A point implicit unstructured grid solver for the euler and Navier–Stokes equations

An upwind finite element technique that uses cell-centred quantities and implicit and/or explicit time marching has been developed for computing hypersonic laminar viscous flows using adaptive triangular grids. The approach is an extension to unstructured grids of the LAURA algorithm due to Gnoffo. A structured grid of quadrilaterals is laid out near a solid surface. For inviscid flows the method is stable at Courant numbers of over 100000. A first-order basic scheme and a higher-order flux-corrected transport (FCT) scheme have been implemented. This technique has been applied to the problem of predicting type III and IV shock wave interactions on a cylinder, with a view to simulating the pressure and heating rate augmentation caused by an impinging shock on the leading edge of a cowl lip of an engine inlet. The predictions of wall pressure and heating rates compare very well with experimental data. The flow features are distinctly captured with a sequence of adaptively generated grids.     

Vocalization and breathing during the first year of life

Vocalization and breathing were studied in 40 healthy infants, including five boys and five girls each at ages 5 weeks, 2.5 months, 6.5 months, and 12 months. Breathing was monitored through the use of a variable inductance plethysmograph that enabled estimates of the volume changes of the rib cage, abdomen, and lung, as well as estimates of selected temporal features of the breathing cycle. Four vocalization types were studied intensively. These included cries, whimpers, grunts, and syllable utterances. Breathing behavior was highly variable across the four vocalization types, demonstrating the degrees of freedom of performance available to the infant to accomplish the aeromechanical drive required. Such behavior was influenced by body length, body position, and age, but not by vocalization type and sex. The protocol established is a useful tool for observing the natural course of the emergence of vocalization and breathing during the first year of life.     

Using profit maximizing scheduling models to structure operational trade-offs and manufacturing strategy issues

Manufacturing plays an increasingly important role in determining the competitiveness of the firm. However, corporate strategy is often formulated with little regard for how these decisions affect operations within the manufacturing system. Detailed models provide a necessary link between manufacturing performance and the functional policies followed by the firm, so that the strengths of the manufacturing system can be consistently reflected in strategic decisions.This paper presents a scheduling model that relates the strategic decisions that determine the type of work that must ultimately be processed by the manufacturing system with the detailed decisions that determine how this work should be scheduled. The model accounts for varying processing time, delay penalty, and revenue characteristics among the jobs available for processing by a single facility, with jobs partitioned in multiple classes such that a setup is incurred each time two jobs of different classes are processed in succession. Given limited processing capacity, the objective is to simultaneously determine the subset of jobs to accept for processing and the associated order in which accepted jobs should be sequenced to maximize the total profit realized by the facility. Problem formulations and dynamic programming algorithms are presented for both the special case in which all available work is from a single job class, and the more general case involving multiple job classes. The insight derived from these models concerning the operational implications of strategic decisions is illustrated through a series of example problems, first focusing on the coordination of marketing and manufacturing policy, and finally by considering important issues related to manufacturing focus.     

THE RELATIONSHIP BETWEEN CARCINOGENIC ACTIVITIES OF POLYCYCLIC AROMATIC HYDROCARBONS AND THEIR SINGLET, TRIPLET, AND SINGLET-TRIPLET SPLITTING ENERGIES AND PHOSPHORESCENCE LIFETIMES

Abstract— The energies of the lowest excited singlet, E_s, and triplet, E_t, states, and singlet-triplet splitting energies, ΔE_s,t, were determined on 18 carcinogenic and 31 noncarcinogenic polycyclic aromatics. A highly significant correlation was found between carcinogenic activity and the energy of the excited singlet state. Compounds with an E_s < 312 kJ/mol were 4.8 times more likely to be carcinogens than those compounds with E_s 312 kJ/mol (P= 0.015). Compounds whose singlet energies fell within the narrow range of 297 ≤E_s≤ 310 kJ/mol were 22.8 times more likely to be carcinogens than those compounds which fell outside this range (P= 0.00006). A significant correlation between carcinogenic activity and E_t energies was not found, while the correlation involving ΔE_s,t energies was intermediate between the E_s and E_t correlations. The phosphorescence lifetimes, τ_p, of the 18 carcinogenic aromatics and 27 of the noncarcinogenic aromatip were determined, and were shown not to be correlated with carcinogenic activity. When either the E_t or ΔE_s,t energies were plotted as a function of E_s it was found that the carcinogens tended to form in an elliptical cluster. Compounds whose E_s and E_t energies placed them within the ellipse were 9.7 times more likely to be carcinogens than those compounds which fell outside the ellipse (P= 0.002), while with the E_s, ΔE_s,t ellipse, compounds which fell inside were 20.6 times more likely to be carcinogens than those which fell outside (P= 0.0004). E_s, E_t, ΔE_s,t and τ_p values were also determined on 12 carcinogenic and 4 noncarcinogenic alkyl substituted benz[a]anthracenes. There was no significant difference between the carcinogens and noncarcinogens and the “elliptical” correlation predicted both the carcinogens and noncarcinogens to be carcinogenic. The results suggest that either some property(ies) of the lowest excited singlet state, but not its energy, or some molecular property(ies) which runs parallel to singlet state energies may be important in determining carcinogenic activity in polycyclic aromatics.     

The fluorescence excitation spectrum of s-tetrazine cooled in a supersonic free jet

The fluorescence excitation spectrum of the ${}^1\text{B}{}_{\mathrm{3u}}\text{(v′ = 0) ←}{}^1\text{A}{}_{\mathrm{g}}\text{(v″ = 0)}$ transition in s-tetrazine has been observed and measured. The sample was cooled to a rotational temperature of <1 K by expansion in a supersonic free jet. In this way the rotational structure arising from asymmetry split low J lines could be observed. The rotational A and B axes of the ²H₁¹²C₂¹⁴N₄ isotope were observed to interchange upon electronic excitation and a theory describing the effect of this interchange upon the optical selection rules has been developed. Analysis of the resolved rotational structure suggests that the geometry change upon electronic excitation is smaller than that deduced from previous analysis of the room temperature optical spectrum.     

The role of frequency selectivity in measures of auditory and vibrotactile temporal resolution.

The purpose of this study was to compare the role of frequency selectivity in measures of auditory and vibrotactile temporal resolution. In the first experiment, temporal modulation transfer functions for a sinusoidally amplitude modulated (SAM) 250-Hz carrier revealed auditory modulation thresholds significantly lower than corresponding vibrotactile modulation thresholds at SAM frequencies greater than or equal to 100 Hz. In the second experiment, auditory and vibrotactile gap detection thresholds were measured by presenting silent gaps bounded by markers of the same or different frequency. The marker frequency F1 = 250 Hz preceded the silent gap and marker frequencies after the silent gap included F2 = 250, 255, 263, 310, and 325 Hz. Auditory gap detection thresholds were lower than corresponding vibrotactile thresholds for F2 markers less than or equal to 263 Hz, but were greater than the corresponding vibrotactile gap detection thresholds for F2 markers greater than or equal to 310 Hz. When the auditory gap detection thresholds were transformed into filter attenuation values, the results were modeled well by a constant-percentage (10%) bandwidth filter centered on F1. The vibrotactile gap detection thresholds, however, were independent of marker frequency separation. In a third experiment, auditory and vibrotactile rate difference limens (RDLs) were measured for a 250-Hz carrier at SAM rates less than or equal to 100 Hz. Auditory RDLs were lower than corresponding vibrotactile RDLs for standard rates greater than 10 Hz. Combination tones may have confounded auditory performance for standard rates of 80 and 100 Hz. The results from these experiments revealed that frequency selectivity influences auditory measures of temporal resolution, but there was no evidence of frequency selectivity affecting vibrotactile temporal resolution.