Spatially resolved X-ray diffraction phase mapping and α → β → α transformation kinetics in the heat-affected zone of commercially pure titanium arc welds

Spatially resolved X-ray diffraction (SRXRD) is used to map the α → β → α phase transformation in the heat-affected zone (HAZ) of commercially pure titanium gas tungsten arc welds. In situ SRXRD experiments were conducted using a 180-μm-diameter X-ray beam at the Stanford Synchrotron Radiation Laboratory (SSRL) (Stanford, CA) to probe the phases present in the HAZ of a 1.9 kW weld moving at 1.1 mm/s. Results of sequential linear X-ray diffraction scans made perpendicular to the weld direction were combined to construct a phase transformation map around the liquid weld pool. This map identifies six HAZ microstructural regions between the liquid weld pool and the base metal: (1) α-Ti that is undergoing annealing and recrystallization; (2) completely recrystallized α-Ti; (3) partially transformed α-Ti, where α-Ti and β-Ti coexist; (4) single-phase β-Ti; (5) back-transformed α-Ti; and (6) recrystallized α-Ti plus back-transformed α-Ti. Although the microstructure consisted predominantly of α-Ti, both prior to and after the weld, the crystallographically textured starting material was altered during welding to produce different α-Ti textures within the resulting HAZ. Based on the travel speed of the weld, the α → β transformation was measured to take 1.83 seconds during heating, while the β → α transformation was measured to take 0.91 seconds during cooling. The α → β transformation was characterized to be dominated by long-range diffusional growth on the leading (heating) side of the weld, while the β → α transformation was characterized to be predominantly massive on the trailing (cooling) side of the weld, with a massive growth rate on the order of 100 μm/s.     

Silicon Nitride Derived from an Organometallic Polymeric Precursor: Preparation and Characterization

Partially crystalline Si₃N₄, with nanosized crystals and a specific surface area greater than 200 m²/g, is obtained by pyrolysis of a commercially available vinylic polysilane in a stream of anhydrous NH₃ to 1000°C. This polymer does not contain N initially. Crystallization to high-purity α-Si₃N₄ proceeds with additional heating above 1400°C under N₂. The changes in crystallinity, powder morphology, infrared spectra, and elemental compositions, for samples annealed from 1000° to 1600°C under N₂, are consistent with an amorphous-to-crystalline transformation. Although macroscopic consolidation and local densification occur at 1400°C, volatilization and accompanying weight loss limit bulk densification. The effect of temperature on specific surface area is examined and related to the sintering process. These results are applicable to pyrolysis, decomposition, and crystallization studies of ceramics synthesized by polymeric precursor routes.     

Preparation of Silicon Carbide/Aluminum Nitride Ceramics Using Organometallic Precursors

Solid solutions of 2H -SiC/AlN can be prepared at temperatures less than 1600°C by rapid pyrolysis ("hot drop") of mixtures of [(Me₃Si)_0.80((CH₂=CH)MeSi)_1.0(MeHSi)_0.35] _n (VPS) or [MeHSiCH₂] _n (MPCS) with [R₂AlNH₂]₃, where R=Et, i -Bu or simply by slow pyrolysis of the precursor mixture in the case of [Et₂AlNH₂]₃. In contrast, slow pyrolysis of mixtures of VPS or MPCS with [ i -Bu₂AlNH₂]₃ yields a composite of 2 H -AlN and 3 C -SiC at 1600°C, which transforms into a single 2 H -SiC/AlN solid solution on heating to 2000°C. The influences of the nature of the precursor and processing conditions on the structure, composition, and purity of the SiC/AlN materials are discussed.     

A power-efficient vertical handover with MIH-based network scanning through consistency check

We propose an power-efficient scanning scheme considering the consistency of the Information Element (IE) for the Media Independent Handover (MIH) based Vertical Handover. Since the Green IT is one of the key issues of the science, we suggested the power saving scheme by extending the information and the event service of the MIH framework to reduce the number of full scanning. We proposed the criteria to select the update MT to quantify the power consumption alongside various network scanning methods. Since the frequent and multiple network scanning incurred by small mobile terminals (MT) is considerable, the scanning avoidance is essential for the framework we suggest. The MIH Information Service (MIIS) provides many usable factors and features for the scanning avoidance. However, because of the absence of the criteria to select the update node, these values are not actually usable. Therefore, we suggest an Energy Efficient Function, which tests the validity of MIIS values and makes a decision on whether to avoid the scanning or not.     

On detecting co-resident cloud instances using network flow watermarking techniques

Virtualization is the cornerstone of the developing third-party compute industry, allowing cloud providers to instantiate multiple virtual machines (VMs) on a single set of physical resources. Customers utilize cloud resources alongside unknown and untrusted parties, creating the co-resident threat—unless perfect isolation is provided by the virtual hypervisor, there exists the possibility for unauthorized access to sensitive customer information through the exploitation of covert side channels. This paper presents co-resident watermarking, a traffic analysis attack that allows a malicious co-resident VM to inject a watermark signature into the network flow of a target instance. This watermark can be used to exfiltrate and broadcast co-residency data from the physical machine, compromising isolation without reliance on internal side channels. As a result, our approach is difficult to defend against without costly underutilization of the physical machine. We evaluate co-resident watermarkingunder a large variety of conditions, system loads and hardware configurations, from a local laboratory environment to production cloud environments (Futuregrid and the University of Oregon’s ACISS). We demonstrate the ability to initiate a covert channel of 4 bits per second, and we can confirm co-residency with a target VM instance in $<$ 10 s. We also show that passive load measurement of the target and subsequent behavior profiling is possible with this attack. We go on to consider the detectability of co-resident watermarking, extending our scheme to create a subtler watermarking attack by imitating legitimate cloud customer behavior. Our investigation demonstrates the need for the careful design of hardware to be used in the cloud.     

Specificity of Systemically Released Cotton Volatiles as Attractants for Specialist and Generalist Parasitic Wasps

Cotton plants under herbivore attack release volatile semiochemicals that attract natural enemies of the herbivores to the damaged plant. The volatiles released in response to herbivory are not only released from the damaged leaves but from the entire cotton plant. We found that cotton plants that released myrcene, (Z)-3-hexenyl acetate, (E)--ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)--farnesene, and (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene systemically from undamaged leaves of caterpillar damaged plants were attractive to the generalist parasitoid Cotesia marginiventris and the specialist parasitoid Microplitis croceipes. Plants from which the caterpillar damaged leaves were removed and that released those compounds systemically were significantly preferred over undamaged control plants in two-choice experiments in a flight tunnel. Artificially damaged cotton plants that released green leafy volatiles and constitutive terpenoids were less attractive for M. croceipes and C. marginiventris. Only C. marginiventris preferred artificially damaged plants over undamaged control plants, whereas M. croceipes showed no preference. The apparent lack of specificity of systemically released compounds in response to different herbivores feeding on the lower leaves is discussed.     

Performance of estimating depth in projection based stereoscopic virtual display

Accurate distance estimation is essential for effective user interaction with objects appearing in the virtual space. Research has shown that the distance estimation in the virtual space is not as accurate as that in the real world. The inaccuracy phenomenon is almost exclusively documented for estimating objects appearing straight ahead of the eye. A collection of the accuracy data for targets located in different angles of view in the visual field may be useful in aiding the design of user‐virtual object interaction. This study collected the object to object distance estimation accuracy for targets displayed stereoscopically. There are five horizontal and two vertical viewing angles and three depths, resulting in a total of 30 locations in the virtual space. The distance estimation for any of the 30 object pairs were performed with or without the aid of spatial cues. Significant factors influencing the accuracy and time of distance estimation were identified. Implications of the finding were discussed with respect to the stereoscopic display environment.     

An introduction to the Information Display Measurement Standard 1, the first display measurement standard from the International Committee for Display Metrology

On June 1, 2012, the Information Display Measurement Standard version 1 was released. This is the first standard from the worldwide standard group, the International Committee for Display Metrology, a standards committee within SID, and it culminates several years worth of development from many contributors at various levels. It has 26 top‐level chapters and a total over 450 sections of all parts, including over 200 measurement sections and 8 appendices that cover 133 topics of display metrology, tutorials, technical discussions, and references. Herein is an overview of the Information Display Measurement Standard version 1, including the structure of the document, tips, tricks, and hidden features, how it is maintained, support material, a breakdown of its contents, and finally, a sampling of four of the over 200 measurements. The standard is available as a free download and can be found on the International Committee for Display Metrology home page — http://www.icdm‐sid.org .     

Spectral preconditioning of Krylov spaces: Combining PLS and PC regression

In regularized regression the vectors that lie in Krylov and eigen subspaces, formed in PLS and PC regressions respectively, provide useful low dimensional approximations for the LS regression coefficient vector. By preconditioning the LS normal equations we provide a framework in which to combine these methods, and so exploit both of their respective advantages. The link between the proposed method to orthogonal signal correction and to cyclic subspace regression is made. The performance of the proposed solution in reducing the dimension of the regression problem, and the shrinkage properties of the resulting coefficient vector, are both examined.     

On the forced vibration of the fiber partially immersed in fluid

In this paper an experimental and theoretical investigation of the forced vibration of a partially immersed fiber has been carried out. An optical method utilizing a forward light scattering pattern has been used to detect a small (<1.0 μm) vibration amplitude of the fiber. The physical and mathematical model of the partially immersed fiber vibration has been put forward. Based on an analytical solution of the model, natural frequencies of the partially immersed fiber vibration have been found; they are consecutive positive roots of the transcendental equation. An “effective” speed of the wave propagation over the fiber has been introduced, which allows one to find the physical meaning of normal modes of the partially immersed fiber vibration. Theoretical predictions agree well with experimental data. The sensor exhibits an excellent sensitivity and could be used for measuring physical properties of fluids and liquid level.