Astigmatism correction of convex aspheres using the subaperture stitching Hindle test

We propose an astigmatism correction method for the subaperture stitching Hindle test to measure hyperbolic convex aspheres. Astigmatic wavefront errors arise from misaligned Hindle setups, mechanical runout errors of the rotational motion for stitching, and the surface error of the target itself. Because these errors are combined, they cannot be separated in the conventional subaperture stitching Hindle tests. We exploited the rotational periodicity of each error to distinguish the surface figure error from other astigmatic error sources and rectified the Hindle test results with a third-order astigmatism. Using the subaperture stitching Hindle test, we averaged two sets of measurement data with a 180° rotational phase difference between them to calculate the astigmatic surface error. The proposed method was verified experimentally by comparing it with the results from a commercial stitching interferometer from QED Technologies; only subnanometer differences in the root-mean-square values were obtained. Therefore, the proposed method calibrated the system errors from the test surface wedge and the rotational decenter easily, thereby reducing the mechanical costs and alignment efforts and making it more accessible than a sophisticated mechanism.

Responses of ticks to immersion in hot bathing water: Effect of surface type, water temperature, and soap on tick motor control

Preventing bites from undetected ticks through bathing practices would benefit public health, but the effects of these practices have been researched minimally. We immersed nymphal and adult hard ticks of species common in the eastern United States in tap water, using temperatures and durations that are realistic for human hot bathing. The effect of (a) different skin-equivalent surfaces (silicone and pig skin), and (b) water temperature was tested on Amblyomma americanum, Dermacentor variabilis and Ixodes scapularis nymphs. Overall, the type of surface had a much larger effect on the nymphs’ tendency to stay in contact with the surface than water temperature did. Most nymphs that separated from the surface did so within the first 10 s of immersion, with the majority losing contact due to the formation of an air bubble between their ventral side and the test surface. In addition, adult Ixodes scapularis were tested for the effect of immersion time, temperature, and soap on tick responsiveness. Some individual adults moved abnormally or stopped moving as a result of longer or hotter immersion, but soap had little effect on responsiveness. Taken together, our results suggest that the surface plays a role in ticks’ tendency to stay in contact; the use of different bath additives warrants further research. While water temperature did not have a significant short-term effect on tick separation, ticks that have not attached by their mouth parts may be rendered unresponsive and eventually lose contact with a person’s skin in a hot bath. It should be noted that our research did not consider potential temperature effects on the pathogens themselves, as previous research suggests that some tickborne pathogens may become less hazardous even if the tick harboring them survives hot-water exposures and later bites the bather after remaining undetected.

Galling wear between ASTM 6061 aluminum and grade D2 tool steel

In the automotive industry, galling is a huge problem either for the tool life or the quality of the stamping metal component. Galling is a severe form of scuffing associated with gross damage to the surface or failure. This work aims to carry out a series of experiments of galling tests at different loads and similar roughness with 6061 aluminum and D2 steel, common materials used in automotive components and tools respectively. A tribometer was employed to generate Galling wear, the button-on-button configuration, according to the ASTM G-196-08 standard. The results show the threshold of minimum load without galling wear. Post-test-surface analysis of the specimens was conducted by confocal microscopy to identify the damage generated during the wear tests. Additionally, a couple of friction tests were carried only to illustrate the friction coefficient behavior under galling conditions.

Electrospun PVP/TiO2 Nanofibers for Filtration and Possible Protection from Various Viruses Like COVID-19

In this study, TiO2 nanofibers were prepared with Polyvinylpyrrolidone (PVP) polymer using sol-gel method via electrospinning technique. Owing to the advantages of small fiber diameter, tunable porosity, low cost, large surface to volume ratio, structure control, light-weight, and less energy consumption, electrospun nanofibers are evolving as an adaptable material with a number of applications, in this case for filtration and environmental/virus protection. Different samples of TiO2/PVP nanofibers have been prepared by changing the parameters to achieve the best result. As the polymer concentration was increased from 6 to 8 wt.% of PVP, diameter of the resultant fibers was seen to be increased, implying decrease in the pore-size of the fibers up to 1.4 nm. Surface morphology has been checked via Scanning Electron Microscope (SEM) images. Crystalline nature has been analyzed by X-Ray Crystallography. Using the Bruanauer-Emmett-Teller (BET) test, surface area and porosity has been checked for the suitable application. The synthesized TiO2/PVP nanofibers have tremendous practical potentials in filtration and environmental remediation applications.

EVALUATION OF THE RANS TURBULENCE MODEL PREDICTIVE CAPABILITY OF FLAT PLATE FILM COOLING

The two-equation turbulence models used for the present study are the commonly used standard k-ॉ model and k-ω model. In order to achieve this target, numerical simulation was initiated in Ansys Fluent to simulate a flow over a flat test surface with a diameter of 4mm straight, circular film cooling hole at angled injections of 25°, 30°, 35°and 40°. The comparison between the numerical calculations and the theoretical results showed the standard k-ω turbulence model gave better predictions against those with the standard k-ω turbulence models. The ability of k-ω model in closely predicting the cooling behavior is due to the precise modeling of the lateral spreading of the film. The isotropic two-equation turbulence models exhibited a huge dissent. The results also indicated that increasing the mass flow rates in the mainstream channels reduces the temperature distribution along the stream-wise direction.

Corrosion of brass subjected to cast-off cooking oil blended with diesel

With the aim of leaving a smaller ecological footprint and to develop fuels which will change the energy needs of the future in a sustainable manner, the present study aims at investigating the corrosion phenomenon of brass using biodiesel fuel from cast-off cooking oil (CCO) in various blending ratios with commercial diesel (5 %, 10 % and 20 %) on brass. The mechanism of corrosion of brass in biodiesel has not been adequately investigated, and in the literature there is still a drop in the knowledge of the corrosion of brass from which many diesel engine parts are made. The corrosion rate of brass has been evaluated by mass loss and electrochemical methods. As a complementary technique, conductivity was monitored before and after each test. Surface morphology was examined by optical microscope. The surface morphology of brass samples in NaCl was coated in dark deposits that indicated corrosion. Some pitting was found in O99, and no significant change was found in oil-diesel blends. There is a positive correlation between the corrosivity and conductivity of the test media. The wettability studies also assisted in determining the non-corrosive nature of biodiesel.

782. A Comparison of Four Different Sampling Methods Used to Recover Contamination from Environmental Surfaces

Background We hypothesized that sampling tools with the largest surface area would be the most efficient at recovering bacteria. To test this hypothesis, we evaluated four different sampling methods to see which was most effective at recovering bacteria from common environmental surfaces. Methods At UNC Medical Center, a 951 bed academic facility, we tested four collection methods: swabs, RODAC (replicate organism detection and counting) plates, Sponge Sticks with manual extraction and Sponge Sticks using extraction with the Seward Stomacher. Laminate and stainless steel surfaces (100 cm²) were used for testing. Known quantities of Staphylococcus aureus (SA) and Klebsiella pneumoniae (KP) were applied across the test surfaces, then allowed to dry prior to sampling. Swab samples were collected by rubbing a moistened swab over the test surface, followed by a dry swab. Both swab tips were broken into a tube of saline and mixed. An aliquot of each was inoculated to agar plates. Each RODAC agar plate was pressed onto a test surface. Sponge Stick samples were collected by rubbing a pre-moistened sponge over the test surface. Each sponge head was ejected into a bag containing saline. For manual agitation, each bag was kneaded by hand for 1 minute. For Stomacher method, bags were processed for 1 minute. The contents of each bag were poured into tubes, then centrifuged. The supernatant was removed from each tube. An aliquot of each was inoculated to agar plates. Plates were incubated at 35°C, then colonies were counted for each plate. Results Comparative recovery rates across surfaces, organism types and sampling methods are shown in the table. Conclusion Organism type, not sampling method, appeared to the most important factor in bacterial recovery. Recovery of SA was significantly higher than KP, likely because it was able to better withstand manipulation and the physical stress of drying on test surfaces. The sampling tool appeared to have the second largest impact. RODAC yielded the highest recovery, followed by swabs, then sponges. Knowing the variable recovery based on method, surface and organism is important for meaningful interpretation of environmental surveillance conducted during outbreak investigations or quality assurance monitoring. Disclosures William Rutala, MS, MPH, PhD, PDI (Professional Disposibles International) (Consultant) David J. Weber, MD, MPH, PDI (Consultant)

Absolute Temperature Thresholds for Detection of Skin Wetness and Dampness on the Hand and their Variation with Sex and Age

The human body has dedicated receptors for sensing temperature and touch, but not wetness. How then is wetness perceived? To test if wetness perception arises from the sensory integration of touch and temperature, and to quantify its measurement in humans, we designed a wetness perception monitor (WPM) which enabled variation of temperature at the fingertips of participants while measuring the pressure exerted on a test surface in the controlled environment of a moisture-free chamber. Thirty randomly selected adults (18+ years) were tested for their perception of dampness/wetness using the WPM. Our data suggest that humans perceive dampness and wetness at average temperatures of 22 ± 0.4°C and 18 ± 0.5°C, respectively, and these sensations are extinguished at temperatures below 16 ± 1°C. Measurements were obtained at an average tactile pressure of 1.5 ± 0.3 kPa. Young adults (18–35 years) sensed wetness at significantly higher temperatures than middle-aged adults (36–55 years) or mature adults (56+ years), who sensed wetness at similar temperatures. We found a surprising sex difference in wetness perception, with females sensing wetness at higher temperatures than males. When the data were screened for outliers, we found that participants whose readings were outside normal ranges, self-reported sensory deficits suggesting that wetness perception could potentially be used as a noninvasive biomarker.

Temperature influence on tire/road noise measurements: recently collected data and discussion of various issues related to standard testing procedures

Air, road, and tire temperatures substantially affect tire/road noise emission. For measuring purposes, one would like to normalize measurements to a reference temperature by means of a reliable correction procedure. Current studies show that temperature effects remain an important source of uncertainty in tire/road noise measurements and tire testing, even after applying the correction terms provided in the various standards. This seems to be the case for the measurement methods used in OBSI, CPX, SPB, and various regulations or directives based on ECE R117. This paper examines a new dataset consisting of 7.5 million temperature measurements aimed at contributing to a better understanding of temperature effects and the ways they relate to air, road, and tire temperatures. It is assumed that tire temperatures are the most relevant for noise corrections; therefore, special studies are made for how tire temperatures relate to air and road (test surface) temperatures. A profound analysis is provided on how these relationships vary over different day times, seasons, and climatic regions. Based on this analysis, the authors provide suggestions for improvement of temperature normalization in current tire/road noise and tire testing standards. Special considerations are devoted to measurements on test tracks having ISO 10844 reference surfaces.

Investigations of improved cooling effectiveness for ramp film cooling with compound angle film cooling jets

Purpose This paper aims to investigate the film cooling effectiveness (FCE) and mixing flow characteristics of the flat surface ramp model integrated with a compound angled film cooling jet. Design/methodology/approach Three-dimensional numerical simulation is performed on a flat surface ramp model with Reynolds Averaged Navier-Stokes approach using a finite volume solver. The tested model has a fixed ramp angle of 24° and a ramp width of two times the diameter of the film cooling hole. The coolant air is injected at 30° along the freestream direction. Three different film hole compound angles oriented to freestream direction at 0°, 90° and 180° were investigated for their performance on-ramp film cooling. The tested blowing ratios (BRs) are in the range of 0.9–2.0. Findings The film hole oriented at a compound angle of 180° has improved the area-averaged FCE on the ramp test surface by 86.74% at a mid-BR of 1.4% and 318.75% at higher BRs of 2.0. The 180° film hole compound angle has also produced higher local and spanwise averaged FCE on the ramp test surface. Originality/value According to the authors’ knowledge, this study is the first of its kind to investigate the ramp film cooling with a compound angle film cooling hole. The improved ramp model with a 180° film hole compound angle can be effectively applied for the end-wall surfaces of gas turbine film cooling.