Arrangement Of Steps Research Articles

Effects of channel structure at inlet region on temperature distribution of proton exchange membrane fuel cells

Enhancing the temperature distribution uniformity in membrane electrodes is crucial for improving the durability and performance stability of proton exchange membrane fuel cells. In this study, we discovered an entrance region in the cathode membrane electrode of proton exchange membrane fuel cells characterized by a rapid rise in temperature. This inlet region shows a notably higher temperature variation rate compared to other regions. This phenomenon is attributed to the temperature difference between the constant temperature fluid supplied by the channel inlet and the heat generation in the cathode catalyst layer. Thus, the impact of channel structure at the entrance region on the temperature distribution of the cathode catalyst layer is investigated, based on a three-dimensional, non-isothermal, two-phase model. Results show that boosting heat transfer in the inlet region is more effective for reducing the average temperature than in other regions. We proposed five kinds of step arrangement schemes and discovered that the step arrangement in the entrance region of the cathode flow channel can increase the temperature uniformity of the cathode catalyst layer by 9.71% without net power loss. Furthermore, this study examines the impact of length, height of entrance steps, and outlet channel height on heat transfer and identifies the optimum value. When severe water flooding occurs, the gas purge coupled with the step-fronted scheme is essential for improving temperature uniformity.

The effect of gabion steps on the hydraulic jump characteristics downstream of stepped spillways

ABSTRACT Gabion steps on stepped spillways can be a suitable alternative to solid impermeable steps due to their economic advantages, ease of implementation, stability through water pressure reduction, and energy dissipation. This study explores hydraulic jumps and the rate of energy dissipation downstream of gabion stepped spillways under different flow regimes. Six stepped spillway models, including a solid spillway with solid steps and five models with gabion steps, were made with different step arrangements in a 26.6° slope (1 V:2 H) facility. The results showed that in stepped spillways with gabion steps and in the nappe flow regime, as a result of seepage flow through the pores of the aggregate and overflow passing the gabion step, there is an increased energy dissipation associated with a smaller sequent depth ratio, the relative length of jumps, and roller length compared to solid and impermeable steps. The reduction in the hydraulic jump depends on the flow regime and the arrangement of the gabion steps. For skimming flows, smaller energy dissipation rates were measured downstream of the gabion step. On average, when gabion steps are placed on all steps, the sequent depth ratio, jump length, and roller length decrease by 3.34%, 8.61%, and 8.14%, respectively, compared to solid steps. The maximum energy dissipation was measured at the downstream end of the gabion steps with a value of 74.4%, which is 5.03% more than that with the solid steps. On the solid stepped spillway, the nondimensional residual head was 4.65, and for the same flow conditions, the average dimensionless residual head on the gabion steps was 4.21.

Characteristics of hydraulic jump and energy dissipation in the downstream of stepped spillways with rough steps

Stepped spillways are used to improve the hydraulic performance of a water-flow structure. This research describes the study of two types of physical models to investigate the impacts of rough steps on stepped spillways in terms of energy dissipation and hydraulic jumps. To this end, six stepped spillway models, including a flat spillway with smooth steps and five models with rough steps using gravel with a given grain size (i.e., d50 = 18.9 mm), were made with different step arrangements. The results showed that stepped spillways with rough steps and in the nappe flow regime show a better performance regarding energy dissipation of about 20.97 % compared to smooth steps. On the smooth stepped spillway, the non-dimensional residual head was 4.65, and for similar operating conditions, the average dimensionless residual head on the rough steps was 2.92. Furthermore, when rough steps are placed on all steps, the hydraulic jump characteristics, including sequent depth ratio, jump length, and roller length, decrease by 3.34, 8.61, and 8.14 %, respectively, compared to smooth steps.

Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized Detection of Nonylphenol.

Conventional photoelectrochemical (PEC) biosensors suffer from the difficulty of visualizing rapid detection and limited accuracy due to a single-signal output. Here, we develop a PEC, electrochromic (EC), and spectral (ST) triple-mode platform for the sensitive visualized detection of nonylphenol (NP). First, the reasonably stepped Fermi energy level arrangement between the defective TiO2 anode and MoO3 cathode enables a remarkable photocurrent response (Mode 1). Then, MoO3 itself is a widely used EC candidate, which can react with free Li-ions to form a LixMoO3 intermediate, and its color will change from white to blue accordingly (Mode 2). More importantly, MoO3 is also a Li-ion host and the potential of LixMoO3 depends on the inserted Li-ion quantity deduced by spectral analysis on residual Li-ions in the electrolyte (Mode 3). The EC signal endows fast visual detection, and triple-mode cross-validation improves reliability and accuracy. As a result, this PEC-EC-ST triple-mode molecularly imprinted sensor has a wide linear range (1-5000 μg L-1), a low detection limit (0.18 μg L-1), selectivity, stability, reproducibility, and actual sample detection capability. This innovative multimode platform not only improves detection reliability but also broadens applications of electrochromic/energy storage materials in biosensors.

Green non-fluorinated gradient anisotropic microcolumn array: Enables droplet transition to a low viscosity state on highly viscous substrates

Superhydrophobic surfaces with low adhesion and self-cleaning properties have broad application prospected in various fields. However, the current methods for preparing low-adhesion superhydrophobic surfaces typically require toxic chemicals or fluorination modifications, which are prone to environmental pollution and health hazards, and still face challenges for applications in industries such as food and medical care. This paper aims to prepare anisotropic gradient array surfaces (AGAS) with low adhesion on stainless steel substrates by WEDM, without the need for modification with low-surface-energy materials. AGAS can achieve a stable Cassie state with a low adhesion performance by controlling the dimensional parameters and structural inclination of columnar arrays. Experiments and numerical simulations show that owing to the anisotropic gradient structure, pinning and de-pinning occur asymmetrically in time at the contact lines of the leading and trailing edges of droplets impacting the AGAS. On AGAS, droplets can jump and roll in the direction of gradient descent during the impact process to complete self-cleaning. Due to the discontinuity of the solid–liquid–gas three-phase contact line and the stepped arrangement of the column array, the prepared surface can achieve low adhesion and self-cleaning properties for many common liquid foods in daily life, including milk and juice.

The hierarchical porous structures of diatom biosilica-based hemostat: From selective adsorption to rapid hemostasis

Here, we developed a Ca2+ modified diatom biosilica-based hemostat (DBp-Ca2+) with a full scale hierarchical porous structure (pore sizes range from micrometers to nanometers). The unique porous size in stepped arrangement of DBp-Ca2+give it selective adsorption capacity during coagulation process, resulted in rapid hemorrhage control. Based on in vitro and in vivo studies, it was confirmed that the primary micropores of DBp-Ca2+gave it high porosity to hold water (water absorption: 78.46 ± 1.12 %) and protein (protein absorption: 83.7 ± 1.33 mg/g). Its secondary mesopores to macropores could reduce of water diffusion length to accelerate blood exchange (complete within 300 ms). The tertiary stacking pores of DBp-Ca2+ could absorb platelets and erythrocytes to reduce more than 50 % of thrombosis time, and provided enough contact between Ca active site and coagulation factors for triggering clotting cascade reaction. This work not only developed a novel DBs based hemostat with efficient hemorrhage control, but also provided new insights to study procoagulant mechanism of inorganic hemostat with hierarchical porous structure from selective adsorption to rapid hemostasis.

HASIL IMPLEMETASI METODE GAME PADA MATA PELAJARAN PENDIDIKAN AGAMA ISLAM TERHADAP MINAT BELAJAR SISWA PADA KELAS VII DI SLB CG YPPCG BINA SEJAHTERA SURAKARTA TAHUN 2022/2023

This study aims to determine the use of the game method. This research is a qualitative research. The subject of the study was SLB CG-YPPCG Bina Sejahtera Surakarta. In this study, data collection methods were used through observation, interviews, and documentation. Meanwhile, data analysis uses data reduction, data presentation, and data verification. The results show that the characteristics of students at SLB CG-YPPCG Bina Sejahtera Surakarta are experiencing slowness in doing something or difficulty in understanding and learning new things. Then the game method used in learning is that the teacher provides learning with an arrangement of simple and sequential steps made with simple and fun games. So with this model learning can improve social and motor skills for mentally retarded children at SLB CG-YPPCG Bina Sejahtera Surakarta.

Evolution of Ge wetting layers growing on smooth and rough Si (0 0 1) surfaces: Isolated {1 0 5} facets as a kinetic factor of stress relaxation

The results of STM and RHEED studies of a thin Ge film grown on the Si/Si(001) epitaxial layers with different surface relief are presented. Process of the partial stress relaxation was accompanied by changes in the surface structure of the Ge wetting layer. Besides the well-known sequence of surface reconstructions (2 × 1 → 2 × N → M × N patches) and hut-clusters faceted with {105} planes, the formation of isolated {105} planes, which faceted the edges of M × N patches, has been observed owing to the deposition of Ge on a rough Si/Si(001) surface. A model of the isolated {105} facet formation has been proposed based on the assumption that the mutual arrangement of the monoatomic steps on the initial Si surface promotes the wetting layer formation with the inhomogeneously distributed thickness that results in the appearance of M × N patches partially surrounded by deeper trenches than those observed in the usual Ge wetting layer grown on the smooth Si(001) surface. Isolated {105} facets are an inherent part of the Ge wetting layer structure and their formation decreases the surface energy of the Ge wetting layer.

Construction of Ag-AgInS2/In2S3/TNR Nanoarray High-Performance Photocatalyst and its Degradation Performance of Tetracycline Hydrochloride

In this work, Ag quantum dot-modified AgInS2/In2S3/TNR nanoarray photocatalysts were prepared by a secondary hydrothermal and wet chemical method. Compared with the unmodified TNR arrays, the modified Ag-AgInS2/In2S3/TNR samples showed a significant increase in light absorption and could utilize more solar energy. In addition, the Ag-AgInS2/In2S3/TNR samples can effectively promote the separation and transfer of electron-hole pairs to enhance the photoelectrochemical and photocatalytic performance of the composites, and the degradation rate of the optimal Ag-AgInS2/In2S3/TNR samples can reach 95.73% for TC-HCl, which is of great importance for environmental protection. The main reasons for the enhanced catalytic performance are: the presence of surface Ag quantum dots and AgInS2 sensitizers greatly increases the absorption of sunlight, allowing more energy to enter the catalytic system; the stepped energy level arrangement of AgInS2/In2S3/TNR nanoarrays can spatially separate electrons and holes, improving the separation efficiency and enhancing the overall performance of the material.

Genetic Types of the tp12cx Strike-Slip Fault Segments and Their Role in Controlling Reservoirs in the Tarim Basin

The change of motion mode of multistage active strike-slip faults controls the segmentary types of strike-slip faults, which is seldom studied.Based on high-precision 3D seismic data and the principle of structural analysis, this paper defines the structural evolution characteristics of the tp12cx strike-slip fault in the key structural period and identifies the fault segmentation types. Combined with the statistical results of drilling production data and fault width, and fault width, it is demonstrated that different fault segments display various reservoir architecture and hydrocarbon potential. The tp12cx strike-slip fault experienced two phases of tectonic activity controlling reservoir development: the middle Caledonian and the late Caledonian to early Hercynian. During the middle Caledonian period, a left-lateral and left-step strike-slip fault was formed. The overlapping segments of the left steps were transtension zones, and the rest were pure strike-slip segments. From the late Caledonian to the early Hercynian, the movement mode changed from left-lateral to right-lateral, and the arrangement of left steps remained unchanged, forming right-lateral and left-step strike-slip faults. That is, as a weak zone, the transtension zones of all the preexisting overlapping segments took the lead in moving into many pure strike-slip segments and maintained the transtensional property. During the right-lateral slipping process of all the original pure strike-slip segments along the fault, they were blocked and squeezed by the surrounding rocks on both sides, forming a series of “positive” flower-shaped fault anticlines, which became overlapping segments, and the fault property became transpressional. Under the continuous action of the right-lateral slipping, a regional right-lateral and right-step strike slip fault formed. The interiors of the right-step-arranged faults were composed of the left-step arranged faults. Among them, the right-step overlapping segments were weakly step overlapping segments were weakly transtensional, and the larger the fault width of the internal left step pure strike slip and overlapping segments, the stronger the dissolution. The deformation of the right-step pure strike-slip segments was weak and basically maintained the characteristics of the previous stage. According to the evolution and superposition of pure strike-slipped and overlapped segments and the changes in fault properties, four types of strike-slip fault segments and corresponding reservoir models are divided. Type I: left-step pure strike-slip segment + left-step transpressional segment + right-step transtensional segment; Type II: left-step transtensional segment + left-step pure strike-slip segment + right-step transtensional segment; Type III: left-step pure strike-slip segment + left-step transpressional segment; and Type IV: left-step transtensional segment + left-step pure strike-slip segment. The fault width and oil production of type II and type IV with transtensional properties are much larger than those of type I and type III with transpressional properties.

Determination of Power Transformers Health Index Using Parameters Affecting the Transformer’s Life

Power transformers are one of the most important parts of a power system, and they are crucial to the system's reliability and energy quality. The “health index” idea is used in this research to evaluate and classify transformers based on their conditions in order to optimize transformer upgrading and replacement decisions. And the transformer is inspected and maintained from various angles by collecting the transformer’s health factor and utilizing the number of this indicator to determine when and how often the transformer should be inspected and maintained. Finally, the health index described in this paper is utilized to review and regularly classify transformers based on their states and improve the renovation replacement method by applying the fuzzy logic method to research this coefficient precisely. The fuzzy health index used in this work has the advantage of being able to be trained using past transformer data. When the training is complete, it can be applied to other transformers, with the goal of achieving optimal functioning for transformers while considering cost and dependability. The specific results of the present article indicate that the health index criterion presented in this article has a high degree of certainty regarding the selection, arrangement, and timing of maintenance and service steps in the evaluated transformers. In addition, when comparing the proposed method to the conventional method for seven sample transformers, the system availability index of the proposed method improved by about 40%.It also had about 25% higher reliability than the conventional method for 7 sample transformers.

SOC Critical Path: A Defensive Kill Chain Model

Different kill chain models have been defined and analyzed to provide a common sequence of actions followed in offensive cyber operations. These models allow analysts to identify these operations and to understand how they are executed. However, there is a lack of an equivalent model from a defensive point of view: this is, there is no common sequence of actions for the detection of threats and their accurate response. This lack causes not only problems such as unstructured approaches and conceptual errors but, what is most important, inefficiency in the detection and response to threats, as defensive tactics are not well identified. For this reason, in this work we present a defensive kill chain approach where tactics for teams in charge of cyber defense activities are structured and arranged. We introduce the concept of SOC Critical Path (SCP), a novel kill chain model to detect and neutralize threats. SCP is a technology–independent model that provides an arrangement of mandatory steps, in the form of tactics, to be executed by Computer Network Defense teams to detect hostile cyber operations. By adopting this novel model, these teams increase the performance and the effectiveness of their capabilities through a common framework that formalizes the steps to follow for the detection and neutralization of threats. In this way, our work can be used not only to identify detection and response gaps, but also to implement a continuous improvement cycle over time.

PENGGUNAAN METODE DIRECT INSTRUCTION PELAJARAN AGAMA ISLAM DALAM MENINGKATKAN KEMAMPUAN BERSOSIALISASI DI SLB CG YPPCG BINA SEJAHTERA MANDIRI

This study aims to determine the use of direct instruction method. This research is a qualitativeresearch. The subject of the study was SLB CG-YPPCG Bina Sejahtera Surakarta. In this study using data collection methods through observation, interviews, and documentation. Meanwhile, data analysis uses data reduction, data presentation, and data verification. The results show that the characteristics of students at SLB CG-YPPCG Bina Sejahtera Surakarta are experiencing slowness in doing something or difficulty in understanding and learning new things. Then the direct instruction method used in learning is that the teacher provides learning with a simple and sequential arrangement of steps. So with this model direct instruction learning can improve social skills for mentally retarded children at SLB CG-YPPCG Bina Sejahtera Surakarta.

Numerical Forced Convection Heat Transfer of Nanofluids over Back Facing Step and Through Heated Circular Grooves

Backward facing step arrangement is a classical case for fluid dynamics and heat transfer research. It is well characterized and therefore, used for benchmarking. However, ongoing studies reveal that the geometry also provide advantages in industry, especially in combustion and burners. This work utilizes computational fluid dynamics to investigate a specific laminar back facing step flow heat transfer case. Aluminium oxide nano particles are considered as an additive to water base fluid, forming nanofluid with different volumetric concentrations. Laminar flow passes a back facing step and encounters three circular grooves at bottom surface. All surfaces are adiabatic except the grooves. Constant surface temperature applies to the grooves. According to the simulation results, a separation bubble after back facing step and a reattachment point occur. Grooves alter expected wake due to physical and thermal interference. Investigation parameters are nano-particle concentration and Reynolds number. Reynolds number changes between 10 and 250. Nano particle volume fraction percentage changes between 2 and 6 percent. Sectional heating downstream of the step poses interesting heat flux in the presence of Aluminium oxide nano-particle concentrations. There is a pseudo-linear relationship between parameters and heat transfer. Combined effects of enhanced thermal conductivity and secondary flow structures are seen. As expected, thermal convection increases as flow velocity and nano-particle concentrations increase. Heat flux and accordingly Nusselt number are highly affected from Reynolds number since flow structure changes dramatically. Also, direct proportion is seen between nano-particle concentration and enhanced convection.

Spin reorientation transition in ultrathin Co films on the vicinal surface Au(788)

In this work, we investigate the structural, morphological and magnetic properties of epitaxial Cobalt ultrathin films grown on the vicinal surface Au(788). The aim was to study the magnetization reversal and determine the influence of the regular arrangement of atomic steps, typical of a vicinal surface. The influence of the Co thickness on the spin reorientation from out-of-plane to in-plane magnetization were investigated by means of the magneto-optical Kerr effect (MOKE). Preparation and surface quality of the Co films were characterized using the surface experimental techniques LEED and STM. A smooth spin reorientation transition, between 8 and 12 atomic monolayers (ML) of Co, was observed from out-of-plane magnetization, between 5 ML and 12 ML of Co, to in-plane magnetization, above 13 ML of Co. Furthermore, the angular dependence of the magnetic hysteresis loops indicates uniaxial magnetic anisotropy parallel to the atomic steps in the surface plane of the system Au/Co/Au(788) for thicknesses between 13 ML and 20 ML of Co.

Enhanced critical magnetic field for monoatomic-layer superconductor by Josephson junction steps

We have studied the monoatomic-layer superconductors formed on semiconducting substrates and investigated the role of steps in superconducting properties. In the present study we found that the steps of the Si(111)-\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}43 Pb reconstructed structure significantly disrupt the electronic states of the superconducting atomic layer and hold Josephson-like vortices under the out-of-plane magnetic field. Because of the strong decoupling, narrow terraces whose width is less than three times the coherence length behave like superconducting nano stripes and exhibit large critical field against the out-of-plane magnetic field. Since monolayer superconductors are intrinsically strong against in-plane magnetic field, superconducting materials highly tolerant against magnetic fields in all directions might be tailored by controlling the step arrangement in the atomic-layer superconductors.

On the Leakage and Dynamic Force Coefficients of a Novel Stepped Shaft Pocket Damper Seal: Experimental and Numerical Verification

Abstract High-performance turbomachinery favors annular seals with a large damping coefficient to ensure rotor system stability. Pocket damper seals (PDSs), a variation of labyrinth seals with axial blades (ribs) and adding circumferential partition walls (ridges), produce a favorable damping performance. To further enhance the damping characteristic and reduce leakage, a novel stepped shaft PDS is hereby introduced. The invention has a unique arrangement of steps on the rotor surface, each facing an upstream rib in a pocket row. Thus, the step and a blade tip form a tight clearance (c1), while the rotor surface and the downstream blade tip make a larger clearance (c2). The convergence–divergence variation of cross-sectional areas along the flow direction increases the PDS damping coefficient. To validate the performance of the novel design, a stepped shaft PDS (c1/c2 = 0.5) with four axial ribs and eight circumferential pockets is built and tested. A comprehensive investigation, experimental and computational, produces the seal leakage and dynamic force coefficients for the stepped shaft PDS, as well as similar performance characteristics for an identical PDS with a smooth rotor surface (c1/c2 = 1, i.e., a uniform clearance PDS). The stepped shaft PDS operates with air at supply pressure (PS) ranging from 1.1 bar to 3.2 bar. The measured leakage for the stepped shaft PDS is 50% of that for the uniform clearance PDS. Computational fluid dynamics (CFD) and bulk flow model (BFM) predictions of leakage agree well with the test data. For PS = 2.3 bar, the test damping coefficient (C) for the stepped shaft PDS is ~1.5 times greater than the one for the uniform clearance PDS. With an increase in PS to 3.2 bar, the stepped shaft PDS shows a two and one half increase in damping coefficient. In comparison to the test data, a CFD model overestimates C by 29% for operation at PS = 3.2 bar, though capturing the variation trend versus whirl frequency. The BFM largely underpredicts C for the stepped shaft PDS and is abandoned for future work. Both the test data and CFD predictions demonstrate the superior damping performance of the stepped shaft PDS, thus providing a novel alternative seal configuration for turbomachinery usage.

Resonant Current Steps in Josephson Structures with a Layer from a Material with Strong Spin–Orbit Interaction

The microwave and magnetic parameters of Josephson Nb/Au/Sr2IrO4/YBa2Cu3Ox mesastructures with a layer of Sr2IrO4, a material representing a Mott antiferromagnetic insulator with a high spin–orbit interaction energy ESO ~ 0.4 eV, were studied. Shapiro steps, oscillating with radiation power, appeared under monochromatic electromagnetic radiation confirm the Josephson properties of these structures. In the presence of a weak magnetic field H < 15 Oe, the voltage–current characteristics (VCCs) had resonant current steps at voltages Vn, which were inversely proportional to the size L of structures in plane. Polarity reversal in the electrical current I led to asymmetry in the arrangement of resonant current steps. At a specified magnetic field H, the voltage Vn remained constant, and the amplitudes of resonant current steps nonmonotonically changed.

Dança e conhecimento: reflexões sobre o corpo vivido

O estudo tem por objetivo abordar a epistemologia da dança, discutindo a produção e o ganho do conhecimento dançado. Os principais temas são o corpo e a motricidade, estruturados por via sensório-motora (perceptivo) durante à prática. Deste modo, o conjunto de experiências ganhas na dança são assumidas como conhecimento vivido ou corporificado, um tipo de saber que o corpo se habitua a (re)conhece como agir e se relacionar no mundo. A base reflexiva eleita para o estudo é fenomenológica a partir de filósofos internacionais da área da ciência da dança e a obra de Merleua-Ponty intitulada “Fenomenologia da Percepção”. Nessa perspectiva, o corpo além de orgânico é considerado como produto sociocultural, histórico e principal agente à efetivação da tríade sensação, percepção, ação. Enquanto que a dança é a oportunidade, que cria intencionalmente na vida dos envolvidos tempo e espaço à interpretação e significação de contextos sociais e subjetivos.

Surface Step Effects on Boundary-Layer Transition Dominated by Tollmien–Schlichting Instability

Surface step effects on boundary-layer transition are modeled using a variable -factor method for transition dominated by Tollmien–Schlichting instabilities. Experimental correlations provide a bounding expression for the change in the critical -factor for transition onset, which provides a predictive means to account for surface steps. An investigation is conducted to assess the applicability of this approach for more general step arrangements. The approach is applied to capturing the superposition of a forward-facing and a backward-facing step in the form of a rectangular protrusion or a wide gap. Results show that a rectangular protrusion is well modeled by a linear combination of steps. However, a wide gap is best represented by a backward-facing step, without regard for the following forward-facing step. The sensitivity to streamwise step position is also investigated. Results show that the method is effective at capturing step effects for step positions in the neighborhood of the instability neutral point, and extending downstream close to the smooth-surface transition location. The effects of steps placed well upstream of the instability neutral point are overpredicted by the step model, likely the result of nonparallel effects on the upstream decay or as a result of the underlying receptivity occurring in the neighborhood of the neutral point.