Conventional Configuration Research Articles

Novel spacer geometries for membrane distillation mixing enhancement

Membrane distillation is an emerging promising desalination method that requires further improvement in order to become industrially viable. Due to the fact that evaporation is the primary process in membrane distillation, one strategy to boost membrane permeate flux is to optimize the energy supply to the water interface by increasing mixing in the hot channel via the use of optimized spacers. Contemporary spacer designs predominantly induce turbulence, resulting in elevated pumping energy requirements. This study introduces novel spacer geometries, inspired by industrial mixer designs, to surmount the limitations of conventional spacer configurations. The mixing efficiency, thermal performance, and pressure drop induced by the two novel geometries are studied and compared to those of commonly utilized spacer designs. It is confirmed, that the first of these novel geometries significantly enhances mixing, whereas the other causes a lower pressure drop and appears to be a viable solution when a spacer is a necessary structural component. In the course of the analysis, it is also shown that the coefficient of variation coupled with the Nusselt number at the membrane can be used to assess spacers' performance.

Optical design of reflective Bragg mirrors for EUV photolithography

In this article. we investigate the optical characteristics of reflective extreme-ultraviolet (EUV) mirrors for the application of lithography for 7 nm node and below. By using the conventional quarter-wavelength stacked Bragg reflective configuration of Si-based metal multilayers centered at soft x-ray 13.5 nm, the maximum reflection is numerically computed to be approximately 0.7 at nearly normal incidence, which is consistent to the typical values reported by Advanced Semiconductor Materials Lithography (ASML) for Mo/Si stacked multilayers. The full width half maximum (FWHM) bandwidth is 0.65∼0.78 nm. In our numerical simulation, moreover, we find Nb/Si reflective mirrors can be potentially utilized to replace Mo/Si stacked multilayers in order to harvest more EUV light inside the scanners.

Design and Evaluation of Aerospike Nozzles for an Upper-Stage Application

Aerospike nozzles are often studied because of their intrinsic self-adaptation behavior to the atmospheric pressure. Another unique feature of aerospike nozzles is their mass- and volume-efficient integration with the underlying vehicle. This latter aspect, if fully exploited, could be of interest for both lower stages operating in the atmosphere and for upper stages operating in vacuum. In this paper, a numerical analysis is carried out of the possible advantages of using an aerospike engine under specific volume constraints of a reference upper-stage configuration, discussing basic aspects of aerospike and internal expansion design, clustering, and plug truncation length. The results of the present preliminary analysis show the extent of possible performance advantages of aerospikes in terms of the specific impulse delivered for a given available volume for the nozzle with respect to a conventional bell configuration.

Interface engineering and defect passivation for enhanced hole extraction, ion migration, and optimal charge dynamics in both lead-based and lead-free perovskite solar cells

The study elucidates the potential benefits of incorporating a BiI3 interfacial layer into perovskite solar cells (PSCs). Using MAPbI3 and MAGeI3 as active layers, complemented by the robust TiO2 and Spiro-OMeTAD as the charge-transport-layers, we employed the SCAPS-1D simulation tool for our investigations. Remarkably, the introduction of the BiI3 layer at the perovskite-HTL interface significantly enhanced hole extraction and effectively passivated defects. This approach minimized charge recombination and ion migration towards opposite electrodes, thus elevating device performance relative to conventional configurations. The efficiency witnessed a rise from 19.28 to 20.30% for MAPbI3 and from 11.90 to 15.57% for MAGeI3. Additionally, MAGeI3 based PSCs saw an improved fill-factor from 50.36 to 62.85%, and a better Jsc from 13.22 to 14.2 mA/cm2, signifying reduced recombination and improved charge extraction. The FF for MAPbI3 based PSCs saw a minor decline, while the Voc slightly ascended from 1.24 to 1.25 V and Jsc from 20.01 to 21.6 mA/cm2. A thorough evaluation of layer thickness, doping, and temperature further highlighted the critical role of the BiI3 layer for both perovskite variants. Our examination of bandgap alignments in devices with the BiI3 interfacial layer also offers valuable understanding into the mechanisms fueling the observed improvements.

Internet of medical things and blockchain-enabled patient-centric agent through SDN for remote patient monitoring in 5G network

During the COVID-19 pandemic, there has been a significant increase in the use of internet resources for accessing medical care, resulting in the development and advancement of the Internet of Medical Things (IoMT). This technology utilizes a range of medical equipment and testing software to broadcast patient results over the internet, hence enabling the provision of remote healthcare services. Nevertheless, the preservation of privacy and security in the realm of online communication continues to provide a significant and pressing obstacle. Blockchain technology has shown the potential to mitigate security apprehensions across several sectors, such as the healthcare industry. Recent advancements in research have included intelligent agents in patient monitoring systems by integrating blockchain technology. However, the conventional network configuration of the agent and blockchain introduces a level of complexity. In order to address this disparity, we present a proposed architectural framework that combines software defined networking (SDN) with Blockchain technology. This framework is specially tailored for the purpose of facilitating remote patient monitoring systems within the context of a 5G environment. The architectural design contains a patient-centric agent (PCA) inside the SDN control plane for the purpose of managing user data on behalf of the patients. The appropriate handling of patient data is ensured by the PCA via the provision of essential instructions to the forwarding devices. The suggested model is assessed using hyperledger fabric on docker-engine, and its performance is compared to that of current models in fifth generation (5G) networks. The performance of our suggested model surpasses current methodologies, as shown by our extensive study including factors such as throughput, dependability, communication overhead, and packet error rate.

The optimization method based on the coupling of genetic algorithm and ant colony algorithm for the exhaust outlet space arrangement

The exhaust outlet space arrangement is a crucial part to avoid casualties and economic losses in the event of contaminant gas leakage. To handle this problem, this work proposed a novel optimization method based on the coupling of the genetic algorithm (GA) and ant colony algorithm optimization (ACO), and the fitness function used in the optimization method is constructed as an implicit form. In this proposed optimization method, the ACO is used to obtain the implicit fitness function value, while the GA is selected to conduct the space arrangement optimization based on the iteration results transferred from ACO. With the help of this novel methodology, the influence of obstacles in space could be well considered into the space arrangement optimization, which leads to a reliable optimization result of the exhaust outlet configuration. Moreover, to validate the accuracy and efficiency of this coupling method, the optimization results are taken into the computational fluid dynamics numerical model to give a comparison with the conventional configuration. The comparison results indicate that the exhaust outlet arrangement following the optimization results shows a lower gas concentration value during the diffusion process. In addition, based on this optimal exhaust outlet space arrangement, the models with various leakage rates are also investigated and discussed in the numerical work. It is believed that the proposed method could provide an effective measure for the space arrangement optimization and the design of gas leakage protection.

Numerical investigation of the aerodynamic performance and loss mechanism in a low bypass ratio variable cycle engine fan

The aerodynamic performance of the variable cycle engine fan changes sharply during mode transition. Investigating the variations of flow structure and understanding the loss mechanism are helpful in providing guidance for the fan design. Three-dimensional models of single bypass and double bypass compression systems are established, and static pressure is applied at the bypass stream outlet to simulate the opening of the mode selection valve. The characteristic band of variable cycle engine fan is obtained by gradually increasing the bypass stream pressure while maintaining specific values for the core stream pressure. Results show that the overall performance of the double bypass configuration, without bypass recirculation, is almost identical to that of the conventional single bypass configuration during the throttling process. With the increase in bypass pressure, the shock wave and the trajectory of tip leakage vortex gradually move forward, thereby increasing the blockage region induced by the interaction between the shock and tip leakage vortex. In addition, the performance of fan with reverse flow is also calculated. The recirculation causes the operating point to move closer to the stability limit, reducing the isentropic efficiency. Additionally, the recirculation changes the radial distribution of axial velocity and total pressure, leading to inlet distortion in the core driven fan stage. Furthermore, the loss mechanism is clarified by modeling the splitter and conducting entropy generation analysis. The sharp expansion of bypass stream could cause severe flow separation, and reducing the curvature of casing can effectively suppress the viscous shear loss.

Preliminary design of a retrofitted ultralight aircraft with a hybrid electric fuel cell power system

Emission-free aerial propulsion can be achieved with a proton-exchange membrane fuel cell (PEM-FC). In the present investigation, this potential is addressed by designing a hybrid electric power system with fuel cells for an ultralight aerial vehicle to be retrofitted from a conventional fossil-fuelled piston engine configuration. The proposed power system includes a fuel cell, a lithium battery, and a compressed hydrogen vessel. A procedure is proposed to find the size of these components that minimizes the total mass and satisfies the target of a size below 200L and uses performance data of commercially available components. A comparison of different energy management approaches, with and without on-board charge of the battery, is performed. The results underline that the optimal solution is to select the size of the fuel cell to meet the cruise electric request and point out that the maximum discharge current of the battery must be regarded as a key issue in sizing this component, because of the very high take-off power.

Experimental Propeller Performance Analysis of Distributed, Single and Isolated configurations

Distributed propulsion (DP) configurations are a promising concept for future aircraft systems. The main objective of the presented experiment is to investigate aerodynamic interactions of such configurations in detail and compare DP results to a single propeller configuration. The experimental setup at the Propulsion Test Facility, TU Braunschweig, features three co-rotating propellers. These are not attached directly to the wing, but are mounted on a separate carrier. This decoupling allows the forces and moments acting on wing and propeller to be considered separately. Additionally, different relative propeller positions are set up easily. In order to eliminate side wall effects, only the centre propeller and the centre wing element are subject of investigation for the distributed configuration. The periodically repeating outboard propellers reduce the wind tunnel interference while providing a true DP setup for the instrumented centre. Additionally to the DP setup, tests for conventional propeller wing configurations (only centre propeller installed) as well as isolated propeller and clean wing tests were performed. Thus, the DP effects on wing and propeller and the effect of the downstream wing on the propeller are clearly identified. The comparison between single propeller and distributed propulsion configurations shows that with distributed propulsion the drag increase is reduced from 326% to 216% compared to a clean wing. This effect is intensified by a greater thrust level and higher angles of attack. In order to identify the distributed propulsion effects, the forces acting on the propeller as well as the resulting efficiency of the propeller are compared between the distributed and single propeller configuration for two different relative propeller positions. The efficiency of the centre propeller is increased due to the outer propellers by approx. 2% to 3%.

Electronic Skin Based on Polydopamine-Modified Superelastic Fibers with Superior Conductivity and Durability.

Owing to their excellent elasticities and adaptability as sensing materials, ionic hydrogels exhibit significant promise in the field of intelligent wearable devices. Nonetheless, molecular chains within the polymer network of hydrogels are susceptible to damage, leading to crack extension. Hence, we drew inspiration from the composite structure of the human dermis to engineer a composite hydrogel, incorporating dopamine-modified elastic fibers as a reinforcement. This approach mitigates crack expansion and augments sensor sensitivity by fostering intermolecular forces between the dopamine on the fibers, the hydrogel backbone, and water molecules. The design of this composite hydrogel elevates its breaking tensile capacity from 35 KJ to 203 KJ, significantly enhancing the fatigue resistance of the hydrogel. Remarkably, its electrical properties endure stability even after 2000 cycles of testing, and it manifests heightened sensitivity compared to conventional hydrogel configurations. This investigation unveils a novel method for crafting composite-structured hydrogels.

Fast and robust multilevel optoelectronic memory based on van der Waals heterostructure

Optoelectronic memory (OEM) has attracted tremendous attention for its great potential to boost the storage capacity of memory chips and break through the von Neumann bottleneck in the post-Moore era. Two-dimensional (2D) van der Waals (vdW) heterostructures, formed by artificially stacking different 2D layered materials, offer tremendous possibilities in OEMs due to their extraordinary capability to integrate and process optical/electrical signals. However, the realization of 2D vdW OEMs with high writing speed and robust memory performance has long been challenging. Here, we report a 2D vdW OEM consisting of tungsten diselenide (WSe2) and hexagonal boron nitride, which functions based on the fast charge transfer dynamics at a 2D interface. The OEM demonstrates high writing speed reaching up to 50 μs, approximately one order of magnitude faster than those of other 2D OEMs. Moreover, the outstanding robustness of such OEM is demonstrated by long retention time exceeding 14 days, together with a broad temperature endurance window from 100 to 420 K. Additionally, through continuously switching laser pulse on the OEM, we achieve 17 distinct current levels (over 4-bit storage) with random access. Our findings envision 2D vdW heterostructure-based OEM as a potential platform to overcome the “memory wall” in the conventional von Neumann configuration and to promote a promising paradigm for big data storage.

Compositional Optimization of Sputtered WO3/MoO3 Films for High Coloration Efficiency.

Thin films of mixed MoO3 and WO3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO3/WO3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO3. Our combinatorial approach allows the localization of the maximum at 5% accuracy.

Comparative study on energy-saving performance of single- and two-stage evaporative-cooling condenser systems

The mechanical vapor compression system (MVC) coupled with the evaporative-cooling condenser is an effective method to improve its high temperature adaptability. However, this hybrid systems typically use an evaporative cooler as a single-stage pre-cooling unit of condenser and is mainly designed for hot–dry climates. In this paper, based on conventional evaporative-cooling condenser configuration, three two-stage evaporative-cooling condenser systems (MVC-TSEC(A), MVC-TSEC(B) and MVC-TSEC(C)) were proposed. The MVC-TSEC(A) consists of one condenser and an indirect/direct evaporative-cooler. The MVC-TSEC(B) and MVC-TSEC(C) have two condensers (in series), which are coupled with a two-stage evaporative cooling system. The refrigerant in the MVC-TSEC(C) forms a counter-flow configuration with the outdoor air, while it is concurrent flow in MVC-TSEC(B). Subsequently, the effects of the ambient parameters and outdoor air flowrate on the three two-stage hybrid systems were analyzed comparatively based on detailed numerical models. Finally, the application potential of these hybrid systems was evaluated comprehensively in hot–humid climates. The results showed that the seasonal COP and energy-saving rate for the MVC-TSEC(C) are reached by 4.2–4.7 and 12.7–21.1 %, respectively. Moreover, the static equipment payback period of the three two-stage hybrid systems are 3.8, 3.3 and 3.0 years, respectively.

Improving the kinematic accuracy of a collaborative continuum robot by using flexure-hinges

Within various unstructured industrial environments, there is often the requirement to conduct remote engineering tasks, such as sampling the structure for analysis prior to decommissioning. Most existing tools are simply not dexterous enough to fulfil this task, and thus new technology is required. We describe here a simple, lightweight, and water-resistant collaborative dual-arm continuum robot system which can aid in this task. To improve the kinematic accuracy of the system, a class of flexible hinges have been combined with a conventional continuum robot configuration. The thickness and width of said flexible hinges can be adjusted to adapt to various tasks. Kinematic and stiffness models have further been developed, incorporating the influence of these flexible hinges. A set of experiments have been conducted to validate the proposed model and demonstrate the advantages of the platform. It was found that the kinematic accuracy of the continuum robot can be improved by a factor of around 10 with the aid of said hinges.

Biomechanical analysis and comparison between ‘Zeta’ miniplate design and conventional miniplate system for fixation of fracture segments in transition zone of parasymphysis body region of mandible – an in vitro study

The parasymphysis area of the mandible is highly dynamic because it is subjected to both occlusal and muscular forces. As a result, the fractures in this transition zone have a special pattern, posing a challenge for surgeons whether to use one miniplate versus two miniplates, as per Champy's recommendations. The commonest complication resulting to treat this area is mental nerve paraesthesia due to the dissection and stretching of the nerve. Hence, an in vitro research study of a newly designed ‘Zeta’ miniplate is performed, to evaluate the biomechanical behaviour using finite element (FE) analysis and biomechanical analysis along with a comparison study with the conventional miniplate configurations. The results showed that the Zeta miniplate produces the lowest stresses 17.511 MPa and the least total structural deformation of 0.0011 mm after applying the maximum occlusal bite force. On application of torsional load, total structural deformation was 0.0004 mm and von Mises (VM) stress value was 0.24 MPa which was lowest when compared with the two miniplate system. Hence, the newly developed Zeta miniplate is superior in terms of stability. Another benefit of its design is that it helps in preventing mental nerve paraesthesia and tooth root damage while fixing and stabilising the fractured bony segments.

Adhesive bonding of glass-fibre thermoplastic composite: process optimisation and sustainability analysis using LCA methodology

In recent years, great attention has been paid to the challenge of integrating more sustainable circular approaches to manufacturing, which involve optimising the entire product cycle, from design to fabrication, assembly and eventual reuse/recycling. In this context, the use of thermoplastic composite materials in combination with adhesive bonding is attracting increasing attention to achieve this dual objective. Therefore, the proposed research focuses on the experimental and statistical optimisation of an adhesive bonding process for glass-fibre–reinforced composite substrates with polypropylene matrix, with the aim of comparing its performance with that of joints made using more conventional configurations, i.e. utilising thermosetting substrates. A low-pressure plasma pre-bonding surface treatment is adopted, and its effectiveness in enhancing joint performance compared to more conventional preparations for plastics is discussed. By varying plasma parameters according to the design of experiments statistical approach, the joint response is studied in terms of tensile shear strength and modelled in accordance with the response surface methodology to identify the optimum condition of process parameters within the established system boundaries. The study found that with optimised pre-treatment, adhesive joints of glass-fibre–reinforced composites with thermoplastic matrices (first scenario) can achieve tensile shear strength (TSS) comparable to that of thermoset composites (second scenario), making them viable options in various applications. Two alternative scenarios—namely, joints with thermoplastic composite or thermoset composite substrates—are then analysed by the life cycle assessment methodology and compared according to their relative environmental impact, demonstrating that glass-fibre thermoplastic composite joints are competitive alternatives to thermoset joints in terms of mechanical static performance achieved, but significantly preferable with regard to environmental sustainability.

Station layout optimization for underwater acoustic positioning system based on combined cone configuration

The theoretical minimum of the geometric dilution of precision (GDOP) for target positioning cannot be achieved because of the coplanar constraint for underwater station configurations, and the conventional single-cone configuration leads to an infinite GDOP. Therefore, this study extends the single-cone configuration to the combined cone configuration. The proposed configuration is theoretically proven to be superimposable, rotatable, and GDOP-rotation-invariant. A criterion based on the global GDOP for underwater targets is constructed to address the problem of a single criterion for station layout optimization. However, traditional optimization algorithms are prone to local optimality and low convergence efficiency. Therefore, an improved adaptive particle swarm optimization (APSO) algorithm is proposed to optimize the configuration of the underwater acoustic positioning systems. Finally, it is verified that the proposed APSO can enhance the global optimality and improve the convergence efficiency of the algorithm. Combined with the measured data of the long baseline system, it is shown that the optimal combined cone configuration significantly reduces the global GDOP and improves the positioning accuracy compared with traditional configurations.

Towards sustainable regional aviation: Environmental potential of hybrid-electric aircraft and alternative fuels

The aviation sector needs to reduce its environmental impacts, like climate change and air pollution. New hybrid-electric aircraft concepts may contribute to abating part of these impacts. But to what extent and under which conditions? This study addresses these questions in the context of regional aviation and identifies technologies and concrete actions required for more environmentally sustainable aviation. The environmental impacts of emerging hybrid-electric aircraft configurations deployed in 2030, 2040, and 2050 have been comprehensively quantified using prospective life cycle assessment. The entire life cycle of the conventional and hybrid-electric aircraft configurations was encompassed, covering various technologies and systems like batteries, fuel cells, hydrogen, and selected alternative aviation fuel (AAF) systems. For these elements, detailed life cycle inventories stemming from primary data, literature, and prospective environmental databases were used, and uncertainty was evaluated. Results showed that hybrid-electric aircraft with Li-ion batteries appear as a promising transition technology in the short-term while aircraft propelled by fuel cells using hydrogen from electrolysis yield important environmental benefits relative to conventional aircraft in longer time horizons. In contrast, the studied AAFs present little or no environmental benefits when considering environmental impacts holistically, demonstrating the need to revise existing AAF frameworks and incentives globally. Environmental burden-shifting from flight emissions in conventional aircraft systems to airport operations and aircraft manufacturing in hybrid-electric aircraft is also observed in the results, thus calling for strengthened support to airports in their sustainability management and increased integration of ecodesign practices in future aircraft design and development.

Enhancing vibration control in stay cables: a modified damping formulation with NS-HDR damper

Cables in cable-stayed bridges have low intrinsic damping, and dampers are often used as a countermeasure for cable vibration control. This paper presents an innovative asymptotic formula for calculating the additional damping in stay cables equipped with Negative Stiffness High Damping Rubber dampers (NS-HDR). The NS-HDR damper incorporates negative stiffness through a pre-compressed spring. The analysis employs models of flexural cables with fixed-fixed or hinged-hinged ends to derive the formulation of attainable damping ratio. The results of the study reveal that the NS-HDR damper, with its negative stiffness feature, exhibits a significantly higher added damping ratio in comparison to the conventional HDR damper configuration. To quantify this increased added damping resulting from negative stiffness, a modification factor is proposed. The accuracy and effectiveness of the proposed damping formula are successfully validated using the Finite Difference Method (FDM). Subsequently, the methodology is applied to design the damping of two existing stay cables (137.82m and 167.18m in length). Field measurements reveal that the damping in these cables falls below the required threshold of 0.5%. The proposed NS-HDR damper offers a viable solution to achieve the required damping ratio. These findings contribute significantly to the understanding and optimization of damping in stay cables employing HDR dampers, presenting potential applications in the field of bridge engineering. The research opens up new possibilities for enhancing vibration control and safety in cable-stayed bridges.

Fiber-cavity ring-down temperature sensor using a transmissive configuration combined with the heterodyne detection technique.

A fiber Bragg grating temperature sensor based on the cavity ring-down technique is reported. A quasi-linear fiber cavity is proposed to reduce optical loss in the cavity instead of a conventional fiber-loop configuration. The heterodyne detection technique is applied to sensitively detect weak pulses from the cavity. A combination of the quasi-linear fiber cavity and heterodyne detection allows the sensitive detection of the decaying pulse trains and high-resolution measurement of the wavelength shift of the Bragg grating induced by the temperature change. A temperature resolution of about 0.01°C is achieved.