• Journal of Korean Association for Spatial Structures
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• v.10 no.1
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• pp.127-134
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• 2010

The dynamic instability for snapping phenomena has been studied by many researchers. Few paper deal with the dynamic bucking under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. We investigate the fundamental mechanisms of dynamic instability when shallow EP(Elliptic Paraboliodal) shell of two degree of freedom are subjected to sinusoidal excitation with direct snapping and indirect snapping. By using Newmark-$\beta$ method, we can get the nonlinear response, and characteristics of the dynamic instability through the running response spectrum by FFT(fast Fourier Transform) and attractors are compared in the phase plane. Dynamic buckling loads are strongly influenced by the relationships between the natural frequency of structures and the dominant frequency of incident excitations.

• KDI Journal of Economic Policy
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• v.20 no.1_2
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• pp.153-230
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• 1998

우리나라의 소득분배문제에 대해서 종래에는 적어도 1980년대 이후 개선되고 있으며, 국제비교에서도 다른 나라에 비해 결코 나쁘지 않다는 평가가 주류를 이루고 있었으나, 최근에는 그에 대한 반론이 만만치 않게 전개되고 있다. 본고에서는 "도시가계연보"의 원자료를 이용한 새로운 추계를 시도하여 1980년대의 소득분배가 지금까지의 통설처럼 그렇게 많이 개선된 것은 아니라는 결과를 제시하였다. 마찬가지로 일부의 반론처럼 1980년대의 소득분배가 실제로 악화되었다는 주장도 과장일 가능성이 크다는 점도 지적하였다. 단, 근로소득의 분배가 개선되고 있음은 분명하나 토지나 주식 등에 의한 불로소득까지 포함하면 결과는 크게 달라질 수 있다. 이 문제의 검증은 아직 끝난 것이 아니며, 올바른 결론에 도달하기 위해서는 앞으로 보다 많은 자료들이 발굴, 분석되어야 할 것이다. 한국의 자산분배에 대해서는 지금까지 자료가 별로 없어서 논의 자체가 어려운 상태였다. 최근 대우경제연구소의 패널 자료를 분석해본 결과, 한국의 부의 분배는 지금까지 알려진 것보다 훨씬 더 불평등하며, 특히 토지 등 실물자산의 불평등이 심각한 것으로 나타났다. 한편 한국의 빈곤은 많이 줄어든 것이 사실이며, 다른 후진국과 비교해서 빈곤 축소에 큰 성과를 거둔 것으로 평가된다. 본고에서 좀더 현실적인 최저생계비를 가정하여 분석해본 결과 한국의 빈곤은 물론 많이 줄어들었지만 아직 상당히 남아 있으며, 빈곤의 크기 자체(빈곤 갭)는 그다지 크지 않은 것으로 나타났다. 본고에서는 이러한 연구결과에 기초해서 우리나라의 분배문제에 대한 평가를 내리고 효율성과 형평성의 조화라는 관점에서 정책의 기본방향을 설정하였으며, 조세정책가 재벌정책에 초점을 맞추어서 정책방향을 논의하였다. 분배정의 관점에서, 우리나라의 세제는 직접세 비중을 높이고, 종합토지세, 상속 증여세 등 재산관련 세제의 기능을 강화하며, 근로자와 비근로자간 세부담의 형평성을 제고하는 방향으로 개편되어야 한다. 그리고 재별의 소유분산 자체보다는 재벌이 자행할 수 있는 경제적 부조리를 막기 위한 장치를 강화하는 것이 중요하다. 상속 증여세제 등의 강화나 기업경영의 투명성을 제고하기 위한 감시장치가 강화되어야 할 것이다. 특히 자유주의자가 강조하는 '정당한 권리의 원칙'으로서 '부정의의 시정'의 원칙이 보다 적극적으로 반영될 수 있어야 하며, 이러한 주장 자체가 시장 메커니즘을 옹호하는 진정한 자유주의 원칙에 입각하고 있다는 점이 강조되어야 할 것이다.

• KDI Journal of Economic Policy
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• v.17 no.1
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• pp.107-126
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• 1995

본(本) 연구(硏究)는 자본거래자유화정도를 명목상의 규제완화여부에 의해 판별하는 종래의 접근방법(接近方法)에서 벗어나, 형식적(形式的) 규제여부(規制與否)에 관계없이 자본거래(資本去來)가 실질적으로 경제적(經濟的) 유인(誘引)에 따라 얼마나 활발하게 이루어지고 있는가를 측정함으로써 자본거래자유화정도(資本去來自由化程度)를 평가할 수 있는 방법을 모색하고 있다. 이와 관련해서 본 연구는 모두 5가지 접근방법을 시도하고 있다. 그 첫째는, 총대외무역량대비 자본거래량비중으로서 자본거래량이 상대적으로 증가하면 자본거래자유화정도가 높다고 본다. 둘째는, 환율절하기대를 감안한 국내외실질 금리차로서 대내외자본거래(對內外資本去來)가 자유로울수록 국내외금리차(國內外金利差)는 낮아질 것이기 때문에, 동 금리차가 낮을수록 자본자유화정도가 높다고 본다. 동 지수로서는 통화선물시장의 존재 여부에 따라 위험포함 및 불포함 대내외금리차를 사용할 수 있다. 셋째로는, 다소 복잡한 계량경제학적 방법을 통해 국내외실질금리간의 연계관계를 측정하는 방법으로서 두번째 방법의 개선에 해당된다. 그리고 넷째로는, 셋째번 방법에 의한 연계관계를 시간변동지수로 전환하여, 시간의 경과에 따른 자본자유화정도의 변화를 측정하고 있다. 마지막으로는, 자본거래를 위험자산의 국제교역관계(國際交易關係)로 파악하여, 무역에 있어서의 산업내교역지수측정방법을 자본거래에 적용하여 자본거래총유출입지수를 측정하였다. 동 지수는 저축투자갭의 보정적(補正的) 거래차원을 넘어 위험자산거래 자체를 위한 자본거래의 정도를 측정함으로써 순수하게 자본거래 자체의 메커니즘에 의해 자생적으로 일어나는 자본거래의 활성화정도에 대한 척도가 될 수 있을 것으로 판단된다. 이상의 방법들을 주로 한국(韓國), 일본(日本), 대만(臺灣) 등에 적용해서 평가한 결과 한국의 자본거래자유화정도(資本去來自由化程度)는 일본에 비해서는 낮지만 대만에 비해서는 높으며, 특히 90년대 들어 크게 향상된 것으로 평가되었다.

• The Journal of Korean Association of Computer Education
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• v.3 no.1
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• pp.51-63
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• 2000

All learners can selection of their work through hypermedia technology in the area provided by usual WBI. Also, it provides learner with individual teaching-learning environment and estimation. RC2 System has the fundamental client/server model, and provides the learning, evaluation algorithms based on the LCPG(Learning Contents Problem Graph) model, the dynamic re-learning mechanism in according to the property of individual. Moreover, it support learning editor to provide interface, which is convenient for teacher, Courseware writer, on the Web

• Elastomers and Composites
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• v.40 no.3
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• pp.188-195
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• 2005

Chemical and physical changes and the contents of functional groups in the carbon black surface after the ozone treatment was investigated using elemental analysis, pH, tint strength, DBP, $N_2SA$, IA, and acid-base reaction. As the treatment time was increased, surface structure, particle size and surface area of carbon black did not change, while surface oxygen contents increased, and pH decreased and then saturated after $1{\sim}2$ hour. The contents of carboxylic, lactone, hydroxyl, and carbonyl groups were analyzed with four bases such as $NaHCO_3,\;Na_2CO_3,\;NaOH$, and $NaOC_2H_5$. Before oxidation, the carbonyl group was dominantly present on the surface, but by increasing the treatment time, the contents of the carboxylic and carbonyl groups increased to a saturated level after $1{\sim}2$ hour. Before and after the oxidation, the lactone and hydroxyl groups were nearly absent. These results showed that the reaction mechanism of carbon black and ozone is similar to that of ethylene and ozone. Weight of oxidized carbon black was increased after treating AIBN, while free radical was slightly decreased by ESR analysis. When carbon black was treated with organic compounds containing mercapto- groups, the results of ESR showed that free radical peak intensity was almost diminished compared to original carbon black.

• Explosives and Blasting
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• v.25 no.1
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• pp.31-43
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• 2007

In most tunnel constructions in South Korea, blasting has been widely used as an excavation method. In tunnel blasting, the center-cut to induce first free surface is very important for enhancing excavation efficiency and reducing vibration caused by exploding. This paper introduces new center-cut method named SAV-cut (Stage Advance V-cut) developed on the concept of V-cut. Significant features of SAV-cut are the center hole and stepwise ignition. Many field tests and numerical analysis were carried out to analyze the mechanical behavior and blasting vibration. From the results, the newly developed SAV-cut was proved as an effective center-cut method for both increasing blasting efficiency and decreasing blasting vibration.

• Journal of the Korean Society for Railway
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• v.18 no.1
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• pp.53-62
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• 2015

LWDT was developed for use as an alternative technique to measure the stiffness of trackbed soils. In this study, numerical and theoretical analyses of LWDT's acting mechanism were performed. The effectiveness of the adapted elastic formula used for calculation of the dynamic modulus, Evd, was investigated theoretically and also numerically by running ABAQUS analysis. The minimum thickness of the upper layer is proposed based on the analysis. Correction factors for the formula of elastic modulus are also proposed in this study. In the future, following field test results and laboratory mechanical tests such as the resonant column test, a guideline for the use of LWDT as a standard test protocol in track construction sites, as a measuring tool for the degree of compaction and/or stiffness and dynamic modulus, will be proposed based on this analysis.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.598-603
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• 2023

Electrochemical ammonia production using catalysts offers a promising alternative to the conventional Haber-Bosch process, allowing for ambient temperature and pressure conditions, environmentally friendly operations, and high-purity ammonia production. In this study, we focus on the nitrogen reduction reactions occurring on the surfaces of ruthenium catalysts, employing first-principles calculations. By modeling reaction pathways for nitrogen reduction on the (0001) and (1000) surfaces of ruthenium, we optimized the reaction structures and predicted favorable pathways for each step. We found that the adsorption configuration of N₂ on each surface significantly influenced subsequent reaction activities. On the (0001) surface of ruthenium, the end-on configuration, where nitrogen molecules adsorb perpendicularly to the surface, exhibited the most favorable N₂ adsorption energy. Similarly, on the (1000) surface, the end-on configuration showed the most stable adsorption energy values. Subsequently, through optimized hydrogen adsorption in both distal and alternating configurations, we theoretically elucidated the complete reaction pathways required for the final desorption of NH₃.

• KDI Journal of Economic Policy
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• v.35 no.4
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• pp.1-29
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• 2013

This paper examines the effect of trade liberalization or globalization, more broadly, on plants' growth as well as on "bi-polarization". To do so, we reviewed the possible theoretical mechanisms put forward by recent heterogeneous firm trade theories, and provided available micro-evidence from existing empirical studies on Korean manufacturing sector. Above all, the empirical evidence provided in this paper strongly suggests that globalization promoted growth of Korean manufacturing plants. Specifically, evidence suggests that exporting not only increases within-plant productivity but also promotes introduction of new products and dropping of old products. However, the empirical evidence also suggest that globalization has some downsides: widening productivity differences across plants and rising wage inequality between skilled and unskilled workers. Specifically, trade liberalization widens the initial productivity differences among plants through learning from export market participation as well as through interactions between exporting and R&D, both of which increase plants' productivity. We also show that there is only a small group of large and productive "superstar" plants engaged in both R&D and exporting activity, which can fully utilize the potential benefits from globalization. Finally, we also show evidence that trade liberalization interacts with innovation to increase the skilled-unskilled wage inequality.

• Explosives and Blasting
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• v.27 no.2
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• pp.1-11
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• 2009

Abstract By investigating the stress redistribution caused by the preceding cut blasting when applying the pre-splitting method to tunnel round, an attempt was made to find conditions that were favorable for the propagation of cracks in contour holes. The investigation of the direction of minor principal stress in the numerical analysis revealed that the most significant factor affecting the change of the direction was the loading condition, while the core shape, rock type, and tunnel depth seemed to be less important in determining the direction of minor principal stress. Moreover, the number of cracks tended to increase with the increase of deviatoric stress. Through the model test of pre-splitting, it is confirmed that the pre-splitting method taking the stress field into account can reduce the extent of yield zone and has advantage in controlling the direction of crack than the conventional one.