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The purpose of this study is to explore the applications of 3D printing in space sectors. The authors have highlighted the potential research gap that can be explored in the current field of study. Three-dimensional (3D) printing is an additive manufacturing technique that uses metallic powder, ceramic or polymers to build simple/complex parts. The parts produced possess good strength, low weight and excellent mechanical properties and are cost-effective. Therefore, efforts have been made to make the adoption of 3D printing successful in space so that complex parts can be manufactured in space. This saves a considerable amount of both time and carrying cost. Thereof the challenges and opportunities that the space sector holds for additive manufacturing is worth reviewing to provide a better insight into further developments and prospects for this technology.

The potentiality of 3D printing for the manufacturing of various components under space conditions has been explained. Here, the authors have reviewed the details of manufactured parts used for zero-gravity missions, subjected to onboard international space station conditions and with those manufactured on earth. Followed by the major opportunities in 3D printing in space which include component repair, material characterization, process improvement and process development along with the new designs. The challenges like space conditions, availability of power in space, the infrastructure requirements and the quality control or testing of the items that are being built in space are explained along with their possible mitigation strategies.

These components are well comparable with those prepared on earth which enables a massive cost saving. Other than the onboard manufacturing process, numerous other components as well as a complete robot/satellite for outer space applications were manufactured by additive manufacturing. Moreover, these components can be recycled onboard to produce feedstock for the next materials. The parts produced in space are bought back and compared with those built on earth. There is a difference in their nature, i.e. the flight specimen showed a brittle nature, and the ground specimen showed a denser nature.

This review discusses the advancements of 3D printing in space and provides numerous examples of the applications of 3D printing in space and space applications. This paper is solely dedicated to 3D printing in space. It provides a breakthrough in the literature as a limited amount of literature is available on this topic. This paper aims at highlighting all the challenges that additive manufacturing faces in the space sector and also the future opportunities that await development.

This paper aims to develop efficient and simple models for thermal distribution, melt pool dimensions and controlled phase change in the laser additive manufacturing (AM) of bulk and powder particles ceramic materials.

This paper proposes new analytical models for the AM of bulk and powder bed ceramic materials. A volumetric moving heat source, along with the complete melting of bulk and powder particle materials, is taken into account. Different values of laser absorption coefficient in solid and liquid states have been used to investigate the phase transformation. Furthermore, the pores and voids dimensions are also included in the modeling. Theoretical predictions have been compared with the experimental analyses and finite element simulations in laser to silicon nitride and laser to alumina interaction. The analysis focuses on the impact of laser power and scanning speed on the melt pool width and depth evolution into the bulk substrate and powder bed.

This study shows that the powder particles exhibit a higher thermal distribution value than the bulk substrate because of voids in the powder layer. The laser beam experiences multiple reflections in the presence of porosity/voids, thus increasing the surface absorption coefficient, which becomes relevant with the increment in the pore/void dimension. A direct relationship has been found between the laser power and melt pool dimensions, while the scanning speed displayed an inverse relationship for the melt pool width and length. Larger melt dimensions were inferred in the case of laser–powder particle interaction compared with laser–bulk substrate interaction. A close correlation was found between the analytical simulations, experimental investigations and numerical simulation results within the range of 4%–8%.

This paper fulfills an identified need to develop efficient and simplified models for ceramics laser AM by taking into account different laser absorption coefficients in solid and liquid form, voids and pores dimensions and controlled phase transformation to avoid vapors and plasma formation. The limitation of the finite element simulation model is that the solution is strongly dependent on the mesh quality and accuracy directly linked to the computation efficiency and time. A finer mesh requires a longer computing time than a coarse mesh. Finite element simulations require, however, specialized skills.

Porosity is a commonly analyzed defect in the laser-based additive manufacturing processes owing to the enormous thermal gradient caused by repeated melting and solidification. Currently, the porosity estimation is limited to powder bed fusion. The porosity estimation needs to be explored in the laser melting deposition (LMD) process, particularly analytical models that provide cost- and time-effective solutions compared to finite element analysis. For this purpose, this study aims to formulate two mathematical models for deposited layer dimensions and corresponding porosity in the LMD process.

In this study, analytical models have been proposed. Initially, deposited layer dimensions, including layer height, width and depth, were calculated based on the operating parameters. These outputs were introduced in the second model to estimate the part porosity. The models were validated with experimental data for Ti6Al4V depositions on Ti6Al4V substrate. A calibration curve (CC) was also developed for Ti6Al4V material and characterized using X-ray computed tomography. The models were also validated with the experimental results adopted from literature. The validated models were linked with the deep neural network (DNN) for its training and testing using a total of 6,703 computations with 1,500 iterations. Here, laser power, laser scanning speed and powder feeding rate were selected inputs, whereas porosity was set as an output.

The computations indicate that owing to the simultaneous inclusion of powder particulates, the powder elements use a substantial percentage of the laser beam energy for their melting, resulting in laser beam energy attenuation and reducing thermal value at the substrate. The primary operating parameters are directly correlated with the number of layers and total height in CC. Through X-ray computed tomography analyses, the number of layers showed a straightforward correlation with mean sphericity, while a converse relation was identified with the number, mean volume and mean diameter of pores. DNN and analytical models showed 2%–3% and 7%–9% mean absolute deviations, respectively, compared to the experimental results.

This research provides a unique solution for LMD porosity estimation by linking the developed analytical computational models with artificial neural networking. The presented framework predicts the porosity in the LMD-ed parts efficiently.

This study aims to outline the current challenges in ultrasonic additive manufacturing (AM). AM has revolutionized manufacturing and offers possible solutions when conventional techniques reach technological boundaries. Ultrasonic additive manufacturing (UAM) uses mechanical vibrations to join similar or dissimilar metals in three-dimensional assemblies. This hybrid fabrication method got attention due to minimum scrap and near-net-shape products.

This paper reviews significant UAM areas in process parameters such as pressure force, amplitude, weld speed and temperature. These process parameters used in different studies by researchers are compared and presented in tabular form. UAM process improvements and understanding of microstructures have been reported. This review paper also enlightens current challenges in the UAM process, process improvement methods such as heat treatment methods, foil-to-foil overlap and sonotrode surface roughness to increase the bond quality of welded parts.

Results showed that UAM could solve various problems and produce net shape products. It is concluded that process parameters such as pressure, weld speed, amplitude and temperature greatly influence weld quality by UAM. Post-weld heat treatment methods have been recommended to optimize the mechanical strength of ultrasonically welded joints process parameters. It has been found that the tension force is vital for the deformation of the pre-machined structures and for the elongation of the foil during UAM bonding. It is recommended to critically investigate the mechanical properties of welded parts with standard test procedures.

This study compiles relevant research and findings in UAM. The recent progress in UAM is presented in terms of material type, process parameters and process improvement, along with key findings of the particular investigation. The original contribution of this paper is to identify the research gaps in the process parameters of ultrasonic consolidation.

For metal additive manufacturing, metallic powders are usually produced by vacuum induction gas atomization (VIGA) through the breakup of liquid metal into tiny droplets by gas jets. VIGA is considered a cost-effective technique to prepare feedstock. In VIGA, the quality and the morphology of the produced particles are mainly controlled by the gas pressure used during powder production, keeping the setup configuration constant.

In VIGA process for metallic additive manufacturing feedstock preparation, the quality and morphology of the powder particles are mainly controlled by the gas pressure used during powder production.

In this study, Inconel-625 feedstock was produced using a supersonic nozzle in a close-coupled gas atomization apparatus. Powder size distribution (PSD) was studied by varying the gas pressure.

The nonmonotonic but deterministic relationships were observed between gas pressure and PSD. It was found that the maximum 15–45 µm percentage PSD, equivalent to 84%, was achieved at 29 bar Argon gas pressure, which is suitable for the LPBF process. Following on, the produced powder particles were used to print tensile test specimens via LPBF along XY- and ZX-orientations by using laser power = 475 W, laser scanning speed = 800 mm/s, powder layer thickness = 50 µm and hatch distance = 100 µm. The yield and tensile strengths were 9.45% and 13% higher than the ZX direction, while the samples printed in ZX direction resulted in 26.79% more elongation compared to XY-orientation.

This study aims to discuss the state-of-the-art digital factory (DF) development combining digital twins (DTs), sensing devices, laser additive manufacturing (LAM) and subtractive manufacturing (SM) processes. The current shortcomings and outlook of the DF also have been highlighted. A DF is a state-of-the-art manufacturing facility that uses innovative technologies, including automation, artificial intelligence (AI), the Internet of Things, additive manufacturing (AM), SM, hybrid manufacturing (HM), sensors for real-time feedback and control, and a DT, to streamline and improve manufacturing operations.

This study presents a novel perspective on DF development using laser-based AM, SM, sensors and DTs. Recent developments in laser-based AM, SM, sensors and DTs have been compiled. This study has been developed using systematic reviews and meta-analyses (PRISMA) guidelines, discussing literature on the DTs for laser-based AM, particularly laser powder bed fusion and direct energy deposition, in-situ monitoring and control equipment, SM and HM. The principal goal of this study is to highlight the aspects of DF and its development using existing techniques.

A comprehensive literature review finds a substantial lack of complete techniques that incorporate cyber-physical systems, advanced data analytics, AI, standardized interoperability, human–machine cooperation and scalable adaptability. The suggested DF effectively fills this void by integrating cyber-physical system components, including DT, AM, SM and sensors into the manufacturing process. Using sophisticated data analytics and AI algorithms, the DF facilitates real-time data analysis, predictive maintenance, quality control and optimal resource allocation. In addition, the suggested DF ensures interoperability between diverse devices and systems by emphasizing standardized communication protocols and interfaces. The modular and adaptable architecture of the DF enables scalability and adaptation, allowing for rapid reaction to market conditions.

Based on the need of DF, this review presents a comprehensive approach to DF development using DTs, sensing devices, LAM and SM processes and provides current progress in this domain.

Universities across the globe are spending an increasing amount of their budgets to offer web-based services to cater information need especially off-campus students. However, the success of web-based services depends on how well the target users are satisfied with the use of the web services. The purpose of this paper is to assess students’ satisfaction with the use of the Allama Iqbal Open University (AIOU) web-based services.

Pilot tested questionnaire-based survey was administered to collect data from a sample of 388; selected through systematic sampling technique from the study’s population consisted of master level students belonged to 11 different academic departments of the Faculty of Social Science and Humanities at the AIOU from all over Pakistan.

Based on 318 useful questionnaires, response rate 82 percent, the results show that majority of the students were satisfied with the use of at the AIOU web-based services except for online mailing books tracking system, library web OPAC and web radio service. However, t-test analysis shows that no difference was found in the opinion of male and female respondents in terms of their satisfaction with the use of the web services. ANOVA results indicate that there was no significant difference depicted in satisfaction with the use of the web services among the respondents enrolled in different disciplines of the faculty. Similarly, no significant difference was found among different age groups. Moreover, the respondents belonging to all five provinces; Punjab, Khyber Pakhtunkhwa, Sindh, Baluchistan, Gilgit Baltistan, and Federal Capital territory showed the same level of satisfaction with the use of the services. The results of regression analysis (R²=0.226) denote that both perceived usefulness and perceived ease of use significantly predicted, 22.6 percent, in students’ satisfaction with the use the web services.

The study provides valuable recommendations which may be helpful for web administration of the university to improve AIOU web-based services.

To the best knowledge, this is the first study conducted to investigate the satisfaction with the use of the university web-based services in distance education’s perspective of Pakistan.

The delivery of information services in higher education is increasingly relying on Web-based systems. The low adoption and underutilization of information systems have been major problems for developing countries such as Pakistan in terms of realizing their full benefits. This study aims to investigate factors affecting student use of Allama Iqbal Open University’s (AIOU) Web-based services by using the Unified Theory of Acceptance and Use of Technology (UTAUT) from the perspective of Pakistani distance education.

This study has adopted quantitative research design with the UTAUT model as a theoretical framework. A self-completion structured questionnaire-based survey has been administered to 388 master’s level students, selected through systematic sampling from the target population. The response rate was 82 per cent (318). All statistical tests have been performed using IBM SPSS (version 20.0) and Process macro for SPSS.

Findings of the model’s hypotheses reveal that performance expectancy, effort expectancy and social influence are significant predictors of student behavioural intention to use AIOU Web-based services, whereas actual student use is dependent on facilitating conditions and student behavioural intention to use. The impact of moderating variables with respect to age, gender and experience did not influence the actual use of the Web services. However, the research model significantly measured (62.1 per cent) the actual use of AIOU Web-based services by the students.

This study is delimited to the UTAUT model to investigate the phenomena. Besides this, the context of the study is the voluntary instead of mandatory usage of Web services. A study conducted in mandatory settings, in which students are bound to use Web services, may have different results.

This is the first attempt to apply the UTAUT model to investigate the factors affecting student use of Web-based services from the perspective of distance education and the findings prove strong support for the model.

The presence of heavy metals in milk causes many acute and chronic physiological dysfunctions in human organs. The present study aims to investigate the heavy metals in cow's and buffalo's milk of two major cities, Karachi and Gujranwala, Pakistan to estimate metal intake by humans from this source.

In total, 48 milk samples from 2 cities were drawn from animals' udder to avoid contamination. Each sample was digested with nitric acid at 105 ^oC (degree Celsius) on a pre-heated electric hot plate to investigate the metals by atomic absorption spectroscopy (flame type). Air-acetylene technique analyzed chromium, cadmium and lead, and the hydride method analyzed arsenic in the milk samples.

The results revealed the highest mean lead concentration (19.65 ± 43.86 ppb) in the milk samples, followed by chromium (2.10 ± 2.33 ppb) and arsenic (0.48 ± 0.73 ppb). Cadmium was not detected in any sample, assuming cadmium's occurrence was below the detection level. The concentrations of all the metals in the samples of the two cities do not differ statistically. Lead concentrations in the buffalo's milk were higher than in cow's milk (p < 0.05). However, the concentrations of arsenic and chromium between buffalo's and cow's milk do not differ statistically. The present study reveals a lower level of metals in the milk than those conducted elsewhere. The mean concentrations of all the metals met the World Health Organization's (WHO) safety guidelines (1993).

Although cadmium causes toxicity in the human body, cadmium could not be measured because cadmium's concentration was below the detection level, which is 1 ppb.

This study will help reduce the toxic metals in our environment, and the sources of heavy metals, particularly from the industrial sector could be identified. The feed and water consumed by the milking animals could be carefully used for feeding them.

This study will help reduce the diseases and malfunction of human organs and organ systems since these heavy metals cause toxicity and carcinogenicity in humans. Arsenic and chromium cause cancer while lead causes encephalopathy (a brain disease).

The study reports heavy metal concentrations in the two attributes of four independent variables of raw milk samples that were scarcely reported from Pakistan.

The purpose of this paper was to systematically collect and review all studies which have been conducted on research data services in libraries across the globe.

Six world-renowned scholarly databases were searched and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used for the identification and selection of eligible studies. The studies were then assessed using a well-renowned framework for the quality assessment of research studies.

The results revealed that the libraries were engaged in providing different types of research data services such as identification, acquisition, management and preservation of research data. They also arranged training programs, supported the publishing and sharing of data and dealt with the licensing and copyright issues related to data.

The results of this study would be helpful for researchers and organizations, especially those engaged in educational activities, in understanding the current scenario of research data services in the world libraries. Furthermore, the findings offer valuable insights to library professionals regarding the types of research support services available globally. This would enable them to play an integral role in planning, designing and implementing such services in their libraries.

To the best of the authors’ knowledge, this study is the first of its kind that systematically collects and reviews the literature on research data services in libraries worldwide.