Tap Changing Transformer based Dual Active Bridge Bi-Directional DC-DC Converter

Shiva S.M,Naga Brahmendra Yadav Gor,Pritam Das,Sanjib Kumar Panda 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Voltage fed Dual Active Bridge (VF-DAB) is the simplest isolated bidirectional DC-DC converter topology with least number of high frequency tank elements. This paper addresses the issue of Phase Shift operated VFDAB when used for energy storage applications due to their variable nature in terminal voltage based on the state of charge. Circulation currents and limitations in the soft-switching range are the main drawbacks of VF-DAB when operated with phase shift control within the two active bridges and widely varying voltage at one port. This affect their overall efficiencies at low and mid loads. In this paper, a modification in VF-DAB is proposed which reduces the drawbacks of the conventional phase shift controlled DAB by having variable transformer turns ratio, thereby improving the efficiency of the overall converter at medium and light loads. The analysis and design guidelines for the proposed converter are briefly explained and validated with experimental results.

Synthesis, Structural Details and Induction of Superconductivity in Ga<SUB>1-x</SUB>Pb<SUB>x</SUB>Sr₂Y<SUB>1-y</SUB>Ca<SUB>y</SUB>CU₂O₇ (x=0.0 to 0.6 & y=0.0 to 0.5)

Shiva Kumar,Anuj Kumar,V.P.S. Awana,H. Kishan 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Microwave-accelerated Solvent and Catalyst Free Synthesis of 3-Indolylhydroquinones

J. S. Yadav,B. V. Subba Reddy,K. Shiva Shankar,T. Swamy,K. Premalatha 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.7

Microwave-accelerated Solvent and Catalyst Free Synthesis of 3-Indolylhydroquinones

Yadav, J.S.,Subba Reddy, B.V.,Shiva Shankar, K.,Swamy, T.,Premalatha, K. Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.7

신충돌안전성평가 대비 통합 H350 더미 모델 및 신경사충돌평가대비 THOR-M 모델 개발 현황

Intaek Lee,Chirag S. Shah,Suraush Khambati,Brock Watson,Nishant Balwan,Zaifei Zhou,Fuchun Zhu,Shiva Shaetty 한국자동차공학회 2014 한국자동차공학회 Workshop Vol.2014 No.9

승객안전성평가용 인체 모형 더미(Anthropomorphic Test Device, 이하 ATD)유한요소모델(Finite Element, FE)은 자동차 충돌 안전성의 조기 확보에 있어서 필연적인 수단으로 사용도가 확대되고 있다. 환경 규제에 의한 재료사용의 규제로 인체모형 모델의 변경 및 충돌 안전 법규의 다양화에 따른 다양한 다양한 인체모형의 출현으로 자동차 내충돌성, 승객보호장치의 신개념 설계대책에 보다 적극적인 대응이 요구되고 있다. 계산기의 계산능력과 코스트효율향상으로 복잡하고 상세한 더미해석 모델이 최근 더욱 실용화단계를 향해 진화하고 있다. 이점은 해석모델의 이용이 짧아진 제품 개발 사이클에 대응할 수 있는 유일한 수단으로 여겨짐과 동시에 정보기술 및 디지털 관리 기술과의 접목으로 코스트와 시간을 더욱더 삭감할 수 있는 이점이 있다는 점에서 투자 필요성이 가속화 되고 있다. 본 논문에서는 실 THOR-M50 と, 통합 Hybrid III 50th 개발 현황과 더불어 유한요소모델의 상세 개발 프로세스에 대해서 설명한다. 두 인체 더미 모델은 전방충돌용 성인 남성모델로서 사용되고 있는 점에서 차량 개발시에 검토되는 하중조건 및 설계하중에서 유사한 점이 있지만 신경사 충돌시험형태에 사용예정인 THOR-M50 모델의 경우가 보다 복잡한 하중조건으로 개발되었다고 할 수 있다. 해석모델의 개발에서도 실제 더미개발과 유사한 방법으로 개발 되는 관계로 전방충돌 형태의 하중 조건으로 고려한 개발프로세스를 설명한다. 더미모델의 형상 및 기하학적 특성은 실제의 3 차원 더미 생산도면 및 스캔데이터로 부터 취득한다. 더미 재질에 적합한 재료모델을 선정함에 있어서 더미 생산 기술의 노하우를 적용하고 다양한 재료시험을 계획한다. 특히 더미제작에 대표적인 재료 형태로서 많이 사용되고 있는 고무재, 포옴재, 알미늄 및 철강 합금재, 그리고 형상 기억 합금 등 다양한 재료에 대해서도 적절한 재료시험을 선정, 실시하여 최신의 재료 모델링 기술을 이용한 최적 재료 파라미터을 추출한다. 소형 시험편시험에서는 평면변형율 인장시험, 평면응력 인장시험 및 압축 시험, 강제 변형율 인장압축 히스테리시험, 순수 전단시험, 다축 인장시험, 동적 변형율 의존 인장 및 압축시험, 동적응력완화 시험등 현재 기술로 가능한 재료 시험을 통틀어 실시하고 있다. 생산시의 재료의 변동특성 및 시험시의 변동을 확인하기 위한 복수 시험편 제작 및 시험편 채취방법을 택하고 있다. 시험편 사이즈의 영향도 복수 시험편 제작 단계 및 유한 요소모델에 의한 확인 단계에서 재확인 한다. 계산 시간의 효율화를 위한 유한요소 사이즈의 영향도 시험편 재료 시험 단계에서 결정한다. 이는 더미 모델 형상의 이산화에 관계하는 기초 데이터를 재료 모델 개발 단계에서 파악하고 데이터베이스 구축을 목적으로 한 중요한 수단으로 여겨지고 있다. 이러한 모델개발 프로세스는 CAE 표준사양요구에 적합하고 신뢰할 수 있는 모델 개발에 중요한 열쇠로서 다양한 단품시험을 시작으로 서브어셈블리, 전체 어셈블리 레벨에서의 검증시험과의 확인까지의 일련의 흐름을 계산역학에 근거한 물리적 의미가 있는 해석 모델개발 프로세스라고 할 수 있다. 이러한 프로세스를 채용하고 있는 또 다른 이유는 상해 메카니즘 이해에 더미 단품 시험 및 어셈블리 시험으로 부터 실차 충돌시험에서의 상해치를 예측 할 수 있는 시스템 개발에 대응 할 수 있으며, 충돌문제의 변동문제를 분산해석 측면에서 대응하는 로버스트 설계 지원을 위함이다. 본 보고에서는 흉부 검정시험에서의 통합 H350 으로 실시한 예와 경부 검정시험에서는 THOR-M50 더미에서 실시한 내용을 예로서 소개한다. 현재의 개발 현황에서는 더미 단품 시험에서 전 어셈블리 레벨까지의 범위에서 각 시험과의 비교로부터 타당한 결과를 보이고 있고, 실제의 차량개발에 충분히 대응 할 수 있는 해석 모델로서 판단되어 이를 보고한다.

Influence of Different Desiccants, Flow Type and Packings on the Liquid Desiccant Dehumidification System: A Review

Sampath Suranjan Salins,Shiva Kumar,S. V. Kota Reddy 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.1

Desiccant cooling mechanism is one of the alternate methods to control the humidity of air and temperature, compared to the conventional vapor compression method of air conditioning. Desiccant cooling doesn’t use harmful chemicals which effect the ozone layer and it saves lots of energy. Summer air condition system can use this technology since it removes the latent heat load from the room effectively and this process is economical. Selection of the appropriate liquid desiccant and packing material is very vital to obtain maximum dehumidification. This paper focuses on the different desiccants and packings used by different researchers to enhance the dehumidification. Simple and hybrid systems are also reviewed, and their comparison are presented based on the construction and dehumidification performance.

Relationship between trajectories of serum albumin levels and technique failure according to diabetic status in peritoneal dialysis patients: A joint modeling approach

( Mehri Khoshhali ),( Iraj Kazemi ),( S. Mohsen Hosseini ),( Shiva Seirafian ) 대한신장학회 2017 Kidney Research and Clinical Practice Vol.36 No.2

Background: In peritoneal dialysis, technique failure is an important metric to be considered. This study was performed in order to identify the relationship between trajectories of serum albumin levels and peritoneal dialysis technique failure on end-stage renal disease patients according to diabetic status. Furthermore, this study was performed to reveal predictors of serum albumin and technique failure simultaneously. Methods: This retrospective cohort study included 300 (189 non-diabetic and 111 diabetic) end-stage renal disease patients on continuous ambulatory peritoneal dialysis treated in Al-Zahra Hospital, Isfahan, Iran, from May 2005 to March 2015. Bayesian joint modeling was carried out in order to determine the relationship between trajectories of serum albumin levels and peritoneal dialysis technique failure in the patients according to diabetic status. Death from all causes was considered as a competing risk. Results: Using joint modeling approach, a relationship between trajectories of serum albumin with hazard of transfer to hemodialysis was estimated as -0.720 (95% confidence interval [CI], -0.971 to -0.472) for diabetic and -0.784 (95% CI, -0.963 to -0.587) for non-diabetic patients. From our findings it was showed that predictors of low serum albumin over time were time on peritoneal dialysis for diabetic patients and increase in age and time on peritoneal dialysis, history of previous hemodialysis, and lower body mass index in non-diabetic patients. Conclusion: The results of current study showed that controlling serum albumin over time in non-diabetic and diabetic patients undergoing continuous ambulatory peritoneal dialysis treatment can decrease risk of adverse outcomes during the peritoneal dialysis period.

Sustainable Energy Techniques Adapted in Buildings to Regulate Moisture Transport and Enhance Thermal Comfort: A Review

Salins Sampath Suranjan,Kumar Shiva,Reddy S. V. Kota,Kuniyil Avin Vivek,kumar Sreejith Sanal 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.3

Heating ventilation air conditioning (HVAC) design mainly deals with moisture and its control. The moisture may be present inside ducts, conditioned spaces, or outdoors. The process of humidification and dehumidification requires equipment for mass and heat transfer, where the transfer of energy and mass takes place at varying concentrations and temperatures. The exchange of mass or heat depends on the type of flow and is conceivably in the form of gas to liquid or liquid–vapor. This paper aims to review the effect of moisture in the buildings and modulate its effect with several humidifying and dehumidifying techniques as sustainable techniques depending upon the external weather conditions to maintain thermal comfort. Various humidification and dehumidification techniques have been discussed with both their merits, limitations, applications and future scope to meet sustainable energy demands.

Study of Deformation Mechanisms of a High-Purity α-Titanium Plate Under Monotonic Loading with the EVPSC-TDT Model

Himanshu Kumar,Gaurav A. Bhaduri,S. G. K. Manikandan,M. Kamaraj,S. Shiva 대한금속ᆞ재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

The primary focus of the study is to explore the influence of annealing on the various properties like phase formation,microstructure evolution and wear analysis of equiatomic AlCoCrFeNiTi high entropy alloy (HEA) coatings developed byatmospheric plasma spray technique. Post deposition, annealing was performed at three different temperatures of 700 °C,900 °C and 1200 °C, respectively, for a time period of 180 min. X-ray diffraction (XRD) studies revealed that AlCoCrFeNiTiHEA coating comprises two BCC solid solution phases. The deposited samples were characterized using scanning electronmicroscopy (FESEM), surface profilometer, chemical analysis using x-ray photoelectron spectroscopy (XPS) and Fouriertransform infra-red spectroscopy (FTIR). The dilution level study revealed the strong metallurgical bonding between coatingand substrate. Microhardness of the AlCrCoFeNiTi was found to be marginally decreased by increasing the annealingtemperature due to coarsening of grains and the deposited coating microhardness was found to be 768.48 ± 16 HV0.2. Weartest analysis performed using the ball-on disc test revealed that, there is a significant decrease in wear resistance after heattreatment at 1200 °C. Beyond 900 °C, annealing decreased the microhardness and wear resistance due to coarsening ofgrains. The wear volume rate of the unannealed as-deposited coating was found to be 2.8 × 10–7 mm3N−1 m−1 and the coatingannealed at 700 °C, 900 °C, and 1200 °C had a wear volume rate of about 2.89 × 10–7 mm3 N−1 m−1, 2.87 × 10–7 mm3 N−1 m−1,7.29 × 10–7 mm3 N−1 m−1, respectively.

Prediction of nonlinear characteristics of soil-pile system under vertical vibration

Biswas, Sanjit,Manna, Bappaditya,Choudhary, Shiva S. Techno-Press 2013 Geomechanics & engineering Vol.5 No.3

In the present study an attempt was made to predict the complex nonlinear parameters of the soil-pile system subjected to the vertical vibration of rotating machines. A three dimensional (3D) finite element (FE) model was developed to predict the nonlinear dynamic response of full-scale pile foundation in a layered soil medium using ABAQUS/CAE. The frequency amplitude responses for different eccentric moments obtained from the FE analysis were compared with the vertical vibration test results of the full-scale single pile. It was found that the predicted resonant frequency and amplitude of pile obtained from 3D FE analysis were within a reasonable range of the vertical vibration test results. The variation of the soil-pile separation lengths were determined using FE analysis for different eccentric moments. The Novak's continuum approach was also used to predict the nonlinear behaviour of soil-pile system. The continuum approach was found to be useful for the prediction of the nonlinear frequency-amplitude response of full-scale pile after introducing the proper boundary zone parameters and soil-pile separation lengths.