Block Shape Research Articles

Impact of cold block shapes on heat transfer and mixed convection in a ventilated square cavity with Ag/water nanofluid

This study investigates mixed convection in a ventilated square cavity filled with an Ag/water nanofluid, containing central cold blocks of various shapes (square, circle, triangle, and ellipse). The goal is to understand the impact of nanoparticle concentration and the geometric shapes of the blocks on heat transfer. In the cavity, the inlet is located in the upper left corner, while the outlet is positioned in the lower right corner. Mixed convection is induced by cooling at the inlet of the ventilated cavity and uniform heating of its lower wall. The equations governing the flow of an incompressible Newtonian nanofluid are assumed to be two-dimensional, stable, and laminar. The finite volume method is used for numerical simulations. The effect of four different geometric shapes of the cold obstacle (circular, square, triangular, and elliptical) on fluid flow and heat transfer rate is also explored. The results show that increasing the nanoparticle concentration enhances heat transfer within the cavity. This improvement is particularly notable when the central cold obstacle takes on a circular shape, leading to better mixed convection and a higher heat transfer rate. The square and triangular shapes yield similar, albeit slightly lower, results, while the elliptical shape is the least effective for heat transfer.

Block Volume and Shape: Comparison of Calculation Methods and Investigation of Possible Relationships

Block Volume and Shape: Comparison of Calculation Methods and Investigation of Possible Relationships

Misses or False Alarms? How Error Type Affects Confidence In Automation Reliability Estimates

Prior research has shown that automation errors—false alarms and misses—differentially impact operator behavior, yet it is not clear why this difference exists. This study examined how the type of automation error, the automation’s reliability, and the number of experiences a person has with an automated system impacts their perception of the system. Participants responded to the correctness of an automation recommendation about the match between pairs of Mega Block shapes while automation reliability, number of trials, and error type varied. At the end of each block, participants provided their estimates of the automation’s reliability, ratings of their confidence in their reliability estimate, and their trust in the system. Our findings indicated that the type of automation error does not impact operator perceptions of the system. Instead, factors such as working memory limitations and pre-existing biases impact these perceptions.

Insight into the mechanism of solution organic fractions on soot oxidation activity enhancement

The particulate matter and soluble organic fraction emitted by diesel engine are hazardous to environment and human health. Exploring the effect mechanism of soluble organic fraction on soot oxidation is beneficial for reducing the emissions. In this study, the effects of four different types of soluble organic fractions on the soot oxidation activity and physicochemical properties are investigated. The results show that the attachment of oxygen-containing soluble organic fractions enhances the soot oxidation and reduces the peak characteristic temperature. However, the low volatility soluble organic fractions without oxygen element inhibit soot oxidation. Additionally, the high volatility soluble organic fractions without oxygen element elicit limited effects on soot oxidation. the contents of aliphatic C-H functional groups, carbonyl CO functional groups, and carboxylic acid O-CO functional groups significantly increase after adding oxygen-containing soluble organic fractions, while the limited increase in functional groups is observed in soluble organic fractions without oxygen element. Solid soluble organic fractions adhere to soot particles in the form of small particles, leading a reduction in the initial particle size distribution, while liquid soluble organic fractions exhibit block and chain shapes around the soot particles, which makes the initial particle size distribution increasing. Moreover, the attachment of all soluble organic fractions disrupts the surface order of soot particle, leading to a decrease in soot graphitization. This study is beneficial for revealing the interaction mechanism between soot and soluble organic fractions.

Natural ventilation potential of teaching building complexes with different block shapes and layout patterns

Natural ventilation significantly enhances building energy efficiency and indoor air quality, thereby reducing virus transmission risks, especially crucial in teaching buildings on university campuses frequently occupied by large numbers of students. This study investigates the design impacts of teaching building complexes on indoor and outdoor wind environments, aiming to propose practical design recommendations. Firstly, a typological analysis of teaching building complexes from ten universities in Guangzhou University Town (GUT) was conducted, screening out several archetypes representing diverse design features. Computational fluid dynamics (CFD) simulations were then performed on 16 hypothetical teaching building complexes derived from these archetypes. The wind velocity distributions and area-weighted wind velocities across various hypothetical scenarios were compared and analyzed, allowing for a thorough assessment of the natural ventilation performance associated with different block shapes and layout patterns. The findings reveal that canyons between buildings have a marginal impact on natural ventilation within scenarios characterized by aligned layouts. In contrast, staggered layouts notably enhance natural ventilation, particularly with orthogonal prevailing winds. Furthermore, semi-enclosed courtyard blocks outperform fully enclosed courtyard blocks in natural ventilation, especially when their openings align with prevailing wind directions. Finally, several practical recommendations were summarized for achieving sustainable teaching building design in similar climate regions. Key contributions include demonstrating the significant influence of block shape and layout on ventilation performance and offering novel insights into optimizing building designs for improved natural ventilation.

Finite-discrete element modelling of fracture development in bimrocks

Block-in-matrix rocks (bimrocks) are a complex geological feature composed of hard blocks in a weak matrix bonded together via a weak interface. The failure mechanism and deformation behavior of the bimrocks is quite complex due to the simultaneous existence of blocks with different shapes, strengths and proportions in a matrix. Therefore, it is of great importance to characterize the bimrocks under different situations. This study employs the combined finite-discrete element method (FDEM) to characterize the failure pattern and load carrying capacity of the bimrocks considering changes in various parameters, including block size, volumetric block proportion (VBP), the strength ratio of block-matrix interface to matrix, and the shape of the blocks (angular, circular, and elliptical shapes). First, the robustness and feasibility of the FDEM in modeling fracture development is verified against an analytical solution as well as a series of experimental tests accompanied with the digital image correlation (DIC) method. Then, the verified model is used to model disc specimens with various block shapes and properties. The results indicate the remarkable influence of VBP, block size and block-matrix interface characteristics on the bimrock mechanical behavior under the same VBP. The results are assessed based on macroscopic observations to investigate the influence of determinative physical properties of bimrocks. The results are also evaluated based on the mode of failure, mode I, II, or mixed mode, to qualitatively elucidate the influence of key factors on the formation of different cracks in different places, including the interface of matrix-blocks or intergrain or intragrain. The results show that since the loading is a quasi-static scheme, all the cracks are intergrain and no intragrain crack is observed for any VBP. The simulations outcomes shows that the block sizes determine the failure pattern, failure mode, and load–displacement behavior, where the larger blocks exhibiting the lowest load carrying capacity due to experiencing more interface breakage in shear. It is found that the VBP is a crucial parameter in the deformation of the bimrocks, showing that the strength of the bimrocks significantly increases with a decrease in the VBPs and the ones with greater VBPs experience more breakage and thus less resistance to loading. The block-interface strength is found to be the most critical factor in the deformation of the bimrocks (regardless of the value of the VBP). Finally, the effect of block shape is shown to have a considerable impact on bimrocks with the higher VBPs (more than 70%).

The Effects of Friction Block Shape on Friction-Induced Wear, Vibration, and Noise of Train Brake Interface at Low Temperature

The Effects of Friction Block Shape on Friction-Induced Wear, Vibration, and Noise of Train Brake Interface at Low Temperature

A centipede-inspired bonded-type ultrasonic actuator with high thrust force density driven by dual-torsional-vibration-induced flexural traveling waves

This paper presents an ultrasonic actuator with high thrust force density driven by dual-torsional-vibration-induced flexural traveling waves. Here, the PZT plates are bonded onto a duralumin vibrating body in a block shape to accomplish a compact configuration and they operate in the 2nd torsional vibrations, whose strong electromechanical coupling effect facilitates the enhancement of the driving force. Interestingly, the operating principle somewhat imitates the movement pattern of the centipede’s feet. To test the validity, first, by using a Mason-equivalent-circuit-based dynamic model, several key dimensions were tuned to increase the driving-force-to-weight ratio. Meanwhile, the driving feet’s configurations are adjusted based on a kinetic model to make the elliptical motion shape close to a circle. Then, an actuator prototype with the size of 48 × 47 × 6 mm3 and the weight of 29 g was fabricated and the moving/loading/positioning performance was evaluated. When the actuator adopts a continuous operation, its maximal sliding speed reached 630 mm/s at the frequency of 24.95 kHz. Moreover, it yielded the maximal thrust force and the maximal output power of 4.38 N and 527.8 mW, corresponding to the thrust force density and the power density of 151.2 N/kg and 18.2 W/kg, respectively. In a stepping operation, the minimal step displacement was 0.91 μm. These results demonstrate that the dual-torsional-vibrations-induced traveling wave allows the actuator to produce the high thrust force density and provides a new actuating principle to design powerful ultrasonic actuators.

Microstructure and properties of hot isostatic pressed/laser remelted Fe3Al/Cr3C2 composites

The effects of Cr3C2 content on the microstructure, hardness and wear resistance of Fe3Al/Cr3C2 composites by hot isostatic pressing and laser remelting were studied. The results showed that, the carbides in the hot isostatic pressed (HIPed) Fe3Al/Cr3C2 composites are in large block or irregular shape, while the in situ formed carbides in the laser remelted (LRed) Fe3Al/Cr3C2 composites are small and dispersed. With the increase of Cr3C2 content, the microhardness of HIPed and LRed Fe3Al/Cr3C2 composites gradually increased, and the microhardness of LRed Fe3Al/Cr3C2 composites is higher than that of HIPed ones. With the increase of Cr3C2 content, the wear resistance of HIPed Fe3Al/Cr3C2 composites increased gradually, while the wear resistance of LRed Fe3Al/Cr3C2 composites first increases and then decreases, and the best wear resistance is obtained when the volume fraction of Cr3C2 is 18%.

Failure behavior and bearing capacity prediction of steel wire-ring nets under rockfall impact using a coordination model-based analysis method

Flexible barriers have been widely used to protect against rockfall disasters. Steel wire-ring nets, which are key components of the barrier system and directly bear impacts, present several unresolved issues, including the prediction of tensile-flexural stiffness and energy absorption considering ring-scale mechanical behaviors, as well as failure behavior under rockfall impact. In this paper, a coordination model for the tensile-flexural stiffness and elastic–plastic energy distribution of steel wire-ring nets is established, and the model parameters, including failure criteria, are calibrated through tests. The failure mechanism and resistance capacity evolution of net rings considering the influence of contact radius is revealed. The full-scale impact tests of nets were conducted to verify the accuracy of the model to predict net failure. The study demonstrates that the coordination model incorporating nonlinear factors in ring-scale can accurately reproduce the stiffness development and energy absorption of the net-ring, laying a foundation for predicting the failure of nets. The predicted net failure energy has an error within 5% of the results from destructive impact tests. The shape and impact attitude of blocks significantly influence the net failure energy, indicating potential safety hazards in net design posed by the assumption of a 26-face polyhedron impact block in current standards.

Optimization of block-scaled integer GeMMs for efficient DNN deployment on scalable in-order vector processors

A continuing rise in DNN usage in distributed and embedded use cases has demanded more efficient hardware execution in the field. Low-precision GeMMs with optimized data formats have played a key role in more memory and computationally-efficient networks. Recently trending formats are block-scaled representations stemming from tight HW-SW co-optimization, that compress network size by sharing exponents per data block. Prior work mostly focuses on deploying such block-scaled GeMM operations on domain-specific accelerators for optimum efficiency at the cost of flexibility and ease of deployment. In this work, we exploit and optimize the deployment of block-scaled GeMMs on fully-programmable in-order vector processors using ARM SVE. We define a systematic methodology for performing design space exploration to optimally match the workload specifications with processor vector-lengths, different microkernels, block sizes and shapes. We introduce efficient intrinsics-based microkernels with effective loop unrollings, and data-transfer efficient fused requantization strategies to maximize kernel performance, while also ensuring several deployment configurations. We enable generalized block-scaled kernel deployments through tunable block sizes and shapes, which helps in accommodating different accuracy-speed trade-off requirements. Utilizing 2D activation blocks instead of conventional 1D blocks, the static and dynamic BS-INT8 configurations yielded on average 3.8x and 2.9x faster speedups over FP32 models respectively, at no accuracy loss for CNN classification tasks on CIFAR10/100 datasets.

Dynamic response of rock sheds to successive rockfall impacts using lightweight expanded clay aggregate (LECA) cushions: An experimental and numerical study

This study investigates the effectiveness of Lightweight Expanded Clay Aggregate (LECA) as a novel cushion material mitigating repeated rockfall impacts on reinforced concrete (RC) slabs in rock sheds. Small-scale impact tests and finite element simulations analyze LECA particle size, cushioning material, block shape, and impact energy level influence on the dynamic response and damage. Results show LECA outperforms sand in attenuating impact forces and transmitted loads under successive impacts, which indicates a better protection effect on the substructure. Smaller LECA particles lead to wider stress distribution angles, longer impact durations, and lower peak forces. Block shape significantly influences impact force, with higher unified nose factors increasing forces. LECA cushions exhibit a dynamic amplification factor less than 1, indicating reduced transmitted loads compared to sand. Under high-impact energy conditions, the LECA cushion limits RC slab deflection within the elastic limit across all block shapes, while sand exceeds the elastic limit, potentially leading to structural failure. LECA mitigates flexural cracking and redistributes loads more uniformly, reducing overall RC slab damage compared to sand. However, localized failure modes require further optimization. This study highlights LECA's potential for enhancing rock shed structural safety and resilience against severe rockfall events, providing insights for optimal mitigation strategies.

Evaporation-induced self-assembly of Janus pyramid molecules from fractal network to core-shell nanoclusters evidenced by small-angle X-ray scattering

Self-assembly of nanoclusters (NCs) is an effective synthetic method for preparing functionalized nanomaterials. However, the assembly process and mechanisms in solutions still remain ambiguous owing to the limited strategies to monitor intermediate assembled states. Herein, the self-assembly process of amphiphilic molecule 4POSS-DL-POM (consisting of four polyhedral oligomeric silsesquioxanes, a dendritic linker, and one polyoxometalate) by evaporation of acetone in a mixed acetone/n-decane solution is monitored by time-resolved synchrotron small-angle X-ray scattering (SAXS). Scattering data assessments, including Kratky analysis, pair distance distribution function, and model fitting, track the self-assembly process of 4POSS-DL-POM from a fractal network to compact NCs, then to core–shell NCs, and finally to superlattice structure. The calculated average aggregation number of a core–shell NC is 11 according to the parameters obtained from core-shell model fitting, in agreement with electron microscopy. The fundamental understanding of the self-assembly dynamics from heterocluster into NCs provides principles to control building block shape and guide target aggregation, which can further promote the design and construction of highly ordered cluster-assembled functional nanomaterials.

Assembly of π-Conjugated [B3O6] Units by Mer-Isomer [YO3F3] Octahedra to Design a UV Nonlinear Optical Material, Cs2YB3O6F2.

Achieving the extreme balance of the key performance requirements is the crucial to breakthrough the application bottleneck for nonlinear optical (NLO) materials. Herein, by assembly of the π-conjugated [B3O6] functional species with the aid of structure-directing property of mer-isomer [YO3F3] octahedra, a new ultraviolet (UV) NLO material, Cs2YB3O6F2 with aligned arrangement of coplanar [B3O6] groups has been synthesized. The polar material exhibits the rare coexistence of the largest second harmonic generation response of 5.6×KDP, the largest birefringence of 0.091 at 532 nm, the shortest Type I phase-matching down to 200.5 nm and deep-ultraviolet transparency among reported acentric rare-earth borates with [B3O6] groups. Remarkably, benefiting from the enhanced bonding force among functional units [B3O6], a firm three-dimensional framework is constructed, which facilitates the growth of large crystals. This can be proved by a block shape crystal with dimensional of 6×5×4 mm3, indicating that it was a promising UV NLO crystal. This work provides a powerful strategy to design UV NLO materials with good performances.

Assembly of π‐Conjugated [B3O6] Units by Mer‐Isomer [YO3F3] Octahedra to Design a UV Nonlinear Optical Material, Cs2YB3O6F2

AbstractAchieving the extreme balance of the key performance requirements is the crucial to breakthrough the application bottleneck for nonlinear optical (NLO) materials. Herein, by assembly of the π‐conjugated [B3O6] functional species with the aid of structure‐directing property of mer‐isomer [YO3F3] octahedra, a new ultraviolet (UV) NLO material, Cs2YB3O6F2 with aligned arrangement of coplanar [B3O6] groups has been synthesized. The polar material exhibits the rare coexistence of the largest second harmonic generation response of 5.6×KDP, the largest birefringence of 0.091 at 532 nm, the shortest Type I phase‐matching down to 200.5 nm and deep‐ultraviolet transparency among reported acentric rare‐earth borates with [B3O6] groups. Remarkably, benefiting from the enhanced bonding force among functional units [B3O6], a firm three‐dimensional framework is constructed, which facilitates the growth of large crystals. This can be proved by a block shape crystal with dimensional of 6×5×4 mm3, indicating that it was a promising UV NLO crystal. This work provides a powerful strategy to design UV NLO materials with good performances.

Can Preschoolers Learn Novel Causal Rules in Pretense?

ABSTRACT Pretend play is often hypothesized in a global sense to be an effective context for young children’s learning, but there is much still to learn about whether all types of information can be learned equally and whether all types of pretend play are equally beneficial. The present study tests whether preschoolers can learn a simple, novel causal rule from a pretend demonstration. American children watched either one (Experiment 1) or two (Experiment 2) experimenters pretend that a wooden box was a “blicket machine” and that certain blocks were “blickets.” In Experiment 1, performance was compared to a control group who saw an experimenter use the same materials in a realistic context. Results show that participants in the control condition outperformed children in the pretend condition in learning the novel causal rule. Data from both experiments combined revealed that, in pretense, participants learned the novel causal rule when the rule involved block color but not when it involved block shape. These results add to previous research on learning from pretense which indicates that learning novel information from pretense is selective and not always as effective as learning from real contexts.

Effects of sintering temperature on the microstructure and mechanical properties of Ni-based alloy

Ni-based alloys were prepared at different sintering temperatures in this study. The effects of sintering temperature on the volume fraction, morphology, and distribution of precipitates in Ni-based alloys, and its impact on mechanical properties were studied. The results show that the microstructure contains γ-Ni, Ni3Si, M7(B, C)3, M23(B, C)6, and a Si-rich multi element phase. The morphology of M7(B, C)3 particles undergoes an evolution of small particles → mainly strip shape → mainly small block shape and nearly spherical shape, accompanying with the dissolution-reprecipitation process of M7(B, C)3 particles caused by the diffusion of Cr element with the increasing of sintering temperature. Meanwhile, the M23(B, C)6 particle is keeping aggregating and growing. The relative density, microhardness, and bending strength of Ni-based alloys also increase. Especially these properties are found to be increase quickly between 1025 °C and 1050 °C. The increase in microhardness and bending strength is attributed to the reduction in the number of residual sintering pores and the increase in the volume fraction and size of precipitates. In addition, the transition of fracture morphology from intergranular fracture mode to a combination of intergranular and partially transgranular fracture mode also contributes to the rise in bending strength.

Facile synthesis of MIL-88A/PVA sponge for rapid tetracycline antibiotics degradation via sulfate radical-advanced oxidation processes

MIL-88A is a metal–organic framework (MOF) material known for its excellent performance in advanced oxidation processes (AOPs). However, due to its powdery nature, MIL-88A may undergo loss during catalytic degradation in flowing solutions, making continuous degradation removal challenging. Herein, we report the synthesis of MIL-88A/PVA sponge composite material by the in-situ integration of MIL-88A with PVA sponge. The composite sponge exhibits excellent removal efficiency of tetracycline antibiotics under the conditions of sulfate radical-advanced oxidation processes (SR-AOPs), achieving a degradation rate exceeding 99.0% within 2 min. Additionally, through fixed-bed column experiments, 1 kg of MIL-88A/PVA can treat 2160 L of wastewater within 24 h, indicating promising industrial applicability. It’s worth noting that this material can be customized into any desired block shape as needed. This work offers a highly promising solution for the application of MOF-based bulk-type catalysts in the treatment of antibiotic pollution using SR-AOPs.

The Influence of Rock Slope Scales of Joint Network and Slope Height on the Stability and Failure Mechanisms

This paper demonstrates the influence of slope geometry and scale of the joint networks on the stability and failure mechanisms in discontinued rock masses. These analyses are based on the finite element method (FEM) to calculate the factor of safety (FOS) and to simulate the explicit discontinuity deformations for different scales of rock masses. The study was carried out through examples of regular jointed models having different slope heights and irregular jointed dry rock slopes. Joints usually decrease the strength of the slopes and suggestively increase slope stability problems. The result shows that the slope stability decreases with increased block size and shape and that the irregular columnar joints are more unfavorable to the slope stability than the regular joints. Furthermore, with dropping the factor of safety and randomly distributed joints the rock failure mechanism appears to shift from structurally controlled for the 50 m slopes towards a step-like failure path for the 100 m and 200 m slopes.

Understanding the rock slope stability along Malshej Ghat, India, using rock mass characterisation and block shape classification techniques

Understanding the rock slope stability along Malshej Ghat, India, using rock mass characterisation and block shape classification techniques