Comparison of Heating Protocols for Detection of Disbonds in Lap Joints

With the increased concern for the safety and reliability of aging aircraft, new nondestructive techniques are being sought for detecting and characterizing defects in these structures. These techniques must be both reliable and economical to impact the current safety of the fleet. To meet both of these requirements, more focus is being placed on large area inspection techniques. These offer the possibility for greatly reduced inspection times as compared to current point measurement techniques

Thermographie Imaging of Defects in Anisotropie Composites

Composite materials are of increasing interest to the aerospace industry as a result of their weight versus performance characteristics. One of the disadvantages of composites is the high cost of fabrication and post inspection with conventional ultrasonic scanning systems. The high cost of inspection is driven by the need for scanning systems which can follow large curve surfaces. Additionally, either large water tanks or water squirters are required to couple the ultrasonics into the part. Thermographic techniques offer significant advantages over conventional ultrasonics by not requiring physical coupling between the part and sensor. The thermographic system can easily inspect large curved surface without requiring a surface following scanner. However, implementation of Thermal Nondestructive Evaluations (TNDE) for flaw detection in composite materials and structures requires determining its limit

Dynamic Dielectric Analysis for Nondestructive Cure Monitoring and Process Control

Dynamic dielectric analysis (DDA) is an instrumental means for quantitative material evaluation and closed loop “smart” cure cycle control. DDA is particularly important to process control because it is one of only a few experimental techniques for conveniently studying the cure process continuously, that is, to examine the cure chemistry throughout the process of going from a monomeric liquid of varying viscosity to a crosslinked, insoluble, high temperature solid [1–3]. The key for achieving this goal is to relate the chemistry of the cure process to the dielectric properties of the polymer system by correlating time, temperature and frequency dependent dielectric measurements with other chemical characterization methods.</p

Insect Pollinated Crops, Insect Pollinators and US Agriculture: Trend Analysis of Aggregate Data for the Period 1992–2009

In the US, the cultivated area (hectares) and production (tonnes) of crops that require or benefit from insect pollination (directly dependent crops: apples, almonds, blueberries, cucurbits, etc.) increased from 1992, the first year in this study, through 1999 and continued near those levels through 2009; aggregate yield (tonnes/hectare) remained unchanged. The value of directly dependent crops attributed to all insect pollination (2009 USD) decreased from $14.29 billion in 1996, the first year for value data in this study, to$10.69 billion in 2001, but increased thereafter, reaching $15.12 billion by 2009. The values attributed to honey bees and non-Apis pollinators followed similar patterns, reaching$11.68 billion and $3.44 billion, respectively, by 2009. The cultivated area of crops grown from seeds resulting from insect pollination (indirectly dependent crops: legume hays, carrots, onions, etc.) was stable from 1992 through 1999, but has since declined. Production of those crops also declined, albeit not as rapidly as the decline in cultivated area; this asymmetry was due to increases in aggregate yield. The value of indirectly dependent crops attributed to insect pollination declined from$15.45 billion in 1996 to $12.00 billion in 2004, but has since trended upward. The value of indirectly dependent crops attributed to honey bees and non-Apis pollinators, exclusive of alfalfa leafcutter bees, has declined since 1996 to$5.39 billion and $1.15 billion, respectively in 2009. The value of alfalfa hay attributed to alfalfa leafcutter bees ranged between$4.99 and $7.04 billion. Trend analysis demonstrates that US producers have a continued and significant need for insect pollinators and that a diminution in managed or wild pollinator populations could seriously threaten the continued production of insect pollinated crops and crops grown from seeds resulting from insect pollination

The Intra-Asian Networks: Japan and Hong Kong in the Nineteenth-Century

Thermal Nondestructive Testing (TNDT) is an increasingly common technique for detecting delaminations in structures[l–7]. Typically, TNDT uses radiative heaters such as flash or quartz lamps to heat the specimen. Before during and after radiative heating, an infrared imager measures the surface temperature. Since this process is a noncontacting and imaging method, it has several advantages over conventional contacting techniques. It is able to rapidly inspect a square meter of structure in minutes. It also is easy to inspect curve surfaces. A principle disadvantage is its lack of sensitivity to delaminations at depths greater than 1/2 the thickness of the structure

A new polysaccharide from nerium indicum elicits neuroprotection against beta-amyloid peptides-induced apoptosis

Conference Theme: Meeting the Challenges of an Aging Populatio

Use of Marginal Oscillator for Acoustic Monitoring of Curing of Epoxy Resin

The attenuation and velocity of ultrasound in epoxy resins have been shown to provide a reliable method of determining the degree of cure of the resin. Most authors have used broadband techniques for measuring velocity of a resin. While broadband measurements inherently provide more information than narrowband, difficulties in achieving sufficient bandwidth to clearly identify echoes of interest has led to the application of digital filters to separate the individual echoes. In this work, a measurement system is described which uses the resin as a narrowband acoustic resonator which is placed in the feedback loop of an amplifier. Using gain control, the system is allowed to marginally oscillate. The frequency of oscillation depends on the velocity of sound in the resin, while the gain necessary to maintain stable oscillations depends on the attenuation of the resin. The use of a narrowband resonant technique results in a measurement system which is accurate, stable, and may be produced at reasonable cost

The Mediterranean benthic herbivores show diverse responses to extreme storm disturbances

Catastrophic storms have been observed to be one of the major elements in shaping the standing structure of marine benthic ecosystems. Yet, little is known about the effect of catastrophic storms on ecosystem processes. Specifically, herbivory is the main control mechanism of macrophyte communities in the Mediterranean, with two main key herbivores: the sea urchin Paracentrotus lividus and the fish Sarpa salpa. Consequently, the effects of extreme storm events on these two herbivores (at the population level and on their behaviour) may be critical for the functioning of the ecosystem. With the aim of filling this gap, we took advantage of two parallel studies that were conducted before, during and after an unexpected catastrophic storm event. Specifically, fish and sea urchin abundance were assessed before and after the storm in monitored fixed areas (one site for sea urchin assessment and 3 sites for fish visual transects). Additionally, we investigated the behavioural response to the disturbance of S. salpa fishes that had been tagged with acoustic transmitters. Given their low mobility, sea urchins were severely affected by the storm (ca. 50% losses) with higher losses in those patches with a higher density of sea urchins. This may be due to a limited availability of refuges within each patch. In contrast, fish abundance was not affected, as fish were able to move to protected areas (i.e. deeper) as a result of the high mobility of this species. Our results highlight that catastrophic storms differentially affect the two dominant macroherbivores of rocky macroalgal and seagrass systems due to differences in mobility and escaping strategies. This study emphasises that under catastrophic disturbances, the presence of different responses among the key herbivores of the system may be critical for the maintenance of the herbivory function