On-line Measurement Method Research Articles

Online Measurement Method of Water Quality in the Sulejow Reservoir

Abstract The paper presents methodology of accurate mobile measurements of water quality parameters such as temperature, dissolved oxygen, chlorophyll “a” concentration, ammonium ion concentration, conductivity, pH and blue-green algae content in water. The measurements (probe EXO 2, YSI, USA) were made on various depths of probe immersion (1.5, 2.5 and 3.5 m) and at different towing speeds of the probe (approx. 5.4 and 9.0 km/h). Static measurements carried out on the same route provided reference values for the measurements in motion to compare the repeatability of static and mobile methods. The tests were also evaluated by observation of probe behavior in motion, e.g. water disturbance intensity, access of light (sun rays) to the sensors. Statistical tests confirmed that the mean values of water quality parameters from mobile measurements with the speed of 5.4 km/h at the depth 1.5 m does not differ from the stationary measurements. Results of statistical analysis prove that water quality parameters can be measured accurately keeping established speed of towing the probe at the fixed depth. Methodology of mobile measurements elaborated in the frame of this work allows to collect vast number of data which can be used to obtain GIS point maps of water quality parameters in large water bodies.

Determination of tubular material parameters in bulging test with three-dimensional digital image correlation method

Tubular material parameters play a major role in part manufactory process planning and reliable finite element simulations. The hydraulic bulging test is one of the most credible ways to determinate tubular material properties, especially flow stress. In this paper, an on-line measurement method based on three-dimensional (3D) digital image correlation method (DIC) is applied to determinate material parameters of tube using Swift law. Both a practical bulging machine and a self-developed measurement system are introduced. The free-bulging test is performed for AlMg2.5 aluminum alloy tube. The axial curvature radius is calculated by extracting the bulging profile based on the cosine model and the axial strain is computed accurately by tracking a series of points around the pole dome. Finite element simulations on tube are conducted to validate the method. The results indicate that the material parameters obtained from the present method are reliable to define the flow stress in the tube hydroforming process.

Investigation on the generation of the waviness errors along feed-direction on flycutting surfaces

Ultra-precision single-point diamond flycutting (SPDF) is an irreplaceable technology for cutting KH2PO4 (KDP) crystals with large size. However, some undesirable waviness errors along feed-direction exist on the machined surface, which could greatly deteriorate the optical performance of KDP crystals. The spindle dynamic characteristic of SPDF plays an important role in the formation of such waviness errors. This paper presents an on-line measurement method with five-capacitance displacement sensors in nanometer range for monitoring the motion errors of the aerostatic spindle. An error transform theory which is based on kinematic error propagation was introduced to obtain the three-dimensional trajectory of the cutting tool. Then, the spindle motion errors and the cutting tool trajectory were analyzed in frequency domain to investigate the main source of the waviness errors. Simultaneously, the three-dimensional topography of work-piece was simulated by combining the motion trajectory and the geometrical morphology of the cutting tool. The results showed that the waviness errors along feed-direction were caused by the spindle rotation fluctuation with a frequency about 10.8 Hz, and the topography simulations showed good agreement with the machining results. Besides, the experimental results indicated that the error can be diminished by changing the spindle control system to the digital control method. This study established the contact between the measured spindle motion errors and the machined surfaces, which contributes to deeper understanding of the dynamic characteristics of the spindle in SPDF.

Measurement of liquid water film thickness on opaque surface with diode laser absorption spectroscopy

Liquid film is usually formed on opaque surfaces in various industrial processes, and the investigation of liquid film is very important for understanding and optimization of the relevant processes. Here, a novel on-line measurement method based on diode laser absorption spectroscopy (DLAS) was developed to determine the film thickness on opaque surfaces. The evaporation process of static liquid films both on a silver-coated mirror (smooth opaque surface) and an aluminum alloy plate (rough opaque surface) were investigated with the proposed method. Ultrasonic pulse-echo method (UPEM) was simultaneously applied to validate the measurement accuracy of DLAS method, it revealed that the average thickness deviation between these two methods during film evaporation process on silver-coated mirror were 4.9% and on aluminum alloy plate were 7.1%, respectively. A flow liquid film on aluminum alloy surface was then studied, it was found that the average thickness deviation between DLAS and UPEM at low flow speed were 6.5% and at higher flow speed were 9.5%, respectively. And the fluctuation frequency of the liquid film at both flow speeds were also in good agreement with these two methods.

Smart NMR Method of Measurement of Moisture Content of Vegetables During Microwave Vacuum Drying

Microwave drying is usually combined with vacuum environment in conjunction with hot air flow to draw the moisture rapidly. The moisture content of the vegetables undergoing drying is hard to measure online. This research designed a microwave vacuum drying (MVD)-low-field nuclear magnetic resonance (NMR) smart device and investigated the feasibility of NMR method for online measurement of state of moisture during MVD. The relation between the signal amplitude (A 2) and the true moisture content (M 1) of six kinds of vegetables (mushroom, carrot, potato, lotus, edamame, vegetable corn) was fitted to estimate if NMR can measure the M 1 of vegetables directly. Results showed that A 2 and M 1 of different fresh vegetables had no single empirical mathematical model to fit. However, for each kind of these vegetables, the A 2 and corresponding M 1 in different MVD stages showed a significant linear relationship. The predicted moisture content (M 2) of mushroom: M 2 = 5.25351 × 10−4 A 2 − 0.34042, R = 0.996; carrot: M 2 = 5.78756 × 10−4 A 2 − 0.14108, R = 0.998; potato: M 2 = 3.10019 × 10−4 A 2 − 0.10612, R = 0.991; lotus: M 2 = 2.32415 × 10−4 A 2 − 0.01573, R = 0.998; edamame: M 2 = 3.13310 × 10−4 A 2 − 0.4198, R = 0.996; vegetable corn: M 2 = 1.69461 × 10−4 A 2 − 0.09063, R = 0.995. The linear models between M 2 and A 2 were able to estimate the end point (M 1 0.950).

Development of a geometric surface area monitor (GSAM) for aerosol nanoparticles

Although geometric surface area (GSA) of nanoparticles has received much attention in many fields (drug delivery, catalysts, inhalation exposure, toxicity, etc.), no appropriate instruments and methods for online measurements of GSA are readily available. Therefore, this study intends to develop a Geometric Surface Area Monitor (GSAM) to measure the GSA of spherical as well as model agglomerate/aggregate nanoparticles in nearly real-time. The GSAM consists of several existing techniques in series, including inertial impaction, unipolar charging, electrostatic precipitation, and electrical current measurement. The GSAM was first evaluated and calibrated by measuring the GSA of monodisperse nanoparticles. Spherical, aggregate, and agglomerate nanoparticles were tested in the calibration. It was found that the measured electrical current was proportional to the surface area concentration. The calibration curves obtained from the measurements of monodisperse particles was then applied for polydisperse spherical particles and compared the measured GSA with that determined by the well-known scanning mobility particle sizer (SMPS) where the GSAM had less than 10% of deviation compared with SMPS.

Quantitative on-line analysis of sulfur compounds in complex hydrocarbon matrices

An improved method for on-line measurement of sulfur containing compounds in complex matrices is presented. The on-line system consists of a specifically designed sampling system connected to a comprehensive two-dimensional gas chromatograph (GC×GC) equipped with two capillary columns (Rtx®-1 PONA×SGE BPX50), a flame ionization detector (FID) and a sulfur chemiluminescence detector (SCD). The result is an unprecedented sensitivity down to ppm level (1 ppm-w) for various sulfur containing compounds in very complex hydrocarbon matrices. In addition to the GC×GC-SCD, the low molecular weight sulfur containing compounds such as hydrogen sulfide (H2S) and carbonyl sulfide (COS) can be analyzed using a thermal conductivity detector of a so-called refinery gas analyzer (RGA). The methodology was extensively tested on a continuous flow pilot plant for steam cracking, in which quantification of sulfur containing compounds in the reactor effluent was carried out using 3-chlorothiophene as internal standard. The GC×GC-FID/-SCD settings were optimized for ppm analysis of sulfur compounds in olefin-rich (ethylene- and propylene-rich) hydrocarbon matrices produced by steam cracking of petroleum feedstocks. Besides that is primarily used for analysis of the hydrocarbon matrix, FID of the GC×GC-FID/-SCD set-up serves to double check the amount of added sulfur internal standard which is crucial for a proper quantification of sulfur compounds. When vacuum gas oil containing 780 ppm-w of elemental sulfur in the form of benzothiophenes and dibenzothiophenes is subjected to steam cracking, the sulfur balance was closed, with 75% of the sulfur contained in the feed is converted to hydrogen sulfide, 13% to alkyl homologues of thiophene while the remaining 12% is present in the form of alkyl homologues of benzothiophenes. The methodology can be applied for many other conversion processes which use sulfur containing feeds such as hydrocracking, catalytic cracking, kerogen evolution, bio-waste pyrolysis, supercritical water treatment, etc.

A new method for online measurement of the concentration of working fluids in absorption refrigeration systems

This paper proposes a new method for online measurement of the concentration of working fluids in absorption refrigeration systems: electrical conductivity is measured to determine the concentration of the solution. Compared with the common density-concentration method, electrical conductivity-concentration method has the same accuracy but helps to save cost when applied in absorption systems with ammonia–salt solutions. This novel method is also suitable for systems with traditional working fluids like water–lithium bromide solution. Electrical conductivities of ammonia–lithium nitrate, ammonia–sodium thiocyanate and water–lithium bromide solutions were measured between (293.15 and 333.15) K, using an Industrial Conductivity Meter. The ammonia mass fraction varied from 0.35 to 0.48 for ammonia–lithium nitrate solution and from 0.35 to 0.50 for ammonia–sodium thiocyanate solution. For water–lithium bromide solution, the mass fraction of lithium bromide was within the range of 40%–60%. The experimental data were correlated as a function of temperature and composition using the extended Casteel–Amis equation. In addition, correlations of refrigerant mass concentration as a function of electrical conductivity and temperature of the solution are proposed.

Measurement and modelling of mass transport properties during the supercritical fluid extraction of emulsions

Supercritical fluid extraction of emulsions (SFEE) is a method used for producing aqueous suspensions, containing encapsulated particles in nanometric scale, through the extraction of an organic phase from an emulsion with supercritical CO2. Optimization of SFEE process conditions is complex as they influence several process steps. In this work, ethyl acetate and dichloromethane o/w emulsions were prepared using soybean lecithin and polaxamers as surfactants and contacted with supercritical CO2. Mass transport properties were measured by magnetic suspension balances, which provide an on-line contactless weight measurement method, and a mass transfer model based on the experimental results was developed. Experimental results indicate that the density of supercritical CO2 has a strong influence in mass transfer parameters, while no influence of other conditions such as type or concentration of surfactant was observed. In the case of dichloromethane/water emulsions, emulsion destabilization took place immediately after pressurization of the system.

A prediction-correction scheme for microchannel milling using femtosecond laser

In this paper, a prediction-correction scheme is proposed to online measure and regulate the milling depth of microchannel using an indicator of laser triggered plasma. Firstly, a prediction model, with respect to the laser fluence and feedrate, is established with several calibration tests using the least square fitting method. It is utilized to change the focal position of objective to track the depth evolution of newly generated surface. Meanwhile, a scanning path for every milling layer with an offset in Z-axis at the beginning and the end of the trajectory, is developed to drive the plasma brightness periodically changing. Then, the milling depth could be obtained when the brightness reaches to the maximum value. By doing so, an online measurement method is presented to estimate the milling depth using the trend of plasma brightness. Furthermore, a correction model is developed to iteratively adjust the feedrate with the online estimated depth. Therefore, the microchannel milling process could be monitored and controlled in a closed-loop manner, in order to accurately regulate the milling depth. Finally, an online measurement and closed-loop microchannel milling is carried out on the self-developed micro-machining center. The effectiveness and correctness of the proposed method are verified by comparing the estimated depth with the actually measured results.

Energy absorption and reaction mechanism for thermal pyrolysis of n-decane under supercritical pressure

In this work, the behavior of mild thermal cracking n-decane was investigated experimentally and numerically. A developed experimental method of electrical heating tube was used to analyze the thermal cracking of n-decane under various temperatures and pressures. The results showed that, at low cracking conversion of 12%, the selectivities of all cracked products are approximately equal to constant values. A one-step global reaction model consisting of 11 species was established for mild-cracking n-decane and a novel on-line density measurement method was developed to improve the precision of residence time calculation, thus the kinetics parameters. The reliability of the reaction model was confirmed through comparing the experimental results with simulated values by using Chemkin program with the deviation less than 10%. The chemical heat sink of thermal cracking n-decane was evaluated and the result showed that the heat absorption provided by chemical endothermic reactions is unnegligible even at low conversion.

The outer diameter detection and experiment of the circular forging using laser scanner

Under the two backup rolls and two rotary rolls, the circular forging is in the rotating state. The continuous rolling of the forging is achieved by cylindrical shell rolling mill. However, the outer diameter detection device is lack during rolling. So the online measurement method of outer diameter and outer diameter shape reconstruction is proposed in this paper. Because the circular forging is rolling all the time, the time sharing scanning is adopted in this measurement method using laser scanner. The scanning of the same cross section is realized though multiple times sharing scanning. The outer diameter shape reconstruction and the size of diameter are realized according to the data processing of multiple scanning. Meanwhile, the maximum, minimum, and average of the outer diameter is measured by this method. This measuring method is feasibility via the experimental measurements in the laboratory and cylindrical shell rolling mill site.

An On-line Automatic Flow Measurement Method for an Open Channel under Complex Flow Conditions

An On-line Automatic Flow Measurement Method for an Open Channel under Complex Flow Conditions

Crack-free ductile mode grinding of fused silica under controllable dry grinding conditions

A crack-free ductile mode grinding of fused silica was realized by a controllable dry grinding process in this research, which is attributed to the improvement of fused silica's ductile machinability induced by the high grinding temperature. The plastic deformation of fused silica consists of shear flow and densification. Plastic deformation mechanisms and cracking behaviors related to densification were investigated firstly by high temperature nanoindentation experiments to reveal the ductile–brittle transition mechanisms. Fused silica exhibits less densification and more shear flow at high temperature than room temperature. The critical ductile–brittle transition load of fused silica is higher at high temperature than room temperature. These results may lead to the improvement of the fused silica's ductile machinability at high temperature. Dry grinding experiments were conducted to investigate the effect of grinding depth. A mathematical model is established to predict the maximum temperature in workpiece. A novel infrared radiation (IR) transmission on-line measurement method was presented to acquire the workpiece temperature in the contact zone directly. The predicted results coincide well with the experiment results. Contrary to the conventional experience, a large grinding depth is beneficial for the surface quality and integrity in the dry grinding of fused silica due to the increased grinding temperature; however, the excessive grinding depth results in grinding wheel burn. The ductile grinding depth of the fused silica increases from sub-micrometers to 5μm by dry grinding which makes the grinding process more controllable and effective.

Probe sampling to map and characterize nanoparticles along the axis of a laminar methane jet diffusion flame

Nanoparticles generated by a laminar methane jet diffusion flame were characterized by direct sampling through the pinhole of a probe and sized with a nano-scanning mobility particle sizer. Particular attention was paid to verify the validity of the probe-sampling technique. Results showed that the particle size distributions (PSD) were strongly affected by sample dilution immediately after extraction. Within the flame, the soot PSD did not become independent of dilution ratio until the sample was diluted several thousand times (depending on initial concentration) within a few milliseconds of extraction. A method for on-line measurement of dilution ratio was also introduced by measuring CO2 concentration continuously during the tests.High spatially resolved experimental results at different heights (typically 1mm apart) along the central axis of the flame showed the evolution of PSD for particles larger than 2nm covering early nucleation and growth to oxidation regions. Moving upward from the fuel-side, prior to the visible flame, the PSD in the particle nucleation region was bimodal (with one of the modes being smaller than 2nm) and gradually turned into a unimodal PSD with a median of 10nm due to particle growth. Nearer to the visible flame, the PSD became bimodal again with the larger-diameter mode growing in magnitude and being made up of ever-larger particles, while the smaller-diameter mode gradually shrunk in size until it vanished. Eventually, as the flow was leaving the visible flame, all the particles gradually oxidized until at the tip of the flame they reached a median diameter of 9nm and in very low concentrations.

Measurement of laser power for photo-triggered drug delivery in vivo

Thus far, despite many investigations have been carried out for photo-triggered drug delivery systems, most of them suffer from an intrinsic drawback of without real-time monitoring mechanism. Incident intensity of light is a feasible parameter to monitor the drug release profiles. However, it is difficult to measure the incident laser power irradiated onto the photo-triggered carriers in drug delivery systems during in vivo therapy. We design an online measurement method based on the fluorescence intensity ratio (FIR) technique through upconversion nanoparticles. FIR value varies with temperature of sample due to the thermal effect induced by the incident laser, which validates the laser power measurement. Effects of rare earth doping concentration, as well as experimental conditions including laser spots and wavelengths on the measurement behavior were also investigated.

On-line three-dimensional point cloud data extraction method for scan-tracking measurement of irregular surface using bi-Akima spline

Abstract Point cloud data extraction is an important process in scan-tracking measurement. In this paper, a new method of on-line three-dimensional point cloud data extraction for scan-tracking measurement is proposed for reducing extremely dense sampled data while maintaining data accuracy during the real-time scan-tracking measuring process. It is inspired from sketch paintings: First outlining the broad contour of the curve and then revising local details till the interpolated curve satisfies the required accuracy. This method adopts bi-Akima spline interpolation for connecting acquired points in NC machining or for point data fitting in reverse engineering. It can reduce efficiently the amount of point data with a smaller data reduction ratio and a smoother machined/fitted surface than conventional three-dimensional chordal method.

탄두의 콘크리트 표적관통 시 주장약에 전파되는 압력의 수치해석

This paper is concerned with the numerical simulation result of pressure propagation to the main charge by warhead penetration into concrete targets. In this study, we developed on-line pressure measurement method in the main charge during warhead penetration. Using the on-line pressure measurement method, we successfully recorded the pressure-time history in the main charge during the field penetration test. Then we compared result of numerical simulations with test data and found that the simulation results are in good agreement with the test results. Finally, through the numerical calculations it is concluded that the installation of liner is effective in reducing pressure level produced in the main charge.

An on-line adaptive estimation method for water holdup measurement in oil–water two-phase flow with a conductance/capacitance sensor

Oil–water two-phase flow widely exists in industrial processes such as petroleum engineering and chemical engineering. Accurate and real-time measurement of water holdup is an important problem requiring urgent solutions. In this work, a conductance and capacitance combination sensor (CCCS) system with four conductance rings and two concave capacitance plates was validated for its measurement performance of in situ water holdup through dynamic experiments. An online adaptive weight Kalman estimation (OAWKE) fusion algorithm for the CCCS system is proposed to fuse the conductance measurement and capacitance measurement. The algorithm has fast and dynamic response for the water holdup measurement of oil–water two-phase flow and has improved measurement precision by the adaptive data fusion method. The OAWKE fusion algorithm also has the ability to deal with the abrupt change of water holdup during the measurement process. Therefore, in the low water conductivity condition (tap water), the CCCS system with the OAWKE fusion algorithm can dynamically estimate the real-time full range water holdup of oil–water two-phase flow, which has prospects in the petroleum industry.

Laser-induced fluorescence method for on-line molecular isotopologues of iodine-127, iodine-129, iodine-131 detected in gaseous media using a tunable diode laser

The letter reports on the development of a laser-induced fluorescence method for on-line selective measurement of 127I2, 129I2, 131I2, 129I127I, 127I131I, 129I131I isotopologue concentrations in gaseous media. The method is based on the excitation of molecular iodine isotopologues’ fluorescence by tunable diode laser (632–637 nm) radiation at three or four wavelengths corresponding to the 127I2, 131I2, 129I127I, 129I131I absorption line centers. Boundary relations for concentrations of simultaneously measured iodine isotopologues is about 10−5–10−6.