• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.140-145
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• 2018

This paper deals with the dynamical analysis of a two-point mooring vessel under surge excitations. The characteristics of nonlinear behaviors are investigated completely including bifurcation and limit cycle according to particular input parameter changes. The strong nonlinearity of the mooring system is mainly caused by linear and cubic terms of restoring force. The numerical simulation is performed based on the fourth order Runge-Kutta algorithm. The bifurcation diagram and several instability phenomena are observed clearly by varying amplitudes as well as frequencies of surge excitations. Stable periodic solutions, called the periodic windows, can be obtained in succession between chaotic clouds of dots in case of frequency ${\omega}=0.4rad/s$. In addition, the chaotic region is unexpectedly increased when external forcing amplitude exceeds 1.0 with the angular frequency of ${\omega}=0.7rad/s$. Compared to the cases for ${\omega}=0.4$, 0.7rad/s, the region of chaotic behavior becomes more fragile than in the case of ${\omega}=1.0rad/s$. Finally, various types of steady states including sub-harmonic motion, limit cycle, and symmetry breaking phenomenon are observed in the two-point mooring system at each parameter value.

• Management & Information Systems Review
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• v.33 no.1
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• pp.45-63
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• 2014

A trading system is a computer trading program that automatically submits trades to an exchange. Mechanical a trading system to execute trade is spreading in the stock market. However, a trading system to trade a single asset might occur instability of the profit because payoff of this system is determined a asset movement. Therefore, it is necessary to develop a trading system that is trade two assets such as a pair trading that is to sell overvalued assets and buy the undervalued ones. The aim of this study is to propose a relative value based trading system designed to yield stable and profitable profits regardless of market conditions. In fact, we propose a procedure for building a trading system that is based on the rough set analysis of indicators derived from a price ratio between two assets. KOSPI 200 index futures and S&P 500 index futures are used as a data for evaluation of the proposed trading system. We intend to examine the usefulness of this model through an empirical study.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.1-8
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• 2006

The purpose of this study was to evaluate normalized jerk according to shoes, slope, and velocity during walking. Eleven different test subjects used three different types of shoes (running shoes, mountain climbing boots, and elevated forefoot walking shoes) at various walking speeds(1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 2.11, 2.33m/sec) and gradients(0, 3, 6, 10 degrees) on a treadmill. Since there were concerns about using the elevated forefoot shoes on an incline, these shoes were not used on a gradient. Motion Analysis (Motion Analysis Corp. Santa Rosa, CA USA) was conducted with four Falcon high speed digital motion capture cameras. Utilizing the maximum smoothness theory, it was hypothesized that there would be differences in jerk according to shoe type, velocity, and slope. Furthermore, it was assumed that running shoes would have the lowest values for normalized jerk because subjects were most accustomed to wearing these shoes. The results demonstrated that elevated forefoot walking shoes had lowest value for normalized jerk at heel. In contrast, elevated forefoot walking shoes had greater normalized jerk at the center of mass at most walking speeds. For most gradients and walking speeds, hiking boots had smaller medio-lateral directional normalized jerk at ankle than running shoes. These results alluded to an inverse ratio for jerk at the heel and at the COM for all types of shoes. Furthermore, as velocity increased, medio-lateral jerk was reduced for all gradients in both hiking boots and running shoes. Due to the fragility of the ankle joint, elevated forefoot walking shoes could be recommended for walking on flat surfaces because they minimize instability at the heel. Although the elevated forefoot walking shoes have the highest levels of jerk at the COM, the structure of the pelvis and spine allows for greater compensatory movement than the ankle. This movement at the COM might even have a beneficial effect of activating the muscles in the back and abdomen more than other shoes. On inclines hiking boots would be recommended over running shoes because hiking boots demonstrated more medio-lateral stability on a gradient than running shoes. These results also demonstrate the usefulness of normalized jerk theory in analyzing the relationship between the body and shoes, walking velocity, and movement up a slope.

• Korean Journal of Construction Engineering and Management
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• v.7 no.5
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• pp.115-127
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• 2006

Although the Korean government have made a plan of housing market with supply and concentrated on the welfare of the people, there are still a lot of problem in housing market for lack of a long-term vision and consistent policy of the government. The plan of 115% of housing diffusion in 2012 is in progress after its acquisition of 100% in 2002, but there are no changes in the rental housing rate of 43% in 2003. In addition, there are getting worse circumstances in the instability of housing market and the low-income bracket, because of the Korean construction firms' bankruptcy with an increase of unsold hosing and a rapid increase of housing prices. The government have made the strategy of revitalizing the economy and regional development by means of a million public rental housing plan for the low-income bracket and welfare. This paper introduces the basic information of the subjective strategy establishment with the analysis of the reciprocal action of influence factors for public rental housing by system dynamics theory and the effect of public rental housing in housing supply market which has a long-term dynamic form.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.714-721
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• 2008

Chemical plants which consume lots of energy are not operating in the best conditions due to their own peculiar nonlinearity, instability, and diverse disturbances. In order to improve this, the plant wide optimization was performed. It is important to select the most appropriate number of decision variables which strongly affect the operating cost because there are too many decision variables which economically have an effect on plant wide. For instance, if all decision variables which can economically affect are applied in optimization and then the result of the optimization is applied to operation, a lot of operating conditions should be going to be changed. As a result of changing a plenty of operating conditions, the cost of the change will absolutely increase. Thus, in this study, the method of selecting the most appropriate decision variables which can influence on saving operation costs was presented in order to optimize plant wide. TPA (Terephthalic-acid) plant is considered as a case study. In other word, after modeling, the most proper decision variables was selected by examining the degree which decision variables influence on operating costs through sensitivity analysis. In TPA process, the three decision variables were selected by the presented method in this study. Then the plant was optimized by selected the decision variables. Consequently, it was seen that the plant are expected to save the 350 million won of energy annually without additional investment for facilities or remodeling of the plant.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.167-172
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• 2004

In the human skin, vitamin C (L -ascorbic acid) that is well known as the activated materials has effects that is skin anti-aging and wrinkle repair by giving impetus to collagen biosynthesis and anti-oxidation, and that is the sun screen, a wound recovering, inhibition melanogenesis and so on. In spite of its effects, vitamin C has the defects of the skin stimulation and easily oxidized instability by water, air, heat and light. For solving their matters, many investigation is advanced and its results are synthesized the various vitamin C derivatives. And yet they have not solved the unstable property of vitamin C and were still insufficient for the comparing with the effect of the pure vitamin C itself. In this study, in order to prepare vitamin C derivative of being improved the stability and to apply vitamin C effect in the skin, we prepared new vitamin C derivative, phytosphingosine ascorbate, by using phytosphingosine, one of sphingolipids, which have a distinguished skin affinity. Phytosphingosine ascorbate can be prepared as the ionic bond between amine group (-NH$_2$) of phytosphingosine and hydroxy group (-OH) of vitamin C by way of the relatively simple reaction. So the structure and properties of the synthesized phytosphingosine ascorbate was confirmed the use of elemental analysis (C 58.3 : H 9.3 : N 2.8 : O 29.5), MALDI TOF-MS (Mw=492.58), Ultraviolet spectra (268.5nm), lH NMR, FT-IR spectra, thermal analysis (m.p=l54$^{\circ}C$), HPLC and so on. And we could confirm the anti-bacterial and anti-oxidation effects. Based on these results, we could confirm to prepare a new material that was expected of both effects of vitamin C and phytosphingosine and that is improved properties of vitamin C.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.2
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• pp.125-131
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• 2018

Ascorbic acid (Vitamin C) has been widely used in skin care formulations. Due to its remarkable effects on anti-oxidation, collagen biosynthesis and whitening, ascorbic acid is considered as an effectible anti-aging active ingredient. But, the instability problems of ascorbic acid in cosmetic formulation such as oxidation, browning and changes in smell is the difficult issue to be overcome for the application of high concentration of ascorbic acid. We tried to stabilize the ascorbic acid in non-aqueous liquid formulation that contains polyol solvent at first. The non-aqueous system was effectible to reduce oxidation. But, ascorbic acid was crystallized in the non-aqueous formulation at the low temperature below $5^{\circ}C$. We tried to develop way to stabilize the ascorbic acid in aqueous solutions to solve the crystallizing problem. In this study, we search the optimal ratio of antioxidant combination, such as zinc sulfate, glutathione and curcuma longa (turmeric) root extract. Formulations were stored at - $16^{\circ}C$, $5^{\circ}C$, $25^{\circ}C$, $40^{\circ}C$, $50^{\circ}C$ and cycle($5-40^{\circ}C$) (in incubator) for a period of eight weeks to investigate their stability. In the stability analysis, the test parameters consisted of color, scent, phase separation and sedimentation. Ascorbic acid stability was checked by HPLC analysis.

• Analytical Science and Technology
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• v.18 no.6
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• pp.552-558
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• 2005

A type of dimethyl sulfide gas CRM in the ppb level was developed for the analysis of trace-level odorous gas in environmental atmosphere. The concentration of dimethyl sulfide ($(CH_3)_2S$) was 10 umol/mol level in the cylinder filled with nitrogen, 1500 psi. And the variability of the concentration for 3 years was about 0.1% due to the adsorption or instability of $(CH_3)_2S$. The gas standards produced simultaneously in 4 bottles and examined by GC-FID were shown with 0.4%, reproducibility of preparation and 0.25%, standard uncertainty due to weighing and purity. The relative expended uncertainty of 1.1% (95% of confidence level, k=2) was assigned to the certified value of 10 umol/mol level of $(CH_3)_2S$ after quantitative evaluation on the purity, mixing, weighing, analysis, adsorption and stability of dimethyl sulfide gas.

• Journal of Korean Society of Transportation
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• v.22 no.6
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• pp.47-54
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• 2004

Recently, a large reduction in domestic aviation demand had roughly shown in the range between 34% and 75% in east central and western corridor of Korea. The reasons for the drop in air traffic demand were the provisioning of several new highway serveces and the national economic difficulties. Since April 2004, moreover, the Korea Train Express(KTX) was operated between Seoul and Daegu in the first phrase of 293Km in KTX operational distance and 258Km in air route distance. The operation of KTX significantly impacted air traffic volume, particularly on the overlapped air routes with KTX routes. This study analyzed the effects on air traffic demand in accordance with the opening of KTX by applying the Stated Preference (SP) survey method, the survey conducted prior to 8 months of the KTX initiative. Also, the comparison of the decreased demand forecast by SP analysis and actual revealed traffic volume during two months service after inauguration of KTX was conducted. The Seoul-Daegu route was analysed using the 3 variables considered access and egress time, fare rate, operational frequency. The result obtained from the analysis showed that air users would be preferred only 14%. Comparatively, however, the actual revealed air passengers after the opening KTX were remained 28%, The less "decreased demand" was caused by the instability of the KTX's operation in the initial stage. Therefore, small numbers of passenger were preferable to airservices rather than high speed railroad service.

• Journal of Veterinary Clinics
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• v.24 no.3
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• pp.325-330
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• 2007

This study was to determine whether canine model which produce acute permanent joint instability in short period without postoperative exercise have a degenerative changes and also evaluated its suitability as an appropriate animal OA models. Ten skeletally mature beagle dogs underwent a unilateral surgical transection of the cranial cruciate ligament and, the medial collateral ligament as well as a medial meniscectomy. The contra-lateral joint was used as control. After 12 weeks, After 12 weeks, the amount of joint damage, inflammation and biochemical change of synovial fluid was evaluated. Histological analysis showed chondrocyte clone formation, hypertrophy of the cartilage and moderate loss of proteoglycans in the experimental joints compared to control joints. In addition, the synovial inflammation in the experimental joints was observed. Biochemical analysis of SF showed significantly increased MMP (matrix metalloproteinase) -2 and -9 in experimental joints compared to control joints. This canine OA model shows the characteristics of degenerative joint disease, and may have a advantages of reducing the time and cost because postoperative exercise is not needed in this OA model.