• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.3
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• pp.575-583
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• 2017

Various types of flow patterns around the stepped weir and spillway, such as the skimming flow over such structures and the wave-type flow with a standing undular hydraulic jump and roller downstream of the structures, are developed in open channels. Unsteady three-dimensional numerical simulations are carried out using a hybrid RANS-LES turbulence modeling approach and the volume of fluid method for resolving free surface fluctuations to represent the turbulent flow including the skimming flow and wave-type flow over a stepped weir installed in a rectangular channel. The comparison of numerical results with an existing experimental measurement reveals that the present numerical simulations reasonably well reproduce the turbulent flow passing the stepped weir, in terms of time-averaged velocity profiles at selected locations downstream of the weir, flow topology characterized by the wave-type and skimming flows, the maximum height and length of the standing wave and the length of reattachment of recirculating zone. The numerical result further elucidates the distinct flow behaviors of the wave-type and skimming flow by presenting instantaneous intense variations of free surface and velocity vectors, the distributions of Reynolds shear stress and turbulent kinetic energy and three-dimensional complex features of coherent structures and total pressure distribution.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1532-1548
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• 2008

The tunnel type spillways is under construction to increasing water reservoir capacity in Dae-am dam. The tunnel outlet was planned to be made after installing slope stabilization system on natural slope there. Generally, the tunnel outlet is made perpendicularly to the slope, but in this case, it had to be made obliquely to the slope for not interrupting flow of river. Because of excavation in condition of natural slope caused to deflecting earth pressure, the outlet couldn't be made. So, artificial ground made with concrete that it was constructed in the outside of tunnel for producing the arching effect which enables to make a outlet. We were planned tunnel excavation was carried out after artificial ground made. Artificial ground made by poor mix concrete of which it was planned that the thickness was at least 3.0m height from outside of tunnel lining and 30cm of height per pouring. Spreading and compaction was planned utilized weight of 15 ton roller machine. In order to access of working truck, slope of artificial ground was designed 1:1.0 and applied 2% slope in upper pert of it for easily drainage of water. In addition to, upper pert of artificial ground was covered with soil, because of impaction of rock fall from upper slope was made minimum. The tunnel excavation of the artificial ground was designed application with special blasting method that it was Super Wedge and control blasting utilized with pre-percussion hole.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.3
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• pp.344-351
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• 2015

Braking force inspection of vehicles in service is certainly one of the most important characteristics that affect vehicle safety. Up to now, in domestic country, the regular safety inspection of vehicles in service has been tested with a roller type brake test (a static braking force inspection system). But, in EU and USA etc. in recent years, it has been tested with a plate type brake test (a dynamic braking force inspection system). In this study, to compare the characteristics of above two test systems, the correlations for the results of braking force are evaluated statistically. As the results, in the case of main braking force, the range of the $R^2$ of the deviation for the left and right side is 0.5386 ~ 0.6231 in the rear axle and 0.0032 ~ 0.0052 in the front axle respectively, then the $R^2$ in the front axle is lower than that in the rear axle and the total variation is unexplained by the least-squares regression line statistically. Also, the p-value for the deviation of the left and right in the front axle is 0.4839 ~ 0.5755, then it has nonsignificant in the front axle. Therefore, the static braking force inspection system can not reflect the inertia force that there is a load transfer from the rear axle to the front axle during braking. Accordingly, it is necessary to adopt the dynamic braking force inspection system which can reflect the inertia force on the regular vehicle safety inspection in domestic country.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.355-360
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• 2006

The damping force of a jaw pad is determined by the displacements of main part when two lockers are locked, after the damping angle of a locker was set up in the wedge type rail damp for a container crane. In this time, of the resistance of wedge frame generates due to several factors, the damping angle of a locker to display the initial clamping force will be changed because of the reduction of displacement of extension bar. This resistance is determined by the eccentric distance between the roller and the wedge, and by the gap between the wedge frame and outer frame. In this study we measured the tensile force of both extension bar through the performance test of the prototype rail damp in order to evaluate the effect of the resistance of wedge frame on the damping force of the wedge type rail clamp.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.630-638
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• 2010

The present investigation has been performed on the mixing behavior and microstructural development during fabrication of Fe micro-nano powder feedstock for a micro-powder injection molding process. The mixing experiment using a screw type blender system was conducted to measure the variations of torque and temperature during mixing of Fe powder-binder feedstock with progressive powder loading for various nano-powder compositions up to 25%. It was found that the torque and the temperature required in the mixing of feedstock increased proportionally with increasing cumulative powder loading. Such an increment was larger in the feedstock containing higher content of nano-powder at the same powder loading condition. However, the maximum value was obtained at the nano-powder composition of not 25% but 10%. It was owing to the 'roller bearing effect' of agglomerate type nano-powder acting as lubricant during mixing, consequently leading to the rearrangement of micro-nano powder in the feedstock. It is concluded that the improvement of packing density by rearrangement of nano-powders into interstices of micro-powders is responsible for the maximum powder loading of about 71 vol.% in the nano-powder composition of 25%.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.271-279
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• 2016

The objective of this study was to determine the effect of the moisture content and pellet mill type on the physical and chemical characteristics of Italian ryegrass (IRG) pellet. Moisture content of raw material significantly (p<0.05) affected IRG pellet formation. Moisture content at 25% was the best condition for IRG pellet formation in terms of shape, power load and temperature changes. The hardness of pellet was decreased when moisture content was increase. However, the hardness of pellet was not affected by pellet mill type. Moisture content at 30% dramatically (p<0.05) decreased the durability compared to moisture content at 25%. Dry matter content of IRG pellet was increased (p<0.05) after pelleting. Total count of microorganism was decreased in pellet due to pressure heat and moisture losses during the pelleting process. These results indicated that the proper moisture content of Italian ryegrass pelleting would be at 25%. In addition, Roll & flat die type would be more suitable than Ring die and Die & flat die type in IRG pelleting. Pelleting works would be beneficial for improving forage quality and long storage.

• Journal of Chest Surgery
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• v.24 no.7
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• pp.674-684
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• 1991

The surgical treatment of tetralogy of Fallot [TOF] was initiated by Blalock and Taussig in 1945 with the establishment of the subclavian artery to pulmonary artery anastomosis. In an imaginative and daring effort, in 1954, Lillehei and collaborators [1955] using controlled cross-circulation, carried out the first intracardiac repair of TOF by closing the ventricular septal defect [VSD] and relieving the pulmonary stenosis under direct vision. Nowadays, total correction is the ideal operation for treatment of TOF and is accomplished with extracorporeal circulation. And the results of surgery for TOF have steadily improved over the years, thanks to important contributions of many surgeons. Nevertheless because of its protean physiologic and anatomic presentation, TOF continues to offer challenges to cardiologist and cardiac surgeons. Thirty two cases of TOF have undergone total corrective surgery using extracorporeal circulation in the Department of Thoracic & Cardiovascular Surgery, Pusan Paik Hospital, Inje University, from Oct. 1985 to Feb. 1990. Clinical considerations were applied to these cases and the results were obtained as follows. 1. The heart lung machine used for extracorporeal circulation was SarnsO 7000, 5-head roller pump, and the number and type of oxygenators were 10 of bubble type and 22 of membrane type. The mean bypass time was 148.9 minutes and the mean aortic cross clamp time was 123.8 minutes. The GIK [glucose-insulin-potassium] solution was used as cardioplegic solution for myocardial protection during operation. 2. 20 cases were male and 12 were female, the mean age was 8 years old and the mean body weight was 25Kg. 3. The preoperative symptoms were cyanosis [29 cases], squatting [27 cases] and etc. The mean values of preoperative Hb., Hct., and SaO2 were 16.5 gm /dl, 50.3%, and 78.5%. 4. Combined anomalies were noticed in 16 cases [50%]. Among them 10 cases were PFO and 6 cases were ASD. 5. The degree of aorta overriding were 25% in 5 cases, 25 ~ 50% in 22 cases and above 50% in 5 cases. The dPA/Ao [ratio of diameter of pulmonary artery trunk to ascending aorta] were below 25% in 5 cases, 25 ~ 50% in 10 cases, 50 ~ 70% in 6 cases and above 75% in 11 cases. 6. The types of RVOT [right ventricular outflow tract] stenosis were valvular and infundibular in 14 cases [43.6%], diffuse hypoplastic type in 12 cases [37.5%], infundibular in 5 cases, and valvular and supravalvular in 1 case. 7. One stage radical corrective surgery was applied to the all cases. In widening of the RVOT, 3 types of patches were used: MVOP [monocusp ventricular outflow patch, Polystan BioprosthesesO] in 3 cases, knitted Dacron vessel patches in 2 cases, and double layer with bovine pericardium and woven Dacron prosthesis in 26 cases. 8. Postoperative complications were occurred in 15 cases. Among them, low output syndrome were occurred in 10 cases [31.3%] and 2 of them were expired postoperatively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.247-252
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• 2005

The wedge type rail clamp has the operating mechanism: First, the jaw pad clamps a rail with small clamping force Next as the wind speed increases, the clamping force of the jaw pad is increased by the wedge. In order to design the wedge type rail clamp, we need to determine the proper wedge angle to minimize the sliding distance of a roller and the proper clamping angle of a locker to generate the initial clamping force of a jaw pad. The researches for the proper wedge angle have conducted, and in this study we conducted the investigation to determine the proper clamping angle of a locker in the rail clamp with wedge angle of $10^{\circ}$. Because the initial damping force of the jaw pad was determined by the clamping angle of the locker, in order to carry out the clamping force of a jaw pad, we measured the locking force applied to a locker with respect to the clamping angle of a locker, such as $3^{\circ},\;4^{\circ},\;5^{\circ},\;6^{\circ},\;$ using a pressure gauge, and compared the results with the FEA results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.2
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• pp.92-99
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• 1991

A moored body in the sea is subjected to second-order wave forces as well as to linear oscillatory ones. The second-order farces contain slowly-varying components, of which the characteristic frequency can be as low as the natural frequency of horizontal motions of the moored body. As a consequence, the slowly-varying force can excite unexpectedly large horizontal excursion of the body, which may cause a serious damage on the mooring system. In design analysis of Turret-type mooring system which is one of the interesting mooring systems for a floating body. the slowly-varying drift forces and the transient motion of the system during weathervaning are very important. In this paper the slowly-varying drift forces were calculated by using the Quadratic Transfer Function with considering the second order free-wave contributions. Additionaly the transient surge motion of the moored body was simulated with including the roll of the time-memory effect. In this simulation the spring constant of the spread Turret mooring system is updated at every time step for considering the nonlinear effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.70-80
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• 2001

A cycloid reducer is one of the rotational velocity reduction equipments of machinery. It has advantages of the higher reduction ratio, the higher accuracy, the easier adjustment of transmission ratio and the smaller workspace than other kinds of reducer. A cycloidal plate gear is a main part of the cycloid reducer. Its tooth shape is peculiar because of gearing with the roller gear that has the several rollers on the circular line. And then it can be designed to contact all teeth to rollers. So, the cycloid reducer has the good characteristics in the dynamic properties and the zero-backlash in the contact motion. It can be used in robots, high-precision machines and high capacity machinery. This paper proposes a new approach for the shape design of the cycloidal plate gear and presents a Computer-Aided-Design program developed by the proposed method. The first part of this paper defines the two types of the cycloid reducers and explains their mechanisms. The second part defines the instant velocity centers for each type of the cycloid reducers and calculates the contact angles and the contact points by using te geometric relationships and the kinematical properties of the reducers. The third part generates the full shape of the cycloidal plate gear by the coordinate transformation technique. Finally, this paper presents two examples for the shape design of the cycloidal plate gear in order to prove the theory of the proposed method in this paper and the accuracy of the \"CycloGear Designer\".