Determination of small-field correction factors for cylindrical ionization chambers using a semiempirical method

Park, Kwangwoo,Bak, Jino,Park, Sungho,Choi, Wonhoon,Park, Suk Won Institute of Physics in association with the Ameri 2016 Physics in medicine & biology Vol.61 No.3

<P>A semiempirical method based on the averaging effect of the sensitive volumes of different air-filled ionization chambers (ICs) was employed to approximate the correction factors for beam quality produced from the difference in the sizes of the reference field and small fields.</P> <P>We measured the output factors using several cylindrical ICs and calculated the correction factors using a mathematical method similar to deconvolution; in the method, we modeled the variable and inhomogeneous energy fluence function within the chamber cavity. The parameters of the modeled function and the correction factors were determined by solving a developed system of equations as well as on the basis of the measurement data and the geometry of the chambers. Further, Monte Carlo (MC) computations were performed using the Monaco<SUP>®</SUP> treatment planning system to validate the proposed method.</P> <P>The determined correction factors (<img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn001.gif'/>) were comparable to the values derived from the MC computations performed using Monaco<SUP>®</SUP>. For example, for a 6 MV photon beam and a field size of 1  ×  1 cm<SUP>2</SUP>, <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn002.gif'/> was calculated to be <img ALIGN='MIDDLE' ALT='$1.125$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn003.gif'/> for a PTW 31010 chamber and <img ALIGN='MIDDLE' ALT='$1.022$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn004.gif'/> for a PTW 31016 chamber. On the other hand, the <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn005.gif'/> values determined from the MC computations were 1.121 and 1.031, respectively; the difference between the proposed method and the MC computation is less than 2%. In addition, we determined the <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn006.gif'/> values for PTW 30013, PTW 31010, PTW 31016, IBA FC23-C, and IBA CC13 chambers as well.</P> <P>We devised a method for determining <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn007.gif'/> from both the measurement of the output factors and model-based mathematical computation. The proposed method can be useful in case the MC simulation would not be applicable for the clinical settings.</P>

Gain or Loss from the Universal Banking System? : Deregulation and its Impact on the US Banking Industry 미국은행산업에서의 규제완화와 그 효과에 관한 연구

Park, Kwangwoo 中央大學校經營硏究所 2004 經營學論集 Vol.30 No.2

This article overview the future of the U.S. banking industry with the legislation of Gramm-Leach-Bliley Financial Services Modernization Act in 1999 by reviewing the extant literature on universal banking. Various advantages and disadvantages from relaxing the separation of commercial banking and investment banking are discussed in this paper. The U.S. experience of universal banking system prior to the Act and the performance of universal banking system in some OECD countries show evidence that universal banking has not harmed the social welfare of the relevant economy. Many existing research results support the case for the universal banking system, yet many possible problems are still to be resolved.

Mergers and Acquisitions in the Banking Industry : A Survey of the Empirical Literature 실증연구 서베이

Park, Kwangwoo 中央大學校經營硏究所 2003 經營學論集 Vol.30 No.1

This paper reviews the extant empirical literature in bank mergers. Banks in general are motivated to merge to improve efficiency, increase market power, expand government safety, or obtain managerial incentives. Earlier studies broadly find that post-merger profit efficiency is improved while there is little or no significant merger-related improvement in cost efficiency. The findings in previous work also show that although merged banks experience some increase in market power especially in intra-market, overall impact of bank consolidation on small business lending is little or negligible, while there is a larger impact on consumer prices of some financial products. The existing literature suggests that there are little merger-induced costs on the financial system due to widened government safety net and increased systemic risk. Finally, implications for fruitful future research are discussed in the conclusion.

Relationship Banking and Compensating Balance : A Theoretical Approach

Park, Kwangwoo 한국금융학회 2003 金融學會誌 Vol.8 No.2

대출기관이 차입자에게 양건예금(compensating balance)을 요구하는 관행은 전세계적으로 오래 전부터 존재하여 왔다. 양건예금은 은행이 정보가 불투명한(informationally opaque) 기업에게 대출할 때 유용하고, 이에 따라 역선택의 문제(adverse selection problems)를 줄일 수 있다. 그 이유는 양건예금이 채무자로부터 확보한 담보의 역할을 수행하기 때문이다. 이 논문은 왜 은행들이 거래기업들에게 대출금의 일부분을 은행에 남겨놓도록 요구하는 지 설명하는 이론적인 모형을 제시하고 있다. 은행은 차입자들에게 대출금의 일부를 은행예금계정에 남겨두도록 요구할 수 있는데, 이를 통해 은행은 효과적으로 대출금을 떼어먹으려는 "가짜기업인"(fake entreperneurs)들에게 융자하는 것을 억제할 수 있다(역선택의 문제감소). 또한, 경영자들은 경영악화의 신호를 받을 때, 사업을 계속하지 않고 청산할 수 있는 동기를 갖게 된다. 마지막으로 이 논문의 모형은 은행이 더 큰 권한을 가지면, 고객에게 더 높은 차입금리를 요구할 수 있는데, 이 경우 기업들은 양건예금을 선호할 수 있음을 보여준다. 실제사례나 실증연구결과들은 우리나라 은행들이 1990년대 후반 금융위기 이후 거래기업에 대한 권한이 대폭 증대되었고, 여러 형태의 지대착취(rent extraction)가 이루어지고 있음을 보여주고 있다. 본 이론은 이러한 발견들에 대한 이론적 기반을 제공하고, 나아가 관계금융의 유용성 논쟁에서 비용적 측면의 견해를 추가적으로 제시한다. The practice of requiring compensating balances to borrowers by the lending institution has been widely used around the world for a number of years. It is especially useful when banks are making loans to informationally opaque firms, thereby reducing adverse selection problems. Anecdotal and empirical evidence suggests that banks in Korea came to exercise power after onset of the financial crisis in late 1990s. Requiring greater portion of borrowed proceeds can be viewed as a typical practice by a main bank to exercise power against their client firms. This paper develops a model which explains why banks ask their clients to put aside part of their borrowed proceeds. An endogenously arisen "compensating balance" that requires the borrower to leave part of the loan proceeds at its checking account at the lending institution appears to have the features in our model. The compensating balance functions as collateral. In the model, the "security-deposit" set aside ahead of time in effect is collateral. A bank can ask the borrower to keep some fraction of the loan proceeds at its account with the bank, so that the bank can effectively rule out "fake" entrepreneurs from taking out loans (i.e., a reduction in adverse selection problem). It also gives incentives to the entrepreneurs to liquidate the project when it receives the bad signal. There exists much recent evidence that when banks gain power, then they can exercise it by charging higher interest rates to their clients or asking compensating balance at the time of lending. Our theory provides theoretical foundation for those findings, and further shows that close bank-firm relationship may result in costly consequences.

Controlling shareholders and financial constraints around the world

Park, Jin Ho,Park, Kwangwoo,Ratti, Ronald Andrew Emerald (MCB UP ) 2018 Managerial finance Vol.44 No.1

<B>Purpose</B><P>The purpose of this paper is to examine the effect of controlling shareholders’ ownership of firms on the firms’ financial constraints in 22 economies for the 1982-2009 period.</P><B>Design/methodology/approach</B><P>The authors employ a generalized method of moments-based instrumental variables estimator to estimate empirical models.</P><B>Findings</B><P>It found that the overinvestment propensity of controlling shareholders becomes less severe with an increase in cash-flow rights. It further indicates that a higher deviation between the control rights and cash-flow rights of controlling shareholders lower their overinvestment propensity, thereby lowering the firm’s financial constraints.</P><B>Originality/value</B><P>The results suggest that a higher protective legal environment for minority shareholders blocks the entrenchment of controlling shareholders and thus benefitting the firm with slackened financing constraints in the given legal origin.</P>

Impact of the Respiratory Motion and Longitudinal Profile on Helical Tomotherapy

Park, So Hyun,Choi, Jinhyun,Kim, JinSung,Ahn, Sohyun,Kim, Min Joo,Lee, Ho,Choi, Seo Hee,Park, Kwangwoo Korean Society of Medical Physics 2018 의학물리 Vol.29 No.1

The $TomoTherapy^{(R)}$ beam-delivery method creates helical beam-junctioning patterns in the dose distribution within the target. In addition, the dose discrepancy results in the particular region where the resonance by pattern of dose delivery occurs owing to the change in the position and shape of internal organs with a patient's respiration during long treatment times. In this study, we evaluated the dose pattern of the longitudinal profile with the change in respiration. The superior-inferior motion signal of the programmable respiratory motion phantom was obtained using AbChes as a four-dimensional computed tomography (4DCT) original moving signal. We delineated virtual targets in the phantom and planned to deliver the prescription dose of 300 cGy using field widths of 1.0 cm, 2.5 cm, and 5.0 cm. An original moving signal was fitted to reflecting the beam delivery time of the $TomoTherapy^{(R)}$. The EBT3 film was inserted into the phantom movement cassette, and static, without the movement and with the original movement, was measured with signal changes of 2.0 s, 4.0 s, and 5.0 s periods, and 2.0 mm and 4.0 mm amplitudes. It was found that a dose fluctuation within ${\pm}4.0%$ occurred in all longitudinal profiles. Compared with the original movement, the region of the gamma index above 1 partially appeared within the target and the border of the target when the period and amplitude were changed. Gamma passing rates were 95.00% or more. However, cases for a 5.0 s period and 4.0 mm amplitude at a field width of 2.5 cm and for 2.0 s and 5.0 s periods at a field width of 5.0 cm have gamma passing rates of 92.73%, 90.31%, 90.31%, and 93.60%. $TomoTherapy^{(R)}$ shows a small difference in dose distribution according to the changes of period and amplitude of respiration. Therefore, to treat a variable respiratory motion region, a margin reflecting the degree of change of respiration signal is required.

축산업 대상 태양광 발전 시스템 효율향상을 위한 430W급 마이크로 컨벤세이터 개발

박광우(Kwangwoo Park),강건민(Geonmin Kang),이상로(Sangro Lee),강선희(Seonheui Kang),김영탁(Youngtak Kim),양주석(Jusuk Yang),김창선(Changsun Kim),김경민(Kyoungmin Kim) 한국신재생에너지학회 2020 한국신재생에너지학회 학술대회논문집 Vol.2020 No.8

양심적 병역 거부에 대한 그리스도교 윤리학적 고찰 및 대안 모색: 슐라이어마허의 그리스도교 윤리학적 관점을 중심으로

박광우(Kwangwoo Park) 연세대학교 신과대학(연합신학대학원) 2019 신학논단 Vol.96 No.-

This study aims at the Christian ethical consideration of conscientious objection to military service in Korea based on the understanding of Christian ethics by Friedrich D. E. Schleiermacher in order to derive the alternative of resolving the conflict over discussion about conscientious objection to military service. The foundation of Schleiermacher’s Christian ethics is the existence of Christians. The existence of Christians is a combination of universality in which they are accepted in an unconditional relationship with God through Christ and specificity in which that relationship actually appears in part. The country is based on individuals carrying out productive activities to form nature based on reason and plays the role of identification, so that the members in the community can be connected with each other. For this, the self-defense of country is justified in the relationship with the other states which is conducted in the diplomatic and martial way. Schleiermacher’s understanding of obligatory military service of Christians is a combination of the existence of Christians and the understanding of the country as the place of their actions. Schleiermacher claimed that obligatory military service is ethically fair to Christians, but Christians must strive for tolerance of the minority that can show new possibilities of national development within the country. He also argued that international peace activities are also important in order to fundamentally restrict war. Here, there are three types of attitudes that must be taken by the Korean church and Christians toward conscientious objection to military service. First, Korean Christians must consider obligatory military service as neighborly love. Second, they must struggle to tolerate conscientious objectors, which are the minority, and amend related laws. Third, they must strive to peacefully resolve the conflict between South and North Korea, which is the source of obligatory military service. The ethical attitude and act of considering the reality of Christians and gradually aiming for the ideal will productively reject the argument about conscientious objection to military service, while also gradually bringing Korea closer to the ‘Kingdom of God’.

공적 예배의 의미 고찰 - 예배에 대한 슐라이어마허의 윤리적 이해를 중심으로

박광우(Kwangwoo Park) 한국기독교학회 2021 한국기독교신학논총 Vol.119 No.-

본 논문은 슐라이어마허의 예배에 대한 윤리적 이해를 바탕으로 코로나 시대와 같은 오늘날 공적 예배가 어떤 의미를 지니는지 알아보고자 한다. 슐라이어마허에 따르면 예배란 자연을 이성으로 문화화하는 윤리 과정 가운데 인간에게 주어진 존재론적 기초를 개성적으로 드러내는 인간의 행위이다. 인간의 실존적 조건인 개성과 공동성은 그의 존재론적 기초인 인간성을 새롭게 드러내거나 상대적으로 규정하는 가운데 상호작용함으로써 인간성의 점진적 개진에 기여한다. 슐라이어마허에게서 공적 예배는 개인의 개성적 종교성을 규정하면서도 개인의 개성적 종교성을 통하여 생동성을 얻는다. 그리고 공적 예배의 이행 핵심은 예배에 참여하는 사람들 간의 상호작용을 통한 개성과 공동성 간의 조화다. 이러한 이해에 따르면 공적 예배는 1) 개인의 종교성을 규정하여 의식시키는 가운데 그 스스로 성찰하도록 하여 자기절대화에 빠지지 않도록 하는 마중물이고, 2) 맹목적으로 강요되는 것이 아니라 개인의 주체적인 종교성을 기초로 한 생동적인 장이며, 3) 공적 예배에 참여하는 사람들이 상호작용하면서 그들의 공동적인 감정, 곧 하느님 나라의 정신을 함께 드러내는 곳이다. This study seeks to describe the significance of public worship within the context of the current Covid-19 pandemic, using Schleiermacher’s ethical understanding of worship. According to Schleiermacher, worship is a human activity which reenacts the ontological basis on which human beings are based through the ethical process of enculturating nature by reason. According to Schleiermacher, Individuality and communality as the existential conditions of human being freshly manifest and relatively define humanity as the ontological basis of human being, they also contribute to the gradual unfolding of humanity through their mutual interaction. For Schleiermacher, public worship plays the role of the providing a framework within which individual religiosity can find meaning and new vitality. The essence of the practice of public worship is the harmony between individuality and communality through the mutual interaction among people engaged in worship. When understood this way, public worship can 1) work as a means to prevent self-absolutization by making the self-conscious of the relativeness of its individual religiosity, 2) as a sphere of vitality that is grounded in the subjective religiosity of individuals and does not force itself on worshipers and 3) as a sphere where public-worship participants interact among themselves and their common feeling, the spirit of the kingdom of God is revealed.

루터의 종교개혁이 독일 문화에 미친 영향들

박광우(Park, Kwangwoo) 순천향대학교 인문학연구소 2020 순천향 인문과학논총 Vol.39 No.2

본 논문은 루터의 종교개혁이 독일 문화와 독일인들의 심성에 얼마나 많은 영향을 끼쳤는가에 대해서 분석을 하고, 그 결과를 토대로 현재 독일인들의 문화생활을 이해하는 데에 목적을 둔다. 루터는 그 당시 종교개혁이라는 사건을 일으키려고 하기보다는 가톨릭의 문제점을 지적하고 개선하려고 했다. 그러나 자신의 의지와는 달리 커다란 사건에 휘말리게 되고 가톨릭과 전혀 다른 길을 가게 된다. 이 과정에서 그는 성서를 모국어인 독일어로 번역했고, 코랄이라는 음악 형식을 발전시켰으며 직업에 대한 소명 의식을 강조하며 개인의 가치와 평등을 존중하는 근대적 사고방식을 발전시켜 오늘날 독일인들의 정신에 많은 영향을 끼치고 있다. 위대한 독일인 10인을 선정하라고 한다면, 그 순위 안에 항상 루터가 포함된다는 사실에서 그는 독일 문화 전반에 걸쳐 지대한 영향을 미치고 있다는 것을 알 수가 있다. This paper aims to analyze to what extent Luther s Reformation influenced German culture and German mentality, and based on the results, to understand the current cultural life of Germans. Luther tried to point out and improve problems of the Catholic church, rather start the Reformation. However, on the contrary, he was caught up in a big occurrance and outset a completely different path from Catholicism. In this process, he translated the Bible into his native language German, developed the musical form called “Choral”, and established a modern way of thinking that emphasizes his vocation to the profession and respects individual values. The fact that Luther is always included in the rankings, when choosing the ten great Germans, shows that he has a profound effect on the German culture.