Synthesis and characterization of wholly aromatic polyamides containing pendent amino and cyano groups

The new pyrazole-ring containing diamine monomer with amino and cyano groups, 1,3-di-p-aminophenyl-4-cyano-5-aminopyrazole (PYA), was prepared from 4-nitrobenzoyl chloride and 4-nitrophenyl hydrazine with 4 steps. The monomer was converted to polyamides with terephthaloyl chloride and isophthaloyl chloride. The amino and cyano groups on the pyrazole-ring were not affected during polymerization. The synthesized polyamides having intrinsic viscosities of 0.92 – 1.18 dL/g were amorphous, and soluble in polar aprotic solvents and boiling acetone and THF. The polymers had high glass transition temperatures and high thermal stability. 5% weight loss temperatures in nitrogen occurred around 490 °C, but these polymers are partially degraded at 300 °C in air due to the amino group on the pyrazole-ring. Received: 6 March 1997/Accepted: 1 April 1997     

3 siblings with identical, rare pneumopathy

Pulmonary alveolar microlithiasis was found in three siblings. Only the youngest of them, a former smoker, developed endstage lung disease. The other two are asymptomatic with normal lung function despite impressive changes on all chest radiographs. The role of smoking in perpetuating microlithiasis and furthering the progression of this disease is discussed.     

Efficient solving methods exploiting sparsity of matrix in real-time multibody dynamic simulation with relative coordinate formulation

In this paper, new methods for efficiently solving linear acceleration equations of multibody dynamic simulation exploiting sparsity for real-time simulation are presented. The coefficient matrix of the equations tends to have a large number of zero entries according to the relative joint coordinate numbering. By adequate joint coordinate numbering, the matrix has minimum off-diagonal terms and a block pattern of non-zero entries and can be solved efficiently. The proposed methods, using sparse Cholesky method and recursive block mass matrix method, take advantages of both the special structure and the sparsity of the coefficient matrix to reduce computation time. The first method solves thenxn sparse coefficient matrix for the accelerations, wheren denotes the number of relative coordinates. In the second method, for vehicle dynamic simulation, simple manipulations bring the original problem of dimensionnxn to an equivalent problem of dimension 6×6 to be solved for the accelerations of a vehicle chassis. For vehicle dynamic simulation, the proposed solution methods are proved to be more efficient than the classical approaches using reduced Lagrangian multiplier method. With the methods computation time for real-time vehicle dynamic simulation can be reduced up to 14 per cent compared to the classical approach.     

Experimental study of miniaturized tip test

A tip test was developed and used successfully for friction measurement between the billet and dies or punches for the cold forging process. In the present investigation, the test was downsized and experimentally investigated to find the size effect on test results. For the test, aluminum alloys of 2024-O and 6061-O were used and the specimen was made into a cylinder of diameter and height of 10.0mm and 5.0mm, respectively. For lubrications, VG32, VG100, grease, and corn oil were used in experiments and tests were also carried out with two different humidity conditions. A micro-hardness test was made to compare the hardness distribution with the strain distribution obtained from the finite element simulation. The load levels and tip distances were measured for Al6061-O specimen with various lubrication conditions and compared to each other to find any correlation between the two. The shear friction factors were determined for various lubrications by using the finite element simulation under the present condition.     

Autoignition and front propagation in low temperature combustion engine environments

In this paper, we computationally investigate the fundamental aspects of autoignition and subsequent combustion phenomena in low temperature combustion (LTC) engine environments using direct numerical simulations (DNS). In particular, the effects of thermal and equivalence ratio stratification on the autoignition and subsequent front propagation in high pressure and stratified hydrogen-air turbulent mixtures are studied using detailed chemistry. Depending on fuel injection timing, exhaust gas recirculation, and wall heat loss, different correlations between temperature (T) – equivalence ratio (?) fields can exist prior to the major heat release event. Here, we investigate three cases with different initial T–? correlations: (A) a baseline case of a uniform composition with temperature inhomogeneities only, (B) uncorrelated T–? fields, and (C) negatively-correlated T–? fields. Numerical diagnostics are developed based on an appropriately defined Damköhler number to distinguish different modes of heat release. It is found that the majority of heat release in the baseline case and the uncorrelated case occurs during the front propagation in the form of both spontaneous ignition fronts as well as deflagration waves, whereas the negatively correlated case ignites predominantly homogeneously.     

Limitations of dual and complementary inorganic–organic electrochromic device for smart window application and its colorimetric analysis

Inorganic tungsten oxide (WO₃) and organic polyaniline (PANI) films were used as the cathodic and anodic electrodes of an inorganic–organic electrochromic device (IOECD). WO₃ was deposited by sputtering while PANI films were electrodeposited on transparent Indium doped Tin Oxide (ITO) glass substrates, respectively. Optical and electrochemical studies were performed to find the optical attenuation, coloration efficiencies, reversibility and response time separately for the individual films as well as for the assembled IOECD. The change in transmittance of WO₃ film was found to be 63.92%. PANI film showed an optical attenuation of 50.69% while the transmission change through the IOECD was equal to 57%. Colorimetric analysis was done to define the colors in the bleached and colored states in terms of L*ab values and xy chromaticity diagram. Factors limiting the performance of an IOECD were analyzed. It was found that in a charge unbalanced dual complementary IOECD, the coloration efficiency is always less than that of one of the constituent electrodes.     

A mathematical study on a unified variational principle with two constrained parameters

In this paper, a parameterized variational principle based on a mixed functional obtained by a linear combination of the total potential energy functional, the modified Hellinger-Reissner functional, and the Hu-Washizu functional with two constrained parameters is proposed, and the mathematical characteristics of the variational equation of the principle are investigated for the analysis of boundary value problems in linear elasticity. It is first proved that the Euler-Lagrange equations of the variational equation is identical to the governing equations for the given problem. Then existence of the unique solution of the variational equation is systematically proved by showing that the energy bilinear form is weakly-coercive. As an application, the stress/strain smoothing can be obtained as a form of mixed FEM based on the variational equation.     

A Windows-based interactive and graphic package for the educationand training of power system analysis and operation

This paper presents a Windows-based interactive graphic package developed by the authors for the education and training of the power system modeling, analysis and operation with a user-friendly graphical user interface (GUI) and visual database management system (VDBMS). To achieve this goal, the package is designed to have following features: a graphic editor to visually edit the power system diagram; Windows-based power system database to interactively manage the data; graphic representations; animation; and interrupting schemes. The application programs in this package include the power flow calculation, transient stability analysis, fault analysis, economic dispatch and automatic load-frequency control. This package may be useful for educational and training purposes     

O/sup 2/ABA: a novel high-performance predictable circuit architecture for the deep submicron era

Current VLSI design techniques focus on four major goals: higher integration, faster speed, lower power, and shorter time-to-market. These goals have been accomplished mainly by deep submicron (DSM) technology along with voltage scaling. However, scaling down of feature size causes larger interwire capacitance which results in large crosstalk between interconnects. In this paper, we propose a novel predictable circuit architecture, named "optimized overlaying array-based architecture" (O/sup 2/ABA), especially suited for the deep submicron regime. O/sup 2/ABA achieves reduction in crosstalk by considering the current directions and by reducing interwire capacitance. The introduction of "unit cell" leads to regularity, which makes the performance predictable even before layout, and shortens design time. O/sup 2/ABA is compared with other design styles, such as custom design and standard cell approach, in terms of coupling capacitance, area, and delay.