To see the other types of publications on this topic, follow the link: Zone velocità.
Journal articles on the topic 'Zone velocità'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Zone velocità.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Liu, Yike, Xu Chang, Futian Liu, and Ye Zheng. "Three-dimensional velocity images beneath the KangDian Tethyan tectonic zone of China." Canadian Journal of Earth Sciences 39, no. 10 (October 1, 2002): 1517–25. http://dx.doi.org/10.1139/e02-053.
Full textAbstract:
Three-dimensional velocity images of the crust and upper mantle beneath the KangDian Tethyan tectonic zone in China are constructed using P-wave travel-time residuals of earthquakes. The KangDian Tethyan tectonic zone is a transitional zone in tectonic structures and an important topographic border line. It is also a zone of concentration of shallow-focus earthquakes. The imaging results indicate that there is a significant lateral heterogeneity in the crust and upper mantle beneath the KangDian Tethyan tectonic zone in China. The velocity images of the upper crust show features closely related to the tectonic features on the surface. A low-velocity layer exists in a very wide range of the mid-crust. Almost all of the major earthquakes took place in the transition strips between high- and low-velocity zones in the crust above 20 km depth. From the velocity images at 20+0 and 50+0 km depth, respectively, we find that the epicenters of strong earthquakes with magnitude larger than 6.0 are almost entirely distributed in the low-velocity zones or on their boundaries.
2
ROTARU, Constantin, Ionică CÎRCIU, Cornel ARAMĂ, and Cristian-George CONSTANTINESCU. "ASPECTS REGARDING VELOCITY DISTRIBUTION IN THE SECONDARY ZONE OF A GAS TURBINE COMBUSTOR." Review of the Air Force Academy 13, no. 3 (December 16, 2015): 33–38. http://dx.doi.org/10.19062/1842-9238.2015.13.3.5.
Full text
3
Cui, Yonggang, Wei Haur Lam, How Tion Puay, Muhammad S. I. Ibrahim, Desmond Robinson, and Gerard Hamill. "Component Velocities and Turbulence Intensities within Ship Twin-Propeller Jet Using CFD and ADV." Journal of Marine Science and Engineering 8, no. 12 (December 15, 2020): 1025. http://dx.doi.org/10.3390/jmse8121025.
Full textAbstract:
This study presents the decays of three components of velocity for a ship twin-propeller jet associated with turbulence intensities using the Acoustic Doppler Velocimetry (ADV) measurement and computational fluid dynamics (CFD) methods. Previous research has shown that a single-propeller jet consists of a zone of flow establishment and a zone of established flow. Twin-propeller jets are more complex than single-propeller jets, and can be divided into zones with four peaks, two peaks, and one peak. The axial velocity distribution is the main contributor and can be predicted using the Gaussian normal distribution. The axial velocity decay is described by linear equations using the maximum axial velocity in the efflux plane. The tangential and radial velocity decays show linear and nonlinear distributions in different zones. The turbulence intensity increases locally in the critical position of the noninterference zone and the interference zone. The current research converts the axial momentum theory of a single propeller into twin-propeller jet theory with a series of equations used to predict the overall twin-propeller jet structure.
4
Volino, Ralph J., Michael P. Schultz, and Christopher M. Pratt. "Conditional Sampling in a Transitional Boundary Layer Under High Freestream Turbulence Conditions." Journal of Fluids Engineering 125, no. 1 (January 1, 2003): 28–37. http://dx.doi.org/10.1115/1.1521957.
Full textAbstract:
Conditional sampling has been performed on data from a transitional boundary layer subject to high (initially 9%) freestream turbulence and strong (K=ν/U∞2dU∞/dx as high as 9×10−6) acceleration. Methods for separating the turbulent and nonturbulent zone data based on the instantaneous streamwise velocity and the turbulent shear stress were tested and found to agree. Mean velocity profiles were clearly different in the turbulent and nonturbulent zones, and skin friction coefficients were as much as 70% higher in the turbulent zone. The streamwise fluctuating velocity, in contrast, was only about 10% higher in the turbulent zone. Turbulent shear stress differed by an order of magnitude, and eddy viscosity was three to four times higher in the turbulent zone. Eddy transport in the nonturbulent zone was still significant, however, and the nonturbulent zone did not behave like a laminar boundary layer. Within each of the two zones there was considerable self-similarity from the beginning to the end of transition. This may prove useful for future modeling efforts.
5
Monk, David J. "Fresnel-zone binning: Fresnel-zone shape with offset and velocity function." GEOPHYSICS 75, no. 1 (January 2010): T9—T14. http://dx.doi.org/10.1190/1.3294576.
Full textAbstract:
The concept of the Fresnel zone has been explored by many workers; most commonly, their work has involved examining the Fresnel zone in the limiting case of zero offset and constant velocity. I have examined the shape of the Fresnel zone for nonzero offset and in the situation of constant velocity gradient. Finite-offset Fresnel zones are not circular but are elliptical and may be many times larger than their zero-offset equivalents. My derivation takes a largely geometric approach, and I suggest a useful approximation for the dimension of the Fresnel zone parallel to the shot-receiver azimuth. The presence of a velocity gradient (velocity increasing with depth) in the subsurface leads to an expansion of the Fresnel zone to an area that is far larger than may be determined through a more usual straight-ray determination.
6
Hou, Rong Guo, Chuan Zhen Huang, Jun Wang, Hong Tao Zhu, and Yan Xia Feng. "Simulation of Gas-Solid-Liquid Three-Phase Flow Inside and Outside the Abrasive Water Jet Nozzle." Materials Science Forum 532-533 (December 2006): 833–36. http://dx.doi.org/10.4028/www.scientific.net/msf.532-533.833.
Full textAbstract:
Simulation of the velocity field of gas-solid-liquid three-phase flow inside and outside the abrasive water jet nozzle was studied by the computational fluid dynamics software (CFD). The complicated velocity field of the flow in the abrasive water jet (AWJ) nozzle and the abrasive track in the nozzle were obtained. In the course of the simulation, the inter-phase drag exchange coefficient model uses Gidaspow model (gas-solid), Wen-yu model (water-solid), Schiller-Naumann model (water-gas) respectively. The simulation results indicate that the swirl is produced in the nozzle and the abrasives are accelerated and moved around the swirl, and they are all distributed along the inner surface of the nozzle, the gas is mostly distributed in the center of swirl. The dispersion of the flow happens when it flows out of the nozzle, it can be divided into three zones, that is core zone, middle zone and border zone. At the core zone the velocity changes little while the velocity changes greatly at the middle zone, the velocity fluctuates greatly at the border zone.
7
MUKHERJEE, SOUMYAJIT. "Simple shear is not so simple! Kinematics and shear senses in Newtonian viscous simple shear zones." Geological Magazine 149, no. 5 (January 17, 2012): 819–26. http://dx.doi.org/10.1017/s0016756811001075.
Full textAbstract:
AbstractThis work develops an analytical model of shear senses within an inclined ductile simple shear zone with parallel rigid boundaries and incompressible Newtonian viscous rheology. Taking account of gravity that tends to drive the material downdip and a possible pressure gradient that drives it upward along the shear zone, it is shown that (i) contradictory shear senses develop within two sub-zones even as a result of a single simple shear deformation; (ii) the highest velocity and least shear strain develop along the contact between the two sub-zones of reverse shear; (iii) for a uniform shear sense of the boundaries, a zone of reverse shear may develop within the top of the shear zone if the pressure gradient dominates the gravity component; otherwise it forms near the bottom boundary; (iv-a) a ‘pivot’ defined by the intersection between the velocity profile and the initial marker position distinguishes two sub-zones of opposite movement directions (not shear sense); (iv-b) a pivot inside any non-horizontal shear zone indicates a part of the zone that extrudes while the other subducts simultaneously; (v) the same shear sense develops: (v-a) when under a uniform shear of the boundaries, the shear zone remains horizontal and the pressure gradient vanishes; or alternatively (v-b) if the shear zone is inclined but the gravity component counterbalances the pressure gradient. Zones with shear sense reversal need to be reinterpreted since a pro-sheared sub-zone can retro-shear if the flow parameters change their magnitudes even though the same shear sense along the boundaries is maintained.
8
Ha. "Estimation of Shear Wave Velocity of Rockfill Zone by Dynamic Analysis using Micro-earthquake Records." Journal of the Korean Society of Civil Engineers 35, no. 1 (2015): 141. http://dx.doi.org/10.12652/ksce.2015.35.1.0141.
Full text
9
ZHAO, X. P., X. Y. GAO, and D. J. GAO. "EVOLUTION OF CHAIN STRUCTURE OF ELECTRORHEOLOGICAL FLUIDS IN FLOW MODEL." International Journal of Modern Physics B 16, no. 17n18 (July 20, 2002): 2697–703. http://dx.doi.org/10.1142/s0217979202012864.
Full textAbstract:
The movement of particles in electrorheological (ER) fluids is analyzed by means of molecular dynamic simulations. We found that the velocity profile of particles can be divided into two zones. One zone near electrodes where particles' velocity profiles change periodically like "breathing type" is called transition zone. The other in the middle of two electrodes where particles move smoothly like a plug is called "plug zone". In addition, the relationship between volume flow rate and relative pressure gradient is simulated out. Factors such as volume flow rate, critical electric field, critical pressure gradient and response time of shutting up were also analyzed respectively.
10
Jin, Qichao, Wenhu Wang, and Ruisong Jiang. "Investigating the Contact Responses of the Roller Cavity Surfaces in the Compressor Blade Rolling Process." Advances in Materials Science and Engineering 2020 (June 30, 2020): 1–11. http://dx.doi.org/10.1155/2020/1286040.
Full textAbstract:
The investigation of the contact responses is the key for evaluating the local wear of dies in the plastic forming process. This paper investigated the contact load distributions and evolutions of the roller cavities in the compressor blade rolling process by the FEM. It was the first study to quantify the distributions and evolutions of the contact responses for rolling irregular components. The results indicated that the maximum contact pressure is generally present at the center of the contact interfaces, and the magnitudes of contact pressure decreased with evolution of the blade rolling process. The rolling contact interfaces can be divided into the backward slip zone, the stick zone, and the forward slip zone based on the shear stress distributions. The stick zone was a narrow belt which separated the forward and the backward slip zone, and the shear stress in the stick zone was nearly zero. The shear stress magnitudes in the forward slip zone were smaller than those in the backward slip zone, and the directions of shear stress in forward and backward slip zones were adverse. The magnitudes of shear stress over the forward and backward slip zones decreased with evolution of the blade rolling process. The distributions of local sliding were in a V-shape, the local sliding in the stick zone was nearly zero, and the bigger sliding in backward and forward slip zones was present at the boundaries of rolling entrance and exit sections. The local sliding velocity magnitudes in the backward slip zones were always bigger than those in the forward slip zones, and the magnitudes of local sliding at the rolling entrance sections were bigger than those at the rolling exit sections. In general, the local sliding velocity magnitudes increased firstly and decreased sharply at 2T/3. The current paper develops the distributions and evolutions of contact responses in the blade rolling process. The contact responses can be used for studying the wear of roller cavities to avoid the accuracy inconsistency of the shaped blade.
11
Shen, Jing, and Mingran Chang. "Effect Analysis of Nitrogen Injection on the Variation of “Oxidation Zone” in Coal Mine Gob Based on Numerical Simulation." Open Fuels & Energy Science Journal 9, no. 1 (September 21, 2016): 47–54. http://dx.doi.org/10.2174/1876973x01609010047.
Full textAbstract:
One of the main reasons for coal mine fire is spontaneous combustion of residual coal in gob. As the difference of compaction degree of coal and rock, the underground gob can be considered as a porous medium and divided into “three zones” in accordance with the criteria. The “three zones” are “heat dissipation zone”, “oxidation zone” and “choking zone”, respectively. Temperature programming experiments are taken and numerical simulation with obtained experimental data is utilized to analyze the distribution of “three zones” in this paper. Different width and depth of “oxidation zone” are obtained when the inlet air velocity is changed. As the nitrogen injection has inhibition effect on spontaneous combustion of residual coal in gob, nitrogen is injected into the gob. The widths of “oxidation zone” are compared before and after nitrogen injection. And ultimately the optimum location and volume of nitrogen injection are found out.
12
Wang, Hongshan, Zhigang Xia, and Weilin Xu. "A study of an embeddable and locatable spinning system via quasi-static mechanical analysis." Textile Research Journal 82, no. 20 (September 27, 2012): 2071–77. http://dx.doi.org/10.1177/0040517512452946.
Full textAbstract:
In this study, a quasi-static model is built to theoretically analyze the distribution of twists and spinning tension in embeddable and locatable spun (ELS) yarn formation zone. Important equations are also derived to determine inner mechanics and external configurations of the ELS yarn formation zones 1, 2 and 3. Analysis results demonstrate that in zones 1 and 2 the tension distribution on the filament and staple strand is directly proportional to their linear mass and square of delivery speed; the larger weight causes a smaller angle between the responding component and the composite strand axis line. The angle between the composite strands 1 and 2 can be simply calculated by dividing the composite yarn velocity by composite strand velocity. Online photographs are provided to validate theoretical analysis of the ELS yarn formation zone configuration and twist distribution in zones 1 and 2.
13
Tomar, Garima, D. S. Malik, and C. K. Jain. "Relationship between macrobenthos and abiotic characteristics of river Alaknanda in a stretch from Chamoli to Devprayag in Garhwal Himalayan region of Uttarakhand, India." Journal of Applied and Natural Science 13, no. 3 (September 15, 2021): 1135–42. http://dx.doi.org/10.31018/jans.v13i3.2721.
Full textAbstract:
Macrobenthos is the best water quality indicator for ecosystem health assessment. The present study aimed to examine the interrelationship between macrobenthos and different water quality parameters of the river Alaknanda at Garhwal Himalaya. Four demarcated sampling zones viz. zone-A (Chamoli to Nandprayag), zone-B (Karanprayag to Rudraprayag), zone-C (Rudraprayag to Srinagar) and zone-D (Srinagar to Devprayag) were taken from its approximately 170 km long stretch during 2016-2018. River water characteristics were analyzed for the important parameters viz. substratum, water temperature (WT), water velocity, pH, electrical conductivity (EC), total dissolved solids (TDS), calcium (Ca), and magnesium (Mg) using standard methods. The results indicated that the river water velocity was the highest 1.02 m/s at zone-C, TDS of 114.19 mgl-1 was maximum at zone-A ; and Ca and Mg were recorded highest 23.17 mgl-1 and 5.44 mgl-1 at zone-A and zone-B, respectively. All abiotic parameters (pH, EC, TDS, DO, Ca and Mg) were recorded to be below BIS/WHO limits. A total of 27 macrobenthos taxa belonging to the five orders such as Coleoptera (6 ind./m2), Diptera (5 ind./m2), Ephemeroptera (8 ind./m2), Hemiptera (4 ind./m2), and Odonata (4 ind./m2) were recorded. Macrobenthos represented an important relationship between the water current and water temperature. The lowest number was reported at zone-C due to the river's high water velocity (1.02 m/s). The changes like biota loss, presence of some pollution indicator species (Cloeon sp., Bateis sp., Emphemera sp.) at zone-C, in sediment structure of habitat were due to the anthropogenic activities on the riverbank of different zones. The study will help in the conservation of macrobenthos diversity of the river Alaknanda.
14
White, D. J., D. A. Forsyth, I. Asudeh, S. D. Carr, H. Wu, R. M. Easton, and R. F. Mereu. "A seismic-based cross-section of the Grenville Orogen in southern Ontario and western Quebec." Canadian Journal of Earth Sciences 37, no. 2-3 (April 2, 2000): 183–92. http://dx.doi.org/10.1139/e99-094.
Full textAbstract:
A schematic crustal cross-section is presented for the southwestern Grenville Province based on reprocessed Lithoprobe near-vertical incidence seismic reflection data and compiled seismic refraction - wide-angle velocity models interpreted with geological constraints. The schematic crustal architecture of the southwest Grenville Province from southeast to northwest comprises allochthonous crustal elements (Frontenac-Adirondack Belt and Composite Arc Belt) that were assembled prior to ca. 1160 Ma, and then deformed and transported northwest over reworked rocks of pre-Grenvillian Laurentia and the Laurentian margin primarily between 1120 and 980 Ma. Reworked pre-Grenvillian Laurentia and Laurentian margin rocks are interpreted to extend at least 350 km southeast of the Grenville Front beneath all of the Composite Arc Belt. Three major structural boundary zones (the Grenville Front and adjacent Grenville Front Tectonic Zone, the Central Metasedimentary Belt boundary thrust zone, and the Elzevir-Frontenac boundary zone) have been identified across the region of the cross-section based on their prominent geophysical signatures comprising broad zones of southeast-dipping reflections and shallowing of mid-crustal velocity contours by 12-15 km. The structural boundary zones accommodated southeast over northwest crustal stacking at successively earlier times during orogeny (ca. 1010-980 Ma, 1080-1060 Ma, and 1170-1160 Ma, respectively). These shear zones root within an interpreted gently southeast-dipping regional décollement at a depth of 25-30 km corresponding to the top of a high-velocity lower crustal layer.
15
Hunt, Martin, Shawn Clark, and Rob Tkach. "Velocity distributions near the inlet of corrugated steel pipe culverts." Canadian Journal of Civil Engineering 39, no. 12 (December 2012): 1243–51. http://dx.doi.org/10.1139/l2012-112.
Full textAbstract:
This paper presents the findings of a study examining the velocity field within the inlet region of a corrugated steel pipe (CSP) culvert model with vertical headwall, 45° wingwall, and projecting end inlet treatments. Also examined are the effects of embedding the culvert below the stream bed and backfilling the culvert with granular material. Three-dimensional velocity distributions were measured in an effort to better understand how these inlet treatments may affect fish passage. The study examined velocity structure within a CSP culvert with a diameter of 0.8 m at a flow rate of 0.175 m3/s. Measurements were recorded using acoustic Doppler velocimeters at four locations; 0.25, 0.5, 1, and 2 diameters downstream of the inlet. The velocity field of each inlet configuration was dominated by a central jet of high velocity flow surrounded by a low velocity recirculation zone. Analysis of the percent area less than Uavg for each inlet treatment found that the projecting end configuration contained the largest low velocity zone. The usefulness of the low velocity recirculation zone as a fish passage corridor may however be limited by the presence of significant vertical and spanwise velocities as well as high shear zones.
16
Vasco, Don W., John E. Peterson, and Ernest L. Majer. "A simultaneous inversion of seismic traveltimes and amplitudes for velocity and attenuation." GEOPHYSICS 61, no. 6 (November 1996): 1738–57. http://dx.doi.org/10.1190/1.1444091.
Full textAbstract:
It is possible to efficiently use traveltime and amplitude information to infer variations in velocity and Q. With little additional computation, terms accounting for source radiation pattern and receiver coupling may be included in the inversion. The methodology is based upon a perturbation approach to paraxial ray theory. The perturbation approach linearizes the relationship between velocity deviations and traveltime and amplitude anomalies. Using the technique, we infer the velocity and attenuation structure at a fractured granitic site near Raymond, California. A set of four well pairs are examined and each is found to contain two zones of strong attenuation. The velocity variations contain an upper low velocity region corresponding to the uppermost attenuating zone. The location of these zones agrees with independent well‐log and geophysical data. The velocity and attenuation anomalies appear to coincide with extensively fractured sections of the borehole and may indicate fracture zones rather than individual fractures.
17
PETERS, N. "The turbulent burning velocity for large-scale and small-scale turbulence." Journal of Fluid Mechanics 384 (April 10, 1999): 107–32. http://dx.doi.org/10.1017/s0022112098004212.
Full textAbstract:
The level-set approach is applied to a regime of premixed turbulent combustion where the Kolmogorov scale is smaller than the flame thickness. This regime is called the thin reaction zones regime. It is characterized by the condition that small eddies can penetrate into the preheat zone, but not into the reaction zone.By considering the iso-scalar surface of the deficient-species mass fraction Y immediately ahead of the reaction zone a field equation for the scalar quantity G(x, t) is derived, which describes the location of the thin reaction zone. It resembles the level-set equation used in the corrugated flamelet regime, but the resulting propagation velocity s*L normal to the front is a fluctuating quantity and the curvature term is multiplied by the diffusivity of the deficient species rather than the Markstein diffusivity. It is shown that in the thin reaction zones regime diffusive effects are dominant and the contribution of s*L to the solution of the level-set equation is small.In order to model turbulent premixed combustion an equation is used that contains only the leading-order terms of both regimes, the previously analysed corrugated flamelets regime and the thin reaction zones regime. That equation accounts for non-constant density but not for gas expansion effects within the flame front which are important in the corrugated flamelets regime. By splitting G into a mean and a fluctuation, equations for the Favre mean [Gtilde]and the variance [Gtilde]″2 are derived. These quantities describe the mean flame position and the turbulent flame brush thickness, respectively. The equation for [Gtilde]″2 is closed by considering two-point statistics. Scaling arguments are then used to derive a model equation for the flame surface area ratio [rhotilde]. The balance between production, kinematic restoration and dissipation in this equation leads to a quadratic equation for the turbulent burning velocity. Its solution shows the ‘bending’ behaviour of the turbulent to laminar burning velocity ratio sT/sL, plotted as a function of v′/sL. It is shown that the bending results from the transition from the corrugated amelets to the thin reaction zones regimes. This is equivalent to a transition from Damköhler's large-scale to his small-scale turbulence regime.
18
Dindar, H., K. Dimililer, Ö. C. Özdağ, C. Atalar, M. Akgün, and A. Özyankı. "VULNERABILITY INDEX ASSESSMENT USING NEURAL NETWORKS (VIANN): A CASE STUDY OF NICOSIA, CYPRUS." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-4/W4 (November 13, 2017): 189–95. http://dx.doi.org/10.5194/isprs-annals-iv-4-w4-189-2017.
Full textAbstract:
Many scholars have used microtremor applications to evaluate the vulnerability index. In order to reach fast and reliable results, microtremor measurement is preferred as it is a cost-effective method. In this paper, the vulnerability index will be reviewed by utilization of microtremor measurement results in Nicosia city. 100 measurement stations have been used to collect microtremor data and the data were analysed by using Nakamura’s method. The value of vulnerability index (Kg) has been evaluated by using the fundamental frequency and amplification factor. The results obtained by the artificial neural network (ANN) will be compared with microtremor measurements. Vulnerability Index Assessment using Neural Networks (VIANN) is a backpropagation neural network, which uses the original input microtremor Horizontal Vertical Spectrum Ratio (HVSR) spectrum set. A 3-layer back propagation neural network which contains 4096 input, 28 hidden and 3 output neurons are used in this suggested system. The output neurons are classified according to acceleration sensitivity zone, velocity zones, or displacement zones. The sites are classified by their vulnerability index values using binary coding: [1 0 0] for the acceleration sensitive zone, [0 1 0] for the velocity sensitive zone, and [0 0 1] for the displacement sensitive zone.
19
Petersson, Per, Magnus Larson, and Lennart Jo¨nsson. "Measurements of the Velocity Field Downstream of an Impeller." Journal of Fluids Engineering 118, no. 3 (September 1, 1996): 602–10. http://dx.doi.org/10.1115/1.2817801.
Full textAbstract:
The velocity field downstream of a model impeller operating in water was measured using a two-component laser doppler velocimeter. The investigation focussed on the spatial development of the mean velocity in the axial, radial, and circumferential direction, although simultaneous measurements were performed of the velocity unsteadiness from which turbulence characteristics were inferred. The measurements extended up to 12 impeller diameters downstream of the blades displaying the properties of the generated swirling jet both in the zone of flow establishment and the zone of established flow. The division between these zones was made based on similarity of the mean axial velocity profile. Integral properties of the flow such as volume and momentum flux were computed from the measured velocity profiles. The transverse spreading of the impeller jet and its development towards self-similarity were examined and compared with non-swirling jets and swirling jets generated by other means.
20
Tang, Xiaonan, Yutong Guan, Hamidreza Rahimi, Prateek Singh, and Yujia Zhang. "Discharge and velocity variation of flows in open channels partially covered with different layered vegetation." E3S Web of Conferences 269 (2021): 03001. http://dx.doi.org/10.1051/e3sconf/202126903001.
Full textAbstract:
The role of vegetation in the natural environment has drawn great interest recently. The vegetation can change the velocity distribution due to its additional resistance on the flow, consequently affecting the nutrient and pollutant transport, and the habitats. Due to the complexity of flow and vegetation interaction, many previous researchers have studied the flow structure of channels with uniform vegetation. Few studies have been done on the flow of open channels partially covered vegetation of different heights on one side of the channel, which commonly exists in natural rivers. Through novel experiments for such a vegetated flow, this paper shows the influence of different layered vegetation on the velocity profile and discharge, which indicates that the velocity in the vegetation zone is significantly smaller than that in the free-flow zone and that the velocity profiles in the short and tall vegetation zones are very different. The flow through the free-flow zone is dominant (about 75%) despite its half width, and its discharge percentage slightly decreases as increasing flow depth.
21
Artichowicz, Luczkiewicz, and Sawicki. "Analysis of the Radiation Dose in UV-Disinfection Flow Reactors." Water 12, no. 1 (January 14, 2020): 231. http://dx.doi.org/10.3390/w12010231.
Full textAbstract:
UV-disinfection reactors may appear in a variety of forms, but it is useful for all types to identify the inflow and outflow zones (those in which the fluid approaches or, respectively, recedes from the radiation source) and the direct radiation zone (in which the flow occurs along the UV lamp). Due to the spatial variability of the velocity field and the radiation intensity, the radiation doses received in different zones of a reactor differ. In this work, theoretical considerations regarding functions describing the variability of UV radiation doses in flow reactors are presented. The most basic parameter of a UV-disinfection reactor is the minimal time required by the fluid to pass through the reactor. Such time depends on the maximum fluid velocity in the reactor. Based on the theoretical analysis of this phenomenon, the doses in different zones of the reactor have been compared for laminar and turbulent flows. The result of the analysis states that UV-disinfection reactors should be designed in such a way to deliver the required amount of radiation to the point at which the fluid velocity is the highest. The other main conclusion resulting from this comparison yields that the most effective in terms of disinfection is the direct radiation zone, whereas the influence of the inflow and outflow zones is negligible.
22
Jeevanjee, Nadir. "Vertical Velocity in the Gray Zone." Journal of Advances in Modeling Earth Systems 9, no. 6 (October 2017): 2304–16. http://dx.doi.org/10.1002/2017ms001059.
Full text
23
Jiang, Hong Tao, Hui Quan Li, and Hao Fan. "Tri-Reforming of Methane over Pt Modified Ni/MgO Catalysts under Atmospheric Pressure – Thermal Distribution in the Catalyst Bed." Applied Mechanics and Materials 252 (December 2012): 255–58. http://dx.doi.org/10.4028/www.scientific.net/amm.252.255.
Full textAbstract:
Thermal distribution in catalyst bed was investigated for the fixed-bed tri-reforming of methane over Pt modified Ni/MgO catalysts under atmospheric pressure, 850 °C, and space velocity of 2000−20000 h−1. The effects of the W/F on the thermal distribution of different catalysts were examined. The results indicated that for Pt modified Ni/MgO catalysts, the temperature profile depended on catalysts preparation method. According to the thermal distribution, for Pt modified Ni/MgO catalysts prepared by sequence method, the catalyst bed can be divided into tow zones: auto-thermo reforming zone and oxygen absent zone. Methane reforming proceeds in both zones together.
24
Wang, Puquan, Daolun Chen, Yunqi Yan, Xinwei She, Bo Feng, Yang Ran, He Peng, Dongyang Li, and Xianquan Jiang. "Hierarchical Morphology and Formation Mechanism of Collision Surface of Al/Steel Dissimilar Lap Joints via Electromagnetic Pulse Welding." Metals 11, no. 9 (September 16, 2021): 1468. http://dx.doi.org/10.3390/met11091468.
Full textAbstract:
The aim of this study was to characterize detailed microstructural changes and bonding characteristics and identify the formation mechanism of collision surface of Al6061–Q355 steel dissimilar welded joints via electromagnetic pulse welding (EMPW). The collision surface was observed to consist of five zones from the center to the outside. The central non-weld zone exhibited a concave and convex morphology. The welding-affected zone mainly included melting features and porous structures, representing a porous joining. The secondary weld zone presented an obvious mechanical joining characterized by shear plateaus with stripes. The primary weld zone characterized by dimples with cavity features suggested the formation of diffusion or metallurgical bonding. The impact-affected zone denoted an invalid interfacial bonding due to discontinuous spot impact. During EMPW, the impact energy and pressure affected the changes of normal velocity and tangential velocity, and in turn, influenced the interfacial deformation behavior and bonding characteristics, including the formation of micropores which continued to grow into homogeneous or uneven porous structures via cavitation, surface tension, and depressurization, along with the effect of trapped air.
25
Wenning, Quinn C., Claudio Madonna, Antoine de Haller, and Jean-Pierre Burg. "Permeability and seismic velocity anisotropy across a ductile–brittle fault zone in crystalline rock." Solid Earth 9, no. 3 (May 29, 2018): 683–98. http://dx.doi.org/10.5194/se-9-683-2018.
Full textAbstract:
Abstract. This study characterizes the elastic and fluid flow properties systematically across a ductile–brittle fault zone in crystalline rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the mylonitic core show that foliation-parallel P- and S-wave velocities systematically increase from the host rock towards the mylonitic core, while permeability is reduced nearest to the mylonitic core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the mylonitic core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow and for the exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in crystalline rocks change in fault zones during the ductile to brittle transitions.
26
Pigulevskiy, P., L. Shumlianska, and Yu Dubovenko. "FIRST RESULTSOF THESEISMICTOMOGRAPHICGEOTRAVERSE "VINNYTSIA – TAGANROG" RESEARCH." Visnyk of Taras Shevchenko National University of Kyiv. Geology, no. 4 (91) (2020): 42–48. http://dx.doi.org/10.17721/1728-2713.91.06.
Full textAbstract:
Methodological aspects and results of studying of the stratigraphic section of the upper mantle along the seismic tomographic geotraverse "Vinnytsia – Taganrog" are considered in the article. To localize mantle anomalies associated with changes in the composition, density of the substrate, temperature, etc., an analysis of the curves of the first and second velocity gradients was used to search for the inflection points of the vp curve. A velocity curve was obtained by constructing a seismotomographic model using the Taylor approximation method. Before the curvature analysis, a smoothing procedure was carried out in accordance with the wavelength. This procedure is important for screening false anomalies, the size of which is responsible for Fresnel zones, since the resolution of the seismic wave has the dimension of the Fresnel zones. According to this technique, the curves of the first and second velocity gradients vp were calculated for the upper mantle under the main tectonic structures of the Ukrainian Shield along the "Vinnytsia – Taganrog" geotraverse. The profile crosses the Podol, Bug megablocks, Golovanev suture zone, Ingul megablock, Kryvyy-Rig-Kremenchug suture zone, Middle-Dnipro megablock, Orekhovo-Pavlograd suture zone and Azov megablock. According to the results, the most significant features of the mantle structure were identified in the depth interval of 50–750 km. A transregional tectonic zone was distinguished (between points 30.0E, 49N and 32.0E, 48.25N), over which the Golovan suture zone (GSZ) and the eastern part of the Bug-Ros megablock and the western part of Ingul, where significant violations of the common mantle border of 660 km are observed – a border between the upper and middle mantle. Under the Podol megablock, this border is located at a depth of 550–560 km. Under GSZ it rises to 450–460 km, and to the east of the suture zone it drops sharply to 660-670 km, where it takes a subhorizontal position. A sharp jump to marks of 450–460 km shows the global breakdown zone and the nature of the contact between different geodynamic mantle regions under the modern platform.
27
Hough, S. E., Y. Ben-Zion, and P. Leary. "Fault-zone waves observed at the southern Joshua Tree earthquake rupture zone." Bulletin of the Seismological Society of America 84, no. 3 (June 1, 1994): 761–67. http://dx.doi.org/10.1785/bssa0840030761.
Full textAbstract:
Abstract Waveform and spectral characteristics of several aftershocks of the M 6.1 22 April 1992 Joshua Tree earthquake recorded at stations just north of the Indio Hills in the Coachella Valley can be interpreted in terms of waves propagating within narrow, low-velocity, high-attenuation, vertical zones. Evidence for our interpretation consists of: (1) emergent P arrivals prior to and opposite in polarity to the impulsive direct phase; these arrivals can be modeled as headwaves indicative of a transfault velocity contrast; (2) spectral peaks in the S wave train that can be interpreted as internally reflected, low-velocity fault-zone wave energy; and (3) spatial selectivity of event-station pairs at which these data are observed, suggesting a long, narrow geologic structure. The observed waveforms are modeled using the analytical solution of Ben-Zion and Aki (1990) for a plane-parallel layered fault-zone structure. Synthetic waveform fits to the observed data indicate the presence of NS-trending vertical fault-zone layers characterized by a thickness of 50 to 100 m, a velocity decrease of 10 to 15% relative to the surrounding rock, and a P-wave quality factor in the range 25 to 50.
28
Aziz Zanjani, Farzaneh, Guoqing Lin, and Clifford H. Thurber. "Nested regional-global seismic tomography and precise earthquake relocation along the Hikurangi subduction zone, New Zealand." Geophysical Journal International 227, no. 3 (July 28, 2021): 1567–90. http://dx.doi.org/10.1093/gji/ggab294.
Full textAbstract:
SUMMARY Seismic and geodetic examinations of the Hikurangi subduction zone (HSZ) indicate a remarkably diverse and complex system. Here, we investigate the 3-D P-wave velocity structure of the HSZ by applying an iterative, nested regional-global tomographic algorithm. The new model reveals enhanced details of seismic variations along the HSZ. We also relocate over 57 000 earthquakes using this newly developed 3-D model and then further improve the relative locations for 75 per cent of the seismicity using waveform cross-correlation. Double seismic zone characteristics, including occurrence, depth distribution and thickness change along the strike of the HSZ. An aseismic but fast Vp zone separates the upper and lower planes of seismicity in the southern and northern North Island. The upper plane of seismicity correlates with low Vp zones below the slab interface, indicating fluid-rich channels formed on top and/or within a dehydrated crust. A broad low Vp zone is resolved in the lower part of the subducting slab that could indicate hydrous mineral breakdown in the slab mantle. In the northern North Island and southern North Island, the lower plane of seismicity mostly correlates with the top of these low Vp zones. The comparison between the thermal model and the lower plane of seismicity in the northern North Island supports dehydration in the lower part of the slab. The mantle wedge of the Taupo volcanic zone (TVZ) is characterized by a low velocity zone underlying the volcanic front (fluid-driven partial melting), a fast velocity anomaly in the forearc mantle (a stagnant cold nose) and an underlying low velocity zone within the slab (fluids from dehydration). These arc-related anomalies are the strongest beneath the central TVZ with known extensive volcanism. The shallow seismicity (<40 km depth) correlates with geological terranes in the overlying plate. The aseismic impermeable terranes, such as the Rakaia terrane, may affect the fluid transport at the plate interface and seismicity in the overlying plate, which is consistent with previous studies. The deep slow slip events (25–60 km depths) mapped in the Kaimanawa, Manawatu and Kapiti regions coincide with low Vp anomalies. These new insights on the structure along the HSZ highlight the change in the locus of seismicity and dehydration at depth that is governed by significant variations in spatial and probably temporal attributes of subduction zone processes.
29
Wang, Haifu, Jianguang Xiao, Yuanfeng Zheng, and Qingbo Yu. "Failure and Ejection Behavior of Concrete Materials under Internal Blast." Shock and Vibration 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/8409532.
Full textAbstract:
In order to investigate the failure and ejection behavior of concrete materials under internal blast, the default Riedel-Hiermaier-Thoma (RHT) concrete model in AUTODYN and a meshfree processor called SPH are employed in this numerical simulation. It is shown that the failure mechanisms are significantly different in these damaged zones. Crushed zone is caused by shear failure while fractured zone is induced by tensile failure, and spalled zone is formed by a combination of shear and tensile failure. In addition, the ejection velocity distribution of the fragmented concrete mass on free surface is examined. The results indicate that the ejection velocity declines monotonously with the increase of the distance to symmetry axis of computational model. On the wall of the prefabricated borehole, two types of fragmented concrete mass are analyzed, and bottom initiation is recommended to eject the fragmented concrete mass effectively. Moreover, an algorithm of average ejection speed is developed to effectively estimate the drill capacity of high velocity, energetic (HE) projectiles. At last, the validity of numerical simulation is verified by physical experiments.
30
Wang, Guan Jun, Gai Li Gao, Dao Liang Li, Bao Lin Hu, and Jun Liu. "Rational Position of Apparatus for Removing Cotton Foreign Fiber in Dynamic Equilibrium." Applied Mechanics and Materials 252 (December 2012): 44–50. http://dx.doi.org/10.4028/www.scientific.net/amm.252.44.
Full textAbstract:
Cotton processing technology in an automatic production line was presented. A pipeline used to set an apparatus for removing the foreign fiber was chosen in the cotton processing technology. The distribution and velocity of the cotton in five positions of the central plane of the pipeline were simulated by the Fluent software. The simulated curves of the cotton distribution and velocity were obtained. According to the curves, there is the optimal length of the cotton conveyed pipeline with a certain cross-section area to set the apparatus for removing the foreign fiber. There is no the steady zone if the pipeline length is shorter than the optimal value, and if longer than it, the pipeline will waste the material and space. The steady zone is determined by the forces. In the certain position of the straight pipeline away from the curved pipeline, the various forces, which act on the cotton or foreign fiber, are in the dynamic equilibrium, and the distribution and velocity of the cotton are steady. For the rectangular pipeline with the cross-section area 2960×120mm , its total length should be 7000mm, the steady zone length of the cotton distribution is about 2500mm, and the steady zone of its velocity is 1000mm. In the common part of their steady zones the apparatus for removing the foreign fiber may be setting rationally.
31
Justice, James H., and Chris Zuba. "Transition zone reflections and permafrost analysis." GEOPHYSICS 51, no. 5 (May 1986): 1075–86. http://dx.doi.org/10.1190/1.1442163.
Full textAbstract:
The usual study of seismic reflections is limited to those from sharply defined contrasts in acoustic impedance. For reflections resulting from transition zones in which acoustic impedance is continuously variable (such as the zones encountered in permafrost), the frequency‐selective nature of attenuation and phase distortion leads to a number of characteristics which may be used in the sense of pattern recognition to identify such reflections. An rms velocity‐analysis procedure can be used to estimate depths and velocity gradients associated with transition zones. Some simple approximations allow us to avoid solving a system of nonlinear equations in many cases of interest, and the result is a practical technique which can be applied to many transition zone reflections at reasonable computational cost.
32
Kopp, Jean-Benoît, and Jérémie Girardot. "Dynamice fracture in a semicristalline polymer: an analysis of the fracture surface." EPJ Web of Conferences 250 (2021): 06012. http://dx.doi.org/10.1051/epjconf/202125006012.
Full textAbstract:
The fracture behaviour of a specific material, a semi-crystalline biobased polymer, was here studied. Dynamic fracture tests on strip band specimens were carried out. Fracture surfaces were observed at different scales by optical and electron microscopy to describe cracking scenarios. Crack initiation, propagation and arrest zones were described. Three distinct zones are highlighted in the initiation and propagation zone: a zone with conical markings, a mist zone and a hackle zone. The conical mark zone shows a variation in the size and density of the conical marks along the propagation path. This is synonymous with local speed variation. Microcracks at the origin of the conical marks in the initiation zone seem to develop from the nucleus of the spherulites. In the propagation zone with complex roughness, the direction of the microcracks and their cracking planes are highly variable. Their propagation directions are disturbed by the heterogeneities of the material. They branch or bifurcate at the level of the spherulites. In the arrest zone, the microcracks developed upstream continue to propagate in different directions. The surface created is increasingly smoother as the energy release rate decreases. It is shown that the local velocity of the crack varies in contrast to the macroscopic speed.
33
Rey-Sanchez, Camilo, Gil Bohrer, Julie Slater, Yueh-Fen Li, Roger Grau-Andrés, Yushan Hao, Virginia I. Rich, and G. Matt Davies. "The ratio of methanogens to methanotrophs and water-level dynamics drive methane transfer velocity in a temperate kettle-hole peat bog." Biogeosciences 16, no. 16 (August 29, 2019): 3207–31. http://dx.doi.org/10.5194/bg-16-3207-2019.
Full textAbstract:
Abstract. Peatlands are a large source of methane (CH4) to the atmosphere, yet the uncertainty around the estimates of CH4 flux from peatlands is large. To better understand the spatial heterogeneity in temperate peatland CH4 emissions and their response to physical and biological drivers, we studied CH4 dynamics throughout the growing seasons of 2017 and 2018 in Flatiron Lake Bog, a kettle-hole peat bog in Ohio. The site is composed of six different hydro-biological zones: an open water zone, four concentric vegetation zones surrounding the open water, and a restored zone connected to the main bog by a narrow channel. At each of these locations, we monitored water level (WL), CH4 pore-water concentration at different peat depths, CH4 fluxes from the ground and from representative plant species using chambers, and microbial community composition with a focus here on known methanogens and methanotrophs. Integrated CH4 emissions for the growing season were estimated as 315.4±166 mgCH4m-2d-1 in 2017 and 362.3±687 mgCH4m-2d-1 in 2018. Median CH4 emission was highest in the open water, then it decreased and became more variable through the concentric vegetation zones as the WL dropped, with extreme emission hotspots observed in the tamarack mixed woodlands (Tamarack) and low emissions in the restored zone (18.8–30.3 mgCH4m-2d-1). Generally, CH4 flux from above-ground vegetation was negligible compared to ground flux (<0.4 %), although blueberry plants were a small CH4 sink. Pore-water CH4 concentrations varied significantly among zones, with the highest values in the Tamarack zone, close to saturation, and the lowest values in the restored zone. While the CH4 fluxes and pore-water concentrations were not correlated with methanogen relative abundance, the ratio of methanogens to methanotrophs in the upper portion of the peat was significantly correlated to CH4 transfer velocity (the CH4 flux divided by the difference in CH4 pore-water concentration between the top of the peat profile and the concentration in equilibrium with the atmosphere). Since ebullition and plant-mediated transport were not important sources of CH4 and the peat structure and porosity were similar across the different zones in the bog, we conclude that the differences in CH4 transfer velocities, and thus the flux, are driven by the ratio of methanogen to methanotroph relative abundance close to the surface. This study illustrates the importance of the interactions between water-level and microbial composition to better understand CH4 fluxes from bogs and wetlands in general.
34
Wolski, Krzysztof, Tomasz Tymiński, and Grzegorz Chrobak. "Numerical modeling of the hydraulic impact of riparian vegetation." E3S Web of Conferences 44 (2018): 00194. http://dx.doi.org/10.1051/e3sconf/20184400194.
Full textAbstract:
This paper presents results of numerical modelling of riverbed segment with riparian vegetation performed with use of CCHE2 software. Vegetation zones are places where dynamic of water flow increases. Therefore, there is a need of careful examination of hydraulic impact structure of such zones. Accurate research is necessary and should be performed with use of physical or numerical models, two or three dimensional. Paper presents distribution of velocity and area of water surface for two variants of vegetation deposition acquired in CCHE2D software and modelled for riverbed with distinctive riparian vegetation. Results point to significant (30–40%) increase of maximal velocities in riverbed with riparian vegetation, while directly near the vegetation there were zones with very low velocities. Local damming occurs before vegetal zone. Maximal shear stress in zones with increased velocity is significantly augmented compared to conditions with no vegetation, which can cause more intensive erosion in those zones
35
Aggarwal, Suresh K. "Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships." International Journal of Spray and Combustion Dynamics 1, no. 3 (September 2009): 339–63. http://dx.doi.org/10.1260/175682709789141537.
Full textAbstract:
In this study, we examine the structure and existence of state relationships in unsteady partially premixed flames (PPFs) subjected to buoyancy-induced and external perturbations. A detailed numerical model is employed to simulate the steady and unsteady two-dimensional PPFs established using a slot burner under normal and zero-gravity conditions. The coflow velocity is parametrically varied. The methane-air chemistry is modeled using a fairly detailed mechanism that contains 81 elementary reactions and 24 species. Validation of the computational model is provided through comparisons of predictions with nonintrusive measurements. The combustion proceeds in two reaction zones, one a rich premixed zone and the other a nonpremixed zone. These reaction zones are spatially separated, but involve strong interactions between them due to thermochemistry and scalar transport. The fuel is mostly consumed in the premixed zone to produce CO and H2, which are transported to and consumed in the nonpremixed zone. The nonpremixed zone in turn provides heat and H-atoms to the premixed zone. For the range of conditions investigated, the zero-g partially premixed flames exhibit a stable behavior and a remarkably strong resistance to perturbations. In contrast, the corresponding normal-gravity flames exhibit oscillatory behavior at low coflow velocities but a stable behavior at high coflow velocities, and the behavior can be explained in terms of a global and convective instabilities. The effects of coflow and gravity on the flames are characterized through a parameter VR, defined as the ratio of coflow velocity to jet velocity. For VR ≤ 1 (low coflow velocity regime), the structures of both 0- and 1-g flames are strongly sensitive to changes in VR, while they are only mildly affected by coflow in the high coflow velocity regime (VR > 1). In addition, the spatio-temporal characteristics of the 0- and 1-g flames are markedly different in the first regime, but are essentially similar in the second regime. A more significant difference in the first regime between these flames is the presence of a flow instability that manifests itself through the self-excited oscillations of the 1-g flame and the concomitant flickering of the nonpremixed reaction zone. For VR ≤ 1, as the coflow velocity is increased, the oscillation amplitude decreases and the oscillation frequency increases, both of which are in accord with previous experimental and computational results concerning 1-g jet diffusion flames. The modified conserved scalar approach is found to be effective in characterizing the flame structure and developing state relationships for both steady and unsteady partially premixed flames. This is demonstrated by the fact that the temperature as well as the major and minor species profiles follow similar state relationships in terms of the modified mixture fraction for the 0- and 1-g flames, even though these flames have markedly different spatio-temporal characteristics.
36
Meilano, Irwan, Agidia L. Tiaratama, Dudy D. Wijaya, Putra Maulida, S. Susilo, and Intan H. Fitri. "Analisis Potensi Gempa di Selatan Pulau Jawa Berdasarkan Pengamatan GPS." Jurnal Lingkungan dan Bencana Geologi 11, no. 3 (December 24, 2020): 151. http://dx.doi.org/10.34126/jlbg.v11i3.352.
Full textAbstract:
ABSTRAKPulau Jawa merupakan salah satu pulau yang memiliki kepadatan penduduk tinggi dengan aktivitas tektonik yang sangat aktif. Hal ini dikarenakan Pulau Jawa terletak di zona konvergensi Lempeng Indo-Australia dan Lempeng Eurasia. Aktivitas tektonik ini menghasilkan kegempaan di zona subduksi dan sesar di daratan Penelitian ini menganalisis pola vektor kecepatan yang dihasilkan melalui pengolahan data stasiun pengamatan GPS (Global Positioning System) CORS (Continuously Operating Reference Station) BIG (Badan Informasi Geospasial) di wilayah Pulau Jawa bagian selatan. Data koordinat harian dianalisis dengan metode PCA (Principal Component Analysis) untuk memisahkan sinyal tektonik berupa data deret waktu global dan non-tektonik berupa data deret waktu lokal dengan penerapan aturan pemilihan varian dominan nilai eigen dalam pembetukan PC (Principal Component) dan orthogonal vektor eigen sebagai bobot dalam meminimalkan korelasi. Hasil dari data deret waktu global dan lokal digunakan untuk menghitung besar kecepatan pergeseran dari tahun 2011 sampai 2018. Hasil pengolahan menunjukkan besar resultan vektor kecepatan pada data awal berselang 0,06 sampai 10,46 mm/tahun, pada data global antara 0,06 mm/ tahun sampai 10,39 mm/tahun, dan data lokal sebesar 0,0037 sampai 1,99 mm/tahun. Variasi spasial vektor kecepatan pengamatan GPS data domain PCA menunjukkan variasi pergeseran horizontal di wilayah Banten bergerak ke arah timur laut; Jawa Barat, Daerah Istimewa Yogyakarta, dan Jawa Tengah bergerak ke arah tenggara; dan Jawa Timur bergerak ke arah timur laut. Hasil dari inversi data pergeseran terhadap slip pada zona subduksi, menunjukkan terjadinya kekurangan slip atau terjadi coupling pada zona subduksi Jawa bagian timur dan barat, sementara terjadi kelebihan slip pada bagian tengah yang merupakan efek postseismic dari gempa Pangandaran 2006.Kata kunci: GPS, PCA, potensi gempa, vektor kecepatanABSTRACTJava is one of the island that has a high population density with very active tectonic activity. This is because Java Island is located in the convergence zone of the Indo-Australian Plate and the Eurasian Plate. This tectonic activity produces seismicity in subduction zones and inland faults. This study analyzes the velocity vector patterns generated through data processing of the GPS (Global Positioning System) CORS (Continuously Operating Reference Station) BIG (Geospatial Information Agency) observation station in the southern part of Java. Daily coordinate data were analyzed using PCA (Principal Component Analysis) method to separate time series of tectonic signals as global data and non-tectonic time series data as local data by applying the rules for selecting dominant variants of eigen values for PC formation and orthogonal eigen vectors as weights in minimizing correlations. The results from global and local time series data were used to calculate the magnitude of the displacement velocity from 2011 until 2018. The processing results show the resultant velocity vector in the initial data intermittent 0.06 to 10.46 mm/year, global data from 0.06 to 10.39 mm/year, and local data of 0.0037 to 1.99 mm/year. The spatial variation of the velocity vector in PCA domain data shows the horizontal displacement in the Banten region to the northeast; West Java, Yogyakarta Special Region, Central Java to southeast; and East Java moving to northeast. The results of the inversion of the surface displacement to slip data in the subduction zone show that there is a slip deficiency or coupling occurs in the subduction zones of Eastern and Western Java, while there is excess slip in the Central Java which is a post-seismic effect of the 2006 Pangandaran earthquake.Keywords: earthquake potential, GPS, PCA, velocity vector
37
Wang, Dong Sheng, Guang Qu, and Jin Lan Su. "Experimental Study on Dilution Ratio of Laser Cladding of Al2O3-13 % TiO2 Ceramic Coating." Advanced Materials Research 978 (June 2014): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amr.978.36.
Full textAbstract:
In this study, Al2O3–13 wt% TiO2ceramic coating was prepared on the substrate of a GH416 Ni-base superalloy by squash presetting laser cladding. The effects of processing parameters on dilution ratio were investigated. The result shows that the coating consists of two zones: the ceramic clad zone and dilution zone. The dilution ratio increases with the increase of laser power, whereas, the dilution ratio decreases with the increase of laser beam moving velocity. However, the coating with a low laser power is difficult to obtain metallurgical bonding to substrate, and with a high moving velocity can easily produce pores. The clad ceramic coatings characterized by a dense structure, no cracks, low dilution, and good metallurgical bonding to substrate were obtained under optimum processing parameters.
38
Gosselin, Jeremy M., Pascal Audet, Clément Estève, Morgan McLellan, Stephen G. Mosher, and Andrew J. Schaeffer. "Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip." Science Advances 6, no. 4 (January 2020): eaay5174. http://dx.doi.org/10.1126/sciadv.aay5174.
Full textAbstract:
Fault slip behavior during episodic tremor and slow slip (ETS) events, which occur at the deep extension of subduction zone megathrust faults, is believed to be related to cyclic fluid processes that necessitate fluctuations in pore-fluid pressures. In most subduction zones, a layer of anomalously low seismic wave velocities [low-velocity layer (LVL)] is observed in the vicinity of ETS and suggests high pore-fluid pressures that weaken the megathrust. Using repeated seismic scattering observations in the Cascadia subduction zone, we observe a change in the seismic velocity associated with the LVL after ETS events, which we interpret as a response to fluctuations in pore-fluid pressure. These results provide direct evidence of megathrust fault-valve processes during ETS.
39
Deng, J. H., C. F. Lee, and X. R. Ge. "Characterization of the disturbed zone in a large rock excavation for the Three Gorges Project." Canadian Geotechnical Journal 38, no. 1 (February 1, 2001): 95–106. http://dx.doi.org/10.1139/t00-080.
Full textAbstract:
Excavation in a rock mass leads to the perturbation of the stress regime, often creating a stress-relieved, locally weakened zone known as the disturbed zone. This paper presents the results of in situ studies that were carried out both in the central rock barrier (or separation block) between the shiplift and the temporary shiplock and in the northern slope of the permanent shiplock of the Three Gorges Project. The vertical extent of the disturbed zone was determined jointly by cross-hole seismic wave penetration testing and borehole elastic modulus testing, and the horizontal extent was assessed by monitoring and evaluating the deformation characteristics. Compared with the undisturbed rock mass, the P-wave velocity of the disturbed zone was reduced by 3438% and the borehole elastic modulus by 1231%. The reductions were caused by the opening of primary structural planes or the extension of apertures due to local sliding along the structural planes. In the disturbed zone, no newly formed fractured planes were found. The observed disturbed zone was compared with the tensile stress zones and the shear-damaged zones calculated by the finite element method. A rock reinforcement scheme was recommended and implemented.Key words: disturbed zone, mechanical properties, brittle rock mass, excavation, finite element method, reinforcement.
40
Xian, Xu, and J. M. Floryan. "FLOW ABOUND TWO-DIMENSIONAL ROUGHNESS ELEMENTS." Transactions of the Canadian Society for Mechanical Engineering 17, no. 1 (March 1993): 67–81. http://dx.doi.org/10.1139/tcsme-1993-0005.
Full textAbstract:
Flow around two-dimensional roughness elements in the form of rectangular blocks has been analyzed for reynolds number 0 ≤Re≤40 and blocks of aspect ratio 0.01 ≤W/h≤∞. A very good agreement exists between numerical and experimental results. The size of the upstream separation zone weakly depends on the length of the block but decreases rapidly with an increase of the Reynolds number. In contrast, the length of the downstream separation zone increases almost linearly as Re increases. While this length depends weakly on the aspect ratio of the block, the velocity magnitude inside the separation zone considerably increases with a decrease of the length of the block. The coupling between the upstream and downstream separation zones rapidly disappears when W/h increases and both zones can be considered independent and identical to those at the upstream and downstream facing steps with W/h≥6.
41
Sosa, Carlos, Alberto Lorenzo, Juan Trapero, Carlos Ribas, Enrique Alonso, and Sergio L. Jimenez. "Specific Absolute Velocity Thresholds during Male Basketball Games Using Local Positional System; Differences between Age Categories." Applied Sciences 11, no. 10 (May 12, 2021): 4390. http://dx.doi.org/10.3390/app11104390.
Full textAbstract:
The aim of this study was (I) to establish absolute specific velocity thresholds during basketball games using local positional system (LPS) and (II) to compare the speed profiles between various levels of competitions. The variables recorded were total distance (TD); meters per minute (m·min); real time (min); maximum speed (Km h−1), distance (m), percentage distance, and percentage duration invested in four speed zones (standing–walking; jogging; running; and high-speed running). Mean and standard deviation (±SD) were calculated, and a separate one-way analysis of variance was undertaken to identify differences between competitions. TD (3188.84 ± 808.37 m) is covered by standing–walking (43.51%), jogging (36.58%), running (14.68%), and sprinting (5.23%) activities. Overall, 75.22% of the time is invested standing–walking, jogging (18.43%), running (4.77%), and sprinting (1.89%). M·min (large effect size), % duration zone 2 (moderate effect size); distance zone 4 (large effect size), and % distance zone 4 (very large effect size) are significantly higher during junior than senior. However, % distance zone 1 (large effect size) and % duration zone 1 (large effect size) were largely higher during senior competition. The findings of this study reveal that most of the distance and play time is spent during walking and standing activities. In addition, the proportion of time spent at elevated intensities is higher during junior than in senior competition.
42
Kubiak, Marcin, Vladimír Dekýš, Tomasz Domański, Pavol Novák, and Zbigniew Saternus. "Computer simulations of thermal phenomena in surface heating process using the real distribution of Yb:YAG laser power." MATEC Web of Conferences 157 (2018): 02021. http://dx.doi.org/10.1051/matecconf/201815702021.
Full textAbstract:
This work concerns mathematical and numerical modelling of temperature field during Yb:YAG laser heating of sheets made of S355 steel with the motion of liquid steel in the fusion zone taken into account. Laser power distribution and the caustics are determined on the basis of the geostatistical kriging method. Temperature field and melted material velocity field in the fusion zone are obtained from the numerical solution of continuum mechanics equations using projection method and finite volume method. Numerical algorithms are implemented into computer solver using ObjectPascal programming language. Computer simulations of Yb:YAG laser heating process are performed for different process parameters. Characteristic zones of experimentally obtained cross sections of heated elements are compared to numerically predicted fusion zone and heat affected zone.
43
García-Alba, Javier, Javier Bárcena, and Andrés García. "Zonation of Positively Buoyant Jets Interacting with the Water-Free Surface Quantified by Physical and Numerical Modelling." Water 12, no. 5 (May 7, 2020): 1324. http://dx.doi.org/10.3390/w12051324.
Full textAbstract:
The evolution of positively buoyant jets was studied with non-intrusive techniques—Particle Image Velocimetry (PIV) and Laser Induce Fluorescence (LIF)—by analyzing four physical tests in their four characteristic zones: momentum dominant zone (jet-like), momentum to buoyancy transition zone (jet to plume), buoyancy dominant zone (plume-like), and lateral dispersion dominant zone. Four configurations were tested modifying the momentum and the buoyancy of the effluent through variations of flow discharge and the thermal gradient with the receiving water body, respectively. The physical model results were used to evaluate the performance of numerical models to describe such flows. Furthermore, a new method to delimitate the four characteristic zones of positively buoyant jets interacting with the water-free surface was proposed using the angle (α) shaped by the tangent of the centerline trajectory and the longitudinal axis. Physical model results showed that the dispersion of mass (concentrations) was always greater than the dispersion of energy (velocity) during the evolution of positively buoyant jets. The semiempirical models (CORJET and VISJET) underestimated the trajectory and overestimated the dilution of positively buoyant jets close to the impact zone with the water-free surface. The computational fluid dynamics (CFD) model (Open Field Operation And Manipulation model (OpenFOAM)) is able to reproduce the behavior of positively buoyant jets for all the proposed zones according to the physical results.
44
Hubral, Peter, Jörg Schleicher, Martin Tygel, and Ch Hanitzsch. "Determination of Fresnel zones from traveltime measurements." GEOPHYSICS 58, no. 5 (May 1993): 703–12. http://dx.doi.org/10.1190/1.1443454.
Full textAbstract:
For a horizontally stratified (isotropic) earth, the rms‐velocity of a primary reflection is a key parameter for common‐midpoint (CMP) stacking, interval‐velocity computation (by the Dix formula) and true‐amplitude processing (geometrical‐spreading compensation). As shown here, it is also a very desirable parameter to determine the Fresnel zone on the reflector from which the primary zero‐offset reflection results. Hence, the rms‐velocity can contribute to evaluating the resolution of the primary reflection. The situation that applies to a horizontally stratified earth model can be generalized to three‐dimensional (3-D) layered laterally inhomogeneous media. The theory by which Fresnel zones for zero‐offset primary reflections can then be determined purely from a traveltime analysis—without knowing the overburden above the considered reflector—is presented. The concept of a projected Fresnel zone is introduced and a simple method of its construction for zero‐offset primary reflections is described. The projected Fresnel zone provides the image on the earth’s surface (or on the traveltime surface of primary zero‐offset reflections) of that part of the subsurface reflector (i.e., the actual Fresnel zone) that influences the considered reflection. This image is often required for a seismic stratigraphic analysis. Our main aim is therefore to show the seismic interpreter how easy it is to find the projected Fresnel zone of a zero‐offset reflection using nothing more than a standard 3-D CMP traveltime analysis.
45
Mathur, Priya, S. R. Mishra, Mahesh Bohra, D. L. Suthar, and S. D. Purohit. "Computational Behavior of Second Law Poiseuille Flow of Micropolar Fluids in a Channel: Analytical Treatment." Journal of Mathematics 2021 (August 3, 2021): 1–13. http://dx.doi.org/10.1155/2021/9945319.
Full textAbstract:
The present analysis explores an analytical treatment for the computation of Poiseuille flow of a micropolar fluid in a channel placed in between two horizontal parallel plates. Both the plates are placed at constant wall temperatures. Therefore, the flow region is portioned into two different zones named zone I and zone II. Eringen’s micropolar fluid flow phenomena are taking place assuming no-slip conditions at the interface. Suitable nondimensional variables are imposed for the transformation of governing equations. Analytical treatment is carried out employing the in-house symbolic command using the MAPLE software. The behavior of several contributing parameters such as material parameters, the couple stresses for both the zones on the velocity, and microrotation profiles are investigated and presented via graphs. The volume flow rate is also calculated and presented via the tabular form. The major outcomes of the results are presented as the higher the Reynolds number, the rate increases significantly. The profile is tiled near the central region with a pick starting from the lower plate region to the central region in zone I and retards from the central region to the upper plate in the zone II, and the profiles of angular momentum seem to be symmetric in nature about the central region that is shown in both the zones.
46
Chen, Xiaofei, Youli Quan, and Jerry M. Harris. "Seismogram synthesis for radially layered media using the generalized reflection/transmission coefficients method: Theory and applications to acoustic logging." GEOPHYSICS 61, no. 4 (July 1996): 1150–59. http://dx.doi.org/10.1190/1.1444035.
Full textAbstract:
A new method based on generalized reflection and transmission coefficients is proposed to calculate the synthetic seismograms in radially multilayered media. This method can be used to efficiently simulate full waveform acoustic logs and crosswell seismic profiles in situations where we need to consider borehole effects. The new formulation is tested by comparing our numerical results with previous available work and shows excellent agreement. Because of the use of the normalized Hankel functions and the normalization factors, this new algorithm for computing seismograms is stable numerically even for high‐frequency problems. To show the applicability of this new approach to full waveform sonic logging, we apply it to investigate the effects of complex invaded zones on the geometrical spreading and attenuation estimation for P‐waves. We find that a damaged zone (its velocity is slower than the unperturbed formation velocity) exhibits a convergence effect on the P‐waves, and a flushed zone (velocity is faster than the unperturbed formation velocity) exhibits a divergence effect on the P‐waves.
47
Thybo, Hans. "The heterogeneous upper mantle low velocity zone." Tectonophysics 416, no. 1-4 (April 2006): 53–79. http://dx.doi.org/10.1016/j.tecto.2005.11.021.
Full text
48
Putrevu, Uday, and Ib A. Svendsen. "Infragravity velocity profiles in the surf zone." Journal of Geophysical Research 100, no. C8 (1995): 16131. http://dx.doi.org/10.1029/95jc01284.
Full text
49
Yu, Shule, and Edward J. Garnero. "Ultralow Velocity Zone Locations: A Global Assessment." Geochemistry, Geophysics, Geosystems 19, no. 2 (February 2018): 396–414. http://dx.doi.org/10.1002/2017gc007281.
Full text
50
Thore, Pierre D., and Corrine Juliard. "Fresnel zone effect on seismic velocity resolution." GEOPHYSICS 64, no. 2 (March 1999): 593–603. http://dx.doi.org/10.1190/1.1444566.
Full textAbstract:
For impedance, velocity resolution depends on Fresnel zone considerations. A change of velocity can be distinguished only if its size is greater than the Fresnel zone. This is demonstrated on synthesized examples where a single velocity anomaly is introduced in a homogeneous medium. (Although unrealistic, this model was designed to exhibit the physical phenomenon in its simplest configuration.) The presence of the velocity anomaly breaks the wavefront into two main parts. The first part, which travels through the anomaly, corresponds to the specular ray and gives rise to an event which we call the ray event since it can be predicted by standard ray‐tracing techniques. The second, which emanates from outside the anomaly, does not correspond to a ray event. Therefore, we call it the nonray event. It travels at the speed of the background medium. The relative amplitude of the two events depends upon the size of the anomaly compared to the size of the Fresnel zone. When the anomaly is larger than the Fresnel zone, then the ray event dominates and the velocity variation is detectable. On the other hand, when the anomaly is smaller than the Fresnel zone, then the nonray event dominates and everything occurs as if there were velocity variation, leading to the wrong velocity model. The physical phenomenon underlying the presence of the nonray event is very pervasive and does not depend on the velocity contrast. It has already been referred to as wavefront healing, but its consequences in terms of velocity resolution have not been outlined in the domain of seismic reflection. The paper is organized in the following way. First, we present the phenomenon and its consequences on velocity analysis on a single model. Then, by changing the model parameters, we show how the respective amplitudes of the nonray event and the ray event and, therefore, the detectability of velocity variations depends on the size of the anomaly. Finally, we present two approaches to describe the physics of the phenomenon: (1) geometrical considerations based on Huyghen’s principle to explain the wave‐front healing phenomenon and (2) a discussion on the Kirchhoff integral to explain how the amplitude ratio of the ray event to the nonray event (and in turn the detectability of the velocity variation) depends on the size of the anomaly compared to the size of the Fresnel zone. In the final part of the paper we give two potential applications of this theory: (1) the use of the Fresnel zone diameter as the minimum length for smoothing velocity horizons and (2) a theoretical scheme for velocity analysis that should improve the velocity resolution: a combination of velocity estimation and wave equation redatuming. No implementation of this scheme has yet been tested.