Compression Section Research Articles

Optimizing synthesis parameters of short carbon fiber reinforced polysulfonamide composites by using response surface methodology

In this paper, the synthesis parameters of short carbon fiber reinforced polysulfonamide composites (SCF/PSA composites) were optimized. Box-Behnken design was applied to conduct the experiments. The influences of temperature, time and composition on mechanical strength of SCF/PSA composites were studied by response surface methodology and grey relational analysis. The results show the composition was the most influential factor and the optimal process parameters are as follows: 372.88 °C (temperature), 29.17 min (time), and 40 wt% (composition). The fracture surface morphology of compression and tension sections of the obtained composites was analyzed by Tungsten filament scanning electron microscopy (TF-SEM).

基于精细积分法和传递矩阵法的变截面压杆临界力

针对变截面压杆临界力提出了一种基于精细积分法和传递矩阵法的组合法。先将压杆离散为若干段，视每段压杆为等截面，采用材料力学理论、平衡原理及矩阵理论，导出了各段压杆的传递矩阵。然后利用相邻段间变形与内力关系，导出了整个变截面压杆的传递矩阵。最后，利用整个压杆两端约束条件，得到了求解变截面压杆临界力的特征方程。结果表明：本方法是一种易于编程、精度易于控制，也易于使用的方法。 A combination method of critical load of variable cross-section compressive rods was put forward based on precise integration method and transfer matrix method. First of all, the rod was divided into many sections and every section was viewed as uniform cross-section; the transfer matrixes of all the compressive sections were deduced according to theory of material mechanics, equilibrium principle and theory of matrix. Then the transfer matrix of whole variable cross-section compressive rod was obtained by means of deformation and internal force relationships between adjacent sections. Finally, a characteristic equation to solve the critical load of the variable cross-section compressive rod was presented. Results show that the present method is an easy one to program, control precisely and use conveniently.

Evaluation of mechanical characteristics of concrete beams under constant loading with alkali-silica reaction

This experiment studies the damaging alkali-silica reaction (ASR) expansion effects on the structural performance and mechanical properties of reinforced concrete beams. The beams were cured under standard conditions. In order to provide in-service situations, flexural loading was applied on beams to induce cracks. The newly formed strains on concrete beams were measured along with the compression and tension sections. The results showed that beams with high reactivity in aggregates suffered from more compression strain. It is noteworthy that increasing compression steel with constant tension steel eventuated to substantial effects on tension expansion. Furthermore, increasing the tension steel, while keeping compression steel constant, resulted in minor influences on compression-expansion. Effects of ASR phenomena on the mechanical characteristics and the expansion of concrete are more important and noticeable on reinforced concrete beams. In concrete beams with ASR, ultimate loading was decreased because of largely irreversible steel strains.

Evaluation of mechanical characteristics of concrete beams under constant loading with alkali-silica reaction

This experiment studies the damaging alkali-silica reaction (ASR) expansion effects on the structural performance and mechanical properties of reinforced concrete beams. The beams were cured under standard conditions. In order to provide in-service situations, flexural loading was applied on beams to induce cracks. The newly formed strains on concrete beams were measured along with the compression and tension sections. The results showed that beams with high reactivity in aggregates suffered from more compression strain. It is noteworthy that increasing compression steel with constant tension steel eventuated to substantial effects on tension expansion. Furthermore, increasing the tension steel, while keeping compression steel constant, resulted in minor influences on compression-expansion. Effects of ASR phenomena on the mechanical characteristics and the expansion of concrete are more important and noticeable on reinforced concrete beams. In concrete beams with ASR, ultimate loading was decreased because of largely irreversible steel strains.

Behavior of Rectangular Hollow Bridge Compression Section by Detail of Cross-tie

Purpose of this study is to investigate structural behavior of the rectangular hollow column with various transverse reinforcement details. Experimental variables are diameter, arrangement details and lateral spacing of cross tie. A total of 66 column specimens have been prepared and tested under axial compressive load. Test results showed that behaviors of column specimens were different depending on the cross tie details. Specimens with cross tie wrapping longitudinal steel and transverse steel have greater strength and ductility than specimens with cross tie wrapping the longitudinal steel.

Longitudinal transport measurements in an energy recovery accelerator with triple bend achromat arcs

Longitudinal properties of electron bunches (energy spread and bunch length) and their manipulation are of importance in free electron lasers (FELs), where magnetic bunch length compression is a common feature of beam transport. Recirculating accelerators and energy recovery linac accelerators (ERLs) have been used as FEL drivers for several decades and control of longitudinal beam transport is particularly important in their magnet lattices. We report on measurements of longitudinal transport properties in an ERL-FEL, the ALICE (Accelerators and Lasers in Combined Experiments) accelerator at Daresbury Laboratory. ALICE is an energy recovery research accelerator that drives an infrared free electron laser. By measuring the time of arrival of electron bunches, the canonical longitudinal transport quantities were measured in the beam transport and bunch compression sections of the lattice. ALICE includes a four-dipole bunch compression chicane providing fixed longitudinal transport, and triple bend achromat arcs including sextupole magnets where the first and second order longitudinal transport can be adjusted. The longitudinal transport properties in these lattice sections were measured and compared with the theoretical model of the lattice. A reasonable level of agreement has been found. The effect of sextupoles in second order, as well as first order, longitudinal correction is considered, with the measurements indicating the level of alignment of the beam to the center of the sextupole.

Uniaxial compression behaviour and soil physical quality of topsoils under conventional and conservation tillage

Considering conventional tillage with a mouldboard plough and conservation tillage with a cultivator or disc harrow, this study analysed whether structural differences in the soil of the lower topsoil led to any difference in this layer's susceptibility to compaction, and also how density changed – in the whole soil and also in the individual aggregates – during the compaction process in both tillage variants. To this end, soil samples were taken from the lower topsoil of seven medium-term and long-term soil tillage trials conducted in Central Europe. Compression tests were performed on these samples and they were also used to determine dry bulk density, aggregate density, air capacity and saturated hydraulic conductivity. The stress/bulk density functions as well as the stress/strain functions from the compression tests were analysed and the precompression stress determined. At two test sites, compaction behaviour was analysed for whole soil and for aggregates separately. In the case of conservation tillage, the soil structure demonstrated higher dry bulk density as well as lower air capacity and saturated hydraulic conductivity. Aggregate density was mostly similar. It increased relatively slowly during compaction, and often not before high loading steps. This is why higher precompression stress values in the variants under conservation tillage were mostly the result of a dense compaction of aggregates, and indicated higher stability against mechanical loads. However, for both variants the virgin compression section of the stress/bulk density functions displayed similar compression behaviour; and generally higher settlement for conventional tillage in the compression test did not result in higher dry bulk densities than with conservation tillage. Stability against mechanical loads in the conservation tillage variants should therefore not be overestimated.

Recent Experiments at NDCX-II: Irradiation of Materials Using Short, Intense Ion Beams

Author(s): Seidl, PA; Ji, Q; Persaud, A; Feinberg, E; Ludewigt, B; Silverman, M; Sulyman, A; Waldron, WL; Schenkel, T; Barnard, JJ; Friedman, A; Grote, DP; Gilson, EP; Kaganovich, ID; Stepanov, A; Treffert, F; Zimmer, M | Abstract: We present an overview of the performance of the Neutralized Drift Compression Experiment-II (NDCX-II) accelerator at Berkeley Lab, and summarize recent studies of material properties created with nanosecond and millimeter-scale ion beam pulses. The scientific topics being explored include the dynamics of ion induced damage in materials, materials synthesis far from equilibrium, warm dense matter and intense beam-plasma physics. We summarize the improved accelerator performance, diagnostics and results of beam-induced irradiation of thin samples of, e.g., tin and silicon. Bunches with over 3x10^10 ions, 1- mm radius, and 2-30 ns FWHM duration have been created. To achieve these short pulse durations and mm-scale focal spot radii, the 1.2 MeV He+ ion beam is neutralized in a drift compression section which removes the space charge defocusing effect during final compression and focusing. Quantitative comparison of detailed particle-in-cell simulations with the experiment play an important role in optimizing accelerator performance; these keep pace with the accelerator repetition rate of ~1/minute.

Exergoeconomic analysis and optimization of a solar driven dual-evaporator vapor compression-absorption cascade refrigeration system using water/CuO nanofluid

In this paper, a novel cascade refrigeration system integrated with flat plate solar collector is modeled and optimized. While LiBrH2O is applied as fluid pair in cascade absorption section, R134a, R1234ze, R1234yf, R407C and R22 fluids are applied in the vapor compression section and the water/copper oxide (CuO) nanofluid is applied as the heat transfer medium inside the collector subsystem. Nanoparticles volume fraction, mass flow rate of strong solution, low pressure of absorption section, collector tilt angle as well as solar collector area are selected as design parameters while the daily thermal and exergy coefficients of performance and total product cost rate are selected as three objective functions. Non-dominated Sort Genetic Algorithm-II (NSGA-II) is individually employed to achieve the final solutions of the system for the best working fluids from the thermodynamic and thermoeconomic viewpoints. The proposed system modeling represents that R134a is the best fluid from the energy and exergy viewpoints with daily energy and exergy coefficients of performance of 9.340% and 0.5815%, respectively and R1234ze with the total product cost rate of 7016 $/year is the best working fluid from the exergoeconomic viewpoint. The optimization results indicate that R134a with 2.4% and 2% improvement of the daily energy and exergy coefficients of performance, respectively, relative to the base case needs minimum collector area with amount of 680 m2 among the other working fluids. In addition, R1234ze with the total product cost rate reduction of 2.4% requires maximum nanoparticles and collector area with values of 0.041 and 702.01 m2, respectively.

Hot-Rolled Steel and Steel-Concrete Composite Design Incorporating Strain Hardening

Current design codes for steel and steel-concrete composite structures are based on elastic, perfectly plastic material behaviour and can lead to overly conservative strength predictions due to the neglect of the beneficial influence of strain hardening, particularly in the case of stocky, bare steel cross-sections and composite beams under sagging bending moments. The Continuous Strength Method (CSM) is a deformation based design method that enables material strain hardening properties to be exploited, thus resulting in more accurate capacity predictions. In this paper, a strain hardening material model, which can closely represent the stress-strain response of hot-rolled steel, is introduced and incorporated into the CSM design framework. The CSM cross-section resistance functions, incorporating strain hardening, are derived for hot-rolled steel sections in compression and bending, as well as hot-rolled steel-concrete composite sections where their neutral axes lie within the concrete slab in bending. Comparisons of the capacity predictions with a range of experimental data from the literature and finite element data generated herein demonstrate the applicability and benefits of the proposed approach.

Performance of a jaws inlet under off-design conditions

Numerical analysis was conducted of a jaws inlet under different working conditions, including angles of attack of 0° and 3°, varying Mach number, and varying back pressure with a constant-area isolator, to investigate its performance and flow fields of starting and unstarting states. Results reveal that the jaws inlet has an enhanced flow capture capability in starting states, with the mass capture ratio higher than 0.96, but relatively reduced working range of inflow Mach numbers. Its performance at a low Mach number is better than that at a high Mach number. Non-uniform flow fields are observed in unstarting cases at low Mach numbers and high back pressures, while separation structures are confined in the pitching compression section. Further increase in Mach number or decrease in back pressure does not result in significant changes in the separation structures. In the unstarting case under a high back pressure, it is hard to achieve restarting through reductions in the back pressure.

Integration between concentrated solar power plant and desalination

AbstractFresh water and electricity production in desert areas via the use of solar radiation represent examples of sustainability. The concentration of solar power by means of parabolic trough (PT-CSP) technology has a great potential not yet exploited in the realm of renewable energy production. A new technology for the solar energy section is being proposed by the authors which uses air as a working fluid. The use of air allows the cycle to be coupled with an inter-cooled compression section and a re-heated expansion section which is called Discrete Ericsson Cycle, (DEC-based plant). The paper presents an integration of such a CSP-DEC plant with desalination: where freshwater is produced according to a Low Temperature Multi Effect Distillation (LT-MED) technology. The LT-MED plant operates on the heat from the air coolers in the inter-stage cooling of the DEC-based plant. This heat is normally expelled to atmosphere. In fact, the heated air has the same temperature ranges required for the operation of ...

Short-pulse, compressed ion beams at the Neutralized Drift Compression Experiment

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target.

Value locality based storage compression memory architecture for ECG sensor node

This paper proposes a value compression memory architecture for QRS detection in ultra-low-power ECG sensor nodes. Based on the exploration of value spatial locality in the most critical preprocessing stage of the ECG algorithm, a cost efficient compression strategy, which reorganizes several adjacent sample values into a base value with several displacements, is proposed. The displacements will be half or quarter scale quantifications; as a result, the storage size is reduced. The memory architecture saves memory space by storing compressed data with value spatial locality into a compressed memory section and by using a small, uncompressed memory section as backup to store the uncompressed data when a value spatial locality miss occurs. Furthermore, a low-power accession strategy is proposed to achieve low-power accession. An embodiment of the proposed memory architecture has been evaluated using the MIT/BIH database, the proposed memory architecture and a low-power accession strategy to achieve memory space savings of 32.5% and to achieve a 68.1% power reduction with a negligible performance reduction of 0.2%.

The Design Optimisation of the Co-extrusion of a Wood-like Grain Surface Composite Polymer Profile

A wood-like grain surface composite polymer profile (or wood-like profile) was fabricated by the extrusion moulding of melting multi-component polymers through a co-extrusion die, with two extruders feeding the co-extrusion die simultaneously. To improve the extrusion velocity uniformity of melting composite polymers, and decrease the distortion of wood-like grain profiles, this study treats the velocity equality among sub-regions in the wood-like profile cross-sections at the exit of the co-extrusion die as its optimisation objective. Meanwhile, the compression section gap, which exerts a significant influence on flow uniformity is selected as the design variable. Finite element numerical simulation and an ERP system are adopted to optimise the design in combination with a CAD/CAE network system co-extrusion die expert database of concurrent engineering. The optimisation design of case studies confirms that the velocity uniformity of the optimised wood-like grain profile melts presents a significant improvement in each sub-region at the exit of the co-extrusion die. Moreover, the distortion of composite profiles is decreased. The structural dimensions and performance of the composite profiles meet industrial demands.

Local buckling and ultimate strength of slender elliptical hollow sections in compression

The local buckling behaviour and ultimate cross-sectional strength of tubular elliptical profiles in compression is examined in this study through numerical modelling. The numerical models were first validated against previous experimental data with good agreement observed, enabling an extensive parametric study to be performed. A total of 270 elliptical sections were simulated in order to examine the influence of cross-section aspect ratio, geometric imperfections and local slendernesses. The obtained ultimate capacities, load–deformation responses and failure modes are discussed. It was found that for lower cross-section aspect ratios the behaviour of the elliptical hollow sections (EHS) was similar to that of cylindrical shells across a number of metrics; however, as the aspect ratio increased, more plate-like stable postbuckling behaviour was observed. Imperfection sensitivity was found to decrease with increasing slenderness and aspect ratio. The influence of the shape of the initial imperfection on the strengths of the EHS columns was also assessed and was found to be generally limited. Finally, a design method has been proposed for Class 4 EHS members that reflects the reduction in capacity due to local buckling with increasing slenderness, but also recognises the improved postbuckling stability with increasing aspect ratio; the proposals were shown to provide safe and accurate predictions for the strengths of the EHS columns with nondimensional local slendernesses up to 2.5 and aspect ratios from 1.1 to 5.0.

Comparative performance study of vapour compression-absorption cascaded system at optimum condensing temperature

The present study thermodynamically analyse a vapour compression-absorption cascaded refrigeration system (CRS) that uses R407C and H2O-LiBr as refrigerants, to determine the optimal condensing temperature of cascade condenser. The optimum condensing temperature of cascade condenser is found to be 18°C for 83.09 kW refrigeration capacity at an evaporating and condensing temperature of 0.4°C and 46.8°C respectively. The optimum condensing temperature is found, to maximise the rational efficiency of CRS and minimise the total irreversibility of system. Further comparative study of CRS with equivalent vapour compression refrigeration system (VCRS) used for water chilling applications shows that the electric power consumption in CRS is reduced by 70% and COP of compression section is improved by 235% as compared to equivalent VCRS.

Designing Compressed Reinforcement Cross-Sections by Curvature and Nominal Stiffness Methods

The paper attempts to discuss the still significant issue of methods of design of the reinforced concrete columns according to PN-EN 1992-1-1:2008/A1:2015-03. Two algorithms of the dimensioning sections were developed according to two standard methods of dimensioning eccentrically compressed sections: the method of nominal stiffness (NS) and the method of nominal curvature (NC). Using both algorithms, computer programs in Excel were created. A comparative analysis of several examples of calculation were performed to compare the results of dimensioning of sections eccentrically compressed. The results obtained by the NC method give about 10% less surface reinforcement when loaded with big eccentricity and over 50% less when small eccentricity is applied.

Experimental study of stainless steel angles and channels in bending

Substantial research has been conducted in recent years into the structural response of stainless steel components, with the focus being primarily on doubly symmetric cross-sections. Limited experimental data exist on non-doubly symmetric stainless steel sections in compression, while there is an absence of such data in bending, despite these sections being widely used in the construction industry as wind posts, lintels and so on. To address this limitation, and to bring an improved understanding of the behaviour of these sections, an experimental study into the flexural response of stainless steel channels bent about their minor axis and angles bent about their stronger geometric axis is described herein. In total, 16 bending tests on austenitic stainless steel beams have been conducted and the obtained results, including the full load-deformation history and observed failure modes have been described. Auxiliary tests on tensile coupons extracted from the tested sections and initial geometric imperfection measurements have also been performed and are reported in detail. The influence of the spread of plasticity and strain hardening on the shift of the neutral axis and the ultimate load carrying capacity is also examined. Based on the obtained test results, the current design provisions of EN 1993-1-4 [1] for these types of cross-sections were assessed and found to be unduly conservative. The effect of strain hardening on the structural response of stocky stainless steel sections and the need to account for it in design has been highlighted.

Short intense ion pulses for materials and warm dense matter research

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1mm within 2ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.