8,362 research outputs found
Thermo-mechanical analysis of dental silicone polymers
Soft lining materials are used to replace the inner surface of a conventional complete denture, especially for weak elderly patients, with delicate health who cannot tolerate the hard acrylic denture base. Most of these patients have fragile supporting mucosa, excessive residual ridge resorption, particularly on the mandibular arch. The application of a soft liner to the mandibular denture allows absorbing impact forces during mastication and relieving oral mucosa. Actually, the silicone rubbers constitute the main family of commercialised soft lining materials. This study was conducted to understand the relationships between the mechanical properties and the physical structure of polysiloxanes. For this purpose, a series of polysiloxanes of various chemical compositions have been investigated. The evolution of their physical structure as a function of temperature has been followed by differential scanning calorimetry (DSC). In order to facilitate comparisons, the mechanical modulus has been analysed upon the same heating rate using dynamic mechanical analysis (DMA). Polysiloxanes actually commercialised as soft denture liners are three-dimensional networks: the flexibility of chains allows a crystalline organisation in an amorphous phase leading to the low value of the shear modulus. The dynamic mechanical analysis shows that they are used in the rubbery state. So, polysiloxanes have steady mechanical properties during physiological utilisation
Anomalous expansion and phonon damping due to the Co spin-state transition in RCoO_3 with R = La, Pr, Nd and Eu
We present a combined study of the thermal expansion and the thermal
conductivity of the perovskite series RCoO_3 with R = La, Nd, Pr and Eu. The
well-known spin-state transition in LaCoO_3 is strongly affected by the
exchange of the R ions due to their different ionic radii, i.e. chemical
pressure. This can be monitored in detail by measurements of the thermal
expansion, which is a highly sensitive probe for detecting spin-state
transitions. The Co ions in the higher spin state act as additional scattering
centers for phonons, therefore suppressing the phonon thermal conductivity.
Based on the analysis of the interplay between spin-state transition and heat
transport, we present a quantitative model of the thermal conductivity for the
entire series. In PrCoO_3, an additional scattering effect is active at low
temperatures. This effect arises from the crystal field splitting of the 4f
multiplet, which allows for resonant scattering of phonons between the various
4f levels.Comment: 15 pages including 5 figure
Wages, prices, and living standards in China, 1738-1925: in comparison with Europe, Japan, and India
The paper develops data on the history of wages and prices in Beijing, Canton, Suzhou/Shanghai in China from the eighteenth century to the twentieth and compare them with leading cities in Europe, Japan and India in terms of nominal wages, the cost of living, and the standard of living. In the eighteenth century, the real income of building workers in Asia was similar to that of workers in the backward parts of Europe but far behind that in the leading economies in northwestern Europe. Real wages declined in China in the eighteenth and early nineteenth centuries and rose slowly in the late nineteenth and early twentieth with little cumulative change for two hundred years. The income disparities of the early twentieth century were due to long run stagnation in China combined with industrialization in Japan and Europe.
Hole density dependence of effective mass, mobility and transport time in strained Ge channel modulation-doped heterostructures
We performed systematic low-temperature (T = 350 mK–15 K) magnetotransport measurements on the two-dimensional hole gas with various sheet carrier densities Ps = (0.57–2.1)×1012 cm–2 formed in the strained Ge channel modulation-doped (MOD) SiGe heterostructures grown on Si substrates. It was found that the effective hole mass deduced by temperature dependent Shubnikov–de Hass oscillations increased monotonically from (0.087±0.05)m0 to (0.19±0.01)m0 with the increase of Ps, showing large band nonparabolicity in strained Ge. In contrast to this result, the increase of the mobility with increasing Ps (up to 29 000 cm2/V s) was observed, suggesting that Coulomb scattering played a dominant role in the transport of the Ge channel at low temperatures. In addition, the Dingle ratio of the transport time to the quantum lifetime was found to increase with increasing Ps, which was attributed to the increase of remote impurity scattering with the increase of the doping concentration in MOD SiGe layers
On-the-fly GPS-based attitude determination using single- and double-differenced carrier phase measurements
Carrier phase measurements are primary observations for GPS attitude determination. Although the satellite-related errors can be virtually eliminated by forming single differences, the baseline-related errors such as line biases are still present in the single-differenced carrier phase measurements. It is, therefore, difficult to resolve the single-differenced integer ambiguities due to the line biases. By forming double differences, the line biases of the single-differenced carrier phase measurements can be effectively removed. However, the main disadvantages of this method lie in the fact that the double-differenced measurements are mathematically correlated and consequently the attitude obtained from the double differences is noisy. This paper presents a new algorithm through which both single and double differences are used simultaneously to resolve these problems in real-time. The solution of the integer ambiguities can be obtained by searching for the most likely grid point in the attitude domain that is independent of the correlation with the double differences. Next, the line biases and corresponding single difference integer ambiguities can be resolved on the fly by using the noisy attitude solution obtained from the previous double difference procedure. In addition, the relationship between the physical signal path difference and the line bias is formed. A new method is also applied to derive the attitude angles through finding the optimal solution of the attitude matrix element. The proposed new procedure is validated using ground and flight tests. Results have demonstrated that the new algorithm is effective and can satisfy the requirement of real-time applications
Precise Pressure Dependence of the Superconducting Transition Temperature of FeSe: Resistivity and ^77Se--NMR Study
We report the precise pressure dependence of FeSe from a resistivity
measurement up to 4.15 GPa. Superconducting transition temperature (T_c)
increases sensitively under pressure, but shows a plateau between 0.5-1.5 GPa.
The maximum T_c, which is determined by zero resistance, is 21 K at
approximately 3.5 GPa. The onset value reaches ~37 K at 4.15 GPa. We also
measure the nuclear spin-lattice relaxation rate 1/T_1 under pressure using
77Se--NMR measurement. 1/T_1 shows that bulk superconductivity is realized in
the zero-resistance state. The pressure dependence of 1/T_1T just above T_c
shows a plateau as well as the pressure dependence of T_c, which gives clear
evidence of the close relationship between 1/T_1T and T_c. Spin fluctuations
are suggested to contribute to the mechanism of superconductivity.Comment: 4pages, 6figures: to be published in J. Phys. Soc. Jpn. Vol.78 No.6
(2009
Beyond the standard model physics at RHIC in polarized pp collision
A polarized hadron collider experiment must have a great discovery potential
for a search of physics beyond the standard model. Experimental data of various
symmetry tests at RHIC are going to be obtained within a few years. The author
developed a simulation tool, studying a sensitivity of hunting contact
interaction at RHIC by measuring parity violating spin asymmetries.Comment: 8 pages, 9 figure, Proc. of Praha-SPIN-200
Action comprehension: deriving spatial and functional relations.
A perceived action can be understood only when information about the action carried out and the objects used are taken into account. It was investigated how spatial and functional information contributes to establishing these relations. Participants observed static frames showing a hand wielding an instrument and a potential target object of the action. The 2 elements could either match or mismatch, spatially or functionally. Participants were required to judge only 1 of the 2 relations while ignoring the other. Both irrelevant spatial and functional mismatches affected judgments of the relevant relation. Moreover, the functional relation provided a context for the judgment of the spatial relation but not vice versa. The results are discussed in respect to recent accounts of action understanding
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