Mechanical Work Research Articles

Alternative energy in Spain and Chile. Forecasts and prospects in the context of the energy transition

The article provides a comparative analysis of the actions and achievements of two states, the Kingdom of Spain and the Republic of Chile, in the field of green energy. Over the last decade both countries have done extensive work on decarbonization of the economy and have become one of the leaders in their regions in terms of the pace of implementation of the energy transition. At the same time the strategies and mechanisms of work of the two states in the field of alternative energy development differ in many respects. Under certain comparable conditions and prerequisites for the development of the industry, with an identical share of alternative sources in the energy sector, Spain and Chile achieved different socio-economic indicators. In order to identify the potential for renewable energy development in Spain and Chile, the authors identified three factors of economic, political and energy character, based on which a forecast for the achievement of green energy targets in accordance with the state strategies of the countries was developed.

A Mini‐Review: The Rise of Triple‐Junction Silicon‐Perovskite‐Perovskite Solar Cells

Recently, the multijunction (MJ) solarcells have gained interest and have a lot of promise going forward. As MJ solarcells with an increasing number of absorber layers can reduce the thermalization and the nonabsorption losses of the device, it has then been proposed to overcome the Shockley–Queisser (S–Q) maximum efficiency limit. The preparation of the metal halide perovskite using a solution processing method with tunable bandgaps has made them an ideal candidate to integrate with the silicon photovoltaic, forming MJ silicon‐perovskite (Si‐PVK) solar cells. Benefitting from these, 33.90% power conversion efficiency (PCE) has been realized for the Si‐PVK MJ solar cell, which is comparable to the S–Q maximum efficiency limit in the range of ≈1.10–≈1.30 eV. Furthermore, the PCE of Si‐PVK solar cells can potentially increase with increasing the number‐junction of perovskite device. Taking advantage of this, the research on the triple‐junction (TJ) silicon‐perovskite‐perovskite (Si‐PVK‐PVK) solar cells has gained attention, although it is still in an early stage of development. In this mini‐review, the working mechanism, the design principle, and the progress of TJ Si‐PVK‐PVK solar cells are discussed. Finally, future outlooks in this field are also provided.

Study on the mechanical properties of geogrid-reinforced tunnel slag and particle breakage

The use of tunnel slag as roadbed filling can save resources and promote the sustainable and low-carbon development of transportation infrastructure.. To investigate the mechanical properties evolution law of tunnel slag as subgrade filler, SEM and large-scale triaxial tests were conducted to analyze its macroscopic, microscopic characteristics and particle breakage behavior. The study focuses on the impact of geogrid on the shear strength, deformation, and particle breakage of tunnel slag and its working mechanism. The results indicate that an increase in soft rock content reduces the shear strength and weakens its dilatancy. The average peak shear strength of grid reinforced dense specimens can be increased by 10%, and the residual shear strength can be increased by about 30%. The relative breakage index increases in an S-shaped pattern with increase in soft rock content. Higher confining pressure and soft rock content leads to more particle breakage, however, particle breakage in the reinforced specimens can be significantly reduced. The research findings contribute to the enhanced design and implementation of waste material repurposing, thereby advancing the sustainable development of infrastructure.

High-intensity interval training with blood-flow restriction enhances sprint and maximal aerobic power in male endurance athletes.

We investigated the concurrent impact of HIIT and blood-flow restriction (BFR) as a novel approach to further enhance maximal aerobic and anaerobic physiology and performances in trained athletes. In a randomized controlled trial, eighteen endurance-trained males (V ̇O2peak 65.6±5.1 ml.min-1.kg-1) included three sessions of HIIT per week (sets of 15-s efforts at 100% maximal aerobic power, interspersed by 15-s recovery) into their usual training for three weeks, either with restriction imposed on both lower limbs at 50-70% of arterial occlusion pressure (BFR group, n=10) or without (CTL group, n=8), and were tested for sprint and endurance exercise performance. The total mechanical work developed during a 30-sec Wingate test increased only in BFR (3.6%, P=0.02). During the Wingate, changes in near-infrared spectroscopy-derived vastus lateralis muscle oxygenation (Δ(deoxy[Hb+Mb]), % arterial occlusion) were attenuated after BFR training (-8.8%, P=0.04). The maximal aerobic power measured during an incremental cycling test increased only in BFR (4.5%, P=0.0004), but there was no change in V ̇O2peak among groups. Both groups improved 5-km cycling time trial performance, but BFR displayed a concomitant greater elevation in [H+] (11%, P=0.02). Changes in other blood variables (e.g., pH, lactate, bicarbonate and potassium ion concentration, hemoglobin) were not different between groups. Combining short-duration HIIT performed at 100% aerobic power with BFR elicited greater changes in sprint performance and maximal aerobic power in endurance athletes, associated with locomotor muscle metabolic adaptations but no meaningful effect on cardiorespiratory fitness.

Effects of Cold Deformation and Heat Treatments on the Microstructure and Properties of Fe-15Cr-25Ni Superalloy Cold-Drawn Bars

The combination of cold deformation and solution aging is an important technological route for the bar processing of superalloy fasteners. The microstructure evolution and mechanical properties are intimately related to the process parameters. In this study, we systematically elucidate the mechanical properties and microstructure evolution of Fe-15Cr-25Ni alloys in different treatment processes and conduct in-depth analysis of the synergistic strengthening mechanism of fine-crystal strengthening, second-phase strengthening, and work hardening on Fe-15Cr-25Ni alloys. The results show that the tensile strength and yield strength at room temperature increase with the increase in grain refinement and dislocation density but decrease with the increase in elongation. After solid-solution treatment, most of the precipitates dissolve into the matrix, and the dislocation density is greatly reduced, resulting in a decrease in strength and an increase in plasticity. After aging, a large amount of γ′ phase was precipitated. Due to the two strengthening effects of dislocation strengthening and second-phase strengthening, the strength of the aging state is more improved than that of the cold-drawing state. The purpose of this study is to provide valuable insights for the industrial production of Fe-15Cr-25Ni superalloys.

Liquid-Solid Triboelectric Nanogenerator-Based DNA Barcode Detection Biosensor for Species Identification.

DNA barcode detection method is widely applied for species identification, which is imperative to evaluate the effect of human economic activities on the biodiversity of ecosystem. However, the wide utilization of existing detection biosensors is limited by bulky and expensive instruments, such as Raman spectroscopy and electrochemical station. Herein, a liquid-solid triboelectric nanogenerator (TENG)-based DNA barcode detection biosensor is proposed, which consists of water flow, fluid channel, and PDMS film attached by specifically designed capture probe. Through sequentially combining capture probe, targeted DNA barcode, and signal probe with Au nanoparticles (NPs), the surface charge density of friction layer of TENG decreases under the effect of AuNPs, verified by the density functional theory (DFT) method. Consequently, the peak value of output current spike signal for targeted DNA is smaller than that for other DNA, which is the working mechanism of the present TENG-based biosensor. Such biosensor successfully recognizes Alvinocaris muricola among different types of Alvinocarididae shrimps, and its low limit detection can reach 1×10-12m. The present work provides a paradigm-shift way to develop an inexpensive and accurate technique to detect DNA barcode for species identification, and paves a novel way for the application of liquid-solid TENG.

Observing Mixed Chemical Reactions at the Positive Electrode in the High-Performance Self-Powered Electrochemical Humidity Sensor.

Electrochemical humidity (ECH) sensors that integrate power generation and humidity sensing have attracted great research attention in recent years. However, the design of high-performance ECH sensors faces many challenges. Namely, the working mechanism of the ECH sensors is still controversial, and related self-powered applications have not been well implemented. To overcome these limitations, this study constructs an ECH sensor with high power-generation and humidity-sensing performance using the KCl/carbon black/halloysite nanotubes (KCl/CB/HNTs) as a humidity-sensing electrolyte. The proposed ECH sensor has a wide humidity-sensing response of 10.9%-91.5% relative humidity (RH), and a single ECH sensor can output 1.46 V with a maximum power of 133.2 μW at 91.5% RH. Particularly, the unprecedented mixed chemical reactions at the positive electrode, including the hydrogen evolution reaction and oxygen reduction reaction, are analyzed using multiple characterization and testing techniques. The analysis results provide solid experimental evidence for the current controversial working mechanism of ECH sensors. Due to the advantage of high-power generation, the proposed ECH sensor can be used for self-powered humidity detection. This study provides a valuable reference for improving the power generation of ECH sensors and solid evidence for clarifying their working mechanism, which could be beneficial for guiding the future development of ECH sensors.

Improved photoresponse performance of self-powered solar-blind UV photodetectors based on n-Si/n-Ga2O3/p-Li:NiO dual-junction

The solar-blind photodetectors (SBPDs) based on the wide-bandgap semiconductor gallium oxide (Ga2O3) exhibit significant potential for applications in military, civilian, and medical fields. Although multiple structural designs of Ga2O3-based SBPDs have been proposed, their performance typically falls short of commercial standards. However, the photoresponse speed of most self-powered PDs decreases rapidly in the solar-blind region. To address this issue, we first prepared high-quality single-crystal β-Ga2O3 films using RF magnetron sputtering, which exhibit an average transmittance exceeding 85% across the 400–800 nm range and possess a relatively smooth surface. Subsequently, a superior performance self-powered SBPD of vertical structure of n-Si/n-Ga2O3/p-Li:NiO dual-junction was fabricated, which possesses a responsivity of 0.18 mA/W, a photo-to-dark current ratio of 395, rapid rise/decay times of 132/148 ms, and a specific detectivity of 1.57 × 109 Jones at 0 V bias under 254 nm illumination. The photocurrent of the device fully recovered to its initial level after experiencing changes in ambient temperature [from room temperature (RT) to 100 °C and back to RT], demonstrating robust stability in harsh environments. In addition, the valence band structures of p-Li:NiO and n-Ga2O3 were investigated in detail using XPS, and the working mechanism of the devices was analyzed based on the Fermi level alignment. The excellent performance of PDs can be attributed to the increased depletion layer width, which generates more photogenerated carriers. Additionally, the separation and transmission of photo-induced carriers are enhanced by the superposition of a double built-in electric field. Our strategy offers a promising approach for achieving high-performance Ga2O3-based photovoltaic PDs.

Insight into gain and transient response characteristics of AlGaN/GaN hetero-junction based UV photodetectors: Case study on the role of incident light intensity

Gain and response speed are two key performance parameters for high sensitivity photodetectors (PDs). However, the effect of incident light intensity on gain and transient response properties of AlGaN/GaN hetero-junction based PDs are still not fully understood. Here, we design and fabricate an AlGaN/GaN hetero-junction based ultraviolet (UV) PD with interdigitated electrodes formed by a conductive two-dimensional electron gas (2DEG) channel, which exhibits a low dark current of 2.92 × 10−11 A and a high responsivity of 3060 A/W at 10 V bias. The high-gain AlGaN/GaN 2DEG PD has a similar working mechanism to those of traditional phototransistors, but its device architecture is evidently simplified. By investigating the variation of gain and transient response characteristics of the 2DEG PD as a function of incident UV light intensity, it has been concluded that the gain of the PD in a low-light intensity region is dominated by hole accumulation-induced electron escape from the 2DEG, while in a high-light intensity region, the gain is dominated by photoconductivity effect and limited by carrier recombination. This study provides guidance for future practical applications of AlGaN/GaN-based PDs in complex UV illumination environments.

Numerical study of Mg(OH)2/MgO thermochemical heat storage reactor coupled with parabolic dish solar system

Systems coupling Mg(OH)2/MgO thermochemical reactor with parabolic dish solar collector (PDSC) have a potential application prospect in solar seasonal heat storage. However, their working mechanism has not been systematically studied and not well understood either. In this study, Mg(OH)2-based thermochemical reactor, which was coupled with PDSC, was numerically studied for the first time using a three-dimensional model. The various working conditions and influencing factors of PDSC system were investigated, and a comprehensive analysis and optimization for the heat storage performance of the reactor such as the reaction time and energy storage rate were conducted. Effects of the fluid inflow temperature, velocity, and fluid pipe distribution on heat storage performance were also unfolded. For instance, when the heating pipe was arranged at 70 mm from the central axis, the reaction time was 15.9 % less than that of evenly arranged at R/2 from the center. Moreover, fins were added to the reactor and the fin shape was optimized using the density-based topology optimization method. It was found that the reaction time was reduced by 42.4 % and was only 12614 s.

Biomimetic nanozyme-based electrochemical sensor integrated with microfluidic cell for on-site uric acid detection

Uric acid (UA) is the key indicator highly associated with gout, and on-site UA detection is of great significance for personalized health management. Herein, we propose an integrated microfluidic electrochemical sensing platform for real-time UA detection. The platform mainly consists of a biomimetic nanozyme-based electrochemical sensor and a microfluidic cell. The biomimetic nanozyme with desirable catalytic activity can effectively promote UA oxidation, and the corresponding working mechanism is clarified through density functional theory calculation. Besides, the well-designed microfluidic cell is capable of impurity removal and sample storage. Based on these designs, the whole process of sample pretreatment and target detection can all be achieved on one integrated platform, allowing for user-friendly test. This developed platform shows satisfactory sensing performance for UA with a detection limit of 4.2 μM. In addition, it is successfully applied to UA determination in artificial saliva and serum samples, showing desirable application prospects in clinical diagnosis.

Light-propelled dimeric micro-rotor in a binary critical mixture

Industrial motors produce either linear or rotational motion, and enabling these engines on micrometer scales would have significant technological implications in the biomedical, biochemical, nanoscience, and nanotechnology areas. In this paper, we report a colloidal dimeric micro-rotor consisting of a pivot particle (isotropic dielectric particle) joined to a carbon Janus particle (anisotropic particle) embedded in a critical mixture. The two particles forming this dimer are trapped and illuminated by an optical tweezer, respectively. The carbon Janus particle heats its surroundings, producing a demixing flow that results in directed rotational motion. The pivot ensures the stability of the dimer’s rotation motion, allowing for a clean circular trajectory with low dispersion between cycles. This system converts thermal energy from the absorption of light by the carbon Janus particle into mechanical rotational work. By adjusting the laser power input energy, we obtained rotational work values ranging from 3300 to 270 kBT per cycle. However, there is a limit in the laser power that induces rotation, which depends on the balance between trapping and demixing forces required for stable rotation. This paper provides an efficient method to construct a rotational micro-rotor with a stable motion (standard deviation = 0,03 µm) for nano and micro devices.

Mathematical model and experimental verification of self-centering energy dissipative brace equipped with disc spring and wedge block

The novel self-centering energy dissipation brace composed of disc spring group and wedge block group (DW-SCB) is introduced. The working mechanism of the DW-SCB and the force mechanism of each component are described. The stress analysis of the disc spring group (DSG) and the wedge block group (WBG) were carried out, and the DW-SCB theoretical prediction model was established. Three specimens with different disc spring preload lengths were fabricated, tested, and discussed. Furthermore, the established theoretical model was verified, and the theoretical model correction method considering the processing and assembly errors of the DSG was proposed. The tested data show that the hysteresis curve of DW-SCB is a typical flag shape, and there is almost no residual displacement after multiple loading. An increase in the preload length of the disc spring increases the yield load and bearing capacity of the DW-SCB but has no change on the stiffness of DW-SCB. All the components of the three specimens were not damaged after multiple loadings, which show that the DW-SCB has stable multiple seismic performance and recoverability. Significant, although the machining error of the disc spring leads to a large error between the experimental and theoretical curve of the DSG, the error correction method of the DSG proposed in this study can improve the prediction accuracy of the theoretical model, making the DW-SCB theoretical prediction model more accurate and reliable. The theoretical model considering the error of DSG can better predict the stiffness and load of DW-SCB, which can provide a reference for engineering design and application.

Design and implementation of a charge-sharing in-memory-computing macro with sparse feature for quantized neural network

With the rapid development of artificial intelligence technology, in-memory computing has become a research hotspot. In this article, we propose an in-memory computing (IMC) architecture that achieves high energy efficiency and performance. Our work is based on the working mechanism of charge sharing, enabling configurable multi-bit Multiply-Accumulate operations. This work employs a unique bit-cell structure to implement sparse strategies at the bit-level in IMC arrays and compensates for errors caused by non-ideal effects, thus achieving better energy efficiency and performance. A hardware-aware quantification method and a hardware simulation model based on Pytorch have been proposed to evaluate the hardware mapping and compare with other charge domain IMC works. The MNIST and CIFAR-10 datasets have been used to validate algorithm models and chip performance, achieving accuracy rates of 97.6% and 90.5%respectively. The IMC chip was fabricated with a 180 nm CMOS process. The measurement shows that the chip achieves an energy efficiency of 41.8 TOPS/W.

Pathways to Resilient and Sustainable Online Education in the New Normal: Interpreting University Teachers’ Willingness to Use Online Teaching Platforms Consistently

In the new normal, online education has become a norm and is considered equally important as traditional face-to-face education. Although online teaching has improved accessibility, reduced management costs, and expanded educational opportunities, there are also some issues, such as whether technology and internet access are widespread and whether the quality of online education is better or worse compared to previous modes. With the rapid development of online education, it is crucial to investigate the key factors influencing university teachers’ continuous usage of online teaching platforms and their working mechanisms, which is of great significance for improving the level of educational informatization and promoting educational modernization. This study mainly explores the continuous usage intention of online teaching platforms by Chinese university teachers under the new normal and its influencing factors, aiming to provide theoretical support and practical insights for improving educational informatization, promoting educational modernization, and designing and optimizing online teaching platforms. This study builds a new theoretical framework based on the technology acceptance model (TAM), UTAUT model, and the theory of planned behavior (TPB). From April to November 2024, 343 questionnaires were collected from Chinese university teachers. Combining structural equation modeling (SEM) and fuzzy-set qualitative comparative analysis (fsQCA), the key factors influencing teachers’ continuous usage of online platforms and their configuration relationships are systematically discussed. Not only are the key factors verified, but the configuration relationships are also revealed, providing deeper insights for universities to design, promote, and optimize online teaching platforms and offering theoretical support and practical guidance for promoting sustainable educational development.

Development and application of replaceable self-centering energy dissipative braces

Aiming to enhance seismic resilience of steel frames, this paper proposes a novel replaceable self-centering energy dissipative brace (RSCEDB), in which the combined disc springs act as self-centering (SC) system and the replaceable slit dampers act as energy dissipating (ED) system. Initially, the configuration details, assembly process of RSCEDB are introduced. Based on the numerical simulations, the working mechanism and hysteretic model of RSCEDB are discussed in depth. After that, a steel frame equipped with RSCEDB (SF-RSCEDB) is presented, and the effect of RSCEDB with various parameters on the performance of the SF-RSCEDB is investigated by numerical simulation. The results indicate that the damage is concentrated in the ED system, while the remaining parts of the RSCEDB remain elastic. The self-centering and energy dissipation capacity of RSCEDB can be flexibly modified by pre-pressure and stiffness of combined disc springs, as well as yield strength of dampers, which is consistent with the prediction of the hysteretic model. Benefiting from the contribution of RSCEDB, the SF-RSCEDB has satisfactory self-centering capacity. Before activation, the RSCEDB serves as a structural component, providing larger lateral stiffness. After activation, the RSCEDB serves as a structural fuse, dissipating most of the seismic energy. With favorable self-centering performance, the damaged dampers can be easily identified and replaced, demonstrating that the SF-RSCEDB possesses excellent seismic resilience. Finally, a resilient design method is proposed for SF-RSCEDB.

واقع ممارسة العلاقات العامة في الجهات الحكومية في المنطقة الشرقية في المملكة العربية السعودية

This research deals with a comprehensive view of the reality of practicing public relations in government agencies in the Eastern Province, by addressing the concepts of public relations and its role in shaping the image of the agency, as a human communication activity, and in light of the radical transformations witnessed by the world and the field of communication due to rapid technological developments and changing public behavior, with the emergence of social media and the increase in public interaction, public relations have become more interactive and transparent. Also, the increasing competition between institutions imposes on public relations practitioners to devise new and innovative strategies to reach the target audience. In light of the fact that public relations is a fundamental pillar in the work of any system, this research deals with part of the reality of public relations in government organizations in the Eastern Province, considering the public relations function an important pillar in building perceptions and relationships with the public. In the Kingdom of Saudi Arabia, after the launch of the Kingdom’s Vision 2030, communication activities have re-emerged in the government work arena, and witnessed a transformation in work methods and mechanisms. These activities focused on reflecting the true image of the achievements of the entities working in the field, and for these activities to stem from a deep understanding of the public and its aspirations, with a focus on new media, as they are the closest to the target group.

Ball Launching Robot and Object Retriever with V- Belt Method and Robotic Arm Method

This research develops a ball launcher and object picker robot controlled remotely /wirelessly using a microcontroller. The robot is designed to enhance mechanical work efficiency and control in the Indonesian robot contest, with the ability to automatically throw balls and collect objects in a designated area. The robot's drive system utilizes DC motors for mobility, with ball launching and pneumatic systems used for the object collection mechanism. This study emphasizes designing a more efficient system that offers good responsiveness, aiming to provide optimal robot control. The test results showed that the robot could perform ball launching with adequate accuracy and collect objects with suitable speed and precision. With the application of this technology, the robot is expected to be useful in various fields, including industry, sports games, education, agriculture, and other entertainment activities. This robot research opens opportunities for further development in more advanced and practical remote control robotic systems.

Compression behavior of CFRP strengthened sawdust-magnesium oxychloride composites columns subjected to eccentric loading

Sawdust-magnesium oxychloride cement composites (SMOCC) are new low-carbon and environmentally friendly building material. Previous studies showed that SMOCC columns perform well under compression, but the addition of eccentricity could induce excessive tensile stress, which may cause premature failure to sawdust fibers. Many engineering applications showed that the use of carbon fiber reinforced polymer (CFRP) could effectively improve the mechanical properties of building components. However, the applicability and feasibility of CFRP in SMOCC columns have not been explored. To overcome this research gap, this paper investigates the working mechanism and reinforcement effectiveness of the CFRP strengthened SMOCC columns subjected to eccentric loading. A total of 16 specimens were designed and tested, the investigated parameters include the arrangement modes of CFRP strips and load eccentricity, whose effects on the failure mode, load capacity, ductility and strain behavior are described and discussed. Moreover, the prediction models were proposed to predict the ultimate bearing capacity of the SMOCC columns. The test results indicate that the strengthening technique was effective, particularly as the bearing capacities and ductility of the CFRP strengthened SMOCC columns increased by 39.40 %-104.38 % and 10.60 %-113.51 %, respectively, when compared with those of the un-strengthened SMOCC columns. Moreover, the enhancing effect increased with an increase in the number of the CFRP strips. As the eccentricity was increased from 10 mm to 30 mm, the CFRP strengthened SMOCC column’s bearing capacity and ductility slightly decreased by 19.99 %-21.24 % and 28.63 %-41.46 %, respectively, but the lateral deflection at the mid-height of columns significantly increased by 26.55 %-61.84 %. Strain distributions within the SMOCC column cross section showed linear variation showing compatibility with elastic bending theory. The results predicted using the proposed models showed good agreement with test results, where the errors are within 10 %.

Experimental and numerical study on hysteresis behaviour of a novel dual-stage friction damper

This study proposes a dual-stage friction damper (DSFD) based on traditional friction dampers, consisting of two series of traditional friction dampers. Consequently, it has two sliding friction forces: a small and a large sliding friction force, unlike the single sliding friction force in traditional friction dampers. This paper first introduces the basic structure and working mechanism of the damper and examines its hysteresis behavior, focusing on its design details. Performance tests were conducted on two friction dampers with different preloads to determine the friction coefficients. Subsequently, cyclic loading tests were performed on the DSFD. The test results showed that the deformation of the proposed DSFD aligned with the anticipated outcomes, with the hysteresis curves exhibiting dual-stage characteristics. The damper displayed an outstanding capacity for energy dissipation. During testing, the preload force on the bolts and the damper′s energy dissipation ability were examined. Furthermore, the damper′s reliability under cyclic loading was evaluated, revealing consistent performance across multiple load cycles. This indicates that the damper can be reused after multiple earthquakes. Moreover, a refined finite element model of the DSFD was developed. The numerical simulation results were in good agreement with the experimental results regarding the hysteresis curves and energy dissipation capacity of the DSFD. The discussion on the optimized design demonstrates the protective role of the sliding plate on the bolts. Finally, a parameter analysis was conducted to examine the influence of change parameters on the damper′s performance.