Preparation and characterization of hydrogenated amorphous germanium and hydrogenated amorphous germanium carbide thin films

Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge[subscript] 1-xC[subscript] x:H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum ~4 x 10[superscript]-7 Torr at various rf power 50 ≤ P ≤ 600 W (0.27-3.3 W/cm[superscript]2), target-substrate distance 1 ≤ d ≤ 7[superscript]\u27\u27, varying partial pressures of Ar, H[subscript]2, and C[subscript]3H[subscript]8, and flow rates f. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron-spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity [sigma][subscript] ph, in particular, was carefully monitored as a function of the deposition conditions to optimize it;The concentration of Ge-H bonds and the optical gap (E[subscript] g), generally decrease as P is increased. E[subscript] g of the a-Ge[subscript] 1-xC[subscript] x:H films range from 0.85-2.3 eV. The ESR results range from 2 x 10[superscript]17 to 2 x 10[superscript]19 spins/cm[superscript]3. Results of annealing showed the enhanced segregation effect of Ge-C bonds ≥300°C. The evolution of bonded hydrogen with temperature is studied;Deposition rates (R[subscript] d) of a-Ge:H films are estimated and compared. The thermalization curve for a Ge target is constructed. R[subscript] d was found to decrease exponentially with increasing d, to decrease with increasing partial pressures of H[subscript]2 and C[subscript]3H[subscript]8 and increasing flow rates. R[subscript] d is maximal at some P[subscript] Ar and is relatively insensitive to the substrate temperature T[subscript] s, and rises linearly with the rf power;Hydrogen incorporation markedly increased [sigma][subscript] ph. The dark conductivity [sigma][subscript] d and [sigma][subscript] ph increase with increasing d, up to an optimal value at d ~ 6[superscript]\u27\u27, increase at f \u3c 1 sccm, and increase with P and T[subscript] s. Incorporation of significant amounts of carbon sharply reduces [sigma][subscript] ph. However, a small amount has little effect on [sigma][subscript] ph. Although all increases in [sigma][subscript] ph are significant relative to those of previously reported rf sputtered a-Ge:H, the results in this work are still much lower than those of glow discharged films, which are lower than those of rf magnetron sputtered films grown in high vacuum (\u3c5 x 10[superscript]-9 Torr). The parallel behavior of [sigma][subscript] d and [sigma][subscript] ph, the relatively long lifetimes of the carriers [tau] ~ 0.8 ms but rather low mobility [mu] ~ 5 x 10[superscript]7 cm[superscript]2/V-sec and low subgap absorption suggest that the transport is dominated by defects near the mobility edge. The failure in identifying the effect of electron bombardment of the growing film by using biased screen suggests that the high values of [sigma][subscript] ph reported from rf magnetron sputtering are probably partially due to the high background vacuum. ftn*DOE Report IS-T-1377. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy

Interface control of ferroelectricity in LaNiO3-BaTiO3 superlattices

LaNiO$_{3}$-BaTiO$_{3}$ superlattices with different types of interfaces are studied from first-principles density-functional theory. It is revealed that the ferroelectricity in the superlattice with (NiO$_2$)$^-$/(BaO)$^0$ interfaces is enhanced from that of the superlattice with (LaO)$^+$/(TiO$_2$)$^0$ interfaces. The origin lies at the polar discontinuity at the interface, which makes the holes localized within the (NiO$_2$)$^-$/(BaO)$^0$ interface, but drives a penetration of electrons into BaTiO$_3$ component near (LaO)$^+$/(TiO$_2$)$^0$ interface. Our calculations demonstrate an effective avenue to the robust ferroelectricity in BaTiO$_3$ ultrathin films.Comment: 14 pages, 6 figure

The difference of boundary effects between Bose and Fermi systems

In this paper, we show that there exists an essential difference of boundary effects between Bose and Fermi systems both for Dirichlet and Neumann boundary conditions: at low temperatures and high densities the influence of the boundary on the Bose system depends on the temperature but is independent of the density, but for the Fermi case the influence of the boundary is independent of the temperature but depends on the density, after omitting the negligible high-order corrections. We also show that at high temperatures and low densities the difference of the influence of the boundary between Bose and Fermi systems appears in the next-to-leading order boundary contribution, and the leading boundary contribution is independent of the density. Moreover, for calculating the boundary effects at high temperatures and low densities, since the existence of the boundary modification causes the standard virial expansion to be invalid, we introduce a modified virial expansion.Comment: 8 page

Effects of degree distribution in mutual synchronization of neural networks

We study the effects of the degree distribution in mutual synchronization of two-layer neural networks. We carry out three coupling strategies: large-large coupling, random coupling, and small-small coupling. By computer simulations and analytical methods, we find that couplings between nodes with large degree play an important role in the synchronization. For large-large coupling, less couplings are needed for inducing synchronization for both random and scale-free networks. For random coupling, cutting couplings between nodes with large degree is very efficient for preventing neural systems from synchronization, especially when subnetworks are scale-free.Comment: 5 pages, 4 figure

4-Eth­oxy-N′-propanoylpyridine-2-carbohydrazide

In the crystal structure of the title compound, C11H15N3O3, mol­ecules are linked into a chain by inter­molecular N—H⋯O hydrogen bonds

Dynamic resource scheduling in cloud radio access network with mobile cloud computing

Nowadays, by integrating the cloud radio access network (C-RAN) with the mobile cloud computing (MCC) technology, mobile service provider (MSP) can efficiently handle the increasing mobile traffic and enhance the capabilities of mobile users' devices to provide better quality of service (QoS). But the power consumption has become skyrocketing for MSP as it gravely affects the profit of MSP. Previous work often studied the power consumption in C-RAN and MCC separately while less work had considered the integration of C-RAN with MCC. In this paper, we present a unifying framework for optimizing the power-performance tradeoff of MSP by jointly scheduling network resources in C-RAN and computation resources in MCC to minimize the power consumption of MSP while still guaranteeing the QoS for mobile users. Our objective is to maximize the profit of MSP. To achieve this objective, we first formulate the resource scheduling issue as a stochastic problem and then propose a Resource onlIne sCHeduling (RICH) algorithm using Lyapunov optimization technique to approach a time average profit that is close to the optimum with a diminishing gap (1/V) for MSP while still maintaining strong system stability and low congestion to guarantee the QoS for mobile users. With extensive simulations, we demonstrate that the profit of RICH algorithm is 3.3× (18.4×) higher than that of active (random) algorithm

Dynamic Resource Scheduling in Mobile Edge Cloud with Cloud Radio Access Network

Nowadays, by integrating the cloud radio access network (C-RAN) with the mobile edge cloud computing (MEC) technology, mobile service provider (MSP) can efficiently handle the increasing mobile traffic and enhance the capabilities of mobile devices. But the power consumption has become skyrocketing for MSP and it gravely affects the profit of MSP. Previous work often studied the power consumption in C-RAN and MEC separately while less work had considered the integration of C-RAN with MEC. In this paper, we present an unifying framework for the power-performance tradeoff of MSP by jointly scheduling network resources in C-RAN and computation resources in MEC to maximize the profit of MSP. To achieve this objective, we formulate the resource scheduling issue as a stochastic problem and design a new optimization framework by using an extended Lyapunov technique. Specially, because the standard Lyapunov technique critically assumes that job requests have fixed lengths and can be finished within each decision making interval, it is not suitable for the dynamic situation where the mobile job requests have variable lengths. To solve this problem, we extend the standard Lyapunov technique and design the VariedLen algorithm to make online decisions in consecutive time for job requests with variable lengths. Our proposed algorithm can reach time average profit that is close to the optimum with a diminishing gap (1/V) for the MSP while still maintaining strong system stability and low congestion. With extensive simulations based on a real world trace, we demonstrate the efficacy and optimality of our proposed algorithm

Maximizing the Profit of Cloud Broker with Priority Aware Pricing

A practical problem facing Infrastructure-as-a-Service (IaaS) cloud users is how to minimize their costs by choosing different pricing options based on their own demands. Recently, cloud brokerage service is introduced to tackle this problem. But due to the perishability of cloud resources, there still exists a large amount of idle resource waste during the reservation period of reserved instances. This idle resource waste problem is challenging cloud broker when buying reserved instances to accommodate users' job requests. To solve this challenge, we find that cloud users always have low priority jobs (e.g., non latency-sensitive jobs) which can be delayed to utilize these idle resources. With considering the priority of jobs, two problems need to be solved. First, how can cloud broker leverage jobs' priorities to reserve resources for profit maximization? Second, how to fairly price users' job requests with different priorities when previous studies either adopt pricing schemes from IaaS clouds or just ignore the pricing issue. To solve these problems, we first design a fair and priority aware pricing scheme, PriorityPricing, for the broker which charges users with different prices based on priorities. Then we propose three dynamic algorithms for the broker to make resource reservations with the objective of maximizing its profit. Experiments show that the broker's profit can be increased up to 2.5× than that without considering priority for offline algorithm, and 3.7× for online algorithm