Sharif Digital Repository

Internet of Things (IoT) devices have strict necessity for power consumption in order to achieve expected battery life. IoT nodes feature extreme power consumption range over 100 dB, between their operating modes. The main focus of this paper is to design and implement a high precision, high dynamic range, low power, and flexible power measurement system, which can be applied to different applications. The proposed system consists of a voltage regulating control loop, zero offset amplifiers, high precision analog to digital converters, and reference voltage. The proper operation of the proposed circuit are verified numerically with simulations and experimental measurements. The implemented... 

In this paper, we propose a new modeling approach for analytical evaluation of normalized throughput and average backoff time for IEEE 802.11 MAC standard in non-saturation mode and with Poisson arrivals. To this end, we map different stages of distributed coordinated function (DCF) onto different components of a closed multi-class BCMP queueing network with arbitrary service time distribution. At the last part of the paper, we illustrate the applicability of the proposed approach by some numerical results in both saturation and non-saturation modes and obtain average backoff time for different arrival rates. © 2007 IEEE  

In the current study, the hybrid effect of a corona discharge and γ-alumina supported Ni catalysts in CO 2 reforming of methane is investigated. The study includes both purely catalytic operation in the temperature range of 923-1023 K, and hybrid catalytic-plasma operation of DC corona discharge reactor at room temperature and ambient pressure. The effect of feed flow rate, discharge power and Ni/γ-Al 2O 3 catalysts are studied. When CH 4/CO 2 ratio in the feed is 1/2, the syngas of low H 2/CO ratio at about 0.56 is obtained, which is a potential feedstock for synthesis of liquid hydrocarbons. Although Ni catalyst is only active above 573 K, presence of Ni catalysts in the cold corona plasma... 

Endurance Wave Analysis (EWA) is a novel, simple, economical but yet reliable method for the integrity assessment of offshore platforms against extreme irregular waves. The current paper presents a framework for the probabilistic assessment of offshore platforms based on EWA. The stochastic nature and the uncertainties in the ocean waves were taken into account by introducing a set of artificial, random and gradually intensifying wave trains. To simulate other uncertainties in the loading and the strength of the structure a Latin Hypercube Sampling (LHS) type of Monte Carlo Simulation (MCS) was employed. The EWA methodology and different structural performance criteria were considered. The... 

Etheno-damaged DNA adducts such as 3,N4- ethenocytosine, N 2,3-ethenoguanine, and 1,N2-ethenoguanine are associated with carcinogenesis and cell death. These inevitable damages are counteracted by glycosylase enzymes, which cleave damaged nucleobases from DNA. Escherichia coli alkyl purine DNA glycosylase is the enzyme responsible for excising damaged etheno adducts from DNA in humans. In an effort to understand the intrinsic properties of these molecules, we examined gasphase acidity values and proton affinities (PA) of multiple sites of these molecules as well as equilibrium tautomerization and base pairing properties by quantum mechanical calculations. We also used calculations to compare... 

Gas-phase acidities of nucleosides, combined with the knowledge of deprotonation sites, could improve our understanding of chemical reactions to biological systems. In this paper, we mainly focus our attention on the influence of cation coordination on acidities of multiple sites in cytosine nucleosides. The acidities of multiple sites in M +-L (where L represents cytosine nucleosides and M + is an alkali metal ion, including Li +, Na + and K +) complexes have been investigated theoretically, employing B3LY P6-311++G(d,p) basis sets. The geometrical characters, gas-phase acidities, sugar puckering and electronic properties of non-deprotonated and/or deprotonated complexes have been... 

Interactions of α-D-glucose with gold, silver, and copper metal clusters are studied theoretically at the density functional theory (CAM-B3LYP) and MP2 levels of theory, using trimer clusters as simple catalytic models for metal particles as well as investigating the effect of cluster charge by studying the interactions of cationic and anionic gold clusters with glucose. The bonding between α-D-glucose and metal clusters occurs by two major bonding factors; the anchoring of M atoms (M = Cu, Ag, and Au) to the O atoms, and the unconventional M.H-O hydrogen bond. Depending on the charge of metal clusters, each of these bonds contributes significantly to the complexation. Binding energy... 

In the present research, two types of drug carriers based on mesoporous silica-coated magnetic graphene oxide, Fe3O4@GO@mSiO2, were synthesised and the pH-responsive behaviour for doxorubicin release was investigated. One type of the carrier was dendrimer-like multi ethylene amine grafted on Fe3O4@GO@mSiO2 and the other was dendrimer-like supramolecular polypseudorotaxane. Herein, α-cyclodextrin was used in the structure of supramolecular nanoparticles as a gatekeeper to inhibit the drug from escaping at neutral pH (the pH of healthy tissue). The drug release profile showed that the supramolecular nanocarrier was more sensitive to the pH changes. The content of drug release was about 100% at... 

Pulse Repetition Interval (PRI) Modulation Detection is an important subsystem of a typical electronic warfare support system. In this paper, a robust, fast, and well designed structure for detection of simple and complex PRI modulations based on statistical and sequential analysis of Pulse Repetition Interval (PRI) is proposed. Accuracy and robustness of the technique against electromagnetic noise are demonstrated via simulations  

Histidine as a natural amino acid is found to be biologically important and is known to function as a nucleophile or enzyme co-factor, or in proton transfer process. The properties of gaseous aromatic amino acid histidine depend on the structural forms it may take in gas-phase. Ab initio method has been used to characterize the gas-phase conformer/tautomers of histidine. Wide range of possible structures for histidine was surveyed at the MM level, and then the geometries of the unique conformers were refined at the B3LYP/6-311++G (d,p) levels. At this theoretical level, 25 conformers were located for both tautomers of histidine i.e., His [NπH] and His [NτH]. The MM level provides a poor... 

Chitosan based polyseudorotaxane was designed as a pH-responsive supramolecular polymeric shell around the mesoporous silica-coated magnetic graphene oxide (Fe3O4@GO@mSiO2). It was used for doxorubicin delivery at cancerous tissue in a controlled manner. The core-shell nanocarrier was formed due to electrostatic interaction between chitosan and carboxylated surface of Fe3O4@GO@mSiO2. The maximum release occurred at pH 5.5 (pH of endosomes) because the shell collapsed at this pH. The drug nanocarrier has potential application in tumor therapy due to good pH-sensitive behavior, improved solubility and high colloidal stability in... 

In the present work a pH responsive drug nanocarrier based on magnetic mesoporous silica nanoparticles (MMSN) and polyethylene glycol-co-polyvinyl pyridine (PEG-co-PVP) was prepared. The core-shell nanocarrier was formed due to electrostatic interaction between protonated polyvinyl pyridine and surface modified MMSN with carboxylate groups. This carrier was used for pH-controllable doxorubicin release. The maximum release was occurred at pH 5.5 (pH of endosomes). This carrier was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, UV-Vis spectrophotometer, scanning electron microscope, and high-resolution transmission electron microscope techniques. Also the...