113 research outputs found
THEORETICAL INVESTIGATION ON OPTICAL PROPERTIES OF 2D MATERIALS AND MECHANICAL PROPERTIES OF POLYMER COMPOSITES AT MOLECULAR LEVEL
Get PDFThe field of two-dimensional (2D) layered materials provides a new platform for studying diverse physical phenomena that are scientifically interesting and relevant for technological applications. Theoretical predictions from atomically resolved computational simulations of 2D materials play a pivotal role in designing and advancing these developments. The focus of this thesis is 2D materials especially graphene and BN studied using density functional theory (DFT) and molecular dynamics (MD) simulations. In the first half of the thesis, the electronic structure and optical properties are discussed for graphene, antimonene, and borophene. It is found that the absorbance in (atomically flat) multilayer antimonene (group V) is comparable to or greater than that for multilayer borophene (group III) and graphene (group IV). The number of layers has a substantial impact on the electrical and optical properties of graphene, antimonene, and borophene. Unlike graphene and antimonene, however, multilayer δ6-borophene exhibits extremely anisotropic electrical and optical characteristics. Overall, our findings imply that multilayer graphene and antimonene are good optical absorbers, particularly in the infrared region of the spectrum, and could be employed as a coating to protect against mid-IR tunable lasers. However, borophene because of its high optical transparency and good metallicity, could be a promising choice for transparent conductive 2D materials with applications in photovoltaics, performance-controlled optoelectronic devices, and touch displays. Molecular-level simulations for monomers with graphene/BN were undertaken to relate the interfacial features with the corresponding mechanical response in terms of strain and stiffness. The results show that the nature of bonding at the interface determines the interaction strength between resin (or hardener) and graphene and that the mechanical response follows the hierarchical order of the interaction strength at the interface. In addition, the change in polarity from graphene to BN monolayer also leads to improved interfacial strength as well as increased transverse stiffness at the molecular level for both resins and hardeners. We have also studied the effect of BN reinforcement with representative cases of cyanate esters, epoxy, and bismaleimide (BMI) resins using molecular dynamics to characterize the bulk level properties of reinforcement/polymer interface. Calculations simulating pull-apart transverse tension experiments find that the non-fluorinated ester interface exhibits higher stiffness and toughness than the fluorinated interface. On the other hand, the epoxy/BN interface is predicted to have significantly lower toughness (or resistance to fracture) than the BMI/BN interface. BMI, thus, appears to be the polymer matrix of choice when considering the BN nanomaterials as reinforcement compared to either cyanate ester or epoxy polymers for structural applications. These results based on molecular simulations emphasize the need to use computational modeling to efficiently and accurately determine molecular-level polymer/surface combinations that yield optimal composite material mechanical performance. This is especially true when designing and developing high-performance composites with nanoscale reinforcement
Knowledge Management Systems Leveraging the Competitive Advantage of Top IT Organizations: A Multi-case Study of Benchmarking Practices
No full textMetal Organic Frameworks for Gas-phase Capacitive Sensing
No full textOLD ChemE/Organic Materials and Interface
Agricultural trade liberalization in the Uruguay Round : one step forward, one step back?
Get PDFAfter evaluating the Uruguay Round's impact on agriculture and border protection in the next decade, the author concludes that while there was significant reform of the rules - particularly the conversion of nontariff barriers into tariffs and the reduction and binding of all tariffs - in practice, trade will probably be liberalized less than expected. The objective of the Round was to reverse protectionism and remove trade distortions. This may not be achieved in practice, at least not until further reductions are carried out in future rounds of negotiations. The major exception to this conclusion is in high-income Asian countries, where protection for major commodities will be significantly reduced. The tariffication and binding of all tariffs on agricultural products represents a significant step forward. Liberalization is implicit because countries are prohhibited from arbitrarily raising tariffs to new higher levels. But many of the newly established tariffs are so high in many countries as to effectively prohibit trade. Patterns of liberalization vary considerably by commodity and by country. Generally, the extent of liberalization was diminished by binding tariffs to the base period of 1986-88, when border protection was at a high point. In most OECD countries, this was worsened by"dirty tariffication:"the new base tariffs offered even greater protection than the nontariff barriers they replaced. Even after the commitments to tariff reductions in the Round, the ad valorem measure of the final binding tariffs will remain higher than the average rate of protection in 1982-93. A number of developing countries in East Asia, Latin America, and the Middle East chose to lock in prior liberalization efforts on some products. But for most commodities, there will be little actual liberalization, since most developing countries chose to bind their tariffs at a maximum level. Even when countries reduced already-bound rates, bound tariffs remained significantly higher than current applied rates, giving countries the flexibility to raise tariffs later. The high level of bound tariffs may allow countries to apply variable tariffs below the bound level, thus failing to stabilize tariffs and improve market access. Moreover, the Round did not touch many of the worst distortions in developing countries, such as import subsidies, export taxes, state-trading monopolies, and domestic policies that implicitly tax agriculture.Trade Policy,Environmental Economics&Policies,Economic Theory&Research,Export Competitiveness,Rules of Origin,Trade Policy,Rules of Origin,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Theory&Research
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