scholarly journals Trends in the Design and Performance of Tantalum Capacitors

1974 ◽  
Vol 1 (1) ◽  
pp. 11-16 ◽  
Author(s):  
L. F. Harris
Keyword(s):  
Surface Area ◽  
Liquid Electrolyte ◽  
Tantalum Powder ◽  
Initial Particle ◽  
Final Surface ◽  
And Performance ◽  
Particle Shapes

This paper shows the type of development that has occurred over recent years in tantalum capacitors, with particular reference to the sintered tantalum powder – liquid electrolyte (wet Ta) system. In the ‘wet’ system, the various defects that arise, such as silver migration, scintillation and field crystallisation, are illustrated and the effect of improvement in initial particle shapes on final surface area is considered.

Analysis of Fractional Composition and Specific Surface of Silicone Dioxide Nanopowders

2020 ◽  
Vol 992 ◽  
pp. 551-555
Author(s):  
O.N. Kravtsova ◽  
G.G. Vinokurov ◽  
N.F. Struchkov
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Fractional Composition ◽  
Nanosized Powder ◽  
Nanosized Powders ◽  
Powder Mixtures ◽  
Angle Scattering ◽  
Intermediate Value ◽  
Particle Shapes

For the development of new compositions of modified powder mixtures a comprehensive analysis of the technical characteristics of powder additives is required. The specific surfaces of nanosized powders of "Tarkosil" silicone dioxide were determined by the experimental method. Therefore, at present, the estimating relationships of sizes, particles shapes and specific surface area of nanosized powder is relevant scientific and practical task. And the particles shape was evaluated by the values of these surfaces. Using the method of small-angle scattering the functions of distribution of the modifying powders particles on their sizes were estimated, and the average values of particles size of "Tarkosil" powder were specified The particle shape of the modifying powders has been estimated according to the specific surface values. The particle shapes of T50 powders are close to isometric (a ball, a cube); particle shapes of T150 powders correspond to a tetrahedron, the particle size T80 and T110 corresponds to the intermediate value of the specific surface area.

A CHAMBER FOR STUDYING THE EFFECT OF RELATIVE HUMIDITY AND SOIL MOISTURE ON INSECT EGGS

1968 ◽  
Vol 100 (4) ◽  
pp. 358-362 ◽  
Author(s):  
J. F. Doane ◽  
R. K. Allan
Keyword(s):  
Soil Moisture ◽  
Relative Humidity ◽  
Surface Area ◽  
Insect Eggs ◽  
Humidity Chamber ◽  
Solution Surface ◽  
And Performance ◽  
Optimum Relationship

AbstractConstruction and performance of a humidity chamber, designed to provide an optimum relationship between volume and conditioning-solution surface area, are described.

Evaluation of talc morphology using FTIR and H/D substitution

Clay Minerals ◽  
2003 ◽  
Vol 38 (2) ◽  
pp. 141-150 ◽  
Author(s):  
E. Ferrage ◽  
F. Martin ◽  
S . Petit ◽  
S. Pejo-soucaille ◽  
P. Micoud ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Lateral Surface ◽  
Ftir Spectra ◽  
Hexagonal Ring ◽  
Particle Shapes

AbstractDeuteration (H/D substitution at 200ºC) was performed on powders of two ground talcs of different particle shapes (different basal/lateral surface ratios). Results indicate that the deuteration process is only efficient on lateral talc surfaces, and suggest that the hydrogens located in the hexagonal ring of the talc basal surfaces are not exchanged. The FTIR spectra collected from the two talc samples show that it is possible to discriminate between particles with the same specific surface area but with different basal/lateral surface ratios using the deuteration process.

Electrical properties of iron-sand columns: Implications for induced polarization investigation and performance monitoring of iron-wall barriers

Geophysics ◽  
2005 ◽  
Vol 70 (4) ◽  
pp. G87-G94 ◽  
Author(s):  
Lee D. Slater ◽  
Jaeyoung Choi ◽  
Yuxin Wu
Keyword(s):  
Relaxation Time ◽  
Surface Area ◽  
Performance Monitoring ◽  
Electrical Response ◽  
Induced Polarization ◽  
Iron Hydroxides ◽  
Interfacial Chemistry ◽  
Reactive Iron ◽  
Volume Formula ◽  
And Performance

We investigate the electrical response (0.1–1000 Hz) of reactive iron barriers by making measurements on zero valent iron ([Formula: see text])-sand columns under the following conditions: (1) variable [Formula: see text] surface area (0.1–100% by volume [Formula: see text] under constant electrolyte chemistry; (2) variable electrolyte activity (0.01–1 mol/liter), valence (mono trivalent), and pH under constant [Formula: see text]-sand composition; and (3) forced precipitation of iron hydroxides and iron carbonates on the [Formula: see text] surface. We model the measurements in terms of conduction magnitude, polarization magnitude, and polarization relaxation time. Our key findings are: (a) Polarization magnitude exhibits a linear relation to the surface area of [Formula: see text], whereas conduction magnitude is only weakly dependent on the [Formula: see text] concentration below 30% by volume [Formula: see text]. (b) Polarization magnitude shows a power law relation to electrolyte activity, with exponents decreasing from 0.9 for monovalent solutions to 0.7 for trivalent solutions. (c) The relaxation time parameter depends on activity and valence in a manner that is partly consistent with the variation in double layer thickness predicted from theory. (d) pH exerts minor control on the electrical parameters. (e) Polarization magnitude and relaxation time both increase as a result of precipitation induced on the surface of [Formula: see text]. Our results show that induced polarization parameters systematically change in response to changes in the [Formula: see text]-electrolyte interfacial chemistry.

scholarly journals Modification, calibration, and performance of the Ultra-High Sensitivity Aerosol Spectrometer for particle size distribution and volatility measurements during the Atmospheric Tomography Mission (ATom) airborne campaign

2018 ◽  
Vol 11 (1) ◽  
pp. 369-383 ◽  
Author(s):  
Agnieszka Kupc ◽  
Christina Williamson ◽  
Nicholas L. Wagner ◽  
Mathews Richardson ◽  
Charles A. Brock
Keyword(s):  
Refractive Index ◽  
Ammonium Sulfate ◽  
Surface Area ◽  
Particle Number ◽  
High Sensitivity ◽  
Counting Efficiency ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
And Performance ◽  
Counting Statistics

Abstract. Atmospheric aerosol is a key component of the chemistry and climate of the Earth's atmosphere. Accurate measurement of the concentration of atmospheric particles as a function of their size is fundamental to investigations of particle microphysics, optical characteristics, and chemical processes. We describe the modification, calibration, and performance of two commercially available, Ultra-High Sensitivity Aerosol Spectrometers (UHSASs) as used on the NASA DC-8 aircraft during the Atmospheric Tomography Mission (ATom). To avoid sample flow issues related to pressure variations during aircraft altitude changes, we installed a laminar flow meter on each instrument to measure sample flow directly at the inlet as well as flow controllers to maintain constant volumetric sheath flows. In addition, we added a compact thermodenuder operating at 300 ∘C to the inlet line of one of the instruments. With these modifications, the instruments are capable of making accurate (ranging from 7 % for Dp < 0.07 µm to 1 % for Dp > 0.13 µm), precise (< ±1.2 %), and continuous (1 Hz) measurements of size-resolved particle number concentration over the diameter range of 0.063–1.0 µm at ambient pressures of > 1000 to 225 hPa, while simultaneously providing information on particle volatility. We assessed the effect of uncertainty in the refractive index (n) of ambient particles that are sized by the UHSAS assuming the refractive index of ammonium sulfate (n= 1.52). For calibration particles with n between 1.44 and 1.58, the UHSAS diameter varies by +4/−10 % relative to ammonium sulfate. This diameter uncertainty associated with the range of refractive indices (i.e., particle composition) translates to aerosol surface area and volume uncertainties of +8.4/−17.8 and +12.4/−27.5 %, respectively. In addition to sizing uncertainty, low counting statistics can lead to uncertainties of < 20 % for aerosol surface area and < 30 % for volume with 10 s time resolution. The UHSAS reduction in counting efficiency was corrected for concentrations > 1000 cm−3. Examples of thermodenuded and non-thermodenuded aerosol number and volume size distributions as well as propagated uncertainties are shown for several cases encountered during the ATom project. Uncertainties in particle number concentration were limited by counting statistics, especially in the tropical upper troposphere where accumulation-mode concentrations were sometimes < 20 cm−3 (counting rates ∼ 5 Hz) at standard temperature and pressure.

scholarly journals Measuring winter precipitation and snow on the ground in northern polar regions

2017 ◽  
Vol 48 (4) ◽  
pp. 884-901 ◽  
Author(s):  
J. R. Janowicz ◽  
S. L. Stuefer ◽  
K. Sand ◽  
L. Leppänen
Keyword(s):  
Environmental Factors ◽  
Best Practices ◽  
Measurement Errors ◽  
Winter Precipitation ◽  
Performance Criteria ◽  
Polar Regions ◽  
Solid Precipitation ◽  
Important Input ◽  
And Performance ◽  
Particle Shapes

Measuring winter precipitation in cold and windy regions is recognized as a difficult task. Nonetheless, the accurate measurement of solid precipitation provides important input data for predicting snowmelt floods and avalanche danger and for monitoring climate change. The difficulties in measuring solid precipitation are associated with environmental factors and technological issues. Environmental factors that contribute to measurement errors include wind, freezing rain, rime, and a large range of solid particle shapes and sizes. Technological issues include gauge configuration, the need for remote, low-power-consumption operation, and difficult conditions for data transmission and retrieval. The objectives of this study were to review currently used gauges for measuring solid precipitation and snow on the ground, to summarize the positive and negative characteristics of each gauge, and to provide a discussion of best practices and design and performance criteria that might be used to stimulate research on new and/or improved precipitation gauges in Northern Research Basin (NRB) countries.

Turbulent Fluid Interfaces and Mixing Efficiency: Dynamics, Optimization, and Regularization

2004 ◽  
Author(s):  
Roberto C. Aguirre ◽  
Haris J. Catrakis
Keyword(s):  
Surface Area ◽  
Large Scale ◽  
Mixing Efficiency ◽  
Fluid Interfaces ◽  
Interfacial Behavior ◽  
Turbulent Fluid ◽  
Control Techniques ◽  
Small Scales ◽  
And Performance ◽  
Improved Design

In many fluid engineering devices, improved design and performance require knowledge of the dynamics of turbulent fluid interfaces. Depending on the device, and the application, the performance may be more sensitive to the large scales or the small scales of the interfaces. We distinguish between cases depending on whether the surface area of, or the volume enclosed by, the interfaces is practically more relevant. For turbulent interfaces, the surface area is dominated by the small scales whereas the volume enclosed is dominated by the large scales. We examine the interfacial dynamics in separated flows and we demonstrate the differences in the area-volume behavior in the context of mixing. Resolution effects on the interfacial behavior reveal that the mixing efficiency is strongly dominated by the large-scale interfacial properties. This has broad implications, at least for fluid-mixing devices, for the development of flow-prediction and flow-control techniques.

scholarly journals Characterization and performance of W-ZSM-5 and loaded Cu/ZsM-5 catalysts

2018 ◽  
Vol 4 (1) ◽  
pp. 137
Author(s):  
Didi Dwi Anggoro ◽  
Nor Aishah Saidina Amin
Keyword(s):  
Metal Oxides ◽  
Surface Area ◽  
Methane Oxidation ◽  
Metal Surface ◽  
Reaction Temperature ◽  
Methane Conversion ◽  
Liquid Hydrocarbons ◽  
Olefin Oxidation ◽  
Metal Surface Area ◽  
And Performance

The metal oxides with sufficiently high dehydrogenation and low olefin oxidation activities reduces the acidity of ZSM-5. As a result, the metal containing ZSM-5 can produce higher hydrocarbons in methane oxidation. Many researchers studied the applicability of HZSM-5 and modify ZSM-5 to methane conversion to liquid hydrocarbons but result of their research still lead to low conversion and selectivity. The modified HZS-5 by loading with Tungsten (W) enhanced its heat resistant performance, and the high reaction temperature (800ºC) did not lead to the loss of W component by sublimation. The loading of HZSM-5 with Tungsten and Cooper (Cu) resulted in an increment in the methane conversion, CO2 and C5+ selectivities. In contrast, CO, C2-3, and H2O selectivities were reduced. The process to convert methane to liquid hydrocarbons (C5+) was dependent on the metal surface area and the acidity of zeolite. The high methane conversion and C5+ selectivity, and low H2O selectivity are obtained by using W/3.0Cu/HZSM-5.  Keywords : Characterization W-ZSM-5, Modified HZSM-5, Tungsten, Copper, Methane  Abstrak  Logam oksida dengan kemampuan dehidrogenasi yang tinggi dan aktifasi oksidasi olefin berkurang dengan sifat keasaman dari ZSM-5. Sebagai hasilnya, ZSM-5 yang mengandung logam dapat memproduksi hidrokarbon rantai panjang dari oksidasi gas metana. Telah banyak para peneliti mempelajari kemampuan HZSM-5 dan ZSM-5 yang telah dimodifikasi untuk mengubah gas metana menjadi hidrokarbon cair tetapi hasil konversi dan selektivitasnya masih rendah. Modifikasi HZSM- 5 dengan penambahan logam Tungsten (W) meningkatkan daya tahan panas dan pada reaksi suhu tinggi (800ºC) tidak menyebabkan hilangnya logam W dikarenakan proses sublimasi. Penambahan logam Tungsten dan Copper (Cu) menyebabkan meningkatnya konversi metana, selektifitas CO2 dan C5+ Sebaliknya, selektifitas CO,C2-3, dan H2O menurun. Proses konversi metana menjadi hidrokarbon cair ditentukan oleh luas permukaan logam dan sifat keasaman dari zeolite.  Penggunaan katalis W/3.0Cu/HZSM-5 menghasilkan konversi metana dan selektifitas C5+ tinggi dan selektifitas H2O rendah.  Kata kunci : Karakterisasi W-ZSM-5, Modifikasi HZSM-5, Tungsten, Copper, Metana

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