Chevron concepts

We start with some elementary information about anisotropic intermolec-ular interactions in liquid crystals and molecular factors that influence the smectic behaviour. The various types of molecular models and commonly accepted concepts reproducing the smectic behaviour are evaluated. Then we discuss in more detail the breaking of head-to-tail inversion symmetry in smectic layers formed by polar and (or) sterically asymmetric molecules and formation of particular phases with one and two dimensional periodicity. We then proceed with the description of the structure and phase behaviour of terminally fluorinated and polyphilic mesogens and specific polar properties of the achiral chevron structures. Finally, different possibilities for bridging the gap between smectic and columnar phases are considered. 

Quill was founded in April 1999 as an industrial consortium, with members from all sectors of the chemical industry. It is based on the well-proven industry/uni-versity cooperative research center (lUCRC) concept developed by the U.S. National Science Foundation and is only the second lUCRC in Europe. There were 17 founding industrial members of the Quill consortium, and the current membership includes (listed alphabetically) bp. Chevron, Cytec, DuPont, Eastman Chemicals, ICI, Invista, Merck, Novartis, Procter and Gamble, SACHEM, SASOL, Shell, Strata, and UOP. Research carried out between QUB and individual companies, or by QUILL itself, has generated more than 20 patent applications, many of which have now been published, from as diverse a range of industries as BNFL, BP Chemicals, Cytec, ICI, Quest International, and Uni-chema Chemie BV. In a recent report in Nature, the need for collaboration between government, industry, and academic institutions to form sustainable chemistry centers was stressed as vital in order to rethink traditional chemistry processes to be not only beneficial to the environment but also to make economic sense for industry. Quill, under the codirection of Professors Kenneth R. Seddon and Jim Swindall OBE, is one of these chemistry centers, and is the first (and... 

Chevron Furcoat Arctic Insulation Systems Concepts... 

Other interesting new chemistry using bioisosteres is presented in the benzylnitramines of American Cyanamid, the vinylogous ureas of Stauffer, the tetrahydrofuranes of Chevron, and triazinones of FMC. The nitramines of this current example seem to function as a bioisostere of a carboxylic acid. The vinylogous ureas are another example of a possible homologous bioisostere at work. And finally, the triazinones appear to behave as imide bioisosteres. These certainly are concepts which merit wider attention. 

A collaborative effort between The University of Mississippi (Seiner), Florida State University (Krothapalli), and Combustion Research and Flow Technology — CRAFT (Dash) has recently been initiated that includes all phases that are required for completion of a successful noise-reduction program. To enable projection of model-scale laboratory acoustic data to full scale, one-tenth-scale models have been constructed. The primary methods being investigated for noise suppression involve the use of micro-air-jet injection, water-drop injection, and modification of nozzle divergent flaps into corrugated shapes with chevrons. All of these concepts are known to produce little impact on aeroper-formance. 

Concepts initially under investigation include those of microjet injection [1] and the use of Bluebell (corrugated) nozzles with tabs/chevrons and/or nozzle lip injection [2]. These concepts embody several types of technologies for jet-noise reduction which include those of conventional vortical mechanisms, turbulent structure alteration, and shock attenuation. 

Another concept considered for noise reduction in jet engines for civil aircraft are aerodynamic devices called chevrons, which are placed along the trailing edges of a jet engine primary and secondary exhaust nozzle. These chevrons need to be fine tuned between noise-benefit and thrust-loss, where a solution has been proposed by using SMA actuators to position the chevron in accordance to the on-ground and cruise level temperatures [47]. 

Chevron introduced a novel concept via the Paragon process that combines high-pressixre hydrocracking with the low-pressure step using ZSM-5 zeolite as a shape-selective catalyst. The second stage provides conditions for the selective cracking of normal and slightly branched paraffins to produce Cj-Cg olefins to further boost the octane number [11]. 

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