As mentioned before two compression methods are considered in this work. ❑ Lempel-Ziv-Welch (LZW) is dictionary base compression algorithm and the idea is to ( 1) start with an initial model, (2) read data piece by piece, (3) update the model and encode the data on the fly. ❑ Adaptive Huffman (AH) is a simple algorithm: (1) Start with a maximally "flat" code tree. (2) Code N symbols from the source and at the same time gather statistics, ie count how many times each symbol appears. (3) Build a new Huffman tree with the new estimated probabilities. (4) Repeat from step 2 until data encoded.
Objectives:To evaluate the success of ultrasonography directed renal access in entering the target calyx from proper entry site and in the direction of renal pelvis during percutaneous nephrolithotomy (PCNL).Materials and Methods:PCNL cases who were operated on by one fellow from May-June 2014 were included in this study. A vertically placed ultrasound probe on the patient flank in prone position was used to identify the preselected target calyx. Needle was advanced through needle holder and fluoroscopy was used to document the entered calyx, site and angle of entry.Results:Successful entering to the target calyx was achieved in 43 cases (91%). Successful entry with appropriate entry site and angle was observed in 34 cases (72%). Reasons for failure were minimal hydronephrosis, upper pole access and high lying kidneys.Conclusions:Although it is feasible to access a preselected calyx by ultrasonography guidance during PCNL, but entry to the calyx from the appropriate site and direction is another problem and needs more experience. In cases of minimal hydronephrosis, superior pole access or high lying kidneys, ultrasonography is less successful and should be used with care.
Internet-based communications is a key solution for enabling low-cost and scalable communication infrastructure for different applications of the smart grid. However, the performance of this network needs to be evaluated practically in the context of smart grid applications based on key metrics such as latency and reliability. This article is a comprehensive evaluation of the United Kingdom Internet network characteristics which will allow the smart grid systems designer to consider the essential parameters for communication applications. This article will focus not only on three smart grid applications, but also the outcome of this research which is relevant to a wider range of Internet of Things (IoT) applications. Different combinations of off-the-shelf wired and wireless last-mile communication technologies are evaluated using real-world transport protocols such as the Transport Control Protocol (TCP)and the User Datagram Protocol (UDP). The performance of TCP/UDP has been tested in a realistic client-server communication test-bed. The results from extensive evaluations show that typical latency values are between 200 and 600 ms for data packets and 50 bytes and kbytes for short control packets. Moreover by applying data compression techniques ,the results can be improved about 5%-20% for different last mile communications. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
The proliferation of plug-in electric vehicles (PEV) and advances in high-speed low latency communication networks redefine the relationships between electricity providers and endusers. A group of PEV owners, coordinated by an aggregator, can participate in ancillary energy markets to stabilize electricity grids and, in return, receive payments for services rendered. However, PEVs are typically parked across a dispersed region possibly with diverse signal strength and data rates. Vehicleto-Grid (V2G) applications have tight latency (e.g., 500 ms to 2 seconds) and packet-loss requirements, hence, the supporting communication infrastructure should be carefully evaluated for real-world implementations. In this paper, we assess the performance of the internet-based 4G cellular network in the United Kingdom to evaluate these key metrics. We develop a low cost and easy deployable testbed platform to collect and analyze the latency and packet loss rate of different package sizes, transport protocols, and signal strengths. Due to availability of hardware resources and city-wide coverage of 4G networks, a single parking lot to aggregator scenario is emulated. The results show that in most cases current 4G network can deliver packets less than 500ms which is required in fast frequency response applications in the UK. On the other hand, for more complex scenarios such as multi-aggregator to distributed clients, there is a need to use 5G and beyond to meet the latency requirements. To the best of authors' knowledge, this is the first study focusing on the field testing and assessment of an actual internet-based communication network for V2G applications.
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