13,224 research outputs found
Preliminary comparison of chemical heat storage systems for saving exhaust gas energy in gasoline and diesel engines
Flexural behaviour of precast segmental concrete beams internally prestressed with unbonded CFRP tendons under four-point loading
This study investigates the use of carbon fibre reinforced polymer (CFRP) tendons on precast segmental beams (PSBs) to tackle the corrosion problems which are likely to occur at joint locations of PSBs prestressed with steel tendons. Up to date, the use of CFRP tendons was extensively documented for monolithic beams while their application on PSBs has not been reported yet. Three precast segmental T-section beams including two beams with unbonded CFRP and one with steel tendons were built and tested under four-point loads in this study. The test results showed that CFRP tendons can be well used to replace the steel tendons on PSBs. The beams with CFRP tendons demonstrated both high strength and high ductility as compared to the beam with steel tendons. However, the stresses in the unbonded CFRP tendons at ultimate loading conditions of the tested beams were low, ranging from only about 66% to 72% of the nominal breaking tensile strength. The type of joints i.e. dry and epoxied, greatly affects the initial stiffness of the beams but has no effect on the opening of joints at ultimate loading stage. Moreover, a comprehensive examination on four existing code equations to predict the stress in the unbonded tendons showed that the four examined codes predicted well the stress at the ultimate loading condition of the unbonded steel tendons, however, they significantly under predicted those in the CFRP tendons. A modification in the strain reduction coefficient used by ACI 440.4R for predicting the stress increment in unbonded CFRP tendons of monolithic beams is therefore proposed for PSBs based on the experimental results
Presence of e-EDCs in surface water and effluents of pollution sources in Sai Gon and Dong Nai river basin
© 2016 This study aimed to assess the presence of estrogenic endocrine disrupting compounds (e-EDCs) including estriol, bisphenol A (BPA), atrazine (ATZ), octylphenol, octylphenol diethoxylate, octylphenol triethoxylate, nonylphenol, Nonylphenol triethoxylate (NPE3), nonylphenol diethoxylate (NPE2) and 17β-estradiol in: (i) Sai Gon and Dong Nai river waters which have been major raw water sources for drinking water supply for Ho Chi Minh City (HCMC) and neighbouring provinces, and (ii) water pollution sources located in their catchment basin. NPE3 and NPE2 were detected in most of the surface water samples. Concentrations of NPE3 were in a range of less than 5.9–235 ng L−1, whereas BPA was detected at significantly high concentrations in the dry season in canals in HCMC. In the upstream of Sai Gon and Dong Nai Rivers, ATZ concentrations were observed at water intake of water treatment plants served for HCMC water supply system. Similarly, high potential risk of NPE2 and NPE3 contamination at Phu Cuong Bridge near Hoa Phu water intake was identified. The significant correlation between NPE2, dissolved organic carbon and total nitrogen was found. Estrogenic equivalent or estrogenic activity of Sai Gon and Dong Nai Rivers was lower than those of the previous studies. Compared with other studies, e-EDCs of pollution in Sai Gon river basin were relatively low
On the Perturbative Nature of Color Superconductivity
Color superconductivity is a possible phase of high density QCD. We present a
systematic derivation of the transition temperature, T_C, from the QCD
Lagrangian through study of the di-quark proper vertex. With this approach, we
confirm the dependence of T_C on the coupling g, namely , previously obtained from the one-gluon exchange approximation
in the superconducting phase. The diagrammatic approach we employ allows us to
examine the perturbative expansion of the vertex and the propagators. We find
an additional O(1) contribution to the prefactor of the exponential from the
one-loop quark self energy and that the other one-loop radiative contributions
and the two gluon exchange vertex contribution are subleading.Comment: 13 pages, 3 figures, revtex, details and discussion expande
Dimethyl 2-[22,24-dimethyl-23-oxo-8,11,14-trioxa-25-azatetracyclo[19.3.1.02,7.015,20]pentacosa-2,4,6,15(20),16,18-hexaen-25-yl]but-2-enedioate
The title compound, C29H33NO8, is a product of the Michael addition of the cyclic secondary amine subunit of the aza-14-crown-4 ether to dimethyl acetylenedicarboxylate. The piperidinone ring exhibits a distorted chair conformation, and the dimethyl ethylenedicarboxylate fragment has a cis configuration with a dihedral angle of 78.96 (5)° between the two carboxylate groups. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds
(2E,25E)-11,14,17,33,36,39,42-Heptaoxapentacyclo[41.4.0.05,10.018,23.027,32]heptatetraconta-1(43),2,5(10),6,8,18,20,22,25,27,29,31,44,46-tetradecaene-4,24-dione
The title compound, C40H40O9, is a product of the double crotonic condensation of bis(2-acetylphenoxy)-3-oxapentane with bis(2-formylphenoxy)-3,6-dioxaoctane. The title macromolecule includes the 31-crown-7-ether skeletal unit and adopts a saddle-like conformation. The two ethylene fragments have E configurations. The volume of the internal cavity of the macrocycle is approximately 125 Å3. In the crystal, the molecules are arranged at van der Waals distances
How cheap can hygienic latrines be?
A construction and operation costing of 12 types of hygienic latrines widely used in rural areas of Vietnam and presented in the Hygienic latrine Manual of the Ministry of Health, using traditional construction materials has been conducted. The cost of latrines using traditional construction materials is ranging from USD37.5 (VIP) to USD194.4 (Septic tank constructed by brick for treatment of black and grey wastewater from sitting bowl toilet). Annually averted O&M costs of Vietnamese latrines range from USD1.86 (VIP) to USD 4.58 (wet latrine with septic tank) per capita per year. Costs of hygienic latrines can be further reduced, applying solutions such as using local materials for construction, reducing the tank volume by using the water-saving flushing devices or applying more frequent tank emptying services and mass production of latrine components. The less a hygienic latrine costs, the more chance for poor people in different places can get access to improved sanitation
Lifetime Effects in Color Superconductivity at Weak Coupling
Present computations of the gap of color superconductivity in weak coupling
assume that the quarks which participate in the condensation process are
infinitely long-lived. However, the quasiparticles in a plasma are
characterized by having a finite lifetime. In this article we take into account
this fact to evaluate its effect in the computation of the color gap. By first
considering the Schwinger-Dyson equations in weak coupling, when one-loop
self-energy corrections are included, a general gap equation is written in
terms of the spectral densities of the quasiparticles. To evaluate lifetime
effects, we then model the spectral density by a Lorentzian function. We argue
that the decay of the quasiparticles limits their efficiency to condense. The
value of the gap at the Fermi surface is then reduced. To leading order, these
lifetime effects can be taken into account by replacing the coupling constant
of the gap equation by a reduced effective one.Comment: 16 pages, 2 figures; explanations on the role of the Meissner effect
added; 2 references added; accepted for publication in PR
Debye screening and Meissner effect in a two-flavor color superconductor
I compute the gluon self-energy in a color superconductor with two flavors of
massless quarks, where condensation of Cooper pairs breaks SU(3)_c to SU(2)_c.
At zero temperature, there is neither Debye screening nor a Meissner effect for
the three gluons of the unbroken SU(2)_c subgroup. The remaining five gluons
attain an electric as well as a magnetic mass. For temperatures approaching the
critical temperature for the onset of color superconductivity, or for gluon
momenta much larger than the color-superconducting gap, the self-energy assumes
the form given by the standard hard-dense loop approximation. The gluon
self-energy determines the coefficient of the kinetic term in the effective
low-energy theory for the condensate fields.Comment: 29 pages, RevTe
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