On the computational power of probabilistic and quantum branching program

In this paper, we show that one-qubit polynomial time computations are as powerful as NC¹ circuits. More generally, we define syntactic models for quantum and stochastic branching programs of bounded width and prove upper and lower bounds on their power. We show that any NC¹ language can be accepted exactly by a width-2 quantum branching program of polynomial length, in contrast to the classical case where width 5 is necessary unless NC¹ = ACC. This separates width-2 quantum programs from width-2 doubly stochastic programs as we show the latter cannot compute the middle bit of multiplication. Finally, we show that bounded-width quantum and stochastic programs can be simulated by classical programs of larger but bounded width, and thus are in NC¹. For read-once quantum branching programs (QBPs), we give a symmetric Boolean function which is computable by a read-once QBP with O (log n) width, but not by a deterministic read-once BP with o (n) width, or by a classical randomized read-once BP with o (n) width which is “stable” in the sense that its transitions depend on the value of the queried variable but do not vary from step to step. Finally, we present a general lower bound on the width of read-once QBPs, showing that our O (log n) upper bound for this symmetric function is almost tight.     

Influence of different parameters and their coupled effects on the stability of alumina nanofluids by a fractional factorial design approach

Nanofluids have been introduced as new-generation fluids able to improve energy efficiency in heat exchangers. However, stability problems related to both agglomeration and sedimentation of nanoparticles have limited industrial-level scaling. A fractional factorial experimental 2^k?1 design was applied in order to evaluate the effects of nanoparticle concentration, surfactant type and concentration, ultrasonic amplitude as well as ultrasonic time on the stability of alumina (Al₂O₃) nanofluids. Commercial alumina nanoparticles (particle diameter <50 nm) were dispersed in deionized water using ultrasonic probe dispersion equipment. Sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants. The stability of the nanofluids in static mode was monitored by visual inspection and UV visible spectroscopy. The results of the experimental design showed that the coupled effects between surfactant type and surfactant concentration and between ultrasonication tip amplitude and ultrasonication time had the most pronounced effects on nanofluid stability. The experimental conditions providing the best stability were 0.5 wt% of Al₂O₃, CTAB, critical micelle surfactant concentration, 30% ultrasonic amplitude and 30 min of ultrasonication.     

A viscoelastic Unitary Crack-Opening strain tensor for crack width assessment in fractured concrete structures

A post-processing technique which allows computing crack width in concrete is proposed for a viscoelastic damage model. Concrete creep is modeled by means of a Kelvin–Voight cell while the damage model is that of Mazars in its local form. Due to the local damage approach, the constitutive model is regularized with respect to finite element mesh to avoid mesh dependency in the computed solution (regularization is based on fracture energy).The presented method is an extension to viscoelasticity of the approach proposed by Matallah et al. (Int. J. Numer. Anal. Methods Geomech. 34(15):1615–1633, 2010) for a purely elastic damage model. The viscoelastic Unitary Crack-Opening (UCO) strain tensor is computed accounting for evolution with time of surplus of stress related to damage; this stress is obtained from decomposition of the effective stress tensor. From UCO the normal crack width is then derived accounting for finite element characteristic length in the direction orthogonal to crack. This extension is quite natural and allows for accounting of creep impact on opening/closing of cracks in time dependent problems. A graphical interpretation of the viscoelastic UCO using Mohr’s circles is proposed and application cases together with a theoretical validation are presented to show physical consistency of computed viscoelastic UCO.     

Internet of Things offloading: Ongoing issues,opportunities, and future challenges

Internet of Things (IoT) has very remarkable advantages over customary communication technologies. However, IoT suffers from different issues, such as limited battery life, low storage capacity, and little computing capacity. For this reason, in many IoT applications and devices, we require an alternative unit to execute the tasks from the user's device and return results. In general, the problem of limited resources by transferring the computation workload to other devices/systems with better resources is addressed by offloading computation. It can be focused on improving the application, extending battery life, or expanding storage capacity. The offloading operation can be performed based on various quality of service (QoS) parameters that contain computational demands for load balancing, response time, application, energy consumption, latency, and other things. Moreover, the systematic literature review (SLR) method is used to identify, assess, and integrate findings from all relevant studies that address one or more research questions on IoT offloading and conduct a comprehensive study of empirical research on offloading techniques. However, we present a new taxonomy for them based on offloading decision mechanisms and overall architectures. Furthermore, we offer a parametric comparison for the offloading methods. As well, we present the future direction and research opportunities in IoT offloading computation. This survey will assist academics and practitioners to directly understand the progress in IoT offloading.     

Flexible Web services integration: a novel personalised social approach

Abstract

Dynamic composition or integration remains one of the key objectives of Web services technology. This paper aims to propose an innovative approach of dynamic Web services composition based on functional and non-functional attributes and individual preferences. In this approach, social networks of Web services are used to maintain interactions between Web services in order to select and compose Web services that are more tightly related to user’s preferences. We use the concept of Web services community in a social network of Web services to reduce considerably their search space. These communities are created by the direct involvement of Web services providers.     

Wood‐flour‐reinforced polyethylene: Viscoelastic behavior and threaded fasteners

The tensile stress relaxation and flexural creep properties of wood‐fiber‐reinforced low‐density polyethylene (WFRP) were measured at various temperatures and stress levels. Power law relations were used to correlate the data, and time‐temperature superposition was applied to tensile stress relaxation results. Stress relaxation in WFRP was similar to that of LDPE and greater than that in spruce. The clamping force and torque characteristics of self‐threading screws and internally threaded inserts were measured in WFRP, and the viscoelastic model was extended to predict the relaxation in screw clamping force as a function of time. Both screw pullout force and the amount of clamping force relaxation were greater in WFRP than in spruce.     

Improvement of photoelectrochemical and optical characteristics of MEH-PPV using titanium dioxide nanoparticles

The use of bulk heterojunctions can increase the efficiency of exciton dissociation in polymer-based photovoltaics. We prepared and characterized bulk heterojunctions of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and titanium dioxide nanoparticles deposited by spin coating on indium tin oxide substrates. The surface morphology of the MEH-PPV+TiO₂ composite films revealed that addition of TiO₂ nanoparticles increased the film roughness. The effect of TiO₂ nanoparticles on the photoelectrochemical and optical characteristics of MEH-PPV polymer heterojunctions was studied. Addition of TiO₂ nanoparticles improved the absorbance of MEH-PPV composite films. Moreover, the photocurrent of the composite devices increased with the TiO₂ nanoparticle concentration. These observations provide an insight into new approaches to improve the light collection efficiency in photoconductive polymers.     

A rapid and novel approach for predicting water sorption isotherms and isosteric heats of different meat types

A rapid and novel approach for predicting sorption isotherms based on the Polanyi theory is proposed. This approach allows the prediction of the sorption isotherms at different temperatures from one experimental isotherm. The theoretical predictions of isotherms and isosteric heats were validated successfully using data from the literature for different meat types. This method allows total experimental time and operation costs to be reduced.     

Hybrid nanostructure of polypyrrole and porous silicon prepared by galvanostatic technique

Nanostructured porous silicon (PS) layer is prepared in a lightly doped p-type substrate (with pores < 5 nm) and used as a working electrode to deposit conducting polypyrrole (PPy) by the electrochemical oxidative polymerization technique in an organic liquid phase. Three distinguishable stages of PPy deposition are observed and recorded under constant applied current: nucleation of polymer at the pore bottom, unidirectional growth of PPy inside the pores, and polymerization outside the PS surface. The hybrid nanostrucutre of PS/PPy shows a significant improvement of electrical conductivity as opposed to the unmodified PS layer. The improved conductivity is observed in spite of the formation of insulating layer of silicon oxides as detected by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) measurements. Systematic study of fabrication and characterization of this organic-inorganic heterosystem, quantification of the PPy in the PS matrix, and the mechanism of filling the nanopores with polymer are presented and thoroughly discussed.