• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.641-646
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• 2008

In this research, recovery of high quality organics from excess activated sludge and its potential as a external carbon sources for BNR process was studied. By simultaneous treatment of alkali and ozone, TSS concentration was reduced by 32%, and RBDCOD fraction was increased by 76.2%, and major constitute of produced organic were acetic acid and propionic acid. Also, nitrogen and phosphorus were greatly solubilized. However, because acid-hydrolyzable phosphorus(AHP) was major part of solubilized phosphorus, $NH_4{^+}-N$ and $PO_4{^3}-P$ concentration were insufficient for effective formation of crystal like as MAP(Magnesium Ammonium Phosphate) and hydroxyapatite. By placing BPR reactor before alkali-ozone treatment reactor, $PO_4{^3}-P$ concentration in pretreated sludge was increased by 1.8 times, and improved potential of phosphorus recovery by crystallization. In experiment of crystallization, hydroxyapatite formation was more easily applied than MAP. By hydroxyapatite formation, $SCOD/PO_4-P$ ratio was greatly increased from 32.7 at control to 141.9 at $Ca^{2+}/PO{_4}^{3-}-P$ mole ratio of 2.4. The results based on this study indicated that the proposed system configuration has potential to reduce the excess sludge production, to recover phosphorus in usable forms as well as utilize organics as a external carbon source in BNR process.

• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1711-1719
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• 2005

In an electro statically actuated nanoelectromechanical system (NEMS) resonator, it is shown that both the resonance frequency and the resonance quality (Q) factor can be manipulated. How much the frequency and quality factor can be tuned by excitation voltage and resistance on a doubly-clamped beam resonator is addressed. A mathematical model for investigating the tuning effects is presented. All results are shown based on the feasible dimension of the nanoresonator and appropriate external driving voltage, yielding up to 20 MHz resonance frequency. Such parameter tuning could prove to be a very convenient scheme to actively control the response of NEMS for a variety of applications.

• Journal of Korea Association of Health Promotion
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• v.1 no.1
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• pp.7-8
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• 2003

The health screening and promotion is an emerging field of clinical preventiemedicine and is proved to be effective for reduction of diseaseprevalence, particularly life-style related diseases in aged population. However, the goal of perodic health screening can be achieved by a reliable health screening that largely depond on the quality of tests. Various tests including ultrasonography, endoscopy, CT and automated blood analyzers are used in health screening. Thesescreening tests are usually sensitive, but not specific to the presence of diseases. It meams the tests produce more false positive results, that demand eztra-expenses for the confirmation of disease. Promising screening tests should be sensitive as well as specific. However, it is not easy to maintain the quality of laboratory tests, because it is affected by various factors, such as instruments, reagents, laboratory methods and human factors. This review focuses on internal and external quality control of laboratory tests and quality management of health screening services to obtain reliable test results.

• Journal of Korean Society for Quality Management
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• v.18 no.2
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• pp.9-17
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• 1990

This paper deals with a FOQ( ; fixed-order quantity) model for spare-part inventory control. In a spare-part inventory problem, stock depletion arises not from external market demand but from internal demand resulting from failures of parts in use. The problem differs from the classical inventory problem in that the demand for a failed part never arises more during stockout period, since the unit remains inoperative when stockout occurs until the failed part is replaced by new one. In the problem under consideration, n identical units are operating simultaneously and failed one is replaced immediately by new one if on-hand spares remain. In order to replenish spares, an order with quantity Q is placed whenever the number of on-hand spares falls to levels. The average annual cost of operating the spare-part inventory system is derived under the assumption that both lifetime of a part and replenishment lead-time distributions are exponential.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.3
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• pp.20-27
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• 2010

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. An active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. Therefore, an active suspension system can have even more improved performance. Some control laws have been proposed for active suspension system, but in this paper, an optimal variable structure control(VSC) is proposed. The VSC method is well suited for a class of nonlinear system and can address the robustness issues to constant modelling errors and disturbances. This paper develops an optimal VSC controller and compares its performance to those of a passive suspension system and an active suspension system with an optimal controller. The transient and frequency responses are analyzed respectively.

• Progress in Medical Physics
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• v.29 no.4
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• pp.123-136
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• 2018

The complex dose distribution and dose transfer characteristics of intensity-modulated radiotherapy increase the importance of precise beam data measurement and review in the acceptance inspection and preparation stages. In this study, we propose a process map for the introduction and installation of high-precision radiotherapy devices and present items and guidelines for risk management at the acceptance test procedure (ATP) and commissioning stages. Based on the ATP of the Varian and Elekta linear accelerators, the ATP items were checked step by step and compared with the quality assurance (QA) test items of the AAPM TG-142 described for the medical accelerator QA. Based on the commissioning procedure, dose quality control protocol, and mechanical quality control protocol presented at international conferences, step-by-step check items and commissioning guidelines were derived. The risk management items at each stage were (1) 21 ionization chamber performance test items and 9 electrometer, cable, and connector inspection items related to the dosimetry system; (2) 34 mechanical and dose-checking items during ATP, 22 multileaf collimator (MLC) items, and 36 imaging system items; and (3) 28 items in the measurement preparation stage and 32 items in the measurement stage after commissioning. Because the items presented in these guidelines are limited in terms of special treatment, items and practitioners can be modified to reflect the clinical needs of the institution. During the system installation, it is recommended that at least two clinically qualified medical physicists (CQMP) perform a double check in compliance with the two-person rule. We expect that this result will be useful as a radiation safety management tool that can prevent radiation accidents at each stage during the introduction of radiotherapy and the system installation process.

• Culinary science and hospitality research
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• v.14 no.4
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• pp.1-13
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• 2008

The antioxidant activity and quality characteristics of bread made from waxy black rice flour(WBRF) and green tea powder were investigated. The bread was manufactured with 1% of green tea powder and 10, 20, 30 or 40% of WBRF(w/w). The group of 40% of WBRF and green tea powder significantly showed the highest bread weight and volume. Lightness(L value) and yellowness(b value) decreased, but redness(a value) increased with increasing WBRF contents in mixture. Hardness, gumminess and chewiness were the lowest in the control group, but springiness was the lowest in the group of 40% of WBRF and 1% of green tea powder. The sensory scores of appearance, external and crumb color, grainy in the group of 40% of WBRF and 1% of green tea powder were the significantly lowest. Overall acceptabilities of the groups of 10% and 30% of WBRF with 1% of green tea powder were not significantly different from the control group. The group of 40% of WBRF and 1% of green tea powder showed the highest DPPH radical scavenging effect and TEAC content. Thus, if the mixture of green tea powder and WBRF would be used, it might be proper to use 1% of green tea powder and 10% of WBRF mixture considering the quality and antioxidant activity of bread.

• Quality Improvement in Health Care
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• v.26 no.2
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• pp.86-94
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• 2020

Purpose: This study aimed to identify current quality control (QC) practices of primary care clinics participating in the National Cancer Screening Program (NCSP) in Korea. Methods: A nationwide survey using a structured questionnaire was conducted among the primary care clinics participating in the NCSP, which were selected by a proportionate stratified sampling. The questionnaire consisted of general information about the responding clinics and the scope of QC activities undertaken. A total of 360 clinics responded and the set of data was then analyzed with Chi-square test and multivariable logistic regression analysis. Results: Among 360 respondents, 332 (92%) reported that they were involved in the QC activities. Most frequently performed QC activities were 'maintenance of facility and instruments' (89%) and 'staff training' (85%). The analysis revealed, with statistical significance (p<.05), that there was an association between certain characteristics of the clinics and the scope of QC activities. These findings also indicated that the diversity of QC practices varies according to the size of the clinics. The clinics screening more types of cancer, those with more screenees, and those with more employees were more likely to implement various QC activities including 'maintenance of facility and instruments', 'external quality control', and 'management of screening data'. Conclusion: To our knowledge, this is the first study to investigate the current status of QC activities conducted among primary care clinics participating in the NCSP. The results of this survey can be used as a basis for further development of policies on quality management of small- and medium-sized primary care clinics in Korea. However, further studies encompassing various aspects of QC activities and management of primary care clinics are needed to assess the current situation in a concise manner.

• Analytical Science and Technology
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• v.13 no.2
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• pp.229-233
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• 2000

The study was carried out to confirm the reliability of standard samples, low concentration $0.74mgN(NO_3)/l$, $0.58mgF^-/l$, high concentration $2.14mgN(NO_3)/l$, $1.25mgF^-/l$, on the base of quality control chart. The analytical results had the precise reliability with standard deviation of 0.010, 0.017, 0.056 and 0.019, respectively. When three persons A, B and C, who had different analytical experiences, analyzed the standard samples six times repeatedly, C person, who had more academic career and analytical experience, produced far better reliability for analytical results. Therefore, these standard samples were very suitable for external quality control test, because all persons' average values for analytical results were close to the values of prepared standard samples.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.5
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• pp.773-787
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• 2020

In the injection molding process, the controlling stability of products quality is a very important factor in terms of productivity. Even when the optimum process conditions for the desired product quality are applied, uncontrollable external factors such as ambient temperature and humidity cause inevitable changes in the state of the melt resin, mold temperature. etc. Therefore, it is very difficult to maintain prodcut quality. In this study, a system that learns the correlation between process variables and product weight through artificial neural networks and predicts process conditions for the target weight was established. Then, when a disturbance occurs in the injection molding process and fluctuations in the weight of the product occur, the stability control of the product quality was performed by ANN predicting a new process condition for the change of weight. In order to artificially generate disturbance in the injection molding process, controllable factors were selected and changed among factors not learned in the ANN model. Initially, injection molding was performed with a polypropylene having a melt flow index of 10 g/10min, and then the resin was replaced with a polypropylene having a melt floiw index of 33 g/10min to apply disturbance. As a result, when the disturbance occurred, the deviation of the weight was -0.57 g, resulting in an error of -1.37%. Using the control method proposed in the study, through a total of 11 control processes, 41.57 g with an error of 0.00% in the range of 0.5% deviation of the target weight was measured, and the weight was stably maintained with 0.15±0.07% error afterwards.