Butcher Algorithms for Linear Electrical Circuits

DEVARAJAN, G.,MURUGESAN, K. 우송대학교 2004 우송대학교 논문집 Vol.9 No.-

본 논문에서 RK Butcher 알고리즘을 사용한 선형전기회로의 분석을 위한 새로운 방법이 선형시불변회로 (linear time invariant electrical circuit) 경우데 제안된다. RK Butcher 알고리즘으로 해석되는 이산(discrete)해는 기존 전기회로의 STWS 방법을 이용한 해석과 비교할 때 더욱 정확한 해를 구할 수 있으며 STWS의 방법과 RK Butcher 알고리즘의 결과를 안정영역으로 비교하였다. 또한, 인덕터 전류와 캐페시터 전압의 오류그래프로 RK Butcher 방법의 우월성을 보여주는데 있다. A new method of analysis for a singular system of linear electric circuit using the RK Butcher algorithm is presented for linear time invariant (LTI) case. The discrete solutions obtained by the RK Butcher algorithms are compared with the exact solutions of the electric circuit problem and are found to be very accurate. Stability regions of the Single Term Walsh Series (STWS) method and the RK Butcher algorithm are presented. Error graphs for inductor currents and capacitor voltages are presented in a graphical form to show the efficiency of this RK Butcher method. This RK Butcher algorithm can be easily implemented in a digital computer and the solution can be obtained for any length of time.

Electrical Characteristics of Catenary

데버랜전고팔(Devarajan Gopal),노영환(Lho Young Hwan),김윤호(Kim Yoon Ho) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-

In this paper, the basic requirements of catenary in railroad traction is explained. Three different types of catenary suspension systems for different terrains, environments and high speed / low speed trains are presented. The essential requirements of catenary such as reliability, cost effectiveness, maintenance and ruggedness requirements are discussed. The catenary materials and safety problems associated in it are dealt.

Some facts and figures of Indian Railways

데버랜전고팔(Devarajan Gopal),노영환(Lho Young Hwan),김윤호(Kim Yoon Ho) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-

Indian Railways runs about 10,000 trains and carries 15 million people daily. Today Indian Railways run efficiently and makes a modest profit in spite of reducing the passenger and freight fares. As Indian Railways has a long history, a brief introduction will be given. Indian Railways has three different gauges (Narrow, Meter and Broad) during British rule and now it is converging to broad gauge in a phased manner. The details will be addressed. As Indian terrain is not that much favorable to Rails. Evolution of rail engines, coaches / wagons which are all manufactured in India are given in details. As India is attaining self sufficiency in almost all fields of Science and Technology, various production units, research units, Journals etc are also discussed. Statistics pertaining to railways both technical and commercial are addressed.

Nitrogen and phosphorous co‑doped carbon nanotubes for high‑performance supercapacitors

Johnsirani Devarajan,Pandurangan Arumugam 한국탄소학회 2023 Carbon Letters Vol.33 No.6

Nitrogen and phosphorous dual-doped carbon nanotubes (N,P/CNT) have been grown in a single-step direct synthesis process by CVD method using iron-loaded mesoporous SBA-15 support, as an electrode material for the energy storage device. For comparison, pristine nanotubes, nitrogen and phosphorous individually doped nanotubes were also prepared. The basic characterization studies clarify the formation of nanotubes and the elemental mapping tells about the presence of the dopant. Under three-electrode investigations, N,P/CNT produced a maximum specific capacitance of about 358.2 F/g at 0.5 A/g current density. The electrochemical performance of N,P/CNT was further extended by fabricating as a symmetric supercapacitor device, which delivers 108.6 F/g of specific capacitance for 0.5 A/g with 15 Wh/kg energy density and 250 W/kg power density. The observed energy efficiency of the device was 92.3%. The capacitance retention and coulombic efficiency were 96.2% and 90.6%, respectively, calculated over 5000 charge–discharge cycles.

Can common finishing treatments used in chef jacket fabrics improve protection against scald injury?

Sushmitha Devarajan,Rachel H. McQueen,ShuQin Wen 한국의류학회 2017 Fashion and Textiles Vol.4 No.1

Chefs and other food preparation workers are at a high risk of scald injuries from hot liquids. Chefs’ clothing has the potential to act as a protective barrier between the skin and the thermal hazard. Although, impermeable barriers coupled with an insulating layer of fabric tend to offer the greatest protection against hot liquid penetration, the potential for heat strain and discomfort to workers may make them impractical in the kitchen environment. This study examined the effects of common finishing treatments used in chef jacket fabrics and the impact of layers on the protection offered against hot water burn injuries. The Teflon® treated fabrics offering combined stain and water repellency, provided the greatest protection with the lowest absorbed energy and longest times to second degree burn injury compared with the other finishes (i.e., regular, water repellent and soil release). Findings also showed that in most cases, increasing the number of layers improved protection provided by the fabric systems, with the Teflon® finished fabrics providing the highest protection against scald injuries as fabric layers increased.

Indian Railway Locomotives with IGBT Based Traction Control Converter

데버랜전고팔(Devarajan Gopal),노영환(Lho Young Hwan),김윤호(Kim Yoon Ho) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-

Standard Gate Turn Off (GTO) Thyristor drive technology results in inhomogeneous turn-on and turn-off transients which in turn needs costly dv/dt and di/dt snubber circuits. Added to this GTO is bulky in size, needs external cooling, slower switching time etc. The development of high voltage Insulated Gate Bipolar Transistor (IGBT) have given new device advantage in the areas where they compete with conventional GTO technology. Indian Railway has developed first IGBT based traction converter and was commissioned in November 2006. Some of the supremacy of IGBT are smaller in size, no external cooling is required, built in power supply which enhances reliability, lower switching losses which leads to higher efficiency, reduced gate drive, high frequency operation in real time etc. These advantages are highlighted along with IGBT Traction system in operation.

Traction IGBT Modules Design Issues and Precautions

데버랜전고팔(Devarajan Gopal),노영환(Lho Young Hwan),김윤호(Kim Yoon Ho) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-

IGBT modules are designed for low loss, rugged for all environments and user friendly. Low on state saturation voltage with high switching speed is the primary concerns. In this paper selection of IGBT, module ratings and characteristics are discussed. The IGBT design topic of protection against over voltage and over current are covered. Emphasis on turn off switching, short circuit switching and necessary precautions are dealt. Selection of IGBT device, gate drive power, and its lay out considerations are covered in detail.

Rail Road Electric Traction System

데버랜전고팔(Devarajan Gopal),노영환(Lho Young Hwan),김윤호(Kim Yoon Ho) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-

In this paper, the details of electric traction voltages which are widely used for metro and mainline trains are presented. The problems encountered in catenaries, pressure of the pantograph pan, catenary contact cross sectional area, materials etc are well covered. Catenary height from the rail for main line, bridges, sheds etc is discussed. The catenary running details and switching of one catenary to another are explained. The dead zones in 3 phase grid as well as in DC are presented here. The pantograph structure, blades, shoes etc. for AC/DC EMUs are dealt. The schematic diagram for electrification systems used for railways are given and explained with typical electrical parameters of Indian Railways.

Performance and emissions analysis on diesel engine fuelled with cashew nut shell biodiesel and pentanol blends

Yuvarajan Devarajan,Beem Kumar Nagappan,Dinesh Babu Munuswamy 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.4

We studied the impact of blending pentanol, a next generation biofuel, with cashew nut shell biodiesel on its performance and emissions characteristics in a constant speed compression ignition engine. Our main objective was to reduce CO, HC, NOX and smoke emission when fueled with neat cashew nut shell biodiesel and the pentanol blends. Cashew nut shell oil is a byproduct from cashew nut industry. Since it is nonedible, it can be used as a promising alternative. Conventional transesterification process was used to convert the cashew nut shell oil into cashew nut shell biodiesel. Pentanol with 98.4% purity was used as an oxygenated additive. The experiment involved three test fuels: neat cashew nut shell biodiesel (C100), Pentanol blended with cashew nut shell biodiesel by 10% volume (C90P10) and Pentanol blended with cashew nut shell biodiesel by 20% volume (C80P20). The feasibility of using neat biofuel (without adding diesel) was also investigated. Experimental work concluded that the test fuels used in this study does not require any modification in engines. In addition, the combustion of fuels was smooth and there was no physical and visible damage in the engine components when fueled with cashew nut shell biodiesel and the pentanol blends. By adding 10% and 20% of pentanol to cashew nut shell biodiesel, significant reduction in CO, HC, NOX and smoke emission was observed. In addition, brake thermal efficiency increased marginally with slight reduction in brake specific fuel consumption.

RK-Butcher알고리듬의 사용에 의한 주기적 진동 문제의 수치적 시뮬레이션

박대철,Devarajan Gopal,V. Murugesh 한국융합신호처리학회 2008 융합신호처리학회 논문지 (JISPS) Vol.9 No.1

In this paper, Runge-Kutta (RK)-Butcher algorithm is proposed to study the periodic and oscillatory problems. Simulation results obtained using RK-Butcher algorithms and the classical fourth order Runge-Kutta (RK(4)) methods are compared with the exact solutions of a few periodic and oscillatory problems to confirm the performance of the proposed algorithm. The simulation results from RK-Butcher algorithms are always found to be very close to the exact solutions of these problems. Further, it is found that the RK-Butcher algorithm is superior when compared to RK(4) methods in terms of accuracy. The RK-Butcher algorithm can be easily implemented in a programming language and a more accurate solution may be obtained for any length of time. RK-Butcher algorithm is applicable as a good numerical algorithm for studying the problems of orbit and two body as it gives the nearly identical solutions. 본 논문은 주기적 진동 문제를 연구하기 위해 Runge-Kutta(RK)-Butcher 알고리듬이 소개되었다. RK-Butcher 알고리듬을 사용하여 얻어진 시뮬레이션 결과와 고전적인 4차 RK(4) 방법을 통해 얻은 결과들을 제안한 알고리듬의 성능을 확인하기 위하여 몇몇 주기적 진동 문제들의 정확한 해와 비교하였다. RK-Butcher 알고리듬의 시뮬레이션 결과는 항상 문제의 정확한 해 RK(4) 방법보다 더 근접한 결과를 줌이 확인되었다. 정확도 측면에서 RK-Butcher 알고리듬이 RK(4) 방법과 비교해볼 때 우수함을 알 수 있다. 제안한 RK-Butcher 알고리듬은 프로그램 언어로 쉽게 구현할 수 있으며 임의 시간에 종료해도 훌륭한 근사적인 해를 얻을 수 있다. RK-Butcher 알고리듬은 짧은 시간내에 이상적인 정확한 해에 근접한 결과를 주기 때문에 궤도 와 두 물체의 문제를 연구하는데 훌륭한 수치 알고리듬으로 적용가능하다.