A Modified Nonparametric Prewhitened Covariance Estimator

Abstract. This paper proposes a fully modified version of the spectral matrix estimator (and the long‐run variance estimator as a special case) proposed originally by Xiao and Linton [Journal of Time Series Analysis (2002) Vol. 23, pp. 215–250], and derives its asymptotic results. A striking feature of the modified spectral matrix estimator is to achieve the convergence rate of O(T ^?8/9) in the mean squared error (MSE), which is usually achieved under the fourth‐order spectral window. However, this estimator does not sacrifice the positive definiteness of the resulting estimate for the rate improvement; it is Hermitian and positive definite in finite samples by construction. The faster convergence rate is established by a multiplicative bias correction of the crude spectral estimator under the second‐order spectral window. The approximations to some sensible definitions of the MSE of the estimator and the bandwidths that minimize the asymptotic MSEs are also derived. Monte Carlo results indicate that for a wide variety of processes the modified spectral matrix estimator reduces the bias without inflating the variance and thus improves the MSE, compared with the crude, bias‐uncorrected estimator.     

Gigacycle fatigue data sheets for advanced engineering materials

Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 10¹⁰ cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 10⁸ cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete. r 2007 Published by Elsevier Ltd.     

Web-top robotics

This paper deals with the use of the World Wide Web (WWW) as a platform for building robotic systems. We revisit the anatomy of the WWW system together with CORBA, the standard object request broker architecture, and show how to map robotic systems on it. We also review the current status of several meta-computing infrastructures for distributed computing on a wide-area network. Several implementation results are also shown     

Gigacycle Fatigue Properties of Hydrogen-Charged JIS-SCM440 Low-Alloy Steel Under Ultrasonic Fatigue Testing

Gigacycle fatigue tests were conducted on hydrogen-charged low-alloy steel. In this study, high- and low-strength specimens were prepared to investigate the effects of hydrogen on internal and surface fractures, respectively. The fatigue tests were conducted mainly by ultrasonic fatigue testing at 20 kHz and additionally by conventional servohydraulic fatigue testing at 50 Hz. All high-strength specimens revealed internal fractures. The fatigue strength of the hydrogen-charged specimens was much lower than that of the uncharged specimens. In the low-strength specimens, the uncharged specimens revealed surface fractures in the short-life regions in addition to internal fractures in the long-life regions. However, the hydrogen-charged specimens revealed internal fractures only that were combined with a much lower fatigue strength. The difference in fracture surfaces was small between the hydrogen-charged and the uncharged specimens, whereas the optically dark areas of the hydrogen-charged specimens seemed smaller than those of the uncharged specimens.     

Nonparametric multiplicative bias correction for kernel-type density estimation on the unit interval

This paper demonstrates that two classes of multiplicative bias correction (MBC) techniques, originally proposed for density estimation using symmetric second-order kernels by Terrell and Scott (1980) and Jones et al. (1995), can be applied to density estimation using the beta and modified beta kernels. It is shown that, under sufficient smoothness of the true density, both MBC techniques reduce the order of magnitude in bias, whereas the order of magnitude in variance remains unchanged. Accordingly, mean squared errors of these MBC estimators achieve a faster convergence rate of O(n^−8/9) for the interior part, when best implemented. Furthermore, the estimators always generate nonnegative density estimates by construction. To implement the MBC estimators, a plug-in smoothing parameter choice method is proposed. Monte Carlo simulations indicate good finite sample performance of the estimators.     

Structure and expression of a cyst specific protein of Acanthamoeba castellanii

OBJECTIVES: To define the lesion-specific role of biplane transesophageal echocardiography in children with left ventricular outflow tract obstructive lesions, the diagnostic accuracy of transthoracic and transesophageal images were compared, and the impact of transesophageal echocardiography on perioperative management was evaluated. BACKGROUND: The reported high postoperative recurrence of left ventricular outflow tract obstructive lesion can be due to its incomplete surgical relief. A full preoperative definition of the lesions would aid in better surgical outcome. The complexity and spectrum of such lesions provide opportunity to evaluate the role of a recently available biplane transesophageal pediatric probe in its diagnosis and surgical management. METHODS: In 16 consecutive patients (11 male patients) with left ventricular outflow tract obstructive lesions and with a mean age of 7.9 +/- 5.7 years (range 0.25 to 20.0 years) and a mean weight of 29 +/- 19 kg (range 4 to 66 kg), the morphologic and hemodynamic findings of standard preoperative transthoracic and intraoperative biplane transesophageal echocardiography were compared with surgical and cardiac catheterization findings (in seven patients) for the diagnostic accuracy and impact on the surgical management of the lesions. RESULTS: Based on the levels of agreement, transesophageal echocardiography demonstrated higher diagnostic sensitivity (chi-squared analysis = 13.4 < 0.001) to the presence and extent of associated lesions (septal hypertrophy, multiple fibromuscular insertions, involvement of aortic and mitral valves not revealed by transthoracic imaging) and trend toward higher sensitivity (Fisher's exact p = 0.17) to primary morphologic diagnoses (abnormal chordal attachments, prolapsed aortic cusp, and tunnel-like outflow tract obstructive lesions missed by transthoracic imaging). As a result of these factors, intraoperative transesophageal imaging changed the surgical plan in 25% of the patients and modified it in an additional 25% of the patients. CONCLUSIONS: Transesophageal echocardiography can be a reliable diagnostic tool and has an important role in the surgical management of left ventricular outflow tract lesions in children.     

Walking biped humanoids that perform manual labour

The Humanoid Robotics Project of the Ministry of Economy, Trade and Industry of Japan realized that biped humanoid robots can perform manual labour. The project developed humanoid robot platforms, consisting of humanoid robot hardware and a package of fundamental software, and explored applications of humanoid robots on them. The applications include maintenance tasks of industrial plants, teleoperation of industrial vehicles, cooperative tasks with a human, guarding the home and office and the care of patients in beds.     

Gigacycle fatigue data sheets for advanced engineering materials

Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 10¹⁰ cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 10⁸ cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete.