Launch Parameters Research Articles

Flight dynamics modeling and stability analysis of a tube-launched tandem wing aerial vehicle during the deploying process

During the subsequent deploying process after the launch, the vehicle experiences dramatic changes in geometry as well as aerodynamics, which cannot be ignored for the flight stability of the aircraft. The investigation on the flight dynamics modeling and stability analysis during the unsteady deploying process is of great significance for the flight control system design and the launch system design. The nonlinear multibody dynamic model of the vehicle, which mainly consists of the airframe and four wings, is established through the Newton–Euler method. Meanwhile, the unsteady vortex lattice method (VLM), which is suitable for tandem wing aircraft and combined with the viscosity effect in light of the strip theory, is proposed to calculate the aerodynamic loads of the vehicle during the deploying process. A series of simulations about the motion of the vehicle after the launch are calculated to analyze the effects of various parameters, including the deploying forms, the start-up time of the power system along with the launching parameters, on the stability of the aerial vehicle in the deployment process. As results indicated, a small difference in the deploying rates of wings and larger deploying rates of wings on the same side are beneficial to the stability of the vehicle during the deploying process. Additionally, it is advantageous to the pitching stability but not the lateral stability of the vehicle when the power system is started earlier. Besides, the attitude control strategy of the vehicle can be formulated in advance by analyzing the attitude of the vehicle with different launch parameters at the launching moment.

LES investigation on cavitating flow structures and loads of water-exiting submerged vehicles using a uniform filter of octree-based grids

The water-exit course of a submerged vehicle launched underwater that moves into the atmosphere is one of the most important considerations in naval applications. In the present work, a large-eddy simulation with a uniform filter of an octree-based isotropic mesh and a high-resolution interface-capturing algorithm is employed to investigate this issue, with a special emphasis on the flow structures and pressure features. Various launch parameters, including the immersion depth, navigation speed, and angle of attack are discussed. The flow structures sensitive to adverse pressure relevant to the water-exit angle are captured and discussed. The flow experiences a laminar-turbulent transition and forms coherent turbulence structures, which develop a series of primary and secondary hairpin vortices. The distribution of pressure is more monotonic and regular on the pressure side of the vehicle as the angle increases, while a propagation of disturbance and a transition to turbulence can occur across the lateral side. Based on the clearly captured evolution of the water surface and cavitation, the cavity shedding induced by a pinch-off effect of the travelling liquid-vapor contact lines is found and investigated. The structural features of turbulence are greatly affected in this case, which contrasts with the noncavitating features. The structures are tuned due to the existence of cavitation, which blocks the hairpin-vortex generation mechanism. The cavity surface is full of Tollmien-Schlichting wave-like vortical structures caused by liquid-vapor interface shearing. Hundreds of monitors are intensively arranged on the vehicle's surface to capture the transient pressure signals, through which the crucial pressure features induced by the growth and collapse of the cavitation are captured.

Статически-детерминированный метод прогнозирования динамических характеристик параллельных программ

In this paper, we consider the problem of prediction of parallel program dynamic characteristics, like execution time, count of floating-point operations, energy consumption, count of memory accesses and others. Prediction of dynamic characteristics allows solving many problems, related to design of new architectures, selection of the most suitable configurations of multiprocessor systems for solving specific problems, porting applications to new systems, task flow planning and more. The task of predicting characteristics is being actively investigated. Increasing complexity of the architectures of modern high-performance systems requires the development of new methods for solving the prediction problem. The article provides an overview of the existing approaches and software for predicting dynamic characteristics and proposes an approach based on a static analysis of the source code of a parallel application. Based on the text of the parallel program, the formal description of the target computing platform and the launch parameters, a method is implemented that allows predicting the operating time, the number of floating-point operations, number of memory accesses, and other characteristics of the parallel application. The applicability of the proposed approach is demonstrated by solving the test 3-dimensional numerical simulation problem on a multiprocessor cluster based on IBM Power8 processors.

Deterministic Throw Model for Longitudinal Rear-End Vehicle to Cyclist Collisions

In this paper a throw distance model for vehicle-cyclist collisions is presented, based on a deterministic approach with a cyclist mass point representation. Vehicle-cyclist collisions are characterized by three distinct impacts, which determine the entirety of the cyclist’s kinematics, also throw distance implicitly. Cyclist kinematics are analyzed by breaking down the motion into multiple phases and assessing the corresponding distance travelled by the cyclist for each phase. The model takes into account massic and cyclist launch parameters, as well as road declivity and ground friction. The verification of the model was carried out in two methods. First, model output data was compared with the results of three real-scale crash-tests performed in a rear impact typology. Secondly, a multibody model was generated for two of the carried-out crash-tests and used to simulate collisions at different vehicle impact velocities (4.1 ∼ 27.8 m/s). Input data for the model was extracted from each simulation and used to compare the results yielded by the model and the multibody software. A comparison between model output data and available field data was also undertaken.

Research on Liquid CO2 Phase Transition Ejection Technology

Due to the low temperature and clean gas, liquid CO2 phase transition ejection technology has outstanding advantages such as high versatility, low launch cost, and environmental friendliness, which will open up a new research field for the development of missile launch technology. Through the study of phase transition characteristics of liquid CO2 in this paper, a mathematical model of internal ballistics of the liquid CO2 phase transition ejection power system is established. And through simulation calculation, the launching parameters such as the pressure in the launcher, the velocity and acceleration of the missile are obtained, and they is compared with the experiment data to verify the validity of the model.

Optical trapping with non-diffracting Airy beams array using a holographic optical tweezers

In this work, we present the experimental optical trap of microparticles with an Airy beams array using holographic optical tweezers. The Airy beams array is attractive for optical manipulation of particles owing to their non–diffracting and autofocusing properties. An Airy beams array is composed of N Airy beams which accelerate mutually and symmetrically in opposite direction, for different ballistic trajectories, that is, with different initial launch angles. Based on this, we developed a holographic optical tweezers system for the generation of non–diffracting beams and with it, we investigate the distribution of optical forces acting on microparticles of an Airy beams array. The results show that the gradient and scattering force on microparticles can be controlled through a launch angle parameter of Airy beams. In addition, it is possible to obtain greater stability for optical trap using an Airy beams array, with interesting possibilities for trapping and guiding of microparticles in a controllable way that can be applied in optical, biological, and atmospheric sciences.

Calculations of groundstroke trajectories in tennis

Numerical and analytical calculations are presented on the flight of a tennis ball and the subsequent bounce off the court for typical groundstrokes. The horizontal flight distance was chosen as 22.77 m, corresponding to a typical shot launched from above the baseline to land 1 m inside the opposite baseline. A wide range of shots was examined by varying the launch speed, launch angle and topspin, using representative values of the lift and drag coefficients, as well as representative values of the coefficients of restitution and friction to determine the launch parameters after the bounce. The results compare favourably with measurements gathered from Hawk-Eye data, and could be used to analyse trajectory data in greater detail and to estimate the effectiveness of different types of groundstrokes.

Optimizing optical trap stiffness for Rayleigh particles with an Airy array beam

Airy array beams are attractive for optical manipulation of particles owing to their non-diffraction and auto-focusing properties. An Airy array beam is composed of N Airy beams that accelerate mutually and symmetrically in opposite directions, for different ballistics trajectories, i.e., with different initial launch angles. Based on this, we investigate the optical force distribution acting on Rayleigh particles. Results show that it is possible to obtain greater stability for optical trapping by increasing the number of beams in the array. Also, the intensity focal point and gradient and scattering force of the array on Rayleigh particles can be controlled through a launch angle parameter.

Optimization Study of High Altitude Micro Gliding Air Vehicle Re-Entry Path Characteristics

Based on the characteristics of the configuration and flight of the micro gliding air vehicle (MGAV), an analysis and optimization for general gliding path of different mission demands is carried out. Firstly, an overall design method and parameters are summarized. Secondly, the equilibrium glide launching parameters are determined based on the general aircraft re-entry equation. The real launching parameter are also developed by considering the real launching facility. Furthermore, the un-controlled maximum-range-towards path characteristics for the real and equilibrium glide are compared and analyzed. The range in equilibrium glide is 5 km larger than real glide. Then, two potential flight demand are explained and the Gauss pseudo-spectral method is adopted to solve the maximum endurance and the maximum endurance and range with the process constraint and final constraint. The first target is 8 minutes longer than the original glide path but the range is 20 km less compared to the maximum range. The second target could keep the maximum range and at the meantime, the endurance could be increased 2 minutes. Finally, the control variables are substituted into the dynamic equations to validate the results. The result shows that the Gauss pseudo-spectral method is an effective and feasible way to solve the optimum gliding path.

Предикторы успешности краудфандингового проекта

<span>В работе методом корреляционно-регрессионного анализа исследованы факторы, которые оказывают влияние на успешный сбор средств через механизм краудфандинга. Изучение данных о более чем 12 тыс. проектов, проведенных в России, позволило выявить связь успешности проекта с параметрами, задаваемыми автором при его запуске, а также информационным сопровождением по мере его реализации. В ходе исследования обнаружен эффект обучения, который проявляется во влиянии опыта автора проекта в краудфандинге на реализацию последующих инициатив, установлена корреляция между успешностью коммерческих инициатив и соответствием вознаграждения взносу спонсора. Полученные данные позволяют глубже понять механизм краудфандинга и лежащие в его основе процессы. Особое внимание уделено использованию краудфандинга в качестве инструмента финансирования молодых компаний и стартапов.</span>

Concurrent query processing in a GPU-based database system.

The unrivaled computing capabilities of modern GPUs meet the demand of processing massive amounts of data seen in many application domains. While traditional HPC systems support applications as standalone entities that occupy entire GPUs, there are GPU-based DBMSs where multiple tasks are meant to be run at the same time in the same device. To that end, system-level resource management mechanisms are needed to fully unleash the computing power of GPUs in large data processing, and there were some researches focusing on it. In our previous work, we explored the single compute-bound kernel modeling on GPUs under NVidia’s CUDA framework and provided an in-depth anatomy of the NVidia’s concurrent kernel execution mechanism (CUDA stream). This paper focuses on resource allocation of multiple GPU applications towards optimization of system throughput in the context of systems. Comparing to earlier studies of enabling concurrent tasks support on GPU such as MultiQx-GPU, we use a different approach that is to control the launching parameters of multiple GPU kernels as provided by compile-time performance modeling as a kernel-level optimization and also a more general pre-processing model with batch-level control to enhance performance. Specifically, we construct a variation of multi-dimensional knapsack model to maximize concurrency in a multi-kernel environment. We present an in-depth analysis of our model and develop an algorithm based on dynamic programming technique to solve the model. We prove the algorithm can find optimal solutions (in terms of thread concurrency) to the problem and bears pseudopolynomial complexity on both time and space. Such results are verified by extensive experiments running on our microbenchmark that consists of real-world GPU queries. Furthermore, solutions identified by our method also significantly reduce the total running time of the workload, as compared to sequential and MultiQx-GPU executions.

Effects of Uncertainties in the Launch Parameters on the Pressure-Equalizing Air Film Around a Vertically Launched Underwater Vehicle

Many uncertain factors in the water-emerging process of a vehicle influence the taking effect of the air film around its shoulder in the load reduction and attitude control. Assuming the launch parameters (launch depth, vehicle velocity, and chamber pressure) as sources of uncertainties, the uncertain evolution process of the air film in the water-emerging process of a vehicle is quantified by adopting the nonintrusive polynomial chaos (NIPC) method with the sample space constructed using linearly independent probabilistic collocation points. A sensitivity analysis was conducted for the key performance indicators of the air film to evaluate the contribution of each uncertain launch parameter.

Numerical Simulation of Rocket Launch Vehicle

Launching of Rocket is a complex phenomenon. There is high chance of failure in such missions. Hence it is necessary to predict the launch path or Trajectory, External disturbances and various other parameters. Numerical Simulation is one such way of predicting launch parameters which helps in taking precautions preventing failure. This Paper presents a platform for simulation of Rocket launch vehicle and control Law validation. The analysis is performed during the Lift-off phase in atmosphere using a mathematical nonlinear dynamic model. Set of six degrees of freedom equations of motion with necessary reference frames and transformations in between them is developed. The Mathematical Model is applied in MATLAB and Simulink simulation which can be easily adjusted for any type of launch vehicle or rocket.

Performance evaluation of mode group power coupling for short reach SDM

Abstract The profound understanding of mode coupling in spatial multiplexed optical systems is required for performance optimization purposes. In this contribution different optical coupler technologies are compared with respect to their bit-error rate (BER) performance as multiplex devices in a (2 × 2) multiple-input multiple-output (MIMO) environment. Therefore, the power coupling coefficients between mode groups for all testbed components are determined at 1327 nm with a method based on impulse response measurements. This method and its refinements are presented in this work. By taking the obtained power coupling coefficients, the MIMO impulse responses are simulated and the corresponding BER performance for different launch parameters is studied. The simulation setup includes single-mode fiber (SMF) to multi-mode fiber (MMF) splices aligned with different radial eccentricities for mode group specific excitation, different multi-mode couplers for mode multiplexing, a 1 km OM4 grade MMF and a multi-mode fusion coupler for demultiplexing. Here, the setup with the customized fusion coupler shows the best BER results in comparison to other coupler technologies. In addition, the optimal choice of the SMF to MMF launch eccentricity highly depends on the implemented coupler technology. Particularly, deviations of 2 μm from the optimal launch setup can lead to a tenfold increase in the BER. It is noteworthy, that the optimal setup does not always include the center launch condition.

Relationships between technique and bat speed, post-impact ball speed, and carry distance during a range hitting task in cricket

The ability of a batsman to clear the boundary is a major contributor to success in modern cricket. The aim of this study was to identify technique parameters characterising those batsmen able to generate greater bat speeds, ball launch speeds, and carry distances during a range hitting task in cricket. Kinematic data were collected for 20 batsmen ranging from international to club standard, and a series of ball launch, bat-ball impact, and technique parameters were calculated for each trial. A stepwise multiple linear regression analysis found impact location on the bat face in the medio-lateral and longitudinal directions and bat speed at impact to explain 68% of the observed variation in instantaneous post-impact ball speed. A further regression analysis found the X-factor (separation between the pelvis and thorax segments in the transverse plane) at the commencement of the downswing, lead elbow extension, and wrist uncocking during the downswing to explain 78% of the observed variation in maximum bat speed during the downswing. These findings indicate that players and coaches should focus on generating central impacts with the highest possible bat speed. Training and conditioning programmes should be developed to improve the important kinematic parameters shown to generate greater bat speeds, particularly focussing on increased pelvis to upper thorax separation in the transverse plane.

Acute effects of different warm-up protocols on highly skilled golfers’ drive performance

ABSTRACTPrevious research has highlighted the positive effect that different warm-up protocols have on golf performance (e.g. Sorbie et al., 2016; Tilley & Macfarlane, 2012) with the design of warm-ups and programmes targeting and improving golf performance through the activation and development of specific muscle groups. This study aimed to examine the acute effects of two warm-up protocols on golf drive performance in comparison to a control condition. Using a randomised counterbalanced design over three testing sessions, twenty-three highly skilled golfers completed the control, dynamic and resistance-band warm-up conditions. Following each condition, a GC2 launch monitor was used to record ball velocity and other launch parameters of ten shots hit with the participants’ own driver. A repeated-measures ANOVA found significant increases in ball velocity (ηp2 = .217) between the control and both the dynamic and resistance-band warm-up conditions but no difference between these latter two, and a reduction in launch angle between control and dynamic conditions. The use of either a dynamic stretching or resistance-band warm-up can have acute benefits on ball velocity but golfers should liaise with a PGA Professional golf coach to effectively integrate this into their golf driving performance.

Analysis of multichannel optical soliton collisions with asymmetric energy in strongly dispersion managed transmission networks considering higher-order effects

We study the interaction properties of optical soliton pulses propagating in a two-channel wavelength-division multiplexed strongly dispersion managed communication system. We analyze the effects of third order dispersion, Raman scattering and self-steepening using an ordinary differential equations model obtained by a variational method applied to the Generalized Nonlinear Schrodinger Equation. The validity of the model is assessed against the integration of the full nonlinear partial differential equations. The variational equations are initially solved for a single pulse in order to identify the launching parameters for each pulse in the first DM cell of the system. One pulse per wavelength is then injected in the transmission link. We then systematically study the evolution of multiplexed soliton trains and analyse the transmission system in terms of residual frequency shifts and interchannel interactions as the map strength is varied, focusing on the ratio of dissimilar peak powers in a broad range of dispersion difference values, concluding that the transmission characteristics improve by using specific values of unequal energies and considering higher-order correction terms. The work presented is an extension of previous analysis where isolated intra-channel two-pulse interactions had been addressed considering pulses with dissimilar energies.

Determining the Effect of an Arc in a Railgun Bore on Emission Efficiency Using B-Dot Probes

The unexpected arcs generated in a railgun bore are one of the major issues affecting emission efficiency. To study the impact of such arcs, a series of experiments with the same launch parameters has been conducted. B-dot probes positioned along the length of the launcher provide data for detecting arc formation phenomena and for measuring the armature velocity. In this paper, two sets of typical signals are discussed. The first set of signals is normal, whereas the other is abnormal in terms of the existence of an arc in the bore during launch. The time interval during which the arc generated and the state of the arc are determined from the magnetic induction curves by integrating the B-dot probe signals. Using a fitting analysis, the displacements and velocities of the armatures are obtained, and the energy distribution of each shot is computed. The results indicate that the generation of an arc in the bore causes a hash launch environment and greatly reduces the emission efficiency.

Study on High-Strength Ring Chain Dynamic Characteristics Under Different Launch Parameters

The aim of this study is to investigate the mechanical characteristics of the high-strength ring chain under various launch parameters and the energy consumption caused by this. Particularly, the contact dynamics simulation was implemented in ABAQUS to study the launch characteristics impacted by different chain speeds different transportation loads, and the results were proved by experiments. The results show that stable stresses under different launch speeds are diverse, and the launch speed providing the optimal performance is 5.6 m/min; stable stresses under different loads are diverse, and in the overload-launch process, the normal force of the chain increases multi-fold so that the chain will be significantly damaged. The share of energy consumption by the friction of high-strength ring chains under idle/no-load operation conditions is 23.8% of the total value. With the rise in loads, the total consumption grows linearly. As a consequence, the results obtained are quite instrumental in the research of ring chain launch characteristics, prediction of chain operating life, and the efficiency improvement of electromotors.

Dynamic Characteristic of High Strength Ring Chain under Different Launch Parameters

The aim of this study is to investigate the mechanical characteristics of the high strength ring chain under various launch parameters and the energy consumption law caused by this. Particularly, the contact dynamics simulation is implemented in Abaqus. In this study, the stress and strain contours of the high strength ring chain under the chain speeds of 1.85 m/min, 5.6 m/min, and 7.8 m/min and under the transportation loads of 2t, 3t, and 3.5t are obtained, plus their stress histories. Simulation results show that the corresponding steady stresses under distinct chain speeds are 748.2 MPa, 754.5 MPa, and 755.6 MPa, determining the optimal chain speed of 5.6m min-1. After reaching the steady state, the maximum stresses under the loads of 2t, 3t, and 3.5t are 774.8 MPa, 758.1 MPa, and 747 MPa, respectively. Furthermore, the experimental results illustrate that the energy consumption caused by the friction among high strength ring chains under no-load operation occupies 23.8% of the resistance consumption. With the rise in loads, the total resistance consumption grows linearly. As a consequence, the research on the dynamic characteristics of the high strength ring chain is valuable for improving the working efficiency of the electromotor.