• Safety and Health at Work
• /
• v.12 no.1
• /
• pp.127-132
• /
• 2021

Background: Herbicides such as glyphosate, paraquat, and 2,4-dichlorophenoxyacetic acid have been reported to cause adverse side effects through production of reactive oxygen species. However, there were no data representing the adverse effects of a mixture herbicide usage in farmers, especially the changes in oxidative marker and antioxidant defense. This study aimed to determine the urinary malondialdehyde (MDA) and glutathione (GSH) level in farmers using mixed herbicides. Methods: Ninety-three farmers were recruited, and two spot urine samples (before and after work) were collected. The urinary MDA level was evaluated by thiobarbituric acid reactive substance assay, and the urinary GSH level was determined using the enzymatic recycling method. Results: Sixty-two percent of the participants were men, and 59% of the participants worked in a farm for 20-40 years. The common combinations of herbicide usage were glyphosate with 2,4-dichlorophenoxyacetic acid (36.5%). There was no significant difference between pre- and post-work urinary MDA and GSH levels among the 3 groups of herbicides. However, the urinary MDA levels in farmers using the combination of glyphosate and paraquat were significantly higher than those found in farmers using glyphosate alone. The associated factors with changes in MDA levels found that the exposure intensity index (B = 0.154), the cumulative exposure intensity index (B = 0.023), and wearing gloves while working (B = -2.347) were found to be significantly associated with MDA level. Conclusion: The results suggest that the combined use of glyphosate and paraquat caused a significant increase in urinary MDA levels. Moreover, intensity of exposure to herbicide and wearing gloves were associated with the level of MDA.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.9
• /
• pp.1187-1192
• /
• 2020

The dronebot combat system is a representative model of the future battlefield in the 4th industrial revolution. In dronebot, unmanned reconnaissance tankrobot can minimize human damage and reduce cost with higher combat power than humans. However, since the battlefield environment is very complex such as obstacles and enemy situations, it is also necessary for the pilot to control the tankrobot. Tankrobot are robots with new ICT technology, capable of hacking attacks, and if there is an abnormality in control, it can pose a threat to manipulation and control. A Bluetooth sniffing attack was performed on the communication section of the tankrobot and the controller to introduce a vulnerability to Bluetooth, and a countermeasure using MAC address exposure prevention and communication section encryption was proposed as a security measure. This paper first presented the vulnerability of tankrobot to be operated in future military operations, and will be the basic data that can be used for defense dronebot units.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.3
• /
• pp.405-411
• /
• 2020

Recently, studies on underwater communication, related to the development of underwater resources, disaster monitoring and defense, have been actively carried out. In the design of wireless communication systems, path loss is the most important information to derive a link budget that is required to guarantee communication reliability by calculating received power level for the given communication link. The underwater acoustic channel have different characteristics according to geographical location and relevant environmental factors such as water temperature, depth, wave height, algae, and turbidity. Subsequently, many research institutes aiming to develop underwater acoustic communication systems are researching actively on the underwater acoustic channels in various sea areas. In Korea, however, studies on the path loss of the acoustic channel are still insufficient. Therefore, in this study, the path loss of the acoustic channel are studied based on measurement data of the at-sea experiment conducted at Geohae-do, southern sea of Korea.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.24 no.1
• /
• pp.1-11
• /
• 2021

Thermal protection system structures such as double-panel structures are used on the skin of the fuselage and wings to prevent the transfer of high heat into the interior of an high supersonic/hypersonic aircraft. The thin-walled double-panel skin can be exposed to acoustic loads by high power engine noise and jet flow noise, which can cause sonic fatigue damage. In order to predict the fatigue life of the skin, the octave bandwidth SPL should be calculated as narrow bandwidth PSD or acoustic load history using interpolation method. In this paper, a method of converting the octave bandwidth SPL acoustic load into a narrow bandwidth PSD and reconstructed acoustic load history was investigated. The octave bandwidth SPL was converted to the narrow bandwidth PSD using various interpolation methods such as flat, log and linear scale, and the probabilistic characteristics and fatigue damage results were compared. It was found that average error of fatigue damage index by the log scale interpolation method was relatively small among three methods.

• Journal of the Korea Society for Simulation
• /
• v.30 no.1
• /
• pp.65-73
• /
• 2021

The maintenance of the guided missiles typically requires the efficient management of spare parts and maintenance time. This study analyzed the impact of the maintenance time on operational availability. This study classifies the maintenance team with consideration of the skill level of the Harpoon guided missile maintenance and the goal is to analyze the impact on the operational availability with the skill levels quantitatively. Based on the real maintenance data of Harpoon guided missiles, a simulation model is constructed and analyzed. The analysis of the simulation result shows the trade-off between the maintenance time and operational availability. It is expected that the simulation model can help the maintenance policies of guided missiles.

• The Journal of the Korea Contents Association
• /
• v.21 no.5
• /
• pp.499-507
• /
• 2021

This study compares the educational effect using real equipment, virtual reality, and video to improve the educational and training effect of the army and verifies which method of education is excellent. The Army has made a lot of efforts to realize the actual training environment, however, it is increasingly difficult to provide the actual training environment because of 1) restrictions on securing training sites and urbanization, 2) deepening conflicts with the people, and 3) difficulties in acquiring defense budget. To resolve these issues, the use of virtual reality(VR) has the advantage to experience actual battlefield indirectly and could save budget by training in a virtual battlefield environment. In particular, in the case of dangerous or expensive weapons systems, is further required. Hence this paper studies how effective virtual reality is compared to the actual weapons system. virtual reality(VR) education is less effective than actual equipment education, but it is higher than video education. Based on this research result, it will be used as a basic data for the analysis of educational effects based in virtual reality(VR).

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.1
• /
• pp.21-30
• /
• 2022

The restart of scramjet engine is almost impossible in case its unstart happens during engine operation. Therefore, it is essential to prognosticate the scramjet engine unstart phenomena. A numerical simulation of a scramjet engine is conducted to investigate the unstart process of the scramjet engine by adjusting the backpressure at the isolator outlet to the engine analysis environment. The start and unstart of the engine are identified by applying a support vector machine (SVM) through the data measured by wall pressure so that the locations of the pressure sensors most suitable for the unstart detection are selected. And the operation conditions in which the engine is avoid to be unstarted are quantified to perceive the safety margin.

• Korean Journal of Veterinary Service
• /
• v.44 no.4
• /
• pp.257-270
• /
• 2021

Since African swine fever (ASF) spread to East Asia, a fatal crisis has occurred in the global pig industry, because Asia is dominant in pig production. Although some studies conducted bibliometric analysis on ASF, few studies compared research networks, and identified subthemes by major keywords. To fill this gap, this study identified the knowledge structure network of the research, its influence, and core research themes by utilizing the bibliometric analysis of 337 ASF-related journal articles over 50 years from 1970 to 2020 on the Web of Science. The result indicated that papers are mainly published in the fields of veterinary science, virology, microbiology, infectious disease and applied microbiology, and in particular, the fields of veterinary science and virology showed unrivaled weights as they account for 73.40%. With regard to cooperative relationships, European countries such as the UK, Germany, Italy, and Denmark, centered on Spain, are actively contributing to the ASF research. China, France, Thailand, Japan, Vietnam, and South Korea are leading research cooperation, centering on the United States. In the early stage of the studies, major keywords appeared to be related to outbreaks, quarantine and diagnosis, and in the middle stage, the keywords were expanded to a wide range of pig diseases. Recently, the keywords are becoming more diverse towards antibodies, cross-border transmission and disease monitoring. Based on data on major keywords related to ASF, this study proposed discussions and implications for activating ASF research including genotype, protein, vaccine, diagnosis, defense against infection and epidemiological investigation.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.4
• /
• pp.1-11
• /
• 2020

In this study, study on the internal ballistic analysis method for single-chamber dual-thrust rocket motors meeting a dual-thrust profile requirement by tailoring the grain burning area is presented. The analysis method, which can acquire variables required for the performance prediction, considering gradual change of burning rate correction factor and specific impulse in the transition phase, is proposed. Improvements compared to the analysis method in the previous study, which do not consider change in the transition phase, are verified through comparison between the newly proposed method and the method in the previous study. Internal ballistic variables are obtained for four different ground firing test conditions using the proposed method, and the performance prediction for each condition is conducted using these variables. These prediction results and the ground test data are in good agreement, so it is confirmed that the performance prediction of dual-thrust motors with same design geometries based on the proposed analysis method is available.

• Advances in nano research
• /
• v.12 no.5
• /
• pp.529-547
• /
• 2022

Graphene is one of the strongest, stiffest, and lightest nanoscale materials known to date, making it a potentially viable and attractive candidate for developing lightweight structural composites to prevent high-velocity ballistic impact, as commonly encountered in defense and space sectors. In-plane twist in bilayer graphene has recently revealed unprecedented electronic properties like superconductivity, which has now started attracting the attention for other multi-physical properties of such twisted structures. For example, the latest studies show that twisting can enhance the strength and stiffness of graphene by many folds, which in turn creates a strong rationale for their prospective exploitation in high-velocity impact. The present article investigates the ballistic performance of twisted bilayer graphene (tBLG) nanostructures. We have employed molecular dynamics (MD) simulations, augmented further by coupling gaussian process-based machine learning, for the nanoscale characterization of various tBLG structures with varying relative rotation angle (RRA). Spherical diamond impactors (with a diameter of 25Å) are enforced with high initial velocity (V_i) in the range of 1 km/s to 6.5 km/s to observe the ballistic performance of tBLG nanostructures. The specific penetration energy (E_p^*) of the impacted nanostructures and residual velocity (V_r) of the impactor are considered as the quantities of interest, wherein the effect of stochastic system parameters is computationally captured based on an efficient Gaussian process regression (GPR) based Monte Carlo simulation approach. A data-driven sensitivity analysis is carried out to quantify the relative importance of different critical system parameters. As an integral part of this study, we have deterministically investigated the resonant behaviour of graphene nanostructures, wherein the high-velocity impact is used as the initial actuation mechanism. The comprehensive dynamic investigation of bilayer graphene under the ballistic impact, as presented in this paper including the effect of twisting and random disorder for their prospective exploitation, would lead to the development of improved impact-resistant lightweight materials.