• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.666-674
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• 2002

A rapid expansion of the moist air or stream through transonic nozzle often leads to not-equilibrium condensation shock, causing a considerable amount of energy loss to the entire flow field. Depending on amount of heat released, condensation shock wave occurs in the nozzle and interacts with the boundary layer flow. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for purpose of alleviation the condensation shock wave in a transonic nozzle. A droplet growth equation is incorporated into two-dimensional wavier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft transonic wind tunnel is made to validate the present computational results. The results obtained show that the magnitude of condensation shock wave is reduced by the current passive control method.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1097-1107
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• 2001

In this paper, the wall following navigation algorithm of the mobile robot using a mono vision system is described. The key points of the mobile robot navigation system are effective acquisition of the environmental information and fast recognition of the robot position. Also, from this information, the mobile robot should be appropriately controlled to follow a desired path. For the recognition of the relative position and orientation of the robot to the wall, the features of the corridor structure are extracted using the mono vision system, then the relative position, the offset distance and steering angle of the robot from the wall, is derived for a simple corridor geometry. For the alleviation of the computation burden of the image processing, the Kalman filter is used to reduce search region in the image space for line detection. Next, the robot is controlled by this information to follow the desired path. The wall following control scheme by the PD control scheme is composed of two control parts, the approaching control and the orientation control, and each control is performed by steering and forward-driving motion of the robot. To verify the effectiveness of the proposed algorithm, the real time navigation experiments are performed. Through the result of the experiments, the effectiveness and flexibility of the suggested algorithm are verified in comparison with a pure encoder-guided mobile robot navigation system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.951-958
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• 2002

Rapid expansion of a moist air or a stream through a supersonic nozzle often leads to non-equilibrium condensation shock wave, causing a considerable energy loss in flow field. Depending on amount of latent heat released due to non-equilibrium condensation, the flow is highly unstable or a periodical oscillation accompanying the condensation shock wave in the nozzle. The unsteadiness of the condensation shock wave is always associated with several kinds of instabilities as well as noise and vibration of flow devices. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for the purpose of alleviation of the condensation shock oscillations in a transonic nozzle. A droplet growth equation is coupled with two-dimensional Navier-Stokes equation system. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft wind tunnel is made to validate the present computational results. The results show that the oscillations of the condensation shock wave are completely suppressed by the current passive control method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.639-650
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• 1999

In this paper, a chattering alleviation VSS controller for the sinusoidal type BLDC motor is designed. Dead Zone function is proposed to change the chattering occurring in the transient state from high frequency to low frequency and time-varying gains are applied for the control input to eliminate the steady state excessive chattering in the conventional ISM. The proposed Dead Zone function represents the sliding layer composed of two switching surfaces and if a state vector exists in this layer, the chattering don't occur. Simulation and experimental results confirm the useful effects of the above algorithm.

• Journal of the Korea Safety Management & Science
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• v.12 no.3
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• pp.37-52
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• 2010

This study is aimed at proposing the national policy for medical device control system in Korea as deeply analysed the present status of the system. On 1979, Korean government had started to inspect 24 kinds of the medical devices such as X-ray diagnostic equipments, medical sterilizer and etc. mostly imported from advanced countries which USA, Germany and Japan for the first time according to the Pharmaceutical Affairs Law. However medical devices were becoming consideration as an important partner of diagnosis, curing and alleviation of diseases by medical doctors and also much important keeping the health at home. Furthermore medical devices industry can be designated as a national growth engine industry. So it is necessary not only to harmonize to international standards but also the harmonization of the system including pre-market application and post-market surveillance, is strongly needed by the Korea Food and Drugs Administration(KFDA).

• Journal of Digital Convergence
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• v.10 no.7
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• pp.245-251
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• 2012

The significance of this study lies in the fact that it looks into the function of games as one of the important leisure activities at the moment when negative perception on overall game industry is becoming an obstacle in settlement of sound game culture. Game is one of the activities enjoyed in leisure time. The main positive effects of game were analyzed classifying them into 10 types including the stress relief and alleviation of tension, diverse identity experience and positive socialization experience, strengthening of self-respect and ideal self-realization, strengthening of independent thinking and problem-solving capacity, motivation for learning, enhancement in physical capacity, decrease in aggressive tendencies, cultivation of awareness on equality, increase in familiarity with the civilization of technology, and strengthening of individuality based on diversity.

• Korean Institute of Interior Design Journal
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• v.25 no.1
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• pp.93-100
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• 2016

Long-life housing means a housing which structural members (Support) such as columns and floor are maintained for a long period of time and the housing can be used for approximately 100 years by replacing components (Infill) such as walls and furniture. The government established "Certification standards of long-life housing construction" on December 24, 2014, requiring the long-life housing certification for construction of apartment houses for over 1,000 households. However, it is necessary to prepare an incentive measure which could be granted to construction related personnel and housing owners due to the effectiveness of such system and recognition that the initial construction cost of long-life housing is high. The purpose of this study is as follows. First, the reasons and necessity of long-life housing cost increase for each construction company, housing owner, infill component manufacturer and designer which are long-life housing related personnel are determined. The direction of incentive grant for supplying long-life housing based on the determined items is established. The result of this study is as follows. First, a special treatment which is higher than the alleviation of construction standards according to the previous ordinance is necessary for construction companies to secure the business feasibility. Also, incentives such as the provision of service space and wide balcony are necessary to improve the preference level of parceling out. Second, financial incentives such as financial support for housing purchase, reduction and exemption of tax (acquisition tax and registration tax), and support of maintenance cost are required for house owners. Third, it is essential to increase opportunities to participate in the market for infill component manufacturers by applying additional points for PQ. Fourth, it is needed to provide compensation for additional human resource and time at the time of designing to designers by preparing the long-life housing design cost standards.

• The Journal of Korean Medicine
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• v.36 no.2
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• pp.43-49
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• 2015

Objectives: We evaluated the effect of the traditional Korean medical therapy of catgut-embedding therapy in patients with carpal tunnel syndrome (CTS). Methods: Thirteen patients(20 hands) with CTS underwent catgut-embedding therapy once per week for a total of 1-4 sessions. We measured the time to tingling in the fingers on performing Phalen's test. We also had patients use a visual analog scale (VAS) to indicate the severity of tingling. We also asked about the awakening time at night due to pain and tingling. We controlled the treatment as being limited to four sessions. Even if a patient had not been treated for four sessions, we ended the patient's treatment if symptoms resolved. Results: Patients who received catgut-embedding therapy showed significant improvements in the clinical symptoms of CTS. After treatment, in a total of 19 hands, the status of fourteen was changed from positive to negative in Phalen's test and the average of tingling occurrence time in that test was delayed. Among the 20 hands, the VAS in eight hands changed to zero and the average of VAS score decreased. Furthermore, in nine patients, four could sleep well without the use of a splint. Conclusions: Patients undergoing this traditional Korean medical therapy showed alleviation of finger tingling after even a single treatment. We thus concluded that this traditional Korean catgut-embedding therapy, may be effective for treating CTS. However, to confirm the effects of catgut-embedding therapy on CTS, further tests are required, including under the defined, strict conditions of a randomized controlled trial.

• Journal of Preventive Medicine and Public Health
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• v.57 no.2
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• pp.108-119
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• 2024

Objectives: Abrupt changes in air pollution levels associated with the coronavirus disease 2019 (COVID-19) outbreak present a unique opportunity to evaluate the effects of air pollution on influenza risk, at a time when emission sources were less active and personal hygiene practices were more rigorous. Methods: This time-series study examined the relationship between influenza cases (n=22 874) and air pollutant concentrations from 2018 to 2021, comparing the timeframes before and during the COVID-19 pandemic in and around Thailand's Khon Kaen province. Poisson generalized additive modeling was employed to estimate the relative risk of hospitalization for influenza associated with air pollutant levels. Results: Before the COVID-19 outbreak, both the average daily number of influenza hospitalizations and particulate matter with an aerodynamic diameter of 2.5 ㎛ or less (PM_2.5) concentration exceeded those later observed during the pandemic (p<0.001). In single-pollutant models, a 10 ㎍/m³ increase in PM_2.5 before COVID-19 was significantly associated with increased influenza risk upon exposure to cumulative-day lags, specifically lags 0-5 and 0-6 (p<0.01). After adjustment for co-pollutants, PM_2.5 demonstrated the strongest effects at lags 0 and 4, with elevated risk found across all cumulative-day lags (0-1, 0-2, 0-3, 0-4, 0-5, and 0-6) and significantly greater risk in the winter and summer at lag 0-5 (p<0.01). However, the PM_2.5 level was not significantly associated with influenza risk during the COVID-19 outbreak. Conclusions: Lockdown measures implemented during the COVID-19 pandemic could mitigate the risk of PM_2.5-induced influenza. Effective regulatory actions in the context of COVID-19 may decrease PM_2.5 emissions and improve hygiene practices, thereby reducing influenza hospitalizations.

• Journal of Elementary Mathematics Education in Korea
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• v.14 no.3
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• pp.583-613
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• 2010

Mathematics anxiety is likely to be a drag on mathematics learning if that is left alone, and it is important to grasp the cause of mathematics anxiety and devise how to get rid of it. The purpose of this study was to examine the cause of mathematics anxiety among elementary school children, to develop a math-friendly activity program geared toward easing mathematics anxiety and to check the effect of the developed program on the alleviation of mathematics anxiety. The subjects in this study were 32 students in a fourth-grade class in I elementary school located in Dongdaemoon-gu, Seoul. A math-friendly activity program was designed to alleviate the mathematics anxiety of the five subfactors-test anxiety, time constraints, comprehension, learning motivation and parent attitude-on which the students scored higher than their pretest collective averages. The mathematics anxiety pretest data, the objectives and content system of the current 7th national mathematics curriculum and the mathematics textbooks for 4-A and 4-B were analyzed to develop the math-friendly activity program that consisted of psychological remedy (positive thinking training) and non-psychological remedy (mathematics activities). After the program was implemented, we analyze the pretest and posttest mathematics anxiety data to determine the effect of the program. As a result, the collective averages of every student on math anxiety and its subfactors were lower in the posttest than in the pretest.