Optimal Phase Sequence Research Articles

Ant Colony Optimization With Look-Ahead Mechanism for Dynamic Traffic Signal Control of IoV Systems

In the era of Internet of Vehicle (IoV), traffic data are obtained by wireless sensor networks (WSNs), which provides convenience for real-time traffic signal control and is expected to further improve the efficiency of the whole system. Traffic signal controllers designed for IoV systems usually fully depend on data transmitted from the IoV system and are limited to the penetration rate of connected vehicles. This work proposes a dynamic ant colony optimization algorithm with the look-ahead mechanism (DALM) with eight no-conflict phases. The needed traffic information in the DALM algorithm is small and can be obtained independently by the system, which makes this method does not fully rely on the vehicle trajectories data and can better protect customer privacy and deal with cyber attack. With the look-ahead mechanism, the forthcoming traffic flow together with the current waiting queue are involved to predict the length of waiting vehicles and the optimal phase sequence is dynamically selected according to shortest green-light duration of candidate phase sequences obtained form the collected real-time traffic data. Experiments conducted under five scenarios with different kinds of traffic flow on SUMO platform show that compared with other four methods, both the total waiting time and the total carbon emissions of vehicles at the intersection are greatly reduced by using the DALM algorithm, especially in high traffic flow situations. The proposed algorithm can greatly improve the efficiency of the intersection in high traffic flow situation and is predictable to benefit the real-time traffic signal control in IoV system.

Influence of phase sequence arrangement on the electromagnetic environment of four-circuit AC line on the same tower

The paper predicts the power frequency electric field (PFEF), audible noise (AN), and radio interference (RI) of double-circuit 220kV and double-circuit 110kV four-circuit lines on the same tower erected on the same tower through the numerical calculation method of electromagnetic environment (EME) of AC transmission lines (TLs). Through a typical tower structure, the influence of the phase sequence (PS) on the EME is analysed, and the optimal and worst PSs are obtained. The optimal PS can significantly improve the EME, especially with a good confinement effect on the electric field’s power frequency. In addition, it also focuses on analyzing the influence degree of PS when the phase spacing, conductor-to-ground height and layer spacing change and establishes the applicable range of the optimal PS.

Controlling Mixed Connected and Non-Connected Vehicle Traffic Through a Diamond Interchange

Diamond interchanges (DIs) allow movement of vehicles between surface streets and freeways for all types of vehicles, including normal non-connected human-driven vehicle (NHDV) traffic and the connected vehicles (CVs). Unlike simple intersections, DIs consist of a pair of closely spaced intersections that are controlled together with complicated traffic movements and heavy demand fluctuations. This paper reviews the movements being controlled at DIs and presents a dynamic programming (DP)-based real-time proactive traffic control algorithm called MIDAS, to control both NHDVs and CVs. Like seminal cycle-free adaptive control methods such as OPAC and RHODES, MIDAS uses a forward recursion DP approach with efficient data structures for any large set of phase movements being controlled at DIs, over a finite-time horizon that rolls forward, and then uses a backward recursion to retrieve the optimal phase sequence and duration of phases. MIDAS captures Eulerian measurements from fixed loop detectors for all vehicles, and also captures Lagrangian measurements like in-vehicle GPS from CVs to estimate link travel times, arrival times, turning movements, etc. For every time horizon MIDAS predicts future arrivals, estimates queues at the interchange, and then minimizes a user-defined metric like delays, stops, or queues at an interchange. The paper compares performances of MIDAS with those of an optimal fixed cycle time signal control (OFTC) scheme and RHODES control on a simulated DI. The simulation is of Phoenix, AZ, DI (on I-17/19th Ave.) that uses the VISSIM micro-simulation platform. Performance is evaluated for various traffic loads and various CV market penetrations. Results show that MIDAS control outperforms RHODES and OFTC.

A Wideband Frequency Divider With Programmable Odd/Even Division Factors and Quadrature/Symmetrical Outputs

An injection-locked frequency divider (ILFD) with odd/even division factor and wide locking range over process and temperature variations is presented. To enhance the locking range of the frequency divider and generate accurate quadrature with 50% duty cycle outputs, a comprehensive analysis of the frequency divider to find the optimal phase sequence for two, three and five division ratios is provided. Generating quadrature and symmetrical outputs with simultaneous realization of even and odd division ratios at low power is the main challenge that is addressed in this paper as the power consumption of existing quadrature circuits is an order of magnitude higher than that of the proposed ILFD. The ILFD is designed and simulated in a 65 nm CMOS technology and the analytical results verified by the circuit simulation results. Post layout simulation results show that the locking range of the divider without any tuning is from 5.4 GHz to 8.5 GHz, 1.1 GHz to 6.1 GHz and 0.1 GHz to 5.3 GHz in divide-by-five, three and two mode for 0 dBm injection signal level, respectively. The phase deviation of the quadrature outputs for dividers is less than 1.8° and the deviation of duty cycle from 50%, is less than 0.4%.

Research on the unbalance degree of four-circuit overhead lines on the same tower with different phase sequence arrangements

The phase sequence arrangements of multi-circuit overhead lines on the same tower, commonly used in extremely high voltage/ultra-high voltage (EHV/UHV) transmission lines, directly affects the symmetry of power transmission systems, which influence the operation of power grid and relay protection. It is difficult to achieve complete transposition of four-circuit overhead lines on the same tower because of their complex structure, and it is a practical and effective way to select a proper phase sequence arrangement to improve the symmetry of the line parameters. This paper presents an evaluation index based method for evaluating the symmetry of four-circuit overhead lines on the same tower and selecting the optimal phase sequence arrangement. First, the unbalance degrees of the single-sequence component and composite-sequence component are defined as the basic evaluation index of the symmetry of the parameters and obtained by the calculation of the line sequence parameters. Furthermore, the unbalance degree comprehensive evaluation index is constructed by the weighted sum based on the ranking of basic evaluation indexes. The weight distribution factors of various unbalance degrees are calculated according to the exponential (0,2) scale algorithm. The unbalance degree comprehensive evaluation index is used to evaluate the symmetry of transmission line parameters and select the optimal phase sequence arrangements of four-circuit overhead lines on the same tower. Finally, the optimal phase sequence arrangements for the different towers with typical structures, such as vertical, horizontal, d-type and e-type towers are obtained by using the above analysis method and verified by simulation of PSCAD/EMTDC.

Complementary peak reducing signals for TDCS PAPR reduction

Transform domain communication systems (TDCSs) are cognitive anti-interference multi-carrier communication systems with dynamic spectrum access. The inherent high peak-to-average power ratio (PAPR) of TDCS reduces the efficiency of the power amplifier. Adaptive waveform generation of the TDCS also causes the PAPR to vary according to the spectral conditions on hand. In this study, a complementary peak reducing signal (CPRS) method is proposed and analysed. It uses all unoccupied frequency bins to transmit data and uses all interfered frequency bins to generate CPRSs. Every data signal and its corresponding CPRS are orthogonal and complementary, so as to fully occupy all frequency bins. Therefore, the PAPR reduction of the composite signal with all frequency bins is considered. Once the optimal pseudo-random phase sequence is determined, the sequence can adapt to all spectral conditions without side information, and the computational complexity for diverse spectral conditions is greatly reduced. Moreover, the orthogonality between the data signal and its CPRS in the frequency domain eliminates distortions and spectral spreading. As a component of the transmitting signal, CPRS may cause bit error rate (BER) loss. This study also proposes a signal power adjustment mechanism to achieve a compromise between PAPR reduction and BER loss.

Method to measure the unbalance of the multiple‐circuit transmission lines on the same tower and its applications

This study proposes a new method for measuring the unbalance of the multiple-circuit transmission lines (MCTLs) on the same tower, which can characterise the physical natures of the line unbalance. First, the impedance and the sequence current of the MCTLs on the same tower are calculated under the consideration of the impact of ground wires. Then, the unbalance suppression methods of the optimal phase sequence arrangement and asymmetry parameter compensation are presented. Finally, the model of the six-circuit transmission lines on the same tower is simulated in PSCAD according to a real project in China. The line unbalance, the impacts of the connection patterns of ground wires on unbalance and the unbalance suppression are simulated and analysed. Simulation results show that the proposed method is applicable and convenient to accurately calculate the parameters of the line unbalance and to select the optimal way to suppress the unbalance. The work can provide the theoretical guidance for the optimal design and the operation of the MCTLs on the same tower.

Triphasic and quadriphasic waveforms are superior to biphasic waveforms for synchronized beating of cardiomyocytes

Background and PurposeWithin pacemaker research few attempts have been made to find an optimal waveform phase sequence that synchronizes beating of cardiomyocytes at an electrode. Multielectrode arrays (MEAs) offer electrophysiological screening of cardiomyocytes serving as a system for preliminary screening of pacing waveform design. Materials and MethodsThe HL-1 cell line was cultured in MEAs until confluence and stimulated with biphasic, triphasic, and quadriphasic waveforms. The amplitudes required for synchronized beating of the cells were determined. ResultsTriphasic and quadriphasic waveforms were more efficient in eliciting synchronized beating of the HL-1 cells compared with the biphasic waveform because it allows significant reductions in synchronizing voltage amplitudes and reductions in supplied stimulus. ConclusionThe MEA system allows for a straightforward manner to investigate effects of waveform design on synchronized beating in cardiomyocytes in vitro. Increased number of phase changes in a pacing waveform seems to be the major reason for the reduction in synchronizing amplitudes.

VISTA

Software designers face many challenges when developing applications for embedded systems. One major challenge is meeting the conflicting constraints of speed, code size, and power consumption. Embedded application developers often resort to hand-coded assembly language to meet these constraints since traditional optimizing compiler technology is usually of little help in addressing this challenge. The results are software systems that are not portable, less robust, and more costly to develop and maintain. Another limitation is that compilers traditionally apply the optimizations to a program in a fixed order. However, it has long been known that a single ordering of optimization phases will not produce the best code for every application. In fact, the smallest unit of compilation in most compilers is typically a function and the programmer has no control over the code improvement process other than setting flags to enable or disable certain optimization phases. This paper describes a new code improvement paradigm implemented in a system called VISTA that can help achieve the cost/performance trade-offs that embedded applications demand. The VISTA system opens the code improvement process and gives the application programmer, when necessary, the ability to finely control it. VISTA also provides support for finding effective sequences of optimization phases. This support includes the ability to interactively get static and dynamic performance information, which can be used by the developer to steer the code improvement process. This performance information is also internally used by VISTA for automatically selecting the best optimization sequence from several attempted. One such feature is the use of a genetic algorithm to search for the most efficient sequence based on specified fitness criteria. We include a number of experimental results that evaluate the effectiveness of using a genetic algorithm in VISTA to find effective optimization phase sequences.

MAP Metric for Blind Phase Sequence Detection in Selected Mapping

Selected mapping (SLM) is a promising technique to reduce the high peak-to-average power ratio (PAR) of orthogonal frequency division multiplexing (OFDM) signals. In this paper, we derive the optimal phase sequence detection metric for blind selected mapping (BSLM) and show that the minimum distance metric is suboptimal. We then define a certain selection criterion in the transmitter which assigns different probabilities to different mapping sequences. These probabilities are integrated into the optimal metric to achieve several dBs of SNR improvement in blind phase sequence detection.

Fast searches for effective optimization phase sequences

It has long been known that a fixed ordering of optimization phases will not produce the best code for every application. One approach for addressing this phase ordering problem is to use an evolutionary algorithm to search for a specific sequence of phases for each module or function. While such searches have been shown to produce more efficient code, the approach can be extremely slow because the application is compiled and executed to evaluate each sequence's effectiveness. Consequently, evolutionary or iterative compilation schemes have been promoted for compilation systems targeting embedded applications where longer compilation times may be tolerated in the final stage of development. In this paper we describe two complementary general approaches for achieving faster searches for effective optimization sequences when using a genetic algorithm. The first approach reduces the search time by avoiding unnecessary executions of the application when possible. Results indicate search time reductions of 65% on average, often reducing searches from hours to minutes. The second approach modifies the search so fewer generations are required to achieve the same results. Measurements show that the average number of required generations decreased by 68%. These improvements have the potential for making evolutionary compilation a viable choice for tuning embedded applications.

Finding effective optimization phase sequences

It has long been known that a single ordering of optimization phases will not produce the best code for every application. This phase ordering problem can be more severe when generating code for embedded systems due to the need to meet conflicting constraints on time, code size, and power consumption. Given that many embedded application developers are willing to spend time tuning an application, we believe a viable approach is to allow the developer to steer the process of optimizing a function. In this paper, we describe support in VISTA, an interactive compilation system, for finding effective sequences of optimization phases. VISTA provides the user with dynamic and static performance information that can be used during an interactive compilation session to gauge the progress of improving the code. In addition, VISTA provides support for automatically using performance information to select the best optimization sequence among several attempted. One such feature is the use of a genetic algorithm to search for the most efficient sequence based on specified fitness criteria. We have included a number of experimental results that evaluate the effectiveness of using a genetic algorithm in VISTA to find effective optimization phase sequences.