• Journal of ILASS-Korea
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• v.29 no.1
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• pp.7-15
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• 2024

This study investigates the performance of 2.0L hybrid vehicles equipped with Liquefied Petroleum Gas (LPG) fuel engines, using energy flow analysis. By incorporating a direct LPG injection system (LPDi), the research aims to overcome the reduced maximum output commonly associated with LPG engines. Moreover, the integration of a hybrid system is explored as a means to enhance vehicle fuel economy while reducing CO₂ and emissions. The study employs data from FTP-75 and HWFET driving cycle to inform future research efforts focused on predicting CO₂ emissions and fuel economy for Hybrid Electric Vehicles utilizing LPG Direct Injection. The findings offer insights into optimizing fuel systems for better environmental and operational performance in hybrid vehicles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3A
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• pp.217-224
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• 2010

In this paper, we propose a hard handover algorithm for a base station's self-optimization, one of the automatic operational technologies for the 3GPP LTE systems. The proposed algorithm simultaneously considers a mixed target sell selection method for optimal selection and a multiple parameter based active hysteresis method with the received signal strength from adjacent cells and the cell load information of the candidate target cells from information exchanges between eNBs through X2 interface. The active hysteresis method chooses optimal handover hysteresis value considering the costs of the various environmental parameters effect to handover performance. The algorithm works on the optimal target cell and the hysteresis value selections for a base station's automatic operational optimization of the LTE system with the gathered informaton effects to the handover performance. The simulation results show distinguished handover performances in terms of the most important performance indexes of handover, handover failure rate and load balancing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.187-187
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• 2012

Solution-processed metal-alloy oxides such as indium zinc oxide (IZO), indium gallium zinc oxide (IGZO) has been extensively researched due to their high electron mobility, environmental stability, optical transparency, and solution-processibility. In spite of their excellent material properties, however, there remains a challenging problem for utilizing IZO or IGZO in electronic devices: the supply shortage of indium (In). The cost of indium is high, what is more, indium is becoming more expensive and scarce and thus strategically important. Therefore, developing an alternative route to improve carrier mobility of solution-processable ZnO is critical and essential. Here, we introduce a simple route to achieve high-performance and low-temperature solution-processed ZnO thin film transistors (TFTs) by employing alkali-metal doping such as Li, Na, K or Rb. Li-doped ZnO TFTs exhibited excellent device performance with a field-effect mobility of $7.3cm^2{\cdot}V-1{\cdot}s-1$ and an on/off current ratio of more than 107. Also, in case of higher drain voltage operation (VD=60V), the field effect mobility increased up to $11.45cm^2{\cdot}V-1{\cdot}s-1$. These all alkali metal doped ZnO TFTs were fabricated at maximum process temperature as low as $300^{\circ}C$. Moreover, low-voltage operating ZnO TFTs was fabricated with the ion gel gate dielectrics. The ultra high capacitance of the ion gel gate dielectrics allowed high on-current operation at low voltage. These devices also showed excellent operational stability.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.2
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• pp.157-163
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• 2015

To establish National Reference Method (NRM) for $PM_{2.5}$, operational performance of 5 different commercial gravimetric-based $PM_{2.5}$ measuring instruments was assessed at Bulkwang monitoring station from January 23, 2014 to February 28, 2014. First, physical properties, design, and functional performance of the instruments were assessed. Evaluation was carried out to determine whether operating method for the instruments and levels of QA/QC activities meet the data quality objectives (DQOs). To verify whether DQOs were satisfied, reproducibility of QA/QC procedures, accuracy, relative sensitivity, limit of detection, margin of error, and coefficient of determination of the instruments were also evaluated. Results of flow rate measurement of 15 candidate instruments indicated that all the instruments met performance criteria with accuracy deviation of 4.0% and reproducibility of 0.6%. Comparison of final $PM_{2.5}$ mass concentrations showed that the coefficient of determination ($R^2$) values were greater than or equal to 0.9995, and concentration gradient ranged from 0.97 to 1.03. All the instruments satisfied criteria for NRM with the estimated precision of 1.47~2.60%, accuracy of -1.90~3.00%, and absolute accuracy of 1.02~3.12%. This study found that one particular type of measuring instrument was proved to be excellent, with overall evaluation criteria satisfied.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.448-455
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• 2007

As Decentralized Generation(DG) becomes more reliable and economically feasible, it is expected that a higher application of DG units would be interconnected to the existing grids. This new market penetration of DG technologies is linked to a large number of factors like technologies costs and performances, interconnection issues, safety, market regulations, environmental issues or grid connection constrains. This paper describes the procedures and results for the mechanical, electrical, and environmental tests of MGT on actual grid-connection under Korean regulations. As one of the achievements, the simulation model of MGT was developed, so that it will be able to analyze or propose new distributed generation system using MGT. The field test was conducted in order to respond to a wide variety of needs for noise reduction and utilization and its performance was evaluated in consideration of its operational problems. The MGT is successfully supplying electricity to Korean grids with satisfying various regulations. The suggested strategy and experience for the evaluation of the distributed generation will be used for the introduction of other distributed generation technologies into the grid in the future.

• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.158-168
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• 2005

In this study, the discharging effluents from have been 9 municipal wastewater treatment plants surveyed for 1 year-period. Statistics including probability distribution, cumulative occurrence concentration and other statistical parameters were presented. In addition, treatment performance and its stability were also discussed. Most of the plants, have an operational problem of high soluble organic content in the secondary effluent which may be associated with the integrated treatment of human and livestock manures. Nitrogen concentration in the effluents were usually higher during the period of summer and winter. It was found that this is mainly due to lack of the proper C/N ratio during the summer, or/and the effects of low temperature and less dilution by dry weather during the winter. Phosphorus concentration is sharply increased in June. Discussion with plant operators told that it is due to the dissolution of phosphate from the sludge accumulated in the primary settling tanks from the early spring to june. During this period, usually, sludge treatment line is highly overloaded with flush-outs of the sediments also stored in the bottom of combined sewer due to the low flow during winter season. Most of the plants can meet new effluent discharge limits of the nitrogen and phosphorus, and total coliform without further treatment.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4191-4203
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• 2023

Robotics applications are greatly needed in hazardous locations, e.g., fusion and fission reactors, where robots must perform delicate and complex tasks under ionizing radiation conditions. The drawback is that some robotic parts, such as active electronics, are susceptible to radiation. It can lead to unexpected failures and early termination of the robotic operation. This paper analyses the ionizing radiation effect from 0.09 to 1.5 Gy/s in robotic components (microcontrollers, servo motors and temperature sensors). The first experiment compares the performance of various microcontroller types and their actuators and sensors, where different mitigation strategies are applied, such as using Radiation-Hardened (Rad-Hard) microcontrollers or shielding. The second and third experiments analyze the performance of a 3-Degrees of Freedom (DoF) robotic arm, evaluating its components' responses and trajectory. This study enhances our understanding and expands our knowledge regarding radiation's impact on robotic arms and components, which is useful for defining the best strategies for extending the robots' operational lifespan, especially when performing maintenance or inspection tasks in radiation environments.

• Environmental Engineering Research
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• v.24 no.3
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• pp.363-375
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• 2019

Micellar-enhanced ultrafiltration (MEUF) is a surfactant-based separation technique and has been investigated for the removal of heavy metals from wastewater. The performance of heavy metals removal from wastewater through MEUF relies on membrane characteristics, surfactant properties, various operational parameters including operating pressure, surfactant and heavy metal concentration, pH of the solution, temperature, and presence of dissolved solutes and salts. This study presents an overview of literature related to MEUF with respect to the all significant parameters including membranes, surfactants, operating conditions and MEUF hybrid processes. Moreover, this study illustrates that MEUF is an adaptable technique in various applications. Nowadays water contamination caused by heavy metals has become a serious concern around the globe. MEUF is a significant separation technique in wastewater treatment that should be acknowledged, for the reason that removal of heavy metals contamination even at lower concentrations becomes achievable, which is evidently made known in the presented review. Hybrid processes presented the better results as compared to MEUF. Future studies are required to continue the experimental work with various combinations of surfactant and heavy metals, and to investigate for the treatment of concentrated solutions, as well as for real industrial wastewater.

• Journal of the Korean Institute of Plant Engineering
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• v.23 no.4
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• pp.5-19
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• 2018

Recently, utilizing the supply chain among companies, major companies support their sub-vendors to establish an environmental management system and transfer the clean production technology(know-how) to them for strengthening of environmental competitiveness. Thus, Green Supply Chain Management(GSCM) became a key successful factor for companies to be environmentally sustainable. This research endeavors to identify the relationship among the inside and outside GSCM implementation activities of Korean manufacturing companies and their financial, operational and environmental performances. Based on a the review of previous research findings, twenty one hypotheses are developed and examined. Total 251 valid responses from 1,634 survey responses are identified and the structural equation models(SEM) are developed and analysed for examining our hypotheses. The result shows that inside GSCM has a positive effect on outside GSCM. Also, it reveals that companies' performances are more positively affected by inside GSCM than by outside GSCM.

• Membrane and Water Treatment
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• v.13 no.3
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• pp.147-166
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• 2022

Liquid-liquid membrane contactor (LLMC), a device that exchanges dissolved gas molecules between the two sides of a hydrophobic membrane through membrane pores, can be employed to extract ammoniacal nitrogen from a feed solution, which is transported across the membrane and accumulated in a stripping solution. This LLMC process offers the promise of improving the sustainability of the global nitrogen cycle by cost-effectively recovering ammonia from wastewater. Despite recent technological advances in LLMC processes, a comprehensive review of their feasibility for ammonia recovery is rarely found in the literature. Our paper aims to close this knowledge gap, and in addition to analyze the challenges and provide potential solutions for improvement. We begin with discussions on the operational principles of the LLMC process for ammonia recovery and membrane types and membrane configurations commonly used in the process. We then assess the performance of the process by reviewing publications that demonstrate its practical application. Challenges involved in the implementation of the LLMC process, such as membrane fouling, membrane wetting, and chemical requirements, are presented, along with discussions on potential strategies to address each. These strategies, including membrane modification, hybrid process design, and process optimization based on cost-benefit analysis, guide the reader to identify key areas of future research and development.