• Journal of Korean Society of Steel Construction
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• v.12 no.3 s.46
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• pp.259-268
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• 2000

In the friction-type joints the external applied load is transmitted by frictional force acting on the contact area of the plates fastened by the high strength bolts. This frictional force is proportional to the product of the bolt clamping force and slip coefficient of the faying surface. But the bolt clamping force is dependent on many factors when the turn-of-nut method is used. The preserved thread length and length-to-diameter ratios are one of the major factors governing the bolt clamping force. This paper presents the correct method of high strength bolt tightening through the experiment on the mechanical properties on sets of high strength bolts in accordance with preserved thread length and length-to-diameter ratios.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.761-767
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• 2019

In the present study, analyses of initial behavior of an air-launched projectile for varying initial conditions are performed by coupling computational fluid dynamics and 6 degrees of freedom calculations. Accuracy of the present numerical methods is validated by comparing the present result with the measured data. Launching safety analyses are carried out for various ejecting conditions by considering weight of the projectile and magnitude of front and rear ejector forces as the major parameters of initial behavior of the projectile. A response surface of the projectile launching safety is obtained in the range of the major parameters. In all the conditions of zero rear ejector force, unsafe launching behavior is observed. As the weight of the projectile decreases, the initial launching behavior becomes more unsafe.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.56-61
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• 2012

The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the durability of concrete have been accomplished, however, it is not easy to review literatures about environmental analysis. Since the durability of concrete depends on the properties of the surface concrete. micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The effect of degree of saturation on chloride diffusivity of concrete is also examined. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete.

• Water for future
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• v.29 no.3
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• pp.143-152
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• 1996

The hydraulics of flow within the covered reach of urban streams is very complicated due to the accumulation and interference effect of eddies around the multiple piers supporting the covering slab. An extensive experimental study is done to quantitatively estimate the backwater rise effect caused by various arrays of multiple piers. The factors governing the backwater rise are found out to be the contraction ratio due to the piers, Froude number of the flow, longitudinal pier spacing, and the length of the covered reach. For a single section of lateral pier arrays the effect of contraction ratio and Froude number on the backwater rise is analyzed and a multiple regression equation is derived. The effect of multiple piers, arrayed in both lateral and longitudinal directions, on the backwater rise is analyzed in terms of the contraction ratio, Froude number,longitudinal pier spacing and the total length of the covered reach. A multiple regression equation for the backwater rise estimation is proposed based on the experimental data collected in the present study.

• Applied Biological Chemistry
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• v.35 no.5
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• pp.382-388
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• 1992

Mycelial growth inhibition activity of forty-one N-substituted phenyl 5-chloro-1,3-dimethylpyrazole-4-carboxamides against Rhizoctonia solani was analysed quantitatively by multiple regression analysis using physicochemical parameters of substituents as independent variables and $pEC_{50}$ as dependent variable. As a result, a quantitative structure-activity relationship was formulated using eight physicochemical parameters, which explains 83% of variance of the fungicidal activity. The most important parameter for the biological activity was log k', as related to the penetration and transport processes in the biological system. The activity also correlated with other hydrophobic parameters$({\pi}_2,\;{\pi}_3)$, an electronic parameter$({\Sigma}{\sigma})$, and steric parameters$(STERIMOL\;parameters\;L_3,\;L_4)$.

• Journal of the Korean Geotechnical Society
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• v.33 no.2
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• pp.35-47
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• 2017

Thermal behavior of soils is mainly focused on thermal conduction, and the study of natural convection is very limited. Increase of soil temperature causes natural convection due to buoyancy from density change of pore water. The limitations of the analysis using fluid dynamics for natural convection in the porous media is discussed and a new numerical analysis is presented for natural convection in porous media using THM governing equations fully coupled in the macroscopic view. Numerical experiments for thermal probe show increase in the uncertainty of thermal conductivity estimated without considering natural convection, and suggest appropriate experimental procedures to minimize errors between analytical model and numerical results. Burial of submarine power cable should not exceed the temperature changes of $2^{\circ}C$ at the depth of 0.2 m under the seabed, but numerical analysis for high permeable ground exceeds this criterion. Temperature and THM properties of the seafloor are important design factors for the burial of power cable, and in this case effects of natural convection should be considered. Especially, in the presence of heat sources in soils with high permeability, natural convection due to the variation of density of pore water should be considered as an important heat transfer mechanism.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.76-76
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• 2015

토양수분은 생태수문학에서 식생과의 상호작용의 중요한 인자이자, 대기와의 상호작용으로 인한 총체적인 물 순환에 밀접한 관련이 있다. 수문학적으로는 증발, 침투, 지하수 함량, 토양 침식, 식생 분포 등을 지배하는 중요한 요소이고, 특히 시 공간적 분포특성은 강수 사상 후 토양으로의 침투 및 토양수분의 재분포, 증발산과 불포화대에서의 오염물의 이송을 예측하는데 매우 중요하다. 또한, '07년 하천법 개정으로 증발산량 및 토양수분량이 신규 수문조사 항목으로 추가되어, 토양수분 측정에 대한 필요성이 높아졌다. 따라서, 2008년 5월, K-water연구원에서는 현재 시험유역으로 운영하고 있는 용담시험유역에 토양수분관측망(6개 관측소)을 구축하였다. 토양수분계는 토양수분을 결정하는 가장 중요한 인자인 강우자료의 획득이 이루어지는 지점에 설치하여 정확도와 신뢰도를 높일 수 있도록 용담시험 유역 내 6개 우량관측소에 설치하였다. 하지만 장비의 노후화에 따른 자료 취득의 어려움으로 인하여 2013년 4월, 토양수분계를 전면 교체하였다. 토양수분계는 기존의 FDR 방식에서 EC 농도에 대한 영향이 가장 적고, 플럭스 타워에 위치한 토양수분계 센서와 동일한 TDR 방식의 센서로 장비를 전면 교체하였다. 센서 설치 장소 변경에 따른 TDR 센서의 검증과 그리고 흙의 종류, 입도, 다짐도, 온도 등에 의한 오차가 발생 여부를 판단하기 위하여 이에 대한 보정을 실시하였다. 원지반 시료채취를 통하여 토양수분량을 측정하였고, TDR 센서에 의해 측정된 토양수분량과 채취된 시료에서 측정된 토양수분량의 결과를 비교하였고, 각 지점별 토양구성비와 전기전도도 조건을 고려하여 각 토층별 계수적용을 달리하여 센서 보정을 실시하였다. 그 결과 기존 센서 제조사에서 제안한 방정식을 그대로 사용하는 것 보다는 센서 검증을 통하여 얻은 계수보정에 의한 토양수분 변환식을 사용하는 것이 정확한 현장 자료를 확보할 수 있고, 신뢰도 높은 자료를 얻을 수 있다고 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.552-552
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• 2017

본래 식용으로 들여온 외래어종은 우리나라 하천에서 토착 어류의 생태계를 교란시키며, 빠르게 서식처를 확산하고 있다. 일반적으로 알려져 있는 외래어종인 배스와 블루길 이외에도 무지개 송어 및 향어도 외래어종으로 분류된다. 본 연구는 외래어종 중 배스와 블루길을 대상으로 여러 환경적 요인에 따른 서식처 형성을 관찰하고 외래어종의 생태활동 변화를 분석하는 것을 목적으로 수행하였다. 여러 연구에 따르면 수온과 용존산소가 담수 어류의 서식환경 구축을 결정하는 매우 중요한 인자임을 알 수 있다. 이에 따라, 외래어종의 서식처 형성에 영향을 미치는 여러 환경적 요인 중 수온을 주요 인자로 선정하여 실험실 실험을 수행하였다. 연구를 수행하기 위해 하천 및 농업용 저수지로부터 배스와 블루길을 채집하였다. 채집된 외래어종을 길이 12 m, 깊이 0.6 m, 폭 1 m의 하천과 유사한 자연적 환경이 갖추어진 수조에 이식하였다. 수조 내 환경은 독립변인인 수온을 제외하고 모두 동일하게 구성하였다. 수조를 3개의 구역으로 구분하여 양 끝단에 냉수대와 온수대를 조성하였으며, 중간부의 평균 수온대를 기준으로 냉수대와 온수대의 수온 차는 약 $1^{\circ}C$이상 유지되도록 설정하였다. 현재까지의 실험 결과에 따르면, 외래어종은 온수대에 서식처를 형성하였다. $1^{\circ}C$의 수온 차에도 매우 민감하게 반응하며, 냉수대에는 서식처를 형성하지 않는 것 또한 확인되었다. 이를 통해 수온이 외래어종의 서식처 형성에 매우 중요한 영향을 미치는 요인인 것으로 판단된다. 연구 과정에서 추가적으로, 먹이 금붕어가 부재할 경우 동종 어식을 하는 것이 관찰되었다. 수조 내 수온에 따른 구역의 구분을 위해 공통으로 설치된 가림판 부근에 외래어종의 군락이 형성된 것을 통해, 향후에는 외래어종의 서식처 형성과 장애물과 같은 지형적인 요인이 미치는 영향에 관한 연구가 필요할 것으로 판단된다. 춘계는 수온의 증가로 외래어종이 더욱 왕성한 활동을 하는 시기이다. 수온이 외래어종의 서식처 형성에 지배적인 영향을 미치는 것이 실험을 통해 확인하였으나, 수온에 대한 민감도에 관한 연구 또한 필요하다. 더불어 외래어종의 계절에 따른 먹이활동 및 생장량 또한 지속적으로 관찰할 것이다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.15
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• pp.1-31
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• 1974

Introducing genes for earliness of wheat varieties is important to develop early varieties in winter wheat. In oder to obtain basic informations on the response of heading to the different day length and temperature treatments and on the inheritance of heading dates, experiments were conducted at the field and greenhouse of the Crop Experiment Station, Suwon. Varieties used in this experiments were, early variety Yecora F70, medium varieties Suke #169, Parker and Yukseung #3, and late varieties Changkwang, Bezostaia, Sturdy and Blueboy. The parents and F$_1$s of partial diallel crosses of above eight varieties were subjected the following four different treatments; 1. high temperature and long day, 2. high temperature and short day, 3. low temperature and long day, and 4. low temperature and short day. The same materials were grown also in field condition. Parents, F$_1$ and F$_2$ generation were grown also in both greenhouse under high temperature and short day and in field. The results obtained were summarized as follow: 1. No effects of temperature and daylength on the number of leaves on the main stem were found when -varieties were vernalized. The number of main stem leaves were fewer for spring type of varieties than for winter type of varieties. 2. The effects of temperature and daylength on the days to flag leaf opening were dependent on the speed of leaf emergence. The speed of leaf emergence were faster for lower leaves than for upper leaves. 3. The response to short day and long day (earliness of narrow sense) of varieties were found to be direct factor responsible to physiology of heading dates in vernalized varieties. Great difference of varieties to heading date was found in high temperature and short day treatment, but less differences were found in high temperature and long day, low temperature and long day and low temperature and short day treatments respectively. The least varietal difference for heading dates was found in the field condition. 4. Changkwang and Parker were found to be the most sensitive to short day treatment (photosensitive) and the heading of these varieties were delayed by short day treatment. No great varietal differences were found among other varieties. 5. Varietal differences of heading dates due to daylength were greater in high temperature than in low temperature. 6. Varietal differences of heading dates due to temperature were not great. but in general the heading dates of varieties were faster under high temperature than under low temperature. 7. Earliness of heading dates was due to partial dominance effect of genes involved in any condition. The degree of dominance was greater under short day than under long day treatment. 8. The varietal differences of heading date under high temperature and long day were due to earliness or narrow sense (response to long day) of varieties. The degree of dominance was greater for Yecora F70, spring type than for other winter type of varieties. No differences or less differences of degree of dominance was found among winter type of varieties. The estimated number of effective factor concerned in the earliness of narrow sense was one pair of allele with minor genes. 9. The insensitivity of varieties to short day treatment in heading dates was due to single dominant gene effect. Under the low temperature the sensitivity of varieties to short day treatment was less apparent. 10. The earliness of short day and long day (earliness of narrow sense) sensitivities of varieties appearea to be due to partial dominance of earliness over lateness. In strict sense, the degree of the dominance should be distinguished. 11. Dominant gene effects were found for the thermo-sensitivity of varieties, and the effect was less, significant than the earliness in narrow sense. 12. One pair of allele, ee and EE, for photosensitivity was responsible for the difference in the heading dates between Changkwang and Suke #169. Two pairs of alleles, ee, enen and EE, EnEn. appeared to be responsible for the difference between Changkwang and Yecora F70. The effects of EE and EnEn were, additive to the earliness and the effects of EE were greater than EnEn under short day. However, the effects of EE were not evident in long day but the effects of EnEn were observed in long day. 13. Two pairs of dominant alleles for the earliness were estimated from the analysis of F$_1$ diallels in the field but the effects of these alleles in F$_2$ were not apparent due to low temperature and short day treatment in early part of growth and high temperature and long day treatment in later part of growth. The F$_2$ population shows continuous variation due to environmental effects and due to other minor gene effects. 14. The heritabilities for heading dates were ranged from 0.51 to 0.72, indicating that the selection in early generation might be effective. The extent of heritability for heading dates varied with environments; higher magnitude of heritability was obtained in short day treatment and high temperature compared with long day and low temperature treatments. The heritabilities of heading date due to response to short day were 0.86 in high temperature and 0.76 in low temperature. The heritabilities of heading date due to temperature were not significantly high. 15. The correlation coefficients of heading dates to the number of grains per spike, weight of 1, 000 grains. and grain yield were positive and high, indicating the difficulties of selections of high yielding lines from early population. But no significant correlation coefficient was obtained between the earliness and the number of spikes, indicating the effective selection for high tillering from early varieties for high yielding.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.4
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• pp.287-296
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• 1996

A mathematical model for the dynamic analysis of the riser system is developed to investigate the effect of internal flow on the free vibration of marine riser system which includes a steady flow inside the pipe. A semi-analytical method using series expansion is employed to derive Eigenvalue problem to facilitate the evaluation of the system frequencies, and its validity is given through the comparison of the solutions with the conventional method using system matrices. The algorithm is implemented to develop computer programs for the estimation of the system frequency. The investigations of the effect of internal flow on system frequency are performed according to the change of parameters such as top tension, internal flow velocity, and so on. It is found that the effect of internal flow can be controlled by the increase of top tension. However, careful consideration has to be given in the design point, particularly for the long riser.