• Korean Chemical Engineering Research
• /
• v.58 no.3
• /
• pp.396-407
• /
• 2020

As fossil fuels are depleted worldwide, alternative resources is required to replace fossil fuels, and biofuels are in the spotlight as alternative resources. Biofuels are produced from biomass, which is a renewable resource to produce biofuels or bio-chemicals. Especially, in order to substitute fossil fuels, the research focusing the biofuel (biodiesel) production based on CO₂ and biomass achieves more attention recently. To produce biomass-based biodiesel, the development of a supply chain network is required considering the amounts of feedstocks (ex, CO₂ and water) required producing biodiesel, potential locations and capacities of bio-refineries, and transportations of biodiesel produced at biorefineries to demand cities. Although many studies of the biomass-based biodiesel supply chain network are performed, there are few types of research handled the uncertainty in CO₂ supply which influences the optimal strategies of microalgae-based biodiesel production. Because CO₂, which is used in the production of microalgae-based biodiesel as one of important resources, is captured from the off-gases emitted in power plants, the uncertainty in CO₂ supply from power plants has big impacts on the optimal configuration of the biodiesel supply chain network. Therefore, in this study, to handle those issues, we develop the two-stage stochastic model to determine the optimal strategies of the biodiesel supply chain network considering the uncertainty in CO₂ supply. The goal of the proposed model is to minimize the expected total cost of the biodiesel supply chain network considering the uncertain CO₂ supply as well as satisfy diesel demands at each city. This model conducted a case study satisfying 10% diesel demand in the Republic of Korea. The overall cost of the stochastic model (US$ 12.9/gallon·y) is slightly higher (23%) than that of the deterministic model (US$ 10.5/gallon·y). Fluctuations in CO₂ supply (stochastic model) had a significant impact on the optimal strategies of the biodiesel supply network.

• Korean Chemical Engineering Research
• /
• v.58 no.4
• /
• pp.541-549
• /
• 2020

The Drug Delivery System (DDS) is defined as a technology for designing existing or new drug formulations and optimizing drug treatment. DDS is designed to efficiently deliver drugs for the care of diseases, minimize the side effects of drug, and maximize drug efficacy. In this study, the optimization of tripolyphosphate (TPP) concentration on the size of Chitosan nanoparticles (CNPs) produced by crosslinking with chitosan was measured. In addition, the characteristics of Fe₃O₄-CNPs according to the amount of iron oxide (Fe₃O₄) were measured, and it was confirmed that the higher the amount of Fe₃O₄, the better the characteristics as a magnetic drug carrier were displayed. Through the ninhydrin reaction, a calibration curve was obtained according to the concentration of γ-aminobutyric acid (GABA) of Y = 0.00373exp(179.729X)-0.0114 (R² = 0.989) in the low concentration (0.004 to 0.02 wt%) and Y = 21.680X-0.290 (R² = 0.999) in the high concentration (0.02 to 0.1 wt%). Absorption was constant at about 62.5% above 0.04 g of initial GABA. In addition, the amount of GABA released from GABA-Fe₃O₄-CNPs over time was measured to confirm that drug release was terminated after about 24 hr. Finally, GABA-Fe₃O₄-CNPs performed under the optimal conditions were spherical particles of about 150 nm, and it was confirmed that the properties of the particles appear well, indicating that GABA-Fe₃O₄-CNPs were suitable as drug carriers.

• Korean Journal of Cognitive Science
• /
• v.19 no.4
• /
• pp.331-367
• /
• 2008

This study aims to validate a web-based neuropsychological testing tool developed by Kwak(2007) and to suggest solutions to potential problems that can deteriorate its validity. When it targets a wider range of subjects, a web-based neuropsychological testing tool is challenged by high drop-out rates, lack of motivation, lack of interactivity with the experimenter, fear of computer, etc. As a possible solution to these threats, this study aims to redesign the user interface of a web-based attention testing tool through three phases of study. In Study 1, an extensive analysis of Kwak's(2007) attention testing tool was conducted to identify potential usability problems. The Heuristic Walkthrough(HW) method was used by three usability experts to review various design features. As a result, many problems were found throughout the tool. The findings concluded that the design of instructions, user information survey forms, task screen, results screen, etc. did not conform to the needs of users and their tasks. In Study 2, 11 guidelines for the design of web-based attention testing tools were established based on the findings from Study 1. The guidelines were used to optimize the design and organization of the tool so that it fits to the user and task needs. The resulting new design alternative was then implemented as a working prototype using the JAVA programming language. In Study 3, a comparative study was conducted to demonstrate the excellence of the new design of attention testing tool(named graphic style tool) over the existing design(named text style tool). A total of 60 subjects participated in user testing sessions where their error frequency, error patterns, and subjective satisfaction were measured through performance observation and questionnaires. Through the task performance measurement, a number of user errors in various types were observed in the existing text style tool. The questionnaire results were also in support of the new graphic style tool, users rated the new graphic style tool higher than the existing text style tool in terms of overall satisfaction, screen design, terms and system information, ease of learning, and system performance.

• Journal of Broadcast Engineering
• /
• v.16 no.2
• /
• pp.216-225
• /
• 2011

Following the proliferation of three-dimensional video contents and displays, many terrestrial broadcasting companies have been preparing for stereoscopic 3DTV service. In terrestrial stereoscopic broadcast, it is a difficult task to code and transmit two video sequences while sustaining as high quality as 2DTV broadcast due to the limited bandwidth defined by the existing digital TV standards such as ATSC. Thus, a terrestrial 3DTV broadcasting with a heterogeneous video codec system, where the left image and right images are based on MPEG-2 and H.264/AVC, respectively, is considered in order to achieve both high quality broadcasting service and compatibility for the existing 2DTV viewers. Without significant change in the current terrestrial broadcasting systems, we propose a joint rate control scheme for stereoscopic 3DTV service based on the heterogeneous dual codec systems. The proposed joint rate control scheme applies to the MPEG-2 encoder a quadratic rate-quantization model which is adopted in the H.264/AVC. Then the controller is designed for the sum of the left and right bitstreams to meet the bandwidth requirement of broadcasting standards while the sum of image distortions is minimized by adjusting quantization parameter obtained from the proposed optimization scheme. Besides, we consider a condition on maintaining quality difference between the left and right images around a desired level in the optimization in order to mitigate negative effects on human visual system. Experimental results demonstrate that the proposed bit rate control scheme outperforms the rate control method where each video coding standard uses its own bit rate control algorithm independently in terms of the increase in PSNR by 2.02%, the decrease in the average absolute quality difference by 77.6% and the reduction in the variance of the quality difference by 74.38%.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.33 no.3
• /
• pp.159-165
• /
• 1997

This paper presents the optimum dimension of 89 ton class stow-net vessel with stern-fishing. The model of basic design is developed by using the optimization techniques referring to objective function and numerous constraints as follows; speed, fishing quantity, fishing days, catch per unit effort(CPUE), and weight/ratio of main dimensions, etc. Thus, the basic design of stow-net fishing vessel is built up by using the optimization of the design variables called the economic optimization criteria, and the objective function represents the criterion which is cost benefit ratio(CBR). The main conclusions are as follows. 1. S/W for decision of optimum hull size is developed in 89 ton class stow-net fishing vessel which is constructed with optimization of the design variables called the economic optimization criteria. 2. For optimum ship dimensions in 89 ton class stow-net fishing vessel, the hull dimensions can be obtained in the range of L= 27.3m, B = 6.6m, D = 2.80m, Cb = 0.695, T/D = 0.80, $\Delta$(displacement)=281.7ton with 10 knots.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.16 no.2
• /
• pp.103-113
• /
• 2014

Under climate change, it is likely that the suitable area for forage crop cultivation would change in Korea. The potential cultivation areas for italian ryegrass (Lolium multiflorum L.), which has been considered one of an important forage crop in Korea, were identified using the EcoCrop model. To minimize the uncertainty associated with future projection under climate change, an ensemble approach was attempted using five climate change scenarios as inputs to the EcoCrop model. Our results indicated that most districts had relatively high suitability, e.g., >80, for italian ryegrass in South Korea. Still, suitability of the crop was considerably low in mountainous areas because it was assumed that a given variety of italian ryegrass had limited cold tolerance. It was predicted that suitability of italian ryegrass would increase until 2050s but decrease in 2080s in a relatively large number of regions due to high temperature. In North Korea, suitability of italian ryegrass was considerably low, e.g., 28 on average. Under climate change, however, it was projected that suitability of italian ryegrass would increase until 2080s. For example, suitability of italian ryegrass was more than 80 in 10 districts out of 14 by 2080s. Because cold tolerance of italian ryegrass varieties has been improved, it would be preferable to optimize parameters of the EcoCrop model for those varieties. In addition, it would be possible to grow italian ryegrass as the second crop following rice in Korea in the future. Thus, it merits further study to identify suitable areas for italian ryegrass cultivation after rice using new varieties of italian ryegrass.

• Radiation Oncology Journal
• /
• v.20 no.4
• /
• pp.396-404
• /
• 2002

Purpose : Many papers support a correlation between rectal complications and rectal doses in uterine cervical cancer patients treated with radical radiotherapy. In vivo dosimetry in the rectum following the ICRU report 38 contributes to the quality assurance in HDR brachytherapy, especially in minimizing side effects. This study compares the rectal doses calculated in the radiation treatment planning system to that measured with a silicon diode the in vivo dosimetry system. Methods : Nine patients, with a uterine cervical carcinoma, treated with Iridium-192 high dose rate brachytherapy between June 2001 and Feb. 2002, were retrospectively analysed. Six to eight-fractions of high dose rate (HDR)-intracavitary radiotherapy (ICR) were delivered two times per week, with a total dose of $28\~32\;Gy$ to point A. In 44 applications, to the 9 patients, the measured rectal doses were analyzed and compared with the calculated rectal doses using the radiation treatment planning system. Using graphic approximation methods, in conjunction with localization radiographs, the expected dose values at the detector points of an intrarectal semiconductor dosimeter, were calculated. Results : There were significant differences between the calculated rectal doses, based on the simulation radiographs, and the calculated rectal doses, based on the radiographs in each fraction of the HDR ICR. Also, there were significant differences between the calculated and measured rectal doses based on the in-vivo diode dosimetry system. The rectal reference point on the anteroposterior line drawn through the lower end of the uterine sources, according to ICRU 38 report, received the maximum rectal doses in only 2 out of the nine patients $(22.2\%)$. Conclusion : In HDR ICR planning for conical cancer, optimization of the dose to the rectum by the computer-assisted planning system, using radiographs in simulation, is improper. This study showed that in vivo rectal dosimetry, using a diode detector during the HDR ICR, could have a useful role in quality control for HDR brachytherapy in cervical carcinomas. The importance of individual dosimeters for each HDR ICR is clear. In some departments that do not have the in vivo dosimetry system, the radiation oncologist has to find, from lateral fluoroscopic findings, the location of the rectal marker before each fractionated HDR brachytherapy, which is a necessary and important step of HDR brachytherapy for cervical cancer.

• Journal of Bio-Environment Control
• /
• v.15 no.2
• /
• pp.125-137
• /
• 2006

Pleurotus eryngii is one of the most promising mushrooms produced on the domestic farms. The quality as well as quantity of Eryngii is sensitively affected by micro climate factors such as temperature, relative humidity, $CO_2$ concentration, and light intensity. To safely produce high-quality Eryngii all the yew round, it is required that the environmental factors be carefully controlled by well designed structures equipped with various facilities and control systems. At the commercial mushroom cultivation houses of permanent frame type (A, B), this study was carried out to find out reasonable range of each environmental factor and yield together with economic and safe structures influencing on the optimal productivity of Eryngii. This experiment was conducted for about two-year ken Nov. 2003 to Dec. 2005 in cultivation house. Ambient temperature during the experiment period was not predominantly different from that of a normal year. The capacity of the hot water boiler and the piping systems were not enough. Because the capacity of electric heater and air circulation were not enough, air temperatures in cultivation house before improvement of system were maintained somewhat lower than setting temperature, and maximum air temperature difference between the upper and lower growth stage during a heating time period was about 5.1. But the air temperatures after system improvement were maintained within the limits range of setting temperature without happening stagnant of air. Air temperature distribution was generally distributed uniform. Relative humidity in cultivation house before , improvement was widely ranged about $44{\sim}100%$. But as the relative humidity after improvement was ranged approximately $80{\sim}100%$, it was maintained within the range of relative humidity recommended. And $CO_2$ concentration was maintained about $400{\sim}3,300mg{\cdot}L^{-1}$ range. The illuminance in cultivation house was widely distributed in accordance with position, and it was maintained lower than the recommended illuminance range $100{\sim}200lx$. The acidity of midium was some lower range than the recommend acidity range of pH $5.5{\sim}6.5$. The yield was relatively ununiform. In case of bottle capacity of 1,300cc, the mushroom of the lowest grade was less than 3%. The consumption electric energy was quite different according to the cultivation season. The electric energy consumed during heating season was much more than that of cooling season.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.26 no.1
• /
• pp.65-78
• /
• 2018

According to the in social aspects such as population growth, urbanization and industrialization, development of livestock industry by meat consumption, amount of organic wastes (containing sewage sludge and food waste, animal manure, etc) has been increased annually in South Korea. Precise monitoring of 11 organic wastes biogas facilities were conducted. The organic decomposition rate of organic wastewater was 68.2 % for food wastes, 66.8 % for animal manure and 46.2 % for sewage sludge and 58.8 % for total organic wastes. As a result of analyzing the biogas characteristics before and after the pretreatment, the total average of the whole facility was measured to be 560 ppm using iron salts and desulfurization, and decreased to 40 ppm when the reduction efficiency was above 90 %. Particularly, when iron salt is injected into the digester, the treatment efficiency is about 93 %, and the average is reduced to 150 ppm. In the case of dehumidification, the absolute humidity and the relative humidity were analyzed. The dew point temperature of the facility where the dehumidification facility was well maintained as $14^{\circ}C$, the absolute humidity was $12.6g/m^3$, and the relative humidity was 35 %. Therefore, it is necessary to compensate for the disadvantages of biogasification facilities of organic waste resources and optimize utilization of biogas and improve operation of facilities. This study was conducted to optimize biogas utilization of type of organic waste(containing sewage sludge and food waste, animal manure) through precision monitoring.

• Journal of Bio-Environment Control
• /
• v.29 no.2
• /
• pp.161-170
• /
• 2020

There is systematic spatial variations in environmental properties due to sensitive reaction to external conditions at plastic greenhouse occupied 99.2% of domestic agricultural facilities. In order to construct 3 dimensional distribution of temperature, relative humidity, CO₂ and illuminance, measurement matrix as 3 by 3 by 5 in direction of width, height and length, respectively, dividing indoor space of greenhouse was designed and tested at experimental site. Linear regression analysis was conducted to evaluate optimal estimation method in terms with horizontal and vertical variations. Even though sole measurement point for temperature and relative humidity could be feasible to assess indoor condition, multiple measurement matrix is inevitably required to improve spatial precision at certain time domain such as period of sunrise and sunset. In case with CO₂, multiple measurement matrix could not successfully improve the spatial predictability during a whole experimental period. In case with illuminance, prediction performance was getting smaller after a time period of sunrise due to systematic interference such as indoor structure. Thus, multiple sensing methodology was proposed in direction of length at higher height than growing bed, which could compensate estimation error in spatial domain. Appropriate measurement matrix could be constructed considering the transition of stability in indoor environmental properties due to external variations. As a result, optimal measurement matrix should be carefully designed considering flexibility of construction relevant with the type of property, indoor structure, the purpose of crop and the period of growth. For an instance, partial cooling and heating system to save a consumption of energy supplement could be successfully accomplished by the deployment of multiple measurement matrix.