Method For Measurement Of Density Research Articles

Compression Behavior of Entrapped Gas in High Pressure Diecasting

Die castings generally contain a large quantity of porosities due to the entrapment of air or gas in molten metal during mold filling. Although the entrapped air or gas is compressed by high casting pressure during pressurization, it will eventually remain in the castings as defects after solidification. Therefore, it is important to clarify the relation between the volume of gas defects and the pressure applied to the molten metal so as to optimize the casting design.In this study, we investigated the compression behavior of entrapped gas during casting. We determined the volume of gas defects and gas content in die castings by density measurement and vacuum fusion extraction method respectively. Then we calculated the gas pressure in the defects from the above volume of defects and gas content, and compared with the die casting pressure. The calculated gas pressure in the defects was found to be not equal to the die casting pressure, but equal to the pressure of the molten metal just before it dropped abruptly due to the complete blocking of the liquid metal channel by solidification. From the experimental results, the behavior of the entrapped gas can be inferred as follows. Immediately after the mold was filled with molten metal, the entrapped gas was instantly compressed. After that, the pressure of molten metal decreased gradually with the progress of solidification of the molten metal channel, and the volume of entrapped gas increased correspondingly until the pressure of the molten metal dropped abruptly. Then the volume of the entrapped gas showed a slight expansion equal to the solidification shrinkage of the enclosed molten metal.The above inference was verified by measuring the volume of the entrapped gas defects in castings made with intentional depressurization carried out at the time when mold filling just finished or halfway through the solidification of the molten metal channel.

Surface grafting density analysis of high anti-clotting PU-Si-g-P(MPC) films

Well-defined zwitterionic polymer brushes with good blood compatibility were studied, grafted from polyurethane (PU) substrate (PU-Si-g-P(MPC)) by surface-initiated reverse atom transfer radical polymerization (SI-RATRP). We found that the structure of polymer brushes and hence their properties greatly depend on the grafting density. To solve the problems of the normal method for grafting density measurement, i.e., more requirements for qualified and proficient instrument operator, we established an effective and feasible way instead of the conventional method of spectroscopic ellipsometer combined with gel permeation chromatograph (ELM/GPC) to calculate the grafting density of PU-Si-g-P(MPC) films by using a software named ImageJ 1.44e in combination with scanning electronic microscope (SEM) or atomic microscope (AFM). X-ray photoelectron spectroscopy (XPS), SEM and AFM were employed to analyze the surface topography and changes of elements before and after graft modification of the synthetic PU-Si-g-P(MPC) biofilms.

Electron density measurements in a pulse-repetitive microwave discharge in air

We have developed a technique for absolute measurements of electron density in pulse-repetitive microwave discharges in air. The technique is based on the time-resolved absolute intensity of a nitrogen spectral band belonging to the Second Positive System, the kinetic model and the detailed particle balance of the N2C3Πu (ν = 0) state. This new approach bridges the gap between two existing electron density measurement methods (Langmuir probe and Stark broadening). The electron density is obtained from the time-dependent rate equation for the population of N2C3Πu (ν = 0) using recorded waveforms of the absolute C3Πu → B3Πg (0-0) band intensity, the forward and reflected microwave power density. Measured electron density waveforms using numerical and approximated analytical methods are presented for the case of pulse repetitive planar surface microwave discharge at the aperture of a horn antenna covered with alumina ceramic plate. The discharge was generated in air at 11.8 Torr with a X-band microwave generator using 3.5 μs microwave pulses at peak power of 210 kW. In this case, we were able to time resolve the electron density within a single 3.5 μs pulse. We obtained (9.0 ± 0.6) × 1013 cm–3 for the peak and (5.0 ± 0.6) × 1013 cm–3 for the pulse-average electron density. The technique presents a convenient, non-intrusive diagnostic method for local, time-defined measurements of electron density in short duration discharges near atmospheric pressures.

Image‐Assisted Gap Estimation, a Simple Method for Measuring Grapevine Leaf Canopy Density

ABSTRACTThis study compared an image analysis method of leaf canopy density measurement, image‐assisted gap estimation (ImAGE), with the commonly used point quadrat (PQ) analysis. For ImAGE, a blue background (plastic tarpaulin) was placed behind the grapevine (Vitis vinifera L.) row and digitally photographed and the image was analyzed using application‐specific software to calculate the area ratio of background to vine canopy. This was used as an estimate of the percentage area of gaps in the leaf canopy. Relationships among PQ leaf layer number (LLN), ImAGE gap area percentage (GAP), and fruit exposure were investigated in New Zealand vineyards during the 2008–2009 season in Hawke's Bay and in the 2008–2009 and 2009–2010 seasons at Pukekohe (Auckland region).. Gap area percentage was closely related (R2 = 0.87) to LLN. Significant relationships (p < 0.01) were also found between canopy density (measured by either method) and percentage severity of botrytis bunch rot at harvest. Image‐assisted gap estimation provides an alternative method to PQ analysis for measuring canopy density that is quicker, less subjective, and nondamaging. Image‐assisted gap estimation would primarily be useful as a low‐cost research tool as it could provide practical and rapid assessments without a significant investment in equipment. It may also help viticulturists achieve target leaf canopy densities for management of disease risk.

Influence of the stacking sequence on the porosity in carbon fiber composites

AbstractSeveral composite laminate structures with different stacking sequences were manufactured to study how the special orientation of the fibers can influence the porosity distribution in the material. Different amounts of porosity were introduced into the laminate during autoclave curing through the application of pressures that differed from the prescribed one. All of the obtained structures were analyzed by ultrasonic inspection to measure the attenuation undergone by the signal through crossing within the material. Subsequently, the attenuation variations were associated with the induced porosity. The obtained results were corroborated by an estimation of the percentage of porosity introduced into the composites structures through the application of a standard method for density measurement. The results prove that there are stacking sequences much more subject to trap air with the consequent formation of the porosity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Measurement of electron density with the phase-resolved cut-off probe method

The phase resolved cut-off probe method, a precise measurement method for the electron density, was recently proposed [J. H. Kwon et al., Appl. Phys. Lett. 96, 081502 (2010)]. This paper presents the measurements of electron density using the method under various experimental conditions (different pressures, powers, chamber volumes, and discharge sources). The result shows that the method is not only in good agreement with the previous method using wave transmittance under various experimental conditions but it is also able to find the cut-off point clearly even under difficult conditions such as high pressure (∼ 1 Torr), high discharge power, and small plasma volume. The details of the experimental setup, the operating mechanism of the probe method, and the data processing procedure (algorithm) are also addressed. Furthermore, the reliability of the measurement method is investigated by using an electromagnetic field simulation with cold plasma model (CST-Drude model, Computer Simulation Technology).

Effect of temperature on gas composition and char structural features of pyrolyzed agricultural residues

The gases and chars produced during fast pyrolysis of maize stalk, rice straw, cotton straw and rice husk at temperatures ranging from 600 to 1000°C were studied by Fourier transform infrared spectroscopy, non-dispersive infrared technique, thermal conductivity detection method, ultimate analysis, X-ray diffraction, helium density measurement and N2 adsorption method. The gas yield increased by more than 80% from 600 to 1000°C, while the char and liquid yield decreased. The content of CO2, CO and CH4 accounted for more than 86%. The CO and CH4 content increased with temperature, while the CO2 content decreased. The hydroxyl, aliphatic CH, carbonyl, olefinic CC and ether groups were lost above 800°C. Carbon skeleton shrinkage increased by more than 23% when the temperature increased from 600 to 1000°C. Maximum porosity appeared at 900°C. This study revealed the relationships between gas composition/char properties and pyrolysis temperature under high heating rate conditions.

Density Measurements of Endothermic Hydrocarbon Fuel at Sub- and Supercritical Conditions

The density of a typical endothermic hydrocarbon fuel (RP-3) at sub- and supercritical conditions is measured using a novel density measurement method which is based on mass conservation equation and can be applied to the density measurement of single phase flow including supercritical fluids. The measurement covers the temperature range of (295 to 796) K under pressures from (0.1 to 5) MPa. The uncertainty of the measurement is within ± 0.635 % according to error analysis. The results are fitted as polynomials to analyze deviations. For the 265 experimental data points, the average absolute deviation (AAD) and the maximum absolute deviation (MAD) are 0.539 % and 3.29 %, respectively. In addition, the isobaric thermal expansion αP is derived from the fitted values of density.

Use of Pulsed Radiography for Investigation of Equations of State of Substances at Megabar Pressures

AbstractA method of density measurement for substances that are isentropically compressed up to megabar pressures is described in the paper. Measurement results for condensed hydrogen isotopes and aluminum are presented. These results, afterwards, are used for construction of hydrogen isotopes “cold” isentropes. Experimental x‐ray images of the facilities with the hydrogen isotopes, compressed up to several megabars are presented in the paper (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thickness scan of metallic layer by photon induced X-ray emission

Simple and efficient method for precise surface density measurement in the range of about few mg/cm 2 for layers consisting of heavy elements, based on photon induced X-ray emission has been developed. The method has been applied to analyze Mott-scattering targets used in the measurement of the transverse electron polarization of electrons emitted in the neutron beta decay. The achieved relative accuracy is 1%. The absolute calibration accuracy of 2.3% was achieved with the atomic absorption spectroscopy.

Interface Trap Density Metrology of State-of-the-Art Undoped Si n-FinFETs

The presence of interface states at the MOS interface is a well-known cause of device degradation. This is particularly true for ultrascaled FinFET geometries where the presence of a few traps can strongly influence the device behavior. Typical methods for interface trap density (D_it) measurements are not performed on ultimate devices but on custom-designed structures. We present the first set of methods that allow direct estimation of D_it in state-of-the-art FinFETs, addressing a critical industry need.

Density measurement algorithm for freeway segment using two point detectors

AbstractDensity is the most important congestion indicator among fundamental traffic flow variables—flow, speed, and density. Measuring density by aerial monitoring, although accurate, cannot be widely used because of its cost and dependency on weather. The conventional method, estimating density based on the relationship between traffic flow and speed as measured by a point detector, does not yield an accurate density value, because the flow is not homogeneous. A new and advanced density measurement method, which is based on the in‐out counting method, is proposed. This method uses average density instead of instantaneous density. By using two point detectors, this method can capture considerable variation in density and is accurate for single and multilane freeway segments. Establishing the number of floating vehicles necessary to obtain a fair approximation of the true density is for future research. Copyright © 2011 John Wiley & Sons, Ltd.

Quantitative Microplasma Electron Number Density Measurement by Coherent Microwave Rayleigh Scattering

In this paper, a method for quantitative measurement of electron number density in a microplasma by coherent microwave Rayleigh scattering is described. Coherent microwave Rayleigh scattering reaches its maximum when the microwave frequency is at its resonance frequency. The resonance frequency depends on the electron number density in the microplasma and the electron-neutral and Coulomb collisional frequencies. When a subnanosecond microwave pulse illuminates the microplasma, the average electron number density can be measured from the frequency analysis of microwave scattering. The technique will be able to quantitatively measure subnanosecond-resolved electron number density evolution in the microplasma.

A Study for Implementation of Density Measurement Equipment for Asphalt Pavement based on the electromagnetic capacitance

In this paper we developed density measurement equipment for Asphalt Pavement based on the electromagnetic capacitance. This kind of Non-Nuclear Density Gauges technology and products is used or studied in USA, Finland, Sweden as standardization of authorized method for pavement density measurement. Effective permitivity of pavement asphalt is characterized in electromagnetic capacitance by the asphalt material, mixed ratio, and harden grade of pavement asphalt. We can get a density value of asphalt by replacing value of electromagnetic capacitance with standard density value and characteristic transformation curve. We are conformed that measurement data according to temperature, humidity, and real field asphalt of our density measurement equipment can be a precise value.

The Comparative Method for Apparent Density Measurement as a Means of Fine Carbonaceous and Inorganic Porous Material Characterization by the Determination of Shape Coefficient

These investigations are a part of work whose aim is an elaboration of a characterization method for porous fine powders with use of densimetric measurements. Especially, attention to methods of shape coefficient determination was given in this work because many other investigations pointed out that knowledge of this parameter is necessary for such studies. Shape coefficient values were determined with the use of Powers's method (K), the quantitative method (1/L), and the new comparative method (1/k). While densimetric measurements in the characterization of solids are a standard, the comparative method of apparent density determination is applied for the calculation of shape coefficients (1/k). The shape coefficient (1/k) characterizes not a single element of the fine solid but a collection of particles in the bed. The coefficient (1/k) represents the out-of-roundness degree of packed grains in relation to a bed of spheres with the same size distribution as the investigated material.

Development of CO2 laser dispersion interferometer with photoelastic modulator

A dispersion interferometer is one of the promising methods of the electron density measurement on large and high density fusion devices. This paper describes development of a CO(2) laser dispersion interferometer with a photoelastic modulator for phase modulation. In order to make the dispersion interferometer free from variations of the detected intensity, a new phase extraction method is introduced: The phase shift is evaluated from a ratio of amplitudes of the fundamental and the second harmonics of the phase modulation frequency in the detected interference signal. The proof-of-principle experiments demonstrate the feasibility of this method.

Apparent motion photometry: evaluation and reliability of a novel method for the measurement of macular pigment

Background/aimsMacular pigment is thought to protect the macula against exposure to light and oxidative stress, both of which may play a role in the development of age-related macular degeneration. The...

Weight Function Control of Moving Least-Squares Interpolants: Application to Axisymmetric Shielding Current Analysis in HTS

The modified basis functions of element-free Galerkin (EFG) method generated by weight function control of moving least-squares interpolants for an axisymmetric problem are investigated. In the axisymmetric problem, a physical quantity of rotating angle direction on the symmetry axis should be zero. By using standard EFG, however, the values on symmetric axis are non zero because the axisymmetric is not considered in basis function. In order to clear up the above problem, the modified basis function of EFG is proposed. The numerical simulation of shielding current density in axisymmetric high-temperature superconductor is adopted for practical applications of modified axisymmetric EFG. The results of computations show that the shielding current density on symmetric axis vanish in both cases. In addition, the experimental critical current density measurement method is reproduced numerically by using the numerical code.

REAL-TIME MEASUREMENT OF ICE CONCENTRATIONS IN ICE SLURRY FLOW

An experimental study was performed to measure the ice concentration of an ice slurry pipe flow in real time. In the present work, we suggest a refractive index measurement method and compare it to freezing point and density measurement methods. To measure the refractive index of the solution, ice particles in the ice slurry should be completely removed and a hydro-cyclone was used in this study instead of a mesh. The results from the measurement method by the refractive index coincided with those by the density within a ±5% error range when the real-time solution density was used. Even though the density measurement method showed good resolution, the results using the initial density of the solution were more than 10% in error compared to those using the real-time density. And the density measurement method has an error range 1.5 times greater than the refractive index measurement method.

The effects of raloxifene on mammographic breast density

Breast density is an independent risk factor for the development of invasive breast cancer (BC). It has been hypothesized that because raloxifene (RLX) has been shown to reduce BC risk, its use will result in reduced breast density. This article provides a review of seven clinical studies that examined the effects of RLX on breast density. Overall, RLX did not increase or decrease mammographic breast density. This article provides a review of the various methods used to determine breast density in these RLX studies and offers a potential explanation as to why the studies failed to show an effect on mammographic density. Presently, no clinical recommendations can be made with regard to RLX and its effects on breast density. To determine the effect of RLX on breast density, larger studies need to be conducted in postmenopausal women with high breast density at baseline who are at high risk for BC, with a standardized method of breast density measurement.