• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.2
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• pp.55-62
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• 2018

In this study, natural period formular is presented for a RC shear wall structure with H-, T-, and L-shaped wall sections. The natural period formular proposed by Goel and Chopra and adopted in ASCE 7-10 was modified by using the ratio of the flange and web wall area. The natural periods of structures with H-shaped wall were numerically obtained, the results indicated that the ASCE 7-10 could not consider the natural period variation according to the length of the flange wall, but the proposed formula could do. Especially, ASCE 7-10 estimated much longer periods than eigenvalue analysis, and this implies that conservative seismic design is difficult. The periods by eigenvalue analysis exist between the upper and lower bounds given by the proposed formula, and conservative design is possible by using the proposed lower bound value. In order to verity the effectiveness of the proposed method, actual residential buildings with various types of flange walls are considered. Ambient vibration tests, eigenvalue analyses, and nonlinear dynamic analyses were conducted and the periods were compared with the values by ASCE 7-10 and the proposed formula. The results showed that the proposed formula could estimate more accurately the periods than ASCE 7-10.

• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.3
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• pp.10-16
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• 1986

This paper deals with a simple, approximate formula to predict the natural frequencies of the sagged cable structures. Assuming that the propagation velocity of the lateral wave is dependent only on the local mass per unit length and local tension, the explicit simple formula to predict the fundamental period is newly derived. The modified form of these formula is also presented for the prediction of the fundamental period of general shaped cable structures. The results of comparison shows fairly good agreements with experimental results and with theoretical ones. This formula is also used to predict the natural frequencies of a long vertical cable and the derived approximate formula in that case, becomes identical to the exact solution.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.60-67
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• 2021

According to the 「Guidelines of Structural Design for Piloti Building」 of the Ministry of Land, Infrastructure and Transport (2018), the natural period of middle and low rise building of upper-walled lower frame type, such as the domestic multiplex house in piloti style, is suggested for safety to apply the existing code formula of the wall structure. However, the current code formula of the wall structure was provided based on actual measurement of high-rise wall-type structures that mainly exhibit bending behavior. So it is considered that it is not suitable for a piloti-type house with four stories or less, where the wall behaves in shear. See also Park et al. (2000) confirmed that the effect of the lower frame part is greater than that of the upper wall part in the natural period of complex structures with 10 or more floors through analytical studies. Therefore, in this study, in order to examine the effect of the lower frame on the natural period of the middle and low-rise piloti structure, the estimation of natural period by the finite element analysis, approximation formula and ccurrent code formula was performed for the target structures with the shear and flexural stiffness of the upper wall and the shear stiffness of the lower frame as variables. As result, it was found that the change in the shear stiffness of the lower frame had a greater effect on the natural period of the whole building than the change in the bending or shear stiffness of the upper wall.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.1
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• pp.1-10
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• 2013

In order to predict inelastic displacement response without nonlinear dynamic analysis, the equal displacement rule can be used for the structures with longer natural periods than the characteristic period, $T_g$, of earthquake record. In the period range longer than $T_g$, peak displacement responses of elastic systems are equal or larger than those of inelastic systems. In the period range shorter than $T_g$, opposite trend occurs. In the equal displacement rule, it is assumed that peak displacement of inelastic system with longer natural period than $T_g$ equals to that of elastic system with same natural period. The equal displacement rule is very useful for seismic design purpose of structures with longer natural period than $T_g$. In the period range shorter than $T_g$, the peak displacement of inelastic system can be simply evaluated from the peak displacement of elastic system by using the inelastic displacement ratio, which is defined as the ratio of the peak inelastic displacement to the peak elastic displacement. Smooth hysteretic behavior is more similar to actual response of real structural system than a piece-wise linear hysteretic behavior such as bilinear or stiffness degrading behaviors. In this paper, the inelastic displacement ratios of the smooth hysteretic behavior system are evaluated for far-fault and near-fault earthquakes. The simple formula of inelastic displacement ratio considering the effect of $T_g$ is proposed.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.4
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• pp.67-74
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• 2007

Rational method has been widely used to calculate peak runoff drainage design or small watershed because of simplicity and convenience. Runoff coefficient(C) is the most important parameter in the rational method which varies according to rainfall intensity, return period, rainfall duration time and soil characteristics. In practice, constant which is value of C in rational formula has been used from the table, originally based on ASCE. These table value does not consider the upper conditions of the depending factors, hence peak runoff calculation could be in correct. Therefore to calculate C in this paper we have devised an improved formula, considering relationship with rainfall duration, return period and CN of NRCS method. This formula is considered to be more reliable and helpful to the hydrologists and engineers to predict correct peak runoff.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.117-124
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• 2003

Wind-induced motions, like acceleration for instance, often influence designs for high-rise buildings. As a consequence, correct assessment of natural frequency becomes important. The empirical expressions used to quantify this parameter at the design phase tend to yield values that are significantly different from each other. This paper is concerned with the natural periods of steel buildings. It describes the vibration measurement methods that were employed for testing buildings. This paper will also present reliable methods of assessing the natural period from ambient vibration tests. Data from measurements on 21 buildings in Seoul were provided while 21 buildings were tested by ambient vibration measurements to obtain the natural periods. While regression formulas of natural periods for steel-frarried tall buildings were suggested,the obtained formula was compared with the empirical expressions of structural standards and the Eigen-value analysis.

• 한국해양학회지
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• v.21 no.4
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• pp.245-258
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• 1986

A two-dimensional numerical model is developed to investigate the phenomenon of forced seiche caused by the incident long waves. This model is applied to Young-il Bay and Pohang New Harbor, where the seiche is most frequently observed and the damage of the seiche is serious compared with the other harbors in Korea. Some results on this study are as follows; 1. The natural periods of the first two modes obtained from the present model are about 70 and 25 minutes respectively for Young-il Bay, and about 25 and 7.5 minutes for Pohang New Harbor. These results are well consistent with those obtained by the theoretical formula, the spectral analysis, and the statistical investigation of the recorded data. 2. Since the fundamental natural period of Pohang New Harbor is almost the same as the second natural period of Young-il Bay, the seiche in Pohang New Harbor can be strongly amplified by the Oscillation in Young-il Bay. Therefore, the most strong seiche in Pohang New Harbor can occur when the long wave of about 25-minute period come into Young-il Bay.

• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.3 s.6
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• pp.89-99
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• 2002

Drought is a very difficult natural disaster to overcome because its beginning and end are not clear to define, and it is widely distributed in space and has long term persistence. The purpose of this study was to evaluate the drought at Mokpo using drought frequency formula suggested by Sharma(1997). The precipitation records for the period 1906-1999 at Mokpo meteorological station are used for drought analysis. The most severe drought year is found to be that of 1995, which is of the 30-year frequency, and 18 drought years are selected based on the 5-year drought frequency.

• Korean Journal of Pharmacognosy
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• v.31 no.3
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• pp.310-319
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• 2000

WooHwangChungSimWon is a traditional prescription formula for treating with hypertension, arteriosclerosis, coma, and stroke in China, Korea, and Japan. In the new prescription of WooHwangChungSimWon, the civet is substituted for the musk, the major component of WooHwangChungSimwon, because of the prohibition law (CITES) on the commercial use of musk. We have made a comparative study of the effects on the hypertension and contractile force of heart between the musk-containing and civet-containing WooHwangChungSimWon. The SHR rats were used for investigating the effects on the hypertension and the rabbits were used for investigating effects on the contractile force of isolated heart. The blood pressure which was recorded during the adminstration period showed that all the samples except the low dose of musk-containing WooHwangChungSimWon decreased the blood pressure, and the effects on the heart works of all the samples were higher than control group, which resulted from the examination of isolated heart. These results suggest that all the musk-containing and civet-containing WooHwangChungSimWon formula have similar protective effects on hypertension and palpitation.

• Herbal Formula Science
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• v.31 no.2
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• pp.81-98
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• 2023

Objectives : This study aimed to analyze the trends in research and development projects related to herbal medicine and natural products in the field of traditional Korean medicine (TKM) over the past 20 years. Methods : Research projects were identified using "Korean medicine" as the subject heading in the National Science and Technology Information Service. The included projects investigated Korean medicine, natural products, or were related to the TKM industry. Data pre-processing and network analysis were performed using Python and Networkx package, and the network was visualized using the ForceAtlas2 visualization algorithm. Results : 1. Over the study period, 4,020 projects were conducted with a research budget of KRW 835.2 billion. Seven institutions performed over 100 projects each, accounting for 2.4% of all participating institutions, and the top 10 institutions accounted for 58.9% of total projects. 2. Obesity was the most frequently mentioned disease-related keyword. Chronic or age-related diseases such as diabetes, osteoporosis, dementia, parkinson's disease, cancer, inflammation, and asthma were also frequent research topics. Clinical research, safety, and standardization were also frequently mentioned. 3. Centrality analysis found that obesity was the only disease-related keyword identified, alongside TKM-related keywords. Standardization, safety, and clinical trials were identified as central keywords. Conclusions : The study found that research projects in TKM have focused on standardizing and ensuring the safety of herbal medicine, as well as on chronic and age-related diseases. Clinical studies aimed at verifying the effectiveness of herbal medicine were also frequent. These findings can guide future research and development in herbal medicine.