Electrical properties of quench-condensed thin film

Electrical properties of thin film have been an issue of interest for a long time and there are many applications in contemporary industry. Interesting characteristics, such as a metal-insulator transition and superconductivity, were investigated and applied to manufacturing of various electrical devices. In this line of study, many experimental techniques have been introduced for precise measurement of the properties of thin film. Quench-condensation is one of the important techniques in the research of thin films. To facilitate this research, we built a quench-condensation apparatus which can be used for a variety of experiments. The apparatus was designed for the fabrication of ultra-thin film and the in-situ measurement at low temperature. The apparatus was shown to operate well for the fabrication of thin films while monitoring the growth in-situ. As a part of the preliminary research, we measured the electrical properties of aluminum thin films at liquid nitrogen temperature by using this apparatus. An investigation of the thickness dependent conduction properties was successively performed in-situ. Experimental data showed agreement with theory, in particular the electrical conduction model of Neugebaur and Webb

Metallic membranes for N2 separation & post-combustion CO2 capture improvement

Carbon (CO2) capture represents an important role in the reduction greenhouse gas emissions. Among various CO2 capture technologies currently investigated, post-combustion capture allows for the retrofitting of existing plants and industrial units. Today, the amine scrubbing is considered the most competitive method for CO2 removal in the flue gases from power plants in comparison to other technologies. Nevertheless, recent work has shown that the energy requirement for solvent recovery can decrease the overall efficiency of the power plants up to 16%1. Moreover, additional costs may occur in the solvent absorption technology because of solvent disposal and its continuous replacement due to chemical deterioration. In contrast, membrane systems usually do not require additional chemicals or solvents. In addition, membranes offer higher energy efficiencies, greater operational flexibility as well as simplicity of operation and maintenance. Polymeric membrane operations are currently being explored for CO2 capture in power plants. However, some issues still remain regarding the scalability and reliability of the polymeric materials under real operating conditions where the temperature is often too high for polymer stability. Metallic membranes, by contrast, usually require high temperature for operation and may be more beneficial in saving energy under high temperature conditions. In particular, their use for N2 removal from coal-fired flue gases located nearby the boiler exit may result in increased concentrations of CO2 and pollutants with a significant reduced gas volume in the downstream, allowing for traditional emissions controls to perform more efficiently and, consequently, lowering the overall energy consumption and capital and operating costs. Therefore, the aim of this work is to explore the potentiality of N2-selective metallic membranes for post-combustion CO2 capture. In particular, the effect of different temperature and pressure conditions as well as the effect of different gas exposure on membrane performance, in terms of N2 permeating flux and ideal selectivity of N2 with respect to other gas is studied and analyzed. Moreover, scanning electron microscope (SEM), electron microprobe analyzer (EMPA), and X-ray photoelectron spectroscopy (XPS) analyses are used for investigating the effect of the different operating conditions on the membrane surface. Based on a preliminary theoretical investigation using density functional theory, the Group V transition metals (e.g., vanadium (V), niobium (Nb) and tantalum (Ta)) show strong affinity toward N2. Therefore, these metals are chosen as membrane materials in this study. Pure V, Nb, and Ta foils with a thickness of 40 μm are used. Dp [kPa] 200 300 400 500 N2 Permeance [mol/s·m2·kPa] 3.23·10-8 2.85·10-8 2.78·10-8 2.55·10-8 Permeation tests with pure gases (He, N2 and CO2) are performed to characterize the membranes in terms of N2 permeating flux and ideal selectivity at different temperature and pressure, which are varied from 400 to 600 °C and from 2.0 to 6 bar, respectively. Nb test results are only shown as a particular example in this abstract. In Table 1, the N2 permeances as a function of Δp are reported. The Nb membrane showed complete selectivity towards N2 permeation at 400 °C and trans-membrane pressure (Dp) greater than 3.0 bar. At lower pressure, no N2 permeating flux through the membrane is detected. The Nb membrane is completely destroyed when the temperature is increased up to 500 °C. EMPA analysis on this membrane showed the presence of oxygen on the surface, as illustrated in Figure 1. Among the metallic membranes used in this study, V membrane showed better performance in terms of N2 permeating flux and long-term stability. Therefore, the future study will be focused on the synthesis and analysis of V alloys in order to enhance the N2 permeance and improve the resistant of membrane towards oxidation

Evaluation of dose rate and uncertainty of fuel debris in a canister for the safe retrieval of damaged nuclear fuel

Damaged fuel from core melting accidents like Three Mile Island and Fukushima Daiichi need to be retrieved and disposed. Retrieval of damaged fuel is considerably more complex than for standard fuel as fuel is relocated and deformed during the accident. Two major aspects need to be considered when planning damaged fuel retrieval: prevent to create conditions in which criticality could be achieved and protect workers and equipment from radiation. In the case of the Fukushima Daiichi Power Plant, damaged fuel cannot be covered with water, making retrieval operations more complex as water provides radiation shielding. This work provides an assessment of the radiation emissions from the Fukushima Daiichi damaged fuel necessary to determine shielding requirements. In an initial scoping study, the photon and neutron dose rate of the fuel debris in a canister was evaluated in several parameters including canister designs, source term, geometry of fuel debris. This study provided the basis for the development of methods for the evaluation of the dose rate and uncertainty. The fuel debris was modeled by using random sampling on the size and distribution of fuel debris in a canister. The model uses the Monte Carlo method and performs random sampling on the geometry of the fuel debris to estimate the average dose rate and its standard deviation. SCALE and MCNP codes were used for neutron and photon transport calculations, and a Python code was developed to generate samples and to manage calculations for the evaluation. The Python code efficiently manages calculations of dose rate and flux by applying multiprocessing and parallel computing. The output data was evaluated by basic statistics, and a method which converts the output data into a cumulative format is proposed for the data fitting and the regression analysis of nonlinear data. The model provided variability and uncertainty of the radiation dose rate and flux in detail. However, this method is time consuming and computationally expensive, therefore, an analytical method is developed to approximately evaluate the flux and uncertainty in relatively short time. The uncertainty of dose rate was evaluated as the standard deviation and the relative range of estimated dose rates. The uncertainty depends on the size of fuel debris, and uncertainty of a canister with larger debris is larger. The standard deviation can be larger than 30% of the average dose rate, and the relative range can be larger than 90% of the average dose rate depending on the condition of fuel debris. The uncertainty increases when canisters are contained in a transport cask which has several canisters in it. The average dose rate also depends on the size of debris, and a canister with larger debris has a smaller dose rate. The distribution of fuel debris in a canister also affects the dose rate and uncertainty. Variability of the dose rate and uncertainty by changes in the location of the detector was also evaluated. The maximum dose rate was estimated at the vertical center of a canister at 1 m from the surface of a canister which is loosely packed with fuel debris. In case of a canister with the close packed fuel debris, the maximum dose rate was estimated at the vertical center of the pile of debris which is not same as the vertical center of a canister. The uncertainty also depends on the vertical location of the detector, and the uncertainty can be minimized when the dose rate is estimated at the vertical center of the debris pile. The dose rate and uncertainty are variable when they are estimated near a canister, therefore, the dose rate and uncertainty of fuel debris can be characterized in more detail when they are estimated near a canister, and this can be applied for the characterization of the fuel debris. Modified designs which can reduce the uncertainty of dose rate were evaluated. The uncertainty can be reduced by dividing the inner space of a canister by using inner containers or partitions which restrict the distribution of fuel debris in the canister. In case of the horizontal division, size of fuel debris can be restricted depending on the number of partitions used for the design. More partitions restrict the size, and uncertainty can be reduced since uncertainty of smaller debris is smaller. Vertical division does not restrict the size and it only restricts the vertical distribution of fuel debris. Even if the horizontal division can minimize the uncertainty when many partitions are installed in a canister, the vertical division of the inner space is more efficient than horizontal division in reduction of the uncertainty. Evaluated results in this dissertation can help the safe retrieval of fuel debris in Fukushima Daiichi nuclear power plant. Models and methods developed in this dissertation can be used for the characterization of damaged nuclear fuel which can be made by an accident in the future. They also can be applied to develop methods to manage spent fuel of advanced nuclear reactors such as the fuel of pebble bed reactors

The Effects of Wet Compression by the Electronic Expansion Valve Opening on the Performance of a Heat Pump System

In this study, by controlling the Electronic Expansion Valve opening, the influence of wet compression on a heat pump system was experimentally investigated in different heating conditions. The results demonstrate that the discharge temperature decreased and the mass flow rate increased, due to quality of the rising liquid droplets. It was also found that the heating capacity and power input of wet compression increased more than that of dry compression, with a superheat of 10 °C. The maximum COP (Coefficient of Performance) exists at a specific quality of ca. 0.94 to 0.90, as the power input in the region of wet compression is proportionally larger than the increase in the heating capacity, according to the decreasing quality. When the Entering Water Temperature of the Outdoor Heat Exchanger was 10 °C, 5 °C, and 0 °C, the COP increased by a maximum of ca. 12.4%, 10.6%, and 10.2%, respectively, in comparison to the superheat of 10 °C. In addition, the superheat at the discharge line is proposed as a proper controlling parameter to adjust the quality at the suction line, by varying the opening of the expansion valve during wet compression

The Effects of Wet Compression by the Electronic Expansion Valve Opening on the Performance of a Heat Pump System

In this study, by controlling the Electronic Expansion Valve opening, the influence of wet compression on a heat pump system was experimentally investigated in different heating conditions. The results demonstrate that the discharge temperature decreased and the mass flow rate increased, due to quality of the rising liquid droplets. It was also found that the heating capacity and power input of wet compression increased more than that of dry compression, with a superheat of 10 °C. The maximum COP (Coefficient of Performance) exists at a specific quality of ca. 0.94 to 0.90, as the power input in the region of wet compression is proportionally larger than the increase in the heating capacity, according to the decreasing quality. When the Entering Water Temperature of the Outdoor Heat Exchanger was 10 °C, 5 °C, and 0 °C, the COP increased by a maximum of ca. 12.4%, 10.6%, and 10.2%, respectively, in comparison to the superheat of 10 °C. In addition, the superheat at the discharge line is proposed as a proper controlling parameter to adjust the quality at the suction line, by varying the opening of the expansion valve during wet compression

Quantitative analysis of polydioxanone thread effects on lid-cheek junction

Background : : Polydioxanone (PDO) thread is commonly used as a skin rejuvenation material in the field of cosmetic medicine. Its usefulness in the aged eye area was described previously, but, to date, no clinical study has proven it. Objective: The purpose of this study was to investigate the rejuvenation effects of PDO thread on the aged lower eye area thorough quantitative and qualitative analysis. Methods : : We examined the changes in the lid-cheek junction in 32 participants who underwent the PDO thread insertion. They were followed up during 12 weeks after PDO thread insertion into the orbital fat area. Participants were categorized into three groups by tear trough grade; the eyelid to junction distance (EJD)/eyebrow to junction distance (BJD) ratio was measured before and after the PDO thread insertion. Differences in EJD to BJD ratio after PDO thread insertion and post-procedural differences in EJD to BJD ratio by tear trough grade were compared by the paired t-test. Results : : After PDO insertion into the infraorbital fat pad area, the overall EJD to BJD ratio significantly decreased from 0.35±0.03 to 0.33±0.04 (p=0.001). The significant post-procedural improvements in EJD to BJD ratio were found in grade 1 group and grade 2 group: 0.35±0.03 to 0.34±0.04 for grade 1 group (p=0.02), and 0.34±0.04 to 0.32±0.04 for grade 2 group (p=0.03); however, the changes were not found in the grade 3 group (p=0.21). Conclusion : : PDO thread insertion into the aged lower eyelid may be an effective method for improving signs of lower aged eyelid particularly in individuals with tear trough group 1 and group 2

Factors Associated with Subsequent Childbirth between Marriage Years in Korea

This study aimed to identify differences in factors associated with subsequent childbirth between the marriage years of 1996–2005 (Group 1) and 2006–2015 (Group 2) using the 2015 National Survey. A total of 5097 eligible participants (2492 and 2605 women in each group, respectively) were included. The main variables consisted of demographic characteristics, socio-economic status, value for child and son, and social support for raising child. For statistical analysis, discrete-time hazard models were used. The common factors associated with subsequent childbirth in both groups were son preference (Group 1: HR = 1.16; 95% CI = 1.06–1.27, Group 2: HR = 1.14; 95% CI = 1.04–1.24) and the favorable value on children (HR = 1.12; 95% CI = 1.01–1.25, HR = 1.11; 95% CI = 1.01–1.22). Only in Group 2, age at the first childbirth (HR = 1.35; 95% CI = 1.31–1.39) and more monthly income (≥4600, <6000: HR = 1.18; 95% CI = 1.04–1.33, ≥6000: HR = 1.15; 95% CI = 1.00–1.32) were significantly associated with subsequent children. Whereas, working women (HR = 0.86; 95% CI = 0.78–0.94) were less likely to have subsequent children. To increase fertility in Korea, the government must provide childcare and deal with factors associated with low fertility considering the reduction in role incomparability for women due to changes in demographic characteristics

Control Strategy of Dual-Winding Motor for Vehicle Electro-Hydraulic Braking Systems

The electro-hydraulic brake (EHB) system of a vehicle should operate normally under all circumstances to ensure automotive safety. This redundant system guarantees the minimum required performance in the event of a critical failure of the brake system. In this study, we propose a redundant motor control strategy for the EHB to fully realize a functional safety design. The EHB system is composed of two identical electronic control units (ECUs), a dual three-phase dual-winding permanent magnet synchronous motor (DW-PMSM), and hydraulic components to generate brake pressure through the movement of an actuator. First, we propose a method to acquire the necessary motor current for generating brake pressure. Second, we present an initial driving method for the DW-PMSM for achieving stability before generating the braking pressure that involves setting the actuator’s origin position without a position sensor. Lastly, we describe a redundant motor control strategy for continuous brake operation depending on whether each ECU experiences system failure. The experimental results showed the effectiveness and feasibility of the control strategy of the dual-winding motor for a functional safety design