Path Speed Research Articles

Continuous Patrolling Games

Continuous Patrolling Sometimes it is necessary to have a Patroller (on foot, in a car, or maybe a drone) move around a network so as to prevent an intruder (the Attacker) from infiltrating or otherwise ruining the network operation. The “attack” could be, for example, removing a painting from the Louvre, crossing a border, or planting a bomb. The first possibility could take place at only a discrete set of points on the network, say, nodes. However, the last two types of attack could take place anywhere. The latter continuous problem has been modelled as a game by Steve Alpern, Thuy Bui, Thomas Lidbetter, and Katerina Papadaki in the article “Continuous Patrolling Games.” The Attacker decides when and where to attack (the duration of the attack is specified by the problem), whereas the Patroller chooses a unit speed path, possibly periodic. If the Patroller passes the attacked point while the attack is going on, he wins the game, as the attack is thwarted. Otherwise the attack is successful, and the Attacker wins the game. The authors determine optimal strategies for both players for many classes of networks and find good strategies that work on any network. These ideas could be adapted to real-life patrolling problems on networks.

Research on the Basketball Goal Recognition Method Based on Improved MobileNet

Moving target detection is involved in many engineering projects, but it is difficult because of the strong time-varying speed and uncertain path. Goal recognition is the key technology of the basketball goal automatic test. Also, accurate and timely judgment of basketball goals has important practical value. Therefore, a basketball goal recognition method based on an improved lightweight deep learning network model (L-MobileNet) is proposed. First of all, the basket detection is carried out by the Hough circle transform algorithm. Then, in order to further improve the detection speed of basketball goals, based on the lightweight network MobileNet, an improved lightweight network (L-MobileNet) is proposed. First of all, for deeply separable convolution, channel compression and block convolution reduce the parameters and computational complexity of the module. At the same time, because block convolution will hinder the information exchange between characteristic channels, an improved channel shuffling method, IShuffle, is introduced. Then, combined with the residual structure to improve the generalization ability of the network, the RLDWS module is constructed. Finally, a more lightweight network L-MobileNet is constructed by using the RLDWS module. The experimental results show that the proposed method can effectively realize the judgment of basketball goals, and the judgment accuracy is improved by 8.35%. At the same time, the amount of parameters and computation is only 29.7% and 53.2% of the original, and it also has certain advantages compared with other lightweight networks.

Memory-Efficient Abstractions for Pathfinding

From an academic perspective there has been a lot of work on using state abstraction to speed path planning. But, this work often does not directly address the needs of the game development community, specifically for mechanisms that will fit the limited memory budget of most commercial games. In this paper we bring together several related pieces of work on using abstraction for pathfinding, showing how the ideas can be implemented using a minimal amount of memory. Our techniques use about 3% additional storage to compute complete paths up to 100 times faster than A*.

Active steering control based on preview theory for articulated heavy vehicles.

This paper investigates the active steering control of the tractor and the trailer for the articulated heavy vehicle (AHV) to improve its high-speed lateral stability and low-speed path following. The four-degree-of-freedom (4-DOF) single track dynamic model of the AHV with a front-wheel steered trailer is established. Considering that the road information at the driver’s focus is the most clear and those away from the focus blurred, a new kind controller based on the fractional calculus, i.e., a focus preview controller is designed to provide the steering input for the tractor to make it travel along the desired path. In addition, the active steering controllers based on the linear quadratic regulator (LQR) and single-point preview controller respectively are also proposed for the trailer. However, the latter is designed on the basis of the articulation angle between the tractor and trailer, inspired by the idea of the driver’s single-point preview controller. Finally, the single lane change maneuver and 90o turn maneuver are carried out. And the simulation results show that compared with the single-point preview controller, the new kind preview controller for the tractor can have good high speed maneuvering stability and low speed path tracking ability by adjusting the fractional order of the controller. On this basis, three different AHVs with the same tractor are simulated and the simulation results show that the AHV whose trailer adopts the single-point preview controller has better high-speed lateral stability and low-speed path tracking than the AHV whose trailer adopts the LQR controller.

Unidirectional Crystal Orientation of Dual-Phase Ni3Al-Based Alloy via Laser Irradiation

Dual-phase Ni3Al-based alloys feature extensive applicability even under high-temperature conditions. We selectively modified the microstructure of a representative dual-phase Ni3Al-based alloy from equi-axed grains to unidirectional grains, using a kW-class high-power laser irradiation technique. On employing the laser probe to linearly scan the Ni-9 at.% Al-16 at.% V alloy specimen, the laser-irradiated region was partially molten and then immediately solidified from the two edges of the molten pool toward the center. Laser irradiation under low-speed scanning increased the molten pool width. The grains in the laser-irradiated region extended preferentially from the two edges toward the center; their crystal orientation was similar to adjacent substrate grains, suggesting epitaxial growth. Therefore, the unidirectional orientation of grains could be extended via wide-range scanning using laser irradiation. This suggests that the microstructure of the alloy can be selectively modified to unidirectional orientated grains by optimizing laser irradiation conditions, such as the power density, scanning speed, and scanning paths. The hardness of the laser-irradiated region decreased due to the phase transformation from the ordered Ni3Al and Ni3V phases to the disordered fcc phase. However, the hardness improved to a value comparable to that of the alloy subjected to heat treatment at 980 °C for 1 h.

A Vision-Based Fuzzy Control to Adjust Compression Speed for a Semi-Dieless Bellows-Forming

A novel semi-dieless bellows forming process with a local heating technique and axial compression has been initiated for the past years. However, this technique requires a high difficulty in maintaining the output quality due to its sensitivity to the processing conditions. The product quality mainly depends on not only the temperature distribution in the radial and axial direction but also the compression ratio during the semi-dieless bellows process. A finite element model has clarified that a variety of temperature produced by unstable heating or cooling will promote an unstable bellows formation. An adjustment to the compression speed is adequate to compensate for the effect of the variety of temperatures in the bellows formation. Therefore, it is necessary to apply a real-time process for this process to obtain accurate and precise bellows. In this paper, we are proposing a vision-based fuzzy control to control bellows formation. Since semi-dieless bellows forming is an unsteady and complex deformation process, the application of image processing technology is suitable for sensing the process because of the possible wide analysis area afforded by applying the multi-sectional measuring. A vision sensing algorithm is developed to monitor the bellows height from the captured images. An adaptive fuzzy has been verified to control bellows formation from 5 mm stainless steel tube in to bellows profile up to 7 mm bellows height, processing speed up to 0.66 mm/s. The adaptive fuzzy control system is capable of appropriately adjusting the compression speed by evaluating the bellows formation progress. Appropriate compression speed paths guide bellows formation following deformation references. The results show that the bellows shape accuracy between target and experiment increase become 99.5% under given processing ranges.

Integrative management of infrastructure and traction equipment at the railway area

Railway transport is in condition of preparation for fulfillment of the forecast increase of transportation. The level of effectiveness and quality of the railways operation is assessed by the period of delivery to the point of destination of required volume of transported freight, which growth increases intensity of infrastructure wear and tear, which requires breaks in trains movement for providing “gaps” for the track repair operations and inevitably results in the delivery time increase.The use of the best speed path of trains is an important component of ensuring energy effectiveness. Transition to the ground process of trains’ movement control allows JSC “RZD” to arrange rhythmic movement of the car traffic movement providing “gaps” in the single opening for the entire ground.Conducted SWOT-analysis determined the risks and potential results of use of the single infrastructure of the railway area in terms of possible additional expenses in the future. Control mechanism of operation costs was proposed, which allows analyzing actual direct expenses and comparing deviations with regard to the set values. Overall algorithm of the model of integrative control of infrastructure and traction resources was formalized, which is illustrated by the example of participants of transportation process at the railway area. The basis of their interaction is the results of integral assessment that generalized various quantity of indicators and assessment factors of transportation process.Mathematical support of procedures of establishing the cost price is implemented in the Intellectual system of control and handling of the locomotive fleet at the area of the railway production infrastructure. Obtained results are integrated in the Automated control system of operation of the single center of infrastructure control and are set for transformation, effective use of the industrial companies potential.Key trends of the geo-economic condition having direct relation to the transportation and logistic operation in Russia determine necessity of effective management of traction resources by means of arrangement of the uniform process of transportation operation of JSC “RZD”, which results in the best use of transportation infrastructure, balanced increase of the volumes of loading and attraction of investments to the railways.

Fabrication of Mesh Patterns Using a Selective Laser-Melting Process

The selective laser-melting (SLM) process can be applied to the additive building of complex metal parts using melting metal powder with laser scanning. A metal mesh is a common type of metal screen consisting of parallel rows and intersecting columns. It is widely used in the agricultural, industrial, transportation, and machine protection sectors. This study investigated the fabrication of parts containing a mesh pattern from the SLM of AISI 304 stainless steel powder. The formation of a mesh pattern has a strong potential to increase the functionality and cost-effectiveness of the SLM process. To fabricate a single-layered thin mesh pattern, laser layering has been conducted on a copper base plate. The high thermal conductivity of copper allows heat to pass through it quickly, and prevents the adhesion of a thin laser-melted layer. The effects of the process conditions such as the laser scan speed and scanning path on the size and dimensional accuracy of the fabricated mesh patterns were characterized. As the analysis results indicate, a part with a mesh pattern was successfully obtained, and the application of the proposed method was shown to be feasible with a high degree of reliability.

DroneTank: Planning UAVs' Flights and Sensors' Data Transmission under Energy Constraints.

We consider an Unmanned Aerial Vehicle (UAV, also known as drone) as an aerial sink to travel along a natural landscape or rural industrial linear infrastructure to collect data from deployed sensors. We study a joint schedule problem that involves flight planning for the drone and transmission scheduling for sensors, such that the maximum amount of data can be collected with a limited individual energy budget for the UAV and the sensors, respectively. On one hand, the flight planning decides the flight speed and flight path based on sensor locations, energy budgets, and the transmission schedule. On the other hand, the transmission schedule decides for each sensor when to deliver data and what transmission power to use based on the energy budgets and flight plan. By observing three import optimality properties, we decouple the joint problem into two subproblems: drone flight planning and sensor transmission scheduling. For the first problem, we propose a dynamic programming algorithm to produce the optimal flight planning. For the second problem, with a flight plan as input, we introduce a novel technique (water-tank), which together with dynamic programming, is the key to achieve an optimal transmission schedule that maximizes data collection. Simulations show that the separately determined flight plan and transmission schedule are near-optimal for the original joint problem.

Approximate solutions for expanding search games on general networks

We study the classical problem introduced by R. Isaacs and S. Gal of minimizing the time to find a hidden point H on a network Q moving from a known starting point. Rather than adopting the traditional continuous unit speed path paradigm, we use the dynamic “expanding search” paradigm recently introduced by the authors. Here the regions S(t) that have been searched by time t are increasing from the starting point and have total length t. Roughly speaking the search follows a sequence of arcs $$a_i$$ such that each one starts at some point of an earlier one. This type of search is often carried out by real life search teams in the hunt for missing persons, escaped convicts, terrorists or lost airplanes. The paper which introduced this type of search solved the adversarial problem (where H is hidden to maximize the time to be found) for the cases where Q is a tree or is 2-arc-connected. This paper’s main contribution is to give two strategy classes which can be used on any network and have expected search times which are within a factor close to 1 of the value of the game (minimax search time). These strategies classes are respectively optimal for trees and 2-arc-connected networks. We also solve the game for circle-and-spike networks, which can be considered as the simplest class of networks for which a solution was previously unknown.

Hide-and-Seek Games on a Network, Using Combinatorial Search Paths

This paper introduces a new search paradigm to hide-and-seek games on networks. The Hider locates at any point on any arc. The Searcher adopts a “combinatorial” path when searching the network: a sequence of arcs, each adjacent to the last, and traced out at unit speed. In previous literature the Searcher was allowed “simple motion,” any unit speed path, including ones that turn around inside an arc. The new approach more closely models real problems such as search for improvised explosive devices using vehicles that can only turn around at particular locations on a road. The search game is zero sum, with the time taken to find the Hider as the payoff. Using a lemma giving an upper bound for the expected search time on a semi Eulerian network, we solve the search game on a network Q3 consisting of two nodes connected by three arcs of arbitrary lengths. When two Q3 networks with unit length arcs are linked by two small central arcs incident at the start node, one of these arcs must be traversed at least three times in an optimal search. This property holds for both combinatorial paths and simple motion paths, and the latter makes it a counterexample to a conjecture of Gal, which said that two traversals were always sufficient.

On the approximation ratio of the Random Chinese Postman Tour for network search

We consider a classic search problem first proposed by Gal in which a Searcher randomizes between unit speed paths on a network, aiming to find a hidden point in minimal expected time in the worst case. This can be viewed as a zero-sum game between the Searcher and a time maximizing Hider. It is a natural model for many search problems such as search and rescue operations; the search for an enemy, a bomb or weapons in a military context; or predator–prey search. A Chinese Postman Tour (CPT) is a minimal time tour of the network that searches all the arcs and a Random Chinese Postman Tour (RCPT) is an equiprobable choice of any given CPT and its reverse. The full class of networks for which a RCPT is optimal is known, but otherwise little is known about the solution of the game except in some special cases that have complicated optimal strategies that would be impractical to implement. The question of how well a RCPT or any other search strategy performs for general networks has never been analyzed. We show that a RCPT has an approximation ratio of 4/3: that is, the maximum expected time it takes to find a point on the network is no greater than 4/3 times that of the optimal search strategy. We then examine the performance of a RCPT in a related search game recently proposed by Alpern in which the Searcher must return to his starting point after finding the Hider.

Standing balance and inter-limb balance asymmetry at one year post primary anterior cruciate ligament reconstruction: Sex differences in a cohort study of 414 patients

BackgroundStatic standing balance can be safely assessed early following anterior cruciate ligament reconstruction (ACLR), and deficits may have important implications for long-term outcomes. This study includes a large cohort of people post-ACLR and has the primary aim of establishing whether inter-limb and sex differences exist, with a secondary aim of assessing the association between static balance variables and other outcome measures. MethodsA total of 414 patients with a primary ACLR performed a 30-s static single leg balance test. Centre of pressure (COP) path length, antero-posterior (AP) and medio-lateral (ML) sway range and slow and fast speed COP path-length were examined. Additional measures included single and triple hop distance and symmetry, knee flexion range of motion, ligament laxity and the International Knee Documentation Committee (IKDC) subjective knee evaluation form. ResultsNo significant inter-limb balance differences were present in females. Significant, yet small to negligible effect size (ES) differences were present in males for ML range (ES=0.19), and AP and ML axis slow speed path length (ES=0.11 and 0.23 respectively). Significant, negligible to moderate effect size (ES range=<0.01 to 0.60) sex differences were observed, with females showing reduced sway compared to males. No balance variables had associations with any other variable that were greater than weak. DiscussionOur findings provide evidence that primary ACLR does not appear to negatively impact single leg standing balance on the operated limb more than the non-operated side. The lack of association with other outcome measures warrants further longitudinal examination into the utility of static standing balance assessment.

Efficient synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H)-ones in the presence of nanocomposites under microwave irradiation

The preparation of quinazolinones has been developed by the condensation of aromatic aldehydes and 2-aminobenzamide in the presence of transition metal-CNTs nanocomposites as novel and recyclable catalyst under microwave and solvent-free conditions. This methodology provides a high speed path for the green and mild synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H)-ones with high structural diversity. The present methodology has advantages such as high activity and reusability of catalysts, heterogeneous nature of catalysts, no use of hazardous organic solvents and green conditions.

Adaptive integral dynamic surface control of a hypersonic flight vehicle

In this article, non-linear adaptive dynamic surface air speed and flight path angle control designs are presented for the longitudinal dynamics of a flexible hypersonic flight vehicle. The tracking performance of the control design is enhanced by introducing a novel integral term that caters to avoiding a large initial control signal. To ensure feasibility, the design scheme incorporates magnitude and rate constraints on the actuator commands. The uncertain non-linear functions are approximated by an efficient use of the neural networks to reduce the computational load. A detailed stability analysis shows that all closed-loop signals are uniformly ultimately bounded and the tracking performance is guaranteed. The robustness of the design scheme is verified through numerical simulations of the flexible flight vehicle model.

Nonlinear Guidance and Control Laws for Three-Dimensional Target Tracking Applied to Unmanned Aerial Vehicles

In this paper, a backstepping-based nonlinear guidance controller is developed, designed for three-dimensional trajectory tracking for an unmanned aerial vehicle. The guidance law design assumes first-order dynamics for the speed, course/heading, and flight path angles. The three-dimensional kinematic model is simplified to yield a seemingly decoupled system that separates the course/heading from the flight path angle. A closed loop stability of the guidance laws via Lyapunov analysis is demonstrated, and the efficacy of the controller is illustrated for three representative cases.

Scan-Based Speed-Path Debug for a Microprocessor

Identifying the actual speed limiting paths in silicon using traditional functional microprocessor tests can be very time-consuming and expensive because of limited observability of internal signals. This paper presents the development of a promising scan-based speed path diagnosis methodology and illustrates its application to a high performance microprocessor design.

Design and Analysis of a Delay Sensor Applicable to Process/Environmental Variations and Aging Measurements

With technology scaling, the deviation between predicted path delay using simulation and actual path delay on silicon increases due to process variation and aging. Hence, on-chip measurement architectures are now widely used due to their higher accuracy and lower cost compared to using external expensive measurement devices. In this paper, a novel path-delay measurement architecture called path-based ring oscillator (Path-RO) which takes into account variations is proposed. Path-RO can perform accurate on-chip path-delay measurement with nearly no impact on functional data path. At the same time, process variations will not affect the measurement accuracy. The accuracy degradation due to aging is also negligible, which enables Path-RO to monitor path delay throughout aging process. This delay sensor is perfectly suitable for fast and accurate speed binning as well. By targeting speed paths, the speed of chip can be binned efficiently even in presence of clock skew. Various simulation results collected by Path-RO inserted into b19 circuit demonstrate its high accuracy and efficiency.

Could graphene construct an effective conducting network in a high-power lithium ion battery?

This study is trying to demonstrate whether graphene is able to construct an effective conducting network for both electron and ion transports in cathode system of a high-power lithium ion battery (LIB), not based on a coin cell, but by employing a commercial soft-packaged 10Ah battery pack as a model system. Compared with the cells using commercial conductive additive (7wt% carbon black and 3wt% conductive graphite), a 10Ah cell using only 1wt% graphene and 1wt% carbon black shows lower internal resistance and higher energy density due to the excellent conductivity of graphene. However, owing to the fact that the planar structure of the graphene sheets blocks fast Li+ ion transport, the steric effect resulted heavy polarization occurs at a relatively high charge/discharge rate (>3C). That is, although flexible and planar graphene helps construct an effective electron transfer network, it retards Li+ ion transport. Thus, for an energy-storing LIB with a low working charge/discharge rate, graphene additive shows apparent superiority over commercial ones even with much less addition fraction and may find its real commercial applications; while, for a high-power LIB which works at higher charge/discharge rate, fast ion transport path is required to be effectively constructed before a real application. Simulation results indicate that further work should be focused on the adjustment of electrode pore structure and modification of graphene steric structure accordingly to construct an unimpeded ion conducting network and provide high speed path for Li+ ion transport.

Planning Smooth and Obstacle-Avoiding B-Spline Paths for Autonomous Mining Vehicles

We study the problem of automatic generation of smooth and obstacle-avoiding planar paths for efficient guidance of autonomous mining vehicles. Fast traversal of a path is of special interest. We consider fourwheel four-gear articulated vehicles and assume that we have an a priori knowledge of the mine wall environment in the form of polygonal chains. Computing quartic uniform B-spline curves, minimizing curvature variation, staying at least at a proposed safety margin distance from the mine walls, we plan high speed paths. We present a study where our implementations are successfully applied on eight path-planning cases arising from real-world mining data provided by the Swedish mining company Luossavaara-Kiirunavaara AB (LKAB). The results from the study indicate that our proposed methods for computing obstacle-avoiding minimum curvature variation B-splines yield paths that are substantially better than the ones used by LKAB today. Our simulations show that, with an average 32.13%, the new paths are faster to travel along than the paths currently in use. Preliminary results from the production at LKAB show an overall 5%-10% decrease in the total time for an entire mining cycle. Such a cycle includes both traveling, ore loading, and unloading.