Explore the vast range of titles available.

Silicon carbide (SiC) bicrystals were prepared by diffusion bonding, and their grain boundary was observed using scanning transmission electron microscopy. The n-type electrical conductivity of a SiC single crystal was confirmed by scanning nonlinear dielectric microscopy (SNDM). Dopant profiling of the sample by SNDM showed that the interface acted as an electrical insulator with a ~2-μm-thick carrier depletion layer. The carrier depletion layer contained a higher number of oxygen impurities than the bulk crystals due to the incorporation of oxygen from the native oxide film during diffusion bonding. Density functional theory calculations of the density of states as a function of the bandgap also supported these findings. The existence of a carrier depletion layer was also confirmed in a p-type polycrystalline SiC ceramic. These results suggest that the electrical conductivity of SiC ceramics was mostly affected by carrier depletion near the grain boundary rather than the grain boundary itself.

This study compared and analyzed changes in the microclimate and thermal environment inside single-span greenhouses covered with a single layer of plastic film, polycarbonate (PC), and glass. The results of the experiment show that the PC-covered greenhouse was the most favorable for managing the nighttime heating effect during the cold season. However, the glass-covered greenhouse was found to be the most favorable for managing the cooling effect during the hot season. Although the plastic-covered greenhouse was inexpensive and easy to install, the air temperature inside varied significantly, and it was difficult to control its indoor environment. The thermal load leveling values showed that the PC-covered greenhouse had the lowest variation, confirming its superiority in terms of environmental control and energy savings. In terms of the overall heat transfer, heat was generally transferred from the interior to the exterior of the greenhouses. In the plastic-covered greenhouse, however, heat was transferred in the opposite direction at night due to the influence of radiant cooling. The occurrence of the minimum and maximum heat transfer values had a tendency similar to that of the occurrence of the minimum and maximum air temperatures inside the greenhouses.

Boiling heat transfer, utilizing latent heat during phase change, has widely been used due to its high thermal efficiency and plays an important role in existing and next-generation cooling technologies. The most critical parameter in boiling heat transfer is critical heat flux (CHF), which represents the maximum heat flux a heated surface can sustain during boiling. CHF is primarily influenced by the wicking performance, which governs liquid supply to the surface. This study experimentally and numerically analyzed the wicking performance of micropillar structures at various temperatures (20–95 °C) using distilled water as the working fluid to provide fundamental data for CHF prediction. Infrared (IR) visualization was used to extract the wicking coefficient, and the experimental data were compared with computational fluid dynamics (CFD) simulations for validation. At room temperature (20 °C), the wicking coefficient increased with larger pillar diameters (D) and smaller gaps (G). Specifically, the highest roughness factor sample (D04G10, r = 2.51) exhibited a 117% higher wicking coefficient than the lowest roughness factor sample (D04G20, r = 1.51), attributed to enhanced capillary pressure and improved liquid supply. Additionally, for the same surface roughness factor, the wicking coefficient increased with temperature, showing a 49% rise at 95 °C compared to 20 °C due to reduced viscous resistance. CFD simulations showed strong agreement with experiments, with error within ±10%. These results confirm that the proposed numerical methodology is a reliable tool for predicting wicking performance near boiling temperatures.

This study comprehensively analyzed the heat loss and total heat transfer coefficient (U-value) of a single-span experimental plastic greenhouse covered with a double layer of 0.1 mm thick polyethylene. The air temperature and heat flux (W m−2) of the greenhouse components were measured from 18:00 to 06:00, and the energy balance equations under steady-state conditions were determined. The heat flux and U-value of the roof, sides, front and rear, and floor of the greenhouse were determined and compared. The results showed that these values for the roof play an important role in determining the heat load in the greenhouse, and that the average heat transfer through the floor is very small. The average U-value of the greenhouse cover is a comprehensive value which takes the U-values of the roof, sides, and front and rear into account through the use of an area–weighted average method. Finally, an average U-value of 3.69 W m−2 °C −1 was obtained through the analysis of the variations in the U-value, as it is related to the difference in air temperature between the interior and exterior of the greenhouse, as well as to the outdoor wind speed. The relationships between the average U-value and those of the roof, sides, and front and rear of the experimental greenhouse were modeled, and were shown to have a highly linear relationship.

Purpose: This study explores the relationship between the performances of national equity funds and business cycles in Korea. Design/methodology/approach: First, this research examines how fund performance is better in recessions than in expansion periods and then analyzes fund performance by dividing funds into active and passive operating styles. Last, what risk factors affect performance with respect to business cycles and operating cycles are investigated. Findings: The empirical findings show that fund performance is affected by the economic variables of short-term interest rates, credit risk spread, growth in money stock, and corporate value.However, the effects change with the business cycle.In addition, the fund performance of overall, internal, and outsourcing investments is better in recessions than in expansion periods, which agrees with foreign studies. Research limitations/implications: When assessing fund managers abilities, not only quantitative performance but also qualitative assessment - economic conditions - become important.It is necessary to evaluate fund performance with a system that considers economic fluctuations. Originality/value: This is the first research to analyze the performance of the national pension fund using the regime-switching model in the Korean market.

(1) Background: We studied how the generation position of air anions in a closed-type plant factory affects the growth characteristics of lettuce and identified the optimal position. (2) Methods: We used LEDs (red/green/blue = 8:1:1) as a light source and set the temperature and RH of the plant factory to 20 ± 2 ℃ and 50% ± 5%, respectively. We grew lettuce under three air anion conditions—sideward, upward, and downward—and compared the growth characteristics to those of a control grown without air anions. We measured the growth characteristics of the lettuce at 3 and 4 weeks after sowing, and the measurement items were shoot fresh weight (FW) and dry weight (DW); leaf area (LA), length (LL), and width (LW); SPAD; antioxidant capacity; and total phenol content. (3) Results: At 4 weeks, FW in the downward treatment condition was 25.3% higher than in the control, and DW showed a similar difference. LA was about 1943.94 cm²/plant in the downward treatment condition, which was about 15.5% higher than in the control. (4) Conclusions: We conclude that air anion generation has a positive effect on lettuce growth, and the optimal generation position for air anions is downward.

Purpose: This study utilizes the KNV measure to evaluate performance of national pension funds of Korea. Design/methodology/approach: First, this study investigates whether fund managers pick stocks in expansions and time the market in recessions. Second, we examine skilled funds that have both high picking skill in booms and high timing skill in recessions. Third, we examine whether skilled managers have timing ability as well as picking ability. Finally, persistence of skill indexes is investigated. Findings: First, market timing skill is more relevant in recessions whereas stock selection skill is more relevant in expansions. Second, the performance differences between superior and inferior funds are persistent over one-year. Finally, there is no evidence that the same fund managers who display superior stock picking skill in expansions show superior market timing skill in recessions. Research limitations/implications: Since no institutions or organizations provide real-time indicators of the business cycle, switching strategy between timing and picking is not available. Originality/value: This is the first research to analyze the national pension fund using KNV methodology in the Korean market.

Purpose: This study criticizes the existing benchmarks of the national equity fund specified by the National Pension Service and proposes alternative benchmarks. Design/methodology/approach: First, this study investigates whether the existing benchmarks returns are affected by the value and momentum factors. Second, we examine the effects of different factors on the benchmark returns of internal and outsourcing investments. Third, we propose three benchmarks by including the value factor and/or momentum factor. Finally, the Sharpe ratios of return-to-risk are used to measure these proposed benchmarks compared to the existing benchmarks. Findings: First, the existing benchmarks of internal and outsourcing investments are associated with value and momentum factors, which have been observed in many other countries. Second, the Sharpe ratios of the three proposed benchmarks - value oriented, momentum oriented, and value & momentum oriented - are always better than the existing benchmarks. Third, the Sharpe ratio of the value oriented benchmark is better than that of the momentum oriented and value & momentum oriented benchmarks. Finally, the Sharpe ratios are better with increased investment weights of value and/or momentum. Research limitations/implications: This study uses the Sharpe ratio to measure the return-to-risk relationship. There could be other measures to capture the relationship. Originality/value: This is the first research to analyze the national pension equity fund with proposed benchmarks in the Korean market.

PurposeThis study introduces the global research and technological trends related to various kinds of Information and Communications Technologies (ICTs) used and applied in the livestock industry by improving productivity via breeding, disease and optimal environment control, and smart business management.MethodPrior research data was collected using “ICT,” “IoT,” “information technology (IT),” “ubiquitous technology,” “smart livestock,” and “big data” as main keywords.ResultsMost livestock farms in Korea adopt smart livestock technology that are mostly used in the 1st or 1.5th generations, while continuous developments are being carried out for technologies of the 2nd and 3rd generations. In the livestock house, camera vision, radio-frequency identification (RFID), beacon sensors, and environmental sensors are used in livestock farms and houses to collect information compiled into a database to introduce an automated system for livestock management.ConclusionThe data collected from each individual and farm can enable precise breeding and ultimately improve the productivity and efficiency of smart livestock systems. It is necessary to prepare a systematic system at the national level for data collection, ownership, and sharing to improve the productivity and efficiency of the smart livestock system.

The aim of this study was to analyze the effects of the planting distance and depth on the power take-off (PTO) load spectrum of a small riding-type transplanter for the optimal design of the transplanter. To measure load data during actual planting operation, a load measurement system was developed using a torque sensor, a data acquisition system, and an inverter. Field experiments were conducted at four planting distances (26 cm, 35 cm, 43 cm, and 80 cm) and three planting depths (85 mm, 105 mm, and 136 mm) in a field with similar soil conditions. The measured load data were inverted into a load spectrum using rain-flow counting and Smith-Watson-Topper (SWT) methods. The safety factor of a transplanter according to the planting conditions was analyzed using the converted load spectrum and commercial software. The load spectrum for all planting conditions showed torque ratios similar within a high cycle region of 108 to 109. The torque ratio increased when the planting depth increased and planting distance decreased in the low cycle region under less than 108 cycles. The safety factors of the PTO driving gear and the driven gear increased as the planting distance increased at all planting depths. When the planting depth decreased at the same planting distance, the safety factor of the PTO gears increased. The results of this study might provide useful information for a transplanter PTO design considering the working load according to the various planting conditions.