Effect Of Sweep Research Articles

Numerical and experimental study on double coaxial gas assisted water jet guided laser machining of superalloy

To achieve more uniform gas film and higher working temperature, the design of film holes on combustion section parts of aero engine is developing towards three trends: smaller diameter, higher aspect ratio and more quantity. To realize the high quality manufacture of small film holes with high aspect ratio, a new water jet guided laser (WJGL) machining method based on double coaxial assistant gas was proposed in this article. An outer coaxial gas jet with high density was added to the existing coaxial jet of water and helium. That outer coaxial gas jet can weaken the interference effect of reverse water and sweep out the low speed water in deep blind hole. The sweep effect of outer coaxial assistant gas was confirmed by simulation and experimental results. The penetration time of Ф0.7 mm holes with depth of 4 mm decreased from 410 s to 173 s with the help of outer coaxial assistant gas. A series of Ф0.7 mm holes with the aspect ratio of 14.6:1 were machined using double coaxial assistant gas WJGL method on superalloy specimens with thermal barrier coatings (TBCs). The roughness of side wall was better than 0.6 μm, and no breakage or stratification was found at the interface of TBCs and matrix. This method can also be used in the manufacture of SiC/SiC ceramic matrix composites (CMCs) parts with deep small holes.

Numerical investigation and modeling of sweep effects on inlet flow field of axial compressor cascades

Swept blades are widely utilized in transonic compressors/fans and provide high load, high through-flow, high efficiency, and adequate stall margin. However, there is limited quantitative research on the mechanism of the effect of swept blades on the flow field, resulting in a lack of direct quantitative guidance for the design and analysis of swept blades in fans/compressors. To better understand this mechanism, this study employs a reduced-dimensional force equilibrium method to analyze more than 1500 swept cascades data. Results verify that circumferential fluctuation terms are responsible for inducing radial migration in the inlet airflow field of the swept blade, resulting in variations in the incidence angle and consequently leading to changes in the characteristics of the swept blade. Thus, a combination of simple functions and machine learning is utilized to model the circumferential fluctuation terms and quantify the sweep mechanism. The prediction accuracy of the model is high, with coefficient of determination greater than 0.95 on the test set. When the model is applied in a meridional flow analysis program, the calculation accuracy of the program for the incidence angle is improved by 0.4° and 0.6° at the design and off-design conditions respectively, compensating for the program's original deficiencies. Meanwhile, the model can also provide quantitative guidance for the design of swept blades, thereby reducing the number of design iterations and improving design efficiency.

Study on the Sweeping Effectiveness of Oil Palm Broom form for Sustainable Domestic Applications

Oil palm broom as a veritable household equipment is fast going into obsolescence partly due to some technical default in their use form and partly due to the crave for some unsustainable perceived alternatives. This study investigates the domestic applications suitability of natural oil palm broom and undertakes an empirical optimisation of the sweeping effectiveness. A field survey was carried out both in urban and rural settings to ascertain the current use of palm broom compared to other synthetic and non-biodegradable equipment acting as challengers. An optimisation process was done in tying of the broom strands. The broom strand lengths and spread angles used to optimize sweeping effectiveness were, 0.2 m, 0.4 m, 0.6 m, 0.8 m and 1.0 m lengths and 10°, 25°, 50°, 75° and 90° spread angles respectively. The results show that 75° strands spread angle and 0.8 m broom length give the best sweeping effectiveness. The determined form herein is easy to use. The oil palm sweeping broom is a natural eco-friendly, cheap and sustainable indispensable cleaning tool for most households and communities due to its unique features. An efficient design of the form configuration of the oil palm sweeping broom will improve on swept area output and also lessen the arduous effects of sweeping. There is need, therefore, to encourage the science and art of its production, especially in rural areas where it has great potential economic value to enhance the standard of living of the producers.

Theoretical and experimental investigation on the stall inception of low-speed axial compressors with swept rotor blades

The effect of rotor blade sweep on the flow stability of low-speed axial compressors is investigated by means of theoretical model, numerical simulations and experimental measurements. Four compressors with forward or backward swept rotors are carefully designed by modifying the tip element location of the baseline rotor. Steady simulation results show that the designed aerodynamic sweep in this work hardly changes the pressure rise and efficiency characteristics of the compressor, which ensures the comparability between these compressors regarding flow stability. The developed stall inception prediction model based on global linear stability analysis and eigenvalue theory is employed to evaluate the stall boundary of compressors after blade sweep designs, and results indicate that the forward sweep slightly improve the flow stability, while the backward sweep has significant deterioration effect. What's more, the circumferential propagation frequency of the perturbation wave at stall onset changes little after the sweep design. The steady and dynamic measurements in experiments for different rotor blades verifies the theoretical conclusions and the prediction accuracy of the theoretical model. Through steady and unsteady flow field analysis, it is found that the forward sweep reduces the diffusion factor, elementary work and blade loading at the rotor tip region, while the backward sweep has the opposite effect and enhances the interaction between the tip leakage flow and the primary flow, which is deemed the contributors to their effect on flow stability.

Ultra-linear broadband optical frequency sweep for a long-range and centimeter-spatial-resolution OFDR.

We demonstrated a long-range and centimeter-spatial-resolution optical frequency domain reflectometry (OFDR) system based on an ultra-linear broadband optical frequency sweep. The high nonlinear sweeping effect of the distributed feedback (DFB) diode laser was suppressed by a pre-distortion method, ensuring that the injection-locking process remained stable during fast tuning over a large span. An optical linear frequency sweep (LFS) with a sweep range and sweep rate of up to 60 GHz and 15 THz/s, respectively, was ultimately obtained by optimizing the injection-locking system. The high performance OFDR based on the proposed LFS achieved a sampling spatial resolution of 1.71 mm. Furthermore, distributed strain sensing was implemented with high-spatial resolutions of about 5 cm and 7 cm in the measurement range over 1 km and 2 km, respectively.

Feedback control of millimeter scale pivot walkers using magnetic actuation

An external magnetic field can be used to remotely control small-scaled robots, making them promising candidates for diverse biomedical and engineering applications. In a previous study, we showed that our magnetically actuated millirobot is highly agile and can perform a variety of locomotive tasks such as pivot walking, tumbling, and tapping in a horizontal plane. In this study, we focus on controlling the locomotion outcomes of this millirobot in the pivot walking mode. A mathematical model of the system is developed and the kinematic model is derived. The role of the sweep and tilt angles in the robot’s motion is also investigated.We study two controllers to regulate the gait of the pivot walker. The first one is a proportional-geometric-based controller, which determines the correct pivot point that the millirobot should use. Then, it regulates the angular velocity proportionally based on the error between the center of the millirobot and the reference trajectory. The second controller is based on a gradient descent optimization technique, which expresses the control action as an optimization problem. These control algorithms enable the millirobot to generate a stable gait while tracking the desired trajectory. A low-cost high-performance magnetic actuator is built to validate the proposed controllers. We conduct a set of different experiments and simulation runs to establish the effectiveness of proposed controllers for different sweep and tilt angles in terms of tracking error. The two controllers exhibit an appropriate performance, but it is observed that the gradient descent-based controller yields faster convergence time, smaller tracking error, and fewer number of steps. Finally, we perform an extensive experimentally parametric analysis of the effect of sweep and tilt angles and step time on the tracking error. As we expect, the optimization-based controller outperforms the geometric-based one.

Dynamic Mechanical Analysis of Cementitious Composites: Test Method Optimization and Materials Characterization

Dynamic mechanical analysis (DMA) applies an oscillating force to a specimen and analyzes the rheological and viscoelastic properties of a material. Since this method is used to characterize the frequency-dependent viscoelastic properties, it is mostly used for polymers, which have high sensitivity to the loading frequency. Cementitious composites are brittle and require more attention to specimen preparation and experimental settings to obtain reliable results. This work develops a DMA test protocol for cementitious composites which includes analyzing the effect of preload test, frequency pretest, and amplitude sweep on properties of cementitious composites. We propose a statistical method to analyze the variation between samples and determine the outliers among the specimens with the same mix to obtain valid test results from a sample group. The dynamic results obtained by using the proposed method are also discussed to serve as the baseline. The experimental setup parameters and statistical analysis presented in this work can be a robust foundation for the DMA analysis of cementitious composites.

Broad-scale variation in human genetic diversity levels is predicted by purifying selection on coding and non-coding elements.

Analyses of genetic variation in many taxa have established that neutral genetic diversity is shaped by natural selection at linked sites. Whether the mode of selection is primarily the fixation of strongly beneficial alleles (selective sweeps) or purifying selection on deleterious mutations (background selection) remains unknown, however. We address this question in humans by fitting a model of the joint effects of selective sweeps and background selection to autosomal polymorphism data from the 1000 Genomes Project. After controlling for variation in mutation rates along the genome, a model of background selection alone explains ~60% of the variance in diversity levels at the megabase scale. Adding the effects of selective sweeps driven by adaptive substitutions to the model does not improve the fit, and when both modes of selection are considered jointly, selective sweeps are estimated to have had little or no effect on linked neutral diversity. The regions under purifying selection are best predicted by phylogenetic conservation, with ~80% of the deleterious mutations affecting neutral diversity occurring in non-exonic regions. Thus, background selection is the dominant mode of linked selection in humans, with marked effects on diversity levels throughout autosomes.

Effect of temperature and heat flux boundary conditions on hydrogen production in membrane-integrated steam-methane reformer

In order to operate reforming plants at maximum efficiency it is important to investigate their operation under various conditions. This study aims to perform a comprehensive computational analysis to examine the effect of thermal boundary conditions on SMR and hydrogen recovery and, consequently, enriching the literature on hydrogen generation through steam-methane reforming. The studied thermal boundary conditions include constant and variable inlet temperature, outer wall temperature, and heat flux on outer wall of the reactor. A constant inlet flow rate of 0.001 kg/s (methane mass flow rate = 0.00018 kg/s), steam-to-methane ratio (or steam-to-carbon ratio, i.e., S/C) of 4 is considered in the reformer side for all the cases. Furthermore, the difference of pressure between both faces of the membrane is kept constant. Sweeping flow is incorporated to further raise the hydrogen partial pressure difference. Steam with flow rate of 0.001 kg/s is used to induce the sweeping effect throughout the study. Constant and variable temperatures/heat fluxes along with the effect of radiation in the reformer and transient inlet temperatures are examined in this study in terms of CH4 conversion ( %), H2 recovery ( %), H2 mass flow rates (kg/s), hydrogen mass flux through the membrane (kg.m−2. s−1), and other important parameters. About 1.7 times increase in methane conversion is noted as the reformer temperature is increased from 500 to 700 °C. The hydrogen recovery is found to decrease with the increase in temperature. Around 57 % and 56 % decrease in methane conversion and 42 % and 11.5 % rise in hydrogen recovery is observed with segmented case as compared to the constant heat flux and constant temperature cases, respectively. As compared to the reference 600 °C constant wall temperature, the increasing temperature profile results in 10.6 % rise in methane reforming and 11.2 % drop in the recovery of hydrogen. On the other hand, the decreasing temperature profile demonstrates 9.4 % decrease in conversion and 10.2 % elevation in recovery rate in contrast with the constant temperature case.

Effects of Sweep on the Flutter of Wraparound Fins

In the field of missile and rocket design, efficiency is a crucial aspect considering factors such as weight, storage, stealth, and cost. Wraparound fins (WAFs) have been used for many years to control the trajectory of missiles and rockets because of their compactness and effectiveness. However, WAFs are structurally more flexible than other types of fins, which may negatively impact their dynamic behavior and aeroelastic response. This can cause catastrophic instabilities, such as flutter. To mitigate these challenges, it is essential to consider both aerodynamic and structural models of WAFs during the design process. In this study, the flutter velocity and frequency of WAFs were investigated in relation to different structural design configurations and sweep angles, in order to understand and improve the aeroelastic performance of swept WAFs.

Settling behavior of polydisperse droplets in homogeneous isotropic turbulence

The settling behavior of polydisperse droplets in homogeneous and isotropic turbulence was measured by an ultra-high-resolution two-dimensional Particle Image Velocimetry. The aim of the present study is to provide new insight on the dependence of multi-scale particle settling behavior on characteristic parameters of two-phase turbulent flow via a sophisticate conditional analysis. The relative settling strength (defined as the ratio of mean droplet settling velocity to root mean square velocity of turbulence), whose effect on droplet settling behavior is of the primary interest, ranges as SvL=0.5–2.0. The turbulence Taylor Reynolds number is Reλ=200–300, and the droplet Stokes number is Stp=0.1–10. Voronoï analysis is performed to obtain the concentration field of discrete droplets from particle images. Particle structures including clusters or voids are detected, and the droplet settling velocities corresponding to various probing conditions, such as Stp, local particle concentration, and size of particle structures, were then analyzed. For the present configuration (droplet net sedimentation), there is a non-monotonic dependency of the settling velocity on local particle concentration. The negative correlation between them occurs in the moderate-concentration sub-regime and is insensitive to the variation of SvL, in which individual droplets interact with turbulent flow independently. It can be well explained by the commonly invoked preferential sweeping mechanisms. On the other hand, the dense-concentration regime, in which droplets prefer to accumulate into clusters, presents a positive correlation; namely, the conditional-averaged settling velocity decreases with the increase in local particle concentration. In this sub-regime, it is not the scale of single particles but the scale of particle clusters and the relative strength of turbulence (measured by SvL) that jointly determines the droplet settling behavior. Such a process, to our knowledge, is consistent with the so-called multi-scale preferential sweeping effect.

Evaluation of chip seal mixture design methods using modified Hamburg wheel tracking test and sweep test

The objective of this study was to identify the most effective chip seal design method and chip sizes by conducting a modified Hamburg wheel tracking test and sweep test. Three chip seal design methods, including Austroads, McLeod, and Vietnam methods, were evaluated to design several chip seal mixtures with varying aggregate sizes (e.g., 12.5, 9.5, 4.75, and 2.36 mm) and binder types. To assess the performance of the chip seal mixtures, aggregate loss and bleeding susceptibility were measured. The sweep test was utilized to determine the amount of aggregate loss caused by the sweeping effect, while the modified Hamburg wheel tracking (HWT) test was developed to estimate the aggregate loss caused by the braking effect using a fixed pneumatic rubber tire. Additionally, a modified Hamburg wheel tracking test with a rolling pneumatic rubber tire was used to assess bleeding susceptibility, and the bleeding area was quantified using an image analysis process. The results indicated that the Austroads design method exhibited the lowest aggregate loss compared to the McLeod and Vietnam methods. Moreover, the consistent findings from both the sweep test and modified HWT test demonstrated the feasibility of using the modified HWT test to simulate aggregate loss caused by the braking effect. The bleeding percentage was found to be affected not only by the binder application rate but also by the aggregate size and the number of layers applied. The Austroads and McLeod chip seal mixtures exhibited an approximately 20 % lower bleeding percentage than that of the Vietnam mixtures. Finally, for a single chip seal, a 9.5 mm chip aggregate was determined to be the optimal size, while for a double chip seal, 4.75 mm and 2.36 mm chips were recommended.

Comparison analysis of cationic-polyacrylamide as flocculant aid in titanium salt coagulants

The combination of organic and inorganic coagulants is considered to be an effective strategy for Humic Acid (HA) removal. In this study, the performance of Titanium-based coagulants aided by Cationic-Polyacrylamide (CPAM) to HA molecules was compared. It was found that CPAM had a higher promotion effect in the TXC system. The reason for why CPAM was more suitable for the TXC system could be explained by analyzing Zeta potential, FTIR, and XPS. By comparing the coagulation mechanism of TiCl4 (TC) and Poly-Titanium Chloride (PTC), we found that complexation was the main mechanism of TC and PTC in acidic and neutral environments. The C-O-Ti Bond was formed by complexing the Ti-OH with the C-OH and -COOH functional groups of HA molecules. Sweeping was the most important removal mechanism of TXC in the neutral and alkaline environment, and CPAM bridged floc through hydrogen bond force for enhancing the sweeping effect. In addition, the role of CPAM in TXC system was further demonstrated by Zeta potential analysis. Both TC and PTC were positively charged in the measured pH range, so the removal of Humic acid was limited by increasing zeta potential. In both neutral and alkaline environments, TXC kept a negative surface charge and CPAM significantly enhanced the adsorption of HA on the TXC floc surface. This study provided clues for the interaction mechanism between titanium salt coagulants and HA, and it also provided a reference for the application of TXC coagulant combined with CPAM flocculant for the removal of HA molecules.

The Impact of Digitalization on Global Trade Law

AbstractThe Article explores the transformations triggered by digitalization in the domain of global trade law and seeks to evaluate the nature and the effects of the unfolding legal adaptation in this field of international law. For this purpose, the Article starts by mapping the sweeping effects of digitalization on trade and trade policies. It then turns to the current regulatory framework for digital trade—first, by sketching the state of affairs in the multilateral forum of the World Trade Organization (WTO) and second, by analyzing the more deliberate regulatory responses to the challenge of digitalization formulated in free trade agreements (FTAs), with a particular focus on some more recent advanced models of digital trade regulation. The Article finally seeks to contextualize and assess the impact of the existing legal framework and its adequacy for the contemporary data-driven economy, pointing also at some current deficiencies and potential setbacks going forward.

Heat Treatment and Dynamic Mechanical Analysis Strain Sweep Effects on the Phase Structure and Morphology of an Fe-28Mn-6Si-5Cr Shape Memory Alloy

Fe-Mn-Si-based shape memory alloys (SMAs) have been extensively investigated since 1982 for various useful properties that enhance the development of different applications such as anti-seismic dampers for very tall buildings, pipe joints, or rail fasteners. In particular, the Fe-28Mn-6Si-5Cr (mass. %) alloy has been mainly used in vibration mitigation or self-adjustable axial displacement applications. Dynamic mechanical analysis (DMA), performed by strain sweeps (SS), enables the monitoring of the evolution of storage modulus and internal friction variations with increasing strain amplitudes at different constant frequencies and temperatures. Thus, applying dynamic bending with various frequencies and amplitudes that actually represents an isothermal mechanical treatment. In the present paper, an Fe-28Mn-6 Si-5Cr (mass. %) SMA was cast by ingot metallurgy, hot-rolled, and water quenched in order to obtain thermally induced martensite and avoid the occurrence of cooling cracks. The influence of the holding time, between 2 and 10 h, at 1050 °C and the effects of DMA-SS performed at three different frequencies were analyzed by a differential scanning calorimetry, an X-ray diffraction, and a scanning electron and atomic force microscopy. The effects of the holding time and mechanical treatment on the structure and morphology of martensite plates were corroborated with the results of the thermal analysis.

Development of a general flow sweeping mixing model and application to a wire-wrapped assembly

Subchannel analysis is an essential tool for analyzing the thermal-hydraulic and safety characteristics during the design of nuclear reactor cores. In the present study, a general flow sweeping mixing model is proposed to describe the flow sweeping effect in subchannel analysis, and the model form can be applied to rod bundles with arbitrary types of spacers. As an example, the general flow sweeping mixing model is applied to a wire-wrapped assembly proposed by Shanghai Jiao Tong University. In this example, the model factors are derived from numerical results, and the model coefficient is determined by experimental data. The model is evaluated by comparing it with existing models and experiment data, and the comparison results show the superiority of the new model. The crossflow rate of subchannel gaps caused by wire along the axial direction can be estimated by new model. The present study provides a new idea for the development of the flow sweeping mixing model used in subchannel analysis.

Effect of SWEEPS and PIPS techniques on dye extrusion in photodynamic therapy procedure after root canal preparation

AimThe aim of this study is to measure and compare the amount of apical extrusion of the methylene blue as photosensitizer using Laser-activated irrigation(LAI) techniques (SWEEPS, PIPS) and photodynamic therapy (PDT). Materials and methods40 single-rooted premolar teeth were selected and their root canals were cleaned and prepared. The photosensitizer, Methylene blue (MB), was used as dye which applied inside the root canals and the access cavities. Then the teeth were randomly allocated to 4 groups. Different techniques (SWEEPS, PIPS, PDT) were used in 3 groups. One group received no activation. Data related to the concentration of the extruded methylene blue was measured using ultraviolet and visible (UV–Vis) absorption spectroscopy. Absorption peak intensity of MB in the wavelength of 668 nm was considered as the concentration index according to Beer Lambert law. Taking into account the normal distribution of this data, one-way ANOVA analysis was used to evaluate the effects of the independent variables on the amount of apical extrusion of the irrigant. ResultsBased on the results of ANOVA analysis, there was no significant difference between the amounts of apical extrusion of MB between different groups (p = 0.628) ConclusionUsing SWEEPS and PIPS techniques, despite diffusion of the photosensitizer, didn't lead to any difference in the amount of apical extrusion. Therefore, these LAI techniques can be used safely for root canal irrigation.

Effect of beneficial sweeps and background selection on genetic diversity in changing environments

Neutral theory predicts that the genetic diversity within a population is proportional to the effective population size. In contrast, the observed genetic diversity for various species vary in a narrow range for several orders of magnitude change in the population sizes (Lewontin’s paradox). The selective sweeps and background selection, reduce the genetic variation at the linked neutral sites and have been studied considering the environment to be selectively constant. However, in a natural population, the selective environment varies with time. Here, we investigate the impact of selective sweeps and background selection on neutral genetic diversity when the selection coefficient changes periodically over time. The reduction in genetic variation due to selective sweeps is known to depend on the conditional fixation time. Here, we find that the effect of changing environment on conditional mean fixation time is most substantial for the randomly mating population than the inbreeding population with arbitrary inbreeding coefficient. We also study the effect of background selection on neutral sites when the selection coefficient of linked deleterious mutation change periodically in time. In the slowly changing environment, we find that neutral heterozygosity is significantly different, and the site frequency spectrum has a different shape than that in the static environment.

Triglobal resolvent analysis of swept-wing wakes

Through triglobal resolvent analysis, we reveal the effects of wing tip and sweep angle on laminar separated wakes over swept wings. For the present study, we consider wings with semi-aspect ratios from $1$ to $4$ , sweep angles from $0^\circ$ to $45^\circ$ and angles of attack of $20^\circ$ and $30^\circ$ at a chord-based Reynolds number of $400$ and a Mach number of $0.1$ . Using direct numerical simulations, we observe that unswept wings develop vortex shedding near the wing root with a quasi-steady tip vortex. For swept wings, vortex shedding is seen near the wing tip for low sweep angles, while the wakes are steady for wings with high sweep angles. To gain further insights into the mechanisms of flow unsteadiness, triglobal resolvent analysis is used to identify the optimal spatial input–output mode pairs and the associated gains over a range of frequencies. The three-dimensional forcing and response modes reveal that harmonic fluctuations are directed towards the root for unswept wings and towards the wing tip for swept wings. The overlapping region of the forcing–response mode pairs uncovers triglobal resolvent wavemakers associated with self-sustained unsteady wakes of swept wings. Furthermore, we show that for low-aspect-ratio wings optimal perturbations develop globally over the entire wingspan. The present study uncovers physical insights on the effects of tip and sweep on the growth of optimal harmonic perturbations and the wake dynamics of separated flows over swept wings.

Do the Street Sweeping and Washing Work for Reducing the Near-ground Levels of Fine Particulate Matter and Related Pollutants?

This research focuses on the properties of near-ground fine particles (PM2.5), ultrafine particles (UFP), black carbon (BC), and polycyclic aromatic hydrocarbons (PAHs) in traffic area. The effects of street sweeping and washing on pollutant levels are evaluated. The X Road with sewage ditch was selected for the stationary samplings to determine the differences between the atmospheric PM2.5 mass concentration, their composition, and potential sources before/after street cleaning processes, as well as the effect of the sewage existence. Results show that there were certain reductions of PM2.5 after the street washing, especially for the road section with drainage ditch. The chemical mass balance model then pointed out the traffic contribution on PM2.5 significantly reduced on the downwind site (from 25.7% to 16.5%). Besides, the spatial distribution of the near-ground PM2.5, UFP, BC, and PAHs were monitored by a mobile platform on an appropriate long, straight, and not heavily traffic Road Y. The monitoring took place at 1 h-before, during washing/sweeping, at 1 h-after, at 1 d-after, at 2 d-after three cleaning strategies, including only sweeping, washing-before-sweeping, and sweeping-before-washing. The monitoring then mapped out the hot spot distribution of pollutants. The PM2.5 mass, UFP number, BC, and PAH concentrations before the street sweeping is 155 µg m–3, 1.2 × 104 # cm–3, BC 3633 ng m–3, and 36 ng m–3. The UFP number concentration of suspended particles after street washing had a trend to reduce, avoided the deterioration of air quality. The strategy, “sweeping-before-washing”, was the best operation method among three to suppress the UFP number concentration by 42%, while all three strategies could effectively reduce the PAH levels. The primary pollutants are more easily reduced by the street-cleaning process, while the secondary one did not.