Mechanical Work Research Articles

Pore structure manipulation‐enhanced sodium storage of calcium‐lignosulfonate‐based hard carbon

AbstractSodium‐ion batteries (SIBs) have attracted a lot of attention owing to their low cost, as well as similar working mechanism and manufacturing technique to lithium‐ion batteries. However, the practical application of SIBs is severely hindered by limited electrode materials. Disordered carbons are reported to be promising as anode materials for SIBs. Here, for the first time, calcium lignosulfonate (LSCa), one papermaking waste, is explored as a novel low‐cost precursor for carbon materials of SIBs. The optimized LSCa‐derived carbon delivers a high reversible capacity of 317 mA h g−1 at 30 mA g−1 with ~60% plateau capacity, and it retains a capacity of 170 mA h g−1 even at 3000 mA g−1. These achievements are ascribed to the larger d002 values, smaller defects, and more closed pores, compared with the original sample from the direct carbonization of LSCa.

Engineering Metal Electron Spin Polarization to Regulate p‐Band Center of Se for Enhanced Sodium‐Ion Storage

AbstractSluggish ion diffusion of large sodium ions is one of the main drawbacks challenging the development of metal selenides‐based anode materials for sodium‐ion batteries (SIBs). A spin‐state regulating strategy is first proposed in this work to lift the p‐band center (ɛp) of Se for a fast Na+ transfer kinetic in (Co,Cu)Se2. By utilizing the electron transfer from Cu to Co, the π‐symmetry t2g of Co is fully occupied to decrease the spin polarization. The resultant electron repulsion between Co and Se weakens Co–Se bond to lift the ɛp of Se. The enhanced sodium adsorption energy effectively accelerates the ion transfer at the active material–electrolyte interface. As a result, the (Co,Cu)Se2/NC electrode exhibits an superior sodium storage performance with a capacity of 445 mAh g−1 at 0.2 A g−1, 312 mAh g−1 at 50 A g−1, and 363 mAh g−1 after 10 000 cycles at 10.0 A g−1. The insight into the working mechanism of regulating spin‐state of metals to lift the p‐band center of Se can provide guidelines for the development of both metal selenides‐based anode material and high‐performance SIBs.

Evaluating a green liquid phase plasma discharge process and working mechanism for remediating cobalt contamination in water

Cobalt is a toxic heavy metal contaminant in water and wastewater causing health concerns and on the other hand, a valuable element to recycle. In this study, performance of a novel and green continuous liquid phase plasma discharge (CLPD) process was investigated for removal and recovery of cobalt from aqueous solution without use of any catalysts or chemicals. The CLPD reactor design features two conductive channels and stable electric discharge at the orifice of two dielectric plates sandwiched among the electrodes. The effects of operating factors of the CLPD process were evaluated with liquid flow rate (25–100 mg/L) and applied power (200–300 W), and the highest removal efficiency of cobalt (93 %) was obtained within 25 min at a 50 ml/min liquid flow rate and 300 W applied power. The CLPD energy efficiency for cobalt removal under this condition was 27.44 g kW-1h−1. Reaction kinetics with scavenger tests revealed that oxidative reactive species, i.e., hydroxyl radical and superoxide radicals, produced at the discharge zone were responsible for cobalt removal from water by producing cobalt oxide particles and the reaction pathways were proposed. The CLPD process not only allowed for the efficient removal of cobalt (II) from water but also synthesized cobalt oxides particles with averaged size of 2.75 µm, which can be applied as catalyst. The overall results indicated that the novel CLPD is a robust and highly effective process to remove and recover cobalt from water.

Steel truss reinforced concrete composite walls: Numerical investigation and design consideration

Conventional design practices for reinforced concrete (RC) structural walls in the lower stories of super high-rise buildings involve employing large thickness and dense reinforcement to ensure satisfactory seismic performance. This is necessary to withstand the considerable gravity and seismic forces caused by the superstructure. However, this approach brings a design challenge in engineering practice because excessively thick RC walls not only occupy useable space but also magnify earthquake forces due to the increased self-weight. For this reason, steel truss RC (STRC) composite walls have been developed to address the above-mentioned shortcomings of conventional designs. This paper elucidates the working mechanism of STRC walls under cyclic loading, indicating that these two diagonal embedded steel elements mainly exhibit truss behavior. The working mechanism is further verified through computational models developed in OpenSees with high accuracy and efficiency. Moreover, the design provisions in the current specification are evaluated in terms of the flexural strength and shear strength of STRC walls. Results show that the flexural strength of the design equations for STRC walls in the current specification is underestimated because the contribution of steel trusses is not considered. The findings of this study offer valuable insights into the engineering application of STRC walls.

Construction of the Glycolysis Metabolic Pathway Inside an Artificial Cell for the Synthesis of Amino Acid and Its Reversible Deformation.

The bottom-up construction of artificial cells is beneficial for understanding cell working mechanisms. The glycolysis metabolism mimicry inside artificial cells is challenging. Herein, the glycolytic pathway (Entner-Doudoroff pathway in archaea) is reconstituted inside artificial cells. The glycolytic pathway comprising glucose dehydrogenase (GDH), gluconate dehydratase (GAD), and 2-keto-3-deoxygluconate aldolase (KDGA) converts glucose molecules to pyruvate molecules. Inside artificial cells, pyruvate molecules are further converted into alanine with the help of alanine dehydrogenase (AlaDH) to build a metabolic pathway for synthesizing amino acid. On the other hand, the pyruvate molecules from glycolysis stimulate the living mitochondria to produce ATP inside artificial cells, which further trigger actin monomers to polymerize to form actin filaments. With the addition of methylcellulose inside the artificial cell, the actin filaments form adjacent to the inner lipid bilayer, deforming the artificial cell from a spherical shape to a spindle shape. The spindle-shaped artificial cell reverses to a spherical shape by depolymerizing the actin filament upon laser irradiation. The glycolytic pathway and its further extension to produce amino acids (or ATP) inside artificial cells pave the path to build functional artificial cells with more complicated metabolic pathways.

Design, preparation and firing characterization of PCB-EBW

Exploding Bridge Wire (EBW) is a special actuator that drives high-temperature and high-pressure plasma. To address the issues of low efficiency and high cost in the preparation process of EBW detonators, an EBW chip based on Printed Circuit Board (PCB) technology was designed and studied. By utilizing a specially designed "S"-shaped transition region and using copper (Cu) as the bridge wire material, the PCB method has enabled batch production of the PCB-EBW device. Four different types of PCB-EBW chips were constructed by designing bridge wires of varying lengths. Subsequently, electro-thermal simulations, electrical explosion performance studies, and shock wave simulations were conducted on the PCB-EBW. It is inferred from the research findings that the main factor triggering the explosive detonation of the PCB-EBW chip is the coupling effect between the high-temperature plasma generated by the electrical explosion and the electrical explosion shock wave. The speculation on the working mechanism of the PCB-EBW was validated by igniting PETN, with the minimum firing voltage determined to be 550 V (for a bridge wire length of 200 μm). This novel EBW design expands the application prospects and provides new insights into the mechanism of EBW for future research.

Mechanisms for HNH-mediated target DNA cleavage in type I CRISPR-Cas systems

The metagenome-derived type I-E and type I-F variant CRISPR-associated complex for antiviral defense (Cascade) complexes, fused with HNH domains, precisely cleave target DNA, representing recently identified genome editing tools. However, the underlying working mechanisms remain unknown. Here, structures of type I-FHNH and I-EHNH Cascade complexes at different states are reported. In type I-FHNH Cascade, Cas8fHNH loosely attaches to Cascade head and is adjacent to the 5' end of the target single-stranded DNA (ssDNA). Formation of the full R-loop drives the Cascade head to move outward, allowing Cas8fHNH to detach and rotate ∼150° to accommodate target ssDNA for cleavage. In type I-EHNH Cascade, Cas5eHNH domain is adjacent to the 5' end of the target ssDNA. Full crRNA-target pairing drives the lift of the Cascade head, widening the substrate channel for target ssDNA entrance. Altogether, these analyses into both complexes revealed that crRNA-guided positioning of target DNA and target DNA-induced HNH unlocking are two key factors for their site-specific cleavage of target DNA.

Category-agnostic semantic edge detection by measuring neural representation randomness

Edge detection plays a fundamental role in computer vision tasks and gains wide applications. In particular, semantic edge detection recently draws more attention due to the high demand for a fine-grained understanding of visual scenes. However, detecting high-level semantic edges hidden in visual scenes is quite challenging. Existing semantic edge detection methods focus on category-aware semantic edges and require elaborate category annotations. Instead, we first propose the category-agnostic semantic edge detection task without additional semantic category annotations. To achieve this goal, we propose to utilize only edge position annotations and leverage the information randomness of semantic edges. Specifically, we align semantic edge positions to the ground truth by maximizing randomness on edge regions and minimizing randomness on non-edge regions in the training process. In the inference process, we first obtain neural representations by the trained network, and then generate semantic edges by measuring neural randomness. We evaluate our method by comparisons with alternative methods on two well-known datasets: Cityscapes (Cordts et al., 2016) and SBD (Hariharan et al., 2014). The results demonstrate our superiority over the alternatives, which is more significant under weak annotations. We also provide comprehensive mechanism studies to verify the generalizability, rationality, and validity of our working mechanism.

Implantable and Semi-Implantable Biosensors for Minimally Invasive Disease Diagnosis

Implantable and semi-implantable biosensors fabricated with biodegradable materials and nanomaterials have gained interest in the past few decades. Functionalized biodegradable materials and nanomaterials are usually employed to satisfy clinical and research requirements because of their advanced properties. Novel fabrication techniques were developed to improve the efficiency and accuracy. Different working mechanisms were facilitated to design different types of sensors. This review discusses the recent developments of implantable and semi-implantable biosensors. The materials and fabrications are browsed, and different types of biomedical sensors for different variables are discussed as a focused topic. The biomedical sensors are discussed according to the targets and working mechanisms, followed by a focus on the nervous system sensing to provide an inspiration that different variables can be studied simultaneously on the single system. In the end, challenges and prospects will be discussed. This review aims to provide information of materials, fabrication approaches, mechanisms, and the state of the art for inspiration in designing novel implantable and semi-implantable biomedical sensors for general diagnostic activities.

Effect of copper on fermentative hydrogen production from sewage sludge: Insights into working mechanisms

The effect of Copper (Cu) on fermentative hydrogen production from sewage sludge (SSL) was firstly explored, and glucose was chosen as typical substrate to make a comparison. Results showed that the stimulative dosages of Cu on hydrogen production from glucose and SSL were 20–60 mg/L and 20–100 mg/L, respectively. The stimulation was more significant to SSL (6.3–43.8 %) than glucose (4.8–16.1 %). 500–1000 mg/L Cu posed obvious inhibition to hydrogen production, and the inhibition was more significant to glucose (80.6–91.9 %) than SSL (25.0–37.5 %), which was due to the protective effect of SSL to hydrogen producers from adsorbing Cu. The exposure enriched the Cu-resistant microorganisms like genus Aeromonas, Comamonas, Pseudomonas and Dechloromonas. Metabolic analysis shows that low dosages of Cu stimulated hydrogen production by strengthening the formate decomposition process, and weakening the lactate formation and homoacetogenesis processes, while high dosages of Cu inhibited hydrogen production by weakening all hydrogen-producing processes including formate decomposition, ferredoxin hydrogenation and glucose decomposition processes.

Sliding connectors for cyclic construction of steel-UHPC composite truss arch bridges: design method and feasibility study

To break through the three major technical bottlenecks of traditional long-span arch bridges, which are excessive self-weight, high cost and difficult construction, a new steel-ultra high performance concrete (UHPC) composite truss arch bridge scheme and a matching cyclic construction method were proposed. The main arch can be divided into several times for closure from the inside out. Special transverse connection devices need to be installed between the arch ribs constructed with successive closures by step. The devices can not only ensure the stability of the arch ribs constructed subsequently, but also do not cause serious stress superposition on the already closed arch ribs. Therefore, sliding connectors for the cyclic construction of new arch bridges and the corresponding simplified modeling method were proposed in this paper. Subsequently, the working mechanism was analyzed, and the design method was proposed. Finally, the feasibility of sliding connectors and the correctness of the corresponding design method were verified by the experiment. The results indicate that it is necessary to install a transverse sleeve structure in the sliding connector, which plays a key role in transverse adjustment. The design of key dimensions in sliding connectors is controlled by the maximum vertical and longitudinal displacements of the inner arch. The outer arch could slide freely under the premise of ensuring stability, and the mechanical superposition response of the inner arch was relatively small. For the inner arch, the vertical displacement at the crown only increased by 10.94 %, and the maximum compressive stress in the UHPC arch ribs only increased by 16.3 %. The sliding connector also has the potential for further optimization to achieve smaller stress superposition.

Heterogeneous activation of self-generated H2O2 by Pd@UiO-66(Zr) for trimethoprim degradation: Efficiency and mechanism

The Fenton reaction is recognized as an effective technique for degrading persistent organic pollutants, such as the emerging pollutant trimethoprim (TMP). Recently, due to the excellent reducibility of active hydrogen ([H]), Pd–H2 has been preferred for Fenton-like reactions and the specific H2 activation of Pd-based catalysts. Herein, a heterogeneous Fenton catalyst named the hydrogen-accelerated oxygen reduction Fenton (MHORF@UiO-66(Zr)) system was prepared through the strategy of building ships in the bottle. The [H] has been used for the acceleration of the reduction of Fe(III) and self-generate H2O2. The systematic characterization demonstrated that the nano Pd0 particle was highly dispersed into the UiO-66(Zr). The results found that 20 mg L−1 of TMP was thoroughly degraded within 90 min in the MHORF@UiO-66(Zr) system under conditions of initial pH 3, 30 mL min−1 H2, 2 g L−1 Pd@UiO-66(Zr) and 25 μM Fe2+. The hydroxyl radical as well as the singlet oxygen were evidenced to be the main reactive oxygen species by scavenging experiments and electron spin resonance. In addition, both reducing Fe(III) and self-generating H2O2 could be achieved due to the strong metal-support interaction (SMSI) between the nano Pd0 particles and UiO-66(Zr) confirmed by the correlation results of XPS and calculation of density functional theory. Finally, the working mechanism of the MHORF@UiO-66(Zr) system and the possible degradation pathway of the TMP have been proposed. The novel system exhibited excellent reusability and stability after six cyclic reaction processes.

Variant‐Localized High‐Concentration Electrolyte without Phase Separation for Low‐Temperature Batteries

AbstractDual‐ion batteries (DIBs) present great application potential in low‐temperature energy storage scenarios due to their unique dual‐ion working mechanism. However, at low temperatures, the insufficient electrochemical oxidation stability of electrolytes and depressed interfacial compatibility impair the DIB performance. Here, we design a variant‐localized high‐concentration solvation structure for universal low‐temperature electrolytes (ν‐LHCE) without the phase separation via introducing an extremely weak‐solvating solvent with low energy levels. The unique solvation structure gives the ν‐LHCE enhanced electrochemical oxidation stability. Meanwhile, the extremely weak‐solvating solvent can competitively participate in the Li+‐solvated coordination, which improves the Li+ transfer kinetics and boosts the formation of robust interphases. Thus, the ν‐LHCE electrolyte not only has a good high‐voltage stability of >5.5 V and proper Li+ transference number of 0.51 but also shows high ionic conductivities of 1 mS/cm at low temperatures. Consequently, the ν‐LHCE electrolyte enables different types of batteries to achieve excellent long‐term cycling stability and good rate capability at both room and low temperatures. Especially, the capacity retentions of the DIB are 77.7 % and 51.6 %, at −40 °C and −60 °C, respectively, indicating great potential for low‐temperature energy storage applications, such as polar exploration, emergency communication equipment, and energy storage station in cold regions.

Navigating the gig economy in Romania: unveiling perceptions of working on on-demand platforms

Purpose This paper aims to explore the realm of gig work and the gig economy in Romania in an attempt to shed light on the mechanisms of this type of work and the reasons and benefits of engaging in gig-related activities.Considering the low conceptual consensus on gig work, the authors aim to explore how participants in this study define and refer to gig work, thus helping to contribute to the current conceptualization and characterizations of gig work and the gig economy. Among the wide range of services encountered within the gig economy, this research focuses on three categories of tasks, as defined within COLLEEM 2018 questionnaire (see Pesole et al., 2018), namely, online creative and multimedia work, online sales and marketing support and online software development and technology work. Design/methodology/approach Based on semistructured interviews with people working in the gig economy in Romania, the authors look to understand the meaning given to gig work and its features. The authors tackle how participants in this study perceive themselves and their work. The authors also look into perceived similarities and differences with other types of independent work. Findings In this paper, findings are organized into two main sections. The first section showcases perceptions about working in the gig economy, including how people involved with this type of work are describing them and their activity and exploring financial insecurities in connection with the independent/gig work. The second section highlights the mechanisms of gig work on digital labor platforms, developing means and ways of reputation-building and their impact on financial earnings. Originality/value This research aims to contribute to a better understanding of the environment and needs of gig workers. Although gig economy and online work are widely covered by field literature, knowledge about the experiences and perceptions of gig workers in emerging markets has more to gain by exploring European Union developing markets.

Variant-Localized High-Concentration Electrolyte without Phase Separation for Low-Temperature Batteries.

Dual-ion batteries (DIBs) present great application potential in low-temperature energy storage scenarios due to their unique dual-ion working mechanism. However, at low temperatures, the insufficient electrochemical oxidation stability of electrolytes and depressed interfacial compatibility impair the DIB performance. Here, we design a variant-localized high-concentration solvation structure for universal low-temperature electrolytes (ν-LHCE) without the phase separation via introducing an extremely weak-solvating solvent with low energy levels. The unique solvation structure gives the ν-LHCE enhanced electrochemical oxidation stability. Meanwhile, the extremely weak-solvating solvent can competitively participate in the Li+-solvated coordination, which improves the Li+ transfer kinetics and boosts the formation of robust interphases. Thus, the ν-LHCE electrolyte not only has a good high-voltage stability of >5.5 V and proper Li+ transference number of 0.51 but also shows high ionic conductivities of 1 mS/cm at low temperatures. Consequently, the ν-LHCE electrolyte enables different types of batteries to achieve excellent long-term cycling stability and good rate capability at both room and low temperatures. Especially, the capacity retentions of the DIB are 77.7 % and 51.6 %, at -40 °C and -60 °C, respectively, indicating great potential for low-temperature energy storage applications, such as polar exploration, emergency communication equipment, and energy storage station in cold regions.

Electrically Conductive Adhesives in Microelectronics Packaging

Abstract Electronic packaging is integral to safeguarding electronic devices while ensuring electrical connectivity and heat dissipation. This paper reviews electrically conductive adhesives (ECAs), focusing on two main types: isotropic conductive adhesives (ICAs) and anisotropic conductive adhesives (ACAs). ECAs offer advantages over traditional solders, including lower processing temperatures, environmental friendliness, and the ability to conform to flexible substrates. The paper explores the working mechanisms of ICAs and ACAs, highlighting their limitations and recent developments aimed at improvement. Key challenges for ICAs include low electrical conductivity and moisture absorption, while ACAs face limitations in fine-pitch applications and electric field-induced particle movement. Recent advancements discussed include the use of organic monolayers, nanofiber integration, magnetic self-assembly, low-temperature sintering of nano-silver particles, and copper nanoparticle fillers. These innovations hold promise for enhancing the electrical conductivity, mechanical strength, and reliability of ECAs. Finally, the paper explores applications of ECAs in die attach, flip-chip bonding, and chip-on-flex (COF) packaging, highlighting their potential for various electronic devices.

Experimental and Modeling Analysis of Mechanical Response of Composite Electrodes in Lithium Batteries.

The mechanical response is one of the main factors that influence the capacity and number of cycles of lithium batteries, which hinder its wide application. Therefore, it is crucial to perform an in-depth investigation of the electro-chemo-mechanical coupling performance and work mechanism of battery electrodes during the electrochemical reaction process. Usually, graphite is the main active material used in commercially used batteries, while silicon is gaining worldwide attention because of its large energy density. Here, graphite and silicon composite electrodes were prepared to obtain the electro-chemo-mechanical response during electrochemical cycling by an in situ bending deformation measurement. The findings indicate that the composite electrodes could induce a large bending deformation, with an increase in the state of charge (C-rate). And, with an increase in the C-rate, the deformation degree of the silicon composite electrode increases, while that of the graphite composite electrode decreases due to the hardening properties of the graphite particles. In addition, increasing the thickness ratio could induce an increase in the peak stress for both composite electrodes. This work gives a detailed analysis of the mechanical properties of composite electrodes and finds the working mechanism of the C-rate and thickness ratio, which can supply suggestions for the development of high-performance batteries.

Peak Oxygen Uptake is Slope Dependent: Insights from Ground Reaction Forces and Muscle Oxygenation in Trained Male Runners

BackgroundThe aim of this study is to explore the effect of treadmill slope on ground reaction forces and local muscle oxygenation as putative limiting factors of peak oxygen uptake in graded maximal incremental running tests. Thirteen trained male runners completed five maximal incremental running tests on treadmill at − 15%, − 7.5%, 0%, 7.5% and 15% slopes while cardiorespiratory and local muscle oxygenation responses as well as ground reaction forces were continuously recorded. Blood lactate concentration and isometric knee extensor torque were measured before and after each test.ResultsPeak oxygen uptake was lower at − 15% slope compared to all other conditions (from − 10 to − 17% lower, p < 0.001), with no difference between − 7.5 and + 15% slope. Maximal heart rate and ventilation values were reached in all conditions. The negative external mechanical work increased from steep uphill to steep downhill slopes (from 6 to 92% of total external work) but was not correlated with the peak oxygen uptake reduction. Local muscle oxygenation remained higher in − 15% slope compared to level running (p = 0.003).ConclusionsSimilar peak oxygen uptake can be reached in downhill running up to − 7.5% slope. At more severe downhill slopes (i.e., − 15%), greater negative muscle work and limited local muscle deoxygenation occurred, even in subjects familiarized to downhill running, presumably preventing the achievement of similar to other condition’s peak oxygen uptake.Key PointsTrained male runners can reach like level running V̇O2peak at moderate but not at severe negative slope.Negative external mechanical work increases with increasing negative slope.At maximal intensity Vastus Lateralis muscle oxygenation is higher in steep negative slope.Knee extensor isometric muscle torque is preserved after maximal level and uphill running, but reduced after downhill running, despite lower blood lactate.Progressive reduction of V̇O2 at maximal effort with increasing negative slope might be related to the metabolic consequences of increased lower limb negative external work (i.e., eccentric muscle actions).

Amphoteric ionic polymer large temperature difference retarder for long sealing section cementing low‐density cement slurry: Preparation, application, and working mechanism

AbstractIn this study, a novel amphoteric ionic large temperature difference retarder (marked with CLL‐1) was prepared by using functional monomer through aqueous solution polymerization method. First, the chemical structure and molecular weight of retarder CLL‐1 were obtained, and then the thermal stability of retarder CLL‐1 was investigated at the temperature range of 40–400°C, and the result shows that the retarder CLL‐1 has well thermal stability, which could be used to control the thickening time of cement slurry at higher temperatures. Second, the influences of retarder CLL‐1 on the settlement stability of cement slurry were studied by the density difference at the temperature of 150, 120, 90, and 30°C, respectively. Third, the thickening time of cement slurry samples with different retarder CLL‐1 adding amount was studied at the temperature range of 80–180°C, and the results showed that the retarder CLL‐1 can adapt well to the working conditions of large temperature difference cementing operations. Simultaneously, the compressive strength of cement slurry with different retarder CLL‐1 adding amount was obtained. Finally, the working mechanism of retarder CLL‐1 at large temperature difference was revealed depends on the methods of x‐ray diffraction, scanning electron microscope, and TG.

Parameter Optimization Method for Metal Surface pBRDF Model Based on Improved Strawberry Algorithm

To study the polarization reflection characteristics of metal surfaces, a parameter optimization method for the polarization bidirectional reflection distribution function (pBRDF) model of metal surfaces based on the improved strawberry algorithm has been proposed. Firstly, the light scattering characteristics of metal surfaces were analyzed and a multi-parameter pBRDF model was constructed. Then, the working mechanism of the strawberry optimization algorithm was investigated and improved by introducing the chaotic mapping and Levy flight strategy to overcome the shortcomings, such as low convergence rate and easily falling into local optimum. Finally, the method proposed in this paper was validated by simulating open-source data from references and the obtained ones with a self-built experimental platform. The results show that the proposed method outperforms those by nonlinear least squares, particle swarm optimization and the original strawberry algorithm in fitting the detected degree of polarization (DOP) data, indicating the modeling accuracy was significantly improved and better suited to characterize the polarized reflection properties of metal surfaces.