Pattern-Reconfigurable MIMO Antenna for High Isolation and Low Correlation

Changyong Rhee,Yongjin Kim,Taejoon Park,Sung-su Kwoun,Byeonggwi Mun,Byungje Lee,Changwon Jung IEEE 2014 IEEE antennas and wireless propagation letters Vol.13 No.-

<P>In this letter, a reconfigurable radiation pattern antenna for multiple-input-multiple-output (MIMO) applications on mobile devices is proposed. The operating frequency band of the antenna is 5.15-5.35 GHz for a wireless local area network (WLAN) 802.11a service. Each antenna is composed of a loop-and-dipole structure, as well as two switches for the reconfigurable radiation pattern, to generate a beam in three different directions. The proposed antenna is designed to have an orthogonally directional radiation pattern with high isolation and a low-correlation coefficient in the MIMO environment.</P>

The Gains from International Investment Diversification: The Korean Case

Rhee,Changyong,Cho,Yoon Je THE KOREAN ECONOMIC SOCIETY 1999 JOURNAL OF ECONOMIC THEORY AND ECONOMETRICS Vol.5 No.1

Using monthly stock price data of 215 companies in 6 Asian countries, this paper estimates the gains from international diversification. By varying the number of stocks in the investor's choice set, we estimate the gains when the set is expanded to include foreign stocks. We find that the international diversification effect can be attained to an extent through domestic investment alone when the number of stocks held increases sufficiently. It implies that, once international lending and borrowing are liberalized through banking and bond market transactions, marginal gains from further opening of the stock market must be small.

貯蓄率의 國際比較에 있어서 文化的 要因의 중요성:미국 census자료를 이용한 實證分析

이창용 韓國計量經濟學會 1996 계량경제학보 Vol.7 No.-

본고는 국제 간 貯蓄率 격차를 설명하는 데 있어 文化的 要因의 중요성을 實證分析하고 있다. 만일 貯蓄率 결정에 있어서 文化的 要因이 중요하다면, 한국가로 이주한 移民者들의 貯蓄率은 出身國의 貯蓄率 격차와 體系的인 관계가 있어야 할 것이다. 移民者들을 소그룹으로 분리하여 가설검정한 Carroll, Rhee and Rhee(1994)와는 달리, 본고는 1980년과 1990년 미국 cencus 자료를 사용함으로써 移民者貯蓄率을 출신국가별로 비교할 수 있었다. 분석결과, 移民者들의 貯蓄率은 出身國에 따라 상이하였으나, 出身國別 貯蓄率과 母國 貯蓄率은 體系的 관계가 없는 것으로 나타났다.

Fundamental Stock Price and Investment

Changyong Rhee,Wooheon Rhee 서울대학교 경제연구소 1995 Seoul journal of economics Vol.8 No.3

This paper examines the issue of whether a firm's investment decisions respond more to market fundamentals than to bubbles. Using firm level data from COMPUSTAT, we design various proxies for market fundamentals based on (i) the dividend approach, (ii) the dividend smoothing approach, and (iii) the earnings approach. From the aggregated micro data, we find that business investment responds more to market fundamentals than to bubbles. On the other hand, results from the panel regressions are inconclusive since most of the explanatory power of the investment regression is derived from the individual firm specific effect.

자산유동화를 통한 학자금대출금리 결정에 관한 연구

이창용(Changyong Rhee),오승곤(Seungkon Oh) 한국경제연구학회 2010 한국경제연구 Vol.28 No.1

본고는 2005년 7윌 18일 「학술진흥 및 학자금대출 선용보증 등에 관한 법률」의 개정을 통해 도입된 학자금대출 유동화제도를 살펴보고, 학자금유동화증권(SLBS)의 가격결정 메커니즘과 타당성을 분석하였다. 유동화를 통한 학자금대출 제도의 가장 큰 특징은 SLBS 채권의 발행을 통하여 대출재원을 조달함에 따라 학자금대출금리가 시장금리에 연동되는 것이다. 그라고 학자금대출금의 조기상환과 유동화에 따른 비용, 금리결정 시점 간의 불일치 등의 위험헤지를 위하여 SLBS 채권에 콜옵션을 부가하였는데, 실제 시장에서는 콜옵션의 행사조건에 따라 만기별로 옵션의 시장가치와 이론가치를 다르게 평가하는 것으로 나타났다. SLBS의 발행역사가 짧고 학자금대출의 조기상환 정보도 충분하지 않을 뿐만 아니라, 조기상환에 대하여 수수료가 부과되지 않는 등의 이유로 행사조건에 따라 투자자들이 콜옵션에 대하여 이론가보다 프리미엄을 더 요구하는 경우도 있어, SLBS 채권의 콜옵션 조항의 조정 뿐만 아니라 조기상환에 대한 수수료 부과, 조기상환 운용펀드 신설 등을 학자금대출 재원의 조달금리를 낮추기 위한 대안으로 제시하였다. This study describes the student loan securitization program created under the amendments to "Sciences Promotion and Credit Guarantee, etc. for School Expense Loans Act" on July 18th, 2005, analyzing properness of pricing mechanism of the student loan backed securities(SLBS). One of the most notable characteristics of the securitization program is the linkage of interest rates between student loan and SLBS, where SLBS is issued at the market price in the Korean bond market. In addition, call options are attached to SLBS to hedge the risks imposed on the costs from early payment and securitization of student loan as well as periodic mismatch between determinations of interest rates on student loan and SLBS. This study also shows the trend of call options attached to SLBS being overvalued at the Korean Bond market under the assumption of partial repurchases. Investors request for higher premium because of SLBS's short history, insufficient information on early payments, no penalty on early payments, and etc. The study suggests some structural reforms that need to be introduced, such as revising the call option specification, imposing penalties on early payments, establishing a fund for early payment, to induce fair prices of SLBS and student loans.

Population Aging and Financial Markets: A Cross-Country Study

Daekeun Park,Changyong Rhee 서울대학교 경제연구소 2007 Seoul journal of economics Vol.20 No.3

Population aging may have different effects on different assets. We investigate the effect of population aging on financial markets by evaluating how population aging affects the size of asset markets. The regression analysis using a cross-country data reveals that although aggregate saving rates will decline significantly as the size of the elderly population continues to rise, aggregate savings themselves will keep increasing for a while as the working age population increases their savings in preparation for the elongated retirement life. The regression analysis also demonstrates that the proportion of the elderly population is positively correlated with the size of the bond market, while the positive relationship with the size of the stock market is not so evident. Such a finding implies that although a general asset price meltdown is not likely, some asset markets will be more adversely affected by population aging.

Business Fixed Investment and the Structure of Adjustment Costs

Tamer Abdelgawad,Changyong Rhee 서울대학교 경제연구소 1998 Seoul journal of economics Vol.11 No.2

This paper empirically tests an irreversible investment model against the standard convex adjustment cost model using panel data from COMPUSAT. It shows that the reduced form of the optimal irreversible investment decision turns out to be a Tobit model with measurement errors in the dependent variable. Our non-nested test indicates that the evidence for the irreversible investment model is weak: Only 5 firms among our total sample of 56 firms strictly prefer the irreversibility specification.

Does Easier Test Reduce Efforts?

Kim, Dae Il,Rhee, Changyong 서울大學校經濟硏究所 2004 經濟論集 Vol.43 No.1-2

This paper investigates whether an easier test in relative evaluation reduces student's efforts to outperform. Each student competes against the field for the pre-determined number of winning prizes where his/her test score depends on three components, basic ability, efforts and luck. In equilibrium, those with marginal ability put forth efforts most. They are marginal in the sense that their ranking in ability distribution is close to the pre-set number of winners. Easiness of a test is modeled as placing abler individuals at a relative disadvantage in test score as an easy question can be answered with a few efforts even by less able individuals or does not require high ability to answer. In relative evaluation where ranking matters, an easier test tends to induce greater efforts among most individuals. This is a result exactly opposite to the common belief that wastefully excessive efforts and expenditure put forth, for example, by the Korean students preparing for the national college entrance exams are attributable to the difficulty of the exams. Further, such test reduces "screening" efficacy, which potentially deteriorates social efficiency in resource allocation.

Macroeconomic Adjustments of the East Asian Economies after the Crisis: A Comparative Study

Yoon Je Cho,Changyong Rhee 서울대학교 경제연구소 1999 Seoul journal of economics Vol.12 No.4

This paper examines the role of macroeconomic environment in the adjustment processes of the East Asian Crisis. It first reviews the macroeconomic development after the crisis in the five East Asian countries (Indonesia, Korea, Malaysia, the Philippines, and Thailand) and contrasts the degree to which each country has been affected by macroeconomic constraints. Based on that, it attempts to make assessments on what caused such a severe economic contraction and recent recovery in the region. Several policy implications follow out of our analysis. First, accommodative macroeconomic policies will be needed to continue for a while, perhaps until a clear sign of inflationary pressure develops, to prevent weakening of the corporate financial structure. Second, resumption of private capital flow will be an essential factor for the fast recovery of these economies. Third, more serious and comprehensive efforts are necessary to encourage the development of capital markets. Fourth, the IMF policy packages to be imposed on the future crisis-hit countries will be needed to be better tuned to individual market circumstances such as corporate leverage ratio, openness of the economy and etc.

The Gains from International Investment Diversification: The Korean Case

Yoon Je Cho,Changyong Rhee 한국계량경제학회 1999 JOURNAL OF ECONOMIC THEORY AND ECONOMETRICS Vol.5 No.1