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1 – 10 of 562Hatice Merve Yanardag Erdener and Ecem Edis
Living walls (LWs), vegetated walls with an integrated growth layer behind, are being increasingly incorporated in buildings. Examining plant characteristics’ comparative impacts…
Abstract
Purpose
Living walls (LWs), vegetated walls with an integrated growth layer behind, are being increasingly incorporated in buildings. Examining plant characteristics’ comparative impacts on LWs’ energy efficiency-related thermal behavior was aimed, considering that studies on their relative effects are limited. LWs of varying leaf albedo, leaf transmittance and leaf area index (LAI) were studied for Antalya, Turkey for typical days of four seasons.
Design/methodology/approach
Dynamic simulations run by Envi-met were used to assess the plant characteristics’ influence on seasonal and orientation-based heat fluxes. After model calibration, a sensitivity analysis was conducted through 112 simulations. The minimum, mean and maximum values were investigated for each plant characteristic. Energy need (regardless of orientation), temperature and heat flux results were compared among different scenarios, including a building without LW, to evaluate energy efficiency and variables’ impacts.
Findings
LWs reduced annual energy consumption in Antalya, despite increasing energy needs in winter. South and west facades were particularly advantageous for energy efficiency. The impacts of leaf albedo and transmittance were more significant (44–46%) than LAI (10%) in determining LWs’ effectiveness. The changes in plant characteristics changed the energy needs up to ca 1%.
Research limitations/implications
This study can potentially contribute to generating guiding principles for architects considering LW use in their designs in hot-humid climates.
Originality/value
The plant characteristics’ relative impacts on energy efficiency, which cannot be easily determined by experimental studies, were examined using parametric simulation results regarding three plant characteristics.
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K.M. Fan, K.W. Wong, W.L. Cheung and I. Gibson
The purpose of this paper is to report on a study of the effect of glass microsphere (GMS) and potassium bromide (KBr) powder as an additive on the reflectance and transmittance…
Abstract
Purpose
The purpose of this paper is to report on a study of the effect of glass microsphere (GMS) and potassium bromide (KBr) powder as an additive on the reflectance and transmittance of TrueFormTM acrylic‐styrene co‐polymer (TF) powder to CO2 laser during selective laser sintering (SLS).
Design/methodology/approach
GMSs and KBr powder were chosen because glass is opaque to CO2 laser while KBr is transparent. The GMSs were treated with silane coupling agent and hydrofluoric acid to study the surface effect on the optical properties of TF/GMS blends. KBr powder was blend with TF powder in an attempt to modify the penetration depth of the laser in the powder bed. An integrating sphere was used to measure the reflectance of the powder bed. In the measurement of transmittance, a power meter was placed below the powder layer, which was supported by a KCl disc, to register the transmitted laser energy through the powder layer.
Findings
For the TF/GMS blends, smaller GMSs gave a higher reflectance while the surface treatments had little effect. The transmittance of both the polymer and the blends were very low. Although bulk KBr is highly transparent to CO2 laser, adding 30 vol% of KBr powder to TF hardly increased the transmittance of the powder bed.
Research limitations/implications
Experiments were carried out on a modified laser engraving machine rather than a commercial SLS machine. The laser energy density used was lower than that for normal SLS processes and no significant changes of physical condition of the powder bed were inflicted. The results only indicate the optical properties in the initial state.
Practical implications
The effects of transparent and non‐transparent fillers on the optical properties of the powder bed are presented.
Originality/value
This work furthers the understanding of heat absorption behavior of the powder bed during SLS.
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Mengqi Yuan and David L. Bourell
The purpose of this paper is to report selected optical properties of laser sintered polyamide 12 blank plates under different monochromatic and white light conditions and to…
Abstract
Purpose
The purpose of this paper is to report selected optical properties of laser sintered polyamide 12 blank plates under different monochromatic and white light conditions and to apply these properties in production of laser sintered lithophanes.
Design/methodology/approach
A UNICO 1201E spectrophotometer was used to measure the transmittance of laser sintered polyamide 12 plates as a function of plate thickness. Monochromatic light-emitting diodes were used to assess the wavelength dependence on the transmission and contrast as captured by a SONY DSC-W55 camera.
Findings
The transmittance decreased with increasing plate thickness which varied significantly depending on the monochromatic wavelength. Highest transmission was observed using green light (525 nm) and poorest transmission was measured for yellow light (589 nm).
Research limitations/implications
There is a limit to the amount of contrast obtained in polyamide lithophanes because the thickness of the plates is limited to less than about 5 mm. Greater thickness results in discernible topology on the lithophane which impairs the quality of the image.
Originality/value
Light transmittance of polyamide 12 plates under different lighting conditions is reported and applied to optically defined laser sintered lithophanes.
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The purpose of this paper is to improve the quality of additive manufactured optically translucent parts by investigating the manufacturing issues, analyzing lithophane production…
Abstract
Purpose
The purpose of this paper is to improve the quality of additive manufactured optically translucent parts by investigating the manufacturing issues, analyzing lithophane production criteria and identifying the best translucent material and additive manufacturing (AM) technology.
Design/methodology/approach
Figured lithophanes were laser sintered on a 3D Systems SinterStation® HiQ™ with varying layer thickness and plate thickness. Laser sintered (LS) polyamide (PA) 12 blanks were cyanoacrylate infiltrated and polished. Optical properties and performance were compared with the original LS blanks. Lithophanes and blanks were manufactured using 3D systems stereo lithography apparatus (SLA)® Viper ™si2 station, and optical properties and lithophane performance were compared with the LS specimens.
Findings
When building in the XY plane, it is optimal to sinter with the minimum layer thickness (0.076 mm) and maximum plate thickness (5 mm). Cyanoacrylate infiltration and polishing assists in reducing the LS PA 12 plate surface roughness, but polishing does not affect the lithophane performance. The best LS candidate should have an absorption coefficient of 0.5/mm using a white light source. Improved resolution but reduced contrast was observed on stereolithography (SL) specimens compared to LS parts.
Research limitations/implications
Transmittance experiments were performed on three SL parts which was not sufficient for optical property calculation. Limited literature was found for new material exploration.
Originality/value
It is the first effort to study systematically quality improvement issues of LS PA optically translucent parts. A comparison is made of optical performance between parts made using LS and SL.
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Tao Wei, Sijin Zhao, Zongzhan Gao, Ke Zhang, Wenxuan Gou and Yangfan Dang
Fatigue and creep are the key factors for the failure of polymethyl methacrylate (PMMA) in the engineering structure, so a great of quantity attention is focused on the life…
Abstract
Purpose
Fatigue and creep are the key factors for the failure of polymethyl methacrylate (PMMA) in the engineering structure, so a great of quantity attention is focused on the life prediction under the creep and fatigue conditions. This paper aims to mainly summarize the traditional life assessment method (S–N curve), life assessment method based on crazing density and life assessment method based on transmittance. S–N curve and classical creep curve are introduced on the traditional life assessment method; the variation of the craze density with the logarithm of cyclic numbers is given in different fatigue load. A linear relationship is obtained, and a higher stress leads to a higher slope, suggesting a faster growth of craze. Furthermore, a craze density model is purposed to describe this relationship; the variation of craze density with the time at different creep load is given. The craze density has two obvious stages. At the first stage, craze density ranged from approximately 0.02 to 0.17, and a linear relationship is obtained. In the following stage, a nonlinear relationship appears till specimen rupture, a new creep life model is proposed to depict two stages. The relationship between transmission and time under creep load is shown. With increasing of time, the transmittance shows a nonlinear decrease. Through polynomial nonlinear fitting, a relationship between the transmittance and residual life can be obtained. To provide reference for the life assessment of transparent materials, the paper compares three life assessment methods of PMMA.
Design/methodology/approach
This paper uses the traditional life assessment method (S–N curve), life assessment method based on crazing density, life assessment method based on transmittance.
Findings
The variation of the craze density with the logarithm of cyclic numbers is given in different fatigue loads. A linear relationship is obtained, and a higher stress leads to a higher slope, suggesting a faster growth of craze. Furthermore, a craze density model is proposed to describe this relationship, and the variation of craze density with the time at different creep loads is given. The craze density has two obvious stages. The relationship between transmission and time under creep load is shown. With increasing of time, the transmittance shows a nonlinear decrease. Through polynomial nonlinear fitting, a relationship between the transmittance and residual life can be obtained.
Originality/value
Fatigue and creep are the key factors for the failure of PMMA in the engineering structure, so a great of quantity attention is focused on the life prediction under the conditions of creep and fatigue. This paper mainly summarizes traditional life assessment method (S–N curve), life assessment method based on crazing density and life assessment method based on transmittance.
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J. Suwanprateeb and W. Suwanpreuk
The aim is to investigate the feasibility of increasing the transparency of the samples or models which were fabricated by three dimensional printing technology and study the…
Abstract
Purpose
The aim is to investigate the feasibility of increasing the transparency of the samples or models which were fabricated by three dimensional printing technology and study the properties of such developed system.
Design/methodology/approach
Polymethyl methacrylate powders were mixed with maltodextrin binders and used as raw materials for 3DP machine to fabricate samples. The samples were then divided into two groups either infiltrating with heat‐cured acrylate infiltrant or subjected to binder elimination prior to infiltration. As‐fabricated and two types of infiltrated samples were characterized to compare the influence of post‐processing on properties such as shrinkage, light transmittance and flexural properties including modulus, strength and strain at break.
Findings
It was observed that the combination of binder elimination and resin infiltration showed the greatest increase in flexural properties and transmittance percentage approaching the values of polymethyl methacrylate sheet and stereolithography samples. Infiltration without binder elimination increased the transmittance of samples slightly in comparison to as‐fabricated samples. This is related to the level of porosity in the samples and the difference in refractive index of different compositions within the samples namely PMMA, binder and infiltrant.
Research limitations/implications
Additional step of binder elimination prior to infiltration is needed and this may take time to complete.
Practical implications
The technique presented can be used to fabricate a translucent and strong 3DP models.
Originality/value
This study demonstrates the factors that are needed to consider increasing the transparency and even strength of 3DP models.
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This paper aims to understand the effect of different foundation designs of passive house on the resultant thermal bridges, at the junction between a wall and a slab on grade.
Abstract
Purpose
This paper aims to understand the effect of different foundation designs of passive house on the resultant thermal bridges, at the junction between a wall and a slab on grade.
Design/methodology/approach
The linear thermal transmittances of some newly developed foundations of passive house are determined. The investigated foundation designs are L-element, U-element and foundation with foam glass technique.
Findings
It is found that the special design of passive house foundation can considerably influence the heat flow through thermal bridges. In this context, it is proposed a new foundation design of passive house, which has relatively low heat loss through thermal bridges. The results are compared with the “default” ISO values used to evaluate the effect of thermal bridges in typical buildings. It is found that there is large difference between the calculated linear thermal transmittances at the investigated foundations of passive house as compared to typical buildings.
Practical implications
The results can hopefully be used to improve the energy efficiency of the passive house.
Social implications
Sustainable solution of buildings.
Originality/value
A new foundation design of passive house is suggested to reduce heat loss through thermal bridges.
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D. MIDGLEY and RICHARDSON
Signal flow graphs for networks of electronic systems are often reduced to transfer functions by Mason's theorem. An interactive software package is presented to make this process…
Abstract
Signal flow graphs for networks of electronic systems are often reduced to transfer functions by Mason's theorem. An interactive software package is presented to make this process fully automated. The nodes are numbered. Input to the program specifies the transmittance between node pairs, first noting the start‐node‐number followed by that of the destination‐node. Transmittances are represented either as real numbers or as a string of characters. With real transmittances the output of the program takes the form of a numerator and a denominator of the transfer function, each as a real number. With character‐string transmittances the numerator and denominator of the output are available both as strings and as arrays of products of prime numbers, where each prime number has uniquely represented an input character string.
Song Hee Koo, Kyungmin Park, Hyunmin Hwang, Youngjae Yoo, Jong Hun Han, Kwonwoo Shin and Jeong Ho Cho
The purpose of this paper is to develop environmentally stable near‐infrared (NIR)‐absorbing windows by blending an NIR‐absorbing dye and a thermally‐crosslinkable polymer.
Abstract
Purpose
The purpose of this paper is to develop environmentally stable near‐infrared (NIR)‐absorbing windows by blending an NIR‐absorbing dye and a thermally‐crosslinkable polymer.
Design/methodology/approach
To enhance the environmental stability of the NIR‐absorbing window, a poly(vinyl phenol‐co‐methyl methacrylate) (poly(VP‐co‐MMA)) prepolymer and a poly(melamine‐co‐formaldehyde) (PMF) cross‐linking agent were mixed, and thermal crosslinking was performed under mild conditions (100°C).
Findings
The resistance of the crosslinked hybrid films to heat, humidity, and ultraviolet radiation damage improved dramatically relative to the pristine NIR‐absorbing dye. The improved environmental stability of the crosslinked NIR hybrid film resulted from the reduced free volume and restrictions in the molecular thermal dynamic motions of the polymer due to the presence of the crosslinked network surrounding the NIR‐absorbing dye molecules.
Originality/value
The methods provided a novel, simple, and practical solution to improving environmentally stability of NIR‐absorbing window.
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The residential sector in Ireland accounted for 25 per cent of energy related CO2 emissions in 2016 through burning fossil fuels, a major contributor to climate change. In support…
Abstract
Purpose
The residential sector in Ireland accounted for 25 per cent of energy related CO2 emissions in 2016 through burning fossil fuels, a major contributor to climate change. In support of Ireland’s CO2 reduction targets, the existing housing stock could contribute greatly to the reduction of space-heating energy demand through retrofit. Approximately 50 per cent of Ireland’s 2m dwellings pre-date building regulations and are predominantly of cavity and solid wall construction, the performance of which has not been extensively investigated at present. Although commitment to thermal upgrade/retrofit of existing buildings may increase under future government policies, the poor characterisation of actual thermal performance of external walls may hinder the realisation of these targets. Thermal transmittance (U-values) of exterior walls represents a source of uncertainty when estimating the energy performance of dwellings. It has been noted in research that the standard calculation methodology for thermal transmittance should be improved. Implementing current U-value calculation methods may result in misguided retrofit strategies due to the considerable discrepancies between in situ measurements and calculated wall U-values as documented in the case studies carried out in this research. If the method of hygrothermal analysis were to be employed as a replacement for the current standard calculation, it could have significant implications for policy and retrofit decision making. The paper aims to discuss this issue.
Design/methodology/approach
This research project analysed a case study situated in Dublin, Ireland. The case studies offer an account of the in situ thermal transmittance of exterior walls and link these to hygrothermally simulated comparisons along with more traditional design U-values.
Findings
The findings of this research identify discrepancies between in situ and design U-values, using measurement, hygrothermal simulation and standard method U-value calculations. The outcomes of the research serve as an introduction to issues emanating from a larger research project in order to encourage researchers to understand and further explore the topic.
Originality/value
It has previously been highlighted that moisture content is linked to the increase in thermal conductivity of building materials, thus reducing the thermal effectiveness and increasing the elemental U-value. Therefore, it is vital to implement reliable prediction tools to assess potential thermal performance values. This paper presents the findings of a critical instance case study in Dublin, Ireland in which an existing west facing external wall in a semi-detached dwelling was analysed, simulated and measured to verify the elemental wall assembly and quantify thermal transmittance (U-value) incorporating the major criteria required for building performance simulation.
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