Geometric Stability Research Articles

Sewable high-performance poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/layered double hydroxide core-shell fiber electrodes for flexible supercapacitors

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based fibers are one of the most competitive fiber-type electrodes but still suffer from low electrochemical surface areas (ECSAs) and oversensitivity to humidity for fiber supercapacitor applications. Herein, through rational design, a sewable core-shell fiber electrode of PEDOT:PSS/waterborne polyurethane (WPU) fiber wrapped with nickel/cobalt-layered double hydroxides (NiCo-LDH) has been synthesized via wet-spinning and solution reaction. The fiber core acts as a conductive channel for charge carrier transport. The NiCo-LDH shell possesses unique hybrid architectures of honeycomb-like nanosheet array and hollow nanocages, which provide numerous electrochemical active sites. Simultaneously, the water barrier effect of the NiCo-LDH shell and the interaction between Co2+/Ni2+ and PSS reduce fiber water uptake, thus endowing the fiber with a better geometric stability with low swelling ratio. The as-prepared PEDOT:PSS/LDH fiber has a large ECSA (4060 cm2 g−1) and ultrahigh conductivities no matter in dry (1237.3 S cm−1) or wet (1018.7 S cm−1) state. It also exhibits a high capacitance (188.5 F g−1 at 1 A g−1) and long lifespan (capacitance retention of 94% after 10,000 cycles). The fiber-based supercapacitor shows superb flexibility with stable capacitive behavior under deformation. These characteristics manifest the potential of PEDOT:PSS/LDH fibers for stable high-performance energy storage to support wearable electronics.

The Residual Stress Relief and Deformation Control of Al Alloy Thin-Walled Antenna Components by Ultrasonic Regulation

The residual stress fields of the initial billet and subsequent machining in the material bring great challenges to the precision machining and geometrical stability of aluminum alloy thin-walled components. To ensure that a certain type of large-sized aluminum alloy thin-walled antenna has a small flatness deformation during forming, this paper firstly employed the ultrasonic critical refraction longitudinal wave (LCR wave) detection method to measure the different depth ranges’ residual stress distribution of 5A06/6061/7075 aluminum alloy plate, both as blanks and after multiple milling. Additionally, the effects of inherent residual stress (IRS) and machining-induced residual stress (MIRS) on the subsequent milling deformation were analyzed. After that, combined with the self-developed ultrasonic stress relief (USR) system, the deformation control effect of a thin-walled plate after eliminating residual stress in each stage was tested. The results show that the ultrasonic stress relief treatment can quickly and efficiently eliminate the IRS and MIRS with small flatness deformation. By introducing the URS treatment in the blank, rough machining, and semi-finishing stages, the components before each subsequent machining are in a low-stress state, and the component deformation can be gradually controlled so that the final thin-walled antenna has a smaller flatness.

Electronic structure reconfiguration of nickel–cobalt layered double hydroxide nanoflakes via engineered heteroatom and oxygen-vacancies defect for efficient electrochemical water splitting

The development of earth-abundant and high-efficiency bifunctional electrocatalysts is extremely desirable for electrochemical water splitting, but there are some critical challenges that need to be addressed. The coordinated tailoring of electronic structure and Bader charge transference by heteroatom doping and oxygen vacancy defects are one of the strongest tactics to enhance the oxygen and hydrogen evolution reactions (OER and HER) of catalysts. Herein, a novel Mo-decorated nickel–cobalt layered double hydroxides 3D honeycomb nanoflake on Ni foam (labeled as Mo-NiCo LDHs(Vo)) as bifunctional electrode materials with enriched oxygen vacancy defects, excellent geometric stability, and enriched active sites was successfully fabricated through a facile hydrothermal reaction strategy. Density functional theory computations and experimental results confirmed that the electrocatalytic intrinsic activity of Mo-NiCo LDHs(Vo) was optimized not only because of the provision of new active sites by the Mo dopants via the construction of defects and oxygen vacancies but also because of the activation of the local electronic structures of the surrounding Ni and Co sites. Consequently, Mo-NiCo LDHs(Vo) exhibited outstanding electrocatalytic performance with an overpotential of 258 mV for OER and 194 mV for HER at a current density of 10 mA/cm2 in an alkaline medium. In addition, the catalyst exhibited excellent long-term stability after 100 h of use as a bifunctional electrode for overall water splitting. This work provides a facile means to fabricate superior, efficient noble metal-free catalysts with well-designed defects at the atomic-level using electronic structure engineering for energy-related applications.

Novel cubic silicane nanosheet as an adsorbing medium for dimethylbutane and methylhexane molecules – a first-principles study

The geometric stability and electronic properties of cubic silicane (c-Si12) nanosheet (hydrogenated silicene) are studied based on the first-principles studies. The c-Si12 monolayer nanosheet possesses an energy band gap of 2.259 eV. We deployed the semiconductor c-Si12 nanosheet as a sensing base material for 2,2-dimethylbutane, 2-methylhexane molecules. Moreover, the adsorption energy results disclose the physical adsorption of target molecules on c-Si12 nanosheet. Furthermore, the variation in the electronic properties of c-Si12 nanosheet is evident from the outcome of charge transfer, electron difference density, band structure, and density of states studies. Besides, the relative energy gap variation of c-Si12 nanosheet is taken into count, which reveals the chemo-resistive nature of c-Si12 nanosheet owing to 2,2-dimethylbutane, 2-methylhexane adsorption. Hence, the novel c-Si12 nanosheet can be employed as a sensing substrate for 2,2-dimethylbutane, 2-methylhexane molecules.

Self-Adaptive Obstacle Crossing of an AntiBot From Reconfiguration Control and Mechanical Adaptation

AbstractOne drawback of wheeled robots is their inferiority to conquer large obstacles and perform well on complicated terrains, which limits their application in rescue missions. To provide a solution to this issue, an ant-like six-wheeled reconfigurable robot, called AntiBot, is proposed in this paper. The AntiBot has a Sarrus reconfiguration body, a three-rocker-leg passive suspension, and mechanical adaptable obstacle-climbing wheeled legs. In this paper, we demonstrate through simulations and experiments that this robot can change the position of its center of mass actively to improve its obstacle-crossing capability. The geometric and static stability conditions for obstacle crossing of the robot are derived and formulated, and numerical simulations are conducted to find the feasible region of the robot’s configuration in obstacle crossing. In addition, a self-adaptive obstacle-crossing algorithm is proposed to improve the robot’s obstacle-crossing performance. A physical prototype is developed, and using it, a series of experiments are carried out to verify the effectiveness of the proposed self-adaptive obstacle-crossing algorithm.

On the implant stability in adaptive multi-catheter breast brachytherapy: Establishment of a decision-tree for treatment re-planning

Background and purposeTo assess implant stability and identify causes of implant variations during high-dose-rate multi-catheter breast brachytherapy. Materials and methodsPlanning-CTs were compared to control-CTs acquired halfway through the treatment for 100 patients. For assessing geometric stability, Fréchet-distance and button-to-button distance changes of all catheters as well as variations of Euclidean distances and convex hulls of all dwell positions were determined. The CTs were inspected to identify the causes of geometric changes. Dosimetric effects were evaluated by target volume transfers and re-contouring of organs at risk. The dose non-uniformity ratio (DNR), 100% and 150% isodose volumes (V100 and V150), coverage index (CI), and organ doses were calculated. Correlations between the examined geometric and dosimetric parameters were assessed. ResultsFréchet-distance and dwell position deviations >2.5 mm as well as button-to-button distance changes >5 mm were detected for 5%, 2%, and 6.3% of catheters, but for 32, 17, and 37 patients, respectively. Variations occurred enhanced in the lateral breast and close to the ribs, e.g. due to different arm positions. Only small dosimetric effects with median DNR, V100, and CI variations of −0.01 ± 0.02, (−0.5 ± 1.3)ccm, and (–1.4 ± 1.8)% were observed in general. Skin dose exceeded recommended levels for 12 of 100 patients. Various correlations between geometric and dosimetric implant stability were found, based on which decision-tree regarding treatment re-planning was established. ConclusionMulti-catheter breast brachytherapy shows a high implant stability in general, but considering skin dose changes is important. To increase implant stability for individual patients, we plan to investigate patient immobilization aids during treatments.

Optimizing interlayer cooling for SUS316L thin wall fabricated by directed energy deposition

The direct energy deposition (DED) process requires proper interlayer cooling (IC) to avoid geometric failure caused by overheating of the midsection. This study suggests an optimum IC step based on a constitutive equation, instead of trial and error, to ensure the geometric stability of DED-processed 316 L stainless steel within a short period. The temperatures after cooling (TC) were acquired per layer of building and precisely measured using a constitutive model. Subsequently, a cooling period to maintain a target TC was calculated for the 30-layered DED specimen using the model. The optimum IC step varied with the number of deposited layers: (i) non-IC up to the fourth layer, (ii) IC step of 1.05 s for the fifth layer, and (iii) IC step of 2.21 s for the subsequent layers. The developed approach resulted in a remarkable improvement in geometric stability (geometric error of 5.9%) compared with the DED specimen fabricated without an IC step (error of 33.5%). Furthermore, the processing time was reduced by 30% compared with a conventional IC step with a fixed interval of 5 s. The developed approach also led to homogeneous grain refinement and a resulting increase in microhardness.

Machine learning-aided Genetic algorithm in investigating the structure–property relationship of SmFe12-based structures

We investigate the correlation between geometrical information, stability, and magnetization of SmFe12-based structures using machine learning-aided genetic algorithm structure generation and first-principle calculation. In parallel with structure generation inherited using the USPEX program, a pool of structures is created for every population using the sub-symmetry perturbation method. A framework using embedded orbital field matrix representation as structure fingerprint and Gaussian process as a predictor has been applied to ranking the most potential stability structures. As a result, the original structure SmFe12 with the well-known tetragonal I4/mmm symmetry is investigated with a parabolic dependence between formation energy and its magnetization by continuous distortions of the unit-cell lattice parameter and individual sites. Notably, a SmFe12 structure with I4/mmm symmetry is found with 7.5% increasing magnetization while keeping the similar formation energy with the most stable structures in this family. With SmFe11CoN family, structures with N interstitial position in the center of Sm and Fe octahedron show outperform all other structures in both ability of stabilization and remaining high magnetization of the original structure. Finally, further investigation using metric learning embedding space brings valuable insight into the correlation between geometrical arrangement, stability, and magnetization of this structure family.

Plasma immobilization of azobenzene dye on polyamide 6 polymer

Plasma treatment of polymeric materials is a cost-effective and efficient technique to modify the surface and change the constituent unit configuration. This research investigates the effects of argon DC glow discharge plasma on pure and DR1 dye-loaded polyamide 6 polymer films and stabilization of dye on the surface. Plasma breaks some bonds and activates the surface through creating reactive structures such as free radical sites on the surface and increases tertiary amides on the surface of polymer. Besides, this process alters surface topographical characteristics and conformation of azobenzene dye which are effective on the durability of the dye on the surface. Plasma causes interactions of the dye with the polymer and immobilizes the dye on the polymer. On the other hand, these interactions lead to changes in the dye's optical and geometric isomeric activity and stability. This work studies the chemical and morphological changes of polyamide 6 by plasma with AFM and spectroscopic methods. Furthermore, the aging of nylon 6 films loaded with DR1 dye is measured, and the conformational changes of the dye are investigated. Plasma stabilizes the dye on the polymer surface through making changes of chemical and physical properties on the surface components.

A Simple Way to Reduce 3D Model Deformation in Smartphone Photogrammetry

Recently, the term smartphone photogrammetry gained popularity. This suggests that photogrammetry may become a simple measurement tool by virtually every smartphone user. The research was undertaken to clarify whether it is appropriate to use the Structure from Motion-Multi Stereo View (SfM-MVS) procedure with self-calibration as it is done in Uncrewed Aerial Vehicle photogrammetry. First, the geometric stability of smartphone cameras was tested. Fourteen smartphones were calibrated on the checkerboard test field. The process was repeated multiple times. These observations were found: (1) most smartphone cameras have lower stability of the internal orientation parameters than a Digital Single-Lens Reflex (DSLR) camera, and (2) the principal distance and position of the principal point are constantly changing. Then, based on images from two selected smartphones, 3D models of a small sculpture were developed. The SfM-MVS method was used, with self-calibration and pre-calibration variants. By comparing the resultant models with the reference DSLR-created model it was shown that introducing calibration obtained in the test field instead of self-calibration improves the geometry of 3D models. In particular, deformations of local concavities and convexities decreased. In conclusion, there is real potential in smartphone photogrammetry, but it also has its limits.

FEM Numerical and Experimental Study on Dimensional Accuracy of Tubes Extruded from 6082 and 7021 Aluminium Alloys.

The extrusion of hollow profiles from hard-deformable AlZnMg alloys by using porthole dies encounters great technological difficulties in practice. High extrusion force accompanies the technological process, which is caused by high deformation resistance and high friction resistance in extrusion conditions. As a result of high thermo-mechanical loads affecting the die, a significant loss of dimensional accuracy of extruded profiles can be observed. The different projects of porthole dies for the extrusion of Ø50 × 2 mm tubes from the 7021 alloy were numerically calculated and then tested in industrial conditions by using a press of 25 MN capacity equipped with a container with a diameter of 7 inches (for 7021 alloy and 6082 alloy for comparison). New extrusion die 3 with modified bridge and mandrel geometry and a special radial-convex entry to the die opening was proposed. FEM was applied to analyse the metal flow during extrusion, geometrical stability of extruded tubes and the die deflection. The photogrammetric measuring method was used to evaluate dimensional accuracy of tubes extruded in different conditions and geometrical deviations in porthole dies elements, especially the bridges and the mandrels. Research revealed a high dimensional accuracy of tubes extruded from the 6082 alloy and from the 7021 alloy by using original extrusion die 3, while much higher dimensional deviations were noted for tubes extruded from the 7021 alloy by using extrusion dies 1 and 2, particularly in relation to the circularity, centricity and wall thickness.

Formation of Bearings Parts Waviness in Centerless Mortise Grinding on Rigid Supports

The formation of waviness on the working surfaces of bearing parts is associated with fluctuations in the size of the cut layer of metal and changes in the components of the cutting force. Laplace operators were used to model the centerless grinding system based on the construction of the transfer function and the characteristic equation. It was found that the formation of waviness depends on the position of the hodograph of the movement of the vector of the center of the part in the complex plane, which in turn depends on the geometric parameters of the rigid supports of the centerless grinder machine. This makes it possible, based on hodographs and the angular orientation of their asymptotes, to determine the geometric stability of the process depending on the angles of adjustment of the rigid supports of the grinder machine. Two methodological approaches were used to confirm the correctness of the hypotheses. The first one is a multiplication of wave’s hodographs. The second one is regeneration displacement and the coincidence of the combined hodograph of regeneration and waviness displacement mechanisms with the hodograph of infinitely rigid machine displacement. The diagrams which allow choosing geometry of adjustment of rigid support that allows to increase or decrease parameters of certain harmonics are developed. The 3D diagram allows setting the local minima, characterized by acceptable geometric adjustment conditions, providing regulated waviness of the working surfaces of bearing parts.

Magneto-electronic property and strain regulation for non-metal atom doped armchair arsenene nanotubes

For the development of high performance magnetic devices, inducing magnetism in non-magnetic materials and flexibly regulating their magneto-electronic properties are very important. According to the density functional theory (DFT), we systematically study the structural stability, magneto-electronic properties, carrier mobility and strain effect for each of armchair arsenene nanotubes doped with non-metallic atoms <i>X</i> (<i>X</i> = B, N, P, Si, Se, Te). The calculated binding energy and formation energy confirm that the geometric stability of AsANT-<i>X</i> is high. With non-metal doping, each of AsANT-<i>X</i> (<i>X</i> = B, N, P) acts as a non-magnetic semiconductor, while each of AsANT-<i>X</i> (<i>X</i> = Si, Se, Te) behaves as a bipolar magnetic semiconductor, caused by the unpaired electrons occurring between X and As. Furthermore, by doping, the carrier mobility of AsANT-<i>X</i> can be flexibly moved to a wide region, and the carrier polarity and spin polarity in mobility can be observed as well. Especially, AsANT-Si can realize a transition among bipolar magnetic semiconductor, half-semiconductor, magnetic metal, and non-magnetic metal by applying strain, which is useful for designing a mechanical switch to control spin-polarized transport that can reversibly work between magnetism and demagnetism only by applying strain. This study provides a new way for the application of arsenene.

Effect of Step Size on the Formability of Al/Cu Bimetallic Sheets in Single Point Incremental Sheet Forming

Single Point Incremental Forming (SPIF) is an unconventional forming process that is suitable for prototype production and small lot production due to the economical tooling cost, short lead time, and the ability to create symmetrical and asymmetrical complex geometries without the use of expensive dies. This article presents the effect of the step size Δz of a forming tool made of 145Cr6 tool steel on the formability and maximum forming angle, mechanical properties, hardness, surface roughness, microstructure and texture of bimetallic Al/Cu sheets. Experiments were conducted at a constant rotational speed and feed rate, with the use of rapeseed oil as a lubricant. The tests were carried out with the use of a forming tool on both sides of the bimetallic sheet. The shape and dimensions of the formed elements are determined by non-contact optical 3D scanning. It has been proved that an increase in the step size Δz affects the deterioration of the surface quality of the specimens (an increase in the Ra parameter from 0.2 μm to approximately 3 μm for the step size of 1.2 mm), while a small step size down Δz favours the geometric stability of the samples. With increasing step size (at Δx = Δy = const.), the drawpiece wall continually thinned until the material fractured. Based on the results, it was shown that increasing the step size Δz over 1.1 mm causes cracking of the drawpieces. Furthermore, greater thinning of the Al/Cu sheet was observed in the range of step size Δz between 0.7 and 1.0 mm for aluminum side and step size Δz ≤ 0.6 mm and Δz ≥ 1.1 mm for copper side. It was also found that the mechanical properties of the bimetal sheet decreased as a result of incremental forming. The greatest decrease in strength and ductility was recorded for a pitch of 1.2 mm. Strength decreased from 230 MPa (for sheet in initial state) to approximately 80 MPa, elongation from 12% to approximately 8.5%, and hardness from 120 HV10 for Cu and 60 HV10 for Al to approximately 30 HV10 for both layers.

Assessment of Two Advanced Aluminium-Based Metal Matrix Composites for Application to High Energy Physics Detectors

The Outer Tracker of the Compact Muon Solenoid (CMS), one of the large experiments at the CERN Large Hadron Collider, will consist of about 13,200 modules, each built up of two silicon sensors. The modules and support structures include thousands of parts that contribute to positioning and cooling the sensors during operation at -30 °C. These parts should be low mass while featuring high thermal conductivity, stiffness and strength. Their thermal expansion coefficient should match that of silicon to avoid deformations during cooling cycles. Due to their unique thermal and mechanical properties, aluminium-carbon fibre (Al/Cf) Metal Matrix Composites are the material of choice to produce such light and stable thermal management components for High Energy Physics detectors. For the CMS Outer Tracker, about 500,000 cm3 of Al/Cf raw material will be required to be produced through a reliable process to guarantee consistent properties throughout parts manufacturing. Two Al/Cf production routes are currently considered: liquid casting by gas-pressure infiltration and a powder metallurgy process based on continuous semi-liquid phase sintering. The dimensional stability of the resulting material is of paramount importance. Irreversible change of shape may be induced by moisture adsorption and the onset of galvanic corrosion at the discontinuous interfaces between Cf and Al. This paper presents the results of an extensive investigation through Computed Microtomography, direct microscopical investigations, analysis of the interfaces and metrology measurements aimed at comparing and interpreting the response to different environments of the respective products. The results obtained confirm the suitability of the two investigated Al/Cf MMCs for application to components of the CMS Outer Tracker, requiring tight geometrical control and microstructural stability over time. However, for PM parts sintered through the semi-liquid phase process, a multilayered protective noble metal coating is necessary the make them impervious to moisture, allowing dimensional stability to be guaranteed and the onset of corrosion phenomena to be avoided, while the product obtained by gas-pressure infiltration has shown less sensitive even to extreme temperature-humidity cycles and may be used uncoated.

Stacking and tuning effects on magneto-electronic and electric contact features for arsenene/Fe3GeTe2 van der Waals heterostructure

Recently, experimentally available Fe3GeTe2 (FGT) monolayer has attracted tremendous research interest due to its long-range ferromagnetic (FM) order. Here, we systematically study the magneto-electronic and electric contact properties of FGT-based van der Waals (vdW) heterostructures integrated by arsenene (As) with multiple stacking patterns. The low binding energy (−117.69 to −52.69 meV atom−1) proves their highly geometric stability, and the high magnetized energy (91.61–213.61 meV/unit cell) and magnetic exchange energy (64.53–84.43 meV/unit cell) provide a strong evidence for magnetism stability. Particularly, the magnetic proximity exchange effect as well as spin transfer and spin rearrangement can enhance the FM coupling in heterostructures, so that the highest Curie temperature T C = 173.93 K is achieved, being 19.73% higher than isolated FGT. Meanwhile, the arsenene is magnetized as well. In particular, metal-induced gap states appear in band gap of original As monolayer. Besides, metal-semiconductor contact performance is improved in constructed heterostructures by lowering electronic Schottky barrier height to nearly obtain Ohmic contact. Magnetic exchange energy rises further to improve magnetic stability with the interlayer spacing narrowed, and T C is increased up to 184.80 K, an increase of 27.21% compared to FGT monolayer. Being attributed to the proximity exchange effect strengthened with a shrunk interlayer spacing, and the electric contact behavior is also boosted further by this compressive strain to realize high-performance electric junction. Our findings provide a new route to extend the applications of FGT by constructing suitable vdW heterostructures.

Walls and asymptotics for Bridgeland stability conditions on 3-folds

We consider Bridgeland stability conditions for three-folds conjectured by Bayer-Macr\`i-Toda in the case of Picard rank one. We study the differential geometry of numerical walls, characterizing when they are bounded, discussing possible intersections, and showing that they are essentially regular. Next, we prove that walls within a certain region of the upper half plane that parametrizes geometric stability conditions must always intersect the curve given by the vanishing of the slope function and, for a fixed value of s, have a maximum turning point there. We then use all of these facts to prove that Gieseker semistability is equivalent to asymptotic semistability along a class of paths in the upper half plane, and to show how to find large families of walls. We illustrate how to compute all of the walls and describe the Bridgeland moduli spaces for the Chern character (2,0,-1,0) on complex projective 3-space in a suitable region of the upper half plane.

Comparative antibacterial analysis of the anthraquinone compounds based on the AIM theory, molecular docking, and dynamics simulation analysis.

Hydroxyanthraquinones and anthraquinone glucoside derivatives are always considered as the active antibacterial components. Comparison of structure characteristics and antibacterial effect of these compounds was performed by applying quantum chemical calculations, atoms in molecules theory, molecular docking, and dynamics simulation procedure. Density functional theory calculation with B3LYP using 6-31G (d, p) basis set has been used to determine ground state molecular geometries. The molecular geometric stability, electrostatic potential, frontier orbital energies, and topological properties were analyzed at the active site. Once glucose ring is introduced into the hydroxyanthraquinone rings, almost all of the positive molecular potentials are distributed among the hydroxyl hydrogen atoms of the glucose rings. In addition, low electron density ρ (r) and positive Laplacian value of the O-H bond of the anthraquinone glucoside are the evidences of the highly polarized and covalently decreased bonding interactions. The anthraquinone glucoside compounds have generally higher intermolecular binding energies than the corresponding aglycones due to the strong interaction between the glucose rings and the surrounding amino acids. Molecular dynamics simulations further explored the stability and dynamic behavior of the anthraquinone compound and protein complexes through RMSD, RMSF, SASA, and Rg. The type of carboxyl, hydroxyl, and hydroxymethyl groups on phenyl ring and the substituent glucose rings is important to the interactions with the topoisomerase type II enzyme DNA gyrase B.

A review on the geotechnical response of fly ash-colliery spoil blend and stability of coal mine dump

Regressive coal mining to meet rising electricity demand has resulted in increased dumps of colliery spoil (CS) and fly ash (FA). These dumps must be adequately managed to avoid environmental hazards. Considering their loose deposition, they fail to attain geotechnical and geometrical stability. The present review article attempts to investigate the stability behaviour of FA-CS blend dumps in terms of geotechnical parameters. It also emphasizes studies that focus on determining the optimum percentage of FA to be used along with CS as a blend. Moreover, it also highlights resource management, implementation, and improvement of the FA-CS blend thereby enhancing geotechnical parameters, viz., compaction, unconfined compressive strength (UCS), calfornia bearing ratio (CBR), and shear strength. These studies have shown that the usage of around 20% of FA by weight in blend with CS, has improved geotechnical properties by 2.5 times their original value. Based on the review performed it is inferred that the blend of FA and CS can be laid effectively in exhausted mining sites and can be used in the construction of roads to these mining sites. • Presented recent state-of-the-art on colliery spoil. • Reviewed past studies related to unstable colliery spoil dump. • A blend of fly ash and spoil proved to be an effective ground improvement approach. • Documented studies related to the geotechnical performance of fly ash- spoil blend. • Safe and environmentally sustainable disposal. • Discussed the future potential of the fly ash-spoil blend in geotechnical engineering.

Stealthy Integrity Attacks for a Class of Nonlinear Cyber-Physical Systems

This article proposes a stealthy integrity attack generation methodology for a class of nonlinear cyber-physical systems. Geometric control theory and stability theory of incremental systems are used to design an attack generation scheme with stealthiness properties. An attack model is proposed as a closed-loop dynamical system with an arbitrary input signal. This model is developed based on a controlled invariant subspace that results from geometric control theory and is decoupled with the system outputs and the nonlinear function. The presence of the arbitrary signal in the attack model provides an additional degree of freedom and constitutes a novel component compared with existing results. The stealthiness of the attack model is rigorously investigated based on the incremental stability of the closed-loop control system, and the incremental input-to-state stability of the anomaly detector. As a result, a sufficient condition in terms of the initial condition of the attack model is derived to guarantee stealthiness. Finally, a case study is presented to illustrate the effectiveness of the developed attack generation scheme.