Status and application of HgCdTe device modeling

In this article, device modeling refers to numerical simulation of semiconductor device physics to predict electrical behavior. The silicon integrated circuit industry provides the example for the use of technology computer-aided design to simulate wafer fabrication processes, and the electrical performance of devices and circuits. This paper first reviews semiconductor device modeling in general, then as applied in work supporting the development and analysis of HgCdTe infrared detectors. Example applications of one- and two-dimensional device modeling are simulation of a bias-selectable, integrated two-color detector, and two-dimensional effects on the spectral response of a HgCdTe detector with composition grading.     

Effects of mercaptopropionic acid as a stabilizing agent and Cd:Te ion ratio on CdTe and CdHgTe quantum dots properties

In the present work, mercaptopropionic acid (MPA) capped CdTe and CdHgTe quantum dots (QDs) are synthesized using a method based on the bottom up approach in aqueous medium. The CdTe QDs were prepared with a two different ratios of Cd:Te (3:1 and 4:1). It was noticed that there was a minimum concentration of MPA for each Cd:Te ratio. The resulting QDs were characterized using optical absorption spectroscopy, energy dispersion X-ray (EDX) and high resolution transmission electron microscopy (HRTEM). It was found that the EDXs of CdTe and CdHgTe QDs showed that the stiochiometric ratios of CdTe obtained with Cd:Te ratio of 3:1 is 50:50 and for CdHgTe is 40:26:34 for 100?% of Hg. The band gap of CdHgTe QDs varies slightly with composition from 2.21?eV for a pure CdTe to 1.4?eV for a CdHgTe with 100?% of Hg. The HRTEM image showed a good dispersed nano-crystalline structure for the CdTe QDs with average size of 3–4?nm. The existence of the lattice planes on the HRTEM images of the QD indicated that the CdTe QDs are highly crystalline. In addition, the CdHgTe QDs size is 12?nm for 100?% of Hg.     

A novel acoustic indoor localization system employing CDMA

Nowadays outdoor location systems have been used extensively in all fields of human life from military applications to daily life. However, these systems cannot operate in indoor applications. Hence, this paper considers a novel indoor location system that aims to locate an object within an accuracy of about 2 cm using ordinary and inexpensive off-the-shelf devices and that was designed and tested in an office room to evaluate its performance.In order to compute the distance between the transducers (speakers) and object to be localized (microphone), time-of-arrival measurements of acoustic signals consisting of Binary Phase Shift Keying modulated Gold sequences are performed. This DS-CDMA scheme assures accurate distance measurements and provides immunity to noise and interference.Two methods have been proposed for location estimation. The first method takes the average of four location estimates obtained by trilateration technique. In the second method, only a single robust position estimate is obtained using three distances while the least reliable fourth distance measurement is not taken into account.The system?s performance is evaluated at positions from two height levels using system parameters determined by preliminary experiments. The precision distributions in the work area and the precision versus accuracy plots depict the system performance. The proposed system provides location estimates of better than 2 cm accuracy with 99% precision.     

Numerical simulation of hydrous transfer within fibrouscement slates

In situ distortion of fibrous-cement slates is brought about by exposure to different temperature and hygrometric gradients across the material. The aim of this research was to understand in detail the effect of each compositional change on the physical properties, and to use this knowledge for the manufacture of slates which would exhibit improved mechanical properties. A previous paper described the experimental measurements conducted to evaluate the impact of changing the composition of the slates on the physical properties controlling hydrous transfer. In the present paper, the physical parameters obtained from the experimental work are used in a numerical model. The numerical model, NSAT, employs a finite-element method to solve the non-linear diffusion equation. The numerical model was validated and subsequent simulations are described. A theoretical model has been obtained which shows good agreement between the results from practical tests at the experimental station and the predictions of the numerical model. The results also confirm the previous hypotheses of the industrial partner. The theoretical model obtained may be used for the prediction and specification of industrial materials having improved mechanical properties, and in particular, exhibiting less distortion.

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Résumé Les déformations locales dans les ardoises de fibrociment peuvent être engendrées par l'existence de gradients de température et d'hygrométrie au sein du matériau. Le but de ce travail est de comprendre en détail l'effet des modifications de composition des ardoises sur leurs propriétés physiques et d'utiliser ces connaissances dans la fabrication d'ardoises présentant de meilleures propriétés mécaniques. Un article précédent a décrit l'effet des traitements subis par les ardoises sur les paramètres physiques influant sur les transferts d'humidité. Dans cet article, les paramètres physiques sont utilisés dans un modèle numérique, NSAT. Le modèle numérique emploie la méthode des éléments finis pour résoudre l'équation non-linéaire de diffusion. D'abord le modèle numérique a été validé. Ensuite d'autres simulations plus complexes sont présentées. Les calculs numériques ont clairement mis en évidence les différents types de comportement de séchage qui correspondent aux diverses observations expérimentales du partenaire industriel. Le modèle numérique peut être utilisé pour la prévision et l'élaboration des matériaux industriels avec un meilleur comportement mécanique. En particulier, une dimunition de la déformation est attendue.

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Editorial note A. Raoof and T. H. Doan are working at the Laboratoire des Matériaux et des Structures du Génie Civil of LCPC, France, which is a RILEM Titular Member. A. Sabouraud is working at Pont-à-Mousson SA, France, which is a RILEM Titular Member.     

Changes in volatile flavour components of soybeans during roasting

Volatile concentrates were prepared from whole soybeans, roasted at 200°C for 10, 20 and 30 min, by steam distillation under reduced pressure followed by ether extraction, and analysed by gas chromatography and gas chromatography-mass spectrometry, in comparison with the volatile concentrate from raw soybean flour.Major flavour components of raw soybean, such as n-hexanol, 1-octen-3-ol and n-hexanal, decreased during the course of roasting, but the rate of this decrease was not rapid, especially between 10 and 20 minutes' roasting. During the roasting period, alkylated pyrazines, oxygenated furans, oxygenated pyrroles and phenols were formed or increased markedly. On the other hand, sensory evaluation showed that a flavour change to ‘desirable’ from ‘beany’ or ‘objectionable’ occurred between 10 and 20 minutes' roasting. These results suggest that roast flavour masks the ‘beany’ flavour in soybean.     

Adenoviral-mediated suicide gene therapy for hepatic metastases of breast cancer

Metastases of breast cancer are a major cause of treatment failure. To evaluate the therapeutic efficacy of suicide gene therapy in metastatic breast cancer, we used the herpes simplex virus thymidine kinase (HSV-tk) gene followed by ganciclovir (GCV) administration to treat breast cancer, generated by an adenocarcinoma cell line MOD in syngeneic mice. The bystander effect of HSV-tk + GCV on tumor cell killing was illustrated by demonstrating complete regression of subcutaneous tumors consisting of 90% parental tumor cells and 10% HSV-tk transformed tumor cells. To establish a model of breast cancer metastases in the liver, tumors were generated by intra-hepatic implantation of MOD cells in syngeneic animals. Two weeks after tumor cell implantation, replication defective adenoviral vectors expressing HSV-tk (ADV.tk), or beta-galactosidease (ADV. beta-Gal) were injected intratumorally, followed by buffer or GCV administration. Treatment with ADV.tk + GCV resulted in significant regression of tumor (P < .001), as assessed by computerized morphometric analysis of residual tumor. This was reflected as a significant prolongation of survival in treated animals (P < .001). These results demonstrate that ADV-mediated suicide gene therapy in vivo can be incorporated in a comprehensive treatment strategy for liver metastases of breast cancer.     

An analytical model to predict the volume of sand during drilling and production

Sand production is an undesired phenomenon occurring in unconsolidated formations due to shear failure and hydrodynamic forces. There have been many approaches developed to predict sand production and prevent it by changing drilling or production strategies. However, assumptions involved in these approaches have limited their applications to very specific scenarios. In this paper, an elliptical model based on the borehole shape is presented to predict the volume of sand produced during the drilling and depletion stages of oil and gas reservoirs. A shape factor parameter is introduced to estimate the changes in the geometry of the borehole as a result of shear failure. A carbonate reservoir from the south of Iran with a solid production history is used to show the application of the developed methodology. Deriving mathematical equations for determination of the shape factor based on different failure criteria indicate that the effect of the intermediate principal stress should be taken into account to achieve an accurate result. However, it should be noticed that the methodology presented can only be used when geomechanical parameters are accurately estimated prior to the production stage when using wells and field data.     

Poly(o-aminophenol) film prepared in the presence of sodium dodecyl sulfate: Application for nickel ion dispersion and the electrocatalytic oxidation of methanol and ethylene glycol

Poly(o-aminophenol) (POAP) was formed by successive cyclic voltammetry in monomer solution in the presence of sodium dodecyl sulfate (SDS) on the surface of a carbon paste electrode. The electrochemical behavior of the SDS-POAP carbon paste electrode has been investigated by cyclic voltammetry in 0.5 M HClO₄ and 5 mM K₄[Fe(CN)₆]/0.1 M KCl solutions as the supporting electrolyte and model system, respectively. Ni(II) ions were incorporated into the electrode by immersion of the polymeric modified electrode having amine groups in 0.1 M Ni(II) ion solution. Cyclic voltammetric and chronoamperometric experiments were used for the electrochemical study of this modified electrode. A good redox behavior of the Ni(III)/Ni(II) couple at the surface of electrode can be observed. The electrocatalytic oxidations of methanol and ethylene glycol (EG) at the surface of the Ni/SDS-POAP electrode were studied in a 0.1 M NaOH solution. Compared to bare carbon paste and POAP-modified carbon paste electrodes, the SDS-POAP electrode significantly enhanced the catalytic efficiency of Ni ions for methanol oxidation. Finally, using a chronoamperometric method, the catalytic rate constants (k) for methanol and ethylene glycol were found to be 2.04 × 10⁵ and 1.05 × 10⁷ cm³ mol⁻¹ s⁻¹, respectively.     

Facile synthesis of polyoxometalate-based composite with doped ternary NiCoFe cations as electrocatalyst for oxygen evolution reaction

The construction of efficient and low-cost electrocatalysts for oxygen evolution reactions (OER) to replace precious catalysts is a necessity to achieve economic production of hydrogen. Herein, we report an efficient tri-metallic electrocatalysts for the OER that is prepared by incorporate nickel, cobalt and iron cations on Triton X-100/phosphotungstic acid organic-inorganic composite without utilize any binders or energy consumer procedure. Considering to the synergy effect of simultaneous absorption of NiCoFe cations on composite substrate, the as-made tri-metallic catalyst exhibits excellent OER activity with a small overpotential of 210 and 330 mV at a current density of 10 and 100 mA cm^?2, respectively. Moreover, remarkable trends in electrocatalytic activity of mono-, bi- and tri-metallic electrocatalysts at low (10 mA) and high (100 mA) current density are observed. In addition, this new families of non-precious metal catalyst shows long-term durability in 1 M KOH.