• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.4
• /
• pp.33-40
• /
• 2020

A sturdy on the adhesion properties of solid propellants, liners, and insulation was carried out according to the types of barrier coats. A barrier coats were used to prevent migration of the plasticizer or curative between the propellant/liner/insulation, and the barrier coat was selected out of Isocyanates with different molecular weight and number of -NCO in one molecule. As a result, it was found that the more the -NCO group and the larger molecular weight, the stronger adhesion. In addition, as a result of experiments about effects of the pot life after applying the barrier coat on bond strength, the adhesion strength was shown to increase as the pot life was short.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 1998.11a
• /
• pp.680-695
• /
• 1998

The objective of this study is to optimize the responses of the creep feed ceramic grinding process simultaneously by an off-1ine multicriteria optimization methodology. The responses considered as objectives are material removal rate, flexural strength, normal grinding force, workpiece surface roughness and grinder power. Alumina material was ground by the creep feed grinding mode using superabrasive grinding wheels. The process variables optimized for the above objectives include grinding wheel specification, such as bond type, mesh size, and grit concentration, and grinding process parameters, such as depth of cut and feed rate. A weighting method transforms the multi-objective problem into a single-objective programming format and then, by parametric variation of weights, the set of non-dominated optimum solutions are obtained. Finally, the multi-objective optimization methodology was tested by a sensitivity analysis to check the stability of the model.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.1
• /
• pp.41-47
• /
• 1984

Increase of the requirements on quality of welded structures necessitates the improvement of known inspection methods and the introduction of progressive new techniques. Non-destructive methods are the most advanced, but there are considerable difficulties in using the methods of radiography with electromagnetic rays and ultrasonic testing in the inspection of dissimilar metal friction welds, because their physical and mechanical properties are changed very rapidly at the interface. The values of simple mechanical test for dissimilar metal friction welds have always been dubious, as the strength of the bond is often greater than that of the softer materials being jointed. Thus, in this paper some conventional mechanical testing methods are examined in an attempt to determine a technique for dissimilar metal friction welds, which will give a reliable quantitative indication of the weld quality. From the considered static and dynamic testing methods the impact bending test on unnotched and notched specimens are the most sensitive to find out the small joining defects in the interface.

• Journal of the Korean Society of Safety
• /
• v.6 no.4
• /
• pp.53-57
• /
• 1991

Engineers of building construction have made efforts to produce more convinient building of good quality through the development of technology and raw materials nowadaye. This study is conducted to recognize problems of exterior tiles through experiments on quality of tiles according to sizes, and to find out and Iecommend most suitaff sizes of tiles. The sizes which are used widely in Construction field are selected as,45$\times$45mm, 57$\times$87mm, 60$\times$108mm, 60$\times$187mm, 96$\times$200mm. Ready mixed compound are used as mortar and Compressed attachment method are used.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.14 no.5
• /
• pp.74-79
• /
• 2005

Spot welding widely used in automotive and aerospace industries has made it possible to produce more precise and smaller electric part by robotization and systemization of welding process. The quality of welding depends upon the size of nugget between the overlapped steel plates. Recently, the thickness of the steel plates becomes much thinner and hence, it introduces the smaller size of nugget. Therefore, it is necessary to develop the criterion to evaluate the quality of weld in order to obtain the optimal welding conditions for the better performance. In this paper, a thin steel plates, 0.1mm through 0.3mm thickness, have been spot-welded at different welding conditions and the nugget sizes are examined by defocused scanning microscopy. The relationships between nugget sizes and weldability have been investigated experimentally. The result of ultrasonic technique shows the good agreement with that of the tensile test.

• Journal of Welding and Joining
• /
• v.19 no.4
• /
• pp.379-383
• /
• 2001

Resistance spot welding has been widely used in the sheet metal joining processes because of low cost, high productivity and convenience. Recently, automobile and aerospace industries are trying to replace partly steel sheets with aluminum alloy sheets. But in the case of dissimilar materials, to apply resistance spot welding has been known to be very difficult owing to the effect of melting temperature. On this study, an effort was made to apply spot welding of dissimilar sheet metals, 2024 aluminum alloy and zinc coated steel sheet, evaluate the spot weld quality with tensile-shear strength test and nondestructive evaluation technique, C-scan image methodology. In this study results, as the current below 11 kA, melting of materials is not achieved well. Also as the current exceeds to 13.5 kA, the more spatters happen at welded zone and tensile-shear strength lowered. So, the feasibility of C-scan image technique proposed in the study is found to be suitable evaluation method for resistance spot weldability.

• Journal of the Semiconductor & Display Technology
• /
• v.23 no.2
• /
• pp.135-142
• /
• 2024

Cu-Cu bonding, one of the key technologies in advanced packaging, enhances semiconductor chip performance, miniaturization, and energy efficiency by facilitating rapid data transfer and low power consumption. However, the quality of the interface bonding can significantly impact overall bond quality, necessitating strategies to quickly detect and classify in-process defects. This study presents a methodology for detecting defects in wafer junction areas from Scanning Acoustic Microscopy images using a ResNet-50 based deep learning model. Additionally, the use of the defect map is proposed to rapidly inspect and categorize defects occurring during the Cu-Cu bonding process, thereby improving yield and productivity in semiconductor manufacturing.

• Journal of the Korean Wood Science and Technology
• /
• v.37 no.1
• /
• pp.87-93
• /
• 2009

Properties and chemical bonding of wood charcoal were investigated to understand the chemistry occurring in wood carbonization. From the pH changes of wood charcoal, it is revealed that it becomes acidic to weakly basic for charcoal carbonized at about $300^{\circ}C$, whereas it turns to basic at higher carbonization temperature higher than $600^{\circ}C$. Also, the ratio of carbon atoms in the charcoal was increased with increasing the carbonization temperature, while those of oxygen and hydrogen atoms. This tendency was significant when the carbonization temperature was increased up to $600^{\circ}C$ and the ratio changes of the atoms became stable at above $600^{\circ}C$. In the changes of chemical bonding, the ratio of C-C bonding was increased and those of C-O-H and C-O-R bonding was decreased significantly. It is considered that bondings connected to oxygen atoms tends to be broken, and the ratio of C-C bonding increased. Consequently, it is expected that this change may causes occurrence of new functional groups. In addition to that, it seems to be that the chemical bondings undergo the partial decomposition, formation, and recombination steps, Because ratio of C=O bonding tended to be increased or decreased by increasing the carbonization temperature. This understanding of chemical bond changes in charcoal can be a compensative consideration on the knowledges made only by physical parameters in the properties of micro-pore which has limited to explain the phenomenon. Also, it is considered that this can be treated as a basic knowledge for upgrading and development of use of wood charcoal.

• Journal of the Korean Applied Science and Technology
• /
• v.32 no.2
• /
• pp.348-361
• /
• 2015

To reduce the effects of greenhouse gas (GHG) emissions, the government has announced the special platform of technologies as parts of an effort to minimize global climate change, and the government distributed biodiesel since 2006 as the further efforts. Although there are some debates about some quality specifications and unbalanced of source (44% from palm oil), more than 400kton/year of biodiesel was produced in 2013. Moreover the amounts will be increased when the RFS is activated. To solve the unbalanced situation and to achieve the diversity of feeds, it is essential that many researches should be considered. Especially, free and bond glycerines are one of the important properties seriously affected to the combustion system in vehicle & cold properties. Previous method (KS M 2412) couldn't cover the biodiesel derived from lauric oil($C_{12:0}$) such as PKO (Palm Kernel Oil), Coconut oil because those compositions are lighter than other conventional biodiesel sources. In this study, we review the existed method and figure out the factors should improve to analysis the glycerine from PKO and Coconut oil biodiesel. Modifying the analysis conditions to enhance the resolution and change the internal standards to avoid the overlapped- peaks between Capric acid ME ($C_{10:0}$) and standard#1(1,2,4-butantriol). From this revised method, we could solve the restrictions of previous methods. And check the possibility of new method to analyze the glycerine in biodiesel regardless of sources.

• Current Photovoltaic Research
• /
• v.9 no.3
• /
• pp.75-83
• /
• 2021

The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si₂O, Si₂O₃) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (V_oc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900℃ declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiO_x/n⁺-poly-Si/SiN_x:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents J_o of this structure on polished surface is 1.3 fA/cm² and for textured silicon surfaces is 3.7 fA/cm² before printing the silver contacts. After printing the Ag contacts, the J_o of this structure increases to 50.7 fA/cm² on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells.