The manufacture of honeycomb cores using Fused Deposition Modeling

Sandwich panels are used in many industries for the advantageous properties of high stiffness, good strength to weight ratio, and impact resistance. This paper investigates properties of thin-walled cores manufactured through Fused Deposition Modeling (FDM); a process which, through a wider design space, could improve the functionality of sandwich panels. The bond strength between the layers of thin walls manufactured through FDM was evaluated through tensile testing. To measure the effect of modified manufacturing speeds, wall thicknesses were varied through the flow rate and nozzle speed. Honeycomb cores using FDM were produced with different toolpaths, and compared with an example of an industry standard Nomex honeycomb core. During tensile testing, thick-walled FDM components exhibited a more ductile failure with a lower yield point when compared to thinner specimens. The ultimate tensile stress remained constant across samples within each of the tested ABS and PLA polymers used. Honeycomb cores produced using FDM were found to have a higher compressive failure force than Nomex honeycomb, and a lower specific strength. The force–displacement curves of compressive failure show a ductile response for thick specimens, consistent with the previous result. These results, combined with the increased flexibility of additive manufacture technologies, could provide a method of manufacturing high strength cores with complex geometry

The manufacture of honeycomb cores using Fused Deposition Modeling

Sandwich panels are used in many industries for the advantageous properties of high stiffness, good strength to weight ratio, and impact resistance. This paper investigates properties of thin-walled cores manufactured through Fused Deposition Modeling (FDM); a process which, through a wider design space, could improve the functionality of sandwich panels. The bond strength between the layers of thin walls manufactured through FDM was evaluated through tensile testing. To measure the effect of modified manufacturing speeds, wall thicknesses were varied through the flow rate and nozzle speed. Honeycomb cores using FDM were produced with different toolpaths, and compared with an example of an industry standard Nomex honeycomb core. During tensile testing, thick-walled FDM components exhibited a more ductile failure with a lower yield point when compared to thinner specimens. The ultimate tensile stress remained constant across samples within each of the tested ABS and PLA polymers used. Honeycomb cores produced using FDM were found to have a higher compressive failure force than Nomex honeycomb, and a lower specific strength. The force–displacement curves of compressive failure show a ductile response for thick specimens, consistent with the previous result. These results, combined with the increased flexibility of additive manufacture technologies, could provide a method of manufacturing high strength cores with complex geometry

Sperm: seminal fluid interactions and the adjustment of sperm quality in relation to female attractiveness

An important predictor of male fitness is the fertilizing efficiency of their ejaculates. Ejaculates are costly to produce and males are predicted to devote greater resources to copulations with reproductively superior females. It is well established that males allocate different numbers of sperm to ejaculates. However, less is known about how males adjust their sperm quality, which has important implications for our understanding of fertilization and the evolution of sexual strategies. Here we test in the fowl, Gallus gallus, whether males adjust their sperm velocity by differentially allocating seminal fluid to copulations with attractive and unattractive females. To disentangle the contributions of sperm and seminal fluid to sperm velocity, we separated and remixed sperm and seminal fluid from ejaculates allocated to females of different attractiveness. We show that dominant males increase the velocity of the sperm they invest in more attractive females by allocating larger ejaculates that contain seminal fluid that increases sperm velocity. Furthermore, we find weak evidence that males also allocate sperm with higher velocity, irrespective of seminal fluid, to more attractive females

Identifying factors likely to influence compliance with diagnostic imaging guideline recommendations for spine disorders among chiropractors in North America: a focus group study using the Theoretical Domains Framework

Background: The Theoretical Domains Framework (TDF) was developed to investigate determinants of specific clinical behaviors and inform the design of interventions to change professional behavior. This framework was used to explore the beliefs of chiropractors in an American Provider Network and two Canadian provinces about their adherence to evidence-based recommendations for spine radiography for uncomplicated back pain. The primary objective of the study was to identify chiropractors’ beliefs about managing uncomplicated back pain without xrays and to explore barriers and facilitators to implementing evidence-based recommendations on lumbar spine xrays. A secondary objective was to compare chiropractors in the United States and Canada on their beliefs regarding the use of spine x-rays. Methods: Six focus groups exploring beliefs about managing back pain without x-rays were conducted with a purposive sample. The interview guide was based upon the TDF. Focus groups were digitally recorded, transcribed verbatim, and analyzed by two independent assessors using thematic content analysis based on the TDF. Results: Five domains were identified as likely relevant. Key beliefs within these domains included the following: conflicting comments about the potential consequences of not ordering x-rays (risk of missing a pathology, avoiding adverse treatment effects, risks of litigation, determining the treatment plan, and using x-ray-driven techniques contrasted with perceived benefits of minimizing patient radiation exposure and reducing costs; beliefs about consequences); beliefs regarding professional autonomy, professional credibility, lack of standardization, and agreement with guidelines widely varied (social/professional role & identity); the influence of formal training, colleagues, and patients also appeared to be important factors (social influences); conflicting comments regarding levels of confidence and comfort in managing patients without x-rays (belief about capabilities); and guideline awareness and agreements (knowledge). Conclusions: Chiropractors’ use of diagnostic imaging appears to be influenced by a number of factors. Five key domains may be important considering the presence of conflicting beliefs, evidence of strong beliefs likely to impact the behavior of interest, and high frequency of beliefs. The results will inform the development of a theorybased survey to help identify potential targets for behavioral-change strategies

Genome editing to the rescue: sustainably feeding 10 billion global human population

Modern animal breeding strategies based on population genetics, molecular tools, artificial insemination, embryo transfer and related technologies have contributed to significant increases in the performance of domestic animals, and are the basis for a regular supply of high quality animal derived food at acceptable prices. However, the current strategy of marker- assisted selection and breeding of animals to introduce novel traits over multiple generations is too pedestrian in responding to unprecedented challenges such as climate change, global pandemics, and feeding an anticipated 33% increase in global population in the next three decades. Here, we propose site-specific genome editing technologies as a basis for “directed” or “rational selection” of agricultural traits. The animal science community envisions genome editing as an essential tool in addressing critical priorities for global food security and environmental sustainability, and seeks additional funding support for development and implementation of these technologies for maximum societal benefit

Single source three dimensional capture of full field plate vibrations

Measurement of the vibrations of plates can offer significant challenges to the experimentalist, particularly when the plates are lightweight, exhibit large amplitude deflections, nonlinear responses or are initially curved. The use of accelerometers adds masses which can change the dynamics of lightweight plates. Large amplitude oscillations and initial curvatures cause complications when using a laser vibrometer, as they make it difficult to get consistent reflections back to the receiver. Furthermore, large or nonlinear oscillations challenge inherent assumptions on which the vibrometer’s algorithms depend. A high speed video camera avoids these issues, but makes it hard to extract numerical data. This paper describes a method that extends the capabilities of a high speed video camera by using a mirror, allowing post-processing software to stereoscopically resolve an array of points on the plate surface to 3D coordinates, capturing the complete shape and position of the plate throughout vibration. This method avoids all the problems mentioned above and gives very clear insight into plate vibration. Some example results of this method are presented, using thermally bistable carbon laminate plates filmed at a 1000 frames per second. These plates pose the challenges described, and also exhibit an unusual oscillatory motion where the plates ‘snap’ between two statically stable states. The method is shown to provide clear insight into the rich dynamics of these plates

Communication and marketing as tools to cultivate the public's health: a proposed "people and places" framework

<p>Abstract</p> <p>Background</p> <p>Communication and marketing are rapidly becoming recognized as core functions, or core competencies, in the field of public health. Although these disciplines have fostered considerable academic inquiry, a coherent sense of precisely how these disciplines can inform the practice of public health has been slower to emerge.</p> <p>Discussion</p> <p>In this article we propose a framework – based on contemporary ecological models of health – to explain how communication and marketing can be used to advance public health objectives. The framework identifies the attributes of people (as individuals, as social networks, and as communities or populations) and places that influence health behaviors and health. Communication, i.e., the provision of information, can be used in a variety of ways to foster beneficial change among both people (e.g., activating social support for smoking cessation among peers) and places (e.g., convincing city officials to ban smoking in public venues). Similarly, marketing, i.e., the development, distribution and promotion of products and services, can be used to foster beneficial change among both people (e.g., by making nicotine replacement therapy more accessible and affordable) and places (e.g., by providing city officials with model anti-tobacco legislation that can be adapted for use in their jurisdiction).</p> <p>Summary</p> <p>Public health agencies that use their communication and marketing resources effectively to support people in making healthful decisions and to foster health-promoting environments have considerable opportunity to advance the public's health, even within the constraints of their current resource base.</p