Electron sources with a hot cathode operating in consumption or generation modes are widely used in many vacuum devices as gas ion sources, thermionic energy converters. The main aim of this work is ...to get information how dynamic properties of the electron source changes within full range of work, therefore the identification of a hot cathode electron source using the step signal and the time domain approach to know dynamic parameters (DC incremental transconductance, time constant, delay time) of the electron source in full range of its operation is made. In the first part, an open-loop system identification using step response method was conducted. For the electron source with a thoriated tungsten cathode (d=0.1 mm, l=45 mm) operating in the range 1 μA to 1 mA, the time constant T varies from 0.71 s to 0.35 s, the delay time T0 from 0.04 s to 0.01 s and the DC incremental transconductance g0 from 0 to 0.0056 S, respectively. In the next step, an approximation of obtained characteristics is made and ultimate gains of thermionic emission current automatic control system for each fixed operating point are estimated. The results of similar investigations for electron sources with an yttrium oxide coated iridium cathode and a tungsten cathode have also been shown. Presented system identification approach can be successfully applied to other types of the hot cathode electron sources.
Industries that rely on additive manufacturing of metallic parts, especially biomedical companies, require material science-based knowledge of how process parameters and methods affect the properties ...of manufactured elements, but such phenomena are incompletely understood. In this study, we investigated the influence of selective laser melting (SLM) process parameters and additional heat treatment on mechanical properties. The research included structural analysis of residual stress, microstructure, and scleronomic hardness in low-depth measurements. Tensile tests with specimen deformation analysis using digital image correlation (DIC) were performed as well. Experiment results showed it was possible to observe the porosity growth mechanism and its influence on the material strength. Specimens manufactured with 20% lower energy density had almost half the elongation, which was directly connected with the porosity growth during energy density reduction. Hot isostatic pressing (HIP) treatment allowed for a significant reduction of porosity and helped achieve properties similar to specimens manufactured using different levels of energy density.
The People's Liberation Army (PLA) seeks not only to equal but also to overtake the US military through seizing the initiative in the ongoing Revolution in Military Affairs (RMA). Chinese military ...leaders believe the form of warfare is changing from today's 'informatised' (信息化) warfare to future 'intelligentised' (智能化) warfare. The PLA's approach to leveraging emerging technologies is likely to differ from parallel American initiatives because of its distinct strategic culture, organisational characteristics, and operational requirements. This research examines the evolution of the PLA's strategic thinking and concepts of operations, seeking to contribute to the military innovation literature by evaluating major theoretical frameworks for the case of China.
China has prioritized quantum science and technology as a critical frontier for its national security and development. To date, Chinese research has already reached a leading position within the ...discipline, enabled by state support and funding, as well as the recruitment and cultivation of talent. The rapid advances on this front can provide a valuable illustration of the dynamics of China's evolving innovation ecosystem, including the increased prominence of leading technology companies, and even start-ups, as serious contenders. China's strategy of military-civil fusion, which aims to create a more integrated ecosystem in science and technology, can contribute to enabling progress in dual-use developments. This case study draws upon the shared framework for this special issue, which provides a method by which to consider the factors that enable defense innovation. Looking forward, these advances could prove consequential for the future strategic balance between China and the United States.
The paper, which is a summary and supplement of previous works and research, presents the results of numerical and physical modeling of the GX2CrNiMoCuN25-6-3 duplex cast steel thin-walled castings ...production. To obtain thin-walled castings with wall in the thinnest place even below 1 mm was used the centrifugal casting technology and gravity casting. The analyzed technology (centrifugal casting) enables making elements with high surface quality with reduced consumption of batch materials and, as a result, reducing the costs of making a unitary casting. The idea behind the production of cast steel with the use of centrifugal technology was to find a remedy for the problems associated with unsatisfactory castability of the tested alloy. The technological evaluation of the cast construction was carried out using the Nova Flow & Solid CV 4.3r8 software. Numerical simulations of crystallization and cooling were carried out for a casting without a gating system and sinkhead located in a mold in accordance with the pouring position. It was assumed that the analyzed cast will be made in the sand form with dimensions 250×250×120 mm.
The Chinese People's Liberation Army (PLA) anticipates that today's advances in emerging technologies, particularly artificial intelligence, could catalyse a new military revolution. Elsa B Kania ...explores how, fearing surprise and seeking strategic opportunity, the PLA is actively pursuing military innovation and exploring new paradigms of military power.
Two MgLiAl alloys of composition 4.5% Li and 1.5% Al (in wt.%) composed of α phase and of 9% Li, 1.5% Al composed of α (hcp) + β (bcc) phases were subjected to twist channel angular pressing (TCAP) ...deformation. Such deformation of α + β alloys caused less effective grain refinement than that of single α phase alloy. However, with increasing number of passes, grain size of single α phase alloy increased and that of β phase in two phase α + β alloy also grew, which suggested the effect of dynamic recrystallization. TEM studies allowed identifying particles of Li2MgAl phase of size of few μm. {001} texture was observed in extruded alloy. Texture studies of extruded and TCAPed single phase hcp alloy indicated texture with {101 – 0} plane perpendicular to the extrusion direction and {0002} plane parallel to the extrusion direction. Duplex α + β alloys showed poor texture development.
The study presents investigations of an influence of various direct current densities on microstructure, residual stresses, texture, microhardness and corrosion resistance of the nickel coatings ...electrodeposited from modified Watt’s baths. The properties of obtained coatings were compared to the nano-crystalline composite Ni/Al
coatings prepared under the same plating conditions. The similarities and differences of the obtained coatings microstructures visible on both their surfaces and cross sections and determined properties were presented. The differences in the growth character of the Ni matrix and in the microstructural properties were observed. All electrodeposited Ni and Ni/Al
coatings were compact and well adhering to the steel substrates. The thickness and the microhardness of the Ni and Ni/Al
deposits increased significantly with the current density in the range 2 - 6 A/dm
. Residual stresses are tensile and they reduced as the current density increased. The composite coatings revealed better protection from the corrosion of steel substrate than pure nickel in solution 1 M NaCl.
Stress causes the activation of both the hypothalamic-pituitary-adrenocortical axis and sympatho-adrenal system, thus leading to the release from the adrenal medulla of catecholamines: adrenaline ...and, to a lesser degree, noradrenaline. It has been established that in addition to catecholamines, the adrenomedullary cells produce a variety of neuropeptides, including corticoliberine (CRH), vasopressin (AVP), oxytocin (OXY) and proopiomelanocortine (POMC) - a precursor of the adrenocorticotropic hormone (ACTH). The aim of this study was to investigate adrenal medulla activity in vitro depending, on a dose of CRH, AVP and OXY on adrenaline and noradrenaline release. Pieces of sheep adrenal medulla tissue (about 50 mg) were put on 24-well plates and were incubated in 1 mL of Eagle medium without hormone (control) or supplemented only once with CRH, AVP and OXY in three doses (10-7, 10-8 and 10-9 M) in a volume of 10 μL. The results showed that CRH stimulates adrenaline and noradrenaline release from the adrenal medulla tissue. The stimulating influence of AVP on adrenaline release was visible after the application of the two lower doses of this neuropeptide; however, AVP reduced noradrenaline release from the adrenal medulla tissue. A strong, inhibitory OXY effect on catecholamine release was observed, regardless of the dose of this hormone. Our results indicate the important role of OXY in the inhibition of adrenal gland activity and thus a better adaptation to stress on the adrenal gland level.
This essay examines China’s drive for innovation as part of its national development strategy and addresses the tensions China faces between retaining control and autonomy in relevant sciences and ...technologies and becoming a global leader in these fields.
MAIN ARGUMENT
The Chinese Communist Party (CCP) has assessed that the world is undergoing “profound changes unseen in a century” in part as a result of rapid advances in science and technology. The Covid-19 pandemic has heightened the impact of these changes and added to the disruption of the current global order. Such conditions present unique challenges and opportunities for China in the course of its national rejuvenation. Xi Jinping has accelerated the pursuit of China’s rise as a great power, and the 14th Five-Year Plan highlights the country’s capacity for innovation and to leverage science and technology in pursuit of that objective. Progress toward this goal, however, has been uneven. Although China aspires to be a new “high ground” in science and technology, the capacity for innovative Chinese technologies to go global may be undermined by a deficit of trust and transparency. If China does emerge as a leader in new frontiers of innovation in the course of the fourth industrial revolution, this shift could present significant implications for the future balance of power.
POLICY IMPLICATIONS
• China’s drive for innovation will continue to confront certain incongruities. While the CCP has prioritized innovation, the imperative of party control may undermine the necessary conditions for it. And while China has risen within and benefited from a world of open science, intense competition in the geopolitical environment is complicating that paradigm.
• China and its technology companies have shown increasing technological prowess (e.g., in coping with the Covid-19 pandemic) but still face technical impediments to overcoming strangleholds in key areas, such as semiconductors, that act as chokepoints.
• For the U.S. to sustain its traditional leadership in science and technology, it will need to revitalize and reinvest in innovation domestically.
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