• Journal of Drive and Control
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• v.20 no.4
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• pp.64-70
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• 2023

Garlic is classified as one of the three essential seasoning vegetables in Korea. In 2023, it was reported that the area under garlic cultivation was 24,700 ha, and the production stood at 318,220 tons. Garlic harvesting mechanization currently stands at 43.8%, and garlic is still collected manually after digging out using diggers, so the process is labor intensive. To reduce garlic production costs and enhance competitiveness, it is necessary to develop a high-performance gathering type harvester in place of the digging type harvester. Therefore, in this study, a gathering-type garlic harvester that can dig and collect simultaneously was designed and manufactured, and the harvest performance by factor was analyzed through a harvest performance test. As a result of the performance test, it was analyzed to perform optimally at a driving speed of 0.11m/s and a transfer speed of 85rpm. Work performance was calculated using the results obtained from the factor performance test.

• Journal of Drive and Control
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• v.20 no.4
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• pp.71-79
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• 2023

In the field of agricultural machinery, various on-field tests are conducted to measure design load for optimal design of agricultural equipment. However, field test procedures are costly and time-consuming, and there are many constraints on field soil conditions due to weather, so research on utilizing simulation to overcome these shortcomings is needed. Therefore, this study aimed to model agricultural soils using discrete element method (DEM) software. To simulate draft force, predictions are made according to travel speed and compared to field test results to validate the prediction accuracy. The measured soil properties are used for DEM modeling. In this study, the soil property measurement procedure was designed to measure the physical and mechanical properties. DEM soil model calibration was performed using a virtual vane shear test instead of the repose angle test. The DEM simulation results showed that the prediction accuracy of the draft force was within 4.8% (2.16~6.71%) when compared to the draft force measured by the field test. In addition, it was confirmed that the result was up to 72.51% more accurate than those obtained through theoretical methods for predicting draft force. This study provides useful information for the DEM soil modeling process that considers the working speed from the perspective of agricultural machinery research and it is expected to be utilized in agricultural machinery design research.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.379-389
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• 2024

Purpose and Method: Crowed Events can lead to sudden accidents caused by unpredictable variables. Therefore, focusing on the '10.29 Itaewon accident' among the representative cases, we examined the accident as the process of occurrence. In addition, improvement measures were suggested through analysis of related legal systems. Result: In the Itaewon accident, a "colony wave phenomenon" occurred due to "ultra-high-density cluster stay". In addition, cluster destruction occurred from a weak location in the cluster due to clusters and pressures in different directions to avoid this. Looking at the laws related to the safety management of Crowed Events, the laws and regulations differ depending on the location and type. Due to the complementary nature of the approach to the legal blind spot, the legal system that uses similar terms of the same concept and is not systematic is causing uncertainty in the application and interpretation of the law. Conclusion: Crowd control and on-site management should be carried out for events when the cluster density is expected to reach 8 people/m² or reached. Consistency should be maintained through the unified application of legislation to related legislation.

• Journal of Drive and Control
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• v.21 no.1
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• pp.38-45
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• 2024

The power delivery is crucial to designing agricultural machinery. Therefore, the tractor-mounted potato harvester was used in this study to conduct the field experiment and analyze the power delivery for each step. This study was focused on an analysis of power delivery from the engine to the hydraulic components for the tractor-mounted harvester during potato harvesting. Finally, the simulation model of a self-propelled potato harvester was developed and validated using the experimental dataset of the tractor-mounted potato harvester. The power delivery analysis showed that approximately 90.22% of the engine power was used as traction power to drive the tractor-mounted harvester, and only 5.10% of the engine power was used for the entire hydraulic system of the tractor and operated the harvester. The statistical analysis of the simulation and experimental results showed that the coefficient of determinations (R²) ranged from 0.80 to 0.96, which indicates that the simulation model was performed with an accuracy of over 80%. The regression models were correlated linearly with the simulation and experimental results. Therefore, we believe that this study could contribute to the design methodology and performance test procedure of agricultural machinery. This basic study would be helpful in the design of a self-propelled potato harvester.

• Journal of Drive and Control
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• v.21 no.1
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• pp.22-30
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• 2024

Gearboxes designed for reciprocating motion operating mechanisms operate under conditions where both the load and speed undergo continuous variations. When conducting durability tests on gearboxes designed for such applications, operating the target gearbox under conditions similar to the intended usage is essential. The gearbox must be operated for the required number of cycles to validate its durability under conditions mirroring its intended usage. This study devised an accelerated test method for gearboxes, which reduces operating angles and operational strokes. The reliability of the accelerated test was verified by comparing the stresses imposed on the gears under general and acceleration conditions through multi-body dynamic simulations. The results confirmed that the maximum contact stress levels under normal and accelerated conditions were within a 0.1% error range, indicating a minimal difference in the gear damage rates. However, a difference in the maximum contact stress results between the normal and accelerated conditions was observed when inertial forces acted on the output shaft due to the operational acceleration of the gearbox. Therefore, when conducting this acceleration test, caution should be exercised to ensure that the operational load on the gearbox, which affects inertia, does not significantly deviate from the conditions observed under normal operating conditions.

• Convergence Security Journal
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• v.24 no.1
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• pp.21-26
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• 2024

The security model in the previous network environment has a vulnerability in which resource access control for trusted users is not properly achieved using the Perimeter model based on trust. The Zero Trust is an absolute principle to assume that the users and devices accessing internal data have nothing to trust. Applying the Zero Trust principle is very successful in reducing the attack surface of an organization, and by using the Zero Trust, it is possible to minimize damage when an attack occurs by limiting the intrusion to one small area through segmentation. ZTNA is a major technology that enables organizations to implement Zero Trust security, and similar to Software Defined Boundary (SDP), ZTNA hides most of its infrastructure and services, establishing one-to-one encrypted connections between devices and the resources they need. In this study, we review the functions and requirements that become the principles of the ZTNA architecture, and also study the security requirements and additional considerations according to the construction and operation of the ZTNA solution.

• Wind and Structures
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• v.38 no.2
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• pp.129-146
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• 2024

Aiming at the problem of non-stationary wind field simulation of downbursts, a non-stationary down-burst generation system was designed by adding a nozzle and program control valve to the inlet of the original wall jet model. The computational fluid dynamics (CFD) method was used to simulate the downburst. Firstly, the two-dimensional (2D) model was used to study the outflow situation, and the database of working conditions was formed. Then the combined superposition of working conditions was carried out to simulate the full-scale measured downburst. The three-dimensional (3D) large eddy simulation (LES) was used for further verification based on this superposition condition. Finally, the wind tunnel test is used to further verify. The results show that after the valve is opened, the wind ve-locity at low altitude increases rapidly, then stays stable, and the wind velocity at each point fluctuates. The velocity of the 2D model matches the wind velocity trend of the measured downburst well. The 3D model matches the measured downburst flow in terms of wind velocity and pulsation characteris-tics. The time-varying mean wind velocity of the wind tunnel test is in better agreement with the meas-ured time-varying mean wind velocity of the downburst. The power spectrum of fluctuating wind ve-locity at different vertical heights for the test condition also agrees well with the von Karman spectrum, and conforms to the "-5/3" law. The vertical profile of the maximum time-varying average wind veloci-ty obtained from the test shows the basic characteristics of the typical wind profile of the downburst. The effectiveness of the downburst generation system is verified.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.53-64
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• 2024

The Yeongnam southeastern region, with Ulsan as its focal point, is planning large-scale floating offshore wind power projects. Additionally, due to the establishment of new nuclear power plants and the extension of existing ones, there is a demand for the expansion of the power grid. The government has announced plans to establish a new power grid for this region as part of the 10th power supply plan. However, there are anticipated challenges in the actual construction phase, primarily because of the presence of national parks and cultural heritage protection zones near Gyeongju. As a result, this study presents an alternative approach that minimizes the creation of new power lines by utilizing existing ones. Using the Power System Simulator for Engineers (PSS/E), an analysis of transient stability was conducted and demonstrated its feasibility.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.119-126
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• 2024

In building information model (BIM), it is difficult to train an artificial intelligence (AI) model due to the lack of sufficient data about individual projects in an architecture firm. In this paper, we present a methodology to correctly train an AI neural network model based on a large language model (LLM) to predict the steel structure product weight ratios in BIM. The proposed method, with the aid of the LLM, can overcome the inherent problem of limited data availability in BIM and handle a combination of natural language and numerical data. The experimental results showed that the proposed method demonstrated significantly higher accuracy than methods based on a smaller language model. The potential for effectively applying large language models in BIM is confirmed, leading to expectations of preventing building accidents and efficiently managing construction costs.

• Korean Journal of Agricultural Science
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• v.51 no.1
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• pp.25-39
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• 2024

This study aimed to determine a method for restoring grasslands to forests in mountainous areas. The study was conducted in an area damaged by trampling due to construction activity and herding. Additionally, there were concerns of hindered tree growth due to the alpine region climate, characterized by the low temperatures, drying, and strong winds. Therefore, forest restoration treatments such as tillage, furrow, and shading were performed to improve growth conditions. From July 2021 to April 2023, soil temperature and moisture were monitored for each treatment plot, and changes in the initial growth and survival rate of Abies holophylla were investigated. Both soil temperature and soil moisture showed significantly higher values during the four seasons in the grassland-furrow treatment plot (p < 0.05). Compared to the grassland-control plot, the average soil temperature in winter was as high as 1.1℃, and the soil moisture in summer was as high as 20.3%. Additionally, the survival rate and relative growth rate were the largest in the grassland-furrow treatment plot. The survival rate was 87.5%, the relative growth rate in terms of height was 0.013, and the relative growth rate in terms of diameter at root collar was 0.023, indicating that furrow treatment had a positive effect on the initial survival and growth of seedlings. These results suggest that furrow treatment may be an appropriate restoration method when implementing forest restoration projects in areas where tree growth is challenged.