• 한국수소및신에너지학회논문집
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• 제7권1호
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• pp.55-62
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• 1996

As an essential step for development of a duel injection hydrogen fueled engine which can obtain high thermal efficiency and power in overall operating range, performance and BFL(back fire limit) equivalance ratio in hydrogen fueled engine with external mixture are investigated. As the results, BFL equivalence ratio in hydrogen fueled engine with external mixture is approximately 0.7. It is deduced that controls of driving conditions are required in transient stage from external mixture type to inner injection type. And in order to increase thermal efficiency, it is also found that BFL equivalence ratio should be expanded as much as possible.

• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.374-381
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• 2007

In order to verify the feasibility of expansion of back-fire limit equivalence ratio in the hydrogen-fueled engine with external mixture, the characteristics of performance and combustion are experimentally analyzed with change of intake/exhaust valve timings under the fixed valve overlap period of $0^{\circ}$ CA(non-valve overlap period). These characteristics are also tested for the change of exhaust valve closing timing while intake valve opening timing is fixed to clear the main cause of back-fire occurrence. As the results, the less valve overlap period center is retarded, the more back-fire limit equivalence ratio increases and back-fire does not occurred after TDC. In addition, it was shown that the control of back-fire is dependent on intake valve opening timing than valve overlap period.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.255-262
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• 2006

To develop a hydrogen fueled engine with external mixture which uses in high reliability, low cost and low pressure, the single cylinder research engine with MCVVT(Mechanical Continuous Variable Valve Timing) system is developed and its basic characteristics analyzed. The MCVVT developed has high reliability and the valve timing change is possible in wide range continuously. Though the mechanical loss due to MCVVT system is increased a little, back-fire suppression research for valve overlap period is no difficulty. It's also confirmed that the hydrogen-fueled engine has lower torque and is possible high lean burn. As fuel-air equivalence ratio is high, as thermal efficiency is remarkable increasing.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.136-141
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• 2013

In order to achieve simultaneously the ultra-low NOx, the high power and the high efficiency in a hydrogen-fueled engine with SI and the external mixture, the effects of low temperature combustion, performance and exhaust are compared and analyzed by the application of the lean boosting. As the results, the decrease rate of the high temperature in the hydrogen is less decreased than the other fuels by high constant-volume specific heat. However, when the conditions of 1.7bar and ${\Phi}=0.33$ are reached by the lean boosting, the maximum gas temperature of hydrogen is decreased under the temperature of NOx formation and it is possible to stabilize combustion below 2% of COVimep. Also, at that condition, it is feasible to achieve simultaneously NOx-free and the power of gasoline level. Therefore, it is found that the lean boosting is useful in the hydrogen-fueled engine.

• 한국수소및신에너지학회논문집
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• 제20권6호
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• pp.464-470
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• 2009

In order to analysis the possibility of high expansion and performance without backfire in a hydrogenfueled engine using external mixture injection, combustion characteristics and performance enhancement were analyzed in terms of retarding valve timing and increasing the boosting pressure. As the results, it was found that thermal efficiency increased by retarding intake valve timing with the same level of supplied energy is over 6.6% by the effect of high expansion including effect of combustion enhancement due to supercharging. It was also shown that the achievement of high power (equal to that of a gasoline engine), low brake specific fuel consumption and low emission (NOx of less than 16 ppm) without backfire in a hydrogen-fueled engine is possible around a boosting pressure of 1.5 bar, intake valve opening time of TDC and $\Phi$=0.35 in fuel-air equivalence ratio.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2606-2613
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• 2022

Spent resin often exceeds radiation limits for safe disposal, creating a need for commercial-scale treatment techniques to reduce resin radioactivity. In this study, the radiological safety of a commercialized spent resin treatment device with a treatment capacity of 1 ton/day was evaluated. The results confirm that the device is radiologically safe in the event of an accident. This device desorbs ¹⁴C from the spent resin, allowing disposal as low-level waste instead of intermediate-level waste. The device also reduces overall waste by recycling the extracted ¹⁴C. Potential accident scenarios were explored to enable dose assessments for both internal and external exposure while preventing further spillage of the device and processing the spilled resin. The scenarios involved the development of a surface fracture on the resin mixture separator and microwave systems, which were operated under pressure and temperature of 0-6 bar and 0-150 ℃, respectively. In the case of accidents with separator and microwave device, the maximum allowable working time of worker were derived, respectively, considering external and internal exposures. When wearing the respirator corresponding to APF 50, in the case of the microwave device accident scenario, the radiological safety was confirmed when the maximum worker worked within 132.1 h.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.282-287
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• 2004

Unielement combustion tests were conducted using coaxial bi-swirl injectors. Major experimental parameters were a recess length and a fuel-side swirl chamber. Combustion efficiency mainly depends on a mixing mechanism for the present coaxial swirl injectors. Low-frequency pressure excitations around 200Hz were observed for all injectors. However, dynamic behaviors considerably differ for an external and an internal mixing case controlled by a recess length. The internal mixing induces mixture to be biased at a specific frequency in a mass flow rate, which results in a relatively high amplitude of pressure fluctuations but results for the external mixing case show that fuel and oxidizer mixture flow carries more complicated, multiple wave characteristics due to broad mixing region as well as disintegration and merging phenomena of propellant films.

• 한국임상수의학회지
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• 제19권2호
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• pp.165-173
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• 2002

The purpose of this study was to evaluate the effect of chitosan-calcium sulfate mixture on early bony consolidation in osteodistracted dogs. The experimental group was divided into 3 groups: saline group(Control), chitosan group(Group CH) and chitosan-calcium sulfate mixture group(Group CH+CS). Four dogs were allocated to each group and classified into B week observation subgroups and 5 week observation subgroups, respectively. Two dogs were allocated to each subgroup. The lateral surface of the left mandibular body was exposed in the subperiosteal plane and vertical osteotomy was carried out on the mandibular body. An external distraction device was applied to the mandibular body. Mandibular distraction was started 5 days after the osteotomy at a rate of 1 m per day for a total of 10 w distraction for 10 days. After completion of distraction, chitosan, chitosan-calcium sulfate and saline were injected into the distracted zone of the group CH, group CH+CS and control. The external device was left in place for 3 or 5 weeks to allow for bony consolidation. Serial radiographs were carried out every week. Two dogs of each group, six dogs in total, were sacrificed at 3 weeks, and the other six dogs at 5 week after distraction. Bone specimens of the distracted mandibles were taken for histologic examination. New bone was not noted in the distracted zone of 3 week observation subgroups in the control and group CH. However, new bone was developed in the group CH+CS with a narrow fibrous interzone in the area of the distracted zone. While osteogenesis was mild in the margin of the distracted Bone of 5 week observation subgroup in the control, new bone was noted much in the group CH and group CH+CS. However, osteogenesis was noted more significantly in the group CH+CS than that of group CH. In conclusion, chitosan-calcium sulfate mixture was more effective on early bony consolidation in distraction osteogenesis

• Journal of Nutrition and Health
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• 제31권4호
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• pp.679-686
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• 1998

This study was performed to determine whether the infusion of nucleosides and a nucleotide mixture directly ito intestinal lumen can induce a regenerative effect on impaired intestinal mucosa. The effects of massive small bowel resention and also total parenteral nutrition were induced by surgical creation of Thirty-Vella fistual in male Sprague-Dawley rats. The rats received saline solution (Control group) or nucleosides and a nucleotide mixture(lower concentration group(Nucl) or higher concentration group (Nuc2) every two days into the fistula. Mucosal protein, DNA , ornithine decarboxylase(ODC) activity, and morphometry were evaluated at 9 or 21 days postoperation in the fistual and also in the residual ileal segment. On the 9th day, mucosal protein, DNA content, and villous surface area in the fistula and also in the residual ileum increased in rats that received nucleosides and a nucleotide mixture of lower concentration (Nuc 1). On the 21 th day, there were no significant differences in intestinal mucosa between the control group and the lower level nucleoside nucleotide mixture-treated group. The fistula villous height of the higher nucleosides and a nucleotide mixture group was higher than in the control rats. Fistula mucosal ODC activities were not significantly different between groups although the mucosal ODC activity of the residual ileal segment was increased on the 9th day. Our data suggests that this animal model is suitable for studying the effect of dietary factors on intestinal mucosal growth and regeneration after villous stropy , differentiating direct effects of diet on the intestine from systemic effects. It is also suggested that external nucleosides and nucleotides have supportive effects on intestinal mucosal regeneration.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.844-851
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• 2009

A soil mixture with low permeability and bentonite as an additive has been highly utilized as a cutoff material in landfills, banks, and dams. Even though it is anticipated that the water can seep through shear failures in the filter layer due to external loads and embankment loads during construction, usually only the coefficient of permeability of the soil mixture is considered rather than the changes of strength from the different amounts of additives. Therefore, the amount of bentonite was changed between 0%~4% in the soil mixture of the bed material to conduct a series of unconfined compressive strength, tensile strength, and shear strength tests on a specimen in order to study the characteristics of the strength. In the result, the unconfined compressive and tensile strength were increased along with the increased amount of bentonite in the low water content; however, the tensile strength in the consolidated-drained shear test generally showed similar values without significant changes.