• 한국대기환경학회지
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• 제20권3호
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• pp.371-380
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• 2004

In the dust separation by using porous filter media, the structure of dust layer deposited on the filter surface of filter medium directly affects the effective filtration. The present study has investigated the specific resistance (K$_2$') of the dust layer and its porosity ($\varepsilon$$_{c}$) for three different filters; FA composite filter, metal fiber filter and stainless filter. The specific resistance (K$_2$') increased and at the same time the cake porosity ($\varepsilon$$_{c}$) decreased with the increase of filtration velocity, possibly due to the compressible effect of dust layer. However, under the low dust concentration, subsequent dust particles would block the open channels through the layer resulting in high specific resistance of the layer. The FA composite filter among three filters was shown to be the most effective filter for dust cake filtration at low filtration velocities less than 0.1 m/s for an approximate dust concentration of 5 g/㎥.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.1004-1007
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• 2005

As a new approach to analyze grinding energy, this paper introduces a specific grinding energy model based on the average grain. Using this model, grinding characteristics such as specific grinding energy of SM45C were investigated with changing variables such as grain size of CBN, workpiece velocity(v) and apparent depth of cut(Z) in down-surface grinding. From the experimental results, the specific grinding energy decreases as the maximum undeformed chip thickness increases.

• 한국정밀공학회지
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• 제14권2호
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• pp.169-177
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• 1997

In this study, investigated are the effects of tool rake angles and the change of cutting conditions on the specific cutting pressure in face milling. The cutting force in face milling is predicted from the double cutting edge model in3-dimensional cutting. Conventional specific cutting pressure model is modified by considering the variation of tool rake angles. Effectiveness of the modified cutting force model is verified by the experiments using special face milling cutters with different cutter pockets and various rake angles. From the comparison of the presented model and the specific cutting pressure, it is shown that the axial force can be predicted by the tangential force, radial force and geometric conditions. Also, the rela- tionship between specific cutting pressure and cutting conditions including feedrate, cutting velocity and depth of cut is studied.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1022-1027
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• 2003

The Motion controllers provide the sophisticated performance and enhanced capabilities we can see in the movements of robotic systems. Several types of motion controllers are available, some based on the kind of overall control system in use. PLC (Programmable Logic Controller)-based motion controllers still predominate. The many peoples use MCU (Micro Controller Unit)-based board level motion controllers and will continue to in the near-term future. These motion controllers control a variety motor system like robotic systems. Generally, They consist of large and complex circuits. PLC-based motion controller consists of high performance PLC, development tool, and application specific software. It can be cause to generate several problems that are large size and space, much cabling, and additional high coasts. MCU-based motion controller consists of memories like ROM and RAM, I/O interface ports, and decoder in order to operate MCU. Additionally, it needs DPRAM to communicate with host PC, counter to get position information of motor by using encoder signal, additional circuits to control servo, and application specific software to generate a various velocity profiles. It can be causes to generate several problems that are overall system complexity, large size and space, much cabling, large power consumption and additional high costs. Also, it needs much times to calculate velocity profile because of generating by software method and don't generate various velocity profiles like arbitrary velocity profile. Therefore, It is hard to generate expected various velocity profiles. And further, to embed real-time OS (Operating System) is considered for more reliable motion control. In this paper, the structure of chip-based precision motion controller is proposed to solve above-mentioned problems of control systems. This proposed motion controller is designed with a FPGA (Field Programmable Gate Arrays) by using the VHDL (Very high speed integrated circuit Hardware Description Language) and Handel-C that is program language for deign hardware. This motion controller consists of Velocity Profile Generator (VPG) part to generate expected various velocity profiles, PCI Interface part to communicate with host PC, Feedback Counter part to get position information by using encoder signal, Clock Generator to generate expected various clock signal, Controller part to control position of motor with generated velocity profile and position information, and Data Converter part to convert and transmit compatible data to D/A converter.

• 지질공학
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• 제31권4호
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• pp.507-522
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• 2021

각 탐사의 반응 값은 지하 매질의 특정 물성에 따라 달라지기 때문에 한가지의 지구물리학적 방법만으로는 탐사목적을 달성하지 못하는 경우가 종종 있다. 특히 지질재해 위험에 취약한 지역을 조사하는 경우, 인명 및 재산피해를 최대한 줄이기 위해 한 가지 이상의 탐사방법을 사용하는 것이 효과적이다. 제방의 안전성 평가를 위한 이 연구에서는 각 탐사결과들을 개별적으로 해석하는 대신 탄성파속도(굴절법에 의한 P파속도와 MASW의 S파속도)와 전기비저항 값들을 통계적으로 분석하여 결정된 임계값들을 기반으로 취약구간과 안전구간 등으로 구분하는 사분면 상관기법을 수행하였다. 임계값은 수평 4층 구조와 경사진 파쇄대에 대한 모델자료를 가지고 수행한 사분면 상관기법을 테스트하는 과정에서 두 개의 속성자료 모두 평균에서 표준편차를 빼준 값으로 결정되었다. 전기비저항-P파속도의 교차출력에 비해 전기비저항과 S파속도를 이용한 교차출력 해석이 제방 시스템의 토양유형, 지반강성 및 암석학적 특성 정보를 보다 충실히 제공하였다. 낮은 S파속도와 높은 전기비저항으로 2사분면에 투영된 느슨한 모래 구역이 취약구간으로 평가되는데 이와 같은 해석은 시추공 표준관입시험에서 보인 중심코어의 N 값 분포로 뒷받침되었다.

• 청정기술
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• 제3권1호
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• pp.106-113
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• 1997

본 연구의 목적은 유동층반응기를 이용하여 층온도와 유속에 따른 석회석입자(천연석회석과 제지슬러지)의 소성과 황화반응 특성에 관해 조사하는 것이었으며, 실험결과는 다음과 같다. 첫째, 층온도는 천연석회석과 제지슬러지 입자의 소성과 황화반응에 매우 큰 영항을 미치는 것으로 나타났으며, 천연석회석의 경우 층온도 $850^{\circ}C$ 또는 $900^{\circ}C$가 최적 온도였고 제지슬러지의 경우 층온도 $800^{\circ}C$가 최적 온도로 조사되었다. 둘째, 유속이 증가할수록 입자의 비표면적은 감소하는 현상을 보였으나 큰 차이를 나타내지는 않았으며, 제지슬러지 입자의 비표면적이 천연석회석 입자의 비표면적 보다 훨씬 큰 것으로 나타났다. 셋째, 유속이 증가할수록 입자의 탈황능이 감소되었으며, 제지슬러지 입자에 의한 흡착량이 천연석회석 입자에 의한 흡착량 보다 큰 것으로 나타났다. 따라서 제지슬러지는 우수한 탈황제라는 것을 확인 할 수 있었으며, 유동층에서 소성반응과 황화반응시 층온도는 매우 중요한 변수라는 것을 알 수 있었다.

• Journal of Acupuncture Research
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• 제18권6호
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• pp.105-113
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• 2001

Objective : This study was performed to evaluate the effect of acupuncture on cerebral blood flow by Transcranial Doppler Ultrasonography(TCD) Method : Monitoring of TCD was examined in 11 healthy women volunteer(mean $age:\;24.5{\pm}2.9\;\;years$) before, during and after acupuncture on Paekoe(GV20). Mean velocity, pulsatility index, systolic velocity and diastolic velocity values are analyzed from DWL. MDX4 at different depths of both middle cerebral artery. Results : The results showed a significant(p<0.05; Friedman test & Wilcoxon signed ranks test) increase in mean velocity, systolic velocity and diastolic velocity decrease in pulsatility index, which was measured at different depths of both middle cerebral artery. Conclusion : These results suggest that acupuncture could have a specific effect on cerebral blood flow.

• 대한원격탐사학회지
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• 제26권3호
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• pp.297-304
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• 2010

Since the change in Doppler centroid according to moving targets brings alteration to the phase in azimuth differential signals of synthetic aperture radar (SAR) data, one can measure the velocity of the moving targets using this effect. In this study, we will investigate theoretically measuring the velocity of an object from azimuth differential signals by using range compressed data which is the interim outcome of treatment from the simulated SAR raw data of moving targets on the background of sea clutter. Also, it will provide evaluation for the elements that affect the estimation error of velocity from a single SAR sensor. By making RADARSAT-1 simulated image as a specific case, the research includes comparisons for the means of velocity measurement classified by the directions of movement in the four following cases. 1. A case of a single target without currents, 2. A case of a single target with tidal currents of 0.5 m/s, 1 m/s, and 3 m/s, 3. A case of two targets on a same azimuth line moving in a same direction and velocity, 4. A case of a single target contiguous to land where radar backscatter is strong. As a result, when two moving targets exist in SAR image outside the range of approximately 256 pixels, the velocity of the object can be measured with high accuracy. However, when other moving targets exist in the range of approximately 128 pixels or when the target was contiguous to the land of strong backscatter coefficient (NRCS: normalized radar cross section), the estimated velocity was in error by 10% at the maximum. This is because in the process of assuming the target's location, an error occurs due to the differential signals affected by other scatterers.

• 한국국방경영분석학회지
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• 제2권1호
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• pp.163-176
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• 1976

The artillery fire is characterized by great damage that can be inflicted simultaneously to an area through concentrated firing. The field artillery guns used in R.O.K. Army are generally old. Thus high values of their velocity errors cause wide dispersion of shell landings. Therefore effects of the concentrated firing is lessened. In this paper a general model which considers all error factors involved in firing in general, is established first. Then from this a basic model which includes the errors involved in concentrated firing only, such as the ballistic error, velocity error, target density function, and damage function, is extracted. Among many weapon systems now in use a specific one called gun 'A' is selected and its concentration effects are measured through computer simulation. The results show that as the velocity error of a battery increases, its target coverage capability, i. e. concentration effect, decreases. Therefore the need arises for the field artillery commander to know beforehand characteristics, i.e. velocity errors, of the guns in his unit and also to carefully examine the problem of battery arrangement with the gun characteristics in mind in order to maximize the damage effects of his artillery unit.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.990-995
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• 1990

A minimum-time trajectory planning for two robot arms with designated paths and coordination is proposed. The problem considered in this paper is a subproblem of hierarchically decomposed trajectory planning approach for multiple robots : i) path planning, ii) coordination planning, iii) velocity planning. In coordination planning stage, coordination space, a specific form of configuration space, is constructed to determine collision region and collision-free region, and a collision-free coordination curve (CFCC) passing collision-free region is selected. In velocity planning stage, normal dynamic equations of the robots, described by joint angles, velocities and accelerations, are converted into simpler forms which are described by traveling distance along collision-free coordination curve. By utilizing maximum allowable torques and joint velocity limits, admissible range of velocity and acceleration along CFCC is derived, and a minimum-time velocity planning is calculated in phase plane. Also the planning algorithm itself is converted to simple numerical iterative calculation form based on the concept of neural optimization network, which gives a feasible approximate solution to this planning problem. To show the usefulness of proposed method, an example of trajectory planning for 2 SCARA type robots in common workspace is illustrated.