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  • Title/Summary/Keyword: Lifting Work

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Stability of EG cylindrical shells with shear stresses on a Pasternak foundation

  • Najafov, A.M.;Sofiyev, A.H.;Hui, D.;Karaca, Z.;Kalpakci, V.;Ozcelik, M.
    • Steel and Composite Structures
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    • v.17 no.4
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    • pp.453-470
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    • 2014
  • This article is the result of an investigation on the influence of a Pasternak elastic foundation on the stability of exponentially graded (EG) cylindrical shells under hydrostatic pressure, based on the first-order shear deformation theory (FOSDT) considering the shear stresses. The shear stresses shape function is distributed parabolic manner through the shell thickness. The governing equations of EG orthotropic cylindrical shells resting on the Pasternak elastic foundation on the basis of FOSDT are derived in the framework of Donnell-type shell theory. The novelty of present work is to achieve closed-form solutions for critical hydrostatic pressures of EG orthotropic cylindrical shells resting on Pasternak elastic foundation based on FOSDT. The expressions for critical hydrostatic pressures of EG orthotropic cylindrical shells with and without an elastic foundation based on CST are obtained, in special cases. Finally, the effects of Pasternak foundation, shear stresses, orthotropy and heterogeneity on critical hydrostatic pressures, based on FOSDT are investigated.

EMG Measurement for Lower Leg of Golf Caddies (골프 진행보조요원의 하지근 피로도)

  • Kim, Soon-Lae;Kwon, Young Gook
    • Korean Journal of Occupational Health Nursing
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    • v.9 no.1
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    • pp.49-55
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    • 2000
  • When standing, walking, or running for extended periods of time, fatigue occurs in the legs. Although there are many ways, to release tense or fatigued leg muscles, in the case that there is insufficient time to relax, an easy way to release leg fatigue is using an inclined step (about 3 minutes). This method was more effective than performing stretching exercises as studied. An experiment was conducted on a golf course in the Kangwon province in Korea. Subjects were chosen randomly and consisted of 5 females and 4 males golf caddies. Their main tasks consisted of pulling golf carts to the bottom of a hill for 8 to 10 hours and sometimes lifting and lowering golf clubs during the duration of one day. EMG was measured after work and after using the previously mentioned inclined Steps for the lower legs using ME3000P. This study investigated the types of inclined Steps which would be most effective and appropriate for golf caddies, whether sex difference had any influence existed between male and female workers. The results showed that a step with a 20 angle was most effective for males and a step with a 25 angle was most effective for females. Females showed faster recovery from fatigue than males. However, there were no statistical significance between males and females.

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A Study on Development of a Marine Docking System for Repair of a Small Coast-Boat (연안 소형선박 수리용 해상 상가시스템 개발)

  • Park, Chung-Hwan;Jang, Dong-Won;Yang, Hyang-Kweon;Jin, Jong-Ryung
    • Journal of Ocean Engineering and Technology
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    • v.22 no.4
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    • pp.78-83
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    • 2008
  • In recent years, small boats used for marine leisure have been steadily increasing because of the increase in national income and the desire for marine leisure. But the repair of such small boats in dry dock has pointed out many faults in small FRP-shipbuilding in terms if workspace and manpower. Lifting a boat from the water to land is done with a crane or by hand using a sling around the bottom of the boat. But dry dock work is limited by the scale of the boat, which corresponds to the crane capacity, with carelessness making it possible to capsize a boat and endanger life. The purpose of this study was the development of a marine docking system that would improve economical efficiency and safety, for which we carried out concept design, model tests, structural analysis, etc.

Risk Assessment in the Loaded Works of Muscular Skeletal Disorder for Mid-old Aged General Hospital Dining Workers (중고령 종합병원 식당종사자의 근골격계 부담 작업에 대한 위험성 평가)

  • Kim, Hee-Soo;You, Young-Youl
    • Journal of the Ergonomics Society of Korea
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    • v.29 no.3
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    • pp.375-382
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    • 2010
  • The purpose of this study was to analyze the risk factors of the musculoskeletal workload of mid-old-age food preparation workers by identifying the differences in the complaints of subjective symptoms between mid-old-age housewives and mid-old-age food preparation workers. This study was carried out on a total of 83 subjects from April 2009 through July 2009: 43 food preparation workers at the catering department of general hospital A, with a high rate of mid-old-age food preparation staff, and 40 full-time housewives (40~59 years old). The analysis of the relationship between the rates of the subjective symptoms of the two groups showed that the mid-old-age food preparation workers had a 7.8-fold higher risk of developing musculoskeletal diseases than the full-time housewives. The musculoskeletal workload of the mid-old-age food preparation workers included repetitive motions, uncomfortable postures, and heavy lifting. It is hoped that this study will help provide mid-old-age people with opportunities for appropriate economic activity and labor and will help improve their work postures and methods as well as their environmental-risk factors.

Numerical analysis for the development of a Mixed-flow In-line duct fan with a high performance (고성능 사류식 In-line duct fan의 개발을 위한 전산해석)

  • Kim, Sung-Kon;Cho, Lee-Sang;Cho, Jin-Soo;Won, Eu-Pil
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.604-609
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    • 2001
  • This numerical analysis uses the lifting surface method and frequency-domain panel method based on the linear compressible aerodynamic theory. Increased knowledge of flow conditions within mixed-flow fan should indicates means of improving performance of these turbomachines. Thus, only an approximate solution is obtained whose prime intent is to recognize the most significant characteristics of the "ideal" geometry. For a given set of operating condition, the flow conditions within mixed-flow fan depend on the geometry of the machine (three-dimensional flow effects) and on the properties of the fluid. But most treatments of the problem have been concerned with the two-dimensional flow effects for incompressible, non-viscous fluids. Interest in the field of mixed-flow fan resulted in the undertaking of a program to develop reliable design procedures that would avoid the need for lengthy development work.

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Upper Limbs Related Muscle Strength and Fatigue During the Wrench Job for Korean Young Aged (렌치 작업에서의 청년층의 상지근력 및 근피로도에 관한 연구)

  • Yoon, Hoon-Yong;Kim, Eun-Sik
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.35 no.2
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    • pp.88-97
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    • 2012
  • The muscle strengths in various postures are still used in the workplace, although mechanization and automation have been continuously accomplished. The aim of this study is to measure the maximum muscle strength and analyze the muscle fatigue during the various wrench jobs which are one of the upper limbs related works. Four hundreds and eighty five college students (243 males and 242 females) participated in this study. Twelve muscle strengths which are using for pulling, pushing, lifting and lowering the wrench with various postures are measured. For every moment, the muscle strengths for both hands were measured. In each measurement, five seconds averaged value and peak value were collected. The averaged value of preferred hand and non-preferred hand was compared. Also, the averaged value of opposite movement was compared through t-test. The fatigue of agonist for each movement was analyzed using EMG analysis. The result of this study can provide some basic information not only in designing the tools in work but also in selection, training and management of workers.

Experimental Analysis of the Ground Take-off Flight of a Butterfly (지면이륙하는 나비의 날개짓 분석)

  • Jang, Young-Il;Lee, Sang-Joon
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.142-143
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    • 2008
  • In the present work, high-speed video images of the ground take-off flight of a live butterfly were captured and their dynamic motions during the first full-stroke were analyzed. To capture the dynamic images of the take-off motion, the experimental setup consisted of a high-speed camera, a Xenon lamp as a light source and a transparent chamber of 15W×15L×17H cm3 in physical size. The ambient temperature and supplementary lighting devices were precisely controlled. The weight and wing span of the butterfly tested in this study was 104 mg and 63.14 mm, respectively. The ground take-off images were captured with 4000 fps with a spatial resolution of (1024×512) pixels. The period of the first full-stroke was 80.5ms and the flapping speed of downstroke was 2 times faster than that of upstroke. As a result, butterflies used the fling and near-clap motion to generate lifting force and an interesting take-off behavior of early pronation and downstroke was observed.

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Biometric Image Cryptographic Algorithm Based on the Property of Wavelet Transform Coefficient (웨이브렛 변환 계수의 특성을 이용한 생체 영상 암호화 알고리즘)

  • Shin, Jonghong
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.12 no.2
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    • pp.41-49
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    • 2016
  • Lossless encryption methods are more applicable than lossy encryption methods when marginal distortion is not tolerable. In this research, the author propose a novel lossless symmetric key encryption/decryption technique. In the proposed algorithm, the image is transformed into the frequency domain using the lifting wavelet transform, then the image sub-bands are encrypted in a such way that guarantees a secure, reliable, and an unbreakable form. The encryption involves scattering the distinguishable frequency data in the image using a reversible weighting factor amongst the rest of the frequencies. The algorithm is designed to shuffle and reverse the sign of each frequency in the transformed image before the image frequencies are transformed back to the pixel domain. The results show a total deviation in pixel values between the original and encrypted image. The decryption algorithm reverses the encryption process and restores the image to its original form. The proposed algorithm is evaluated using standard security and statistical methods; results show that the proposed work is resistant to most known attacks and more secure than other algorithms in the cryptography domain.

Optimization for Drop and Lift of the SONAR Under the Limited Installment Space Using the GA (GA를 이용한 제한된 설치환경 하에서의 소나 투하 및 인양 장비의 최적화)

  • Park, Seong-Hak;Chung, Won-Jee;Kim, Hyo-Gon;Choi, Jong-Kap
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.25 no.5
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    • pp.321-328
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    • 2016
  • Cranes are generally used to drop or lift equipment or materials. The present study focuses on equipment used for dropping and lifting the sonar system for undersea exploration. This study deals with a GA-based MATLAB(R) simulation for the design optimization of a new overboarding prototype with a two degree-of-freedom mechanism, including a parallelogram link, which is efficient in sonar system operation and maintenance. First, the strengths and weaknesses of the existing overboarding mechanisms are analyzed. The new mechanism to solve these problems is then suggested. For the proposed mechanism, the GA-based MATLAB(R) simulation technique is applied to the proposed mechanism to optimize the link lengths and the actuator lengths. By doing this, the mechanism cannot interfere in the hull's internal environment. Hence, the work range of motion (ROM) is satisfied, and good torque-angle properties are obtaind. The developed technology will be helpful in calculating the maximized output torque of the actuator for the application in practice using a similar type of the proposed mechanism.

Characteristics of Middle Slab Stresses in Double-Deck Tunnel During Maintenance (복층터널 중간슬래브 유지관리에 따른 응력분포 특성 분석)

  • Cho, Young Kyo;Lee, Young Hoon;Park, Beom Keun;Kim, Seong-Min
    • International Journal of Highway Engineering
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    • v.19 no.6
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    • pp.47-56
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    • 2017
  • PURPOSES : The purpose of this study is to investigate the stresses of the middle slab in a double-deck tunnel owing to the slab lift to replace the underlying elastic pads during maintenance work. METHODS : The middle slab was divided into three different sections: typical section, expansion joint section, and emergency passageway section. Finite element analysis models of these three sections of middle slab were developed, and the stress distribution and maximum stresses were obtained using the models when the middle slab was lifted to replace the underlying elastic pads. Various slab lifting methods were examined in this study such as one-, two-, and multiple-point lifts, distributed lifts, and one or both slab side edge lifts. RESULTS : When the slab side edge is lifted, the longitudinal stresses of the slab are almost the same as the principal stresses. This implies that the governing stresses are the longitudinal stresses. The maximum stresses with both-edge lifts are generally smaller than those with one-edge lifts at all three sections of middle slab. CONCLUSIONS : If the middle slab in a double-deck tunnel is lifted for maintenance, the slab should be lifted at multiple points along the longitudinal direction to reduce the tensile stresses.