Deceleration Process Research Articles

Насыщение магнитосферы во время супербурь: новые результаты техники инверсии магнитограмм

From data of three three superstorms we study new features of the saturation process of the polar cap magnetic flux deceleration of its area at strengthening the solar wind (SW). It is shown that the saturation of the polar cap is observed at growth of the SW dynamic pressure and vertical IMF component for both signs. Saturation is realized not only during the passage of interplanetary magnetic clouds, but also at significant enhancement of SW density, when the SW thermal pressure is comparable with the pressure of the interplanetary magnetic field. We assume that at such condiitions the saturation is caused not only by a decrease in the efficiency of reconnection at the dayside magnetopause, but mainly by a finite magnetosphere compressibility –stopping the magnetopause compression due to the rapid Eathward growth of the geomagnetic field, ie, interior magnetospheric structure of the geomagnetic field

Study on the effects of ionization seeds on pulse detonation characteristics

Ionization phenomenon is happened on the wave front due to the presence of high temperature and pressure in the detonation process. Plasma produced in the detonation process can be used as magnetohydrodynamic (MHD) generator or flow controlled by the external magnetic field. However, it is necessary to increase the ionization efficiency by adding metal ions with lower ionization potential owing to the limited amount of plasma produced by detonation. In this paper, a model of pulse detonation engine with ionization seeds was established. The Conservation Element and Solution Element (CE/SE) method was deduced to simulate the interaction between plasma and detonation process. The influence of ionization seed contents on the electrical conductivity and detonation characteristic parameters was analyzed, and the MHD control of detonation process was realized by adding the external electromagnetic field device. The results showed that it had a little influence on the detonation process but a great influence on the generation of detonation plasma by the addition of a certain amount of ionized seed. The ion mass fraction and electrical conductivity in the detonation tube were first increased and then decreased with the increase of ionization seed content, which reached the maximum at the ionization seed mass fraction of 0.05. The acceleration and deceleration process could be achieved by the MHD control.

Sound quality evaluation of high-speed train interior noise by adaptive Moore loudness algorithm

An online experiment to acquire the interior noise of a China Railways High-speed (CRH) train showed that it was mainly composed of middle-low frequency components and could not be described properly by linear or A-weighted sound pressure level (SPL). Thus, the appropriate way to evaluate the high-speed train interior noise is to use sound quality parameters, and the most important is loudness. To overcome the disadvantages of the existing loudness algorithms, a novel signal-adaptive Moore loudness algorithm (AMLA) based on the equivalent rectangular bandwidth (ERB) spectrum was introduced. The validation reveals that AMLA can obtain higher accuracy and efficiency, and the simulated dark red noise conforms best to the high-speed train interior noise by loudness and auditory assessment. The main loudness component of the interior noise is below 27.6 ERB rate (erbr), and the sound quality of the interior noise is relatively stable between 300–350 km/h. The specific loudness components among 12–15 erbr stay invariable throughout the acceleration or deceleration process while components among 20–27 erbr are evidently speed related. The unusual random noise is effectively identified, which indicates that AMLA is an appropriate method for sound quality assessment of the high-speed train under both steady and transient conditions.

Alternative arresting system design for truck escape ramps

ABSTRACTEach year road accidents claim numerous lives involving run away trucks unable to stop on steep declines. Various passive arresting systems, commonly known as truck escape ramps, are installed on dangerous highway declines to promote highway safety. Truck escape ramps can be divided into three categories: gravity escape ramps, sand or gravel ramps, and arrestor bed escape ramps. However, none of these solutions can control and/or predict the behaviour of a vehicle during the deceleration process within the truck escape ramp. Secondary accidents such as rolling over or rolling back can occur due to the uncontrollable nature during truck deceleration on the truck escape ramp. Existing rescue solutions for the truck after it is arrested in the truck escape ramp often requires complicated procedures with corresponding high costs to remove the captured vehicle and passengers. This paper presents an alternative vehicle arresting system consisting of variable sized prefabricated deformable units made using cementitious materials. Each deformable unit is an independent block and deforms upon truck tire contact. Consequently, the system generates a predictable force that acts opposite to the vehicle motion direction. Results of a 40-ton heavy-duty truck traveling at a 56 km/hr entry speed without braking are included.

Observation of plasma microwave emission during the injection of supersonic plasma flows into magnetic arch

The process of plasma deceleration during the injection of supersonic plasma flow across the magnetic field of an arched configuration is experimentally demonstrated. Pulsed plasma microwave emission in the electron cyclotron frequency range is observed. It is shown that the frequency spectrum of plasma emission is determined by the position of the deceleration region in the magnetic field of the magnetic arc, and its bandwidth is defined by the magnetic field inhomogeneity in the deceleration region. The observed emission can be related to the cyclotron mechanism of wave generation by non-equilibrium energetic electrons in the dense plasma.

Double Position Servo Synchronous Drive System Based on Cross-Coupling Integrated Feedforward Control for Broacher

Synchronization errors directly deteriorate the machining accuracy of metal parts and the existed method cannot keep high synchronization precision because of external disturbances. A new double position servo synchronous driving scheme based on semi-closed-loop cross-coupling integrated feedforward control is proposed. The scheme comprises a position error cross-coupling feedforward control and a load torque identification with feedforward control. A digital integrated simulation system for the dual servo synchronous drive system is established. Using a 20 t servo broacher, performance analysis of the scheme is conducted based on this simulation system and the simulation results show that systems with traditional parallel or single control have problems when the worktable works with an unbalanced load. However, the system with proposed scheme shows good synchronous performance and positional accuracy. Broaching tests are performed and the experimental results show that the maximum dual axis synchronization error of the system is only 8 μm during acceleration and deceleration processes and the error between the actual running position and the given position is almost zero. A double position servo synchronous driving scheme is presented based on cross-coupled integrated feedforward compensation control, which can improve the synchronization precision.

A visualized study of the motion of individual bubbles in a venturi-type bubble generator

As an equipment for generating millimeter- or micrometer-sized bubbles, venturi-type bubble generator has a great potential application in online poison gas removal for molten salt reactor, water treatment, mineral flotation, flue gas desulphurization, even in drug delivery, etc. While the process of generating bubbles in a venturi tube is quite different from that in a conventional tube. A visualized study was carried out to illustrate the details of the transportation of individual bubbles in a venturi-type bubble generator. Sizes, velocity, acceleration of the bubbles were obtained by Digital Image Analysis (DIA) method. An extremely rapid deceleration and intense breakup process was observed nearby the entrance of the diverging section of the bubble generator. Bubbles with average diameter larger than 1.5 mm were usually split before collapse, while the smaller one collapsed directly without split. Within several millimeters, the velocity of the bubbles were almost reduced by half, which is believed to play a key role for triggering their collapse. Once a bubble was decelerated to its minimum velocity, it was collapsed promptly into many tiny bubbles around the position of 8–10 mm from the inlet of the diverging section. Increasing the liquid flow rate could intensify the collapse process, while its influence on the position of collapse was weak.

Installations Criterion of Deceleration Device in Volumetric Hydraulic Drive

A criterion for the installation of the deceleration device in the executive mechanism in volumetric hydraulic drive with inertia loading is proposed. For this purpose, the positioning of the executive mechanism realized on the rigid support, which is the inner surfaces of the side covers of the hydraulic cylinder, is considered. The deceleration process occurs due to the displacement of the working fluid from the end clearance between the side surfaces of the piston and the cover. The criterion is based on the evaluation of the deceleration force when the hydraulic motor is stopped. To form the condition for the installation of the deceleration device of the executive mechanism to the two-position drive, the following approach is used: in the absence of special requirements, the brake device must be installed if the maximum force at stopping the hydraulic motor on the rigid support exceeds 0.2 ... 0.5 of the limiting static force on the piston of the hydraulic cylinder. The criterion includes such basic parameters of the hydraulic drive: the mass of moving parts transferred to the rod, the initial speed of the piston movement, the nominal pressure, the kinematic viscosity of the working fluid and the piston diameter.

Theoretical Modelling of Film-Forming Mechanisms Under Transient Conditions: Application to Deceleration and Experimental Validation

This paper proposes an analytical model for line (1D) and point contacts (2D), based upon the Ertel’s hypothesis to predict the evolution of film thickness in steady-state and transient conditions in elastohydrodynamic lubrication. This theoretical approach, applied to a velocity ramp at constant deceleration, is perfectly supported by experimental results in terms of film thickness distribution during the deceleration process and in terms of central film thickness at the vanishing of the entrainment velocity. This work emphasizes the role of the transport effects of the lubricant at the instantaneous entrainment velocity on the time and length scales at which the film thickness disturbances induced by the deceleration process occur until the complete halting of the surfaces.

Designing Sustainable Public Transportation: Integrated Optimization of Bus Speed and Holding Time in a Connected Vehicle Environment

Developing public transportation and giving priority to buses is a feasible solution for improving the level of public transportation service, which facilitates congestion alleviation and prevention, and contributes to urban development and city sustainability. This paper presents a novel bus operation control strategy including both holding control and speed control to improve the level of service of transit systems within a connected vehicle environment. Most previous work focuses on optimization of signal timing to decrease the bus signal delay by assuming that holding control is not applied; the speed of buses is given as a constant input and the acceleration and deceleration processes of buses can be neglected. This paper explores the benefits of a bus operation control strategy to minimize the total cost, which includes bus signal delay, bus holding delay, bus travel delay, acceleration cost due to frequent stops and intense driving. A set of formulations are developed to explicitly capture the interaction between bus holding control and speed control. Experimental analysisand simulation tests have shown that the proposed integrated operational model outperforms the traditional control, speed control only, or holding control only strategies in terms of reducing the total cost of buses. The sensitivity analysis has further demonstrated the potential effectiveness of the proposed approach to be applied in a real-time bus operation control system under different levels of traffic demand, bus stop locations, and speed limits.

Evolution of Initial Atmospheric Corrosion of Carbon Steel in an Industrial Atmosphere

The evolution of initial corrosion of carbon steel exposed to an industrial atmosphere in Shenyang, China, has been investigated by gravimetric, XRD, SEM/EDS and electrochemical techniques. The kinetics of the corrosion process including the acceleration and deceleration processes followed the empirical equation D = Atn. The rust formed on the steel surface was bi-layered, comprised of an inner and outer layer. The outer layer was formed within the first 245 days and had lower iron content compared to the inner layer. However, the outer layer disappeared after 307 days of exposure, which is considered to be associated with the depletion of Fe3O4. The evolution of the rust layer formed on the carbon steel has also been discussed.

A cellular automata (CA) model for motorized vehicle flows influenced by bicycles along the roadside

SummaryOn many urban low‐grade or branch roads, especially in medium or small cities in China, bicyclists and motorists commonly share the non‐barrier road surface. Because bicycles are unpredictable and unstable when moving, motorized vehicles must reduce their speed to safely approach and overtake them. In this study, the gradual deceleration process a motorized vehicle undergoes before it passes a bicycle was analyzed. The motorist was assumed to prefer a comfortable deceleration and to select a higher deceleration rate only when the distance to the bicycle was insufficient to reduce the car's speed to the expected value at a comfortable deceleration rate. Cellular automata (CA) simulations were used to reveal the flow characteristics of motorized vehicles reacting to bicycles traveling along the roadside, and the results show that for the general velocities of motorized vehicles and bicycles traveling on urban branch roads, the road capacity for motorized vehicles is not related to the number of bicycles present. However, the average travel time of motorized vehicles is significantly affected by the presence of bicycles when the number of motorized vehicles on the road is small. In addition, motorized vehicles' average travel time is more influenced by disturbances in the flow of motorized vehicles than by bicycles when the number of motorized vehicles on the road is large. Field observations and surveys were used to validate the traffic behaviors and simulation results. Copyright © 2016 John Wiley & Sons, Ltd.

Anisotropy of low energy direct photons in relativistic heavy ion collisions

Using the Wigner function approach for electromagnetic radiation fields, we investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions. The angular distribution reveals information of the initial geometric configurations, which is reflected in the anisotropic parameter v2, with an increasing v2 as energy decreases. This behavior is qualitatively different to the v2 from the hadrons produced in the collisions.

Effects of design conditions and irreversibilities on the dimensions of ejectors in refrigeration systems

A thermodynamic model for the design of ejectors is described, validated and applied for conditions prevailing in refrigeration systems. Contrary to previous models the present one determines all the dimensions of the ejector and uses polytropic (instead of isentropic) efficiencies thus taking into account the effects of the pressure ratio on the entropy increase during the irreversible acceleration and deceleration processes. The results include dimensions and fluid properties for a base case as well as a parametric study which analyzes the effect of inlet and outlet conditions on the dimensions and efficiencies of the acceleration, deceleration and mixing processes. The parametric study coupled to recommended constraints from the literature leads to the determination of design conditions for which the axial evolution of pressure, temperature and velocity are determined. The effects of the polytropic efficiency on the ejector dimensions and the efficiencies of the processes taking place in the ejector are also presented and analysed. It is also shown that the total exergy losses increase linearly when the mixing efficiency decreases.

The effects of injection modes on instantaneous particle deposition in a realistic human nasal cavity.

To understand the instantaneous particle deposition in nasal cavity, effects of two injection models on particle deposition characteristic were discussed in this paper. Based on a realistic human nasal cavity geometry obtained from CT scans, a comparison of deposition pattern in the nasal cavity between single injection and continuous injection was investigated through the Lagrangian approach. The instantaneous airflow field was simulated with the tidal volume of 159 and 318 mL by two sine wave curves at inlet. For the case of single injection, particles have finished deposition in the first half of inhalation, and a negative correlation between the tidal volumes and deposition can be observed when the particle diameter was larger than 10 µm. Moreover, particles were mainly deposited in the turbinate area that was beneficial for aerosol therapy. The inertial parameter was not suitable to predict the particle deposition in the case of single injection. With respect to continuous injection, a reduction in total deposition caused by the deceleration process of inhalation can be observed after 1.5 s. The deposition was closely associated with the time-varying flow field, and particles were mainly deposited in the anterior region and turbinate area. Besides, the particle deposition increased with the inertial parameter for continuous injection. The results indicated that the injection modes had an influence on both the total deposition and local deposition pattern in the nasal cavity. Copyright © 2016 John Wiley & Sons, Ltd.

Deceleration processes of secondary electrons produced by a high-energy Auger electron in a biological context

Purpose: To simulate the deceleration processes of secondary electrons produced by a high-energy Auger electron in water, and particularly to focus on the spatial and temporal distributions of the secondary electron and the collision events (e.g. ionization, electronic excitation, and dissociative electron attachment) that are involved in the multiplication of lesions at sites of DNA damage.Materials and methods: We developed a dynamic Monte Carlo code that considers the Coulombic force between an ejected electron and its parent cation produced by the Auger electron in water. Thus our code can simulate some return electrons to the parent cations. Using the code, we calculated to within the order of femtoseconds the temporal evolution of collision events, the mean energy, and the mean traveling distance (including its spatial probability distribution) of the electron at an ejected energy of 20 eV.Results: Some of the decelerating electrons in water in the Coulombic field were attracted to the ionized atoms (cations) by the Coulombic force within hundreds of femtoseconds, although the force did not significantly enhance the number of ionization, electronic excitation, and dissociative electron attachment collision events leading to water radiolysis.Conclusions: The secondary electrons are decelerated in water by the Coulombic force and recombined to the ionized atoms (cations). Furthermore, the some return electrons might be prehydrated in water layer near the parent cation in DNA if the electrons might be emitted from the DNA. The prehydrated electron originated from the return electron might play a significant role in inducing DNA damage.

A multi-order FRFT self-adaptive filter based on segmental frequency fitting and early fault diagnosis in gears

Abstract To effectively diagnose gear failure at an early stage, a multi-order Fractional Fourier transform (FRFT) self-adaptive filter based on segmental frequency fitting (MFSFF) is proposed to separate the feature components with curved frequency from the gearbox’s transient conditions. First, a linear multi-scale segmentation method (LMSS) is developed to divide the signal with curved frequency into segments with nearly linear frequency; then, a method for determining the FRFT filter parameters by fitting the frequency curve (DFFPFF) is developed to calculate the FRFT filter parameters for each signal segment, and the signal in each segment is filtered by an FRFT filter using these parameters to determine the MFSFF. The vibration of the gearbox’s acceleration and deceleration process is analyzed using an MFSFF and the filtered signal is demodulated. The experimental results show that LMSS is able to divide any signal with curved frequency into minimal segments with nearly linear frequency; DFFPFF is exact, fast, not influenced by the vibration source or the number of components, and able to determine the FRFT filter parameters for each signal segment accurately; the feature component of the gearbox’s transient condition is accurately extracted by an MFSFF, and the other components and noise are removed simultaneously. Early gear failure is diagnosed exactly by demodulation of the extracted feature component, which is difficult to identify using the traditional method.

Research and Implementation of Real-Time Computing Algorithm of S Curve Acceleration and Deceleration for Step Motor

The paper established real-time computing algorithm of S Curve to control the process of acceleration and deceleration for step motor on the basis of a reasonable start frequency. Moreover, this paper used economic embedded ARM STM32F103RCT as the main control chip to control the step motor, which realized this designed real-time computing algorithm. Finally, the relevant testing indicated that the algorithm can realize the rapid response of start and stop for step motor, and can effectively avoid undesirable phenomenon of step losing, overshoot and oscillation.

Ejector design and performance prediction

This paper proposes a 1-D thermodynamic model for determining the critical pressure ratio, the mixing efficiency and all the dimensions of an optimum ejector providing the highest possible compression ratio for fixed inlet conditions and mass flowrates of the motive and suction fluids. The maximization of the back pressure is obtained subject to constraints imposed by the 2nd law of thermodynamics and the requirements that the flow must be subsonic at the diffuser entrance, that the mixing efficiency must be positive but smaller than one and that the length to diameter ratio for the constant area duct must be between fixed limits recommended in previous studies. The paper also describes a method for determining the off-design performance of a fixed geometry ejector which reproduces the experimental relations between the entrainment ratio, the compression ratio and the inlet conditions of the two fluids. The model uses a fixed polytropic efficiency (rather than the fixed isentropic efficiency used in previous studies) to simulate the acceleration and deceleration processes thus taking into account the effect of the pressure ratio during off-design operation. Examples of its application for isentropic and irreversible acceleration/deceleration of a perfect gas are provided and their results are analysed and compared.

Experimental observations of turbulent flame propagation effected by flame acceleration in the end gas of closed combustion chamber

In present study, a new designed constant volume combustion bomb (CVCB) equipped with an orifice plate and visualized by high speed schlieren photography has been employed to study the turbulent flame propagation effected by flame acceleration in the end gas region. The orifice plate is employed to achieve flame acceleration and obtain different turbulent flames at different equivalence ratios. We investigate the flame propagation speed, the formation mechanism of compression front, the influence of flame acceleration on the end-gas as well as the flame structure changes. The results show that the laminar flame can be accelerated and transferred to a wrinkled turbulent flame through the orifice plate significantly and there forms a clear compression front ahead of the turbulent flame. The flame propagation speed without orifice plate shows the trend of initial increase and consequence decrease in the confined space. Moreover, the turbulent flame propagation speed shows the significantly different trend and demonstrates the “M” shape evolution including the self-acceleration, unstable and deceleration process. Finally, the evolution of turbulent flame in the end gas of the confined chamber was described in detail with three stages: compression front formation, flame front distortion and reverse propagation.