1,721 research outputs found
Job Analysis System for Civil Engineers in Construction Companies
Job research and analysis studies are the reports that detail the system andenvironmental conditions and performance of each job for obtaining higher efficiency andreducing the unit cost. In order to do the job analysis properly, information and data regardingthe job have to be evaluated accurately and realistically. The originating point of the article isbased on this definition and requirement. In the study, the established job analysis model hasbeen built on system approach. Steps of the model consist of input-preliminary preparation,process-analysis and conclusion phases.In accordance with the model suggested, a job analysis form has been developed to beused in improvement of functions of various human resources and in selection of civil engineersat manager position of construction companies during the study. The form specifies the jobprofile and personal requirements of civil engineers and gives information about time researchstudies aimed at efficiency. Form data has been collected by interviewing 50 (fifty) civilengineers at manager position working at large and medium sized construction firms, in order tobe used in job analysis discipline. In the study, information and data obtained by job analysisform have been analyzed by statistical methods and the results have been compared to similarliterature findings
Tuning the Transport Properties of Gases in Porous Graphene Membranes with Controlled Pore Size and Thickness
Porous graphene membranes emerged as promising alternatives for gas separation applications due to their atomic thickness enabling ultra-high permeance, but suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate large number of uniform small pores on the graphene surface. Here, we introduce a pore narrowing approach via gold deposition onto porous graphene surface to tune the pore size and thickness of the membrane to achieve large number of small pores. Through our systematic approach, we determined the ideal combination as pore size below 3 nm obtained at the thickness of 100 nm to attain high selectivity and high permeance. The resulting membrane showed a H2 /CO2 separation factor of 31.3 at H2 permeance of 2.23 × 105 GPU (1 GPU = 3.35 × 10-10 mol s-1 m-2 Pa-1 ), which is the highest value reported to date in the 105 GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, -5.3 versus -21 kJ mol-1 for H2 and CO2 , respectively, increased surface-gas interactions and molecular sieving effect with decreasing pore size. This article is protected by copyright. All rights reserved
Fundamental structure of Fresnel diffraction: natural sampling grid and the fractional Fourier transform
Cataloged from PDF version of article.Fresnel integrals corresponding to different distances can be interpreted as scaled fractional Fourier transformations observed on spherical reference surfaces. We show that by judiciously choosing sample points on these curved reference surfaces, it is possible to represent the diffracted signals in a nonredundant manner. The change in sample spacing with distance reflects the structure of Fresnel diffraction. This sampling grid also provides a simple and robust basis for accurate and efficient computation, which naturally handles the challenges of sampling chirplike kernels. © 2011 Optical Society of America
Distribution of mast cells in lung tissues of rats exposed to biomass smoke
This study was designed to evaluate the distribution of mast cells in the lung tissues of rats exposed to biomass smoke. Fifty six female Wistar albino adult rats were used. They were divided into two experimental groups (control and biomass smoke-treated), each containing 28 animals. Control rats were not exposed to the biomass smoke at any time during the experiment. Rats in the treatment group were exposed daily (one hour) to biomass smoke for 3, 6 or 9 months. Lung tissues samples were obtained under deep anesthesia from the randomly selected 7 animals in both groups. Lung tissues were fixed in Mota’s fixative (BLA) for 24 h and embedded in paraffin. Sections of 6 μm thickness were cut and stained with 0.5% toluidine blue in 0.5 N hydrochloric acid at pH 0.5 for 30 min. The numbers of mast cell in lung tissues of the animals exposed to the biomass for 6 or 9 months were significantly (P<0.05) higher than controls. This study showed that long term exposure to biomass smoke was associated with the increased number of mast cells in the lung.
Seismic data reveal eastern Black Sea Basin structure
Rifted continental margins are formed by progressive extension of the lithosphere. The development of these margins plays an integral role in the plate tectonic cycle, and an understanding of the extensional process underpins much hydrocarbon exploration. A key issue is whether the lithosphere extends uniformly, or whether extension varies\ud
with depth. Crustal extension may be determined using seismic techniques. Lithospheric extension may be inferred from the waterloaded subsidence history, determined from\ud
the pattern of sedimentation during and after rifting. Unfortunately, however, many rifted margins are sediment-starved, so the subsidence history is poorly known.\ud
To test whether extension varies between the crust and the mantle, a major seismic experiment was conducted in February–March 2005 in the eastern Black Sea Basin (Figure 1), a deep basin where the subsidence history is recorded\ud
by a thick, post-rift sedimentary sequence. The seismic data from the experiment indicate the presence of a thick, low-velocity zone, possibly representing overpressured sediments. They also indicate that the basement and\ud
Moho in the center of the basin are both several kilometers shallower than previously inferred. These initial observations may have considerable impact on thermal models of the petroleum system in the basin. Understanding\ud
the thermal history of potential source rocks is key to reducing hydrocarbon exploration risk. The experiment, which involved collaboration between university groups in the United Kingdom, Ireland, and Turkey, and BP and\ud
Turkish Petroleum (TPAO), formed part of a larger project that also is using deep seismic reflection and other geophysical data held by the industry partners to determine the subsidence history and hence the strain evolution of\ud
the basin
Infrared renormalons and single meson production in proton-proton collisions
In this article, we investigate the contribution of the higher twist Feynman
diagrams to the large- inclusive pion production cross section in
proton-proton collisions and present the general formulae for the higher twist
differential cross sections in the case of the running coupling and frozen
coupling approaches. The structure of infrared renormalon singularities of the
higher twist subprocess cross section and the resummed expression (the Borel
sum) for it are found. We compared the resummed higher twist cross sections
with the ones obtained in the framework of the frozen coupling approximation
and leading twist cross section. We obtain, that ratio for all values of
the transverse momentum of the pion identical equivalent to ratio .
It is shown that the resummed result depends on the choice of the meson wave
functions used in calculation. Phenomenological effects of the obtained results
are discussed.Comment: 28 pages, 13 figure
Fast light-switchable polymeric carbon nitride membranes for tunable gas separation
Switchable gas separation membranes are intriguing systems for regulating the transport properties of gases. However, existing stimuli-responsive gas separation membranes suffer from either very slow response times or require high energy input for switching to occur. Accordingly, herein, we introduced light-switchable polymeric carbon nitride (pCN) gas separation membranes with fast response times prepared from melamine precursor through in-situ formation and deposition of pCN onto a porous support using chemical vapor deposition. Our systematic analysis revealed that the gas transport behavior upon light irradiation is fully governed by the polarizability of the permeating gas and its interaction with the charged pCN surface, and can be easily tuned either by controlling the power of the light and/or the duration of irradiation. We also demonstrated that gases with higher polarizabilities such as CO2 can be separated from gases with lower polarizability like H2 and He effectively with more than 22% increase in the gas/CO2 selectivity upon light irradiation. The membranes also exhibited fast response times (<1 s) and can be turned “on” and “off” using a single light source at 550 nm
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