计量经济分析 = Econometric analysis

Carbon nanotube–polymer composites: Chemistry, processing, mechanical and electrical properties

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

https://www.ece.lsu.edu/mcu/lawss/add_materials/FaultDetectionPart1.pdf

A Review of Process Fault Detection and Diagnosis Part I : Quantitative Model-Based Methods

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

New techniques and procedures are described that enable one to measure the mechanical properties of polysilicon films that are 3.5 /spl mu/m thick. Polysilicon is deposited onto a silicon substrate which is then etched away to leave a tensile specimen in the middle of the die. The grip ends of the structure are glued to the grips of a linear air bearing attached to a piezoelectrically actuated loading system. Strain is measured directly on the specimen with laser interferometry. The specimens are fabricated at the Microelectronics Center of North Carolina with their MUMPs process. The results of 48 tests on five different sets of MUMPs specimens yield the following material properties: Young's modulus=169/spl plusmn/6.15 GPa, Poisson's ratio=0.22/spl plusmn/0.011, and tensile strength=1.20/spl plusmn/0.15 GPa These values have a reasonably low coefficient of variation which demonstrates the consistency of both the processing and the measurement techniques.

Measurements of Young's modulus, Poisson's ratio, and tensile strength of polysilicon

Process fault detection and diagnosis using neural networks—I. steady-state processes

Single wall carbon nanotubes (SWNTs) and vapor grown carbon fibers (VGCFs) were compounded with poly(acrylonitrile-co-butadiene-co-styrene) (ABS) to create composite materials for use with Extrusion Freeform Fabrication (EFF). The composite materials possessed homogeneously dispersed fibers that were oriented with EFF processing. The VGCF and SWNT reinforced materials processed by EFF displayed improved tensile modulus compared to similarly processed ABS and composite material with isotropic fiber orientation, and the SWNT reinforced material displayed the highest properties, strength and modulus, of the materials studied. The materials containing oriented VGCFs and SWNTs showed modulus improvements of 44 and 93%, respectively.

Single wall nanotube and vapor grown carbon fiber reinforced polymers processed by extrusion freeform fabrication

Rectangular columns are often used in bridge pier design, and they make up the majority of building columns. Columns in need of strengthening and retrofit are very common. This paper presents results of a comprehensive experimental investigation on the behavior of axially loaded rectangular columns that have been strengthened with glass fibre reinforced polymer (GFRP) wrap. This paper is intended to examine several aspects related to the use of glass FRP fabrics for strengthening rectangular columns subjected to axial compression. The objectives of the study are as follows: (1) to evaluate the effectiveness of external GFRP strengthening for rectangular Concrete Columns (2) to evaluate the effect of number of GFRP layers on the ultimate load and ductility of confined concrete and (3) to evaluate the effect of the aspect ratio of the column on the effectively confined cross-section. To cover a wide range of cross-sectional dimension ratios, three aspect ratios (a/b, where a and b are, respectively, the longer and shorter sides of the cross-section) were studied: a/b = 1.0, a/b = 1.25, and a/b = 1.66. Specimens with zero, one, and two layers of GFRP wrap were investigated. Totally nine specimens were subjected to axial compression which includes three control specimens. All the test specimens were loaded to failure in axial compression and the behavior of the specimens in the axial and transverse directions was investigated.

Ranji Vaidyanathan

Papers

Measurements of Young's modulus, Poisson's ratio, and tensile strength of polysilicon

Process fault detection and diagnosis using neural networks—I. steady-state processes

Single wall nanotube and vapor grown carbon fiber reinforced polymers processed by extrusion freeform fabrication

Behaviour of reinforced concrete rectangular columns strengthened using GFRP

Trabecular scaffolds created using micro CT guided fused deposition modeling