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关键词： 分数阶微分包含   Hadamard型   积分边值条件   α-ψ-Ciric多值映射  

摘要： 利用多值映射的不动点定理,给出一类带有积分边值Hadamard型分数阶微分包含解的存在性定理,并将已有的单值结果推广到多值.

关键词： 高考数学   综合考查   恒成立问题   导数问题   单调区间   解析几何   证明不等式   求导公式  

摘要： 整体而言,高考数学全国各卷从难度、深度及广度上逐年加大了对导数问题的考查力度.命题主要分为三个层次:第一层次主要考查求导公式,求导法则与导数的几何意义,往往与解析几何联系.第二层次是导数的简单应用,包括求函数的单调区间、极值、最值等解决生活中的优化问题.第三层次是综合考查,如零点、证明不等式、恒成立问题、求参数等.

关键词： Range management   Prescribed fire   Restoration   Encroachment   Mesquite savanna  

摘要： Rangelands worldwide have experienced significant shifts from grass-dominated to woody-plant dominated states over the past century. In North America, these shifts are largely driven by overgrazing and landscape-scale fire suppression. Such shifts reduce productivity for livestock, can have broad-scale impacts to biodiversity, and are often difficult to reverse. Restoring grass dominance often involves restoring fire as an ecological process. However, many resprouting woody plants persist following disturbance, including fire, by resprouting from protected buds, rendering fire ineffective for reducing resprouting woody plant density. Recent research has shown that extreme fire (high-energy fires during periods of water stress) may reduce resprouting capacity. This previous research did not examine whether high-energy fires alone would be sufficient to cause mortality. We created an experimental framework for assessing the "buds-protection-resources" hypothesis of resprouting persistence under different fire energies. In July-August 2018 we exposed 48 individuals of a dominant resprouting woody plant in the region, honey mesquite (Prosopis glandulosa), to two levels of fire energy (high and low) and root crown exposure (exposed vs unexposed) and evaluated resprouting capacity. We censused basal and epicormic resprouts for two years following treatment. Water stress was moderate for several months leading up to fires but low in subsequent years. Epicormic and basal buds were somewhat protected from low-and high-energy fire. However, epicormic buds were protected in very few mesquites subjected to high-energy fires. High-energy fires decreased survival, caused loss of apical dominance, and left residual dead stems, which may increase chances of mortality from future fires. Basal resprout numbers were reduced by high-energy fires, which may have additional implications for long-term mesquite survival. While the buds, protection, and resources components of resprouter pe

关键词： RF-to-DC power converter   CMOS rectifiers   wide input range   efficiency   energy harvesting   wireless power transfer  

摘要： This paper presents a wide dynamic-range CMOS rectifier with high efficiency and high sensitivity for RF energy harvesting. A new adaptive-biasing scheme is implemented using stacking diodes with dynamic threshold voltage to mitigate the reverse-leakage current of the NMOS rectifying devices at high RF power levels. The proposed design employs the adaptive-biasing technique to control the conduction of the PMOS rectifying devices with self-bulk biasing of the feedback diodes to minimize the leakage current. The proposed novel techniques extend the dynamic range of the RF-to-DC power converter with high efficiency, which is 17 times better than a conventional cross-coupled rectifier. The prototype is implemented using a standard 65 nm CMOS technology and occupies a 0.0093 mm(2) active area. The proposed design achieves a peak power conversion efficiency (peak PCE) of 73%, -18.8 dBm 1-V sensitivity, and a superb dynamic range of 17.3 dB with efficiency greater than 80% of its peak PCE, which outperforms the state-of-the-art RF CMOS rectifiers, when operating at UHF 900 MHz with a 100-K ohm load.

关键词： Computer vision  

摘要： This article presents a method that enables a finite element (FE) model to remesh itself for updating the geometric changes caused by structural damages, using computer vision (CV) techniques and geometric analyses. Currently, there is no mature automatic approach to utilize the information of structural damage detection (SDD) for structural state awareness. Thus, the purpose of this study is to automate the pipeline from the accomplishment of SDD to numerical analyses for fast structural capacity evaluation. CV techniques are used to determine the shapes and dimensions of both structural components and damages. Geometric analyses are used to develop the algorithms for automatically deleting, generating, and splitting the elements of FE models for updating the geometric changes. Experiments are performed on a plate and a C-shaped steel crossbeam of a bridge to demonstrate the effectiveness of the proposed method and algorithms.

关键词： Fractional-Lucas functions   Fractional differential equations   Optimization method   Pseudo-operational matrix of fractional derivative   Modified operational matrix of derivative  

摘要： The paper investigates the numerical solution of the multi-dimensional fractional differential equations by applying fractional-Lucas functions (FLFs) and an optimization method. First, the FLFs and their properties are introduced. Then, according to the pseudo-operational matrix of derivative and modified operational matrix of fractional derivative, we present the framework of numerical technique. Also, for computational technique, we evaluate the upper bound of error. As a result, we expound the proposed scheme by solving several kinds of problems. Our computational results demonstrate that the proposed method is powerful and applicable for nonlinear multi-order fractional differential equations, time-fractional convection-diffusion equations with variable coefficients, and time-space fractional diffusion equations with variable coefficients.

关键词： Free convection   Differentially and equally heated channel   Numerical velocity field reconstruction   Temperature field detection   Infrared imaging   CFD  

摘要： This paper describes a method of reconstructing velocity fields, i.e. a numerical reconstruction procedure (NRP) that involves the numerical processing of experimentally measured temperature distributions in free convection heat transfer. The NRP consists in solving only the continuity and Navier-Stokes equations with an additional source term. This term is proportional to a known temperature (e.g. from a thermal imaging camera) and replaces the Fourier-Kirchhoff equation, which also means that the NRP does not require boundary conditions associated with the temperature to be formulated. In order to verify the NRP, the experimental results of two published cases were taken into consideration. In the first case, the temperature and velocity distributions were determined during free convection heat transfer in a closed cavity, i.e. in a vertical channel formed between differentially heated plates. Subsequently, the velocity distributions obtained by the NRP were compared directly with the experimental results. However, in order to verify the correctness of this method for the entire field, not just for the individual locations, free convection heat transfer measurements in an open channel formed between two isothermal, equally heated plates were considered. A thermal imaging camera was used to detect the temperature field in air. In this case, verification of the NRP method required the results obtained in the form of a reconstructed velocity field to be compared with a field obtained using standard numerical calculations (SNC). Importantly, the NRP provides new opportunities for thermal imaging cameras equipped with a mesh for air temperature detection, for example, the visualisation of air velocity fields in free convective heat transfer. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://***/licenses/by/4.0/ )

关键词： Filtering   Dual band   Passband   Phase shifters   Resonant frequency   Impedance   Topology   Differential phase shifter   dual-band   filtering passband   synthesis design  

摘要： This article proposes the synthesis design method of the dual-band differential phase shifters with independent filtering passbands and predetermined phase shifts. The filtering unit of the proposed phase shifter adopts a simple branch-line structure, which possesses its characteristics of controllable dual-band frequency ratios and bandwidths. Meanwhile, the Schiffman phase alignment element holds the capability of achieving different predetermined phase shifts in dual band. In our design, dual-mode resonator and dual-mode J-inverter models for the filtering units are equivalently established, and the amplitude and phase closed-form formulas for the proposed dual-band phase shifter are further numerically obtained for the first time. This proposed work features new synthesis method, integrated higher order filtering response with two independently prescribed bandwidths, and concurrent predetermined dual-band phase shifts. Design procedures are provided in detail for a quick design. Finally, two dual-band phase shifters with different frequency ratios and phase shifts are designed and demonstrated. The experimental and measured results match well.

关键词： uterine neoplasms  

摘要： Correspondence to Dr Zheng Yuan Ng, Department of Gynaecological Oncology, KK Women's and Children's Hospital, Singapore 229899; ngzhengyuan@*** Inflammatory myofibroblastic tumors of the uterus are uncommon mesenchymal neoplasms with intermediate malignant potential.1 Previously classified under 'inflammatory pseudo-tumors', inflammatory myofibroblastic tumors most commonly involve the lungs and intra-abdominal soft tissue.2 Accurate identification is important given the risk of local recurrence (25%) and distant metastasis (2%).1 Approximately half of inflammatory myofibroblastic tumors harbor rearrangements in the anaplastic lymphoma kinase (ALK) gene on chromosome 2p23.1 ALK is a transmembrane tyrosine kinase which undergoes translocation with various fusion partners, resulting in the 3′ kinase portion of ALK being joined to the 5′ portion of a constitutively expressed gene, forming a fusion oncogene.3 A common breakpoint is intron19, resulting in dissociation of 3′ exons 20–29 from 5′ exons 1–19.4 Previously described fusion partners with ALK include IGFBP5, THBS1, FN1, and TIMP3.2 Unlike soft tissue or pulmonary inflammatory myofibroblastic tumors, ALK is the only receptor tyrosine kinase implicated in uterine inflammatory myofibroblastic tumors to date. There should be a higher index of suspicion for inflammatory myofibroblastic tumors when managing women with fibroids in the younger age group, during pregnancy, or with submucosal/polypoidal location.1 Adverse prognostic factors include delayed diagnosis, incomplete resection, tumor size >7 cm, predominant myxoid pattern, moderate–severe atypia, infiltrative borders, and high mitotic count.2 4 Where possible, morcellation should be avoided or contained in-bag to reduce the likelihood of abdominopelvic recurrence. Accurate diagnosis of inflammatory myofibroblastic tumors may allow targeted therapy with tyrosine kinase inhibitors in cases of recurrence, particularly in young women who want to preserve t