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Jihun Cha,장은지,정민,김도연,김다홍,이영규,박순철,김균석,정완상 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.2
In this paper, we consider the damped harmonic oscillator with a time-dependent damping constant and a time-dependent angular frequency, which is actually the generalized Caldirola-Kanai Hamiltonian. For some choices of the time-dependent damping constant and the time-dependent angular frequency, we investigate the exact solutions. We also obtain the corresponding conserved quantities and finally discuss the quantum damped harmonic oscillator with a time-dependent damping constant and a time-dependent angular frequency.
전기자동차용 납산, 리튬이온 구동축전지팩 성능특성 비교
차지훈(Jihun Cha),박용성(Yongsung Park),배중호(Joongho Bae),이광범(Kwangbum Lee),정혁(Hyuck Jung) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Successful commercialization of electric vehicle is depended on research and development level of traction battery being main component of Electric vehicle. Standard test procedure for Li-ion traction battery for performance, reliability and safety is under discussion in the standard of ISO-12405. This paper evaluated Energy-Capacity, Power and Energy efficiency at fast charging of Lead-acid and Li-ion battery pack in the view of ISO/DIS 12405-2. By the tests, This paper confirms the certain performance gap between commercialized Pb-acid and Li-ion traction battery pack. This performance gap would be caused by different material characteristic including chemical potential and internal resistance. The result of this paper could be applied to basic data when designing Battery Management System of traction battery pack. Also this paper evaluated the validity of test procedures of ISO/DIS 12405-2 by actual test.
자동차 안전기준 중 구동축전지 출력시험 개정을 위한 연구
차지훈(Jihun Cha),김경삼(Gyungsam Kim),정혁(Hyuk Jung),최동석(Dongseok Choi),이슬기(Seulki Lee),이광범(Kwangbum Lee),권해붕(Haeboung Kwon),용기중(Geejoong Yong) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Increasing needs about how to evaluate maximum power of traction battery lead R&D of power test procedure for traction battery by supporting of MLTM(Ministry of Land, Transport and Maritime Affairs). To be adopted KMVSS, This power test procedure would be specific, possibly repeatable and anti-design-regulatable. As a first step for this R&D, other power test procedure for traction battery had been studied even though module level test procedure not a pack level. Traction battery"s dynamic power performance pattern had been also studied. On this paper, the power test procedure Ver. 1.0 developed by this R&D is evaluated by commercialized traction battery.
Cha, Hyojung,Chung, Dae Sung,Bae, Suk Young,Lee, Min‐,Jung,An, Tae Kyu,Hwang, Jihun,Kim, Kyung Hwan,Kim, Yun‐,Hi,Choi, Dong Hoon,Park, Chan Eon WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.12
<P><B>Abstract</B></P><P>Two anthracene‐based star‐shaped conjugated small molecules, 5′,5″‐(9,10‐bis((4‐hexylphenyl)ethynyl)anthracene‐2,6‐diyl)bis(5‐hexyl‐2,2′‐bithiophene), HBantHBT, and 5′,5″‐(9,10‐bis(phenylethynyl)anthracene‐2,6‐diyl)bis(5‐hexyl‐2,2′‐bithiophene), BantHBT, are used as electron‐cascade donor materials by incorporating them into organic photovoltaic cells prepared using a poly((5,5‐E‐alpha‐((2‐thienyl)methylene)‐2‐thiopheneacetonitrile)‐alt‐2,6‐[(1,5‐didecyloxy)naphthalene])) (PBTADN):[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC<SUB>71</SUB>BM) blend. The small molecules penetrate the PBTADN:PC<SUB>71</SUB>BM blend layer to yield complementary absorption spectra through appropriate energy level alignment and optimal domain sizes for charge carrier transfer. A high short‐circuit current (<I>J</I><SUB>SC</SUB>) and fill factor (FF) are obtained using solar cells prepared with the ternary blend. The highest photovoltaic performance of the PBTADN:<B>BantHBT</B>:PC<SUB>71</SUB>BM blend solar cells is characterized by a <I>J</I><SUB>SC</SUB> of 11.0 mA cm<SUP>−2</SUP>, an open circuit voltage (<I>V</I><SUB>OC</SUB>) of 0.91 V, a FF of 56.4%, and a power conversion efficiency (PCE) of 5.6% under AM1.5G illumination (with a high intensity of 100 mW<SUP>−2</SUP>). The effects of the small molecules on the ternary blend are investigated by comparison with the traditional poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl‐C61‐butyric acid methyl ester (PC<SUB>61</SUB>BM) system.</P>
Cha, Jeehyun,Lihm, Hoseob,Kim, Yoonyoung,Kang, Jihun Korean Society for Hospice and Palliative Care 2019 한국호스피스.완화의료학회지 Vol.22 No.4
목적: 높은 수준의 호스피스 및 완화의료 교육은 한국 의과대학 교육과정에 필요하다. 하지만 이와 연관된 연구는 많지 않은 실정이며 이에 본 연구는 호스피스와 완화의료 교육 과정을 마친 의과 대학생의 호스피스와 완화의료에 대한 인지 및 태도 변화를 연구하기 위해 수행 되었다. 또한 의과대학의 기본 교육 과정 안에서 호스피스 교육과정의 역할에 대해서도 탐구하고자 한다. 방법: 호스피스와 완화의학에 대한 통합적인 교육과정을 마친 총 76명의 의학과 4학년 학생이 자기 기입 형태의 설문조사에 참여 하였다. 교육 과정을 마친 후 수업 전과 비교하여 수업 후의 후의 호스피스 및 완화의료에 대한 지식과 태도를 조사하였다. 결과: 교육 과정을 이수한 이후 가장 큰 변화는 호스피스 및 완화의료 세팅에서 적절한 마약성 진통제를 사용할 수 있는가 하는 부분에서 나타났다(3.50점 vs 5.32 점; P≤0.001). 수업 전과 비교하여 수업 이후 호스피스와 완화의료에 대한 태도를 나타내는 질문인 "나는 호스피스와 완화의료의 목표와 역할을 바르게 알고 있다"고 답한 학생은 17명(22.4%)에서 65명(85.6%)으로 증가하였다. 또한 "예비의사로서 나는 호스피스와 완화의료의 바른 적용 시점을 알고 있다"고 답한 학생은 수업 전의 22명(28.9%)과 비교하여 65명(85.6%)으로 증가하였다. 결론: 통합적인 호스피스 완화의료 교육과정은 의과 대학생의 호스피스 및 완화의료에 대한 인식과 태도를 긍정적인 방향으로 변화시킬 수 있다. Purpose: High-quality hospice and palliative medicine curricula are necessary in Korean medical schools. This study evaluated changes in students' knowledge and attitudes toward both hospice and palliative care following the completion of a course on these topics, as well as the course's overall role in the basic medical education curriculum. Methods: Questionnaires measuring knowledge and attitudes were collected before and after the course from 76 fourth-year medical students, who had received instructions integrating both hospice and palliative care in 2016. Results: The questionnaire item "Select the correct answer on the use of opioid pain control in hospice and palliative care" changed the most in terms of number of correct answers pre- and post-course (3.50 and 5.32, respectively; P<0.001). Pre- and post-course, the numbers of students who answered "Strongly Agree" and "Agree" to questions concerning their attitudes toward hospice and palliative care ("I know the purposes and roles of hospice and palliative care") were 17 (22.4%) and 65 (85.6%), respectively (P≤0.001). Affirmative responses also increased for "As a pre-physician, I know when to describe and advise hospice and palliative care to patients", from 22 (28.9%) to 65 (85.6%; P≤0.001). Conclusion: This study showed that comprehensive hospice education in the form of an integrated educational course might promote changes in medical students' knowledge and attitudes toward hospice and palliative medicine.
A 15-MHz 1-3 piezocomposite concave array transducer for ophthalmic imaging
Jung Hyui Cha,Byungwoo Kang,Jihun Jang,Jin Ho Chang IEEE 2015 and Frequency Control Vol.62 No.11
<P>Because of the spherical shape of the human eye, the anterior segments of the eye, particularly the cornea and the lens, create high levels of refraction and reflection of ultrasound which negatively affect the performance of linear and convex arrays. To minimize the ultrasound energy loss, a 15-MHz concave array transducer was designed, fabricated, and characterized; its footprint is able to mesh well with the shape of the cornea. The concave array has a curvature with a radius of 15 mm and 128 elements with a 1.44λ pitch. Its elevational focus and view angle are 30 mm and 72.3°, respectively, thus allowing the imaging area to cover the retinal region of interest in the posterior segment. As an active layer, a 1-3 piezocomposite was designed and fabricated in response to the bidirectional (i.e., azimuthal and elevational) curvature of the concave array and the high coupling coefficient. From the performance evaluation, it was found that the completed concave array is able to provide a center frequency of 15.95 MHz and a -6-dB fractional bandwidth of 67.8% after electrical tuning has been conducted. The crosstalk level was measured to be less than -25 dB. It was verified that the concave array is robust to the refraction and reflection from the cornea through pulse-echo testing using a custom-made eye-mimicking phantom. Furthermore, images of both the wire-target phantom and the ex vivo porcine eye were acquired by the finished concave array, which was connected to a commercial ultrasound scanner equipped with a research package. The evaluation results demonstrated that the developed concave array transducer is a possible alternative to conventional arrays for effectively imaging the posterior segment of the eye.</P>
On Rate-adaptive LDPC-based Cross-layer SVC over Bursty Wireless Channels
( Yongju Cho ),( Jihun Cha ),( Hayder Radha ),( Kwang-deok Seo ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.9
Recent studies have indicated that a significant improvement in wireless video throughput can be achieved by Cross Layer Design with Side-information (CLDS) protocols. In this paper, we derive the operational rate of a CLDS protocol operating over a realistic wireless channel. Then, a Rate-Distortion (R-D) empirical model for above-capacity Scalable Video Coding (SVC) is deduced to estimate the loss of video quality incurred under inaccurate rate estimation scenarios. Finally, we develop a novel Unequal Error Protection (UEP) scheme which leverages the characteristics of LDPC codes to reduce the distortion of video quality in case of typically-observed burst wireless errors. The efficacy of the proposed rate adaptation architecture over conventional protocols is demonstrated by realistic video simulations using actual IEEE 802.11b wireless traces.
An Efficient Type Codec for Point Data in Lightweight Applications Scene Representation (LASeR)
YeSun Joung,Jihun Cha,Won-Sik Cheong,Young-kwon Lim,Kyuheon Kim 한국전자통신연구원 2005 ETRI Journal Vol.27 No.6
Recently, MPEG has opened activity to standardize scene representation for lightweight applications such as in mobile phones. The standard is named lightweight applications scene representation (LASeR) and can be applied to improve and make efficient rich media applications and services on mobile devices. In this standard, we proposed an efficient type codec for point data to maximize the bit efficiency of LASeR. In this paper, we describe the new method and the test results of the proposed scheme.