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51.
52.
In this numerical study, steady laminar mixed-convection heat transfer in a two-dimensional square lid-driven cavity with a modified heated wall is investigated over a range of Richardson numbers, including 0.01, 1, and 10. The heated bottom wall of the cavity is characterized by rectangular, triangular, and sinusoidal wave shapes. The cooled top wall of the cavity is sliding with constant velocity, while the vertical walls are kept stationary and adiabatic. The governing equations are solved using a finite-volume technique. The results are presented in the form of streamlines, isotherms, and Nusselt number plots. The effects of the number of undulations and the amplitude on the flow field and heat transfer are also investigated. The predicted results demonstrate that the heat transfer enhancement is generally observed with the modification of the heated wall, while the improvement is found to be more profound for the case of rectangular wave and at low Richardson number. 相似文献
53.
High metal contamination in toys and low-cost jewelry is a widespread problem, and metals can become bioavailable, especially via oral pathway due to common child-specific behaviors of mouthing and pica. In this review, the U.S., Canadian, and European Union (EU) legislations on metals in toys and jewelry are evaluated. A literature review on content, bioavailability, children's exposure, and testing of metals in toys and low-cost jewelry is provided. A list of priority metals is presented, and research needs and legislative recommendations are addressed. While the U.S. and Canadian legislations put emphasis on lead exposure prevention, other toxic elements like arsenic and cadmium in toy materials are not regulated except in paint and coatings. The EU legislation is more comprehensive in terms of contaminants and scientific approach. Current toy testing procedures do not fully consider metal bioavailability. In vitro bioaccessibility tests developed and validated for toys and corresponding metal bioaccessibility data in different toy matrices are lacking. The U.S. and Canadian legislations should put more emphasis on metal bioavailability and on other metals in addition to lead. A two-step management approach with mandatory testing of toys for total metal concentrations followed by voluntary bioaccessibility testing could be implemented. 相似文献
54.
Ersel Ozkazanc Sibel Zor Hatice Ozkazanc H. Yuksel Guney Ufuk Abaci 《Materials Chemistry and Physics》2012
In this study, morphological, thermal and dielectric properties of chemically synthesized polyaniline (PANI) and its cerium(III)-nitrate-hexahydrate (Ce(NO3)3·6H2O) doped composites with various doping levels were investigated. Characteristic bands of emeraldine salt (ES)-form of PANI was clearly observed in UV–visible (UV–vis) and Fourier transform infrared (FTIR) spectroscopies. Thermal analyses carried out by Differential scanning calorimetry (DSC) indicated that there was a glass transition at about 70 °C and the doping process increased thermal stability of the polymer. In the surface morphologies examined by scanning electron microscopy (SEM), various microstructures depending on the doping level were observed. Real dielectric constant exhibited a significant decrease due to the increase in the doping level especially at higher frequencies. Conductivity mechanisms of PANI and its composites were investigated by universal power law as conventional models could not provide a complete picture for all the samples. Dramatic increases up to 45, 35 and 30 times in the conductivity of 10% doped PANI were observed for 300, 350 and 400 K, respectively. 相似文献
55.
In this study, the impact of cyclic wetting and drying on swelling behavior of lime-stabilized clayey soils has been investigated. Swelling potential and swelling pressure tests have been carried out on soil mixtures with various amounts of kaolinite–bentonite clays, and on a high plasticity clayey soil sample. The tests have been repeated after the addition of lime to the lime-treated samples in different preparation. In each cycle the tested samples were allowed air dry to their initial water content thus shrinking to their initial height, which is called ‘partial shrinkage’ method. The results showed that the initial beneficiary effect of lime stabilization was lost after the first cycle and the swelling potential increased at the subsequent cycles. On the other hand, the swelling potential and the swelling pressure of the untreated soil samples started decreasing after the first cycle and they reached equilibrium after the fourth cycle. 相似文献
56.
L Davico C Sacerdote G Ciccone L Pegoraro S Kerim G Ponzio P Vineis 《Canadian Metallurgical Quarterly》1998,7(12):1123-1125
In a previous epidemiological study on acute myelocytic leukemia (M. M. Crane et al., Cancer Epidemiol. Biomark. Prev., 5: 639-644, 1996), clonal aberrations in chromosome 8 have been reported to be in excess in smokers and in workers exposed to paints. In that study, cytogenetics was performed after therapy. In our report, we describe a population-based survey on nonlymphocytic leukemias in northern Italy, in which 79 patients (acute myelocytic leukemia, myelodysplastic syndromes, or other nonlymphocytic leukemias) were studied before cytotoxic therapy. We found 9 aberrations involving chromosome 8 (six +8, two -8, and one translocation), whereas abnormalities involving chromosomes 5 and 7 occurred with a low frequency compared with previous studies. Aberrations involving chromosome 8 were associated with smoking (odds ratio, 6.3; 95% confidence interval, 0.9-42.3; among smokers of 10 or more cigarettes/day: odds ratio, 14.2; 95% confidence interval, 1.4-142.3); +8 aberrations were found in 1 of 24 nonsmokers and in 5 of 38 smokers. Three +8 aberrations were found in 22 subjects potentially exposed to solvents or polycyclic aromatic hydrocarbons. The low frequency of chromosome 5 and 7 aberrations in our population-based series (compared with other studies) can be attributed to the recruitment before cytotoxic therapies. Aberrations involving chromosome 8 (particularly +8) were associated with smoking habits. Chromosome 8 includes the c-myc oncogene. 相似文献
57.
This article is about bleaching of soybean fibers. Although the studies related to dyeing of soybean fibers have been found in the literature, little has been reported on the effect of bleaching. The natural color of soybean protein fibers is pale yellow or cream, and it is therefore usually necessary to bleach them to improve their whiteness. Different bleaching treatments combined with ozonation were performed in order to establish the effect on whiteness, yellowness, lightness, wettability, hydrophility, moisture sorption, and fiber damage properties of knitted soybean fabric. As a result of study, bleaching process combined with ozonation (ozonation + oxidative bleaching + reductive bleaching) supplied soybean fabric with a white appearance (highest whiteness degree), highest hydrophility, and minimal fiber damage. 相似文献
58.
Kerim Guney B. Babayigit A. Akdagli 《Electrical Engineering (Archiv fur Elektrotechnik)》2007,90(2):147-153
In this paper, a clonal selection algorithm (CLONALG) based on clonal selection principle of immune system has been used for
null steering in the antenna radiation pattern by controlling only the element positions of a linear array. Numerical examples
of Chebyshev pattern with the single, multiple and broad nulls imposed at the directions of interference are given to show
the accuracy and flexibility of the CLONALG. The sensitivity of the achieved patterns due to small variations of the element
positions is also investigated by truncating the element positions. 相似文献
59.
Kerim Kucuk 《Journal of Mining Science》2011,47(1):47-54
The studies done about shallow tunnels have been going on extensively. In the shallow tunnels especially driven in population
dense areas, soil-rock problems are encountered as well as ground water. Although ground water is the most common problem,
it does not take place so much in literature. During tunneling, the drainage of the groundwater is the most important point
that should be considered. In some cases, the drainage of ground water through the tunnel cause ground settlements in the
surrounding buildings. This problem particularly seen in weak soil/rock formations could be turned into a handicap by the
surface injection applications. Sometimes, injection application to prevent settlement problem and to reinforce the ground
creates risky conditions such as face burst, roof collapse during tunneling. This problematic situation risks both the work
safety and the environmental safety. This study investigates retrospectively the collapse of the tunnel roof and faces burst
during the construction of Izmir Metro 2nd phase. Eventually, in the zone where ground water regime exists and very weak formation
is present, injection study did not seem to serve the purpose. 相似文献
60.
ABSTRACTThe importance of ratchetting-fatigue interaction is garnering interest due to complex failure mechanism of rail welds under cyclic loading. The objective of this paper is to investigate the fatigue characteristics of continuous welded rails (CWRs) and the effect of residual stress on fatigue-ratchetting interaction. For this purpose, UIC60 rails have been modeled using a three-dimensional finite element model, including a combination of nonlinear kinematic and isotropic hardening. In addition, the interaction between cyclic loading and the effect of residual stress on fatigue is taken into consideration. Finite element model is validated against representative experimental findings. Smith–Watson–Topper (SWT) method is utilized in order to estimate the fatigue life of rail welds under static and cyclic loading. Lower fatigue life is predicted with increasing load due to the contact between rails and wheels. Simulation results also show that failure in the form of ratchetting occurs during the 10,236th cycle, while failure corresponds to the 15,290th cycle and the 145,161st cycle based on the SWT and Coffin-Manson fatigue models, respectively. These findings suggest that investigations on ratchetting and fatigue should be carried out simultaneously to estimate the failure of the CWRs. 相似文献