Conventional One-dimensional Model Research Articles

Improving seismic remote sensing of typhoon with a three-dimensional Earth model.

Typhoon-induced P-wave microseisms can be observed using seismological arrays and analyzed for the seismic monitoring of ocean storms. This paper presents a frequency-domain beamforming (FB) method that integrates a three-dimensional (3-D) Earth model to better capture the heterogeneities in the subsurface structure, and therefore yield more accurate ray-tracing and travel-time predictions. This method is applied to the Super Typhoon Lupit (2009) using seismological array observations from the Northeast China Extended Seismic Array (NECESSArray) and high-sensitivity seismograph network in Japan (Hi-net). The results show that the localized P-wave microseism source regions based on the 3-D model are in better agreement with the theoretical source regions and typhoon centers than those based on a conventional one-dimensional (1-D) model. The significance of using a 3-D model instead of a 1-D model in the FB method is further investigated by comparing the consistency of the localization results for the two different arrays, with the localized source regions being more mutually concordant when using the 3-D model. The results demonstrate that integrating the 3-D model into the FB method improves the accuracy of locating the typhoon-induced P-wave microseism source regions.

Performance Analysis of Bandwidth Allocation Based on Dynamic User Priority for Indoor Visible Light Communication Ultra-Dense Networks

Focusing on the high user density in visible light communication ultra-dense networks (VLC-UDNs), this paper proposes a resource allocation method based on dynamic user priority (DUP). Firstly, this paper establishes the DUP model, which realizes a multi-dimensional measurement for differences of users. Considering the variety of network environments, we dynamically select multiple features of users and achieve the calculation of DUP by fuzzy logic (FL). Secondly, the throughput-maximizing resource allocation (TMRA) scheme with user priority guarantee is proposed. Thirdly, the lower bound of the proposed DUP-TMRA is derived. Simulation results show that the proposed multi-dimensional DUP model outperforms the conventional one-dimensional DUP model and fixed priority model. In addition, the proposed TMRA scheme outperforms the conventional proportion allocation scheme. Finally, in comparisons of system throughput, the proposed DUP-TMRA achieves 4% performance improvement against the conventional required data rate proportion allocation (RPA) method. In comparisons of fairness, DUP achieves the modest performance. In comparisons of satisfaction, when the average blocking probability is higher than 0.45, the proposed DUP-TMRA improves the proportion of satisfied users against the conventional RPA method by up to 17.5%.

ECG Arrhythmia Classification Using STFT-Based Spectrogram and Convolutional Neural Network

The classification of electrocardiogram (ECG) signals is very important for the automatic diagnosis of heart disease. Traditionally, it is divided into two steps, including the step of feature extraction and the step of pattern classification. Owing to recent advances in artificial intelligence, it has been demonstrated that deep neural network, which trained on a huge amount of data, can carry out the task of feature extraction directly from the data and recognize cardiac arrhythmias better than professional cardiologists. This paper proposes an ECG arrhythmia classification method using two-dimensional (2D) deep convolutional neural network (CNN). The time domain signals of ECG, belonging to five heart beat types including normal beat (NOR), left bundle branch block beat (LBB), right bundle branch block beat (RBB), premature ventricular contraction beat (PVC), and atrial premature contraction beat (APC), were first transformed into time-frequency spectrograms by short-time Fourier transform. Subsequently, the spectrograms of the five arrhythmia types were utilized as input to the 2D-CNN such that the ECG arrhythmia types were identified and classified finally. Using ECG recordings from the MIT-BIH arrhythmia database as the training and testing data, the classification results show that the proposed 2D-CNN model can reach an averaged accuracy of 99.00%. On the other hand, in order to achieve optimal classification performances, the model parameter optimization was investigated. It was found when the learning rate is 0.001 and the batch size parameter is 2500, the classifier achieved the highest accuracy and the lowest loss. We also compared the proposed 2D-CNN model with a conventional one-dimensional CNN model. Comparison results show that the 1D-CNN classifier can achieve an averaged accuracy of 90.93%. Therefore, it is validated that the proposed CNN classifier using ECG spectrograms as input can achieve improved classification accuracy without additional manual pre-processing of the ECG signals.

Influence of heat conductivity and pore size of porous materials on the efficiency of cylindrical radiative burners with filtrational gas combustion

The problem of filtrational gas combustion wave stabilization in a porous cylindrical burner with different pore sizes and heat conductivities of porous carcass is numerically investigated. Simulation is carried out within the framework of the conventional one-dimensional diffusion-thermal model of filtrational gas combustion with allowance for radiative heat losses from the external surface of the burner. The data on influence ofthe carcass pore size and the thermal conductivity ofporous material on the radiative efficiency is investigated.

Theoretical investigation and experimental verification of a mathematical model for counter-flow spray separation tower

Despite the fact that the conventional one-dimensional model for counter-flow spray separation tower is advanced in reasonable accuracy as well as time and computational resources saving, it fails to describe the physical processes in details. In this paper, the concept of supersaturated state of the moist air was introduced, then a new sectional one-dimensional model was developed with a detailed derivation. A prototypic apparatus was set up and the reliability of the model was validated by the experimental study. When predicting the outlet solution temperature and outlet moist air wet bulb temperature, the relative errors would be more pronounced with a bigger heat and mass transfer driving potential, but they would not exceed 3.59% and 9.54% respectively under the experimental conditions. The simplifying assumptions, the ignored heat and mass transfer at cyclone region and the measuring errors are mainly blamed for the predicted errors. An in-depth heat and mass transfer investigation was conducted with the help of the validated model by studying the profiles of humidity ratio and moist air dry bulb temperature. The proposed model succeeded in capturing the state transformation of the air flow along the axis of the tower and the effects of the operating parameters on the process profiles are discussed.

3ω slope comparative method for fluid and powder thermal conductivity measurements

By analyzing the relationship among the heat penetration depth, measurement frequency and detector characteristic parameters, a simple and practical [Formula: see text] slope comparative method has been proposed. The corresponding measurement system for measuring the thermal properties of fluids and powder materials was established and verified using several specimens with known thermophysical parameters, such as alcohol, distilled water, and air. Compared to the two-dimensional model, the data processing of the method is relatively simple and quick. Due to the elimination of errors introduced by the detector parameter measurement, the measurement accuracy of the method is higher than the conventional one-dimensional model. By using an appropriate frequency range, the new method is time saving and convenient for measuring the thermal conductivity of fluids and powders with low thermal conductivity. Based on the analysis, the effective thermal conductivity of nano-SiO2 powder is accurately determined.

Magnetization plateaus in a doping finite Ising chain

We study the magnetization plateaus of a finite Ising chain. Based on the transfer-matrix method, we derived the exact formula of the average magnetization. Compared to the conventional one-dimensional Ising model, the finite chain can present more plateaus due to the open boundary. As the impure spin with single-ion anisotropy presented, the system exhibits more exotic magnetization plateaus and spin configurations. We also explore the effects of various anisotropies on the magnetization process.

Magnetic properties and thermodynamics of decorated Ising chain with pendants of arbitrary spin

The decorated Ising chain with pendants of arbitrary spin and the single-ion anisotropy is exactly solved by the transfer matrix method. The solutions reveal abundant novel properties than the conventional one-dimensional Ising model. It is compared with the experimental data of a necklace-like molecule-based magnet, that gives a qualitative consistency.

Importance of electronic state of two-dimensional electron gas for electron injection process in nano-electronic devices

We report the unexpected temperature dependence of electron tunneling from the two-dimensional electron gas (2DEG) to the Si-dot in a Si-dots floating gate metal-oxide-semiconductor (MOS) capacitor. We indicate that this temperature dependence of the electron tunneling cannot be explained by the conventional one-dimensional tunneling model, and show that it is necessary for a new model which includes the geometrical factor of the system. To extract a mechanism of the electron injection process from the 2DEG to the nano-structure, we have employed the numerical simulation, which includes both the geometrical condition of the system and the experimental setup. We suggest in our new tunneling model that the main contribution to the electron tunneling is induced by the wave-packet-like state of the electron below the Si-dots. We successfully show that the temperature dependence of the electron injection voltage in the Si-dots floating gate MOS capacitor fits our model. This indicates that the spatial distribution of electron density in the two-dimensional electron gas would play a crucial role in the electron tunneling.

The inaccuracy of conventional one-dimensional parallel thermal resistance circuit model for two-dimensional composite walls

This investigation is to show that two-dimensional steady state heat transfer problems of composite walls should not be solved by the conventionally one-dimensional parallel thermal resistance circuits (PTRC) model because the interface temperatures are not unique. Thus PTRC model cannot be used like its conventional recognized analogy, parallel electrical resistance circuits (PERC) model which has the unique node electric voltage. Two typical composite wall examples, solved by CFD software, are used to demonstrate the incorrectness. The numerical results are compared with those obtained by PTRC model, and very large differences are observed between their results. This proves that the application of conventional heat transfer PTRC model to two-dimensional composite walls, introduced in most heat transfer text book, is totally incorrect. An alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to the two-dimensional composite walls with isothermal boundaries. Results with acceptable accuracy can be obtained by the new model.

Numerical estimation of dynamic behavior of viscoelastic elastomer specimen

Dynamic deformation behavior of a cylindrical specimen made of viscoelastic elastomers was investigated numerically by solving the two-dimensional elastic wave equations. In order to enhance the accuracy of the viscoelastic property calculations, a pseudospectral analysis of two-dimensional elastic wave equation was employed. This allowed us to exclude the use of the form factor derived from the conventional one-dimensional model. Using the present method, an assessment of the conventional form factor concept was attempted. The present two-dimensional method was then utilized to predict a forced vibration response of the elastomer samples under periodic excitation. Obtained numerical results were compared with those using the simplest one-dimensional model. Applicable range of the form factor was examined. Empirical formulas to correct static and dynamic form factors for elastic deformation mode, which are suitable for engineering applications, are suggested.

Incorrectness of conventional one-dimensional parallel thermal resistance circuit model for two-dimensional circular composite pipes

This study is to prove that two-dimensional steady state heat transfer problems of composite circular pipes cannot be appropriately solved by the conventional one-dimensional parallel thermal resistance circuits (PTRC) model because its interface temperatures are not unique. Thus, the PTRC model is definitely different from its conventional recognized analogy, parallel electrical resistance circuits (PERC) model, which has unique node electric voltages. Two typical composite circular pipe examples are solved by CFD software, and the numerical results are compared with those obtained by the PTRC model. This shows that the PTRC model generates large error. Thus, this conventional model, introduced in most heat transfer text books, cannot be applied to two-dimensional composite circular pipes. On the contrary, an alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to a two-dimensional composite circular pipe with isothermal boundaries, and acceptable results are returned.

Optimally accurate thermal-wave cavity photopyroelectric measurements of pressure-dependent thermophysical properties of air: Theory and experiments

An experimental technique for the measurement of thermal properties of air at low pressures using a photopyroelectric (PPE) thermal-wave cavity (TWC) was developed. In addition, two theoretical approaches, a conventional one-dimensional thermal-wave model and a three-dimensional theory based on the Hankel integral, were applied to interpret the thermal-wave field in the thermal-wave cavity. The importance of radiation heat transfer mechanisms in a TWC was also investigated. Radiation components were added to the purely conductive model by linearizing the radiation heat transfer component at the cavity boundary. The experimental results indicate that the three-dimensional model is necessary to describe the PPE signal, especially at low frequencies where thermal diffusion length is large and sideways propagation of the thermal-wave field becomes significant. Radiation is found to be the dominant contributor of the PPE signal at high frequencies and large cavity lengths, where heat conduction across the TWC length is relatively weak. The three-dimensional theory and the Downhill Simplex algorithm were used to fit the experimental data and extract the thermal diffusivity of air and the heat transfer coefficient in a wide range of pressures from 760 to 2.6 Torr. It was shown that judicious adjustments of cavity length and computational best fits to frequency-scanned data using three-dimensional photopyroelectric theory lead to optimally accurate value measurements of thermal diffusivity and heat transfer coefficient at various pressures.

Impact of attenuator models on computed traveling wave tube performances

Radio frequency characteristics of helix traveling wave tubes are analyzed with a one-dimensional numerical model that includes a new, more rigorous, self-consistent attenuator model. The nonlinear properties of the beam-wave interaction, including gain, phase distortion, and intermodulation distortion, are analyzed and compared with simulations using a conventional one-dimensional model of the attenuator. The comparative results show that the small signal gain is about 2–5dB smaller with the new model than with the conventional and wave phase has a difference of 2°–6° between the new and conventional models in the intermediate and large signal regions. The amplitude modulation/phase modulation (AM/PM) conversion from the new model shows a slower reach to maximum than that from the conventional, and when the large input signal is applied, the conventional model’s AM/PM conversion oscillates more quickly compared to the new. Under two-frequency excitation, the fundamental tones are about 5–7dB smaller with the new model than the conventional, while the intermodulation products are approximately 10dB smaller relative to the conventional model.

Improved one-dimensional model of a tubular packed bed reactor

The major drawback of one-dimensional models of tubular fixed bed reactors, which are often used if the computational effort should be small, is the fact that the reaction rate is calculated using the average temperature over the cross-section of the reactor. The difference between this reaction rate and the average reaction rate over the cross-section becomes increasingly significant with increasing temperature difference over the radius of the reactor and with increasing activation energy of the reaction(s). Improved versions of the one-dimensional model, such as that of Hagan et al. [1988. A simple approach to highly sensitive tubular reactors. SIAM Journal of Applied Mathematics 48, 1083–1091] are available, which use an analytical approximation of the radial temperature profile to improve the prediction of the average reaction rate. However, application of these models involves solving of implicit equations. Here, a new model is proposed as an alternative to the existing one-dimensional models. It has the same form as the conventional one-dimensional model and contains only explicit functions. It is demonstrated that, at conditions not too close to runaway, the new model performs better than the well-known α -model.

Modeling of Hyperconcentrated Sediment-Laden Floods in Lower Yellow River

This paper presents a rapid forecast model for simulating hyperconcentrated sediment-laden floods in the Lower Yellow River. The model is a hybrid of a conventional one-dimensional mathematical model for unsteady sediment-laden flow and an artificial neural networks model for encapsulation of numerical results. The former provides detailed river flood routing information under typical scenarios, whereas the latter extracts modeling outputs from the former and establishes a station-specific model for efficient flood forecasting. Three typical floods that occurred in the Lower Yellow River in 1977, 1982, and 1996 are simulated. Not only the hybrid model predictions are found to be in close agreement with measured data, but also the computational speed is significantly enhanced. It is found that sediment transport is of significance with regard to the flooding behavior of hyperconcentrated flows. Therefore, the model presented herein is of particular use for rivers with high sediment concentration.

An analytical two-dimensional model for circular spreading-resistance temperature sensor based on thin silicon film

An analytical two-dimensional model is developed to explain the minority-carrier exclusion effect in circular spreading-resistance temperature (SRT) sensor fabricated on thin silicon film. The model can be used to show the relation between minority-carrier exclusion length and maximum operating temperature of the sensor under different bias currents and different doping levels. Comparison is made between the proposed model and the conventional one-dimensional model used for similar sensors with rectangular shape. Experimental results show that the new model is more accurate than the one-dimensional model for predicting the characteristics of the circular SRT sensor.

Latent heat effect on growth rate in the traveling liquidus-zone method

In order to obtain a homogeneous crystal by using the traveling liquidus-zone (TLZ) method, a conventional one-dimensional model is used to determine an appropriate sample translation rate. Although the conventional model predicts the appropriate translation rate, the latent heat effect is unknown since the conventional model is based on pure solution growth. Therefore, a new model including the latent heat is introduced to investigate the latent heat effect. By considering the new model, the maximum latent heat effect αmax is obtained. The αmax is negligibly small under the condition that the InAs mole fraction is far enough from 0 or 1 in the case of an InGaAs crystal. In order to estimate the actual latent heat effect α, one-dimensional numerical simulations with and without the latent heat are carried out. From the numerical results, the applicable limit of the TLZ method is discussed in the case of In0.3Ga0.7As crystals. The growth rate, which is regarded as a pure melt growth, is also discussed by extrapolating the α dependency.

Semi‐empirical model for site effects on acceleration time histories at soft‐soil sites. Part 1: formulation and development

AbstractA criterion is developed for the simulation of realistic artificial ground motion histories at soft‐soil sites, corresponding to a detailed ground motion record at a reference firm‐ground site. A complex transfer function is defined as the Fourier transform of the ground acceleration time history at the soft‐soil site divided by the Fourier transform of the acceleration record at the firm‐ground site. Working with both the real and the imaginary components of the transfer function, and not only with its modulus, serves to keep the statistical information about the wave phases (and, therefore, about the time variation of amplitudes and frequencies) in the algorithm used to generate the artificial records. Samples of these transfer functions, associated with a given pair of soft‐soil and firm‐ground sites, are empirically determined from the corresponding pairs of simultaneous records. Each function included in a sample is represented as the superposition of the transfer functions of the responses of a number of oscillators. This formulation is intended to account for the contributions of trains of waves following different patterns in the vicinity of both sites. The properties of the oscillators play the role of parameters of the transfer functions. They vary from one seismic event to another. Part of the variation is systematic, and can be explained in terms of the influence of ground motion intensity on the effective values of stiffness and damping of the artificial oscillators. Another part has random nature; it reflects the random characteristics of the wave propagation patterns associated with the different events. The semi‐empirical model proposed recognizes both types of variation. The influence of intensity is estimated by means of a conventional one‐dimensional shear wave propagation model. This model is used to derive an intensity‐dependent modification of the values of the empirically determined model parameters in those cases when the firm‐ground earthquake intensity used to determine these parameters differs from that corresponding to the seismic event for which the simulated records are to be obtained. Copyright © 2004 John Wiley & Sons, Ltd.

Imaging with lithium niobate/epoxy composites

Lithium niobate, LiNbO 3, is a very promising material for high temperature applications in non-destructive testing because of its high Curie temperature. However, for commercial applications LiNbO 3 has often been neglected because of its low electromechanical coupling coefficients. This paper explores the potential of LiNbO 3 composites, by means of room temperature characterization and measurements, for further use in operation in high temperature transducers. LiNbO 3 composites of 1–3 connectivity in an epoxy matrix with volume fractions of LiNbO 3 of 33% and 54% were fabricated. The composites were characterized by electrical impedance measurements and the results were compared with modelled impedance characteristics. Many parameters were predicted accurately, including an improvement of more than 75% in thickness mode electromechanical coupling coefficient, from k T=0.17 for bulk LiNbO 3 to k T=0.32 for composite material. Some large discrepancies between simulation and experiment were also identified when a conventional one-dimensional model was used to calculate equivalent composite material parameters; however, finite element modelling was more accurate. After characterization, the composite was configured for use as a linear array. Functional measurements were conducted on steel blocks with a side drilled hole to represent a crack tip. This was detected by the array and visualized in time-of-flight diffraction B-scan images.