Underwater Pulse-Current FCAW - Part 2: Bubble Behaviors and Waveform Optimization

Underwater pulse-current wet welding was proposed in part 1 of this two-part report. The novel technology obtained improved metal transfer and welding process stability. The main reason for droplet oversizing and long transfer cycles was found to be the deviated large droplet stage. In this part, the waveform optimization for both bubble behaviors and metal transfer were investigated. Efforts were made for shortening the duration of the deviated large droplet stage. Pulse current influences on bubble evolution was studied. It was found that two different separation modes can be adjusted by appropriately changing the current values when the bubbles are necking. Quickly reducing the welding cur-rent can sharply lower the impact force on the droplets due to intense gas flow changes inside. Under the optimized pulse current, the range of the metal transfer cycle became narrower, and droplet diameters were smaller than that of the original condition. Stable and improved metal transfer processes were achieved with a frequency of 7.52 Hz and an average droplet diameter of 2.4 mm, which was about 1.5 times the wire diameter. The optimized pulse waveform greatly improved weld formation with less spatter and a more uniform appearance.

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Underwater Pulse-Current FCAW - Part 1: Waveform and Process Features

Welding Journal ◽

10.29391/2020.99.013 ◽

2020 ◽

Vol 99 (05) ◽

pp. 135s-145s ◽

Cited By ~ 1

Author(s):

CHUANBAO JIA ◽

◽

JUNFEI WU ◽

YANFEI HAN ◽

YONG ZHANG ◽

...

Keyword(s):

Pulse Current ◽

Short Circuit ◽

Droplet Diameter ◽

Low Frequency ◽

Welding Process ◽

Welding Current ◽

Experimental System ◽

Flux Cored Arc Welding ◽

The Stability ◽

Repulsive Forces

The typical metal transfer mode in conventional underwater wet flux cored arc welding (FCAW) delivers large droplet repulsive transfer with low frequency. The process stability and the weld quality are seriously deteriorated with significant spatter and frequent arc extinctions. It is thought the repulsive forces applied on droplets can be reduced by rapidly decreasing the welding current, making the droplets sag and oscillate. A novel underwater pulsecurrent FCAW was proposed to periodically regulate the forces applied on droplets. The experimental system was developed with specially designed pulse current and reliable arc length control. Visual and electrical signals were collected simultaneously to study the process features. It was found that the maximum droplet diameter decreased to less than 5 mm; the temporary arc-extinguishing frequency decreased significantly; there was almost no short-circuit transfer and surface-tension transfer; and the stability of the welding process was significantly improved.

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Characteristic of Hyperbaric GMAW Metal Transfer at 1-12 Bar Argon Environment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.900.565 ◽

2014 ◽

Vol 900 ◽

pp. 565-569

Author(s):

Kai Li ◽

Hong Ming Gao ◽

Hai Chao Li ◽

Shan Gong

Keyword(s):

High Speed ◽

Ambient Pressure ◽

Welding Process ◽

Axial Direction ◽

Metal Transfer ◽

Large Droplet ◽

Camera System ◽

Transfer Mode ◽

Feeding Speed ◽

Different Characteristics

The metal transfer behavior in hyperbaric GMAW process was investigated by using a high speed camera system with infrared laser as backlight. The metal transfer mode at 1-12bar argon environment shows different characteristics. Three kinds were observed: large droplet repelled transfer, projected repelled transfer and hyperbaric streaming transfer. Large droplet repelled transfer occurs mostly in the welding process with low feeding speed and relatively low welding voltage. Projected repelled transfer appears at middle feeding speed and high ambient pressure. Transfer tracks of former two modes deviate from the axial direction of welding wire. The spatter is produced more frequently in the projected repelled transfer mode. Hyperbaric streaming transfer is found meanly at high feeding speed and relatively high voltage. Because of its stability reflected from metal transfer process, hyperbaric GMAW process with hyperbaric streaming transfer mode should be employed preferentially.

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Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200192 ◽

2020 ◽

Vol 92 (3) ◽

pp. 30901

Author(s):

Suvanjan Bhattacharyya ◽

Debraj Sarkar ◽

Ulavathi Shettar Mahabaleshwar ◽

Manoj K. Soni ◽

M. Mohanraj

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Thermal Performance ◽

Working Fluid ◽

The Novel ◽

Heat Exchanger Tube ◽

Heat Transfer Augmentation ◽

Corrugated Tube ◽

The Impact ◽

Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

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Wacana Kolonial dalam Novel Max Havelaar: Sebuah Kajian Poskolonial

Metahumaniora ◽

10.24198/metahumaniora.v7i3.18862 ◽

2017 ◽

Vol 7 (3) ◽

pp. 411

Author(s):

Abu Bakar Ramadhan Muhamad

Keyword(s):

Point Of View ◽

The Other ◽

The Novel ◽

Colonial Discourse ◽

The Impact ◽

The Voice

AbstrakHegemoni kolonialisme dalam budaya poskolonial merupakan alasan penelitian inikemudian mengkaji wacana kolonial dalam novel Max Havellar (MH) khususnya dampakditimbulkannya. Dampak dimaksud adalah posisi keberpihakan pemikiran tersirat darikarya tersebut. Hasil pembahasan menunjukkan, secara temporal maupun permanen MHmenyuarakan ketidakadilan dalam kondisi-kondisi kolonial menyangkut penindasan sangpenjajah terhadap terjajah. Hanya saja, upaya mengatasnamakan atau mewakili suarakaum terjajah terbukti mengimplikasikan ciri ideologis statis kerangka kolonialisme(orientalisme); yakni cara pandang Eropasentris, di mana “Barat” sebagai self adalah superior,dan “Timur” sebagai other adalah inferior. Dalam konteks poskolonialisme, MH dengan sifatkritisnya yang berupaya “menyuarakan” nasib pribumi terjajah, justru menampilkan stigmapenguatan kolonialitas itu sendiri secara hegemonik. Artinya, “menyuarakan” nasib pribumidimaknai sebagai keberpihankan kolonial yang kontradiktif, di mana stigma penguatankolonialitas justru lebih terasa, ujung-ujungnya melanggengkan hegemoni kolonial. Tidakmembela yang terjajah, tetapi memperhalus cara kerja mesin kolonial.AbstractThe hegemony of colonialism in the culture of postcolonial society is the reason this studythen examines the colonial discourse in the novel Max Havellar (MH) in particular the impactit brings. The impact in question is the implied position of thought in the work. The resultsof the discussion show that, temporarily or permanently, MH voiced injustice in the colonialconditions regarding the oppression of the colonist against the colonized. However, the effort toname or represent the voice of the colonized has proven to imply a static ideological characterin the framework of colonialism (orientalism); ie Eropacentric point of view, in which “West” asself is superior, and “East” as the other is the inferior. In the context of postcolonialism, MH withits critical nature that seeks to “voice” the fate of the colonized natives, actually presents thestigma of strengthening coloniality itself hegemonicly. That is, “voicing” the fate of the pribumiis interpreted as a contradictory colonial flare, where the stigma of strengthening colonialityis more pronounced, which ultimately perpetuates the hegemony of colonialism. No longerdefending the colonized, but refining the workings of the colonial machinery.

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Association and treatment of diabetes in patients affected by Covid-19

International Journal of Research in Pharmaceutical Sciences ◽

10.26452/ijrps.v11ispl1.3591 ◽

2020 ◽

Vol 11 (SPL1) ◽

pp. 1198-1201

Author(s):

Syed Yasir Afaque

Keyword(s):

Diabetes Mellitus ◽

Prognostic Value ◽

Heart Diseases ◽

The Novel ◽

The World ◽

Treatment Of Diabetes ◽

Coronavirus Infection ◽

Composite Outcomes ◽

Novel Coronavirus ◽

The Impact

In December 2019, a unique coronavirus infection, SARS-CoV-2, was first identified in the province of Wuhan in China. Since then, it spread rapidly all over the world and has been responsible for a large number of morbidity and mortality among humans. According to a latest study, Diabetes mellitus, heart diseases, Hypertension etc. are being considered important risk factors for the development of this infection and is also associated with unfavorable outcomes in these patients. There is little evidence concerning the trail back of these patients possibly because of a small number of participants and people who experienced primary composite outcomes (such as admission in the ICU, usage of machine-driven ventilation or even fatality of these patients). Until now, there are no academic findings that have proven independent prognostic value of diabetes on death in the novel Coronavirus patients. However, there are several conjectures linking Diabetes with the impact as well as progression of COVID-19 in these patients. The aim of this review is to acknowledge about the association amongst Diabetes and the novel Coronavirus and the result of the infection in such patients.

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The ground-level ozone concentration is inversely correlated with the number of COVID-19 cases in Warsaw, Poland

Air Quality Atmosphere & Health ◽

10.1007/s11869-021-01009-7 ◽

2021 ◽

Author(s):

Oskar Wiśniewski ◽

Wiesław Kozak ◽

Maciej Wiśniewski

Keyword(s):

Wind Speed ◽

Ozone Concentration ◽

Inverse Correlation ◽

Ground Level ◽

Viral Agent ◽

The Novel ◽

Weather Factors ◽

Ground Level Ozone ◽

The Many ◽

The Impact

AbstractCOVID-19, which is a consequence of infection with the novel viral agent SARS-CoV-2, first identified in China (Hubei Province), has been declared a pandemic by the WHO. As of September 10, 2020, over 70,000 cases and over 2000 deaths have been recorded in Poland. Of the many factors contributing to the level of transmission of the virus, the weather appears to be significant. In this work, we analyze the impact of weather factors such as temperature, relative humidity, wind speed, and ground-level ozone concentration on the number of COVID-19 cases in Warsaw, Poland. The obtained results show an inverse correlation between ground-level ozone concentration and the daily number of COVID-19 cases.

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The High-Rate Sealed MRPC to Promote Pollutant Exchange in Gas Gaps: Status on the Development and Observations

Applied Sciences ◽

10.3390/app11114722 ◽

2021 ◽

Vol 11 (11) ◽

pp. 4722

Author(s):

Botan Wang ◽

Xiaolong Chen ◽

Yi Wang ◽

Dong Han ◽

Baohong Guo ◽

...

Keyword(s):

Gas Flow ◽

High Rate ◽

Stable Operation ◽

Beam Test ◽

High Luminosity ◽

Rate Test ◽

3D Printed ◽

Resistive Plate Chambers ◽

The Impact ◽

Current Behavior

This work reports the latest observations on the behavior of two Multigap Resistive Plate Chambers (MRPC) under wide high-luminosity exposures, which motivate the development and in-beam test of the sealed MRPC prototype assembled with low-resistive glass. The operation currently being monitored, together with previous simulation results, shows the impact of gas pollution caused by avalanches in gas gaps, and the necessity to shrink the gas-streaming volume. With the lateral edge of the detector sealed by a 3D-printed frame, a reduced gas-streaming volume of ~170 mL has been achieved for a direct gas flow to the active area. A high-rate test of the sealed MRPC prototype shows that, ensuring a 97% efficiency and 70 ps time resolution, the sealed design results in a stable operation current behavior at a counting rate of 3–5 kHz/cm2. The sealed MRPC will become a potential solution for future high luminosity applications.

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SARS-CoV-2/DENV co-infection: a series of cases from the Federal District, Midwestern Brazil

BMC Infectious Diseases ◽

10.1186/s12879-021-06456-2 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Heidi Luise Schulte ◽

José Diego Brito-Sousa ◽

Marcus Vinicius Guimarães Lacerda ◽

Luciana Ansaneli Naves ◽

Eliana Teles de Gois ◽

...

Keyword(s):

Clinical Signs ◽

Federal District ◽

Therapeutic Interventions ◽

Diagnostic Process ◽

The Novel ◽

Prevention Measures ◽

Laboratory Findings ◽

Novel Coronavirus ◽

The Impact

Abstract Background Since the novel coronavirus disease outbreak, over 179.7 million people have been infected by SARS-CoV-2 worldwide, including the population living in dengue-endemic regions, particularly Latin America and Southeast Asia, raising concern about the impact of possible co-infections. Methods Thirteen SARS-CoV-2/DENV co-infection cases reported in Midwestern Brazil between April and September of 2020 are described. Information was gathered from hospital medical records regarding the most relevant clinical and laboratory findings, diagnostic process, therapeutic interventions, together with clinician-assessed outcomes and follow-up. Results Of the 13 cases, seven patients presented Acute Undifferentiated Febrile Syndrome and six had pre-existing co-morbidities, such as diabetes, hypertension and hypopituitarism. Two patients were pregnant. The most common symptoms and clinical signs reported at first evaluation were myalgia, fever and dyspnea. In six cases, the initial diagnosis was dengue fever, which delayed the diagnosis of concomitant infections. The most frequently applied therapeutic interventions were antibiotics and analgesics. In total, four patients were hospitalized. None of them were transferred to the intensive care unit or died. Clinical improvement was verified in all patients after a maximum of 21 days. Conclusions The cases reported here highlight the challenges in differential diagnosis and the importance of considering concomitant infections, especially to improve clinical management and possible prevention measures. Failure to consider a SARS-CoV-2/DENV co-infection may impact both individual and community levels, especially in endemic areas.

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Influence of post weld heat treatment on tensile properties of cold metal transfer (CMT) arc welded AA6061-T6 aluminium alloy joints

Journal of the Mechanical Behavior of Materials ◽

10.1515/jmbm-2019-0015 ◽

2019 ◽

Vol 28 (1) ◽

pp. 135-145 ◽

Cited By ~ 2

Author(s):

Addanki Ramaswamy ◽

Sudersanan Malarvizhi ◽

Visvalingam Balasubramanian

Keyword(s):

Heat Treatment ◽

Tensile Properties ◽

Gas Metal Arc Welding ◽

Weight Ratio ◽

Welding Process ◽

Metal Transfer ◽

Post Weld Heat Treatment ◽

Cold Metal Transfer ◽

Cold Metal ◽

Weld Heat

AbstractAluminium alloys of 6xxx series are widely used in the fabrication of light weight structures especially, where high strength to weight ratio and excellent weld-ability characteristics are desirable. Gas metal arc welding (GMAW) is the most predominantly used welding process in many industries due to the ease of automation. In this investigation, an attempt has been made to identify the best variant of GMAW process to overcome the problems like alloy segregation, precipitate dissolution and heat affected zone (HAZ) softening. Thin sheets of AA6061-T6 alloy were welded by cold metal transfer (CMT) and Pulsed CMT (PCMT). Among the two joints, the joint made by PCMT technique exhibited superior tensile properties due to the mechanical stirring action in the weld pool caused by forward and rearward movement of the wire along with the controllable diffusion rate at the interface caused by shorter solidification time. However, softening still exists in the welded joints. Further to increase the joint efficiency and to minimize HAZ softening, the joints were subjected to post weld heat treatment (PWHT). Approximately 10% improvement in the tensile properties had been observed in the PWHT joints due to the nucleation of strengthening precipitates in the weld metal and HAZ.

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Experimental studies on the possibility of using a pulsed laser for spot welding of thin metallic foils

Open Engineering ◽

10.1515/eng-2020-0076 ◽

2020 ◽

Vol 10 (1) ◽

pp. 674-680

Author(s):

Piotr Sęk

Keyword(s):

Experimental Studies ◽

Pulsed Laser ◽

Welding Process ◽

Pulse Mode ◽

Weld Strength ◽

Spot Welds ◽

Butt Welding ◽

Strength Tests ◽

Metallic Foils ◽

The Impact

AbstractThe purpose of the experiment was to study the influence of the laser beam in pulse mode on metallic foils in order to obtain a spot weld. The welding process was carried out using the overlap weld method, using spot welds in various quantities. The Nd - YAG BLS 720 pulsed laser was used to conduct the experiment. The impact of the number of spot welds on the value of force needed to break the sample was examined. A number of measurements were carried out to determine the best process parameters. Butt welding and overlap welding were also performed using a continuous weld consisting of spot welds. Weld strength tests were performed to select the most appropriate parameters for the process under consideration.

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