• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.99-112
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• 2021

The prediction of maneuverability is very important in the design process of an underwater vehicle. In this study, we predicted the steady turning ability of a symmetrical underwater vehicle while considering interactions between the yaw rate and drift/rudder angle through a simulation-based methodology. First, the hydrodynamic force and moment, including coupled derivatives, were obtained by computational fluid dynamics (CFD) simulations. The feasibility of CFD results were verified by comparing static drift/rudder simulations to vertical planar motion mechanism (VPMM) tests. Turning motion simulations were then performed by solving 2-degree-of-freedom (DOF) equations with CFD data. The turning radius, drift angle, advance, and tactical diameter were calculated. The results show good agreement with sea trial data and the effects on the turning characteristics of coupled interaction terms, especially between the yaw rate and drift angle.

• The Korean Journal of Nuclear Medicine
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• v.35 no.2
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• pp.100-112
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• 2001

Purpose: The purpose of this study was to establish optimal imaging acquisition conditions for the GE $Advance^{TM}$ PET imaging system by performing the acceptance tests designed by National Electrical Manufacturers Association (NEMA) protocol and General Electric Medical Systems (GEMS) test procedures. Materials and Methods: Performance tests were carried out with $^{18}FDG$ radioactivity source and phantoms by using a standard acquisition mode. Transaxial resolution and scatter traction tests were performed with a line source and axial resolution with a point source, respectively. A cylindrical phantom made of polymethylmethacrylate (PMMA) was used to measure sensitivity, count rate losses and randoms, uniformity correction, and attenuation inserts were added to measure remaining tests. The test results were acquired in a diagnostic acquisition mode and analyzed mainly on high sensitivity mode. Results: Transaxial resolution and axial resolution were measured as average of 4.65 mm and 3.98 mm at 0 cm, and 6.02 mm and 6.71 mm at 20 cm on high sensitivity mode, respectively. Average scatter fraction was 9.87%, and sensitivity was $225.8kcps/{\mu}Ci/cc$ of trues. Activity at 50% deadtime was $4.6{\mu}Ci/cc$, and the error of count rate correction at that activity was from 1.49% to 3.83%. Average nonuniformity for total slice w3s 8.37%. The accuracy of scatter correction was -0.95%. The accuracies of attenuation correction were 5.68% for air, 0.04% for water and -6.51% for polytetrafluoroethylene (PTFE). Conclusion: The results satisfied most acceptance criteria, indicating that the GE $Advance^{TM}$ PET system can be optimally used for clinical applications.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.151-159
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• 2017

This study deals with characteristics and risk of a PM based on user survey result, road driving test and data analysis of PM accident. Text mining method is applied to extract PM accident data from Big Data, which are claim data of private insurance company. Road driving test and survey on safety, convenience, noise, overtake ability, steering ability, and climbing ability of PM are performed to evaluate user's safety and convenience considering domestic road condition. As the result of claim data analysis, annual average increase rate of PM accident is 47.4% and average compensation of personal mobility is higher than that of bicycle by maximum 1.5 times. 79.8% of PM accident is self-caused accident due to unskilled driving and age-specific diagnosis rate of driver over 60 is higher than that of under 60. Diagnosis rate of over 60 at lower limb, foot, rib and spine is especially higher than that of under 60. As the result of road driving test and user survey, satisfaction level on safety and convenience of PM is evaluated as close to that of bicycle and satisfaction level of PM is increased after boarding. Overtake ability, steering ability, and climbing ability of PM are evaluated as same or better than that of bicycle but warning equipment to pedestrian or bike such as horn is required because noise level of PM during driving is too low. Finally, user survey result shows that bicycle road is suitable for PM and safety standard, advance-education and insurance are required for PM. It is suggested that drivers' license for PM can be replaced by advance-education. Results of this study can be used to prepare safety measures and legal basis for PM operation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.857-870
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• 2017

The use of shield TBM is gradually increasing due to the urbanization of social infrastructures. Reliable estimation of advance rate is very important for accurate construction period and cost. For this purpose, it is required to develop the prediction model of advance rate that can consider the ground properties reasonably. Based on the database collected from field, statistical prediction procedure for field penetration index (FPI) was modularized in this study to calculate penetration rate of shield TBM. As output parameter, FPI was selected and various systems were included in this module such as, procedure of eliminating abnormal dataset, preprocessing of dataset and ridge regression with best subset selection. And it was finally validated by using field dataset.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.53-56
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• 2005

A Laboratory study was conducted to evaluate the kinetics of oxidation of trichloroethylene (TCE) in groundwater by potassium permanganate $(KMnO_4)$, Consumption of permanganate by TCE and aquifer materials was also evaluated to obtain an appropriate injection rate of $KMnO_4$. TCE degradation by $KMnO_4$ in the absence of aquifer material showed effective with pseudo-first order rate constant, $k_{obs}=1.8110^{-3}\;s^{-1}\;at\;KMnO_4=500mg/L$. TCE oxidation by $KMnO_4$ was found to be second order reaction and the rate constant, $k=0.65{\pm}0.08\;M^{-1}s^{-1}$, was independent of pH changes. $KMnO_4$ consumption rate by groundwater sampled from field site was not significant, indicating that groundwater containing negligible amount of dissolved organic matter does not have any influence on the $KMnO_4$ degradation. Meanwhile, aquifer materials from field site were actively reacted with permanganate, resulting in the significant consumption of $KMnO_4$. It might be attributed to the existence of metal oxides in aquifer materials, Based on the rate constants obtained from this study, appropriate injection rate of permanganate and TCE removal rate in groundwater could be estimated.

• Tunnel and Underground Space
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• v.30 no.6
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• pp.540-550
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• 2020

Machine learning has been actively used in the field of automation due to the development and establishment of AI technology. The important thing in utilizing machine learning is that appropriate algorithms exist depending on data characteristics, and it is needed to analysis the datasets for applying machine learning techniques. In this study, advance rate is predicted using geotechnical and machine data of TBM tunnel section passing through the soil ground below the stream. Although there were no problems of application of statistical technology in the linear regression model, the coefficient of determination was 0.76. While, the ensemble model and support vector machine showed the predicted performance of 0.88 or higher. it is indicating that the model suitable for predicting advance rate of the EPB Shield TBM was the support vector machine in the analyzed dataset. As a result, it is judged that the suitability of the prediction model using data including mechanical data and ground information is high. In addition, research is needed to increase the diversity of ground conditions and the amount of data.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.520-533
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• 2021

It is necessary to increase the blasting efficiency in order to minimize the economic loss caused when the excavation cross section is reduced due to the stability problem of underground mining development, and for this, a new blasting design is proposed. In this study, the blasting efficiency of the general design in the field, the suggestion designI, which added two columns to production blasting, and the suggestion design II, which added one column to create asymmetry, is compared. Advance rate and fragmentation were selected as the evaluation index of the blasting efficiency. In the case of advance rate, compared to the normal, the suggestionI improved by 6.07% and the suggestionII improved by 4.65%. In the case of fragmentation, based on P80, compared to the normal, the suggestionI reduced about 58% and the suggestionII was about 47%. Accoording to the evaluation index, the suggestion designI shows better blasting efficiency than the suggestion designII. But considering the additional work time and cost required for the suggestion designI due to the insignificant difference in the evaluation index results, the asymmetry V-cut, the suggestion designII, is judged to be a more suitable blasting design for the site.

• Tunnel and Underground Space
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• v.34 no.3
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• pp.185-195
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• 2024

The Incheon Metro Line 1 Geomdan Extension Phase 1 is the first project in South Korea where both a roadheader and TBM (Tunnel Boring Machine) are being used together. The shield TBM tunnel section is 1,057 m long, and is mostly composed of rock, including the section beneath the Airport Railroad and the Gyeongin Ara Waterway. A 7.8 m earth pressure balance shield TBM was used for tunnel excavation. The average monthly advance rate for both the North and South tracks is 239.1 m, with a maximum monthly advance rate of 334.5 m. This technical article comprehensively evaluates the productivity of the shield TBM, focusing on the TBM excavation performance. Above all, it aims to provide useful reference material for the successful execution of shield TBM tunnel construction.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.1-7
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• 2008

Recent trends of development in small size gasoline engines are both to have higher compression ratio for the purpose of improved fuel consumption and to advance spark timing up to DBL in a low to mid engine speed region for a good acceleration performance of vehicles. However, there occurs the deviation of corrected engine torque results during engine performance test on dynamometer because test conditions influence the onset of knock. Therefore, this research shows the test deviation of corrected engine torque decreases when knock correction rate is used.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.162-167
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• 2000

Construction machinery includes an engine enclosure separated from a cooling system enclosure by a wall to reduce noise and advance cooling system performance. For this structure, however, the axial fan cannot be of benefit to the engine room, and so the temperature rise in the engine room makes several bad conditions. This paper proposes that hot air in engine room is evacuated tv secondary pipe using jet pump. This paper demonstrates the structure and the effect of jet pump and useful guideline on design of area, length, and shape of secondary pipe to maximize the effect of jet pump.