A fuzzy set-based approach to origin–destination matrix estimation in urban traffic networks with imprecise data

An important issue in the management of urban traffic networks is the estimation of origin–destination (O–D) matrices whose entries represent the travel demands of network users. We discuss the challenges of O–D matrix estimation with incomplete, imprecise data. We propose a fuzzy set-based approach that utilises successive linear approximation. The fuzzy sets used have triangular membership functions that are easy to interpret and enable straightforward calibration of the parameters that weight the discrepancy between observed data and those predicted by the proposed approach. The method is potentially useful when prior O–D matrix entry estimates are unavailable or scarce, requiring trip generation information on origin departures and/or destination arrivals, leading to multiple modelling alternatives. The method may also be useful when there is no O–D matrix that can be user-optimally assigned to the network to reproduce observed link counts exactly. The method has been tested on some numerical examples from the literature and the results compare favourably with the results of earlier methods. It has also been successfully used to estimate O–D matrices for a practical urban traffic network in Brazil.     

New dicationic derivatives of dibenzotetraaza[14]annulene: tuning DNA-binding properties

Four new water-soluble derivatives of dibenzotetraaza[14]annulene have been synthesized, bearing meso substituents with different structures and dimensions: 3-(N,N,N-trimethylammonium)propyl, 3-(N-pyridinium-1-yl)propyl, 2-[3-(N,N,N-trimethylammonium)propoxy]benzoyl, and 2-[3-(N-pyridinium-1-yl)propoxy]benzoyl. The crystal structures of 3-(trimethylammonium)propyl and (N,N,N-trimethylammonium)propoxy]benzoyl derivatives were determined by single crystal X-ray analysis. According to the UV-vis titrations, thermal denaturation experiments, and ethidium bromide displacement assays, all compounds presented here interact strongly with double stranded (ct)-DNA. The product equipped with 3-(trimethylammonium)propyl pendant groups and two positive charges interacts with DNA in one dominant binding mode, whereas the other three derivatives revealed more complex mixed-type interactions. The results have been discussed in terms of dimensions, geometry, and electronic properties of the evaluated compounds, on the basis of corresponding crystallographic data.     

N-dimensional rings with an isolated singular point having nonzero K?n

We construct examples of normal affine k-algebras of dimension N with an isolated singular point and nonzero K _–N , giving counter-examples to a conjecture of Weibel.     

Thermal treatment,spectroscopic analyses,and electrical properties of poly(copper 2,3,9,10,16,17,23,24-octacyanophthalocyanine)

Thermal treatment of novel poly(copper 2,3,9,10,16,17,23,24-octacyanophthalocyanine), PCOCP, has been carried out at different temperatures in an inert atmosphere. As polyacrylonitrile, the polymer can be thermally cyclized through the cyano groups to produce semiconductive and conductive materials. Polymeric copper octacyanophthalocyanine material with a conductivity as high as 5–8 (Ω cm)^-1 was prepared. Weight loss, electrical data, infrared, and photoacoustic results of the thermally treated copper octacyanophthalocyanine polymer are discussed.     

Configuration and optimization of semiconductor gas sensors as gas chromatographic detectors

A tin oxide, gas-sensitive semiconductor sensor was configured as a gas chromatographic detector and its performance was optimized. Two sensor housings were compared but little difference was found in performance. The flow rate and temperature of the column and the internal heater voltage of the sensor affected both the sensitivity and peak shape. The temperature of the sensor surface was the most critical parameter. Optimal conditions for the gas chromatographic detection of a mixture of alkanes (C₁–C₅) and hydrogen were identified by using the simplex technique. The detection limit for hydrogen was improved by a factor of five to 20 ppb (v/v), illustrating the value of optimization and the excellent sensitivity of the detector. It is concluded that semiconductor gas sensors offer significant advantages as gas chromatographic detectors for the determination of reducing gases.     

Determination of organometallic compounds by capillar gas chromatography – inductively coupled plasma mass spectrometry

The separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC-ICP-MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC-ICP-MS has been extended considerably beyond that possible in earlier studies (retention indices up to 3400).     

Improving the accuracy of the spatial discretization in finite-difference electrochemical kinetic simulations, by means of the extended Numerov method

The fourth-order accurate, three-point finite-difference Numerov spatial discretization provides accurate and efficient solutions to the time-dependent governing differential equations of electrochemical kinetics in one-dimensional space geometry, when the equations contain first time derivatives of the solution, second spatial derivatives, and homogeneous reaction terms only. However, the original Numerov discretization is not applicable when the governing equations involve first spatial derivative terms. To overcome this limitation, an appropriately extended Numerov discretization is required. We examine the utility of one of such extensions, first described by Chawla. Relevant discrete formulae are outlined for systems of linear governing equations involving first derivative terms, and applied to five representative example models of electrochemical transient experiments. The extended Numerov discretization proves to have an accuracy and efficiency comparable to the original Numerov scheme, and its accuracy is typically up to four orders of magnitude higher, compared to the conventional, second-order accurate spatial discretization, commonly used in electrochemistry. This results in a considerable improvement of efficiency. Therefore, the application of the extended Numerov discretization to the electrochemical kinetic simulations can be fully recommended.     

An accurate and stable nitrate-selective electrode for the in situ determination of nitrate in agricultural drainage waters

A field evaluation of a novel nitrate-ion selective electrode (ISE) was undertaken by continuous immersion over a period of 5 months in agricultural drainage weirs. The nitrate sensor N,N,N-triallyl leucine betaine was covalently attached to polystyrene-block-polybutadiene-block-polystyrene (SBS) using a free radical initiated co-polymerisation, to produce a rubbery membrane which was incorporated into a commercially available electrode body. A measurement unit was constructed comprising the nitrate-ISEs, a reference electrode and a temperature probe connected through a pre-amplifier to a data-logger and battery supply. A temperature correction algorithm was developed to accomodate the temperature changes encountered in the drainage weirs. The nitrate results obtained with the ISEs at hourly intervals compared very favourably (R2 = 0.99) with those obtained with laboratory automated chemical determinations made on contemporaneous samples of drainage in a concentration range 0.47-16 ppm nitrate-N. The ISEs did not require re-calibration and no deterioration in performance or fouling of the membrane surface was observed over four months of deployment.