Three-dimensional linear dynamic analysis of buildings with 32-bit virtual-memory minicomputers

This paper focuses on computer-aided analysis of three-dimensional buildings with 32-bit, virtual-memory minicomputers. Various floor, inertial, geometry, stiffness, and displacement models of three-dimensional buildings are discussed with respect to implications for computational efficiency. From this discussion a model for three-dimensional buildings is selected for use with virtual-memory minicomputers. This paper also treats the use of symbolic manipulation, dynamic allocation of memory, and matrix storage and manipulation to achieve computational efficiency. Examples with computational statistics illustrate the ideas presented.     

手动或自动操作的双向可控硅测试仪

双向可控硅是双向交流开关,可以在最高600V电压下控制高达25Arms电流的负载。它们用于电机速度、加热器和白炽灯的控制。逻辑型双向可控硅对微控制器驱动器件尤有吸引力。微控制器输出端口可以直接驱动一只双向可控硅,因为可控硅的触发电流只有3～10mA。与所有电子器件一样．双向可控硅也存在一些内部问题,在将其用于某个设计以前可以检测这些问题。     

Bridging a Culture: The Design of Museo Soumaya

Fernando Romero and Armando Ramos of Fernando Romero EnterprisE (FREE) describe how the firm's design for an iconic museum in Mexico City, which adopted complex computational techniques, required them to develop an integrated and highly collaborative approach to design; with a central digital 3-D model being applied throughout the construction phase.     

Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

Despite the important role of strontium aluminosilicate glasses in various technologies, there is no available phase diagram for this ternary system in the ACerS-NIST Phase Equilibria Diagrams Database. Establishing the liquidus surface (liquidus temperature T_liq and primary devitrification phase) is crucial for glass composition design, because the liquidus temperature is intimately connected with the glass-forming ability of the melt. In this work, we have determined the liquidus surface by X-ray diffraction phase analyses of isothermally reacted samples from powder mixtures of 24 compositions. In the composition range of interest for industrial glasses, T_liq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO₂, SiO₂+Al₂O₃, and SrO contents, respectively. By comparison with the phase diagrams for CaO-Al₂O₃-SiO₂ and MgO-Al₂O₃-SiO₂ systems, we have found that for the highest [RO]/[Al₂O₃] ratios, T_liq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging to the SrO-Al₂O₃-SiO₂ family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature.     

Highly Diastereo‐ and Enantioselective Catalytic Domino Thia‐Michael/Aldol Reactions: Synthesis of Benzothiopyrans with Three Contiguous Stereocenters

Highly enantioselective organocatalytic domino thia‐Michael/aldol reactions between 2‐mercaptoacetophenone and α,β‐unsaturated aldehydes are presented. The reactions proceed with excellent chemo‐, diastereo‐ and enantioselectivity to give the corresponding benzothiopyran derivatives in high yields with up to >15:1 dr and 96 to >99 % ee.     

Half‐Sandwich Scorpionate Vanadium,Iron and Copper Complexes: Synthesis and Application in the Catalytic Peroxidative Oxidation of Cyclohexane under Mild Conditions

The new half‐sandwich scorpionate complexes [hydridotris(1‐pyrazolyl)methane]vanadium trichloride, ([VCl₃{HC(pz)₃}] 1 (pz=pyrazolyl), [tris(1‐pyrazolyl)methanesulfonate]vanadium trichloride, [VCl₃{SO₃C(pz)₃}] 2 , [hydrido(1‐pyrazolyl)methane]iron dichloride, [FeCl₂{HC(pz)₃}] 3 , lithium [tris(1‐pyrazolyl)methanesulfonate]dichloroferrate, Li[FeCl₂{SO₃C(pz)₃}] 4 , and [tris(1‐pyrazolyl)methanesulfonate]copper chloride, [CuCl{SO₃C(pz)₃}] 5 were synthesized, characterized and shown to act, as well as the related (tripyrazolylmethane)copper dichloride, [CuCl₂{HC(pz)₃}] 6 , as selective catalysts (or catalyst precursors) for the peroxidative oxidation (with hydrogen peroxide) of cyclohexane to cyclohexanol and cyclohexanone, under mild conditions (at room temperature and using an aqueous solution of H₂O₂). The iron complexes are the most active ones (reaching TON values up to ca. 690), the effects of a variety of factors are reported and the reaction is shown to proceed via both C‐ and O‐centred radical mechanisms, conceivably involving a metal‐based oxidant.     

Absence of ferromagnetism in ferroelectric Mn-doped BaTiO3 nanofibers

Pure and Mn-doped barium titanate nanofibers were synthesized by the electrospinning method. The morphology, microstructure and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy and transmission electron microscopy. After annealing at 850°C, we obtain nanofibers a few μm long, formed by nanoparticles of irregular shape with sizes around 100 nm. X-ray diffraction and Raman spectroscopy show that a partial phase transition from tetragonal to hexagonal takes place for BaTi_0.90Mn_0.10O₃. Vibrational phonon modes were calculated for BaTiO₃ within the density functional theory (DFT) framework. Ferroelectricity has been probed on pure and Mn-doped BaTiO₃ nanofibers, by means of piezoresponse force microscopy in an atomic force microscope, confirming the polar domain switching behavior of the fibers. The measured piezoelectric coefficient d₃₃ were 31 and 22 pm/V for BaTiO₃ and BaTi_0.90Mn_0.10O₃. Magnetic properties of the samples were probed in a superconducting quantum interference device. Diamagnetic and paramagnetic behaviors were found in pure and Mn-doped samples, respectively.     

Temperature stimuli-responsive nanoparticles from chitosan-graft-poly(N-vinylcaprolactam) as a drug delivery system

This work describes the preparation of thermosensitive chitosan-graft-poly(N-vinylcaprolactam) nanoparticles by ionic gelation and their potential use as a controlled drug delivery system, using doxorubicin as a model drug. A systematic study of the effect of the main processing parameters on both the size and thermoresponsive behavior of nanoparticles was investigated. The size of the particles is strongly dependent on the length of the poly(N-vinylcaprolactam) grafted chains and the concentration of the copolymer and crosslinking agent solutions. The molecular structure of the copolymer plays an essential role in the phase transition temperature of the particles, which decreases with the length of PVCL grafted chain. The system displayed proper drug-association parameters, and the drug-loaded nanoparticles exhibited dose-dependent cytotoxicity. A significant increase in the doxorubicin delivery rate was observed above the phase transition temperature (40 °C). These features indicate that these nanoparticles are suitable for the development of a new thermally controlled anti-cancer drug delivery system. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47831.