bluuebunny/crossref_metadata_2025 huggingface dataset:
Reading for the Stimmung? About the Ontology of Literature Today
Authors: Gumbrecht Hans Ulrich
Published: October 2008

For some years now, inside observers have felt that literary studies has arrived at a moment of stagnation. Not only has a fifty-year-long sequence of changing “paradigms” come to a standstill since the final years of the twentieth century; not only are we longing for new “master thinkers” who do not appear; but, epistemologically, we seem to be stuck in the extreme (and unfruitful) tension between seeing literary texts as “allegories” of the impossibility of language to refer to any outside referent (following the dogma of “deconstruction” and the linguistic turn) and a somehow naïve optimism regarding the capacity of literary texts to refer to an outside world as it is implicitly carried and sometimes professed by “cultural studies.” In this situation, the concept of Stimmung (most frequently illustrated by metaphors of being wrapped into, say, weather, or the sound of music) offers an alternative view of the ontology of literature, without falling back into the long-frustrated attempts to “define literature.” Many (if not all) of the texts that we call “literary” provide us with exactly this impression of “being wrapped” into the material world—a material world in which texts can evoke a material impression (the “lightest” possible material impression, however) through effects of prosody. “Reading for the `Stimmung'” can connect us with unusual immediacy to the Stimmung of a past historical period and a different cultural environment. “Reading for the `Stimmung'” may open new perspectives for the historical analysis and aesthetic appreciation of literary texts, and, at the same time, bring us back to a number of scholarly concerns that we have abandoned since the late 1970s.
Flexibility foils filter function: structural limitations on suspension feeding
Authors: Ferner Matthew C. , Gaylord Brian
Published: October 2008

Suspension feeders rely on filter structures of a variety of forms to capture food particles. Much effort has been devoted to examining the operation of such filters, but mechanistic evaluations have generally represented filter elements with artificially stiff cylinders. We extended this previous work to investigate how bending affects the function of flexible cylindrical filter elements. Scaled models of filters were constructed from materials with elastic moduli comparable to material stiffnesses of invertebrate appendages (1–177 GPa). These models were mounted on a sled to mimic the protrusion of filters away from an animal's body or from the substratum, and were towed through a vat of syrup to generate relative fluid motion at low Reynolds numbers (Re <10–3, based on cylinder diameter and tow speed). Flow between filter elements was quantified at multiple positions along their lengths, and a hydrodynamic index of filter performance (`leakiness') was calculated. Leakiness generally increased with cylinder Re and distance from the filter base. At higher flexibilities, however, streamwise bending and lateral narrowing of the filter reduced projected area and slowed flow between elements. This effect decreased leakiness and reversed the otherwise monotonic trend for increased leakiness at higher cylinder Re. Additional experiments showed that filters composed of stouter elements were less susceptible to bending but experienced lower leakiness because of their reduced ability to transcend boundary layers formed over surfaces to which they attached. These findings indicate that filter bending can strongly alter the performance of particle capture apparatus in suspension feeders.
FRAP analysis of molecular diffusion inside sea-urchin spermatozoa
Authors: Takao Daisuke , Kamimura Shinji
Published: October 2008

In sea-urchin spermatozoa, energy required for flagellar motility is provided by ATP diffusion from mitochondria located at the proximal ends of the flagella along with the creatine shuttle system. However, no direct analysis of the diffusion rates inside flagella has been carried out thus far. Using a FRAP (fluorescence recovery after photobleaching) technique, we determined the diffusion coefficients of fluorescein-derivatives (calcein,carboxyfluorescein and Oregon Green) to be 63–64 μm2s–1. Although these values are about one third of the estimates that were previously used for theoretical calculations, we concluded that the rate of ATP diffusion inside spermatozoa was high enough to support the continuous motility of sea-urchin sperm flagella if the creatine shuttle system is working. We also investigated the diffusion rate through the `neck'region between the head and tail. When the head region of a calcein-loaded spermatozoon was photobleached, slow recovery of head fluorescence along with the decrease of fluorescence signal in the tail region was observed. It suggests that small molecules such as calcein (Mr, 622.54)can move beyond the boundary between the head and the flagellum. We expect that these findings regarding the diffusion properties inside spermatozoa will provide us with more general insights into the energy equilibrium and material transportation by passive diffusion inside eukaryotic cilia and flagella.
Reflected polarization guides chironomid females to oviposition sites
Authors: Lerner Amit , Meltser Nikolay , Sapir Nir , Erlick Carynelisa , Shashar Nadav , Broza Meir
Published: October 2008

Chironomids (Diptera: Chironomidae; non-biting midges) are known to be carriers of the Vibrio cholerae bacterium, responsible for the fatal cholera disease in humans. It was recently discovered that chironomid females choose their oviposition site by a visual cue. In this study, we test the hypothesis that this visual cue is the linear polarization of light reflected from the water surface. We conducted two multiple choice field experiments using egg traps with different light intensities and polarizations. With controlled illumination, a higher number of eggs was found under both high intensity and high polarization. Under natural illumination, no eggs were found in the unpolarized traps, and the egg number increased with the percentage polarization regardless of the light intensity. Field measurements showed that at sunset, when chironomids are active, the intensity of light reflected from their natural ponds decreases by 96%, while the percentage polarization remains stable and high at 60%. Furthermore, the percentage polarization is positively correlated with the total organic carbon (TOC)concentration in the water. Orthogonal alignment of the microvilli found in ommatidia from the ventral part of the female eye may provide the anatomical basis for polarization sensitivity. We conclude that the percentage polarization of reflected light is the cue by which chironomid females choose their oviposition site. It is a stable cue and can provide information on the amount of food available to the larvae in the water. Based on our results, we suggest that manipulating the polarization of reflected light is a viable way to control chironomid populations and mitigate cholera dispersion.
Traditional allometric analysis fails to provide a valid predictive model for mammalian metabolic rates
Authors: Packard Gary C. , Birchard Geoffrey F.
Published: October 2008

The field of biological allometry was energized by the publication in 1997 of a theoretical model purporting to explain 3/4-power scaling of metabolic rate with body mass in mammals. This 3/4-power scaling exponent, which was first reported by Max Kleiber in 1932, has been derived repeatedly in empirical research by independent investigators and has come to be known as`Kleiber's Law'. The exponent was estimated in virtually every instance,however, by fitting a straight line to logarithmic transformations of data and by then re-expressing the resulting equation in the arithmetic scale. Because this traditional method may yield inaccurate and misleading estimates for parameters in the allometric equation, we re-examined the comprehensive data set that led Savage and colleagues to reaffirm the view that the metabolic rate of mammals scales to the 3/4-power of body mass. We found that a straight line fitted to logged data for the basal metabolic rate (BMR) of mammals ranging in size from a 2.4 g shrew to a 3672 kg elephant does not satisfy assumptions underlying the analysis and that the allometric equation obtained by back-transformation underestimates BMR for the largest species in the sample. Thus, the concept of 3/4-power scaling of metabolic rate to body mass is not well supported because the underlying statistical model does not apply to mammalian species spanning the full range in body size. Our findings have important implications with respect to methods and results of other studies that used the traditional approach to allometric analysis.
Comparative visual function in five sciaenid fishes inhabiting Chesapeake Bay
Authors: Horodysky Andrij Z. , Brill Richard W. , Warrant Eric J. , Musick John A. , Latour Robert J.
Published: October 2008

Maintaining optimal visual performance is a difficult task in the photodynamic coastal and estuarine waters in which western North Atlantic sciaenid fishes support substantial commercial and recreational fisheries. Unavoidable tradeoffs exist between visual sensitivity and resolution, yet sciaenid visual systems have not been characterized despite strong species-specific ecomorphological and microhabitat differentiation. We therefore used electroretinographic techniques to describe the light sensitivities, temporal properties, and spectral characteristics of the visual systems of five sciaenids common to Chesapeake Bay, USA: weakfish(Cynoscion regalis), spotted seatrout (Cynoscion nebulosus),red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus) and spot (Leiostomus xanthurus). Benthic sciaenids exhibited higher sensitivities and broader dynamic ranges in white light V/logI experiments than more pelagic forms. Sensitivities of the former were at the lower (more sensitive) end of an emerging continuum for coastal fishes. Flicker fusion frequency experiments revealed significant interspecific differences at maximum intensities that correlated with lifestyle and habitat, but no specific differences at dimmer intensities. Spectral responses of most sciaenids spanned 400—610 nm, with significant diel differences in weakfish and Atlantic croaker. Weakfish, a crepuscular predator, also responded to ultraviolet wavelengths; this characteristic may be more useful under less turbid conditions. Collectively,these results suggest that sciaenids are well adapted to the dynamic photoclimate of the coastal and estuarine waters they inhabit. However, the recent anthropogenic degradation of water quality in coastal environments, at a pace faster than the evolution of visual systems, has amplified the importance of characterizing visual function in managed aquatic fauna.
Gas dynamics analysis of an air pocket in the metal-stamping process
Authors: Hwang S-J , Park W-G , Kim C , Oh S-W
Published: October 2008

Metal stamping is widely used in the mass production process utilized in the automobile industry. During the stamping process, air may be trapped between the draw die and the panel and/or between the punch and the panel. The pressure of the trapped air pocket builds up as the punch moves downwards. The high pressure of the air pocket induces imperfections on the panel surface and creates a situation where an extremely high tonnage of punch is required to reach the home position. To prevent these problems, many air ventilation holes are drilled through the draw die and the punch. However, most die makers drill excessive air ventilation holes on a trial-and-error basis and waste labour time and cost. The present work has developed a mathematical formulation for computing the pressure of the air pocket at a given cross-sectional area of air ventilation holes, which is based on the ideal gas with an isentropic relation. The pressure of the air pocket was compared with the commercial computational fluid dynamics (CFD) code and experiments. It was found that the pressure agreed well with the results of the CFD code and experiments. The present work also used inverse design methodology to calculate the cross-sectional area of the air ventilation holes, which did not exceed the prescribed maximum pressure of the air pocket.
Energy recovery for battery electric vehicles
Authors: Ye M , Bai Z-F , Cao B-G
Published: October 2008

An efficient energy recovery system for battery electric vehicles (BEVs) is developed and tested. The principle and characteristics are analysed in detail. Then the mathematical model is derived step by step. Combining the merits and the defects of H2 optimal control and H∞ robust control, the robust hybrid controller is designed to guarantee both the system performance and the robust stability. The comparative simulated and experimental results showed that the dynamic performance and robust stability of the proposed scheme were superior to those of the proportional-integral method; the vehicle recycled more kinetic energy during braking and the driving range was increased.
Experimental investigations on combustion of jatropha methyl ester in a turbocharged direct-injection diesel engine
Authors: Anand K , Sharma R P , Mehta P S
Published: October 2008

Suitability of vegetable oil as an alternative to diesel fuel in compression ignition engines has become attractive, and research in this area has gained momentum because of concerns on energy security, high oil prices, and increased emphasis on clean environment. The experimental work reported here has been carried out on a turbocharged direct-injection multicylinder truck diesel engine using diesel fuel and jatropha methyl ester (JME)-diesel blends.

The results of the experimental investigation indicate that an increase in JME quantity in the blend slightly advances the dynamic fuel injection timing and lowers the ignition delay compared with the diesel fuel. A maximum rise in peak pressure limited to 6.5 per cent is observed for fuel blends up to 40 per cent JME for part-load (up to about 50 per cent load) operations. However, for a higher-JME blend, the peak pressures decrease at higher loads remained within 4.5 per cent. With increasing proportion of JME in the blend, the peak pressure occurrence slightly advances and the maximum rate of pressure rise, combustion duration, and exhaust gas temperature decrease by 9 per cent, 15 per cent and 17 per cent respectively. Although the changes in brake thermal efficiencies for 20 per cent and 40 per cent JME blends compared with diesel fuel remain insignificant, the 60 per cent JME blend showed about 2.7 per cent improvement in the brake thermal efficiency. In general, it is observed that the overall performance and combustion characteristics of the engine do not alter significantly for 20 per cent and 40 per cent JME blends but show an improvement over diesel performance when fuelled with 60 per cent JME blend.
An experimental study of the spray from an air-assisted direct fuel injector
Authors: Jin S H , Brear M , Watson H , Brewster S
Published: October 2008

The transient behaviour of the fuel spray from an air-assisted direct-injection spark ignition (DISI) fuel injector has been investigated experimentally in a constant-volume chamber. As the chamber and injection pressures were varied, ensemble-averaged planar images of the laser-induced fluorescence (LIF) and Mie scattering from the spray were obtained to measure the Sauter mean diameter (SMD) using the laser sheet drop-sizing (LSD) technique. The root mean square (r.m.s.) SMD was also calculated by combination of the r.m.s. LIF and r.m.s. Mie scattering signals. The effect of the injection and chamber pressures and the ambient air density on the SMD, spray tip penetration, and dispersion of the air-assisted fuel injector are determined. In keeping with recent numerical studies by the group, vortex structures appear to be shed from the injector tip in back-illuminated images, indicating that the air and liquid motion are strongly coupled. These results also show that the spray penetration and SMD vary significantly with injection and chamber density, and scalings of the spray's overall SMD and penetration are proposed that achieve reasonable clustering in the experimental results.
Simulation of cavitation in outward-opening piezo-type pintle injector nozzles
Authors: Giannadakis E , Papoulias D , Theodorakakos A , Gavaises M
Published: October 2008

The onset and development of cavitation in the annular needle seat passage of piezo-driven outward-opening pintle injector nozzles used with spray-guided direct-injection gasoline engines are studied using a Eulerian-Lagrangian computational fluid dynamics cavitation model. Cavitation is formed because of the fluid acceleration taking place at the needle sealing area and it has been found to be affected by its geometric details. Various submodels for nucleation and bubble formation, further bubble growth and collapse, as well as bubble break-up and transport are incorporated into the model. Qualitative model validation is performed against experimental data reported elsewhere in large-scale nozzle replicas, showing similar cavitation patterns to be formed. These consist of vapour pockets rather than a continuous vapour film and develop transiently in a rather chaotic manner around the circumferential needle sealing area, even under stationary geometry and fixed-flowrate conditions. Further transient effects associated with the fast opening and closing of the piezo-controlled needle valve are also presented.
Low-sooting combustion in a small-bore high-speed direct-injection diesel engine using narrow-angle injectors
Authors: Fang T-G , Coverdill R E , Lee C-F F , White R A
Published: October 2008

An optically accessible high-speed direct-injection diesel engine was used to study the effects of injection angles on low-sooting combustion. A digital high-speed camera was employed to capture the entire cycle combustion and spray evolution processes under seven operating conditions including post-top-dead centre (TDC) injection and pre-TDC injection strategies. The nitrogen oxide (NO x) emissions were also measured in the exhaust pipe. In-cylinder pressure data and heat release rate calculations were conducted. All the cases show premixed combustion features. For post-TDC injection cases, a large amount of fuel deposition is seen for a narrower-injection-angle tip, i.e. the 70° tip, and ignition is observed near the injector tip in the centre of the bowl, while for a wider-injection-angle tip, namely a 110° tip, ignition occurs near the spray tip in the vicinity of the bowl wall. The combustion flame is near the bowl wall and at the central region of the bowl for the 70° tip. However, the flame is more distributed and centralized for the 110° tip. Longer spray penetration is found for the pre-TDC injection timing cases. Liquid fuel impinges on the bowl wall or on the piston top and a fuel film is formed. Ignition for all the pre-TDC injection cases occur in a distributed way in the piston bowl. Two different combustion modes are observed for the pre-TDC injection cases including a homogeneous bulky combustion flame at earlier crank angles and a heterogeneous film combustion mode with luminous sooting flame at later crank angles. In terms of soot emissions, NO x emissions, and fuel efficiency, results show that the late post-TDC injection strategy gives the best performance.
Development of a new lumped-parameter model for vehicle side-impact safety simulation
Authors: Deb A , Srinivas K C
Published: October 2008

The current paper describes a simple and yet comprehensive lumped-parameter model (LPM) for simulating the National Highway Traffic Safety Administration (NHTSA) side-impact safety tests for passenger vehicles. The LPM includes new lumped masses, not previously reported in a single multibody model, for key vehicle side-structure systems identified with the help of an energy-based study conducted using explicit finite element analysis of two passenger vehicles. In addition to the vehicle side structure, lumped masses for the NHTSA side-impact barrier and ‘rest of vehicle’, the latter implying the mass of the vehicle minus the combined mass of the side-structure subsystems considered in the LPM, have been incorporated so that the total mass of the system corresponds to that of an actual vehicle—barrier system in a NHTSA side-impact test (Lateral Impact New Car Assessment Program (LINCAP) or FMVSS 214). The lumped masses are interconnected with elastic—plastic springs. A unique feature of the present model is the inclusion of two lumped side-impact dummies for obtaining predictions of the front and rear (thoracic trauma index (TTI)). The validity of the present LPM is established by performing LS-DYNA-based LINCAP simulations of two real-world vehicles, namely the Dodge Neon and Dodge Intrepid, and obtaining a reasonably good correlation of the computed structural and occupant responses as well as TTI (front and rear) with the corresponding test results reported by the NHTSA.
Genetic optimization of a fuzzy active suspension system based on human sensitivity to the transmitted vibrations
Authors: Montazeri-Gh M , Soleymani M
Published: October 2008

Optimization of a vehicle fuzzy active suspension (AS) controller was previously performed on the basis of the amplitude of transmitted vibrations to the body. However, ride comfort depends strongly on the human sensitivity, which is a function of not only the amplitude but also the frequency contents of the transmitted vibrations. In this paper, genetic optimization of a fuzzy AS system based on the human sensitivity to the transmitted vibrations is presented. For this purpose, a fuzzy logic controller (FLC) is initially proposed for the AS system control. The FLC parameters are then tuned using a genetic algorithm (GA). The tuning process is first formulated as a single-objective optimization problem based on the human sensitivity and conventional r.m.s. amplitude criteria separately. The simulation results reveal that the optimization of a fuzzy AS based on the common r.m.s. amplitude criterion not only does not result in the optimal ride index, but also causes a considerable increase in the energy consumption. Moreover, in order to accommodate the conflicting characteristics of the AS system, the FLC parameters are tuned on the basis of a multi-objective fitness function incorporating human sensitivity, suspension travel, and energy consumption. The simulation results prove the effectiveness of the optimized FLC in hitting the simultaneous targets of ride comfort improvement as well as suspension travel and energy consumption reduction.
A frequency response function-based updating technique for the finite element model of automotive structures
Authors: Lee D-C , Han C-S
Published: October 2008

Today's automotive industry uses finite element analysis (FEA) in a huge variety of applications in order to optimize structures and processes before hardware is produced. Efficiencies can be enhanced and margins are reduced because the external loads and structural properties are identified with higher confidence. The accuracy of FEA predictions has become increasingly important and directly influences the competitiveness of a product on the market. Because automotive structures are under dynamic environments, the correlation on the basis of static deformations independent of the mass and damping parameters do not provide a valuable reference from the view of the dynamic characteristics. In this paper, by systematically comparing the results from analytical and experimental analysis techniques, finite element (FE) models can be validated by the deterministic and robust design on the basis of each tolerance of design parameters, and improved so that they can be used with more confidence in further analysis. Making use of different types of test datum, a recommended procedure is to use a sequence of analysis in which mass, stiffness, damping, and external loading are validated and, if necessary, updated.
Achieving Environmental Goals in a Competitive Electricity Market?: Post-Colonial Hong Kong, Public Choice and the Role of Government
Authors: Lo Alex Y. H.
Published: October 2008

This paper critically assesses the discourse of electricity market liberalization in Hong Kong, China and makes policy recommendations from an environmental perspective. For both economic and environmental reasons, local advocates urge for an immediate opening of the electricity market currently monopolized by two private companies. Their neglect of the fact that a competitive green power market is a function of adequate public support in the form of market demand may place the environmental agenda at a disadvantage. Given that environmental issues are yet a dominant concern in this growth-oriented economy, a new facilitative role of the government is of particular importance to prevent the market from being dominated by short-term, rational economic behaviours. Mild changes with an emphasis of a transformation in the roles of different players, which the government is hesitant to initiate, are suggested.
Illuminating Household Energy Demand and the Policies for Its Reduction
Authors: Crosbie Tracey , Stokes Melody , Guy Simon
Published: October 2008

The amount of energy used to light homes in the UK continues to rise, despite the availability of compact fluorescent light (CFL) bulbs and significant policy efforts to reduce energy demand for domestic lighting. This paper examines household lighting demand, in the UK, from a socio-technical perspective, drawing on recent in-depth interview data. This research indicates that mood lighting is becoming increasingly significant, that a desire to have stylish interiors can override environmental principles, and that household lighting practices are heavily influenced by the media. The paper concludes that lighting policy must place greater emphasis on engaging with those involved in the design and promotion of household lighting, if we are to significantly reduce energy demand in this sector.
Experimental Investigation of the Entropy Noise Mechanism in Aero-Engines
Authors: Bake F. , Kings N. , Fischer A. , Röhle I.
Published: October 2008

It is assumed by theory, that entropy noise emitted by combustion systems increases rapidly with rising Mach number in the nozzle downstream of the combustion chamber. Model experiments have been carried out to verify the existence of this sound generating mechanism. A dedicated test facility was built, in which entropy waves are generated in a controlled way by unsteady electrical heating of fine platinum wires immersed in the flow. Further experiments have been carried out in a model combustor test rig where a broadband noise phenomenon, presumably related to indirect noise generation mechanisms, was found.
Thermo-Acoustic Stability of a Helicopter Gas Turbine Combustor Using Large Eddy Simulation
Authors: Boudier G. , Lamarque N. , Staffelbach G. , Gicquel L.Y.M. , Poinsot T.
Published: October 2008

Compressible Large Eddy Simulation (LES) of turbulent reacting flows potentially offers a realistic representation of the physical phenomena involved in thermoacoustic instabilities. Coupled with Helmholtz solvers, which provide a mean of identification of the acoustic eigenmodes in complex geometries, that advanced numerical tool may provide a very powerful environment to assess the stability of real engine combustion chambers. The common use of a fully unstructured LES solver and a Helmholtz eigenmode tool proves here to be very useful to diagnose two operating points of a real gas turbine chamber which are known to operate with self-sustained oscillations. If the geometrical complexity and proper computational domain are chosen, the two thermo-acoustic instabilities are very well reproduced. Predictibility of LES for such problems is thus demonstrated provided that issues pertaining to the inlet acoustic impedances can be properly answered.
Flame Dynamics and Combustion Noise: Progress and Challenges
Authors: Candel S. , Durox D. , Ducruix S. , Birbaud A.-L. , Noiray N. , Schuller T.
Published: October 2008

This article proposes a review of the state of knowledge in the field of combustion noise. The survey comprises an initial discussion of indirect and direct noise sources and their general characteristics, a summary of expressions devised to estimate combustion noise from turbulent flames, a discussion of the fundamental equations describing sound emission from a reactive region and an evaluation of scaling methods for combustion noise. An account is provided of a set of experiments on noise radiation from perturbed laminar flames. Sources of intense radiation of sound are identified and theoretical expressions of the pressure field are compared with detailed measurements from well controlled experiments. These experiments indicate that flame dynamics determine to a great extent the radiation of sound from flames. This is further demonstrated with experiments dealing with effects of confinement. Links between combustion noise and combustion instabilities are drawn on this basis. These two aspects are usually treated separately but they are manifestations of similar processes. Much of the current effort in the field of combustion noise focuses on numerical estimation techniques using modern computational tools. The state of the art is less advanced than in computational aeroacoustics (CAA) but it is possible to foresee that computational combustion acoustics (CCA) will progressively evolve into a well established scientific field.
The Effect of Training with Accentuated Eccentric Load Counter-Movement Jumps on Strength and Power Characteristics of High-Performance Volleyball Players
Authors: Sheppard Jeremy , Hobson Suki , Barker Michael , Taylor Kristie , Chapman Dale , McGuigan Mike , Newton Rob
Published: October 2008

The purpose of this study was to evaluate the training effects of using accentuated eccentric load counter-movement jumps on lower-body power characteristics in high-performance volleyball players. Sixteen volleyball players training full time with the state high-performance team participated in this 5 week training study. Prior to and at the completion of the study, jump squat testing with a lightweight (350 g) bar was conducted to determine kinetic and kinematic values for the lower body. Players were divided into either the accentuated eccentric load counter-movement jump group (AEJ) or normal (body-mass) counter-movement jump group (BMJ). The increases in displacement, velocity, and power values observed in the AEJ group were superior to those of the BMJ (p = 0.001–0.05, d = 1.06–1.97). The results of this study indicate that training with additional load during the eccentric phase of a counter-movement jump yields superior jump squat performance in comparison to typical counter-movement jump training in volleyball players who are already performing a high volume of jumping.
New Ideas for High Performance Coaches: A Case Study of Knowledge Transfer in Sport Science
Authors: Reade Ian , Rodgers Wendy , Spriggs Katie
Published: October 2008

Research related to how coaches learn concludes that coaches most often learn from other coaches. So far, there has been little evidence to suggest that coaches rely on sport scientists for their information, which would indicate minimal interaction between sport scientists and coaches. The purpose of this study was to determine the type and source of new ideas that high-performance coaches use to understand the extent to which sport science is the source of those ideas. This project utilized a single case study design involving a group of 20 high-performance coaches in 12 different sports in a university environment, which one would expect to be conducive to interaction between sport scientists and coaches. The method included the administration of a questionnaire, followed by a structured personal interview. Our findings suggest that these coaches do believe that sport science can contribute to coaching, are interested in having a sport scientist work with them, and are motivated to find and implement new ideas in their sport programs. Despite this, most of the respondents indicated they usually get those new ideas from other coaches, or from coaching clinics and seminars, and not from sport scientists or their written work. Reasons stated included a lack of time to look for new ideas and hence the use of expedient sources, and a lack of interest in academic publications.
SMG6 is the catalytic endonuclease that cleaves mRNAs containing nonsense codons in metazoan
Authors: Huntzinger Eric , Kashima Isao , Fauser Maria , Saulière Jérôme , Izaurralde Elisa
Published: October 2008

Messenger RNAs harboring nonsense codons (or premature translation termination codons [PTCs]) are degraded by a conserved quality-control mechanism known as nonsense-mediated mRNA decay (NMD), which prevents the accumulation of truncated and potentially harmful proteins. In Drosophila melanogaster, degradation of PTC-containing messages is initiated by endonucleolytic cleavage in the vicinity of the nonsense codon. The endonuclease responsible for this cleavage has not been identified. Here, we show that SMG6 is the long sought NMD endonuclease. First, cells expressing an SMG6 protein mutated at catalytic residues fail to degrade PTC-containing messages. Moreover, the SMG6-PIN domain can be replaced with the active PIN domain of an unrelated protein, indicating that its sole function is to provide endonuclease activity for NMD. Unexpectedly, we found that the catalytic activity of SMG6 contributes to the degradation of PTC-containing mRNAs in human cells. Thus, SMG6 is a conserved endonuclease that degrades mRNAs terminating translation prematurely in metazoa.
Dynamic Programming, Integral Polyhedra and Horn Clause Knowledge Base
Authors: Jeroslow Robert G. , Wang Jinchang
Published: October 2008

We show how the structure of proofs in a Horn clause knowledge base is completely described by certain of the extreme solutions to a suitable “dual” linear constraint set. The extreme points of this linear system are integer vectors, and give the count of the number of times that a given proposition is used in a proof of a “target” proposition. The “primal” to this dual provides the pointwise maximum vector which solves a set of dynamic programming recursions, and the latter recursions are derived from the Horn clause knowledge base. Variation in the facts or in the rules of the knowledge base corresponds to changes in only the criterion vector of the dual linear program. This linear programming approach to inference in expert systems also allows for the detection of “near proofs.” The latter are, by definition, proof structures which would become valid, if only exactly one more fact were known to be true. The first author, Robert G. Jeroslow, deceased August 31, 1988.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
A Formal Development of Event Graphs as an Aid to Structured and Efficient Simulation Programs
Authors: Som Tapas K. , Sargent Robert G.
Published: October 2008

Schruben introduced event graphs as a graphical technique for visualizing event-oriented system structures. In this paper, a formal framework for event-oriented simulation is introduced and event graphs are examined using this framework. Comprehensive rules are presented for identifying situations where event execution order priorities may be necessary. The concept of expanded event graphs and super events are introduced. A procedure for generating expanded event graphs which show hierarchy and possible grouping of events as one single unit without violating predefined execution order priorities is described. Expanded event graphs generated by this procedure can be used as bases for structured and efficient simulation programs.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
Analysis of Stiff Markov Chains
Authors: Reibman Andrew , Trivedi Kishor , Kumar Sanjaya , Ciardo Gianfranco
Published: October 2008

Continuous-time Markov chains (CTMC) are widely used mathematical models. Reliability models, queueing networks, and inventory models all require transient solutions of CTMC. The cost of CTMC transient solution increases with size, stiffness, and mission time. To eliminate stiffness and reduce the cost of solution, approximation techniques have been proposed. In this paper, we describe a software package for the specification and solution of stiff CTMC. As an interface, we use a language for the description of Markov chains. The language also provides facilities for controlling the solution procedure. Both exact and approximate solution techniques are provided. To conclude the paper, we use several examples to show the use of our specification language and the utility of our approximation technique.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
An Implementation of a Primal-Dual Interior Point Method for Linear Programming
Authors: McShane Kevin A. , Monma Clyde L. , Shanno David
Published: October 2008

The purpose of this paper is to describe in detail an implementation of a primal-dual interior point method for solving linear programming problems. Preliminary computational results indicate that this implementation compares favorably with a comparable implementation of a dual affine interior point method, and with MINOS 5.0, a state-of-the-art implementation of the simplex method.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
Editor's Introduction
Authors: Greenberg Harvey J.
Published: October 2008

The six papers in this issue deal with computational logic, fuzzy optimization, algorithm analysis, simulation, and heuristic search.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
Algorithmic Enhancements to the Method of Centers for Linear Programming Problems
Authors: Boggs Paul T. , Domich Paul D. , Donaldson Janet R. , Witzgall Christoph
Published: October 2008

Interior point algorithms for solving linear programming problems are considered. The techniques are derived from a continuous version of Huard's method of centers that yields a family of trajectories in the feasible region that all converge to an optimal solution. The tangential direction of these trajectories is the dual affine direction. Deficiencies in some of these trajectories are discussed, and the need to recenter is argued. Several new algorithms that use the dual affine direction and a recentering direction in a multidirection approach are then derived. The most promising of these algorithms is based on minimizing the cost function on a sequence of two-dimensional cross sections of the feasible region. Numerical results are presented.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
Modeling Networks with Dynamic Topologies
Authors: Moose Robert L.
Published: October 2008

Dynamic hierarchical networks represent an architectural strategy for employing adaptive behavior in applications sensitive to highly variable external demands or uncertain internal conditions. The characteristics of such architectures are described, and the significance of adaptive capability is discussed. The necessity for assessing cost/benefit tradeoffs leads to the use of queueing network models. The general model, a network of M/M/1 queues in a random environment, is introduced and then is simplified so that the links may be treated as isolated M/M/1 queues in a random environment. This treatment yields a formula for approximate mean network delay by combining matrix-geometric results (mean queue length and mean delay) for the individual links. A discrete event simulation model is defined as a basis for cross-validation of the analytic model. Conditions under which the analytic model is considered valid are identified through comparison of the two models.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
Continuous Models for Capacity Design of Large Packet-Switched Telecommunication Networks
Authors: LeBlanc Larry J. , Simmons Ronald V.
Published: October 2008

We formulate nonlinear programming models for design of large-scale packet-switched telecommunication networks. In these models, the network’s link capacities and source-destination message routes are chosen simultaneously. Although leased communication lines are available only in discrete units of capacity, public telephone lines with high-speed modems can be used to augment them, thus effectively obtaining fractional equivalents of leased-line capacity. Therefore, our network-design models contain continuous link-capacity variables. These continuous models can be solved for ϵ-optimal solutions, even for networks with hundreds or thousands of nodes. We examine conventional link delay functions used by previous researchers and suggest an alternative class of convex delay functions. Using computer simulation to analyze link delays, we compare the convex delay function to the conventional one. We conclude, for our assumed message-length distribution, that the convex delay function predicts the simulated delays more accurately than the conventional one when flow-capacity ratios larger than or equal to 0.80 are ignored. However, the conventional delay function fits the simulated delays more accurately than the convex one when these high-congestion ratios are considered. Thus, in network-design models in which flow-capacity ratios must be less than 80%, our convex model can be more accurate than the nonconvex conventional one. Computational results show that our models give very good solutions for different size networks with up to 100 nodes.

INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.
An Efficient Algorithm for a Class of Two-Resource Allocation Problems
Authors: Armstrong R. , Gu S. , Lei L.
Published: October 2008

We propose an efficient algorithm for the two resource allocation problem defined on a series-parallel graph, where nodes represent tasks, and arcs represent precedence relationships. The completion time of each task is inversely proportional to the amount of resource allocated, and the objective is to minimize the length of the longest path on the graph. Our algorithm is derived based on a formal analysis of the primal and Lagrangian dual optimal solutions. The resulting search process always ends up with one of three exclusive cases. For the first two cases, a closed form solution exists. For the third case, a bisectional search is used. The computational complexity of the algorithm is thus bounded fromabove by O(Nlog(1/ɛ)), where N is the total number of tasks, and ∈ is any given accuracy.
Interconnecting LANs and a FDDI Backbone Using Transparent Bridges: A Model and Solution Algorithms
Authors: Kaefer Frederick , Park June S.
Published: October 2008

In this article, we construct a mathematical model to design the topology of a network interconnecting a number of local area networks (LANs) and a fiber-distributed data interface (FDDI) backbone using IEEE 802.1 transparent bridges. The model allows parallel bridge links between subnets and yields a two-node-connected topology for survivability. The model determines the routing tree on a given topology according to the IEEE Standard protocol, which uses as input only user-supplied parameters such as bridge IDs, port IDs, and path costs. The model ensures that none of the network components (LANs, FDDI, and bridge links) are congested even in the failure of a LAN or a bridge link. We develop a path cost adjustment algorithm and a tabu search algorithm to find a low-cost feasible topology. Through computational experiments, we identify the characteristics of feasible topologies found under varying traffic conditions. Under light traffic conditions (i.e., when LANs' total slack capacity is large relative to the total intersubnet traffic demand), the topology is close to a ring which costs much less than the conventional star topology. Under heavy traffic, the topology tends to be a ring augmented by parallel bridge links between LANs and the FDDI. Finally, we discuss how effective various heuristic ideas—such as uncapacitated, two-connected topology design heuristics, the short-term tabu list and the long-term tabu list—are with respect to improving the solution quality. We also present a Lagrangian relaxation-based lower bounding procedure and report the gap between the best feasible value and the lower bound. The parsimonious property of uncapacitated, two-connected topology design problems is employed in this dual partitioning procedure.
Numerical Methods for Fitting and Simulating Autoregressive-to-Anything Processes
Authors: Cario Marne C. , Nelson Barry L.
Published: October 2008

An ARTA (AutoRegressive-to-Anything) Process is a time series with arbitrary marginal distribution and autocorrelation structure specified through finite lag p. We develop an efficient numerical method for fitting ARTA processes and discuss its implementation in the software ARTAFACTS. We also present the software ARTAGEN that generates observations from ARTA processes for use as inputs to a computer simulation. We illustrate the use of the software with a real-world example.
An Exact Solution Approach Based on Shortest-Paths for p-Hub Median Problems
Authors: Ernst A. T. , Krishnamoorthy M.
Published: October 2008

The problem of locating hub facilities arises in the design of transportation and telecommunications networks. The p-hub median problem belongs to a class of discrete location-allocation problems in which all the hubs are fully interconnected. Nonhub nodes may be either uniquely or multiply allocated to hubs. The hubs are uncapacitated and the total number of hubs, p is specified a priori. We describe a novel exact-solution approach for solving the multiple-allocation case of the p-hub median problem and show how a similar method can be adapted for solving the more difficult single-allocation case. The methods for both of these solve shortest-path problems to obtain lower bounds, which are used in a branch-and-bound scheme to obtain the exact solution. Numerical results show the superiority of this new approach over traditional LP-based methods.
On Formal Semantics and Analysis of Typed Modeling Languages: An Analysis of Ascend
Authors: Bhargava Hemant K. , Krishnan Ramayya , Piela Peter
Published: October 2008

The use of strong typing, exemplified in the Ascend modeling language, is a recent phenomenon in executable modeling languages for mathematical modeling. It is also one that has significant potential for improving the functionality of computer-based modeling environments. Besides being a strongly typed language, Ascend is unique in providing operators that allow dynamic type inference, a feature that has been shown to be useful in assisting model evolution and reuse. We develop formal semantics for the type system in Ascend—focusing on these operators—and analyze its mathematical and computational properties. We show that despite the strong interactions between various statements involving the operators, the language does possess certain desirable mathematical and computational properties. Further, our analysis identifies general issues in the design and implementation of type systems in mathematical modeling languages. The methods used in the article are applicable beyond Ascend to a class of typed modeling languages that may be developed in the future.