Monitoring of Concrete Deterioration Caused by Steel Corrosion using Electrochemical Impedance Spectroscopy(EIS) (EIS를 활용한 철근 부식에 따른 콘크리트 손상 모니터링)
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- Journal of the Korea Institute of Building Construction
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- v.22 no.6
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- pp.651-662
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- 2022
The electrochemical impedance spectroscopy(EIS) method was used to evaluate the concrete deterioration process related to chloride-induced steel corrosion with various corrosion levels(initiation, rust propagation and acceleration periods). The impressed current technique, with four total current levels of 0C, 13C, 65C and 130C, was used to accelerate steel corrosion in concrete cylinder samples with w/c ratio of 0.4, 0.5, and 0.6, immersed in a 0.5M NaCl solution. A series of EIS measurements was performed to monitor concrete deterioration during the accelerated corrosion test in this study. Some critical parameters of the equivalent circuit were obtained through the EIS analysis. It was observed that the charge transfer resistance(Rc) dropped sharply as the impressed current increased from 0C to 13C, indicating a value of approximately 10kΩcm2. However, the sensitivity of Rc significantly decreased when the impressed current was further increased from 13C to 130C after corrosion of steel had been initiated. Meanwhile, the double-layer capacitance value(Cdl) linearly increased from 50×10-6μF/cm2 to 250×10-6μF/cm2 as the impressed current in creased from 0C to 130C. The results in this study showed that monitoring Cdl is an effective measurement parameter for evaluating the progress of internal concrete damages(de-bonding between steel and concrete, micro-cracks, and surface-breaking cracks) induced by steel corrosion. The findings of this study provide a fundamental basis for developing an embedded sensor and signal interpretation method for monitoring concrete deterioration due to steel corrosion at various corrosion levels.
Background: Base on types of tumor, the types of expressed tumor is diverse and the difference in its expression rate is even more various. Due to such reasons an animal model is absolutely needed for a clinical research of lung cancer. The author attempted oncogenesis by cultivating a cell line of non-small cell carcinoma and then injecting it inside thoracic cavities of nude mice. The author conducted quantitative analyses of HER2/neu tumor gene - an epidermal growth factor receptor (EGFR) related to lung cancer, and TGF-
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
Background: The Damus-Kaye-Stansel (DKS) procedure is a proximal MPA-ascending aorta anastomosis used to relieve systemic ventricular outflow tract obstructions (SVOTO) and pulmonary hypertension. The purpose of this study was to review the indications and outcomes of the DKS procedure, including the DKS pathway and semilunar valve function. Material and Method: A retrospective review of 28 patients who underwent a DKS procedure between May 1994 and April 2006 was performed. The median age at operation was 5.3 months (
Medication is widely accepted as an effective method to reduce the problem of attention deficit, hyperactivity, impulsivity, resistance and violence of ADHD children. However, it does not provide us with the solution on the conflicting routinized behavioral patterns to gain a high level of self-control and acceptable behavior. As a way of replacing medication, this study applies the social skills training program for ADHD children and measures the level of improvement of social skills and the change of the behavioral patterns. The experiment is carried out on 16 children ranged from 6 to 13 years of age for 10 weeks. The patients are divided into three groups:a pure ADHD group, an ADHD group with conduct disorder, an ADHD group with mental retardation and other symptoms. The change of symptoms and the change of social skills are measured by the Child Behavior Checklist(CBCL), the ADD-H Comprehensive Teacher’s Rating Scale(ACTeRS) and the Social Skills Rating Scale(SSRS), and finally Mastson Evaluation of Social Skills for Youth(MESSY). Wilcoxon signed ranks test is used to evaluate the effect of the treatment, and Kruskal-Wallis test is also used to measure the change after the treatment in each of the three groups. In the ADHD group with conduct disorder, the examination of the effect of the treatment shows a significant reduction of violence in the area of behavior(p<.05), and a significant difference of activity and social skills in the area of social competent(p<.001). In the ADHD group with mental retardation and other symptoms, a significant rise of social skills is found in the area of social skills evaluation (p<.05). However, there is no significant difference of effect by the treatment among the three groups. In addition, the current examination shows that the social skills training program does not make a statistically significant contribution to the social skills of the ADHD children. On the other hand, the training helps some children, when it is suitable for the characteristics and accompanying symptoms of the children:it reduces the level of violence in the ADHD group with conduct disorder, and it raises the social skills in the ADHD group with mental retardation. In other words, the social skills training program will reduce the conduct disorder and helps peer relation for ADHD children.
It was conducted to identify all 47 isolates obtained from infected fruits of pepper and boxthorn, and to investigate the mycological characteristics and the response to fungicides. All of 11 isolates from pepper were identified as Colletotrichum acutatum included into A2 group. Among 36 isolates from boxthorn, 14 isolates were identified as C. gloeosporioides, and the others were done as C. acutatum, which were composed as A1 group with 15 isolates and A3 with 7 isolates. After incubating the isolates on PDA at
As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.
The inner and outer environment surrounding companies becomes more insecure and unpredictable due to sudden changes. Because the change of environment surrounding companies can deeply affect the existence of companies, continuous innovation of organization is required to develope management ability. Also, to conquer insecure present and future of companies effectively, organizations of companies have voluntarily coped with insecurities and intense competitions through endless organization innovation. Externally, globalization, openness, and relaxed regulation intensify competitions; consumers' requests get varied; consciousness of members of organizations have changed. Due to those factors, companies are placed in a situation that they should practice endless inner innovation. Internally, competitive power has weakened due to decline in productivity and inefficiency of indirect parts of company has increased. From those factors, managers increasingly request inner innovation and pursue organization innovation for the purpose of effective usage of extra resources and being prepared for the future. The managers who operate organization innovation think that systematized approach to organization innovation is the most practical, and actually operate the thought. However, the negative side of the thought is not neglectable. To minimize inner and outer resistance and to operate organization innovation successfully, some innovation strategies that properly reflect several issues related to organization innovation should be prepared. Another words, organization innovation should be operated differently by cases that if it focuses on personal perspective or on organization's. For many cases of our country, several techniques of organization innovation have been adopted in a short time and operated without making its original use. Therefore, this study looks into major Issues that should be considered for more successful operation of organization innovation, from both personal aspect and organizational aspect. When considering such aspects and operate organization innovation, there is more possibility to succeed on organization innovation. Now, Korean companies have overcame trial period and reborn as global companies. Take warnings by the ordeal under IMF administration, this is time to secure international competitive power by using developed innovation techniques and transform to superior company. Managers need to recognize that to try successful organization innovation is the shortcut to reborn as competitive company, and should take a continuous and profound search for decisive factors to succeed on organization innovation. To operate successful organization innovation, first, at the step of planning organization. innovation, the company should understand the company's capability, position in market and relationship with competitors. Then, the company should establish a distinguished innovation strategy which is of the whole company's aspect, so that the company can freely choose various technique of organization innovation that suits for the company's capability and needs, and unfold the organization innovation movement. Establishing strategy in the aspect of the total company is very important because it offers clear focus of the purpose of adopt, priority and distribution of resources. Second, at the step of operating organization innovation, the company should define concrete purpose and method to evaluate the results that are expected to obtain by adopting organization innovation in advance. While pushing forward, the company should set proper time of examination(milestone) and inspect if expected results are shown. Third, at the step of afterward management of operating organization innovation, the company requires a thorough afterwards verification if targeted results are obtained and of confirmation of successful or failure factors. Also, the company should cultivate specialists in the company who can accumulate and continuously spread the know-how learned during organization innovation promotion, so the know-how don't remain only in certain departments or to a few people in charge. The company should also give effort to maintain the accumulated innovation techniques to be continued.
Recently, there have been frequent occurrences of ground sink in the urban area, which have resulted in human and material damage and are accompanied by economic losses. This is caused by artificial factors such as soil loss, poor compaction, horizontal excavation due to the breakage of the aged sewage pipe, and lack of water proof at vertical excavation. The ground sink can be prevented by preliminary restoration and reinforcement through exploration, but it can be considered that it is not suitable for urgent restoration by the existing method. In this study, a model experiment was carried out to simulate the in-ground cavities caused by groundwater flow for developing non-excavation urgent restoration in underground cavity and the range of the relaxation zone was estimated by detecting the around the cavity using a relaxation zone detector. In addition, disturbance region and relaxation region were separated by injecting gypsum into cavity formed in simulated ground. The shape of the underground cavity due to the groundwater flow was similar to that of the failure mode III formed in the dense relative density ground due to water pipe breakage in the previous study. It was confirmed that the relaxed region detected using the relaxation zone detector is formed in an arch shape in the cavity top. The length ratio of the relaxation region to the disturbance region in the upper part of the cavity center is 2: 1, and it can be distinguished by the difference in the decrease of the shear resistance against the external force. In other words, it was confirmed that the secondary damage should not occur in consideration of the expandability of the material used as the injecting material in the pre-repair and reinforcement, and various ground deformation states will be additionally performed through additional experiments.