Current Design Methodologies Research Articles

Miniature gallium phase-change cells for in situ thermometry calibrations in space

The melting point of gallium, 29.7646 °C, makes it a very convenient fixed point for in situ calibration of thermometry in space applications such as Earth observation. NPL and RAL Space have collaborated to develop a miniature ‘phase-change cell’ using gallium. This report describes the modelling, construction and thermal metrological performance of miniature phase change gallium cells. These cells are intended to be embedded in the calibration blackbody structure, near the temperature sensors, for the purpose of in situ recalibration of those sensors. In this study, the blackbody structure was simulated by a monolithic aluminium block, and the phase-change cell and thermometers were embedded within the block. A thermal model of the system was also developed using Comsol Multiphysics® and validated against the experimental results, which provides useful information on further optimisation of the system. Under the (realistic) test conditions in this study, the phase-change cell, containing 2.1 g of gallium, was able to produce clearly defined melting curves with a duration of several hours and melting range of less than 5 mK, which represents sufficient performance for the envisaged application. Overall it has been shown that the current design methodology is fit for purpose and represents a solid foundation for raising the technology readiness level sufficiently for in-flight use.

Discovery of Inhibitors for Proliferating Cell Nuclear Antigen Using a Computational-Based Linked-Multiple-Fragment Screen.

Proliferating cell nuclear antigen (PCNA) is a central factor in DNA replication and repair pathways that plays an essential role in genome stability. The functional roles of PCNA are mediated through an extensive list of protein–protein interactions, each of which transmits specific information in protein assemblies. The flexibility at the PCNA–protein interaction interfaces offers opportunities for the discovery of functionally selective inhibitors of DNA repair pathways. Current fragment-based drug design methodologies can be limited by the flexibility of protein interfaces. These factors motivated an approach to defining compounds that could leverage previously identified subpockets on PCNA that are suitable for fragment-binding sites. Methodologies for screening multiple connected fragment-binding events in distinct subpockets are deployed to improve the selection of fragment combinations. A flexible backbone based on N-alkyl-glycine amides offers a scaffold to combinatorically link multiple fragments for in silico screening libraries that explore the diversity of subpockets at protein interfaces. This approach was applied to discover new potential inhibitors of DNA replication and repair that target PCNA in a multiprotein recognition site. The screens of the libraries were designed to computationally filter ligands based upon the fragments and positions to <1%, which were synthesized and tested for direct binding to PCNA. Molecular dynamics simulations also revealed distinct features of these novel molecules that block key PCNA–protein interactions. Furthermore, a Bayesian classifier predicted 15 of the 16 new inhibitors to be modulators of protein–protein interactions, demonstrating the method’s utility as an effective screening filter. The cellular activities of example ligands with similar affinity for PCNA demonstrate unique properties for novel selective synergy with therapeutic DNA-damaging agents in drug-resistant contexts.

Approximate ponding analysis by amplified first-order analysis

When water accumulates on the roof of a building, the resulting loads and deflections mutually depend on each other. This nonlinear effect, known as ponding, can cause collapse of insufficiently stiff and strong structures. There is a growing recognition of the limitations of current design methodologies for ponding. Newer methods of design have been proposed that overcome the limitations of the existing methodologies. These newer methods rely on the ability of the engineer to perform a nonlinear ponding analysis. Several methods exist for performing this type of analysis accurately. However, many design situations do not require full accuracy and an approximate method would be useful to practicing structural engineers. This work addresses this need by presenting an approximate ponding analysis method in which nonlinear results are obtained through amplification of first-order analysis results. Development of the methodology is described, an example is presented, and the accuracy of the method is discussed along with suggestions for future improvements. The availability of this method of analysis will allow wider adoption of newer and more rigorous methods of design for ponding.

Deep-Learning-Based Wireless Resource Allocation With Application to Vehicular Networks

It has been a long-held belief that judicious resource allocation is critical to mitigating interference, improving network efficiency, and ultimately optimizing wireless communication performance. The traditional wisdom is to explicitly formulate resource allocation as an optimization problem and then exploit mathematical programming to solve the problem to a certain level of optimality. Nonetheless, as wireless networks become increasingly diverse and complex, e.g., in the high-mobility vehicular networks, the current design methodologies face significant challenges and thus call for rethinking of the traditional design philosophy. Meanwhile, deep learning, with many success stories in various disciplines, represents a promising alternative due to its remarkable power to leverage data for problem solving. In this paper, we discuss the key motivations and roadblocks of using deep learning for wireless resource allocation with application to vehicular networks. We review major recent studies that mobilize the deep learning philosophy in wireless resource allocation and achieve impressive results. We first discuss deep learning assisted optimization for resource allocation. We then highlight the deep reinforcement learning approach to address resource allocation problems that are difficult to handle in the traditional optimization framework. We also identify some research directions that deserve further investigation.

Probabilistic framework for the assessment of the flexural design of concrete sleepers

An extensive study of the flexural performance of monoblock prestressed concrete sleepers in a light rail system was conducted as part of a research program funded by the Federal Transit Administration. Five consecutive sleepers deployed on the track were instrumented with strain gauges at their critical design cross-sections (center and rail seats) to obtain relevant flexural information during an uninterrupted period of 14 months. Results were compared with the projected design capacities obtained from the application of current design standards, resulting in glaring differences. The current design methodologies were deemed insufficient for the development of optimal design solutions for light rail applications. Furthermore, structural reliability analysis is employed to study the flexural capacity of the sleeper design. A capacity model based on the material and geometric properties of the sleeper design was developed. The demand model was derived from the field flexural data of over 27,000 train passes, fitting this information to predefined probability distributions. Four limit-state functions were defined to represent the typical flexural failure modes. The probability of failure was calculated using first-order reliability method, second-order reliability method, and Monte Carlo simulation. Ultimately, the analysis yielded consistent results for the three methods, showing largely low probability of failure at both design cross-sections under the studied demand level. In conclusion, the sleeper's capacity was higher than the existing field demands, indicating an overly conservative design approach.

Behaviour of Two-Tiered Geosynthetic-Reinforced Soil Walls

The literature studies and current design methodologies of reinforced soil wall show increases in tensile stresses in reinforcement with increase in height of wall. This results in decrease of spacing between reinforcement and ultimately increases in cost of construction. Alternatively, the reinforced soil wall can be constructed in tiered fashion to improve aesthetic and reduce cost of construction. This paper focuses on the performance of two-tiered-reinforced soil-retaining walls with different offset lengths. A numerical model of geosynthetic-reinforced soil-retaining wall with a concrete-block facing reported in literature is simulated using commercial finite element software ANSYS. The backfill soil is modelled using the Drucker–Prager plasticity model. The concrete facing is simulated as elastic material and reinforcement with non-linear material properties. The results obtained from numerical model are validated with those from physical model studies reported in literature. Using validated model parameters, two-tiered-reinforced soil walls with different offset lengths are simulated. Four models of 0 offset, 1.2-m offset, 2.0-m offset and 3.0-m offset are developed to study the effects of tiered wall. The offset lengths are determined as intermediate offset distance and large setback distance as per FHWA (2010). The walls are studied for horizontal displacement of facing, strain developed in backfill soil and in reinforcement layers. The maximum horizontal displacements of reinforced soil wall decrease with increase in offset length of tiered wall. By considering the strain variation in soil, two deformation zones—shear deformation zone near the facing and compaction zone below the upper tier facing—are identified. The strains in compaction zone of lower tier increase with increase in offset length. The reinforcement strains in top reinforcement layer of lower tier decrease with increase in offset length.

Crashworthy structures for future vehicle architecture of autonomous pods and heavy quadricycles on public roads: A review

With the development and deployment of lightweight vehicles to the market, inclusive of autonomous pods, a review of advanced crashworthy structures and the design methodology has been conducted as it is thought that super-lightweight vehicles may pose significant risk to the occupants if they are involved in a crash. It is suggested that tests should include oblique and multiple velocity impacts to cater for the effects of assisted driving systems of future vehicles. A review of current crash structures and design methodologies revealed that the most recent research do not cater to multiple crash scenarios, nor a shorter crush allowance, therefore resulting in poor crashworthiness performance. In addition, the arbitrary seat positioning shown in autonomous pods’ concepts vastly increases the risk to occupants. Greater enhancements to passive crashworthiness are imperative. To this end, functionally graded vehicle structures should be designed as it has been found that these can provide optimized solutions. Research into nonlinear optimization methods for computationally expensive problems will become central to this.

Challenges and Status on Design and Computation for Emerging Additive Manufacturing Technologies

The revolution of additive manufacturing (AM) has led to many opportunities in fabricating complex and novel products. The increase of printable materials and the emergence of novel fabrication processes continuously expand the possibility of engineering systems in which product components are no longer limited to be single material, single scale, or single function. In fact, a paradigm shift is taking place in industry from geometry-centered usage to supporting functional demands. Consequently, engineers are expected to resolve a wide range of complex and difficult problems related to functional design. Although a higher degree of design freedom beyond geometry has been enabled by AM, there are only very few computational design approaches in this new AM-enabled domain to design objects with tailored properties and functions. The objectives of this review paper are to provide an overview of recent additive manufacturing developments and current computer-aided design methodologies that can be applied to multimaterial, multiscale, multiform, and multifunctional AM technologies. The difficulties encountered in the computational design approaches are summarized and the future development needs are emphasized. In the paper, some present applications and future trends related to additive manufacturing technologies are also discussed.

A closed-form solution for the seismic racking and rocking behavior of rectangular tunnels

Current design methodologies for underground structures subjected to earthquake action are based on closed-form solutions of the so-called racking coefficient, which relates the soil free-field distortion deformation to the structure distortion deformation. Existent closed-form expressions for this racking coefficient are derived for circular tunnel geometries embedded in an elastic and homogeneous medium, while expressions for rectangular geometries are based on analogies of the circular case. In this paper, a new and intuitive methodology derived from first principles to obtain a closed-form expression for the racking coefficient for rectangular-like tunnel geometries buried at a sufficient depth is presented, and it is shown that it provides a good fit to finite element analyses results. Similarly, a procedure to obtain closed-form expressions for the rocking rotation of the structure, and the racking deformation profile at different distances from the soil-tunnel interface is presented.

A review of the design methods of complex topology structures for 3D printing

As a matter of fact, most natural structures are complex topology structures with intricate holes or irregular surface morphology. These structures can be used as lightweight infill, porous scaffold, energy absorber or micro-reactor. With the rapid advancement of 3D printing, the complex topology structures can now be efficiently and accurately fabricated by stacking layered materials. The novel manufacturing technology and application background put forward new demands and challenges to the current design methodologies of complex topology structures. In this paper, a brief review on the development of recent complex topology structure design methods was provided; meanwhile, the limitations of existing methods and future work are also discussed in the end.

Experimental verification of current seismic analysis methods of reinforced soil walls

The paper investigates the accuracy of two limit equilibrium design approaches used for seismic stability analyses of reinforced soil walls. Responses from a series of reinforced soil wall models, tested on shaking table, are compared to similar responses predicted using both NCMA, and AASHTO/FHWA design guidelines. First, orientation of the soil slip surface measured during subsequent base shaking was compared to the values predicted analytically. Comparison results suggested that the current design methods tend to under predict the size of the soil failure wedge at different input base acceleration amplitudes. Therefore, the current equation proposed to predict the angle of soil slip surface is modified to match measured values. Second, the horizontal and vertical seismic coefficients used in the current seismic analysis methods are compared to values inferred from shaking table accelerometer responses. Results indicated that equations suggested to calculate horizontal acceleration coefficient for design of reinforced soil walls are non-conservative for input base acceleration larger than 0.3 g. Finally, dynamic earth force magnitudes and locations, and dynamic reinforcement force increments measured from shaking table model tests are used to identify sources of conservatism and non-conservatism of the current design methodologies. Different modifications have been suggested to reduce conservativeness or increase the safety of the design guidelines.

Centrifuge modelling of monopiles subjected to lateral loading

Monopiles are the most common foundation type used for fixed-bottom substructures in offshore wind installations. In an offshore environment, the predominant load is cyclic, which affects the stiffness and deformation properties of foundation systems, especially monopiles. To investigate the effect of cyclic loading on a short (rigid) steel monopile, a set of displacement-controlled ηg laboratory tests were designed. This paper presents the procedure and results of eight centrifuge tests investigating monopile behaviour when subjected to lateral monotonic and cyclic loading. The general trend of monotonic response is in good agreement with the results of similar experimental studies, however, much softer behaviour was observed compared to the equivalent Winkler model on API p-y curves. The cyclic tests focused on the stiffness and deformation properties of a soil-pile system under fatigue loading. Increases, decreases or no changes in secant stiffness were observed depending on the regime of the applied cyclic displacements which are in contradiction to current design methodology where only cyclic degradation is assumed. Influence of load cycling on cyclic bending moments along the pile shaft was discussed and found to be of minor significance

Sensitivity analysis methods for mitigating uncertainty in engineering system design

AbstractFor many engineering systems, current design methodologies do not adequately quantify and manage uncertainty as it arises during the design process, which can lead to unacceptable risks, increases in programmatic cost, and schedule overruns. This paper develops new sensitivity analysis methods that can be used to better understand and mitigate the effects of uncertainty in system design. In particular, a new entropy‐based sensitivity analysis methodology is introduced, which apportions output uncertainty into contributions due to not only the variance of input factors and their interactions, but also to features of the underlying probability distributions that are related to distribution shape and extent. Local sensitivity analysis techniques are also presented, which provide computationally inexpensive estimates of the change in output uncertainty resulting from design modifications. The proposed methods are demonstrated on an engineering example to show how they can be used in the design context to systematically manage uncertainty budgets—which specify the allowable level of uncertainty for a system—by helping to identify design alternatives, evaluate trade‐offs between available options, and guide decisions regarding the allocation of resources.

Design Reverso: uma nova abordagem para análise e desenvolvimento de artefatos

Este artigo possui como objetivo apresentar o Design Reverso, que consiste em uma nova abordagem de desenvolvimento de produtos, e para tal realizou-se uma análise das metodologias de design de 1920 até os dias atuais, com o propósito de demonstrar que estas mantêm uma estrutura semelhante e linear de desenvolvimento de produtos. Já o Design Reverso tem como premissa, de forma diferenciada das metodologias vigentes de design, partir de um artefato já existente para chegar a uma nova solução, sendo composta por duas etapas de análise: generalista e estruturada. Essa abordagem ainda se encontra em fase de desenvolvimento e, por isso, este artigo não apresenta resultados conclusivos. O Design Reverso não possui a pretensão de ser uma nova metodologia, mas sim uma ferramenta de apoio, que pode contribuir ou complementar as metodologias vigentes, colaborando principalmente com os docentes e acadêmicos de design, uma vez que possibilitará uma nova forma de desenvolvimento de produtos.

State-of-the-art of 3D printing technology of cementitious material—An emerging technique for construction

In recent few years, significant improvement has been made in developing largescale 3D printer to accommodate the need of industrial-scale 3D printing. Cementitious materials that are compatible with 3D printing promote rapid application of this innovative technique in the construction field with advantages of cost effective, high efficiency, design flexibility and environmental friendly. This paper firstly reviews existing 3D printing techniques that are currently being used in commercial 3D printers. It then summarizes three latest development of largescale 3D printing systems and identifies their relationships and limiting factors. Thereafter, critical factors that are used to evaluate the workability and printable performance of cementitious materials are specified. Easy-extrusive, easy-flowing, well-buildable, and proper setting time are significant for cementitious material to meet the critical requirements of a freeform construction process. Finally, main advantages, potential applications and the prospects of future research of 3D printing in construction technology are suggested. The objective of this work is to review current design methodologies and operational constraints of largescale 3D printing system and provide references for optimizing the performance of cementitious material and promote its responsible use with largescale 3D printing technology.

A critical review of preparation design and workability measurement of concrete material for largescale 3D printing

In recent few years, significant improvement has been made in developing largescale 3D printers to accommodate the need of industrial-scale 3D printing. It is of great feasibility to construct structural components and buildings by means of 3D concrete printing. The major issues of this innovative technique focus on the preparation and optimization of concrete materials which possess favourable printable properties as well as the measurement and evaluation methods of their workability. This paper firstly introduces three largescale 3D printing systems that have been successfully applied in construction industry. It then summarizes the commonly used raw materials in concrete manufacturing. Critical factors that should be particularly controlled in material preparation are specified. Easy-extrusive, easy-flowing, well-buildable, proper setting time and low shrinkage are significant for concrete mixture to meet the critical requirements of a freeform construction process. Thereafter, measuring methods that can be employed to assess the fresh and hardened properties of concrete at early stages are suggested. Finally, a few of evaluation methods are presented which may offer certain assistance for optimizing material preparation. The objective of this work is to review current design methodologies and experimental measurement and evaluation methods for 3D printable concrete materials and promote its responsible use with largescale 3D printing technology.

Compressive stress distribution in prestressed concrete and its effect on railroad crosstie design

Recently, track mileage with concrete crossties has been increasing throughout the world. In North America, for example, approximately 30 million crossties are currently in service on Class I freight railroads. It is essential to understand the concrete crosstie bearing capacity and flexure behavior for both design and safety purposes. The American Railway Engineering and Maintenance-of-Way Association (AREMA) Recommended Practices and Australian Standard’s (AS) current flexural design methodologies consider rail seat loads to be vertically transferred to the neutral axis. However, the International Union of Railways (UIC) assumes rail seat loads are distributed at a 45 degree angle to the neutral axis. This load distribution behavior is commonly seen in the design of concrete corbels and spread footings, but is not well documented in the design of concrete crossties, and different assumptions (i.e. in AREMA and UIC design methods) will result in different designs. Better understanding the load distribution in concrete crossties will help to improve the design of concrete crossties and optimize their performance. This study presents preliminary results from an on-going research project at the University of Illinois at Urbana-Champaign (UIUC) focused on concrete crosstie mechanical behavior. A parametric study using three-dimensional (3D) finite element modeling (FEM) was performed to investigate stress distribution below the rail seat and quantify the corresponding distribution angles in prestressed concrete crosstie under static wheel loading. Laboratory experiments were also performed and successfully validated the results obtained from the numerical simulations. The results from both numerical simulation and laboratory experiments indicate the stress distribution angle under rail seat is not constant which disagrees with the assumptions in UIC 713R. Moreover, the stress distribution angle under rail seat is found to be sensitive to crosstie support conditions, and its value follows a direct relationship with rail seat load magnitude. The findings from this study can help to optimize prestressed concrete crosstie bearing capacity design.

The Best-of-n Problem in Robot Swarms: Formalization, State of the Art, and Novel Perspectives

The ability to collectively choose the best among a finite set of alternatives is a fundamental cognitive skill for robot swarms. In this paper, we propose a formal definition of the best-of-n problem and a taxonomy that details its possible variants. Based on this taxonomy, we analyze the swarm robotics literature focusing on the decision-making problem dealt with by the swarm. We find that, so far, the literature has primarily focused on certain variants of the best-of-n problem while other variants have been the subject of only a few isolated studies. Additionally, we consider a second taxonomy about the design methodologies used to develop collective decision-making strategies. Based on this second taxonomy, we provide an in-depth survey of the literature that details the strategies proposed so far and discusses the advantages and disadvantages of current design methodologies.

Using Kahoot! in the Classroom to Create Engagement and Active Learning: A Game-Based Technology Solution for eLearning Novices

Instructional games are gaining acceptance in the classroom as the eLearning merits of student engagement and immediate feedback are recognized. Within higher education, the use of these tools is often limited due to lack of time, insufficient experience, or doubts regarding the scholarly merits of such activities. Kahoot! is a popular eLearning tool that can easily be used to add vitality, student engagement, and meta-cognitive supports to higher education classrooms with limited instructor or student training required. The free online learning platform has gained wide acceptance globally with more than 30 million users worldwide, and it is based on current user-centered and behavioral design methodologies. Student responses and our experiences using Kahoot! in graduate and undergraduate classrooms indicate that students welcome the use of this game. The real-time feedback provides opportunities for professors in various disciplines to tailor their instruction based on student understanding on quizzes while the surveys allow for anonymous classroom participation, which further engages all students.

Stability of Open Top Cylindrical Steel Storage Tanks: Design of Top Wind Girder

Design of the top wind stiffeners of aboveground storage tanks designed to the requirements of API 650 is investigated. The current design methodology is based on intuition and experience without a sound technical justification. This paper investigates a diameter limit to be used in the design of the top stiffener ring by using finite-element analysis (FEA) in a parametric study. Linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) were performed on cylindrical storage tanks. By modeling tanks with different diameters and limiting the design of top stiffener ring for a diameter of 170-ft (52-m), the buckling loads are investigated. It was found that the 170-ft (52-m) diameter is a suitable upper limit to design the top stiffener rings for larger diameters.