• Earthquakes and Structures
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• v.18 no.4
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• pp.507-517
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• 2020

This study aims to present new frequency-related seismic intensity parameters (SIPs) based on the Hilbert-Huang Transform (HHT) analysis. The proposed procedure is utilized for the processing of several seismic accelerograms. Thus, the entire evaluated Hilbert Spectrum (HS) of each considered seismic velocity time-history is investigated first, and then, a delimited area of the same HS around a specific frequency is explored, for the proposition of new SIPs. A first application of the suggested new parameters is to reveal the interrelation between them and the structural damage of a reinforced concrete frame structure. The index of Park and Ang describes the structural damage. The fundamental frequency of the structure is considered as the mentioned specific frequency. Two statistical methods, namely correlation analysis and multiple linear regression analysis, are used to identify the relationship between the considered SIPs and the corresponding structural damage. The results confirm that the new proposed HHT-based parameters are effective descriptors of the seismic damage potential and helpful tools for forecasting the seismic damages on buildings.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3423-3426
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• 2012

Dielectric measurement on binary mixtures of Allyl chloride (ALC) with 2-Pentanone (2-PE) and 2-Hexanone (2-HE) has been carried out over the entire concentration range using Time Domain Reflectometry (TDR) technique at various temperatures in microwave frequency range of 10 MHz to 10 GHz. The static dielectric constant, excess static dielectric constant (${\varepsilon}^E_S$), effective Kirkwood correlation factor ($g^{eff}$) of binary mixtures over entire concentration range were determined to study the effect of increasing alkyl group of ketones on hetero molecular interaction. It was found that magnitude of excess static dielectric constant of mixtures increases with increase of alky group of ketones. The study reveals that the dipole moment of Allyl chloride in mixture have antiparallelism tendency where as 2-pentanone and 2-hexanone have parallelism tendency. Excess static dielectric constant is also fitted to Redlich-Kister equation to get information about rates of multimers formation.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.283-288
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• 2013

This paper describes development of a high speed Doppler OFDI system for non-invasive vascular imaging. Doppler OFDI (optical frequency domain imaging) is one of the phase-resolved second generation OCT (optical coherence tomography) techniques for high resolution imaging of moving elements in biological tissues. To achieve a phase-resolved imaging, two temporally separated measurements are required. In a conventional Doppler OCT, a pair of massively oversampled successive A-lines is used to minimize de-correlation noise at the expense of significant imaging speed reduction. To minimize a de-correlation noise between targeted two measurements without suffering from significant imaging speed reduction, several methods have been developed such as an optimized scanning pattern and polarization multiplexed dual beam scanning. This research represent novel imaging technique using frequency multiplexed dual beam illumination to measure exactly same position with aimed time interval. Developed system has been verified using a tissue phantom and mouse vessel imaging.

• Korean Journal of Acupuncture
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• v.20 no.3
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• pp.49-60
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• 2003

The aim of this study was to examine the effects of electroacupuncture(EA) at the PC6 (Naegwan) on normal humans using KarhunenLoeve decomposition method. Electroencephalogram(EEG) is a multi-scaled signal consisting of several components of time series with different dominant frequency ranges and different origins. EEG KarhunenLoeve decomposition method exibit site-specific and state-related differences in specific frequency bands. In this study, KarhunenLoeve decomposition method was used as a measure(D2) of complexity. 30 channel EEG study was carried out in 10 subjects (10 males; $age=21.4{\pm}0.5$ years). Results : We found that the average values and standard deviations of D2 at FP1, FP2, FTC1, FTC2, TT1, TT2, T4, TCP1, P3, P4, T6, OZ channel (p<0.05) were higher than during the acupuncture treatment, and the average values and standard deviations of D2 at F3, F8 channels(p<0.05) were lowered than during the acupuncture treatment. However, the comparison with that before and after the treatment shows no significant differences in all channels.

• Journal of the Korea Safety Management & Science
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• v.13 no.4
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• pp.25-33
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• 2011

Workers in logistics centers also are exposed to serious musculoskeletal disorders the same as workers in general manufacturing due to operating forklifts and other labor duties. The frequency of these work related injuries decreases, workers' job satisfaction In addition, it causes many employees questioning a job change, which is regarded as the primary factor which drops the productivity. In this paper, we conducted a survey ti perceive the correlation between work related injuries in the fields of distribution centers and job satisfaction. Furthermore we made statistical analysis with our findings. The results of our analysis showed that the frequency of work related injuries due to workers' repetitive loading and unloading work is the primary factor which lowers job satisfaction. In order to improve aforementioned problem we propose first of all loading and unloading on pallet basis, second of all automation and computerization of logistics systems, and third of all ensurinf sufficient break time.

• Physical Therapy Korea
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• v.25 no.3
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• pp.27-38
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• 2018

Background: At present time, smartphones have become very popular and powerful devices, and smartphone applications with the good validity have been designed to assess human balance ability. Objects: The purpose of this study is to evaluate the feasibility of smartphone acceleration in the assessment of postural control ability for six different conditions. Methods: Twenty healthy college-aged individuals volunteered. Static balance ability was measured twice with one-day interval using smartphone application and 3D motion capture system under the six different conditions. Results: Dominant frequencies for each test condition did not show significant differences except for two conditions. The intra-rater correlation coefficient between the first and second tests showed high correlations in six conditions(r>.70, p<.05). Smartphone acceleration and the acceleration calculated from the 3D marker position data showed high correlation coefficient(r>.80, p<.001). Conclusion: Acceleration recorded from a smartphone could be useful assessment variables for balance test in the clinical field.

• Journal of Power Electronics
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• v.5 no.3
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• pp.198-205
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• 2005

The mechanical system of a drive can often be modeled as a two- or three-mass-system. The load is coupled to the driving motor by a shaft able to perform torsion oscillations. For the automatic tuning of the control, it is necessary to know the mathematical description of the system and the corresponding parameters. As the manpower and setup-time necessary during the commissioning of electrical drives are major cost factors, the development of self-operating identification strategies is a task worth pursuing. This paper presents an identification method which can be utilized for the assisted commissioning of electrical drives. The shaft assembly can be approximated as a two-mass non-rigid mechanical system with four parameters that have to be identified. The mathematical background for an identification procedure is developed and some important implementation issues are addressed. In order to avoid the excitation of the system with its natural resonance frequency, the frequency response can be obtained by exciting the system with a Pseudo Random Binary Signal (PRBS) and using the cross correlation function (CCF) and the auto correlation function (ACF). The reference torque is used as stimulation and the response is the mechanical speed. To determine the parameters, especially in advanced control schemes, a numerical algorithm with excellent convergence characteristics has also been used that can be implemented together with the proposed measurement procedure in order to assist the drive commissioning or to achieve an automatic setting of the control parameters. Simulations and experiments validate the efficiency and reliability of the identification procedure.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1815-1820
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• 2017

In this paper, a study was conducted to estimate the maximum muscle strength which is a standard for selecting exercise intensity in weight training. We designed a device that estimates the muscle fatigue from the EMG signal, expecting to show a correlation between peak muscle strength and fatigue. Curl - Dumbbell was performed using a 4 kg dumbbell and the frequency change of the EMG was observed. At this time, the designed device acquires the signal using the MCU and finally Matlab was used to confirm the change in the center frequency value. The results of 10 subjects were analyzed using SPSS regression analysis. The statistical results showed a correlation of $R^2$ 0.583 and Significant probability of 0.010, and the relation of Y = 8.144-2.097 (slope (MDF)) was obtained. In conclusion, if the wearable device is manufactured in the form of a wearable device and the user can recommend the exercise intensity, the system will be able to retry the more efficient exercise.

• Journal of Periodontal and Implant Science
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• v.39 no.2
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• pp.185-192
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• 2009

Purpose: The aim of this study was to examine the correlation of the subjective and the objective evaluation of edentulous ridge bone quality, and to evaluate the change of the dental implant stability in each bone density group for early healing period after implant installation. Methods: Sixty-seven implants(Osstem implant$^{(R)}$, Seoul, Korea) were included in this study. We evaluated the bone density by 2 methods. The one was the subjective method which was determined by practitioner s tactile sense, the other was the objective bone type was based on Hounsfield units. The implant stability in each bone type group was assessed by resonance frequency analyzer(Osstell mentor$^{(R)}$). Data were analyzed for the change of the implant stability, and they were compared to verify the difference of groups at the time of installation, 2, 6, 10, 14 weeks postoperatively. Spearman's correlation was used to demonstrate the correlation between the subjective and the objective evaluation of the bone density, and analysis of variance(ANOVA) was used to analyze the differences of implant stability at each time point. Results: There was no close relation between the subjective and the objective evaluation of the bone density(r=0.57). In the subjective groups, there was statistically significant difference between the type 1 and 3 at 10 weeks and between the type 2 and 3 at 14 weeks. In the objective groups, there was no statistically significant difference between the D 1, 2, 3, 4, and 5 group with regard to RFA from baseline to 14 weeks(P>0.1). Conclusions: The implant stability increased over time during the study, and it was improved with bone density proportionally after 2weeks postoperatively. It is recommended that the decision of bone density is base on Hounsfield unit for implant loading time.

• Journal of Korean Society of Transportation
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• v.35 no.5
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• pp.423-433
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• 2017

During recent 5 years, it was recorded that 20% of total accident frequency and 30% of total number of death have been occurred due to drowsy driving. Drowsy driving accident is result from the loss of driving ability due to driver's accumulated fatigue. Continuous driving time can be measured as a surrogate variable to quantify the level of fatigue. The main purpose of this research is to investigate statistical correlation between the proportion of continuous driving vehicle (more than 2 hours) and the number of drowsy accidents. To carry this out, continuous driving time was measured using GPS route-guidance trajectory data. Also, accident frequency, traffic volume and segment length were collected to estimate safety performance function (SPF) for Jungbunearuk expressway in Korea. Through various types of estimated SPFs, statistical correlation was analyzed based on estimated statistical indices. This research can provide theoretical background for enforcement to regulate commercial vehicle driver's continuous driving time. In addition, throughout the trajectory data expansion, it is expected that strategy for anti-drowsy driving facilities installation can be established based on the suggested methodology.