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.

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 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.

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.

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.

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.

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

Nitrate control strategies in an activated sludge wastewater treatment process

Wenhao Shen,Erpan Tao,Xiaoquan Chen,Dawei Liu,류홍빈 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.3

We studied nitrate control strategies in an activated sludge wastewater treatment process (WWTP) basedon the activated sludge model. Two control strategies, back propagation for proportional-integral-derivative (BP-PID)and adaptive-network based fuzzy inference systems (ANFIS), are applied in the WWTP. The simulation results showthat the simple local constant setpoint control has poor control effects on the nitrate concentration control. However,the ANFIS (4*1) controller, which considers not only the local constant setpoint control of the nitrate concentration,but also three important indices in the effluent--ammonia concentration, total suspended sludge concentration and totalnitrogen concentration--demonstrates good control performance. The results also prove that ANFIS (4*1) controllerhas better control performance than that of the controllers PI, BP-PID and ANFIS (2*1), and that the ANFIS (4*1)controller is effective in improving the effluent quality and maintaining the stability of the effluent quality.

Chlorophyll Content Estimation from Spad, Chlorophyll Fluorescence and Leaf ReflectanceProperties

Wenhao An,Hua Xiao,Alin Shen 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Probabilistic Evaluation of Progressive Collapse Resistance of Truss String Structures Considering Structural Uncertainties

Wenhao Liu,Bin Zeng,Zhen Zhou,Yifan Zheng 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.5

Truss string structures (TSSs) are often prone to the risk of progressive collapse owing to critical member failures in accidental events. Moreover, the randomness of material properties, cross-sectional dimensions, and construction errors can inevitably lead to fluctuations in the collapse resistance of structures. Thus, to avoid catastrophic collapse of TSSs, it is essential to investigate the resistance to progressive collapse of TSSs considering structural uncertainties. In this study, three limit states of TSSs under key member failures are defined. In addition, a probabilistic evaluation methodology for the progressive collapse resistance of single TSSs considering structural uncertainties is proposed and extended to spatial TSSs. The analysis reveals that the external load of single or spatial TSSs reaching different limit states due to cable failure is less than that of the failure of the bottom chord of the support. Furthermore, the fragility analysis shows that the progressive collapse resistance of TSSs exposed to the failure of the bottom chord of the support is greater than that of cable failure, the cable failure should be given more attention than the failure of the bottom chord of the support in the structural design and post-maintenance of TSSs. The sensitivity analysis indicates that the performance of single TSSs against progressive collapse is more sensitive to the variability of random parameters. In addition, the spatial effect can considerably enhance the performance of TSSs against progressive collapse when the bottom chord of the support fails, whereas the improvement is marginal when the cable fails.