A convertor and user interface to import CAD files into worldtoolkit virtual reality systems

Virtual Reality (VR) is a rapidly developing human-to-computer interface technology. VR can be considered as a three-dimensional computer-generated Virtual World (VW) which can sense particular aspects of a user's behavior, allow the user to manipulate the objects interactively, and render the VW at real-time accordingly. The user is totally immersed in the virtual world and feel the sense of transforming into that VW. NASA/MSFC Computer Application Virtual Environments (CAVE) has been developing the space-related VR applications since 1990. The VR systems in CAVE lab are based on VPL RB2 system which consists of a VPL RB2 control tower, an LX eyephone, an Isotrak polhemus sensor, two Fastrak polhemus sensors, a folk of Bird sensor, and two VPL DG2 DataGloves. A dynamics animator called Body Electric from VPL is used as the control system to interface with all the input/output devices and to provide the network communications as well as VR programming environment. The RB2 Swivel 3D is used as the modelling program to construct the VW's. A severe limitation of the VPL VR system is the use of RB2 Swivel 3D, which restricts the files to a maximum of 1020 objects and doesn't have the advanced graphics texture mapping. The other limitation is that the VPL VR system is a turn-key system which does not provide the flexibility for user to add new sensors and C language interface. Recently, NASA/MSFC CAVE lab provides VR systems built on Sense8 WorldToolKit (WTK) which is a C library for creating VR development environments. WTK provides device drivers for most of the sensors and eyephones available on the VR market. WTK accepts several CAD file formats, such as Sense8 Neutral File Format, AutoCAD DXF and 3D Studio file format, Wave Front OBJ file format, VideoScape GEO file format, Intergraph EMS stereolithographics and CATIA Stereolithographics STL file formats. WTK functions are object-oriented in their naming convention, are grouped into classes, and provide easy C language interface. Using a CAD or modelling program to build a VW for WTK VR applications, we typically construct the stationary universe with all the geometric objects except the dynamic objects, and create each dynamic object in an individual file

Wigner Lattice Order, Collective Mode, and Superconductivity in La1.985Sr0.015CuO4+delta System

We have studied far-infrared charge dynamics of Sr- and O- co-doped La1.985Sr0.015CuO4+delta with delta = 0.024 (p = 0.063 per Cu) and delta = 0.032 (p = 0.07). We found that two-dimensional Wigner lattice order is the ground state of cuprates away from half-filling. We found that the presence of 2D Wigner lattice and the pinned Goldstone mode is essential for the cuprate physics and superconductivity. We propose that all the high Tc physics are based on the existence of these peculiar 2D electron lattices.Comment: 12 pages, 7 figures, 47 reference

Dinuclear platinum(II) sulfide–thiolate complexes [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ containing fluorinated substituents and the identification of a SC₆F₅ π interaction in the crystal structure of [Pt₂(μ-S)(μ-SCH₂C₆F₅)(PPh₃)₄]BPh₄•2C₆H₆

Reactions of the platinum(II) sulfido complex [Pt₂(μ-S)₂(PPh₃)₄] with the alkyl iodides ICH₂CH₂(CF₂)nCF₃ (n = 3, 7) gives good yields of the monoalkylated products [Pt₂(μ-S){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]⁺, which were isolated as PF₆⁺or BPH₄⁻ salts, and characterised by ESI mass spectrometry, NMR spectroscopy and elemental analysis. The complex [Pt₂(μ-S){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]⁺ appears to have normal reactivity for this type of complex, namely reaction with Ph₃PAuCl to give [Pt₂(μ-SAuPPh₃){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]₂⁺, and reaction with Me₂SO₄ to give [Pt₂(μ-SMe){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]₂⁺. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with C₆F₅CH₂Br gave [Pt₂(μ-S)(μ-SCH₂C₆F₅)(PPh₃)₄]⁺, isolated as BPh₄⁻ its salt, and characterised by NMR spectroscopy and a single-crystal X-ray structure determination. The C₆F₅ group lies above the {Pt₂S₂} core of the complex as a result of a SC₆F₅ π interaction, in contrast to the published structure of [Pt₂(μ-S)(μ-SCH₂C₆H₅)(PPh₃)₄]PF₆, where the C₆H₅ group projects away from the {Pt₂S₂} core

Universal optimal hole-doping concentration in single-layer high-temperature cuprate superconductors

We argue that in cuprate physics there are two types, hole content per CuO$_2$ plane ($P_{pl}$) and the corresponding hole content per unit volume ($P_{3D}$), of hole-doping concentrations for addressing physical properties that are two-dimensional (2D) and three-dimensional (3D) in nature, respectively. We find that superconducting transition temperature ($T_c$) varies systematically with $P_{3D}$ as a superconducting \textquotedblleft $dome$\textquotedblright with a universal optimal hole-doping concentration $P_{3D}^{opt.}$ = 1.6 $\times$ 10$^{21}$ cm$^{-3}$ for single-layer high temperature superconductors. We suggest that $P_{3D}^{opt.}$ determines the upper bound of the electronic energy of underdoped single-layer high-$T_c$ cuprates.Comment: 8 pages, 4 figures; added references ;accepted for the publication in Supercond. Sci. Technol ; Ref. 13 is revise

Modelling, identification and application of phenomenological constitutive laws over a large strain rate and temperature range

A review of the different phenomenological thermo-viscoplastic constitutive models often applied to forging and machining processes is presented. Several of the most common models have been identified using a large experimental database (Hor et al., 2013). The latter consists of the tests were done in compression on cylindrical shaped specimens and in shear using hat-shaped specimens. The comparison between these different models is shown that the group of decoupled empirical constitutive models (e.g. the Johnson and Cook (1983) model), despite their simple identification procedures, are relatively limited, especially over a large range of strain rates and temperatures. Recent studies have led to the proposal of coupled empirical models. Three models in this class have also been studied. The Lurdos (2008) model shows the best accuracy but requires a large experimental database to identify its high number of parameters. After this comparison, a constitutive equation is proposed by modifying the TANH model (Calamaz et al., 2010). Coupling between the effects of strain rate and temperature is introduced. This model is easier to identify and does not require knowledge of the saturation stress. Compared to other models, it better reproduces the experimental results especially in the semi-hot and hot domains. In order to study real machining conditions, an orthogonal cutting tests is considered. The comparison between experimental test results and numerical simulations conducted using the previously identified constitutive models shows that the decoupled empirical models are not capable of reproducing the experimental observations. However, the coupled constitutive models, that take into account softening, improve the accuracy of these simulations

Superconductivity and non-metallicity induced by doping the topological insulators Bi2Se3 and Bi2Te3

We show that by Ca-doping the Bi2Se3 topological insulator, the Fermi level can be fine tuned to fall inside the band gap and therefore suppress the bulk conductivity. Non-metallic Bi2Se3 crystals are obtained. On the other hand, the Bi2Se3 topological insulator can also be induced to become a bulk superconductor, with Tc ~ 3.8 K, by copper intercalation in the van der Waals gaps between the Bi2Se3 layers. Likewise, an as-grown crystal of metallic Bi2Te3 can be turned into a non-metallic crystal by slight variation of the Te content. The Bi2Te3 topological insulator shows small amounts of superconductivity with Tc ~ 5.5 K when reacted with Pd to form materials of the type PdxBi2Te3

Unified electronic phase diagram for hole-doped high-Tc cuprates

We have analyzed various characteristic temperatures and energies of hole-doped high-Tc cuprates as a function of a dimensionless hole-doping concentration (pu). Entirely based on the experimental grounds we construct a unified electronic phase diagram (UEPD), where three characteristic temperatures (T*'s) and their corresponding energies (E*'s) converge as pu increases in the underdoped regime. T*'s and E*'s merge together with the Tc curve and 3.5kBTc curve at pu - 1.1 in the overdoped regime, respectively. They finally go to zero at pu - 1.3. The UEPD follows an asymmetric half-dome-shaped Tc curve in which Tc appears at pu - 0.4, reaches a maximum at pu - 1, and rapidly goes to zero at pu - 1.3. The asymmetric half-dome-shaped Tc curve is at odds with the well-known symmetric superconducting dome for La2-xSrxCuO4 (SrD-La214), in which two characteristic temperatures and energies converge as pu increases and merge together at pu - 1.6, where Tc goes to zero. The UEPD clearly shows that pseudogap phase precedes and coexists with high temperature superconductivity in the underdoped and overdoped regimes, respectively. It is also clearly seen that the upper limit of high-Tc cuprate physics ends at a hole concentration that equals to 1.3 times the optimal doping concentration for almost all high-Tc cuprate materials, and 1.6 times the optimal doping concentration for the SrD-La214. Our analysis strongly suggests that pseudogap is a precursor of high-Tc superconductivity, the observed quantum critical point inside the superconducting dome may be related to the end point of UEPD, and the normal state of the underdoped and overdoped high temperature superconductors cannot be regarded as a conventional Fermi liquid phase.Comment: 17 pages, 8 figures, and 10 tables. Accepted for the publication of the Physical review

Relation between fruit density and beta-carotene content in ripe mango

β-carotene content is one of the main factors that determines the nutritional quality and orange color of ripe mango fruit. It is known as the pro vitamin A, and it is generally the predominant carotenoid in ripe mango. Currently, fresh fruit sector demands a reliable nondestructive indicator to better predict the nutritional quality of ripe mango, and especially in terms of β-carotene content. Fruit density has been applied in horticulture sector to predict dry matter or maturation stage of mango. It would interesting to know if it can be a relevant non-destructive indicator of the carotenoid content in fruits Therefore, the aim of this study was to identify the relationship between mango density and β-carotene content at the ripe stage. Mangoes (cv. 'Kent'), from Ivory Coast, Peru, and Brazil were selected from a mango importer in France at a green mature stage (day 0). Then, all mangoes were ripened at 18 °C and 80% of relative humidity. Color of ripe mango pulp and β-carotene contents were assessed 11 and 15 days after (day 0) corresponding to a ripe stage of consumption. Fruit density was significantly correlated to the pulp color and β-carotene contents of ripe mangoes, whatever the origin (p-value < 0.05). Mango fruits with a high density were characterized by high value of Chroma, lower value of Hue angle, and high contents in β-carotene. β-carotene content was found in range of [92-307 μg.100g.FM-1] for low density mango, and in range of [365-924 μg.100g.FM-1] for high density mango. So, fruit density, measured at the green-mature stage, could be a reliable indicator to predict the nutritional quality of mango fruit at the ripening stage, which is extremely useful for fresh fruit sector for grading or sorting mango fruit early in the supply chain