Complementarity in a Closed-Loop Aharonov-Bohm Interferometer

강기천,장동인,이후종,정윤철 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

We study complementarity in a two-terminal closed-loop Aharonov-Bohm interferometer with a quantum dot embedded in an arm of the ring and a nearby charge detector capacitively coupled to the quantum dot. We show that perfect charge detection does not give full information of the electronic path, so it does not completely suppress the interference. We propose that this property can be verified even in the limit of weak charge detection by investigating the dephasing of the first and the second harmonics of the Aharonov-Bohm oscillation. The first harmonic of the AB oscillation is reduced monotonically as a function of the charge detection strength. In contrast, the second harmonic interference remains unaffected due to the fact that charge detection is not able to detect the electronic path responsible for the second harmonic. Our theory confirms that the particle-like behavior of an electron emerges from the path information itself rather than from the disturbance.

The Choice of Export Destinations and Its Determinants: Evidence from Korean Exports

강기천 한국경제학회 2013 The Korean Economic Review Vol.29 No.1

Empirical evidence shows that zeros in a bilateral export matrix are very common and non-zeros are extremely concentrated across destinations. According to the simple version of Melitz (2003) model, variations in market size, as well as variable and fixed trade costs across destinations are potential candidates for explaining the stylized facts on the incidence of zeros and non-zeros in a trade matrix. Using Korean disaggregate export data (HS 10-digit level), this paper finds that export participation depends on destination-specific factors such as destination income, distance, local distribution cost, and fixed entry costs associated with the destination language, institution, and information. In line with this theory, the empirical findings suggest that destination-specific factors are important for shaping the country’s export entries.

Local Geometric Phase and Quantum-state Tomography for a Superconducting Qubit Threaded by a Magnetic Flux

강기천 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.4

We investigate the local geometric phase induced by Faraday’s law of induction in a superconductingcharge qubit threaded by an Aharonov-Bohm flux. A quantum-state reconstruction scheme,which is based on measurement of three complementary quantities, that is, the extra charge and twolocal currents, is introduced. We find that, while the variation of the local phase with magnetic fieldis determined by Faraday’s law, incorporation of the time-reversal symmetry enables complete determinationof the local phase. This procedure clearly demonstrates that the local geometric phaseis a physical quantity (aside from a global phase factor), in contrast to the standard description ofthe Aharonov-Bohm effect.

서평: William C. Kirby, Empires of Ideas: Creating the Modern University from Germany to America to China. Cambridge, Massachusetts & London, England: The Belknap Press of Harvard University Press, 2022. 504 pp.

강기천 한국과학사학회 2023 한국과학사학회지 Vol.45 No.3

심도별 토량환산계수와 토공량 변화에 관한 실험적 연구

강기천,신경철,윤성규,Gichun Kang,Kyoungchul Shin,Seong-kyu Yun 한국토지주택공사 토지주택연구원 2023 LHI journal of land, housing, and urban affairs Vol.14 No.3

토공계획은 자연상태의 원지반 토량을 절취하여 흐트러진 상태의 토량을 운반하고 성토지반의 활용도에 따라 다짐을 하는 과정에서 토질의 체적변화를 고려하여 수립하여야 한다. 흙의 상태에 따른 체적의 변화를 구하기 위해 일반적으로 심도 2m 깊이에서 시험굴 조사를 통해 얻어진 토량환산계수를 사용하게 되며, 굴착 깊이에 따른 토질의 성질을 고려하지 않고 전체 토공량에 일률적으로 적용하다 보니 토공량 산정에 오차가 발생하고 있다. 특히 신도시 택지개발과 같이 대량의 토공량이 필요한 조성공사의 경우 작은 오차에도 토공량의 차이는 크게 발생하게 된다. 본 연구에서는 심도 2m이상 토질의 물리적 특성을 조사하고 기존의 설계기준인 심도 2m의 토량환산계수와 비교 검토한 결과 굴착 심도가 깊고 대규모 토공사의 경우 심도별 토량환산계수(C)를 적용할 경우 절토량을 줄일 수 있는 것으로 나타났다.

How much have been the export products changed from homogeneous to differentiated? Evidence from China, Japan, and Korea

강기천 ELSEVIER SCIENCE INC 2008 CHINA ECONOMIC REVIEW Vol.19 No.2

The Difference in Regional Trade Margins and Its Determinants: Evidence from Korea

강기천,이기동 한국무역학회 2013 Journal of Korea trade Vol.17 No.4

This paper decomposes the extensive and intensive margins of the 16 Korean regions’exports over the sample period from 2000 to 2010, using regional export datadis-aggregated at the HS 10-digit level. We find that there is a large disparity in theextensive and intensive margins among Korean regions. Consistent with internationaltrade theories, the size of a region’s economy (GDP, income, and population) hasa significant and appropriately signed effect on the extensive and intensive margins. However, the effects work dominantly through the intensive margin rather than theextensive margin. We also find that regional innovation activity only has a positiveeffect on the extensive margin, and regional infrastructure variables are found to havea strong effect on the two margins. This paper contributes to the literature regardingthe extensive and intensive margins of a country’s regional trade.

조밀한 모래지반에서 수평재하속도에 따른 말뚝의 수평저항 특성

강기천,박혜정,윤성규,김지성 한국지반신소재학회 2023 한국지반신소재학회 논문집 Vol.22 No.3

최근 말뚝기초의 수평저항력에 대한 연구들이 활발히 이루어지고 있다. 말뚝기초의 수평저항력에 대한 실험연구들의 경우변위제어법 또는 하중제어법을 사용하고 있다. 하지만 변위제어법의 경우 말뚝에 가해지는 하중의 속도에 따라 말뚝의 수평저항력이 달라진다. 따라서 본 연구에서는 모형실험을 통해 수평재하속도에 따른 말뚝기초의 수평저항력 변화를 파악하고자한다. 실험결과 말뚝두부에 가해지낸 수평재하속도가 빠를수록 말뚝의 수평저항력이 감소하는 경향을 보였다. 이를 확인하기위해 재하속도에 따른 지반과 말뚝의 측면변경 모형실험을 추가적으로 진행하였으며, 그 결과 재하속도가 빠를수록 말뚝의회전절점의 깊이가 감소하였다. 역해석을 통해 수평재하 속도에 따른 회전절점의 깊이 변화를 파악하였다. 수평재하속도에따른 말뚝기초의 수평저항력과 회전절점의 깊이 변화를 통해, 말뚝의 수평재하시험시 재하속도는 1.5mm/min 이내로 시험하는 것을 제안하였다. Recently, research on the lateral resistance of pile foundations has been actively conducted. In experimental studies on the lateral resistance of pile foundations, displacement control or load control methods are used. However, in the case of the displacement control method, the lateral resistance of the pile varies depending on the rate of the load applied to the pile. Therefore, this study seeks to determine the change in lateral resistance of pile foundations according to lateral loading rate through model experiments. The experimental results showed that the lateral resistance of the pile tended to decrease as the lateral loading rate applied to the pile head increased. In order to confirm this, a model experiment of the side change of the ground and pile according to the loading rate was additionally conducted. Through inverse analysis, the change in the depth of the rotation point according to the lateral loading rate was identified. Through the change in the lateral resistance of the pile foundation and the depth of the rotating point according to the lateral loading rate, it was proposed to test the loading rate within 1.5 mm/min during the lateral loading test of the pile

Substitution Elasticity and Gains from Trade Variety in South Korea

강기천 한국무역학회 2022 Journal of Korea trade Vol.26 No.7

Purpose – Recent international studies have largely focused on measuring the welfare gains from increased trade varieties. To adequately capture the variety gains, it is of importance to estimate the elasticity of substitution between varieties of trade goods because it is one of the key parameters to determine the magnitude of the variety gains. Using the import data of South Korea, this paper shows that the elasticities vary substantially across the estimators, which affects the magnitude of the gains from trade. Design/methodology – Empirical studies working on the gains from trade variety have heavily depended on the estimation methods for the elasticity of substitution between trade varieties, developed by Feenstra (1994) and refined by Broda and Weinstein (2006). We estimate and compare the estimated elasticities for 8,945 HS 10 goods of South Korea, obtained from the three estimation methods: Feenstra’s weighted least square (F-WLS), Feenstra’s feasible generalized least square (FFGLS), and Broda and Weinstein’s feasible generalized least square (BW-FGLS). Findings – Using the estimated elasticities from the F-FGLS, considered as a suitable estimator, A typical Korean consumer saved 228 dollars per year by the greater access to new import varieties. This leads to gains from imported variety of 2.06% of GDP. In 2017, a typical Korean consumer would gain by 611 dollars, compared with 2000. China is the country with the largest contribution (28.4%), followed by Japan and USA. About 50% of all the welfare gains come from the imports from the three main trade partners. The Southern Asian countries are more important to the South Korean welfare gain than the Western European countries. Originality/value – Existing studies have chosen one of the methods without any criterion for the choice and then estimated the elasticities of substitution between varieties of trade goods. This paper focuses on the estimation specifications and methods as the cause of the disparity in estimated elasticities and welfare gains from trade variety. According to the Ramsey RESET and White tests, the F-FGLS estimates are relatively better compared to the F-WLS and BW-FGLS estimates. As another contribution, this paper provides the first measure of the welfare gains from trade variety for South Korea, using the estimated elasticities of substitution between trade varieties.

모래지반에서 쐐기모델을 이용한 단말뚝의 극한수평저항력 산정

강기천,김지성 한국지반공학회 2016 한국지반공학회논문집 Vol.32 No.12

본 연구에서는 Strain wedge 해석모델을 이용하여 수평하중이 작용하는 단말뚝의 극한수평저항력 산정식을 제안하였다. 저항특성은 쐐기 후면부의 수평저항토압, 쐐기 측면부의 전단저항, 그리고 말뚝과 지반의 마찰저항으로 구분하였고, 이들의 합으로써 극한수평저항력을 산정하였다. 제안된 식을 기존의 쐐기 이론과 현장실험, 유한차분법과비교분석하였다. 그 결과 제안식의 값이 기존의 쐐기 이론과 1.03%, 현장실험과는 0.40∼3.32%, 유한차분법과는 6.02%의차이를 보였다.