• Geophysics and Geophysical Exploration
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• v.8 no.3
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• pp.218-223
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• 2005

This study considers to electrical resistivity characteristics for clay minerals types and contents in fractured and fault zone. The electrical resistivity is measured for an artificial agar specimen with clay minerals instead of a natural rock. The artificial agar specimen with clay minerals was special worked in study. The clay minerals used are Kaolinite and Montmorillonite in test, the clay mineral contents increases until $0\~40\%$ to the same specimen. As results, the electrical resistivity of the specimen decreased gradually as the clay mineral contents increases for all types of clay minerals. Montmorillonite shows remarkably lower resistivity than Kaolinite, although its clay content is fewer than that of Kaolinite. Also, a proposed experimental expression shows a good correlation coefficient as high as 0.89 or more in all clay minerals.

• The Korean Journal of Financial Studies
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• v.9 no.1
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• pp.69-93
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• 2003

본 연구는 자사주매입에 대한 공시가 기업가치에 어떠한 영향을 미칠것이며 공시일 전후 주가반응이 자사주매입 한도 변경에 따라 시장에서 어떻게 반응할 것인지 그리고 아직 학계에서 다루어지지 않은 미시적인 관점에서 실제 자사주매입 비율에 영향을 미치는 요인이 무엇인지에 관해 실증분석을 실시하였다. 실증분석 결과 자사주매입 공시일 전후 유의적인 양(+)의 비정상초과수익률을 나타내었으며, 한도확대 이후 누적비정상수익률은 유의적으로 증가하였다. 목표매입비율이 클수록 유의적으로 누적비정상수익률은 증가하는 것으로 나타나고 있어 자사주 취득에 대한 저평가 가설을 지지하는 것으로 해석된다. 예기치 않은 현금흐름은 대체로 누적비정상수익률과 양(+)의 유의적인 관계를 보여 예기치 않은 현금흐름이 많은 기업일수록 자사주매입의 정보효과가 크게 나타나 Stephens & Weisbach(1998)의 결과와 일치하였다. 또한, 자사주매입 이후 1개월의 성과를 나타내는 누적비정상수익률은 실제 자사주매입 비율과 유의적인 부(-)의 관계를 보여 공시 이후 주가가 상승할수록 목표대비 실제 자사주매입액은 감소하여 경영자가 공시 이후 주가변화추이에 따라 자사주매입 수량을 조정하고 있는 것으로 파악되었다.

• Resources Recycling
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• v.19 no.2
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• pp.10-18
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• 2010

This research investigates the feasibility of ceramic specimens made from Primary clay and Red Hwangto with MSWI fly ash. Specimens preduced by mix-design maximum 20 wt% MSWI fly ash were analysed by SEM, UTM, ICP, etc. As a result of measurement,$P_{10}$ specimen was improved on bending strength and $R_5$ specimen was improved on compressive and bending strength. Also amount of extracted heavy metal was suitable for regulatory limits. This indicates that MSWI fly ash is indeed suitable for the partial replacement of ceramic materials in bricks.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.160-160
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• 2011

현대의 건설기술은 자원절약과 환경보전이라는 시대적 흐름 속에, 자원순환과 지속 가능한 친환경 건설기술 개발은 차세대 연구분야로써, 연구가 시급한 분야가 되었다. 최근에는 골재 수급불균형 문제를 해결하고 동시에 자원순환을 위한 방안으로서 건설폐기물로부터 생산된 순환골재를 콘크리트용 천연골재의 대체재로 활용하기 위한 연구개발이 이루어지고 있다. 지속가능형 건설기술을 국내 독자 기술로 확립하고 건설현장에서 발생하는 폐기물의 순환시스템을 확고하게 구축하여 순환자원에 의한 국가경쟁력 강화를 기대할 수 있다. 본 연구의 목적은 순환골재 콘크리트의 역학적 특성을 개선하기 위해 순환골재 콘크리트 공시체를 제작하여 강도 및 강성을 검증하는 것이다. 실험방법으로 순환굵은골재의 치환 비율을 0%에서 100%까지 변화시킨 공시체를 제작하고 각 공시체의 정적 극한강도 거동을 비교 분석하였다. 하중은 공시체가 파괴가 발생 할 때까지 변위제어 방식으로 재하 하였으며 이 때 공시체의 파괴거동은 설치된 계측센서들을 이용하여 계측 및 분석하였다. 실험결과 공시체의 압축강도는 순환굵은골재 치환률이 25% 미만일 경우 일반 콘크리트 압축강도의 95% 이상의 구조성능을 갖지만, 순환굵은골재 치환률이 100%인 경우, 일반콘크리트 압축강도의 85% 수준의 구조성능을 나타냈다. 강성은 FRP 부재의 순환골재 치환률에 따라 최대 14%의 강성차이를 보였다. 이를 통해 순환골재 치환률이 높을수록 순환골재 표면의 폐모르타르와 이물질의 영향으로 재료간의 부착강도가 감소되어 강도와 강성이 저하되었음을 확인하였다.

• The Korean Journal of Financial Management
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• v.10 no.2
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• pp.181-211
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• 1993

증권관리위원회에 신고된 내부자거래는 6개월이내 단기투자에 따른 이익을 회사에 반환하여야 하므로 단기정보를 이용할 가능성이 낮다. 따라서 Fischer(1992)는 상장회사의 임원과 주요주주 등의 주식거래를 증권관리위원회에 신고하도록 하는 제도는 미공개 내부정보를 이용한 내부자거래를 방지하는 효과적 인 방법이라고 주장하고 있다. 본 연구에서는 증권거래소에 신고된 내부자의 거래자료와 상장기업의 기업정보공시자료를 이용하여 내부자의 주식거래가 미공개 내부정보를 이용하고 있는 지를 검토하였다. 1989년부터 1992년까지 4년간 증권거래소에 신고된 상장회사 내부자의 주식거래 중 거래후 1개월내에 기업정보의 공시가 있는 경우를 연구대상으로 한 실증분석결과 이러한 내부자의 주식거래가 일반적으로 미공개된 기업정보를 이용하고 있지 않는 것으로 나타났다. 내부자의 주식 매수 또는 매도후 기업정보 공시시 주가가 상승 또는 하락하는 경우가 각각 약 50%를 차지하고 있으며 내부자의 주식거래후 정보공시 빈도 수도 기대치보다 낮았다. 또한 주식거래에 따른 내부자거래이익은 매도시에는 내부자의 주식거래후 공시된 정보 내용에 따라 결정되며, 정보공시시 주가가 상승하는 비율이 약 50%이고 내부자거래이익이 0보다 작아 매도이후에 주가가 하락할 것이라는 예측은 지지되지 않았다. 내부자거래후 200 거래일까지 누적초과수익률을 분석한 결과에서도 매도시에는 정보이용 가능성이 있지만 매수시에는 내부자거래이익이 작아 정보이용 가능성이 없었다. 또한 내부자종류에 따른 내부자거래이익이 차이가 없어 증권거래소에 신고된 내부자의 주식거래는 곧 공개될 기업정보의 이용과는 관련이 적은 것으로 생각된다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.6
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• pp.1393-1405
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• 2012

This study intends to help establishing guidelines on providing easier access to security status-related information about business and public institutions by interested parties such as investors and civic societies, and to push ahead with the compulsory execution of the information security disclosure. We suggest a draft for the information disclosure system by reviewing the existing disclosure systems and validate the draft by surveying experts. It is expected that the result of this study will be the basis for the adoption of the information security disclosure system and be used as a referential material in the establishment of the relevant policy.

• Journal of the Korean Geotechnical Society
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• v.28 no.3
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• pp.15-23
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• 2012

An internal friction angle, which is one of strength parameters of granular soils, can be obtained from direct shear tests or triaxial tests. The result of traixial tests can be influenced by various experimental conditions such as confining pressure, shearing rate, specimen diameter and height, and end constraint. In this study, undrained and drained shearing behaviors of Nakdong River sand were investigated for loose (Dr = 40%) and dense (Dr = 80%) specimens with 5, 7, and 10 cm in diameter. Friction angles such as undrained total stress friction angle, undrained effective stress friction angle, and drained friction angle obtained from Mohr's stress circle slightly increased and then decreased as a diameter of a specimen increased from 5, 7 to 10 cm, regardless of relative densities. The difference between friction angles caused by different specimen size was at maximum 4.5 degrees for undrained total stress friction angle of dense specimen. In most cases, there was little difference between friction angles of large and small specimens, which was less than 2 degrees. The difference between an effective friction angle from undrained tests and a drained friction angle from drained tests was at maximum 7 degrees for loose samples but negligible for dense samples.

• Management & Information Systems Review
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• v.28 no.4
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• pp.155-174
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• 2009

The purpose of this paper is to analyze the stock market performances CAR of reorganized firms and study the disclosure effect of completion of reorganization to examine whether there exists significant economic merit for the institutionalized continuation of unprofitable firms. The main results of this paper can be summarized as follows. First, the average stock market performances for +12 months after the completion of reorganization compared to those for -6 months before the proposal of reorganization show consistently negative returns. Second, to see whether there exist significant differences between the stock market performances of reorganized firms and those of normal firms with similar characteristics, CAR's measured from -6 months before the proposal of reorganization to +12 months after the completion of reorganization are statistically tested, which results in significantly negative values starting +5 months after the completion of reorganization. Finally, to see the disclosure effect of the news of completion of reorganization, daily CAR's are measured and tested, which shows positive values only for -20 days and -19 days before the disclosure, and shows negative values for the whole periods up to +20 days after the disclosure. The results of the paper imply consistently that the reorganized firms have no better performances compared to the similar normal firms, and the performances do not improve even after the completion of reorganization, which casts serious doubts upon the current forms of the institutionalized continuation of unprofitable firms.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.207-215
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• 2009

Cemented soils or concrete are usually cured under moisture conditions and their strength increases with curing time. An insufficient supply of water to cemented soils can contribute to hydration process during curing, which results in the variation of bonding strength of cemented soils. In this study, by the consideration of in situ water supply conditions, cemented sand with cement ratio less than 20% is prepared by air dry, wrapped, moisture, and underwater conditions. A series of unconfined compression tests are carried out to evaluate the effect of curing conditions on the strength of cemented soils. The strength of air dry curing specimen is higher than those of moisture and wrapped cured specimens when cement ratio is less than 10%, whereas it is lower when cement ratio is greater than 10%. Regardless of cement ratio, air dry cured specimens are stronger than underwater cured specimens. A strength increase ratio with cement ratio is calculated based on the strength of 4% cemented specimen. The strength increase ratio of air dry cured specimen is lowest and that of wrapped, moisture, and underwater cured ones increased by square. Strength of air dry cured specimen drops to maximum 30% after wetting when cement ratio is low. However, regardless of cement ratio, strength of moisture and wrapped specimens drops to an average 10% after wetting. The results of this study can predict the strength variation of cemented sand depending on water supply conditions and wetting in the field, which can guarantee the safety of geotechnical structures such as dam.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.375-382
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• 2004

The compressive strength of concrete is used as the most basic and important material Property when reinforced concrete structures are designed. It has become a problem to use this value, however, because the control specimen sizes and shapes are different from every country. In this study, the effect of specimen sizes and shapes on compressive strength of concrete specimens was experimentally investigated based on fracture mechanics. Experiments for the Mode I failure was carried out by using cylinder, cube, and prism specimens. The test results are curve fitted using least square method(LSM) to obtain the new parameters for the modified size effect law(MSEL). The analysis results show that the effect of specimen sizes and shapes on ultimate strength is apparent. In addition, correlations between compressive strengths with size, shape, and casting direction of the specimen are investigated. For cubes and prisms the effect of placing direction on the compressive strength was investigated.