• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.847-852
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feed-water heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare wall thinning range according to change entrance nozzle diameter and position with reference numerical analysis model's wall thinning range, various numerical analysis models applied. In case of changing diameter, four different diameter is applied. And a side of nozzle position, two different position-vertical type and parallel type-is applied. And then this paper describes operation of numerical analysis which is composed similar condition with real feed water heater. In conclusion, this study shows effective design for shall wall thinning by changing nozzle diameter and position.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.44-50
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• 2006

This paper describs about the technique of ultra-precision machining for an infrared(IR) camera aspheric mirror. A 200 mm diameter aspheric mirror was fabricated by SPDTM(Single Point Diamond Turning Machine). Aluminum alloy as mirror substrates is known to be easily machined, but not polishable due to its ductility. Aspheric large reflector without a polishing process, the surface roughness of 5 nm Ra, and the form error of ${\lambda}/2\;({\lambda}=632.8\;nm)$ for reference curved surface 200 mm has been required. The purpose of this research is to find the optimum machining conditions for cutting reflector using Al6061-T651 and apply the SPDTM technique to the manufacturing of ultra precision optical components of Al-alloy aspheric reflector. The cutting force and the surface roughness are measured according to each cutting conditions feed rate, depth of cut and cutting speed, using diamond turning machine to perform cutting processing. As a result, the surface roughness is good when feed rate is 1mm/min, depth of cut $4{\mu}m$ and cutting speed is 220 m/min. We could machined the primary mirror for IR camera in diamond machine with a surface roughness within $0.483{\mu}m$ Rt on aspheric.

• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.155-163
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• 2017

Submerged bodies moving underwater behave differently based on their type and assigned mission. This paper describes the dynamic characteristics, including the stability, turning ability, and operational ability, of submerged bodies in relation to design parameters such as the tail cone angle, shape of the control plate, and length of the parallel middle body. A submerged body operated in other countries is adopted as a reference for the dynamic characteristics, its principal dimensions and the shape of the bare hull and appendages are used for comparison. This paper suggests a few candidate hull forms based on changes in the typical design parameters. Finally, the dynamic characteristics for these candidate hull forms are defined.

• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.419-428
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• 2019

Phytases are enzymes that can hydrolyze phytate and its salts into inositol and phosphoric acid, and have been utilized to increase the availability of nutrients in animal feed and mitigate environmental pollution. However, the enzymes' low thermostability has limited their application during the feed palletization process. In this study, a combination of B-value calculation and protein surface engineering was applied to rationally evolve the heat stability of Escherichia coli phytase. After systematic alignment and mining for homologs of the original phytase from the histidine acid phosphatase family, the two models 1DKL and 1DKQ were chosen and used to identify the B-values and spatial distribution of key amino acid residues. Consequently, thirteen potential amino acid mutation sites were obtained and categorized into six domains to construct mutant libraries. After five rounds of iterative mutation screening, the thermophilic phytase mutant P56214 was finally yielded. Compared with the wild-type, the residual enzyme activity of the mutant increased from 20% to 75% after incubation at $90^{\circ}C$ for 5 min. Compared with traditional methods, the rational engineering approach used in this study reduces the screening workload and provides a reference for future applications of phytases as green catalysts.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.2
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• pp.103-111
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• 2021

A series of experiments have been carried out by using National Geographic Information Institute(NGII)'s Continuously Operating Reference Station (CORS) data with various strategies to analyze the impact of multi-GNSS measurements on baseline processing. The results of baseline processing were compared in terms of ambiguity fixing rate, precision, and hypothesis tests were conducted to confirm the statistical difference. The combination of multi-GNSS measurements has helped to improve ambiguity fixing rate, especially under harsh positioning environments. Combination of GPS, Galileo, BeiDou could get better precision than that of GPS, GLONASS, Galileo, and adding QZSS made the baseline solution's vertical component more precisely. The hypothesis tests have statistically confirmed that the inclusion of the multi-GNSS in the baseline processing enables not only to reduce field observation time length but also to enhance the solution's precision. However, it is of interest to notice that results of the baseline solution are dependent upon the software used. Hence, comprehensive studies should be performed shortly to derive the best practice to select the appropriate software.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.156-161
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• 1992

In this research a monitoring system for turning using NC information and the current of feed motor as a monitoring signal was developed. The overall system consists of modules such as learning process, NC data transmission, generation of forecast information, signal acquisition, monitoring and post process. In the learning process, the reference data and the cutting force equation necessary for monitoring are obtained from the accumulated monitoring results. In the generation of forecast information, the information of forecasted cutting forces is acquired from the cutting force equation and NC program and appended to each NC block as a monitor code. Reliability of monitoring is improved by using the monitor code in the real-time monitoring. Monitoring module is divided into two parts : the off-line monitoring where errors of NC program are checked and the on-line monitoring where the level of motor current is monitored during cutting operations. If the actual current level exceeds the limit value provided by the monitor code in the level monitoring, it is recognized as abnormal. In the event of abnormal status, the post processor sends the emergency stop signal to NC controller to stop the operation. Actual experiments have shown that the developed monitoring system works well.

• Toxicological Research
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• v.22 no.4
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• pp.339-348
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• 2006

Misaengtang (MST), a formula of Korean herbal medicines, has been used as a weight-controlling recipe. We have investigated two experiment of body weight regulation by MST In rats. i) The anti-obesity effect of MTS on a high fat diet-induced obesity, male Sprague-Dawley rats were fed with a high-fat diet containing 30% in the absence or presence of MST (0.3, 1 or 3%) or a reference orlistat (0.05%) for 6 weeks. ii) weight-decrease effect of MST on normal diet, same animal were fed with a normal diet in the absence or presence of MST (3%) for 6 weeks. And the body weights, daily feed and water consumptions, organ weights, fat weights serum biochemistry were measured. In both experiments, MST and orlistat did not affect the body weight gain. But orlistat significantly increased the feed and water consumptions, leading to low-feed efficiency, and orlistat markedly reduced abdominal, paratesticular and perirenal fat weights, although increased the kidney weights. In MST, low dose (0.3%) of MST decreased the perirenal fat and increased the kidney weights in rats fed HFD, and MST 3% decreased the abdominal fat weights in rats fed normal diet. In addition, Orlistat caused changes in parameters of hepatotoxicity (AST and glucose), nephrotoxicity (BUN and B/C ratio) and lipid metabolism (HDL and triglycerides). In comparison, MST decreased AST, ALP and ALT, the hepatotoxicity markers, and somewhat improved the hepatic fatty degeneration. Taken together, it is suggested that MST does not exert anti-obesity activity as well as remarkably direct effects, but MST may be potentially benefit for dietary cure and exercise-cure of obesity.

• Journal of Aquaculture
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• v.12 no.1
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• pp.25-30
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• 1999

This study was carried out to produce the seedling of the larvae and juveniles of pale chup, Zacco platypus (Cyprinidae) in terms of artificial hatching, feeding behavior and growth rates. The total lengths of the newly hatched larvae were 7.6~8.2mm (mean: 7.97mm). The hatched larvae rose to the surface 3 days after hatching. The larvae were fed Daphnia, rotifer, Artemia and powdered feed. Hatching experiments were conducted in jar incubators under the different water temperature conditions, $20~32^{\circ}C$. The highest hatching rate was at $26^{\circ}C$ after 47 hours. Jar incubators was the highest hatching rate (89%), and cage and Californian incubators were useful and relatively high hatching rates (>89%). The size of the larvae 50 days after hatching were 30.0mm (25.6~32.0mm). As the water temperatures was increased, the growth rate of the larvae was also increased. Especially, the growth rates were favorable over $26^{\circ}C$, but survival was the worst at $32^{\circ}C$. This species was quick to accept assorted feed after hatching. The assorted feeds for flounder and rockfish better than that of carp in reference to growth rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.940-946
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• 2015

The turning clearance angle changes the machining characteristics. In this study, three workpiece materials, machine structural carbon steel, chrome-molybdenum steel and stainless steel, were examined. The experiments revealed how the features of selected materials changed when they were processed with machining operation. To find the surface roughness of workpiece materials, the workpiece materials, which have a higher tensile strength, showed a much better surface roughness in the surface roughness tester. Moreover, the process feed rate was compared between 0.07 mm/rev and 0.10 mm/rev. When the process feed rate was 0.07 mm/rev, the surface roughness has superior results without reference to the quality of the materials. According to this research on the turning clearance angle, the best roughness value was observed when the quality of the materials were $0.9^{\circ}$, whereas the worst roughness was observed when quality of the materials was $0.3^{\circ}$.

• Journal of The Korean Society of Grassland and Forage Science
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• v.42 no.3
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• pp.176-182
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• 2022

The aim of this study was to investigate dry matter productivity and nitrate nitrogen content in the growth stages of barnyard millet (Echinochloa esculenta) cultivated for feed, which was treated with different nitrogen fertilization levels. An early variety of barnyard millet (cv. Shirohie) was used for the test, and the different treatments with nitrogen fertilizer were as follows: 50% (N-40 kg/ha, T1), 100% (N-80 kg/ha, reference amount, T2), 150% (N-120 kg/ha, T3), 200% (N- 160 kg/ha, T4), 250% (N-200 kg/ha, T5), and 300% (N-240 kg/ha, T6). Sowing was done on May 13, 2021 and plants were harvested for four stage; vegetative stage, elongation stage, heading stage, and milk stage. The length of the millet increased significantly as the amount of nitrogen fertilization increased during the harvest period (p<0.05), but the difference was insignificant during the milk stage (p>0.05). Moreover, barnyard millet dry matter yield increased significantly as the levels of nitrogen fertilization increased (p<0.05), but there was no significant difference in dry matter yield among nitrogen fertilization levels during the heading stage (p>0.05). Chlorophyll also was significantly higher in T5 (250%) at all harvesting times, whereas nitrate nitrogen content was highest at the vegetative stage, gradually decreased as growth progressed, and lowest at the milk stage. Finally, as the nitrogen fertilization levels increased, the nitrate nitrogen content was significantly higher in all treatment groups (p<0.05). Therefore, our results suggest that the most appropriate nitrogen fertilizer levels is between 150%-200%, considering the dry matter yield, feed ingredients and nitrate nitrogen content in barnyard millet for feed.