Comparison of two models for a high temperature reactor coupled to a gas turbine

This paper presents two independent dynamic models of a nuclear gas turbine power plant. Both the high temperature nuclear reactor (HTR) and its energy conversion system (ECS) based on a direct Brayton cycle have been modelled. One model utilises RELAP5 for the ECS, the other Aspen Custom Modeler (ACM). The reactor model used in both models is a point kinetic model derived from a detailed reactor model. The ECS model is described and compared componentwise, with an emphasis on the turbomachinery. The total plant models are compared with each other by calculating two representative transients: one load rejection transient and one transient with the system at part load.     

Surgical treatment of aneurysms of the left ventricle. Immediate and long-term results. Apropos of a consecutive series of 121 cases

From 1978 to 1992, 121 cases of postinfarction left ventricular aneurysm (99 males, 22 females, mean age 60 years) were operated on. The authors insist on a high rate of clinical arhythmogenicity (31.4%) and associated mechanical complications (21%). 76% of patients were in functional NYHA class III or IV. Resection was performed in 90% of patients, plication in 10%. 58% underwent coronary artery bypass grafting (1.7 graft/patient), 16% encircling ventriculotomy, 8% mitral valve replacement and 13% closure of ventricular septal defect. Operative mortality was 14.9% (10% when other mechanical complications where excluded). 5-year survival is 67.9%. Late cardiac deaths are as follow: left ventricular failure (1.8% A/P), Sudden death (1.4% A/P), Myocardial infarction (0.6% A/P). 82% of survivals are in functional NYHA class I or II. Only functional class NYHA III or IV is predictive of late death. We conclude that postinfarction left ventricular aneurysm remains a high risk complication especially when associated with other mechanical complications. When arhythmogenicity is present we suggest rhythmologic surgery and in all cases, complete revascularization.     

Reply to Comment on “Ewald summation technique for one-dimensional charge distributions”

We explain why the methods in Langridge, Hart and Crampin [Comput. Phys. Commun. 134 (2001) 78] suffice for the evaluation of the lattice sums entering the Madelung matrix describing multipole interactions in systems with one-dimensional translational periodicity.     

Metadata's role in a scientific archive

Computational and laboratory experiments generate masses of data that must be stored reliably, with minimal effort on each researcher's part, and must be retrievable for decades. The storage environment must also work seamlessly across scientific disciplines and capture all of a file system's features in a semantically-based catalog that provides Boolean, keyword, and tree-based data access. The authors describe a metadata-based archive for scientific data that provides flexible archive storage for very large data sets. The system uses metadata to organize and manage the data without imposing predefined metadata formats on scientists.     

Shape memory properties of Ni-Ti based melt-spun ribbons

Shape-memory properties of equiatomic NiTi, Ni₄₅Ti₅₀Cu₅, and Ni₂₅Ti₅₀Cu₂₅ ribbons made by melt spinning have been studied by temperature inducing the martensitic transformation under constant tensile loads. Recoverable strains above 4 pct can be obtained under ∼100 MPa loads for the NiTi and Ni₄₅Ti₅₀Cu₅ ribbons, transforming to B19’ martensite. The B19 martensite is formed in the Ni₂₅Ti₅₀Cu₂₅ ribbon after crystallization, and according to the lowering in transformation strain as Cu content increases, the recoverable strain is close to 2.5 pct for ∼150 MPa load. The transformation temperatures exhibit a linear dependence on the applied stress, which can be quantitatively described by means of a Clausius-Clapeyron type equation. The NiTi and Ni₄₅Ti₅₀Cu₅ ribbons exhibited some degree of two-way shape-memory effect (TWSME) after thermomechanical cycling. Texture analyses performed on the different ribbons allow us to better understand the transformation strains obtained in each ribbon. The amounts of shape-memory effect (SME) and nonrecoverable strain shown by the studied ribbons are of the same order as those already observed in bulk materials, which makes melt spinning an ideal substitute to complicated manufacturing processes if really thin samples are needed. However, applicable stresses in melt-spun ribbons are limited by a relatively “premature” brittle fracture caused by irregularities in ribbon thickness.     

Nonholonomic Mobile Manipulators: Kinematics, Velocities and Redundancies

We consider nonholonomic mobile manipulators built from an n _a joint robotic arm and a nonholonomic mobile platform with two independently driven wheels. Actually, there is no efficient kinematic formalism for these systems which are generally characterized by their high number of actuators. So, kinematic modelling is presented with particular emphasis on redundancy. Whereas kinematic redundancy is well known in the holonomic case, it is pointed out that it is necessary to define velocity redundancy in the case of nonholonomic systems. Reduced velocity kinematics based on quasi-velocities are shown to provide an efficient formalism. Two examples of mobile manipulators are presented. Finally, reduced velocity kinematics and velocity redundancy are shown to be adequate tools in order to realize operational task while optimizing criteria such as manipulability.     

3 Jahre Akkreditierung Stand, Erfahrungen, Probleme

Vor 3 Jahren ist ein beispielloser Prozess zur Umgestaltung des deutschen Hochschulwesens angelaufen. Mit dem Übergang zu Bachelor- und Masterstudiengängen wurde eine Qualitätssicherung nach Art der international üblichen Akkreditierung erforderlich.     

Theories, theoretical orientation, and theoretical dimensions: Comment on Poznanski and McLennan (1995).

J. J. Poznanski and J. McLennan's (see record 1996-07039-001) article helpfully integrates research on a topic of considerable importance. Their derivation of two second-order "factors" (analytic-experiential and objective-subjective), as well as five more specific factors, in theoretical orientation is particularly helpful. In this comment, I seek to clarify how therapists' preferences for certain techniques relate to theoretical orientation. Reasons for the slow pace of research on multi-item self-report measures of theoretical orientation are suggested, as is an alternative measurement approach to that recommended by Poznanski and McLennan. (PsycINFO Database Record (c) 2010 APA, all rights reserved)