Block Layers Research Articles

Three-dimensional finite element and analytical modelling of tyre–soil interaction

Tyre–soil interaction models were developed for the investigation of tyre dynamic behaviours with two different approaches: finite element method and analytical method. In the finite element model the 3D tyre was modelled as a non-linear solid assembly consisting of tread block, belt and carcass layers, sidewall, beads and rim, and the soil modelled as a 3D object was attributed with the elasto-plastic mechanical behaviour. In the analytical model the contact between deformable tyre and soft soil is described by non-linear springs and dampers in the radial direction and shear stress-displacement model in the tangential direction. The equations accounting for the analytical model were integrated in the multi-body simulation software-ADAMS. Simulations with these two different tyre–soil interaction models were carried out to study the longitudinal slip-longitudinal force and slip angle-lateral force relationship.

A Study on Green Organic Light-Emitting Diodes with High Electron Mobility in Hole Block and Electron Transport Layers

The electron mobility and hole blocking ability of BPhen, BCP, and ET137 were investigated by fabricating an electron only device and hole only device, respectively. Although it was observed that ET137 has the highest electron mobility, the device with ET137 as electron transporting layer was unable to obtain high efficiency alone and it was necessary to use a hole blocking layer because of the poor hole blocking ability due to the high-lying HOMO energy level. We fabricated green-emitting phosphorescent devices with various hole blocking layers and electron transporting layers. It was demonstrated that the high electron mobility of the electron transporting layer and hole blocking layer leads to high efficiency in organic light-emitting diodes. The device with BPhen and ET137 as hole blocking layer and electron transporting layer, respectively, showed the best efficiency properties. The maximum values of luminous efficiency, power efficiency, and quantum efficiency were 41.1 cd/A, 26.9 Im/W and 12.4%, respectively.

Inverted Organic Solar Cells with ZnO Nanowalls Prepared Using Wet Chemical Etching in a KOH Solution

We report on the photovoltaic (PV) performances of inverted organic solar cells (IOSCs) that were fabricated from PCBM:P3HT polymer with a ZnO thin film and ZnO nanowalls as electron transport and hole block layers. ZnO thin film on ITO/glass substrate was deposited using a simply aqueous solution route. ZnO nanowall structures were obtained via wet chemical etching of ZnO thin films in a KOH solution. The power conversion efficiency (PCE) of the IOSC with ZnO nanowalls was significantly improved by 44% from 1.254% to 1.811% compared to that of the IOSC with ZnO thin film. The short circuit current in IOSCs fabricated with the ZnO nanowalls was increased mainly due to the increase in the charge transport interface area, as a result of enhancement in the PCE. This work suggests a method for fabricating efficient PV devices with a larger charge transport area for future prospects.

Structural Behavior of Mortarless Interlocking Load Bearing Hollow Block Wall Panel under Out-Of-Plane Loading

Experimental and numerical investigation of interlocking mortarless wall panels with 1.0 m height, 1.2 m width and 150 mm thickness are conducted. Behaviour of both hollow and partially grouted masonry wall panels is studied. The panels were tested under constant pre-compressive vertical load and out-of-plane lateral load. Lateral load carrying capacity, deflection at mid height, dry joint opening between block layers and mode of failure are investigated. Strain characteristics throughout the loading process are also monitored. A finite element analysis is presented for the system and a good agreement between the experimental and modelling results is achieved. Parametric study using the finite element model is also presented and the effect of different parameters; amount of pre-compressive load and slenderness ratio is studied. The study reveals that pre-compressive vertical load and reinforcement significantly affect the structural behaviour of mortarless walls under out-of-plane loading. Useful expressions for the capacity are obtained from the analysis.

Measurement of elasticity of thin elastic layers with radiation force and wave propagation methods

In the field of tissue engineering, monitoring the elasticity of developing tissue cultures is important for evaluating their growth and maturation. In this work, we used wave propagation methods to measure the elasticity of thin tissue-mimicking layers to test the feasibility of measuring the elasticity of developing tissue cultures. We developed finite element and analytical models for investigating this problem and found good agreement between the results from both models. We used ultrasound radiation force to induce propagating waves, and the waves are measured using high frame rate ultrasound imaging at 10 kHz. The wave modes were identified and compared with an analytic model for Rayleigh wave propagation in a thin elastic layer bound to a solid substrate. The same gelatin mixture was used to make phantoms 1, 4, and 50 mm thick, where the phantom with 50 mm thickness was used as control and evaluated with shear wave imaging methods. The analytic model was used to fit data from experiments in the large block and thin layers of 1 and 4 mm thick, and the measured shear moduli were 22.7, 21.8, and 22.5 kPa, respectively. These results provide a validation for measurement of elasticity in thin elastic layers.

Magnetic Ordering in V-Layers of the Superconducting System of Sr2VFeAsO3

Results of transport, magnetic, thermal, and 75As-NMR measurements are presented for superconducting Sr2VFeAsO3 with an alternating stack of FeAs and perovskite-like block layers. Although apparent anomalies in magnetic and thermal properties have been observed at ~150 K, no anomaly in transport behaviors has been observed at around the same temperature. These results indicate that V ions in the Sr2VO3-block layers have localized magnetic moments and that V-electrons do not contribute to the Fermi surface. The electronic characteristics of Sr2VFeAsO3 are considered to be common to those of other superconducting systems with Fe-pnictogen layers.

Improved color purity and electroluminescent efficiency obtained by modulating thicknesses and evaporation rates of hole block and electron transport layers

In this work, a series of electroluminescent (EL) devices based on trivalent europium (Eu3+) complex Eu(TTA)3phen (TTA=thenoyltrifluoroacetone, phen=1,10-phenanthroline) were fabricated by selecting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and tris(8-hydroxyquinoline) aluminum (Alq3) as hole block and electron transport materials, respectively. Interestingly, we found the transport of electrons decreases gradually with increasing thicknesses and evaporation rates of BCP and Alq3 layers. Analyzing carrier distribution and EL spectra, we conclude that appropriately modulating the thicknesses and evaporation rates is an efficient way to decrease the accumulation of electrons in HBL, thus suppressing the EL of hole block material. On the other hand, decreasing the transport of electrons can also facilitate the balance of holes and electrons on Eu(TTA)3phen molecules, thus further enhancing the EL efficiency. As a result, pure Eu3+ emission with the efficiency as high as 8.49cd/A was realized by controlling the thicknesses and evaporation rates of BCP and Alq3 layers to be 30nm and 0.10nm/s, 40nm and 0.10nm/s, respectively.

Universal scaling of the [formula omitted]-axis dc conductivity for underdoped high-temperature cuprate superconductors

The coexistence of ‘metallic-like’ in-plane dc conductivity and ‘semiconducting-like’ out-of-plane ( c -axis) dc conductivity ( σ c ) , generating huge anisotropy in underdoped high-temperature cuprate superconductors (HTCSs), defies our current understanding of metals. In this report, we present an intrinsic doping dependence of σ c . We find that σ c for underdoped HTCSs is universally scaled to the σ c value at the optimal doped-hole concentration. The universal scaling behavior suggests that there are three intrinsic processes that contribute to σ c : (i) the doping-dependent-activated gap; (ii) the exponential doping dependences, and (iii) the tunneling between adjacent CuO 2 block layers. They are the essential underlying characteristics of the c -axis transport for all HTCSs.

Effect of number of filaments on the critical current density in multifilamentary Bi-2223 tape

The critical current property of Bi2Sr2Ca2Cu3Ox(Bi-2223) silver-sheathed tape has been remarkably improved by application of ConTrolled Over Pressure (CT-OP) process with adjusting temperature and oxygen partial pressure. For further improvement of the property of Bi-2223 tapes, the effect of number of filaments on the critical current density Jc was investigated. It was found that Jc was higher and its decrease with increasing magnetic field was weaker in the tape with larger number of filaments. In addition, the irreversibility field Bi increased with increasing filament number. The field-angle anisotropy Jc(0°)/Jc(90°) of the tape with the largest filament number was smallest, where the field-angle was measured from the a–b plane. However, the out-of-plane misorientation angle is fairly small in this tape. Hence, the low field-angle anisotropy in this tape seems to be attributed to improved superconductivity in the block layers in the superconducting region near the interface with silver matrix.

Block Layering Approach in TAST Codes

Threaded Algebraic Space Time (TAST) codes developed by Gamal et al. is a powerful class of space time codes in which different layers are combined and separated by appropriate Diophantine number . In this paper we introduce a technique of block layering in TAST codes, in which a series of layers (we call it Block layers) has more than one transmit antenna at the same time instant. As a result we use fewer layers (Diophantine numbers) for the four transmit antennas scheme, which enhances the coding gain of our proposed scheme. In each block layer we incorporate Alamouti’s transmit diversity scheme which decreases the decoding complexity. The proposed code achieves a normalized rate of 2 symbol/s. Simulation result shows that this type of codes outperforms TAST codes in certain scenarios.

Formation of phase structure and crystallization behavior from disordered melt for ethylene-isoprene block copolymers and their blends

The structure formation and crystallization kinetics in crystallization from a disordered melt were investigated for a polyethylene-polyisoprene block copolymer (LEI) having M n = 3.2 × 10 4 and 53 wt% of polyethylene content and for its blends with the corresponding homopolymers, polyethylene (PE) and polyisoprene (PIp), using synchrotron small-angle X-ray scattering techniques (SAXS) and differential scanning calorimetry (DSC). For LEI copolymer and the blends, no microphase separation structure was observed in the molten state. In the crystalline state of the neat LEI, the first and higher order scattering peaks were clearly observed, in which the intensity of the higher order peaks was considerably strong. This unusual behavior of the higher order peaks was explained by the lamellar insertion model of Hama and Tashiro. From the analyses based on this model and one-dimensional electron density correlation function with a three phase model, the phase structure in the crystalline state of the neat LEI was concluded to be a regular lamellar structure consisting of crystalline lamella of PE block and amorphous layers of PE and PIp blocks. This phase structure was quite different from that reported previously for a polyethylene-polyisoprene block copolymer (HEI) with a higher molecular weight in which HEI crystallized with keeping the microphase separation structure in the melt. For the blends of LEI with PIp homopolymer, the phase structure is affected by the blend composition, while for the blends with PE homopolymer, the phase structure depended on the crystallization temperature as well as the molecular weight and composition of the added PE. The Avrami index was 2–3 for neat LEI, all blends and PE homopolymers.

An introduction of a multi‐soil‐layering system: a novel green technology for wastewater treatment in rural areas

AbstractMulti‐soil‐layering (MSL) systems are designed for municipal wastewater, livestock wastewater and polluted river water treatments. They are mainly composed of soil mixture block layers and water‐permeable layers (PL). The MSL system overcomes many of the shortcomings of conventional soil treatment systems such as easy clogging, large land requirement and low hydraulic loading rate. This paper summarizes the structure, purification mechanism and practical application of the systems for different kinds of wastewater treatment. The paper also compares MSL systems with other decentralized systems such as wetland and compact filter systems in their respective structures and treatment efficiencies. Finally, the paper gives a rough evaluation of the lifespan and cost of an MSL system based on its material composition.

Single-crystal neutron diffraction study of short-range magnetic correlations inTb5Ge4

We present a single-crystal neutron diffraction study of the magnetic short-range correlations in ${\text{Tb}}_{5}{\text{Ge}}_{4}$ which orders antiferromagnetically below the Neel temperature ${T}_{N}\ensuremath{\approx}92\text{ }\text{K}$. Strong diffuse scattering arising from magnetic short-range correlations was observed in wide temperature ranges both below and above ${T}_{N}$. The antiferromagnetic ordering in ${\text{Tb}}_{5}{\text{Ge}}_{4}$ is described to consist of strongly coupled ferromagnetic block layers in the $ac$ plane that stack along the $b$ axis with weak antiferromagnetic interlayer coupling. Diffuse scattering was observed along both ${a}^{\ensuremath{\ast}}$ and ${b}^{\ensuremath{\ast}}$ directions indicating three-dimensional short-range correlations. Moreover, the $q$ dependence of the diffuse scattering is Squared Lorentzian in form suggesting a strongly clustered magnetic state that may be related to the proposed Griffiths-like phase in ${\text{Gd}}_{5}{\text{Ge}}_{4}$.

Oxygen Vacancy Ordering in the Double-layered Ruddlesden−Popper Cobaltite Sm2BaCo2O7−δ

A new oxygen-deficient Ruddlesden−Popper (RP) cobaltite Sm2BaCo2O7−δ (δ ≈ 1.0) has been synthesized and the crystal structure elucidated by Rietveld analysis of X-ray powder diffraction (XRD) data and transmission electron microscopy (TEM). The phase crystallizes in a primitive orthorhombic unit cell, with lattice parameters a = 5.4371(4) A; b = 5.4405(4) A and c = 19.8629(6) A, and space group Pnnm. Contrary to other oxygen-deficient cobalt RP phases, the oxygen vacancies are located in the equatorial positions of the [CoO] layers to give an intralayer structure similar to Sr2Mn2O5, which is not usually observed for cobalt-containing materials. The Sm3+ and Ba2+ cations show a strong preference for distinct sites, with the majority of the larger Ba2+ cations situated in the perovskite block layers and Sm3+ cations predominantly in the rock salt layers. Magnetic susceptibility data demonstrate the strong antiferromagnetic (AFM) character of Sm2BaCo2O7−δ.

Practical techniques for purging deleted data using liveness information

The layered design of the Linux operating system hides the liveness of file system data from the underlying block layers. This lack of liveness information prevents the storage system from discarding blocks deleted by the file system, often resulting in poor utilization, security problems, inefficient caching, and migration overheads. In this paper, we define a generic "purge" operation that can be used by a file system to pass liveness information to the block layer with minimal changes in the layer interfaces, allowing the storage system to discard deleted data. We present three approaches for implementing such a purge operation: direct call, zero blocks, and flagged writes, each of which differs in their architectural complexity and potential performance overhead. We evaluate the feasibility of these techniques through a reference implementation of a dynamically resizable copy on write (COW) data store in User Mode Linux (UML). Performance results obtained from this reference implementation show that all these techniques can achieve significant storage savings with a reasonable execution time overhead. At the same time, our results indicate that while the direct call approach has the best performance, the zero block approach provides the best compromise in terms of performance overhead and its semantic and architectural simplicity. Overall, our results demonstrate that passing liveness information across the file system-block layer interface with minimal changes is not only feasible but practical.

Discommensurate Structure in [(Ca0.90Sr0.10)2CoO3]0.61CoO2

The crystal structure of partly Sr-substituted Co-121, i.e., “Ca 3 Co 4 Co 9 ”, single crystal is studied by means of the electron diffraction measurements and high-resolution transmission electron microscopy (HREM). The crystal structure consists of two interpenetrating subsystems of a CoO 2 sheet and a distorted three-layered (Ca,Sr) 2 CoO 3 rock-salt (RS)-type block layers, which belong to a triclinic system. Both subsystems have common a -, c -axes and α-, β-, γ-angle with a = 4.8267(1) A, c = 10.9214(3) A, α= 90.916(2)°, β= 98.291(5)°, and γ= 89.957(3)°. On the other hand, the crystal structure is modulated parallel to the b -axis, along which the CoO 2 sheet has b 1 = 2.8346(1) A and the (Ca,Sr) 2 CoO 3 RS-type block layer has b 2 = 4.6391(2) A, respectively. On the basis of the b 1 / b 2 ratio and analyzed chemical compositions, the structure analogue is formulated as [(Ca 0.90 Sr 0.10 ) 2 CoO 3 ] 0.61 CoO 2 . In electron diffraction patterns, there are many new satellite reflections, namely 010\ba...

Use and acceptability of reduced‐weight Portland cement bags in masonry construction: An observational pilot study

AbstractBackground Mason tenders are involved in semi‐ and unskilled work in support of bricklayers and block layers. Their work consists of manually transporting building materials and equipment, supplying individual brick/block layers with materials, and mixing and stocking mortar.Objective The purpose of this pilot study is to determine the current availability and acceptability of reduced‐weight Portland cement bags among mason contractors, cement suppliers, and manufacturers as a vehicle to decrease the exposure of mason tenders to physical risk factors for musculoskeletal disorders (MSD).Methods Forty‐six producers, suppliers, and contractors that use Portland cement bags were used in this observational exploratory study. A questionnaire was administrated over the phone and data were collected regarding availability, practice of use, and preferences between full‐ and reduced‐weight Portland cement bags.Results Only 17% of the companies produce/supply/use the reduced‐weight cement bags. The main factors mentioned by the companies that influence the nonuse of small bags are reduced demand; increased cost; storage, shipping, and handling difficulty; special equipment requirements; and special packaging. Only 11% of companies interviewed are aware of the National Institute for Occupational Safety and Health (NIOSH) lifting recommendations that the maximum lifted weight should be 51 lb.Conclusions This exploratory study suggests that reduced cement bags may not be in wide use by producers/suppliers/users of Portland cement. A full‐scale study is recommended to confirm these practices and find ways to significantly reduce the risk to which masonry workers are exposed.Application The potential application of this study can be the development of new guidelines regarding the production/supplying/usage of 47 lb cement bags. © 2008 Wiley Periodicals, Inc.

Charge density wave formation inR2Te5(R=Nd, Sm, and Gd)

The rare earth $(R)$ tellurides ${R}_{2}{\mathrm{Te}}_{5}$ have a crystal structure intermediate between that of $R{\mathrm{Te}}_{2}$ and $R{\mathrm{Te}}_{3}$, consisting of alternating single and double Te planes sandwiched between $R\mathrm{Te}$ block layers. We have successfully grown single crystals of ${\mathrm{Nd}}_{2}{\mathrm{Te}}_{5}$, ${\mathrm{Sm}}_{2}{\mathrm{Te}}_{5}$, and ${\mathrm{Gd}}_{2}{\mathrm{Te}}_{5}$ from a self-flux and we describe here evidence for charge density wave formation in these materials. The superlattice patterns for all three compounds are relatively complex, consisting at room temperature of at least two independent wave vectors. Consideration of the electronic structure indicates that, to a large extent, these wave vectors are separately associated with sheets of the Fermi surface which are principally derived from the single and double Te layers.

Origin of shadow bands in high-Tc cuprate superconductors studied by high-resolution angle-resolved photoemission spectroscopy

We report high-resolution angle-resolved photoemission spectroscopy on single-layered cuprate superconductor (Bi,Pb)2(Sr,La)2CuO6+δ as a function of temperature and doping level, to elucidate the origin of shadow band (SB). We found that the intensity of SB is invariable with respect to temperature, doping, and substitution constituents of block layers, indicating that antiferromagnetic correlation is not responsible for the emergence of SB. Observation of similar SB in Bi2Sr2CaCu2O8+δ and La1.85Sr0.15CuO4, but not in YBa2Cu3O7−δ further supports the structural origin of SB.

Static and Dynamic Characteristics of Thermoelectric Ceramics

Structural characteristics of the high performance cobaltite thermoelectric semiconductors have been studied intensively by means of X-ray and neutron diffraction measurements and high resolution electron microscopy (HREM). These cobaltites consists of CoO2 triangular conducting sheets and several different types of block layers, i.e., Na, Ca, Sr single layers, three or four layered rock-salt layers, where Co-O2 square lattices are situated at their middle, and Bi-O or Tl-O double layers plus alkaline oxygen layers. Cold neutron scattering technique is employed to search possible low-energy excitation modes, being unique for nearly 1D and 2D crystals, and phonon density of states, DOS, of several high performance cobaltites at temperatures in the range from 10K to the ambient. Low energy, i.e., less than 2meV, excitation modes were found in the three different thermoelectric ceramics, i.e., γ -Na0.7CoO2, [Ca2CoO3]pCoO2, and [Ca2(Cu,Co)2O4]pCoO2. Possible origin of these low energy excitations are discussed in terms of low-energy corrugation mode generated due to weak chemical bondings, for which Van-der-Waals force dominates, between the CoO2 conduction sheets. These characteristics could be the key to realize low thermal conductivity and high-ZT of these ceramics.