Existence of two periodic solutions of a ratio-dependent Holling-Taner model with infinite delay and prey harvest

This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions for the existence of at least two positive periodic solutions of this model is established.

Existence of Four Periodic Solutions of a Ratio-Dependent Predator-Prey Model with Exploited Terms

We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence degree theory, we establish sufficient conditions for the existence of at least four positive periodic solutions of this model.

PERIODICITY IN A DELAYED SEMI-RATIO-DEPENDENT PREDATOR-PREY SYSTEM

A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of positive periodic solution is studied.A set of easily verifiable sufficient conditions are obtained.

Interaction between collinear periodic cracks in an infinite piezoelectric body

The problem of collinear periodic cracks in an infinite piezoelectric body is studied. Effect of saturation strips at the crack-tips is taken into account. By means of the Stroh formalism and the conformal mapping technique, the general periodic solutions for collinear cracks are obtained. The stress intensity factors and the size of saturation strips are derived analytically, and their dependencies on the ratio of the periodicity on the half-length of the crack are analyzed in detail. Numerical results show the following two facts. （1） When h/l 〉 4.0, the stress intensity factors become almost identical to those of a single crack in an infinite piezoelectric body. This indicates that the interaction between cracks can be ignored in establishing the criterion for the crack initiation in this case. （2） The speed of the saturation strip size of periodic cracks approaching that of a single crack depends on the electric load applied at infinity. In general, a large electric load at infinity is associated with a slow approaching speed.

Stochastic resonance in a time-delayed asymmetric bistable system with mixed periodic signal

This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A general approximate Fokker-Planck equation and the expression of the signal-to-noise ratio are derived through the small time delay approximation at both fundamental harmonics and mixed harmonics. The effects of the additive noise intensity Q, multiplicative noise intensity D, static asymmetry r and delay time T on the signal-to-noise ratio are discussed. It is found that the higher mixed harmonics and the static asymmetry r can restrain stochastic resonance, and the delay time τ can enhance stochastic resonance. Moreover, the longer the delay time τ is, the larger the additive noise intensity Q and the multiplicative noise intensity D are, when the stochastic resonance appears.

Analysis on Predominant Periods Distribution by Microtremor Observations for Seismic Disaster Prevention in Yokohama, Japan Using GIS

In recent years, predictions of damage from earthquakes have been made on a prefectural scale, and expectations exist that more detailed damage forecasts should be made even on a city/town/village scale. It is important to know detailed ground characteristics to do damage prediction on a fine scale. Using GIS is the best way to communicate this planar disaster prevention information to the general public. Yokohama City is the second largest city in Japan and developed as part of the capital region of Metropolitan Tokyo. Recently, the population of this city has reached about 3,000,000, and economic and cultural facilities, social infrastructure, and residential complexes are concentrated in this city. The capital region, including Yokohama City, was attacked by the 1923 Great Kanto Earthquake (M7.9) and Yokohama City was devastated by this earthquake. From the research so far, it is known that the H/V spectrum obtained from microtremor observation has a good correlation with the ground characteristics. The authors have been conducting high-density tremor observations that have been ongoing since the 1990s, mainly in Kanagawa Prefecture, Japan. Here, we have organized the predominant periods obtained from the observation results for Yokohama City. The entirety of Yokohama City was divided into 250 m × 250 m meshes and their centers were used as microtremor observation sites. Excluding sites that could not be used due to geographical conditions, observations were made at approximately 5700 sites. So, we compared the data obtained separately, such as the period, terrain classification, and amplification characteristics. The distribution maps of predominant periods in Yokohama City show that the city contains a lot of artificially transformed land, and consequently, the distribution of predominant periods is not uniform. However, it can be seen that the periods become gradually longer, moving from the higher elevation eastern part toward the lower elevation western part. Investigation of the site amplification factors and detailed topographical classifications indicates a clear correlation with the predominant period distribution.

表面平齐的并联微穿孔板吸声结构特性仿真研究

针对火箭发动机燃气高温高速射流通道内噪声控制的工程需要,提出了一种表面平齐的并联微穿孔板吸声结构设计方案。基于微穿孔板吸声理论,建立了COMSOL微穿孔板吸声结构吸声性能仿真模型,对该类并联微穿孔板吸声结构的吸声特性进行了仿真研究,分析了并联结构的背腔深度比、周期和单体宽度等多种参数对吸声性能的影响。结果表明,通过合理选择微穿孔板参数,以及并联共振腔深度、周期比、单体宽度等参数,可以得到吸声带宽、吸声系数较优的吸声结构,且加工制造与安装维护简单,研究成果可用于高温高速射流通道内的强噪声辐射环境控制。

Analysis on Rules of Investment Decision Based on Payback Period of Dynamic Investment

The index of payback period of dynamic investment is an improvement on index of payback period of static investment, which is the problem that the rules to evaluate the project are feasible or not. This paper proves that rules shall be apt when using payback period of dynamic investment to evaluate the project feasibility under the condition of keeping the dynamic evaluation index to evaluate the same scheme and the consistent feasibility.

The Medieval Warm Period and Little Ice Age in the Daihai Area, North China

Rb/Sr ratio, CaCO\-3 content, organic carbon (C\-\{org\}) concentration, magnetic susceptibility and clay mineralogy of 4.0 m sediments samples recovered from Daihai Lake, northern China, are presented in the paper. Weathering and paleoclimatic change history during the last 2300 years is reconstructed in terms of the variations of Rb/Sr ratios in the sediment sequence, including the Little Ice Age and Medieval Warm Period. Our results suggest that the evolution processes of weathering and paleoclimate can be rebuilt in terms of the variations of Rb/Sr ratios in the lake sediment sequence, in combination with magnetic susceptibility, C\-\{org\}, \{CaCO\-3\} contents and clay mineralogy.

Characteristics of response spectra for long-periods of main-shock recordings of the Chi-Chi earthquake

Current practice uses predictive models to extrapolate long-period response spectra based on far-field recordings in moderate and weak earthquakes. However, the spectra are not long enough and the data are often not reliable, which means that the seismic design code cannot accurately define seismic design requirements for long-period structures. The near-field recordings in the main-shock of the Chi-Chi earthquake have a large signal-to-noise ratio （SNR）, which makes them suitable for studying the long-period acceleration response spectrum up to 20 sec. The acceleration response spectra from 246 stations within 120 km of the causative fault are statistically analyzed in this paper. The influence of distance and site conditions on long-period response spectrum is discussed, and the shapes of the amplification spectra are compared with the standard spectra specified in the seismic design code of China. Finally, suggestions for future revisions to the code are proposed.

中性粒细胞与淋巴细胞比值和嗜酸性粒细胞对AECOPD患者出院后1年内COPD相关再入院的预测价值

目的探究中性粒细胞/淋巴细胞比率(NLR)和嗜酸性粒细胞计数(EOS)对慢性阻塞性肺疾病急性加重期(AECOPD)患者出院后1年内慢性阻塞性肺疾病(COPD)相关再入院的预测价值。方法将2020年12月至2022年6月阜阳市第二人民医院收治的100例AECOPD患者纳入本次回顾性研究,将出院后1年内有≥1次再入院记录的患者纳入再入院组(n=35),其他患者纳入非再入院组(n=65)。比较两组的临床资料(包括一般资料、实验室检查资料、治疗方法和死亡情况)。根据NLR、EOS的预测AECOPD再入院的受试者工作特征(ROC)曲线截断值将患者分组,分别为高NLR组(n=43)和低NLR组(n=57)、低EOS组(n=51)和高EOS组(n=49)。比较各组的住院时间、1年内COPD相关再入院情况和死亡情况,采用Logistic回归分析NLR、EOS预测AECOPD再入院的风险。结果再入院组患者住院时间为(16.68±6.44)d,明显长于非再入院组[(14.02±6.26)d],全身糖皮质激素使用患者比率为28.57%,明显少于非再入院组(53.85%),NLR为8.57±3.16,显著低于非再入院组(13.97±3.79),EOS为(0.25±0.07)×10^(9)/L,显著高于非再入院组[(0.12±0.06)×10^(9)/L],差异均有统计学意义(P<0.05)。低NLR组1年内COPD相关再入院次数和人数占比分别为(1.32±0.34)次、46.51%,均高于高NLR组[(0.83±0.31)次、26.32%],差异均有统计学意义(P<0.05)。高EOS组1年内COPD相关再入院次数和人数占比分别为(1.35±0.40)次、44.90%,均高于低EOS组[(0.81±0.37)次、25.49%],差异均有统计学意义(P<0.05)。Logistic回归分析显示,低NLR(<4.85)与高EOS(≥0.1×10^(9)/L)与1年内COPD相关的再入院风险相关[OR=4.394(95%CI:1.152~8.203);OR=4.699(95%CI:1.152~8.583)]。结论入院时的NLR和EOS可能与AECOPD患者出院后1年内COPD相关再入院有关,可作为预测出院后再住院的生物标志物。

Periodic Modulation of Nonlinearity in a Two-Core Photonic Crystal Fiber: A Numerical Investigation

We present a numerical investigation of the propagation and the switching of ultra-short pulses (100 fs) in a two-core nonlinear coupler of photonic crystal fibers constructed with periodically modulated the non-linearity fiber (PMNL-PFC). Our simulations are taking into account different amplitude and frequency modulations of the PMNL-PFC. A coupler for coupling whose length is Lc = 1.8 cm, the transmission characteristics, the compression factor, the crosstalk (Xtalk) and extinction ratio (Xratio) levels of the first order solitons were studied for low to high pump energies considering 2Lc. By an analysis on the reference channel (channel 2), it is observed that at low modulation frequencies an increase occurs in the switching power increasing transmission efficiency. For high modulation frequencies, the transmitted energy efficiency loses. The switching pulses are stronger for low frequency and high amplitude modulation. The Xtalk is a function of the measurement made on the secondary channel (channel 1). It was observed that this unwanted high-frequency energy increases to lessen the measure of the amplitude modulation. In summary, we have demonstrated that introduction of a non-linearity profile takes the periodically modulated PMNL-PFC to strong variations at transmission efficiency, Xtalk, Xratio a function of frequency and modulation amplitude and the input power.

混播比例及乳酸菌剂对四川农区燕麦/箭筈豌豆混合青贮品质的影响

为解析四川农区冬闲田燕麦/箭筈豌豆的最佳混播比例及混播混贮比例,选取“贝勒”燕麦(Avena sativa L.)和“川北”箭筈豌豆(Vicia sativa L.)为原料,设置1∶0(T1)、3∶1(T2)、1∶1(T3)、1∶3(T4)、0∶1(T5)共5个混播比例,在燕麦开花期/箭筈豌豆结荚前期刈割,青贮时设置不添加乳酸菌剂的对照组(CK)和添加乳酸菌剂组(IN),青贮60 d后分析样品的营养品质、发酵品质并进行微生物计数.研究发现,随着混播中箭筈豌豆占比的增加,混播饲草中粗蛋白和粗灰分含量显著上升(P<0.01),青贮后,CK与IN组饲草中的干物质、中性洗涤纤维和酸性洗涤纤维含量呈下降趋势,粗蛋白和粗灰分含量呈上升趋势.T5(箭筈豌豆单播)处理下CK组和IN组的pH和乳酸菌数量较其它处理显著升高(P<0.01),T1的pH较各比例显著降低(P<0.01),所有组别均未发现肠杆菌和霉菌存在.相同混播比例下,IN组比CK组有更低的干物质损失、pH、氨态氮和有机酸含量及乳酸菌数量(P<0.01),IN组比CK组有更高的可溶性碳水化合物含量(P<0.01).综上,在燕麦和箭筈豌豆混播比例为1∶3时原料营养品质及青贮发酵品质更为优质、均衡.

基于结构等效周期选择和谱匹配地震动记录对RC框架结构地震易损性分析的影响

选择合适的地震动记录和地震动强度指标是结构地震易损性分析的基础。首先,分别以加速度反应谱S_(a)(T_(1))值和S_(a)(T_(eq))值为强度指标选取两组地震动记录各20条,并运用谱匹配方法对其进行基于目标设计谱的匹配;其次,输入匹配前后4组地震动记录分别对一个5层和一个11层钢筋混凝土(RC)框架结构模型进行增量动力分析,进而分析谱匹配方法以及不同强度指标对最大层间位移角、结构地震易损性、最大残余层间位移角和抗倒塌储备系数的影响。分析结果表明:输入谱匹配后的两组地震动记录,结构地震易损性结果的离散性明显降低且各损伤状态下50%超越概率对应的谱加速度S_(a)(T_(1),5%)和S_(a)(T_(eq),5%)未发生明显偏差;随着结构损伤程度的增大,以S_(a)(T_(eq))为强度指标可以更有效地减小易损性分析结果的离散性;以抗倒塌储备系数为参考指标,S_(a)(T_(1),5%)作为强度指标进行地震动记录的选取有可能高估结构抗倒塌能力,应考虑以S_(a)(T_(eq),5%)为强度指标更优。

短周期线性密集台阵揭示的粤东地区地壳结构特征

利用跨江西省、广东省、福建省布设的225个短周期密集台阵观测时长为58d的远震波形数据,采用P波接收函数H-κ扫描叠加和共转换点(CCP)叠加两种方法,对研究区下方地壳厚度、泊松比分布和接收函数成像进行研究。结果表明:1)研究区地壳厚度和泊松比具有明显的分块性,并与断裂分布有关,地壳厚度变化总体上表现为由西北向东南由薄变厚再逐渐减薄的趋势,变化范围为27.1~33.9km,平均地壳厚度为29.9km,且地壳厚度变化与地表起伏符合地壳均衡理论。2)研究区泊松比变化范围为0.21~0.33,平均泊松比为0.26,整条测线泊松比大于0.25的部分占比70.83%,属于高泊松比区域,原因可能为研究区多发育断裂破碎带,俯冲板块物质的深部熔融导致地幔物质沿断裂部分上涌,使得地壳中石英含量减少。3)研究区在距地表10~15km范围内存在一个较为连续的负极性界面,结合前人研究,将其解释为华夏地块东部广泛存在的低速层顶部界面,在距地表15~20km范围内存在地壳低速体,发育位置偏向内陆方向。

调制周期与调制比对Cu/Nb纳米多层膜结构和性能的影响

为研究调制周期λ和调制比η对Cu/Nb纳米多层膜结构和性能的影响,用磁控溅射沉积Cu/Nb多层膜,λ=30~150 nm,η=1、1.5及2。多层膜微观结构与形貌用X射线衍射仪、扫描电镜及原子力显微镜分析,性能用微力拉伸仪、纳米压痕仪及四探针仪测试。结果表明,Cu/Nb多层膜的结构和性能受控于λ和η。Cu和Nb层分别呈Cu(111)和Nb(110)织构,且均为纳米晶结构。在Cu/Nb界面处,Cu扩散进入Nb层。表面Cu层颗粒尺寸随Cu层增厚而增大。随λ或η减小,Cu/Nb多层膜的屈服强度σ_(0.2)、显微硬度H和电阻率ρ都呈增加趋势。而裂纹萌生临界应变ε_(c)则与1/λ或η呈正相关。

考虑时间效应的钢渣填料动力特性与微观结构研究

钢渣是冶金行业的第二大废弃物,充分利用废弃钢渣代替部分砂石料作为新型的土工填料,符合“绿色经济”与“可持续发展”战略。因钢渣材料有别于砂石料,化学成分复杂,而力学特征具有时效特性,采用共振柱试验研究考虑水化期影响的钢渣动力特性,分析动剪切模量和阻尼比等动力特性变化规律;基于Hardin-Drnevich双曲线模型描述考虑时间效应的钢渣动力特性,采用Boltzman函数描述最大动剪切模量随水化期变化的关系,给出最大阻尼比范围;并与传统砂土的动力特性对比,得出水化前钢渣动剪切模量略高于传统细砂,水化90 d后可达到标准砂的最大动剪切模量,工程中可以用钢渣作为一种填料代替砂土。最后,通过微观电子显微镜方法分析不同水化期下的钢渣微观结构,发现水化产物Aft相较于其他水化产物生成时间较晚,Aft和C-S-H所组成的胶凝结构是影响钢渣动力特性时效特征的主要因素。

大湾煤矿初始拉沟位置的选择

为了实现大湾煤矿工程建设合理发展,尽快投入生产,提高经济效益,提出了2个初始拉沟位置的方案,并分析了矿建工程量、矿建投资、均衡剥采比等指标对不同方案的影响。结果表明:方案1在采场北部露头沿煤层走向拉沟,倾向推进,矿建工程量较小,矿建投资较小,均衡剥采比均衡期较长,但均衡剥采比较大;方案2从采场西部沿煤层倾向拉沟,走向推进,矿建工程量较大,矿建投资较大,均衡剥采比均衡期短,一期均衡剥采比较大,二期均衡剥采比较小;若扩大方案1矿建工程量,可降低均衡剥采比,但会增加投资。综合分析2种方案,最终确定方案1且不增加矿建工程量为较为合适的拉钩位置方案。

斜率与变统计周期微细电火花脉冲识别系统

针对电压阈值法不能很好统计开路时长和改变放电电压时需要调节电压阈值等问题。提出一种基于斜率比值和变统计周期的脉冲识别方法,该方法使检测装置直接用于微细电火花粗磨、精磨两种不同开路电压的加工情形中,不需要调节电压阈值且能有效的统计开路时长,从而提高检测效率和精度。首先使用NI采集卡和LabVIEW软件开发脉冲识别系统,该系统可对间隙电压进行显示、连续存储以及对文件进行拆分,接着对斜率比值法和变统计周期法进行理论分析并编写脉冲识别与统计程序,最后进行放电状态检测的实验验证。结果表明:该方法能够识别不同脉冲且适用于不同放电电压情形,程序结果与实际结果较吻合,证明了该方法的有效性和实用性。

不同品种百香果果实转色期糖酸品质性状评价

【目的】研究黄果百香果和紫果百香果等主栽品种和自育品种果实转色过程中糖酸组分的动态变化,对培育优质品种、优质果品生产、果实的适时采收具有重要意义。【方法】以钦蜜、壮乡蜜宝、中百6号、黄香1号、台农、满天星等品种为供试材料,按果实转色的5个主要时期进行取样。并对糖酸组分含量进行相关性分析。【结果】随着果实转色成熟,百香果果肉可溶性固形物含量呈先升高后降低的趋势,壮乡蜜宝、中百6号、黄香1号、台农和满天星的可滴定酸含量呈逐渐降低的趋势。除钦蜜的固酸比随着果实转色逐渐增大外,其余品种的固酸比均呈先上升后下降的趋势。在百香果果实转色过程中蔗糖含量均呈先上升后下降的趋势,柠檬酸含量变化均随着果实转色呈现出逐渐下降的趋势。不同百香果品种成熟期的糖酸组分均呈现出显著差异,其中中百6号果实中的果糖和葡萄糖含量显著高于其他品种。6个百香果品种的果实中酸组分以柠檬酸为主,占比达到68.27%~84.22%,其中台农果实中的柠檬酸、总酸和可滴定酸含量高于其他品种。固酸比分析结果表明,黄果百香果的固酸比高于紫果,固酸比从高到低依次为钦蜜>壮乡蜜宝>黄香1号>中百6号>台农>满天星。【结论】百香果不同品种的糖酸组分比例在果实不同发育期中存在差异。紫果百香果和黄果百香果均属于柠檬酸优势型。转色期T2~T4是百香果果实品质变化的关键时期。随着果实成熟均出现退糖现象,且黄果百香果的固酸比大于紫果。果实完全成熟时,钦蜜果实中的固酸比显著高于其他品种。百香果果实固酸比主要受柠檬酸含量的影响,且成反比。