Current ANSI Research Articles

Modeling Supercontinuum Lasers to Simulate Damage Thresholds on the Retina

Laser damage thresholds depend on the amount of energy absorbed, and in this specific case, energy absorbed by the retina. The goal of our research is to simulate a supercontinuum laser source and compare the resulting damage to that of the current ANSI approach. To calculate retinal damage we utilize the Arrhenius integral, which returns numerical values for laser-induced damage with values ranging from zero to one depending on the severity. Our simulations use numerical analysis to iterate through different coordinates in space and time to return data representative of the physical situation after we expose the eye to a gaussian laser beam. We have performed simulations ranging from a singular laser source up to a three-laser source and are currently working towards an automated method of generating these complex configurations in the hopes of more efficiently replicating the damage properties of a specific laser product and comparing it to the existing ANSI approach.

Annoyance perception of complex multi-tone noise signals in both harmonic and inharmonic structures within the built environment

Assorted building mechanical systems generate tonal components within the background noise of built environments. In most cases, this type of noise includes multiple tones in harmonic or inharmonic structures rather than a single tone. However, there is limited information on the comprehensive annoyance caused by multiple tones as perceived by human occupants. Two current standards, ISO 1996-2 and ANSI S1.13, propose calculation methods to address tones in noise, but those methods only analyze the tones individually. This paper aims to investigate how each tone contributes to overall annoyance perception when complex tones are present in background noise. Noise stimuli with five-tone complexes between 125 Hz to 2 kHz were artificially generated for subjective testing. The levels of each tone were randomly adjusted for every trial, and both harmonic and inharmonic structured tone complexes were utilized. Ten musically trained subjects participated in the subjective test involving paired comparisons. Each participant was asked to choose which noise stimulus is more annoying between two noise signals. Perceptual weighting analysis is applied to the results to compute a spectral weighting function for overall annoyance. The performance of the derived spectral weighting function is examined against annoyance ratings of actual building mechanical noises.

How should we move forward with the next version of the ANSI S3.4 loudness standard?

Recent updates to the international loudness standard ISO 532 reflect both increased understanding of loudness and the use of loudness standards by the acoustics and engineering communities. Both are inspiration to consider revising ANSI S3.4-2007. The current ANSI standard is based on Moore and Glasberg’s model of loudness for stationary sounds. The new ISO 532-2 is a revision of this. The new ISO 532-1 is based on Zwicker’s time-varying loudness, and will replace the current ISO 532B, also based on Zwicker’s loudness model but for stationary sounds. For people who are not developing loudness models but are using them to assess sounds or noise, there are a number of other issues, e.g., loudness of very low frequency sounds, and exposure assessment based on loudness. These will be discussed and possible directions in updating the current ANSI standard are presented.

The Angle of Inclination of Extension Ladders

For extension ladders and other non-self supporting ladders, setting the angle of inclination of the ladder is a critical step in the set up process. The angle of the ladder influences: 1) the potential for a ladder to slide out at the base, 2) the overall strength of the system, and 3) the biomechanics of the climber/user on the ladder. A field study was conducted where over 120 real world ladder installations were documented, including angle of inclination, site conditions, and use. The average angle of inclination in the field study was 67.7 ± 4.9 degrees. Research was further conducted to assess the effectiveness of existing ladder labels for setting the ladder at the instructed 75.5 degree angle of inclination. 45 participants set up extension ladders following the “anthropometric” label (appendices of current ANSI A14 ladder safety standards), and/or the backward “L” label (historic ANSI A14 label). The average set up angle for the “anthropometric” label was 74.1 ± 3.2 degrees. This is consistent with calculations of the expected angle of inclination using anthropometric data. The calculated angles ranged from 74.9 to 75.2 degrees. The average angle of inclination for the backward “L” label was 72.7 ± 2.7 degrees. These results indicate that the current “anthropometric” label resulted in a set up angle consistent with anthropometric calculations and significantly higher than documented in real world ladder use.

Some factors affecting loudness measurement and prediction

The current ANSI standard (ANSI S3.4, 2007) estimates the loudness of sustained sound, but many naturally occurring sounds have time-varying levels. Glasberg and Moore (2002) published a model for the prediction of time-varying sounds and this aspect should be considered as part of a revision to the ANSI standard. To assess the predictions of the dynamic model, loudness magnitude estimation functions were obtained for 24 listeners using pure tones (0.5 and 1.0 kHz), vowels, spondees, and speech-shaped noise (SSN) presented at levels from 40 to 90 dB SPL. Inferred equal-loudness levels from the fitted loudness functions were compared to the model predictions. The loudness model was qualitatively consistent with the behavioral data. The model predicted SSN to be louder than vowels and spondees which would be louder than tones; however, the model over-predicted the loudness differences. Possible explanations for the over-prediction include biases in loudness judgments, cognitive factors regarding learned expectations for loudness, assumptions regarding the free-field-to-headphone transfer function, and the model’s over-prediction of spectral, loudness summation, a result found recently (Schlittenlacher et al., 2014) for the ANSI standard and DIN 45631.

In vivo imaging of retinal pigment epithelium cells in age related macular degeneration.

Morgan and colleagues demonstrated that the RPE cell mosaic can be resolved in the living human eye non-invasively by imaging the short-wavelength autofluorescence using an adaptive optics (AO) ophthalmoscope. This method, based on the assumption that all subjects have the same longitudinal chromatic aberration (LCA) correction, has proved difficult to use in diseased eyes, and in particular those affected by age-related macular degeneration (AMD). In this work, we improve Morgan's method by accounting for chromatic aberration variations by optimizing the confocal aperture axial and transverse placement through an automated iterative maximization of image intensity. The increase in image intensity after algorithmic aperture placement varied depending upon patient and aperture position prior to optimization but increases as large as a factor of 10 were observed. When using a confocal aperture of 3.4 Airy disks in diameter, images were obtained using retinal radiant exposures of less than 2.44 J/cm(2), which is ~22 times below the current ANSI maximum permissible exposure. RPE cell morphologies that were strikingly similar to those seen in postmortem histological studies were observed in AMD eyes, even in areas where the pattern of fluorescence appeared normal in commercial fundus autofluorescence (FAF) images. This new method can be used to study RPE morphology in AMD and other diseases, providing a powerful tool for understanding disease pathogenesis and progression, and offering a new means to assess the efficacy of treatments designed to restore RPE health.

Viability of Hybrid Poplar in ANSI Approved Cross-Laminated Timber Applications

The development of cross-laminated timber (CLT) technology has opened up new opportunities for low-density hardwood species, which have traditionally not been rated as construction-grade materials for structural engineering applications. Several characteristics of CLT, namely thermal performance, seismic behavior, and speed of construction, have raised interest among designers. The CLT technology has recently been used for residential and nonresidential multistory buildings and it has been identified as one of the ways of achieving tall timber building construction. As CLT gains acceptance in the industry, low-density wood species, not specified in current ANSI standards, need to be investigated for potentially successful use in CLT panels. This paper presents a study that demonstrates the viability of a Forest Stewardship Council (FSC) certified sustainable plantation grown low-density species, hybrid poplar (marketed as Pacific Albus), for use in performance-rated CLT panels by following the ANSI/APA PRG-320-2012: Standard for performance-rated cross-laminated timber shear and bending test guidelines to determine the structural viability of the CLT panels.

Visual and Physiological Optics

Visual and Physiological Optics

Research to improve extension ladder angular positioning

A leading cause for extension ladder fall incidents is a slide-out event usually related to suboptimal ladder inclination. An improved ladder positioning method or procedure could reduce the risk of ladder stability failure and the related fall injury. The objective of the study was to comparatively evaluate the effectiveness of a multimodal angle indicator with other existing methods for extension ladder angular positioning.Twenty experienced and 20 inexperienced ladder users participated in the study. Four ladder positioning methods were tested in a controlled laboratory environment with 4.88 m (16 ft) and 7.32 m (24 ft) ladders in extended and retracted positions. The positioning methods included a no-instruction method, the current standard anthropometric method, and two instrumental methods – a bubble level indicator, and a multimodal indicator providing direct feedback with visual and sound signals. Performance measures included positioning angle and time.The results indicated that the anthropometric method was effective in improving the extension ladder positioning angle (p < 0.001); however, it was associated with considerable variability and required 50% more time than no-instruction. The bubble level indicator was an accurate positioning method (with very low variability), but required more than double the time of the no-instruction method (p < 0.001). The multimodal indicator improved the ladder angle setting as compared to the no-instruction and anthropometry methods (p < 0.001) and required the least time for ladder positioning among the tested methods (p < 0.001).An indicator with direct multimodal feedback is a viable approach for quick and accurate ladder positioning. The main advantage of the new multimodal method is that it provides continuous feedback on the angle of the device and hence does not require repositioning of the ladder. Furthermore, this indicator can be a valuable tool for training ladder users to correctly apply the current ANSI A14 standard anthropometric method in ladder angular positioning.The multimodal indicator concept has been further developed to become a hand-held tool in the form of a smart phone application.

Optimization Analysis of Thin-Walled High Pier

According to the restriction of the stability and intensity, size optimization of the high piers’ section is calculated by using the current FEM software ANSYS, by means of differential coefficient. The results of the calculation and analysis indicate that the parameter optimization of the piers’ section of Long-span continuous rigid frame bridges is feasible by using the optimization model together with the finite element method, and the results are provided reference for optional design of similar bridge

Characterization of mouthguard materials: Physical and mechanical properties of commercialized products

Objectives Contemporary mouthguard materials need to perform consistently over a wide range of possible temperatures (−20 to 40 °C). Therefore the specific aim of this study was to characterize commercialized mouthguard materials’ properties and investigate the effect of temperature on these properties. Methods Five commercially representative thermoplastic mouthguard materials (Essix™ Resin, Erkoflex™, Proform™-regular, Proform™-laminate, and Polyshok™) were tested. The durometer hardness, water absorption, tear strength, and impact attenuation of the mouthguard materials were measured according to ASTM D2240-05, D570-98 (2005), D624-00, and ASTM D6110-06f (modified) guidelines. Tests were conducted on five separate specimens at both room 23 ± 2 °C and intra-oral 37 ± 2 °C temperatures. Independent t-tests ( α = 0.05) were used to test for differences between room and intra-oral temperatures. Results Material hardness decreased ( p < 0.05) from room to intra-oral temperatures for all mouthguard materials. Water absorption increased ( p < 0.05) from room to intra-oral temperatures for all mouthguard materials. Tear strength decreased ( p < 0.05) from room to intra-oral temperatures for all mouthguard materials. Impact attenuation between room and intra-oral temperatures was different ( p < 0.05) for the Erkoflex™, Proform™-laminate, and Polyshok™ material respectfully. However, there was no difference between temperatures for the Essix™ Resin ( p = .058) or Proform™-regular ( p = .275) materials. Significance Temperature measureably affects the physical and mechanical properties of mouthguard materials. It is particularly noteworthy that none of the commercialized products met current ANSI and SAI standards for impact attenuation.

The relationship between the minimum zone circle and the maximum inscribed circle and the minimum circumscribed circle

Following the minimum zone criterion set forth in the current ANSI and ISO standards, evaluation of roundness error is formulated as a non-differentiable unconstrained optimization problem and hard to handle. The maximum inscribed circle and minimum circumscribed circle are all easily solved by iterative comparisons, so the relationship between the minimum zone circle and maximum inscribed circle, minimum circumscribed circle is proposed to solve efficiently the minimum zone problem. Based on the known minimum zone circle, the maximum inscribed circle and minimum circumscribed circle can be easily determined. The relationship is implemented and validated with the data available in the literature.

Numerical modeling of sonic boom propagation from hypersonic aircraft

A numerical study of sonic boom propagation from hypersonic aircraft is performed including the effects of nonlinearity, atmospheric absorption and dispersion, and atmospheric stratification. A second-order split-step algorithm, which alternates application of nonlinearity in the time domain and complex absorption in the frequency domain, allows for a faster convergence of results with fewer range steps than with conventional first-order algorithms. Nonlinearity is calculated using the potential, the integral of the pressure, as proposed by Burgers and later applied to sonic booms by Hayes et al. This method, an alternative to Landau's law of equal areas, efficiently locates the shock position by selecting the maximum potential in multivalued regions. Definition of atmospheric absorption at high altitudes is important for modeling the propagation of sonic booms from hypersonic aircraft. Some aspects of an extended absorption model by Sutherland and Bass are adopted, therefore, which extend absorption predictions above the 20 km limit of the current ISO and ANSI standards. The study is completed using the meteorological conditions at two locations, Le Havre, France and Edwards Air Force Base, CA, USA, over the course of a year. [Work supported by European Union through ATLLAS AST5-CT-2006-030729, meteorological data provided by ECMWF.]

A Critique of the ANSI Standard on Role-Based Access Control

In 2004, the American National Standards Institute approved the Role-Based Access Control standard to fulfill need among government and industry purchasers of information technology products for a consistent and uniform definition of role based access control (RBAC) features. Such uniform definitions give IT product vendors and customers a common and unambiguous terminology for RBAC features, which can lead to wider adoption of RBAC and increased productivity. However, the current ANSI RBAC Standard has several limitations, design flaws, and technical errors that, it unaddressed, could lead to confusions among IT product vendors and customers and to RBAC implementations with different semantics, thus defeating the standard's purpose.

Robert W. Young and the A-weighting for acoustical measurements

In 1985, the ASA Technical Committee S1: Acoustics, drafted the amendment ANSI S1.4A to the current sound level meter standard ANSI S1.4-1983. The aim was to provide A-weighting tolerances to frequencies above 16 kHz for measurement of short-duration transient signals. Dr. Young gave a lot of support during the preparation of that amendment. The current international sound level meter standard IEC 61672-1 (2002): Specifications, has A-weighting tolerances that allow less capable microphones to be used in Class 1 instruments. Under the above IEC standard, microphones that are not capable of measuring sound beyond 16 kHz can be used in IEC Class 1 sound level meters. Some pros and cons will be discussed.

A Review of Accelerated Test Methods for Predicting the Image Life of Digitally-Printed Photographs &amp;#x2013; Part II

This paper gives an overview of the various factors affecting the permanence of digitally-printed photographs.1 Accelerated test methods are discussed, with emphasis on light stability tests specified with past and current ANSI and ISO Standards, future ISO Standards, and the &#x201C;de facto&#x201D; test method standards now widely used in the imaging industry, such as the predictive &#x201C;Display Permanence Rating&#x201D; test method developed by Wilhelm Imaging Research and the predictive stability test methods employed by Eastman Kodak for evaluation of Kodak Ultima Picture Paper (ColorLast, 2003 type). Light stability data for representative products evaluated with these two &#x201C;de facto&#x201D; test methods are given, and the major factors that account for the large differences in outcomes are presented.The potentially large impact of reciprocity failures in highintensity accelerated light stability tests is illustrated with longterm test data for an inkjet paper printed with dye-based inks. The importance of the selection of the spectral power distribution of the illumination source employed for accelerated light stability tests is emphasized.

Quantifying Telecoil Performance: Understanding Historical and Current ANSI Standards

Quantifying Telecoil Performance: Understanding Historical and Current ANSI Standards

Correlating Changes in Densitometry and Colorimetry in the Context of the Light-Induced Fade of Inkjet Photographic Prints

The current ANSI standard method for evaluating the image stability of photographic prints (ANSI IT9.9-1996) calls for the use of densitometry in order to determine the extent of light-induced fade and to provide an estimate of print-life under real-world conditions. End-of-life criteria based on densitometry can involve monitoring simultaneously as many as 24 different end-points (excluding changes to Dmin). Conceivably, end-of-life criteria based on colorimetric measures such as &#x394;E or &#x394;C could reduce the number of end-points from 24 to as few as 7&#x2014;one criterion for each primary (cyan, magenta, yellow), secondary (blue, green, red), and neutral (gray/black) test patch. In the context of evaluating inkjet photographic prints based on hundreds of different combinations of various manufacturers' inks and receivers, we have been following the kinetics of dye-fade by both Status A densitometry and CIELAB colorimetry. In this report, we will begin to explore the empirical correlation between densitometric and colorimetric measures of color change.

A steepest descent algorithm for circularity evaluation

This paper presents a novel algorithm for evaluating the circularity of a mechanical part by using measurement points obtained with a coordinate measuring machine (CMM). Following the minimum zone criterion set forth in the current ANSI and ISO standards, evaluation of circularity is formulated as a non-differentiable unconstrained optimization problem, and based on the geometric representation of the necessary and sufficient condition for the optimal solution, an efficient steepest descent optimization procedure is proposed to find the circularity value. The steepest descent direction is determined by the method of calculating the minimum translational distance between two convex polygons, which is initially introduced in the field of robot path planning, and the length of the moving step is exactly determined by a presented geometrical method. A computational geometry-based method for pre-processing the measured data is also proposed. In comparison with existing methods, this algorithm has the advantages of computational efficiency and high precision. Simulations and practical example confirm the validity of the presented algorithm.

Crosstalk mitigation in DMT VDSL with impulse noise

Crosstalk and impulse noise are two principal sources of degradation in very-high-rate digital subscriber line (VDSL) transmission systems. The traditional single-user data detector for such systems merges crosstalk into the background noise, which is assumed to be white and Gaussian. Recent research has explored the nature of crosstalk signals and shown the potential benefits of multiuser detection (MUD) for VDSL signals with strong crosstalkers. Impulse noise is one of the most difficult transmission impairments to suppress, and is poorly characterized and understood as well. In DSL transmission, impulse noise is typically combated with interleaved forward-error correction (FEC). However, recent data indicate that a significant minority of impulse-noise events are longer than the maximum error-correcting capacities of the default interleaved FEC provided within current ANSI standards. Thus, it is of interest to consider signal processing methods that can jointly mitigate crosstalk and impulse noise. In this paper, we explore such a technique based on a recently developed robust M-detector structure for MUD in non-Gaussian ambient noise.