Fusion characteristics in P-GMAW of mild steel

The influence of process parameters on deposition and fusion characteristics of mild steel with Pulsed Gas Metal Arc Welding has been investigated using a transistorized power supply. A simple model of melting behaviour has been developed which allows the prediction of dilution behaviour and explains the interplay between mass and heat in P-GMAW. In order to predict heat affected zone area, a model driven from the former one has also been developed. Deposition characteristics were studied taking the care of studying the influence of each welding parameter at each time, whenever it was possible. Emphasis was given to shielding gas mixture which was found to significantly influence metal transfer mode and arc stability. A systematic approach to choose process parameters in Pulsed Gas Metal Arc Welding with a constant current power supply is proposed. It was found that mean current and welding speed play the most important role in determining fusion characteristics, thus, based on a simple model, methods of controlling these aspects are suggested. Emphasis was placed on understanding dilution behaviour. It was found possibility to develop.procedures allowing the independent choice of deposition rate and dilution behaviour and to give an account of many observations with simple models of melting phenomena. The developed model is combined with calorimetric heat transfer measurements to investigate the result that only a small fraction of the total process power is required to melt the observed fusion areas. A "dual Heat" source fusion model is suggested where plate melting is largely in response to direct arc heating, providing means of optimising plate dilution and thereby reducing the risk of fusion defects. A generalized representation of fusion characteristics is given which allows independent selection of required fusion characteristics to be assessed.Ph

Robotic friction stir welding—Seam-tracking control, force control and process supervision

Purpose – This study aims to enable robotic friction stir welding (FSW) in practice. The use of robots has hitherto been limited, because of the large contact forces necessary for FSW. These forces are detrimental for the position accuracy of the robot. In this context, it is not sufficient to rely on the robot’s internal sensors for positioning. This paper describes and evaluates a new method for overcoming this issue.Design/methodology/approach – A closed-loop robot control system for seam-tracking control and force control, running and recording data in real-time operation, was developed. The complete system was experimentally verified. External position measurements were obtained from a laser seam tracker and deviations from the seam were compensated for, using feedback of the measurements to a position controller.Findings – The proposed system was shown to be working well in overcoming position error. The system is flexible and reconfigurable for batch and short production runs. The welds were free of defects and had beneficial mechanical properties.Research limitations/implications – In the experiments, the laser seam tracker was used both for control feedback and for performance evaluation. For evaluation, it would be better to use yet another external sensor for position measurements, providing ground truth.Practical implications – These results imply that robotic FSW is practically realizable, with the accuracy requirements fulfilled.Originality/value – The method proposed in this research yields very accurate seam tracking as compared to previous research. This accuracy, in turn, is crucial for the quality of the resulting material.Keywords Friction stir welding, Robotics, Force control, Seam-tracking control, Control, Sensors, Robot weldin

Anlisis Technology Acceptance Model Pada Industri Perbankan

The first aim of this study was to determine the influence perception of the perceived benefits (PU) and perceived ease of use (PEU) of the attitude (ATU) in receiving information technology (ATI). This research is an explanatory research. Respondents are bank employees as much as 118 peoples. To test the effect of each variable used structural equation modeling analysis techniques (SEM). The results showed a variable perception ease of use (PEU) positive and significant impact on the attitude of using IT (ATU). Variable perception perceived benefits (PU) is positive but not significant effect on attitudes using IT (ATU). Variable perception easy to use (PEU) positive and significant impact on the perceived benefits perception variables (PU). Variable attitude of using IT (ATU) positive and significant impact on the acceptance of IT (ATI). There are research findings that do not support the results of previous studies, namely, perception perceived benefits (PU) but not significant positive effect on the attitude of using IT (ATU). This shows the attitude of the management agreed that the use of information technology is an important banking and its presence is felt very beneficial to the organization and operational staff, but not the key element in determining the attitude to use IT. The management should be able to realize the quality of skilled workers and professional service. The banking industry can standardize that can be used as a reference for the development of IT. IT use also should be able to grow the level of trust and a culture conducive to the customer as a party that directly or indirectly affect the use of IT

Human mesenchymal stromal cells inhibit tumor growth in orthotopic glioblastoma xenografts

Background: Mesenchymal stem/stromal cells (MSCs) represent an attractive tool for cell-based cancer therapy mainly because of their ability to migrate to tumors and to release bioactive molecules. However, the impact of MSCs on tumor growth has not been fully established. We previously demonstrated that murine MSCs show a strong tropism towards glioblastoma (GBM) brain xenografts and that these cells are able to uptake and release the chemotherapeutic drug paclitaxel (PTX), maintaining their tropism towards the tumor. Here, we address the therapy-relevant issue of using MSCs from human donors (hMSCs) for local or systemic administration in orthotopic GBM models, including xenografts of patient-derived glioma stem cells (GSCs). Methods: U87MG or GSC1 cells expressing the green fluorescent protein (GFP) were grafted onto the striatum of immunosuppressed rats. Adipose hMSCs (Ad-hMSCs), fluorescently labeled with the mCherry protein, were inoculated adjacent to or into the tumor. In rats bearing U87MG xenografts, systemic injections of Ad-hMSCs or bone marrow (BM)-hMSCs were done via the femoral vein or carotid artery. In each experiment, either PTX-loaded or unloaded hMSCs were used. To characterize the effects of hMSCs on tumor growth, we analyzed survival, tumor volume, tumor cell proliferation, and microvascular density. Results: Overall, the AD-hMSCs showed remarkable tropism towards the tumor. Intracerebral injection of Ad-hMSCs significantly improved the survival of rats with U87MG xenografts. This effect was associated with a reduction in tumor growth, tumor cell proliferation, and microvascular density. In GSC1 xenografts, intratumoral injection of Ad-hMSCs depleted the tumor cell population and induced migration of resident microglial cells. Overall, PTX loading did not significantly enhance the antitumor potential of hMSCs. Systemically injected Ad- and BM-hMSCs homed to tumor xenografts. The efficiency of hMSC homing ranged between 0.02 and 0.5% of the injected cells, depending both on the route of cell injection and on the source from which the hMSCs were derived. Importantly, systemically injected PTX-loaded hMSCs that homed to the xenograft induced cytotoxic damage to the surrounding tumor cells. Conclusions: hMSCs have a therapeutic potential in GBM brain xenografts which is also expressed against the GSC population. In this context, PTX loading of hMSCs seems to play a minor role

Risk factors associated with adverse fetal outcomes in pregnancies affected by Coronavirus disease 2019 (COVID-19): a secondary analysis of the WAPM study on COVID-19.

Objectives To evaluate the strength of association between maternal and pregnancy characteristics and the risk of adverse perinatal outcomes in pregnancies with laboratory confirmed COVID-19. Methods Secondary analysis of a multinational, cohort study on all consecutive pregnant women with laboratory-confirmed COVID-19 from February 1, 2020 to April 30, 2020 from 73 centers from 22 different countries. A confirmed case of COVID-19 was defined as a positive result on real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assay of nasal and pharyngeal swab specimens. The primary outcome was a composite adverse fetal outcome, defined as the presence of either abortion (pregnancy loss before 22 weeks of gestations), stillbirth (intrauterine fetal death after 22 weeks of gestation), neonatal death (death of a live-born infant within the first 28 days of life), and perinatal death (either stillbirth or neonatal death). Logistic regression analysis was performed to evaluate parameters independently associated with the primary outcome. Logistic regression was reported as odds ratio (OR) with 95% confidence interval (CI). Results Mean gestational age at diagnosis was 30.6+/-9.5 weeks, with 8.0% of women being diagnosed in the first, 22.2% in the second and 69.8% in the third trimester of pregnancy. There were six miscarriage (2.3%), six intrauterine device (IUD) (2.3) and 5 (2.0%) neonatal deaths, with an overall rate of perinatal death of 4.2% (11/265), thus resulting into 17 cases experiencing and 226 not experiencing composite adverse fetal outcome. Neither stillbirths nor neonatal deaths had congenital anomalies found at antenatal or postnatal evaluation. Furthermore, none of the cases experiencing IUD had signs of impending demise at arterial or venous Doppler. Neonatal deaths were all considered as prematurity-related adverse events. Of the 250 live-born neonates, one (0.4%) was found positive at RT-PCR pharyngeal swabs performed after delivery. The mother was tested positive during the third trimester of pregnancy. The newborn was asymptomatic and had negative RT-PCR test after 14 days of life. At logistic regression analysis, gestational age at diagnosis (OR: 0.85, 95% CI 0.8-0.9 per week increase; pPeer reviewe

High-power fiber laser cutting parameter optimization for nuclear Decommissioning

For more than 10 years, the laser process has been studied for dismantling work; however, relatively few research works have addressed the effect of high-power fiber laser cutting for thick sections. Since in the nuclear sector, a significant quantity of thick material is required to be cut, this study aims to improve the reliability of laser cutting for such work and indicates guidelines to optimize the cutting procedure, in particular, nozzle combinations (standoff distance and focus position), to minimize waste material. The results obtained show the performance levels that can be reached with 10 kW fiber lasers, using which it is possible to obtain narrower kerfs than those found in published results obtained with other lasers. Nonetheless, fiber lasers appear to show the same effects as those of CO2 and ND:YAG lasers. Thus, the main factor that affects the kerf width is the focal position, which means that minimum laser spot diameters are advised for smaller kerf widths

Heat conduction modelling to optimize the laser beam profile for pulsed conduction mode welding

Godkänd; 2015; 20151117 (jessun