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Equalizing charger based on multi‑windings transformer and voltage‑doubler rectifiers
Chao Wu,Hong-kai Zhang,Shan-shou Li,Zheng-fei Li,Jia-rong Kan 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2
Energy storage batteries are currently composed of a large number of low-voltage battery cells. The state of charge of the cells is different due to the characteristic differences between cells. This causes some of the cells to be over-charged during charging and some of the cells to be over-discharging during discharging. To improve this phenomenon, this paper proposes a battery charger with an equalizing function that works during the charging and discharging processes. A performance comparison among the proposed charger and other similar topologies is carried out. The operational principle of the proposed strategy is analyzed and a control strategy with only a single voltage loop is proposed, which can guarantee two-stage charging. Experimental results show that the proposed charger can simultaneously achieve a high efficiency and the requirement of voltage equalization between cells.
Identifying Opinion Leader in the Internet Forum
Chao Wu,Chunlin Li,Wei Yan,Youlong Luo,Xijun Mao,Shumeng Du,Mingming Li 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.11
Opinion leader is an authority person who has great influence in BBS. Their linguistic behavior has a huge impact on net citizen’s behavior and thought. In this paper, we propose an algorithm called OLRA (Opinion Leader PageRank Algorithm) based on topic-field to identify opinion leaders in the Internet forum. In the algorithm the closeness degree factor and sentiment analyses are taken into consideration. Meanwhile, these two authority values are defined as the weight of links among users. The data is collected from a number of posts on Tianya forum which is a famous forum in China. In the experiment, the algorithm is compared with Interest-based PageRank algorithm, online time Algorithm, and Experience-based Algorithm, the result shows that the OLRA algorithm can identify opinion leaders than others in the Internet forum effectively.
High-Performance Supercapacitor based on the NaOH Activated D-Glucose Derived Carbon
Chao Wu,Jiang Xu,Jianning Ding,Ningyi Yuan,Pengtao Yan,Ruijun Zhang,Huihan Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.7
In this work, a mechanism of catalytic graphitization of D-glucose derived carbon during NaOH activation process is disclosed. The catalytic graphitization is caused by sodium atom, which is produced in the reaction between NaOH and carbon. Due to the combined action of activation and catalytic graphitization resulting from the NaOH, the activated D-glucose derived carbon behaves as a hierarchical micro- and meso-porous structure and has high electrical conductivity. Electrochemical investigations demonstrate that the activated sample exhibits an outstanding rate capability (70% of capacity retention even at a scan rate of 2 V s-1) and high specific capacitance (106 F g-1) in 6 M KOH aqueous electrolyte, which makes it a promising electrode material for high-power supercapacitors.
Monitoring Analysis and Numerical Simulation of the Land Subsidence in Linear Engineering Areas
Chao Jia,Xiao Yang,Jing Wu,Pengpeng Ding,Chao Bian 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7
Non-uniform land subsidence can cause subgrade deformation and threaten the safety of linear projects such as high-speed railways. The Lunan high-speed railway is taken as the research background. Combined with the hydrogeological and engineering geological conditions, the regional land subsidence is analyzed by the combined method of the differential interferometric synthetic aperture radar (D-InSAR) and small baseline subset interferometric synthetic aperture radar (SBAS-InSAR), which is verified by using precise leveling and GPS monitoring data. The accurate land subsidence analysis of large-scale linear engineering is realized. The distribution situation and change laws of land subsidence in linear engineering areas are revealed. Then, a three-dimensional coupled numerical model of land subsidence along a large-scale linear project is established by using the finite difference method. The spatial distribution characteristics of land subsidence in the linear engineering area are quantitatively analyzed and predicted. The main factors affecting land subsidence and the degree of land subsidence are discussed while keeping the pumping rate constant. The results show that: 1) The combined method of D-InSAR and SBAS-InSAR has high accuracy in the land subsidence monitoring of linear engineering. 2) There are five non-uniform settlement funnels along the Lunan high-speed railway. The groundwater over-extraction and coal mining are the main reasons for the land subsidence. 3) Realizing water source conversion and reduce groundwater exploitation are the main factors in linear engineering areas as soon as possible.
A Simple Reversible Watermarking Scheme Based on Difference Expansion
Chao-Ming Wu,Cheng-Kang Wu,Houshou Chen 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
A simple reversible watermarking scheme based on block-wise difference expansion is proposed. Pixels in a block are expanded with respect to a common reference point. The maximum capacity will exceed 0.5 bpp if the block size is larger than 2. According to local variances of the reference points, blocks introducing small distortion by difference expanding are selected firstly to embed watermark. In Tian’s difference expansion algorithm, the embedding of the location map causes large overhead cost, apparently in low payload region. A good lossless compression algorithm is required to reduce this cost but the complexity is increased. In the proposed algorithm, a simple all 0 pattern is used to distinguish between non-expandable and expandable blocks. In this way, the location map is no longer necessary and the complexity of the scheme will be reduced.
The Effects of Technology Gap between FDI firms and Domestic Firms on the Technology Spillovers
Chao Wu,Keunyeob Oh 충남대학교 경영경제연구소 2019 경영경제연구 Vol.41 No.2
FDI 기업의 기술파급효과에 대한 기존 연구는 일관되지 않은 결과를 보여주는데, 이는 기업의 기술 흡수 능력 차이 때문일 것으로 생각된다. 따라서 본 논문은 국내 제조업의 기업데이터를 활용하여 FDI 기술 파급효과가 기업들의 생산성에 미치는 영향이 흡수능력에 달려 있는지 연구하였다. 분석을 위해 국내 기업과 FDI 업체 간 기술격차를 흡수능력의 대리변수로 활용하였으며 다음의 결과를 얻었다. 먼저, 기술격차와 파급효과 사이의 선형 관계를 가정하고 분석하였을 경우, 흡수 능력이 약할수록 기술파급효과는 작은 것으로 나타났다. 그러나, 2차 함수 모형을 이용하여 분석한 결과, 기술 파급과 흡수능력의 상호작용 항이 총요소생산성(TFP)과 역 U-형태 관계를 갖는다는 것을 발견하였다. 따라서, 파급효과가 최대화 되기 위한 최적수준 격차라는 것이 존재할 수 있는 것으로 보인다. 이러한 결과는 FDI기업과 국내기업들의 기술격차가 너무 크거나 너무 작으면 기술 파급효과는 그리 크지 않을 것을 의미한다. The studies on the technology spillover of FDI firms show inconsistent results, which may be because of the different technology absorption capacity of enterprises. This paper used firm-level data of manufacturing industry in Korea from 2005-2014, which were derived from the Korea Information Service Financial Analysis System (KIS-FAS) database. In order to study whether the impact of FDI technology spillover on productivity depends on the absorptive capacity. Technology gap between domestic firms and FDI firms is used as a proxy variable for absorptive capacity. When we assume the linear relationship between the gap and spillovers, it appears that the weaker the absorptive capacity, the smaller the impact of FDI on technology spillovers. However, the results of the quadratic model analysis show that the interaction term of absorptive with technology spillovers have an inverted U-shape relationship to the TFP. This result seems that there could exist a certain extent appropriate level of gap. If the gap is too large or too low, technology spillover would not be quite large.
Wu, Chao,Li, Fang,Jiao, Shun-Chang Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.10
The objective of this retrospective study was to investigate prognostic factors associated with survival of patients with extensive stage small cell lung cancer (ES-SCLC). Included were 200 patients admitted to the Liberation Army General Hospital with a diagnosis of ES-SCLC. The demographics of patients, disease characteristics, pre-treatment biochemical parameters and therapeutic plan were assessed or evaluated. Univariate analysis found that second-line chemotherapy, radiotherapy, and no liver metastasis were associated with improved survival. Tumor response to first-line chemotherapy and normal initial hemoglobin levels were also associated with a survival benefit (all P-values ${\leq}$ 0.0369). Multivariate Cox regression analysis indicated that liver metastasis and the total number of all chemotherapy cycles were independent prognostic factors of survival. The morbidity risk in patients with liver metastasis was 2.52-fold higher than that in patients without liver metastasis (hazard ratio (HR)=2.52 (1.69-3.76); P<0.0001). However, one unit increase in the total number of chemotherapy cycles decreased the risk of death by 0.86-fold (HR=0.86 (0.80-0.92); P<0.0001). Absence of liver metastasis and ability of a patient to receive and tolerate multiple lines of chemotherapy were associated with longer survival.