Estimation of structure crack propagation based on multiple factors correction

By deriving the stress concentration factor of theestimation approach for residual fatigue life’ an estimationapproach for structure crack propagation based on multiplefactors correction is proposed. Then’ the quantitativeexpression among the structure factor’ stress ratio’ loadingtype’ the manufacture processing factor and the crackpropagation is achieved. The proposed approach iimplemented in a case study for an instance structure’ and theinfluences of correction factors on the crack propagation areanalyzed. Meanwhile’ the probabilistic method based onWeibull distribution probability density function is selected toevaluate the precision of the corrected estimation approach’and the probability density of results is calculated by theprobability density function. It is shown that the resultsestimated by the corrected approach is more precise than thoseestimated by the fracture mechanics, and they are closer to thetest data.

Determination of velocity correction factors for real-time air velocity monitoring in underground mines

When there are installations of air velocity sensors in the mining industry for real-time airflow monitoring, a problem exists with how the monitored air velocity at a fixed location corresponds to the average air velocity, which is used to determine the volume flow rate of air in an entry with the cross-sectional area. Correction factors have been practically employed to convert a measured centerline air velocity to the average air velocity. However, studies on the recommended correction factors of the sensor-measured air velocity to the average air velocity at cross sections are still lacking. A comprehensive airflow measurement was made at the Safety Research Coal Mine, Bruceton, PA, using three measuring methods including single-point reading, moving traverse, and fixed-point traverse. The air velocity distribution at each measuring station was analyzed using an air velocity contour map generated with Surfer~. The correction factors at each measuring station for both the centerline and the sensor location were calculated and are discussed.

Research on the distribution characteristics of explosive shock waves at different altitudes

There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes.At present,there are many studies on plain explosion shock waves,but there are few studies on the distribution characteristics of plateau explosion shock waves,and there is still a lack of complete analysis and evaluation methods.This paper compares and analyzes shock wave overpressure data at different altitudes,obtains the attenuation effect of different altitudes on the shock wave propagation process and proposes a calculation formula for shock wave overpressure considering the effect of altitude.The data analysis results show that at the same TNT equivalent and the same distance from the measuring point,the shock wave overpressure at high altitude is lower than that at low altitude.With the increase in the explosion center distance of the measuring point,the peak attenuation rate of the shock wave overpressure at high altitudes is smaller than that at low altitudes,and the peak attenuation rate of the shock wave overpressure at high altitudes gradually intensifies with increasing proportional distance.The average error between the shock wave overpressure and measured shock wave overpressure in a high-altitude environment obtained by using the above calculation formula is 11.1389%.Therefore,this method can effectively predict explosion shock wave overpressure in plateau environments and provides an effective calculation method for practical engineering tests.

Simultaneous Determination of Five Components in Operculina turpethum

[Objectives]This study was conducted to establish a method for the simultaneous determination of caffeic acid, rutin, ononin, luteolin, and apigenin in Operculina turpethum(L.) S. Manso. [Methods]With ononin from O. turpethum as the internal reference, the five components were separated by HPLC, and the contents of various components were calculated according to the relative correction factors of ononin with caffeic acid, rutin, luteolin, and apigenin. Meanwhile, the calculated results of quantitative analysis of multi-components by single marker(QAMS) were compared with the determined values of the external standard method. [Results] The linear relationship of the five components in their respective ranges was good(r=0.999 9). The average recovery was in the range of 97.48%-101.05%, and the RSD values were in the range of 1.04%-2.71%. The results obtained by QAMS were close to those obtained by the external standard method. [Conclusions] The method is accurate, stable and adaptable, and can be used for the determination of five flavonoids in O. turpethum.

New scale factor correction scheme for CORDIC algorithm

To overcome the drawbacks such as irregular circuit construction and low system throughput that exist in conventional methods, a new factor correction scheme for coordinate rotation digital computer（ CORDIC） algorithm is proposed. Based on the relationship between the iteration formulae, a new iteration formula is introduced, which leads the correction operation to be several simple shifting and adding operations. As one key part, the effects caused by rounding error are analyzed mathematically and it is concluded that the effects can be degraded by an appropriate selection of coefficients in the iteration formula. The model is then set up in Matlab and coded in Verilog HDL language. The proposed algorithm is also synthesized and verified in field-programmable gate array （FPGA）. The results show that this new scheme requires only one additional clock cycle and there is no change in the elementary iteration for the same precision compared with the conventional algorithm. In addition, the circuit realization is regular and the change in system throughput is very minimal.

Experimental Investigation and Prediction Model of the Loads Exerted by Oblique Internal Solitary Waves on FPSO

By using a 30-meter-long wave flume equipped with a double-plate wave maker,a series of depression ISWs were generated in a density stratified two-layer fluid and the forces exerted by oblique internal solitary waves(ISWs)on fixed FPSO model had been measured.According to the laboratory experiments,a numerical flume taken the applicability of KdV,eKdV and MCC ISWs theories in consideration was adopted to study the force components.Based on the experimental data and the force composition,the simplified prediction model was established.It was shown that the horizontal and transversal loads consisted of two parts:the Froude−Krylov force that could be calculated by integrating the dynamic pressure induced by ISW along the FPSO wetted surface,as well as the viscous force that could be obtained by multiplying the friction coefficient Cfx(C_(fy)),correction factor K_(x)(K_(y))and the integration of particle tangential velocity along the FPSO wetted surface.The vertical load was mainly the vertical Froude−Krylov force.Based on the experimental results,a conclusion can be drawn that the friction coefficient Cf and correction factor K were regressed as a relationship of Reynolds number Re,Keulegan-Carpenter number KC,upper layer depth h1/h and ISW accident angleα.Moreover,the horizontal friction coefficient Cfx yielded the logarithmic function with Re,and transversal friction coefficient C_(fy)obeyed the exponent function with Re,while the correction factors K_(x)and K_(y)followed power function with KC.The force prediction was also performed based on the regression formulae and pressure integral.The predicted results agreed well with the experimental results.The maximum forces increase linearly with the ISWs amplitude.Besides,the upper layer thickness had an obvious influence on the extreme value of the horizontal and transversal forces.

Thermal Fission Rate Calculated Numerically by Particles Multi-passing over SaddlePoint

Langevin simulation of the particles multi-passing over the saddle point is proposed to calculate thermal fission rate. Due to finite friction and the corresponding thermal fluctuation, a backstreaming exists in the process of the particle descent from the saddle to the scission. This leads to that the diffusion behind the saddle point has influence upon the stationary flow across the saddle point. A dynamical correction factor, as a ratio of the flows of multi- and first-overpassing the saddle point, is evaluated analytically. The results show that the fission rate calculated by the particles multi-passing over the saddle point is lower than the one calculated by the particle firstly passing over the saddle point, and the former approaches the results at the scission point.

Period-doubling bifurcation in two-stage power factor correction converters using the method of incremental harmonic balance and Floquet theory

In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance （IHB） and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.

Spectral Dependence on the Correction Factor of Erythemal UV for Cloud, Aerosol, Total Ozone, and Surface Properties: A Modeling Study

Radiative transfer modal simulations were used to investigate the erythemal ultraviolet （EUV） correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors （CFEUV） for UV-A [CFEUV（A）] and UV-B [CFEUV（B）] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV（A） and CFEUV（B） were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV（A） and CFEUV（B） ranged from -5.0% to 25.0% for aerosols, and from -9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV（A） was negligible compared with that in CFEUV（B） because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions （i.e., surface albedo and surface altitude） was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%-4.1% per 0.1 albedo change, depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV（B） was twice that of CFEUV（A）, because the Rayleigh optical depth increased significantly at shorter wavelengths.

Revisiting the Bjerrum's correction factor:Use of the liquidity index for assessing the effect of soil plasticity on undrained shear strength

The undrained shear strength （su） of fine-grained soils that can be measured in situ and in laboratory isone of the key geotechnical parameters. The unconfined compression test （UCT） is widely used in laboratoryto measure this parameter due to its simplicity; however, it is severely affected by sampledisturbance. The vane shear test （VST） technique that is less sensitive to sample disturbance involves acorrection factor against the soil plasticity, commonly known as the Bjerrum＇s correction factor, m. Thisstudy aims to reevaluate the Bjerrum＇s correction factor in consideration of a different approach and arelatively new method of testing. Atterberg limits test, miniature VST, and reverse extrusion test （RET）were conducted on 120 remolded samples. The effect of soil plasticity on undrained shear strength wasexamined using the liquidity index instead of Bjerrum＇s correction factor. In comparison with the resultobatined using the Bjerrum＇s correction factor, the undrained shear strength was better representedwhen su values were correlated with the liquidity index. The results were validated by the RET, whichwas proven to take into account soil plasticity with a reliable degree of accuracy. This study also showsthat the RET has strong promise as a new tool for testing undrained shear strength of fine-grained soils.

A novel arc welding inverter with unit power factor based on DSP control

A novel inverter power source is developed characterized with constant output current and unit power factor input. Digital signal processor （ DSP ） is used to realize power factor correction and control of back-stage inverter bridge of the arc welding inverter. The fore-stage adopts double closed loop proportion and integration （PI） rectifier technique and the back- stage adopts digital pulse width modulation （ PWM） technique. Simulated waves can be obtained in Matlab/Simulink and validated by experiments. Experiments of the prototype showed that the total harmonic distortion （THD） can be controlled within 10% and the power factor is approximate to 1.

Effect of Window Opening Percentage on the Air Flow Rate of Wind-Driven Natural Ventilation Rooms

According to the investigations of window opening percentage (WOP) of Shanghai in 2011, the WOP varies significantly from season to season and thus affects the air flow rate of natural ventilation rooms. A three-dimensional computional fluid dynamic(CFD) model was applied to simulating the flow fields in a street canyon under different wind speed and WOP. The numerical simulations show that WOP has a significant influence on the static pressure distribution of the downwind building. Therefore, a correction factor k can be used for calculating the flow rate of wind-driven natural ventilation. The results show that k ranges from 0.43 to 0.49 when WOP is 4.44%; when WOP increases to 9.78%, the correction factor k lies in 0.32 and 0.36.

Analytical modelling and free vibration analysis of piezoelectric bimorphs

An efficient and accurate analytical model for piezoelectric bimorph based on the improved first-order shear deformation theory （FSDT） is developed in this work. The model combines the equivalent single-layer approach for mechanical displacements and a layerwise-type modelling of the electric potential. Particular attention is devoted to the boundary conditions on the outside faces and to the interface continuity conditions of the bimorphs for the electromechanical variables. Shear correction factor （k） is introduced to modilfy both the shear stress and the electric displacement of each layer. And the detailed mathematical derivations are presented. Free vibration problem of simply supported piezoelectric bimorphs with series or parallel arrangement is investigated for the closed circuit condition, and the results for different length-to-thickness ratios are compared with those obtained from the exact 2D solution. Excellent agreements between the present model prediction with k=-8/9 and the exact solutions are observed for the resonant frequencies.

A new high-performance AC/DC power factor correction switching converter based on one-cycle control technology and active floating-charge technology

A new family of converters,high-performance AC/DC power factor correction(PFC) switching converters with one-cycle control technology and active floating-charge technology,was derived and experimentally verified.The topology of a single-phase CCM and DCM Boost-PFC switching converter was also analyzed.Its operating prniciples and control methods were expounded.Based on these,a new type of AC/DC switching converter circuits for PFC combined with one-cycle control technology was presented herein.The proposed AC/DC switching converter significantly helps improve the converter efficiency and its power factor value.

Analytical modeling of sandwich beam for piezoelectric bender elements

Piezoelectric bender elements are widely used as electromechanical sensors and actuators, An analytical sandwich beam model for piezoelectric bender elements was developed based on the first-order shear deformation theory （FSDT）, which assumes a single rotation angle for the whole cross-section and a quadratic distribution function for coupled electric potential in piezoelectric layers, and corrects the effect of transverse shear strain on the electric displacement integration. Free vibration analysis of simplysupported bender elements was carried out and the numerical results showed that, solutions of the present model for various thickness-to-length ratios are compared well with the exact two-dimensional solutions, which presents an efficient and accurate model for analyzing dynamic electromechanical responses of bender elements.

A New Thermodynamic Calculation Method for Binary Alloys Part II:Exploring the Correction Factor Function

A new method of revising activity values has been derived based on the so called correction factor function for binary alloys with a large difference between two components. The correction factor is a function of physical properties formed by the difference of two components. Its absolute value increases with the enhancement of the difference in the character of components. It can be either positive or negative and the rules for selecting the sign of correction factor have been analyzed. Results are in good agreement with the experimental values.

Performance Evaluation of a Permanent Magnet Electric-Drive- Reconfigured Onboard Charger with Active Power Factor Correction

This paper presents a comprehensive charging operation for an electric-drive-reconfigured onboard charger(EDROC)with active power factor correction(APFC).The charging topology exclusively utilizes the three-phase permanent magnet synchronous motor(PMSM)propulsion system as a three-channel boost-type converter in which only a contactor and a small diode bridge are added.First,the operation scenario of the EDROC is introduced.Second,the relationship between electromagnetic torque and rotor position is investigated.Third,the current ripple cancellation of the EDROC is discussed in detail.Moreover,to implement the single-phase APFC along with charging voltage/current regulation of propulsion battery,control strategies including current balancing and synchronous/interleaving PWM strategies are incorporated.Finally,200W proof-of-concept prototype-based tests are conducted under different operation scenarios.

Calibration of local magnitude scale for Hindukush continental subduction zone

Hindukush is an active subduction zone where at least one earthquake occurs on daily basis.For seismic hazard studies,it is important to develop a local magnitude scale using the data of local seismic network.We have computed local magnitude scale for Hindukush earthquakes using data from local network belonging to Center for Earthquake Studies(CES)for a period of three years,i.e.2015–2017.A total of 26,365 seismic records pertaining to 2,683 earthquakes with magnitude 2.0 and greater,was used with hypocentral distance less than 600 km.Magnitude scale developed by using this data comes to be M_(L)=logA+0.929logr+0.00298r-1.84.The magnitude determined through formulated relation was compared with that of standard relation for Southern California and relation developed by the same authors for local network for Northern Punjab.It was observed that Hindukush region has high attenuation as compared to that of Southern California and Northern Punjab which implies that Hindukush is tectonically more disturbed as compared to the said regions,hence,seismically more active as well.We have calculated station correction factors for our network.Station correction factors do not show any pattern which probably owes to the geological and tectonic complexity of this structure.Standard deviation and variance of magnitude residuals for CES network determined using Hutton and Boore scale and scale developed in this study were compared,it showed that a variance reduction of 44.1%was achieved.Average of magnitude residuals for different distance ranges was almost zero which showed that our magnitude scale was stable for all distances up to 600 km.Newly developed magnitude scale will help in homogenization of earthquake catalog.It has been observed that b-value of CES catalog decreases when magnitude is calculated by using newly developed magnitude scale.

Intelligent power factor compensation equipment of three phase low voltage loads

An intelligent power factor correction scheme is presented for three phase low power factor loads. This new scheme is able to perform individual phase sensing of parameters by monitoring at all times to sense a change in system parameters and affects individual phase correction by applying the exact amount of reactive components needed for each phase, and can also reduce negative sequence current caused by the load to improve system balance. An optimization criterion is used for the proper calculation of reactive power steps in a power compensation installation of capacitor banks. The criterion is enabled by sampling measurements performed on the electrical plant examined within specific interval of time.

Implementation strategy for soft switching PFC with low output voltage

This paper proposes a novel implementation strategy for soft switching PFC whose circuit is simple and can achieve low voltage output directly. The main circuit adopts current mode full-bridge converter and all the power switches can realize ZCS or ZVS in the way of phase-shlfted control, using the leakage inductance of the transformer, the junction capacitor of the switches and the stored energy of the output capacitor. The problems such as the function of phase-shlfted link in control circuit, the implementation conditions of soft switching and bias restrained are analyzed. The adoption of constant frequency PWM control makes the design of the input and output filter link and the high frequency transformer simple. The transformation ratio regulation so as to achieve low voltage output and electrical insulation can be realized by using high frequency transformer.