• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.147-156
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• 2007

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigate the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a energy loss ratio of cable potential, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, it is assumed to exist three kinds of multi-mode patterns such as ambient vibration, support excitation and rain-win induced vibration. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5. In case of support excitation or rain-wind induced vibration is between 0.5 and 1.0. In this study, the effects of cable sag and inclination angle are included in the asymptotic design equation of damped cable structures.

• Microbiology and Biotechnology Letters
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• v.17 no.5
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• pp.475-480
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• 1989

The extracellular polysaccharide was isolated from the culture of Ps. delafieldii and its rheological property was evaluated. The aqueous solution was extremely viscous and shows pseudoplastic behaviour. The flow behaviour index and apparent viscosity of 1 ％solution were 0.09 and 1169 mPa·s. The solution was stable over pH change but did not have thermal stability. The activation energy of flow of 1 ％ solution was 4.44 kcal/mole. The concentration dependency could be expressed double logarithmically.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2168-2180
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• 2014

In this paper, a generalized power loss algorithm for multilevel neutral-point clamped (NPC) PWM inverters is presented, which is applicable to any level number of multilevel inverters. In the case of three-level inverters, the conduction loss depends on the MI (modulation index) and the PF (power factor), and the switching loss depends on a switching frequency, turn-on and turn-off energy. However, in the higher level of inverters than the three-level, the loss of semiconductor devices cannot be analyzed by conventional methods. The modulation depth should be considered in addition, to find the different conducting devices depending on the MI. In a case study, the power loss analysis for the three- and five-level NPC inverters has been performed with the proposed algorithm. The validity of the proposed algorithm is verified by simulation for the three-and five-level NPC inverters and experiment for three-level NPC inverter.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.99-107
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• 2017

In this work, the nutation control of rigid spacecraft with only two momentum wheels is addressed by applying the feedback linearization technique. In this strategy, the primary performance index is to regulate the nutational angle by the momentum control of wheels. The spacecraft attitude equations of motion are transformed to a general linearized form by feedback linearization technique, including a guaranteed control law promising the internal dynamics stability to accomplish the nutation angle small. It is proven that the configuration of inertia properties plays a key role in analyzing spacecraft energy level. The behavior of the momentum wheels is also studied analytically and numerically. Finally, the effectiveness of the proposed nonlinear control law for the momentum transfer is verified by conducting numerical simulations.

• Journal of Nutrition and Health
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• v.30 no.2
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• pp.177-186
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• 1997

To evaluate the effectiveness of nutritional supplements for cancer patients, the study was performed in 30 cncer patients, receiving chemotherapy. Patients were randomly divided into two groups -15 patients for the nutritionally supplemented group and 15 patients for the control group. Patients of the supplemented group were nutritionally supported with a commercial product for 9 weeks. Nutritional status of the patients was detrmined by dietary intake data, anthropometric measurements and hematological analysis at the beginning and after 3, 6 and 9 weeks of supplemental priod. Mean daily intake levels of energy, protein, calcium, phosphorus, thiamin, riboflavin, niacin and asorbic acid for the supplemented group were significantly higher than those of control group. Significant increase in mid-arm circumference, triceps skinfold thickness and arm fat area were observed in supplemented group during the study period. However, the changes of body weight, body mass index and arm muscle area were not significantly increased. Serum transferrin level improved slightly by nutritioal support, but serum albumin levle did not change significantly. There data show that nutritional status of cancer patients receiving chemotherapy can be improved by utritional supplementation for 9 weeks.

• Structural Engineering and Mechanics
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• v.39 no.3
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• pp.411-425
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• 2011

This paper illustrates the results of a seismic vulnerability study aimed to derive the fragility curves for typical Algerian reinforced concrete bridge piers using an analytical approach. Fragility curves express the probability of exceeding a certain damage state for a given ground motion intensity (e.g., PGA). In this respect, a set of 41 worldwide accelerometer records from which, 21 Algerian strong motion records are included, have been used in a non-linear dynamic response analyses to assess the damage indices expressed in terms of the bridge displacement ductility, the ultimate ductility, the cyclic loading factor and the cumulative energy ductility. Combining the damage indices defined for 5 damage rank with the ground motion indices, the fragility curves for the bridge piers were derived assuming a lognormal distribution.

• Steel and Composite Structures
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• v.13 no.4
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• pp.383-396
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• 2012

In order to develop a verification method for extremely low cycle fatigue (ELCF) of steel structures, the initiation mechanism of ductile cracks is investigated in the present study, which is the first step of brittle fracture, occurred in steel bridge piers with thick-walled sections. For this purpose, a total of six steel columns with small width-thickness ratios were tested under cyclic loading. It is found that ductile cracks occurred at the column base in all the specimens regardless of cyclic loading histories subjected. Moreover, strain history near the crack initiation location is illustrated and an index of energy dissipation amount is proposed to evaluate deformation capacity of structures.

• Structural Engineering and Mechanics
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• v.68 no.3
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• pp.277-287
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• 2018

This paper presents the experimental study of nine pieces of reinforced concrete (RC) short columns. RC short columns were tested with cyclic loading with displacement control under the influence of constant axial load with load index of 0.2. Three columns within the tested nine columns are reference columns which have the details of the reinforcement given in the modern regulations and six of them are 150 mm and 100 mm externally collared columns. In addition to the parameter of the collar spacing, aspect ratio (as=2-1.5-1) is also considered as a parameter. The data obtained from experimental results have shown that externally collar contributes significantly to increasing the shear resistance of RC short columns and limiting the shear dominant behavior. It has been observed that the effectiveness of the externally collar increases with the decrease of the aspect ratio.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.95-105
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• 1997

Structures subjected to strong seismic excitation may undergo inelastic deformation cycles. The resulting cumulative fatigue damage process reduces the ability of structures and components to withstand seismic loads. Yet, the present earthquake resistance design methods focus mainly on the maximum displacement ductility, ignoring the effect of the cyclic responses. The damage parameters closely related to the cumulative damage need to be properly reflected on the aseismic design methods. In this study, two cumulative damage assessment methods derived from the plastic fatigue theory are investigated. The one is based on the hysteretic ductility amplitude, and the other is based on the dissipated hysteretic energy. Both methods can consider the maximum ductility and the cyclic behavior of structural response. The validity of two damage methods has been examined for single degree of freedom structures with various natural frequencies against two different earthquake excitations.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.69-74
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• 2008

This study is to analyze and compare on the sky condition of cloud amount and measured solar horizontal irradiation in Seoul. Sky cover method is determination of sky condition used by cloud amount of the Meteorological Administration. And HCI method is determination of sky condition used by measured solar horizontal irradiation. The HCI methods of Erbs et al.(1982), Orgill and Hollands(1977) appear a lot of error because of the air pollution such as smog phenomenon or yellow sand phenomenon and so on. Therefore, The purpose of this study is to improve the method for determination of sky condition.