Mechanical Action Research Articles

Compact, portable, automatic sample changer stick for cryostats and closed-cycle refrigerators

Beamlines are facilities that produce and deliver highly focused and intense beams of radiation, typically x rays, synchrotron radiation, or neutrons, for scientific research purposes. Millions of dollars are spent annually to maintain and operate these scientific beamlines, oftentimes running continuously between cycles. To reduce human intervention and improve productivity, mechanical sample changers are often commissioned for use. Designing sample changers is difficult because mechanical parts can be bulky, expensive, and challenging to design for instruments with low volume access, high radiation, and cryogenic environments. We present a portable and inexpensive sample changer stick that can hold and manipulate up to four samples, specifically designed for use with cryogenic closed-cycle refrigerators. The sample changer stick enables rapid and efficient exchange of samples without manual intervention, and is compatible with standard sample mounts such as vanadium cans. The sample changer stick includes a motorized rotation and lancing mechanism, which enables the precise positioning of each sample in the neutron beam, while ensuring compatibility with the operating temperatures and vacuum conditions required for closed-cycle refrigerators. The design has been successfully tested at the VISION beamline at the Spallation Neutron Source. The mechanical action and software controls are detailed. The sample changer stick is a valuable tool for scientists working with cryogenic closed-cycle refrigerators.

Joint Action and Competition between Centrifugal, Magnetorotational, and Magnetic Buoyancy Instabilities

Instabilities driven by some combination of rotation, velocity shear, and magnetic field in a stratified fluid under gravity play an important role in many astrophysical settings. Of particular note are the centrifugal instability, the magnetorotational instability, and magnetic buoyancy instability. Here, we consider a Cartesian model of an equatorial region incorporating all the physical ingredients necessary to study their competition. We investigate the linear instability to interchange (“axisymmetric”) modes of an inviscid, perfectly conducting, isothermal gas, including the effects of rotation, velocity shear, and poloidal and toroidal magnetic fields. The stability problem can be reduced to a second-order boundary value problem, with the growth rate as the eigenvalue. We can make analytic progress through consideration of the physically relevant regime in which the transverse horizontal wavenumber k ≫ 1. Via a perturbation analysis, with 1/k as the small parameter, we can derive the growth rate and the spatial dependence of the eigenfunctions: the unstable modes are strongly localized in the vertical direction, being either wall modes (localized near a boundary of the domain) or body modes (localized in the interior). We describe the conditions under which the joint action of the separate instability mechanisms leads to enhancement or suppression of the instability. Our analytical results are supplemented by numerical solutions of the stability problem. The most unstable mode found analytically is typically in excellent agreement with that found numerically through consideration of a wide range of wavenumbers. Finally, we discuss how our results relate to the solar tachocline.

In-Depth Understanding of Hardmetal Corrosion Performance Reveals a Path to the Electrochemical Demolition of Scrap

Recycling of hardmetal scrap is strategic for critical raw materials recovery. Available recycling processes are polluting and have a large carbon footprint. Attempts to exploit controlled corrosion failed in industrial practice, owing to self-limiting processes. We revisit the corrosion route, in view of gaining the fundamental knowledge enabling high-throughput recovery. We selected the worst-case approach of highly corrosion-resistant CoNiWC-based hardmetal grades and neutral aqueous electrolyte at room temperature. Systematic electrochemical measurements, UV–Vis spectroscopy and SEM microscopy disclosed that, even though there is no hope to overcome the self-limiting corrosion rate, nevertheless, by exploiting the mechanical action of anodic O2 evolution acting precisely at the interface between the residual active material and the corrosion film, the latter can be efficiently removed, periodically reactivating the hardmetal corrosion in a way that results in an ultra-high scrap destruction rate, of interest for real-life industrial processes.

Impact of copper oxide nanoparticles on the physiology of different microalgal species

Sublethal concentrations of CuO NPs were added to the medium in the amounts of 3000, 2500, 1000, and 400μg L−1, respectively, to determine the main trends of changes in the morpho — physiological, biochemical and structural indicators of the microalgae Dunaliella salina (Teod.), Isochrysis galbana Parke, 1949; Thalassiosira weissflogii (Grunow) G.A. Fryxell & Hasle, 1977; and Prorocentrum cordatum (Ostenfeld) Dodge, 1975. Nearly every aspect of algae physiology is impacted by NPs, which also cause changes in the integrity of cell wall, an increase in cell volume, and a rise in the number of dead or inactive cells in culture. Reactive oxygen species production rises, metabolic activity of cells falls, mitochondrial membranes depolarize. The four studied species — D. salina, I. galbana, Th. weissflogii and P. cordatum — are arranged in a row, starting with the most resistant to the effects of NPs CuO. The 2% release of Cu2+ copper ions from CuO NPs is not the main cause of the harmful effects of NPs on cells. The mechanical action of CuO NPs, which damages cell membranes and aggregates NPs on the algae’s surface, is primarily responsible for their inhibitory effect on algae. P. cordatum and Th. weissflogii, which have dense shells in comparison to D. salina and I. galbana with ultrathin cell membranes, did not produce cells that were more resilient to the effects of CuO NPs. The photosynthetic system of the tested algae species exhibited high functional tolerance to the impacts of copper oxide nanoparticles. Fluorescent measures (Fv/Fm, rETR) can be used to determine a pollutant’s capacity to obliterate microalgae. It is shown that there is a connection between the unrestrained increase in CuO NPs concentration in water and the potential harm to the primary production of aquatic ecosystems.

Ballistic Performance, Thermal and Chemical Characterization of Ubim Fiber (Geonoma baculifera) Reinforced Epoxy Matrix Composites.

The search for unexplored natural materials as an alternative to synthetic components has driven the development of novel polymeric composites reinforced with environmentally-friendly materials. Natural lignocellulosic fibers (NLFs) have been highlighted as potential reinforcement in composite materials for engineering applications. In this work, a less known Amazonian fiber, the ubim fiber (Geonoma baculifera), is investigated as a possible reinforcement in epoxy composites and was, for the first time, thermally characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, its chemical structure was elucidated by Fourier transform infrared spectroscopy (FTIR). Ballistic tests were also performed against the threat of a 7.62 mm high-speed lead projectile. The results were statistically analyzed by the Weibull statistical analysis method. FTIR analysis showed the functional groups normally found for NLFs highly rich in cellulose, hemicellulose, and lignin. The TGA/DTG results showed the onset of thermal degradation for the composites (325~335 °C), which represents better thermal stability than isolated ubim fiber (259 °C), but slightly lower than that of pure epoxy (352 °C). The DSC results of the composites indicate endothermic peaks between 54 and 56 °C, and for the ubim fibers, at 71 °C. Ballistic tests revealed higher energy absorption in composites with lower fiber content due to the more intense action of the brittle fracture mechanisms of the epoxy resin, which tended to dissipate more energy. These failure mechanisms revealed the presence of river marks, cracks, and broken fibers with a detachment interface. These results may contribute to the production of ubim fiber-reinforced composites in engineering applications, such as ballistic armors.

Autonomic cardiovascular control during exercise.

The cardiovascular response to exercise is largely determined by neurocirculatory control mechanisms that help to raise blood pressure and modulate vascular resistance which, in concert with regional vasodilatory mechanisms, promote blood flow to active muscle and organs. These neurocirculatory control mechanisms include a feedforward mechanism, known as central command, and three feedback mechanisms, namely, 1) the baroreflex, 2) the exercise pressor reflex, and 3) the arterial chemoreflex. The hemodynamic consequences of these control mechanisms result from their influence on the autonomic nervous system and subsequent alterations in cardiac output and vascular resistance. Although stimulation of the baroreflex inhibits sympathetic outflow and facilitates parasympathetic activity, central command, the exercise pressor reflex, and the arterial chemoreflex facilitate sympathetic activation and inhibit parasympathetic drive. Despite considerable understanding of the cardiovascular consequences of each of these mechanisms in isolation, the circulatory impact of their interaction, which occurs when various control systems are simultaneously activated (e.g., during exercise at altitude), has only recently been recognized. Although aging and cardiovascular disease (e.g., heart failure, hypertension) have both been recognized to alter the hemodynamic consequences of these regulatory systems, this review is limited to provide a brief overview on the action and interaction of neurocirculatory control mechanisms in health.

Geometric and physical interpretation of the action principle

We give a geometric interpretation for the principle of stationary action in classical Lagrangian particle mechanics. In a nutshell, the difference of the action along a path and its variation effectively “counts” the possible evolutions that “go through” the area enclosed. If the path corresponds to a possible evolution, all neighbouring evolutions will be parallel, making them tangent to the area enclosed by the path and its variation, thus yielding a stationary action. This treatment gives a full physical account of the geometry of both Hamiltonian and Lagrangian mechanics which is founded on three assumptions: determinism and reversible evolution, independence of the degrees of freedom and equivalence between kinematics and dynamics. The logical equivalence between the three assumptions and the principle of stationary action leads to a much cleaner conceptual understanding.

Formation of white etching layer on rails due to coupled thermal and mechanical actions

The formation mechanism of the white etching layer (WEL) on the rail steel material has been confirmed via two different routes; thermal-induced WEL by phase transformation and mechanical-induced WEL by severe plastic deformation. In this study, a combination of thermal and mechanical processes was performed to examine the synergistic interaction of two formation mechanisms of the WEL on rails. An experiment was conducted on the rail steel material using a Gleeble thermo-mechanical simulation system. The results confirmed that the martensitic WEL is formed by phase transformation from rapid quenching at a temperature below the critical point of material phase transformation, under 550 °C, when high hydrostatic pressure is applied. The application of combined thermal and mechanical action induced martensite with the presence of retained austenite. The microstructure of the transition zone between the WEL and the base material contains partial and full dissolution of cementite, broken pearlite lamella, and dislocation density, confirming that both thermal and mechanical processes are involved in the phase transformation of the material.

Prediction of Compressive Strength of Biomass-Humic Acid Limonite Pellets Using Artificial Neural Network Model.

Due to the detrimental impact of steel industry emissions on the environment, countries worldwide prioritize green development. Replacing sintered iron ore with pellets holds promise for emission reduction and environmental protection. As high-grade iron ore resources decline, research on limonite pellet technology becomes crucial. However, pellets undergo rigorous mechanical actions during production and use. This study prepared a series of limonite pellet samples with varying ratios and measured their compressive strength. The influence of humic acid on the compressive strength of green and indurated pellets was explored. The results indicate that humic acid enhances the strength of green pellets but reduces that of indurated limonite pellets, which exhibit lower compressive strength compared to bentonite-based pellets. Furthermore, artificial neural networks (ANN) predicted the compressive strength of humic acid and bentonite-based pellets, establishing the relationship between input variables (binder content, pellet diameter, and weight) and output response (compressive strength). Integrating pellet technology and machine learning drives limonite pellet advancement, contributing to emission reduction and environmental preservation.

Peculiarities of some Fmoc-dipeptides gelation in DMSO/water medium

The possibility of the gels formation with a high-water content of 90% v/v using Fmoc-dipeptides without mechanical actions or pH-switching was demonstrated. For the first time, the formation of a colloid gel based on Fmoc-LL dipeptide was discovered. The effect of side substituents in the amino acid residues of Fmoc-dipeptides in the range of GG, AA, LL, and FF on their ability to form gels in DMSO/water systems was thoroughly studied. Non-linear dependence of gel formation kinetics in dipeptide/DMSO/water systems, gel properties, and supramolecular organization in xerogels on the size of side substituents was observed. The results obtained give a new insight into the mechanism of gelation with low-molecular-weight gelators based on Fmoc-dipeptides and may be useful for the preparation of new supramolecular or colloidal gels.

The preparation of hexaphenylsilole-based conjugated microporous polymer for fluorescence sensing o-nitrophenol

A first hexaphenylsilole-based conjugated microporous polymer, termed THPS, was prepared by a Friedel-Crafts arylation reaction of 1,1,2,3,4,5-hexabenylthirole with 2,4,6-trichloro-1,3,5-triazine catalyzed by anhydrous aluminium trichloride (AlCl3) in 1,2-dichloroethane. Its Brunauer–Emmett–Teller and Langmuir surface area reached up to 1579 and 2081 m2 g−1, and total pore volume and micropore pore volume were severally 0.8325 and 0.7322 cm3 g−1. THPS could fluorescence-sense o-nitrophenol with high sensitivity and selectivity. Its fluorescence quenching constant (KSV) and limits of detection (LODs) were severally 8.32 × 103 L mol−1 and 3.61 × 10-10 mol L−1. The fluorescence quenching of THPS by o-nitrophenol was originated from the combined action of both photo-induced electron transfer mechanism and resonance energy transfer mechanism.

Unloading-slippage mechanism of coal bump in gateroad of longwall

Coal bump seriously threatens the safe and efficient mining of coal, and the research on the occurrence mechanism of coal bump is of great significance. The roadway coal bump accounts for 86.8% of the total. The occurrence of coal bump in gateroad is summarized. It is considered that hard roof and hard coal are the geological characteristics of coal bump, and the sliding instability of rib coal mass is the failure characteristics of coal bump. Based on the elastic foundation theory, the upward deflection characteristics of the front and lateral roof of the working face under the condition of hard roof are analyzed, and compared with the engineering practice of roof rebounding. Taking the roadway coal mass as the research object, the unloading sliding mechanical model of roof-coal-floor composite structure is established. By analyzing the relationship between horizontal ground stress of coal mass, frictional force of coal-roof and coal-floor and tensile resistance of coal mass, the critical equation of coal bump is established. It is proposed that the vertical pressure of coal seam is reduced due to the upward deflection of the roof, and the coal mass loses its clamping and moves into the roadway after overcoming the friction between roof and floor and the tensile strength of coal mass under the action of horizontal ground stress, that is, the unloading and slippage mechanism of coal bump in hard roof mining roadway. The model reasonably explains the causality of coal bump in hard roof mining roadway. Based on the unloading-slippage model, the principle of influencing factors of coal bump, includes the buried depth, roof strength, roof elastic modulus and roof thickness, coal mass strength and elastic modulus. Finally, two coal bump events, ''8.2'' coal bump in Tangshan coal mine and ''11.11'' coal bump in Hongyang mine are analyzed and the unloading-slippage mechanism are the reasoning of two events.

Development of a high-contrast fluorescent ligand that targets G-quadruplexes by introducing a triazole rotor onto the dibenzoquinoxaline scaffold

In this study, we developed a potential dual-function ligand targeting G-quadruplexes (G4s) by introducing a triazole rotor onto the dibenzoquinoxaline scaffold. This ligand not only had potential in high-contrast imaging of G4s either in vitro or in cellulo, but also proved to inhibit cancer cell growth as well as migration possibly through a G4-mediated action of mechanism. Altogether, this ligand had possibility to develop into a theranostic agent for cancer diagnosis and therapy in the future.

Atomistic removal mechanisms of nano polishing single-crystal SiC in hydroxyl free radical aqueous solution

Single-crystal SiC has been widely applied for electronic devices. Photocatalysis assisted chemical mechanical polishing (PCMP) is an efficient global flattening technology for finishing SiC, but the atomic level removal mechanism is still under discussion. In this paper, the atomic behavior of removal with hydroxyl free radical (·OH) aqueous solution was investigated using the ReaxFF molecular dynamics (MD) simulation. The theoretical analysis shows that ·OH oxidation of SiC can occur spontaneously, and the mechanical behavior would be able to increase the potential energy and reduce the reaction barrier the reactants. The simulation results show that with only chemical oxidation occurs, the SiC surface adsorbed O, H or -OH to produce Si-O*H2, Si-OH2, Si-OH, Si-H2O, Si-H*O*-H2O, Si-H2O*, Si-O*H* and Si-H, etc, no Si atoms were observed to detach from the SiC substrate. Nevertheless, if the mechanical action was applied, some Si and C atoms break off the substrate by forming SiO, SiO2, CO, CO2 or chain, and the other Si or C atoms were detached by the adsorption on the abrasive. In addition, no atoms break away from the substrate in H2O solution. The force F x in H2O solution is less than that in ·OH aqueous solution because of the lubrication of H2O solution. Furthermore, it is found that the mechanical action applied, the more -H and -O adsorbed on the SiC surface result in the more Si and C atoms are removed. The experimental results show that SiC wafer could be oxidized by ·OH under the mechanical action of diamond abrasive particles. This study reveals that the removal of Si and C atoms from the substrate is the result of the combined action of chemical oxidation and mechanical sliding, which is helpful to explain the dynamic process of the oxidation and removal of Si and C atoms on the atomic level in the SiC PCMP. Furthermore, it provides a valuable method reveal the material removal mechanism.

A broadband near-infrared nanoemitter powered by mechanical action

A broadband near-infrared nanoemitter powered by mechanical action

Autowave nature of the Lüders deformation in a substitutional FCC alloy

Lüders deformation in an aluminum-magnesium alloy was studied in a wide range of loading rates. It was found that the deformation is always accompanied by the propagation of deformation fronts, which move either continuously or intermittently depending on the strain rate. The kinetics of fronts is determined by the reaction of active deformable media to an external mechanical action and is determined by the autowave nature of plastic deformation.

Principle of virtual action in continuum mechanics

Principle of virtual action in continuum mechanics

INTEGRATED LEARNING IN A MODERN SCHOOL IN THE CONTEXT OF DISTANCE EDUCATION

The article is aimed at defining the concept of integrated learning and features of the implementation of this educational technology in modern general education institutions. In defining the key concept, the mechanisms of integration between the basic disciplines, which are appropriate for the use of integrated learning in the modern school, are considered. It is noted that integration can be carried out by two key mechanisms, each of which is aimed at the perception of pupils of the surrounding world as a whole, regardless of which aspect of science is its knowledge.The article reveals the essence of the integrated approach to education, its significance and impact on changing the structure of a particular subject, which is an important element in improving the effectiveness of the educational process. In addition, the article describes in detail the action of mechanisms in the implementation of the basics of an integrated lesson, as well as the content and operation of didactic principles for implementing an integrated approach.The main research methods are: Analysis of literature sources, observation, survey, generalization and statistical analysis.The article focuses on identifying opportunities for introducing distance learning into Ukrainian education using an integrative approach.The main results of the study give grounds for asserting that the active and professional use of distance education opportunities by teachers will contribute to solving the educational problems that have arisen in modern Ukraine. These changes will help build new ways of development and prospects for Ukrainian educators, based on the relevance and widespread use of online education.The authors proposed their own definitions of the concepts "value orientations", "personal values", "value orientations of Ukrainian youth".

Physical-Performance Changes Over the Season: Are They Related to Game-Performance Indicators in Elite Men Volleyball Players?

The development and influence of physical capabilities and game action performance over the course of the season are a big challenge for coaches and players. The aims of the present study were to examine (1)the seasonal changes in the physical capabilities (mechanical and kinematic) and game-performance indicators in top-level men volleyball players and (2)the relationship between these physical capabilities and game-performance indicators in official matches. Eleven top-level players participated. Players were physically tested 3 times during the season. Before each test, players' match performance (11 sets) was analyzed according to the level of opposition and match location. The percentage of change, statistical differences over the season (Friedman and Wilcoxon tests), and associations between variables (Spearman r) were calculated (P < .05) among mechanical (force-velocity profile during vertical jump and bench press), kinematic (jump height and spike ball speed), and game action performance features (coefficient, efficacy, and percentage of errors in serve, attack, and block). The theoretical maximal force and velocity during vertical jump and bench press, respectively; the peak spike ball speed; and the serve efficacy significantly increased over the season. Moreover, there was a significant reduction in serve errors as the jump height increased (r = -.44; P = .026), as well as a significant increase in serve errors as the peak spike ball speed increased (r = -.62; P = .001). These findings reveal how the physical and game action performance variables evolve and interact during the season. This may help coaches and trainers to monitor and analyze the most relevant volleyball performance factors.

Practical Application of Body Mechanics Principles in the Process of Health Workers Doffing Personal Protective Equipment

To examine the application effect of body mechanics principles in the process of health workers doffing personal protective equipment (PPE). A total of 360 health workers from a Fangcang shelter hospital, also known as alternate care site, in Shanghai were involved in a centralized 1-day training concerning essential skills for taking off PPE. The training was focused on integrating body mechanics principles, including expanding the support surface, lowering the center of gravity, reducing the shift in the the center of gravity, using the principle of leverage, and creating the appropriate operating space, in the PPE doffing process. Through remote video monitoring and recording, observations were made of the physical stability, pollution risks, and operational smoothness of the health workers when they applied body mechanics principles in their actions. The results of binary logistic regression showed that, compared with the actions taken without applying body mechanics principles, performing the operation of the body leaning forward and then slightly leaning backward was positively correlated with stability in the doffing process (odds ratio [O R]=3.291, 95% confidence interval [ CI]: 1.627-6.656), negatively correlated with pollution risks ( OR=0.203, 95% CI: 0.100-0.412), and positively correlated with operational smoothness ( OR=20.847, 95% CI: 8.061-53.916); performing the operation of taking off the boot sleeve in a horse-riding stance, with one foot standing ahead of the other, was positively correlated with stability ( OR=5.299, 95% CI: 1.041-26.957), negatively correlated with pollution risks ( OR=0.079, 95% CI: 0.009-0.692), and positive correlated with operational smoothness ( OR=16.729, 95% CI: 1.238-226.077); performing the operation of taking off the boot sleeve by lifting the heel and then the toes was positively correlated with stability ( OR=19.361, 95% CI: 8.391-44.671), negatively correlated with pollution risks ( OR=0.181, 95% CI: 0.084-0.393), and positively correlated with operational smoothness ( OR=10.977, 95% CI: 3.764-32.008); performing the operation of the leaning forward and keeping the face looking forward when taking off the mask was positively correlated with stability ( OR=2.935, 95% CI: 1.412-6.101), negatively correlated with pollution risks ( OR=0.123, 95% CI: 0.059-0.258), and positively correlated with operational smoothness ( OR=18.126, 95% CI: 6.665-49.297). In the process of medical staffs doffing PPE, correct and proper mechanical postures and actions can effectively assist medical staffs to maintain balance and stability and reduce the risks of infection, which has major significance and should be widely incorporated in personal protection skills training and applied in clinical practice.