Investigation of Non-ideality Factors for a P3HT: PCBM Based Bulk Heterojunction Organic Solar Cell in Presence of Silver Nanoparticles

Sakshi Koul,Najeeb-ud-din Hakim 한국전기전자재료학회 2020 Transactions on Electrical and Electronic Material Vol.21 No.3

Solar cells are a potential option to meet the growing energy requirements of humans. Organic solar cells (OSCs) represent a class of solar cells that is a part of the third generation solar cell technology. The quest for obtaining enhanced OSC efficiencies has led to the incorporation of metallic nanoparticles (NPs) in the OSCs. Metallic NPs increase the incident light absorption instances, thus increasing the obtainable cell efficiencies. Diff erent parameters and factors need to be considered for obtaining the optimum NP specifications. Investigations of the mechanism of light absorption after the introduction of NPs in the OSC are critical. Hence theoretical simulations for such OSCs are important. An overview of the different solar cell characterization techniques is presented in this paper. Simulations are carried out for these characterization techniques to study the behavior of the P3HT:PCBM based OSC in which silver NPs are incorporated in the active layer. The simulations are carried out for the cell structure in the presence of diff erent non-ideality factors. The non-idealities include mobilitylimitations, presence of traps, recombination losses, low generation, presence of non-ideal values of series and shunt resistances, the effect of doping, etc. The simulated characterization techniques can be utilized for the performance study and parameter extraction of these NP incorporated OSCs.

Recent Advances in the Determination of Optimal Active Layer Thickness for Bulk Heterojunction Organic Solar Cells

Sakshi Koul,Najeeb-ud-din Hakim 한국전기전자재료학회 2018 Transactions on Electrical and Electronic Material Vol.19 No.5

Organic solar cells have gathered much research interest in recent years because of their advantages like low-cost, fl exibilityand light-weight. This paper presents a fi rst of its kind, critical review of the theoretical and experimental studies performedto determine the outcome of changing active layer thickness on the working of a bulk heterojunction organic solar cell. Thefunctional principles of an organic solar cell along with its typical parameters are briefl y outlined. This paper discusses thefeatures of the active layer and response of these features to changing active layer thickness which determines the deviceperformance. Subsequently we describe the changes occurring in the parameters of the solar cell, followed by a detailedaccount of the optimal thickness ranges for diff erent bulk heterojunction solar cells. A concise description of the donor andacceptor material properties is also presented. In the last section, simulations performed by changing active layer thicknessfor two diff erent active layer material combinations have been presented, wherein we used poly(3-hexylthiophene): P3HT asthe electron donor and phenyl-C 61 -butyric acid methyl ester: PCBM as the electron acceptor for one cell and the other cellhas poly(9,9-dioctylindenofl uorene- co -benzothiadiazole): PIF8BT and N ′-bis(1-ethylpropyl)-3,4,9,10-perylene tetracarboxydiimide: PDI as donor and acceptor respectively. The paper concludes with a brief discussion of the applicability of annealingprocess to improve the optimal active layer thickness ranges of organic solar cells.

졸업논문(卒業論文) : 양단(兩斷)된 국가(國家)의 통일문제(統一問題) -한국(韓國)과 독일(獨逸)의 경우(境遇)-

백행걸 ( Haeng Koul Paik ) 국방대학교 안보문제연구소 1965 국방연구 Vol.18 No.-

유니버셜 관절을 이용한 2차원 레이저 영상 구현

김종걸(Jong Koul Kim),김태강(Tae Kang Kim),이건영(Keon Young Yi) 대한전기학회 2000 대한전기학회 학술대회 논문집 Vol.2000 No.7

ON WEYL FRACTIONAL CALCULUS AND H-FUNCTION TRANSFORM

Raina, R.K.,Koul, C.L. Department of Mathematics 1981 Kyungpook mathematical journal Vol.21 No.2

결정연신법으로 연신한 고밀도 폴리에틸렌 배향물의 비선형 동적 점탄특성 발현 메커니즘

조남주,이상걸 釜山大學校生産技術硏究所 1997 生産技術硏究所論文集 Vol.53 No.-

결정연신법으로 연신한 고밀도 폴리에틸렌(HDPE) 배향물의 피로과정에서의 비선형 점탄특성을 비선형 점탄성 파라미터, NVP(Nonlinear Viscoelastic Parameter)로 평가하였다. NVP는 가해준 변형에 대한 응답 응력파의 기본 응력파(선형적 응답)로 부터의 차이를 직접 측정하여 이를 규격화한 것이다. 피로과정에서의 비선형 점탄특성의 발현은 HDPE 배향물의 피로강도에 지대한 영향을 미친다는 사실을 알 수 있었으며, NVP가 고분자재료의 내피로성을 평가하는 척도로서 사용 가능하다는 사실이 증명되었다. 또한, 피로과정에서의 고차구조 변화와 비선형 점탄특성과의 관계를 조사한 결과, 반복 변형이 HDPE 배향물의 무정형 영역 또는 미결정의 경계면에 집중하면 할수록 NVP 값은 커지고 비선형 점탄특성이 현저해 짐을 알았다. 한편, 주위온도가 HDPE 배향물의 피로과정에서의 비선형 점탄특성에 미치는 영향을 검토한 결과, α-₁결정완화영역인 323K에서는 반복 변형이 라멜라간의 무정형 영역뿐만 아니라 mosaic block간에도 인가되어 NVP 값이 실온보다 감소하였으며, crack의 성장원이 되는 mosaic block간에 반복 변형이 가해지므로 피로강도는 실온보다 감소하였다. 또, α-₂결정완화영역인 350K에서는 라멜라 결정이 점탄성적인 거동을 하므로 무정형 영역 및 결정 영역이 함께 변형을 받게 되어 NVP 값은 실온보다 감소하였으며, 피로강도는 반복 변형이 비교적 균일하게 가해지므로 α-₁결정완화영역에서보다 증가하였다. Nonlinear dynamic viscoelasticity under cyclic fatigue for the oriented high-density polyethylene(HDPE) drawing at α₂-crystalline relaxation temperature was discussed in terms of nonlinear viscoelastic parameter(NVP) defined as the contribution of higher harmonics of Fourier expanded stress signal. It was clarified that the appearance of nonlinear viscoelasticity remarkably reduced the fatigue strength of the oriented HDPE. And also, it was confirmed that NVP could be used as an index of fatigue lifetime or fatigue strength for polymeric solids. Also, it could be concluded from the results of higher-order structural change during fatigue process that nonlinear dynamic viscoelasticity of the oriented HDPE originated from the deformation of the amorphous and/or crystallite boundary regions rather than that in the crystalline phase itself. In the case of a cyclic fatigue test at the α₁-crystalline relaxation temperature, since the degree of cyclic strain concentration in the amorphous region decreased because of the deformation in the intermosaic block region, the magnitude of NVP became smaller than that at room temperature. Also, the fatigue strength was lower than those at the other ambient temperatures, because lamellar crystals were decomposed into small mosaic block crystals whose interfaces became the origin of crack growth under cyclic straining. In the case of a cyclic fatigue test at the α₂-crystalline relaxation temperature, because of a more homogeneous sample deformation and the decrease of cyclic strain concentration in the amorphous and/or crystallite boundary regions, the magnitude of NVP became smaller than that at room temperature. The fatigue strength was greater than that at the α₁-crystalline relaxation temperature due to the more homogeneous sample deformation.

Compact Bent-Corner Orthogonal Beam Switching Antenna Module for 5G Mobile Devices

Karthikeya G. S.,Koul Shiban K.,Poddar Ajay K.,Rohde Ulrich L. 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.1

Typically, users engage with smartphones in either single-hand or dual-hand mode. To design antennas that operate at 28 GHz and have high pattern integrity for both modes of operation, an orthogonal beam switching module is required as a single phased-arrays would fail. First, a corner bent corporate fed array operating at 28 GHz is proposed, which has a forward gain of 8.5 dBi and a high-front-to-back ratio of 20 dB. Second, a corner bent printed Yagi antenna that also operates in the 28 GHz band is proposed. Both the corner bent antennas are compatible with the panel edge of commercial smartphones. The radiation from both antennas is mostly directed away from the user. A corner bent co-polarized orthogonal beam switching module is presented and characterized. The antenna module also has a shared ground, making it a potential candidate for future 5G smartphones. Detailed results are presented with adequate justification.

세그먼트 블록 공중합체의 표면 분자 운동성과 항혈전성

조남주,이영수,이상걸 釜山大學校生産技術硏究所 1998 生産技術硏究所論文集 Vol.54 No.-

Hard 및 soft segment가 다른 여러 종의 세그먼트 블록 공중합체를 제조하여, 생체모의환경 하에서의 재료의 표면 화학 조성 및 분자 운동성을 X선 광전자 분광기(XPS)와 동적 접촉각 측정으로 평가하였다. 그 결과, 수화상태에서는 물-고체간의 계면 자유 에너지를 최소로 하기 위하여 표면 자유 에너지가 높은 성분이 표면에 석출됨을 알 수 있었다. 특히, polyethylene glycol(PEG)과 같은 친수성의 soft segment를 갖는 세그먼트 블록 공중합체의 경우에는 수화상태에서 PEG 사슬이 표면에 농축되어 표면 자유 에너지가 크게 증가하였다. 이러한 주위환경 변화에 따른 표면 분자 운동성은 bulk의 분자 운동성에 많은 영향을 받았다. 한편, 세그먼트 블록 공중합체의 항혈전성은 물-고체 계면에서의 마이크로 상 분리 상태에 크게 영향을 받았다. Segmented block copolymers with various hard and soft segment components were prepared. The surface characteristics of segmented block copolymers in various environments was investigated by means of X-ray photoelectron spectroscopy (XPS) and dynamic contact angle measurements. These measurements revealed that in a hydrated state, the higher surface free energy component is enriched on surface in order to minimize the interfacial free energy between water and the solid surface. In particular, segmented block copolymers with hydrophilic soft segment such as polyethylene glycol(PEG) showed a large increase in surface tension in a hydrated state. Also, the surface molecular mobility was strongly correlated with bulk molecular motion. It was clearly marked that the antithrombogenicity of segmented block copolymers was influenced by microphase separation at the surface in a hydrated state.

Rickettsial Infections among the Undifferentiated Febrile Patients Attending a Tertiary Care Teaching Hospital of Northern India: A Longitudinal Study

Mansoor Tabeen,Fomda Bashir Ahmad,Koul Ajaz Nabi,Bhat Mushtaq Ahmad,Abdullah Nazima,Bhattacharya Sudip,Saleem Sheikh Mohd 대한감염학회 2021 Infection and Chemotherapy Vol.53 No.1

Background: Acute undifferentiated febrile illness (AUFI) is one of the most daunting challenges a physician faces in such settings. Among AUFI, rickettsial infections are most common and related infections (such as anaplasmosis, ehrlichiosis, and Q fever) which are caused by an unusual type of bacteria that can live only inside the cells of another organism. The present study was therefore planned with an objective to estimate the prevalence of rickettsial infection among patients of undifferentiated fever and to determine any association of socio-demographic characteristics with rickettsial disease. Materials and Methods: Patients presenting with febrile illness and admitted or attending out-patient department of Sher-i-Kashmir Institute of Medical Sciences, Srinagar was approached and recruited in the study. Weil Felix Assay, enzyme-linked immunosorbent assay and indirect immunofluorescence assay were done to detect the anti-rickettsial antibodies. Serological evidence of a fourfold increase in IgG-specific antibody titer reactive with spotted fever group rickettsial antigen by indirect immunofluorescence antibody assays between paired serum specimens was considered a confirmatory diagnosis for the rickettsial disease. Results: Most of the patients were males 61.6%, and most 46.2% were in the age group of 20 -39 years. Most of the patients, 80.8% belonged to rural areas, and 48% belonged to the upper middle (II) class of the socio-economic class according to modified Kuppuswamy scale. Of the studied participants, a majority, 47.0%, were determined undiagnosed, while 15.4% studied participants were diagnosed to have a rickettsial disease. In patients positive for typhus group, 67.8% were IgM positive, 28.5% were IgG positive, and only 3% were positive for IgM and IgG. In patients positive for Scrub Typhus Group, 32.7% were positive for IgM, and 62.0% were positive for IgG, and only 5.0% were positive for both IgM and IgG. In patients positive for spotted fever group, 36.1% were positive for IgM, and 58.5% were positive for IgG, and only 5.5% were positive for both IgM and IgG. The prevalence of rickettsial disease was found to be 11.3%. Conclusion: Rickettsial diseases, typhoid and brucellosis, were the most prevalent diseased diagnosed among patients reporting to hospitals with undifferentiated febrile illness. Clinicians must consider rickettsial diseases as one of the differential diagnosis while treating patients with fever.

A Tutorial: Applications of Clinical Self-Efficacy Principles to Mentoring of SLP Assistants

Rubini Pasupathy,Renee Bogschutz,Rajinder Koul 한국언어재활사협회 2017 Clinical Archives of Communication Disorders Vol.2 No.1

There are an increasing number of speech-language pathology assistants (SLP-As) in the public school settings under the supervision of speech-language pathologists (SLPs) in the United States. One of the functions of SLPs is to mentor and facilitate the development of SLP-As. The primary aim of this tutorial is to use the social cognitive model of self-efficacy to enhance the knowledge and skills of SLP-As. Literature in social cognitive theory indicates that self-efficacy is a predictor of performance, particularly in education and health domains. Effectively incorporating the self-efficacy framework in the mentoring of SLP-As will improve clinical performance and outcomes, as well as increase job satisfaction and retention of SLP-As in the school setting.