• Advances in nano research
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• v.15 no.1
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• pp.59-65
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• 2023

In this present article, the mechanical behavior of single-walled black phosphorene nanotubes (SW-αPNTs) is simulated using molecular dynamics (MD). The proposed model is subjected to the axial loading and the effects of morphological parameters, such as the mono-vacancy defect and strain rate on the tensile behavior of the zigzag and armchair SW-αPNTs are studied as a pioneering work. In order to assess the accuracy of the MD simulations, the stress-strain response of the current MD model is successfully verified with the efficient quantum mechanical approach of the density functional theory (DFT). Along with reproducing the DFT results, the accurate MD simulations successfully anticipate a significant variation in the stress-strain curve of the zigzag SW-αPNTs, namely the knick point. Predicting such mechanical behavior of SW-αPNTs may be an important design factor for lithium-ion batteries, supercapacitors, and energy storage devices. The simulations show that the ultimate stress is increased by increasing the diameter of the pristine SW-αPNTs. The trend is identical for the ultimate strain and stress-strain slope as the diameter of the pristine zigzag SW-αPNTs enlarges. The obtained results denote that by increasing the strain rate, the ultimate stress/ultimate strain are respectively increased/declined. The stress-strain slope keeps increasing as the strain rate grows. It is worth noting that the existence of mono-atomic vacancy defects in the (12,0) zigzag and (0,10) armchair SW-αPNT structures leads to a drop in the tensile strength by amounts of 11.1% and 12.5%, respectively. Also, the ultimate strain is considerably altered by mono-atomic vacancy defects.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.72-78
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• 2015

According to the report of the WHO, workers have been exposed to much job strain such as job load, responsibility, role, interpersonal conflict etc. In Korea, studies on job strain started to become active from 1990s and now hundreds of studies are actively under going or publishing so that the studies are contributing to development and improvement of job strain. Representative measurement models of job strain are Job Strain Model of Karasek, Job Stress Model of NOISH, Korea Occupational Stress Scale, JSQ(Job Stress Questionnaire), K-OSI(Korea Version of Occupational Stress Inventory) etc. (Lee Kwan-Suk, 2012 ; KOSHA, 2003). Among them, Job Strain Model of Karasek had been loved by many researchers of job strain before Korea Occupational Stress Scale was developed. Job Strain Model of Karasek had been fitted to Korean style and then, used to analyze job strain of Korean people so that this Scale highly contributed to seeking relationship with cardiovascular disease, musculoskeletal disease caused by job, smoking, drug, alcohol poisoning, and pulse(Lee Kwan-Suk, 2012). But as this Model was studied and developed based on foreign culture and life pattern, a model fit to Korea was developed to measure job strain for Korean people, which is Korea Occupational Stress Scale now most frequently used in measuring job strain. Accordingly, after this study made questionnaire survey about same population using the two methods used most frequently in measuring job strain, the study investigated what features appeared, what correlations appear between two models, and comparatively analyzed characteristics each independent and dependent variable. Based on this, the study aimed to exactly express job strain of Korean people. The subjects of the study were a population of 233, and Karasek's Questionnaire and KOSS's Questionnaire were surveyed at the same time. The results were analyzed by statistical program to obtain significant difference between two models. Four particular groups were divided with Job Strain Model of Karasek and the four particular groups were measured with Korea Occupational Stress Scale. And job strain come from combination of two models was measured, with which new comparative analysis method was suggested.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.55-62
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• 2010

The settlements by liquefaction seldom occur uniformly because of soil homogeneity, however differential settlements are major cause of the damages to structures. From the past researches, author paid attention to the fact that stress history during undrained cyclic shear process affects greatly on the volumetric strains of the post-liquefaction. Therefore, the effect of the residual shear strain in cyclic shear process was examined in this study. The experiment apparatus based on strain control with volumetric strain control device was used for the study to investigate the effect of the residual strain on the relationship between volumetric strain and effective stress of clean and granite sandy soil. It could be seen an insignificant difference in the volumetric strain after liquefaction under various residual shear strain conditions in the case of clean sand. On the other hand, in granite sandy soil, the volumetric strain after liquefaction was small when the lower level of the residual shear strain was applied. And, the residual shear strain during cyclic shear affected the shape of the relation curve between effective stress and volumetric strain as well.

• Journal of agriculture & life science
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• v.45 no.6
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• pp.115-124
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• 2011

This study was conducted to find a useful alternative herbivore system with which to study the effects of ultraviolet exposure on the pathogenicity and survival of Korean isolated entomopathogenic nematodes (Heterorhabditis sp. 202 strain, Heterorhabditis sp. Gyeongsan strain, Steinernema sp. 223 strain, S. carpocapsae Pocheon strain, S. glaseri Dongrae strain and S. longicaudum Nonsan strain). Pathogenicity of entomopathogenic nematodes against silkworm, Bombyx mori, differed depending on the nematode species and strain and instar of silkworm challenged. Steinernematidae were relatively more pathogenic to the 5th instar silkworms, whereas Heterorhabditidae were more pathogenic to the 1st instars. UV-C exposure was harmful to entomopathogenic nematodes. All nematodes were killed within 60 minutes of exposure of UV-C, and after 10 min of exposure they caused only 6.7% corrected mortality of silkworms. Silkworms were not infected when they were fed S. carpocapsae Pocheon strain treated mulberry leaves which were exposed to UV intensity of about $2.3mW/cm^2$ for 4 hours in the field. Pathogenicity of S. carpocapsae was not significantly reduced after 1 hour of exposure to $4.0mW/cm^2$ UV intensity on the mulberry leaves against silkworms.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.215-222
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• 2009

In this study, steel and FRP jackets are used to confine concrete cylinders. The FRP jacket behaviors compositely with concrete since there is bonding between them. However, the used steel jacket in this study do not behavior compositely with concrete since there is not an adhesive between them. The steel jackets are attached by external forces and the welding. This study suggests the measuring method of the axial strain for the confined concrete cylinders showing noncomposite behavior with the jackets and the correcting method of the measured strain for the composite-behavior jackets. For the noncomposite-behavior steel jacket, the axial strain of the steel surface does not represent the axial strain of the concrete inside. Also, a compressormeter can not be used. Thus, the two rigid plates at the top and bottom of a cylinder are placed and the distance of the two plates are measured and used for estimating the axial strain of the concrete. For the composite-behavior FRP jacket, the vertical strain measured on the FRP surface can be used for estimating the axial strain of the concrete. However, the vertical strain on the FRP surface contains the tensile strain due to the bulge of the concrete and, thus, the tensile strain should be corrected from the vertical strain. The corrected verticals strains compared with the measured strain or a existing constitute model; the result is satisfactory. The uncorrected stress-strain curves have the potential to under estimate the ductile behavior and the energy-dissipation-capacity of the composite-behavior FRP jackets.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.64-69
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• 1999

Polyacrylonitrile(PAN)-based carbon fiber tows were heat-treated by the internal resistance heating method under the certain load. To consider the strain behavior of the fiber tows during heat-treatments, 1200~$2200^{\circ}C$, strain changes of those were measured. It was observed that the larger longitudinal strain was induced under the larger stretching stress. The changes in the strain are different from the temperature regions below and above $1700^{\circ}C$. Obtained apparent activation energies under the stretching stresses of 70 and 322 MPa from time-strain curves were 67.46 and 52.27kJ$mol^{-1}$, respectively. Therefore, it was known that the larger stretching stresses effectively reduce the apparent activation energy of the fiber structure development of the fiber tows.

• Smart Structures and Systems
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• v.20 no.1
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• pp.11-22
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• 2017

The long-term effect of ambient temperature on bridge strain is an important and challenging problem. To investigate this issue, one year data of strain and ambient temperature of a long-span cable-stayed bridge is studied in this paper. The measured strain-time history is decomposed into two parts to obtain the strains due to vehicle load and temperature alone. A linear regression model between the temperature and the strain due to temperature is established. It is shown that for every $1^{\circ}C$ increase in temperature, the stress is increased by 0.148 MPa. Furthmore, the extreme value distributions of the strains due to vehicle load, temperature and the combination effect of them during the remaining service period are estimated by the average conditional exceedance rate approach. This approach avoids the problem of declustering of data to ensure independence. The estimated results demonstrate that the 95% quantile of the extreme strain distribution due to temperature is up to $1.488{\times}10^{-4}$ which is 2.38 times larger than that due to vehicle load. The study also indicates that the estimated extreme strain can reflect the long-term effect of temperature on bridge strain state, which has reference significance for the reliability estimation and safety assessment.

• Transactions of Materials Processing
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• v.28 no.6
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• pp.354-360
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• 2019

The plastic strain ratio is one of the factors that affect the deep drawability of metal sheets. The plastic strain ratio of fully annealed Cu sheet is low because its texture has {001}<100>. In order to improve the deep drawability of Cu sheet, it is necessary to increase the plastic strain ratio of Cu sheet. This study investigate the increase of plastic strain ratio of a Cu sheet after the first asymmetry rolling and annealing, and the second asymmetry rolling and annealing in air and Ar gas conditions. The average plastic strain ratio (R_m) was 0.951 and |ΔR| value was 1.27 in the initial Cu sheet. After the second 30.1% asymmetric rolling and annealing of Cu sheet at 1000℃ in air condition, the average plastic strain ratio (R_m) was 1.03 times higher. However, |ΔR| was 0.12 times lower than that of the initial specimen. After the second 18.8% asymmetric rolling and annealing of Cu sheet at 630℃ in Ar gas condition, the average plastic strain ratio (R_m) was 1.68 times higher and |ΔR| was 0.82 times lower than that of the initial specimen. These results are attributed to the change of the texture of Cu sheet due to the different annealing conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.397-404
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• 1999

It is essential to measure load transfer mechanism of pile to check the appropriateness of assumptions made for design purpose and to continuously monitor the behavior of pile foundation. Through many attempts to monitor the behavior of super-structure in civil engineering area using several optical fiber sensors have been made, application of optical fiber sensor technology on pile foundation has not been tried up to now. Load transfer of model piles during compression loading was measured by optical fiber sensors and compared with the measurement by strain gauges. Fiber Bragg Grating(FBG) sensor system was used since it has many advantages, such as easy multiplexing, high sensitivity, and simple fabrication. Besides the model pile tests, uniaxial tension test of steel bar and compression tests of mortar specimen were carried out to evaluate the performance of FBG sensors in embedded environments. The shift of refilming wavelength due to the strain in FBG sensor is converted to the strain at sensor location and the dependence between them is 1.28 pm/${\mu}$ strain. FBG sensors embedded in model pile showed a better survivability than strain gauges. Measured results of load transfer by both FBG sensors and strain gauges were similar, but FBG sensors showed a smoother trend than those by strain gauge. Based on the results of model pile test, it was concluded that the use of FBG sensor for strain measurement in pile has a great potential for the analysis of pile load transfer.

• Journal of Microbiology
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• v.44 no.1
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• pp.113-120
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• 2006

Candida tropicalis was treated with ultraviolet (UV) rays, and the mutants obtained were screened for xylitol production. One of the mutants, the UV1 produced 0.81g of xylitol per gram of xylose. This was further mutated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and the mutants obtained were screened for xylitol production. One of the mutants (CT-OMV5) produced 0.85g/g of xylitol from xylose. Xylitol production improved to 0.87 g/g of xylose with this strain when the production medium was supplemented with urea. The CT-OMV5 mutant strain differs by 12 tests when compared to the wild-type Candida tropicalis strain. The XR activity was higher in mutant CT-OMV5. The distinct difference between the mutant and wild-type strain is the presence of numerous chlamvdospores in the mutant. In this investigation, we have demonstrated that mutagenesis was successful in generating a superior xylitol-producing strain, CT-OMV5, and uncovered distinctive biochemical and physiological characteristics of the wild-type and mutant strain, CT-OMV5.