Array Of Blocks Research Articles

X-code double parity array operation with two disk failures

X-code extends parity coding for correcting single disk failures in RAID 5 to two disks. Similar to RAID 6 X-code uses the minimum level of redundancy by dedicating the capacity of two out of N disks to check disks, but unlike RAID 6 it solely relies on parity codes, which are placed horizontally rather than vertically. The parity groups in X-code are defined as diagonals with positive and negative slopes. This study is mainly concerned with X-code arrays with two disk failures, since it requires a multistep recovery process, while its operation is otherwise similar to RAID 6. We use examples to gain insight into the cost of recovery and to develop an algorithm to estimate recovery cost for reconstructing two failed disks. We observe that disk loads are unbalanced and the overall load increase depends on the separation of the failed disks. Cyclically shifting or randomly permuting successive N × N arrays of blocks may be used to reduce the load increase to the mean across all of the possible ( N − 1 ) / 2 distances of the failed disks. We also present an improvement in recovery cost for single disk failures.

Extreme light-bending power

Metamaterials are best known for their ability to bend light in the opposite direction to that of all materials found in nature. A hidden ability of these man-made materials has now been discovered. See Letter p.369 Metamaterials, artificially designed composites with electromagnetic properties unobtainable in the natural world, are providing new opportunities for fundamental research as well as for useful applications. So far, the search for materials with a negative refractive index has been a priority, but to extend the scope for novel 'transformation optics' applications, materials with an unnaturally high refractive index would be similarly useful. Bumki Min and colleagues have now produced a broadband, flexible terahertz metamaterial with an unprecedentedly high refractive index of 38.6. Based on layered arrays of I-shaped thin gold building blocks, the new metamaterial provides a starting point for work on small-footprint cloaking devices, wide-angle lenses and slow-light devices.

Gas phase synthesis and field emission properties of 3D aligned double walled carbon nanotube/anatase hybrid architectures

A 3D hybrid architecture composed of macroscopic, vertically aligned CNT blocks which are formed via a metal catalyzed CVD process followed by deposition of TiO(2) on the CNT side walls in nanocrystalline or amorphous form is presented. The morphology of the deposited TiO(2) can be tailored by the deposition method employed. Depositing TiO(2) from the gas phase by employing the organometallic precursor Ti[OCH(CH(3))(2)](4) leads to formation of nanocrystalline anatase or rutile particles with a dense coverage on the surface and within the 3D CNT scaffold. Phase pure TiO(2) (anatase) is formed between 500 and 700 °C, while higher temperatures resulted in rutile modification of TiO(2). Below 500 °C, TiO(2) forms an amorphous oxide layer. At higher temperatures such initially formed TiO(2) layers segregate into particles which tend to crystallize. In contrast, when generating TiO(2) by oxidation of Ti metal which is deposited by vaporization onto the 3D CNT block array, and subsequently oxidized in air or controlled O(2) atmosphere this leads to a porous layer with a particular nanostructure on top of the CNT blocks. First studies of the fabrication and field emission of the new 3D CNT/TiO(2) hybrid cathodes display good and stable FE characteristics with onset fields for current density of 1 μA cm(-2) of 1.7 to 1.9 V μm(-1), while the average field enhancement factor is in the range between 2000 and 2500 depending on the O(2) base pressure during the measurements.

LARGE-EDDY SIMULATION ON SCALAR TRANSFER PHENOMENA BETWEEN URBAN SURFACE AND ATMOSPHERE

The authors performed a numerical simulation of scalar transfer phenomena between an urban surface and atmosphere. A parallelized large-eddy simulation model was adopted for the simulation. Two types of regular block arrays, a square array and staggered array, were arranged on the floor of computational domains. It was assumed that area scalar source was installed on the floor of arrays and scalar fluxes were estimated by using a wall function based on a logarithmic law. The results are summarized as follows. (1) The flow statistics of the normalized wind speed and turbulence intensity above a canopy showed good agreement with that obtained experimentally. (2) Scalar profiles shows self-similarity after 3rd rows. (3) Scalar boundary layer develops rapidly especially the edge of the scalar source area because of upward wind due to roughness.

Mathematical Derivation of Spatially-Averaged Momentum Equations for an Urban Canopy Model Using Underlying Concepts of the Immersed Boundary Method

We propose a new approach to derive spatially-averaged momentum equations for an urban canopy model that resolves buildings vertically and not horizontally. First, in order to mathematically describe the actual momentum field as a completely continuous field, the underling concepts of the immersed boundary method are employed, where we assume that (i) the entire simulation space, including that occupied by buildings, is filled with a fluid, and (ii) an external body force field exists that reduces the wind speed to zero at all positions coinciding with the space occupied by the buildings. Then, in order to obtain the required spatially-averaged momentum equations in a self-consistent manner, a spatial-averaging operation is applied to the Navier–Stokes equations that include a term representing the external force field. The applied spatial-averaging operation is equivalent to the conventional spatial filtering operation used in large-eddy simulations. To examine the significance of the subgrid-scale (SGS) stresses of the spatially-averaged momentum equations, a numerical simulation is performed for a flow around a regular array of cubical blocks with a grid resolution that is sufficient to resolve the blocks. By estimating the individual terms in the spatially-averaged momentum equations using the simulation results, we show that the SGS stresses contribute significantly to the spatially-averaged momentum budget, and therefore they should not be neglected in urban canopy modelling.

Afterimage—Mind Frame

Afterimage - Mind Frame is an interactive visual installation in which the 'medium' of the artwork is the mind. That is, it uses the physical phenomenon of afterimage in such a way that the viewer sees a familiar image in an empty picture frame. This is a gallery installation that allows audiences to experience first hand how afterimages work, by seeing a famous painting emerge on a blank canvas simply by focusing on the projection of seemingly random moving white dots. The abstract moving white blocks projected inside the picture frame play for a few seconds then go blank then play again and so on, continuously. When the array of blocks stops moving, an afterimage of a familiar famous painting is revealed in the otherwise blank frame. The array of tiny, moving blocks forms a very vague representation of the original image and although it is not very clear, the audience is eventually able to perceive a well-defined impression of the subject. This occurs because the afterimage forms as a result of a combination of physical and psychological processes. The former relates to how the vision system works and the latter relates to the fact that the original image is retrieved automatically from memory. The image formed by focusing on the moving white blocks projected in the frame is then combined neurologically with the memory of the original image from the brain. Therefore audiences don't see just the afterimage, but the afterimage plus the original image from their own memory, which fills in the details more fully as they remember the original image. Afterimage - Mind Frame encourages the audience to interact, and in a sense, the audience and the piece perform together. This allows for an uncanny glimpse of how perception and memory work together to form the world as they see it.

DERIVATION AND EVALUATION OF SUBGRID SCALE KINETIC ENERGY EQUATION

We derive a subgrid scale (SGS) kinetic energy equation of an urban canopy model by employing the concept used in the immersed boundary method. The spatial averaging operation used in the derivation is equivalent to the conventional filtering operation used in large-eddy simulations (LES). The derived SGS kinetic energy equation has a term concerning the drag force of buildings (external-force term), in addition to the terms of conventional SGS kinetic energy equation. Furthermore, by using the results of a LES of the flow around a regular array of cubical blocks with a grid resolution sufficient to resolve the blocks, we investigate the budget for the time-mean SGS kinetic energy equation. As a result, we confirm that local equilibrium between production term and dissipation term of SGS kinetic energy is not satisfied in the canopy of the cubical blocks; contributions to the gain or loss of SGS kinetic energy from the external-force and dispersion terms are also prominent. The external-force term contributes to the gain of SGS kinetic energy in the most part of the canopy.

Numerical Investigations of Mean Winds Within Canopies of Regularly Arrayed Cubical Buildings Under Neutral Stability Conditions

Recently, several attempts have been made to model the wind velocity in an urban canopy in order to accurately predict the mixing and transport of momentum, heat, and pollutants within and above the canopy on an urban scale. For this purpose, unverified assumptions made by Macdonald (Boundary-Layer Meteorol 97:25–45, 2000) to develop a model for the profile of the mean wind velocity within an urban canopy have been used. In the present study, in order to provide foundations for improving the urban canopy models, the properties of the spatially-averaged mean quantities used to make these assumptions have been investigated by performing large-eddy simulations (LES) of the airflow around square and staggered arrays of cubical blocks with the following plan area densities: λ p = 0.05, 0.11, 0.16, 0.20, 0.25, and 0.33. The LES results confirm that the discrepancy between the spatial average of wind velocity and Macdonald’s five-point average of wind velocity can be large in both types of arrays for large λ p . It is also confirmed that Prandtl’s mixing length varies significantly with height within the canopy, contrary to Macdonald’s assumption for both types of arrays and for both small and large λ p . On the other hand, in accordance with Macdonald’s assumption, the sectional drag coefficient is found to be almost constant with height except in the case of staggered arrays with high λ p .

Advances in labor analgesia.

The pain of childbirth is arguably the most severe pain most women will endure in their lifetimes. The pain of the early first stage of labor arises from dilation of the lower uterine segment and cervix. Pain from the late first stage and second stage of labor arises from descent of the fetus in the birth canal, resulting in distension and tearing of tissues in the vagina and perineum. An array of regional nerve blocks, systemic analgesic, and nonpharmacologic techniques are currently used for labor analgesia. Nonpharmacologic methods are commonly used, but the effectiveness of these techniques generally lacks rigorous scientific study. Continuous labor support has been shown to decrease the use of pharmacologic analgesia and shorten labor. Intradermal water injections decrease back labor pain. Neuraxial labor analgesia (most commonly epidural or combined spinal-epidural) is the most effective method of pain relief during childbirth, and the only method that provides complete analgesia without maternal or fetal sedation. Current techniques commonly combine a low dose of local anesthetic (bupivacaine or ropivacaine) with a lipid soluble opioid (fentanyl or sufentanil). Neuraxial analgesia does not increase the rate of cesarean delivery compared to systemic opioid analgesia; however, dense neuraxial analgesia may increase the risk of instrumental vaginal delivery.

Design for an IO block array in a tile-based FPGA

A design for an IO block array in a tile-based FPGA is presented. Corresponding with the characteristics of the FPGA, each IO cell is composed of a signal path, local routing pool and configurable input/output buffers. Shared programmable registers in the signal path can be configured for the function of JTAG, without specific boundary scan registers/latches, saving layout area. The local routing pool increases the flexibility of routing and the routability of the whole FPGA. An auxiliary power supply is adopted to increase the performance of the IO buffers at different configured IO standards. The organization of the IO block array is described in an architecture description file, from which the array layout can be accomplished through use of an automated layout assembly tool. This design strategy facilitates the design of FPGAs with different capacities or architectures in an FPGA family series. The bond-out schemes of the same FPGA chip in different packages are also considered. The layout is based on SMIC 0.13 μm logic 1P8M salicide 1.2/2.5 V CMOS technology. Our performance is comparable with commercial SRAM-based FPGAs which use a similar process.

Aerodynamic Parameters of Regular Arrays of Rectangular Blocks with Various Geometries

The aerodynamic effects of various configurations of an urban array were investigated in a wind-tunnel experiment. Three aerodynamic parameters characterising arrays—the drag coefficient (Cd), roughness length (zo) and displacement height (d)—are used for analysis. Cd is based on the direct measurement of the total surface shear using a floating element, and the other two parameters are estimated by logarithmic fitting of the measured wind profile and predetermined total drag force. The configurations of 63 arrays used for measurement were designed to estimate the effects of layout, wind direction and the height variability of the blocks on these parameters for various roughness packing densities. The results are summarised as follows: (1) The estimated Cd and zo of the staggered arrays peak against the plan area index (λp) and frontal area index (λf), in contrast with values for the square arrays, which are less sensitive to λp and λf. In addition, the square arrays with a wind direction of 45° have a considerably larger Cd, and the wind direction increases zo/H by up to a factor of 2. (2) The effect of the non-uniformity of roughness height on zo is more remarkable when λf exceeds 20%, and the discrepancy in zo is particularly remarkable and exceeds 200%. (3) The effect of the layout of tall blocks on Cd is stronger than that of short blocks. These results indicate that the effects of both wind direction and the non-uniformity of the heights of buildings on urban aerodynamic parameters vary greatly with λp and λf; hence, these effects should be taken into account by considering the roughness packing density.

Calculation of the Scattered Radiation Profile in 64 Slice CT Scanners Using Experimental Measurement

Introduction: One of the most important parameters in x-ray CT imaging is the noise induced by detected scattered radiation. The detected scattered radiation is completely dependent on the scanner geometry as well as size, shape and material of the scanned object. The magnitude and spatial distribution of the scattered radiation in x-ray CT should be quantified for development of robust scatter correction techniques. Empirical methods based on blocking the primary photons in a small region are not able to extract scatter in all elements of the detector array while the scatter profile is required for a scatter correction procedure. In this study, we measured scatter profiles in 64 slice CT scanners using a new experimental measurement. Material and Methods: To measure the scatter profile, a lead block array was inserted under the collimator and the phantom was exposed at the isocenter. The raw data file, which contained detector array readouts, was transferred to a PC and was read using a dedicated GUI running under MatLab 7.5. The scatter profile was extracted by interpolating the shadowed area. Results: The scatter and SPR profiles were measured. Increasing the tube voltage from 80 to 140 kVp resulted in an 80% fall off in SPR for a water phantom (d=210 mm) and 86% for a polypropylene phantom (d = 350 mm). Increasing the air gap to 20.9 cm caused a 30% decrease in SPR. Conclusion: In this study, we presented a novel approach for measurement of scattered radiation distribution and SPR in a CT scanner with 64-slice capability using a lead block array. The method can also be used on other multi-slice CT scanners. The proposed technique can accurately estimate scatter profiles. It is relatively straightforward, easy to use, and can be used for any related measurement.

Mapping the train model for earthquakes onto the stochastic sandpile model

We perform a computational study of a variant of the “train” model for earthquakes [Phys. Rev. A 46, 6288 (1992)], where we assume a static friction that is a stochastic function of position rather than being velocity dependent. The model consists of an array of blocks coupled by springs, with the forces between neighbouring blocks balanced by static friction. We calculate the probability, P(s), of the occurrence of avalanches with a size s or greater, finding that our results are consistent with the phenomenology and also with previous models which exhibit a power law over a wide range. We show that the train model may be mapped onto a stochastic sandpile model and study a variant of the latter for non-spherical grains. We show that, in this case, the model has critical behaviour only for grains with large aspect ratio, as was already shown in experiments with real ricepiles. We also demonstrate a way to introduce randomness in a physically motivated manner into the model.

Large-eddy simulation for flow and dispersion in urban streets

Large-eddy simulations (LES) with our recently developed inflow approach (Xie, Z.-T., Castro, I.P., 2008a. Efficient generation of inflow conditions for large-eddy simulation of street-scale flows. Flow Turbul. Combust., vol. 81(3), pp. 449–470.) have been used for flow and dispersion within a genuine city area – the DAPPLE site, located at the intersection of Marylebone Rd and Gloucester Pl in Central London. Numerical results up to second-order statistics are reported for a computational domain of 1.2 km (streamwise) × 0.8 km (lateral) × 0.2 km (in full scale), with a resolution down to approximately one meter in space and one second in time. They are in reasonable agreement with the experimental data. Such a comprehensive urban geometry is often, as here, composed of staggered, aligned, square arrays of blocks with non-uniform height and non-uniform base, street canyons and intersections. Both the integrative and local effect of flow and dispersion to these geometrical patterns were investigated. For example, it was found that the peaks of spatially averaged u rms , v rms , w rms and < u′ w′> occurred neither at the mean height nor at the maximum height, but at the height of large and tall buildings. It was also found that the mean and fluctuating concentrations in the near-source field is highly dependent on the source location and the local geometry pattern, whereas in the far field (e.g. >0.1 km) they are not. In summary, it is demonstrated that full-scale resolution of around one meter is sufficient to yield accurate prediction of the flow and mean dispersion characteristics and to provide reasonable estimation of concentration fluctuations.

The effect of a tall tower on flow and dispersion through a model urban neighborhood : Part 2. Pollutant dispersion

This article is the second in a two-paper series presenting results from wind tunnel and computational fluid dynamics (CFD) simulations of flow and dispersion in an idealized model urban neighborhood. Pollutant dispersion results are presented and discussed for a model neighborhood that was characterized by regular city blocks of three-story row houses with a single 12-story tower located at the downwind edge of one of these blocks. The tower had three significant effects on pollutant dispersion in the surrounding street canyons: drawing the plume laterally towards the tower, greatly enhancing the vertical dispersion of the plume in the wake of the tower, and significantly decreasing the residence time of pollutants in the wake of the tower. In the wind tunnel, tracer gas released in the avenue lee of the tower, but several blocks away laterally, was pulled towards the tower and lifted in the wake of the tower. The same lateral movement of the pollutant was seen in the next avenue, which was approximately 2.5 tower heights downwind of the tower. The tower also served to ventilate the street canyon directly in its wake more rapidly than the surrounding areas. This was evidenced by CFD simulations of concentration decay where the residence time of pollutants lee of the 12-story tower was found to be less than half the residence time behind a neighboring three-story building. This same phenomenon of rapid vertical dispersion lee of a tower among an array of smaller buildings was also demonstrated in a separate set of wind tunnel experiments using an array of cubical blocks. A similar decrease in the residence time was observed when the height of one block was increased.

DESIGN OF A 4X4 SQUARE MICROSTRIP PLANAR ARRAY

Wind profiling radars operating in Doppler beam swinging mode needs to have large antenna array in order to have a narrow beam for wind direction accuracy. To meet the above requirement, in the present work an array with 16 elements configured in a 4X4 square matrix is designed. The antenna inserted is a coaxial probe (Probe Feed) to the patch near its resonance in 'L' band is carried out. Principal plane 2-dimensional radiation patterns at 1.28GHz have been computed for single element and 4X4 planar arrays. The results of linearly polarized coaxial probe single element are generated by using IE3D software. Using this single element as basic building block, a2X2 and 4X4 planar arrays was designed. The results obtained are presented succinctly. The inferences from the design of coaxial probe antenna are presented. The Impedance Band-Width, 3-dB Beam Width and Gain for a single element as well as a 4X4 planar array are compared.

An Expanded Set of Amino Acid Analogs for the Ribosomal Translation of Unnatural Peptides

BackgroundThe application of in vitro translation to the synthesis of unnatural peptides may allow the production of extremely large libraries of highly modified peptides, which are a potential source of lead compounds in the search for new pharmaceutical agents. The specificity of the translation apparatus, however, limits the diversity of unnatural amino acids that can be incorporated into peptides by ribosomal translation. We have previously shown that over 90 unnatural amino acids can be enzymatically loaded onto tRNA.Methodology/Principal FindingsWe have now used a competition assay to assess the efficiency of tRNA-aminoacylation of these analogs. We have also used a series of peptide translation assays to measure the efficiency with which these analogs are incorporated into peptides. The translation apparatus tolerates most side chain derivatives, a few α,α disubstituted, N-methyl and α-hydroxy derivatives, but no β-amino acids. We show that over 50 unnatural amino acids can be incorporated into peptides by ribosomal translation. Using a set of analogs that are efficiently charged and translated we were able to prepare individual peptides containing up to 13 different unnatural amino acids.Conclusions/SignificanceOur results demonstrate that a diverse array of unnatural building blocks can be translationally incorporated into peptides. These building blocks provide new opportunities for in vitro selections with highly modified drug-like peptides.

Development of SEU-robust, radiation-tolerant and industry-compatible programmable logic components

Most of the microelectronics components developed for thefirst generation of LHC experiments have been defined and designedwith very precise experiment-specific goals and are fully optimizedfor these applications. In an effort to cover the needs for genericprogrammable components, often needed in the real world, anindustry-compatible Programmable Logic Device (PLD) and anindustry-compatible Field-Programmable Gate Array (FPGA) are now underdevelopment. This effort is targeted to small volume applications orto the cases where small programmable functions are required to fix asystem application. The PLD is a fuse-based, 10-input, 8-I/O generalarchitecture device compatible with a popular commercial part, and isfabricated in 0.25 μm CMOS. The FPGA under development is insteada 32 × 32 logic block array, equivalent to ≈ 25k gates,to be fabricated in 0.13 μm CMOS. The work focusses on the designof SEU-robust registers which can be employed for configurationstorage as well as for user data flip-flops. The SEU-robust registerswere tested in a heavy-ion beam facility; test results are presented.

Proposal of permanent magnet repulsive maglev transportation system: possibility of automobile with magnetic levitation

AbstractThis paper describes a maglev transportation system for automobiles. The track is an array of permanent magnet blocks, and the levitating body is the bedplate which consists of permanent magnet plates, propulsion coils, levitation coils, and guidance coils. The feature of this system is that an automobile equipped with the bedplate is free to approach into the track or to swerve from the track by using four wheels with the lift. The force acting on the levitating body is calculated on the assumption that each permanent magnet can be expressed as a surface current. From the calculation results, it is proven that an automobile of 4.35 m length, 1.8 m width, and 1700 kg weight can run at a speed of 500 km/h against the air resistance force of 3704 N on the condition that the battery has an output of 337.5 V and a capacity of 190 Ah. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 65– 76, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20491

Online Fault Tolerance for FPGA Logic Blocks

Most adaptive computing systems use reconfigurable hardware in the form of field programmable gate arrays (FPGAs). For these systems to be fielded in harsh environments where high reliability and availability are a must, the applications running on the FPGAs must tolerate hardware faults that may occur during the lifetime of the system. In this paper, we present new fault-tolerant techniques for FPGA logic blocks, developed as part of the roving self-test areas (STARs) approach to online testing, diagnosis, and reconfiguration . Our techniques can handle large numbers of faults (we show tolerance of over 100 logic faults via actual implementation on an FPGA consisting of a 20 times 20 array of logic blocks). A key novel feature is the reuse of defective logic blocks to increase the number of effective spares and extend the mission life. To increase fault tolerance, we not only use nonfaulty parts of defective or partially faulty logic blocks, but we also use faulty parts of defective logic blocks in nonfaulty modes. By using and reusing faulty resources, our multilevel approach extends the number of tolerable faults beyond the number of currently available spare logic resources. Unlike many column, row, or tile-based methods, our multilevel approach can tolerate not only faults that are evenly distributed over the logic area, but also clusters of faults in the same local area. Furthermore, system operation is not interrupted for fault diagnosis or for computing fault-bypassing configurations. Our fault tolerance techniques have been implemented using ORCA 2C series FPGAs which feature incremental dynamic runtime reconfiguration