Mean Value Of Velocity Research Articles

Are the spectral Doppler indices of ovarian arteries indicative of antral follicular development and predictive of ovulatory responses and embryo yields in superovulated ewes?

Nineteen ewes received 200 mg of pFSH administered in eight decreasing doses from Days 1 to 4, starting three days before CIDR® device removal. Ten ewes received an injection of 350 μg of estradiol benzoate at CIDR® device insertion (Group E) and nine animals served as controls (Group C). B-mode and spectral Doppler ultrasonographic examinations were performed daily throughout superovulatory treatment to enumerate ovarian antral follicles and to determine ovarian blood flow indices, respectively. There were no differences (P > 0.05) in superovulatory responses between left and right ovaries/uterine horns or the two groups of animals. End-diastolic velocity (EDV) and mean velocity (Vm) values were greater (P < 0.05) on Days 1 and 2, and peak systolic velocity (SVp) was greater (P < 0.05) on Day 3 in Group C than in Group E. In Group E 15 correlations was recorded among indices (SVp, Vm, EDV, flow velocity integral-FVI, and pulsatility index-PI) and follicles numbers in different size classes on Days 1, 2 and 4, and seven correlations among indices (SVp, EDV, Vm, and vascular resistance index-RI) and superovulatory/embryo results (numbers of regressing corpora lutea, numbers/percentages of degenerated embryos and viability rates) on Days 1, 2 and 3. In Group C, there were three correlations among EDV and RI and medium-sized/large follicle numbers on Days 1 and 3, and five correlations among indices (EDV, RI and PI) and superovulatory/embryo results (numbers of luteinized unovulated follicles, degenerated embryos and unfertilized eggs) on Days 2 or 4. There was a lack of consistency in the velocimetric correlates of antral follicle numbers and superovulatory responses between the left and right side. Therefore, the usefulness of ovarian arterial indices to predict ovine superovulatory outcomes remains equivocal and requires further confirmatory studies.

Reliability and magnitude of loaded countermovement jump performance variables: a technical examination of the jump threshold initiation

ABSTRACT Different thresholds have been used to determine the start of the force-time analysis during countermovement jump testing. This study examined the influence of the jump starting threshold on the reliability and magnitude of loaded countermovement jump (CMJ) performance variables. Seventeen males were tested during two sessions using five loading conditions (17–30–45–60–75 kg). The CMJ performance was analysed with a force platform. The initiation of the eccentric phase was defined as the first instant in which the vertical ground reaction force was below system weight by 10 N, 50 N, 1% of system weight (1%SW), 10% of system weight (10%SW) and five standard deviations of system weight minus 30 ms (5SDSW). The 50 N, 10%SW and 5SDSW provided a higher reliability for the mean values of velocity and power as well as for the temporal variables only during the eccentric phase compared to the 10 N and 1%SW threshold (CV ratio>1.15). The magnitude of several variables collected during both phases for the 50 N, 10%SW and 5SDSW thresholds significantly differed with respect to 10 N and 1%SW thresholds (p< 0.05). These results suggest that the jump starting threshold may influence both the reliability and magnitude of loaded CMJ performance variables, especially during the eccentric phase.

The interplay between cognitive tasks and vision for upright posture balance in adolescents.

BackgroundThe control of an upright stance in humans is important in medicine, psychology, and physiology. The maintenance of upright stance balance depends not only on sensory information from proprioceptive, vestibular, cutaneous, and visual sources but also on cognitive resources. The present study investigated the effects of cognitive tasks while standing with eyes open on upright stance balance in adolescents. We hypothesized that performing a cognitive task while standing with eyes open would increase body sway among these adolescents and that the upright posture would thus become less stable.MethodsA static balance assessment system comprising a force platform connected to a computer was used to evaluate the stability of the upright stance among 21 healthy adolescents under six conditions: no cognitive task, a relatively easy cognitive task, or the same cognitive task made more difficult, with each task being performed while the eyes were open and again while the eyes were closed. The participants performed mental calculations as fast as possible by subtracting either 3 or 18 from a random three-digit number continuously, for the simple cognitive task or the difficult cognitive task, respectively. Each calculation was completed within 10 s. The evaluation indexes used to measure upright posture stability were the root mean square (RMS) of the total body sway in the mediolateral and anteroposterior directions, the mean velocity (MV) value of the total body sway, and the Romberg quotient (RQ) of these values.ResultsThe RMS (p < 0.01) and MV (p < 0.01) values of the upright posture sway were lower when participants performed no cognitive task and their eyes were open than when their eyes were closed. When their eyes were open, compared with no cognitive task, the values of the measures evaluating upright posture sway were higher, meaning the stance was less stable, while performing either the simple or the more difficult cognitive task (RMS: simple task, p < 0.01; difficult task, p < 0.05; MV: simple task, p < 0.01; difficult task, p < 0.01) although no significant differences were detected for the RMS or MV values between the simple and more difficult cognitive tasks. The RQs for both the RMS and the total MV values of the upright posture sway during performance of the difficult cognitive task were significantly lower than when the participants performed no task.ConclusionPerformance of a cognitive task significantly reduced the upright posture balance in adolescents during eyes open although increased task difficulty did not show a greater effect. The interference between the performance of a cognitive task and the visual control of an upright stance may be attributable in part to cognitive and visual processing streams competing for common central resources, consistent with the Multiple Resource Theory of information processing.

Characteristics of solar wind rotation

ABSTRACT Over 54 yr of hourly mean value of solar wind velocity from 1963 November 27 to 2017 December 31 are used to investigate characteristics of the rotation period of solar wind through autocorrelation analysis. Solar wind of high velocity is found to rotate faster than low-velocity wind, while its rotation rate increases with increasing velocity, but in contrast for solar wind of low velocity, its rotation rate decreases with increasing velocity. Our analysis shows that solar wind of a higher velocity statistically possesses a faster rotation rate for the entire solar wind. The yearly rotation rate of solar wind velocity does not follow the Schwable cycle, but it is significantly negatively correlated to yearly sunspot number when it leads by 3 yr. Physical explanations are proposed to these findings.

The value of virtual touch tissue imaging quantification in the differential diagnosis between benign and malignant breast lesions.

To evaluate the value and diagnostic performance of virtual touch tissue imaging quantification (VTIQ) and to determine the optimum cut-off value for differential diagnosis between benign and malignant breast lesions. Conventional ultrasonography (US) and VTIQ were performed in 454 patients with 466 breast lesions with a Siemens Acuson S3000 ultrasound machine. All lesions were assessed by an ultrasound Breast Imaging Reporting and Data System (BI-RADS) and confirmed by histopathology. The maximum, mean, and minimum shear wave velocity (SWV) values were quantitatively measured in m/s within the regions of interest (ROIs) and ranged from 0.5 to 10m/s. The sensitivity, specificity, accuracy, and area under the receiver operating curve (AUC) of the VTIQ, BI-RADS, and combined data were compared. Among the 466 breast lesions, 266 were benign and 200 were malignant. All of the SWV values of the malignant lesions were significantly greater than those of the benign ones (P < 0.05). The optimal cut-off values for SWVmax, SWVmin, SWVmean, and SWVmax/SWVmin obtained from ROC analysis were 5.37m/s, 3.08m/s, 4.04m/s, and 1.83, respectively. Logistic regression analysis revealed that BI-RADS was an independent risk factor for the differential diagnosis of breast lesions, whereas SWV values were not independent risk factors. VTIQ is useful in the differential diagnosis between benign and malignant breast lesions. The combination of VTIQ and ultrasonic BI-RADS can improve the diagnostic performance.

Evaluation of subclinical atherosclerosis by ultrasound radiofrequency data technology in patients with Behçet's disease.

We aimed to evaluate subclinical atherosclerosis based on carotid intima-media thickness (CIMT) and arterial stiffness measurements in patients with Behçet's disease (BD), using ultrasound (US) radiofrequency (RF) data technology. We included 33 BD patients and 33 healthy controls in this study. The participants did not have any primary cardiovascular risk factors, such as diabetes mellitus, hypertension, hyperlipidemia and obesity. All participants were evaluated using Doppler ultrasonography. Arterial stiffness and CIMT measurements were performed in bilateral common carotid arteries using the US RF data technology. The right, left and mean CIMT values were similar between the patient and control groups (P >0.05). There was also no statistically significant difference in the right side α and β stiffness indices despite higher values in the patient group (P> 0.05). The right, left and mean distensibility coefficient (DC) and compliance coefficient (CC) values of the patient group were significantly lower than the control group (P< 0.05). The left and mean α- and β-stiffness indices, and the right, left and mean pulse wave velocity (PWV) values were significantly higher in the patient group (P< 0.05). We found higher mean CIMT and PWV values, and α- and β-stiffness indices in patients with mucocutaneous involvement compared with those with major organ involvement, while the mean DC and CC values were lower in the former. However, these results did not reach a statistically significant level. This study demonstrated evidence of subclinical atherosclerosis in BD in the absence of major atherosclerotic risk factors.

Effect of grid sensitivity on the performance of wall adapting SGS models for LES of swirling and separating–reattaching flows

The present study assesses the performance of the Wall Adapting SGS models along with the Dynamic Smagorinsky model for flows involving separation, reattachment and swirl. Due to the simple geometry and wide application in a variety of engineering systems, the Backward-Facing Step (BFS) geometry and Confined Swirling Flow (CSF) geometry are invoked in the present case. The calculation of the SGS stresses employs three models, namely, the Dynamic Smagorinsky model, the Wall Adapting Local Eddy viscosity (WALE) model and the Dynamic WALE model. For studying the effect of the grid sensitivity, the simulations are performed over two sets of grids with different resolutions based on the non-dimensional wall distance parameter ( y+ ). Grids corresponding to y+= 70 and y+= 20 are employed for the subsonic flow over the BFS while grids corresponding to y+= 40 and y+= 20 are employed for supersonic flow over the BFS and for confined swirling flow geometry. The validation against the experimental results includes the mean flow fields and the turbulent stresses obtained for each case. The results reveal that for the fine grid (y+= 20), the near wall eddy viscosity profile for the WALE model is better than both the Dynamic WALE and the Dynamic Smagorinsky model. The difference between the predictions of the coarse and fine grids for Dynamic Smagorinsky and the WALE model is high whereas, the Dynamic WALE model is almost insensitive to the grid resolutions considered for the present case. The mean velocity and pressure values as well as the turbulent quantities predicted by the Dynamic WALE model are closest to the experimental values for all the cases.

Seasonal, annual, and interannual variability in MLT quasi-two-day waves over the low-latitude region Kolhapur (16.8°N; 74.2°E)

This study presents the quasi-two-day wave (Q2DW) characteristics of the mesosphere and lower thermosphere (MLT) region obtained by taking hourly mean values of horizontal wind velocities for 4 years (August 2013–July 2017) through continuous measurements using a medium-frequency (MF) radar (operating frequency – 1.98 MHz) located at the low-latitude Indian station Kolhapur (16.8°N; 74.2°E). The MF radar located at Kolhapur was upgraded in 2013, and these results of Q2DW have been reported for the first time after upgrading. The present study investigated variability in seasonal, annual, interannual, and solar indices of Q2DWs traveling in zonal (EW) and meridional (NS) components in the MLT region. The Q2DW activity is observed to be stronger during austral summer (January–February) (EW = ∼5 m/s and NS = ∼8–10 m/s) than during boreal summer (June–July) (EW = ∼5 m/s and NS = ∼6–8 m/s). The Q2DW amplitudes are larger in the meridional component than in the zonal one. A strong semiannual oscillation (SAO) has been observed in Q2DWs, with peak during January–February and June–July. In addition, small enhancement is seen in meridional Q2DW in October (∼5–6 m/s). It is observed that the entire spectrum (40–60 h) measured between 86 and 94 km contributes to the SAO amplitudes during January–February and June–July, whereas the waves measured between 42 h and 52 h contribute to enhancement in October similar to that reported elsewhere. In general, the Q2DW amplitude shows large interannual variability. The easterlies developed in the global circulation model in Northern hemisphere during May intensify up to around summer solstice. Q2DW activity peaks during westerly shear zone and intensifies with time at a lower thermospheric altitude (above 90 km). Small positive correlations (r = 0.2 for sunspot number and r = 0.1 for 10.7 cm solar flux) have been observed between Q2DW amplitudes and solar activity.

Evaluation of mean velocity and mean speed for test ventilated room from RANS and LES CFD modeling

The paper presents and discusses data for the ventilation airflow in an isothermal room corresponding to the Nielsen et al. (1978) test computed with Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) approaches. As LES computations provide directly both the speed and velocity components data, the difference between the mean speed and mean velocity values is computed and discussed. For the RANS computations that give the mean velocity data only, application of the velocity-to-speed conversion procedure based on the turbulence kinetic energy field provided by a turbulence model resulted in accurate mean speed evaluation.

Verification of the seismic P-wave velocities under Moho boundary: Central Poland case study, LUMP profile

The tectonic settings investigated by several seismic projects in previous research targeting the structure in Central Poland mainly focused on the Earth’s crust. In this paper, we present P-wave velocity verification in the uppermost mantle beneath LUMP profile towards SSE-NNW. Using recordings of 36 DATA-CUBE recorders from ca. 300–490 km far earthquake in coal mine “Janina” in southern Poland, we calculated travel times to verify P-wave velocity below the Moho boundary from previous studies. It shows that a significantly lower mean velocity value should be used for the upper mantle while counting these offsets of travel times in the SSE-NNW direction than that used on previous profiles. We present two possible models: first, the most simple one that fits the observed first arrivals, and the second with a low-velocity layer beneath the Moho boundary. In both cases, we used a priori crustal model focusing only on P-wave velocity in the uppermost mantle. Both of them significantly improved adjustment of travel times to the observed data. To evaluate the tendency of adopting too high velocities beneath the Moho, we used also 11 broadband stations, Reftek 151-121 “Observer”, from “13 BB Star” passive experiment and 6 STS-2 seismometers from permanent stations of the Polish Seismological Network (PLSN).

On mean flow universality of turbulent wall flows. I. High Reynolds number flow analysis

ABSTRACTThe universality and mathematical physical structure of wall-bounded turbulent flows is a topic of discussions over many decades. There is no agreement about questions like what is the physical mean flow structure, how universal is it, and how universal are theoretical concepts for local and global flow variations. These questions are addressed by using latest direct numerical simulation (DNS) data at moderate Reynolds numbers Re and experimental data up to extreme Re. The mean flow structure is explained by analytical models for three canonical wall-bounded turbulent flows (channel flow, pipe flow, and the zero-pressure gradient turbulent boundary layer). Thorough comparisons with DNS and experimental data provide support for the validity of models. Criteria for veritable physics derived from observations are suggested. It is shown that the models presented satisfy these criteria. A probabilistic interpretation of the mean flow structure shows that the physical constraints of equal entropies and equally likely mean velocity values in a region unaffected by boundary effects impose a universal log-law structure. The structure of wall-bounded turbulent flows is much more universal than previously expected. There is no discrepancy between local logarithmic velocity variations and global friction law and bulk velocity variations. Flow effects are limited to the minimum: the difference of having a bounded or unbounded domain, and the variation range of mean velocity values allowed by the geometry.

SPATIOTEMPORAL CHANGES IN VELOCITY OF MELLOR GLACIER, EAST ANTARCTICA USING LANDSAT-8 DATA

Abstract. Glaciers all over the world are experiencing changes at varying stages due to changing climatic conditions. Minuscule changes in the glaciers in Antarctica can thus have major implications. The velocity of glaciers is important in several aspects of glaciology. A glacier’s movement is caused by different factors such as gravity, internal deformation present in the ice, pressure caused by accumulation of snow, basal sliding etc. The velocity of a glacier is an important factor governing mass balance and the stability of the glacier. A glacier which moves fast generally brings more ice towards the terminus than a slow moving glacier. Thus, the glacier velocity can determine its load carrying capacity and gives indication on the ‘health’ of the glacier. Measurement of the ice flow velocity can help model glacier dynamics and thus provide increasing insights on different glacier subtleties. However, field measurements of velocity are limited in spatial and temporal domains because these operations are manual, tedious and logistically expensive. Remote sensing is a tool to monitor and generate such data without the need for physical expeditions. This study uses optical satellite imagery to understand the mechanisms involved in the movement of a glacier. Optical image correlation method (COSI-Corr module) is chosen here as the promising method to derive displacement of a moving glacier. The principle involved in this technique is that two images acquired at different times are correlated to find the shift in the position of moving ice, which is then treated as displacement in the time interval. Employing this technique we estimated the velocity of Mellor glacier (73°30′S, 66°30′E), a tributary glacier of the Amery Ice Shelf, Antarctica, over a span of four years from 2014 to 2017. Correlation is performed using Landsat-8 panchromatic images of 15 m resolution. Optical images from Landsat 8 often have noise due to atmospheric conditions such as cloud cover, so we used only those images cloud with cloud cover less than 10%. The glacier is covered in 128 path frame and 112 by Landsat-8. The correlation frequency was calculated using the correlator engine. Window size taken here is 256 and step sizes is 64 for both x and y dimensions. Once the correlation is calculated for an image pair for a specific time-period, we obtain three different outputs. Two of them indicated displacement (one in x direction and another in y direction) and the remaining output provided signal to noise ratio. The band math tool using displacement outputs in ENVI software performed velocity calculations. This gives us a raster image showing velocity at each point or pixel. Some errors such as noise persist and their correction is performed in ArcGIS software. In order to get pure signals, we removed all the signals with a signal to noise ratio less than 0.9 and this was carried out using raster calculator tool. All the resultant velocity rasters were interpolated and bias was calculated between seasons of two consecutive years. Two maps were generated for each year, one for early summer i.e. from January to April and one from September to December using the resultant velocity raster. The mean values of velocities found for Mellor glacier from Jan-April 2014, 2015, 2016 and 2017 were 374.06 ma−1, 413.59 ma−1, 278.62 ma−1 and 406.66 ma−1, respectively. Velocities for September-December 2014, 2015, 2016 and 2017 were found to be 334.63 ma−1, 334.43 ma−1, 367.37 ma−1 and 381.31 ma−1, respectively. The biases are computed for all the seasons of four years and root mean square (RMSE) values are estimated. These RMSE values signify the season-wise variations in the velocities. RMSE values for season of Jan–April 2014–15, 2015–16 and 2016–17 were 75.92 ma−1, 147.82 ma−1, and 133.33 ma−1, respectively. Similarly, RMSE values for season of September-December 2014–15, 2015–16 and 2016–17 are 35.7 ma−1, 51.29 ma−1 and 35.84 ma−1 respectively. The results showed variations in velocities for different seasons. We plan to integrate this data with the discharge rates, to estimate mass balance and melting rates of the glacier to decipher mechanisms at work for the Mellor glacier.

Impact of hydrodynamics on clay particle deposition and biofilm development in a labyrinth-channel dripper

To better understand the physical and biological clogging in drip-irrigation, a study was conducted on the impacts of hydrodynamic conditions on clay particle deposition and biofilm development in drippers using an optical method. A transparent milli-fluidic system composed of labyrinth channels was used to identify areas most susceptible to particle clogging using two different types of clay suspensions: sodium bentonite and kaolin. The impact of salt addition [(NaCl) = 200 mg L− 1] on the clay deposition was also analyzed. Biofilm development was studied using the same methodology using a nutritive solution (chemical oxygen demand, COD = 200 mg L−1). In addition, fluid dynamics simulations were performed along the labyrinth channel to understand the effect of flow behaviour on the fouling. Computational fluid dynamics results show two types of flow topology: high velocity in the main flow (around 1 m s− 1) and low velocity in the vortex zones (less than 0.2 m s− 1) found in the channel corners. Using an optical method, kaolin deposition and biofilm growth in the dripper were observed to occur mainly in the inlet channel and initial vortex zones, which are characterized by lower mean velocity and turbulent kinetic energy values. This part of the dripper can be considered as a bottleneck that amplifies the fouling phenomena and which should be optimized. With the addition of NaCl, kaolin particles tend to form bigger flocs. Therefore, more significant particle deposition is observed, but this is not the case of bentonite for which no fouling is observed along the dripper.

Evaluation of a Healthy Pregnant Placenta with Shear Wave Elastography

Background: The placenta is a soft organ with vital importance. Increased placental stiffness was reported in pathological conditions emerging during pregnancy, such as diabetes mellitus and hypertension. Nowadays, placental stiffness can be quantitatively measured using the shear wave elastography (SWE) technique. Objectives: We aimed to assess the factors affecting elasticity by finding the normal elastogram values of healthy pregnancy placentas using the SWE technique due to the importance of early diagnosis in risky pregnancies. Patients and Methods: In total, 288 healthy pregnant women in the second or third trimester were included in our prospective study. The pregnant women who had pathology in their fetus and its appendices or a posteriorly located placenta were excluded from the study. Obstetric ultrasonography and a placental elasticity assessment were performed in all the pregnant women. Speed values were obtained from five different locations of the placenta, including the central S1, S2, S3, S4 and peripheral P regions. The elasticity of the regions were compared, and the factors affecting elasticity were investigated. Results: There were significant differences among the velocity values obtained from five different areas of the placenta. The mean velocity values obtained from the central region were higher than those of the peripheral region (P < 0.001). There was also a significant difference in the mean velocity measurements obtained from the central region (P < 0.001). The hardest region of the placenta was the maternal surface, while the softest region was the peripheral surface. The elastographic velocity values of the placenta were found to correlate with maternal age, body mass index, placental localization, thickness, and grade, whereas it did not correlate with gravidity, parity, gestational week, and amniotic fluid index . Conclusion: The elasticity of the placenta varied according to the region and surface, whereas it did not change according to gestational week. It may be convenient to use the elasticity values obtained by SWE from specified regions in the follow-up of placentas in high-risk pregnancies. However, considering the affecting factors and contradictory study results, a large number of large-scale studies is required to strengthen the efficiency of SWE in the placental assessment.

Correlation between histopathological grading and shear-wave elastography in evaluating invasive carcinoma of no special type.

The present study aimed to investigate the correlation between histologic grade and shear-wave elastography in evaluating invasive breast carcinoma of no special type (NST). A total of 84 breast lesions in 80 patients (age range, 32–64 years) were retrospectively evaluated. The patients underwent B-mode ultrasound and virtual touch tissue quantification diagnosis. A semi-quantitative method was then applied in order to determine the histologic grade of the invasive carcinoma of NST according to the grading system published by the World Health Organization. Among the 84 breast lesions, 14 (16.7%) were classified as Grade I, while 29 (34.5%) and 41 (48.8%) were determined to be of Grade II and Grade III, respectively. The size of the breast lesions increased with the increase in histological grade (P<0.001). In addition, 29.3% of the Grade-III breast lesions exhibited acoustic enhancement, while the majority of the Grade-I breast lesions (78.6%) exhibited acoustic shadowing (P=0.002). Furthermore, a higher histopathological grade was closely correlated with a higher mean, minimum and maximum shear-wave velocity value (P<0.05). In conclusion, regarding the evaluation of invasive breast carcinoma of NST, the histologic grade was strongly correlated with tissue stiffness; a higher histologic grade was associated with a harder lesion. Therefore, shear-wave elastography may provide important clinical reference values.

Hemodynamics in diabetic human aorta using computational fluid dynamics.

Three-dimensional (3D) computational aortic models have been established to reproduce aortic diseases such as aortic aneurysm and dissection; however, no such models have been developed to study diabetes mellitus (DM). To characterize biomechanical properties of the human aorta with DM, reconstructed aortic CT images were converted into DICOM format, and imported into the 3D segmentation using Mimics software. This resulted in a 3D reconstruction of the complete aorta, including three branches. We applied a pulsatile blood pressure waveform for the ascending aorta to provide a biomimetic environment using COMSOL Multiphysics software. Hemodynamics were compared between the control and DM models. We observed that mean blood flow velocity, aortic pressure, and von Mises stress values were lower in the DM model than in the control model. Furthermore, the range of aortic movement was lower in the DM model than in the control model, suggesting that the DM aortic wall is more susceptible to rupture. When comparing biomechanical properties in discrete regions of the aorta, all values were higher in the ascending aorta for both control and DM models, corresponding to the location of most aortic lesions. We have developed a compute based that integrates advanced image processing strategies and computational techniques based on finite element method to perform hemodynamics analysis based on CT images. Our study of image-based CFD analysis hopes to provide a better understanding of the relationship between aortic hemodynamic and developing pathophysiology of aortic diseases.

Velocity and stretch characteristics at the leading edge of an aerodynamically stabilized flame

High swirl flows with vortex breakdown are frequently used to create recirculating flow regions for flame stabilization. This paper experimentally characterizes flame stabilization in such flows, motivated by the fact that conditions under which they enable (or do not enable) aerodynamically stabilized flames are not well understood. Such flames are substantially more difficult to experimentally characterize than shear layer stabilized flames, as the flame leading edge moves around significantly and may or may not coincide with a diagnostic laser sheet, in contrast to the near-fixed leading edge of shear layer stabilized flames. This paper characterizes the leading edge conditions, based upon simultaneous stereo Particle Image Velocimetry (sPIV), OH Planar Laser-Induced Fluorescence (PLIF) and OH* chemiluminescence data. Frames are conditionally analyzed when the flame's most upstream point was captured in the laser sheet. These conditioned frames were used to determine the coordinates, local flow velocity and full, three-dimensional, hydrodynamic strain component of flame stretch at the dynamically evolving flame leading edge. Results are taken at two conditions, 70 m/s and 45 m/s axial velocity, referred to as case 1 and 2, respectively. These data show that the leading edge of the flame precesses off-axis, with additional uncorrelated radial and axial motions. The conditioned mean flame stretch rate is positive in both cases, due to the bulk flow deceleration from the high velocity nozzle flow into the larger diameter combustor. Mean strain or velocity values conditioned on the leading flame edge are substantially different from mean values calculated at the same location. For example, the case 1 mean conditioned axial velocity at the flame leading edge is 9 m/s, while the mean axial velocity at the same location is 4 times higher, 36 m/s. In addition, the case 1 mean hydrodynamic strain rate is 3.6 times higher than the corresponding laminar flame extinction stretch rate, κext, calculated from detailed kinetics for the high velocity case, while less than half of κext in case 2. The mean strain rate predicted from bulk velocity scaling changes by a factor of 70/45 between the two cases, a value confirmed by measurements. However, the conditioned mean stretch values differ by a factor of 14. This result illustrates that additional work is needed to understand stretch scalings in such flames. Furthermore, they show that current correlations for flame stability do not capture much of the intermittency that is present in swirl flows with precessing flow features, and illustrates the need for continued work in very basic physics of how and when flames are stabilized aerodynamically.

Comparison of the Velocity and Power Parameters During Loaded-Squat Jump Exercise of National Athletes in Different Branches

The aim of this investigation is to compare velocity and power variables during loaded-squat jump (SJLoaded) exercise of national athletes dealing with different sports branches and to identify whether velocity and power parameters become different or not according to branches. In accordance with this purpose, a total of 36 national athletes (age: 20.3±1.68 years; height: 173.5±6.46 cm; weight: 72.3±10.29 kg) composed of 12 wrestlers (age: 19.5±.90 years; height: 172.3±6.19 cm; weight: 75.5±13.9 kg), 12 arm wrestlers (age: 20.5±2.02 years; height: 174.7±4.76 cm; weight: 72.6±8.31 kg) and 12 kickboxers (age: 20.7±1.81 years; height: 173.5±8.29 cm; weight: 68.9±6.94 kg) dealing with different sports branches have voluntarily participated in this study. For identifying velocity and power parameters, SJLoaded exercise was executed with an external load that corresponds to 40% of body weights of the athletes by utilizing an isoinertial velocity transducer (T-Force dynamic measurement system) and values of mean velocity (MV), mean propulsive velocity (MPV), peak velocity (PV), mean power (MP), mean propulsive power (MPP) and peak power (PP) were determined. All data analyzes were performed in the SPSS 16.0 statistical program. Firstly, in order to analyze data, it was determined that the data indicated normal distribution by looking at the Shapiro-Wilk coefficient regarding the normality of the distribution of the data. Therefore one-way analysis of variance (One-way ANOVA) was utilized to identify statistical significant differences among athletes competing in different branches with regard to the velocity and power variables during the SJLoaded exercise. According to analyze results, no statistical significant difference wasn’t seen among branches with regard to MV [f (2.33) = 1.306], MPV [f (2. 33)=2.195], PV [f (2. 33)=2.242], MP [f (2. 33)=1.225], MPP [f (2. 33)=2.787] and PP [f (2. 33)= 2.607] parameters during SJLoaded exercise (p&gt;0.05). The velocity and power parameters obtained in the SJLoaded exercise don’t differ according to the branches.

Analysis of the IAEA benchmark on heat transfer in a 4 × 4 rod bundle with mixing grid

The IAEA is organizing a Coordinated Research Project (CRP) on the application of Computational Fluid Dynamics (CFD) for nuclear reactor design. Within this CRP, an open benchmark is organized on fluid mixing in rod bundles. KAERI has offered precise experimental data of the velocity field downstream of a mixed twist/split type mixing grid. Additionally, temperature measurements in various axial and azimuthal locations of a partly heated rod were made available by KAERI. The experimental set up consists of a 2000 mm long bundle of 4 × 4 rods with pitch to diameter ratio of 1.35, placed in a square housing of 142 × 142 mm. Each rod has a diameter of 25.4 mm. The mixing grid is located at 2/3 height of the channel with 5 spacer grids located upstream and 3 downstream of the mixing grid. These experiments are analysed with the TrioCFD code. Turbulence is treated with the RANS approach by using a non-linear eddy viscosity model. The comparison of measured and calculated mean velocity fields is presented. Measured profiles of velocity mean values were calculated correctly for the central sub-channel and the gap of rod-to-rod both close and far from the mixing grid. The measured temperature is underestimated by the calculations, on one hand due to the localization of the thermocouples inside the wall of the rod and on the other hand due to the used thermal boundary condition called “imposed heat flux”. A first order correction procedure helps to understand the detected discrepancy between experiment and calculation.

Velocity distribution of women's 30-km cross-country skiing during Olympic Games from 2002-2014.

Within several investigated endurance sport disciplines the distribution of load of the best competitors has a manner of evenly or slightly rising velocity values. Unfortunately many other competitors have usually diminishing values or when they are very poor they have evenly values. The aim of this study was to investigate distribution of velocity within 30-km cross-country female skiers. Cross-country skiing runs were investigated of Olympic Games 2002-2014 (Salt Lake City, Turin, Vancouver, Sochi). At every race two 15 km or three 10 km loops of the same vertical profile were taken into account. The competitors were divided onto: A) winners; B) medalists; C) competitors who obtained places 4 to 10 at the finish line (medium runners); and D) competitors who obtained places 11 to 30 at the finish line (poor runners). Velocity data presented on the web pages of several institutions were utilized. The competitors had their velocity distributed in a manner with usually diminishing values. While comparing velocity of sequential loops with the mean velocity the difference for the poor runners reached the value of almost 6%, which was too high. There was significant (usually negative) correlation coefficient between values of velocity deviation for the first and second loops and the mean value of velocity for the entire distance for the better runners and mixed, i.e. positive and negative values for the poorer runners. It was postulated investigations of velocity distribution should be introduced in coaching in order to inform competitors about their running. This advises is especially important for the poorer runners. Up to now cross-country skiers run for themselves. It should be discussed whether the tactics used by road and track runners, i.e. running with pace makers, can be introduced in cross country skiing. Also the use of a drone during training can be used in order to maintain proper pace.