• Journal of Magnetics
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• v.16 no.1
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• pp.51-57
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• 2011

A power supply for magnetic-stimulation devices was designed via a control algorithm that involved a start current application based on a resonant converter. In this study, a new power supply for magnetic-stimulation devices was designed by controlling the pulse repetition frequency and pulse width. The power density could be controlled using the start-current-compensation and ZCS (zero-current switching) resonant converter. The results revealed a high-repetition-frequency, high-power magnetic-stimulation device. It was found that the stimulation coil current pulse width and that pulse repetition frequency could be controlled within the range of 200-450 ${\mu}S$ and 200-900 pps, respectively. The magnetic-stimulation device in this study consisted of a stimulation coil device and a power supply system. The maximum power of the stimulation coil from one discharge was 130 W, which was increased to 260 W using an additional reciprocating discharge. The output voltage was kept stable in a sinusoidal waveform regardless of the load fluctuations by forming voltage and current control using a deadbeat controller without increasing the current rating at the starting time. This paper describes this magnetic-stimulation device to which the start current was applied.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.277-277
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• 2020

연속 측정된 수위자료를 유량자료로 환산하는 방법중의 하나인 수위-유량관계곡선식은 국내에서 널리 사용된다. 현장에서 측정된 유량자료로 개발되는 수위-유량관계곡선식(이하 곡선식)은 일반적으로 측정성과의 정확도가 그 정도를 좌우하지만, 개발과정에서 개발자의 주관적인 판단에 의해 좌우되기도 한다. 정확한 곡선식을 개발하기 위해 개발자는 수리학적 특성(수위-${\sqrt{Q}}$, 수위-유속, 수위-단면적 등)을 검토하고, 수문학적 특성(상하류 관계, 유출분석 등)을 검토하여 최종 곡선식을 결정하게 된다. 이러한 여러 검토들 중에 수위-${\sqrt{Q}}$ 검토는 비록 정성적인 검토임에도 불구하고 곡선식의 구간분리, 기간분리, 성과의 이상유무, GZF(Gauge Height of Zero flow) 등을 확인할 수 있는 방법으로 실무에 많이 이용된다. 대부분의 곡선식은 측정성과를 기반으로 개발되어 내삽부분에서는 그 정확도가 상당히 높다고 할 수 있지만 외삽부분은 구간분리의 위치, GZF 등에 따라 큰 차이를 보일 수 있다. 그러나 기존의 수위-${\sqrt{Q}}$ 에 의한 정성적인 검토는 개발자의 숙련도에 따라 곡선식의 정확도가 좌우되는 경향이 있다. 본 연구에서는 수위-${\sqrt{Q}}$ 검토의 이론적 배경을 살펴보고 일본 곡선식의 사례를 응용하여 수위-${\sqrt{Q}}$ 검토의 정량화를 시도하였다. 또한 보다 객관적인 구간분리 위치 결정 및 GZF산정의 방법을 제시하여 개발과정에서의 오류를 최소화 할 수 있고 이는 정확한 유량자료의 생산으로 이어질 것으로 기대된다.

• Journal of Intelligence and Information Systems
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• v.22 no.1
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• pp.43-61
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• 2016

Customer reviews help potential customers make purchasing decisions. However, the prevalence of reviews on websites push the customer to sift through them and change the focus from a mere search to identifying which of the available reviews are valuable and useful for the purchasing decision at hand. To identify useful reviews, websites have developed different mechanisms to give customers options when evaluating existing reviews. Websites allow users to rate the usefulness of a customer review as helpful or not. Amazon.com uses a ratio-type helpfulness, while Yelp.com uses a count-type usefulness index. This usefulness index provides helpful reviews to future potential purchasers. This study investigated the effects of sentiment and readability on useful votes for customer reviews. Similar studies on the relationship between sentiment and readability have focused on the ratio-type usefulness index utilized by websites such as Amazon.com. In this study, Yelp.com's count-type usefulness index for restaurant reviews was used to investigate the relationship between sentiment/readability and usefulness votes. Yelp.com's online customer reviews for stores in the beverage and food categories were used for the analysis. In total, 170,294 reviews containing information on a store's reputation and popularity were used. The control variables were the review length, store reputation, and popularity; the independent variables were the sentiment and readability, while the dependent variable was the number of helpful votes. The review rating is the moderating variable for the review sentiment and readability. The length is the number of characters in a review. The popularity is the number of reviews for a store, and the reputation is the general average rating of all reviews for a store. The readability of a review was calculated with the Coleman-Liau index. The sentiment is a positivity score for the review as calculated by SentiWordNet. The review rating is a preference score selected from 1 to 5 (stars) by the review author. The dependent variable (i.e., usefulness votes) used in this study is a count variable. Therefore, the Poisson regression model, which is commonly used to account for the discrete and nonnegative nature of count data, was applied in the analyses. The increase in helpful votes was assumed to follow a Poisson distribution. Because the Poisson model assumes an equal mean and variance and the data were over-dispersed, a negative binomial distribution model that allows for over-dispersion of the count variable was used for the estimation. Zero-inflated negative binomial regression was used to model count variables with excessive zeros and over-dispersed count outcome variables. With this model, the excess zeros were assumed to be generated through a separate process from the count values and therefore should be modeled as independently as possible. The results showed that positive sentiment had a negative effect on gaining useful votes for positive reviews but no significant effect on negative reviews. Poor readability had a negative effect on gaining useful votes and was not moderated by the review star ratings. These findings yield considerable managerial implications. The results are helpful for online websites when analyzing their review guidelines and identifying useful reviews for their business. Based on this study, positive reviews are not necessarily helpful; therefore, restaurants should consider which type of positive review is helpful for their business. Second, this study is beneficial for businesses and website designers in creating review mechanisms to know which type of reviews to highlight on their websites and which type of reviews can be beneficial to the business. Moreover, this study highlights the review systems employed by websites to allow their customers to post rating reviews.

• Journal of Acupuncture Research
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• v.32 no.2
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• pp.23-33
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• 2015

Objectives : This study was designed to assess the general distribution and clinical effectiveness of Korean medical treatment on lumbar disc herniation. Methods : This is an observational study. 72 patients admitted to Daejeon Jaseng Hospital of Korean Medicine with a diagnosis of herniated intervertebral disc(HIVD) by lumbar-CT of lumbar-MRI were observed from July, 2014 to April, 2015. They were analyzed according to sex, age, the period of disease, causal factors, symptoms on admission, admission day, disc herniation type and treatment efficacy. All patients received a combination of treatments during hospitalization, including acupuncture, Chuna, herbal medicines and physical therapy. A zero to ten numerating rating scale(NRS) assessing pain, Oswestry disability index(ODI) and EuroQol-5 dimension(EQ-5D) was used before and after treatments. Results : Average admission duration was $28.00{\pm}12.85$ days in lumbar disc patients. For lumbar patients, lower back pain NRS decreased from $5.89{\pm}2.00$ to $3.42{\pm}1.87$(p<0.001) and radiating pain from $5.96{\pm}2.12$ to $3.38{\pm}1.83$(p<0.001). ODI decreased from $46.69{\pm}19.25$ to $35.69{\pm}16.67$(p<0.001), and EQ-5D index increased from $0.63{\pm}0.26$ to $0.71{\pm}0.20$(p<0.05) after treatment in lumbar disc patients. Conclusions : Korean medical combination treatment might be effective in reducing pain and improving quality of life for patients with lumbar disc herniation. This study further confirmed the efficacy of Korean medical treatment on HIVD.

• Science of Emotion and Sensibility
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• v.20 no.3
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• pp.13-22
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• 2017

Emotion has a direct influence such as decision-making, perception, etc. and plays an important role in human life. For the convenient and accurate recognition of high-arousal negative emotion, the purpose of this paper is to design an algorithm for analysis using the bio-signal. In this study, after two emotional induction using the 'normal' / 'fear' emotion types of videos, we measured the Galvanic Skin Response (GSR) signal which is the simple of bio-signals. Then, by decomposing Tonic component and Phasic component in the measured GSR and decomposing Skin Conductance Very Slow Response (SCVSR) and Skin Conductance Slow Response (SCSR) in the Phasic component associated with emotional stimulation, extracting the major features of the components for an accurate analysis, we used a discrete wavelet transform with excellent time-frequency localization characteristics, not the method used previously. The extracted features are maximum value of Phasic component, amplitude of Phasic component, zero crossing rate of SCVSR and zero crossing rate of SCSR for distinguishing high-arousal negative emotion. As results, the case of high-arousal negative emotion exhibited higher value than the case of low-arousal normal emotion in all 4 of the features, and the more significant difference between the two emotion was found statistically than the previous analysis method. Accordingly, the results of this study indicate that the GSR may be a useful indicator for a high-arousal negative emotion measurement and contribute to the development of the emotional real-time rating system using the GSR.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.205-213
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• 2002

This paper deals with the implementation of three-phase VSI systems which can control the power regenerated from DC bus line to AC supply. The overall system consists of the line-to-line voltage and line current sensors, an actual power calculator using d-q transformation method, a complex power controller with PI control scheme, a gating signal generator for modified ｑ-conduction mode, a DPLL for frequency followup, and Power circuits. Control board is constructed by using a 32-bit DSP TMS32C32, two EFLDs , six ADCs, and a DAC. To verify the performance of the proposed system, we designed and constructed the propotype with the power rating of 5kVA at AC 220V. Experimental results show that the regenerated active power is well controlled to its command vague and the regenerated reactive power still remained at nearly zero through all operating modes.

• Journal of Acupuncture Research
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• v.31 no.2
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• pp.153-163
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• 2014

Objectives : To investigate the clinical results of patients who were diagnosed with grade II spondylolithesis treated with Korean medicine of relaxative Chuna and Gangchuk herbal medicine. Methods : We reviewed medical records of four patients diagnosed with grade II spondylolisthesis. Each patient has taken intensive Korean medical admission treatment at Mokhuri Hospital. All patients received treatments of Gangchuk herbal medicine, relaxative Chuna and acupuncture during admission period. Before treatment and every after 7-day treatment the patient's pain and walking distance without pain were assessed. The zero minimum to ten maximum pain numeric rating scale(NRS) was used to determine the degree of pain. Results : Average admission duration was 23 days. All the patients' NRS decreased from median figure of 7.5[the minimum 7 to the highest 8] to median figure of 1[the minimum 0 to the highest 2]. Walking distance without pain increased from a median of 55 m[the minimum 20 m to the highest 100 m] to median of 165 m[the minimum 100 m to the highest 250 m]. Conclusions : Intensive conservative korean medical treatment was effective in reducing pain and functional improvement for grade II lumbar spondylosisthesis patients.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.232-237
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• 2004

In many application of DC-DC converters, loads cannot be specified in advance, i.e., their amplitudes are suddenly changed from the zero to the maximum rating. Generally, design conditions are changed for each load and then each controller is re-designed. Then, a so-called robust DC-DC converter which can cover such extensive load changes and also input voltage changes with one controller is needed. Analog control IC is used usually for the controller of DC-DC converter. Simple integral control etc. are performed with the analog control IC. However it is difficult to retain sufficient robustness of DC-DC converter by these techniques. The authors proposed the method of designing an approximate 2-degree-of-freedom (2DOF) controller of DC-AC converter. This controller has an ability to attain sufficient robustness against extensive load and DC power supply changes. For applying this approximate 2DOF controller to DC-DC converter, it is necessary to improve the degree of approximation for better robustness. In this paper, we propose a method of designing good approximate 2DOF digital controller which makes the control bandwidth wider, and at the same time makes a variation of the output voltage very small at a sudden change of resistive load. The proposed good approximate 2DOF digital controller is actually implemented on a DSP and is connected to a DC-DC converter. Experimental studies demonstrate that this type digital controller can satisfy given specifications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1152-1162
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• 2011

In this paper, a single-phase DC-AC inverter using two embedded Z-source converters is proposed. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The output AC voltage of the inverter is obtained by the difference of output capacitor voltages of each converter. The output voltage of each converter take shape of the asymmetrical AC waveform centering zero voltage. Therefore, the proposed inverter can generate the same output voltage despite low VA rating L-C elements, compared to the conventional inverter using high DC voltage with AC ripple. To verify the validity of the proposed system, the PSIM simulation was achieved under the condition of rapid increase of DC source (110[V]${\rightarrow}$150[V]) and R-load (50[${\Omega}$]${\rightarrow}$300[${\Omega}$]). For controlling the voltage of the inverter system, the one-cycle controller was adopted. As results, the proposed inverter output the constant AC voltage (220[V]rms/60[Hz]) for all conditions. Also, the R-L load and nonlinear diode load were adopted for the proposed inverter loads, and we could know that the its output voltage characteristics were as good as the pure R-load. Finally, the RMS and THD of output AC voltage were examined for the different loads, input DC voltages and reference voltage signals.

• Journal of Acupuncture Research
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• v.31 no.4
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• pp.21-28
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• 2014

Objectives : Lumbar disc herniations are common conditions which induce severe pain and disability. We assessed the clinical effectiveness of Korean medical combination treatment. Methods : This is an observational study. We reviewed the medical records of 46 patients with lumbar disc herniations, who attended intensive Korean medical combination treatments at Mokhuri Neck and Back Hospital, Korea during March, 2012 to October, 2012. All the patients took combination treatments of acupuncture, Chuna and herbal medicines during the hospitalization treatments. Zero to ten pain numerating rating scale(NRS) of pain and SF-36 were assessed before and after treatments. Results : During the period, 46 patients with lumbar disc herniation participated in the treatments, respectively. Average admission duration were 20.32 days(SD 9.67) in lumbar disc patients. For lumbar patients, low back pain NRS decreased from $5.84{\pm}2.58$ to $2.12{\pm}1.74$(p<0.001) and radiating pain from $6.25{\pm}2.30$ to $2.59{\pm}1.97$(p<0.001). Total SF-36 score increased significantly after treatment in lumbar disc patients(p<0.001). Conclusions : Korean medical combination treatment might be effective in reducing pain and improving life quality of patients with lumbar disc herniation.