Development of operation-aided system for chemical processes

This paper presents the development of a knowledge-based operation-aided system for polypropylene process. The important part of this system is the search for the root cause of faults by detecting and analyzing the symptoms which occurred in the process in the case of abnormal situations. In this system, an artificial neural network which is able to handle pattern recognition is used for qualitative interpretation of sensor data and generating symptoms. For effective fault diagnosis, two causal effect models which are based on SDG (Signed Directed Graph) are developed. One model, RCED (Reduced Cause Effect Digraph) uses only the measurable sensor data of the process and is constructed off-line and stored in the knowledge base of the system. The other model, PGTT (Pattern Graph Through Time) is generated in the real-time mode during the diagnosis period. It is generated from symptoms—status and/or tendency change—and can handle dynamic state effectively. By implementing the developed qualitative interpretation method and two causal effect graph models, the operation-aided system for the polypropylene process, FINDS/PP (Fault Isolation aNd Detection System/PolyPropylene) was developed. This system was developed with the expert system tool G2 and showed good results.     

Negative-differential transconductance characteristics at room temperature in 30-nm square-channel SOI nMOSFETs with a degenerately doped body

Negative-differential transconductance characteristics at room temperature with a peak-to-valley ratio of about two were observed in 30-nm square-channel silicon-on-insulator nMOSFETs with degenerately doped bodies. High channel-doping concentration creates the degeneracy in the p-type body of the self-aligned SOI MOSFET and consequently, enables band-to-band tunneling between degenerate body and source-drain. I/sub DS/-V/sub DS/ curves in the negative drain bias region also show band-to-band tunneling current as in the case of forward-biased p-n tunnel junctions.     

A unified fast recursive algorithm for data shuffling in variousorders

Data shuffling in a particular order is frequently required in signal processing applications. The authors present fast recursive algorithms, of order O(N), for shuffling a data sequence in various orders, e.g. bit reversed, Gray code, and other related orders, under a unified framework. These algorithms are computationally efficient in that every permutation index is essentially computed by a single logical or arithmetic operation between a previous index and a proper offset. The proposed algorithms can be used for the fast Fourier transform, fast Hartley transform, and mutual conversion among three typical forms of the Walsh transform     

Microdischarge in microbridge plasma display with holes in thecathode

A new microbridge plasma display structure with holes in the cathode has been fabricated and operated at high gas pressure (400-700 Torr). With a hole diameter of 100 μm, the slope of the I-V curve in the discharge cell of the new structure is positive at 700 Torr. It is found that the discharge in this new structure has about 100 kohm internal resistance, and the discharges are stable when operated without current limiting resistors. The operating current in the new structure is about 50 μA with smaller 75 μm diameter holes in the cathode     

Demagnetization due to inverse magnetostriction effects inlongitudinal thin film media

Unpredictable mechanical stresses that occur during the operation of hard disk drives can degrade the recorded signal. On the basis of a micromagnetic analysis and the calculated stress field during head-disk impact, inverse magnetostriction effects in longitudinal recording thin film media are considered and demagnetization due to head-disk impact is simulated numerically. Thin film media are modeled as planar hexagonal arrays of hexagonally shaped grains. The computation uses the conjugate gradient algorithm to minimize the variation of the total energy. In particular, the effect of the stress on the relaxation process is investigated. Also the change in the remanent magnetization due to repetitive head-disk impacts is calculated. We obtained results indicating that the effect of the impact stress during dynamic loading is not so significant as to cause data loss during operation for the longitudinal thin film media     

Design and performance evaluation of a new medium access controlprotocol for local wireless data communications

This paper proposes a new medium access control protocol for wireless data communications in local area, called the reservation-based multiple access with variable frame length (RMAV). We design RMAV under the consideration that the population of wireless terminals and the system load frequently change and are almost unpredictable in wireless data communications. RMAV is based on the slot reservation scheme and adopts a frame structure with variable length. The frame length increases as the number of active terminals and/or the system load increases. We evaluate the performance of RMAV by analysis and computer simulation. Due to its adaptability to traffic patterns, RMAV offers short delay in light load conditions and high throughput in heavy load conditions     

Optical backplane system using waveguide-embedded PCBs and optical slots

As discussed in this paper, a practical optical backplane system was demonstrated, using a waveguide-embedded optical backplane board, processing boards, and optical slots for board-to-board interconnection. A metal optical bench was used as a packaging die for the optical devices and the integrated circuit chips in both the transmitter and the receiver processing boards. The polymer waveguide was produced by means of a hot-embossing technique and was then embedded following a conventional lamination processes. The average propagation loss of these waveguides was approximately 0.1 dB/cm at 850 nm. The dimension and optical properties of the waveguide in an optical backplane board were unchanged after lamination. As connection components between transmitter/receiver processing boards and an optical backplane board, optical slots were used for easy and repeatable insertion and extraction of the boards with a micrometer-scale precision. A 1/spl times/4 850-nm vertical-cavity surface-emitting laser array was used with 2 dBm of output power for the transmitter and a p-i-n photodiode array for the receiver. This paper successfully demonstrates 8 Gb/s of data transmission between the transmitter processing board and the optical backplane board.     

The chemical and physical properties of electrochemically prepared polyaniline perchlorate (PAP)

Polyaniline perchlorate (PAP) was synthesized by electrochemical oxidation from 0.2 M aniline in acetonitrile solution containing 0.1 M tetraethylammonium perchlorate as supporting electrolyte. From polarographic and cyclic voltammetry results, the values of the half-wave potential (E_1/2), transfer coefficient (α), and number of electrons related to the electrode reaction (n) were calculated to be 825 mV, 0.894, and 1, respectively. The morphology of the PAP film was observed by using an SEM analyzer. From thermal analysis of the PAP sample, the reaction rate (R) for its thermal decomposition was obtained from the TGA result and a exothermic peak at 330°C was also observed in the DSC curve. The electrical conductivity of the PAP pellet was measured at temperatures from ?170 to 25°C. From a plot of conductivity vs. 1/T, the activation energy (E_a) was obtained to be 0.14 eV. The conduction mechanism in a pressed pellet of PAP is suggested to be electronic hopping conduction. The values of the ESR parameters were calculated from an ESR curve for PAP at room temperature.     

Practical issues and solutions on installation of viscoelastic dampers in a 46‐story reinforced concrete building structure

The purpose of this study is to evaluate the performance of viscoelastic dampers (VEDs) practically used for enhancing the serviceability of a 46‐story reinforced concrete residential building structure. Considering that a bracing system for the installation of VEDs is not appropriate for a residential building because it occupies a large interior space, a method for installing VEDs at the midspan of a horizontal beam connecting the core and exterior columns is proposed. These VEDs control the total structural response in a similar way to a general outrigger system. The results from numerical analysis indicate that VEDs are effective for reducing not only mean components but also fluctuating ones of wind‐induced responses by providing additional damping as well as stiffness. Copyright © 2007 John Wiley & Sons, Ltd.