Cyclic Flow Research Articles

Experimental and numerical investigation of texture evolution and the effects of intragranular backstresses in aluminum alloys subjected to large strain cyclic deformation

Strain hardening in FCC metals and alloys can be accompanied by the formation of deformation induced dislocation microstructures. These microstructures tend to form dislocation cells or nets which are characterized by three-dimensional tangles of dislocations that serve as “cell walls” and less dense internal regions “cell interiors”. The presence of such dislocation microstructure induces intragranular backstresses due to blockage of dislocation passage leading to kinematic hardening at the macroscopic scale. The present work focuses on the effects of dislocation induced backstresses and the accompanying texture evolution on strain hardening behavior of AA 6063-T6 extruded aluminum alloy during cyclic forward-reverse-forward (FRF) simple shear deformation. The accompanying texture evolution is characterized using electron backscatter diffraction (EBSD) texture measurements. The development of the underlying dislocation substructure during the cyclic simple shear loading is determined using transmission electron microscopy (TEM). Furthermore, a new crystal plasticity backstress hardening model is proposed to incorporate the effects of intragranular backstresses due to the dislocation cells substructure. The hardening model is validated by comparing the numerically predicted results against the experimental cyclic simple shear flow response as well as texture evolution. An excellent agreement is found between the simulated and experimental results. In particular, the proposed model is able to predict the experimentally observed Bauschinger effect as well as the accompanying texture evolution during cyclic simple shear testing. The applicability of the proposed backstress hardening model is further validated by applying it to different cyclic strain paths (i.e. tension-compression-tension (TCT) and compression-tension-compression (CTC)) for different strain amplitudes. The numerically predicted results show good agreement to the corresponding experimental cyclic test results.

Patterning of ultrathin polymethylmethacrylate films by in-situ photodirecting of the Marangoni flow

Laser heating and Marangoni flow result in the formation of surface structures with different geometries and shape on thin polymer films. By laser beam irradiation combined with a sample movement the solid polymethylmethacrylate (PMMA) films are heated and undergo phase transition which leads to a material flow. Since the laser beam has a non-linear distribution of energy, the PMMA film is heated inhomogeneously and a surface tension gradient in a lateral direction is introduced. During this procedure additional phenomena such as “reversible” or cyclic polymer flow also take place. The careful choice of experimental conditions enables the preparation of patterns with sophisticated geometries and with hierarchical pattern organization. Depending on initial PMMA film thickness and speed of the sample movement line arrays are created, which can subsequently be transformed into the crimped lines or system of circular holes. In addition, the introduction of a constant acceleration in the sample movement or a laser beam distortion enables the preparation of regularly crimped lines, ordered hexagonal holes or overlapped plates.

Enhancing residual trapping of supercritical CO2 via cyclic injections

AbstractWe utilize synchrotron X‐ray tomographic imaging to investigate the pore‐scale characteristics and residual trapping of supercritical CO2 (scCO2) over the course of multiple drainage‐imbibition (D‐I) cycles in Bentheimer sandstone cores. Capillary pressure measurements are paired with X‐ray image‐derived saturation and connectivity metrics which describe the extent of drainage and subsequent residual (end of imbibition) scCO2 trapping. For the first D‐I cycle, residual scCO2 trapping is suppressed due to high imbibition capillary number (Ca ≈ 10−6); however, residual scCO2 trapping dramatically increases for subsequent D‐I cycles carried out at the same Ca value. This behavior is not predicted by conventional multiphase trapping theory. The magnitude of scCO2 trapping increase is hysteretic and depends on the relative extent of the sequential drainage processes. The hysteretic pore‐scale behavior of the scCO2‐brine‐sandstone system observed in this study suggests that cyclic multiphase flow could potentially be used to increase scCO2 trapping for sequestration applications.

A High-Current, Stable Nonaqueous Organic Redox Flow Battery

Nonaqueous redox flow batteries are promising in pursuit of high energy density storage systems owing to the broad voltage windows (>2 V) but currently are facing key challenges such as limited cyclability and rate performance. To address these technical hurdles, here we report the nonaqueous organic flow battery chemistry based on N-methylphthalimide anolyte and 2,5-di-tert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene catholyte, which harvests a theoretical cell voltage of 2.30 V. The redox flow chemistry exhibits excellent cycling stability under both cyclic voltammetry and flow cell tests upon repeated cycling. A series of Daramic and Celgard porous separators are evaluated in this organic flow battery, which enable the cells to be operated at greatly improved current densities as high as 50 mA cm–2 compared to those of other nonaqueous flow systems. The stable cyclability and high-current operations of the organic flow battery system represent significant progress in the development of promising nonaqu...

Advanced testing method to evaluate the performance of respirator filter media

ABSTRACTFilter media for respirator applications are typically exposed to the cyclic flow condition, which is different from the constant flow condition adopted in filter testing standards. To understand the real performance of respirator filter media in the field it is required to investigate the penetration of particles through respirator filters under cyclic flow conditions representing breathing flow patterns of human beings. This article reports a new testing method for studying the individual effect of breathing frequency (BF) and peak inhalation flow rate (PIFR) on the particle penetration through respirator filter media. The new method includes the use of DMA (Differential Mobility Analyzer)-classified particles having the most penetrating particle size, MPPS (at the constant flowrate of equivalent mean inhalation flow rate, MIFR) as test aerosol. Two condensation particle counters (CPCs) are applied to measure the particle concentrations at the upstream and downstream of test filter media at the same time. Given the 10 Hz sampling time of CPCs, close-to-instantaneous particle penetration could be measured. A pilot study was performed to demonstrate the new testing method. It is found that the effect of BF on the particle penetration of test respirator filter media is of importance at all the tested peak inhalation flow rates (PIFRs), which is different from those reported in the previous work.

Cytochrome b 6 f function and localization, phosphorylation state of thylakoid membrane proteins and consequences on cyclic electron flow

Both the structure and the protein composition of thylakoid membranes have an impact on light harvesting and electron transfer in the photosynthetic chain. Thylakoid membranes form stacks and lamellae where photosystem II and photosystem I localize, respectively. Light-harvesting complexes II can be associated to either PSII or PSI depending on the redox state of the plastoquinone pool, and their distribution is governed by state transitions. Upon state transitions, the thylakoid ultrastructure and lateral distribution of proteins along the membrane are subject to significant rearrangements. In addition, quinone diffusion is limited to membrane microdomains and the cytochrome b 6 f complex localizes either to PSII-containing grana stacks or PSI-containing stroma lamellae. Here, we discuss possible similarities or differences between green algae and C3 plants on the functional consequences of such heterogeneities in the photosynthetic electron transport chain and propose a model in which quinones, accepting electrons either from PSII (linear flow) or NDH/PGR pathways (cyclic flow), represent a crucial control point. Our aim is to give an integrated description of these processes and discuss their potential roles in the balance between linear and cyclic electron flows.

Multi-degree cyclic flow shop robotic cell scheduling problem with multiple robots

This paper deals with the cyclic flow shop robotic cell scheduling problem with multiple robots, in which parts are processed successively on multiple machines with lower and upper bounds on processing times and the robots execute the transportation of parts between the machines. A novel mixed-integer linear programming model has been proposed for this problem. The proposed model simultaneously determines the optimal degree of the cyclic schedule and the optimal sequencing of the robots moves, which in return maximises the throughput rate. The validity of the proposed model is examined by a computational study on a set of randomly generated problem instances and solved using commercial optimisation software GAMS. The computational experiments indicate the efficiency of proposed model.

Transient gas liquid flow in hilly terrain pipelines

Two phase flow in a hilly terrain pipeline, composed of uphill and downhill sections, exhibits a complex transient behavior at low flow rates owing to the accumulation of liquid in the low elbows and gas in the top elbows. At low flow rates gravity has a dominant effect, while frictional losses can be neglected.In this work a simplified modeling approach is proposed that is able to predict the transient behavior of gas and liquid flowing in a complex terrain pipeline with multiple valleys. The condition that marks the boundary between severe slugging cyclic behavior and steady state flow is included.An experimental system which consists of three hilly sections was constructed. The experimental data were compared to the predicted results, yielding reasonable agreement in spite of the simplifying model assumptions.

Unsteady particle tracking of micro-particle deposition in the human nasal cavity under cyclic inspiratory flow

In this study, a fully unsteady computational fluid dynamics (CFD) model was used and the transient airflow properties during the entire breathing cycle, including inhalation and exhalation in a human nasal cavity, were evaluated. Unsteady particle tracking was performed to find the particle motion and deposition in the nasal airway using a Lagrangian approach. In most of earlier computer simulations, the assumption of quasi-steady or steady airflows averaged over the inhalation cycle were typically used to reduce the computational cost. In the present work particular attention was given to assessing the accuracy of these assumptions and their consequence on particle deposition in a human nasal cavity with paranasal sinuses. The simulation results for the airflow field showed significant differences between the unsteady and quasi-steady cases at low breathing rates near the beginning and end of the inspiration cycle. For breathing under a rest condition with a frequency of 0.25Hz, the quasi-steady airflow assumption in the nasal cavity was found to be reasonable when the instantaneous Strouhal number was smaller than 0.2.The instantaneous deposition of micro-particles was also studied, and the effects of unsteady accelerating and decelerating flows on the deposition fraction were examined. The simulation results showed that the deposition fractions were affected by the accelerating and decelerating airflows during the inhalation phase. The simulated micro-particle depositions under the cyclic breathing condition were compared with those for steady breathing with an equivalent mean airflow rate. It was found that while the general trend was similar, the steady breathing simulation with the mean airflow rate during inhalation cannot accurately predict the total micro-particle deposition for cyclic breathing, particularly for 1–5µm particles. Furthermore, the predicted regional depositions by the steady breathing were markedly different from those obtained under cyclic breathing.

Capture and recycle of industrial CO2 emissions using microalgae

A novel cyclic flow photobioreactor (PBR) for the capture and recycle of CO2 using microalgae was designed and deployed at a coal-fired power plant (Duke Energy’s East Bend Station). The PBR was operated continuously during the period May–September 2015, during which algae productivity of typically 0.1–0.2 g/(L day) was obtained. Maximum CO2 capture efficiency was achieved during peak sunlight hours, the largest recorded CO2 emission reduction corresponding to a value of 81 % (using a sparge time of 5 s/min). On average, CO2 capture efficiency during daylight hours was 44 %. The PBR at East Bend Station also served as a secondary scrubber for NO x and SO x , removing on average 41.5 % of the NO x and 100 % of the SO x from the flue gas. The effect of solar availability and self-shading on a rudimentary digital model of the cyclic flow PBR was examined using Autodesk Ecotect Analysis software. Initial results suggest that this is a promising tool for the optimization of PBR layout with respect to the utilization of available solar radiation.

Magnetocaloric Cooling Device with Reciprocating Motion of the Magnetic Field Source

This paper describes the magnetic cooling device model designed and built at the Institute of Non-Ferrous Metals in Gliwice, which utilizes reciprocating motion of a magnetic field source and a cyclic flow of a coolant through regenerator. The regenerator made from gadolinum made it possible to obtain an adiabatic temperature change of 2.5 K at the magnetic field of 0.8 T. The magnetic field source was built using neodymium magnets according to our own technology. For the heat transfer, a liquid having the specific heat of about 4000 J/(kg K) has been applied. We have also developed and applied a special driving system enabling reciprocating motion of the magnetic field source and of the pistons in the hot and cold heat exchangers. The tests were made with this cooling model showing that it was possible to obtain, at the frequency of 0.5 Hz, the liquid temperature gradient of 4 K. The potential energy savings resulting from application of this device have been evaluated and compared with the literature data presenting a pre-industrial prototype of the magnetic refrigerator utilizing similar solutions to those applied in our cooling model.

Influence of Clinically Relevant Mechanical Forces on Vascular Smooth Muscle Cells Under Chronic High Glucose: An In Vitro Dynamic Disease Model

In this study, we subjected vascular smooth muscle cells (VSMC) to acute and chronic high glucose conditions under physiologically relevant levels of cyclic strain and low wall shear forces to compare phenotypic modulation and thus conceptualize a dynamic-disease test model which captures cellular response more accurately in comparison with static cultures. P2-P6 rat aortic smooth muscle cells were seeded on type I collagen-coated silicone membranes and subjected to 0-7% cyclic strain at 1Hz and 0.3dynes/cm(2) shear stress from flow for 24hr under acute (25mM d-glucose, 84hr) and chronic high glucose conditions (25mM d-glucose, 3-4weeks). Samples were analyzed for cell proliferation, percent apoptosis, cellular hypertrophy, and expression levels of smooth muscle contractile state-associated markers with 0.05 level of significance. Concomitant application of cyclic strain and flow shear resulted in an overall increase in proliferation of VSMCs under both acute and chronic high glucose conditions as compared with normal glucose control (P<0.0001). Application of both cyclic strain and cyclic strain shear resulted in a significant increase in percent apoptosis with chronic high glucose treatment in comparison with both normal glucose controls (P<0.0001) and acute high glucose (P<0.0001). Cellular hypertrophy as estimated by measuring cell area and aspect ratio revealed a significantly altered morphology due to concomitant loading under chronic high glucose conditions with significantly higher cell area (P<0.0001) and lower aspect ratio (P<0.0001) indicative of a relatively rounded morphology as compared with normal glucose controls. Western blot analysis demonstrated reduced expression of SM α-actin (P<0.0001), calponin (P<0.0001), and SM22α (P=0.0008) for concomitant loading under chronic high glucose treatment as compared with normal glucose controls. Concomitant application of cyclic strain and low wall shear stress resulted in greater phenotypic modulation of VSMCs due to chronic high glucose treatment as compared with normal glucose controls, thus implicating cellular-response differences which may impact progression of in-stent restenosis in diabetic patients with poorly controlled hyperglycemia. Similarity of VSMC response from our study to existing preclinical models of diabetes and reports of altered phenotype of VSMCs isolated from diabetic patients substantiate the relevance of our dynamic disease test model.

Multi-degree cyclic flow shop robotic cell scheduling problem: Ant colony optimization

This paper deals with the multi-degree cyclic robotic flow shop cell scheduling problem with multiple robots. All the parts are processed successively through the machines with standard processing times while single gripper robots perform the transportation operations of parts between the machines. Due to the special characteristics of the considered problem, a metaheuristic algorithm based on ant colony optimization has been proposed. The proposed algorithm simultaneously determines the optimal degree of the cyclic schedule, the robot assignments for the transportation operations, and the optimal sequence of robots' moves, which in return maximize the throughput rate. The efficiency of the proposed metaheuristic algorithm is examined by a computational study on a set of randomly generated problem instances.

Parallel metaheuristics for the cyclic flow shop scheduling problem

In the paper there was proposed a new method of detection of block properties for cyclic flow shop problem with machine setups that uses patterns designated for each machine by solving the adequate traveling salesman problem. The proposed method is intended to be run in the environment of shared memory in concurrent computations, such as coprocessors, GPU, or machines with multi-core CPUs. The proposed method of accelerating the review of the neighborhood through the use of the blocks was tested on two parallel metaheuristics: tabu search and simulated annealing.

Performance of an improperly sized and stretched-out loose-fitting powered air-purifying respirator: Manikin-based study

ABSTRACTThe objective of this study was to investigate the protection level offered by a Powered Air-Purifying Respirator (PAPR) equipped with an improperly sized or stretched-out loose-fitting facepiece using constant and cyclic flow conditions. Improperly sized PAPR facepieces of two models as well as a stretched-out facepiece were tested. These facepieces were examined in two versions: with and without exhaust holes. Loose-fitting facepieces (size “large”) were donned on a small manikin headform and challenged with sodium chloride (NaCl) aerosol particles in an exposure chamber. Four cyclic flows with mean inspiratory flows (MIFs) of 30, 55, 85, and 135 L/min were applied using an electromechanical Breathing Recording and Simulation System (BRSS). The manikin Fit Factor (mFF) was determined as the ratio of aerosol concentrations outside (Cout) to inside (Cin) of the facepiece, measured with a P-Trak condensation particle counter (CPC). Results showed that the mFF decreased exponentially with increasing MIF. The mFF values of the stretched-out facepiece were significantly lower than those obtained for the undamaged ones. Facepiece type and MIF were found to significantly affect the performance of the loose-fitting PAPR. The effect of the exhaust holes was less pronounced and depended on the facepiece type. It was concluded that an improperly sized facepiece might potentially offer relatively low protection (mFF < 250) at high to strenuous workloads. The testing was also performed at a constant inhalation flow to explore the mechanism of the particle-facepiece interaction. Results obtained with cyclic flow pattern were consistent with the data generated when testing the loose-fitting PAPR under constant flow conditions. The time-weighted average values of mFF calculated from the measurements conducted under the constant flow regime were capable of predicting the protection under cyclic flow regime. The findings suggest that program administrators need to equip employees with properly sized facepieces and remove stretched-out ones from workplace. Manufacturers should emphasize the importance of proper sizing with their user instructions.

PETO Interacts with Other Effectors of Cyclic Electron Flow in Chlamydomonas

While photosynthetic linear electron flow produces both ATP and NADPH, cyclic electron flow (CEF) around photosystem I (PSI) and cytochrome b6f generates only ATP. CEF is thus essential to balance the supply of ATP and NADPH for carbon fixation; however, it remains unclear how the system tunes the relative levels of linear and cyclic flow. Here, we show that PETO, a transmembrane thylakoid phosphoprotein specific of green algae, contributes to the stimulation of CEF when cells are placed in anoxia. In oxic conditions, PETO co-fractionates with other thylakoid proteins involved in CEF (ANR1, PGRL1, FNR). In PETO-knockdown strains, interactions between these CEF proteins are affected. Anoxia triggers a reorganization of the membrane, so that a subpopulation of PSI and cytochrome b6f now co-fractionates with the CEF effectors in sucrose gradients. The absence of PETO impairs this reorganization. Affinity purification identifies ANR1 as a major interactant of PETO. ANR1 contains two ANR domains, which are also found in the N-terminal region of NdhS, the ferredoxin-binding subunit of the plant ferredoxin-plastoquinone oxidoreductase (NDH). We propose that the ANR domain was co-opted by two unrelated CEF systems (PGR and NDH), possibly as a sensor of the redox state of the membrane.

ОСОБЕННОСТИ АДАПТАЦИИ В ЖИЗНЕННОМ ЦИКЛЕ РАЗВИТИЯ ПРЕДПРИЯТИЯ

The aim of study is structuring of life cycle stages of organization in accordance with the changes in it, and taking into account mechanisms that make it possible to identify the point of transition from one stage of the life cycle to the next one. Methods. We used a comparison method, which revealed the similarities and differences between alive and economic systems in the process of their life cycle. There were also used the empirical and theoretical methods, such as methods of analogy, abstraction and deduction. They allowed establishing specific characteristics of the organization transition to a new stage of its life cycle in a number of essential features, means the basis of the particular nature and purpose of the organization to adapt to environmental conditions. The result of this study is to determine the basic characteristics of the enterprise behavior at stages of its life cycle development from the perspective of an evolutionary approach to the development of economic systems. Significant changes in the activities of the enterprise include the existence of a variety of transients, which are specific and determined by the features of the environment in which they occur. Ordering of the properties of the environment that create the conditions for the operation and development of enterprises, also showed, that one of the properties is adaptation, that connects the possibilities of the environment with the potential for development of internal. Comparative characteristics of the principles of alive and economic systems has allowed revealing many similarities. However, the economic system are developed under human control, based on his knowledge and skills, which enabled to justify adaptation to the environment as the main managerial transition characteristic to a new stage of development. Adaptation and its competitive nature determine the range of basic management techniques in a cyclic flow of the organization development. This approach allows to justify the type of adaptation and development cycle of the enterprise and to determine the direction of its further positive long-term changes in the competitive struggle. The practical significance. Revealed essence of adaptation in the process of organization life cycle, not only allows identifying the transition to a different phase of development, but also helps to identify the challenges that the organization faced in the process of achieving the goal. The essence of adaptation considered in three processes of organization activity: the main, auxiliary and management, allowing identifying the characteristics of each development cycle and their priorities for organizations. Value/originality. The novelty of this study is a comparative description of the basic principles of alive and economic systems, the identification of the properties of external environment of the organization, which creates conditions for the functioning and development of organizations, and the selection on their basis the adaptation mechanism as the basic property of evolutionary systems. As well, as value of the adaptation at each stage of development of the organization to ensure its long-term development.

Precise Observation of Growth of Surface Oxide Layer for Pd and Cu Nanoparticles During Oxidative/Reductive Gases Cyclic Flow Studied by Real-Time-Resolved XAFS Spectroscopy

Precise Observation of Growth of Surface Oxide Layer for Pd and Cu Nanoparticles During Oxidative/Reductive Gases Cyclic Flow Studied by Real-Time-Resolved XAFS Spectroscopy

Snail tecnologies and cultures in the age of mobility: mobile communication and identities in the Shuar time/space

In mobile ontology and in the Shuar dynamic, cyclic, one-dimensional worldview, time and space flow simultaneously (de Salvador y Martínez, 2015b; Martínez, &amp; de Salvador, 2015; Martínez et al., 2015). Authors such as Ling and Haddon emphasised the influence of mobile phones on human movement patterns, pointing out that they offer “freedom of contact”, given their nomadic nature, and the possibility to free ourselves from the spatial context and enter a space of communicative flows, where only time exists. The Where - as a Shuar would say - that is, Space, marches on together with time, in a global spatial-temporal dimension. Since mobile phones draw us closer to a nomadic life, turning us into snails (Fortunati, 2005) that carry a whole network of relationships in the back, an analysis of the uses of mobile phones (from this point of view) by a nomadic people such as the Shuar seems particularly interesting. The endlessly spiralling snail metaphor, which the Shuar use to describe their worldview, and the characterisation of nature resemble today’s mobile technology we all carry about. This essay is intended to emphasise the worldviews of the Mobile Age and the Indigenous, Shuar Age so as to analyse the similarities and differences in the spatial-temporal conception, as well as its impacts on identity.

Fractional order modelling of the cumulative deformation of granular soils under cyclic loading

To model the cumulative deformation of granular soils under cyclic loading, a mathematical model was proposed. The power law connection between the shear strain and loading cycle was represented by using fractional derivative approach. The volumetric strain was characterized by a modified cyclic flow rule which considered the effect of particle breakage. All model parameters were obtained by the cyclic and static triaxial tests. Predictions of the test results were provided to validate the proposed model. Comparison with an existing cumulative model was also made to show the advantage of the proposed model.