• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.145-151
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• 2003

Using computational fluid dynamics (CFD) method, we investigated three-dimensional fluid flow field and particle movement with respect to the injected gas flow rate variation in typical cyclone separator system. The results of numerical investigation were deduced by coupling the analysis of fluid flow field with Wavier-stokes equation and the tracking of the particle trajectory with Langrangian approach. It was shown that the increasing of injected gas flow rate resulted in the increasing of pressure loss in the separator. This change of inner pressure had an effect on an aspect of the fluid flow in the separator. Particle movement was determined by fluid flow in the separator and was fully depended on a diameter of particles under the fixed flow rate. Increasing of injected gas flow rate was led to an increasing of the trace of particle, so the particles moved to the lower part of the separator. For this reason, the minimum diameters of the particles were decreased and increased the separation rate under the fixed particle diameter. In conclusion, the changes of injected gas flow rate have an important factor to the fluctuation of the fluid flow field and particle trajectory in the separator.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.131-139
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• 1996

The response of the arc sensor using the welding current and/or welding voltage as its outputs has been obtained by the analysis and/or experiments of the static characteristics of arc sensor. But in order to improve the reliability of arc sensor, it is necessary to know its dynamic characteristics. So in this paper, it is presented the dynamic model of arc sensor including the power source, arc voltage, electrode burnoff rate, and wire feed rate. A numerical simulation of the dynamic model of arc sensor was implemented, computing the welding current with input of CTWD. The results of computer simulations and experiments of $CO_2$arc welding showed that a linear relationship between weaving center - weld line distance and current area difference was established. Additionally, a real-time weld seam tracking system interfaced with industrial welding robot was constructed, the result of the weld seam tracking experiment for weld line with an initial offset error of 5$^{\circ}$was good.

• Journal of Welding and Joining
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• v.8 no.3
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• pp.70-78
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• 1990

The harsh nature of welding environments makes welding a prime candidate for process automation. Among the variety of welding processes available, gas metal arc welding is one of the most frequently used methods, primarily because it is highly suited to a wide range of applications, and also to automation. Automatic seam tracking method is one of the most demanded techniques for automatic control of arc welding. In this study a seam tracking system has been developed by using the welding arc itself as a sensor. This paper described the principle and experimental result of the arc sensor system, as well as the development and application of the automatic CO_2$ welding for the horizontal fillet welding. A basic problem in horizontal fillet welding is the prevention of hanging bead formation such as undercut at the vertical plate and overlap at the horizontal plate. To produce the symmetric bead shape, the relationship of bead shape to welding parameters(welding velocity, weaving width, weaving speed, tip to workpiece distance) was also investigated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.11
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• pp.535-540
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• 2014

This paper investigates the exhaust effectiveness of smoke, in the case of fire in a large atrium space. Numerical analysis was conducted to simulate transient fire growth in a test room, modeled by the Murcia atrium fire test. Various indices representing the exhaust performance of the exhaust system were obtained, such as the height of the smoke layer, and the instantaneous and accumulative capture efficiency of the smoke. The residual life time of smoke from the fire was also obtained, by injecting tracer gases at the fire location, depending on the airflow rate, and the location of the exhausts. The capture efficiency based on smoke concentration at the exhausts exhibits how much smoke can be removed by the exhaust system; whereas, the exhaust effectiveness based on residual life time indicates how rapidly the smoke can reach the exhaust locations, before being exhausted. The definitions and meanings of the indices to be used in representing the exhaust performance of a smoke exhaust system installed in a large space are discussed.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.55-63
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• 1998

Among the position sensing methods available, the arc sensor which utilizes the electrical signal obtained from the welding arc itself is one of the most prevalently used methods, because it has an advantage that no particular sensing device is necessary and real-time sensing of a groove position is possible directly under the arc. The authors have already developed a seam tracking system that contains a new arc sensor algorithm, which uses the relative welding current variation according to the tip-to-workpiece distance in GMA welding. In this study a torch height control algorithm for automatic weld seam tracking was proposed for completing the previous system, which uses an on-off control technique. To implement the torch height control algorithm during weld seam tracking the system parameters which include 2nd averaging range, weighting factor for 2nd moving averaging, and Z-directional basic compensation distance were determined by experimental analysis. Finally the two different height control methods, one is simple on-off control and the other on-off control using a reference current value , were compared in their tracking abilities.

• Composites Research
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• v.27 no.2
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• pp.59-65
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• 2014

Most of energy are obtained from oil, coal, and natural gas, most likely, fossil fuel which is limited throughout the world. Recently, high crude oil price, climate change, oil depletion, etc. are main reason to get attention to non-fossil energy including renewable energy in the world. In this study, we studied analysis and design of structure system composed of pultruded fiber reinforced polymer composite (PFRP) which has many advantages such as high specific strength and stiffness, high corrosion resistance and chemical resistance. For the design and construction of floating-type structure, PFRP structural members may be the first choice. Design of tracking-type floating PV generation structure was performed by using the results of the finite element analysis. The structure is fabricated and installed on the water surface. Before the installation of the structure, safety related problems associated with installation and operation are investigated using the finite element simulation and it was found that the structure is safe enough to resist externally applied loads.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.151-155
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• 2006

In these days, welding is the most commonly used metallic connection technology and also is the fundamental production technology of the modem industrial, which is used in various areas of the industrial fields, such as shipbuilding, automobiles, airplanes and plant facilities. However welding process produces strong light, electric currents, and fume gases etc., and the welding automation is not so easy compared to the other works of manufacturing industries which produce the standardized products in large quantities. So it is difficult to weld and detect the all kinds of seams automatically by a specific sensor. In this paper the sensor applying strain gauges is used to detect the seams of triangular wave form. With the auto carriage having the sensor we proposed the experiment to weld and track the seam automatically.

• Journal of Welding and Joining
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• v.8 no.1
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• pp.23-30
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• 1990

The robotic welding has been adapted positively in many welding shops forthe purpose of improving the welding efficiency and liberating operators from the severe working atmosphere. But for a large-size structure with thick plates like ship-building and every kind of plants manufacturing, the application of the arc welding robots is not established yet. The reason is assumed that the conventional arc welding robots are not adaptive for multi-pass welding of thick plates whose grooves are not so accurate. As one solution to this problem, a guidance system which uses the welding arc itself as a sensor is largely used. In this study the velocity controller which changes the tip to workpiece distance for regulating the weld proposed. The proportional and integral gain of velocity controller were determined by using the computer simulation of the control system, and the simulation results compared with the experimental ones. It was revealed that the developed control system using the arc sensor principle has a good capability of tracking the weld joint, although some more studies will be needed to refine the model of arc current.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1979.05a
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• pp.8.2-8
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• 1979

Acute obstruction of the upper airway from trachea, a foreign body or Iaryngospasm may lead to death in a few minutes. The immediate restoration of an adequate airway in these patients may be lifesaving. Spontaneous respiration by means of a needle inserted into the trachea was studied in 21 rabbits using 16, 18, and 20 gauge extrcatheters. The results are as follows; 1) Airway resistance was markedly increased in all experimental animals. consequently tidal volume was also significantly decreased, but this seems to be compensatory by increased of respiratory frequency in l6G group. 2) Blood gas analysis revealed adequate pulmonary ventilation through the constricted airway (about 1/3 of normal sized trachea) during 60 minutes. In the other hand, hypercarbia, hypoxemia, and metabolic acidosis were developed in the group with severe constriction of the upper airway (about 1/4-1/6 of normal sized trachea). 3) The further study is postulated to confirm the the possibility of application of needle trcheostomy in man, but the rabbits were tolerable to the constricted airway with a small sized needle (l6G) into the trachea for 60 minutes.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.49-54
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• 2011

In this paper, we represent a mobile robot which can recognize chemical odor, measure concentration, and track its source indoors. The mobile robot has the function of smell that can sort several gases in experiment such as ammonia, ethanol, and their mixture with neural network algorithm and measure each gas concentration with fuzzy rules. In addition, it can not only navigate to the desired position with vision system by avoiding obstacles but also transmit odor information and warning messages earned from its own operations to other nodes by multi-hop communication in wireless sensor network. We suggest the way of odor sorting, concentration measurement, and source tracking for a mobile robot in wireless sensor network using a hybrid algorithm with vision system and gas sensors. The experimental studies prove that the efficiency of the proposed algorithm for odor recognition, concentration measurement, and source tracking.