Behavior In Various Applications Research Articles

Inducing hydrophobicity in stainless steel 304 by mechanical texturing and chemical functionalization

This study investigates the impact of combined texturing by micromachining and chemical functionalization on the wetting behavior and water condensation on stainless steel 304. The transition from Wenzel to Cassie-Baxter or impregnated Cassie-Baxter regimes is investigated. Understanding this transition is critical for advancing surface engineering, as it enables precise control over wetting behavior for various applications. Herein, we report on the wire EDM (wEDM) machining on stainless steel 304 to produce two distinct microstructure patterns with directional canals or pyramidal structure, and their performance in water condensation. These patterns significantly impact water condensation performance. wEDM is employed to create surface roughness, followed by phosphoric acid treatment and chemical functionalization with trichloro-1H,1H,2H,2H-perfluorooctyl silane. Contact angle measurements reveal a synergistic effect between groove direction and silane coating, leading to hydrophobic surfaces and dropwise water condensation. Specimens with directional canals exhibit a contact angle of 150°, while specimens with pyramidal structures exhibit 151o. Roll-off angle experiments showcased distinct behavior among specimens featuring canals or pyramidal structures. Specimens with canals exhibit notably lower roll-off angles compared to both flat surfaces and those with pyramidal patterns, leading to a dependence of roll-off angles on the orientation of canals. In humid environments, micromachined specimens exhibit superior water condensation capability compared to untreated SS304 surfaces. Chemically functionalized grooved specimens present larger condensate droplet diameters than flat surfaces. An enhancement in water condensation and a sevenfold higher latent heat transfer coefficient is reported. Specimens with chemical functionalization achieve corrosion protection with an efficiency reaching 82.9%.

Preparation and Physicochemical Properties of a Thermosensitive Hydrogel-based Lipopeptide Biosurfactant

Background: Temperature-sensitive (thermo-sensitive) formulations are a novel drug delivery dosage form that shows bio-inspired behavior in various applications. The structure and properties of a thermosensitive polymer are critical in designing an intelligent biometric polymer that contains lipopeptide biosurfactants. Objectives: In this study, thermo-sensitive hydrogels with lipopeptide biosurfactants as a potential wound dressing dosage form were formulated and examined regarding physicochemical properties. Methods: The lipopeptide biosurfactants were isolated from the Acinetobacter junni B6 bacterial strain and loaded on a formulation of poloxamer 407® and carboxymethyl cellulose as a gelling agent. Numerous experiments were carried out to evaluate the physicochemical properties of these formulations, such as the stability, spreadability, release profile, and kinetic. Results: The formulation (Poloxamer 407® (19% w/v), carboxymethyl cellulose (2% w/v), lipopeptide biosurfactants (5mg/mL), benzyl alcohol (1% v/v), and 0.1mL polyethylene glycol 400) was select as the optimum formulation. The selected formulation released 26.9% of the lipopeptide biosurfactants with anomalous transport kinetics after 10 hours. Conclusions: The results showed that a thermo-sensitive formulation could help achieve a sustained release of lipopeptide biosurfactants and potentially be used as a dressing formulation for wounds in future studies.

Quantitative measurements of changes in agglomerate size with oscillatory shear strain in polymer nanocomposites using online dielectric analysis

Shear strains during processing affect the agglomerate size of nanoparticles in nanocomposites and their final behavior in various applications. In this study, dielectric characterization technique as a novel and well-effective method is applied for quantitative measurement of average agglomerate size in polymer nanocomposites under shear strain sweep, combining with an existing analytical model. Examining how changes in filler content, surface energy and polarity of particles and the matrix control the strain-dependency of agglomerates size, two different nanoparticles, namely, titanium dioxide (TiO2) and carbon black (CB), with same average diameters and volumes were added to polystyrene (PS). It was found that larger agglomerates were present in the PS/CB nanocomposite prior to shearing and the CB agglomerates were less prone to deagglomeration under shear strain. This behavior was attributed to higher polarity of CB nanoparticles, leading to higher tendency for agglomeration and higher resistance to shear, in respect to TiO2 nanoparticles.

Review on latent thermal energy storage using phase change material

One of the appealing technologies that contributes to raising the energy storage density is latent heat thermal energy storage. The heat of fusion is isothermally stored at a temperature representing the temperature at which a phase-change material transitions between phases. The current research provides a review of how phase transition materials are used in melting and solidification. Generally, the range of working temperature extends from -20 °C to 200 °C for solidification and melting applications. The first range (-20 to 5 °C) is employed for commercial and domestic refrigeration. The second range (5 to 40 °C) is utilized to lower the energy requirements for air-conditioning applications. The applications includes in third range (40 to 82 °C) are solar collector and heating of water. Applications of absorption cooling, waste electricity generations, and heat recovery are operated at high temperature range (82 to180 °C). There are various types of PCMs for all the above temperature ranges. The present review paper will discuss the application field, Geometry, PCM type, heat transfer augmentation technique and their effects on the performance. The conclusions are mentioned to give more insight about the PCM behavior in various applications.

Enhanced corrosion resistance of CoCrFeMnNi high entropy alloy using heterogeneous structure design

High entropy alloys (HEAs) with heterogeneous grain structure exhibit an unprecedented combination of high strength and high ductility. Therefore, it is imperative to clarify corrosion behavior for various applications. In the present work, the corrosion behavior of harmonic structured (HS) CoCrFeMnNi HEAs with different shell fractions was investigated. The inhomogeneity of corrosion in the HS CoCrFeMnNi HEAs was revealed. The peculiar core-shell network structure is beneficial to the corrosion resistance compared with the conventional coarse-grained (CG) or ultrafine-grained (UFG) structure. The shell fraction of approximately 30% is the optimized design for corrosion resistance.

Investigation of fatigue behavior of Kevlar composites with nano-Graphene filled epoxy resin

The fatigue behaviour of Kevlar based fibre-reinforced composites is often less studied and requires further investigation. The objective of this study is to investigate the fatigue behaviour of the Kevlar composites reinforced epoxy infused with Graphene nanoparticles. Most of the engineering components used in defense, aerospace, biomedical, automobile industries and military appliance use aramid fiber as primary structural component. The Kevlar has low compressive strength and other cons there by limiting its mechanical and electrical behavior in various applications. In this study, kevlar-49 and graphene nanoparticle infused epoxy are sandwiched together using vacuum resin infusion technique. The difference in visual appearance of Graphene, Graphite and Carbon Nanotubes often leads to misconception; hence to visualize the graphene nanoparticle in a non-destructive format, the Raman Spectroscopy was performed. The fatigue test was then conducted at constant stress amplitude having an R ratio of 0.2 with frequency of 10 Hz, in accordance to ASTM D3479. The fatigue limit was observed at 1,005,498 million cycles. The visual view of the fatigue experiment illustrates the damage propagation of the developed composites which is started by matrix cracking followed by fiber breakage and delamination between Kevlar fiber layers once the developed composite reaches the failure point. Thus, this development of Nanoparticle reinforced composite shows good agreement findings and has high potential to replace or reduce the usage of general synthetic fibers.

Discrete Element Analysis of the Strength Anisotropy of Fiber-Reinforced Sands Subjected to Direct Shear Load

Soil reinforcement with natural or synthetic fibers enhances its mechanical behavior in various applications. Fiber-reinforced sands (FRS) can be relatively anisotropic because of the fiber self-weight and the compaction technique. However, the microscopic mechanisms underlying the anisotropy are still poorly understood. This study used a discrete element approach to analyze the microscopic mechanisms underlying the strength anisotropy of FRS due to fiber orientation. Analysis of contact networks revealed that the optimum fiber orientation angle is perpendicular to the main direction of strong contact force in direct shear testing. These fibers produced the largest increase in shear zone thickness, normal force around the fiber body, effective contact area, tensile force along fibers, and energy storage/dissipation. This study is valuable for further understanding of the mechanical behaviors of FRS.

A Cache Replacement Policy with Considering Fluctuation Patterns of Total Priority Value

In recent computer systems, a high-performance memory system is required for improving the computing performance. To improve the performance of the memory system, the capacity and the associativity of cache memories tend to be enlarged in all the memory hierarchy. Therefore, a high-performance cache replacement policy is required, which can be implemented with a small overhead and can adapt the behavior of various applications. Under such a situation, the adaptive demotion policy with considering global fluctuations of priority values (ADP-G) is proposed. ADP-G is based on the adaptive demotion policy (ADP) which can adapt the behavior of various applications by changing its insertion, promotion, demotion and selection (IPDS) policies. ADP-G selects the appropriate IPDS policies from two alternatives, one is suitable for a temporal locality and the other has a scan/thrashing tolerant. For this selection, ADP-G uses the global fluctuations of priority values of all the blocks in the cache. Although ADP-G is a high-performance cache replacement policy as compared with conventional ones, it causes a problem when the performance of the scan/thrashing tolerant IPDS policies is higher than that of the temporal locality IPDS policies. This paper discusses a novel cache replacement policy to solve this problem. At first, the fluctuation patterns of total priority value in several benchmarks are analyzed. As a result, two characteristics are observed which are useful to detect that the running application the suitable for the temporal locality IPDS policies or the scan/thrashing tolerant IPDS policies. Based on this analysis, a cache replacement policy with considering fluctuation patterns of total priority value is proposed, and it is called ADP-P. ADP-P has two states which suitable for the temporal locality and the scan/thrashing tolerant. To detect the suitable state, ADP-P uses the total of the priority values of all the blocks in the cache, and the value is stored in the global total register (GTR). When the state is for the temporal locality, the state is changed to the scan/thrashing tolerant state if the reduction of GTR is larger than the threshold value. When the state is for the scan/thrashing tolerant, the state is changed to the temporal locality state if the fluctuation of GTR which is larger than the threshold value is not caused for a fixed number of cache accesses. Experimental results show the proposed cache replacement policy achieves a reduction of cache misses compared to LRU policy and ADP-G. When the L3 cache size is 4MB, in the geometric mean of all the benchmarks, the proposed cache replacement policy achieves a 6.0% and 11% MPKI reduction compared to ADP-G and LRU policy, respectively.

Measurement Challenges in Dynamic and Nonequilibrium Nanoscale Systems.

Biological systems exhibit strikingly sophisticated properties, including adaptability, directed motion, regulation, and self-organization. Such systems are often described as being "nonequilibrium" or "out-of-equilibrium", and it can be instructive to think of them as adopting thermodynamic states that require a constant supply of energy to maintain. Despite their ubiquity, systems that demonstrate these abilities require a remarkably stringent set of chemical requirements to exist. Broadly speaking, they must be (a) capable of consuming some external source of energy that (b) acts as a fuel to do some form of work, (c) all while maintaining highly organized structural features at the nanometer length scale that persist in space and over time. It remains a grand challenge in the field of chemistry to synthesize artificial systems capable of similarly complex nonequilibrium behavior both as a means for greater fundamental understanding and as a way to imbue non-natural structures with dynamic behavior for various applications. Yet an oft-overlooked challenge in this field involves not just the synthesis of nonequilibrium materials but also their characterization. The requirements for measuring nanometer-scale systems of nonequilibrium building blocks with the appropriate temporal and spatial resolution are demanding and have heretofore been largely unavailable to researchers. In this Perspective, we highlight challenges and recent advances in the measurement of dynamic nanoscale systems. We argue that progress in this area is crucial and must occur in parallel to synthetic goals if any meaningful understanding is to occur.

NANOFIBRILLATED CELLULOSE, THE SMALL PROMISING FIBER: CHARACTERISTICS AND POTENTIALITIES

Cellulose: an abundant, biodegradable and renewable plant material that is available all around the globe, from which nanofibrillated cellulose (a homogeneous suspension of fibers with nanometer-scale diameters) can be extracted. The nanofibrillated cellulose, in what concerns its range of application, may completely or partially replace other materials due to its particular physical properties. Knowing its characteristics and properties is important in understanding its behavior in various applications. In light of this remarks, the objective of this research was to extract the nanocellulose from bleached eucalyptus pulp through mechanical milling to characterize the resulting nanofibrillated cellulose and compare both. The nanofibrillated cellulose presented a very distinct appearance in relation to the original cellulose pulp when they were analysed in the same concentrations, demonstrating greater water absorption and fibrillar interweaving. The nanofibrillated material showed different responses in comparison to the original in terms of dimensions, thermal stability, crystallinity, viscosity, and degree of polymerization. The nanofibrillated cellulose displays the same chemical composition through infrared analysis and has diameters of around 21.7 nm, smaller than the cellulose diameter of 11.4 μm. The nanofibrillated cellulose also exhibits lower thermal resistance: its decomposition temperature was about 20 ºC lower than that of the original cellulose pulp, and its crystallinity index has decreased. As for viscosity and degree of polymerization, there was reduction of 25% compared to the original material. The results presented hereby indicate that the nanofibrillated cellulose has unique features in relation to the original cellulose pulp, which supports its application as an alternative to existing materials.

Mechanical behavior of porcine thoracic aorta in physiological and supra-physiological intraluminal pressures.

Understanding the mechanical behavior of aorta under supra-physiological loadings is an important aspect of modeling tissue behavior in various applications that involve large deformations. Utilizing inflation-extension experiments, the mechanical behavior of porcine descending thoracic aortic segments under physiological and supra-physiological intraluminal pressures was investigated. The pressure was changed in the range of 0-70 kPa and the deformation of the segment was determined in three dimensions using a custom-made motion capture system. An orthotropic Fung-type constitutive model was characterized by implementing a novel computationally efficient framework that ensured material stability for numerical simulations. The nonlinear rising trend of circumferential stretch ratio [Formula: see text] from outer toward inner wall was significantly increased at higher pressures. The increase in [Formula: see text] from physiological pressure (13 kPa) to 70 kPa was 13% at the outer wall and 22% at the inner wall; in this pressure range, the longitudinal stretch ratio [Formula: see text] increased 20%. A significant nonlinearity in the material behavior was observed as in the same pressure range, and the circumferential and longitudinal Cauchy stresses at the inner wall were increased 16 and 18 times, respectively. The overall constitutive model was verified in several loading paths in the [Formula: see text] space to confirm its applicability in multi-axial loading conditions.

Applications of Hyphenated Liquid Chromatography Techniques for Polymer Analysis

We find polymers everywhere in our daily activities, for example, as a part of consumer electronics products, healthcare devices, vehicles, etc. Analytical characterization of such materials is an important step towards understanding their properties and behavior in various applications. The increase of material complexity driven by highly demanding requirements for many applications necessitates the use of sophisticated analytical techniques to obtain sufficient insight into the structure of these materials. Coupling of liquid chromatography with other information-rich instrumental techniques becomes more and more important in the field of polymer characterization. Such combination can enable simultaneous separation, identification, and quantification of polymer sample components. In addition, it can provide information on interdependence of two polymer properties, e.g., molecular weight and chemical composition. Different hyphenated systems may be applied to address different problems in polymer research and development and a selection of the right technique may not be an easy and straightforward task. In this paper, the applications of LC-NMR, LC-IR, LC-Raman, LC-MS, LC-MALDI, LC × LC, and LC × Py-GC for polymer analysis are reviewed, their advantages and limitations are discussed, and practical challenges for the implementation of these techniques in a lab are addressed. Different hyphenated options are compared to facilitate selection of a suitable instrument for the particular problem at hand.

On the robustness of Type-1 and Interval Type-2 fuzzy logic systems in modeling

Research on the robustness of fuzzy logic systems (FLSs), an imperative factor in the design process, is very limited in the literature. Specifically, when a system is subjected to small deviations of the sampling points (operating points), it is of great interest to find the maximum tolerance of the system, which we refer to as the system’s robustness. In this paper, we present a methodology for the robustness analysis of interval type-2 FLSs (IT2 FLSs) that also holds for T1 FLSs, hence, making it more general. A procedure for the design of robust IT2 FLSs with a guaranteed performance better than or equal to their T1 counterparts is then proposed. Several examples are performed to demonstrate the effectiveness of the proposed methodologies. It was concluded that both T1 and IT2 FLSs can be designed to achieve robust behavior in various applications, and preference one or the other, in general, is application-dependant. IT2 FLSs, having a more flexible structure than T1 FLSs, exhibited relatively small approximation errors in the several examples investigated. The methodologies presented in this paper lay the foundation for the design of FLSs with robust properties that will be very useful in many practical modeling and control applications.

Adaptive Control Design Based on Adaptive Optimization Principles

Recently, we introduced an adaptive control design for linearly parameterized multi-input nonlinear systems admitting a known control Lyapunov function (CLF) that depends on the unknown system parameters. The main advantage of that design is that it overcomes the problem where the estimation model becomes uncontrollable (at regions of the state space where the actual system is controllable). However, the resulted adaptive control design is quite complicated and, moreover, it exhibited poor transient behavior in various applications. In this technical note, we propose and analyze a new computationally efficient adaptive control design that overcomes the aforementioned shortcomings. The proposed design is based on an adaptive optimization algorithm introduced recently by the author, which makes sure that the parameters to be optimized (which correspond to the controller parameters in this technical note) are modified so as to both lead to a decrease of the function to be minimized and satisfy a persistence of excitation condition. The main advantage of the proposed adaptive control design is that it can produce arbitrarily good transient performance outside (a) the regions of the state space where the actual system becomes uncontrollable and (b) a region of the parameter estimates space which shrinks exponentially fast. It is also worth noting that the class of systems where the proposed algorithm is applicable is more general than that of our previous work; however, it has to be emphasized that, due to the fact that the proposed algorithm involves the use of random sequences, all the established stability and convergence results are guaranteed to hold with probability one.

The Next Generation Blowing Agents: From One Single Product to a Product Range

In the context of the HCFC-141b phase out, the two candidates HFC-365mfc and HFC-245fa have been selected over the last few years, as reported in previous papers. Since our last presentation, a lot of work has been performed to increase our knowledge of these new products and to study their behavior in various applications. Although HFC-365mfc and HFC-245fa are promising candidates, a single HFC blowing agent cannot match all the outstanding characteristics of traditional fluorocarbon blowing agents: right boiling point, non flammability, cost effectiveness..., to name but a few. It is very unlikely that a single blowing agent will cover all the future needs of the polyurethane industry. Such a trend is already seen today with at least seven physical blowing agents finding commercial applications in the different sectors of the industry (HCFC-141b, HCFC-22/HCFC-142b, HFC-134a, cyclopentane, pentane or isopentane). The main reason why HFC blowing agents will be used in the future is their ability to give foams with optimized thermal conductivity. However, because of possible condensation phenomena at low temperature for relatively high boiling blowing agents, the rating of different blowing agents is a function of temperature. We have now measured foam thermal conductivity over the temperature range between -20°C and +45°C for several blowing agents, including HFC-245fa, HFC-365mfc, pentane isomers and blends thereof. Included in this study are the newly discovered low boiling azeotropes of HFC-365mfc with all three pentane isomers. In this paper, we will especially show that the evolution of thermal conductivity with temperature can be a very good selection criteria to find the most appropriate blend for a specific application.