• Structural Engineering and Mechanics
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• 제30권6호
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• pp.713-732
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• 2008

Serviceability and durability of the concrete members can be seriously affected by the corrosion of steel rebar. Carbonation front and or chloride ingress can destroy the passive film on rebar and may set the corrosion (oxidation process). Depending on the level of oxidation (expansive corrosion products/rust) damage to the cover concrete takes place in the form of expansion, cracking and spalling or delamination. This makes the concrete unable to develop forces through bond and also become unprotected against further degradation from corrosion; and thus marks the end of service life for corrosion-affected structures. This paper presents an analytical model that predicts the weight loss of steel rebar and the corresponding time from onset of corrosion for the known corrosion rate and thus can be used for the determination of time to cover cracking in corrosion affected RC member. This model uses fully the thick-walled cylinder approach. The gradual crack propagation in radial directions (from inside) is considered when the circumferential tensile stresses at the inner surface of intact concrete have reached the tensile strength of concrete. The analysis is done separately with and without considering the stiffness of reinforcing steel and rust combine along with the assumption of zero residual strength of cracked concrete. The model accounts for the time required for corrosion products to fill a porous zone before they start inducing expansive pressure on the concrete surrounding the steel rebar. The capability of the model to produce the experimental trends is demonstrated by comparing the model's predictions with the results of experimental data published in the literature. The effect of considering the corroded reinforcing steel bar stiffness is demonstrated. A sensitivity analysis has also been carried out to show the influence of the various parameters. It has been found that material properties and their inter-relations significantly influence weight loss of rebar. Time to cover cracking from onset of corrosion for the same weight loss is influenced by corrosion rate and state of oxidation of corrosion product formed. Time to cover cracking from onset of corrosion is useful in making certain decisions pertaining to inspection, repair, rehabilitation, replacement and demolition of RC member/structure in corrosive environment.

• Structural Engineering and Mechanics
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• 제72권1호
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• pp.31-41
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• 2019

Structural integrity assessment of piping components is of paramount important for remaining life prediction, residual strength evaluation and for in-service inspection planning. For accurate prediction of these, a reliable fracture parameter is essential. One of the fracture parameters is stress intensity factor (SIF), which is generally preferred for high strength materials, can be evaluated by using linear elastic fracture mechanics principles. To employ available analytical and numerical procedures for fracture analysis of piping components, it takes considerable amount of time and effort. In view of this, an alternative approach to analytical and finite element analysis, a model based on relevance vector machine (RVM) is developed to predict SIF of part through crack of a piping component under fatigue loading. RVM is based on probabilistic approach and regression and it is established based on Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Model for SIF prediction is developed by using MATLAB software wherein 70% of the data has been used for the development of RVM model and rest of the data is used for validation. The predicted SIF is found to be in good agreement with the corresponding analytical solution, and can be used for damage tolerant analysis of structural components.

• 한국동물위생학회지
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• 제24권1호
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• pp.31-41
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• 2001

This study was carried out to identify causative agents from california mastitis test(CMT) positive mastitic milk, and to examine the antimicrobial susceptibility of 50 heads in Seongju and Chilgok area of Gyeongbuk province. Sulfadimethoxine sodium(SMS) was intramuscularly administered once to four mastitis Infected dairy cattle at the rate of 10mg/kg body weight. After injection of SMS, the depletion rate of serum and milk from the cattle were periodically measured for five days. The CMT positive number from 50 heads showed 46% and that of 200 quarters was 47(23.5%). From 39 quarters of 47 heads 39 different microorganisms were identified. These organisms were classified into 12 species : Staphylococcus aureus 8(20.5%), Sta hemolyticus 6(15.4%), Streptococcus bovis 4(10.3%), Sta hyicus 3(7.7%), Sta epidemidis. Sta xylosus, Sta sciuri 2(5.1%), Str agalactiae 2(5.1%), Escherichia coli(10.3%), three Enterobacter cloacae(7.7%), two Ent aerogenes(5.1%) and one Salmonella spp(2.6%). As the results of antibiotic susceptibility test, gentamicin(Gm, 11 species 27 strains, 69.5%), cephalotin(Cf, 9 species 24 strains, 61.5%), sulfamethoxazole(Stx, 8 species 14 strains, 43.6%), tetracycline(Tc, 8 species 14 strains, 35.9%), and streptomycin(Sm), lincomycin(Lm), cefoperazon(Cp) and penicillin(Pc) have a highly resistance(7.7% ～5.1%). However, carbenicillin (Cb), amikacin(Ah) have no susceptible for all drugs. The mean residual concentration of SMS in serum according to the time lapsed were showed 33.964 $\pm$ 4.435ppm at the 4 hours after intramuscularly injection(AII). It was significantly(p<.05) decreased to 6.596 $\pm$ 3.402, 0.217 $\pm$ 0.119 and 0.005 $\pm$ 0.004ppm at the 1st, 3rd and 5th day AII. The mean concentration of SMS in milk was significantly(p<.05) decreased from 0.920 $\pm$ 0.42ppm to 0.084 $\pm$ 0.016ppm between 8 hours and 1 day AII. As the results of this experiments, sulfadimethoxine was residued at the level of no less than 0.01ppm in milk on the 2nd day AII. Thus, this results would be able to be used the basic index for prevention of sulfonamides residue in milk after treatment of dairy mastitis.

• 한국철도학회논문집
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• 제20권1호
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• pp.64-75
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• 2017

철도궤도 상부 흙노반은 궤광으로부터 전달된 열차하중을 지지하고 분산하는 기능을 갖는다. 성토체의 일반적인 흙노반은 흙재료를 다짐하여 조성하며 차량 반복하중에 의해 공용중 잔류침하가 발생하는 데 일정부분 기여한다. 흙노반의 잔류침하는 회복불가능한 영구변형이어서 궤도틀림 등 궤도 안전성을 크게 저하시킨다. 그럼에도 불구하고 현재까지 흙노반재료에 대한 역학적 시험을 바탕으로 합리적인 잔류침하 관리기준이 제시된 바 없다. 반면에 흙노반의 현장관리 및 판정기준은 강성평가 또는 현장들밀도시험에 의해서만 이루어지고 있어 불합리하다. 본 연구에서는 흙노반이 경험하는 전단응력비(${\tau}/{\tau}_f$)와 구속압(${\sigma}_3$)을 수치해석을 통해 구하고 이를 반영한 실내 흙노반 영구변형시험방법을 제시하였다. 제시된 시험방법을 이용하여 대표적인 철도건설현장 흙노반 재료로 만든 다짐시편에 대하여 반복삼축시험을 실시하였으며 이로부터 향후 잔류침하의 추정에 활용할 수 있는 기본 영구변형예측모델 모델계수를 구속압 및 전단응력비 수준별로 제시할 수 있었다.

• 한국안전학회지
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• 제35권5호
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• pp.121-127
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• 2020

Since the Fukushima nuclear accident in 2011, the public were concerned about the safety of Nuclear Power Plants (NPPs) in extreme natural disaster situations, such as earthquakes, flooding, heavy rain and tsunami, have been increasing around the world. Accordingly, the Stress Test was conducted in Europe, Japan, Russia, and other countries by reassessing the safety and response capabilities of NPPs in extreme natural disaster situations that exceed the design basis. The extreme natural disaster can put the NPPs in beyond-design-basis conditions such as the loss of the power system and the ultimate heat sink. The behaviors and capabilities of NPPs with losing their essential safety functions should be measured to find and supplement weak areas in hardware, procedures and coping strategies. The Loss of Ultimate Heat Sink (LUHS) accident assumes impairment of the essential service water system accompanying the failure of the component cooling water system. In such conditions, residual heat removal and cooling of safety-relevant components are not possible for a long period of time. It is therefore very important to establish coping strategies considering all available equipment to mitigate the consequence of the LUHS accident and keep the NPPs safe. In this study, thermal hydraulic behavior of the LUHS event was analyzed using RELAP5/Mod3.3 code. We also performed the sensitivity analysis to identify the effects of the operator recovery actions and operation strategy for charging pumps on the results of the LUHS accident.

• 농약과학회지
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• 제12권2호
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• pp.148-154
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• 2008

상추의 안전한 생산을 위한 재배기간 중 농약 잔류량 변화추이와 최종 소비단계에서의 농산물 안전성 평가 자료로 활용하기 위하여 lambda-cyhalothrin과 deltamethrin의 기준량 및 배량을 각각 상추에 살포한 후 시료를 경시적으로 채취하여 GC-ECD로 잔류 농약을 분석하였다. 시험 농약의 검출한계는 모두 $0.001\;mg{\cdot}kg^{-1}$ 이었으며 분석법의 회수율은 $0.2\;mg{\cdot}kg^{-1}$ 수준에서 101.2-104.3%, $1.0\;mg{\cdot}kg^{-1}$ 수준에서 99.7-103.8% 이었다. 각 약제의 상추 중 잔류량은 시간이 경과함에 따라 점차 감소하는 것으로 나타났으며, lambda-cyhalothrin과 deltamethrin의 생물학적 반감기는 기준량 살포의 경우 1.7일과 1.4일, 배량 살포의 경우는 1.8일과 1.4일 이었다. Lambda-cyhalothrin과 deltamethrin의 초기 잔류량은 모두 잔류 허용기준 이상이었으나 수확예정 일의 잔류농도는 모두 잔류허용기준 미만이었으며, 수확예정 일의 잔류량으로 산출한 시험 농약의 ADI 대비 EDI의 비율은 기준량과 배량 처리구에서 모두 1% 미만이었다.

• Journal of Nutrition and Health
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• 제38권3호
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• pp.232-241
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• 2005

Today, the role of kindergarten is more important as nutrition provider through snack and meal services. Desirable kinds and amounts of food items at school lunch menu were important factors of nutrients intakes in children. This study was performed to assess the kindergarten's meal service program (snack and lunch) and the consumption amount of lunch according to each dishes. Twenty four institutions that cared over one hundred children were observed at Seoul and Kyunggido area. Well-trained observers checked meal and snack serving activity and foodservice facilities by formal checklist. And using the weighing method assessed the consumption levels of food items at lunch. During 3 days, 30 children in each kindergarten were selected randomly according to age, observers measured serving and residual weight of each food. The data was compiles by performing ANOVA-test using SPSS WIN 10.0. The result were as follows: 1) Foodservice facilities in kindergarten was limited to provide qualified foodservice. $91.7\%$ of institution had kitchen, $41.7\%$ had dinning. The kitchen equipment possession rate was $12.5\%$ (oven), $30.8\%$ (heating cabinet), $58.3\%$ (refrigerator). The rate of using document about foodservice was used $83.3\%$ (menu list), $41.7\%$ (daily foodservice record), $25\%$ (standard recipe). $41.7\%$ of institution employed licensed dietitian. Only $41.7\%$ of subjects preserved meal after daily meal service. 2) Meal serving size was decided by teacher, $54.5\%$ at snack and $43\%$ at lunch and pre-divided individual portion type was $36.4\%$ at snack and $28.6\%$ at lunch. The rate of cleaning activity before meal was $72.2\%$ at snack, $90.5\%$ at lunch. And nutrition or sanitation education activity was more performed at lunch time, for examples brushing teeth activity was $12.5\%$ at snack $85.7\%$ at lunch. 3) The consumption amounts of plain cooked rice was $112.7{\pm}26.1{\cal}g$, cooked rice and cereal was $93.06{\pm}27.97{\cal}g$, curry rice was $208.35{\pm}64.84{\cal}g$ and the consumption amounts of these main dishes was significantly different by age (p < 0.001). The consumption amounts of soup was very different according to children's preference. The consumption amounts of seaweed soup was $120.18{\pm}82.13{\cal}g$, wild sesame and bean-paste soup was $40.64{\pm}23.16{\cal}g$. The consumption range of kimchis was from $6{\cal}g\;to\;13{\cal}g$, jorim (braised food) was from $3{\cal}g\;to\;25{\cal}g$, fried food (include stir fried, deep fat fried, pan fried) was from $14.5{\cal}g\;to\;22{\cal}g$, vegetable dish was from $3{\cal}g\;to\;16{\cal}g$. These consumption amount of each dishes was not reached recommended portion size of nutritionally planning menu by nutritionist.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권3호
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• pp.428-451
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• 2010

Traffic matrix-based anomaly detection and DDoS attacks detection in networks are research focus in the network security and traffic measurement community. In this paper, firstly, a new type of unidirectional flow called IF flow is proposed. Merits and features of IF flows are analyzed in detail and then two efficient methods are introduced in our DDoS attacks detection and evaluation scheme. The first method uses residual variance ratio to detect DDoS attacks after Recursive Least Square (RLS) filter is applied to predict IF flows. The second method uses generalized likelihood ratio (GLR) statistical test to detect DDoS attacks after a Kalman filter is applied to estimate IF flows. Based on the two complementary methods, an evaluation formula is proposed to assess the seriousness of current DDoS attacks on router ports. Furthermore, the sensitivity of three types of traffic (IF flow, input link and output link) to DDoS attacks is analyzed and compared. Experiments show that IF flow has more power to expose anomaly than the other two types of traffic. Finally, two proposed methods are compared in terms of detection rate, processing speed, etc., and also compared in detail with Principal Component Analysis (PCA) and Cumulative Sum (CUSUM) methods. The results demonstrate that adaptive filter methods have higher detection rate, lower false alarm rate and smaller detection lag time.

• 수산해양기술연구
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• 제53권2호
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• pp.187-195
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• 2017

We have studied the efficient operation of the radar and the appropriateness of the installation location, when constructing the VTS system. As the Civil-Military Complex Harbour (Kangjeong Port) is completed in 2016, we set the control area within 10 nautical miles centering on Kangjeong Port, and found out and removed the operational radar blind area of VTS system to provide safe navigation information for vessels that navigating this area. Assuming that two international cruise ships entering at the same time, we performed the radar simulation and compared the images by considering the three sites of Kangjeong Port, Miaksan and Seoguipo Port. Simulation results for a single radar installed at Kangjung Port indicate that the blind area was largely affected by two large cruise ships and the surrounding islands. The blind area due to Kogunsan was considerably large when installed in Miaksan, but the blind area due to the influences of Beomseom, Moonseom and Seopseom was negligibly large. It seems that additional radar installation is necessary as a complementary solution to solve this blind area. When two radars were installed at Miaksan and Kangjeong Port, the residual blind area due to the Seopseom was $0.25km^2$ at 0.1~0.33 nautical miles in the southeast direction from Seopseom. In addition, the remaining blind area with two cruise ships mutually influenced was $0.18km^2$, which did not occur with a single cruise ship.

• 한국항해항만학회지
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• 제31권6호
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• pp.515-521
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• 2007

컨테이너 화물의 복합운송시스템 중에서 체화현상은 항만에서 가장 심각하다. 이러한 문제를 해결하기 위해 해상과 육상의 경계선에서 체선체화 문제를 발생시키는 컨테이너 크레인의 직업효율을 향상시키는 방법을 생각할 수 있다. 이를 위해 본 연구에서는 가능한 범위에서 트롤리를 목표지점까지 빠르게 이동시키는 동시에 목표위치에서의 흔들림도 짧은 시간 내에 제어하는 문제를 다루고 있다. 제어 전략으로 설계된 구간에서 최적의 성능과 강인성이 보장되는 LQ 제어와 제약조건에서 최적화가 가능한 실수코딩 유전알고리즘을 결합한다. 컴퓨터 시뮬레이션을 통해 제안한 제어기가 설정한 설계사양을 완벽하게 만족하는 것을 보임으로 그 유효성을 증명한다.