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A multi-band antenna array is proposed for 5G massive MIMO systems. The presented antenna not only exhibits multi-band operation but also generates the polarization diversity characteristic which makes it suitable for multi-mode operation. Its configuration contains eight modified planar-inverted F antenna (PIFA) elements located at different corners of the smartphone mainboard. For ease integration and design facilitation, the antenna elements and ground plane are etched on the same layer. For S11≤ -10 dB, PIFA elements of the MIMO design operate at the frequency ranges of 2.5-2.7 GHz, 3.4-3.8 GHz, and 5.6-6 GHz covering the LTE 2600, 42/43, and 47 operation bands. Due to the placement of the antenna elements, the proposed design can support both vertical and horizontal polarizations. Fundamental characteristics of the proposed design are investigated. It offers good S-parameters, acceptable isolation, dual-polarized radiation coverage, and sufficient efficiency. In addition, the calculated TARC and ECC results of modified PIFAs are low over the operation bands.

Explicit Congestion Notification (ECN) as a main part of the Internet congestion control was originally designed with a single queue in mind. But, nowadays data centers industry trends to have multiple queues per-port in its switches. This type of mismatch can affect the scheduling schemes and hence leads to remarkable performance degradation in multi-queue switches. For instance, when some of the queue buffers of the switch exceed the considered thresholds, all the packets belonging to the same shared port could get ECN mark. To cope with this challenge, we propose Priority-ECN, a first systematic solution to this problem. The first intuition of Priority-ECN lies in the fact that if any packet gets marked, it should be prioritized to pass a route quicker than the others to notify the condition of the network in an early stage. This presents a full view of instantaneous demand from all senders. The second intuition is that if any packet gets marked in the queue buffer, Priority-ECN will not consider them in the marking decision again in the output port buffer. The third intuition is to reach the goal of high throughput without sacrificing the latency. So, we use an approach similar to Cut Payload (CP), which drops the payloads of packets, rather than the metadata, when a queue reaches the threshold. We do so through dual couple buffer in output port and catch the advantage of CP to implement an efficient scheme to obtains near optimal flow completion times across different flow sizes with very low latency.

In this paper, we propose Deep-RL—a marking decision with Deep Reinforcement Learning (DRL) via per-port for solving the erroneously marking problems in multi-queue multi service scenarios of Data Center Networks (DCNs). We formulate the statement as a DRL problem and use Deep Neural Network (DNN) to achieve the best possible policy for the agent. In this way we can model the complex DCNs in order to obtain the optimal threshold in the output port when the marked packets from queue buffers are not a concern. Unlike prior research that focused on mathematical models or used machine learning in DCN, Deep-RL is a novel DRL based method, which optimizes the real value of threshold with continues action space. Thus, this fact makes our work incomparable with previous research. To the best of our knowledge, we are the first to discuss the problem with DRL and DNN. Simulation results demonstrate that Deep-RL utilizes the buffer capacity at exactly 30% and achieves near optimal flow completion time.

The nature and physical parameters of dielectric barrier discharges (DBDs) are determined by the presence of dielectric material in the discharge gap. The charging of the dielectric barrier is responsible for the non-thermal regime as it limits the local energy dissipation. In an operating DBD residual surface charges can influence the distribution and development of the plasma in the following discharge cycles1. In order to learn more about residual surface charge role an experiment with a rotating dielectric electrode and a pin electrode (325 μm tip radius) is realized2. The rotating dielectric barrier enables DBD-operation with DC high voltage and, the remaining surface charges are removed by a second grounded electrode which is sliding over the dielectric. Thus, single, repetitive microdischarges in air at atmospheric pressure are ignited without participation of residual surface charges. These microdischarges were investigated by ICCD camera, electrical measurements and time-correlated single photon counting (sub-ns, sub-mm and spectral resolution). For positive polarity of the pin electrode a positive streamer starting from the middle of the gap followed by a secondary wave starting from the metal electrode is observed. For negative polarity an anode directed wave of light and a weaker glow in front of the cathode are obtained.

US power system is faced with proliferation of renewable generation in its transmission and distribution networks. Renewable energy integration in power systems have caused specific concerns for system planners and operators because of its intermittent and variable nature. This paper focuses on the benefits of using battery energy storage systems for the integration of wind energy. Several scenarios for using the battery are examined in this paper and their benefits discussed in order to justify the investment in a BESS. Results are provided using a combination of simulations and real-life data for each scenario to demonstrate the quantifiable benefits that result from using battery storage to integrate wind energy resources.

Hierarchical learning as another way to scale up reinforcement learning and enable its applications to very hard learning problems. Hierarchical learning is a divide-and-conquer technique a complex learning problem is decomposed into small pieces so that they can be easily solved. The option framework is one way to using hierarchical learning in reinforcement learning. In this paper we have used the free-energy based function approximation (FE-RBM) to determine the option initiation set. Our proposed method calculates the output for each of the input (including state and subgoal) according to negative free energy of an RBM. Learning is done by stochastic gradient descent and mean-squared error. The experimental results showed that this method has efficient functionality to create options. Moreover, it has a reasonable generalization ability for unvisited states.

Plasma cathodes have attracted much attention in recent years, and various types of such cathodes have been developed and tested by different research groups. In these types of electron sources, a bulk plasma is generated inside a vessel, which has an orifice at its front plate. Then, by applying a positive potential outside the vessel, electrons of the bulk plasma are extracted from this orifice. Various plasma sources, such as helicon, electron cyclotron resonance (ECR), microwave and radio frequency (RF) are used for the bulk plasma generation of the plasma cathode devices. Compact geometry, easy generation, and high density and efficiency of the RF plasma make it preferable for the plasma cathode applications. In this study, the operation procedures and characteristics of a prototype RF cathode device are described. In addition, some experimental results from the testing of the prototype RF cathode are presented.

Development of reliable, successful and robust technologies for space systems demands realistic testing facilities. Low pressure levels are required for simulating the space vacuum conditions in earth's orbit or interplanetary-space. Therefore, establishment of a vacuum facility devoted specifically to the testing of thrusters is needed in order to develop, study and test thrusters to be deployed on spacecraft or satellites. In this study, the design, acquisition and manufacturing processes, and capabilities of a 1.5 m diameter and 2.7 m long cylindrical vacuum facility, that will primarily be used for the development and testing of electric spacecraft thrusters, at the Bogazici University Space Technologies Laboratory (BUSTLab) are presented.

Anode spots are potential structures formed by immersing an electrode into a bulk plasma and biasing the electrode to a sufficiently high electric potential. This structure is a quasineutral region which is separated from the bulk plasma by a double layer boundary1. Double layer is a sheath-like region which sustains a potential difference between to different plasmas. When the anode spot forms in front of the positively biased electrode, a jump occurs in the extracted electron current to this electrode.

Multiple voltage regulating devices, such as on-load tap changer (OLTC), step voltage regulators (SVRs), switching capacitors banks work in tandem with each other to regulate voltage in the distribution network. These conventional devices are based on volt/var optimization strategies that work in a time coordinated method. However, in case of distribution systems with Photovoltaic (PV) generations, a dynamically responsive voltage regulating device is required. Case studies are performed investigating voltage regulation at the PV bus during ramp up/down case. An alternate method using an energy storage device to regulate the target PV bus voltage during ramp up/down of PV power is proposed. A novel ramp rate control algorithm based on the current state of charge is also discussed. A benchmark MV distribution network model is developed and simulated in PSCAD/EMTD environment and the results validate the proposed coordinated voltage control strategy.

Growing numbers of utilities are experiencing proliferation of Plug-in Electric Vehicles (PEV) and Photovoltaic Distributed Generation (PV-DG) in their distribution systems. Charging patterns of PEVs tend to increase the original day-time and evening peak demands of distribution feeders, while PV-DG units are highly intermittent energy sources. Therefore, the integration of large amount of PEVs and PV-DGs represents a significant challenge for distribution planning and operations. As an emerging technology, Distributed Energy Storage (DES) is a promising alternative to improve the reliability and efficiency of distribution systems. DES serves as an energy buffer to manage demand and supply fluctuations. Through proper control algorithms, DES has the potential to facilitate the integration of both, PEVs and PV-DG units. Previous works have studied the mitigation of steady state impacts of PEVs and PV-DG units by using DES systems. However, this topic has not been fully investigated from a dynamic analysis perspective. This paper discusses the utilization of DES to alleviate dynamic impacts of PEVs and PV-DG units on power distribution systems. This alternative is analyzed by using models of PV-DGs, PEV and DES developed in PSCAD. Results of dynamic simulations, including voltage profiles at critical points on a test distribution feeder and operations of Load Tap Changer (LTC) are presented and discussed. Simulation results show the potential of DES for improving dynamic performance of distribution feeders with PEVs and PV-DGs proliferation.

In recent years the installation of wind farms have had significant growing. This growth of wind energy has made the policy makers to regulate the wind farms. At the same time researchers put their effort to develop control strategies that the wind generators could fulfill the grid code requirements. Among all the grid connection codes, low voltage ride through (LVRT) is one of the major challenges. This paper proposes a new LVRT method to control the DFIG based wind turbines during voltage sags. This control strategy is based on current vector orientation and employs the grid side converter in a series connection with the grid. The performance of this method is analyzed with simulation results during grid fault.

The utility industry is expecting a proliferation of Plug-in Electric Vehicles (PEV). This has prompted increasing interest in evaluating the potential impacts of PEVs on power distribution system planning and operations, as well as in proposing mitigation approaches that allow their seamless integration. In addition, there is a noticeable growth in the number of solar photovoltaic distributed generation (PV-DG) being interconnected to distribution feeders in North America and other regions. The rising penetration of PV-DG may also lead to important impacts on power distribution systems, particularly due to the intermittent nature of its output caused by cloud cover. As an emerging technology, Distributed Energy Storage (DES) aims to improve the reliability, efficiency, and controllability of the power distribution system and to facilitate the integration of distributed generations. This paper discusses the integration of all these technologies from a technical perspective and investigates how DES may be used as a means for mitigating the impacts of PEV charging and PV-DG interconnection. Results of simulations conducted on an actual distribution feeder are presented and discussed.

Several information spreading algorithms for social networks have been proposed by researchers during the past few years. However, the main challenge is to find out the best algorithm with the lowest running time for a given communication graph. In this paper, we address the problem of information spreading in the context of social networks. We compare the running times of three well known information spreading algorithms in the field by using real data collected from the Face book website. We prove the importance of 1-whiskercommunities for the speed of information spreading algorithms in social networks by comparing the performance of different spreading algorithms with and without 1-whiskers. Our results are important since they highlight the effect of 1-whiskers as the main communication bottlenecks for information spreading and the need for development of more efficient algorithms in this field.

Rapid growth of grid-connected photovoltaic distributed generation (PV-DG) provides many benefits such as clean energy, reduced emissions and creation of new green jobs. However, given its intermittent nature, large scale penetration of PV-DG may challenge the quality and reliability of the grid. This paper evaluates the impact of PV-DG on distribution system voltages. The paper describes the models used for the study, discusses the impacts of PV-DG, and presents the results of detailed simulations. The results show that PV-DG can cause both steady-state and transient overvoltages along the feeder, and may create additional tap operations of line voltage regulators. Finally, the paper proposes a mitigation strategy to eliminate overvoltages, reduce additional tap operations, and validates the proposed method with simulation results.

Predicting human mobility is considered as a challenging problem. In this paper, we formulate the problem of human contact prediction as a graph inference problem. We show the importance of using offline social information for predicting people's contacts motivated by homophily theory. We also prove that by using the small-world network properties of the contact graphs, we can reconstruct the missing part of a contact graph where only part of the graph is known. Our results are promising because they allow researchers to reconstruct the missing parts in experimentally measured human mobility traces when only partial traces are obtainable.

This article show different mobile database security threats that may be occurs for mobile database in the real world and gives possible solution to eliminate them. Mobile database is a specialized class of distributed systems. There are security challenges due to the distributed nature of the mobile database application and the hardware constraints of mobile devices. In this document, we will deals with the subject of security in four fields. These four areas include: Security of mobile device, security of operating system on mobile device, security of mobile database and security of mobile network. We identify a set of security vulnerabilities on mobile database and try to apply appropriate technique to decrease side affect for mobile database security. Important security issues for mobile device, mobile operating system and mobile network that maybe affect on mobile database security are discussed along with possible solution. Finally, for more security, this paper offers a comprehensive solution that may be applied to distributed database.

The Session Initiation Protocol (SIP) has gained momentum and is being widely used both in the Internet and Next Generation Telecommunications network as the core signaling protocol. SIP operation relies on SIP servers which are responsible for forwarding of SIP messages. It has been shown that the performance of SIP servers is largely degraded during overload conditions due to the built in message retransmission mechanism of SIP. This is an obstacle in wide deployment of SIP for a realistic situation. In this paper we propose a distributed and adaptive window based overload control algorithm, which controls the amount of calls that are forwarded to a downstream SIP server in an attempt to prevent it from being overloaded. Our scheme uses the call establishment delay as a measure of the amount of load on the downstream server and unlike other methods does not rely on explicit feedback. Using simulations we show that our proposed method performs better than a commonly used overload control algorithm and exhibits fast convergence and is stable.

Theoretical frameworks and simulation environments are proven to be very useful in evaluating conventional wired settings. However, due to the inclusion of various deficiency parameters which naturally exist in wireless channels modelling the communication behaviour in MANETs become much more complex. To overcome these major problems and create a realistic test platform for MANET research, we propose the use of inexpensive OLPC XO laptops that provide by default a Linux-based open source operating system, multi-hop mesh networking capabilities and a configurable wireless adapter. We believe that a design based on this hardware can substantially reduce the cost and time spent during the implementation and deployment of MANET testbeds and help researchers to focus on the systems to be deployed rather than the testbed itself.

Session Initiation Protocol (SIP) is adopted as the main signaling protocol for the IP Multimedia Subsystem (IMS). Large deployment of SIP servers in Next Generation Networks (NGN) requires studying the behavior and performance of SIP servers under both normal and overload conditions, which may happen in such networks with a vast number of users. In this paper a measurement-based study is performed to assess SIP proxy server performance under different configurations, and for different underlying transport protocols, for both inter-domain and intra-domain calls. Test results show the effectiveness of configuration and distance on SIP signaling performance. Therefore a great attention must be paid during SIP servers deployment.