Development of an Automated Multiple Material Stereolithography Machine

An automated Multiple Material Stereolithography (MMSL) machine was developed by integrating components of a 3D Systems 250/50 stereolithography (SL) machine in a separate stand-alone system and adapting them to function with additional components required for MMSL operation. We previously reported retrofitting a 250/50 SL machine with multiple vats to accommodate multiple material fabrication for building a wide variety of multi-material models (Wicker et al., 2004). In the MMSL retrofit, spatial constraints limited the multiple vats located circumferentially on a vertical rotating vat carousel to cross-sectional areas of approximately 4.5-inches by 4.5-inches. The limited build size of the retrofitted 250/50 motivated the full development of a new system with multiple material build capabilities comparable to the build envelope of the original 250/50 machine. The new MMSL machine required fabrication of a large system frame, incorporating various 250/50 components and software, and adding a variety of new components and software. By using many existing components and software, the previous engineering development of 3D Systems could be directly applied to this new technology. Components that were transferred from an existing 250/50 to the MMSL machine included the complete optical system (including the optics plate with laser, mirrors, beam expander, scanning mirrors, and focusing lens), the rim assembly (including the laser beam profilers), the associated controllers (computer system, scanning mirror controller, power supply-vat controller) and the wiring harness. In addition to the new frame, the MMSL machine required the development of a new rotating vat carousel system, platform assembly, multi-pump filling/leveling system, and a custom LabVIEW® control system to provide automated control over the MMSL process. The overall operation of the MMSL system was managed using the LabVIEW® program, which also included controlling a new vat leveling system and new linear and rotational stages, while the 3D Systems software (Buildstation 4.0) was retained for controlling the laser scanning process. As a demonstration of MMSL technology, simple multi material parts were fabricated with vertically and horizontally oriented interfaces. The fully functional MMSL system offers enormous potential for fabricating a wide variety of multiple material functional devices.Mechanical Engineerin

Multiple test chamber exposes materials to various environments

Multiple compartment test chamber exposes several material specimens to various environmental conditions for prolonged periods. The specimens are individually mounted in chamber compartments, rotated to various positions, and measured through optical windows to determine progressive changes in the material properties

Study of multiple hologram recording in lithium niobate

The results of detailed experimental and theoretical considerations relating to multiple hologram recording in lithium niobate are reported. The following problem areas are identified and discussed: (1) the angular selectivity of the stored holograms, (2) interference effects due to the crystal surfaces, (3) beam divergence effects, (4) material recording sensitivity, and (5) scattered light from material inhomogeneities

Don't interpret focus : why a presuppositional account of focus fails, and how a presuppositional account of givenness works

This paper advances a purely presuppositional analysis of intonation. I first show that a inspiring recent article by Geurts and van der Sandt (Theoretical Linguistics, 2004) that pursues the same goal cannot account for multiple foci. Then, I show that if it is assumed that destressed rather than focussed material is semantically marked, multiple foci are accounted for correctly

Using Individual and Group Multiple-Choice Quizzes to Deepen Students\u27 Learning

For years, I was highly skeptical about using multiple-choice questions to assess law students\u27 learning.\u27 Clients, after all, do not ask lawyers to solve multiple-choice problems. I have realized, however, that multiple-choice quizzes can be a highly effective technique to include in any doctrinal class. Well-designed multiple-choice quizzes can help students in any size class learn foundational doctrine, provide feedback to teachers and students, develop students\u27 interpersonal skills, and prepare students for the bar exam. Having used multiple-choice quizzes in first year and upper-level courses for several years, I now value multiple-choice quizzes as an effective first step in preparing students to engage in solving complex legal problems. When used with other assessments\u27 as part of a comprehensive, coherent, and intentional overall course design, multiple-choice quizzes are effective in preparing law students for the deep learning necessary to practice law effectively. This Article focuses on a particular approach to using multiple choice quizzes. In this approach, a one-semester course is broken into five to seven modules, and students individually complete a scheduled, closed-book, multiple-choice quiz toward the beginning of each new course module, before the material is formally covered in class but after students have completed reading on the topic. Each quiz primarily tests students on foundational doctrine for the new module and incorporates previous course material. After taking the multiple choice quiz individually, students immediately retake the same quiz in small groups, earning grades for both their individual and group quiz scores. Following the group quiz, students can appeal the answers their group got wrong. At the end of the multiple-choice quiz process, the teacher provides a mini-lecture, focusing on those multiple-choice questions and topics that were most challenging. This Article first shows why using this method of multiple-choice quizzes is effective and appropriate in law school doctrinal classes. The remainder of the Article suggests how to design and use these quizzes to maximize their effectiveness

Storage battery comprising negative plates of a wedge shaped configuration

An improved silver-zinc battery particularly suited for use in an environment where battery operation is subjected to multiple charge/discharge cycling over extended periods is described. The battery seperator system, containing a highly absorbent material continguous with the surfaces of the plates and multiple semi-permeable membranes interposed between the plates, is also characterized

Joint Material and Illumination Estimation from Photo Sets in the Wild

Faithful manipulation of shape, material, and illumination in 2D Internet images would greatly benefit from a reliable factorization of appearance into material (i.e., diffuse and specular) and illumination (i.e., environment maps). On the one hand, current methods that produce very high fidelity results, typically require controlled settings, expensive devices, or significant manual effort. To the other hand, methods that are automatic and work on 'in the wild' Internet images, often extract only low-frequency lighting or diffuse materials. In this work, we propose to make use of a set of photographs in order to jointly estimate the non-diffuse materials and sharp lighting in an uncontrolled setting. Our key observation is that seeing multiple instances of the same material under different illumination (i.e., environment), and different materials under the same illumination provide valuable constraints that can be exploited to yield a high-quality solution (i.e., specular materials and environment illumination) for all the observed materials and environments. Similar constraints also arise when observing multiple materials in a single environment, or a single material across multiple environments. The core of this approach is an optimization procedure that uses two neural networks that are trained on synthetic images to predict good gradients in parametric space given observation of reflected light. We evaluate our method on a range of synthetic and real examples to generate high-quality estimates, qualitatively compare our results against state-of-the-art alternatives via a user study, and demonstrate photo-consistent image manipulation that is otherwise very challenging to achieve