Evaluation of strain averaging area and strain estimation errors in a spheroidal left ventricular model using synthetic image data and speckle tracking

Background In majority of studies on speckle tracking echocardiography (STE) the strain estimates are averaged over large areas of the left ventricle. This may impair the diagnostic capability of the STE in the case of e.g. local changes of the cardiac contractility. This work attempts to evaluate, how far one can reduce the averaging area, without sacrificing the estimation accuracy that could be important from the clinical point of view. Methods Synthetic radio frequency (RF) data of a spheroidal left ventricular (LV) model were generated using FIELD II package and meshes obtained from finite element method (FEM) simulation. The apical two chamber (A2C) view and the mid parasternal short axis view (pSAXM) were simulated. The sector encompassed the entire cross-section (full view) of the LV model or its part (partial view). The wall segments obtained according to the American Heart Association (AHA17) were divided into subsegments of area decreasing down to 3 mm2. Longitudinal, circumferential and radial strain estimates, obtained using a hierarchical block-matching method, were averaged over these subsegments. Estimation accuracy was assessed using several error measures, making most use of the prediction of the maximal relative error of the strain estimate obtained using the FEM derived reference. Three limits of this predicted maximal error were studied, namely 16.7%, 33% and 66%. The smallest averaging area resulting in the strain estimation error below one of these limits was considered the smallest allowable averaging area (SAAA) of the strain estimation. Results In all AHA17 segments, using the A2C projection, the SAAA ensuring maximal longitudinal strain estimates error below 33% was below 3 mm2, except for the segment no 17 where it was above 278 mm2. The SAAA ensuring maximal circumferential strain estimates error below 33% depended on the AHA17 segment position within the imaging sector and view type and ranged from below 3–287 mm2. The SAAA ensuring maximal radial strain estimates error below 33% obtained in the pSAXM projection was not less than 287 mm2. The SAAA values obtained using other maximal error limits differ from SAAA values observed for the 33% error limit only in limited number of cases. SAAA decreased when using maximal error limit equal to 66% in these cases. The use of the partial view (narrow sector) resulted in a decrease of the SAAA. Conclusions The SAAA varies strongly between strain components. In a vast part of the LV model wall in the A2C view the longitudinal strain could be estimated using SAAA below 3 mm2, which is smaller than the averaging area currently used in clinic, thus with a higher resolution. The SAAA of the circumferential strain estimation strongly depends on the position of the region of interest and the parameters of the acquisition. The SAAA of the radial strain estimation takes the highest values. The use of a narrow sector could increase diagnostic capabilities of 2D STE.

Drying Tectona grandis boards using the simulating solar kiln conditions technique

Timber cracking, drying stress residuals, and the change of moisture content profile were investigated during the drying of Tectona grandis boards in a conventional laboratory kiln. The study applied a technique that simulated solar kiln conditions using a conventional laboratory kiln to dry timber, based on Vientiane’s climatic conditions (Laos). The theoretical recharge and discharge model was used to generate the potential drying schedule for the Vientiane area; then the drying schedule was mimicked in a conventional laboratory kiln. Timber cracking and drying stress residual were monitored and measured using Image J software, and the change of moisture content profile was determined, based on the oven dry method. Measured moisture content data were compared with the theoretical drying model. The results showed that teak boards, of 25 mm thick, had no cracking. The drying stress residual was 0.8 ± 0.3 mm with the maximum of 1.53 mm. The initial average moisture content of 62% decreased to 12% within 16 d, while the case and core moisture contents reached 12% and 14%, respectively. The drying model described the changes of moisture content profile during drying, with a maximal error of 5%.

A new hybrid radiative transfer method for massive star formation

Context. Frequency-dependent and hybrid approaches for the treatment of stellar irradiation are of primary importance in numerical simulations of massive star formation. Aims. We seek to compare outflow and accretion mechanisms in star formation simulations. We investigate the accuracy of a hybrid radiative transfer method using the gray M1 closure relation for proto-stellar irradiation and gray flux-limited diffusion (FLD) for photons emitted everywhere else. Methods. We have coupled the FLD module of the adaptive-mesh refinement code RAMSES with RAMSES-RT, which is based on the M1 closure relation and the reduced speed-of-light-approximation. Our hybrid (M1+FLD) method takes an average opacity at the stellar temperature for the M1 module, instead of the local environmental radiation field. Due to their construction, the opacities are consistent with the photon origin. We have tested this approach in radiative transfer tests of disks irradiated by a star for three levels of optical thickness and compared the temperature structure with the radiative transfer codes RADMC-3D and MCFOST. We applied it to a radiation-hydrodynamical simulation of massive star formation. Results. Our tests validate our hybrid approach for determining the temperature structure of an irradiated disk in the optically-thin (2% maximal error) and moderately optically-thick (error smaller than 25%) regimes. The most optically-thick test shows the limitation of our hybrid approach with a maximal error of 65% in the disk mid-plane against 94% with the FLD method. The optically-thick setups highlight the ability of the hybrid method to partially capture the self-shielding in the disk while the FLD alone cannot. The radiative acceleration is ≈100 times greater with the hybrid method than with the FLD. The hybrid method consistently leads to about + 50% more extended and wider-angle radiative outflows in the massive star formation simulation. We obtain a 17.6 M⊙ star at t ≃ 0.7τff, while the accretion phase is still ongoing, with a mean accretion rate of ≃7 × 10−4 M⊙ yr−1. Finally, despite the use of refinement to resolve the radiative cavities, no Rayleigh–Taylor instability appears in our simulations, and we justify their absence by physical arguments based on the entropy gradient.

Influence of Wilbraham-Gibbs Phenomenon on Digital Stochastic Measurement of EEG Signal Over an Interval

Measurement methods, based on the approach named Digital Stochastic Measurement, have been introduced, and several prototype and small-series commercial instruments have been developed based on these methods. These methods have been mostly investigated for various types of stationary signals, but also for non-stationary signals. This paper presents, analyzes and discusses digital stochastic measurement of electroencephalography (EEG) signal in the time domain, emphasizing the problem of influence of the Wilbraham-Gibbs phenomenon. The increase of measurement error, related to the Wilbraham-Gibbs phenomenon, is found. If the EEG signal is measured and measurement interval is 20 ms wide, the average maximal error relative to the range of input signal is 16.84 %. If the measurement interval is extended to 2s, the average maximal error relative to the range of input signal is significantly lowered - down to 1.37 %. Absolute errors are compared with the error limit recommended by Organisation Internationale de Métrologie Légale (OIML) and with the quantization steps of the advanced EEG instruments with 24-bit A/D conversion

Simulation of the Space Turntable Angular Velocity Measurement

For better design and control of the space turntable, a model for measuring its angular velocity was built. The model utilized a two-axis space turntable to perform the simulation basing on the coordinate conversion theory. The measuring simulation went on with the help of MATLAB software using different carrier attitude angles. It shows the maximal error in the sub astral point longitude and/or latitude is 0.00785 degrees when comparing with the STK results, certifying the validity of the models. The satellite attitude angles have influence on the angular velocity, the maximal azimuth angular velocity is 3.784 deg per sec, yet the elevation's is 0.6945 deg per sec when the attitude angles are all 20 degrees. This simulation process provides some guidance for designing, controlling and calibrating the space turntable.

Research on the Meter Coefficient and Simulation Analysis of a New Swirlmeter

The configuration of a new swirlmeter is designed. The hollow cylindric fluid axial-symmetrically in cylindric pipe is analyzed, and then the algebra expression of meter coefficient is deduced. An impeller of swirl generator attaching to a specimen of swirlmeter is designed according to the deducing process. Simulations and experiments test the method of measuring flowrate by measuring the rotation frequency of ball is feasible. Comparing the results of simulations and experiments with that of algebra expression derived from deducing in theory the maximal error is 7.8%. At last, the reasons resulting in the errors are discussed which the next researches will continue to minus the errors. The conclusion will be applied in designing the impeller of swirl generator and measuring the flow by the new swirlmeter.

Experimental Study on the Shaft Laser Cladding Bending and the Establishment of the Empirical Formula

In order to study the influence of the layer of the laser cladding to the bending degree, obtain the mathematical formulation in shaft laser cladding bending and derive the empirical formula, the laser cladding test for shaft was designed. The laser cladding test had been proceeded at the same cladding area and different layer of cladding. The results of the experiment show that the shaft is bended facing the laser beam. The bending degree and the layer of laser cladding are at the direct proportion. At the same time mathematical formulation in shaft laser cladding bending has been established and the parameter which is used to measure the degree of the bending has been obtained. Empirical formula between bending degree and the layer of laser cladding has been established. The circular run-out formula along the shaft length has been derived. The calculated value and the measured value are of the goodness fit. The maximal error is 0.035mm, and the average error is 0.017mm. It illustrates that the mathematic formulation is correct and the empirical formula has high accuracy.