Backward Path Research Articles

To What Extent Does Not Wearing Shoes Affect the Local Dynamic Stability of Walking?: Effect Size and Intrasession Repeatability

Local dynamic stability (stability) quantifies how a system responds to small perturbations. Several experimental and clinical findings have highlighted the association between gait stability and fall risk. Walking without shoes is known to slightly modify gait parameters. Barefoot walking may cause unusual sensory feedback to individuals accustomed to shod walking, and this may affect stability. The objective was therefore to compare the stability of shod and barefoot walking in healthy individuals and to analyze the intrasession repeatability. Forty participants traversed a 70 m indoor corridor wearing normal shoes in one trial and walking barefoot in a second trial. Trunk accelerations were recorded with a 3D-accelerometer attached to the lower back. The stability was computed using the finite-time maximal Lyapunov exponent method. Absolute agreement between the forward and backward paths was estimated with the intraclass correlation coefficient (ICC). Barefoot walking did not significantly modify the stability as compared with shod walking (average standardized effect size: +0.11). The intrasession repeatability was high (ICC: 0.73-0.81) and slightly higher in barefoot walking condition (ICC: 0.81-0.87). Therefore, it seems that barefoot walking can be used to evaluate stability without introducing a bias as compared with shod walking, and with a sufficient reliability.

Finding the Optimal Social Trust Path for the Selection of Trustworthy Service Providers in Complex Social Networks

Online Social networks have provided the infrastructure for a number of emerging applications in recent years, e.g., for the recommendation of service providers or the recommendation of files as services. In these applications, trust is one of the most important factors in decision making by a service consumer, requiring the evaluation of the trustworthiness of a service provider along the social trust paths from a service consumer to the service provider. However, there are usually many social trust paths between two participants who are unknown to one another. In addition, some social information, such as social relationships between participants and the recommendation roles of participants, has significant influence on trust evaluation but has been neglected in existing studies of online social networks. Furthermore, it is a challenging problem to search the optimal social trust path that can yield the most trustworthy evaluation result and satisfy a service consumer's trust evaluation criteria based on social information. In this paper, we first present a novel complex social network structure incorporating trust, social relationships and recommendation roles, and introduce a new concept, Quality of Trust (QoT), containing the above social information as attributes. We then model the optimal social trust path selection problem with multiple end-to-end QoT constraints as a Multiconstrained Optimal Path (MCOP) selection problem, which is shown to be NP-Complete. To deal with this challenging problem, we propose a novel Multiple Foreseen Path-Based Heuristic algorithm MFPB-HOSTP for the Optimal Social Trust Path selection, where multiple backward local social trust paths (BLPs) are identified and concatenated with one Forward Local Path (FLP), forming multiple foreseen paths. Our strategy could not only help avoid failed feasibility estimation in path selection in certain cases, but also increase the chances of delivering a near-optimal solution with high quality. The results of our experiments conducted on a real data set of online social networks illustrate that MFPB-HOSTP algorithm can efficiently identify the social trust paths with better quality than our previously proposed H_OSTP algorithm that outperforms prior algorithms for the MCOP selection problem.

Target-in-the-loop coherent beam combination of 100 W level fiber laser array based on an extended target with a scattering surface

Target-in-the-loop coherent beam combination (TIL CBC) of a 100 W level fiber laser array has been demonstrated. In the experiment, the beams from nine 10 W level fiber amplifiers achieve a scattering surface target after transmitting 10 m in free space. When the phase control system goes into close loop, atmosphere turbulence could be effectively compensated and a stable fringe pattern could be obtained on the scattering surface with 85% fringe contrast. To our best knowledge, this is the TIL CBC with the highest output power and the largest number of laser beams. Additionally, the effect of atmosphere turbulence on the backward paths on TIL CBC has been studied experimentally.

EDARD: efficient data access based on rumour dissemination in wireless sensor networks

In this paper, we present a rumour dissemination protocol named: efficient data access based on rumour dissemination (EDARD). EDARD ensures an information uniform distribution to enhance data accessibility in wireless sensor networks. In EDARD, rumours (event occurrences) and queries (requests of information) are disseminated through trajectories as straight as possible preventing backward paths. The straitening trajectory – based on a selective next hop choice and the forking procedure introduced in EDARD protocol have the objective to find data and establish paths to the source event in short delays with fewer transmissions. Simulation and comparison results show that EDARD protocol achieves improvements in terms of query delivery rate, data access time and network traffic.

Consistent schemes for non-adiabatic dynamics derived from partial linearized density matrix propagation

Powerful approximate methods for propagating the density matrix of complex systems that are conveniently described in terms of electronic subsystem states and nuclear degrees of freedom have recently been developed that involve linearizing the density matrix propagator in the difference between the forward and backward paths of the nuclear degrees of freedom while keeping the interference effects between the different forward and backward paths of the electronic subsystem described in terms of the mapping Hamiltonian formalism and semi-classical mechanics. Here we demonstrate that different approaches to developing the linearized approximation to the density matrix propagator can yield a mean-field like approximate propagator in which the nuclear variables evolve classically subject to Ehrenfest-like forces that involve an average over quantum subsystem states, and by adopting an alternative approach to linearizing we obtain an algorithm that involves classical like nuclear dynamics influenced by a quantum subsystem state dependent force reminiscent of trajectory surface hopping methods. We show how these different short time approximations can be implemented iteratively to achieve accurate, stable long time propagation and explore their implementation in different representations. The merits of the different approximate quantum dynamics methods that are thus consistently derived from the density matrix propagator starting point and different partial linearization approximations are explored in various model system studies of multi-state scattering problems and dissipative non-adiabatic relaxation in condensed phase environments that demonstrate the capabilities of these different types of approximations for treating non-adiabatic electronic relaxation, bifurcation of nuclear distributions, and the passage from nonequilibrium coherent dynamics at short times to long time thermal equilibration in the presence of a model dissipative environment.

E<sup>2</sup>AODV Protocol for Load Balancing in Ad-Hoc Networks

Problem statement: In mobile ad hoc networks there are a number of challenges in providing quality of service routing with energy efficiency and load balancing. Most routing protocols do not consider the problem of load balance. A routing protocol called energy Efficient Ad-hoc on Demand Vector (E2AODV) is proposed. It addresses the quality of service issues such as throughput, end to end delay, load distribution and energy. Approach: This study presents a scheme to balance the load with energy efficiency considering both congestion and the nodes energy usage. A threshold value was used to judge if intermediate node was overloaded, variable and changing along with nodes interface queue length around the backward path. Results: The routing protocol called energy Efficient Ad hoc on Demand Vector (E2AODV) that is intended to provide a reliable transmission with low energy consumption was compared with Ad-hoc on Demand Vector (AODV) in terms of the packet delivery ratio, average end to end delay, load distribution and node energy consumption. Conclusion/Recommendation: E2AODV protocol chooses an optimum path with low energy usage. It provides a better scheme to balance the load with energy efficiency and packet delivery ratio. It can be further enhanced as a secure routing protocol for mobile ad-hoc networks.

An effective heuristic for computing many shortest path alternatives in road networks

We propose a simple and effective heuristic that allows fast generation of a large set of shortest path alternatives in weighted directed graphs. The heuristic is based on existing deviation path algorithms for exact k shortest paths. It precalculates a backward shortest path tree and thus avoids doing many shortest path computations, but as a result it does not necessarily find the exact set of k shortest paths. Computational results on real-world road networks are reported. Our tests show that the quality of the paths produced by the heuristic is most satisfactory: typically, the kth path found by the heuristic is less than 1% longer than the exact kth shortest path, for values of k up to 10,000. Moreover, the heuristic runs very fast. We also show how the heuristic can be enhanced to an exact k shortest paths algorithm, which performs well in comparison with the existing exact k shortest path algorithms.

Acceleration feedback in a lithographic tool

Acceleration feedback increases the mass of a system as experienced by disturbance forces. A high bandwidth is required to avoid phase lag in the position control loop. This article splits the acceleration controller in a forward and backward path to create the original process behavior for the position controller, removing the high-bandwidth requirement. Digital controller effects, incorporation of plant dynamics, and implications for setpoint feedforward are discussed. The method is implemented in the stage of a lithographic scanner operating at nanometer accuracy in semiconductor manufacturing. It is shown that the low-frequent disturbance rejection is considerably improved without impacting higher-frequency performance.

An extended AUDI algorithm for simultaneous identification of forward and backward paths in closed-loop systems

In closed-loop system identification, most of the existing methods only focus on the forward path, yet few on simultaneous identification of the forward and backward paths. Meanwhile, an augmented UD identification (AUDI) algorithm has been proved effective in open-loop system identification, but it only extracts the forward path information, while not including the backward path information provided in an augmented information matrix, which is helpful for the closed-loop system identification. In this paper, an extended AUDI (EAUDI) is proposed to simultaneously identify the model orders and parameters of both forward and backward paths of a closed-loop system. The conditions of identifiability and uniform convergence for closed-loop systems using the EAUDI algorithm are also given. The effectiveness of this algorithm is demonstrated by a numerical example.

Cutter Location Generation Method for Improving Feedrate and Machining Accuracy Based on Control Characteristics of Machine Tool

All types of NC machine tool interpolation are fundamentally based on linear interpolation, using the minimum interpolation unit of the drive. However, linear interpolation causes issues when machining curved surfaces, such as the feedrate not reaching the command feedrate and fluctuations occurring unexpectedly. These are mainly due to the NC interpolation process, and feedrate limiters. In addition, linear interpolation also decreases machining accuracy through inner cornering errors which are caused by acceleration and deceleration. Finally, it also lowers surface quality, by causing tatami patterns during zigzag cutting, due to differences in the locations of acceleration and deceleration in the forward and backward paths. Thus, in order to solve such problems, a method of generating cutter location data with consideration to the machine tool control characteristics, which are the NC sampling time, the feedrate limiters, and acceleration and deceleration, is proposed. The effectiveness of the proposed method is confirmed by simulations and experiments. Compared with a commercial CAM system, the proposed method increases the feedrate, smoothes acceleration and deceleration, and reduces the cutting time by approximately 50%. The proposed method also improves the surface quality and eliminates tatami patterns.

An Inductive Link-Based Wireless Power Transfer System for Biomedical Applications

A wireless power transfer system using an inductive link has been demonstrated for implantable sensor applications. The system is composed of two primary blocks: an inductive power transfer unit and a backward data communication unit. The inductive link performs two functions: coupling the required power from a wireless power supply system enabling battery-less, long-term implant operation and providing a backward data transmission path. The backward data communication unit transmits the data to an outside reader using FSK modulation scheme via the inductive link. To demonstrate the operation of the inductive link, a board-level design has been implemented with high link efficiency. Test results from a fabricated sensor system, composed of a hybrid implementation of custom-integrated circuits and board-level discrete components, are presented demonstrating power transmission of 125 mW with a 12.5% power link transmission efficiency. Simultaneous backward data communication involving a digital pulse rate of up to 10 kbps was also observed.

An integrated approach for main path analysis: Development of the Hirsch index as an example

AbstractThis study enhances main path analysis by proposing several variants to the original approach. Main path analysis is a bibliometric method capable of tracing the most significant paths in a citation network and is commonly used to trace the development trajectory of a research field. We highlight several limitations of the original main path analysis and suggest new, complementary approaches to overcome these limitations. In contrast to the original local main path, the new approaches generate the global main path, the backward local main path, multiple main paths, and key‐route main paths. Each of them is obtained via a perspective different from the original approach. By simultaneously conducting the new, complementary approaches, one uncovers the key development of the target discipline from a broader view. To demonstrate the value of these new approaches, we simultaneously apply them to a set of academic articles related to the Hirsch index. The results show that the integrated approach discovers several paths that are not captured by the original approach. Among these new approaches, the key‐route approach is especially useful and hints at a divergence–convergence–divergence structure in the development of the Hirsch index.

Finite element analysis and experimental investigation on deformation mechanism of non-axisymmetric tube spinning

This paper developed 3D elastoplastic finite element analysis (FEA) models to investigate non-axisymmetric tubes neck spinning. The three-roller mandreless neck spinning process was simulated by commercial FEA software, MSC. Marc. The distribution of the transient von Mises stresses in the contact zone between the roller and the blank, and the equivalent plastic strains after spinning were obtained. The locations and causes of fractures were analyzed. The thickness distribution of the spun workpiece was investigated numerically and experimentally. It shows that during 3D non-axisymmetric tubes spinning, diametral elongation and fractures mostly occur at the opening end of workpiece, which considered as the primary location of defects. Fractures may also occur easily at the initial spinning area, which may be considered a secondary location of defects. The distributions of equivalent stresses and strains are non-uniform during both offset and oblique 3D non-axisymmetric tubes spinning. The maximum stress and strain values occur at the location where the biggest offset or inclination is induced, while the minimum values occur at the opposite location of 180° away from the maximum values. For the oblique tube, however, the strain distribution changes gradually along the axial direction, which is different from that of the offset tube. Thinning occurs during forward path spinning and thickening occurs during backward path spinning. Therefore, for multipath neck spinning processes, forward and backward paths should be applied alternately to avoid excessive thinning or thickening of workpiece.

An Efficient Agent Based Rumor Propagation for Wireless Sensor Networks

In the context of Wireless Sensor Networks (WSNs), in this paper, the authors present a new agent based routing protocol named Fast Rumor Agents protocol (FRA). The FRA protocol optimizes the agent (respectively the query) propagation through the network preventing backward paths. With FRA, a rumor must have a straight trajectory, reducing the total overhead of the network. Performances comparisons of ZRR and FRA protocols show that the main contributions of FRA protocol are the reduction of time of path establishment, the overhead caused in the network, and consequently, the energy consumption.

Performance Improvement of Delay-Based TCPs in Asymmetric Networks

Delay-based TCPs detect network congestion in the early stage and successfully prevent periodic packet loss that usually occurs in loss-based TCPs. It has been demonstrated that delay-based algorithms outperform loss-based schemes in many aspects. However, a delay-based TCP may not prevent unnecessary throughput degradation in asymmetric networks and when the congestion occurs in the backward path over symmetric links. In this letter, we modify the mechanism of measuring RTT value for delay-based TCPs without clock synchronization. Based on the simulation results, we show the effectiveness and utilities.

Iterative linearized density matrix propagation for modeling coherent excitation energy transfer in photosynthetic light harvesting

Rather than incoherent hopping between chromophores, experimental evidence suggests that the excitation energy transfer in some biological light harvesting systems initially occurs coherently, and involves coherent superposition states in which excitation spreads over multiple chromophores separated by several nanometers. Treating such delocalized coherent superposition states in the presence of decoherence and dissipation arising from coupling to an environment is a significant challenge for conventional theoretical tools that either use a perturbative approach or make the Markovian approximation. In this paper, we extend the recently developed iterative linearized density matrix (ILDM) propagation scheme [E. R. Dunkel et al., J. Chem. Phys. 129, 114106 (2008)] to study coherent excitation energy transfer in a model of the Fenna-Matthews-Olsen light harvesting complex from green sulfur bacteria. This approach is nonperturbative and uses a discrete path integral description employing a short time approximation to the density matrix propagator that accounts for interference between forward and backward paths of the quantum excitonic system while linearizing the phase in the difference between the forward and backward paths of the environmental degrees of freedom resulting in a classical-like treatment of these variables. The approach avoids making the Markovian approximation and we demonstrate that it successfully describes the coherent beating of the site populations on different chromophores and gives good agreement with other methods that have been developed recently for going beyond the usual approximations, thus providing a new reliable theoretical tool to study coherent exciton transfer in light harvesting systems. We conclude with a discussion of decoherence in independent bilinearly coupled harmonic chromophore baths. The ILDM propagation approach in principle can be applied to more general descriptions of the environment.

The Research and Simulation of Trajectory Generation Method for Tractor-Trailer Mobile Robot

The tractor-trailer mobile robot (TTMR) is composed of a tractor and multiple trailers. It belongs to a typical nonholonomic, underactuated system. The general control theory can hardly be applied to this system. Because of the multi-body tractor-trailer mobile robot existence, the moving trajectory control is very complicated, especially backward path control becomes a difficult problem for this kind of robot control. This paper takes parking trajectory generation for example, makes tentativeness on tractor-trailer mobile robot to generate the trajectory based on Repeatedly Direct Kinematics (RDK) method. The feasible forward and backward trajectory generations algorithm for tractor-trailer mobile robot are proposed. The design complexity and existing singularity for tractor-trailer mobile robot system are solved. Simulations show the effectiveness of the proposed method.

Enhanced domain disjoint backward recursive TE path computation for PCE-based multi-domain networks

The ability of computing optimal routes poses new challenges when extending it to larger multi-domain network scenarios, as the quality of these computed end-to-end inter-domain routes depends on the selection of the domain sequence to be traversed. In the scope of the Internet Engineering Task Force (IETF), the Path Computation Element (PCE) Working Group has not provided definitive solutions to address the domain sequence selection problem, being still a work in progress. To this goal, the Path Computation Flooding (PCF) approach appears as a possible extension to Backward Recursive PCE-based Computation (BRPC) to calculate optimal end-to-end inter-domain paths without requiring a pre-configured domain sequence. Nonetheless, PCF presents major scalability issues in terms of network control overhead and path computation complexity, thus pleading for more accurate domain sequence selection techniques. This paper describes two novel mechanisms to establish inter-domain paths calculating the sequence of domains to be crossed when it is not known in advance. Both procedures make a good trade-off between the control overhead introduced and the accuracy of the computed end-to-end route. The obtained simulation results show the benefits of the proposed contributions, drastically reducing the control overhead while keeping the connection blocking probability close to the optimal values.

Distributed Transmit Beamforming without Phase Feedback

Phase feedback and adjustment between wireless nodes greatly reduce the power efficiency of distributed beamforming. In this paper, we propose a distributed transmit beamforming method without any phase feedback between nodes. The concept of our approach is to have the received signals retrace their ways, so that the phase offset of the forward path compensates that of the backward path; as a result, signals from different nodes in-phase combine at the destination. Therefore, the received power or the communication range is increased. In order to implement the concept of "retracement", we also propose a transceiver prototype which is based on the Direct Digital Synthesis technique. Experimental and simulation results validate the effectiveness of our approach.

Control Method of Motion Error Compensation for NC Machine Tools

Servo systems of NC machine tools must minimize trajectory control tracking error by preventing machine resonance and trajectory error between forward and backward paths by improving symmetry. To address such issues, we propose two-degree-of-freedom control using a reference model and a servo control method with the mechanical-characteristics-compensator to compensate for machine vibration. Results of experiments confirmed the effectiveness of our proposed control.