Investigating the consistency of woodwind instrument manufacturing by comparing five nominally identical oboes

For large-scale woodwind instrument makers, producing instruments with exactly the same playing characteristics is a constant aim. This paper explores manufacturing consistency by comparing five Howarth S10 student model oboes. Psychophysical testing involving nine musicians is carried out to investigate perceived differences in the playing properties of the two Howarth oboes believed to be most dissimilar. Further testing, involving one musician and combinations of the five oboes, provides information regarding the relative playabilities of the instruments at specific pitches. Meanwhile, input impedance measurements are made on the five oboes for fingerings throughout the playing range and their bore profiles are measured. The main findings are (1) the two instruments used in the preliminary psychophysical testing are perceived as identical by most of the musicians, although differences are identified by two players when playing the note F6 and by one player when playing in the lowest register, (2) a variation in the playability of F6 across the five oboes is due to differences in the elevation of the C key, and (3) variations in the playing properties in the lowest register are related to input impedance differences,which, in turn, appear to be at least partly due to bore profile differences.     

Regimes of frictional sliding of a spring-block system

In the context of rate-and-state friction, we revisit the crossover between the creep and inertial regimes in the dynamics of a spring-block system as observed and described in the dry friction experiment of Heslot et al. (1994) and Baumberger et al. (1994). We show that the transition between the quasi-static motion of a spring-block and its dynamic motion occurs at a lower sliding velocity than that which minimises the steady-state friction coefficient. We perform a weakly nonlinear stability analysis combined with numerical studies with the continuation package Auto. In particular, attention is focused on the change of nature the Hopf bifurcation from supercritical to subcritical, as observed by Heslot et al. Comparing the results obtained for different friction laws, we conclude that the weakly nonlinear analysis provides a possible criterion for distinguishing which friction laws may be physically relevant.     

A coupled column generation,mixed integer approach to optimal planning of intensity modulated radiation therapy for cancer

Approximately 40% of all U.S. cancer cases are treated with radiation therapy. In Intensity-Modulated Radiation Therapy (IMRT) the treatment planning problem is to choose external beam angles and their corresponding intensity maps (showing how the intensity varies across a given beam) to maximize tumor dose subject to the tolerances of surrounding healthy tissues. Dose, like temperature, is a quantity defined at each point in the body, and the distribution of dose is determined by the choice of treatment parameters available to the planner. In addition to absolute dose limits in healthy tissues, some tissues have at least one dose-volume restriction that requires a fraction of its volume to not exceed a specified tighter threshold level for damage. There may also be a homogeneity limit for the tumor that restricts the allowed spread of dose across its volume. We formulate this planning problem as a mixed integer program over a coupled pair of column generation processes -- one designed to produce intensity maps, and a second specifying protected area choices for tissues under dose-volume restrictions. The combined procedure is shown to strike a balance between computing an approximately optimal solution and bounding its maximum possible suboptimality that we believe holds promise for implementations able to offer the power and flexibility of mixed-integer linear programming models on instances of practical scale.A portion of the work of Dr. Langer, Mr. Thai and Dr. Preciado-Walters was supported by National Science Foundation grant ECS-0120145 and National Cancer Institute 1R41CA91688-01. Dr. Rardin is participated while on rotation as Program Director for Operations Research and Service Enterprise Engineering at the National Science Foundation.     

Conic Linear Programming Duals for Classes of Quadratic Semi-Infinite Programs with Applications

Journal of Optimization Theory and Applications - In this paper, we first present strong conic linear programming duals for convex quadratic semi-infinite problems with linear constraints and...     

Use of Vilsmeier reagent for the solid-phase synthesis of 1,5-disubstituted 4,5-dihydro-1H-imidazoles and disubstituted 4,5-dihydro-1H-imidazolylbenzimidazoles

The solid-phase synthesis of novel imidazolines and dihydroimidazolylbenzimidazoles is described. Resin-bound diamines, derived from resin-bound N-acylated amino acid amides, were cyclized using Vilsmeier reagent to yield imidazolines following cleavage. Similarly, cyclization of resin-bound tetraamines having two secondary amines and an o-dianiline yielded dihydroimidazolylbenzimidazoles following cleavage.