• Journal of ILASS-Korea
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• v.25 no.4
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• pp.188-195
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• 2020

To meet stringent emission regulations of automotive engines, fuel injection control techniques have advanced based on reliable and fast computing prediction models. This study aims to develop a reliable lightweight prediction model of fuel injection rates using a small number of input parameters and based on simple fluid dynamic theories. The prediction model uses the geometry of the injector nozzle, needle motion data, injection conditions and the fuel properties. A commercial diesel injector and US No. 2 diesel were used as the test injector and fuel, respectively. The needle motion data were measured using X-ray phase-contrast imaging technique under various fuel injection pressures and injection pulse durations. The actual injector rate profiles were measured using an injection rate meter for the validation of the model prediction results. In the case of long injection durations with the steady-state operation, the model prediction results showed over 99 % consistency with the measurement results. However, in the case of short injection cases with the transient operation, the prediction model overestimated the injection rate that needs to be further improved.

• Journal of ILASS-Korea
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• v.27 no.4
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• pp.181-187
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• 2022

For carbon neutrality, direct-injection hydrogen engines are attracting attention as a future power source. It is essential to estimate the transient injection rate of hydrogen for the optimization of hydrogen injection in direct injection engines. However, conventional injection rate measurement techniques for liquid fuels based on the injection-induced fuel pressure change in a test section are difficult to be applied to gaseous fuels due to the compressibility of the gas and the sealing issue of the components. In this study, a momentum flux measurement technique is introduced to obtain the transient injection rate of gaseous fuels using a force sensor. The injection rate calculation models associated with the momentum flux measurement technique are presented first. Then, the volumetric injection rates are estimated based on the momentum flux data and the calculation models and compared with those measured by a volumetric flow rate meter. The results showed that the momentum flux measurement can detect the injection start and end timings and the transient and steady regimes of the fuel injection. However, the estimated volumetric injection rates showed a large difference from the measured injection rates. An alternative method is suggested that corrects the estimated injection rate results based on the measured mean volumetric flow rates.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.1
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• pp.21-30
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• 2022

PURPOSE: This study examined the effects of treadmill training with taping on the affected ankle joint on the gait and balancing ability in patients with sub-acute stroke. METHODS: Nineteen patients with sub-acute hemiplegic stroke in a rehabilitation hospital were assigned randomly to either the experimental group (n = 10), who received treadmill training with taping on the affected ankle joint or the control group (n = 9), who received general treadmill training. All participants performed 60 min of comprehensive rehabilitation therapy (five sessions per week for four weeks). Each group received treadmill training with or without taping on the affected ankle joint for 20 min (three sessions per week for four weeks). The gait and balancing ability were measured before and after the four-week training. RESULTS: Post-training scores of 10-meter walk test (10 MWT), timed up and go (TUG) test, and center of pressure (COP) path length and velocity for the experimental group increased significantly compared to that pre-training (p < .05). The experimental group showed a larger decrease in the 10 MWT and TUG test than the control group (-3.5 s vs. -1.01 s, p < .05; -4.9 s vs. -1.7 s, p < .05; respectively) CONCLUSION: Treadmill training with taping on the affected ankle joint might improve the gait and balancing ability of stroke patients and is considered a more effective method for improving gait and balancing ability than the method of general treadmill training.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.85.1-85.1
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• 2010

$Cu(In,Ga)Se_2$ (CIGS) thin film solar cell is currently 19.5% higher efficiency and developing a large area technology. The structure of CIGS solar cell that make five unit layers as back contact, light absorption, buffer, front transparent conducting electrode and antireflection to make them sequentially forming. Materials and various compositions of thin film unit which also manufacture a variety method used by the physical and chemical method for CIGS solar cell. The construction and performance test of evaporator for CIGS thin film solar cell has been done. The vapor pressures were changed by using vapor flux meter. The vapor pressure were copper (Cu) $2.1{\times}10^{-7}{\sim}3.0{\times}10^{-7}$ Torr, indium (In) $8.0{\times}10^{-7}{\sim}9.0{\times}10^{-7}$ Torr, gallium (Ga) $1.4{\times}10^{-7}{\sim}2.8{\times}10^{-7}$ Torr, and selenium (Se) $2.1{\times}10^{-6}{\sim}3.2{\times}10^{-6}$ Torr, respectively. The characteristics of the CIGS thin film was investigated by using X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and photoluminescence (PL) spectroscopy using a He-Ne laser. In PL spectrum, temperature dependencies of PL spectra were measured at 1137 nm wavelength.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.150-150
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• 2016

Mankind is enjoying a great convenience of their life by the rapid growth of secondary industry since the Industrial Revolution and it is possible due to the invention of huge power such as engine. The automobile which plays the important role of industrial development and human movement is powered by the Engine Module, and especially Diesel engine is widely used because of mechanical durability and energy efficiency. The main work mechanism of the Diesel engine is composed of inhalation of the organic material (coal, oil, etc.), combustion, explosion and exhaust Cycle process then the carbon compound emissions during the last exhaust process are essential which is known as the major causes of air pollution issues in recent years. In particular, COx, called carbon oxide compound which is composed of a very small size of the particles from several ten to hundred nano meter and they exist as a suspension in the atmosphere. These Diesel particles can be accumulated at the respiratory organs and cause many serious diseases. In order to compensate for the weak point of such a Diesel Engine, the DPF(Diesel Particulate Filter) post-cleaning equipment has been used and it mainly consists of ceramic materials(SiC, Cordierite etc) because of the necessity for the engine system durability on the exposure of high temperature, high pressure and chemical harsh environmental. Ceramic Material filter, but it remains a lot of problems yet, such as limitations of collecting very small particles below micro size, high cost due to difficulties of manufacturing process and low fuel consumption efficiency due to back pressure increase by the small pore structure. This study is to test the possibility of new structure by direct infiltration of SiC Whisker on Carbon felt as the next generation filter and this new filter is expected to improve the above various problems of the Ceramic DPF currently in use and reduction of the cost simultaneously. In this experiment, non-catalytic VS CVD (Vapor-Solid Chemical Vaporized Deposition) system was adopted to keep high mechanical properties of SiC and MTS (Methyl-Trichloro-Silane) gas used as source and H2 gas used as dilute gas. From this, the suitable whisker growth for high performance filter was observed depending on each deposition conditions change (input gas ratio, temperature, mass flow rate etc.).

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.3
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• pp.127-135
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• 2023

Purpose : This study was performed to evaluate the effects of magnetic therapy (MT) on pain threshold, blood flow, and balance in patients with knee osteoarthritis. Methods : A single-blind, randomized controlled trial (RCT) was conducted with 30 patient with knee osteoarthritis. They were randomly allocated 2 groups; magnetic therapy group (MTG; n=15) and placebo magnetic therapy group (PG; n=15). The MTG group received 30 minutes magnetic therapy and 20 minute conservative physical therapy (Hotpack, ICT), magnetic therapy was conducted in magnetic therapy device (OM-100, NUGA, Korea). In the placebo magnetic group received 30 minutes placebo magnetic therapy and 20 minute conservative physical therapy. Each group performed 50 minutes a day 3 times a week for 8 weeks. The primary outcome pressure pain threshold test, blood flow, balance ability were measured by a pressure threshold meter (Commander algometer, JTECH medical, USA), laser dofler image (Moor LDI2-IR, Moor instruments, USA), balance measurement system (BioRescue, Marseille, France). The measurement were performed before and after the 8 weeks intervention period. Results : Both groups demonstrated significant improvement of outcome in pain threshold, blood flow, and balance ability during intervention period. magnetic therapy group revealed significant differences in pain threshold, blood flow, and balance as compared to the placebo magnetic therapy group groups (p<.05). Our results showed that magnetic therapy was more effective than placebo therapy on pain threshold, blood flow, and balance in patients with knee osteoarthritis. Conclusion : Our findings indicate that magnetic therapy can improve pain threshold, blood flow, and Balance, highlight the benefits of magnetic therapy. This study will be able to be used as an intervention data for recovering pain threshold, blood flow, and balance in patients with knee osteoarthritis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.249-265
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• 1995

The performance of a refrigerant mixture of propane(R290)/isobutane(R600a) as a substitute for CFC12 was investigated in a domestic refrigerator with single evaporator. A thermodynamic cycle simulation indicated an increase in COP of a 1.7 to 2.4% with R-290/600a in the composition range of 0.2 to 0.6 mass fraction of R290 compared to CFC12. For the tests, two units($299{\ell}$, $465{\ell}$) were used. All refrigeration components remained the same throughout the tests, except that the length of capillary tube and amount of charge were changed for the mixture. The refrigerators were fully instrumented with more than 20 thermocouples, 2 pressure transducers, and watt/watt-hour meter for each refrigerator. 'Energy consumption test' and 'no load pulldown test' were performed under the same condition. The experimental results obtained with the same compressor indicated that R-290/600a mixture at 0.6 mass fraction of R290 showed a 3 to 5% increase in energy efficiency and a faster cooling speed compared to CFC12. The R-290/600a mixture showed a shorter compressor on-time and a lower compressor dome temperature than CFC12. In conclusion, the proposed hydrocarbon mixture seems to be an appropriate candidate to replace CFC12 without causing more environmental problems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1051-1060
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• 2003

The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm ; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.4
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• pp.163-174
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• 2020

PURPOSE: This study examined the effects of Robot Tilt-table Training (RTT) on the lower extremity strength, balance, gait, and satisfaction with rehabilitation, in patients with subacute stroke (less than six months after stroke onset), and requiring intensive rehabilitation. METHODS: A total of 29 subacute stroke patients were divided into an RTT group (n = 14) and a Body Weight Support Treadmill Training (BWSTT) group (n = 15). The mean age of patients was 62 years. RTT and BWSTT were performed for four weeks, three times a week, for 30 minutes. Isometric strength of the lower extremities before and after intervention was compared by measuring the maximal voluntary isometric contraction of the lower extremity muscles. To compare the balance function, the center of pressure (COP) path-length and COP velocity were measured. Timed Up & Go test (TUG) and 10 Meter Walking Test (10 MWT) were evaluated to compare the gait function. A satisfaction with rehabilitation survey was conducted for subjective evaluation of the subject's satisfaction with the rehabilitation training imparted. RESULTS: In the intra-group comparison, both groups showed significant improvement in lower extremity strength, balance, gait, and satisfaction with rehabilitation, by comparing the parameters before and after the intervention (p < .05). Comparison of the amount of change between groups revealed significant improvement for all parameters in the RTT group, except for the 10 MWT (p < .05). CONCLUSION: Both groups are effective for all variables, but the RTT group showed enhanced efficacy for variables such as lower extremity strength, balance, gait, and satisfaction with rehabilitation, as compared to the BWSTT group.

• Journal of Korean Physical Therapy Science
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• v.29 no.4
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• pp.86-95
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• 2022

Background: The purpose of this study is to investigate the effect of ultra-thin microcurrent patch application on pain, tenderness, trunk flexion, and trunk extension in patients with back pain. Design: pretest-posttest design: single blind. Methods: Thirty men and women diagnosed with chronic back pain were classified into 15 microcurrent application groups and 15 placebo groups. Changes in pain were observed on a visual analog scale, tenderness was observed with a digital tenderness meter, and changes in trunk flexion and trunk extension angles were evaluated with a posture analyzer. The paired t-test was used to see the changes within each group before and one week after the experiment, and the independent t-test was used to see the change in the difference between the groups, and the significance level was 0.05. Results: In both the experimental group and the control group, there was a significant difference in pain within and between groups(p<0.05). In the experimental group, there were significant differences in the intra- and inter-group changes in the erector spinae muscle tenderness and low back pain disorder index(p<0.05). In the experimental group, there was a significant difference in the change in trunk flexion and extension within the group(p<0.05). Conclusion: In this study, it was confirmed that the application of ultra-thin microcurrent was effective for pain, tenderness, and movement of back extension in patients with low back pain. It is expected that it will be used as a basic data for microcurrent therapy and as a treatment method for improving the function of patients with back pain in the future.