Optimization of the sulfolane extraction plant based on modeling and simulation

An optimization system, based on modeling and simulation, was developed for a sulfolane extraction plant. The primary objective of the operation of this plant is to increase benzene composition, which is mostly affected by the recycle streams in the plant. In this work the optimal recycle streams were identified and resulting product compositions were evaluated. In the optimization, suitable parametric models for each process unit were obtained first from the steady-state rigorous modeling and simulation of the sulfolane extraction plant. The parametric models were then employed to develop the optimization system based on the SQP scheme. Results of simulations show promise for further economic improvements over present operation states.     

Multistage decision-directed channel estimation scheme for DS-CDMAsystem with M-ary orthogonal signaling

A multistage decision-directed channel estimation scheme is proposed for a coherent direct-sequence code-division multiple-access (DS-CDMA) system with M-ary orthogonal signaling. The receiver with a multistage decision-directed channel estimator makes alternate use of symbol detection and channel estimation in an iterative manner, resulting in a multistage structure where each stage consists of an estimator and a detector. The estimator obtains the estimates of the channel by using the decisions from the detector in the previous stage, and the detector uses these estimates for coherent detection of the transmitted symbols. Modifications to the process of generating the channel estimates and the decision variables are made to mitigate the error propagation in successive stages. It is shown that the performance of the proposed estimation scheme is better than the conventional scheme, especially for channels with high diversity order. The gain is mostly achieved by two stages for channels with low diversity order and by five stages for channels with high diversity order. The proposed scheme can be used to increase the capacity of DS-CDMA systems currently operating in such environments     

Watt-level Ka- and Q-band MMIC power amplifiers operating at lowvoltages

Ka- and Q-band watt-level monolithic power amplifiers (PAs) operating at a low drain bias of 3.6 V are presented in this paper. Design considerations for low-voltage operation have been carefully studied, with an emphasis on the effect of device models. The deficiency of conventional table-based models for low-voltage operation is identified. A new nonlinear device model, which combines the advantages of conventional analytical models and table-based models, has been developed to circumvent the numerical problems and, thus, to predict optimum load impedance accurately. The model was verified with load-pull measurements at 39 GHz. To implement a low-voltage 1-W monolithic-microwave integrated-circuit amplifier, careful circuit design has been performed using this model. A Q-band two-stage amplifier showed 1-W output power with a high power gain of 15 dB at 3.6-V drain bias. The peak power-added efficiency (PAE) was 28.5% and 1-dB compression power (P_{1 dB}) was 29.7 dBm. A Ka-band two-stage amplifier showed a P_{1 dB} of 30 dBm with 24.5-dB associated gain and 32.5% PAE. Under very low dc power conditions (P_dc<2 W, V_ds=3.4 V), the amplifiers showed 29-dBm output power and PAE close to 36%, demonstrating ultimate low-power operation capability. To the best of our knowledge, this is the first demonstration of watt-level PA's under 3.6-V operation at 26 and 40 GHz. Compared with the published data, this work also represents state-of-the-art performance in terms of power gain, efficiency, and chip size     

RS-485网络设计降低功耗问题

本文主要讨论在ＲＳ－４８５网络设计中,如何在保持良好的传输特性的同时降低率损耗。     

Base station location in a cellular CDMA system

We consider a cellular CDMA system in which blocking is enforced when the relative interference exceeds a certain threshold level. This paper addresses a radio network design problem in such a CDMA system. Given the data of call‐traffic distributed over the service area and potential sites of base stations, the objective of the problem is to locate base stations so as to minimize the associated cost for establishing base stations while keeping the probability of blocking under control. We develop an efficient algorithm for solving the design problem. Computational experiments with real‐world data are conducted to show both the efficiency and the practicality of the proposed design method. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fabrication of polymeric large-core waveguides for opticalinterconnects using a rubber molding process

Polymeric large-core (47 μm×41 μm) optical waveguides for optical interconnects have been fabricated by using a rubber molding process. For low-cost low-loss large-core waveguides, our newly developed thick-photoresist patterning process is used for a master fabrication. Also a low-loss thermocurable polymer, perfluorocyclobutane (PFCB), is used in fabricating optical waveguides by rubber molding for the first time. The propagation loss is measured to be 0.4 dB/cm at the wavelength of 1.3 μm, and 0.7 dB/cm at the wavelength of 1.55 μm     

An analytical model of simultaneous switching noise in CMOS systems

An accurate and analytical model for simultaneous switching noise (SSN) on ground lines in CMOS circuits is presented. This model can compute SSN for the case where only some drivers switch and the others remain quiet, that is, the model considers the loading effects on the quiet drivers. It was confirmed that the proposed model is more accurate than the existing ones through HSPICE simulation using the level 28 model for short-channel MOSFETs. The proposed model can provide useful design guides for CMOS driver circuits     

Dynamic analysis of shift quality for clutch to clutch controlled automatic transmission

Dynamic characteristics of a shift quality are investigated for a clutch to clutch controlled automatic transmission. Dynamic models of the hydraulic control system and the geartrains are obtained using Bondgraph. Based on the dynamic models, a simulation tool is developed to evaluate the shift quality. Using the simulation tool, shift performances for a 1–2 upshift and a 4-2 downshift are investigated and are compared with test results. It is found that the simulation tool is able to predict the pressure profiles of the clutch and brake, output torque, and turbine speed for a given input duty signal. It is expected that the simulation tool developed in this work can be used to improve the shift quality for the clutch to clutch controlled automatic transmission by saving time and cost in the tests.     

Stress and fracture analyses of nuclear power plant LP turbine rotor discs

Fracture phenomenon has been reported on blades, rotors, connections and rotor discs of LP turbines of nuclear power plants, which is caused by fatigue, stress corrosion and erosion. In this study, as a tool of reliability evaluation, a number of stress and fracture analyses were performed on the defected area under various operating conditions using the finite element method. Possible defects on key-way and rotor disc were assumed to be two-dimensional cracks and centrifugal force, temperature distribution and shrink-fit effect were included as external loads. From stress analysis results, stress intensity factors were obtained and these values can be utilized to evaluate reliability and predict remaining lifetime of the turbine discs.     

Mode I field intensity factors of infinitely long strip in piezoelectric media

We consider the problem of determining the singular stresses and electric fields in a piezoelectric ceramic strip containing a Griffith crack under in-plane normal loading within the framework of linear piezoelectricity. The potential theory method and Fourier transforms are used to reduce the problem to the solution of dual integral equations, which are then expressed to a Fredholm integral equation of the second kind. Numerical values on the field intensity factors are obtained, and the influences of the electric fields for PZT-6B piezoelectric ceramic are discussed.