Optical modeling and computational analysis of improved daylight collector geometry for a tubular skylight.

A carefully designed daylight collector for a tubular skylight is necessary to serve the occupants' illumination needs under the dynamic trajectory of the sun. This work simulated an improved configuration of a passive daylight collector comprising parabolic and conical reflectors in a modeled room using the lighting software tool TracePro. Results indicated that the lighting performance of the proposed design configuration was significantly enhanced under low altitude sun in comparison with conventional tubular skylights (with revolved parabolic and cylindrical reflectors) [Light. Res. Technol.52, 495 (2020)10.1177/1477153519872794] and hemispherical transparent dome as daylight collectors by more than ∼30%-40% and ∼110%-130%, respectively.

Mean wavelength-based Fresnel lens solar collector for eliminating the hotpot problem in daylighting systems.

In this paper, the mean-wavelength-based Fresnel lens was designed by merging the modified edge ray principle and idea of superposition. The bottom-to-top approach optimizes the design of individual prisms according to the predetermined plastic optical fiber (POF) bundle size. The simulated optical efficiency of the collector for the sun's visible spectrum (380-740 nm) light is 82.93% with a uniformity ratio of 0.434. Based on the designed collector, the daylighting system can deliver 199.38 lumens via a 10 m long POF bundle with an efficiency of 23.78%. The thermal analysis revealed that the maximum temperature on the focus plane was 49.7°C.

Modeling a UVC irradiation standalone system for inactivating Mycobacterium tuberculosis from indoor spaces.

After the outbreak of the COVID-19 pandemic, a rise in demand has occurred for efficient designs of disinfection systems that utilize ultraviolet-C (UVC) radiation to inactivate airborne microorganisms effectively. This paper proposes what we believe to be a novel standalone system for inactivating Mycobacterium tuberculosis (which requires a higher dosage value than SARS-CoV-2) from a medium size room of 12.5f t×12.5f t×9f t. The structure consists of a UVC source at the center and a spiral pathway guiding the air around the UVC source, thus increasing the residence time of the aerosol particle. The top and bottom louvre and a hollow cylindrical cover (comprising four external cover segments) enclose the UVC source and prevent the danger of direct exposure to indoor occupants. The whole system is modeled in SolidWorks, and flux leakage was examined using the RayViz tool in SolidWorks. Optical/radiometric analysis in ray tracing software TracePro provided the UVC flux value at different locations of the standalone system. Flow simulation carried out in SolidWorks helped calculate aerosol particles' residence time at different airflow trajectories. The designed standalone system demonstrated the capability of delivering 1.87 times more dosage than is required to inactivate Mycobacterium tuberculosis from the ambient air. The standalone system achieves a ventilation rate, i.e., air changes per hour value of 10, according to guidelines from the Council of Scientific & Industrial Research, India.

UVC-Based Air Disinfection Systems for Rapid Inactivation of SARS-CoV-2 Present in the Air.

The World Health Organization (WHO) declared in May 2021 that SARS-CoV-2 is transmitted not only by close contact with infectious respiratory fluids from infected people or contaminated materials but also indirectly through air. Airborne transmission has serious implications for the control measures we can deploy, given the emergence of more transmissible variants. This emphasizes the need to deploy a mechanism to reduce the viral load in the air, especially in closed and crowded places such as hospitals, public transport buses, etc. In this study, we explored ultraviolet C (UVC) radiation for its ability to inactivate the SARS-CoV-2 particles present in aerosols and designed an air disinfection system to eliminate infectious viruses. We studied the virus inactivation kinetics to identify the UVC dosage required to achieve maximum virus inactivation. Based on the experimental data, UVC-based devices were designed for the sanitization of air through HVAC systems in closed spaces. Further, a risk assessment model to estimate the risk reduction was applied which showed that the use of UVC radiation could result in the reduction of the risk of infection in occupied spaces by up to 90%.

Random adaptive tool path for zonal optics fabrication.

Deterministic optics fabrication using sub-aperture tools has been vital for manufacturing precision optical surfaces. The fabrication process requires the tool influence function and the tool path to calculate the dwell time that guides the tool to bring surface quality within tight design tolerances. Widely used spiral and raster paths may leave excess waviness from the tool path, and the unavoidable constant removal layer is added to obtain positive dwell time. This waviness can be removed by either using smaller tools sequentially or randomizing the tool path. However, the existing tool-path solutions can hardly adapt to different surface aperture shapes and localized surface errors. Process efficiency and accuracy are also not well considered in tool-path planning. We propose an innovative zonal Random Adaptive Path (RAP) to solve these problems in this study. Firstly, RAP can be flexibly adapted to different surface aperture shapes by introducing part boundary. Secondly, an average threshold strategy is used in the RAP planning to improve efficiency, enabling the surface errors to be selectively corrected. Finally, the threshold is performed in several passes within one processing cycle, each with its RAP, until the desired residual is achieved. The performance of the proposed RAP is studied by comparing it with the conventional tool paths. The results demonstrated that RAP takes the least processing time and achieves the best surface quality, which verifies the effectiveness of RAP in deterministic optics fabrication.

Parametric removal rate survey study and numerical modeling for deterministic optics manufacturing.

Surface errors directly affect the performance of optical systems in terms of contrast and resolution. Surface figure errors at different surface scales are deterministically removed using controlled material removal rate (MRR) during a precision optics fabrication process. We systematically sectioned the wide range of MRR space with systematic parameters and experimentally evaluated and mapped the MRR values using a flexible membrane-polishing tool. We performed numerical analysis with a tool influence function model using a distributed MRR-based Preston's constant evaluation approach. The analysis procedure was applied to a series of experimental data along with the tool influence function models to evaluate removal rates. In order to provide referenceable survey data without entangled information, we designed the experiments using Taguchi's L27 orthogonal array involving five control parameters and statistically analyzed a large number of programmatic experiments. The analysis of variance showed that the most significant parameters for achieving a higher MRR are the spot size and active diameter.

Fiber Bragg grating sensor for measurement of impact absorption capability of mouthguards.

BACKGROUND: There is no standard technique to monitor impact absorption capability of mouthguards. Earlier investigations have established that strain transferred to the teeth through mouthguard is a good indication of their efficiency. In the present study, a unique experimental scheme utilizing fiber Bragg gratings (FBGs) as distributed strain sensors is proposed and investigated to estimate impact absorption capability of custom-made mouthguard. The proposed methodology is useful due to advantages such as, very small size and flexibility for ease of bonding, self-referencing, and multiplexing capability of using FBG sensors. MATERIAL AND METHODS: Finite-element analysis was performed to simulate the stress distribution due to impact on the mouthguard. The FBGs were fabricated by exposing the core of photosensitive fiber to intense Ultra-Violet light through a 'phase mask'. One FBG sensor was bonded on the jaw model and another on the mouthguard surface at similar positions, so that both gratings are simultaneously affected by impact. Two different sets of the sensors were used, one for the anterior region and another for posterior region. The impact was produced using customized pendulum device with interchangeable impact objects i.e. cricket ball, hockey ball, and steel ball. Response of gratings was monitored using optical spectrum analyzer and strain induced due to each impact was determined from the Bragg wavelength shifts for each grating. RESULTS AND CONCLUSIONS: Strain induced due to impact was calculated from the Bragg wavelength shifts. Difference in the strain values for the two gratings is interpreted as impact energy absorbed by the mouthguard. The Bragg wavelength shifts (induced strain) for FBG bonded on the jaw model was much lower than the shift for FBG bonded on the mouthguard, indicating that most of the impact energy is absorbed by the mouthguard.