• Journal of the Korean Society for Heat Treatment
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• v.20 no.1
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• pp.11-16
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• 2007

The fatigue properties of Ti-Ni shape memory alloy wires were investigated. In Ni-rich Ti-Ni shape memory alloys, $Ti_3Ni_4$ precipitates formed by aging treatments are believed to vary the shape memory and mechanical properties. In this study, the effect of aging temperature and aging time on shape memory properties and fatigue life were investigated using Ti-50.9 at% Ni alloy wires. The specimens were solution-treated at 1073 K for 3.6 ks followed by aging at 573 K, 673 K and 773 K for periods between 3.6 ks and 3600 ks. It was found that the fatigue life under a constant stress decreased with increasing aging temperature. When the specimens were aged at 573 K for periods between 36 ks and 360 ks, superior shape memory and fatigue properties were obtained. The fatigue life also decreased when the test temperature and strain amplitude increased. It was concluded that the fatigue life exhibited a linear relationship with the critical stress for slip.

• Journal of the Korea Safety Management & Science
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• v.16 no.4
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• pp.63-69
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• 2014

The large-sized, complex, and multi-storied construction industry caused the increasing construction amount together with insufficient skilled workers to increase the probability of occurring accident, resulting in the most construction accidents next to manufacturing industry. Death accidents have risen to serious level, compared construction industry with manufacturing industry along the numbers of workers. Due to the main feature of one-time industry receiving orders, open-air dispersed production activity and the long-complex production process, the continuous efforts to prevent and manage safety accidents were made but the results were of no effect. They didn't deeply analyze the falling accidents that consist of half death accidents in construction industry. This study has classified in detail Missteps, Slip, Trip, Unstability and the others on the basis of gait characteristics, occurrence types, frequency and intensity of death accidents. This study suggested the effective methods on the construction safety management according to the causes of falling accidents. This study will be expect to be used as the basic data in the procedure and the program of safety management.

• Journal of Powder Materials
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• v.19 no.3
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• pp.226-231
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• 2012

In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 ${\mu}m$ at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.967-976
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• 2016

This paper presents a 3D carrier-smoothed GNSS/DR (Global Navigation Satellite System/Dead Reckoning) integrated system for precise ground-vehicle trajectory estimation. For precise DR navigation on sloping roads, the AHRS (Attitude Heading Reference System) methodology is employed. By combining the integrated carrier phase of GNSS and DR sensor measurements, a vehicle trajectory with an accuracy of less than 20cm is obtained even when cycle slip or change of visibility occur. In order to supplement the weak GNSS environment with DR successfully, the DR sensor is precisely compensated for using GNSS Doppler measurements when GNSS visibility is good. By integrating a multi-GNSS receiver with low-cost IMU, a precise 3D navigation system for land vehicles is proposed in this paper. For real-time implementation, a decoupled Kalman filter is employed in the integrated system. Through field experiments, the performance of the proposed system is verified in various road environments, including sloping roads, good-visibility areas, high multi-path areas, and under-ground parking areas.

• Journal of the Korean Home Economics Association
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• v.23 no.2
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• pp.21-28
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• 1985

This study is to furnish basic data for making appropriate and comfortable pillow. This research was carried out in reference to 260 males and 339 females whose ages are above 20 in Daegu, from Aug. 1. 1984 to Oct. 15. 1984. RESULTS : 1. In the shape of pillow, the western style is more used than Korean style. 2. The mean size, 50.9$\times$29.1 cm, of pillows is too small for the preceding studies of which, the most comfortable size is 65$\times$45 cm. 3. The mean height, 10.1 cm, of pillows is much higher than the appropriate height, 5.0$\pm$1cm, in the preceding studies. 4. The mean weight, 1587g, of pillows seems to be too heavy. 5. The most used stuffing of pillows is fascicular fibers, the second chaff, the third husks of buckweat, the fourth sponge, and then feather, 6. Considering of pillow-slip material, 68.8% of pillows consist o synthetic fiber.7. The mean compression rate 14.5% is much lower than the comfortable compression rate 40~50 in the preceding studies. 8. Considering the way obtainment, ready-made articles are more used than the domestic-made articles. 9. The same pillows are used throughout for seasons, and that seems not to be appropriate because climate is changeable according to seasons in our country. 10. The sterilization by sunlight is rarely carried out and that is unhygienic because pillows used to absord much of sweat during using time.

• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.45-55
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• 2018

The arched stone bridge has been continuously deteriorated and damaged by the weathering and corrosion over time, and also natural disaster such as earthquake has added the damage. However, masonry stone bridge has the behavior characteristics as discontinuum structure and is very vulnerable to lateral load such as earthquake. So, it is necessary to analyze the dynamic behavior characteristics according to various design variables of arched stone bridge under seismic loads. To this end, the arched stone bridge can be classified according to arch types, and then the discrete element method is applied for the structural modelling and analysis. In addition, seismic loads according to return periods are generated and the dynamic analysis considering the discontinuity characteristics is carried out. Finally, the dynamic behavior characteristics are evaluated through the structural safety estimation for slip condition.

• Earthquakes and Structures
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• v.7 no.5
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• pp.609-626
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• 2014

The capabilities of a high-resolution Digital Image Correlation (DIC) system are presented within the context of deformation measurements of full-scale concrete columns tested under reversed cyclic loading. The system was developed to have very high-resolution such that material strains on the order of the cracking stain of concrete could be measured on the surface of full-scale structural members. The high-resolution DIC system allows the measurement of a wide range of deformations and strains that could only be inferred or assumed previously. The DIC system is able to resolve the full profiles of member curvatures, rotations, plasticity spread, shear deformations, and bar-slip induced rotations. The system allows for automatic and objective measurement of crack widths and other damage indices that are indicative of cumulated damage and required repair time and cost. DIC damage measures contrast prevailing proxy damage indices based on member force-deformation data and subjective damage measures obtained using visual inspection. Data derived from high-resolution DIC systems is shown to be of great use in advancing the state of behavioral knowledge, calibrating behavioral and analytical models, and improving simulation accuracy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.733-743
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• 2000

We solve the integral representation of the Navier-Stokes equations in a lagrangian view by tracking the particles, which have vortex strengths. We simulate the unsteady viscous flow around an impulsively started cylinder using the vortex particle method. Particles are advanced via the Biot-Savart law for a lagrangian evolution of particles. The particle strength is modified based on the scheme of particle strength exchange. The solid boundary satisfies the no-slip boundary condition by the vorticity generation algorithm. We newly modify the diffusion scheme and the boundary condition for simulating an unsteady flow efficiently. To save the computation time, we propose the mixed scheme of particle strength exchange and core expansion. We also use a lot of panels to ignore the curvature of the cylinder, and not to solve the evaluation of the surface density. Results are compared to those from other theoretical and experimental works.

• Wind and Structures
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• v.4 no.4
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• pp.299-314
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• 2001

A study of wind effects was carried out at the Boundary Layer Wind Tunnel Laboratory (BLWTL) for the projected 558-m high free-standing telecommunication and observation tower for Jakarta, Indonesia. The objectives were to assist the designers with various aspects of wind action, including the overall structural loads and responses of the Tower shaft and the antenna superstructure, the local wind pressures on components of the exterior envelope, and winds in pedestrian areas. The designers of the Tower are the East China Architectural Design Institute (ECADI) and PT Menara Jakarta, Indonesia. Unfortunately, the project is halted due to the financial uncertainties in Indonesia. At the time of the stoppage, pile driving had been completed and slip forming of the concrete shaft of the Tower had begun. When completed, the Tower will exceed the height of the CN-Tower in Toronto, Canada by some 5 m.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.516-527
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• 2011

This paper considers a numerical analysis of ship maneuvering performance in the high amplitude incident waves by adopting linear and nonlinear ship motion analysis. A time-domain ship motion program is developed to solve the wave-body interaction problem with the ship slip speed and rotation, and it is coupled with a modular type 4-DOF maneuvering problem. Nonlinear Froude-Krylov and restoring forces are included to consider weakly nonlinear ship motion. The developed method is applied to observe the nonlinear ship motion and planar trajectories in maneuvering test in the presence of incident waves. The comparisons are made for S-175 containership with existing experimental data. The nonlinear computation results show a fair agreement of overall tendency in maneuvering performance. In addition, maneuvering performances with respect to wave slope is predicted and reasonable results are observed.