• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.838-848
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• 2015

One of the most important operations in nuclear power plants is load following, in which an imbalance of axial power distribution induces xenon oscillations. These oscillations must be maintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation is considered to be a constraint for the load following operation. In this paper, the design of a sliding mode control (SMC), which is a robust nonlinear controller, is presented.SMCis ameansto control pressurized water nuclear reactor (PWR) power for the load following operation problem in a way that ensures xenon oscillations are kept bounded within acceptable limits. The proposed controller uses constant axial offset (AO) strategy to ensure xenon oscillations remain bounded. The constant AO is a robust state constraint for the load following problem. The reactor core is simulated based on the two-point nuclear reactor model with a three delayed neutron groups. The stability analysis is given by means of the Lyapunov approach, thus the control system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications and moreover, the SMC exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness, and stability. Results show that the proposed controller for the load following operation is so effective that the xenon oscillations are kept bounded in the given region.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2009.04a
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• pp.155-160
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• 2009

Safety of residents could be considered and then increased when we plan, design, and operate a city. In Korea, CPTED (Crime Prevention through Environmental Design) is currently being applied to new towns. However, it is not systemized and neither efficient, for there are no constraint provisions, and the foreign cases are not specifically customized to the current situation of the country. This means, the introduction of CPTED is an indispensable fact, but there are limits to the budget aids and actual application, for there is no legal base to support it. This study, therefore, aims to find the limits from analyzing related laws and regimes, administrative regulations, and applied cases, and to deduct improvement plans based on examined foreign cases. In this Study, the supporting system of foreign CPTED related laws and regulations was analyzed around the cases of England and U.S.A, and based on that information, the present condition and limits of CPTED related laws and regulations of Korea were deducted. As a result of this study, there were no constraint provisions to apply the design guidelines to actual planning, and there were limits on backup aid and actual application due to the lacking of analyzing the relevant area. Also, an acceptable framework must be arranged by the revision of laws and ordinances to compel the system, and link it with the CPTED certification system which will revitalize the whole system.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1933-1936
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• 2016

Heavy metals are known to disrupt important physiological processes in living cells, and have been responsible for various pathological conditions with possible contributions to cancer development. Food contamination have been identified as one of the ways humans are exposed to heavy metals. In developing countries like Nigeria, the regulatory framework for enforcing compliance with globally acceptable exposure to deleterious contaminants is poor. In the current study, thirteen samples of cured meat products of diverse origin marketed in South-west Nigeria were evaluated for lead, cadmium, chromium and nickel contents using the atomic absorption spectroscopy technique. All the samples analysed contained cadmium between 0.35 and 1.20 ppm, levels considered higher than acceptable limits in consumable products. Lead, chromium and nickel were not detected in any of the samples. As known cumulative poisons, there is the need for stringent regulatory control of these heavy metals in cured meat products imported into or produced indigenously in the country in order to minimize the risks to public health.

• Journal of the Ergonomics Society of Korea
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• v.18 no.1
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• pp.1-12
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• 1999

The objective of this study was to investigate the metabolic energy consumption rate of the psychophysical Maximum Acceptable Weight of Loads (MAWLs) for different manual materials handling tasks. Lifting activities with four different lifting frequencies (2, 5, 8, 11 lifts/min) for a lifting range (from floor to 76cm height) were studied. The oxygen consumption rate and heart rate were measured or recorded while subjects were lifting their MAWLs. It was found that the relationship between MAWL and frequency can be described best by the exponential function with the R-sq value 0.9865 for this study. Psychophysical MAWL decreased from 22.38 to 7.48 kg, while the oxygen consumption rate with the MAWL increased from 717.8 to $1114.7m{\ell}-O_2/min$ as the frequency increased from 2 to 11 lifts/min. Heart rate also increased from 104.5 to 120.7 bpm. The ratio of oxygen consumption for the MAWL to the Physical Work Capacity (PWC) ranged from 28 to 43%. The MAWLs were greater than or equal to the Maximum Permissible Limits (MPLs) when the frequencies were higher than 8 lifts/min. It seems that the MAWLs by psychophysical approach when the frequencies were higher than 8 lifts/min tend to be overestimated from the viewpoint of the physiological criterion of the oxygen consumption rates. From these findings it is suggested that the NIOSH Guideline should not be directly applied to Korean without reasonable modifications.

• Food Science of Animal Resources
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• v.41 no.2
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• pp.335-342
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• 2021

Vitamin B12 deficiency may lead to serious health issues in both infants and adults. A simple analytical method involving sample pretreatment with enzyme, followed by cyanide addition under acidic conditions; separation on an immunoaffinity column; and high-performance liquid chromatography (HPLC) was developed for the rapid detection and quantitation of vitamin B12 in powdered milk. Detection limit and powdered milk recovery were determined by quantitative analysis. The limits of detection and quantitation were 2.71 and 8.21 ㎍/L, respectively. Relative standard deviations of the intra-day and inter-day precisions varied in the ranges of 0.98%-5.31% and 2.16%-3.90%, respectively. Recovery of the analysis varied in the range of 83.41%-106.57%, suggesting that the values were acceptable. Additionally, vitamin B12 content and recovery in SRM 1849a were 54.10 ㎍/kg and 112.24%, respectively. Our results suggested that the analytical method, including the sample pretreatment step, was valid. This analytical method can be implemented in many laboratory-scale experiments that seek to save time and labor. Therefore, this study shows that immunoaffinity-HPLC/ultraviolet is an acceptable technique for constructing a reliable database on vitamin B12 in powdered milk containing starch as well as protein and/or fat in high amounts.

• Korean journal of food and cookery science
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• v.16 no.2
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• pp.195-201
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• 2000

An investigation was conducted to evaluate the hygienic status of university foodservice operation by using conventional swabbing technique plus standard plate count and ATP bioluminescence assay. The results of the study were as follows: 1) For all kitchen boards, knives, feeding trays, and dish towels tested, there was an overall agreement at 84.7% level between the results obtained using ATP bioluminescence and plate count when using a pass/fail cut-off of 3$\times$ control values for ATP assay and 40 CFU(colony forming unit)/㎠ for plate count. 2) The agrement rate between ATP assay and standard plate count was 87.5% for the samples before use, 29.2% for those during use, and 42.7% for those after cleaning and sanitizing. 3) The plate counts of three university foodservice operations for kitchen board, kitchen knife, feeding tray and dish towel were within the acceptable limits when tested before using. However, none of them were within the acceptable limits when tested during using and after cleaning and sanitizing. 4) Above results suggested that an immediate action needs to be taken to reduce the potential danger of cross-contamination and also effective sanitary control methods needs to be developed to improve the sanitary condition.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.1
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• pp.109-120
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• 2000

In the analysis of the common categories, moisture contents and organic concentrations were not much different according to the types of industry or treatment facilities. When heavy metals contribution of the sludge from domestic and industrial wastewater treatment facilities was analyzed, As, Hg and Cr concentrations were relatively high among 42 standards of the fertilizer law. As concentration war higher in 28 of 42 facilities (67%) than limits of the fertilizer law. Hg concentration was not acceptable in the 21 of 42 facilities (50%). Cr concentration was not acceptable in 9 of 42 facilities (21%). From these results, It is found that As is the most frequently detectable component and contaminant than any other heavy metals in sludges. The data from this experiment was also compared with the guidelines of harmful organics and the rest of heavy metals that are regulated by some of the foreign countries. Be, Se and Mo concentrations were lower than the limits. Among the organics, the average concentration of PCB (10 samples) was 26.2 ppb. The highest concentration was 162.6 ppb in the sludge of the municipal wastewater treatment facilities and the lowest concentration was 2.14 ppb from the skin manufacturing industry. From the leaching analysis of re-manufacturing goods from the sludge, most of them was acceptable on the regulation law but Cr concentration was over the limit.

• Earthquakes and Structures
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• v.12 no.5
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• pp.583-589
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• 2017

In this study, result of a field investigation of railway traffic-induced vibrations is provided to examine acceptability levels of ground vibration and to evaluate the serviceability of a liquid-storage tank. Free field attenuation of the amplitudes as a function of distance is derived by six accelerometers and compared with a well-known half-space Bornitz's analytical solution which considers the loss of the amplitude of waves due to geometrical damping and material damping of Rayleigh. Bornitz's solution tends to overlap vertical free field vibration compared with in-situ measured records. The vibrations of the liquid-storage tank were compared with the USA, Federal Transportation Railroad Administration (FTA) criteria for acceptable ground-borne vibrations and with the criteria in DIN 4150-3 German standard. Comparing the thresholds stated in DIN 4150-3, absolute peak particle velocities are within the safe limits, however according to FTA velocity level at the top of the water tank exceeds the allowable limits. Furthermore, it is intended to indicate experimentally the effect of the kinematic interaction caused by the foundation of the structure on the free-field vibrations.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.20-36
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• 2001

The purpose of this paper is estimating environmental carving capacity of Seoul Metropolitan Area for a sustainable city management using system dynamics model. A sustainable development requires a society to define sustainability constraints or environmental limits, environmental carving capacity. Environmental carving capacity can be defined as the level of human activity which a region can sustain at an acceptable quality of life level. This concept of environmental carving capacity has several important application to sustainable city planning and management. If the limitation of a human activity can be supported by a scientific data on carving capacity, the resulting decision and actions could more easily win public support for a sustainable development. However, one of the key issues is how to operationalize the carving capacity. In this paper, the environmental carving capacity was operationalized as a maximum number of industry structure, population, and housing that can sustain certain level of environmental quality of Seoul Metropolitan Area. The model developed in this paper consisted off sectors: population, housing, industry, land, and environmental sector. The model limits its main focus on the NO$_2$level of ambient air of Seoul. Carving capacity Seoul Metropolitan Area was estimated by figuring out the maximum number of population, industry structure, housing at an equilibrium point that sustain a desirable NO$_2$level. Based on the model estimation, several policy implications for a sustainable city management was discussed.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E3
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• pp.153-163
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• 2002

A laboratory- scale dual-column biofilter system was used to study the biofiltration of dimethyl disulfide (DMDS). The gas flow rate and DMDS concentration to the biofilter were varied to study their effect on the remov-al of dimethyl disulfide. Operating parameters such as pH, temperature, and water content were monitored during the biofilter operation and necessary precautions were taken to keep these parameters within the acceptable limits. It was observed that the removal efficiency of DMDS was optimal at neutral pH values. After five month op-eration, the neutralization of the filter beds with sodium carbonate became necessary for the optimum operation of the biofilters. The microbial population already present in the compost mixtures was found to be adequate in treat-ing DMDS. The compost mixtures were found to be similar in terms of biofiltration efficiency of DMDS. However, pressure drops observed in the first column compost mixture (compost/ peat mulch) was extremely high, making this compost economically not feasible. The second mixture (compost/bark) provided pressure drops within accept-able limits. A minimum residence time of 30 seconds at the optimal operating conditions appeared to be adequate for achieving high removal efficiencies (>90%).