Boundary Effects Research Articles

The impact of poverty alleviation policy on the industrial structure: Evidence from the Qinba Mountain contiguous poverty-stricken areas

In 2015, the Chinese government issued the Decision on Poverty Alleviation(DPA), requiring poverty-stricken areas to develop local characteristic industries based on their resource endowments, to promote industrial structure diversification and industrial structure upgrading through industry-driven poverty alleviation. However, existing research lacks empirical analysis to evaluate it. Therefore, this paper takes poor counties in the Qinba Mountain contiguous poverty-stricken areas(QMCPA) as an example, using the difference in difference model and boundary effect model to evaluate whether DPA has promoted industrial structure upgrading and industrial structure diversification in poor counties. The results show that the DPA has promoted industrial structure upgrading and improved industrial structure diversification in the QMCPA. However, the effectiveness of it is not sufficient. Poor counties have failed to maintain the policy requirement of developing characteristic industries based on local natural resource endowments, leading to a decline in the degree of industrial structure diversification in the later period of the policy. This study indicates that local governments should strive to develop advantageous industries and form a division of labor and cooperation with neighboring areas, strengthen inter-regional cooperation and contact, and enhance anti-risk capabilities to avoid homogenized competition. Studying the changes in industrial structure in the QMCPA has important significance for the long-term stable development and poverty elimination of various poor areas.

Investigation of the asymmetric flow structure in a hydrocyclone

AbstractThe flow field of a hydrocyclone was investigated using both computational fluid dynamics (CFD) and particle image velocimetry (PIV). A refractive index matching method was employed to improve the precision of the PIV measurements. The CFD results are in good agreement with PIV measurements. Detailed analysis reveals significant axial asymmetry in the velocity components, with the radial velocity component exhibiting notable disparities. This observation is supported by quantitative data comparing different sections of the hydrocyclone. It is further found that the asymmetry might be mainly attributed to the secondary vortexes with the single inlet of the hydrocyclone. And the secondary vortexes, superimposed on the primary flow rather than existing on its own, spiral downwards from near the inlet towards the underflow orifice. It is hypothesized that specific boundary effects and pressure gradients play a pivotal role in the formation of secondary flows. This assumption is grounded on both theoretical considerations and empirical observations, suggesting that these factors significantly influence the flow dynamics within the hydrocyclone. The insights gained from our measurement methodology and enhanced understanding of secondary flows within hydrocyclones are not only poised to serve as valuable references for fellow researchers but also have the potential to inform the design and operational optimization of hydrocyclones for improved efficiency and performance.

Development of dynamic centrifuge models for measurement and visualization of deformation mechanisms in liquefiable soils

Recent advancements in geotechnical physical modeling have enabled visualization and analysis of deformation mechanisms in soil sections through the integration of Particle Image Velocimetry (PIV) in dynamic centrifuge modeling. PIV requires a rigid wall container. In this paper, we summarize the design considerations that enable reliable measurement and visualization of soil deformation mechanisms at the University of Colorado (CU) Boulder’s 400 g-ton, 5.5 m radius centrifuge facility. The primary objective of this system is to investigate the response of complex and stratigraphically variable, saturated granular soil deposits beneath shallow-founded structures, though it can also be used for other configurations that benefit from advanced visualization in the centrifuge. The setup aims to enable quantification and visualization of different deformation mechanisms, including shear, volumetric, and soil ejecta formation, near and away from structures. The paper provides detailed design considerations for the system components, including a rigid container with a transparent Perspex wall and duct seal inclusions, a linear-elastic single-degree of freedom (SDOF) structure, soil texture, a potential ground improvement technique, and a high-speed camera system. Through fully-coupled, three-dimensional (3D) nonlinear finite element analyses, we investigate the influence of container type, domain size, and duct seal geometry on boundary effects, with consideration of nonlinearities within various soil profile configurations with and without the presence of a building model. The findings highlight the critical impact of proximity to lateral boundaries of the container on accelerations, excess pore pressures, foundation settlement, tilt, and shear strains, as well as the benefits of duct seal in reducing those boundary effects. The results also show that the extent of boundary effects on key performance measures depends on the properties of the container, soil layers, and ground motion. The simulations also show that surface ejecta potential within stratigraphic soil profiles is highly sensitive to the depth of the groundwater table and variations in soil permeability, which must be considered in designing experimental programs that investigate the development of soil ejecta.

High Carrier Mobility and Promising Thermoelectric Module Performance of N-Type PbSe Crystals.

The scarcity of Te hampers the widespread use of Bi2Te3-based thermoelectric modules. Here, the thermoelectric module potential of PbSe is investigated by improving its carrier mobility. Initially, large PbSe crystals are grown with the temperature gradient method to mitigate grain boundary effects on carrier transport. Subsequently, light doping with <1mole‰ halogens (Cl/Br/I) increases room-temperature carrier mobility to ~1600cm2V-1s-1, achieved by reducing carrier concentration compared to traditional heavy doping. Crystal growth design and light doping enhance carrier mobility without affecting effective mass, resulting in a high power factor ~40µWcm-1K-2 in PbSe-Cl/Br/I crystals at 300K. Additionally, Cl/Br/I doping reduces thermal conductivity and bipolar diffusion, leading to significantly lower thermal conductivity at high temperature. Enhanced carrier mobility and suppressed bipolar effect boost ZT values across the entire temperature range in n-type PbSe-Cl/Br/I crystals. Specifically, ZT values of PbSe-Br crystal reach ~0.6 at 300K, ~1.2 at 773K, and the average ZT (ZTave) reaches ~1.0 at 300-773K. Ultimately, ~5.8% power generation efficiency in a PbSe single leg with a maximum temperature cooling difference of 40K with 7-pair modules is achieved. These results indicate the potential for cost-effective and high-performance thermoelectric cooling modules based on PbSe.

Ensemble learning model for concrete delamination depth detection using impact echo

Delamination in concrete structures typically arises from the expansion of steel bar corrosion and the separation of the bonding layer. The presence of these delamination defects leads to a reduction in overall structural integrity, safety, and longevity. However, the delamination depth localization remains challenging. To address this issue, this paper introduces a predictive approach that combines time-frequency features extracted from vibration signals with ensemble learning models. The innovation presented in this paper can be summarized in two key aspects: (1) Signal time-frequency spectrograms are transformed into image features using the Histogram of Oriented Gradients (HOG) method, which serves as input attributes. The utilization of ensemble learning models facilitates both rapid and precise depth estimation of delamination signals, especially those with shallow defects. (2) By analyzing the time-frequency spectrogram of the vibration signals, a double exponential model is established between the depth-to-thickness ratio of delamination and the pixel matrix Eulerian distance. This may provide a new perspective for the depth estimation of delamination defects whose corresponding main frequencies are difficult to locate due to the influence of geometry and boundary effects. Laboratory experiments were conducted on concrete slab with simulated delamination defects at different depths to confirm the proposed method's effectiveness.

Engineering the flexibility and elastic modulus of graphene by heterojunctions

Graphene shows both superior flexibility and excellent mechanical strength. The fabricated graphene samples usually contain various defects like grain boundaries, which can either enhance or weaken the mechanical strength of graphene. So, exploring the effects of grain boundaries on the flexibility of graphene is useful in designing graphene-based flexible devices. Employing the first-principles calculation, flexibilities of graphene heterojunctions were studied, aiming to tailor the flexibility of graphene by heterojunctions. Here, by connecting armchair (AC) and zigzag (ZZ) graphene through grain boundaries, graphene heterojunctions with tunable AC to ZZ ratio were constructed. It was found that bending moduli, as well as Young’s moduli, of graphene heterojunctions are lower than the pristine graphene and can be further tailored by the AC to ZZ ratio, making graphene heterojunctions more flexible than graphene. Particularly, changing the AC to ZZ ratio can even alter the relative flexibility of graphene heterojunctions in different directions. Therefore, graphene heterojunction provides an approach to engineer the flexibility of graphene, which is helpful in understanding the mechanical properties of two-dimensional materials and designing the flexible devices.

Is cute AI more forgivable? The impact of informal language styles and relationship norms of conversational agents on service recovery

Conversational agents are increasingly handling a significant volume of service interactions and are projected to handle up to 95% of customer service interactions. However, like any service provider, conversational agents are not immune to service failures, which can result in negative customer experiences. Within the context of interactions between conversational agents and consumers, the informal linguistic strategies employed by conversational agents have been recognized as vital in recovering customer satisfaction after service failures. Nevertheless, research on how these linguistic strategies impact customer responses following service failures is still in its early stages. This study delves into the informal language styles used by conversational agents after service failures, examining the comparative effects of cute language styles (as informal language styles) and literal language styles (as formal language styles) on service recovery. Drawing upon the mind perception theory and the stimulus–organism–response (SOR) model, this research also unveils the underlying dynamics of whimsical and kindchenschema cuteness on customers’ forgiveness, along with literal language styles, in the context of service recovery. Furthermore, this study investigates the moderating influence of exchange and communal relationships, taking into account the boundary effects of relationship norms. To explore these hypotheses, three experiments were conducted. The findings of this research offer valuable theoretical insights and practical implications for designing linguistic strategies employed by conversational agents.

Effect of yttrium-doped grain boundary on sintering behavior and properties of transparent ZnAl2O4 ceramics

Pore-closed ZnAl2O4 ceramic can hardly be pressureless sintered from conventional (>100 nm) powder, which restricts the fabrication of the transparent ceramic by capsule-free hot isostatic pressing technique. This work focused on the effect of yttrium-doping on the microstructural evolution in the sintering of a ∼180-nm ZnAl2O4 powder. At a concentration of 300 or 600 ppm, the yttrium ions segregated along the grain boundaries and contributed to ordered nanostructures, which could suppress abnormal grain growth in both air sintering and hot isostatic pressing. The optimized Y-doped ZnAl2O4 transparent ceramic owned good visible light transmittance (>65 %) and a wide transmission range (6.0 μm at the 60 % transmittance) at a thickness of 1.5 mm, as well as high thermal conductivity (24.9 W·m−1·K−1) and reasonable mechanical properties (Vickers hardness of 12.9 GPa and Young’s modulus of 281.3 GPa), meeting the application requirements for infrared windows.

The impact of administrative boundaries on foreign direct investments in China's Yangtze River Delta region

We investigate the theoretical mechanisms that underpin the influence of administrative boundaries on foreign direct investment (FDI), taking into account the dual impact of administrative boundary effects. Using panel data from Yangtze River Delta counties collected between 2011 and 2019, we empirically investigate administrative boundaries' effect on FDI within these regions. The findings show that from 2011 to 2019, China's Yangtze River Delta had a consistently positive but moderate global Moran's I index, indicating limited spatial interconnectivity among county-level FDIs. Inter-county FDI in the Yangtze River Delta is hampered by provincial administrative boundaries, with cross-provincial FDI disparities greater than those within the same province. Notably, the Anhui-Zhejiang border experienced a temporary shift from a negative to a positive effect coefficient between 2011 and 2015, whereas other interprovincial boundaries consistently had negative coefficients. The FDI boundary barrier effect is attributed to natural barriers, administrative boundaries, and government performance assessments. In contrast, the boundary intermediary effect results from economic activity diffusion, inter-regional industrial relocation, and inter-regional geographical interaction. This study examines the impact of administrative boundaries on regional economic development through the lens of FDI, intending to provide useful insights for promoting balanced regional development in China and other developing countries. Furthermore, it guides international investors on their ventures in China, attempting to enrich their decision-making framework with strategic perspectives on the country's investment environment.

Photochemical Design for Diverse Controllable Patterns in Self-Wrinkling Films.

Harnessing the spontaneous surface instability of pliable substances to create intricate, well-ordered, and on-demand controlled surface patterns holds great potential for advancing applications in optical, electrical, and biological processes. However, the current limitations stem from challenges in modulating multidirectional stress fields and diverse boundary environments. Herein, this work proposes a universal strategy to achieve arbitrarily controllable wrinkle patterns via the spatiotemporal photochemical boundaries. Utilizing constraints and inductive effects of the photochemical boundaries, the multiple coupling relationship is accomplished among the light fields, stress fields, and morphology of wrinkles in photosensitive polyurethane (PSPU) film. Moreover, employing sequential light-irradiation with photomask enables the attainment of a diverse array of controllable patterns, ranging from highly ordered 2D patterns to periodic or intricate designs. The fundamental mechanics of underlying buckling and the formation of surface features are comprehensively elucidated through theoretical stimulation and finite element analysis. The results reveal the evolution laws of wrinkles under photochemical boundaries and represent a new effective toolkit for fabricating intricate and captivating patterns in single-layer films.

Thermodynamic survey of a reactive MHD couple stress fluid through saturated porous substances with convective boundary conditions

This study explores the thermodynamic behavior of a reactive hydromagnetic liquid flowing through permeable materials, with convective cooling applied to the walls. This study holds practical significance in optimization of thermal management systems and it is crucial for enhancing the efficiency of controlling thermal runaway. The flow is modeled as a system of partial differential equations which are numerically solved. The modified Adomian Decomposition Method and Pade approximation technique are utilized in solving the equations. The results acquired for velocity and temperature distributions are thereby employed to estimate entropy generation rate with critical values over numerous effects of various boundaries over improvement of thermal runaway utilizing Pade approximation technique to show the significant impact of convective cooling term (Biot number) and other thermophysical parameters on the fluid flow. The outcomes show that fluid velocity continuously increases with rising values of inverse couple stress and fluid temperature increases Biot number.

Homogenic Boundary Effect Boosted Oxygen Evolution Reaction in α/β‐NiMoO4 for Rechargeable Aqueous Zn‐Air Battery

AbstractRechargeable Zn‐air batteries (ZAB) represent a promising avenue for sustainable energy storage, boasting high energy density, cost‐effectiveness, scalability, and environmental friendliness. However, the sluggish redox kinetics and limited cycle life of bifunctional oxygen evolution/reduction (OER/ORR) electrocatalysts impede the further practical development of ZABs. In this study, homogenic boundary effect within α/β‐NiMoO4 is introduced as a superior electrocatalyst for ZAB. Through in situ poikilothermic X‐ray diffraction, X‐ray absorption spectroscopy, and theoretical investigations, the active Ni atoms exhibit more effective electron transfer at α/β‐NiMoO4 due to the homogenic boundary effect is unveiled. Furthermore, the presence of oxygen vacancies and lattice distortions at these boundaries significantly reduces the thermodynamic barrier of OER to a mere 0.46 V. Consequently, α/β‐NiMoO4 demonstrates a remarkably low overpotential of 270 mV at 10 mA cm−2 for the bottlenecked OER, along with prolonged durability (150 h) and a high specific capacity (745 mAh g−1 at 5 mA cm−2) for ZAB. This study underscores the efficacy of homogenic boundary effects in enhancing electrocatalytic activities, offering great promise for the advancement of sustainable energy systems.

Formation and evolution of laminar thermal structures: correlation to the thermal boundary layer and effects of heating time

We report an experimental study of the formation and evolution of laminar thermal structures generated by a small heat source, with a focus on their correlation to the thermal boundary layer and effects of heating time $t_{heat}$ . The experiments are performed over the flux Rayleigh number ( $Ra_f$ ) range $2.1\times 10^6 \leq Ra_f \leq 3.6\times 10^{7}$ and the Prandtl number ( $Pr$ ) range $28.6 \leq Pr \leq 904.7$ . The corresponding Rayleigh number ( $Ra= t_{heat}\,Ra_{f}/\tau _0\,Pr$ ) range is $900 \leq Ra \leq 4\times 10^{4}$ , where $\tau _0$ is a diffusion time scale. For thermal structures generated by continuous heating (i.e. starting plumes), their formation process exists three characteristic times that are well reflected by changes in the thermal boundary layer thickness. These characteristic times, denoted as $t_{emit}$ , $t_{recover}$ and $t_{static}$ , correspond to the moments when the plume emission begins and completes, and when the thermal boundary layer becomes quasi-static, respectively. Their $Ra_f$ – $Pr$ dependencies are found to be $t_{emit}/\tau _0\sim Ra_f^{-0.41}\,Pr^{0.41}$ , $t_{recover}/\tau _0\sim Ra_f^{-0.48}\,Pr^{0.48}$ and $t_{static}/\tau _0\sim Ra_f^{-0.49}\,Pr^{0.33}$ , respectively. Thermal structures generated by finite $t_{heat}$ exhibit similar evolution dynamics once $t_{heat} \ge t_{emit}$ , with the accelerating stage behaving like starting plumes and the decay stage like thermals (i.e. a finite amount of buoyant fluids). It is further found that their maximum rising velocity experiences a transition in the $Ra$ -dependence from $Ra$ to $(Ra\ln Ra)^{0.5}$ at $Ra \simeq 6000$ ; and their maximum acceleration reaches the value of starting plumes at $t_{heat}\simeq t_{recover}$ , and remains unchanged for larger $t_{heat}$ . In particular, the maximum rising velocity for the cases with $t_{heat} = t_{recover}$ follows a scaling relation $Ra_f^{0.37}\,Pr^{-0.37}$ , in contrast to the relation $Ra_f^{0.48}\,Pr^{-0.48}$ for starting plumes. This study provides a more comprehensive understanding of laminar thermal structures, which are relevant to a range of processes in nature and laboratory systems such as Rayleigh–Bénard convection.

Effects of asymmetric coupling and boundary on the dynamic behaviors of a random nearest neighbor coupled system

Effects of asymmetric coupling and boundary on the dynamic behaviors of a random nearest neighbor coupled system

A comparative study on ballistic performance of 3D woven fabrics under different boundary conditions

The potential of 3D woven fabrics as impact resistant material is increasingly recognized. Clarifying their ballistic response under varying boundary conditions is essential prior to deployment. This study aims to investigate the influence of various boundary conditions on the ballistic performance of 3D woven fabrics. Three aramid interlock woven fabrics, each with the same layer count, were designed and fabricated. A verified finite element model of ballistic impact at the yarn level was constructed for a comprehensive analysis. The influence of various boundary conditions on ballistic performance, including ballistic curve, stress distribution, back deformation, and energy absorption, is analyzed. It indicates that boundary conditions significantly affect the impact resistance and response mechanism of the fabrics. Among the different conditions, the fabric under Warp-sides held exhibits greater sensitivity. In the study, the fabric with vertical through-thickness warp yarn structure has smaller out-of-plane displacement, while the fabric with a multi-layer warp yarn structure exhibits better stability in energy absorption performance. The study investigates the response and performance of fabric configurations subject to various boundary conditions, and findings are valuable for the creation of 3D woven fabric designs that leverage boundary effects.

Modeling the failure process of rock masses using a 3D nodal-based continuous-discontinuous deformation analysis method

A three-dimensional nodal-based continuous-discontinuous deformation analysis method (3D-NCDDAM) is developed in this study for modeling the failure process of rock masses. In the 3D-NCDDAM, four-node tetrahedral elements which can be automatally generated are used to discretize the problem domain. To reduce computational cost, and effectively model the failure process of rock masses at concerned regions, the problem domain is devided into two types of regions, namely, the “non-destructive region” and “possible destructive region”. The non-destructive region is mainly used to reduce the boundary effects on the numerical results, and is regarded transitional zone in which the failure of rock masses is not considered. For the possible destructive region, artificial joint elements are inserted, and the failure of these joint elements is used to represent fracture initiation and propagation in rock masses. Additionally, the contact potential which is initially proposed in finite-discrete element method (FDEM) is incorporated into the 3D-NCDDAM to simuate the opening and slipping of discontinuous structural planes involved in rock masses’ failure process. Note that the difficultly in determing contact types in the traditional 3D discontinuous deformation analysis (3D-DDA) method is avoided in the 3D-NCDDAM. The proposed 3D-NCDDAM can be treated as a hybrid method, which inherite both the advantage of DDA method and FDEM. To validate the 3D-NCDDAM, seven numerical examples are conducted. The numerical results indicte that the 3D-NCDDAM can effectively model the failure process of rock masses in both experimental scale and engineering scale.

Aluminum nitride‐based ceramics with excellent thermal shock resistances

AbstractCeramics were susceptible to thermal shock failure. In this work, aluminum nitride‐based ceramics with excellent thermal shock resistance were developed. Thermal shock resistance was evaluated in the temperature range of 1200–1600°C by thermal cycling of 10, 20, 30, and 50 times. The phase composition, microstructure, and mechanical properties of the ceramics before and after the thermal shock were investigated. After 50 thermal cycles, the retention rates of the flexural strength and fracture toughness were 81.7% and 113.1%, respectively. The excellent thermal shock resistance was attributed to the combined effects of amorphous grain boundaries that passivate the propagation of microcracks and in‐situ precipitation of nanocrystalline particles during thermal cycles, both of which provide useful guidelines for developing ceramics with better thermal shock resistances.

Boundary Effect Under 2D Newtonian Gravity Potential in the Phase Space

Boundary Effect Under 2D Newtonian Gravity Potential in the Phase Space

Preliminary Implications of Viscoelastic Ray Theory for Anelastic Seismic Tomography Models

ABSTRACT The recent developments in general viscoelastic ray theory provide a rigorous mathematical framework for anelastic seismic tomography. They provide closed-form solutions of forward ray-tracing and simple inverse problems for anelastic horizontal and spherical layered media with material gradients. They provide ray-tracing computation algorithms valid for all angles of incidence that account for changes in wave speed, attenuation, and trajectory of anelastic P and S body waves induced by anelastic boundaries. They account for theoretical predictions that seismic waves refract as inhomogeneous waves across anelastic boundaries for all angles of incidence, which in turn accounts for energy carried by plane waves along seismic boundaries at head wave critical angles and wide-angle refracted (WAR) ray paths that are not predicted by elastic models. Exact viscoelastic ray-tracing numerical results for various models provide examples that illustrate the effects of anelastic boundaries on the travel times and amplitudes of seismic waves. They show the effects are strongly dependent on angle of incidence. For near-critical and wide angles of incidence the anelastic effects on travel times and amplitudes can be large and are not explained by elastic ray theory, but the effects on travel times can be relatively small and difficult to distinguish from those for elastic media for pre-near-critical angles of incidence. The results for some models indicate that reflected anelastic WAR waves may be observable at the surface and possibly account for some prominent seismic arrivals not explained by elasticity. These preliminary results suggest that the application of exact viscoelastic ray-tracing computation algorithms to exploration and teleseismic data sets can reveal new insights regarding the properties and distribution of anelastic materials in the Earth.

Application of Silicon Nanowires

Abstract:: Silicon Nanowires (SiNWs), a novel category of nanomaterials, exhibit several outstanding properties, including superior transistor performance, quantum tunneling effects, and remarkable electrical and optical capabilities. These properties are expected to contribute significantly to the development of future nanodevices, such as sensors and optoelectronic components. The potential for device miniaturization with SiNWs is based on their ease of monocrystallization. This leads to a reduced rate of hole-electron complexes and their extensive specific surface area that promotes boundary effects, thereby diminishing conductivity. Characterized by unique structural attributes, SiNWs hold promise for a wide range of applications in various sectors. To date, multiple methods have been established for SiNW fabrication, including solgel, electrochemical, laser ablation, chemical vapor deposition, and thermal vapor deposition techniques. Subsequently, the focus has shifted to the application of SiNWs in electronics, energy, and biomedicine. SiNWs are instrumental in producing high-performance electronic devices, such as field-effect transistors, sensors, and memory units. They also exhibit outstanding photovoltaic properties, making them suitable for high-efficiency solar cell and photocatalyst production. Additionally, SiNWs are poised to make significant contributions to biomedicine, particularly in biosensors, drug delivery systems, and tissue engineering materials. This article provides a concise review of the current status of SiNWs in electronics, sensing devices, and solar cell applications, and their roles in high-performance transistors, biosensors, and solar cells. It concludes with an exploration of the challenges and prospects for SiNWs. In summary, the unique attributes of SiNWs establish them as a versatile nanomaterial with broad applicability. This review offers a comprehensive overview of SiNW research and theoretical insights that may guide similar studies. The insights into recent SiNW research presented here are intended to inform future applications and investigations involving these nanomaterials.