• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.52-63
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• 1998

The impact programmer for impact test was designed and the impact analysis was conducted. The effects of the material and geometric parameters on the impact force and pulse shape were investigated. The impact characteristics were examined by experimental and finite element method. The impact test was conducted with free drop impact tester. The ABAQUS/Explicit 5.5 version was used for finite element analysis. The geometric parameters of the conical and dome type impact programmer were analyzed. The polyurethane impact programmers were fabricated and tested. The effects of the hardness and thickness of the impact programmer were studied. The peak acceleration and time duration of impact programmer have close correlation with the hardness, impact energy and thickness of the impactor. The experiment was good agreement with analytical predictions. The impact pulse shape generated with polyurethane impact programmer was half sine shape. The maximum impact force was proportional to impact energy. The impact acceleration was decreased with thickness of impact programmer. The maximum impact time duration level was about 2 msec.

• Steel and Composite Structures
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• v.27 no.6
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• pp.691-702
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• 2018

This paper presents experimental and analytical results of fiber reinforced polymer (FRP) confined steel tubular columns under transverse impact loads. Influences of applied impact energy, thickness of FRP jacket and impact position were discussed in detail, and then the impact responses of FRP confined steel tubes were compared with bare steel tubes. The test results revealed that the FRP jacket contributes to prevent outward buckling deformation of steel at the clamped end and inward buckling of steel at the impact position. For the given applied impact energy, specimens wrapped with one layer and three layers of FRP have the lower peak impact loads than those of the bare steel tubes, whereas specimens wrapped with five layers of FRP exhibit the higher peak impact loads. All the FRP confined steel tubular specimens displayed a longer duration time than the bare steel tubes under the same magnitude of impact energy, and the specimen wrapped with one layer of FRP had the longest duration time. In addition, increasing the applied impact energy leads to the increase of peak impact load and duration time, whereas increasing the distance of impact position from the clamped end results in the decrease of peak impact load and the increase of duration time. The dynamic analysis software Abaqus Explicit was used to simulate the mechanical behavior of FRP confined steel tubular columns, and the numerical results agreed well with the test data. Analytical solution for lateral displacement of an equivalent cantilever beam model subjected to impact load was derived out. Comparison of analytical and experimental results shows that the maximum displacement can be precisely predicted by the present theoretical model.

• Journal of the East Asian Society of Dietary Life
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• v.20 no.3
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• pp.473-480
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• 2010

This study examined the different meal duration expectations and dining characteristics of customers each stage of service (order, cook, check), and investigated the impact of perceived meal duration on customers' satisfaction. The procedures consisted of four phases. During the first phase, the different meal duration expectations and dining characteristics of customers of an Italian restaurant in Seoul were examined by survey at each stage of service. The second phase investigated the impact of perceived meal duration on customer' satisfaction. The third phase compared perceived meal duration and actual meal duration. The last phase suggested appropriate meal duration for maximization of customer' satisfaction. We also examined the effects of meal time (lunch or dinner) on meal duration preferences. Customer satisfaction was decreased with longer perceived meal duration for the order and check stages and too short perceived meal duration for the cook stage. To determine appropriate meal duration for each service stage, the relationship between perceived and actual meal durations was examined. This study confirms that customers dining at restaurants preferred a longer cook time and that a shorter meal duration at dinner decreased satisfaction ratings more when compared to lunch.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.100-107
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• 2011

As construction duration significantly influences the performance and the success of construction projects, it is necessary to appropriately manage the impact factors affecting construction duration. Recently, interest in the construction industry has been rising due to the recent change in the construction legal system, and the competition among the construction companies on construction time. However, the impact factors are extremely diverse. The existing productivity data on impact factors is not sufficient to properly identify the impact factor and measure the productivity from various perspectives, such as subcontractor, time, crew, work and so on. In this respect, a multidimensional analysis by a data warehouse is very helpful in order to view the manner in which productivity is affected by impact factors from various perspectives. Therefore, this research proposes a method that effectively takes the diverse productivity data of impact factors, and generates a multidimensional analysis. Decision tree analysis, a data mining technique, is also applied in this research in order to supply construction managers with appropriate productivity data on impact factors during the construction management process.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.306-312
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• 2018

To navigate in ice-covered waters, the ice-breaking process is required. The ice-breaking mode depends on material properties of sea ice and ice conditions. The ice-breaking mode is classified into ramming and continuous ice-breaking. The ramming is effective on large ice features, such as thick ice ridge and icebergs, and the continuous ice-breaking is on level ice. In general, the impact time duration of crushing or bending on ice sheets is from 0.2 to 1.0 second. However, impact duration in ramming will be increased. The Korean ice-breaking research vessel ARAON conducted her research voyage in the Antarctic sea during the winter of 2012. The IBRV ARAON measured strain in ramming and continuous ice-breaking. Strain gauge signals were recorded during the planned ice-breaking performance and the unplanned ice transits in heavy ice conditions. The aim of this study is to investigate the ice load signals measured in ramming processes under the heavy ice condition. Based on the time history of the signals, a raising time, a half-decaying time and time duration were investigated and compared with the previous study which was suggested the five profiles of the ice load signals.

• Computational Structural Engineering
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• v.9 no.3
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• pp.187-197
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• 1996

An explicit direct time integration method based solution algorithm is presented to predict dynamic buckling response of Euler column. On the basis of large deflection beam theory, a plane frame finite element is formulated and implemented into the solution algorithm. The element formulation takes into account geometrical nonlinearity and overall buckling of steel structural frames. The solution algorithm employs the central difference method. Using the computer program developed by the author, dynamic instability behavior of Euler column under impact loading is investigated by considering the time variation of load, load magnitude, and load duration. The free vibration of Euler column caused by a short duration impact load is also studied. The validity and efficiency of the present formulation and solution algorithm are verified through illustrative numerical examples.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.503-513
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• 2006

The duration time of aircraft noise event is also an important factor for the evaluation of civil aircraft noise, which is considered as a notable characteristic of military aircraft noise. SEL is proved as a suitable noise metric for the measuring military aircraft noise of various flight pattern considering the duration time of noise event. This study reviews whether SEL is a suitable for measuring civil aircraft noise and study shows SEL is fairly compensating the duration time of civil aircraft noise event for the evaluation of aircraft noise. Noise metric for the evaluation aircraft noise based on SEL is more appropriate than based on $L_{MAX}$ for compensating duration time of noise event either military aircraft or civil aircraft. In this reason, current formula of WECPNL based on energy average of measured $L_{MAX}$ for the evaluation of aircraft noise impact in 'Test Method of Noise and Vibration of Korea' is recommended to be amended to formula of WECPNL based on energy average of measured SEL considering compensation of noise event duration time, if WECPNL is not based on measured EPNL, a metric compensating duration time.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.1
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• pp.24-30
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• 2024

The gas-gun test is a experimental approach employed to validate the operational or structural stability when subjected to the impact energy encountered during launch or target collision. Predicting the outcomes of the gas-gun test has traditionally relied on empirical knowledge, due to numerous factors such as the bird assembly's shape, weight, material, and flight velocity. However, due to the nonlinearity and complex interactions between these variables, numerous tests are necessary to identify the necessary requirements, resulting in significant expense and time consumption during the process. The objective of this study is to forecast the variations in impact energy in future tests by developing a numerical model and analysis that aligns with the test outcomes, utilizing the ABAQUS Explicit. The outcome of the numerical analysis produced a framework that anticipates the peak g and the duration of the actual gas-sun test results, throughout post-processing techniques using FFT and LPF filters.

• Journal of the East Asian Society of Dietary Life
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• v.19 no.2
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• pp.278-286
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• 2009

Restaurants have two strategic levers for revenue management: duration control and demand-based pricing. Reducing dining times, especially during peak periods, can add considerable revenue for restaurants. Managing meal duration, however, can be far more complex than manipulating the price. This paper examines dining duration expectations for restaurants types(Family, Korean, Quick service restaurant), customers characteristics(gender, age, occupation, meal period, visiting frequency, dining occasion, dining companions) using an a adaptation of a price sensitivity measurement tool, naming it 'Time Sensitivity measurement tool' or TSM. The TSM is then used to derive the optimal time points, and the range of acceptable times. The results demonstrate that there is a relatively wide spread of acceptable dining duration times in family restaurant. Furthermore, the optimal time points was shorter than the mean expected dining times, which suggests that many restaurants may be able to shorten dining duration without compromising customer satisfaction. The paper explores whether demographic and dining variables have an impact on time preferences, and finds whether gender, age, meal periods, visiting frequency, and dining companion effects are significant. Specifically, women in their thirties tended to prefer a significantly longer dining times for dinner.

• Journal of Wetlands Research
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• v.22 no.1
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• pp.1-7
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• 2020

Non-point pollution adversely affects the water system and its influence is increasing. In order to manage such nonpoint source pollution, the government has conducted studies on LID (Low Impact Development) facilities and various efficiency evaluations. In this study, the actual installed permeable block facility among the various LID facilities was analyzed the effluent reduction rate, the residual rainfall analysis, the runoff duration time and the reduction rate of the maximum inflow and outflow for the rainfall runoff control and the results were compared the other facilities. The analysis results show that the reduction efficiency is high in order of impermeable block, filter type permeable block, and clearance type permeable block, and the graph showing the relationship between the rainfall intensity and the runoff duration time is presented. This graph can be helpful in the design of facilities such as the facility capacity selection according to the reproduction period of the permeable block facility similar to this.