Noise power spectra of optical two-beam interferometers induced by the laser phase noise

Dynamic range of many optical signal processing and sensing devices incorporating two-beam interferometers (such as Mach-Zehnder and Michelson interferometers) can be limited by random phase fluctuations of the optical source emission field. This paper is concerned with the intensity fluctuations, originating from the laser source phase noise, at the output of a two-beam interferometer. Closed-form theoretical expressions are presented for the autocovariance function, variance, and noise power spectral density of the instantaneous output intensity which are valid for any optical biasing phase and any source coherence time. Application of the results in the noise performance evaluation of optical devices incorporating two-beam interferometers will also be shown.     

Preoxidation treatment using HCl/HF vapor

Replacement of the conventional two-step sequence of aqueous HF dummy oxide strip and wet clean by a one-step vapor phase HCl/HF/H₂ O strip was investigated. Results indicated improvements in the electrical endurance of grown silicon dioxide and that the vapor mixture containing HCl was effective in reducing the detrimental effects caused by deliberately introduced contaminants. Compared with the conventional wet cleans, a 20% improvement in oxide lifetime was observed. Further improvements should be possible with proper optimization of the quantative composition or the constituents of the vapor     

A branch-and-bound algorithm for single machine scheduling with quadratic earliness and tardiness penalties

This paper considers the problem of scheduling a single machine, in which the objective function is to minimize the weighted quadratic earliness and tardiness penalties and no machine idle time is allowed. We develop a branch and bound algorithm involving the implementation of lower and upper bounding procedures as well as some dominance rules. The lower bound is designed based on a lagrangian relaxation method and the upper bound includes two phases, one for constructing initial schedules and the other for improving them. Computational experiments on a set of randomly generated instances show that one of the proposed heuristics, used as an upper bound, has an average gap less than 1.3% for instances optimally solved. The results indicate that both the lower and upper bounds are very tight and the branch-and-bound algorithm is the first algorithm that is able to optimally solve problems with up to 30 jobs in a reasonable amount of time.     

Optimizing blocking flow shop scheduling problem with total completion time criterion

The blocking flow shop scheduling problem has found many applications in manufacturing systems. There are a few exact methods for solving this problem with different criteria. In this paper, efforts will be made to optimize the total completion time criterion for this problem. We present two mixed binary integer programming models, one of which is based on the departure times of jobs from machines, and the other is based on the idle and blocking times of jobs. An initial upper bound generator and some lower bounds and dominance rules are also developed to be used in a branch and bound algorithm. The algorithm solves 17 instances of the Taillard's benchmark problem set in less than 20 min.     

A method for bulk power system reliability evaluation based on local coherency

The problem of bulk power system reliability evaluation is considered and a new solution approach is proposed. Bulk power system models are generally not coherent in the sense of reliability theory. Conditions are derived on network topology to guarantee coherency. Only parallel structure systems satisfy these conditions. Noncoherency of a power system may be the effect of only a subset of its transmission lines. Thus the concept of local coherency is introduced. A decomposition approach to bulk power system reliability evaluation based on the concept of local coherency is developed. Sufficient conditions for local coherency are derived.     

Grid Integration of Wind Generation Considering Remote Wind Farms: Hybrid Markovian and Interval Unit Commitment

Grid integration of wind power is essential to reduce fossil fuel usage but challenging in view of the intermittent nature of wind. Recently, we developed a hybrid Markovian and interval approach for the unit commitment and economic dispatch problem where power generation of conventional units is linked to local wind states to dampen the effects of wind uncertainties. Also, to reduce complexity, extreme and expected states are considered as interval modeling. Although this approach is effective, the fact that major wind farms are often located in remote locations and not accompanied by conventional units leads to conservative results. Furthermore, weights of extreme and expected states in the objective function are difficult to tune, resulting in significant differences between optimization and simulation costs. In this paper, each remote wind farm is paired with a conventional unit to dampen the effects of wind uncertainties without using expensive utility-scaled battery storage, and extra constraints are innovatively established to model pairing. Additionally, proper weights are derived through a novel quadratic fit of cost functions. The problem is solved by using a creative integration of our recent surrogate Lagrangian relaxation and branch-and-cut. Results demonstrate modeling accuracy, computational efficiency, and significant reduction of conservativeness of the previous approach.      

A new thin film composite nanofiltration membrane based on PET nanofiber support and polyamide top layer: preparation and characterization

The main objective of this study was to prepare thin film nanofibrous composite (TFNC) membranes based on self-support nanofibrous mats. To this end, polyethylene terephthalate nanofibrous supports were produced by electrospinning technique and subsequently heat treatment was performed to increase mechanical stability of the mats. Then, interfacial polymerization procedure was applied for preparation of TFNC nanofiltration membranes. For comparison, the thin film composite (TFC) nanofiltration membrane was prepared by the same conditions based on polyethersulfone ultrafiltration membrane prepared through phase inversion method. Chemical structure, morphology and mechanical properties were studied by using ATR-FTIR, SEM and tensile tests, respectively. Also, filtration performance was investigated by water flux, rejection, water contact angle and MWCO determination. Results showed that the TFNC nanofiltration membrane had higher salt rejection and four times higher water flux than the TFC nanofiltraion membrane (Na₂SO₄ rejection and pure water flux were (93 ± 3)%, (34 ± 2.3) L./m²h and (67 ± 4)%, (8 ± 0.9) L./m²h for TFNC and TFC, respectively). At the end, the filtration performance of PET TFNC-NF membrane was compared with other nanofibrous nanofiltration membranes.

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Rapid thermal multiprocessing for a programmable factory foradaptable manufacturing of ICs

This paper presents an overview of research at Stanford University on the development of concepts of a programmable factory, based on a new generation of flexible multifunctional equipment implemented in a smaller flexible factory. This approach is demonstrated through the development of a novel single wafer Rapid Thermal Multiprocessing (RTM) reactor with extensive integration of sensors, computers and related technology for specification, communication, execution, monitoring, control, and diagnosis to demonstrate the programmable nature of the RTM. The RTM combines rapid thermal processing and several other process environments in a single chamber, with applications for multilayer in-situ growth and deposition of dielectrics, semiconductors and metals. Because it is highly instrumented, the RTM is very flexible for in-situ multiprocessing, allowing rapid cycling of ambient gases, temperature, pressure, etc. It allows several processing steps to be executed sequentially in-situ, while providing sufficient flexibility to allow optimization of each processing step. This flexibility is partially the result of a new lamp system with three concentric rings each of which is independently and dynamically controlled to provide for better control over the spatial and temporal optical flux profile resulting in excellent temperature uniformity over a wide range of process conditions namely temperatures, pressures and gas flow rates. The lamp system has been optimally designed through the use of a newly developed thermal simulator. For equipment and process control, a variety of sensors for real-time measurements and a model based control system have been developed     

Control of MMST RTP: repeatability, uniformity, and integration forflexible manufacturing [ICs]

A real-time multivariable strategy is used to control the uniformity and repeatability of wafer temperature in rapid thermal processing (RTP) semiconductor device manufacturing equipment. This strategy is based on a physical model of the process where the model parameters are estimated using an experimental design procedure. The internal model control (IMC) law design methodology is used to automatically compute the lamp powers to a multizone array of concentric heating zones to achieve wafer temperature uniformity. Control actions are made in response to real-time feedback information provided by temperature sensing, via pyrometry, at multiple points across the wafer. Several modules, including model-scheduling and antiovershoot, are coordinated with IMC to achieve temperature control specifications. The control strategy, originally developed for prototype equipment at Stanford University, is analyzed via the customization, integration, and performance on eight RTP reactors at Texas Instruments conducting thirteen different thermal fabrication operations of two sub-half-micron CMOS process technologies used in the the Microelectronics Manufacturing Science and Technology (MMST) program     

Time-domain addressing of remote fiber-optic interferometric sensor arrays

This paper describes and analyzes a particular application of high duty-cycle time-division multiplexing to the separation and identification of signals from an interferometric sensor array. Using the method discussed here, the coherence length of the laser is no longer a severe design constraint. Also, the source phase-induced intensity noise which limits some other multiplexing methods may be overcome, leading to a higher sensitivity. The arrays of all-passive remote sensors exhibit minimal crosstalk between sensors, and have downlead insensitivity. A synthetic heterodyne demodulation technique prevents environmentally induced signal fading. Analysis includes coupling ratios for all directional couplers in the system, signal and noise spectra, minimum detectable phase shift, and the effect of ac coupling on noise and crosstalk. An experimental all-fiber implementation of a two sensor array has yielded a measured sensitivity of approximately 10 μrad/sqrt{Hz}over a range of signal frequencies, and a crosstalk level of better than 55 dB.