Estimating and mitigating agriculture GHG emissions: uncertainties and policy reforms

Global climate change has been one of the challenging environmental concerns facing policy makers in the past decade. The characterization of the wide range of greenhouse gas emissions sources and sinks as well as their behavior in the atmosphere remains an on‐going activity in many countries. Lebanon, being a signatory to the Framework Convention on Climate Change, is required to submit and regularly update a national inventory of greenhouse gas emissions sources and removals. Accordingly, an inventory of greenhouse gases from various sectors was conducted following the guidelines set by the United Nations Intergovernmental Panel on Climate Change. The inventory indicated that the agriculture sector contributes about seven percent to the total greenhouse gas emissions. This paper proposes mitigation scenarios to reduce emissions from this sector based on country‐specific technical, economic and environmental characteristics. Economic evaluation and uncertainty in the emission estimation process as well as policy reforms are also addressed in the context of agricultural emissions reduction.     

Electrical and optical properties of (Sb2Se3)2 (Sb2Te3)1 thin films

A study of the synthesized (Sb₂Se₃)₂ (Sb₂Te₃)₁ glassy system has been carried out, X-ray diffraction (XRD) patterns and differential thermal analysis (DTA) of the system studied were used to obtain an insight into the structural information. An investigation of the electrical and optical properties of (Sb₂Se₃)₂ (Sb₂Te₃)₁ thin films prepared by thermal evaporation having different thicknesses (89.2, 214, 223 nm) and annealing temperatures ranging from 300 to 473 K has been carried out. The effect of the thickness and heat treatment on the activation energy E for d.c. conductivity and the density of localized states at the Fermi level N(E_F) were carried out. The electrical conductivity measurements depend on the thickness and annealing temperature, and exhibit two types of conduction mechanisms. Optical absorption measurements have been made on as-deposited and annealed films for the investigated system. The optical transition was found to be indirect. The optical energy gap (E_opt) decreases with increasing thickness and annealing temperatures (below T_g). The corresponding band is approximately twice the conduction activation energy. This effect is interpreted in terms of the density of states model proposed by Mott and Davis. © 2002 Kluwer Academic Publisher     

Degradation of cellulose nitrate with fast neutrons and gamma rays and their application in radiation dosimetry

Fast and moderated neutrons emitted from ²⁵²Cf as well as low doses of gamma rays from ⁶⁰Co, produce damaging effects in cellulose nitrate which can be determined viscometrically by calculating the average molecular weight at different doses.Samples were exposed to different doses of gamma rays (1 × 10^?4 to 1 Gy) and fission neutron fluences (10⁵–10¹¹ n/cm²) in free space and on a paraffin phantom. The effect of phantom thickness and phantom-to-detector distance on the detector readout have been investigated.The results revealed that the predominant bulk effects of radiation on CN is accelerated degradation by random chain scission.Empirical formulae have been given to calculate the absorbed doses of gamma rays and fast neutrons from the measured average molecular weight of the irradiated samples.     

Approximating the Pareto curve to help solve biobjective design problems

When faced with multiple objectives, designers have to find ways to combine these objectives to find the solution that satisfies acceptable trade-off levels. In this paper, we present a methodology based on approximating the Pareto set of biobjective problems and presenting these trade-off graphs to the designer to facilitate decisions on trade-off. Once a solution is selected from the approximated set, the designer can select to either set a target on one or both objectives and use one of two methods to find the sought after solution. The paper details the methodology and applies it to three structural problems of increasing complexity, showing that the procedure provides also useful feedback even in the case of nonconvex Pareto sets. Received October 18, 2000     

Coupled determination of gravimetric and elastic effects on two resonant chemical sensors: love wave and microcantilever platforms

The objective of this paper is to couple theoretical and experimental results from microcantilevers and Love-wave acoustic devices in order to identify and separate mass loading effects from elastic effects. This is important in the perspective of sensing applications. For that, a thin-film polymer is deposited on both resonant platforms. It is demonstrated that microcantilevers are essentially mass sensitive. They allow one to determine the polymer layer thickness, which is validated by optical profilometry measurements. Then, taking into account this thickness, theoretical modeling and experimental measurements with Love-wave devices permit one to estimate an equivalent elastic shear modulus of the thin-film polymer at high frequency. Results are interesting if one is to fully understand and optimize (bio)chemical sensor responses.     

A taxonomy and decision support for the design and manufacture of types of product families

The realization that designing products in families can and does have significant technological and economic advantages over traditional single product design has motivated increasing interest in recent years in formal design tools and methodologies for product family design. However, currently there is no guidance for designers in the first key strategic decisions of product family design, in particular determining the type of product family to design. Hence, in this paper, first a taxonomy of different types of product families is presented which consists of seven types of product families, categorized based on number of products and time of product introduction. Next a methodology is introduced to support designers in deciding which type of product family is appropriate, based upon early knowledge about the nature of the intended product(s) and their intended market(s). From this information it follows both which manufacturing paradigm and which fundamental design strategies are appropriate for each type of product family. Finally, the proposed methodology is illustrated through a case study examining a family of whitewater kayaks.     

Optimal design for additive manufacturing of heterogeneous objects using ultrasonic consolidation

Rapid prototyping (RP) technologies, such as Laser Engineering Net Shaping (LENS®) and Ultrasonic Consolidation (UC), can be used to fabricate heterogeneous objects composed of more than one material, wherein spatially varied microscopic structural details produce continuously or discretely changing mechanical or thermal properties on a macroscopic scale. These objects are engineered to achieve a potentially enhanced functional performance. Past research on the design of such objects has focused on representation, modeling, and desired functional performance. However, the inherent constraints in RP processes, such as system capability, size and shape of raw materials, and processing time, lead to fabricated objects that may not meet the designer's original intent. To overcome this situation, the research presented in this paper focuses on developing an approach— Design for Additive Manufacturing (DfAM)—to implement identified manufacturing constraints into the design process. Previous work has applied DfAM to the design of heterogeneous objects fabricated using the LENS® process. Two manufacturing constraints for this process, namely the achievable volume fractions and the processing time, were identified and incorporated into the DfAM. In this paper, the DfAM approach is extended to the design and manufacture of heterogeneous objects for the UC process. Constraints on the possible volume fraction values and on the gradient material direction are two identified manufacturing limitations, which are incorporated into the design process. An element-based finite element (FE) representation is extended to model layered heterogeneous objects. Each element is composed of metal foils of different materials according to specific design parameters. An evolutionary-based optimizer is used for its ability to handle the type of multi-modal problems encountered in the design of heterogeneous objects. The multi-criteria design problem, consisting of finding the optimal material composition along the build direction, that satisfies the functions of minimum weight and structural deformation, is implemented and solved. A three-dimensional I-beam made of two materials—aluminum for lightweight and steel for better strength characteristics—is used to illustrate the DfAM approach and its implementation for the design of heterogeneous objects using the UC process.     

An image-based multivariate generalized likelihood ratio control chart for detecting and diagnosing multiple faults in manufactured products

Image-capturing systems are increasingly being used in manufacturing shop floors since they can reliably capture important aesthetic information pertaining to the quality of manufactured parts in real time. State-of-the-art image-monitoring applications have focused on the detection of a single fault; however, the number of fault clusters per image in industrial applications can be numerous. To address this issue, we propose the use of a multivariate generalized likelihood ratio (MGLR) control chart for monitoring industrial products whose quality is described by a specific pattern (e.g. uniform patterns in LED screens or decorative patterns in textile products). Our method is specifically designed for greyscale images that are typical outputs of real-time industrial image-capturing systems. Extensive computer simulations show that the proposed method can detect the occurrence of single and multiple faults. We also present an experimental study to highlight how practitioners can implement and make use of the MGLR control chart in image-monitoring applications.     

Simultaneous optimization of force and placement of friction dampers under seismic loading

It is known that the use of passive energy-dissipation devices, such as friction dampers, reduces considerably the dynamic response of a structure subjected to earthquake ground motions. Nevertheless, the parameters of each damper and the best placement of these devices remain difficult to determine. Some articles on optimum design of tuned mass dampers and viscous dampers have been published; however, there is a lack of studies on optimization of friction dampers. The main contribution of this article is to propose a methodology to simultaneously optimize the location of friction dampers and their friction forces in structures subjected to seismic loading, to achieve a desired level of reduction in the response. For this purpose, the recently developed backtracking search optimization algorithm (BSA) is employed, which can deal with optimization problems involving mixed discrete and continuous variables. For illustration purposes, two different structures are presented. The first is a six-storey shear building and the second is a transmission line tower. In both cases, the forces and positions of friction dampers are the design variables, while the objective functions are to minimize the interstorey drift for the first case and to minimize the maximum displacement at the top of the tower for the second example. The results show that the proposed method was able to reduce the interstorey drift of the shear building by more than 65% and the maximum displacement at the top of the tower by approximately 55%, with only three friction dampers. The proposed methodology is quite general and it could be recommended as an effective tool for optimum design of friction dampers for structural response control. Thus, this article shows that friction dampers can be designed in a safe and economic way.