Synthesis and crystal structure of some new cadmium (II) macrocyclic Schiff-base complexes containing piperazine moiety

The metal templated Cd(II) cyclocondensation of 2,6-diacetylpiridine or 2,6-pyridinedicarbaldehyde and two different amines containing piperazine moieties have been investigated. The resulting ligands, L¹ and L² are 16- and L³ and L⁴ 17-membered pentaaza macrocycles. The complexes have been characterized by a variety of methods including IR, ¹H, ¹³C NMR, DEPT, COSY(H,H), HMQC(H,C), FAB spectrometry and conductivimetry measurements. The crystal structures of [CdL²Cl](CH₃OH)ClO₄ (2) and [CdL⁴(NO₃)(H₂O)]ClO₄ (4) have been also determined, and it was shown that the geometry of the Cd(II) ion in the complexes is slightly distorted pentagonal pyramidal and pentagonal bipyramidal, respectively. The gas-phase structures of ligands, L² and L⁴ and their Cd(II) complexes have also theoretically studied.     

Effects of TLCD with maneuverable flaps on vibration control of a SDOF structure

Tuned liquid column damper (TLCD) is a class of auxiliary damping device which is used to dissipate vibrational energy of structures when excited by dynamic loading. Damping control of TLCDs is an important parameter to achieve the maximum benefit of TLCDs when attached to the structure. Herein, a new method of controlling damping is proposed by installing maneuverable flaps into TLCD (TLCD + MF). The damping value of the TLCD is controlled by the closing angle of the flaps. This method is simple in concept, more applicable in construction, and it is an effort to make the TLCD more controllable, (i.e. semi-active). Dynamic characteristics of such TLCD + MF system are investigated in this study. It is observed that by increasing the closing angle, the damping ratio of the TLCD + MF system increases. In addition, it is found that the mistuning of frequency becomes ignorable below the closing angle of 50°. The efficiency of the TLCD + MF in reducing response of structures under harmonic excitation is also studied. It is shown that existence of the flaps improves the performance of combined structure and the TLCD + MF system in terms of damping ratio and structural responses. The TLCD + MF system with the closing angle of 50° reduces the acceleration and displacement responses about 20 % more than conventional TLCDs.     

Models and computational algorithms for maritime risk analysis: a review

Due to the undesirable implications of maritime mishaps such as ship collisions and the consequent damages to maritime property; the safety and security of waterways, ports and other maritime assets are of the utmost importance to authorities and researches. Terrorist attacks, piracy, accidents and environmental damages are some of the concerns. This paper provides a detailed literature review of over 180 papers about different threats, their consequences pertinent to the maritime industry, and a discussion on various risk assessment models and computational algorithms. The methods are then categorized into three main groups: statistical, simulation and optimization models. Corresponding statistics of papers based on year of publication, region of case studies and methodology are also presented.     

Bernstein polynomial basis for numerical solution of boundary value problems

The purpose of this paper is to propose a computational method for the approximate solution of linear and nonlinear two-point boundary value problems. In order to approximate the solution, the expansions in terms of the Bernstein polynomial basis have been used. The properties of the Bernstein polynomial basis and the corresponding operational matrices of integration and product are utilized to reduce the given boundary value problem to a system of algebraic equations for the unknown expansion coefficients of the solution. On this approach, the problem can be solved as a system of algebraic equations. By considering a special case of the problem, an error analysis is given for the approximate solution obtained by the present method. At last, five examples are examined in order to illustrate the efficiency of the proposed method.     

A new simple approach to predict entropy of fusion of nitroaromatic compounds

In this paper, a new model is introduced to predict entropy of fusion of nitroaromatic compounds, which can be used for some well-known high explosives such as 2,4,6-trinitrotoluene (TNT) and N-methyl-N,2,4,6-tetranitroaniline (TETRYL). Novel correlation contains two different functions for which elemental composition and symmetry of nitroaromatic compounds are used to present additive and non-additive contributions, respectively. The presence of some molecular fragments may influence the value of non-additive function. The root-mean-square (rms) deviation of predictions of entropy of fusion from 66 measured values (corresponding to 61 molecules) is 7.88 J/K mol. The predicted results are compared with one of the best available semi-empirical methods, which show the reliability of the new method is relatively good.     

Multisubject activation detection in fMRI by testing correlation of data with a signal subspace

In this article, a generalized likelihood ratio test is proposed to assess the correlation between multisubject functional MRI (fMRI) time series and bases of a signal subspace for detecting the existence of group activation in each voxel of the brain. The signal subspace is generated by a design matrix using the time series of the desired effects. The proposed method leads to testing the product of eigenvalues of a specific matrix. The eigenvector corresponding to the largest eigenvalue is the weighting vector for the linear combination of time series of various subjects that has the maximum correlation with the signal subspace. In another method, namely, canonical correlation analysis, the largest eigenvalue of the above matrix is tested for activation detection. Surrogate data on resting state (no activation) are generated by randomization and used to estimate the statistical distribution of these parameters under the null hypothesis condition. A postprocessing step is applied to prevent false detection of voxels that are not sufficiently active (among subjects) by defining a minimum ratio for the active population. The proposed methods are applied on simulated and experimental fMRI data, and the results are compared with those of the general linear model (GLM; using the SPM and FMRISTAT toolboxes). The proposed methods showed higher detection sensitivity as compared with the GLM for activation detection in simulated data. Similarly, they detected more activated regions than did the GLM from multisubject experimental fMRI data on a visual (sensorimotor) event-related task.     

Advertisement allocation for generalized second-pricing schemes

Recently, there has been a surge of interest in algorithms that allocate advertisement space in an online revenue-competitive manner. Most such algorithms, however, assume a pay-as-you-bid pricing scheme. In this paper, we study the query allocation problem where the ad space is priced using the well-known and widely used generalized second-price (GSP) scheme. We observe that the previous algorithms fail to achieve a bounded competitive ratio under the GSP scheme. On the positive side, we present online constant-competitive algorithms for the problem.     

A direct approach to the Weiss conjecture for bounded analytic semigroups

We give a new proof of the Weiss conjecture for analytic semigroups. Our approach does not make any recourse to the bounded H ^∞-calculus and is based on elementary analysis.     

Effect of 2D Image Resolution on 3D Stochastic Reconstruction and Developing Petrophysical Trend

Multi-resolution digital rock physics (DRP) makes it possible to up-scale petrophysical properties from micron size to core sample size using two-dimensional (2D) thin section images. Resolution of 3D images and sample size are challenging problems in DRP where high-resolution images are acquired from small samples using inefficient and expensive micro-CT facilities. Three-dimensional stochastic reconstruction is an alternative approach to overcome these challenges. In this paper, we use multi-resolution images and investigate effect of 2D image resolution on 3D stochastic reconstruction and development of petrophysical trends for our two sandstone and carbonate original representative volume elements (RVEs). The proposed method includes three steps. In the first step, the spatial resolution of our original RVEs is decreased synthetically. In the second step, stochastic RVEs are realized for each resolution using two perpendicular images, correlation functions, and phase recovery algorithm. In the reconstruction method, a full set of two-point correlation functions (TPCFs) is extracted from two perpendicular 2D images. Then TPCF vectors are decomposed and averaged to realize 3D stochastic RVEs. In the third step, petrophysical properties like relative and absolute permeability as well as porosity and formation factor are computed. The output is used to develop trends for petrophysical properties in different resolutions. Experimental results illustrate that the proposed method can be used to predict petrophysical properties and reconstruct 3D RVEs for resolutions unavailable in the acquired 2D or 3D data.