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Ary Bachtiar Krishna Putra(아리바시아 크리시나 부트라),Ho Keun Kang(강호근),Dae Hee Lee(이대희),Soo Whan Ahn(안수환) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Numerical predictions and experiment of a hydrodynamic and thermally developed turbulent flow through square channels with one or two ribbed walls were performed to determine the pressure drop and heat transfer. The CFX software package was used for the computations. The rough wall had 45°-inclined square ribs. All four walls in the channel were heated, and a uniform heat flux was maintained on the entire inner heat transfer channel area. Experimental data were also obtained for four Reynolds numbers ranging from 7,600 to 24,900, a pitch-to-rib-height ratio of 8.0, and a rib-height-to-channel hydraulic diameter ratio of 0.0667. The numerical results were in agreement with the experimental data and showed that the values of the local heat transfer coefficient and friction factor in a square channel with two ribbed walls were greater than those with one ribbed wall.
Heat Transfer and Friction Behaviour in a Channel with an Inclined Perforated Baffle
Ary Bachtiar Krishna Putra,Soo Whan Ahn 대한설비공학회 2008 International Journal Of Air-Conditioning and Refr Vol.16 No.2
The effects of the inclined perforated baffles on the distributions of the local heat transfer coefficients and friction factors for air flows in a rectangular channel were determined for Reynolds numbers from 23,000 to 57,000. Four different types of the baffle are used. The inclined baffles have the width of 19.8 ㎝, the square diamond type hole having one side length of 2.55 ㎝, and the inclination angle of 5°, whereas the corresponding channel width-to-height ratio was 4.95. Results show that the heat transfer and friction factor depend significantly on the number of baffle holes and Reynolds number. The friction factor decreases with increasing Reynolds number and the number of holes on the baffle, and the heat transfer performance of baffle type Ⅱ (3 hole baffle) has the best value.
Heat Transfer and Friction Behaviour in a Channel with Inclined Perforated Baffle
Ary Bachtiar Krishna Putra(아리바시아 크리시나 부트라),Soo Whan Ahn(안수환) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.11
This experimental study investigates the local heat transfer enhancement characteristics and the associated frictional head loss in a rectangular channel with a single inclined baffle. Four different types of the baffle are used. The inclined baffles have the width of 19.8 em, the square diamond of 2.55 ㎝ × 2.55 ㎝, and the inclination angle of 5˚. Reynolds number is varied between 23,000 and 57,000. Results show that the heat transfer and friction factor depend significantly on the number of baffle holes and Reynolds number. The friction factor decreases with increasing Reynolds number and the number of holes on the baffle. It is found that the heat transfer performance of baffle type Ⅱ (3 hole baffle) has the best values.
THE ACTIVE REAR STEERING FOR HANDLING YAWING MOTION BASED ON CONTROL SIDE SLIP
Ary Subagia,H.Y. Kang,S.M.Yang 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The directional stability becomes main case in handling vehicle during turn round with high speed. Since turning is the critical motion related to make a vehicle be unstable, steering system is an important to control vehicle’s trajectory. Generally, the vehicle used two wheel steering system. The two wheels steering in high speed turning can give effect unstable motion. It is caused by yawing effect in the centre of gravity of a vehicle. The yawing motion can influence under-steer in low speed and over-steer in high speed. This study is used to control side slip and turning direction of vehicle in low and high speed. The side slip angle (β) is formed by centre of gravity along the longitudinal axis of a vehicle. This angle is influences the yawing motion that make vehicle unstable. The purpose of this study is to control a yawing motion to improve the stability of vehicle on directional turning. It can move the rear wheel to opposite or same direction component to front wheel steering. The rear wheel steering is using a rack and pinion mechanism driven by DC motor. The simulation is determining the rear wheel angle using the control side slip to handle the yawing motion close to yawing motion Ackermann. The vehicle speeds are 20, 40, 60, 80, and 100 km/h in this simulation and the front wheel angle (δf) 5, 15, 25 and 35 deg. Active rear steering can be controlling the real yawing motion always very close to the yawing Ackermann hence vehicle can be made stable in the line. In addition, side slip (β) is an effective control to trajectory of under-steer and over-steer because the tires slip angle is low.
Fluid Flow Resistance in a Channel with Wire-mesh Baffles
Ary Bachtiar Krishna Putra(아리바시아 크리시나 부트라),Soo Whan Ahn(안수환) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.10
An experimental investigation was conducted to examine the fluid flow resistance in rectangular channel with two inclined wire mesh baffles. Two different types of wire meshes, namely dutch weave and plain weave, were used as baffle materials in this experiment. Three kinds of baffles with different mesh specifications were made up of dutch weave type and four different kinds of baffles were made up of plain weave type. The stainless steel wire mesh baffles were mounted on bottom wall with varied angle of baffle inclination. Reynolds numbers were varied from 23,000 to 57,000. Results show that the number of mesh of the baffle plate plays an important role on friction factor behavior. It is found that baffle plate with the most number of mesh (type SA) has the highest fluid flow resistance.
Ary, Moustapha Ibrahim,Kang, Thomas H.K. Korea Concrete Institute 2012 International Journal of Concrete Structures and M Vol.6 No.1
Fiber-Reinforced Polymers (FRP) are used to enhance the behavior of structural components in either shear or flexure. The research conducted in this paper was mainly focused on the shear-strengthening of reinforced and prestressed concrete beams using FRP. The main objective of the research was to identify the parameters affecting the shear capacity provided by FRP and evaluate the accuracy of analytical models. A review of prior experimental data showed that the available analytical models used to estimate the added shear capacity of FRP struggle to provide a unified design equation that can predict accurately the shear contribution of externally applied FRP. In this study, the ACI 440.2R-$08^1$ model and the model developed by Triantafillou and Antonopoulos$^2$ were compared with the prior experimental data. Both analytical models failed to provide a satisfactory prediction of the FRP shear capacity. This study provides insights into potential reasons for the unsatisfactory prediction.
Heat Transfer Enhancement in a Channel with Wire-mesh Baffles
Ary Bachtiar Krishna Putra(아리바시아 크리시나 부트라),Soo Whan Ahn(안수환) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.10
The heat transfer characteristics of flow through two inclined wire-mesh baffles in a rectangular channel were investigated experimentally with varying the mesh number of wire screens and inclination angle of the baffles. Two different types of wire meshes, namely dutch weave and plain weave, were used in this experiment. Three kinds of baffle plates with different mesh specifications in the dutch weave and four different kinds in the plain weave were manufactured. Baffles were mounted on bottom wall with varied angle of inclination. Reynolds number was varied from 23,000 to 57,000. It is found that the placement of inclined wire-mesh baffles in the channel affects the heat transfer characteristics by combining both jet impingement and flow disturbance. The wire screen modified the flow structure leading to a change in the heat transfer characteristics. The results show that the baffle plate with the most number of mesh (type SA) has the highest heat transfer rate.
Weighted Fast Adaptation Prior on Meta-Learning
Tintrim Dwi Ary Widhianingsih,강대기 한국인터넷방송통신학회 2019 Journal of Advanced Smart Convergence Vol.8 No.4
Along with the deeper architecture in the deep learning approaches, the need for the data becomes very big. In the real problem, to get huge data in some disciplines is very costly. Therefore, learning on limited data in the recent years turns to be a very appealing area. Meta-learning offers a new perspective to learn a model with this limitation. A state-of-the-art model that is made using a meta-learning framework, Meta-SGD, is proposed with a key idea of learning a hyperparameter or a learning rate of the fast adaptation stage in the outer update. However, this learning rate usually is set to be very small. In consequence, the objective function of SGD will give a little improvement to our weight parameters. In other words, the prior is being a key value of getting a good adaptation. As a goal of meta-learning approaches, learning using a single gradient step in the inner update may lead to a bad performance. Especially if the prior that we use is far from the expected one, or it works in the opposite way that it is very effective to adapt the model. By this reason, we propose to add a weight term to decrease, or increase in some conditions, the effect of this prior. The experiment on fewshot learning shows that emphasizing or weakening the prior can give better performance than using its original value.
Heat Transfer and Friction Behaviour in a Channel with an Inclined Perforated Baffle
Krishna Putra, Ary Bachtiar,Ahn, Soo-Whan The Society of Air-Conditioning and Refrigerating 2008 International Journal Of Air-Conditioning and Refr Vol.16 No.2
The effects of the inclined perforated baffles on the distributions of the local heat transfer coefficients and friction factors for air flows in a rectangular channel were determined for Reynolds numbers from 23,000 to 57,000. Four different types of the baffle are used. The inclined baffles have the width of 19.8cm, the square diamond type hole having one side length of 2.55cm, and the inclination angle of $5^{\circ}$, whereas the corresponding channel width-to-height ratio was 4.95. Results show that the heat transfer and friction factor depend significantly on the number of baffle holes and Reynolds number. The friction factor decreases with increasing Reynolds number and the number of holes on the baffle, and the heat transfer performance of baffle type II (3 hole baffle) has the best value.