Turn-ON and Turn-OFF Times for a Laminar Jet

1973 ◽  
Vol 95 (2) ◽  
pp. 155-160 ◽  
Author(s):  
S. Abramovich ◽  
A. Solan
Keyword(s):  
Experimental Data ◽  
Time Lag ◽  
Experimental Results ◽  
Time Lags ◽  
Laminar Jet ◽  
Turn On ◽  
Switching Times ◽  
Laminar Jets ◽  
Jet Nozzle ◽  
Time Required

Experimental results of the speed of travel of a disturbance in front of suddenly switched-on and switched-off submerged laminar jets are presented. The results show that the time lag for a switched-off jet is approximately one half the time required for a particle moving in front of a switched on jet to reach a certain distance from the jet nozzle. The time lags for an instantaneous change in the jet intensity is approximately the same as that for switching the whole jet on and off. These experimental data can be used to calculate the switching times of turbulence amplifiers.

scholarly journals Mock-up Test of Time Lag in Floor Heating Systems with PCM

2019 ◽  
Vol 111 ◽  
pp. 06061
Author(s):  
Sung Ho Choi ◽  
Tae Won Kim ◽  
Jin Chul Park
Keyword(s):  
Surface Temperature ◽  
Time Lag ◽  
Heating System ◽  
Time Lags ◽  
Heating Systems ◽  
Floor Surface ◽  
Time Required ◽  
Floor System ◽  
Change Material ◽  
Floor Heating

This research analyzes the time lag, which is a thermal storage performance parameter, when a phase change material is applied to the floor heating system of a mock-up laboratory. The following results are obtained. In terms of the time required for the floor surface temperature to reach 30 °C, the time lag of Room 2 (i.e., the room with the PCM-based floor system) was observed to be 15 min. Additionally, in terms of the time required for the floor surface temperature to decrease to 22 °C, Room 2 exhibited a time lag of 5 h 2 min. Therefore, the study concluded that longer time lags are observed with floor heating systems with PCM.

scholarly journals Detection of Important Scenes in Baseball Videos via a Time-Lag-Aware Multimodal Variational Autoencoder

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2045
Author(s):  
Kaito Hirasawa ◽  
Keisuke Maeda ◽  
Takahiro Ogawa ◽  
Miki Haseyama
Keyword(s):  
Time Lag ◽  
Experimental Results ◽  
New Method ◽  
Time Lags ◽  
Feature Transformation ◽  
Audio Features ◽  
Variational Autoencoder ◽  
Feature Correlation ◽  
Latent Features ◽  
Video And Audio

A new method for the detection of important scenes in baseball videos via a time-lag-aware multimodal variational autoencoder (Tl-MVAE) is presented in this paper. Tl-MVAE estimates latent features calculated from tweet, video, and audio features extracted from tweets and videos. Then, important scenes are detected by estimating the probability of the scene being important from estimated latent features. It should be noted that there exist time-lags between tweets posted by users and videos. To consider the time-lags between tweet features and other features calculated from corresponding multiple previous events, the feature transformation based on feature correlation considering such time-lags is newly introduced to the encoder in MVAE in the proposed method. This is the biggest contribution of the Tl-MVAE. Experimental results obtained from actual baseball videos and their corresponding tweets show the effectiveness of the proposed method.

Developing Region of Laminar Jets With Parabolic Exit Velocity Profiles

1981 ◽  
Vol 103 (2) ◽  
pp. 322-327 ◽  
Author(s):  
G. W. Rankin ◽  
K. Sridhar
Keyword(s):  
Experimental Data ◽  
Approximate Solution ◽  
Velocity Distribution ◽  
Velocity Profiles ◽  
Exit Velocity ◽  
Parabolic Profile ◽  
Laminar Jet ◽  
Laminar Jets ◽  
Developing Region

An approximate solution to the velocity distribution in a submerged axisymmetric, laminar jet which issues from a long tube is presented. The solution is a modification of that of Okabe [17] and takes into account the changes that occur in the parabolic profile downstream of the jet exit. Comparisons are made with experimental data and other approximate theories taken from the literature.

scholarly journals In Vitro Model of Mycobacterial Growth Arrest Using Nitric Oxide with Limited Air

2008 ◽  
Vol 53 (1) ◽  
pp. 157-161 ◽  
Author(s):  
Syed Hussain ◽  
Muhammad Malik ◽  
Lanbo Shi ◽  
Maria Laura Gennaro ◽  
Karl Drlica
Keyword(s):  
Nitric Oxide ◽  
In Vitro Model ◽  
Transition Period ◽  
Time Lag ◽  
Growth Arrest ◽  
Ring Structure ◽  
Time Lags ◽  
Vitro Model ◽  
Mycobacterial Growth

ABSTRACT An in vitro model of mycobacterial growth arrest was developed using Mycobacterium bovis BCG. When an exponentially growing culture was transferred to an evacuated tube, growth continued; treatment with a source of nitric oxide (diethylenetriamine-nitric oxide adduct [DETA-NO] at 50 μM) halted growth immediately, and aeration restored growth. When the period of growth arrest exceeded 4 h, a time lag occurred before aeration could restore growth. The lag time was maximal (24 h) after 16 h of growth arrest. These time lags indicated that one transition period was required for cells to achieve full arrest of growth and another for them to recover fully from growth arrest. DETA-NO-induced growth arrest failed to protect from the lethal effects of anaerobic shock, which caused rapid lysis of both growing and growth-arrested cells. While growth arrest had little effect on the lethal action of rifampin, it eliminated isoniazid lethality. Growth arrest reduced but did not eliminate fluoroquinolone lethality. Two fluoroquinolones, moxifloxacin and gatifloxacin, were equally lethal to exponentially growing cells, but moxifloxacin was more active during growth arrest. This difference is attributed to the fluoroquinolone C-7 ring structure, the only difference between the compounds. Collectively these data characterize a new system for halting mycobacterial growth that may be useful for evaluating new antituberculosis agents.

scholarly journals A Novel Gate Drive Circuit for Suppressing Turn-on Oscillation of Non-Kelvin Packaged SiC MOSFET

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2449
Author(s):  
Hongyan Zhao ◽  
Jiangui Chen ◽  
Yan Li ◽  
Fei Lin
Keyword(s):  
Thermal Conductivity ◽  
Breakdown Voltage ◽  
Basic Principle ◽  
Double Pulse ◽  
Experimental Results ◽  
Switching Frequency ◽  
Turn On ◽  
Proof Testing ◽  
Gate Driver ◽  
Drive Circuit

Compared with a silicon MOSFET device, the SiC MOSFET has many benefits, such as higher breakdown voltage, faster action speed and better thermal conductivity. These advantages enable the SiC MOSFET to operate at higher switching frequencies, while, as the switching frequency increases, the turn-on loss accounts for most of the loss. This characteristic severely limits the applications of the SiC MOSFET at higher switching frequencies. Accordingly, an SRD-type drive circuit for a SiC MOSFET is proposed in this paper. The proposed SRD-type drive circuit can suppress the turn-on oscillation of a non-Kelvin packaged SiC MOSFET to ensure that the SiC MOSFET can work at a faster turn-on speed with a lower turn-on loss. In this paper, the basic principle of the proposed SRD-type drive circuit is analyzed, and a double pulse platform is established. For the purpose of proof-testing the performance of the presented SRD-type drive circuit, comparisons and experimental verifications between the traditional gate driver and the proposed SRD-type drive circuit were conducted. Our experimental results finally demonstrate the feasibility and effectiveness of the proposed SRD-type drive circuit.

IRREVERSIBLE INVESTMENT, OPERATING FLEXIBILITY, AND TIME LAGS

2010 ◽  
Vol 27 (02) ◽  
pp. 271-286 ◽  
Author(s):  
RYUTA TAKASHIMA ◽  
MAKOTO GOTO ◽  
MOTOH TSUJIMURA
Keyword(s):  
Time Lag ◽  
Peak Load ◽  
Price Volatility ◽  
Optimal Investment ◽  
Capacity Expansion ◽  
Fixed Cost ◽  
Time Lags ◽  
Investment Timing ◽  
Power Company ◽  
Optimal Investment Problem

We consider an optimal investment problem when a firm such as an electric power company has the operational flexibility to expand and contract capacity with fixed cost. This problem is formulated as an impulse control problem combined with optimal stopping. Consequently, we obtain optimal investment timing, optimal capacity expansion and contraction timing, and the investment value. We also show investment, capacity expansion and contraction rule are influenced by the price volatility and the initial capacity is also influenced by the ratio between base-load plant and peak-load plant. In addition, we investigate how time lag between investment and operation influences the investment rule.

Convective Losses From Cavity Solar Receivers—Comparisons Between Analytical Predictions and Experimental Results

1983 ◽  
Vol 105 (1) ◽  
pp. 29-33 ◽  
Author(s):  
A. M. Clausing
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Analytical Model ◽  
Excellent Agreement ◽  
Experimental Results ◽  
Simple Analytical Model ◽  
Refined Model ◽  
Wall Area

Cavity solar receivers are generally believed to have higher thermal efficiencies than external receivers due to reduced losses. A simple analytical model was presented by the author which indicated that the ability to heat the air inside the cavity often controls the convective loss from cavity receivers. Thus, if the receiver contains a large amount of inactive hot wall area, it can experience a large convective loss. Excellent experimental data from a variety of cavity configurations and orientations have recently become available. These data provided a means of testing and refining the analytical model. In this manuscript, a brief description of the refined model is presented. Emphasis is placed on using available experimental evidence to substantiate the hypothesized mechanisms and assumptions. Detailed comparisons are given between analytical predictions and experimental results. Excellent agreement is obtained, and the important mechanisms are more clearly delineated.

A Technique for the Laboratory Determination of Recirculation in Single Needle Dialysis

1993 ◽  
Vol 16 (2) ◽  
pp. 63-70 ◽  
Author(s):  
N.A. Hoenich ◽  
P.T. Smirthwaite ◽  
C. Woffindin ◽  
P. Lancaster ◽  
T.H. Frost ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Experimental Results ◽  
New Technique ◽  
Treatment Efficiency ◽  
Single Lumen ◽  
Theoretical Predictions ◽  
Lumen Catheter ◽  
A New Technique

Recirculation is an important factor in single needle dialysis and, if high, can compromise treatment efficiency. To provide information regarding recirculation characteristics of access devices used in single needle dialysis, we have developed a new technique to characterise recirculation and have used this to measure the recirculation of a Terumo 15G fistula needle and a VasCath SC2300 single lumen catheter. The experimentally obtained results agreed well with those established clinically (8.5 ± 2.4% and 18.4 ± 3.4%). The experimental results have also demonstrated a dependence on access type, pump speeds and fistula flow rate. A comparison of experimental data with theoretical predictions showed that the latter exceeded those measured with the largest contribution being due to the experimental fistula.

scholarly journals Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates

2019 ◽  
Vol 49 (6) ◽  
pp. 1521-1539
Author(s):  
Yu-Kun Qian ◽  
Shiqiu Peng ◽  
Chang-Xia Liang
Keyword(s):  
Time Lag ◽  
Effective Diffusivity ◽  
Delta Function ◽  
Spreading Rate ◽  
Particle Dispersion ◽  
Small Scale ◽  
Time Lags ◽  
Conservative Tracer ◽  
Stirring Effect ◽  
Short Time

AbstractThe present study reconciles theoretical differences between the Lagrangian diffusivity and effective diffusivity in a transformed spatial coordinate based on the contours of a quasi-conservative tracer. In the transformed coordinate, any adiabatic stirring effect, such as shear-induced dispersion, is naturally isolated from diabatic cross-contour motions. Therefore, Lagrangian particle motions in the transformed coordinate obey a transformed zeroth-order stochastic (i.e., random walk) model with the diffusivity replaced by the effective diffusivity. Such a stochastic model becomes the theoretical foundation on which both diffusivities are exactly unified. In the absence of small-scale diffusion, particles do not disperse at all in the transformed contour coordinate. Besides, the corresponding Lagrangian autocorrelation becomes a delta function and is thus free from pronounced overshoot and negative lobe at short time lags that may be induced by either Rossby waves or mesoscale eddies; that is, particles decorrelate immediately and Lagrangian diffusivity is already asymptotic no matter how small the time lag is. The resulting instantaneous Lagrangian spreading rate is thus conceptually identical to the effective diffusivity that only measures the instantaneous irreversible mixing. In these regards, the present study provides a new look at particle dispersion in contour-based coordinates.

Validating Numerical CFD Simulations With Experimental Data for Turbulence Phenomena in Axial Flow Gas Turbine Diffusers

2009 ◽  
Author(s):  
Farrokh Zarifi-Rad ◽  
Hamid Vajihollahi ◽  
James O’Brien
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Axial Flow ◽  
Experimental Results ◽  
Scale Model ◽  
Data Set ◽  
Pressure Profiles ◽  
Scale Models ◽  
Inlet Conditions

Scale models give engineers an excellent understanding of the aerodynamic behavior behind their design; nevertheless, scale models are time consuming and expensive. Therefore computer simulations such as Computational Fluid Dynamics (CFD) are an excellent alternative to scale models. One must ask the question, how close are the CFD results to the actual fluid behavior of the scale model? In order to answer this question the engineering team investigated the performance of a large industrial Gas Turbine (GT) exhaust diffuser scale model with performance predicted by commercially available CFD software. The experimental results were obtained from a 1:12 scale model of a GT exhaust diffuser with a fixed row of blades to simulate the swirl generated by the last row of turbine blades five blade configurations. This work is to validate the effect of the turbulent inlet conditions on an axial diffuser, both on the experimental front and on the numerical analysis approach. The object of this work is to bring forward a better understanding of velocity and static pressure profiles along the gas turbine diffusers and to provide an accurate experimental data set to validate the CFD prediction. For the CFD aspect, ANSYS CFX software was chosen as the solver. Two different types of mesh (hexagonal and tetrahedral) will be compared to the experimental results. It is understood that hexagonal (HEX) meshes are more time consuming and more computationally demanding, they are less prone to mesh sensitivity and have the tendancy to converge at a faster rate than the tetrahedral (TET) mesh. It was found that the HEX mesh was able to generate more consistent results and had less error than TET mesh.

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