Geometry Factors Research Articles

The Effect of Climate Conditions on the Relation between Energy Efficiency and Urban Form

Urban sustainability has been connected to form and compactness of the urban tissue. At the same time the relationship between urban form and energy efficiency is strongly affected by climate. This paper investigates the effect of climate conditions on the relation between urban morphology and energy efficiency of urban blocks, focusing on the Greek city context. A set of building block typologies is analyzed with regard to their form factors such as S/V ratio, coverage ratio and building ratio for the climatic conditions of two cities, each one belonging to a different climatic zone. Heating and cooling loads are calculated at an urban block scale for the climate of the city of Thessaloniki (zone C) and of the city of Heraklion (zone A) in order to draw conclusions about the relation between geometry factors and energy efficiency. The results of the research indicate that there is a strong relationship between urban morphology factors and energy efficiency and that the total load demand of urban blocks can be described as a function of form parameters. Results of the research, concerning the energy demand calculation, are valuable since they indicate the energy profile of each typology according to climate and can be used for defining different urban strategies towards sustainability in a context-based climate dependent analysis.

Topographic recording of the Slalom racing route in snow

Purpose: The purpose of the present research was the study and evaluation of the theodolite’s (topographic speedometer) use in tracing a path in slalom racing on snow conditions with 58 gates and also to record the optimal method of tracing a slalom route in relation to: a) the "velocity" of the race track (degree of difficulty of slalom), b) safety of tracing the slalom route. Methods: This research was based on methodology and measurements of a race track in giant slalom with 35 gates in the ski resort "3-5 Pigadia" of Naoussa - Greece. The topographic speedometer was fixed in place at the start of the route. From this point, measurements were taken, for the placement of all 58 gates throughout the route. The measurement was taken using the pole-prism, placed in each interior gate turn, at which the theodolite was aimed. With the help of topographic speedometer the following geometrical parameters have been registered: distance between the gates (Δs), altitude difference of points (Δh) with an accuracy up to 1cm, terrain slope (θ), gate angular deviation (δ) with an accuracy of up to 1 minute of the angle (°). This allows the creation of the top-view, side-view (profile) and three-dimensional aspect of the track, under race conditions on snow and not on dry ground. Results: The correlation coefficient (r) between the geometry factor (V.gs) and average the above geometry parameters had the following respective values: V.gs -Ms = 0,15, V.gs -Mθ = - 0,52, V.gs -Mδ = - 0,29 for 58 gates on a level of statistical significance of p < 0,05. Conclusions: The first part comprised of 10 gates was the "fastest" (V.gs = 18 degrees) of the total slalom route in Naoussa with 58 gates (V.gs = 14 degrees). With the above criteria, slaloms will be compared to each other and will be evaluated against age and safety.

Probabilistic Assessment of Crack Failure of Reactor Pressure Vessel (RPV) Cladding Material

To design a Reactor Pressure Vessel (RPV), material property like crack must be considered as it is an unavoidable property of materials. Presence of crack in materials must be kept within limit to prevent material’s failure. So, crack propagation must be analyzed and observed. In this paper, crack propagation due to stress and materials fracture toughness of reactor pressure vessel cladding has been observed to estimate cumulative probability of crack failure using Probabilistic Fracture Mechanics (PFM). Average crack size is guessed as 3 mm and geometry factor is considered as 1.12 to analyze edge crack. Final crack analysis range has been found to be 1.8 mm with crack propagation rate of ± 30% of its average size. Variation of critical crack size and crack initiation point for several design stresses and fracture toughness has been investigated with probabilistic fracture mechanics technique. The observed crack propagation by calculating final crack size and the cumulative crack failure probability of the reactor pressure vessel materials are presented in this work.Journal of Bangladesh Academy of Sciences, Vol. 41, No. 2, 237-245, 2017

Dependence of (Photo)electrochemical Properties on Geometry Factors of Hydrothermally Synthesized Delafossite Copper Gallium Oxide CuGaO2 toward Oxygen Evolution Reaction

The recent surge of alternative clean energy with minimal environmental impact in a cost-effective way has attracted great interest in the exploration of new materials and/or structures as efficient electrodes for industry-level (photo)electrochemical water splitting. Delafossites with a general formula of ABO2 as a type of earth-abundant materials are expected to serve as ideal alternatives for water electrolysis. In this work, by fine-tuning the synthesis procedure of delafossite CuGaO2 via surfactant assisted hydrothermal route, we investigated the dependence of their (photo)electrochemical properties on geometry factors. More specifically, the synthesized CuGaO2 samples were characterized by powder XRD, SEM, EDX, XPS, FT-IR, UV-Vis, and BET surface area measurements. Moreover, their electrocatalytic and photoelectrocatalytic performance were tested and compared toward oxygen evolution reaction (OER). Based on cyclic voltammetry and electrochemical impedance spectroscopy, their onset potential, current density, Tafel slope, charge transfer resistance, and stability were investigated. It was found that the synthesized delafossite CuGaO2 nanoflakes with the smallest dimensions exhibited the best (photo)electrocatalytic performance and could serve as a potential candidate for cost-effective and active electrode material.

Mathematical modelling for fatigue life prediction of a symmetrical 65Si7 leaf spring

Leaf spring is a suspension component which is designed to sustain a required fatigue life before its failure or permanent set. The fatigue life of a leaf spring depends upon the various factors like geometry, design, material, processing, fatigue strength reduction and some uncontrollable factors. To determine the effect of variation of individual factor on the fatigue life is always a challenging task as the experimental procedure is time consuming and costly. Also no such attempt has been made to predict this effect. The work presented in this paper depicts the effect of variation of an individual factor on the fatigue life of a leaf spring. A computer program has been written in FORTRAN, for determination of the fatigue life of a light commercial vehicle, has been validated experimentally. Two processing factors, five strength reduction factors, one design factor, one material factor and two geometry factors have been considered for investigation in this work. The effect of variation of one factor at time on the fatigue life of the leaf spring has been determined and modelled using statistical tool NCSS. The regression model has been depicted and validated analytically and experimentally.

Optimisation of the Bauer Equation Using the Least Squares Method for Thermoplastics Turning

A number of equations are available for predicting the output of machining processes. These equations are most commonly used for the prediction of surface roughness after tooling. Surface roughness can be influenced by many factors, including cutting parameters, tool geometry and environmental factors such as the coolant used. It is difficult to create a universally applicable equation for all machining because of the variations in different materials' behaviours (e.g. metal, wood, plastic, composite, ceramic). There are also many differences between the various types of machining process such as the machining tools, rotational or translational movements, cutting speeds, cutting methods, etc. The large number of parameters required would make such an equation unusable, and difficult to apply quickly. The goal is thus to create a simple formulation with three or four inputs to predict the final surface roughness of the machined part within adequate tolerances. The two main equations used for this purpose are the Bauer and Brammertz formulas, both of which need to be optimised for a given material. In this paper, the turning of thermoplastics was investigated, with the aim of tuning the Bauer formula for use with thermoplastics. Eleven different plastics were used to develop a material-dependent surface roughness equation. Only new tooling inserts were used to eliminate the effects of tool wear.

Effect of geometry factors on the priority of σ-hole⋯π and π-hole⋯π bond in phosphorescent cocrystals formed by pyrene or phenanthrene and trihaloperfluorobenzenes

The effect of geometric factors on the assembly of luminescent cocrystals between pyrene or phenanthrene and trihaloperfluorobenzenes.

Geometry factor obtained from wall heat transfer coefficient in high Reynolds number elbow flow

Geometry factor obtained from wall heat transfer coefficient in high Reynolds number elbow flow

Early-stage design strategies

Decisions made at early stages of the design are of the utmost importance for the energy-efficiency of buildings. Wrong decisions and design failures related to a building’s general layout, shape, façade transparency or orientation can increase the operational energy tremendously. These failures can be avoided in advance through simple changes in the design. Using extensive parametric energy simulations by DesignBuilder, this paper investigates the impact of geometric factors for the energy-efficiency of high-rise office buildings in three climates contexts: Amsterdam (Temperate), Sydney (Sub-tropical) and Singapore (Tropical). The investigation is carried out on 12 plan shapes, 7 plan depths, 4 building orientations and discrete values for window-to-wall ratio. Among selected options, each sub-section determines the most efficient solution for different design measures and climates. The optimal design solution is the one that minimizes, on an annual basis, the sum of the energy use for heating, cooling, electric lighting and fans. The results indicate that, the general building design is an important issue to consider for high-rise buildings: they can influence the energy use up to 32%. For most of the geometric factors, the greatest difference between the optimal and the worst solution occurs in the sub-tropical climate, while the tropical climate is the one that shows the smallest difference. In case of the plan depth, special attention should be paid in a temperate climate, as the total energy use can increase more than other climates. Regarding energy performance, the following building geometry factors have the highest to lowest influence: building orientation, plan shape, plan depth, and window-to-wall ratio.

MR Brain Image Edge Detection Guided with Distribution of Noise and Artifact

Magnetic resonance imaging (MRI) has revolutionized radiology in past four decades. MR image edge detection can identify anatomy boundaries and extract features for image analysis applications like segmentation and recognition of anatomy structures. Traditional MR image edge detection methods directly identify discontinuities in MR image domain without considering distribution of noise and aliasing artifact produced from MR scanner and reconstruction. It is difficult to suppress effects of noise and aliasing artifact during the edge detection process. In this project, a novel MR brain image edge detection method is proposed, which is based on parallel MRI reconstruction method. Distribution of noise and aliasing artifact is characterized by geometry factor map that also guides edge detection process for avoiding detection of noise and aliasing artifact. A collaborative learning strategy is applied on voting edges for producing the final edge detection. Experimental results show that the proposed method not only keep anatomy structure boundaries without missing edge components, but also avoid detection of noise and artifact with wrong edges.

街区尺度屋顶绿化热效应及其与城市形态结构之间的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 街区尺度屋顶绿化热效应及其与城市形态结构之间的关系 DOI: 10.5846/stxb201708111449 作者: 作者单位: 南京工业大学绿色建筑与生态城市实验室,南京工业大学绿色建筑与生态城市实验室,南京工业大学绿色建筑与生态城市实验室,南京工业大学绿色建筑与生态城市实验室,南京工业大学绿色建筑与生态城市实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学青年基金项目（41401179，51408303）；江苏省自然科学基金项目（BK20140941，BK20161547） Thermal effects of block-scale roof greening and their relationships with urban geometry Author: Affiliation: Laboratory of Green Building and Eco-city, NANJING Tech University,Laboratory of Green Building and Eco-city, NANJING Tech University,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究探讨大面积屋顶绿化如何改善城市冠层内部三维空间的热环境，改善效果与城市形态结构之间存在的关系。基于三维小气候模型ENVI-met 4.2，开展街区尺度屋顶绿化热效应研究。在南京市选择具有不同形态结构特征的8个典型样区，每个样区设置2种朝向（街道与主导风向平行或相交）、3种屋顶绿化情景（传统光屋顶、简易型绿化、复合型绿化），共对48种情景进行了微气候模拟与分析。结果表明，街区尺度屋顶绿化产生的"冷岛"可从屋面扩散到地面空间，缓解城市冠层热岛效应。白天14：00时，8个样区屋顶1.5 m高处的降温强度最高可达0.64℃，样区平均降温强度最大值为0.44℃；地面1.5 m高处的降温最大值为0.55℃，样区平均降温强度最大值为0.25℃。建筑高度、高宽比、容积率与屋面、地面降温强度之间均存在显著负相关关系；建筑密度与屋面降温强度显著正相关，但与地面降温强度之间无显著相关性。总的来说，紧凑低层建筑区和开敞低层建筑区实施屋顶绿化后产生的降温效应明显高于紧凑和开敞高层建筑区；建筑高度和密度相同时，街道走向与主导风向呈45°夹角比与主导风向平行具有更高的降温强度。研究结果能够促进对亚热带城市地区建筑-植被-大气相互关系的深入认识，并为屋顶绿化实践提供指导。 Abstract:Many studies reported that green roofs can notably alleviate roof-level surface and air temperatures, cutting building cooling loads and energy consumption. However, few studies have explored how large-scale roof greening affects the three-dimensional thermal environment of the urban canopy layer and how green-roof thermal performance correlates with urban geometry. This research investigated the block-scale green-roof thermal performance and its relationships with urban geometry factors by applying the three-dimensional microclimate model ENVI-met 4.2 in Nanjing City. Eight study plots with distinguished urban forms in conjunction with two orientations and three roof greening options generated a total of 48 scenarios for ENVI-met modeling and analysis. Results suggested that block-scale roof greening not only cooled the roof-level ambient atmosphere, but could ameliorate the ground-level microclimate. At 14:00 during the day, the air temperature reduction at 1.5 m height above the roof surface could reach 0.64℃ with an average reduction of 0.44℃. The maximum and average air temperature reductions at 1.5 m height above the ground were 0.55℃ and 0.25℃, respectively. Building height, height-to-width ratio, and floor area ratio had significant negative correlations with both the roof and ground level thermal effects. Building density was positively related with roof-level thermal effects, but had no significant correlation with ground-level thermal effects. Overall, compact low-rise and open low-rise building areas exhibited much higher cooling effects than compact and open high-rise building areas. Study sites with S-N orientation had better thermal performance than SW-NE orientated sites. These findings can deepen our understanding of building-vegetation-climate interactions in urban areas and provide a reference for roof greening practice in humid subtropical cities. 参考文献 相似文献 引证文献

Fracture anisotropy in texturized lithium disilicate glass-ceramics

Lithium disilicate glass-ceramics show great potential in the fabrication of anisotropic structures due to their high-strength needle-form crystalline phase subjective to processing-induced alignment. Here we explore this strategy by focusing on the mechanistic aspects of fracture. Through different variations of the fracture toughness test we demonstrate the effect of bulk crystal orientation on fracture energy, toughening mechanisms, crystal size and aspect ratio. Using the anisotropic Poisson's ratio of the Li2Si2O5 crystal phase obtained by Resonant Ultrasound Spectroscopy, we apply the new geometry factor developed by Strobl et al. to provide a more accurate insight into the anisotropic crack propagation behavior in LS2 glass-ceramics. Raman spectra and X-Ray Diffraction patterns are resolved for the Li2Si2O5 phase aligned at plane parallel, anti-plane and random orientations.We show that Li2Si2O5 crystallites oriented perpendicular to the crack growth plane tended to induce large scale crack deflection unless the crack was forced into a straight path, thereby promoting crystallite fracture, increased KIc-values and accentuated R-curve behavior. Crystal aspect ratio and residual stresses in the glass have been identified as important influencing factors on crack growth behavior and toughening mechanisms.

Controlling energy absorption capacity of combined bitubular tubes under axial loading

The purpose of this study was to investigate the effect of geometry on the energy absorption of aluminum tubes with different cross-section and the effect of combined bitubular tubes to absorb more energy under axial crushing. In the experimental part, aluminum tubes with circular and square cross-section were prepared and then the quasi-static tests with static loading rate were performed and the load-deflection diagrams in each test were obtained. A numerical model is proposed based on finite element analysis to simulate the collapse process considering the non-linear responses due to material behavior, contact and large deformation. The comparison of numerical and experimental results showed that the present model provides an appropriate procedure to determine the collapse mechanism, crushing load and the amount of energy absorption. The validated finite element model was then used for the parametric studies, in order to determine the effect of the geometry factors such as combined substitution of bitubular tubes, multi-cell reinforced and flat end-capped on the energy absorption. The primary outcome of the study is new research information which will facilitate the design of thin-walled tubes as energy absorbers in crushing applications.

Insights on the mechanism of water-alcohol separation in multilayer graphene oxide membranes: Entropic versus enthalpic factors

Experimental evidence has shown that graphene oxide (GO) can be impermeable to liquids, vapors and gases, while it allows a fast permeation of water molecules. Theoretical studies to understand the filtration mechanisms come mostly from water desalination, while very few works have been dedicated to alcohol dehydration. In this work, we have investigated the molecular level mechanism underlying the alcohol/water separation inside GO membranes. A series of Molecular Dynamics and Grand-Canonical Monte Carlo simulations were carried out to probe the ethanol/water and methanol/water separation through GO membranes composed of multiple layered graphene-based films with different interlayer distance values and number of oxygen-containing functional groups. Our results show that the size exclusion and membrane affinities are not sufficient to explain the selectivity. Besides that, the favorable water molecular arrangement inside GO 2D-channels forming a robust H-bond network and the fast water permeation are crucial for an effective separation mechanism. In other words, the separation phenomenon is not only governed by membrane affinities (enthalpic mechanisms) but mainly by the geometry and size factors (entropic mechanisms). Our findings are consistent with the available experimental data and contribute to clarify important aspects of the separation behavior of confined alcohol/water in GO membranes.

A new push‐pull sample design for microscale mode 1 fracture toughness measurements under uniaxial tension

AbstractA sample geometry is proposed for performing microscale tensile experiments based on a push‐pull design. It allows measuring mode 1 fracture toughness under uniform far‐field loading. Finite element simulations were performed to determine the geometry factor, which was nearly constant for Young's moduli spanning 2 orders of magnitude. It was further verified that mode 1 stress intensity factor KI is nearly constant over the width of the tension rods and an order of magnitude higher than KII and KIII. Notched samples with different a/w ratios were prepared in (100)‐oriented Si by a combination of reactive ion etching and focused ion beam milling. The mode 1 fracture toughness KI,q was constant with a/w and in average 1.02 ± 0.06 MPa√m in good agreement with existing literature. The geometry was characterized and experimentally validated and may be used for fracture toughness measurements of all material classes. It is especially interesting when a uniaxial, homogeneous stress field is desired, if crack tip plasticity is important, or when positioning of the indenter is difficult.

Stress intensity factor solutions for fretting fatigue using stress gradient factor

This paper presents stress intensity factor (SIF) solutions for fretting fatigue conditions by including a stress gradient factor (SGF) to correct the classic geometry factor for tension semi-infinite strip (TSIS) specimen. This gradient factor considers the stress gradient due to the pressure of the pad on the surface of the specimen, which creates a high concentration of stresses around the contact of the bodies. To obtain these solutions, 2D finite element model simulations were performed varying important fretting parameters, namely: coefficient of friction, bulk stress intensity, pad radius and material. All configurations respected a partial slip contact condition and the results obtained show agreement with the ones obtained analytically. Weight functions were used to obtain stress intensity factors under mode I, then to compute the SGF, which were fit into equations with a unique structure, varying only coefficients. To consider real problems, a 3D correction factor was introduced. The final SGF presented a general form to compute SIF under fretting conditions when applied in suggested methods, such as: Strain-based Fracture Mechanics, Theory of Critical Distances (TCD) and Stress Gradient.

Geometry-Modulated Magnetoplasmonic Optical Activity of Au Nanorod-Based Nanostructures.

Comprehension and modulation of optical activity at nanoscale have attracted tremendous interest in the past decades due to its potential application in many fields including chemical/biological sensing, artificial metamaterials, asymmetric catalysis, and so forth. As for the conventional molecular materials, magnetic field is among the most effective routes in inducing and manipulating their optical activity; whereas the magnetic optical activity at nanoscale calls for deeper understanding, especially for anisotropic noble metal nanoparticles. In this work, distinctly different magnetic circular dichroism (MCD) responses are demonstrated in gold nanorods (GNRs) with a derivative-shaped MCD signal corresponding to the transverse surface plasmon resonance (TSPR) band and a Gaussian-shaped signal at the position of the longitudinal surface plasmon resonance (LSPR) band. Furthermore, changing the aspect ratio of GNRs easily regulates such magnetoplasmonic CD response. More interestingly, GNR assemblies with different geometric configuration (end-to-end and side-by-side) show structure-sensitive magnetoplasmonic CD response. Armed with theoretical calculation, we clearly elucidate the intrinsic relationship of the resultant magnetoplasmonic CD response with the optical symmetry and geometry factor inside one-dimensional GNRs. This work not only greatly benefits our understanding toward the nature of SPR mode in anisotropic plasmonic nanostructures but also opens the way to achieve tunable magnetoplasmonic response, which will significantly advance the design and application of optical nanodevices.

Investigating the effects of PDC cutters geometry on ROP using the Taguchi technique

At times, the polycrystalline diamond compact (PDC) bit’s performance dropped and affects the rate of penetration (ROP). The objective of this project is to investigate the effect of PDC cutter geometry and optimize them. An intensive study in cutter geometry would further enhance the ROP performance. The relatively extended analysis was carried out and four significant geometry factors have been identified that directly improved the ROP. Cutter size, back rake angle, side rake angle and chamfer angle are the stated geometry factors. An appropriate optimization technique that effectively controls all influential geometry factors during cutters manufacturing is introduced and adopted in this project. By adopting L9 Taguchi OA, simulation experiment is conducted by using explicit dynamics finite element analysis. Through a structure Taguchi analysis, ANOVA confirms that the most significant geometry to improve ROP is cutter size (99.16% percentage contribution). The optimized cutter is expected to drill with high ROP that can reduce the rig time, which in its turn, may reduce the total drilling cost.

Design, Fabrication, and Characterization of Scandium Aluminum Nitride-Based Piezoelectric Micromachined Ultrasonic Transducers

This paper presents the design, fabrication, and characterization of piezoelectric micromachined ultrasound transducers (PMUTs) based on scandium aluminum nitride (ScxAl1–xN) thin films (x = 15%). ScAlN thin film was prepared with a dual magnetron system and patterned by a reactive ion etching system utilizing chlorine-based chemistry with an etching rate of 160 nm/min. The film was characterized by X-ray diffraction, which indicated a crystalline structure expansion compared with pure AlN and a well-aligned ScAlN film. ScAlN PMUTs were fabricated by a two-mask process based on cavity SOI wafers. ScAlN PMUTs with 50- and 40- $\mu \text{m}$ diameter had a large dynamic displacement sensitivity measured in air of 25 nm/V at 17 MHz and 10 nm/V at 25 MHz, twice that of AlN PMUTs with the same dimensions. The peak displacement as a function of electrode coverage was characterized, with maximum displacement achieved with an electrode radius equal to 70% of the PMUT radius. Electrical impedance measurements indicated that the ScAlN PMUTs had 36% greater electromechanical coupling coefficient ( $\text{k}_{\mathrm {t}}^{2})$ compared with AlN PMUTs. The output pressure of a $7\times7$ ScAlN PMUT array was 0.7 kPa/V at ~1.7 mm away from the array, which is approximately three times greater that of an $8\times8$ AlN PMUT array with the same element geometry and fill factor measured at the same distance. Acoustic spreading loss and PMUT insertion loss from mechanical transmit to receive were characterized with a 15 $\times $ 15 ScAlN PMUT array via hydrophone and laser Doppler vibrometer. [17509-2017]

Effect of lost charged particles on the breakdown characteristics of the gaseous electrical discharge in non-uniform axial electric field

The secondary emission coefficient is a valuable parameter for numerical modeling of the discharge process in gaseous insulation. A theoretical model has been developed to consider the effects of the radial electric field, non-uniformity of the axial electric field, and radial diffusion of charged particles on the secondary emission coefficient. In the model, a modified breakdown criterion is employed to determine the effective secondary electron emission, γeff. Using the geometry factor gi which is introduced based on the effect of radial diffusion of charged particles on the fraction of ions which arrive at the cathode, the geometry-independent term of γeff (Δi) was obtained as a function of the energy of the incident ions on the cathode. The results show that Δi is approximately a unique function of the ion energy for the ratios of d/R = 39, 50, 77, 115, and 200. It means that the considered mechanisms in the model are responsible for the deviation from Paschen's law.