Comparison between friction stir and submerged arc welding applied to joining DH36 and E36 shipbuilding steel

With the impending development of FSW tools for steel with useful lifetimes, attention has turned to the mechanical properties of the welds that can be made in a range of industrially significant steels. This work reports on a comparative study undertaken to examine the use of friction stir and submerged arc welding on DH36 and E36 shipbuilding steels. The study made an assessment of the distortion induced in fabricating plates by the two welding techniques, and provides initial comparative data on weld tensile strength, toughness and fatigue life. In each case, friction stir welding was shown to outperform submerged arc welding

High-throughput screening of encapsulated islets using wide-field lens-free on-chip imaging

Islet microencapsulation is a promising solution to diabetes treatment, but its quality control based on manual microscopic inspection is extremely low-throughput, highly variable and laborious. This study presents a high-throughput islet-encapsulation quality screening system based on lens-free on-chip imaging with a wide field-of-view of 18.15 cm^2, which is more than 100 times larger than that of a lens-based optical microscope, enabling it to image and analyze ~8,000 microcapsules in a single frame. Custom-written image reconstruction and processing software provides the user with clinically important information, such as microcapsule count, size, intactness, and information on whether each capsule contains an islet. This high-throughput and cost-effective platform can be useful for researchers to develop better encapsulation protocols as well as perform quality control prior to transplantation

The Paleoindian Component at Charlie Lake Cave (HbRf39), British Columbia

Charlie Lake Cave (HbRf 39) is a stratified site in northeastern British Columbia, Canada, containing a flutedpoint component at the base of the excavated deposits. The small artifact assemblage includes a fluted point, stone bead, core tool, and retouched flake. A diverse associated fauna includes fish, birds, and mammals, indicating a more open environment than exists today. Radiocarbon dates suggest that the artifact assemblage was deposited about 10,500 years ago.   Article Summary by Jonathan C. Driver, May 2015             This was the first major publication about Tse’K’wa and it focuses on what for many people was the most exciting find at the site – a very early occupation of so-called “Paleoindian” people.             There continues to be considerable debate about when the first people came to the Americas. In the 1980’s (and continuing today), the weight of evidence supports a long-held belief that the ancestors of the indigenous peoples of the Americas made their initial migration from somewhere in northeast Asia.  However, the timing of this movement, the context in which it occurred, and the date are still contentious. (It is, of course, a simplification to describe this as a single event. There is plenty of evidence for a number of major migrations across the Bering Strait, and it is likely that there was a flow of people and ideas in both directions over thousands of years).             In the 1980’s, as today, virtually all archaeologists agree that “Paleoindian” cultures dating to the end of the last glacial period (about 12,000 BC) indicate a well-established population throughout the Americas by that time, although there is still considerable debate about when the first ancestors of Paleoindians arrived in the Americas.             While the way of life of these peoples must have varied across different environments found in North and South America, the most distinctive Paleoindian artifacts in North America are a kind of stone spear point, known as “fluted points”.  Fluted points were chipped from fine-grained rocks, such as chert, jasper and obsidian, and generally had a long, lanceolate outline. In order to fit the base of the point into the shaft of the spear, it was thinned by striking off some flakes that ran from the base towards the sharp tip, creating a shallow channel or “flute” on one or both surfaces of the stone spearpoint.             Fluted points have been found in association with extinct animals, most commonly woolly mammoth and extinct forms of bison, but also with horse and camel, primarily  in the central and western half of the USA. Due to different geological and soil conditions in eastern USA, most fluted point sites there do not preserve animal bone. In 1983 when a fluted point was found at Tse’K’wa, there was only one site in all of Canada where fluted points had been found in association with organic material that could be radiocarbon dated – at Debert, in Nova Scotia where charcoal in the soil provided some dates. Tse’K’wa was the first site in Canada that produced a fluted point in association with animal bones that had clearly been butchered by people – in this case an extinct form of bison – and the first site in Canada in which a fluted point was found at the bottom of a long sequence of later cultural periods. The unique soil conditions at the Tse\u27K\u27wa site have enabled archaeologists to use radio carbon dating on fluted points and animal remains to gain further insight into the lifestyles and timeline of early human occupation of Canada.             Also of significance was the location of Tse’K’wa just to the east of the Rockies. Archaeologists had proposed that one route into the Americas during the late ice age was between the Rocky Mountain glaciers to the west and the massive ice sheets that covered Canada to the east – this so-called “ice-free corridor” might have allowed early hunters to move from unglaciated areas of Siberia and Alaska into the vast uninhabited continents to the south of the ice. Although fluted points had been picked up from ploughed fields in BC and Alberta, before the excavations at Tse’K’wa none of them had been radiocarbon dated, and so it was difficult to relate them to known dates of glaciers and post-glacial landscapes

Analisa Kelayakan Investasi Asphalt Mixing Plant

Proyek konstruksi merupakan proses dimana rencana/desain dan spesifikasi paraperencana dikonversikan menjadi struktur dan fasilitas fisik. Dalam setiap proyek yang dikerjakan, pasti dibutuhkan suatu alat. Beberapa Perusahaan kontraktor memilih untuk membeli alat sebagai pilihan untuk berinvestasi. Dalam penelitian ini, akan dibahas mengenai kelayakan investasi peralatan yang berkaitan dengan pekerjaan pengaspalan jalan, yaitu Asphalt Mixing Plant. Metode analisa kelayakan yang akan digunakan adalah metode Net Present Value. Penelitian ini bertujuan untuk mengetahui kelayakan investasi dari Asphalt Mixing Plant

The lesbian, gay, bisexual and transgender community online: discussions of bullying and self-disclosure in YouTube videos

Computer-mediated communication has become a popular platform for identity construction and experimentation as well as social interaction for those who identify as lesbian, gay, bisexual or transgender (LGBT). The creation of user-generated videos has allowed content creators to share experiences on LGBT topics. With bullying becoming more common amongst LGBT youth, it is important to obtain a greater understanding of this phenomenon. In our study, we report on the analysis of 151 YouTube videos which were identified as having LGBT- and bullying-related content. The analysis reveals how content creators openly disclose personal information about themselves and their experiences in a non-anonymous rhetoric with an unknown public. These disclosures could indicate a desire to seek friendship, support and provide empathy

Grain Physics and Rosseland Mean Opacities

Tables of mean opacities are often used to compute the transfer of radiation in a variety of astrophysical simulations from stellar evolution models to proto-planetary disks. Often tables, such as Ferguson et al. (2005), are computed with a predetermined set of physical assumptions that may or may not be valid for a specific application. This paper explores the effects of several assumptions of grain physics on the Rosseland mean opacity in an oxygen rich environment. We find that changing the distribution of grain sizes, either the power-law exponent or the shape of the distribution, has a marginal effect on the total mean opacity. We also explore the difference in the mean opacity between solid homogenous grains and grains that are porous or conglomorations of several species. Changing the amount of grain opacity included in the mean by assuming a grain-to-gas ratio significantly affects the mean opacity, but in a predictable way.Comment: 19 pages, 6 figures, accepted for publication in Ap

Cataclysmic Variables and a New Class of Faint UV Stars in the Globular Cluster NGC 6397

We present evidence that the globular cluster NGC 6397 contains two distinct classes of centrally-concentrated UV-bright stars. Color-magnitude diagrams constructed from U, B, V, and I data obtained with the HST/WFPC2 reveal seven UV-bright stars fainter than the main-sequence turnoff, three of which had previously been identified as cataclysmic variables (CVs). Lightcurves of these stars show the characteristic ``flicker'' of CVs, as well as longer-term variability. A fourth star is identified as a CV candidate on the basis of its variability and UV excess. Three additional UV-bright stars show no photometric variability and have broad-band colors characteristic of B stars. These non-flickering UV stars are too faint to be extended horizontal branch stars. We suggest that they could be low-mass helium white dwarfs, formed when the evolution of a red giant is interrupted, due either to Roche-lobe overflow onto a binary companion, or to envelope ejection following a common-envelope phase in a tidal-capture binary. Alternatively, they could be very-low-mass core-He-burning stars. Both the CVs and the new class of faint UV stars are strongly concentrated toward the cluster center, to the extent that mass segregation from 2-body relaxation alone may be unable to explain their distribution.Comment: 11 pages plus 3 eps figures; LaTeX using aaspp4.sty; to appear in The Astrophysical Journal Letter

A Glimpse Far into the Future: Understanding Long-term Crowd Worker Quality

Microtask crowdsourcing is increasingly critical to the creation of extremely large datasets. As a result, crowd workers spend weeks or months repeating the exact same tasks, making it necessary to understand their behavior over these long periods of time. We utilize three large, longitudinal datasets of nine million annotations collected from Amazon Mechanical Turk to examine claims that workers fatigue or satisfice over these long periods, producing lower quality work. We find that, contrary to these claims, workers are extremely stable in their quality over the entire period. To understand whether workers set their quality based on the task's requirements for acceptance, we then perform an experiment where we vary the required quality for a large crowdsourcing task. Workers did not adjust their quality based on the acceptance threshold: workers who were above the threshold continued working at their usual quality level, and workers below the threshold self-selected themselves out of the task. Capitalizing on this consistency, we demonstrate that it is possible to predict workers' long-term quality using just a glimpse of their quality on the first five tasks.Comment: 10 pages, 11 figures, accepted CSCW 201