• Journal of IKEEE
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• v.26 no.2
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• pp.150-159
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• 2022

In this paper, we propose a physics simulation for augmented reality (AR) billiards content. The characteristics of the physics simulation for the proposed AR billiards content are as follows. First, physical equations are derived by calculating the force and moment of inertia applied to the billiards ball to realize the motion of the billiards ball similar to the real one in the AR environment. Then, we determine the velocity and angular velocity of the virtual billiards ball associated with the rotation of the virtual billiards ball with respect to the impact point. Second, using some vectors such as incidnet vector, normal vector, reflection vector, the trajectory of the virtual billiards ball would be implement. these equations are applied to AR environment so that AR billiards content could be implement. This physics simulation allows users to feel like the real world using a virtual pool table and induce them to interact with the real environment. As a result of the experiment, the accuracy range between the path of the real billiards ball and the path of the virtual billiards ball was calculated to be 97.75% to 99.11%. Therefore, it was determined that the performance of the physics simulation for the AR billiards content proposed in this paper performs similarly to the path of the real billiards ball.

• Composites Research
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• v.29 no.2
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• pp.73-78
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• 2016

In this paper, The concept of a wheel with carbon fiber composite is to replace the conventional material used for a wheel hub, such as plastic, with a disk-type hub made of carbon fabric and epoxy resin. The impact load from the ground under real conditions was considered; a low-velocity impact test was conducted to evaluate the impact performance of the carbon wheel and compare it with that of a conventional plastic wheel. This study applied a 70 J impact load as a test condition. The impact energy was controlled in the test by adjustment of height and weight of impactor. The use of a carbon disk wheel hub was confirmed to reduce weight and generate an excellent repulsive force at low energy under conditions similar to real driving conditions. The results showed that the maximum load increased proportionally depending on the impact load, but the growth of the maximum load was reduced at a 20 J impact load and tended to decrease at a 45 J impact load. The carbon wheel showed excellent properties ; the level of rebounding was 35.3% and 19.1% of the total impact energy at impact loads of 5 J and 10 J, respectively. On the other hand, the carbon disk wheel rebounded less than 5% of the total energy due to crack generation of the thin carbon hub for impact loads of more than 20 J.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.199-199
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• 2019

친환경적인 산업기술인 초미세기포(Ultra Fine Bubble, 이하 UFB) 제조 기술은 농업, 수처리, 그리고 환경재생 등 다양한 분야에서 적용되고 있다. UFB는 1,000nm 이하의 크기를 가진 기포로서 용존산소를 통한 농작물 성장 촉진 및 수중의 대장균 및 세균제거 등 다양한 성질을 지니고 있다. 본 연구는 기존의 방식과는 다르게 자왜현상을 메카니즘으로 갖는 타격식으로 제조된 UFB 생성장치를 통해 생성된 200nm이하의 크기를 가진 UFB를 실제 딸기 농장에 적용하여 딸기의 성장을 모니터링하고 살균 성능을 가진 화학제품과 UFB를 대장균에 적용하여 대장균 제거효율을 비교하였다. 딸기농장에 기존에 사용되던 지하수 대신 UFB를 주입하여 딸기성장 초기단계의 DO농도를 측정하고 딸기 생식단계에 산소포화도에 대한 질산염의 농도를 측정하여 상관관계를 분석하였으며 각각의 딸기 열매를 수확하여 무게를 비교하였다. 또한 대장균이 함유되어있는 대변을 채취하여 살균 성능을 가진 화학제품과 UFB수를 각각 대장균이 포함된 실험원수와 반응시켜 배양하고 검출된 대장균 개체 수에 확인하여 제거효율을 비교분석 하였다. 딸기성장 초기단계의 DO농도 측정결과 DO농도가 6~9ml/L로 높게 유지되고 있음을 확인하였고 딸기 생식단계에서 산소포화도가 일정하게 유지되고 있음에 따라 질산염의 농도가 점차 감소하는 것을 확인하였다. 또한 수확한 열매의 무게는 각각 37g, 19g으로 UFB수를 통해 재배된 딸기가 약 2배 이상 높은 것으로 나타났다. 이와 같은 결과는 수중의 용존산소가 딸기 성장 초기에 뿌리의 발육에 긍정적인 영향을 미치고 질산염을 원활하게 섭취하게 하여 딸기의 성장이 촉진되었고 열매의 무게가 증가하였다고 판단된다. 또한 대장균이 함유된 원수, 원수+화학제품, 원수+UFB를 접종하여 대장균과 반응시켜 배양하여 대장균 개체 수를 확인한 결과, 원수의 경우 약 600개의 대장균의 개체수가 나타났고, 원수+화학제품의 경우 검출된 대장균의 개체 수는 약 300개 정도로 나타났다. 이를 희석한 비율을 계산하여 대장균 개체 수를 나타내면 원수 약 6000개/ml, 원수+화학제품 약 6000개/ml로 비슷하게 나타난다. 반면, 원수+UFB 경우 검출된 대장균의 개체 수는 1개로 희석한 비율을 계산하여 대장균 개체 수를 나타내면 약 20개/ml로 나타난다. 이와 같은 결과를 통해 UFB는 99.9%의 대장균 제거효율을 보였으며, 화학제품은 대장균 제거효율을 보이지 않았다. 따라서 화학제품은 항균기능은 작용하지만 살균기능은 거의 없다고 판단하였고, UFB의 경우 기포가 소멸하면서 발생되는 초고온, 초고압을 형성하여 주변에 존재하는 대장균을 제거하였거나, 기포가 소멸할 때 발생되는 OH 라디칼을 통해 대장균의 세포를 화학적으로 분해시켜 대장균을 제거하였다고 보인다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.49-55
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• 2021

Recently, a small tracking radar requires the development of a small millimeter wave tracking radar having a high range resolution that can acquire and track a target in various environments and disable the target system with a single blow. Small millimeter wave tracking radar with high range resolution needs to implement a signal processor that can process wide bandwidth signals in real time and meet the requirements of small tracking radar. In this paper, we designed a signal processor that can perform the role and function of a signal processor for a small millimeter wave tracking radar. The signal processor for the small millimeter wave tracking radar requires the real-time processing of input signal of OOOMHz center frequency and OOOMHz bandwidth from 8 channels. In order to satisfy the requirements of the signal processor, the signal processor was designed by applying the high-performance FPGA (Field Programmable Gate Array) and ADC (Analog-to-digital converter) for pre-processing operations, such as DDC (Digital Down Converter) and FFT (Fast Fourier Transform). Finally, the signal processor of the small millimeter wave tracking radar was verified via performance test.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.4
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• pp.9-20
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• 2011

Future warfare paradigm is changing to network-centric warfare and effects-based operations. In order to find first and strike the enemy in the battlefield, friendly unit requires real-time target acquisition, intelligence collection, accurate situation assessment, and timely decision. The rapid development in advanced sensor technology and wireless networks requires a significant change in operational concepts of the battlefield surveillance. In particular, the introduction of a battlefield surveillance sensor network system is a big challenge to the ground forces which have lack of automated information collection assets. Therefore this paper proposes an ontology-based context-aware framework for the battlefield surveillance sensor network system which is needed for early finding the enemy and visualizing the battlefield in the ground force operations. Compared with the performance of existing systems, the one of the proposed framework has shown highly positive results by applying the context systems evaluation method. The framework has also proven to be satisfactory by the structured evaluation method using device collaboration. Since the proposed ontology-based context-aware framework has a lot of advantages in terms of scalability and reusability, the ground force's reconnaissance and surveillance system can be widely applied to expand in the future. And, ontology-based model has some weak points such as ontology data size, processing time, and limitation of network bandwidth. However, these problems can be resolved by customizing properly to fit the mission and characteristics of the unit. Moreover, development of the next-generation communication infrastructure can expedite the intelligent surveillance and reconnaissance service and may be expected to contribute greatly to expanding the information capacity.

• Journal of Mushroom
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• v.15 no.3
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• pp.150-154
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• 2017

A self-propelled turner was developed to produce mushroom compost at low costs and high efficiency, and the uniformity of compost produced by an excavator, compost mixer, and self-propelled turner was compared. The material of the compost was mixed with rice straw and chicken manure at a dry weight ratio of 3:1. After the final turning, internal temperature distribution, water content of the compost pile, ash ratio, and uniformity of the compost pile were examined. After the compost was completed, the water content was $69.9{\pm}0.54%$, $72.1{\pm}0.15%$, and $74.5{\pm}0.82%$, respectively. The length of rice straw was $47.5{\pm}15.4cm$, $24.9{\pm}10.1cm$, and $31.0{\pm}10.6cm$, respectively. The ash content in the dry weight of each compost was $25.0{\pm}6.2%$, $33.6{\pm}4.2%$, and $28.2{\pm}1.1%$, respectively. The deviation in the length of rice straw was affected by the linear velocity of the spinner in the compost mixer and the self-propelled turner, which were 21.5 m/sec and 9 m/sec, respectively. As a result, the most uniform mushroom compost was produced by the self-propelled turner.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.507-515
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• 2015

This paper proposes a filtering method for effective state vector estimation of highly maneuvering target. It is needed to hit the point called 'sweet spot' to increase the kill probability in missile interception. In paper, a filtering method estimates the length of a moving target tracked by a frequency modulated continuous wave (FMCW) radar. High resolution range profiles (HRRPs) is generated from the radar echo signal and then it's integrated into proposed filtering method. To simulate the radar measurement which is close to real, the study on the properties of scattering point of the missile-like target has been conducted with ISAR image for different angle. Also, it is hard to track the target efficiently with existing Kalman filters which has fixed measurement noise covariance matrix R. Therefore the proposed method continuously updates the covariance matrix R with sensor measurements and tracks the target. Numerical simulations on the proposed method shows reliable results under reasonable assumptions on the missile interception scenario.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.737-742
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• 2015

Course correction munition are a weapson system for precision attacks and are assembled by applying a ballistic control system to existing projectiles. The roll control system is a subsystem of the ballistic control system and is placed between the guidance and control units inside of the projectile, which undergoes a 5000g lateral acceleration. Thus, it is very important to design the system to endure this load. Many developed countries evaluate the performance and safety of course correction munitions' parts using live-fire gun launch tests or a soft recovery system. However, these methods are expensive and slow. Thus, in this study, we develop impact analysis model of the roll control system using CAE. We apply the code to simulate impact phenomenon and use Johnson-Cook material model for modeling the high strain rate effect on the materials. We also design bearings in detail to analyze their behavior and verify the reliability of CAE model through gas-gun impact tests of the roll control system.

• Journal of KIISE
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• v.42 no.8
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• pp.1057-1064
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• 2015

The tactical network is system based on wireless networking technologies that ties together surveillance reconnaissance systems, precision strike systems and command and control systems. Several alternative paths exist in the network because it is connected as a grid to improve its survivability. In addition, the network topology changes frequently as forces and combatants change their network access points while conducting operations. However, most Internet routing standards have been designed for use in stable backbone networks. Therefore, tactical networks may exhibit a deterioration in performance when these standards are implemented. In this paper, we propose Priority based Multi-Path routing with Local Optimization(PMPLO) for a tactical backbone network. The PMPLO separately manages the global and local metrics. The global metric propagates to other routers through the use of a routing protocol, and it is used for a multi-path configuration that is guaranteed to be loop free. The local metric reflects the link utilization that is used to find an alternate path when congestion occurs, and it is managed internally only within each router. It also produces traffic that has a high priority privilege when choosing the optimal path. Finally, we conducted a simulation to verify that the PMPLO can effectively distribute the user traffic among available routers.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.1-10
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• 2008

Shear wave velocity($V_S$), which can be obtained using various seismic tests, has been emphasized as representative geotechnical dynamic characteristic mainly for seismic design and seismic performance evaluation in the engineering field. For the application of conventional geotechnical site investigation techniques to geotechnical earthquake engineering, standard penetration tests(SPT) and piezocone penetration tests(CPTu) together with a variety of borehole seismic tests were performed at many sites in Korea. Through statistical modeling of the in-situ testing data, in this study, the correlations between $V_S$ and geotechnical in-situ penetrating data such as blow counts(N value) from SPT and piezocone penetrating data such as tip resistance ($q_t$), sleevefriction($f_s$), and pore pressure ratio($B_q$) were deduced and were suggested as an empirical method to determine $V_S$. Despite the incompatible strain levels of the conventional geotechnical penetration tests and the borehole seismic tests, it is shown that the suggested correlations in this study are applicable to the preliminary estimation of $V_S$ for Korean soil layers.