Mass Density Measurements Research Articles

Nanoscale measurement of the absolute mass density of polymers

Recent progress in the performance of polymer electronics devices has depended heavily on detailed knowledge of the properties of the active polymer materials. While many advanced conjugated polymer materials are being synthesized, the limited quantities produced severely restrict opportunities to measure their physical properties. In particular, the absolute mass density is a basic material property that impacts on many other important properties, yet it is very difficult to measure when in limited quantity. Here, we report a method to spatially resolve the absolute mass density of polymer materials at the nanoscale and measure values for polystyrene (1028 (43) kg/m3), PMMA (1140 (26) kg/m3), PFB (727 (51) kg/m3), and F8BT (749 (26) kg/m3). We estimate that the measurement method could be applied to sample quantities less than 1 picogram.

Correction of the photoelectron heating efficiency within the global ionosphere‐thermosphere model using Retrospective Cost Model Refinement

Many physics-based models are used to study and monitor the terrestrial upper atmosphere. Each of these models has internal parameterizations that introduce bias if they are not tuned for a specific set of run conditions. This study uses Retrospective Cost Model Refinement (RCMR) to remove internal model bias in the Global Ionosphere Thermosphere Model (GITM) through parameter estimation. RCMR is a low-cost method that uses the error between truth data and a biased estimate to improve the biased model. Neutral mass density measurements are used to estimate an appropriate photoelectron heating efficiency, which is shown to drive the modeled thermosphere closer to the real thermosphere. Observations from the Challenging Mini-Payload (CHAMP) satellite taken under active and quiet solar conditions show that RCMR successfully drives the GITM thermospheric mass density to the observed values, removing model bias and appropriately accounting for missing physical processes in the thermospheric heating through the photoelectron heating efficiency.

Non-linear ultrasonic characterisation of heat-damaged cement paste

This paper focuses on the experimental characterisation of the elastic properties of sound and heat-damaged cement paste for different water contents: w/c = 0.3, 0.4 and 0.5. Damage is first assessed from mass density and wave velocity measurements. Linear acoustic methods were carried out but they did not permit an efficient evaluation of the earliest stages of damage. The goal of this research is to assess damage-induced non-linearities in the behaviour of heat-damaged cement paste. The method is based on the higher harmonic generation (HHG) technique. An empirical law is proposed to relate the non-linear elastic parameter β to the cement water content and to temperature. This is expected to give new insights in the field of non-destructive testing (NDT) methods; in particular, non-linear acoustic methods are expected to enable early failure diagnosis and thus reducing maintenance costs of infrastructure.

Investigation of the Dielectric and Mechanical Properties for Magnetron Sputtered BCN Thin Films

Boron carbon nitride (BCN) thin films were deposited by a dual target DC and RF sputtering technique. The films were deposited using various combinations of nitrogen and argon working gases and B4C, BN, and C targets. X-ray photoelectron spectroscopy and Fourier-transform infra-red spectroscopy were utilized, respectively, to investigate the changes in chemical composition and bonding that occurred for films deposited under various N2/Ar gas flow ratios and DC/RF target powers. The composition and bonding were correlated to separate measurements of the BCN mass density, dielectric constant, Young's modulus, and hardness. All BCN films were observed to have relatively low mass densities ranging from 2.0–2.5 g/cm3. BN rich BCN films were observed to be insulating with relatively low dielectric constants of 3.9–4.6 and Young's modulus and hardness values of 110–150 GPa and 5–13 GPa, respectively. BC rich BCN films were observed to be comparatively leaky dielectrics but did exhibit extreme mechanical properties with Young's modulus and hardness values exceeding in some cases 300 GPa and 30 GPa, respectively.

Interpretation of different molecular packing in the micelles of lyotropic nematic and cholesteric phases via mass density measurements

Lyotropic nematic and cholesteric mixtures were produced by dissolving amino acid based racemic surfactants, potassium N-dodecanoyl-dl-alaninate (dl-KDDA) and potassium N-dodecanoyl-dl-serinate (dl-KDDS), and their l-enantiomer surfactants (l-KDDA and l-KDDS) in a mixture of sodium sulfate (Na2SO4)/1-decanol (DeOH)/water, separately. Polarizing light microcopy (PLM) and mass density measurements were applied to each mixture. The textures of all phases were investigated by PLM. Mass density measurements showed that the cholesteric phases of both l-KDDA and l-KDDS exhibited larger mass density values than their dl-KDDA and dl-KDDS nematic phases, respectively. This result was supported by our previous small-angle X-ray scattering study. The difference between micelle volumes of cholesteric and nematic phases was explained by different molecular packing of dl- and l-forms of the same surfactant molecules in the achiral and chiral micelles, respectively. This indicated that mass density measurement may be a useful way to detect the different molecular packing in the micelles which causes the increase or decrease in the micelle size or volumes qualitatively as it is expected.

Influência de variáveis de sinterização na microestrutura de peças de PTFE moldadas por prensagem isostática

O politetrafluoretileno (PTFE) é utilizado em extensa gama de aplicações críticas devido à sua excelente resistência química e térmica, baixa energia superficial e propriedades tribológicas. Devido à sua elevada viscosidade no estado fundido, o PTFE não pode ser transformado pelos métodos tradicionais de extrusão e injeção, sendo o principal método de transformação deste polímero a prensagem sob temperatura ambiente, seguida de sinterização a temperaturas acima do ponto de fusão. O tempo de sinterização é definido de acordo com as dimensões da peça fabricada, podendo variar de poucas horas até vários dias para peças de grande volume. Avaliações sobre a influência dos extremos de tempo e temperatura de sinterização, atualmente adotados na indústria, sobre a microestrutura cristalina do PTFE, são escassas na literatura científica, sendo o principal objetivo deste estudo. Placas em PTFE foram sinterizadas variando-se a temperatura entre 360 ○C e 390 ○C e o tempo entre 10 e 10.000 min. Calorimetria exploratória diferencial (DSC), medidas de perda de massa e de densidade e microscopia eletrônica de varredura (MEV) foram utilizadas. Os resultados das medidas de perda de massa indicaram que a degradação do PTFE aumenta com o tempo e temperatura de sinterização. Análises das entalpias de fusão e medidas de densidade apontam indiretamente a redução na massa molar e aumento no grau de cristalinidade com o aumento do tempo e temperatura de sinterização. As análises em MEV possibilitaram a observação direta da microestrutura cristalina, indicando uma tendência de aumento da largura das lamelas com o tempo e temperatura de sinterização. Os resultados obtidos podem auxiliar no controle da microestrutura do PTFE durante o processamento, o que é bastante útil para a fabricação de peças em PTFE com desempenho otimizado.

Evaluation of the prevalence and correlated factors for decreased bone mass density among pre- and post-menopausal educated working women in Saudi Arabia.

Most of the previous studies on osteoporosis have focused on post-menopausal women, and more research is needed to evaluate its prevalence in pre-menopausal women. This study was carried out to evaluate the prevalence and correlated factors for decreased bone mass density among pre- and post-menopausal women. This was a cross-sectional study carried out in Applied Medical Sciences College under King Saud University. All pre- and post-menopausal women working there were invited to participate in the study. Measurement of bone mass density was done by quantitative ultrasound densitometry. One-fourth of the pre-menopausal females had osteopaenia. There was a significant correlation between having osteoporosis and increasing age, fertility period, parity, menopausal duration, gynaecological age, and presence of co-morbidity, especially hypertension and diabetes mellitus. Pre-menopausal females had high prevalence of osteopaenia (24.8%), and it is recommended to implement health education campaigns demonstrating the preventive measures of osteoporosis.

Resonant Steel Tuning Forks for Precise Inline Viscosity and Mass Density Measurements in Harsh Environments

The principle of using steel tuning forks for viscosity and mass density measurements is investigated. From recorded frequency responses of fully immersed tuning forks, resonance frequencies and quality factors are evaluated and related to the liquids mass densities and viscosities. The benefit of these resonators is their mechanical rigidity which allows the application in harsh environments and mechanical cleaning processes without detuning or damaging the device. The setup was particularly devised that only the resonator itself but no excitation or read-out mechanisms get wetted by the sample liquid. The results obtained with a circular cross-sectioned tuning fork in different liquids are shown and discussed.

Symmetric Plate Resonators for Viscosity and Density Measurement

In this contribution, we present a symmetric arrangement of resonating plates for viscosity and mass density measurement. Regarding the oscillation mode, the design resembles that of micro machined tuning forks and is based on previously introduced resonating plate designs. It exhibits similar sensitivity to viscosity and mass density as the single plate resonators while having a lower damping when operated in the tuning fork mode. In this contribution we introduce the new design, present the results of FE simulations in order to determine the associated eigenmodes and examine the effects of the used actuation method on the sensor. Measurement results are presented which show the general dependence of the tuning fork design on viscosity and mass density as well as the differences exhibited by different modes, particularly the in phase and out of phase vibration modes of the plates.

A Spiral Spring Resonator for Mass Density and Viscosity Measurements

Abstract Most recently introduced viscosity and mass density sensors utilize vibrating resonant mechanical structures interacting with the sample fluid where the resonance frequency and the quality factor are affected by both, the fluid's viscosity and its mass density. Unlike singly clamped beams, straight, doubly clamped structures are advantageous when using electromagnetic excitation and read-out based on Lorentz forces which allow high excitation forces and read-out signals. However, classical straight beams such as bridges are subjected to high cross-sensitivities of their resonance frequencies to ambient temperature. To overcome high spurious temperature dependencies but to benefit from the straight doubly clamped approach, a spiral spring resonator applicable as viscosity and mass density sensor has been designed.

A discussion of possible measurement techniques for muddy sediments and of the related modeling challenges

Present paper draws on recent work of the late William Carey at Dodge Pond, CT, and on related modeling efforts at RPI. Carey affirmed that muddly sediments can have a substantial air bubble content. The water, solid particles (clay), and bubbles lead to a low sound speed that for low frequencies is explained by a modification of the Mallock-Wood formula. Independent measurements of mass density and sound speed should enable estimates of the fractional composition. The attenuation of sound in muddy sediments without bubbles is small, much smaller than of sandy sediments, and this is explained in terms of the card house model because of the very small size of the clay particles. The larger bubbles are randomly dispersed and have flattened shapes (also explained by the card-house model), and lead to scattering and reflection phenomena. Speculations are made as to whether inversion techniques can be devised to determine bubble shapes and size distributions. The small shear modulus of muddy segments has been tentatively explained in terms of electrostatic effects inherent to the card-house model, and this can possibly be measured by interface waves. Paper also suggests that penetrometer measurements, guided by theoretical modeling, may lead to useful inferences.

<i>In Situ</i> Non-Destructive Examination of Timber Elements

Structural timber is a traditional construction material. Timber structures belong to essential parts of almost all historical buildings, especially roof and ceiling structures. Their actual condition affects durability of the whole building, therefore it is necessary to check the conditions of the structure regularly and take care of possible undesirable changes. If these structures have historical value we have to use non-destructive or semi-destructive methods during this investigation. Penetration methods in combination with ultrasonic method are used nowadays [. Penetration devices are suitable to determine the density, surface and internal biological degradation, growth defects and moisture content of the element. The density and the velocity of ultrasonic wave represent input information to derive dynamical modulus of elasticity. Penetration devices work on the principle of measuring the depth of penetration of a steel tip or on the principle of resistance drilling. Another method of determining the density of inbuilt element is the radial core. These methods are semi-destructive. It is the subject matter of the authors research to replace these penetration methods by radiometric measure of mass density. This method is based on the principle of gamma rays dispersion or on the principle of gamma rays absorption in a timber element. Radiometry as a measurement of density is often used for concrete constructions and asphalt pavement now. This measurement can be applied to the inbuilt elements, which is its a main advantage.

Data assimilation and driver estimation for the Global Ionosphere–Thermosphere Model using the Ensemble Adjustment Kalman Filter

This paper proposes a differential inflation scheme and applies this technique to driver estimation for the Global Ionosphere–Thermosphere Model (GITM) using the Ensemble Adjustment Kalman Filter (EAKF), which is a part of the Data Assimilation Research Testbed (DART). Driver estimation using EAKF is first demonstrated on a linear example and then applied to GITM. The Challenging Minisatellite Payload (CHAMP) neutral mass density measurements are assimilated into a biased version of GITM, and the solar flux index, F10.7, is estimated. Although the estimate of F10.7 obtained using DART does not converge to the measured values, the converged values are shown to drive the GITM output close to CHAMP measurements. In order to prevent the ensemble spread from converging to zero, the state and driver estimates are inflated. In particular, the F10.7 estimate is inflated to have a constant variance. It is shown that EAKF with differential inflation reduces the model bias from 73% down to 7% along the CHAMP satellite path when compared to the biased GITM output obtained without using data assimilation. The Gravity Recovery and Climate Experiment (GRACE) density measurements are used to validate the data assimilation performance at locations different from measurement locations. It is shown that the bias at GRACE locations is decreased from 76% down to 52% as compared to not using data assimilation, showing that model estimation of the thermosphere is improved globally.

Real-Time Viscosity and Mass Density Sensors Requiring Microliter Sample Volume Based on Nanomechanical Resonators

A microcantilever based method for fluid viscosity and mass density measurements with high temporal resolution and microliter sample consumption is presented. Nanomechanical cantilever vibration is driven by photothermal excitation and detected by an optical beam deflection system using two laser beams of different wavelengths. The theoretical framework relating cantilever response to the viscosity and mass density of the surrounding fluid was extended to consider higher flexural modes vibrating at high Reynolds numbers. The performance of the developed sensor and extended theory was validated over a viscosity range of 1-20 mPa·s and a corresponding mass density range of 998-1176 kg/m(3) using reference fluids. Separating sample plugs from the carrier fluid by a two-phase configuration in combination with a microfluidic flow cell, allowed samples of 5 μL to be sequentially measured under continuous flow, opening the method to fast and reliable screening applications. To demonstrate the study of dynamic processes, the viscosity and mass density changes occurring during the free radical polymerization of acrylamide were monitored and compared to published data. Shear-thinning was observed in the viscosity data at higher flexural modes, which vibrate at elevated frequencies. Rheokinetic models allowed the monomer-to-polymer conversion to be tracked in spite of the shear-thinning behavior, and could be applied to study the kinetics of unknown processes.

Quantification of Thermal Resistance of Transient-Liquid-Phase Bonded Cu/Al/Cu Interfaces for Assembly of Cu-Based Microchannel Heat Exchangers

Transient liquid phase (TLP) bonding of Cu structures with a thin elemental Al intermediate bonding layer is being used to assemble Cu-based, enclosed, microchannel heat exchangers (MHEs). The heterogeneous Cu/Al/Cu TLP bonding interface region, formed during the TLP bonding process, impacts heat transfer of the assembled MHE device. To evaluate the thermal resistance of TLP bonded Cu/Al/Cu interface regions, transient flash measurements were performed across bonding interface regions formed under various conditions, in combination with detailed structural examination and measurements of bulk mass density and specific heat. The flash method is shown to yield quantitative measurements of interfacial thermal resistance values. Our results provide guidance to developing bonding protocols for Cu-based MHEs with optimized heat transfer performance.

Online measurement of mass density and viscosity of pL fluid samples with suspended microchannel resonator

Physical characterization of viscous samples is crucial in chemical, pharma and petroleum industry. For example, in the refining industry of petroleum, water percentage is verified by measuring the density of a sample. In this article we present a suspended microchannel resonator (SMR) which uses 5pL of a fluid sample and measures its density with a resolution of 0.01kg/m3 and a sensitivity of 16Hz/kg/m3. The resonator can also simultaneously measure viscosity of the solutions with an accuracy of 0.025mPas. The SMR is part of a system which contains packaging and tubing to deliver samples to the resonator. The system can easily handle multiple viscous fluids to measure their densities and viscosities. The SMR is transparent, facilitating visual inspection of the microchannel content.

Transport Properties of Bulk Thermoelectrics: An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat, and Thermal Conductivity

For bulk thermoelectrics, improvement of the figure of merit ZT to above 2 from the current values of 1.0 to 1.5 would enhance their competitiveness with alternative technologies. In recent years, the most significant improvements in ZT have mainly been due to successful reduction of thermal conductivity. However, thermal conductivity is difficult to measure directly at high temperatures. Combined measurements of thermal diffusivity, specific heat, and mass density are a widely used alternative to direct measurement of thermal conductivity. In this work, thermal conductivity is shown to be the factor in the calculation of ZT with the greatest measurement uncertainty. The International Energy Agency (IEA) group, under the implementing agreement for Advanced Materials for Transportation (AMT), has conducted two international round-robins since 2009. This paper, part II of our report on the international round-robin testing of transport properties of bulk bismuth telluride, focuses on thermal diffusivity, specific heat, and thermal conductivity measurements.

Coriolis mass flow metering for three-phase flow: A case study

Previous work has described the use of Coriolis mass flow metering for two-phase (gas/liquid) flow. As the Coriolis meter provides both mass flow and density measurements, it is possible to resolve the mass flows of the gas and liquid in a two-phase mixture if their respective densities are known. To apply Coriolis metering to a three-phase (oil/water/gas) mixture, an additional measurement is required. In the work described in this paper, a water cut meter is used to indicate what proportion of the liquid flow is water. This provides sufficient information to calculate the mass flows of the water, oil and gas components. This paper is believed to be the first to detail an implementation of three-phase flow metering using Coriolis technology where phase separation is not applied.Trials have taken place at the UK National Flow Standards Laboratory three-phase facility, on a commercial three-phase meter based on the Coriolis meter/ water cut measurement principle. For the 50mm metering system, the total liquid flow rate ranged from 2.4kg/s up to 11kg/s, the water cut ranged from 0% to 100%, and the gas volume fraction (GVF) from 0 to 50%. In a formally observed trial, 75 test points were taken at a temperature of approximately 40°C and with a skid inlet pressure of approximately 350kPa. Over 95% of the test results fell within the desired specification, defined as follows: the total (oil+water) liquid mass flow error should fall within ±2.5%, and the gas mass flow error within ±5.0%. The oil mass flow error limit is ±6.0% for water cuts less than 70%, while for water cuts between 70% and 95% the oil mass flow error limit is ±15.0%.These results demonstrate the potential for using Coriolis mass flow metering combined with water cut metering for three-phase (oil/water/gas) measurement.

GENERALIZATION OF RINDLER POTENTIAL AT CLUSTER SCALES IN RANDERS–FINSLERIAN SPACETIME: A POSSIBLE EXPLANATION OF THE BULLET CLUSTER 1E0657-558?

The data of the Bullet Cluster 1E0657-558 released on November 15, 2006 reveal that the strong and weak gravitational lensing convergence κ-map has an 8σ offset from the Σ-map. The observed Σ-map is a direct measurement of the surface mass density of the Intracluster medium (ICM) gas. It accounts for 83% of the averaged mass-fraction of the system. This suggests a modified gravity theory at large distances different from Newton's inverse-square gravitational law. In this paper, as a cluster scale generalization of Grumiller's modified gravity model (Phys. Rev. Lett.105 (2010) 211303), we present a gravity model with a generalized linear Rindler potential in Randers–Finslerian spacetime without invoking any dark matter. The galactic limit of the model is qualitatively consistent with the MOND and Grumiller's. It yields approximately the flatness of the rotational velocity profile at the radial distance of several kpcs and gives the velocity scales for spiral galaxies at which the curves become flattened. Plots of convergence κ for a galaxy cluster show that the peak of the gravitational potential has chances to lie on the outskirts of the baryonic mass center. Assuming an isotropic and isothermal ICM gas profile with temperature T = 14.8 keV (which is the center value given by observations), we obtain a good match between the dynamical mass M T of the main cluster given by collisionless Boltzmann equation and that given by the King β-model. We also consider a Randers+dark matter scenario and a Λ-CDM model with the NFW dark matter distribution profile. We find that a mass ratio η between dark matter and baryonic matter about 6 fails to reproduce the observed convergence κ-map for the isothermal temperature T taking the observational center value.

Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers

Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work.