• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.45 no.4
• /
• pp.109-117
• /
• 2022

Most of real-world decision-making processes are used to optimize problems with many objectives of conflicting. Since the betterment of some objectives requires the sacrifice of other objectives, different objectives may not be optimized simultaneously. Consequently, Pareto solution can be considered as candidates of a solution with respect to a multi-objective optimization (MOP). Such problem involves two main procedures: finding Pareto solutions and choosing one solution among them. So-called multi-objective genetic algorithms have been proved to be effective for finding many Pareto solutions. In this study, we suggest a fitness evaluation method based on the achievement level up to the target value to improve the solution search performance by the multi-objective genetic algorithm. Using numerical examples and benchmark problems, we compare the proposed method, which considers the achievement level, with conventional Pareto ranking methods. Based on the comparison, it is verified that the proposed method can generate a highly convergent and diverse solution set. Most of the existing multi-objective genetic algorithms mainly focus on finding solutions, however the ultimate aim of MOP is not to find the entire set of Pareto solutions, but to choose one solution among many obtained solutions. We further propose an interactive decision-making process based on a visualized trade-off analysis that incorporates the satisfaction of the decision maker. The findings of the study will serve as a reference to build a multi-objective decision-making support system.

• Korean Chemical Engineering Research
• /
• v.61 no.4
• /
• pp.505-516
• /
• 2023

Plastic's ease of processing drives its growing production, resulting in a surge of plastic waste. Addressing this issue, catalytic upcycling emerges as a promising remedy. Various metals (Ru, Pt, etc.) and supports (TiO₂, CeO₂, etc.) have been employed for the chemical recycling of polyolefin plastics. Strategies to enhance liquid fuel selectivity and minimize methane include manipulating particle size, introducing heterogeneous metals, and tuning support characteristics. Simultaneously, endeavors to optimize catalysts by reducing precious metal usage were pursued. This study explores enhancing economic viability in hydrogenolysis and hydrocracking reactions, underscoring the potential of catalystdriven upcycling to tackle plastic waste.

• Korean Journal of Environment and Ecology
• /
• v.31 no.6
• /
• pp.564-577
• /
• 2017

We investigated whether external environmental factors acted as a trigger for flowering in the draft bamboo (Sasa borealis (Hack.) Makino) blooming area of Mt. Baekwoon located in Gwangyang, South Jeolla Province. We then considered the cause for flowering, flowering patterns and life history strategies of the draft bamboo based on the investigation. There were no differences in soil, physical conditions, and light amount between the draft bamboo flowering and non-flowering areas. The precipitation and temperature of the areas in Korea and Japan where it blossomed from 2014 to 2017 were similar to the normal year values (for the past 30 years). Moreover, most of the draft bamboo died after flowering on a large scale, but some did not, or some culms were developed again. In other words, the draft bamboo bloomed simultaneously regardless of external environmental factors, and most of the culms were dead, but some were left alive. Therefore, it is considered that the flowering is triggered by the specific genes (referred as to clock genes) expressed periodically by a biological clock rather than the external environmental factors. Meanwhile, the draft bamboos generally bloom on a large scale by synchronizing with other ones in the distance but may also bloom several times separately on a small scale. It may be a kind of an insurance system established to disperse the risk of failed sexual propagation when flowering once in a lifetime. The results reveal that the long-period monocarpy of the draft bamboo has been strengthened to optimize the sexual propagation to overcome the increased environmental instability caused by the expansion of distribution of tropical bamboos and bamboo species to the temperate regions.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.42 no.1
• /
• pp.47-55
• /
• 2005

This work describes an 8b 240 MS/s CMOS ADC as one of embedded core cells for high-performance displays requiring low power and small size at high speed. The proposed ADC uses externally connected pins only for analog inputs, digital outputs, and supplies. The ADC employs (1) a two-step pipelined architecture to optimize power and chip size at the target sampling frequency of 240 MHz, (2) advanced bootstrapping techniques to achieve high signal bandwidth in the input SHA, and (3) RC filter-based on-chip I/V references to improve noise performance with a power-off function added for portable applications. The prototype ADC is implemented in a 0.18 um CMOS and simultaneously integrated in a DVD system with dual-mode inputs. The measured DNL and INL are within 0.49 LSB and 0.69 LSB, respectively. The prototype ADC shows the SFDR of 53 dB for a 10 MHz input sinewave at 240 MS/s while maintaining the SNDR exceeding 38 dB and the SFDR exceeding 50 dB for input frequencies up to the Nyquist frequency at 240 MS/s. The ADC consumes, 104 mW at 240 MS/s and the active die area is 1.36 ㎟.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.12 s.354
• /
• pp.65-73
• /
• 2006

This work presents a 14b 200KS/s $0.87mm^2$ 1.2mW 0.18um CMOS algorithmic A/D converter (ADC) for intelligent sensors control systems, battery-powered system applications simultaneously requiring high resolution, low power, and small area. The proposed algorithmic ADC not using a conventional sample-and-hold amplifier employs efficient switched-bias power-reduction techniques in analog circuits, a clock selective sampling-capacitor switching in the multiplying D/A converter, and ultra low-power on-chip current and voltage references to optimize sampling rate, resolution, power consumption, and chip area. The prototype ADC implemented in a 0.18um 1P6M CMOS process shows a measured DNL and INL of maximum 0.98LSB and 15.72LSB, respectively. The ADC demonstrates a maximum SNDR and SFDR of 54dB and 69dB, respectively, and a power consumption of 1.2mW at 200KS/s and 1.8V. The occupied active die area is $0.87mm^2$.

• Journal of Life Science
• /
• v.28 no.9
• /
• pp.1062-1067
• /
• 2018

Reliable labeling of fish products can reassure consumers regarding the identity and quality of seafoods. Therefore, techniques that can identify adulteration or mislabeling are valuable. To rapidly identify two Trachurus species, Trachurus japonicus and Trachurus novaezelandiae, a highly efficient, rapid, duplex polymerase chain reaction (PCR) having two species-specific primers simultaneously was identified. This species-specific primer focused on a single nucleotide mismatch in the 3'-terminal base of a primer designed in the mitochondrial cytochrome c oxidase (COI) subunit I DNA. To optimize the duplex PCR condition, gradient PCR reactions were conducted to determine the primer annealing temperature and the primer concentration. The PCR's product was observed on the gel, suggesting that DNA molecules may be useful in differentiating the two species. The length of the amplification fragments were 103 bp for Trachurus japonicus and 214 bp for Trachurus novaezelandiae, which, along with the species-specific primer visualized by agarose gel electrophoresis, enabled accurate distinction of the species of the Trachurus genus. These results indicate that the duplex PCR, which has a species-specific primer based on single nucleotide polymorphism (SNP), can be useful for rapidly differentiating the two species of Trachurus. This duplex PCR analysis is simple, rapid, and reliable, and could be beneficial to protecting consumers' rights.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.16 no.3
• /
• pp.301-308
• /
• 2018

Anthropogenic radioactive noble gases formed by nuclear fission are significant indicators used to monitor the nuclear activity of neighboring countries. In particular, radioactive xenon, owing to its abundant generation and short half-life, can be used to detect nuclear testing, and radioactive krypton has been used as a tracer to monitor the reprocessing of nuclear fuels. Released radioactive noble gases are in the atmosphere at infinitesimal amounts due to their dilution in the air and their short half-life decay. Therefore, to obtain reliable and significant data when performing measurement of noble gases in the atmosphere, the minimum detectable activity (MDA) for noble gases should be defined as low as possible. In this study, the MDA values for radioactive xenon and krypton were theoretically obtained based on the BfS-IAR system by collecting both noble gases simultaneously. In addition, various MDA methods, confidence level and analysis conditions were suggested to reduce and optimize MDA with an assessment of the factors affecting MDA. The current investigation indicated that maximizing the pretreatment efficiency and performance maintenance of the counter were the most important aspects for Xe. In the case of Kr, since sample activities are much higher than those of Xe, it is possible to change the target MDA or to simplification of the analysis system.

• Progress in Medical Physics
• /
• v.3 no.1
• /
• pp.63-69
• /
• 1992

Recently, stereotactic radiosurgery plan is required with the information of 3-D image and dose distribution. The purpose of this research is to develop 3-D radiosurgery planning system using personal computer. The procedure of this research is based on three steps. The first step is to input the image information of the patient obtained from CT or MR scan into personal computer through on-line or digitizer. The position and shape of target are also transferred into computer using Angio or CT localization. The second step is to compute dose distribution on image plane, which is transformed into stereotactic frame coordinate. and to optimize dose distribution through the selection of optimal treatment parameters. The third step is to display both isodose distribution and patient image simultaneously using superimpose technique. This prototype of radiosurgery planning system was applied recently for several clinical cases. It was shown that our planning system is fast, accurate and efficient while making it possible to handle various kinds of image modelities such as angio, CT and MRI. It is also possible to develop 3-D planning system in radiation therapy using beam's eye view or CT simulation in future.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.9
• /
• pp.1305-1310
• /
• 2010

In a practical design process, the method of extracting the design space information of the complex system for verifying, improving, and optimizing the design process by taking into account the design variables and their shape tolerance is very important. Finite element analysis has been successfully implemented and integrated with design of experiment such as D-Optimal array; thus, a response surface model and optimization tools have been obtained, and design variables can be optimized by using the model and these tools. Then, to guarantee the robustness of the design variables, a robust design should be additionally performed by taking into account the statistical variation of the shape tolerance of the optimized design variables. In this study, a new approach based on the use of the response surface model is proposed; in this approach, the standard normal distribution of the shape tolerance is considered. By adopting this approach, it is possible to simultaneously optimize variables and perform a robust design. This approach can serve as a means of efficiently modeling the trade-off among many conflicting goals in the applications of finite element analysis. A case study on the robust optimal design of disc brakes under thermal loadings was carried out to solve multiple objective functions and determine the constraints of the design variables, such as a thermal deformation and weight.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.1
• /
• pp.51-56
• /
• 2012

Crashworthy fuel cells have been widely implemented to rotorcraft and rendered a great contribution for improving the survivability of crews and passengers. Since the embryonic stage of military rotorcraft history began, the US army has developed and practised a detailed military specification documenting the unique crashworthiness requirements for rotorcraft fuel cells to prevent most fatality due to post-crash fire. Foreign manufacturers have followed their long term experience to develop their fuel cells, and have reflected the results of crash impact tests on the trial-and-error based design and manufacturing procedures. Since the crash impact test itself takes a long-term preparation efforts together with costly fuel cell specimens, a series of numerical simulations of the crash impact test with digital mock-ups is necessary even at the early design stage to minimize the possibility of trial-and-error with full-scale fuel cells. In the present study a number of numerical simulations on fuel cell crash impact tests are performed with a crash simulation software, Autodyn. The resulting equivalent stresses are further analysed to evaluate a number of appropriate design parameters and the artificial neural network and simulated annealing method are simultaneously implemented to optimize the crashworthy performance of fuel cells.