Angle Of Gradient Research Articles

Unravelling the relation between free volume gradient and shear band deflection induced extra plasticity in metallic glasses

Previous experiments have revealed that the controllable introduction of structural gradients in metallic glasses (MGs) can endow the materials with extra plasticity due to the gradient-induced deflection of shear bands. However, the relation between the spatial structural gradient and the initiation of shear band deflection remains unclear. The current study has been focused on investigating the relationship between the improved mechanical properties of MGs and structural gradients specified by the distribution of the intrinsic free volume. Molecular dynamics (MD) simulations are firstly performed on homogeneous MG models containing various initial free volume values, showing that the shear band angle increases with decreasing free volume under uniaxial compression, whereas higher shear band angle is observed under uniaxial tension with increasing free volume. Based on the asymmetric behaviors of MGs under compression and tension, a theoretical model is developed to quantitatively characterize the influence of free volume on the mechanical response of MGs, which incorporates a failure criterion based on free volume generation during external loadings. The model can be further utilized to interpret and predict the fracture strain, shear band angle, maximum stress, and fracture surface morphology of gradient structured MGs in both simulations and experiments. The relationship between free volume gradient and shear band deflection induced extra plasticity established in this study provides valuable guidance for the structural design of MGs with enhanced mechanical properties.

Experiment, CFD simulation and field synergy characteristics analysis of hot-air drying process in a spouted bed

Combining experimental and simulation methods, the hot-air drying process in the spouted bed was studied from the perspective of heat and mass transfer and multiphase physical field synergy. Based on the experimental system, the rate of drying curve was determined, and a drying prediction model was established and verified. The analysis of the drying characteristics shows that the heat and mass transfer in the spouted bed mainly occurred in the center of the spouting and fountain region, followed by the annulus region, and finally on both sides of the fountain region. The dimensionless parameter σ that simultaneously considered the synergy angle of velocity-velocity gradient and velocity-pressure gradient indicated that the gas drag was mainly concentrated near the gas inlet. The synergy coefficient SC of the velocity-temperature-concentration field was more affected by the variation coefficient of the velocity-concentration field and less affected by the variation coefficient of the velocity-temperature field.

Analysis of light field and flow field of vortex rods tube photobioreactor based on field synergy principle

A new static mixer called the vortex rod static mixer was introduced into the photobioreactor. This study focused on the vortex rod tubular reactor as the subject of investigation. The effects of different incident light field intensities (I0 = 375 μmol/(m2·s), 800 μmol/(m2·s), and 1200 μmol/(m2·s)) on reactor efficiency were simulated using the CFD simulation method, considering variations in vortex rod arrangement (60°, 90°, and 120°) and tilt angle (α = 27°, 36°, 45°, 54°, and 63°). In the SST turbulence simulation flow field results, the movement process of algae cells in the tube was simulated using the particle tracking module. By taking into account the average frequency of the light-dark cycle, the enhancement efficiency of the light-dark cycle, and the synergy angle of the light gradient and velocity field, the following results were obtained: the optimum tilt angle for the vortex rod is α = 45°. For incident light field intensities of I0 = 375 μmol/(m2·s) and 800 μmol/(m2·s), the 60° arrangement yielded the best results, resulting in a 54.491 % and 66.258 % increase in cycle frequency, an 18.747 % and 22.795 % enhancement in efficiency, and an average |cosβ| = 0.68055. For an incident light field intensity of I0 = 1200 μmol/(m2·s), the 90° arrangement proved to be the most effective, resulting in a 57.580 % increase in cycle frequency, an 18.058 % enhancement in efficiency, and an average |cosβ| = 0.68975.

Gravity Data Enhancement Using the Exponential Transform of the Tilt Angle of the Horizontal Gradient

Detecting the boundaries of geologic structures is one of the main tasks in interpreting gravity anomalies. Many methods based on the derivatives of gravity anomalies have been introduced to map the source boundaries. The drawbacks of traditional methods are that the estimated boundaries are divergent or false boundaries appear in the output map. Here, we use the exponential transform of the tilt angle of the horizontal gradient to improve the edge detection results. The robustness of the presented method is illustrated using synthetic data and real examples from the Voisey’s Bay Ni-Cu-Co deposit (Canada) and the Tuan Giao (Vietnam). The findings show that the presented technique can produce more precise and clear boundaries.

Structural mapping of the west central Arabian Shield (Saudi Arabia) using downward continued magnetic data

In this study, we have applied a stable downward continuation technique to magnetic anomalies from the global geomagnetic field model MAG2V3 to improve the resolution of magnetic data of the west central Arabian Shield, Saudi Arabia. Then, advanced interpretation methods such as the tilt angle of the horizontal gradient (TAHG), horizontal gradient of a modified tilt angle (HGSTDR), and enhanced horizontal gradient (EHGA) have been applied to downward continued magnetic dataset to highlight the main structural features in the region. The observed geologic structures from the magnetic analysis revealed NW-SE, NE-SW, and ENE-WSW orientations in the west central Arabian Shield. The depths of these structures were computed by the analytic signal (AS) technique and the obtained result shows depths varying from 1.2 to 9.2 km. This study provided a new map of the subsurface geological structures for a better understanding of the tectonic evolution of the west central Arabian Shield.

An integrated approach of advanced methods for mapping geologic structures and sedimentary thickness in Ukelle and adjoining region (Southeast Nigeria)

High-resolution aeromagnetic data were enhanced using recent and advanced filters to map the geologic structures of the Ukelle and adjoin region (Southeast Nigeria). Aeromagnetic data were reduced to the equator (RTE) and upward continued to 100 m. Subsequently, enhancement operations like the tilt angle of the horizontal gradient (TAHG), logistic function of the horizontal gradient (LTHG), and fast sigmoid function (FSED) operations were carried out. The results from these filters indicated that the ENE-WSW, NE-SW, NNE-SSW, and NNW-SSE orientations dominate the structural pattern of the Ukelle region. In addition, the edge filters delineated NE-SW trending synclinal structures that match the location of thick (500-1400 m) sedimentation obtained by the tilt-depth (TD) method. Furthermore, the structural map obtained from remote sensing data validated the lineament orientations and position of the NE-SW trending synclinal structure. The results also showed that the study location’s southeastern and northwestern flanking portions, controlled by extensive Santonian igneous intrusions and metamorphisms, are characterized by high lineaments and thin (0-500 m) sedimentation. The observed thin sedimentation is believed to be caused by widespread Santonian tectonic events in the area. At the same time, related geologic structures served as migration pathways and accumulation zones for rift mineralization.

Aeromagnetic and structural characterization of dyke swarms in southeast Brazil: Evidence for Cenozoic reactivation of the Guapiara lineament, Ponta Grossa Arch

The Guapiara Lineament located on the northern edge of the Ponta Grossa Arch, Southeastern São Paulo state, Brazil, it is an important morphostructural feature defined by dykes oriented in NW-SE direction. The main objective of this work is applying new techniques for enhancing magnetic anomalies of the Guapiara Lineament and other structures, and using aeromagnetic data as support for the analysis of structure reactivation. Aerogeophysical techniques included qualitative and semiquantitative approaches (Euler Deconvolution and Radial Average Spectrum), we used the vertical and horizontal gradients, as well as deep magnetic sources and shallow magnetic sources filters, for an in-depth magnetic-structural characterization that was further correlated with the outcropping geology. We have also applied upward continuation (2000m) in the anomalous magnetic field map which was the basis for applying the Total Horizontal Gradient of the Analytical Signal (TDY), Analytic Signal Amplitude (ASA), Tilt angle (TDR), Total Horizontal Derivative of the Tilt Angle (TDR-THDR) and Tilt Angle of the Horizontal Gradient (TAHG) to improve our interpretations of the regional framework. The magnetic trends of the Guapiara Lineament are superimposed on the NE-SW (e.g.: Cubatão Lineament) and E-W (e.g.: São Sebastião Lineament) anomalies, which are considered structural inheritances of the Proterozoic basement. We report a set of reactivated N40–70W and E-W strike-slip faults showing the same orientation as the mapped magnetic lineaments. Moreover, they seem to be associated to deformational features in the dyke swarm, which was interpreted as evidence of Cenozoic tectonic reactivation.

Maximum thickness control in topology optimization using an inflection-point-based geometric constraint

In density-based topology optimization, the design space is parameterized by assigning a density to each element that discretizes the domain. However, establishing a limit on the maximum attainable thickness of the structural components in this framework is non-trivial. To control the thickness, knowledge of both the central axis of the components and the elements that reside beyond a specified thickness is required for penalizing the correct design variables. This study proposes a geometric constraint-based method for exerting control over the maximum allowable thickness of the structural members in topology optimization. The central axis of the structural components is traced by identifying the inflection points of the density distribution, where the density is locally maximum. By computing the angle of the spatial gradient of the density distribution and taking their divergence, the inflection points can be reliably located in all regions of the design domain. Based on geometric information, domains of elements beyond the specified thickness from the inflection points are constructed. Then, a constraint is defined to penalize material formation only in these elements. As a result, control over the maximum thickness of the structural components can be achieved during topology optimization. The framework can also be utilized to regulate the minimum thickness of the structural components by enforcing material formation within a specified thickness. Special measures are implemented to enable the formation of junction regions within the domain while preserving the imposed thickness constraint. The proposed method is applied to topology optimization of minimum compliance and heat conduction problems to demonstrate its applicability.

Application of High-Precision Filters on Airborne Magnetic Data: A Case Study of the Ogoja Region, Southeast Nigeria

Aeromagnetic data from the Ogoja region, Southeast Nigeria, were enhanced using high-precision methods including the tilt angle of total horizontal gradient (TAHG), the softsign function (SF), and the improved logistic function (IL) with the aim of creating a new structural map. This new map can help improve the understanding of the trend, spatial distribution, and pattern of the lineaments. The TAHG, SF, and IL methods generated geologic structures with correlating trends, distributions, and patterns. However, the SF and IL techniques mapped the borders of geologic structures more precisely. The lineaments extracted from the SF and IL maps were reduced to equator (RTE) magnetic data, and a GIS was used to create structural maps with NE–SW, NW–SE, NNE–SSW, and NNW–SSE orientations. Furthermore, the depths (0–2100 m) of these geologic structures were estimated using the tilt depth technique (TDT). The high lineament density and thin sedimentation observed in the study area were triggered by the widespread Santonian igneous intrusions associated with the Abakaliki Anticlinorium. The techniques applied in our study can be employed in areas with the same conditions around the world for the precise delineation of geologic structures from magnetic and gravity data.

Structural interpretation of potential field data using the enhancement techniques: a case study

The enhancement techniques of potential field data are commonly used to detect the boundary locations of geological structures. There are many different techniques for estimating the source boundaries. Through synthetic examples and Bouguer data from the southern Red Sea, we have evaluated the performance of 15 enhancement techniques. The findings show that the tilt angle of horizontal gradient (TAHG) and fast sigmoid (FSED) techniques perform better than other techniques under almost all scenarios. Moreover, these two techniques can avoid producing false structures or connected structures as other techniques. The extracted lineaments from the TAHG and FSED were compared with surface faults of the study area. As a result, major differences are caused by rifting effect on the oceanic crust. The obtained results provide valuable information to better understand the structural features of the southern Red Sea and to introduce a more reliable structural interpretation.

High precision structural mapping using edge filters of potential field and remote sensing data: A case study from Wadi Umm Ghalqa area, South Eastern Desert, Egypt

Recently, detecting the edges and geologic structures (deep and shallow) from potential field sources provides a fundamental tool for interpreting geological structures. Therefore, the high precision computation of the edges of potential sources is becoming an essential requirement for studying subsurface structures. In this study, nine common detectors like tilte angle (TA), Theta-map (TM), Horizontal tilt angle (TDX), hyperbolic tilt angle (HTA), Improved tilt angle (ITA), Tilt angle of the total horizontal gradient (TTHG), Tilt angle of the total gradient (TTG), improved Theta-map (ITM), and improved logistic (IL) were applied. These filters have been tested on theoretical models and real data (aeromagnetic) from the Wadi Umm Ghalqa area, South Eastern Desert of Egypt. The obtained results have shown that the improved logistic (IL) filter could detect edges more successfully than the other eight filters. The results of the IL method were used to generate new accurate structural maps for local and deep components of the investigated area. Moreover, surface structures obtained from remote sensing data were considered to control the interpretation of the mapped subsurface lineaments. Hence, the IL method can be utilized as a sharp tool for the high precision structural imaging of the potential data.

Estimating Effectiveness of Some Methods for Detecting Edge of Potential Field Sources

This paper presents a comparative study of effectiveness of edge detection methods such as total horizontal gradient, analytic signal amplitude, tilt angle, gradient amplitude of tilt angle, theta map, horizontal tilt angle, tilt angle of total horizontal gradient, tilt angle of analytic signal, improved theta map, and total horizontal gradient of improved tilt angle. The effectiveness of each method was estimated on synthetic magnetic data and synthetic gravity anomaly data with and without noise. The obtained results show that the tilt angle of gradient amplitude can detect all the edges more clearly and precisely. The applicability of each method is demonstrated on the aeromagnetic anomaly data from the Zhurihe region of Northeast China, and Bouguer gravity anomaly data from a region of North Vietnam. The results computed by the tilt angle of horizontal gradient were also in accord with the geologic structures of the areas.

Flow of shear-thinning fluids through porous media

Pseudo-plastic fluids exhibit a non-linear stress-strain relationship which can provoke large, localized viscosity gradients. For the flow of such fluids in porous media the consequence is a strong variability of the effective permeability with porosity, angle of the macroscopic pressure gradient, and rheological parameters of the fluid. Such a variability is investigated on the basis of adjoint homogenization theory for a Carreau fluid in an idealized porous medium geometry, highlighting differences with respect to the Newtonian case. It is shown in particular that the more we depart from Newtonian conditions, the more the (often used) hypothesis of an effective viscosity in Darcy’s law is a poor approximation, for the effective permeability tensor becomes strongly anisotropic.

Comparison of different approaches of computing the tilt angle of the total horizontal gradient and tilt angle of the analytic signal amplitude for detecting source edges

Comparison of different approaches of computing the tilt angle of the total horizontal gradient and tilt angle of the analytic signal amplitude for detecting source edges

Investigation of the near-wake behaviour of a utility-scale wind turbine

Super-large-scale particle image velocimetry and flow visualization with natural snowfall is used to collect and analyse multiple datasets in the near wake of a 2.5 MW wind turbine. Each dataset captures the full vertical span of the wake from a different perspective. Together, these datasets compose a three-dimensional picture of the near-wake flow, including the effect of the tower and nacelle and the variation of instantaneous wake expansion in response to changes in turbine operation. A region of high-speed flow is observed directly behind the nacelle, and a region of low-speed flow appears behind the tower. Additionally, the nacelle produces a region of enhanced turbulence in its wake while the tower reduces turbulence near the ground as it breaks up turbulent structures in the boundary layer. Analysis of the instantaneous wake behavior reveals variations in wake expansion – and even periods of wake contraction – occurring in response to changes in angle of attack and blade pitch gradient. This behaviour is found to depend on the region of operation of the turbine. These findings can be incorporated into wake models and advanced control algorithms for wind farm optimization and can be used to validate wind turbine wake simulations.

Mathematical model to calculate the critical value of the angle of gradient for a tractor-mounted tilther

The article is devoted to the search for a mathematical model convenient for practical calculations to determine the critical value of the angle of gradient for the tractor-mounted heavy tilther. It shows the existing mathematical model, which is then refined based on the stiffness of the elastic tractor wheels and their vertical reactions offset. Three methods of solving the resulting equations are analyzed, upon which the optimal one is chosen. As a result, a simple and convenient in practice mathematical model to determine the critical value of the angle of gradient for the tractor-mounted implement is obtained. The analysis of the calculation results showed that depending on the operating conditions and the weight of the tractor counterweight, the differences between the results calculated using the traditional and refined models can reach more than 4 degrees, which is very important to ensure the hill climbing safety.

Mapping of Structural Lineaments and Fracture Zones around the Central Indian Ridge (10°S - 21°S) using EIGEN 6C4 Bouguer Gravity Data

ABSTRACT The purpose of the present study is to map the structural lineaments and fracture zone around the Central Indian Ridge (10°S - 21°S) using EIGEN 6C4 Bouguer gravity data. This would help to better understand the evolution of the Indian Ocean Triple Junction (IOTJ), Central Indian Ridge (CIR) and the Ocean floor in the vicinity. In this study, a comparison of three different edge detection techniques have been made to validate the TAHG (tilt angle of total horizontal gradient) and the THVH (Tilt angle of vertical derivative of total horizontal gradient) edge detection techniques over the rudimentary total horizontal derivative (THD) technique. Synthetic model study was performed considering the major problems of the standard edge detection process. Results of the three edge detection techniques were compared critically and validated with the satellite-derived EIGEN 6C4 Bouguer gravity data. The lineaments exhibit NE-SW and NNW-SSE trends over the ocean. The NE-SW trend represents the current spreading direction of the CIR (Central Indian Ridge), whereas NNW-SSE trend representing the lineaments formed due to ridge jump during magnetic anomaly 20 and 18.

Stabilization and Control of Single-Wheeled Vehicle with BLDC Motor

To stabilize a single-wheel vehicle is necessary to know the angle of gradient of the platform with respect to the horizontal axis and also the movement of the vehicle. This can be detected in several ways. Accelerometers and gyroscopes are small, accurate and energy-saving today. They provide analogue or digital output. In the introduction we will describe the basic parameters of accelerometer and gyroscope. We will describe the principle of digital signal processing from both sensors. In the next section we look at the effect of dynamic acceleration on the sensors and the elimination of this phenomenon with a complementary filter. We explain, what it is a complementary filter, benefits and internal structure. We will include a short code in the C language for data processing from the output.

Control and stabilization of single-wheeled electric vehicle with BLDC engine

Abstract To stabilize a single-wheel vehicle, it is necessary to know the angle of gradient of the platform with respect to the horizontal axis and also the movement of the vehicle. This can be detected in several ways. Accelerometers and gyroscopes are small, accurate and energy-saving today. They provide analog or digital output. In the introduction we will describe the basic parameters of accelerometer and gyroscope. We will also describe the principle of digital signal processing from both sensors. In the next section we look at the effect of dynamic acceleration on the sensors and the elimination of this phenomenon by means of a complementary filter. We explain what is a complementary filter, benefits, and structure. We will include a short code in the C language for data processing.

Self-Lubricanting Slippery Surface with Wettability Gradients for Anti-Sticking of Electrosurgical Scalpel.

Soft tissue sticking on electrosurgical scalpels in minimally invasive surgery can increase the difficulty of operation and easily lead to medical malpractice. It is significant to develop new methods for anti-sticking of soft tissue on electrosurgical scalpels. Based on the characteristics of biomimetic ultra-slippery surface, a self-lubricating slippery surface with wettability gradients on electrosurgical scalpel was designed and fabricated. Non-uniformly distributed cylindrical micro pillars, which constitute the wettability gradients, were prepared by an electrolytic etching process and the theoretic of the spontaneous liquid spreading process was analyzed. The silicophilic property of wettability gradients surface was modified by octadecyltrichlorosilane (OTS) self-assembling coat with biocompatible liquid lubricant dimethyl silicone oil. The contact angle of gradient’s surface at different temperatures was measured. The transportation behaviors of both water and dimethyl silicone oil on the wettability gradient’s surface were investigated; the results illustrate that the wettability gradient’s slippery surface can successfully self-lubricate from regions with low pillar density to regions with high pillar density, ascribed to the unbalanced Young’s force. The anti-sticking capability of the electrosurgical scalpel with self-lubricating slippery surface was tested. Both the adhesion force and adhesion mass under different cycles were calculated. The results suggest that the as-prepared slippery surface has excellent anti-sticking ability associated with better durability.