Optimal Split Ratio Research Articles

Optimizing Throughput in a MIMO System With a Self-Sustained Relay and Non-Uniform Power Splitting

We present a novel approach to maximizing the transmission rate in a MIMO relay system, where all nodes are equipped with multiple antennas and the relay is self-sustained by harvesting energy. We formulate an optimization problem and use dual-characterization to derive a closed-form solution for the optimal power splitting ratio and precoding design. We propose an efficient primal-dual algorithm to jointly optimize the power allocation at source and relay for transmission and the power splitting at relay for energy harvesting, and show that using non-uniform power splitting is optimal. Numerical results demonstrate the significant rate gain of non-uniform power splitting over traditional uniform splitting especially at low source transmit power. We also analyze our algorithm numerically and demonstrate its efficiency at reducing the run-time by several orders of magnitudes compared to a standard solver, \textcolor{blue}{and existing algorithms in literature

Investigation of Optimal Split Ratio for High-Speed Permanent-Magnet Brushless Machines

The split ratio, i.e., the ratio of rotor outer diameter to stator outer diameter, is one of the most vital design parameters for permanent-magnet (PM) machines due to its significant impact on the machine torque or power density. However, it has been optimized analytically in the existing papers with due account only for the stator copper loss, which is reasonable for low-to-medium speed PM machines. For high-speed PM machines (HSPMMs), the negligence of stator iron loss and the mechanical stress on the rotor will lead to a deviation of optimal split ratio and actual torque capability. In this paper, the optimal split ratio of HSPMM is investigated analytically with the consideration of stator iron loss as well as the mechanical stress on the rotor. The influence of air-gap length and rotor pole pairs on the optimal split ratio is elaborated. Both the analytical and finite-element analysis reveal that the optimal split ratio for HSPMM will be significantly reduced, when stator iron loss and mechanical constraints are taken into account.

Secure Decode-and-Forward Relay SWIPT Systems With Power Splitting Schemes

Simultaneous wireless information and power transfer (SWIPT) is a promising technology to mitigate the power constraint problem in wireless sensor networks by harvesting energy from received signals. A two-hop communication system is studied, where a relay node uses SWIPT to harvest energy and forward data. An eavesdropper exists and receives information both from the source and the relay. We considered two energy harvesting models, linear and nonlinear ones. The closed-form expression of the system's outage probability under information-theoretic physical layer security is derived for both models. We also analyze the optimal power splitting ratio and optimal relay distance with the aim to minimize the secrecy outage probability. For the nonlinear model, we derived the closed-form expression of the optimal power splitting ratio after the circuit becomes saturated.

Optimal Transmission Schemes for DF Relaying Networks Using SWIPT

This paper considers a simultaneous wireless information and power transfer (SWIPT) based decode-and-forward relaying network, where the “harvest-then-forward” strategy is employed. We focus on designing optimal static and dynamic transmission schemes of joint time allocation and power splitting to conduct the relay in terms of outage performance and ergodic performance, respectively. In particular, the analytical expressions for the outage probability and ergodic capacity are derived to determine the optimal static power splitting (PS) and time allocation (TA) ratios. Moreover, we study the dynamic transmission scheme and formulate two joint optimization problems to minimize the outage probability and maximize the instantaneous channel capacity. Considering that the two optimization problems are nonconvex, a split-step iterative method is proposed to obtain the optimal dynamic PS ratio and TA ratio for minimizing the outage probability, and an alternate convex optimization method is employed to solve the problem of maximizing the instantaneous channel capacity. Simulation results verify the advantages of the proposed schemes over three peer schemes.

Analytical and Experimental Investigation of a Silicon Photonic Two-Stage Mach–Zehnder Delay Interferometer-Type Polarization Beam Splitter

We report the analytical and experimental results of a silicon photonic polarization beam splitter (PBS) consisting of two-stage Mach-Zehnder delay interferometers (MZDIs). The delay length of each MZDI was designed to achieve constructive and destructive interferences for the TE and TM modes simultaneously. First, we have fabricated and estimated a single-stage MZDI-type PBS. Owing to the difference of the in-phase or out-of-phase conditions between TE and TM modes in case of the designed delay length of the MZDI, the center wavelengths of the transmissivity for both the constructive and destructive interference are different for the TE and TM modes. Thus, the polarization extinction ratio (PER) was as small as 5 dB within the C-band. To improve the PER, a two-stage MZDI structure was introduced. In addition, the length of the multimode interferometer type optical splitter was determined to have an optimal splitting ratio of 50:50 for the TM mode for the shortest wavelength within the operating wavelength range. The center wavelength of the MZDIs was shifted to achieve the widest possible bandwidth with a large PER. We have fabricated the silicon photonic PBS to achieve a PER larger than 15 dB. The measurements showed good agreement with the simulations.

Split ratio optimization of high torque density PM BLDC machines considering copper loss density limitation and stator slot leakage

The paper deals with analytical modeling and design optimization of electrical machines as basic energy conversion elements in power systems. A new method is proposed for designing high torque density PM BLDC (Permanent Magnet Brushless Direct Current) machines with analytically derived optimal split ratio, applicable even to large high pole count machines with considerable impact of the stator slot leakage and with limited value of copper loss density. The method relies on the fact that the product of the electric loading and the current density does not depend on the machine size, while it is primarily determined by the cooling conditions. Moreover, the method also considers the influence of the stator slot leakage on the optimal split ratio. It is shown that the method provides an accurate optimum of the machine design for a wide range of machine sizes and cooling conditions. At the same time, the optimum design can be found for different machine sizes without any need to update the input data. It is shown that the impact of the stator slot leakage is significant for large machines with a high pole count, where an increase of the leakage shifts the optimum towards larger values of the split ratio. The results of the analytical optimization are thoroughly verified by computer simulations using finite element analysis (FEA).

Investigation of Optimal Split Ratio in Brushless Dual-Rotor Flux-Switching Permanent Magnet Machine Considering Power Allocation

This paper investigates an optimal split ratio for a brushless dual-rotor flux-switching permanent magnet (BDR-FSPM) machine. Based on the design theory of conventional FSPM machine, the split ratio of the BDR-FSPM machine is deduced and redefined. And the crucial factors which have close relationship with the split ratio are determined, consisting of power split ratio, magnetic loading, PM pole width, and stator pole width. To conveniently explore the optimal split ratio, the response surface method is purposely utilized for conducting optimization, where the magnetic loading and output torque are chosen to be the objectives. In addition, considering the application requirement of hybrid electric vehicles, the concept of power allocation is proposed and integrated into the optimization process of split ratio. Then based on the optimal split ratio, the machine performances are analyzed in detail, including air gap flux density, back-electromotive force (EMF), coupled-EMF, and torque performances. Finally, a prototyped BDR-FSPM machine is manufactured and tested to verify the validity of the proposed split ratio optimization and machine design approach.

STUDI EKSPERIMENTAL PENGARUH KECEPATAN ALIRAN MASUK, SPLIT – RATIO DAN DIAMETER VORTEX FINDER TERHADAP UNJUK KERJA LIQUIDLIQUID CYLINDRICAL CYCLONE (LLCC) SEPARATOR

The large number of ports in Indonesia generate a lot of waste oil that contaminate the ocean around the port. However, the pollution prevention is not supported by a good facility. Hydrocyclone separator can be used as an alternative to supporting conventional separataor technologies such as vessel type separator or gravitational based separator to prevent the waste oil pollution. The purpuse of this study is to determine the effect of split ratio, inlet mixture velocity, and vortex finder diameter on the performance of the liquid-liquid cylindrical cyclone (LLCC). Oil (Kerosene) and water were selected as the working fluid and a red color (dye) was given to the oil to enable visualization . Performance of LLCC determined from watercut that produced from separation process. The examined inlet mixture velocity are 0.7 m/s, 0.9 m/s and 1.1 m/s with split-ratio 5%, 15%, 30%, 45%, 60%, 75% and 90%. . All of them are tested with vortex finders that have diameters 18 mm, 22 mm and 27 mm with 0 mm depth. The oil volume fraction inlet is kept constant at 25%. The result showed that LLCC was capable to separating oil-water mixture and produced watercut on underflow reaches 100%. The increasing of split-ratio will increase the watercut until reached the maximum value for all diameter of vortex finder. The condition when the oil content begin to move to the underflow on certain split-ratio is called oil drag. The split-ratio that used before oil drag occurs is called Optimum Split Ratio (OSR). LLCC should operated on OSR to obtain the best performance. The OSR is shifted to the higher split-ratio for higher inlet mixture velocity. The increasing of vortex finder diameter did not change LLCC performance significantly.

Fast design method of variable flux reluctance machines

In this paper, a fast design method is developed based on a combination of analytical and finite element (FE) methods for variable flux reluctance machines (VFRMs). Firstly, the feasibility of using analytical method in optimization under unsaturated condition is confirmed. Then, by applying the FE method, the influence of magnetic saturation is considered. Compared with the unsaturated case, the optimal split ratio for magnetically saturated case is increased by 1~1.2 times, the optimal rotor pole arc ratio varies within 0.33~0.44, and the stator pole arc ratio remains the same. Based on this, the optimal structural parameters can be initially set by analytical method and then refined by the FE method. Due to the fast speed of analytical method, less variable counts and narrowed variation ranges, the proposed method is significantly faster than the conventional pure FE based global optimization. Finally, the proposed method is used for optimizing the 6-stator-slots VFRMs having different numbers of rotor poles. The 6-stator-slot/7-rotor-pole (6s/7r) VFRM is found to have the highest torque density. It is prototyped and tested to verify the analyses.

Low-Complexity Power Control and Energy Harvesting Algorithms for Wiretap Channels Employing Finite-Alphabet Input Schemes

We discuss the design rules of an energy-efficient wireless wiretap channel in this paper. On the transmitter side, we investigate the optimal power control policy for secrecy rate maximization over wiretap channels with the bit-interleaved coded modulation scheme. On the receiver side, an energy harvesting algorithm is used to collect wireless signal energy without degrading the secrecy rate performance. These objectives are challenging as the closed-form solution to the mutual information of finite-alphabet input schemes remains unknown. In this paper, we derive a closed-form relationship between the secrecy rate and the signal-to-noise ratio (SNR) by transforming the SNR from the linear domain to the logarithm domain. The optimal power control policy (PCP) can be easily obtained by exhaustive search in a small interval, whereas the traditional search is performed over the entire SNR range. We also propose a sub-optimal PCP algorithm that significantly reduces the search complexity with only a minor performance loss. The optimal power splitting ratio is studied to save energy while achieving the target secrecy rate. We show that if the transmission power is too high, the receiver is unable to simultaneously harvest energy from the wireless signals and achieve the target secrecy rate.

Gas-liquid flow splitting in T-junction with inclined lateral arm

This paper studies the gas-liquid flow splitting in T-junction with inclined lateral arm. The separation mechanism of the T-junction is related to the pressure distribution in the T-junction. It is shown that the separation efficiency strongly depends on the inclination angle, when the angle ranges from 0° to 30°, while not so strongly for angles in the range from 30° to 90° Increasing the number of connecting tubes is helpful for the gas-liquid separation, and under the present test conditions, with four connecting tubes, a good separation performance can be achieved. Accordingly, a multi-tube Y-junction separator with four connecting tubes is designed for the experimental investigation. A good agreement between the simulated and measured data shows that there is an optimal split ratio to achieve the best performance for the multi-tube Y-junction separator.

Simultaneous Wireless Information and Power Transfer in Cellular Two-Way Relay Networks With Massive MIMO

In this paper, we study an energy-harvesting cellular two-way relay network with massive multiple-input multiple-output, where multiple energy-harvesting mobile stations (MSs) communicate with a base station (BS) via an energy-harvesting relay station (RS). A signal space alignment (SSA) based simultaneous wireless information and power transfer (SWIPT) protocol is proposed for efficient energy harvesting and information exchange. We analyze the performance of the proposed SSA-SWIPT scheme, and derive closed-form expressions for the asymptotic signal-to-interference-plus-noise ratios and the achievable sum-rate when the numbers of antennas at the BS and the RS go large simultaneously. We also investigate the optimal power splitting ratios at the RS and the MSs to maximize the achievable sum-rate. Numerical results are provided to verify the analysis and it is shown that employing massive antennas can improve the efficiencies of wireless energy harvesting and information transmission.

Performance comparison among three different Stokes vector direct-detection receivers

Stokes vectors direct detection (SV-DD) is an effective solution for short-reach optical communications. In this Letter, we investigate two-dimensional-modulation direct-detection systems based on three Stokes vector receivers (SVRs). The influences of three key factors including the states-of-polarization (SOP), the splitting ratio of the coupler, and the excess loss (EL) are studied in detail. It is shown that the splitting ratio for achieving optimum performance will be changed with SOP and EL conditions. Among these SVRs, the 3×3 coupler-based receiver with its optimal splitting ratio shows the best bit error rate performance and stability against the change of SOP.

Analytical prediction of optimal split ratio of consequent‐pole permanent magnet machines

For consequent-pole permanent magnet (CPM) machines, the permanent magnet (PM)-arc ratio and split ratio have great influence on the output torque. This study establishes general relationship of the output torque/torque density with PM-arc ratio and split ratio considering the effects of slot/pole number combinations and the tooth-tips. In addition, both the optimal PM-arc ratio and split ratio for maximising the torque density are analytically derived and confirmed by finite-element analysis. It is found that the optimal PM-arc ratio is determined by the ratio of the airgap length to the PM thickness. It is demonstrated that the optimal split ratio depends on the ratio of average airgap flux density below one slot to maximum flux density in the stator iron k B γ and the number of slots for the slots per pole q ≤ 1 .5 or the number of poles for q > 1 .5 . Moreover, it is found that the optimal split ratio decreases with the ratio k B γ , which depends on the PM thickness and PM-arc ratio, and it is reduced when the effect of the stator tooth-tips is taken into consideration. The experimental results on the 12-slot/10-pole CPM machine are given to verify these analyses.

The Impact of Transceiver Noise on Digital Nonlinearity Compensation

The efficiency of digital nonlinearity compensation (NLC) is analyzed in the presence of noise arising from amplified spontaneous emission noise (ASE) as well as from a non-ideal transceiver subsystem. Its impact on signal-to-noise ratio (SNR) and reach increase is studied with particular emphasis on split NLC, where the digital back-propagation algorithm is divided between transmitter and receiver. An analytical model is presented to compute the SNR's for non-ideal transmission systems with arbitrary split NLC configurations. When signal-signal nonlinearities are compensated, the performance limitation arises from residual signal-noise interactions. These interactions consist of nonlinear beating between the signal and co-propagating ASE and transceiver noise. While transceiver noise-signal beating is usually dominant for short transmission distances, ASE noise-signal beating is dominant for larger transmission distances. It is shown that both regimes behave differently with respect to the optimal NLC split ratio and their respective reach gains. Additionally, simple formulas for the prediction of the optimal NLC split ratio and the reach increase in those two regimes are reported. It is found that split NLC offers negligible gain with respect to conventional digital back-propagation (DBP) for distances less than 1000 km using standard single-mode fibers and a transceiver (back-to-back) SNR of 26 dB, when transmitter and receiver inject the same amount of noise. However, when transmitter and receiver inject an unequal amount of noise, reach gains of 56% on top of DBP are achievable by properly tailoring the split NLC algorithm. The theoretical findings are confirmed by numerical simulations.

Wireless Energy Harvesting Two-Way Relay Networks with Hardware Impairments.

This paper considers a wireless energy harvesting two-way relay (TWR) network where the relay has energy-harvesting abilities and the effects of practical hardware impairments are taken into consideration. In particular, power splitting (PS) receiver is adopted at relay to harvests the power it needs for relaying the information between the source nodes from the signals transmitted by the source nodes, and hardware impairments is assumed suffered by each node. We analyze the effect of hardware impairments on both decode-and-forward (DF) relaying and amplify-and-forward (AF) relaying networks. By utilizing the obtained new expressions of signal-to-noise-plus-distortion ratios, the exact analytical expressions of the achievable sum rate and ergodic capacities for both DF and AF relaying protocols are derived. Additionally, the optimal power splitting (OPS) ratio that maximizes the instantaneous achievable sum rate is formulated and solved for both protocols. The performances of DF and AF protocols are evaluated via numerical results, which also show the effects of various network parameters on the system performance and on the OPS ratio design.

Global parameter optimization and criterion formula of supercritical carbon dioxide Brayton cycle with recompression

Supercritical carbon dioxide (S-CO2) Brayton cycle has caught the attention in many fields, especially the field of nuclear reactors. The recompression cycle is considered to be one of the most feasible cycles to solve the pinch problem of heat exchanger. Aiming at the disadvantages of conventional cycle analysis, this paper proposed sensitivity analysis of several parameters and global parameter optimization. The result of sensitivity analysis showed that maximum pressure and efficiency of turbine had the most influential power upon relevant parameters that may determine the final cycle efficiency, followed by re-compressor efficiency, split ratio and main compressor efficiency, with total pressure loss the least. Based on the sensitivity analysis, the thermodynamic parameters optimizing with cycle efficiency as its objective function was presented in this paper. The global parameter optimization results indicated that, for the recompression cycle, the optimal pressure and split ratio could maximize the cycle efficiency. The cycle efficiency could be maximized to 0.447 by adjusting the split ratio and the maximum pressure to 0.687 and 27.75MPa, while the heat source temperature was 600°C, the efficiency of the compressor and re-compressor was 0.8 and the efficiency of turbine was 0.9. Depending on the simulation dates of optimization, criterion formulas of cycle efficiency, maximum pressure and split ratio under the best operating conditions were established. With the input values of given system parameters, the key cycle parameters under the best operating conditions could be received easily and accurately by the criterion formulas.

Optimal Energy Management for HEVs in Eco-Driving Applications Using Bi-Level MPC

Wide usage of vehicle’s onboard navigation system offers vehicles better terms to improve energy efficiency. In this paper, a computationally effective energy management strategy using model predictive control (MPC) is proposed to find the energy optimal torque split, gear shift, and velocity control of a parallel hybrid electric vehicle (HEV). We consider the vehicles in urban driving, where the vehicle trajectory is constrained by the infrastructure (road signs) and other vehicles (traffic). Restricted by the discrete gear ratio, nonlinear dynamics of the vehicles, and especially different time scales between velocity trajectory and torque split optimization, finding these control variables in one optimal problem is quite challenging. Thus, this paper uses bi-level methodology to reduce computational time and simplify the hybrid optimal problem by decoupling its components into two subproblems. In the outer loop, the optimal velocity trajectory is obtained by solving a nonlinear time-varying optimal problem using a Krylov subspace method to improve computational efficiency. In the second subproblem, we provide an explicit solution of the optimal torque split ratio and gear shift schedule by combining Pontryagin’s minimum principle and numerical methods in the framework of MPC. Simulation results on an AMESim model of an HEV with seven-speed automated manual transmission over multiple driving cycles are presented. The results indicate that both energy efficiency and computational speed are improved.

Traffic engineering in hybrid SDN networks with multiple traffic matrices

Traffic engineering (TE) is an efficient tool for optimizing traffic routing and balancing the flows in networks. Traffic is dynamic, previous TE optimization over a single traffic matrix (TM) have some limitations, because a single TM can have big measurement errors and is insufficient to depict the traffic flucuations. Thus, we consider using multiple TMs to overcome these limitations. With the emergence of Software Defined Networking (SDN), we can route flows more flexibly and better balance the flows over multiple TMs. However, due to the difficulties of full SDN deployment, hybrid SDN networks will be the prevailing architectures in the near future. Therefore, optimizing the routing over multiple TMs in a hybrid SDN network is of great interest.In this paper, we first formulate the problem of TE over multiple TMs and prove its NP-hardness. Next, we propose a heuristic algorithm for optimizing routing over multiple TMs by combining offline weight setting optimization with online splitting ratio optimization. Furthermore, we prove that the routes obtained in our algorithm are loop-free, and we provide an upper and lower bound of our proposed algorithm. Finally, we evaluate our method on measured traffic datasets with three network topologies. The results of extensive experiments demonstrate that the maximum link utilization of a network can be optimized better using our proposed algorithm.

Energy-Harvesting Decode-and-Forward Relaying Under Hardware Impairments

In this paper, we propose a decode-and-forward relaying scheme under the effects of hardware impairments. In this proposed scheme, a cooperative relay uses a power-splitting receiver to harvest energy from the radio-frequency signals of a source node and applies a decode-and-forward technique to process the arriving signals. The system performance of the proposed protocol is analyzed in terms of the exact outage probability. Monte Carlo simulation is used to verify the theoretical analysis. Performance evaluations show that the proposed protocol performs best at an optimal power splitting ratio, and outperforms a direct transmission scheme when the relay is far to the destination. The optimal power splitting ratio is obtained more precisely using the golden section search method. In addition, serious effects of hardware impairments robustly diminish the system performance of the proposed protocol and the direct transmission protocol. Finally, the outage probability expressions match the simulation values well.