• 한국강구조학회 논문집
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• 제17권2호통권75호
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• pp.195-206
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• 2005

6m-6m의 2경간 연속합성보에 대한 실험적 연구를 수행하였다. 유로코드에서 제시하고 있는 균열폭 제어 규정의 근거를 살펴보고 인장강화 효과를 고려한 균열상태에 따른 균열폭 계산식 유도과정을 제시하였다. 부모멘트 인장을 받는 바닥판의 거동을 초기균열, 안정화 균열로 나누어서 연속합성보의 거동을 평가하였다. 실험결과로부터 연성 기준을 만족하는 최소철근비는 현재 도로교설계기준보다 낮춰도 될 것으로 판단된다. 균열을 일으킨 연속합성보의 휨강성 평가에서는 안정화균열 이전단계까지는 비균열단면으로 보는 것이 적절하다. 인장철근의 응력과 균열폭의 관계식을 실험결과를 이용하여 제시하였다.

• Structural Engineering and Mechanics
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• 제67권6호
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• pp.555-563
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• 2018

Architectural fabrics membranes have not only the structural performance but also act as an efficient cladding to cover large areas. Because of the direct relationship between form and force distribution in tension membrane structures, form-finding procedure is an important issue. Ideally, once the optimal form is found, a uniform pre-stressing is applied to the fabric which takes the form of a minimal surface. The force density method is one of the most efficient computational form-finding techniques to solve the initial equilibrium equations. In this method, the force density ratios of the borders to the membrane is the main parameter for shape-finding. In fact, the shape is evolved and improved with the help of the stress state that is combined with the desired boundary conditions. This paper is evaluated the optimum amount of this ratio considering the curvature of the flexible boarders for structural configurations, i.e., hypar and conic membranes. Results of this study can be used (in the absence of the guidelines) for the fast and optimal design of fabric structures.

• 대한토목학회논문집
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• 제14권6호
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• pp.1309-1317
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• 1994

앵커리지 (Anchorage)가 주케이블을 지지하는 전형적인 현수교에서는 행거를 가설한 후에 보강형을 순차적으로 가설하기 때문에 시공시 행거에 별도의 긴장력이 필요없다. 이와는 달리 자정식 현수교는 가교각으로 보강형을 지지한 후 행거를 설치하게 된다. 따라서 행거 가설시 초기 긴장력을 가할 필요가 있으며 이 후 계속되는 시공과정에 의해 장력이 지속적으로 변화하게 된다. 따라서 행거의 가설방법을 변화시켜가며 이에 따른 행거장력의 변화 양상을 파악하여 가장 효율적으로 행거를 가설할 수 있는 방법을 결정할 필요가 있다. 이를 위하여 본 연구에서는 해석적인 방법을 제시하였다. 현수교 시공의 진행에 따라 단계적으로 변화하는 구조계를 모사할 수 있는 사공단계해석 알고리즘을 제시하였다. 또한 자정식 현수교에서 발생할 수 있는 기하비선형 해석모델을 제시하였다. 실물 교량을 대상으로 제시된 해석방법에 따라 가장 효과적이라고 생각되는 시공방법을 제시하였다.

• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.139-150
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• 1996

H/T(High Tension) bolt is generally being used in joining the members of steel structure. It has some difficulties in management such as an adequate fastening force and a selection of proper instrument for fastening. T/S(Torque Shear Type High Tension) bolt which is more convenient and easier than H/T bolt in quality control has recently been developed. T/S bolts are produced and widely used these days in domestic, but those have not a detail regulation for their on. Those are only being used according to the specification for the H/T bolts. In this study, we tried to confirm the soundness of T/S bolts by the fatigue test of the modified specimens. First, we measured the reduction rate of the initial axial force with time at bolts. Second, we investigated the slip forces of bolts when the test specimen is loaded in tension. Third, we implemented the fatigue tests. During the test, we measured the variation of the axial forces of bolts under the cyclic loading. Finally, we compared and analyzed the fatigue behavior of H/T and T/S bolt, by S-N curve diagrams that are obtained in this study.

• 한국세라믹학회지
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• 제48권6호
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• pp.600-603
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• 2011

The microstructure of particle stabilized wet foams can be tailored by using parameters including the amphiphile concentration, contact angle, and surface tension. The influence of these parameters on the porosity is satisfactorily described in terms of a combined influence of the contact angle and surface tension of the initial suspensions that are directly affected by the amphiphile concentration. The resulting macroporous structures exhibited a total porosity of 82%. The foam cells were predominantly closed due to the air bubbles of the original wet foams being completely covered.

• Advances in Computational Design
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• 제7권4호
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• pp.281-295
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• 2022

Tensile property is one of the excellent properties of ultra-high performance concrete (UHPC), and uniaxial tensile test is an important and challenging mechanical performance test of UHPC. Traditional uniaxial tensile tests of concrete materials have inherent defects such as initial eccentricity, which often lead to cracks and failure in non-test zone, and affect the testing accuracy of tensile properties of materials. In this paper, an original integrated design scheme of mould and end fixture is proposed, which achieves seamless matching between the tension end of specimen and the test fixture, and minimizes the cumulative eccentricity caused by the difference in the matching between the tension end of specimen and the local stress concentration at the end. The stress analysis and optimization design are carried out by finite element method. The curve transition in the end of specimen is preferred compared to straight line transition. The rationality of the new integrated design is verified by uniaxial tensile test of strain hardening UHPC, in which the whole stress-strain curve was measured, including the elastic behavior before cracking,strain hardening behavior after cracking and strain softening behavior.

• Journal of Microbiology and Biotechnology
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• 제12권3호
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• pp.431-436
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• 2002

Effects of fertilizer additions for oil degradation were examined in sand seashore mesocosms. Within 37 days, up to $85\%$ removal was achieved by the addition of slow-release type fertilizer (SRF) with the initial degradation rate of 423.3 mg oil $(kg sand)^-1\;day^-1$. The removal was mostly of biological origin based on the changes of $C_17$ /pristane and $C_18$/phytane ratios from 2.60 to 0.81 and from 3.55 to 1.29, respectively. The addition of oleophilic fertilizer (Inipol EAP22) was less effective and resulted in the removal of $64\%$ of the added oil ($3\%$, v/v) with a lower initial degradation rate. Petroleum-degrading bacteria had achieved a value of $1{\times}10^8$ CFU $(g sand)^-1$ at Day 3 and this peak exactly coincided with the initial degradation in the SRF-treated mesocosm. In this mesocosm, surface tension values were decreased drastically during Days 3 and 8, suggesting that microbially-produced surface-active agents actively enhanced the oil degradation rate and cell proliferation. Although the Inipol-treated mesocosm appeared to show significantly enhanced oil degradation compared to that of the untreated control mesocosm, Inipol was found to be less effective than SRF in enhancing a true oil-degrader when compared under similar experimental conditions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.202-207
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• 1992

The objective of this study is to develop analytical techniques of polymer impregnated concrete flexural members for its proper applications. crystalline methylmethacrylate(MMA) is chosen as a monomer of polymer impregnants, On the basis of members. fracture toughness, fracture energy , critical crack width, and tension softening relations near crack tip are formulated in terms of member depth, initial notch length and the flexural strength of normal concrete. The structural analysis rocedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. It is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

• 음성과학
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• 제11권1호
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• pp.65-72
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• 2004

The force of articulation is different between voiced and voiceless consonants in the binary opposition system. However, the Korean voiceless stop consonants have a triple opposition system: lenis, aspirated, and glottalized. The aim of this study is to find the primary distinctive feature between the force of articulation and the aspiration for the three different types of Korean stops. Two native speakers of the Seoul dialect participated to this study. The corpus was composed of less than eight syllabic words containing consonants in word-initial position and intervocalic position. Radiocinematography and Mingography were used to analyze the articulatory tension and acoustic characteristics. Korean stops have independent features of articulatory tension and aspiration, in which the indices are different according to position. However, in this system which does not have the opposition of sonority, the force of articulation is the primary distinctive feature and the feature of aspiration is subsidiary.

• 한국염색가공학회지
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• 제11권6호
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• pp.18-23
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• 1999

PET POY(pre-oriented-yam) were treated by false twister to high bulky. False twister have many processing parameters velocity ratio(VR), belt cross angle$(\theta)$, 1st heater temp. and K(twisting tension/untwisting tension). we analyzed the effect of properties of textured polyester yam on processing condition. Initial modulus, thermal stress, No. of snarl is decreased by 1st heater. In VR=1.97, Dry and wet shrinkage is increased but is decreased by 1st heater in VR=1.564. K/S and cristallinity tend to increase by decreasing VR.