• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.30-37
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• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m／min. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.4
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• pp.353-358
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• 1994

Grain yields of errect-leaved corn hybrids were reported to be increased as planting density(PD) increased compared to those of horizontal leaf type hybrids. This trial was conducted to investigate the difference between errect and horizontal-leaved hybrids in response to different PD. Grain yields of both type hybrids were decreased at the highest PD, however, that of horizontal-leaved hybrid, Ga209 ${\times}$ Ki14A, was decreased more than errect-leaved hybrids which indicated varietal difference in response to PD. Responses to PD for days to tasseling, plant height, ear height, and leaf angle were not significant, also, PD ${\times}$ hybrid interactions were not observed. Yield components were decreased as PD increased and there were no PD ${\times}$ hybrid interactions for these characters. Leaf angle was negatively correlated with grain yield and yield components except for kernel weight.

• Journal of Korean Society of Steel Construction
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• v.13 no.6
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• pp.651-659
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• 2001

The main purpose of this paper is to present an analytical method for free vibration of stepped horizontally curved members on two-parameter elastic foundation. The ordinary differential equations governing the free vibration of such beams are derived as non-dimensional forms including the effects of rotatory inertia and shear deformation. The governing equations are solved numerically for the circular, parabolic, sinusoidal and elliptic curved beams with hinged-hinged, hinged-clamped and clamped-clamped end constraints. As the numerical results, the lowest four natural frequency parameters are presented as the functions of various non-dimensional system parameters. Also the typical mode shapes are presented.

• Journal of the Korean Solar Energy Society
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• v.35 no.1
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• pp.81-87
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• 2015

Recently, in order to prevent increasing energy usages in the international community, many countries have attempted to develop the innovative renewable energy systems. Among the renewable energy systems, Ground source heat pump(GSHP) system which supply the heating, cooling and hot water in the building has been attracted by its stability of heat production and high efficiency. However, the initial drilling costs become very expensive and the construction period takes longer the other systems, because GSHP system needs more than 100 m depth drilling. In this study, in order to reduce initial costs of the GSHP, the building integrated geothermal system using the horizontal heat exchanger was developed. The heating and cooling load in the standard housing model was calculated by a simulation and the system design capacity in the high-rise apartment was decided by the total load. Based on the system design capacity, the high-rise apartments were applied to a BIGS and vertical GSHP system and there are analyzed about initial costs. In the result, the initial cost of BIGS could reduce 24% of the initial cost of the vertical GSHP system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.249-257
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• 2012

The reinforced earth method is financially viable. Furthermore, it overcomes environmental limitations and is therefore employed in retaining walls, slopes, foundations, roads, embankments, and other structures. However, in some cases, reinforced retaining walls are not strong enough in the curved sections and can collapse. Such mishaps are believed to occur because of an unsatisfactory analysis of the curved sections of a reinforced retaining wall. Accordingly, with the aim of investigating the workability and structural safety of curved sections of various types, this study investigates the differences in the estimated horizontal displacements of curved sections of various types and subsequently uses this information to study and analyze preliminary data so that appropriate measures can be taken to resolve alignment issues. The results of an experiment reveal that when a load is applied to curved sections of both concave and convex types, the largest horizontal displacement occurs at the center of the section. In the concave form, the earth pressure force is directed inward, whereas in the convex form, this force is directed outward. As a result, the horizontal displacement in convex forms is larger than that in concave forms. Convex reinforced earth structures are subjected to earth pressures as well as lateral earth pressure, therefore horizontal displacements in convex curved sections is larger than that of concave curved sections.

• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.119-125
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• 2005

The horizontal reflectometer, which uses a neutron beam in the reactor, provides scientists a set of unique tools offering destruction-free investigation of biological membranes in the native-like environments in nano-meter scale. As an intial stage for the development of the first Korean neutron reflectometer with a horizontal sample geometry, we performed the instrumental simulation using MCSTAS, Monte Carlo Simulations of Triple Axis Spectrometers for neutron ray-tracing simulation. The results indicated that modeling of the overall instrument geometry based on the thermal neutron source with a wavelength of 2.55 $2.5{\AA}$ at HANARO was successfully performed, and further the optimization of the individual components of the instrument, including the collimator, monochromators, filter and supermirror has been made.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.146-148
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• 2001

LIGBT의 캐소드에 전류 제한 능력이 있는 LDMOS를 직렬 연결하여 LIGBT의 전류가 기생 사이리스터가 동작하게 되는 지점까지 증가하는 것을 억제함으로써 기생 사이리스터의 동작으로 인한 LIGBT의 불안정 동작 효과적으로 방지하는 새로운 구조의 LIGBT를 제안한다. 또한 턴-오프 시에 LDMOS의 전류 차단 능력에 의해 전류가 기존의 소자에 비해 빠르게 감소하는 효과로 인해 빠른 스위칭 속도를 얻을 수 있었다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.221-226
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• 2002

This paper presents the thermal characteristics analysis of a high-speed HMC(horizontal machining center) with spindle speed of 30,000rpm and fried rate of 40m/min. The spindle speed is achieved by introducing angular contact ball bearings, oil-jet lubrication method, oil jacket cooling method, and so on. The spindle system is a motor-separated type composed of the main spindle and sub-spindle which are mechanically connected by the flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front to and rear bearings of the sub-spindle. The thermal analysis model of HMC is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution and heat flow under the various testing conditions related to spindle speed and feed rate.

• Journal of Sensor Science and Technology
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• v.5 no.2
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• pp.9-14
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• 1996

We have fabricated the vacuum magnetic sensor with a lateral field emitter arrays constructed on n-Si substrate, and investigated its magnetic characteristics. The device consists of 100 field-emitter tips with a $10{\mu}m$ pitch, gate, and split-anodes which are laterally structured. The electron-emission characteristics from the emitter followed the Fowler-Nordheim tunnelling theory. The sensor has good linear characteristics and high sensitivity of 825 %/T.

• New & Renewable Energy
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• v.10 no.3
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• pp.6-13
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• 2014

This paper presents a computational study of thermal performance and construction cost of horizontal ground heat exchangers (GHEs). GLD (ground loop design) simulations of various type of GHEs were carried out. Construction costs were also calculated based on standard estimating, and compared with vertical type GHE system. Besides that, dummy regression analysis was conducted to study the influence of design parameters on the simulation results in horizontal ground heat exchanger system.