2,786 research outputs found

    Characterization by full-size testing of pultruded frame joints for the Startlink house

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    Presented in this paper are test results to determine the moment-rotation characteristics of joint details for a portal frame specific to a pultruded fiber reinforced polymer assembly for the Startlink house. Two joints having beam-to-column dowel connections, with and without extra adhesively bonding, were statically loaded in increments of moment or rotation to ultimate failure. The floor beam and stud column members are bespoke closed-sections developed for the Startlink lightweight building system. The serviceability design calculations for the demonstrator house to be constructed in Bourne, England, assumed the frame’s joints to be rigid. Clauses in EN 1993-1-8:2005 have been applied to classify the measured rotational stiffnesses against the rigid requirement, and an evaluation is made of the modes of failure with respect to the joint’s design moments. Only the joint with extra bonding between the mating surfaces of members is found to be classified as rigid. Both joints are shown to have an acceptable joint strength

    Carbon--The First Frontier of Information Processing

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    Information is often encoded as an aperiodic chain of building blocks. Modern digital computers use bits as the building blocks, but in general the choice of building blocks depends on the nature of the information to be encoded. What are the optimal building blocks to encode structural information? This can be analysed by substituting the operations of addition and multiplication of conventional arithmetic with translation and rotation. It is argued that at the molecular level, the best component for encoding discretised structural information is carbon. Living organisms discovered this billions of years ago, and used carbon as the back-bone for constructing proteins that function according to their structure. Structural analysis of polypeptide chains shows that an efficient and versatile structural language of 20 building blocks is needed to implement all the tasks carried out by proteins. Properties of amino acids indicate that the present triplet genetic code was preceded by a more primitive one, coding for 10 amino acids using two nucleotide bases.Comment: (v1) 9 pages, revtex. (v2) 10 pages. Several arguments expanded to make the article self-contained and to increase clarity. Applications pointed out. (v3) 11 pages. Published version. Well-known properties of proteins shifted to an appendix. Reformatted according to journal styl

    Peripheral soldering of flip chip joints on passive RFID tags

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    Flip chip is the main component of a RFID tag. It is used in billions each year in electronic packaging industries because of its small size, high performance and reliability as well as low cost. They are used in microprocessors, cell phones, watches and automobiles. RFID tags are applied to or incorporated into a product, animal, or person for identification and tracking using radio waves. Some tags can be read from several meters away or even beyond the line of sight of the reader. Passive RFID tags are the most common type in use that employ external power source to transmit signals. Joining chips by laser beam welding have wide advantages over other methods of joining, but they are seen limited to transparent substrates. However, connecting solder bumps with anisotropic conductive adhesives (ACA) produces majority of the joints. A high percentage of them fail in couple of months, particularly when exposed to vibration. In the present work, failure of RFID tags under dynamic loading or vibration was studied; as it was identified as one of the key issue to explore. Earlier investigators focused more on joining chip to the bump, but less on its assembly, i.e., attaching to the substrate. Either of the joints, between chip and bump or between antenna and bump can fail. However, the latter is more vulnerable to failure. Antenna is attached to substrate, relatively fixed when subjected to oscillation. It is the flip chip not the antenna moves during vibration. So, the joint with antenna suffers higher stresses. In addition to this, the strength of the bonding agent i.e., ACA also much smaller compared to the metallic bond at the other end of the bump. Natural frequency of RFID tags was calculated both analytically and numerically, found to be in kilohertz range, high enough to cause resonance. Experimental investigations were also carried out to determine the same. However, the test results for frequency were seen to be in hundred hertz range, common to some applications. It was recognized that the adhesive material, commonly used for joining chips, was primarily accountable for their failures. Since components to which the RFID tags are attached to experience low frequency vibration, chip joints fail as they face resonance during oscillation. Adhesives having much lower modulus than metals are used for attaching bumps to the substrate antennas, and thus mostly responsible for this reduction in natural frequency. Poor adhesive bonding strength at the interface and possible rise in temperature were attributed to failures under vibration. In order to overcome the early failure of RFID tag joints, Peripheral Soldering, an alternative chip joining method was devised. Peripheral Soldering would replace the traditional adhesive joining by bonding the peripheral surface of the bump to the substrate antenna. Instead of joining solder bump directly to the antenna, holes are to be drilled through antenna and substrate. S-bond material, a less familiar but more compatible with aluminum and copper, would be poured in liquid form through the holes on the chip pad. However, substrates compatible to high temperature are to be used; otherwise temperature control would be necessary to avoid damage to substrate. This S-bond would form metallic joints between chip and antenna. Having higher strength and better adhesion property, S-bond material provides better bonding capability. The strength of a chip joined by Peripheral Soldering was determined by analytical, numerical and experimental studies. Strength results were then compared to those of ACA. For a pad size of 60 micron on a 0.5 mm square chip, the new chip joints with Sbond provide an average strength of 0.233N analytically. Numerical results using finite element analysis in ANSYS 11.0 were about 1% less than the closed form solutions. Whereas, ACA connected joints show the maximum strength of 0.113N analytically and 0.1N numerically. Both the estimates indicate Peripheral Soldering is more than twice stronger than adhesive joints. Experimental investigation was carried out to find the strength attained with S-bond by joining similar surfaces as those of chip pad and antenna, but in larger scale due to limitation in facilities. Results obtained were moderated to incorporate the effect of size. Findings authenticate earlier predictions of superior strengths with S-bond. A comparison with ACA strength, extracted from previous investigations, further indicates that S-bond joints are more than 10 times stronger. Having higher bonding strength than in ACA joints, Peripheral Soldering would provide better reliability of the chip connections, i.e., RFID tags. The benefits attained would pay off complexities involved in tweaking

    The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey

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    We present the design and performance of the multi-object fiber spectrographs for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999 on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, the spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II surveys, enabling a wide variety of Galactic and extra-galactic science including the first observation of baryon acoustic oscillations in 2005. The spectrographs were upgraded in 2009 and are currently in use for BOSS, the flagship survey of the third-generation SDSS-III project. BOSS will measure redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alpha absorption of 160,000 high redshift quasars over 10,000 square degrees of sky, making percent level measurements of the absolute cosmic distance scale of the Universe and placing tight constraints on the equation of state of dark energy. The twin multi-object fiber spectrographs utilize a simple optical layout with reflective collimators, gratings, all-refractive cameras, and state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in two channels over a bandpass covering the near ultraviolet to the near infrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on proven heritage, the spectrographs were upgraded for BOSS with volume-phase holographic gratings and modern CCD detectors, improving the peak throughput by nearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000 nm, and increasing the number of fibers from 640 to 1000 per exposure. In this paper we describe the original SDSS spectrograph design and the upgrades implemented for BOSS, and document the predicted and measured performances.Comment: 43 pages, 42 figures, revised according to referee report and accepted by AJ. Provides background for the instrument responsible for SDSS and BOSS spectra. 4th in a series of survey technical papers released in Summer 2012, including arXiv:1207.7137 (DR9), arXiv:1207.7326 (Spectral Classification), and arXiv:1208.0022 (BOSS Overview

    Identifying future assembly methods in Scania´s wheel axle factory

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    Robot Learning-Based Pipeline for Autonomous Reshaping of a Deformable Linear Object in Cluttered Backgrounds

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    open2noThis work was supported in part by the European Union’s Horizon 2020 Research and Innovation Program as part of RIA Project Robotic tEchnologies for the Manipulation of cOmplex DeformablE Linear objects (REMODEL) under Grant 870133.In this work, the robotic manipulation of a highly Deformable Linear Object (DLO) is addressed by means of a sequence of pick-and-drop primitives driven by visual data. A decision making process learns the optimal grasping location exploiting deep Q-learning and finds the best releasing point from a path representation of the DLO shape. The system effectively combines a state-of-the-art algorithm for semantic segmentation specifically designed for DLOs with deep reinforcement learning. Experimental results show that our system is capable to manipulate a DLO into a variety of different shapes in few steps. The intermediate steps of deformation that lead the object from its initial configuration to the target one are also provided and analyzed.openZanella R.; Palli G.Zanella R.; Palli G

    Nonterrestrial utilization of materials: Automated space manufacturing facility

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    Four areas related to the nonterrestrial use of materials are included: (1) material resources needed for feedstock in an orbital manufacturing facility, (2) required initial components of a nonterrestrial manufacturing facility, (3) growth and productive capability of such a facility, and (4) automation and robotics requirements of the facility

    A double-sided silicon micro-strip super-module for the ATLAS inner detector upgrade in the high-luminosity LHC

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    The ATLAS experiment is a general purpose detector aiming to fully exploit the discovery potential of the Large Hadron Collider (LHC) at CERN. It is foreseen that after several years of successful data-taking, the LHC physics programme will be extended in the so-called High-Luminosity LHC, where the instantaneous luminosity will be increased up to 5 × 1034 cm−2 s−1. For ATLAS, an upgrade scenario will imply the complete replacement of its internal tracker, as the existing detector will not provide the required performance due to the cumulated radiation damage and the increase in the detector occupancy. The current baseline layout for the new ATLAS tracker is an all-silicon-based detector, with pixel sensors in the inner layers and silicon micro-strip detectors at intermediate and outer radii. The super-module is an integration concept proposed for the strip region of the future ATLAS tracker, where double-sided stereo silicon micro-strip modules are assembled into a low-mass local support structure. An electrical super-module prototype for eight double-sided strip modules has been constructed. The aim is to exercise the multi-module readout chain and to investigate the noise performance of such a system. In this paper, the main components of the current super-module prototype are described and its electrical performance is presented in detail

    PCB Quality Metrics that Drive Reliability (PD 18)

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    Risk based technology infusion is a deliberate and systematic process which defines the analysis and communication methodology by which new technology is applied and integrated into existing and new designs, identifies technology development needs based on trends analysis and facilitates the identification of shortfalls against performance objectives. This presentation at IPC Works Asia Aerospace 2019 Events provides the audience a snapshot of quality variations in printed wiring board quality, as assessed, using experiences in processing and risk analysis of PWB structural integrity coupons. The presentation will focus on printed wiring board quality metrics used, the relative type and number of non-conformances observed and trend analysis using statistical methods. Trend analysis shows the top five non-conformances observed across PWB suppliers, the root cause(s) behind these non-conformance and suggestions of mitigation plans. The trends will then be matched with the current state of the PWB supplier base and its challenges and opportunities. The presentation further discusses the risk based SMA approaches and methods being applied at GSFC for evaluating candidate printed wiring board technologies which promote the adoption of higher throughput and faster processing technology for GSFC missions
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