Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

A noncontact measurement technique for the density and thermal expansion coefficient of solid and liquid materials

A noncontact measurement technique for the density and the thermal expansion coefficient of refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator (HTESL) at the Jet Propulsion Laboratory in which 2–3 mm diam samples can be levitated, melted, and radiatively cooled in vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045–1565 °C. The result for the liquid phase density can be expressed by rho=8.848+(6.730×10^−4)×T (°C) g/cm^3 within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by beta=(9.419×10^−5) −(7.165×10^−9)×T (°C) K^−1 within 0.2% accuracy

Programmable Spectrometry -- Per-pixel Classification of Materials using Learned Spectral Filters

Many materials have distinct spectral profiles. This facilitates estimation of the material composition of a scene at each pixel by first acquiring its hyperspectral image, and subsequently filtering it using a bank of spectral profiles. This process is inherently wasteful since only a set of linear projections of the acquired measurements contribute to the classification task. We propose a novel programmable camera that is capable of producing images of a scene with an arbitrary spectral filter. We use this camera to optically implement the spectral filtering of the scene's hyperspectral image with the bank of spectral profiles needed to perform per-pixel material classification. This provides gains both in terms of acquisition speed --- since only the relevant measurements are acquired --- and in signal-to-noise ratio --- since we invariably avoid narrowband filters that are light inefficient. Given training data, we use a range of classical and modern techniques including SVMs and neural networks to identify the bank of spectral profiles that facilitate material classification. We verify the method in simulations on standard datasets as well as real data using a lab prototype of the camera

High-speed imaging in fluids

High-speed imaging is in popular demand for a broad range of experiments in fluids. It allows for a detailed visualization of the event under study by acquiring a series of image frames captured at high temporal and spatial resolution. This review covers high-speed imaging basics, by defining criteria for high-speed imaging experiments in fluids and to give rule-of-thumbs for a series of cases. It also considers stroboscopic imaging, triggering and illumination, and scaling issues. It provides guidelines for testing and calibration. Ultra high-speed imaging at frame rates exceeding 1 million frames per second is reviewed, and the combination of conventional experiments in fluids techniques with high-speed imaging techniques are discussed. The review is concluded with a high-speed imaging chart, which summarizes criteria for temporal scale and spatial scale and which facilitates the selection of a high-speed imaging system for the applicatio

Mapping immaterial flows : how consumption invisibilizes labor : the satellite and shipping container

The kiosk system went down and everyone missed their flight. I had this experience recently at Chicago O’Hare International airport when I was flying to Austin. It affirmed the importance of understanding networks and how their working (or in this case, the lack thereof) immobilizes goods and people. Usually, when you check in for a flight, there is a kiosk, a station where you can print out your ticket, bag tags, and receipt. This automation of airline customers and their luggage is routine and due to its speed, allows a lot more people to obtain services. A standard of speed and ease of access is therefore coupled and expected. When this automation is no longer available, people lose their shit or more elegantly stated, the artifice of entitlement becomes gruesomely apparent. I understand everyone has a place to go and we won’t get their soon enough. However, the system is down and the airline workers are doing their best. Of course, once the network is back in place, the kiosks will resume operation and yes, they will arrange a later flight. But in a global economy where networked spaces are equated solely to make money at an expedient pace, how do we get people to understand other ways to respond to a malfunction? The common assumption is that systems are supposed to be perfect and a glitch or a malfunction is an exception, however it is quite the reverse. What if networks weren’t based on dualism? The binary being either: an all digital internet of everything kind of space or a cyberpunk infused reversion to the analog. Instead, what should be thought of and put into place is a multiplicity of network configurations such as A to Z, alif to bari yay, 1 to a 1000, uno to millón. This is what I propose in my research and arts practice: how do we build multiplicity and equity in systems? Networks are not arbitrarily put into place, they have funders, users, buyers, beneficiaries, and losers involved. Therefore, they are porous flows, exchanges, and axioms, always open to change. My research lies in between histories of media, technology, and globalization. I investigate these themes through performance, sculptural installations, reading groups, and workshops that focus on the role of technology. Specifically, my practice is focused on objects that are produced from global circuits and their embedded codes, encompassing both the technological and sociological. I investigate the history of objects such as the satellites and shipping containers and make immaterial streams tangible. The specific objects of the satellite and shipping container carry information that frames notion of historic and present day globalization facilitated by technology. The sections of this text are not necessary meant to be read sequentially, there are organized like nodes. In the first node, I will examine the role of satellites in my projects, Satellites and TELL A STAR. Satellites project examines Our World, the first global transmission (1967) through a sculptural installation, video and website. This project critiques the notion of techno-utopianism, a idea that technology will resolve all inequalities plaguing humanity. Then, I will review TELL A STAR, a 3-channel installation, where I divert the history of the first American satellite, Telstar (1962) through the lens of Afrofuturism, archival research and fluidity of identity. In the second node, I will review my project, Con-tain-er, its installation and performative elements and the role of “flows” within global shipping networks. Near the ending node, the role of networks, “junk,” and the use of workshops will be examined as part of my arts practice. Demanding the creation of more inclusive and divergent networks is central to imagining fluidity. It is within reach, we need to imagine it.Studio Ar

Design of a scanning laser radar for spaceborne applications, phase 3

Design of scanning laser radar for spaceborne application

Speeding up liquid crystal SLMs using overdrive with phase change reduction

Nematic liquid crystal spatial light modulators (SLMs) with fast switching times and high diffraction efficiency are important to various applications ranging from optical beam steering and adaptive optics to optical tweezers. Here we demonstrate the great benefits that can be derived in terms of speed enhancement without loss of diffraction efficiency from two mutually compatible approaches. The first technique involves the idea of overdrive, that is the calculation of intermediate patterns to speed up the transition to the target phase pattern. The second concerns optimization of the target pattern to reduce the required phase change applied to each pixel, which in addition leads to a substantial reduction of variations in the intensity of the diffracted light during the transition. When these methods are applied together, we observe transition times for the diffracted light fields of about 1 ms, which represents up to a tenfold improvement over current approaches. We experimentally demonstrate the improvements of the approach for applications such as holographic image projection, beam steering and switching, and real-time control loops

Design strategies for optimizing holographic optical tweezers setups

We provide a detailed account of the construction of a system of holographic optical tweezers. While much information is available on the design, alignment and calibration of other optical trapping configurations, those based on holography are relatively poorly described. Inclusion of a spatial light modulator in the setup gives rise to particular design trade-offs and constraints, and the system benefits from specific optimization strategies, which we discuss.Comment: 16 pages, 15 figure

Programmable diffractive optics for laser scanning confocal microscopy

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