Original Configuration Research Articles

A Kinematics-Based Optimization Design for the Leg Mechanism of a Novel Earth Rover

Abstract This paper proposes a general kinematic-based design method for optimizing the side-mounted leg mechanism of BJTUBOT, a novel multi-mission quadrupedal Earth rover. The focus issue lies in designing structural improvements that not only enhance its kinematic performance but also prevent singularity, all while meeting the demands for miniaturization and lightweight without deviating from the original leg design concept. To solve this issue, a novel 3-UPRU&PPRR mechanism is envisaged based on the original configuration. Around the unique structural features of this mechanism, its inverse kinematic solution and Jacobian matrix are calculated, and a coupled motion relation between a key limb and its moving platform (MP) is presented. In order to achieve singularity avoidance, some typical singularity configurations based on line geometry analysis are given. In accordance with this result, an initial configuration for multi-objective dimensional optimization is presented. To further enhance its kinematic performance, we introduce the use of the GCI (global conditional index) performance at extreme positions as one of the optimization criteria based on the NSGA-II (Non-dominated Sorting Genetic Algorithm) algorithm, and directly measuring the crowding distance using the position vector of the U (universal) joints on the moving platform. This optimized mechanism prototype is demonstrated in a single-leg Adams simulation, which exhibits good velocity mapping effects and displacement accuracy. Finally, a new BJTUBOT prototype was constructed based on the optimized leg, and its flexibility was tested with various classical forms of motions. The workflow in this paper significantly improves the leg performance under the current design needs.

Numerical investigation of the flows and heat transfer characteristics of internal cooling channels with separated ribs in gas turbine blades

Gas turbine engines play a crucial role in numerous industrial domains, including power generation, aviation, and marine propulsion. One of the major challenges in designing gas turbine engines is managing the high temperature generated by the combustion process. Internal cooling is a commonly used technique to maintain the temperature of critical components, such as turbine blades, within a safe operating range. Rib turbulators are widely used in internal cooling systems to enhance heat transfer performance by promoting turbulence in the fluid flow. Nevertheless, the existence of a continuous rib within the cooling channel can result in elevated temperatures near the rib section, potentially diminishing the overall system efficiency. In response to this challenge, a new rib turbulator design, denoted as the “separated rib,” has been introduced to mitigate the high-temperature zone. Through the utilization of the passing-gap design in the separated rib configuration, the coolant flow passes through the gap, effectively eliminating the region of extreme heat and augmenting the secondary flow. Consequently, it results in a notable enhancement of heat transfer performance within the ribbed channel. The numerical simulations are performed by solving three-dimensional (3D) Reynolds-averaged Navier–Stokes equations using the commercial software ANSYS CFX. The working fluid is steam, and the heat transfer performance is evaluated in terms of the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). The results show that the separated rib configuration has approximately 17.3% higher Nusselt number than the original ribbed configuration when the Reynolds number (Re) changes from 5000 to 60 000. The separated rib configuration consistently shows higher TPF values between about 1.6 and 1.9 than the original rib configuration, where TPF is smaller than 1.35. Furthermore, the heat transfer correlation related to the Reynolds number was developed to predict heat transfer performance. The heat transfer correlations align closely with the numerical simulation results, showing about 17.4% and 34.3% improvements in Nu and TPF, respectively, for our newly designed system compared to the old version.

Study on the lignin-derived sp2–sp3 hybrid hard carbon materials and the feasibility for industrial production

Hard carbon has been widely used in anode of lithium/sodium ion battery, electrode of supercapacitor, and carbon molecular sieve for CO2 capture and hydrogen storage. In this study the lignin derived hard carbon products are investigated, and the conclusions are abstracted as follows. (1) The lignin derived hard carbon products consist of microcrystal units of sp2 graphene fragments, jointed by sp3 carbon atoms and forming sp2–sp3 hybrid hard carbon family. (2) From the lignin precursors to the sp2–sp3 hybrid hard carbon products, most carbon atoms retain their original electron configurations (sp2 or sp3) and keep their composition in lignin. (3) The architectures of lignin-derived hard carbon materials are closely dependent on the forms of their lignin precursors, and could be preformed by different pretreatment techniques. (4) The carbonization of lignin precursors follows the mechanism “carbonization in situ and recombination nearby”. (5) Due to the high carbon ratio and abundant active functional groups in lignin, new activation techniques could be developed for control of pore size and pore volume. In general lignin is an excellent raw material for sp2–sp3 hybrid hard carbon products, a green and sustainable alternative resource for phenolic resin, and industrial production for lignin derived hard carbon products would be feasible.

A METHODOLOGICAL APPROACH FOR AN AUGMENTED HBIM EXPERIENCE THE ARCHITECTURAL THRESHOLDS OF THE MOSTRA D'OLTREMARE

Abstract. Digital survey and parametric-semantic modeling of historical or conventional building artifacts are becoming progressively more oriented toward HBIM (Heritage Building Information Modelling) to XR (Extended Reality) digital fruition projects. This encompasses a wide range of applications, from technical management to historical-scientific popularization of the architectural heritage. In this sense, the research explores the potential of BIM-to-XR virtualization systems concerning the systematization of historiographic documentation and interaction between different types of datasets for managing and disseminating the heritage. In particular, the research presents a prototypal experience conducted on Mostra d'Oltremare in Naples, Italy, a mid-20th-century exhibition center. In particular, the northwest access area had a rationalist layout, while the current configuration strongly differs from the monumental, exedra-shaped one built on a project by Arch. Stefania Filo Speziale, which was largely destroyed by World War II bombing. Thus, to document and facilitate the analysis of the original configurations, the original archival sources have been digitized and cataloged; moreover, reality-based integrated digital survey campaigns have been performed for the acquisition of metric-morphological data of the complex and the segmentation of the characteristic chromatic features of the residual decorative apparatuses. This has enabled the development of a BIM-oriented multi-scale information repository to enrich the real environment with digital content, thus creating an augmented reality experience. The latter has been introduced to create a virtual tool for querying and manipulating BIM databases, using the potential of visual programming languages and traditional scripts to create a two-way flow of data between BIM and AR.

Synthesis and characterization of capsaicin nanoparticles: An attempt to enhance its bioavailability and pharmacological actions

Abstract Herein, capsaicin nanoparticles (NPs) were prepared by two different methods, namely, evaporative precipitation of nanosuspension (EPN) and anti-solvent precipitation with a syringe pump (APSP). The nanoparticles of the necessary sizes were obtained after optimizing experimental parameters such as the solvent-to-anti-solvent ratio and stirring speed. They had spherical shapes and an average diameter of 171.29 ± 1.94 and 78.91 ± 0.54 nm when prepared using the EPN and APSP methods, respectively. Differential scanning calorimetry and an X-ray diffractometer showed that the capsaicin crystallinity decreased. FTIR results showed that the NPs were produced with their original configuration and did not result in the synthesis of any additional structures. The NP formulation had a desirable drug content. They surpassed the unprocessed drug in solubility and displayed the desired stability. Capsaicin NP cream showed many folds of enhanced analgesic, anti-inflammatory, and antimicrobial effects compared to unprocessed capsaicin.

Adaptive dynamic safety domain for different sailing conditions

The problem of navigation safety is considered, in particular, the problem of developing an algorithm for an adaptive dynamic safety domain for various navigation conditions is investigated. The risk assessment of a ship approach situation is based on the safety domain as the minimum area around the ship into which an oncoming ship should not enter. Navigation conditions are considered in accordance with the rules of COLREG‑72 for navigation of vessels with limited visibility and being in sight of each other. To solve this problem, the navigation areas are classified. For further analysis, a table for the conditions and areas of navigation to identify the shape of the domains is created. The hydro meteorological situation, which takes into account the navigation conditions, and as a consequence, the need to increase the size of the safety domain, is considered. Changes in the parameters and shape of ship safety domains for different navigation conditions have been identified. For each district and navigation conditions, an original configuration of the security domain is proposed. The dynamic changes of the domain during movement in traffic separation systems and channels are separately considered. Using an example, a situation when the bow of the domain crosses the dividing line, which can lead to the appearance of false dangerous targets, is simulated. To avoid such situations, a dynamic domain with a changing shape in the form of an ellipse for swimming in a traffic separation system and channels, taking into account sailing conditions with limited visibility and in sight of each other is proposed. For the calculation, an algorithm to determine the shape of the domain under different visibility conditions and navigation areas has been compiled. Calculations for the case when the vessel enters a turn in traffic separation systems and narrow spaces have been performed. The deformation of the domain during rotation is shown.

How Marginal Value of Time Influences Optimality when Remanufacturing to Multiple Generations

Because a product’s value decays over time, recovered items (cores) cannot regain their original value when remanufactured—even if kept in pristine condition. We consider a Remanufacturing Original Equipment Manufacturer who can remanufacture recovered cores to their original configuration or upgrade them to current technology. He sells new and remanufactured items concurrently. Each production period signifies an upgrade of the product’s features to a new technological generation. We use our novel modeling of Marginal Value of Time (MVT) to perform a rigorous structural decomposition over all potentially optimal values of costs, consumers’ valuations, core availability, and MVT to determine conditions under which cores should be restored to their original configuration and those conditions under which cores should be upgraded to current technology. We also show that for only a very small region of the parameter space (1.58% of remanufacturing instances) does concurrently offering both generations of remanufactured units provide greater profit than does remanufacturing to the optimal single generation. Furthermore, the average improvement in these instances is negligible (0.42%).

Optimizing the Retrofit Design and Operation of Multi-Energy Systems Integrated With Energy Networks

Abstract In the literature, there is a lack of tools able to optimize contextually the design and operation of a multi-energy system in its entirety, encompassing both (i) the number, type, and size of the energy conversion and storage plants supplying the end users of the system with the required energy and (ii) the geometry and capacity of the distribution networks delivering that energy to the users. Moreover, rarely the retrofit design problem is considered, where “retrofit design” refers to the addition of new capacity to components initially available in existing systems. Here, a general method is proposed to simultaneously optimize the retrofit design and operation of a multi-energy system and the associated energy networks. The goal consists of finding the additional capacity to be added to the already available components—energy conversion and storage plants, energy networks—and the new components to be installed in order to comply with given reduction targets in carbon emissions while keeping the life cycle cost of the system at a minimum. A district composed of commercial and residential buildings operating in a microgrid is considered as a case study. Heat can be provided to the end users via a district heating network, while electricity can be either generated on-site or imported from the national power grid. Results of the retrofit design problem show a contextual reduction of 35% in CO2 emission and 20% in life cycle cost with respect to the original system configuration.

Left atrial appendage inversion: First computational study to shed light on the phenomenon

Inversion of the left atrial appendage is a rare phenomenon, which may occur during the de-airing maneuvers associated to routinely performed surgery procedures, such as cardiopulmonary bypass or left ventricular assist device implantation. In this case, the body of the inverted appendage can obstruct the mitral valve leading to severe complications. The mechanisms are still poorly known, and more specific studies are needed to better understand its causes and identify mitigating strategies. The current study attempts to gain a better comprehension of the conditions and the factors favourable to left atrial appendage inversion. Four patient specific appendage morphologies, obtained from computerised tomography and representative of the main typologies commonly used for the appendage classification (chicken wing, cactus, cauliflower, and windsock), were used for the study. The numerical models were subjected to the same loading pattern, made of subsequent different pressure curves.Results show that the morphologies invert and recover their original anatomical configuration at different pressure loads, indicating that their tendency to invert is associated to their specific morphological features. Moreover, the analysis highlights that, although restoring the physiological left atrium pressure is not sufficient to induce appendage recovery, pressures well below the ventricular ones can induce the return to the natural configuration.All models recovered the anatomical configuration at pressures well below the ventricular pressure (about 100 mmHg), suggesting that basic trans-catheter maneuvers, e.g. producing temporary mitral regurgitation, could be attempted to correct the appendage configuration, prior to opt for more invasive surgical approaches.

Investigation of dislocation and twinning behavior in HMX under high-velocity impact employing molecular dynamics simulations.

Under the ReaxFF/lg force field, the multiscale shock technique (MSST) was employed to investigate the decomposition behavior of perfect, dislocated, and twinned octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) at a velocity of 11 km/s. This study aimed to analyze the changes in system temperature, bond formation and breaking, variations in the number of small molecules, and the number of clusters. The results indicated that the sensitivity of dislocated HMX was the lowest, while the sensitivity of twinned and perfect HMX was comparable. Comparing the formation and breaking of bonds in HMX during the shock process, it was found that the change in the number of bonds in dislocated HMX was similar to that in perfect HMX, whereas twinning accelerated the breaking of bonds. By analyzing the changes in small molecular fragments (CO, CO2, H, H2, H2O, N2, N2H, NH2, NO, NO2, and O) during the shock process of HMX, it was found that dislocation had a relatively minor effect on the small molecular fragments, while twinning promoted the generation of CO, H, NO, and O and accelerated the decomposition of NO. A comparison of the number, weight, and atomic ratio of clusters under perfect, dislocated, and twinned conditions revealed that under the influence of shock, the number of clusters initially increased sharply and then decreased slowly. Meanwhile, compared to the perfect and dislocated explosives, the number of clusters under the twinned structure was significantly fewer, indicating that the twinned structure could reduce cluster formation. The proportion of oxygen to carbon in the twinned HMX was lower than that in the perfect and dislocated explosives, possibly due to the higher content of small molecular fragment O in twinned HMX. Different structures of HMX crystals were constructed, including twinned defect structure (with a supercell containing 6458 atoms), dislocation defect structure (with a supercell containing 2352 atoms), and perfect structure (also with a supercell containing 2352 atoms). The modeling of defect crystal structures was carried out using the Atomsk software. For the twinned defect structure, we first constructed a mirror symmetric structure of the original configuration and then merged these two structures together. For the dislocation defect structure, we shifted a segment of the originally ordered perfect crystal structure by a certain distance using Atomsk. Before conducting the simulations, we performed geometric optimization of the models using the conjugate gradient (CG) algorithm and carried out 10 ps of NVT and NPT simulations to equilibrate the energy, temperature, and other parameters within the system. Finally, a 50-ps MSST impact simulation was performed using Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS).

Fatigue responses of metallic glass‐based stochastic network nanomaterial: Superior strain‐hardening ability

AbstractEngineering materials commonly suffer from cumulative and irreversible damage during cyclic deformation, leading to fatigue failure. Developing materials with better fatigue resistance is imperative. This work reports a metallic glass network nanomaterial that possesses superior strain‐hardening ability. After a certain number of fatigue tests, the peak stress of the nanomaterial can even be up to four times its original value. This superior strain‐hardening ability originates from the unique plastic mechanism. During cyclic deformation, localized shear transformation zones form and develop, especially in the stress concentration regions. Ligaments crosslinked to these regions cannot sustain their original configurations and contract toward these plastic hinges, resulting in the collapse and coalescence of voids. This densification enhances the engineering stress during each cycle. The fatigue features can be altered by adjusting the cyclic frequency. Stronger strain‐hardening ability can be achieved at lower cyclic frequencies.

Ecological network analysis and optimization of resilience and efficiency for electric power systems design

The simultaneous increase in natural disasters and human dependence on critical infrastructures for essential services such as water, electricity, etc., places ever-increasing demands on the reliable, safe, resilient design and operation of these infrastructures, with a trade-off between continuity of supply (safety and resilience) and quality of supply (reliability and efficiency) at limited cost. With this in mind, a new methodology for the analysis of electric power systems inspired by natural ecosystems is proposed here and applied to representative systems from literature. Information theory is used to quantify the results of the ecological network analysis (ENA) performed. The analysis shows that electric power systems are more efficient than reliable and vulnerable to disasters. A flow matrix is constructed from the available IEEE systems data, quantified and analyzed using information theory, and finally validated by contingency analysis and SCOPF analysis. The original network configurations are compared to random generated topologies. Comparisons are also made with ENA-inspired configurations. The latter show significantly fewer violations in each contingency scenario compared to the original configurations, further supporting the use of ENA to balance power system efficiency and resilience. Thus, ENA can be used to develop power systems with balanced efficiency and resilience.

Structural Assessment of a Masonry Arch Bridge before and after a traditional inner arch retrofitting technique

To assess the structural behaviour of masonry arch bridge and identify the occurrence of damage reliable numerical models to perform accurate nonlinear structural analyses are needed. The innovative strategy known as Discrete Macro-Element Model (DMEM) is here employed to simulate the performance of a masonry arch bridge before and after a traditional structural retrofitting. The adopted numerical strategy assures a geometrically consistent model characterized by a very low computational burden and reliable results. As case study, a masonry arch bridge located in Maletto (Italy), belonging to the rail network, around Etna volcano, called Ferrovia CircumEtnea (FCE). The bridge has been built in 19th century and was subjected to a structural retrofitting in 1984, because of a light settlement of the central pier due to landslide. The bridge was reinforced with the introduction of a supplemental thin inner reinforced concrete arch, at the intrados of the existing stone arches, externally confined by an external steel corrugated thick plate also used as formworks. In this paper the HiStrA bridge software, where the DMEM is implemented, is used for providing a structural assessment of the bridge in its original configuration and after the structural retrofitting. Both push-down and push-over analyses are performed clearly showing the efficacy of the adopted traditional retrofitting strategy.

On-chip light sheet illumination for nanoparticle tracking in microfluidic channels.

A simple and inexpensive method is presented to efficiently integrate light sheet illumination in a microfluidic chip for dark-field microscopic tracking and sizing of nanoparticles. The basic idea is to insert an optical fiber inside a polydimethylsiloxane (PDMS) elastomer microfluidic chip and use it as a cylindrical lens. The optical fiber is in this case no longer seen as only an optical waveguide but as a ready-made micro-optical component that is inexpensive and easy to source. Upon insertion, the optical fiber stretches the PDMS microchannel walls, which has two effects. The first effect is to tone down the intrinsic ripples in the PDMS that would otherwise create inhomogeneities in the light sheet illumination. The second effect is to remove any obliqueness of the channel wall and constrain it to be strictly perpendicular to the propagation of the illumination, avoiding the formation of a prismatic diopter. Through calculations, numerical simulations and measurements, we show that the optimal configuration consists in creating a slowly converging light sheet so that its axial thickness is almost uniform along the tracked area. The corresponding thickness was estimated at 12 μm, or 10 times the depth of field of the optical system. This leads to an at least six-fold increase in the signal-to-noise ratio compared to the case without the cylindrical lens. This original light-sheet configuration is used to track and size spherical gold nanoparticles with diameters of 80 nm and 50 nm.

Calculation and analysis of a ventilation and cooling scheme for aircraft brake assembly

The slow cooling of brake assembly of civil aircraft is one of the major constraints on the operational efficiency of the aircraft. Aiming at the engineering problem of brake carbon heatpacks in flight cooling, this article proposes a ventilation and cooling scheme for aircraft brake assembly, which is based on the original configuration of the main landing gear compartment of the aircraft. By adding the design of the intake duct and exhaust grille, external cooling airflow is introduced to cool the brake carbon heatpacks during flight. This article confirms the cooling effect through simulation calculations and experimental data. This article can provide a reference for the ventilation and cooling design of civil aircraft brake assembly.

Rand Protease: The Role of Calcium-Binding Site on Stability with Mutagenesis and The Effectiveness on Leather Dehairing

Bacillus subtilis produces a number of proteases, which are highly demanded in various industries, especially the thermostable one. Rand protease, originally isolated from B. subtilis, has thermostability and other remarkable properties such as organic solvent tolerance and pH stability. However, its vulnerability to instability-induced degradation has limited its applications. Because Rand protease contains two calcium ions for folding, activation, and, above all, stability, previous studies have shown that boosting the calcium-binding affinity enhances stability. Therefore, Rand protease’s susceptibility to degradation could be remedied by discovering the calcium-binding site having the greatest impact on stability for further calcium-binding affinity improvement. This was done with an in silico mutagenesis approach whereby one calcium-binding site was mutated to alanine and evaluated either the RMSD, the deviation of the mutated configuration from the original configuration using YASARA, or stability in terms of kcal/mol using HotSpot Wizard. The result found that calcium-binding sites Leu75 from YASARA and Tyr171 from HotSpot Wizard have higher influences on stability (our target). This result was also validated using Pymol, ExPASy ProtParam, and Molprobity. Additionally, Rand protease-chemical formulation dehairs leather best without additional metal ions at pH 7.0 and for 18 h. It also produced higher-quality leather with smaller pores and softer leather than chemical formulations. In contrast, hair breakage was observed in calcium treatment, which is compatible with the low dehairing activity achieved. In conclusion, Leu75 and Tyr171 are vital for calcium stabilisation and this enzyme has demonstrated its crucial efficacy in the leather dehairing industry.

Tri-axial shaking table testing of lighting support systems with pulley friction dampers and integrated dummy masses

Investigating pulley wireway systems equipped with friction dampers as alternatives to traditional exposed raceway light fixtures, this study adheres to the ICC-ES AC156 standard and evaluates the impact of system mass and connector types on seismic behavior using shaking table tests. The key findings indicate that an increased system mass variably affects the fundamental frequency of the system, depending on the type of connectors. In terms of earthquake performance, direct connectors outperformed pole connectors in the original system configuration, and the addition of dummy masses significantly reduced seismic energy while stabilizing acceleration responses in pole connector systems. Moreover, the study underscores the critical importance of minimizing pole length in systems using pole connectors and adopting a lower mounting height in systems with direct connectors to improve seismic performance.

Evaluation of an improved indirect solar dryer for Curcuma Amada without and with stone chips as thermal energy storage: An investigation on kinetics, energy, exergy, quality and economic aspects

The drying kinetics, energy, exergy, quality, and economic studies of a solar dryer with and without energy storage have been conducted. The original configuration of a solar air collector (SAC) has been modified by adding waste stone chips beneath the absorber plate. Data related to mass loss, solar radiation, and temperatures were gathered during the experiments in both the configurations. Curcuma Amada samples had initial moisture of 87.4 % and achieved an equilibrium moisture level of 4.4 % within 8 h in the dryer equipped with waste beverage canned absorber plate and storage (SDCWS) and for dryer without storage (SDCWOS) it took 26 h. Out of the eleven drying models tested, the Midilli and Kucuk model exhibited the most favorable fit for Curcuma Amada in both the experiments. The average efficiencies for the collector and dryer were 67.26 % and 21.88 %, respectively, in SDCWOS. In contrast, the efficiencies for the collector and dryer were 87.95 % and 29.63 %, respectively, in the SDCWS. Exergy parameters such as in, out, loss, efficiency, improvement potential, waste exergy ratio, and sustainability index were estimated for both the configurations. Quality analysis was further carried out for both SDCWOS and SDCWS in terms of total polyphenol content, total flavonoid content and color. The estimated energy payback periods were 1.7 years for SDCWOS and 0.47 year for SDCWS, considering a 20-year lifespan. In all assessed aspects, the SDCWS configuration showed more favorable outcomes. The results of this study have the potential to positively impact the sustainable advancement of agricultural drying techniques within rural areas.

Experimental study on the heat transfer characteristics of a novel self-driven cooling system

Based on the operating principles of the loop heat pipe, a heat sink, designed as a cold plate with an internal fluid channel, is installed in the extended condensation section of the loop heat pipe. Copper foams with varying porosity were employed as porous media to fill the heat sink channel, enhancing heat transfer efficiency. Experimental results demonstrate that the designed system can be initiated and operate stably, achieving a maximum heat flux of 38 W/cm2 at the heat sink. This represents a remarkable 90 % increase in heat dissipation capacity compared to the original loop heat pipe configuration. Furthermore, a detailed analysis of the parameters influencing system performance is conducted, along with an investigation into the interrelationships between different components of the system, leading to the proposal of corresponding optimization strategies.

Toward three-dimensional DNA industrial nanorobots.

Nanoscale industrial robots have potential as manufacturing platforms and are capable of automatically performing repetitive tasks to handle and produce nanomaterials with consistent precision and accuracy. We demonstrate a DNA industrial nanorobot that fabricates a three-dimensional (3D), optically active chiral structure from optically inactive parts. By making use of externally controlled temperature and ultraviolet (UV) light, our programmable robot, ~100 nanometers in size, grabs different parts, positions and aligns them so that they can be welded, releases the construct, and returns to its original configuration ready for its next operation. Our robot can also self-replicate its 3D structure and functions, surpassing single-step templating (restricted to two dimensions) by using folding to access the third dimension and more degrees of freedom. Our introduction of multiple-axis precise folding and positioning as a tool/technology for nanomanufacturing will open the door to more complex and useful nano- and microdevices.