Results 1 - 10 of 20
Results 1 - 10 of 20. Search took: 0.016 seconds
|Sort by: date | relevance|
[en] This study was designed to clarify the three dimensional features of naso-maxillary complex in cleft lip and palate (CLP) by using computed tomography (CT) and to examine its change following an upper dental arch expansion. Sequential CT images with 2mm-thickness were obtained for 11 unilateral CLP boys (UCLP), 6 bilateral CLP boys (BCLP) and 4 boys without cleft (non-cleft). Additionally, two serial sets of upper dental cast before and after dental arch expansion coupled with CT images in UCLP were used to evaluate the effect of dental arch expansion on the naso-maxillary complex. UCLP demonstrated a remarkable naso-maxillary deformity characterized by a decreased volume of maxillary sinus in comparison with the non-cleft patients. Both the volume and shape of nasal cavity were significantly different between the cleft and non cleft side. Naso-maxillary morphology of BCLP, however, was similar to that of the non cleft except for the decreased volume of alveolar arch. Comparative study of UCLP and BCLP showed a significant difference in naso-maxillary morphology. There were some significant correlations between the dental arch expansion and change of each naso-maxillary component, suggesting the effect of expansion stress on the naso-maxillary complex in UCLP. However, deformation caused by expansion stress varied, depending on each component of the naso-maxillary complex. (author) 61 refs
[en] The manned deep-space exploration is a hot topic of the current space activities. The continuous supply of thermal and electrical energy for the scientific equipment and human beings is a crucial issue for the lunar outposts. Since the night lasts for periods of about 350 h at most locations on the lunar surface, massive energy storage is required for continuous energy supply during the lengthy lunar night and the in-situ resource utilization is demanded. A lunar based solar thermal power system with regolith thermal storage is presented in this paper. The performance analysis is carried out by the finite-time thermodynamics to take into account major irreversible losses. The influences of some key design parameters are analyzed for system optimization. The analytical results shows that the lunar based solar thermal power system with regolith thermal storage can meet the requirement of the continuous energy supply for lunar outposts. - Highlights: • A lunar based solar thermal power system with regolith thermal storage is presented. • The performance analysis is carried out by the finite-time thermodynamics. • The influences of some key design parameters are analyzed.
[en] The lattice constants and equilibrium atomic volume of α-uranium were calculated by Density Functional Theory (DFT). The first principles calculation results of the lattice for α-uranium are in agreement with the experimental results well. The thermodynamic properties of α-uranium from 0 to 900 K and 0–100 GPa were calculated with the quasi-harmonic Debye model. Volume, bulk modulus, entropy, Debye temperature, thermal expansion coefficient and the heat capacity of α-uranium were calculated. The calculated results show that the bulk modulus and Debye temperature increase with the increasing pressure at a given temperature while decreasing with the increasing temperature at a given pressure. Volume, entropy, thermal expansion coefficient and the heat capacity decrease with the increasing pressure while increasing with the increasing temperature. The theoretical results of entropy, Debye temperature, thermal expansion coefficient and the heat capacity show good agreement with the general trends of the experimental values. The constant-volume heat capacity shows typical Debye T"3 power-law behavior at low temperature limit and approaches to the classical asymptotic Dulong-Petit limit at high temperature limit. - Highlights: • Thermodynamic properties of α-U were predicted systematically with quasi-harmonic Debye model. • Summarizations of the corresponding experimental and theoretical results have been made for the EOS and other thermodynamic parameters. • The calculated thermodynamic properties show good agreement with the experimental results in general trends.
[en] The low grade heat utilization is not only an inevitable option to solve the energy and environment problems, but also a critical issue for many remote power applications and planetary explorations. In this study, a novel design called a heat engine aerobot which can convert planetary atmospheric energy to electricity is proposed and analysed. A dynamic theoretical model is established and some key issues, such as the thermodynamic performance and conversion efficiency are analysed. It shows that the heat engine aerobot is capable to convert the low grade atmospheric energy to electricity during its self-sustained vertical oscillation movement. Parametric analysis shows that some design parameters, such as the nozzle number, the nozzle outlet diameter, the initial liquid mass and the turbine start height may have significant influence on the energy generation performance. - Highlights: • A novel heat engine for low grade atmospheric energy utilization was proposed. • A theoretical model was established and the dynamic behaviour was simulated. • The parametric effects on its thermodynamic performance were analysed
[en] Objective: To investigate the value of various diagnostic methods used in subarachnoid hemorrhage (SAH) for providing the best choice of method at different periods and for different etiology. Methods: The clinical information and results of lumbar puncture, CT, MRA, DSA were analyzed retrospectively in 122 patients suffering from SAH at different periods in order to investigate the sensitivity of positive findings and analyze the cause of negative findings. Results: Acute headache, vomit, meningeal irritation sign, the change of eyeground were the useful early clinical manifestation. The positive rate of lumbar puncture was 100% and the positive rate of CT was 92% within 72 hours after onset. The positive findings of MRI, MRA were 45.55% in etiological diagnosis, while those of DSA were 70.83% (including 28 cases of aneurysm, 30 of arteriovenous malformation AVM, 5 of dural arteriovenous fistula, 2 of vasculitis, 1 of lateral sinus thrombus). MRI detected vascular malformation of spinal cord in 2 cases. Conclusion: Specific symptom and lumbar puncture are the methods of choice for confirmation diagnosis in patients suffering from SAH within the acute period. Negative result in CT can't rule out SAH. DSA is better than MRA in etiological diagnosis. The actual result etiology could be revealed by MR or spinal cord angiography when all results of CT, MRA , and DSA are normal. (authors)
[en] CoWO4 nanorods were synthesized at 453 K for 12 h by a hydrothermal technology from Na2WO4 . 2H2O and CoCl2 . 6H2O in the presence of sodium dodecyl sulfate (SDS). The as-synthesized CoWO4 nanorods were characterized by various techniques of X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray detector. Luminescent properties of the samples were measured at room temperature. The results showed that CoWO4 products are nanorods with diameters of about 20 nm, and lengths ranging between 100 and 200 nm. CoWO4 nanorods display a very strong PL peak at 453 nm with the excitation wavelength 300 nm. The possible formation mechanism of CoWO4 nanorods was suggested
[en] ZnWO4 nanorods with a bundle-like structure were synthesized at 180 C for 12 h by a hydrothermal technology from Na2WO4.2H2O and ZnSO4.7H2O in the presence of sodium dodecyl sulfate (SDS). The as-synthesized bundle-like structure of ZnWO4 nanorods was characterized by various techniques: TEM, XRD and EDS. The luminescence properties of the bundle-like structure of the ZnWO4 nanorods were investigated by photoluminescence (PL) spectroscopy. (orig.)
[en] 9Cr3W low activation martensitic steel was designed by adding more tungsten and adjusting microalloy elements such as V, Ta, Ti and N. The microstructure and hardening, aging and transformation behavior were investigated. Tensile and charpy impact tests were performed. 9Cr3W steel has greatly improved high temperature instantaneous strength compared with the existing low activation ferritic/martensitic steels such as Eurofer97. Feasibility of the steel was analysed for in-core component and fuel cladding application in supercritical water cooled reactor. 9Cr3W steel has advantages in tensile properties at elevated temperature relative to zircaloy and T91 steel and exhibits a lower ductile-brittle transition temperature and a higher upper shelf energy than T91 steel, indicating a superior impact toughness. However, instantaneous strength of 9Cr3W steel at elevated temperature is not high as AL316 austenite stainless steel for the use of in-core component and fuel cladding application in supercritical water cooled reactor. (authors)
[en] CNS series ferritic/martensitic (F/M) steel and Mod-AL-6XN steel was developed aim at critical water cooled reactor in-core components and structure materials for future commercial fusion reactor and different scales and batches of these steel were fabricated. The cold and hot deformation processes, heat treatment parameters and the relationship of microstructure and properties were invested intensively. At last, thick plate. sheet and seamless steel tube were fabricated. The tensile strength of CNS-Ⅰ, CNS-Ⅱ and Mod-CNS-Ⅱ steel at room temperature were 680 MPa, 800 MPa and 917 MPa, respectively, and the total elongation of these steels were 24.5%, 22.5% and 20% respectively. At 600℃ the tensile strength of these steels were 365 MPa, 423 MPa and 482 MPa, respectively, and the total elongation were 23.5%, 22% and 31%, respectively. The ductile to brittle transition temperature (DBTT) of these steel were -90℃, -25℃ and -55℃, respectively. The tensile strength of Mod-AL-6XN and AL-6XN were 745 MPa and 565 MPa at room temperature and 500℃, the total elongation of Mod-AL-6XN were 53.3% and 60.4%, respectively. At last, CSN series steel and Mod-AL-6XN steel were tested at supercritical water at different conditions to evaluating the corrosion behavior of these steels. The results show that the austenitic steel has better corrosion resistance than F/M steels and increasing in weight percent of Cr in F/M steel can improve their corrosion resistance. After the corrosion tests a two layer oxide scale were identified on all steels. Fe was enriched in the outer oxide layer and depleted in the inner oxide layer and the distribution of Cr was opposed to Fe. The outer oxide layer was mainly composed of Fe3O4, and the inner oxide layer was mainly FeCr2O4. (authors)
[en] The gas temperature of a stratospheric airship plays an important role in its flight dynamics. A multi-nodes heat transient model is proposed and evaluated by the theoretical solutions of the adiabatic processes and the high altitude flight test data. A thermodynamic analysis code for stratospheric airships (TACSA) is developed to investigate the ascent subcooling induced by the thermodynamic expansion and the descent superheating induced by the thermodynamic compression. The simulation results show that the airship volume, vertical speed and the solar radiation have evident influence on the ascent subcooling descent superheating effects. - Highlights: • A multi-nodes heat transient model for stratospheric airships is proposed. • The thermal behaviors of the ascent and descent processes are predicted. • The volume, vertical speed and solar radiation have significant influence