Coil State Research Articles

Thermally Regulated Flocculation-Coalescence Process by Temperature-Responsive Cationic Polymeric Surfactant for Enhanced Crude Oil-Water Separation

Polymeric surfactants play a crucial role in the flocculation-assisted coalescence process due to their unique bridging effect. However, the steric hindrance induced by their large molecules severely impedes the coalescence of oil droplets. Herein, temperature-responsive polymeric surfactants (quaternary ammonium chitosan-g-PNIPAM, Q-g-PN) with thermally-modulated structure were designed by integrating thermal responsive moieties onto cationic chitosan. The as-prepared Q-g-PN exhibited enhanced oil-water separation efficiency through a thermally regulated flocculation-coalescence process. At low temperatures, the thermal-responsive Q-g-PN remains in a flexible hydrophilic extended state, facilitating the flocculation of dispersed oil droplets through bridging via electrostatic interaction. At high temperatures, the Q-g-PN structure collapses into a hydrophobic coil state, reducing steric hindrance and enhancing hydrogen bonding to asphaltenes, thus effectively promoting oil droplet coalescence. Bottle tests demonstrated that the demulsification performance of Q-g-PN could reach up to 94% with the Q-g-PN concentration only of 0.001wt% via the proposed temperature-regulated flocculation-coalescence process, which was further confirmed by investigating oil droplet behavior and phase transition of Q-g-PN during through molecular dynamic (MD) simulation of the reaction process. This work presents new insights into enhancing oil-water separation efficiency by regulating the flocculation-coalescence process through precise modulation of the molecular interactions between polymer surfactants and emulsion droplets.

The Inter-channel Interference Cancellation Algorithm for Wireless Magnetic Induction MIMO Communication System Based on Zero-forcing Precoding

Abstract The wireless magnetic induction MIMO system can enhance the data transmission rate in near-field magnetic induction communication, but it also suffers from severe inter-channel interference issues. This paper introduces precoding techniques into the wireless magnetic induction MIMO system, employing the zero-forcing precoding algorithm to eliminate interference between different channels. Firstly, leveraging the characteristic that the channel state of magnetic induction transmit-receive coils is determined solely by the physical parameters of the coils, channel estimation is performed to obtain the channel gain matrix for wireless magnetic induction communication. Subsequently, the obtained channel matrix is subjected to zero-forcing precoding to eliminate interference caused by coupling between different channels. Simulation results indicate that the data transmission rate of the wireless magnetic induction MIMO system is significantly higher after applying zero-forcing precoding compared to the rate without it. Additionally, the system’s data transmission rate decreases as the distance between the transmitting and receiving coils increases.

A multi-objective optimization approach to design bistable collapsible tubular mast

The collapsible tubular mast (CTM) is a deployable structure made of two omega shaped shells, with each omega composed of three arc segments. In the bistable CTM (Bi-CTM), in addition to the strain energy well associated with the stable deployed state, another strain energy well can be found corresponding to the stable coiled state. The arcs’ geometries influence the existence of the second strain energy well and the associated stable coiled radius, responsible for the boom’s packaging efficiency. Besides packaging efficiency, factors like bending stiffness are also contingent on the geometries of the arcs, leading to significant trade-offs among these metrics. In this work, we propose a multi-objective optimization (MOO) to find optimal compromises that balance these conflicting requirements of a CTM. Particularly, a coupling analytical models and evolutionary algorithms (EA) technique is presented, utilizing and bench-marking various state-of-the-art EAs. The MOO approach gives as output the Pareto front, a set of the non-dominated design points, which showcases different trade-offs solutions tailorable for specific space-applications. Different design points are presented and discussed based on higher-level considerations.

Molecular-level understanding of membrane fouling formation during ultrafiltration of high-saline organic wastewater: Insights from molecular dynamics simulations

Membrane technology has been prevalently employed to treat high-saline organic wastewater, yet the ongoing hurdle of membrane fouling impedes the advancement and widespread implementation of membrane processes. To date, limited works had been devoted to comprehending the mechanisms of fouling development influenced by high salinity, particularly from the perspective of intermolecular interactions at a deeper level. This work filled the knowledge gap by deciphering the mechanisms underlying humic acid (HA) fouling formation under high salinity mainly using molecular dynamics (MD) simulations, which overcome the spatial scale limitation of traditional experiments and provide new mechanistic insights from the molecular level. The MD results demonstrated that Na+ primarily coordinated and bonded with the carboxyl oxygen and hydroxyl oxygen of HA through Na–O bonds, which reduced the surface charge of HA and solubility in water. Subsequently, HA swiftly migrated and deposited on membrane surface, with the molecular configuration dramatically changed from coiled state to elongated state observed under high salinity. Compared to the scenario without salt, the distribution of HA was found to be more concentrated and closer to the membrane surface, and the position of the lowest free energy decreased significantly from 0.88 nm to 0.5 nm, reflective of complete adsorption occurred. The results of real fouling experiments verified the enhanced fouling formation indeed occurred induced by high salinity, where notable NaCl crystallization appeared on the fouling layer, potentially heightening the porosity and roughness of fouling layer. This work proposed the in-depth HA fouling mechanisms under high-saline conditions from the intermolecular interaction perspective, which should offer theoretical guidance for fouling control when treating high-saline organic wastewater using membrane-based techniques.

Rational design and efficient synthesis of cyclic polymers with visualized molecular topology and unique dielectric properties

Cyclic polymers without chain ends have attracted increasing attention because of the unique physical properties. However, the direct visualization of cyclic topology remains a formidable challenge, because the cyclic chains with flexible backbone or strong intramolecular interaction usually existed in a coiled state rather than cyclic topology. Herein, monocyclic and bicyclic polymers were prepared via blocking-cyclization technique, and the molecular topology of cyclic polymer containing phenyl pendant was directly observed depending on the reduced intrachain entanglement. The structure and characteristics of cyclic polymers were investigated, and the difference between cyclic polymer and linear counterpart was demonstrated. Compared to linear polymer, cyclic polymer exhibited improved dielectric properties, and bicyclic polymer displayed further increased dielectric constant and energy storage density than monocyclic polymer possessing the same repeating units. Therefore, this research presents a facile strategy in the design and construction of cyclic polymers with directly visualized topology and unique dielectric properties.

MR Safety of Inductively Coupled and Conventional Intraoral Coils.

Intraoral coils (IOCs) in magnetic resonance imaging (MRI) significantly improve the signal-to-noise ratio compared with conventional extraoral coils. To assess the safety of IOCs, we propose a 2-step procedure to evaluate radiofrequency-induced heating of IOCs and compare maximum temperature increases in 3 different types of IOCs. The 2-step safety assessment consists of electric field measurements and simulations to identify local hotspots followed by temperature measurements during MRI. With this method, 3 different coil types (inductively coupled IFC, transmit/receive tLoop, and receive-only tLoopRx) were tested at 1.5 T and 3 T for both tuned and detuned coil states. High SAR and regular MRI protocols were applied for 2 coil positions. The measured E field maps display distinct hotspots for all tuned IOCs, which were reduced by at least 40-fold when the IOCs were detuned. Maximum temperature rise was higher when the coils were positioned at the periphery of the phantom with the coil planes parallel to B0. When neither active nor passive detuning was applied, maximum temperature increase of ΔT = 1.3/0.5/1.8 K was found for IFC/tLoop/tLoopRx coils. Hotspots detected by E field measurements, and simulations were consistent. In the simulations, the results were different for homogeneous phantoms compared with full anatomical models. The 2-step test procedure is applicable to different coil types. The results indicate that a risk for radiofrequency-induced heating exists for tuned IOCs, so that adequate detuning circuits need to be integrated in the coils to ensure safe operation.

Adsorption and Structuration of PEG Thin Films: Influence of the Substrate Chemistry.

This study investigates polyethylene glycol (PEG) homopolymer thin film adsorption on gold surfaces of controlled surface chemistry. The conformational states of physisorbed PEG are analyzed through polarization modulation infrared reflection-absorption spectrometry (PM-IRRAS). The PM-IRRAS principle is based on specific optical selection rules allowing the detection of surface-specific FTIR response of thin polymer films on the basis of differential reflectivity at the polymer/substrate interface for p- and s-polarized light. The intensification of the electric field generated at the PEG/substrate interface for p-polarized IR light in comparison with s-polarized light permits the analysis of PEG chain anisotropy and conformational changes induced by the adsorption. Results showed that PEG adsorbs on model substrates having a rather hydrophilic character in a way that the PEG chains spread parallel to the surface. In the case of a very hydrophilic substrate, the adsorbed PEG chains are in a stable thermodynamic state which allows them to arrange and crystallize as stacked crystalline lamellae after adsorption. The surface topography and morphology of the PEG thin films were also investigated by atomic force microscopy (AFM). While in the bulk state, PEG crystallizes in the form of large spherulites; on substrates whose adsorption is favored by surface chemistry, PEG crystallizes in the form of stacked lamellae with a thickness equal to 20 nm. Conversely, on a hydrophobic substrate, the PEG chains do not crystallize and adsorption occurs in the statistical coil state.

Elastic particle model for coil-stretch transition of dilute polymers in an elongational flow

The phenomenon of the ‘coil-stretch’ (C-S) transition, wherein a long-chain polymer initially in a coiled state undergoes a sudden configuration change to become fully stretched under steady elongational flows, has been widely recognized. This transition can display intricate hysteresis behaviours under specific critical conditions, giving rise to unique rheological characteristics in dilute polymer solutions. Historically, microscopic stochastic models and Brownian dynamics simulations have shed light on the underlying mechanisms of the transition by uncovering bistable configurations of polymer chains. Following the initial work by Cerf (J. Chem. Phys., vol. 20, 1952, pp. 395–402), we introduce a continuum model in this study to investigate the C-S transition in a constant uniaxial elongational flow. Our approach involves approximating the unfolding process of the polymer chain as an axisymmetric deformation of an elastic particle. We make the assumption that the particle possesses uniform material properties, which can be represented by a nonlinear, strain-hardening constitutive equation to replicate the finite extensibility of the polymer chain. Subsequently, we analytically solve for the steady-state deformation using a polarization method. By employing this reduced model, we effectively capture the C-S transition and establish its specific correlations with material and geometric properties. The hysteresis phenomena can be comprehended through a force-balance analysis, which involves comparing the externally applied viscous forces with the intrinsic elastic responsive forces. We demonstrate that our model, while simple, unveils rich elastohydrodynamics of the C-S transition.

DNA binding reveals hidden interdomain allostery of a MazE antitoxin from Mycobacterium tuberculosis

Type II toxin−antitoxin (TA) systems are ubiquitously distributed genetic elements in prokaryotes and are crucial for cell maintenance and survival under environmental stresses. The antitoxin is a modular protein consisting of the disordered C-terminal region that physically contacts and neutralizes the cognate toxin and the well-folded N-terminal DNA binding domain responsible for autorepression of TA transcription. However, how the two functional domains communicate is largely unknown. Herein, we determined the crystal structure of the N-terminal domain of the type II antitoxin MazE-mt10 from Mycobacterium tuberculosis, revealing a homodimer of the ribbon-helix-helix (RHH) fold with distinct DNA binding specificity. NMR studies demonstrated that full-length MazE-mt10 forms the helical and coiled states in equilibrium within the C-terminal region, and that helical propensity is allosterically enhanced by the N-terminal binding to the cognate operator DNA. This coil-to-helix transition may promote toxin binding/neutralization of MazE-mt10 and further stabilize the TA–DNA transcription repressor. This is supported by many crystal structures of type II TA complexes in which antitoxins form an α-helical structure at the TA interface. The hidden helical state of free MazE-mt10 in solution, favored by DNA binding, adds a new dimension to the regulatory mechanism of type II TA systems. Furthermore, complementary approaches using X-ray crystallography and NMR allow us to study the allosteric interdomain interplay of many other full-length antitoxins of type II TA systems.

Helix-coil and solvation-induced reentrant nematic-smectic A transitions in a polypeptide solution

ABSTRACT A simple model is introduced to describe re-entrant isotropic-nematic and nematic-smectic A phase transitions mediated helix-coil transition and solvation within individual liquid crystalline semiflexible polymers in a solution. We consider hydrogen bonding between the polymer and solvent molecules (solvation) as an intermolecular interaction and helix-coil transformations of the polymer as an intramolecular interaction. The helix part is rigid and can form nematic and smectic A phases. On the other hand, the solvation prevents liquid crystalline ordering of the polymer chains. At high temperatures, a polymer is in a coiled state without solvation. With decreasing temperatures, solvation and helix-coil transitions compete in the individual semiflexible polymers, and the re-entrant phase transitions occur. We also discuss the chain conformation by calculating Kuhn length.

An In Silico Comparative Study of Eleven Wasp Venom Allergens: An Arena for Therapeutic Approach

Peptide toxins in animals as part of the chemical arsenal for predation and/or protection, and they can also safeguard the host from pathogenic infections. Insects including the hymenopterans generate a battery of toxic bactericidal or bacteriostatic molecules which are small multifunctional, linear peptides that cause pain, have antimicrobial effects, and inflammatory processes . The toxins under the experiment are active against gram-positive, gram-negative bacteria and fungi. The present in silico study aims to predict the physicochemical attributes like molecular weight, theoretical pI, amino acid composition, extinction co-efficient, estimated half-life, instability index, aliphatic index and grand average of hydropathy (gravy) of wasps’ (class: Insecta; order: Hymenoptera) 11 wasp venom allergens through Expasy Protparam & Pepstat software tools. The secondary structures of the toxins were predicted using psi-Blast-based secondary structure prediction GOR4 tools revealing the % α helix, extended β strand, random coil and ambiguous state reflecting a comparative picture of physicochemical parameters of these defensins. 3D Homology modelling of these toxins was accomplished through Swiss-model webserver tool and validated through various in silico tools like ANOLEA, ProSA-web, QMean4 determining Z score, PROCHEK establishing the 3D models of these toxins. Use of Inter Pro, CDD, PROSITE, P fam, Tox DL, PrDOS software predicted the protein family, protein toxicity, protein disorder respectively. Scratch Protein Predictor software tools predicted cysteine – cysteine bonds. Docking of the eleven (11) wasp venom allergens individually with bacterial cell wall component N-acetylglucosamine was done by CB DOCK webserver resulting negative affinity scores reflecting towards the strong binding between the mentioned 11 toxins and N-acetylglucosamine indicating that the mentioned wasps’ toxin molecules might be used as potential antibacterial therapeutic molecules binding to N-acetylglucosamine leading to an avenue to the probable bacterial drug discovery.

Application Of Wasps’ Defensins As Anti-Fungal Therapeutic Molecules: An In Silico Comparative Study

Animal peptide toxins as part of chemical arsenal for predation and/or protection that can safeguard host from pathogenic infections. Hymenopterans generate toxic bactericidal or bacteriostatic molecules, called defensins are small multifunctional, linear, polycationic peptides causing pain, have antimicrobial effects. Defensins are active against gram-positive, gram-negative bacteria and fungi. The present in silico study aims to predict the physicochemical attributes like molecular weight, theoretical pI, amino acid composition, extinction co-efficient, estimated half-life, instability index, aliphatic index and grand average of hydropathy (gravy) of 09 different wasps’ defensins using Expasy Protparam tool. The secondary structures of the toxins were predicted using psi-Blast-based PSIPRED, SOPMA tools revealing % α helix, extended β strand, random coil and ambiguous state reflecting a comparative physico-chemical parameters of these defensins. 3D Homology modelling of these toxins was accomplished through Swiss-model webserver and validated through ProSA-web, QMean4 determining Z score,PROCHEK establishing the 3D models of these defensins. Use of InterPro, CDD, ToxDL, PrDOS software predicted protein family, conserved domain, protein toxicity, protein disorder respectively. CYSCON and CYSPRED tools predicted cysteine-cysteine bonds. Docking of the nine (09) wasps’ defensins individually with fungal cellwall component 1,4 Beta-D-Glucan was done by DockThor webserver resulting negative affinity scores refleting strong binding between the defensins and 1,4 beta-D-Glucan indicating that the mentioned wasps’ defensin molecules might be used as potential antifungal therapeutic molecules binding to 1, 4 Beta-D-Glucan indicating an avenue to antifungal drug discovery.

The human eIF4E:4E-BP2 complex structure for studying hyperphosphorylation.

The cap-dependent mRNA translation is dysregulated in many kinds of cancers. The interaction between eIF4E and eIF4G through a canonical eIF4E-binding motif (CEBM) determines the efficacy of the cap-dependent mRNA translation. eIF4E-binding proteins (4E-BPs) share the CEBM and compete with eIF4G for the same binding surface of eIF4E and then inhibit the mRNA translation. 4E-BPs function as tumor repressors in nature. Hyperphosphorylation of 4E-BPs regulates the structure folding and causes the dissociation of 4E-BPs from eIF4E. However, until now, there has been no structure of the full-length 4E-BPs in complex with eIF4E. The regulation mechanism of phosphorylation is still unclear. In this work, we first investigate the interactions of human eIF4E with the CEBM and an auxiliary eIF4E-binding motif (AEBM) in eIF4G and 4E-BPs. The results unravel that the structure and interactions of the CEBM are highly conserved between eIF4G and 4E-BPs. However, the extended CEBM (ECEBM) in 4E-BPs forms a longer helix than that in eIF4G. The residue R62 in the ECEBM of 4E-BP2 forms salt bridges with E32 and E70 of eIF4E. The residue R63 of 4E-BP2 forms two special hydrogen bonds with N77 of eIF4E. Both of these interactions are missing in eIF4G. The AEBM of 4E-BPs folds into a β-sheet conformation, which protects V81 inside a hydrophobic core in 4E-BP2. In eIF4G, the AEBM exists in a random coil state. The hydrophilic residues S637 and D638 of eIF4G open the hydrophobic core for solvents. The results show that the ECEBM and AEBM may be responsible for the competing advantage of 4E-BP2. Finally, based on our previous work (J. Zeng, F. Jiang and Y. D. Wu, J. Chem. Theory Comput., 2017, 13, 320), the human eIF4E:4E-BP2 complex (eIF4E:BP2P18-I88) including all reported phosphorylation sites is predicted. The eIF4E:BP2P18-I88 complex is different from the existing experimental eIF4E:eIF4G complex and provides an important structure for further studying the regulation mechanism of phosphorylation in 4E-BPs.

Bistable Deployable Composite Booms with Parabolic Cross Sections

The stable extended and coiled states of thin-shelled composite booms with parabolic cross sections are investigated in this paper. These conic shapes potentially offer greater stiffness properties when compared to circular cross sections, which is critical for improving the load-bearing performance of deployed booms. Inducing bistability through composite layups in parabolic booms would allow for controllable self-deployment due to a less energetic coiled state when compared to monostable booms. An inextensional analytical model is used to predict the stable coiled diameters of tape spring and collapsible tubular mast (CTM) booms with parabolic cross sections. The parabolic section is discretized into circular segments using biarc spline interpolation, which allows them to be integrated into the strain energy minimization procedure used to obtain the equilibrium states. When the parabolic booms are parametrically compared against circular booms with identical layups, flattened height, and mass, the former are found to generally have better stiffness performance while being less efficient in stowed volume, as evidenced by larger coiled diameters. Analytical coiled diameters and their strain energy are verified with finite element simulations for an optimal parabolic tape spring and CTM booms. Additional validation of the parabolic tape spring’s coiled diameter is provided by experimental measurements of boom specimens.

Conformational and Structural Changes in Chickpea Proteins Caused by Simulated Salivary Alterations in the Elderly.

The impact of salivary alterations on chickpea protein structure in the elderly has not been well documented. This study aimed to understand the role of simulated salivary alterations in the conformational properties and secondary structure of the chickpea protein isolate (CPI). Whey protein isolate (WPI) was used as the reference. Protein dispersions (10%) were subjected to in vitro oral processing under simulated salivary conditions in both the elderly and adult subjects. Proteins and their oral counterparts were characterized in terms of their composition, charge, size, solubility, water absorption, molecular weight (MW), and secondary structure (Circular Dichroism and Raman spectroscopy). Under condition of simulated oral digestion in the elderly population, the ordered secondary protein structure was significantly affected, decreasing α-helix by ~36% and ~29% in CPI and WPI compared to the control (adult) population, respectively. An increase in the unordered random coil state was observed. These results could be attributed to an increase in electrolytes in the salivary composition. The structure of CPI is more stable than that of WPI because of its higher MW, more rigid structure, less charged surface, and different amino acid compositions. This study is meaningful in understanding how alterations in the elderly oral system affect protein conformation and is expected to improve the understanding of plant-based protein digestibility.

Electromagnetic-Actuated Soft Tactile Device Using a Pull–Push Latch Structure

Tactile devices composed of tactile pixels enable dynamic formulation of surface morphological features. It however remains a challenge for soft tactile devices to reliably achieve low-power control of each tactile pixel while maintaining high spatial resolution. In this paper, we proposed a novel pull-push latch structure and developed a programmable electromagnetic-actuated soft tactile device. Each tactile pixel of the device is individually controlled by a coil. The pull-push latch structure is capable of maintaining the pit depth of tactile pixels without energy consumption. By simultaneously controlling the current direction and on-off state of multiple coils, our tactile device with 3 mm spatial resolution can reliably form different tactile patterns. The energy consumption of a single coil is 59.15 mJ in a 6-s work cycle, which is about 0.34% of that of the tactile device without the latch structure. The user study indicates that the average discrimination accuracy of different patterns rendered by our tactile device is greater than 81%.

Analysis and tests of non-uniform wrapping process of tape spring

A tape spring, which has a high ratio of retraction and deployment, is a type of basic deployable member that plays an important role in deployable structures. This paper is focused on the non-uniform wrapping process of a tape spring that the fixed end section preserves the initial shape. A theoretical method is presented to predict the non-uniform wrapping process of a metallic tape spring based on classical theories about the bending behavior of this type of tape spring. There are two possible shapes for a tape spring after the non-uniform wrapping process, namely a polygon or a continuous curve. The boundary lines of the two possible shapes are studied, and it is shown that the shape depends on the radius of the central cylindrical hub. A finite element model is built using the commercial software ABAQUS to verify the reliability of the theoretical model. Experimental measurement is also conducted to record the shape change process of a tape spring. The comparisons of the results of the three different methods show that they are in good agreement with each other, which means that the theoretical model can be used to predict the non-uniform wrapping behavior of the tape spring. Additionally, the behavior of four tape springs during the non-uniform wrapping process is studied, and the results show that the shapes of multiple tape springs in a coiled state correspond to that of a single tape spring.

Hydrophobic Homopolymer's Coil-Globule Transition and Adsorption onto a Hydrophobic Surface under Different Conditions.

Unstructured proteins can modulate cellular responses to environmental conditions by undergoing coil-globule transitions and phase separation. However, the molecular mechanisms of these phenomena still need to be fully understood. Here, we use Monte Carlo calculations of a coarse-grained model incorporating water's effects on the system's free energy. Following previous studies, we modeled an unstructured protein as a polymer chain. Because we are interested in investigating how it responds to thermodynamic changes near a hydrophobic surface under different conditions, we chose an entirely hydrophobic sequence to maximize the interaction with the interface. We show that a slit pore confinement without top-down symmetry enhances the unfolding and adsorption of the chain in both random coil and globular states. Moreover, we demonstrate that the hydration water modulates this behavior depending on the thermodynamic parameters. Our findings provide insights into how homopolymers and possibly unstructured proteins can sense and adjust to external stimuli such as nanointerfaces or stresses.

Preparation and Evaluation of an Elastic Cushion with Waste Bamboo Fiber Based on Sitting Pressure Distribution of the Human Body

Waste bamboo fibers are mostly in a spiral coil state and exhibit a certain degree of elasticity, which has the potential to be used as elastic cushion filler. However, there are few studies on its application to elastic cushions. In order to efficiently use waste bamboo fibers, a bamboo-based elastic cushion (BEC) was prepared and evaluated. The BEC units were prepared by mixing bamboo waste fibers with ES fibers and dividing them into five grades according to elastic modulus. The BECs were arranged with BEC units based on the sitting pressure distribution of the human body and evaluated using objective and subjective methods. The appropriate process of BEC units was a heating temperature of 150 °C, heating time of 50 min, and bamboo proportion of 50~75%.The elastic modulus of units had a clear influence on the sitting pressure distribution of the BEC. With the increasing elastic modulus of BEC units, the maximum pressure and average pressure of the BEC first decreased and then increased, while the contact area showed an opposite trend. Additionally, the comfort rating of the BEC with higher elastic modulus units was higher, and the appropriate elastic modulus range was 0.25~0.40 MPa. The BECs made with units with different elastic moduli increased the comfort rating by 12.8% compared with that with the same units, and the sciatic node was the most sensitive part for humans when sitting on the BEC. The results could provide data support for the application of waste bamboo fibers in elastic cushions.

Реалізація методів розрахунку в спеціалізованій комп’ютерній системі напружено-деформованого і температурного стану рулонів сталевих штаб

Реалізація методів розрахунку в спеціалізованій комп’ютерній системі напружено-деформованого і температурного стану рулонів сталевих штаб