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In this paper, a reasonable explanation is given to unify notch effect and geometric size effect into notch geometric feature effect (NGFE), and energy gradient is utilized to depict the influence of the NGFE on the critical distance. The correlation of energy gradient with critical distance and fatigue life is discussed respectively. The weight index of the high energy region is used to quantify the contribution of the high energy region to the fatigue damage. Finally, a model of the reconstructed critical distance theory considering the geometric notch characteristic effect is established. The fatigue test of Q355 (D) alloy steel notched components was carried out, and the evaluation precision of the presented method is compared with Yang' model and Shen' model combining with the existing fatigue test data of En8. The results indicate that prediction results of the proposed method are consistent with the test results. Highlights: Based on the energy gradient to characterize notch geometric feature effect, the critical distance theory is reconstructed.The association degree of the energy gradient with fatigue life and critical distance is discussed.The high energy region weight index is defined to quantify the contribution of high energy region to fatigue damage. [ABSTRACT FROM AUTHOR]

The ultrasonic spot welding (USW) is widely used in the joining of multilayer Cu or Al tabs in the lithium-ion battery. Due to the high-frequency vibration of the sonotrode and various deformation in each interface, the friction behavior is complex which makes it difficult to simulate the welding process of multilayer specimens. In this paper, an efficient and accurate finite element model (FEM) was proposed via introducing the interface heat flux to equivalent the heat generation by the friction. The total heat flux was determined by the heat transfer analysis and the proportion of each interface was determined based on the analysis of the friction behavior. Then, the FEM was validated by comparing the simulated temperature and deformation with experimental results. Finally, the FEM was applied to simulate the USW process of four, five, and ten layers of copper and aluminum foils in order to characterize the gradient of the ultrasonic energy. It was found that the heat generation concentrated in middle interfaces was 65% of the total in the welding of four-layer copper foils. The heat generation was mainly related to the welding parameters and the proportion was related to the size of tips and the structure of specimens. The plastic strain varied in specimens because of the gradient of the input energy. It was most obvious in the welding of 10-layer aluminum foils that the maximum equivalent plastic strain (PEEQ) in the fifth interface was 92.9% smaller than the top interface. [ABSTRACT FROM AUTHOR]

In the present paper, the energy gradient method is implemented to study the instability of 2-D laminar backward-facing step (BFS) flow under different Reynolds numbers and expansion ratios. For this purpose, six different Reynolds numbers (50 ≤ Re ≤ 1000) and two various expansion ratios of 1.9423 and 3 are considered. We compared our results of the present study with existing experimental and numerical data and good agreement is achieved. To study of fluid flow instability, we evaluated the distributions of velocity, vorticity and energy gradient function K. The results of our study show that as the expansion ratio decreases the flow becomes more stable. We also found that the origin of instability in the entire flow field is located on the separated shear layer nearby the step edge. In addition, we approved that the inflection point on the profile of velocity corresponds to the maximum of vorticity resulted to the instability.

Energy and environmental stability are positively correlated with species richness along broad‐scale spatial gradients in terrestrial ecosystems, so their relative importance in generating and preserving diversity cannot be readily disentangled. This study seeks to exploit the negative correlation between energy and stability along the oceanic depth gradient to better understand their relative contribution in shaping broadscale biodiversity patterns. We develop a conceptual framework by simulating speciation and extinction along energy and stability gradients to generate expected patterns of biodiversity for a suite of complementary phylogenetic diversity metrics. Using a time‐calibrated molecular phylogeny for New Zealand marine ray‐finned fishes and a replicated community ecological sampling design, we then modelled these metrics along large‐scale depth and latitude gradients. Our results indicate that energy‐rich shallow waters may be an engine of diversity for percomorphs, but also suggest that recent speciation occurs in ancient fish lineages in the deep sea, hence questioning the role of energy as a key driver of speciation. Despite potentially facing high extinction early in their evolution, ancient phylogenetic lineages specialized for the deep‐sea were likely preserved by environmental stability during the Cenozoic. Furthermore, intermediate depths might be a 'museum' (or zone of overlap) for distinct lineages that occur predominantly in either shallow or deep‐sea waters. These intermediate depths (500–900 m) may form a 'phylogenetic diversity bank', perhaps providing a refuge during ancient (Mesozoic) extreme anoxic events affecting the deep sea and more recent (Pliocene–Pleistocene) climatic events occurring in shallow ecosystems. Finally, the phylogenetic structures observed in fish communities at intermediate depths suggest other processes might restrict the co‐occurrence of closely related species. Overall, by combining a conceptual framework with models of empirical phylogenetic diversity patterns, our study paves the way for understanding the determinants of biodiversity across the largest habitat on earth. [ABSTRACT FROM AUTHOR]

Flow friction is the key to studying water movement and has been one of the most important research topics in hydraulics and river dynamics. The roughness coefficient in the Manning formula represents friction applied to the flow by channel and changes with the river section characteristics, water level, and flow velocity. However, the Manning formula tends to simulate the friction with little variability, which contributes to large errors in the simulation of water level and flow velocity. To solve this problem, we proposed an improved friction formula based on the relationships between roughness coefficient and energy gradient and developed a differential model of one-dimensional flow with the proposed friction formula. The developed model was tested against both the experimental flood data and observed flow data in Qiantang River, China. The results indicated that the proposed friction formula provides a better simulation of target friction than the original Manning friction formula. The parameters in the proposed friction formula are less sensitive to the river section characteristics. Our results also showed that the developed differential model using the proposed friction formula can simulate the water level and flow velocity well in both the calibration and validation period and can improve the simulation of water level in tidal reach. [ABSTRACT FROM AUTHOR]

• Signals tested in manufacturing were used to reflect the energy characteristics. • The energy output of non-pulsed arc and pulsed arc is different. • Pulsed arc matched with pulsed droplet transfer is more suitable for WAAM. • A higher h / w is obtained by pulsed arc in pulsed droplet transfer mode. The non-pulsed arc and pulsed arc were used in wire-arc additive manufacturing (WAAM) of aluminum alloys. Arc signals about arc current and voltage synchronized with the acoustic emission (AE) detected in manufacturing were used as information source to identify the droplet transfer mode. The calculations of probability density distribution, power spectrum distribution and energy gradient to synchronous time-domain signals were used to investigate the characteristics of metal droplet transfer and energy transfer. As a result, it was found that the characteristics of arc power signals and AE signals in WAAM process have a close relationship with the droplet transfer and arc ignition, and could reflect the variations of energy characteristics. The energy output characteristics of non-pulsed arc and pulsed arc during droplet transfer process are different. The matching of pulsed arc and pulsed droplet transfer mode obtains the best thermal and mechanical transfer characteristics, which is more suitable for the WAAM manufacturing process. No matter whether pulsed arc or non-pulsed arc is adopted, the energy output of arc should not be excessive, otherwise the energy output and the impact effect of arc and droplet transfer may be not conducive to the forming efficiency and quality of WAAM manufacturing. [ABSTRACT FROM AUTHOR]

The paper aims to apply the complex-octonions to explore the variable gravitational mass and energy gradient of several particles in the external ultra-strong magnetic fields. J. C. Maxwell was the first to introduce the algebra of quaternions to study the physical properties of electromagnetic fields. Some scholars follow up this method in the field theories. Nowadays, they employ the complex-octonions to analyze simultaneously the physical quantities of electromagnetic and gravitational fields, including the field potential, field strength, field source, linear momentum, angular momentum, torque, and force. When the octonion force is equal to zero, it is able to deduce eight independent equilibrium equations, especially the force equilibrium equation, precessional equilibrium equation, mass continuity equation, and current continuity equation. In the force equilibrium equation, the gravitational mass is variable. The gravitational mass is the sum of the inertial mass and a few tiny terms. These tiny terms will be varied with not only the fluctuation of field strength and of potential energy, but also the spatial dimension of velocity. The study reveals that it is comparatively untoward to attempt to measure directly the variation of these tiny terms of gravitational mass in the ultra-strong magnetic field. However it is not such difficult to measure the energy gradient relevant to the variation of these tiny terms of gravitational mass. In the complex-octonion space, the gravitational mass is a sort of variable physical quantity, rather than an intrinsic property of any physical object. And this inference is accordant with the academic thought of "the mass is not an intrinsic property any more" in the unified electroweak theory. [ABSTRACT FROM AUTHOR]

In the present paper, the energy gradient method is implemented to study the instability of 2-D laminar backward-facing step (BFS) flow under different Reynolds numbers and expansion ratios. For this purpose, six different Reynolds numbers (50 ≤ Re ≤ 1000) and two various expansion ratios of 1.9423 and 3 are considered. We compared our results of the present study with existing experimental and numerical data and good agreement is achieved. To study of fluid flow instability, we evaluated the distributions of velocity, vorticity and energy gradient function K. The results of our study show that as the expansion ratio decreases the flow becomes more stable. We also found that the origin of instability in the entire flow field is located on the separated shear layer nearby the step edge. In addition, we approved that the inflection point on the profile of velocity corresponds to the maximum of vorticity resulted to the instability. [ABSTRACT FROM AUTHOR]

• A modified energy gradient is given for multiaxial notched specimens. • A calculation method of equivalent strain energy is proposed. • Several key factors affecting the fatigue life of notched specimens are considered. • A general procedure for fatigue life prediction of notched specimens is presented. The distribution of energy field on the crack initiation plane directly affects the crack initiation behavior. Therefore, studying the energy gradient is of crucial help for accurate evaluation of the fatigue performance for the notched specimen. Firstly, the energy distribution on the critical plane is characterized by the sixth-order polynomial. Meanwhile, the relative energy gradient is adopted to calculate the critical distance. Secondly, considering the influence of energy gradient, size effect and non-proportional additional strengthening, a general procedure is explored. Finally, the experimental data of Al7050, En8 and C40 is utilized for model validation and the comparison results show that prediction results of the proposed model in this paper is superior to other models. [ABSTRACT FROM AUTHOR]

ZnO@TiO 2 core–shell nanostructures have been manipulated with metal ion dopants to create DSSC photoanodes with reduced charge transfer recombination. ZnO and TiO 2 were modified by doping with Cd and Mg, respectively, resulting in a reduction in the band-gap for Cd:ZnO and an increase in the band-gap for Mg:TiO 2 . A series of core–shell nanostructures based on a ZnO or a Cd:ZnO core and TiO 2 or a Mg:TiO 2 shell have been investigated as DSSC photoanodes. In another series, the core–shell materials were reversed for complete evaluation of our hypothesis. The structures of the core–shell nanoparticles, optoelectronic and interfacial charge transfer of the DSSCs were analyzed by XRD, SEM, TEM, XPS, Mott-Schottky experiment, UV–vis DRS, J – V and EIS measurements. The power conversion efficiencies (PCEs) of DSSCs based on these core–shell structures were observed to depend on the flat band of the shell oxide relative to that of the core oxide. DSSCs with Cd:ZnO@Mg:TiO 2 and Cd:ZnO@TiO 2 photoanodes achieved V oc and FF values comparable to those of DSSCs with TiO 2 anodes. A moderate energy gradient and high potential barrier in these core–shell structures resulted in longer effective electron lifetimes and lower electron recombination in the corresponding DSSCs. The low PCE registered for DSSCs with anodes of Cd:ZnO@Mg:TiO 2 and Cd:ZnO@TiO 2 were attributed to the presence of a high proportion of rutile phase, caused by sintering at 650 °C and lower dye adsorption as a result larger particle sizes caused by Cd doping. [ABSTRACT FROM AUTHOR]

Wave action in sandy beach surf zones and its influence on species composition were evaluated at three sites at Pontal do Paraná, Paraná State, between June/2004 and May/2005. At each sampling site, five hauls were performed monthly using a 15 m long, 2.6 m height beach seine with a 5 mm mesh-size. Samplings were carried out at low water spring tides during daylight. A total of 26,866 fishes were collected, amounting to a total weight of 84,838 kg, which were distributed amongst 28 families and 63 taxa. Multi- and univariated methods used indicated that sheltered and moderately exposed beach samples had similar ichthyofaunal composition, being clupeids and engraulids the most abundant at these beaches. Although abiotic factors differed significantly between beaches, depth appears to exert the major influence on ichthyofauna structure by providing less turbulent waters which might have permitted shoals maintenance. Conversely, exposed beach samples differed largely from the other beaches and were influenced primarily by wave height and salinity variables. These were displayed at CCA diagram and through the occurrence of P. virginicus, M. littoralis and T. goodei.A ação das ondas em zonas de arrebentação de praias arenosas e sua influência na composição de espécies foram avaliadas em três praias em Pontal do Paraná, Paraná, entre junho/2004 e maio/2005. Cinco arrastos mensais foram realizados em cada local amostral durante maré de sizígia em período diurno, usando uma rede de arrasto de 15 m de comprimento, 2,6 m de altura e malha de 5 mm. Um total de 26.866 peixes foram coletados pesando aproximadamente 84 kg e distribuídos em 28 famílias e 63 taxa. Métodos multi- e univariados utilizados indicaram que as amostras das praias protegidas e moderadas foram semelhantes em composição da ictiofauna, sendo os clupeídeos e engraulídeos os mais abundantes nestas praias. Por mais que os fatores abióticos sejam diferentes entre as praias, a profundidade parece exercer maior influência na estruturação da ictiofauna provendo águas menos turbulentas, o que pode ter permitido a manutenção de cardumes. Em tendência oposta, as amostras da praia exposta diferem em grande parte das outras sendo influenciada principalmente pelas variáveis altura de onda e salinidade mostradas no diagrama CCA e pela ocorrência de P. virginicus, M. littoralis e T. goodei.

The structure-borne acoustic emission (AE) signals during gas metal arc welding (GMAW) on 2024 aluminum alloy were detected in real-time and analyzed to find the characteristics of metal droplet transfer (MDT) in welding process. The analysis of time domain and frequency domain was introduced. The energy gradient was used to describe the rate of energy variation during the metal droplet transfer. The results showed that the MDT event of AE signals reflects a mass of transient information about metal droplet transfer in GMAW process. The MDT frequency and the average grain size were increased along with the raise of welding heat input. The increasing welding heat input raised the MDT frequency and the energy input by the metal droplet transferred into the molten pool. According to the energy gradient, the process of short-circuiting transfer of metal droplet was comprised of three parts. The energy gradient and energy transfer coming from the metal droplet transfer were increased along with the welding heat input raised in GMAW process. Therefore, it is possible to study the metal droplet transfer of GMAW by the analysis to the AE signals detected in welding. [ABSTRACT FROM AUTHOR]

The stability of the centrifugal pump has not been well revealed because of the complexity of internal flow. To analyze the flow characteristics of a centrifugal pump operating at low capacity, methods of numerical simulation and experimental research were adopted in this paper. Characteristics of the inner flow were obtained. Standard k-ɛ turbulence models were used to calculate the inner flow of the pump under off-design conditions. The distribution of the energy gradient function K was obtained by three-dimensional numerical simulation at different flow rates. The relative velocity component was acquired from the absolute velocity obtained in particle image velocimetry. By comparing with experimental results, it was found that flow instability occurs at the position of maximum K. The flow stability reduces with an increasing flow rate. The research results provide a theoretical basis for the optimization design of a centrifugal pump. [ABSTRACT FROM AUTHOR]