Algebraic tools for the performance evaluation of discrete eventsystems

It is shown that a certain class of Petri nets called event graphs can be represented as linear time-invariant finite-dimensional systems using some particular algebras. This sets the ground on which a theory of these systems can be developed in a manner which is very analogous to that of conventional linear system theory. Some preliminary basic developments in that direction are shown. Several ways in which one can consider event graphs as linear systems are described. These correspond to approaches in the time domain, in the event domain, and in a two-dimensional domain. In each of these approaches, a different algebra has to be used for models to remain linear, but the common feature of these algebras is that they all fall into the axiomatic definition of `dioids'. A unified presentation of basic algebraic results on dioids is provided     

Plasma-induced charging evaluation using SCA and PDM tools

Plasma-induced charging has been characterized using unpatterned oxide wafer charging technique. Charging distributions correlate to gate oxide charging damage with antennae structure. Modification of the process by lowering pressure and increasing gas flow led to a significant decrease of the plasma-induced charging and the gate oxide damage     

Drain-induced barrier-lowering analysis in VSLI MOSFET devices using two-dimensional numerical simulations

In recent publications the drain-induced barrier-lowering (DIBL) effect has been included in the determination of the drain current of short-channel MOSFET's by way of analytical expressions. The validity of these published expressions has not been verified so far for small-geometry devices of different parameters. Further, the relationship between the threshold voltage shift and the barrier lowering due to the DIBL effect has not been clarified in the literature. In our present paper we carried a detailed study of the drain-induced barrier lowering in ion-implanted 1-µm VLSI MOSFET devices, leading to a better understanding and clarification of the fundamental mechanisms involved in the DIBL variation and its effect on the threshold voltage and subthreshold current. Further, we found that the calculated DIBL parameters of the analytical model reported in the literature do not agree with the numerically computed values. Hence we determined a set of new geometry parameters η andB/Afor the DIBL threshold relationship that can be used with the analytical model. Our work stresses the necessity of the use of two-dimensional numerical simulations when accurate evaluation of the DIBL effect in short-channel MOSFET's is required. Also, our results should be useful for calibrating existing analytical MOSFET models. In addition, our data and method could be used as a design tool for performance optimization of micrometer and submicrometer devices.     

Redefining performance evaluation tools for real-time QRS complex classification systems

In a heartbeat classification procedure, the detection of QRS complex waveforms is necessary. In many studies, this heartbeat extraction function is not considered: the inputs of the classifier are assumed to be correctly identified. This communication aims to redefine classical performance evaluation tools in entire QRS complex classification systems and to evaluate the effects induced by QRS detection errors on the performance of heartbeat classification processing (normal versus abnormal). Performance statistics are given and discussed considering the MIT/BIH database records that are replayed on a real-time classification system composed of the classical detector proposed by Hamilton and Tompkins, followed by a neural-network classifier. This study shows that a classification accuracy of 96.72% falls to 94.90% when a drop of 1.78% error rate is introduced in the detector quality. This corresponds to an increase of about 50% bad classifications.     

Modeling and performance analysis of cluster tools using Petri nets

The performance of cluster tools is gaining ever-increasing importance as the semiconductor industry migrates to larger wafer sizes, and smaller device geometries. Customers demand higher throughput-to-footprint ratios for semiconductor equipment. Cluster tool throughput is the outcome of complex interactions of various subsystems, and there is a critical need for appropriate tools that aid in understanding these interactions, and their effects on throughput. Current methods for throughput analysis are not very well oriented toward understanding the dynamics in cluster tool processing. In this paper we present a procedure to model cluster tools using Petri nets. These models help designers to comprehend the flow of wafers during processing. While Petri nets have been used extensively in the modeling and analysis of diverse manufacturing processes/systems, this to the best of our knowledge is the first attempt to specifically model cluster tools. A state cycle analysis is discussed next; this method enables equipment designers to extract steady state throughput information, as well as understand the interplay of subsystems during the wafer Row. Two example configurations are used to illustrate Petri net-based model building and analysts. These two examples encompass a variety of design features found in the industry today, e.g., sequential and parallel processing, single and dual end effector robots, anticipatory and simple scheduling     

CAD tools to optimize power MOSFET performance using channelreverse conduction

In this paper, a contribution to the characterization of power MOS transistors under optimized switching behavior is presented. This behavior is shown to be appropriate for improving the performance of new high frequency power processing topologies. Reverse conduction through the channel resistance is imposed, thus avoiding the problem of integral diode recovery time without resorting to external diodes. Control circuit design is discussed. Advantages and drawbacks are analyzed and tested in a series resonant converter. An insight into MOSFET reverse conduction modeling is presented, aimed at the development of an accurate model for computer aided design of topologies using the MOSFET's bidirectional paths. Simulation results are shown to prove the accuracy of the model     

A comparative study of temperature sensitivity of InGaAsP andAlGaAs MQW lasers using numerical simulations

We used numerical simulation to compare the temperature sensitivity of an InGaAsP MQW laser emitting at 1.55 μm and an AlGaAs MQW laser at 0.82 μm. By artificially changing the InGaAsP laser gradually into a structure similar to the AlGaAs laser, we gained quantitative insight into how each material or structural parameter causes the relatively low T₀ of the InGaAsP MQW laser. Using a typical MQW structure we demonstrated the relative importance of parameters involving Auger recombination, current leakage over the quantum barrier, optical confinement and band offset. We found that if these parameters were made the same as the AlGaAs laser, the T₀ of the InGaAsP laser was even better than that of the AlGaAs laser. Our numerical simulation confirmed that the Auger recombination is the main cause of low T₀ in MQW InGaAsP lasers. We also discovered that thermal current leakage over the barrier and Auger recombinations are correlated with each other and both factors must be improved to increase the T₀ of InGaAsP lasers to that of AlGaAs lasers     

The philosophy of performance evaluation

When engineering company revenues decline the typical reaction is to cut costs. At engineering companies, that means layoffs because the primary cost in engineering is staff salary. Work is priced with salary costs as a foundation. Other costs-indirect, overhead, and general/administrative-are layered on to generate the multiplier that determines the cost of each hour charged to the customer. So cost cutting begins with payroll and the inevitable performance evaluation or forced ranking. At its core, competitive evaluation based on costs often denies the employer and the employee the benefits of the potential collaborative value creation in a team and pits one individual against another, placing an inherent limit on cooperation. To be fair and to minimize abuse, the process must be as objective as possible. Results should not be a surprise to those being ranked who are aware of criteria. To be valuable, however, it must allow some subjective assessment of value creation but provide enough subjectivity in a ranking process to identify and consider the value of creativity that opens it up to potential compromise. Too often the mandate to cut costs is used to justify targeting those who have fallen from grace in their managers' eyes, and such a ranking process becomes the tool of choice.     

Quench performance and field quality of the LHC preseries superconducting dipoles

The preseries production of the LHC main superconducting dipoles is presently being tested at CERN. The foremost features of these magnets are: twin structure, six block two layer coils wound from 15.1 mm wide graded NbTi cables, 56 mm aperture, polyimide insulation and stainless steel collars. The paper reviews the main test results of magnets tested to day in both normal and superfluid helium. The results of training performance, magnet protection, electrical integrity and the field quality are presented in terms of the specifications and expected performance of these magnets in the future accelerator.     

The idealized behavior of finite-length dipoles

The author shows how, in the case of a thin, finite-length, center-fed, radiating dipole, supported by a sinusoidal current distribution, it is possible to approximate the far-field behavior of the dipole by the behavior of an idealized omnidirectional element. Typically, the radiation-intensity factor of the idealized element is that of a simple sine term, raised to some exponent (power). It has been common practice in the past to approximate, where possible, the behavior of such dipoles by the behavior of an idealized element, with an integer value for the exponent. This has allowed for ease of integration in determining the parameters of interest to the designer, such as the dipole radiation resistance and directivity. The determination of these parameters would otherwise require the numerical evaluation of a combination of sine-integral and cosine-integral terms, which, although straightforward, is tedious. It is shown here that, for dipoles not exceeding about one wavelength, it is more appropriate to represent the behavior of the dipole by that of an idealized model, with non-integer values for the exponent. Such an approach would not normally circumvent the numerical integrations but, in the light of previous discoveries, it is possible to produce approximate results for the radiation resistance, the directivity, and the half-power beamwidth that are very close to their exact values. Furthermore, these results can be determined with ease for a variety of different dipole lengths, using only a hand-held, non-programmable pocket calculator     

The improvement of tri-plate line performance by using corrugatedtransitions

A novel structure is investigated for the improvement of tri-plate line (TPL) performance. Based on experience in the design of horn antennas, we introduce corrugations of the transition section of the TPL in order to achieve better field uniformity and to reduce the return loss. A corrugated transition waveguide may be viewed as the cascade of bifurcated metal waveguides. We employed the building-block approach, which breaks the overall structure into cascaded subcells, each of which may be analyzed rigorously by the mode-matching method. Thus, the input-output relation of each subcell is obtained as well as that of the overall structure. This enables us to carry out a parametric study on the field distribution inside the TPL test fixture, so that we can optimize its design for any required specifications     

A comparison of etched-geometry and overgrown silicon permeable base transistors by two-dimensional numerical simulations

Etched-geometry and overgrown Si permeable base transistors (PBT's) are compared by using two-dimensional numerical simulations. Because of the asymmetry of the etched structure, two biasing conditions are possible (etched-collector and etched-emitter) and both are considered. The base-to-collector transfer characteristics of PBT devices have two regions of operation. At low base-to-emitter voltages, barrier-limited current flow is observed, The two-dimensional nature of the depletion region near the Schottky-contact base grating results in a smaller electron barrier and thus a larger collector current in the etched structures than in the overgrown structure. At high base-to-emitter bias levels, charge is limited from entering the base region of the etched-emitter structure and from leaving the base region of the etched-collector device. The resulting parasitic feedback effects lead to a deviation from the square-law behavior found in the collector characteristics of the overgrown PBT. Because of the absence of semiconductor material directly above the base grating lines in the etched devices, these structures have lower device capacitances. They also have smaller transconductances at high base-to-emitter voltages. The important consequence of this is that overgrown and etched structures have comparable predicted maximum values of the small-signal unity short-circuit current-gain frequency and maximum frequency of oscillation. Fabrication-related effects are discussed qualitatively and GaAs PBT operation is considered in light of the present simulations.     

信息安全风险评估及辅助工具应用

信息安全风险评估是构建信息安全保障体系的重要手段。论文阐述了信息安全风险评估技术,在此基础上开发了风险评估辅助软件,并进行了软件的应用研究。     

Some analytical tools for the global performance evaluation of packet switching networks based on virtual paths

We present a simple model for the global performance evaluation of a packet switching network. Through a detailed analytical treatment, a set of formulae is derived which allow a compact and reliable evaluation of the most significant statistical properties of the network, such as the arrival probabilities, the queue states distribution and the mean utilizations of the links. Starting from the knowledge of these quantities, the network can be characterized also taking into account the mutual interaction between different nodes. An example is given with reference to a mesh-connected structure.     

Production follow-up of the LHC main dipoles through magnetic measurements at room temperature

In this paper, we review the tools used for controlling the production of the LHC main dipoles through warm magnetic measurements. For the collared coil measurements, control limits are based on the statistics relative to the pre-series production. For the cold mass, the difference between collared coil and cold mass is considered, allowing a very stringent test. In both cases, measurements are split in straight part average, variations and coil ends contributions. Two different alarm levels exist in case the measured field is out of limits. The analysis can be carried out at the manufacturer and allows detection of anomalies in the measured magnetic field. These can be either due to wrong measurements or caused by assembly defects. Techniques used to work out information on the magnet assembly from the field harmonics are outlined. We summarize the experience gathered on about 180 collared coils and 120 cold masses, pointing out the bad cases and investigating the reliability of the measurements.     

Engine performance evaluation using a combustion probe signal analyzer

A two-channel combustion probe signal analyzer to detect variations in the combustion quality in spark ignition engines was built and its performance investigated. The combustion probe signal was obtained by applying a small positive bias to the center electrode of the spark plug of interest. This was accomplished by the insertion of an adaptor between the distributor cap and the spark plug wire. Use of the adapter showed no apparent effect on engine operating characteristics. Experiments investigating the correlation between several engine operating parameters and the combustion quality parameters "impaired combustion" and "slow combustion" were carried out. The parameters varied were A/F (air to fuel ratio), spark advance, engine speed, nonenriched cold start, and NOxand hydrocarbon concentrations in the exhaust. Dynamometer mounted 400 CID production engine was used. Good agreement was found to exist between the variation in the combustion probe signal analyzer's counts and progressively induced impairments of the combustion process.     

Quantitative performance evaluation of the lossless compressionapproach using pole-zero modeling

A technique for lossless compression of seismic signals is proposed. The algorithm employed is based on the equation-error structure, which approximates the signal by minimizing the error in the least square sense and estimates the transfer characteristic as a rational function or equivalently, as an autoregressive moving-average process. The algorithm is implemented in the frequency domain. The performance of the proposed technique is compared with the lossless linear predictor and the differentiator approaches for compressing seismic signals. The residual sequence of these schemes is coded using arithmetic coding. The suggested approach yields compression measures (in terms of bits per sample) lower than the lossless linear predictor and the differentiator for compressing different classes of seismic signals     

Modelling and evaluation of surgical performance using hidden Markov models

Minimally invasive surgery has become very widespread in the last ten years. Since surgeons experience difficulties in learning and mastering minimally invasive techniques, the development of training methods is of great importance. While the introduction of virtual reality-based simulators has introduced a new paradigm in surgical training, skill evaluation methods are far from being objective. This paper proposes a method for defining a model of surgical expertise and an objective metric to evaluate performance in laparoscopic surgery. Our approach is based on the processing of kinematic data describing movements of surgical instruments. We use hidden Markov model theory to define an expert model that describes expert surgical gesture. The model is trained on kinematic data related to exercises performed on a surgical simulator by experienced surgeons. Subsequently, we use this expert model as a reference model in the definition of an objective metric to evaluate performance of surgeons with different abilities. Preliminary results show that, using different topologies for the expert model, the method can be efficiently used both for the discrimination between experienced and novice surgeons, and for the quantitative assessment of surgical ability.     

Improvement of mini-fab uptime by using multitask and multifunctional tools

Multitask and multifunctional tools can process alternative operations, for example, LPCVD depositions of both Poly Si and SiN films with good repeatability and few particulates. Using those tools, we can reduce the total number of tools and the number of "only-one" tools which exist for a type of tool in the fab. We have also evaluated mini-fab availabilities using both a full calculation method and an approximate calculation method. The results show that tool reduction is more effective in obtaining good fab availability and uptime. The reduction of "only-one" tools is very important to improving mini-fab availability. The approximate calculation is simple for estimating the fab availability and offers the possibility to extend mega-fab estimations. It is also possible to use in the case that there are variations of MTTR, MTBF, and excess tool numbers.     

Impact of spacing and gain imbalance between two dipoles on HSPA throughput performance

The throughput performance of two parallel half-wavelength dipoles with different antenna spacings and antenna gain imbalances for two frequency bands in a live high-speed packet access (HSPA) network is reported. It was found that an antenna spacing of 0.25 wavelengths and gain imbalances of up to 6 dB are sufficient to provide significant throughput gain for the same transmit power, or equivalently, an increase in network coverage for a given throughput, as compared to a single dipole.