• Radiation Oncology Journal
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• v.33 no.3
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• pp.172-178
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• 2015

Purpose: To investigate clinical outcomes of synchronous head and neck and esophageal cancer (SHNEC). Materials and Methods: We retrospectively reviewed 27 SHNEC patients treated with curative intent at a single institution. The treatment modality for individual cases was usually determined on a case by case basis. Results: The median follow-up duration for the surviving patients was 28.2 months. The most common site of head and neck cancer was hypopharyngeal carcinoma (n = 21, 77.7%). The lower esophagus was the most common location of esophageal carcinoma (n = 16, 59.3%). The 2-year progression-free survival (PFS) and overall survival (OS) rates were 57.5% and 39.6%. Major pattern of failure was locoregional recurrence in the study patients. Esophageal cancer stage, the Eastern Cooperative Oncology Group (ECOG) performance status, and pretreatment weight loss were significant prognostic factors for OS in univariate analysis. Treatment-related death was observed in two patients, and one patient developed a grade 4 late treatment-related complication. Conclusion: Although the survival outcome for SHNEC is poor, long-term survival might be achievable with aggressive treatment with stage I-II esophageal cancer and good performance.

• Journal of Korea Multimedia Society
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• v.4 no.5
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• pp.430-438
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• 2001

In this paper, we present the design and implementation of a web-based distance learning system supporting the collaborative browsing. Our system consists of an education affair management system, a video conferencing server/client, a white-board server/client, a session manager and a web browser sharing system. Among other things, our collaborative web browser is unique and not found in any other system. The web browser shows synchronously the same web pages as the lecturer moves through them. Therefore, it allows the student to feel real-time surfing gust as the lecturer would. The session manager supports multi-user and multi-group, and integrates various synchronous collaborative component into one distance learning system by providing the same session data and information of users in a session group. Our collaborative browsing system can increase the efficiency of distance learning and provides the effect of learning in the same classroom by supporting various synchronous functionalities, such as collaborative browsing.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.538-545
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• 2001

In this paper a gearless drive system using a permanent-maget synchronous motor for high speed elevators is addressed. The application of permanent magnet synchronous motor to an elevator traction machine enables several improvements including higher efficiency better ride comfort smaller size and lighter weight and so on A PWM boost converter has been also adopted so that DC-link voltage regulation bi-directional power flow and controllable power factor with reduced input current harmonics are possible. To increase the reliability and performance of overall control system the unified control board which can include the car and group controller as well as PWN converter/inverter controller has been designed based on a DSP TMS320VV33. In addition the dynamic load simulator system has been developed so that the drive system of high speed elevator can be tested and evaluated without and limitation on ride distance. Some experimental results are given to verify the effectiveness of the developed system.

• Journal of Digital Convergence
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• v.18 no.12
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• pp.69-79
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• 2020

This study is to explore factors to consider for effective operation of synchronous online education in college. Synchronous online education is expanding in higher education. However, there is insufficient to comprehensively identify key components based on the learners' experience and perception. Using qualitative analysis on content of group interview and multidimensional scale analysis, the experience and perception of learners were identified. For the effective operation, interaction should be considered important, and rapport between learners needs to be built. In addition to improving the system in which activity tools are integrated, instructors should play mainly facilitator role, and learners have to manage the environment for immersion. For the types of online education, learners were divided into the dimension of 'activity' and 'temporality'. Further, it is to develop optimized design strategies considering its characteristics.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.313-319
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• 2006

This paper addresses improving the voltage stability limit of interface flow between two different regions in an electric power system using the Static Synchronous Series Compensator (SSSC). The paper presents a power flow analysis model of a SSSC, which is obtained from the injection model of a series voltage source inverter by adding the condition that the SSSC injection voltage is in quadrature with the current of the SSSC-installed transmission line. This model is implemented into the modified continuation power flow (MCPF) to investigate the effect of SSSCs on the interface flow. A methodology for determining the interface flow margin is simply briefed. As a case study, a 771-bus actual system is used to verify that SSSCs enhance the voltage stability limit of interface flow.

• Journal of Magnetics
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• v.20 no.4
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• pp.387-393
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• 2015

Torque ripple is necessarily generated in interior permanent magnet synchronous motors (IPMSMs) due to the non-sinusoidal distribution of flux density in the air gap and the magnetic reluctance by stator slots. This paper deals with an asymmetric rotor shape to reduce torque ripple which can make sinusoidal flux density distribution in the air gap. Meanwhile the average torque is relatively increased by the asymmetric rotor. Response surface method (RSM) is applied to find the optimum position of the permanent magnets for the IMPSM with improved torque performance. Consequently, an asymmetric structure is the result of RSM and the structure has disadvantage of a mechanical stiffness. Finally, the performance of suggested shape is verified by finite element analysis and structural analysis is conducted for the mechanical stiffness.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.57-59
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• 2001

This paper presents the shape optimization to minimize the BEMF(Back Electro-Motive Force) harmonics of PM type synchronous generators. RSM(Response Surface Methodology) is used to find the optimal solution. We used the 2D-Finite Element Method to obtain the observed data of the BEMF and SQP(Sequential Quadratic Problem method) is used to solve the constrained nonlinear optimization problem.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.313-320
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• 2013

The fractional slot windings are widely used in rotating machine in order to increase the flexibility of design and improve the voltage waveform. However, the MMF wave of fractional-slot windings are found to contain unique harmonic component, which are designated as even order space flux harmonics, fractional number flux harmonics, or both. They may cause stray loss and stator core vibration. This paper proposes new winding methods "novel interspersed windings" and "expanded group windings" to reduce these harmonics. The advantages of two proposed windings are verified by using numerical analysis and measurement test of winding model.

• Journal of Advanced Information Technology and Convergence
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• v.10 no.2
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• pp.1-13
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• 2020

This paper presents an emergency brushless synchronous generator having rotating exciter status monitoring and protection functions. For monitoring the rotating exciter status, a wireless rotor status detector and a digital AVR(Automatic Voltage Regulator), which has a wireless communication capability, are proposed. The proposed rotor status detector detects temperatures of exciter armature and main field windings and input voltage and current of the main field. Therefore, it is possible to protect the generator from the over-temperature of windings and detect the exciter bridge diode fault. Furthermore, the proposed digital AVR has rotor status monitoring and protection function, and remote generator tuning, wireless group parallel operation function. So the operator can efficiently operate the generator using a smartphone from a remote area.

• Journal of Gastric Cancer
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• v.6 no.4
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• pp.237-243
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• 2006

Purpose: This study was conducted to evaluate the treatment outcomes and the prognosis for gastric cancer patients with hepatic metastasis. Materials and Methods: This retrospective study was based on the medical records of 85 gastric cancer patients with hepatic metastasis (62 synchronous and, 23 metachronous) who received chemotherapy with or without resectional therapy from March 1990 to March 2006. The survival rate was analyzed according to clinicopathologic factors and therapeutic factors, such as whether or not a gastrectomy, a hepatic resection, and/or chemotherapy had been performed. Results: The median survival of gastric cancer patients with hepatic metastasis was 11 months (synchronous: 11 months and metachronous: 17 months). The rates of gastrectomies and hepatic resections in the synchronous group were 24.1% and 16.1%, respectively A 23.5% prevalence of extra-hepatic metastasis was observed. The median survivals of patients who underwent a gastrectomy with a hepatic resection, a gastrectomy alone, and non-surgical treatment were 60, 18, and 9 months, respectively (P<0.05). The disease-free median survival of the metachronous group was 8 ($3{\sim}39$) months. There was no difference in initial pathologic stage and frequency of hepatic metastasis after the gastrectomy in the metachronous group. In the synchronous group, extra-hepatic metastasis, a gastrectomy as the operative procedure, a hepatic resection as the operative procedure and the response to chemotherapy were statistically significant in the univariate analysis, and a hepatic resection as the operative procedure, the response to chemotherapy, and extra-hepatic metastasis were independant prognostic factors identified by the multivariate analysis. In the metachronous group, extra-hepatic metastasis, the response to chemotherapy and differentiation were statistically significant in the univariate analysis, and extra-hepatic metastasis was an independent prognostic factor identified by the multivariate analysis. Conclusion: An aggressive surgical therapy and effective chemotherapy are necessary in the treatment of gastric cancer patients with hepatic metastasis. (J Korean Gastric Cancer Assoc 2006;6:237-243)