• Title, Summary, Keyword: Direct Method

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A Study on Simulation of Shift Sensitivity of Small Forklift Transmission using Direct Control Method (직접제어 방식을 이용한 소형 지게차 변속감도 시뮬레이션에 관한 연구)

  • Jeong, Y.M.;Yang, S.Y.
    • Journal of Drive and Control
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    • v.11 no.4
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    • pp.8-14
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    • 2014
  • The transmission control method of a small forklift is classified into a pilot control method and a direct control method. In the pilot control method, the complex hydraulic circuit consists of many components, making the production process too costly and time consuming. The direct control method contains fewer components that can be configured to simple hydraulic circuits. As another advantage, the input profile easily changes the shift sensitivity of the transmission. Therefore, this research considers the characteristics of the direct control method in the development of hydraulic system design. This paper will present a simulation of the direct control transmission using AMESim. First, modeling of the direct control method is obtained and simulated with real parameters. The simulation results then are carried out and compared with the experimental results to verify and analyze the characteristics of the direct control method.

Comparison of Ultrasonic Velocities between Direct and Indirect Methods on 30 mm × 30 mm Spruce Lumber

  • OH, Sei Chang
    • Journal of the Korean Wood Science and Technology
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    • v.48 no.4
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    • pp.562-568
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    • 2020
  • This study investigates the relationship between ultrasonic velocity and density in the direct method, the effect of distance between transducers in the indirect method, and the difference between the direct and indirect methods with transducers placed at a distance of 200 mm in nondestructive ultrasonic testing of spruce lumber. The direct method using 54 kHz ultrasonic transducers was applied to two planes, namely, radial section (LR) and tangential section (LT) of samples. The indirect method measurements were taken using the same transducers. Two velocities were measured at the top and bottom of the LT plane and at the two sides of the LR plane; the two values for each plane were averaged. The relationship between density and ultrasound velocity in the direct method demonstrated a positive correlation between the two variables. The difference between the two planes, LT and LR, was not statistically significant. Moreover, the distance between the transducers in the indirect method affected ultrasound velocity, with the ultrasonic velocity increasing as the distance between the transducers became larger. A transducer distance of 200 mm yielded a close approximation of the direct method results with a ratio of 0.87. Finally, no statistical evidence of a difference between the two planes in the indirect method was found. If the direct method, which requires access to two surfaces, is impractical, the indirect method can be applied.

The Suitability of 3-dimensional Body Scan Method in Measuring Body Surface Area (체표면적 측정을 위한 3차원 스캔법의 적합성에 대한 연구)

  • 한현숙;남윤자
    • Textile Science and Engineering
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    • v.41 no.3
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    • pp.223-229
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    • 2004
  • The purpose of this study was to examine the characteristic of the 3-dimensional scan method in measuring body surface area (BSA). The BSA difference between 3D scan method and direct method was checked by mannequins of Korean women. We used paper coating as a direct method, and in 3D scan method we used WB4 scanner. As a result of experiment with geometrical forms, repeatability was better in direct method with the simple geometry, but with more complex geometry, it was better in 3D scan method. The accuracy was better in 3D scan method than direct method at both geometrical forms. The comparison between BSA of two methods by body segments showed that there was large difference in hand, feet, and front bodice which had complex structure or was hidden from the scan. We also examined the change of surface area by editing the 3D scan data. The body parts enhanced highly by editing was foot, head and upper arm, and the BSA of the 3D scan data was close to that of direct method after editing. Difference of whole BSA between 3D scan and direct method was within 2%. So we suggest that 3D Scan method can be used in measurement of BSA.

Direct strength method for high strength steel welded section columns

  • Choi, Jong Yoon;Kwon, Young Bong
    • Steel and Composite Structures
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    • v.29 no.4
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    • pp.509-526
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    • 2018
  • The direct strength method adopted by the AISI Standard and AS/NZS 4600 is an advanced design method meant to substitute the effective width method for the design of cold-formed steel structural members accounting for local instability of thin plate elements. It was proven that the design strength formula for the direct strength method could predict the ultimate strength of medium strength steel welded section compressive and flexural members with local buckling reasonably. This paper focuses on the modification of the direct strength formula for the application to high strength and high performance steel welded section columns which have the nominal yield stress higher than 460 MPa and undergo local buckling, overall buckling or their interaction. The resistance of high strength steel welded H and Box section columns calculated by the proposed direct strength formulae were validated by comparison with various compression test results, FE results, and predictions by existing specifications.

Improved Direct Method for Computing a Closest Voltage Collapse Point (최단전압붕괴점을 계산하는 개선된 직접법)

  • Nam, Hae-Kon;Song, Chung-Gi
    • Proceedings of the KIEE Conference
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    • pp.231-234
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    • 1997
  • This paper presents improved direct method for calculating the closest saddle node bifurcation (CSNB) point, which is also applicable to the selection of appropriate load shedding, reactive power compensation point detection. The proposed method reduced dimension of nonlinear equation compared with that of Dobson's direct method. The improved direct method, utilizing Newton Iterative method converges very quickly. But it diverges if the initial guess is not very close to CSNB. So the direct method is performed with the initial values obtained by carrying out the iterative method twice, which is considered most efficient at this time. Since sparsity techniques can be employed, this method is a good choice to a large scale system on-line application. Proposed method has been tested for 5-bus, New England 30-bus system.

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An Ergonomic Analysis on Working Posture Associated with Dental Treatment Using Indirect Viewing Method (간접보기 도구를 이용한 치과 진료 관련 작업자세에 대한 인간공학적 분석)

  • Son, Chang-Won;Choi, Soon-Young;Park, Dong-Hyun
    • Journal of the Korea Safety Management and Science
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    • v.12 no.2
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    • pp.55-64
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    • 2010
  • This study tried to focus on nontraditional job that has not been studied in terms of the subjects associated with MSDs(Musculoskeletal Disorders). Specifically, dental procedure was the job to be analyzed in this study. An alternative method as well as a traditional method for viewing teeth while performing simulated dental procedures. Four graduated students did both methods(direct view and indirect view) as the subjects in this study. The method based on indirect view used a video camera and monitor to view the teeth. The experiment was conducted five times for each subject. The major findings in this study were as follows; 1) Job speed was increased with the repetitions for both methods, 2) Difference of Neck flexion between direct and indirect methods was statistically siginificant(Neck flexion for indirect method was dramatically decreased), 3) Difference of job speed between direct and indirect methods was statistically significant(Job speed for direct method was faster than that of indirect method), 4) Difference of error rate between direct and indirect methods was statistically significant(error rate for direct method was lower than that of indirect method), 5) Even though indirect method did not provide better performance in terms of job speed and error rate yet, it seemed to need a trade-off between two methods in the future since indirect method provided better working postures than that of direct method.

A Study on Applying the Direct Control Method for Small Forklift Transmission System (직접 제어 방식을 적용한 소형 지게차 변속 시스템에 관한 연구)

  • Jeong, Y.M.;Lim, K.;Yang, S.Y.
    • Journal of Drive and Control
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    • v.10 no.4
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    • pp.34-40
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    • 2013
  • The transmission control method of small forklift is classified into pilot control method and direct control method. In pilot control method, the hydraulic circuit which consists a lot of components is very complex so the production process is too costly and time consuming. The direct control method contains fewer components that can be configured to simple hydraulic circuit. It has more advantages because the shift sensitivity of transmission is changed easily via the input profile. In this paper, the controller design and the input profile for system are studied to apply to the direct control method. The input profile consists of Fill section, Hold section and Ramp section. The characteristic of each section is obtained through experiment. As the result, the shift sensitivity and starting performance are effected by Fill section and Hold section.

A Study on a Performance Analysis of Direct-Conversion Receiver In Additive White Gaussian Noise Channel (AWGN 채널환경에서 Direct-Conversion 수신기의 성능분석에 관한 연구)

  • 조형래;김철성;박성진
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.4
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    • pp.668-675
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    • 2001
  • Recently, the performance of the commercial PCS(Personal Communication Service) system has been improved to the uppermost limit and ultimately the next generation mobile communication is to be realized by IMT-2000 (International Mobile Communication-2000) to provide multimedia services. Therefore, the new type receiving system is researched actively and one of the most important part in a receiver is direct conversion method. The direct conversion method is suitable for low power consumption, small size, MMIC, and low price, which is to be adopted to the next generation mobile communication systems. In this case, however, several problems occur due to DC-offset. The DC-offset suppresses amplification of the required signal because of the leakage signal of frequency synthesizer in the system. In this thesis, the removing method of DC-offset was considered. There are four removing techniques of DC-offset, which are AC-coupling, large capacitor, DC-feedback loop, and DC-free coding. Among these, the AC-coupling method is the most simplest method and the DC-feedback loop method has the best performance. Then, the performance of the AC-coupling method and DC-feedback loop method are evaluated by HP's ADS simulation tool. As a result, the AC-coupling method cannot be used to the digital communication systems due to data loss. On the other hand, it was confirmed that the DC-feedback loop method is suitable for the direct conversion receiver.

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Fabrication and Properties Analysis of MEA for PEMFC (고분자전해질 연료전지용 MEA 제조 및 특성평가)

  • Cho Y.H.;Cho Y.H.;Park I.S.;Sung Y.E.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.230-234
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    • 2005
  • Fabrication of MEA is important factor for proton exchange membrane fuel cell (PEMFC). MEA of PEMFC with hot pressing and direct coating method were prepared, and performances were evaluated and compared each other. The effect of MEA preparation methods, hot pressing methods and direct coating methods, on the cell performance was analyzed by impedance spectroscopy and SEM. The performance of PEMFC with direct coating method was better than with hot pressing method because membrane internal resistance and membrane-interfacial resistance were reduced by elimination of hot pressing process in MEA fabrication. In addition the micro structure of MEA with direct coating method reveals uniform interface between membrane and catalyst layer.

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Predictive Direct Power Control in MMC-HVDC System (MMC-HVDC 시스템의 예측 기반 직접전력제어)

  • Lee, Kui-Jun
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.6
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    • pp.403-407
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    • 2018
  • This study proposes a predictive direct power control method in a modular multilevel converter (MMC) high-voltage direct-current (HVDC) system. The conventional proportional integral (PI)-based control method uses a cascaded connection and requires an optimal gain selection procedure and additional decoupling scheme. However, the proposed control method has a simple structure for active/reactive power control due to the direct power control scheme and exhibits a fast dynamic response by predicting the future status of system variables and considering time delay. The effectiveness of the proposed method is verified by simulation results.