• 한국유체기계학회 논문집
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• 제16권6호
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• pp.19-25
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• 2013

The effect of tip gap height on heat/mass transfer characteristics on the floor of cavity squealer tip has been investigated in a turbine cascade for power generation by employing the naphthalene sublimation technique. The squealer rim height is chosen to be an optimal one of $h_{st}/c$ = 5.51% for the tip gap height-to-chord ratios of h/c = 1.0, 2.0, 3.0 and 4.0%. The results show that heat transfer on the cavity floor is strongly dependent upon the behavior of the cavity flow falling down onto the floor. For lower h/c, the floor heat transfer is influenced by the tip leakage flow falling down along the inner face of the suction-side squealer, whereas the floor heat transfer for higher h/c is augmented mainly due to the impingement of leakage flow on the floor near the leading edge. Compared to the plane tip surface heat transfer, the cavity floor heat transfer is less influenced by h/c. For h/c = 1.0%, the average thermal load is as low as a half of the plane tip surface one, and the difference in the thermal load between the two cases tends to decrease with increasing h/c.

• 대한치과보철학회지
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• 제44권1호
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• pp.85-102
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• 2006

Statement of problem: Currently, there are some 20 different geometric variations in implant/abutment interface available. The geometry is important because it is one of the primary determinants of joint strength, joint stability, locational and rotational stability. Purpose: As the effects of the various implant-abutment connections and the prosthesis height variation on stress distribution are not yet examined this study is to focus on the different types of implant-abutment connection and the prosthesis height using three dimensional finite element analysis. Material and method. The models were constructed with ITI, 3i TG, Bicon, Frialit-2 fixtures and solid abutment, TG post, Bicon post, EstheticBase abutment respectively. And the super structures were constructed as mandibular second premolar shapes with 8.5 mm, 11 mm, 13.5 mm of crown height. In each model, 244 N of vertical load and 244 N of $30^{\circ}$ oblique load were placed on the central pit of an occlusal surface. von Mises stresses were recorded and compared in the crowns, abutments, fixtures. Results: 1. Under the oblique loading, von Mises stresses were larger in the crown, abutment, fixture compared to the vertical loading condition. 2. The stresses were increased proportionally to the crown height under oblique loading but showed little differences with three different crown heights under vertical loading. 3. In the crown, the highest stress areas were loading points under vertical loading, and the finish lines under oblique loading. 4. Under the oblique loading, the higher stresses were located in the fixture/abutment interface of the Bicon and Frialit-2 systems compared to the ITI and TG systems. Conclusions: The stress distribution patterns of each implant-abutment system had difference among them and adequate crown height/implant ratio was important to reduce the stresses around the implants.

• Wind and Structures
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• 제32권4호
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• pp.371-391
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• 2021

Tornadoes are the most devastating meteorological natural hazards. Many empirical and theoretical numerical models of tornado vortex have been proposed, because it is difficult to carry out direct measurements of tornado velocity components. However, most of existing numerical models fail to explain the physical structure of tornado vortices. The present paper proposes a new empirical numerical model for a tornado vortex, and its load effects on a low-rise and a tall building are calculated and compared with those for existing numerical models. The velocity components of the proposed model show clear variations with radius and height, showing good agreement with the results of field measurements, wind tunnel experiments and computational fluid dynamics. Normal stresses in the columns of a low-rise building obtained from the proposed model show intermediate values when compared with those obtained from existing numerical models. Local forces on a tall building show clear variation with height and the largest local forces show similar values to most existing numerical models. Local forces increase with increasing turbulence intensity and are found to depend mainly on reference velocity Uref and moving velocity Umov. However, they collapse to one curve for the same normalized velocity Uref / Umov. The effects of reference radius and reference height are found to be small. Resultant fluctuating force of generalized forces obtained from the modified Rankine model is considered to be larger than those obtained from the proposed model. Fluctuating force increases as the integral length scale increases for the modified Rankine model, while they remain almost constant regardless of the integral length scale for the proposed model.

• 소성∙가공
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• 제11권1호
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• pp.84-89
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• 2002

This study is concerned with the analysis of the forming characteristics of radial-forward extrusion. Angle between radial and forward extrusion, gap height, and friction factor are considered as important design factors to affect forming characteristics in radial-forward extrusion. The rigid-plastic finite element method is adopted to analyze the effects of design factors on forming loads. The incremental rates of loads are nearly constant except the deformation zone from radial to forward extrusion. The smaller angle induces lesser force increment, therefore forming load increases as the angle increases. Maximum load also increases as gap-height decreases and friction factor increases.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.31-34
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• 2002

In this study, thermal analysis of a thermal capacitor, which is used to cool the current lead in conduction-cooled superconducting systems, was done. The temperature difference across a thermal capacitor was calculated by using heat conduction equation. Effect of heat load, total thickness, height and length of a thermal capacitor on the temperature difference were show. Using the results in this work, total thickness and heat height of a thermal capacitor can be determined for given heat load and given temperature difference. This work can be used practically in design for every superconduction system using a current lead.

• 한국정밀공학회지
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• 제12권9호
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• pp.126-136
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• 1995

Copper magnetron anode of a microsave-over consists of an cylindrical outer-tube and various inner-vanes. The magnetron anode is produced by the complex processes; vane blanking, pipe cutting and silver-alloy brazing of vanes. Recently, the backward extrusion process for forming vanes has been developed to avoid the complex procedures. The developed process is analyzed by using upper-bound elemental technique (UBET). In the UBET analysis, the upper-bound load, the configuration and the vane-height of final extruded product are determined by minimizing the roral power consumption with repect to chosen parameters. To verify theoretical analysis, experiments have been carried out with pure plasticine billets at room temperature, using different web-thickness and number of vanes. The theoretical predictions both for forming load and vane-height are in reasonable agreement with the experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.710-715
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• 2001

This research is presented for optimizing the coefficients of spring and damper by impact load which is applied to a trailer when the containers are loaded up trailer. The procedure utilize the condition that two containers, initial velocity of container, initial height of container and maximum of suspension stroke. The coefficients of spring and damper are calculated numerically through Newmark method uses finite difference expansions. The procedure of calculation is applied by one DOFs of mass-spring-damper system. The coefficients of spring and damper have large value as increase of height or decrease of stroke. The result of calculation is investigated and is used AGV design.

• 한국생산제조학회지
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• 제8권3호
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• pp.83-91
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• 1999

In this paper, we suggest a virtual machining system that can simulate cutting forces of ball end milling at the stage of part design. Cutting forces, here, are estimated from the machanistic model that uses the concept of specific cutting farce coefficient. To this end, we need undeformed chip thickness which is used for calculating chip load. It is derived from the Z-map data of a CAD model. That is, chip load is the height difference between the cutting tool and the workpiece at an arbitrary position. The tool contact point is referred from the cutter location data. On the other hand, the workpiece height is acquired from the Z-map model of a CAD data. From the experimental verification, we can simulate machining process effectively to the slot and the side cutting of ball end mill.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.204-208
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• 1995

Copper magnetron anode of a microwave-oven consists of an cylindrical outer-tube and various inner-vanes. The magnetron anode is produced by the complex process ; vane blanking, pipe cutting and sliver-alloy brazing of vanes. Recently, the backward extrusion process for forming vanes has been developed to avoid the complex procedures. The developed process is analyzed by using upper-bound elemental technique(UBET). In the UBET analysis, the upper-bound load, the configuration and the vane-height of final extruded product are determined by minimizing the total power consumption with respect to chosen parameters. To verify theoretical analysis, experiments have been carried out with pure plasticine billets at room temperature, using different web-thickness and number of vanes. The theoretical predictions both for forming load and vane-height are in reasonable agreement with the experimental results.

• 국제초고층학회논문집
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• 제2권4호
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• pp.323-330
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• 2013

The ASHRAE Technical Committee for Tall Buildings, TC 9.12, has defined a tall building as one whose height is greater than 300 feet (91m). Since the publication of the HVAC Design Guide for Tall Commercial Buildings in 2004, there were only about 300 buildings taller than 200 meters; this number has risen to 600 in 2010 and the prediction 765 buildings taller than 200 meters in 2012. There has also been an introduction of two new classes of tall buildings: ${\bullet}$ Mega tall, which are buildings taller than 300 m, and ${\bullet}$ Super tall, which are buildings taller than 600 m. The effect of ambient air temperature over the height of buildings, especially Mega tall and Super tall buildings. The ambient climatic conditions vary with altitude and these changes in ambient conditions can seriously affect load calculations and performance of super and mega tall buildings. This paper presents revised calculations for stack effect for Tall, Mega Tall and Super tall Buildings.