• Title/Summary/Keyword: Design stabilization

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Flow Characteristics of An Atmospheric Pressure Plasma Torch

  • Moon, Jang-H.;Kim, Youn-J.;Han, Jeon-G.
    • Journal of the Korean institute of surface engineering
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    • v.36 no.1
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    • pp.69-73
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    • 2003
  • The atmospheric pressure plasma is regarded as an effective method for surface treatments because it can reduce the period of process and doesn't need expensive vacuum apparatus. The performance of non-transferred plasma torches is significantly depended on jet flow characteristics out of the nozzle. In order to produce the high performance of a torch, the maximum discharge velocity near an annular gap in the torch should be maintained. Also, the compulsory swirl is being produced to gain the shape that can concentrate the plasma at the center of gas flow. In this work, the distribution of gas flow that goes out to atmosphere through a plenum chamber and nozzle is analyzed to evaluate the performance of atmospheric pressure plasma torch which can present the optimum design of the torch. Numerical analysis is carried out with various angles of an inlet flow velocity. Especially, three-dimensional model of the torch is investigated to estimate swirl effect. We also investigate the stabilization of plasma distribution. For analyzing the swirl in the plenum chamber and the flow distribution, FVM (finite volume method) and SIMPLE algorithm are used for solving the governing equations. The standard k-model is used for simulating the turbulence.

A Transdisciplinary Approach for Water Pollution Control: Case Studies on Application of Natural Systems

  • Polprasert, Chongrak;Liamlaem, Warunsak
    • Environmental Engineering Research
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    • v.19 no.3
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    • pp.185-195
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    • 2014
  • Despite the enormous technical and economic efforts to improve environmental conditions, currently about 40% of the global population (or 2 billion people) are still lack access to safe water supply and adequate sanitation facilities. Pollution problems and transmission of water- related diseases will continue to proliferate. The rapid population growth and industrialization will lead to a reduction of arable land, thus exacerbating the food shortage problems and threatening environmental sustainability. Natural systems in this context are a transdisciplinary approach which employs the activities of microbes, soil and/or plants in waste stabilisation and resource recovery without the aid of mechanical or energy-intensive equipments. Examples of these natural systems are: waste stabilisation ponds, aquatic weed ponds, constructed wetlands and land treatment processes. Although they require relatively large land areas, the natural systems could achieve a high degree of waste stabilisation and at the same time, yield potentials for waste recycling through the production of algal protein, fish, crops, and plant biomass. Because of the complex interactions occurring in the natural systems, the existing design procedures are based mainly on empirical or field experience approaches. An integrated kinetic model encompassing the activities of both suspended and biofilm bacteria and some important engineering parameters has been developed which could predict the organic matter degradation in the natural systems satisfactorily.

Fabrication of the EBG structure for GNSS (Global Navigation Satellite Service 를 위한 EBG 구조체 제작)

  • Jang, Young-Jin;Chung, Ki-Hyun;Cho, Seung-Il;Yeo, Sung-Dae;Kim, Jong-Un;Kim, Seong-Kweon
    • Journal of Satellite, Information and Communications
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    • v.9 no.4
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    • pp.42-46
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    • 2014
  • In this paper, a coil typed electromagnetic band gap (EBG) structure to be inserted in the printed circuit board (PCB) inner layer in order to stabilize the PCB power line is proposed and implemented for global-navigation satellite service (GNSS) with the bandwidth from 1.55GHz to 1.81GHz. From the measurement result of the PCB board including EBG structure, the insertion loss(S21) was measured below about -50dB. From these results, it is expected that the stabilization of power delivery network (PDN) structure in the PCB circuit design should be improved and the preparation to EMI will be effective.

Waypoint Tracking of Large Diameter Unmanned Underwater Vehicles with X-stern Configuration (X-stern 배열을 가진 대형급 무인잠수정의 경로점 추적)

  • Kim, Do Wan;Kim, Moon Hwan;Park, Ho-Gyu;Kim, Tae-Yeong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.2
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    • pp.387-393
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    • 2017
  • This paper focuses on a horizontal waypoint tracking and a speed control of large diameter unmanned underwater vehicles (LDUUVs) with X-stern configuration plane. The concerned design problem is converted into an asymptotic stabilization of the error dynamics with respect to the desired yaw angle and surge speed. It is proved that the error dynamics under the proposed control scheme based on the linear control and the feedback linearization can be considered as a cascade system; the cascade system is asymptotically stable if its nominal systems are so. This stability connection enables to separately deal with the waypoint tracking problem and the speed control one. By using the sector nonlinearity, the nominal system with nonlinearities is modeled as a polytopic linear parameter varying (LPV) system with parametric uncertainties. Then, sufficient linear matrix inequality (LMI) conditions for its asymptotic stabilizability are derived in the sense of Lyapunov stability criterion. An example is given to show the validity of the proposed methodology.

Combustion Stability and the Properties of Methane/Air Mixture Subjected to Unsteady Flow Fluctuations (비정상 유동의 메탄/공기 혼합기 반응안정성 효과 연구)

  • Lee, Eui-Ju;Oh, Chang-Bo
    • Journal of the Korean Society of Safety
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    • v.26 no.5
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    • pp.1-6
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    • 2011
  • Flame extinction and the chemistry of stoichiometric methane/air mixture were investigated numerically in the PSR(perfectly stirred reactor). For the study, PSR code was modified to be possible to unsteady calculation, and the sinusoidal fluctuation was subjected to the residence time. In the region of residence time far from the extinction limit, combustion mode was strongly dependent on the frequency. The low frequency excitation provided the quasi-steady behavior on the temperature and the concentrations of related species, but small variation of temperature was observed under high frequency. In the region of residence time near the extinction limit, the mixture subjected above 1 KHz was still reacting even though extinction had to be occurred under quasi-steady concept. The attenuation of extinction limit resulted from that chemical time was comparable to the flow time. The mean mole fractions of both NO and CO were almost same regardless of imposed frequency. However, the average mole fraction of $C_2H_2$ was decreased as increasing frequency, which implies that soot yield might be reduced at the higher frequency of flow excitation. The result provides the basic concept for flame stabilization, and it will be used to design a mild combustor.

Effects of Active Vibration Exercise Using a Flexi-Bar on the Activity of Scapular Stabilizing Muscles: A Randomized Controlled Trial

  • Park, Chibok;Kim, Byeonggeun
    • Journal of International Academy of Physical Therapy Research
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    • v.11 no.1
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    • pp.1975-1980
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    • 2020
  • Background: It has been argued that changes in muscle activity in the upper trapezius and serratus anterior may or may not cause shoulder joint pain and dysfunction. Objective: To investigate the effects of active vibration exercise on muscle activity regarding scapular stabilization using a flexi-bar. Design: A randomized controlled trial. Methods: A total of 24 subjects were randomly assigned to a flexi-bar group with active vibration and general stick group with non-active vibration. Both groups performed the same four action programs for 6 weeks, three times a week for 30 minutes at a time. The upper trapezius muscle, middle trapezius muscle, lower trapezius muscle and serratus anterior muscle of the dominant side was measured by electromyography before and after the 6 weeks of exercise. The independent t-test and paired t-test were used to analyze data. Results: There was a significant difference between groups in upper trapezius muscle and serratus anterior muscle activity after exercise (P<.05). Also, there was a significant difference in upper trapezius muscle and serratus anterior muscle activity before and after exercise in the flexi-bar group (P<.05). Conclusion: This study demonstrates that active vibration exercise using a flexi-Bar contribute to reduce the activity of the upper trapezius muscle and promote the activity of the serratus anterior muscle.

Effects of Yoga during Pregnancy on Weight Gain, Delivery Experience and Infant's Birth Weight (임산부 요가가 임부의 체중증가, 분만경험 및 출생체중에 미치는 영향)

  • Ji, Eun-Sun;Cho, Kyol-Ja;Kwon, Hyun-Jeong
    • Women's Health Nursing
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    • v.15 no.2
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    • pp.121-129
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    • 2009
  • Purpose: The purpose of this study was to examine the effect of the yoga during pregnancy on the maternal weight, delivery experience and infant birth weight. Method: The nonequivalent control group pre test-post test design was used. The participants were the healthy pregnant women, whose pre-pregnancy BMI was normal, gestational period was more than 20 weeks. The final sample consisted of 21 mother-infant dyads for experimental group and 20 dyads for control group and who agreed to participate in this study. Data were collected from February I st to December 15th, 2006. The Qi exercise prenatal program was carried out for 90 minutes a day, 2 times a week for 12 weeks. The data were analyzed using SPSS 16.0 Program. Result: The degree of maternal weight gain(p<.001), labor pain(p<.001), discomfort after delivery(p<.001) and infant's birth weight(p<.00I) were significantly different between two groups. Conclusion: The yoga during pregnancy managed weight gain of mothers. Therefore, this study suggests that yoga during pregnancy to promotes stabilization can be beneficial for maintaining healthy weight, decreasing labor pain and discomfort after delivery for pregnant women and increasing infant's birth weight.

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Effect of Taping Technique Applied to Adults with Knee Instability on Landing Error Scoring System, Lower Extremity Joint Angle

  • Son, Jin-Kyu;Park, Sam-Ho;Lee, Myung-Mo
    • Physical Therapy Rehabilitation Science
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    • v.10 no.4
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    • pp.406-413
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    • 2021
  • Objective: The purpose of this study was to investigate effects of taping technique applied to knee instability. Design: Cross sectional study. Methods: Twenty-six participants with knee instabilityparticipated in this study. They were randomly assigned to the Kinesio taping (KT) group (n=13) and the dynamic taping (DT) group (n=13). Both groups applied knee stabilization taping techniques. In order to compare the effects of each taping technique, the change in the landing error scoring system (LESS) and lower extremity joint angle wasrecorded before and after the intervention. Results: Both groups significantly decreased in the change before and after the LESS (p<0.05). At the joint angle of the lower extremities, KT group significantly reduced the valgus angle at the max knee flexion (p<0.05). In DT group knee joint flexion and hip joint flexion angles were significantly increased at foot contact (p<0.05). In max knee flexion, the knee joint flexion angle was significantly increased (p<0.05). In foot contact, max knee flexion, the knee joint valgus angle was significantly increased (p<0.05). DT group showed more significant changes in knee joint flexion angle at foot contact and hip joint flexion angle at max knee flexion. Conclusions: Dynamic taping is a clinically applicable intervention method for lowering the risk of non-contact injury in participants with knee instability and for knee stability during rehabilitation exercises.

Effects of Therapeutic Exercise on Pain, Physical Function, and Magnetic Resonance Imaging Findings in a Patient with Multilevel Lumbar Disc Herniation: A Case Report

  • Kim, Ahram;Lee, Hoseong
    • Journal of International Academy of Physical Therapy Research
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    • v.10 no.1
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    • pp.1725-1733
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    • 2019
  • Background: In some clinical guidelines followed in clinical practice, nonsurgical treatments are recommended as the primary intervention for patients with lumbar disc herniation (LDH). However, the effect of a therapeutic exercise program based on stabilization of the lumbar spine for treatment of multilevel LDH has not been evaluated thoroughly. Objective: To investigate the effects of therapeutic exercise on pain, physical function, and magnetic resonance imaging (MRI) findings in a patient with multilevel LDH. Design: Case Report Methods: A 43-year-old female presented with low back pain, radicular pain and multilevel LDH (L3-L4, L4-L5, L5-S1). The therapeutic exercise program was conducted. in 40-min sessions, three times a week, for 12 weeks. Low back and radicular pain, lumbar disability, and physical function were measured before and after 6 and 12 weeks of the exercise program. MRI was performed before and after 12 weeks of the program. Results: After 6 and 12 weeks of the therapeutic exercise, low back and radicular pain and lumbar disability had decreased, and lumbar range of motion (ROM) was improved bilaterally, compared with the initial values. Also improved at 6 and 12 weeks were isometric lumbar strength and endurance, and the functional movement screen score. The size of disc herniations was decreased on MRI obtained after 12 weeks of therapeutic exercise than on the pre-exercise images. Conclusions: We observed that therapeutic exercise program improved spinal ROM, muscle strength, functional capacity, and size of disc herniation in LDH patient.

End-to-end-based Wi-Fi RTT network structure design for positioning stabilization (측위 안정화를 위한 End to End 기반의 Wi-Fi RTT 네트워크 구조 설계)

  • Seong, Ju-Hyeon
    • Journal of Korea Multimedia Society
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    • v.24 no.5
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    • pp.676-683
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    • 2021
  • Wi-Fi Round-trip timing (RTT) based location estimation technology estimates the distance between the user and the AP based on the transmission and reception time of the signal. This is because reception instability and signal distortion are greater than that of a Received Signal Strength Indicator (RSSI) based fingerprint in an indoor NLOS environment, resulting in a large position error due to multipath fading. To solve this problem, in this paper, we propose an end-to-end based WiFi Trilateration Net (WTN) that combines neural network-based RTT correction and trilateral positioning network, respectively. The proposed WTN is composed of an RNN-based correction network to improve the RTT distance accuracy and a neural network-based trilateral positioning network for real-time positioning implemented in an end-to-end structure. The proposed network improves learning efficiency by changing the trilateral positioning algorithm, which cannot be learned through differentiation due to mathematical operations, to a neural network. In addition, in order to increase the stability of the TOA based RTT, a correction network is applied in the scanning step to collect reliable distance estimation values from each RTT AP.