The influence of high performance matrices on fracture behavior of concrete

Modification of cement matrices by the addition of micro particle pozzolanic materials such as silica fume and fly ash is known to improve the strength of concrete, but its contributions to fracture behavior remains unclear. In this study, the influence of replacing cement by silica fume and fly ash on the cement matrix-coarse aggregate interfacial bond, compressive stress-strain behavior and fracture behavior of concrete is investigated. While the linear elastic fracture mechanics (LEFM) concept is not appropriate for concrete, a nonlinear fracture model based on the load vs. load-line deflection and the load vs. crack-mouthopening displacement (CMOD) responses of the three-point bend tests on notched beams is proposed and validated. Instead of using the LEFM based Two-Parameter Fracture Model that cannot adequately describes fracture processes in concrete, the proposed model is capable of generating the load vs. crack growth curve and the fracture resistance curve, and seems to be more appropriate for studying fracture behavior of concrete. Incorporating silica fume in concrete mixture is found to have many beneficial effects on cement matrix-coarse aggregate interface, but less likely to improve the toughness of the cement matrix itself The enhanced interfacial bond due to silica fume produces a more homogeneous concrete, which is responsible for the high strength, but more brittle concrete. It is shown that improving interfacial bond has positive effect on the pre-peak fracture behavior of concrete (e.g. the critical energy release rate, GC), but does not necessarily improve the overall fracture behavior (e.g. the fracture energy, GF, and the brittleness). In this study, coal fly ashes were fractionated into various size ranges by the air classifier method. It is found that replacing cement by very fine fly ash (with average particle size less than 3 microns) can enhance both the toughness of cement matrix and the interfacial bond, which results in high strength and less brittle concrete. The coarser fly ashes, which are porous and less reactive, are shown to enhance the interfacial bond, but produce brittle cement matrix. By reducing the particle size of fly ash, incorporating fly ash in cement matrix can improve both the strength and brittleness of concrete

A Zero Bias Pixel Sensor and its Zero-Bias Column Buffer-Direct-Injection Circuit

Two pixel sensors, namely active pixel sensor (APS) and pseudo-active pixel sensor (PAPS), are reviewed to show that APS suffers from dark current while PAPS suffers from leakage current. Then a new pixel sensor called  zero bias pixel sensor (ZBPS) in which only two MOS switches in addition to the photodiode are used, one for connecting the pixel’s photodiode to a column bus and the other for bypassing it. A zero-bias column buffer-direct-injection (ZCBDI) circuit, which is similar to a regulated cascode amplifier, is used to control the voltage at column bus at zero. All ZBPS pixels are guaranteed to work at zero voltage at all times to eliminate the dark current as well as leakage current. A case of a 10 µm x 10 µm ZBPS pixel designed with standard 0.18 µm CMOS process is studied through simulation. This pixel generates a photocurrent within a range from 1 pA to 100 nA. To handle a large variation of photocurrent while maintaining zero column voltage, the ZCBDI is designed using differential cascode, common source, and buffer stages and then compensated for 50 degree phase margin. Transient simulation shows that the pixel steady state response time is around 1.406 ms, leading to at most 5.5 frames per second for an image of 128 x 128 ZBPS pixels. The fill factor of ZBPS for this case is around 59%

直状せん断工具の押付けを受ける樹脂・紙層板材の切断特性に対する工具条件の影響

国立大学法人長岡技術科学大

Photocatalytic Degradation of Phenol Using Nb-Loaded ZnO Nanoparticles

Niobium-doped Zinc Oxide nanoparticles (Nb-doped ZnO NPs) in the range of 20 and 40 nm were synthesized by Flame Spray Pyrolysis (FSP) technique. The crystalline phase, morphology and size of the nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectroscopy. The specific surface area of the nanoparticles was measured by nitrogen adsorption (BET analysis). The pure ZnO and Nb-doped ZnO NPs were found to have the clear spherical, hexagonal and rod-like morphologies. To the best of our knowledge, the application of Nb-doped ZnO NPs as a photocatalyst has not been reported yet. In this study, the photocatalytic activities of pure ZnO and Nb-doped ZnO NPs were determined by studying the mineralization of phenol under UV light illumination. The results indicated that all Nb-doped ZnO NPs have better photocatalytic activity than the pure ZnO nanoparticles. It was found that, 0.50 mol% Nb-doped ZnO NPs exhibited the fastest response to the degradation of phenol

A novel synthesis of light transmission from upcycled polyethylene terephthalate polymer and low-density polyethylene for greenhouse design in tropical climate

To support the circular economy in Thai’s agriculture, the main interviewed challenges point to knowledge and knowhow for greenhouse structure and system boosting up productivities. One popular material that possibly affected productivity is transparent polymer film, which can be recycled based on material property and blowing machine condition. This paper investigates the light transmittance performance of transparent polyethylene terephthalate polymer (PET) and low-density polyethylene (LDPE) sheets for use in low-energy greenhouses in tropical climates. The aim of the study is to optimize the thermal performance and light transmittance of these materials to support plant growth and human comfort. The study focuses on seven stages of plant growth, each of which requires different light characteristics including 1) seed, 2) germinating, 3) young seedling, 4) older vine, 5) flowering, 6) fruit bearing and 7) harvesting and drying. Each stage requires different light characteristics, e.g. light intensity, red light, blue light, white light and ultraviolet (UV) and pulsed light (PL). The methodology involves selecting PET and LDPE materials, preparing samples for thermal property and lighting laboratory tests and analysing the results based on suitable criteria. The findings show that LDPE sheets have 28.78% lower light transmittance than PET sheets, making them suitable for supporting the seedling stage and older vines of plant growth. PET sheets, on the other hand, deliver a high intensity of red light, making them suitable for stimulating photosynthesis in older vines and during the harvesting process. The study highlights the importance of considering both thermal performance and light transmittance when selecting materials for low-energy greenhouses in tropical climates

Influence of Ground Calcium Carbonate Waste on the Properties of Green Self-Consolidating Concrete Prepared by Low-Quality Bagasse Ash and Rice Husk Ash

Bagasse ash (BA) and rice husk ash (RHA) are by-products from electricity power plants. Ground calcium carbonate waste (GCW) is the by-product of the mining of calcium carbonate (CaCO3) in the color pigment manufacturing industry. Both BA and RHA are classified as low-quality pozzolanic materials, differing from GCW, which contains a high calcium oxide (CaO) content that leads to products equivalent to the hydration reaction. Therefore, GCW is likely able to improve the properties of self-consolidating concrete (SCC) incorporating BA and RHA. This paper discusses the production of green self-consolidating concrete (gSCC) and identifies the benefit of using GCW in gSCC prepared by triple combined GCW (10 and 20 wt%), BA (10, 20, and 30 wt%), and RHA (20 wt%). The results indicate that the majority of the gSCC retain acceptable flowability. The differences in the levels of gSCC substitution and the V-funnel flow results show general correlations with the increase in GCW. The gSCC prepared by 10 wt% GCW associated with 10 wt% BA and 20 wt% RHA was improved significantly. The filling and passing abilities of the gSCC were improved by using GCW. In addition, gSCC achieved mechanical property development and was able to minimize the consumption of OPC by up to 40%

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After implementation of the National Economic and Social Development Plan (1961-1966), Thailand experienced increasing high rates of economic growth. However by mid 1997, Thailand's economy was slipping into the so-called "Thailand financial crisis": falling property prices, slowing exports, rising trade deficits, and the devaluation of the Thai baht. This raises concern about the future. The purpose of this thesis is to examine Thai economic policies leading up to current crisis. Using hypothesis of Williamson and Haggard, the country's economic reforms will be evaluated. From these finding, several conclusions will be drawn concerning the country's economic future.http://archive.org/details/anevaluationoffi1094532703NARoyal Thai Navy authorApproved for public release; distribution is unlimited