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Search Results: 1 - 10 of 22915 matches for " Jiahang Yuan "
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Research on the Mechanism of Power Supply Interruption Risk for Important User Based on Interpretative Structural Model  [PDF]
Wei Dong, Cunbin Li, Jiahang Yuan
Journal of Service Science and Management (JSSM) , 2017, DOI: 10.4236/jssm.2017.106041
Abstract: In order to effectively manage the safety risk for power supply to important power user, and increase power supply safety and reliability, interpretative structural model is used to explore the generation mechanism of power supply & utility system safety risk and the risk element transfer path. Based on analysis of risk element, interpretative structural model of power supply risk generation mechanism is constructed. This model analyzes the hierarchical relationship between each risk element and transmission path, and then reveals the power safety risk generation mechanism, identifies the key risk element to be supervised by power supply companies & users, and helps the power supply and utility company to improve the power safety management.
Obtaining digital elevation data in different terrain and physiognomy regions with spaceborne InSAR and its application analysis
Xinjian Shan,Xiaoyu Song,Jiahang Liu,Changlin Wang
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9195
Abstract: Synthetic Aperture Radar Interferometry (for short, InSAR) is a new kind of earth observation technology, which has obtained great development in recent ten years and has a great development potential and successful future. In this note, three typical regions with different physiognomies and terrains have been selected as study regions to extract their Digital Elevation Model (DEMs). Compared with the existing 1: 250000 DEM and by analyzing their results, we have obtained its accuracy and applicable scopes. The results show that in the region (plains, mountains or highlands) with dry surface and sparse vegetation, because of the better correlatability of images, the DEM obtained by InSAR is evidently better than the existing 1: 250000 DEM and the accuracy can reach 4–6 m; in the thick-vegetation-covering region, correlatability between images descends and the accuracy of InSAR DEM can only reach about 30 m worse than its existing 1: 250000 DEM; in the middle covering field, the accuracy of InSAR DEM with tandem images can reach about 10 m as well; yet in water space, such as lakes and rivers, InSAR DEM shows a big error since there is only quite faint signal reflected to the sensor. Then the conclusion has been got: in the west of China, where it has a lack-vegetation and dry ground, InSAR is completely feasible to be applied to such a complicated nature environment region.
Obtaining digital elevation data in different terrain and physiognomy regions with spaceborne InSAR and its application analysis

SHAN Xinjian,SONG Xiaoyu,LIU Jiahang,WANG Changlin,

科学通报(英文版) , 2002,
Abstract: Synthetic Aperture Radar Interferometry (for short, InSAR) is a new kind of earth observation technology, which has obtained great development in recent ten years and has a great development potential and successful future. In this note, three typical regions with different physiognomies and terrains have been selected as study regions to extract their Digital Elevation Model (DEMs). Compared with the existing 1: 250000 DEM and by analyzing their results, we have obtained its accuracy and applicable scopes. The results show that in the region (plains, mountains or highlands) with dry surface and sparse vegetation, because of the better correlatability of images, the DEM obtained by InSAR is evidently better than the existing 1: 250000 DEM and the accuracy can reach 4–6 m; in the thick-vegetation-covering region, correlatability between images descends and the accuracy of InSAR DEM can only reach about 30 m worse than its existing 1: 250000 DEM; in the middle covering field, the accuracy of InSAR DEM with tandem images can reach about 10 m as well; yet in water space, such as lakes and rivers, InSAR DEM shows a big error since there is only quite faint signal reflected to the sensor. Then the conclusion has been got: in the west of China, where it has a lack-vegetation and dry ground, InSAR is completely feasible to be applied to such a complicated nature environment region.
Continuous simulation of hypothetical physics processes with multiple free parameters
Jiahang Zhong,Run-Sheng Huang,Shih-Chang Lee
Physics , 2011, DOI: 10.1016/j.nima.2012.03.026
Abstract: We propose a new approach to simulate hypothetical physics processes which are defined by multiple free parameters. Compared to the conventional grid-scan approach, the new method can produce accurate estimations of the detector acceptance and signal event yields continuously over the parameter space with fewer simulation events. The performance of this method is illustrated with two realistic cases.
A program for the Bayesian Neural Network in the ROOT framework
Jiahang Zhong,Run-Sheng Huang,Shih-Chang Lee
Physics , 2011, DOI: 10.1016/j.cpc.2011.07.019
Abstract: We present a Bayesian Neural Network algorithm implemented in the TMVA package, within the ROOT framework. Comparing to the conventional utilization of Neural Network as discriminator, this new implementation has more advantages as a non-parametric regression tool, particularly for fitting probabilities. It provides functionalities including cost function selection, complexity control and uncertainty estimation. An example of such application in High Energy Physics is shown. The algorithm is available with ROOT release later than 5.29.
非自治广义Birkhoff 系统的半负定矩阵梯度系统表示
A semi-negative definite matrix gradient system representation for non-autonomous generalized Birkhoff system

王嘉航,张毅
WANG Jiahang
,ZHANG Yi

- , 2018,
Abstract: 研究非自治广义Birkhoff 系统的半负定矩阵梯度系统表示。给出了非自治广义Birkhoff 系统成为半负定矩阵梯度系统的条件,利用半负定矩阵梯度系统的性质来研究解的稳定性。举例说明结果的应用
Optimization of Waste Gate Drive Circuit of Two-Stage Turbocharging System
Optimization of Waste Gate Drive Circuit of Two-Stage Turbocharging System

Fujun Zhang,Jiahang Chang,Tao Cui,Meng Xia
- , 2017, DOI: 10.15918/j.jbit1004-0579.201726.0310
Abstract: A two stage turbocharging control system was proposed, in which the pressure regulator valve with a close-loop pressure adjusting function instead of a high speed on-off solenoid valve, is used as a driving mechanism of waste gate. A digital-analog (DA)conversion circuit based on pulse width modulation (PWM) generates one analog voltage signal required by the pressure regulating valve control. The principle of the DA conversion circuit was analyzed, meanwhile, the performance of the conversion circuit was improved by adopting a speed-up capacitor, which helps to increase the stability and responsiveness of the control voltage generated by the conversion circuit; the structure parameters of the circuit was optimized by simulation. After the optimization, the ripple wave of circuit output voltage was kept within 16.mV under the 12.bit conversion accuracy, the conversion time of the circuit could be reduced to 4.ms. The engine bench test show that the turbocharging boost pressure control system which adopted the circuit had a rather good stable control accuracy(the steady state within 0.8%) and dynamic response(the regulation time is less than 4.s).
A two stage turbocharging control system was proposed, in which the pressure regulator valve with a close-loop pressure adjusting function instead of a high speed on-off solenoid valve, is used as a driving mechanism of waste gate. A digital-analog (DA)conversion circuit based on pulse width modulation (PWM) generates one analog voltage signal required by the pressure regulating valve control. The principle of the DA conversion circuit was analyzed, meanwhile, the performance of the conversion circuit was improved by adopting a speed-up capacitor, which helps to increase the stability and responsiveness of the control voltage generated by the conversion circuit; the structure parameters of the circuit was optimized by simulation. After the optimization, the ripple wave of circuit output voltage was kept within 16.mV under the 12.bit conversion accuracy, the conversion time of the circuit could be reduced to 4.ms. The engine bench test show that the turbocharging boost pressure control system which adopted the circuit had a rather good stable control accuracy(the steady state within 0.8%) and dynamic response(the regulation time is less than 4.s).
Non-Negativity Preserving Numerical Algorithms for Problems in Mathematical Finance  [PDF]
Yuan Yuan
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.93024
Abstract:
We give a study result to analyze a rather different, semi-analytical numerical algorithms based on splitting-step methods with their applications to mathematical finance. As certain subsistent numerical schemes may fail due to producing negative values for financial variables which require non-negativity preserving. These algorithms which we are analyzing preserve not only the non-negativity, but also the character of boundaries (natural, reflecting, absorbing, etc.). The derivatives of the CIR process and the Heston model are being extensively studied. Beyond plain vanilla European options, we creatively apply our splitting-step methods to a path-dependent option valuation. We compare our algorithms to a class of numerical schemes based on Euler discretization which are prevalent currently. The comparisons are given with respect to both accuracy and computational time for the European call option under the CIR model whereas with respect to convergence rate for the path-dependent option under the CIR model and the European call option under the Heston model.
Research on Evaluating Indices System for IT in I-Campus
高校信息化评价指标体系研究

Qin Jiahang,Xu Xin,Su Xinning,
秦嘉杭
,许鑫,苏新宁

现代图书情报技术 , 2006,
Abstract: This paper analyses evaluating indices system for IT in informatization campus. According to the evaluating indices system for IT in enterprise, we construct this evaluating indices system for IT in I-Campus, including essential indices and review indices.
Administration of Simvastatin after Kainic Acid-Induced Status Epilepticus Restrains Chronic Temporal Lobe Epilepsy
Chuncheng Xie, Jiahang Sun, Weidong Qiao, Dunyue Lu, Lanlan Wei, Meng Na, Yuanyuan Song, Xiaohua Hou, Zhiguo Lin
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024966
Abstract: In this study, we examined the effect of chronic administration of simvastatin immediately after status epilepticus (SE) on rat brain with temporal lobe epilepsy (TLE). First, we evaluated cytokines expression at 3 days post KA-lesion in hippocampus and found that simvastatin-treatment suppressed lesion-induced expression of interleukin (IL)-1β and tumor necrosis factor-α (TNF-α). Further, we quantified reactive astrocytosis using glial fibrillary acidic protein (GFAP) staining and neuron loss using Nissl staining in hippocampus at 4–6 months after KA-lesion. We found that simvastatin suppressed reactive astrocytosis demonstrated by a significant decrease in GFAP-positive cells, and attenuated loss of pyramidal neurons in CA3 and interneurons in dentate hilar (DH). We next assessed aberrant mossy fiber sprouting (MFS) that is known to contribute to recurrence of spontaneous seizure in epileptic brain. In contrast to the robust MFS observed in saline-treated animals, the extent of MFS was restrained by simvastatin in epileptic rats. Attenuated MFS was related to decreased neuronal loss in CA3 and DH, which is possibly a mechanism underlying decreased hippocampal susceptibility in animal treated with simvastatin. Electronic encephalography (EEG) was recorded during 4 to 6 months after KA-lesion. The frequency of abnormal spikes in rats with simvastatin-treatment decreased significantly compared to the saline group. In summary, simvastatin treatment suppressed cytokines expression and reactive astrocytosis and decreased the frequency of discharges of epileptic brain, which might be due to the inhibition of MFS in DH. Our study suggests that simvastatin administration might be a possible intervention and promising strategy for preventing SE exacerbating to chronic epilepsy.
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