Effective Width Research Articles

A tentative study on the effect of tunnel width on the maximum temperature under the ceiling in tunnel fires

Maximum gas temperature under the ceiling in tunnel fires has been studied experimentally and numerically. Full scale burning test in tunnel with length 100 is carried out. Three different pool fires with approximate maximum heat release rate of 0.6, 1.0 and 5MW were set up. The smoke temperature is collected by the Fiber-optic Bragg grating system. CFD simulations were carried out to study the effect of tunnel width on the maximum temperature. By analyzing the experimental and numerical simulation results, a critical point of ratio B/H and two stages concerning the varying of B/H are proposed to clarify the influence of tunnel width, meanwhile we conclude that it is interdependent between the ratio of H/B and the ventilation velocity when discussing the maximum gas temperature in tunnel fires.

Trophic position determines the persistence of neotropical understory birds after forest disturbance.

Habitat loss and degradation are key drivers of the current biodiversity crisis. Most research focuses on the question of which traits allow species to persist in degraded habitats. We asked whether a species' trophic position or niche width influences the resilience of species in degraded habitats and to what extent habitat degradation affects trophic interactions between species. We used nitrogen isotope ratios (15N:14N, expressed as δ15N value) to quantify and compare trophic positions and niche widths of understory birds inhabiting old-growth and young secondary forests in the Pacific lowlands of Costa Rica. We found that a species' trophic position rather than its trophic niche width determined its persistence in secondary forests. Species feeding at lower trophic levels in old-growth forests were less likely to persist in secondary forests than those occupying a higher trophic position in old-growth forests. This pattern is likely induced by the occurrence of relatively large-bodied habitat specialists with a flexible and high-trophic level diet in secondary forests. These habitat specialists likely caused generalist bird species to lower their trophic position relative to conspecifics in old-growth forests. Regarding trophic niche widths, species in secondary forests tend to have larger niche widths than old-growth forest species. However, as old-growth forest specialists and generalists did not differ in their niche widths, no systematic effect of trophic niche width on species persistence after forest disturbance was found. This is the first study that shows a systematic effect of trophic position on the persistence of a wide range of bird species in a disturbed forest ecosystem. It therefore provides important insights into species' responses to habitat degradation and the conservation value of secondary forests. To improve habitat quality for old-growth forest birds and facilitate avian seed dispersal, the creation of large contiguous forest patches should be prioritised when implementing reforestation measures.

Wind Flow Characteristics on a Vertical Farm with Potential Use of Energy Harvesting

The response to the climate emergency requires solutions that address multiple sustainability targets, which could be conducted by merging scientific research from areas that have traditionally evolved separately. This investigation presents advances in that direction by studying a building prototype designated for vertical farming, which enables the wind energy potential across built-up areas to be explored, in this case through the implementation of micro-wind turbines on the surface of the prototype. The study includes a parametric analysis consisting of varying locations of wind turbines across the building envelope, and the width of ventilation corridors. The effects of different widths of outdoor ventilation corridors, various locations, and additional wind angles on the capacity to harvest wind resources were investigated. The results showed that the 5 m wide outdoor corridor has the best ventilation effect, and the wind turbine placed on the roof has the best wind energy potential. The efficiency of wind turbines decreases significantly when multiple devices are placed at the same height on the façades, although overall, the potential for energy harvesting seems incremental.

In-plane gate induced transition asymmetry of spin-resolved Landau levels in InAs-based quantum wells

The crossover from quasi-two- to quasi-one-dimensional electron transport subject to transverse electric fields and perpendicular magnetic fields is studied in the diffusive to quasi-ballistic and zero-field to quantum Hall regime. In-plane gates and Hall-bars have been fabricated from an InGaAs/InAlAs/InAs quantum well hosting a 2DEG with a carrier density of about 6.8 × 1011 cm−2, a mobility of 1.8 × 105 cm2/Vs, and an effective mass of 0.042me after illumination. Magnetotransport measurements at temperatures down to 50 mK and fields up to 12 T yield a high effective Landé factor of g*=16, enabling the resolution of spin-split subbands at magnetic fields of 2.5 T. In the quantum Hall regime, electrostatic control of an effective constriction width enables steering of the reflection and transmission of edge channels, allowing a separation of fully spin-polarized edge channels at filling factors ν = 1 und ν = 2. A change in the orientation of a transverse in-plane electric field in the constriction shifts the transition between Zeeman-split quantum Hall plateaus by ΔB ≈ 0.1 T and is consistent with an effective magnetic field of Beff ≈ 0.13 T by spin-dependent backscattering, indicating a change in the spin-split density of states.

Numerical investigations of the restriction effects on a ship navigating in pack-ice channel

This paper adopts Computational Fluid Dynamics (CFD) method and Discrete Element Method (DEM) to simulate a ship navigating in pack-ice channel considering the effects of channel restriction. First, from the simulations of the ship sailing in open-water channel by CFD, it is found that the effects of channel width on water resistance is more pronounced than the impacts by level-ice thickness. Then, based on the stable and converged flow field obtained by CFD simulations, the CFD-DEM coupling method is applied to reveal the effects of channel width and level ice thickness on ship-ice-water interactions and ice resistances at different ship speeds. The results indicate that as the channel width decreases, the accumulation of pack ice in the areas of bow and midship intensifies. The ice resistances on the bow and midship increase notably, and the lateral ice forces exhibit pronounced asymmetric and random characteristics. In extremely narrow pack-ice channels, lower ship speed results in lager ice resistance and lateral ice force on the ship. In addition, as the level ice thickness decreases, the pack ice is more easily squeezed below the level ice, resulting in the decreases of ice resistance and lateral ice force.

Global Buckling Resistance of Cold-Formed Steel Beams with Omega-Shaped Sections

The absence of analytical expressions in current codes for evaluating the critical moment for lateral–torsional buckling of cold-formed beams with omega-shaped sections presents a fundamental challenge when assessing their resistance to global buckling. In response to this challenge, a comparative study was conducted to explore various approaches for calculating the critical moment. This involved both analytical and numerical analyses, using different methods available in codes and computational tools. The analytical analysis followed the Effective Width Method, employing the expression proposed in ENV 1993-1-1:1992, which is commonly used for evaluating the critical lateral–torsional moment of hot-rolled profiles. Numerical analyses were then performed using the ABAQUS v6.13, GBTUL v2.0, and CUFSM v5.05 software packages. The ABAQUS model, validated with results obtained from an experimental campaign, serves as the reference model. Upon assessing the bending moment resistances according to European, Brazilian, and American standards, consistency was found among these standards. However, it became evident that using the analytical expression proposed for hot-rolled profiles is inadequate for evaluating the critical lateral–torsional moment of CFS omega-shaped profiles. Conversely, the agreement between the ABAQUS, GBTUL, and CUFSM results suggests their utility as reliable tools for estimating the elastic critical lateral–torsional buckling moment.

The effect of Air Gap Width on the Focal Properties of Objective Snorkel Lens

The current research dealt with studying the effect of air gap width on the objective properties of the magnetic Snorkel lens used in the scanning electron microscope. The structure of the lens was designed and its properties were studied, and the axial magnetic flux density distribution was calculated (Bz) using the electron optical design program (EOD), The results indicated that the maximum value of the magnetic flux density (Bmax) increased with a decrease in the width of the air gap (S), accompanied by a decrease in the half-width, spherical and chromatic aberrations, and an increase in the resolution of the analysis.

Entropic velocity distribution for sediment-laden flows with a modified dip estimation model at data-scarce river sites

ABSTRACT This study proposes an entropic velocity-distribution and dip-position (y max) model for sediment-laden (SL) flows. Unlike previous studies, the proposed entropic distribution incorporates the effect of suspended sediment (SS) and y max, to improve velocity predictions near bed and water surface in SL flows. A new dampened mixing length for SL flows is proposed in terms of SS concentration. Moreover, the effect of channel bed roughness (k s), slope (S), SS, width (B) and flow depth (H) on y max is studied. Further, a comprehensive model for y max is proposed as a bivariate function of B/H and k s/H for natural channels. A comparative analysis is presented with the existing models, which shows the proposed equations provide higher accuracy with fewer parameters and a better representation of physical processes in SL flows. Subsequently, the proposed equations are applied at three gauged sites (Mahanadi River, India), showing their suitability to obtain velocity at data-scarce river sites.

Effect of partitions on flow mechanism and heat transfer in thermal convection

The effect of gap width and partition thickness on the flow mechanism and heat transfer of partitioned thermal convection is investigated using a thermal lattice Boltzmann method from Ra = 8 × 106 to Ra = 1 × 108. Partitioning effects on the heat transfer and the physical mechanism of flow are analyzed using the velocity field and temperature field of the convection. Numerical simulation results show that the optimal gap width decreases and that the optimal partition thickness increases with increasing Rayleigh number (Ra). Gap width and partition thickness have a joint effect on the heat transfer. We have counted the comprehensive influence of dimensionless gap width (D*) and dimensionless partition thickness (S*) on diaphragm heat on Nu under Ra = 108. The results show that the global maximum of Nu appears in the regions of 0.004<D*<0.006 and 0.02<S*<0.035. Two important factors affecting the partitioned thermal convection have been found. In addition, an interesting relationship between the average Nusselt number and the presence of leakage vortices is also discussed in this study.

Experimental and numerical investigations of high-strength cold-formed steel multi-limb built-up section columns

This paper investigates the buckling behaviour and load-carrying capacity of G550 high-strength cold-formed steel multi-limb built-up section columns under axial compression. Each built-up section consists of multiple lipped and unlipped channel sections connected by self-tapping screws. The C3U1 section is formed by three C-sections (i.e. lipped channel section) and one U-section (i.e. unlipped channel section), while the C2U2 section is formed by two C-sections and two U-sections. The experimental programme involved tensile coupon tests, measurements of initial geometrical imperfection, and column tests on ten C3U1 and ten C2U2 multi-limb built-up section columns. The numerical modelling programme was then performed, with the nonlinear finite element models created and validated against the experimental results. The applicability of the codified Effective Width Method and Direct Strength Method for predicting the strengths of G550 high-strength cold-formed steel multi-limb built-up section columns, as specified in the American Specification and Australian Standard, was then evaluated. The evaluation results showed that the codified Effective Width Method led to rather conservative and less accurate failure load predictions for G550 high-strength cold-formed steel multi-limb built-up section columns, while the codified Direct Strength Method provided accurate and consistent failure load predictions and thus applicable to the design of G550 high-strength cold-formed steel multi-limb built-up section columns. Concerning the lack of design guidelines specifically for multi-limb built-up sections, a modified Direct Strength Method was thus proposed as an alternative design method and shown to provide accurate failure load predictions.

Correlation of CPT measurements and relative density of LEAP-2017 and LEAP-2020 centrifuge models

Miniature cone penetration tests (CPTs) were conducted during the LEAP 2017 and LEAP 2020 centrifuge experiments to characterize and quantify the soil deposit properties. A total of 43 CPTs were obtained for deposits with varying relative densities. All experiments were performed using Ottawa F-65 Sand and used the same CPT tool model. A comprehensive study was undertaken to assess the quality and consistency of the CPT data. Outlier and regression analyses were used to develop an empirical relation to evaluate the relative density of Ottawa sand (centrifuge) deposits from measurements of the CPT tip resistance. This relation provides an estimate of the mean relative density profile, and associated standard deviation to quantify uncertainty. The relation accounts for the overburden pressure influence and the potential effects of container width (when the used container is narrow). The experimental results were found to have a good consistency with a regression R2 equal to 0.85.

Turbulent spot formation in three-dimensional yukawa liquids using large-scale molecular dynamics simulation—effect of system size

We have performed classical ‘first principles’ 3D Molecular Dynamics (MD) simulation of plane-Couette flow (PCF) in a 3D Yukawa liquid. The main aim of the present investigation is to study the effect of stream-wise (flow-direction) and span-wise (transverse direction to the flow) width on the subcritical transition to turbulence in plane Couette flow (PCF), separately. In the past, taking very large-aspect ratio systems, subcritical transition to turbulence in PCF has been studied in great detail. However, the effect of stream-wise and span-wise width on the turbulent dynamics separately, have not been studied in detail. In the present work, we have investigated the effect of stream-wise and span-wise width or length and found that the stream-wise length enhances the large-scale energy, which gives rise to strong large-scale flow, and span-wise width enhances the small-scale energy, which gives rise to strong small-scale structures. In other words, topology of the turbulent spot is observed to change with the change in system size. The spectral separation between the modes governing the large and small-scale dynamics improves with the increase in system sizes. The connection between the stream-wise vortices and the stream-wise velocity streaks is investigated in details. We have found that the number stream-wise velocity streaks is one unit larger than the number of stream-wise vortices. A qualitative comparison between the results obtained from the MD simulation and the hydrodynamics experiment is presented in this article. The behavior of the system was observed to vary with the range of interactions among the dust grains.

Oxide growth in high-strain tolerance thermal barrier coating with segmented vertical cracks

Segmented vertical cracks in high-strain-tolerance thermal barrier coating (TBC) systems provide fast diffusion pathways for oxygen, leading to the accelerated growth of thermally grown oxide (TGO) interfaces. This results in a competition between enhanced strain tolerance and accelerated oxidation. Here, the effects of crack width on oxygen diffusion and TGO growth in TBCs with segmented vertical cracks and underlying mechanism were investigated experimentally and numerically. The findings reveal a critical crack width of approximately 4 μm, underscoring the importance of selecting an appropriate segmented vertical crack width to design TBCs with superior strain tolerance and sufficient oxidation resistance.

A computational method for calculating the electrical and thermal conductivity of random composites

In the present work, for the first time, the electrical–thermal conductivity of a composite random material is correlated with the number of conductive paths, the mean path length, and the mean effective path width measured in a representative surface element (RSE) by Monte Carlo sampling. This work is organized in two parts. The theoretical calculation takes place in the first part for the correlation of conductive paths by adopting three approaches (incremental with respect to accuracy and complexity) based on: (i) one-component straight paths; (ii) one-component non-straight paths; (iii) multi-component non-straight paths. In the second part, a novel numerical methodology for the calculation of the conductance of the RSE through the conductive paths, mean path length and the mean effective path is developed for the general model of multi-component non-straight line paths based on Ohm’s law. In addition, a methodology that reduces the calculated conductivity from the microscale to the macroscale is proposed, that takes into account the probability of percolation for finite sizes and the average value of the conductivity from the samples in which percolation occurs. After the necessary consistency steps and verification of the method and its implementation on random binary material systems, it is further applied to solve synthetic continuous percolation problems at the microscale and macroscale. The results and the accuracy of the calculations are in close agreement with existing models. The electrical Direct Current (DC) and thermal conductivity follow the same scaling relation and the proposed methodology can be applied at the same stage without additional cost. In a random binary medium the simulations showed that a scaling law of conductivity is followed by an exponent value close to 1.3. In addition, the number of conductive paths, the average length of the paths, and the effective width follow scaling laws with exponents 1.44±0.01 , −0.25±0.01 and −0.39±0.01, respectively.

Hybrid Fiber Influence on the Crack Permeability of Cracked Concrete Exposed to Freeze-Thaw Cycles.

This paper describes hybrid fiber's influence on the crack permeability of cracked concrete exposed to freeze-thaw cycles. A permeability setup and a laser-scanning setup have been designed to measure the crack permeability and the fractured surface roughness of cracked hybrid fiber-reinforced concrete, containing polypropylene fiber and steel fiber, under a splitting tensile load. The results show that, when the effective crack width of the specimens is less than 25 μm, the rough crack surface significantly reduces the concrete's crack permeability. As the crack width increases, the effect of the concrete crack surface on crack permeability gradually decreases, and the crack permeability of the concrete is closer to the Poiseuille flow model. The permeability parameter α derived from the Poiseuille flow model is effective for assessing the crack permeability of concrete. Compared to the modified factor ξ of crack permeability, the permeability parameter α can effectively evaluate and quantify the development trend of crack permeability within a certain range of crack widths. The permeability parameter α of SF20PP2.3, subjected to the same freeze-thaw cycles, decreases by 16.3-94.8% compared to PP4.6 and SF40, and SF20PP2.3 demonstrates a positive synergistic effect on the crack impermeability of cracked concrete. The crack impermeability of SF40PP2.3, subjected to the same freeze-thaw cycles, lies between that of PP6.9 and SF60. The roughness of crack surface (X) and the crack permeability (Y) are highly correlated and follow an exponential curve (Y = 1.0415 × 107·e-6.025·X) in concrete. This demonstrates that hybrid fibers enhance crack impermeability by increasing the crack surface roughness. Furthermore, the combination of polypropylene fiber and steel fiber effectively promotes the formation of micro-cracks and facilitates the propagation of multiple cracks in the concrete matrix. This combination increases the head loss of water flow through the concrete and decreases the crack permeability.

Effects of Pulse Width and Electrical Energy of Low‐Voltage Nanosecond Pulsed Electric Fields on Mitochondria in Cancer Cells

Nanosecond pulsed electric fields (nsPEFs) have recently shown promise as a cancer therapy. Although nsPEF‐induced apoptotic responses have been observed, the stress on individual cell components has not been quantified. Therefore, the authors built a cell equivalent circuit, including mitochondria, to quantitatively calculate the voltage, electric field, and electrical energy applied to the cell components in the frequency domain. Additionally, pulse width and electrical energy changed in mitochondrial membrane potential over time. The results indicated that the change of pulsed voltage switched the cell stimulation pathway, resulting in different mitochondrial membrane potentials over time. The frequency response analysis confirmed that the potential on mitochondrial membranes increased under shorter pulse width conditions. This suggested that the frequency analysis provided in this paper is useful for relating the site of cellular stimulation to induce physiological effects. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Study on CFRP-Strengthened Welded Steel Plates with Inclined Welds Considering Welding Residual Stress.

Welded steel plates are widely used in various structural applications, and the presence of inclined welds is often encountered in practical scenarios. Carbon fiber reinforced polymer (CFRP) has been proven to be effective for strengthening steel structures. However, the behavior of CFRP-strengthened welded steel plates with inclined welds, particularly considering the influence of welding residual stress, is limited. This paper aims to investigate the tensile behavior of CFRP-strengthened welded Q355 steel plates with inclined welds considering welding residual stress (WRS). First, WRS data were obtained by the X-ray diffraction (XRD) method at different locations. The maximum tensile and compressive residual stresses are 0.39 and 0.14 times the yield strength of the steel, respectively. Then, finite element models were established to investigate the effects of weld angles, weld width, and height on the WRS distribution of welded steel plates. Finally, the tensile performance of CFRP-strengthened welded plates with WRS was studied by numerical simulation. The results showed that the weld angles have little effect on the distribution pattern of residual stress but significantly affect the peak tensile WRS. When the weld angle changes from 0° to 60°, the peak tensile WRS decreases significantly from 0.32 to 0.06 times the yield strength of steel; furthermore, the influence of weld width and height on WRS is relatively limited. Under tension loading, the maximum stress occurs near the weld. The ends of the weld enter the yielding state later than the middle part of the weld due to the distribution of the WRS. As the weld angle increases and the length of the weld increases, the stress in the weld zone decreases, while the stress in the base material zone correspondingly increases. In addition, CFRP strengthening can reduce the magnitude of stress. This study provides preliminary references for understanding the tensile behavior of CFRP-strengthened welded steel plates with inclined welds.

End‐to‐end demonstration for CubeSatellite quantum key distribution

AbstractQuantum key distribution (QKD) provides a method of ensuring security using the laws of physics, avoiding the risks inherent in cryptosystems protected by computational complexity. Here, the authors investigate the feasibility of satellite‐based quantum key exchange using low‐cost compact nano‐satellites. The first prototype of system level quantum key distribution aimed at the Cube satellite scenario is demonstrated. It consists of a transmitter payload, a ground receiver and simulated free space channel to verify the timing and synchronisation (T&amp;S) scheme designed for QKD and the required high loss tolerance of both QKD and T&amp;S channels. The transmitter is designed to be deployed on various up‐coming nano‐satellite missions in the UK and internationally. The effects of channel loss, background noise, gate width and mean photon number on the secure key rate (SKR) and quantum bit error rate (QBER) are discussed. The authors also analyse the source of QBER and establish the relationship between effective signal noise ratio (ESNR) and noise level, signal strength, gating window and other parameters as a reference for SKR optimisation. The experiment shows that it can tolerate the 40 dB loss expected in space to ground QKD and with small adjustment decoy states can be achieved. The discussion offers valuable insight not only for the design and optimisation of miniature low‐cost satellite‐based QKD systems but also any other short or long range free space QKD on the ground or in the air.

Optimized Design of Anchor Plates for 2200 MPa-Class Prestressing Anchorage Zones

The strength of prestressed steel strands has developed towards high strength, increasing from 1860 MPa to over 2200 MPa. The stress in the prestressed anchorage zone is more concentrated and complex, and the anchor plates for dispersed loads need to be optimized in design. This article proposes a design scheme for adding a middle pressure-bearing step based on the existing anchor plate and then establishes a 1/4 model of the concrete anchoring area of the anchor plate for finite element analysis. Based on the theory of the strut-and-tie model, the position of the middle pressure-bearing step is determined according to the maximum angle of the strut-and-tie model. Then, carry out force transfer tests in the anchorage zone for verification. The research results indicate that after adding a middle pressure bearing step to the anchor plate, the angle between the strut-and-tie model in the anchorage zone increases, and the bearing capacity improves. The position of the middle pressure-bearing step in the anchor plate is different, and the angle between the strut-and-tie models is different. According to the middle step position parameter, λ (the ratio of the effective width of the middle step to the distance from the middle step to the end face of the anchor plate) is 0.533 to optimize the anchor plate, and the bearing capacity of its anchorage zone is relatively high. The main tensile and main compressive stresses of the anchor plate after optimization increased by 6.2% and 5.74%, respectively, compared to the anchor plate before optimization. The main tensile stress of the spiral reinforcement under the anchor plate decreased by 0.59%, the main compressive stress decreased by 2.89%, and the von-Mises stress decreased by 2.32%. The side surface tensile stress of concrete under the anchor plate was reduced by 4.3 percent. Finally, three concrete specimens were poured for force transfer testing in the anchorage zone, verifying the safety and reliability of the optimized anchor plate in the 2200 MPa-level prestressed anchorage zone.

Wide Riparian Zones Inhibited Trace Element Loss in Mining Wastelands by Reducing Surface Runoff and Trace Elements in Sediment.

The diffusion of trace elements in mining wastelands has attracted widespread attention in recent years. Vegetation restoration is an effective measure for controlling the surface migration of trace elements. However, there is no field evidence of the effective riparian zone width in mining wastelands. Three widths (5 m, 7.5 m, and 10 m) of Rhododendron simsii/Lolium perenne L. riparian zones were constructed in lead-zinc mining wastelands to investigate the loss of soil, cadmium (Cd), copper (Cu), arsenic (As), lead (Pb), and zinc (Zn). Asbestos tiles were used to cut off connections between adjacent plots to avoid hydrological interference. Plastic pipes and containers were used to collect runoff water. Results showed that more than 90% of trace elements were lost in sediment during low coverage and heavy rainfall periods. Compared with the 5 m riparian zone, the total trace element loss was reduced by 69-85% during the whole observation period in the 10 m riparian zone and by 86-99% during heavy rain periods in the 10 m riparian zone, which was due to reduction in runoff and concentrations of sediment and trace elements in the 10 m riparian zone. Indirect negative effects of riparian zone width on trace element loss through runoff and sediment concentration were found. These results indicated that the wide riparian zone promoted water infiltration, filtered soil particles, and reduced soil erosion and trace element loss. Riparian zones can be used as environmental management measures after mining areas are closed to reduce the spread of environmental risks in mining wastelands, although the long-term effects remain to be determined.