Traditional Pulses Research Articles

Aerial Base Station Assisted Cellular Communication: Performance and Trade-Off

The use of Aerial Base Stations (ABSs) has received a great deal of attention in academia and industry as a means to support the cellular communication traffic growth. In this article, we focus on obtaining the optimal altitude of an ABS using two criteria - maximum cell coverage area and minimum Symbol Error Rate (SER). Our study is done by using a probabilistic air-to-ground channel model, developed for low altitude aerial platforms via simulations on a commercial ray tracing software, for different scenarios like Urban High Rise, Urban, and Suburban. The probability distributions of the received power of the ground users and of the power delay profile at optimal ABS altitude are provided as a function of the size of the cell area. For the SER analysis, we present a system model based on Generalized Frequency Division Multiplexing (GFDM), in a time-frequency grid that is compatible with Long Term Evolution, by implementing parameters for low latency communication at the physical layer. The impact of “Better than Nyquist” pulses on the GFDM system is evaluated in terms of SER performance. From the presented results, a significant improvement is demonstrated compared to the traditional Nyquist pulses.

Morphology-Controllable Ultrafast Fiber Lasers Based on Intracavity Manipulation of Transverse Modes

The performances of mode-locked fiber lasers rest with the design and configuration of the cavity, and their temporal morphologies are rarely linked with the modulation of transverse modes. Here, we demonstrate a morphology-controllable ultrafast fiber laser based on the intracavity manipulation of transverse modes, capable of producing dual-color pulses, narrowband picosecond pulses, and broadband femtosecond pulses. Unlike traditional multicolor pulses with unequal group velocities, the dual-color pulse operates in a synchronous state, displaying a multipeak structure where the modulation period relies on the group-delay difference of two modes in the fiber. Simulation results fully reproduce the experimental observations and show that the laser follows the minimum-loss principle with pulse morphologies depending on the mode-interference-induced filtering effect. This work connects transverse-mode modulation with pulse morphology, providing a stable and cost-effective laser source for terahertz-wave generation and nonlinear spectroscopy.

The Complementarity of Amino Acids in Cooked Pulse/Cereal Blends and Effects on DIAAS.

The aim was to study the complementary effect between cereals and pulses on protein quality. The values for the digestible indispensable amino acid score (DIAAS) in cooked cereals and pulses, given alone, and blends of cooked cereals and pulses, were determined. True ileal digestibility (TID) values of amino acids for adult humans were obtained. It is difficult to determine ileal amino acid digestibility in humans directly, and for this reason, the growing pig is often used to obtain such values, as a preferred animal model. Seven growing pigs fitted with a T-cannula at the terminal ileum were allotted to a 7 × 6 incomplete Latin square with seven semi-synthetic diets (cooked mung bean, adzuki bean, millet, adlay, mung bean + millet, adzuki bean + adlay, and an N-free diet) and six 7-day periods. The mean TID values for crude protein differed significantly (p < 0.05), with millet having the highest digestibility (89.4%) and the adzuki bean/adlay mixture having the lowest (79.5%). For lysine, adzuki bean had the highest TID (90%) and millet had the lowest (70%). For the mean of all the amino acids, there was a significant (p < 0.05) effect of diet, with the TID ranging from 72.4% for the adzuki bean/adlay mixture to 89.9% for the adzuki beans. For the older child, adolescent, and adult, the DIAAS (%) was 93 for mung beans, 78 for adzuki beans, 22 for millet, 16 for adlay, and 66 for mung beans + millet, and 51 for adzuki beans + adlay. For mung beans, valine was first-limiting, and the SAA for adzuki beans, while lysine was first-limiting for the other foods. Chinese traditional diets, containing both cereals and pulses, are complementary for most, but not all of the indispensable amino acids.

Tunable period-multiplying Q-switched pulse outputs based on birefringence induced multiwavelength tuning in a linear erbium-doped fiber oscillator

A tunable period-multiplying Q-switched erbium-doped fiber laser based on birefringence induced multiwavelength tuning in a linear cavity is demonstrated. By carefully adjusting the polarization controller to control birefringence filter effect under the pump power of 204 mW, period-doubling, period-tripling and period-quadrupling operations corresponding to dual-, quadruple- and triple-wavelength pulses are experimentally demonstrated, respectively. Unlike the traditional period-multiplying pulses operating in the narrow control parameters, they can persistently exist under constantly changing pump power from 204 mW to 117 mW. We attribute them to the intrinsic property of laser system with multiwavelength pulse emissions across 1530- and 1550-nm gain regions. And multiwavelength tuning provides the versatility of period-multiplying pulses. To the best of our knowledge, it is the first demonstration of the persistent and tunable period-multiplying Q-switched pulse outputs. This could offer an attractive alternative seed source integrated with all-optical modulation for applications requiring modulated Q-switched pulse sequences such as multiple-pulse laser-induced breakdown spectroscopy and processing.

Mode-Locked Tm³⁺-Doped Fiber Laser With CV Mode Output Using a Cascading Chirped LPFG

A passively mode-locked Tm3+-doped fiber laser based on the mechanism of nonlinear polarization rotation and cascading chirped long period fiber grating (LPFG) to generate ultrafast cylindrical vector (CV) mode output is proposed and demonstrated. The fiber laser output traditional soliton pulses operating at 1878.8 nm with a 3 dB bandwidth of 3.94 nm. The pulse duration of the laser is ~1.05 ps with a repetition rate of 18.766 MHz. A cascading chirped LPFG, fabricated in a few-mode fiber by a CO2 laser, serves as a broadband transverse mode converter to achieve ultrafast CV mode generation. The LPFG has a 10 dB bandwidth (corresponding to conversion efficiency of 90%) of 20 nm from 1877 nm to 1897 nm, which perfectly covers the wide mode-locked spectrum. High purity radially and azimuthally polarized modes are obtained through adjusting the polarization controllers, and the mode purity is calculated to be about 95.1% and 94.9% for TE01 and TM01. To our best knowledge, this is the first mode-locked fiber laser emitting CV modes in $2~\mu \text{m}$ waveband using a broadband LPFG as a mode converter.

Advantages of the Optimum Pulse Moment in Surface NMR and Application in Groundwater Exploration.

The surface nuclear magnetic resonance (SNMR) method is widely used in groundwater detection because of its sensitivity to hydrogen in water and direct water detection. However, low signal-to-noise ratios (SNRs) restrict the development of this technique. An optimum pulse sequence is designed according to correspondence between the pulse moment strength and its best detection depth. Because only selection of the pulse intensity distribution according to the target aquifer depth is required and the "on-resonance" pulse pattern is still employed, this pulse sequence emission can be easily achieved using existing SNMR instrumentation. Numerical simulation results and field experiments show that, compared with traditional exponential growth pulses, the optimum pulse sequence effectively improves the SNR of the SNMR method. The aquifer boundary, water content, and pore characteristics of the inversion result are thus more consistent with characteristics of underground structures. Additionally, because the optimum pulse sequence focuses most of the pulse moments in the target depth range, in situations where two aquifers are separated by a relatively narrow aquitard, it is better able to resolve the individual aquifers than the traditional pulses. Optimum pulse moments improve the SNR by enhancing the signal amplitude, compared with various filtering methods, and obtain a better detection effect. This kind of pulse sequence can be used as an alternative pulse sequence form of the SNMR method.

A modification of γ-encoded RN symmetry pulses for increasing the scaling factor and more accurate measurements of the strong heteronuclear dipolar couplings

Symmetry based γ-encoded RNnν elements are broadly used in magic-angle spinning solid-state NMR experiments to achieve selective recoupling of the heteronuclear dipolar interactions. The recoupled dipolar couplings in such experiments are scaled by a factor, Ksc, which theoretically depends on the chosen symmetry numbers N, n, and ν. However, the maximum theoretical value of Ksc for γ-encoded RNnν pulses is limited to ~0.25, resulting in long RNnν experiment times. Also, the dependence of Ksc on the experimental parameters can result in systematic errors in the experimental determination of the dipolar couplings, especially at low and moderate MAS rates. In this manuscript, we investigate the use of MODifiEd RNnν symmetry (MODERNnν(ϕM)) pulses that increase the dipolar scaling factor by at least 1.45 fold compared to γ-encoded RNnν. The second advantage of MODERNnν(ϕM) pulses with respect to traditional RNnν pulses is the reduced influence of experimental parameters on Ksc, which allows for more accurate measurement of short-range distances. The robustness of MODERNnν(ϕM) is compared with γ-encoded R1423 symmetry pulses. The enhanced performance is demonstrated on two uniformly-13C-enriched samples, N-acetyl valine and the microcrystalline protein GB1, at a 31.111 kHz MAS rate.

Stimulus waveform design for decreasing charge and increasing stimulation selectivity in retinal prostheses.

Retinal degenerative diseases, such as retinitis pigmentosa, begin with damage to the photoreceptor layer of the retina. In the absence of presynaptic input from photoreceptors, networks of electrically coupled AII amacrine and cone bipolar cells have been observed to exhibit oscillatory behaviour and result in spontaneous firing of ganglion cells. This ganglion cell activity could interfere with external stimuli provided by retinal prosthetic devices and potentially degrade their performance. In this work, the authors computationally investigate stimulus waveform designs, which can improve the performance of retinal prostheses by suppressing undesired spontaneous firing of ganglion cells and generating precise temporal spiking patterns. They utilise a multi-scale computational model for electrical stimulation of degenerated retina based on the admittance method and NEURON simulation environments. They present a class of asymmetric biphasic pulses that can generate precise ganglion cell firing patterns with up to 55% lower current requirements compared to traditional symmetric biphasic pulses. This lower current results in activation of only proximal ganglion cells, provides more focused stimulation and lowers the risk of tissue damage.

Wire electrochemical micromachining of Ni-based metallic glass using bipolar nanosecond pulses

The up-and-coming trend of product miniaturization alongwith application of novel materials with extreme properties has created a challenge for machining industry. Newly developed wire electrochemical micromachining (WECMM), as an important nontraditional micromachining technique, has been identified as a promising method for fabrication of microcomponents on a wide range of conductive materials. However, in many cases, the processing performance is typically limited by the properties of tool cathode and the mass transport rate in the interelectrode, which plays a crucial role in further development of this technique. Herein, the use of bipolar nanosecond pulses is innovatively proposed to help reduce the deposition of electrolysis products on the tool electrode and the underlying mechanism is systematically analyzed. Helical carbon nanotube fiber (CNF) was used as a new tool cathode in vibration-assisted WECMM to enhance the mass transport rate. The microshaping characteristics of the proposed method using bipolar nanosecond pulses were then investigated using a Ni-based metallic glass that exhibits typical passivation behavior in dilute acidic electrolytes as a representative example. Compared with traditional unipolar pulses, the use of bipolar pulses could effectively inhibit passive film growth on the machining surface of metallic glasses. In addition, no tool wear occurred for CNF that the original surface morphology became rougher only at excessive negative voltages. Finally, functional microcomponents were successfully fabricated with overall improved processing performance.

The Various Angles of Outphasing PAs: Competitiveness of Outphasing in Efficient Linear PA Applications

The demand for linear and highly efficient RF amplifiers has continued to rise without showing signs of stopping, as the world looks to the implementation of 5G. Modern communication signals gave rise to the demand, as the desire to efficiently utilize the limited electromagnetic spectrum led to widespread use of amplitude- and phase-modulated signals, e.g., LTE and LTE Advanced, that use carrier aggregation to achieve broader bandwidths. The defense industry may provide even more applications, as electronic warfare techniques make use of multitone and sometimes noise-like signals that have statistics similar to communication signals. Radars are required to limit emissions in adjacent bands, but traditional rectangular pulses have high out-of-band emissions. Gaussian pulse shaping can be used to improve spectral efficiency, limiting emissions and sidelobes, while adding amplitude modulation [1].

Reduction of Muscle Contractions during Irreversible Electroporation Therapy Using High-Frequency Bursts of Alternating Polarity Pulses: A Laboratory Investigation in an Ex Vivo Swine Model

PurposeTo compare the intensity of muscle contractions in irreversible electroporation (IRE) treatments when traditional IRE and high-frequency IRE (H-FIRE) waveforms are used in combination with a single applicator and distal grounding pad (A+GP) configuration. Materials and MethodsAn ex vivo in situ porcine model was used to compare muscle contractions induced by traditional monopolar IRE waveforms vs high-frequency bipolar IRE waveforms. Pulses with voltages between 200 and 5,000 V were investigated, and muscle contractions were recorded by using accelerometers placed on or near the applicators. ResultsH-FIRE waveforms reduced the intensity of muscle contractions in comparison with traditional monopolar IRE pulses. A high-energy burst of 2-μs alternating-polarity pulses energized for 200 μs at 4,500 V produced less intense muscle contractions than traditional IRE pulses, which were 25–100 μs in duration at 3,000 V. ConclusionsH-FIRE appears to be an effective technique to mitigate the muscle contractions associated with traditional IRE pulses. This may enable the use of voltages greater than 3,000 V necessary for the creation of large ablations in vivo.

Bipolar Microsecond Pulses and Insulated Needle Electrodes for Reducing Muscle Contractions During Irreversible Electroporation.

To minimize the effect of muscle contractions during irreversible electroporation (IRE), this paper attempts to research the ablation effect and muscle contractions by applying high-frequency IRE (H-FIRE) ablation to liver tissue in vivo. An insulated needle electrode was produced by painting an insulating coating on the outer surface of the needle electrode tip. A series of experiments were conducted using insulated needle electrodes and traditional needle electrodes to apply H-FIRE pulses and traditional monopolar IRE pulses to rabbit liver tissues. The finite element model of the rabbit liver tissue was established to determine the lethal thresholds of H-FIRE in liver tissues. Muscle contractions were measured by an accelerometer. With increased constitutive pulse width and pulse voltage, the ablation area and muscle contraction strength are also increased, which can be used to optimize the ablation parameters of H-FIRE. Under the same pulse parameters, the ablation areas are similar for the two types of electrodes, and the ablation region has a clear boundary. H-FIRE and insulated needle electrodes can mitigate the extent of muscle contractions. The lethal thresholds of H-FIRE in rabbit liver tissues were determined. This paper describes the relationships between the ablation area, muscle contractions, and pulse parameters; the designed insulated needle electrodes can be used in IRE for reducing muscle contraction. The study provides guidance for treatment planning and reducing muscle contractions in the clinical application of H-FIRE.

Food and Nutrition Insecurity in Selected Rural Communities of KwaZulu-Natal, South Africa-Linking Human Nutrition and Agriculture.

Lack of access to nutritious and balanced diets remains a major impediment to the health and well-being of people living in rural areas. The study utilizes a qualitative systematic approach to conduct an environmental scan and review of scientific literature of studies conducted in South Africa, specifically KwaZulu-Natal (KZN). Availability and access to nutritious, diverse and balanced diets were identified as key constraints for achieving food and nutrition security as well as for human health and well-being. This has led to both under- and over-nutrition, with the former, in particular stunting, affecting children under 5 years. A high incidence of over-nutrition, both overweight and obesity, was observed among black African females. In South Africa, poor people rely mostly on social grants and cannot afford a balanced diet. Under these circumstances, agriculture could be used to increase availability and access to diverse and nutritious foods for the attainment of a balanced diet. The wider use of traditional vegetable crops and pulses could improve availability and access to healthy and locally available alternatives. The promotion of household and community food gardens, and the use of nutrient dense crops with low levels of water use, i.e., high nutritional water productivity, offers prospects for addressing malnutrition in poor rural areas.

Femtosecond, two-photon-absorption, laser-induced-fluorescence (fs-TALIF) imaging of atomic hydrogen and oxygen in non-equilibrium plasmas

Femtosecond, two-photon-absorption laser-induced fluorescence (fs-TALIF) is employed to measure space- and time-resolved distributions of atomic hydrogen and oxygen in moderate-pressure, non-equilibrium, nanosecond-duration pulsed-discharge plasmas. Temporally and spatially resolved hydrogen and oxygen TALIF images are obtained over a range of low-temperature plasmas in mixtures of helium and argon at 100 Torr total pressure. The high-peak-intensity, low-average-energy fs pulses combined with the increased spectral bandwidth compared to traditional ns-duration laser pulses provide a large number of photon pairs that are responsible for the two-photon excitation, which results in an enhanced TALIF signal. Krypton and xenon TALIF are used for quantitative calibration of the hydrogen and oxygen concentrations, respectively, with similar excitation schemes being employed. This enables 2D collection of atomic-hydrogen and -oxygen TALIF signals with absolute number densities ranging from 2 × 1012 cm−3 to 6 × 1015 cm−3 and 1 × 1013 cm−3 to 3 × 1016 cm−3, respectively. These 2D images are the first application of TALIF imaging in moderate-pressure plasma discharges. 1D self-consistent modeling predictions show agreement with experimental results within the estimated experimental error of 25%. The present results can be used to further the development of higher fidelity kinetic models while quantifying plasma-source characteristics.

PSWF函数在CDMA系统脉冲整形中的应用

适当的脉冲整形对降低码分多址(Code Division Multiple Access, CDMA)通信系统中的多址干扰(Multiple Access Interference, MAI)具有良好的效果。本文针对这一问题，提出将椭圆球面波函数(Prolate Spheroidal Wave Functions, PSWF)引入CDMA系统进行脉冲整形，通过理论分析和Matlab仿真，与常规波形进行了对比，研究了该函数对CDMA系统通信性能的优化情况。理论分析和仿真结果均证明：在能量有限条件下，本文提议的PSWF_4、PSWF_3具有比其他常规波形更优的通信性能。 Proper pulse shaping is useful for reducing Multiple Access Interference (MAI) in CDMA system. In this paper, several prolate spheroidal wave functions (PSWF) are selected as the shaping pulses for CDMA communication system, further analyzed and compared with traditional pulses to improve system performance. Theoretical analysis and Matlab simulation results show that PSWF_4 and PSWF_3 which are proposed in our paper have better system performances compared with other traditional pulses in the power limited condition.

Bradyrhizobium kavangense sp. nov., a symbiotic nitrogen-fixing bacterium from root nodules of traditional Namibian pulses.

Eight strains of symbiotic bacteria from root nodules of local races of cowpea (Vigna unguiculata) and Bambara groundnut (Vigna subterranea) grown on subsistence farmers' fields in the Kavango region, Namibia, were previously characterized and identified as a novel group within the genus Bradyrhizobium. To clarify their taxonomic status, these strains were further characterized using a polyphasic approach. In phylogenetic analysis of the 16S rRNA gene sequence the novel group was most closely related to Bradyrhizobium iriomotense EK05T and Bradyrhizobium ingae BR 10250T, and to 'Bradyrhizobium arachidis' CCBAU 051107 in the ITS sequence analysis. Phylogenetic analysis of concatenated glnII-recA-rpoB-dnaK sequences placed the strains in a lineage distinct from named species of the genus Bradyrhizobium. The species status was validated by results of DNA-DNA hybridization. Phylogenetic analysis of nifH and nodC genes placed the novel strains in a group with 'B. arachidis' CCBAU 051107. The combination of phenotypic characteristics from several tests including carbon source utilization and antibiotic resistance could be used to differentiate representative strains from recognized species of the genus Bradyrhizobium. Novel strain 14-3T induces effective nodules on Vigna subterranea, Vigna unguiculata, Arachis hypogaea and Lablab purpureus. Based on the data presented, it is concluded that the strains represent a novel species of the genus Bradyrhizobium, for which the name Bradyrhizobium kavangense sp. nov. is proposed. The type strain is 14-3T [ = DSM 100299T = LMG 28790T = NTCCM 0012T (Windhoek)]. The DNA G+C content of strain 14-3T is 63.8 mol% (Tm).

Optimal Pulses Robust to Insufficient Synchronization for OFDM/OQAM Systems

In this paper, a novel pulse shaping method is presented for Orthogonal frequency division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) systems. Designed as a linear combination of normalized Hermite functions, the proposed pulse is optimized with respect to interference caused by insufficient synchronization such as carrier frequency offset (CFO) and timing offset (TO). The optimization problem, based on signal-to-interference ratio (SIR) maximization criterion, is carried out using an efficient iterative algorithm. Simulation results show that this optimal pulse outperforms traditional prototype pulses in the presence of insufficient synchronization.

A novel scheme for synchronous optical sampling based on multicast parametric process

We propose a novel scheme for synchronous optical sampling based on multicast parametric process. The linearly chirped and time-broadened pulses are utilized to replace the traditional mode-locked sampling pulses. An optical sampling rate of 80 Gbit/s is realized by using only one sampling source with repetition rate of 10 GHz.

Design of Robust Pulses to Insufficient Synchronization for OFDM/OQAM Systems in Doubly Dispersive Channels

This paper presents a pulse shaping method robust to insufficient synchronization in orthogonal frequency division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) systems over doubly dispersive (DD) channels. The proposed pulse is designed as a linear combination of several well localized Hermite functions. The coefficients optimization problem is modeled as a nonconvex constrained fractional programming problem based on the signal-to-interference ratio (SIR) maximization criterion. An efficient iterative algorithm is applied to simplify the problem to a series of quadratically constrained quadratic program (QCQP) problems which can be solved by semidefinite relaxation (SDR) method. Simulation results show that the proposed pulse is superior to traditional pulses with respect to SIR performance over DD channels in the presence of carrier frequency offset (CFO) and timing offset (TO).

Determinants of crop diversity in the regions of Bangladesh (1990–2008)

The paper measures the level of crop diversity and identifies factors influencing diversification using a panel data of 17 regions of Bangladesh covering a 19 year period (1990–2008). Results revealed the trends that agricultural areas allocated to high‐yielding variety rice, spices and vegetables has increased, while areas cultivating traditional rice, minor cereals, oilseeds, pulses, jute and sugarcane has declined at variable rates across regions with significant differences. The level of crop diversity is also significantly different across regions and has decreased in 2008 from its 1990 level in most regions except Faridpur, Khulna and Sylhet. Among the determinants, an increase in the relative prices of vegetables and urea fertilizer, extension expenditure, labour stock per farm, average farm size, irrigation and a reduction in livestock per farm significantly increase crop diversity. Price policies to improve vegetable prices and investment in irrigation infrastructure and extension services are suggested to promote crop diversity in Bangladesh.