176 research outputs found
Mechanical properties of fibre metal laminates reinforced with carbon, flax and sugar palm fibre-based composites
Get PDFFibre metal laminate (FML) consists of sheet metal and fibre prepreg stacked
alternatively in 2/1 or 3/2 lay-up and cured to form the laminate. The commercially
available FML such as CARALL (Carbon fibre reinforced aluminum metal laminate),
GLARE (Glass laminate aluminum reinforced epoxy) and ARALL (Aramid fibre
reinforced aluminum metal laminate) based on the synthetic fibres have limitations like
difficulties in recycling, degradability and disposal problems. These factors push the
need for environment friendly material. From the literature review, it has been identified
that the studies on the natural fibre reinforced FML and the metal surface treatments
other than the standard chromic acid anodizing are limited. Also, the impact of aging
effects on the mechanical properties of natural fibre reinforced FML has never been
studied. In this research, a new class of FML reinforced with the carbon fibres and
natural fibres like flax and sugar palm has been fabricated using the hand lay-up and hot
press technique. Their mechanical properties under various loads with respect to the
metal surface treatment, fibre stacking sequence, hygrothermal and sub-zero aging
effects were studied. Based on the results from the experiments, it could be seen that
sanding followed by silane treatment could be used as a metal surface treatment for
FML, as it provides superior properties over the FML with sanded metal surface. Among
the studied configurations, FML with the pure flax fibres exhibited the highest strength,
stiffness and fatigue life. Hybridization of flax with sugar palm also has led to significant
improvement in the properties compared to the FML with sugar palm fibres. On the other
hand, FML specimens exposed to the aging under the moisture/temperature, failed at
lower loads, possessed lower strength and stiffness than the unexposed or dry specimens.
The degradation in properties was more severe in case of hygrothermal conditioning than
the sub-zero exposure. This is because hygrothermal conditioning resulted in 6-8%
increase in thickness swelling due to the moisture absorption by natural fibres in the laminate, weakening of the interfacial bonding strength and degradation of the natural
fibre reinforced composite ply as evident from the presence of multiple cracks in the
microstructure of the hygrothermally aged FML specimens. To summarize, FML with
the pure flax fibres has shown better mechanical properties; longer fatigue life and fibre
bridging effect which is critical to sustain larger number of cycles before the failure. The
degradation in mechanical properties and physical changes in the FML due to the aging
indicates the need to evaluate their behavior if they are required to use in the structures
operating under such environmental conditions
Suitability of electrospun nanofibers for textile applications
No full textElectrospinning technology has started to be used and applied in many different areas today. Electrospinning (or also called electrostatic fiber spinning) is an innovative and effective technique that uses an electric field to produce fine fibers up to nanometers in diameter. These electrospun fibers could be utilized in many different areas as filtration, composite, medical, membrane materials, etc. Commercial production of nanofiber materials and their use in industry are increasing. The increase in the number of commercializable products has increased the interest in nanofiber production. In this chapter, the production of electrospun nanofibers and their use in the textile field are examined. © 2024 selection and editorial matter, Chandrasekar Muthukumar, Senthilkumar Krishnasamy, Senthil Muthu Kumar Thiagamani, and Mariyappan Shanmugam; individual chapters, the contributors
Correcting C-band radar reflectivity and differential reflectivity data for rain attenuation: a self-consistent method with constraints
Get PDFQuantitative use of C-band radar measurements of reflectivity (Zh) and differential reflectivity (Zdr) demands the use of accurate attenuation-correction procedures, especially in convective rain events. With the availability of differential phase measurements (Φdp) with a dual-polarized radar, it is now possible to improve and stabilize attenuation-correction schemes over earlier schemes which did not use Φdp. The recent introduction of constraint-based correction schemes using Φdp constitute an important advance [8], [9]. In this paper, a self-consistent, constraint-based algorithm is proposed and evaluated which extends the previous approaches in several important respects. Radar data collected by the C-POL radar during the South China Sea Monsoon Experiment (SCSMEX) are used to illustrate the correction scheme. The corrected radar data are then compared against disdrometer-based scattering simulations, the disdrometer data being acquired during SCSMEX. A new algorithm is used to retrieve the median volume diameter from the corrected Zh, corrected Zdr, and Kdp radar measurements which is relatively immune to the precise drop axis ratio versus drop diameter relation. Histograms of the radar-retrieved Do compared against Do from disdrometer data are in remarkable good agreement lending further validity to the proposed attenuation-correction scheme, as well as to confidence in the use of C-band radar for the remote measurement of rain microphysics.The work of V. N. Bringi and V. Chandrasekar was supported by the NASA/TRMM Grant NAG5-7717 and -7876
Cross validation of observations from the GPM dual-frequency precipitation radar and dual-polarization S-band ground radars
Get PDF2018 Spring.Includes bibliographical references.This research presents a comparative study of observations and various products of the Global Precipitation Measurement (GPM) Mission Satellite with dual polarization S-Band Ground Radars. The GPM mission is a joint venture by the NASA and the JAXA. The radar on board the core observatory is a dual-frequency precipitation radar (DPR) capable of simultaneously operating at 13.6 GHz (Ku band) and 35.5 GHz (Ka band). The DPR is expected to revolutionize the way precipitation is measured from space through its dual-frequency observations. Ground Validation is one of the most critical aspects of the GPM mission. The best way of doing this is by direct comparison of the space-based observations with well calibrated dual polarization ground radar measurements. Before any direct comparisons can be made, volume matching of the data is necessary due to the difference in observation geometry and resolution volume of both the system. In this study, a methodology developed by Bolen and Chandrasekar (2001) for aligning TRMM satellite data with ground radar data is followed. This technique was extended by Schwaller and Morris (2011). Radar reflectivity and rainfall rate product comparison study have been performed in detail. Vertical profiles have been studied thoroughly. Various case studies of simultaneous GPM-DPR and ground radar observations have been carefully chosen. Ground validation operational NEXRAD sites have been considered from all over the USA. Comparison studies with research radars such as CSU-CHILL and NASA N-POL have also been conducted. The GPM satellite's profile classification module's products are also evaluated. Results from Hydrometeor classification method by Bechini and Chandrasekar (2015) for ground radars have been extensively used for validating DPR's melting layer detection capability in different types of precipitation system. In this study, a new method developed by Le et al (2017) for identification of snow falling on the ground has been considered. Ground validation comparisons have been performed with observations from ground radars and the results are presented
ROPE: the Rutgers Online Proxy Evaluator
No full textThe Simultaneous Proxy Evaluation (SPE) architecture provides one way to measure the performance of proxy caches. It includes the novel ability to compare prefetching proxy cache performance, but poses a number of implementation challenges. In this report we describe our prototype implementation of SPE, the Rutgers Online Proxy Evaluator (ROPE). We discuss a number of issues raised during development, describe validation tests, and demonstrate the use of our prototype in two experiments to simultaneously evaluate up to four publicly available proxy cache implementations. We measure bandwidth used and response latencies, but also discover unexpected caching bugs in two of the proxies tested.Technical report DCS-TR-44
Flammability of fiber-based composites
No full textIn recent years, the development of composites for enhancement of flame retardant properties has occurred. Studies on this have largely been focused on utilization of jute fabric as structure reinforcement along with biopolymer, such as polylactic acid, as a matrix. These composite matrices are most commonly fabricated using a solution casting technique. The presence of biopolymer within the composite structure plays a decisive role in optimization of the overall performance of bio-nanocomposites. Keeping the focus on biopolymer as a key component, this chapter reveals the current state and future prospective of bio-based nanocomposite structures, along with field applications and unsolved problems
Serine protease identification (in vitro) and molecular structure predictions (in silico) from a phytopathogenic fungus, Alternaria solani
Get PDFCitation: Chandrasekaran, M., Chandrasekar, R., Sa, T., & Sathiyabama, M. (2014). Serine
protease identification (in vitro) and molecular structure predictions (in silico) from a
phytopathogenic fungus, Alternaria solani. Retrieved from http://krex.ksu.eduSerine proteases generally share a relatively high degree of sequence identity and play a major role in the diversity of biological processes. Here we focus on three-dimensional molecular architecture of serine proteases from Alernaria solani. The difference in flexibility of active binding pockets and electrostatic surface potential distribution of serine proteases in comparison with other fungal species is reported in this study. In this study we have purified a serine protease from the early blight pathogen, Alernaria solani. MALDI-TOF-MS/MS analysis revealed that protease produced by A. solani belongs to alkaline serine proteases. AsP is made up of 403 amino acid residues with molecular weight of 42.1kDa (Isoelectric point (pI)-6.51) and molecular formula C[subscript 1859]H[subscript 2930]N[subscript 516]O[subscript 595]S[subscript 4]. The follow-up research on the molecular structure prediction is used for assessing the quality of A. solani Protease (AsP). The AsP protein structure model was built based on its comparative homology with serine protease using the program, MODELER. AsP had 16 β-sheets and 10 α-helices, with Ser[superscript 350] (G347-G357), Asp[superscript 158] (D158-H169) and His[superscript 193] (H193-G203) in separate turn/coil structures. Biological metal binding region situated near the 6th-helix and His[superscript 193] residue is responsible for metal binding site. In addition, the calcium ion is coordinated by the carboxyl groups of Lys[superscript 84], Ile[superscript 85], Lys[superscript 86], Asp[superscript 87], Phe[superscript 88], Ala[superscript 89], Ala[superscript 90] (K84-A90) for first calcium (Ca[superscript 2+]) binding site and carbonyl oxygen atom of Lys[superscript 244], Gly[superscript 245], Arg[superscript 246], Thr[superscript 247], Lys[superscript 248], Lys[superscript 249], and Ala[superscript 250] (K244–A250), for second Ca[superscript 2+] binding site. Moreover, Ramachandran plot analysis of protein residues falling into most favored secondary structures were determined (83.3%). The predicted molecular 3D structural model was further verified using PROCHECK, ERRAT and VADAR servers to confirm the geometry and stereo-chemical parameters of the molecular structural design. The functional analysis of AsP 3D molecular structure predictions familiar in the current study may provide a new perspective in the understanding and identification of antifungal protease inhibitor designing
High-Level Power Estimation and Optimization of DRAMs
No full textEmbedded systems have become an integral part of our life in the last few years in multifarious ways, be it in mobile phones, portable audio players, smart watches or even cars. Most embedded systems fall under the category of consumer electronics, such as televisions, mobile devices, and wearable electronics. With several players competing in this market, manufacturers of embedded systems continue to add more functionality to these devices to make them more user-friendly, and often equip them with a very high resolution display and graphics support, and better computing and Internet capabilities. Unfortunately, they are often constrained by tight power/energy budgets, since battery capacity does not improve at the same rate as computing power. While there is clearly much progress to be made in harnessing all the possibilities of embedded systems, limitations in battery capacities, thermal constraints and power/energy budgets surely hinder this progress. Although technology scaling has traditionally addressed both the power minimization and high-performance requirements, with Moore's law nearing its limits, the development of energy-efficient system designs has become critically important. Thus, to be able to continue to provide new and improved features in embedded systems, design-time and run-time power management and minimization holds the key. As a consequence, power optimization has become one of the most defining aspects of designing modern embedded systems. To design such high-performance and energy-efficient embedded systems, it is extremely important to address two basic issues: (1) accurate estimation of power consumption of all system components during early design stages and (2) deriving power optimization solutions that do not negatively impact system performance. In this thesis, we aim to address these two issues for one of the most important components in modern embedded systems: DRAM memories. Towards this, we propose a high-precision DRAM power model (DRAMPower) and a set of performance-neutral DRAM power-down strategies. DRAMPower is a high-level DRAM power model that performs high-precision modeling of the power consumption of different DRAM operations, state transitions and power-saving modes at the cycle-accurate level. To further improve the accuracy of DRAMPower's power/energy estimates, we derive better than worst-case and realistic measures for the JEDEC current metrics instead of vendor provided worst-case measures from device datasheets. Towards this, we modify a SPICE-based circuit-level DRAM architecture and power model and derive better than worst-case current measures under nominal operating conditions applicable to a majority of DRAM devices (>97%) with any given configuration (capacity, data width and frequency). Besides these better than worst-case current measures, we also propose a generic post-manufacturing power and performance characterization methodology for DRAMs that can help identify the realistic current estimates and optimized set of timing measures for a given DRAM device, thereby further improving the accuracy of the power and energy estimates for that particular DRAM device. To optimize DRAM power consumption, we propose a set of performance-neutral DRAM power-down strategies coupled with a power management policy that for any given use-case (access granularity, page policy and memory type) achieves significant power savings without impacting its worst-case performance (bandwidth and latency) guarantees. We verify the pessimism in DRAM currents and four critical DRAM timing parameters as provided in the datasheets, by experimentally evaluating 48 DDR3 devices of the same configuration. We further derive optimal set of timings using the performance characterization algorithm, at which the DRAM can operate successfully under worst-case run-time conditions, without increasing its energy consumption. We observed up to of 33.3% and 25.9% reduction in DRAM read and write latencies and 17.7% and 15.4% improvement in energy efficiency. We validate DRAMPower model against a circuit-level DRAM power model and verify it against real power measurements from hardware for different DRAM operations. We observed between 1-8% difference in power estimates, with an average of 97% accuracy. We also evaluated the power-management policy and power-down strategies and observed significant energy savings (close to theoretical optimal) at very marginal average-case performance penalty without impacting any of the original latency and bandwidth guarantees.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Preparation and characterization of sugar palm fibers
Get PDFVarious natural products from the sugar palm tree have been in use in Malaysia for hundreds of years. Sugar palm fiber, known as black fiber, is obtained from the sugar palm tree and can be used as reinforcement in composites. Sugar palm fibers are available in ready-to-use form and do not require secondary processing. Fibers can also be obtained from the frond, the bunch, and the trunk, with the main source being the hairy fiber, locally called ijuk, which wraps around the trunk. In this chapter, we review the mechanical, physical, chemical, thermal and moisture absorption properties of the sugar palm fibers studied by various researchers
Polarimetric X-Band weather radar: High-resolution rainfall estimation
No full textWeather observations are conventionally performed by C-band weather radars with spatial and temporal resolution of 1 km and 5 min, respectively. However, in recent years, C-band weather radars have been upgraded from single to dual-polarimetric to improve the quality of their measurements. Still, these spatial and temporal resolutions might be undesirable for the detection of localized heavy rainfall which might be necessary to model fast rainfall-runoff processes in urbanized areas. Therefore, X-band weather radars have been introduced to increase the resolution of rainfall rate (R) estimation. For example, in the USA, a network of dual-polarimetric X-band radars has been used to estimate rainfall rates of severe storms at high-resolution (Wang and Chandrasekar, 2010). In Western Europe, the RainGain project includes a network of X-band radars to obtain high-resolution rainfall rates to cope with urban flooding (http://www.raingain.edu).Atmospheric Remote SensingGeoscience and Remote Sensin
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