Investigation of Various Techniques for Controlled Void Formation in Fiberglass/Epoxy Composites

The effect of porosity in composite materials has been studied for years due to its deleterious effects on mechanical properties, especially matrix dominated properties. Currently there is an increasing use of composites in infrastructure worldwide, for example bridge components, residential and building structures, marine structures such as piers and docks, and large industrial chemical tanks. Most of these applications use fiberglass composites. Unfortunately, most of the published literature has focused on carbon fiber composites, in which fiber diameter and gas-fiber interactions are different than fiberglass composites. Therefore, the present study was undertaken to revisit the effect of porosity but specifically in fiberglass composites. The goal of this experimental study was to implement and evaluate various methods for creating porosity in fiberglass composites in a controlled manner in terms of obtaining repeatable void content, morphology, and location within the laminate. The various methods included using different amounts of autoclave pressure, adding a small amount of water between prepreg layers, and using dry fabric layers to starve the laminate of resin. Ultrasonic C-scan nondestructive evaluation was used to assess the quality of the cured panels, as well as optical and electron microscopy and void content measurements via resin burn-out. The cured panels were mechanically tested using the short beam shear (SBS) method. The results showed that the water spray method proved to be the best in terms of producing noticeably different levels of porosity, although the panels required drying to remove residual water after cure. The voids from all three techniques were either oval or elongated in-plane between the plies, but they were not uniformly distributed in-plane. The use of C-scan proved to be helpful for characterizing overall uniformity of each panel, although the results could not be used to directly compare void content between panels. The use of SBS testing was successful for evaluating void dominated properties in panels with high void content, although it was not very sensitive to coupons with lower void contents. Several interesting observations are offered in this manuscript of the fracture surface details and their relation to the SBS load deflection curves. Overall, it was found that the failure mechanisms were mixed mode and the voids did not serve as failure initiation sites. However, the voids participated mainly in the horizontal propagation of cracks between layers, presumably making it easier when they were intersected by a crack and reducing SBS strength

Maximum Likelihood Estimation of Search Costs

In a recent paper Hong and Shum (forthcoming) present a structural methodology to estimate search cost distributions. We extend their approach to the case of oligopoly and present a maximum likelihood estimate of the search cost distribution. We apply our method to a data set of online prices for different computer memory chips. The estimates of the search cost distribution suggest that consumers have either quite high or quite low search costs so they either search for all prices in the market or for at most three prices. According to Kolmogorov-Smirnov goodness-of-fit tests, we cannot reject the null hypothesis that the observed prices are generated by the mode

Climate mediates the effects of disturbance on ant assemblage structure

Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about howclimate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effectwas manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk. © 2015 The Author(s) Published by the Royal Society. All rights reserved

Com o diabo no corpo: os terríveis papagaios do Brasil colônia

Desde a Antiguidade, papagaios, periquitos e afins (Psittacidae) fascinaram os europeus por seu vivo colorido e uma notável capacidade de interação com seres humanos. A descoberta do Novo Mundo nada faria além de acrescentar novos elementos ao tráfico de animais exóticos há muito estabelecido pelos europeus com a África e o Oriente. Sem possuir grandes mamíferos, a América tropical participaria desse comércio com o que tinha de mais atrativo, essencialmente felinos, primatas e aves - em particular os papagaios, os quais eram embarcados em bom número. Contudo, a julgar pelos documentos do Brasil colônia, esses voláteis podiam inspirar muito pouca simpatia, pois nenhum outro animal - exceto as formigas - foi tantas vezes mencionado como praga para a agricultura. Além disso, alguns psitácidas mostravam-se tão loquazes que inspiravam a séria desconfiança de serem animais demoníacos ou possessos, pois só três classes de entidades - anjos, homens e demônios - possuíam o dom da palavra. Nos dias de hoje, vários representantes dos Psittacidae ainda constituem uma ameaça para a agricultura, enquanto os indivíduos muito faladores continuam despertando a suspeita de estarem possuídos pelo demônio. Transcendendo a mera curiosidade, essa crença exemplifica o quão intrincadas podem ser as relações do homem com o chamado “mundo natural”, revelando um universo mais amplo e multifacetado do que se poderia supor a princípio. Nesse sentido, a existência de aves capazes de falar torna essa relação ainda mais complexa e evidencia que as dificuldades de estabelecer o limite entre o animal e o humano se estendem além dos primatas e envolvem as mais inusitadas espécies zoológicas.Since ancient times, parrots and their allies (Psittacidae) have fascinated Europeans by their striking colors and notable ability to interact with human beings. The discovery of the New World added new species to the international exotic animal trade, which for many centuries had brought beasts to Europe from Africa and the Orient. Lacking large mammals, tropical America participated in this trade with its most appealing species, essentially felines, primates and birds - especially parrots - which were shipped in large numbers. It should be noted, however, that at times these birds were not well liked. In fact, according to documents from colonial Brazil, only the ants rank higher than parrots as the animals most often mentioned as agricultural pests. On the other hand, some of these birds were so chatty that people suspected them to be demonic or possessed animals, since only three classes of beings - angels, men and demons - have the ability to speak. Nowadays, several Psittacidae still constitute a threat to agriculture, and the suspicion that extremely talkative birds were demon possessed has also survived. More than a joke or a mere curiosity, this belief exemplifies how intricate man’s relationships with the “natural world” may be. In this sense, the existence of birds that are able to speak adds a further twist to these relationships, demonstrating that the problem of establishing a boundary between the animal and the human does not only involve primates, but also includes some unusual zoological species

Selected Writings of Donald F. Lach and Alma S. Lach

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/1/iceshow.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/8/1999TavernClubDisplay.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/9/2000TavernClubDisplay.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/32/TavernClubSummer2002.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/15/2003TavernClubDisplay.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/10/2004TavernClubDisplay.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/11/Alma-S-Lach-Exhibit (1)4800.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/14/Alma-S-Lach-Exhibit (1)2400.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/13/Alma-S-Lach-Exhibit (1)1200.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/12/Alma-S-Lach-Exhibit (1)600.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/3/01Ted-3-4-a-copy.tifhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/4/02Nik-red-a-2 copy.TIFhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/5/03Nick-r~7-c copy.TIFhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/6/04nick-rose-13-b copy.TIFhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/7/05Nick-r~1-c--a-copy.tifhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/16/Lach01Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/17/Lach02Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/18/Lach03Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/19/Lach04Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/20/Lach05Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/21/Lach06Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/22/Lach07Writings.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/23/Lach01Reviews.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/24/Lach02Reviews.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/25/Lach03Reviews.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/26/Lach04Reviews.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/27/Lach01Corres.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/28/Lach02Corres.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/29/Lach03Corres.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/30/AL_photosCappadocia.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/31/OralHistory.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/33/AlmaLachMSchildhood.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/34/BangladeshPhotos.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/35/CambodiaPhotos.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/36/HawaiiPhotos.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/37/JapanPhotos.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/38/TaiwanPhotos.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/39/IndiaPhotos.ziphttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/40/Alma Lach’s Kitchen.pptxhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/41/AlmaLachDisplay.pptxhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/42/Alma Lach’s Kitchen4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/43/Alma Lach invitation.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/60304/44/LachExhibitionUCJuly31.pd

Asia on the Eve of Europe's Expansion

Map in the frontispiece of the included book based on an original map by Sandra Lach (now, [email protected]). The book is peer-reviewed. There is also a file listing a box by box inventory of the works of Donald F. Lach housed in a special collection in the Joseph Regenstein Library of the University of Chicago. Permission from that library is needed for access to those materials. For materials not housed in that collection, and possible permission to use them, please contact [email protected]. Context for the general works of Donald F. Lach is also provided in SummaryDFL.pdf.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58763/1/lach.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/58763/4/Regenstein Inventory, Papers, 1942-1987.pd