Practical Design Criteria Research Articles

Low-Cost Satellite-Based Correction Service for Precise Point Positioning in Latin America

Global Navigation Satellite Systems (GNSS) applications have been continuously expanding during the last years. When centimeter-level accuracy is required, the use of a single conventional GNSS receiver is not suitable because of the presence of different error sources that degrade the quality of its measurements. Precise Point Positioning (PPP) methods depend on applying corrections to significantly improve the accuracy of a single receiver allowing to obtain centimeter-level performance. This paper focuses on the design of a satellite-based service that broadcast the open access corrections for PPP generated by the International GNSS Service (IGS) being appropriate for real-time applications. The proposed system is based on the Argentinian geostationary satellite ARSAT 2 capable of providing service to Latin America. The system requirements and specifications are defined in order to deliver a good quality of service reducing the complexity and the cost of the users receivers. Thoroughly analyzes and calculations carried out demonstrate that, adopting practical design criteria, a low-cost implementation is possible. We present the main characteristics of the uplink ground station and downlink user receivers. Moreover, different user receiver architectures as well as the design of a simple antenna are proposed. Simulation results using real data show that our solution is able to provide up to centimeter-level accuracy achieving a performance similar to other costly commercial correction services.

On the Evolution of the Optimal Design of WDS: Shifting towards the Use of a Fractal Criterion

Several researchers have proposed methodologies for addressing the problem of designing optimal water distribution systems. Metaheuristic approximations are studied the most due to the vast solution space. In search of reducing computational time, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) has been tested with retrofitting from the Optimal Power Use Surface (OPUS) methodology. A previous study demonstrates how OPUS significantly improves the results since it seeks to reduce energy losses in the network, in order to approximate minimum-cost designs using fewer hydraulic executions. However, more research is still needed to determine applicable hydraulic criteria that allow an enhanced comprehension of optimal designs. Therefore, this paper aims to understand the characteristics of near-optimal solutions using designs from the retrofitted OPUS/NSGA-II Pareto fronts of four distinct networks (Hanoi, Balerma, Fossolo, and Modena). Moreover, fractal characteristics of the networks’ energy dissipation, flow, and diameter distribution have been analyzed for this purpose. In this way, outcomes suggest that the hydraulic gradient line box dimension in optimal designs approaches a value of two, demonstrating that objects resemble a single-plane surface. These promising results propose fractal analysis as a practical design criterion due to its hydraulic significance and low computational cost.

Study on Numerical Algorithm of the N-S Equation for Multi-Body Flows around Irregular Disintegrations in Near Space

There has been a concern that the accurate numerical simulation of multi-body flow, which is caused by the multiple disintegrations of expired spacecraft re-entering into the near space, has a critical bottleneck impact on the falling area of the disintegrated debris. To solve this problem, an O-type grid topology method has been designed for the multi-body flow field of irregular debris formed by multiple disintegrations in near space, and a finite-volume implicit numerical scheme has been constructed for the Navier-Stokes equations to solve the aerodynamic interference characteristics of irregular multi-body flow, and further the N-S equation numerical algorithm has been established for the irregular multi-body flows in near space. The reliability of the method has been verified by the comparison of the present computation and the experiment of the low-density wind tunnel for the two-body flow of sphere, cylinder and square scripts. The objects of this study are from the multiple disintegrations of the Tiangong-1 spacecraft during uncontrolled re-entry into the atmosphere, including propelling cylinders and low-temperature lock cabinets. A series of simulations of multi-body flow mechanisms around different combinations have been carried out with varied shapes and spacing. As a result, it is found that when the distance of irregular debris (e.g., two propelling cylinders) in the near space is in the range of Δy < 3D or Δx < D, there is an obvious multi-body interference between debris, and the flow characteristics are obviously changed. When the distance between the debris in near space reaches a certain level, the influence of mutual interference can be ignored. For example, when the y-direction distance between multiple bodies is greater than 3D, the flow interference tends to be small and can be ignored, and we can regard them as two separate pieces to be carried out by the numerical prediction of flight track and falling area in engineering application. The results provide a practical design criterion for the integrated simulation platform which is used to simulate the multi-physics complex aerodynamics of space vehicles from the free-molecule flow of the outer space to the near-ground continuum flow.

Transitioning solid-state batteries from lab to market: Linking electro-chemo-mechanics with practical considerations

<h2>Summary</h2> Li-metal solid-state batteries (SSBs) are promising candidates to supplant Li-ion batteries for a variety of different applications, including electric vehicles, due to their potential to provide a stepwise improvement in performance and safety. However, the benefits of SSBs are also accompanied by a unique set of challenges, which currently hinder their widespread commercialization. This perspective provides an overview of some of these unique challenges and their connection to the electrochemical, thermal, and mechanical properties of the SSB materials. Recent advances in understanding and overcoming these challenges are discussed. In an effort to establish more rigorous manufacturing, performance, and operation specifications, insights were solicited from three global automakers. In this context, we emphasize the importance of further mechanistic understanding of these systems using consistent testing protocols and data analysis methods, guided by practical input and design criteria proposed by automakers and other industrial parties.

Modeling advanced security aspects of key exchange and secure channel protocols

Abstract Secure connections are at the heart of today’s Internet infrastructure, protecting the confidentiality, authenticity, and integrity of communication. Achieving these security goals is the responsibility of cryptographic schemes, more specifically two main building blocks of secure connections. First, a key exchange protocol is run to establish a shared secret key between two parties over a, potentially, insecure connection. Then, a secure channel protocol uses that shared key to securely transport the actual data to be exchanged. While security notions for classical designs of these components are well-established, recently developed and standardized major Internet security protocols like Google’s QUIC protocol and the Transport Layer Security (TLS) protocol version 1.3 introduce novel features for which supporting security theory is lacking. In my dissertation [20], which this article summarizes, I studied these novel and advanced design aspects, introducing enhanced security models and analyzing the security of deployed protocols. For key exchange protocols, my thesis introduces a new model for multi-stage key exchange to capture that recent designs for secure connections establish several cryptographic keys for various purposes and with differing levels of security. It further introduces a formalism for key confirmation, reflecting a long-established practical design criteria which however was lacking a comprehensive formal treatment so far. For secure channels, my thesis captures the cryptographic subtleties of streaming data transmission through a revised security model and approaches novel concepts to frequently update key material for enhanced security through a multi-key channel notion. These models are then applied to study (and confirm) the security of the QUIC and TLS 1.3 protocol designs.

Optimization of fiber volume fraction to enhance reinforcing efficiency in hybrid fiber reinforced strain hardening cementitious composite

The steel fibers were generally used to improve the compressive strength of hybrid fiber reinforced strain hardening cementitious composite (SHCC) due to its higher strength and modulus. It is crucial to rationally design the volume fraction of fibers to maximize the role of different fibers in hybrid fiber reinforced SHCC. In this study, a design philosophy was proposed to guide the synthesis of hybrid fibers reinforced SHCC with saturated multiple cracking. The practical design criteria were determined by the joint use of cracking saturation index and pseudo strain hardening (PSH) performance indices. Finally, the design criteria were used to determine the volume fraction of steel fiber in hybrid fiber reinforced SHCC. Based on the proposed method, the optimum steel fiber volume fraction of 0.68% in hybrid fiber reinforced SHCC with 1.5% volume fraction of PE fibers was obtained for a designated matrix.

Approximate Compressor-Based Multiplier Design Methodology for Error-Resilient Digital Signal Processing

As many digital signal processing (DSP) applications such as digital filtering are inherently error-tolerant, approximate computing has attracted significant attention. A multiplier is the fundamental component for DSP applications and takes up the most part of the resource utilization, namely power and area. A multiplier consists of partial product arrays (PPAs) and compressors are often used to reduce partial products (PPs) to generate the final product. Approximate computing has been studied as an innovative paradigm for reducing resource utilization for the DSP systems. In this paper, a 4:2 approximate compressor-based multiplier is studied. Approximate 4:2 compressors are designed with a practical design criterion, and an approximate multiplier that uses both truncation and the proposed compressors for PP reduction is subsequently designed. Different levels of truncation and approximate compression combination are studied for accuracy and electrical performance. A practical selection algorithm is then leveraged to identify the optimal combinations for multiplier designs with better performance in terms of both accuracy and electrical performance measurements. Two real case studies are performed, i.e., image processing and a finite impulse response (FIR) filter. The design proposed in this paper has achieved up to 16.96% and 20.81% savings on power and area with an average signal-to-noise ratio (SNR) larger than 25[Formula: see text]dB for image processing; similarly, with a decrease of 0.3[Formula: see text]dB in the output SNR, 12.22% and 30.05% savings on power and area have been achieved for an FIR filter compared to conventional multiplier designs.

Facade-Integrated Semi-Active Vibration Control for Wind-Excited Super-Slender Tall Buildings

Nowadays, skyscrapers are getting higher and more slender due to inner-city concentration, which makes the structure more susceptible to dynamic excitations. The design of super-slender skyscrapers is governed primarily by wind excitation. A traditional Tuned Mass Damper (TMD) has been installed in many skyscrapers to mitigate wind-induced vibrations, which has been proven to be very reliable. However, it needs large additional mass and huge installation space near the top of the building, which makes TMD not optimal for super-slender skyscrapers. In this paper, a semi-active distributed-Multiple Tuned Facade Damper (d-MTFD) using movable facade elements as damping mass is investigated. The facade elements at the upper stories of the building are parallel movable to the primary structure. Electrical Machines (EM) as variable damper are integrated in their connections to realize semi-active vibration control, which makes the system more effective and robust. For real application, a practical design criterion is that the relative displacement of the facade elements cannot be too large, otherwise it makes the occupants feel uncomfortable. Therefore, multi-objective Genetic Algorithm (GA)-optimized on-off groundhook semi-active control is applied, where two control objectives are optimized. One control objective is to minimize the peak top floor acceleration and the other control objective is to minimize the maximum peak relative displacement of all the facade elements. As a result, a Pareto Front shows that better vibration suppression performance and smaller facade relative displacement can be achieved using the multi-objective optimized controller.

Experimental investigation on buckling‐restrained braces using mortar‐filled steel tubes with steel lining channels

SummaryA new type of buckling‐restrained braces (BRBs) using mortar‐filled steel tubes with steel lining channels is proposed to reduce the frictional force between the core member and the restraining member. After covering the core plate with the unbonding material, steel lining channels are set on the surface along the longitudinal direction, thus transforming the contact property between the core plate and the restraining member from steel–mortar interface to steel–steel interface. First, comparative cyclic tests are conducted on two new BRBs with steel lining channels and one conventional BRB. All the specimens exhibit stable hysteretic performance without visible global or local instability prior to failure. It is confirmed that the steel lining channels can improve the interface evenness between the core plate and the restraining member, reduce the compression strength adjustment factor, and improve the low‐cycle fatigue behavior and energy dissipation capacity of the BRB. Furthermore, the analytical model for the local stability of the restraining tube is proposed when the core plate buckles about the strong axis, and the corresponding practical design criteria are provided. The influence of various core plate layouts on the local stability of the restraining tube is finally investigated.

Separation Mechanism and Construction of Surfaces with Special Wettability for Oil/Water Separation.

Oil leakage and the discharge of oil/water mixtures by domestic and industrial consumers have caused not only severe environmental pollution and a threat to all species in the ecosystem but also a huge waste of precious resources. Therefore, the separation of oil/water mixtures, especially stable emulsion, has become an urgent global issue. Recently, materials containing a special wettability feature for oil and water have drawn immense attention because of their potential applications for oil/water separation application. In this paper, we systematically summarize the fundamental theories, separation mechanism, design strategies, and recent developments in materials with special wettability for separating stratified and emulsified oil/water mixtures. The related wetting theories that unveil the physical underlying mechanism of the oil/water separation mechanism are proposed, and the practical design criteria for oil/water separation materials are provided. Guided by the fundamental design criteria, various porous materials with special wettability characteristics, including those which are superhydrophilic/underwater superoleophobic, superhydrophobic/superoleophilic, and superhydrophilic/in-air superoleophobic, are systemically analyzed. These superwetting materials are widely employed to separate oil/water mixtures: from stratified oil/water to emulsified ones. In addition, the materials that implement the demulsification of emulsified oil/water mixtures via the ingenious design of the multiscale surface morphology and construction of special wettability are also discussed. In each section, we introduce the design ideas, base materials, preparation methods, and representative works in detail. Finally, the conclusions and challenges for the oil/water separation research field are discussed in depth.

A methodology for the design of dam spillways with wedge shaped blocks based on numerical modeling

Wedge shaped blocks spillways are an innovative solution that allows spilling over the downstream shoulder of earth and rock-fill dams in a safe way. However, they have been barely used as main spillway due to the lack of practical design criteria. An innovative procedure for computer-aided design of wedge shaped blocks spillways is presented in this paper. It includes the design of the drainage and supporting layer considering its seepage capacity and stability. The leakage flow through the joints between blocks is estimated by means of a numerical model calibrated and validated from experimental results. Stability against sliding of the downstream shoulder or the drainage layer is ensured, considering the properties of the granular material selected by the designer and non-linear resistance laws. The procedure will also suggest the shape of a toe protection.

Acoustic Compressibility of Caenorhabditis elegans

The acoustic compressibility of Caenorhabditis elegans is a necessary parameter for further understanding the underlying physics of acoustic manipulation techniques of this widely used model organism in biological sciences. In this work, numerical simulations were combined with experimental trajectory velocimetry of L1 C. elegans larvae to estimate the acoustic compressibility of C. elegans. A method based on bulk acoustic wave acoustophoresis was used for trajectory velocimetry experiments in a microfluidic channel. The model-based data analysis took into account the different sizes and shapes of L1 C. elegans larvae (255 ± 26 μm in length and 15 ± 2 μm in diameter). Moreover, the top and bottom walls of the microfluidic channel were considered in the hydrodynamic drag coefficient calculations, for both the C. elegans and the calibration particles. The hydrodynamic interaction between the specimen and the channel walls was further minimized by acoustically levitating the C. elegans and the particles to the middle of the measurement channel. Our data suggest an acoustic compressibility κCe of 430 TPa−1 with an uncertainty range of ±20 TPa−1 for C. elegans, a much lower value than what was previously reported for adult C. elegans using static methods. Our estimated compressibility is consistent with the relative volume fraction of lipids and proteins that would mainly make up for the body of C. elegans. This work is a departing point for practical engineering and design criteria for integrated acoustofluidic devices for biological applications.

Criteria for designing low-loss and wide operation range variable inlet guide vanes

Critical factors influencing the variable inlet guide vane (VIGV) profile loss at high incidence condition were studied by using numerical methods and a practical design criterion for designing wide low-loss operation range VIGVs in axial-flow compressor was proposed. At first, to acquire research samples, a series of airfoils with different shapes were generated for two selected representative VIGV cascade cases. Steady simulations based on Reynolds-Averaged Navier–Stokes method, carried out by commercial software CFX and validated with experimental data after grid independent study, were first conducted to predict the aerodynamic performances, the surface velocity distributions and the boundary-layer behaviors of the generated airfoils. Based on the simulated results, the influences of geometric parameters on airfoil performances were analyzed and the geometric features of low-loss VIGV airfoil were revealed. Further analysis indicated that the magnitude of airfoil loss at high incidence condition were mainly influenced by the scales of two boundary-layer separation regions: one at the leading edge caused by the high adverse pressure gradient induced by the suction spike and the other one caused by the adverse pressure gradient induced by the re-acceleration flow. To reveal the influence of the suction spike and the re-acceleration flow on the scales of separation regions, two practical parameters Dspike and Are were defined. It was found that there exists an optimized range of the Dspike and Are which could keep the separation flow to a small scale at high incidence condition and can be used as a surface velocity design criterion for designing wide low-loss operation range VIGVs. Moreover, the methods for choosing the airfoil geometric parameters to achieve the preferred surface velocity distribution were discussed. Finally, the developed design criterion was used to guide the airfoil modification of an axial-flow compressor VIGV and achieved an average of 19%, 52% and 73% loss coefficient reduction at three high stagger angle operating points, which confirms the applicability and effectiveness of the design criterion in three-dimensional environment.

Reconstruction procedure of the thermodynamic cycle of organic Rankine cycles (ORC) and selection of the most appropriate working fluid

Organic Rankine cycles (ORC) are part of heat recovery technologies, which allow thermal wastes to be converted into a mechanical power. These systems are suitable for various applications characterized by a large range of source and sink temperatures. Nonetheless, the selection of the organic working fluid is essential during ORC design processes; they have a major impact on the overall engine performance. Several works have been intending to develop appropriate methodologies to determine the optimal working fluid. Recently, an optimization approach independent of the organic fluid, has been proposed in the open literature, where optimal operating conditions are expressed in terms of equivalent temperatures and overall heat transfer surface areas. However, at the end, the primitive variables under which the real system must operate, should be determined. Within this framework, for a given working fluid, this paper presents a reconstruction method of a traditional thermodynamic cycle that allows actual thermodynamic variables (pressures, temperatures, mass flow rates) to be calculated. Furthermore, a methodology is also proposed for selecting the most appropriate organic working fluid, subjected to environmental and practical engineering design criteria. To emphasize the potential of the proposed approach, the entire procedure is then applied to a particular case study.

Study on the criterion to determine the bottom deployment modes of a coilable mast

A practical design criterion that allows the coilable mast bottom to deploy in local coil mode was proposed. The criterion was defined with initial bottom helical angle and obtained by bottom deformation analyses. Discretizing the longerons into short rods, analyses were conducted based on the cylinder assumption and Kirchhoff's kinetic analogy theory. Then, iterative calculations aiming at the bottom four rods were carried out. A critical bottom helical angle was obtained while the angle changing rate equaled to zero. The critical value was defined as a criterion for judgement of bottom deployment mode. Subsequently, micro-gravity deployment tests were carried out and bottom deployment simulations based on finite element method were developed. Through comparisons of bottom helical angles in critical state, the proposed criterion was evaluated and modified, that is, an initial bottom helical angle less than critical value with a design margin of −13.7% could ensure the mast bottom deploying in local coil mode, and further determine a successful local coil deployment of entire coilable mast.

Effect of build orientation on the mechanical reliability of 3D printed ABS

PurposeIncreasing use of 3D printing techniques to manufacture consumer products and open-source designs raises the question of “What is the mechanical reliability of 3D printed parts?” Therefore, the purpose of this paper is to investigate the impacts of build orientation on the mechanical reliability of acrylonitrile butadiene styrene (ABS) produced using 3D printing.Design/methodology/approachTensile tests on ABS specimens were performed with and without a hole in the center, which were produced by fused deposition modeling (FDM). Seven sets of approximately 30 specimens were printed in XY, XZ and C+45 orientations to obtain reliable fracture statistics. Weibull analysis was performed to quantify the variation in the tensile strength.FindingsThe Weibull analysis showed that the reliability of FDM produced ABS can be as low as advanced ceramics. Weibull moduli of specimens without a hole were between 26 and 69, and specimens with a hole had Weibull moduli between 30 and 41. P-type deviations from the Weibull statistics were observed. The XZ orientation resulted in the highest average fracture strength for specimens with and without a hole, and C+45 orientation resulted in the lowest strength.Practical implicationsAs the Weibull distribution relates the applied stress to probability of failure, the Weibull analysis provides a practical design criterion to achieve specific reliability levels for additively manufactured parts.Originality/valueThis study, for the first time, provides Weibull statistics for FDM-produced ABS parts, which can be used to predict mechanical reliability.

Sustainability assessment of energy services using complex multi-layer system models

Energy providing companies are facing legal restrictions concerning environmental targets effecting design and operation of their energy services. Thus, optimizing energy services based on sustainable criteria plays a crucial role in providing clean, affordable and profitable business solutions in the energy field. The aim of this work is to help decision makers in design and optimization of energy services through the development of a methodology which uses two energy services (district heating and thermal insulation) as practical design criteria, which are stated as cross-cutting technologies to increase sustainable heat supply. Within this approach, both the requirements and effects of policy targets are implemented for system configuration. For that, a multi-layer energy service system is developed and assessed using a case-study, where an existing decentralized reference system is substituted by a central biomass-fired plant. In addition, a new method, called ”method relation analysis” (MRA) is proposed, which provides a tool to investigate the effects of different evaluation techniques on the design of the energy system and is exemplary shown for carbon footprint and emergy analysis. This offers the possibility for analyzing the dependency of different assessment criteria and gives insight on how policy targets influence sustainable system configuration. The two energy services showe different outcomes in terms of sustainability. Raising heat from the biomass plant increases environmental, while thermal insulation mainly effects technological sustainability. Optimum design values for the biomass plant vary between around 60% of thermal load for carbon footprint and around 20% for emergy analysis. Carbon emissions always shows better results than the reference system. The proposed MRA assessment shows unique improvements for system analysis providing information on system comparison, assessment results and their behavior.

Simulation-based optimization of in–stream structures design: bendway weirs

Bendway weirs are one of the most practical in–stream rock structures utilized to protect the outer bend of meandering streams and rivers from erosion. We present development of a simulation-based paradigm for effective design of bendway weir structures to enhance meandering stream bank stability and control lateral migration. To do so, we employ the St. Anthony Falls Laboratory Virtual StreamLab (VSL3D) code to elucidate the flow and sediment transport phenomena induced by interaction of flow, mobile bed, and in–stream structures in large rivers under prototype conditions. We carried out numerous numerical experiments to systematically simulate various arrangements of bendway weir in two river test-beds and gaining insights into the physical mechanisms via which such bendway weirs modify turbulent flow, sediment transport and scour processes. The so-gained physical insights are then taken into account to develop a set of practical physics-based design criteria for optimal placement of bendway weirs in large rivers.

Seismic performance of controlled spine frames with energy-dissipating members

Recently, various controlled rocking systems have been proposed in seismic design to prevent damage concentration and to achieve self-centering against a wide range of input ground motion intensities. However, several obstacles must be overcome before these systems can be applied to actual buildings; for example, the requirement for large, self-centering post-tensioned strands and special treatment at uplift column bases must be addressed. This paper proposes a non-uplifting spine frame system with energy-dissipating members without post-tensioned strands, its self-centering function is achieved by envelope elastic-moment frames. The system is applied to an actual building constructed in Japan. Conventional shear damper and uplifting rocking systems with post-tensioned strands developed in prior studies are also applied to the same building structures, and the performances of the three systems, including damage distribution, energy dissipation, self-centering, robustness against severe earthquakes, and irregular stiffness, are compared and discussed through numerical simulations based on practical design criteria.

Optimised design for magnetorheological brake using DOE methods

Nowadays, the automobile systems like suspension, transmission, braking and clutch systems are controlled through the wire concept. To overcome the drawbacks of the existing conventional hydraulic braking system (CHB), magnetorheological brake (MRB) is introduced in this project. CHB require complex mechanical parts to dissipate energy. A magnetorheological fluid (MRF) brake is more efficient than conventional braking system in terms of weight reduction and response time. The research work is concerned with the development of a new braking system which employs MRF as working medium. MRB design proposed in earlier studies is to be further improved according to additional practical design criteria and constraints and more in-depth electromagnetic finite element analysis. The design procedure comprises the selection of materials for MRB, creating an analytical model for finding the braking torque produced by the MRB and finite element analysis of the MRB.