8,870 research outputs found
Speech enhancement with MAP estimation and ICA-based speech features
No full textThe authors present a denoising algorithm based on Gabor-like speech features extracted by independent component analysis, that demonstrates much improved signal-to-noise ratio and recognition rates.This research was supported as a Brain Science Researc Center and Engineering department research programme by the Korean Ministry of Science and Technology. Te-Won Lee was partially supported by a National Science Foundation Grant (CCR-9902961)
Lysophospholipids increase ICAM-1 expression in human umbilical cord vein endothelial cells through a Gi- and NFkB-dependent mechanism.
No full textScheduling single-armed cluster tools with reentrant wafer flows
No full textA cluster tool for semiconductor manufacturing consists of several single-wafer processing chambers and a wafer-handling robot in a closed environment. The use of cluster tools is extended to reentrant processes such as atomic layer deposition, where a wafer visits a processing chamber more than once. Such a reentrant wafer flow complicates scheduling and control of the cluster tool and often causes deadlocks. We examine the scheduling problem for a single-armed cluster tool with various reentrant wafer flows. We develop a convenient method of modeling tool operational behavior with reentrant wafer flows using Petri nets. By examining the net model, we then develop a necessary and sufficient condition for preventing a deadlock. We also show that the cycle time for the asymmetric choice Petri net model for a reentrant wafer flow can be easily computed by using the equivalent event graph model. From the results, we systematically develop a mixed integer programming model for determining the optimal tool operation sequence, schedule, and cycle time. We also extend a workload measure for cluster tools with reentrant wafer flows. Finally, we discuss how our results can be used for engineering a cluster tool. We compare two proposed strategies, sharing and dedicating, of operating the parallel processing chambers for identical process steps.The Brain Korea 21 Fun
Adhesion strength of leadframe/EMC interfaces
No full textCu-based leadframe sheets were oxidized in alkaline solutions to produce brown and/or black oxide on the surfaces, and molded with epoxy molding compound (EMC). The adhesion strength of leadframe/EMC interface was measured using sandwiched double-cantilever beam (SDCB) specimens and pull-out specimens. Results showed that the adhesion strength of leadframe/EMC interface was inherently very poor but could be increased drastically with the nucleation of acicular CuO precipitates. The presence of smooth-faceted Cu(2)O on the surface of the leadframe gave close to zero fracture toughness (G(C)) and suitable pull strength (PS). A direct correlation between G(C) and PS showed that PS can be a measure of G(C) only in a limited range
Scheduling a wet station for wafer cleaning with multiple job flows and multiple wafer-handling robots
No full textA wet station performs a cleaning process in semiconductor manufacturing. It consists of several processing baths and multiple wafer-handling robots. It simultaneously processes multiple wafer types with different processing sequences. Robot collisions and deadlocks should be prevented. There are also strict no-wait time constraints where, after a wafer is cleaned in a chemical bath, it should immediately be removed from the bath and rinsed at a water bath. We examine the scheduling problem when different jobs are repetitively processed in cyclic order. We propose a way of modelling a Petri net for the wet station operation. By examining the Petri net model, we develop conditions for preventing deadlocks and collisions. We show that the Petri net model, which is apparently an asymmetric Petri net, is behaviourally equivalent to an event graph, for which cycle time computation and many analysis methods are available. Based oil these findings, we develop a mixed integer programming model for determining the robot task sequences, the jobs in progress at the baths, and a timing schedule, which are free from deadlocks and collisions, satisfy the no-wait time constraints, and minimize the cycle time. We discuss the computational results
Effects of chemical oxidations on the fracture toughness of leadframe/EMC interfaces
No full textCu-based leadframe sheets were oxidized by a chemical oxidation method, which formed two kinds of oxides on its surface, a brown one and a black one. The oxidation characteristics of each oxide were studied and then to measure the adhesion strength of the leadframe/EMC interface as a function of fracture toughness, the oxidized leadframe samples were molded with an epoxy molding compound (EMC) and machined to form sandwiched double-cantilever beam (SDCB) specimens. SEM and XRD studies on the surfaces of the oxidized leadframe as well as the measurement of fracture toughness showed that the interfacial fracture toughness is directly related to the formation of acicular CuO precipitates on the surface of the leadframe. However, once a continuous layer of CuO precipitates formed on the surface of the leadframe (brown oxide) or on the Cu2O layer (black oxide), the interfacial fracture toughness is found to saturate regardless of a further oxide thickening. The size of the acicular precipitates seems to have a secondary effect on the interfacial Fracture toughness
- …
