Influence of Water Molecules on Polarization Behavior and Time–Frequency Dielectric Properties of Cellulose Insulation

Wen Hao,Cheng Lin,Jiang Yi,Zhu Taiyun,Chen Zhong,Dai Xize,Gao Chenyu 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.3

Oil-immersed power transformer plays an important role in power transmission and transformation engineering. Moisture is one of the important factors to determine its insulation performance. Molecular simulation technique is used to study the mechanism of water molecules on the micro polarization behavior of cellulose insulation materials. The number of hydrogen bonds, solubility parameters, total dipole moment and polarizability are analyzed. These characteristics explain the action mechanism of water molecules on cellulose insulation. At the same time, the time domain and frequency dielectric response of cellulose insulation materials with diff erent moisture content are explored. The dielectric modulus spectrum is introduced to replace the traditional frequency dielectric spectroscopy to characterize the micro relaxation process of cellulose insulation under diff erent moisture content. Finally, the characteristic parameters are extracted from the polarization, depolarization current and dielectric modulus spectrum curves to evaluate the moisture content of cellulose insulation materials. The results show that the number of hydrogen bonds, binding energy density, solubility parameter, total dipole moment and polarizability increase with the increase of water content. It should be noted that dielectric modulus spectroscopy can eff ectively characterize the relaxation behavior of cellulose insulation materials. The moisture content of cellulose insulation can be quantitatively evaluated by DC conductivity, insulation resistance, imaginary part relaxation peak of dielectric modulus and integral value of real part and imaginary part of dielectric modulus.

An API Calls Monitoring-based Method for Effectively Detecting Malicious Repackaged Applications

Wenhao Fan,Yuan’an Liu,Bihua Tang 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.8

The number of mobile applications on Android platform has largely increased in recent years. The security problems, as one of the outcomes induced by the popularity of Android, become more and more critical. Malicious repackaged applications (MRAs) perform malicious behaviors through malware developers embedding malicious codes into the benign origin applications (BOAs), which threat the security of users’ finance and privacy. In this paper, a method based on API calls monitoring is proposed to effectively detect MRAs. We discuss the characteristics of behaviors and analyze the differences in API calls between MRAs and their BOAs. A MRA detection model is established, which builds up the super-sphere for each BOA via a SVDD algorithm. The model can detect the abnormal behaviors of MRAs which deviate the normal behaviors of corresponding BOAs. Experiments are carried out on imitated and real MRAs, where the results demonstrate the effectiveness of our method for detecting the singly and multiply contaminated BOAs.

The effect of inlet pressure distortion on the performance of an axisymmetric compact tube heat exchanger with radial counter flow type for hypersonic pre-cooled aero-engine

Wenhao Ding,Qitai Eri,Bo Kong,Changsheng Wang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

The compact tube heat exchanger located behind the air-intake can achieve quick cooling of high-temperature air to ensure the normal operation of the pre-cooled aeroengine. It has great impact on the engine’s performance. The total pressure distribution at the heat exchanger inlet is inevitably uneven due to the influence of the air-intake. This paper studies the effect of three typical inlet distortions with different amplitudes using porous model and dual cell model. The results indicated that the outlet total pressure distortion is not sensitive to the inlet total pressure distortion. However, it affects the total pressure recovery and the total temperature distortion at the outlet by altering the pressure loss in the heat exchanger upstream and the flux distribution at the heat-transfer-zone entrance, respectively. This leads to a reduction of heat transfer. The effect of inlet distortions varies with distortion type. And it becomes more severe with increasing distortion.

Energy Efficient Traffic Allocation for Resource-constrained Multi-homed WSN Gateway

Wenhao Fan,Bihua Tang,Yuan’an Liu 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.10

WSN (Wireless Sensor Network) gateway acts as a bridge between WSN and external networks. Currently, rapid growing demands from various IoTs (Internet of Things) applications are posing critical challenges to the data transmission capability of such gateway. As a promising solution, multi-homed WSN gateway, which is equipped with multiple network interfaces, can obtain enhanced parallel data transmission by jointly utilizing multiple RATs (Radio Access Technologies). However, the multi-homed gateway is a resource-constrained device, so it’s crucial to guarantee the efficiency for both data throughput and resource consumption. Delay and buffer size, simulation results validate that the proposed algorithm can allocate To this end, an energy efficient traffic allocation algorithm for resource-constrained multi-homed WSN gateway is proposed in this paper, which aims at minimizing the gateway's power consumption while guaranteeing the transmission the traffic optimally for the gateway with different constraints and configurations, and it can significantly promote the gateway's energy efficiency in comparison to the traditional method.

The Research Trend of Employability in HE From 2000 to 2019--A Visual Analysis Using Citespace

( Wenhao Chen ),( Youngsup Hyun ) 경북대학교 중등교육연구소 2020 Asia Pacific Journal of Educational Research Vol.3 No.2

Employability is about having the capability to gain initial employment, maintain employment and obtain new employment. Research on employability in each country is increasing because of the serious situation of graduate unemployment. There are lots of studies on employability from the range of its concept, key elements, to supports to raise the employability in higher education. Employability has been variously defined in terms of organization and policy. As long as the various studies about employability were published, it had been difficult to identify a big picture and directions for future research. CiteSpace, which is designed to analyze existing literature by co-citation networks, can provide a clear picture of the research in this field. This paper investigated and visualized the research trends of employability in higher education around the world. We constructed a framework for trends analyses based on theoretical reviews. All the data was collected on Scopus, one of the largest abstract and citation database of peer-reviewed literature. 661 articles published in international journals in past 2 decades were collected and analyzed. In terms of contributing countries, the major driving force is from the United Kingdom, and Australia. Yorke M, Harvey L and Tomlinson M are top cited authors. In terms of the popularity of research topics, recent employability research has mainly focused on university activities, class act, career planning, lunar side and international internship.

Isoperistaltic side-to-side anastomosis for the surgical treatment of Crohn disease

Wenhao Chen,Junjie Zhou,Min Chen,Congqing Jiang,Qun Qian,Zhao Ding 대한외과학회 2022 Annals of Surgical Treatment and Research(ASRT) Vol.103 No.1

Purpose: Increasing evidence has shown an association of surgical technique, particularly anastomotic configuration, with postoperative recurrence of CD. This pilot study aimed to evaluate short-term outcomes of isoperistaltic side-to-side anastomosis (ISSA) employed on Crohn disease (CD) patients. Methods: Data were retrieved from a prospectively maintained database. Postoperatively, all patients were followed up with close endoscopic (ileocolonoscopy) surveillance. Results: From January 2017 to May 2021, 30 patients diagnosed with CD who underwent ISSA were compared with 45 CD patients who underwent antiperistaltic side-to-side anastomosis (ASSA). The 2 groups were comparable in baseline demographics and clinical characteristics. No significant differences were observed between groups regarding postoperative safety issues, including anastomotic leak, abdominal/pelvic abscess, length of hospital stay, readmission rate within 30 days, etc. At postoperative 24th month, reduced endoscopic recurrence was observed in the ISSA group compared with that in the ASSA group (18 of 24, 75.0%, . 36 of 38, 94.7%; P = 0.024). Regarding surgical recurrence, there was 0% in the ISSA group . 4.4% (2 of 45) in the ASSA group (P = 0.510). Conclusion: In this study, we aimed to explore the influence of ISSA on postoperative recurrence in CD patients, and the preliminary results show that ISSA was technically safe and feasible, and appears to be effective in reducing postoperative recurrence in CD patients. However, our conclusion was underpowered due to small sample size and inadequate follow- up. We proposed ISSA be considered as another alternative option in the toolbox of inflammatory bowel disease surgeons when performing anastomosis on CD patients.

Ground Effects on the Vortex-induced Vibration of Bridge Decks

Wenhao Mao,Zhiyong Zhou,Ai Huilin 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

The present study investigated the ground effects on the VIV of a closed box girder based on wind tunnel tests and numerical methods. First, we presented a vibration measurement system for wind-tunnel test to simulate ground effects on the bridge girder. Second, we investigated the Strouhal number (St), the VIV lock-in phenomena over a range of wind velocities, and the maximum VIV amplitudes and their change laws in correlation with the height from the ground in two different ground conditions. The outcomes showed the following: that a low height from the ground can lead to high St numbers; that ground effects did not change the width of VIV lock-in range, but did impel VIVs to occur earlier in the uniform flow field; and that the maximum VIV amplitudes was reduced and the VIV lock-in range narrowed in the turbulent flow field. Finally, we conducted the numerical simulation method to study the ground effect mechanism on VIVs. The numerical results showed that the periodic vortex shedding will generate periodic forces on the structure, which leads to the occurrence of VIVs. Ground effects can speed up vortex shifting, whereas aerodynamic forces on the deck are weakened.

Effect of post-annealing conditions on electrical and optical properties of AZO thin film on flexible PET substrates

Wenhao YAO,Kun LIU,Shulei CHEN,Xiaojie LIU,Dongyang WANG,Yingchao NING,Dechun BA,Guangyu DU,Yaoshuai BA 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

A New Triterpenoid Saponin from Pulsatilla cernua

Wenhao Fan,Yongnan Xu,Jianyu Liu,Yixia Gong,Jing Ma,Nan Zhou 한국생약학회 2013 Natural Product Sciences Vol.19 No.2

A new oleanane-type triterpenoid saponin together with six known saponins were isolated from the roots of Pulsatilla cernua. Their structures were elucidated on the basis of spectroscopic data, including 2D NMR spectra and chemical evidence. Compounds 1 and 6 are reported from this genus for the first time.

Spectrum Allocation based on Auction in Overlay Cognitive Radio Network

( Wenhao Jiang ),( Wenjiang Feng ),( Yang Yu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.9

In this paper, a mechanism for spectrum allocation in overlay cognitive radio networks is proposed. In overlay cognitive radio networks, the secondary users (SUs) must first sense the activity of primary users (PUs) to identify unoccupied spectrum bands. Based on their different contributions for the spectrum sensing, the SUs get payoffs that are computed by the fusion center (FC). The unoccupied bands will be auctioned and SUs are asked to bid using payoffs they earned or saved. Coalitions are allowed to form among SUs because each SU may only need a portion of the bands. We formulate the coalition forming process as a coalition forming game and analyze it by game theory. In the coalition formation game, debtor-creditor relationship may occur among the SUs because of their limited payoff storage. A debtor asks a creditor for payoff help, and in return provides the creditor with a portion of transmission time to relay data for the creditor. The negotiations between debtors and creditors can be modeled as a Bayesian game because they lack complete information of each other, and the equilibria of the game is investigated. Theoretical analysis and numerical results show that the proposed auction yields data rate improvement and certain fairness among all SUs.