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        Stochastic Bounded Consensus Tracking of Second-Order Multi-Agent Systems with Measurement Noises based on Sampled-Data with Small Sampling Delay

        Zhihai Wu,Li Peng,Linbo Xie,Jiwei Wen 제어·로봇·시스템학회 2014 International Journal of Control, Automation, and Vol.12 No.1

        This paper is devoted to the stochastic bounded consensus tracking problems of second-order multi-agent systems, where the control input of each agent can only use the information measured at the sampling instants from its neighbors or the virtual leader with a time-varying reference state, the measurements are corrupted by random noises, and the signal sampling process induces the small sampling delay. The augmented matrix method, the probability limit theory and some other techniques are employed to derive the necessary and sufficient conditions guaranteeing the mean square bounded consensus tracking. We show that the convergence of the proposed protocol simultaneously depends on the constant feedback gains, the network topology, the sampled period and the sampling delay, and that the static consensus tracking error depends on not only the above mentioned factors, but also the noise intensity and the upper bound of the velocity and the acceleration of the virtual leader. The obtained results cover no sampling delay as its one special case. Simulations are provided to demonstrate the effectiveness of the theoretical results.

      • KCI등재

        WLSD: A Perceptual Stimulus Model Based Shape Descriptor

        ( Jiatong Li ),( Baojun Zhao ),( Linbo Tang ),( Chenwei Deng ),( Lu Han ),( Jinghui Wu ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.12

        Motivated by the Weber`s Law, this paper proposes an efficient and robust shape descriptor based on the perceptual stimulus model, called Weber`s Law Shape Descriptor (WLSD). It is based on the theory that human perception of a pattern depends not only on the change of stimulus intensity, but also on the original stimulus intensity. Invariant to scale and rotation is the intrinsic properties of WLSD. As a global shape descriptor, WLSD has far lower computation complexity while is as discriminative as state-of-art shape descriptors. Experimental results demonstrate the strong capability of the proposed method in handling shape retrieval.

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        Dewatering of a 32.55 m Deep Foundation Pit in MAMA Under Leakage Risk Conditions

        Jianxiu Wang,Xiaotian Liu,Jiaxing Liu,Linbo Wu,Qingfeng Guo,Qian Yang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

        A 2,250 mm whirlpool foundation pit is located in Donghai Island, Zhanjiang City, Guangdong Province, China. The layers of theisland are composed of multi-aquifers and multi-aquitards (MAMA). The aquifers are intersected by partial aquitard lenses. A largeconfined aquifer is frequently interbedded and separated into several sub-confined aquifers by partial aquitards. In the 2,250 mmfoundation pit, the water level of two confined aquifers was reduced to satisfy excavation requirements and prevent water inrush. Construction of the 32.55 m deep foundation pit encountered MAMA and potential defects of the diaphragm wall. The pumpingwells in the second confined aquifer were used to reduce the water level to ensure the safety of bottom excavation. The pumpingwells in the first confined aquifer were used to reduce the water level under emergency conditions to prevent potential water inrushand piping from the defects of the diaphragm wall. Field pumping tests and numerical simulations were performed to determine therisk of leakage and verify the capability of the pumping wells to reduce the water level. Quicksand occurred during shallowexcavation because of leakage although the confined aquifer had been cut off and pumped for a long time. Three pumping wells wereinstalled to reduce the water level. When the foundation pit was excavated to a depth of 24 m, water inrush occurred at the middle ofthe pit bottom although the water level of the dewatered aquifer had been reduced to below the excavation face. A 90 m deepborehole was found where the underlying confined aquifer below the first aquifer induced the water inrush. Although the upper waterlevel was reduced, the high water level in the deep part still induced water inrush. The pumping wells in the second aquifer were allopened, and the water level of the underlying confined aquifer was reduced. After the water level was reduced to below the pitbottom, the borehole was filled, and the water inrush stopped. However, water inrush occurred on the cracks of the diaphragm wall aspredicted. The pre-installed pumping wells were opened to control the water inrush. The deepest foundation pit on the island wasconstructed successfully after dealing with the water inrush and leakages.

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        Research on Brownout Characteristics of Helicopter Approach Flight Based on the Unsteady Momentum Source Model Coupled with DEM

        Qing Li,Yong-jie Shi,Guohua Xu,Linbo Wu 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2

        In order to numerically simulate the brownout phenomenon encountered by helicopters in a sandy environment, a new coupled method is established that takes into account the accuracy and efficiency of calculation. In this method, the computational fluid dynamics (CFD) method based on the unsteady momentum source model and the discrete-element method (DEM) based on discrete dynamics are coupled to deal with this two-phase flow problem. In order to verify the validity of the calculation method, the results were compared with available real aircraft brownout flight test results, the results of the RANS method based on overset grids, and the results of the viscous vortex particle method (VVPM). Then, by applying the established method, a numerical simulation of the brownout phenomenon of a typical helicopter approach maneuver was carried out. The results show that after maneuvering descent changes into near-ground forward flight, the sand cloud that is generated is widely distributed and has a lower concentration near the fuselage, and the overall particle saltation characteristics are similar to those at higher forward flight speeds. This means that the phenomenon of brownout is reduced for a certain period of time in the approach chosen in this paper.

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