Search Results

You are looking at 1 - 10 of 44 items for

  • Author or Editor: D. Yu x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

We introduce a new class of sequences called NBVS to generalize GBVS, essentially extending monotonicity from “one sided” to “two sided”, while some important classical results keep true.

Restricted access

В данной работе для ог раниченнойn-мерной о бластиω с границей, состоящей из многообразийS иΓ размерности соот ветственноn−1 иm (0≦m<n), определяется некото рый весовой класс (ω) диф ференцируемых функц ий с вырождениями наS иΓ.

Restricted access

Abstract

Fractal theory has been proved effective to characterize the complex pore structure. In this article, the fractal method is utilized to study the structure property of fibrous assemblies. The box dimension parameter is applied to characterize the pore structure of fibrous assemblies by analyzing the electronic scanning microscope images of the fibrous assemblies. Furthermore, a fractal model for predicting effective heat conductivity is established. Experiment is conducted to verify the model, and good agreement is found between the experimental and theoretical results. The fractal model is also compared with the previous models for predicating heat conductivity, and the former is proved to be more accurate.

Restricted access

Summary By employing a novel idea and simple techniques, we substantially generalize the Turán type inequality for rational functions with real zeros and prescribed poles established by Min [5] to include L p spaces for 1≤ p ≤ ∞ while loosing the restriction ρ > 2 at the same time.

Restricted access

Abstract

Radiative heat transfer could be a significant contribution to the total heat transfer within the highly porous materials. This article reports on the use of a conventional instrument, viz. Fourier transform infrared (FTIR) spectroscopy, for the characterization of radiative heat properties of fiber assemblies with low bulk densities. Experimental measurements on spectral transmission with FTIR were performed on five types of fiber assemblies commonly used for insulating materials. From the measurements, radiative heat conductivity was determined by calculating extinction coefficient using Beer's Law and applying the diffusion approximation approach. Bulk density, fiber arrangement, and temperature influences to radiative heat transfer were discussed. Results show that radiative heat conductivity decreases with bulk density and that of the random arranged fiber assemblies shows lower radiative heat conductivity than the random ball and parallel arranged fiber assemblies. Radiative heat conductivity is proportional to the cubic temperature. The existing theoretical model was modified by comparing theoretical and experimental radiative heat conductivity results.

Restricted access

Abstract  

The neutron activation method has been applied to study the rare earth element distribution is phosphate raw material. The conditions and the results of the analysis are given in the paper.

Restricted access

Abstract  

The international community presently lacks the ability to determine the quality and credibility of environmental measurements that is required to make sound decisions in matters related to international security, public health, and investment-related considerations. The ultimate goal of the work described in this article is to develop a credible information base including measurement capability for determination of environmental contamination and the potential for proliferation of material components of chemical or nuclear weapons. This study compared the accuracy obtained by six Russian and six U.S. laboratories for samples representative of classes of trace metals, dioxin-furans, and radioactive substances. The results obtained in this work indicate that current estimates for laboratory accuracy are likely overly optimistic. The weaknesses discovered by this prototype U.S. — Russia, study also exist within the broader international community of laboratories. Further work is proposed to address the urgent need for the international community to improve performance evaluations for analytical measurements.

Restricted access

Abstract  

Carrier-free astatotyrosine has been synthesized using an electrophilic reaction in acidic media. Temperature of 150–160°C and reaction time of 20–30 min were chosen as optimal conditions for the synthesis of astatotyrosine. Under the selected conditions the yield was about 90%.

Restricted access

Abstract  

Racemic tritium-labelled amino acids were separated into optical isomers by chromatography on a chiral polyacrylamide sorbent filled with copper ions. The polyacrylamide sorbent is synthesized by Mannich's reaction through the action of formaldehyde and L-phenylalanine upon polyacrylamide Biogel P-4 in an alkali phosphate buffer. Tritiumlabelled amino acids are eluted by a weak alkali solution of ammonium carbonate. Data are presented on the ligand exchange chromatography of amino acids depending on the degree to which the sorbent is filled with copper ions and on the eluent concentration. Conditions are suggested for the quantitative separation of amino acid racemates. Amino acids are isolated from the eluent on short columns filled with sulfonated cation exchanger in the H+ form. HPLC on modified silica gel sorbents is also used for the analysis of tritium-labelled optically active amino acids. Amino acids are eluted by a weakly acidic water-methanol solution containing ammonium acetate. UV and scintillation flow type detectors are used.

Restricted access