wei Korean Institute of Information Scientists and Eng 2011 Journal of Computing Science and Engineering Vol.5 No.2

          Recent research indicates that transient errors will increasingly become a critical concern in microprocessor design. As embedded processors are widely used in reliability-critical or noisy environments, it is necessary to develop cost-effective fault-tolerant techniques to protect processors against transient errors. The register file is one of the critical components that can significantly affect microprocessor system reliability, since registers are typically accessed very frequently, and transient errors in registers can be easily propagated to functional units or the memory system, leading to silent data error (SDC) or system crash. This paper focuses on investigating the impact of register file soft errors on system reliability and developing cost-effective techniques to improve the register file immunity to soft errors. This paper proposes the register vulnerability factor (RVF) concept to characterize the probability that register transient errors can escape the register file and thus potentially affect system reliability. We propose an approach to compute the RVF based on register access patterns. In this paper, we also propose two compiler-directed techniques and a hybrid approach to improve register file reliability cost-effectively by lowering the RVF value. Our experiments indicate that on average, RVF can be reduced to 9.1% and 9.5% by the hyperblock-based instruction re-scheduling and the reliability-oriented register assignment respectively, which can potentially lower the reliability cost significantly, without sacrificing the register value integrity.

        • SCOPUS

          An Interference Matrix Based Approach to Bounding Worst-Case Inter-Thread Cache Interferences and WCET for Multi-Core Processors

          Yan, Jun,Zhang, Wei Korean Institute of Information Scientists and Eng 2011 Journal of Computing Science and Engineering Vol.5 No.2

          Different cores typically share the last-level cache in a multi-core processor. Threads running on different cores may interfere with each other. Therefore, the multi-core worst-case execution time (WCET) analyzer must be able to safely and accurately estimate the worst-case inter-thread cache interference. This is not supported by current WCET analysis techniques that manly focus on single thread analysis. This paper presents a novel approach to analyze the worst-case cache interference and bounding the WCET for threads running on multi-core processors with shared L2 instruction caches. We propose to use an interference matrix to model inter-thread interference, on which basis we can calculate the worst-case inter-thread cache interference. Our experiments indicate that the proposed approach can give a worst-case bound less than 1%, as in benchmark fib-call, and an average 16.4% overestimate for threads running on a dual-core processor with shared-L2 cache. Our approach dramatically improves the accuracy of WCET overestimatation by on average 20.0% compared to work.

        • SCIESCOPUSKCI등재

          Base Station Placement for Wireless Sensor Network Positioning System via Lexicographical Stratified Programming

          Yan, Jun,Yu, Kegen Korean Society for Internet Information 2015 KSII Transactions on Internet and Information Syst Vol.9 No.11

          This paper investigates optimization-based base station (BS) placement. An optimization model is defined and the BS placement problem is transformed to a lexicographical stratified programming (LSP) model for a given trajectory, according to different accuracy requirements. The feasible region for BS deployment is obtained from the positioning system requirement, which is also solved with signal coverage problem in BS placement. The LSP mathematical model is formulated with the average geometric dilution of precision (GDOP) as the criterion. To achieve an optimization solution, a tolerant factor based complete stratified series approach and grid searching method are utilized to obtain the possible optimal BS placement. Because of the LSP model utilization, the proposed algorithm has wider application scenarios with different accuracy requirements over different trajectory segments. Simulation results demonstrate that the proposed algorithm has better BS placement result than existing approaches for a given trajectory.

        • KCI등재

          Brittle fracture and plastic creep of the completely decomposed granite presented in CT

          Yanjun Shang,Zhongqi Yue,박형동,현창욱 한국자원공학회 2015 Geosystem engineering Vol.18 No.6

          Completely decomposed granite (CDG) with different structures shows different patterns in deformation and failure as brittle fracture or as plastic creep in triaxial test. It is necessary to monitor and to compare the fabric changes due to stress in real time during test. By means of the computerized tomography (CT) technique for monitoring deformation and failure of soils in real time without suspending the mechanical test and disturbing samples, a newly designed triaxial test machine was used to test CDG from Hong Kong in a procedure of saturation, consolidation and undrained condition. It was found that CT data (images and values) depicts the failure patterns as brittle fracture or as plastic creep at 3-D in real time. The results were concordant with stress–strain curves and observation of the appearance of samples before and after tests.

        • KCI등재

          Characteristics and formation mode of salt-bearing series in typical rift valley basin, eastern China

          Yanjun Zhao,Chenglin Liu,Hua Zhang,Licheng Wang,Baokun Liu,Fenglin Lv 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.1

          The Shulu Sag is a typical rift valley basin in easternChina, where the formation mechanism of Cenozoic salt-bearingseries has been poorly understood. In this paper, petrologic analysis,X-ray powder Diffraction (XRD) analysis and the analysis ofhalite ion concentrations of the first member of the Shahejie Formationfrom two drilling cores were conducted to interpret theformation mechanism of these salt-bearing series in Shulu Sag. Theresults indicated that the salt-bearing series is mainly composed of calcilutiteor mudstone at top and bottom, and anhydrite-bearing haliteand thin interbeds of salt-bearing calcilutite and dark grey shale inthe middle part. These thin interbeds with porphyritic or petalshapedglauberite crystals or some thinner dark grey shale interbedsseparated halites into several members with the average thicknessof only 9~12 cm in the two drilling holes. This typical rhythmicpattern due to frequent alternation of concentration was evidencedby the variation of chemical composition and hydrogen isotopes ofhalite fluid inclusions. The presence of large number of primaryfluid inclusions within chevron crystals and vertically orientedbottom-growth crystals showed that the halite were precipitated inshallow water (<60 cm). These features are direct evidence for thisfrequent alternation of dissolution and concentration of brines andterrigenous detrital-chemical shallow-water sedimentary model ofthese small rift-valley basins in eastern China.

        • KCI등재

          Enhanced Production of Human Epidermal Growth Factor under Control of the phoA Promoter by Acetate-tolerant Escherichia coli DB15 in a Chemically Defined Medium

          Yanjun Zhang,Zhimin Li,Qin Ye 한국생물공학회 2010 Biotechnology and Bioprocess Engineering Vol.15 No.4

          The phoA expression system is an efficient one and is successfully used in foreign gene expression. In a previous study, it was found that pH during the expression phase had a significant effect on extracellular hEGF production under control of the phoA promoter by Escherichia coli DA19, an acetate-tolerant strain of E. coli DH5α, in a chemically defined medium, but the level of hEGF production was only 75.5 mg/L. E. coli DB15 is another acetate tolerant mutant of DH5α. In the present study, production of hEGF under control of the phoA promoter by DB15 was further investigated. When transition from the growth phase,where phosphate was abundant, to the expression phase where phosphate was limited, was performed based on cell density, the extracellular hEGF reached 165 mg/L, twice that when transition was based on dissolved oxygen. Furthermore, adding 0.22 g/L of CaCl2 during the growth phase, further increased hEGF production to 228 mg/L,which is 3-fold the level produced by DA19 (pAET-8)cultured in the same medium.

        • KCI등재

          From in situ stress and discontinuities to the strength of granites: comparison and case study

          Yanjun Shang,박형동,Guangxiang Yuan,Yuanchun Sun,Qian Gao 한국지질과학협의회 2008 Geosciences Journal Vol.12 No.4

          The distinctive weathering profile and discontinuity of granites, dipping slightly at shallow depths and steeply in larger depths, are regarded as being due to their physical and geo-mechanical properties. This paper compares vertical stress (Sv) and overlain weight (h) drawn from different kinds of in situ stress measurements, as well as coefficients of lateral stress. Stress trends are connected with discontinuities (joints and dykes), which reveal their relationships in space and dip angles of joints and dykes are compared in space, together with shear plane plunges and the strength of rocks from laboratory tests. As a result, it was found that the relict structural geo-stress contributes to maximum horizontal stress, especially at shallow depths. The most common feature is the high coefficient of lateral stress, which is mostly attributed to unloading in shallow depths and stress concentration at a certain depth after the erosion of overlain beds and the exposure of granites at the ground surface. Therefore, the weathering profiles and weathered capsule of granites could be interpreted from this viewpoint. One of the two main features of this paper is the connection of the extraordinary values of the lateral coefficient of in situ stress with unloading and the typical weathering profile at shallow depths. Another is the comparison of the shear stress and strength from in situ and laboratory tests, with a series of data from the same location and depth. The distinctive weathering profile and discontinuity of granites, dipping slightly at shallow depths and steeply in larger depths, are regarded as being due to their physical and geo-mechanical properties. This paper compares vertical stress (Sv) and overlain weight (h) drawn from different kinds of in situ stress measurements, as well as coefficients of lateral stress. Stress trends are connected with discontinuities (joints and dykes), which reveal their relationships in space and dip angles of joints and dykes are compared in space, together with shear plane plunges and the strength of rocks from laboratory tests. As a result, it was found that the relict structural geo-stress contributes to maximum horizontal stress, especially at shallow depths. The most common feature is the high coefficient of lateral stress, which is mostly attributed to unloading in shallow depths and stress concentration at a certain depth after the erosion of overlain beds and the exposure of granites at the ground surface. Therefore, the weathering profiles and weathered capsule of granites could be interpreted from this viewpoint. One of the two main features of this paper is the connection of the extraordinary values of the lateral coefficient of in situ stress with unloading and the typical weathering profile at shallow depths. Another is the comparison of the shear stress and strength from in situ and laboratory tests, with a series of data from the same location and depth.

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