High Power Ratio Research Articles

A New Approach to Enhance Performance of OFDM using BCH and Newly Designed Filter

Orthogonal frequency division multiplexing (OFDM) is a multicarrier communication technique and it has capability to rise above the frequency-selective fading problem, which is common in wireless broadband communications. This has made it popular since last few years. The OFDM system suffers from a number of drawbacks such as the high peak-toaverage power ratio (PAPR). Many PAPR reduction techniques used either destroy the system performance, which is the clipping technique or increases the overall complexity of the system, such as the selective mapping (SLM). In this paper a unique approach has been proposed to obtain a new code from the existing codes in order to reduce the bit error rate (BER), to mitigate the gap between the performance and Shannon limit while the bounded peak average power ratio (PAPR) of OFDM symbol is guaranteed. A new code based on the BCH with a Barthannwin Wave Filter has been proposed to achieve the desired results. General Terms BCH with Barthannwin Wave Filter

Position Servo Control Technology Based on Sliding Mode Variable Structure for Permanent Magnet Linear Synchronous Motor

The traditional rocket and missile actuator usually uses the hydromantic servo system or pneumatic servo system, because of their better dynamic characteristic and structural adaptability. While with heavy weight, complex structure and expensive cost, it is difficult to realize. The permanent magnet active current servo motor has many advantages, such as high torque, small inertia, high efficiency, the high ratio of power to inertia, cramped construction, firmness, easy maintaining and high reliability. The electrical servo system using the permanent magnet active current servo motor as the power unit satisfies the need of the tactical missile gas vane and air vane servo system, because the range of its transmitted power is wide, its response is quick, and control power is low. This paper analyzed the pole shoe’s shape optimization characteristic against the interior permanent magnet synchronous motor for actuator, presents the design method and main process of permanent magnet synchronous motor for actuator using the field-circuit method. Optimal design can be acquired by the equivalent magnetic circuit method and the finite-element method conveniently and precisely. The analytical result of the prototype motor validated the feasibility of the optimization design.

Comparison of a Single Optimized Coil and a Helmholtz Pair for Magnetic Nanoparticle Hyperthermia

Magnetic nanoparticles in a tumor can induce therapeutic heating when energized by an alternating magnetic field from a current-carrying coil outside the body. We analyzed a single-turn, air-core coil carrying a filamentary current to quantify the power absorbed by: a) magnetic nanoparticles at depth in tissue and b) superficial tissue in response to induced eddy currents; we defined this quotient as power ratio (PR). Given some limit on the eddy current heating tolerated by an alert patient, maximizing the PR maximizes the power absorbed in the tumor; all else being equal, this increases the thermal dose delivered to the tumor. The mean eddy current heating rate tolerated in four clinical studies we reviewed equaled 12.5 kW/m (3). We differentiated our analytical expression for PR with respect to the radius of the coil to find the value of radius that maximizes PR. Under reasonable simplifying assumptions, the optimal value of coil radius equaled 1.187 times the depth of the nanoparticle target below the body surface. We also derived the PR of two coils surrounding the body configured as a Helmholtz pair. We computed PR for combinations of nanoparticle depths below the surface and axial locations with respect to the coils. At depths less than 4.6 cm, the optimized single coil had a higher PR than that of the Helmholtz pair and furthermore produced less total ohmic heating within the coil. These results were independent of driving frequency, nanoparticle concentration, tissue electrical conductivity, and magnetic nanoparticle heating rate, provided the latter is assumed to be proportional to the product of frequency and the square of the local magnetic field. This paper supports the clinical application of current-carrying coils to deliver efficacious hyperthermia therapy to tumors injected with magnetic nanoparticles.

Development of adaptive perturb and observe‐fuzzy control maximum power point tracking for photovoltaic boost dc–dc converter

This study presents an adaptive perturb and observe (P&O)-fuzzy control maximum power point tracking (MPPT) for photovoltaic (PV) boost dc–dc converter. P&O is known as a very simple MPPT algorithm and used widely. Fuzzy logic is also simple to be developed and provides fast response. The proposed technique combines both of their advantages. It should improve MPPT performance especially with existing of noise. For evaluation and comparison analysis, conventional P&O and fuzzy logic control algorithms have been developed too. All the algorithms were simulated in MATLAB-Simulink, respectively, together with PV module of Kyocera KD210GH-2PU connected to PV boost dc–dc converter. For hardware implementation, the proposed adaptive P&O-fuzzy control MPPT was programmed in TMS320F28335 digital signal processing board. The other two conventional MPPT methods were also programmed for comparison purpose. Performance assessment covers overshoot, time response, maximum power ratio, oscillation and stability as described further in this study. From the results and analysis, the adaptive P&O-fuzzy control MPPT shows the best performance with fast time response, less overshoot and more stable operation. It has high maximum power ratio as compared to the other two conventional MPPT algorithms especially with existing of noise in the system at low irradiance.

Role of power ratio on ductility-dip cracking of Ni-Cr-Fe weld

n an austenitic Ni-Cr-Fe weld, the susceptibility for ductility-dip cracking increased with increasing power ratio for a given heat input. The solidification sub-grain width increases with increasing power ratio. Only in the case of relatively high power ratio which is defined as the power divided by the cross-sectional area of deposited metal, Auger electron spectroscope specimens show the solidification sub-grain boundary cracking, and the freshly fractured surface shows the strong sulfur and oxygen peaks. While the temperature gradient might be low in the high power ratio and thus the thermal tensile stress be overall low, the susceptibility for ductility-dip cracking increases with increasing power ratio. This may be attributed to the impurities more enriched at the solidification sub-grain boundaries resulting from the high power ratio.

Involvement of the sympatho-vagal balance in the formation of respiration-dependent oscillations in the human cardiovascular system

The effect of deep breathing controlled in both rate and amplitude on the heart rate variability (HRV) and respiration-dependent blood flow oscillations was studied in the forearm and finger-pad skin of healthy 18- to 25-year-old volunteers. In order to reveal the effects of the divisions of the autonomic nervous system on the amplitudes of respiratory sinus arrhythmia (RSA) and skin blood flow oscillations, we studied the indices of the cardiovascular system in two groups of subjects with respectively lower and higher values of the sympatho-vagal balance. This index was calculated as a ratio of low frequency and high frequency HRV spectral power (LF/HF) under the conditions of spontaneous breathing. It was found that, in subjects with a predominant parasympathetic tone, the amplitudes of RSA and the rate of blood flow in the finger-pad skin were higher compared to subjects with a predominant sympathetic tone during respiration with the frequency lower than 4 cycle/min. In the forearm skin, where sympathetic innervation is weaker compared to the finger-pad skin, there were no significant differences in respiration-dependent oscillations of the rate of blood flow in two groups of subjects.

OFDM Wireless Downhole Transmission Systems and Proposed SLM Method for PAPR Reduction

At present, mud pulse transmission systems are widely used in downhole data transmission. But the systems are very low in transmission efficiency, only 5-10 bits/s, with very large anti-inter-symbol-interference (ISI). It cannot meet high requirements for high-speed transmission of modern logging system. The development of communication technology has laid some foundation for this requirement. For this purpose, the Orthogonal Frequency Division Multiplexing (OFDM) Wireless Downhole Transmission Systems are proposed for the first time because of their high transmission rate, anti-inter-symbol-interference (ISI), and high spectral efficiency, etc. Due to non-linear power amplifier (PA) of logging systems with limited dynamic range, the drawbacks of high peak-average power ratio (PAPR) may outweigh all the potential benefits of OFDM wireless downhole transmission systems. Selective mapping (SLM) method can reduce the PAPR of OFDM logging signals without distortion. But at the receiver, the conventional SLM method needs exact bits of side information (SI) to recover the data signal. The probability of erroneous SI detection has a significant influence on the error performance of the system. And individual transmissions of SI result in the reduction of bandwidth efficiency. To restore the exact data signal, our scheme codes the SI bits by linear block codes (LBC), and is easily decoded by syndrome decoding. And then the coding SI bits are superimposed onto the logging signals to omit SI bits transmission. The theory and simulation results show that the proposed method has better performance than the conventional one. Accordingly, the OFDM wireless downhole transmission systems can tackle the high PAPR problem, and highten the transmission rate of logging signals.

Energy and Environmental Implications of Hybrid and Electric Vehicles in China

The promotion of hybrid and electric vehicles (EVs) has been proposed as one promising solution for reducing transport energy consumption and mitigating vehicular emissions in China. In this study, the energy and environmental impacts of hybrid and EVs during 2010–2020 were evaluated through an energy conversion analysis and a life cycle assessment (LCA), and the per-kilometer energy consumptions of gasoline, coal, natural gas (NG), oil, biomass, garbage and electricity for EVs and HEVs were estimated. Results show that the EVs and HEVs can reduce the energy consumption of vehicles by national average ratios of 17%–19% and 30%–33%, respectively. The study also calculated the detailed emission factors of SO2, NOX, VOC, CO, NH3, PM10, PM2.5, OC, EC, CO2, N2O, CH4, Pb and Hg. It is indicated that the HEVs can bring significant reductions of NOX, VOC and CO emissions and lesser decreases of SO2 and CO2 for a single vehicle. The EVs could decrease many of the VOC, NH3, CO and CO2 emissions, but increase the SO2, NOX and particles by 10.8–13.0, 2.7–2.9 and 3.6–11.5 times, respectively. In addition, the electricity sources had significant influence on energy consumption (EC) and emissions. A high proportion of coal-fired energy resulted in large ECs and emission factors. The total energy consumption and pollutants emission changes in 2015 and 2020 were also calculated. Based on the energy use and emission analysis of HEVs and EVs, it is suggested that EVs should be promoted in the regions with higher proportions of hydropower, natural gas-fired power and clean energy power, while HEVs can be widely adopted in the regions with high coal-fired power ratios. This is to achieve a higher energy consumption reduction and pollutant emission mitigation. Moreover, the results can also provide scientific support for the total amount control of regional air pollutants in China.

Apodized distributed feedback fiber laser with asymmetrical outputs for multiplexed sensing applications

The spectral characteristics of four different types of apodized fiber Bragg gratings with a single π phase shift are analyzed based on the simulation. The 2-discrete Gaussian apodization is proved to have the most effective suppression to grating side mode. A novel asymmetrical distributed feedback fiber laser based on this apodization structure is presented and fabricated as well. The grating has a -20 dB side-mode suppression. The laser exhibits a high power ratio of backward to forward outputs. It has a relative intensity noise of -90 dB/Hz and a linewidth of 20k Hz operating in a single polarization longitudinal mode.

A Partition Dummy Sequence Insertion PAPR Reduction Method of the OFDM System

OFDM (Orthogonal Frequency Division Multiplexing) technique has been widely adopted in many wireless communication systems due to its high data-rate transmission ability and robustness to the multipath fading channel. One major drawback of the OFDM signal is the high peak-toaverage power ratio (PAPR) problem. The high PAPR results in the in-band distortion and out-of-band radiation when the OFDM signal is fed into a nonlinear power amplifier (PA). In this paper, we propose a partition dummy sequence insertion (PDSI) method to reduce the PAPR problem. Simulation results of the PAPR reduction and bit error rate (BER) performance for the proposed method are evaluated to demonstrate its capabilities.

A novel unequal‐power divider based on synthetic quasi‐tem transmission line design

AbstractThis article well proposed a novel miniature unequal Wilkinson power divider using dual transmission line (DTL) design scheme with synthetic quasi‐TEM transmission line whose name is called complementary conducting strip (CCS). Our study technically and theoretically compared the miniaturized unequal Wilkinson power divider (UWPD) consisting of high‐impedance CCS and low‐impedance DTL with traditional microstrips. Under same conditions of process, simulation skill, and electrical performance, the analyses at operating frequency of 2.4 GHz result in that the area needed for CCS DTL UWPD with a power dividing ratio of 5 to 1 is merely 53% of traditional microstrips, input return loss is above 22 dB, isolation figure is over 21 dB, insertion loss of two output ports are 1.5 dB and 8.51 dB, respectively, and a fairly high output power ratio of 5 to 1 is exhibited. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2012

High frequency oscillations in the subthalamic nucleus: A neurophysiological marker of the motor state in Parkinson's disease

Increasing evidence suggests that abnormal oscillatory activity in basal ganglia and cortex plays a pivotal role in the pathophysiology of Parkinson's disease. Recordings of local field potentials from subthalamic nucleus of patients undergoing deep brain stimulation have focused on oscillations occurring at frequencies below 100 Hz in the alpha, beta and gamma range and suggested that, in particular, an increase of beta band oscillations underlies slowing of movement in Parkinson's disease. Recent findings showing that the amplitude of high frequency oscillations (> 200 Hz) couples with the phase of beta activity have raised the important question about the role of subthalamic high frequency oscillations in Parkinson's disease. To investigate functional characteristics and clinical relevance of high frequency oscillations, we recorded local field potentials from 18 subthalamic nuclei of 9 akinetic-rigid Parkinsonian patients with implanted deep brain stimulation electrodes and still externalised leads before and after intake of levodopa. We identified two distinct bands of high frequency oscillations, one centred around 250 Hz and another one around 350 Hz that show characteristic levodopa dependent amplitude and coupling behaviours. Administration of levodopa changed the power ratio between the two high frequency bands towards the component centred around 350 Hz in all 18 nuclei under study (p < 10 − 4 ). Moreover, this power ratio correlated significantly with the Unified Parkinson's Disease Rating Scale hemibody akinesia/rigidity subscore (r = 0.3618, p = 0.015), but interestingly not with beta peak power (p = 0.1) suggesting that levodopa induced changes in high frequency and beta oscillations are at least potentially independent of each other. Accordingly, a combined parameter composed of power ratio of high frequency oscillations and beta peak power significantly increased the correlation with the motor state (r = 0.45, p = 0.004). These results indicate that a shift from slower to faster frequencies of the spectrum greater than 200 Hz represents a prokinetic neurophysiological marker underlying levodopa induced motor improvement in Parkinson's disease.

2A1-I10 空気圧アクチュエータを用いた拮抗駆動に関する研究(ワイヤ駆動系の機構と制御)

Recently, pneumatic servo systems have been applied in several systems, such as pneumatic robot systems, aspherical glass molding machines, and a precise positioning stage to isolate vibration. Because air has a number of advantages, including compressibility, high power ratio, and low heat generation. Antagonistic drive is widely used in pneumatic robots to transform linear motion to rotation. However, the drive system is affected by the friction caused by tension and becomes unstable when the stiffness of the system becomes higher. Therefore, the control method and the configuration of the valves for the drive have still room for study. In this paper, we focus on antagonistic drive system with pneumatic actuators. Arrangement of the servo valves, the control method of the system and the influence of tension to the controllability are studied. Experimental results indicated that tension should be set by the minimum tension T_0. We also confirmed that the responsibility of the system can be improved by using the four servo valves for a single joint.

Preparation and Characteristics of Nanoscale Diamond-Like Carbon Films for Resistive Memory Applications

We propose diamond-like carbon (DLC) as the resistance change material for nonvolatile memory applications. Nanoscale DLC films are prepared by filtered cathodic vacuum arc technique and integrated to W/DLC/W structure devices. The deposited DLC film has a thickness of about 20 nm and high sp3 fraction content. Reversible bistable resistive switching from a high resistance state to a low resistance state, and vice versa, is observed under appropriate unipolar stimulation pulses. High resistance switching ratio (larger than a thousand times) and low level of switching power (about 11 μW) are demonstrated. We propose that the mechanism of the repetitive resistive switching is the growth and breakage of conductive sp2-like filaments in the predominantly sp3-type insulating carbon upon applications of voltage pulses, which is consistent with the experimental results.

Side Band Power reduction in OFDM

In the recent past, wireless communications have experienced a fast growth due to the high mobility that they allow. However, wireless channels have some disadvantages, like multi-path fading, that make them difficult to deal with. A modulation scheme that efficiently deals with selective fading channels is OFDM. An important disadvantage of OFDM systems is their high peak-toaverage power ratio (PAPR). Clipping and filtering can be a simple and effective method of reducing the peak-to-average power ratio (PAPR). But this results in an increase in Side Band / out-of-band (OOB) power, which increases PAPR. In this paper, it is shown that if the OOB power is attenuated in step by step fashion instead of abrupt reduction, then PAPR can also be reduced. Simulation results related to this using MATLAB are presented.

60-GHz Self-Heterodyne Through-Repeater Systems with Suppressed Third-Order Intermodulation Distortions

We present a 60-GHz wireless through-repeater system based on self-heterodyne transmission scheme with the potential to optimize the carrier-to-interference and noise ratio (CINR) performance according to the transmission distance. The phase-noise degradation through a 60-GHz repeater link is not a serious concern when we employ the self-heterodyne transmission scheme. Multichannel interferences caused by third-order intermodulation distortions are efficiently suppressed by setting a high power ratio of LO carrier to RF signals in the self-heterodyne transmission. However, this high power ratio results in a lower carrier-to-noise ratio (CNR) and becomes unsuitable for improving link performance if the transmission distance increases. In order to facilitate a solution, we propose and make an embodiment of 60GHz self-heterodyne transmitters that provide flexible control over the power ratio of LO to RF in a range of 10dB ranges. With them, we successfully demonstrate terrestrial digital broadcasting signals on five channels and optimize their performance for wireless through-repeater applications.

2D divertor design calculations for the national high-power advanced torus experiment

The national high-power advanced torus experiment is a concept for a new facility to address the FESAC theme of ‘taming the plasma-material interface’. This concept exploits the compactness and excellent access provided by low aspect ratio to achieve a high ratio of exhaust power to major radius in order to study the integration of high-performance, long-pulse plasmas with a reactor-relevant high heat flux plasma boundary. Predictions of the scrape-off-layer plasma characteristics are presented, as calculated with the 2D edge modeling code SOLPS. Calculations in a variety of magnetic geometries indicate that very high levels of divertor heat flux can be expected, with peak values far in excess of the power handling capabilities of presently-used materials. Possible methods to reduce the heat flux to acceptable levels are discussed.

Increased Heart Rate Variability but Normal Resting Metabolic Rate in Hypocretin/Orexin-Deficient Human Narcolepsy

We investigated autonomic balance and resting metabolic rate to explore their possible involvement in obesity in hypocretin/orexin-deficient narcoleptic subjects. Resting metabolic rate (using indirect calorimetry) and variability in heart rate and blood pressure were determined in the fasted resting state. Subjects included 15 untreated, hypocretin-deficient male narcoleptics and 15 male controls matched for age and body mass index. Spectral power analysis revealed greater heart rate and blood pressure variability in hypocretin-deficient male narcoleptic patients (heart rate: p = 0.01; systolic blood pressure: p = 0.02; diastolic: p < 0.01). The low to high frequency ratio of heart rate power did not differ between groups (p = 0.48), nor did resting metabolic rate (controls: 1767 +/- 226 kcal/24 h; patients: 1766 +/- 227 kcal/24h; p = 0.99). Resting metabolic rate was not reduced in hypocretin-deficient narcoleptic men and therefore does not explain obesity in this group. Whether the increased heart rate and blood pressure variability--suggesting reduced sympathetic tone--is involved in this regard remains to be elucidated.

Frequency domain interpretation of power ratio metric for cognitive radio systems

SoftWare radio (SWR) is an enabling technology for cognitive radio (CR) systems which promises to (de) modulate any signal, at any frequency. SWR signal therefore is composed of different standard&apos;s signals, and each standard&apos;s signal is either multicarrier or multiplex of single carriers. This combination leads to high temporal fluctuations and thus SWR signal inherits high peak to average power ratio (PAPR) or simply high power ratio (PR). Nonlinear analogue components (amplifiers, converters etc.) cause distortions (in and out of band distortion) for high PR signals which result in system performance degradation. Usually PR problem is addressed in time domain, and here frequency domain interpretation of PR which is more appropriate in SWR context is presented. Gaussian equivalence between SWR signal and orthogonal frequency division multiplexing (OFDM) signal is proved first to accentuate high PR issue in SWR as OFDM suffers the same problem. Then frequency domain interpretation of PR metric is discussed which results in a PR upper bound. This PR upper bound depends only upon spectral values of the signal thus associates spectrum with PR. As a result this bound assists in spectrum access for CR systems by providing PR metric information related to any available bandwidth. Thus bandwidth allocation in a spectrum access scenario under PR constraint is simplified.

Generation of Two Self-Pumped Phase-Conjugated Waves at Different Wavelengths Using Single Photorefractive Crystal

Two self-pumped phase-conjugated waves at different wavelengths are successfully generated using an undoped barium titanate crystal. With one signal beam at a wavelength of 514.5 nm incident to the (100) face of the crystal and the other at a wavelength of 488.0 nm incident to the opposite (100) face with an offset of 2 mm, two phase-conjugated images are produced even at high power ratios between the signal beams. The use of two different wavelengths prevents interference between the two signal beams, resulting in the generation of phase-conjugated waves over a wide dynamic range.