Alternative Geometries Research Articles

Experimental investigation of an alternative battery pack thermal management system

Placing the batteries in PCM (Phase Change Material) filled containers causes a thermal imbalance in the pack because the heat can be dissipated from the sides, but it is accumulated in the center. An alternative geometry is proposed and tested to solve this problem. The thermal performance of the proposed battery pack structure employing PCM has been experimentally studied in free convection conditions. The battery pack is formed by placing 12 test batteries in the same size of 26650 LiFePO4 in custom-designed aluminum (Al 6065) chamber. The single-piece chamber consists of three subchambers connected by straight, rectangular, and parallel fins. The cells are positioned in the 4S3P arrangement. Three different PCMs with different melting temperatures are utilized, and their effect on the battery pack temperature is sought under a stagnant air environment (21 °C). The pack has been tested during discharging at 2C (1.3 W), 3C (2.75 W), and 5C (7.83 W). The heat generation values are adopted from the literature. The maximum temperature in the cells and the maximum temperature deviation between the cells are monitored while the cells are being charged or discharged for different test procedures. Instead of placing PCM and cells in a single case like in studies in the literature, a tailor-made finned geometry helped provide a more homogenous temperature in the cells thanks to the finned structure on the air side. In this way, the maximum temperature difference inside the battery pack is kept below 5 °C for all cases except the extreme case of cyclic 5C discharge/charge analysis with CrodaTherm47. The maximum temperature of the battery pack could be kept below the critical value (60 °C) only when CrodaTherm37 was employed for three consecutive cycles at a discharge rate of 5C/7.83 W as the fin temperatures could be kept at the optimum level, and the PCMs latent heat can be exploited the most.

A novel wearable biosensor for real-time alcohol detection

Alcohol misuse has become a major public health concern worldwide. The development of an accurate, non-invasive, and cost-effective method for real-time alcohol detection would have important applications for monitoring and preventing alcohol misuse. This paper proposes a novel wearable biosensor for real-time alcohol detection in sweat. The biosensor uses alcohol oxidase immobilized on a screen-printed electrode to amperometrically detect ethanol in sweat samples. An artificial sweat solution was used to optimize the sensor design and evaluate its analytical performance. The optimized biosensor demonstrated a linear response to ethanol in the concentration range of 0.1–1.0 g/dL, with a limit of detection of 0.02 g/dL. On-body trials of the wearable biosensor provided rapid measurements that strongly correlated with blood alcohol content. This approach could offer a convenient solution for continuous, non-invasive alcohol monitoring to help reduce alcohol misuse and promote healthy behaviors. Further research on long-term use, alternate electrode geometries, and fully integrated wearable designs is warranted.

Compressive molding of engineered tissues via thermoresponsive hydrogel devices.

Biofabrication of tissues requires sourcing appropriate combinations of cells, and then arranging those cells into a functionally-useful construct. Recently, organoids with diverse cell populations have shown great promise as building blocks from which to assemble more complex structures. However, organoids typically adopt spherical or uncontrolled morphologies, which intrinsically limit the tissue structures that can be produced using this bioassembly technique. Here, we develop microfabricated smart hydrogel platforms in thermoresponsive poly(N-isopropylacrylamide) to compressively mold microtissues such as spheroids or organoids into customized forms, on demand. These Compressive Hydrogel Molders (CHyMs) compact at cell culture temperatures to force loaded tissues into a new shape, and then expand to release the tissues for downstream applications. As a first demonstration, breast cancer spheroids were biaxially compacted in cylindrical cavities, and uniaxially compacted in rectangular ones. Spheroid shape changes persisted after the tissues were released from the CHyMs. We then demonstrate long-term molding of spherical brain organoids in ring-shaped CHyMs over one week. Fused bridges formed only when brain organoids were encased in Matrigel, and the resulting ring-shaped organoids expressed tissue markers that correspond with expected differentiation profiles. These results demonstrate that tissues differentiate appropriately even during long-term molding in a CHyM. This platform hence provides a new tool to shape pre-made tissues as desired, via temporary compression and release, allowing an exploration of alternative organoid geometries as building blocks for bioassembly applications.

Boiling sodium and melting salt: Evaluation and optimisation of a novel solar–thermal system concept

The phase-change phenomenon facilitates efficient heat transfer and the storage of a large amount of heat close to an upper-bound temperature limit. In this paper, a novel solar-thermal system configuration is evaluated and optimised, where liquid sodium is boiled in a receiver and energy is stored through the melting and freezing of NaCl salt. Polar and surround field configurations of a 1 MWe sodium-boiler plant were investigated where co-optimisation of solar multiple, field parameters, receiver geometry and storage parameters was performed to obtain lowest possible levelised cost of electricity (LCOE); this compared to a 100 MWe two-tank molten salt plant optimised via the same method. The LCOE values obtained for the 1 MWe sodium-boiler plant was 128.3 USD/MWh for a polar field configuration and 144.9 USD/MWh for a surround field configuration, compared to 107.1 USD/MWh for the 100 MWe two-tank molten salt system. Whilst promising for smaller-scale systems, the analysis identifies limitations and challenges associated with high operating temperatures and low receiver flux limits, which opens the possibilities for the investigation of lower-temperature phase change materials (PCMs) and alternative PCM geometries. • Phase change thermal energy storage is coupled with a boiling sodium solar receiver. • A detailed physical model is used to optimise the design for lowest energy cost. • The system achieves 128 USD/MWhe at 1 MWe scale with 14 h of storage.

Seakeeping behavior of hexagonal catamaran hull form as an alternative geometry design of flat-sided hull vessel

The Flat-sided Hull Vessel was introduced to simplify and create an efficient ship production process by eliminating the fairing work, bending, and curved panel line assembly. The built process simplification is expected that the FSHV can be produced by the traditional boat yard. However, the flat hull concept has slightly increased resistance performance. Therefore, implementing a resistance reduction device is endorsed to improve the boat's performance. The focus of the research is to identify the influence of the flat hull concept on sea keeping behavior. The hexagonal catamaran hull form was developed on the dead rise angle, angle of attack, and stern angle variation. Furthermore, the response amplitude operator and the motion spectral density of heave, roll, and pitch motion were calculated. Otherwise, the sea keeping performance of the hexagonal catamaran is compared to the original rounded catamaran. The results show that the hexagonal catamaran hulls have better sea keeping performance in the Beam Sea. However, the conventional catamaran has demonstrated superiority over the hexagonal catamaran in the Bow Quartering and Head Sea conditions.

Dissecting the active galactic nucleus in Circinus – III. VLT/FORS2 polarimetry confirms dusty cone illuminated by a tilted accretion disc

ABSTRACT We present polarimetric maps of the Circinus galaxy nucleus in the BVRI bands, obtained with VLT/FORS2. Circinus is the closest Seyfert 2 galaxy and harbours an archetypal obscured active galactic nucleus (AGN). Recent high angular resolution imaging revealed that a major fraction of its mid-infrared (MIR) emission is coming from the polar region. Previously, we demonstrated that these observations are consistent with a model of a compact dusty disc and a hyperboloid shell, resembling a hollow cone on larger scales. Here, we focus on the AGN core, up to 40 pc from the central engine, and compare the observations to the radiative transfer models. Polarization maps reveal a conical structure, coinciding with the ionization cone. The wavelength-dependence of the polarization degree indicates that scattering on dust grains is producing polarization. The observed polarization degree ($\approx 1-3{{\ \rm per\ cent}}$) is lower than predicted by the models; however, this is only a lower limit, since stellar emission dominates the total flux in the optical. The observed polarization angle (≈30°) is reproduced by the model of a dusty disc with a hollow cone that is illuminated by a tilted anisotropic central source. An accretion disc aligned with the ionization cone axis, and alternative dust geometries, such as a paraboloid shell, or a torus enveloped by ambient dust, are inconsistent with the data. We conclude that the optical polarimetric imaging supports earlier evidence for the presence of dust in the polar region, tentatively associated with dusty outflows.

Alternative Geometries for 3D Bioprinting of Calcium Phosphate Cement as Bone Substitute.

In the literature, many studies have described the 3D printing of ceramic-based scaffolds (e.g., printing with calcium phosphate cement) in the form of linear structures with layer rotations of 90°, although no right angles can be found in the human body. Therefore, this work focuses on the adaptation of biological shapes, including a layer rotation of only 1°. Sample shapes were printed with calcium phosphate cement using a 3D Bioplotter from EnvisionTec. Both straight and wavy spokes were printed in a round structure with 12 layers. Depending on the strand diameter (200 and 250 µm needle inner diameter) and strand arrangement, maximum failure loads of 444.86 ± 169.39 N for samples without subsequent setting in PBS up to 1280.88 ± 538.66 N after setting in PBS could be achieved.

Antenna-based reduced IR absorbers for high-performance microbolometers.

Absorbers for long-wavelength infrared (LWIR) are designed to have a reduced geometry fitted to a gold cross antenna and numerically studied. Compared to the square membrane geometry widely used in conventional microbolometers, the reduced geometry results in smaller thermal capacities of the vanadium dioxide (VO2) and silicon nitride (Si3N4) layers. However, near-field focusing by the cross antenna leads to a high LWIR absorption. Calculations show that the temperature change per incident energy increases with a decrease in the arm width, and the reduced absorber surpasses the square geometry for all incident angles and polarizations. The antenna-based reduced absorber studied here could serve as an alternative geometry for high-performance microbolometers.

Analysis of explosive energy distribution at Pit 7 West PT. Makmur Mandiri Utama Binungan Suaran - Berau, East Kalimantan Province

Blasting geometry and blasting material filling are closely related to the rock mass characteristics and the geological conditions to obtain ideal fragmentation. Blastability Index analysis, including Description of Rock Mass, Combined Plane Spacing, Combined Plane Orientation, Specific Gravity Influencey, and Hardness, are the alternative geometry experiment conducted to overcome the problem of rock fragmentation so that the speed of excavation equipment can increase according to the productivity of Komatsu PC2000 plan at PT. BUMA Jobsite BINSUA. Furthermore, the actual rock values obtained from blasting location and alternative geometry recommendations using R.L.Ash theory combined with Vertical Energy Distribution theory. In the C2 layer with a rock factor value of 5.95, the recommended load is 7.2 m, space is 8.3 m, and the VED explosive power is 48%. In layer D2 the rock factor value is 6.89 with a load of 7.5 m, space of 8.3 m, and 55% VED explosive charge. While in the DU layer, the rock factor value is 6.39 with a load of 7.3 m, 8.4 m space, and 51% VED filling of explosives. Prediction of blasting fragmentation analysis using Kuz-ram theory obtained fragmentation > 100 cm, namely 14.99% for the C2 layer, 14.84% for the D2 layer, and 14.82% for the DU layer.

Additive Manufacturability Analysis of Multiscale Aperiodic Structures: A Statistical Mechanics Approach

Abstract This paper introduces heuristics based upon statistical mechanics to assist in additive manufacturability analysis of multiscale aperiodic structures. The heuristics associate structural properties at a statistical level with manufacturability. They are derived from four topological properties of the complex network representations of multiscale aperiodic structures. The validity of these heuristics is assessed in two ways. First, cross-model validation compares the manufacturability determined by these heuristics when applied to computationally designed crumpled structures and a microCT scan of the same structures when additively manufactured. Second, external validity assesses the correctness of the heuristics given design parameters that increase the potential for manufacturing errors. The results show the significance of statistical mechanics in providing insight into the additive manufacturability of multiscale aperiodic structures. The paper concludes by discussing the generality of this approach for alternative geometries and provides designers with a framework for interpreting manufacturability from a statistical mechanics perspective.

Helicene Structure between DNA and Cyanuric Acid: The Role of Noncovalent Interactions.

The self-assembly between DNA and small organic molecules can expand the structural space of and introduce novel functionalities to DNA nanomaterials. In particular, it was demonstrated that poly(adenosine) DNA self-assembles with cyanuric acid (CA) to form a triplex helical structure. Previous molecular dynamics simulations showed that the DNA-CA assemblies adopt a novel noncovalent helicene structure that has a continuous helical hydrogen bond network. This article explores why the assemblies adopt the helicene geometry instead of an alternative planar hexameric rosette geometry. Analysis of the hydrogen bonding and stacking interaction energies indicates that constraining the system to the hexameric rosette geometry strains the hydrogen bonds without significantly improving the interaction energy. Molecular dynamics simulations for the assemblies between adenosine nucleosides and CA confirm that the formation of helicene structure is primarily driven by base-pair interactions and not because of the DNA backbone.

An Optimization Framework for Silicon Photonic Evanescent-Field Biosensors Using Sub-Wavelength Gratings.

Silicon photonic (SiP) evanescent-field biosensors aim to combine the information-rich readouts offered by lab-scale diagnostics, at a significantly lower cost, and with the portability and rapid time to result offered by paper-based assays. While SiP biosensors fabricated with conventional strip waveguides can offer good sensitivity for label-free detection in some applications, there is still opportunity for improvement. Efforts have been made to design higher-sensitivity SiP sensors with alternative waveguide geometries, including sub-wavelength gratings (SWGs). However, SWG-based devices are fragile and prone to damage, limiting their suitability for scalable and portable sensing. Here, we investigate SiP microring resonator sensors designed with SWG waveguides that contain a “fishbone” and highlight the improved robustness offered by this design. We present a framework for optimizing fishbone-style SWG waveguide geometries based on numerical simulations, then experimentally measure the performance of ring resonator sensors fabricated with the optimized waveguides, targeting operation in the O-band and C-band. For the O-band and C-band devices, we report bulk sensitivities up to 349 nm/RIU and 438 nm/RIU, respectively, and intrinsic limits of detection as low as 5.1 × 10−4 RIU and 7.1 × 10−4 RIU, respectively. This performance is comparable to the state of the art in SWG-based sensors, positioning fishbone SWG resonators as an attractive, more robust, alternative to conventional SWG designs.

Squeeze-out and bond strength of patterned Cu[sbnd]Sn SLID seal-frames

Control of Sn squeeze-out due to the presence of liquid phase and bond pressure is important in CuSn SLID bonding. This work studies the impacts of seal-frame design for limiting this squeeze-out. Three alternative seal-frame geometries are evaluated and compared to a traditional continuous seal-frame with respect to squeeze-out and shear strength. The alternative designs include open spaces to accommodate squeeze-out and are: 1) One mating partner with 3 × 50 μm wide rails and 25 μm gaps. 2) Previous geometry with 50 μmx200 μm square hatches added across the rails with a pitch of 75 μm. 3) One 150 μm wide mating partner leaving 25 μm of open area at either side. For all geometries, the other mating partner is a continuous 200 μm wide seal-frame. A 46 % reduction in squeeze out could be seen in the bond with asymmetric bonding partners, but no significant reduction was measured for the geometry with rails and the geometry with hatches. The hatched, railed and asymmetric seal-frames displayed shear strengths of 57 ± 13 MPa, 80 ± 18 MPa, and 48 ± 30 MPa respectively, which was significantly higher than that of the traditional continuous bonds which only measured 17 ± 7 MPa. Fracture surface analysis showed no correlation between fracture modes and differences in shear strengths.

Effect of bow hull form on the buckling strength assessment of the corner bracket connection

The aim of the paper is to study the influence on the structural strength assessment, in terms of fore end weight, in the conversion process from a conventional to an inverted bow hull of a platform supply vessel under bow flare impact loads. Linear and elastic buckling analyses of the corner bracket connection (deck beam with web frame) located in the fore body are obtained from modifications to its geometry and the inclusion of different stiffening methods. A series of numerical and experimental analyses are undertaken with the design and construction of a new auxiliary structure. The most effective combination (bracket geometry and stiffening method) is established and alternative geometries that optimize the local weight of the corner bracket are proposed by means of topology optimization, obtaining an innovative bracket geometry (omega bracket) that minimises weight while maintaining constant buckling strength. The results obtained establish useful and valuable design criteria that save material and weight to the ship's structure.

Numerical Investigation on the PM Emission Potential of Metal Sulphides Open Storage

Numerical simulations of the wind flow around isolated stockpiles of bulk material are performed to assess the emission potential (P) of particulate matter (PM) from the pile surfaces exposed to wind erosion (i.e., industrial wind erosion). The analysis is focused on two metal sulphides (lead and zinc sulphides), which are typically stored in the open yards of industrial plants that operate in the commodity sector for the production of non-ferrous metals. The EPA methodology is applied to the numerical simulated flow fields to quantify the effect of the wind stress over the erodible surfaces of the two ores. Two alternative open bay geometries and different volumes of material stocked within the enclosing walls are considered. Moreover, the protective effect of the walls is assessed by comparing the same pile configurations without walls. This is found to be highly dependent on the wind direction, as well as to the pile configuration. A methodology that can be easily customized to specific industrial sites is proposed to define the best storage configuration for PM emission prevention and control.

Vorogrid: A static‐aware variable‐density Voronoi mesh to design the tube structure tessellation of tall buildings

AbstractIn the context of tall building design, the tube concept represents one of the most performing systems. The diagrid is the widespread type of tube system and consists of a diagonal grid of beams that wraps the building, forming a diamond pattern. It performs as lateral bracing and is additionally able to sustain vertical loading through axial forces. Despite its efficiency, a growing interest is recently observed in alternative geometries to replace the diagrid pattern and improve the architectural impact conferred by the building skin aesthetics on the urban environment. The paper pursues the use of a Voronoi mesh, in which the geometry of the cells is steered to known schemes for the structural design of a cantilever tube structure. The objective is to mimic a macroscopic structural behavior through a topology and size modification of the Voronoi mesh that increases the density for creating resisting paths with higher stiffness. The paper proposes a novel method Vorogrid for designing a new class of tall buildings equipped with an organic‐looking and mechanically sound tube structure, which makes them a valuable alternative to competitors (diagrid, hexagrid, random Voronoi). Diagrids and hexagrids still remain more efficient in terms of forces and displacements but are characterized by a more usual appearance, instead Vorogrid offers more design control and better performances on average with respect to random Voronoi structures. This method is streamed into a pipeline that includes grid initialization strategies, geometric and structural optimization to mitigate the effects of the grid randomness, and structural sizing.

Utilization of coupled eigenmodes in Akiyama atomic force microscopy probes for bimodal multifrequency sensing

Akiyama atomic force microscopy probes represent a unique means of combining several of the desirable properties of tuning fork and cantilever probe designs. As a hybridized mechanical resonator, the vibrational characteristics of Akiyama probes result from a complex coupling between the intrinsic vibrational eigenmodes of its constituent tuning fork and bridging cantilever components. Through a combination of finite element analysis modeling and experimental measurements of the thermal vibrations of Akiyama probes we identify a complex series of vibrational eigenmodes and measure their frequencies, quality factors, and spring constants. We then demonstrate the viability of Akiyama probes to perform bimodal multi-frequency force sensing by performing a multimodal measurement of a surface’s nanoscale photothermal response using photo-induced force microscopy imaging techniques. Further performing a parametric search over alternative Akiyama probe geometries, we propose two modified probe designs to enhance the capability of Akiyama probes to perform sensitive bimodal multifrequency force sensing measurements.

An experimental and numerical investigation on buckling strength assessment of perforated plates under combined in-plane loads

Openings and cut-outs are widely used in ship structures for inspection, maintenance, service purposes, and lightning of the structure, reducing the buckling strength of the plates. This paper presents linear and elastic buckling analyses of the perforated plates, located in the double bottom floor of a container ship, under mutual interaction of both geometric discontinuities (opening and cut-outs) and subjected to combined in-plane loads (longitudinal compression, transverse compression, biaxial compression, and in-plane edge shear loading). A series of experimental and numerical analyses are undertaken on perforated plates under the determination of the influence of different stiffening methods, their relation to the load condition and different values of the plate slenderness ratio. The most effective stiffening method is obtained and alternative geometries that optimize the weight of the structure are proposed by means of topology optimization. The results shown are useful for understanding this structural failure and provide design and recommendation guidelines, improving the quality of the hull inspections and the ability to evaluate the structural defects.

The Effect of Flow Channel Geometry on Thermomechanical Performance of Printed Circuit Heat Exchanger (PCHE)

Abstract The carbon-free energy systems such as nuclear can benefit from compact and highly efficient heat exchanger technologies. The plate-type compact heat exchangers such as the printed circuit heat exchanger (PCHE) holds promise to fulfill these requirements. This work presents the thermal-hydraulic and structural analysis of PCHE for molten salt applications with thermal energy storage. In this study, three distinct types of geometry are chosen for the analysis, i.e., the zigzag channel type, the airfoil fin type, and the slotted fin type. For the working fluid, FLiBe (Li2BeF4) and solar salt (60% NaNO3 and 40% KNO3) are chosen for hot side and cold side, respectively. Titanium grade 5 is chosen as the structural material. The study is conducted by computational fluid dynamics (CFD) and finite element method (FEM) analysis. The thermomechanical behavior including pressure drop, fluid temperature, velocity profile, stress, and deformation of the flow channel were considered in this work. From the results, the zigzag channel geometry gives the best thermal hydraulic performance in terms of heat transfer and pressure drop. The structural analysis shows that the stress intensity has an exponential growth with power generation level with zigzag channel geometry being the highest out of three geometries. Overall, the zigzag channel PCHE is still the most suitable geometry for this application. Zigzag channel geometry should be substituted with an alternative geometry at a high-power application having both airfoil-fin and slotted-fin geometry at relatively identical stress intensity.

EM-driven size reduction and multi-criterial optimization of broadband circularly-polarized antennas using pareto front traversing and design extrapolation

Maintaining small size has become an important consideration in the design of contemporary antenna structures. In the case of broadband circularly polarized (CP) antennas, miniaturization is a challenging process due to the necessity of simultaneous handling of electrical and field properties (reflection, axial ratio, gain), as well as ensuring sufficient frequency range of operation, especially at the lower edge of the antenna bandwidth. An additional difficulty is that—for the sake of reliability—the design process has to be based on full-wave electromagnetic simulation tools. This is a computationally expensive endeavor because rendering the minimum-size design under the assumed constraints concerning the operating frequencies requires rigorous numerical optimization, which entails massive evaluations of the structure at hand. This paper describes an algorithmic framework for efficient identification of broadband CP antenna designs that realize the best possible trade-offs (Pareto set) between the antenna size and its operating bandwidth. The designs are generated sequentially by solving local optimization tasks targeting explicit reduction of the antenna footprint with implicit constraints imposed on the reflection and axial ratio characteristics. The data accumulated during the previous iterations is employed to yield good initial points for further stages by means of inverse surrogates and extrapolation. Low cost of the process is ensured by sparse sensitivity updates within the trust-region gradient-based algorithm being the main optimization engine. The proposed methodology is demonstrated using three examples of wide-slot CP structures with the trade-off designs representing broad ranges of achievable antenna sizes and operating bandwidth. The framework can be used to assess the antenna suitability for particular application areas as well to conclusively compare alternative CP geometries from the point of view of achievable miniaturization rate and capability of fulfilling given performance requirements.