General Design Criteria Research Articles

Guidelines for thermal management design of hydride containers

Hydrogen storage by means of hydride forming alloys has been intensely studied during last three decades. Container heat management is among the most relevant aspects of study in this field, particularly because in many cases it is the limiting factor for charge and discharge rate. However, given the complexity of the container system and the great variety of possible configurations (type of absorbing material, geometry of the container, hydrogen charge pressure, cooling temperature, etc.), according to the authors' best knowledge, yet there is no general rule for hydride containers design. In this paper we propose general design guidelines using non-dimensional parameters to assess the thermodynamic and kinetics behavior in order to predict the absorption fill up time. ► A general design criterion for hydride containers is proposed. ► Heat transfer, kinetic and reaction time are summarized in dimensionless parameters. ► Three different hydrides are studied (Ti 1.1 CrMn, LaNi 5 and Mg). ► Results are validated with analytical solution and with other authors experiments.

Conversion of Existing Roundabouts into Turbo-Roundabouts: Case Studies from Real World

Compared with roundabouts the main advantages of turbo-roundabouts are the reduction in the number of potential conflicting points and the lower speed of vehicles passing through the intersection, they both can improve safety conditions at the junction. Moreover, the physical delimitation among lanes limits the side-by-side accident risk. These aspects make turbo-roundabouts more appropriate than roundabouts when a higher level of safety has to be guaranteed, particularly in presence of relevant pedestrian and two-wheels traffic volumes. The present paper has three main objectives: (1) to discuss general design criteria and functional principles of turbo roundabouts, (2) to give the geometric design principles of the central island and circulating lanes and (3) to present three case studies from real world concerning the conversion of existing roundabouts into turbo roundabouts.

Designing Bio‐Inspired Adhesives for Shear Loading: From Simple Structures to Complex Patterns

AbstractThe gecko has inspired numerous synthetic adhesive structures, yet under shear loading conditions, general design criteria remains underdeveloped. To provide guidance for bio‐inspired adhesives under shear, a simple scaling theory is used to investigate the relevant geometric and material parameters. The total compliance of an elastic attachment feature is described over many orders of magnitude in aspect ratio through a single continuous function using the superposition of multiple deformation modes such as bending, shear deformation, and tensile elongation. This allows for force capacity predictions of common geometric control parameters such as thickness, aspect ratio, and contact area. This superposition principal is extended to develop criteria for patterned interfaces under shear loading. Importantly, the adhesive patterns under shear are controlled through the compliance in the direction of loading. These predictions are confirmed experimentally using macroscopic building blocks over an extensive range of aspect ratio and contact area. Over 25 simple and complex patterns with various contact geometries are examined, and the effect of geometry and material properties on the shear adhesion behavior is discussed. Furthermore, all of these various attachment features are described with a single scaling parameter, offering control over orders of magnitude in adhesive force capacity for a variety of applications.

Safety Classifications for the Fusion DEMO Plant of Korea

Regulatory requirements and industrial codes and standards (C&S) are to be compulsory top-tier prerequisites for the design and construction of the fusion DEMO plant of Korea (DEMO Plant) as it will have safety-related functions to mitigate radiation hazards to the environment. However, these prerequisites will be developed in parallel with the design and construction of DEMO Plant due to the first-of-a-kind nature of the DEMO Plant. To overcome this dilemma, a tentative set of general design criteria and classification criteria that are to be applicable for the design studies of DEMO Plant is proposed, making use of the commonalities between the DEMO Plant and existing nuclear power plants (NPPs). To determine the tentative set, the radiation release to the environment and consequences of the postulated events in the DEMO Plant are analyzed with rough approximation assuming the inherent safety of a fusion DEMO reactor. The classification criteria of the tentative set include safety class, IEEE electrical classes, quality groups, and seismic categories for the structures, systems, and components of the DEMO Plant. As it will take considerable time and substantial amounts of investment to develop the regulatory requirements and C&S, the use of ASME Section III for the design study of DEMO Plant is also proposed to make the best use of the commonalities between the DEMO Plant and existing NPPs.

Genetically Engineered Plasmonic Nanoarrays

In the present Letter, we demonstrate how the design of metallic nanoparticle arrays with large electric field enhancement can be performed using the basic paradigm of engineering, namely the optimization of a well-defined objective function. Such optimization is carried out by coupling a genetic algorithm with the analytical multiparticle Mie theory. General design criteria for best enhancement of electric fields are obtained, unveiling the fundamental interplay between the near-field plasmonic and radiative photonic coupling. Our optimization approach is experimentally validated by surface-enhanced Raman scattering measurements, which demonstrate how genetically optimized arrays, fabricated using electron beam lithography, lead to order of ten improvement of Raman enhancement over nanoparticle dimer antennas, and order of one hundred improvement over optimal nanoparticle gratings. A rigorous design of nanoparticle arrays with optimal field enhancement is essential to the engineering of numerous nanoscale optical devices such as plasmon-enhanced biosensors, photodetectors, light sources and more efficient nonlinear optical elements for on chip integration.

Remarks on Diversity-Multiplexing Tradeoffs for Multiple-Access and Point-to-Point MIMO Channels

In this paper, we answer several open questions related to diversity-multiplexing tradeoffs (DMTs) for point-to-point and multiple-access (MAC) MIMO channels. By analyzing the DMT performance of a simple code, we show that the optimal MAC-DMT holds even when the channel remains fixed for less than <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Knt</i> + <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nr</i> -1 channel uses, where <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> is the number of users, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nt</i> is the number of transmit antennas of each user, and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nr</i> is the number of receive antennas at receiver. We also prove that the simple code is MAC-DMT optimal. A general code design criterion for constructing MAC-DMT optimal codes that is much more relaxed than the previously known design criterion is provided. Finally, by changing some design parameters, the simple code is modified for use in point-to-point MIMO channels. We show the modified code achieves the same DMT performance as the Gaussian random code.

Application of fuzzy logic for the integration of environmental criteria in ecodesign

The ecodesign of a product implies that different potential environmental problems of diverse nature must be considered, apart from the general design criteria (i.e., technical, functional, ergonomic, aesthetic or economical). In this sense, an ecodesign tool integrating the criteria provided by three environmental evaluation methodologies, namely Ecological Footprint (EF), Life Cycle Assessment (LCA) and Environmental Risk Assessment (ERA), has been constructed on the basis of fuzzy logic reasoning and features. This idea enabled the decision making at process and product level taking into account the values of the different indicators at a time. The relative importance of each of them has been established through the definition of membership functions as inputs to the fuzzy inference reasoning procedure in the case of a specific product. As a result, a Fuzzy EcoDesign Index (FEcoDI) was obtained. A well known case study was used to test the tool. Different packaging materials for a beverage bottle were considered to identify the most environmentally friendly option.

Heat Management in Single and Multi-injection Microstructured Reactors: Scaling Effects, Stability Analysis, and Role of Mixing

The exothermic reactions with fast intrinsic kinetics when carried out in conventional reactors are often limited by heat transfer. This results in the formation of hot spots, which affects product distribution of complex reactions and may lead to reactor runaway. Microstructured reactors (MSR) have been successfully used for this type of reaction, gaining increased temperature control and enhanced safety. Although different MSR concepts have been applied to various processes, the general design criteria are still poorly discussed in the literature. In this review, temperature management in conventional single injection MSR is described. The important issues, such as reactor safety and stability, along with the role of mixing, are discussed in detail. Subsequently, the multi-injection reactor concept is introduced and a simplified model developed to investigate the temperature profile is presented. Finally, the benefits and critical issues in the design of multi-injection MSR are highlighted.

Reverse osmosis hybrid membrane inter-stage design: A comparative performance assessment

A Hybrid membrane Inter-stage Design (HID) combines membranes of different nominal flux and salt rejection – i.e. different models –, in the same pressure vessel of seawater reverse osmosis racks. The HID experiences reported in the literature show there are no quantitative analysis published and very few seawater reverse osmosis plants have used it to date. The main objective of this paper is to present the results of a thorough computer assessment of this innovative design for conventional seawater reverse osmosis installations. Two types of analysis have been conducted for all representative models of membranes. Firstly, membrane replacement with a view to reduce the energy consumption due to lower working pressures while the plant capacity remains unchanged. Secondly, to increase plant capacity by reducing the specific energy consumption while maintaining the power consumption of the plant. A general HID design criterion has been defined for the three main membrane manufacturers – i.e. Filmtec, Hydranautics and Toray. Moreover, the quantitative results are useful for retrofitting plants thanks to membrane replacement.

An Extended User Evaluation of the Apple Inc. iPod Touch to Aid the U.S. Marine Corps

An Extended User Evaluation (EUE) was completed to determine if a handheld device aided Marines in the performance of their primary occupational duties while deployed in an operational environment. The focus of the evaluation was to gather usability insights, under operational conditions, that would translate into generalized design criteria for future mobile devices. Marines were provided with iPod touches, or Marine Pods (MPods), with preconfigured sets of information and tools to be used during in-theater operations. The evaluation spanned a seven-month deployment and consisted of monthly surveys. A majority of Marines found the MPod to be a useful resource and tool as a primary source of information during field operations and a secondary source of information in shop. Two user categories were identified: informational and general. Informational users employed the MPods primarily for access to technical publications to support maintenance operations. General users primarily employed the MPods for entertainment, note taking, and physical training.

Sustainable and safe design of footwear integrating ecological footprint and risk criteria

The ecodesign of a product implies that different potential environmental impacts of diverse nature must be taken into account considering its whole life cycle, apart from the general design criteria (i.e. technical, functional, ergonomic, aesthetic or economic). In this sense, a sustainability assessment methodology, ecological footprint (EF), and environmental risk assessment (ERA), were combined for the first time to derive complementary criteria for the ecodesign of footwear. Four models of children′s shoes were analyzed and compared. The synthetic shoes obtained a smaller EF (6.5 gm 2) when compared to the leather shoes (11.1 gm 2). However, high concentrations of hazardous substances were detected in the former, even making the Hazard Quotient ( HQ) and the Cancer Risk ( CR) exceed the recommended safety limits for one of the synthetic models analyzed. Risk criteria were prioritized in this case and, consequently, the design proposal was discarded. For the other cases, the perspective provided by the indicators of different nature was balanced to accomplish a fairest evaluation. The selection of fibers produced under sustainable criteria and the reduction of the materials consumption was recommended, since the area requirements would be minimized and the absence of hazardous compounds would ensure safety conditions during the use stage.

Graphical retrieval method for orthorhombic anisotropic materials

We apply the equivalent theory to orthorhombic anisotropic materials and provide a general unit-cell design criterion for achieving a length-independent retrieval of the effective material parameters from a single layer of unit cells. We introduce a graphical retrieval method and phase unwrapping techniques. The graphical method utilizes the linear regression technique. Our method can reduce the uncertainty of experimental measurements and the ambiguity of phase unwrapping. Moreover, the graphical method can simultaneously determine the bulk values of the six effective material parameters, permittivity and permeability tensors, from a single layer of unit cells.

Modeling and simulation of direct output current control for LCL-interfaced grid-connected inverters with parallel passive damping

Conventional grid-connected inverters with a single inductor filter have the disadvantages of the large volume, high cost and system dynamic restriction. One of attractive solutions is to replace the first-order L filters with the third-order LCL filters. However, Instability phenomenon often appears in practical applications of the direct output current control for the LCL-interfaced grid-connected inverters. In order to clarify the point, the system control model is developed and the characteristic equation is deduced. Based on the Routh-Hurwitz stability criterion, a significant conclusion is reached that instability is inevitable in the direct output current control for the LCL-interfaced inverters without damping whatever P, PI or PID control is used. Conventional solutions are putting resistances in series with the LCL filter so as to improve the system stability margin, which is well known as the series passive damping. Nevertheless, the feasibilities of the parallel passive damping are rarely discussed. This paper reveals, for the first time, the precise-quantified relationship between the parallel resistances, control parameters and stability margins so as to provide a general design criterion for the direct output current control for the LCL-interfaced grid-connected inverters. And then the influence of nonlinear factors such as the switching and over modulation saturation on the validity of conclusions is discussed. In agreement with the theoretical analysis, the simulation results demonstrate that the parallel passive damping can effectively enhance the system stability of the direct output current control for the LCL-interfaced grid-connected inverters with the ultra-low extra losses.

Computational study of P tBu 3 as ligand in the palladium-catalysed amination of phenylbromide with morpholine

We have investigated the full catalytic cycle for the coupling of phenylbromide with morpholine (Buchwald–Hartwig amination), catalysed by the synthetically relevant Pd(P t Bu 3) complex, with computational methods. The experimentally observed utility of this catalyst can be related to the energetically accessible ligand dissociation from the initial Pd(0) species, combined with a low barrier to oxidative addition and sterically unfavourable dimer formation. Furthermore, the steric bulk of the P t Bu 3 ligand allows for a low-coordinate, dissociative pathway and facile reductive elimination over the competing, undesirable β-hydride elimination pathway. Evaluating the full catalytic cycle with one of the most versatile catalyst complexes used experimentally has allowed us to evaluate the most likely catalytic pathway and relate this to general ligand design criteria, as well as providing validation for the computational approach used.

A simplicity-guided approach toward molecular set–reset memories

Photochromic switches fulfill the general molecular design criteria for the surprisingly straightforward small-scale integration of seemingly complex set-reset latches. The implications of this re-interpretation are discussed with the example of a dithienylethene photochrome. The concept is shown to be valid for a multitude of well-introduced bistable switches with clearly differentiated output signals, e.g., optical signals for the presented example.

Development and Demonstration of a Fault Current Limiting HTS Cable to be Installed in the Con Edison Grid

The US Department of Homeland Security is currently funding the design, development and demonstration of an inherently fault current limiting HTS cable, called Secure Super Grids, under the Hydra project with Con Edison. The cable is 300 m long and is being designed to carry 96 MVA at a distribution level voltage of 13.8 kV. The cable will be built using cable system experience gained by AMSC and Ultera (a Southwire and nkt Cables joint venture) on previous projects. The underground cable will be permanently installed and energized in New York City in 2010. The project is led by American Superconductor who is teamed with Ultera and Con Edison. This paper describes the general goals and design criteria of the project. An overview of the concept of Secure Super Grids and advantages of this type of cable are presented in a grid-based network modeling. In addition, the design issues such as tailoring of the HTS wire to provide adequate thermal stability and electrical properties both under normal operation and during a fault are presented.

Cooperative multiple trellis coded modulation

In this paper, we consider the general design criteria, properties and explicit code design procedures for cooperative multiple trellis coded modulation (CMTCM) schemes over Rayleigh fading channels. The cooperative system of interest utilizes the decode and forward protocol based on orthogonal transmissions from the cooperating terminals to the destination. We design full diversity cooperative multiple trellis codes using asymmetric constellations that at a frame error probability of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> provide around 10-12 dB gains over non-cooperative coded modulation without sacrificing the data rate and/or bandwidth efficiency. This is achieved by expanding the baseline constellation used in the non-cooperative transmission, designing the signal constellation to be asymmetric, and adopting multiple mappings among users. The consistent performance gains due to coding, asymmetry, and mappings of symbols onto the constellation are evaluated in terms of the frame error probability. We present simulation results that support the theoretical designs and illustrate the viability of the proposed cooperative MTCM technique.

Design Guidelines for In‐Plane Mechanical Properties of SiC Fiber‐Reinforced Melt‐Infiltrated SiC Composites

In‐plane tensile stress–strain, tensile creep, and after‐creep retained tensile properties of melt‐infiltrated SiC–SiC composites reinforced with different fiber types were evaluated with an emphasis on obtaining simple or first‐order microstructural design guidelines for these in‐plane mechanical properties. Using the minimatrix approach to model stress–strain behavior and the results of this study, three basic general design criteria for stress and strain limits are formulated, namely a design stress limit, a design total strain limit, and an after‐creep design retained strength limit. It is shown that these criteria can be useful for designing components for high‐temperature applications.

Influence of check dams on debris-flow run-out intensity

Abstract. Debris flows are very dangerous phenomena claiming thousands of lives and millions of Euros each year over the world. Disaster mitigation includes non-structural (hazard mapping, insurance policies), active structural (drainage systems) and passive structural (check dams, stilling basins) countermeasures. Since over twenty years, many efforts are devoted by the scientific and engineering communities to the design of proper devices able to capture the debris-flow volume and/or break down the energy. If considerable theoretical and numerical work has been performed on the size, the shape and structure of check dams, allowing the definition of general design criteria, it is worth noting that less research has focused on the optimal location of these dams along the debris-flow pathway. In this paper, a methodological framework is proposed to evaluate the influence of the number and the location of the check dams on the reduction of the debris-flow intensity (in term of flow thickness, flow velocity and volume). A debris-flow model is used to simulate the run-out of the debris flow. The model uses the Janbu force diagram to resolve the force equilibrium equations; a bingham fluid rheology is introduced and represents the resistance term. The model has been calibrated on two muddy debris-flow events that occurred in 1996 and 2003 at the Faucon watershed (South French Alps). Influence of the check dams on the debris-flow intensity is quantified taking into account several check dams configurations (number and location) as input geometrical parameters. Results indicate that debris-flow intensity is decreasing with the distance between the source area and the first check dams. The study demonstrates that a small number of check dams located near the source area may decrease substantially the debris-flow intensity on the alluvial fans.

Dendritic macromolecules for organic light-emitting diodes

The general concepts, design criteria, and physical parameters, such as component placement and electroluminescence, that relate to the construction of OLED devices are described, followed by a discussion of the current literature detailing the use of branched and dendritic materials as the key electroluminescent elements of single- and multi-layered fabricated devices. Their configurations, efficiencies, emission intensities, and molecular structural implications are also delineated and discussed. This critical review should appeal to researchers in the synthetic, material, and physical sciences (122 references).