• Explosives and Blasting
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• v.30 no.2
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• pp.29-42
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• 2012

Variables influencing the free face movement due to rock blasting include the physical and mechanical properties, in particular the discontinuity characteristics, explosive type, charge weight, burden, blast-hole spacing, delay time between blast-holes or rows, stemming conditions. These variables also affects the blast vibration, air blast and size of fragmentation. For the design of surface blasting, the priority is given to the safety of nearby buildings. Therefore, blast vibration has to be controlled by analyzing the free face movement at the surface blasting sites and also blasting operation needs to be optimized to improve the fragmentation size. High-speed digital image analysis enables the analyses of the initial movement of free face of rock, stemming optimality, fragment trajectory, face movement direction and velocity as well as the optimal detonator initiation system. Even though The high-speed image analysis technique has been widely used in foreign countries, its applications can hardly be found in Korea. This thesis aims at carrying out a fundamental study for optimizing the blast design and evaluation using the high-speed digital image analysis. A series of experimentation were performed at two large surface blasting sites with the rock type of shale and granite, respectively. Emulsion and ANFO were the explosives used for the study. Based on the digital images analysis, displacement and velocity of the free face were scrutinized along with the analysis fragment size distribution. In addition, AUTODYN, 2-D FEM model, was applied to simulate detonation pressure, detonation velocity, response time for the initiation of the free face movement and face movement shape. The result show that regardless of the rock type, due to the displacement and the movement velocity have the maximum near the center of charged section the free face becomes curved like a bow. Compared with ANFO, the cases with Emulsion result in larger detonation pressure and velocity and faster reaction for the displacement initiation.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.3
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• pp.191-200
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• 2017

Proper packaging design can meet both the environmental and economic aspects of packaging materials by reducing the use of packaging materials, waste generation, material costs, and logistics costs. Finite element analysis(FEM) is used as a useful tool in various fields such as structural analysis, heat transfer, fluid motion, and electromagnetic field, but its application in the field of packaging is still insufficient. Therefore, the application of FEM to the field of packaging can save the cost and time in the future research because it is possible to design the package by computer simulation, and it is possible to reduce the packaging waste and logistics cost through proper packaging design. Therefore, this study investigated the FEM papers published in Korea for the purpose of helping research design using FEM program in the field of packaging in the future. In this paper, we analyzed the 29 papers that were directly related to the analysis of FEM papers published in domestic journals from 1991 to 2017. As a result, we analyzed the research topic, FEM program, and analysis method using each paper, and presented the direction that can be applied in future packaging field. When the FEM is applied to the packaging field, it is possible to change the structure and reduce the thickness through the stress and vibration analysis applied to the packaging material, thereby reducing the cost by improving the mechanical strength and reducing the amount of the packaging material. Therefore, in the field of packaging research in the future, if the FEM is performed together, economical and reasonable packaging design will be possible.

• Journal of Korean Academy of Nursing
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• v.25 no.3
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• pp.597-607
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• 1995

1960년대 이후 인공호흡기(mechanical ventilator)의 보급과 최근 의료과학의 발달, 간호의 질적 향상의 결과로 저체중출생아를 포함한 고위험 신생아의 생존율이 높아져왔다. 호흡장애증후군(RDS)은 일차적으로 폐포의 완전한 확장을 위해 필요한 계면활성물질(surfactant)의 부족, 미발달된 심폐기능에 의한 병리적 현상으로 저체중아의 가장 큰 원인이 되어왔다. RDS로 인해 인공호흡기에 의존해 있는 저체중아의 경우 적절한 산소공급과 이를 위한 호흡의 유지는 치료의 가장 큰 핵심이 되며, 이를 위한 기관내 흑은 비인두 흡인 (nasopharyngeal suction)은 신생아 중환자실(NICU)의 가장 중요한 간호행위가 되어왔다. 인공호흡기를 위한 기관삽관은 그 자체가 기도의 성모운동을 방해하고 기침반사를 억제시켜 폐 분비물의 효과적 배출을 억제하며, 특히 저체중아의 경우 조산과 관련하여 미발달된 흥곽운등과 심폐기능은 폐분비물의 이동을 저해하는 요소이다. 따라서 기도내의 분비물의 이동을 효과적으로 하여 흡인 시에 최대한의 효과를 돕기 위해 흥곽 물리요법(chest physiotheraphy : CPT)의 한 형태인 흉곽진동법 (Chest Vibration : CV)가 행해져 왔다. 그러나 저체중아를 위한CV의 임상적 적용은 그 대상의 생리적 특성, CV의 적용부위(site)와 기간(duration)에 대한 과학적 근거 없이 만성감염이나 폐질환을 가진 성인이나 cystic fibrosis환자를 위한 CV protocol을 무분별하게 채택하여 저체중아에게 행하여져 왔다 이에 본 연구자는 저체중아에 대한 CV의 안전성을 평가하고, 이에 기초하여 저체중아에게 바람직한CV의 형태를 알아보고자 본 연구를 시작하였다. 연구설계는 CV의 안전성을 평가하기 위한 실험연구이다. CV의 안전성은 RDS치료의 가장 일차적 목표인 oxygenation변화에 의해 평가될 수 있으므로, 본 실험 연구에서는 Pulse oximeter에 의해 계속적으로 측정된 산소포화 변화(oxygen saturation change)를 측정하였다. 실험대상은 미국동부에 위치한 대학병원의 NICU에 입원하여 RDS와 관련된 호흡장애로 인공호흡기에 의존해 있는 10명의 저체중아였다. 인공호흡기에 의존된 모든 저체중아는 Pulse oximeter와 심폐기능 측정기(cardiopulmonary monitor)에 의해 산소공급과 호흡상태가 계속 측정되고 있었다. 실험대상의 평균 출생시 몸무게는 평균 1,3050gm(SD=580.6)이었고, 임신월령 은 평균 28.6주(SD=3.1)였다. RDS가 그들의 일차적 진단명이었고, 그중 4명은 pneumonia, atelectasis의 합병증을 가지고 있었다. 10명중 6명은 intermittent mandatory ventilation(IMV)의 형태로, 4명은 continuous positive airway pressure(CPAP)의 형태로 인공호흡기에 의존되어 있었고 CV시의 FiO2는 평균 42.3(SD=21.2)였다. CV는 중환아용 소형진동기 (minivibrator)를 이용해 가각 10명 의 간호사에 의해 행하여 졌고, 최소 22초에서 최대 100초 동안 실시되었다. 50%의 간호사는 30초에서 40초간 CV를 실시하였으며, CV의 적용부위도, 전후 흉곽부위, 혹은 병변이 있는 좌 우측, 흑은 양쪽 흉벽 등으로 다양했고, 적용방법도 원형으로 돌려가며(circular motion), 혹은 아래에서 위로, 혹은 아무런 기준없이 간호사의 기호에 따라 다양하게 적용되었다. 산소포화의 변화는 CV가 행해지기 전.후로 5초동안 관찰되었다. 연구의 결과, 산소포화 변화는 비 모수통계(non parametric statistics)의 일종인 Matched Paired Wilcoxon test로 분석 한 결과 CV후에 3%의 감소를 보였다(P<.05). 저체중아에 있어 산소포화의 3%감소는 임상적으로 중요한 의미가 없다고 사료되어지며, 실제 흡인전의 과도호흡에 의해 CV를 행하기 이전의 산소공급수준으로 돌아 왔다. CV실시 기간과 산소포화와의 상관관계는 비 모수통계인 Spearman rho correlation coefficient를 이용하여 분석하였는데, 이 두 변수는 서로 관계가 없는 것으로 나타났다(P>.05) 또한 CV와 흡인 후에 각각의 간호사들에게 CV를 필요로 한 저체중아의 기준, 적용부위, 기간, 방법등에 대한 기준을 물었으나 대상의 특성에 따른 간호사정에 의존하기보다는 간호사 각자의 선호하는 방법이나 습관에 라 행하는 것으로 나타났다. 결론적으로 CV와 산소포화 변화와의 관계, NICU에서 관찰된 CV의 임상적 적용을 기초로 저체중아에게 안전한 CV protocol은 신생아용 소형 진동기를 이용하여, 양쪽 흉곽의 늑골하측 변연 부위(low lateral costal margin)에서 시작하여 흉골 중앙부위 방향으로 30초 동안 진동기를 적용하는 것이 좋은 것으로 나타났다. 이에 CV의 효과를 평가하기 위한 보다 과학적인 접근방법으로, CV와 흡인의 결과인 가래(sputum)에 대한 연구를 제언하는 바이다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.7
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• pp.586-603
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• 2004

One of the subtle problems that make noise control difficult for engineers is “the invisibility of noise or sound.” The visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical or numerical means to visualize the sound field have been attempted and as a result, a great deal of progress has been accomplished, for example in the field of visualization of turbulent noise. However, most of the numerical methods are not quite ready to be applied practically to noise control issues. In the meantime, fast progress has made it possible instrumentally by using multiple microphones and fast signal processing systems, although these systems are not perfect but are useful. The state of the art system is recently available but still has many problematic issues : for example, how we can implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently it is often difficult to determine the origin of the noise and the spatial shape of noise, as highlighted in the title. The first part of this paper introduces a brief history, which is associated with “sound visualization,” from Leonardo da Vinci's famous drawing on vortex street (Fig. 1) to modern acoustic holography and what has been accomplished by a line or surface array. The second part introduces the difficulties and the recent studies. These include de-Dopplerization and do-reverberation methods. The former is essential for visualizing a moving noise source, such as cars or trains. The latter relates to what produces noise in a room or closed space. Another mar issue associated this sound/noise visualization is whether or not Ivecan distinguish mutual dependence of noise in space : for example, we are asked to answer the question, “Can we see two birds singing or one bird with two beaks?"

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1189-1194
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• 2011

The Maglev train is operated by levitating from a power of a large number of magnets and moving without direct contact to railway track so that reduces noise and vibration due to mechanical friction. Also, the Maglev passes sharp curves and steep hill without any difficulties. The Maglev has a potential to be an alternative transport system urban areas. For successful commercializing of Maglev, the organization of interface for safety and reliability of third rail system are one of the key considerations. Especially, the components of the third rail system, such as power rail, expansion joints, FRP section insulator, and supporter with epoxy insulator, should be durable, convenient for construction, and easy to maintenance. This paper analyzes the characteristics of the third rail system components and proposes organization of interface for system engineering. The operating tests of KIMM for the proposed third rail system verify the safety. Also, this paper analyzes the life cycle of the system components to improve the system reliability and evaluation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.1
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• pp.36-45
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• 2017

Abstract It is necessary to verify the properties of an inertial measurement unit in the flight environment before applying to military applications. In this paper, we presented a new approach to verify an inertial measurement unit(IMU) in regard to the performance and the robustness in flight environments for the high-dynamics vehicle systems. We proposed two methods for verification of an IMU. We confirmed normal operation of an IMU and properties in flight environment by using direct comparison method. And we proposed real time multi-navigation system to complement the first method. The proposed method made it possible to compare navigation result at the same time. Therefore, it is easy to analyze the performance of an inertial navigation system and robustness during the vehicle flight. To verify the proposed method, we carried out a flight test as well as an experimental test of flight vibration on the ground. As a result of the experiment, we confirmed flight environment properties of an IMU. Therefore, we shows that the proposed method can serve the reliability improvement of IMU.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.39.3-40
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• 2015

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is the near-infrared instrument optimized to the first small satellite of NEXTSat series. The capability of both imaging and low spectral resolution spectroscopy in the near-infrared range is a unique function of the NISS. The major scientific mission is to study the cosmic star formation history in local and distant universe. For those purposes, the main targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optical design of the NISS with two linear variable filters is optimized to have a wide field of view ($2deg.{\times}2deg.$) as well as the wide wavelength range from 0.95 to $3.8{\mu}m$. The mechanical structure is considered to endure the launching condition as well as the space environment. The dewar inside the telescope is designed to operate the infrared detector at 80K stage. From the thermal analysis, we confirmed that the telescope and the dewar can be cooled down to around 200K and 80K, respectively in order to reduce the large amount of thermal noise. The stray light analysis is shown that a light outside a field of view can be reduced below 1%. After the fabrications of the parts of engineering qualification model (EQM), the NSS EQM was successfully assembled and integrated into the satellite. To verify operations of the satellite in space, the space environment tests such as the vibration, shock and thermal-vacuum test were performed. Here, we report the results of the critical design review for the NISS.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.436-441
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• 2009

A fiber optic sensor is prospective to be applied to structural health monitoring. Especially, a fiber Bragg grating(FBG) sensor is one of the most popular sensors for the structural health monitoring. The FBG sensor has several demodulation systems for tracking the shift of the Bragg wavelength. The dynamic bandwidth is dependent on the demodulation system. In this paper, the sensing mechanism is that the slope of the optical spectrum of FBG could be used as its sensitivity when the tunable laser shot the monochromatic laser wavelength at the highest slope point. In this technique, the high sensitivity is guaranteed even though the sensing range is limited. In an example of the application, the composite plate embedding a FBG sensor was manufactured by using an autoclave method and the above sensing mechanism was applied to the composite plate. Firstly, the natural frequencies of the plate were successfully measured by the FBG sensor during the impact hammer test. Secondly, a high-power speaker was used to force the plate to be vibrated at the specific frequency that was one of the natural frequencies. During the shaking, the FBG sensor measures the dynamic characteristics and ESPI was also used to measure the mode shape. From the two dynamic tests, the availability of the FBG sensor system and the ESPI was proven as a technique for measuring the dynamic characteristics of composite structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.627-633
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• 2020

Assembly process data can be gathered in real time in a manufacturing execution system (MES) server using proximity sensors, barcodes, RFID, ZigBee, Bluetooth, wireless sensor networks, etc. Although this is suitable for identifying process flow and checking production progress, it is difficult to trace the location of individual workers in real time for missing work or trajectories within the work area. To overcome this, the location and trajectory of the working tool can be analyzed in real time through a position tracking system of an operator's working tool. It can instruct the operator to perform a consistent working process. Productivity and quality improvement can be achieved by an alarming or blocking operator with possible assembly defects during the assembly process in real time. To this end, we developed a real-time tool position-tracking sensor system based on Ultra Wide Band (UWB) trilateration using a Kalman filter to eliminate mechanical vibration and radio communication noise.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1255-1262
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• 2012

Look into the nuclear power plant of Wolsong currently, it is controlled in order to required operating pressure with PI controller. PI controller has a simple structure and satisfy design requirements to gain setting. However, It is difficult to control without changing the gain from produce changes in parameters such as loss of the valves and the pipes. To solve these problems, the dynamic change of the PI controller gain, or to compensate for the PI controller output is desirable to configure the controller. The aim of this research and development in the parameter variations can be controlled to a stable controller design which is reduced an error and a vibration. Proposed PI/NN control techniques is the PI controller and the neural network controller that combines a parallel and the neural network controller part is compensated output of the controller for changes in the parameters were designed to be robust. To directly evaluate the controller performance can be difficult to test in real processes to reflect the characteristics of the process. Therefore, we develope the simulator model using the real process data and simulation results when compared with the simulated process characteristics that showed changes in the parameters. As a result the PI/NN controller error and was confirmed to reduce vibrations.