Correlation of strength of 75 mm diameter and 100 mm diameter cylinders for high strength concrete

Results of statistical analysis of test data are presented to establish if there is a correlation between the strength of 75- and 100-mm-diameter cylinders for concrete with strength between 110 and 160 MPa. A linear regression analysis showed that strength measured on 75-mm cylinders is within 5% of the corresponding strength measured on 100-mm cylinders. A more detailed analysis of the difference between the mean strengths of the two sizes of cylinder of each group of the tests indicated that 75- and 100-mm cylinders measure the concrete strength within 4%. It is concluded that 75-mm cylinders are suitable for compressive strength testing of high strength concrete (>100 MPa). For strength of concrete greater than 150 MPa, 75-mm cylinders are likely to measure smaller concrete strength than the corresponding 100-mm cylinders.     

80／100mm发泡聚乙烯板材挤出机的生产应用

介绍了台湾省生产的CC/EOE-80/100型发泡聚乙烯板材挤出机的生产工艺、主要设备、主要原料及产品规格。     

Imposing dynamic structures on fluidised beds

Structuring fluidised beds can increase the conversion and selectivity, and facilitate control and scale-up. Two methods for introducing a dynamic structure into gas–solid fluidised beds are compared based on their overall hydrodynamics: electric field enhanced fluidisation and distributed secondary gas injection by a fractal injector. It is shown that, under various conditions, these systems lead to significant decreases in bubble size and bubble hold-up and to an increase in the number of bubbles. It was found that the electric field enhancement can lead to homogeneous fluidisation at lower flow rates, and the distributed secondary flow leads to smaller bubbles at higher flow rates.     

Oil Sand Slurry Conditioning Tests in a 100 mm Pipeline Loop

Fresh oil sand slurries were prepared and tested in a 100 mm pipeline loop at 37°C to evaluate the effects of average flow velocity, slurry air content and air injection method (bulk or continuous) on slurry conditioning, i.e., the evolution of the in‐pipe processes that promote gravity separation of bitumen‐air aggregates from the remainder of the slurry. The potential separability of the bitumen in the slurry was evaluated using a slurry Conditioning Index (CI). When no air was injected into the slurry, the slurry CI was low (≤0.1), indicating very poor conditioning. An increase in flow velocity from 2 m/s to 4 m/s and injection of 5% air (by volume) dramatically improved the slurry CI, to ～ 0.6. The improved slurry conditioning observed at the higher velocity is explained by the increased force of fluid turbulence experienced by the particles and the greatly enhanced bitumen‐air contact.     

Bubble Size Distributions for Dispersed Air – Water Flows in a 100 mm Horizontal Pipeline

The bubble size distributions of air dispersed in water flowing in a 100 mm horizontal pipeline were studied. Size distributions were obtained with a high‐speed digital camera at axial positions 0.5, 15.3 and 42.3 m from the air injection point. Air was injected into the pipeline through a narrow tube extending into the pipe, perpendicular to the pipe axis. The effects of average water velocity, air concentration, and injection nozzle diameter on the evolution of bubble size distribution with axial pipe position were studied. For the lowest air concentration of 0.07%, equilibrium bubble size distributions were dependent only on water velocity. Nozzle injection diameter did not affect the downstream bubble size distributions at air concentrations of 0.07% and 0.3%. Levich's break‐up theory was found to over‐predict the experimental d_max for each test condition.     

Permeability and dynamic elastic moduli of controlled porosity ultra-precision aerostatic structures

Porous ceramic aerostatic bearings enable precise and smooth motion and improved stiffness compared with widely used orifice restrictor bearings. However, the processing techniques so far used are too complex or rely in lowering the sintering temperature to increase fluid flow.     

Strain mode of general flow: Characterization and implications for flow pattern structures

Understanding the mixing capability of mixing devices based on their geometric shape is an important issue both for predicting mixing processes and for designing new mixers. The flow patterns in mixers are directly connected with the modes of the local strain rate, which is generally a combination of elongational flow and planar shear flow. We develop a measure to characterize the modes of the strain rate for general flow occurring in mixers. The spatial distribution of the volumetric strain rate (or non‐planar strain rate) in connection with the flow pattern plays an essential role in understanding distributive mixing. With our measure, flows with different types of screw elements in a twin‐screw extruder are numerically analyzed. The difference in flow pattern structure between conveying screws and kneading disks is successfully characterized by the distribution of the volumetric strain rate. The results suggest that the distribution of the strain rate mode offers an essential and convenient way for characterization of the relation between flow pattern structure and the mixer geometry. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2563–2569, 2016     

Influence of horizontal return bend on the two‐phase flow pattern in a 6.9 mm diameter tube

The two‐phase flow pattern for air‐water mixtures inside a 6.9 mm U‐tube is reported to have curvature ratios of 3?7.1. At a lower total mass flux of 50 kg/m²·s and a quality of 0.1, or at a larger curvature ratio of 7.1, no influence on the flow patterns is seen. However, if the curvature ratio is reduced to 3, the flow pattern in the recovery region just after the return bend is temporally turned from stratified flow into annular flow. For a quality larger than 0.4, the annular flow pattern prevails in the entire tube. For G = 400 kg/m²·s and x < 0.01, the size of the plug in the downstream is usually larger than that in the upstream due to the coalesce in the return bend. This coalescence phenomenon continues to further increase the total mass flux at the lower quality region. For a total mass flux above 500 kg/m²·s, the bubbly flow pattern in the upstream region may become intermittent.     

Additive manufacturing,quasi-static and dynamic compressive behaviours of ceramic lattice structures

Ceramic lattice structures (CLSs) are used for construction in common and extreme environments because of the extraordinary properties of ceramics. In this study, we designed and additively manufactured CLSs with distinct structural parameters to explore their quasi-static and dynamic compressive behaviours in detail. It was demonstrated that both the relative density (?ρ) and inclination angle (ω) had a significant impact on the quasi-static and dynamic mechanical properties of the CLSs. Furthermore, the mathematical relationships between the quasi-static compressive properties, including quasi-static compressive strength (QS), quasi-static Young’s modulus (QY), and quasi-static energy absorption (QE), versus ?ρ and ω obeyed the Gibson–Ashby and Deshpande and Fleck models, respectively. It was revealed by experiment and simulation that as the stiffness increased, the quasi-static failure mode of the CLSs changed from a parallel-vertical-inclined mixed mode to a parallel-vertical mode. In addition, the relationship between the dynamic mechanical properties of the CLSs versus ?ρ and ω also followed the Gibson–Ashby and Deshpande and Fleck models. The exceptional dynamic increase factor indicated that CLSs are highly suitable for extreme environments. These findings will aid in the research and development of customised additively manufactured CLSs.     

Computational fluid dynamic analyses of catalytic combustors for 100 kW-class molten carbonate fuel cell

The asymmetric inner structure of a catalytic combustor causes wall cracking because of regional overheating. Thus, a symmetric shape is proposed in the present work and analyses of the computational fluid dynamics of the existing combustor and the proposed type have been performed. A simulation of the revised combustor without a swirl device revealed that the flow of gases is concentrated on the center of the combustor and only catalysts around the center are used. In the revised combustor with a swirl device, the overall temperatures were estimated to be uniform. However, near the swirl device, high temperature exceeding 1,700 K was measured. Therefore, a heatproof surface coating on the swirl device is necessary for protection of the material. At the initial start-up of the catalytic combustor, hydrogen and natural gas are used. When only natural gas is used, the simulation indicated that the gas does not burn in the revised combustor without a swirl device. However, in the combustor with the swirl device, methane of 34.8% volume burns in the simulation. On the other hand, when hydrogen and natural gas are burned together, methane of 91.7% volume burns in the simulation.     

Defining topological equivalences in protein structures by means of a dynamic programming algorithm

An automatic algorithm for defining topological equivalencesin protein structures is presented. The algorithm is based ona dynamic programming technique and self-consistent scoringmethod. We have used it to align pairs of similar protein structuresof several protein families and to identify recurrent structuraldomains in aspartic proteinase 2APR. Its ability to find suboptimalpaths permits a thorough comparison of proteins at each levelin the hierarchy of the protein structure: secondary structure,super-secondary structure, domain and entire globular structure.The algorithm has been extended to the structure alignment ofribonucleic acid and can be extended to the structure alignmentof any linear polymer.     

Nanoscale lithography with visible light: optical nonlinear saturable absorption effect induced nanobump pattern structures

Industrial approaches to improve lithographic resolution usually rely upon short-wavelength laser or charged particles of even shorter wavelengths. However, nanoscale lithography with visible light is more effective for practical applications because of its low cost, easy operation, and so on. In the current work, a technical scheme for the optical nonlinear saturable absorption effect to induce nanobump pattern structures is proposed. The theoretical simulation indicates that the spot size can be squeezed and reduced to about 1/12 the original spot size using Si thin films as a nonlinear saturable absorption material, and GaN semiconductor diode as the laser source. The high-density digital versatile disk tester was used as the direct laser writing apparatus to verify the technical scheme. Nanostructures with a size of ～80 nm were obtained. This size is ～1/10 the spot size at optical diffraction limit.     

Synthesis and dynamic mechanical analysis of nanocomposite UV crosslinkable 100% solid acrylic pressure sensitive adhesives

A synthesis and characterization of nanocomposite solventless acrylic UV crosslinkable pressure sensitive adhesives is presented. Different prepolymers were synthesized using bulk polymerization procedure. The reaction mixture consisted of acrylic monomers (2-ethylhexyl acrylate, acrylic acid and t-butyl acrylate), azobisisobutyronitrile initiator, chain transfer agent n-dodecylmercaptan and unsaturated UV photoinitiator 4-acryloyloxybezophenone. Different formulations with different amounts of modified and unmodified montmorillonite (MMT) clays were tested and the prepolymer was characterized by viscosity measurements. UV crosslinking process was monitored using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Gel phase amount in crosslinked samples was determined by Soxhlet extraction. Clay dispersion in polymer matrix was investigated by X-ray diffraction analysis (XRD). Three basic adhesive properties, the tack, peel and shear strength were measured and the viscoelastic properties of crosslinked adhesive films were characterized using dynamic mechanical analysis (DMA). Results of the study showed high increase in prepolymer viscosity, when hydrophobic types of MMT clays were added in the reaction mixture. The addition of clay had a negative effect on UV crosslinking process. XRD analysis confirmed complete exfoliation and/or intercalation of modified clays in polymer matrix, depending on modifier amount and type. Results of adhesive properties testing showed a major influence of clay addition on adhesive properties, especially on shear strength. DMA analysis showed an increase in storage modulus (G′) and a decrease of tan δ values for adhesives synthesized with clay what also concurs with higher shear strength and implies an improved cohesion of adhesive.     

Effect of crosslink structures on dynamic mechanical properties of natural rubber vulcanizates under different aging conditions

The effects of crosslink structures on the dynamic mechanical properties (DMPs) of unfilled and carbon black N330‐filled natural rubber (NR) vulcanizates cured with conventional (CV), semiefficient (SEV), and efficient (EV) cure systems and having about the same total crosslink densities were investigated before and after aerobic and anaerobic aging at 100°C. The three unfilled NR vulcanizates cured with the CV, SEV, and EV systems had about the same mechanical loss factor (tan δ) values at about 0°C but showed some apparent differences in the tan δ values in the order EV > SEV > CV at relatively high temperatures of 40–80°C before aging. However, N330‐filled NR vulcanizates gave higher tan δ values than the unfilled vulcanizates and showed little effect of the crosslink types on the tan δ at different temperatures over the glass‐transition temperature (T_g) before aging. Aerobic heat aging increased the T_g and tan δ values of the vulcanizates over a wide range of temperatures from ?80 to 90°C that was mainly due to the changes in the total density and types of crosslinks. The unfilled vulcanizates cured with the CV system showed the greatest change in DMP because of their poor resistance to heat aging. Aerobic heat aging of NR vulcanizates caused a more significant change in the DMP than anaerobic heat aging because of the dominant effect of the oxidative degradation during aerobic heat aging on the main‐chain structure, crosslink structures, and DMPs of the vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 710–718, 2001     

A non-Gaussian pattern matching based dynamic process monitoring approach and its application to cryogenic air separation process

Principal component analysis (PCA) based pattern matching methods have been applied to process monitoring and fault detection. However, the conventional pattern matching approaches do not specifically take into account the non-Gaussian dynamic features in chemical processes. Furthermore, those techniques are more focused on fault detection instead of fault diagnosis. In this study, a non-Gaussian pattern matching based fault detection and diagnosis method is developed and applied to monitor cryogenic air separation process. First, independent component analysis (ICA) models are built on the normal benchmark and monitored data sets along sliding windows. The IC subspaces from the benchmark and monitored data are then extracted to evaluate the non-Gaussian patterns and detect process faults through a mutual information based dissimilarity index. Further, a difference subspace between the two IC subspaces is computed to characterize the divergence of the dynamic and non-Gaussian patterns between the benchmark and monitored data. Subsequently, the mutual information between the IC difference subspace and each process variable direction is defined as a new non-Gaussian contribution index for fault identification and diagnosis. The presented approach is applied to a simulated cryogenic air separation plant and the monitoring results are compared against those of PCA based pattern matching techniques and ICA based monitoring method. The application study demonstrates that the developed non-Gaussian pattern matching approach can effectively monitor the complex air separation process with superior fault detection and diagnosis capability.     

A novel dynamic membrane reactor concept with radial‐flow pattern for reacting material and axial‐flow pattern for sweeping gas in catalytic naphtha reformers

Naphtha reforming units are of high interest for hydrogen production in refineries. In this regard, the application of membrane concept in radial‐flow tubular naphtha reactors for hydrogen production is proposed. Because of the importance of the pressure drop problem in catalytic naphtha reforming units, the radial‐flow reactors are proposed. A radial‐flow tubular membrane reactor (RF‐TMR) with the radial‐flow pattern of the naphtha feed and the axial‐flow pattern of the sweeping gas is proposed as an alternative configuration for conventional axial‐flow tubular reactors (AF‐TR). The cross‐sectional area of the tubular reactor is divided into some subsections in which walls of the gaps between subsections are coated with the Pd‐Ag membrane layer. A dynamic mathematical model considering radial and axial coordinates ((r, z)‐coordinates) has been developed to investigate the performance of the new configuration. Results show ～300 and 11 kg/h increase in aromatic and hydrogen production rates in RF‐TMR compared with AF‐TR, respectively. Furthermore, smaller catalyst particles with higher efficiency can be used in RF‐TMR due to a slight pressure drop. The enhancement in aromatics (octane number) and hydrogen productions owing to applying simultaneously the membrane concept and radial‐flow pattern in naphtha reactors motivates the application of RF‐TMR in refineries. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Experimental and computational fluid dynamic study of reacting gas jet in liquid: Flow pattern and heat transfer

The flow behavior of a jet reactor (consisting of a gaseous jet submerged in a molten-metal bath) is very complex. These are operated at high temperatures (1500–3000 K) and need to be contained within a heavy metal enclosure. The design of such reactors requires a prior knowledge of the jet dimensions, flow pattern and heat transfer characteristics. However, the fuel opaqueness and the high temperature of the jet create difficulties in observing the reaction mass visually and therefore the literature contains a very brief account of the experimental measurements of the flow pattern. Hence, a systematic study has been undertaken with a reaction pair (HCl gas jet submerged in aqueous NH₃), which has the potential for simulating the real systems. The present work is concerned with the CFD simulations by employing k–ε turbulence model and large eddy simulations (LES). The measurements and simulations have been carried out over a wide range of gas velocities (53–323 m/s) and these have been compared with the CFD simulations. A comprehensive comparison has also been made between the k–ε and the LES for the mean flow, temperature and the turbulent kinetic energy. An attempt has been made to understand the relative performance of these models. Further, complete energy balance has been established between the energy supply rate through the jet and the energy dissipation rate within the reactor. The plume characteristics obtained from CFD simulations have been compared qualitatively with the photographic images.     

Use of an in vitro dynamic culture system to assess flow shear forces upon cell adhesion within different structures

The cover image is based on the Research Article Use of an in vitro dynamic culture system to assess flow shear forces upon cell adhesion within different structures by Xingyou Hu et al., DOI: 10.1002/jctb.5834 .

     

Prediction of the structures of proteins with the UNRES force field, including dynamic formation and breaking of disulfide bonds

The presence of disulfide bonds is essential for maintaining the structure and function of many proteins. The disulfide bonds are usually formed dynamically during folding. This process is not accounted for in present algorithms for protein-structure prediction, which either deduce the possible positions of disulfide bonds only after the structure is formed or assume fixed disulfide bonds during the course of simulated folding. In this work, the conformational space annealing (CSA) method and the UNRES united-residue force field were extended to treat dynamic formation of disulfide bonds. A harmonic potential is imposed on the distance between disulfide-bonded cysteine side-chain centroids to describe the energetics of bond distortion and an energy gain of 5.5 kcal/mol is added for disulfide-bond formation. Formation, breaking and rearrangement of disulfide bonds are included in the CSA search by introducing appropriate operations; the search can also be carried out with a fixed disulfide-bond arrangement. The algorithm was applied to four proteins: 1EI0 (alpha), 1NKL (alpha), 1L1I (beta-helix) and 1ED0 (alpha + beta). For 1EI0, a low-energy structure with correct fold was obtained both in the runs without and with disulfide bonds; however, it was obtained as the lowest in energy only with the native disulfide-bond arrangement. For the other proteins studied, structures with the correct fold were obtained as the lowest (1NKL and 1L1I) or low-energy structures (1ED0) only in runs with disulfide bonds, although the final disulfide-bond arrangement was non-native. The results demonstrate that, by including the possibility of formation of disulfide bonds, the predictive power of the UNRES force field is enhanced, even though the disulfide-bond potential introduced here rarely produces disulfide bonds in native positions. To the best of our knowledge, this is the first algorithm for energy-based prediction of the structure of disulfide-bonded proteins without any assumption as to the positions of native disulfides or human intervention. Directions for improving the potentials and the search method are suggested.