Andreas Klinkert

Surgical case scheduling as a generalized job shop scheduling problem

Surgical case scheduling allocates hospital resources to individual surgical cases and decides on the time to perform the surgeries. This task plays a decisive role in utilizing hospital resources efficiently while ensuring quality of care for patients. This paper proposes a new surgical case scheduling approach which uses a novel extension of the Job Shop scheduling problem called multi-mode blocking job shop (MMBJS). It formulates the MMBJS as a mixed integer linear programming (MILP) problem and discusses the use of the MMBJS model for scheduling elective and add-on cases. The model is illustrated by a detailed example, and preliminary computational experiments with the CPLEX solver on practical-sized instances are reported.

A new neighborhood and tabu search for the Blocking Job Shop

The Blocking Job Shop is a version of the job shop scheduling problem with no intermediate buffers, where a job has to wait on a machine until being processed on the next machine. We study a generalization of this problem which takes into account transfer operations between machines and sequence-dependent setup times. After formulating the problem in a generalized disjunctive graph, we develop a neighborhood for local search. In contrast to the classical job shop, there is no easy mechanism for generating feasible neighbor solutions. We establish two structural properties of the underlying disjunctive graph, the concept of closures and a key result on short cycles, which enable us to construct feasible neighbors by exchanging critical arcs together with some other arcs. Based on this neighborhood, we devise a tabu search algorithm and report on extensive computational experience, showing that our solutions improve most of the benchmark results found in the literature.

Feasible insertions in job shop scheduling, short cycles and stable sets

Insertion problems arise in scheduling when additional activities have to be inserted into a given schedule. This paper investigates insertion problems in a general disjunctive scheduling framework capturing a variety of job shop scheduling problems and insertion types. First, a class of scheduling problems is introduced, characterized by disjunctive graphs with the so-called short cycle property, and it is shown that in such problems, the feasible selections correspond to the stable sets of maximum cardinality in an associated conflict graph. Two types of insertion problems are then identified where the underlying disjunctive graph is through- or bi-connected. For these cases, it is shown that the short cycle property holds and the conflict graph is bipartite, allowing to derive a polyhedral characterization of all feasible insertions. An efficient method for deciding whether there exists a feasible insertion, and a lower and upper bound procedure for the minimum makespan insertion problem are developed. For bi-connected graphs, this procedure solves the insertion problem to optimality. The obtained results are applied to three extensions of the classical Job Shop, the Multi-Processor Task, Blocking and No-Wait Job Shop, and two types of insertions, job and block insertion.

Fourier spectra and formant patterns of German vowels produced at F0 of 70–850 Hz

Previous studies of vowel synthesis and of natural vowels have indicated: (1) a correlation between the lower formants and F0 for F0>175 Hz; (2) intelligibility and spectral differences of vowels with high F0>500 Hz; (3) severe methodological problems of formant frequency estimation for F0>300 Hz; (4) formant number alterations (appearance of different numbers of relevant formants for one vowel); (5) formant pattern ambiguity (appearance of the same formant pattern for different vowels). The purpose of this study was to replicate these findings. A large sample of the German vowels /i,y,e,o/,e,■,o,u/ produced in isolation as well as in CVC context was investigated. There were 18 674 recordings made of 35 men, 44 women, and 20 children. Isolated vowels were produced at different levels of F0, and with different intensities. A listening test was performed. Fourier spectra, LPC spectra and spectral constancy were analyzed. The results strongly support the five indications mentioned. In particular, for isolate...

The spectral difference of different vowels: Toward a new acoustical concept

When isolated vowels were produced beyond F0 of speech (F0>150 Hz for men, F0>300 Hz for women and children), the related formant patterns were found to deviate substantially from the values of formant statistics, and the formant frequency variations proved to be nonsystematic (for details, see poster Klinkert and Maurer). Moreover, formant frequency estimation for vocalizations with F0>400 Hz is highly problematical, although many vocalizations remain unambiguous in the vowel identity up to F0=700 Hz and even above. The nonsystematic formant variations and the methodological problem of formant frequency estimation hardly allow for a normalization of formant patterns. Dynamic spectral properties do often not appear in isolated vowels. Thus, for the acoustic theory of vowel sounds, the question arises as to whether there is a concept to determine the physical correlates of the sounds apart from formants. A first approach toward such a concept is described for voiced vowels: A hypothesis is presented which ...