• Transactions of the KSME C: Technology and Education
• /
• v.2 no.1
• /
• pp.9-13
• /
• 2014

Nowadays, among several reasons for customers to choose their own cars, NVH performance plays much important role. The concern for the car interior noise is increasing recently, because electric cars and hybrid cars generate less engine noise which was the main noise of traditional cars. According to oversea references, high Lateral Dynamic Stiffness (LDS) of vehicle wheels is described to reduce Structure Bone Noise (SBN) which is being generated while driving cars. However availablet test standards and test results are not enough, in this study the interior noise has been measured after attaching a same tyre to several wheels which has different Lateral Dynamic Stiffness. The test has verified that the interior noise differs depending on Lateral Dynamic Stiffness of wheels. As to this, the reduction of the interior noise can be possible with the optimal design of the wheel.

• Journal of Auto-vehicle Safety Association
• /
• v.8 no.4
• /
• pp.12-17
• /
• 2016

NHTSA (National Highway Traffic Safety Administration) has offered consumers the vehicle safety information on their car since 1978. NHTSA believes that they contribute auto makers to develop safer vehicle for customers, which will result in even lower numbers of deaths and injuries resulting from motor vehicle crashes. NHTSA has been studied why people are still dying in frontal test despite of the use of many restraints system and they understand that current test does not reflect real world crash data such as oblique and corner impact test. As a result, NHTSA announced that a new test method will be introduced to use of enhanced biofidelic dummy and new crash avoidance technology evaluation from 2019. New and refined injury criteria will be applied to Head / Neck / Chest / Lower Leg. BrIC(Brain Injury Criterion)value in NHTSA test results using THOR dummy from 2014 to 2015 was average 0.91 and 1.24 in driver and passenger dummies. IIHS 64kph SOF test is the most likely to new frontal oblique test in an aspect of offset impact which is being studied by NHTSA. In this paper, we focused on head injury, especially brain injury - BrIC and conducted IIHS 64kph SOF (Small Offset Front) test with Hybrid III dummy to evaluate the injury for BrIC. Based on the test results, these data can be predicted BrIC level and US NCAP rating with current vehicle.

• Transactions of Materials Processing
• /
• v.29 no.4
• /
• pp.194-202
• /
• 2020

In this paper, experimental and numerical study on a combined sheet metal forming and plate forging of a seal part of a passenger car's hub bearing is conducted to develop the new process of which target is to remove machining process by plate forging and to achieve near-net shape manufacturing. The previous process of a sheet metal forming inevitably needed a machining process for making stepped sheet after conventional sheet metal forming in a progressive way. The stepped sheet is intended to be formed by plate forging in this study. Through the systematic way of developing the combined forming process using solid elements based-elastoplastic finite element method (FEM), several conceptual designs are made and an optimized process design in terms of geometric dimensioning and tolerance of straightness of the thin part is found, which is exposed to bending in metal forming of axisymmetric part. The predicted straightness measured by the slope angle of the tilted thin region is compared with the experimental straightness, showing that they are in a good agreement with each other. Through this study, a systematic approach to optimal process design, based on elastoplastic FEM with solid elements, is established, which will contribute to innovating the conventional small-scaled sheet metal forming processes which can be dealt with by solid elements.

• Environmental Engineering Research
• /
• v.24 no.4
• /
• pp.699-710
• /
• 2019

Electric vehicles (EVs) are spreading rapidly and many counties are promoting hybrid and fully EVs through legislation. Therefore, an increasing amount of lithium ion batteries will reach the end of their usable life and will require effective and sustainable end-of-life management plan which include landfill disposal or incineration. The current research focuses on more sustainable methods such as remanufacturing, reuse and recycling in order to prepare for future battery compositions and provide insights to the need recycling methods to be developed to handle large amounts of batteries sustainably in the near future. The two most prominent material recovery techniques are hydrometallurgy and pyrometallurgy which are explored and assessed on their relative effectiveness, sustainability, and feasibility. Hydrometallurgy is a superior recycling method due to high material recovery and purity, very low emissions, high prevalence of chemical reuse and implementation of environmentally sustainable compounds. Expanding recycling technologies globally should take the research and technologies pioneered by Umicore to establish a sustainable recycling program for end-of-life EVs batteries. Emerging battery technology of Telsa show the most effective designs for high performance batteries includes the use of silicon which is expected to increase capacity of batteries in the future.

• Journal of the Korean Society for Railway
• /
• v.20 no.4
• /
• pp.466-473
• /
• 2017

Recently, domestic railway related institutes are developing pantographs for high speed trains; to lighten the upper arm, this device has a composite structure of CFRP (Carbon Fiber Reinforced Plastic) and aluminum instead of conventional steel. In the case of KTX-Sancheon, the pantograph must have a large current capacity because this system is of power-car type, supplying all necessary power for the train through a single pantograph. If the thickness of the pipe is arbitrarily increased in order to increase the current carrying capacity, without analyzing the thermal characteristics of the aluminum pipe, the increase in the weight of the upper arm may cause degradation of the current collecting performance. Therefore, in this paper, using the thermal analysis technique, we analyze the temperature change characteristics of the aluminum pipe of the upper arm over time, while receiving power at the stationary state of the KTX-Sancheon; we also examine the adequacy of the minimum thickness of the aluminum pipe in accordance with the proposed pantograph flow capacity.

• Journal of Korea Port Economic Association
• /
• v.26 no.2
• /
• pp.36-48
• /
• 2010

This primary purpose of this study is to suggest strategy a green-logistics strategy of Gwanyang bay area. The Green growth is the new growth concept based on the low carbon and environment-friendly industry. The new paradigm on the global economy growth requests a established logistics industry to be shifted into establishing the environment-friendly green logistics system. Some findings derided from this study are follows: Frist, in order to establish a environment-friendly green growth foundation, it is necessary to attract a green industry such as solar cell, wind force, hybrid car etc. Second, a green logistics system has to be established, including a green port strategy and reducing emission of carbon.

• Journal of Intelligence and Information Systems
• /
• v.23 no.2
• /
• pp.19-38
• /
• 2017

Collaborative filtering (CF) algorithm has been popularly used for implementing recommender systems. Until now, there have been many prior studies to improve the accuracy of CF. Among them, some recent studies adopt 'hybrid recommendation approach', which enhances the performance of conventional CF by using additional information. In this research, we propose a new hybrid recommender system which fuses CF and the results from the social network analysis on trust and distrust relationship networks among users to enhance prediction accuracy. The proposed algorithm of our study is based on memory-based CF. But, when calculating the similarity between users in CF, our proposed algorithm considers not only the correlation of the users' numeric rating patterns, but also the users' in-degree centrality values derived from trust and distrust relationship networks. In specific, it is designed to amplify the similarity between a target user and his or her neighbor when the neighbor has higher in-degree centrality in the trust relationship network. Also, it attenuates the similarity between a target user and his or her neighbor when the neighbor has higher in-degree centrality in the distrust relationship network. Our proposed algorithm considers four (4) types of user relationships - direct trust, indirect trust, direct distrust, and indirect distrust - in total. And, it uses four adjusting coefficients, which adjusts the level of amplification / attenuation for in-degree centrality values derived from direct / indirect trust and distrust relationship networks. To determine optimal adjusting coefficients, genetic algorithms (GA) has been adopted. Under this background, we named our proposed algorithm as SNACF-GA (Social Network Analysis - based CF using GA). To validate the performance of the SNACF-GA, we used a real-world data set which is called 'Extended Epinions dataset' provided by 'trustlet.org'. It is the data set contains user responses (rating scores and reviews) after purchasing specific items (e.g. car, movie, music, book) as well as trust / distrust relationship information indicating whom to trust or distrust between users. The experimental system was basically developed using Microsoft Visual Basic for Applications (VBA), but we also used UCINET 6 for calculating the in-degree centrality of trust / distrust relationship networks. In addition, we used Palisade Software's Evolver, which is a commercial software implements genetic algorithm. To examine the effectiveness of our proposed system more precisely, we adopted two comparison models. The first comparison model is conventional CF. It only uses users' explicit numeric ratings when calculating the similarities between users. That is, it does not consider trust / distrust relationship between users at all. The second comparison model is SNACF (Social Network Analysis - based CF). SNACF differs from the proposed algorithm SNACF-GA in that it considers only direct trust / distrust relationships. It also does not use GA optimization. The performances of the proposed algorithm and comparison models were evaluated by using average MAE (mean absolute error). Experimental result showed that the optimal adjusting coefficients for direct trust, indirect trust, direct distrust, indirect distrust were 0, 1.4287, 1.5, 0.4615 each. This implies that distrust relationships between users are more important than trust ones in recommender systems. From the perspective of recommendation accuracy, SNACF-GA (Avg. MAE = 0.111943), the proposed algorithm which reflects both direct and indirect trust / distrust relationships information, was found to greatly outperform a conventional CF (Avg. MAE = 0.112638). Also, the algorithm showed better recommendation accuracy than the SNACF (Avg. MAE = 0.112209). To confirm whether these differences are statistically significant or not, we applied paired samples t-test. The results from the paired samples t-test presented that the difference between SNACF-GA and conventional CF was statistical significant at the 1% significance level, and the difference between SNACF-GA and SNACF was statistical significant at the 5%. Our study found that the trust/distrust relationship can be important information for improving performance of recommendation algorithms. Especially, distrust relationship information was found to have a greater impact on the performance improvement of CF. This implies that we need to have more attention on distrust (negative) relationships rather than trust (positive) ones when tracking and managing social relationships between users.

• Archives of design research
• /
• v.13 no.3
• /
• pp.59-68
• /
• 2000

This thesis is about design spirit demanded by the 21st century vehicle design studied in consideration of city commuter. First of all, going over the transition of the last century vehicle design led to the arrangement of the changes in vehicle models. Even though the invention of vehicles brought about immense improvement in living standard of the people, it also brought about other factors that were harmful for human living. Through this realization the main fact that should be emphasized is that the vehicles in 21s1 century should not be a threat to the human life or be the main cause for the environmental pollution of the earth. With the question as to whether the vehicles development direction at the beginning of the year 2000 like the Retro design and Hybrid-Compact car development is appropriate to these demands, the development of City Commuter vehicle (the most human and environment-friendly concept which can also serve as the connecting means in transportation system) and its case studies were compared. Through this, the design spirit that should be inherent in environment and vehicle human and vehicle relationships and the design factors needed for the continuous development of the vehicles were arranged.(classified) Rather than suggesting a new direction for the specific style for vehicle design, this thesis is to emphasize that to improve the standard living of the people with vehicle as a product that will be continually produced in the 21st century, the morals and the mission of the designers about the environment and humanity recovery should be the core of the active movement and education of vehicle design.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.2
• /
• pp.592-597
• /
• 2013

The heat generated at the motor and inverter inside the electric compressor of inverter built-in type is mainly cooled by refrigerant and generally, there is not a thermal problem. However, the close relation of heat transfer from the motor and inverter parts to the compression part affects on compressor efficiency. Also, according to the surrounding environment and system operation condition, the increased temperature of the motor and inverter can affect the power density of the motor system, and especially, the inverter may be prevented to operate by the temperature limits. In this study, we performed thermo-flow analysis of electric compressor motor system, and investigated the heat dissipation enhancement of the motor and inverter. The motor part in the operation region of the electric compressor was generally maintained at low temperature and the inverter part at high compressor speed was lower temperature than the temperature limit of $85^{\circ}C$. However, the case of the inverter at low speed harsh condition was in excess of $10^{\circ}C$. Therefore, in order to solve the thermal problem, the heat reduction technology of the motor and inverter is essential as well as the improvement of flow path in the compressor.

• Journal of Korean Society of Transportation
• /
• v.32 no.2
• /
• pp.93-105
• /
• 2014

This study evaluated the relative efficiency of mobile emission reduction countermeasures through a Data Envelopment Analysis (DEA) approach and determined the priority of countermeasures based on the efficiency. Ten countermeasures currently applied for reducing greenhouse gases and air pollution materials were selected to make a scenario for evaluation. The reduction volumes of four air pollution materials(CO, HC, NOX, PM) and three greenhouse gases($CO_2$, $CH_4$, $N_2O$) for the year 2027, which is the last target year, were calculated by utilizing both a travel demand forecasting model and variable composite emission factors with respect to future travel patterns. To estimate the relative effectiveness of reduction countermeasures, this study performed a super-efficiency analysis among the Data Envelopment Analysis models. It was found that expanding the participation in self car-free day program was the most superior reduction measurement with 1.879 efficiency points, followed by expansion of exclusive bus lanes and promotion of CNG hybrid bus diffusion. The results of this study do not represent the absolute data for prioritizing reduction countermeasures for mobile greenhouse gases and air pollution materials. However, in terms of presenting the direction for establishing reduction countermeasures, this study may contribute to policy selection for mobile emission reduction measures and the establishment of systematic mid- and long-term reduction measures.