Uncertainty Analysis of Dynamic Thermal Rating of Overhead Transmission Line

Zhou, Xing,Wang, Yanling,Zhou, Xiaofeng,Tao, Weihua,Niu, Zhiqiang,Qu, Ailing Korea Information Processing Society 2019 Journal of information processing systems Vol.15 No.2

Dynamic thermal rating of the overhead transmission lines is affected by many uncertain factors. The ambient temperature, wind speed and wind direction are the main sources of uncertainty. Measurement uncertainty is an important parameter to evaluate the reliability of measurement results. This paper presents the uncertainty analysis based on Monte Carlo. On the basis of establishing the mathematical model and setting the probability density function of the input parameter value, the probability density function of the output value is determined by probability distribution random sampling. Through the calculation and analysis of the transient thermal balance equation and the steady- state thermal balance equation, the steady-state current carrying capacity, the transient current carrying capacity, the standard uncertainty and the probability distribution of the minimum and maximum values of the conductor under 95% confidence interval are obtained. The simulation results indicate that Monte Carlo method can decrease the computational complexity, speed up the calculation, and increase the validity and reliability of the uncertainty evaluation.

A Gray-Box Parameters Identification Method of Voltage Source Converter Using Vector Fitting Algorithm

Weihua Zhou,Yanbo Wangy,Zhe Chen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper presents a vector fitting (VF) algorithmbased gray-box structure and parameters identification method for voltage source converter(VSC). Terminal impedance frequency responses of VSC is first measured by frequency scanning method. Then, these impedance frequency responses are fitted by a polynomial transfer function using VF algorithm. Finally, the theoretical terminal impedance formulas of possible control structures are compared with the fitted transfer function. The actual control structure can be selected, and the actual internal parameters can be identified. Simulation results are given to validate effectiveness of the proposed method. The proposed gray-box method can identify both the circuit and controller information even if no internal information of the VSC is provided by vendors due to industrial confidence. In addition, the effect of measurement noise on parameters identification accuracy can be mitigated by increasing the order of the fitted transfer function.

Uncertainty Analysis of Dynamic Thermal Rating of Overhead Transmission Line

Xing Zhou,Yanling Wang,Xiaofeng Zhou,Weihua Tao,Zhiqiang Niu,Ailing Qu 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.2

Dynamic thermal rating of the overhead transmission lines is affected by many uncertain factors. The ambienttemperature, wind speed and wind direction are the main sources of uncertainty. Measurement uncertainty isan important parameter to evaluate the reliability of measurement results. This paper presents the uncertaintyanalysis based on Monte Carlo. On the basis of establishing the mathematical model and setting the probabilitydensity function of the input parameter value, the probability density function of the output value is determinedby probability distribution random sampling. Through the calculation and analysis of the transient thermalbalance equation and the steady- state thermal balance equation, the steady-state current carrying capacity, thetransient current carrying capacity, the standard uncertainty and the probability distribution of the minimumand maximum values of the conductor under 95% confidence interval are obtained. The simulation resultsindicate that Monte Carlo method can decrease the computational complexity, speed up the calculation, andincrease the validity and reliability of the uncertainty evaluation.

Postthrombolytic Antiplatelet Use for Patients with Intercerebral Hemorrhage without Extensive Parenchymal Involvement Does Not Worsen Outcome

Weihua Jia,Lichun Zhou,Xiaoling Liao,Yuesong Pan,Yongjun Wang 대한신경과학회 2015 Journal of Clinical Neurology Vol.11 No.4

Background and Purpose It is unclear whether postthrombolytic antiplatelet (AP) therapy after thrombolytic-related hemorrhage without extensive parenchymal involvement (THEPI) afects the clinical outcome. Tis study explored whether AP administration in patients with THEPI afects short- and long-term outcomes. Methods All of the data for this study were collected from the Trombolysis Implementation and Monitor of Acute Ischemic Stroke in China (TIMS-China) registry. Patients with THEPI were assigned to either the AP (AP therapy should be commenced 24 h afer intravenous thrombolysis) or AP-naïve groups. THEPI was defned according to European-Australasian Acute Stroke Study II criteria. Te 90-day functional outcome, 7-day National Institutes of Health Stroke Scale (NIHSS) score, and 7-day and 90-day mortalities were compared between the AP and AP-naïve groups. Logistic regression analysis was used to evaluate the effects of AP therapy on the short- and long-term clinical outcomes. Results Of the 928 patients enrolled from those in the TIMS-China registry (n=1,440), 89 (9.6%) had nonsymptomatic intracerebral hemorrhage (ICH) within 24–36 h afer thrombolysis; 33 (37%) of these patients were given AP therapy (AP group) and 56 (63%) were not (APnaïve group). No significant differences were found for the risk of 7-day aggravated ICH (p=0.998), 7-day NIHSS score (p=0.5491), 7-day mortality [odds ratio (OR)=3.427; 95% confdence interval (95% CI)=0.344–34.160; p=0.294], 90-day mortality (OR=0.788, 95% CI=0.154– 4.040, p=0.775), or modifed Rankin score 5 or 6 at 90-days (OR=1.108, 95% CI=0.249–4.928, p=0.893) between the AP and AP-naïve groups afer THEPI. Conclusions Early administration of postthrombolytic AP therapy afer THEPI does not worsen either the short- or long-term outcome. AP therapy may be a reasonable treatment option for patients with THEPI to reduce the risk of ischemic stroke recurrence.

Antitumor Activities and Immunomodulatory Effects of Ginseng Neutral Polysaccharides in Combination with 5-Fluorouracil

Weihua Ni,Xu Zhang,Bo Wang,Yan Chen,Han Han,Yuying Fan,Yifa Zhou,Guihua Tai 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.2

A neutral polysaccharide fraction (WGPN) prepared from Panax ginseng C.A. Meyer by hot water extraction and DEAE-cellulose chromatography was tested for its anticancer activity alone and in combination with 5-fluorouracil (5-FU) in Sarcoma-180 (S180) tumor-bearing mice by intragastric administration. WGPN alone inhibited S180 tumor growth in a bell-shaped dose–response curve, and the combination with 5-FU showed a synergistic effect. Studies of various immunological activities in S180-bearing mice revealed that WGPN stimulated the proliferation of lymphocytes, increased natural killer cell cytotoxicity, enhanced the phagocytosis and nitric oxide production by macrophages, and increased the level of tumor necrosis factor-α in serum. In combination with 5-FU, WGPN mitigated damage to the immune system caused by 5-FU in S180-bearing mice. These results suggest that WGPN might be a potential adjuvant for chemotherapeutic drugs.

Effect of 20 mg/day Atorvastatin: Recurrent Stroke Survey in Chinese Ischemic Stroke Patients with Prior Intracranial Hemorrhage

Weihua Jia,Lichun Zhou 대한신경과학회 2013 Journal of Clinical Neurology Vol.9 No.3

Background and Purpose Treatment with atorvastatin (80 mg) in stroke secondary prevention for patients with prior intracranial hemorrhage (ICH) has been associated with a higher frequency of ICH. The aim of this study was to determine whether 20 mg/day atorvastatin is linked to stroke recurrence in Chinese ischemic stroke patients with prior ICH. Methods A single-center retrospective cohort study was conducted, involving 354 cases from 395 Chinese in-patients who had ischemic stroke with prior ICH history in Beijing Chaoyang hospital from May 1, 2005 to October 31, 2010. Survivors were followed by telephone interviews for 12-60 months. Cox regression and Kaplan-Meier plot analysis were used to evaluate the effect of 20 mg/day atorvastatin on cerebral infarction and ICH recurrence. Results The overall rate of stroke recurrence was lower in the 20 mg/day atorvastatin group(χ2=6.687, p=0.022) than in the control group. The incidence of cerebral hemorrhage was increased by 20 mg/day atorvastatin for ischemic stroke cases with a history of ICH compared tothose not receiving the drug, but the difference was not significant [hazard ratio (HR)=1.097,95% confidence interval (CI)=0.800-1.243, p=0.980]. The incidence of ischemic stroke recurrence was significantly reduced in subjects receiving atorvastatin (HR=0.723, 95% CI=0.578-0.862, p=0.028), and the mean duration of all stroke recurrences was significantly prolonged,compared with those not exposed to the drug (χ2=5.351, p=0.021). The mean duration of ICH recurrence appeared to have shortened with atorvastatin, but the difference was not significant (χ2=0.680, p=0.480), and the mean duration of cerebral infarction recurrence was significantly prolonged (χ2=8.312, p=0.004). Conclusions Medication with 20 mg/day atorvastatin may be beneficial in reducing ischemic stroke recurrence in ischemic stroke patients with a history of ICH and is not associated with an increased risk of ICH recurrence.

AC-SPWM-Cycloconverter Based on An Extended Chopper Scheme

Qianzhi Zhou,Weihua Wu,Jianwei Lin 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

A novel cycloconverter based on chopper scheme is proposed, which is entirely different from the former cycloconverters based on phase-shift control, so leading to higher power factor than that of the latter, also in price of minimum power device numuber. Two kinds methods are derived for determining the relationships between Duty-Cycle and other parameters by means of different Area-Equivalent criteria. The single and 3-phase topologies and the ac-SPWM control strategy are introduced, which can realize variable frequency and variable voltage operation at the same time. Also some key simulations and experimental results show the validity of the conversion as well as the applicable prospect of the new cycloconverter-category.

Interactive Effects of Ultraviolet Radiation and Dissolved Organic Carbon on Phytoplankton Growth and Photosynthesis in Sanya Bay, Northern South China Sea

Jianzu Liao,Weihua Zhou,Jie Xu,Xiangcheng Yuan,Yuxian Liang,Yajuan Guo,Hui Huang,Sheng Liu,Aimin Long 한국해양과학기술원 2019 Ocean science journal Vol.54 No.4

The effects of a simulated climate change scenario, i.e., increased ultraviolet radiation (UVR) and dissolved organic carbon (DOC), on the growth and photosynthesis of tropical coastal phytoplankton were evaluated in Sanya Bay, northern South China Sea, in summer. Microcosm experiments were conducted at two contrasting stations (Stns S1 and S2) with three different UVR treatments and two DOC addition treatments. Our results showed that natural sunlight UVR or increased UV-B did not affect phytoplankton biomass and primary production. However, increased UV-B significantly decreased the proportion of picophytoplankton and the efficiency of carbon fixation at Stn S2. DOC enhancement caused negative effects on primary production under natural sunlight UVR only at Stn S1. Interactive effects of UVR and DOC addition on phytoplankton biomass and primary production were detected at Stn S1, due to the negative effects of DOC being eliminated under the increased UV-B condition. The lack of interactive effects at Stn S2 were likely due to the differences with Stn S1 in terms of light acclimation and biological interaction. In summary, this future climate change scenario will probably not affect the photosynthetic CO2 fixation and biomass of natural phytoplankton in Sanya Bay.

Phosphorus balance in typical rainfield of black soil region in northeast China

Cailian Hao,Weihua Xiao,Yuyan Zhou,Ying Wang 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.4

This research aimed to evaluate the phosphorus balances at field level in black Soil Region in northeast China, which is one of three black soil regions in world and is one of the most important agricultural production regions in China. By using the soil nutrient balance method, the phosphorus balances were calculated for 11 fields representing four tillage practices [Conventional tillage system (TCT), No-tillage with straw covered system (TNT), Reduced tillage system (TRT) and Contour tillage system (TTT)], three vegetation recovery measures [Conventional tillage management (TCT), Vegetation recovery management (VVR) and Bare management (VB)], three land’s slope (3°, 5° and 7°) and three land's length (20 m, 40 m and 60 m). Processes quantified included mineral fertilizer, organic matter and atmospheric deposition (inputs) and harvested products, surface runoff and soil erosion (outputs). Measurements of phosphorus flows were made in the 11 fields and the phosphorous balance of various experiment plots was assessed in a quantified manner in 2013. Moreover, the rainfall, the tillage practices, the flow output and sand output of experiment plots of different slope gradients and lengths and the relations between dissolved phosphorus and particulate phosphorus of 2013 were also analyzed. Results shows that VVR and VB are phosphorus deficiency and the others are phosphorus surplus. Rainfall are the main sources of phosphorus inputs for VVR and VB among the 11 experiment plots, while chemical fertilizers are the main sources for the other 9 zones. Crop harvest and soil erosion are the main outputs of phosphorus in the 11 zones, except in VVR and VB. This research provides support to the farmland nutrient management and the prevention and control of non-point source pollution within the region.

A simple data assimilation method to improve atmospheric dispersion based on Lagrangian puff model

Li, Ke,Chen, Weihua,Liang, Manchun,Zhou, Jianqiu,Wang, Yunfu,He, Shuijun,Yang, Jie,Yang, Dandan,Shen, Hongmin,Wang, Xiangwei Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7

To model the atmospheric dispersion of radionuclides released from nuclear accident is very important for nuclear emergency. But the uncertainty of model parameters, such as source term and meteorological data, may significantly affect the prediction accuracy. Data assimilation (DA) is usually used to improve the model prediction with the measurements. The paper proposed a parameter bias transformation method combined with Lagrangian puff model to perform DA. The method uses the transformation of coordinates to approximate the effect of parameters bias. The uncertainty of four model parameters is considered in the paper: release rate, wind speed, wind direction and plume height. And particle swarm optimization is used for searching the optimal parameters. Twin experiment and Kincaid experiment are used to evaluate the performance of the proposed method. The results show that the proposed method can effectively increase the reliability of model prediction and estimate the parameters. It has the advantage of clear concept and simple calculation. It will be useful for improving the result of atmospheric dispersion model at the early stage of nuclear emergency.