Computer-controlled Data Acquisition Research Articles

Non-Uniform Drying Shrinkage in Robocasted Green Body Ceramic Products

The formation of defects, due to drying, in robocasted ceramic objects is an important issue arising from non-uniform shrinkage of the material during this step in the process. Common methods for shrinkage measurement are not well suited to the small size of robocasted cords or the complexity of robocasted objects. Innovative methods for shrinkage measurement were developed using non-destructive optical vision techniques with computer-controlled data acquisition, allowing measurement on millimetric cords and on specific zones of a product. The study of a single porcelain cord revealed an anisometric shrinkage related to the orientation of grains during extrusion. A differential shrinkage at the macroscopic scale was also measured on a robocasted object, indicating a moisture content gradient in the material. The methods presented in this paper are of particular relevance to real-time control of the drying process for robocasted objects.

Application of Laser Raman Spectroscopy of Ferroelectric Nanomaterial BaTiO3 in the Design of Color Spotlight Products on Stage

With the improvement of people’s material requirements, the demand for lighting materials is higher and higher. This study mainly discusses the application of the laser Raman spectroscopy of ferroelectric nanomaterial BaTiO3 in the design of color spotlight products on the stage. Firstly, the effects of different electrospinning parameters on BaTiO3 nanofibers were studied. Then, the samples were spun under the best spinning parameters and annealed at 600°C, 650°C, 700°C, and 750°C, and then the phase structure, morphology, and piezoelectric properties of the samples at four different annealing temperatures were characterized. In this study, the laser Raman signal converges to the incident slit of the monochromator through the lens. After grating splitting, the signal is obtained through CCD. Finally, the spectral curve is recorded by the computer-controlled data acquisition software winspec/32 and saved as an .spe file. The spectral data to be processed need to be smoothed. The luminescence intensity of BaTiO3 with flower structure is weak, which is mainly caused by the different crystal forms of the matrix. By analyzing the content of each element, it is found that BA/Ti = 1/2, and it can be inferred that the proportion of BaTiO3 and TiO2 is about 6%. The XRD spectra of the samples obtained at different temperatures (−25, 0, 30, 50, and 70°C) corresponded to the standard card BaTiO3 one-to-one, and no impurity peaks were found, indicating that the obtained samples are pure phases. This research will promote the application of nanomaterials in color spotlight products.

Digital frequency domain approach for fluorescence lifetime spectroscopy of the cornea using an enhanced confocal scanning microfluorometer

We report on enhancement to a confocal scanning microfluorometer (CSMF) for depth-resolved frequency domain lifetime spectroscopy across the cornea. Fluorescence was detected by a photomultiplier tube (PMT; R928P, Hamamatsu) and coupled to computer-controlled data acquisition module (K520, Digital Frequency Domain, ISS Inc.).The digital frequency domain (DFD) module performed acquisition of PMT pulses for further calculation of phase (ϕ) and modulation (M) in the emission of the sample, relative to excitation pulses, at 30 harmonics. As per the DFD approach, fluorescence lifetime (τ) was calculated by tanϕ =ωτ, where ω= 2πf with f being the excitation harmonic in Hz. The modulation depth can be calculated byM=1/√(1+ω2τ2). The DFD module was also used to pulse the excitation laser (450 nm; ISS Model N742) with the repetition rate of up to 10 MHz (fundamental frequency). Apart from coupling to DFD module, two other modifications were incorporated to enhance the CSMF: first, a sighting optic was constructed and placed before the PMT for rapid and precise confocal alignment of the excitation and emission slits, and second, a stepper motor was interfaced to the vertical nanostage for rapid depth scanning. These enhancements have enabled the CSMF to consistently produce a depth resolution of 7 µm during transcorneal scans with a 40x water immersion objective (Zeiss; WD = 1.2 mm, NA= 0.75). Overall, the CSMF is now capable of measuring transcorneal fluorescence lifetime with a wide array of fluorophores exhibiting lifetimes in the range of µs to nanoseconds.

Developing of an automation for therapy dosimetry systems by using labview software

Abstract Traceability, accuracy and consistency of radiation measurements are essential in radiation dosimetry, particularly in radiotherapy, where the outcome of treatments is highly dependent on the radiation dose delivered to patients. Therefore it is very important to provide reliable, accurate and fast calibration services for therapy dosimeters since the radiation dose delivered to a radiotherapy patient is directly related to accuracy and reliability of these devices. In this study, we report the performance of in-house developed computer controlled data acquisition and monitoring software for the commercially available radiation therapy electrometers. LabVIEW® software suite is used to provide reliable, fast and accurate calibration services. The software also collects environmental data such as temperature, pressure and humidity in order to use to use these them in correction factor calculations. By using this software tool, a better control over the calibration process is achieved and the need for human intervention is reduced. This is the first software that can control frequently used dosimeter systems, in radiation thereapy field at hospitals, such as Unidos Webline, Unidos E, Dose-1 and PC Electrometers.

Automatic emissive probe apparatus for accurate plasma and vacuum space potential measurements

We have developed an automatic emissive probe apparatus based on the improved inflection point method of the emissive probe for accurate measurements of both plasma potential and vacuum space potential. The apparatus consists of a computer controlled data acquisition card, a working circuit composed by a biasing unit and a heating unit, as well as an emissive probe. With the set parameters of the probe scanning bias, the probe heating current and the fitting range, the apparatus can automatically execute the improved inflection point method and give the measured result. The validity of the automatic emissive probe apparatus is demonstrated in a test measurement of vacuum potential distribution between two parallel plates, showing an excellent accuracy of 0.1 V. Plasma potential was also measured, exhibiting high efficiency and convenient use of the apparatus for space potential measurements.

Automatic emissive probe apparatus for efficient plasma potential measurements.

The improved inflection point method of emissive probe is the most accurate method for plasma potential measurements, but its manual operation is quite cumbersome and time-consuming. This paper describes the design and test of an automatic emissive probe apparatus for efficient plasma potential measurements. The apparatus consists of a computer controlled data acquisition (DAQ) card, a working circuit composed of a biasing unit and a heating unit, as well as the emissive probe. The main feature of the apparatus is that both the biasing scan and the heating scan of the probe are controlled by the computer program through analog outputs of the DAQ card, which easily realizes the required timing between the biasing and heating scans of the probe. The apparatus can automatically execute the improved inflection point method of emissive probe and give the plasma potential result. The advantages of high-accuracy, high-efficiency, and durability of probe filament make the apparatus promising for extensive use in plasma potential measurements.

Positive ion mass spectrometry for fragmentation of anthracene by low energy electron impact

SynopsisWe have studied the fragmentation of anthracene molecules induced by low energy electron impact. A reflectron time-of-flight mass spectrometer has been used to mass resolve and detect positively charged fragments. Using computer controlled data acquisition, mass spectra have been measured as a function of electron impact from 5 to 100 eV. The mass spectra show clear indications of double and triple ionization. Ion yield curves and appearance energies for most of the positive ions have been extracted from the data.

A note on calculation of efficiency and emissions from wood and wood pellet stoves

In recent years, national laws and international regulations have introduced strict limits on efficiency and emissions from woody biomass appliances to promote the diffusion of models characterized by low emissions and high efficiency. The evaluation of efficiency and emissions is made during the certification process which consists in standardized tests. Standards prescribe the procedures to be followed during tests and the relations to be used to determine the mean value of efficiency and emissions. As a matter of fact these values are calculated using flue gas temperature and composition averaged over the whole test period, lasting from 1 to 6 hours.Typically, in wood appliances the fuel burning rate is not constant and this leads to a considerable variation in time of composition and flow rate of the flue gas. In this paper we show that this fact may cause significant differences between emission values calculated according to standards and those obtained integrating over the test period the instantaneous mass and energy balances. In addition, we propose some approximated relations and a method for wood stoves which supply more accurate results than those calculated according to standards. These relations can be easily implemented in a computer controlled data acquisition systems.

Thermochemical Characterization of Bio- and Petro-diesel Fuels Using a Novel Laser-Heating Technique

A state-of-the-art, rapid laser-heating technique, referred to as the laser-driven thermal reactor, was used to characterize National Institute of Standards and Technology Standard Reference Material (SRM) diesel and biodiesel fuels, as well as a prototype biodiesel fuel. Also described are the various issues associated with carrying out these measurements under different operating conditions (i.e., temperature, pressure, heating rate, and sample mass). The technique provides measurement of various relevant thermochemical characteristics; for this investigation the focus was on the sample endothermic/exothermic behavior, specific heat release rate, and total specific heat release. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a vacuum chamber, along with integrated optical, gas-supply, and computer-controlled data-acquisition subsystems. At the center of the reactor, the sample and substrate rest on a thermocouple. The reactor is heated from opposing sides by a near-...

Electron impact fragmentation of adenine: partial ionization cross sections for positive fragments

Using computer-controlled data acquisition we have measured mass spectra of positive ions for electron impact on adenine, with electron energies up to 100 eV. Ion yield curves for 50 ions have been obtained and normalized by comparing their sum to the average of calculated total ionization cross sections. Appearance energies have been determined for 37 ions; for 20 ions for the first time. All appearance energies are consistent with the fragmentation pathways identified in the literature. Second onset energies have been determined for 12 fragment ions (for 11 ions for the first time), indicating the occurrence of more than one fragmentation process e.g. for 39 u (C2HN+) and 70 u (C2H4N 3 + ). Matching ion yield shapes (118–120 u, 107–108 u, 91–92 u, and 54–56 u) provide new evidence supporting closely related fragmentation pathways and are attributed to hydrogen rearrangement immediately preceding the fragmentation. We present the first measurement of the ion yield curve of the doubly charged parent ion (67.5 u), with an appearance energy of 23.5 ± 1.0 eV.

English

Propulsive efficiencies of Micro Air Vehicle propellers over operating range is playing very important role in enhancing the endurance of the MAVs. These propellers are powered by brushless mini motors whose efficiencies are low in comparison to bigger size motors and are varying over a range of operation. Generally propulsive efficiencies are evaluated by measuring the input power of drive motor and its efficiencies from commercial catalogue. Uncertainty in propulsive efficiency estimation results from the uncertainty in motor efficiencies which vary with load, speed; local heating of the miniature motors, and also compounded by uncertainty in low velocity air flow measurements. To alleviate this, novel method of simultaneous measurement of propellers shaft torque, thrust and rotational speed is configured by CSIR-NAL and procured from M/s MAGTROL SA, Switzerland along with the computer controlled data acquisition system. Wind tunnel testing in uninstalled condition, measurement techniques and data analysis method adapted has yielded realistic assessment of propulsive efficiencies of mini propellers used in micro air vehicles. Maximum propulsive efficiencies of 70% are measured at advance ratio of 0.65 in comparison to 58% from earlier method for 6inch 3bladed mini propeller and computed values of 3D steady state CFD analysis using ANSYS FLUENT are closer to measured values.

In Situ Monitoring of Dispersion Dynamics of Carbon Nanotubes during Sonication Using Electrical Conductivity Measurements

The main challenge in the fabrication of carbon nanotube‐ (CNT‐) based composite materials is the optimization of the sonication time in order to obtain homogenous and uniform dispersion of CNTs. Past studies mostly relied on postprocessing characterization techniques to address this issue. In the present, however, in situ monitoring of dispersion dynamics of CNTs in distilled water is carried out using instantaneous conductivity measurements. Using a computer controlled data acquisition system, the time evolution of the solution conductivity was carefully recorded. The data were then used to evaluate the intensity of turbulent fluctuations, which clearly highlighted the existence of three distinct sonication phases. During the first phase, the conductivity fluctuations initially increased attaining ultimately a maximum, thus indicating the occurrence of large agglomerates of CNTs. During the second phase of sonication, the solution conductivity showed a rather steep increase while fluctuations steadily declined. This phenomenon can be attributed to the breakdown of large CNT agglomerates, resulting in greater dispersion homogeneity of CNTs. During the third phase, after almost 650 kJ/L of sonication energy, the conductivity increase was almost negligible. The fluctuation intensity also remained constant during this phase signifying that the further sonication was no longer required.

Experimental investigation on vibration characteristics of woven carbon fabric-reinforced composite beams of various cross-sectional shapes

Vibration characteristics of carbon/epoxy composite beams await increased attention in structural industries such as aerospace, automotive, machine tools, marine industries. The objective of the present work is to investigate and analyze the shape effects of carbon/epoxy composite beams on vibration behavior. Specimens were fabricated using woven carbon fabric for basic shapes: I, box, and channel sections by hand layup method. The fabricated beams were subjected to impulse frequency response test under cantilever and fixed-end boundary conditions for free vibration test up to 3.5 kHz. Vibration response was measured using piezoelectric transducer and was recorded using computer-controlled data acquisition system for analyzing its behavior. The vibration characteristic of beams with various shapes shows modified performance under different boundary conditions. The experimental mode shapes and modal frequencies of beams are discussed and compared for successive resonance sets. At a lower frequency range of 3.5 kHz, the experimental modal responses of beam that were compared with modal results of finite element method analysis using software ANSYS V12® exhibited acceptable deviation in error maximum of up to 8.2%. Further, all deformed mode shapes of various shaped beams tested at increased frequency level of 12 kHz using finite element software were also observed and discussed.

Electron impact fragmentation of thymine: partial ionization cross sections for positive fragments

We have measured mass spectra for positive ions for low-energy electron impact on thymine using a reflectron time-of-flight mass spectrometer. Using computer controlled data acquisition, mass spectra have been acquired for electron impact energies up to 100 eV in steps of 0.5 eV. Ion yield curves for most of the fragment ions have been determined by fitting groups of adjacent peaks in the mass spectra with sequences of normalized Gaussians. The ion yield curves have been normalized by comparing the sum of the ion yields to the average of calculated total ionization cross sections. Appearance energies have been determined. The nearly equal appearance energies of 83 u and 55 u observed in the present work strongly indicate that near threshold the 55 u ion is formed directly by the breakage of two bonds in the ring, rather than from a successive loss of HNCO and CO from the parent ion. Likewise 54 u is not formed by CO loss from 82 u. The appearance energies are in a number of cases consistent with the loss of one or more hydrogen atoms from a heavier fragment, but 70 u is not formed by hydrogen loss from 71 u.

Measured Anchor Rod Tightening of High-Mast Light Poles in Alaska

The Alaska Department of Transportation and Public Facilities owns and maintains 124 high-mast lighting poles (HMLPs) in south-central Alaska. Some of the anchor nuts that secured these poles, 100 ft and taller, to their foundations had been found to loosen without apparent cause. In this study, the axial force was measured in the 1½-in. (38-mm) diameter anchor rods of one HMLP during the tightening of new rods. These rods had a relatively low grip-length to diameter ratio of approximately 3. The force was measured by strain gauges mounted in a small hole along the anchor rod axis and a computer-controlled data acquisition system. The FHWA tightening procedure was followed. This included a snug-tight condition, followed by 60° of turn-of-the-nut method. The snug-tight condition was created by the full force of a workman pulling on a 24-in. (610-mm) wrench. A specified verification torque was applied to the nuts after 1 week to ensure adequate tension in the anchor rods. It was found that after the tightening procedure, the axial force in several of the 12 rods exceeded their yield capacity. In each rod that yielded, the axial force caused by the snug-tight condition was higher than the anticipated values. It was concluded that several variables contributed to the yielding. These included snug-tight axial loads that were higher than expected, effects of low grip-length to diameter ratios, and an unnecessarily large verification torque.

PERFORMANCE AND EXHAUST EMISSION CHARACTERISTICS OF A DIESEL ENGINE USING ALTERNATIVE FUELS

The present work introduces an improvement performance and reduces the exhaust emissions of Diesel engine. The experimental comparative study of the combustion characteristics and exhaust emissions for a single cylinder Diesel engine using LPG-Diesel and CNG-Diesel dual fuels separately are studied. Different ratios of LPG and CNG in Diesel fuel up to 70% were used respectively. The test rig was furnished with a computer-controlled data acquisition system and the necessary measuring instruments to measure and record ignition delay, combustion duration, peak cylinder pressure, dual specific fuel consumption and exhaust emissions. The engine was tested at different speeds and loads. The results indicated that the ignition delay of both LPG-Diesel and CNG-Diesel dual fuel are obviously longer than that of Diesel fuel only. The combustion duration for the two cases is slightly reduced with the increase of gaseous fuel ratio at low speeds; however, it increases at high speeds. As gaseous fuel ratio is increased, the peak cylinder pressure is slightly reduced at low loads, however, at high loads; the peak cylinder pressure strongly decreases. The level of NOx emissions under dual fuel operation is lower than normal Diesel operation at different gaseous fuel ratios. CO and HC emissions for the two cases decrease with the increase of gaseous fuel ratio. The dual specific fuel consumption slightly increases with the increase of gaseous fuel ratio. The final results showed that when using CNG dual fuel, the combustion performance increases while the exhaust emissions decrease compared with Diesel and LPG dual fuel.

Development of High Power Electron Beam Measuring and Analyzing System for Microwave Vacuum Electron Devices

Abstract The measurement and analysis of high power electron beam during its formation and transmission are the basic scientific problems and key techniques for the development of high performance microwave vacuum electron devices, which are widely used in the fields of military weapon, microwave system and scientific instruments. In this paper, the dynamic parameters measurement and analysis system being built in Institute of Electronics, Chinese Academy of Sciences (IECAS) recently are introduced. The instrument are designed to determine the cross-section, the current density, and the energy resolution of the high power electron beam during its formation and transmission process, which are available both for the electron gun and the electron optics system respectively. Then the three dimension trajectory images of the electron beam can be rebuilt and display with computer controlled data acquisition and processing system easily. Thus, much more complicated structures are considered and solved completely to achieve its detection and analysis, such as big chamber with 10-6 Pa high vacuum system, the controlled detector movement system in axis direction with distance of 600 mm inside the vacuum chamber, the electron beam energy analysis system with high resolution of 0.5%, and the electron beam cross-section and density detector using the YAG: Ce crystal and CCD imaging system et al. At present, the key parts of the instrument have been finished, the cross-section experiment of the electron beam have been performed successfully. Hereafter, the instrument will be used to measure and analyze the electron beam with the electron gun and electron optics system for the single beam and multiple beam klystron, gyrotron, sheet beam device, and traveling wave tube etc. thoroughly.

Experimental Investigation of the Transient Performance of a Turbocharged Compression Ignition Engine at Different Operating Conditions

In this work, an experimental investigation was conducted in order to study the transient performance of turbocharged compression ignition engine at different operating conditions. The experimental work was performed on a test rig comprising a four stroke 5.67 liters water-cooled turbocharged compression ignition engine and a Heenan hydraulic dynamometer. Instrumentation included devices for measuring engine speed, load, exhaust smoke level, exhaust temperature, fuel pump rack travel, turbocharger speed, and inlet air manifold pressure. The test facility was provided with a computer controlled data acquisition system to enable fast and accurate measuring and evaluating the engine response to sudden demand of increased load or speed. Two groups of tests were carried out. In the first group, the transient response of the engine to sudden acceleration demands was measured. During these tests, the dynamometer water flow rate was kept constant at pre-adjusted values namely 0, 10, 20, 30 and 50 % of the engine full load then the engine was accelerated from the initial speed of 1000 rpm to the target speed by quickly moving the fuel pump control lever forward to its maximum travel position. Measurement of the engine response to the sudden increase indynamometer load was performed in the second group of tests. The fuel pump control lever was locked at its initial setting at initial speed of 2000 rpm and initial load of 20, 30, 40 and 50% from the engine full load then the load was increased suddenly to its maximum value. It is shown that the response time at which the engine speed reach to the desired valuecorrespond to full fuel pump rack position increases with the increase of the initial brake torque. Very slow response was noticed at initial loading of 30 and 50% this due to the increase of resisting load quickly to a higher value which suppresses the engine speed increase due to the decrease of the surplus torque (engine minus resisting torques). Duringload acceptance tests it was shown that as the initial load decreases , „harder‟ turbocharger lag period, lower air–fuel ratio, higher crankshaft deceleration and lower engine speed were obtained, Which initiate larger governor displacement which increase the amount of fuel injected to increase the fuel load to the desired full load conditions

Characterization of the Heat Transfer Boundary Conditions during Cooling of a Horizontal Disk with a Water Column

To model the microstuctural and mechanical responses of quenched metallic components, the evolution of the thermal field must be known precisely; the latter, in turn, depends on accurate values of the thermal boundary conditions. In this work, the heat transfer boundary conditions on both sides of a stainless steel disk, held horizontally while a water column impinged on its lower surface to cool it from 850°C to room temperature, were characterized as heat flux histories which are functions of the radial coordinate. Thermal responses, measured with embedded thermocouples and a computer-controlled data acquisition system, were used to estimate the heat flux histories by solving the corresponding inverse heat conduction problem (IHCP), considering radial symmetry. The optimization problem also included the estimation of sub-areas associated with different heat extraction rates on both the lower and upper surfaces of the disk. The fluctuating interaction between the water column and the cooling disk was captured in the estimated heat flux histories. The estimated thermal boundary conditions were validated by computing the thermal response at the thermocouple locations by solving the direct heat conduction problem (DHCP) with a computer program based on the finite-element method. A good agreement between experimentally determined and computed thermal responses was observed, thus verifying the methodology employed.

Anomalous sea surface reverberation scale model experiments

Low frequency sea surface sound backscattering from ∼100 Hz to a few kHz observed from the 1960s broadband measurements using explosive charges to the Critical Sea Test measurements conducted in the 1990s is substantially higher than explained by rough sea surface scattering theory. Alternative theories for explaining this difference range from scattering by bubble plumes/clouds formed by breaking waves to stochastic scattering from fluctuating bubble layers near the sea surface. In each case, theories focus on reverberation in the absence of the large-scale surface wave height fluctuations that are characteristic of a sea that produces bubble clouds and plumes. At shallow grazing angles, shadowing of bubble plumes and clouds caused by surface wave height fluctuations may induce first order changes in the backscattered signal strength. To understand the magnitude of shadowing effects under controlled and repeatable conditions, scale model experiments were performed in a 3 m × 1.5 m × 1.5 m tank at the Technical University of Denmark. The experiments used a 1 MHz transducer as the source and receiver, a computer controlled data acquisition system, a scale model target, and a surface wave generator. The scattered signal strength fluctuations observed at shallow angles are characteristic of the predicted ocean environment. These experiments demonstrate that shadowing has a first order impact on bubble plume and cloud scattering strength and emphasize the usefulness of model scale experiments for studying underwater acoustic events under controlled conditions.