Apparent movement phenomena on CRT displays - Threshold determinations of apparent movements of pulsed light sources

Apparent movement phenomena on cathode ray tube displays - threshold determinations of apparent movements of pulsed light source

The Effect of Stainless Steel 304 Surface Roughness on Ice Adhesion Shear Strength of Accreted Impact Ice

Aircraft in-flight icing is problematic due to the ad-verse effect on vehicle performance. It occurs when supercooled water droplets (SCWD) present in clouds, under the appropriate environmental conditions, col-lide with the aircraft surface resulting in accretion of ice (i.e., impact icing). Impact ice can range from clear/glaze to rime or a combination of the two (i.e., mixed) with the type determined by the air temperature (0 to -20C), liquid water content (LWC, 0.3-0.6 g/cu.m), and droplet size [median volumetric diameter (MVD) of 15-40 m] present during accretion.1 These impact icing events generally occur at temperatures ranging from 0 to -20C. Below -20C, ice crystals dominate the environment and typically do not adhere to the aircraft surface. A main difference between an impact icing occurrence and a slow growth icing (i.e., freezer ice) one is the speed of the icing event. Besides environmental conditions, ice adhesion strength (IAS) to a metallic substrate depends upon surface roughness. It is known that increasing surface roughness and decreasing temperature lead to in-creases in IAS

Blue Light Second Harmonic Generation In The Organic Crystal Ortho-Dicyanovinyl-Anisole

Type I phase matched second harmonic generation (SHG) in the organic crystal ortho-Dicyanovinyl-anisole (DIVA) has been measured for a range of near infrared fundamental wavelengths (855-960 nm). Turning curves for type I phase matched SHG were derived from measured refractive index values and show noncritical phase matching at 860. Measured type I phase matched SHG is in close agreement with the calculated results and gives effective SHG coefficients ranging from 1.9 to 5.9 times as large as d(32) Of potassium niobate. (C) 1997 American Institute of Physics

Synthesis and Characterization of Copolyimides Containing Fluorine and Silicon Surface Modifying Agents

Understanding the effects that monomer chemistries have on material properties allows for fine tuning of polymer synthesis for current and future applications. In order to develop polymeric based coatings that have minimal surface adhesion characteristics when exposed to a variety of contaminants, a more thorough understanding of fundamental structure-property relationships is needed. In the aeronautics field, one concept to improve fuel efficiency of future aircraft is to modify the wing design to enable laminar flow. There is a concern that contaminants such as insect residue and other debris will adhere to airflow surfaces and have sufficient height to disrupt laminar flow thereby increasing drag with concomitant loss of fuel efficiency. One potential solution would be a polymer surface or coating that prevents or minimizes adhesion of such contaminants. As part of a structure-property relationship study involving modification of surface properties, a series of copolyimides containing both fluorine and silicon surface modifying agents (SMAs) were prepared and characterized. Based on knowledge of structure-property relationships with polyimides containing either type of SMA, it was hypothesized that the combination of two different surface-modifying agents may lead to unique surface properties as the two SMAs competed for surface area at the polymer-air interface. Copolyimides for this study were prepared through a multi-step synthesis using an aromatic dianhydride with equimolar amounts of diamino functionalities comprised of an aromatic diamine along with two SMAs. Films were cast from copoly(amide acid) solutions that were subsequently thermally imidized under a nitrogen atmosphere. Polyimide films and coatings were characterized using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), ultravioletvisible spectroscopy (UV-Vis), contact angle goniometry (CAG), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to determine chemical, thermal, and surface properties. Select samples were subject to high velocity insect impacts in a small scale wind tunnel and the resulting residues were characterized for height and surface area and compared to those of a control surface

Influence of Surface Properties and Impact Conditions on Adhesion of Insect Residues

Insect residues can cause premature transition to turbulent flow on laminar flow airfoils. Engineered surfaces that mitigate the adhesion of insect residues provide, therefore, a route to more efficient aerodynamics and reduced fuel burn rates. Areal coverage and heights of residues depend not only on surface properties, but also on impact conditions. We report high speed photography of fruit fly impacts at different angles of inclination on a rigid aluminum surface, optical microscopy and profilometry, and contact angle goniometry to support the design of engineered surfaces. For the polyurethane and epoxy coatings studied, some of which exhibited superhydrophobicity, it was determined that impact angle and surface compositions play critical roles in the efficacy of these surfaces to reduce insect residue adhesion

Combining genomics and epidemiology to track mumps virus transmission in the United States.

Unusually large outbreaks of mumps across the United States in 2016 and 2017 raised questions about the extent of mumps circulation and the relationship between these and prior outbreaks. We paired epidemiological data from public health investigations with analysis of mumps virus whole genome sequences from 201 infected individuals, focusing on Massachusetts university communities. Our analysis suggests continuous, undetected circulation of mumps locally and nationally, including multiple independent introductions into Massachusetts and into individual communities. Despite the presence of these multiple mumps virus lineages, the genomic data show that one lineage has dominated in the US since at least 2006. Widespread transmission was surprising given high vaccination rates, but we found no genetic evidence that variants arising during this outbreak contributed to vaccine escape. Viral genomic data allowed us to reconstruct mumps transmission links not evident from epidemiological data or standard single-gene surveillance efforts and also revealed connections between apparently unrelated mumps outbreaks