• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.474-483
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• 1996

In this paper, as a part of the method improving stability, the load-flow calculation in D.C. power system and the models for stability analysis are studied with A.C-D.C. interconnected power systems transmission performed. Moreover, the theory is established in relation to each control method of D.C. power systems. Then the stability of A.C-D.C.interconnected power systems is compared and considered by the way of dividing the operating control method of the rectifier inverter converter into ACR-AVR, APR-A.gamma.R, A.alpha.R-ACR. The dynamics characteristic of terminal voltage, frequency, active-reactive power and rotor angle of the generator with disturbances and load fluctuations is considered. In addition, the characteristic of direct voltage, direct current, power and control systems. From this the comparative analysis of the direct current control method, the possibility of the stability analysis of A.C.-D.C. interconnected power system is considered. (author). refs., figs., tabs.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.9 no.2
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• pp.19-24
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• 2011

Purpose : This study is to examine the effects of transcranial direct current stimulation on the excitability of the central neuron. Methods : This study selected 24 suitable women in their twenties. A positive electrode of transcranial direct current stimulation was placed on the primary motor area (M1) C4 and a negative electrode was placed on the left supraobital. A stimulation of 0.04mA/$cm^2$ was applied for 20 minutes. H-reflex and V wave used diagnostic electromyography. An active electrode was placed at the muscle belly of the medial gastrocnemius muscle at a prone posture. An electrical stimulation was given to the posterior tibial nerve. Measurements were made before and after the stimulation. All data were analyzed with SPSS 12.0 and between each measuring before and after the change of the H-reflex and V wave amplitude. Results : There were no significant differences in all H wave, M wave, and V wave amplitude before and after transcranial direct current stimulation. There were no significant differences in the change of H/M ratio and V/M ratio before and after transcranial direct current stimulation. Conclusion : We know that transcranial direct current stimulation cannot have an influence on a normal grown-up person's central neuron.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.4
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• pp.201-210
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• 2021

Purpose : There is a lack of research on this field in the Republic of Korea, especially those that have seen the effect of interaction between transcranial direct current stimulation and computerized cognitive rehabilitation therapy. This study divided 30 dementia patients into a treatment group, which received transcranial direct current stimulation and computerized cognitive rehabilitation, and a control group, which received pseudo-transcranial direct current stimulation and pseudo-computerized cognitive rehabilitation. This study evaluated the effects of these treatments on the visual perception, cognition functions, and daily activities of dementia patients. Methods : Fifteen subjects were allocated to the treatment group and the other 15 subjects were allocated to the control group. Treatments were given at intervals of five sessions per week (30 minutes per session) for six weeks (30 times in total). This study used the Neurobehavioral Cognitive Status Examination (NCSE) to examine cognitive functions, MVPT to evaluate visual perception, and FIM to test daily living activities before and after applying the treatments. Results : The results of this study showed that cognitive functions, visual perception, and daily living activities significantly (p<.05) improved after the intervention in the treatment group and the control group. The changes in cognitive functions, visual perception, and daily living activities due to the treatments were significantly different between the groups (p<.05). Conclusion : The results indicated that transcranial direct current stimulation and computerized cognitive rehabilitation therapy improved visual perception and daily living activities by increasing cognitive functions. Consequently, it was found that the simultaneous application of transcranial direct current stimulation in conjunction with a computerized cognitive rehabilitation program was an intervention method that could positively affect the visual perception, cognitive function, and daily living activities of dementia patients. Based on the results of this study, the study of arbitration protocols for demential will have to be more active.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.4
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• pp.105-117
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• 2021

Purpose : This study examined the effect of transcranial direct current stimulation (tDCS) combined high intensity interval training (HIIT) on the aerobic exercise capacity of college soccer players. Methods : The subjects of this study were 30 college soccer players. They were divided into a high intensity interval training group combining transcranial direct current stimulation (Group I) and a high intensity interval training group (Group II). Each group had 15 subjects randomly assigned. After receiving general soccer training, each group additionally received high intensity interval training combined with transcranial direct current stimulation and high intensity interval training for 30 minutes 5 times a week for 8 weeks. Their VO₂max and 20 meter shuttle run test, Yo-Yo intermittent recovery test were analyzed before the intervention. After 8 weeks of intervention, the above items were re-measured and an intergroup analysis was performed. Results : As a result of comparative analysis of VO₂max intake between groups, 20 meter shuttle run test and Yo-Yo intermittent recovery test, a statistically significant difference was found. The high intensity interval training group (Group I) combined with transcranial direct current stimulation showed a significant difference in aerobic exercise capacity compared to the high intensity interval training group (Group II). Conclusion : These results showed that high intensity interval training group combined with transcranial direct current stimulation was more effective for aerobic exercise. Based on this study, this study proposes an effective program for patients as well as elite athletes. In the future, it is necessary to develop an effective transcranial direct current stimulation program and to study how to apply it for various patients.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.3
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• pp.155-164
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• 2021

Purpose : The purpose of this study is to investigate the effects of transcranial direct current stimulation and virtual reality program application on cognition and depression of patients with mild cognitive impairment, and to find an intervention method that can enhance active participation of patients with mild cognitive impairment. Methods : In this study, 50 mild cognitive impairment patients were divided into a treatment group (25 patients) and a control group (25 patients). The treatment group was applied with a transcranial direct current stimulation and a virtual reality program, while the control group received a placebo transcranial direct current stimulation and a virtual reality program. Both groups received five 50-minute sessions per week (one session per day) for six weeks (total of 30 sessions). NCSE was used to evaluate the cognitive functions of the patients before and after treatment intervention. Moreover, K-BDI was conducted to examine the depression of the patients. Results : As a result of the transcranial direct current stimulation and a virtual reality program intervention, the cognitive function of both treatment and control group significantly (p<.05) improved, and the depression of both treatment and control group significantly (p<.05) decreased. Moreover, the changes in cognitive functions and depression were significant between the two groups¸ treatment and control group (p<.05). Conclusion : The results of the study showed that the application of the transcranial direct current stimulation and virtual reality program significantly improved the cognitive function of mild cognitive impairment patients and decreased the depression of them. Therefore, it could be concluded that the transcranial direct current stimulation and virtual reality program was an intervention method which positively affects the cognitive function and depression of mild cognitive impairment patients.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.2
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• pp.109-117
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• 2023

Purpose : Transcranial direct current stimulation is noninvasive method of cerebral cortical stimulation applied as an intervention to facilitate recovery in stroke patients. The purpose of this study was to examine the effects of transcranial direct current stimulation on depression and anxiety in stroke patients with the aim to finding a reliable method to reduce depression and anxiety in stroke patients. Methods : This study was conducted at A hospital located in D city from December 2022 to February 2023. Patients diagnosed with stroke were selected according to predefined study criteria and divided into two groups. 9 patients in experimental group underwent transcranial direct current stimulation and traditional occupational therapy, while 9 patients in the control group underwent sham transcranial direct current stimulation and traditional occupational therapy for 20 min per session 3 times per week for a total of 8 weeks. Beck depression inventory (BDI) and Beck anxiety inventory (BAI) were used to evaluate depression and anxiety in the patients before and after intervention. Wilcoxon signed rank test was used to compare differences before to after intervention. Mann-Whitney U test was used to compare the two groups. Differences with p<.05 were considered statistically significant. Results : First, both the experimental and control groups presented significant statistical difference before and after intervention on depression (p<.01). Comparison of two groups after intervention showed significant statistical difference in depression (p<.05). Second, the groups presented significant statistical difference before and after intervention on anxiety (p<.01). After intervention, the two groups showed significant statistical difference in anxiety (p<.05). Conclusion : Results of the present study demonstrated the effects of transcranial direct current stimulation on depression and anxiety in stroke patients, suggesting it may be a useful method of rehabilitation in this patient population; as such, further studies are warranted.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1367-1374
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• 2016

This paper presents a discrete-time version of voltage and current limited operation using an enhanced direct torque and flux control method for interior permanent magnet synchronous motor (IPMSM) drives. A command voltage vector for airgap torque and stator flux regulation can be uniquely determined by the finite-settling-step direct torque and flux control (FSS-DTFC) algorithm under physical constraints. The proposed command voltage vector trajectories can be developed to achieve the maximum inverter voltage utilization for the discrete-time current limit (DTCL)-based FSS-DTFC. The algorithm can produce adequate results over a number of the potential secondary upsets found in the steady-state current limit (SSCL)-based DTFC. The fast changes in the torque and stator flux linkage improve the dynamic responses significantly over a wide constant-power operating region. The control strategy was evaluated on a 900W IPMSM in both simulations and experiments.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.337-342
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• 2005

Direct torque control (DTC) was originally developed for induction machine drives, and, more recently has been applied to permanent magnet brushless AC (BLAC) drives. In this paper, the performance of DTC controlled brushless DC (BLDC) drives is compared with that of PWM current controlled BLDC drives, both with and without current shaping. Both simulation and experimental results are presented, as well as the analysis of the resulting torque waveforms. It is shown that, in addition to exhibiting a fast torque response, a DTC controlled BLDC drive has a significantly lower low-frequency torque ripple than the PWM current controlled BLDC drive without current shaping, and that it is easier to implement than PWM current control with current shaping.

• Therapeutic Science for Rehabilitation
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• v.8 no.4
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• pp.7-18
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• 2019

Objective : This systematic review aimed to investigate the impact of transcranial direct current stimulation combined with constraint-induced movement therapy (CIMT) in patients with stroke Methods : PubMed and NDSL databases were employed to review literature published between January 2009 and December 2018. The main search terms were "Transcranial direct current stimulation" or "tDCS," "Constraint-induced movement therapy" or "CIMT," "Upper extremity function," "Upper limb," and "Stroke." Based on the inclusion and exclusion criteria, 6 articles were selected. Furthermore, intervention effects on upper extremity function, activities of daily living, and cortical activity were assessed. Results : The current intensity, application time, and protocol of the CIMT varied the between studies. However, the intervention procedures to perform CIMT immediately after transcranial direct current stimulation was the same. Transcranial direct current stimulation combined with CIMT was effective in improving upper limb function and activities of daily living in patients with stoke and had a significant effect on cerebral cortex activation. Conclusions : This study provides information on transcranial direct current stimulation combined with CIMT for use by clinical therapists. Further studies are needed to standardize the stimulation time, current intensity, and electrode attachment position. Furthermore, randomized controlled trials, including long-term follow up, are needed for larger populations using the most appropriate CIMT protocol.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.162-169
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• 2000

A Direct Drive Valve(DDV) hydraulic actuation system which is commonly used as an aircraft's control surface driving actuator has multi-loop control structure to ensure its safety operation. However, because of not perfect matching of one self channel characteristics with the others, the servo valve driving current of each channel can be widely different. Therefore, the long-time use of DDV actuator without any correction of these channel current offsets will cause the problem of performance or life expectancy degradation due to unwanted heats in the linear motor. A current equalization loop structure which can minimizes current offsets between channels is introduced and designed. The performance of the current equalization loop is investigated and verified through the analytic and experimental ways.