Passive vibration isolation of reaction wheel disturbances using a low frequency flexible space platform

Reaction wheel assemblies (RWAs) are momentum exchange devices used in fine pointing control of spacecrafts. Even though the spinning rotor of the reaction wheel is precisely balanced to minimize emitted vibration due to static and dynamic imbalances, precision instrument payloads placed in the neighborhood can always be severely impacted by residual vibration forces emitted by reaction wheel assemblies. The reduction of the vibration level at sensitive payloads can be achieved by placing the RWA on appropriate mountings. A low frequency flexible space platform consisting of folded continuous beams has been designed to serve as a mount for isolating a disturbance source in precision payloads equipped spacecrafts. Analytical and experimental investigations have been carried out to test the usefulness of the low frequency flexible platform as a vibration isolator for RWAs. Measurements and tests have been conducted at varying wheel speeds, to quantify and characterize the amount of isolation obtained from the reaction wheel generated vibration. These tests are further extended to other variants of similar design in order to bring out the best isolation for given disturbance loads. Both time and frequency domain analysis of test data show that the flexible beam platform as a mount for reaction wheels is quite effective and can be used in spacecrafts for passive vibration control. (C) 2011 Elsevier Ltd. All rights reserved.

Unzipping and binding of small interfering RNA with single walled carbon nanotube: A platform for small interfering RNA delivery

In an effort to design efficient platform for siRNA delivery, we combine all atom classical and quantum simulations to study the binding of small interfering RNA (siRNA) by pristine single wall carbon nanotube (SWCNT). Our results show that siRNA strongly binds to SWCNT surface via unzipping its base-pairs and the propensity of unzipping increases with the increase in the diameter of the SWCNTs. The unzipping and subsequent wrapping events are initiated and driven by van der Waals interactions between the aromatic rings of siRNA nucleobases and the SWCNT surface. However, molecular dynamics (MD) simulations of double strand DNA (dsDNA) of the same sequence show that the dsDNA undergoes much less unzipping and wrapping on the SWCNT in the simulation time scale of 70 ns. This interesting difference is due to smaller interaction energy of thymidine of dsDNA with the SWCNT compared to that of uridine of siRNA, as calculated by dispersion corrected density functional theory (DFT) methods. After the optimal binding of siRNA to SWCNT, the complex is very stable which serves as one of the major mechanisms of siRNA delivery for biomedical applications. Since siRNA has to undergo unwinding process with the effect of RNA-induced silencing complex, our proposed delivery mechanism by SWCNT possesses potential advantages in achieving RNA interference. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3682780]

Design and implementation of spectrum sensing for cognitive radios with a frequency-hopping primary system

In this work, spectrum sensing for cognitive radios is considered in the presence of multiple Primary Users (PU) using frequency-hopping communication over a set of frequency bands. The detection performance of the Fast Fourier Transform (FFT) Average Ratio (FAR) algorithm is obtained in closed-form, for a given FFT size and number of PUs. The effective throughput of the Secondary Users (SU) is formulated as an optimization problem with a constraint on the maximum allowable interference on the primary network. Given the hopping period of the PUs, the sensing duration that maximizes the SU throughput is derived. The results are validated using Monte Carlo simulations. Further, an implementation of the FAR algorithm on the Lyrtech (now, Nutaq) small form factor software defined radio development platform is presented, and the performance recorded through the hardware is observed to corroborate well with that obtained through simulations, allowing for implementation losses. (C) 2015 Elsevier B.V. All rights reserved.

The W-11-4A platform comprehensive strength monitoring system

A comprehensive strength monitoring system used on a fixed jacket platform is presented in this paper. The long-term monitoring of W-11-4A platform achieved. Structural responses (strain and acceleration) at selected locations, as well as associated environmental parameters, have been obtained. The emphasis of the paper is placed on the system design, and the instrumentation and operation methodology employed in the monitoring of the structural responses. The performance of the system and the characteristic results obtained during its 13-month operation are also summarized.

A design for commercial production of catfish (Clarias lazera) in multiple cages

The findings are given of a preliminary study on the appropriate economical feeding rate which would enhance the growth of catfish (Clarias lazera) in cages in Lyi-ojoo Lake, Nike, Nigeria, providing also the details of the design of a practical floating platform that can be used for the culture of fish in multiple cages

Experimental Research On Fatigue Property Of Steel Rubber Vibration Isolator For Offshore Jacket Platform In Cold Environment

Jacket platform is the most widely used offshore platform. Steel rubber vibration isolator and damping isolation system are often used to reduce or isolate the ice-induced and seismic-induced vibrations. The previous experimental and theoretical studies concern mostly with dynamic properties, vibration isolation schemes and vibration-reduction effectiveness analysis. In this paper, the experiments on steel rubber vibration isolator were carried out to investigate the compressive properties and fatigue properties in different low temperature conditions. The results may provide some guidelines for design of steel rubber vibration isolator for offshore platform in a cold environment, and for maintenance and replacement of steel rubber vibration isolator, and also for fatigue life assessment of the steel rubber vibration isolator. (C) 2009 Elsevier Ltd. All rights reserved.

Tissue engineering active biological machines : bio-inspired design, directed self-assembly, and characterization of muscular pumps simulating the embryonic heart

Biological machines are active devices that are comprised of cells and other biological components. These functional devices are best suited for physiological environments that support cellular function and survival. Biological machines have the potential to revolutionize the engineering of biomedical devices intended for implantation, where the human body can provide the required physiological environment. For engineering such cell-based machines, bio-inspired design can serve as a guiding platform as it provides functionally proven designs that are attainable by living cells. In the present work, a systematic approach was used to tissue engineer one such machine by exclusively using biological building blocks and by employing a bio-inspired design. Valveless impedance pumps were constructed based on the working principles of the embryonic vertebrate heart and by using cells and tissue derived from rats. The function of these tissue-engineered muscular pumps was characterized by exploring their spatiotemporal and flow behavior in order to better understand the capabilities and limitations of cells when used as the engines of biological machines.

Design and construction of a static tester for blue ray optical storage

Blue ray optical storage is one of the important trends in the area of information storage, and attracts a number of researchers. Static tester for blue ray optical storage plays an important role in storage media research. We designed and constructed a static tester, in which modularization makes it very convenient to expand function. Employment of modulation/demodulation technique weakens test error so as to increase test precision. Focus move mode and the nano-positioners facilitate the relocation of recording marks. Only one laser with wavelength 406.7 nm is used. In this paper, system design and characteristics are represented in detail, and some experimental results are also given to show that the static tester can perform successfully, acting as research platform for blue ray optical storage. (c) 2005 Elsevier GmbH. All rights reserved.

Intrinsic motivation and design of ICT for the ageing population

Chapter 11 Intrinsic Motivation and Design of ICT for ... Information and Communication Technology (ICT) systems provide an increasingly promising platform with which to improve the efficiency and effectiveness of healthcare, ...

Risk based lifetime costs assessment of a ground source heat pump (GSHP) system design: Methodology and case study

Space heating accounts for a large portion of the world's carbon dioxide emissions. Ground Source Heat Pumps (GSHPs) are a technology which can reduce carbon emissions from heating and cooling. GSHP system performance is however highly sensitive to deviation from design values of the actual annual energy extraction/rejection rates from/to the ground. In order to prevent failure and/or performance deterioration of GSHP systems it is possible to incorporate a safety factor in the design of the GSHP by over-sizing the ground heat exchanger (GHE). A methodology to evaluate the financial risk involved in over-sizing the GHE is proposed is this paper. A probability based approach is used to evaluate the economic feasibility of a hypothetical full-size GSHP system as compared to four alternative Heating Ventilation and Air Conditioning (HVAC) system configurations. The model of the GSHP system is developed in the TRNSYS energy simulation platform and calibrated with data from an actual hybrid GSHP system installed in the Department of Earth Science, University of Oxford, UK. Results of the analysis show that potential savings from a full-size GSHP system largely depend on projected HVAC system efficiencies and gas and electricity prices. Results of the risk analysis also suggest that a full-size GSHP with auxiliary back up is potentially the most economical system configuration. © 2012 Elsevier Ltd.

Design and formulation of functional pluripotent stem cell-derived cardiac microtissues.

Access to robust and information-rich human cardiac tissue models would accelerate drug-based strategies for treating heart disease. Despite significant effort, the generation of high-fidelity adult-like human cardiac tissue analogs remains challenging. We used computational modeling of tissue contraction and assembly mechanics in conjunction with microfabricated constraints to guide the design of aligned and functional 3D human pluripotent stem cell (hPSC)-derived cardiac microtissues that we term cardiac microwires (CMWs). Miniaturization of the platform circumvented the need for tissue vascularization and enabled higher-throughput image-based analysis of CMW drug responsiveness. CMW tissue properties could be tuned using electromechanical stimuli and cell composition. Specifically, controlling self-assembly of 3D tissues in aligned collagen, and pacing with point stimulation electrodes, were found to promote cardiac maturation-associated gene expression and in vivo-like electrical signal propagation. Furthermore, screening a range of hPSC-derived cardiac cell ratios identified that 75% NKX2 Homeobox 5 (NKX2-5)+ cardiomyocytes and 25% Cluster of Differentiation 90 OR (CD90)+ nonmyocytes optimized tissue remodeling dynamics and yielded enhanced structural and functional properties. Finally, we demonstrate the utility of the optimized platform in a tachycardic model of arrhythmogenesis, an aspect of cardiac electrophysiology not previously recapitulated in 3D in vitro hPSC-derived cardiac microtissue models. The design criteria identified with our CMW platform should accelerate the development of predictive in vitro assays of human heart tissue function.

Design and control of a climbing robot based on hot melt adhesion

Robust climbing in unstructured environments has been one of the long-standing challenges in robotics research. Among others, the control of large adhesion forces is still an important problem that significantly restricts the locomotion performance of climbing robots. The main contribution of this paper is to propose a novel approach to autonomous robot climbing which makes use of hot melt adhesion (HMA). The HMA material is known as an economical solution to achieve large adhesion forces, which can be varied by controlling the material temperature. For locomotion on both inclined and vertical walls, this paper investigates the basic characteristics of HMA material, and proposes a design and control of a climbing robot that uses the HMA material for attaching and detaching its body to the environment. The robot is equipped with servomotors and thermal control units to actively vary the temperature of the material, and the coordination of these components enables the robot to walk against the gravitational forces even with a relatively large body weight. A real-world platform is used to demonstrate locomotion on a vertical wall, and the experimental result shows the feasibility and overall performances of this approach. © 2013 Elsevier B.V. All rights reserved.

The design and verification of FPGA CAD toolset

This paper introduces a complete CAD toolset for the implementation of digital logic in a Field-Programmable Gate Array (FPGA) platform. Compared with existing academic toolsets, this toolset introduces formal verification in each step of the tool flow, especially the formal verification of the configuration bitstream. The FPGA CAD tool verification flow using Formality is presented in detail. Using plug-in technology, we have developed an integrated FPGA design kit to incorporate all tools together.

Design of the IMP microbeam irradiation system for 100 MeV/u heavy ions

Abstract A state-of-the-art high energy heavy ion microbeam irradiation system is constructed at the Institute of Modern Physics of the Chinese Academy of Sciences. This microbeam system operates in both full current intensity mode and single ion mode. It delivers a predefined number of ions to preselected targets for research in biology and material science. The characteristic of this microbeam system is high energy and vertical irradiation. A quadrupole focusing system, in combination with a series of slits, has been designed to optimize the spatial resolution. A symmetrically achromatic system leads the beam downwards and serves simultaneously as an energy analyzer. A high gradient quadrupole triplet finally focuses a C6+ ion beam to 1 µm in the vacuum chamber within the energy range from 10 MeV/u to 100 MeV/u. In this paper, the IMP microbeam system is described in detail. A systematic investigation of the ion beam optics of this microbeam system is presented together with the associated aberrations. Comparison is made between the IMP microbeam system and the other existing systems to further discuss the performance of this microbeam. Then the optimized initial beam parameters are given for high resolution and high hitting efficiency. At last, the experiment platform is briefly introduced.