PURPOSES : When fire event occurs in tunnel the reinforced concrete is exposed to very high temperature at a very short time period. This study investigates the tensile behavior of steel rebar that experienced high temperature. METHODS : The steel rebar was exposed to 200, 400, 600, and 800℃ following the ISO 834 temperature-time fire curve. Hightemperature- exposed steel rebars were tested using the UTM for their yielding and tensile strengths, and elongation rate. RESULTS : Up to an exposure temperature of 600℃, the tensile properties of the rebar did not vary considerably. However, at 800℃ (which corresponds to a temperature rise time of approximately 22 min), the rebar lost its yielding and tensile strength by approximately 27 and 13%, respectively, compared to the control specimen. Further, the elongation rate increased after exposure to 600℃. The above fundamental tensile test results can be a good reference for future guidelines in the repair manual for tunnels after severe fire events. CONCLUSIONS : When steel rebar experiences high temperatures of 800℃, the yield strength of the rebar reduces approximately 27%. This strength reduction can cause severe structural damage to tunnels that use reinforced concrete as the primary structural elements.

본 논문은 사카모토 류이치(坂本龍一)와 알바 노토(Alva noto)의 2번째 콜라보레이션 앨범「인센(Insen)」의 수록 곡 중‘아우라(Aurora)’를 연구곡으로 선정하여 곡에 나타난 선택적 주파수 샘플링 기법을 중심으로 분석하였다. 선택적 주파수 샘플링 기법으로 만들어진 샘플들을 음악적 기능에 따라 4가지 유형으로 분류하였다. 각 샘플들의 특성은 스펙트로그램(Spectrogram)을 사용하여 분석하였다. 연구 곡에서 각 샘플들은 음악적 기능에 따라 다르게 제작되고 사용되었다는 특징이 있었다. 이는 샘플링 기법이 응용될 수 있는 확장성을 보여준다. 이러한 연구 결과에 따라 선택적 주파수 샘플링 기법을 필요로 하는 음악과 작곡가, 편곡가들에게 활용 방안을 제시하였다.

본 연구에서는 Cellulose Nano-Crystals (CNCs) 수용액을 이용하여 시멘트 페이스트의 강도 향상에 대한 실험을 수행하고 이 연구결과를 토대로 하여 CNC 혼입에 따른 섬유보강 고인성 시멘트 복합체의 강도 특성에 관한 실험을 진행하였다. 먼저, CNC의 최적 배합비를 결정하기 위한 일환으로, 골재를 포함하지 않은 시멘트 페이스트의 강도 특성을 비교하기 위해 CNC 혼입율에 따라 수용액을 제조하였다. CNC 혼입율은 시멘트 대비 0.1, 0.2, 0.4 vol.%를 주요 변수로 하였고, 이에 따른 휨강도는 0.4 vol.%에서 플레인 시험체와 비교시 최대 8 배까지 강도가 증가하는 것을 확인할 수 있었다. 이 연구결과와 기존 연구결과를 토대로 하여, 본 연구에서는 0.4, 0.8 및 1.2 vol.%의 CNC 혼입율을 주요변수로 한 강섬유와 아마섬유를 활용한 섬유보강 고인성 시멘트 복합체 시험체를 제작한 후 역학적 강도 특성을 평가하여 섬유보강 고인성 시멘트 복합체의 구조적 성능을 규명하였다.

We investigate that the impact of freshwater organism exposed to the salinity environment by the frequent rainfall following climate change. To evaluate the stress response following salinity exposure, we assessed the survival rate, molting success rate, the developmental period and mouthpart deformities in Chironomus riparius. In addition, we measured the molecular responses of biomarker gene, gene expression of heat shock protein 70 (HSP70) in C. riparius exposed to salinity after 96 hour. The C. riparius survival rates were showed on time dependent manner and not observed survival organisms above 15 psu at day 4. The pupation and emergence of C. riparius were not seen above 15 psu, and the molting success rate was less than 20% at 10 psu. The developmental retardation of C. riparius was well observed in the pupation and emergence period and was delayed by 4 days at 10 psu compared to the control and 5 psu. The mouthpart deformities after salinity exposure at 96 or 72 hour were observed at 10 psu and 15 psu. The expression of C. riparius HSP70 level was significantly increased exposure to 5 psu and 10 psu. Thus, salinity has been caused to be various ecotoxicological and molecular stress responses on freshwater organisms similar to harmful substances such as EDCs and so on.

The purpose of this study is to analyse the job-satisfaction of police officer. The subjects of this study are selected by convenience sampling of random sampling method. The population is male and female incumbent police officers in Seoul and Gyeonggi province. The 347 cases are used to analyse the job-satisfaction among 400 police officers who answer the question. The Jod-Satisfaction Survey(Choi, 2001) are used for collecting data. In consequence of and 4 sub-factors(job-satisfaction) are found. Cronbach's alpha coefficient revealed .058~.804, .846~.871, respectively. For the statistical analysis, SPSS version 12.0 are utilized. The verification of research hypothesis are conducted by T-test, ANOVA, correlation, and multiple-regression. The significance level of all tests are set at .05. The findings of this study can be summarized as follows: Based on the demographic factors, the differences in life-style among police officers are identified. There is significant differences in gender and ages on individualism and accomplishment, in marital status on individualism and fashion-pursuing, and in income level on fashion-pursuing and accomplishment. There is also significant differences in education, religion, position and service period on accomplishment, individualism and fashion-pursuing.

A deflection of a RC structure increases when sustained loads are applied in it. In this paper, a parametric study of long-term deflection was performed according to concrete strength, creep coefficient and ratio of sustained load for each design provisions. Results show that a long-term deflection in KSCDC is able to apply an effect of creep using an effective modulus of elasticity.

The minimum reinforcement ratio is an important design factor to prevent a brittle failure in RC flexural members. A minimum reinforcement ratio is presented by assuming an effective depth of cross-section and moment arm lever in CDC and KHBDC. In this study, it suggests that a rational method for minimum reinforcement ratio is calculated by material model and force equilibrium. As results, a minimum reinforcement ratio using a p-r curve in KHBDC is evaluated about 52~80% of recent design code’s value and it induces an economical design. And also, a ductility capacity in case of placing this minimum reinforcement amount is evaluated about 89% of recent design code’s value, but ductility in a member is 7 or more, so it has a sufficient ductility capacity. Therefore, it is judged that a minimum reinforcement ratio using p-r curve has a theoretical rationality, safety and economy in a flexural member design.

A minimum reinforcement ratio is an important factor to prevent a brittle failure for RC flexural members. In this paper, a parametric study of minimum reinforcement ratio is performed according to concrete strength, steel yield strength and cover depth ratio for each design provisions. A minimum reinforcement ratio using a stress-strain model is suggested. And results show that this mode is able to reflect material strength and cross-section properties properly.

의성 옥동광산에 적치되어 있는 광미는 미세분말로 이루어져 있으며, 주 구성광물은 황철석, 섬아연석, 녹니석, 일라이트, 사장석, 스멕타이트, 석고 등이다. 점토광물 중 스멕타이트는 광미 적치장 상부에 집중되어 있고 하부로 갈수록 녹니석이 증가한다. 석고는 광미 적치장 표면에 주로 나타나는데 이는 광미와 반응한 침출수가 증발하면서 침출수에 포함된 Ca와 SO4가 반응하여 침전된 증발잔류물로 추정된다. 전자현미경 관찰 결과 광미에 포함된 섬아연석은 표면뿐만 아니라 내부까지 풍화되어 있는 것으로 보아 오랜 시간동안 지하수와 반응하여 다량의 Zn과 SO4를 침출수에 부가되었을 것으로 추정된다.