• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.56-62
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• 2013

The system analysis and design program of the liquid rocket engine has been developed for preliminary conceptual design process. The program analyzes the engine system and obtains optimal design variables by optimization methods such as genetic algorithm for the higher specific impulse and thrust to weight ratio using given input parameters and requirements. For the users' convenience, the GUI has been offered. The 3-dimensional model for the visualization of results has been interconnected with the CATIA program. The results are expected to be applied to the design process of the space launch vehicle for the analysis and selection of the propulsion system.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.803-809
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• 2023

This paper analyzes and evaluates to optimally build a data collection system essential for factory energy management systems on an edge-based lightweight platform. A "Sensor/OPC-UA simulator" was developed based on sensors in an actual food factory and used to evaluate the storage engine of edge devices. The performance of storage engines in edge devices was evaluated to suggest the optimal storage engine. The experimental results show that when using the RocksDB storage engine, it has less than half the memory and database size compared to using InnoDB, and has a 3.01 times faster processing time. This study enables the selection of advantageous storage engines for managing time-series data on devices with limited resources and contributes to further research in this field through the sensor/OPC simulator.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.8-18
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• 2024

The present study concerns reduced order modeling of a marine diesel engine, which can be used for outlier detection in status monitoring and carbon intensity index calculation. Principal Component Analysis (PCA) is introduced for the reduced order modeling, focusing on the feasibility of detecting and treating nonlinear variables. By cross-correlation, it is found that there are seven non-linear data channels among 23 data channels, i.e., fuel mode, exhaust gas temperature after the turbocharger, and cylinder coolant temperatures. The dataset is handled so that the mean is located at the nominal continuous rating. Polynomial presentation of the dataset is also applied to reflect the linearity between the engine speed and other channels. The first principal mode shows strong effects of linearity of the most data channels to show the linearity of the system. The non-linear variables are effectively explained by other modes. second mode concerns the temperature of the cylinder cooling water, which shows small correlation with other variables. The third and fourth modes correlates the fuel mode and turbocharger exhaust gas temperature, which have inferior linearity to other channels. PCA is proven to be applicable to data given in binary type of fuel mode selection, as well as numerical type data.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.8-12
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• 2015

Non-esterified bio-diesel fuel saves cost by no esterified process and its performance was more similar to diesel oil than esterified bio-diesel fuel when the fuel blended 95% diesel oil and 5% it was used on diesel engine with electronic control system. A performance optimization is necessary for application of non-esterified bio-diesel fuel blended with diesel oil 95% on the latest diesel engine. In this study, test using fractional factorial design was accomplished at 25% and 50% partial load in order to evaluate influence of controllable 6 factors on responses such as specific fuel consumption, nitrogen oxides and coefficiency of variation of indicated mean effective pressure as basic experiment for performance optimization of this fuel. It is cleared that the injection timing and common rail pressure of 6 factors are mainly effective and its effect level is different according to load.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.62-80
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• 2021

The requirements for the next-generation propulsion system and for a good propellant have been summarized. The characteristics and effectiveness of kerosene, hydrogen, and methane, which are the fuels that are mainly attracting attention in Korea and abroad, were compared with each other. As a result of the comparison, methane was evaluated to be more advantageous than other fuels in reliability, cost, reusability, maintenance, eco-friendliness, safety, lifespan, technical difficulties, engine cycle selection, application of common bulkhead, and non-disassembly/reassembly delivery. And in terms of performance, the specific impulse of methane is higher than that of kerosene, so the efficiency of the launch vehicle can be increased. Methane's properties incluidng eco-friendliness, low-temperature combustion, long life, and maintenability make it beneficial for reuse and for the development of multi-purpose engines.

• Tribology and Lubricants
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• v.37 no.5
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• pp.172-178
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• 2021

An injector is a mechanical device present inside the engine. Its main function is to supply an appropriate volume of fuel into the combustion chamber, which is directly related to the overall engine efficiency of a car. During the operation of an injector, a magnetic force lifts the parts of the injector from closed position to open position which generates a horizontal force on the needle. The horizontal force acts on a different position from that of the center of mass of the needle. Therefore, this causes eccentricity in the needle and the generation of a tilting motion during the lifting operation which can result in wear. However, appropriate selection of clearances for these parts can prevent wear. In this study, lubrication analysis is conducted to determine the optimum clearance of parts with sliding motion inside the injector. The height functions are derived considering the dynamic behavior and relative velocity of the parts. Using the derived height function, the pressure profiles are calculated for the lubricated surfaces from the Reynolds' equation. Subsequently, the fluid reaction forces are calculated. The equations of motions are applied to the fluid reaction forces and external forces are solved to calculate the minimum film thickness between each part with variation in the clearances. Finally, the optimum clearances are determined. The effect of the clearances on the behavior of the moving parts is presented and discussed.

• Journal of Navigation and Port Research
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• v.48 no.3
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• pp.221-231
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• 2024

The aim of this study was to enhance the safety and care of mental health for seafarer working in passenger ship workspaces. Brightness, color values, and color distribution were investigated with issues and improvement ways identified through seafarers' interviews. Firstly, previous studies, references, current policy, regulations, and accident case studies were reviewed. Color compositions of wheelhouse and engine room of M Ship were then surveyed in the field. Color values of each space were analyzed using a colorimeter. Colormeter analysis of brightness and color measurements in the wheelhouse and engine areas indicated that ceilings, walls, and floors were generally dark, with the engine area being very dark. Regarding color, green and blue were distributed in the ceiling of the wheelhouse and engine area, while red and blue were in the walls and floors of the wheelhouse and engine area. According to interviews with seafarers currently working at engine rooms, they responded about their experience of near miss incidents due to a decrepit indoor environment, a dark working environment, slippery and bright flooring, and stairs that were not suitable for domestic users. Thus, when installing lighting in the future, the brightness of the space should be improved by distinguishing between night and day. A lighting plan considering the location of lighting, level of shadow formation and contrast, reflectance of the facility, glare, color of light, floor color plan, and material selection is needed. A facility design suitable for domestic users is also needed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.285-288
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• 2006

Genetic Algorithms(GA) which searches optimum solution using natural selection and the law of heredity has been applied to teaming algorithms in order to estimate performance deterioration of the aircraft gas turbine engine. The compressor, gas generation turbine and power turbine are considered for estimation for performance deterioration of a complex component at design point was conducted. As a result of that, complex defect diagnostics has been conducted. As a result, the accuracy of diagnostics were verified with its relative error with in 10% at each component.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.188-196
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• 2014

The spray and combustion characteristics of n-dodecane fuel were investigated in a CVCC (constant volume combustion chamber). The selection of ambient conditions for the spray followed ECN (engine combustion network) guidelines, which simulates the ambient condition of diesel engines at start of fuel injection. ECN is a collaboration network whose main objective is to establish an internet library of well-documented experiments that are appropriate for model validation and the advancement of scientific understanding of combustion at conditions specific to engines. Therefore repeatability of the experiments with high accuracy was important. The ambient temperature was varied from 750 to 930 K while the density was fixed at around $23kg/m^3$. The injection pressure of the fuel was varied from 500 to 1500 bar. The spray was injected in both non-reacting ($O_2$ concentration of 0%) and reacting conditions ($O_2$ concentration of 15%) to examine the spray and the combustion characteristics. Direct imaging with Mie Scattering was used to obtain the liquid penetration length. Shadowgraph was implemented to observe vapor length and lift-off length at non-reacting and reacting conditions, respectively. Pressure data was analyzed to determine the ignition delay with respect to the spray and ambient conditions.

• Journal of Internet Computing and Services
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• v.19 no.2
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• pp.49-56
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• 2018

Internet news consumption is rapidly growing in Korea, and majority of that is being done through Naver, Korea's primary search engine. Naver is also the go-to search engine for smartphone use. This study analyzed 824 most popular news accessed via mobile gears; the news items were selected from Naver's 'Daily Top 10 Stories,' dating from March 2016 to December 2016. The results indicate that entertainment news were the most viewed, while political and social issue news were the most liked and commented by mobile users. With regard to news value, 'prominence' and 'impact' were the two most important factors that influenced a user's news selection process in a mobile environment. The degree of a news' 'prominence' was the most important factor that determined the number of views, while 'impact' was critical to determining "the most commented-upon" and "the most liked" news. The results also indicate that mobile news consumers prefer more dramatic storylines and events that incite public anger or grief, threaten the safety of citizens, or evoke emotional sympathy rather than 'hard news' about such subjects as politics and economics.