Carvajal, Sergio A.Medina, Andres F.Bohorquez, Andres J.Sanchez, Ciro A....
7页
查看更多>>摘要：The determination of calibration intervals of instruments is an important task for assuring confidence in mea-surements. The methods available to estimate these intervals usually require a large database or are based on non-probabilistic approaches. Given the limitations related with the collection of data, it is highly desirable to include in the analysis previous knowledge about the performance of the instrument, this can be done through Bayesian inference. This paper presents an approach based on this method which combines robust techniques for estimation of calibration intervals with commonly available metrological information such as tolerance, speci-fications or experimental data of similar instruments. The proposed approach can be used with a small sample size contrary to other methodologies that are not adequate for this purpose.
查看更多>>摘要：Online relative location measurement of spatial geometric features is necessary for the high-precision manufacturing of long rotating parts. However, existing methods are imperfect because they are limited by the rotation state of the measured object or the measurement allowable space. To solve these problems, this study proposes a robust online measurement approach based on angle and size transfer, size transfer and analytical geometry theories. A polyhedral prism is used to synchronously calibrate the zero position of the laser displacement sensor, then a geometric model of the rotation angle corresponding to the sensor displacement change is established. Using only the displacement data, the 3-D relative location of multiple geometric features on different parallel planes is deduced by analytical geometry theory. The phase angle measurement of a diesel engine camshaft was used to verify the method. The results show that the method has high measurement precision, good stability and high efficiency.
查看更多>>摘要：This study aims to provide some references on understanding the uniaxial compression behaviors of concrete corroded by sulfuric acid. Six groups of concrete cylinder specimens were immersed in sulfuric acid solution with pH approximate to 0.95 for different days. 3D laser scanning technology was applicated to obtain 3D coordinates of the points on the corroded cylindrical surface. The irregular cross sectional areas of each specimen were calculated at intervals of 1 mm along the longitudinal axis by MATLAB. The elastic modulus, peak strain, ultimate strain and peak stress were calculated through the experimental complete stress-strain curves. It showed that as the corrosion time increased, the elastic modulus, peak strain and peak stress gradually decreased. The ultimate strain decreased first and then increased over time. The parameters of the stress-strain model including the ascending and descending stages were obtained by fitting the experimental data. The relationship between the mechanical properties and mass loss was explored.
查看更多>>摘要：The premise of improving the ride comfort of all-terrain crane by controlling the active suspensions is to realize the accurate identification of the road level. Existing researches on road level identification using vehicle responses are mostly based on small vehicles with two axles, while few researches on multi-axle large vehicles. This paper analyzes the response parameters of all-terrain crane when driving on typical roads, and proposes a method of road level identification based on the Support Vector Machine (SVM) by using the data of oil pressure and displacement of active suspensions. The training of SVM is completed by using the models of random road and all-terrain crane to generate the response information of vehicle traveling on each level of road. The accuracy of the models and the identification results are verified. The verified results on an independent test set show that the identification accuracy of road level can reach 98%.
查看更多>>摘要：Crown gall is one of the destructive diseases of Rosa hybrida L. caused by Agrobacterium tumefaciens. Development of galls leads to an overall weakness, reduction in foliage, water stress, and loss of vigor of the infected plants. We have designed an electrochemical DNA-based biosensor for T-DNA detection. Pencil graphite electrode (PGE) was modified with a nanocomposite including reduced graphene oxide (RGO) and Au nanoparticles. The biosensor sensing element consists of a single-stranded DNA (ss-DNA) from the tms2 gene which binds to thiol gold nanoparticles (GNPs). Under the optimal experiments, the proposed biosensor displayed a wide linear range from 1.0 x 10-13 to 1.0 x 10-9 M with a limit of detection (LOD) of 0.87 x 10-13 M towards target DNA. Experimental analysis on real samples confirmed its application. The proposed biosensor showed an easy and quick detection with high efficiency which was specific to T-DNA contamination of A. tumefaciens, and exhibited high reproducibility and stability.
查看更多>>摘要：Experimentally, X-ray production cross-sections are measured, but ionization cross-sections are calculated theoretically. The uncertainty of the measured L X-ray production cross-section is mainly statistics and detector-efficiency driven. But the experimental ionization cross-section involves many other factors because the relationship between the production and ionization cross section involves various atomic parameters and thus its uncertainty equation is complex. Consequently, determining the measurement uncertainty in L subshell ionization cross-section is always difficult. We have studied this issue in the simplest way, where the rule of weighted propagation of relative uncertainty is utilized. We notice that larger uncertainties are involved in atomic parameters relevant to L-1 (2s(1/2)) subshell than those associated with the other two L-2 (2p(1/2)) and L-3 (2p(3/2)) subshells. Hence, comparison between theory and experiment would give higher emphasis on L-2 and L-3 subshell ionization cross sections. We believe this work makes us aware that the appropriate uncertainty evaluation is extremely important for providing the right judgement on the data.
查看更多>>摘要：The optimization of the combustion process in internal combustion engines requires a thorough knowledge of the phenomena that take place inside injection system components responsible for fuel delivery. The beginning and end of fuel injection is difficult to accurately determine because fuel is delivered at very high pressure, the displacement of moving components generally does not exceed 500 mu m. The article proposes an original solution for accurate and reliable measurement of the displacement of an injector's moving components. Injector characteristics can be accurately described based on the registered values of displacement and the electrical pulse that controls injector opening. A mathematical model that describes injection processes and accounts not only for electric and hydraulic phenomena, but also for the pressure-induced strain of the control piston was also proposed. The model was developed on the assumption that injection pressure is propagated by the fuel supply line and the injector's moving components. The conducted measurements and modeling results indicate that the deformation of the control piston and pressure propagation resulting from changes in fuel pressure significantly affect the injector's operating parameters. This aspect has been largely neglected by the research studies conducted to date.
查看更多>>摘要：Longitudinal ultrasonic vibration-assisted milling (LUVAM) was performed to improve the machinability and surface quality of titanium alloys Ti-6Al-4V under dry conditions. Effects of ultrasonic amplitude on the three component cutting forces, cutting temperature, surface topography and 3D surface roughness (Sa and Sq) were investigated. The results show that, the cutting forces in both longitudinal and feed directions decrease with the increasing amplitude from 0 to 6 mu m, as well as the average and maximum cutting temperature. Accordingly, the surface topography of Ti-6Al-4V becomes more uniform when ultrasonic amplitude reaches to 6 mu m. Sa and Sq decrease by 35.1% and 34.0%, respectively, when the ultrasonic amplitude increases from 0 to 6 mu m. The machinability and surface quality of Ti-6Al-4V are improved via this dry LUVAM, duo to the thermal-mechanical coupling resulted from large-amplitude ultrasonic vibration. The established approaches have potential applications in dry or near dry cutting of difficult-to-machine alloys with LUVAM.
查看更多>>摘要：In the underwater SINS/DVL integrated navigation system, the calibration problem between SINS and DVL sensors is one of the critical factors affecting the accuracy of integrated navigation. Traditional calibration methods usually require long-term filter estimation or require the vehicle to operate specific maneuvers, which have limitations. In this paper, a DVL calibration algorithm using a particle swarm optimization (PSO) algorithm is proposed. The SINS/GPS integrated navigation velocity and DVL output velocity are constructed into two point sets, thereby converting the calibration problem into a Wahba problem and using the particle swarm optimization algorithm to solve the optimal rotation matrix. Simulation experiments and semi-physical experiments show that the proposed calibration method can quickly and accurately estimate the scale factor and installation misalignment angle between SINS and DVL sensors, and the integrated navigation accuracy after calibration is significantly improved. Compared with the conventional calibration approaches, the calibration performance of the proposed method is better.
查看更多>>摘要：This study presents a fiber optic liquid level sensor (FOLLS) by acquiring information from the amplitude of spectral fast Fourier transform (FFT) in a specified narrow wavelength range. The sensing light path is simply formed by embedding a section of Panda-type polarization-maintaining fiber (PMF) into the sensing arm of a conventional Michelson interferometer (MI) structure. The output composite spectrum consists of two parts: the fine interference fringes due to MI optical path difference (OPD) and the envelope fringes stemming from the PMF's birefringence. By applying liquid level variations on the sensing structure, shifts in envelope wavelength indicate a sensitivity of-0.193 nm/cm, and a liquid level resolution of 1 mm can be easily acquired. Furthermore, by demodulating the amplitude after spectral FFT in a specific narrow wavelength range, and intensity sensitivity of 1.906 dB/cm is achieved, leading to a greatly improved overall resolution of 0.03 mm in liquid level measurement. Besides, the sensing element is sealed and packaged by two sheets of silicone rubber, which can be thrown into liquid when in use, thus easing the sensor installation. Moreover, due to the proposed demodulation method, the sensor is insensitive to the light source power jitter, reference arm phase shift and optical spectral analyzer wavelength shift. Therefore, the merits of the proposed sensor include high precision, high stability, ease of installation, which are beneficial in pore water pressure and liquid level monitoring.
NSTL
Elsevier