Lamb波模态体声波压电谐振器仿真研究

随着现代通信技术的发展,对高性能射频器件的需求愈加急迫。体声波(BAW)谐振器凭借其独特的优势,满足了高频应用领域的需求,成为当下射频器件中热门的研究方向之一。该文提出一种基于叉指电极的兰姆波S0模态BAW谐振器,并讨论了支撑锚结构和压电材料对器件的品质因数(Q)值的影响,仿真分析了4种锚结构和3种压电材料下器件的品质因数情况。同时基于仿真得到的氮化铝BAW谐振器单元,采用梯形级联方式得到频带在70.36~71.45 MHz的BAW滤波器,插入损耗>-1 dB,能够适用于高频窄带应用范围。

Artificial Intelligence-Based Sentiment Analysis of Dynamic Message Signs that Report Fatality Numbers Using Connected Vehicle Data

This study presents results from sentiment analysis of Dynamic message sign (DMS) message content, focusing on messages that include numbers of road fatalities. As a traffic management tool, DMS plays a role in influencing driver behavior and assisting transportation agencies in achieving safe and efficient traffic movement. However, the psychological and behavioral effects of displaying fatality numbers on DMS remain poorly understood;hence, it is important to know the potential impacts of displaying such messages. The Iowa Department of Transportation displays the number of fatalities on a first screen, followed by a supplemental message hoping to promote safe driving;an example is “19 TRAFFIC DEATHS THIS YEAR IF YOU HAVE A SUPER BOWL DON’T DRIVE HIGH.” We employ natural language processing to decode the sentiment and undertone of the supplementary message and investigate how they influence driving speeds. According to the results of a mixed effect model, drivers reduced speeds marginally upon encountering DMS fatality text with a positive sentiment with a neutral undertone. This category had the largest associated amount of speed reduction, while messages with negative sentiment with a negative undertone had the second largest amount of speed reduction, greater than other combinations, including positive sentiment with a positive undertone.

Comparison of Genomes of the Hepadnaviridae Family

Background: The Hepadnaviridae family is composed of small hepatotropic DNA viruses, divided into two main genera: Avihepadnavirus, which infects birds;and Orthohepadnavirus, which infects mammals. The human hepatitis B virus (HBV) is a member of the latter family and contains a relaxed circular double-stranded DNA genome of approximately 3 kb, and the objective of this study is to evaluate the genetic diversity of the genome of the Hepadnaviridae family. Materials and Methods: For this study, we evaluated the 26 NCBI reference sequences of the Hepadnaviridae family. Result: The two main genera, Avihepadnavirus and Orthohepadnavirus, show low similarity between them. The Orthohepadnavirus, to which HBV belongs, has two important hosts, monkeys and bats, while the genus, which infects humans, has greater diversity but is similar to the viruses that infect monkeys. The Paraepadnavirus isolated from the white sucker fish and the Herpetohepadnavirus from the Tibetan frog showed strong similarity with the Avihepadnavirus found in birds. The Metahepadnavirus isolated from the bluegill fish was the Hepadnaviridae which had the greatest difference, with less than 20% similarity using CLC Sequence Viewer. Conclusion: The Hepadnaviridae genomic replication cycle involves a late reverse transcriptase (RT) step. This polymerase, however, does not have proofreading activity, resulting in genetic variability in the Hepadnaviridae family.

Modelling and Analysis of the Hubble Diagram of 280 Type SNIa Supernovae and Gamma Ray Bursts Redshifts with Analytical and Empirical Redshift/Magnitude Functions

Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding or static universe. At redshifts > 2 - 3 ΛCDM models show a poor agreement with the observed data. Based on the results presented in this paper, the Hubble diagram test does not necessarily support the idea of expansion according to the big-bang concordance model.

Investigation on the streamer propagation in atmospheric pressure helium plasma jet by the capacitive probe

In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges and the mean propagation velocity of the guided ionization waves are measured by the capacitive probe method in the discharge region.The space charges in the guided ionization waves are found to increase with the applied voltage,which enhances both the electric field near the streamer head and the propagation velocity.The applicability of the streamer mechanism to the propagation of the guided ionization waves is validated by this electrical diagnostic method.

Runtime Power Allocation Based on Multi-GPU Utilization in GAMESS

To improve the power consumption of parallel applications at the runtime, modern processors provide frequency scaling and power limiting capabilities. In this work, a runtime strategy is proposed to maximize performance under a given power budget by distributing the available power according to the relative GPU utilization. Time series forecasting methods were used to develop workload prediction models that provide accurate prediction of GPU utilization during application execution. Experiments were performed on a multi-GPU computing platform DGX-1 equipped with eight NVIDIA V100 GPUs used for quantum chemistry calculations in the GAMESS package. For a limited power budget, the proposed strategy may deliver as much as hundred times better GAMESS performance than that obtained when the power is distributed equally among all the GPUs.

Persistence of Dioxin TCDD in Southern Vietnam Soil and Water Environments and Maternal Exposure Pathways with Potential Consequences on Congenital Heart Disease Prevalence in Vietnam

Waterlogged soils and submerged sediments in wetlands and agricultural lands used for rice paddies and aquaculture have anaerobic conditions that slow and prevent the photo and microbial degradation of dioxin TCDD (2,3,7,8-tetracholorodibenzo-p-dioxin), enabling it to persist in environments for long periods. Over 1.6 million ha of land in southern Vietnam were sprayed with 2,4,5-T herbicides (e.g. Agent Orange) contaminated with dioxin TCDD during the Vietnam War (1961-1971);45% of these ha received four or more spray flight missions. Dioxins are endocrine disrupters and may induce cardiovascular disease, growth, and developmental defects, diabetes, hormonal dysfunctions and disruptions, certain cancers, and chloracne. Outpatient screening clinic 2020 data on Vietnamese children suspected of congenital heart disease (CHD) showed the childhood CHD prevalence rate in Vietnam of 13.356/1000, significantly elevated compared to the Asian CHD prevalence rate of 3.531/1000. CHD prevalence rate differences between North Vietnam (2.541/1000) and south of the 17th parallel (10.809/1000) were significant. Vietnamese farmers, especially pregnant women whose occupations involve daily contact with soil and sediments where dioxin TCDD persists in the environment may be at risk of dioxin accumulation from dermal exposure and bioaccumulation via diet. There is an urgent need for funded longitudinal genetic and clinical studies to assess CHD and other organ system childhood malformations due to in utero TCDD exposure. We recommend an integrated research design involving 1) site-specific locations that received high volumes and multiple spray loads of herbicides during the Vietnam War;2) soil sampling of submerged and waterlogged soils and sediments where TCDD may not have degraded;3) production areas of agriculture, fisheries, and other aquatic products;4) risk assessment dioxin levels in foods where TCDD is likely to bioaccumulate;5) child-bearing age and pregnant women with potentially high sensitivity to long-term low dose exposure, and 6) men and women in occupations that are in daily contact with contaminated soil and sediments as part of their job routines.

In-Field Corn Residue Management for Bioenergy Use: Potential Effects on Selected Soil Health Parameters

In the U.S. biofuel industry is using corn (Zea mays L.) residue mix (CRM) consisting of corncob and stover for cellulosic ethanol and biogas production. The field storage method left different depths of CRM on the field after its removal, where negative effects on plant growth were observed. The objective of this study is to evaluate the CRM effect on selected soil health indicators. The field study conducted with four different depths of CRM, two tillage systems (no-till (NT) and chisel plow (CP), and three nitrogen (N) rates (0, 180, and 270 kg⋅N⋅ha−1) in a randomized complete block design with split-split arrangements in three replications in a continuous corn system from 2010 to 2012 at the Agronomy Research Farm at Iowa State University. The findings of this study showed a negative effect on soil organic carbon (SOC) change across all treatments at 0 - 15 cm (−0.35 to −0.03 Mg⋅ha−1⋅yr−1), while at 15 - 30 cm there was an increase in SOC rate (0.13 to 0.40 Mg⋅ha−1⋅yr−1) after 2-yr. In addition, soil aggregate-associated C of macro-aggregates decreased by 8%, while micro-aggregates increased by 2%. Soil microbial biomass carbon (MBC) across tillage and N rates for 2.5 & 7.5 CRM treatments increased by 14% in June to July 2011, while in 2012 increased by 9%. However, at the 15 cm soil depth, soil bulk density (ρb), soil penetration resistance (SPR), and soil pH showed no significant differences among CRM treatments. The findings of this study showed that in-field CRM management can affect certain soil health parameters in the short term.

Dynamic evolution of low-viscosity fuel particle distribution driven by constant flow

The effects of mass concentration and injection pressure on the atomization characteristics of low-viscosity fuel spray are studied in a constant-volume chamber.Microscopic spray parameters are measured by laser diffraction at different axial and radial positions downstream of the nozzle.The results show that the atomization effect is inhibited linearly with the increase of mass concentration.The increase of injection pressure promotes the droplet breakup.However,the trend gradually weakens and becomes more noticeable at high concentrations.Comparing with the concentration,the influence of the injection pressure on the atomization characteristics is dominant.Although low concentration and high injection pressure can promote the droplet breakup,they also increase the probability of droplet collision,resulting in droplet aggregation.This is more evident in low-viscosity fuels.The droplet size increases in the axial direction owing to the aggregation.However,the diameter decreases in the radial direction owing to the outward deflection of small droplets caused by air turbulence and entrainment.In addition,the high-velocity airflow significantly promotes the droplet breakup near the nozzle and spray axis regions and inhibits the aggregation effect.However,the lower-viscosity fuels keep smaller droplet sizes and better atomization in the whole spraying process,which is easier to realize than the higher-viscosity fuels.Overall,low concentration,high injection pressure,and low viscosity of fuel have beneficial effects on the droplet breakup.This is very important for improving the atomization effect of fuel.

Soil Organic Carbon Dynamics in Eroding and Depositional Landscapes

As a requisite to determining management practice effects on stored soil organic carbon (SOC) stock in a landscape unit, the baseline SOC stock with depth must be determined and the land use, management practices and erosion-induced changes measured periodically or over a period of time. The SOC loss and additions due to soil erosion, transport and deposition must be accounted for or be quantified when determining the real impact of the management practices on net SOC stock over time. Quantifying the SOC loss due to erosion will help avoid over estimation of the management practice performances. Appropriate soil sampling designs and sampling procedures are needed to establish a SOC stock baseline and to monitor and verify new SOC storage or sequestration as a result of a management practice. The Dinesen Prairie landscape in western Iowa, USA was sampled to provide a SOC stock baseline and then the adjacent cropland was sampled to determine the past impact of land use change, management practices and erosion on SOC stock retention. After 100 to 150 years of farming, the entire cropland landscape retained only 49% of the baseline prairie SOC stock. Only the cropland toe-slope (TS) retained more SOC stock than the prairie TS as a result of the erosion, transport and deposition of SOC rich sediment on the TS.

Verification of an Explicitly Coupled Thermal-Phase Field-Mechanical Electromagnetic (TPME) Framework by the Method of Manufactured Solutions

An explicitly coupled two-dimensional (2D) multiphysics finite element method (FEM) framework comprised of thermal, phase field, mechanical and electromagnetic (TPME) equations was developed to simulate the conversion of solid kerogen in oil shale to liquid oil through in-situ pyrolysis by radio frequency heating. Radio frequency heating as a method of in-situ pyrolysis represents a tenable enhanced oil recovery method, whereby an applied electrical potential difference across a target oil shale formation is converted to thermal energy, heating the oil shale and causing it to liquify to become liquid oil. A number of in-situ pyrolysis methods are reviewed but the focus of this work is on the verification of the TPME numerical framework to model radio frequency heating as a potential dielectric heating process for enhanced oil recovery. Very few studies exist which describe production from oil shale;furthermore, there are none that specifically address the verification of numerical models describing radio frequency heating. As a result, the Method of Manufactured Solutions (MMS) was used as an analytical verification method of the developed numerical code. Results show that the multiphysics finite element framework was adequately modeled enabling the simulation of kerogen conversion to oil as a part of the analysis of a TPME numerical model.

Changes in Human Hair Induced by UV- and Gamma Irradiation

The effect of UV- and 137Cs gamma radiation on the structural and chemical integrity of human hair was studied to determine the feasibility of using human hair as a non-invasive biomarker of radiation exposure to ionized gamma- and non-ionized UV-radiation. Steady state tryptophan (Trp) fluorescence and chemical analytical methods were used to evaluate the molecular integrity of Trp fluorophores and SH-groups in hair proteins and to assess the radiation induced damage quantitatively. It was found that human hair fibers were progressively damaged by exposure to both UV- and ionized gamma radiation. Damage to the hair was evidenced by a decrease in the fluorescence intensity as a result of observed depletion of the amino acid tryptophan as well as significant reduction in a number of free SH-groups in hair proteins. Hair damage was dose-dependent for exposures between 0 and 10.0 Gy and 0 - 20 J/cm2 of UV-radiation. Additional results demonstrate that hair-fibers exposed to gamma rays, with much higher quantum energy than UV, undergo a smaller extent of changes in Trp fluorescence than when exposed to lower or equal energy of UV-irradiation. The stable Trp fluorophore appears to be extremely sensitive to UV-radiation in contrast to the ionized gamma radiation whose damage is originated from the reaction of free radicals and direct deposition of energy. We conclude that fluorescence spectroscopy represents a useful tool in the quantitative evaluation of the radiation exposure and could also be used for the rapid and non-invasive assessment of radiation dose i.e. biodosimeter. The approach is simple, non-invasive and appears to have considerable potential that enables quantitative evaluation of radiation dose exposure in a single hair fiber.

复杂系统视角下数字领域“smart”概念的国际标准化共识构建及应用

进入数字时代,伴随大数据和人工智能技术快速发展和普遍应用,带有“smart”的指称不断涌现,然而关于“smart”概念的认知尚缺少跨领域和跨国际标准组织的标准化共识构建研究。采用ISO 704:2022的概念构建原则和方法,基于复杂系统论视角,对数字领域国际标准定义中涉及“smart”的概念特征进行了识别。基于跨领域国际标准组织专家的研讨、问卷调查和国际共识构建,提出了适应于复杂系统数字领域“smart”的通用概念,并将其用于指导《智慧城市城市智能服务体系构建指南》国家标准的制定过程。该研究对推进国家标准和国际标准兼容具有重要战略意义。

阿克量级放射性同位素分析的加速器质谱分析技术及其进展

加速器质谱(AMS)技术已发展成为测试超低含量长寿命放射性核素的最灵敏手段,探测限降低至阿克量级。该文对加速器质谱的基本原理、加速器质谱仪基本结构、仪器经历的四代发展演化情况以及加速器质谱相关的关键技术进行了综述,以便于感兴趣的科研人员或从事相关交叉研究的青年科技工作者了解加速器质谱的技术原理、发展趋势、应用领域和范围,促进该技术的应用和学科交叉融合创新。近10年来,我国加速器质谱技术发展快速,仪器设备急剧增加,实验室建设和应用领域发展迅猛,在建及建成各类设备二十余台,设备类型愈发多样化,测试核素同样经历了最初的14C单一核素到现在“主流长寿命放射性核素”的近乎全覆盖扩展,应用范围不断扩大,对我国加速器质谱实验室的建设发展情况进行梳理和汇总也正得其时。加速器质谱技术除了推动传统的基础科学研究外,必将在对全球气候、环境污染、公众健康和国际性的核材料安全防护等热点问题的研究中做出越来越大的贡献,发挥越来越重要的作用。

基于D3QN的火力方案优选方法

针对在多类弹药协同攻击地面工事类目标任务中火力方案优选效率低的问题,提出一种基于双层决斗DQN(dueling double deep Q network,D3QN)的火力方案优选方法。该方法将打击过程建模为马尔科夫决策过程(Markov decision processes,MDP),设计其状态空间和动作空间,设计综合奖励函数激励火力方案生成策略优化,使智能体通过强化学习框架对策略进行自主训练。仿真实验结果表明,该方法对地面工事类目标的火力方案进行决策,相较于传统启发式智能算法能够获得较优的火力方案,其计算效率和结果的稳定性相较于传统深度强化学习算法具有更明显的优势。

Venlo型温室柱脚螺栓节点力学性能

为研究连栋温室柱脚节点尺寸对节点承载力的影响,依托珠海某Venlo型温室项目,基于《混凝土结构设计规范》《化工设备基础设计规定》以及《混凝土结构构造手册》对中柱基础短柱和边柱柱脚节点的构造进行设计,通过数值模拟和节点试验研究了中柱基础短柱柱脚节点的抗弯性能、边柱柱脚节点的抗剪性能以及破坏机理。结果表明:2种节点的屈服荷载和极限荷载随着节点构造尺寸的减小而降低,其破坏过程可划分为3个阶段:弹性阶段、屈服阶段、极限承载力阶段。中柱基础短柱柱脚节点破坏模式为受拉侧混凝土锥形破坏,边柱柱脚节点的破坏模式为混凝土楔形体破坏,研究结果可为连栋温室柱底地脚螺栓节点设计提供参考。

轻骨料水泥基多功能吸波材料的制备及有限元分析

为分析轻骨料种类及粒径对吸波材料性能的影响,采用五种从微米级至毫米级粒径的轻骨料制备了轻质水泥基吸波材料,测试其电磁参数和反射损耗(RL),采用有限元分析方法构建了二维截面模型,模拟吸波材料内部电磁场分布情况,并测试了吸波材料的力学性能和导热系数。结果表明,增加轻骨料掺量和增大粒径可改善水泥基材料的阻抗匹配性能,提升平均RL,拓宽有效吸波频宽,吸收峰向高频移动。20 mm厚度时,吸波材料在低频1.2 GHz处最优RL为-29.1 dB,在较高频5.9 GHz处最优RL为-20.9 dB,有效吸波频宽最宽可达14.49 GHz。有限元模拟结果表明,轻骨料可改变电磁波传输方向,增加电磁波损耗途径,相邻骨料之间可产生较强损耗,其次是在骨料内部产生损耗,这为骨料种类、粒径选择与轻质吸波材料设计提供理论基础。增大轻骨料粒径会降低吸波材料的密度、力学强度与导热系数,使其吸波效能更好,保温效果更优。

Fragipan Horizon Changes Using Annual Ryegrass and Other Admendments

A greenhouse experiment was conducted involving intact fragipan soil cores of 50 cm thickness after removing the topsoil horizons. The cores were maintained in moist condition throughout the experiment and received several treatments with various amendments for different periods ranging from 9 to 17 months. The amendments included annual ryegrass or Festulolium residues, powder limestone and various humate compounds alone or in combination with the grass residues. The results suggested a significant effect of ryegrass and Festulolium in reducing penetration resistance into the top 10 cm of the fragipan within 9 - 17 months, particularly when used in combination with certain humate materials such as Leonardite. Apparently, this is the result of the release of certain soluble organic compounds from the plant residues or the humate amendments that increase the solubility of Si and Al associated with the fragipan brittleness, thus decreasing the density of the compacted fragipan material.

高功率化学电源体系发展及军事应用分析

在全面电动化的背景下,各类电子产品应用的时空域快速转变对所配备的电池供电能力提出了更为苛刻的工况和环境适应要求,亟待发展充电时间短、小体积大电流输出的电源系统。本综述对近年来受到广泛关注的高功率化学电源体系在大倍率充放电领域的进展进行了梳理,包括锂离子电池、钠离子电池、赝电容电容器、离子型电容器(锂/钠/钾离子等)、铅炭电池等,分别从电极材料、电解质调控和电池结构等角度出发,重点分析了当前影响各电源体系在其功率性能方面的发展瓶颈、能力水平以及亟待突破的关键技术,并对其在低温启动、动力供电和脉冲响应等军事应用领域及所增益效能进行了分析研究。综合分析表明,针对不同的应用场景,为进一步遴选性能更好、更匹配的化学电源体系服务于装备的迭代升级和应用创新,通过构筑高稳定性和导电性的电极材料,宽温域、高电导率的电解质材料和改良电池结构从而减小内阻的途径,显著提升功率性能,并明确提出高功率电池存在最佳工作区间和最优工作策略的问题,尤其是在大电流充放电和脉冲工况下,这对于后续如何根据实际工况用好电池具有借鉴意义。有望在提升各化学电源体系的功率性能的同时,以最佳的系统管控方法和应用策略进一步提升电池的循环寿命、能量转换效率、安全性和可靠性,获得满足市场所需和军民急用的高功率电源产品。

基于单辆通行车激励的车桥耦合理论梁式桥阻尼比识别研究

提出一种在单辆通行车激励的情况下,基于车桥耦合理论识别桥梁阻尼比的方法.首先,将集成化检测车设计为单自由度体系,利用集成在检测车上的传感器采集信号并滤波获取桥梁一阶响应信号,通过相邻峰值点做比值并取平均得到桥梁一阶阻尼比,理论推导出检测车停靠在桥面任一位置均可识别出桥梁一阶阻尼比.其次,考虑通行车车速、检测车停靠位置、环境噪音、桥梁阻尼比和通行车阻尼对识别结果的影响,通过数值模拟验证该方法的有效性,并与工程上经典的随机子空间法和文献方法进行对比.最后,在梁式桥实桥试验进行初步验证,说明本文方法的工程适用性.研究结果表明:所提方法对检测车在桥面上的停靠位置没有具体要求,避免了路面粗糙度对阻尼比识别结果的影响,通行车的阻尼和车速在一定范围内对阻尼比识别无明显影响,并且在信噪比30 dB以上可识别出桥梁一阶阻尼比,具有较好的鲁棒性,操作简单且不需要封桥,可有效促推在实际工程中进行桥梁一阶阻尼比识别.