• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.52-58
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• 1998

The spray characteristics of air-assisted fuel injection and its effects on the engine combustion was investigated in this study. The atomization characteristics of a Bosch fuel injector inserted into the air-assist adapter were measured using particle motion analysis system. Droplet size decreased with air supplied and fine spray with below $60\mu\textrm{m}$ of SMD was acquired under the conditions of air-assist pressure over 0.5bar. The lean combustion performance of a 1.8L DOHC engine equipped with air-assist adapters was tested on the dynamometer. When the assistant air pressure is 1.0bar, lean limit recorded the highest value, and CO, HC emissions were decreased at the pressure over 1.0bar.

• Advances in concrete construction
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• v.1 no.2
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• pp.137-149
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• 2013

The first part of this two-part paper discussed some basic considerations on bond strength and its effect on strain localization and plastic deformation capacity of cracked structural concrete, and analytically evaluated the impacts of the hardening behavior of reinforcing steel and concrete quality on the basis of the Tension Chord Model. This second part assesses the impacts of the most frequently encountered construction details of existing concrete structures which may not satisfy current design code requirements: bar ribbing, bar spacing, and concrete cover thickness. It further evaluates the impacts of the additional structure-specific features bar diameter and crack spacing. It concludes with some considerations on the application of the findings in practice and an outlook on future research needs.

• Structural Engineering and Mechanics
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• v.23 no.4
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• pp.369-386
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• 2006

The influence of reinforcement buckling on the flexural response of reinforced concrete members is studied. The stress-strain response of compression reinforcement is determined computationally using a large-strain finite element model for bars of varied diameter, length, and initial eccentricity, and a mathematical expression is fitted to the simulation results. This relationship is used to represent the response of bars in compression in a moment-curvature analysis of a reinforced concrete cross section. The compression bar may carry more or less force than a tension bar at a corresponding strain, depending on the relative influence of Poisson effects and bar slenderness. Several cross-section analyses indicate that, for the distances between stirrups prescribed in modern concrete codes, the influence of inelastic buckling of the longitudinal reinforcement on the monotonic moment capacity is very small and can be neglected in many circumstances.

• Journal of ILASS-Korea
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• v.1 no.4
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• pp.32-39
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• 1996

Fuel spray in the MPI gasoline injector and its atomization characteristics are investigated with both macroscopic and microscopic visualization systems. The Bosch injector is inserted into an air-assist spray adapter which is designed to be fabricated and assembled easily. particle motion analysis system is used to measure the SMD of injector, where the assistant air pressure is varied from 0.0 to 1.5bar with fuel pressure 2.8bar. Droplet size decreased with higher air pressure and fine fuel spray with below $60{\mu}m$ of SMD is acquired at the assistant air pressure over 0.5bar.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.39-45
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• 2012

In this paper, process conditions are investigated for elimination of the grain coarsening and improved material flow during forging process by both of experiments and FEM analysis. Particular interest has been given to understand role of preform shape on the grain coarsening behavior and magnitude of the hammer forging load. As the results of FEM simulation by using DEFORM-3D, the simulated forging loads were 2,200ton in the case of a machined bar which is machined from 65mm to 60mm diameter, and below 1,900ton in the case of machined preform, respectively. The use of preform has been beneficial for reduction of the forging load and elimination of the grain coarsening. However, in the case of as received bar and the round bar, which was machined to 2.5mm thickness in surface layer, some degree of local grain coarsening behavior has been observed. The optimized preform shape could be properly designed by applying the FEM simulation.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.508-513
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• 1996

The purpose of this paper, having chosen the connection method, filled by High-strength mortar, in conncetion of PC member, is to study the mechanical behaviour and practical usage of the method. The paper estimates the connection ability of Reinforced-bar, that is, Sleeve considering the effect of Reinforced-bar's dimeter. Sleeve's length and diameter in the structural behaviour of mortar-filled connection, therefore the behaviour of Splice-Sleeve exists in concrete practically. This paper discusses the effect of the concrete in Splice-Sleeve. Also, to estimate structural behaviour in a practical wall panel, the upper and bottom wall panels are produced and the behaviour of Splice-Sleeve is discussed. And then Vertical Tie Bar being designed by using Precast method, this paper presents the various application and the practicable method using Splice-Sleeve.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.3
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• pp.98-104
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• 2009

The objective of this paper is to investigate the effect of factors on the dynamic stiffness variation of boring bar. The experiment was carried out by Taguchi Method and Orthogonal array table. The results indicate that overhang was found out to be dominant factor with 95% confident intervals and feed rate and depth of cut were insignificant. In addition, analysis of loss function shows that loss value increased sharply from 3D to 4D(D is a shank diameter). Consequently, there is critical point which changes property of dynamic stiffness.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.853-859
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• 2008

As a new system of steel pipe pile cap reinforcement, the application of perforated flat bar bolted to the steel pipe pile head was suggested for the improvement of structural performance of footing structure. This study investigates the structural characteristics of perforated flat bar shear connectors according to shape and diameter of hole, number of rebars passing through the hole and the depth of settlement. The result shows several requirements to ensure sufficient pull-out resistance and ductility such as that the hole diameter excluding diameter of rebar should exceed the size of aggregates; the hole should be perforated with diameter as the half of plate height; and the adequate depth of settlement should be ensured for the optimal performance.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.465-471
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• 2015

This study proposed V-shaped tie bar method as an alternative of internal cross-tie for reinforced concrete columns in order to enhance the constructability and confinement effectiveness of the lateral tie bars. A total of 35 pull-out specimens were prepared with the parameters of concrete compressive strength and bending angle and embedment length of the V-shaped bar to examine the bond stress-slip relationship of the V-shaped tie bar. The bond strength of the V-shaped tie bars with the bending angle not exceeding $60^{\circ}$ was higher than the predictions obtained from the equations of CEB-FIP provision. Considering the constructability and bond behavior of the V-shpaed tie bar, the bending angle and embedment length of such bar can be optimally recommended as $45^{\circ}$ and 6db, respectively, where db is the diameter of the tie bar.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.6
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• pp.506-513
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• 1992

Several experiments were conducted to classify the variablity of field emergence rate among the major soybean(Glycine max. (L) Merril) cultivars. The results obtained are summerized as follows. The speed of emergence is highly correlated with diameter of hypocotyl. As increasing the seed depth, emergence percentage of small seed is higher than that of large seed, and emergence of large seed at seeding depth 5cm is higher than that of small seed, at seeding depth 7cm. Emergence percentage in clay, clay : sand :(1 : 1), sand : vermiculite(1 : 1), clay : (1 : 1), sand, vermiculite are 65, 80, 84, 89, 90 and 91%, respectively. As the soil water potential was decreasing from-0.1 to-0.5 bar, emergence percentage is increasing. The highest emergence percentage was shown at -0.5 bar, and the lowest emergence percentage at -0.7 bar.