• Journal of the Korean Society for Precision Engineering
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• v.3 no.1
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• pp.40-49
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• 1986

Crack, craze and void are common defects which may be found in the bulk of polymeric materials such as either themoplastics or thermosets. The healing phenomena, autohesion, of these defects are known to be a intrinsic material property of various polymeric materials. However, only a few experimental and theoretical investigations on crack, void and craze healing phenomena for various polymeric materials have been reported up to date [1, 2, 3]. This may be partly due to the complications of healing processes and lacking of appropriate theoretical developments. Recently, some investigators have been urged to study the healing phenomena of various polymenic materials since the significance of the use of polymer based alloys or composites has been raised in terms of specific strength and energy saving. In the earlier published reports [1, 2, 3, 4], the crack and void healing velocity, healing toughness and some other healing mechanical and physical properties were measured experimentally and compared with predicted values by utilizing a simple model such as the reptation model under some resonable assumptions. It seems, however, that the general acceptance of the proposed modeling analyses is yet open question. The crack healing processes seem to be complicate and highly dependent on the state of virgin material in terms of mechanical and physical properties. Furthermore, it is also strongly dependent on the histories of crack, craze and void development including fracture suface morphology, the shape of void and the degree of disentanglement of fibril in the craze. The rate of crack healing may be a function of environmental factors such as healing temperature, time and pressure which gives different contact configurations between two separated surfaces. It seems to be reasonable to assume that the crack healing processes may be divided in several distinguished steps like stress relaxation with molecular chain arrangement, surface contact (wetting), inter- diffusion process and com;oete healing (to obtain the original strength). In this context, it is likely that we no longer have to accept the limitation of cumulative damage theories and fatigue life if it is probable to remove the defects such as crack, craze and void and to restore the original strength of polymers or polymer based compowites by suitable choice of healing histories and methods. In this paper, we wish to present a very simple and intuitive theoretical model for the prediction of healed fracture toughness of cracked or defective polymeric components. The central idea of this investigation, thus, may be the modeling of behavior of chain molecules under healing conditions including the effects of chain scission on the healing processes. The validity of this proposed model will be studied by making comparisons between theoretically predicted values and experimentally determined results in near future and will be reported elsewhere.

• Korean Journal of Veterinary Research
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• v.55 no.2
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• pp.133-139
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• 2015

The increasing uses of zinc oxide nanoparticles (nZnO) in industrial and personal care products raise possible danger of using nZnO in human. To determine whether ZnO induces size-dependent anomalies during embryonic organogenesis, mouse embryos on embryonic day 8.5 were cultured for 2 days under 50, 100, and $150{\mu}g$ of nZnO (< 100 nm) or micro-sized ZnO (mZnO; $80{\pm}25{\mu}m$), after which the morphological changes, cumulative quantity of Zn particles, and expressions of antioxidant and apoptotic genes were investigated. Although embryos exposed to $50{\mu}g$ of ZnO exhibited no defects on organogenesis, embryos exposed to over $100{\mu}g$ of ZnO showed increasing anomalies. Embryos treated with $150{\mu}g$ of nZnO revealed significant changes in Zn absorption level and morphological parameters including yolk sac diameter, head length, flexion, hindbrain, forebrain, branchial bars, maxillary process, mandibular process, forelimb, and total score compared to the same dose of mZnO-treated embryos. Furthermore, CuZn-superoxide dismutase, cytoplasmic glutathione peroxidase (GPx) and phospholipid hydroperoxidase GPx mRNA levels were significantly decreased, but caspase-3 mRNA level was greatly increased in nZnO-treated embryos as compared to normal control embryos. These findings indicate that nZnO has severer teratogenic effects than mZnO in developing embryos.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.15
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• pp.6131-6136
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• 2014

Objective: Epidemiology studies have reported conflicting results between glutathione S-transferase Mu-1 (GSTM1), glutathione S-transferase theta-1 (GSTT1) and glutathione S-transferase pi-1 (GSTP1) and ovarian cancer (OC) susceptibility. In this study, an updated meta-analysis was applied to determine whether the deletion of GSTM1, GSTT1 and GSTP1 has an influence on OC susceptibility. Methods: A published literature search was performed through PubMed, Embase, Cochrane Library, and Science Citation Index Expanded database for articles published in English. Pooled odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated using random or fixed effects models. Heterogeneity between studies was assessed using the Cochrane Q test and $I^2$ statistics. Sub-group analysis was conducted to explore the sources of heterogeneity. Sensitivity analysis was employed to evaluate the respective influence of each study on the overall estimate. Results: In total, 10 published studies were included in the final analysis. The combined analysis revealed that there was no significant association between GSTM1 null genotype and OC risk (OR=1.01, 95%CI: 0.91-1.12). Additionally, there was no significant association between GSTT1 genetic polymorphisms and OC risk (OR=0.98, 95% CI: 0.85-1.13). Similalry, no significant associations were found concerning the GSTP1 rs1695 locus and OC risk. Meanwhile, subgroup analysis did not show a significant increase in eligible studies with low heterogeneity. However, sensitivity analysis, publication bias and cumulative analysis demonstrated the reliability and stability of the current meta-analysis. Conclusions: These findings suggest that GSTs genetic polymorphisms may not contribute to OC susceptibility. Large epidemiological studies with the combination of GSTM1 null, GSTT1 null and GSTP1 Ile105Val polymorphisms and more specific histological subtypes of OC are needed to prove our findings.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.6
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• pp.847-854
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• 2014

Different herbs and spices have been used as feed additives for various purposes in poultry production. This study was conducted to assess the effect of feed supplemented with black pepper (Piper nigrum), turmeric powder (Curcuma longa), coriander seeds (Coriandrum sativum) and their combinations on the performance of broilers. A total of 210 (Cobb) one-d-old chicks were divided into seven groups of 30 birds each. The treatments were: a control group received no supplement, 0.5% black pepper (T1), 0.5% turmeric powder (T2), 2% coriander seeds (T3), a mixture of 0.5% black pepper and 0.5% turmeric powder (T4), a mixture of 0.5% black pepper and 2% coriander seed (T5), and a mixture of 0.5% black pepper, 0.5% turmeric powder and 2% coriander seeds (T6). Higher significant values of body weight gain during the whole period of 5 weeks (p<0.001) were observed in broilers on T1, T3, T5, and T6 compared to control. Dietary supplements with T1, T2, T3, and T6 improved the cumulative G:F of broilers during the whole period of 5 weeks (p<0.001) compared with control. The dressing percentage and edible giblets were not influenced by dietary supplements, while higher values of relative weight of the liver (p<0.05) were obtained in T5 and T6 compared to control. The addition of feed supplements in T5 and T6 significantly increased serum total protein and decreased serum glucose, triglycerides and alkaline phosphatase concentrations compared with the control group (p<0.05). Broilers on T6 showed significant decrease in the serum glutamate pyruvate transaminase concentration (p<0.05) compared to control. The broilers having T5 and T6 supplemented feed had relatively greater antibody titre (p<0.001) at 35 d of age than control. It is concluded that dietary supplements with black pepper or coriander seeds or their combinations enhanced the performance and health status of broiler chickens.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.525-535
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• 2009

In this paper a heuristic method for identifying individual pipes in water pipe networks to determine specific sections of the pipes that need to be replaced due to deterioration. An appropriate minimum pipe length is determined by selecting the pipe length that has the greatest variance of the average cumulative break number slopes among the various pipe lengths used. As a result, the minimum pipe length for the case study water network is determined as 4 m and a total of 39 individual pipe IDs are obtained. The economically optimal replacement times of the individual pipe IDs are estimated by using the threshold break rate of an individual pipe ID and the pipe break trends models for which the General Pipe Break Prediction Model(Park and Loganathan, 2002) that can incorporate the linear, exponential, and in-between of the linear and exponetial failure trends and the ROCOFs based on the modified time scale(Park et al., 2007) are used. The maximum log-likelihoods of the log-linear ROCOF and Weibull ROCOF estimated for the break data of a pipe are compared and the ROCOF that has a greater likelihood is selected for the pipe of interest. The effects of the social costs of a pipe break on the optimal replacement time are also discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.257-263
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• 2010

We studied about the difference of division public announcements by corporation size and ownership structure from 1999 to 2005. The results is as follow : First, we found most positive numbers in division corporation's CAR. This supports the existing research that corporation division is evaluated positively in the market. We found CAR as largest shareholders' holding more than 40%, which is greater than 0-20% & 20-40%, that shows relatively more negative CAR. So, the exceeded largest shareholders' holding rate (i.e., over 40%) can be a factor for decreasing corporations' value. Also, most positive CAR shows relatively small variation regarding corporation size knowing that big sized corporations have relatively small variation than small sized corporations. Second, we studied about relationship between corporate ownership structure and division public effects and found relatively a little effect by large shareholders, foreign investors' holding variables on division public.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.4
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• pp.251-256
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• 2016

The increase in carbon stock and sustainability of crop production are the main challenges in agricultural fields relevant to climate change. Methane is the most important greenhouse gas emitted from paddy fields. This study was conducted to investigate the effects of tillage and cultivation methods on methane emissions in rice production in 2014 and 2015. Different combinations of tillage and cultivation were implemented, including conventional tillage-transplanting (T-T), tillage-wet hill seeding (T-W), minimum tillage-dry seeding (MT-D), and no-tillage-dry seeding (NT-D). The amount of methane emitted was the highest in T-T treatment. In MT-D and NT-D treatments, methane emissions were significantly decreased by 77%, compared with that in T-T treatment. Conversely, the soil total carbon (STC) content was higher in MT-D and NT-D plots than in tillage plots. In both years, methane emissions were highly correlated with the dry weight of rice ($R^2=0.62{\sim}0.96$), although the cumulative emissions during the rice growing period was higher in 2014 than in 2015. T-T treatment showed the highest $R^2$ (0.93) among the four treatments. Rice grain yields did not significantly differ with the tillage and cultivation methods used. These results suggest that NT-D practice in rice production could reduce the methane emissions and increase the STC content without loss in grain yield.

• Journal of Trauma and Injury
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• v.26 no.3
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• pp.198-206
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• 2013

Purpose: This study was performed to calculate and analyze the effective radiation doses from computed tomography (CT) and radiologic intervention in patients in the emergency department (ED) with trauma critical pathway (CP) activation and further to estimate the lifetime attributable risks (LARs) for the incidence of and mortality from cancers induced by the radiation dose. Methods: Through a retrospective electrical chart review of 104 injured patients who trauma critical pathway were activated from November 2012 to March 2013, we calculated effective radiologic doses by taking the product of the dose-linear product of the scan and the conversion coefficient. After a determination of the image results, we divided the patients into two groups, negative or positive, and calculated the effective dose for each group. With these results, we estimated the LARs for the incidence of and the mortality from cancers by using the table in the Biologic Effects of Ionizing Radiation (BEIR)-VII report. Results: A total of 76 patients were enrolled. The mean age was $49.0{\pm}8.5$ years. The mean injury severity score (ISS) was $12.7{\pm}8.4$. The cumulative effective dose (CED) for individual patients varied from 2.8 mSv to 238.8 mSv, and the mean was $47.6{\pm}39.9$ mSv. The CED in patients with an $ISS{\geq}16$($63.2{\pm}26.6$ mSv) was higher than that of patients whose ISS<16($33.5{\pm}23.1$ mSv) (p<0.001). The CED in patients who were treated with surgery or intervention($69.0{\pm}45.2$ mSv) was higher than that of patients who were treated conservatively($33.6{\pm}22.4$ mSv) (p<0.001). The LARs for cancer incidence and mortality were $328.5{\pm}308.6$ and $189.0{\pm}159.3$ per 100,000 people, respectively. Conclusion: The CED and the LAR for trauma CP-activated patients in the ED were significant, so efforts should be made to decrease the effective dose received by severely injured patients.

• Weed & Turfgrass Science
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• v.3 no.1
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• pp.19-28
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• 2014

Research was initiated in greenhouse to investigate effects of polymer, calcium, perlite and chitosan on the growth of Kentucky bluegrass (KB). A total of 24 treatment combinations were used in the study. Treatments were made of water-swelling polymer (WSP), calcium, perlite, and chitosan in soil organic amendment (SOA). Significant differences were observed in germination rate, turfgrass coverage, turfgrass density and top growth among treatments. Germination rate, density and plant height varied with time after seeding. A proper mix of WSP is considered to be lower than 3% for turfgrass coverage and density. Regarding survival capability and top growth, however, it was good under 6%. Overall KB growth was more influenced by calcium and perlite than chitosan. Calcium and perlite were the most effective elements for early survival capacity and turfgrass density, respectively. But no effect was found by chitosan. Top growth increased with three elements, being perlite > calcium > chitosan. The chitosan was effective in early germination, but there was no effect on top growth until 3 weeks, when compared with others. A further study is needed for investigating the effect of these materials on the growth characteristics in mixtures of sand and SOA before a field application.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.129-136
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• 2018

The estimation of the fatigue design life for large welded structures is usually performed using the liner cumulative damage method such as Palmgren-Miner rule or the equivalent damage method. When a fatigue crack is detected in a welded steel structure, the residual service life has to be estimated base on S-N curve method and liner elastic fracture mechanics. In this study, to examine the 3D fatigue crack behavior and estimate the fatigue life of out-of-plane gusset fillet welded joint, the fatigue tests were carried out on the model specimens. Investigations of three-dimensional fatigue crack propagation on gusset welded joint was used the finite element analysis of FEMAP with NX NASTRAN and FRANC3D. Fatigue crack growth analysis was carried out to demonstrate the effects of aspect ratio, initial crack length and stress ratio on out-of-plane gusset welded joints. In addition, the crack behaviors of fatigue tests were compared with those of the 3D crack propagation analysis in terms of changes in crack length and aspect ratio. From this analysis result, SIFs behaviors and crack propagation rate of gusset welded joint were shown to be similar fatigue test results and the fatigue life can also be predicted.