• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.10a
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• pp.3-15
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• 2007

• Geomechanics and Engineering
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• v.22 no.1
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• pp.81-95
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• 2020

Measurement of the unconfined compressive strength (UCS) of the rock is critical to assess the quality of the rock mass ahead of a tunnel face. In this study, extensive field studies have been conducted along 3,885 m of the new Nagasaki tunnel in Japan. To predict UCS, a hybrid model of artificial neural network (ANN) based on genetic algorithm (GA) optimization was developed. A total of 1350 datasets, including six parameters of the Measurement-While- Drilling data and the UCS were considered as input and output parameters respectively. The multiple linear regression (MLR) and the ANN were employed to develop contrast models. The results reveal that the developed GA-ANN hybrid model can predict UCS with higher performance than the ANN and MLR models. This study is of great significance for accurately and effectively evaluating the quality of rock masses in tunnel engineering.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.3
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• pp.354-361
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• 2014

The Unified Power Flow Controller (UPFC) can flexibly manage power flow and maintain line voltage. The UPFC consists of two inverters in parallel side and series side. In parallel side, the reactive power can be compensated to improve the power factor. In series side, the voltage drop can be compensated to maintain proper line voltage. It is necessary for the operation in both sides to output the current and the voltage quickly and accurately. As the method for the UPFC control, the deadbeat control with state observer is applied. The deadbeat control is able to realize a quick response of the current and voltage control for only a sampling period compared with the general PI control. A principle and simulation results are presented in this paper.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.512-517
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• 1998

In a matrix converter, input side and output side are coupled with each other through switching elements. Since disturbances on either side affect directly on the other side, it requires a high-speed on-line control system to compensate them. We proposed in previous papers a new control strategy and an on-line control circuit for a matrix converter. The control circuit could keep the output voltage at commanded value against fluctuation in the supply voltage. Furthermore wave forms of the output voltage and the input current were always kept sinusoidal. The switching pattern was generated by comparing modified voltage references with a carrier. The carrier was synchronized with the supply voltage using a PLL system, which made the control circuit complicated and costly. This paper discusses on the possibility of an asynchronized carrier. Experiment results show the input current distortion in case of asynchronous carrier is bigger than that of synchronous carrier. However, the deterioration can be minimized by increased carrier frequency.

• ALGAE
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• v.23 no.4
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• pp.251-255
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• 2008

In Gamak Bay, Paralytic Shellfish Poisoning (PSP) was first detected from seafoods in 2003, however the toxin source is unknown yet. In this study, we report potential PSP producers of toxic dinoflagellates, describing morphology and abundance of cysts isolated from surface sediment of Gamak Bay. The most abundant type in these cysts was characterized with ellipsoidal and transparent wall identical to Alexandrium catenella and/or A. tamarense. Germination experiment of the cysts revealed that all motile cells germinated were morphologically identified as A. tamarense. This result suggests that A. tamarense may relate to PSP contaminations in Gamak Bay. Moreover, bottom water temperature in Gamak Bay is favorable for germination of A. tamarense cysts. Further studies are required to carry out the PSP monitoring for preventing the risk of PSP events that may outbreak in future at Gamak Bay.

• Journal of Photoscience
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• v.9 no.2
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• pp.482-484
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• 2002

UV irradiation activates various intracellular signaling pathways causing cell death in a DNA damage-dependent and an independent manner. As DNA photoproducts, major forms of DNA damage, are maximally formed by UV light at 260-nm, short wavelength UV (UVC) is more harmful than middle wavelength UV (UVB). However, the differences or similarities in responses of DNA damage-independent intracellular signaling molecules to UVB and UVC are not elucidated. We examined activation of signaling molecules towards apoptosis in normal human fibroblastic cells after irradiation with UVB or UVC at a dose generating the equal amount of DNA photoproducts. Both UVB and UVC induced transient phosphorylation of ERK and sustained phosphorylation of p38. Phosphorylation of p53 at Ser15 and at Ser392 residues were also observed, which were inhibited by a phosphoinositide 3-kinase inhibitor, wortmannin. In contrast, an antioxidant N-acetyl-cysteine and a p38 inhibitor SB203580 suppressed only Ser392 phosphorylation, suggesting that UV-induced oxidative stress and p38 activation were involved in the phosphorylation of this site. The apoptic signals such as mitochondrial cytochrome C release and annexin V binding were then observed. Overall, no difference was found in chronological responses of p53, MAPK, and apoptosis between UVB-irradiated and UVC-irradiated cells. These results suggested that DNA damage-independent intracellular signaling molecules similarly responded to UVB and UVC when the equal level of DNA photoproducts were generated.

• Journal of Environmental Impact Assessment
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• v.7 no.2
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• pp.103-112
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• 1998

Nature-friendly river project has became common practice in Japan. In order to make it available for the conservation and rehabilitation of desirable water environment, water criteria for water environmental assessment must be established. Especially, the criteria estimating the effects on ecosystem in and around river should be constructed. In this paper, classification method for water quality has been developed using biological indices and applied to observed data in Honmyo River, Nagasaki, Japan. Modified PI method (BI') has been suggested and those of three most abundant species resulted effective estimate for an overall water quality with comparatively simple procedure. Extensive database management code was prepared for the comprehensive ecological monitoring of river basin, which includes various biota. That system enables easy access of all the ecological data for a dissemination of a sound and sustainable water environment. The result of this study could improve knowledge base, serve making consensus for citizens, and help river management plans. In Japan, citizen's realization and action are the most critical factor for nature-friendly river restoration project.

• Safety and Health at Work
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• v.5 no.1
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• pp.7-12
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• 2014

Background: In Japan, more than 60% of employees are reported to suffer from anxiety and stress. Consequently, Japanese society has begun to address such important issues as psychogenic disability and job-related suicide. Furthermore, given the aging of society and the surge in the number of elderly people requiring care, it is necessary to adequately and proactively support employees who care for their elderly relatives. The purpose of the present study was to investigate caregiver burden in caring for elderly relatives and work-related stress factors associated with mental health among employees. Methods: We studied 722 men and women aged 18-83 years in a cross-sectional study. The K10 questionnaire was used to examine mental health status. Results: The proportion of participants with a high K10 score was 15% (n = 106). Having little conversation with their supervisor and/or coworkers significantly increased the risk of depression [odds ratio (OR) 1.8], as did high job overload (OR 2.7) and job dissatisfaction (OR 3.8), compared with employees who frequently conversed with their supervisor and/or coworkers. Caring for elderly relatives as a prominent characteristic of an employee was a significant risk factor for depression (OR 2.1). Conclusion: The present study demonstrated that employees who were caring for elderly relatives were significantly associated with an increased risk of depression. To prevent depressive disorders, it may be important to focus on reducing the work-caregiving role conflict, as well as enhancing employees' job control and better rewarding their efforts in the workplace.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.126-131
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• 2014

This paper discusses stability of new simplified sensorless vector control systems of induction motors (IM). The simplified sensorless systems estimate the flux angle by using the output voltage of d-axis PI current controller to achieve the q-axis flux zero. Two simplified sensorless systems are studied. The difference of two systems is the presence or absence of a q-axis PI current controller. The systems stability is compared by deriving linear state equations and showing root loci and unstable regions. Furthermore, transient responses and experiment results make clear the stability of the proposed system.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.25-28
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• 1996

Recently, AC variable-speed motors are used for many steel rolling mill drive systems, because of their low maintenance and enhanced control performance. We have been applied GTO inverters for these AC motor drive systems since 1993. We have developed world largest 6-inch diameter GTO and large capacity 3-level GTO inverter up to 20000(kVA). As an example, in this paper, we describe the main circuit, system arrangement and control features of the 6-inches GTO inverters to drive rougher mills for hot strip mill of Pohang Iron & Steel Co., Ltd. The motor capacity is 6000(kW), and it's overload is 250(%).