• Research in Plant Disease
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• v.26 no.4
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• pp.239-249
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• 2020

To find out the cause of the fire blight outbreak in apples and pears of Korea in 2019, we investigated disease appearing situation of thirty fire blight infected orchards, and interviewed farmers to determine the cultivation characteristics. Fire blight occurred mostly in orchards that had infected more than 2 years before. The cause of this were as follows: farmers did not know the symptoms of the disease properly. It is presumed that it has spread from the first occurrence to the surrounding orchards by flower-visiting insects or farmers and to a short distance or a long distance by the same cultivator or co-farmer. These series of processes repeated in the newly spreading area, and then disease reports increased as farmers became aware of fire blight. To minimize the spread of fire blight in Korea, it suggested that thorough education of farmers for early diagnosis and quantitative detection technology that can diagnose even in no symptom showing plants. And chemical or biological spraying systems suitable for domestic cultivation methods, which are producing large fruits, and molecular epidemiological studies of pathogens.

• Journal of the Korean Regional Science Association
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• v.37 no.2
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• pp.17-33
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• 2021

This study empirically analyzes the effect of the spread of COVID-19 and the implementation of social distancing on the number of park users. To this end, we analyzed the time series data on the number of users and the COVID-19 outbreak at Olympic Park, a large-scale comprehensive urban park located in Songpa-gu, Seoul, and four neighborhood parks in the same municipality. And this was compared with the effect on the change in the number of users around Jamsil Lotte World, a representative indoor complex leisure space in Seoul. The analysis results are as follows: First, in small neighborhood parks located in residential areas, the number of users increased by 3 to 6% on average due to the implementation of the social distancing measures and the increase in the number of confirmed COVID-19 cases. In particular, it was found that changes in park use were sensitive to the increase in the intensity of social distancing. On the other hand, the number of users around Jamsil Lotte World decreased by 38% on average, and in the case of Olympic Park, the number of users decreased by 1.9% on average due to the spread of COVID-19. Considering that the number of the vehicle users representing remote users of Olympic Park has decreased by 23% on average, it is estimated that there is little change in the number of users in the surrounding areas. This suggests that urban parks, especially neighborhood parks in residential areas, play a role as a major refuge and leisure space for urban people in the event of a pandemic disaster such as COVID-19, and therefore need to be properly supplied and maintained.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.4
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• pp.465-473
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• 2021

Since the past, ships have hoisted national flags as a means of indicating their nationality. Both domestically and internationally, laws and conventions related to the nationality and hoisting of the flag have been enacted because it is significant that the nationality of a ship is a matter of the jurisdiction of the ship. Nevertheless, there are differences in domestic and international regulations related to the hoisting of the flag of a ship, and if the flag is not hoisted irrespective of the intention, there may be a difference in interpretation as to whether or not the ship will be regarded unconditionally as a stateless ship. However, there is no disagreement locally or abroad about the necessity of indicating the nationality of ships. Therefore, I would like to propose a method to indicate and confirm the nationality of the ship by using wireless communication equipment with hoisting the flag as the only way to express its nationality, reflecting the situation of the era such as high-speed, larger and unmanned ship. Representatively, the method utilizes the automatic identification system(AIS), which is one of the equipment legally installed in the ship, and includes the ship's nationality in its information. If the nationality information is included in the AIS, nationality can be identified earlier and even from a distance, and there will not be instances of nationality not being identified because the flag is not hoisted or the flag is damaged. In addition, it is expected that the problem of nationality indication can be solved even when vessels are unmanned in future.

• Journal of the Korean earth science society
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• v.41 no.6
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• pp.647-657
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• 2020

Infrasound signals associated with the 29 May 2004 offshore Uljin earthquake (Mw 5.1) were recorded at infrasound arrays of CHNAR (epicentral distance of 321 km) and TJNAR (256 km). Back-azimuths, indicating the directions to source locations, varied more than 28° broadly for the long-lasting signals over several minutes. From the analysis of the back-projecting location method and attenuation correction for infrasound propagation, the infrasound waves were to be generated by the interaction (diffraction) between seismic waves and topography in an area of ~4,600 ㎢ connecting the Samcheok-Uljin-Pohang regions. The maximum sound source pressure (BSP) was estimated to be 11.1 Pa. This result was consistent with the peak sound pressure (PSP) calculated by the Rayleigh integral approximation to the peak ground acceleration (PGA) dataset. In addition, the minimum PGA that was detectable at the two arrays was estimated to be ~3.0 cm s-2. Although the earthquake occurred offshore, diffracted infrasound signals were effectively generated by ground motions when seismic surface waves passed through high-topographic regions in the eastern Korean Peninsula. The relationship between infrasound source pressure and PGA can be applicable to characterize the ground motions in areas with insufficient seismological observatories.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.566-572
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• 2020

In a wireless power transmitter, the characteristics and effects of wireless power transmission between two induction coils are investigated, and a power converter circuit and a battery charger/discharger circuit using wireless power transmission technology are proposed. The advantage of wireless power transmitters and wireless chargers is that, instead of the existing plug-in-mounted wired charger (OBC; on-board charger), the user can wirelessly charge the battery without connecting the power source when charging power to the battery. There is. In addition, the advantage of wireless charging can bring about an energy efficiency improvement effect by using the secondary side rectifier circuit and the receiving coil, but the large-capacity long-distance wireless charging method has a limitation on the transmission distance, so many studies are currently being conducted. The purpose of the study is to study the transmitter circuit and receiver circuit of a wireless power transmission device using a primary coil, a secondary coil, and a half bridge series resonance converter, which can transmit power of a non-contact type power transmitter. As a result, a new topology was applied to improve the power transmission distance of the wireless charging system, and through an experiment according to each distance, the maximum efficiency (95.8%) was confirmed at an output of 3 kW at an 8 cm transmission distance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.141-148
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• 2022

In this study, the structural behavior of reinforced concrete members under simultaneous axial and blast loads was analyzed. Nonlinear dynamic analysis verification was performed using the experimental data of panels under fundamental blast load as well as those of reinforced concrete columns subjected to axial and blast loads. Because Autodyn is a program designed only for dynamic analysis, an analysis process is devised to simulate the initial stress state of members under static loads, such as axial loads. A total of 80 nonlinear dynamic finite element analysis procedures were conducted by selecting parameters corresponding to axial load ratios and scaled distances ranging 0%~70% and 1.1~2.0 (depending on the equivalent of TNT), respectively. The structural behavior was compared and analyzed with the corresponding degree of damage and maximum lateral displacement through the changes in axial load ratio and scaled distance. The results show that the maximum lateral displacement decreases due to the increase in column stiffness under axial loads. In view of the foregoing, the formulated analysis process is anticipated to be used in developing blast-resistant design models where structural behavior can be classified into three areas considering axial load ratios of 10%~30%, 30%~50%, and more than 50%.

• Journal of the Korea Society for Simulation
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• v.31 no.3
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• pp.45-54
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• 2022

This paper is about designing and implementing the simulation training equipment (simulator) for the CBRN Reconnaissance Vehicle-II (armor type). The simulation training equipment (simulator) is a military training equipment in a virtual environment that analyzes the training using various CBRN equipment according to the CBRN situation and make a professional report. The controller or training instructor can construct a scenario using the instructor control system for a possible CBRN situation, spread the situation, and observe the process of the trainee performing the propagated situation appropriately. All process can be monitored and analyzed by the system, and it can be recorded, so it is also used for AAR (After Action Review). To implement CBRN situation training in a virtual environment, instructor control (IOS), host (HOS), video (IGS), input/output device (IOC), and sound (ACS) were implemented, a long-range chemical automatic detector (LCA), a combined chemical detector (CAD), a control (MCC) and an operation (OCC) computer were developed as simulators. In this paper, the design and development of simulation training equipment for CBRN Reconnaissance Vehicle-II (armor type) was conducted, and the performance was verified through integrated tests and acceptance tests.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.471-484
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• 2022

This study examined the effects of topography and buildings around the automated synoptic observing system (ASOS) on the observation environment of air temperatures and wind speeds and directions using a computational fluid dynamics(CFD) model. For this, we selected 10 ASOSs operated by the Korea Meteorological Administration. Based on the data observed at the ASOSs in August during the recent ten years, we established the initial and boundary conditions of the CFD model. We analyzed the temperature observation environment by comparing the temperature change ratios in the case considering the actual land-cover types with those assuming all land-cover types as grassland. The land-cover types around the ASOSs significantly affected the air temperature observation environment. The temperature change ratios were large at the ASOSs around which buildings and roads were dense. On the other hand, when all land covers were assumed as grassland, the temperature change ratios were small. Wind speeds and directions at the ASOSs were also significantly influenced by topography and buildings when their heights were higher or similar to the observation heights. Obstacles even located at a long distance affected the wind observation environments. The results in this study would be utilized for evaluating ASOS observation environments in the relocating or newly organizing steps.

• Journal of Broadcast Engineering
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• v.27 no.6
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• pp.936-939
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• 2022

As air combat system technologies developed in recent years, the development of air defense systems is required. In the operating concept of the anti-aircraft defense system, selecting an appropriate armament for the target is one of the system's capabilities in efficiently responding to threats using limited anti-aircraft power. Much of the flying threat identification relies on the operator's visual identification. However, there are many limitations in visually discriminating a flying object maneuvering high speed from a distance. In addition, as the demand for unmanned and intelligent weapon systems on the modern battlefield increases, it is essential to develop a technology that automatically identifies and classifies the aircraft instead of the operator's visual identification. Although some examples of weapon system identification with deep learning-based models by collecting video data for tanks and warships have been presented, aerial vehicle identification is still lacking. Therefore, in this paper, we present a model for classifying fighters, helicopters, and drones using a convolutional neural network model and analyze the performance of the presented model.

• 한국노년학
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• v.41 no.2
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• pp.253-270
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• 2021

We examined if intergenerational proximity might be associated with upstream financial transfer from adult children to older parents, and whether adult child gender might moderate the association. We considered siblings' proximity to parents, as well as that of the adult child. Prior work conducted in the US and other countries has suggested that children living further from parents might provide financial support to compensate for instrumental support provided more by siblings living closer to parents. Data were drawn from the Korean Longitudinal Study of Ageing (2014). Our analytic sample consisted of older adults 60+ and their children aged 35 and 55. None of the children co-resided with parents. Parental households consisted of either widowed individuals or married couples. For within-family analyses, fixed effects and random effects regression models were estimated. Results suggest first, sons living within a 30-minute distance, or within an hour to two-hour distance provided more monetary support to married parents compared to daughters. Second, contrary to existing findings, greater financial assistance was provided by sons and daughters when no children lived within an hour distance from their parents. For widowed parents living alone, intergenerational proximity was not associated with the amount of financial transfer from adult children.