Identification of tool and product effects in a mixed product and parallel tool environment

In the semiconductor manufacturing industry, production resembles an automated assembly line in which many similar products with slightly different specifications are manufactured step-by-step, with each step being a complicated physiochemical batch process performed by a number of tools. This constitutes a high-mix production system for which effective run-to-run control (RtR) and fault detection control (FDC) can be carried out only if the states of different tools and different products can be estimated. However, since in each production run, a specific product is performed on a specific tool, absolute individual states of products and tools are not observable. In this work, a novel state estimation method based on analysis of variance (ANOVA) is developed to estimate the relative states of each product and tool to the grand average performance of this station in the fab. The method is formulated in the form of a recursive state estimation using the Kalman filter. The advantages of this method are demonstrated using simulations to show that the correct relative states can be estimated in production scenarios such as tool-shift, tool-drift, product ramp-up, tool/product-offline and preventive maintenance (PM). Furthermore, application of this state estimation method in RtR control scheme shows that substantial improvements in process capabilities can be gained, especially for products with small lot counts. The proposed algorithm is also evaluated by an industrial application.     

Studies on a LaF3‐coated MgO protecting layer in AC‐plasma‐display panels

A new protecting layer, a LaF₃‐coated MgO layer, in color AC‐plasma‐display panels (PDPs) was studied in order to overcome the weakness of the conventional single MgO protecting layer. The material characteristics of the new layer were examined by using variations in the deposition process. The display characteristics were also examined by implementing their processes to actual PDPs. It was demonstrated that this method is effective in lowering the firing and sustaining voltages of PDPs and enhancing the brightness of the panel as well.     

A 2‐in. a‐Si:H TFT‐LCD with embedded backlight control TFT sensors with various channel widths

Abstract— A 2.0‐in. a‐Si:H TFT‐LCD with embedded TFT sensors for the control of the backlight intensity according to the ambient light intensity has been developed. Two types of a‐Si:H TFT sensors with various channel widths were embedded into a TFT backplane with bottom‐ and top‐gate structures for measuring the ambient light and backlight illumination, respectively. The output signal, measured by a readout IC, increased with backlight intensity until 20,000 lux.     

Biomechanical evaluation of nursing tasks in a hospital setting

A field study was conducted to investigate spinal kinematics and loading in the nursing profession using objective and subjective measurements of selected nursing tasks observed in a hospital setting. Spinal loading was estimated using trunk motion dynamics measured by the lumbar motion monitor (LMM) and lower back compressive and shear forces were estimated using the three-dimensional (3D) Static Strength Prediction Program. Subjective measures included the rate of perceived physical effort and the perceived risk of low back pain. A multiple logistic regression model, reported in the literature for predicting low back injury based on defined risk groups, was tested. The study results concluded that the major risk factors for low back injury in nurses were the weight of patients handled, trunk moment, and trunk axial rotation. The activities that required long time exposure to awkward postures were perceived by nurses as a high physical effort. This study also concluded that self-reported perceived exertion could be used as a tool to identify nursing activities with a high risk of low-back injury.     

A connection rule for alpha-carbon coarse-grained elastic network models using chemical bond information

A sparser but more efficient connection rule (called a bond-cutoff method) for a simplified alpha-carbon coarse-grained elastic network model is presented. One of conventional connection rules for elastic network models is the distance-cutoff method, where virtual springs connect an alpha-carbon with all neighbor alpha-carbons within predefined distance-cutoff value. However, though the maximum interaction distance between alpha-carbons is reported as 7 angstroms, this cutoff value can make the elastic network unstable in many cases of protein structures. Thus, a larger cutoff value (>11 angstroms) is often used to establish a stable elastic network model in previous researches. To overcome this problem, a connection rule for backbone model is proposed, which satisfies the minimum condition to stabilize an elastic network. Based on the backbone connections, each type of chemical interactions is considered and added to the elastic network model: disulfide bonds, hydrogen bonds, and salt-bridges. In addition, the van der Waals forces between alpha-carbons are modeled by using the distance-cutoff method. With the proposed connection rule, one can make an elastic network model with less than 7 angstroms distance cutoff, which can reveal protein flexibility more sharply. Moreover, the normal modes from the new elastic network model can reflect conformational changes of a given protein better than ones by the distance-cutoff method. This method can save the computational cost when calculating normal modes of a given protein structure, because it can reduce the total number of connections. As a validation, six example proteins are tested. Computational times and the overlap values between the conformational change and infinitesimal motion calculated by normal mode analysis are presented. Those animations are also available at UMass Morph Server (http://biomechanics.ecs.umass.edu/umms.html).     

Fast transmission CT for determining attenuation maps using a collimated line source, rotatable air-copper-lead attenuators and fan-beam collimation

We describe a technique using a line source and a rotatable air-copper-lead assembly to acquire gamma transmission computed tomographic (TCT) data for determining attenuation maps to compensate SPECT emission scans. The technique minimizes problems associated with discriminating 99mTc transmission and 201Tl emission photons and requires only a modest increase in total study time. A 99mTc line source and a stacked foil ("multislat") collimator are placed near the focal line of a fan-beam collimator (114 cm focal length) mounted on one detector of a triple-camera SPECT system. We acquired TCT data of plastic rod and anthropomorphic thorax phantoms to investigate the capability of the line source and rotatable air-copper-lead attenuators to determine attenuation maps. The data were acquired with and without 5.4 MBq (145 microCi) of 201Tl placed in the myocardial chamber of the thorax phantom. Phantoms also were scanned using a curved transmission slab source mounted to a parallel-hole collimator. Fan-beam TCT images have improved resolution compared with parallel-beam TCT images. Two patient scans also were performed to evaluate the clinical usefulness of fan-beam TCT. The rotatable air-copper-lead attenuator method eliminates contamination of emission data by transmission photons and reduces spill-over of emission data into the transmission energy window for some cases. Results show the feasibility of using fast, sequential or interlaced transmission scans of a line source within a rotatable air-copper-lead attenuator assembly to obtain accurate attenuation maps for SPECT attenuation compensation.     

Disordering of the Ni3Si intermetallic compound by mechanical milling

The ordered f c c intermetallic compound Ni₃Si was mechanically milled in a high-energy ball mill. The severe plastic deformation produced by milling induced transformations with increasing milling time as follows: ordered f c c disordered f c c nanocrystalline f c c. The structural and microstructural evolution with milling time was followed by X-ray diffraction, TEM, hardness tests, and differential scanning calorimetry (DSC). Complete disordering occurred at milling times of 2 h and kept the saturated H of the DSC peak in the range of estimated enthalpy even after 60 h milling. The structural development during milling of the f c c solid solution for Ni₃Si was presumably dominated by the formation and refinement of a dislocation cell structure into microcrystallites which eventually reached nanometre dimensions.     

Development and optimal design of a HDD spindle motor with pulling magnet to reduce electrical loss

A conventional hard disk drive (HDD) spindle motor has a pulling plate to generate the axial magnetic force. However, the pulling plate consumes significant amount of iron loss due to the alternating magnetic field on the pulling plate. We propose the new design of a HDD spindle motor with pulling magnet to generate the pre-load as well as to eliminate the iron loss of the pulling plate. We also develop an optimal design methodology to minimize iron and copper losses from the spindle motor of a computer HDD while maintaining the same level of torque ripple and pulling force. The new design is optimized by the developed optimal design methodology. A metamodel is constructed from the three-dimensional finite element analysis of the magnetic field and the meta-modeling techniques, and the accuracies of the metamodels are discussed. The proposed optimal design problem is solved by the progressive quadratic approximation method. The proposed design reduces the electrical loss of the HDD spindle motor by 30.42?% while maintaining the same level of torque ripple and pulling force.     

Integration of evolutional BOMs for design of ship outfitting equipment

PLM (Product Lifecycle Management) as well as enterprise information systems commonly use the BOM (Bill of Material) as a means of communication during product development. BOM has been used for product design, production scheduling, procurement, manufacturing and maintenance as it contains the part list of a subassembly or assembly product. BOM currently plays a key role in the PLM environment because it is an essential product information platform in the industry. In practice, product data should be arranged based on the BOM and product structure. Many shipyards or PLM vendors have attempted to develop a PLM adequate for shipbuilding. However, it is always the premise of the successful PLM implementation to prepare the efficient product structure and BOM.This paper suggests an enterprise BOM which addresses the hierarchy of parts and assembly, product structure and product information of outfitting equipment in marine vessel design. In order to express the evolution of product structures and outfitting information during the ship design, the enterprise BOM is modeled by the structure BOM and the display BOM. Concepts are developed for modeling all levels of product relations with a uniform set of relationships supported by the enterprise BOM. It is shown that the architecture of the structure BOM can be used to define the relationships between assemblies, parts, and a multi-view of an evolutional BOM in ship design. The architecture of the outfitting BOM is also presented using an example of a piping system.     

A method for evaluating fault coverage using simulated fault injection for digitalized systems in nuclear power plants

The fault coverage for digital system in nuclear power plants is evaluated using a simulated fault injection method. Digital systems have numerous advantages, such as hardware elements share and hardware replication of the needed number of independent channels. However, the application of digital systems to safety-critical systems in nuclear power plants has been limited due to reliability concerns. In the reliability issues, fault coverage is one of the most important factors. In this study, we propose an evaluation method of the fault coverage for safety-critical digital systems in nuclear power plants. The system under assessment is a local coincidence logic processor for a digital plant protection system at Ulchin nuclear power plant units 5 and 6. The assessed system is simplified and then a simulated fault injection method is applied to evaluate the fault coverage of two fault detection mechanisms. From the simulated fault injection experiment, the fault detection coverage of the watchdog timer is 44.2% and that of the read only memory (ROM) checksum is 50.5%. Our experiments show that the fault coverage of a safety-critical digital system is effectively quantified using the simulated fault injection method.