• Progress in Medical Physics
• /
• v.28 no.4
• /
• pp.156-163
• /
• 2017

To verify the usefulness of a steam sterilizer equipped with an electronic Bowie-Dick test system, this study was carried out using two methods, utilizing both a steam sterilizer and an electronic Bowie-Dick tester. The first method is to confirm the error detection of the chemical Bowie-Dick test pack and the electronic Bowie-Dick tester in a malfunctioning sterilizer environment. For this purpose, the Bowie-Dick test program for the steam sterilizer was used to test three types of test packs commonly used in hospitals and the electronic Bowie-Dick tester by changing the set values of temperature, time, and vacuum frequency. The second is an experiment to check the sterilizer's normal operation with the electronic Bowie-Dick tester and the usefulness of grasping the cause of the malfunction. The results showed that the sterilization temperature was the same as that of the test pack at a temperature $1{\sim}6^{\circ}C$ lower than the reference temperature of $134^{\circ}C$. In the test with the sterilization exposure time as a variable, there was a normal discoloration at a time difference of 30~90 s. In the experiment using the number of vacuum cycles, the test was correct by performing the normal discoloration only at the normal condition of 3 times. The test results of 30 hospitals were 100 failure tests by a total of 291 Bowie-Dick tests. Of these, the failure factors related to an internal temperature that the chemical test packs could not detect were the greatest, and the four factors related to temperature, including the internal temperature, were found to be 71.18% of total malfunctions. In addition, the Bowie-Dick tester was provided within 30 min after the start of the Bowie-Dick test to confirm the performance of the sterilizer and the detailed cause. A steam sterilizer equipped with an electronic Bowie-Dick test system is used to manage individual sterilizers. In the current steam sterilizer with many temperature-related errors, it is possible to check the malfunction of the temperature difference that the test pack cannot detect, and the cause of error for the sterilizer is immediately detected after the test. The steam sterilizer equipped with the electronic Bowie-Dick test system assists with infection control with accurate sterilizer performance assurance.

• Journal of The Korean Association of Information Education
• /
• v.26 no.3
• /
• pp.187-195
• /
• 2022

Recently, with interest in metaverse, attempts are being made to utilize the metaverse platform in various forms. In this paper, we focused on the educational application potential of metaverse, and developed and applied a metaverse STEAM program to provide an effective learning experience to learners in non-face-to-face educational situations. The developed program utilizes Minecraft and ZEPETO, familiar to students, as metaverse learning platforms, and consists of a total of 16 lessons of 5 modules in the form of modules so that alternative classes can take place in the educational field. Through this, the learner's change in STEAM attitude and learning satisfaction were measured, and through the developed STEAM program, the learner's interest, consideration, communication, usefulness, self-concept, self-efficacy, and career choice areas significantly increased. In addition, positive results were confirmed in all areas of the learner satisfaction test related to satisfaction, interest, and overall class. In the future, considering the characteristics of the metaverse, it is necessary to break free from the constraints of time and space to communicate anew, and various learner-centered educational approaches based on a high degree of freedom and immersion should be implemented.

• Nuclear Engineering and Technology
• /
• v.54 no.11
• /
• pp.4348-4358
• /
• 2022

The thermal-hydraulics phenomena in a containment during an accident will necessarily include radiative heat transfer (i) within the gas mixture due to the high radiative absorption and emission of steam and (ii) between the gas mixture and the surrounding structures. The analysis of some previous PANDA experiments (PSI, Switzerland) demonstrated the importance of the proper modelling of radiation for the benefit of numerical simulations. These results together with dedicated scoping calculations conducted for the present experiments indicated that the radiative heat transfer is considerable, even for a very low amount of steam (≈2%). The H2P2 series conducted in the large-scale PANDA facility at the Paul-Scherrer-Institut (PSI) in the framework of the OECD/NEA HYMERES-2 project is intended to enhance the understanding of thermal radiation phenomena and to provide a benchmark for corresponding numerical simulations. Thus, the test matrix was tailored around the two opposite extremes: either gas compositions with small steam content such that radiative heat transfer phenomena can be neglected. Or gas mixtures containing larger amounts of steam, so that radiative heat transfer is expected to play a dominant role. The H2P2 series consists of 5 experiments designed to isolate the radiation phenomena from convective and diffusive effects as much as possible. One vessel with a diameter of 4 m and a height of 8 m was preconditioned with different mixtures of air / steam at room and elevated temperatures. This was followed by the build-up of a stable helium stratification at constant pressure in the upper part of the vessel. After that, helium was injected from the top into the vessel which leads to an increase of the vessel pressure and a corresponding elevation-dependent and transient rise of the gas temperature. It is shown that even the addition of small amounts of steam in the initial gas atmosphere considerably impacts the radiative heat transport throughout all phases of the experiments and markedly influences i) the monitored gas peak temperature, ii) the temperature history during the compression and iii) the following relaxation phase after the compression was stopped. These PANDA experiments are the first of its kind conducted in a large scale thermal-hydraulic facility.

• Journal of Korean Elementary Science Education
• /
• v.42 no.4
• /
• pp.605-617
• /
• 2023

In this study, a STEAM program emphasizing the engineering design process was developed and applied to investigate its effects on the creative engineering problem-solving proficiency and self-directed learning ability of elementary school students. In addition, the study compared and analyzed differences according to gender. The program was conducted across five sessions targeting 141 students in the fourth grade in an elementary school in the Gyeongin area. The study measured the creative engineering problem-solving disposition and self-directed learning ability of the students before and after the STEAM program. It also administered satisfaction and perception tests. The result confirmed that the STEAM program that emphasizes the engineering design process is effective in improving the creative engineering problem-solving propensity and self-directed learning ability of elementary school students, particularly female ones. Analyzing differences in changes based on gender, the study pinpointed significant improvements among female students in all factors except for the subfactor communication and collaboration within tendencies toward creative engineering problem-solving. For male students, the study observed significant effects in the factors engineering design and communication and collaboration. Lastly, the study discussed the educational implications of the findings.

• Korean Chemical Engineering Research
• /
• v.61 no.3
• /
• pp.479-486
• /
• 2023

In this study, we investigated the effect of the Ce_xZr_1-xO₂ (CZ) addition onto Ni/Al₂O₃ catalysts on the catalytic performance in methane steam reforming. In the reaction results, the CZ-added Ni/Al₂O₃ catalyst showed higher CH₄ conversion and H₂ yield under the same reaction conditions than Ni/Al₂O₃. From the characterization data, the two catalysts had similar support porosity and Ni dispersion, confirming that the two properties could not determine the catalytic performance. However, the oxygen vacancy over the CZ-added Ni/Al₂O₃ catalyst induced an efficient steam activation at low reaction temperatures, resulting in an increase in the catalytic activity and H₂ yield.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.5
• /
• pp.380-388
• /
• 2002

This paper describes the optimum design for low-pressure steam turbine rotor of 1,000 MW nuclear power plant by using a combined genetic algorithm, which uses both a genetic algorithm and a local concentrate search algorithm (e.g. simplex method). This algorithm is not only faster than the standard genetic algorithm but also supplies a more accurate solution. In addition, this algorithm can find the global and local optimum solutions. The objective is to minimize the resonance response (Q factor) and total weight of the shaft, and to separate the critical speeds as far from the operating speed as possible. These factors play very important roles in designing a rotor-bearing system under the dynamic behavior constraint. In the present work, the shaft diameter, the bearing length, and clearance are used as the design variables. The results show that the proposed algorithm can improve the Q factor and reduce the weight of the shaft and the 1st critical speed.

• Transactions of the Korean hydrogen and new energy society
• /
• v.13 no.2
• /
• pp.119-126
• /
• 2002

The methanol partial oxidation using commercial $CuO/ZnO/Al_2O_3$ catalysts in a plug flow reactor was studied in the temperature range of $200{\sim}250^{\circ}C$ at atmospheric pressure, It was achieved the high activities by Cu-based catalysts and the selectivity of $CO_2$/$H_2$ was 100% when $O_2$ was fully convened. The reactivity changes and their hysteresis with increasing/decreasing temperatures were observed due to the chemical state differences between the oxidation and the reduction on the Cu surface, It was suggested as the two-step reaction: the complete oxidation and the following steam reforming for methanol, which was indicated by the distributions of final products vs. the residence time. In addition, the complete oxidation step was shown to be extremely fast and the total reaction rate can be controlled by the steam reforming reaction.

• Nuclear Engineering and Technology
• /
• v.47 no.3
• /
• pp.267-283
• /
• 2015

The main objective of this study is to investigate experimentally the two-phase flow characteristics in terms of the direct contact condensation of a steam-water stratified flow in a horizontal rectangular channel. Experiments were performed for both air-water and steam-water flows with a cocurrent flow configuration. This work presents the local temperature and velocity distributions in a water layer as well as the interfacial characteristics of both condensing and noncondensing fluid flows. The gas superficial velocity varied from 1.2 m/s to 2.0 m/s for air and from 1.2 m/s to 2.8 m/s for steam under a fixed inlet water superficial velocity of 0.025 m/s. Some advanced measurement methods have been applied to measure the local characteristics of the water layer thickness, temperature, and velocity fields in a horizontal stratified flow. The instantaneous velocity and temperature fields inside the water layer were measured using laser-induced fluorescence and particle image velocimetry, respectively. In addition, the water layer thickness was measured through an ultrasonic method.

• Nuclear Engineering and Technology
• /
• v.49 no.3
• /
• pp.621-631
• /
• 2017

Many developing countries considering the introduction of nuclear power find that large-scale reactor plants in the range of 1,000 MWe to 1,600 MWe are not grid appropriate for their current circumstance. By contrast, small modular reactors are generally too small to make significant contributions toward rapidly growing electricity demand and to date have not been demonstrated. This paper proposes a radically simplified re-design for the nuclear steam cycle for a medium-sized reactor plant in the range of 600 MWe. Historically, balance of plant designs for units of this size have emphasized reliability and efficiency. It will be demonstrated here that advances over the past 50 years in component design, materials, and fabrication techniques allow both of these goals to be met with a less complex design. A disciplined approach to reduce component count will result in substantial benefits in the life cycle cost of the units. Specifically, fabrication, transportation, construction, operations, and maintenance costs and expenses can all see significant reductions. In addition, the design described here can also be expected to significantly reduce both construction duration and operational requirements for maintenance and inspections.

• Corrosion Science and Technology
• /
• v.20 no.2
• /
• pp.69-76
• /
• 2021

In this work, we have performed a corrosion failure analysis of a leaking tube connected to an upper header of a condensate pre-heater in a heat recovery steam generator. It was revealed that the leakage position in the tube was the location where the materials were easily vulnerable due to tensile residual stresses induced by the material manufacturing process and welding process. In addition to an imbalance in the module induced by temperature difference during operation of the pre-heater, the weight of the modules and thermal fatigue provoked a type of stress of tensile-tensile fatigue on the tube. Thus, the leakage position of the pre-heater was exposed to the tensile stress on the inner surface of the tube facing the gas, which rendered the unstable oxide layer susceptible to corrosion and the formation of pits on the water side. The cracks propagated along with the degraded microstructure in a transgranular cracking mode under fatigue loading and finally resulted in water leakage.