摘要：
We investigate the transmission properties of super-Gaussian pulses at a moving temporal boundary. The incident spectrum of super-Gaussian pulses, determined by different shape parameters, affects the reflected and transmitted pulse energy and the sidelobes distribution after crossing the temporal boundary. When the incident pulse is an initial unchirped super-Gaussian pulse or a super-Gaussian pulse with a small chirp parameter, the reflected pulse energy increases and the transmitted pulse energy decreases as the incident pulse shape parameter increases. When the incident pulse with a initial chirp and |C| >= 2, the incident pulse spectrum mainlobe energy increases as the shape parameter increases, resulting in reflected pulse energy decreases and transmitted pulse energy increases. This study also discusses the pulse splitting occurs in the anomalous dispersion region. The super-Gaussian pulse sidelobes can theoretically be removed by creating two temporal boundaries.
摘要：
To investigate the vortex-induced vibration (VIV) of a flexible cable in the uniform flow, experiments were conducted using a flexible cable with an external diameter of 80mm and a length of 10.48m in the wind tunnel. The characteristics of multi-modal VIV, time-frequency and traveling wave behavior of the flexible cable were analyzed. Moreover, the effects of twist direction, diameter and the single/double helical wire on the VIV characteristics of the flexible cable were investigated. It is found that the flexible cable experiences single and multi-modal VIVs in uniform flow at different incoming wind speeds, respectively. For the multi-modal VIV of the flexible cable, the vibration over the time history is dominated by two adjacent modal frequencies and shows a phenomenon of beat vibration. The multi-modal VIV responses of the flexible cable show a mix of standing and traveling wave behaviors, in which the effects of standing wave are more pronounced near both ends and the effects of traveling wave are more dominant in the middle region of the flexible cable. The twist direction of the helical wire has little effect on the VIV responses of the flexible cable. The VIV amplitudes of the flexible cable can be reduced by a single helical wire. With the diameter of the helical wire increases, the suppression effects of the single or double helical wire on the VIV of the flexible cable can be improved. Particularly, the double helical wire with diameter 0.10D can effectively suppress the VIV of the flexible cable.
摘要：
This paper proposes a novel concurrent learning -based adaptive boundary observer designed to tackle the joint estimation problem of system states and unknown parameters for a class of hyperbolic partial differential equation systems under the circumstance of unsatisfied persistent excitation conditions. By leveraging concurrent learning technique, an adapted data points selection algorithm is employed concurrently with current data to construct the adaptation law of unknown parameters, which overcomes the limitations imposed by persistent excitation conditions and ensures exponential convergence of estimation errors of unknown parameters under finite excitation conditions. Furthermore, combining the ideas of backstepping and swapping filters on the basis of uncertain estimation, a concurrent learning -based adaptive boundary observer is designed, accompanied by rigorous theoretical analysis and proofs to demonstrate its capability of achieving exponential convergence in estimation. Finally, the corresponding illustrative simulations are given to show the effectiveness of the proposed methodology.
期刊：
International Journal of Microstructure and Materials Properties,2024年17(1):32-48 ISSN：1741-8410
作者机构：
[Hai Long] School of Design and Art, Changsha University of Science and Technology, Changsha, 410114, China;[Shanjun Long] The 23rd Metallurgical Construction Group Co., Ltd. of Minmetals, Changsha, 410116, China
摘要：
To improve the mechanical properties of UV cured 3D printing materials after curing, this paper proposes a study on the mechanical properties of UV cured 3D nanofibre printing materials. The THBP modified nano TiO2 is prepared as a subsequent auxiliary material, epoxy acrylate (EA) as a prepolymer, dipropylene glycol diacrylate (DPGDA) as a monomer, and phenyl bis (lithium phenyl-2,4,6-trimethylbenzoylphosphinate) phosphine oxide as a photoinitiator. A UV curable 3D printing material was prepared by adding THBP modified nano TiO2 in different proportions, and analysing the mechanical properties of the materials prepared. THBP modified nano TiO2 with different proportions of self synthesised THBP was added in order to achieve the research of strengthening and toughening modification and to improve its mechanical properties. The experimental results show that when the content of TEBP-TiO2 is 5 wt%, the tensile strength and impact strength of the samples prepared after UV curing reach the maximum value of 51.3 MPa and 22.1 KJ/m2, respectively. With the gradual increase of the content of THBP-TiO2, the initial decomposition temperature and the maximum decomposition temperature of the materials increase. The residual mass of thermal decomposition is increased and the thermal stability is improved.
作者机构：
[Yonggang Huang] College of Civil Engineering, Hunan City University, Yiyang, China;China Light Industry Changsha Engineering Co., Ltd., Changsha, China;[Guiyao Wang] College of Civil Engineering, Changsha University of Science and Technology, Changsha, China;[Jingliang Fu] China Light Industry Changsha Engineering Co., Ltd., Changsha, China<&wdkj&>College of Civil Engineering, Changsha University of Science and Technology, Changsha, China
通讯机构：
[Yonggang Huang] C;College of Civil Engineering, Hunan City University, Yiyang, China
关键词：
Vetiver root;Root–soil interface;Expansive soil;Pullout test
摘要：
Studying the pullout characteristics of roots can help to gain a deeper understanding of the interaction mechanism between plants and soil, and provide theoretical support and practical guidance for engineering applications. This paper aims to investigate the pulling characteristics of the root–soil interface in expansive soil reinforced by vetiver roots. For this purpose, the study focuses on exploring the correlation between the pullout force (PF) required to extract the roots and the pullout displacement caused by the extraction. The research also examines how the geometry of the roots affects the pulling characteristics of the root–soil using a pullout test. It is found that with increasing root diameter, root length segment (RLS), root volume, and root surface area (RSA), the maximum PF increases. The highest correlation coefficient was found between RSA and maximum PF, which explained 81.4% of the variation in maximum PF. Then, the functional relationship between RLS and PF is established. Using RSA to predict the maximum PF of vetiver root is relatively reasonable. The assessment of PF must consider RSA indicators. The increase in RSA due to a high number of roots results in the improvement of the PF of vetiver root. These findings could assist in enhancing the strength of expansive soils.
摘要：
The media plays an important role in detecting corporate financial fraud. However, little systematic research exists on the impact of media reports on corporate fraud detection; thus, our understanding of the impact is limited. Therefore, we are committed to determining how the configuration of different media report content systematically detects corporate fraud by logistical regression, grounded theory and qualitative comparative analysis (QCA). First, the media reports are classified into three major categories and 35 subclasses to determine their features through fraud triangle theory and grounded theory. Then, based on a dataset of 110 fraudulent listed companies and 110 matched listed companies from 2010 to 2020, three major features comprising 10 subclasses are identified by the logistical regression method. The causal configurations of the features of media reports that detect corporate fraud are explored using the QCA method. The results show that five particular associations can interpret corporate fraud revelation by meeting the equifinality and asymmetric causality principles. Finally, the combined model is proposed. Through 56 fraudulent listed companies and 56 matched listed companies from 2021 to 2022, the combined model is proven to be most effective in detecting corporate fraud. In summary, we offer theoretical contributions to corporate fraud detection and empirical experiences for corporate managers and regulators.
摘要：
[目的]在无信号控制的自动驾驶环境下,自动驾驶车辆的通行轨迹将与过街行人产生大量冲突,如何利用交通控制手段使行人安全通过交叉口,并避免对自动驾驶车辆的通行造成较大的干扰,是亟待解决的关键问题.[方法]本文提出一种基于冲突相位组的自动驾驶交叉口行人过街控制方法,将到达交叉口的车辆流向分为4个冲突相位组,在各相位组内单独分配通行时间,基于冲突相位组对自动驾驶车辆和行人过街的通行时间进行建模;在穿插式通行模式的基础上,使用行人信号灯保障行人过街需求,建立考虑行人二次过街的自动驾驶交叉口交通控制模型.模型以交叉口各流向需求量与实际交通量乘积之和最大为目标,以各流向允许车辆通行的时间比例和行人信号灯状态为决策变量,综合考虑交通流量、行人和车辆通行权等约束,建立混合整数线性规划模型(mixed-integer linear program,MILP),该控制模型可为各流向的车辆和行人分配通行权.[结果]本文模型的车均延误较定时控制方案的降低26.74％,较单次过街模型的降低11.53％,人均延误较定时控制方案的降低51.66％,较单次过街模型的降低36.20％.这表明本文模型能有效提升交叉口的通行效率.[结论]本文模型能根据自动驾驶车辆和行人的通行需求,对交叉口时空通行权进行分配,有效保障行人过街安全.
摘要：
The low carbon footprint and superior properties of geopolymer make it a potentially suitable alternative to ordinary Portland cement, which has been one of the dominating research focuses in the last decades. However, the mechanisms of geopolymeric reactions and the nanostructure of geopolymer are still questionable. Besides, some undesired properties in geopolymer synthesis limit the field application of geopolymers. This paper focused on the current knowledge of the reaction chemistry and nanostructure of geopolymer and factors affecting metakaolin-based geopolymer synthesis. A systematic summary of the reaction process, chemical bonds in geopolymer, and models of geopolymer were provided to better understand the reaction mechanisms of geopolymerization. Various factors important to geopolymer's properties, including Si/Al ratio, Na/Al ratio, type of alkaline activator and alkali cation, water/solid ratio, and curing condition, were comprehensively reviewed to guide the geopolymer synthesis. Through this review, we hope to promote this field's continued growth and development and encourage the wider adoption of geopolymers as a sustainable alternative to traditional construction materials.
摘要：
Magnetic nanoporous materials represent a new emerging category of magnetic materials for construction of magnetic resonance sensors. In this study, we adopted the metal-organic framework materials, MIL-101(Fe), as the precursor to prepare series nanoporous-carbon-Fe(3)O(4) (NPC-Fe(3)O(4)) composites. Results showed that Fe(3)O(4) were uniformly distributed in MIL-101(Fe) and the size of MNP was precisely tuned at different pyrolysis temperatures, conferring the optimal NPC-Fe(3)O(4)-450°C composite with dramatically improved T(2) relaxivity. The NPC-Fe(3)O(4)-450°C composite was modified with antibodies and antigens, respectively, for detection of aflatoxin B(1) in various food samples with complicated matrix. Range from 0.010ngmL(-1) to 2.0ngmL(-1), extreme low detection limit of 5.0pgmL(-1), and satisfied recoveries were successfully achieved, indicating excellent anti-matrix effect. These findings offer a new dimension to engineer novel magnetic materials with improved relaxivity for simple and easy sensing of food hazards in complicated food matrix without any purification or separation procedures.
