• Steel and Composite Structures
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• v.14 no.3
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• pp.243-265
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• 2013

Distortional and local buckling are important factors that influences the bearing capacity of steel-concrete composite box-beam. Through theoretical analysis of distortional buckling forms, a stability analysis calculation model of composite box beam considering rotation of steel beam top flange is presented. The critical bending moment calculation formula of distortional buckling is established. In addition, mechanical behaviors of a steel beam web in the negative moment zone subjected separately to bending stress, shear stress and combined stress are investigated. Elastic buckling factors of steel web under different stress conditions are calculated. On the basis of local buckling analysis results, a limiting value for height-to thickness ratio of a steel web in the elastic stage is proposed. Numerical examples are presented to verify the proposed models.

• Journal of Astronomy and Space Sciences
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• v.32 no.2
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• pp.137-140
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• 2015

The results of the study of ionospheric variations in the summer months of 1998-2002 at an ionospheric station of vertical sounding "Petropavlovsk-Kamchatsky" are presented. Anomalous variations of virtual sporadic-E height (h'Es), Es blanketing frequency (fbEs), and the critical frequency of the ionospheric F2 layer (foF2) (which can be attributed to the possible earthquake precursors) are selected. The high efficiency of the selection of ionospheric earthquake precursors based on the several parameters of Es and F2 layers is shown. The empirical dependence, which reflects the connection between the lead-time of the earthquake moment, the distance to the epicenter from the observation point, and the magnitude of the earthquake are obtained. This empirical dependence is consistent with the results of the detection of earthquake precursors by measuring the physical parameters of the Earth's crust in the same region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.50-53
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• 2001

In this study, gate leakage current mechanism has been analyzed for GaAs MESFET with different temperatures ranging from 27$^{\circ}C$ to 300$^{\circ}C$ . It is expected that the thermionic and field emission at the MS contact will dominate the current flow. Thermal cycle is applied to test the reliability of the device. From the results, it is proved that thermal stress gradually increases the gate leakage current at the same bias conditions and leads to the breakdown and failure mechanism which is critical in the field equipment. Finally the gate contact under the repeated thermal shock has been tested to check the quality of Schottky barrier and the current will be expressed in the analytical from to associate with the electrical characteristics of the device.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.22-32
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• 1998

Separate type thermosyphon has larger critical heat flux than non-loop type thermosyphon, because the flooding phenomenon of vapor and liquid occurring in non-loop one does not occur. The experimental study has been carried out separate type thermosyphon with single tube. An investigation of heat transfer characteristics in separate type thermosyphon is performed experimentally. Heat transfer coefficients in an evaporator and condenser were measured experimentally. The effects of liquid filling ratio, height difference, cooling temperature and heat flux on the heat transfer coefficients were examined. As a result, the reasonable range of the liquid filling ratio and the dependence of heat transfer on vapor temperature and heat flux are obtained.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.405-408
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• 1999

A prototype of solenoidal superconducting magnet using Bi-2223/Ag multi-filamentary tapes was fabricated and tested to investigate its performance. The Bi-2223/Ag tapes were prepared by powder-in-tube method. The dimensions of magnet, which was stacked with 9 double pancakes, were 90 mm in height, 74 mm in outer diameter and 40 mm in clear core. The axial maximum magnet field at the center of the solenoidal magnet was about 0.12 T, and the critical current of coil conductor was about 9 A at 77.3 K.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.451-460
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• 2006

While sludge settles down in a batch column, sludge concentration becomes high. Sludge concentration change is one of the most critical causes of the sludge settling velocity variation. Therefore, sludge concentration change causes sludge index to change. SVI is more sensitive than other sludge indexes to the change of sludge concentration. And if sludge-water interface has reached final height within 30minutes, SVI is not suitable for prediction of sludge settling characteristic, Therefore, SVIs of each sludge are, in some cases, different although each sludge has the same settling velocity. But SVI has been widely used to interpret sludge settling characteristic by a simple testing method. This work has two purposes. The first purpose is to predict sludge settling velocity by using sludge-water interface settling velocity. And the second purpose is to develop new sludge settling characteristic index to exactly interpret sludge settling characteristic by overcoming the limit of SVI.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.7
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• pp.508-519
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• 1991

A new heuristic two-dimensional symbolic layout compaction approach is developed. After conventional one-dimensional compaction steps, all the components on the critical paths that define the height or width of the given layout are found and rearranged to reduce layout size. During this process, constraints in both x and y directions are considered and pitch-matching of ports for hierarchical compaction can be achieved to reduce the amount of the design data. This approach generated the smallest area for several examples we have tried when compared with other published results. The expected run time can be bouned by OT$_1$, where T$_1$ is the run time of a typical one-dimensional compactor.

• International Journal of High-Rise Buildings
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• v.3 no.3
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• pp.199-204
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• 2014

W-Project is 70-story mixed-use residential building complex project in Busan, the second biggest city in South Korea. As it is a high rise building complex located at the coast, the residents have great ocean view from the height. Though, there were many difficult challenges to be solved to secure structural safety and meet the serviceability requirements. As it is located on the reclaimed land, securing the foundation bearing capacity on soft soil is the first issue to be solved for the stable structure. W-Project. Busan on the way usual track of typhoon, wind load on structure is also critical for structural safety and serviceability for occupants due to wind vibration. This paper will address process of lateral load resisting structural system of W-Project.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.384-388
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• 1997

Recently,direct rolling process has been drawing increasing interests because production cost be greatly reduced by eliminating subsequent hot rolling processes. Such a process has been characterized to prosuce thin steel strip (thickness 1~5mm) directly from molten metal and to skip over the conventional hot rolling processes. However, since there are several process parameters, which affect the quality of product,and their relationship between the parametersare very complex,it is therefore very difficult to realize the process design and the quality control. To overcome these difficulties quantitative relationship between the parameters are investigated through a numerical analysis. Form these results, it is found that solidification final point is the most important paramter which is critical to quality of the strip. Also,the multiple regression model is obtianed to determine their relationship from the solidification final point and roll separating force which can be easily estimated

• Structural Monitoring and Maintenance
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• v.2 no.1
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• pp.49-64
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• 2015

This paper presents a method for assessing the risk of wave run-up and overtopping of existing coastal defences and for analysing the probability of failure of the structures under future hydraulic conditions. The recent UK climate projections are employed in the investigations of the influence of changing environments on the long-term performance of sea defences. In order to reduce the risk of wave run-up and overtopping caused by rising sea level and to maintain the present-day allowances for wave run-up height and overtopping discharge, the future necessary increase in crest level of existing structures is investigated. Various critical failure mechanisms are considered for reliability analysis, i.e., erosion of crest by wave overtopping, failure of seaside revetment, and internal erosions within earth sea dykes. The time-dependent reliability of sea dykes is analysed to give probability of failure with time. The results for an example earth dyke section show that the necessary increase in crest level is approximately double of sea level rise to maintain the current allowances. The probability of failure for various failure modes of the earth dyke has a significant increase with time under future hydraulic conditions.