scholarly journals Characteristics of aeration in the flow downstream of a radial gate with a sudden fall-expansion aerator in a discharge tunnel

2017 ◽  
Vol 18 (3) ◽  
pp. 790-798
Author(s):  
Shuai Li ◽  
Jianmin Zhang ◽  
Xiaoqing Chen ◽  
Gordon G. D. Zhou ◽  
Jiangang Chen
Keyword(s):  
Bimodal Distribution ◽  
Cavitation Damage ◽  
Discharge Tunnel ◽  
Stable Regime ◽  
Physical Experiments ◽  
Bottom Cavity ◽  
Lateral Cavity ◽  
Pressure Regime ◽  
Radial Gate ◽  
The Impact

Abstract The mechanisms of cavitation damage in flood releasing tunnels remain unclear. In this study a series of physical experiments and numerical calculations were conducted to investigate the flow pattern, pressure distribution and cavitation downstream of a sudden fall-expansion aerator in a discharge tunnel. When the radial gate was partly open, the bottom cavity length reduced drastically, the lateral cavity disappeared, and the flow cavitation index near the sidewalls was less than 0.2. The pressure on the floor and sidewalls can be divided into four regimes: the cavity regime, the impact regime, the reflective regime and the stable regime. The time-average pressure is subject to a unimodal distribution when the gate is fully open, whereas a bimodal distribution is presented when the gate is partly open. The negative pressure regime presented an elliptic shape. Cavitation erosion occurred easily on lateral expansion sidewalls in the tunnel with the radial gate partly open.

scholarly journals Zeolite Tuff and Recycled Ceramic Sanitary Ware Aggregate in Production of Concrete

2019 ◽  
Vol 11 (6) ◽  
pp. 1782 ◽  
Author(s):  
Jacek Szulej ◽  
Paweł Ogrodnik ◽  
Beata Klimek
Keyword(s):  
Phase Composition ◽  
Bimodal Distribution ◽  
Sanitary Ware ◽  
Ceramic Ware ◽  
Sieve Analysis ◽  
Production Plant ◽  
Concrete Production ◽  
Aluminous Cement ◽  
Ceramic Sanitary Ware ◽  
The Impact

The article presents the results of research on the use of ceramic ware waste as aggregate in concrete production. Four concrete mixtures with aluminous cement were prepared, each with a different admixture of clinoptilolite. The only used aggregate was crushed waste ceramic sanitary ware obtained from a Polish sanitary fixture production plant. As part of the studies, a compressive test of cubic samples at different curing times ranging from 7 to 90 days was performed. Prior to the preparation of the samples, a sieve analysis and an elemental analysis of the obtained aggregate were conducted. In the framework of the testing, the bimodal distribution of clinoptilolite grains was determined, as well as its chemical composition. The conducted compressive tests demonstrated high strength of concrete containing ceramic aggregate and aluminous cement with an addition of clinoptilolite. In order to determine the impact that adding zeolite exerts on the phase composition and the structure of concrete samples, an analysis of the phase composition (XRD) and scanning electron microscopy examination (SEM) were performed. Furthermore, tests of abrasion, water penetration under pressure and frost resistance were conducted, determining particular properties of the designed mixtures. The abrasion tests have confirmed that the mixtures are highly abrasion-resistant and can be used as a topcoat concrete layer. The conducted tests of selected properties have confirmed the possibility of using waste ceramic cullet and a mineral addition of clinoptilolite in concrete production.

scholarly journals Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion

2022 ◽  
Vol 8 ◽  
Author(s):  
Ao Li ◽  
Aixia Zhu ◽  
Di Kong ◽  
Chunwei Wang ◽  
Shiping Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Soybean Lecithin ◽  
Average Particle Size ◽  
Soy Protein Isolate ◽  
In Vitro Digestion ◽  
Bimodal Distribution ◽  
Average Particle ◽  
Food Ingredients ◽  
The Impact

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

Modeling and analysis of soft robotic fingers using the fin ray effect

2020 ◽  
Vol 39 (14) ◽  
pp. 1686-1705
Author(s):  
Xiaowei Shan ◽  
Lionel Birglen
Keyword(s):  
Contact Forces ◽  
Accurate Estimation ◽  
Modeling And Analysis ◽  
Physical Experiments ◽  
Fin Ray ◽  
And Performance ◽  
Difficult Challenge ◽  
Kinetostatic Model ◽  
Individual Contact ◽  
The Impact

Soft grasping of random objects in unstructured environments has been a research topic of predilection both in academia and in industry because of its complexity but great practical relevance. However, accurate modeling of soft hands and fingers has proven a difficult challenge to tackle. Focusing on this issue, this article presents a detailed mathematical modeling and performance analysis of parallel grippers equipped with soft fingers taking advantage of the fin ray effect (FRE). The FRE, based on biomimetic principles, is most commonly found in the design of grasping soft fingers, but despite their popularity, finding a convenient model to assess the grasp capabilities of these fingers is challenging. This article aims at solving this issue by providing an analytic tool to better understand and ultimately design this type of soft fingers. First, a kinetostatic model of a general multi-crossbeam finger is established. This model will allow for a fast yet accurate estimation of the contact forces generated when the fingers grasp an arbitrarily shaped object. The obtained mathematical model will be subsequently validated by numerically to ensure the estimations of the overall grasp strength and individual contact forces are indeed accurate. Physical experiments conducted with 3D-printed fingers of the most common architecture of FRE fingers will also be presented and shown to support the proposed model. Finally, the impact of the relative stiffness between different areas of the fingers will be evaluated to provide insight into further refinement and optimization of these fingers.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The collapse of cavitation bubbles and the pressures thereby produced against solid boundaries

1966 ◽  
Vol 260 (1110) ◽  
pp. 221-240 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Experimental Information ◽  
Liquid Jets ◽  
Steam Turbines ◽  
Jet Formation ◽  
Cavitation Damage ◽  
Cavity Collapse ◽  
New Ideas ◽  
The Impact ◽  
Shape Changes

Our object is to present a broad review of this subject as a branch of hydrodynamics, referring both to the well known ‘implosion’ mechanism first analysed by Lord Rayleigh and, more particularly, to the recently perceived possibility that effects of equally great violence, such as to damage solid boundaries, may arise through the impact of liquid jets formed by collapsing cavities. In §2 a few practical facts about cavitation damage are recalled by way of background, and then in §3 the significance of available theoretical and experimental information about cavity collapse is discussed. The main exposition of new ideas is in §4, which is a review of the factors contributing to shape changes and eventual jet formation by collapsing cavities. Finally, in §5, some new experimental observations on the unsymmetrical collapse of vapour-filled cavities are presented.

Preliminary Results Related to the Design of Virtual Probes for Use in a Nano-Manipulation Test-Bed

2005 ◽  
Author(s):  
Anant Trivedi ◽  
J. Cecil
Keyword(s):  
Information Model ◽  
Enterprise Modeling ◽  
Nano Particles ◽  
Test Bed ◽  
Considerable Saving ◽  
Pull Out ◽  
Physical Experiments ◽  
Information Models ◽  
The Impact ◽  
Manipulation Process

This paper discusses the design of virtual probe tip models for use in a nano-manipulation research test-bed (NMRT). The proposed NMRT would help study the feasibility of a given manipulation technique in a virtual environment before physical experiments. For example, NMRT would be able to help users determine if a specific kind of probe tip can be used to pull out a nano-particle from a given substrate. A virtual probe tip model (for instance) would consider the given geometry and material of probe tip and simulate its behavior in a manipulation application in a physics based virtual reality environment. Such a virtual analysis and overall approach would result in considerable saving in time and financial resources with substantial application potential in medical and biotechnology fields where nanoparticle manipulation is useful. Expandability of the NMRT is made possible by designing an ‘information oriented’ or ‘information intensive’ model for a target set of nano-manipulation activities, which maps in detail various attributes related to a target nano-manipulation process [1]. In this approach, information models based on “engineering Enterprise Modeling Language” (eEML) are used. For example, consider an existing information model for interaction of a probe tip with a spherical particle; a user can use an existing information model, or modify it quickly to study the impact of two approaches (eg. manipulation strategy-A versus strategy-B, which may apply a different probe-tip for gripping). For a target nano-manipulation process (for example, the assembly of nano particles using an Atomic Force Microscope probe as a gripper), an information model can represent the core attributes influencing the target process; influencing criteria including constraints, information inputs, and physical inputs can be modeled explicitly and used to drive a target analysis or simulation activity.

scholarly journals Scale effect on mean pressures: study of two reduced models of a ski jump spillway

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
João Gerdau de Borja ◽  
Daniela Guzzon Sanagiotto ◽  
Marcelo Giulian Marques ◽  
Alba Valéria Brandão Canellas ◽  
Cassius Palauro
Keyword(s):  
Scale Effect ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Jet Flow ◽  
Reduced Models ◽  
Physical Experiments ◽  
Scour Hole ◽  
Scour Holes ◽  
Energy Dissipation System ◽  
The Impact

ABSTRACT The ski jump type spillway is present in large Brazilian dams. After the operation of this type of spillway, a scour hole is originated downstream of the spillway toe, complementing the energy dissipation system, because the jet is cushioned by the waterbed. As the excavation of the scour hole evolves, its shape changes, with the induction of different behaviors of the jet flow within the waterbed. The importance of this scientific study is due to the fact that scour holes downstream of ski jump spillways are in constant transformation, which can cause changes in the patterns of dynamic pressures caused on the bottom. Unexpected erosions can cause instability in the submerged slopes of the pit, jeopardizing the foundation of the dam. In this work it was proceeded physical experiments, by sectional modeling (2D), in two reduced models of 1:50 and 1:100 scales, considering two stages of erosion depths in solid bottom (fixed). It was analyzed the impact site of the jet flow on the bottom, which has the major mean dynamic pressure. As result, it was possible to identify the scale effect in the pressure coefficient between the two models tested, which allowed the adjustment of trend lines that aid to estimate the pressures that occur in prototypes, increasing safety in operation of ski jump spillways.

scholarly journals Validation Metrics for Deterministic and Probabilistic Data

2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Kathryn A. Maupin ◽  
Laura P. Swiler ◽  
Nathan W. Porter
Keyword(s):  
Computational Models ◽  
Modern Science ◽  
Probabilistic Data ◽  
Validation Metrics ◽  
Physical Experiments ◽  
History Of ◽  
Computational Modeling And Simulation ◽  
History Of Use ◽  
The Impact ◽  
Application Specific

Computational modeling and simulation are paramount to modern science. Computational models often replace physical experiments that are prohibitively expensive, dangerous, or occur at extreme scales. Thus, it is critical that these models accurately represent and can be used as replacements for reality. This paper provides an analysis of metrics that may be used to determine the validity of a computational model. While some metrics have a direct physical meaning and a long history of use, others, especially those that compare probabilistic data, are more difficult to interpret. Furthermore, the process of model validation is often application-specific, making the procedure itself challenging and the results difficult to defend. We therefore provide guidance and recommendations as to which validation metric to use, as well as how to use and decipher the results. An example is included that compares interpretations of various metrics and demonstrates the impact of model and experimental uncertainty on validation processes.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Damage to solids caused by cavitation

1966 ◽  
Vol 260 (1110) ◽  
pp. 245-255 ◽  
Keyword(s):  
Mechanical Properties ◽  
Cavitation Erosion ◽  
Cavitation Resistance ◽  
Steam Turbines ◽  
Single Event ◽  
Cavitation Damage ◽  
Erosion Damage ◽  
Highly Sensitive ◽  
Wide Range ◽  
The Impact

This paper describes the early stages of cavitation damage observed in cavitating venturi tunnels. The cavitating fluids were water and mercury, and a wide range of specimen materials were used. The damage was found to consist of single-event symmetical craters and irregular fatigue-type failures. The degree of damage was highly sensitive to minor flow perturbations, and this is discussed. The effect of stress level in the specimen before testing, and relations between cavitation resistance and the mechanical properties of the materials are considered.

scholarly journals Delirium, frailty and mortality: interactions in a prospective study of hospitalized older people

2017 ◽  
Author(s):  
Melanie Dani ◽  
Lucy H Owen ◽  
Thomas A Jackson ◽  
Kenneth Rockwood ◽  
Elizabeth L Sampson ◽  
...  
Keyword(s):  
Cox Regression ◽  
Frailty Index ◽  
Bimodal Distribution ◽  
Mortality Rates ◽  
Acute Illness ◽  
Health States ◽  
Mortality Statistics ◽  
National Mortality ◽  
A Prospective Study ◽  
The Impact

AbstractBackgroundIt is unknown if the association between delirium and mortality is consistent for individuals across the whole range of health states. A bimodal relationship has been proposed, where delirium is particularly adverse for those with underlying frailty, but may have a smaller effect (perhaps even protective) if it is an early indicator of acute illness in fitter people. We investigated the impact of delirium on mortality in a cohort simultaneously evaluated for frailty.MethodsWe undertook an exploratory analysis of a cohort of consecutive acute medical admissions aged ≥70. Delirium on admission was ascertained by psychiatrists. A Frailty Index (FI) was derived according to a standard approach. Deaths were notified from linked national mortality statistics. Cox regression was used to estimate associations between delirium, frailty and their interactions on mortality.ResultsThe sample consisted of 710 individuals. Both delirium and frailty were independently associated with increased mortality rates (delirium: HR 2.4, 95%CI 1.8-3.3, p<0.01; frailty (per SD): HR 3.5, 95%CI 1.2-9.9, p=0.02). Estimating the effect of delirium in tertiles of FI, mortality was greatest in the lowest tertile: tertile 1 HR 3.4 (95%CI 2.1-5.6); tertile 2 HR 2.7 (95%CI 1.5-4.6); tertile 3 HR 1.9 (95% CI 1.2-3.0).ConclusionWhile delirium and frailty contribute to mortality, the overall impact of delirium on admission appears to be greater at lower levels of frailty. In contrast to the hypothesis that there is a bimodal distribution for mortality, delirium appears to be particularly adverse when precipitated in fitter individuals.

scholarly journals Semi-Automated Extraction of the Distribution of Single Defects for nMOS Transistors

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 446
Author(s):  
Bernhard Stampfer ◽  
Franz Schanovsky ◽  
Tibor Grasser ◽  
Michael Waltl
Keyword(s):  
Field Effect Transistors ◽  
Bimodal Distribution ◽  
Oxide Semiconductor ◽  
Vertical Position ◽  
Trap Level ◽  
Operating Characteristics ◽  
Large Area ◽  
Switching Speed ◽  
Oxide Defects ◽  
The Impact

Miniaturization of metal-oxide-semiconductor field effect transistors (MOSFETs) is typically beneficial for their operating characteristics, such as switching speed and power consumption, but at the same time miniaturization also leads to increased variability among nominally identical devices. Adverse effects due to oxide traps in particular become a serious issue for device performance and reliability. While the average number of defects per device is lower for scaled devices, the impact of the oxide defects is significantly more pronounced than in large area transistors. This combination enables the investigation of charge transitions of single defects. In this study, we perform random telegraph noise (RTN) measurements on about 300 devices to statistically characterize oxide defects in a Si/SiO 2 technology. To extract the noise parameters from the measurements, we make use of the Canny edge detector. From the data, we obtain distributions of the step heights of defects, i.e., their impact on the threshold voltage of the devices. Detailed measurements of a subset of the defects further allow us to extract their vertical position in the oxide and their trap level using both analytical estimations and full numerical simulations. Contrary to published literature data, we observe a bimodal distribution of step heights, while the extracted distribution of trap levels agrees well with recent studies.

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