728 research outputs found
Numerical thermo-mechanical stress analysis for HVDC cables
Calculating the current rating of paper insulated HVDC cables under low ambient temperatures can require additional mechanical considerations. Under rapid cable heating or cooling processes, an extremely high mechanical stress or a rapid pressure drop can develop due to the strong impregnant thermal expansion or contraction respectively. This may cause plastic deformation of the sheath or the creation of voids. This paper demonstrates the importance of this thermo-mechanical constraint through the application of finite element modelling techniques which permit a coupling of the thermal and mechanical properties within the cable. The results show that the FEA technique can be fully applied to analyze the internal thermo-mechanical stress distribution of the cable and calculate the resulting mechanical stress-limited rating, which provides an alternative to an analytical method previously developed by the same author
Seed dimorphism nutrients and salinity differentially affect seed traits of the desert halophyte Suaeda aralocaspica via multiple maternal effects.
Background: Maternal effects may influence a range of seed traits simultaneously and are likely to be context-dependent. Disentangling the interactions of plant phenotype and growth environment on various seed traits is important for understanding regeneration and establishment of species in natural environments. Here, we used the seed-dimorphic plant Suaeda aralocaspica to test the hypothesis that seed traits are regulated by multiple maternal effects.Results: Plants grown from brown seeds had a higher brown:black seed ratio than plants from black seeds, and germination percentage of brown seeds was higher than that of black seeds under all conditions tested. However, the coefficient of variation (CV) for size of black seeds was higher than that of brown seeds. Seeds had the smallest CV at low nutrient and high salinity for plants from brown seeds and at low nutrient and low salinity for plants from black seeds. Low levels of nutrients increased size and germinability of black seeds but did not change the seed morph ratio or size and germinability of brown seeds. High levels of salinity decreased seed size but did not change the seed morph ratio. Seeds from high-salinity maternal plants had a higher germination percentage regardless of level of germination salinity.Conclusions: Our study supports the multiple maternal effects hypothesis. Seed dimorphism, nutrient and salinity interacted in determining a range of seed traits of S. aralocaspica via bet-hedging and anticipatory maternal effects. This study highlights the importance of examining different maternal factors and various offspring traits in studies that estimate maternal effects on regeneration. © 2012 Wang et al.; licensee BioMed Central Ltd
Further study on 5q configuration states in the chiral SU(3) quark model
The structure of the configuration states with strangeness
is further studied in the chiral SU(3) quark model based on our
previous work. We calculate the energies of fifteen low configurations of the
system, four lowest configurations of with
partition , four of with
partition and seven of
with partition . Some modifications are
made in this further study, i.e., the orbital wave function is extended as an
expansion of 4 different size harmonic oscillator forms; three various forms
(quadratic, linear and error function form) of the color confinement potential
are considered; the states with partition are added, which are unnegligible in the case and were
not considered in our previous paper, further the mixing between configurations
and is
also investigated. The results show that the T=0 state is still always the
lowest one for both and states, and
state is always lower than that of .
All of these modifications can only offer several tens to hundred MeV effect,
and the theoretical value of the lowest state is still about 245 MeV higher
than the experimental mass of . It seems to be difficult to get the
calculated mass close to the observed one with the reasonable parameters in the
framework of the chiral SU(3) quark model when the model space is chosen as a
cluster.Comment: 16 page
A study of pentaquark state in the chiral SU(3) quark model
The structure of the pentaquark state uudd-sbar is studied in the chiral
SU(3) quark model as well as in the extended chiral SU(3) quark model, in which
the vector meson exchanges are included. Four configurations of JP=1/2- and
four of JP=1/2+ are considered. The results show that the isospin T=0 state is
always the lowest one for both JP=1/2- and JP=1/2+ cases in various models. But
the theoretical value of the lowest one is still about 200-300 MeV higher than
the experimental mass of . It seems that a dynamical calculation should
be done for the further study.Comment: 9 page
Contact Deformation Behavior of an Elastic Silicone/SiC Abrasive in Grinding and Polishing
An elastic abrasive of the new type having the advantage of effectively controlled contact pressure and uniform deformation was developed. It provides complete lamination of the surface, effective treatment of the curved mold cavity, as well as improves the processing efficiency. It permits of fine cavity surface finishing.Розроблено пружний абразив нового типу, що дозволяє ефективно регулювати контактний тиск у поєднанні з рівномірним деформуванням. Пружний абразив забезпечує повне ламінування поверхні, збільшує ефективність обробки вигнутої порожнини ливарної форми та дозволяє виконувати тонку обробку поверхні порожнини.Разработан упругий абразив нового типа, позволяющий эффективно регулировать контактное давление в сочетании с равномерным деформированием. Упругий абразив обеспечивает полное ламинирование поверхности и эффективную обработку изогнутой полости литейной формы, а также позволяет выполнять тонкую отделочную обработку поверхности полости
Towards an engineering model for curve squeal
Curve squeal is a strong tonal noise that may arise when a railway vehicle negotiates a curve. The wheel/rail contact model is the central part of prediction models, describing the frictional instability occurring in the contact during squeal. A previously developed time-domain squeal model considers the wheel and rail dynamics, and the wheel/rail contact is solved using Kalker’s nonlinear transient CONTACT algorithm with Coulomb friction. In this paper, contact models with different degree of simplification are compared to CONTACT within the previously developed squeal model in order to determine a suitable contact algorithm for an engineering curve squeal model. Kalker’s steady-state FASTSIM is evaluated, and, without further modification, shows unsatisfying results. An alternative transient single-point contact algorithm named SPOINT is formulated with the friction model derived from CONTACT. Comparing with the original model results, the SPOINT implementation results are promising and similar to results from CONTACT
Information strategy failure:personal interaction success, in urban residential food waste segregation
AbstractDirect measurements were taken of residential food waste sorting in a sample from over 5000 communities (5 million households) assigned to a pilot program delivered by government branches in Shanghai which relied on an information strategy for implementation. The results are compared to a population of N = 36 similar communities (36,000 households) assigned to a different program which involved considerable personal interaction. The results show that the information–based program communities did not noticeably sort their waste, whereas those given personal interaction approaches were very successful, with purity rates of 95%(8) and extra costs of about 50 RMB (8 USD) per household. This is a rare direct comparison of two different programs at such large scales, 6–36 months after launch, and suggests that personal interaction approaches should be considered by policy makers. Qualitative key informant interviews yielded data on each program's activities, which provide suggestions for further studies of the underlying behaviour change determinants involved
Oxalate formation under the hyperarid conditions of the Atacama desert as a mineral marker to provide clues to the source of organic carbon on Mars
In this study, we report the detection and characterization of the organic minerals weddellite
(CaC2O4 · 2H2O) and whewellite (CaC2O4 · H2O) in the hyperarid, Mars-like conditions of the Salar Grande,
Atacama desert, Chile. Weddellite and whewellite are commonly of biological origin on Earth and have great
potential for preserving records of carbon geochemistry and possible biological activity on Mars if they
are present there. Weddellite and whewellite have been found as secondary minerals occurring inside the
lower detrital unit that fills the Salar Grande basin. The extremely low solubility of most oxalate minerals
inhibits detection of oxalate by ion chromatography (IC). Crystalline oxalates, including weddellite and
whewellite, were detected by X-ray diffraction (XRD). The association of weddellite with surface biota and its
presence among subsurface detrital materials suggest the potential of a biological origin for Salar Grande
weddellite and whewellite. In this regard, biological activity is uniquely capable of concentrating oxalates
at levels detectable by XRD. The complementary detection of oxalate-bearing phases through IC in the upper
halite-rich unit suggests the presence of a soluble oxalate phase in the basin that is not detected by XRD.
The formation, transport, and concentration of oxalate in the Salar Grande may provide a geochemical
analogue for oxalate-bearing minerals recently suggested to exist on Mars
Discovery of New Natural Products by Intact-Cell Mass Spectrometry and LC-SPE-NMR: Malbranpyrroles, Novel Polyketides from Thermophilic Fungus Malbranchea sulfurea
Six photosensitive polyketides, malbranpyrroles A-F, were discovered from the thermophilic fungus Malbranchea sulfurea by using intact-cell desorption/ionization on silicon mass (ICD-MS) and LC-SPE-NMR. These two strategies facilitate the searching and structural determination of unstable natural products. The ICD-MS indicated that only brown hyphae of M. sulfurea can produce malbranpyrroles. The biosynthetic pathway of malbranpyrroles was evidenced by (13)C isotope precursors and amino acid feeding experiments. The cytotoxicity data revealed that the conformation of the conjugated system in malbranpyrroles does not affect cytotoxic potency against cancer cell lines. In addition, the chlorine atom was shown to be the pharmacophore for cytotoxicity
Search for Invisible Decays of and in and
Using a data sample of decays collected with the BES
II detector at the BEPC, searches for invisible decays of and
in to and are performed.
The signals, which are reconstructed in final states, are used
to tag the and decays. No signals are found for the
invisible decays of either or , and upper limits at the 90%
confidence level are determined to be for the ratio
and for . These are the first
searches for and decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo
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