MODIFIED SCHEME BASED ON SEMI-ANALYTIC APPROACH FOR COMPUTING NON-PROBABILISTIC RELIABILITY INDEX

A new computation scheme proposed to tackle commensurate problems is devel- oped by modifying the semi-analytic approach for minimizing computational complexity. Using the proposed scheme, the limit state equations, usually referred to as the failure surface, are obtained from transformation of an interval variable to a normalized one. In order to minimize the computational cost, two algorithms for optimizing the calculation steps have been proposed. The monotonicity of the objective function can be determined from narrowing the scope of interval variables in normalized infinite space by incorporating the algorithms into the computational scheme. Two examples are used to illustrate the operation and computational efficiency of the approach. The results of these examples show that the proposed algorithms can greatly reduce the computation complexity without sacrificing the computational accuracy. The advantage of the proposed scheme can be even more efficient for analyzing sophistic structures.     

PREDICTION FOR FORMING LIMIT OF AL2024T3 SHEET BASED ON DAMAGE THEORY USING FINITE ELEMENT METHOD

This paper presents the application of anisotropic damage theory to the study of forming limit diagram of A12024T3 aluminum alloy sheet. In the prediction of limiting strains of the aluminum sheet structure, a finite element cell model has been constructed. The cell model consists of two phases, the aluminum alloy matrix and the intermetallic cluster. The material behavior of the aluminum alloy matrix is described with a fully coupled elasto-plastic damage constitutive equation. The intermetallic cluster is assumed to be elastic and brittle. By varying the stretching ratio, the limiting strains of the sheet under biaxial stretching have been predicted by using the necking criterion proposed. The prediction is in good agreement with the experimental findings. Moreover, the finite element cell model can provide information for understanding the microscopic damage mechanism of the aluminum alloy. Over-estimation of the limit strains may result if the effect of material damage is ignored in the sheet metal forming study.     

Surface dynamics of noisy viscoelastic films by adiabatic approximation

Surface dynamics is sometimes used to determine the rheological properties of soft materials. In typical data analyses, surface capillary waves are included without incorporating thermal noise. A phenomenological expression for the time-dependent power spectral density has been proposed to account for thermal noise and shown to agree well with experiment. In this paper, we investigate the surface dynamics of viscoelastic films with thermal noise by using an adiabatic approximation involving fast quasi-equilibrium elastic vibrations to derive the power spectral density. Our result justifies the use of the phenomenological expression.     

Asymmetric synthesis of (triaryl)methylamines by rhodium-catalyzed addition of arylboroxines to cyclic N-sulfonyl ketimines

Asymmetric addition of arylboroxines to cyclic N-sulfonyl ketimines proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of benzosultams, where a triaryl-substituted stereogenic carbon center was created with high enantioselectivity (93-99% ee). The chiral benzosultams were transformed into the chiral (triaryl)methylamines by breaking the cyclic structure.     

Quantitation of plasma angiotensin II in healthy Chinese subjects by a validated liquid chromatography tandem mass spectrometry method

Quantitation of plasma angiotensin (Ang) II, the active mediator of the renin–angiotensin system, is challenging owing to its low physiological concentration. We report a validated liquid chromatography–mass spectrometry (LCMS) method to overcome this challenge. Ang II was extracted from EDTA plasma by an offline solid-phase extraction procedure with a Waters MAX μElution plate. LCMS quantitation was performed on the Waters TQS system, monitoring the 3+ ions of the peptide. The analytical performance of the LCMS method was validated. The stability of Ang II was studied with or without the presence of a protease inhibitor. Local reference intervals were established from 143 healthy normotensive subjects (57% female, 21–60 years old). The Ang II LCMS method had a measurable range of 3.3–700 pmol/L. The between-batch precision coefficient of variation was <7% over Ang II concentrations of 8.6–110 pmol/L. No significant matrix interference and carryover were observed. There was no significant difference in Ang II concentration in EDTA blood and plasma for at least 2h and 1 h at room temperature, respectively. Ang II was stable for at least 1 year when stored at −80°C, with or without the protease inhibitor. Age-dependent Ang II reference intervals were established: 4.4–17.7 pmol/L (21–30 years) and 3.9–12.8 pmol/L (31–60 years). The present LCMS method is suitable for quantitation of plasma Ang II to study the renin-angiotensin system.     

Ruthenium(II) porphyrin-catalyzed amidation of aromatic heterocycles

[reaction: see text] Ruthenium(II) porphyrin-catalyzed amidation of aromatic heterocycles with iminoiodanes under mild conditions (CH(2)Cl(2), 4 A molecular sieves, ultrasound, 40 degrees C) was achieved in moderate to good yields (up to 84%) and conversions (up to 99%). Only the N,N-ditosylamidated product was obtained for reactions involving heteroarenes, where X = O, S, or NTs. N-Alkyl- and N-aryl-substituted pyrroles, on the other hand, were shown to give the 3,4-diaminated adduct.     

A Practical Route to Chiral Phenylalanine via the Condensation of Keto Acids with Amides and Asymmetric Hydrogenation

The condensation of β-phenylpyruvic acid with amides gave olefinic intermediates in good yields (75-80%). The asymmetric catalytic hydrogenation of α-acetamidocinnamic acid with high enantioselectivity is described.     

Alpha particle bias ionization in a pulsed nitrogen laser

This work reports the role of alpha particles generated by Americium (²⁴¹Am) stripes placed inside the discharge channel in providing a bias ionized background plasma before, during, and after the discharge of the N₂ TE UV laser (337.1 nm) circuit. The enhancement in stimulated radiation output characteristics in terms of gas pressure, charging voltage, and pulse width, with and without alpha particles, are shown. The increased laser yield is interpreted qualitatively through plasma impedance in the discharge circuit. PACS 42.60.By; 42.60.Lh     

Construction of improved estimators in multiparameter estimation for continuous exponential families

A unified theory of simultaneous estimation of parameters for the continuous exponential family is presented. Estimators are constructed that improve on the standard ones (the maximum likelihood, UMVUE or best invariant estimator). These improved estimators shift the standard ones towards possibly non-zero points or data based points.