• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.87-91
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• 2015

This paper reports the design of solenoid in a coilgun for high velocity of projectile in a coilgun system, according to diameter of coil. Coilgun using a magnetic force means a mechanism that can control the magnetic material. When momentarily supply a large current to the solenoid instantaneous magnetic field is created around the coil, the projectile is fired by receiving a magnetic force towards the center of the coil, based on the right-hand rule of Fleming. The velocity of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coilgun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. In this paper, whether it is possible fire looking for the optimal number of turns according to the diameter of the coil from AWG #6 to AWG #18 for the design of the solenoid coil, and comparative analysis firing rate associated with it.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• Korean Journal of Agricultural Science
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• v.46 no.2
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• pp.239-256
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• 2019

The quality of tomatoes drastically changes according to storage conditions, such as temperature, humidity, and air composition. High storage temperatures result in the degradation of the firmness and color of tomatoes and in decay by bacteria, whereas chilling injury and softening can be caused by storage at low temperatures. The gas composition in the storage and packaging are other parameters that influence the quality and shelf life of tomatoes by preventing excessive transpiration and respiration. In addition, tomato quality is dependent on the degree of maturity and harvest season. Because there are many quality parameters, it is necessary to systemically establish an optimal standard, and this approach requires collecting and reviewing various data on storage conditions. The aim of this review was to provide basic information by comparing and analyzing studies on the changes in tomato quality (firmness, color, lycopene content, and acidity of tomatoes) during storage and to describe a few models that can assess the quality parameters. Many studies have provided results from experiments on the effects of postharvest control (e.g., storage temperature, packaging film, and gas treatment, as reviewed above) on tomato quality including firmness, soluble solids content, and lycopene content. However, it is still necessary to conduct an overall analysis of the published conditions and to determine the best method for preserving the quality of tomatoes as well as other fruits.

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.603-616
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• 2023

This study was conducted to investigate the productivity, meat quality, blood variables, stress responses, and litter quality of broilers offered feed with different levels of Glycine (Gly) supplementation under heat stress condition. A total of 760 one-day-old Ross 308 broiler males were randomly assigned to one of the four dietary treatment groups: (1) basal diet (control; CON); (2) basal diet + Gly 0.1% (Gly 0.1%); (3) basal diet + Gly 0.2% (Gly 0.2%); and (4) basal diet + Gly 0.3% (Gly 0.3%). The environments for all the treatments groups were maintained according to broiler rearing guidelines from day 1 to day 21, and heat stress condition (32 ± 1℃, 60 ±5%) was created from day 22 to the end. The addition of Gly increased weight gain and affected feed intake (p < 0.05). Gly 0.1% group had higher pH and ferric reducing antioxidant power (FRAP) in the chicken meat and lower heterophil (HE)/lymphocyte (LY) ratio in the blood (p < 0.05). In particular, Gly 0.2% treatment group had lower serum corticosterone level (p < 0.05) than other groups. For jejunum morphology, the addition of Gly 0.2% significantly reduced the depth of the crypts (p < 0.05). However, the addition of Gly did not significantly affect litter quality (p > 0.05). In conclusion, the addition of glycine improved productivity and meat quality, alleviated heat stress, and improved intestinal function. Further studies are needed to determine the optimal level and mechanism of action of the additive when ingested.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.99-106
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• 2004

This paper presents some comparisons between Cournot-Nash and Stackelberg game in bi-level program, composed of both upper level program and lower level one. The upper level can be formulated to optimize a specific objective function, while the lower formulated to express travelers' behavior patterns corresponding to the design parameter of upper level problem. This kind of hi-level program is to determine a design parameter, which leads the road network to an optimal state. Bi-level program includes traffic signal control, traffic information provision, congestion charge and new transportation mode introduction as well as road expansion. From the view point of game theory, many existing algorithms for bi-level program such as IOA (Iterative Optimization Assignment) or IEA (Iterative Estimation Assignment) belong to Cournot-Nash game. But sensitivity-based algorithms belongs to Stackelberg one because they consider the reaction of the lower level program. These two game models would be compared by using an example network and show some results that there is no superiority between the models in deterministic case, but in stochastic case Stackelberg approach is better than that of Cournot-Nash one as we expect.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.26-35
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• 2013

Outbreak of animal infectious diseases such as foot-and-mouth disease, avian influenza are becoming prevalent worldwide. For prevent the further infection, tremendous numbers of the infected or culled stocks are buried around farm. This burial method can generate a wide range of detrimental components such as leachate, nutrient, salt, and pathogenic bacteria, consequently. In this study, for the stabilization of livestock carcasses leachate, advanced oxidation processes utilizing the Fenton reaction was investigated in lab-scale experiments for the treatment for $COD_{Cr}$ of livestock carcass leachate. $COD_{Cr}$ reduction by the Fenton oxidation was investigated response surface methodology using the Box-Begnken methods were applied to the experimental results. A central composite design was used to investigate the effects of the independent variables of pH ($x_1$), dosage of $FeCl_2{\cdot}4H_2O$ ($x_2$) and dosage of $H_2O_2$ ($x_3$) on the dependent variables $COD_{Cr}$ concentration ($y_1$). A 1 M NaOH and $H_2SO_4$ was using for pH control, $FeCl_2{\cdot}4H_2O$ was used as iron catalyst and NaOH was used for Fenton reaction. The optimal conditions for Fenton oxidation process were determined: pH, dosage of $FeCl_2{\cdot}4H_2O$ and dosage of $H_2O_2$ were 3, 0.6 g (0.0151 M) and 7 mL(0.259 M), respectively. Statistical results showed the order of significance of the independent variables to be pH > initial concentration of ferrous ion > initial concentration of hydrogen peroxide.

• Fisheries and Aquatic Sciences
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• v.20 no.11
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• pp.30.1-30.10
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• 2017

Small-scale fish farmers in developing countries are faced with challenges owing to their limited information on aquaculture management. Nile tilapia farmers in Teso North Sub-County recorded lower yields than expected in 2009 despite having been provided with required inputs. Water quality was suspected to be the key factor responsible for the low yields. This study sought to assess the effects of earthen pond water physico-chemical parameters on the growth of Nile tilapia in six earthen fish ponds under semi-intensive culture system in Teso North Sub-County. The study was longitudinal in nature with pond water and fish being the units of analysis. Systematic sampling was used to select five ponds while a control pond was purposively selected based on its previously high harvest. Four ponds were fed by surface flow and two by underground water. Each pond was fertilized and stocked with 900 fry of averagely 1.4 g and 4.4 cm. Physico-chemical parameters were measured in-situ using a multi-parameter probe. Sixty fish samples were randomly obtained from each pond fortnightly for four months using a 10 mm mesh size and measured, weighed and returned into the pond. Mean range of physico-chemical parameters were: dissolved oxygen (DO) 4.86-10.53 mg/l, temperature $24-26^{\circ}C$, pH 6.1-8.3, conductivity $35-87{\mu}S/cm$ and ammonia 0.01-0.3 mg/l. Temperature (p = 0.012) and conductivity (p = 0.0001) levels varied significantly between ponds. Overall Specific Growth Rate ranged between 1.8% (0.1692 g/day) and 3.8% (1.9 g/day). Ammonia, DO and pH in the ponds were within the optimal levels for growth of tilapia, while temperature and conductivity were below optimal levels. As temperature and DO increased, growth rate of tilapia increased. However, increase in conductivity, pH and ammonia decreased fish growth rate. Temperature and DO ranging between 27 and $30^{\circ}C$ and 5-23 mg/l, respectively, and SGR of 3.8%/day and above are recommended for higher productivity.

• Asian Spine Journal
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• v.12 no.6
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• pp.1085-1091
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• 2018

Study Design: Case-control. Purpose: To determine optimal cut-off value for body mass index (BMI) in predicting surgical success in patients with lumbar spinal canal stenosis (LSCS). Overview of Literature: BMI is an essential variable in the assessment of patients with LSCS. Methods: We conducted a prospective study with obese and non-obese LSCS surgical patients and analyzed data on age, sex, duration of symptoms, walking distance, morphologic grade of stenosis, BMI, postoperative complications, and functional disability. Obesity was defined as BMI of ${\geq}30kg/m^2$. Patients completed the Oswestry Disability Index (ODI) questionnaire before surgery and 2 years after surgery. Surgical success was defined as ${\geq}30%$ improvement from the baseline ODI score. Receiver operating characteristic (ROC) analysis was used to estimate the optimal cut-off values of BMI to predict surgical success. In addition, correlation was assessed between BMI and stenosis grade based on morphology as defined by Schizas and colleague in total, 189 patients were eligible to enter the study. Results: Mean age of patients was $61.5{\pm}9.6years$. Mean follow-up was $36{\pm}12months$. Most patients (88.4%) were classified with grades C (severe stenosis) and D (extreme stenosis). Post-surgical success was 85.7% at the 2-year follow-up. A weak correlation was observed between morphologic grade of stenosis and BMI. Rates of postoperative complications were similar between patients who were obese and those who were non-obese. Both cohorts had similar degree of improvement in the ODI at the 2-year followup. However, patients who were non-obese presented significantly higher surgical success than those who were obese. In ROC curve analysis, a cut-off value of ${\leq}29.1kg/m^2$ for BMI in patients with LSCS was suggestive of surgical success, with 81.1% sensitivity and 82.2% specificity (area under the curve, 0.857; 95% confidence interval, 0.788-0.927). Conclusion: This study showed that the BMI can be considered a parameter for predicting surgical success in patients with LSCS and can be useful in clinical practice.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.330-338
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• 2018

The proportional-integral-derivative(PID) controller has been widely used in the industry because of its robust performance and simple structure in a wide range of operating conditions. However, the AVR(Automatic Voltage Regulator) as a control system is not robust to variations of the power system parameters. Therefore, it is necessary to use PID controller to increase the stability and performance of the AVR system. In this paper, a novel design method for determining the optimal PID controller parameters of an AVR system using the particle swarm optimization(PSO) algorithm is presented. The proposed approach has superior features, including easy implementation, stable convergence characteristic and good computational efficiency. In order to assist estimating the performance of the proposed PSO-PID controller, a new performance criterion function is also defined. This evaluation function is intended to reflect when the maximum percentage overshoot, the settling time are given as design specifications. The ITAE evaluation function should impose a penalty if the design specifications are violated, so that the PSO algorithm satisfies the specifications when searching for the PID controller parameter. Finally, through the computer simulations, the proposed PSO-PID controller not only satisfies the given design specifications for the terminal voltage step response, but also shows better control performance than other similar recent studies.

• Journal of Environmental Impact Assessment
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• v.23 no.4
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• pp.296-314
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• 2014

In recent years, Ministry of Environment (MOE) has been implementing a phased strengthening of the effluent standards for sewage treatment plants. In this regard, a comprehensive system should be developed to help check the appropriateness of such standards by specifying the grounds for standard-setting and investigating the current operation of sewage treatment plants clearly. It is necessary to establish a new standard-setting system for the effluent that is in a closer connection with the environmental criteria and rating systems. In the United States, the federal government provides guidelines on the least provisions and requirements for the Publicly Owned Treatment Works (POTWs). Local governments set the same or stricter guidelines that reflect the characteristics of each state. In Japan, the sewage treatment plants are subject to both the effluent standards and the discharge acceptable limits to pubic waters under the sewerage law. Specific requirements and limits are set in accordance with local government regulations. The European Union imposes sewage treatment plants with different provisions for effluent standards, depending on the sensitivity of public waters to eutrophication. The effluent standards for sewage treatment plants are classified by pollutant loads discharged to receiving waters. MOE also needs to introduce systems for setting new parameter standards on a POTW effluent by applying statistical means and treatment efficiencies or optimal treatment techniques, as seen in the cases of the US National Pollutant Discharge Elimination System (NPDES) or the EU Integrated Pollution Prevention and Control (IPPC).