Technology For Several Years Research Articles

Challenges in Tensile Testing of Thermoplastic Composites Reinforced with Chopped Carbon Fibre Produced by Fused Filament Fabrication Method

Additive manufacturing is a relatively new technology that has recently undergone noticeable develop-ment, which includes several types of technologies based on the gradual deposition of material in layers. The most widespread method is Fused Filament Fabrication, which belongs to an extrusion technique. The typical feature of extrusion methods is material deposition in the filaments form. Therefore, printer users cannot apply the same approach to products as with conventional technologies. The authors of the paper have been working with the mentioned technology for several years. The primary goal of the research is the investigation how printing parameters affect the mechanical properties of laminates reinforced with chopped carbon fibres. Based on experience and knowledge, the authors report in this article the most common challenges encountered in the preparation process of specimens for tensile testing. This knowledge can also help ordinary users of 3D printers, who also face these challenges without being aware of the impact of these pitfalls on mechanical properties.

Application Areas of Ionic Hydraulic Fluids

AbstractIonic liquids, as high‐tech technical fluids, have been in practical application in various fields of technology for several years. The search for ionic liquids suitable for use within hydraulic systems, as another new very important field of technology, has taken more than a decade. The development included the identification of material properties important for usage as a hydraulic fluid, an extensive preselection process and laboratory testing of suitable ionic liquids, as well as long‐term testing using real hydraulic components under real operating conditions. Based on the findings, potential areas of industrial application of ionic liquids as hydraulic fluids are presented, which arise from their extraordinary physicochemical properties.

Videoconferencing of Involuntary Commitment Hearings in the COVID Era.

Involuntary commitment hearings have been conducted utilizing videoconferencing technology for several years. There is limited information available in the published psychiatric literature pertaining to the use of this technology for commitment proceedings. The University of North Carolina Hospitals adopted a remote videoconferencing (tele-hearing) format for its civil commitment proceedings in response to the COVID-19 pandemic, and this provided us with the opportunity to investigate the use of such an arrangement. In this article, we review the use of videoconferencing for commitment hearings. We also review select case law related to the utilization of this technology for commitment hearings, which reveals that the courts have not been in full agreement about the legality of a virtual commitment tele-hearing format. Given that the general use of virtual platforms has expanded during the COVID-19 pandemic and many individuals and organizations are gaining confidence in operating this technology, more institutions may decide to shift to a virtual commitment scheme or make a commitment tele-hearing format permanent after the pandemic.

Defining Digital Competence for Older Preschool Children.

Recent studies show that by the age of 5-7, children have already had experience using technology for several years. Discussions about the impact of digital interaction on children are ongoing. Nevertheless, it is becoming clear that there is a need to develop concepts and tools that will help children in the process of exploring the digital world. One of such concepts can be that of digital competence. It refers to the readiness of an individual to apply digital technologies efficiently and safely in various spheres of life. To determine the content of digital competence for modern children of older preschool age. The study included interviewing children, organizing interaction of a child with a digital device, playing a card game, and having their parents answer survey questions. Our study found that older preschool children had a general idea of how to use digital technologies and could name those functions which they had observed or used themselves. The main purpose of the children's interactions with digital devices was entertainment. Most of the preschoolers demonstrated low motivation for learning how to use digital devices, and had not developed ideas about how to use digital devices in everyday life safely and effectively. The concept of digital competence can be applied to the study of issues related to the interaction of older preschool children with the digital environment. The results we obtained can help educators and parents to develop strategies for the appropriate and child-friendly interaction of preschoolers with the digital environment.

Practical Considerations for Implementing Virtual Care in Physical Medicine and Rehabilitation: For the Pandemic and Beyond.

This article outlines a practical approach to quickly implementing virtual care for physiatrists. This skill is relevant not only during times of a pandemic, when face to face care is impossible, but is also valuable when caring for patients who have physical, financial, logistic, or other challenges to on-site care. Key themes covered in this article include selecting appropriate virtual care platforms, consenting patients for virtual care and conducting successful virtual visits. It also reviews strategies for performing virtual physical examinations and engaging learners in virtual care.

Low temperature (Ts/Tm < 0.1) epitaxial growth of HfN/MgO(001) via reactive HiPIMS with metal-ion synchronized substrate bias

Low-temperature epitaxial growth of refractory transition-metal nitride thin films by means of physical vapor deposition has been a recurring theme in advanced thin-film technology for several years. In the present study, 150-nm-thick epitaxial HfN layers are grown on MgO(001) by reactive high-power impulse magnetron sputtering (HiPIMS) with no external substrate heating. Maximum film-growth temperatures Ts due to plasma heating range from 70 to 150 °C, corresponding to Ts/Tm = 0.10–0.12 (in which Tm is the HfN melting point in K). During HiPIMS, gas and sputtered metal-ion fluxes incident at the growing film surface are separated in time due to strong gas rarefaction and the transition to a metal-ion-dominated plasma. In the present experiments, a negative bias of 100 V is applied to the substrate, either continuously during the entire deposition or synchronized with the metal-rich portion of the ion flux. Two different sputtering-gas mixtures, Ar/N2 and Kr/N2, are employed in order to probe effects associated with the noble-gas mass and ionization potential. The combination of x-ray diffraction, high-resolution reciprocal-lattice maps, and high-resolution cross-sectional transmission electron microscopy analyses establishes that all HfN films have a cube-on-cube orientational relationship with the substrate, i.e., [001]HfN||[001]MgO and (100)HfN||(100)MgO. Layers grown with a continuous substrate bias, in either Ar/N2 or Kr/N2, exhibit a relatively high mosaicity and a high concentration of trapped inert gas. In distinct contrast, layers grown in Kr/N2 with the substrate bias synchronized to the metal-ion-rich portion of HiPIMS pulses have much lower mosaicity, no measurable inert-gas incorporation, and a hardness of 25.7 GPa, in good agreement with the results for epitaxial HfN(001) layers grown at Ts = 650 °C (Ts/Tm = 0.26). The room-temperature film resistivity is 70 μΩ cm, which is 3.2–10 times lower than reported values for polycrystalline-HfN layers grown at Ts = 400 °C.

Nb 3 Sn superconducting magnets for electron cyclotron resonance ion sources

Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb(3)Sn superconducting technology for several years. At the moment, Nb(3)Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb(3)Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6-7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb(3)Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13-15 T. Because of the brittleness and strain sensitivity of Nb(3)Sn, particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell pretensioned with water-pressurized bladders, and we analyze the expected coil stresses with a two-dimensional finite element mechanical model.

Securities Analysts and Incumbent Response to Radical Technological Change: Evidence from Digital Photography and Internet Telephony

A large body of research has explored the factors that impede established firms' responses to radical technological changes. While it is widely acknowledged that managers face pressures from financial markets to choose strategies that maximize shareholder value, little work in the technological change literature has considered the possible influences of public equity markets and the securities analysts who mediate them on incumbent firms challenged with technological change. In this paper, I begin to address the topic by empirically exploring how securities analysts react to the different strategies undertaken by incumbent firms faced with radical technological change. I study the question in two settings: the shift to digital technology in photography and the advent of Voice over Internet Protocol (VoIP) technology in wireline telecommunications. I find evidence that analysts are more attentive and positive toward incumbents' strategies that extend and preserve the existing technology than toward strategies that respond directly to the new technology. In these settings, analysts largely ignore incumbents' strategies that directly incorporate the new technology for several years following the discontinuity. This study provides insights into the nature and direction of analysts' reactions to firms' strategies in the context of technological change, and is a first step toward better understanding of the potential role of analysts' and financial markets in incumbent adaptation.

Acoustic emission as a monitoring method in prestressed concrete bridges health condition evaluation

A system, based on acoustic emission (AE) monitoring technique, has been studied at Kielce University of Technology for several years. A reference-signals database has been prepared based on laboratory tests on samples, beams and full-scale girders. The developed reference data has been verified during field monitoring of prestressed and post-tensioned concrete bridges. Some phenomena, which are usually very difficult or even impossible to discover by the traditional methods, were detected by this system.

A very low-cost pressure sensor with extremely high sensitivity

Abstract A new type of piezoresistive pressure sensor has been fabricated by polymer thick-film technology. The resistor bridge is screen-printed and cured onto a flexible substrate, which has been successfully used in hybrid technology for several years. Because of the high flexibility of the substrate, high sensitivity can be achieved at low cost. During the realization, several technological problems arising from the material characteristics of the substrate have to be overcome. The most difficult one is the appropriate handling of the flexible substrate during screen-printing, curing and soldering without generating built-in stresses. This is the reason why a new technology has in fact been developed. As a result, an extremely sensitive pressure sensor has been realized at a low cost.

OPTICAL WAVEGUIDES IN ANALYTICAL CHEMISTRY: RECENT ADVANCES

Achievements in guided wave optics have had a great influence on many areas of technology for several years. Fibre optic communication links, sensors for various parameters, recently developed distributed temperature sensors, integrated optical switches, etc. are all applications that are commercially available. The field of analytical chemistry is no exception in this growing technology. In order to compete with well‐established chemical‐sensing instrumentation, optical waveguide chemical sensors (OWCSs) must show all the qualities of such instrumentation. OWCSs combine well‐known features of sensors, based on waveguide optics, with optical methods of chemical analysis and offer advantages over other types of chemical sensor. OWCSs are electrically passive, corrosion‐resistant, can respond to analytes for which other chemical sensors are not available, and referencing can be carried out optically. They allow multicomponent measurements at several wavelengths, have a common technology for fabrication of sensors for different chemical and physical parameters and are easily compatible with telemetry etc. Further, only OWCSs are capable of distributed sensing. However, interference from ambient light, temperature, long‐term instability, relatively slow response time, and limited dynamic range may be a problem for some types of OWCS. These disadvantages can be considerably reduced using various methods.

Summary of Gas-Cooled reactor programs

This report has been compiled by Gas-Cooled Reactor Associates (GCRA) as a central source of summary-level information on the present status of High-Temperature Gas-Cooled Reactor (HTGR) programs in the world and on future plans for the continued development and deployment of HTGRs. Most of the information concerns the programs in the United States, the Federal Republic of Germany, Japan and the Soviet Union; countries that have had large programs related to HTGR technology for several years. Summary-level information is also provided in the report on the nature of the HTGR-related efforts in several other countries who either have an increasing interest in the technology and/or who are performing some development effort related to HTGR technology. Similarly, the report contains an summary-level update on the MAGNOX and AGR reactor programs, in recognition that these gas-cooled reactors were predecessors of the HTGR and have provided some of the bases from which the HTGR has evolved. Most of the new information for this report was gathered from material presented at the Eleventh International Conference on the HTGR held in Dimitrovgrad, USSR on June 19–20, 1989, the subsequent International Atomic Energy Agency Technical Committee Meeting on Gas-Cooled Reactor Technology, Safety and Siting held at the same site on June 21–23, 1989 and from several correspondents closely connected on a regular basis with the activities discussed.

Spray‐dryer scrubbers for high‐sulfur coal combustion. Solution of the energy problem in the U.S. may depend to a high degree on our ability to burn high‐sulfur coals with environmental safety. A progress report

Spray-dryer scrubbers for sulfur-dioxide removal from flue gases have been a developing technology for several years. Because spray-dryer scrubbers offer several potential advantages over wet scrubbing, they are attractive to the utility industry. Some of these advantages are: 1) a simpler waste-disposal problem, 2) higher energy efficiency, 3) lower water comsumption, 4) lower capital cost, 5) lower operating costs, 6) less exotic materials of construction, 7) simpler operation, and 8) ability to consume some plant waste water in the spray dryer. The paper provides a broad survey of the state of the art as it might be useful to electric utilitites using high-sulfur coal.