Spectral analysis of semi-actively controlled structures subjected to blast loading

This paper investigates the possibility of controlling the response of typical portal frame structures to blast loading using a combination of semi-active and passive control devices. A one storey reinforced concrete portal frame is modelled using non-linear finite elements with each column discretised into multiple elements to capture the higher frequency modes of column vibration response that are typical features of blast responses. The model structure is subjected to blast loads of varying duration, magnitude and shape, and the critical aspects of the response are investigated over a range of structural periods in the form of blast load response spectra. It is found that the shape or length of the blast load is not a factor in the response, as long as the period is less than 25% of the fundamental structural period. Thus, blast load response can be expressed strictly as a function of the momentum applied to the structure by a blast load. The optimal device arrangements are found to be those that reduce the first peak of the structural displacement and also reduce the subsequent free vibration of the structure. Semi-active devices that do not increase base shear demands on the foundations in combination with a passive yielding tendon are found to provide the most effective control, particularly if base shear demand is an important consideration, as with older structures. The overall results are summarised as response spectra for eventual potential use within standard structural design paradigms

One Line or Two? Perspectives on Piecewise Regression

Sometimes we are faced with data that could reasonably be represented either as a single line, or as two or more line segments. How do we identify the best breakpoint(s), and decide how many segments are ''really'' present? Most of us are taught to distrust piecewise regression, because it can be easily abused. The best method for identifying the breakpoint varies according to specifics of the data; for example, the minimum sum of squares method excels for ''well-behaved'' data. In some cases, hidden Markov methods are more likely to succeed than are more ''obvious'' methods. Likewise, the most appropriate method for deciding between one or two lines depends on your expectations and understanding of the data: an unexpected break requires more justification than an expected one, and some decision criteria (e.g., the Akaike Information Criterion) are less strict than others (e.g., the Bayesian Information Criterion). This presentation will review some options and make specific, practical recommendations

RADIONUCLIDE TRANSPORT IN FRACTURED TUFF UNDER EPISODIC FLOW CONDITIONS

The current conceptual model of radionuclide transport in unsaturated fractured rock includes water movement in fractures, with migration of the entrained radionuclides being retarded by diffusion into and sorption within the rock matrix. Water infiltration and radionuclide transport through low-permeability unsaturated fractured rock are episodic and intermittent in nature, at least at local scales. Under episodic flow conditions, the matrix is constantly imbibing or draining, and this fluctuating wetness both drives two-way advective movement of radionuclides, and forces changes in the matrix diffusivity. This work is intended to examine, both experimentally and numerically, how radionuclide transport under episodic flow conditions is affected by the interacting processes of imbibition and drainage, diffusion, and matrix sorption. Using Topopah Spring welded volcanic tuff, collected from the potential repository geologic unit at Yucca Mountain for storing high-level nuclear waste, we prepared a saw-cut fracture core (length 10.2 cm, diameter 4.4 cm, and fracture aperture 100 {micro}m). The dry core was packed into a flow reactor, flushed with CO{sub 2}, then saturated via slow pumping (0.01 mL/min) of synthetic groundwater. The fractured core was then flushed with air at >97% relative humidity (to simulate in situ unsaturated fractured rock conditions at Yucca Mountain), then the episodic transport experiment was conducted. Episodic flow involved 4 cycles of tracer solution flow within the fracture, followed by flushing with high humidity air. Each flow episode contained a different suite of non-sorbing and sorbing tracers, which included {sup 3}H, ReO{sub 4}{sup -} (a chemical analog for {sup 99}TcO{sub 4}{sup -}), I{sup -} (for {sup 129}I{sup -}), Sr and Cs (for {sup 90}Sr and {sup 137}Cs), plus the radionuclides {sup 235}U, {sup 237}Np, and {sup 241}Pu. These radionuclides span a variety of sorption strengths and represent a large fraction of the radionuclides of concern at the potential Yucca Mountain repository. Meanwhile, the non-sorbing {sup 3}H and ReO{sub 4}{sup -} serve as diffusivity tracers with different aqueous diffusion coefficients. Liquid effluent from the flow reactor was collected for multi-elemental analyses using ICP-MS, as well as liquid scintillation counting for {sup 3}H, to obtain the breakthrough curves of non- or less-retarded tracers. After the flow-tests were complete, the flow reactor was opened and the distribution of strongly retarded tracers within the fractured core characterized by laser ablation coupled with ICP-MS. A numerical model was developed, based on the NUFT (Non-isothermal, Unsaturated-saturated Flow and Transport) computer code, to describe the experimental system, compare with, and interpret experimental results

PORE CONNECTIVITY, EPISODIC FLOW, AND UNSATURATED DIFFUSION IN FRACTURED TUFF

We use an integrated approach consisting of experiments and complementary pore-scale network modeling to investigate the occurrence of sparsely connected pore spaces in rock matrices at Yucca Mountain, Nevada, and their implications for matrix diffusion. Imbibition results indicate that pore spaces in devitrified tuff are not well-connected, and that this lack of connectivity is further compounded by episodic flow in fractured devitrified tuff with low matrix permeability. A rigorous methodology for investigating chemical transport in fractured rock under episodic conditions, employing a suite of both sorbing and non-sorbing tracers (including radionuclides U-235, Np-237, and Pu-242), has been developed and implemented. In addition, gas diffusion and synchrotron microtomography techniques have been under development to examine the scaling issues of diffusion and pore connectivity. Preliminary results from experiments and modeling work are presented in this paper, confirming the need to reexamine our understanding of matrix diffusion and to evaluate the impact on diffusive radionuclide retardation of episodic fracture flow and low pore connectivity

A simple boiling-based DNA extraction for RAPD profiling of landfarm soil to provide representative metagenomic content

Landfarm soils are employed in industrial and petrochemical residue bioremediation. This process induces selective pressure directed towards microorganisms capable of degrading toxic compounds. Detailed description of taxa in these environments is difficult due to a lack of knowledge of culture conditions required for unknown microorganisms. A metagenomic approach permits identification of organisms without the need for culture. However, a DNA extraction step is first required, which can bias taxonomic representativeness and interfere with cloning steps by extracting interference substances. We developed a simplified DNA extraction procedure coupled with metagenomic DNA amplification in an effort to overcome these limitations. The amplified sequences were used to generate a metagenomic data set and the taxonomic and functional representativeness were evaluated in comparison with a data set built with DNA extracted by conventional methods. The simplified and optimized method of RAPD to access metagenomic information provides better representativeness of the taxonomical and metabolic aspects of the environmental samples.Conselho Nacional de Pesquisa e Desenvolvimento (CNPq) [558272/2009-6]Conselho Nacional de Pesquisa e Desenvolvimento (CNPq)Fundacao de Amparo a Pesquisa do Estado da Bahia (FAPESB)Fundacao de Amparo a Pesquisa do Estado da Bahia (FAPESB

A global database of lake surface temperatures collected by in situ and satellite methods from 1985–2009

Peer reviewe

Measuring the depth of invasion in vulvar squamous cell carcinoma: interobserver agreement and pitfalls

Aims: The depth of invasion is an important prognostic factor for patients with vulvar squamous cell carcinoma (SCC). The threshold of 1 mm distinguishes between FIGO stages IA and ≥IB disease and guides the need for groin surgery. Therefore, high interobserver agreement is crucial. The conventional and the alternative method are described to measure the depth of invasion. The aims of this study were to assess interobserver agreement for classifying the depth of invasion using both methods and to identify pitfalls. Methods and results: Fifty slides of vulvar SCC with a depth of invasion approximately 1 mm were selected, digitally scanned and independently assessed by 10 pathologists working in a referral or oncology centre and four pathologists in training. The depth of invasion was measured using both the conventional and alternative method in each slide and categorised into ≤1 and >1 mm. The percentage of agreement and Light’s kappa for multi-rater agreement were calculated, and 95% confidence intervals were calculated by bootstrapping (1000 runs). The agreement using the conventional method was moderate (κ = 0.57, 95% confidence interval = 0.45–0.68). The percentage of agreement among the participating pathologists using the conventional method was 85.0% versus 89.4% using the alternative method. Six pitfalls were identified: disagreement concerning which invasive nest is deepest, recognition of invasive growth and where it starts, curved surface, carcinoma situated on the edge of the tis

Galaxy bulges and their massive black holes: a review

With references to both key and oft-forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centres of galaxies. It then presents the historical development of the near-linear (black hole)-(host spheroid) mass relation, before explaining why this has recently been dramatically revised. Past disagreement over the slope of the (black hole)-(velocity dispersion) relation is also explained, and the discovery of sub-structure within the (black hole)-(velocity dispersion) diagram is discussed. As the search for the fundamental connection between massive black holes and their host galaxies continues, the competing array of additional black hole mass scaling relations for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590 references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer Publishin