• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.36 no.3
• /
• pp.249-254
• /
• 2023

La_0.7-xCe_xSr_0.3MnO₃ specimens were fabricated by a solid state reaction method and structural and electrical properties with variation of Ce⁴⁺ contents were measured. All specimens exhibited a polycrystalline rhombohedral crystal structure, and the (110) peaks were shifted to low angle side with increasing the amount of Ce⁴⁺ contents. As Ce⁴⁺ ions with different ion radii and charges are substituted with La³⁺ ions, electrical properties are thought to be affected by changes in the double exchange interaction between Mn³⁺-Mn⁴⁺ ions due to distortion of the unit lattice, a decrease in oxygen vacancy concentration, and an increase in lattice defects. Resistivity gradually decrease as the amount of Ce⁴⁺ added increased, and negative temperature coefficient of resistance (NTCR) properties were shown in all specimens. In the La_0.5Ce_0.2Sr_0.3MnO₃ specimens, electrical resistivity, TCR and B-value were 31.8 Ω-cm, 0.55%/℃ and 605 K, respectively.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.2
• /
• pp.66-73
• /
• 2008

In this study, the characterization of minor livestock's excretions in terms of unit load generation and discharge was conducted by investigation and analysis of urine, manure and wastewater from stall of fowl, duck, horse, deer, goat and sheep. The results are summarized as follows: The unit load generation of fowl estimated by discharged amount and concentration analysis increases in egg layers due to the difference of planting head numbers, feed stuffs and manure disposal. In case of deer unit load generation by herbivora were calculated to be higher than data from existing references because of the gap between weight per livestock and the generation amounts of manure and urine. In case of sheep unit load generation by urine were analyzed two times higher than by manure but unit load generation by manure were reported higher than by urine in references, so large differences between this and previous study resulted.

• Journal of the Korea Safety Management & Science
• /
• v.15 no.3
• /
• pp.151-161
• /
• 2013

This paper proposes a strategic model of linkage between productivity metrics and financial accounting metrics to properly evaluate the financial effect of TPM activities and the business performance. This linkage strategy provides a connection tool for clear communication between factory-level and headquarters that the metrics proposed by this paper ultimately improves a quality of support from the management by receiving the factors required for productivity activities in the practical field. This factor includes such as equipment, raw materials and labors. Here, we propose that chain reaction models using break down structure of productivity metrics and financial metrics enhance the knowledge sharing of KPI (Key Performance Indicator) which generally tend to create oversimplified communication between management in headquarters and employees in the practical fields. The productivity metrics include OEE(Overall Equipment Effectiveness) of TPM (Total Productive Maintenance), OLE (Overall Labor Effectiveness) of PAC(Performance and Analysis and Control) activities, and OYE (Overall Yield Effectiveness) of TMM(Total Material Management) activities. The financial accounting metrics include ROE(Return on Equity), ROA(Return on Asset), and AVR(Added-Value Rate). The suggested chain reaction model selects the financial metrics as initial stage and branch down until final stage of productivity metrics. When demand exceeds supply, an ideal speed rate, the lean OEE strategy can be initially applied to reduce the gap between the demand and supply, then apply variable costing to estimate correct amount of operating profit. In addition, the paper presents a new type of model for linkage between financial accounting metrics including CAPEX(Capital Expenditure), OPEX(Operating Expenditure), EVA(Economic Added Value), DCL(Degree of Combined Leverage), and TPM productivity activities including AM(Autonomous Maintenance), PM(Preventive Maintenance), MP(Maintenance Prevention) and QM(Quality Maintenance). In order to support the evidence of proposed linkage strategy, a case analysis on 52 projects from national TPM contest from 2011 to 2012 is analyzed. The case presents the classification of CAPEX and OPEX activities from TPM, and proposes the correct implementation of financial effect for TPM projects.

• Journal of the Microelectronics and Packaging Society
• /
• v.7 no.2
• /
• pp.21-27
• /
• 2000

To develop the underfill materials which are required for the new process of semi-conductor industry, the properties of epoxy/anhydride/cobalt(II) catalyst system with two types of fused silica(1 $\mu\textrm{m}$, 8 $\mu\textrm{m}$) are studied as a function of filler fraction. According to the curing profile, the optimum catalyst amount was 1.0 wt% for full curing at the conditions of $160^{\circ}C$/l5 min., and we could conclude that the viscosity has superior effect on the real flaw through the relationship between surface tension and viscosity data. The underfills which were filled with 1 $\mu\textrm{m}$ fused silica did not show good flowability, but they should be useful by improving the viscosity for a future process which has small gaps. The underfills which were filled with 8 $\mu\textrm{m}$ fused silica showed good flowability when the filler contents were 55~60 vol%. The model which was referred by Matthew can predict the real flow length only when the underfill has high viscosity and low surface tension.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.416-416
• /
• 2016

Organic-inorganic metal halide perovskite solar cells have received attention because it has a number of advantages with excellent light harvesting, high carrier mobility, and facile solution processability and also recorded recently power conversion efficiency (PCEs) of over 20%. The major issue on perovskite solar cells have been reached the limit of small area laboratory scale devices produced using fabrication techniques such as spin coating and physical vapor deposition which are incompatible with low-cost and large area fabrication of perovskite solar cells using printing and coating techniques. To solution these problems, we have investigated the feasibility of achieving fully printable perovskite solar cells by the blade-coating technique. The blade-coating fabrication has been widely used to fabricate organic solar cells (OSCs) and is proven to be a simple, environment-friendly, and low-cost method for the solution-processed photovoltaic. Moreover, the film morphology control in the blade-coating method is much easier than the spray coating and roll-to-roll printing; high-quality photoactive layers with controllable thickness can be performed by using a precisely polished blade with low surface roughness and coating gap control between blade and coating substrate[1]. In order to fabricate perovskite devices with good efficiency, one of the main factors in printed electronic processing is the fabrication of thin films with controlled morphology, high surface coverage and minimum pinholes for high performance, printed thin film perovskite solar cells. Charge dissociation efficiency, charge transport and diffusion length of charge species are dependent on the crystallinity of the film [2]. We fabricated the printed perovskite solar cells with large area and flexible by the bar-coating. The morphology of printed film could be closely related with the condition of the bar-coating technique such as coating speed, concentration and amount of solution, drying condition, and suitable film thickness was also studied by using the optical analysis with SEM. Electrical performance of printed devices is gives hysteresis and efficiency distribution.

• Journal of the Korean Ceramic Society
• /
• v.52 no.4
• /
• pp.294-298
• /
• 2015

Blocking layers with nano carbon blacks (NCBs) were prepared by adding 0.0 ~ 0.5 wt% NCBs to the $TiO_2$ blocking layer. Then, dye sensitized solar cells (DSSCs) were fabricated with a $0.45cm^2$ active area. TEM and micro-Raman spectroscopy were used to characterize the microstructure and phases of the NCBs, respectively. Optical microscopy and AFM were used to analyze the microstructure of the $TiO_2$ blocking layer with NCBs. UV-VIS-NIS spectroscopy was used to determine the band gap of the $TiO_2$ blocking layer with NCBs. A solar simulator and potentiostat were used to determine the photovoltaic properties and impedance of DSSCs with NCBs. The energy conversion efficiency (ECE) increased from 3.53 to 6.20 % when the NCB content increased from 0.0 to 0.3 wt%. This indicates that the effective surface area and electron mobility increased in the $TiO_2$ blocking layer with NCBs. However, the ECE decreased when the NCB content was increased to over 0.4 wt%. This change occurred because the effective electron transport area decreased with the addition of excessive NCBs to the $TiO_2$ blocking layer. The results of this study suggest that the ECE of DSSCs can be enhanced by adding the appropriate amount of NCBs to the $TiO_2$ blocking layer.

• Journal of Information Technology Services
• /
• v.18 no.5
• /
• pp.165-182
• /
• 2019

An equity crowdfunding system of Korea has been introduced since January 25, 2016. The crowdfunding has contributed to remove the funding gap for startups in Korea. In the three years since the introduction of the system, the amount issued has been growing annually 31 percent. In 2018, the general investors who participated in equity crowdfunding, account for 93.8% of the total market size. General investors are a large part of equity crowdfunding. Investors, however, are facing the information asymmetry problems. General investors rely heavily on the investment prospectus provided by startups to obtain the information they need to determine their investment decisions. Under these circumstances, startups have the incentive to provide information that is advantageous to them, and investors are likely to be adversely affected by the investment prospectus. In this study, we collected the novel crowdfunding prospectus dataset: a total of 459 investment prospectus and conducted a morphological analysis. The analysis showed that the more positive the word, the higher the success rate of investors' subscriptions. We also compared projects that were heavily invested by general investors with projects that were heavily invested by professional investors. Then, we were able to examine that the success rates of project subscription, which were heavily invested by general investors, were higher than the projects of professional investor type. It can be interpreted as a general investor driven crowdfunding market. Based on these results, we propose three policies. First, the supervisor should be strengthened to provide more detailed information on investment risk factors in the prospectus. Second, the crowdfunding intermediary should monitor information provided by startups. Third, an investor should be asked to add a question to the investment compliance test that allows the investor to recognize the problem in the manual.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.04a
• /
• pp.19-19
• /
• 2009

Dynamic Stall is a flow phenomenon which occurs on the retreating side of helicopter rotor blades during forward flight. It also occurs on blades of stall regulated wind turbines under yawing conditions as well as during gust loads. Time scales occurring during this process are comparable on both helicopter and wind turbine blades. Dynamic Stall limits the speed of the helicopter and its manoeuvrability and limits the amount of power production of wind turbines. Extensive numerical as well as experimental investigations have been carried out recently to get detailed insight into the very complex flow structures of the Dynamic Stall process. Numerical codes have to be based on the full equations, i.e. the Navier-Stokes equations to cover the scope of the problems involved: Time dependent flow, unsteady flow separation, vortex development and shedding, compressibility effects, turbulence, transition and 3D-effects, etc. have to be taken into account. In addition to the numerical treatment of the Dynamic Stall problem suitable wind tunnel experiments are inevitable. Comparisons of experimental data with calculated results show us the state of the art and validity of the CFD-codes and the necessity to further improve calculation procedures. In the present paper the phenomenon of Dynamic Stall will be discussed first. This discussion is followed by comparisons of some recently obtained experimental and numerical results for an oscillating helicopter airfoil under Dynamic Stall conditions. From the knowledge base of the Dynamic Stall Problems, the next step can be envisaged: to control Dynamic Stall. The present discussion will address two different Dynamic Stall control methodologies: the Nose-Droop concept and the application of Leading Edge Vortex Generators (LEVoG's) as examples of active and passive control devices. It will be shown that experimental results are available but CFD-data are only of limited comparison. A lot of future work has to be done in CFD-code development to fill this gap. Here mainly 3D-effects as well as improvements of both turbulence and transition modelling are of major concern.

• Journal of the Korea Concrete Institute
• /
• v.27 no.4
• /
• pp.387-397
• /
• 2015

In the present study, to enhance the constructability, a composite slab system using deck plate and micro steel fiber concrete was studied. In the proposed slab system, on-situ re-bar placement is not required. Steel fibers replace the temperature reinforcement. The present study focused on the crack control at the slab top in the continuous composite slab without spliced bars. Eight continuous slabs with various parameters were tested under vertical loading. The test parameters were the amount and types of micro steel fibers, types of deck plate, and the use of top bars in the continuous slab. To evaluate the crack resistance of the slabs, crack widths were measured in the continuous slabs. The test results showed that although the top spliced bars were not used, cracking were restrained by large flexural stiffness of the composite sections.

• Journal of Ecology and Environment
• /
• v.31 no.3
• /
• pp.167-176
• /
• 2008

Atmospheric N deposition has far-reaching impacts on forest ecosystems, including on-site impacts such as soil acidification, fertilization, and nutrient imbalances, and off-site environmental impacts such as nitrate leaching and nitrous oxide emission. Although chronic N deposition has been believed to lead to forest N saturation, recent evidence suggests that N retention capacity, particularly in the forest floor, can be surprisingly high even under high N deposition. This review aims to provide an overview of N retention processes in the forest floor and the implications of changing C-N interactions for C sequestration. The fate of available N in forest soils has been explained by the competitive balance between tree roots, soil heterotrophs, and nitrifiers. However, high rates of N retention have been observed in numerous N addition experiments without noticeable increases in tree growth and soil respiration. Alternative hypotheses have been proposed to explain the gap between the input and loss of N in N-enriched, C-limited systems, including abiotic immobilization and mycorrhizal assimilation, both of which do not require additional C sources to incorporate N in soil N pools. Different fates of N in the forest floor have different implications for C sequestration. N-induced tree growth can enhance C accumulation in tree biomass as observed across temperate regions. C loss from forests can amount to or outweigh C gain in N-saturated, declining forests, while another type of 'C-N decoupling' can have positive or neutral effects on soil C sequestration through hampered organic matter decomposition or abiotic N immobilization, respectively.