양자 터널링 현상을 이용한 대전된 BTZ 블랙홀의 열역학적 안정성 연구

김홍빈 한국물리학회 2018 새물리 Vol.68 No.9

The purpose of this study is to investigate the thermodynamic stability of charged Banados-Teitelboim-Zanelli (BTZ) black holes defined in (2+1) dimensions. To accomplish this goal, we used the picture in which Hawking radiation is understood to be a quantum tunneling process. First of all, we calculated the probability amplitude of neutral massive scalar particles for the classically forbidden trajectory that goes from inside the BTZ black hole to outside by using the null geodesic method and the Hamilton-Jacobi method, respectively. In that calculation, we see the contributions of higher-order terms which amount to the back reaction effect of the Hawking radiation. Using those higher-order terms, we read off the heat capacity of the black holes from the second-order ($\omega^2$) term with respect to the energy of the emitted particle and conclude that charged BTZ black holes are stable thermodynamically in the region of positive temperature. 본 연구의 목적은 (2+1) 차원에서 정의되는 대전된 BTZ (Banados-Teitelboim-Zanelli) 블랙홀의 열역학적 안정성을 알아보는 것이다. 이를 위해 본 연구에서는 호킹 복사를 일종의 양자 터널링 과정으로 묘사하는 접근 방식을 사용하였다. 우선, 질량을 가지는 중성 스칼라 입자가 고전적으로 금지된 경로 즉, BTZ 블랙홀의 내부에서 외부로 터널링하는 확률 진폭을 영지름길 (null geodesic) 방법과 해밀턴-야코비 방법을 사용하여 각각 계산하였다. 이 과정에서 호킹 복사의 되튀김 효과에 해당하는 고차항의 기여가 나타나는데, 그 중 방출 입자의 에너지에 대한 이차 ($\omega^2$) 항으로부터 블랙홀의 열용량을 알아낸 후 이로부터 대전된 BTZ 블랙홀이 온도가 0보다 큰 영역에서 열역학적으로 안정적이라는 결론을 얻었다.

장 관점에 기반한 두 개의 축전기 패러독스의 해석

김홍빈,지영래 한국물리학회 2017 새물리 Vol.67 No.12

본 논문에서는 에너지 보존 법칙이 성립하지 않는 것처럼 보이는 두 개의 축전기 패러독스를 해소하는 대학생들의 설명을 유형별로 소개한 후, 전자기장의 관점에서 패러독스를 설명하는 한 가지 방식을 제안하였다. 많은 대학생들이 학부 과정에서 포인팅 벡터라는 개념을 학습하였음에도 불구하고 두 개의 축전기로만 이루어진 단순한 회로에 대해서조차 전자기장이 실어 나르는 에너지 흐름에 대한 적절한 설명을 제시하지 못하였다. 전자기장을 통해 각각의 축전기에서 에너지가 어떻게 방출되고 흡수되는지에 대한 구체적인 과정을 이해하는데 도움을 줄 수 있는 설명 방식을 제안한다. In this paper, we present undergraduate students' explanation on the two-capacitor paradox, which may seem to violate the energy conservation law. We also suggest a way of explaining the paradox based on the concept of electromagnetic fields. Although many of the undergraduate students have learned the concept of Poynting vectors, they cannot provide a proper explanation of the energy flow through electromagnetic fields even when the circuit consists of simply two capacitors. We present an explanation that will help students to understand the mechanism of energy emission from and absorption by each capacitor through the electromagnetic fields.

골수이식 후 발생하는 감염증(1985∼1996)

김홍빈,박상원,김의석,김남중,신동현,오명돈,박선양,김병국,최강원 대한감염학회 1999 감염 Vol.31 No.4

대학생들의 다중극 전개에 대한 이해의 어려움과 이에 대한 해소 방안 : 1차원 전하 분포를 중심으로

김홍빈,이경호 한국물리학회 2016 새물리 Vol.66 No.7

The multipole expansions of the electric potential appearing in electrostatics provide a useful method of characterizing local charge distributions. Students may familiarize themselves with mathematical tools, such as Legendre polynomials, spherical harmonics, and perturbation theory, by studying this topic in an upper-level electromagnetism course. Especially, perturbation theory is the typical way of approaching problems in physics, so the multipole expansion is very important when it comes to physics education. In this study, we introduced students' difficulties appearing in the weekly reports that they submitted and classified them into several types. Then, we analyzed the structure of the prominent difficulties. After that, we revealed the physical meaning of each term in the multipole expansion in a way analogous to the gravitational potential. In this way, we propose a better way to teach the subject that will minimize the potential difficulties experienced by students and will concentrate on the essence of the subject as a perturbative expansion. 정전기학에서 등장하는 전위의 다중극 전개는 국소적인 전하 분포의 양상에 관한 유용한 정보를 제공한다. 학생들은 대학 전공 전자기학 과정에서 다중극 전개를 학습함으로써 물리학의 전형적인 문제 접근 방식이라 할 수 있는 섭동 이론 뿐만 아니라, 드장드르 다항식, 구면조화함수 등 수학적인 테크닉을 익힐 수 있기 때문에 물리교육의 측면에서 이는 매우 중요한 주제라 할 수 있다. 본 논문에서는 전자기학을 수강하는 학생들이 제출한 주간보고서에 나타난 다중극 전개에 대한 학생들의 어려움을 분석하고, 이를 몇 가지 유형으로 분류한 다음 이 중 특징적인 어려움의 원인구조를 파악하였다. 그리고 1차원 전하분포를 통해 다중극 전개의 각 항들이 나타내는 물리적 의미를 중력의 경우와 비교하여 드러내고자 하였다. 이를 통해 해당 주제를 학습할 때 학생들이 느낄 수 있는 여러 가지 어려움들을 효과적으로 해소함과 동시에 섭동 전개로써의 다중극 전개의 본질에 더욱 집중할 수 있는 교수법을 제안하였다.

유기발광다이오드를 이용한 Photobiomodulation 기반 스킨케어 효과

김홍빈,정혜정,진석근,이병일,안재성,Kim, Hongbin,Jeong, Hyejung,Jin, Seokgeun,Lee, Byeongil,Ahn, Jae Sung 한국광학회 2021 한국광학회지 Vol.32 No.5

Photobiomodulation (PBM)-based therapy, which uses a phenomenon in which a light source of a specific wavelength band promotes ATP production in mitochondria, has attracted much attention in the fields of biology and medicine because of its effects on wound healing, inflammation reduction, and pain relief. Research on PBM-based therapy has mainly used lasers and light-emitting diodes (LEDs) as light sources and, despite the advantages of organic light-emitting diodes (OLEDs), there have been only a few cases where OLEDs were used in PBM-based therapy. In this research, the skin-care effect of PBM was analyzed using red (λ = 620 nm), green (λ = 525 nm), and blue (λ = 455 nm) OLED lighting modules, and was compared to the PBM effect of LEDs. We demonstrated the PBM-based skin-care effect of the red, green, blue OLED lighting modules by measuring the increase in the amount of collagen type-1 synthesis, the inhibition of melanin synthesis, and the suppression of nitric oxide generation, respectively.

1·2차 병원의 임상검체에서 분리된 황색포도구균의 항균제 내성양상

김홍빈,사종문,유재일,김봉수,이영선,윤옥진,윤혜령 대한감염학회 2000 감염 Vol.32 No.4

Motion Analysis of A Wind-Wave Energy TLP Platform Considering Second-order Wave Forces

김홍빈,민은홍,허상환,구원철 한국해양공학회 2022 한국해양공학회지 Vol.36 No.6

Offshore wind energy has become a major energy source, and various studies are underway to increase the economic feasibility of floating offshore wind turbines (FOWT). In this study, the characteristics of wave-induced motion of a combined wind-wave energy platform were analyzed to reduce the variability of energy extraction. A user subroutine was developed, and numerical analysis was performed in connection with the ANSYS-AQWA hydrodynamic program in the time domain. A platform combining the TLP-type FOWT and the Wavestar-type wave energy converter (WEC) was proposed. Each motion response of the platform on the second-order wave load, the effect of WEC attachment and Power take-off (PTO) force were analyzed. The mooring line tension according to the installation location was also analyzed. The vertical motion of a single FOWT was increased approximately three times due to the second-order sum-frequency wave load. The PTO force of the WEC played as a vertical motion damper for the combined platform. The tension of the mooring lines in front of the incident wave direction was dominantly affected by the pitch of the platform, and the mooring lines located at the side of the platform were mainly affected by the heave of the platform.

MgIn2S4 半導體 薄膜의 光吸收 特性

김홍빈,조동산 全南大學校 師範大學 科學敎育硏究所 1984 科學敎育硏究誌 Vol.9 No.1

Polycrystalline MgIn2S4 thin films were prepared by the spray pyrolysis method, and then the substrate temperature was from 300℃ to 350℃. The Crystal structure of the MgIn2S4 thin films was cubic with lattice constant a= 10.886Å, and the optical energy gaps were measured to be 1.93eV at substrate temperature 300℃, and 1. 92eV at 350℃, respectively. AIso, the energy gap of theMgIn2S4(Co) thin films doped with cobalt (20mole %) was 1.68eV, and that of MgIn2S4 (Cr) thin films doped with chromium (20mole %) was 2.15eV.

Numerical and experimental study of the dynamic response of a wind-wave combined energy platform under WEC motion constraints

김홍빈,구원철 대한조선학회 2024 International Journal of Naval Architecture and Oc Vol.15 No.-

The motion response of a wind–wave-combined energy platform with and without a wave energy converter (WEC) was analyzed using numerical simulations and wave tank experiments. The effects of the WEC power takeoff (PTO) and WEC motion constraints on the motion response of the platform were also analyzed. The analyzed model consisted of cylindrical WECs attached to a spar-shaped floating offshore wind turbine (FOWT) from front to back. Numerical analysis was performed using a potential-flow-based hydrodynamic program (ANSYS AQWA) based on the boundary element method to perform time domain analysis. Nonlinear Froude–Krylov forces and hydrostatic forces were considered to improve the accuracy of the numerical results. The dynamic interactions between the FOWT and the mooring lines were considered. The numerical results showed good agreement with the experimental data. The pitch and heave of the combined platform were reduced significantly by the motion of the WEC attached to the FOWT. In particular, the rotational motion of the WEC had the greatest impact on the motion reduction of the platform. This effect helped reduce the mooring tension. On the other hand, the pitch response of the platform increased slightly when the WEC was fixed to the platform (no motion) or when a large PTO coefficient was applied.

커피전문점 서비스품질 속성이 전반적 만족도에 미치는 대칭 및 비대칭 분석 -스타벅스와 이디야 비교 분석-

김홍빈,차석빈 한국관광학회 2017 관광학연구 Vol.41 No.4

The identification of primary service quality attributes that generate customer satisfaction is critical to organizational success. This study investigates the symmetric and asymmetric nature of the relationship between service quality attributes and overall customer satisfaction using two brand coffee shops (Starbucks and Ediya). Findings show that there are six dimensions of 24 service quality attributes. (employee service, shop facilities, collateral service, the brand, the menu, & the coffee quality). Within this symmetric relationship, most of the service factors positively affect the overall satisfaction with both brands. However, within an asymmetric relationship based on a three-factor model of customer satisfaction, many of the aforementioned attributes are classified differently. Employee service & shop facilities are identified as 'performance factors', while collateral service, brand, menu, & coffee quality are 'basic factors' for Starbucks. On the contrary, menu is identified as a 'performance factor', shop facility as 'excitement factor', and collateral service & brand are 'basic factors' for Ediya. Differences between a traditional symmetric approach and an asymmetric approach using a three-factor model of customer satisfaction are delineated. Furthermore, the theoretical and practical implications of the results are discussed. 고객만족을 창출하는 주요 서비스품질 속성을 찾아내는 것은 기업의 성공에 중요한 사항이다. 본 연구는 스타벅스와 이디야 커피전문점의 서비스품질 속성에 대한 만족과 전반적 만족 간 대칭적 및 비대칭적 관계를 비교분석하였다. 분석결과, 24개의 서비스품질 속성은 6개 서비스 요인(직원서비스, 매장 시설, 부대 서비스, 브랜드, 멘, 커피 품질)으로 도출되었다. 두 브랜드 간 대칭적 비교 분석에서는 유의한 모든 요인들이 전반적인 만족에 긍정적인 영향을 미치는 것으로 나타났다. 이에 비해 세 요인 고객만족 모델을 활용한 두 브랜드 간 비대칭적 비교 분석에서는 서비스품질 속성들이 서로 다르게 분류되었다. 스타벅스의 경우 직원서비스와 매장시설은 실행요인, 부대서비스, 브랜드, 메뉴, 커피품질은 기본요인으로 각각 구분되었고, 이디야의 경우 메뉴는 실행요인, 매장시설은 감동요인, 부대서비스와 브랜드는 기본 요인으로 각각 구분되었다. 본 연구는 서비스품질 속성과 전반적 만족 간 전통적인 대칭적 접근방식과 세 요인 고객만족 모델을 이용한 비대칭적 접근방식의 차이점과 분석결과에 따른 학문적, 실무적 시사점을 논의하였다.