Asymptotic distributions for weighted estimators of the offspring mean in a branching process

It is known that conditional least squares estimator (CLSE) of the offspring mean for the process with a stationary immigration is not asymptotically normal. In the paper, we demonstrate that for the process with non-stationary immigration it may have a normal limit distribution. Considering a discrete time branching process Z(n) with time-dependent immigration, whose mean and variance vary regularly with nonnegative exponents α and β, respectively, we show that 1+2α is the threshold for asymptotic normality of the estimator. It will be proved that if β<1+2α, the estimator is asymptotically normal with two different normalizing factors, and if β>1+2α its limiting distribution is not normal, but can be expressed in terms of certain functionals of the time-changed Wiener process. When β=1+2α, the limiting distribution depends on the behavior of the slowly varying parts of the mean and variance. We derive all possible limit distributions of the weighted CLSE based on observations {Z(r+1),Z(r+2),…,Z(n)} as n→∞ and r=[n ε], 0≤ε<1. Conditions guaranteeing the strong consistency of the proposed estimator will be derived.     

A dimension reduction approach for conditional Kaplan–Meier estimators

Many quantities of interest in survival analysis are smooth, closed-form functionals of the law of the observations. For instance, the conditional law of a lifetime of interest under random right censoring, and the conditional probability of being cured. In such cases, one can easily derive nonparametric estimators for the quantities of interest by plugging-into the functional the nonparametric estimators of the law of the observations. However, with multivariate covariates, the nonparametric estimation suffers from the curse of dimensionality. Here, a new dimension reduction approach for survival analysis is proposed and investigated in the right-censored lifetime case. First, we consider a single-index hypothesis on the conditional law of the observations and propose a \(\sqrt{n}-\)asymptotically normal semiparametric estimator. Next, we apply the smooth functionals to this estimator. This results in semiparametric estimators of the quantities of interest that avoid the curse of dimensionality. Confidence regions for the index and the functional of interest are built by bootstrap. The new methodology allows to test the dimension reduction assumption, can be extended to other dimension reduction methods and can be applied to closed-form functionals of more general censoring mechanisms.     

Analysis of load–strain models for RC square columns confined with CFRP

This article presents the comparison between 6 theoretical models of axially confined concrete columns with the experimental results of 7 tested columns of different authors. This study analysed the accuracy of 6 different confinement models for square columns taking into account the results of experimental tests on 7 RC columns confined with CFRP sheets with different dimensions and carried out by different authors. The profile of curves, the peak/failure values, the stress–strain and axial–to–lateral relations were studied to conclude which models show the best correlation with the experimental test results. Quantification of this deviation was carried out for key parameters. Some models predicted peak values with reasonable accuracy – Manfredi & Realfonzo, Campione & Miraglia, Lam & Teng, Pellegrino & Modena – although for the whole load–strain behaviour only the model of Faustino, Chastre & Paula seemed to be reasonably accurate in most cases.     

Fabrication of Cryogenic Readout Circuits with n-type GaAs-JFETs for Low Temperature Detectors

We present the design and fabrication of cryogenic readout integrated circuits (ROICs) for Superconducting Tunneling Junctions using the SONY n-type GaAs-JFETs, which have good current-voltage characteristics and low noise performance even at <1 K. In order to fabricate the ROICs, we have designed simple GaAs-JFET amplifiers based on the measurement results of the GaAs-JFETs at <4.2 K: source follower amplifier, common source amplifier, and two types of cascode amplifiers. The obtainable gain of the cascode active load amplifiers is >100. These amplifiers were fabricated with the other circuit elements as an integrated circuit. We also show initial test results of the cascode active load amplifier.     

Asymptotic behavior of robust estimators in partially linear models with missing responses: the effect of estimating the missing probability on the simplified marginal estimators

In this paper, we consider a semiparametric partially linear regression model where missing data occur in the response. We derive the asymptotic behavior of the robust estimators for the regression parameter and of the weighted simplified location estimator introduced in Bianco et al. (Comput. Stat. Data Anal. 54:546–564, 2010a). For the latter, consistency results and the asymptotic distribution are derived when the missing probability is known and also when it is estimated.     

Reference Bayesian methods for recapture models with heterogeneity

In the context of capture–recapture experiments heterogeneous capture probabilities are often perceived as one of the most challenging features to be incorporated in statistical models. In this paper we propose within a Bayesian framework a new modeling strategy for inference on the unknown population size in the presence of heterogeneity of subject characteristics. Our approach is attractive in that parameters are easily interpretable. Moreover, no parametric distributional assumptions are imposed on the latent distribution of individual heterogeneous propensities to be captured. Bayesian inference based on marginal likelihood by-passes some common identifiability issues, and a formal default prior distribution can be derived. Alternative default prior choices are considered and compared. Performance of our formal default approach is favorably evaluated with two real data sets and with a small simulation study.     

Large complete bandgaps in a two-dimensional square photonic crystal with isolated single-atom dielectric rods in air

It is well known that the square lattice of isolated single-atom dielectric rods in air does not give rise to complete bandgaps even when asymmetry is introduced to lift some degeneracy. However, in this paper, a new kind of two-dimensional square photonic crystal with isolated single-atom dielectric rods in air formed by holographic lithography is proposed, and the relation between their photonic bandgap properties and their specific holographic design are systematically analyzed. In addition to the large complete relative bandgap, namely 9.68% gap/midgap ratio for the dielectric constant contrast of 13.6:1, this structure has very large tolerance on the system parameters and fabrication conditions. This fact can greatly relax the experimental requirements. This work may demonstrate the unique feature and advantages of photonic crystals made by the holographic method and provide a guideline for their design and fabrication.     

A phase-field model for simulating the growth of αsideplates with branching in titanium alloys

<正>In recent years, titanium and titanium alloys are widely used in the fields of aerospace, oceans, etc. due to their high strength to weight ratio, good toughness and excellent corrosion resistance[1]. Various microstructures and mechanical properties can be obtained simply by varying the thermomechanical processing or heat treatment. As an example, the Widmanst?tten structure may possess good tensile strength, fracture toughness,     

Optimal age replacement scheduling for a random work system with random lead time

System maintenance and spare parts are two closely related logistics activities since maintenance generates the demand for spare parts. Most studies on integrated models of preventive replacement and inventory of spare parts have focused on age replacement scheduling, while random replacement policy, which is sensible and necessary in practice, is rarely discussed and applied. The purpose of this paper is to present a generalised age replacement policy for a system which works at random time and considers random lead time for replacement delivery. To model an imperfect maintenance action, we consider that the system undergoes minimal repairs at minor failures and corrective replacements at catastrophic failures. Before catastrophic failures, the system is replaced preventively at age T or at the completion of a working time, whichever occurs first. The main objective is to determine an optimal schedule of age replacement that minimises the mean cost rate function of the system in a finite time horizon. The existence and uniqueness of optimal replacement policy are derived analytically and computed numerically. It can be seen that the proposed model is a generalisation of the previous works in maintenance theory.     

Boundary Integral Equation for Eddy-Current Problems with Dirichlet Boundary Condition

A boundary integral equation (BIE) is developed for the eddy-current (EC) problems with Dirichlet boundary condition by considering the difference between the field without cracks and the one with cracks. Once the field and its normal derivative are given for the structure in the absence of cracks, normal derivative of the scattered field on the surface can be calculated by solving this integral equation numerically. For infinite-domain problems, this equation is more efficient than the conventional BIE due to a smaller computational region needed. Four kinds of two-dimensional EC problems have been solved using this integral equation. The surface impedance for different cases is presented in this paper. Numerical results are compared with analytical solutions and published numerical results. There are good agreements between them. Also, this concept can be extended to three-dimensional problems with other boundary conditions.     

Large Bolometer Arrays with Superconducting NbSi Sensors for Future Space Experiments

New techniques in microelectronics allow to build large arrays of bolometers filling the focal plane of submillimeter and millimeter telescopes. The expected sensitivity increase is the key for the next generation of space experiments in this wavelength range. Superconducting bolometers offer currently the best prospects in terms of sensitivity and multiplexed readout. We present here the developments led in France based on NbSi alloy thermometers. The manufacturing process of a 23 pixel array and the test setup are described.      

Optimal confidence intervals on the variation for operators and gauge in manufacturing process with repeated measurements

It is necessary to measure the attributes of the parts in any manufacturing process. It is also important to monitor measurement system in the manufacturing process because repeated measurements of the attributes include variability as well as target value. This paper considers variabilities due to repeated measurements, operators, and gauge in a measurement system. The measurement system is statistically modeled as a two-factor mixed model with one covariate and interaction. That is, this model employs J operators randomly chosen to conduct measurements on I randomly selected parts from a manufacturing process. In this experiment each operator measures each part K times. This paper aims to provide engineering practitioners with statistically optimal confidence intervals on the variation due to operators and gauge resulted from a measurement system statistically modeled. The optimal confidence intervals are based on a moderate large sample method (MLS) and a generalized p-value method (GEN). The confidence intervals proposed can be useful tools to determine whether a manufacturing process is adequate for monitoring a measurement system.     

Compatible priors for Bayesian model comparison with an application to the Hardy–Weinberg equilibrium model

Suppose we entertain Bayesian inference under a collection of models. This requires assigning a corresponding collection of prior distributions, one for each model’s parameter space. In this paper we address the issue of relating priors across models, and provide both a conceptual and a pragmatic justification for this task. Specifically, we consider the notion of “compatible” priors across models, and discuss and compare several strategies to construct such distributions. To explicate the issues involved, we refer to a specific problem, namely, testing the Hardy–Weinberg Equilibrium model, for which we provide a detailed analysis using Bayes factors.     

Development of High Count-Rate Digital Processing System with SpaceWire for TES-Calorimeter Array

A digital processing system for a TES microcalorimeter array is being developed based on “SpaceWire” interface. In this system, we introduced a trigger logic which can handle double-pulse events due to high count rate in future X-ray missions and several application on the ground experiments. The detailed design and performance of this system is described.      

Calibration System with Modulated Polarization Source for Superconducting Detectors at 0.1 K

We developed a calibration system with a modulated polarization source for superconducting detectors at the 0.1-K stage in a dilution cooler. Our target application for this system is detector calibration for observations of the cosmic microwave background polarization. For this application, the calibration system is required to generate a well-characterized polarization signal in a wide frequency range; e.g., 20–300 GHz. The calibration system is attached at the bottom of the 0.1-K stage. Radio absorbers, which are attached to the inner wall of a cylindrical metal shield, emit unpolarized black-body radiation (4.5 K). The radiation reflects off an aluminum mirror at 120 K, which induces a linearly polarized component because of the finite emissivity of the mirror; the magnitude of the polarization is 60 mK in this configuration. The axis of polarization can be varied by rotation of the mirror. Therefore, the detectors measure the modulated polarization; however, unpolarized radiation into the detector is maintained constant. We succeeded in cooling the system properly. The sample stage for setting the detector achieved a temperature below 0.1 K under the 5 K load condition (some of the radiation from the absorbers and the mirror emission, 0.5 K). High-frequency components of emission from the mirror are shielded by using two thermal filters: polytetrafluoroethylene and nylon 66.     

Optimising two dwell point policies for AS/RSs with input and output point at opposite ends of the aisle

Automated storage and retrieval systems (AS/RSs) are widely used for storing and retrieving products in all types of warehouses. Dwell point policy is a vital control policy that can greatly affect the performance of AS/RSs. In this paper, we study dwell point policies in AS/RSs with input and output stations at opposite ends of the aisle. We first propose two dwell point policies. We find that five existing dwell point policies in the literature are special cases of exactly one of our policies. We then develop expected travel time models for the proposed policies, solve these models with the objective of minimising expected travel time, and obtain closed-form solutions for the optimal dwell location(s). We prove that one proposed policy dominates the other in terms of expected travel time. Numerical experiments are performed to quantify the percentage gap of expected travel time between the proposed policies and policies in the literature. We find that, in some situations, the better proposed policy can achieve up to 8%–10% reduction in expected travel time in comparison with the best literature policy. A real-data case study validates that these situations arise with high probability in typical daily warehouse operations.     

An efficient space–time based simulation approach of wind velocity field with embedded conditional interpolation for unevenly spaced locations

The classical spectral representation method (SRM) has been extensively used in the simulation of multivariate stationary Gaussian random processes. Due to the application of fast Fourier transform (FFT), the simulation is usually efficient. However, for processes with a large number of simulation points, it becomes necessary to enhance the simulation efficiency. One example is the wind velocity field along a large-span bridge, where hundreds of wind velocity fluctuations are required. In the case of bridges built over a homogeneous terrain such as coastal area or flat plain, the wind velocity field can be modeled as a multivariate homogeneous random process i.e., the auto power spectral densities (PSDs) at evenly-spaced simulation points are same and the cross PSD is a function of separation distance between two simulation points. Furthermore, in some applications, additional simulation points need to be included to a set of uniformly distributed points in order to make the wind velocity field consistent to the structural dynamic analysis requirement.In this paper, a hybrid approach of space–time random-field based SRM and proper orthogonal decomposition (POD)-based interpolation is developed for simulating the above wind velocity process. In this approach, the random-field based SRM is used to simulate the multivariate homogeneous random process composed of a set of uniformly distributed simulation locations while POD-based interpolation is used to conditionally generate the wind velocities at a few unevenly distributed points using the previously simulated wind velocities. The idea of the former is based on transforming the simulation of the homogeneous random process into that of the corresponding space–time random field where the phase angle is assumed to be zero and the coherence function must be an even function in terms of separation distance. Through this procedure, customary requirement for spectral matrix decomposition is eliminated and application of two dimensional FFT can improve the simulation efficiency dramatically. The shortcomings of this method include a slight approximation regarding the simulated sample and the non-ergodicity for the correlation function. The numerical example of a homogeneous wind velocity field along a bridge deck shows that the proposed random field-based method is very efficient in terms of accuracy and efficiency when the number of simulation locations is large and the POD-based interpolation also has good performance.     

Simulation of Transient Response of Ir-TES for Position-Sensitive TES with Waveform Domain Multiplexing

We are developing a new x-ray microcalorimeter based on a superconducting transition edge sensor (TES) as an imaging sensor. Our measurement shows unique waveforms which we consider as an expression of thermal nonuniformity of TES films. This arises from the different thermal responses, so that response signal shapes would vary according to the position of the incident x-ray. This position dependency deteriorate the measured energy resolution, but with appropriate waveform analysis, this would be useful for imaging device. For more inspection, we have developed a simulation code which enables a dynamic simulation to obtain a transient response of the TES by finite differential method. Temperature and electric current distributions are calculated. As a result, we successfully obtained waveform signals. The calculated signal waveforms have similar characteristics to the measured signals. This simulation visualized the transition state of the device and will help to design better detector.      

A new spanning tree-based genetic algorithm for the design of multi-stage supply chain networks with nonlinear transportation costs

The design of configuration and the transportation planning are crucial issues to the effectiveness of multi-stage supply chain networks. The decision makers are interested in the determination the optimal locations of the hubs and the optimal transportation routes to minimize the total costs incurred in the whole system. One may formulate this problem as a 0-1 mixed integer non-linear program though commercial packages are not able to efficiently solve this problem due to its complexity. This study proposes a new spanning tree-based Genetic Algorithm (GA) using determinant encoding for solving this problem. Also, we employ an efficient heuristic that fixes illegal spanning trees existing in the chromosomes obtained from the evolutionary process of the proposed GA. Our numerical experiments demonstrate that the proposed GA outperforms the other previously published GA in the solution quality and convergence rate.