Geometrical Arrangement Research Articles

Optimization design of mode-selective ring core photonic lantern based on coupled local mode theory

In this paper, optical field transmission characteristics of a mode-selective ring core photonic lantern (MSRCPL) are theoretically analyzed and its optimization design is also investigated. This MSRCPL is based on a tapered fiber bundle of coreless fiber and glass capillary with low refractive index. Mode evolution characteristics in the taper region and mode coupling characteristics at the splicing point are analyzed. The coupled local mode theory (CLMT) is used to optimize the structure of a 3-port MSRCPL and a 5-port MSRCPL. The impact of taper length, taper shape, taper waist, and geometric arrangement on mode selectivity are calculated. Calculation results indicate that the mode selectivities of the optimized 3-port and 5-port MSRCPL are higher than 23 dB and 18 dB, respectively.

On the magnetic bistability of small iron clusters used in scanning tunneling microscopy tip preparation

The combination of electron spin resonance with scanning tunneling microscopy has resulted in a unique surface probe with sub-nm spatial and neV energy resolution. The preparation of a stable magnetic microtip is of central importance, yet, at the same time remains one of the hardest tasks. In this work, we rationalize why creating such microtips by picking up a few iron atoms often results in magnetically stable probes with two distinct magnetic states. By using density functional theory, we show that randomly formed clusters of five iron atoms can exhibit this behavior with magnetic anisotropy barriers of up to 73 meV. We explore the dependence of the magnetic behavior of such clusters on the geometrical arrangement and find a strong correlation between magnetic and geometric anisotropy—the less regular the cluster the higher its magnetic anisotropy barrier. Finally, our work rationalizes the experimental strategy of obtaining stable magnetic microtips.

The Deflection Limit of Slab-Like Topologically Interlocked Structures

Abstract Topologically interlocked structures (TIS) are structural assemblies that achieve stability and carrying capacity through the geometric arrangement of interlocking blocks, relying solely on contact and friction forces for load transfer. Unlike beam-like TIS, whose deflection never exceeds the height of the blocks, the deflection of slab-like TIS often does. Yet, the upper limit of deflection of slab-like TIS, a key parameter defining their loading energy capacity, remains unexplored. Here, we establish a theoretical upper bound for the deflection capacity of slab-like TIS and outline a systematic design strategy to approach this upper bound. This strategy is based on engineering the contact interfaces such that the non-central blocks are more engaged in the structural response, leading to a more global and holistic deformation mode with higher deflections. We demonstrate the application of this strategy in a numerical case study on a typical slab-like TIS and show that it leads to an increase in deflection by a factor of 3.5, yielding a value closer to the upper bound than previously reported in the literature. We find that the resulting deflection mode engages all the blocks equally, avoids localized sliding modes, and resembles that of monolithic equivalents. Lastly, we show that the strategy not only maximizes TIS’ deflection capacity but also their loading energy capacity.

Heat transfer enhancement using combined microchannel with vertical rectangular micro fins

This paper focuses on the numerical optimisation of a combined hybrid microchannel heat sink with rectangular solid fins. The axial length and volume are fixed, and external structure is allowed to vary. The simulation was performed on an elemental unit cell of the microchannel heat sink . The purpose of the optimisation is to discover an optimal geometric arrangement in internal and external configurations that minimises peak temperature in the microchannel heat sink. A high-density uniform heat flux of 250 W/cm2 is assumed to be dissipated on the bottom wall of the unit cell by microelectronics circuit boards devices. Computational fluid dynamic code was used to discretized the fluid domain and solve a set of governing equations. The influence of hydraulic diameter, external structural shape and fluid velocity on peak temperature and global thermal resistance, is discussed. Coolant or water of Reynolds number range 400 to 500 in a forced convection laminar flow is introduced through the inlet of the computational domain to remove the heat at the bottom of the rectangular block microchannel. The results show that when the fluid velocity is increased from 9.8 to 12.3 m/s across the axial length of the micro heat sink, more heat is removed from the bottom of the combined heat sink. The results revealed that the pump power increased by 37.1% in combined microchannels with fins and from by 27.2% in finless micro heat sink. The result of the study is validated with what is documented in open literature for a traditional micro heat sink with circular flow channel and the trends agree.

Elucidation of crystal structures using Bragg's peaks and Nuclear Magnetic Resonance chemical shifts for polymorphic forms of (E)-4-Bromo-2-[(phenylimino)methyl]phenol

Polymorphic Form-I and Form-II of (E)-4-Bromo-2-[(phenylimino)methyl]phenol [4B2PMP] commonly known as N-salicylidene have been identified. Form-I and Form-II are synthesized in the temperature at 283 K and 333 K respectively. In both forms, the molecule shows some resembling structures in the geometrical arrangements but differing in properties. Structural affirmation accomplished by well-defined strong Bragg's diffraction pattern through powder X-Ray diffraction patterns with assigning Nuclear magnetic resonance chemical shifts and its data analysis. Intramolecular OH⋯N weak hydrogen bond between the -OH phenol group and the imine =N- group found in both forms but differing in torsion angles. Optical behavior studied through Diffuse-Reflectance UV–VIS spectroscopy. The Molecular docking approach exhibits ligand (4B2PMP) – protein (DNA Gyrase B) interaction against Escherichia coli shows variations between the two forms which is due to the unique property of crystal polymorphism. Polymorphism makes 4B2PMP-Form II crystal have the highest binding affinity than Form I crystal.

The KM3NeT infrastructure: Status and first results

KM3NeT is a research infrastructure in construction under the Mediterranean Sea. It hosts two large volume neutrino Cherenkov telescopes: ARCA at a depth of 3500 m, located offshore Sicily, and ORCA, 2500 m under the sea level, offshore the southern French coast. The two detectors share the same detection principle and technology and the same data acquisition design, the only difference being the geometrical arrangement of the optical sensors. This allows to span a wide range of neutrino energy and cover a large scientific program: The study of neutrino properties, first of all neutrino mass ordering, the identification and study of high energy neutrino astrophysical sources, indirect dark matter searches and core collapse supernovae detection.

Development of an impulsive motion generator inspired by cocking slip joint of snapping shrimp.

We propose an impulsive motion generator inspired by snapping shrimp. The proposed device mimics the geometrical arrangement of a unique claw joint calledcocking slip jointand integrates it with an artificial rack-pinion actuator mechanism rather than adopting the musculoskeletal system as it is. The design approach allows the proposed device to reproduce the impulsive slip motion through the torque reversal and unlatching mechanism of the underlying unique joint by using a single servo motor. Static and dynamic analyses revealed that the actuator force required to store and release elastic energy was remarkably small compared with the resulting acceleration force and rotation/tip speed. Through simulations and experiments, we validated the mechanical analyses and confirmed that the resulting ultrafast slip motion was comparable with the claw closure of snapping shrimp based on the cocking slip joint. Moreover, from an engineering perspective, the motion profiles are modifiable through design parameters, and the repeatability of the impulsive slip motion is satisfactory.

Cardiomyocyte orientation recovery at micrometer scale reveals long-axis fiber continuum in heartwalls.

Coordinated cardiomyocyte contraction drives the mammalian heart to beat and circulate blood. No consensus model of cardiomyocyte geometrical arrangement exists, due to the limited spatial resolution of whole heart imaging methods and the piecemeal nature of studies based on histological sections. By combining microscopy and computer vision, we produced the first-ever three-dimensional cardiomyocyte orientation reconstruction across mouse ventricular walls at the micrometer scale, representing a gain of three orders of magnitude in spatial resolution. We recovered a cardiomyocyte arrangement aligned to the long-axis direction of the outer ventricular walls. This cellular network lies in a thin shell and forms a continuum with longitudinally arranged cardiomyocytes in the inner walls, with a complex geometry at the apex. Our reconstruction methods can be applied at fine spatial scales to further understanding of heart wall electrical function and mechanics, and set the stage for the study of micron-scale fiber remodeling in heart disease.

Magnetic force-based cell manipulation for in vitro tissue engineering.

Cell manipulation techniques such as those based on three-dimensional (3D) bioprinting and microfluidic systems have recently been developed to reconstruct complex 3D tissue structures in vitro. Compared to these technologies, magnetic force-based cell manipulation is a simpler, scaffold- and label-free method that minimally affects cell viability and can rapidly manipulate cells into 3D tissue constructs. As such, there is increasing interest in leveraging this technology for cell assembly in tissue engineering. Cell manipulation using magnetic forces primarily involves two key approaches. The first method, positive magnetophoresis, uses magnetic nanoparticles (MNPs) which are either attached to the cell surface or integrated within the cell. These MNPs enable the deliberate positioning of cells into designated configurations when an external magnetic field is applied. The second method, known as negative magnetophoresis, manipulates diamagnetic entities, such as cells, in a paramagnetic environment using an external magnetic field. Unlike the first method, this technique does not require the use of MNPs for cell manipulation. Instead, it leverages the magnetic field and the motion of paramagnetic agents like paramagnetic salts (Gadobutrol, MnCl2, etc.) to propel cells toward the field minimum, resulting in the assembly of cells into the desired geometrical arrangement. In this Review, we will first describe the major approaches used to assemble cells in vitro-3D bioprinting and microfluidics-based platforms-and then discuss the use of magnetic forces for cell manipulation. Finally, we will highlight recent research in which these magnetic force-based approaches have been applied and outline challenges to mature this technology for in vitro tissue engineering.

Enhanced strength-ductility synergy of laser additive manufactured stainless steel/Ni-based superalloy dissimilar materials characterized by bionic mechanical interlocking structures

The unique mechanism of toughness enhancement found in natural materials has served as inspiration for the development of a new generation of dissimilar metal materials (DMMs). Here we present a bionic mechanical interlocking structure strategy that stainless steel 316L and Inconel 625 DMMs with an enhanced strength-conductivity trade-off processed by laser additive manufacturing (AM), possessing an ultimate tensile strength of 675.64 MPa, and a uniform elongation of 33.6%. The incompatible deformation between SS316L (plastic deformation) and IN625 (non-deformation) contributes to overcoming the strength-ductility trade-off. The integration of alternating soft and hard non-uniform structures plays a pivotal role in effectively absorbing and dissipating the energy introduced by external loads during crack propagation. This geometric arrangement and multilevel structure at the interface notably reduces the effective stress intensity factor along the crack path, leading to added resistance against loading. The multi-strengthening mechanism coupled with the heterogeneous deformability gives the material excellent strength-ductility synergy, especially the bionic mechanical interlocking structure extending the crack expansion path, which helps to avoid premature failure of weak interface layers. These findings will provide new insights into the controlled design of high-performance DMMs, which highlights the potential to inherit merits from constitutive materials for better strength-ductility combinations.

X-ray absorption spectroscopy study of the electronic and structural properties of hexavalent chromium adsorbed by volcanic ashes

X-ray absorption spectroscopy (XAS) was used to characterize the volcanic ash (VA) materials as a low-cost and natural environmental adsorbent for the sorption of Cr (VI). The batch adsorption method was employed to synthesize the sample of chromium (VI) sorbed by VA. The results showed that the Cr-VA material is in the chromium oxidation state (III) and can be described as a composition of Cr2O3 (47.9%), FeCr2O4 (45.2%), and Na2Cr2O7 (6.9%). The promotion of the 1s Cr core electron implies the electronic transitions 1s to 3d(t2g) and 1s to 3d(eg). The first and second shells in the Cr-VA material were coordinated with the oxygen and chromium atoms in a distorted geometrical arrangement. The adsorption mechanism was associated with the chemical reduction of Cr (VI) to Cr (III) via an ion-exchange process. The XAS technique significantly contributes to the characterization of environmental VA, which can be proposed as an economical and alternative adsorbent for the sorption of Cr from contaminated wastewater.

Nano‐sized Co(II), Ni(II), and Zr(IV) complexes of quinaldine‐based azo dye for promising therapeutic and catalytic applications: Synthesis, characterization, density functional theory studies and molecular docking

Novel azo dye containing the heterocyclic quinaldine nucleus, 3‐((2‐methylquinolin‐4‐yl)diazenyl)naphthalen‐2‐ol HL, and its Co(II), Ni(II) and Zr(IV) nano‐sized metal chelates have been synthesized and fully characterized by alternative analytical and spectral techniques. The finding indicated that the ligand coordinated as a monobasic bidentate via azo nitrogen and hydroxyl oxygen atom, resulting in octahedral geometry towards Co(II) and Zr(IV) complexes, and square planer geometry towards Ni(II) metal ion. Theoretical studies by DFT/B3LYP/6‐311+G(d,p)/LANLDZ including energetic parameters, geometrical optimization, dipole moment, and HOMO–LUMO energy gap were applied to support the geometrical arrangement of the complexes. The produced complexes were generated at the nanoscale, as evidenced by the average particle size from TEM. The average particle size calculated from TEM images for Co(II), Ni(II), and Zr(IV) complexes is 6.0, 12.0, and 5.5 nm, respectively. The antibacterial activity of the ligand compared with its metal complexes shows enhanced activity over the metal complexes against different types of bacteria. Antitumor efficacy of the compounds was tested against A‐549 and PANC‐1 cells, compared with the vinblastine standard. The cytotoxic efficiency of both Co(II) and Ni(II) complexes exceeded that of vinblastine. The anticancer activity of the Zr complex was then studied using molecular docking to determine the interactions between this molecule and PANC‐1. Docking studies revealed that the Zr complex produces four hydrogen bond contacts with the active amino acid residues Arg 136 and Asp 140, two hydrophobic interactions with Val 50 and Leu 147, and two electrostatic interactions with Arg 136. Also, the catalytic property of the free ligand and nanocomplexes were tested on the oxidative degradation of methyl violet 2B dye in the presence of H2O2. The following arrangement was observed for the pseudo‐first‐order rate constants: Co(II) complex (0.068 min−1) > Ni(II) complex (0.066 min−1) > Zr(IV) complex (0.061 min−1) > HL (0.037 min−1).

Quantum interaction between two entangled non point-like objects in the presence of boundaries

We explore, in the framework of linearized quantum gravity, the quantum gravitational quadrupole-quadrupole interaction between two entangled non point-like objects in the presence of both Dirichlet and Neumann boundaries. The results show that, compared to the case without boundaries, the interaction can be either enhanced or weakened depending on the geometrical arrangement of the objects with respect to the boundaries. In the limit when the two-object system is placed very close to the Dirichlet boundary, the near-regime interaction potential is larger than that of the pure vacuum case when the two objects are placed perpendicular to the boundary but smaller when parallel to it, while, in the far regime, such strong and weak relations between potentials are just opposite to that in the near regime. And, there exists a new r^{-2} far-regime behavior of the interaction potential under the perpendicular configuration. For the case of Neumann boundary, the strong and weak relations between the interaction potentials under perpendicular or parallel configurations and the case without boundary are opposite to the Dirichlet circumstance both in the near and far regimes. Besides, the novel r^{-2} far-regime behavior occurs for the parallel rather than perpendicular configuration in the presence of Neumann boundary.

Critical ignition conditions for propane/air premixtures impinging on electric heated surfaces: An experimental study

To contribute to exact predictions of the ignition of flammable mixture by a hot surface and ensure safety against fire, this study aims to clarify the critical ignition condition of a propane/air premixture impinging on a hot surface with external heating. The ignition threshold of heat flux depends on the flow velocity, but that of temperature hardly depends on flow velocity and equivalence ratio. The ignition occurred at the position where the residence time of species was the longest. It corresponds to the position of the lowest heat transfer coefficient. The temperature boundary layer thickness played a significant role in the ignition process as only the heat flux from the top, bottom, and back surfaces of the heater contributed to ignition in the presence of forced convection. The prediction model of the ignition threshold of heat flux and temperature was derived through dimensional analysis. This model effectively explains the ignition characteristics, regardless of the differences in thermal convection mode, dimensions, and geometric arrangements of a heater, as confirmed by comparison with reference data. Additionally, the ignition threshold of temperature can be predicted if the external heating power is known, and it is useful to assess the fire risk.

Giant Spontaneous Magnetostriction in MnTe Driven by a Novel Magnetostructural Coupling Mechanism

AbstractA comprehensive x‐ray scattering study of spontaneous magnetostriction in hexagonal MnTe, an antiferromagnetic semiconductor with a Néel temperature of TN = 307 K, is presented. The largest spontaneous magnetovolume effect known for an antiferromagnet is observed, reaching a volume contraction of |ΔV/V| > 7 × 10−3. This can be justified semiquantitatively by considering bulk material properties, the spatial dependence of the superexchange interaction, and the geometrical arrangement of magnetic moments in MnTe. The highly unusual linear scaling of the magnetovolume effect with the short‐range magnetic correlations, beginning in the paramagnetic state well above TN, points to a novel physical mechanism, which is explained in terms of a trilinear coupling of the elastic strain with superposed distinct domains of the antiferromagnetic order parameter. This novel mechanism for coupling lattice strain to robust short‐range magnetic order casts new light on magnetostrictive phenomena and also provides a template by which the exceptional magnetostrictive properties of MnTe might be realized in a wide range of other functional materials.

Enhancing energy absorption through sequential instabilities in mechanical metamaterials.

Structural components designed to absorb energy and shield a more valuable structure ideally require mechanical properties that combine a relatively high load-carrying capacity followed by a practically zero stiffness. This ensures that a specified energy quantity may be absorbed within a limited displacement and that any stress transfer to the valuable structure is minimized. Material damage has been historically mobilized to provide such properties, but this obviously renders such components to be single-use. By contrast, mobilization of elastic instability can also provide the desired combination of properties but without necessarily damaging the material. This reveals an intriguing possibility of such components being potentially repairable and theoretically re-usable with no significant loss in performance. A series of analytical, finite-element and experimental studies are presented for a bespoke mechanical metamaterial arrangement that is designed to buckle sequentially and behave with the desired 'high strength-low stiffness' characteristic. It is found that the various axial and rotational stiffnesses associated with the geometric arrangement and its constituent connections may be tuned to provide the desired mechanical behaviour within the elastic range and delay the onset of significant damage, thereby rendering the concept of harnessing instability to be feasible.

Machine learning–based estimation method for the mechanical response of composite cellular structures

Cellular materials, including porous materials, are widely utilized in engineered and natural systems because their mechanical performance undergoes changes such as compressive deformation and energy absorption under impact loading. The mechanical response of these materials is notably influenced by their inherent cellular structure, specifically the geometric arrangement pattern. Nonuniform arrangements can result in significant variations in mechanical performance, posing challenges for material selection and the geometrical design of cellular structures. In this study, we established a machine learning (ML)–based approach to design the geometric arrangement (architecture) of cellular materials, aiming to achieve improved mechanical performance under uniaxial compression. In particular, we investigated the peak force at the plateau region and the work of energy absorption until structural densification occurs. Various patterns of internal geometry were modeled using the finite element method, and uniaxial deformation behavior was simulated to generate the training data for the ML approach. A neural network was employed as the ML method, correlating the cellular geometric patterns with the mechanical performance, including force–displacement curves and the relationship between peak force and work during energy absorption. The results indicate that the proposed method can accurately predict the mechanical response of any given geometric pattern within the defined scope. Thus, this approach is valuable for discovering cellular structures that can achieve desired mechanical responses.

The enhancement of energetic and exergetic performance of embedded twisted rib turbulator over absorber plate of solar air heater

Owing to present investigation, a stochastic analysis is conducted to numerically optimize the energetic and exergetic efficiencies of embedded twisted rib turbulator over absorber plate of solar air heaters (SAHs). These efficiencies are assessed taking into account temperature rise and design characteristics. The criterion in context to energy efficiency do not take into consideration the pumping force which is needed to blow the air from the duct. Therefore, estimating the energy distribution of solar air heaters becomes a difficult task when evaluating their exergetic or effective efficiency. The experimental work determined the Nu and fr correlations in the term of geometrical configurations which are considered for evaluating the thermal behavior and compared to prior findings with smooth plate. The Optimal turbulator parameters were defined by the exergetic efficiency criterion in terms of the Reynolds and insolation.Maximum improvements in energetic and exergetic efficiencies were reported as ηth=1.81;ηeff=1.79andηII=1.82 times over smooth plate for a geometric arrangement with P/e =8, α =60°, y/e = 3 and Re = 5000. The maximum differences between simulated and experimental results, when taken into account, resulted ±6%. The current methodology also tackles the methods to research novel artificial turbulator to increase the energetic and exergetic performance of a SAHs, making it feasible to develop a design plot for the turbulator parameter without having to spend a lot of money on actual trials.

A Methodology to Assess the Sloshing Effect of Fluid Storage Tanks on the Global Response of FLNG Vessels

The sloshing effect of fluid storage tanks of a Floating Liquefied Natural Gas (FLNG) vessel causes variations in its global motion response. These acceleration and motion alterations can affect the safe performance of the FLNG vessels. The classification societies’ rules are employed to standardize the storage tanks’ configuration of FLNG vessels. Herein, we report a methodology to assess the sloshing effect on the global motion response of an FLNG vessel considering four geometrical arrangements of tanks and different fluid filling fractions. This methodology includes the hydrodynamic effect in operating and storm conditions from the Gulf of Mexico using a return period of 100 years. In addition, our methodology considers the influence of the internal fluid of each tank to estimate the accelerations and motions of the vessel. This methodology can be implemented to estimate the stability of an FLNG vessel under different environmental conditions. Thereby, the naval engineers could choose the best geometrical configuration of the storage tanks for safe behavior of a vessel under different operating and extreme environmental conditions.

MgSiP2: An Infrared Nonlinear Optical Crystal with a Large Non‐Resonant Phase‐Matchable Second Harmonic Coefficient and High Laser Damage Threshold

AbstractSuperior infrared nonlinear optical (NLO) crystals are in urgent demand in the development of lasers and optical technologies for communications and computing. The critical challenge is to find a crystal with large non‐resonant phase‐matchable NLO coefficients and high laser damage threshold (LDTs) simultaneously, which however scale inversely. This work reports such a material, MgSiP2, that exhibits a large second harmonic generation (SHG) coefficient of d14≈d36 = 89 ± 5 pm V−1 at 1550 nm fundamental wavelength, surpassing the commercial NLO crystals AgGaS2, AgGaSe2, and ZnGeP2. First principles theory reveals the polarizability and geometric arrangement of the [SiP4] tetrahedral units as the origin of this large nonlinear response. Remarkably, it also exhibits a high LDT value of 684 GW cm−2, which is six times larger than ZnGeP2 and three times larger than CdSiP2. It has a wide transparency window of 0.53–10.35 µm, allowing broadband tunability. Further, it is Type I and Type II phase‐matchable with large effective SHG coefficients of deff,I ≈80.2 pm V−1 and deff,II ≈73.4 pm V−1. The outstanding properties of MgSiP2 make it a highly attractive candidate for optical frequency conversion in the infrared.