Environmental, Safety, and Health Considerations: Composite Materials in the Aerospace Industry

The Aerospace Industries Association, Suppliers of Advanced Composite Materials Association, and the National Aeronautics and Space Administration co-sponsored a conference on 'Environmental, Safety, and Health Considerations--Composite Materials in the Aerospace Industry.' The conference was held in Mesa, Arizona, on October 20-21, 1994. Seventeen papers were presented in four sessions including general information, safety, waste, and emissions from composites. Topics range from product stewardship, best work practice, biotransformation of uncured composite materials, to hazardous waste determination and offgassing of composite materials

Emergence of Blind Areas in Information Spreading

Recently, contagion-based (disease, information, etc.) spreading on social networks has been extensively studied. In this paper, other than traditional full interaction, we propose a partial interaction based spreading model, considering that the informed individuals would transmit information to only a certain fraction of their neighbors due to the transmission ability in real-world social networks. Simulation results on three representative networks (BA, ER, WS) indicate that the spreading efficiency is highly correlated with the network heterogeneity. In addition, a special phenomenon, namely \emph{Information Blind Areas} where the network is separated by several information-unreachable clusters, will emerge from the spreading process. Furthermore, we also find that the size distribution of such information blind areas obeys power-law-like distribution, which has very similar exponent with that of site percolation. Detailed analyses show that the critical value is decreasing along with the network heterogeneity for the spreading process, which is complete the contrary to that of random selection. Moreover, the critical value in the latter process is also larger that of the former for the same network. Those findings might shed some lights in in-depth understanding the effect of network properties on information spreading

Diffusion of water in kernels of corns and sorghums

Call number: LD2668 .T4 1962 C4

Integration of active GaAs based optoelectronics onto Si substrates

Controlled heteroepitaxy and integration of arsenide based III-V compounds onto Si surfaces have been an important enabling technology for high efficiency solar cells and light emitters in satellite and optical interconnect applications. However, obtaining high crystal quality III-V compounds on Si, such as GaAs on Si is still challenging: (1) anti-phase domain (APD) boundary formation as the result of the polar GaAs growth on non-polar Si system, (2) a high density of threading dislocations generated by 4.1% lattice constant mismatch, and (3) the 62% thermal expansion coefficient mismatch leading to cracks during the cooling process. The objective of this research is to obtain arsenide based III-V compounds monolithically integrated onto Si surfaces being APD-free with chemically abrupt GaAs/Si interfaces and possessing excellent optoelectronic properties. Patterned growth scheme by molecular beam epitaxy (MBE) is the approach I undertook to integrate GaAs based III-V compounds onto exactly oriented Si substrates. And the research consists of the following three stages to fulfill the objective.(1) Precise positioning and low defect density selective area epitaxy for self-assembled/catalyst-free GaAs nanodisks on SiO2 masked exactly oriented Si(100) substrates: Pure zincblende GaAs nanodisks with precise positioning and low defect density are demonstrated by selective area epitaxy. Defects in the epilayers are reduced by strain relaxation through facets formation and by a lateral overgrowth scheme atop the SiO2 mask.(2) High-quality and defect-free GaAs thin film on SiO2 masked exactly oriented Si(111) substrates by a two-step growth technique: Taking advantages of low energy for both Si(111) surface and GaAs/Si(111) interface, the two-step grown GaAs of total ∼175 nm atop patterned Si(111) substrates exhibits atomically smooth surface morphology, single crystallinity and a remarkably low defect density.(3) Successful integration of InGaAs/GaAs double heterostrucure onto SiO2 masked exactly oriented Si(111) substrates with remarkably reduced thermal stress: The atomically smooth and high crystalline quality InGaAs/GaAs DH is realized. The confined misfit dislocations at the nucleation layer and nearly threading dislocation-free buffer layer contribute to the atomically sharp GaAs/Si interface. The remarkable reduction in the thermally induced stress corroborates the effectiveness of the square shape pattern design. Optical properties and carrier dynamics are characterized by micro-photoluminescence (µ-PL) and time-resolved PL

Improving One-class Recommendation with Multi-tasking on Various Preference Intensities

In the one-class recommendation problem, it's required to make recommendations basing on users' implicit feedback, which is inferred from their action and inaction. Existing works obtain representations of users and items by encoding positive and negative interactions observed from training data. However, these efforts assume that all positive signals from implicit feedback reflect a fixed preference intensity, which is not realistic. Consequently, representations learned with these methods usually fail to capture informative entity features that reflect various preference intensities. In this paper, we propose a multi-tasking framework taking various preference intensities of each signal from implicit feedback into consideration. Representations of entities are required to satisfy the objective of each subtask simultaneously, making them more robust and generalizable. Furthermore, we incorporate attentive graph convolutional layers to explore high-order relationships in the user-item bipartite graph and dynamically capture the latent tendencies of users toward the items they interact with. Experimental results show that our method performs better than state-of-the-art methods by a large margin on three large-scale real-world benchmark datasets.Comment: RecSys 2020 (ACM Conference on Recommender Systems 2020

Huge local field enhancement in perfect plasmonic absorbers

In this Letter we theoretically study the possibility of total power absorption of light in a planar grid modelled as an effective sheet with zero optical thickness. The key prerequisite of this effect is the simultaneous presence of both resonant electric and magnetic modes in the structure. We show that the needed level of the magnetic mode is achievable using the effect of substrate-induced bianisotropy which also allows the huge local field enhancement at the same wavelength where the maximal absorption holds.Comment: 4 pages, 4 figure