• The KSFM Journal of Fluid Machinery
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• v.16 no.2
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• pp.5-9
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• 2013

The aim of present study is to evaluate the stability of GM(Metacentric Height) calculation and investigate the damping effect of free rolling test. Moreover, GZ(Righting arm in stability) curve shows that it can provide reasonable design conditions for Fish boat. The roll damping characteristics of the improved model for an 7.9 ton class fishing boat are investigated through the free roll test in towing tank. The safety and boarding sensitivity are evaluated by GM calculation and roll motion period. Therefore, the results in this paper describe that the effect for improved hull is more improved than the original hull.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.4
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• pp.249-258
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• 2003

In this study, the stability of armor blocks of rubble-mound breakwaters is investigated based on the 2-dimensional hydraulic model test with irregular waves. Amor blocks were used the three types; rock, cube and tetrapod. And Hudson formula and van der Meer formula which are used for calculating the weight of armor blocks are considered. Hudson formula was developed from regular wave tests, while van der Meer formula was developed from irregular wave tests. The purpose of this paper is to compare and test two selected stability formulas using the experimental data.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.471-476
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• 2001

The main object of this study is to develop a reliable FEM simulation technique for stability test using ABAQUS software and to clarify the effect of base profile of a steel D&I(drawn and ironed) can on the dome reversal pressure. For the can after body making simulation, two kind of stability test, dome buckle test and axial crush test are performed. The factors studied in the base profile on the dome reversal pressure are the base diameter, the rim radius, the dome shoulder radius, the dome radius and the dome depth. Within the limits before the occurrence of normal snap-through buckling of dome, the dome reversal pressure is improved by decreasing the base diameter, increasing the dome depth or increasing the dome shoulder depth.

• Journal of Fashion Business
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• v.26 no.6
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• pp.105-115
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• 2022

Wearing a mask is still advised since COVID-19 continues to spread. However, masks may also irritate the skin and cause mask acne, often known as "maskne", which is a type of acne mechanica caused by friction between the skin and clothing. Therefore, there is a need to develop an effective maskne cosmetic. In this study, we made the maskne cosmetics containing humulus lupulus extract and copper tripeptide-1 and investigated its stability and safety. To measure stability, a centrifugation test and heat-cool cycling were done, and changes in viscosity and pH were measured for 8 weeks. The Cumulative Irritation Test (CIT, WKIRB-202111-HR-096) was performed and positive reactions were determined by the ICDRG criteria. The results indicated that the samples were stable after centrifugation, temperature cycling, viscosity, and pH tests. In addition, cosmetic safety test results revealed that maskne cosmetics containing humulus lupulus extract and copper tripeptide-1 did not cause any skin responses. These findings indicate that prepared maskne cosmetics' stability and safety were comparable to those of currently available commercial cosmetics.

• Smart Structures and Systems
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• v.25 no.2
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• pp.155-167
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• 2020

This paper demonstrates a real-time hybrid substructuring (RTHS) shake table test to evaluate the seismic performance of a base isolated building. Since RTHS involves a feedback loop in the test implementation, the frequency dependent magnitude and inherent time delay of the actuator dynamics can introduce inaccuracy and instability. The paper presents a robust stability and performance analysis method for the RTHS test. The robust stability method involves casting the actuator dynamics as a multiplicative uncertainty and applying the small gain theorem to derive the sufficient conditions for robust stability and performance. The attractive feature of this robust stability and performance analysis method is that it accommodates linearized modeled or measured frequency response functions for both the physical substructure and actuator dynamics. Significant experimental research has been conducted on base isolators and dampers toward developing high fidelity numerical models. Shake table testing, where the building superstructure is tested while the isolation layer is numerically modeled, can allow for a range of isolation strategies to be examined for a single shake table experiment. Further, recent concerns in base isolation for long period, long duration earthquakes necessitate adding damping at the isolation layer, which can allow higher frequency energy to be transmitted into the superstructure and can result in damage to structural and nonstructural components that can be difficult to numerically model and accurately predict. As such, physical testing of the superstructure while numerically modeling the isolation layer may be desired. The RTHS approach has been previously proposed for base isolated buildings, however, to date it has not been conducted on a base isolated structure isolated at the ground level and where the isolation layer itself is numerically simulated. This configuration provides multiple challenges in the RTHS stability associated with higher physical substructure frequencies and a low numerical to physical mass ratio. This paper demonstrates a base isolated RTHS test and the robust stability and performance analysis necessary to ensure the stability and accuracy. The tests consist of a scaled idealized 4-story superstructure building model placed directly onto a shake table and the isolation layer simulated in MATLAB/Simulink using a dSpace real-time controller.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.45-51
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• 2003

This paper presents a method to improve lateral stability of a four-seat canard aircraft, Velocity-173. Longitudinal stability of Velocity-173 is rather good, but lateral stability is relatively poor. A small panel which increases the area of vertical tail is designed and manufactured. In a design process, AAA(Advanced Aircraft Analysis) is used to predict the change in stability. Flight test is performed to validate the effect of a small panel attached under the vertical panel. Maximum likelihood estimation method is used to extract lateral controllability / stability derivatives from flight test data. This work validates the effect of a small panel attached under the vertical tail.

• Journal of Environmental Science International
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• v.28 no.11
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• pp.1033-1040
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• 2019

The National Environmental Specimen Bank (NESB) has set up a plan to develop reference materials in the facility for assuring analytical quality and validating analytical methods for its monitoring samples. Some of the crucial characteristics that reference materials must consist of are homogeneity and stability of both intra and inter-bottles. In this study, we examined the homogeneity and stability of cryogenically-milled muscle samples, from Common Carp (Cyprinus carpio) for total mercury. Homogeneity was tested using ANOVA analysis and regression analysis was used to test short-term stability. The variations of total mercury concentration did not significantly differ between the intra and the inter-bottle (F=0.8, p=0.37). Additionally, relative standard deviation of the total mercury concentration showed low values (2.28%). For the short-term stability test, total mercury variations were not statistically significant as demonstrated by the result of the regression analysis (F ratio = 3.11, p = 0.18). This suggests that the cryogenic-milling process has statistically proven the degree of homogeneity and short-term stability for samples of carp muscles in the chemical analysis for total mercury.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.1
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• pp.149-160
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• 2001

In this paper, the stability analyses were performed for masonry retaining wallls in Seoul subway System. This masonry retaining wallls were reinforced with earth anchor system for the construction, but it was removed after construction. Therefore, the stability of masonry retaining wallls should be checked after the earth anchors removed. For stability analysis of masonry retaining wallls. FDM analysis(FLAC Ver.3.3) and slope stability analysis (SLOPE/W) were performed applying the test results from laboratory and field tests(Schmidt hammer test, cack examination). As conclusion, the tension force of earth anchors should be kept, therefore, substitutional method was required in order to keep the tension force of earth anchor system.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.953-955
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• 1993

In this paper we propose a new stability theorem and a robust stability condition for linguistic fuzzy model systems in state space. First we define a stability in linear sense. After representing the fuzzy model by a system with disturbances, A necessary and sufficient condition for the stability is derived. This condition is proved to be a sufficient condition of the fuzzy model. The Q in the Lyapunov equation is iteratively adjusted by an gradient-based algorithm to improve its stability test. Finally, stability robustness bounds of a system having modeling error is derived. An example is also included to show that the stability test is powerful.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1905-1913
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• 2011

The dynamic characteristic of bogie that is driving system of railway vehicle is very important regarding decision of vehicle characteristics as running safety and comport. The dynamic characteristic test of bogie is tested on full size in place on field testing on track. But, the testing on the full size caused many problems. To overcome these problem by full size test, the Railway Safety Research Center in Seoul National University of Science & Technology developed 1/5 scale size of small scale derailment simulator and is currently testing running stability of 1/5 scaled bogie. Also To take effectively advantage of running stability test using small scale derailment simulator in actuality design and reliability estimation, it is necessary comparison and examination with field test and theoretical analysis result In this paper. to achieve running stability analysis of 1/5 scaled bogie on small scale derailment. the program using MATLAB that is fast compose and analysis the motion equation of Saemaul power bogie is developed. It is achieved analysis according to various specification (weight, size, suspension, etc..) and is evaluated corelation between test result and dynamic characteristic of actual railway vehicle.