Optimal Design Rules Research Articles

Fast modelling of deeply and fully etched gratings based on the Bloch–Floquet theorem

AbstractA model of deeply and fully etched gratings (also identified as one‐dimensional waveguide photonic bandgap structures), based on the Bloch–Floquet theorem, has been developed to perform a complete analysis of the electromagnetic (e.m.) wave propagation in the structure, assumed of finite extension, i.e. to determine mode propagation constants, electromagnetic field harmonics and total field distribution, transmission and reflection coefficients, total forward and backward power flow in the structure, guided power and total losses.Comparisons with other accurate numerical methods confirm the accuracy of the new one, whose main advantages are the quickness and the possibility to determine a great amount of information and figures of merit in a few seconds (for each operating wavelength). Moreover, the model allows the designer a complete view of the physical and geometrical device features, so it permits to draw design rules for optimization of photonic bandgap (PBG) waveguide device design. Copyright © 2001 John Wiley & Sons, Ltd.

Analysis of an axisymmetric deep-drawn part forming using reduced forming steps

Numerical simulations have been widely used to assist part and process design. In this paper, deep-drawing processes of an axisymmetric part with a complex geometry are analyzed with the aim of reducing possible forming steps. The existing practice requires a 10-step drawing. Our approach combines a optimization scheme, design rules and numerical tests using the finite-element analysis incorporated with a damage model. As a result, the 10-step drawing is reduced to a 6-step drawing. Additionally, the new process design yields a lower maximum void volume fraction in the sheet, meaning a more formable process and a slightly higher press load.

Robust and accurate single nucleotide polymorphism genotyping by dynamic allele-specific hybridization (DASH): design criteria and assay validation.

We recently introduced a generic single nucleotide polymorphism (SNP) genotyping method, termed DASH (dynamic allele-specific hybridization), which entails dynamic tracking of probe (oligonucleotide) to target (PCR product) hybridization as reaction temperature is steadily increased. The reliability of DASH and optimal design rules have not been previously reported. We have now evaluated crudely designed DASH assays (sequences unmodified from genomic DNA) for 89 randomly selected and confirmed SNPs. Accurate genotype assignment was achieved for 89% of these worst-case-scenario assays. Failures were determined to be caused by secondary structures in the target molecule, which could be reliably predicted from thermodynamic theory. Improved design rules were thereby established, and these were tested by redesigning six of the failed DASH assays. This involved reengineering PCR primers to eliminate amplified target sequence secondary structures. This sophisticated design strategy led to complete functional recovery of all six assays, implying that SNPs in most if not all sequence contexts can be effectively scored by DASH. Subsequent empirical support for this inference has been evidenced by approximately 30 failure-free DASH assay designs implemented across a range of ongoing genotyping programs. Structured follow-on studies employed standardized assay conditions, and revealed that assay reproducibility (733 duplicated genotypes, six different assays) was as high as 100%, with an assay accuracy (1200 genotypes, three different assays) that exceeded 99.9%. No post-PCR assay failures were encountered. These findings, along with intrinsic low cost and high flexibility, validate DASH as an effective procedure for SNP genotyping.

Mechanical stress and deformation of SMT components during temperature cycling and PCB bending

A very common method to predict the reliability of components soldered on printed circuit board (PCB) or substrates is by bending tests and temperature cycle tests, for instance between ‐55°C and 125°C (up to 2,000 cycles at 1h cycle period). Sensitive SMD constructions such as chips with ball grid array mounting or multilayer chip capacitors (MLCC) are often a major issue due to their “flex cracking” problems. This paper describes the real behaviour of deformation at temperature cycling and PCB bending of chip components (body size 0603). By using the piezoresistive effect in thick film resistors the effects of stress on the alumina body can be determined and described for the whole temperature range of interest. The complete system of component, PCB/substrate and solder joint will be discussed and different influences will be isolated. It will be shown that CTE‐matching of the component and substrate does not lead to an optimum situation. The influence of the solder joint plays an important part. Optimization potentials and design rules for the whole system will be given. The basis of this paper is a quite unusual “measurement tool” the effect of piezoresistivity. The investigation into that phenomenon will be described very thoroughly first.

Impediment Current Compensation Scheme of Wound Rotor Induction Motor with Flywheel using Low Power Converter

The paper presents the low power inverter controlled wound rotor induction motor-based compensation scheme for impediment current in the power distribution system. The impediment current means the harmonic current, reactive current, unbalanced current and the peak active current. One of the cost-effective and reliable solutions for compensation is the wound rotor induction motor with a flywheel when the rotor is excited by the low power inverter/converter system. From the economical standpoint, the motor speed should be controlled in the vicinity of the synchronous speed when the peak load current is compensated for by the kinetic energy of the flyweel. This kind of load leveling should be performed under the restriction of limited power capacity of the inverter.The authors propose the optimum design rules of the control loops to satisfy the load leveling specifications. The effectiveness of the proposed approaches have been verified by experiments.

Bi-directional optical backplane bus for general purpose multi-processor board-to-board optoelectronic interconnects

We report for the first time a bidirectional optical backplane bus for a high performance system containing nine multi-chip module (MCM) boards, operating at 632.8 and 1300 nm. The backplane bus reported here employs arrays of multiplexed polymer-based waveguide holograms in conjunction with a waveguiding plate, within which 16 substrate guided waves for 72 (8/spl times/9) cascaded fanouts, are generated. Data transfer of 1.2 Gbt/s at 1.3-/spl mu/m wavelength is demonstrated for a single bus line with 72 cascaded fanouts. Packaging-related issues such as transceiver size and misalignment are embarked upon to provide a reliable system with a wide bandwidth coverage. Theoretical treatment to minimize intensity fluctuations among the nine modules in both directions is further presented and an optimum design rule is provided. The backplane bus demonstrated, is for general-purpose and therefore compatible with such IEEE standardized buses as VMEbus, Futurebus and FASTBUS, and can function as a backplane bus in existing computing environments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

1-to-27 highly parallel three-dimensional intra- and inter-board optical interconnects

The authors present a novel interconnection scheme for highly parallel three-dimensional (3-D) optical intra- and inter-board fan-out using substrate guided waves in conjunction with a two-dimensional (2-D) multiplexed hologram array. 1-to-27 passive highly parallel optical fan-out was demonstrated for the first time. Optimum design rules are presented together with experimental results. The effort of employing substrate guided waves in conjunction with a 2-D multiplexed holograms array provides the capability of 3-D multi-stage intra- and inter-board massively parallel interconnects. As a result, the coupling from a laser diode to multi-stage two dimensional detector arrays and/or fiber array can thus be realized.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design limitations of highly parallel free-space optical interconnects based on arrays of vertical cavity surface-emitting laser diodes, microlenses, and photodetectors

We utilize a novel diffraction formalism to study the crosstalk effect in a highly parallel free-space optical interconnect based on two-dimensional arrays of surface-emitting laser diodes, microlenses, and photodetectors. The diffraction induced crosstalk between adjacent laser diodes in each detector to the system limitations is investigated. Optimum design rules and formulas are given for the first time, to include the relation of channel packaging density and interconnect length to the design parameters of the optical interconnect components. The design formulas developed here yield an optimum detector size and indicate a tradeoff between channel packaging density and interconnect length. The feasibility of such a free-space interconnect with a channel packaging density of 3460 channels/cm/sup 2/ and 2.0 cm interconnection length is determined using typical parameters of detector radius from /spl sim/5 to /spl sim/45 /spl mu/m, lens radius of 85 /spl mu/m, and laser diode radius of /spl sim/5 pm operating at wavelength 0.67 pm for signal-to-noise ratio above 17 dB. Some experiments were conducted to measure the diffraction induced crosstalk and optical link efficiency.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

N+ dopant exponential profiles for silicon solar cells

Abstract A numerical model of solar cells is described, which provides optimum design rules for exponential N+ dopant profiles for heavily doped emitter regions. The model gives a useful insight into the relative impact of surface and bulk recombination on device performance. Results agree well with theorical models.

GaAs/AlGaAs and InGaAs/AlGaAs MODFET inverter simulations

Although MODFET's have exhibited the fastest switching speed for any digital circuit technology, there is as yet no clear consensus on optimal inverter design rules. We therefore have developed a comprehensive MODFET device model that accurately accounts for such high gate bias effects as transconductance degradation and increased gate capacitance. The device model, which agrees with experimental devices fabricated in this laboratory, is used in the simulation of direct-coupled FET logic (DCFL) inverters with saturated resistor loads. Based on simulation results, the importance of large driver threshold voltage not only for small propagation delay times but for wide logic swings and noise margins is demonstrated. Furthermore, minimum delay times are found to occur at small supply voltages as seen experimentally. Both of these results are attributed to the reduction of detrimental high gate bias effects. The major effect of reducing the gate length on delay time is to decrease the load capacitance of the gate. Using 0.25-µm gates, delay times of 5 and 3.6 ps at 300 and 77 K, respectively, are predicted. Finally, the recently introduced In-GaAs/AlGaAs MODFET's are shown to have switching speeds superior to those of conventional GaAs/AlGaAs MODFET's.

On yield-optimizing design rules

Integrated circuit design rules represent a trade-off between the probability that a given die will yield and the physical size of that die. Optimum design rules maximize the average number of good dice on a wafer. The authors present a methodology for calculating design rules that are optimum in this sense. The development involves four points: (1) any design rule can be represented physically by a key-and-target structure; (2) such key-and-target structures lend themselves to suitable mathematical analysis; (3) the average yield of a given ensemble of design rules may be estimated by computer simulation and (4) the most efficient design rules may be estimated by the methods of stochastic optimization.

Determining IC layout rules for cost minimization

A general and practical method for design rule optimization (i.e. IC cost minimization) is presented, and then demonstrated in detail for specific examples. The optimum design rules are shown to be insensitive to chip area or defect density, but strongly dependent on tolerance sizes, number of masking levels, and to a parameter which will be defined as the `area overhead factor'. Throughout the development, limitations and assumptions are thoroughly discussed, with the overall result that the method is shown to be immediately useful for arbitrary, but well characterized, fabrication processes and lithography equipment.

THEORY OF BLANKET DESIGN FOR DAMS ON PERVIOUS FOUNDATIONS

A theory of design of blankets for dams on pervious foundations is presented. Rules for optimal design of rectangular and triangular blankets are formulated. Analysis is given for trapezoidal blankets also. Only the blankets on the upstream side of the dams are considered because the downstream blankets are not effective in reducing the uplift force. They will need to be made much stronger than the upstream blankets in order to withstand the unbalanced uplift force. Usually on the downstream side, drainage holes are provided to relieve the uplift pressure. Analysis shows that the triangular blankets are more effective than the rectangular and trapezoidal ones.

Dispersion phenomena in reactors for flow analysis

Both coiled open tubular reactors and packed-bed reactors can be used in flow analysis. Band broadening and pressure drop in these reactors are discussed. Theoretical analysis shows that packed-bed reactors are to be preferred. It is shown that for a given residence time and equal band-broadening values the pressure drop over a packed-bed reactor is lower than over a coiled open tubular reactor. Rules for optimal design are given for coiled tubular reactors and packed-bed reactors. The application of both reactors is shown for the spectrophotometric determination of phosphate with a vanadomolybdate reagent yielding a yellow colour.

Horizontally multi-layered a-Si photo-voltaic cells A new type of high voltage photo-voltaic device

A new type of plasma-deposited amorphous silicon photovoltaic cell having a high out-put voltage has been developed. Structure of the new devices is a horizontally multilaminated p-i-n unit cell with a indium-tin-oxide heteroface window expressed as a conventional symbols of ITO/(p-i-n) m/SS. The open-circuit voltage V oc is nearly proportional to the number of repititions of around 4% have been obtained with V oc ranging from 0.6 to 2.4 V by applying a simple optimum design rule to the cell-construction parameters.

A new type of amorphous silicon photovoltaic cell generating more than 2.0 V

A new type of plasma-deposited amorphous silicon photovoltaic cell having a horizontally multilayered p-i-n unit-cell structure has been developed. The open-circuit voltage Voc is nearly proportional to the number of repetitions of the p-i-n unit cell. Almost-constant energy-conversion efficiencies of around 4% have been obtained with Voc ranging from 0.6 to 2.4 V by applying a simple optimum design rule to the cell-construction parameters.

Post-column reactor systems in liquid chromatography

Summary The sensitivity and selectivity of standard liquid chromatographic detectors such as photometers, fluorimeters and coulometric cells can be substantially improved by coupling the exit of the chromatographic column to a chemical reaction system. The additional band broadening in these reactors should be reduced to an acceptable value by an appropriate design of the system. Three types of reactors are used: tubular reactors, packed bed reactors and gas-segmented liquid flow systems. The performances and characteristics of these reactor systems are compared and some specific instrumental problems (mixing, noise level) are discussed. Rules for optimal design are given. The choice of the reactor system depends on the speed and the complexity of the reaction involved. This is illustrated by a number of practical applications of both simple, fast reactions and slower reactions that consist of several steps. Results on band broadening in the reactors and on detection limits are given. Some systems are suitable for the determination of sub-nanogram amounts.

Noise in FM receivers with negative frequency feedback

The purpose of this two-part investigation is to shed light on the physical effects responsible for the threshold behavior of FM receiving systems, especially those applying negative frequency feedback (FMFB systems), and to obtain quantitative relations for optimal design of such systems. First a new method is applied (in Part I) to the description of threshold effects in conventional FM receivers, giving access to the phenomena implied in a more lucid and mathematically simpler manner than obtained by previous theoretical investigations of other authors. By use of suitable approximations the output spectra and signal-to-noise ratios can be derived from the amplitude distribution of the noise envelope. The mthematical expressions obtained are relatively simple and well suited to numerical evaluation. Numerical calculations carried out by computer agree very well with the results available in the literature for some relatively restricted cases. The new method is then applied to the more involved problem of deriving the output noise spectra, at and below threshold, of an FMFB system, a problem that cannot be solved by conventional, mathematically rigid methods. The results obtained are shown (in Part II) to be in complete agreement with measurements carried out on different systems. Rules for optimal design of FMFB systems are given which permit the lowest threshold value to be determined without impairment to overall system performance.