Use In Technical Applications Research Articles

Recent insights into the world of dual-function bacterial sRNAs.

Dual-function sRNAs refer to a small subgroup of small regulatory RNAs that merges base-pairing properties of antisense RNAs with peptide-encoding properties of mRNA. Both functions can be part of either same or in another metabolic pathway. Here, we want to update the knowledge of to the already known dual-function sRNAs and review the six new sRNAs found since 2017 regarding their structure, functional mechanisms, evolutionary conservation, and role in the regulation of distinct biological/physiological processes. The increasing identification of dual-function sRNAs through bioinformatics approaches, RNomics and RNA-sequencing and the associated increase in regulatory understanding will likely continue to increase at the same rate in the future. This may improve our understanding of the physiology, virulence and resistance of bacteria, as well as enable their use in technical applications. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

Environmental Effects on Strength and Failure Strain Distributions of Sheep Wool Fibers.

Sheep wool is an eco-friendly, renewable, and totally recyclable material increasingly used in textiles, filters, insulation, and building materials. Recently, wool fibers have become good alternatives for reinforcement of polymer composites and filaments for 3D printing. Wool fibers are susceptible to environmental degradation that could shorten their lifetime and limit applications. This study reports on the mechanical properties of sheep wool fibers under the impact of humid air and UV irradiation. The results of single fiber tensile tests showed a noticeable gauge length effect on the fibers’ strength and failure strain. Long (50 mm) fibers possessed about 40% lower characteristics than short (10 mm) fibers. Environmental aging decreased the elastic modulus and strength of the fibers. Moisture-saturated fibers possessed up to 43% lower characteristics, while UV aging resulted in up to a twofold reduction of the strength. The most severe degradation effect is observed under the coupled influence of UVs and moisture. The two-parameter Weibull distribution was applied for the fiber strength and failure strain statistical assessment. The model well predicted the gauge length effects. Moisture-saturated and UV-aged fibers were characterized by less extensive strength dependences on the fiber length. The strength and failure strain distributions of aged fibers were horizontally shifted to lower values. The results will contribute to be reliable predictions of the environmental durability of sheep wool fibers and will extend their use in technical applications.

Characterizing and predicting the self-folding behavior of weft-knit fabrics

Self-folding behavior is an exciting property of weft-knit fabrics that can be created using just front and back stitches. This behavior is easy to create, but not easy to anticipate and currently cannot be predicted by the existing computer-aided design software that controls industrial knitting machines. This work identifies the edge deformation behaviors that lead to self-folding in weft knits, and methods to characterize the mechanical forces driving these behaviors with regard to chosen manufacturing parameters. With this data and analysis of the fabric deformations, the self-folding behavior was purposely controlled using calculated scaling factors. Furthermore, theoretical equations were developed to mathematically predict these scaling factors, minimizing the trial and error required to design with self-folding behavior and create textiles with novel engineered properties. By understanding the mechanisms responsible for creating these three-dimensional self-folding textiles, they can then be designed in a programmable manner for use in technical applications.

Systematic design of particle dampers for horizontal vibrations with application to a lightweight manipulator

Particle damping has become a favorable passive damping technique for lightweight structures, however, its complex dimensioning process hinder its wide use in technical applications. In this paper, a multilevel design tool chain is presented to enable a systematic design and dimensioning process of particle dampers. Thereby various numerical models and experimental tests are combined. This starts with investigations of the micro-mechanical behavior of single particle impacts. Continuing, with analyzing the properties of vibrated granular matters inside a container and ending with designing a damper for a desired structure. The good agreement of the models and their efficiency for the damper design and dimensioning are finally demonstrated on an elastic lightweight manipulator undergoing a horizontal, transient vibration. Using this design toolchain, a new and much more efficient damper design for low amplitude vibrations is introduced using the rolling attribute of spheres. By separating the particle damper into several layers, high damping of the elastic lightweight manipulator is achieved.

On one method of risk evaluating in geotechnical mechanics tasks

To increase the efficiency of the existing labor protection system at industrial enterprises of Ukraine, there was a need for its improvement. It was decided to do it based on systems management of labor protection and risk control. However, it turned out that risks can be identified not in each technical system. Most of the processes in technical applications are deterministic, and therefore the concept of risk is not applicable, since none of the parameters of the system is a random variable. Since it is impossible to determine the degree of risk, then the only possible way out is to assess a degree of influence of this or that parameter on the performance of the entire system. So, for deterministic mathematical models (MM), the influence of the parameters can be determined by the methods of the theory of sensitivity (ST). However, the ST has not yet received widespread use in technical applications due to the significant complexity of research. In order to determine sensitivity, it is proposed to use in technical applications performance criterion approximation, which characterizes the risk of the process going beyond the performance limits, instead of ST. If approximation of a selected criterion is represented in the form of a product of power functions, each of which depends only on one parameter, then, according to the exponents, it is possible to approximately establish its sensitivity to variations in the parameters. The greater is an exponent, the more this parameter influences the criterion. Thus, it is possible not only to carry out an approximate assessment of the influence of the parameters on the criterion itself, but also to make conclusions regarding the risk of the system going beyond the permissible limits. The experience of successful use of the method of sequential approximation (SAM) in applied problems of mechanics allows not only to obtain an analytical form of the criterion at a point, but also to expand a solution of practical problems to the entire domain of function. The errors of such expanding, as a rule, do not exceed 5‑7 %, which is sufficient for most applied problems of geotechnics. The accuracy of determining the criterion can be increased to the required level by narrowing an area of its definition, i.e. parameter change intervals. A hypothesis of existence of representation of functions in the form of a product of functions, each of which depends on one parameter, is formulated. The efficiency of the use of power functions for an approximate assessment of the system risks when it going beyond the limits of operability is shown. Keywords: theory of sensitivity, variation of parameters, approximation of a function, approximate estimate, small error.

Experimental Investigation of Adiabatic Gas-Liquid Flow Regimes and Pressure Drop in Slit Microchannel

The flow regimes and pressure drop in a slit microchannel with a height of 164 μm and width of 10 mm are studied experimentally. The boundaries between the regimes are precisely determined using the developed procedure. The homogeneous flow model and the separated flow model are considered for determining the frictional pressure drop. Experimental data are compared with theoretical models. For the homogeneous flow model, the Dukler correlation gives good agreement with experimental data with a mean absolute error of 12%. A new correlation, which describes the experimental data with a mean absolute error of 8.1%, is proposed for the homogeneous flow model. For the separated flow model, the Hwang and Kim correlation gives the best agreement with a mean absolute error of 12.8%. The dependence of the pressure drop in the film flows (annular and stratified regimes) on the mass gas quality has been investigated. It is shown that the minimal pressure drop for the film flows is achieved in the stratified regime; thus, it is the most promising for the use in technical applications.

New Equations for Sea Water Density Calculation Based on Measurements of the Sound Speed

Density is one of the most important properties of seawater and is used in various marine research and technology. Traditionally, in the practice of oceanographic research, it is customary to con-sider density as a dependent parameter, which is a function of several other parameters taken as independent. Usually the following three parameters are used as the independent parameters: temperature, hydrostatic pressure and salinity. The issues of temperature and hydrostatic pressure measuring in situ are technologically well developed, while in the salinity measuring there are still unsolved problems. This is due to the fact that salinity is such a property that it is simply impossi-ble to determine directly in situ. To eliminate the problems associated with measurements of sa-linity, the authors developed the special new kind equation. That equation of the new kind ex-press the density of sea water through independent and in situ measured parameters: temperature, hydrostatic pressure and sound speed. The novelty of this approach is that using of the sound speed as the independent parameter makes it possible to exclude measurements of salinity. The authors developed two such new equations for the different cases of using. The first new equa-tion is intended for use in technical applications and reproduces the sea water density in a wide range of the aquatic environment parameters with a root mean square deviation of 0.062 kg/m3. The second more precise new equation is intended for scientific applications and reproduces the sea water density in a narrower oceanographic range of parameters with a root mean square devi-ation of 0.0018 kg/m3.

Coupled influence of strain rate and heterogeneous fibre orientation on the mechanical behaviour of short-glass-fibre reinforced polypropylene

Short-fibre-reinforced thermoplastic polymers (SFRT) are appealing materials for use in technical applications, due to high rigidity/density ratio, in particular. However, SFRT have complex anisotropic mechanical behaviour, because of specificities of thermoplastic matrix behaviour and heterogeneous reinforcement characteristics, in particular in terms of fibre orientation. For instance, matrix behaviour can be viscoelastic and/or viscoplastic (i.e. sensitive to strain rate) pressure sensitive, damageable, etc. Moreover, mechanisms of load transmission from matrix to fibres, at fibre/matrix interface, are still not very well known, although they play a crucial role in SFRT mechanical behaviour. For instance, there is no information about their eventual strain-rate sensitivity. In this study, the 3D microstructure of an injection-moulded short-fibre-reinforced polypropylene is reconstructed using micro-computed tomography. The tensile macroscopic behaviour of the composite is then studied under different angles of loading with respect to injection flow direction and different displacement rates, in quasi-static and dynamic range (from 1mm/min to 1m/s). The anisotropy of the composite behaviour can therefore be analysed not only in terms of dependence on macroscopic loading direction, but also on actual fibre distribution of orientation relatively to tensile direction, at the microscopic scale. In an original way, coupled influence of fibre orientation and strain rate is then studied. One of the most significant results is that fibre/matrix interfacial behaviour, which governs load transmission from matrix to fibres, does not show strain rate sensitivity for the considered composite and strain-rate range (5.10−4 to 50 s−1).

Fabric-Reinforced Cementitious Matrix (FRCM): A New Italian Guideline under Development

In addition toFibre-Reinfocedcomposite materials, which are made of long glass/carbon/aramid fibers embedded in a polymer matrix (FRP), the use ofFRCMcomposites (Fabric-Reinforced Cementitious Matrix) is becoming more and more widespread. As far as this specific case, the inorganic matrix guarantees many advantages, especially when dealing with masonry substrates, including a good compatibility from both a physical and a chemical point of view and the possibility of wet lay-up application. Despite their wide use in technical applications, the constitutive behavior and the failure mechanisms of FRCMs have not been adequately studied. As a consequence, a final assessment upon which criteria have to be used for verification and qualification ofFRCMsis still missing. In the context of a recent experimental program-still under development-cooperated by many Italian academic laboratories, that is aimed at detecting the main features of the constitutive behavior of these materials, a discussion seems to be appropriate on the initial experimental results obtained at Salerno University on manyFRCMspecimens tested under uniaxial tensile loads.

Covering All the Bases: A Martini Coarse-Grained Force Field for DNA

Deoxyribonucleic acid or DNA is not only important as the keeper of our genes but due to its self-recognition properties and programmability it has found use in technical applications like nanostructures, crosslinkers and tethers. One of the tools used to study the conformational dynamics and interactions of DNA are molecular dynamics simulations. DNA is most often simulated using all-atom force fields, which describe the properties of DNA quite well but their computational cost severely limits the number of base pairs and accessible time scales. Coarse-grained models can extend the length and time scales by clustering groups of atoms into single interaction sites. Several coarse-grained DNA models have been developed but few of these are compatible with models for other biomolecules or with common simulation packages. We present a model of DNA using the coarse-grained MARTINI force field that maps roughly four heavy atoms into one interaction site, describes the solvent explicitly and is orders of magnitudes faster than fully atomistic force fields. The DNA model is compatible with all other MARTINI models enabling its use in studying a wide range of biomolecular systems.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Performance assessment of regularly structured Composite Latent Heat Storages for temporary cooling of electronic components

Phase Change Materials (PCM) are very reliable cooling devices. However their low thermal conductivity is a major drawback for the widespread use in technical applications. This paper presents an approach to design Composite Latent Heat Storages (CLHS) combining the PCM with an aluminum frame-structure for transport of thermal energy. These new designs require a generalized assessment taking varying compositions into account.Thus different assessment parameters are presented based on material properties, heat storage composition and the transient thermal behavior. The material properties depend on the PCM, while the heat storage composition depends on the geometry and determines the systems weight. The transient assessment is based on FEM-simulations and shows the performance with respect to idealized reference heat storages. This allows the performance assessment of CLHS of different sizes and compositions with respect to important boundary conditions like volume or mass, that depend on the application.

Mechanical properties of natural fiber hybrid composites based on renewable thermoset resins derived from soybean oil, for use in technical applications

AbstractNatural fiber composites are known to have lower mechanical properties than glass or carbon fiber reinforced composites. The hybrid natural fiber composites prepared in this study have relatively good mechanical properties. Different combinations of woven and non‐woven flax fibers were used. The stacking sequence of the fibers was in different orientations, such as 0°, +45°, and 90°. The composites manufactured had good mechanical properties. A tensile strength of about 119 MPa and Young's modulus of about 14 GPa was achieved, with flexural strength and modulus of about 201 MPa and 24 GPa, respectively. For the purposes of comparison, composites were made with a combination of woven fabrics and glass fibers. One ply of a glass fiber mat was sandwiched in the mid‐plane and this increased the tensile strength considerably to 168 MPa. Dynamic mechanical analysis was performed in order to determine the storage and loss modulus and the glass transition temperature of the composites. Microstructural analysis was done with scanning electron microscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Weaving of 3D fabrics: A critical appreciation of the developments

The paper critically reviews the various developments that have taken place in the area of weaving 3D fabrics. Various methods have been evolved and each is unique in its own way. Each method is suited for specific end use applications. Thus, fabrics could be woven with different structures and profiles to fit specific requirements. The unique features of each method have been highlighted. The major differences between the 2D and 3D methods of weaving have been pointed out. 3D fabrics could be manufactured on the 2D conventional weaving machines with certain modifications. The 3D fabrics are basically intended for use in technical applications. Fabrics could be produced with special profiles and shapes to cater to specific applications. Methods have been evolved for producing 3D fabrics to be used as advanced composite preforms, by weaving on a conventional loom by modifying the shedding and take–up devices. Yet another interesting recent development is the utility of the 3D weaving concept to produce bifurcated vascular prosthesis.

Surfaces and their representation and approximation for technical applications

Surfaces have a wide use in technical applications, computer graphics, engineering, CAD systems as well as in many other fields. One of the biggest problems is how to represent or approximate surfaces for these applications. In this paper we show that some of them can be obtained as an envelope surface of a one-parametrical set of surfaces. This set of surfaces can be generated by moving and transforming one surface. Then, the envelope is the boundary of the union of a set of surfaces. We present many examples and pictures. Unfortunately, most of the surfaces used in applications are not easy to generate in such an exact form; it is necessary to use some approximations. Skin surfaces and approximations by them is a good choice for some problems. We deal briefly with the theoretical part and then introduce an algorithm for smooth patches generating.

Ultrasonic cleaning of submerged membranes for drinking water applications

Ultrasonic cleaning of membranes used in water purification and waste water treatment is under investigation for avoiding fouling and scaling on the membranes. So far chemicals are used, but their use is under scrutinity for safety, waste removal and health issues. Chemicals often even do not solve the cleaning problem durably. For applications in the part of drinking water treatment it is necessary to ensure the filtered water is really clean. Therefore in the presented experiment the outflow is constantly controlled by turbidity measurements and by using a particle counter in an online system. A pilot plant for sonication of submerged membranes to produce drinking water from surface water was constructed and placed at the Rhine water works in Biebesheim. It could be shown that sonication with 130 kHz when backflushing the membranes only works with following air overflow. Then the permeability keeps high. No damage of the membranes occurs like often has been found in former studies. Only 30 seconds of sonication after 30 min of filtration are enough to keep high performance of the membranes. Thus energy demand is low, which is a pre-condition for an economical use in technical applications.