• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.110-116
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• 2005

Suitable compositions which are sinterable at low temperature in the $BaO-B_{2}O_{3}-ZnO$ glass system were investigated as a function of the ratio between BaO and ZnO. The effect of $Al_{2}O_3$ filler on densification and physical characteristics of the glass was also examined. When the amount of $Al_{2}O_3$ filler increased, the densification rate and the values of dielectric constant, thermal expansion coefficient and hardness in the glass-filler composites decreased gradually. The decreasing rate of the physical properties accelerated when fine $Al_{2}O_3$ filler was used. However, the fracture toughness of the composite rather increased due to the existence of filler particles and pores which effectively suppressed crack propagation with addition of fine $Al_{2}O_3$ filler.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.355-360
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• 2000

There are many changed while a design is completed. Therefore, if the impact of the design changes is estimated, it may result in the improvement of design efficiency. But, the design changes have various types and affect other parts of the design system. Hence, it is difficult to deal with design changes directly. The purpose of this research is to develop a systematic change propagation tracing algorithm and a method of change impact analysis and then, to implement a change impact analysis system. Process based design is set up for the field of this research. Also the design, composed of design parameters and constraints, is set up for the subject of the research. Change propagation tracing algorithm traces change propagation based on the following concept : If the design parameters are changed, other parameters within the constrains including them may be changed. Using the result of change propagation tracing algorithm, changeable parameters, constraints and tasks can be found. The method of change impact analysis, to calculate change impact value from this changeable tasks, is developed. Change propagation tracing algorithm and the method of change impact analysis are implemented into change impact analysis system and it is applied to the redesign of 2 stage gear drives. It can support different kinds of design activities systematically. especially, at the redesign step, where many design change alternatives exist, change impact value of each alternative exist, change impact value of each alternative is calculated and design change is performed toward direction to minimize the impact of design change. Consequently, it is expected to improve the efficiency of the whole design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.521-526
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• 2014

In this study, closed-cell aluminum foam with an initial crack was investigated to produce an axial load-time graph. Using the 10-kN Landmarks of MTS Corporation, a 15-mm/min velocity of mode I shape was applied to the aluminum foam specimen using the displacement control method. ABAQUS 6.10 simulation was used to model and analyze the identical model in three dimensions under conditions identical to those of the experiment. The energy release rate was calculated on the basis of an axial load-displacement graph obtained from the experiment and a transient image of the crack length, and then an FE model was analyzed on the basis of this fracture energy condition. The relation between load and displacement was discussed; it was found that the aluminum foam deformed somewhat less than the adhesive layer owing to the difference in elastic modulus.

• Fire Science and Engineering
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• v.32 no.4
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• pp.17-24
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• 2018

This paper presents a numerical analysis of flow inside a water nozzle for fire fighting and observes the effect of the variation in primary components on internal flow. In order to observe the performance of water nozzles, they have been systematically designed and modelled, applying boundary conditions obtained from field experiments (inlet pressure at pump : 4 bar, and pressure outlet : atmospheric pressure). In addition, the governing equations were calculated to obtain velocity, pressure inside the nozzle. Two main parameters (the presence and length of sub-pipes) were considered with the aim to observe the detail internal flow characteristics. It is found that the base model is not significant on flow characteristics, but a negative effect (i. e. the reverse flow) at the entrance region of sub-pipe. On the other hand, the reverse flow was vanished when making the length of sub-pipe double.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1877-1882
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• 2013

Smart Utility Network (SUN) is not only a core technology of intelligent green home networks but also a future technology which can be applicable to various areas instead of ZigBee. SUN should be compliment with IEEE 802.15.4g standard and can provide high link margin and stable communication data-rate for poor communication surrounding. This paper describes how to design the system simulation environment for the SUN RF transceiver, and also reports the required block-level specification for each circuit and various implementation impairments. Finally, the measured performances of the fabricated RF transceiver, which has utilized the system simulation results, completely satisfies the IEEE 802.15.4g SUN PHY standard.

• Journal of the korean veterinary medical association
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• v.46 no.6
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• pp.527-543
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• 2010

구제역은 소 돼지 사슴 면양 산양 고라니 노루 등 우제류 동물에서 발생하는 제1종 가축전염병으로 빠른 시간내에 동물의 입 발굽 젖꼭지 등에 수포를 형성하는 것이 특징이다. 감염된 소의 혓바닥, 잇몸, 입술, 입 내부점막, 주둥이에 크기가 다양한 수포가 형성된다. 심한 경우에 혀 전체 넓은 부위에서 궤양이 형성될 수 있다. 수포는 24시간이내에 정상적으로는 파열되며, 그 수포액은 $10^8/ml$의 역가를 갖는 바이러스를 함유한다. 상피가 떨어지고, 유연이 심해지며, 타액이 입 주변에 흔건히 흘러내린다. 입 주변 병변과 동시 또는 이어서 수포가 발굽에 형성되며, 부분적으로 발굽갓띠 또는 제부의 갈라진 틈에서 생성되어 통증과 파행의 원인이 된다. 수포는 보통 유두와 유방에 발생되며, 때로는 세균성 유방염을 발생시킨다. 생산성의 감소는 보통 25% 정도로 추정된다. 돼지는 초기에 파행, 발열, 의기소침, 식욕부진이 있다. 소 보다 발굽에서 더욱 증상이 심하다. 유두, 유선, 콧등에 수포가 형성된다. 혀의 병변은 소보다 심하지 않다. 잠복기가 2~14일 (소에서의 약 6.2일, 돼지에서는 약 10.2일)로 짧고, 전파가 매우 빠르며 경제적 피해가 크기 때문에 국제 교역에서도 규제대상이 되는 질병이다. 구제역의 병인체는 피코르나바이러스과 아프토바이러스속에 속하는 구제역 바이러스로 현재까지 7개의 혈청형(A, O, C, Asia 1, SAT 1, SAT 2 및 SAT 3)이 알려져 있다. 이 전염병은 동물전염병 중에서 가장 악명 높은 전염병이다. 세계동물보건기구 (OIE)에서도 각 국간에 국제적인 위협을 최소화하기 위하여 질병의 발생을 보고해야 하는 질병으로 특별 관리하고 있다. 2006년 이후 최근까지 아시아 지역에서 지속적으로 많은 발생을 보이고 있다. 금년 들어 중국, 대만, 일본, 몽골, 우리나라까지 발생되어 이 질병의 위험성에 대하여 다시 한번 생각하게 하였다. 구제역의 재발방지를 위하여 최근 동북아시아 지역의 발생상황과 향후 구제역의 발생억제 또는 발생시 긴급 대응을 위하여 해야 할 일은 무엇인지 알아보자.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.487-495
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• 2012

The yaw control, a major part of the wind turbine, is closely related to the efficiency of electric power production and the mechanical load. The yaw error, which results from the nacelle not being appropriately aligned in the wind direction, not only decreases the power output but also reduces the lifetime of the wind turbine as a result of large fatigue loads. However, the yawing rate cannot be increased indefinitely because of constraints on mechanical loads. This paper investigates the characteristics of an active yaw control system, the basic principle of the system, and mechanical loads around the yaw axis during yawing.

• Journal of Sensor Science and Technology
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• v.8 no.6
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• pp.461-468
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• 1999

In this paper, we have implemented a gas recognition system for classification and identification of explosive gases such as methane, propane, and butane using a sensor array and an artificial neural network. Such explosive gases which can be usually detected in the oil factory and LPG pipeline are very dangerous for a human being. We analyzed the characteristics of a multi-dimensional sensor signals obtained from the nine sensors using the principal component analysis(PCA) technique. Also, we implemented a gas pattern recognizer using a multi-layer neural network with error back propagation learning algorithm, which can classify and identify the sorts of gases and concentrations for each gas. The simulation and experimental results show that the proposed gas recognition system is effective to identify the explosive gases. And also, we used DSP board(TMS320C31) to implement the proposed gas recognition system using the neural network for real time processing.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.392-399
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• 2014

The underwater acoustic communication is characterized by doubly spread channels, which are the delay spread due to multiple paths and the doppler spread due to environmental fluctuations or a moving platform. An equalizer is used to remove the inter-symbol interferences that the delay spread causes, but an equalizer doesn't use an acoustic environment such as a multipath. However, a passive time-reversal mirror is simpler than an equalizer because a matched filter is implemented numerically at the receiver structure along with one-way propagation. In this paper, a passive time-reversal mirror is applied to remove interferences due to a multipath in sea-going experimental data in East Sea in Oct. 2010 and improved communication performance is confirmed. The performance is verified by comparing the signal-to-interference plus noise ratio before/after passive time-reversal mirror. It is also performed independently of the passive time-reversal mirror and adaptive equalizer and the bit error rate is compared to verify the performance of underwater acoustic communication.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.34-39
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• 2010

Due to big demand for satellite and communication service using personal handheld terminals, demand for satellites with huge antennas is increasing correspondingly. While such large antennas are realized by various types of deployable antennas, the reflecting surface is made by many facets irrespective of deploying mechanisms. In order to analyze the faceted-reflector more accurately, an existing ray-tracing method is improved. The algorithm allows the rays to cross each other, which is the main characteristic of the faceted-reflector, and takes unevenness of amplitude and phase over the aperture plane into consideration. For the study of the effect of facet configuration, facet generating algorithm is devised. From the analysis algorithm and the facet-generating algorithm, it has been found that the number of facets in a radial direction affects both directivity and sidelobe level. On the other hand, the number of facets in a circumferential direction affects sidelobe level only.