abstract: Modern manufacturing systems are part of a complex supply chain where customer preferences are constantly evolving. The rapidly evolving market demands manufacturing organizations to be increasingly agile and flexible. Medium term capacity planning for manufacturing systems employ queueing network models based on stationary demand assumptions. However, these stationary demand assumptions are not very practical for rapidly evolving supply chains. Nonstationary demand processes provide a reasonable framework to capture the time-varying nature of modern markets. The analysis of queues and queueing networks with time-varying parameters is mathematically intractable. In this dissertation, heuristics which draw upon existing steady state queueing results are proposed to provide computationally efficient approximations for dynamic multi-product manufacturing systems modeled as time-varying queueing networks with multiple customer classes (product types). This dissertation addresses the problem of performance evaluation of such manufacturing systems. This dissertation considers the two key aspects of dynamic multi-product manufacturing systems - namely, performance evaluation and optimal server resource allocation. First, the performance evaluation of systems with infinite queueing room and a first-come first-serve service paradigm is considered. Second, systems with finite queueing room and priorities between product types are considered. Finally, the optimal server allocation problem is addressed in the context of dynamic multi-product manufacturing systems. The performance estimates developed in the earlier part of the dissertation are leveraged in a simulated annealing algorithm framework to obtain server resource allocations. / Dissertation/Thesis / Doctoral Dissertation Industrial Engineering 2020

This talk discusses optimized collective algorithms and the benefits of leveraging independent hardware entities in a pipelined manner. The resulting approach uses overlap of computation and communication to reach this task. Different examples are given.

The large-scale, mid-latitude circulation in the upper troposphere is dominated by Rossby waves. The jet stream flows along the wave structure and surface cyclones can be found ahead of the troughs of the waves, propagating eastward. This propagation is here estimated as the zonal phase speed which is quantified using spectral analysis, producing a unique, global daily value for each day of the winter season (DJF) between 1979 and 2019. From this data set phase speed events are defined as periods of more than four consecutive days of the top or bottom 5\% phase speed values, resulting in 15 low phase speed events and 22 high phase speed events. During events of low phase speed the 2m temperature is higher than the climatology at high latitudes and lower over Europe and Siberia. Zonal wind speed at 10m and 250hPa is also found to be lower than the climatology over both the Pacific and Atlantic storm track. Furthermore, low phase speed events are found to be occurring when blocking is present on either one or both storm tracks. During high phase speed events there is an overall increase in zonal wind speed both at 10m and 250hPa over both storm tracks as well as total magnitude of wind over western Europe. These findings suggest a link of high phase speed events to windstorms over Europe. A subjective classification indicates that at the onset of high phase speed events blocking is found mainly in two regions, one at high latitudes outside the Siberian coast and one at low latitudes outside the coast of Japan, suggesting enhanced temperature gradients at the entrance of the Pacific could cause these events. / Den storskaliga cirkulationen över mellanbredderna i den övre troposfären domineras av Rossbyvågor. Dessa är en vågstruktur som formas från Jordens rotation och vorticitet och associeras med det starka flödet från jetströmmen som återfinns längs vågstrukturen. På grund av vorticiteten uppstår cykloner framför vågornas tråg och hela systemet propagerar österut. Propageringen uppskattas här som fashastighet och kvantifieras med spektralanalys, en metod där interpolering från ett spektrum används snarare än teoretiska beräkningar. Detta producerar ett unikt och globalt dygnsmedel under vintersäsongen (December, Januari, Februari) mellan 1979 och 2019, där vintern väljs på grund av den stora variabiliteten i fashastighet som observeras då. Från denna data definieras fashastighetsevent som fyra eller fler dagar i sträck med de högsta eller lägsta 5 \%-värdena, vilket resulterar i 15 event med låg fasthastighet och 22 event med hög fashastighet. Under eventen med låg fashastighet är temperaturen vid 2m högre än klimatologin vid höga breddgrader och lägre över Europa och Sibirien. Den zonala vinden vid 10m och 250hPa är också lägre än klimatologin över både lågtrycksbanan över Stilla havet och Atlanten. Vidare så fann vi att låg fashastighet uppstår i samband med atmosfärisk blockering över en eller båda lågtrycksbanor. Under event med hög fashastighet observeras en ökning i zonal vindstyrka både vid 10m och 250hPa över båda lågtrycksbanorna samt en ökad styrka i den totala magnituden av vinden över västra Europa. Dessa fynd tyder på en länk mellan hög fashastighet och vindstormar i Europa. Vid starten av event med hög fashastighet återfinns atmosfärisk blockering främst i två regioner, en vid höga breddgrader utanför den Sibiriska kusten och en vid låga breddgrader utanför Japans kust, vilket tyder på att ökade temperaturgradienter vid början av lågtrycksbanan över Stilla havet kan orsaka dessa event.

In this work, we investigate job-shop problems where limited capacity buffers to store jobs in non-processing periods are present. In such a problem setting, after finishing processing on a machine, a job either directly has to be processed on the following machine or it has to be stored in a prespecified buffer. If the buffer is completely occupied the job may wait on its current machine but blocks this machine for other jobs. Besides a general buffer model,also specific configurations are considered.The key issue to develop fast heuristics for the job-shop problem with buffers is to find a compact representation of solutions. In contrast to the classical job-shop problem,where a solution may be given by the sequences of the jobs on the machines, now also the buffers have to be incorporated in the solution representation. In this work, we propose two solution representations for the job-shop problem with buffers. Furthermore, we investigate whether the given solution representations can be simplified for specific buffer configurations. For the general buffer configuration it is shown that an incorporation of the buffers in the solution representation is necessary, whereas for specific buffer configurations possible simplifications are presented. Based on the given solution representations we develop local search heuristics in the second part of this work. Therefore, the well-known block approach for the classical job-shop problem is generalized to the job-shop problem with specific buffer configurations.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Bibliography: leaves 159-163. / by Brian Bennett Reinhold. / Ph.D.

No description available.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 218-225. / by Randall M. Dole. / Ph.D.

It is necessary to have certain flight information available to control the airplane. This information is usually displayed on flight instruments, which are located on the dashboard of the aircraft. In case of loss of indication or misleading indication of certain devices, control of the aircraft can be very complicated or even impossible. The dissertation deals with the issue of loss of information indication from aerometric instruments (especially from the airspeed indicator). The work contains research on the course of degradation of total pressure measurements using a Pitot tube. Based on this research, it is possible to design a new system for detecting blockage of the Pitot tube, which will increase aviation safety. The phenomenon described was investigated in a wind tunnel and in real conditions. Furthermore, the work defines instructions for the compilation of an emergency procedure, which the pilot could use in the event of a fault condition with aerometric instruments. The real possibilities of use were demonstrated on a Cessna 172SP aircraft during the validation experiment. The validation experiment proved the possibilities of the safe usage of the emergency procedure during flight. The final part of the work is focused on the evaluation of possible changes in the creation of reliability and safety analyzes with regard to the application of new knowledge based on this work.

No description available.

Modelling is an important technique in the comprehension and management of complex systems. Queueing network models capture most relevant information from computer system and network behaviour. The construction and resolution of these models is constrained by many factors. Approximations contain detail lost for exact solution and/or provide results at lower cost than simulation. Information at the resource and interactive command level is gathered with monitors under ULTRIX'. Validation studies indicate central processor service times are highly variable on the system. More pessimistic predictions assuming this variability are in part verified by observation. The utility of the Generalised Exponential (GE) as a distribution parameterised by mean and variance is explored. Small networks of GE service centres can be solved exactly using methods proposed for Generalised Stochastic Petri Nets. For two centre. systems of GE type a new technique simplifying the balance equations is developed. A very efficient "building bglloocbka"l. is presented for exactly solving two centre systems with service or transfer blocking, Bernoulli feedback and load dependent rate, multiple GE servers. In the tandem finite buffer algorithm the building block illustrates problems encountered modelling high variability in blocking networks. ': . _. A parametric validation study is made of approximations for single class closed networks of First-Come-First-Served (FCFS) centres with general service times. The multiserver extension using the building block is validated. Finally the Maximum Entropy approximation is extended to FCFS centres with multiple chains and implemented with computationally efficient convolution.