Difficult Engineering Challenge Research Articles

Modeling and development of a narrowband gas-combustion infrasound source

An invaluable tool in characterization of any receiver, propagation path, or detection system, is a source with known and repeatable signal characteristics. This talk will discuss development of a well-controlled narrowband infrasound source with frequency capabilities over the 0.1 to 10.0 Hz band. Design of a transportable sound source within this band is a difficult engineering challenge. The simple source equation, which will govern any portable infrasound source due to the long wavelengths, shows this fundamental difficulty. As frequency decreases, volume displacement must increase by the squared inverse factor of frequency in order to maintain an equal pressure at equal range. To combat this, the authors have developed a source system that uses gas combustion to displace large volumes in the open atmosphere using the gaseous and highly heated combustion constituents of propane and atmospheric oxygen. Measurements have verified the capability of generating narrowband signals with reasonable signal-to-noise ratio (SNR) over the full band at close range. Signals at 1 Hz have been measured with reasonable SNR to ranges greater than 2 km. Development of the infrasound source prototype, experimental measurements, and modeling of the acoustic pressure output will be discussed.

Optimal Solution of reactive power dispatch under normal and contingency condition using Rao algorithms

Rao suggested three straight forward, metaphor-free optimization strategies to address the challenging optimization issue. These algorithms are approaches for optimization without parameters. As a result, no parameter modification unique to an algorithm is needed. This feature makes these algorithms simple to use and effective at resolving a wide range of difficult engineering and scientific challenges. This paper’s main objective is to use the Rao method to resolve the reactive power dispatch problem under both regular and emergency circumstances. The suggested method’s reliability was tested using these techniques in standard IEEE 30 bus test systems. Overall reactive power dispatch (RPD) results of Rao algorithms were matched with those of recently published well-known methods. Rao algorithms produce accurate and competitively priced numerical results.

Recyclable, Repairable, and Fire-Resistant High-Performance Carbon Fiber Biobased Epoxy

Due to the global environmental concerns caused by the ever-increasing environmental impact, landfill materials, and CO2 emission, there is a critical need in the elaboration of sustainable composite materials. Advanced material composites used in the production of high-performance products to solve some of the most difficult engineering challenges are having a key role in decarbonization by their light weight, higher performance, and increasing durability. In this work, sustainable carbon fiber reinforced composites (CFRCs) have been engineered with an environmentally friendly epoxy resin derived from natural and renewable compounds employing an industrial feasible manufacturing protocol. The thermosetting resin with a biobased organic carbon content (BOC) of ∼77% was synthesized by combining a renewable based monomer, the triglycidyl ether of phloroglucinol (TGPh), with hexahydro-4-methylphthalic anhydride (HMPA). The developed CFRCs show high performance with high glass transitions Tg > 350 °C, a high storage modulus ∼42 GPa, a high interlaminar shear strength ∼63 MPa, and a compressive strength ∼400 MPa. In addition, the outgassing tests show that both the resin and the CFRCs are compliant for space application. Moreover, the biobased CFRCs exhibit chemical recyclability, reprocessability, and excellent intrinsic flame resistance.

Optimal Tuning of Power System Stabilizers for a Multi-Machine Power Systems Using Hybrid Gorilla Troops and Gradient-Based Optimizers

This work discusses the production of a novel hybrid algorithm by combining the gorilla troops optimizer (GTO) with the gradient-based optimizers (GBO) approach. The novel approach is called GTO-GBO, it is offered as a useful tool for optimizing the power system stabilizer (PSS) used in the IEEE four-generator, two-area multi-machine power system subjected to a three-phase short-circuit fault. MATLAB/Simulink software was utilized to carry out the assessments. The suggested approach is initially evaluated using multiple benchmark functions with unimodal and multimodal properties. The results are then compared to other competing algorithms (artificial ecosystem optimizer, artificial rabbits optimizer, Coati Optimization Algorithm, and northern goshawk optimization). The comparisons with various algorithms reveal the developed hybrid GTO-GBO algorithm’s considerable promise. This demonstrates the GTO-GBO algorithm’s improved balance of global and local search stages. The proposed GTO-GBO algorithm’s performance is also evaluated by developing an optimum performing PSS for further examination, allowing observation of its capabilities for difficult real-world engineering challenges. To illustrate the applicability and superior performance of the suggested hybrid algorithm for such a complicated real-world engineering problem, the PSS damping controller is formulated as an optimization problem, and the developed GTO-GBO algorithm is used to search for optimal controller parameters. The latter case’s findings are compared to the competitive optimization algorithms where the GTO-GBO demonstrates the efficiency and robustness of this suggested optimization algorithm to enhance power system stability.

Coherent infrasound generation using an air-propane burner

An invaluable tool in characterization of any receiver, propagation path, or detection system, is a source with known and repeatable signal characteristics. This talk will discuss development and evaluation of a coherent (non-explosive, periodic, with controlled duration) infrasound source with frequency capabilities in the sub-hertz to several hertz band. Design of a practical sound source within this band is a difficult engineering challenge. The simple source equation, which will govern any portable human-fabricated infrasound source due to the long wavelengths, shows this fundamental difficulty. As frequency decreases volume displacement must increase by the squared inverse factor of frequency in order to maintain an equal pressure amplitude at equal range. For this reason, the authors investigate utilizing the high energy density available in gas combustion to periodically displace large volumes of air within the open atmosphere. Prototype testing has verified the capability of generating continuous signals at a fundamental frequency of 0.25–1.5 Hz in the farfield—or ranges from the source where pressure and particle velocity are roughly in-phase. Harmonics of this fundamental are also generated throughout the 0.25–4.0 Hz band with reasonable signal-to-noise ratio. Development of the infrasound source prototype as well as experimental testing and results will be discussed.

Touch, Texture and Haptic Feedback: A Review on How We Feel the World around Us

Touch is one most of the important aspects of human life. Nearly all interactions, when broken down, involve touch in one form or another. Recent advances in technology, particularly in the field of virtual reality, have led to increasing interest in the research of haptics. However, accurately capturing touch is still one of most difficult engineering challenges currently being faced. Recent advances in technology such as those found in microcontrollers which allow the creation of smaller sensors and feedback devices may provide the solution. Beyond capturing and measuring touch, replicating touch is also another unique challenge due to the complexity and sensitivity of the human skin. The development of flexible, soft-wearable devices, however, has allowed for the creating of feedback systems that conform to the human form factor with minimal loss of accuracy, thus presenting possible solutions and opportunities. Thus, in this review, the researchers aim to showcase the technologies currently being used in haptic feedback, and their strengths and limitations.

Assessing the suitability of bridge-scour-monitoring devices

Bridge scour is a complex bridge-management problem. It is also a difficult forensic engineering challenge, as the greatest risk occurs during large flows and flood events, when visual inspection of the bridge piers is often not possible. This paper presents a review of scour prediction and modelling methods, whose results are used to determine the key parameters that scour-monitoring systems need to capture. Then, a review of existing monitoring approaches and technologies for scour monitoring is presented. The paper concludes with the proposal of a novel rating system for evaluating different scour-monitoring techniques. The new rating system is trialled ex-post for seven previously published bridge-scour-monitoring case studies to illustrate the use of the new methodology.

High-Strength Superstretchable Helical Bacterial Cellulose Fibers with a "Self-Fiber-Reinforced Structure".

As a hydrogel membrane grown on the gas-liquid interface by bacterial culture that can be industrialized, bacterial cellulose (BC) cannot give full play to the advantages of its natural nanofibers. Conversion to the properties of nanofibers from high-performance to macrofibers represents a difficult material engineering challenge. Herein, we construct high-strength BC macrofibers with a "self-fiber-reinforced structure" using a dry-wet spinning method by adjusting the BC dissolution and concentration. The macrofiber with a tensile strength of 649 MPa and a strain of 17.2% can be obtained, which is one of the strongest and toughest cellulose fibers. In addition, the macrofiber can be fabricated to a superstretchable helical fiber without adding other elastomers or auxiliary materials. When the helical diameter is 1.6 mm, the ultimate stretch reaches 1240%. Meanwhile, cyclic tests show that the mechanical properties and morphology of the fiber remained stable after 100 times of 100% cyclic stretching. It is exciting that the helical fiber also owns outstanding knittability, washability, scalability, and dyeability. Furthermore, superstretchable functional helical BC fibers can be fabricated by embedding functional materials (carbon materials, conductive polymers, etc.) on BC or in the spinning dope, which can be made to wearable devices such as fiber solid-state supercapacitors. This work provides a scalable way for high-strength superstretchable and multifunctional fibers applied in wearable devices.

Farfield coherent infrasound generation using an air-propane burner.

An invaluable tool in the characterization of any receiver, propagation path, or detection system is a source with known and repeatable signal characteristics. This article presents the theoretical development and engineering design of a coherent (nonexplosive, periodic with controlled duration) infrasound source in the sub-hertz to several hertz band. Design of a sound source within this band is a difficult engineering challenge. The simple source equation, which will govern any portable human-fabricated infrasound source due to the long wavelengths, shows this fundamental difficulty. As frequency decreases, volume displacement must increase by the squared inverse factor of frequency in order to maintain an equal pressure amplitude at equal range. For this reason, the authors evaluate using the high energy density available in gas combustion to periodically displace large volumes of air within the open atmosphere. Prototype testing has verified the capability of generating continuous signals at a fundamental frequency of 0.25 Hz in the farfield-ranges in which pressure and particle velocity can be considered in-phase-where the product of the acoustic wavenumber and range is near 4.7. The generation of frequency content throughout the 0.25-4.0 Hz band with a reasonable signal-to-noise ratio was also demonstrated.

Investigations in performance of a gas-combustion infrasound source

Designing a coherent (non-explosive) sound source within the infrasound band (0.1–4 Hz in our case) is a difficult engineering challenge. This is due to the large air mass that must be moved to created useful signal levels. The fundamental simple source equation, which will govern almost any human-made infrasound source due to the long wavelengths, shows this fundamental difficulty. As frequency decreases, the volume velocity must increase by the inverse factor of the frequency decrease in order to maintain an equal pressure amplitude at equal range. In other words, 1000 times the cubic volume of air must be moved at 0.1 Hz as compared to 100 Hz, in order to maintain an equal output pressure amplitude! For this reason, a novel method has been proposed to skirt this engineering challenge; using the large energy density available in gas combustion for periodic thermal expansion of an air mass. This talk builds on previous work by the authors (Smith and Gabrielson, J. Acoust. Soc. Am. 137, 2407, 2015 and Smith and Gabrielson, J. Acoust. Soc. Am. 143, 1808, 2018) and presents comparisons of a 1st-order thermodynamic model and empirical measurements using a large liquid-propane burner system from a hot air balloon.

Rocksalt nitride metal/semiconductor superlattices: A new class of artificially structured materials

Artificially structured materials in the form of superlattice heterostructures enable the search for exotic new physics and novel device functionalities, and serve as tools to push the fundamentals of scientific and engineering knowledge. Semiconductor heterostructures are the most celebrated and widely studied artificially structured materials, having led to the development of quantum well lasers, quantum cascade lasers, measurements of the fractional quantum Hall effect, and numerous other scientific concepts and practical device technologies. However, combining metals with semiconductors at the atomic scale to develop metal/semiconductor superlattices and heterostructures has remained a profoundly difficult scientific and engineering challenge. Though the potential applications of metal/semiconductor heterostructures could range from energy conversion to photonic computing to high-temperature electronics, materials challenges primarily had severely limited progress in this pursuit until very recently. In this article, we detail the progress that has taken place over the last decade to overcome the materials engineering challenges to grow high quality epitaxial, nominally single crystalline metal/semiconductor superlattices based on transition metal nitrides (TMN). The epitaxial rocksalt TiN/(Al,Sc)N metamaterials are the first pseudomorphic metal/semiconductor superlattices to the best of our knowledge, and their physical properties promise a new era in superlattice physics and device engineering.

Data-Interpretation Methodologies for Non-Linear Earthquake Response Predictions of Damaged Structures

Seismic exposure of buildings presents difficult engineering challenges. The principles of seismic design involve structures that sustain damage and still protect inhabitants. Precise and accurate knowledge of the residual capacity of damaged structures is essential for informed decision-making regarding clearance for occupancy after major seismic events. Unless structures are permanently monitored, modal properties derived from ambient vibrations are most likely the only source of measurement data that is available. However, such measurement data is linearly elastic and limited to a low number of vibration modes. Structural identification using hysteretic behavior models that exclusively relies on linear measurement data is a complex inverse engineering task that is further complicated by modeling uncertainty. Three structural identification methodologies that involve probabilistic approaches to data interpretation are compared: error-domain model falsification, Bayesian model updating with traditional assumptions as well as modified Bayesian model updating. While noting the assumptions regarding uncertainty definitions, the accuracy and robustness of identification and subsequent predictions are compared. A case study demonstrates limits on non-linear parameter identification performance and identification of potentially wrong prediction ranges for inappropriate model uncertainty distributions.

Тестирование возможностей открытого кода BEM++ по решению задач акустики

Testing of capabilities of open-source BEM++ code for simulation of acoustics problems at medium and high frequencies is presented. The BEM++ library is a universal tool, which allows to build discrete models for boundary integral operators (single-, double- and adjoint double-layer potential operators and hypersingular boundary operators) and solve boundary element method problems for Helmholtz, Laplace and Maxwell equations using Python libraries. Solution for the test problem of scattering plane wave on spherical obstacle with using BEM++ demonstrates good convergence with the results of analytical solutions. The relative errors satisfy to acceptable values 5% in solving engineering tasks, this fact allows to use this library as an alternative to commercial software. Capability of BEM++ library to calculate acoustic fields for frequencies from 5 Hz to 5 kHz enables move to solving more difficult engineering challenges of the aerospace industry. The main restriction for this is a time of computation, because only shared-memory technology of the code parallelization is implemented. However, open architecture of the library allows to remove this disadvantage. Meshes for BEM++ can have big size and be based on E geometric model with complex geometrical objects. Also, it should be noted, that for implementation to engineering practice it is desirable to integrate the library with existing interactive systems of pre- and post-processing, for example, with Salome.

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New method and uncertainty estimation for plate dimensions and surface measurements

Dimensional and surface quality for tile plate manufacturing control is facing difficult engineering challenges. One of these challenges being that plates in large-scale mass production contain geometrically uneven surfaces. There is a traditional measurement method used to assess the tile plate dimensions and surface quality based on standard specifications: ISO-10545-2: 1995, EOS-3168-2: 2007 and TIS 2398-2:2008. A new measurement method of the dimensions and surface quality for ceramic oblong large-scale tile plate has been developed compared to the traditional method. The strategy of the proposed method is based on CMM straightness measurement strategy instead of the centre point in the traditional method. Expanded uncertainties budgets in the measurements of each method have been estimated in detail. The capability of accurate estimations of real actual results of centre of curvature (CC), centre of edge (CE), warpage (W) and edge crack defects parameters has been achieved according to standards. Moreover, the obtained results showed not only a more accurate method but also improved the quality of tile plate products significantly.

Assessing requirements-related risks through probabilistic goals and obstacles

Requirements completeness is among the most critical and difficult software engineering challenges. Missing requirements often result from poor risk analysis at requirements engineering time. Obstacle analysis is a goal-oriented form of risk analysis aimed at anticipating exceptional conditions in which the software should behave adequately. In the identify-assess-control cycles of such analysis, the assessment step is not well supported by existing techniques. This step is concerned with evaluating how likely the obstacles to goals are and how likely and severe their consequences are. Those key factors drive the selection of most appropriate countermeasures to be integrated in the system goal model for increased completeness. Moreover, obstacles to probabilistic goals are currently not supported; such goals prescribe that some corresponding target property should be satisfied in at least X % of the cases. The paper presents a probabilistic framework for goal specification and obstacle assessment. The specification language for goals and obstacles is extended with a probabilistic layer where probabilities have a precise semantics grounded on system-specific phenomena. The probability of a root obstacle to a goal is thereby computed by up-propagation of probabilities of finer-grained obstacles through the obstacle refinement tree. The probability and severity of obstacle consequences is in turn computed by up-propagation from the obstructed leaf goals through the goal refinement graph. The paper shows how the computed information can be used to prioritize obstacles for countermeasure selection toward a more complete and robust goal model. A detailed evaluation of our framework on a non-trivial carpooling support system is also reported.

New Measurement Method and Uncertainty Estimation for Plate Dimensions and Surface Quality

Dimensional and surface quality for plate production control is facing difficult engineering challenges. One of these challenges is that plates in large-scale mass production contain geometric uneven surfaces. There is a traditional measurement method used to assess the tile plate dimensions and surface quality based on standard specifications: ISO-10545-2: 1995, EOS-3168-2: 2007, and TIS 2398-2: 2008. A proposed measurement method of the dimensions and surface quality for ceramic oblong large-scale tile plate has been developed compared to the traditional method. The strategy of new method is based on CMM straightness measurement strategy instead of the centre point in the traditional method. Expanded uncertainties budgets in the measurements of each method have been estimated in detail. The capability of accurate estimations of real actual results for centre of curvature (CC), centre of edge (CE), warpage (W), and edge crack defects parameters has been achieved according to standards. Moreover, the obtained results not only showed better accurate new method but also improved the quality of plate products significantly.

Technology on the Move: Recent and Forthcoming Innovations for Tracking Migratory Birds

Basic questions about the life histories of migratory birds have confounded scientists for generations, yet we are nearing an era of historic discovery as new tracking technologies make it possible to determine the timing and routes of an increasing number of bird migrations. Tracking small flying animals as they travel over continental-scale distances is a difficult logistical and engineering challenge. Although no tracking system works well with all species, improvements to traditional technologies, such as satellite tracking, along with innovations related to global positioning systems, cellular networks, solar geolocation, radar, and information technology are improving our understanding of when and where birds go during their annual cycles and informing numerous scientific disciplines, including evolutionary biology, population ecology, and global change. The recent developments described in this article will help us answer many long-standing questions about animal behavior and life histories.

Tracking of Metallic Objects Using a Retro-Reflective Array at 26 GHz

The detection and tracking of targets in highly cluttered environments often poses a difficult engineering challenge as the strong clutter backscatter contained in the scene makes it difficult to distinguish the target of interest. A design concept to aide in standoff detection and tracking of large metallic objects in a warehouse setting is presented. This includes the design and implementation of an active retro-reflective array system that is able to determine the precise location and identification of an object. To accomplish this, a unique series fed grounded coplanar waveguide patch antenna is designed and implemented with minimal cross coupling among elements. This compact array has a relatively large radar cross-section (RCS) while maintaining the desired retro-reflectivity. Additionally, a tilted beam is incorporated in the linear series-fed array to isolate the large RCS of the planar array structure at boresight from the desired modulated, retro-reflective RCS. This method for enhanced detection is implemented at 26 GHz. The incorporation of the high-speed PIN switches into the array structure provide the tag with a unique identification. Measurement results for the modulated RCS from such an array in a cluttered environment are presented.

Design of Tall Formworks by a Finite-Element Model

The design of formworks for holding fresh concrete possesses a difficult engineering challenge. Present standards assume fresh concrete to have a nonviscous fluid behavior when calculating the lateral pressure to which the formwork walls will be the subject. This paper describes a finite-element model to determine these pressures, taking into account the interaction between the fresh concrete and the formwork wall. The use of this numerical model shows that present standards may underestimate the lateral pressures that can be exerted particularly with respect to tall formworks. The paper also discusses the influence of different mechanical variables on the results returned by the proposed model. The proposed model may be of use to practicing engineers and of interest to researchers examining load distributions in formworks.