• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.89-96
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• 2008

This paper investigates the effect of blade deformation, caused by manufacturing inaccuracies, on the performance of a 2-stage axial steam turbine. A high fidelity 3D coordinate Measurement Machine has been employed to obtain the exact geometrical model of the blades. A Streamline Curvature solver was used to predict the overall performance of the turbine. During the manufacturing process of the casts and of the blades themselves, several types of errors can occur which lead to a different geometry from that envisaged by the designer. The main objective of this study is to investigate the effect of those errors on the performance of a 2-stage experimental axial steam turbine. A high fidelity measurement of the actual geometry of both stator and rotor blades has been carried out, using a 3D Coordinate Measurement Machine. The cross sections of the blades obtained by the measurement were compared with those produced by the design process to evaluate the change in blade inlet/exit angles. In addition, the geometrical deviations from the initial design have been subjected to a statistical study in order to locate the nature of the error. The actual(measured) model has been used as input into a Streamline Curvature solver to evaluate its performance. Finally, a comparison with the performance plots of the original geometry has been carried out. A measurable change of efficiency as well as in the total power delivered by the turbine was found. This suggests that the accumulated error caused during the manufacturing procedure plays a significant role in the overall performance of the machine by making it less efficient by more than 1%. Reverse engineering techniques are proposed to predict and alleviate these errors leading thereby to a final design of each stage with improved performance.

• 한국습지학회지
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• 제20권4호
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• pp.432-445
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• 2018

조성 후 5년이 경과한 생태공학적 수질정화 비오톱을 대상으로 식생 및 수환경 분석을 수행하였다. 그 결과, 총 36과에 속하는 91종의 유관속식물종이 확인되었으며 갈대, 달뿌리풀, 줄, 큰잎부들 그리고 애기부들 등 초기 식재된 대형정수식물들이 주된 식생 요소로 확인되었다. 또한, 전기전도도(P < 0.01)를 포함하여 질산태(P < 0.05) 및 암모니움태 질소(P < 0.001)와 칼륨(P < 0.05), 나트륨(P < 0.01) 및 마그네슘(P < 0.01) 등에서 수질정화 효과가 확인되었다. 그 중에서도 질산태 및 암모니움태 질소의 경우 인공습지를 경유하는 과정을 통해 각각 약 60% 및 30% 수준으로 감소하는 수질 개선 효과를 나타내었다. 15개의 단위습지(다중셀습지)가 곡류형 하천과 같은 형태로 조성됨에 따른 '분리성'과 '곡률'은 본 인공습지가 온전한 생태공학적 수질정화 비오톱으로서 지속적으로 기능할 수 있도록 기여한 것으로 판단된다. 인공습지 조성에 있어, 습지로 하여금 다양한 기능들을 안정적으로 수행할 수 있도록 함으로써 습지의 생태적 가치를 제고하는 생태공학적 디자인 요소 반영을 적극 제안하는 바이다.

• Computers and Concrete
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• 제14권5호
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• pp.599-612
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• 2014

This paper presents the effects of the construction stages using time dependent material properties on the structural behaviour of concrete arch dams. For this purpose, a double curvature Type-5 arch dam suggested in "Arch Dams" symposium in England in 1968 is selected as a numerical example. Finite element models of Type-5 arch dam are modelled using SAP2000 program. Geometric nonlinearity is taken into consideration in the construction stage analysis using P-Delta plus large displacement criterion. In addition, the time dependent material strength variations and geometric variations are included in the analysis. Elasticity modulus, creep and shrinkage are computed for different stages of the construction process. In the construction stage analyses, a total of 64 construction stages are included. Each stage has generally $6000m^3$ concrete volume. Total duration is taken into account as 1280 days. Maximum total step and maximum iteration for each step are selected as 200 and 50, respectively. The structural behaviour of the arch dam at different construction stages has been examined. Two different finite element analyses cases are performed. In the first case, construction stages using time dependent material properties are considered. In the second case, only linear static analysis (not considered construction stages) is taken into account. Variation of the displacements and stresses are obtained from the both analyses. It is highlighted that construction stage analysis using time dependent material strength variations and geometric variations has an important effect on the structural behaviour of arch dams. The maximum longitudinal, transverse and vertical displacements obtained from construction stages and static analyses are 1.35 mm and 0 mm; -8.44 and 6.68 mm; -4.00 and -9.90 mm, respectively. In addition, vertical displacements increase from the base to crest of the dam for both analyses. The maximum S11, S22 and S33 stresses are obtained as 1.60MPa and 2.84MPa; 1.39MPa and 2.43MPa; 0.60MPa and 0.50MPa, respectively. The differences between maximum longitudinal, transverse, and vertical stresses obtained from construction stage and static analyses are 78%, 75%, and %17, respectively. On the other hand, there is averagely 12% difference between minimum stresses for all three directions.

• 한국의류산업학회지
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• 제17권5호
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• pp.781-792
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• 2015

This study aims to develop a spring/fall motorcycle jacket for quick service transporter. Depending on the results of the previous research, this study produced the tested jacket which was improved in material, pattern, and design. For the tested jacket, 100% polyester fabric excellent in strength, durability and abrasion-resistance was selected as a major material, and Cordura was used as a partial material to improve the strength and abrasion-resistance of the sleeve side lines, elbow and shoulder areas. The retro-reflection material was applied partially in order to improve visibility of the jacket in the night or in a dark place. A total of 7 pockets were composed in the jacket for the sufficient storage spaces. The functional design elements such as the 2-way zipper and the placket at the center front, the action pleats at the upper part of back armholes, the pit-zip at armpit were applied. In addition, the sleeve pattern was bent with the shape of elbow curvature in time of driving and the back length of the jacket was lengthened 4cm. As a result of the appearance assessment, there was a significant difference from the existing jacket in all items but chest size, shoulder width, cuffs circumference, and jacket hemline circumference. In motion adaptability and field activity appropriateness assessments, the assessment grade for all items was found to be commonly higher than that of the existing jacket, and thus, the tested jacket was assessed to be suitable for a motorcycle jacket design for the quick service transporters.

• Journal of Korean Neurosurgical Society
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• 제54권3호
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• pp.207-210
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• 2013

Objective : To compare spinopelvic parameters in young adult patients with spondylolysis to those in age-matched patients without spondylolysis and investigate the clinical impact of sagittal spinopelvic parameters in patients with L5 spondylolysis. Methods : From 2009 to 2012, a total of 198 young adult male patients with spondylolysis were identified. Eighty age-matched patients without spondylolysis were also selected. Standing lateral films that included both hip joints were obtained for each subject. Pelvic incidence (PI), sacral slope (SS), pelvic tilt, lumbar lordosis angle, sacral inclination, lumbosacral angle, and sacral table angle were measured in both groups. A comparative study of the spinopelvic parameters of these two groups was performed using SPSS 15.0 (SPSS Inc., Chicago, IL, USA). Results : Among the aforementioned spinopelvic parameters, PI, SS and STA were significantly different between patients with spondylolysis and those without spondylolysis. PI and SS were higher in the spondylolysis group than in the control group, but STA was lower in the spondylolysis group than in the control group. Conclusion : PI and SS were higher in the spondylolysis group than in the control group, but STA was lower in the spondylolysis group than in the control group. Patients with spondylolysis have low STA at birth, which remains constant during growth; a low STA translates into high SS. As a result, PI is also increased in accordance with SS. Therefore, we suggest that STA is an important etiologic factor in young adult patients with L5 spondylolysis.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.997-1016
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• 2015

The contribution of tensioned concrete between cracks (tension-stiffening) cannot be ignored when analysing deformation of reinforced concrete elements. The tension-stiffening effect is crucial when it comes to adequately estimating the load-deformation response of steel reinforced concrete and the more recently appeared fibre reinforced polymer (FRP) reinforced concrete. This paper presents a unified methodology for numerical modelling of the tension-stiffening effect in steel as well as FRP reinforced flexural members using the concept of equivalent deformation modulus and the smeared crack approach to obtain a modified stress-strain relation of the reinforcement. A closed-form solution for the equivalent secant modulus of deformation of the tensioned reinforcement is proposed for rectangular sections taking the Eurocode 2 curvature prediction technique as the reference. Using equations based on general principles of structural mechanics, the main influencing parameters are obtained. It is found that the ratio between the equivalent stiffness and the initial stiffness basically depends on the product of the modular ratio and reinforcement ratio ($n{\rho}$), the effective-to-total depth ratio (d/h), and the level of loading. The proposed methodology is adequate for numerical modelling of tension-stiffening for different FRP and steel reinforcement, under both service and ultimate conditions. Comparison of the predicted and experimental data obtained by the authors indicates that the proposed methodology is capable to adequately model the tension-stiffening effect in beams reinforced with FRP or steel bars within wide range of loading.

• 한국수산과학회지
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• 제48권4호
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• pp.474-482
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• 2015

This study aims to investigate the patterns and incidence rates of morphological deformities during artificial fingerling production of blackhead seabream (BSB, Acanthopagrus schlegeli) juveniles by visual and soft X-ray observations of BSB juveniles (n=881) collected from four industrial hatcheries. Using both methods, we observed seven types of external deformity ($11.2{\pm}4.4%$) and eight types of skeletal deformity ($53.4{\pm}5.1%$). Lordosis occurred in all hatcheries with the highest frequency and the mean frequency was $13.1{\pm}4.4%$ (24.5% in total abnormal) by soft X-ray. Although they had a similar standard length (SL), juveniles with lordosis had a significantly lower condition factor and body weight than normally developed juveniles (P<0.05); normal distribution curves of histogram of body proportions, i.e., body height (BH)/head length (HL) and trunk (=SL-HL)/BH, indicated differences between normally developed juveniles and those with lordosis. In addition, 59% of juveniles with lordosis had vertebral curvature of less than $20^{\circ}$, generally at the $17^{th}$ vertebrae. It is expected that the above results will be used as basic data necessary for determining the cause of lordosis and for developing techniques to prevent this symptom in the fingering production industry of BSB juveniles.

• 한국운동역학회지
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• 제30권1호
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• pp.17-25
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• 2020

Objective: The purpose of this study is to provide a better understanding of long turn mechanism by describing long turns after kinematic analysis and provide skiers and winter sports instructors with data through which they are able to analyze right postures for turns in skiing in a systematic, rational and scientific manner. Method: For this, a mean difference of kinematic variables (the center of gravity (CG) displacement of distance, trajectory, velocity, angle) was verified against a total of 12 skiers (skilled and unskilled, 6 persons each), regarding motions from the up-start to down-end points for long turns. Results: First, concerning the horizontal displacement of CG during a turn in skiing, skilled skiers were positioned on the right side at the upstart and edge-change points at a long turn. There was no difference in anteroposterior and vertical displacements. Second, in terms of CG-trajectory differences, skilled skiers revealed a significant difference during a long turn. Third, regarding skiing velocity, skilled skiers were fast at the edge-change and maximum inclination points in long turns. Fourth, there was no difference in a hip joint in terms of a lower limb joint angle. In a knee joint, a large angle was found at the up-start point among skilled skiers when they made a long turn. Conclusion: In overall, when skilled and unskilled skiers were compared, to make a good turn, it is required to turn according to the radius of turn by reducing weight, concerning the CG displacement. Regarding the CG-trajectory differences, the edge angle should be adjusted via proper inclination angulation. In addition, a skier should be more leaned toward the inside of a turn when they make a long turn. In terms of skiing velocity, it is needed to reduce friction on snow through the edging and pivoting of the radius or turn according to curvature and controlling ski pressure. Regarding a lower limb joint angle, it is important to make an up move by increasing ankle and knee angles instead of keeping the upper body straight during an up motion.

• 대한두개안면성형외과학회지
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• 제21권4호
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• pp.219-224
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• 2020

Background: Repair of the orbital floor following trauma or tumor removal remains a challenge because of its complex three-dimensional shape. The purpose of the present study is to understand normal orbital floor anatomy by investigating its differences across four groups (Caucasian American and East Asian, males and females) via facial bone computed tomography (CT). Methods: A total of 48 orbits in 24 patients between 20 and 60 years of age were evaluated. Although most patients underwent CT scanning following trauma, the orbital walls were intact in all patients. Linear and angular measurements of the orbital floor were obtained from CT images. Results: Orbital floor width, length, angle between the orbital floor and medial wall, and distance from the inferior orbital rim to the lowest point of the orbital floor did not show a statistically significant difference between groups. Angles made by the infraorbital rim, the lowest point of the floor, and the anterior border of the infraorbital fissure were statistically significantly wider in East Asian females than in male groups. The floor depth in East Asian females was significantly smaller compared to all the other groups. Conclusion: East Asian female population had smaller curvature and depth of an orbital floor than the other groups, which means racial and sex-related differences should be considered in the orbital floor reconstruction.

• 대한기계학회논문집A
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• 제25권3호
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• pp.510-519
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• 2001

The tensile and fracture toughness tests have been conducted to investigate the degradations of mechanical properties induced mainly by neutron irradiations in Zr-2.5Nb CANDU pressure tube materials operated in Wolsung Unit-1. the tests were performed at room, 150, 200, 250, 300 $\^{C}$ for the irradiated and unirradiated specimens in hot cell. The specimens were directly machined from the tube retaining original curvature using specially designed electric discharge machine(EDM). From the tensile tests of the irradiated specimens, it was found that tensile strength was increased and total elongation was decreased compared to those of the unirradiated ones. The active voltages in the fracture toughness tests for the irradiated showed the discontinuous abrupt increases caused by crack jumping in lower temperature. In the crack resistance curves we found the stable crack growth in the unirradiated, whereas the unstable and three crack growth stages in the irradiated specimens due to the accumulated irradiation defects. The various fracture characteristic values in the irradiated are remarkably lower than those of the unirradiated. Through the fractography, we found in the irradiated that smaller dimple and shorter fissures than the unirradiated, and that the fractured surface had three regions that were flat, transition and slant/shear area. These can explain the difference in the crack growth characteristic values of the irradiated and the unirradiated ones.