• Title/Summary/Keyword: Single impact

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Impact of hydrogen on rupture behaviour of Zircaloy-4 nuclear fuel cladding during loss-of-coolant accident: a novel observation of failure at multiple locations

  • Suman, Siddharth
    • Nuclear Engineering and Technology
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    • v.53 no.2
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    • pp.474-483
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    • 2021
  • To establish the exclusive role of hydrogen on burst behaviour of Zircaloy-4 during loss-of-coolant accident transients, an extensive single-rod burst tests were conducted on both unirradiated as-received and hydrogenated Zircaloy-4 cladding tubes at different heating rates and internal overpressures. The visual observations of cladding tubes during bursting as well as post-burst are presented in detail to understand the effect of hydrogen concentration, heating rate, and internal pressure. Impact of hydrogen on burst parameters-burst stress, burst strain, burst temperature-during loss-of-coolant accident transients are compared and discussed. Rupture at multiple locations for hydrogenated cladding at lower internal pressure and higher heating rate is reported for the very first time. A novel burst criterion accounting hydrogen concentration in nuclear fuel cladding is proposed.

The Impact of COVID-19 Regional Cash Subsidies on the Sales of Local Businesses in South Korea

  • KIM, MEEROO;OH, YOON HAE
    • KDI Journal of Economic Policy
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    • v.43 no.2
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    • pp.103-123
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    • 2021
  • This paper examines the impact of the regional cash subsidies which were granted in some districts in addition to the national universal stimulus payment in South Korea related to the COVID-19 pandemic. We evaluate the effects of the cash distribution per resident on aggregate credit and debit card sales and sales by industry using the difference-in-difference method. The increment in card spending due to the cash subsidy is about 1.58%p in total, and this effect is concentrated within a single month. The consumption stimulating effect is prominent among (semi)-durable goods that do not require close interactions between customers and sellers. In contrast, the effect is relatively small in the high-contact face-to-face service sectors and restaurants, areas the COVID-19 pandemic hit directly. On the other hand, some service sectors where customers could wear face masks, such as education and fitness, experienced a substantial sales boost due to the cash subsidy.

Measuring the Impact of Change Orders on Project Performances by Building Type

  • Juarez, Marcus;Kim, Joseph J.
    • International conference on construction engineering and project management
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    • 2022.06a
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    • pp.179-187
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    • 2022
  • The project performances can be measured in terms of meeting the project schedule, budget, and conformance to functional and technical specifications. Numerous studies have been conducted to examine the causes and effects of change orders for both vertical and horizontal construction, respectively. However, these studies mainly focus on a single project type, so this paper examines the impact of change order for cost growth and schedule overruns using four different building types to close the gap in the change order research area. A total of 211 building projects are collected from four building types: healthcare, residential, office, and education. Statistical analyses using ANOVA tests and linear regression models are used to examine the created metric $CO/day on the cost and schedule impacts. The results found that mean $CO/day values were not statistically different among building types, and that the sum of change orders is a statistically significant predictor of $CO/day. The results will help project stakeholders mitigate the negative change orders effects can be a challenge for project managers and researchers alike.

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PROJECT MANAGEMENT STRATEGY FOR SUSTAINABLE INTEGRATION OF STADIUMS

  • Sven Schmedes
    • International conference on construction engineering and project management
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    • 2011.02a
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    • pp.269-272
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    • 2011
  • The impact of a new stadium on the urban context and regional development is significant. Especially where several new stadiums are built for single mega events like the Olympic Games, Commonwealth Games or the Soccer World Cup the impact is even higher. Objective of this paper is to identify and analyze the key drivers for sustainable integration of stadiums within the existing context. The level of sustainability is analyzed based on four different categories: urban, social, environmental and economics. Particular focus is on the project management strategy for implementation of the key drivers during pre-design, design and execution. In conclusion key elements of the project management strategy for sustainable integration of a stadium within the urban, environmental, social and economic context are summarized.

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Impact and post-impact of ring supports: Eigenfrequency response at nano-scale

  • Madiha Ghamkhar;MohamedA. Khadimallah;Muzamal Hussain;Abdelouahed Tounsi
    • Structural Engineering and Mechanics
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    • v.88 no.2
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    • pp.109-115
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    • 2023
  • In this paper, frequencies of zigzag structure of carbon nanotubes isinvestigated based on Donnell shell theory. These tubes are wrapped with the ring supports in the axial direction. The fundamental frequency curves displayed in article show the dependence of vibrations attributes to zigzag single walled carbon nanotubes. Various zigzag indices are introduced against the variation of length to predict the vibration. Also, the influence of ring supports is sketched with proposed structure for frequency analysis. The frequencies of zigzag tube decreases as the length increases. It is observed that the frequencies decreases with ring support and have higher frequencies without ring. The problem is formulated using Partial Differential Equation. Three expressions of modal deformation displacement functions is used for the elimination of temporal variation to form the solution in the eigen from. For the stability of present study the results are compared with experimentally and numerically in the open text.

A Design for a Fuzzy Logic based Frequency Controller for Efficient wind Farm Operation (풍력발전단지의 효율적 운영을 위한 퍼지로직 기반 주파수 제어기 설계)

  • Kim, Se Yoon;Kim, Sung Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.2
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    • pp.186-192
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    • 2014
  • Recently wind energy penetration into power systems has increased. Wind power, as a renewable energy source, plays a different role in the power system compared to conventional power generation units. As long as only single and small wind power units are installed in the power system, wind power does not influence power system operation and can easily be integrated. However, when wind power penetration reaches a significantly high level and conventional power production units are substituted, the impact of wind power on the power system becomes noticeable and must be handled. The connection of large wind turbines and wind farms to the grid has a large impact on grid stability. The electrical power system becomes more vulnerable to and dependent on wind energy production, and therefore there is an increased concern about the large wind turbines impact on grid stability. In this work, a new type of fuzzy logic controller for the frequency control of wind farms is proposed and its performance is verified using SimWindFarm toolbox which was developed as part of the Aeolus FP7 project.

Impact of Conceptual Combination Pattern and Goal Congruence on User Experience : Focused on IPTV Design Factors (디지털 서비스의 결합유형과 목적 일치도가 사용자 경험에 미치는 영향 : IPTV 서비스의 디자인 요소를 중심으로)

  • Kim, So-Lyung;Park, Ji-Young;Kim, Jin-Woo
    • Korean Management Science Review
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    • v.27 no.3
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    • pp.43-70
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    • 2010
  • Influences of convergent services on the overall industry has become noticeable. Various services are becoming to converge into a single platform because of ever-hanging needs of digital service users. However, few studies have investigated how users' perception of convergent services as well as the quality of experience that service users have while using the convergent services. Therefore, this study aims at identifying perceived patterns of convergent services by IPTV users, which is one of the representative convergent-ervice platforms. It also aims at identifying the impact of perceived convergence pattern on the relationship between goal congruency among individual services and the quality of user experience. Two empirical studies were conducted to accomplish the research goals. We have constructed two prototypes of convergent digital services in the IPTV environment and conducted controlled experiments to verify the research hypotheses. The results indicate that design similarities of two services substantially influence the perceived patterns of convergent services. It was also found that the perceived convergent patterns have significant moderating effects on the impact of perceived goal congruence upon the quality of user experience. This paper ends with limitations as well as implications of the study results.

Mechanical Properties of Low-Pressure Die Cast A356-T6 alloys for Automotive Wheels (Alloy Wheel용 저압 주조 A356-T6 합금의 기계적 특성)

  • Yoo, Bong-Jun;Kim, Jeong-Ho;Yoon, Hyung-Seok;Ur, Soon-Chul
    • Journal of Korea Foundry Society
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    • v.34 no.1
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    • pp.6-13
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    • 2014
  • The mechanical properties of low-pressure die cast (LPDC) A356-T6 automotive road wheels are evaluated and correlated with their corresponding microstructures. In this study, two types of alloy wheels processed using different LPDC gating system are investigated. The yield stress, tensile stress, and elongation values tested at room temperature are correlated with the secondary dendrite arm spacing (SDAS) with respect to the gating system, and are also compared with similar studies. The SDAS and precipitates are examined using optical microscopy, scanning electron microscopy (SEM) and energy-dispersive spectroscopy. The phase information is also investigated using X-ray diffraction. Charpy impact tests are also performed from $-100^{\circ}C$ to $200^{\circ}C$, and the fracture surfaces are examined using SEM. The impact energy is demonstrated to increase with increasing temperatures without exhibiting specific transition behaviors as in other nonferrous alloys. The fracture toughness is also evaluated using three point bend test with single-edged bend specimens. The obtained fracture toughness values are in good agreement with those in similar studies.

A Elastic Analysis for the Impact Response Analysis of Two-Layered Cylindrical Shells (2층 원통쉘의 탄성 충격응답 해석)

  • Park, Sung Jin;MIKAMI, Takashi
    • Journal of Korean Society of Steel Construction
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    • v.12 no.6
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    • pp.639-648
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    • 2000
  • A model analysis is used to predict the impact response of a simply supported elastic circular cylindrical shell composed of two bonded isotropic layers. The governing equations for a two-layered cylindrical shell are derived on the basis of an improved theory for the single-layer shell which includes the effects of transverse shear deformation and rotary inertia. Calculations are made for the specific case of the steel-concrete cylindrical shell subjected to a suddenly applied load. The solutions show that the method yields very good results. Therefore the proposed method is useful not only for a better investigating of the response characteristics of the shell but also available for a check on other numerical methods such a FEM.

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Performance Tests of a High Capacity Buffer Coupling System using a Hydraulic Device (유압 장치를 이용한 철도 연결기용 고용량 충격완충기의 성능시험)

  • Kim, Namwook;Park, Yeong-il
    • Journal of the Korean Society of Safety
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    • v.31 no.1
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    • pp.33-40
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    • 2016
  • Coupling systems under train's collision should take the impact by absorbing the impact energy caused from the collision, so the systems are very important parts for the safety of the trains. However, it is not easy to evaluate the performance of the system because it requires a huge testing facility, which is able to control the impact and to handle many safety issues. In this paper, test results are provided, which are obtained from collision tests of a single train having a coupling system in the front, and the results are analyzed in order to understand the characteristics and the dynamic behaviors of energy absorbing materials in the coupling system, such as a hydraulic buffer, and two rubber buffers. The results show that the force of each component could be empirically described by the compression displacement and velocity. The analyzed results will be applied to simulation models, and advanced studies wouuld be available if the simulation models are well validated with the test results.