• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.148-156
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• 2013

Since the demand for new military vehicle to fulfill the necessary conditions such as multi-purpose, high-mobility, and survivability has raised continuously from the army, the prototype of a Korean light tactical vehicle was developed to meet these requirements using our own technology. In particular, the new tactical vehicle was equipped with a double wishbone independent suspension to improve ride and handling and maximize off-road driving performance. In this paper, a comprehensive virtual durability process to evaluate the service life of the prototype is presented. A reliability of the trimmed body model based on CATIA data was verified by comparison result between mode analysis and modal test. The dynamic model was constructed using ADAMS/Car, and then the weight distribution and lateral slope driving performance of it were compared with the results of static weight and lateral slope tests. The validity of the VTL(Virtual Test Lab) was checked with test results from the 3-inch spaced impact road. The durability performances of trimmed body and suspension components were evaluated through MSM(Modal Superposition Method) fatigue analysis. It is shown that the virtual durability process could be a helpful tool to find out the weak areas and improve their structures in developing new military vehicle.

• Geomechanics and Engineering
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• v.17 no.1
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• pp.81-95
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• 2019

Due to the importance of soil reinforcement using geotextiles in geotechnical engineering, study and investigation into long-term performance, design life and survivability of geotextiles, especially due to installation damage are necessary and will affect their economy. During installation, spreading and compaction of backfill materials, geotextiles may encounter severe stresses which can be higher than they will experience in-service. This paper aims to investigate the installation damage of geotextiles, in order to obtain a good approach to the estimation of the material's strength reduction factor. A series of full-scale tests were conducted to simulate the installation process. The study includes four deliberately poorly-graded backfill materials, two kinds of subgrades with different CBR values, three nonwoven needle-punched geotextiles of classes 1, 2 and 3 (according to AASHTO M288-08) and two different relative densities for the backfill materials. Also, to determine how well or how poorly the geotextiles tolerated the imposed construction stresses, grab tensile tests and visual inspections were carried out on geotextile specimens (before and after installation). Visual inspections of the geotextiles revealed sedimentation of fine-grained particles in all specimens and local stretching of geotextiles by larger soil particles which exerted some damage. A regression model is proposed to reliably predict the installation damage reduction factor. The results, obtained by grab tensile tests and via the proposed models, indicated that the strength reduction factor due to installation damage was reduced as the median grain size and relative density of the backfill decreases, stress transferred to the geotextiles' level decreases and as the as-received grab tensile strength of geotextile and the subgrades' CBR value increase.

• Maritime Security
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• v.7 no.1
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• pp.31-60
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• 2023

This study proposes a new convergence weapon system that combines the covert placement and detection abilities of a self-propelled mobile mine with the rapid tracking and attack abilities of supercavitating rocket torpedoes. This innovative system has been designed to counter North Korea's new underwater weapon, 'Haeil'. The concept behind this convergence weapon system is to maximize the strengths and minimize the weaknesses of each weapon type. Self-propelled mobile mines, typically placed discreetly on the seabed or in the water, are designed to explode when a vessel or submarine passes near them. They are generally used to defend or control specific areas, like traditional sea mines, and can effectively limit enemy movement and guide them in a desired direction. The advantage that self-propelled mines have over traditional sea mines is their ability to move independently, ensuring the survivability of the platform responsible for placing the sea mines. This allows the mines to be discreetly placed even deeper into enemy lines, significantly reducing the time and cost of mine placement while ensuring the safety of the deployed platforms. However, to cause substantial damage to a target, the mine needs to detonate when the target is very close - typically within a few yards. This makes the timing of the explosion crucial. On the other hand, supercavitating rocket torpedoes are capable of traveling at groundbreaking speeds, many times faster than conventional torpedoes. This rapid movement leaves little room for the target to evade, a significant advantage. However, this comes with notable drawbacks - short range, high noise levels, and guidance issues. The high noise levels and short range is a serious disadvantage that can expose the platform that launched the torpedo. This research proposes the use of a convergence weapon system that leverages the strengths of both weapons while compensating for their weaknesses. This strategy can overcome the limitations of traditional underwater kill-chains, offering swift and precise responses. By adapting the weapon acquisition criteria from the Defense force development Service Order, the effectiveness of the proposed system was independently analyzed and proven in terms of underwater defense sustainability, survivability, and cost-efficiency. Furthermore, the utility of this system was demonstrated through simulated scenarios, revealing its potential to play a critical role in future underwater kill-chain scenarios. However, realizing this system presents significant technical challenges and requires further research.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.1
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• pp.1-6
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• 2004

The 490 and 380 performance records of Karan Fries and Karan Swiss cows developed through crossbreeding followed by inter-se mating were evaluated for production, reproduction performance and disposal rate. Duration of study (1982-92) was grouped into five periods (1982-83; 1984-85; 1986-87; 1988-89; 1990-92) and each year was divided into four seasons (Winter: Dec.-Jan.; Spring: Feb.-March; Summer: April-June; Rainy: July-Sept.; Autumn: Oct.-Nov). Data were also classified according to sire and level of inbreeding. The least squares means of FLY (first lactation yield -305 days), FLL (first lactation length), FSP (first service period), FDP (first dry period), FCI (first calving interval ), MY/FLL (milk yield per day of first lactation length), MY/FCI (milk yield per day of first calving interval), EBV (expected breeding value) and EBE (expected breeding efficiency) were $3,173{\pm}82$ kg, $34611{\pm}$days, $143{\pm}11$ days, $75{\pm}6$ days, $423{\pm}11$ days, $10.6{\pm}0.2$ kg, $8.9{\pm}0.2$ kg, $3,380{\pm}26$ kg, and $88.2{\pm}1.3$% respectively in Karan Fries. Corresponding estimates in Karan Swiss cows were $2,616{\pm}82$ kg, $328{\pm}8$ days, $148{\pm}12$ days, $103{\pm}9$ days, $435{\pm}13$ days, $8.9{\pm}0.2$ kg, $7.2{\pm}0.3$ kg, $2,924{\pm38}$ kg and $86.0{\pm}3.8$% respectively. The effect of sire was significant on FLY, MY/FLL, MY/FCI and EBV in both the herd (p<0.01). The 10 and 15% sires showed superiority (FLY) over herd average of 11 and 7% in Karan Fries and 32 and 21% in Karan Swiss cattle respectively. Inbreeding has adversely and significantly (p<0.05) affected the FLY, MY/FLL, MY/FCI and survivability of Karan Fries females; FDP and disposal through culling of Karan Swiss heifers. The Karan Fries heifers with inbreeding above 12.5% performed 16% lower FLY to herd average. The effect of season of calving was significant on FLL, FSP and FCI (p<0.05) in Karan Fries. Summer calvers ($361{\pm}12$) were have higher lactation length and autumn calvers ($329{\pm}14$) had minimum. Period of calving significantly influenced the FSP, FCI, MY/FLL and MY/FCI in Karan Fries and FLY, MY/FLL and MY/FCI in Karan Swiss. Production efficiency traits in Karan Fries herd witnessed higher yield in the last two periods whereas, Karan Swiss heifers showed fluctuating performance. The findings suggested judicious use of available genetic variability, keeping of inbreeding under safer level and managemental interventions for the consistent improvement of both herds.

• Reproductive and Developmental Biology
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• v.39 no.3
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• pp.77-81
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• 2015

This study was carried out to evaluate the effects of embryonic stage and toxicities of cryoprotectant on the rates of survival and development of the cryopreserved mouse early embryo and finally to establish the cryopreservation method of surplus embryos obtained during assisted reproductive technology. Toxicities of two cryoprotectants, dimethyl sulfoxide (DMSO) and ethylene glycol (EG) were investigated using a murine embryo model. Female F-1 mice were stimulated with gonadotropin, induced ovulation with hCG and mated. Two cell embryos were collected and cultured after exposure to either DMSO or EG. Embryo development was evaluated up to the blastocyst stage. The total cell count of blastocysts that were treated with DMSO ($68.1{\pm}24.1$) at the 2-cell stage was significantly lower than that were treated with EG ($81.2{\pm}27.0$) or the control ($99.0{\pm}18.3$) (p<0.001). On comparison of two cryoprotectant treated groups, the DMSO treated group showed a decreased cell count compared with the EG treated group (p<0.05). Both DMSO ($15.4{\pm}1.5$) and EG ($10.2{\pm}1.4$) treated groups showed higher apoptosis rates of cells in the blastocyst compared with the control ($6.1{\pm}0.9$, p<0.0001). In addition, the DMSO treated group showed more apoptotic cells than the EG treated group (p<0.001). The potential toxicity of cryoprotectants was uncovered by prolonged exposure of murine embryos to either DMSO or EG at room temperature. When comparing two cryoprotective agents, EG appeared to be less toxic than DMSO at least in a murine embryo model.