• Computers and Concrete
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• 제4권3호
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• pp.243-257
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• 2007

A novel method for recognition, characterization, and quantification of deterioration in bridge components and laboratory concrete samples is presented in this paper. The proposed scheme is based on grey level co-occurrence matrix texture analysis using Haar's discrete wavelet transform on concrete imagery. Each image is described by a subset of band-filtered images containing wavelet coefficients, and then reconstructed images are employed in characterizing the texture, using grey level co-occurrence matrices, of the different types and degrees of damage: map-cracking, spalling and steel corrosion. A comparative study was conducted to evaluate the efficiency of the supervised maximum likelihood and unsupervised K-means classification techniques, in order to classify and quantify the deterioration and its extent. Experimental results show both methods are relatively effective in characterizing and quantifying damage; however, the supervised technique produced more accurate results, with overall classification accuracies ranging from 76.8% to 79.1%.

• 대한산업공학회지
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• 제16권2호
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• pp.1-9
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• 1990

The control of deterioration processes for which only incomplete state information is available is examined in this study. When the deterioration is governed by a Markov process, such processes are known as Partially Observable Markov Decision Processes (POMDP) which eliminate the assumption that the state or level of deterioration of the system is known exactly. This research investigates a two state partially observable Markov chain in which only deterioration can occur and for which the only actions possible are to replace or to leave alone. The goal of this research is to develop a new jump algorithm which has the potential for solving system problems dealing with continuous state space Markov chains.

• Tuberculosis and Respiratory Diseases
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• 제70권1호
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• pp.51-57
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• 2011

Background: Early recognition and treatment of sepsis would improve patients' outcome. But it is difficult to distinguish between sepsis and non-infectious conditions in the acute phase of clinical deterioration. We studied serum level of procalcitonin (PCT) as a method to diagnose and to evaluate sepsis. Methods: Between 1 March 2009 and 30 September 2009, 178 patients had their serum PCT tested during their clinical deterioration in the medical intensive care unit. These laboratories were evaluated, on a retrospective basis. We classified their clinical status as non-infection, local infection, sepsis, severe sepsis, and septic shock. Then, we compared their clinical status with level of PCT. Results: The number of clinical status is as follows: 18 non-infection, 33 local infection, 39 sepsis, 26 severe sepsis, and 62 septic shock patients. PCT level of non-septic group (non-infection and local infection) and septic group (sepsis, severe sepsis, septic shock) was $0.36{\pm}0.57$ ng/mL and $18.09{\pm}36.53$ ng/mL (p<0.001), respectively. Area under the curve for diagnosis of sepsis using cut-off value of PCT >0.5 ng/mL was 0.841 (p<0.001). Level of PCT as clinical status was statistically different between severe sepsis and septic shock ($^*severe$ sepsis; $4.53{\pm}6.15$ ng/mL, $^*septic$ shock $34.26{\pm}47.10$ ng/mL, $^*p$ <0.001). Conclusion: Level of PCT at clinical deterioration showed diagnostic power for septic condition. The level of PCT was statistically different between severe sepsis and septic shock.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.60-65
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• 2017

We designed and fabricated the engine oil monitoring sensor to measure engine oil deterioration through increased vehicle mileage. Since the condition of the engine oil can be affected by the state of the vehicle and its operating conditions, it should be directly measured and determined in every vehicle. The fabricated sensor has an aluminum parallel capacitor structure that measures capacitance related with the dielectric constant, which is one of the indices of oil deterioration. The size of the capacitor is small enough that it could be easily adapted on the oil level gauge without introducing any change in the design. The fabricated device is installed in the diesel engine to measure the change in capacitance accurately as the vehicle moved from 0 km (new engine oil state) to 11,364 km. The results showed the maximum value at around 5,000 km, and the values plateaued as mileage increased, corresponding with the measurement result of the TAN (Total Acid Number). Based on the results, the condition of the oil must be monitored regularly though oil change is recommended once the vehicle has traveled the distance of around 10,000 km.

• 한국방재학회 논문집
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• 제8권5호
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• pp.15-21
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• 2008

본 연구의 목적은 현재 지방자치단체에서 수행하는 상수관로 개량 및 교체 사업시 상수관로의 노후도 평가를 위한 항목별 가중치를 산정하는 것이다. 상수도시스템에 상수관로의 노후도 항목은 지역 및 위치, 토지이용 등의 특성에 영향을 받을 수 있다. 본 연구에서는 국내외 자료를 바탕으로 국내 실정에 맞는 노후도 항목 16개를 선정하였다. 또한, 노후도 항목별 세분화된 가중치 산정을 위해 실무업체를 선정하여 해당 전문가들을 대상으로 노후도 항목별 중요도에 대한 설문을 실시하였다. 설문 조사 방법으로는 델피법을 이용하여 이 결과를 바탕으로 계층적분석과정(AHP)을 적용하여 노후항목별 가중치를 산정하였다. 분석결과 국내 실무에 적합한 16개 결함항목별 점수배점표를 작성하여 명확한 판단기준을 마련하였으며 관거 개량사업에 있어서 복잡한 의사결정 문제들에 대한 활용 가능성을 제시하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.970-979
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• 2006

Construction of underground structure requires higher standard of planning and design specifications than in surface construction. However, high construction cost and difficult working environment limit design level and construction quality. One of the most sensitive factors to be considered are infiltration and external pore-water pressures. Development of pore-water pressure may accelerate leakage and cause deterioration of the lining. In this paper, the development of pore-water pressure and its potential effect on the linings are investigated using physical model tests. A simple physical equipment model with well-defined hydraulic boundary conditions was devised. The deterioration procedure was simulated by controlling both the permeability of filters and flowrate. Development of pore-water pressure was monitored on the lining using pore pressure measurement cells. Test results identified the mechanim of pore-water pressure development on the tunnel lining which is the effect of deterioration of drainage system. The laboratory tests were simulated using coupled numerical method, and shown that the deterioration mechanism can be reproduced using coupled numerical modelling method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.225-228
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• 2005

This paper was accomplished for analyzing the reason of the above deterioration happened on the deck of concrete bridge. The bridge was constructed at 660m above the sea level having more freezing and snowing days. Therefore, it is placed on the particular condition sprinkling $CaCl_2$ enough for keeping up with moderate traffic condition. When it is considered to the former condition, the bridge can be assumed to potentialities for combined deterioration with freezing-thawing under sprinkling deicing chemical. Core specimens were gathered from the concrete deck for clearing the reason of the above deterioration exactly, and it is used for various tests for measuring the compressive strength, elastic modulus, content of $Cl^-$, freezing-thawing at the fresh and salt water. As a result of freezing-thawing test, the specimen at the fresh water has over 90$\%$ of durability factor, but another specimen at 1$\%$ of salt water has 0$\%$ of durability factor at 140 cycles of the freezing-thawing. The result means that frost damage is sccelerated at the salt water. Therefore, the deterioration of the concrete deck is estimated to be occured by combined effects of freezing-thawing and chloride ion attack.

• 설비공학논문집
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• 제27권2호
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• pp.103-111
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• 2015

In general, no particularly well-established standards have been in place so far, for the method of evaluating the deteriorated level of pipes and ducts of industrial facilities. For that reason, the evaluation depends upon various studies which are based on the analysis of the residual life, thickness thinning, closure rate, and scale thickness that measure a few specific positions of pipes. It also depends upon the expertise in business operation and the specific techniques conducted by the inspection companies and institutions. This research introduces the concept of measuring units per section and the selection method of measurement points per section. Furthermore, specific methodologies were developed to plan and analyze deterioration level of industrial pipes and ducts by engineers and managers using a section map. Consequently, applying the outcomes from this study to the plant equipment of the incineration facility resulted in saving 42% of the repairing and remodeling cost.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1393-1395
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• 2004

Arresters are the best protective device on electrical power systems against transient overvoltages generated by lightning and/or switching operation. Nonetheless, arresters will be deteriorated due to absorption of moisture in the environments of its use, repetition in the protective operation to overvoltages, and some defects at manufacturing. It is therefore important to estimate the electrical characteristic changes of ZnO blocks. In this paper, an accelerated deterioration test by a standard lightning impulse current was carried out to extract parameters needed for diagnosing arrester deterioration, and leakage current components were measured. Total energy applied to the ZnO blocks at each time is 1,050[J] in 8/20[${\mu}s$] impulse current. From the experimental results, we proposed electrical parameters and leakage current level to diagnose arrester soundness.

• 한국구조물진단유지관리공학회 논문집
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• 제17권1호
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• pp.55-63
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• 2013

본 연구는 우리나라에서 가장 일반적인 중소규모의 비내진 상세를 가진 건축물을 대상으로, 노후도를 고려하여 내진성능을 평가하였다. 평가결과, 준공 후 24년이 경과되었으나 노후도는 대체로 양호한 것으로 평가되었고, 1차, 2차 내진성능평가는 기준지표를 만족하지 못하는 것으로 나타났다. 3차 내진성능평가에서는 층간변위비를 기준으로 목표성능은 만족하지만 보강이 필요한 것으로 판단되었다. 대상 건축물에 벽체보강, 가새보강, 댐퍼보강을 한 후 내진성능평가를 실시한 결과, 보강방법에 상관없이 층간변위비는 현저히 감소하여 즉시거주수준을 만족하는 수준으로 나타났다. 그러나 벽체보강의 경우 밑면전단력이 2배 이상 증가되어 기존기초에 대한 검토가 필요하다.