Earticle

코로나 팬더믹을 전후한 기간(2008.7~2020.6)을 총3기로 구분하여, 원‧달러와 원‧엔환율의 변동 성의 특성과 동조성현상 및 전이효과를 GARCH류 모형을 이용하여 분석한 결과는 다음과 같다. 첫째, 충격의 반감기분석에서, 제3기(코로나 팬더믹기)에는 원‧달러와 원‧엔환율의 중앙시차가 모두 짧아졌다. 이 결과는 코로나19라는 충격이 가해진 후 지속성이 약화되어 시장에 정보가 즉각적으로 반영되어 균형상태로 돌아오는 반감기가 매우 짧아졌음을 시사한다. 둘째, 환율의 동조성현상의 경우, 전기의 원‧엔환율 변동이 당기의 원‧달러환율에 양(+) 방향의 동조화효과가 있음을 확인하였다. 셋째, 변동성의 전이효과 분석의 경우, 전기의 원‧엔환율 변동이 당기의 원‧ 달러환율에 양(+) 방향의 위험의 전이효과가 있음도 확인되었다. 넷째, 변동성 증감 분석의 경 우, 제2기(엔화약세기)에는 통계적으로 유의한 원‧달러 환율변동성의 감소효과가 나타났으나, 제3기(코로나 팬더믹기)에는 환율변동성의 증가효과가 양(+)의 값으로는 나타났지만 통계적 유의성은 없었다. 다섯째, 충격의 비대칭성 분석의 경우, 원‧달러환율 변동성에 비대칭성이 존 재하지 않은 것으로 나타났는데, 이는 원‧달러환율 변동성은 외부적 영향력보다는 펀더멘털이 더 영향력이 있었음을 시사한다.

Purpose : The major object of this study is to investigate the coupling effect & volatility spillover effect between won-yen and won-dollar exchange rate before and after the COVID-19 pandemic. Research design, data, methodology : This study focuses on analysing both the volatility of exchange rate and the coupling effect & volatility spillover effect from Won-Yen to Won-Dollar with daily exchange rate data(2008.7~2020.6) by using GARCH, Dummy-GARCH, and Dummy-GJR models. Results : Firstly, in view of market persistency, the median lag of Won-Yen & Won-Dollar exchange rate of the COVID-19 pandemic period was found much smaller than those of the previous periods. Secondary, the positive coupling effect was found from Won-Yen to Won-Dollar exchange rate. Thirdly, the positive volatility spillover effect was detected from Won-Yen to Won-Dollar exchange rate. Fourthly, any evidence was not found in detecting the asymmetry effect of volatility of Won-Dollar exchange rate. Fifthly the expansion of the volatility of Won-Dollar exchange rate was found positively elastic, however, it had no statistical significance in the COVID-19 pandemic period. Conclusions : This paper suggested the importance of the risk management of exchange rate by revitalizing the exchange fluctuation insurance, and diversifying trade settlement currencies including Yen.

본 연구는 주담대시장의 금리변동성이 서울 주택가격과 전세가격의 변동성에 미치는 동조화 효과와 변동성의 전이효과에 대해 월별자료(2008.1~2021.6)로 GARCH-타입 모형을 이용하여 분석한 결과는 다음과 같다. 첫째, 주담대 금리변동성에서 ARCH효과는 통계적으로 유의성 있게 확인이 되었으나, GARCH 효과는 통계적 유의성이 결여되었다. 둘째, 주담대 금리변동성의 비대칭성효과는 확인되었으 나, 주택매매 및 전세의 가격변동성의 비대칭성효과는 확인되지 않았다. 셋째, 주택매매의 경 우에 동조화효과는 전기의 주담대 금리변동성이 당기의 주택가격변동성과 음(-)의 관계로 나 타났으나 통계적 유의성은 없었고, 변동성의 전이효과는 통계적으로 유의한 역(-)방향의 변동 성의 전이효과가 확인되었다. 넷째, 주택전세의 경우는 전기의 주담대 금리변동성이 당기의 전세가격변동성에 통계적으로 유의한 동조화효과와 변동성의 전이효과가 음(-)의 관계로 확인 되어, 역방향의 변동성의 전이효과가 있었음이 입증되었다. 따라서 지속된 저금리정책으로 인해 주담대 금리변동성이 축소되면서, 역으로 주택가격의 변 동성이 확대되었음을 시사한다. 결국 금융당국도 저금리정책을 지속하는 상황에서 자금흐름 모니터링을 강화하는 등 정책적 주의가 필요하였고, 개별경제 주체도 소위 ‘영끌’ 같은 빚내서 투자에 나서는 부동산투자 행위는 향후 금리상승기에 금리변동성 확대에 따른 주택가격하락 의 위험(risk)에 노출될 우려로 우선적 위험관리의 필요성이 있음을 시사한다.

Purpose : The main object of this study is to analyse the coupling effect and volatility spillover effect from mortgage loan rate to housing sales price & rental price in Seoul. Research design, data, methodology : This paper focuses on investigating both the volatility of mortgage loan rate and the coupling effect & volatility spillover effect from mortgage loan rate to housing sales price & rental price with monthly time-series(2008.1~2021.6) by using GARCH-type models. Results : Firstly, the ARCH effect was found, however, the GARCH effect was not detected in the volatility of mortgage loan rate. Secondary, the asymmetry effect of volatility of mortgage loan rate was found, however, any evidence was not found in the case of housing sales price & rental price. Thirdly, the negative coupling effect was found from the volatility of mortgage loan rate to housing sales price & rental price. Fourthly, the negative volatility spillover effect was detected from the volatility of mortgage loan rate to housing sales price & rental price. Conclusions : This paper suggested the low volatility of mortgage loan rate led to the high volatility of housing sales price & rental price in Seoul.

본 연구는 환율변동성이 교역조건 변화에 미치는 동조화효과와 위험의 전이효과에 대해 글로 벌 금융위기 이전(제1기: 2001.1~2008.12)과 이후(제2기: 2009.1~2021.2)로 구분해 분석한 결과 는 다음과 같다. 첫째, 충격의 지속성 분석 결과, 중앙시차(ML)는 1.26으로 계산되었는데, 이는 충격의 지속성 이 반감기가 1.26개월로 비교적 짧게 계산되어 외환시장의 효율성의 간접적인 증거로 사료된 다. 둘째, 비대칭성 분석 결과, 환율변동성의 비대칭성 존재하지 않았으며, 특히, 글로벌 금융 위기 이후인 제2기에는 변동성이 작아졌다. 셋째, 동조화효과 분석결과, 전기의 원・달러환율 변동이 당기의 상품교역조건에 정(+)방향의 동조화효과가 있었음을 시사한다. 넷째, 위험의 전 이효과 분석 결과, 환율변동성이 상품교역조건에 미치는 전이효과는 전기의 원・달러환율 변 동이 당기의 상품교역조건 변동에 정(+)방향의 변동성의 전이효과가 있었음이 입증되었다. 다 섯째, 조건부 공분산분석 결과, 환율변동성과 소득교역조건의 변화 간에는 정(+)방향 동조화효 과가 나타났다. 이는 환율상승(원화약세)에 따른 수출가격의 하락으로 인한 수출물량의 증대 로 소득교역조건이 지속적으로 상승해 왔음을 시사한다. 따라서 수출산업의 경쟁력을 위해 무역금융측면에서는 ‘환변동보험’ 등 무역보험제도의 활성 화와 수출입 결제통화의 효율적 포트폴리오 구성 등을 통한 환위험관리가 바람직하다.

Purpose : The main purpose of this paper is to analyse the impacts of the coupling effect and volatility spillover effect on the rate of terms of trade(TOT). Research design, data, methodology : This study focuses on investigating both the volatility of exchange rate and the coupling effect & volatility spillover effect from Won-Dollar exchange rate to commodity terms of trade(CTOT) & income terms of trade(ITOT) with monthly data(2001.1~2021.2) by using GARCH type models. Results : Firstly, the median lag(ML) of Won-Dollar exchange rate which was estimated relatively small means an indirect evidence of the efficiency of foreign exchange market. Secondary, no evidence was found in detecting the asymmetry effect of volatility of Won-Dollar exchange rate. Thirdly, the positive coupling effect was found from Won-Dollar to CTOT. Fourthly, the positive volatility spillover effect was detected from Won-Dollar to CTOT. Fifthly, in terms of conditional covariance, the positive coupling effect was found from Won-Dollar to ITOT. Conclusions : This paper suggested the efficient risk management of exchange rate by strengthening the trade insurance system, and composing the efficient portfolio of trade settlement currencies in order to enhance the competitiveness of Korean export.

Superconducting coplanar waveguide (SCPW) resonators with high quality (Q) factor are widely used for developing quantum sensors and quantum information processors. Here we conducted numerical simulations of SCPW resonators to investigate the relationship between the Q factor and the coupling capacitance of the resonator. Varying the geometrical shape of both ends and coupling parameters of the SCPW resonator resulted in a change of the coupling capacitances and the Q factor as well. Our calculation results indicate that the performance of the SCPW resonator is highly sensitive to the capacitive coupling and searching for an optimal coupling condition would be crucial for developing high-performance SCPW resonator.

As a result of the medium coupling, propagation characteristics of ultrasonic waves guided by a multi-phase medium can be different from those in a homogeneous system. This phenomenon becomes prominent for a medium consisting of phases with considerably distinct material and physical properties (e.g., submerged structures or human bones covered with soft tissues). In this study, the coupling effect arising from both fluid and soft tissues on wave propagation in engineering structures and human bone phantoms, respectively, was explored and calibrated quantitatively, with a purpose of enhancing the precision of ultrasonic-wave-based non-destructive evaluation (NDE) and clinical quantitative ultrasound (QUS). Calibration results were used to rectify conventional NDE during evaluation of corrosion in a submerged aluminium plate, and QUS during prediction of simulated healing status of a mimicked bone fracture. The results demonstrated that with the coupling effect being appropriately taken into account, the precision of NDE and QUS could be improved.

A model based on two coupled generalized Langevin equations is proposed to investigate the trans-stilbene photoisomerization dynamics. In this model, a system which has two independent coordinates is considered and these two system coordinates are coupled to the same harmonic bath. The direct coupling between the system coordinates is assumed negligible and these two coordinates influence each other through the frictional coupling mediated by solvent molecules. From the Hamiltonian which is equivalent to the coupled generalized Langevin equations, we obtain the transition state theory rate constants of the stilbene photoisomerization. The rates obtained from this model are compared to experimental results in n-alkane solvents.

In this paper, electro-mechanical coupling of cellulose-based Electro-Active Paper (EAPap) actuator is investigated by measuring induced strain and mechanical properties with and without electric excitation. The maximum induced in-plane strain is measured at the orientation angle of 45? samples. The elastic modulus and strength of EAPap are increased with electric excitation and the orientation angle of $45^{\circ}$ samples shows the largest increment of mechanical properties. From the observations, shear piezoelectricity is considered as the major piezoelectric mode of EAPap.

The two-degree-of-freedom direct drive induction motor, which is capable of linear, rotary and helical motion, has a wide application in special industry such as industrial robot arms. It is inevitable that the linear motion and rotary motion generate coupling effect on each other on account of the high integration. The analysis of this effect has great significance in the research of two-degree-of-freedom motors, which is also crucial to realize precision control of them. The coupling factor considering the coupling effect is proposed and addressed by 3D finite element method. Then the corrected mathematical model is presented by importing the coupling factor. The results from it are verified by 3D finite element model and prototype test, which validates the corrected mathematical model.

In the fabrication of joined materials between anodized aluminum alloy and polymer, the performance of the metal-polymer joining is greatly influenced by the chemical properties of the oxide film. In a previous study, the dependence of physical joining strength on the thickness, structure, pore formation, and surface roughness of films formed on aluminum alloys is investigated. In this study, we investigated the effect of silane coupling treatment on the joining strength and sealing performance between aluminum alloy and polymer. After a two-step anodization process with additional treatment by silane, the oxide film with chemically modified nanostructure is strongly bonded to the polymer through physical and chemical reactions. More specifically, after the two-step anodization with silane treatment, the oxide film has a three-dimensional (3D) nanostructure and the silane components are present in combination with hydroxyl groups up to a depth of 150 nm. Accordingly, the joining strength between the polymer and aluminum alloy increases from 29 to 35 MPa, and the helium leak performance increases from 10-2-10-4 to 10-8-10-9 Pa ㎥ s-1.

The effects of amino silane coupling agent on the AC electrical treeing and breakdown behaviors in an epoxy/layered silicate (1 wt%) were examined in needle-plate electrode geometry. A layered silicate was exfoliated in an epoxy base resin by using our AC electric field apparatus. To measure the tree initiation and propagation and the breakdown rate, an alternating current (AC) of 10 kV (60 Hz) was applied to the specimen in needle-plate electrode arrangement with a $30^{\circ}C$ insulating oil bath. In the epoxy/amino silane system, the tree initiation time was 11.5 times higher and the breakdown time was 17.9 times higher than those of the neat epoxy resin. The tree initiation time in the epoxy/layered silicate (1 wt%) system with the amino silane was 2.0 times higher, and the breakdown time was 1.5 times higher than those of the epoxy/layered silicate (1 wt%) system.

The magnetization and/or resistivity of high $T_c$ superconductors ($YBa_2Cu_3O_{7-\delta}$(YBCO) single crystal, $Bi_2Sr_2CaCu_2O_8$ (Bi-2212) single crystal, $Tl_2Ba_2CaCu_2O_8$ (Tl-2212) film, $HgBa_2Ca_2Cu_3O_8$ (Hg-1223) film) have been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the magnetization and conductivity exhibits a critical behavior consistent with the three-dimensional XY model. The dynamic critical exponent z does not sensitively vary with a type of the superconductors. The value of z ranges from 1.5 to $1.8{\pm}0.1$. However, the static critical exponent ${\nu}$ is the most largely increased in Tl-2212 that has a weaker interlayer coupling strength than YBCO; the value of ${\nu}$ is 0.669, 0.909, 1.19, and 1.338 for YBCO, Bi-2212, Hg-1223, and Tl-2212 respectively. The results indicate that the weak interlayer coupling along the c-axis of high $T_c$ superconductors near $T_c$ does not influence the dynamic critical exponent z (the same value of superfluid $^4He$), but significantly increases the static critical exponent ${\nu}$.