• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.69-75
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• 2005

Recently it was reported that the vibration problems on the oil pipe support structure of the crude oil carrier were occurred. in order to investigate the vibration characteristics and the causes of the vibration occasionally. the vibration measurements and impact tests for the oil Pipe structure were carried out. From the measurement results severe vibration was caused by the resonance between the transversal natural frequency of the structure and $6^{th}$ order excitation force of the main engine. Providing the proper countermeasures a series of the vibration analyses were carried out based on the measurement results. From the analysis results, it was concluded that the vibration characteristics of the oil pipe structure were affected by the oil pipes, support structure itself, upper deck structure and the installation spaces and the standard design was established for the crude oil carriers.

• 한국동물위생학회지
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• 제40권2호
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• pp.143-147
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• 2017

A Korean domestic short hair (1-year-old, male) presented with 2 to 3 weeks of seizures, aggressive behavior, vomiting, anorexia, and lethargy. The frequency of seizure had gradually increased from once a week to once every 3 hours. Physical and neurologic examination, diagnostic screening tests, including complete blood count (CBC), serum chemistry, electrolyte, coagulation test, X-ray, ultrasonography, and urinalysis were performed. Feline Leukemia Virus (FeLV), Feline Immunodeficiency Virus (FIV) and Toxoplasma spp. All tested negative, but the Feline Corona Virus (FCoV) kit revealed a positive result. To determine the exact diagnosis, magnetic resonance imaging (MRI) was performed but yielded no specific findings. The patient was then diagnosed with idiopathic epilepsy and treatment of phenobarbital was initiated. A month's treatment with phenobarbital proved ineffective as symptoms worsened. Zonisamide was then selected as an additional anticonvulsant. After adding zonisamide, symptoms improved, and seizures abated for 15 months. This is the first case report in South Korea describing the use of phenobarbital and zonisamide in the treatment of a cat with idiopathic epilepsy.

• 복식문화연구
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• 제10권6호
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• pp.680-696
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• 2002

The aim of this study was to identify the components of customer-based fashion brand equity which was built from customers´perception to equity. As a method, both literature review and empirical research were made. This study performed in three stages from May to November in 2001. In the exploratory step. focus-group interview was conducted 5 times for gathering responses related to fashion brand equity, and free association test of 17 respondents was additionally conducted. In pilot study, 40 university students were surveyed and the data were analyzed in order to identify the components of fashion brand equity and to develop questionnaire. In the main research, 905 university students evaluated fashion brand equity in order to analyze the components of fashion brand equity in customers´perception. Statistical analyses were performed with SAS program using factor analysis, cronbach´α, frequency, and mean. The results of this study was as fellows. First, fashion brand equity was defined in terms of four components; customer-brand resonance, brand imagery/customer feeling, brand performance/customer judgment and brand awareness. Second, fashion brand equity was multi-dimensional brand attitude, which could be measured by 29 variables that were different from uni-dimensional evaluation of previous studies.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.94-99
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• 2000

When operating NC lathe, gear box which is equipped with gear train and spindle sometimes generates loud noise and excessive vibrations. In order to identify their causes, In this study, torsional and lateral vibration characteristics including critical speeds of the gear train-spindle system are first analyzed by using torsional and lateral vibration models of the gear train and shafts. Natural frequencies and modes of the gear box structure are also analyzed by impulse hammer test. Furthermore, measured vibration and noise signals are analyzed and compared with theoretical analysis results. At last it is concluded that the cause of the excessive mise and vibration is the resonance between gear meshing frequency including its side bands, shaft bending and torsional vibration frequencies, and the natural frequencies of th gear box structure. Consequently the noise and vibration levels are greatly reduced by avoiding resonance between them through the redesign of the gear module.

• Tribology and Lubricants
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• 제35권1호
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• pp.71-76
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• 2019

The differential planetary gear reducer as a main component of the concrete mixer driving mechanism requires a strong torque to mix concrete compounds. As this component is currently dependent on imports, it is necessary to develop it by conducting a study on vibration analysis and the resonance problem. The noise and vibration of a concrete mixer reducer increase owing to the transmission error of planetary gears, and the damage of components occurs owing to the problems in design and production. In this study, the tooth-passing frequency is calculated to evaluate the noise and vibration of a mixer reducer, and a fast Fourier transform (FFT) analysis is conducted through a vibration test using an acceleration sensor. The vibration of the reducer is measured at three points of input and output of the shaft and planetary gear housing with fixed and variable revolutions per minute. The operating conditions of gears and bearings are evaluated by performing the FFT analysis, and the resonance problem is verified. The results show that No. 1 pinion and ring gears revolve disproportionately. The amplitude values appear high, and the wear of tooth faces occur in tooth-passing frequencies and harmonic components of No. 1 and No. 2 pinion-ring gears. Therefore, we conclude that design changes in the reducer and a correction of tooth profiles are required.

• 항공우주시스템공학회지
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• 제9권2호
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• pp.51-56
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• 2015

In the vibration test, Most of the test specifications is standardized methods of sinusoidal excitation. However, in accordance with the ability of the test equipment progress and developments of electronic technology, methods of random vibration test is standardized in the MIL standard. Therefore, in this study, we tried to analyze Missile Guidance Structure using a finite element analysis with ABAQUS 6.13 that is commercial program. First, Random response analysis is analyzed. Following analyzing the results, we wanted to find the model that is lightweight and resonance does not occur.

• International Journal of Railway
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• 제3권3호
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• pp.83-89
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• 2010

This paper attempts to extract the fundamental dynamic properties, i.e. natural frequencies, damping ratios of the 48 m-long, $20^{\circ}$ skewed real bridge with PSC girders wrapped by a steel plate. The forced vibration test is achieved by mounting 12 Hz-capacity of artificial oscillator on the top of bridge deck. The acceleration histories at the 9 different locations of deck surface are recorded using accelerometors. From this full-scaled vibration test, the two possible resonance frequencies are detected at 2.38 Hz and 9.86 Hz of the skewed bridge deck by sweeping a beating frequency up to 12 Hz. The absolute acceleration/energy exhibits much higher in case of higher-order twist mode, 9.86 Hz due to the skewness of bridge deck which leads asymmetric situation of vibration. This implies the test bridge is under swinging vertically in fundamental flexure mode while the bridge is also flickered up and down laterally at 9.86 Hz. This is probably by asymmetric geometry of skewed deck. A detailed 3D beam-shell bridge models using finite elements are performed under a series of train loads for modal dynamic analyses. Thereby, the effect of skewness is examined to clarify the lateral flickering caused by asymmetrical geometry of bridge deck.

• Journal of Periodontal and Implant Science
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• 제50권1호
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• pp.56-66
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• 2020

Purpose: A stability-measuring device that utilizes damping capacity analysis (DCA) has recently been introduced in the field of dental implantology. This study aimed to evaluate the sensitivity and reliability of this device by measuring the implant stability of ex vivo samples in comparison with a resonance frequency analysis (RFA) device. Methods: Six implant beds were prepared in porcine ribs using 3 different drilling protocols to simulate various implant stability conditions. Thirty-six pork ribs and 216 bone-level implants measuring 10 mm in height were used. The implant beds were prepared using 1 of the following 3 drilling protocols: 10-mm drilling depth with a 3.5-mm-diameter twist drill, 5-mm drilling depth with a 4.0-mm-diameter twist drill, and 10-mm drilling depth with a 4.0-mm-diameter twist drill. The first 108 implants were external-connection implants 4.0 mm in diameter, while the other 108 implants were internal-connection implants 4.3 mm in diameter. The peak insertion torque (PIT) during implant placement, the stability values obtained with DCA and RFA devices after implant placement, and the peak removal torque (PRT) during implant removal were measured. Results: The intraclass correlation coefficients (ICCs) of the implant stability quotient (ISQ) results obtained using the RFA device at the medial, distal, ventral, and dorsal points were 0.997, 0.994, 0.994, and 0.998, respectively. The ICCs of the implant stability test (IST) results obtained using the DCA device at the corresponding locations were 0.972, 0.975, 0.974, and 0.976, respectively. Logarithmic relationships between PIT and IST, PIT and ISQ, PRT and IST, and PRT and ISQ were observed. The mean absolute difference between the ISQ and IST values on a Bland-Altman plot was -6.76 (-25.05 to 11.53, P<0.05). Conclusions: Within the limits of ex vivo studies, measurements made using the RFA and DCA devices were found to be correlated under a variety of stability conditions.

• 대한치과보철학회지
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• 제45권1호
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• pp.98-106
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• 2007

Statement of problem: Current tendencies of the implant macrodesign are tapered shapes for improved primary stability, but there are lack of studies regarding the relationship between the implant macrodesign and primary stability. Purpose: The purpose is to investigate the effect of implant macrodesign on the implant primary stability by way of resonance frequency analysis in the bovine rib bones with different kinds of quality. Material and method: Fifty implants of 6 different kinds from two Korean implant systems were used for the test. Bovine rib bones were cut into one hundred pieces with the length of 5 cm. Among them forty pieces of rib bones with similar qualities were again selected. For the experimental group 1, the thickness of cortical part was measured and 20 pieces of rib bones with the mean thickness of 1.0mm were selected for implant placement. For the experimental group 2, the cortical parts of the remaining 20 pieces of rib bones were totally removed and then implants were placed on the pure cancellous bone according to the surgical manual. After placement of all implants, the implant stability quotient(ISQ) was measured by three times, and its statistical analysis was done. Results: There are statistically significant differences in ISQ values among 4 different kinds of Avana system implants in the experimental group 2. For the experimental group 1, Avana system implants showed significantly different ISQ values, but when differences in the thickness of cortical parts were statistically considered, did not show any significant differences in ISQ values. Among Oneplant system implants, there are no significant differences in ISQ values for the experimental group 2 as well as for the experimental group 1. Conclusion: Within the limits of this study, bone quality and implant design have some influences on the primary stability of implants. Especially in the bone of poor quality, tapered shape of implants are more favorable for the primary stability of implants.

• 한국지반공학회논문집
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• 제33권12호
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• pp.59-73
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• 2017

3차원 유한요소 프로그램(PLAXIS 3D)를 이용한 수치해석을 통하여 동적표면하중 하에서지반-말뚝 구조물의 상호작용을 평가하였다. 수치해석에 의한 진동대 실험 형태의 하중조건 및 지반시스템에 대한 동적 p-y곡선을 산정하고 이를 통하여 말뚝-지반의 조건, 말뚝의 선단부 조건, 재하조건 등을 고려하여 매개변수 연구를 하였다. 그 결과 주파수 1.4Hz 입력 진동수가 모형 말뚝-지반 시스템의 고유진동수 1.4Hz와 거의 일치하여 공진 현상이 발생하여서 다른 진동수의 결과와 비교시 다른 p, y 값을 보이고 있다. P-y 곡선에서 이를 대표할 수 있는 경향선을 나타내는 3차 다항함수로 표현하여 결과를 정리하였다. 특히 단독 말뚝의 경우 지배적인 곡선의 형태가 수학적인 증명을 통해 타원(ellipse)임을 밝혀냈다. P-y곡선의형태가 타원인 경우는 타원 방정식을 직접 지반-구조물의 동적설계나 해석에 이용하는 것이 바람직하다고 판단된다.