Multi-section Model Research Articles

Ultrasound quantification of pleural effusion volume in supine position: comparison of three model formulae

BackgroundTo investigate the accuracy of three model formulae for ultrasound quantification of pleural effusion (PE) volume in patients in supine position.MethodsA prospective study including 100 patients with thoracentesis and drainage of PE was conducted. Three model formulae (single section model, two section model and multi-section model) were used to calculate the PE volume. The correlation and consistency analyses between calculated volumes derived from three models and actual PE volume were performed.ResultsPE volumes calculated by three models all showed significant linear correlations with actual PE volume in supine position (all p < 0.001). The reliability of multi-section model in predicting PE volume was significantly higher than that of single section model and slightly higher than that of two section model. When compared with actual drainage volume, the intra-class correlation coefficients (ICCs) of single section model, two section model and multi-section model were 0.72, 0.97 and 0.99, respectively. Significant consistency between calculated PE volumes by using two section model and multi-section model existed for full PE volume range (ICC 0.98).ConclusionBased on the convenience and accuracy of ultrasound quantification of PE volume, two section model is recommended for pleural effusion assessment in routine clinic, though different model formulae can be selected according to clinical needs.

Risk management and components’ coordination assessment in the design of a composite riverine flood defence system

ABSTRACT Flood control is one of the most important and difficult tasks in river basin management in terms of present several uncertainties. This study aims to follow the risk management and coordination analysis in designing a riverine flood defence system, actually, a composite multi-section flood control levee system considering the aleatory and epistemic uncertainties using contagious distributions. A stochastic optimization model was developed based on Monte Carlo analysis for uncertainty propagation, and then the system's optimum dimensions were computed in the single-section and multi-section cases for overall comparisons. Using the concept of ‘scenario probability’, the coordination of the system and its individual components was analysed. The results indicated that by increasing the complexity (from a single-section to a multi-section model) and by the separation of uncertainties (into epistemic and aleatory), the coordination of the system decreases 130% and 30%, respectively. Moreover, it was found that when economic uncertainty was considered, unexpected results may be obtained so that by increasing the system dimensions the total cost decreases. Finally, after analysing the sample histograms of the system's components, several distributions have been suggested. When there are vast datasets that might be confusing for decision-makers, the systematic method proposed here makes risk management easier.

Application of a Lumped Multi-Section Model for Analyzing the Thermal Performance of a Small-Scale Biomass Boiler

The stationary lumped-cell model was developed and used to simulate the thermal characteristics of domestic biomass boiler with helically coiled tube heat exchanger (HCHE). The device serves as the heat source for ORC (Organic Rankine Cycle) unit and utilizes the thermal oil as the medium transferring the heat to the unit. Most of studies available in the literature refer to the CFD simulations for water flow in tube coils or in one- or two-turn coil elements. These investigations are basically focused on the determination of Nusselt number. The proposed herein model aims at determining the thermal performance of flue gas-oil HCHE while providing low CPU time. To demonstrate the model possibilities, it was used to predict the flue gas temperatures at the inlet and outlet from the heat exchange zone, based on measurement data regarding the outlet temperature of thermal oil. Six test series were considered. The computation results appeared to be in satisfactory agreement with experimental results (the discrepancies do not exceed 12%). The investigations showed that the used approach may be recommended as an alternative method that allows for fast prediction of thermal parameters for units of complex geometries, in particular the multi-coil heat exchangers.

Research on earthquake dynamic behavior of uneven multi-section subway tunnel in transverse direction

Model tests are carried out in this research to investigate the dynamic behavior of multi-section cut-and-cover subway tunnels in the transverse direction by seismic motion, which has not been fully investigated up to now. Multi-section model and general single-track box-section model tunnels are installed in a soil vessel, and it is found that the sectional force corresponds to that obtained in the tunnel design. Then, L2 earthquake motion (Spectrum II), based on the design standard for railway structures, is applied to the soil vessel. The test results show that the bending moment and shear force are comparatively large in the center wall, although the tendency is different in the loading direction. Moreover, the results of a 3D dynamic finite element analysis for an evaluation of the model tests show approximately the same situation. This research provides various findings for establishing a seismic analysis method for multi-section cut-and-cover subway tunnels.

Impact of Polarization- and Mode-Dependent Gain on the Capacity of Ultra-Long-Haul Systems

Motivated by the recent interest in single-mode semiconductor optical amplifiers and multimode erbium-doped fiber amplifiers, we present a unified, comprehensive treatment of the effect of polarization- and mode-dependent gain (PDG and MDG) on the capacity of ultra-long-haul transmission systems. We study the problem using simulations of a multisection model, including the effects of PDG or MDG and polarization mode dispersion (PMD) or modal dispersion. We also analytically derive exact expressions for the capacity distribution of PDG-impaired single-mode systems. In agreement with previous work, we find that PDG and MDG cause fluctuations in capacity, which reduces average capacity and may cause outage. We show that the multimode systems studied, with at least $D = 14$ spatial/polarization modes, have sufficient modal diversity and frequency diversity to strongly suppress capacity fluctuations and reduce outage probability so that the outage capacity approaches the average capacity. We show that single-mode systems, by contrast, inherently provide low modal and frequency diversity, making them more prone to outage. To alleviate this problem, frequency diversity can be increased by artificially inserting PMD. Finally, we quantify the PDG/MDG requirements of optical amplifiers to ensure that the average capacity is close (within a 1-2 dB effective SNR loss) to the theoretical optimum. We show that these PDG/MDG requirements are stringent, especially considering the minimum-mean-square error linear equalizers implemented in typical multiple-input multiple-output receivers.

Neutrino-4 experiment on search for sterile neutrino with multi-section model of detector

In order to carry out research in the field of possible existence of a sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. The prototype of a multi-section neutrino detector with liquid scintillator volume of 350 l was installed in the middle of 2015. It is a moveable inside the passive shielding detector, which can be set at distance range from 6 to 11 meters from the reactor core. Measurements of antineutrino flux at such small distances from the reactor core are carried out with moveable detector for the first time. The measurements carried out with detector prototype demonstrated a possibility of measuring a reactor antineutrino flux in difficult conditions of cosmic background at Earth surface.

Semi-Analytical Modelling of Linear Mode Coupling in Few-Mode Fibers

This paper reviews and extends a method for the semi-analytical solution of the coupled linear differential equations that describe the linear mode coupling arising in few-mode fibers due to waveguide imperfections. The semi-analytical solutions obtained proved to be accurate when compared to numerical solution methods. These solutions were integrated into a multisection model with split-steps for mode dispersion and mode coupling. Simulations using this model matched the analytical predictions for the statistics of group-delays in few-mode fiber links, considering different coupling regimes with and without mode delay management.

Multi-section cellular automata model of traffic flow

It is more common for drivers to pass through multiple sections to reach destinations instead of single road section. Howerver, most of researches concentrate on improving the effect in an independent section. Based on traditional cellular automata traffic model, a multi-section model is proposed by regarding serverl road sections as a traffic system. In this model, different sections of the road might have different lengths, numbers of lanes or maximal speeds. And vehicles travel from one section to another. The main difficulty lies in dealing with the relationships among the traffic flows of different sections. Besides basic rules in NaSch model, the vehicle inflow rule, crossroad randomization brake rule and crossroad inflow rule is added in this paper to enable vehicles to flow between sections. At the beginning of section, to avoid conflicting at crossroads under open boundary condition, the concept of car pool is introduced when new vehicles enter into sections. Before arriving at the end of section, crossroad randomization brake is used to simulate the influences of crossroads. Speed decreases in probability until lower than a maximal crossroad speed. When leaving the section, vehicles go to the next section with a straight ratio. Also, new vehicles may enter according to traffic condition. Therefore, cellular automata of different sections can be connected in series.Finally, numerical simulation is demonstrated to study the influences of important parameters, including traffic inflow probability, maximal crossroad speed and crossroad randomization brake probability. Compared with traditional models, this model focuses on connecting sections. And improvements of basic models can be implanted easily, thereby increasing the accuracy of the whole model in the future. The experimental result are as follows. 1) According to space-time graphs of different inflow probabilities, there is a new kind of traffic flow called mixed flow. Traffic congestion often starts from crossroads, and spreads to the whole section. And traffic jams in previous section might relieve traffic pressure in latter section. 2) With the increase of traffic inflow probability, crossroads tends to have a greater influence on average speed as well as average traffic density. What is more, the moderate increase of vehicle numbers could cause the road capacity to drop rapidly if it exceeds the threshold value.

Study on multi-section, nonlinear model of flashover in a long–narrow confined space

The particularity in building structures of long–narrow spaces makes it different from the study of flashover model from the conventional theory. In this article, based on the nonlinear dynamics theory, a multi-section model was proposed to analyze the phenomenon of flashover. In this model, long–narrow confined space was divided into several sections, and each section was further divided into two zones, as hot smoke layer and cold air layer. The continuity equation and energy equation for each control volume defined from thermal smoke layer were established. The critical radius for the onset of flashover has been determined theoretically. In this article, a comparison with experiment for a multi-section, nonlinear model of flashover is presented, and the modeling results are compared with the experimental data which were obtained through a batch of fire tests in a reduced scale, long–narrow confined space. The theoretical calculation results agree reasonably well with measured results, in which the critical temperature and fire radius of flashover can be predicted. In general, for the polypropylene cribs, the predicted results are broadly consistent with the experimental results when the fire radius is below this critical value, but for heptane and wood cribs, the predicted value is a little higher. However, the model is useful in predicting the critical fire radius and temperature for flashover. In this article, the relationship between the characteristic parameters of fuel and the critical radius of fire source has also been investigated, which is linear growth.

Experimental Validation of a Reflective Semiconductor Optical Amplifier Model Used as a Modulator in Radio Over Fiber Systems

We improve and validate the multisection model for a bulk reflective semiconductor optical amplifier (RSOA) as a modulator in radio over fiber (RoF) systems. The RSOA model was developed using the symbolically defined devices (SDD) component under Agilent advanced design systems (ADS) software. An accurate parameter extraction method based on ADS optimization tools is presented. The intrinsic parameters of RSOA are obtained. Here the model is used to assess the static characteristics, harmonic and intermodulation distortions, and transmission performance of RSOA. Simulations have been validated with experimental results providing good agreement.

Analytic approach to the small-signal frequency response of saturated semiconductor optical amplifiers using multisection model

An analytic solution derived by multisection model to the small-signal frequency response (SSFR) of wavelength conversion based on cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs) is presented. The result contains details that can affect the characteristics of SSFR significantly more than previous ones.

Robust identification for multi-section freeway traffic models

Since it is difficult to fit measured parameters using the conventional traffic model, a new traffic density and average speed model is introduced in this paper. To determine traffic model structures accurately, a model identification method for uncertain nonlinear system is developed. To simplify uncertain nonlinear problem, this paper presents a new robust criterion to identify the multi-section traffic model structure of freeway efficiently. In the new model identification criterion, numerically efficient U-D factorization is used to avoid computing the determinant values of two complex matrices. By estimating the values of U-D factor of data matrix, both the upper and lower bounds of system uncertainties are described. Thus a model structure identification algorithm is proposed. Comparisons between identification outputs and simulation outputs of traffic states show that the traffic states can be accurately predicted by means of the new traffic models and the structure identification criterion.

Laboratory evaluation of time domain reflectometry for continuous monitoring of stream stage, channel profile, and aqueous conductivity

Time domain reflectometry (TDR) operates by propagating a radar frequency electromagnetic pulse down a transmission line while monitoring the reflected signal. As the electromagnetic pulse propagates along the transmission line, it is subject to impedance by the dielectric properties of the media along the transmission line (e.g., air, water, and sediment), reflection at dielectric discontinuities (e.g., air‐water or water‐sediment interface), and attenuation by electrically conductive materials (e.g., salts and clays). Taken together, these characteristics provide a basis for integrated stream monitoring, specifically, concurrent measurement of stream stage, channel profile, and aqueous conductivity. Requisite for such application is a means of extracting the desired stream parameters from measured TDR traces. Analysis is complicated by the fact that interface location and aqueous conductivity vary concurrently and multiple interfaces may be present at any time. For this reason a physically based multisection model employing the S11 scatter function and Debeye parameters for dielectric dispersion and loss is used to analyze acquired TDR traces. Here we explore the capability of this multisection modeling approach for interpreting TDR data acquired from complex environments, such as encountered in stream monitoring. A series of laboratory tank experiments was performed in which the depth of water, depth of sediment, and conductivity were varied systematically. Comparisons between modeled and independently measured data indicate that TDR measurements can be made with an accuracy of ±3.4 × 10−3 m for sensing the location of an air‐water or water‐sediment interface and ±7.4% of actual for the aqueous conductivity.

Analysis in distributed Raman amplification

We theoretically analyze a distributed Raman amplification (DRA) with counter-pumped by combining multi-section model and target shooting arithmetic, present the evolutions of the signal power, the pump power, the DRS power and optical signal–noise-ratio (OSNR) along the transmission fiber with different pump powers in two different cases: one is without an isolator and another with an isolator, find from those evolutions that there exists an optimal placement for the isolator so that DRA has maximum OSNR and gain, and that with an isolator put optimally, the gain of DRA can be gotten by effective value of input pump.

Theoretical Study on Wavelength Conversion Based on Cross Phase Modulation Using Semiconductor Optical Amplifiers

Performances of wavelength converted signal by cross phase modulation (XPM) using semiconductor optical amplifiers (SOA's) were studied by the use of the multi-section model. Results show that they are related to both the phase arm bias current of the XPM wavelength converter and its operation. When the conversion is under the in-phase operation, the peak extinction ratio (ER) and the chirp frequency of the converted signal increase according to the decrease of the phase arm bias current, but the input signal power dynamic range decreases. When the converter is under the out-of-phase operation, the chirp frequency decreases with the decrease of the phase arm bias current, while the peak ER and the input power dynamic range keep almost the same when the phase arm bias current changes.

Theoretical model of a multisection time domain reflectometry measurement system

A multisection model is presented to simulate electromagnetic wave propagation in an unmatched time domain reflectometry (TDR) probe and layered soil system. The model uses a linear‐time‐invariant feedback system to model each section and links each section in a bottom‐up fashion. Multiple sections can be incorporated in this model by a simple extension of a single‐section system. An unmatched TDR probe system is modeled by dividing it into equivalent sections and matching the simulated waveform with the actual waveform. The excellent match between the simulated and the recorded waveforms verifies the model. This model eliminates the requirement of a matched 50‐Ω probe handler in probe design for dielectric measurement. It can also be used to assist probe design and TDR data interpretation. The reflected waveforms in layered soil specimens are modeled, and the simulated waveforms are compared to those obtained from experiments. The method of using apparent dielectric constant to obtain average volumetric water content is examined for the layered soil system. The results show that apparent dielectric constant is applicable for the measurement of average volumetric water content for a layered soil, but caution has to be used when interpreting the waveforms.

Modelling of single-phase nonuniform transmission lines in electromagnetic transient simulations

An exponential single-phase line model is introduced to represent nonuniform transmission lines. When the line parameters are assumed to vary exponentially, a set of two-port equations can be formed in the frequency domain, which contain frequency-dependent functions. These functions are then synthesized with rational functions of the minimum-phase-shift type. Utilizing a fast recursive convolution technique, the time-domain equations of the proposed model reduce to a form similar to those in Bergeron's method. Plus, the model is compatible with general electromagnetic transients programs such as the EMTP. Time-domain simulations with the proposed model show good agreement with published experimental results, and with those produced by a cascade multi-section model where the line is divided into many short sections of uniform transmission lines.

Improved planar spiral transformer theory applied to a miniature lumped element quadrature hybrid

In this paper, an improved method of determining the primary-to-secondary coupling capacitance for planar spiral transformers (PST's) is presented, which enhances previous work. A more general monolithic microwave integrated circuit (MMIC) compatible lumped element multisection model is also presented based on symmetric-width uniformly coupled transmission lines. These techniques were developed to design a 90/spl deg/ hybrid as a MMIC with a center frequency of 2.5 GHz. The design was frequency scaled to 0.5 GHz and fabricated in the microwave integrated circuit (MIC) for verification. Producibility is enhanced and coupling is effectively increased with the novel use of series capacitors which cancel some of the self-inductance of the transformers. Measured results are presented for both a quadrature hybrid and the individual PST used in the quadrature hybrid. The measured results show excellent agreement with the computer models.

Transient analysis of diode switching circuits using asymptotic waveform evaluation

An efficient transient analysis of diode switching circuits using the asymptotic waveform evaluation (AWE) technique is presented. The method accurately simulates the excess carrier redistribution phenomenon in a diode junction using a reduced order model. The diode model is derived by directly solving the carrier continuity equations in an analogous manner to that of the AWE solution to transmission-line equations. The method efficiently calculates the poles and the residues of the diode model by recursively generating the moments of the carrier concentrations. It reduces the computational cost by an order of magnitude over that for Linvill's multisection model of ladder or lattice networks of many lumped elements used to model carrier diffusion and the recombination process. The pole-residue model is capable of providing an increasingly accurate approximation to the characteristics of a diode under all operating conditions. The diode recovery phenomenon is simulated for illustration, and the improved accuracy is verified by comparisons with results from conventional methods and published works.

Tunability of multisection DFB lasers

Using a comprehensive multisection model taking into account spatial hole burning, we study the stability and tunability of various multielectrode DFB lasers. For each structure, we determine the emission wavelength, the output power and the spectrum as a function of the injected currents and find a good agreement with experimental results. For the first time, different structures are examined with the same model, leading to fruitful comparisons.