2,024 research outputs found
Multiple Input-Multiple Output Cycle-to-Cycle Control of Manufacturing Processes
Cycle-to-cycle control is a method for using feedback to improve product quality for processes that are inaccessible within a single processing cycle. This limitation stems from the impossibility or the prohibitively high cost of placing sensors and actuators that could facilitate control during, or within, the process cycle. Our previous work introduced cycle to cycle control for single input-single output systems, and here it is extended to multiple input-multiple output systems. Gain selection, stability, and process noise amplification results are developed and compared with those obtained by previous researchers, showing good agreement. The limitation of imperfect knowledge of the plant model is then imposed. This is consistent with manufacturing environments where the cost and number of tests to determine a valid process model is desired to be minimal. The implications of this limitation are modes of response that are hidden from the controller. Their effects on system performance and stability are discussed.Singapore-MIT Alliance (SMA
Robustness of individual score methods against model misspecification in autoregressive panel models
Forced dynamic dewetting of structured surfaces: Influence of surfactants
We analyse the dewetting of printing plates for gravure printing with
well-defined gravure cells. The printing plates were mounted on a rotating
horizontal cylinder that is half immersed in an aqueous solution of the anionic
surfactant sodium 1-decanesulfonate. The gravure plates and the presence of
surfactants serve as one example of a real-world dewetting situation. When
rotating the cylinder, a liquid meniscus was partially drawn out of the liquid
forming a dynamic contact angle at the contact line. The dynamic contact angle
is decreased on a structured surface as compared to a smooth one. This is due
to contact line pinning at the borders of the gravure cells. Additionally,
surfactants tend to decrease the dynamic receding contact angle. We consider
the interplay between these two effects. We compare the height differences of
the meniscus on the structured and unstructured area as function of dewetting
speeds. The height difference increases with increasing dewetting speed. With
increasing size of the gravure cells this height difference and the induced
changes in the dynamic contact angle increased. By adding surfactant, the
height difference and the changes in the contact angle for the same surface
decreased. We further note that although the liquid dewets the printing plates
some liquid is always left in the gravure cell. At high enough surfactant
concentrations or high enough dewetting speed, the dynamic contact angles in
the structured surface approach those in flat surfaces. We conclude that
surfactant reduces the influence of surface structure on dynamic dewetting
Differentially Private Model Selection with Penalized and Constrained Likelihood
In statistical disclosure control, the goal of data analysis is twofold: The
released information must provide accurate and useful statistics about the
underlying population of interest, while minimizing the potential for an
individual record to be identified. In recent years, the notion of differential
privacy has received much attention in theoretical computer science, machine
learning, and statistics. It provides a rigorous and strong notion of
protection for individuals' sensitive information. A fundamental question is
how to incorporate differential privacy into traditional statistical inference
procedures. In this paper we study model selection in multivariate linear
regression under the constraint of differential privacy. We show that model
selection procedures based on penalized least squares or likelihood can be made
differentially private by a combination of regularization and randomization,
and propose two algorithms to do so. We show that our private procedures are
consistent under essentially the same conditions as the corresponding
non-private procedures. We also find that under differential privacy, the
procedure becomes more sensitive to the tuning parameters. We illustrate and
evaluate our method using simulation studies and two real data examples
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