The treatment and resource utilization of sludge from municipal sewage treatment plants is an important environmental issue. Cement kiln co-processing offers a promising solution, but challenges remain, particularly regarding sludge properties and feasibility in kiln systems. This study analyzes the characteristics of three pretreated sludges: mechanically dewatered sludge, deeply dewatered sludge, and lime-dried sludge. Using techniques such as thermogravimetric analysis (TGA) and X-ray diffraction (XRD), this study investigates their calorific values and raw material utilizability in co-processing. As the sludge moisture content decreases from interstitial to bound water, energy consumption per ton of evaporated water rises, particularly below 30%. At 10 °C/min heating, energy consumption for mechanically dewatered sludge at 80%, 30%, and 10% moisture was 3573, 8220, and 34,751 kJ/kg, respectively; for deeply dewatered sludge at 60%, 30%, and 10%, the values were 4398, 7550, and 11,504 kJ/kg. Keeping moisture content above 30% before kiln entry reduces energy use and enhances calorific value. Sludge utilizability as a raw material depends on its pretreatment. The ash composition of deeply and mechanically dewatered sludge resembles iron-rich raw materials, while lime-dried sludge aligns more with limestone. The utilizable ash content was 23.3%, 8.1%, and 46.3%, respectively, with lime-dried sludge showing the highest potential. This study provides insights into sludge properties and their co-processing potential in cement kilns, offering scientific and technical support for practical applications.

This letter analyzes the spectral and energy efficiency of an intelligent reflecting surface (IRS)-assisted the dual unmanned aerial vehicles (UAVs) in target detection with hardware support, where devices first harvest energy from a power station (PS) in the downlink (DL) and then transmit information to a data sink in the uplink (UL). However, in order to increase the spectral efficiency, most existing works on dual UAVs adopted the simplified linear energyharvesting methodology and also cannot guarantee the detection performance. To improve system property, we optimize the beamforming coefficients on the basis of improved semidefinite relaxation (SDR) to minimize the total transmit power subject to the signal-to-noise (SNR) of the receiving antenna reaches the standard. Moreover, we analyze the energy saving effect of optimized system. The simulation results show that with the increased number of elements in the IRS, the proposed method has better detection probability and higher energy efficiency.

结合大数据交叉学科背景下的复合型工科人才培养需求,提出结合学生的专业研究领域,采用层层递进的原则进行实验案例设计,以智能制造领域为例,介绍机器学习课程的实验方案、实验内容、教学方案、评价方案设计等.

Proper management of sewage sludge has become a pressing environmental issue in China in recent years. As an eco-friendly disposal method, co-processing sludge in cement kilns has attracted widespread attention. In this paper, NOx concentration changes in a cement kiln simulation with sewage sludge additions were analyzed experimentally under different temperature and oxygen content levels, and the reaction was studied by FTIR and gas chromatography-mass spectrometry (GC/MS). The most significant reduction of NOx emission was achieved at 900 degrees C and 3% oxygen content level, with an average reduction of 61.1 mg of NOx per gram of dry sludge and the peak point of NOx emission reduction was at 180 degrees C, 300 degrees C, 375 degrees C and 430 degrees C. The NOx reduction was mainly attributed to the conversion of NOx to N-2 under a certain temperature range by the reducing substances released via the decomposition of free ammonia and protein in sludge. In order to achieve the best conditions for NOx emission reduction, sludge was added to the precalciner in the production test, resulting in an average NOx concentration reduction of 67 mg/m(3) than that without addition of sewage sludge. The study analyzed synergistic treatment sludge reduction effect on NOx emission reduction through multiple experiments. These results provide a guide for the optimal conditions for reducing NOx emissions during the co-processing of sewage sludge in cement kilns.

The double-beam system with a viscoelastic layer is a classical mechanical model for many beam-type composite structures. However, few studies have been able to optimize the structure from the perspective of structural damping characteristics. To fully understand the damping characteristics of the viscoelastic double-beam system, an analysis method based on dynamic stiffness method and Wittrick-Williams algorithm is presented in this paper. Through numerical case studies, five typical parameters of the viscoelastic double-beam system are discussed to investigate their influence on the damping characteristic of the system. Finally, the conclusions are used to parametric analysis for a kind of double-sheathing cable systems. Results show that the damping coefficient of the connection layer have a significant effect on the damping characteristic of the double-sheathing cable system compared with other design parameters. The proposed methods and conclusions obtained in this paper are helpful to design and optimize the structural parameters of engineering structures, thus having certain application and promotional value. (C) 2019 Elsevier Inc. All rights reserved.

With the increase of the span and height of modern engineering structures, the design length and complexity of the cable structure are constantly increasing, whose dynamic problem has become the key to structural design, performance monitoring and maintenance, and vibration control. Therefore, it is necessary to study and develop a unified dynamic analysis theory for complex cable system to meet the requirements of calculation accuracy and efficiency. In view of this, a unified dynamic analysis method for dynamic analysis of complex cable system is proposed in this paper on the basis of the classical dynamic stiffness method. In this paper, the dynamic stiffness method has been enhanced in multiple aspects, which not only retains the advantages of high computational efficiency and wide application range but also overcomes its technical bottlenecks in analysis of shallow-sag cable system considering the damping effect, composite cable systems, and multisegment cable systems. The proposed method can not only be used to the structural design of the complex cable system but also be extended to the vibration control of the system during the service period.

The invention provides a bridge live load optimization and identification system based on multi-source redundant information. The system is characterized in that the system comprises a number of dynamic strain gauges with different numbers for collecting dynamic strain data of a bridge structure, at least one bridge traffic monitoring device used for generating a vehicle monitoring video, and a calculating processing device used for performing calculation to acquire a live load of a bridge. The calculation processing device comprises a dynamic strain processing unit which processes the dynamicstrain data of the bridge structure to acquire the peak of a static component thereof, a video vehicle identification unit which identifies the vehicle monitoring video to acquire position information, a vehicle coordinate conversion unit which converts the position information to acquire the actual position coordinate of a vehicle, a vehicle weight calculation unit which calculates the weight ofthe vehicle according to the peak of the static component, the actual position coordinates and the impact surface of the bridge, and a vehicle weight statistics checking unit which is used to performstatistics on the vehicle weight so as to check the vehicle weight as the live load of the bridge.

As an important composite beam structure, the double-beam system with a viscoelastic connection layer has a wide range of applications in engineering. Accurate analysis of its dynamic characteristics is an imperative requirement for the design, monitoring and evaluation, or vibration control of these structures. Existing researches usually introduce some simplifications or assumptions, and ignore the damping characteristics of the structure in most cases, which results in inaccurate dynamic analysis results of such double-beam structures and cannot meet the actual requirements. For this reason, a generalized mechanical model that can consider the damping factor is established in this paper to accurately simulate the double-beam system with a viscoelastic connection layer, and its dynamic characteristics are accurately analyzed by dynamic stiffness method. On this basis, the effects of structural parameters on the modal frequencies and mode shapes of the system are studied. The results show that the stiffness of the connection layer has little effect on the system mode; the modal frequencies of the double-beam system can be reduced by increasing the mass or damping coefficient of the connection layer, where the influence of damping on the low-order modes of the system is very significant, but its effect on the higher-order modes are clearly inferior to that of mass.

Due to the difficulty of establishing fixed reference points, it is difficult to monitor displacement of a civil engineering structure in the field for long term. Although to integrate acceleration signals numerically is a common and low-cost displacement measurement method, the schemes proposed in the field of seismology are not suitable for long-term structural monitoring environment because of batch calculations of existing algorithms. In this paper, combining a baseline correction technique based on recursive least squares, a recursive high-pass filter and a recursive integrator, through multi-round baseline correction, filtering and integration, the authors develop an online and real-time acceleration integral scheme. This scheme is then applied to a numerical simulation case and a shaking table test, where the accuracy and reliability are proved. Finally, the applicability of the scheme in real monitoring environment is confirmed through utilizing it to monitor displacement of a real bridge. (C) 2019 Published by Elsevier Ltd.

In this study, the dynamic characteristic of an inclined and tensioned double-beam system is investigated. The double-beam system consists of two elastic beams, which are quite different in mass and stiffness, and are continuously connected by a layer of elastic springs. The beam with larger stiffness and mass is under a tensile axial loading. The oscillatory differential equations of this double-beam system are established by considering the effects of sag, flexural rigidity, boundary conditions, inclined angle of real inclined beams, and other factors simultaneously. Based on the governing equations, the element transverse dynamic stiffness matrix and global transverse dynamic stiffness matrix are derived to obtain the dynamic equilibrium equation of the system in a dynamic stiffness form. Using this, the system is simplified into a four degree-of-freedom simple oscillatory system and consequently the theoretical frequency characteristic equation is proposed for this double beam system. A numerical equation rooting approach is developed to solve the dynamical properties of the proposed equation. With the numerical case studies, the dynamic characteristics and its variation laws of a double-beam system are investigated. It shows that the proposed semi theoretical semi numerical methods can give an accurate solution for the double beam system, and rules revealed in this study are help for comprehending the dynamical behavior of double beam like engineering structures theoretically.

As the commonly found double-beam structures in engineering have a distributed spring connection layer, the dynamic stiffness method is employed to establish the exact dynamic stiffness matrix and frequency equation. The complex transcendental frequency equation of the double-beam structure considered herein is solved by an improved Wittrick–Williams algorithm, resulting in an accurate analysis of its dynamic characteristics. Based on this, the effect of various parameters on its dynamic characteristics is investigated. The results indicate that owing to the impact of the spring connection layer, structural parameters, boundary conditions, and other factors, the periodicity of the modal frequencies of the double-beam is disrupted; consequently, the values of two adjacent frequencies are very close or even equal. In addition, the modal shapes of the double-beam are also affected by the above factors. The influencing law is complex and varies with different orders. However, for a single-beam structure, a reverse modal shape may form at some orders of the modes of the double-beam structures.

The fluctuating wind power spectrum (FWPS) in given specifications could only represent the second-order probabilistic characteristic, which indicates that it is not capable of fully expressing the stochastic wind field. Estimation and modeling of the fluctuating wind amplitude spectrum (FWAS) as well as the fluctuating wind phase spectrum (FWPhS) by using measured wind velocity data can make up for the deficiencies mentioned above. A high-resolution nonparametric spectral estimation algorithm—amplitude and phase estimation (APES)—is used to estimate the FWAS and the FWPhS, using the field measured wind velocity data of a certain cable-stayed bridge in Shanghai, China. An empirical expression (eFWAS) is introduced by dimensional analysis to model the random FWAS, and its specific Davenport form is proposed according to field measured data. The parameters of the Davenport eFWAS model are estimated by using the above measured FWAS, and three specific applications of this model are put forward when different known conditions are met. Compared with the measured FWAS, the stochastic Davenport eFWAS model proposed in this paper can accurately describe the statistical properties of the local wind field and improve the modeling accuracy of the FWAS, which is important in antiwind structural design and safety assessment.

With the help of the dynamic stiffness method, the problem of dynamic characteristics analysis of an engineering structure can be transformed into the problem of solving the transcendental frequency equation. The Wittrick-Williams algorithm can provide the upper and lower bounds of any given modal frequency, so that the numerical solution of the equation can be obtained. However, for a complex beam-like structure, the method is no longer suitable because it is difficult to determine the corresponding the clamped-clamped frequency. For this reason, this paper proposes an improved Wittrick-Williams algorithm—hypothetical structure method, which calculates the clamped-clamped frequency count of the original structure indirectly through the “hypothetical structure” so that the dynamic characteristics analysis problem of the complex beam-like structure can be solved. Two typical beam structure examples and a complex double beam-like structure example are used to verify the accuracy and effectiveness of the proposed method.

The dynamic stiffness method is an exact method for structural dynamic analysis. By separating the variable of the displacement function in frequency domain, the dynamic stiffness matrix and frequency equation of the structure are obtained, and the structural dynamic analysis can then be achieved by solving the transcendental frequency equation. For undamped systems, the frequency equation can be accurately solved by the Wittrick-Williams algorithm, however, the frequency equation of damped structures is a complex transcendental equation and many root-search techniques performing well in real field including the Wittrick-Williams algorithm are no longer applicable. Therefore, the application of dynamic stiffness in damped structures is a major challenge and has not been well resolved. In view of this, aiming at the classically damped system in the project, this paper has improved the dynamic stiffness method from two aspects, (1) The calculation principle. By performing the variable separation in Laplace domain instead of frequency domain, this paper established the relationship between damped frequency and undamped frequency by a proposed method for the calculation of the damping ratio, thus avoiding the solution of the hard-to-solve complex transcendental frequency equation; (2) The solution method. To make the method widely applicable, an improved Wittrick-Williams algorithm is given in this paper to solve the frequency equation of complicated systems. Finally, numerical examples are used to verify the accuracy and universality of the proposed method. (C) 2018 Elsevier Ltd. All rights reserved.

In order to express outlet deviation angle of turbomachine stator, outlet deviation angle dominantly expressed by fluid velocity distribution was derived based on equivalent moment of momentum under the condition of certain CFD simulation design parameters. On this basis, response surface function of outlet deviation angle was constructed by CFD simulation data of orthogonal experiment. The validity of the response surface function was proved by CFD simulation data of confirmatory models. An effective method is provided for calculating outlet deviation angle of turbomachine stator.

This paper uses the calibration method of the equal strength beam,selects the relevant parameters,and designs a small strain calibrating equipment,which is used to calibrate the small strain of 0.1με level.The feasibility of this method is verified preliminarily by mechanics of materials.Taking some other factors that can't be solved by mechanics of materials into consideration,we also employ the finite element method to analyze the effects of these factors to the calibrating accuracy,and mention the corresponding modifying methods to make the calibration result meet the expectant accuracy.

Introduced herein is a new structural damping identification approach based on a two-dimensional (2D) amplitude and phase estimation (APES) method. The original APES method is suitable for application to an undamped and complex harmonic vibration signal. Hence, it has to be modified for application to real damped vibration signals such as the vibration test signals in engineering structures. This modified approach will be named as dr_APES. It can transform one-dimensional (1D) signals in time domain into their corresponding signals in the 2D domain of frequency and damping factor. By applying this dr_APES approach, the three-dimensional (3D) amplitude spectrum, with peaks corresponding to the vibration modes, can be obtained for any given vibration signals. By accurately locating the coordinates of the peaks, modal frequencies and damping factors can be identified. Owing to the high-resolution of the location of 2D ordinates of the spectral line and the value of spectrum, the accurate location of peaks can be estimated, and therefore, the modal frequencies and damping factor can be accurately determined. This is demonstrated by a numerical case study. Moreover, by applying the proposed approach to a real onsite dynamic test on two cables in a cable-stayed bridge, the inherent damping of the two cables was identified accurately, thereby verifying the ability of proposed damping identification approach in meeting the requirement of weak damping characteristics identification in flexible structures such as naked cables.

In this paper, the motion differential equations of the bi-directional functionally graded Timoshenko beam are established using Hamilton’s principle. The material properties of the beam change exponentially in both axial and thickness directions. Using the variable substitution method, state space differential equations of the structure are established. First, the dynamic stiffness matrix is formed using the traditional method. Then, the author proposes a new method to directly form an exact dynamic stiffness matrix by using state space differential equations, and this method is compared with the traditional dynamic stiffness matrix method. At the same time, the natural frequency of the structure is computed by combining the Wittrick–William algorithm with a non-iterative algorithm. The influence of gradient parameters α,β on the fundamental frequency, mode shape and frequency response function is analysed through the establishment of the dynamic stiffness matrix of the overall structure. Finally, using the Lagrange equation and the method of modal superposition, structural dynamic differential equations under a harmonic moving load are derived. Using the precise integration method, the dynamic response of the displacement is computed and the influence of gradient parameters α,β on the dynamic response is analysed.

对多点激励下的振型方程进行了推导,简化成类似于一致激励下的振型方程形式,导出多点激励下的振型参与系数和振型等效地震波,从而可由反应谱判断多点激励对结构振动的影响.以一座试设计的主跨1 400 m斜拉桥为例,采用振型分析法分析了考虑行波效应的超大跨斜拉桥振动机理.通过拟静力法分析了行波效应引起的各支承点地震动位移的差异对超大跨斜拉桥结构变形的影响,同时,利用位移输入法,对超大跨斜拉桥进行了地震时程分析,研究了行波效应对超大跨斜拉桥顺桥向耗能体系地震损伤的影响.研究结果表明:行波效应减小了耗能辅助墩的耗能作用,增大了桥塔的地震损伤,对超大跨斜拉桥顺桥向耗能体系地震反应的影响是不利的.视波速为1 000～3 000 m·s-1范围内的长周期地震动作用下行波效应的影响尤为显著,因此在超大跨斜拉桥地震反应分析时必须考虑.