• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.258-265
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• 2017

At the early stage of the development of high speed propulsion systems, the designers suffer from the lack of both the quantity and the quality of test data. In that situation, the associated uncertainties could not be modeled as probabilistic distribution since probabilistic modelling requires large amount of data. In this paper, instead, the information provided by experts based on their experience and engineering knowledge was used to model uncertainty using the evidence theory. In designing the DCR(Dual Combustion Ramjet) engine, the combustion efficiencies, not well understood and little data existing, are assumed to have been provided by experts. And the uncertainties are quantified by Evidence theory. The quantified uncertainties are incorporated into the optimization. The design variables, area of inlet and area of combustor exit, have been found while satisfying reliability margins of thrust and thermal choking. The results show a reasonable design of the engine under the uncertain circumstances.

• Geotechnical Engineering
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• v.2 no.3
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• pp.37-50
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• 1986

The uncertainties encountered in the stability analysis for the foundation of offshore structures on clay are formulated in probabilistic terms and used to evaluate the reliability of the foundation design. The major sources of uncertainty are: soil properties, f.ave loads, and methods of analysis. The major part of the uncertainty in safety factor is contributed by the uncertainty in the undrained shear strength. All sources of uncertainties that affect the shear strength of clay are modeled and systematically analyzed. The in situ undrained shear strengths are evaluated by laboratory tests and cone penetration tests. The undrained shear strengths from the laboratory test and CPT, respectively at Statfjord B site in the North Sea, are used as an example in risk analysis. Using the CPT alone, the failure probability on sliding of gravity platform at Statfjord B is much larger than the failure probability using the laboratory undrained shear strengths. The major uncertainty of using the CPT as the estimate of th2 undrained shear strength of clay results from the correlation between the cone resistance and the undrained shear strength.

• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.31-38
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• 2013

After debris flow caused damage during recent years, many scholars and engineers have thrown their effort into analyzing risk from debris flow in Korea. But it is hard to predict damage by debris flow taken place in wide area. Recently, SINMAP program is widely well used to estimate the amount of debris flow and its' range. In order to make frequent use of it, the most important thing is selection of accurate input parameters. In-situ experiments, which are avaliable in the mountain, is to be suggested to get dependable input parameters for SINMAP. Those are permeability, cohesion, density, friction angle and thickness in SINMAP. To get those, test pit, block sampling, in-situ density test, auger boring, permeability test on ground surface, borehole shear test and dynamic cone test and so forth were selected. In addition, the reliability of the results will be increased through comparing with those by laboratory tests. Hence, the experiments are hard to enter the sites without temporary road and, if possible, licensing and many times are needed, too. Small size experiments are indeed necessary to get accurate parameters.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.297-312
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• 2018

In order to assess the safety diagnosis and grouting reinforcement effect of old reservoir facility, local governments and public offices mainly use electrical resistivity survey. However, electrical resistivity survey is a qualitative evaluation that varies the resistivity value by various exploration conditions. It is also difficult to grasp the stiffness change directly related to the stability of reservoir, thus an electrical resistivity survey is not applicable to continuous stability monitoring after grouting. The purpose of this study is to investigate and validate the quantitative evaluation of reinforcement effect of reservoir with cement grouting through shear velocity (Vs), which is closely related to the stiffness (${\mu}$) of the ground. This study was carried out on two reservoir facilities. The reinforcement effect was evaluated by comparing the permeability test, standard penetration test, down-hole test and MASW(Multi-channel Analysis of Surface wave) survey before and after cement grouting. Shear wave velocity changes before and after grouting were analyzed by phase velocity difference and inversion analysis, respectively, and the reliability of the analytical results was evaluated by comparing with field test results. Shear wave velocity increases to 5~10% in case of the D levee, and 10~20% in the levee of H reservoir. These results are showed similar pattern to the field test results.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.47-53
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• 2022

With the recent development of defense technology, various aircraft armaments/equipments are being developed. Among them, cruise guided weapons(missile) for launching aircraft can be installed on aircraft aftersecuring reliability and safety through varioustests. In order to avoid collision with aircraft, missile separated from aircraft must release restraint of wing at the specified time, control wing in the specified direction. In order to confirm this, a test system that can control MIL-STD-1760 according to safety separation procedure and verify release performance is required. test system needs a function to check circuit for release of restraints and a function to check driving performance by controlling MIL-STD-1760. In addition, test system should be simulate environment separated from aircraft. This paper presented a testsystemthat can verify circuit and driving performance mounted on missile according to the safety separation procedure, and it was confirmed that it was normally separated from aircraft through flight tests.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.1
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• pp.17-22
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• 2016

Flexible organic light-emitting diode (OLED) devices consist of multi-stacked thin films or layers comprising organic and inorganic materials. Due to thermal coefficient mismatch of the multi-layer films, warpage of the flexible OLED is generated during high temperature process of each layer. This warpage will create the critical issues for next production process, consequently lowering the production yield and reliability of the flexible OLED. In this study, we investigate the warpage behavior of the flexible OLED for each bonding process step of the multi-layer films using the experimental and numerical analysis. It is found that the polarizer film and barrier film show significant impact on warpage of flexible OLED, while the impact of the OCA film on warpage is negligible. The material that has the most dominant impact on the warpage is a plastic cover. In order to minimize the warpage of the flexible OLED, we estimate the optimal material properties of the plastic cover using design of experiment. It is found that the warpage of the flexible OLED is reduced to less than 1 mm using a cover plastic of optimized properties which are the elastic modulus of 4.2 GPa and thermal expansion coefficient of $20ppm/^{\circ}C$.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.91-97
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• 2008

In this paper, in-situ technique for measuring hydraulic conductivity of Excavation Disturbed Zone (EDZ) in a direct way and its application to an Underground Research Laboratory (URL) site were introduced. It was understood that both the EDZ oriented test equipment as a hardware and analysis/evaluation technique as a software should be integrated for upgrading a quality of estimated EDZ hydraulic conductivity. The well-estimated EDZ hydraulic conductivity is expected to enhance a reliability of stability evaluation for caverns under groundwater table and design of a waterproof or drainage system as well as a grout system.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.11-17
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• 2009

The drop impact reliability comes to be important for evaluation of the life time of mobile electronic products such as cellular phone. The drop impact reliability of solder joint is generally affected by the kinds of pad and reflow number, therefore, the reliability evaluation is needed. Drop impact test proposed by JEDEC has been used as a standard method, however, which requires high cost and long time. The drop impact reliability can be indirectly evaluated by using high speed shear test of solder joints. Solder joints formed on 3 kinds of surface finishes OSP (Organic Solderability Preservation), ENIG (Electroless Nickel Immersion Gold) and ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) was investigated. The shear strength was analysed with the morphology change of intermetallic compound (IMC) layer according to reflow number. The layer thickness of IMC was increased with the increase of reflow number, which resulted in the decrease of the high speed shear strength and impact energy. The order of the high speed shear strength and impact energy was ENEPIG > ENIG > OSP after the 1st reflow, and ENEPIG > OSP > ENIG after 8th reflow.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.35-40
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• 2007

The pull strength and fracture mechanism were investigated to evaluate the reliability and compatibility of Sn-8Zn-3Bi joints, the solder paste on lead and lead-free plating under thermal shock conditions. At the Sn-8Zn-3Bi solder joint, no crack initiation was observed during thermal shock test. After 1000 cycles, the strength of the solder joint decreased not sharply but reduced gradually compared with initial conditions. The decrement of strength was affected by ${\gamma}-Cu_5Zn_8$ IMC growth which caused the IMC fracture on the fracture surface and a change in fracture mode and initial crack point. Clearly, the Sn-8Zn-3Bi solder shows good reliability properties and compatibility with lead-free plated Cu LF under thermal shock temperatures between 248K and 423K.

• The KIPS Transactions:PartD
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• v.10D no.2
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• pp.293-300
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• 2003

As Internet has grown rapidly and been more complex by technology in connection with Web and requirement of business, qualify and reliability of Web application are getting important. It is necessary to study about testing method along with design technique specially in Web application. This paper explains automation method of user interface test to make test cases about user input form with HTML pages using by built-in browser objects. Examples shows the possibility of testing automation with Javascript objects get mapped. Overhead of writing Javascript can be reduced by making script generator. Generated test scripts are repeatedly used in regression testing Web-based application.