• Journal of the Korean Recycled Construction Resources Institute
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• 제7권3호
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• pp.216-223
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• 2019

The objective of this study is to propose a reliable stress-strain model in compression for lightweight concrete using bottom ash aggregates and air foam(LWC-BF). The slopes of the ascending and descending branches in the fundamental equation form generalized by Yang et al. were determined from the regression analyses of different data sets(including the modulus of elasticity and strains at the peak stress and 50% peak stress at the post-peak performance) obtained from 9 LWC-BF mixtures. The proposed model exhibits a good agreement with test results, revealing that the initial slope decreases whereas the decreasing rate in the stress at the descending branch increases with the increase in foam content. The mean and standard deviation of the normalized root-square mean errors calculated from the comparisons of experimental and predicted stress-strain curves are 0.19 and 0.08, respectively, for the proposed model, which indicates significant lower values when compared with those(1.23 and 0.47, respectively) calculated using fib 2010 model.

• Journal of Cardiovascular Imaging
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• 제30권2호
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• pp.112-122
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• 2022

BACKGROUND: Few studies have utilized right atrial (RA) strain to evaluate right ventricular (RV) diastolic dysfunction in preterm infants with bronchopulmonary dysplasia (BPD). We aimed to evaluate the associations of RA strain with BPD severity and respiratory outcomes in preterm infants with BPD. METHODS: We retrospectively studied 153 infants with BPD born before 32 weeks of gestational age at CHA Bundang Medical Center. Peak longitudinal right atrial strain (PLRAS) was obtained using velocity vector imaging and compared among infants across BPD severity. Conventional echocardiographic parameters and clinical characteristics were also evaluated. RESULTS: In infants with severe BPD, mean gestational age (27.4 ± 2.1 weeks) and mean birth weight (971.3 ± 305.8 g) were significantly smaller than in those with mild BPD (30.0 ± 0.9 weeks, 1,237.3 ± 132.2 g) and moderate BPD (29.6 ± 1.3 weeks, 1,203.2 ± 214.4 g). PLRAS was significantly lower in infants with severe BPD (26.3 ± 10.1%) than in those in the moderate BPD group (32.4 ± 10.9%) or mild BPD group (31.9 ± 8.3%). Tricuspid E/e' and maximum RA volume index were similar across BPD severity. A decrease in PLRAS was significantly correlated with increased duration of mechanical ventilation duration; however, tricuspid E/e' and maximum RA volume index were not. CONCLUSIONS: Evaluating PLRAS with other parameters in infants with BPD might detect RV diastolic dysfunction. Longer follow-up and larger study populations may elucidate the association between PLRAS and respiratory outcomes in infants with BPD.

• Computers and Concrete
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• 제26권3호
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• pp.293-307
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• 2020

The aim of this paper is to develop design-oriented models for the prediction of the ultimate strength and ultimate axial strain for concrete confined with glass fiber-reinforced polymer (GFRP) wraps. Twenty of most used and recent design-oriented models developed to predict the strength and strain of GFRP-confined concrete in circular sections are selected and evaluated basing on a database of 163 test results of concrete cylinders confined with GFRP wraps subjected to uniaxial compression. The evaluation of these models is performed using three statistical indices namely the coefficient of the determination (R²), the root mean square error (RMSE), and the average absolute error (AAE). Based on this study, new strength and strain models for GFRP-wrapped concrete are developed using regression analysis. The obtained results show that the proposed models exhibit better performance and provide accurate predictions over the existing models.

• Child Health Nursing Research
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• 제11권4호
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• pp.472-480
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• 2005

Purpose: Purpose of this study was to identify the effects on maternal role strain, maternal role confidence and maternal identity of a maternal role promotion program for mothers of premature infants. Method: A quasi-experimental non-equivalent pre-and-post test was used to compare the two groups. The data were collected from 62 mothers from September 10. 2003 to August 30, 2004 at Neonatal Intensive Care Unit(NICU) located in S. city and K. city. The maternal role promotion program was provided three times during the period from two-three days after the baby's admission to 1 month after the baby's discharge. The instruments for measurement were the Perceived Role Difficulty & Steffensmeier Scale, Self Confidence Scale and Semantic Differential Scale. Data were analyzed by means of frequency, mean and SD, $x^2$-test and t-test. Results: There were significant differences in maternal role strain level between the experimental and control group (t=2.163, p=.035), in the maternal role confidence between the two groups(t=-5.645, p=.000) and in maternal identity between the two groups(t=-4.923, p=.000). Conclusion: The results of this study indicate that the maternal role promotion program had positive effects in decreasing maternal role strain levels and increasing maternal role confidence and maternal identity.

• Steel and Composite Structures
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• 제28권1호
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• pp.1-11
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• 2018

In this paper, local ratcheting behavior of 1045 steel plates with circular cutout was investigated. Experimental tests were carried out by a Zwick/Roell HB 100 servo hydraulic machine. In order to measure the local strain at notch root, a data acquisition system with strain gauge was used. Various notch diameters and distances of strain gauges mounted from the notch root were found influential in the magnitude of local ratcheting strain. It was found that the local maximum principal stress plays a crucial role in increasing the local plastic deformation. Numerical simulation was done by ABAQUS software using nonlinear isotropic/kinematic hardening model. Material parameters of hardening model were attained from several stabilized cycles of flat specimens subjected to symmetric strain cycles. The nonlinear kinematic hardening model along with the Neuber's rule was employed to assess local ratcheting at the notch root of steel plates. The results of the numerical simulations agreed closely with those measured values in this study. Both ratcheting progress and mean stress relaxation occurred simultaneously at the notch root.

• Korean Journal of Veterinary Research
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• 제60권2호
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• pp.55-59
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• 2020

This study was purposed to make the referenced range of stomach antral contraction strain in 50 dogs using 2-dimensional speckle tracking. In addition, the strain results were compared among body condition scores to reveal the correlations of obesity among the subjects of the study. Finally, the medetomidine group that was comprised of 10 dogs was compared with the normal group to identify the medetomidine pharmacologic effect in the stomach antral contraction. Clinically healthy 50 dogs were recruited for the study. In an ultrasonographic examination, the stomach antrum region was scanned, and at least one cycle of antral contraction was recorded. The peak strain of antral contraction in healthy dogs was 58.2 ± 20.47% (mean ± SD). The obesity group showed a high strain result and there were significant correlations between the body condition score (BCS) 2, BCS 3 groups and BCS 8 group. The medetomidine group revealed a low strain result and was significantly correlated with normal group. Two-dimensional speckle tracking was useful to the evaluation of stomach motility disorders.

• Korean Journal of Microbiology
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• 제55권1호
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• pp.61-63
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• 2019

Streptococcus sp. strain NM belonging to Firmicutes was isolated from head and neck cancer patients. Here, we report the draft genome sequence of strain NM with a size of approximately 1.90 Mbp and a mean G+C content of 39.3%. The draft genome included 1,845 coding sequences, and 12 ribosomal RNA and 58 transfer RNA genes. In the draft genome, genes involved in the antimicrobial resistance, hemolysis and defense system have been identified.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제8권4호
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• pp.222-224
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• 1975

Three strains of common carp, i. e. , Israeli carp, red-and-white, and golden strains, were stocked in the same pond, and their growth rates were compared with following results: From August 12 to November 21 in 1975, fingerlings of the three strains of common carp, Cyprinus carpo, each weighing about 0.5 g with total length of 2 to 3 cm, were stocked. The pond had an area of $316m^2$ with a mean water depth of 55cm, and the bottom was covered with a 20 to 30 cm thick layer of silt containing a considerable amount of decaying organic materials. Feed given was prepared with equal amounts of fish meal and polished barley, of which, in addition, $10\%$ green grass and $1\%$ table salt were mixed together when prepared into paste feed using a chopper after boiling the barley. Total protein content of the feed was $34.9\%$ in dry state with $5\%$ moisture content. Total feed given was 30.08 kg calculated in dry state to produce 20.588 kg of the common carp fingerlings, thus the feed coefficient being 1.51. By strains, the harvested Israeli carp ranged 98 to 311g each with a mean weight of $172.69g(100\%)$, red-and-white strain 15 to 318g with mean of $104.1g(60.3\%)$, and the golden strain 30 to 268g with mean of $128.7g(74.6\%)$. During the rearing season mean water temperature was $23.9^{\circ}C$ and the assumed main growth period with the water temperature above $15^{\circ}C$ was, upto the end of October, for 80 days with a mean water temperature of $23.9^{\circ}C$. Taking this main growth period as the basis for growth rate analysis, the mean daily increments, expressed as the attained body weight in times of the starting weight, become 1.075786 times (or the Israeli strain, 1.06901 times for the red-and-white strain, and 1.07185 times for the golden strain.

• The Journal of Korean Academy of Prosthodontics
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• 제33권3호
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• pp.539-549
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• 1995

The purpose of this study was to determine the accuracy of 3 implant impression methods by using strain gauge. The models used for this study were partially edentulous mandibular acrylic resin casts Model A, with two abutment analogs in #46,47 extraction site, represented two implant parallel to to the adjacent natural tooth. Model B represent an anterior implant parallel to the adjacene natural tooth and a posterior implant exhibiting a 15-degree lingual inclination. Master framework were fabricated on the master model, and 3 strain gauges were attached to a master framwork to determine the passivity of fit of the framework to sample casts made by the three impression techniques. The master framework was attached to each sample cast with gold screws, which were tightened with the torque driver to ensure a consistent toque application of 10 Ncm. Universal Digital Measuring System UCAM-5BT was used for strain measuring. Impression techniques studid were : 1. unsplinted tapered impression coping, polyvinyl siloxane, stock tray 2. unsplinted squared impression coping, polyether, custom tray 3. squared impression coping splinted with Duralay resin, polyether, custom tray Through analysis on data from this study, the following conclusions were obtained. 1. There were no statistically significant differences between the mean strain recorded from the sample casts made with the tree impression. But only strain values of model A(parallel group) Y-axis was signifcantly differed between Technique 1 and 3(P<0.05). 2. There was no statistically significant difference between model A(parallel group) and model B(15-degree divergent group).

• Journal of the Korean institute of surface engineering
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• 제41권3호
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• pp.121-128
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• 2008

High strength 7xxx aluminum alloys have been applied to automotive bump back beam of the some limited model for light weight vehicle. The aluminum bump back beam is manufactured through extrusion, bending and welding. The residual stress given on these processes combines with the corrosive atmosphere on the road spreaded with corrosive chemicals to melt snow to occur the stress corrosion cracking. The composition of commercial 7xxx aluminum has Zn/Mg ratio about 3 and Cu over 2 wt% for better strength and stress corrosion cracking resistivity. But this composition isn't adequate for appling to the automotive bump back beam with high resistance to extrusion and bad weldability. In this study the composition of 7xxx aluminum alloy was modified to high Zn/Mg ratio and low Cu content for better extrusion and weldability. To estimate the resistivity against stress corrosion cracking of this aluminum alloy by slow strain rate test, the corrosion atmosphere and strain rate separate the stress corrosion cracking from conventional corrosion must be investigated. Using 0.6 Mol NaCl solution on slow strain rate test the stress corrosion cracking induced fracture was not observed. By adding 0.3% $H_2O_2$ and 0.6M $Na_2SO_4$ to 1M NaCl solution, the corrosion potential and current density of polarization curve moved to active potential and larger current density, and on the slow strain rate test the fracture energy in solution was lower than that in pre-exposure. These mean the stress corrosion cracking induced fracture can be estimated in this 1M NaCl + 0.3% $H_2O_2$ + 0.6M $Na_2SO_4$ solution. When the strain rate was below $2{\times}10^{-6}$, the stress corrosion cracking induced fracture start to be observed.