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Under unsteady operating conditions in turbomachinery, the performance is unable to respond rapidly enough to follow characteristic curves for the steady condition. To design a reliable turbomachinery under unexpected unsteady conditions, we evaluated the dynamic transfer matrix of a three-dimensional centrifugal impeller. The working fluid is incompressible air. To make the current results more applicable in a broader sense such as pumps, all parameters and results were normalized. The experimental results showed a more significant negative slope in the unsteady performance curve compared to that in the steady performance curve. This was mainly caused by the phase delay of the pressure rise to the pulsating flowrate. We clarified the changes in gain and phase delay under unsteady conditions by conducting numerical simulations. The numerical results showed that the unsteady pressure rise was primarily generated by inertia and power terms in the unsteady energy conservation equation. The power term was predominantly influenced by the angular momentum flowrate difference and the change rate of angular momentum. Each term was quantitatively evaluated, and its contribution to the unsteady pressure rise was discussed. Within the range of frequencies tested in this study, the transfer matrix for the three-dimensional centrifugal impeller could be effectively approximated through a first-order lag approximation considering a series-connected derivative system. We believe that our findings can be extended to centrifugal pumps when disregarding the compressibility effects such as cavitation. [ABSTRACT FROM AUTHOR]

In China, the Grain for Green Program (GGP) is an ambitious project to convert croplands into natural vegetation, but exactly how changes in vegetation translate into changes in soil organic carbon remains less clear. Here we conducted a meta‐analysis using 734 observations to explore the effects of land recovery on soil organic carbon and nutrients in four provinces in Southwest China. Following GGP, the soil organic carbon content (SOCc) and soil organic carbon stock (SOCs) increased by 33.73% and 22.39%, respectively, compared with the surrounding croplands. Similarly, soil nitrogen increased, while phosphorus decreased. Outcomes were heterogeneous, but depended on variations in soil and environmental characteristics. Both the regional land use and cover change indicated by the landscape type transfer matrix and net primary production from 2000 to 2020 further confirmed that the GGP promoted the forest area and regional mean net primary production. Our findings suggest that the GGP could enhance soil and vegetation carbon sequestration in Southwest China and help to develop a carbon‐neutral strategy. [ABSTRACT FROM AUTHOR]

As an affordable form of public transit, the metro still faces first- and last-mile problems. Integration of dockless bike sharing (DBS) and the metro offers a reasonable solution to this problem. However, an in-depth exploration of the spatio-temporal characteristics and determinants of DBS–metro integration, especially meteorological indicators, is lacking. The spatiotemporal characteristics of the transfer volume on weekdays and weekends in Beijing were analyzed. Geographically weighted regression was utilized to investigate the effects of the significant determinants on the spatial variation of the transfer volume. The results indicate that the transfer volume is concentrated within the Fifth Ring Road in Beijing. The effects of education services and metro station density were negatively correlated with transfer volume. As expected, population density and enterprises positively affect transfer volume, whereas wind speed and relative humidity have negative effects. These findings provide new insights into the promotion of DBS–metro integration. [ABSTRACT FROM AUTHOR]

Knowledge of flame responses to acoustic perturbations is of utmost importance to predict thermoacoustic instabilities in gas turbine combustors. However, measuring transfer functions linking acoustic quantities upstream and downstream of flames are very challenging in practical systems and these measurements can significantly deviate from state-of-the-art models. Moreover, there is a lack of studies investigating the effect of hydrogen enrichment on the response of natural gas (NG) flames. In this work, measurements of flame transfer matrices (FTMs) of turbulent H2/NG flames in an atmospheric combustor featuring an axial swirler burner have been performed, allowing us to unravel the transition between FTM in fully premixed (FP) and in technically premixed (TP) conditions. Furthermore, imaging of OH* chemiluminescence and OH-planar laser induced fluorescence are obtained for characterizing the topology of the flame for varying H2 fraction and mixing conditions. Transfer matrices are measured using the multimicrophone method for H2 fractions ranging from 12% to 43% in power. Afterward, the flame transfer functions (FTFs), which linearly relate the coherent fluctuations of the heat release rate to the acoustic velocity oscillations, are obtained from the FTM by using the Rankine-Hugoniot jump conditions across the flame. Using the OH* chemiluminescence intensity as a surrogate for the heat release rate, the FTF based on this optical measurement is also extracted and compared to the one exclusively obtained with the multimicrophone method. As expected, the two different methods are in very good agreement for the FP case and significantly differ for the TP case. Indeed, chemiluminescence fluctuations cannot be directly linked to heat release rate fluctuations when the acoustic forcing induces equivalence ratio fluctuations at the flame, making the optical method unusable for TP configurations. We also show that the two methods agree in the high end of the explored excitation frequency range and we provide an explanation to this intriguing finding. Moreover, we investigate the sensitivity of the FTM measurement to the estimate of the speed of sound in the rig in FP conditions. Finally, the measured FTFs are fitted with FTF models based on multiple distributed time delays. This allows us to explain the frequency dependence and the hydrogen fraction dependence of the gain and the phase in FP and TP conditions. [ABSTRACT FROM AUTHOR]

Acoustic metamaterial attains uncommon material properties over natural material such as negative effective mass density, negative effective bulk modulus, or both. To start with, the present research demonstrates and establishes robust method to estimate and measure acoustic metamaterial properties of a Helmholtz resonator analytically using transfer matrix (TM) method and experimentally in detail. The proposed method extracts the reflection and transmission coefficients from corresponding TM to evaluate the effective acoustic metamaterial properties. For a single Helmholtz resonator, the effective bulk modulus has been observed negative; however, the effective density remains positive. In order to attain double negative material properties, the perforated panel (PP) and microperforated panel (MPP) have been introduced in parallel to resonator. The 1D electro-acoustic modeling has been carried out for all configurations to estimate effective properties analytically. Successively, the experiments have been conducted to measure the effective properties from acoustic metamaterial prospective. The analytical and experimental investigations on five different cases reveal that one can attain negative effective compressibility and effective density by cascading two PPs or MPPs with a finite duct. Moreover, by backing a Helmholtz resonator from both sides with two PPs or MPPs in parallel, one can attain double negative properties comparatively higher than earlier configuration in low-frequency zone in broadband. In total, eight different configurations have been investigated analytically and experimentally, where it has been demonstrated that the proposed compact model is more effective than a finite array of same Helmholtz resonators. [ABSTRACT FROM AUTHOR]

The paper elaborates the principally new variant of finite element method in application to plate problem. It differs from classical FEM approach by, at least, three points. First, it uses the strong differential formulation rather than the weak one and suppose the approximate analytical solution of all differential equations. Second, it explicitly uses all geometrical and physical parameters in the procedure of solution, rather than some chosen ones, for example, displacement and angles of rotation as usually done in FEM formulation. Third, the conjugation between adjacent elements occurs between the adjacent sections rather than in polygon vertexes. These conditions require the continuity of displacements, angles, moments and forces. Each side of rectangular elements is characterized by 6 main parameters, so, at whole there are 24 parameters for each rectangular element. The right and upper sides’ parameters are considered as output ones, and they are related with lower and left sides ones by matrix equations, which allows to apply transfer matrix method for the compilation of the resulting system of equations for the whole plate. The numerical examples for the thin-walled and Mindlin plates show the high efficiency and accuracy of the method. [ABSTRACT FROM AUTHOR]

Transmission loss is a very important acoustic characteristic of the muffler. In order to improve the efficiency of the double-load method for measuring the transmission loss of themuffler, this paper proposes a single-step measurement method for transmission loss of muffler. In addition, the simulationmodel of the single-step measurement method is established based on the finite element acoustic analysis. For the model, the calculation method of the transmission loss of the muffler is deduced from the theoretical knowledge of the transfermatrix. In the simulation, the sound pressure data of six positions in the model are obtained, and the transfer matrix is used to calculate the transmission loss of the muffler. Then, two simulation comparison experimentswere done. In order to verify the validity of the single-step measurement method, the first comparison experiment was to compare the transmission loss of themuffler simulated by the single-stepmeasurement method with their theoretical transmission loss in the finite element acoustic analysis. The results of the simulation validation test cases showed that the transmission loss of the muffler obtained by the single-step measurementmethodwas consistent with the theoretical value. The second comparison experiment was to compare the transmission loss obtained by the singlestep measurement method with the transmission loss obtained by the double-load method. The results of the simulation validation test cases showed that at certain frequencies, the transmission loss obtained by the single-step measurement method was more accurate than the transmission loss obtained by the double-load method. In conclusion, the single-step measurement method proposed in this paper can accurately obtain the transmission loss of the muffler with only one measurement, which improves themeasurement efficiency. [ABSTRACT FROM AUTHOR]

Sharp wave treatment for 1-D gas dynamic problem is still a challenge for modern numerical methods. They often require too many space and time steps, produce spurious oscillation of solution, exhibit a strong numerical dissipation or divergence of results. This paper is further extension of authors’ idea of employment the analytical solution for space coordinate, where time step is a parameter which used in the space solution. Its peculiarity consists in development of additional linearization procedure of dependence between the pressure and density. It is performed in premise that actual pressure for each space element is close to the basic pressure, attained at previous moment of time. The efficiency of method is tested on the very popular task of Sod, where two different ideal gases in a tube are separated by diaphragm, which is suddenly broken. The problem considered in Lagrangian coordinates formulation. The results obtained show the very good method efficiency, which requires the essentially lesser time and space steps, leads to no spurious oscillation and give consistent and predictable results with respect to meshing. The accuracy of method is mostly controlled by time step, which should be larger than clearly stated theoretical lower limit. Other advantage of method is that it can calculate the process to any desired time moment, and space meshing can be variable in time and space and can be easily adapted during the process of calculation. [ABSTRACT FROM AUTHOR]

The paper offers a new approach to modeling atmospheric turbulence consisting of turbulent cells whose size is larger than the optical beam width. Particular turbulent cells are approximated by an optical element matrix. The ray transfer matrix method is presented, through which the optical elements can be described in the matrix form. A deflection simulation was performed that indicated the behavior of the optical beam by passing through the optical element. Furthermore, the calculation of the deflection vector is described together with a cascade model of turbulent cells. The matrix calculation for the cascade of optical elements is also expressed. [ABSTRACT FROM AUTHOR]

The earthquake and its secondary geological disasters have some long-term effects on vegetation recovery, and the spatiotemporal differentiation of vegetation coverage in earthquake-stricken areas are often not valued by researchers. Beichuan County in Sichuan Province is the worst-hit area during Wenchuan earthquake, tracking the vegetation coverage in this disaster area can provide feedback for post-earthquake ecological restoration. Based on remote sensing (RS) and Geographic information system (GIS), this paper relies on dimidiate pixel model (DPM) and vegetation coverage transfer matrix to explore the vegetation coverage of the earthquake worst-hit area. The results show that the overall level of vegetation coverage in Beichuan county is high, and earthquakes are dominant in the areas with high vegetation coverage. Besides, earthquake can do most severe damages to the areas with high vegetation coverage, followed by medium damage impacting to the areas with medium vegetation coverage, but the damage of other areas are relatively small. From 2007 to 2020, the average vegetation coverage in Beichuan County decreased from 0.835 in 2007 to 0.755 in 2008, then gradually recovered to 0.826 in 2020, experiencing a sharp decline and then a steady increase. The recovery of vegetation coverage is improved over time, but the spatiotemporal differences of the recovery process are obvious. Elevation has the largest driving force on vegetation coverage (q = 0.569, p less than 0.001), followed by temperature and rainfall; the interaction between factors has a significant increasement in the spatial differentiation of vegetation coverage, indicating that vegetation coverage is a combination result of multiple factors. The research findings can help construct the scientific management of the eco-environment in the disaster area, it can also help builda medium to long-term ecological restoration plan according to the variation in vegetation coverage. [ABSTRACT FROM AUTHOR]

Against the backdrop of global warming, carbon emissions have become a major concern. Carbon emissions from land use (CELU) play a significant role in shaping the efforts to reduce carbon emissions and achieve carbon neutrality. Using the China Land Cover Dataset (CLCD) alongside socioeconomic data, we conducted comprehensive CELU calculations for Hubei Province. Our approach involves integrating a Markov time transfer matrix to delineate the spatiotemporal evolution characteristics of CELU, employing the Tapio elastic adaptation model to analyze the decoupling of CELU from economic development, and leveraging geographic detectors to identify the primary influencing factors and their interactions, both internally and externally. Subsequently, we formulated recommendations for low-carbon development in response to our findings. The key results are as follows. (1) Between 1995 and 2019, the total CELU in Hubei Province exhibited a consistent increase, characterized by an initial acceleration in growth followed by a gradual slowdown. (2) During the same period, Hubei Province witnessed multiple types of CELU decoupling, with weak decoupling emerging as a prevailing trend. (3) The explanatory power (q -values) of both internal and external factors influencing the CELU in Hubei Province ranged from 0.179 to 0.935. Moreover, the interaction results for these factors exceeded 0.5, indicating a significant overall effect. This study presents a low-carbon development strategy that offers a robust scientific basis for government policymakers to craft emission reduction strategies. Additionally, it serves as a valuable reference for fostering long-term high-quality socioeconomic development. • From 1995 to 2019, the total amount of CELU in Hubei Province increased. • Weak decoupling is the dominant direction in the relationship between CELU and GDP. • The overall interaction between internal and external influencing factors is significant. • Clear carbon control goals should be established, and effective low-carbon development measures should be formulated. [ABSTRACT FROM AUTHOR]

In this paper, an in-plane Z-shaped structure with multi-span elastic supports is proposed to investigate the natural frequency and transmission response through employing in-plane governing equation and transfer matrix method. Based on the solutions of transverse vibration and torsional vibration, the total transfer matrix for the Z-shaped structure withmulti-span elastic supports is derived. Furthermore, natural frequencies andmode shapes of the Z-shaped structure are calculated. Finite element simulationmethod (FEM) is conducted here to verify the theoretical results. In order to effectively evaluate the vibration reduction performance, transmission response of the Z-shaped structure under different boundary supports and multispan elastic supports is analyzed. This work is significant for the vibration reduction of in-plane Z-shaped structure, especially the multi-span elastic support case in engineering applications. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new type of coupled muffler for diesel engine was proposed based on the principle of split-stream rushing and multi-unit coupling theory, and a coupling study of noise attenuation performance was carried out. The one-dimensional transfer matrix method was used to establish a transfer matrix mathematical model of the new muffler. The relative importance of the impact on the transmission loss for the coupled muffler was then able to be ranked by experimental design and MATLAB software calculation. From this, the combination of parameters with the optimal transmission loss was obtained. The transmission loss tests without airflow and the insertion loss tests with airflow between the optimal model of the coupled muffler and the original muffler supplied with the engine were verified respectively. The tests of pressure loss between the coupled muffler and the original muffler were also completed. The results show that the transmission losses of the coupled muffler in 0–2000 Hz and 0–200 Hz without airflow were 6 dB and 8 dB higher than that of the original muffler, the insertion losses of the coupled muffler in 0–2000 Hz and 0–200 Hz with airflow are 6 dB and 7 dB higher than that of the original muffler, and the noise peaks in the source spectrum are well controlled by the coupled muffler. The pressure losses of the coupled muffler are lower than that of the original muffler, which verifies that the coupling structure could reduce the airflow velocity in the muffler to improve noise attenuation performance and aerodynamic performance of the muffler at the same time. © 2022 Institute of Noise Control Engineering. [ABSTRACT FROM AUTHOR]

We performed a theoretical analysis on collection of equilateral triangular holes with consideration for sound wave attenuation within the tube and then calculated the sound-absorption coefficient and transmission loss. We then compared these results with experimental values. In the experiment, we measured the sound-absorption coefficient and transmission loss of a test sample using impedance measurement tubes with two and four microphones. We estimated the sound-absorption coefficient and transmission loss because of the dimensions of a collection of equilateral triangular holes through theoretical analysis and then compared these results with experimental values. In the present analysis, the propagation constant and characteristic impedance were introduced into a one-dimensional transfer matrix. Considering the effects of sound wave attenuation in the tubule from three-dimensional analysis, we derived the propagation constant and characteristic impedance. Values for the sound-absorption coefficient and transmission loss obtained through the analysis of holes as triangles rather than as circles gave calculation results closer to the experimental values. This is because this method more suitably simulates the effects of the boundary layer that occupies the space within the hole. The results show that the sound absorption coefficient and transmission loss of triangular honeycombs can be estimated with sufficient accuracy using only geometric dimensions and physical properties. © 2022 Institute of Noise Control Engineering. [ABSTRACT FROM AUTHOR]

In this study, the sound-absorption coefficients of a pin-holder structure consisting of a group of cylinders were estimated and compared with the experimental values for the case where sound waves are incident in the direction perpendicular to the cylinder's axis. To estimate the sound-absorption coefficient, the gap in the pinholder structure is divided into elements and approximated as being between two parallel planes, taking the exact shape of the divided elements into account. The characteristic impedance and propagation constant of the approximated clearances were calculated and treated as a one-dimensional transfer matrix. The transfer matrices for each element were used to calculate the sound-absorption coefficient. The calculated theoretical values were compared with the experimental ones. In the experiment, the samples were fabricated using a 3D printer, and the soundabsorption coefficient was measured using a two-microphone impedancemeasurement tube. Although the experimental and theoretical values differed, they showed similar trends. We also found that the prediction error in the practical sound-absorption coefficient could be reduced by adjusting the diameter of the pins used in the calculation. © 2022 Institute of Noise Control Engineering. [ABSTRACT FROM AUTHOR]

In this investigation, a fuzzy-based micrometer level control design with a guaranteed trajectory tracking performance for piezoelectric actuators which naturally have hysteresis effects is proposed. Nominal dynamics of the controlled piezoelectric actuators are described by adopting Takagi and Sugeno fuzzy models initially. Via interpolating Takagi and Sugeno local fuzzy model, a robust fuzzy-based controller is developed to eliminate hysteresis, modeling uncertainties and external disturbances. Meanwhile, the tracking error is expected to be reduced as small as possible with respect to all bounded desired trajectories. This proposed fuzzy-based controller has an easy to implement control structure. The trajectory tracking design problem of piezoelectric actuators of this study is transferred to a linear matrix inequality problem, and based on the convex optimization technique, the solution of the trajectory tracking design problem of piezoelectric actuators can be solved efficiently. From the simulation results, it is obvious that this proposed fuzzy-based control design possesses robustness property and can converge tracking errors to zero in micrometer level. [ABSTRACT FROM AUTHOR]

To comply with noise regulations in residential areas, low-noise electrical transformers must be developed. However, it is difficult to accurately reflect the frequency characteristics of the transformer, which have a large influence on the noise produced, because the high voltage and current make it impossible to experimentallymeasure the internal excitation forces involved. In this paper, we propose a new method using an experimental apparatus for estimating the internal excitation forces experienced by transformers whose results accurately reflect the actual frequency characteristics of the transformer. To estimate the excitation force, the pressure distribution data outside the enclosure of a transformer was experimentally measured by the experimental apparatus based on a beamforming method, and the transfer function from the excitation source to the noise radiation was derived numerically. The excitation force was then derived using the pressure distribution data and transfer function. Based on the estimated excitation force, the contribution of each vibration transmission path was derived using transfer path analysis with integrated transfer function matrix as a basis for creating an effective noise reduction plan. The noise reduction plan based on our method was able to reduce transformer noise sufficiently to meet the noise standard set in standard transformer export contracts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Poles and zeros assignment problem by state feedbacks in positive continuous-time and discrete-time systems is analyzed. It is shown that in multi-input multi-output positive linear systems by state feedbacks the poles and zeros of the transfer matrices can be assigned in the desired positions. In the positive continuous-time linear systems the feedback gain matrix can be chosen as a monomial matrix so that the poles and zeros of the transfer matrices have the desired values if the input matrix B is monomial. In the positive discrete-time linear systems to solve the problem the matrix B can be chosen monomial if and only if in every row and every column of the n × n system matrix A the sum of n-1 its entries is less than one. [ABSTRACT FROM AUTHOR]

Carbon nanotube field‐effect transistors (CNTFETs) have been widely studied as a promising technology to be included in post‐complementary metal‐oxide‐semiconductor integrated circuits. Despite significant advantages in terms of delay and power dissipation, the fabrication process for CNTFETs is plagued by fault occurrences. Therefore, developing a fast and accurate method for estimating the reliability of CNTFET‐based digital circuits was the main goal of this study. In the proposed method, effects related to faults that occur in a gate's transistors are first represented as a probability transfer matrix. Next, the target circuit's graph is traversed in topological order and the reliabilities of the circuit's gates are computed. The accuracy of this method (less than 3% reliability estimation error) was verified through various simulations on the ISCAS 85 benchmark circuits. The proposed method outperforms previous methods in terms of both accuracy and computational complexity. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the transfer matrix method valley-spin caloritronic transport properties of ferromagnetic silicene superlattice are investigated theoretically under ac-field effect of various frequencies. The purpose of this work is to describe resolved thermoelectric parameters such as (charge, spin and valley) Seebeck and Peltier coefficients and electronic thermal conductance, by photon-assisted tunneling probability bases. An oscillatory behavior is resulted for all investigated thermoelectric parameters in this investigation. These oscillations might be due to photon assisted tunneling. The improved values of charge, spin, valley power factors might be due to quantum confinement effect, which leads to enhancements of charge, spin, valley figure of merits as indicated from the obtained results. Also, results show that ferromagnetic silicene superlattice is good to use as energy harvesting thermoelectric nanodevice (Seebeck coefficient), and may be used as nanoelectronic devices cooler (Peltier coefficient). So, this present research shows that ferromagnetic silicene superlattice is good promising for flexible thermoelectric power generation. [ABSTRACT FROM AUTHOR]

This paper studies secure wireless transmission from a multi-antenna transmitter to a single-antenna intended receiver overheard by multiple eavesdroppers with considering the imperfect channel state information (CSI) of wiretap channel. To enhance security of communication link, the artificial noise (AN) is generated at transmitter. We first design the robust joint optimal beamforming of secret signal and AN to minimize transmit power with constraints of security quality of service (QoS), i.e., minimum allowable signal-to-interference-and-noise ratio (SINR) at receiver and maximum tolerable SINR at eavesdroppers. The formulated design problem is shown to be nonconvex and we transfer it into linear matrix inequalities (LMIs). The semidefinite relaxation (SDR) technique is used and the approximated method is proved to solve the original problem exactly. To verify the robustness and tightness of proposed beamforming, we also provide a method to calculate the worst-case SINR at eavesdroppers for a designed transmit scheme using semidefinite programming (SDP). Additionally, the secrecy rate maximization is explored for fixed total transmit power. To tackle the nonconvexity of original formulation, we develop an iterative approach employing sequential parametric convex approximation (SPCA). The simulation results illustrate that the proposed robust transmit schemes can effectively improve the transmit performance. [ABSTRACT FROM AUTHOR]

The unit cabin has been used to construct internal ship space for improved efficiency and to reduce budgetary costs in shipbuilding. Because the cavity is placed between unit cabins, the noise of one room is transmitted through the sound insulating panel, the cavity, and the opposite sound-insulating panel. In this study, by developing a transfer matrix of the cavity between structures, airborne noise between unit cabins was predicted. A sandwich panel, which is usually used in ships, was employed to construct a double panel, and the sound insulation performance was confirmed by changing the thickness of the cavity. To improve the reliability of numerical results, they were compared with those from experiments conducted. The results showed that as the cavity size increases, the overall sound insulation performance improves. A parameter study was also conducted on the density, Young's modulus, thickness, and thickness ratio of the core of the sandwich panel. To improve the sound insulation performance, increasing the density of the core is preferable to increasing the core thickness. The panel thickness ratio should be increased to avoid performance degradation as a result of the resonance frequency. [ABSTRACT FROM AUTHOR]

This paper proposes a novel two-stage method for the design of a suboptimal model-matching controller in an output feedback closed-loop system (OFCLS) using the concept of squared magnitude function (SMF). A streamlined procedure for selection of a reference model, based on a linear quadratic regulator (LQR) with integral action (LQRI) having optimum values for the elements of the weighting matrices and the degree of interaction is proposed. The degrees of the numerator and denominator polynomials of the elements of the OFCLS transfer function matrix (TFM) are obtained from those of the plant and the chosen controller structure. In the first stage of the controller design, taking the LQRI-based closed-loop system (LCLS) as a reference model, the OFCLS is obtained using the approximate model-matching (AMM) technique based on the SMF concept. The approximation method involves a higher-order approximation for stable multiple-input-multiple-output (MIMO) lower-order systems. In the second stage, controller parameters are obtained using the exact model-matching (EMM) method with information about the OFCLS and plant TFMs. The proposed controller design method outperforms the method presented in the literature on integral squared error index. The simulation and experimental results illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A simple method of controller design for multi-input multi-output (MIMO) processes have been proposed in frequency domain. The intensive calculation for the inverse of the process transfer function matrix is simplified to a great extent by evaluating the process transfer function matrix at a low frequency point. The desired closed loop transfer functions are derived for the process using a single tuning parameter for each diagonal element of the process transfer function matrix which represents the desired closed loop time constant. Centralized PI controllers are then designed using a model matching technique by evaluating the transfer functions at a low frequency point. The PI controllers provide acceptable performances for lag dominated as well as time-delay dominated processes and is also applicable to high-dimensional processes. The proposed method is extended for the non-square MIMO processes using two approaches one of which squares up the process transfer function matrix to apply the proposed technique while the other is based on pseudo-inverse evaluation of the process transfer function matrix at a low frequency point. • Design of centralized PI controller for low and high-dimensional MIMO processes. • Process matrix inverse calculation simplified by evaluating at a low frequency point. • Non-square processes squared with small gain considered at missing diagonal elements. • Alternatively, for non-square processes, pseudo-inverse is considered. [ABSTRACT FROM AUTHOR]

The Fiber Fabry–Perot (FFP) cavities are reported as various types of sensors in conventional experiments while rarely reported in application of frequency stabilization. We fabricated 10 cm, 30 cm, 50 cm Single Mode Fiber Fabry–Perot (SMF-FP) cavity with parallel end faces to serve as a frequency reference. The thermoelectric cooler (TEC) and piezoelectric transducer (PZT) are configured on the cavity structure for frequency coarse tuning and fine tuning. By establishing the transfer matrix model of light resonant process in the SMF-FP, the birefringence and thermal effect of resonance peak is explained, and the relationship between the locking error signal and the input polarization is analyzed. It provides a method to improve the precision and stability of frequency locking by optimizing the input polarization performance. Finally, The Allan variance after the frequency locking reached 2. 8 × 1 0 − 10 at 10s of the integral time, which is higher half an order magnitude than the stability of free running. The research work is of great significance to the compact frequency reference with low cost and high precision. • Establishing Jones matrix of the SMF-FP and analyzing the influence of input polarization on the frequency locking. • Analyzing the characteristic of SMF-FP with different lengths for frequency locking. • The locking result on the arbitrary detuning frequency achieved 2. 8 × 1 0 − 10 at 10 s of the integral time by locking on the temperature-controlled SMF-FP. [ABSTRACT FROM AUTHOR]

The present article discusses a Green's function-based semi-analytical method to predict the transmission loss of a lined Helmholtz resonator with annular air gap. In the analysis, the walls of the chamber are assumed to be acoustically rigid except at the neck portion where it is treated as a piston source moving with uniform velocity. The Green's function is developed as the summation of eigenfunctions of the central duct. The cumulative effect of the lined portion and the annular air gap including the perforated screens is incorporated as the reflection coefficient in the eigenfunctions. By using the Kirchhoff-Helmholtz integral equation, the velocity potential generated by the piston inside the chamber is evaluated. A transfer matrix relating the acoustic pressure and volume velocity across the neck in the main duct is formulated. The effect of the neck length is included as an added inertance to the impedance in the transfer matrix. The results obtained from the proposed method are validated with the developed numerical models and the experimental data available in the literature. A parametric study has been conducted to investigate the effect of porosity of the perforated screens, thickness and flow resistivity of the absorptive material on the transmission loss of the chamber. [ABSTRACT FROM AUTHOR]

In this study, a theoretical analysis of the acoustic characteristics of a pin holder structure was conducted. In addition, the sound absorption coefficient, entering its clearance through the geometrical dimension of the clearance or the physical property of air, was calculated. The analysis model approximates the aperture of a pin holder structure as the clearance between two parallel surfaces. Thus, the propagation constant and characteristic impedance were obtained and treated as a one-dimensional transfer matrix. Subsequently, the sound absorption coefficient was calculated using the transfer matrix method and was compared with the experimental results. In the experiment, a two-microphone impedance tube was used to measure the sound absorption coefficient of the test samples. We attempted to perform a simple yet accurate estimation using these procedures. The theoretical analysis values exhibited a similar tendency to that of the experimental values. [ABSTRACT FROM AUTHOR]

Copyright of KPI Science News is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To examine the dynamic characteristics of turbomachinery and cavitation, the pulsating flow rates should be evaluated. As it is difficult to measure these pulsating flow rates quantitatively, systematic research has not been conducted on the dynamic characteristics of turbomachinery and cavitation. In this paper, an unsteady energy equation for a venturi tube has been proposed to measure pulsating flow rates. The pulsating flow rates were calculated using two methods based on the unsteady energy equation for incompressible flows. The first method calculated a pulsating flow rate by using the Euler method. The second one calculated the complex amplitude of a pulsating flow rate using a transfer function derived from the linearized unsteady energy equation. We analytically examined the order of magnitude for unsteady terms. The results indicated that the unknown unsteady loss was much smaller than the unsteady momentum. In the experiment, pulsating flows were generated by a reciprocating piston, and the given pulsating flow was measured using a hot wire anemometer. The pulsating flow rates evaluated by using the proposed methods were validated via numerical simulation and experiment. In particular, the influence of amplitudes on the evaluation of pulsating flow rates was numerically examined. Therefore, the nonlinear effect could be evaluated by using the proposed method, and the time-averaged loss coefficient was enough to evaluate the pulsating flow rate coefficient. The proposed unsteady venturi flowmeter can be applied to a wide range of research fields, such as analyzing dynamic characteristics of flows. [ABSTRACT FROM AUTHOR]

Copyright of KPI Science News is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present a one-shot, purely data-driven, method for controller certification. The method is based on an analysis presented in previous works, where theoretical results have been given showing that certification can be obtained by the estimation of the H ∞ -norm of a very specific transfer matrix, but without actually pursuing this approach. Accordingly, we propose a procedure for the estimation of the H ∞ -norm directly from closed-loop input–output data, which is based on the Markov parameters. Our procedure requires only a single batch of input–output data collected from the plant, unlike previous data-driven approaches, which may require many data batches collected under different circumstances. We also show that the same approach can be applied when the data are acquired in open loop and that the same formulation allows estimation of the closed-loop performance. Simulation examples illustrate the method's features and show that it is significantly more accurate than other known methods when fed by the same data set. Finally, we provide experimental results in a three-tank liquid processing plant to illustrate the method's practical applicability. • One-shot data-driven certification for multivariable control. • Outperforms classical system identification approach. • H ∞ -norm estimation with only one single batch of data. • Experimental validation of the proposed procedure. [ABSTRACT FROM AUTHOR]

The annulus fibrosus of the intervertebral disc exhibits an unusual transversal behavior for which a constitutive representation that considers as well regional effect, chemical sensitivity and time-dependency has not yet been developed, and it is hence the aim of the present contribution. A physically-based model is proposed by introducing a free energy function that takes into account the actual disc annulus structure in relation with the surrounding biochemical environment. The response is assumed to be dominated by the viscoelastic contribution of the extracellular matrix, the elastic contribution of the oriented collagen fibers and the osmo-induced volumetric contribution of the internal fluid content variation. The regional dependence of the disc annulus response due to variation in fibers content/orientation allows a micromechanical treatment of the soft tissue. A finite element model of the annulus specimen is designed while taking into consideration the 'interlamellar' ground substance zone between lamellae of the layered soft tissue. The kinetics is designed using full-field strain measurements performed on specimens extracted from two disc annulus regions and tested under different osmotic conditions. The time-dependency of the tissue response is reported on stress-free volumetric changes, on hysteretic stress and transversal strains during quasi-static stretching at different strain-rates and on their temporal changes during an interrupted stretching. Considering the effective contributions of the internal fluid transfer and the extracellular matrix viscosity, the microstructure-based chemo-mechanical model is found able to successfully reproduce the significant features of the macro-response and the unusual transversal behavior including the strong regional dependency from inner to outer parts of the disc: Poisson's ratio lesser than 0 (auxetic) in lamellae plane, higher than 0.5 in fibers plane, and their temporal changes towards usual values (between 0 and 0.5) at chemo-mechanical equilibrium. The underlying time-dependent mechanisms occurring in the tissue are analyzed via the local numerical fields and important insights about the effective role of the interlamellar zone are revealed for the different disc localizations. The structural complexity of the annulus fibrosus has only been appreciated through recent experimental contributions and a constitutive representation that considers as well regional effect, chemical sensitivity and time-dependency of the unusual transversal behavior has not yet been developed. Here, a microstructure-based chemo-viscoelastic model is developed to highlight the interlamellar-induced time-dependent response by means of a two-scale strategy. The model provides important insights about the origin of the time-dependent phenomena in disc annulus along with regional dependency, essential for understanding disc functionality. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects. [ABSTRACT FROM AUTHOR]

In noise source identification based on the inverse boundary element method (IBEM), the boundary vibration velocity is predicted based on the field pressure through a transfer matrix of the vibration velocity and field pressure established on the Helmholtz integral equation. Because the matrix is often ill-posed, it needs to be regularized before reconstructing the vibration velocity. Two regularization methods and two methods of selecting the regularization parameter are investigated through the simulation analysis of a pulsating sphere. The result of transfer matrix regularization is further verified through the reconstruction of the vibration of an aluminum plate. Additionally, to reduce the large errors at some frequencies in the reconstruction result, increasing the number of measuring points is more effective than reducing the distance between the measurement plane and the sound source. [ABSTRACT FROM AUTHOR]

Highlights • Analytical expression for the finite Airy beam in the misaligned slab system with a rectangular aperture is deduced. • The effects of aperture size and misaligned factors on beam evolution are explored. • The special cases of beam propagating in various kinds of slab systems are illustrated. Abstract In this letter, we deduce the approximate analytical formula for the finite Airy beam propagating in the misaligned slab system with a rectangular aperture by using the generalized Huygens-Fresnel integral equation, the light transfer matrix and expanding the hard-edged rectangular function into a finite sum of complex Gaussian function. The particular cases of this beam propagating in the apertured aligned slab system, unapertured misaligned slab system and unapertured aligned one are further illustrated through numerical examples as well. The effects of aperture size and misaligned factors on beam evolution in these slab structures are developed, which can provide a fast and effective method for investigating other kinds of pseudo non-diffracting laser beams through the rectangularly apertured misaligned slab system because most of the optical devices are slightly misaligned more or less in the practical application. [ABSTRACT FROM AUTHOR]

Abstract Muffling devices are essential parts of any vehicle/machine that uses internal combustion engines. From automotive manufacturers point of view, they contribute massive sheet metal processing and production time, especially mufflers that are produced at high rates for commercial vehicles. This paper is concerned with applying manufacturing procedures to reduce the production cost of any commercial automotive mufflers through theoretical studies and experimental measurements verification. Mufflers design parameters such as transmission loss, flow generated noise and pressure drop were selected for performance judgment, parameters were simulated and experimentally measured. The transfer matrix method was used to calculate the propagation of sound waves along the muffler. A commercial automotive muffler with a hybrid combination of dissipation and reflection was selected for application and a new design was proposed for this muffler with a reduced manufacturing cost. The manufacturing processes were reduced by 77.7% and consequently the cost relative to the original muffler. [ABSTRACT FROM AUTHOR]

In order to achieve high speed of tufting machine, the oval gear is used as tte transmiision mechanism between the main shaft and the slave shaft. And then, mathematical model of tufting machine spindle system is established by transfer matrix method. Finally, the dynamic reaction force of the connection and the unbalanced response of the joint between the general ttfttng machine and the improved spindle system are studied by using Matlab numerical simulation. The analysis results show that when the spindle speed reaches 1 000 r/min, the dynamic reaction force of the improved spindle system at the jomt is far less than that of the general tufting machine, and the unbalanced response is reduced from 0.22 mm to 0.10 mm. [ABSTRACT FROM AUTHOR]

A new method for computation of positive realizations of given transfer matrices of fractional linear continuous-time linear systems is proposed. Necessary and sufficient conditions for the existence of positive realizations of transfer matrices are given. A procedure for computation of the positive realizations is proposed and illustrated by examples. [ABSTRACT FROM AUTHOR]

Generally, heavier noise control treatments are favored over lighter treatments since heavier acoustical materials generally insulate (block) noise sources more effectively than do lighter materials. In automotive applications, however, heavier materials cannot always be adopted because of concerns about the total weight of the vehicle. Thus, it would be useful to identify lightweight acoustical treatments that can mitigate vehicle interior noise. Automotive sound packages have both absorption and transmission characteristics, and there is inevitably a trade-off between these two. Therefore, it is important to study the exchange between the absorption and transmission of acoustical materials particularly as it pertains to weight. Here, we describe a procedure, based on plane wave analysis, that can be used to identify weight reduction opportunities by adjusting the acoustical properties of a generic sound package, consisting of a fibrous layer and a flexible microperforated panel surface treatment, so that it meets a target sound pressure level in a downstream interior space. It has been found for the configuration studied here that there are lightweight sound package configurations that can maintain acoustical performance equivalent to that of heavier noise treatments, and further, it has been found that the lightest treatments tend to favor barrier performance rather than absorption. Further, the impact of acoustical leaks is considered, and it has been found that even very small leaks can result in a very substantial weight penalty if a specified level of acoustical performance is to be ensured. [ABSTRACT FROM AUTHOR]

A computational acoustic model has been prepared to estimate the cabin noise of a commercial aircraft with a tail suspension engine based on SEA method. The main noise sources such as engine and TBL have been calculated and the primary transfer path of the aircraft fuselage has been analyzed. After that, a transfermatrix method is applied to calculate the transmission loss of the panel structures, and to evaluate effectively and rapidly the acoustic insulation of themultilayer structure combined by the skin panel, blankets and trim panel. The results display that the sound level in the rear of the aircraft exceeds the passenger cabin acoustical comfortable requirement. A series of noise treatments should be considered to the panels which are the main transfer path of external noise into the cabin. Meanwhile, an optimal approach should be applied to the aircraft and validated by flight test. The results show that (1) the ceiling panel of cockpit is the main transfer path of TBL excitation into the cabin, while the window side panel and trim panel located at the rear of the fuselage are the main transfer path of the engine noise into the cabin; (2) the sound insulation performance of the side wall panel would be improved by increasing the density and thickness of the blanket and adding the damping layers on it; and (3) the cabin noise level would be reduced about 3 dB when the optimal panel configuration is applied to the aircraft with the penalty of adding weight about 45 kg. [ABSTRACT FROM AUTHOR]

To study the dynamics of a vehicular missile system and determine initial disturbances of a missile, the multi-rigidflexible launch dynamics model of a vehicular missile system is developed by using transfer matrix method for multibody system and launch dynamics theory. The overall transfer equation, overall transfer matrix, and characteristics equation of the system are deduced based on the automatic deduction theorem of overall transfer equation of multibody system. The equation governing the motion of the vehicular missile system is obtained by using the orthogonality of augmented eigenvector and body dynamics equations of the system. The launch dynamics equations of a missile are deduced, in which the mass misalignment and dynamic imbalance of the missile are considered. By combining (he equation governing the motion of the system and launch dynamics equations of the missile, the launch dynamics equations of the vehicular missile system are developed. The vibration characteristics, dynamics response of the system, and initial disturbances of the missile are simulated. The simulation results show that the eigenfrequencies obtained by the proposed method and ordinary dynamics method have good agreement. Some factors that influence missile's motion and initial disturbances are analyzed. The paper provides an effective approach to study the launch dynamics of a vehicular missile system. [ABSTRACT FROM AUTHOR]

This paper presents a numerical solution for the thick cylinders made of functionally graded materials (FGMs) with a constant Poisson's ratio and an arbitrary Young's modulus. We define two fundamental solutions which are derived from an ordinary differential equation under two particular initial boundary conditions. In addition, for the single layer case, we can define the transfer matrix N. The matrix gives a relation between the values of stress and displacement at the interior and exterior points. By using the assumed boundary condition and the transfer matrix, we can obtain the final solution. The transfer matrix method also provides an effective way for the solution of multiply layered cylinder. Finally, a lot of numerical examples are present. [ABSTRACT FROM AUTHOR]

Low critical rotary speed and large vibration in the metal drive-line system of heavy-duty machine tool affect the machining precision seriously. Replacing metal drive-line with the CFRP drive-line can effectively solve this problem. Based on the composite laminated theory and the transfer matrix method (TMM), this paper puts forward a modified TMM to analyze dynamic characteristics of CFRP drive-line system. With this modified TMM, the CFRP drive-line of a heavy vertical miller is analyzed. And the finite element modal analysis model of the shafting is established. The results of the modified TMM and finite element analysis (FEA) show that the modified TMM can effectively predict the critical rotary speed of CFRP drive-line. And the critical rotary speed of CFRP drive-line is 20% higher than that of the original metal drive-line. Then, the vibration of the CFRP and the metal drive-line were tested. The test results show that application of the CFRP drive shaft in the drive-line can effectively reduce the vibration of the heavy-duty machine tool. [ABSTRACT FROM AUTHOR]

Bipartite graph-based drug–target interactions (DTIs) prediction methods are commonly limited by the sparse structure of the graph, resulting in acquiring suboptimal node feature representations. In addition, these defective node features will also interfere with the representation quality of corresponding edge features. To alleviate the sparsity of bipartite graph and get better node representation, according to the prior Knowledge Graph (KG), we developed a novel prediction model based on Variational Graph Auto-Encoder (VGAE) combined with our proposed dual Wasserstein Generative Adversarial Network with gradient penalty strategy (dual-WGAN-GP) for generating edge information and augmenting their representations. Specifically, GA-ENs first utilized dual-WGAN-GP to fill possible edges by a prior KG containing various molecular associations knowledge when constructing a bipartite graph of known DTIs. Moreover, we utilized the KG transfer probability matrix to redefine the drug–drug and target–target similarity matrix, thus constructing the final graph adjacent matrix. Combining graph adjacent matrix with node features, we learn node representations by VGAE and augment them by utilizing dual-WGAN-GP again, thus obtaining final edge representations. Finally, a fully connected network with three layers was designed to predict potential DTIs. Extensive experiment results show that GA-ENs has excellent performance for DTIs prediction and could be a supplement tool for practical DTIs biological screening. • In KGSM, drug–drug and target–target similarity matrices were redefined based on a prior KG to ensure that they were consistent with the bipartite graph in data source. • In dual-WGAN-GP, Wasserstein Generative Adversarial Network with gradient penalty (WGAN-GP) and the correlation between prior knowledge graph and bipartite graph were fully utilized to alleviate the sparsity of bipartite graph. • Moreover, we creatively used WGAN-GP to get more differentiated edge features, which were fused with parameters to get more comprehensive edge representations. This dual embedding method can effectively deal with the over-smooth problem caused by two-layer GCN. [ABSTRACT FROM AUTHOR]

In this numerical investigation, the design of new optical Fabry–Perot filters according to hybrid Periodic/Non-Periodic, one-dimensional photonic structures are proposed. The purpose of the paper is to design and optimize new Fabry–Perot filters to be used in optical systems and instruments. The hybrid structures studied are Periodic/[Fibonacci] P /Periodic and Periodic/[Cantor] P /Periodic, where P is the repetitive number of Fibonacci or Cantor sequence. The materials constituting the layers of the hybrid structure are the SiO 2 and the TiO 2 . The transmission spectra are determined using the Transfer Matrix Method (TMM). We show that the number, the position of the transmission peaks, the finesse coefficient (F) and the quality factor (Q) depend on the repetitive number (P), the light-incidence angle ( θ ) and the Polarization modes (TE and TM). All of these parameters are optimized to obtain a Fabry–Perot filters with high finesse coefficient (F), high quality factor (Q), minimum number of layers and minimum thickness. By comparing with other research works, the hybrid Periodic/Cantor structure is the best one which permits to obtain a Fabry–Perot filter with high Finesse coefficient F = 17300 . On the other hand, the hybrid Periodic/Fibonacci structure makes it possible to achieve the best high quality factor Q = 311600 . [ABSTRACT FROM AUTHOR]

The paper presents a calculation of slender concrete column resistance with a non-linear analysis which takes into account a contribution of second order theory, non-linear distribution of concrete stresses in cross-section and cracking. The Transfer Matrix Method was used as a step by step method for calculation of nodal forces and deformation vectors and modified rigidities of reinforced concrete segments. Also Newton method for searching equivalence of normal forces and bending moments on each step of calculation and central cross-section of column segment is explained in details. Theoretical results are compared with another non-linear software and realized experiment. [ABSTRACT FROM AUTHOR]

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