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The crystal plastic theory was used to examine the effect of film-cooling hole arrangements on mechanical properties of cooled turbine blade. The finite element method was used to analyze the maximum von Mises stress and resolved shear stress of an octahedral slip system considering the number of rows, diameter, spacing, and tangential-to-longitudinal hole spacing (h/l) ratio. The different arrangements were found to have a significant influence on the maximum von Mises stress and resolved shear stress. For the triangular arrangement, the von Mises stress and resolved shear stress were highest with double rows, followed by a single row and then triple rows. For the quadrilateral arrangement, the stresses were highest with double rows, followed by triple rows and then a single row. Increasing the spacing or decreasing the diameter reduced the maximum von Mises stress and weakened the multi-hole interference effect. Both the maximum von Mises stress and resolved shear stress decreased with the h/l ratio.
Four complete platysiagid fish specimens are described from the Luoping Biota, Anisian (Middle Triassic), Yunnan Province, southwest China. They are small fishes with bones and scales covered with ganoine. All characters observed, such as nasals meeting in the midline, a keystone-like dermosphenotic, absence of post-rostral bone, two infraorbitals between dermosphenotic and jugal, large antorbital, and two postcleithra, suggest that the new materials belong to a single, new Platysiagum species, P. sinensis sp. nov. Three genera are ascribed to Platysiagidae: Platysiagum, Helmolepis and Caelatichthys. However, most specimens of the first two genera are imprints or fragmentary. The new, well-preserved specimens from the Luoping Biota provide more detailed anatomical information than before, and thus help amend the concept of the Platysiagidae. The Family Platysiagidae was previously classed in the Perleidiformes. Phylogenetic analysis indicates that the Platysiagidae is a member of basal Neopterygii, and its origin seems to predate that of Perleidiformes. Moreover, platysiagid fishes are known from the Middle Triassic of the western Tethys region. The newly found specimens of platysiagids from Luoping provide additional evidence that both eastern and western sides of the Tethys Ocean were biogeographically more connected than previously thought.
The purpose of this study is to highlight the effectiveness and necessity of the computational methods applications for architecture conceptual designs and improve the use of advanced simulation tools in urban planning. The results can provide the urban designers, planners and other decision makers with useful design information for assessing human wind comfort of the surrounding open spaces of public buildings in an urban area. Among different kinds of public buildings, museum architecture is of significant social value and importance for the augmentation of urban image. Using the Guggenheim Museum Bilbao for the case study, this investigation performed CFD simulations of the airflow over the museum to characterize the wind environments around the buildings. The predicted wind speed distributions were used to determine the wind comfort level of the featured spots around the museum for evaluating the suitability allowing visitors to sit or stand at the pedestrian plane for extended periods.
Chitotriosidase, secreted by activated macrophages, is a biomarker of activated macrophages. In this study, we explored whether chitotriosidase could be adopted as a biomarker to evaluate the curative effect on tuberculosis (TB). Five counties were randomly selected out of 122 counties/cities/districts in Hunan Province, China. Our cases were all TB patients who were newly diagnosed or had been receiving treatment at the Centers for Disease Control (CDCs) of these five counties between April and August in 2009. Healthy controls were selected from a community health facility in the Kaifu district of Changsha City after frequency-matching of gender and age with the cases. Chitotriosidase activity was evaluated by a fluorometric assay. Categorical variables were analysed with the χ2 test. Measurement data in multiple groups were tested with analysis of variance and least significant difference (LSD). Correlation between chitotriosidase activity and the degree of radiological extent (DRE) was examined by Spearman's rank correlation test. The average chitotriosidase activity levels of new TB cases, TB cases with different periods of treatment (<3, 3–6, >6 months) and the control group were 54·47, 34·77, 21·54, 12·73 and 10·53 nmol/h.ml, respectively. Chitotriosidase activity in TB patients declined along with the continuity of treatment. The chitotriosidase activity of both smear-positive and the smear-negative pulmonary TB patients decreased after 6 months' treatment to normal levels (P < 0·05). Moreover, chitotriosidase activity was positively correlated with DRE (r = 0·607, P < 0·001). Our results indicate that chitotriosidase might be a marker of TB treatment effects. However, further follow-up study of TB patients is needed in the future.
To understand the clinical epidemiology and molecular characteristics of human bocavirus (HBoV) infection in children with diarrhoea in Guangzhou, South China, we collected 1128 faecal specimens from children with diarrhoea from July 2010 to December 2012. HBoV and five other major enteric viruses were examined using real-time polymerase chain reaction. Human rotavirus (HRV) was the most prevalent pathogen, detected in 250 (22·2%) cases, followed by enteric adenovirus (EADV) in 76 (6·7%) cases, human astrovirus (HAstV) in 38 (3·4%) cases, HBoV in 17 (1·5%) cases, sapovirus (SaV) in 14 (1·2%) cases, and norovirus (NoV) in 9 (0·8%) cases. Co-infections were identified in 3·7% of the study population and 23·5% of HBoV-positive specimens. Phylogenetic analysis revealed 14 HBoV strains to be clustered into species HBoV1 with only minor variations among them. Overall, the detection of HBoV appears to partially contribute to the overall detection gap for enteric infections, single HBoV infection rarely results in severe clinical outcomes, and HBoV sequencing data appears to support conserved genomes across strains identified in this study.
The transport properties of the atomic scale side contact between different metals (Au, Ag, Pt, Cu, Ni, Pd) and graphene with open zigzag ends have been studied from first-principles electron transport calculations. According to the contact configurations, we find the weakly interacting metals (Au, Ag, Pt and Cu) can form chemical bonds at the open graphene’s atomic edges, while the strongly interacting ones form chemical bonds in the whole contact region. Comparing with the case of end contact which could effectively decrease the contact resistance, the atomic scale side contact shows better transport properties than the end contact. And the graphene/metal side contact with hydrogen terminated graphene edge show obviously large resistance than the ones with open graphene edge, which signifies the importance of the termination of graphene edge in graphene/metal contact.
We are developing a purely commensal survey experiment for fast (<5 s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.
In proton exchange membrane fuel cells (PEMFCs), a low interfacial pressure between the bipolar plates and the membrane exchange assembly (MEA) results in a high contact resistance. Conversely, an excessive interfacial pressure reduces the porosity of the gas diffusion layer (GDLs) and may damage the proton exchange membrane (PEM). Consequently, the performance of a PEMFC is critically dependent upon the clamping method. Accordingly, this study emphasizes the development of a numerical methodology for analyzing clamping of a PEMFC and constructs a detailed three-dimensional (3D) full-scale finite element (FE) model of a PEMFC with the traditional and most popular point-load design as an example. The numerical method is first validated by experiments. A series of simulations are then performed on the example cases (i.e. 2-bolt, 4-bolt or 6-bolt) to analyze their behaviors on the contact pressure between the bipolar plates and the MEA and the corresponding effects on the GDL porosity and the contact resistance, under the constraints that the membrane and gaskets remain within their respective elastic limits and the porosity of the GDL has a value higher than 0.5. Overall, to complete the analysis procedures proposed in this paper, the results show that the six-bolt clamping mode with a tightening torque of 16 N-m achieves a uniform pressure distribution and a high interfacial pressure, and therefore represents the optimal clamping mode for the performed example cases.
Pneumonia is an important cause of mortality and morbidity in infants. However, information of risk factors for pneumonia in children aged <6 months is limited. This study aimed to evaluate the risk factors and their contribution to infantile pneumonia in a large population-based survey. Of 24 200 randomly sampled main caregivers invited, 21 248 (87·8%) participated in this study. A structured questionnaire was used to interview the main caregivers. Information regarding whether hospitalization was required, family environment, and medical history were obtained. The prevalence of pneumonia was 0·62% in our study cohort. Multivariate logistic regression analysis showed that preterm birth, congenital cardiopulmonary disease, antibiotic use during pregnancy, maternal overweight, daily prenatal exposure to environmental tobacco smoke, maternal smoking during pregnancy, and visible mould on walls at home are risk factors associated with infantile pneumonia. Further study is warranted to investigate the causality and mechanisms of these novel factors.
The aortic pulse wave velocity (PWV) is a useful clinical index to assess the aortic compliance and cardiovascular risk in a noninvasive manner. In this research, our previously developed axial velocity profile method (Yu et al., ) was modified to be more user-friendly and applied to the study of PWV of diabetic patients for the first time, using phase-contrast magnetic resonance imaging (PC-MRI) technique to analyze the spatial and temporal profiles of the axial velocity along the descending aorta for measurement of the aortic PWV. The PWV results from healthy volunteers and diabetic patients were studied and compared. It is shown that the PWV of diabetic patients is much higher than that of health volunteers, the aortic compliance of diabetic patients is substantially worse than that of health volunteers. These results are in good agreement with early studies using different measurement techniques of PWV. The axial velocity profile method is again validated and proven to be a useful tool of long-term prognosis for patients with diabetes mellitus or hypertension.
A methodology to characterize nanoporous thin films based on a novel combination of high-resolution specular x-ray reflectivity and small-angle neutron scattering has been advanced to accommodate heterogeneities within the material surrounding nanoscale voids. More specifically, the average pore size, pore connectivity, film thickness, wall or matrix density, coefficient of thermal expansion, and moisture uptake of nanoporous thin films with non-homogeneous solid matrices can be measured. The measurements can be performed directly on films up to 1.5 µm thick while supported on silicon substrates. This method has been successfully applied to a wide range of industrially developed materials for use as low-k interlayer dielectrics.
High-resolution X-ray reflectivity and small angle neutron scattering measurements are used as complementary techniques to characterize the structure and properties of porous thin films for use as low-k interlevel dielectric (ILD) materials. With the addition of elemental composition information, the average pore size, porosity, pore connectivity, matrix density, average film density, film thickness, coefficient of thermal expansion, and moisture uptake of porous thin films are determined. Examples from different classes of materials and two analysis methods for small angle neutron scattering data are presented and discussed.
The structures and properties of the HSQ film during the cage/network transformation were studied by curing at 300°C for 1 hour. The experimental results show that the ratio of the network/cage structure of the cured HSQ film increases from 0.21 to 0.39 by curing. The porosity of the cured film increases from 10.0% to 12.3 %, while the refractive index decreases from 1.413 to 1.376 during curing. These results suggest that the dependence of the structure and properties of the HSQ film by curing. The CMP characteristics of HSQ were studied by using different kinds of slurries and surfactant. The CMP results of polishing HSQ suggest that the hardness and charge status of the abrasive, the interaction of the surfactant with the abrasive and film surface significantly affect the polishing results.
In this study, a novel inflatable belt-type clamp is introduced and its performance is verified. Finite element simulations are performed to compare the performance of three different aorta clamping systems. In every case, the aorta is modeled as a simple hollow cylinder made of linearly elastic material. For a traditional surgical clamp in which the jaws remain inclined to one another as they close around the aorta, the maximum normal stress within the aorta wall is found to be 806kPa. It is shown that the numerical results are in good qualitative agreement with the experimental results obtained using a pressure sensitive film. The simulation results for a modified clamp in which the jaws remain parallel during the clamping operation show that the maximum normal stress is reduced to 222kPa. However, two regions of maximum stress are induced within the aorta wall. Finally, the numerical results for a novel inflatable belt-type clamp show that the maximum normal stress is equal to approximately 221kPa. In contrast to the modified clamp, the stress is uniformly distributed around the perimeter of the aorta, and thus the risk of aortic dissection is significantly reduced.
The experimental results for different structures of contact image sensor are reported in this paper, which includes Schottky barrier, p-i junction, p-l-n junction, and MIS structures. The J-V characteristics of p-i-n a-Si: H contact image sensor under dark and illuminated conditions have been simulated by solving the Poisson's equation and the continuity equations, and the results are correlated with the experiments. The dependence of the dark and photo currents on the parameters such as the density of states in the gap, intrinsic layer width, dopant concentrations of p* layer and n+ layer are discussed.
Dielectric layers of thin silicon carbon nitride (SiCxNy) films have been prepared by ion beam sputtering deposition (IBD). For submicron metal-insulator-Si (MIS) based device applications, a dielectric of low interface roughness, increased capacitance/area with lower leakage on decreasing scale is highly desirable. We address these aspects for the IBD SiCxNy films on p-type Si and present their structural, optical and electrical characteristics as a function of the deposition conditions. Ultraviolet-visible transmittance and spectroscopic ellipsometry were employed to study the optical properties of the SiCxNy films. For electrical measurements, Al gate electrodes were fabricated on SiCxNy films to form metal-nitride-silicon (MNS) diodes. Characteristic I-V and photoconductivity measurements of the MNS are presented.
We proposed a concise and novel scheme to determine the crystallographic misorientation of heteroepitaxial structures. In addition to subtle high-resolution transmission electron microscope images, the information revealed from selected-area diffraction patterns at the interfaces offers another path to determine the angles of misorientations. The principle is to extract the basically three-dimensional misorientation information from a two-dimensional selected-area diffraction pattern through the employment of the Laue circle
The water-soluble self-acid-doped conducting polyanilines, poly(aniline-co-Npropanesulfonic acid aniline) (PAPSAH) and sulfonic acid ring substituted polyaniline (SPAN), in aqueous solutions at full concentration range are characterized. The PAPSAH and SPAN can be cast into free standing films from their aqueous solutions and have the doping level, about 0.3. Their conductivities at room temperature are about the same (10−2 S/cm). As temperature increases, conductivities of PAPSAH and SPAN increase to the maxima about 10−1 S/cm at 110°C and 190°C respectively. Above these temperatures, their conductivities drop resulting from thermal undoping accompanying with a loss of some polarons. The incorporation of PVA into PAPSAH and SPAN provides excellent flexibility and only slightly decreased conductivity (10−3 S/cm at equal weight %). Applications of these two polymers and their blends in electron beam lithography and light emitting diode are studied.
Continuous polycrystalline SiCN films with high nucleation density have been successfully deposited by using CH3NH2, as carbon source gas in an ECR-CVD reactor. Fom the kinetic point of view, using CH3NH2, as carbon source could provide more abundant active carbon species in the gas phase to enhance the carbon incorporation in the SiCN films. The compositions of the SiCN films analyzed from Rutherford Backscattering Spectroscopy showed that higher [CH3NH2,]/[SiH4] ratio led to higher carbon content in the films. Moreover, a lower carbon content was measured when the film was deposited at higher substrate temperature. The direct band gap of the aforementioned SiCN films determined using PzR is around 4.4 eV, indicating a wide band gap material for blue-UV optoelectronics.