Window Research Articles

АКСИОЛОГИЯ ГОРОДСКОГО ПРОСТРАНСТВА РОМАНА А. ИЛИЧЕВСКОГО «ЧЕРТЕЖ НЬЮТОНА»

Based on the material of the novel “Newton's Drawing”, the article proves that the art space is a kind of key to understanding the value foundations of life discovered by A. Ilichevsky. The author's statement is considered as the main thesis: space is a text, reading which allows you to get closer to understanding yourself and the world. Moreover, reading a spatial text in Ilichevsky is akin to reading a pictorial or musical text. Hence, in the novel there are many musical and artistic associations that reveal the author's meaning of the main urban spaces – Moscow and Jerusalem, considered in detail by the characters. This is evidenced by the selected individual places of Moscow and Jerusalem by Ilichevsky. The motive of glass is defined as particularly significant in the novel. It is set by images of various optical devices: a microscope, a telescope, a camera. And the images of temple-stained glass windows, museum glasses, the house of the hero's father and, finally, a landscape lens complete it. As a result, a complex bifocal spatial picture is created, revealing the boundary between the visible and the invisible, the past and the present, the universe and man.

Numerical Analysis of the Effects of Different Window-Opening Strategies on the Indoor Pollutant Dispersion in Street-Facing Buildings

The idling of automobiles at street intersections can lead to pollutant accumulation which impacts the health of residents in street-facing buildings. Previous research focused on pollutant dispersion within street canyons and did not consider the coupling of indoor and outdoor pollutants. This paper employs the computational fluid dynamics (CFD) method to simulate the dispersion characteristics of vehicle emission pollutants in street canyons, primarily investigating the indoor and outdoor pollutant dispersion patterns under various window opening configurations (single-sided ventilation, corner ventilation, and different positions of the glass under corner ventilation). Additionally, the study considers the impacts of the aspect ratio and ambient wind speed. Studies have shown that corner ventilation is effective in reducing indoor pollutant levels. When the two window glass positions are far away from the center of the intersection, the average CO mass fraction in the single-sided ventilation room is reduced by 87.1%. The average indoor CO mass fraction on the leeward side decreases with the increasing wind speed and aspect ratio. At a wind speed of 8 m/s, the average indoor CO mass fraction on the leeward side decreases to 2.45 × 10−8. At an aspect ratio of 2, the indoor CO mass fraction on the leeward side decreases with increasing floors before stabilizing at approximately 4.77 × 10−9. This study suggests optimal window opening strategies to reduce indoor pollutant levels in street-facing buildings at street intersections, offering guidance to indoor residents on window ventilation practices.

Redox Potential Based Self-Powered Electrochromic Devices for Smart Windows.

Energy-efficient glass windows are pivotal in modern infrastructure striving toward the "Zero energy" concept. Electrochromic (EC) energy storage devices emerge as a promising alternative to conventional glass, yet their widespread commercialization is impeded by high costs and dependence on external power sources. Addressing this, redox potential-based self-powered electrochromic (RP-SPEC) devices are introduced leveraging established EC materials like tungsten oxide (WO3) and vanadium-doped nickel oxide (V-NiO) along with aluminum (Al) as an anode. These devices produce open circuit voltages (OCV) exceeding ±0.3V, enabling autonomous operation for multiple cycles. The WO3 film exhibits 1% transmission and 88% modulation in the colored state at 550nm with a mere 260nm thickness. The redox interactions facilitate coloring and bleaching cycles without external power, while photo-charging rejuvenates the system. Notably, the inherent voltages of the RP-SPEC device offer dual functionality, powering electronic devices for up to 81h. Large-area (≈28 cm2) device feasibility is demonstrated, paving the way for industrial adoption. The RP-SPEC device promises to revolutionize smart window technology by offering both energy efficiency and autonomous operation, thus advancing sustainable infrastructure.

Designing solar control coatings

A solar control coating for window glass endeavors to transmit as much daylight as possible for the human eye and reflect as much solar heat as possible. A silver film that is thick enough to reflect the solar energy in the infrared can be divided into two or three sub-layers and combined with dielectric layers to anti-reflect (AR) the visible light. The combination of a metal and dielectric layer–pair acts as a two-layer AR coating at the wavelengths of the visible spectrum and maximizes the potential transmittance of the metal layer. The longer wavelengths in the infrared are reflected because they are outside of the AR band.

A fast method to prepare highly isotropic and optically adjustable transparent wood-based composites based on interface optimization

The production design of transparent materials using wood flour as the substrate aims to improve the value-added utilization rate of waste wood, and explore the preparation process of energy-saving building materials. This paper reports a rapid method for the preparation of transparent wood-based composites (TW-OTS) with high isotropy and optical adjustability, which changes the high energy consumption of bleaching wood flour in the past. Using the fluffy and porous structure of wood flour, the wood flour was bleached by hydrogen peroxide drop coating method assisted with ultraviolet light, and then hydrophobicized and impregnated with epoxy resin. The interfacial bonding and optimization mechanism of organic polymer Octadecyl trichlorosilane (OTS), wood fiber and resin at the micro scale were systematically studied in order to improve the optical parameters, mechanical strength and thermal properties of the composites, so as to balance the relationship between the structure and properties. TW-OTS based on interface optimization has excellent transmittance (80.1 %), thermal insulation performance, mechanical strength, and biocompatibility. If 1 % chitosan is added to the resin, the antibacterial properties of the sample can be added. This material can be used in energy-saving building windows, medical equipment, ecological home products, and other fields.

A sustainable utilization approach of waste biomass resources to smart materials for buildings

Resource utilization of solid waste promotes resource conservation, energy transformation and sustainable development. In this study, we developed a synthetic strategy for converting biomass waste, such as waste bamboo powder, into a smart material with thermochromic properties - hydroxypropyl cellulose (HPC). The synthesis process includes extraction of cellulose and modification with hydroxypropyl groups. The maximum extraction efficiency of cellulose from raw bamboo powder was up to 48 % by carefully adjusting the reaction conditions including NaOH concentration, reaction time, and treatment temperature. The maximum yield of modification process was achieved to 1.32 g/g by optimizing alkalization temperature, alkalization time, NaOH concentration, propylene oxide concentration, etherification temperature and etherification time. The samples were characterized by a variety of techniques such as FTIR, 1H NMR, XRD, SEM to validate the micro-structure of the extracted cellulose the HPC materials. Moreover, this study explored the potential application of HPC hydrogel in smart window application, and evaluated its building energy saving efficiency under different climate conditions through computational simulation. The corresponding results showed that the HPC hydrogel smart window could have significant energy saving potential compared to ordinary clear glass window. This novel approach of converting waste resources into high valued thermochromic materials for smart windows, not only reduces waste disposal demand for excessive land-use and energy consumption but also shows a positively contributes to sustainable development, environmental protection, as well as energy conservation.

A flexible reverse-mode liquid crystal/polymer composite film with low driving voltage and high stability for energy-efficient smart windows

ABSTRACT Smart windows are attractive considering their contribution to energy efficiency and privacy protection. However, the achievement of flexible reverse-mode film with good stability and well electro-optical performance for smart windows remains a fascinating challenge in recent years. Herein, we reported a low-driving-voltage, high-stability flexible reverse-mode liquid crystal/polymer composite film for energy-efficient smart windows by the formation of polymer structure with a polyhedral oligomeric silsesquioxane (POSS) core and strong epoxy resin as chains. The experimental results suggested that the polymer can not only stabilise the planar state of the cholesteric liquid crystal in the zero field but also provide enough support to the continuous liquid crystal phase on flexible substrate. Besides, the optimised optical device could be fully driven at 30 V (lower than safety voltage, 36 V) and keep contrast ratio of 100. Moreover, the flexible film showed outstanding optical regulation performance and excellent cycle stability under electric field. The strategy used in this research would open new doors for the development of energy-efficient smart windows in buildings.

Spår av förändrande materialitet i en sockenkyrka under senmedeltiden. En fallstudie av Åseda kyrka

Traces of changing materiality of a parish church during the late Middle Ages – A case study of the church of Åseda. Åseda is located in the vicinity of Växjö in Småland, and during a restoration of the church in 1936, various archaeological objects werefound. These finds have been dated but never discussed in-depth by anyone. This article aims to further the understanding of this church by analyzing stained window glass, coins and what has been interpreted as the remains of a triumphal wall.The nave and western part of the chancel date back to the end of the 15th century, but there is evidence that an older church is located in the same location. The three categories of materiality are not discussed to contest the dating of the 15th-centurychurch. Instead, this article focuses on the reflection of Medieval society and the perception of the church, which can be interpreted through studying these objects. The three chosen categories of archaeological finds help shed light on the churcholder than the one dated to the late 15th century. Changes to the church architecture and contacts with other areas are highlighted by studying objects not directly tied to the construction of a church. These changes must have radically changed how the parishioners perceived the church.

Flame retardancy, photostability, and thermal properties of vanillin-epoxidized soybean oil composites reinforced with walnut shell

Vanillin produced from lignin is an environmentally friendly compound having various active structures that can be crosslinked with hexanediamine and epoxidized soybean oil (ESO) to form water resistant composite. Inclusion of ammonium dihydrogen phosphate (ADP) could render the composite flame retardant, but its mechanical properties could be influenced. Therefore, walnut shell powder (WSP), as a common biomass waste, can be incorporated to improve its hardness and compressive strength. A matrix named VHEA was prepared by the condensation of vanillin, hexanediamine, ESO, and ADP. WSP was used as the skeleton for blending with VHEA to create VHEAW composite. Mechanical properties, dimensional stability, UV-resistance, thermal conductivity and flame retardancy of the composites were evaluated. The inclusion of WSP at a ratio of 1:1 to VHEA improved the compressive strength, Brinell hardness and flexural strength of the composite. Meanwhile, its water contact angle reaches 131.48 °, indicates its superior hydrophobicity. It also has high UV resistance and good flame retardancy as the LOI value is as high as 35.1 %, and its peak heat release rate is as low as 123.19 kW/m2. Its outstanding thermal insulation and flame retardancy, combined with excellent UV-resistance, render it suitable for various building components, including roofing, exterior siding, windows, and doors.

Comparison of empirical and mechanistic blood lead models for children

Childhood exposure to lead can result in increased blood lead levels, which can have detrimental health effects. Models that can predict blood lead level based on exposure to floor and window sill dust lead at varying concentrations are useful tools for informing policy decisions. We compare an empirical model relating blood lead in children to the lead content of household dust, with a mechanistic model that simulates lead exposure in children through their daily activities. The empirical model is constructed using 1999–2004 NHANES data, while the mechanistic model is validated using 2011–2016 NHANES data. The models are evaluated at dust loadings ranging from 0.18 – 43 µg/ft2 and the resulting blood leads are compared. Specific demographic variables are chosen to simulate individuals are generated with “typical,” “high end,” and “low end” exposures in the empirical model; these are directly compared with the median, 95th, and 5th percentile results from the mechanistic model. For a child with “typical” lead exposure, the 95 % confidence interval for computed blood lead values contained the median blood lead value from the mechanistic model at all dust lead exposure levels considered. Similar results hold when comparing the 95th percentile to “high end” and 5th percentile to “low end”. The blood lead level computed by the mechanistic model increases more quickly with respect to dust loading than the empirical model, particularly at higher loadings. The empirical and mechanistic models generate similar blood lead distributions across the range of dust loadings considered, particularly at low loadings. The mechanistic model may be more appropriate for higher loadings due to limitations inherit in the structure of the empirical model.

Static and dynamic glazing integration for enhanced building efficiency and indoor comfort with thermochromic and electrochromic windows

Effective building energy efficiency requires understanding fenestration’s role in regulating indoor temperatures. Therefore, this study investigates the impact of integrating static glazing with dynamic coatings on building energy efficiency and indoor comfort in a lightweight structure situated in a semi-arid climate. Employing a comprehensive numerical model developed using EnergyPlus and Radiance tools, various static commercial glass window configurations are evaluated to assess their effects on energy consumption, thermal and visual comfort, and economic and environmental considerations. This analysis includes assessments of thermal comfort using PMV and PPD indicators and evaluations of visual comfort based on daylighting and glare metrics. The findings highlight the advantages of incorporating thermochromic and electrochromic films, demonstrating significant improvements in building energy efficiency and interior thermal and visual comfort. Notably, double glazing emerges as the most economically efficient and environmentally viable option, resulting in a reduction of emissions by 1522.38 kgCO2/year, with a payback period of 12.86 years. Furthermore, combining thermochromic and electrochromic coatings with optimal static glazing leads to a remarkable 26 % reduction in energy consumption. These results underscore the potential of dynamic coatings to enhance building energy performance while ensuring occupant comfort. This research approach provides valuable insights into sustainable building design, emphasizing the integrated impact of glazing solutions on energy use, comfort, and environmental sustainability.

The Intersection of Architectural Conservation and Energy Efficiency: A Case Study of Romanian Heritage Buildings

In Europe, it is estimated that 14% of existing buildings were built before 1919, whereas 26% were built before 1945. In Romania, about 31% of the buildings date from before 1961, contributing to the current stock of old buildings with historic and architectural value in the country. This paper illustrates the current state of buildings with historic and architectural value in Romania, alongside a case study of a representative administrative building in Câmpulung, Romania. The analysis of the Town Hall building in Câmpulung, Romania, demonstrates that potential energy savings of up to 47.53% can be achieved by implementing interventions such as upgrading windows, insulating the attic, and installing photovoltaic panels. The highest energy reduction is obtained by replacing the window glass with a value of 18.16% with attic insulation with a value of 16.1%. This paper also presents indoor measurements of temperature and humidity in different offices positioned in the north and the south. The study conducted on the south façade office revealed consistent temperatures ranging from 21.7 °C to 24.4 °C, with an average of 23.31 °C. However, the humidity levels fluctuated considerably, ranging from 17.1% to 39.1%, with an average of 26.89%. The sun-exposed section of the building saw relatively stable temperature conditions, but the varying humidity levels could have a detrimental impact on the quality of the indoor atmosphere and potentially decrease the effectiveness of the workforce. By contrast, the north façade office exhibited lower and more fluctuating temperatures, ranging from 19.8 °C to 23.6 °C, with an average of 21.74 °C. Additionally, it had higher and more stable humidity levels, ranging between 19.5% and 41.7%, with an average of 29.83%. A thermographic analysis was performed on the north façade of the Câmpulung Town Hall, utilizing thermal imaging technology to detect areas of heat loss, and thus identifying the energy inefficiency problems of the building’s exterior. The investigation found notable variations in temperature, especially around the windows, where temperatures could be as high as 14.1 °C, highlighting the insufficiency of the building’s antiquated timber-framed windows in preventing energy loss.

Experimental and numerical studies on the seismic performance of fully cast‐in‐situ concrete exterior walls

AbstractTo investigate differences in the seismic performance of the main structure between a window sill wall and a coupling beam under two different flexible connections, two coupled shear wall specimens with concrete window sill walls and one counterpart specimen without infill walls (S‐1) were designed for quasistatic tests. The test results indicated the following: In specimen S‐2, fully disconnected by polyvinyl chloride (PVC) tubes, the coupling beam and window sill wall formed a double coupling beam working mode. The failure mode of the main structure of specimens S‐1 and S‐2 was the beam‐hinge mechanism. In specimen S‐3, which was partially disconnected by extruded polystyrene board strips, the coupling beam and the window sill wall worked together as an integral beam and underwent shear failure, revealing significant differences in failure mode compared to S‐1. In addition, the relative deformation between the first‐floor window wall and the main structure of specimen S‐2 could occur, and the interaction between the two was relatively small compared with that of specimen S‐3. Similarly, compared with those of specimen S‐1, the peak loads of specimens S‐2 and S‐3 were approximately 52.37% and 79.99% greater, respectively. The ductility coefficient of S‐2 was equivalent to that of S‐1, while the displacement ductility coefficient of S‐3 decreased by approximately 41.95% compared to that of S‐1. The connection between the main structure and the concrete infill wall with PVC effectively reduced the interaction between the two components and reduced the damage. Finally, MSC. Marc software was used to establish a solid model and simplified model of the equivalent compression bars of all the specimens, and the results were compared with the test results.

Maintaining or replacing a building's windows: a comparative life cycle study

PurposeEnergy-efficiency measures have always been important when renovating aging building stock. For property owners, window intervention is a recurring issue. Replacement is common to reduce operational heating energy (OHE) use, something many previous building renovation studies have considered. Maintaining rather than replacing windows has received less attention, especially for multi-residential buildings in a subarctic climate where there is great potential for OHE savings. The objective was to assess the life cycle (LC) climate impact and costs of three window maintenance and replacement options for a 1980s multi-residential building in subarctic Sweden.Design/methodology/approachThe options’ embodied and operational impacts from material production, transportation and space heating were assessed using a life cycle assessment (LCA) focusing on global warming potential (LCA-GWP) and life cycle costing (LCC) with a 60-year reference study period. A sensitivity analysis was used to explore the impact of uncertain parameters on LCA-GWP and LCC outcomes.FindingsMaintaining instead of replacing windows minimized LC climate impact and costs, except under a few specific conditions. The reduced OHE use from window replacement had a larger compensating effect on embodied global warming potential (E-GWP) than investment costs, i.e. replacement was primarily motivated from a LC climate perspective. The LCA-GWP results were more sensitive to changes in some uncertain parameters, while the LCC results were more robust.Originality/valueThe findings highlight the benefits of maintenance over replacement to reduce costs and decarbonize window interventions, challenging property owners’ preference to replace windows and emphasizing the significance of including maintenance activities in future renovation research.

РОЛЬ ВІТРАЖІВ В СУЧАСНОМУ ОЗДОБЛЕННІ ІНТЕР’ЄРІВ ЖИТЛОВИХ ПРИМІЩЕНЬ

Stained glass has attracted the attention of art critics and scientists for centuries. Stained glass art plays a special artistic role in decorating windows, doors, and ceilings. In addition to the traditional use of stained glass windows, they are used in the design of modern interiors. Although stained-glass windows are not a common design solution in interior design, they are increasingly used for their individualization in modern decoration. In the process of researching decorative decoration of modern interiors with the use of stained glass, new techniques and technologies of their implementation, compositional solutions, their color range were considered, and the main features of artistic expression were revealed. In modern interiors of residential premises, you can find stylized decorative and ornamental stylized stained-glass compositions, which are characterized by a linear division of the glass canvas with the use of faceted glass elements. With the help of stained glass windows, the space of the living room is filled with warm or cold, monochrome or polychrome colors, which enhances the visual perception of certain interior elements. Stained glass compositions using traditional and modern production technologies were analyzed and their role in modern interior design was determined.

Balancing preservation and utilization: Window retrofit strategy for energy efficiency in historic modern building

In modern historic buildings, the decline in energy efficiency due to aging necessitates both the preservation of historical value and the need for energy retrofits. However, the windows cannot be altered due to the historical significance of the building's windows in terms of design and materials. Retrofitting windows in modern historic buildings require a more multifaceted improvement than other envelopes. This research examines the energy efficiency of a retrofit strategy that adds double-glazed windows to existing exterior windows. Through the application of retrofit technology, the performance of the windows and their impact on indoor temperature and relative humidity were analyzed. The research conducted an energy performance analysis using building energy simulations to assess energy savings. To ensure accurate energy efficiency evaluation, on-site indoor temperature and relative humidity monitoring, as well as non-destructive thermal performance assessments, were performed. The results revealed a 35 % improvement in airtightness with window retrofit. Based on these results, simulation results showed a 17 % reduction in annual cooling energy consumption and a 24 % reduction in annual heating energy consumption following the implementation of retrofit strategies. Thermal performance improvements proved effective in reducing cooling energy consumption, while airtightness improvements were more effective for heating energy consumption reduction. Consequently, for buildings requiring both heating and cooling, the double-glazed windows retrofit strategy emerged as an energy effective retrofit approach capable of enhancing both airtightness and thermal performance. This retrofit will unlock new possibilities for the preservation and revitalization of modern historic buildings, allowing them to continue their legacy.

Flexible wafer-scale bifunctional metasurface based on nanoimprinting

Metasurfaces have demonstrated remarkable capabilities in manipulating light fields across diverse applications. However, current research tends to examine these functionalities in isolation, prompting a growing interest in integrating different functionalities within a singular metasurface device. In this paper, we propose and experimentally demonstrate a bifunctional metasurface capable of providing concealment and sensing functions simultaneously. Specifically, the proposed nanostructure effectively operates as a one-way mirror, exhibiting an average reflection rate of approximately 90% under external illumination, alongside an absorption rate of 87.9% from the opposite direction of incidence. This functionality renders it suitable for privacy-enhancing building windows. Meanwhile, this nanostructure also integrates liquid sensing capabilities boasting a sensitivity of 464 nm/RIU, which is particularly valuable for monitoring liquid-based corrosion. The experimental performance of the prepared 6-inch nanohole-patterned metasurface closely aligns with the simulations, and the utilization of flexible polyethylene terephthalate (PET) film, coupled with nanoimprint lithography technology, enables a direct and cost-effective manufacturing process that can be scaled up for widespread applications.

Lattice Boltzmann simulation of effects of realistic boundary conditions on volumetric radiation‐conduction melting of a novel cylindrical enclosure filled with phase change materials

AbstractIn this research, a novel solar latent heat thermal energy storage (LHTES) system, including the cylindrical enclosures filled with a phase change material (PCM), is proposed, which can be installed on the building windows to alleviate the drawbacks of traditional PCM‐filled double‐glazed windows, such as daylight hindrance and leakage. The lattice Boltzmann method (LBM) is used to simulate the volumetric radiation‐conduction melting of the PCM within a single cylinder of the proposed LHTES system with considering more realistic conditions such as convective boundary condition, shadow effect, and variable solar radiation angle compared with the available works in the literature. As such, several boundary conditions are assessed, and parameters such as cylinder diameter, extinction coefficient, scattering albedo, solar angle, shadow effect, and natural convection heat transfer coefficient are studied on the time history of the melting fraction and charging time. The results revealed that considering the applied conditions, such as convection heat loss to the environment and shadow, significantly affects the charging time of the system. It is shown that the charging time for convective boundary condition with , , and increases, respectively, by 11%, 30%, and 50% relative to a case with the insulated boundary condition without the shadow effect and 38%, 91%, and 175% compared with the insulated case with a 90° shadow.

Investigation of the Photochromism of WO3, TiO2, and Composite WO3-TiO2 Nanoparticles.

We report the synthesis of WO3, TiO2, and TiO2-WO3 nanoparticles by a polyol route, with the objective of studying the influence of the preparation method on their photochromic properties. By combining transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and diffuse reflectance experiments, we show that low W6+ concentrations and high ripening temperatures allow the preparation of WO3 nanoparticles with high photochromic efficiency. WO3-TiO2 nanocomposites (NCs) prepared by the introduction of a TiO2+ solution in a WO3 nanoparticle suspension exhibit a strong coloring photochromism, which is attributed to the TiO2 coating of the WO3 nanoparticles as it involves the formation of W-O-Ti oxo-bonds in place of W5+-νO defects. Especially, after an oxidative treatment in order to obtain an initial pale-yellow material, such WO3-TiO2 NCs exhibit a fully reversible photochromism with a large contrast between the colored and bleached state. They could therefore be incorporated in hybrid smart films for solar control on building window glasses. On the other hand, while the WO3-TiO2 NCs are functionalized with DPA (n-dodecyl phosphonic acid), the as-prepared nanocomposites exhibit exacerbated coloring contrast but with a nearly nonreversible photochromism (very limited bleaching), which makes them good candidates for the fabrication of smart UV-sensor devices that can indicate the cumulative UV dose which is received.

Effects of Different Oxidation Methods on the Wetting and Diffusion Characteristics of a High-Alumina Glass Sealant on 304 Stainless Steel.

Glass-to-metal seals are a very important element in the construction of vacuum tubes, electric discharge tubes, pressure-tight glass windows in metal cases, and metal or ceramic packages of electronic components. This paper presents the influence of different pretreatment methods on the high-temperature wettability of 304 stainless steel by high-alumina glass sealing. The pretreatment of the steel included laser surface melting and pre-oxidizing. The bonding characteristics of glass and stainless steel directly depend on the wettability in terms of the measured wetting angle, the type of oxide formed at the stainless steel surface, and the microstructural changes during the manufacturing process. The oxide film thickness on the stainless steel surface was evaluated to determine the optimal parameters. The film was wetted with high-alumina glass powder at different temperatures. The results showed that pre-oxidation decreased the wetting angle from 56.2° to 33.6°, while for the laser-melted surface, the wetting angle decreased from 49.8° to 31.5°. Scanning electron microscopy (SEM) revealed that the oxide film on the laser-melted surface was thicker and denser than that formed on the pre-oxidized surface. The present work shows that laser surface melting has a greater beneficial influence on the wetting and diffusion characteristics of 304 stainless steel sealed by high-alumina glass.