• Title/Summary/Keyword: impact-load

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Rediction of Stage Efficiency Variation of a USC High Pressure Steam Turbine by Computational Fluid Dynamics (유동해석을 이용한 고압증기터빈 단효율 변화 예측)

  • Kang, Soo Young;Jang, Hyuck Jun;Lee, Jeong Jin;Kim, Tong Seop;Park, Seong Jin;Hong, Gi Won
    • The KSFM Journal of Fluid Machinery
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    • v.20 no.2
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    • pp.17-25
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    • 2017
  • Prediction of performance and operating characteristics of a state-of-the-art ultra-supercritical (USC) steam turbine is an important issue in many ways. Theoretical and empirical correlation equations, developed a few decades ago, have been widely used in commercial programs for a prediction of performance. To improve of these correlation equations and apply them to the high pressure turbine of a USC steam turbine, computational fluid dynamic analysis was carried out and correlation equations to calculate efficiency variation of each stage were made. Both fluid dynamic characteristic and thermodynamic performance was analyzed for the development of the correlation equations. In particular, the impact of flow addition through an overload valve (OLV) between stages was examined throughly. The trend of pressure drop due to the flow mixing by the OLV flow addition was analyzed and an efficiency correlation equation considering the OLV flow was also made.

Moving Load Analysis of Bridge Structures Using Experimental Modal Data (실험적 모우드 계수를 이용한 교량의 주행하중 해석)

  • 이형진
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.3
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    • pp.409-420
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    • 2002
  • This paper proposed a technique of structural re-analysis for the evaluation of dynamic responses of bridge structure under moving loads using experimental modal results. For successful structural re-analysis, it is required to have accurate estimation techniques of the modal characteristics of bridge structures. The natural frequencies and mode shapes were identified by direct fourier analysis techniques and damping ratios by the random decrement method, respectively. An interpolation method was also proposed for the extension of mode shape measured on limited DOFs. Second, the structural reanalysis was performed using moving mass model and identified modal parameters. The results from the reanalysis show that the proposed technique is very reasonable to evaluate the actual behavior of bridge structures under moving loads.

Prevention of Work-related Musculoskeletal Disorders in Grapes Pinching by Using Electro-motion Scissors Designed Ergonomically

  • Chae, Hye-Seon;Kim, Sung-Cheol;Kim, Kwan-Woo;Lee, Kyung-Suk;Kim, Hoy-Cher;Park, Keun-Sang
    • Journal of the Ergonomics Society of Korea
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    • v.30 no.6
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    • pp.749-755
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    • 2011
  • Objective: The purpose of this study is to assess the reducing effect of workload on developed electro-motion scissors. Methods: To achieve this, we measured the pressure distribution, Joint angle of fingers and JSI(Job Strain Index) for electro-motion scissors and hand-operated scissor in objective assessment and surveyed the uncomfortable degree in subjective assessment. Results: As a result, The peak of pressure in the electro-motion scissors was generally lower than the hand-operated scissors. JSI and overall joint angle of fingers for the electro-motion scissors were remarkably lower than the hand-operated scissors. Also, the subjective uncomfortable degree showed that the uncomfortable point of electro-motion scissors were generally lower than the hand operated scissors. Conclusion: The impact of reducing the work load as well as distributing the pressure around the hand by using electro-motion scissors during grapes pinching was confirmed.

Buckling analysis of nanocomposite cut out plate using domain decomposition method and orthogonal polynomials

  • Jamali, M.;Shojaee, T.;Kolahchi, R.;Mohammadi, B.
    • Steel and Composite Structures
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    • v.22 no.3
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    • pp.691-712
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    • 2016
  • In this editorial, buckling analytical investigation of the nanocomposite plate with square cut out reinforced by carbon nanotubes (CNTs) surrounded by Pasternak foundation is considered. The plate is presumed has square cut out in center and resting on Pasternak foundation. CNTs are used as amplifier in plate for diverse distribution, such as uniform distribution (UD) and three patterns of functionally graded (FG) distribution types of CNTs (FG-X, FG-A and FG-O). Moreover, the effective mechanical properties of nanocomposite plate are calculated from the rule of mixture. Domain decomposition method and orthogonal polynomials are applied in order to define the shape function of nanocomposite plate with square cut out. Finally, Rayleigh-Ritz energy method is used to obtain critical buckling load of system. A detailed parametric study is conducted to explicit the effects of the dimensions of plate, length of square cut out, different distribution of CNTs, elastic medium and volume fraction of CNTs. It is found from results that increase the dimensions of plate and length of square cut out have negative impact on buckling behavior of system but considering CNTs in plate has positive influence.

Crosslinkable Warm-melt-Polyurethanes Offer Instant-fix Characteristics

  • Merz, Peter W.
    • Journal of Adhesion and Interface
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    • v.3 no.1
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    • pp.37-42
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    • 2002
  • Adhesives are becoming increasingly accepted for advanced engineering/boding tasks. Therefore the understanding of the basic principles and the benefits of elastic bonding and structural bonding respectively is of utmost importance. Structural bonding means adhesive performance in load-bearing environments. Furthermore. the time to achieve handling strength has an impact on the economics of an assembly line. The paper gives briefly a summary about the fundamentals of elastic bonding and discusses different adhesive systems in the context of handling strength. Hereby the focus lies on the Warm Melt Technology, and its potential is compared to standard adhesives (l-part, 2-part and Booster Technology, a special 2-C system). Examples illustrate their economical benefits. Main Points : ${\bullet}$ The basic principles and benefits of elastic bonding ${\bullet}$ Warm-melt Technology in comparison with standard adhesives ${\bullet}$ Handling strength an economic issue ${\bullet}$ Combination with Booster-Technology, a special 2-C PUR system ${\bullet}$ Presentation of real world applications Learning Objectives: ${\bullet}$ Fundamentals of elastic bonding ${\bullet}$ Warm-melt Technology: correlation between chain length and cristallinity ${\bullet}$ Handling strength and curing speed of various systems in comparison ${\bullet}$ Real world applications illustrate the potential of the Warm-melt Technology.

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Influence of Workplace Bullying and Leader-Member Exchange on Turnover Intention among Nurses (간호사의 직장 내 약자 괴롭힘, 리더-구성원 교환관계가 이직의도에 미치는 영향)

  • Han, Mi Ra;Gu, Jeung Ah;Yoo, Il Young
    • Journal of Korean Academy of Nursing Administration
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    • v.20 no.4
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    • pp.383-393
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    • 2014
  • Purpose: The purpose of this descriptive study was to identify the impact of workplace bullying and LMX (Leader-Member Exchange) on turnover intention among nurses. Methods: The participants were 364 nurses from the Seoul metropolitan area who were attending a continuing education program. A structured questionnaire was used for data collection and data were analyzed using the SPSS/Window program. Hierarchical multiple regression analysis was performed to verify the effect of variables on turnover intention. Results: Higher workplace bullying was associated with higher turnover intention. Workplace bullying was negatively correlated with leader-member exchange. The most influential factors for turnover intention were LMX (${\beta}=-7.22$, p<.001), work load (${\beta}=2.96$, p=.003), and workplace bullying (${\beta}=2.64$, p=.009). These factors accounted for 28% of the variance in turnover intention. Conclusion: The study results indicate that there is need to develop strategies to prevent workplace bullying and cultivate a good relationship between nursing managers and nurses to lower nurses' turnover intention.

An Evaluation of Blast Resistance of Partially Reinforced CFT Columns using Computational Analysis (전산해석을 이용한 부분 보강된 CFT 기둥의 폭발저항성능 평가)

  • Kim, Han-Soo;Wee, Hae-Hwan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.5
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    • pp.503-510
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    • 2015
  • In this paper, the blast resisting performance of partially reinforced CFT columns was compared with the normal CFT columns to evaluate the effect of reinforcing with steel plates. Autodyn which is a specialized hydro-code for analysis of explosion and impact was used to simulate the structural behavior of the CFT columns under the blast loadings. The interaction between concrete and surrounding steel plates was modeled with friction and join option to represent the realistic damage of columns. According to the analysis, the partially reinforced CFT column showed enhanced blast resisting performance than the normal CFT columns. Also the improvement of blast resisting performance was depended on the height of reinforcing steel plates.

Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

  • Ha, Seung-Ryong
    • The Journal of Advanced Prosthodontics
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    • v.7 no.6
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    • pp.475-483
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    • 2015
  • PURPOSE. The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS. The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS. Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION. The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

Application of numerical models to determine wind uplift ratings of roofs

  • Baskaran, A.;Borujerdi, J.
    • Wind and Structures
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    • v.4 no.3
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    • pp.213-226
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    • 2001
  • Wind uplift rating of roofing systems is based on standardised test methods. Roof specimens are placed in an apparatus with specified table size (length and width) then subjected to the required wind load cycle. Currently, there is no consensus on the table size to be used by these testing protocols in spite of the fact that a table size plays a significant role in evaluating the performance. This paper presents a study with the objective to investigate the impact of table size on the performance of roofing systems. To achieve this purpose, extensive numerical experiments using the finite element method have been conducted to investigate the performance of roofing systems subjected to wind uplift pressures. Numerical results were compared with results obtained from experimental work to benchmark the numerical modeling. Required table size and curves for the determinations of appropriate correction factors are suggested. This has been completed for various test configurations with thermoplastic waterproofing membranes. Development of correction factors for assemblies with thermoset and modified bituminous membranes are in progress. Generalization of the correction factors and its usage for wind uplift rating of roofs will be the focus of a future paper.

Large scale fire test on a composite slim-floor system

  • Bailey, C.G.
    • Steel and Composite Structures
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    • v.3 no.3
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    • pp.153-168
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    • 2003
  • This paper discusses the results and observations from a large-scale fire test conducted on a slim floor system, comprising asymmetric beams, rectangular hollow section beams and a composite floor slab. The structure was subjected to a fire where the fire load (combustible material) was higher that that found in typical office buildings and the ventilation area was artificially controlled during the test. Although the fire behaviour was not realistic it was designed to follow as closely as possible the time-temperature response used in standard fire tests, which are used to assess individual structural members and forms the bases of current fire design methods. The presented test results are limited, due to the malfunction of the instrumentation measuring the atmosphere and member temperatures. The lack of test data hinders the presentation of definitive conclusions. However, the available data, together with observations from the test, provides for the first time a useful insight into the behaviour of the slim floor system in its entirety. Analysis of the test results show that the behaviour of the beam-to-column connections had a significant impact on the overall structural response of the system, particularly when the end-plate of one of the connections fractured, during the fire.