Deceleration Zone Research Articles

Study of the Impact of Initial Moisture Content in Oil Impregnated Insulation Paper on Thermal Aging Rate of Condenser Bushing

This paper studied the impact of moisture on the correlated characteristics of the condenser bushings oil-paper insulation system. The oil-impregnated paper samples underwent accelerated thermal aging at 130 °C after preparation at different initial moisture contents (1%, 3%, 5% and 7%). All the samples were extracted periodically for the measurement of the moisture content, the degree of polymerization (DP) and frequency domain dielectric spectroscopy (FDS). Next, the measurement results of samples were compared to the related research results of transformer oil-paper insulation, offering a theoretical basis of the parameter analysis. The obtained results show that the moisture fluctuation amplitude can reflect the different initial moisture contents of insulating paper and the mass ratio of oil and paper has little impact on the moisture content fluctuation pattern in oil-paper but has a great impact on moisture fluctuation amplitude; reduction of DP presents an accelerating trend with the increase of initial moisture content, and the aging rate of test samples is higher under low moisture content but lower under high moisture content compared to the insulation paper in transformers. Two obvious “deceleration zones” appeared in the dielectric spectrum with the decrease of frequency, and not only does the integral value of dielectric dissipation factor (tan δ) reflect the aging degree, but it reflects the moisture content in solid insulation. These types of research in this paper can be applied to evaluate the condition of humidified insulation and the aging state of solid insulation for condenser bushings.

Variation of bulk Lorentz factor in AGN jets due to Compton rocket in a complex photon field

Radio-loud active galactic nuclei are among the most powerful objects in the universe. In these objects, most of the emission comes from relativistic jets getting their power from the accretion of matter onto supermassive black holes. However, despite the number of studies, a jet's acceleration to relativistic speeds is still poorly understood. It is widely known that jets contain relativistic particles that emit radiation through several physical processes, one of them being the inverse Compton scattering of photons coming from external sources. In the case of a plasma composed of electrons and positrons continuously heated by the turbulence, inverse Compton scattering can lead to relativistic bulk motions through the Compton rocket effect. We investigate this process and compute the resulting bulk Lorentz factor in the complex photon field of an AGN composed of several external photon sources. We consider various sources here: the accretion disk, the dusty torus, and the broad line region. We take their geometry and anisotropy carefully into account in order to numerically compute the bulk Lorentz factor of the jet at every altitude. The study, made for a broad range of parameters, shows interesting and unexpected behaviors of the bulk Lorentz factor, exhibiting acceleration and deceleration zones in the jet. We investigate the patterns of the bulk Lorentz factor along the jet depending on the source sizes and on the observation angle and we finally show that these patterns can induce variability in the AGN emission with timescales going from hours to months.

High‐speed imaging of Strombolian eruptions: Gas‐pyroclast dynamics in initial volcanic jets

AbstractHigh‐speed imaging of Strombolian explosions brings into view the motion of pyroclasts upon leaving the volcanic vent. The erupted gas‐pyroclast mixtures form jets with well‐defined leading vortex rings that rise at almost constant velocity proportional to the time‐averaged velocity of pyroclasts. The ejection velocity of pyroclasts decreases over time and defines a conical profile centered on the jet central streamline. Pyroclast deceleration patterns are related to their velocity and compatible with drag force but are also strongly controlled by jet dynamics. These patterns include constant, decreasing, or abruptly increasing decelerations up to 104 m s−2. Nonuniform deceleration focuses at the jet sides and, mostly, in a narrow zone across the vortex ring. This deceleration zone is trailed by a reduced drag zone, where deceleration is drastically reduced. In these highly transient eruptions, both zones move upward and attenuate over time. Our results provide the first quantitative mapping of reduced drag zones.

An Examination of the Relationship Between Movement Demands and Rating of Perceived Exertion in Australian Footballers

This study aimed to determine whether a relationship existed between movement demands, match events, and perceptual match load, as determined by rating of perceived exertion (RPE) in professional Australian footballers. The movement variables were collected between 1 and 22 times using global positioning system units from 21 players during the 2011 and 2012 Australian Football League seasons. A range of movement demands and match events were collected to obtain a complete insight into the physical demands and work rates of these athletes. These data were separated into the high-load (HL, ≥9) and low-load (LL, ≤8) RPE groups. A Mann-Whitney U-test, independent samples t-test, and effect sizes were used to determine whether any differences existed between the 2 groups and the size of the difference. The results revealed that the HL groups covered more distance, spent more time, and produced more efforts at the high deceleration zone (2.4-6.7%). Further, the HL group had more possessions and disposals of the football than the LL group (9.2-29.6%). The findings have highlighted the importance of monitoring accelerations, decelerations, and instantaneous power outputs to obtain a comprehensive insight into the physical demands placed on team sport athletes. Furthermore, the results demonstrate that training sessions should involve a focus on drills that are composed of both skill development and physical stimulus element.

Deceleration efficiencies of shrub windbreaks in a wind tunnel

Abstract Artemisia and Salix are dominant shrub species for windbreaks in arid areas of China, and they show similar features to shrubs in other arid areas of the world. We compared the mean velocity fields and shelter effects of two shrub windbreaks with different layouts. For a single plant of Artemisia, the higher the free airflow velocity is, the more the wind velocity around two sides of the plant increases. The velocity gradient around a single plant of Salix is smaller than that around an Artemisia plant due to the difference in the plant shapes. Seven new velocity zones in the horizontal direction appear when airflow passes through an Artemisia windbreak, including four deceleration zones and three acceleration zones. The mean velocity field that is affected by a Salix windbreak can be divided into a deceleration zone in the front, an acceleration zone above, a vortex zone behind and a restoration zone downwind of the vortex zone. Shelter effects of the shrub windbreaks vary with the wind velocity and are influenced by the construct of the windbreaks. Shrub windbreaks that have a complex construction have better shelter effects than simple ones. The shelter effects of plant windbreaks are also influenced by the growth features of the plants. Considering the plant characteristics and the shelter effects of Salix and Artemisia windbreaks, it is optimal to plant these two windbreaks together in a sand-control system. This research is intended to be useful for sand movement control in arid areas.

Experimental investigation of a pulse line ion accelerator in Lanzhou

In order to put the Pulse Line Ion Accelerator (PLIA) concept to its practical application, a small experimental platform was built. It was found that the actual axial electric field is smaller than the theoretical calculation, so the accelerated ions will enter into the deceleration zone before leaving the helix, which will seriously affect the acceleration process. Based on the improved parameters, the He+ with 24 keV is accelerated to 55 keV, and the proof-of-principle experiment is completed on this platform.

A Distinct Patch of Road Visual Guidance System – The Design of 2D Stereo Deceleration Zone

City Visual Guidance System is the standard of communication in the order life, to the general, text and images can express all kinds of city mark, but the traffic signs which contains specific information need trained drivers through several conversion, which response delay time enough impacted on traffic safety, such as setting the hard deceleration strip on the road. This thesis presents the design of 2D stereo deceleration zone, with plane logo produced the stereo image effect, this active and timely means can ensure the driving safety, and does not damage the vehicle, also can be used for the extension, is a distinct patch of Road Visual Guidance System.

In-line monitoring of particle size in a fluid bed granulator: Investigations concerning positioning and configuration of the sensor

According to the ICH Q8 guideline, analytic technologies (PAT) are important tools for characterization and optimization of pharmaceutical manufacturing processes. Particle size as a critical quality attribute for granules is therefore an important parameter that should be monitored during the fluid bed granulation process. This work focusses on optimizing position and configuration of an SFT-sensor for the in-line measurement of particle size distribution in a Glatt GPCG 3 fluid bed granulator. As model-substances, different grades of microcrystalline cellulose were used. The in-line measured particle size and particle rate in the sensor were evaluated. A sensor position in the deceleration zone of the granulator was found to be promising for in-line particle size measurement. Most reliable data were generated in this position when the probe was placed in a distance of 11cm from the chamber wall to avoid bias by the inlet air stream. No major influence of rotation angle of the probe was found in this position. Furthermore, an entire fluid bed granulation process was successfully monitored with the sensor installed in the optimized setting.

Hydrodynamic experiments on dacryoconarid shell telescoping

It is not uncommon that small conical dacryoconarid shells are found inserted one into another. Although this phenomenon has been studied for decades, and interparticle collisions in turbulent flows have largely considered to be responsible, no satisfactory explanation has been provided. We performed experiments under laboratory conditions using narrow aluminium cones as replicas of these shells. Two different flow regimes were tested to mimic the probable hydrodynamic conditions in the ocean. First, large-scale rhythmic back and forth coherent motion of water over the seabed was reproduced in an oscillating sloshing tank (sloshing mode). Second, small-scale irregular stirring motion in turbulent bulk was imitated in cylindrical containers placed into a shaker (mixing mode). With sloshing, a high production of irreversibly telescoped cones was present in clear water and at driving frequencies comparable to the upper limits known for sea waves. With shaking, both coalescence and break-up of the cones were observed, as the quasi-random hydrodynamic forces generated by vigorous liquid motion were roughly comparable with the mechanical forces holding the cones together. However, the stability of the clusters of telescoped cones in the shaker could be enhanced with the addition of fine solid particles (suspended silt). In addition, a simple mathematical model was suggested for the flow interaction with a submerged conical particle in the case of the sloshing mode, providing an interesting insight into the evolution of strong deceleration zones.

Multiple Sprint Exercise with a Short Deceleration Induces Muscle Damage and Performance Impairment in Young, Physically Active Males

Multiple Sprint Exercise with a Short Deceleration Induces Muscle Damage and Performance Impairment in Young, Physically Active Males The purpose of the present study was to identify whether a bout of high-intensity multiple sprints elicits exercise-induced muscle damage (EIMD) of a similar magnitude to drop jumps. Methods: Ten physically active male volunteers (mean ± SD; 27 ± 3 y, 1.78 ± 0.06 m, 78.4 ± 7.5 kg) completed 10×10 drop jumps (DRP) and a bout of 40×15 m sprints with a 5 m deceleration zone (SPR) in a randomised repeated-measures crossover study. Muscle damage indices (creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), perceptual soreness and affective valence, range of motion and limb girth) and performance markers (vertical jump, agility and sprint performance) were gathered at baseline and 1, 24, 48 and 72 h post exercise. Results: The study findings revealed a significant Test by Time interaction for 15 m sprint performance (P 0.05). Conclusion: This study indicates that a bout of multiple sprints with a short deceleration phase elicits greater reductions in sprint performance than drop jumps. This should be considered by individuals using similar sprint protocols in an applied context and by individuals looking to conduct research into EIMD using ecologically valid exercise protocols.

NC가공에서 허용오차를 고려한 가공속도 최적화에 관한 연구

Article history: In numerical control (NC) machining, a machining error in equipment generally occurs for a variety of reasons. If there is a change in direction in the NC code, the characteristics of the automatic acceleration or deceleration function cause an overlap of each axis of the acceleration and deceleration zones, which in turn causes a shift in the actual processing path. Many studies have been conducted for error calibration of the edge as caused by automatic acceleration or deceleration in NC machining. This paper describes a geometric interpretation of the shape and processing characteristics of the operating NC device. The paper then describes a way to determine a feedrate that achieves the desired tolerance by using linear and parabolic profiles. Experiments were conducted by the validate equations using a three-axis NC machine. The results show that the machining errors were smaller than the machine resolution. The results also clearly demonstrate that the NC machine with the developed system can successfully predict machining errors induced with a change in direction.

On the creation of wall shear stress by helical flow structures in stented coronary vessels

AbstractThe post-operative situation in a stented vessel is characterised by struts which extend into the vessel lumen. These barriers on the surface provoke a topological change of the blood flow inducing flow deceleration and stagnation zones. Low values of wall shear stress (WSS) especially up- and downstream of the struts are found accordingly. Clinical studies correlate the occurrence of complications like restenosis and thrombosis with the alteration of the spatial WSS distribution. In this study 3D computational models were used to characterise the flow topology of three different stent types. For this purpose steady state simulations of the flow field within a simplified stented coronary artery were performed. The stent types differ in their strut patterns so that the variation of the induced flow structures can be observed. The aim of these investigations is to evaluate the effect of a purposeful flow control by altering the design of the struts. An improved alignment of the struts will be able to guide the flow to benefit the spatial WSS distribution. To compare the performance of the different stent types the size of the area charged with a WSS value below 0.5 Pa is used as a criterion. We will demonstrate that those strut pattern which generate helical flow structures significantly reduce the critical region of low WSS values.

Development of a multiple opposing jets’ burner for premixed flames

A burner was developed to accommodate multiple opposing premixed flames, where the turbulence stimulated by impingement was found to extend the stability limits of methane/air mixtures. The opposing jets established closed loop flow currents in a number of sectors, which is twice that of the jets thus providing more eddies within a stronger turbulent flame structure. The stagnation zone for four opposing jets was testified to be larger than that for two jets such that it was able to sustain higher reactive jet velocities up to 14.2 m/s at larger flow shearing rates. Increasing the number of opposing jets and decreasing their separation distance provided higher rates of heat/mass transfer into the ports. As the flow deceleration zone was enlarged, the correspondingly higher burning capacities were correlated to the port diameter, the separation distance, the number of jets, Reynolds number, and the strain rate. Strain rates of growing magnitudes up to 13,080 s−1 were sustained at jet velocities as high as 21.8 m/s. At such velocities and upon increasing the ratio of the jet diameter to the separation distance, the turbulent kinetic energy was found to exhibit one local peak, as the strain rate due to impingement became enriched by the jet radial shearing effects. A lean blowout equivalence ratio of 0.59 was pronounced as a basis for acquiring low NO x emissions. The burner serves as a potential prototype for increasing the power-to-weight ratio of the combustion chambers like those utilized in furnaces, boilers, gas turbines, as well as jet-propelled vehicles with effectively minimized emissions of pollutants.

Modeling the freestream parameter effect on unsteady boundary layers with positive pressure gradients

The dynamic and thermal parameters of steady and unsteady wall boundary layers are studied on the basis of a two-equation turbulence model under high freestream turbulence intensity and the action of a longitudinal pressure gradient. The freestream parameter effect on the development of dynamic and thermal processes in a steady developed turbulent boundary layer in the flow deceleration zone with a positive pressure gradient is investigated using the modified K-ɛ model. The boundary layer structure is studied and the calculated profiles of the velocity and the kinetic energy of turbulence are compared with the experimental data for the preseparation region. The possibility of the theoretical description of developed turbulent regimes by a quasi-steady turbulence model in the case of periodic temporal dependence of the freestream velocity is shown. An analysis of the calculated parameters of the dynamic and thermal unsteady turbulent boundary layers makes it possible to determine their properties at different oscillation parameters for regions with both zero and positive pressure gradients. The numerical results are compared with experimental data.

The effect of water immersion on the recovery of team-sport-specific exercise

Introduction: The purpose of the present study was to examine the effects of two hydrotherapy techniques, cold water immersion (CWI) and contrast-water therapy (CWT), on the recovery of team-sport-specific exercise tests following muscle-damaging exercise. Methods: Seven male, team-sport players (mean±SD age: 21±2 y, body mass:76.8±7.2 kg) completed a preliminary familiarisation trial for three team-sport-specific exercise tests (TESTS), which included an all-out 30-m sprint test, two agility T-tests (left and right) and a vertical jump test. Three experimental trials were subsequently carried out, each separated by one week, using a counter-balanced cross-over design. On each visit a resting fingertip blood sample and a rating of perceived muscle soreness (PMS) was collected. Participants then performed the TESTS, followed by a 5-min rest period. A repeated sprint exercise (RSE) protocol was then performed to induce muscle damage, which comprised of 15 × 30-m sprints with a 10-m deceleration zone. Sprints were separated by 1 min. A second fingertip blood sample and PMS score was collected immediately after the RSE and a second set of TESTS were performed 10 min after the RSE. Participants then received either CWI, CWT or no water immersion (CON). The next day (24–28 h later) a final fingertip blood sample and PMS score was collected and a final set of TESTS were completed. Results and conclusion: There were no changes in plasma CK over time and no significant interaction effects between the three intervention groups (P > 0.05). The PMS increased from baseline to 24–28 h in the CON group (P 0.05). The PMS was significantly higher for CON compared with CWT after 24–28 h (P 0.05). There were no significant differences in performance during the TESTS between the three intervention groups across any of the three time points (pre RSE, post RSE or after 24–28 h; P > 0.05). These data suggest that the RSE may not have induced sufficient muscle damage to increase plasma CK levels, which may explain why the recovery interventions did not have a significant effect on performance of the TESTS. However, the differences in PMS changes indicate that hydrotherapy may be effective in suppressing the perception of muscle soreness when biochemical and performance markers are unchanged.

A Discretion Algorithm of S-Curve Acceleration and Deceleration

A new method of sampled-data S-curve acceleration/deceleration for industrial robots and CNC machine tools was put forward, which can deal with the low velocity zone called “tail” in a deceleration zone. The equations of acceleration and deceleration were detailed, which improved the productivity by avoiding the calculation of the deceleration point at every sampled time. According to the distance of the trajectory, the trajectory can be divided into normal block, short block I type and short block II type. Aiming at each block, the equations of distance, acceleration, velocity and Jerk were given and the discrete equation of each method was presented. We have implemented our algorithm in both simulation environment and real CNC systems and conducted a series of experiments. The experimental results demonstrate that the proposed method is effective.

Measurement and Comparison of Acceleration and Deceleration Zones at Traffic Control Intersections

Acceleration and deceleration characteristics are basic driving behaviors that influence signal control and road geometry. Most previous studies focused on acceleration and deceleration rates under ideal conditions, i.e., on characteristics of lead vehicles, which might not adequately reflect the full spectrum of traffic operations. This paper presents a methodology for determining acceleration and deceleration rates and zone lengths for vehicles approaching and leaving intersections under likely uncongested traffic conditions, regardless of queue position. These characteristics are derived from speed profiles gained from vehicles equipped with Global Positioning System (GPS) instrumentation. With the speed profiles obtained from GPS-equipped vehicles, a series of data-processing algorithms is developed to measure the acceleration and deceleration behavior of vehicles approaching and departing an intersection. Acceleration and deceleration rates and zone lengths are estimated for several road categories. These zone lengths are compared with recommended values from AASHTO's A Policy on Geometric Design of Highways and Streets (Green Book), in which it is seen that the zone lengths under light traffic conditions are longer than the Green Book's values. In addition, determined acceleration and deceleration rates and zone lengths are found to depend on the underlying assumptions and calculation methods of the analysis.

Exercise-Induced Muscle Damage Following a Bout of Sport Specific Repeated Sprints

Exercise-induced muscle damage (EIMD) is a popular area of investigation; however, many of the existing methods to induce muscle damage lack specificity to a sporting context. The aim of this investigation was to examine the extent of damage precipitated from a sport-specific, repeated sprint protocol and therefore elucidate its suitability as an appropriate model to investigate EIMD. Twenty male subjects (age 22 +/- 2 years, height 178 +/- 6.6 cm, mass 84.6 +/- 13.6 kg in mean +/- SD) volunteered. Following a standardized warm-up, they conducted 15 x 30 m sprints with a 10-m deceleration zone in which subjects were required to come to a complete halt; each repetition was separated by 60 seconds of rest. Maximum isometric force (MVC), serum creatine kinase activity (CK), muscle soreness (DOMS), and limb girth were taken immediately before and at 24 hours, 48 hours, and 72 hours after exercise to elucidate the extent of muscle damage. There were significant time effects for all dependent variables. CK and DOMS were significantly elevated above baseline for 72 hours postexercise (p < 0.05), whereas MVC was significantly lower and limb girth remained significantly elevated for 48 hours postexercise (p < 0.05). These data show that the repeated sprint protocol with a rapid deceleration precipitates significant levels of damage in the days following the exercise bout and therefore may be used as a suitable alternative to examine the damage response from a sport specific repeated sprint mode of exercise.

Computer simulation of EHD flows in a needle-plane electrode system

Complex investigation of the structure of electrohydrodynamic (EHD) flows in a needle-plane electrode system is carried out on the basis of analysis of experimental data and the results of computer simulation. An algorithm of iterative simulation of the volume charge distribution in a fluid is developed. Simulation is carried out using the ANSYS system. The fields of velocities and pressures, as well as electric characteristics of EHD flows, are calculated. Analysis of the results reveals a number of features of EHD flows in the electrode system under investigation. Peculiarities of the band structure are determined, and the characteristic size of the low-pressure zone near the active electrode, as well as the sizes of the acceleration and deceleration zones of the fluid in the electrode gap, is determined.

Wear behaviour of zinc-based alloys as influenced by alloy composition, nature of the slurry and traversal distance

In this study, the influence of microstructural alterations brought about by adding silicon on the slurry wear behaviour of a zinc-based alloy has been investigated. Wear tests were conducted using sample rotation method at a speed of 4.71 m/s over a range of traversal distance and sand concentration in the test environment. The electrolyte (i.e. liquid part of the slurry) contained chloride and sulphate ions which are essential constituents of mine water. The study suggests maximum wear loss and rate of the samples in the liquid-only medium. The presence of suspended sand particles in the liquid led to substantially decrease the wear rate/loss. A comparison of the wear response of the samples in the liquid plus sand environments showed that intermediate concentration, i.e. 40%, of the suspended sand particles in the test environment caused maximum wear rate/loss. However, this was substantially less than the liquid-only medium. The wear loss increased with traversal distance. The slope of the wear loss versus traversal distance plots was high initially followed by a reduced slope at longer traversal distances. This trend was very clearly visible in the liquid-only environment. Increasing traversal distance initially led to higher wear rate. This was followed by the attainment of a wear rate peak, a reduction in wear rate and finally a steady state wear rate at longer traversal distances. The average (cumulative) wear rate versus average (cumulative) wear loss plots showed acceleration, steady state and deceleration zones depending on the test conditions. Silicon particles, generated as a result of silicon addition in the alloy system, led to improved wear behaviour. Observed wear characteristics of the samples have been explained on the basis of operating wear mechanisms such as corrosion, erosion and abrasion. Predominance of one mechanism of material removal over the other(s) and the nature of various reaction products formed on the affected surfaces were thought to be responsible for specific wear behaviour of the samples under a given set of conditions. Examination of affected surfaces and subsurface regions further supported the wear characteristics of the specimens.