One-directional Flow Research Articles

Unraveling the Caribbean Origins, Makers, and Wearers of the Robe à la creole , c. 1780–1815

Abstract: In 1783, Marie Antoinette shocked the French public with a portrait that depicted her in a thin, white muslin dress. Although later known (because of its connection to the queen) as the chemise a la reine , the dress was originally described as a " robe à la creole " in her diary and was inspired by the gowns worn by the wives of plantation owners in the French Caribbean. This article investigates the "creole" origins, makers, and wearers of this garment in the British and French Caribbean, arguing that it was not only the product of the labors of enslaved and free Caribbean women of color, but that their parallel interactions with the robe also worked to disrupt and subvert the racist neoclassical connotations that came to surround the dress in Europe. Moving back and forth between Europe and the Caribbean, this essay explores how the dissemination of fashion was not a one-directional flow from the metropole to its colonies, but rather part of a wider network of circulation and dialogue between the two.

Numerical study of Tesla valve flow field on proton exchange membrane fuel cell performance

Effective flow channels in proton exchange membrane fuel cells (PEMFCs) can provide sufficient reactant and a more uniform reactant distribution, which allows the fuel cells to operate with high performances. The Tesla valve structure is thought to be a feasible structure for channel design due to its one-directional flow characteristics, yielding different performances with different flow directions. Numerical studies were conducted in this work to investigate the impacts of the channel structure, flow direction, and excess air coefficient on the fuel cell performance. Three types of flow channels (straight, symmetric Tesla valve, and asymmetric Tesla valve) and two flow directions (forward and reverse) were studied. The results showed that the maximum power density of the reversed asymmetric Tesla valve increased by 10.08 % compared to that of the conventional straight channel. Detailed research revealed that the Tesla valve resulted in a more intense flow than the conventional straight channel. The symmetric Tesla valve resulted in a greater pressure drop than the asymmetric valve. The Tesla valves with reverse flow could significantly limit the formation of an oxygen dead zone. Hence, enhanced Z-direction mass transfer and the lowest standard deviations of the oxygen and water distributions were observed. The effects of the excess air coefficient on the net power density were also studied. Increasing the excess air mass to the cathode facilitated the enhancement of the electrode voltage but required more parasitic power due to the growth in the pressure drop along the flow channel.

Novel experimental technique to evaluate soil thermal conductivity in a transient state

novel experimental technique to evaluate soil thermal conductivity in a transient state

A Two-Step Matheuristics for Order-Picking Process Problems with One-Directional Material Flow and Buffers

The necessity for undertaking this research is driven by the prevailing challenges encountered in logistic centers. This study addresses a logistic order-picking issue involving unidirectional conveyors and buffers, which are assigned to racks and pickers with the objective of minimizing the makespan. Subsequently, two variations of a two-step matheuristic approach are proposed as solution methodologies. These matheuristics entail decomposing the primary order-picking problem into two subproblems. In the initial step, the problem of minimizing the free time for pickers/buffers is solved, followed by an investigation into minimizing order picking makespan. An experimentation phase is carried out across three versions of a distribution center layout, wherein one or more pickers are allocated to one or more buffers, spanning 120 test instances. The research findings indicate that employing a mathematical programming-based technique holds promise for yielding solutions within reasonable computational timeframes, particularly when distributing products to consumers with limited product variety within the order. Furthermore, the proposed technique offers the advantages of expediency and simplicity, rendering it suitable for adoption in the process of designing and selecting order-picking systems.

Abrasive water flow polishing of superalloy microholes drilled by electrical discharge machining

Superalloy microholes resulting from electrical discharge drilling (EDD) can have recast layers and microcracks on the machined surfaces. In this study, the abrasive water flow polishing (AWFP) of superalloy microholes machined by EDD was investigated. The recast layer and surface roughness resulting from the EDD process were evaluated through orthogonal experiments. The machining mechanism of AWFP was analyzed. The effects of AWFP parameters were investigated experimentally. The results show that the material removal rate and surface roughness at the hole exit were better than those at the entrance for one-directional fluid flow during the process. Garnet abrasives achieved better polished roughness and a lower material removal rate than alumina abrasives. The taper angle of the target holes changed slightly from positive to negative after AWFP. The corner edge was slightly rounded on the fluid inlet side. Using a bidirectional fluid resulted in better dimensional uniformity and surface roughness at the entrance and exit. This study verified that AWFP can remove the recast layer and microcracks on the hole wall caused by EDD and reduce the surface roughness from an initial Ra of 5.7 μm to an Ra of 0.6 μm.

Information flow among stocks, bonds, and convertible bonds.

This study examines the information flow between convertible bonds (CBs) and other investment assets, such as stocks and bonds. In particular, we employ transfer entropy (TE) as a proxy for the causal effect between the two assets considering that one of the most widely used methods, Granger causality, requires strict assumptions. When adopting TE, we find that asymmetric information flow arising between assets depends on macroeconomic phases. The stock and bond markets affected the CB market prior to and during the global financial crisis, respectively. In the post-crisis period, we find no meaningful information exchange between CBs and other investment assets concerning their return series. However, we observe a significant cause-effect relationship between CBs and stocks in the rise-fall patterns of their price series. The findings suggest that the appearance of one-directional information flow depends on macroeconomic conditions and the level of data, for example, return series or price fluctuations. Accordingly, investors could exploit this pattern predictability in their portfolio management. In addition, policymakers must closely monitor the information flow among the three markets. When any two markets exchange information in a state of strong market integration, unbalanced regulation between them could lead to market distortions and regulatory arbitrage.

Peristaltic micropump using polyvinyl chloride gels with micropatterned surface

This paper presents a pump using polyvinyl chloride (PVC) gel. PVC gels are compliant, have a simple structure, and exhibit large deformation at voltages in the range of 100–1000 V, which make them suitable for micropumps. In this study, a PVC gel sheet with a surface pattern that enhances active deformation in the thickness direction was employed for the fabrication of a pump. To this end, the PVC gel sheet was sandwiched between three sets of anode and cathode electrodes, after which voltages were sequentially applied to these electrodes to generate a peristaltic deformation of the gel sheet, thus pushing the liquid and creating a one-directional flow. Various pumps were fabricated using PVC gel sheets with different surface patterns, and the pumps were characterized. The pumps exhibited an outline dimension of 35 mm × 25 mm with a thickness of 4 mm, corresponding to a total volume of 3.5 × 103 mm3. The results revealed that the pump fabricated using a 174-μm-high pyramid-patterned gel sheet generated a flow rate of 224.1 µL/min at an applied voltage of 800 V and a driving frequency of 3 Hz. This observed value is comparable to or better than those of existing pumps based on smart materials.

Householding and Land Ownership: Constructing a Typology of Circular Migration of Cambodian Migrant Workers in Thailand

Labor migration is no longer a linear movement or even a one-way and one-directional flow of labor. The advancements in transportation and communication technologies have changed trans-border mobility from permanent to a large extent, circular. Interestingly, the wage gap between labor-sending and labor-receiving countries is not the only reason triggering the move. Working abroad has become a decision made by Cambodian households, resulting in about one million Cambodian migrant workers in Thailand. Migrant workers, especially undocumented laborers, are more vulnerable to abuse, exploitation, and trafficking. In response, this irregularity facilitates the circularity of these migrant workers. To explore this phenomenon, this paper attempts to construct the typology of circular migration, namely quasi-permanent migration, sojourning, and return. Qualitative methods consisting of group and individual interviews were employed in interviewing Cambodian workers in Rayong, Thailand, and returnees in Kampong Cham, Cambodia. The findings suggest that land-owning Cambodian households adopt a householding strategy, work in Thailand, and migrate circularly back home periodically.

Experimental Study on The Performance of One-Directional and Bi-Directional Flow Conditions Across In-Line Tube Banks Heat Exchanger

The one-directional flow condition and the bi-directional flow condition are two flow conditions that can be found in many energy systems depending on the nature of the flow and the working mechanism of the system. This paper reports the differences in heat transfer performance for an in-line tube banks heat exchanger that is placed in the one-directional and the bi-directional flow conditions. The experiments involve the use of a blower as a flow inducer for one-directional flow while a loudspeaker with a constant frequency of 14.2 Hz is used as a flow inducer for bi-directional flow condition. A quarter wavelength resonator with 4 mm wall thickness and a length of 6600 mm was used in the investigation. The results of velocity and temperature were recorded using a hotwire anemometer and a type-K thermocouple, respectively. Results show that the behaviour of velocity and temperature in one-directional and the bi-directional flow conditions over an in-line heated tube banks are different with a maximum difference of 52 % for velocity and 79 % for temperature.

Microfluidic one-directional interstitial flow generation from cancer to cancer associated fibroblast

Tumors, unlike normal tissue, have vascular anomalies and create interstitial flow (IF), which allows soluble substances from cancer cells to be transported directionally toward the tumor stroma. In the stroma, IF activates fibroblasts. Cancer-associated fibroblasts (CAFs) are formed from stimulated cells and aid cancer growth. A microfluidic device was designed to generate a one-directional flow of a small volume mimicking IF from donor cells to recipient at steady-state conditions only based on the medium evaporation from reservoirs with different diameter. The IF carried substances from donor cells, which stimulated the activation of fibroblasts on the receiving side, as well as their migration and stellate formation. Matrix metallopeptidases 9 and 14 as well as CAF markers such as fibroblast activation protein alpha, vimentin, and alpha-smooth muscle actin are abundantly expressed in the migrating fibroblasts. The created platform mimicked one-directional delivery in tumor stroma. This will allow researchers to investigate how cancer cells activate and differentiate stromal cells. Statement of significanceWe show how to provide continuous one-directional interstitial flow (IF) in a microfluidic device without using any power source and instrumentation. This microfluidic technology was used to simulate the tumor microenvironment. Fibroblasts in the tumor stroma are activated and migrated toward cancer cells, as recapitulated by co-culture of cancer cells as donor and fibroblasts as recipient under the one-directional IF. We believe that soluble substances from cancerous cells delivered by the one-directional IF efficiently regulated the development of cancer-associated fibroblasts (CAFs), as shown by increasing roundness and decreased circularity, taking on a stellate morphology, and by enhanced invasion into a type I collagen hydrogel. Migrating fibroblasts into the hydrogel had significant levels of MMP-9, MMP-14, FAP, vimentin, and αSMA, all of which are CAF markers, bearing a capacity to form hot stroma affecting tumor malignancy.

Scaling law of the one-direction flow characteristics of symmetric Tesla valve

ABSTRACT A Tesla valve is a kind of micro-valve without moving parts. Due to the great difference between the reverse and forward flow, the Tesla valve is often used in passive fluid control devices. However, most of the current Tesla valve components are optimized and designed based on asymmetric structures. In this study, a Tesla valve pipe system model with symmetric structure is proposed. The characteristics of fluid flow and pressure drop were studied by finite element method and dimensional analysis. First, the pressure drop characteristics of symmetric and asymmetric Tesla valves with different Reynolds number are considered. The results show that the better the symmetry, the better the one-direction flow characteristics of Tesla valve system. Afterwards, through parametric analysis, computational fluid dynamics was used to verify flow characteristics of completely symmetrical Tesla valve system. The shunt angle, shunt pipe diameter and number of valves have significant effects on the pressure drop characteristics of the system. Eventually, based on numerical simulation results, by using the dimensional analysis method, the modification parameter was introduced to obtain the scaling law between the pressure drop and other parameters of the completely symmetrical Tesla valve piping system.

Development and Evaluation of Mobile Two-way Reversible Air Flow Flat-bed Paddy Dryer

A mobile two-way air flow flat-bed paddy dryer of 3-tonne capacity was developed and evaluated. With the provision of a two-way air flow arrangement for reversal of air direction, drying was uniform along the grain bed depth of 500 mm without the need to mix the grain during drying. The moisture content differential among different layers at 200 mm spacing was 3.1% and 0.80% for one-way upward and two-way reversible air flow mode, respectively. Specific energy consumption was 4.86 MJ.kg-1 and 4.34 MJ.kg-1, whereas the drying efficiency was 49.4% and 55.3% for conventional onedirectional and bi-directional reversible air flow mode, respectively. Head rice yield was 4.4% more for paddy dried in two-way reversible air flow mode as compared to conventional one-direction upward air flow drying. The cost of drying was less in twoway (reversible) air flow mode (` 9.80 per kg water) as compared to one-direction air flow mode ( ₹ 11.06 per kg water).

Experimental and numerical studies of one-directional and bi-directional flow conditions across tube banks heat exchanger

Bi-directional flow condition imposes different fluid dynamics and temperature changes compared to that of the usual one-directional flow condition. Bi-directional flow can be found in applications like thermoacoustic systems that offer a green technology for at least two major applications: refrigeration and power production. The technology is appealing as an alternative to traditional systems as it offers the replacement for the use of harmful working media and exhausted resources with the use of inert gaseous with relatively fewer moving mechanisms. As the fluid dynamics and heat transfer of bi-directional flow in a thermoacoustic working environment is less known, it is difficult to estimate losses and gain, especially during the design stage. This paper reveals the differences to be expected in the behaviour of flow and heat transfer through experimental as well as Computational Fluid Dynamics (CFD) results of one-directional and bi-directional flow conditions. Two different drivers were used to create the two different flow conditions: a loudspeaker for the bi-directional flow and a centrifugal blower for the one-directional flow. Both conditions were monitored based on flow amplitude that is calibrated between the two drivers. Results of velocity, temperature and, vorticity are recorded for Reynolds number that ranges between 270 and 1700. Analyses are supplemented with data from validated two-dimensional computational fluid dynamics models that were solved using the Shear-Stress-Transport (SST) k-ω turbulence model with second-order accuracy for all equations. Interesting features of differences in temperature and velocity changes between the one-directional and the bi-directional flows are reported. The temperature and velocity at upstream and downstream locations of the tube banks heat exchanger are almost the same for bi-directional cases but are significantly different when a one-directional flow is flowing over the heated tubes. In addition, the interplay between natural and forced convections is seen to affect the results that were recorded for the two flow conditions. The presence of thermally developing and fully developed regions is also discussed. The results indicate that the heat transfer behaviour of bi-directional flow is not the same as in the one-directional flow and the future calculation for heat transfer for bi-directional flow conditions of thermoacoustic must be carefully done with consideration of changes of flow conditions between the one-directional and the bi-directional flow conditions so that error could be minimized in the evaluation of the system’s performance.

Effects of enzyme-based removal of collagen and elastin constituents on the biaxial mechanical responses of porcine atrioventricular heart valve anterior leaflets

The leaflets of the atrioventricular heart valves (AHVs) regulate the one-directional flow of blood through a coordination of the extracellular matrix components, including the collagen fibers, elastin, and glycosaminoglycans. Dysfunction of the AHVs, such as those caused by unfavorable microstructural remodeling, lead to valvular heart diseases and improper blood flow, which can ultimately cause heart failure. In order to better understand the mechanics and remodeling of the AHV leaflets and how therapeutics can inadvertently cause adverse microstructural changes, a systematic characterization of the role of each constituent in the biomechanical properties is appropriate. Previous studies have quantified the contributions of the individual microstructural components to tissue-level behavior for the semilunar valve cusps, but not for the AHV leaflets. In this study, for the first time, we quantify the relationships between microstructure and mechanics of the AHV leaflet using a three-step experimental procedure: (i) biaxial tension and stress relaxation testing of control (untreated) porcine AHV anterior leaflet specimens; (ii) enzyme treatment to remove a portion of either the collagen or elastin constituent; and (iii) biaxial tensile and stress relaxation testing of the constituent-removed (treated) specimens. We have observed that the removal of ∼100% elastin resulted in a ∼10% decrease in the tissue extensibility with biaxial tension and a ∼10% increase in the overall stress reduction with stress relaxation. In contrast, removal of 46% of the collagen content insignificantly affected tissue extensibility with biaxial tension and significantly increased stress decay (10%) with stress relaxation. These findings provide an insight into the microstructure-mechanics relationship of the AHVs and will be beneficial for future developments and refinements of microstructurally informed constitutive models for the simulation of diseased and surgically intervened AHV function. Statement of significanceThis study presents, for the first time, a thorough mechanical characterization of the atrioventricular heart valve leaflets before and after enzymatic removal of elastin and collagen. We found that the biaxial tensile properties of elastin-deficient tissues and collagen-deficient are stiffer. The fact of elastin supporting low-stress valve function and collagen as the main load-bearing component was evident in a decrease in the low-tension modulus for elastin-deficient tissues and in the high-tension modulus for collagen-deficient tissues. Our quantification and experimental technique could be useful in predicting the disease-related changes in heart valve mechanics. The information obtained from this work is valuable for refining the constitutive models that describe the essential microstructure-mechanics relationship.

Drivers and Barriers for Implementation and International Transferability of Sustainable Pop-up Living Systems

In the current urban system, characterised by a one-directional flow of resources from the rural environment to the cities, the construction sector plays a critical role in supporting the transition from a linear to a circular economy. In this framework, temporary pop-up environments act as an innovative and sustainable type of living system. These are structures conceived as temporary from the outset, based on characteristics like flexible light-weight technologies, fast and easy assembly operations, temporary occupation of the ground and adaptability to different uses, needs and target groups. Great importance is placed on construction reversibility and environmental sustainability. In the framework of the interdisciplinary research project ‘Urban Pop-Up Housing Environments and Their Potential as Local Innovation Systems’, six scenarios of application for temporary pop-up environments for the city of Vienna have been developed, taking into consideration technical, urban and social aspects, on the basis of local uses and climatic conditions. In order to explore drivers and barriers of the scenarios regarding the transferability of the concepts, online questionnaire sessions were conducted with an international audience. The feedback obtained by the participants allowed an analysis of the applicability of the concepts to other urban environments under comparable conditions at the international level. The paper presents the results obtained from the questionnaire sessions, allowing insight on the international perception of temporary pop-up environments and, specifically, strengths and weaknesses of the scenarios, as well as their possible applicability in the local contexts of the respondents. It was observed that while the perceptions of what requirements temporary housing must fulfil in order to be sustainable are quite uniform among the experts, the identified barriers for implementation within the different international contexts differed greatly. The designs of these temporary housing scenarios, which rely heavily on local resources and systems, are strongly interwoven with the fabric and conditions of the city they were conceptualised for. While this serves to promote the sustainability of these solutions, it poses a particular challenge for the international transferability, requiring heavy adaptation for other contexts.

Temperature and Velocity Changes Across Tube Banks in One-directional and Bi-directional Flow Conditions

Temperature and Velocity Changes Across Tube Banks in One-directional and Bi-directional Flow Conditions

Exact solutions of the Navier–Stokes equations for describing an isobaric one-directional vertical vortex flow of a fluid

The article proposes a family of exact solutions to the Navier–Stokes equations for describing isobaric inhomogeneous unidirectional fluid motions. Due to the incompressibility equation, the velocity of the inhomogeneous Couette flow depends on two coordinates and time. The expression for the velocity field has a wide functional arbitrariness. This exact solution is obtained by the method of separation of variables, and both algebraic operations (additivity and multiplicativity) are used to substantiate the importance of modifying the classical Couette flow. The article contains extensive bibliographic information that makes it possible to trace a change in the exact Couette solution for various areas of the hydrodynamics of a Newtonian incompressible fluid. The fluid flow is described by a polynomial depending on one variable (horizontal coordinate). The coefficients of the polynomial functionally depend on the second (vertical) coordinate and time; they are determined by a chain of the simplest homogeneous and inhomogeneous partial differential parabolic-type equations. The chain of equations is obtained by the method of undetermined coefficients after substituting the exact solution into the Navier–Stokes equation. An algorithm for integrating a system of ordinary differential equations for studying the steady motion of a viscous fluid is presented. In this case, all the functions defining velocity are polynomials. It is shown that the topology of the vorticity vector and shear stresses has a complex structure even without convective mixing (creeping flow).

Effects of Enzyme-Based Removal of Collagen and Elastin Constituents on the Biaxial Mechanical Responses of Porcine Atrioventricular Heart Valve Anterior Leaflets

The leaflets of the atrioventricular heart valves (AHVs) regulate the one-directional flow of blood through a subtle coordination of the tissue's extracellular matrix (ECM) components, including collagen fibers, elastin fibers, and glycosaminoglycans. Dysfunction of the AHVs, such as those caused by unfavorable microstructural remodeling, results in valvular heart diseases and improper blood flow that can eventually lead to heart failure. To better understand mechanics and remodeling of the AHV leaflets and how therapeutics may inadvertantly cause adverse microstructural changes, a systematic characterization of the role of each ECM constituent in the biomechanical properties is warranted. Previous studies have quantified the contributions of the microstructural components to the tissue-level behavior for the semilunar valve leaflets, but not for the AHV leaflets. In this study, for the first time, we quantify the AHV leaflet microstructure-mechanics relationships, by using a three-step experimental procedure: (i) biaxial tensile and stress relaxation testing of the control (untreated) porcine AHV anterior leaflet specimens; (ii) enzyme treatment for removing a portion of either the collagen or elastin constituent; (iii) biaxial tensile and stress relaxation testing of the constituent-removed (treated) specimens. We observed that removing about 25-50% collagen from the leaflets resulted in a ~3% increase in the extensibility of the tissue and a ~50% increase in the stress relaxation behavior. Meanwhile, the removal of approximately 90-99% elastin led to a ~10% decrease in the extensibility of the leaflets and a ~75% increase in the stress relaxation behavior. These findings provide insight into the microstructure-mechanics relationship of the AHVs, and will be beneficial in the future developments and refinements of microstructurally informed constitutive models to simulate diseased and surgically-intervened AHV function.

Heat Transfer Across Tube Banks With a Passive Control Vortex Generator in Steady One-Directional and Oscillatory Flows

Fluid can flow in one-directional (normal flow) or oscillatory conditions. Fluid flow in some energy system involved oscillatory flow condition. The use of vortex generator has been proven to improve heat transfer in the case of one-directional flow but the impact of vortex generator in oscillatory flow condition is yet unknown. This study focusses on the heat transfer performance across a heated tube banks using a Computational Fluid Dynamics (CFD) model. Two flow conditions were modelled: steady one-directional and oscillatory flow conditions. Two-dimensional CFD models of steady flow and oscillatory flow were solved using the SST k-? turbulence model for two different cases of heated tube banks with and without the vortex generators. The heat transfer performance for both flow conditions were analysed by considering a heat transfer parameter known as Colburn-j factor. Results showed that the use of a vortex generator increased the heat transfer enhancement, regardless of the flow conditions. However, it is also noted that the heat transfer behaviour in a steady flow and an oscillatory flow is not the same, especially with the appearance of secondary flows in the system. The difference is discussed with respect to dimensionless quantity of Colburn j-factor, the non-dimensionless quantity, and the amplitude of temperature field. The result indicates that the heat equation in the steady flow condition is not very suitable to be directly used in oscillatory flow conditions. Appropriate heat equation needs to be properly addressed for situations that involve oscillatory flow motion.

A Fault Level-Based System to Control Voltage and Enhance Power Factor Through an On-Load Tap Changer and Distributed Generators

The on-load tap changer is critical for voltage regulation, however, its voltage regulation philosophy is suitable for one-directional power flow power systems. Since distributed generators introduce bidirectional power flow, the conventional operation of the on-load tap changer will be highly impacted, resulting in high voltage magnitudes that exceed acceptable limits, frequent voltage magnitude fluctuations, and the increase in overall reactive power supply when distributed generators start absorbing/injecting reactive power. Therefore, an adaptive control system is proposed on this paper that alters the existing voltage regulation philosophy of the on-load tap changer and also coordinate the voltage regulation capabilities of distributed generators with those of the on-load tap changer for optimal overall voltage regulation and the reduction of reactive power that flows through the power system, enhancing the power factor thereof. The proposed control system will change the centralized, and single-variable busbar voltage monitoring technique of the conventional philosophy with a decentralized, and multi-variable strategy that controls voltage based on the average voltage of the entire distribution network. The control system will calculate the on-load tap changer and distributed generators setpoints based on the overall average network voltage, average voltage deviation from nominal voltage, generators points of connection voltage and the total reactive power that flows through the power transformer. The control system was tested on a 22kV network modelled in MATLAB SIMULINK and the results attained revealed that the proposed multi-stage control system can successfully control voltage and simultaneously improve power factor.