Unidirectional Parallel Research Articles

Evaluation of flow and heat transfer behavior in parallel flow copper electro-refining cell with different inlet arrangements

Parallel flow copper electro-refining cell technology has been developed for over a decade, and the flow field in these cells is significantly influenced by the arrangement of the electrolyte inlets. Four computational fluid dynamics models were developed to compare the flow and heat transfer characteristics of the electrolyte under varying electrolyte inlet arrangements. These models include bi-directional parallel flow (BPF), staggered parallel flow (SPF), top inlet unidirectional parallel flow (UPF-T), and bottom inlet unidirectional parallel flow (UPF-B). Flow and heat transfer simulations were conducted for each model. The simulation results indicate that the BPF and SPF electro-refining cells exhibit varying degrees of kinetic energy loss, which leads to lower volume-weighted average velocities and impacts the rapid circulation of the electrolyte. The UPF-B is the most effective in terms of both flow uniformity and flow velocity, with the UPF-T following closely behind. The temperature in the inter-pole area is elevated when the SPF and UPF-T are arranged, which is more conducive to the diffusion of copper ions. The copper cathode production efficiency and deposition uniformity are enhanced by the UPF-B arrangement, which enables the liquid to be supplied to the inter-pole area more rapidly and uniformly.

The Design and Testing of a PEA Powered Ankle Prosthesis Driven by EHA.

Several studies have shown that actuation concepts such as Serial elastic actuator (SEA) can reduce peak power and energy consumption in ankle prostheses. Proper selection and design of the actuation concepts is important to unlock the power source potential. In this work, the optimization design, mechanical design, control scheme, and bench experiments of a new powered ankle-foot prosthesis is proposed. The actuation concept of this prosthesis is parallel elastic actuator (PEA) composed of electro-hydrostatic actuator (EHA) as the power kernel and a unidirectional parallel spring as the auxiliary energy storage element. After the appropriate motor and transmission ratio was selected, a dynamic model of the PEA prosthesis was built to obtain the appropriate spring parameters driven by biological data. The design of the hydraulic and mechanical system and the controller were provided for the implementation of the designed system. Bench experiments were performed to verify the performance. The results showed that the designed prosthesis meets the biomechanical dynamics requirements. This result emphasizes the feasibility of the EHA as a power source and actuator and provides new ideas for the design of ankle-foot prostheses.

The study of different unidirectional input parallel output series connected DC‐DC converters for wind farm based multi‐connected DC system

The study of different unidirectional input parallel output series connected <scp>DC‐DC</scp> converters for wind farm based <scp>multi‐connected DC</scp> system

Effects of fiber and matrix properties on the compression strength of carbon fiber reinforced polymer composites

The axial compressive strength of carbon fiber reinforced polymer composites (CFRP) is significantly lower than the tensile strength, which hinders its wide applications. The failure mechanism of CFRP under unidirectional compression parallel to the fiber alignment direction is complex, but research on this issue is limited. In order to understand this mechanism more deeply and intuitively, a two-dimensional microscopic numerical model is proposed. The influences of various properties of the fiber and matrix on the compressive strength of CFRP are investigated, including the axial elastic modulus of the fiber (Ef1), the transverse elastic modulus of the fiber (Ef2), the shear modulus of the fiber (Gf12), the elastic modulus of the matrix (Em), the proportional strength limit of the matrix (σp), the yield strength of the matrix (σs) and the degree of initial fiber misalignment. Results show that the model is capable of explaining the failure mechanism of CFRP under a unidirectional compressive load. Shear stress plays an important role in the compressive failure process. The localization of shear stress caused by initial fiber misalignment leads to plastic yield of the matrix and finally a kink band. Changes in these propertiesdirectly affect the concentration of shear stress in the defect areas, thereby affecting the compressive strength of the CFRP. When the values of Ef1, Ef2, Gf12, Em, σp, σs are separately increased by 10% or the degree of initial fiber misalignment is decreased by 10%, the compressive strength of CFRP is increased by 2.33%, 0%, 0.39%, 3.38%, 1.17%, 2.30% and 2.52% respectively. Em has the greatest influence on the compressive strength of CFRP, followed by the initial fibermisalignment. The effects of the plastic properties of the matrix on the compressive strength of CFRP are obvious.

Spatial mapping of exciton transition energy and strain in composition graded WS2(1−x)Se2x monolayer

We studied the optical properties of a composition graded WS2(1−x)Se2x alloy monolayer. A symmetric gradual composition gradient from a Se-rich center to the relatively less Se-rich edges of an equilateral triangle shaped flake is confirmed by Raman mapping. Photoluminescence (PL) mapping shows a large 100 meV variation in the exciton energy, resulting from the composition dependent bandgap variation and carrier localization. The alloying leads to symmetry breaking and large nonlinear optical susceptibility. Second harmonic generation (SHG) mapping was carried out to study the non-linear properties and additionally to determine the lattice strain of the alloy flake. In contrast to PL and Raman mappings, SHG intensity is found to be spatially uniform. However, polarization dependent SHG reveals a unidirectional strain parallel to the (zigzag) edge of the flake, in addition to the sixfold symmetry expected from the transition metal dichalcogenide (TMD) lattice. Our results suggest potential applications of composition graded TMD alloys as ultra-compact color-tunable light sources and miniaturized spectrometers.

Constructing the image of Japan as a tourist destination: translation procedures for culture-specific items

ABSTRACT This study investigates translation procedures employed for culture-specific items (CSIs) in Japanese tourism texts. Quantitative corpus-based methods were used to examine a unidirectional parallel corpus of texts gathered from websites promoting tourism to regional destinations. The aim of the analysis was to determine whether, and if so how, translation procedures for CSIs are conditioned by CSI category, and the impact exerted at the macro level on the image of Japan as a tourist destination. The analysis reveals that CSI category is a conditioning factor modulating the choice of translation procedure. Drawing on Lawrence Venuti’s conceptual framework of domestication and foreignisation, the findings suggest a predominant tendency towards domestication in the translation of CSIs in Japanese tourism literature, airbrushing the strangeness of the source text. A key contribution is the incorporation of quantitative methods to analyse the translation of CSIs in tourism texts, notably in culturally remote source and target language communities.

A layers-overlapping strategy for robotic wire and arc additive manufacturing of multi-layer multi-bead components with homogeneous layers

Robotic wire and arc additive manufacturing (WAAM) systems are required to provide predictable and efficient operations to fabricate solid metallic parts with high morphological fidelity and geometric accuracy. Since the metallic parts are fabricated based on a layer-by-layer principle, the interactions between the neighboring beads and layers strongly influence the geometric accuracy of the fabricated part. The layers-overlapping process has been studied and a traditional layers-overlapping model (T-LOM) has been published in the literature. This paper proposes a layers-overlapping strategy (LOS), based on which a revised layers-overlapping model (R-LOM) was proposed for the fabrication of multi-layer multi-bead (MLMB) components with homogeneous layers. A mathematical model for layers-overlapping is presented, which considers the material shortage areas at the edges of the layers. This is important since the material shortage areas result in a situation that the component width is smaller than the expected value. In addition, they will be accumulated when multiple layers are overlapped through normal unidirectional parallel (NUP) paths. The proposed LOS addresses two aspects: (i) the deposition amount of the first bead and the last bead in the lap layers should be increased and (ii) the deposition position of the first bead and the last bead in the lap layers should be moved towards the edges with a given offset distance. Validation experiments were designed and conducted to test the proposed concepts and models. The experimental results indicated that (i) the R-LOM enables the MLMB components to achieve the expected width and (ii) for components deposited with NUP paths, the R-LOM eliminates the effect of accumulation of material shortage areas on the first bead and increases the surface flatness.

Debitagem laminar no Sul do Brasil: Habemus nucleos!

Durante a pré-história, a debitagem laminar é um modo de produção característico de determinados períodos e regiões. No Brasil, no momento, foi reconhecida em três sítios arqueológicos situados no alto vale do rio Uruguai (SC/RS), em contextos sedimentares que datam do Holoceno inicial. Até hoje, somente os produtos dessa debitagem, as lâminas, tinham sido encontrados. A falta dos núcleos impedia um entendimento completo do processo de lascamento desses suportes. Graças à retomada das pesquisas na região desde 2013, foi possível coletar núcleos associados a essa produção laminar. Nesse artigo, descrevemos cinco desses núcleos. Suas análises demonstram que essa debitagem laminar corresponde a um único conceito. A estrutura volumétrica do núcleo que resulta desse conceito respeita as seguintes normas: 1) Os núcleos apresentam duas superfícies: um dorso plano e uma superfície de debitagem convexa mas relativamente achatada. Em uma extremidade, uma pequena superfície plana serviu de plano de percussão; 2) A debitagem começa por uma fase de inicialização durante a qual o plano de percussão é produzido por uma grande retirada. Em função das propriedades naturais do volume inicial, o dorso do núcleo é obtido, seja durante a seleção do bloco, seja por uma preparação por grandes retiradas transversais. Quando existem ainda, os negativos de retiradas da inicialização da superfície de debitagem indicam um método centrípeto; 3) As lâminas são sempre produzidas por um método unidirecional paralelo. A variabilidade desta debitagem é principalmente relacionada à técnica de lascamento: a percussão com pedra e a percussão com percutor orgânico foram utilizadas para a obtenção das lâminas. As informações tecnológicas fornecidas pelos núcleos aqui analisados são coerentes com essas observações oriundas da análise das lâminas. Com esses dois estudos consegue-se atingir um conhecimento completo desse sistema de produção do alto vale do rio Uruguai durante o Holoceno inicial, a única debitagem laminar documentada até hoje no Brasil.

Maximum Spreading of Liquid Drops Impacting on Groove-Textured Surfaces: Effect of Surface Texture.

Maximum spreading of liquid drops impacting on solid surfaces textured with unidirectional parallel grooves is studied for drop Weber number in the range 1-100 focusing on the role of texture geometry and wettability. The maximum spread factor of impacting drops measured perpendicular to grooves, βm,⊥ is seen to be less than that measured parallel to grooves, βm,∥. The difference between βm,⊥ and βm,∥ increases with drop impact velocity. This deviation of βm,⊥ from βm,∥ is analyzed by considering the possible mechanisms, corresponding to experimental observations-(1) impregnation of drop into the grooves, (2) convex shape of liquid-vapor interface near contact line at maximum spreading, and (3) contact line pinning of spreading drop at the pillar edges-by incorporating them into an energy conservation-based model. The analysis reveals that contact line pinning offers a physically meaningful justification of the observed deviation of βm,⊥ from βm,∥ compared to other possible candidates. A unified model, incorporating all the above-mentioned mechanisms, is formulated, which predicts βm,⊥ on several groove-textured surfaces made of intrinsically hydrophilic and hydrophobic materials with an average error of 8.3%. The effect of groove-texture geometrical parameters on maximum drop spreading is explained using this unified model. A special case of the unified model, with contact line pinning absent, predicts βm,∥ with an average error of 6.3%.

Plastic strain localization in periodic materials with wavy brick-and-mortar architectures and its effect on the homogenized response

Biomimetic or bio-inspired microstructures are increasingly being explored as a source of inspiration for material innovation. The goal of this study is to aid future design of biomimetic materials by conducting analysis of material architectures that resemble brick-and-mortar microstructures found in nacre. Specifically, this study explores the thus-far undocumented combined effects of waviness and platelet architecture on composite material ductility under unidirectional loading parallel and perpendicular to the reinforcing platelets. Model material architectures, comprised of discontinuous silicon carbide platelets suspended in aluminum matrix, that mimic nacre’s microstructure were constructed for analysis with the finite-volume direct averaging micromechanics (FVDAM) theory. The silicon carbide platelets play the role of nacre’s load-bearing calcite phase while the aluminum matrix mimics the combined effects of hierarchical load transferring mechanisms and organic protein matrix. The FVDAM simulations indicate that the introduction of waviness leads to an increase in ductility. Just as significant to material performance is the degree of relative shift between wavy rows of discontinuous hard-phase platelets. The effect of shift on ductility was found to be most significant when introduced to a degree that disrupted unit cell symmetry and when applied to configurations with low amplitude-to-wavelength ratios. The differences in the observed homogenized response are rooted in the local microstructure-controlled stress and resulting plastic strain fields that are identified in this investigation.

Effective connectivity between superior temporal gyrus and Heschl's gyrus during white noise listening: linear versus non-linear models.

Purpose:This fMRI study is about modelling the effective connectivity between Heschl’s gyrus (HG) and the superior temporal gyrus (STG) in human primary auditory cortices.Materials & methods:Ten healthy male participants were required to listen to white noise stimuli during functional magnetic resonance imaging (fMRI) scans. Statistical parametric mapping (SPM) was used to generate individual and group brain activation maps. For input region determination, two intrinsic connectivity models comprising bilateral HG and STG were constructed using dynamic causal modelling (DCM). The models were estimated and inferred using DCM while Bayesian Model Selection (BMS) for group studies was used for model comparison and selection. Based on the winning model, six linear and six non-linear causal models were derived and were again estimated, inferred, and compared to obtain a model that best represents the effective connectivity between HG and the STG, balancing accuracy and complexity.Results:Group results indicated significant asymmetrical activation (puncorr < 0.001) in bilateral HG and STG. Model comparison results showed strong evidence of STG as the input centre. The winning model is preferred by 6 out of 10 participants. The results were supported by BMS results for group studies with the expected posterior probability, r = 0.7830 and exceedance probability, ϕ = 0.9823. One-sample t-tests performed on connection values obtained from the winning model indicated that the valid connections for the winning model are the unidirectional parallel connections from STG to bilateral HG (p < 0.05). Subsequent model comparison between linear and non-linear models using BMS prefers non-linear connection (r = 0.9160, ϕ = 1.000) from which the connectivity between STG and the ipsi- and contralateral HG is gated by the activity in STG itself.Conclusion:We are able to demonstrate that the effective connectivity between HG and STG while listening to white noise for the respective participants can be explained by a non-linear dynamic causal model with the activity in STG influencing the STG-HG connectivity non-linearly.

Dynamic contact angle beating from drops impacting onto solid surfaces exhibiting anisotropic wetting

This paper reports an experimental investigation of low Weber number water drops impacting onto solid surfaces exhibiting anisotropic wetting. The wetting anisotropy is created by patterning the solid surfaces with unidirectional parallel grooves. Temporal measurements of impacting drop parameters such as drop base contact diameter, apparent contact angle of drop, and drop height at the center are obtained from high-speed video recordings of drop impacts. The study shows that the impact of low Weber number water drops on the grooved surface exhibits beating phenomenon in the temporal variations of the dynamic contact angle anisotropy and drop height at the center of the impacting drop. It is observed that the beating phenomenon of impacting drop parameters is caused by the frequency difference between the dynamic contact angle oscillations of impacting drop liquid oriented perpendicular and parallel to the direction of grooves on the grooved surface. The primary trigger for the phenomenon is the existence of non-axisymmetric drop flow on the grooved surface featuring pinned and free motions of drop liquid in the directions perpendicular and parallel to the grooves, respectively. The beat frequency is almost independent of the impact drop Weber number. Further experimental measurements with solid surfaces of different groove textures show that the grooved surface with larger wetting anisotropy may be expected to show a dominant beating phenomenon. The phenomenon is gradually damped out with time and is fully unrecognizable at higher drop impact Weber numbers.

Impact of water drops onto the junction of a hydrophobic texture and a hydrophilic smooth surface

Wettability gradient surfaces play a significant role in control and manipulation of liquid drops. The present work deals with the analysis of water drops impacting onto the junction line between hydrophobic texture and hydrophilic smooth portions of a dual-textured substrate made using stainless steel material. The hydrophobic textured portion of the substrate comprised of unidirectional parallel groove-like and pillar-like structures of uniform dimensions. A high-speed video camera recorded the spreading and receding dynamics of impacting drops. The drop impact dynamics during the early inertia driven impact regime remains unaffected by the dual-texture feature of the substrate. A larger retraction speed of drop liquid observed on the hydrophobic portion of the substrate during the impact of low velocity drops makes the drop liquid on the higher wettability portion to advance further (secondary drop spreading). The net horizontal drop velocity towards the hydrophilic portion of the dual-textured substrate decreases with increasing drop impact velocity. The available experimental results suggest that the movement of bulk drop liquid away from the impact point during drop impact on the dual-textured substrate is larger for the impact of low inertia drops.

Design, fabrication and analysis of micromachined high sensitivity and 0% cross-axis sensitivity capacitive accelerometers

This paper presents the design and fabrication of three MEMS based capacitive accelerometers. The first design illustrates the achievement of an accelerometer with 0% cross-axis sensitivity and has been fabricated using PolyMUMPs, a multi-user surface-micromachining process. A unidirectional parallel plate configuration is utilized in this design to illustrate the achievement of 0% cross-axis sensitivity and an acceptable performance range. In addition, a method is introduced to improve the sensitivity of a capacitive sensor employing a transverse configuration based on the relationship of initial gaps setup in comb-finger arrangements. A design based on this technique and the PolyMUMPs fabrication process is illustrated which demonstrates a sensitivity value of 4.07 fF/µm, with a nonlinearity of 2.05% for a ±3 µm sensor operating range. The last design based on this method and the SOIMUMPs fabrication process exhibits a sensitivity of 3.45 pF/µm for ±1 µm operating range of the sensor.

Dislocation structure in interfaces between Si wafers with hybrid crystal orientation

AbstractDislocation structure in Si(110)/Si(001) wafer bonding (WB) structures have been studied by transmission electron microscopy (TEM). The behavior of intermediate native oxide layers during high temperature annealing, the nature of interfacial dislocations and dislocation generation mechanisms are the main issues of this work. Samples were fabricated by direct hydrophilic WB of 200 mm wafers with native oxide. The as‐bonded structures containing 140‐nm thick layers were thermally annealed in the temperature range 1150 to 1200 °C. The dislocation structure composed of a pattern of unidirectional parallel but broken dislocation arrays is formed in the structures with partial or entire dissolution of the oxide layer. The contrast of broken dark lines usually observed in TEM bright field micrographs is supposed to be caused by integral effect of steps compensating twist misorientation and arrays of 60‐degree dislocations. We suggest that nucleation of dislocation loops at the interface due to the agglomeration of intrinsic point defects is a plausible mechanism of dislocation generation. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Current carrying blob filaments and edge-localized-mode dynamics

The model of blob-filament propagation in the scrape-off layer (SOL) of a tokamak is extended to include objects that carry a large net unidirectional current parallel to the magnetic field. Under experimentally realistic conditions, the blob-filament structure and propagation are influenced by magnetostatic forces. Some aspects of the model may be relevant to the SOL propagation of edge-localized modes.

Gravity-driven film flow down an inclined wall with three-dimensional corrugations

The gravity-driven flow of a liquid film down an inclined wall with three-dimensional doubly periodic corrugations is investigated in the limit of vanishing Reynolds number. The film surface may exhibit constant or variable surface tension due to an insoluble surfactant. A perturbation analysis for small-amplitude corrugations is performed, wherein the wall geometry is expressed as a Fourier series consisting of a linear superposition of two-dimensional oblique waves defined by two base vectors. Each of the constituent perturbation flows over the individual oblique waves is further decomposed into a two-dimensional flow transverse to the oblique waves and a unidirectional flow parallel to the waves. Both the transverse and the parallel flow are calculated by carrying out an analysis in oblique coordinates, similar to that conducted for two-dimensional flow. The particular cases of flow down a wall with oblique two-dimensional, orthogonal three-dimensional, and hexagonal three-dimensional corrugations are considered. The results illustrate the surface velocity field and the distribution of the surfactant. The three-dimensional wall geometry is found to reduce the surface deformation with respect to its two-dimensional counterpart by increasing the effective wave numbers and decreasing the effective capillary number encapsulating the effect of surface tension.

Bioinspired Rattan-Derived SiSiC/Zeolite Monoliths: Preparation and Characterisation

In the present article, a three-step process for the preparation of SiSiC/zeolite composites is presented. Rattan-derived SiSiC composites were obtained via a two-step biotemplating liquid silicon infiltration process (LSI). The LSI process, consisting of pyrolysis of the biotemplates (Rattan stems) followed by reactive infiltration of the carbon preforms with liquid silicon at 1550 °C, led to the formation of SiSiC ceramic composites. The SiSiC replicas (59 wt.% of SiC, 40 wt.% of solidified Si, 1 wt.% carbon) faithfully reproduced the macrostructure of Rattan and exhibited an open porosity between 20 and 40 vol.%, with unidirectional parallel microchannels in the range of ∼100–300 μm in diameter. In a third stage MFI-type zeolite (Silicalite-1 and ZSM-5) coatings were developed on the SiSiC ceramic supports via a partial conversion of the substrate into zeolite (support self-transformation method). The metallic Si in the support was partially dissolved under hydrothermal conditions in a reaction mixture consisting of deionised water, template (TPABr) and NaOH, but without any external Si-source. The influence of different synthesis parameters in the development of the zeolite coating is discussed in detail. The resulting products were characterised by X-ray diffraction, TGA, N 2 adsorption/desorption and SEM-EDX. The filtrates were analysed by ICP-OES. SEM and adsorption measurements revealed that biomorphic cellular SiSiC/zeolite composites possess bimodal (micro-/macro-) porosity. In the final SiSiC/zeolite composite, a maximum zeolite loading up to 40 wt.% was calculated on the basis of TGA and XRD analyses. Thermal shock tests showed that a good coating adherence to the SiSiC substrate was obtained. In addition, a SiSiC/ZSM-5 monolith was also tested as structured catalyst for n-hexane cracking.

A Unified Approach to the Analysis of Unidirectional and Bi-Directional Parallel Flow Heat Exchangers

Virtually all sources devoted to heat exchanger theory, (in particular the heat transfer textbooks), start the analyses of the main thermal features of various heat exchangers by emphasizing the differences between the two basic flow arrangements: (i) the unidirectional parallel flow (in the literature often called parallel flow or co-current flow), and (ii) bidirectional flow (in the literature often called counterflow or counter-current flow). This is justified by a convincing argument that the two arrangements correspond to the two theoretical limits of performance. Namely, among all possible flow arrangements, the unidirectional flow is characterized with the smallest and the bi-directional with the largest effectiveness. Modeling of the two arrangements is, as a rule, performed simultaneously but separately. More importantly, the concept of heat exchanger effectiveness is usually introduced as the ratio of the heat transfer rate, exchanged in a given heat exchanger, and the maximum possible heat transfer rate that could be exchanged in a hypothetical bidirectional flow (counterflow) heat exchanger of an infinitely large thermal (and physical!) size. In contrast, this paper promotes a unified approach to both flow arrangements and advocates the use of the effectiveness definition based on a notion of the dimensionless outlet temperature of fluid stream. It is argued that this approach evades pedagogical drawbacks of formal integration of two mathematical models and, more importantly, eliminates the need for an introduction of a vague concept of ‘infinitely large counter-current heat exchanger’. Instead, a unified analysis of a single model should be performed and the effectiveness should be introduced as a figure of merit that takes into account performance only of the actual heat exchanger. This approach leads to the same final results as the conventional one, but it follows methodologically a simpler path, without a need for an early introduction of vague (although plausible) thermodynamic concepts.

Simple and flexible SAS and SPSS programs for analyzing lag-sequential categorical data.

This paper describes simple and flexible programs for analyzing lag-sequential categorical data, using SAS and SPSS. The programs read a stream of codes and produce a variety of lag-sequential statistics, including transitional frequencies, expected transitional frequencies, transitional probabilities, adjusted residuals, z values, Yule's Q values, likelihood ratio tests of stationarity across time and homogeneity across groups or segments, transformed kappas for unidirectional dependence, bidirectional dependence, parallel and nonparallel dominance, and significance levels based on both parametric and randomization tests.