Window Surface Research Articles

Ultraviolet-reflective film applied to windows reduces the likelihood of collisions for two species of songbird.

Perhaps a billion birds die annually from colliding with residential and commercial windows. Therefore, there is a societal need to develop technologies that reduce window collisions by birds. Many current window films that are applied to the external surface of windows have human-visible patterns that are not esthetically preferable. BirdShades have developed a short wavelength (ultraviolet) reflective film that appears as a slight tint to the human eye but should be highly visible to many bird species that see in this spectral range. We performed flight tunnel tests of whether the BirdShades external window film reduced the likelihood that two species of song bird (zebra finch, Taeniopygia guttata and brown-headed cowbird, Molothrus ater) collide with windows during daylight. We paid particular attention to simulate the lighting conditions that birds will experience while flying during the day. Our results indicate a 75–90% reduction in the likelihood of collision with BirdShades-treated compared with control windows, in forced choice trials. In more ecologically relevant comparison between trials where all windows were either treated or control windows, the estimated reduction in probability of collision was 30–50%. Further, both bird species slow their flight by approximately 25% when approaching windows treated with the BirdShades film, thereby reducing the force of collisions if they were to happen. Therefore, we conclude that the BirdShades external window film will be effective in reducing the risk of and damage caused to populations and property by birds’ collision with windows. As this ultraviolet-reflective film has no human-visible patterning to it, the product might be an esthetically more acceptable low cost solution to reducing bird-window collisions. Further, we call for testing of other mitigation technologies in lighting and ecological conditions that are more similar to what birds experience in real human-built environments and make suggestions for testing standards to assess collision-reducing technologies.

Dynamic aberration correction for conformal aircraft windows using the inner window surface and a fixed lens array.

A static solution to dynamic aberrations for conformal aircraft windows with a large range of look angles is reported. The solution uses the inner window surface and a fixed lens array near the image plane to correct the dynamic window aberrations at different look angles. The inner window surface is first used to balance the dynamic aberrations of the full field of regard. Then a lens array is implanted in front of the image, and the dynamic aberrations are corrected by designing the surface shape and rotation direction of each lens unit in the array. The principle of the solution is discussed, and a design example shows that the solution can realize the dynamic aberration correction introduced by the conformal window with a field of regard of ±42∘. Compared to other dynamic or static correctors, this solution takes into account the large field of regard, the light weight and the stability of the optoelectronic system.

Novel reparation method for polymethyl methacrylate optical windows of aircrafts damaged by service environment

The optical properties of polymethyl methacrylate (PMMA) with varying degrees of artificial scratches have been studied with the aim of reproducing the change of visibility of an aircraft’s PMMA optical windows after being damaged in their service environment. A novel maintenance method that can perfectly restore the optical property of PMMA has been identified and employed in the repair of the scratches that are formed on the surface of PMMA. This convenient and low-cost method entails polishing PMMA with different types of sandpaper to remove the scratches, and then spin-coating the repair solution in order to restore the optical properties of PMMA. The effect of this repair mechanism and parameters of the repair process were studied. The results indicated that the optical performance of PMMA is closely related to the mesh size of sandpaper, and improper parameter selection destroys the general effect of the repair. When the number of sandpaper mesh is low, the size of the abrasive particle is relatively larger, which can cause deeper friction marks on the surface of PMMA optical windows. Surface treatment using 5000 mesh sandpaper lowers surface roughness (Ra=0.566 nm), and optical transmittance in visible range can be restored to more than 88%.

A building unit decomposition model for energy leakage by infrared thermography image analysis

A quantitative energy leakage model was developed based on the thermography image data measured for both external and internal building surfaces. The infrared thermography images of both surfaces of doors, windows, and walls of an office building in the Hengqin Campus of University of Macao were taken at various times in a day for four seasons. The transient heat flux for sample units were obtained based on measurements of the seasonal transient local temperature differences and calculations of the effective thermal conductivity from the multiple-layer porous medium conduction model. Effects of construction unit types, orientations, and seasons were quantitatively investigated with unit transient orientation index factors. The corresponding electric energy consumption was calculated based on the air conditioning system coefficient of performance of heat pump and refrigerator cycles for different seasons. The model was validated by comparing to the electric meter records of energy consumption of the air conditioning system. The uncertainties of the predicted total building energy leakage are about 14.7%, 12.8%, 12.4%, and 15.8% for the four seasons, respectively. The differences between the predicted electric consumption and meter values are less than 13.4% and 5.4% for summer and winter, respectively. The typical daily thermal energy leakage value in winter is the highest among the four seasons. However, the daily electric energy consumption by the air conditioning system in summer and autumn is higher than that in winter. The present decomposition model for energy leakage is expected to provide a practical tool for quantitative analysis of energy leakage of buildings.

Diffraction in grating optical filters with angular-selective light transmission

The effect of diffraction on the directional light transmittance of grating optical filters designed for smart windows is studied. The filter has an angular selective light transmission due to two thin-film gratings formed by "non-transmissive" (absorptive, reflective or scattering) parallel strips on the surfaces of a single or double glazed window. Methods are considered for calculating the op-timal slope angle of two filter’s gratings, their relative position on the opposite window surfaces and the widths of the strips of both gratings to minimize light transmission on a specific date and time of day for a given latitude and longitude of the building and azimuth of the window. A meth-od has been developed for calculating the diffraction at the input and output gratings of the filter with regard for a complex movement of the Sun relative to the window and a corresponding change in the incidence angle of the solar beams on the gratings. To evaluate a decrease in the light transmittance of the filter due to diffraction, an additional factor is introduced into the calcu-lation equation. Geometric parameters of the filters and diffraction are calculated. The values of the diffraction factor are 0.9999992 and 0.9999998 for single or double glazed windows, respec-tively, i.e., the influence of diffraction on the light transmittance of the grating filter can be ne-glected.

Experimental and numerical study of heat transfer from a window with an internal Venetian blind

For windows with internal shading devices, accurate calculations of the thermal transmittance, solar heat gain, and window surface temperature require knowledge of the heat transfer by ventilation between the room and the unclosed cavity formed between the glazing surface and the shading devices. In this study, experiments and numerical analyses (CFD) were conducted to evaluate the effects of the blind slat angle and temperature difference pattern on the airflow characteristics and heat transfer. For the airflow rates near the glass surface and the blind surface in the cavity, the airflow rates were larger as the temperature difference increased but were not significantly affected by the blind slat angle in neither experiment nor CFD. Comparing the results between the heat transfer of the experiment and CFD, the CFD trend was in line with that of the experiment. The convective heat transfer from the glass and the blind seemed to be unaffected by the slat angle. The method to estimate the heat transfer by ventilation from the unclosed cavity to the room, presented in this study, seemed to be viable. These results provide fundamental knowledge regarding window energy and surface temperature calculations for the models that have spacing between glass to shading more than 100 mm.

Thermal comfort under asymmetric cold radiant environment at different exposure distances

Radiator heating (RH) and floor heating (FH) exhibit disparate indoor asymmetric environments. In addition, the indoor microenvironment at different locations remarkably varies owing to the cold radiation generated by the surface of exterior walls and windows (EWWs) in winter in the severe cold region of China. The impacts of the exposure distance from the cold radiation on human thermal comfort should be addressed. In this study, an experiment was conducted in a controlled climate chamber, and 66 college students were recruited as volunteers to investigate their physical and psychological responses. The mean radiant temperature (MRT) and the radiant temperature asymmetry (△tpr) were used to assess the environment. The results indicated that compared to MRT in the FH, that in the RH is closer to the ambient air temperature. The horizontal and vertical radiant asymmetries concurrently affected the RH system in the chamber, whereas only the vertical asymmetry played a crucial role in the FH environment. Among the physiological responses, the skin temperature and the heart rate significantly decreased as the distance from the EWWs was reduced in the RH environment, whereas the blood pressure demonstrated no remarkable difference. When the subjects were in comfortable but non-uniform environments, the thermal acceptability was affected by the thermal sensation of multiple local body parts. In a slightly cold environment, the limit of the vertical radiant asymmetric temperature in the FH was 3.6 °C. The experimental results of this study can serve as a reference for thermal designs of buildings.

Investigation of Interaction of Cs Atoms with Sapphire Surface by Means of an Ultrathin Cell and the Second-Derivative Spectrometry of Vapor Absorption

The influence of interaction of Cs atoms with a dielectric surface on position and shape of the hyperfine components of the D2 line in the case of nanometer-scale distance between the atom and the surface is investigated. Using a wedged nanocell enabled investigating the dependence of shift of all hyperfine components of the D2 line corresponding to Fg = 3 → Fe = 2, 3, 4 and Fg = 4 → Fe = 3, 4, 5 transitions on distance L between the atoms and the surface of a sapphire window in the interval from 50 to 400 nm. At L smaller than 100 nm, atomic transitions experience strong broadening due to van der Waals interaction and shift to lower frequencies (the red shift). Calculation of the second derivative (SD) of the absorption spectra of vapors in a nanocell allows spectrally resolving the hyperfine components of an atomic transition down to L ~ 50 nm and determining the van der Waals interaction coefficient C3. It is demonstrated that the spectrum experiences an additional red shift with increase in the density of atoms at L < 100 nm. In contrast, a blue shift occurs with increase in the density of atoms at relatively large distances between the atoms and the surface (L ~ 400 nm). The above results are important for development of miniature submicron-size devices containing alkali metals.

Image-Based Rendering of Cars using Semantic Labels and Approximate Reflection Flow

Image-Based Rendering (IBR) has made impressive progress towards highly realistic, interactive 3D navigation for many scenes, including cityscapes. However, cars are ubiquitous in such scenes; multi-view stereo reconstruction provides proxy geometry for IBR, but has difficulty with shiny car bodies, and leaves holes in place of reflective, semi-transparent windows on cars. We present a new approach allowing free-viewpoint IBR of cars based on an approximate analytic reflection flow computation on curved windows. Our method has three components: a refinement step of reconstructed car geometry guided by semantic labels, that provides an initial approximation for missing window surfaces and a smooth completed car hull; an efficient reflection flow computation using an ellipsoid approximation of the curved car windows that runs in real-time in a shader and a reflection/background layer synthesis solution. These components allow plausible rendering of reflective, semi-transparent windows in free viewpoint navigation. We show results on several scenes casually captured with a single consumer-level camera, demonstrating plausible car renderings with significant improvement in visual quality over previous methods.

Multipactor discharge in circular waveguide window

To study the multipactor effect on the surface of a circular waveguide window excited by the TE11 mode, the effects of the radius of the window, frequency, and style of polarization of the electromagnetic field and the reflection coefficient of the incident wave are examined in this paper using a Monte Carlo algorithm and theoretical analysis. The results show that the character of the multipactor is dominated by the longitudinal velocity of the secondary electrons, which is directly proportional to the square of their oscillatory velocity and inversely proportional to the phase velocity of the RF field. Either increasing the radius of the window disk or decreasing the field frequency leads to the aggravation of multipactor discharge. Moreover, applying the circularly polarized TE11 mode in a circular waveguide window generates electrons at a higher velocity normal to the window disk than that with linearly polarized TE11 mode transmission. In addition, the increase in the reflection coefficient of the incident wave imposes a longitudinal gradient force in the vicinity of the window disk, which also boosts the longitudinal velocity of the secondary electrons and degrades multipactor discharge upstream of the window box.

Time-Resolved Temperature-Jump Infrared Spectroscopy at a High Repetition Rate.

Time-resolved temperature-jump infrared absorption spectroscopy at a 0.5 to 1 kHz repetition rate is presented. A 1 kHz neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pumping an optical parametric oscillator provided >70 µJ, 3.75 µm pump pulses, which delivered a temperature jump via excitation of the O-D stretch of a D2O solution. A 10 kHz train of mid-infrared probe pulses was used to monitor spectral changes following the temperature jump. Calibration with trifluoroacetic acid solution showed that a temperature jump of 10 K lasting for tens of microseconds was achieved, sufficient to observe fast processes in functionally relevant biomolecular mechanisms. Modeling of heating profiles across ≤10 µm path length cells and subsequent cooling dynamics are used to describe the initial <100 ns cooling at the window surface and subsequent, >10 µs cooling dynamics of the bulk solution.

Wide electrochemical window of screen-printed electrode for determination of rapamycin using ionic liquid/graphene composites.

A disposable screen-printed carbon electrode (SPCE) modified with anionic liquid/graphene composite (IL/G) exhibits a wider potential window, excellent conductivity, and specific surface area for the improvement in the voltammetric signal of rapamycin detection. The modified composite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Theelectrochemical behavior of rapamycin at the modified SPCE was investigated by cyclic and square wave voltammetry in 60:40 EtOH: 0.1M LiClO4 atpH 5.0. A high reproducible and well-defined peak with a high peak current were obtained for rapamycin detection at a position potential of + 0.98V versus Ag/AgCl. Under the optimized conditions, the rapamycin concentration in the range 0.1 to 100μM (R2 = 0.9986) had a good linear relation with the peak current. The detection limit of this method was 0.03μM (3SD/slope). The proposed device can selectively detect rapamycin in the presence of commonly interfering compounds. Finally, the proposed method was successfully applied to determine rapamycin in urine and blood samples with excellent recoveries. These devices are disposable and cost-effective and might be used as an alternative tool for detecting rapamycin in biological samples and other biological compounds. Graphical abstract Schematic presentation of wide electrochemical window and disposable screen-printed sensor using ionic liquid/graphene composite for the determination of rapamycin. This composite can enhance the oxidation current and expand the potential for rapamycin detection.

The impact of a view from a window on thermal comfort, emotion, and cognitive performance

Visual connection to nature has been demonstrated to have a positive impact on attention restoration, stress reduction, and overall health and well-being. Inside buildings, windows are the primary means of providing a connection to the outdoors, and nature views even through a window may have similar effects on the occupants. Given that humans recognize environments through multi-sensory integration, a window view may also affect occupants’ thermal perception. We assessed the influence of having a window with a view on thermal and emotional responses as well as on cognitive performance. We conducted a randomized crossover laboratory experiment with 86 participants, in spaces with and without windows. The chamber kept the air and window surface temperature at 28 °C, a slightly warm condition. The outcome measures consisted of subjective evaluations (e.g., thermal perception, emotion), skin temperature measurements and cognitive performance tests. In the space with versus without windows, the thermal sensation was significantly cooler (0.3 thermal sensation vote; equivalent to 0.74 °C lower), and 12% more participants were thermally comfortable. Positive emotions (e.g., happy, satisfied) were higher and negative emotions (e.g., sad, drowsy) were lower for the participants in the window versus the windowless condition. Working memory and the ability to concentrate were higher for participants in the space with versus without windows, but there were no significant differences in short-term memory, planning, and creativity performance. Considering the multiple effects of window access, providing a window with a view in a workplace is important for the comfort, emotion, and working memory and concentration of occupants.

Infrared Thermography Diagnostics of Air Permeability Through Building Openings – Assessment of its Reliability

Abstract The presented paper deals with an analysis of the reliability of a diagnostic method of air permeability through building openings (windows, doors, glass walls) by the application of infrared thermography. A test sample of a plastic double casement window was experimentally tested for air permeability and watertightness in a large pressure chamber. Different levels of the tightness were adjusted between the casement and frame part of the window. Additionally, the window test sample was measured in the large climate chamber with variant air pressure differences. Moreover, the surface temperatures were measured on the window by thermocouples and subsequently compared with images directly taken by infrared thermography. The effect of the increased air infiltration can be detected by infrared thermography but cannot quantify the overall air permeability of the window. The distribution of the exterior window surface temperature is influenced by several factors which should be taken into consideration in the final assessment of the window.

Embedding physics domain knowledge into a Bayesian network enables layer-by-layer process innovation for photovoltaics

Process optimization of photovoltaic devices is a time-intensive, trial-and-error endeavor, which lacks full transparency of the underlying physics and relies on user-imposed constraints that may or may not lead to a global optimum. Herein, we demonstrate that embedding physics domain knowledge into a Bayesian network enables an optimization approach for gallium arsenide (GaAs) solar cells that identifies the root cause(s) of underperformance with layer-by-layer resolution and reveals alternative optimal process windows beyond traditional black-box optimization. Our Bayesian network approach links a key GaAs process variable (growth temperature) to material descriptors (bulk and interface properties, e.g., bulk lifetime, doping, and surface recombination) and device performance parameters (e.g., cell efficiency). For this purpose, we combine a Bayesian inference framework with a neural network surrogate device-physics model that is 100× faster than numerical solvers. With the trained surrogate model and only a small number of experimental samples, our approach reduces significantly the time-consuming intervention and characterization required by the experimentalist. As a demonstration of our method, in only five metal organic chemical vapor depositions, we identify a superior growth temperature profile for the window, bulk, and back surface field layer of a GaAs solar cell, without any secondary measurements, and demonstrate a 6.5% relative AM1.5G efficiency improvement above traditional grid search methods.

Validation of a radiative transfer model with measurements of UV radiation inside a commercial aircraft

A radiative transfer model for the determination of UV radiation on arbitrarily oriented surfaces is validated by spectral measurements taken directly on the inner surface of a cockpit window of an Airbus A321-231 during a flight from Frankfurt, Germany to Málaga, Spain on 23 August 2018. The simulations consider the UV spectral range from 290 to 400 nm and take into account both the measured spectral transmittance of a cockpit window as well as its construction-related orientation. Comparisons are performed for selected route segments with largely cloud-free conditions. The cruising level of the Airbus on these segments was nearly constant between 11.27 and 11.29 km. UV irradiance measurements at the cockpit window give values within a range of 19 and 26 W m−2. The comparison of modelled and measured irradiances show a very good agreement, i.e. the relative differences between simulated and measured values range from −2.1% to +4.3%. In addition, horizontally and vertically oriented sensors are simulated for the same flight. The validation results generally underpin the application potential of the model. As an example of this, UV irradiances incident on differently oriented surfaces, as could occur inside and outside of a future flying taxi on a short-haul flight between Munich and Augsburg at low cruising level, are shown.

Studies on internal surface heat transfer in the window area

In this paper reporting preliminary results from the ongoing research, heat transfer phenomena at window surfaces and adjacent areas of the building envelopes are studied. In the first step, in-situ observation of balcony door based on indirect estimation of temperature distribution close to window surface was carried out by means of infrared imaging (IR). In the second step, more advanced full-scale experiments were performed in a well-insulated laboratory testing room with floor heating, equipped with one window, under well controlled steady-state conditions. A combination of IR with particle imaging velocimetry (PIV) was used here with extra focus on situation close to the window frame at window sill. In such areas the reduced heat transfer by convection can be observed. As a consequence, the condensation risk free situation there seems not to be always guaranteed even by high performing building components despite the results of standard heat transfer calculations used in design practice.

Study on the pack rolling process factor of Ti-6Al-4V alloy

Pack rolling method is preferred to conventional rolling method to process thin sheets or foils out of titanium alloys because of their relatively narrow processing window and possible surface contamination during the elevated temperature processing. In this paper, the core sheets of 5mm thick with equiaxed alpha + transformed beta structure were encapsulated in mild steel cover material and hot rolled in a four high reversing hot rolling mill. The following results were obtained; The optimal pack assembly condition and pack rolling process factor were produced. The effect that the difference in deformation resistance of cover material and core material in pack rolling has been considered. The S45C mild steel is the most suitable for the cover material. The cover material is subjected to the same rolling process as the core material when the initial core and total thickness ratio is 0.3. The reduction in pack rolling should be selected in the range of 20% to 25% to produce flat sheet. Tensile properties of the pack rolled sheet are isotropic in both RD and TD rolling direction which meet the requirements of the standard AMS4911.

Enhancing the sensitivity of the reference electrode free AlGaN/GaN HEMT based pH sensors by controlling the threshold voltage

The threshold voltage (VT) of the AlGaN/GaN HEMT based pH sensor was adjusted by the method of the photoelectrochemical (PEC) oxidation on the GaN cap layer surface. After the PEC oxidation treatments, the VT of the device shifted from -3.46 V to -1.15 V and the gate voltage (VG) corresponding to the maximum transconductance (gmMAX) position (VG|gmMAX) of the device shifted from -2.6 V to -0.1 V. The drain current (ID) variation per pH of the AlGaN/GaN HEMT based pH sensor without reference electrode increased from 0.7 μA to 14 μA when the drain voltage (VD) was 0.5 V. The sensitivity of the reference electrode free AlGaN/GaN HEMT based pH sensor can be significantly increased by regulating the VT to make VG|gmMAX approached the equivalent VG when liquid droplet on the sensing window surface (VG-EQU), which is beneficial to the miniaturization and integration of the AlGaN/GaN HEMT based sensors in the future.

A Study on Multi-Objective Parametric Design Tool for Surround-Type Movable Shading Device

This study presents a multi-objective parametric design tool for four-axis surround-type movable shading device using solar position tracking in Seoul, South Korea. In order to explore large numbers of possible forms of shades, generic algorithms are utilized with real-time simulation of the performative criteria such as solar radiation, daylight glare probability (DGP), and solar shielding rate on window surface. This study outlines a workflow using a multi-objective engine called Octopus that runs within Grasshopper 3D, a parametric design tool, in addition to environmental performance simulation plug-in Ladybug. The workflow utilizes a performance-based design tool, which allows the designer to explore, sort, and filter solutions, and visually compare alternative solutions in terms of energy saving and indoor daylight quality in order to determine the optimal form of shade changing its shape every one hour. The result of deriving and analyzing the optimal shade shape through the genetic algorithm proposed in this study is as follows: On the one hand, on the summer solstice, shade shapes with shielding areas of almost 100% should be derived to achieve the most effective reduction of the direct solar radiation. The proposed movable shading device reduced direct solar radiation by 52.40% and 57.20% in the south- and east-facing windows, respectively. On the other hand, in winter when solar heat gain is important, the absence of sunshade is optimal in terms of heating load. However, in order to improve the indoor light environment, it is confirmed that it is possible to derive a certain shape of sunshade according to the sun’s trajectory. On the winter solstice, the problem of glare arises from 10:00 to 15:00 in the south and 10:00 in the east. Therefore, the proposed four-axis movable shading device can be configured to have a minimum protrusion length satisfying DGP less than 0.35 in winter.