169,796 research outputs found
Spontaneous otoacoustic emissions and relaxation dynamics of long decay time OAEs in audiometrically normal and impaired subjects
No full textThe relationship between hearing loss, detected by measuring the audiometric threshold shift, and the presence of long-lasting otoacoustic emissions, has been studied in a population of 66 adult males, by analyzing the cochlear response in the 80 ms following the subministration of a click stimulus. Most long-lasting OAEs are also recognizable as Synchronized Spontaneous OAEs (SSOAEs). The OAE characteristic decay times were evaluated according to the model by Sisto and Moleti [J. Acoust. Sec. Am. 106, 1893 (1999)]. The starting hypothesis, confirmed by the results, is that long decay time and large equilibrium amplitude are both manifestations of the effectiveness of the active feedback mechanism. The prevalence and frequency distribution of long-lasting OAEs, and of their SSOAE subset, have been separately analyzed for normal and impaired ears. No long-lasting OAE was found within the hearing loss frequency range, but several were found in impaired ears outside the hearing loss range, both at lower and higher frequencies. This result suggests that the correlation between the presence of long-lasting OAEs and good cochlear functionality be local in the frequency domain. The monitor of the OAE decay time is proposed as a new possible method for early detecting hearing loss in populations exposed to noise. (C) 2001 Acoustical Society of America
Modeling an assembly line for configuration and flow management
No full textIn its basic form the management control of a flexible production system requires to assign a set of operations to a set of machines, and to connect machines by a transportation network, such that a number of constraints is satisfied and some efficiency index is optimized. The aim of the work is to give a general framework to formulate and model, in a formal way, different subproblems arising from embedding an assembly process on different configurations of a flexible production system. Because of the complexity of the overall problem, it is useful to have simple and well structured layouts and procedures that help the design and operation of flexible systems. These layouts and procedures induce additional constraints, due to the products' and the process' features. The paper also investigates the complexity of various subcases of the problem. (C) 1998 Elsevier Science Ltd, All rights reserve
Part routing in Flexible Assembly Systems
No full textThis paper deals with the problem of part routing and scheduling in flexible manufacturing systems with the goal of increasing the throughput. The flexible system we consider is strongly characterized by the inclusion of assembly among the manufacturing operations to be performed on a mix of part batches. In particular, we point out hte logic structure of some basic decision problem through a set of combinatorial models. We analyze two basic assembly problems characterized by batches of large and small size, respectively
Applicazione di un software per l’elaborazione della pianificazione assistenziale all’interno di un setting cardiologico
No full textTask Assignment and Sub-assembly Scheduling in Pipeline Assembly Systems
No full textThis paper deals with models for flow management problems in flexible assembly systems (FAS's). The system consists of a set of machines that must perform the assembly of a number of parts, possibly of different types. Each part type requires a set of operations; the precedence relations among the operations are specified by an assembly tree. Machines are provided with limited-capacity tool magazines and a finite buffer for holding parts. Each machine can be tooled to perform only a particular subset of the operations required by the whole process. One problem is that of finding a feasible assignment of operations to machines and a feasible schedule of the subassemblies in order to minimize the completion time of all of the parts. In this paper, the problem is analysed as a case of pipelined assembly, i.e., when the FAS is characterized by a serial transportation system (flow line) and there exists a dominating path in the assembly tree. Typically, this happens when there is a main pallet and all of the other components are assembled directly on it in a given sequence. We present polynomial-time dynamic programming algorithms for solving the problem for both single-type and multitype production. The approach is more general than typical ALB algorithms. © 1995 IEE
On the detection of early cochlear damage by otoacoustic emission analysis
No full textTheoretical considerations and experimental evidence suggest that otoacoustic emission parameters may be used to reveal early cochlear damage, even before it can be diagnosed by standard audiometric techniques. In this work, the statistical distributions of a set of otoacoustic emission parameters chosen as candidates for the early detection of cochlear damage (global and band reproducibility, response level, signal-to-noise ratio, spectral latency, and long-lasting otoacoustic emission presence) were analyzed in a population of 138 ears. These cars have been divided, according to a standard audiometric test, in three classes: (1) ears of nonexposed bilaterally normal subjects, (2) normal cars of subjects with unilateral noise-induced high-frequency hearing loss, and (3) their hearing impaired ears. For all analyzed parameters, a statistically significant difference was found between classes 1 and 2. This difference largely exceeds the difference observed between classes 2 and 3. This fact suggests that the noise exposure, which was responsible for the unilateral hearing loss. also caused subclinical damage in the contralateral, audiometrically normal, car. This is a clear indication that otoacoustic emission techniques may be able to early detect subclinical damages. (C) 2002 Acoustical Society of America
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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