Dynamic Performance of a Complex Distillation System to Separate a Five‐Component Hydrocarbon Mixture

Distillation is one of the most used separation processes in chemical industry, although it is a highly energy‐intensive operation. For multicomponent distillation, complex structures have been proposed in previous works, which may allow energy savings. Nevertheless, it is mandatory to understand the dynamic characteristics of such complex structures. In this work, the dynamic performance of a dividing‐wall‐based structure for the separation of a five‐component mixture is studied. A sensitivity analysis is performed on the structure in terms of the interlinking streams, performing a singular value decomposition analysis to selected cases with different operational conditions. The designs with the lowest energy duties also showed the best open‐loop properties.     

A metalanguage design for sessions with group decision support systems

This paper proposes a metalanguage for representing communication among participants in a session of a group decision support system (GDSS). Such a vehicle can be used for setting standards and designing specific user interfaces with GDSS.Three different roles of participants are identified: chairperson, chauffeur and regular participant. The tasks and activities of each role are analyzed. Based on the analysis, communications requirements are derived. The requirements lead to a design of a metalanguage consisting of 15 different commands. The paper concludes by displaying the structure and syntax of each command.The work described here is conceptual and could be considered as a proposal for GDSS language design.     

Performance evaluation of nonsynchronized initial random access for mobile broadband systems

In this paper, a comparative analysis of the performance of the nonsynchronized initial random access channel in Mobile WiMAX and E-UTRA systems under different conditions (fast fading, multiuser interference) is carried out. The analysis is focused on the correlation properties of the code sequences used in each case. We evaluate their ability to provide low values for false alarm and erroneous detection probabilities (detecting a sequence that has not been transmitted) at the same time as guaranteeing low nondetection probabilities of the effectively transmitted sequences. Results show the promising performance of the E-UTRA scheme, even in high mobility scenarios, where the Doppler effect requires additional considerations to guarantee the correct system operation.     

Electrodeposited Quantum Dots. 6. Epitaxial Size Control in Cd(Se,Te) Nanocrystals on {111} Gold

Size control in epitaxial Cd(Se, Te) quantum dots (QDs) electrochemically deposited on {111} textured Au is achieved by mismatch tuning. The formation of QDs as a form of relaxation of heteroepitaxial strain energy is demonstrated. The increased lattice parameter resulting from incorporation of small amounts of Te in the CdSe lattice leads to reduced mismatch-induced strain energy and therefore larger QD size. While the QD interatomic spacings at the interface are shown to be unchanged due to the heteroepitaxy with the Au substrate, the perpendicular QD d-spacings (along the c-axis) strongly increase with increasing Te content due to strain relaxation.     

Hermitian finite-element method for inhomogeneous waveguides

A finite-element method (FEM) based on Hermitian fifth-degree polynomials is established in order to determine the field within a closed waveguide filled with inhomogeneous material. As with the method based on the Lagrangian approximation, spurious solutions are eliminated when the divergence-free constraint is satisfied and the boundary conditions are explicitly enforced. However, the smooth (C¹) Hermitian approximation allows the direct elimination of the axial field component in each triangle element. This procedure results in a reduction of the computer memory needed and in programming efficiency. As the Hermitian FEM uses smooth basis functions, the method also increases the quality of the field solutions. The method has been applied to mode characterization in waveguides. Several comparisons with Lagrangian FEM demonstrate the advantages of the Hermitian FEM. Some difficulties arising in cases of waveguides with sharp edges are discussed. A solution based on mesh refinement near the sharp edges is proposed     

Therapists' helpful and unhelpful situations with LGBT clients: An exploratory study.

The purpose of this exploratory study was to identify a broad range of variables that characterize psychotherapists' perceptions of helpful and unhelpful therapy experiences of lesbian, gay, bisexual, and transgender individuals. In-depth, semistructured interviews were conducted with a diverse sample of 14 psychotherapists to identify such variables and patterns among them. Results suggest that a wide range of variables, including the therapeutic relationship, therapist response to the client's sexual orientation/gender identity, type of presenting concern, and the therapy environment, may affect the therapy experiences of this population. The data also suggest that factors such as ethnicity, gender identity, therapy needs, and socioeconomic status should be considered when providing mental health services to this population. Clients dealing with multiple types of marginalization may be particularly challenging for practitioners. Implications for future research and clinical practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

HF单边带解调器

图1所示电路用于补充“设计实例(Design Idea)”栏目以前的一篇文章渗考文献1)。图中的调制器使用了一个移相网络,把一个低频的(声频)信号分成同相和90°相差(正交)的两个分量。这里的移相网络比其他移相电路优越之处在于,它产生的移相误     

Transfer of mercury and methylmercury along macroinvertebrate food chains in a floodplain lake of the Beni River, Bolivian Amazonia

We have evaluated the mercury and methylmercury transfers to and within the macroinvertebrate communities of a floodplain lake of the Beni River basin, Bolivia, during three hydrological seasons and in two habitats (open water and vegetation belt). Using the stable isotopes δ¹³C and δ¹⁵N, six trophic chains were identified during a previous study. Four are based on only one source: seston, organic matter from the bottom sediment, periphyton and macrophytes. Two are based on mixed sources (seston and periphyton in one case, periphyton and macrophytes in the other). During sampling, we found only one taxon that had surface sediment organic matter as food source and very few taxa whose trophic source was constituted by macrophytes. The periphyton was the most important source during all seasons; it produced the longest chain, with three trophic positions. Whatever the season and trophic source, all collected macroinvertebrates contained methyl mercury and the latter was biomagnified in all trophic chains that we identified. The biomagnification of methylmercury through invertebrate trophic chains accurately reflected the existence and length of these chains. Biomagnification was virtually non-existent in the sediment-based chain, low and restricted to the dry season in the macrophyte-based chain. It was significant in the seston-based chain, but limited by the existence of only two trophic levels and restricted to the wet season. Finally, it was very effective in the periphyton-based chain, which offers the highest rate of contamination of the source but, above all, the largest number of trophic levels.     

Structural performance of alkali/acid-ultrasound modified Agave fibers during the melt mixing process with polyvinyl alcohol

This study aims to investigate changes in the structural properties of alkali/acid-ultrasound modified Agave fibers and their performance immersed on a polyvinyl alcohol (PVA) matrix with plasticizer during melt mixing processing. Structural analysis revealed that ultrasound enhances the effectiveness of the conventional alkaline/acid treatments to modify fibers since the simultaneous treatment increased the partial removal of lignocellulosic components, water molecules, and amorphous regions which improved their processability on a PVA matrix. Specific energy consumption values indicated that during melt mixing the modified fibers required more energy to expose the chains of cellulose fraction to function as an interaction site for PVA chains. Once the mixture was homogenized, the fiber-matrix interactions promoted high viscosity, friction, and mechanical stress in the chamber. Therefore, the modified fibers restricted the interaction between plasticizer and PVA in the obtained films, resulting in a highly structured, and reinforced network, increasing the storage modulus as dynamic mechanical analysis indicated. These findings highlight a feasible way to valorize Agave fibers and allow the understanding of the matrix-fiber interactions during melt mixing processing, useful to predict the structural and mechanical properties of the films.