• Journal of the Semiconductor & Display Technology
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• v.17 no.1
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• pp.76-83
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• 2018

The electron energy probability function (EEPF) is of significant importance since the plasma chemistry such as the rate of ionization is determined by the electron energy distribution function. It is usually assumed to be Maxwell distribution for 0-D global model. Meanwhile, it has been observed experimentally that the form of EEPF of Ar plasma changes from being two-temperature to Druyvesteyn like as the gas pressure increases. Thus, to apply the 0-D global model of Maxwellian distribution to the non-Maxwellian plasma, we investigated the relative contribution of two distinct electrons with different temperatures. The contributions of cold/hot electrons to the equilibrium state of the plasma have attracted interest and been researched. The contributions to the power and particle balance of cold/hot electrons were studied by comparing the result of the global model considering all combinations of electron temperatures with that of 1-D Particle-in-Cell and Monte Carlo collision (PIC-MCC) simulation and the results of studies were analyzed physically. Furthermore, comparisons term by term for variations of the contribution of cold/hot electrons at different driving currents are presented.

• Advances in materials Research
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• v.8 no.1
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• pp.11-24
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• 2019

This paper presents a review study for energy-efficient gas turbines (GTs) with cycles which contributes significantly towards sustainable usage. Nonetheless, these progressive engines, operative at turbine inlet temperatures as high as $1600^{\circ}C$, require the employment of highly creep resistant materials for use in hotter section components of gas turbines like combustion chamber and blades. However, the gas turbine obtain its driving power by utilizing the energy of treated gases and air which is at piercing temperature and pushing by expanding through the several rings of steady and vibratory blades. Since the turbine blades works at very high temperature and pressure, high stress concentration are observed on the blades. With the increasing demand of service, to provide adequate efficiency and power within the optimized level, turbine blades are to be made of those materials which can withstand high thermal and working load condition for longer cycle time. This paper depicts the recent developments in the field of implementing the best suited materials for the GTs, selection of proper Thermal Barrier Coating (TBC), fracture analysis and experiments on failed or used turbine blades and several other designing and operating factors which are effecting the blade life and efficiency. It is revealed that Nickel based Superalloys were promising, Cast Iron with Zirconium and Pt-Al coatings are used as best TBC material, material defects are the foremost and prominent reason for blade failure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.110-115
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• 2019

$Pb(Sb_{0.5}Nb_{0.5})_x(Zr_{0.51}Ti_{0.49})_{1-x}O_3$ (abbreviation: PSN-PZT) ceramics were synthesized, using conventional bulk ceramic processing technology, with various PSN doping contents. The maximum density of PSN-PZT was 97% of the theoretical density in the samples sintered at $1,250^{\circ}C$. The maximum values of the piezoelectric properties achieved using the conventional processes were: $k_p$ of 0.625, $d_{33}$ of 531 pC/N, and $g_{33}$ of $33mV{\cdot}m/N$. Finally, we fabricated a piezo-speaker with the optimized PSN-PZT ceramics. The SPL of the speaker was measured at a distance of 1 m, with a driving voltage of $40V_{rms}$ in the frequency range of ~300 Hz to 9 kHz. The measured $SPL_{max}$ was at a very high level (95 dB), which was superior in quality in comparison with those of other commercial products.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.1
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• pp.25-30
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• 2021

The differential gear system is a device designed to distribute the driving force of both vehicle wheels and control the rotational speed when the vehicle turns on a curve. The differential device consists of a differential gear case, a ring gear, and a pressure ring. A differential pinion gear and side gear are mounted on the differential pinion shaft inside the differential gear case. In this study, a pin press-fitting device that mounts the pinier gear and side gear to the differential pinion shaft in the differential gear case was designed, and a jig device for pin press-fitting using servo press was developed. In addition, by precisely measuring the pin press-in load and press-in distance according to the pin hole diameter of the differential gear shaft, the optimization of the pin pressin process was established.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.835-842
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• 2022

In this study, the membrane degassing process of the sweep gas - vacuum combination type was proposed for ammonia wastewater treatment. The effect of pH, initial ammonia concentration and scale-up on ammonia degassing performance was investigated. As a result, as the pH and the initial ammonia concentration increased, the degassing permeate flux was improved. On the other hand, the ammonia mass transfer coefficient increased as the initial ammonia reduced, which seems to be due to the driving force of the sweep gas-vacuum combination type membrane degassing system proposed in this study. In addition, 80 mg NH₃/min of the ammonia degassing rate was achieved using a 6×28 inch size module. Better degassing performance is expected if consideration for maintaining vacuum pressure is involved in the scale-up design.

• The Journal of Economics, Marketing and Management
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• v.6 no.4
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• pp.29-39
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• 2018

Purpose - With the improvement of people's living standards, traveling abroad has become a common way for people to release the pressure of life and work. In economics, this kind of way can affect the international trade. Because of this background, this paper sets BRICS countries as an example to explore the impact of cross-border tourism on bilateral trade. Research design, data, and Methodology - The annual time series data sets form 1998 to 2016 are used to perform an empirical analysis under a series of econometric approaches such as the Phillips-Perron test and the Engle-Granger two-step test. In this paper, the cross-border tourism and the bilateral trade will be used to conduct an empirical analysis based on the econometric approaches to analyze the impact of cross-border tourism on bilateral trade. Results - The finding of this paper show that there is a long-run relationship between cross-border tourism and bilateral trade in this sample. Moreover, the cross-border tourism is the Granger causality of bilateral trade. Namely, the cross-border tourism can promote the development of bilateral trade. Conclusions - In short, the evidences that this paper presents show that the cross-border tourism is a driving factor that impacts the bilateral trade in the sample of BRICS countries.

• Safety and Health at Work
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• v.14 no.3
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• pp.340-346
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• 2023

Background: Truck driving is a highly sedentary occupation that places workers at risk for chronic health conditions, such as obesity and high blood pressure. The primary purpose of this study was to objectively describe truck drivers' typical physical activity (PA) patterns. Methods: We used ~7-10-day baseline PA actigraphy data samples from drivers in the Safety & Health Involvement For Truckers (SHIFT) study (n = 394). Driver PA patterns (e.g., average number of ≥10 minute Freedson bouts per week, time in bouts, and common days/times for PA) were summarized with descriptive analyses. We also compared objective accelerometer data to self-reports. Results: Drivers' weekly PA averaged 14.4 minutes (SD = 37.0), and most PA occurred between 5-6 pm on Tuesdays and Wednesdays. Drivers overestimated self-reported weekly exercise by over 60 min/week compared to accelerometer data. Conclusion: Our results suggest that objective PA assessment may be warranted over self-report when possible, and timing may be key in future PA intervention work with truck drivers.

• Current Photovoltaic Research
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• v.11 no.4
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• pp.108-113
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• 2023

Pressure to reduce costs in the current solar market is driving the development and implementation of new module designs and prompting the use of new materials and components. In order to utilize the variability of each material that makes up the module, it is essential to understand the basic characteristics of the material. In this article, we evaluate light degradation after UV irradiation as an encapsulation material. Measure and analyze the results of various characteristic tests for discoloration, optical and electrical property degradation before and after UV accelerated testing. To evaluate weathering stability, UV tests were performed comparing existing EVA and UVT-EVA, POE and improved low-cost POE. Even in the weather resistance test with a total UV exposure of 60 kW/m², the properties of the encapsulants were mostly stable. EVA and POE-based encapsulants showed slight differences, and these slight differences are believed to pose a threat to long-term stability. This study is a basic analysis of encapsulation research for PV modules and will be helpful in understanding future development and encapsulant properties.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4477-4490
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• 2023

Fuel locking mechanisms (FLMs) are essential in upward-flow research reactors to prevent accidental fuel separation from the core during reactor operation. This study presents a novel design concept for a remotely controlled plate-type nuclear fuel locking mechanism. By employing electromagnetic field analysis, we optimized the design of the electromagnet for fuel unlocking, allowing the FLM to adapt to various research reactor core designs, minimizing installation space, and reducing maintenance efforts. Computational flow analysis quantified the drag acting on the fuel assembly caused by coolant upflow. Subsequently, we performed finite element analysis and evaluated the structural integrity of the FLM based on the ASME boiler and pressure vessel (B&PV) code, considering design loads such as dead weight and flow drag. Our findings confirm that the new FLM design provides sufficient margins to withstand the specified loads. We fabricated a prototype comprising the driving part, a simplified moving part, and a dummy fuel assembly. Through basic operational tests on the assembled components, we verified that the manufactured products meet the performance requirements. This remote-controlled micro locking mechanism holds promise in enhancing the safety and efficiency of plate-type nuclear fuel operation in upflow research reactors.

• Journal of Wetlands Research
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• v.14 no.1
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• pp.75-87
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• 2012

Hyporheic zone is a region beneath and alongside a stream, river, or lake bed, where there is mixing of shallow groundwater and surfacewater. Hyporheic exchange controls a variety of physical, biogeochemical and thermal processes, and provides unique ecotones in a aquatic ecosystem. Field and experimental observations, and modeling studies indicate that hyporheic exchange is mainly in response to pressure gradients driven by the geomorphological features of stream beds. In the reach scale of a stream, pool-riffle structures dominate the exchange patterns. Flow over a pool-riffle sequence develops recirculation zones and stagnation points, and this flow structures make irregular pressure gradient which is driving force of the hyporheic exchange. In this study, 3 D hydro-dynamic model solves the Reynolds-averaged Navier-Stokes equations for the surface water and Darcy's Law and the continuity equation for ground water. The two sets of equations are coupled via the pressure distribution along the interface. Simulation results show that recirculation zones and stagnation points in the pool-riffle structures dominantly control the upwelling and downwelling patterns. With decrease of recirculation zones, length of donwelling zone formed in front of riffles is reduced and position of maximum downwelling point moves downward. The numerical simulation could successfully predict the behavior of hyporheic exchange and contribute the field study, river management and restoration.