• Journal of Chest Surgery
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• v.16 no.4
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• pp.547-554
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• 1983

Implantation of Dual Chamber Pacemakers Which sense in the Atrium and the Ventricle, and sequentially or synchronously trigger impulses in the both chambers, has led us to the near realization of the ideal "Physiologic Pacing". We have experienced two cases of implantation of Dual chamber pacemaker in September and October, 1983. One patient was a 21-year-old male who had postoperative complete heart block since he was taken Total correction of TOF in May, 1983 . We implanted transvenously a dual chamber pacemaker, VDD type, through the left subclavian vein. In the other patient who came to the emergency room for partial obstruction of small bowels with severe abdominal pain, nausea and vomiting, in whom heart block was found, we implanted a DDD type pacemaker through the left subclavian puncture. The pacemakers have been functioning well postoperatively for more than two months, and the conditions of patient were uneventful.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.110-122
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• 2008

Pneumatic vibration isolator typically consisting of dual-chamber pneumatic springs and a rigid table are widely employed for proper operation of precision instruments such as optical devices or nano-scale equipments owing to their low stiffness- and high damping-characteristics. As environmental vibration regulations for precision instruments become more stringent, it is required to improve further the isolation performance. In order to facilitate their design optimization or active control, a more accurate mathematical model or complex stiffness is needed. Experimental results we obtained rigorously for a dual-chamber pneumatic spring exhibit significantly amplitude dependent behavior, which cannot be described by linear models in earlier researches. In this paper, an improvement for the complex stiffness model is presented by taking two major considerations. One is to consider the amplitude dependent complex stiffness of diaphragm necessarily employed for prevention of air leakage. The other is to employ a nonlinear model for the air flow in capillary tube connecting the two pneumatic chambers. The proposed amplitude-dependent complex stiffness model which reflects dependency on both frequency and excitation amplitude is shown to be very valid by comparison with the experimental measurements. Such an accurate nonlinear model for the dual-chamber pneumatic springs would contribute to more effective design or control of vibration isolation systems.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.233-235
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• 2015

This study is to investigate the combustion instability of the variation of combustion chamber length in dual swirl gas turbine model combustor. When equivalence ratio was fixed at 1.1, as the length of the combustion chamber increases the value of the frequency decreased in 7kW while the value of the frequency was constant in 4kW. The analysis of flame behaviors by high speed camera was conducted to identify such trend.

• Journal of the Korean Society of Combustion
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• v.2 no.1
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• pp.17-27
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• 1997

It is well known that NOx formation has a strong dependence on the maximum temperature and correspondingly with the maximum chamber pressure of a closed combustion system. However, in a case of impinging-jet-flame (IJF hereafter) combustion with opposed dual pre-chambers, low $NO_x$ formation with high pressure could be achieved, but its mechanism has not been clearly understood so far. In this study, a three-dimensional analysis is adopted to resolve time-variant local properties that might indicate the mechanism of IJF combustion. Numerical results are verified by comparing them with experiments. The IJF combustion in a vessel with no pre-chamber, with single pre-chamber, and with dual pre-chambers is studied. The orifice diameter and the volumetric ratio of pre-chamber are used as geometric parameters. The effects of main-chamber ignition delay time and combustion time of main-chamber, orifice exit velocity, orifice exit temperature, turbulent kinetic energy of main-chamber and spatial distribution of temperature in the latter stage of combustion are investigated. A longer main-chamber ignition delay and a shorter main-chamber combustion time suppress the formation of high temperature region with respect to mean temperature, which consequently results in less NO production.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.74-80
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• 2006

This paper presents the characteristics of electromagnetic field uniformity in a reverberation chamber that can be used alternatively for the analysis, test and evaluation of electromagnetic interference and immunity. The dual-band diffuser, which can be used at two different frequency bands in a reverberation chamber, is applied, and it is made of two different single-band Schroeder's Quadratic Residue Diffusers. The FDTD method is used to analyze the field characteristics. Compared with single-band diffuser, the dual-band diffuser shows the improvement in not only expansion of test frequency band but also in characteristics of the field uniformity, polarity, power efficiency, and tolerance. Therefore, the reverberation chamber with the dual-band diffuser is a better facility, for the analysis and measurement of electromagnetic interference and immunity, than the reverberation chamber with a single-band diffuser.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.4
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• pp.50-60
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• 1987

Combustion characteristics of opposed-jet-flames spouting out from dual prechambers of a divided combustion chamber were investigated by using high speed schilieren photography and chamber pressure measurement. Result shows that opposed-jet-flames are characterized by the parameter ( $A_{ori}$/ $V_{p}$) and there exists a certain critical value of ( $A_{ori}$/ $V_{p}$)c which distinguishes flame propagation patterns in the main chamber. Also higher chamber pressure and shorter total burning time can be derived by adopting this dual prechamber divided combustion chamber, which would lead a possibility of an appropriate combustion method of high load and low emissions.ons.ons.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.58-64
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• 2014

Hydraulic dual chamber, as the simulator for a dual pulse rocket motor, was tested by a high pressure device with various orifice-hole size being applied. Pressure difference occurs between 1st chamber and 2nd chamber depending on area ratio of the orifice to nozzle throat. Studying a design configuration of the orifice is essential to the motor development because pressure difference severely affects the rocket motor performance. It is noticed in this study that energy dissipation is caused by the vortex flow originating from the orifice as the 2nd chamber is operated. The flow field is simulated by a commercial computational fluid dynamics program, ANSYS FLUENT V14.5.

• Journal of mucopolysaccharidosis and rare diseases
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• v.1 no.1
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• pp.28-30
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• 2015

Biologics present a challenge to both the manufacturer and end user. They must usually be formulated as parenterals. However, they are often unstable in liquid form, due to their complex structure and composition. In that case, they must be manufactured using highly specialized processes, such as lyophilization (freeze-drying). Lyophilization nearly eliminates stability issues. Reducing a compound's sensitivity to temperature prolongs its shelf life. However, reconstitution can be cumbersome, involving multiple steps that increase the potential for error. Dual-chamber technology provides an effective alternative, combining a lyophilized drug and diluent in a closed system and enabling reconstitution in a few simple steps.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.815-824
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• 2013

Pneumatic exciters can be good replacements of electrodynamic, piezoelectric and hydraulic exciters owing to simple structure and large exciting force. One problem to be solved is a slow response caused by compressibility of air. Desirable frequency response characteristics of exciter are constant magnitude and zero degree phase, because users want no time delay between input signal and output force. For this reason, frequency range of pneumatic exciters is limited about 0~1 Hz. Therefore, expansion of frequency range is an important issue when designing the pneumatic exciter. In this paper, the pneumatic exciter which has same structure with active pneumatic isolator is dealt with. The dynamic characteristics are presented, and its limitation of expanding frequency range is shown based on analytical studies. Then the pneumatic exciter with dual-chamber is suggested to overcome this problem. Based on simulation study, a design method is presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.325-329
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• 2017

In this study, the combustion experiment of hydrocarbon-kerosene fueled dual mode ramjet combustor was performed at mach number 3.5~6.0 conditions. Through the experiment, the temperature and the pressure distribution inside the combustion chamber were measured and the combustion characteristics inside the combustion chamber were investigated. In the mach number 3.5~5.0 range, it was able to identify subsonic combustion in the downstream combustion chamber. In the mach number 6.0 condition, the injected fuel from the injectors was naturally fired, and it was possible to confirm that supersonic combustion was successful in the upper chamber.