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RISS 인기검색어
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- 저자 : Yiqun Yang (검색결과 5 건)
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YIQUN DENG,BIN YANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.2
In this paper, we present a facile process for preparing 3 mol.% yttria-fully-stabilized zirconia (3Y-FSZ) nanopowders by molten salts/coprecipitation method at low temperature. By this method, precursor powders in molten salts have a high reactivity and diffusivity, and react easily and completely, which can greatly reduce the synthesis temperature. Furthermore, the synthesis procedure involves neither mechanical mixing nor repeated grinding and thus ultrapure nanopowders with a better uniformity and fewer agglomerates can be obtained. The results illustrated that 3Y-FSZ nanopowders particle diameters ranging from 7 nm to 10 nm were successfully synthesized at 500°C.
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Yiqun Wang,Yongpan Liu,Cong Wang,Zewei Li,Xiao Sheng,Hyung Gyu Lee,Naehyuck Chang,Huazhong Yang IEEE 2016 IEEE transactions on computer-aided design of inte Vol.35 No.2
<P>Energy harvesting from natural environment gives range of benefits for the Internet of things. Scavenging energy from photovoltaic (PV) cells is one of the most practical solutions in terms of power density among existing energy harvesting sources. PV power systems mandate the maximum power point tracking (MPPT) to scavenge the maximum possible solar energy. In general, a switching-mode power converter, an MPPT charger, controls the charging current to the energy storage element (a battery or equivalent), and the energy storage element provides power to the load device. The mismatch between the maximum power point (MPP) current and the load current is managed by the energy storage element. However, such architecture causes significant energy loss (typically over 20%) and a significant weight/volume and a high cost due to the cascaded power converters and the energy storage element. This paper pioneers a converter-less PV power system with the MPPT that directly supplies power to the load without the power converters or the energy storage element. The proposed system uses a nonvolatile microprocessor to enable an extremely fine-grain dynamic power management in a few hundred microseconds. This makes it possible to match the load current with the MPP current. We present detailed modeling, simulation, and optimization of the proposed energy harvesting system including the radio frequency transceiver. Experiments show that the proposed setup achieves an 87.1% of overall system efficiency during a day, 30.6% higher than the conventional MPPT methods in actual measurements, and thus a significantly higher duty cycle under a weak solar irradiance.</P>
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Winding strategy of driving cable based on dynamic analysis of deployment for deployable antennas
Yiqun Zhang,Dongwu Yang,Zihan Sun,Na Li,Jianghua Du 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.11
An optimization method for the winding strategy of the driving cable is proposed based on a dynamic analysis of the AstroMesh antenna deployment. First, considering the effects of the cable net and friction, the driving force for deployment is deduced according to energy conservation. Thereafter, an optimization model is constructed, with the objective of minimum deployment driving power, using design variables consisting of control parameters of the winding length curve of the driving cable; this curve is described by the Bezier curve. Moreover, corresponding to the winding process of the driving cable before and after optimization, deployment experiments for a 2-m aperture deployable antenna prototype are conducted. Finally, the validity and rationality of the optimization method are verified by comparing the simulation and experimental results.
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Naigang Hu,Yiqun Zhang,Guigeng Yang,Dongwu Yang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8
Various uncertainties existing in the manufacturing process, such as imperfect cable lengths and uncertain boundary node locations, will unavoidably deteriorate the shape precision of cable-network antennas. In this paper, an adaptive Kriging-based method is developed to investigate the global sensitivity of uncertain parameters and discover the influential factors. Existing strategies in literature usually use relative error of function values to measure the metamodel accuracy and then to determine when the sequential sampling process should be stopped. However, these indicators are mostly developed based on function values, not the sensitivity indices. Therefore, it is difficult to determine how small the indicators should be for efficiently defining an accurate metamodel for sensitivity analysis. In this paper, a straightforward sensitivity-based indicator is developed to measure the metamodel accuracy, which is defined as the weighted average of absolute errors of sensitivity values between two successive iterations. A use-controlled threshold, combined with the new indicator, can provide an automatic stopping criterion for the adaptive metamodel building process. The proposed method can provide a uniform framework to detect the convergence status effectively for problems with different uncertainties and dimensions. A numerical example and two cable-network antenna examples considering different manufacturing uncertainties are illustrated to validate the new method.
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Life Prediction of Hydraulic Concrete Based on Grey Residual Markov Model
Li Gong,Xuelei Gong,Ying Liang,Bingzong Zhang,Yiqun Yang 한국정보처리학회 2022 Journal of information processing systems Vol.18 No.4
Hydraulic concrete buildings in the northwest of China are often subject to the combined effects of lowtemperaturefrost damage, during drying and wetting cycles, and salt erosion, so the study of concretedeterioration prediction is of major importance. The prediction model of the relative dynamic elastic modulus(RDEM) of four different kinds of modified concrete under the special environment in the northwest of Chinawas established using Grey residual Markov theory. Based on the available test data, modified values of thedynamic elastic modulus were obtained based on the Grey GM(1,1) model and the residual GM(1,1) model,combined with the Markov sign correction, and the dynamic elastic modulus of concrete was predicted. Thecomputational analysis showed that the maximum relative error of the corrected dynamic elastic modulus wassignificantly reduced, from 1.599% to 0.270% for the BS2 group. The analysis error showed that the modelwas more adjusted to the concrete mixed with fly ash and mineral powder, and its calculation error wassignificantly lower than that of the rest of the groups. The analysis of the data for each group proved that themodel could predict the loss of dynamic elastic modulus of the deterioration of the concrete effectively, as wellas the number of cycles when the concrete reached the damaged state.
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