Chain Mechanism Research Articles

Using Mechanochemistry to Activate Commodity Plastics as Initiators for Radical Chain Reactions of Small Organic Molecules.

Radical initiators such as azo compounds and organic peroxides have been widely used to facilitate numerous transformations of free radicals, which enable the efficient synthesis of structurally complex molecules, natural products, polymers, and functional materials. However, these high-energy reagents are potentially explosive and thus often require special precautions or delicate operating conditions. We postulated that a more convenient and safer alternative for radical chain initiation could be developed by mechanical activation of thermodynamically stable covalent bonds. Here, we show that commodity plastics such as polyethylene and poly(vinyl acetate) are capable of acting as efficient initiators for radical chain reactions under solvent-free mechanochemical conditions. In this approach, polymeric mechanoradicals, which are generated by homolytic cleavage of the polymer chains in response to the applied mechanical energy provided by ball milling, react with tris(trimethylsilyl)silane to initiate radical chain dehalogenation of organic halides. Preliminary calculations support our proposed force-induced radical chain mechanism.

Trans-Cyclooctenes as Scavengers of Bromine Involved in Catalytic Bromination.

Scavengers that capture reactive chemical substances are used to prevent the decomposition of materials. However, in the field of catalysis, the development of scavengers that inhibit background pathways has attracted little attention, although the concept will open up an otherwise inaccessible reaction space. In catalytic bromination, fast non-catalyzed background reactions disturb the catalytic control of the selectivity, even when using N-bromoamide reagents, which have a milder reactivity than bromine (Br2 ). Here, we developed a trans-cyclooctene (TCO) bearing a 2-pyridylethyl group to efficiently retard background reactions by capturing Br2 in bromocyclization using N-bromosuccinimide. The use of less than a stoichiometric amount of the TCO was sufficient to inhibit non-catalyzed reactions, and mechanistic studies using the TCO revealed that in situ-generated Br2 provides non-catalyzed reaction pathways based on a chain mechanism. The TCO is useful as an additive for improving enantioselectivity and regioselectivity in catalytic reactions. Cooperative systems using the TCO with selective catalysts offer an alternative strategy for optimizing catalyst-controlled selectivity during bromination. Moreover, it also served as an indicator of Br2 involved in catalytic reaction pathways; thus, the TCO was useful as a probe for mechanistic investigations into the involvement of Br2 in bromination reactions of interest.

Preparation of novel silver borates by soft hydrothermal synthesis in sealed tubes: New representatives of larderellite and veatchite families

New silver-based representatives of the larderellite and veatchite families, Ag2B10O14(OH)4∙H2O (1) and Ag2B5O8(OH)∙H2O (2) respectively, have been prepared using a soft hydrothermal synthetic approach inside a sealed silica tube. Both structures are built of the pentaborate groups yet exhibit various dimensionality: 2D for 1 and 1D for 2. The silver atoms in 1 exhibit noticeable anharmonicity approximated using Gram–Charlie approach. 1 was additionally characterized by thermal analysis, high-temperature X-ray powder diffraction and IR spectroscopy. Thermal expansion of 1 is strongly anisotropic (α11 = 38, α22 = −13, α33 = 14 × 10−6 °С−1) which is related with the hinge mechanism of the larderellite chains from corner-sharing pentaborate groups. Topology and complexity analysis of these compounds within the larderellite and veatchite families is presented.

Do Social Exchange Relationships Influence Total-Quality-Management Involvement? Evidence from Frontline Employees of International Hotels.

This study delves into the assessment of the quality of social exchange relationships in the workplace, specifically focusing on leader-member exchange (LMX) and team-member exchange (TMX), to forecast employee Total Quality Management (TQM) involvement within the hospitality industry. Employing Structural Equation Modeling (SEM), the study evaluates multiple hypotheses, utilizing data collected from 811 frontline employees in international tourist hotels located in Taiwan. The findings demonstrate that both LMX and TMX exhibit direct positive influences on employee TQM involvement. Moreover, through mediated path analyses, it is evident that both LMX and TMX exert indirect positive impacts on employee TQM involvement, by means of self-efficacy and job satisfaction. These results elucidate a clear causal chain mechanism underlying the behavior of employee TQM involvement within such social relationships. The study's revelations carry significant implications for the hospitality industry, shedding light on the nuanced dynamics of these social relationships and their impact on employee behavior concerning TQM involvement. The discussions encompassing the implications of these findings in the realm of hospitality are thoroughly explored and detailed.

Self-assembly of ferromagnetic particles into chains and spin under the control of traveling magnetic field

In this paper, the spin phenomenon of self-assembly of ferromagnetic particles to form particle chains under the action of a traveling magnetic field (TMF) is investigated, and a TMF generator is designed and fabricated to experimentally observe the self-assembly and spin phenomenon of ferromagnetic particles under the action of TMF. The TMF generator is capable of generating a TMF, which is an alternating motion magnetic field with sinusoidally varying and translating magnetic induction, under the action of which a chain of self-assembled ferromagnetic particles is subjected to an alternating magnetic force thereby generating a spin motion. By analyzing the spin mechanism of the self-assembled ferromagnetic particle chain, the relationship between the rotational velocity of the spin motion of the particle chain and the frequency of the three-phase AC power supply of the TMF generator was obtained. Adjusting the frequency of the three-phase AC power supply of the TMF generator can control the spin velocity of the particle chain. TMF generator enable ferromagnetic particles to self-assemble to form particle chains and drive the particle chains to spin controllably, which has a wide range of applications in micro-robotics, biomedicine, and microfluidics.

Exports and economic growth: relationships and threshold analysis for the Southern Africa customs union

This study examines the short-run and long-run relationships between exports and economic growth in the Sothern Africa Customs Union (SACU), as well as the corresponding threshold level. The study used panel data covering the period 1980 to 2021 and employed the Autoregressive Distributed Lag (ARDL) Bounds to test for co-integration relationships, and the Generalized Least Squares (GLS) to determine the respective threshold level. Exports positively support economic growth both in the short-run and in the long-run in SACU. There is long-run bidirectional causality between exports and economic growth. The minimum threshold for exports is 59%. That is, exports only start contributing significantly to economic growth when they are above 59% of the Gross Domestic Product (GDP). SACU should put in place economic policies and regulations that are skewed towards the improvement of the competitiveness of its local products on the global market and also strategically consider export-oriented industrialization strategies. Efforts should also be channeled towards the implementation of bilateral and multilateral trade agreements and harnessing the synergic benefits through the adoption of deliberate value chain mechanisms and initiatives.

The Dielectrophoretic Alignment of Biphasic Metal Fillers for Thermal Interface Materials.

Pad-type thermal interface materials (TIMs) with composite structures are required to exhibit high thermal conductivity while maintaining conformal contact with the heat sink, which is strongly influenced by the type and content of the thermally conductive filler. This study presents that biphasic metal particles can be effectively aligned using the dielectrophoretic chaining (DEP-C) mechanism, thereby enhancing the thermal conductivity of a pad-type TIM. A eutectic gallium-indium (EGaIn) alloy liquid metal and solid copper were used as the filler materials with two different phases. The biphasic metal particle mixture of EGaIn and Cu (EGaIn-Cu) were better aligned by DEP-C than when they presented individually because fusion between the two particles increased the effective size. As expected, the thermal conductivity of the TIM composites increased when DEP-C aligned the filler. Notably, TIMs with both EGaIn-Cu fillers showed the largest increase in thermal conductivity, of up to 64.6%, and the highest thermal conductivity values after DEP-C application compared to TIMs with only the EGaIn or Cu filler. Finally, the heat dissipation performance of the TIM composite on a lit light-emitting diode is shown, where the TIM with DEP-C-aligned fillers exhibits improved performance.

Structural Dynamics of E6AP E3 Ligase HECT Domain and Involvement of a Flexible Hinge Loop in the Ubiquitin Chain Synthesis Mechanism.

Ubiquitin (Ub) ligases E3 are important factors in selecting target proteins for ubiquitination and determining the type of polyubiquitin chains on the target proteins. In the HECT (homologous to E6AP C-terminus)-type E3 ligases, the HECT domain is composed of an N-lobe and a C-lobe that are connected by a flexible hinge loop. The large conformational rearrangement of the HECT domain via the flexible hinge loop is essential for the HECT-type E3-mediated Ub transfer from E2 to a target protein. However, detailed insights into the structural dynamics of the HECT domain remain unclear. Here, we provide the first direct demonstration of the structural dynamics of the HECT domain using high-speed atomic force microscopy at the nanoscale. We also found that the flexibility of the hinge loop has a great impact not only on its structural dynamics but also on the formation mechanism of free Ub chains.

TMSCF3-Mediated Conversion of Salicylates into α,α-Difluoro-3-coumaranones: Chain Kinetics, Anion-Speciation, and Mechanism.

As reported by Zhao, the TBAT ([Ph3SiF2]-[Bu4N]+)-initiated reaction of ethyl salicylate with TMSCF3 in THF generates α,α-difluoro-3-coumaranones via the corresponding O-silylated ethoxy ketals. The mechanism has been investigated by in situ 19F and 29Si NMR spectroscopy, CF2-trapping, competition, titration, and comparison of the kinetics with the 3-, 4-, 5-, and 6-fluoro ethyl salicylate analogues and their O-silylated derivatives. The process evolves in five distinct stages, each arising from a discrete array of anion speciations that modulate a sequence of silyl-transfer chain reactions. The deconvolution of coupled equilibria between salicylate, [CF3]-, and siliconate [Me3Si(CF3)2]- anions allowed the development of a kinetic model that accounts for the first three stages. The model provides valuable practical insights. For example, it explains how the initial concentrations of the TMSCF3 and salicylate and the location of electron-withdrawing salicylate ring substituents profoundly impact the overall viability of the process, how stoichiometric CF3H generation can be bypassed by using the O-silylated salicylate, and how the very slow liberation of the α,α-difluoro-3-coumaranone can be rapidly accelerated by evaporative or aqueous workup.

Demulsification efficiency and mechanism of hydrophobic carbon chains modified hyperbranched polyethylenimide on oil-in-water emulsion

A series of amphiphilic hyperbranched polyethylenimine (HPEI-Cn) with different length hydrophobic carbon chains were synthesized by amidation modification of hyperbranched polyethylenimine (HPEI), which can be used for separation of oil-in-water emulsion. The demulsification effect of HPEI-Cn under different demulsifier concentration, temperature, settling time and pH value were evaluated by bottle test method. The results indicated that the demulsification efficiency (DE) of HPEI-Cn increased with the increase of graft length of carbon chain. Encouragingly, the HPEI-C16 had the characteristics of small amount (50 mg/L), short settling time (30 min) and wide temperature adaptation range (20–60 °C). Through three-phase contact angle tests (CA), dynamic interfacial tension tests (IFT), elastic modulus analysis, Zeta potential and microscope observation, the demulsification mechanism of HPEI-Cn was systematically revealed. The excellent DE of HPEI-C16 was attributed to the high interfacial activity and appropriate length of hydrophobic groups. On the one hand, the high interfacial activity drives hyperbranched macromolecules to rapidly diffuse and adsorb to the oil-water interface. On the other hand, it contains appropriate hydrophobic carbon chains C16 to flocculate and coalesce oil droplets, thus achieving efficient demulsification.

How will CBAM affect the decarbonisation of steel industry in China? A system dynamics approach

EU's Carbon Border Adjustment Mechanism (CBAM) has been promulgated. The steel industry is included in CBAM, which will undoubtedly affect the export trade of China's steel manufacturers to the EU. It is necessary to analyse the impact of CBAM on China’s steel industry quantitatively. By establishing a system dynamics model that can simulate the operation mechanism of the steel supply chain in China, we have clarified the impacts of CBAM on the China's steel export and carbon reduction. Moreover, we have reasonably set up scenarios that represent the possible decarbonisation paths of China's steel industry and evaluated the implementation effect of each policy in these scenarios. The analysis shows that CBAM will lead to a decrease of 32% in export volume and a loss of 58% in export profits for China's steel exporters. The environmental benefits of CBAM are limited. Due to the low trade exposure, CBAM is unable to promote a large-scale carbon reduction in the China’s steel industry. Although CBAM will bring great pressure to steel exporters, a comprehensive policy of adopting more emission reduction measures can greatly improve the carbon reduction efficiency, effectively reduce the negative impact of CBAM, and maintain the stability of steel exports.

Operations research approaches for improving coordination, cooperation, and collaboration in humanitarian relief chains: A framework and literature review

Given the considerable number of actors in the humanitarian space, coordination is essential for successful disaster response. Furthermore, the sheer size of challenges and limited resources increasingly highlight the need for improved cooperation and collaboration in humanitarian supply chains. A significant number of studies in the literature explore the 3Cs (coordination, cooperation and collaboration), using conceptual, empirical and analytical methods. This paper aims to provide an overview and analysis of the Operations Research (OR) approaches that support decision making for improved 3Cs in humanitarian relief chains and to identify future research directions. To achieve this aim, we first present a holistic view of the discussions in the literature and derive a conceptual framework for 3C mechanisms in humanitarian operations. Based on our framework, we analyse studies that develop OR methods to address the design and management of 3C mechanisms in humanitarian relief chains. We also identify current gaps and future research directions.

Accurate Detection and Smoothness-Oriented Avoidance Method of Singularity in 5-Axis CNC Machining

As an inherent flaw in the kinematic chain mechanism of 5-axis machine tools, singularity can induce dramatic changes in machine axes motion and unfavorable fluctuations in feedrate. For effective singularity avoidance, it is desirable to first achieve accurate and efficient singularity detection and then eliminate the singularity without impairing tool orientation smoothness. This paper presents a novel approach for accurately detecting and smoothly avoiding the singularity in 5-axis CNC machining. In the detection method, two exclusion criteria are presented to efficiently exclude most non-singular segments of the tool orientation spline, and a curve intersection-based algorithm is thus developed to accurately identify the singular segments. In the singularity avoidance method, a concept of admissible tool orientation annulus (ATOA) is introduced, which serves to confine the range and magnitude of the tool orientation spline’s adjustments, and a local adjustment algorithm is then developed to enable the escape of the tool orientation from the singular region with controllable direction and deviation, while maintaining its continuity and smoothness. The effectiveness of singularity avoidance and the kinematic performance of the tool orientation modified by our method, are comparable to a state-of-the-art singularity avoidance algorithm. Finally, the conducted experiments validate the proposed method.

Analysis of Emission Reduction Mechanism of High-Tiered Carbon Tax under Green and Low Carbon Behavior

This article studies the emission reduction mechanism of high-tiered carbon taxes under green and low-carbon behavior in single and two-stage supply chains. First, based on the Cournot game model, it explores the impact of high-tiered carbon tax policies on supply chain carbon reduction decisions in the green exchange market. By analyzing the effects of implementing a high-tiered carbon tax policy, the basic characteristics of its implementation are identified, and the advantages of a high-tiered carbon tax compared to a unified carbon tax are summarized. Second, it establishes a carbon reduction technology investment cost-sharing model and a carbon tax cost-sharing model under the high-tiered carbon tax policy. It analyzes and studies the impact of high-tiered carbon tax policies on balancing the relationship between members of the two-level supply chain through optimal decision-making of the two-level supply chain under two cost-sharing strategies, revealing the emission reduction mechanism of the two-level supply chain under high-tiered carbon tax policies. The results indicate that there are extreme points in the emission reduction rates of producers in the green exchange market under both the high-tiered carbon tax policy and the unified carbon tax policy. It shows that the two cost-sharing strategies can effectively alleviate the cost burden for producers, increase their marginal profits, and promote further improvement in emission reduction. It explores the emission reduction mechanism of high-tiered carbon taxes and future research should delve into the emission reduction mechanism of high-tiered carbon taxes in different carbon emission departments and regions.

An Integrated Kinematic Mapping and Fourier Method to Design Spherical Coupled Serial Chain Mechanisms for Single-Joint Rehabilitation

Abstract Robotic devices are capable of reducing the physical burden on rehabilitation therapists and providing training programs of good repeatability, high efficiency, and high precision. When designing the kinematic structure for rehabilitation robots, there has been a growing interest toward one-degree-of-freedom (DOF) end-effector mechanisms due to their simpler structure and less complicated control algorithms. Compared with current one-DOF mechanism designs that are mainly customized for multi-joint robotic training, spherical coupled serial chain (SCSC) mechanisms are proposed in this paper to specifically deliver the single-joint robotic training, which is of equal importance to the effective physical recovery. Using kinematic mapping theory, the end-effector motion of SCSC mechanisms can be naturally transformed to two trigonometric curves composed of finite Fourier series in two separate planes of the image space. This novel formulation helps to establish an analytical and direct relationship between the design parameters of the SCSC mechanism and the harmonic parameters of the image-space representation of the task rehabilitation motion. The result is a simple and effective method for kinematic synthesis of SCSC mechanisms for generation of single-joint motion with an arbitrary number of spherical poses. An example of designing SCSC mechanisms for shoulder-joint rehabilitation is presented at the end of this paper to illustrate the feasibility of the proposed method.

Dynamic equilibrium mechanism of the closed-loop electric vehicle industry chain based on super-network model

At present, electric vehicle (EV) development has been widely accepted as a coping strategy by countries encountering environmental issues. However, there remain some uncertainties surrounding the future of China’s EV industry. The super-network provides an effective solution to the research on optimising subject decisions in a multilevel network model. On this basis, a closed-loop super-network model of the EV industrial chain system is proposed, which involves four different participants: EV manufacturer, sales company, consumer market, and recycling company. Furthermore, the variables are extracted based on practice, the behavioural strategies of each participant are analysed, and the dynamic equilibrium is determined with variational inequalities. Through numerical analyses, a further study is conducted on the main influencing factors and the extent of their impact on the dynamic equilibrium of the system. According to the results, the main research questions are answered, and some suggestions are made on the formulation of appropriate regulations.

Auction-based deep learning-driven smart agricultural supply chain mechanism

Agricultural product prices are subject to significant fluctuations due to variations in sales cycles, impacting people's quality of life and farmers' income while potentially giving rise to social problems. To address this issue in the smart agriculture supply chain, advancements in technologies like big data and artificial intelligence have made it feasible to predict agricultural product demand and price trends. Among the research methods, deep learning, being highly reliant on data and possessing multi-layered implicit information, has emerged as the most popular research method, exhibiting better data representation and prediction capabilities. In this study, we propose an end-to-end agricultural product price prediction model that combines complementary ensemble empirical mode decomposition (CEEMD) with long short-term memory (LSTM). The prediction generated by this model will provide guidance throughout various supply chain links, including production, harvesting, storage, and logistics. Moreover, the study aims to develop auction mechanisms based on the prediction results to achieve an optimal allocation of agricultural products. To address issues of low computational efficiency and limited benefit distribution in the auction process, this study introduces a deep learning-based iterative bilateral auction algorithm (DL-IDA), which improves upon existing methodologies by leveraging the power of deep learning. Empirical analysis is conducted using the daily price of Fuji apples at the Beijing Xinfadi market. The results demonstrate that the CEEMD-LSTM model proposed in this study exhibits superior performance in predicting agricultural product prices. Furthermore, experimental findings validate the effectiveness and superiority of DL-IDA. Compared to existing iterative bilateral auction algorithms, DL-IDA offers better performance in terms of running time, social welfare, buyer benefits, seller benefits, and broker benefits. Consequently, it can contribute to a transparent pricing mechanism for agricultural products.

Nanoscale analysis of magnetic chains consisting of cobalt mesospheres by full‐field transmission x‐ray tomography

AbstractFull‐field transmission x‐ray tomography can obtain 3D morphology and configurations of nanoscale materials. In this study, we further demonstrate the feasibility of this technique using magnetic chains consisting of cobalt mesospheres. The preliminary images presented in this article clearly reveal that three types of cobalt nanoparticles, namely, hollow, core–shell, and solid were found for magnetic chain synthesis. Furthermore, the tomographic analyses revealed the growth mechanism of magnetic chains self‐assembled by cobalt nanoparticles. We may claim that the spatial resolution and contrast characteristics of the full‐field transmission x‐ray tomography can satisfy the research requirements of nanomaterial science. Hence, transmission x‐ray tomography could be a powerful complementary method for imaging and analysis of nanoscale materials.

Thermal runaway chain reaction determination and mechanism model establishment of NCA-graphite battery based on the internal temperature

The measurement of battery internal temperature directly affects the determination of the sequence of thermal runaway chain reaction and the choice of model heat sources, and the optimal combination identification of kinetic parameters corresponding to each heat source is the premise of establishing model. This paper focuses on the Lix(Ni0.8Co0.15Al0.05)O2-graphite pouch battery with built-in thermocouple. Based on the stage division of thermal runaway behavior and the decoupling of irreversible exothermic reaction between battery components, the thermal runaway mechanism is determined. Then, the optimal combination of kinetic parameters is determined by combining the DSC tests under variant heating rates, the Kissinger's method and the genetic algorithm. Furthermore, a thermal runaway model considering hierarchical properties is established, and the thermal contribution of six exothermic reactions at each stage of thermal runaway is quantified. Anode+electrolyte and cathode+anode contribute 53.8% and 18.7% respectively to the heat accumulation before thermal runaway. Internal short circuit accounts for 27.5%, and the heat is released instantaneously, directly triggering thermal runaway. This work has important reference significance for the design of battery safety warning system and the battery modification strategy.

Verification of 3D DDA-SPH coupling method and its application in the analysis of geological disasters

At present, discontinuous deformation analysis (DDA) is in an active development stage and its application in the field of geohazards is expanding. Recently, the DDA method has been coupled with smooth particle hydrodynamics (SPH) to analyze some geohazards involving fluid-solid interactions (FSI) and has shown good prospects in the field. However, the interaction between rocks and water in geological disasters is extremely complex and the comprehensive verifications of the simulation results between the block and fluid under different interactive modes are never found. To solve this problem, we first introduced the basic principle of the DDA and SPH method, followed by the coupling algorithm of the two methods. Then, the correctness of the coupling method was verified through analyses of fluid and solid movement by adopting the dam break test, Scott Russell's wave generator experiment, water entry test of a single sphere, and landslide-generated impulsive wave, which represent different interaction modes between blocks and fluids respectively. Finally, based on the 3D DDA-SPH method, this paper simulated the chain disasters of the water inrush induced by tunnel collapse and the dam instability induced by slope sliding, and analyzed the chain mechanism between the different disasters, which illustrates the feasibility of 3D DDA-SPH coupling method in simulating the FSI problem in geotechnical engineering.