• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.913-920
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• 2005

Compared to previous in-vitro test, FE model showed reliable motion patterns. A finite element model of a 50th percentile male neck was developed to study the mechanics of whiplash injury while the rear impacts. The model was consisted of the whole cervical vertebrae including part of occipital, intervertebral discs. which were modeled using linear viscoelastic materials and posterior elements. The sliding interfaces were defined to simulate contact phenomena in facet joints and in odontoid process. All ligaments and atlanto-occipital membrane were modeled as nonlinear bar elements. Only muscle elements were not considered. Motion of each cervical vertebra was obtained from the dynamic simulation with a MADYMO model for 15 km/h $40\%$ rear end offset impacts. Soft tissue neck injury(STNI) was investigated with a developed FE model. In FE model analysis, the high stress was appeared at C3/C4 disc in offset impact. Further research is still needed in order to improve the developed neck FE model for many different crash patterns.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.4
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• pp.358-363
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• 2006

This paper demonstrates a new non-contact electronic joystick using single hall sensor which detects a horizontal vector of the magnetic field. Furthermore, in this paper, it is mathematically modeled that nonlinear characteristics between the output of hall sensor and the movement of joystick bar. The dynamic horizontal vector of magnetic flux is detected by the hall sensor while a permanent magnet is rotated with the joystick bar, which has two dimension detecting area. Using the nonlinear adjustment equations, the output signals of hall sensor have been linearized to give higher accuracy in the two dimension movement. Finally, through the real experiments, it is showed that the single hall sensor structure mechanism is superior to the dual sensor structure in sensing the two-dimensional motion without offset.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.581-582
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• 2009

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.361-364
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• 2008

This study was performed to estimate the anchorage behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Therefore, the steel bar and the steel tendon must be unified in both ends and compressive and tensile force be offset. Anchorage dimension of 6 test specimens was designed under PTI specification which defined maximum stress and deformation to estimate structural behavior. Test results showed that the stress and the deformation of anchorage were within limits if the steel bar behaviored elastically.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.97-103
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• 2013

This study proposes a path generation technique for simultaneous five-axis driving for ball bar measurement, which is equivalent to cone frustum machining as mentioned in the NAS979 standard. The technique is generalized for a 3D circular path, and it is applicable to all machine tools regardless of their structural configurations. A mathematical machine input model that consists of a five-axis machine tool, ball-bar measurement and conical path information as inputs is presented for easy NC code generation, simulation for various test conditions, and a measurement test. The movement range of rotary axes, which depends on various conditions, is mathematically analyzed based on the proposed conical path model. Moreover, the effect of the movement range on various conditions (apex angle and inclination angle, ball bar tilting acceptance angle, offset position of workpiece ball, etc.) is analyzed.

• ETRI Journal
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• v.38 no.4
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• pp.685-694
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• 2016

A surface micromachined piezoresistive pressure sensor with a novel internal substrate vacuum cavity was developed. The proposed internal substrate vacuum cavity is formed by selectively etching the silicon substrate under the sensing diaphragm. For the proposed cavity, a new fabrication process including a cavity side-wall formation, dry isotropic cavity etching, and cavity vacuum sealing was developed that is fully CMOS-compatible, low in cost, and reliable. The sensitivity of the fabricated pressure sensors is 2.80 mV/V/bar and 3.46 mV/V/bar for a rectangular and circular diaphragm, respectively, and the linearity is 0.39% and 0.16% for these two diaphragms. The temperature coefficient of the resistances of the polysilicon piezoresistor is 0.003% to 0.005% per degree of Celsius according to the sensor design. The temperature coefficient of the offset voltage at 1 atm is 0.0019 mV and 0.0051 mV per degree of Celsius for a rectangular and circular diaphragm, respectively. The measurement results demonstrate the feasibility of the proposed pressure sensor as a highly sensitive circuit-integrated pressure sensor.

• Structural Engineering and Mechanics
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• v.38 no.3
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• pp.261-281
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• 2011

A new method of formulation of a class of elements that are immune to mesh distortion effects is proposed here. The simple three-noded bar element with an offset of the internal node from the element center is employed here to demonstrate the method and the principles on which it is founded upon. Using the function space approach, the modified formulation is shown here to be superior to the conventional isoparametric version of the element since it satisfies the completeness requirement as the metric formulation, and yet it is in agreement with the best-fit paradigm in both the metric and the parametric domains. Furthermore, the element error is limited to only those that are permissible by the classical projection theorem of strains and stresses. Unlike its conventional counterpart, the modified element is thus not prone to any errors from mesh distortion. The element formulation is symmetric and thus satisfies the requirement of the conservative nature of problems associated with all self-adjoint differential operators. The present paper indicates that a proper mapping set for distortion immune elements constitutes geometric and displacement interpolations through parametric and metric shape functions respectively, with the metric components in the displacement/strain replaced by the equivalent geometric interpolation in parametric co-ordinates.

• Journal of the Korean housing association
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• v.13 no.3
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• pp.45-53
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• 2002

The purpose of this study is to examine the characteristics of unit plans in the high-rise mixed-use condominium and to provide the data fur architectural planning and design. The tools of statistical analysis are frequency, percentage, mean, cross-tab, and correlation. The results of this study are as fellows; The most frequently found shape of unit is a deformed polygon. The common rooms in housing units are dressing room, powder room, offset-kitchen, family room, passage, hallway, and foyer. The specially prepared spaces are wash room, home bar, independent porch, and garden. As to room size and area ratio in a dwelling unit, those of living room are biggest and highest irrespective of unit size. As the floor area of unit increases, does the size of each room and space but the area ratio of each room decreases. This research is made to develop an Apartment Information System. This integrated information system is to be designed to provide residents of high-rise mixed-use condominiums with convenient, economical, and safe life.

• Journal of Korea Foundry Society
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• v.22 no.4
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• pp.155-159
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• 2002

Magnesium alloys have high strength to weight ratio and are extremely attractive for applications in transport industry. Most of structural magnesium alloys are manufactured by die casting process. The tensile properties of AZ91HP magnesium alloy were investigated after die casting under various die casting conditions. After die casting by using cold chamber machine, the volume porosity of specimens was examined with density method. With the increase of the volume porosity of specimens, both the tensile strength and elongation were significantly decreased, however the 0.2% offset strength was almost independent of the amount of porosity. With the increase of crystal pressure from 500 to 900 bar during die casting, the volume porosity was decreased, which resulted in the increase of the tensile strength. The mould temperature within the range of $150{\sim}250^{\circ}C$ has not influenced the microstructure with the eutectic phase and tensile properties of specimens. The tensile strength was the highest at 90m/sec of gate speed.