• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1755
  • 645
  • 442
  • 273
  • 153
  • 71
  • 47
  • 42
  • 30
  • 30
  • 30
  • 30
  • 30
  • 29
  • 28
  • Tagged with
  • 4318
  • 709
  • 565
  • 459
  • 336
  • 313
  • 309
  • 303
  • 302
  • 300
  • 286
  • 263
  • 259
  • 229
  • 208
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

An analytical and experimental study of a tuned acoustic absorber /

Smith, David Lynn January 1973 (has links)
No description available.
232

The Effect of an Externally Applied Magnetic Field on the Hydrogen Absorption Properties of LaNi5

Bruce, David 10 1900 (has links)
Hydrogen fuel cell applications are set to ameliorate the world's energy woes, yet there still exists problems that need to be overcome in terms oftheir fuelling. While compressed storage, cryogenic storage, chemical storage, and adsorptive storage solutions exist, none meet the requirements that are needed to facilitate a replacement for the gasoline powered automobile. Metal hydrides have been long studied as an alternative method for storing hydrogen safely and efficiently, with significant developments being made in advanced alloys. While this research is beneficial, it was theorized that an externally applied magnetic field might augment the storage properties of existing magnetically susceptible metal hydrides, without trial and error alloy development. Constant volume hydrogen absorption experiments were conducted using LaNi5 in order to test this theory. A known amount of LaNi5 was exposed to hydrogen, with the absorption equilibrium data collected over a period of 6 hours. An equal sample was then exposed to hydrogen with a 0.7 Tesla applied field applied to the sample. There was a distinct difference between the absorption curves of the two equal samples, with the sample under the influence of the magnetic field achieving an absorption of only 0.60% wt. in comparison with the unmodified sample which absorbed 0.88% wt. It was concluded that the presence of an externally applied magnetic field has a negative effect on the overall capacity of LaNis through the prevention of a shift in the inner lattice structure of LaNis that would otherwise permit an increased hydrogen capacity. This effect while negative in terms of overall storage capacity could have a possible benefit in terms of the desorption of the stored hydrogen, as the magnetic field could be used in lieu of an increase in temperature in order to drive the hydrogen from the fully filled structure. / Thesis / Master of Applied Science (MASc)
233

Determining Effective Lifetime of Minority Carriers in Silicon Through Modulated Free Carrier Absorption

Petursson, Karl 11 1900 (has links)
The minority carrier lifetime is a valuable parameter for determining the electrical properties of semiconductors. It is particularly useful in the fabrication of solar cells as minority carrier lifetime is directly related to device efficiency. Pump-probe techniques, in which a pump laser of photon energy above the bandgap energy of the material is used to excite free carrier populations while a sub-bandgap probe laser is used to monitor the change in excess carrier density have been demonstrated to be an effective, non-contact, method to measure the minority carrier lifetime, particularly well-suited for use as an in-line measurement apparatus for the solar cell manufacturing processes In this thesis a non-contact, optical, pump-probe method has been used to determine the minority carrier lifetime of float zone and Czochralski grown <100> silicon samples through measurements of modulated free carrier absorption. The equivalence between measurements performed using the transmitted part of the probe beam and those made with the reflected part have been demonstrated on bare silicon wafers, as well as measurement of effective minority carrier lifetime of a completed solar cell, demonstrating the ability of this technique to measure the effective minority carrier lifetime at any stage of the solar cell manufacturing process. / Thesis / Master of Applied Science (MASc)
234

The Infrared Absorption Spectrum of Portlandite [Ca(OH)2]

Woelfle, John 09 1900 (has links)
The Infrared absorption of a single crystal of portlandite, over a temperature range from room temperature to below the melting point of hydrogen, was studied with both polarized and unpolarized radiation. The apparatus and experimental techniques are described, and the results and their significance in relation to earlier experimental work on the crystal structure of portlandite are discussed. / Thesis / Master of Science (MS)
235

Sound absorption by living plants

Horoshenkov, Kirill V., Khan, Amir, Benkreira, Hadj January 2013 (has links)
No
236

Solid activity coefficients of phosphate adsorbed by soil

Fu, Yong, 1948- January 1988 (has links)
The data of 14 soils were used to compute the ion activity product (IAP), the ratio of the ion activity product and to the solubility product (Ksp) of the pure minerals (IAP/Ksp) and to estimate the solid activity coefficients (SAC) of the soil components. The value of IAP and SAC of AlPO4 differs from soil to soil and increases with increasing P added to soil in acid soils and for calcium phosphate in basic soils. Magnesium apparently did not cause P adsorption or precipitation in the soils studied. The SAC of aluminum phosphate ranged from 10 to 10000 in acid soils. The mole fraction of the total phosphate in soil seemed to be a more satisfactory basis for calculating the concentration of the solid phase than was measurements of the available phosphate.
237

ADSORPTION OF TRICHLOROETHYLENE AND CARBON TETRACHLORIDE ON SYNTHETIC AND NATURAL ADSORBENTS.

Kalimtgis, Konstandinos. January 1985 (has links)
No description available.
238

Nonlinear Optical Absorption and Refraction Study of Metallophthalocyanine Dyes

Wei, Tai-Huei 12 1900 (has links)
This dissertation deals with the characterization of the nonlinear absorption and refraction of two representative metallophthalocyanine dyes: chloro aluminum phthalocyanine dissolved in methanol, referred to as CAP, and a silicon naphthalocyanine derivative dissolved in toluene, referred to as SiNc. Using the Z-scan technique, the experiments are performed on both the picosecond and nanosecond timescales at a wavelength of 0.532 μm.
239

Biophysical characteristics of small intestine ephithelial cells with particular reference to the effect of aldosterone and hydrocortisone

Noble, Hugh MacAskill January 1969 (has links)
No description available.
240

A comparison of absorption methods

JÖNSSON, EMMA January 2013 (has links)
This report is an attempt to find an absorption method that is more suitable for IKEA. Several different methods and standards from around the world are compared to see their pros and cons. The methods are compared both theoretically and practically. The practically comparison is made in a round robin were 14 different fabric is tested in three different methods. Two of the methods in the round robin are compared against each other and the result from a home test to see if the methods can show what the customer experience. The results from the round robin is used to recommend a proper method and requirement level that suit IKEA the best, based on their demands and requirements. / Program: Magister i textilteknologi

Page generated in 0.0589 seconds