Observations on the vibration of axially-tensioned elastomeric pipes conveying fluids

A study of the effect of axial tension on the vibration of a single-span elastomeric pipe clamped at both ends conveying fluid has been carried out both experimentally and theoretically. A new mathematical model using a penalty function technique and the method of kinematic correction and fictitious loads has been developed. The influence of flowing fluid and axial tension on natural frequencies and mode shapes of the system has been described using this model and compared with experimental observations. Linear and non-linear dynamic response of the harmonically excited pipe has also been investigated for varying flow velocities and initial axial tensions

Reliability of AlGaN/GaN high electron mobility transistors on low dislocation density bulk GaN substrate: Implications of surface step edges

To enable gaining insight into degradation mechanisms of AlGaN/GaN high electron mobility transistors, devices grown on a low-dislocation-density bulk-GaN substrate were studied. Gateleakage current and electroluminescence (EL) monitoring revealed a progressive appearance of EL spots during off-state stress which signify the generation of gate current leakage paths.Atomic force microscopy evidenced the formation of semiconductor surface pits at the failure location, which corresponds to the interaction region of the gate contact edge and the edges ofsurface steps

Failure Analysis of Flow-induced Vibration Problem of in-serviced Duplex Stainless Steel Piping System in Oil and Gas Industry

Failure of the duplex stainless steel piping system in oil and gas industry can have disastrous effects. In this study, a novel method of failure analysis of flow-induced vibration problem of in-serviced duplex stainless steel piping system is proposed. The proposed non-destructive technique is able to determine a suitable operating condition for continuous operation without failure. The technique relies on the combined operation of operational modal analysis, operating deflection shape analysis and linear elastic finite element analysis. The effect of different operating conditions for two distinct valve opening cases (i.e. fully opened and partially opened) on the dynamic stress is examined, and they are utilised for forecasting purpose in failure analysis. The result shows that maximum operating conditions are 360 and 400 mmscfd for fully opened and partially opened flow control valves, respectively. Beyond this limit, the piping system most likely will fail

Improving productivity through work measurement : a cooperative approach; Management advisory services practice aids. Technical consulting practice aid, 09

https://egrove.olemiss.edu/aicpa_guides/1097/thumbnail.jp

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact

Proposed physiologic functions of boron in plants pertinent to animal and human metabolism.

Boron has been recognized since 1923 as an essential micronutrient element for higher plants. Over the years, many roles for boron in plants have been proposed, including functions in sugar transport, cell wall synthesis and lignification, cell wall structure, carbohydrate metabolism, RNA metabolism, respiration, indole acetic acid metabolism, phenol metabolism and membrane transport. However, the mechanism of boron involvement in each case remains unclear. Recent work has focused on two major plant-cell components: cell walls and membranes. In both, boron could play a structural role by bridging hydroxyl groups. In membranes, it could also be involved in ion transport and redox reactions by stimulating enzymes like nicotinamide adenine dinucleotide and reduced (NADH) oxidase. There is a very narrow window between the levels of boron required by and toxic to plants. The mechanisms of boron toxicity are also unknown. In nitrogen-fixing leguminous plants, foliarly applied boron causes up to a 1000% increase in the concentration of allantoic acid in leaves. In vitro studies show that boron inhibits the manganese-dependent allantoate amidohydrolase, and foliar application of manganese prior to application of boron eliminates allantoic acid accumulation in leaves. Interaction between borate and divalent cations like manganese may alter metabolic pathways, which could explain why higher concentrations of boron can be toxic to plants

Terror from the Sky: Unconventional Linguistic Clues to the Negrito Past

Within recorded history. most Southeast Asian peoples have been of southern Mongoloid physical type, whether they speak Austroasiatic, Tibeto-Burman, Austronesian, Tai-Kadai, or Hmong-Mien languages. However, population distributions suggest that this is a post-Pleistocene phenomenon and that for tens of millennia before the last glaciation ended Greater Mainland Southeast Asia, which included the currently insular world that rests on the Sunda Shelf, was peopled by short, dark-skinned, frizzy-haired foragers whose descendants in the Philippines came to be labeled by the sixteenth-century Spanish colonizers as negritos, a term that has since been extended to similar groups throughout the region. There are three areas in which these populations survived into the present so as to become part of written history: the Philippines, the Malay Peninsula, and the Andaman Islands. All Philippine negritos speak Austronesian languages, and all Malayan negritos speak languages in the nuclear Mon-Khmer branch of Austroasiatic, but the linguistic situation in the Andamans is a world apart. Given prehistoric language shifts among both Philippine and Malayan negritos, the prospects of determining whether disparate negrito populations were once a linguistically or culturally unified community would appear hopeless. Surprisingly, however, some clues to a common negrito past do survive in a most unexpected way

Candidate Water Vapor Lines to Locate the H2O Snowline through High-dispersion Spectroscopic Observations. III. Submillimeter H2 16O and H2 18O Lines

In this paper, we extend the results presented in our former papers on using ortho-H216O line profiles to constrain the location of the H2O snowline in T Tauri and Herbig Ae disks, to include submillimeter para-H216O and ortho- and para-H218O lines. Since the number densities of the ortho- and para-H218O molecules are about 560 times smaller than their 16O analogs, they trace deeper into the disk than the ortho-H216O lines (down to z = 0, i.e., the midplane). Thus these H218O lines are potentially better probes of the position of the H2O snowline at the disk midplane, depending on the dust optical depth. The values of the Einstein A coefficients of submillimeter candidate water lines tend to be lower (typically <10‑4 s‑1) than infrared candidate water lines. Thus in the submillimeter candidate water line cases, the local intensity from the outer optically thin region in the disk is around 104 times smaller than that in the infrared candidate water line cases. Therefore, in the submillimeter lines, especially H218O and para-H216O lines with relatively lower upper state energies (∼a few 100 K) can also locate the position of the H2O snowline. We also investigate the possibility of future observations with ALMA to identify the position of the water snowline. There are several candidate water lines that trace the hot water gas inside the H2O snowline in ALMA Bands 5–10

A Small Angle Scattering Sensor System for the Characterization of Combustion Generated Particulate

One of the critical issues for the US space program is fire safety of the space station and future launch vehicles. A detailed understanding of the scattering signatures of particulate is essential for the development of a false alarm free fire detection system. This paper describes advanced optical instrumentation developed and applied for fire detection. The system is being designed to determine four important physical properties of disperse fractal aggregates and particulates including size distribution, number density, refractive indices, and fractal dimension. Combustion generated particulate are the primary detection target; however, in order to discriminate from other particulate, non-combustion generated particles should also be characterized. The angular scattering signature is measured and analyzed using two photon optical laser scattering. The Rayleigh-Debye-Gans (R-D-G) scattering theory for disperse fractal aggregates is utilized. The system consists of a pulsed laser module, detection module and data acquisition system and software to analyze the signals. The theory and applications are described

Identification of novel vascular targets in lung cancer

Background: Lung cancer remains the leading cause of cancer-related death, largely owing to the lack of effective treatments. A tumour vascular targeting strategy presents an attractive alternative; however, the molecular signature of the vasculature in lung cancer is poorly explored. This work aimed to identify novel tumour vascular targets in lung cancer. Methods: Enzymatic digestion of fresh tissue followed by endothelial capture with Ulex lectin-coated magnetic beads was used to isolate the endothelium from fresh tumour specimens of lung cancer patients. Endothelial isolates from the healthy and tumour lung tissue were subjected to whole human genome expression profiling using microarray technology. Results: Bioinformatics analysis identified tumour endothelial expression of angiogenic factors, matrix metalloproteases and cellsurface transmembrane proteins. Predicted novel tumour vascular targets were verified by RNA-seq, quantitative real-time PCR analysis and immunohistochemistry. Further detailed expression profiling of STEAP1 on 82 lung cancer patients confirmed STEAP1 as a novel target in the tumour vasculature. Functional analysis of STEAP1 using siRNA silencing implicates a role in endothelial cell migration and tube formation. Conclusions: The identification of cell-surface tumour endothelial markers in lung is of interest in therapeutic antibody and vaccine development