• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.510-519
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• 2013

In this study, the spray characteristics of a pressure swirl atomizer classified into a liquid sheet-type swirl nozzle for Urea-SCR system were investigated experimentally with the variation of injection pressure. The length to diameter ratio ($l_o/d$) of the nozzle was 3.1, and the swirler was set inside the nozzle tip to give injecting fluid angular momentum. The injection duration of the nozzle was controlled by PWM (pulse width modulation) modes. The development processes of the spray were imaged by a 2-D PIV system, and the change of spray angle was measured. The atomization characteristics, including axial velocity and SMD, were measured using a 2-D PDA system with the injection pressures at room temperature and ambient pressure conditions. As the experimental results, the injection pressure had a significant impact on the spray structure showing a different shape around the spray leading edge, and the smaller SMD was observed with increasing injection pressures, which was similar to that of the previous work.

• Journal of ILASS-Korea
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• v.25 no.4
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• pp.188-195
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• 2020

To meet stringent emission regulations of automotive engines, fuel injection control techniques have advanced based on reliable and fast computing prediction models. This study aims to develop a reliable lightweight prediction model of fuel injection rates using a small number of input parameters and based on simple fluid dynamic theories. The prediction model uses the geometry of the injector nozzle, needle motion data, injection conditions and the fuel properties. A commercial diesel injector and US No. 2 diesel were used as the test injector and fuel, respectively. The needle motion data were measured using X-ray phase-contrast imaging technique under various fuel injection pressures and injection pulse durations. The actual injector rate profiles were measured using an injection rate meter for the validation of the model prediction results. In the case of long injection durations with the steady-state operation, the model prediction results showed over 99 % consistency with the measurement results. However, in the case of short injection cases with the transient operation, the prediction model overestimated the injection rate that needs to be further improved.

• Journal of the Korean GEO-environmental Society
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• v.7 no.4
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• pp.63-71
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• 2006

This study was conducted to evaluate air injection mode on stabilization of landfill gas and to predict the time for landfill mining. It took 8 times longer for pulse aeration to get to aerobic condition, compared to continuous aeration. It was evaluated that continuous aeration mode is more preferable than pulse mode for rapid air exchange in landfill mining. High correlation ($r^2$ = 0.95) was found between continuous aeration time and time to maintain aerobic condition when $0.2m^3/min$ of air was continuously injected and stopped. The aerobic condition ($CH_4$ < 5%) was maintained for 1.5 times longer than aeration time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.367-370
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• 2006

This paper deals with the modeling and simulation of the internal flowfield in a valveless airbreathing pulse detonation engine (PDE) currently under experimental development at the U.S. Naval Postgraduate School. The system involves no valves in the airflow path, and the isolation between the inlet and combustor is achieved through the gasdynamics in an isolator. The analysis accommodates the full conservation equations in axisymmetric coordinates, and takes into account variable properties for ethylene/oxygen/air system. Chemical reaction schemes with a single progress variable are implemented to minimize the computational burden. Detailed flow evolution during a full cycle is explored and propulsive performance is calculated. Effect of initiator mass injection rate is examined and results indicate that the mass injection rate should be carefully selected to avoid the formation of recirculation zones in the initial cold flowfield. Flow evolution results demonstrate a successful detonation transmission from the initiator to the combustor. However, strong pressure disturbance may propagate upstream to the inlet nozzle, suggesting the current configuration could be further refined to provide more efficient isolation between the inlet and combustor.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.265-270
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• 2000

We investigate the effects of the power and wavelength of externally injection seeded light on timing jitter and pulse width in a gain-switched $1.55\mu\textrm{m}$ DFB semiconductor laser by numerical simulation based on the transmission line laser model. As external seeding power increases, the timing jitter decreases and the pulse width increases. The lowest timing jitter is observed when the seed wavelength is aligned with the chirped spectrum center. By external seeding, we can decrease the timing jitter up to 1/2.7 without noticeable increase in pulse width. Our simulation results reasonably well agree with our sampled experiment and the other published papers. This proves the validity of our model to analyze a system based on a semiconductor laser. laser.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.515-518
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• 2005

A concrete is easy to happen crack. So it requires crack-repair work to solve quality deteriorations of a building because of cracks. When crack is filled with crack-repair materials, it is difficult to find out how depth it was injected. So in this study we evaluated the injection depth with using indirect and oblique methods, ultrasonic pulse measurement method of NDT. The results of this study showed that both methods are possible to evalute penetration depth of crack-repair materials and indirect methods is thought to be more useful one than obliqure one.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.3
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• pp.254-262
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• 1990

In the active power filter, the PWM method for controlling the power converter plays an important role for the performance and the efficiency of the filter. In this paper, a new PWM method for the single phase current source type active power filter is presented, which is intended particularly for obtaining the maximum efficiency of the compensation. This method is basically based upon the optimized injection method, but in contrast to the existing method, this method adapts the optimized injection method by putting not only the pulse width, but also the pulse position into control variables. By doing this, when the number of pulses per one cycle is N, lower order harmonics up to the Nth order can be completely eliminated by the filter. So, this method is much more efficient than any other existing method. These characteristics are well verified by the computer simulations and the experiments.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.166-170
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• 2000

A wavelength tunable all-optical clock recovery using a semiconductor optical amplifier in a fiber ring cavity is proposed and demonstrated at the wavelength of 1530 nm to 1570 nm. A synchronized optical pulse train is recovered from 10 Gbps and 30 Gbps randomly generated optical pulse streams with injection locking technique. Also, the system responses to the perturbation and the input average power variation are analyzed by a large-signal model based on time-domain travelling wave equation. ation.

• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.223-230
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• 2009

For pulse trigger way and the energy injection rate according to PET ($Pause^{10-90}$ $Energy^{20-40}$ $Trigger^{1-7}$) function, indeed, human body condition, period of dormancy in this research about this back correctly adjustment possible and designed harmless micro carrying along style hair exclusion so that can design and manufacture and run special quality examination and Xenon flash lamp to crawl in human body. Because creating individual's skin model to do stable treatment by light transmission way by skin impedance and measure, must embody treatment special quality of most suitable that draw skin color, energy, wave length, approximately, transmission time, pulse delay etc. and want. Specially, saved standard of war treatment pulse modeling by skin impedance, and manufacture pulse modeling system of most suitable by skin subordinate, and embody suitable treatment pulse. Specially, embody as could do root of a hair exclusion being emitted in pulse form using multi wave length of 560nm, 590nm, 640nm, 755nm and embodied clinical data. If become research repletion furthermore little more, is seen that can approximate in commercialization.

• Journal of Acupuncture Research
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• v.24 no.5
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• pp.207-217
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• 2007

Objectives: We investigated the safty of distilled Astragali Radix Herbal Acupuncture, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture on vital sign -BP, pulse, resperation-in adult man. Methods : We investigated on 106 healthy volunteers consisted of each 30 subjects in experiment (distilled Astragali Radix Herbal Acupuncture, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture) group and 30 subjects in control(Normal Saline) group. Study form was a randomized, placebo-controlled, double-blind clinical trial. 30 subjects in each experiment group were injected distilled Astragali Radix Herbal Acupuncture, Wild Ginseng Herbal Acupuncture, Rehmannia glutinosa Herbal Acupuncture at $GB_{21}$(Kyonjong) and 30 subjects in control group were injected Normal Saline at $GB_{21}$ (Kyonjong). except of 2 subjects(in control group) who can't be measured and 10 subjects(6 in experiment group and 4 in control group) who move or make unforceable error during measuring. Finally each 25. subject, subject, subject in experiment group and 24 subject in control group are studied. We measured resperation by PolyG-I and BP & pulse by electric manometer on 5 times : before injection per 5 minutes during and after injection per 10 minutes during 35 minutes. The SPSS 13.0 for windows was used to analyze the data and the Student t test(between two groups) were used to verify the result. Results : 1. After distilled Astragali Radix Herbal Acupuncture injection, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture , systolic BP is not significantly change in all experiment time. 2. After distilled Astragali Radix Herbal Acupuncture injection, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture , diastolic BP is not significantly change in all experiment time. 3. After distilled Astragali Radix Herbal Acupuncture injection, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture , pulse is not significantly change in all experiment time. 4. After distilled Astragali Radix Herbal Acupuncture injection, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture , resperation is not significantly change in all experiment time. Conclusions : The results suggest that distilled Astragali Radix Herbal Acupuncture, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture in healthy adult man don't influence vital sign within normal range. This result is derived from that distilled Astragali Radix Herbal Acupuncture, Wild Ginseng Herbal Acupuncture and Rehmannia glutinosa Herbal Acupuncture in healthy adult man are safety.