Laser-Based Ultrasonics on Gr/Epoxy Composite a Systems Analysis

Critical issues are examined in the application of laser generation and detection of ultrasound to the inspection of large area air-frame composites. Among these issues are surface roughness, signal-to-noise ratio, insensitivity to the path length between the part and detector, and wide-band versus narrow-band generation. Supporting experiments are reported on broad-band and narrow-band generation in Gr/Epoxy panels and angular reflectance measurements on painted and unpainted Gr/Epoxy. On the basis of these measurements, a laser-in/laser-out systems analysis is carried out for a 10 mm diameter delamination about 1 cm deep. The analysis assumes that a Spherical Fabry-Perot interferometer is used for detection and a 10 nsec laser pulse with a peak power of 13 MW/cm2 for generation. The estimates indicate a S/N ≈ 20 dB for a detection probe laser power of about 400 mW.</p

Noncontact Material Testing Using Low-Energy Optical Generation and Detection of Acoustic Pulses

We will discuss preliminary results on the use of a low-energy laser and a sensitive laser interferometer for noncontact material testing of metals and nonmetals. There have been numerous reports [1–12] on the use of lasers to generate acoustic signals, but this is the first use of a relatively low-energy tunable laser source and improved interferometer to measure acoustic waveforms in both metals and nonmetals [13]. The use of a laser interferometer for the noncontact detection of acoustic pulses has also been reported previously [14–20], but we now report the use of a sensitive “non-Michelson” interferometer with increased signal-to-noise capabilities. The combination of these features allows noncontact, low-energy optical generation and optical detection in a variety of materials, in potentially hostile environments, and provides accurate accoustic waveforms which can be used to characterize specimens. These results, therefore, begin to demonstrate the feasibility of a portable (entirely) optical system for the nondestructive evaluation of materials

A Preliminary Study on The Thought of Maritime Defence in Modern China and Japan: with special reference to Wei Yuan [1794-1857], Xu Jiyu [1795-1873], Hayashi Shihei [1738-1793] and Sakuma Shozan [1811-1864]

Lasers offer a non-contact method for generating ultrasound. The main advantages are that specimen can be scanned more easily and the complications of a coupling layer or liquid are eliminated. Also, more accurate velocity measurements can be obtained using lasers and for holographic generation, higher frequency coherent waves can be obtained. Lasers have been used to generate ultrasonic waves in many configurations, including the generation of bulk longitudinal and shear waves, Rayleigh waves along solid surfaces, and Lamb modes in solid layers. General reviews of laser generation techniques can be found in [1] and [2]

Association between simple anthropometric indices and cardiovascular risk factors

OBJECTIVE: To identify which of the three simple anthropometric indices, body mass index (BMI), waist-to-hip ratio (WHR) and waist circumference (WC), best predicts cardiovascular risk factors, and to determine if the association between the anthropometric indices and cardiovascular risk factors varies with gender. DESIGN AND METHODOLOGY: A cross-sectional population-based survey was carried out during 1995-1996. One thousand and ten Chinese people (500 men and 510 women) aged 25-74y were recruited as subjects for the study. Metabolic profiles and anthropometric indices were measured. RESULTS: Partial correlation and co-variance analyses showed that WC exhibited the highest degree of association with almost all of the studied metabolic profiles for both men and women. We observed significant gender differences in the association between central or general obesity with cardiovascular risk factors. BMI had an independent and significant association with metabolic risks in men, but not in women, whereas WHR was more strongly correlated with metabolic risks for women than for men. Logistic regression analysis further confirmed the magnitude of the association between the obesity indices and metabolic risks. Among the studied metabolic variables, serum insulin showed the highest degree of association with the obesity indices, followed by plasma glucose, triglyceride, HDL and blood pressure. Total cholesterol and LDL-cholesterol had a small but significant correlation with obesity. No threshold values in the relation between either the anthropometric indices and metabolic values, or with hypertension, diabetes and dislipidemia were observed. CONCLUSION: The association of central or general obesity and metabolic syndrome varied with gender. In addition, the useful anthropometric predictors for cardiovascular risk factors were BMI and WC for men, and WC and WHR for women.link_to_subscribed_fulltex

Supporting ranking pattern-based aggregate queries in sequence data cubes

Sequence data processing has been studied extensively in the literature. In recent years, the warehousing and online-analytical processing (OLAP) of archived sequence data have received growing attentions. In particular, the concept of sequence OLAP is recently proposed with the objective of evaluating various kinds of so-called Pattern-Based Aggregate (PBA) queries so that various kinds of data analytical tasks on sequence data can be carried out efficiently. This paper studies the evaluation of ranking PBA queries, which rank the results of PBA queries and return only the top-ranked ones to users. We discuss how ranking PBA queries drastically improve the usability of S-OLAP systems and present techniques that can evaluate various kinds of ranking PBA queries efficiently. Copyright 2009 ACM.link_to_OA_fulltex