Large Parameter Variations Research Articles

Large-Scale Surface Mass Balance of Ice Sheets from a Comprehensive Atmospheric Model

The surface mass balance for Greenland and Antarctica has been calculated using model data from an AMIP-type experiment for the period 1979–2001 using the ECHAM5 spectral transform model at different triangular truncations. There is a significant reduction in the calculated ablation for the highest model resolution, T319 with an equivalent grid distance of ca 40 km. As a consequence the T319 model has a positive surface mass balance for both ice sheets during the period. For Greenland, the models at lower resolution, T106 and T63, on the other hand, have a much stronger ablation leading to a negative surface mass balance. Calculations have also been undertaken for a climate change experiment using the IPCC scenario A1B, with a T213 resolution (corresponding to a grid distance of some 60 km) and comparing two 30-year periods from the end of the twentieth century and the end of the twenty-first century, respectively. For Greenland there is change of 495 km3/year, going from a positive to a negative surface mass balance corresponding to a sea level rise of 1.4 mm/year. For Antarctica there is an increase in the positive surface mass balance of 285 km3/year corresponding to a sea level fall by 0.8 mm/year. The surface mass balance changes of the two ice sheets lead to a sea level rise of 7 cm at the end of this century compared to end of the twentieth century. Other possible mass losses such as due to changes in the calving of icebergs are not considered. It appears that such changes must increase significantly, and several times more than the surface mass balance changes, if the ice sheets are to make a major contribution to sea level rise this century. The model calculations indicate large inter-annual variations in all relevant parameters making it impossible to identify robust trends from the examined periods at the end of the twentieth century. The calculated inter-annual variations are similar in magnitude to observations. The 30-year trend in SMB at the end of the twenty-first century is significant. The increase in precipitation on the ice sheets follows closely the Clausius-Clapeyron relation and is the main reason for the increase in the surface mass balance of Antarctica. On Greenland precipitation in the form of snow is gradually starting to decrease and cannot compensate for the increase in ablation. Another factor is the proportionally higher temperature increase on Greenland leading to a larger ablation. It follows that a modest increase in temperature will not be sufficient to compensate for the increase in accumulation, but this will change when temperature increases go beyond any critical limit. Calculations show that such a limit for Greenland might well be passed during this century. For Antarctica this will take much longer and probably well into following centuries.

A medium-resolution wave hindcast study over the Central and Western Mediterranean Sea

The present study is aimed at determining the confidence limits of design wave parameters derived from numerical modeling—for both extremes and operational conditions—over the Central and Western Mediterranean Sea. The paper presents the methodology and results of an extensive validation activity conducted on a chain of medium-resolution third-generation wave models used for hindcast purposes. The stringent requirements of state-of-the-art coastal and offshore engineering applications over this area make the adoption of medium- or high-resolution hindcast wave and wind models almost mandatory because of the complex coastal geometry, bathymetry, and orography that in turn lead to large variations of the design wave parameters even within small regions. The chains of nested meteorological and wave models used in this hindcast study belong to the ETA and WaveWatch III families, respectively. In this study the wind and wave numerical models have been run over the past 20 years, with increasing resolutions of the wave models from 0.2° up to 0.04°. The results presented herein have 0.1° resolution for both wind and wave models. The wave data obtained are compared with available measurements from 14 wave buoys in coastal zones in the Central and Western Mediterranean Sea.

Gain Scheduled Control: Switched Polytopic System Approach

Gain Scheduled Control: Switched Polytopic System Approach

Fault-tolerant A/D converter using analogue voting

Analogue and digital circuits are both prone to failure because of device degradations, transient upsets and large parametric variations. Redundancy techniques, such as N-tuple modular redundancy, have been widely used to correct faulty behaviour of components and achieve high reliability for digital circuits. In this study, the authors propose a redundancy based fault-tolerant methodology for analogue circuits. In particular, the authors focus on highly reliable analogue-to-digital converter, which is a critical component in many mixed-signal systems. The authors methodology employs redundant analogue blocks and chooses the best result using an innovative analogue voter. Simulation results are reported to verify the concepts, measure the system's reliability and trade off reliability against cost and power.

Design method of ideal vehicle models in adaptive steering driver-combined-vehicle systems

The behaviour of combined vehicles is easily affected by the uncertainties of vehicle parameters. It may be very difficult for the drivers to achieve good handling stability. If the behaviour of actual combined vehicles tracks the designed ideal vehicle models, the good handling property can be maintained for the large uncertain variation of vehicle parameters. Then, the authors have proposed the adaptive steering controllers to achieve good handling property. However, in the conventional schemes, just only one ideal vehicle model is designed for various drivers. For each driver, if an adequate ideal vehicle model is selected, the better handling stability can be achieved. In this paper, a new design method to design ideal vehicle models of adaptive steering driver-combined-vehicle systems for various drivers is proposed. Carrying out numerical simulations, it is shown that good handling performance can be achieved when the actual vehicles track the designed ideal vehicle models.

Reproductive biology of female blue shark Prionace glauca in the southeastern Pacific Ocean

An understanding of reproductive biology is important in evaluating the potential impacts of fisheries on shark population dynamics. Reproductive biology of the female blue shark (Prionace glauca) was evaluated using data collected in the Chinese Longline Fishery Scientific Observer Programme in the southeastern Pacific Ocean during July–November 2003 (Trip 1) and February–December 2006 (Trip 2). The fork length of gravid females varied from 170 to 246 cm (mean = 201 cm) in Trip 1 and from 168 to 220 cm (mean = 188 cm) in Trip 2. Gravid size was significantly different among months. The relationship between the proportion of gravid females and female size could be quantified by a logarithmic model. Litter size varied from 13 to 68 (mean 35) and was weakly correlated with maternal size. The sex ratio of captured blue sharks was significantly different from 1:1, while the sex ratio of pups was not significantly different from 1:1. Pup size (combined sexes) ranged from 12 to 39 cm FL, with mean of 27 cm. No significant differences were detected in length distribution and median length between female and male pups. This study suggests that there are large spatial and temporal variations in key reproductive parameters of the blue shark, which should be considered in the assessment and management.

Chemistry of hot springs along the Eastern Lau Spreading Center

The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc. Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc. In 2005, we collected 81 samples of vent water from six hydrothermal fields along the ELSC. The chemistry of these waters varies both within and between vent fields, in response to changes in substrate composition, temperature and pressure, pH, water/rock ratio, and input from magmatic gases and subducted sediment. Hot-spring temperatures range from 229° to 363 °C at the five northernmost fields, with a general decrease to the south that is reversed at the Mariner field. The southernmost field, Vai Lili, emitted water at up to 334 °C in 1989 but had a maximum venting temperature of only 121 °C in 2005, due to waning activity and admixture of bottom seawater into the subseafloor plumbing system. Chloride varies both within fields and from one field to another, from a low of 528 mmol/kg to a high of 656 mmol/kg, and may be enriched by phase separation and/or leaching of Cl from the rock. Concentrations of the soluble elements K, Rb, Cs, and B likewise increase southward as the volcanic substrate becomes more silica-rich, especially on the Valu Fa Ridge. Iodine and δ 7Li increase southward, and δ 11B decreases as B increases, apparently in response to increased input from subducted sediment as the arc is approached. Species that decrease southward as temperature falls are Si, H 2S, Li, Na/Cl, Fe, Mn, and 87Sr/ 86Sr, whereas pH, alkalinity, Ca, and Sr increase. Oxygen isotopes indicate a higher water/rock ratio in the three systems on Valu Fa Ridge, consistent with higher porosity in more felsic volcanic rocks. Vent waters at the Mariner vent field on the Valu Fa Ridge are significantly hotter, more acid and metal-rich, less saline, and richer in dissolved gases and other volatiles, including H 2S, CO 2, and F, than the other vent fields, consistent with input of magmatic gases. The large variations in geologic and geophysical parameters produced by back-arc spreading along the ELSC, which exceed those along mid-ocean ridge spreading axes, produce similar large variations in the composition of vent waters, and thus provide new insights into the processes that control the chemistry of submarine hot springs.

Studying the CO–CO 2 characteristics of SOFC anodes by means of patterned Ni anodes

The high potential of solid oxide fuel cells (SOFC) arises due to the high degree of efficiency and fuel flexibility. However, the elementary kinetic steps of the anodic processes taking place at the boundary of electrolyte–anode–gas are still largely unknown. Patterned Ni anodes on Y 2O 3-stabilized ZrO 2 are regarded as a promising method to determine these kinetics. In analogy to our previous study with patterned Ni anodes for the H 2–H 2O system, this study is systematically devoted to the elementary kinetics of the CO electrochemical oxidation in CO–CO 2 gas mixtures. Data analysis is backed by extensive knowledge on patterned anode stability and dynamics gained during previous studies. The electrochemical characterization is performed for a large parameter variation range ( pCO 2, pCO and T) by electrochemical impedance spectroscopy. Contrary to the characterization in H 2–H 2O atmosphere no slow relaxation processes were observed and the degradation rate is smaller. Changes in parameter dependency over the investigated parameter range indicate different reaction mechanisms as a function of gas composition. Only slightly higher polarization losses are observed for CO oxidation compared to H 2. The comparison of the results from patterned anodes to high-performance Ni/8YSZ cermet anodes employed in anode supported cells yields good agreement.

Uncertainties and optimized sampling in surface roughness characterization

Usage of 3D roughness parameters measurements requires knowledge of uncertainty causes in order to design proper measurement procedures. Even on apparently homogeneous machined surfaces, large local variations in 3D roughness parameters have previously been reported. This paper introduces and tests a concept for optimized sampling based on local-, and global topography analysis, using measurements of the Sa parameter on a large machined component as a practical example. It is shown that more than 40 measurements of Sa may be needed to attain a stable value, but that choice of an appropriate sampling strategy may reduce this requirement considerably. The results point to a possible route to minimize required measurements and contribute to the development of the best-practice when using 3D surface structure metrology.

Challenges for Nanoscale MOSFETs and Emerging Nanoelectronics

Complementary metal-oxide-semiconductor (CMOS) technology scaling has been a main key for continuous progress in silicon-based semiconductor industry over the past three decades. However, as the technology scaling enters nanometer regime, CMOS devices are facing many serious problems such as increased leakage currents, difficulty on increase of on-current, large parameter variations, low reliability and yield, increase in manufacturing cost, and etc. To sustain the historical improvements, various innovations in CMOS materials and device structures have been researched and introduced. In parallel with those researches, various new nanoelectronic devices, so called "Beyond CMOS Devices," are actively being investigated and researched to supplement or possibly replace ultimately scaled conventional CMOS devices. While those nanoelectronic devices offer ultra-high density system integration, they are still in a premature stage having many critical issues such as high variations and deteriorated reliability. The practical realization of those promising technologies requires extensive researches from device to system architecture level. In this paper, the current researches and challenges on nanoelectronics are reviewed and critical tasks are summarized from device level to circuit design/CAD domain to better prepare for the forthcoming technologies.

Extraction ofP11resonances fromπNdata

We show that two ${P}_{11}$ nucleon resonance poles near the $\ensuremath{\pi}\ensuremath{\Delta}$ threshold, obtained in several analyses, are stable against large variations of parameters within a dynamical coupled-channels analysis based on meson-exchange mechanisms. By also performing an analysis based on a model with a bare nucleon state, we find that this two-pole structure is insensitive to the analytic structure of the amplitude in the region below the $\ensuremath{\pi}N$ threshold. Our results are ${M}_{\mathrm{pole}}=({1363}_{\ensuremath{-}6}^{+9}\ensuremath{-}i{79}_{\ensuremath{-}5}^{+3})$ and $({1373}_{\ensuremath{-}10}^{+12}\ensuremath{-}i{114}_{\ensuremath{-}9}^{+14})$ MeV. We also demonstrate that the number of poles in the 1.5-GeV $\ensuremath{\leqslant}W\ensuremath{\leqslant}$ 2-GeV region could be more than one, depending on how the structure of the single-energy solution of SAID is fitted. For three-pole solutions, our best estimated result of a pole near $N(1710)$ listed by Particle Data Group is $({1829}_{\ensuremath{-}65}^{+131}\ensuremath{-}i{192}_{\ensuremath{-}110}^{+88})$ MeV, which is close to the results of several previous analyses. Our results indicate the need for more accurate $\ensuremath{\pi}N$ reaction data in the $W>$ 1.6-GeV region for high-precision resonance extractions.

MO‐EE‐A2‐03: Comparison of Four NTCP Models to Describe Dose‐Response for Radiation‐Induced Optic Neuropathy and Retinopathy

Purpose: To compare four NTCP models to predict dose‐response for the incidence of radiation‐induced optic neuropathy (RION) and retinopathy (RIRP). Method and Materials: Logistic, log‐logistic, Poisson‐based and probit models were used to describe dose‐response. Fits to four data sets were obtained: RION in 101 patients treated twice‐daily (BID) and 172 patients treated once daily (QD), RIRP in 78 BID and 108 QD patients. Doses used in dose‐response analysis were converted to isoeffective dose in 2‐Gy fractions using α/β=1.76 Gy for RION and 2.65 Gy for RIRP. Maximum‐likelihood profile method was used to obtain model parameter values, D50 and γ, and corresponding confidence intervals. Results: Within the dose range bounded by available clinical data, the model predictions were similar. For data sets spanning a broad range of incidence a reasonable consistency between model parameters was observed, however, the log‐logistic model consistently showed larger D50 and shallower normalized slope γ. Specifically, for incidence of RION among patients treated QD, D50 ranged from 94.2 to 104.7 Gy and γ from 0.88 to 1.41. Model parameters for RIRP in the QD group were D50 from 72.2 to 74.0 Gy and γ from 1.51 to 2.16; in the QD group from 72.2 to 74.0 Gy and from 0.84 to 1.20, respectively. A large variation in model parameters was observed for RION in patients treated BID who showed incidence of complications spanning the range up to 20%. D50 ranged from 96.3 to 125.2 Gy and y from 0.80 to 1.56. Conclusion: Log‐logistic model tends to lead to larger D50 and lower γ compared to other models. Statements regarding normal tissue radiosensitivity and steepness of dose‐response based on model parameters should be made carefully as the latter are not only model‐dependent but also sensitive to the range of complication incidence exhibited by clinical data.

SPARE—A Scalable Algorithm for Passive, Structure Preserving, Parameter-Aware Model Order Reduction

This paper describes a flexible and efficient new algorithm for model order reduction of parameterized systems. The method is based on the reformulation of the parameterized system as a perturbation-like parallel interconnection of the nominal transfer function and the nonparameterized transfer function sensitivities with respect to the parameter variations. Such a formulation reveals an explicit dependence on each parameter which is exploited by reducing each component system independently via a standard nonparameterized structure preserving algorithm. Therefore, the resulting smaller size interconnected system retains the structure of the original system with respect to parameter dependence. This allows for better accuracy control, enabling independent adaptive order determination with respect to each parameter and adding flexibility in simulation environments. It is shown that the method is efficiently scalable and preserves relevant system properties such as passivity. The new technique can handle fairly large parameter variations on systems whose outputs exhibit smooth dependence on the parameters, also allowing design space exploration to some degree. Several examples show that besides the added flexibility and control, when compared with competing algorithms, the proposed technique can, in some cases, produce smaller reduced models with potential accuracy gains.

Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol particles. For local and continental polluted aerosols the measurements indicate high aerosol loads. However, measurements associated with the local path indicate enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for continental aerosols, from West directions with less free tropospheric contribution. The largest lidar ratios, of the order of 70 sr, are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values were estimated for different aerosol categories. Scatter plot between lidar ratio values and Ångström exponent values for local and continental polluted aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for continental aerosols with west and northwest directions that follow downward movement when arriving at our site constantly low lidar ratios almost independent of size are found.

A Novel Method for the Diagnosis of the Incipient Faults in Analog Circuits Based on LDA and HMM

Diagnosis of incipient faults for electronic systems, especially for analog circuits, is very important, yet very difficult. The methods reported in the literature are only effective on hard faults, i.e., short-circuit or open-circuit of the components. For a soft fault, the fault can only be diagnosed under the occurrence of large variation of component parameters. In this paper, a novel method based on linear discriminant analysis (LDA) and hidden Markov model (HMM) is proposed for the diagnosis of incipient faults in analog circuits. Numerical simulations show that the proposed method can significantly improve the recognition performance. First, to include more fault information, three kinds of original feature vectors, i.e., voltage, autoregression-moving average (ARMA), and wavelet, are extracted from the analog circuits. Subsequently, LDA is used to reduce the dimensions of the original feature vectors and remove their redundancy, and thus, the processed feature vectors are obtained. The LDA is further used to project three kinds of the processed feature vectors together, to obtain the hybrid feature vectors. Finally, the hybrid feature vectors are used to form the observation sequences, which are sent to HMM to accomplish the diagnosis of the incipient faults. The performance of the proposed method is tested, and it indicates that the method has better recognition capability than the popularly used backpropagation (BP) network.

Upper mantle deformation beneath the North American–Pacific plate boundary in California from SKS splitting

In order to constrain the vertical and lateral extent of deformation and the interactions between lithosphere and asthenosphere in a context of a transpressional plate boundary, we performed teleseismic shear wave splitting measurements for 65 permanent and temporary broadband stations in central California. We present evidence for the presence of two anisotropic domains: (1) one with clear E–W trending fast directions and delay times in the range 1.5 to 2.0 s and (2) the other closely associated with the San Andreas Fault system with large azimuthal variations of the splitting parameters that can be modeled by two anisotropic layers. The upper of the two layers provides fast directions close to the strike of the main Californian faults and averaged delay times of 0.7 s; the lower layers show E–W directions and delay times in the range 1.5 to 2.5 s and thus can be compared to what is observed in stations that require a single layer. We propose the E–W trending anisotropic layer to be a 150 to 200 km thick asthenospheric layer explained by the shearing associated with the absolute plate motion of the North American lithosphere. The shallower anisotropic layer ought to be related to the dynamics of the San Andreas Fault system and thus characterized by a vertical foliation with lineation parallel to the strike of the faults localized in the lithosphere. We also propose that the anisotropic layer associated with each fault of the San Andreas Fault system is about 40 km wide at the base of the lithosphere.

Probabilistic study of the strength of steel scaffold systems

Steel support scaffold systems are characterised by the large variations of geometric and mechanical parameters, notably joint stiffness, initial geometric imperfections, yield stress and load eccentricity. This paper investigates the effects of these uncertainties on the ultimate strength of multi-storey steel support scaffold frames through a rational statistical framework and a second-order inelastic finite element analysis (advanced analysis). A series of stick type steel scaffold systems with cuplok joints were studied. The statistical data for the basic random variables were acquired through field measurements and laboratory tests. By comparison to load tests, the bias and variability of advanced analysis were estimated. The basic random variables and the model uncertainty are propagated through Monte Carlo simulation to obtain the statistics of system strength. The first-order reliability method is then employed to estimate the reliability of steel scaffold systems designed by advanced analysis.

Uncertainty and sensitivity analysis of biokinetic models for radiopharmaceuticals used in nuclear medicine

Mathematical models for kinetics of radiopharmaceuticals in humans were developed and are used to estimate the radiation absorbed dose for patients in nuclear medicine by the International Commission on Radiological Protection and the Medical Internal Radiation Dose (MIRD) Committee. However, due to the fact that the residence times used were derived from different subjects, partially even with different ethnic backgrounds, a large variation in the model parameters propagates to a high uncertainty of the dose estimation. In this work, a method was developed for analysing the uncertainty and sensitivity of biokinetic models that are used to calculate the residence times. The biokinetic model of (18)F-FDG (FDG) developed by the MIRD Committee was analysed by this developed method. The sources of uncertainty of all model parameters were evaluated based on the experiments. The Latin hypercube sampling technique was used to sample the parameters for model input. Kinetic modelling of FDG in humans was performed. Sensitivity of model parameters was indicated by combining the model input and output, using regression and partial correlation analysis. The transfer rate parameter of plasma to other tissue fast is the parameter with the greatest influence on the residence time of plasma. Optimisation of biokinetic data acquisition in the clinical practice by exploitation of the sensitivity of model parameters obtained in this study is discussed.

High-Density, Low Temperature Ignited Operations in FFHR

New control method of the unstable operating point in the helical reactor FFHR makes the ignition study on the high density and low temperature operation possible. Proportional-integral-derivative (PID) control of the fueling with the error of the fusion power of e'DT(Pf) = −(Pfo − Pf) can stabilize the unstable operating point. Here Pfo(t) is the fusion power preset value and Pf(t) is the measured fusion power. Although the large parameter variation would lose its control due to the inherently unstable nature, it is possible to control the ignited operation by pellet injection with the pellet size between 12 mm and 16 mm. Unstable ignited operation is robust against disturbances such as impurity increments by fueling feedback alone. However, if the heating power feedback control is added, robustness to the disturbances is improved, and an operational regime with respect to the integration time and derivative time is expanded.

Neural network-based robust control for hypersonic flight vehicle with uncertainty modelling

Aerodynamic parameters of hypersonic flight vehicle are extremely sensitive to flight condition for its high flight velocity. These usually make the model parameters vary in large range and normal robust control method invalid. This paper evaluates the model uncertainties by traversing the variation values of the flight states. Neural network control is introduced to eliminate the large variations of the model parameters and neural network-based robust controller is designed to realise the tracking control of hypersonic flight vehicle. The simulation results demonstrate the validity of the proposed approach.