• Journal of the Korean institute of surface engineering
• /
• v.41 no.3
• /
• pp.109-113
• /
• 2008

High strength 7xxx series Al-Zn-Mg alloy have been investigated for using light weight automotive parts especially for bump back beam. The composition of commercial 7xxx aluminum has the Zn/Mg ratio about 3 and Cu over 2 wt%, but this composition isn't adequate for appling to automotive bump back beam due to its high resistance to extrusion and bad weldability. In this study the Zn/Mg ratio was increased for better extrusion and Cu content was reduced for better welding. With this new composition we investigated the effect of composition on the resistivity against stress corrosion cracking. As the Zn/Mg ratio is increased fracture energy obtained by slow strain rate test was decreased, which means degradation of SCC resistance. While the fracture energy was increased with Cu contents although it is below 1%, which means improvement of SCC resistance. These effects of composition change on the SCC resistivity were identified by observing the fracture surface and crack propagation.

• Journal of Plant Biotechnology
• /
• v.47 no.2
• /
• pp.118-123
• /
• 2020

The black seed coat of soybeans contain anthocyanins which promote health. However, mature soybean seeds contain anti-nutritional factors like lipoxygenase, lectin and Kunitz Trypsin Inhibitor (KTI) proteins. Furthermore, these seeds can be used only after the genetic elimination of these proteins. Therefore, the objective of this study was to develop novel soybean genotypes with black seed coat and triple recessive alleles (lx1lx1lx2lx2lx3lx3, titilele) for lipoxygenase, lectin, and KTI proteins. From a cross of parent1 (lx1lx2lx3/lx1lx2lx3, ti/ti, Le/Le) and parent2 (lx1lx2lx3/lx1lx2lx3, Ti/Ti, le/le), 132 F₂ seeds were obtained. A 3:1 segregation ratio was observed during F₂ seed generation for the inheritance of lectin and KTI proteins. Between a cross of the Le and Ti genes, the observed independent inheritance ratio in the F₂ seed generation was 9: 3 : 3 : 1 (69 Le_Ti_: 32 leleTi_: 22 Le_titi: 9 leletiti) (χ²=2.87, P=0.5 - 0.1). From nine F₂ seeds with triple recessive alleles (lx1lx1lx2lx2lx3lx3, titilele genotype), one novel strain posessing black seed coat, and free of lipoxygenase, lectin and KTI proteins, was selected. The seed coat color of the new strain was black and the cotyledon color of the mature seed was green. The weight of 100 seeds belonging to the new strain was 35.4 g. This black soybean strain with lx1lx1lx2lx2lx3lx3, titilele genotype is a novel strain free of lipoxygenase, lectin, and KTI proteins.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.5
• /
• pp.239-248
• /
• 2011

In order to improve the quality of strain images in medical ultrasound imaging, displacements need to be accurately estimated. In this paper, in order to apply one-dimensional displacement estimation methods to two-dimensional motion estimation, the axial and lateral displacements are separately estimated. In order to estimate lateral displacements, one-dimensional signals aligned in the lateral direction are converted to analytic signals, which are then crosscorrelated. Strain images are produced by first compensating two-dimensional displacements for lateral motion with lateral motion displacement estimates obtained from the proposed lateral displacement estimation algorithm and then estimating axial displacements. Both phantom and human data experiments show that the proposed method provides better signal-to-noise ratio and contrast-to-noise ratio characteristics than a conventional strain imaging method that utilizes axial displacement estimates only.

• Geomechanics and Engineering
• /
• v.29 no.2
• /
• pp.99-111
• /
• 2022

Instability of bolted rock mass has been a major hazard in the underground coal mining industry for decades. Developing effective support guidelines requires understanding of complex bolted rock mass failure mechanisms. In this study, the dynamic failure behavior, mechanical behavior, and energy evolution of a laboratory-scale bolted specimens is studied by conducting laboratory static-dynamic coupled loading tests. The results showed that: (1) Under static-dynamic coupled loading, the stress-strain curve of the bolted rock mass has a significant impact velocity (strain rate) correlation, and the stress-strain curve shows rebound characteristics after the peak; (2) There is a critical strain rate in a rock mass under static-dynamic coupled loading, and it decreases exponentially with increasing pre-static load level. Bolting can significantly improve the critical strain rate of a rock mass; (3) Compared with a no-bolt rock mass, the dissipation energy ratio of the bolted rock mass decreases exponentially with increasing pre-static load level, the ultimate dynamic impact energy and dissipation energy of the bolted rock mass increase significantly, and the increasing index of the ratio of dissipation energy increases linearly with the pre-static load; (4) Based on laboratory testing and on-site microseismic and stress monitoring, a design method is proposed for a roadway bolt support against dynamic load disturbance, which provides guidance for the design of deep underground roadway anchorage supports. The research results provide new ideas for explaining the failure behavior of anchorage supports and adopting reasonable design and construction practices.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.4
• /
• pp.45-55
• /
• 2015

The stability of the adjcent structures or slopes under blasting is typically evaluated using an empirical vibration attenuation curve or dynamic numerical analysis. To perform a dynamic analysis, it is necessary to determine the blast load and the damping ratio of rock mass. Various empirical methods have been proposed for the blast load. However, a study on representative values of damping ratio of a rock mass has not yet been performed. Therefore, the damping ratio was either ignored or selected without a clear basis in performing a blast analysis. Selection of the dampring ratio for the rock mass is very difficult because the vibration propagation is influenced by the layout and properties of the rock joints. Besides, the vibration induced by blasting is propagated spherically, whereas plane waves are generated by an earthquake. Since the geometrical spreading causes additional attenuation, the damping ratio should be adjusted in the case of a 2D plane strain analysis. In this study, we proposed equivalent damping ratios for use in continuum 2D plane strain analyses. To this end, we performed 2D dynamic analyses for a wide range of rock stiffness and investigated the characteristics of blast vibration propagation. Based on numerical simulations, a correlation between the attenuation equation, shear wave velocity, and equivalent damping ratio of rock mass is presented. This novel approach is the first attempt to select the damping ratio from an attenuation relationship. The proposed chart is easy to be used and can be applied in practice.

• Asian-Australasian Journal of Animal Sciences
• /
• v.23 no.12
• /
• pp.1645-1656
• /
• 2010

This study was conducted to investigate the effects of strain on broiler performance, and age at slaughter and postchilling (PC) aging time on meat quality traits. A total of 500 one-day-old chicks (250 Hubbard classic and 250 Lohman) were reared under commercial conditions. Half of the broiler birds from each strain were slaughtered at 32 days and the other half at 42 days old. At each processing day, 168 carcasses were randomly selected (84 Hubbard and 84 Lohman) and divided into groups of 28 carcasses within each strain, and aged for 0, 4 and 24 h after chilling. Average weekly body weight was comparable between strains. Feed conversion ratio was higher (p<0.05) for the Hubbard strain during the second and third week of age. Initial carcass pH was significantly (p<0.05) affected by age where younger birds (32-d-old) had lower pH values than older (41-d-old) birds. Breast temperature was higher (p<0.001) for Lohman than Hubbard at 0, 2 and 4 h of PC. Younger birds had a lower breast temperature (p<0.001) at all measured times of PC. Thaw loss, cook loss and water holding capacity were not significantly affected by strain, age or aging time. Lohman strain had more tender meat (p<0.05) than Hubbard strain, and tenderness was improved with the increase of broiler age and aging time. Meats from Hubbard were lighter and less red than those from Lohman strain where younger birds had darker color. In conclusion, strain, age at slaughter and PC aging duration are critical to breast meat quality characteristics, and 4 h of aging are required before deboning in order to obtain more tender fillets.

• 한국연소학회:학술대회논문집
• /
• 2014.11a
• /
• pp.243-244
• /
• 2014

The opposed flow flame in a mesoscale channel was constructed to observe the flame stabilization behaviors at low strain rate conditions (<$10s^{-1}$). The purpose of this study is to get the overall flame behaviors of partially premixed flames with oxygen enhanced conditions at low strain rates. The oxygen ratio in oxidizer was changed from 18 to 30 %. Conclusively, the flame extinction limit approached to about $1s^{-1}$, and divided into three representative regimes corresponding to self propagating flame, transitional flame, quenching flame regimes.

• Journal of the Korean Society of Combustion
• /
• v.4 no.1
• /
• pp.131-139
• /
• 1999

A Numerical Analysis of NOx production in Hydrogen-Air flame is performed using the quasi-laminar reaction modelling. As results, in low global strain rate region, $U_F/D_F\;{\leq}\;50,000$, the quasi-laminar reaction modelling reproduces the experimentally observed EINOx half power scaling that the ratio of EINOx and flame residence time, $L_f^3(D_F^2U_F)$, is proportional to the square root of global strain rate. Thus, it suggests that turbulence-chemistry interaction has a minor impact on the trend of NOx production in low global strain rate region. However, the quasi-laminar reaction modelling predicts the higher temperature and NOx than experimentally observed. This overprediction may be due to the lack of radiation and quasi-laminar reaction modelling.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.2 s.95
• /
• pp.31-38
• /
• 1999

Square cups have been drawn to 20mm~60mm in depth and displacements and strains have been analysed by FEM and experiment. Displacements and strains on the corner flange of square cups have been compared with those of cylindrical cups. The results have shown that shear strains take place on corner flanges of square cups, it is necessary to adopt effective strain for comparing of stains and the effective strains on the corner flange in square cups are smaller than those in cylindrical ones.

• Steel and Composite Structures
• /
• v.36 no.2
• /
• pp.179-186
• /
• 2020

In this paper, the forced resonance vibration of porous functionally graded (FG) curved nanobeam is examined. In order to capture the hardening and softening mechanisms of nanostructure, the nonlocal strain gradient theory is employed to build the size-dependent model. Using the Timoshenko beam theory together with the Hamilton principle, the equations of motion for the curved nanobeam are derived. Then, Navier series are used in order to obtain the dynamical deflections of the porous FG curved nanobeam with simply-supported ends. It is found that the resonance position of the nanobeam is very sensitive to the nonlocal and strain gradient parameters, material variation, porosity coefficient, as well as geometrical conditions. The results indicate that the resonance position is postponed by increasing the strain gradient parameter, while the nonlocal parameter has the opposite effect on the results. Furthermore, increasing the opening angle or length-to-thickness ratio will result in resonance position moves to lower-load frequency.