Starch,Sucrose, and Rezol® IL800 as Density Modifiers for Polyurethane Rigid Foams Formulated by Recycled Polyol

Waste polyurethane rigid foam (PUF) is recycled by the glycolysis process. The recycled product is used in a polyol blend, applied in a new foam formulation. Polyurethane rigid foams formulated by recycled polyols are highly dense compared to rigid foams formulated by virgin polyols. As these foams are mostly used in insulation, they make an extra mass to the main product or system that is insulated. Therefore, it is important to decrease their density as much as possible.

Some density modifiers such as starch, sucrose, and REZOL^® IL800 were investigated to recognize their effect on PUF's density.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.     

Heat Capacity of Defective Semiconducting Carbon Nanotubes

Using a random tight-binding model within the coherent potential approximation, the effects of boron and nitrogen doping on the temperature dependence of the specific heat of semiconducting zigzag carbon nanotubes are studied. It is shown that the electronic specific heat capacity behaves anomalously when the temperature is lowered. The presence of this anomaly is clarified on the basis of the idea of the so-called Schottky anomaly. More importantly, in the presence of dopants, the position of this anomaly moves towards higher temperatures and its height shifts down as the dopant concentration is increased. Such behavior is attributed to the substantial modifications in the density of states.     

Black Nickel Coating and Color Anodized Layers for Solar Absorber

Solar selective absorbers are considered as an essential part of a thermal solar collector for which the optical properties are dependent upon their structure and surface morphology. In this paper, optical properties of Ni-pigmented anodized are compared with black electroless nickel coatings. The effect of heat treatment on optical properties of the coatings was also investigated. Anodized films were formed in 6 M phosphoric acid followed by a black coloration process. Scanning electron microscope was used to study the morphology, and X-ray diffraction was employed to identify the phases present. Evaluation of optical properties was carried out by spectral reflectance. Evaluation of the optical characteristics showed that Ni-pigmented anodized and black electroless samples, after heat treatment, had the highest absorption coefficient at about 0.98 as well as the lowest emission coefficient. The ξ factor reached about 6 in heat treated Ni-pigmented anodized layer and offered optimal properties in this research.     

Cryptanalysis of an iterated halving-based hash function: CRUSH

Iterated Halving has been suggested as a replacement to the Merkle?Damga?rd (MD) construction in 2004 anticipating the attacks on the MDx family of hash functions. The CRUSH hash function provides a specific instantiation of the block cipher for Iterated Halving. The authors identify structural problems with the scheme and show that they can trivially identify collisions and second preimages on many equal-length messages of length ten blocks or more. The cost is ten decryptions of the block cipher, this being less than the generation of a single digest. In addition, these attacks can be used to differentiate CRUSH from a random oracle in O(1). The authors show that the complexity of finding a preimage in the unpadded CRUSH with the length encoding is negligible and extend this attack on CRUSH with the length encoding in cost O(2/sup 32/). This attack is a multi-preimage attack, since the attacker can produce a large number of messages for a given message digest for the cost of O(2/sup 32/). Hence, this attack can be used as a multi-collision and a multisecond- preimage as well. They show that if the attacker knows the last 64-bits of the message digest in advance, he can do the time-consuming part of the attack off-line. The authors show that even if Iterated Halving is repaired, the construction has practical issues that means it is not suitable for general deployment.     

Decoupled adaptive neuro-fuzzy (DANF) sliding mode control system for a Lorenz chaotic problem

This paper introduces a decoupled adaptive neuro-fuzzy (DANF) sliding mode control system for the chaos control problem in a system without precise system model information. It has on-line learning ability to deal with the parametric uncertainty and disturbance by adjusting the control parameters and no constrained conditions and prior knowledge of the controlled plant is required in the design process. Also, a decoupled adaptive sliding mode controller is developed to control the chaotic Lorenz system for comparison. Finally, the effectiveness of the proposed decoupled adaptive sliding mode and DANF sliding mode controllers are demonstrated by some simulated results.     

Pipe damper,Part I: Experimental and analytical study

In this paper the behavior of steel pipes, filled and unfilled with concrete, is studied under cyclic shear to examine the possibility of their use as a seismic damper. Two specimens of steel pipes filled inside with concrete are tested under monotonic and cyclic shear. Four other specimens of bare steel pipes are tested under fully reversed cyclic shear loading. The results show that the bare steel pipes are capable of absorbing a great amount of energy under a severe cyclic shear loading with a stable hysteretic behavior. This behavior is also simulated using the finite element method. Then, parametric studies are performed to investigate the effects of variations in geometrical properties of the pipe on its hysteretic behavior. A simplified bi-linear model is proposed to approximate the hysteretic behavior of the steel pipe as a metallic-yielding damper.     

An efficient parallel algorithm for the longest path problem in meshes

The longest path problem is the problem of finding a simple path with the maximum number of vertices in a given graph, and so far it has been solved polynomially only for a few classes of graphs. This problem generalizes the well-known Hamiltonian path problem, hence it is NP-hard in general graphs. In this paper, first we give a sequential linear-time algorithm for the longest path problem in meshes. Then based on this algorithm, we present a constant-time parallel algorithm for the problem, which can be run on every parallel machine.     

A powerful hybrid clustering method based on modified stem cells and Fuzzy C-means algorithms

One of the simple techniques for Data Clustering is based on Fuzzy C-means (FCM) clustering which describes the belongingness of each data to a cluster by a fuzzy membership function instead of a crisp value. However, the results of fuzzy clustering depend highly on the initial state selection and there is also a high risk for getting the best results when the datasets are large. In this paper, we present a hybrid algorithm based on FCM and modified stem cells algorithms, we called it SC-FCM algorithm, for optimum clustering of a dataset into K clusters. The experimental results obtained by using the new algorithm on different well-known datasets compared with those obtained by K-means algorithm, FCM, Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Ant Colony Optimization (ACO), Artificial Bee Colony (ABC) Algorithm demonstrate the better performance of the new algorithm.