• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.393-400
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• 2013

Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates.

• Geomechanics and Engineering
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• v.18 no.1
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• pp.11-20
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• 2019

The purpose of this study was to propose a new approach for quantifying in situ rock mass damage, which would include a degree-of-damage and the degraded strength of a rock mass, along with its prediction based on real-time Acoustic Emission (AE) observations. The basic approach for quantifying in-situ rock mass damage is to derive the normalized value of measured AE energy with the maximum AE energy, called the degree-of-damage in this study. With regard to estimation of the AE energy, an AE crack source location algorithm of the Wigner-Ville Distribution combined with Biot's wave dispersion model, was applied for more reliable AE crack source localization in a rock mass. In situ AE wave attenuation was also taken into account for AE energy correction in accordance with the propagation distance of an AE wave. To infer the maximum AE energy, fractal theory was used for scale-independent AE energy estimation. In addition, the Weibull model was also applied to determine statistically the AE crack size under a jointed rock mass. Subsequently, the proposed methodology was calibrated using an in situ test carried out in the Underground Research Tunnel at the Korea Atomic Energy Research Institute. This was done under a condition of controlled incremental cyclic loading, which had been performed as part of a preceding study. It was found that the inferred degree-of-damage agreed quite well with the results from the in situ test. The methodology proposed in this study can be regarded as a reasonable approach for quantifying rock mass damage.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.37-44
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• 2013

PURPOSES: This study is to develop the deduct value curves for the calculation of pavement condition index of asphalt airfield pavement. METHODS: To develop the deduct value curves of asphalt airfield pavement, panel rating was conducted to decide the pavement condition based on pavement distress type, severity, and density. RESULTS: Results show that standard deviation of deduct values by panel rating is increased at higher severity level and as damage density increases. The deduct value of alligator cracking show the highest. CONCLUSIONS: The deduct value curves based on panel rating could be used without existing problems which were occurred in Shahin's method.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.591-596
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• 2001

The purpose of this study is to examine the change of half value breadth and residual stress during fatigue process in S45C Steel by X-ray diffraction. For S45C Steel, the relationship between the change in fatigue damage of the specimen and the half value breadth, and residual stress of X-ray diffraction profiles during the fatigue processes has been investigated. The half value breadth(HVB) decreases in he early period of fatigue cycle. The change of HVB is relation to cyclic work hardening. In $10{\sim}20%$ of ratio of fatigue life, the change in the half value breadth is not marked. During fatigue process, the residual stress is changed with fatigue cycle increasing.

• The Korean Journal of Nuclear Medicine
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• v.3 no.2
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• pp.1-16
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• 1969

The double tracer study on erythrokinetics was carried out experimentally with radioactive iron ($^{59}Fe$) and chromium ($^{51}Cr$) in rabbits. The 0.1% canthalidin solution and 1% pot. perchlomate solution was given subcutaneously to 20 rabbits respectively. 3 and 6 days after injection, the blood chemistry, urine examination, ferrokinetics and apparent half survival time of RBC were ($^{51}Cr\;T\frac{1}{2}$)determined. Following were the results: 1) Red blood cell hematocrit and hemoglobin values were moderately reduced and B.U.N. and serum creatinine values were slight]y inercased in the canthalidin group, while B.U.N. and serum creatinine values were within normal limits in the pot. perchlomate group. Reticulocyte values were slight]y increased in the canthalidin group, while was normal range in the pot. perchlomate group. 2) Blood chemistry finding was not significant statistically in both experimental groups, but serum iron value was moderately reduced in both group. 3) Plasma volume was unchanged in both group, but red cell volume and whole blood volume were slightly reduced in both groups. 4) Results of ferrokinetics were as follows: i) The plasma iron disappearance rate was delayed in both groups. Plasma iron turnover rate, red cell iron utilization and red cell iron turnover rate were decreased in both groups, and then red cell iron turnover rate was more decreased than plasma iron turnover rate in both groups. Circulating red cell iron was slight]y increased in canthalidin group and red cell iron concentration was within normal range in both groups. ii) P.I.T.R.-R.C.I.T. value was moderately increased in the canthalidin group and slightly increased in the pot. perchlomate group. Reticulocyte index, red cell iron turnover index, plasma iron turnover index and effective erythropoiesis index were whole]y reduced in both groups. iii) The red cell life span was slightly shortened in the canthalidin group while was within normal range in pot. perchlomate group. The pathologic finding of renal biopsy of the canthalidin group shows a selective damage in glomerulus, while shows almost normal range or slight damage in tubules. And that of the pot. perchlomate group shows a selective damage in tubules with slight damage of glomerulus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.139-148
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• 2008

The direct inspection of the outward aspects by field engineers is the important and critical part for structural safety assessment according to the related reports. This study presents an improved method of the state assessment for concrete floor slab by separating and evaluating the individual damage types. First, the various types of damage symptoms are separated, which have been included and dealt in a group. Secondly, they are weighted and scored independently based on the present guide and references. Overall procedures other than the above are retained as same as possible to avoid the confusion. The proposed method is applied and tested to a performed assessment project for a bridge for validation. The result shows that it is reasonable and applicable in respect that it is able to make up for the controversial points of the present guide revealed in practices. Careful check of excessively deteriorated parts in addition to the reasonable assessment of system by this method grants the structural repair and reinforcement propriety and economy, and assures of more safety. Twofold appraisal of this approach expands the applicable areas of value engineering to the structural maintenance.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.5
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• pp.499-508
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• 2010

This study proposed a life cycle impact assessment index that can indicate the environment-related information of the product in monetary value such that the national geographical, environmental, and social features are fully reflected based on a damage-oriented model. First, the estimation process was classified into characterization, damage assessment, and integration stages considering the six biggest impact categories: resource depletion, global warming, ozone depletion, acidification, eutrophication, and photochemical oxidant creation. Moreover, this study came up with the 16 category endpoints related to the 6 impact categories, and the damage function, to the 4 largest safeguard subjects. The integration indices of finally identified impact categories were KRW 21.8/kg Sb, KRW 6.19/kg$CO_2$, KRW 53,000/kg CFC-11, KRW 13,100/kg $SO_2$, KRW 2,310/kg ${PO_4}^{3-}$, and KRW 3,030/kg $C_2H_4$. Using the results of this research, environmental impacts based on the environmental load generated throughout the entire life cycle of a product can serve as a single index in monetary value; thus enhancing understanding and utilization of the results of life cycle impact assessments.

• Journal of Korean Neurosurgical Society
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• v.44 no.5
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• pp.308-313
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• 2008

Objective: The serum S100 protein has been known to reflect the severity of neuronal damage. The purpose of this study was to assess the prognostic value of the serum S100 protein by Elecsys S100 immunoassay in patients with subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH) and to establish reference value for this new method. Methods: Serum S100 protein value was measured at admission, day 3 and 7 after bleeding in 42 consecutive patients (SAH : 20, ICH : 22) and 74 healthy controls, prospectively. Admission Glasgow coma scale (GCS) score, Hunt & Hess grade and Fisher grade for SAH, presence of intraventricular hemorrhage, ICH volume, and outcome at discharge were evaluated. Degrees of serum S100 elevation and their effect on outcomes were compared between two groups. Results: Median S100 levels in SAH and ICH groups were elevated at admission (0.092 versus $0.283{\mu}g/L$) and at day 3 (0.110 versus $0.099{\mu}g/L$) compared to healthy controls ($0.05{\mu}g/L;$ p<0001). At day 7, however, these levels were normalized in both groups. Time course of S100 level in SAH patient was relatively steady at least during the first 3 days, whereas in ICH patient it showed abrupt S100 surge on admission and then decreased rapidly during the next 7 days, suggesting severe brain damage at the time of bleeding. In ICH patient, S100 level on admission correlated well with GCS score (r=-0.859; p=0.0001) and ICH volume (r=0.663; p=0.001). A baseline S100 level more than $0.199{\mu}g/L$ predicted poor outcome with 92% sensitivity and 90% specificity. Logistic regression analyses showed Ln (S100) on admission as the only independent predictor of poor outcome (odd ratio 36.1; 95% CI, 1.98 to 656.3) Conclusion: Brain damage in ICH patient seems to develop immediately after bleeding, whereas in SAH patients it seems to be sustained for few days. Degree of brain damage is more severe in ICH compared to SAH group based on the S100 level. S100 level is considered an independent predictor of poor outcome in patient with spontaneous ICH, but not in SAH. Further study with large population is required to confirm this result.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.53-60
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• 2018

To diagnosis the local damages of the steel plates, magnetic flux leakage (MFL) method that is known as a adaptable non-destructive evaluation (NDE) method for continuum ferromagnetic members was applied in this study. To analysis the sensitivity according to thickness of steel plate in MFL method based damage diagnosis, several steel plate specimens that have different thickness were prepared and three depths of artificial damage were formed to the each specimens. To measured the MFL signals, a MFL sensor head that have a constant magnetization intensity were fabricated using a hall sensor and a magnetization yoke using permanent magnets. The magnetic flux signals obtained by using MFL sensor head were improved through a series of signal processing methods. The capability of local damage detection was verified from the measured MFL signals from each damage points. And, the peak to peak values (P-P value) extracted from the detected MFL signals from each thickness specimen were compared each other to analysis the MFL based local damage detection sensitivity according to the thickness of steel plate.

• Transactions of Materials Processing
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• v.20 no.1
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• pp.48-53
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• 2011

Fasteners are used to join the various electronic products and machines. So, the quality and reliability of the fastener are strongly requested. In this study, the analyses of the multi-stage cold forging of TORX screws for storage parts are carried out. In manufacturing of TORX screws, crack and folding defects are observed. Therefore, the analysis is focused on the prediction of the defects. Based on the analysis results, the upper die and process conditions are redesigned to reduce the defects. The upper die shape for preform forming is redesigned to prevent folding and sharp shape change. The Cockroft-Latham damage criterion is introduced to predict the crack initiation. Analysis results shows that the maximum Cockroft-Latham damage value is decreased by 40% in the forming using the modified upper die.