• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.4
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• pp.185-194
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• 2010

A pumpjet propulsor (PJP) was designed for an underwater body (UWB) with axi-symmetric configuration. Its performance was predicted through CFD study and models were manufactured. The propulsor design was evaluated for its propulsion characteristics through model tests conducted in a Wind Tunnel (WT). In the concluding part of the study, evaluation of the cavitation performance of the pumpjet was undertaken in a cavitation tunnel (CT). In order to assess the cavitation free operation speeds and depths of the body, cavitation tests of the PJP were carried out in behind condition to determine the inception cavitation numbers for rotor, stator and cowl. The model test results obtained were corrected for full scale Reynolds number and subsequently analyzed for cavitation inception speeds at different operating depths. From model tests it was also found that the cavitation inception of the rotor takes place on the tip face side at higher advance ratios and cavitation shifts towards the suction side as the RPS increases whereas the stator and cowl are free from cavitation.

• Geomechanics and Engineering
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• v.16 no.2
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• pp.113-124
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• 2018

Under repeated loading, the residual stresses within the subgrade and subsoil can accelerate the deformation of the road structures. In this paper, a series of laboratory cyclic loading model tests and small-scale model tests were conducted to investigate the dynamic stress response within soils under different loading conditions. The experimental results showed that a dynamic stress accumulation effect occurred if the soil showed cumulative deformation: (1) the residual stress increased and accumulated with an increasing number of loading cycles, and (2) the residual stress was superimposed on the stress response of the subsequent loading cycles, inducing a greater peak stress response. There are two conditions that must be met for the dynamic stress accumulation effect to occur. A threshold state exists only if the external load exceeds the cyclic threshold stress. Then, the stress accumulation effect occurs. A higher loading frequency results in a higher rate of increase for the residual stress. In addition to the superposition of the increasing residual stress, soil densification might contribute to the increasing peak stress during cyclic loading. An increase in soil stiffness and a decrease in dissipative energy induce a greater stress transmission within the material.

• Korean Management Science Review
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• v.28 no.1
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• pp.141-158
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• 2011

This study concerns with an applicability of the management science approach to the score adjustment among the College Scholastic Aptitude Test(CSAT) optional subjects. A linear programming model is developed to minimize the sum of score distortions between optional subjects. Based on the analysis of the 377,089 CSAT(2010) applicants' performances in social science test section, this study proposes a new approach for the score equating or linking method of the educational measurement theory. This study makes up for the weak points in the previous linear programming model. First, the model utilize the standard score which we can get. Second, the model includes a goal programming concept which minimizes the gap between the adjusting goal and the result of the adjustment. Third, the objective function of the linear programing is the weighted sum of the score distortion and the number of applicants. Fourth, the model is applied to the score adjustment problem for the whole 11 optional subjects of the social science test section. The suggested linear programming model is a generalization of the multi-tests linking problem. So, the approach is consistent with the measurement theory for the two tests and can be applied to the optional three or more tests which do not have a common anchor test or a common anchor group. The college admission decision with CSAT score can be improved by using the suggested linear programming model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.787-794
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• 2010

This paper aims to evaluate the effect of each material ingredient on mechanical and dynamic performance and to determine an optimal mixing condition of a rubber granule layer. To minimize the required number of tests, the test matrix was established by using the design of experiments (DOE). The tensile tests were then performed to identify the mechanical properties. Also, to evaluate the dynamic performance that the IAAF has required for athletics tracks for athletes' safety and balance, a series of impact tests were performed by using the so-called the "artificial athlete" machine. Finally, the response surface methodology was used to decide the optimal mixing conditions needed to achieve a high level of mechanical properties and dynamic performance.

• The Journal of Industrial Distribution & Business
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• v.13 no.12
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• pp.59-71
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• 2022

Purpose: Re-handling is an important factor that reduces the productivity of container terminals. The purpose of this paper is to propose an algorithm to find the order of container movement in order to minimize the number of re-handling in the process of carrying-out. Research design, data and methodology: This paper proposes an algorithm to set the optimal carry-out order and conducted tests to evaluate the performance of the algorithm proposed in this paper. 1. tests comparing the performance of an algorithm proposed in an existing study with that proposed in this paper. 2. Performance tests for bays with complex structures. Results: Test 1 shows that the algorithm proposed in this paper performs better than the existing algorithm. Test 2 shows that the proposed algorithm can also be used in bays with considerably high complexity and that there is no major problem with using it in the field. Conclusion: While we can conclude that the proposed algorithm as a carry-out algorithm is more effective than conventional methods, research is needed on how to handle more complex bays more effectively. This is because the larger the bay, the more container combinations increase, making it difficult to find the best carry-out order.

• Structural Monitoring and Maintenance
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• v.9 no.1
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• pp.1-27
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• 2022

Extensive laboratory tests were conducted to investigate the effect of load amplitude, geogrid position, and number of geogrid layers, thickness of ballast layer and clay stiffness on behavior of reinforced ballast layer and induced strains in geogrid. A half full-scale railway was constructed for carrying out the tests, the model consists of two rails 800 mm in length with three wooden sleepers (900 mm × 10 mm × 10 mm). The ballast was overlying 500 mm thickness clay in two states, soft and stiff state. Laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, soil pressure and pore water pressure induced in the clay were measured in reinforced and unreinforced ballast cases. It was concluded that the effect of frequency on the settlement ratio is almost constant after 500 cycles. This is due to that the total settlement after 500 cycles, almost reached its peak value, which means that the ballast particles become very close to each other, so the frequency is less effective for high contact particles forces. The average maximum vertical stress and pore water pressure increased with frequency.

• Geomechanics and Engineering
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• v.4 no.2
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• pp.121-134
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• 2012

The paper presents the results of identification, monotonous and cyclic triaxial tests on a potentially liquefiable soil from the Guadeloupe island. The material is a very soft clayey soil whose susceptibility to liquefaction is not clear when referring to index properties such as grain size distribution, plasticity, etc. The classifications found in the literature indicate that the material has rather a "clay-like" behaviour, i.e., is not very susceptible to liquefaction, but its properties are very close to the threshold values given by the authors. Cyclic triaxial tests carried out on the material under different conditions show that liquefaction is possible for a relatively important level of cyclic deviator or number of cycles. The second part of the paper is devoted to the study of the recovery of the soil after liquefaction and possibly reconsolidation. For the specimens tested without reconsolidation, that simulated the soil immediately after an earthquake, the recovery is nearly non-existent but the drop in pore pressure during extension results in a small available strength. On the contrary, after reconsolidation, the increase in strength of the liquefied specimens is quite large, compared to the initial state, but with unchanged failure envelopes.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.5
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• pp.427-436
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• 2010

The printer sound has many aspects which define its quality because the printer has lots of components and its operation is very complicated. These sound qualities are related to the international competition in printer markets. Recordings inside anechoic chamber were analyzed and a large number of sounds were stimulated using digital signal processing technique. First subjective tests of the printer sound were conducted using semantic different method. By applying factor analysis to the subjective response, two important factors of sound quality were extracted. Second subjective tests were conducted to evaluate the quietness and the impulsiveness of the printer sounds. On the other hand, sound metrics are calculated applying psychoacoustic theories. In this paper, the nonlinear relation between subjective evaluation and sound metrics was identified using artificial neural network and the printer sound quality index was developed. Later, subjective sound quality evaluation will be estimated and evaluated using this index.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2702-2713
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• 2022

A steam generator tube rupture accompanying a core damage may cause the fission product to be released to environment bypassing the containment. In such an accident, the steam generator is the major path of the radioactive aerosol release. AEOLUS facility, the scaled-down model of Korean type steam generator, was built to examine the aerosol removal in the steam generator during the steam generator tube rupture accident. Integral and separate effect tests were performed with the facility for the dry and flooded conditions, and the decontamination factors were presented for different tube configurations and submergences. The dry test results were compared with the existing test results and with the analyses to investigate the aerosol retention physics by the tube bundle, with respect to the particle size and the bundle geometry. In the flooded tests, the effect of submergence were shown and the retention in the jet injection region were presented with respect to the Stokes number. The test results are planned to be used to constitute the aerosol retention model, specifically applicable for the analysis of the steam generator tube rupture accident in Korean nuclear power plants to evaluate realistic fission product behavior.

• Geomechanics and Engineering
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• v.23 no.4
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• pp.381-392
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• 2020

The difficulties, challenges and limitations faced in standard pressuremeter testing in the measurement of low soil deformations led a number of researchers to think about the possible modification of the equipment, and especially the replacement of the volumeter by a Hall Effect sensor. This article is a major contribution in this direction. It makes an attempt to detail the design, manufacture and operation of the new equipment. The calibration of the various components was carried out according to the rules presently in force. This proposal was applied, on an exploratory basis, to the data of a real site located in France. The authors present the preliminary results of some cyclic pressuremeter tests, previously carried out in the laboratory, on a sandy material, and they then provide a basic interpretation of these results. The findings indicated that the proposed apparatus is capable of providing high-quality information about constraints and deformations. Although these tests were performed within the laboratory, it was possible to analyze the power, quality, performance and insufficiencies of the proposed equipment.