• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.440-441
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• 2006

We have studied the narrow viewing angle liquie crystal displays (LCDs) using a hybrid aligned nematic liquid crystal (LC) cell driven by a fringe field. The device using a LC with positive dielectric anisotropy has a relatively low transmittance. This paper describes how to improve light efficiency by optimizing electrode structure. The results show that the device exhibits a high transmittance of 90%, low driving voltage and narrow viewing angle less than $20^{\circ}$ along horizontal direction which is highly effective for private display application.

• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.30-39
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• 2014

The cross flow turbine is economical because of its simple structure. For remote rural region, there are needs for a more simple structure and very low head cross flow turbines. However, in this kind of locations, the water from upstream always flows into the turbine with some other materials such as sand and pebble. These materials will be damage to the runner blade and shorten the turbine lifespan. Therefore, there is a need to develop a new type of cross flow turbine for the remote rural region where there is availability of abundant resources. The new design of the cross flow turbine has an inlet open duct, without guide vane and nozzle to simplify the structure. However, the turbine with inlet open duct and very low head shows relatively low efficiency. Therefore, the purpose of this study is to optimize the shape of the turbine inlet to improve the efficiency, and investigate the internal flow of a very low head cross flow turbine. There are two steps to optimize the turbine inlet shape. Firstly, by changing the turbine open angle along with changing the turbine inlet open duct bottom line (IODBL) location to investigate the internal flow. Secondly, keeping the turbine IODBL location at the maximum efficiency achieved at the first step, and changing the turbine IODBL angle to improve the performance. The result shows that there is a 7.4% of efficiency improvement by optimizing turbine IODBL location (open angle), and there is 0.3% of efficiency improvement by optimizing the turbine IODBL angle.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.858-863
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• 2001

In this paper, the test and result of flow and combustion for 21AFR lean fuel models are described. The necessity to develop the low emission combustor has been issued from the concern on the increase of green house and the destruction of ozone layer. To evaluate the flow and combustion performance of new designed 21AFR lean modules, the hydraulic tests in stereo lithographic airflows models, the low pressure combustion tests in three injectors model for weak extinction and ignition and the high pressure combustion tests in single sector for NOx, SAE and efficiency are performed. The low pressure tests reveal that the governing parameters in weak extinction and ignition at atmospheric condition are prefilmer length, swirl flow rotation direction, secondary swirl angle and flow split. As a results of combustion test at high pressure, the efficiency and smoke level are satisfied with performance targets, but EINOx of 17.8 is higher than target value of 13.1. The high pressure tests show that the main parameters influenced on NOx are primary swirl angle, swirl flow rotation direction, heatshield exit angle and liner mixing hole location.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1132-1137
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• 2002

In this paper, the test results of the combustion for 2 IAFR lean fuel models are described. The need for the low emission combustor has been issued from the concern on the increase of green house and the destruction of ozone layer. To evaluate the flow and combustion performance of newly designed 21AFR lean modules, the hydraulic tests in stereolithographic airflows models, the low pressure combustion tests in three injectors model for weak extinction and ignition and the high pressure combustion tests in single sector for NOx, SAE and efficiency are performed. The low pressure tests reveal that the governing parameters in weak extinction and ignition at atmospheric condition are prefilmer length, swirl flow rotation direction, secondary swirl angle and flow split. As a result of combustion test at high pressure, the efficiency and smoke level are satisfied with performance targets, but EINOx of 17.8 is higher than target value of 13.1 The high pressure tests show that the main parameters influenced on NOx are primary swirl angle, swirl flow rotation direction, heatshield exit angle and liner mixing hole location.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.148-152
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• 2005

Atmospheric low-temperature plasma was produced using dielectric barrier discharge (DBD) plate-type plasma reactor and high frequency of 13.56 Hz. The surfaces of polyimide films for insulating and packaging materials were treated by the atmospheric low-temperature plasma. The contact angle of 67$^{\circ}$ was observed before the plasma treatment. The contact angle was decreased with deceasing the velocity of plasma treatment. In case of oxygen content of 0.2 %, electrode gap of 2 mm, the velocity of plasma treatment of 20 mm/sec, and input power of 400 W, the minimum contact angle of 13$^{\circ}$ was observed. The chemical characteristics of polyimide film after the plama treatment were investigated using X-ray photoelectron spectroscopy (XPS), and new carboxyl group bond was observed. The surfaces of polyimide films were changed into hydrophilic by the atmospheric low-temperature plasma. The polyimide films having hydrophilic surface will be very useful as a packaging and insulating materials in electronic devices.

• Journal of Acupuncture Research
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• v.23 no.5
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• pp.1-10
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• 2006

Objectives : Low back pain is common symptom in clinics. The purpose of this study is to examine the effects of spiral taping on the low back pain patients. Methods : A total of 60 patients with low back pain were assigned to two groups : taping group and non taping group. Patients were evaluated and analyzed VAS, ODI(Oswestry Disability Index), lumbar flexion angle and lumbar extension angle. Results and Conclusion : 1. VAS score of pain was significantly decreased in the taping group(p<.05), compared with the non taping group. 2. Lumbar flexion angle was significantly increased in the taping group(p<.05).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.45-46
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• 2006

We have studied the viewing angle control using a twist nematic liquid crystal display (TN-LCDs). These TK-LCDs have the characteristics, of which is not good image quality, for examples low Contrast ratio and gray scale inversion problems at upper and down viewing direction. TN-LCDs have the function of switching between the wide viewing mode and narrow viewing angle mode using two tilted LC layers. Tilt angles of the two LC layers, $14^{\circ}$ and $60^{\circ}$ were required in both wide viewing angle and narrow viewing angle modes, respectively. Consequently, this device is compatible with two image performances of which the wide viewing angle mode and Narrow viewing angle mode.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.149-163
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• 2004

This study analyzed kinematic variables about the cross step, the delivery and the release for women's javelin athletics recorded over 50m in the 2004 Busan International Athletics Competition. It was used the Kwon3D Motion Analysis Package Ver. 3.1 Program(Kwon, 2000) for analysing the kinematic variables about the distance, the velocity, and the angle, then we had the results as follows; 1 In the Cross step phase, the COG velocity was low because their step length was short. To keep the CM velocity from the approach to the last cross over step contact, the athletes have to keep the longer step length within about 130% of the athletics' height. 2. In the Delivery phase, the athletics' COG height was gradually lower, and the deceleration of the COG was going up. As the same in the cross step, Therefore the athletes have to increase the step length within about 100% of their height, in order to increasing the COG velocity. And it was shown they have to make small angle of the elbow as possible from the right foot contact to the left foot contact in order to being the big acceleration of the upperarm at the release phase. 3. In the release phase, it was shown to being low position of the release point as the COG was low and then the release velocity of the upperarm was low. Specially when the shoulder lean lateral angle is big at the release phase, it was shown they have a excessive release angle. And, when it was shown the high rotation angle of the shoulder, the shoulder was opened forward bigger than the trunk was opened forward. So the transmission of velocity from the proximal segments was a fast change.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.1-7
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• 2007

The effect of injector geometries including the injection angle and number of nozzle holes on homogeneous charge compression ignition (HCCI) engine combustion has been investigated in an automotive-size single-cylinder diesel engine. The HCCI engine has advantages of simultaneous reduction of PM and NOx emissions by achieving the spatially homogenous distribution of diesel fuel and air mixture, which results in no fuel-rich zones and low combustion temperature. To make homogeneous mixture in a direct-injection diesel engine, the fuel is injected at early timing. The early injection guarantees long ignition delay period resulting in long mixing period to form a homogeneous mixture. The wall-impingement of the diesel spray is a serious problem in this type of application. The impingement occurs due to the low in-cylinder density and temperature as the spray penetrates too deep into the combustion chamber. A hole-type injector (5 holes) with smaller angle ($100^{\circ}$) than the conventional one ($150^{\circ}$) was applied to resolve this problem. The multi-hole injector (14 holes) was also tested to maximize the atomization of diesel fuel. The macroscopic spray structure was visualized in a spray chamber, and the spray penetration was analyzed. Moreover, the effect of injector geometries on the power output and exhaust gases was tested in a single-cylinder diesel engine. Results showed that the small injection angle minimizes the wall-impingement of diesel fuel that results in high power output and low PM emission. The multi-hole injector could not decrease the spray penetration at low in-cylinder pressure and temperature, but still showed the advantages in atomization and premixing.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.329-338
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• 2014

The purpose of this study was to analyze of the rider postural alignments according to the fitting of stirrups lengths during walk of high level riders. Participants selected as subject were consisted of horse riders of high level (age: $47.66{\pm}3.51yrs$, height: $168.40{\pm}4.84cm$, body weight: $73.36{\pm}15.58kg$, low extremity length: $94.76{\pm}3.98cm$, career: $23.33{\pm}5.77yrs$) and walk with 3 types of stirrup lengths(ratio of low extremity 68.04%, 73.25%, 78.48%). The variables analyzed were consisted of the displacement of Y axis (center of mass, head, thigh, shank and foot), FR angle, LR angle, dynamic postural stability index (DPSI), coefficient of variation (CV%), and distance (X axis) of low extremity limb between right and left. The displacement of Y axis in COM, thigh, shank, foot limbs were not statistically significant, but movements of head showed greater distance of B type and C type than that of A type during 1 stride of walk. The FR and LR angle in trunk of horse rider, dynamic postural stability index and, coefficient of variation didn't show significant difference statistically according to the fitting of stirrup lengths. Also the distance (X axis) of low extremity in thigh and shank didn't show significant difference statistically in between right and left, but right and left foot showed greater distance in C type than that of B and A types during walk in horse back riding. The hip and ankle joint angle not statistically significant according to stirrups lengths, But knee joint angle showed more extended according to the increase of stirrups lengths during stance and swing phase in walk.