scholarly journals Effects of Using Channelling Devices to Increase Efficiency of Hydrokinetic Devices

2015 ◽  
Vol 52 (2) ◽  
pp. 3-12
Author(s):  
A. Kalnacs ◽  
J. Kalnacs ◽  
A. Mutule ◽  
V. Entins
Keyword(s):  
Flow Control ◽  
Flow Velocity ◽  
Cross Section ◽  
Power Output ◽  
High Importance ◽  
Different Types ◽  
The Cross ◽  
Increase Efficiency ◽  
Flow Velocities

Abstract In the rivers of Latvia and of many other countries the flow velocity in the places that are most suitable for installation of hydrokinetic devices is 0.4 to 0.9 m/s. In a stream or a river the hydrokinetic devices can reach full efficiency starting from about twice higher flow velocities. It is advisable to at least double this velocity thus increasing the efficiency and power output of the hydrokinetic devices installed in such places. Since Latvia has abundance of slow rivers and almost none are fast, research in this field is of high importance. Diversified technical methods are known that allow increasing substantially the efficiency of hydrokinetic devices. These methods include the use of diffusers, concentrators, different types of other channelling devices and means of flow control. Desirable effects are achieved through changing the cross-section and/or direction of a flow, its pressure, minimizing the turbulence, etc. This work substantiates the use of such devices for increasing the efficiency of hydrokinetic devices. A method is proposed for evaluation of the effects on power output gained owing to the use of channelling devices. Results show that the efficiency of hydrokinetic devices can be increased by at least 110%.

scholarly journals Dependence of the Cross Section of the Cut Layer on the Specific Cutting Resistance

2019 ◽  
Vol 254 ◽  
pp. 04008
Author(s):  
Jana Petrů ◽  
Tomáš Zlámal ◽  
Lukáš Drábek ◽  
Jiří Hajnyš ◽  
Dalibor Jurok
Keyword(s):  
Cross Section ◽  
Cutting Speed ◽  
Cutting Depth ◽  
Cutting Resistance ◽  
Refractory Nickel Alloy ◽  
Different Types ◽  
Cutting Inserts ◽  
The Cross ◽  
Measurement And Evaluation ◽  
Longitudinal Turning

This article deals with the study of the effect of cross section of the cut layer of material and its influence on the specific cutting resistance. Measurement and evaluation were carried out using two machined materials, according to the designation W.Nr. carbon steel 1.1191, which is a reference material for the steel grade and refractory nickel alloy 2.4856. For the purpose of the experiment, longitudinal turning technology with two interchangeable CNMG 120408 SM and CNMX 1204A2 – SM cutting inserts was chosen. According to the recommended index insert values, two different types of cutting conditions were chosen for each material so that the cross section of the chip remained the same during machining. For each material, the cutting speed was constant and the feed rate and cutting depth were changed. The main goal of the experimental work was comparison of the specific cutting resistance in dependence on different cross section of the removed layer of material. On the basis of measuring of cutting forces by dynamometer Kistler the resulting cutting force was determined and the size of the specific cutting resistance was calculated.

Zur optim alen Auskopplung bei gefalteten Lasern hoher Verstärkung

1969 ◽  
Vol 24 (5) ◽  
pp. 867-869 ◽  
Author(s):  
D. Rosenberger
Keyword(s):  
Uniform Distribution ◽  
Transmission Coefficient ◽  
Cross Section ◽  
Power Output ◽  
High Gain ◽  
High Mode ◽  
Line Broadening ◽  
The Cross

Abstract The optimum transmission coefficient and power output of folded high-gain lasers are calculated assuming homogeneous line broadening and a uniform distribution of the unsaturated gain over the cross section. The results are applied to CO2 lasers with high mode density.

scholarly journals Technical Note: Flow velocity and discharge measurement in rivers using terrestrial and unmanned-aerial-vehicle imagery

2020 ◽  
Vol 24 (3) ◽  
pp. 1429-1445 ◽  
Author(s):  
Anette Eltner ◽  
Hannes Sardemann ◽  
Jens Grundmann
Keyword(s):  
Flow Velocity ◽  
Unmanned Aerial Vehicle ◽  
Cross Section ◽  
Flow Characteristics ◽  
Technical Note ◽  
Surface Flow ◽  
Contactless Measurement ◽  
Aerial Vehicle ◽  
The Impact ◽  
Flow Velocities

Abstract. An automatic workflow to measure surface flow velocities in rivers is introduced, including a Python tool. The method is based on particle-tracking velocimetry (PTV) and comprises an automatic definition of the search area for particles to track. Tracking is performed in the original images. Only the final tracks are geo-referenced, intersecting the image observations with water surface in object space. Detected particles and corresponding feature tracks are filtered considering particle and flow characteristics to mitigate the impact of sun glare and outliers. The method can be applied to different perspectives, including terrestrial and aerial (i.e. unmanned-aerial-vehicle; UAV) imagery. To account for camera movements images can be co-registered in an automatic approach. In addition to velocity estimates, discharge is calculated using the surface velocities and wetted cross section derived from surface models computed with structure-from-motion (SfM) and multi-media photogrammetry. The workflow is tested at two river reaches (paved and natural) in Germany. Reference data are provided by acoustic Doppler current profiler (ADCP) measurements. At the paved river reach, the highest deviations of flow velocity and discharge reach 4 % and 5 %, respectively. At the natural river highest deviations are larger (up to 31 %) due to the irregular cross-section shapes hindering the accurate contrasting of ADCP- and image-based results. The provided tool enables the measurement of surface flow velocities independently of the perspective from which images are acquired. With the contactless measurement, spatially distributed velocity fields can be estimated and river discharge in previously ungauged and unmeasured regions can be calculated, solely requiring some scaling information.

THE PHOTONEUTRON CROSS SECTIONS FOR THE REACTIONS Br81 (γ,n) Br80 AND Br81 (γ,n) Br80* AND AN ANALYSIS OF THE RATIO BETWEEN THESE CROSS SECTIONS

1952 ◽  
Vol 30 (5) ◽  
pp. 476-487 ◽  
Author(s):  
L. Katz ◽  
L. Pease ◽  
H. Moody
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Point Of View ◽  
Photonuclear Reactions ◽  
Shape Characteristic ◽  
Elementary Analysis ◽  
Different Types ◽  
The Cross

Cross-section curves have been measured as a function of energy for the reactions Br81(γ,n)Br80 and Br81(γ,n)Br80* and the ratio between these cross sections has been examined critically. The curves exhibit the peaked shape characteristic of photonuclear reactions with maximum cross sections of 88 and 42 millibarns respectively. It is shown that the ratio of the cross sections depends on the spins of the excited levels in which the Br80 nucleus is left prior to γ cascading and thus on the reaction leading to it. An elementary analysis based on this point of view gives results consistent with the ratio measured for six different types of reactions.

The shape of free jets of water under gravity

1976 ◽  
Vol 76 (4) ◽  
pp. 625-640 ◽  
Author(s):  
E. O. Tuck
Keyword(s):  
Free Surface ◽  
Aspect Ratio ◽  
Flow Velocity ◽  
Cross Section ◽  
Cross Sections ◽  
Cross Flow ◽  
Free Jets ◽  
Elliptic Cross ◽  
Cross Flow Velocity ◽  
The Cross

A study is made of the form taken by a slender jet of water whose only boundary is a free surface. The only forces acting are inertial and gravitational. Attention is paid to the cross-flow velocity components and to the development of the shape of the cross-section of the jet as it progresses. It is established that a jet with initially elliptic cross-sections can remain elliptical, and the variation in the aspect ratio along the jet is determined.

EELS STUDY OF SINGLE CRYSTALLINE NiO(100)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 341-344 ◽  
Author(s):  
A. GORSCHLÜTER ◽  
H. MERZ
Keyword(s):  
Cross Section ◽  
Primary Energy ◽  
Low Loss ◽  
Single Crystalline ◽  
New Information ◽  
Different Types ◽  
Insulating Gap ◽  
The Cross ◽  
D Orbitals ◽  
Localized Electrons

A detailed EELS study of NiO(100) cleaved in UHV has been performed to obtain new information about the origin of the insulating gap and about the nature of weak excitations within the gap. The low loss intensity of the inneratomic d-d excitations within the gap is strongly dependent on the primary energy whereas the cross section for the first excitations across the gap is approximately constant. This can be explained by different types of O 2p- Ni 3d hybridization. We assume that the first transitions across the gap are due to excitations of localized electrons in the p-d orbitals of a Ni-O cluster.

scholarly journals Flow velocity and discharge measurement in rivers using terrestrial and UAV imagery

2019 ◽  
Author(s):  
Anette Eltner ◽  
Hannes Sardemann ◽  
Jens Grundmann
Keyword(s):  
Flow Velocity ◽  
Cross Section ◽  
Flow Characteristics ◽  
Surface Flow ◽  
Spatially Distributed ◽  
Adcp Measurements ◽  
River Reach ◽  
Definition Of ◽  
The Impact ◽  
Flow Velocities

Abstract. An automatic workflow to measure surface flow velocities in rivers is introduced, including a Python tool. The method is based on PTV and comprises an automatic definition of the search area for particles to track. Tracking is performed in the original images. Only the final tracks are geo-referenced, intersecting the image observations with water surface in object space. Detected particles and corresponding feature tracks are filtered considering particle and flow characteristics to mitigate the impact of sun glare and outliers. The method can be applied to different perspectives, including terrestrial and aerial (i.e. UAV) imagery. To account for camera movements images can be co-registered in an automatic approach. In addition to velocity estimates, discharge is calculated using the surface velocities and wetted cross-section derived from surface models computed with structure-from-motion and multi-media photogrammetry. The workflow is tested at two river reaches (paved and natural) in Germany. Reference data is provided by ADCP measurements. At the paved river reach highest deviations of flow velocity and discharge reach 5 % and 4 %, respectively. At the natural river deviations are larger (up to 31 %) due to the irregular cross-section shapes hindering accurate contrasting of ADCP- and image-based results. The provided tool enables the measurement of surface flow velocities independently of the perspective from which images are acquired. With the contact-less measurement spatially distributed velocity fields can be estimated and river discharge in previously ungauged and unmeasured regions can be calculated.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Energy Distribution in Electron Beams

1972 ◽  
Vol 30 ◽  
pp. 568-569
Author(s):  
Tamotsu Ohno
Keyword(s):  
Electron Beam ◽  
Energy Distribution ◽  
Cross Section ◽  
Integral Curve ◽  
Electron Beams ◽  
Electron Gun ◽  
Angular Divergence ◽  
Apparent Increase ◽  
Integral Width ◽  
The Cross

The energy distribution in an electron; beam from an electron gun provided with a biased Wehnelt cylinder was measured by a retarding potential analyser. All the measurements were carried out with a beam of small angular divergence (<3xl0-4 rad) to eliminate the apparent increase of energy width as pointed out by Ichinokawa.The cross section of the beam from a gun with a tungsten hairpin cathode varies as shown in Fig.1a with the bias voltage Vg. The central part of the beam was analysed. An example of the integral curve as well as the energy spectrum is shown in Fig.2. The integral width of the spectrum ΔEi varies with Vg as shown in Fig.1b The width ΔEi is smaller than the Maxwellian width near the cut-off. As |Vg| is decreased, ΔEi increases beyond the Maxwellian width, reaches a maximum and then decreases. Note that the cross section of the beam enlarges with decreasing |Vg|.

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