Constant Ratio Research Articles

Identification of an upper limit to the laser pulse duration in photonic band-edge liquid crystal lasers

Photonic band-edge liquid crystal (LC) lasers are an exciting field of research, offering potential in a range of applications from medical imaging to holographic projection. Much work has been done on improving the performance of LC lasers. However, due to historical limitations in pumping techniques, very little experimental work into the temporal dynamics of LC lasers has been published. In this paper, a laser diode pump source with a variable pulse duration is used to investigate the temporal characteristics of the resultant LC laser pulses, while maintaining a constant ratio of pump pulse energy to LC laser threshold. The existence of an upper limit to the output pulse duration of stimulated emission from an LC laser is presented, with a value of 3.5 (±0.1) ns for a DCM-doped cell and 5.2 (±0.2) ns for a Coumarin504-doped cell, irrespective of the laser diode pump pulse lengths, which exceed these values. Evidence is provided to show that the remainder of the optical energy within the pump pulse results in fluorescence emission. The results are in good agreement with the theory of organic dye dynamics and may provide possible future opportunities for electronic control of laser linewidth and coherence in addition to pump parameter optimization for improved LC laser performance.

Effect of AO 4426 on damping properties of PVA/CPE-AO 2246

Abstract To investigate the influence of AO 2246 and AO 4426 on the damping properties of polyvinyl alcohol/chlorinated polyethylene (PVA/CPE) composites, a series of composites were prepared by adding AO 4426 into PVA/CPE-AO 2246 under the constant mass ratio of hindered phenol in the composites. The dynamic mechanical properties and microstructure of materials were investigated by DMA, DSC, SEM, and FT-IR. The results showed that a new damping peak appeared near 50 °C by adding AO 4426, which indicated phase separation between AO 4426 and the matrix occurred. With the increase of AO 4426, the damping peaks in the low-temperature section were improved. The value of low-lying region between the double damping peaks, when the hindered phenol coexisted was higher than that of the composites containing only AO 4426, which indicated that the damping temperature domain of the composites was effectively broadened. At the melting temperature of AO 4426 microcrystalline and AO 2246 microcrystalline, no obvious peaks were observed simultaneously, indicating that the hindered phenols inhibited the crystallization of each other.

Carboxyethylsilanetriol-Functionalized Al-MIL-53-Supported Palladium Catalyst for Enhancing Suzuki–Miyaura Cross-Coupling Reaction

The application of metal–organic frameworks (MOFs) has attracted increasing attention in organic synthesis. The modification of MOFs can efficiently tailor the structure and improve the property for meeting ongoing demand in various applications, such as the alteration of gas adsorption and separation, catalytic activity, stability, and sustainability or reusability. In this study, carboxyethylsilanetriol (CEST) disodium salt was used as a dual-functional ligand for modified Al-MIL-53 to fabricate CEST-functionalized Al-MIL-53 samples through a hydrothermal reaction of aluminum nitrate, terephthalic acid, and CEST disodium salt by varying the molar ratio of CEST to terephthalic acid and keeping a constant molar ratio of Al3+/-COOH of 1:1. The structure, composition, morphology, pore feature, and stability were characterized by XRD, different spectroscopies, electron microscopy, N2 physisorption, and thermogravimetric analysis. With increasing CEST content, CEST-Al-MIL-53 still preserves an Al-MIL-53-like structure, but the microstructure changed compared with pure Al-MIL-53 due to the integration of CEST. Such a CEST-Al-MIL-53 was used as the support to load Pd particles and afford a catalyst Pd/CEST-Al-MIL-53 for Suzuki–Miyaura C-C cross-coupling reaction of aryl halides and phenylboronic acid under basic conditions. The resulting Pd/CEST-Al-MIL-53 showed a high catalytic activity compared with Pd/Al-MIL-53, due to the nanofibrous structure of silicon species-integrated CEST-Al-MIL-53. The nanofiber microstructure undergoes a remarkable transformation into intricate 3D cross-networks during catalytic reaction, which enables the leachable Pd particles to orientally redeposit and inlay into these networks as the monodisperse spheres and thereby effectively preventing Pd particles from aggregation and leaching, therefore demonstrating a high catalytic performance, long-term stability, and enhanced reusability. Obviously, the integration of CEST into MOFs can effectively prevent the leaching of active Pd species and ensure the re-deposition during catalysis. Moreover, catalytic performance strongly depended on catalyst dosage, temperature, time, solvent, and the type of the substituted group on benzene ring. This work further extends the catalytic application of hybrid metal–organic frameworks.

Ultrasound-assisted efficient targeting of doxorubicin to the tumor microenvironment by lyso-thermosensitive liposomes of varying phase transition temperatures.

Premature drug release is the primary hindrance to the effective function of the lyso-thermosensitive liposomes (LTSLs) of doxorubicin (Dox), known as ThermoDox® for the treatment of cancer. Herein, we have optimized LTSLs by using a combination of phospholipids (PLs) with high transition temperatures (Tm) to improve the therapeutic outcome in an assisted ultrasound approach. For this, several Dox LTSLs were prepared using the remote loading method at varying molar ratios (0 to 90%) of DPPC (Tm 41°C) and HSPC (Tm 54.5°C), as well as a constant molar ratio of MSPC (10%), DSPE-mPEG2000 (4%). The treatment efficacy was explored by using ultrasound as external hyperthermia (HT) (40-42℃) in mice bearing C26 murine colon carcinoma. All the formulations had an average diameter of around 110 nm, PDI ≤ 0.15, zeta potential of around -12 mV, and Dox encapsulation of >90%. The cytotoxicity results indicated a higher IC50 value of Dox-LTSLs compared to the ThermoDox® (F0: DPPC:MSPC:DSPE-mPEG2000, 90:10:4), attributed to the faster Dox release in F0 formulation devoid of HSPC. Among various formulations, F25 (DPPC: MSPC: DSPE-mPEG2000: HSPC, 65:10:4:25) showed the highest cellular uptake at 42℃ and significantly improved the antitumor and survival efficacy in mice bearing C26 colon carcinoma in combination with ultrasonic HT compared to F0. Collectively, results demonstrated that optimizing the rigidity of the liposomal bilayers through the combinatorial selection of PLs of different transition temperatures could improve the plasma stability of the liposome, and hence ameliorate the outcome of therapy in assistance with an effective HT approach.

Age-Dependent Flexural Properties of Fiber Reinforced Concrete Used in Thin Overlays

This paper presents measured age-dependent flexural properties of fiber-reinforced concrete (FRC) as are used in the design of thin overlay pavements. A laboratory investigation was performed to quantify the pavement design properties, particularly residual strength ratio of FRC as a function of age. Four different types of structural macro-fibers, made of steel or polypropylene, and of different lengths or aspect ratios were investigated. Also different fiber volume contents from 0%, 0.5%, and 1.0% were studied for all fiber types and ages. The results confirmed that there is a significant agedependency to the residual strength ratio. The short steel FRC at high fiber volume content was the only mixture which showed constant residual strength ratio as a function of time. All other FRC mixtures exhibited a reduced residual strength ratio when tested at later ages.

Research on the Parameter Configuration Law of Transfer of Ultramicro Liquid by Pipetting Needle Based on the Quasi-static State.

Microscale device surface encapsulation needs to use ultrafine liquid transfer technology. This technology can transfer a liquid from a donor surface to a receptor surface in a controlled manner. However, the requirement of microscale encapsulation for liquid transfer amounts is generally at the pL level. Controlling liquid transfer volume, ensuring consistency, and ensuring droplet position accuracy became more difficult at this level. In light of the existing pipetting needle transfer ultramicro liquid transfer technology and considering a slow stretching liquid bridge can maintain a constant liquid transfer ratio, we conducted in-depth research on the parameter configuration law of liquid transfer at the pL level. This study reveals the parameter configuration law under the condition of constant transfer ratio through the Young-Laplace equation and the Navier-Stokes equation. Research has shown that the initial distance and capillary number (Ca) affect the transfer ratio at a slow stretching speed. Through ultramicro liquid transfer experiments, with stretching speeds between 0.01 and 0.5 mm/s, the transfer ratio remained constant, the accuracy of the rheology-Cross model in predicting liquid transfer ratios was verified, and the absolute deviation rate between the actual and the predictive transfer ratio is 6.26%. This research plays a crucial role in enhancing the precision and success rate of microscale liquid transfer.

The influence of feed molar flow rate on key streams properties and duties in ethanol-water azeotropic distillation process

Investigation on the influence of near azeotropic feed molar flow rate on properties of key streams connecting main process units of an ethanol-water azeotropic distillation pilot processis presented. The heterogeneous azeotropic distillation model with cyclohexane entrainer was configured in Aspen Plus® V10 commercial simulation software. Property analysis and prediction of plant’s performancewere achieved using Non-Random Two Liquid Redlich-Kwong thermodynamic model. Both residual curve maps and ternary diagrams were used to determineseparation possibility and presence of ethanol-water azeotrope in the formed ternary mixtureduring distillation synthesis. The process convergence was addressed using flowsheet convergence and balance node. Distillation of ethanol- water azeotropic mixture was simulated at constant recycle ratio (R = 5), numberof stages (N = 12) and pressure (P = 1 atm). Data obtained were analysed in MS Excel 2013. Results showed that simultaneous increase ofmolar flow rate of the near azeotropic feed and feed ethanol concentration improves ethanol purity but results in retrograde phenomenon which may humper plant’s performance and increase stream flow rates and therefore increase energy duties. The condenser duty of the main column wasaround 90.94% higher than the recycle column’scondenser duty. Also, reboiler duty of the main column were nearly 90.25% higher than the recycle column’s reboiler duty.It was concluded that setting 18 to 20 kmol/h feed molar flow rate enhances higher energy efficiency and improves ethanol product purity. Careful distillation synthesis and plant’s monitoring are recommended to improve ethanol-water azeotropic distillation plant’s performance and address retrograde phenomena.

Kinetic Isotope Effect in the Unfolding of a Protein Secondary Structure: Calculations for Beta-Sheet Polyglycine Dimers as a Model.

In the present work, we performed calculations of the kinetic isotope effect (KIE) on H/D, 14N/15N, 16O/18O, and 12C/13C isotopic substitution in the dissociation of beta-sheet polyglycine dimers of different lengths into two monomer chains. This dissociation reaction, proceeding via breaking of the interchain hydrogen bonds (H-bonds), is considered to be a model of unfolding of the secondary structure of proteins. The calculated strengthening of the interchain hydrogen bonds N-H⋯O=C due to heavy isotope substitution decreases in the row H/D >> 14N/15N > 16O/18O > 12C/13C. The KIE for H/D substitution, defined as the ratio of the rate constants k(H)k(D), was calculated with the use of a "completely loose" transition state model. The results of the calculations show that a very high H/D isotope effect can be achieved for proteins even with moderately long chains connected by dozens of interchain H-bonds. The results obtained also indicate that the heavy isotope substitution in the internal (interchain) and external H-bonds, located on the periphery of a dimer, can provide comparable effects on secondary structure stabilization.

Protective role of hematin in alcohol oxidase-mediated glycerol oxidation: Akinetic modeling approach.

Mathematical modeling of complex multi-catalytic reaction pathways is a powerful tool not only for determining optimal operational conditions but also for gaining insights into the kinetic behavior of efficient yet product-sensitive enzymes. This approach was applied to the biooxidation of glycerol using oxidases, aided by hematin, a natural mimic of heme peroxidases and catalases, which acts as a scavenger for enzymatically produced H2O2. The bi-catalytic reaction system was coupled with the formation of a colored imine product from phenol and 4-aminoantipyrine, enabling spectrophotometric monitoring of reaction kinetics. Alcohol oxidase (AOX) from Komagataella pastoris (formerly Pichia pastoris) was submitted to this strategy to overcome some kinetic drawbacks previously observed with galactose oxidase (GAO) from Dactylium dendroides. Although both enzymes exhibited comparable oxidation yields, computer-aided kinetic analyses revealed significant differences in efficiency and sensitivity to H2O2. AOX demonstrated two orders of magnitude greater efficiency and a similarly higher affinity for glycerol. However, AOX showed a stronger tendency to bind H2O2 compared to hematin or GAO, as suggested by the ratio of the inhibition constant (kinh) to the activation constant (k1) for hematin. The kinetic model was also used to simulate optimal conditions for enhancing the stability of AOX and hematin. Reducing glycerol concentration or increasing hematin concentration improved AOX stability, while the addition of phenol helped preserve hematin. The predicted stabilities turn the AOX/hematin/phenol system promising for biosensing or analytical applications.

Trajectory‐Based Safety Analysis of Electric Battery Taxis

This paper utilizes trajectory data of electric taxis in Shenzhen to first study the driving characteristics of electric taxis from different indicators such as travel/driving speed, overspeed ratio, and overspeed amplitude. A combination weighting VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) evaluation method based on Nash equilibrium is constructed to comprehensively assess the operation safety of electric taxis in various spatiotemporal scenarios. The results show that the average driving speed and overspeed amplitude of battery electric taxis is 39.14 km/h and 22.78%, which is 1.27 and 1.72 times that of fuel taxis. The average overspeed ratio, average acceleration and deceleration and total acceleration and deceleration frequency are all more than twice those of fuel taxis. The average acceleration, deceleration, and idle time ratios of battery electric taxis are 0.27, 0.24 and 0.43, respectively, with a constant speed time ratio of only 0.06. The proposed combination weighting VIKOR evaluation method outperforms other evaluation methods in comprehensively considering data discreteness and correlation. Electric taxis have the highest operational safety on arterial roads, while the safety on minor arterial roads and local roads is relatively poor, especially on weekends. In all spatiotemporal scenarios, the overall operation safety of electric taxis is lower than that of fuel taxis. The research results can provide theoretical support for the formulation of effective measures and policies to reduce dangerous driving behavior of electric taxis.

Numerical investigation on mixed convection with nanofluids in vertical channels with opposing moving plate

Abstract A numerical investigation on 2-dimensional steady-state mixed convection in a vertical channel asymmetrically heated with water-alumina (Al2O3) nanofluids is performed to evaluate the thermal and fluid dynamic behavior. The interest in this problem is related to several technological applications such as nuclear reactors and electronic components. Nanoparticles have a diameter of 30 nm and four different values of concentration (from 0 to 6%). The computational domain is made up of the channel and two lateral reservoirs, which simulate the external ambient. The channel is bounded by two vertical parallel plates with a constant aspect ratio. One of the plates is heated with a constant heat flux, while the other is considered adiabatic and is moving in the opposite direction of the buoyancy force. The governing equations are numerically solved with finite volume method by means of the ANSYS-Fluent code. Four different values of wall heat flux (with Ra=7×102 to 106) and six different velocities of the unheated plate (with Re=1 to 102) are considered. Results are presented in terms of velocity, temperature, pressure and stream function. Finally, correlations for the prediction of the average Nusselt number along the heated plate are presented.

A unified method for detonation-induced elastoplastic response of multiple interacting materials

This work is concerned with the elastoplastic response of multiple interacting materials under extreme conditions, due to the combustion and transition to detonation of condensed phase explosives. A new unified system of equations is developed to model the phase transition from a condensed phase to gas in explosives, as well as the elastoplastic behavior of solids. This system amalgamates the unified Godunov–Peshkov–Romenski model of solid and fluid mechanics with a diffuse-interface, reactive model. The theoretical foundations of this approach, including the mathematical model and the corresponding algorithm for its numerical solution, have been described in a previous communication by these authors. In this work, we extend the system of equations to handle an arbitrary number of interacting materials, both inert and reactive, across multiple spatial dimensions. The extension to multiple reactive materials relies on a constant density ratio assumption between reactants and products, avoiding the complex multidimensional root-finding procedures typically required in diffuse-interface multi-explosive formulations with thermal equilibrium assumptions. Additionally, we develop an appropriate numerical algorithm for the solution of this extended model, incorporating adaptive mesh refinement to efficiently capture fine-scale material interactions. For validation purposes, we consider a broad set of benchmarks from the literature, including an explosives-filled vessel and the sensitization of explosives through cavities and solid beads. The capabilities of this method are demonstrated through a confined multi-explosive rate stick problem and a multi-material detonator configuration. Various types of explosives and confining materials are considered throughout these test problems, highlighting the method's versatility.

Optimization of the Process of Batch Distillation of Binary Mixtures

The method of dynamic optimization, known as maximum principle of Pontryagin, is presented. It is applied to the process of batch rectification of binary mixtures, with aim of solving the problem of minimum time (for given distillate quantity of specified composition) or maximum distillate quantity of specified composition (for given batch time). The optimum profiles of reflux ratio are found for seven different separation tasks, based on semi-rigorous model without holdups. The results obtained for distillate quantity are compared to respective results obtained with constant reflux ratio and constant distillate composition working policies, and also with the results of other authors. The solution algorithms for all the three working policies are given. Computer implementation of the algorithms is performed in programming language FORTRAN.

Force of adhesion between droplets and super-hydrophobic surfaces: Closed-form analytical expressions.

Super-hydrophobic and liquid-repellent surfaces can be characterized experimentally in tensile adhesion experiments with the force (FAdh) required to detach a droplet from such surfaces, but analytical expressions that relate FAdh to the surface energy, w, are still missing. In this work, we derive analytical expressions for FAdh between droplets or radius r and super-hydrophobic surfaces on which the contact angle is greater than 150°. By applying the general condition for the onset of instability in different mechanical configurations, we find FAdh = -πwr and FAdh ≈ -(4/5)πwr, for the fixed-force and fixed-grip configurations, respectively, as well as other expressions that depend on the ratio of the spring constant of a generic force measuring apparatus to the surface tension of the liquid composing the droplet. These expressions open the possibility of retrieving w or, equivalently, the receding contact angle, by measuring FAdh on these systems.

On the tailoring of radially FGM hollow spheres, cylinders and disks

Homogeneous and isotropic thick spheres, cylinders, and thin disks subjected to constant internal and/or external pressures are not easily designed in an economical way due to the localized occurrence of maximum equivalent stress. It has been analytically shown that using a radial functionally graded material (FGM) can enhance the design process by ensuring that the maximum shear stress or the circumferential stress component remains constant along the radius of the body. This problem is an inverse one. An isotropic FGM in linear static analysis can be defined by two elastic constants: Young's modulus E(r) and Poisson's ratio ν(r). In this study, focusing on mechanical loading, the conditions for the existence of a solution for E(r) in the inverse problem are derived, assuming a constant Poisson's ratio and using two commonly applied stress criteria in design. Additionally, the advantages of employing FGMs over homogeneous materials are demonstrated by comparing the maximum equivalent stresses in both cases.

Optimizing the hyperbaric chamber pressurization profile during standard hyperbaric oxygen therapy

Mátity L, Burman, Cronje F. Optimizing the hyperbaric chamber pressurization profile during standard hyperbaric oxygen therapy. Undersea Hyperb Med. 2024 Fourth Quarter; 51(4):377-385. Middle ear barotrauma (MEBT) is the most common complication in providing hyperbaric oxygen therapy (HBO2). This study explored the impact of altering the shape of the time-pressure curve with the aim of reducing the occurrence of MEBT and optimizing the HBO2 experience during the pressurization process. Four distinct mathematically derived protocols—Constant Pressure Difference (CPD), Constant Volume Difference (CVD), Constant Ratio (CR), and Inverted Constant Ratio (ICR)—were investigated using computer simulations on a simple ear model. Results indicated varying levels of ear strain during pressurization. The CR pressurization demonstrated balanced ear strain levels and outperformed other modalities in several measures, including the impact on the simulated ear cavity volume. The potential for enhanced patient comfort through the application of sophisticated pressurization protocols warrants further research to validate and extend the findings of this study in real-world HBO2 settings. Keywords: barotrauma; compression; constant ratio; descent; middle ear; pressure

Frequency-independent damping models for a high-rise building with simultaneous horizontal and vertical seismic motions

Recent seismic analyses indicate that the structural damping ratio should be considered frequency-independent, for safe and accurate estimations. In response, damping models like the Wilson–Penzien (WP) damping model, that is one of the modal damping, provide frequency independence across all modes; however, these models require considerable computational resources, especially for large-scale models. While Rayleigh damping is computationally efficient, it maintains a nearly constant damping ratio only within a limited frequency range. To address these limitations, several alternative damping models have been introduced, such as uniform (UN), causal hysteretic (CH), and extended Rayleigh (ER). We use the factor Wξ to represent the frequency range where the damping ratio remains approximately constant, defined as the ratio of maximum to minimum frequencies (fmax/fmin), within a specified tolerance of the target damping ratio. For Rayleigh damping, Wξ = 3.7, while the CH and ER models achieve Wξ values greater than 20. Although the UN model achieves a high Wξ, it demands large computational resources in the implicit analyses, commonly used for seismic response studies. In this study, we address the simultaneously inputting horizontal and vertical seismic motion into a large-scale dynamic analysis model of a high-rise building. In this analysis, horizontal, vertical, and local beam vibration modes spanning a wide frequency range appeared. Considering that these modes require the same damping ratio, damping models with Wξ values of 50 or higher are desirable. However, this threshold considerably exceeds Wξ values achievable with the existing models, rendering these models unsuitable for the intended application. Therefore, we propose and validate the efficiency of two new damping models (ER-W and CH19) that meet this requirement by improving existing models. Using these damping models, it is possible to analyze the horizontal and vertical modes and local vibration modes of the beam, assuming a simultaneous horizontal and vertical input to a high-rise building.

Innovative Use of Adenosine-Free Constant Resistance Ratio to Evaluate Distal Blood Flow during Perfusion Balloon Dilation: A Case Report

Coronary interventional therapy effectively achieves myocardial reperfusion in coronary heart disease. New surgical instruments may enhance treatment selectivity and reduce discomfort. The constant resistance ratio (cRR) is a non-congestive measurement that directly assesses coronary function without vasodilators including adenosine, simplifying operations and minimizing drug side effects compared to fractional flow reserve (FFR). As a novel device in interventional treatment, the perfusion balloon (PB)'s ability to preserve distal blood flow during inflation is not been fully understood. The case aims to evaluate the extent of blood flow preservation by using cRR.

A Multi‐Time Stepping Algorithm for the Modelling of Heterogeneous Structures With Explicit Time Integration

ABSTRACTHeterogeneous solids often exhibit complex dynamic behavior, requiring simulations to use varying time steps. However, the conventional use of a single‐time step for the entire domain can be inefficient. This article proposes a multi‐time stepping algorithm that addresses this challenge by relaxing the constraint for an integer or constant time step ratio between subdomains and eliminating the need for kinematic interpolation. The algorithm ensures the satisfaction of the Courant‐Friedrichs‐Lewy condition, deviating only to allow subdomains to remain in synchronization. Consequently, less integration steps are performed in comparison to state‐of‐the‐art asynchronous integrators. We extend to the coupling of multiple subdomains, where each subdomain has its time step. Simulating stress wave propagation in metamaterials demonstrates that the proposed algorithm significantly accelerates simulation time, without sacrificing accuracy.

Elastic Properties of C-Type Lanthanide Sesquioxides

In this study, we have presented the solid-state theory of plasma oscillations to investigate the anisotropic elastic properties such as three independent static elastic stiffness constants (Cij: C11, C12 & C44) of C-type Ln2O3 lanthanide solids. The calculated values of the static elastic stiffness constants of Ln2O3 are in excellent agreement with the theoretical results obtained by using ab-initio techniques. The values of elastic stiffness constants (Cij) exhibit a linear relationship when plotted against their plasma energies and lie on a straight line. To further examine the validity of the present estimations on elastic moduli and other parameters of these materials. The mechanical moduli such as bulk modulus (B), shear modulus (G), Young modulus (E), Poisson’s ratio (ν), shear wave constant (Cs), Cauchy pressure (C*), Lame’s coefficient (λ and µ), Kleinman parameter (ξ) Grunesien parameter (γ), Zener anisotropic constant (Z) and Pugh ratio (G/B) of lanthanide solids have also been investigated. For the lanthanide sesquioxide materials, the values of static elastic stiffness constants Cij and elastic moduli were presented for the first time. Unfortunately, in the current study, for many parameters of these materials, experimental results were not found for a comparison with our theoretical predictions. Our estimations agree well with the available experimental data and other theoretical reports.