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As observed in the COVID-19 pandemic, RNA viruses continue to rapidly evolve through mutations. In the absence of effective therapeutics, early detection of new severely pathogenic viruses and quarantine of infected people are critical for reducing the spread of the viral infections. However, conventional detection methods require a substantial amount of time to develop probes specific to new viruses, thereby impeding immediate response to the emergence of viral pathogens. In this study, we identified multiple types of viruses by obtaining the spectral fingerprint of their surface proteins with probe-free surface-enhanced Raman scattering (SERS). In addition, the SERS-based method can remarkably distinguish influenza virus variants with several surface protein point mutations from their parental strain. Principal component analysis (PCA) of the SERS spectra systematically captured the key Raman bands to distinguish the variants. Our results show that the combination of SERS and PCA can be a promising tool for rapid detection of newly emerging mutant viruses without a virus-specific probe.

Electrolytic copper foil is a thin copper film material manufactured by electroplating and is mainly used as a circuit material to transmit electrical signals in printed circuit boards of electronic products such as TVs, PCs, and smartphones. Recently, it has been widely used as a negative current collector for lithium-ion batteries, which is essential for mobile IT and electric vehicles. The electrodeposited drum material is composed of CP Ti, which exhibits corrosion resistance and has a light weight, and welding is essential for processing in the form of a drum. Therefore, when the microstructures of the base metal and the welded part differ, these differences are reflected in the surface of the copper foil, which results in poor quality. Therefore, in this study, a welding process that required a low heat input while minimizing the size of the weld was used, and the change in the grain size was studied through plastic deformation and recrystallization heat treatment of the weld structure. Following the recrystallization heat treatment after the rolling of the plasma welded specimen, it was found that the calculation results of the recrystallization heat treatment were consistent with the actual conditions of the heat treatment, and the microstructure of the weld metal became finer as the rolling reduction rate increased.

Automobile manufacturers have recently focused their research on the concurrent improvement of fuel efficiency and stability. To implement lightweight body structures, the joining of dissimilar materials, such as advanced high-strength steel (AHSS) and carbon fiber-reinforced polymer (CFRP), is the most important, whereas fusion welding, which is the conventional welding process, is inapplicable owing to the difference in mechanical properties between materials. Thus, the development of an appropriate dissimilar material joining process is of utmost importance, considering productivity and safety. Self-piercing riveting (SPR), a representative lightweight material joining process, has no limitation in terms of applicable materials and has the advantage of improved joint strength. However, as the requirements on the mechanical properties of materials in the industry are continuously increasing, there is a need to further develop the process. Therefore, this study introduces the electromagnetic self-piercing riveting(E-SPR), a joining process that uses high electrical energy to discharge the high electrical energy charged in the capacitor to the working coil located in the head of the C-frame. In particular, this process enables high-quality joining parts to be secured by improving the formability of a material with poor formability under a high strain rate. Consequently, a simple piece of E-SPR equipment was manufactured, and an Al/Steel and Al/CFRP joint was further fabricated. The results of a preliminary test reported a quality equal to or higher than that of the previously reported SPR joint. Based on these research results, further studies on processes and equipment for commercialization will be conducted in the future.

Diabetes mellitus (DM) is one of the most researched metabolic diseases worldwide. It leads to extensive complications such as cardiovascular disease, nephropathy, retinopathy, and peripheral and central nervous system through an inability to produce or respond to insulin. Although oxidative stress-mediated mitophagy has been reported to play an important role in the pathogenesis of DM, specific studies are still lacking as well as remain highly controversial. Here, we found that Parkin-mediated mitophagy in pancreatic β cells under streptozotocin (STZ)-diabetic stress was induced by Polo-like kinase 3 (Plk3) and inhibited by the transcription factor Forkhead Box O3A (FOXO3A). STZ stress induces mitochondrial recruitment of Parkin through Plk3-mediated mitochondrial reactive oxygen species (ROS) generation, which causes pancreatic cell damage. Conversely, FOXO3A acts as negative feedback to prevent diabetic stress by inhibiting Plk3. Meanwhile, antioxidants including N-acetylcysteine (NAC) and natural COA water scientifically block these mitochondrial ROS and mitochondrial recruitment of Parkin by inhibiting Plk3. Through a 3D organoid ex vivo model, we confirmed that not only ROS inhibitors but also mitophagy inhibitory factors such as 3-MA or Parkin deletion can compensate for pancreatic cell growth and insulin secretion under STZ diabetic stress. These findings suggest that the Plk3-mtROS-PINK1-Parkin axis is a novel mitophagy process that inhibits pancreatic β-cell growth and insulin secretion and FOXO3A and antioxidants may provide new alternatives for effective diabetes treatment strategies in the future.

The car industry is currently working to integrate the conflicting requirements of environmental legislation and customer demands for high-performance and safety by developing lightweight vehicles. To meet these very different goals, automotive components are being manufactured from alloys that include including lightweight materials such as aluminum and magnesium. However, existing welding and forming processes such as fusion welding, any that use heat in general, and low-velocity press forming can all cause defects. Therefore, Electromagnetic pulse technology has become the focus. Electromagnetic pulse technology is a high-velocity process that uses electromagnetic forces for welding and forming processes. In particular, because of its good flexibility, environmentally friendly process, and high-quality dissimilar weldment, the technology can potentially resolve the challenges in welding and forming processes for lightweight materials that have low weldability and formability. In particular, Korea’s research on electromagnetic pulse technology was started in 2008 by KITECH. These studies include the basic theory, crafting of applications, and simulation. Currently, electromagnetic pulse research has focused on the dissimilar sheets and tubular workpieces for applications in the automobile industry, which includes the propeller shaft. Although electromagnetic pulse technology research remains limited compared to other manufacturing processes, with the continuous increase in market demand in the automobile and electronics industries, interest in electromagnetic pulse technology research will also continue to increase

This study aimed to analyze the moderating effect of sleep quality and the moderated moderation effect of education level on the relationship between depression and suicidal ideations among middle-aged parents of adolescent children. This is a secondary analysis of a survey collected from a cross-sectional study. The inclusion criteria were middle-aged parents of adolescent children in D city, South Korea, who answered the survey questionnaires. A total of 178 completed questionnaires were used for the analysis. The moderating effect of sleep quality (B = −0.03, p = 0.736) and education level (B = −1.80, p = 0.029) on the relationship between depression and suicidal ideations was shown. It was confirmed that the moderating effect of sleep quality on the effect of depression on suicidal ideations differed according to the subject’s education level. The findings have implications for mental healthcare providers who can be educated on sleep hygiene based on the subject’s education level.

Cryogenic-electron microscopy (cryo-EM) is the preferred method to determine 3D structures of proteins and to study diverse material systems that intrinsically have radiation or air sensitivity. Current cryo-EM sample preparation methods provide limited control over the sample quality, which limits the efficiency and high throughput of 3D structure analysis. This is partly because it is difficult to control the thickness of the vitreous ice that embeds specimens, in the range of nanoscale, depending on the size and type of materials of interest. Thus, there is a need for fine regulation of the thickness of vitreous ice to deliver consistent high signal-to-noise ratios for low-contrast biological specimens. Herein, an advanced silicon-chip-based device is developed which has a regular array of micropatterned holes with a graphene oxide (GO) window on freestanding silicon nitride (Six Ny ). Accurately regulated depths of micropatterned holes enable precise control of vitreous ice thickness. Furthermore, GO window with affinity for biomolecules can facilitate concentration of the sample molecules at a higher level. Incorporation of micropatterned chips with a GO window enhances cryo-EM imaging for various nanoscale biological samples including human immunodeficiency viral particles, groEL tetradecamers, apoferritin octahedral, aldolase homotetramer complexes, and tau filaments, as well as inorganic materials.

Background: This study was conducted to examine job stress, sleep quality, and fatigue and identify major variables that influence work engagement in order to develop an intervention program for shift duty nurses to enhance their work engagement. Methods: The subjects of this study were 170 nurses working with shift duty at one university hospital and one general hospital located in G city. Data were collected from February to March 2018 with structured questionnaires, and analyzed by descriptive statistics, t-test, ANOVA, Scheffe’s test, Pearson correlation coefficients, and multiple regression. Results: The mean scores of job stress, sleep quality, fatigue, and work engagement were 3.87, 1.57, 4.64, and 2.36, respectively. The work engagement was negatively correlated with job stress, sleep quality, and fatigue. The most powerful variable influencing work engagement was sleep quality and the model showed explanatory power of 22.5%. Conclusions: The results of this study indicate that the quality of sleep is most important factor affecting work engagement of shift nurses. This study suggest that it is necessary a variety of strategies in order to improve the quality of sleep and to intervene in job stress and fatigue, eventually lead to enhancing nursing performance.

Mitochondria are intracellular energy generators involved in various cellular processes. Therefore, mitochondrial dysfunction often leads to multiple serious diseases, including neurodegenerative and cardiovascular diseases. A better understanding of the underlying mitochondrial dysfunctions of the molecular mechanism will provide important hints on how to mitigate the symptoms of mitochondrial diseases and eventually cure them. In this review, we first summarize the key parts of the genetic processes that control the physiology and functions of mitochondria and discuss how alterations of the processes cause mitochondrial diseases. We then list up the relevant core genetic components involved in these processes and explore the mutations of the components that link to the diseases. Lastly, we discuss recent attempts to apply multiple genetic methods to alleviate and further reverse the adverse effects of the core component mutations on the physiology and functions of mitochondria.

Retroviral vectors show long-term gene expression in gene therapy through the integration of transgenes into the human cell genome. Murine leukemia virus (MLV), a well-studied gammaretrovirus, has been often used as a representative retroviral vector. However, frequent integrations of MLV-based vectors into transcriptional start sites (TSSs) could lead to the activation of oncogenes by enhancer effects of the genetic components within the vectors. Therefore, the MLV integration preference for TSSs limits its wider use in clinical applications. To reduce the integration preference of MLV-based vectors, we attempted to perturb the structure of the viral integrase that plays a key role in determining integration sites. For this goal, we inserted histones and leucine zippers, having DNA-binding property, into internal sites of MLV integrase. This integrase engineering yielded multiple mutant vectors that showed significantly different integration patterns compared with that of wild-type vector. Some mutant vectors did not prefer the key regulatory genomic domains of human cells, TSSs. Moreover, a couple of engineered vectors did not integrate into the genomic sites near the TSSs of oncogenes. Overall, this study suggests that structural perturbation of integrase is a simple way to develop safer MLV-based retroviral vectors for use in clinical applications.

Purpose: The welding quality and reducing production cost could be achieved by developing the automatic on-line welding quality monitoring system. However, investigation of welding fault to quantify the welding quality on the horizontal-position welding has been concentrated. Therefore, MD (Mahalanobis Distance) method on the vertical-position welding process by analysing the transform arc voltage and welding current gained from the on-line monitoring system has been applied. Design/methodology/approach: The transformed welding current and arc voltage data were taken from the experiment whereby the data number was 2500 data/s. The prediction of Contact Tip to Work Distance (CTWD) to gain best welding quality using the waveform variations were then taken from the experimental results. MD was employed to quantify the welding quality by analysing the transformed arc voltage and welding current. Finally, the optimal CTWD setting has verified the developed algorithms through additional experiments. Two kinds of experiments has been carried out by changing welding parameters artificially to verify the sensitivity and feasibility of WQ (Welding Quality) based on the concepts of MD and normal distribution. Findings: The results represented that WQ was fully capable of quantifying and qualifying the welding faults for automatic vertical-position welding process. Research limitations/implications: The arc welding process on the vertical-position compared to a horizontal-position welding is much more difficult because the metal transfer is influenced by the gravity force. To solve the problem, a new algorithm to monitor and control the welding fault during the arc welding process has been developed. Furthermore, optimization of welding parameters for the vertical-position welding process was really difficult to use the developed algorithms because they are only useful in selecting stored data and not for evaluating the effect of the variation of welding parameters on the weld ability. Practical implications: The developed algorithm could be achieved the highest welding quality at 15mm CTWD setting which the welding quality is 99.50% for the start section and 99.68% at the middle section. Originality/value: This paper proposed a new algorithm which employed the concepts of MD (Mahalanobis Distance) and normal distribution to describe a good quality welding.

Recently, trends in lightweight materials and their fabrication process have been focused on reducing global warming and environmental pollution. Therefore, the demand for aluminum is increasing as representative lightweight material. In general, a fusion welding process, such as high-speed GTA (Gas tungsten arc) welding, is used to join aluminum sheet, or for mechanical joining which accomplished using a rivet process. However, it is difficult to ensure a high-quality joint, given that various defects are often reported. Therefore, in this study, we propose not only welding aluminum sheets using a MPW (Magnetic pulse welding) process, but also analyzing characteristics of these joints through experimental and numerical analyses. In order to achieve this objective, a proper coil type was selected after preliminary testing in which a MPW process was performed using 0.5 mm thick A5052 sheets. After the welding, the characteristics on joint were analyzed using a peel test and optical microscope. Although there was an overlapping zone, and the coil shape was quadrangular, a circular joint shape was achieved with no evidence of welding in the center of the joint. These tests confirmed that nonuniform distributions of electromagnetic forces cause the only overlapping zone, located on the adjacent edge of the coil.

Tandem arc welding is a guarantor for high efficiency and cost saving since the quantity of wire which is deposited in the welding is approximated 30% greater that in conventional welding. The welding process is now being successfully applied in many industries. However, in the case of tandem arc welding, good quality and high productivity should depend on the welding parameters. Therefore, an intelligent algorithms for the automatic tandem arc welding process has been necessarily required. In this study, a predictive model based on the neural network by using the data acquired during tandem gas metal arc (GMA) welding process has been developed. To verify the reliability of the developed predictive model, a mutual comparison with the surface of the top-bead width obtained from actual experiments has been analyzed.

Generally welding is one of the most important processes to have a strong influence on the quality and productivity from a manufacture-based industry such as shipbuilding, automotive and machinery. The GMA(Gas Metal Arc) welding process involves large number of interdependent welding parameters which may affect product quality, productivity and cost effectiveness. To solve such problems, mathematical models are required to select the welding parameters for GMA welding process. In this study, the GMA welding process was studied using the information generated during the welding. The statistical analysis of a generalized regression approach was conducted by the following three methods: Firstly using the mathematical model (linear regression, 2nd regression); Secondly GA(Genetic Algorithm) with intelligent models; And finally using response surface analysis of models to develop the relationships between welding parameters and bead width as welding quality.

Electrohydraulic forming (EHF), high-velocity forming technology, can improve the formability of a workpiece. Accordingly, this process can help engineers create products with sharper edges, allowing a product’s radius of curvature to be less than 2 mm radius of curvature. As a forming process with a high-strain rate, the EHF process produces a shockwave and pressure during the discharge of an electrical spark between electrodes, leading to high-velocity impact between the workpiece and die. Therefore, the objective of this research is to develop an EHF process for forming a lightweight materials case with sharp edges. In order to do so, we employed A5052-H32, which has been widely used in the electric appliance industry. After drawing an A5052-H32 Forming Limit Diagram (FLD) via a standard limiting dome height (LDH) test, improvements to the formability via the EHF process were evaluated by comparing the strain between the LDH test and the EHF process. From results of the combined formability, it is confirmed that the formability was improved nearly twofold, and a sharp edge with less than 2 mm radius of curvature was created using the EHF process.

One of the main challenges of the automatic arc welding process which has been widely used in various constructions such as steel structures, bridges, autos, motorcycles, construction machinery, ships, offshore structures, pressure vessels, and pipelines is to create specific welding knowledge and techniques with high quality and productivity of the production-based industry. Commercially available automated arc welding systems use simple control techniques that focus on linear system models with a small subset of the larger set of welding parameters, thereby limiting the number of applications that can be automated. However, the correlations of welding parameters and bead geometry as welding quality have mostly been linked by a trial and error method to adjust the welding parameters. In addition, the systematic correlation between these parameters have not been identified yet. To solve such problems, a new or modified models to determine the welding parameters for tandem GMA (Gas Metal Arc) welding process is required. In this study, A new predictive model called STACO model, has been proposed. Based on the experimental results, STACO model was developed with the help of a standard statistical package program, MINITAB software and MATLAB software. Cross-comparative analysis has been applied to verify the reliability of the developed model.

In robotic GMA (Gas Metal Arc) welding process, heat and mass inputs are coupled and transferred by the weld arc and molten base material to the weld pool. The amount and distribution of the input energy are basically controlled by the obvious and careful choices of welding process parameters in order to accomplish the optimal bead geometry and the desired mechanical properties of the quality weldment. To make effective use of automated and robotic GMA welding, it is imperative to predict online faults for bead geometry and welding quality with respect to welding parameters, applicable to all welding positions and covering a wide range of material thickness. To successfully accomplish this objective, two sets of experiment were performed with different welding parameters; the welded samples from SM 490A steel flats adopting the bead-on-plate technique were employed in the experiment. The experimental results of current and voltage waveforms were used to predict the magnitude of bead geometry and welding quality, and to establish the relationships between weld process parameters and online welding faults. MD (Mahalanobis Distance) technique is employed for investigating and modeling of GMA welding process and significance test techniques were applied for the interpretation of the experimental data. Statistical models developed from experimental results which can be used to control the welding process parameters in order to achieve the desired bead geometry based on weld quality criteria.

Recently, there has been a trend in the manufacturing process to focus on the durability of cable lug joint, especially in welding process due to the poor cable lug joint causes many troubles on products and workers during manufacturing process. Therefore development of high quality cable lug joint is important for successful manufacturing process and safety of worker. The Magnetic Pulse Forming(MPF) is one of efficient way to developed a high quality cable lug joint. In MPF, a high strain rate forming process, utilizes a high velocity oblique collision on the workpiece to be formed in required shape. The objective of this paper is to develop of high quality cable lug joint using electromagnetic force. To successfully accomplish this goal, section and electrical contact temperature of developed cable lug joint has been compared with various cable lug joint. Electrical contact temperature of developed cable lug joint by electromagnetic force is lower than manufactured cable lug joint by pressurer and hydraulic pressurer.

The high cost of manufacturing and manufacturing time is required for preliminary experiment by manufacturing various type of coil every time for the forming of the required shape, it is essentially required to develop the coil design technology using a FEM. Thus, in order to form the required shape, it is important to design the coil using a FEM and predict the final forming product. Therefore, in this study developed electro-mechanical coupled FE-model for thin aluminum plate forming using electromagnetic force. In order to carry out this, magnetic pulse forming was carried by electromagnetic forming system total energy of 24kJ. Peck current and discharge speed acquired through magnetic pulse forming experiment using Rogowski current waveform transducer was used as input data in electromagnetic FE-model. Then, calculated electromagnetic force between forming coil and workpiece through the developed electromagnetic model was inputted as a load of mechanical FE-model for the prediction of thin aluminum plate forming shape. As results, developed electromagnetic-mechanical coupled model shall be able to be usefully used when designing the forming coil to secure the required forming shape later.

Magnetic pulse welding process, one of high speed welding processes, uses electromagnetic force from discharged current through a working coil which develops a repulsive force between the induced currents flowing parallel and in the opposite direction in the pipe to be welded. For achieving the successful weldment and using this process, the design of working coil is the most important factor, because working coil has to generate a high-intensity magnetic field on the surface of the workpiece during the process. Therefore, the objective of this study is to analyze the distribution of electromagnetic force of square working coil for magnetic pulse welding. For this, FE-model has been developed to analyze the distribution of electromagnetic force; after that, distribution of electromagnetic force, results of numerical analysis and experimental results for verifying the developed FE-model were compared. A 3-dimensional electromagnetic FE-model has been developed using a general commercial computer program, ANSYS/EMAG code. The shape and material of square working coil were decided through literature surveys. For the experiment, an MPW equipment W-MPW manufactured by WELDMATE Co., Ltd. was employed; also the materials were the Al 1070, SM45C for Al and Steel square pipe and rod respectively. After the experiment, leakage test was used to verify the weldability. Also weld joints were observed on longitudinal cross-section by microscope. The electromagnetic force generated was the greatest one at the center adjacent to square working coil, decreasing as moving into the edge. As the result of Al/Steel welding experiment, weldment of square Al pipe was not completed at the corner of weldment. These results are similar to the output data from developed electromagnetic FE-model where electromagnetic force decreases as moving into the corners of square working coil.

Recently, there has been a trend in the automotive industry to focus on the improvement of lightweight materials, such as aluminum and magnesium because the welding of dissimilar metals causes many welding defects. Magnetic pulse welding (MPW), one of the solid state welding technologies, uses electromagnetic force from current discharged through a working coil which develops a repulsive force between the induced currents flowing parallel and in the opposite direction in the tube to be welded. The objective of this paper is to develop a numerical model for analysis of the interaction between the outer pipe and the working coil using a finite element method (FEM) in the MPW process. Four Maxwell equations are solved using a general electromagnetic mechanics computer program, ANSYS/EMAG code. Experiments were also carried out with a W-MPW60 machine manufactured by WELMATE CO., LTD. with the Al1070 and SM45C for Al pipe and steel bar respectively. The calculated and measured results were compared to verify the proposed model.

Magnetic pulse forming is based on the principle of generation of a repulsive force called, Lorentz force due to opposing magnetic fields of adjacent conductors. Magnetic pulse forming of light weight materials such as aluminum, magnesium has been studied by many universities, institutes due to its advantages. But magnetic pulse forming is a complicated research area involving different topics in electromagnetic mechanics, plastic working, and materials mechanics. Therefore, development of FE-model of magnetic pulse forming process is a useful approach for better insight into workpiece deformation mechanics with electromagnetic interaction and further provides design and quality control information. To successfully accomplish this objective, a 3-dimensional ax-symmetric electromagnetic numerical model has been developed. The equation was solved using a general mechanics computer program, ANSYS EMAG and LS-DYNA code.

Generally a MPF(Magnetic pulse forming) process refers to the high velocity and high strain rate deformation of a low-ductility materials driven by electromagnetic forces that are generated by the rapid discharge current through the forming coil. The goal of this study was to investigate the main design parameter in MPF. To achieve the above objectives, An intelligent system which consisted of thin 5053 aluminum sheet and bar forming coil was employed for the experiment. The measured strain data have been analyzed using the developed electromagnetic FE-model. The analysis data showed that the uniform electromagnetic force is one of most important design parameters in MPF process.

Industries such as gas, oil, petrochemical, chemical, and electric power have generally employed for the operation and used to enlarge the equipment or structures that require a high capital investment. In order to meet these requirements, the industries are increasingly moved toward saving the experimental verifications and computer simulation. Therefore industries to reduce the maintenance costs without compromising operational safety have been forced on finding better and more efficient methods to inspect their equipment and structures. It was motivated to meet the industrial needs and to secure and maintain the institute's technical initiative and leadership in the development of this new and exciting technology. Also, the system with many sensors could be detected the weld defects, and was useful for real-time monitoring. This paper is focused on the development of the real-time non-contract monitoring system as an efficient tool for the experimental study of weld defects based on the relationship between the measured voltage and input parameters. The monitoring technology involves the use of Ms S (Magnetostrictive Sensors) for the generation and detection of the guided waves. The developed system was employed to the experimental study in order to fine the weld defects for steel object with artificial defects used in the welding field.

Magnetic Pulse Welding (MPW) is not only one of the most useful welding processes for the dissimilar metal joining which uses cylindrical materials such as a pipe, but also a new technology for metal welding by means of repulsive force on account of the interaction between magnetic part of working coil and current induced in an outer pipe. Since the factors effected on quality of MPW are the charged voltage, the gap between inner pipe and outer pipes and a thickness of an outer pipe, the this study was focused on the investigation of the effect of process parameters and development of the mathematical model for the prediction on a quality of joint using Response Surface Method (RSM). To achieve the objective, the MPW equipment manufactured by WELDMATE CO., LTD. has been employed and applied for the materials such as the Al 1070, SM45C for Al and steel pipe respectively. After the sequent experiment, leakage test has been done to verify efficiency of the welding. The experimental values have been shown the good agreement with the predicted ones, indicating suitability of mathematical model employed. It is concluded that the gap between outer pipe and inner rod is one of major process parameters for influence on quality of joint while Al/steel pipe welding using the MPW. [doi:10.2320/matertrans.L-MZ201131]

배기가스 및 연비와 직결되어 있는 자동차 중량 절감의 중요성이 강조됨에 따라 자동차 경량화 기술은 환경 친화적인 자동차 개발의 핵심기술로 연구되고 있다. 그러나 소비자의 편의성 추구, 안전기준의 강화 등으로 중량은 지속적으로 증가하고 있어 이를 혁신적으로 절감할 수 있는 기술 개발이 요구된다. 따라서 차체 중량의 경량화를 위한 새로운 가공 및 조립 기술의 개발, 최적화 설계 기술 도입 등이 고려되고 있으며 특히, 대체 경량 재료의 적용에 연구가 집중되고 있다. Table 1은 국외 자동차업체에서 고급차종의 차체 및 부품에 적용되고 있는 강재를 알루미늄, 마그네슘과 같은 경량재로 대체하여 스페이스 프레임에 적용한 사례이다

Automatic welding systems are widely used for high-volume production industries, where the cost of related equipment is justified by the large number of pieces to be made. Detailed movement devices are required, including predetermined welding parameter sequences and timers, to form the weld joints. Automatic gas metal arc welding processes require new mathematical models to predict optimal welding parameters for a given bead geometry to accomplish the desired mechanical properties of the weldment. The developed algorithm should be able to be employed across a wide range of material thicknesses and all welding positions, and available in analytical form to be easily applied to the welding robot with high degree of confidence in predicting bead dimensions. Therefore, this study investigated welding voltage, arc current, welding speed, contact tube weld distance, and welding angle on bead reinforcement area for automated gas metal arc welding processes using a central composite design to generate response surface methodology and artificial neural network models. Average absolute deviation was used to compare accuracy between the two models. Analysis of variance showed coefficients of determination of 0.894 and 0.948 with average absolute deviation 4.01% and 3.11% for the response surface methodology and artificial neural network models, respectively. This suggests that artificial neural network is a better modeling technique for predicting bead reinforcement area compared to response surface methodology.

Even though polyethyleneoxide (PEO)-polyethyleneglycol (PEG) blends have been used widely for sustained release matrix tablets, evaluations of the effects of PEG or PEO on the matrix properties have been limited. In order to evaluate gelling behavior and drug release profiles of PEG, various contents of the polymers were investigated through a robust experimental design method. When exposed to an aqueous environment, the PEO-PEG matrix hydrated slowly and swelled, causing a thick gel layer to form on the surface, the thickness of which increased significantly depending on the PEG contents. Since polyacrylate plates were used for the study, the matrix was not completely hydrated and gelled even after 5h. However, the results could be applied to the time-oriented responses RD (robust design) models to obtain optimal settings and responses for the observed times. The optimal settings of PEO and PEG were 94.26 and 140.04 mg, respectively (PEG rate of 148.57%). Moreover, as the amount of PEG increased, the release rate also increased. When the formulation contained more than 150% of PEG, most of the drug loaded in the tablet was released in about 12 h. When the amount of PEG was less than 100%, the drug release rate was sustained significantly. Based on the RD optimization model for drug release, the optimal settings were PEG and PEO of 124.3 and 110 mg, respectively (PEG rate of 88.50%). Therefore, PEG rate of about 90-150% is suggested for matrix tablet formulations, and the exact ratio could be formulated according to the resulting tablet's properties.

With the advance of the robotic arc welding process, procedure optimization which selects the welding procedure and predicts bead geometry that will be deposited is increased. A major concern involving procedure optimization should define a welding procedure which can be shown to be the best with respect to some standard and chosen combination of process parameters which give an acceptance balance between production rate and the scope of defects for a given situation. In this paper, bead-on-plate welding using an infrared thermography during robotic CO2 welding process has been conducted to obtain the thermal profile characteristics and develop the empirical models which influence process parameters on bead width with the help of a standard statistical package program SAS. The comparison with values of coefficient of multiple correlations for curvilinear and linear equations presents no differences, which indicate that the developed equations are reasonably suitable.

Recent trends of welding system have been focused on the development of new process in order to achieve better quality, higher productivity and friendly to the environmentally in welding process. The Magnetic Pulse Welding(MPW) process is based on the principle of a tremendous amount of energy compressed and discharged for an extremely short period of time. The purpose of this paper is to investigate welding characteristics according to the distributions of an electromagnetic force on the weldment using a finite element method and to find the optimal process parameters such as input current and frequency. To successfully accomplish this objective, a 2-dimensional axisymmetric electromagnetic numerical model has firstly been developed. The equation was solved using a general electromagnetic mechanics computer program, ANSYS code. The comparison between the calculated and measured results has been carried out to verify the developed system.

Welding deformation during the assembly process is affected by not only local shrinkage due to rapid heating and cooling, but also root gap and misalignment between parts to be welded. Therefore, the prediction and control of welding deformation have become of critical importance. In this study, it was focused on the development of the 3-axis apparatus for real-time measurement of the welded deformation. To achieve the objective, a D-H algorithm has been carried out to check the behavioral and performance evaluation for the developed robot. The sequence experiments were taken the base materials of 400×200×4.5mm plate for butt welding. The real-time experimental measurements are in good agreement with the measured results.Key Words : GMA(Gas Metal Arc) Welding, Welding distortion, CATIA Simulation, D-H Algorithm 1. 서 론 현재 국내외 조선소에서 건조되고 있는 모든 대형 선박은 블록 건조공법에 의해 생산되고 있다. 선체 블록은 판 부재 간의 연결을 위한 맞대기용접, 판 부재에 보강재를 부착하기 위한 필릿용접으로 조립되는데, 각 용접 조립작업은 필연적으로 용접변형을 수반하고 조립단계의 진행에 따라 변형은 계속 누적된다. 용접공정은 국부적인 가열에 의해 두 물체를 접합하는 것이 일반적이며, 구조물에 국부적인 가열은 열응력을 발생시키고, 발생한 열응력은 열변형을 생성한다

In the process to manufacture for metallic structures, control of welding deformation is one of an importantproblems connected with reliability of the manufactured structures so that welding deformation should be measured and controlled with quickly and actively. Also, welding parameters which have as lot of effects on welding deformation such as arc voltage, welding current and welding speed can also be controlled. Theobjectives for this study were to develop a simple 2-D FEM to calculate not only the transient thermalhistories but also the sizes of fusion and heat-affected zone (HAZ) in multi pass arc welds including the butt and fillet weld type with dissimilar thickness, and to concentrate on a developed model for the finding the parameters of Godak’s moving heat source model based on a GA. The developed model includes a GA program using MATLB and GA toolbox, and a batch mode thermal model using ANSYS software. Not only the thermal model was verified by comparison with Goldak’s work but also the developed model was validated with molten zone section experimental data.Key Words : Weld distortion, Genetic algorithm, Double-ellipse heat input model, Finite element method

출원번호출원명 출원인출원연도US6977361 Molecular bonding of vehicle frame components using magnetic impulse welding techniquesDana Co. Ltd. 2005US687596 Apparatus for electromagnetic forming, joining and weldingFord Motor Company 2005US6548791 Energy storage apparatus and inductor tools for magnetic pulse welding and formingInli, LLC 국외 전자기 펄스 용접 기술은 이스라엘 Pulsar사의 2003US6389697 Fabricating automotive spaceframes using electromagnetic forming or magnetic pulse weldingFuel Cell and Integrators, Inc. 2002US6104012Molecular bonding of vehicle frame components using magnetic impulse welding techniquesDana Co. Ltd. 2000US5981921Method of magnetic pulse welding an end fitting to a driveshaft tube of a vehicular driveshaftDanaCo. Ltd. 1999US5824998Joining or welding of metal objects by a pulsed magnetic forcePulsar Welding Ltd. 1998* 「마그네틱 응용기술 및 시장분석」 (주) 비아글로벌 2006

최근 금속가공산업은 자동차, 조선 기계, 전자 등의 부품소재 제조에 있어 핵심적인 산업으로 자리하고 있다. 특히 가장 많은 비중을 차지하고 있는 용접산업은 저임금을 바탕으로 한 중국기술의 추격과 선진국의 고품질화에 직면하고 있으며 이러한 문제를 해결하기 위하여 친환경 공정기술의 개발과 신기술을 통한 제품의 부가가치 제고가 요구된다. MPW는 자기장에 의한 전자기력을 사용하므로 물리적인 접촉 없이 금속을 가공하는 방법으로서, 용접(brazing과 soldering 포함), 금형 및 소성가공공정에서 환경오염 발생원인 용접재료, 가스, 용가재, 플럭스, 윤활유 및 세척유 등이 필요 없이도 고품질의 제품을 생산할 수 있는 친환경적인 공정기술이다. 그 외에도 도금된 상태에서 작업이 가능하여 기존의 공정에서 결함이 발생되었을 때 재도금을 실시하는 후공정이 생략되어 도금공정에서 배출되는 오염물질도 줄일 수 있고, 작업이 수 μs 하에서 이루어지기 때문에 전력소모가 매우 적으며 작업시간을 절약할 수 있는 장점을 갖고 있다

In this article, a high-speed forming press using electromagnetic pulse force is designed with the finite element analysis. The punch of the press is fixed to an aluminum plate driven by electromagnetic pulse force. The force is the repulsive force between the aluminum plate and the coil. The coil is supplied with a high-voltage AC current impulse from the capacitor, and then the magnetized aluminum plate moves upward at high speed to perform the pressing. For the analysis of the pressing, the coupled analysis of electromagnetic field and rigid-body dynamics of the aluminum plate is performed with a commercial finite element software, ANSYS, and the rigid-body dynamics theory. A simple upsetting test is performed with the high-speed press.

A novel three-layered tablet consisting of a water-soluble mid-layer and two barrier layers with swellable polymers was investigated to develop a preferable once-a-day formulation containing terazosin HCl as a hydrophilic model drug. When the tablet was exposed to a release medium, the medium quickly permeated to the mid-layer and the two barrier layers swelled surrounding the mid-layer rapidly. It facilitated the tablet to absorb a lot of water compared with monolithic matrix. Moreover, formation of a lot of pores in the tablet during dissolution could be observed, suggesting significant water absorption in the inner matrix and swollen polymers of the tablet. Barrier layers influenced drug release profiles significantly, potentially due to differences in viscosity after swelling that produce different diffusion coefficients and mechanical strength. The drug in the mid-layer showed the sigmoid type of release pattern because a period of time might be needed to release the drug from the mid-layer through the barrier layers, but the drug in barrier layers showed the typical release pattern of monolithic matrix. As the amount of water-soluble excipient in the mid-layer increased, the degree of swelling also increased, suggesting that its amount in the layer may affect the overall swelling properties of the tablet. It was also shown that more hydrophilic mid-layer caused faster erosion rate, which was related to the results of swelling property. The three-layered tablets showed more consistent release kinetics than the matrix tablets. These results can give good information for the development of sustained drug delivery systems, especially once-a-day administration.

Purpose The purpose of this study was to evaluate the utility of specific IgE (sIgE) concentrations for the diagnosis of immediate-type egg and cow's milk (CM) allergies in Korean children and to determine the optimal cutoff levels. Methods In this prospective study, children ≥12 months of age with suspected egg or CM allergy were enrolled. Food allergy was diagnosed by an open oral food challenge (OFC) or through the presence of a convincing history after ingestion of egg or CM. The cutoff levels of sIgE for egg white (EW) and CM were determined by analyzing the receiver operating characteristic curves. Results Out of 273 children, 52 (19.0%) were confirmed to have egg allergy. CM allergy was found in 52 (23.1%) of 225 children. The EW-sIgE concentration indicating a positive predictive value (PPV) of >90% was 28.1 kU/L in children 90% PPV. EW-sIgE levels of 3.45 kU/L presented a negative predictive value (NPV) of 93.6% in children

Catalytic double carbonylation of diiodomethane in triethylorthoformate in the presence of a homogeneous rhodium complex gives diethylmalonate in a fairly good yield.