A Framework for Performing Statistical Testing of Distributed Systems

Buffer-equipped relay selection schemes in cooperative communication offer evident performance gains in terms of the outage probability and throughput. However, it brings in the increased delay which can be reduced by increasing the selection probability of relay-to-destination links. In this paper, a controlling parameter, termed as the buffer limit, is proposed for the buffer occupancy, which modifies the selection of the corresponding (transmitting and receiving) links of the relay and also has its impact on the average delay and throughput. The probability of selecting the transmitting and receiving channels is directly controlled by reallocating the weights of links considering the buffer limit. A link having the largest weight is activated, and the corresponding relay is chosen for transmission or reception. We evaluate the outage probability, average end-to-end queuing delay, and average throughput using Markov modeling of the status of the buffers at relays. Analytical findings are studied for various values of the buffer limit and confirmed by means of the Monte Carlo simulations. The proposed scheme works as the max-weight relay selection scheme when the buffer limit is set to 1/2 of the buffer size. The suggested scheme is compared with the existing schemes. The outage probability is traded with the average end-to-end queuing delay or the average throughput by adjusting the values of the buffer limit.

The false positive rate and false negative rate of partial discharge warning of distribution network sensors are high, and the detection delay is too long. An improved random forest and multi-source feature fusion method is proposed. Firstly, a multi-source feature pool containing time domain, frequency domain, and environmental features is constructed to screen high-correlation features; secondly, a dynamic weight allocation mechanism is designed to optimize the combination of subjective weights of analytic hierarchy process and objective weights of random forest feature importance based on game theory to minimize the sum of comprehensive weight deviations; finally, the random forest algorithm is improved, and adaptive tree depth adjustment and weighted voting mechanism are introduced. Experiments show that the average false positive rate of this method in the measured data is 9.43%; the false negative rate is reduced to $12.0 \%-18.0 \%$; the average response delay is 64.2 ms, which provides reliable technical support for active defense of distribution network.

The effect of process variation (PV) on delay is a major reason to deteriorate the performance in advanced technologies. The performance of different routing algorithms is determined with/without PV for various traffic patterns. The saturation throughput and average message delay are used as performance metrics to evaluate the throughput. PV decreases the saturation throughput and increases the average message delay. PV increases the average message delay by up to 90% and decreases the saturation throughput by up to 29% compared with nominal characteristics of different routing algorithms. Adaptive routing algorithm should be manipulated with the PV. A novel PV delay and congestion aware routing (PDCR) algorithm is proposed for asynchronous network-on-chip design. PDCR is adaptive, low cost, and scalable. The novel routing algorithm outperforms different adaptive routing algorithms in the average delay and saturation throughput for various traffic patterns. PDCR can achieve up to 12%–32% average message delay lower than that of other routing algorithms. Moreover, the proposed scheme yields improvements in saturation throughput by up to 11%–82% compared with other adaptive routing algorithms.

As the IEEE 802.16e Wireless Metropolitan Access Network (WMAN) supports the mobility of a mobile station (MS), increasing MS power efficiency has become an important issue. In this paper, we analyze the sleep-mode operation for an efficient power saving mechanism for delay-guaranteed services in the IEEE 802.16e WMAN and observe the effects of the operating parameters related to this operation. For the analysis we use the M/GI/1/K queueing system with multiple vacations, exhaustive services and setup times. In the analysis, we consider the power consumption during the wake-mode period as well as the sleep-mode period. As a performance measure for the power consumption, we propose the power consumption per unit time per effective arrival which considers the power consumption and the packet blocking probability simultaneously. In addition, since we consider delay-guaranteed services, the average packet response delay is also considered as a performance measure. Based on the performance measures, we obtain the optimal sleep-mode operation which minimizes the power consumption per unit time per effective arrival with a given delay requirement. Numerical studies are also provided to investigate the system performance and to show how to achieve our objective.

Low-latency computational-task execution can be achieved by leveraging device-to-device offloading and parallel processing over nearby extreme edge devices (EEDs), a paradigm known as extreme edge computing (EEC). However, EEC performance is challenged by device spatial randomness with intermittent wireless connectivity, limited device computing power, time-varying availability, and device failures. This paper introduces a novel spatiotemporal analytical framework for EEC by integrating stochastic geometry with an absorbing continuous-time Markov chain (ACTMC) to capture the interplay between communication and computation. Modeling a large-scale millimeter-wave network, we derive tractable expressions for the average task response delay and the task completion probability under both random and location-aware EED selection. Numerical results quantify the impact of location-awareness and unveil the existence of an optimal task segmentation that minimizes delay, which depends on network parameters and EED capabilities. We also demonstrate that device failures and EED scarcity exacerbate delay, which can be mitigated through a collaborative load-balancing approach between EEC and Multi-Access Edge Computing (MEC) schemes. Simulations and sensitivity analyses validate the proposed framework and offer design insights for optimizing system performance.

Diffusion and sorption of radionuclides in potential host rocks are key processes controlling the safe geological disposal of radioactive waste. To set reliable parameters of diffusion and sorption relevant to safety assessment, it is necessary to understand these processes under laboratory and in situ conditions, and to confirm the consistency or the relationship of these parameters (D e and K d ) between both conditions. This paper focused on comparative experiments and modeling of diffusion and sorption of Cs for both in situ and laboratory conditions in siliceous mudstone in the 350 m Gallery at the Horonobe Underground Research Laboratory (URL) in northern Hokkaido, Japan. The D e values for Cs were consistent between in situ and laboratory results, indicating typical cation excess and porewater salinity effects. The effect of the diffusion direction, parallel or perpendicular to the bedding plane was not significant. The K d values for Cs were also consistent between in situ and laboratory results, indicating the porewater salinity effect. The clay-based modeling approach, which accounts for the major contributions of clay minerals through cation excess diffusion by electrostatic interaction at the clay surface, and the component additive cation exchange reactions, could interpret the diffusion and sorption behaviors of Cs under different salinity conditions and for both in situ and laboratory conditions.

In this article, we address the goal of achieving performance gains under heavy-load and fast fading conditions. CoopMACI protocol proposed in Proceedings of the IEEE International Conference on Communications (ICC), Seoul, Korea, picks either direct path or relay path based on rate comparison to enhance average throughput and delay performances. However, CoopMACI performance deteriorates under fading conditions because of lower direct path or relay path reliability compared to UtdMAC (Agarwal et al. LNCS, 4479, 415-426, 2007). UtdMAC was shown to perform better than CoopMACI in terms of average throughput and delay performances because of improved transmission reliability provided by the backup relay path. Although better than CoopMACI, UtdMAC does not fully benefit from higher throughput relay path (compared to the direct path), since it uses relay path only as a secondary backup path. In this article, we develop a cooperative MAC protocol (termed as instantaneous relay-based cooperative MAC--IrcMAC) that uses channel coherence time and estimates signal-to-noise ratio (SNR) of source-to-relay, relay-to-destination, and source-to-destination links, to reliably choose between relay path or direct path for enhanced throughput and delay performances. Unique handshaking is used to estimate SNR and single bit feedbacks resolve contentions among relay nodes, which further provides source node with rate (based on SNR) information on source-to-destination, source-to-relay, and relay-to-destination links. Simulation results clearly show that IrcMAC significantly outperforms the existing CoopMACI and the UtdMAC protocols in wireless ad hoc network. Results show average throughput improvements of 41% and 64% and average delay improvementd of 98.5% and 99.7% compared with UtdMAC and CoopMACI, respectively.

Mobility load balancing (MLB) is a function where cells suffering from overload forward their load to other cells, which perform early handover for load balancing by adjusting handover parameters. The downlink user traffic performance impacts by the proposed MLB operation has been evaluated and compared through computer simulations in the paper. According to the results, we found that the proposed MLB algorithm achieve MLB gain of as much as 4.1% in average throughput and 12.9% in average delay, and MLB cost of as much as 1.3% in average standard deviation on mobile user equipments (UEs). On the other hand, with regard to fixed UEs, we obtained no MLB gain in average throughput, and MLB cost of as much as 5.5% in average delay and 2.7% in average standard deviation. These results inform that the proposed MLB algorithm is more efficient to mobile UEs than fixed UEs in association with user traffic impact aspect.

With the increasing development of distributed system application, distributed system security is facing the heavy challenge. To arrive at the goal of intensifying the behavior trustworthiness and controllability of distributed systems, we focus on building the trustworthy model between distributed system and user behaviors and strengthening the manageability of distributed systems. By setting up the trustworthy computing circumstance and supplying the trustworthy validation and the active protection based on identity and behavior for trustworthy distributed system, we may defend the unaware viruses and intrusion. Furthermore, the controllability of behavior trust is studied. It can be predicted trust level under the multi-trust-attribute conditions. The experiment results show the .NET Framework of creating user behavior log to provide evidences for behavior trust forecast and control.

Energy efficiency is considered a significant concern in the deployment and operation of data networks. The network devices need an enormous amount of energy to function, which leads to an increase in energy consumption in the data center networks (DCNs). Software-defined networking (SDN) solves the problem by adjusting the energy consumption proportionate to the amount of traffic. The network devices with low load can be turned into switch-OFF mode after transferring the traffic to another device. This energy-saving approach by analyzing the user’s traffic demand increases the overall network utilization. In this work, we study the energy optimization problem using multipath routing in SDN-enabled data center networks (SD-DCN). We formulate the energy optimization as an integer linear program (ILP) problem to minimize the active Open vSwitch (OVS) switches in the network. To solve the problem in polynomial time, we propose a heuristic approach to route the traffic flows in the SD-DCN. The proposed approach is tested over data center network topologies – Fat-Tree and BCube. The simulation results show that our proposed approach presents an enhancement of 24%, 16%, and 15% in average delay, throughput, and energy savings in the Fat-Tree topology compared to the benchmark schemes. Further, our proposed approach achieves 17%, 19%, and 17% enhancement in average delay, throughput, and energy savings in the BCube topology compared to the benchmark schemes.

High molecular weight HPAM's tend to be highly shear sensitive. Various components of polymer mixing and distribution systems pose risk to the integrity of HPAMs due to high shear experienced at valves, chokes and other flow control devices. At a minimum, this risk can severely impact chemical EOR operating cost due to polymer degradation and consequential viscosity loss of the injectate. Low-shear, low-cost polymer injection distribution systems have the potential to reduce polymer usage, maintain injection stream viscosity, and enable integration into brownfield facilities. Lower viscosity losses translate into optimized operating and capital cost for CEOR pilot and full field projects. The objective of this work was to determine the equipment (piping), process, and polymer parameters that affect viscosity loss due to shear degradation. In this work, polymers were evaluated from two different vendors. The effects of molecular weight, chemical concentration, and brine salinity on polymer sensitivity to viscosity loss due to shear degradation were investigated. Polymer solutions were either blended on site or purchased pre-blended in synthetic brine solutions. Pumped by a positive displacement, low-shear pump, the solutions flowed through a mass meter and were delivered to a distribution system component at various flow rates. For flow control devices, pressure differentials were adjusted at fixed flow rates. Polymer solution samples were collected upstream and downstream of the tested component. Samples were taken in no-shear sample collectors. Pressure upstream and downstream of the test component and flow rate were recorded during the flow test. Viscosity was measured with a Brookfield viscometer at ambient temperature. When higher concentration solutions were tested, viscosity was measured of diluted samples at target concentration to determine amount of shear degradation as evidenced by viscosity loss. Results indicate that viscosity degradation of polymer solutions does occur in flow control devices and is directly correlated to pressure differential across the pipe device. Internal geometry has little impact on the amount of degradation. Velocity has little impact on the amount of degradation. Polymer molecular weight and structure both affect the amount of degradation due to shear as does solution concentration. Generally, viscosified brine solutions will lose viscosity when flowed through devices with greater than 50 psi differential pressure in the range of 15-50% of initial viscosity. Using more concentrated polymer streams and diluting to target concentration after flow control will reduce the amount of viscosity loss. Based on the laboratory results, design and operating condition, recommendations can be made for polymer injection distribution systems to minimize shear degradation of the flowing viscosified brine stream.

Low complexity resource allocation and scheduling algorithms for downlink SDMA systems

WiMAX (Worldwide Interoperability for Microwave Access) is a wireless communication standard. Today largely used as a mode of transmission and access to broadband Internet. WiMAX is based upon IEEE Standard 802.16, it supports Point-to-MultiPoint (PMP) as well as Mesh mode. In this work, our main objective is to compare through simulations, the QoS performance parameters (Average throughput, average jitter and average delay) of NOAH (NO Ad-Hoc Routing Agent) and DSDV (Destination-Sequenced Distance-Vector routing), under Random Waypoint Mobility Model by varying the nodes speed. Simulator NS-2 was used. The simulation results show that NOAH routing protocol performed better than DSDV protocol in term of average jitter and average delay, however average throughput values of both protocols are almost similar.

This study assessed the effects of oxygen and ozone nanobubbles on gill morphology, weight gain, and mortality of Pacific white shrimp (Penaeus vannamei), as well as the level of Vibrio parahaemolyticus and water quality of shrimp culture tanks under lab conditions. Two experiments were carried out with oxygen macrobubble, ozone macrobubble, oxygen nanobubble, ozone nanobubble, and control treatments (air-stone macrobubble). Experiments were done in triplicate in 100 L tanks with 15‰ saline water, and 20 shrimp per tank. Tanks in Experiment 1 were not inoculated with bacteria; tanks in Experiment 2 were inoculated with V. parahaemolyticus at a concentration of 106 CFU/mL. The results revealed that short treatments with ozone nanobubbles had minimal impact on shrimp gills, mortality, and growth rates, reduced V. parahaemolyticus concentration in water compared to the other groups, and improve water quality. These laboratory results indicate that ozone nanobubble treatment may be useful for controlling V. parahaemolyticus. More work is needed to find the best protocol to apply the technology on a commercial scale.

The iPhone’s validity for measuring steps has been mainly investigated under laboratory conditions, while studies that include real-world conditions are still scarce. We examined the validity of iPhones in measuring steps in real-world walking conditions, while using direct observation with video as reference. A sample of 100 adults who owned an iPhone 5S or higher was included and participants were randomly allocated to one of two protocols. Limits of Agreement (LoA), Mean Absolute Percentage Error (MAPE), linear-regression and Bland-Altman analyses were carried out. In Protocol-1, which includes straight-line and zigzag conditions, we observed a low MAPE lower than 4%. Bland-Altman analyses assessed a high accordance of approximately 6 steps under both conditions. Differences between the iPhone and direct observation were only noticeable in straight-line condition (p = 0.002). Likewise, protocol-2 (three 50-step conditions: an upward 5 % slope, a flat surface, and a downward -5% slope) showed low MAPE values (3.78 %) for the upward slope, 2.41 % for the downward slope, and 2.37 % in absence of slope), and differences between the iPhone and direct observation were only observed for the downward slope (p = 0.017), with the iPhone overestimating. Our findings revealed that iPhone might be a reliable tool for monitoring walking in real-life conditions, however, downward slope seems to generate overestimation, which deserves future investigation.