Conventional SMA Research Articles

Analysis of the compactibility of bituminous mixtures for reflective crack relief interlayers (RCRI)

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC – asphalt concrete, AC AF – asphalt concrete “anti-fatigue”, SMA – stone mastic asphalt and SMA-MA – stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100–160C°) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture.

Influence of performance-graded binders on enhancing asphalt mixture performance with epoxy resin and crumb rubber powder

The evaluation of asphalt mixture fatigue performance holds increasing significance in the context of asphalt concrete pavement and various polymer modifiers. This study focuses on assessing the fatigue and reflection crack performance of two asphalt types: a conventional 10 mm SMA mixture with a fixed PG grade (PG 76–22) and a modified asphalt employing SBS, available in multiple grades (ranging from PG 76–22 to PG 82–22). Additionally, this study incorporates crumb rubber powder (CRP-6%) and epoxy resin (ER-4%) into the conventional SBS-modified SMA binder, reducing conventional asphalt binder consumption and promoting the utilization of recycled waste materials. To achieve this goal, comprehensive evaluations of fatigue cracking performance were conducted on SMA mixtures through multiple stressed creep and recovery tests, Texas overlay tests, and direct tensile cyclic fatigue tests. The results reveal that the modified binder exhibited superior strain recovery and a reduced strain rate in comparison to the reference binder under creep loads at MSCR levels of 0.1 and 3.2 KPa. The findings also indicate a 19.5% load reduction in the modified asphalt mixture with PG 72–22 binders, epoxy, and CRP after 1000 cycles, compared to 39.8% for the conventional mixture with a PG 76–22 binder. Moreover, the modified mixture demonstrated significant improvements, with 3.7 times more repetitions and 3.9 times more interactions to failure at strain levels of 330 and 360, respectively. Importantly, the research highlights the superior fatigue crack resistance performance of the PG 76–28 grade mixture compared to PG 76–22, positioning it as an optimal choice for aged concrete overlay applications. In conclusion, this study contributes to the development of more durable and reliable polymer-modified SMA mixtures enhanced with epoxy and crumb rubber, facilitating the advancement of sustainable road infrastructure.

Enhancing Mechanical Behavior and Energy Dissipation in Fiber-Reinforced Polymers through Shape Memory Alloy Integration: A Numerical Study on SMA-FRP Composites under Cyclic Tensile Loading.

Conventional fiber-reinforced polymers (FRPs) have a relatively linear stress-strain behavior up to the failure point. Therefore, they show brittle behavior until the failure point. Shape memory alloys, in addition to having high ductility and good energy dissipation capability, are highly resistant to corrosion and show good performance against fatigue. Therefore, using the SMA fibers in the production of FRPs can be a suitable solution to solve the problem of the brittle behavior of conventional FRPs. SMA fibers can be integrated with a polymeric matrix with or without conventional fibers and create a new material called SMA-FRP. This study investigates the effect of using different volume fractions of conventional fibers (carbon, glass, and aramid) and SMA fibers (NiTi) in the super-elastic phase and the effect of the initial strain of SMA fibers on the behavior of SMA-FRP composites under cyclic tensile loading. Specimens are designed to reach a target elastic modulus and are modeled using OpenSees (v. 3.5.0) finite element software. Analyzing the results shows that in the SMA-FRP composites that are designed to reach a target elastic modulus, with an increase in the volume fraction of SMA fibers, the maximum stress, residual strain, and strain hardening ratio are reduced, and the ability to energy dissipation capability and residual stress increases. It was also observed that increasing the percentage of the initial strain of SMA fibers increases the maximum stress and energy dissipation capability and reduces the residual strain and yield stress. In the investigation of the effect of the type of conventional fibers used in the construction of composites, it was found that the use of fibers that have a larger failure strain increases the maximum stress and energy dissipation capability of the composite and reduces the strain hardening ratio. In addition, increasing the elastic modulus of conventional fibers increases the residual strain and residual stress of the composites.

An enhanced slime mould algorithm based on adaptive grouping technique for global optimization

When solving global optimization problems by metaheuristic algorithms (MAs), an important issue is how to keep a balance between convergence and diversity. This article develops an enhanced slime mould algorithm called AGSMA to address the above issue. In AGSMA, the entire population is divided into two subpopulations. The size of each subpopulation is dynamically tuned based on the average fitness value. Afterward, different from the search equation in conventional SMA, a new search mechanism is raised to discover more promising regions. Furthermore, an efficient learning operator is devised to discourage premature convergence. The comparison of the raised AGSMA on several benchmark functions and practical engineering problems with selected state-of-the-art methods demonstrates that the developed algorithm performs effectively and competitively. The source code of AGSMA is publicly available at https://github.com/denglingyun123/Enhanced-slime-mould-algorithm.

ESMA-OPF: Enhanced Slime Mould Algorithm for Solving Optimal Power Flow Problem

In this work, an enhanced slime mould algorithm (ESMA) based on neighborhood dimension learning (NDL) search strategy is proposed for solving the optimal power flow (OPF) problem. Before using the proposed ESMA for solving the OPF problem, its validity is verified by an experiment using 23 benchmark functions and compared with the original SMA, and three other recent optimization algorithms. Consequently, the ESMA is used to solve a modified power flow model including both conventional energy, represented by thermal power generators (TPGs), and renewable energy represented by wind power generators (WPGs) and solar photovoltaic generators (SPGs). Despite the important role of WPGs and SPGs in reducing CO2 emissions, they represent a big challenge for the OPF problem due to their intermittent output powers. To forecast the intermittent output powers from SPGs and WPGs, Lognormal and Weibull probability density functions (PDFs) are used, respectively. The objective function of the OPF has two extra costs, penalty cost and reserve cost. The penalty cost is added to formulate the underestimation of the produced power from the WPGs and SPGs, while the reserve cost is added to formulate the case of overestimation. Moreover, to decrease CO2 emissions from TPGs, a direct carbon tax is added to the objective function in some cases. The uncertainty of load demand represents also another challenge for the OPF that must be taken into consideration while solving it. In this study, the uncertainty of load demand is represented by the normal PDF. Simulation results of ESMA for solving the OPF are compared with the results of the conventional SMA and two further optimization methods. The simulation results obtained in this research show that ESMA is more effective in finding the optimal solution of the OPF problem with regard to minimizing the total power cost and the convergence of solution.

An All-Textile Dual-Band Antenna for BLE and LoRa Wireless Communications

In this paper, a dual-band conductive textile-based wearable antenna operating at LoRa-868 MHz and BLE-2.4 GHz is presented. The proposed antenna is intended for accurate geolocation, tracking and communication applications in the military, industrial and telemedicine industries. The low-profile patch antenna is suitable for integrating into clothing. It is composed of three textile layers: top and bottom silver-ink-printed polystyrene fabrics, and a neoprene substrate. To utilize the flexible and restorable properties of these textile materials, the proposed antenna is directly fed by a flexible cable using an aperture-coupled feeding technique. This method not only eliminates the use of the conventional, bulky, and metallic SMA connector but also introduces a secondary resonance at 2.4 GHz, enabling the dual-band property. Using a thin coaxial cable fixed on the aperture slot for proximity coupling, a compact antenna size of 150 mm2 is obtained that can easily be attached and detached on existing cloths. The proposed structure has been fabricated and measured in an anechoic chamber to verify the performance. Measured gain of 3.28 dBi and 3.25 dBi was realized for LoRa and BLE at an antenna size of 0.61 λg × 0.61 λg × 0.012 λg (where λg is guided wavelength at 868 MHz) with a front-to-back ratio (FBR) of greater than 10 dBi.

Evaluation of Fatigue Potential for Crumb Rubber Modified Bitumen in Stone Mastic Asphalt Mixes

SMA is a gap graded mix composed of a high concentration of coarse aggregate that is held together in a thick asphalt film by a matrix of mineral filler and stabilizers. Since natural aggregates have become expensive, hence Reclaimed Asphalt Pavement (RAP) can be reused in pavement construction to reduce the environmental hazardous due to disposal problems. Since the RAP contains used aggregates, it is highly prone to fatigue, thermal and reflective cracking effect. Rheological and chemical properties of aged bitumen in RAP can be enhanced by use of untreated waste oils such as waste engine oil as rejuvenators. This research presents a study on fatigue performance of SMA mix with Reclaimed Asphalt Pavement (RAP) materials with and without rejuvenators and results were compared with conventional SMA mix. The materials used were first characterized by common laboratory tests. Then the three SMA mixes are tested using several laboratory test procedures: Marshall Stability, indirect tensile strength, moisture susceptibility, and indirect tension fatigue test. The optimum proportions of the of the mixes with highest stability are selected from the Marshall stability test. The indirect tensile strength test results show that the SMA mix replaced with RAP without rejuvenators showed higher tensile strength ratio and resistance to moisture damage when compared to conventional mix and optimum RAP replacement mix with rejuvenators. The fatigue test was conducted for the three optimum mixes at different temperature and stresses. The fatigue test results showed that at lower temperature and stresses, the RAP replaced SMA without rejuvenator offered better fatigue resistance than those with rejuvenator and conventional SMA mix. At higher temperatures, the RAP replaced SMA mix with rejuvenator offered similar fatigue lifecycle as conventional mix. However, at high stresses, conventional SMA mix offered better fatigue lifecycle. Increase in failure stresses resulted in decrease of number of fatigue cycles and increased in initial tensile strain of the mix. Thus, with the use of RAP substantial decrease in cost can be achieved without compromising the fatigue characteristic of the SMA mix.

Assessment of crumb rubber Stone Mastic asphalt potential to be used in Angola

The work aims to contribute to the functional validation of a rubber modified SMA 12.5, blended by the dry process, and avoid the bitumen drainage, to be an alternative to conventional cellulose fibers SMA and improve the overall durability of the SMA mixture. The mixtures analyzed were evaluated for water sensitivity, permanent deformation, deformability, fatigue resistance, and ageing. The drawn conclusion was that rubber modified SMA fits well the objective of constituting a surface course resistant to heavy vehicles' actions under high temperature conditions, having the potential to be used in paving technology in Angola or other similar reality.

All-electrical switching and electrothermo-optical response of a tristable smectic-A liquid crystal

A unique switching mechanism in the smectic-A (SmA*) phase involving textural change between any two among the planar, homeotropic and focal conic states is investigated. Exploiting the temperature-dependent textural transition characteristics of a SmA* liquid crystal (LC), we proposed a multi-stable switching scheme relying on AC voltage to induce the dielectric effect and pseudo-dielectric heating. This mechanism exhibits desirable properties for LC cells with anti-parallel planar surface treatment. Compared with the electrical operation mode of conventional SmA devices, the optical states enabled by this approach show superior qualities in both transmittance and haze value. The revealed features, including the in-phase switching, tunable operating temperature and excellent optical performance, show great potential for applications in smart glass and other energy-saving devices.

Thermally stable poly(styrene-maleic anhydride) layer modified by ion-beam for liquid crystal orientation

We report uniform and homogeneous liquid crystal (LC) alignment using ion beam (IB)-irradiated poly(styrene-maleic anhydride) (SMA) films as an alignment layer when the IB incidence angle is controlled. The molecular polarity on the SMA surface increased with IB irradiation, especially at an incidence angle of 30°, resulting in strong van der Waals forces between the LC molecules and the surface. Atomic force microscopy and X-ray photoelectron spectroscopy were used to determine the LC alignment mechanism. Chemical structure analysis indicated that the orientation of LC molecules was due to van der Waals forces and selective breaking of C–C bonds by IB irradiation. The potential application of SMA substrates as alignment layers for display devices was further supported by their higher thermal stability (220 °C) compared with that of conventional rubbed SMA (160 °C) and rubbed polyimide (160 °C). Therefore, LC cells with IB-irradiated SMA are potential candidates for alternative alignment layers in LC applications.

The relevance of strategic management accounting to popular culture: The world of West End Musicals

The study of accounting and popular culture presents an exciting new research agenda for management accountants. This study examines this development from a strategy perspective. Specifically, this paper adds to our knowledge of the potential for Strategic Management Accounting in action by studying the novel setting of the world of West End Musicals. Using a case study approach, this study challenges conventional SMA thinking from a ‘strategy-as-practice’ perspective, using the process of developing a popular theatre portfolio of activities. Findings indicate that strategy is a complex practice which is an inherently social process: Theatre producers negotiate a route to the market that is mediated by validating intermediary organizations that contribute and communicate the reputation of new cultural products and thereby support the strategic process.

Dielectric Study of Liquid Crystals with Large Electroclinic Effect

Here we report results of the study of tilt angle and birefringence of some “high-electroclinic” materials having similar molecular structure with two and three siloxane spacers. The structure of these LC materials were studied by dielectric spectroscopy, birefringence and tilt angle measurements. Three of the four studied materials with a siloxane fragment are the deVries materials, but the siloxane-free sample is conventional SmA phase and is thus different. Possible models for the molecular structures of deVries SmA* phases are discussed.

A HIGH TEMPERATURE SUPERCONDUCTOR MICROWAVE FILTER WORKING IN C-BAND FOR THE SARDINIA RADIO TELESCOPE

A planar band-pass filter based on High Temperature Superconductor (HTS) has been designed for possible implementation in the cryogenic front-end of the C-band receiver for the Sardinia Radio Telescope. The band-pass filter is designed to operate at relatively high frequencies: center frequency 6.7 GHz with 30% bandwidth. Seven nominally identical filters have been fabricated to test different carrier materials and connector types aimed to keep the fabrication of the HTS filter simpler and more cost competitive. In addition to the conventional approach, silver plating, copper carriers and SMA connectors have been used. Cryogenic scattering parameter measurements show a good agreement with numerical results: the average of the transmission losses turns out to be in the range 0.15–0.25 dB depending on the prototypes, whereas the reflection coefficient is below -16 dB. The insertion loss has been also measured by using a radiometric approach based on the cold attenuator method showing consistent results with those given by the Vector Network Analyzer. Multiple cool-down measurements have been performed successfully proving the data repeatability both in short- and medium-term. Concerning alternative technical solutions, the SMA connectors and silver plating appear to be valid options whereas the copper carriers are inclined to destroy the circuit. Finally, numerical simulations and experimental measurements on a traditional copper filter operating at 20 K show that the HTS filter improves the losses of about 0.2 dB with respect to the copper one.

The importance of the bottom layer in double-layer porous asphalt for noise reduction

Double-layer porous asphalt concrete (DPAC) surfaces are generally considered to be the acoustically most effective low noise road surfaces ready for implementation. While DPAC used on highways in warm climates may have an average life of around 8 years, in Scandinavia with severe winter climate DPAC usually survive only about 3 years; partly due to wear of studded tyres. An ongoing project in Sweden, applying DPAC and single-layer porous asphalt (PAC), the latter consisting of the top layer of the DPAC, on motorway E4 in Jönköping-Huskvarna, has revealed interesting performance. Initial noise reduction was 7.5 dB(A) compared to a set of reference surfaces (conventional SMA 0/16). Amazingly, after one year of operation this noise reduction is unchanged. Most interesting is that the noise reduction difference between the single-layer and double-layer PAC is approx. 5 dB(A). Since the single-layer PAC is identical to the 30 mm thick top layer in the DPAC (although 5-8 mm thicker), it follows that 2/3 of the noise reduction is due to the bottom layer of the DPAC; i.e. what lies approx. 35-40 mm below the top surface. The paper will discuss the effect of the bottom layer on the overall acoustical efficiency of the DPAC.

Design and evaluation of gap-graded asphalt rubber mixtures

This paper describes the evaluation of the design and performance of gap-graded asphalt rubber mixtures (GGAR) under laboratory conditions with one type of asphalt binder, three crumb rubbers, and four gap-graded gradations of one aggregate type. The resulting mixture samples were tested and evaluated for their high-temperature performance and fatigue resistance and their performance was compared with that of conventional Stone Matrix Asphalt mixtures (SMA). For mixture design, GGAR can have mineral filler content less than that of SMA and have the volume of air voids larger than typical values for an SMA. As a result, the optimum asphalt content is also larger than that of SMA. The laboratory testing results indicate that GGAR performs as well as SMA with respect to high-temperature and has better fatigue resistance than a conventional SMA. More field tests should be carried out on GGAR in various environmental conditions to determine its optimum manufacture and long term performance.

A Broadband Complex Permittivity Probe Using Stepped Coaxial Line

This paper proposes the stepped coaxial line sensor using the reflection coefficient in microwave range for complex permittivity measuring. The proposed probe is adapted from the conventional SMA connector which is cheap and easy to fabricate. The analysis model of the probe has been done by using FDTD method with the reference material such as the distilled water. The stepped SMA probe presents the accurate result compared with the convention one. The permittivity values of the concentrated alcohols of 10%, 15% and 20% as DUTs at 24oC in a frequency range of 0.1 GHz to 6 GHz have been measured using the proposed probe. Also, the measurement of salted butter permittivity has been performed. The measured results are more accurate compared with the commercial probe.

Cyclic degradation of antagonistic shape memory actuated structures

Antagonistic shape memory actuated structures exploit opposing pairs of one-wayshape memory alloy (SMA) linear actuators to create devices capable of a fullyreversible response. Unlike many conventional reversible SMA devices they do notrequire bias force components (springs) to return them to their pre-actuatedconfiguration. However, the repeated use of SMA antagonistic devices results in theaccumulation of plastic strain in the actuators which can diminish their actuationstroke. We have investigated this phenomenon and the effect of shape memoryalloy pre-strain upon it for near equi-atomic NiTi actuators. We find that thedegradation eventually stabilizes during cycling. A thermomechanical treatment hasbeen found to significantly reduce degradation in cyclic response of the actuators.

Mesomorphic behaviour in bent‐shaped molecules with side wings at different positions of a central naphthalene core

Six bent‐shaped molecules were prepared with central bent cores based on 2,7‐, 1,7‐, 1,6‐, 1,3‐, 1,2‐ and 2,3‐dihydroxynaphthalene groups with side wings containing a Schiff's base moiety and dodecyloxy tail, N(2,7), N(1,7), N(1,6), N(1,3), N(1,2) and N(2,3). All of the compounds form fluid smectic mesophases and their mesomorphic behaviour and properties are discussed in terms of their molecular structure. The compounds are categorized into two groups; in one of them, N(2,7), N(1,6) and N(1,3), the bent cores have a bent angle of 120° between the side wings, whereas in the other, N(1,7), N(1,2) and N(2,3), the bent angle is 60°. The typical banana molecule, N(2,7), in the first group, forms a chiral blue phase that shows two distinguishable domains with opposite optical rotations and circular dichroism. Under an electric field, the chiral blue phase is transformed to strongly birefringent B2 phase which possesses a basically homochiral SmCAPA structure. N(1,3) also forms a chiral blue phase, but, in contrast, N(1,6), where the side wings are asymmetrically substituted, forms a typical antiferroelectric B2 phase with the racemic SmCSPA structure. N(1,2) and N(2,3) of the other group assume a U‐like shape to form a conventional SmA phase. Of interest is the fact that N(1,7) forms a chiral blue phase irrespective of having a small bent angle of 60°. This indicates that the distance between side wings as well as the bent angle plays an important role for the formation of banana‐shaped smectic phases.

Development of Anti-Loosening Nuts Using Shape Memory Alloys

A new kind of self-locking nuts which can prevent the fastener from loosening is developed using shape memory alloy The transverse clamping force of SMA nuts on bolts caused by shape memory effect will always exist in the fastener, which can prevent it from vibrational loosening A simplified method is proposed to estimate the loosening moment of the SMA nuts on the bolts. Comparison experiments on the conventional steel and SMA nuts were carried out on a vibration rig. Results show that the SMA nuts have good anti-loosening capability.

A review of textures of the TGBA* phase under different anchoring geometries

Polarizing microscope textures of the twist grain boundary A* (TGBA*) phase are reviewed for two different compounds in different geometries with different surface treatments giving monostable planar and homeotropic boundary conditions. The textures are discussed in the light of the helical structure of the TGBA* phase. Depending on the compound, the underlying phase is either SmA* or SmC*, whereas the adjacent phase at higher temperature is cholesteric (N*). Sample preparations in wedge-shaped cells subjected to a slight temperature gradient exhibit TGBA* textures much more typical for the cholesteric than for the ordinary SmA* phase. For instance, Grandjean steps and fingerprint textures are observed for planar and homeotropic boundary conditions, respectively. Preparation of smectic droplets clearly reveals the helical axis of the TGBA* phase to be perpendicular to the helical axis of the helielectric SmC* phase. For thin samples, a suppression of the TGBA* helix leading to a surface-induced structure corresponding to a conventional bulk SmA* phase is observed. Under certain conditions, a cholesteric phase in the vicinity of a twist inversion point may exhibit very similar textures to the TGBA* phase near the transition to the SmA* phase. On exemplified textures similarities are discussed and differences pointed out.