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Objective: To evaluate adiposity after anterior cruciate ligament reconstruction (ACLR): i) cross-sectionally (1-year post-ACLR) compared to uninjured controls; ii) longitudinally up to 5 years post-ACLR; and iii) associations with patient-reported symptoms and physical performance. Methods: In 107 individuals post-ACLR and 19 controls, we assessed global (BMI), peripheral (subcutaneous adipose tissue thickness on the posteromedial side of knee MRI), and central (waist circumference in ACLR group) adiposity. Patient-reported symptoms (Knee injury and Osteoarthritis Outcome Score) and physical performance (hop for distance) were evaluated at 1 and 5 years post-ACLR. Linear regression models evaluated adiposity between groups. Paired t-tests evaluated changes in adiposity from 1- to 5 years post-ACLR. Linear regression models analyzed adiposity's associations with patient-reported symptoms and physical performance at 1-year post-ACLR, changes in symptoms and performance over 4 years post-ACLR, and longitudinal changes in adiposity and symptoms and performance, controlling for age, sex, and activity level. Results: Individuals 1-year post-ACLR were associated with higher average global (3 ​kg/m2) and peripheral adiposity (2.3 ​mm). From 1- to 5 years post-ACLR, higher average global (0.58 ​kg/m2) and central (5 ​cm) adiposity, and lower average peripheral adiposity (1.3 ​mm) were observed. In general, adiposity at one-year post-ACLR was negatively associated with patient-reported symptoms and physical performance, and changes from 1 to 5 years post-ACLR. Increases in adiposity were negatively associated with changes in patient-reported symptoms and physical performance over four years post-ACLR. Conclusion: Greater global and central adiposity is a feature of young adults following ACLR and influences current and future patient-reported symptoms and physical performance.

Aiming at the problems of low accuracy of determining attack nodes and large detection error in the wormhole attack detection method of power communication sensor networks, a wormhole attack detection method based on hops is proposed. Firstly, the working process of power communication sensor network nodes is analyzed; Regard the node area as a closed circle, set the distance between nodes and communication radius in the area, and determine the wormhole attack location; Then, introduce the hop number, replace the linear distance between attack nodes with the hop distance of hop number, the centroid position is calculated by polygon calculation, the node hop distance is determined, and the wormhole attack probability is calculated; Finally, the average hop distance between wormhole attack nodes is calculated, and the path hop distance of attack behavior is corrected with the help of objective function and minimum mean square error criterion to complete attack detection. The experimental results show that the detection accuracy of this method is 98%, and the detection error is only 2.6%, so it has application value. [ABSTRACT FROM AUTHOR]

Learning and exploring the connectivity of unknown networks represent an important problem in practical applications of communication networks and social-media networks. Modeling large-scale networks as connected graphs is highly desirable to extract their connectivity information among nodes to visualize network topology, disseminate data, and improve routing efficiency. This paper investigates a simple measurement model in which a small subset of source nodes collect hop distance information from networked nodes in order to generate a virtual coordinate system (VCS) for networks of unknown topology. We establish the VCS to define logical distance among nodes based on principal component analysis and to determine connectivity relationship and effective routing methods. More importantly, we present a robust analytical algorithm to derive the VCS against practical issues of missing and corrupted measurements. We also develop a connectivity inference method which classifies nodes into layers based on the hop distances and derives partial information on network connectivity.

The relay positions or hop distances in a multi-hop relaying scheme is an important parameter that can be optimized in order to mitigate the angle-of-arrival variance or pointing error in a free-space optical (FSO) backhaul link. In this study, we have optimized the relay positions for amplify-and-forward and decode-and-forward relays in a multi-hop unmanned aerial vehicle-based relaying scheme for FSO. Particularly, we have shown that a significant performance improvement may be achieved by optimizing the outage probability as a function of the hop distance for amplify-and-forward relays when the relays are constrained by a finite power gain. Additionally, we have discovered that for a low signal-to-noise ratio channel, the optimal hop distance of a particular hop for decode-and-forward relays is inversely proportional to angle-of-arrival variance in that hop. [ABSTRACT FROM AUTHOR]

Abstract Background Rehabilitation following anterior cruciate ligament (ACL) reconstructions is based mainly on comprehensive progressive exercise programmes using a multi-dimensional approach. Elastic knee sleeves may be useful adjuncts to rehabilitation. The aim of this study was to determine the immediate and 6-week effects of wearing a knee sleeve on person-reported outcomes and function in participants who had undergone an ACL reconstruction and who had residual self-reported functional limitations. Methods Individuals with ACL reconstruction in the previous 6 months to 5 years were recruited. Immediate effects of a commercially-available elastic knee sleeve on single-leg horizontal hop distance were explored using a cross-over design. Following this first session, participants were randomised into a Control Group and a Sleeve Group who wore the sleeve for 6 weeks, at least 1 h daily. Outcome measures for the randomised clinical trial (RCT) were the International Knee Documentation Classification Subjective Knee Form (IKDC-SKF) score, the single-leg horizontal hop distance, and isokinetic quadriceps and hamstring peak torque. Linear mixed models were used to determine random effects. Where both limbs were measured at multiple time points, a random measurement occasion effect nested within participant was used. Results Thirty-four individuals (16 women) with ACL reconstruction completed the cross-over trial. Hop distance for the injured side during the sleeve condition increased by 3.6 % (95 % CI 0.4–6.8 %, p = 0.025). There was no evidence of differential changes between groups for the IKDC-SKF (Sleeve Group n = 15; Control Group n = 16; p = 0.327), or relative improvement in the injured side compared to the uninjured side for the physical performance measures (Sleeve Group n = 12, Control Group n = 12; three-way interaction p = 0.533 [hop distance], 0.381 [quadriceps isokinetic peak torque], and 0.592 [hamstring isokinetic peak torque]). Conclusions Single-leg hop distance of the ACL reconstructed side improved when wearing a knee sleeve. Wearing the knee sleeve over 6 weeks did not lead to enhanced improvements in self-reported knee function, hop distance and thigh muscle strength compared to the control group. Trial registration The trial was prospectively registered with the Australia New Zealand Clinical Trials Registry No: ACTRN12618001083280 , 28 June 2018.

The distance-based critical node problem involves identifying a subset of nodes in a network whose removal minimises a pre-defined distance-based connectivity measure. Having the classical critical node problem as a special case, the distance-based critical node problem is computationally challenging. In this article, we study the distance-based critical node problem from a heuristic algorithm perspective. We consider the distance-based connectivity objective whose goal is to minimise the number of node pairs connected by a path of length at most k, subject to budgetary constraints. We propose a centrality based heuristic which combines a backbone-based crossover procedure to generate good offspring solutions and a centrality-based neighbourhood search to improve the solution. Extensive computational experiments on real-world and synthetic graphs show the effectiveness of the developed heuristic in generating good solutions when compared to exact solution. Our empirical results also provide useful insights for future algorithm development. [ABSTRACT FROM AUTHOR]

Abstract Wireless sensor network (WSN) possesses very broad application prospect in many fields, where the node location technology is one of the key technologies of WSN. Distance vector hop (DV-Hop) localization algorithm is a widely used algorithm in this technology, and it uses routing exchange protocol to make unknown nodes obtain beacon node information which will be used for coordinate calculation, therefore there exists certain error for the algorithm itself. Aiming at the disadvantage of large error existing in the traditional wireless sensor network location algorithm based on DV-Hop, an improved DV-Hop algorithm based on hop thinning and distance correction is proposed. The minimum hop is corrected by introducing received signal strength indication (RSSI) ranging technology, and the average hop distance is corrected by weighted average value of hop distance error and estimated distance error. Subsequently, the overall improvement on the location performance of the Hop-DV location algorithm is realized, and the location error is reduced. Under the Matlab simulation environment, the simulation experiment on the improved algorithm is carried out. The experimental results show that the improved algorithm reduces the location error and has higher location accuracy.

Background: Rehabilitation following anterior cruciate ligament (ACL) reconstructions is based mainly on comprehensive progressive exercise programmes using a multi-dimensional approach. Elastic knee sleeves may be useful adjuncts to rehabilitation. The aim of this study was to determine the immediate and 6-week effects of wearing a knee sleeve on person-reported outcomes and function in participants who had undergone an ACL reconstruction and who had residual self-reported functional limitations.Methods: Individuals with ACL reconstruction in the previous 6 months to 5 years were recruited. Immediate effects of a commercially-available elastic knee sleeve on single-leg horizontal hop distance were explored using a cross-over design. Following this first session, participants were randomised into a Control Group and a Sleeve Group who wore the sleeve for 6 weeks, at least 1 h daily. Outcome measures for the randomised clinical trial (RCT) were the International Knee Documentation Classification Subjective Knee Form (IKDC-SKF) score, the single-leg horizontal hop distance, and isokinetic quadriceps and hamstring peak torque. Linear mixed models were used to determine random effects. Where both limbs were measured at multiple time points, a random measurement occasion effect nested within participant was used.Results: Thirty-four individuals (16 women) with ACL reconstruction completed the cross-over trial. Hop distance for the injured side during the sleeve condition increased by 3.6 % (95 % CI 0.4-6.8 %, p = 0.025). There was no evidence of differential changes between groups for the IKDC-SKF (Sleeve Group n = 15; Control Group n = 16; p = 0.327), or relative improvement in the injured side compared to the uninjured side for the physical performance measures (Sleeve Group n = 12, Control Group n = 12; three-way interaction p = 0.533 [hop distance], 0.381 [quadriceps isokinetic peak torque], and 0.592 [hamstring isokinetic peak torque]).Conclusions: Single-leg hop distance of the ACL reconstructed side improved when wearing a knee sleeve. Wearing the knee sleeve over 6 weeks did not lead to enhanced improvements in self-reported knee function, hop distance and thigh muscle strength compared to the control group.Trial Registration: The trial was prospectively registered with the Australia New Zealand Clinical Trials Registry No: ACTRN12618001083280 , 28 June 2018. [ABSTRACT FROM AUTHOR]

To compare self-report and functional outcomes between participants with anterior cruciate ligament reconstruction (ACLR) with age and activity matched controls. Cross-sectional study. University laboratory-based study. Twenty-five participants (30.8 ± 9.7 years; 13 women), two to ten years post anterior cruciate ligament reconstruction; 24 controls (31.0 ± 10 years, 13 women). Knee Osteoarthritis and Injury Outcome Score (KOOS), Tegner, Marx Activity and Fear of Re-injury scales, and SF-12; isokinetic quadriceps and hamstring peak torque and single-leg hop distance. There were no between-groups differences for the Tegner and the Marx Activity Scales. The ACLR group had lower KOOS dimensions (p < 0.001), SF-12 Physical Component Scores (p = 0.008), and higher Fear of Reinjury Scores (<0.001) than the controls. No significant differences were found for physical performance measures between the ACLR and the control groups. Significant between-side differences for the ACLR group were evident for concentric quadriceps (p < 0.001) and concentric hamstring peak torque (p = 0.002), and hop distance (p < 0.001). Knee-specific symptoms and function, activity and quality of life were lower, and fear of re-injury was higher for participants with ACLR than controls. Side-to-side thigh muscle strength and hop distance deficits were evident for the ACLR group. • 18 of 25 participants, 2–10 years post ACL reconstruction had 'symptomatic' knees. • The ACLR group had lower symptoms, function, and quality of life scores than Controls. • The ACLR group had higher Fear of Re-injury scores than Controls. • Long-term muscle strength and hop distance asymmetries were evident in the ACL group. [ABSTRACT FROM AUTHOR]

As an intrinsic part of the Internet of Things (IoT) ecosystem, machine-to-machine (M2M) communications are expected to provide ubiquitous connectivity between machines. Millimeter-wave (mmWave) communication is another promising technology for the future communication systems to alleviate the pressure of scarce spectrum resources. For this reason, in this paper, we consider multi-hop M2M communications, where a machine-type communication (MTC) device with the limited transmit power relays to help other devices using mmWave. To be specific, we focus on hop distance statistics and their impacts on system performances in multi-hop wireless networks (MWNs) with directional antenna arrays in mmWave for M2M communications. Different from microwave systems, in mmWave communications, wireless channel suffers from blockage by obstacles that heavily attenuate line-of-sight signals, which may result in limited per-hop progress in MWNs. We consider two routing strategies aiming at different types of applications and derive the probability distributions of their hop distances. Moreover, we provide their baseline statistics assuming the blockage-free scenario to quantify the impact of blockages. Based on the hop distance analysis, we propose a method to estimate the end-to-end performances (e.g., outage probability, hop count, and transmit energy) of the mmWave MWNs, which provides important insights into mmWave MWN design without time-consuming and repetitive end-to-end simulation. [ABSTRACT FROM AUTHOR]

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As low powered, battery operated nodes are used in wireless sensor networks, conservation of energy at all levels of system design is very essential. In this paper, we focus on the efficient transmission of data over a noisy channel by selecting optimal energy efficient values for the physical layer parameters. We introduce an energy metric called "Effectually Received bit Energy" (ERE) which is the amount of energy spent in a successful transmission over a given channel. By minimizing this metric, we find the optimum hop distance and optimal transmit energy for different modulation schemes. The results which are obtained in this paper can be useful to the network designers for selecting the suitable hop distance, transmit energy and the modulation scheme that will help in maximizing the lifetime of the network. [ABSTRACT FROM AUTHOR]

ABSTRACT Wireless sensor networks (WSNs) are susceptible to various attacks, and these attacks pose a major threat to the normal functioning of WSNs. Jamming is one such attack, which affects network operations by blocking frequencies. Hence, the need of defending such attack is of utmost importance. This paper proposes three variants of a data forwarding scheme using multi-level multi-tier architecture, which employs judicious surfing of a pair of channels to defend jamming attack in WSNs. Variant I defends the attack at the cost of an affordable delay. Improvement of the scheme in minimizing data transmission time is made in variant II. Further improvement in transmission time is made in variant III and is made more realistic by introducing sensing capability at all tiers, thereby increasing network coverage. Simulation is performed to establish each of the successor's variant's improvement over its predecessor. The performance of the scheme in terms of area coverage, packet delivery ratio, and control message overhead is compared with an existing jamming-defending scheme for infrastructure-based wireless network. Finally, comparison results establish that although the proposed scheme is equivalent to its infrastructure-based counterpart in terms of coverage, it provides a more lightweight solution and maintains improved performance in terms of packet delivery ratio. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Wireless mesh network (WMN) is a new multi-hop network for broadband accessing to internet. However, there exists a server unfairness problem based on different hop distances in WMN. To solve this problem, the unfairness issue was analyzed in test-bed experiment and NS2 simulation. A dynamic queue management scheme E-QMMN was proposed, which allocates the queue buffer according to the hop distance of every flow. The experimental results show that the proposed scheme can not only increase the hop distance fairness of the legacy scheme at most 50%, but also reduce the average round trip time at least 29% in congested WMN environments. [ABSTRACT FROM AUTHOR]

The performance analysis of a wireless network significantly depends on the routing-related statistics. Power consumption, multihop communication delay, and position estimation are among the parameters that are affected by the routing scheme. In this paper, statistical parameters of the most forward within range routing in 1-D ad hoc networks are investigated. Several parameters, such as the probability mass function (pmf) of the number of broadcast hops, the probability density function of the connectivity distance for a given number of hops, and the pmf of the number of hops between the source and the destination, are derived. For cases where the exact analytical results are recursive and complicated, good approximate nonrecursive formulas are also derived. We verify the correctness of the exact formulas and the precision of the approximate results by simulations. Some applications of the derived statistical parameters are also presented. [ABSTRACT FROM PUBLISHER]

We introduce a notion of t-quasi-spanner as an alternative to classical t-spanners. Our motivation for quasi-spanner comes from a problem of computing a sparse backbone for ad hoc wireless networks with fixed transmission ranges. We study computational complexity of the problem of computing sparsest quasi-spanner. Then we concentrate on the case t = 2 and give a distributed algorithm for computing a 2-quasi-spanner with linear number of edges. Finally, we give a modification of our algorithm which performs well on a class of random ad hoc networks. [ABSTRACT FROM AUTHOR]

Wireless sensor network (WSN) possesses very broad application prospect in many fields, where the node location technology is one of the key technologies of WSN. Distance vector hop (DV-Hop) localization algorithm is a widely used algorithm in this technology, and it uses routing exchange protocol to make unknown nodes obtain beacon node information which will be used for coordinate calculation, therefore there exists certain error for the algorithm itself. Aiming at the disadvantage of large error existing in the traditional wireless sensor network location algorithm based on DV-Hop, an improved DV-Hop algorithm based on hop thinning and distance correction is proposed. The minimum hop is corrected by introducing received signal strength indication (RSSI) ranging technology, and the average hop distance is corrected by weighted average value of hop distance error and estimated distance error. Subsequently, the overall improvement on the location performance of the Hop-DV location algorithm is realized, and the location error is reduced. Under the Matlab simulation environment, the simulation experiment on the improved algorithm is carried out. The experimental results show that the improved algorithm reduces the location error and has higher location accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the hop distance optimization problem in ad hoc networks where cooperative multi-input-single-output (MISO) is adopted to improve the energy efficiency of the network. We first establish the energy model of multihop cooperative MISO transmission. Based on the model, the energy consumption per bit of the network with high node density is minimized numerically by finding an optimal hop distance, and, to get the global minimum energy consumption, both hop distance and the number of cooperating nodes around each relay node for multihop transmission are jointly optimized. We also compare the performance between multihop cooperative MISO transmission and single-input-single-output (SISO) transmission, under the same network condition (high node density). We show that cooperative MISO transmission could be energy-inefficient compared with SISO transmission when the path-loss exponent becomes high. We then extend our investigation to the networks with varied node densities and show the effectiveness of the joint optimization method in this scenario using simulation results. It is shown that the optimal results depend on network conditions such as node density and path-loss exponent, and the simulation results are closely matched to those obtained using the numerical models for high node density cases. [ABSTRACT FROM PUBLISHER]