• Textile Coloration and Finishing
• /
• v.32 no.4
• /
• pp.199-207
• /
• 2020

Recently, as the demand for masks increases, the use of filter-replaceable cotton masks is increasing. A filter-replaceable cotton mask is one of the ways to solve the environmental problems of a disposable nonwoven mask because only the filter can be replaced after washing. Cotton fiber products are known to be environmentally friendly, but cotton products dyed with general synthetic dyes are not safe for humans. In this study, to prepare of cotton mask applied with natural dyeing, the optimal dyeing conditions are set when dyeing with gallnut extract. A polychromatic natural dye that changes color by mordant, and the functionalities of gallnut dyeing fabrics are evaluated. The experimental method is dyed the gallnut by temperature and time by concentration to set the optimal conditions. The color fastness rating grade of aluminium potassium sulfate dodecahydrate, copper(ll) sulfate pentahydrate, and iron(ll) chloride tetrahydrate were evaluated after the pre/post mordanting.

• Advances in nano research
• /
• v.10 no.1
• /
• pp.91-99
• /
• 2021

Silicene is an emerging two-dimensional (2D) semiconductor material which has been envisaged to be compatible with conventional silicon technology. This paper presents a theoretical study of uniformly doped silicene with aluminium (AlSi3) Field-Effect Transistor (FET) along with the benchmark of device performance metrics with other 2D materials. The simulations are carried out by employing nearest neighbour tight-binding approach and top-of-the-barrier ballistic nanotransistor model. Further investigations on the effects of the operating temperature and oxide thickness to the device performance metrics of AlSi3 FET are also discussed. The simulation results demonstrate that the proposed AlSi3 FET can achieve on-to-off current ratio up to the order of seven and subthreshold swing of 67.6 mV/dec within the ballistic performance limit at room temperature. The simulation results of AlSi3 FET are benchmarked with FETs based on other competitive 2D materials such as silicene, graphene, phosphorene and molybdenum disulphide.

• Membrane and Water Treatment
• /
• v.13 no.4
• /
• pp.183-189
• /
• 2022

This study seeks towards an optimal way to control sulfate ions in semiconductor wastewater effluent with potential eco-toxicity. We developed a system based on ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O). The basic idea is that the pH of the water is raised to approximately 12 with Ca(OH)₂. After, aluminium salt is added, leading to the precipitation of ettringite. Lab-scale batch and continuous experiment results with real semiconductor wastewater demonstrated that 1.5 and 1 of stoichiometric quantities for Ca²⁺ and A³⁺ with pH above 12.7 could be considered as the optimal operation condition with 15% of sludge recycle to the influent. A mixed AlCl₃ + Fe reagent was selected as the beneficial Al³⁺ source in ettringite process, which resulted in 80% of sludge volume reduction and improved sludge dewaterability. The results of continuous experiment showed that with precipitation as ettringite, sulfate concentration can be stably reduced to less than 50 mg/L in effluent from the influent 2,050 ± 175 mg/L on average (1,705 ~ 2,633 mg/L).

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.9 no.2
• /
• pp.93-103
• /
• 1980

A small domestic solar water heating system in thermosyphonic flow was tested in Seoul. The system consisted of four flat plate aluminium roll bond type collectors of total effective area $3.28m^2$ and a $280{\iota}$ storage tank. It was tilted $52^{\circ}$ relative to the horizon. And the collector plate, collector tube and storage tank were equiped with 14 thermocouples. As the results, the following facts were found; 1) To provide water at $55^{\circ}C$ for a family of four in Seoul, a collector area of $3-4m^2$ and a storage capacity of $180{\iota}- 200{\iota}$ are suggested. And this system can supply hot water at above $45^{\circ}C$ day about. 2) In the late afternoon hours, it might be advantageous to stop the flow in the system as heat losses to the environment increase unduly. 3) Without any hot water consumption throughout the day, water temperature distributions inside the storage tank was found almost linear. This indicates essentially no mixing inside the storage tank. 4) In case of a small domestic solar water heating system, it is better to employ a single transparent cover rather than double one.

• Computers and Concrete
• /
• v.31 no.4
• /
• pp.327-335
• /
• 2023

The most popular building material, concrete, is intrinsically linked to the advancement of humanity. Due to the ever-increasing complexity of cementitious systems, concrete formulation for desired qualities remains a difficult undertaking despite conceptual and methodological advancement in the field of concrete science. Recognising the significant pollution caused by the traditional cement industry, construction of civil engineering structures has been carried out successfully using Geopolymer Concrete (GPC), also known as High Performance Concrete (HPC). These are concretes formed by the reaction of inorganic materials with a high content of Silicon and Aluminium (Pozzolans) with alkalis to achieve cementitious properties. These supplementary cementitious materials include Ground Granulated Blast Furnace Slag (GGBFS), a waste material generated in the steel manufacturing industry; Fly Ash, which is a fine waste product produced by coal-fired power stations and Silica Fume, a by-product of producing silicon metal or ferrosilicon alloys. This result demonstrated that GPC/HPC can be utilised as a substitute for traditional Portland cement-based concrete, resulting in improvements in concrete properties in addition to environmental and economic benefits. This study explores utilising experimental data to train artificial neural networks, which are then used to determine the effect of supplementary cementitious material replacement, namely fly ash, Ground Granulated Blast Furnace Slag (GGBFS) and silica fume, on the compressive strength, tensile strength, and modulus of elasticity of concrete and to predict these values accordingly.

• Nuclear Engineering and Technology
• /
• v.55 no.8
• /
• pp.2873-2878
• /
• 2023

The purpose of this study is to perform radiation monitoring by acquiring gamma images and real-time optical images for ^99mTc vial source using charge couple device (CCD) cameras equipped with the proposed compact gamma camera. The compact gamma camera measures 86×65×78.5 mm³ and weighs 934 g. It is equipped with a metal 3D printed diverging collimator manufactured in a 45 field of view (FOV) to detect the location of the source. The circuit's system uses system-on-chip (SoC) and field-programmable-gate-array (FPGA) to establish a good connection between hardware and software. In detection modules, the photodetector (multi-pixel photon counters) is tiled at 8×8 to expand the activation area and improve sensitivity. The gadolinium aluminium gallium garnet (GAGG) measuring 0.5×0.5×3.5 mm³ was arranged in 38×38 arrays. Intrinsic and extrinsic performance tests such as energy spectrum, uniformity, and system sensitivity for other radioisotopes, and sensitivity evaluation at edges within FOV were conducted. The compact gamma camera can be mounted on unmanned equipment such as drones and robots that require miniaturization and light weight, so a wide range of applications in various fields are possible.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.24 no.1
• /
• pp.102-109
• /
• 1987

This study is carrier out to investigate the carrier injection and the characteristics of trapping for the CVD deposited Al2O3 film on Si substrates. Samples used are metal -Al2O3-Si Structure in which metal field plates are used with Aluminium or God. Canier injection and trapping, which result in flat band voltalge shift, occur at fields as low as 1~2 MV/cm. An approximate method is proposed for computing the location of the centroid of the trapped electrons in this paper. Results show that carriers are trapped near the injecting interface at fields less than about 5MV/cm. Because of continued charging, a steady state can not be reached. Therefore the unique I-V curve is obtained when the traps are initially empty. By utilization of applied voltage on each point of the fresh device sample, it is measured the I-V surves for two polarities of applied voltage. The current densities observed in the Al2O3 films are much larger than those obtained in SiO2.

• Coupled systems mechanics
• /
• v.12 no.5
• /
• pp.409-418
• /
• 2023

A coupled algorithm is proposed which first considers the creation of porous structure of the material and then the simulations of response of mechanical components with porous structure to a variable load history. The simulations are carried out by the Prandtl operator approach in the finite element method (FEM) which enables structural simulations of mechanical components subjected to variable thermomechanical loads. Temperature-dependent material properties and multilinear kinematic hardening of the material can be taken into account by this approach. Several simulations are then performed for a tensile-compressive specimen made of a generic porous structure and mechanical properties of Aluminium alloy AlSi9Cu3. Variable mechanical load history has been applied to the specimens under constant temperature conditions. Comparison of the simulation results shows a considerable elastoplastic stress-strain response in the vicinity of pores whilst the surface of the gauge-length of the specimen remains in the elastic region of the material. Moreover, the distribution of the pore sizes seems more influential to the stress-strain field during the loading than their radial position in the gauge-length.

• Journal of radiological science and technology
• /
• v.37 no.4
• /
• pp.273-278
• /
• 2014

Bone density measurement use of diagnosis of osteoporosis and it is an important indicator for treatment as well as prevention. But errors in degree of precision of BMD can be occurred by status of patient, bone densitometer and radiological technologist. Therefore the author evaluated that how BMD changes according to the condition of the patient. As Lumbar region, which could lead to substantial effects on bone density by diverse factors such as the water, food, intentional bowels. We recognized a change of bone mineral density in accordance with the height of the water tank and in the presence or absence of the gas using the Aluminum Spine Phantom. We also figured out the influence of bone mineral density by increasing the water and food into a target on the volunteers. Measured bone mineral density through Aluminum Spine Phantom had statistically significant difference accordance with increasing the height of water tank(p=0.026). There was no significant difference in BMD according to the existence of the bowl gas(p=0.587). There was no significant difference in a study of six people targeted volunteers in the presence or absence of the food(p=0.812). And also there was no significant difference according to the existence of water(p=0.618). If it is not difficult to recognize the surround of bone in measuring BMD of lumbar bone, it is not the factor which has the great effect on bone mineral density whether the test is after endoscopic examination of large intestine and patient's fast or not.

• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.4
• /
• pp.240-246
• /
• 2013

$SF_6$ is the most important greenhouse gas with the highest GWP (global warming potential). The $SF_6$ decomposition study was performed with silicon carbide with aluminium oxide by microwave irradiation. DRE (Decomposition and Removal Efficiencie) of $SF_6$ were evaluated by GC-TCD unit using 3,000 ppm $SF_6$ gas. DRE of $SF_6$ was increased by $Al_2O_3$ contents to 10~30 wt%, otherwise $Al_2O_3$ content of 40~50 wt% was decreased. DRE of $SF_6$ up to 99.99% have been achieved in SiC-$Al_2O_3$ (20 wt%) and SiC-$Al_2O_3$ (30 wt%) above $900^{\circ}C$. Also, the DRE of SiC-$Al_2O_3$ (30 wt%) at $700^{\circ}C$ showed 96.72%. In addition to consideration microwave input energy and $Al_2O_3$ content, SiC-$Al_2O_3$ (30 wt%) can be suggested the best material to control $SF_6$. The results of this study suggest it is important to control content of $Al_2O_3$ in SiC for decomposition of $SF_6$ with microwave energy.