• 한국군사과학기술학회지
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• 제14권5호
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• pp.818-824
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• 2011

In this paper, we proposed a phase noise model of a frequency synthesizer for a radar system. Especially, it was proposed a phase noise model in a DAS(Direct Analog Synthesizer) and a frequency up converter system using Leeson's model. The proposed phase noise model was derived from the measurement data of model 1 and evaluated by adapting to model 2 and model 3 frequency synthesizers. The prediction phase noise by modeling was totally matched to the measured data and the effective analysis of the phase noise was done in a frequency synthesizer and a frequency converter of radar system.

• 농업과학연구
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• 제45권2호
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• pp.308-316
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• 2018

The Korean government introduced the $6^{th}$ industrialization in the agricultural sector to increase farmers' income and value-added agricultural products. The U.S. government has also supported farmers' efforts to increase their income and value-added products in a similar way even though the $6^{th}$ industrialization is not the usual concept in the U.S. Especially, direct-to-consumer and intermediated marketing is one of the main methods to increase farmers' income and value-added agricultural products in the U.S. The purpose of this paper was to analyze direct-to-consumer and intermediated marketing in the U.S., through a survey and frequency analysis. The results of this study are as follows: First, U.S. farmers have shifted their concern and efforts from direct-to-consumer marketing to intermediated marketing because intermediated marketing may offer higher value-added agricultural products. However, consumers' perception and interest are higher for direct-to-consumer marketing than for intermediated marketing of agricultural products and related services. Consumers also will increase the portion of consumption of agricultural products and related services through direct-to-consumer marketing. This difference between farmers and consumers may cause difficulties in increasing farmers' income and value-added agricultural products in the U.S. Korean farmers may have same problem in the future, even though they have not encountered it yet. Especially, the Korean government needs to develop the capabilities of farmers so that they can solve this problem.

• 한국정밀공학회지
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• 제20권2호
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• pp.209-217
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• 2003

In this paper, the dynamic system modeling and the state sensitivity analysis of the spin-coater system are proposed for the reduction of the vibration. In the respect of modeling, the spin-coater system is considered to be composed of servomotor, spindle, supporting base and so on. Each component of model is combined and derived to 3 dimensional equations. The combined model is verified by experimental values of actual system in the frequency domain. By direct differentiation of the constraint equations with respect to kinematic design variables, such as eccentricity of spindle, moment of inertia, rotational stiffness and damping of supported base, sensitivity equations are derived to the verified state equations. Sensitivity of design variables could be used for vibration reduction and natural frequency shift in the frequency domain. Finally, dominant design variables are selected from the sensitivity analysis.

• 통상정보연구
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• 제18권3호
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• pp.181-201
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• 2016

본 연구에서는 우리나라 중소기업의 수출기업화를 유도하기 위한 결정요인이 무엇인지 분석하기 위해 거래비용이론을 기반으로 중소기업의 거래비용 및 수출기업화 요소가 기업의 수출결정에 어떻게 작용하는지를 파악하고자 하였다. 거래비용이론에서는 제조업의 유통거래에 있어 거래비용 증가 시, 관련 유통거래를 내부화한다고 설명하고 있는데 본 연구는 기존 간접수출에 의한 국내 판매와 이를 내부화한 직접수출 즉, 수출기업화의 거래구조 선택으로 이를 응용하였다. 실증분석결과 중소기업은 거래특유자산이나 국내시장 마케팅 역량이 부족하거나, 혹은 수요 감소와 사업 환경 악화, 경쟁심화 등 시장의 위협요소가 증가하는 경우에는 거래기업의 기회주의에 크게 노출 될 수 있다. 이 경우 중소기업의 기존 간접수출방식에 의한 계약거래는 높아진 기회주의로 인해 부정적인 영향을 받아 거래구조를 변경하여 직접수출 거래방식으로 계약구조 변화를 선택하게 된다.

• 한국생산제조학회지
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• 제7권6호
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• pp.110-116
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• 1998

For the vibration analysis of 3-dimensional piping system containing fluid flow, a transfer matrix method is presented. The fluid velocity and pressure were considered, that coupled to longitudinal and flexural vibrations. Transfer matrices and point matrices were derived from direct solutions of the differential equations of motion of pipe conveying fluids, and the variations of natural frequency with flow velocity for 3-dimensional piping system were investigated.

• 소음진동
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• 제6권4호
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• pp.469-474
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• 1996

Dynamic stability of an axially oscillating cantilever beam is investigated in this paper. The equations of motion are derived and transformed into non-dimensional ones. The equations include harmonically oscillating parameters which originate from the motion-induced stiffness variation. Using the equations, the multiple scale perturbation method is employed to obtain a stability diagram. The stability diagram shows that relatively large unstable regions exist around the frequencies of the first bending natural frequency, twice the first bending natural frequency, and twice the second bending natural frequency. The validity of the diagram is proved by direct numerical simulations of the dynamic system.

• Human Ecology Research
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• 제58권4호
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• pp.483-496
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• 2020

This study examined the effects of eating alone, meal type, and dietary lifestyles on healthy eating capability of one-person households. We analyzed the mediation effects of weekly frequencies of each meal type taken by one-person households between eating habits such as eating alone and dietary lifestyles of one-person households and healthy eating capability. We also analyzed data from the 2019 Food Consumption Behavior Survey using a sample of 688 one-person households. Factor analysis, latent profile analysis, structural equation model analysis was conducted; direct and indirect effects of independent variables were tested using bootstrap method. The major results were as follows. Frequency of eating alone was about 10 times a week on average; one-person households had home-made meals about 12 times a week, for restaurant meals, 4 times, for delivered/take-out food, 0.39 times, and for other types, 0.44 times. Weekly frequencies of eating alone and meal types taken by one-person households were significantly different among the different socio-demographic groups. Dietary lifestyle was classified into four classes: traditional, health ignorant, food lifestyle ignorant, and balanced. Eating alone and dietary lifestyle had a significant effect on weekly frequency of each meal type. Frequencies of eating alone, balanced dietary lifestyle, and taking home-made meals had a positive direct effect on healthy eating capability, and frequency of taking delivered or take-out food and food consumption ignorant lifestyle had a negative direct effect. Eating alone, balanced and traditional dietary lifestyles had a positive indirect effect through the meal type; however, watching Mug-bang had a negative indirect effect.

• 대한간호학회지
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• 제17권1호
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• pp.9-23
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• 1987

Nursing service, as the largest user of labor resources, has become concerned about appropriate allocation of staffing resources. Therefore, this project was designed to measure quantitatively the direct nursing care provided to patients and to develop a new patient classification system based on the direct nursing care activities. The initial step in the development of the classification instrument was to identify the content of direct nursing activities. The frequency with which these activities were carried out, the total time spent in carrying them out and the average time for one performance of each of the nursing activities was calculated. The next step was to select the items for the classification instrument taking into account these direct nursing activities. A list of 40 items was prepared. These items were then classified into 8 major categories: personal hygiene, moving ＆ exercise, nutrition & elimination, observation, medication, treatment, collecting specimens and other care activities for severity ill patients. Each item was assigned a value unit based on the average time required by the nursing staff to complete the specific item. The third step was to determine the practicality of the items and value units, so an attempt was made to establish content validity for these items and units by obtaing a consensus from 8 head nurses, representing eight different departments. The 4th step was to conducted a pilot study to establish the score range for the classification boundaries. For this purpose an instrument was designed using the list of items and value units and a prepared classification criteria as a guideline to validate the patient classification. A judgment group consisting of 52 supervisory nurses and head nurses were asked to select the proper patient to fit each classification criteria and to fill out the instrument for each patient. The total value unit and the frequency for each classification group was calculated. According to the frequency distribution, the score range for the classification group was determined as follows : 0~15 for groupI, 16~30 for group II, 31~50 for group III, and above 51 for group IV. Finally a patient classification form was developed.

• Advances in Computational Design
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• 제8권3호
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• pp.237-253
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• 2023

Torque ripple content and variable switching frequency operation of conventional direct torque control (DTC) are reduced by the integration of space vector modulation (SVM) into DTC. Integration of space vector modulation to conventional direct torque control known as SVM-DTC. It had been more frequently used method in renewable energy and machine drive systems. In this paper, SVM-DTC is used to control the rotor side converter (RSC) of a wind driven doubly-fed induction generator (DFIG) because of its advantages such as reduction of torque ripples and constant switching frequency operation. However, flux and torque ripples are still dominant due to distorted current waveforms at different operations of the wind turbine. Therefore, to smoothen the torque profile a Neural Network Controller (NNC) based SVM-DTC has been proposed by replacing the PI controller in the speed control loop of the wind turbine controller. Also, stability analysis and simulation study of DFIG using process reaction curve method (RRCM) are presented. Validation of simulation study in MATLAB/SIMULINK environment of proposed wind driven DFIG system has been performed by laboratory developed prototype model. The proposed NNC based SVM-DTC yields superior torque response and ripple reduction compared to other methods.

• 대한전기학회논문지:전력기술부문A
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• 제52권5호
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• pp.241-249
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• 2003

This paper describes a novel approach for performing eigenvalue analysis and frequency domain analysis of multi-machine power system. The salient feature of this approach is a direct approach for constructing the state matrix equations of linearized power systems about its operating point using modular technique. These state matrix equations are then used to obtain eigenvalues and mode shapes of the system, and frequency response, or Bode, plots of selected transfer functions. The proposed program provides a flexible tool for systematic analyses of tuning PSS's parameters. The paper also presents its application to the analyses of a single-machine infinite bus system and two-area system with 4 machines.