Thermal conductivity of anisotropic spin - 1/2 two leg ladder:Green's function approach

We study the thermal transport of a spin-1/2 two leg antiferromagnetic ladder in the direction of legs. The possible effect of spin-orbit coupling and crystalline electric field are investigated in terms of anisotropies in the Heisenberg interactions on both leg and rung couplings. The original spin ladder is mapped to a bosonic model via a bond-operator transformation where an infinite hard-core repulsion is imposed to constrain one boson occupation per site. The Green's function approach is applied to obtain the energy spectrum of quasi-particle excitations responsible for thermal transport. The thermal conductivity is found to be monotonically decreasing with temperature due to increased scattering among triplet excitations at higher temperatures. A tiny dependence of thermal transport on the anisotropy in the leg direction at low temperatures is observed in contrast to the strong one on the anisotropy along the rung direction, due to the direct effect of the triplet density. Our results reach asymptotically the ballistic regime of the spin - 1/2 Heisenberg chain and compare favorably well with exact diagonalization data

Experimental study of combustion characteristics of nanoscale metal and metal oxide additives in biofuel (ethanol)

An experimental investigation of the combustion behavior of nano-aluminum (n-Al) and nano-aluminum oxide (n-Al2O3) particles stably suspended in biofuel (ethanol) as a secondary energy carrier was conducted. The heat of combustion (HoC) was studied using a modified static bomb calorimeter system. Combustion element composition and surface morphology were evaluated using a SEM/EDS system. N-Al and n-Al2O3 particles of 50- and 36-nm diameters, respectively, were utilized in this investigation. Combustion experiments were performed with volume fractions of 1, 3, 5, 7, and 10% for n-Al, and 0.5, 1, 3, and 5% for n-Al2O3. The results indicate that the amount of heat released from ethanol combustion increases almost linearly with n-Al concentration. N-Al volume fractions of 1 and 3% did not show enhancement in the average volumetric HoC, but higher volume fractions of 5, 7, and 10% increased the volumetric HoC by 5.82, 8.65, and 15.31%, respectively. N-Al2O3 and heavily passivated n-Al additives did not participate in combustion reactively, and there was no contribution from Al2O3 to the HoC in the tests. A combustion model that utilized Chemical Equilibrium with Applications was conducted as well and was shown to be in good agreement with the experimental results

A novel approach for water quality management in water distribution systems by multi-objective booster chlorination

Copyright © 2012 International Journal of Civil EngineeringCompared to conventional chlorination methods which apply chlorine at water treatment plant, booster chlorination has almost solved the problems of high dosages of chlorine residuals near water sources and lack of chlorine residuals in the remote points of a water distribution system (WDS). However, control of trihalomethane (THM) formation as a potentially carcinogenic disinfection by-product (DBP) within a WDS has still remained as a water quality problem. This paper presents a two-phase approach of multi-objective booster disinfection in which both chlorine residuals and THM formation are concurrently optimized in a WDS. In the first phase, a booster disinfection system is formulated as a multi-objective optimization problem in which the location of booster stations is determined. The objectives are defined as to maximize the volumetric discharge with appropriate levels of disinfectant residuals throughout all demand nodes and to minimize the total mass of disinfectant applied with a specified number of booster stations. The most frequently selected locations for installing booster disinfection stations are selected for the second phase, in which another two-objective optimization problem is defined. The objectives in the second problem are to minimize the volumetric discharge avoiding THM maximum levels and to maximize the volumetric discharge with standard levels of disinfectant residuals. For each point on the resulted trade-off curve between the water quality objectives optimal scheduling of chlorination injected at each booster station is obtained. Both optimization problems used NSGA-II algorithm as a multi-objective genetic algorithm, coupled with EPANET as a hydraulic simulation model. The optimization problems are tested for different numbers of booster chlorination stations in a real case WDS. As a result, this type of multi-objective optimization model can explicitly give the decision makers the optimal location and scheduling of booster disinfection systems with respect to the trade-off between maximum safe drinking water with allowable chlorine residual levels and minimum adverse DBP levels

Anti-Candida activity of ethanolic extracts of Iranian endemic medicinal herbs against Candida albicans

It has long been known that herbs and their extracts have antimicrobial activities. Heracleum lasiopetalum Boiss., Satureja bachtiarica Bunge., Thymus daenensis Celak., Echiophora platyloba L., Dracocephalum multicaule Benth., Kelussia odoratissima Mozaff. and Achillea kellalensis Boiss. are Iranian endemic plant species that have been traditionally used as medicinal herbs and spices in different regions of Iran especially Central Zagross. Seven ethanolic extracts of endemic medicinal herbs and one extract of native medicinal herb (Stachys lavandulifolia Vahl.) collected from Chaharmahal va Bakhtiari province of Iran were assayed for the in vitro antifungal activity against Candida albicans (ATCC1023), using agar dilution methods. Most of the extracts showed relatively high anti-Candida activity against the tested fungi with the diameter of inhibition zone ranging between 8 and 17 mm. The extracts of S. bachtiarica and T. daenensis exhibited high inhibitory effect against C. albicans. The extracts of S. bachtiarica and T. daenensis were characterized using HPLC, the major components of S. bachtiarica and T. daenensis were carvacrol and thymol, respectively. The minimum inhibitory concentration (MIC) values for active extract range between 25 and 50 µg/ml. In conclusion, it can be said that the extract of some of the Iranian endemic medicinal plants (S. bachtiarica and T. daenensis) could be used as natural anti-Candida

Forensic Traceability Index in Digital Forensic Investigation

Digital crime inflicts immense damage to users and systems and now it has reached a level of sophistication that makes it difficult to track its sources or origins especially with the advancements in modern computers, networks and the availability of diverse digital devices. Forensic has an important role to facilitate investigations of illegal activities and inappropriate behaviors using scientific methodologies, techniques and investigation frameworks. Digital forensic is developed to investigate any digital devices in the detection of crime. This paper emphasized on the research of traceability aspects in digital forensic investigation process. This includes discovering of complex and huge volume of evidence and connecting meaningful relationships between them. The aim of this paper is to derive a traceability index as a useful indicator in measuring the accuracy and completeness of discovering the evidence. This index is demonstrated through a model (TraceMap) to facilitate the investigator in tracing and mapping the evidence in order to identify the origin of the crime or incident. In this paper, tracing rate, mapping rate and offender identification rate are used to present the level of tracing ability, mapping ability and identifying the offender ability respectively. This research has a high potential of being expanded into other research areas such as in digital evidence presentation

Virtual Machine based Autonomous Web Server

Enterprises are turning to Internet technology to circulate information, interact with potential customers and establish an e-commerce business presence. These activities are depending highly on Web server and maintaining good server security has been a requirement for avoiding any malicious attacks especially web defacements and malware. Web server administrators should be alert and attentive to the status of the server at all time. They need to be persistent in monitoring the server in order to detect any attempted attacks. This is an advantage for a web server that is maintained by a big company that has a big budget to hire a knowledgeable web server administrator, for a new established small company it will only burden their expenses. To overcome this problem, this paper proposes a low cost system called Autonomous Web Server Administrator (AWSA) that is fully developed using open source software. AWSA combines several computing concepts such as Virtual Machine, Intrusion Detection System and Checksum. AWSA offers a Virtual Machine based Web server that has the ability to automatically detect intrusions and reconstruct corrupted data or the file system without any human intervention