• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.22-28
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• 1999

Small amplitude in-phase oscillations of multi-cylinders are considered both numerically and experimentally. Flow field is separated into inner and outer regions. The basic unsteady solution is obtained analytically and the secondary flow, termed as steady streaming flow, can be obtained numerically by using Finite Volume Code with Panel Method. The Particle Induced Velocimetry, one of whole field measurements, is introduced for comparison with numerical flow visualization quantitatively. Among the algorithms for PIV, the Three Step Vector Searching Technique is applied to reduce CPU time. Small but non-zero damping coefficient, that is important in lightly damped system can be obtained with varying number of bodies and distances.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.536-542
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• 2000

The purpose of this study is to evaluate the effect of stream quality by the farmer＇s livestock wastes management in a typical small agricultural watershed. AGNPS model has the capability to adjust the level of pollutant load from farmstead and the fertilization level of upland field. A small agricultural watershed(4.12 $\textrm{km}^2$) which has as livestock farmhouses located in Gosan-myun, Ansung-gun was selected. AGNPS data were prepared by using Arc/info and Idrisi. 4 storm events in 1999 was used for runoff calibration, and 2 storm event which is measured in hourly-base at 4 locations along the stream were used for water quality(TN, TP) calibration. Model＇s behavior to stream quality for 3 cases was investigated. First, the variation of pollution produced from the cattle shed affected little to the stream quality because the cattle sheds were roofed. Second, the good management of ground in farmstead affected to stream quality with 11% and 17% decrease in TN and TP, respectively. Third, the reduction of fertilization level to upland field affected to stream quality with 27.2% and 38.5% decrease in TN and TP, respectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.535-542
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• 2012

Recently, the study on small-sized reconnaissance robot has been progressed through grafting robot technology to military fields for minimizing the casualties. Especially, throwable robots have been focusing for their's efficiency in anti-terror operation. However, it is impossible to launch throwable robot to long range(approximately 100m) by hand. So we need another type of robots, so called launchable robots, which can launch farther and is more accurate by launcher. In this paper, we presented the process of developments of launchable robots('launchbot') which are available for remote launch from collection of user's opinions to field test. Based on the opinions of users, we established the goal of development, designed and manufactured the robots. Through the field test, we found that our launchable robot satisfied the performance requirements.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.53-60
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• 1998

In this paper, the principle of operation, the part characteristic, characteristic of component movement, analysis are carried out for camcoder iris assembly which is one of the important element component in Video camera large projection TV instrument. And some Know-how for development of element component is also included. The magnetic field circuit for the small and simple structure with low power consumption is introduced and new materials of yoke for small motor system is suggested. Especially, the relation with remained magnetic field and operation duration time is analyzed by experimental results. Some problems of nonlinear torque characteristics included in this system is considered to obtain the simple and low cost structure in domestic production. Furthermore, development procedure is suggested for iris assembly and some methods to reduce the burr with some check points for small precise accessories are explained.

• Steel and Composite Structures
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• v.37 no.2
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• pp.229-251
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• 2020

In this paper, dynamic buckling of a smart sandwich nanotube is studied. The nanostructure is composed of a carbon-nanotube with inner and outer surfaces coated with ZnO piezoelectric layers, which play the role of sensor and actuator. Nanotube is under magnetic field and ZnO layers are under electric field. The nanostructure is located in a viscoelastic environment, which is assumed to obey Visco-Pasternak model. Non-local piezo-elasticity theory is used to consider the small-scale effect, and Kelvin model is used to describe the structural damping effects. Surface stresses are taken into account based on Gurtin-Murdoch theory. Hamilton principle in conjunction with zigzag shear-deformation theory is used to obtain the governing equations. The governing equations are then solved using the differential quadrature method, to determine dynamic stability region of the nanostructure. To validate the analysis, the results for simpler case studies are compared with others reported in the literature. Then, the effect of various parameters such as small-scale, surface stresses, Visco-Pasternak environment and electric and magnetic fields on the dynamic stability region is investigated. The results show that considering the surface stresses leads to an increase in the excitation frequency and the dynamic stability region happens at higher frequencies.

• Food Science of Animal Resources
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• v.43 no.6
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• pp.975-988
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• 2023

The fatty acid composition and small molecular metabolites in breast and leg meat of Yanjin blackbone chickens (YBC) and Piao chickens (PC) were detected by gas chromatography-mass spectrometry and liquid chromatography-quadrupole static field orbital trap mass spectrometry. Thirty-two fatty acids were detected, and the total fatty acid content of PC was significantly higher than that of YBC (p<0.05). Oleic acid, linoleic acid, palmitic acid, stearic acid, and arachidonic acid were the main fatty acids in the two chicken varieties, and the composition of fatty acids in the two varieties were mainly unsaturated fatty acids, being more than 61.10% of the total fatty acids. Meanwhile, 12 and 16 compounds were screened out from chicken legs and chicken breasts of YBC and PC, respectively, which had important contributions to the differences between groups.

• Current Optics and Photonics
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• v.8 no.1
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• pp.97-104
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• 2024

In aerial cameras, image quality is easily affected by weather, temperature, and the attitude of the aircraft. Aiming at this phenomenon, based on the theory of two-step zoom optical systems, a dual-band optical-despun two-step zoom optical system is designed. The system has a small field of view of 2.00° × 1.60°, and a large field of view of 4.00° × 3.20°. In the zoom process, the wavelength range is 0.45-0.70 ㎛ and 0.75-1.10 ㎛, and the size of the optical system is 168 mm (L) × 90 mm (W) × 60 mm (H). The overall lens weight is only 170.8 g, which has advantages for miniaturization and light weight. At the Nyquist frequency of 104 lp/mm, the modulation transfer function of the visible-light optical system is more than 0.44, and that of the near-infrared optical system is more than 0.30, both of which have good imaging quality and tolerance characteristics in the range of -45 to 60 ℃.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.129-138
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• 1994

It is well recognized that accurate analysis of lateral earth pressure is very signficant factor which determines the design amount of braced cut walls and braced systems. Many researchers, Peck, Terzaghi-Peck and so on, make a study about lateral earth pressure to act on the flexible walls. But these studies trouble accurate to multy layered systems like inland areas in Korea. This study is compared with the field messurement data to estimate the earth pressure distributions in multy layered areas and the empirical earth pressure distributions. The conclusions are as follows : At final excavation depth, the lateral earth pressure which messured by field instrument is smaller than the empirical earth pressure. (About 1.85~5.32 times). In the case of considering the soft rock layer to the final excavation depth, the messured earth pressure is safe to be compared with empirical earth pressure. The messured earth pressure distributions are like that the upper soil layer is small the middle soil layer is large, the rock mass layer is very small.

• ETRI Journal
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• v.24 no.6
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• pp.455-461
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• 2002

This paper reports on estimating the Schottky barrier height of small contacts using a thermionic-field emission model. Our results indicate that the logarithmic plot of the current as a function of bias voltage across the Schottky diode gives a linear relationship, while the plot as a function of the total applied voltage across a metal-silicon contact gives a parabolic relationship. The Schottky barrier height is extracted from the slope of the linear line resulting from the logarithmic plot of current versus bias voltage across the Schottky diode. The result reveals that the barrier height decreases from 0.6 eV to 0.49 eV when the thickness of the barrier metal is increased from 500 ${\AA}$ to 900 ${\AA}$. The extracted impurity concentration at the contact interface changes slightly with different Ti thicknesses with its maximum value at about $2.9{\times}10^{20}\;cm^{-3}$, which agrees well with the results from secondary ion mass spectroscopy (SIMS) measurements.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.194-196
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• 2006

This paper deals with design of a small-scaled permanent magnet generator (PMG) for wind power applications. First, this paper determines rated power and rated speed of the PMG from measured characteristics of wind turbines. Second, we derive analytical solutions for the open-circuit field in order to determine optimum magnet thickness and pole pitch/arc ratio. Third, on the basis of open circuit field solutions, stator magnetic circuit is designed. And then, a diameter of stator coil which agree with a required current density is calculated, and its turns are determined from the area of slot. Finally, finite element (FE) method is employed for validity of the designed PMG and, the back-emf measurements are also given to confirm the design.