• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.126-131
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• 2012

Tire force is one of important parameters which determine vehicle dynamics. However, it is hard to measure tire force directly through sensors. Not only the sensor is expensive but also installation of sensors on harsh environments is difficult. Therefore, estimation algorithms based on vehicle dynamic models are introduced to estimate the tire forces indirectly. In this paper, an estimation system for estimating lateral force and states is suggested. The state-space equation is constructed based on the 3-DOF bicycle model. Extended Kalman Filter, Unscented Kalman Filter and Ensemble Kalman Filter are used for estimating states on the nonlinear system. Performance of each algorithm is evaluated in terms of RMSE (Root Mean Square Error) and maximum error.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.605-610
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• 2007

In this paper a dynamic behavior(natural frequency) of a cracked cantilever beam subjected to follower force is presented. In addition, an analysis of the flutter and buckling instability of a cracked cantilever beam subjected to a follower compressive load is presented. Based on the Euler-Bernoulli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter instability based on the variation of the first two resonant frequencies of the beam. Besides, the effect of the crack's intensity and location on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Computational Structural Engineering
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• v.8 no.4
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• pp.159-171
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• 1995

The parameters describing a complete hysteresis loop include pinch force, drift offset, effective stiffness, unloading and reloading trangential stiffness. Analytical equations proposed to quantify the nonlinear, inelastic behavior of reinforced shear walls can be used to predict these parameters as a function of axial load and drift ratio. For example, drift offset, effective stiffness, and first and second unloading and reloading tangential stiffness are calculated using equations obtained from test data for a desired drift ratio or ductility level. Pinch force can also be estimated for a given drift ratio and axial load. The effective virgin stiffness at the first yield and its post yield reduction can be estimated. The load deflection response of flexural reinforced concrete shear walls can now be estimated based on the effective wall stiffness that is a function of axial force and drift ratio.

• Journal of Technology Innovation
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• v.16 no.2
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• pp.201-223
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• 2008

This paper studies the supply and demand of Industrial Technology Labor-force(ITL) and analyzes the determinate of ITL shortage in Korean manufacturing. We classified the industry into four categories-high technology industries, medium-high technology industries, medium-low technology industries and low technology industries-based on its R&D intensity like OECD. For the empirical analyses we use a survey data collected from 5,703 enterprises. The key findings are as follows: Firstly, a large majority of ITL is engaged in more technology-intensive industries but the categories that are exposed to more serious labor-force shortage problem are medium-high technology industries and low technology industries. Secondly, in the terms of supply factor, the ITL shortage problems are mainly due to the avoidance of ITL jobs. And the demand point, the reason is that the most of ITL are not researchers but production managers. Thirdly, the cause of imbalance between supply and demand of ITL are different by the technological categories. For example, in the high technology industries, the supply factors, such as average wage and turnover rate played more important role in the imbalance. But in the low technology industries the demand factors, such as per capita sales and the ratio of ITL in all employees were relatively much more important. Based on the findings, we discovered some political meanings such as the necessity to plan various policies to resolve the shortage problem of ITL according to the technological categories, etc.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.555-560
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• 2014

This paper presents a microparticle separator using a spiral microchannel. A particle separator based on the dean vortex was designed, fabricated, and characterized. Two different spiral microchannels were fabricated. Width and initial radius of rotation in the spiral microchannel were fixed to $300{\mu}m$ and 1.75 mm, respectively. Two different depths of the microchannels were designed at $50{\mu}m$ and $80{\mu}m$. In this experimental study, the equilibrium position of microparticles was monitored by using fluorescent microbeads. In the case of a low dean number (<1.0), lift force and dean drag force were similar, indicating that microbeads were distributed to almost all areas across microchannels. However, in the case of a high dean number (>1.0), dean drag force rather than lift force was dominant, indicating that microbeads moved toward the inner wall of the spiral microchannel.

• Transactions of Materials Processing
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• v.24 no.2
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• pp.77-82
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• 2015

By investigating the practical use of trim punch configurations for shearing of vehicle panels, the current study first reviews the shearing angle as part of the shearing die design. Based on this review, four different types of trim punch shapes (i.e., horizontal, slope, convex, and concave type) and shearing angles(i.e., 0.76°, 1.53°, 2.29°, 3.05°, 3.81°) were investigated. In order to conduct shearing experiments, four types of trim punch dies were made. The four trim punch dies were tested under various conditions. The experiments used the four trim punch shapes and the five shearing angles. The shearing force varied by shape and decreased from horizontal, slope, convex, to concave for the same shearing angle. The magnitude of shearing force showed differences between the convex and the concave shapes due to the influence of constrained shearing versus free shearing. The test results showed that compared to the horizontal trim punch shearing force, the decrease of the slope, convex, and concave shearing forces were 22.6% to 60.4%. Based on the results, a pad pressure of over 30% is suggested when designing a shearing die.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1217-1238
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• 2016

Mega composite structure systems have been widely used in high rise buildings in China. Compared to other structures, this type of composite structure systems has a larger cross-section with less weight. Concrete filled steel tubular (CFST) laced column to box-beam connections are gaining popularity, in particular for the mega composite structure system in high rise buildings. To enable a better understanding of the destruction characteristics and aseismic performance of these connections, three different connection types of specimens including single-limb bracing, cross bracing and diaphragms for core area of connections were tested under low cyclic and reciprocating loading. Hysteresis curves and skeleton curves were obtained from cyclic loading tests under axial loading. Based on these tested curves, a new trilinear hysteretic restoring force model considering rigidity degradation is proposed for CFST laced column to box-beam connections in a mega composite structure system, including a trilinear skeleton model based on calculation, law of stiffness degradation and hysteresis rules. The trilinear hysteretic restoring force model is compared with the experimental results. The experimental data shows that the new hysteretic restoring force model tallies with the test curves well and can be referenced for elastic-plastic seismic analysis of CFST laced column to composite box-beam connection in a mega composite structure system.

• Journal of Aerospace System Engineering
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• v.15 no.6
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• pp.42-49
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• 2021

To develop a high-resolution electro-optical/infrared (EO/IR) payload to be mounted on a high-speed and performance fighter aircraft in an external POD for acquiring daytime and nighttime image information on tactical targets, simulations, including flight environments and maneuvers, should be performed. Such simulations are pertinent to predicting the performance of several variables, such as aerodynamic force and inertia load acting on the payload. This paper describes the development of a flight data acquisition and analysis system based on flight simulation software (SW) for mission simulation of super-maneuverability fighter equipped with EO/IR payload. The effectiveness of the system is verified through comparison with actual flight data. The proposed flight data acquisition and analysis system based on FlightGear can be used as an M&S tool for system performance analysis in the development of the EO/IR payload.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1495-1507
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• 2022

The improvement of thermal-hydraulic analysis techniques is essential to ensure the safety and reliability of nuclear power plants. The one-dimensional two-fluid model has been adopted in state-of-the-art thermal-hydraulic system codes. Current constitutive equations used in the system codes reach a mature level. Some exceptions are the partition method of wall friction in the momentum equation of the two-fluid model and the interfacial drag force model for a horizontal two-phase flow. This study is focused on deriving the partition method of wall friction in the momentum equation of the two-fluid model and modeling the interfacial drag force model for a horizontal bubbly flow. The one-dimensional momentum equation in the two-fluid model is derived from the local momentum equation. The derived one-dimensional momentum equation demonstrates that total wall friction should be apportioned to gas and liquid phases based on the phasic volume fraction, which is the same as that used in the SPACE code. The constitutive equations for the interfacial drag force are also identified. Based on the assessments, the Rassame-Hibiki correlation, Hibiki-Ishii correlation, Ishii-Zuber correlation, and Rassame-Hibiki correlation are recommended for computing the distribution parameter, interfacial area concentration, drag coefficient, and relative velocity covariance of a horizontal bubbly flow, respectively.

• Steel and Composite Structures
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• v.43 no.2
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• pp.229-240
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• 2022

The main objective of this work is presenting a mathematical model for the concrete slab with fiber reinforced polymer (FRP) layer under the impact load. Impacts are assumed to occur normally over the top slab and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The structure is assumed viscoelastic based on Kelvin-Voigt model. Based on the sinusoidal shear deformation theory (SSDT), energy method and Hamilton's principle, the motion equations are derived. Applying DQM, the dynamic deflection and contact force of the structure is calculated numerically so that the effects of mass, velocity and height of impactor, boundary conditions, FRP layer, structural damping and geometrical parameters of structure are shown on the dynamic deflection and contact force of system. Results show that considering structural damping leads to lower dynamic deflection and contact force. In addition, increasing the impact velocity of impactor yields to increases in the maximum contact force and deflection while the contact duration is decreased. The result shows that the contact force and the central deflection of the structure decreases and the contact time decreases with assuming FRP layer.