Mean Round-trip Time Research Articles

Tele-robotic distal gastrectomy with lymph node dissection on a cadaver.

The purpose of this study is to evaluate the performance of tele-robotic distal gastrectomy (tele-RDG) with lymph node dissection (LND) using a novel Japanese-made surgical robot hinotori™ (Medicaroid, Kobe, Japan) in a cadaver with a presumptive gastric cancer. The Cadaveric Anatomy and Surgical Training Laboratory (CAST-Lab.) at Hokkaido University and Kushiro City General Hospital (KCGH) are connected by a guaranteed type line (1 Gbps), and the distance between the two facilities is 250 km. A patient cart was installed at CAST-Lab, and a surgeon cockpit was installed at KCGH. Tele-RDG with D2 LND was performed on an adult human cadaver. In all surgical processes, the communication environment was stable without image degradation, and the mean round trip time was 40 milliseconds (36.5-55 milliseconds). For tele-RDG with D2 LND, the operation time was 199 minutes without any technical problems. Tele-RDG using hinotori™ was feasible and similar to local robotic RDG.

Arrhythmogenic vulnerability of re-entrant pathways in post-infarct ventricular tachycardia assessed by advanced computational modelling.

Substrate assessment of scar-mediated ventricular tachycardia (VT) is frequently performed using late gadolinium enhancement (LGE) images. Although this provides structural information about critical pathways through the scar, assessing the vulnerability of these pathways for sustaining VT is not possible with imaging alone.This study evaluated the performance of a novel automated re-entrant pathway finding algorithm to non-invasively predict VT circuit and inducibility. Twenty post-infarct VT-ablation patients were included for retrospective analysis. Commercially available software (ADAS3D left ventricular) was used to generate scar maps from 2D-LGE images using the default 40-60 pixel-signal-intensity (PSI) threshold. In addition, algorithm sensitivity for altered thresholds was explored using PSI 45-55, 35-65, and 30-70. Simulations were performed on the Virtual Induction and Treatment of Arrhythmias (VITA) framework to identify potential sites of block and assess their vulnerability depending on the automatically computed round-trip-time (RTT). Metrics, indicative of substrate complexity, were correlated with VT-recurrence during follow-up. Total VTs (85 ± 43 vs. 42 ± 27) and unique VTs (9 ± 4 vs. 5 ± 4) were significantly higher in patients with- compared to patients without recurrence, and were predictive of recurrence with area under the curve of 0.820 and 0.770, respectively. VITA was robust to scar threshold variations with no significant impact on total and unique VTs, and mean RTT between the four models. Simulation metrics derived from PSI 45-55 model had the highest number of parameters predictive for post-ablation VT-recurrence. Advanced computational metrics can non-invasively and robustly assess VT substrate complexity, which may aid personalized clinical planning and decision-making in the treatment of post-infarction VT.

Prospects and Challenges of Water Management Stakeholders in the Rural Communities of the Noun Division, West Region, Cameroon

Seven years after the formulation of the Sustainable Development Goals (SDGs), uncertainty looms on whether the 2030 targets would be achieved. In the Noun Division of Cameroon diverse stakeholders have made substantial efforts to meet the 2030 SDG on the provision of portable water to the rural communities. Despite these laudable efforts, access to portable water remains a topical issue in the Division. The focus of this study was to assess the prospects and challenges of water management stakeholders in the provision of portable water to the rural communities of the Noun Division. In order to meet this objective, a total of 400 questionnaires were randomly administered to household heads in rural councils with the help of traditional authorities. International, national, regional and local stakeholders involved in the management of water resources were interviewed. The “17 in 1” and “iQ. BAC” water test kits were respectively used to analyse the chemical properties of drinking water sources in situ and faecal content within 48 hours. Descriptive and inferential statistical techniques were used to analyse quantitative data while content and narrative analysis were used for qualitative data. Findings revealed that local, national and international portable water management stakeholders prioritised the improvement of portable water sources over other parameters. Whereas the proportion of people who depended on unimproved water sources reduced from 79.92% in 2015 to 57.52% in 2022, that with mean round trip time of over 30 minutes rather increased from 49.62% to 50.38%. Moreover, 50% of the interviewee indicated that portable water is expensive in the area, suggesting why 42.3% of the population still rely on streams today. Five sampled streams analysed with the iQ. BAC test kit tested positive for total coliform while confirmatory laboratory analysis revealed E. coli concentration of 11-100MPN/100ml in Njimom which according to WHO is synonymous to medium risk. The “17 in 1” test kit revealed abnormal concentration of lead (0.03-0.05 ppm) and sulphate (400-800 ppm) mainly in streams and boreholes. PCA identified five main components that account for 72.71% variance in the hydrochemistry of drinking water sources. Though, none of the four scenarios developed revealed complete access to improve drinking water in rural areas of the Noun Division by 2030, Njimom and Foumbot showed remarkable progress under the most probable scenario (50% increase in current effort) considered to be the most realistic. Water governance stakeholders should quadruple their current efforts in improving portable water sources and adopt a holistic approach that engulfs water quality improvement if they wish to make significant progress on SDG 6.1.

Modeling and improving named data networking over IEEE 802.15.4

Named Data Networking (NDN) is a promising architecture that aims to natively satisfy emerging applications such as the Internet of Things (IoT). Therefore, enabling NDN in real-world IoT deployments is becoming essential in order to benefit from Information Centric Networking (ICN) features. To design realistic NDN-based communication solutions for IoT, revisiting mainstream technologies such as low-power wireless standards may be the key. In this paper, we explore NDN forwarding over IEEE 802.15.4 following two steps. First, we mathematically model a broadcast-based forwarding strategy for NDN over constrained networks with the IEEE 802.15.4 technology in mind. The model estimates the number of frames transmitted and the mean round-trip time per request, under content popularity considerations. Second, based on mathematical and experimental observations of the broadcast-based forwarding at network level, we elaborate Named-Data Carrier-Sense Multiple Access (ND-CSMA), an adaptation of the Carrier-Sense Multiple Access (CSMA) algorithm used in IEEE 802.15.4. Results show that adaptations such as ND-CSMA may be reasonably envisioned to improve NDN efficiency with current IoT technologies.

Realization of Mobile Femtocells: Operational and Protocol Requirements

Femtocells are commissioned in wide range of commercial systems, such as CDMA, GSM, LTE, Wi-Fi, and WiMAX, and offer economically viable solutions to improve network scalability and indoor coverage. The ability to offer multitude of context-aware and value added services, and per-user customization have caught world-wide research interest on femtocells. In this article, we have investigated the feasibility to use femtocells as short-range mobile base stations, and discussed the demanding architectural requirements and challenges. The protocol stack on legacy femtocells must be modified to realize mobility. Mobility introduces new challenges in security and user privacy. Firstly, we analyze several candidate mobility protocols that are deployable on Mobile Femtocells (MFs). Among them, Host Identity Protocol (HIP) was chosen due to enhanced support in flexible mobility, security and end-user privacy. Secondly, we propose the indispensable modifications that enable device mobility, and the suitable transport architecture options based on direct IP links and relay chains. Finally, with the simulation results, the proposal is verified, and the architectural options are evaluated. That, in turn, proves the proposed mobility protocol has low latency in location locking with respect to another competing protocol and low resource utilization as it is depicted from mean round trip time.

Optimization of expanded ensemble methods

Expanded ensemble methods, designed to sample a range of an order parameter lambda of interest, can be optimized to overcome the difficulties associated with traversing large free-energy barriers or rugged landscapes. The optimization strategy of Trebst et al. [Phys. Rev. E 70, 046701 (2004)] is based on finding suitable biasing weights for inter-lambda transitions that maximize the number of round trips that the system performs between the lower and upper lambda bounds. In this work, this optimized-ensemble methodology is extended by finding weights that minimize the mean round-trip time tau (between the lambda end states) for a Markovian walk. Applications are presented for an atomistically detailed model and for systems where one needs to sample a wide range of concentrations or compositions. A less rigorous method that implements a dual tau minimization (for both upward and downward trajectories) is found to be harder to converge but produce more round trips than a method based on a single tau minimization for all trajectories. While the proposed methods do not always minimize the true tau, they have performances that are either similar or better than those of the original optimized-ensemble method and provide useful information to characterize deviations from Markovian dynamics in the sampling of the lambda space.

On the long-run behavior of equation-based rate control

We consider unicast equation-based rate control, where, at some points in time, a source adjusts its rate to f(p,r). Here p is an on-line estimate of the loss-event rate, r, of the mean round-trip time, both as observed by this source, and f is a TCP throughput formula. It was generally believed that such a source would be TCP-friendly, that is, under the same operating conditions, its long-run time-average send rate (throughput) would not be larger than that of a TCP source. Our goal is to identify whether, and how far, this is true. First, we identify factors that play a role in TCP friendliness and find that it is important to study them separately. Then we analyze the importance of individual factors. A first factor is conservativeness (= throughput not larger than f(p,r)). We show that conservativeness is influenced by some convexity properties of f(p,r) with respect to p, and the covariance of the loss process. We show that in many real life cases these conditions result in conservativeness and, sometimes, excessive conservativeness. This explains the previously observed phenomena of throughput-drop when losses are high and f is the so-called PFTK formula. The second factor is that the source may experience considerably different loss-event rate than a TCP source. We identify and analyze two limit cases where this may lead to either TCP-friendliness or, in contrast, non-TCP-friendliness. Other factors such as round trip time and obedience of TCP to its own formula are found to be less significant. Our claims are obtained by analysis, and verified by numerical examples, simulations, laboratory and Internet experiments. Our results suggest that TCP-friendliness is difficult to verify in practice, whereas conservativeness is easier.

Optimizing the ensemble for equilibration in broad-histogram Monte Carlo simulations

We present an adaptive algorithm which optimizes the statistical-mechanical ensemble in a generalized broad-histogram Monte Carlo simulation to maximize the system's rate of round trips in total energy. The scaling of the mean round-trip time from the ground state to the maximum entropy state for this local-update method is found to be O ( [N ln N](2) ) for both the ferromagnetic and the fully frustrated two-dimensional Ising model with N spins. Our algorithm thereby substantially outperforms flat-histogram methods such as the Wang-Landau algorithm.

RUN-TIME ADJUSTED CONGESTION CONTROL FOR MULTIMEDIA: EXPERIMENTALS RESULTS

Multimedia communications over Internet should achieve adequate quality of service (QoS) while maintaining 'fairness' in network resources allocation with respect to competing connections. The fairness is usually achieved by means of the congestion control, which could induce high variations on the perceived throughput and then affecting the QoS. On the other hand, the variations of throughput of the multimedia communication can be neglected if a minimum average throughput is guaranteed to the playout buffer used by the application. These considerations can be exploited to solve the conflicting requirements of fairness and QoS. The transport protocol proposed here is a modified version of the window-based datagram congestion control protocol, that implements a TCP-like congestion control mechanism wherein the multiplicative decrease of the congestion window is controlled by a non-linear function. Experimental results show that this modified congestion control algorithm, which in turn is adjusted at run-time based on the estimated mean round-trip time, is capable to provide the average throughput required by the encoding technique adopted for the multimedia data compression, while guaranteeing the required fairness with respect to competing TCP connections.

Two elevators serving up-traffic

A model is described for the motion of two elevators serving traffic only from a single lobby floor to multiple higher floors. Over a certain range of passenger arrival rates, the average round trip time of an elevator can be approximated by a linear function of the number of passengers carried which, in turn, is proportional to the time since the last elevator departure from the lobby (the headway). A pair of deterministic equations for the means of two state variables describes the approximate evolution of the system behavior. These equations lead to a very strange chaotic type of motion in the two-dimensional state space. For moderately light traffic the two elevators tend to travel close together, but for heavy traffic the headways tend to be nearly uniformly distributed over the mean round trip time of a single elevator.