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Modeling and Analysis of a Buck/Boost Bidirectional Converter with Developed PWM Switch Model
Wang Jianhua,Zhang Fanghua,Gong Chunying,Chen Ran 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
The aim of this paper is to provide a general method for bidirectional converter simulation and evaluation. A developed PWM switch model is proposed for bidirectional power flow application. A typical buck/boost bidirectional converter is chosen as a test bench for evaluation. Small signal analysis results show mode transition between battery charging and discharging modes. It provides a fast simulation tool to investigate steady and transient response of converters. The accuracy of the modeling technique is verified by a detailed comparison of simulated results with the developed PWM switch model and component circuit.
Slotted ALOHA Based Greedy Relay Selection in Large-scale Wireless Networks
( Fengchen Ouyang ),( Jianhua Ge ),( Fengkui Gong ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10
Since the decentralized structure and the blindness of a large-scale wireless network make it difficult to collect the real-time channel state or other information from random distributed relays, a fundamental question is whether it is feasible to perform the relay selection without this knowledge. In this paper, a Slotted ALOHA based Greedy Relay Selection (SAGRS) scheme is presented. The proposed scheme allows the relays satisfying the user`s minimum transmission request to compete for selection by randomly accessing the channel through the slotted ALOHA protocol without the need for the information collection procedure. Moreover, a greedy selection mechanism is introduced with which a user can wait for an even better relay when a suitable one is successfully stored. The optimal access probability of a relay is determined through the utilization of the available relay region, a geographical region consisting of all the relays that satisfy the minimum transmission demand of the user. The average number of the selection slots and the failure probability of the scheme are analyzed in this paper. By simulations, the validation and the effectiveness of the SAGRS scheme are confirmed. With a balance between the selection slots and the instantaneous rate of the selected relay, the proposed scheme outperforms other random access selection schemes.
Qiang Ma,Shuqian Cao,Tao Gong,Jianhua Yang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11
Fault feature extraction of the rolling bearing under strong background noise is always a difficult problem in bearing fault diagnosis. At present, most of the research focuses on weak signal extraction under Gaussian white noise and has certain practical significance. However, the noise in engineering is often complex and changeable, Gaussian white noise cannot fully simulate the actual strong background noise. Poisson white noise is a type of typical non-Gaussian noise, which widely exists in complex mechanical impact. It is of great significance to study the weak fault feature extraction of a faulty bearing under this type of noise. At the same time, variable speed conditions occupy most rotating machinery speed conditions. Non-stationary vibration signals make it difficult to extract fault features, and the frequency spectrum ambiguity will occur because of speed fluctuation. To solve the above problems, a method of weak feature extraction of a faulty bearing based on computed order analysis (COA) and adaptive stochastic resonance (SR) is proposed. Firstly, by numerical simulation, the nonstationary fault characteristic signal corrupted with strong Poisson noise is transformed into a stationary signal in the angle domain by COA. Secondly, the influence of the parameters of the pulse arrival rate and noise intensity of Poisson white noise on the optimal SR response in the angle domain are studied, and the influence of the parameters of Poisson white noise on the fault feature extraction is given. Then, adaptive SR method is used to extract and enhance fault feature information. Finally, the effectiveness of this method in weak fault characteristic signal extraction under strong Poisson noise is verified by experiments. Numerical simulation and experimental results verify the effectiveness of the proposed method in bearing fault diagnosis under strong Poisson noise and variable speed conditions.
Cuihua Wang,Duo Rong,Wenquan Zhang,Bin Gong,Jianhua Wu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9
The flow and heat transfer characteristics of magnetic nanofluids in a circular channel under the action of magnetic fields were studied through numerical simulation based on the finite element method. The results show that there are obvious secondary vortices on the cross-section, and a swirling flow is formed in the duct under the coupling effects of the magnetic field, velocity distribution, and thermal variations which destroys the boundary layer, accelerates the mixing of fluids, and enhances heat transfer. In the studied range, the maximum heat transfer coefficient can be increased by 102.65 %, and the maximum comprehensive heat transfer factor J is 1.69 compared to the ferrofluid not affected by the external magnetic field. In addition, the effect of enhancing heat transfer gradually decreases with the increase of θ, until heat transfer is slightly inhibited when the magnetic field is parallel to the flow direction.
KGd(MoO4)2:Eu3+ as a promising red phosphor for light-emitting diode application
Linghong Yi,Liya Zhou,Zhengliang Wang,Jianhua Sun,Fuzhong Gong,Weiping Wan,Wei Wang 한국물리학회 2010 Current Applied Physics Vol.10 No.1
A red phosphor KGd(MoO4)2:Eu3+ was prepared by solid-state reaction technique at high temperature. Its photoluminescent property was investigated and the optimum concentration of Eu3+ doped in the KGd(MoO4)2 is 25 mol%. Compared with Y2O2S:0.05Eu3+, the obtained KGd(MoO4)2:Eu3+ shows wider excitation band around 400 nm, higher intensity of Eu3+ 5D0.7F2 emission upon excitation 393 nm, and the CIE chromaticity coordinates (x = 0.655, y = 0.345) are closer to the standard of National Television Standard Committee (NTSC). The optical properties of KGd(MoO4)2:Eu3+ suggest that it is an efficient red-emitting phosphor for light-emitting diode applications.
Xinyan Xie,Fang Hou,Li Li,Yanlin Chen,Lingfei Liu,Xiu Luo1,Huaiting Gu,Xin Li,Jiajia Zhang,Jianhua Gong,Ranran Song 대한신경정신의학회 2019 PSYCHIATRY INVESTIGATION Vol.16 No.5
Objective: To evaluate the association of GRIK2 and NLGN1 with autism spectrum disorder in a Chinese population. Methods: We performed spatio-temporal expression analysis of GRIK2 and NLGN1 in the developing prefrontal cortex, and examined the expression of the genes in ASD cases and healthy controls using the GSE38322 data set. Following, we performed a case-control study in a Chinese population. Results: The analysis using the publicly available expression data showed that GRIK2 and NLGN1 may have a role in the development of human brain and contribute to the risk of ASD. Later genetic analysis in the Chinese population showed that the GRIK2 rs6922753 for the T allele, TC genotype and dominant model played a significant protective role in ASD susceptibility (respectively: OR=0.840, p=0.023; OR=0.802, p=0.038; OR=0.791, p=0.020). The NLGN1 rs9855544 for the G allele and GG genotype played a significant protective role in ASD susceptibility (respectively: OR=0.844, p=0.019; OR=0.717, p=0.022). After adjusting p values, the statistical significance was lost (p>0.05). Conclusion: Our results suggested that GRIK2 rs6922753 and NLGN1 rs9855544 might not confer susceptibility to ASD in the Chinese population.
Yin, Fugui,Yin, Yulong,Kong, Xiangfeng,Liu, Yulan,He, Qinghua,Li, Tiejun,Huang, Ruilin,Hou, Yongqing,Shu, Xugang,Tan, Liangxi,Chen, Lixiang,Gong, Jianhua,Kim, Sung Woo,Wu, Guoyao Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.9
This study was conducted to investigate the effects of Acanthopanax senticosus extract (ASE) as a dietary additive on gut microflora in weaned piglets. A total of sixty pigs were weaned at 21 d of age (BW = $5.64{\pm}0.23kg$) and allocated on the basis of BW and litter to three dietary treatments in a randomized complete block design. The dietary treatments were: control group (basal diet), antibiotics group (basal diet+0.02% colistin), and ASE group (basal diet+0.1% ASE). On d 7, 14 and 28 after consuming the experimental diets, five piglets per group were sacrificed and then the contents from the jejunum, ileum and cecum were collected to determine changes in the microbial community by using a polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique and estimating the contents of Lactobacillus and E. coli by in vitro culturing methods. The results showed that the ASE promoted the microflora diversity in the cecum. Enumeration of bacteria in the gut contents showed that the number of Lactobacillus increased (p<0.05), while that of E. coli decreased (p<0.05) when compared with the other 2 groups as the days of age progressed post-weaning. These findings suggested that the ASE, as a substitute for dietary antimicrobial products, could improve the development of the normal gut microflora and suppress bacterial pathogens, and effectively promote a healthy intestinal environment.