Structural Analysis Techniques Research Articles

Fabrication of B–CuO nanostructure and B -CuO/rGO binary nanocomposite: A comparative study in the context of photodegradation and antimicrobial activity assessment

This paper reports the synthesis of a cost-effective, stable, and reproducible Boron-doped copper oxide (B–CuO)/Reduced graphene oxide (rGO) binary nanocomposite. A conventional wet chemical synthetic route was used to fabricate the binary nanocomposite. X-ray diffraction (XRD) studies were performed to check the phase purity and crystallinity, scanning electron microscopic (SEM) technique for structural and morphological analysis, energy dispersive spectroscopy (EDX) for surface composition, and Fourier transform infrared spectroscopy (FT-IR) for functional group identification. The experimental results confirmed the formation of the pure nanocomposite. The photocatalytic activity of B–CuO and B–CuO/rGO binary nanocomposite was tested for Methylene blue (MB) dye degradation under sunlight. The B–CuO/rGO binary nanocomposite exhibited improved photocatalytic competence (98%) as compared to B–CuO (85%) in 90 minutes. The antimicrobial activity was measured against four bacterial strains viz. Escherichia coli (E.Coli), Bacillus amyloliquefaciens (B. amyloliquifaciens), Pseudomonas putida (P. putida), Bacillus subtilis (B. subtilis) and one fungal strains Rhizoctonia solani (R. solani). The minimum inhibitory concentration (MIC) was also calculated and it was found that B–CuO/rGO binary nanocomposite exhibited an excellent MIC of 62.2 μg/mL, against the gram-negative E. Coli.

Bimetallic-Derived Catalytic Structures for CO2-Assisted Ethane Activation.

ConspectusIn recent years, the simultaneous upgrading of CO2 and ethane has emerged as a promising approach for generating valuable gaseous (CO, H2, and ethylene) and liquid (aromatics and C3 oxygenates) chemicals from the greenhouse gas CO2 and large-reserved shale gas. The key challenges for controlling product selectivity lie in the selective C-H and C-C bond cleavage of ethane with the assistance of CO2. Bimetallic-derived catalysts likely undergo alloying or oxygen-induced segregation under reaction conditions, thus providing diverse types of interfacial sites, e.g., metal/support (M/M'Ox) interface and metal oxide/metal (M'Ox/M) inverse interface, that are beneficial for selective CO2-assisted ethane upgrading. The alloying extent can be initially predicted by cohesive energy and atomic radius (or Wigner-Seitz radius), while the preference for segregation to form the on-top suboxide can be approximated using the work function, electronegativity, and binding strength of adsorbed oxygen. Furthermore, bimetallic-derived catalysts are typically supported on high surface area oxides. Modifying the reducibility and acidity/basicity of the oxide supports and introducing surface defects facilitate CO2 activation and oxygen supplies for ethane activation.Using in situ synchrotron characterization and density functional theory (DFT) calculations, we found that the electronic properties of oxygen species influence the selective cleavage of C-H/C-C bonds in ethane, with electron-deficient oxygen over the metal (or alloy) surface promoting nonselective bond scission to produce syngas and electron-enriched oxygen over the metal oxide/metal interface enhancing selective C-H scission to yield ethylene. We further demonstrate that the preferred structures of the catalyst surfaces, either alloy surfaces or metal oxide/metal inverse interfaces, can be controlled through the appropriate choice of metal combinations and their atomic ratios. Through a comprehensive comparison of experimental results and DFT calculations, the selectivity of C-C/C-H bond scission is correlated with the thermodynamically favorable bimetallic-derived structures (i.e., alloy surfaces or metal oxide/metal inverse interfaces) under reaction conditions over a wide range of bimetallic catalysts. These findings not only offer structural and mechanistic insights into bimetallic-derived catalysts but also provide design principles for selective catalysts for CO2-assisted activation of ethane and other light alkanes. This Account concludes by discussing challenges and opportunities in designing advanced bimetallic-derived catalysts, incorporating new reaction chemistries for other products, employing precise synthesis strategies for well-defined structures with optimized site densities, and leveraging time/spatial/energy-resolved in situ spectroscopy/scattering/microscopy techniques for comprehensive structural analysis. The research methodologies established here are helpful for the investigation of dynamic alloy and interfacial structures and should inspire more efforts toward the simultaneous upgrading of CO2 and shale gas.

Inactivation mechanisms of influenza A virus under pH conditions encountered in aerosol particles as revealed by whole-virus HDX-MS.

Multiple respiratory viruses, including influenza A virus (IAV), can be transmitted via expiratory aerosol particles, and aerosol pH was recently identified as a major factor influencing airborne virus infectivity. Indoors, small exhaled aerosols undergo rapid acidification to pH ~4. IAV is known to be sensitive to mildly acidic conditions encountered within host endosomes; however, it is unknown whether the same mechanisms could mediate viral inactivation within the more acidic aerosol micro-environment. Here, we identified that transient exposure to pH 4 caused IAV inactivation by a two-stage process, with an initial sharp decline in infectious titers mainly attributed to premature attainment of the post-fusion conformation of viral protein haemagglutinin (HA). Protein changes were observed by hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) as early as 10 s post-exposure to acidic conditions. Our HDX-MS data are in agreement with other more labor-intensive structural analysis techniques, such as X-ray crystallography, highlighting the ease and usefulness of whole-virus HDX-MS for multiplexed protein analyses, even within enveloped viruses such as IAV. Additionally, virion integrity was partially but irreversibly affected by acidic conditions, with a progressive unfolding of the internal matrix protein 1 (M1) that aligned with a more gradual decline in viral infectivity with time. In contrast, no acid-mediated changes to the genome or lipid envelope were detected. Improved understanding of respiratory virus fate within exhaled aerosols constitutes a global public health priority, and information gained here could aid the development of novel strategies to control the airborne persistence of seasonal and/or pandemic influenza in the future. IMPORTANCE It is well established that COVID-19, influenza, and many other respiratory diseases can be transmitted by the inhalation of aerosolized viruses. Many studies have shown that the survival time of these airborne viruses is limited, but it remains an open question as to what drives their infectivity loss. Here, we address this question for influenza A virus by investigating structural protein changes incurred by the virus under conditions relevant to respiratory aerosol particles. From prior work, we know that expelled aerosols can become highly acidic due to equilibration with indoor room air, and our results indicate that two viral proteins are affected by these acidic conditions at multiple sites, leading to virus inactivation. Our findings suggest that the development of air treatments to quicken the speed of aerosol acidification would be a major strategy to control infectious bioburdens in the air.

Incorporating self-employed maintainers into WEEE formal recycling system: A system dynamic approach

The establishment and operation of a formal recycling system for waste electrical and electronic equipment is an important measure to reduce environmental hazards and improve the recycling of resources, but how to incorporate self-employed maintainers into the system has formed an important research gap. Based on the perspective of extended producer responsibility, we argue that self-employed maintainers are required to assume the corresponding environmental responsibility for the environmental externality caused by informal maintenance activities. Using qualitative structural analysis techniques of system dynamics approach with quantitative simulation analysis techniques, we construct an incentive model for self-employed maintainers’ participation in formal recycling system, based on which we propose four incentive strategies. A simulation analysis is further conducted by using the case of waste mobile phones recycling in Qingdao to verify the effectiveness of our incentive model and strategies.

Barriers to Tourism Travel Service Business Cooperation with Pioneering Tourism Villages in Tabanan Regency

Tourism villages in Bali Province have reached 37.26% of the existing villages and only 2 are in the independent category. Tabanan Regency has a number of pilot tourism villages and the majority are more than five years old. Obstacles to increasing the status of a tourist village are thought to occur due to the lack of tourists and the ability of managers to cooperate with the tourism industry. Research needs to be done to overcome barriers to the establishment of cooperation between tourism villages and industry. The problems described need to be solved by formulating a strategy. The pilot Tourism Village which is the location of the research focus has great potential but has experienced obstacles. This study aims to: analyze the role of Tourism Travel business(1), barriers to cooperation between tourism travel business and pilot Tourism Village(2), and develop a management strategy of pilot tourism village in Tabanan Regency(3). This study used qualitative descriptive method. The Data was obtained through in-depth interviews with eight experts. Obstacles are described using coding techniques and then strategies are made to overcome them. The strategy was prepared using Intepretive Structural Modeling analysis techniques. The results showed that UPW has a role in assessing cooperation proposals consisting of details of tourist activities offered, equipment required, price details, feed back, matching proposal descriptions, uniqueness, service quality, cleanliness, and safety. Barriers to cooperation occur due to the location of the tourist village, the potential benefits of the formation of cooperation, and tourist interest. The strategies formed to overcome these obstacles are increasing the competence of human resources in Pilot tourism villages, packaging of industry-standard tourism products, accelerating cooperation between tourism villages and the tourism industry. Suggestions in this study is the implementation of a strategy that is in accordance with the strategy model that has been formed.

Protocol for the development of coarse-grained structures for macromolecular simulation using GROMACS.

Coarse-grained simulations have emerged as a valuable tool in the study of large and complex biomolecular systems. These simulations, which use simplified models to represent complex biomolecules, reduce the computational cost of simulations and enable the study of larger systems for longer periods of time than traditional atomistic simulations. GROMACS is a widely used software package for performing coarse-grained simulations of biomolecules, and several force fields have been developed specifically for this purpose. In this protocol paper, we explore the advantages of using coarse-grained simulations in the study of biomolecular systems, focusing specifically on simulations performed using GROMACS. We discuss the force fields required for these simulations and the types of research questions that can be addressed using coarse-grained simulations. We also highlight the potential benefits of coarse-grained simulations for the development of new force fields and simulation methodologies. We then discuss the expected results from coarse-grained simulations using GROMACS and the various techniques that can be used to analyze these results. We explore the use of trajectory analysis tools, as well as thermodynamic and structural analysis techniques, to gain insight into the behavior of biomolecular systems.

Topology optimization of rib patterns for a freeform composite structure

This paper presents an algorithm for the design of efficient and stable composite freeform shell structures. The design workflow combines form-finding, structural analysis, and optimization techniques. To illustrate it, the paper provides a case study of the design and optimization of carbon fiber-reinforced polymer shell. After form-finding of the the initial structural shape, topology optimization was conducted to develop the reinforcing rib pattern to increase its buckling resistance. The use of optimized rib layouts greatly increased the rigidity of the shell, which was confirmed by finite element simulations.[copyright information to be updated in production process]

A novel single-step explicit time integration method based on momentum corrector technique for structural dynamic analysis

In this study, a novel single-step explicit time integration method based on momentum corrector technique is proposed. The algorithmic procedure is formulated using cubic B-spline interpolation and Taylor series expansion. The momentum corrector is introduced to enhance solution accuracy of problems, especially for discontinuous load problems. Through the theoretical analysis of local truncation errors, spectral radius, algorithmic damping and period elongation, several parameter cases are obtained to achieve enhanced accuracy and stability. Numerical examples, including a standard single-degree-of-freedom problem, two discontinuous load problems, a seismic response analysis problem, a wave propagation problem and a nonlinear problem, are tested. The results illustrate the new method achieves high level of accuracy for discontinuous load problems, while simultaneously exhibiting significant accuracy improvement when dealing with other problems.

Probing the RNA Structure of a Satellite RNA of Cucumber Mosaic Virus Using SHAPE Method

Selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) is a widely used technique for RNA structure analysis using N-methylisatoic anhydride (NMIA) treatment that has been proven to be applicable to different types of RNA templates. In this study, we performed the structural analysis of the viral satellite RNA of cucumber mosaic virus TA-Tb (satCMV TA-Tb) using the SHAPE method. In the preliminary experiment, we optimized the protocol of SHAPE method for analyzing satCMV TA-Tb by determining a suitable quantity of template RNA. This optimization effectively reduced the appearance of a large number of intense bands in the NMIA-untreated sample lane, along with a strong overall background signal that prevented the clear elucidation of the RNA structure. SHAPE analysis indicated the presence of non-structured, single-stranded flexible regions throughout satCMV TA-Tb with prominent flexible stretches located around nucleotide positions 145 to 200. The positions of these flexible regions were particularly consistent with a secondary structure of satCMV TA-Tb predicted by mfold software v.2.3, which consisted of five 5′- and 3′-proximal stem-loops and one internal large multi-branched stem-loop. Sequence alignment and secondary RNA structure prediction of other satCMV sequences that are phylogenetically the same group with satCMV TA-Tb also suggested the presence of 5′- and 3′-proximal stem-loop structures. Our data provide the structural basis for elucidating the mechanism by which satCMV TA-Tb regulates the pathogenicity and replication of its helper virus.

Failures of Minimum Variance Analysis in Diagnosing Planar Structures in Space

Minimum variance analysis of the magnetic field (MVAB), among various techniques of planar structure analysis, is most widely used for its numerical simplicity and loose requirements for data. Through a large number of studies based on MVAB, a global picture of the solar wind intermittency has been established. However, the huge discrepancy between the results from MVAB and other techniques like timing/triangulation implies that the uncertainty of MVAB is a crucial issue that is not fully understood. Utilizing Cluster data, we establish a data set comprised of 6752 discontinuities, whose orientations are precisely determined by timing, as a benchmark for testing MVAB. We find that the scatter of the MVAB normals around the timing normal can be reduced by elevating the threshold for the eigenvalue ratio λ 2/λ 3 and narrowing the data window to which MVAB is applied. The misidentification of discontinuities with < 0.4, Δ∣ B ∣/∣ B ∣ < 0.2 as rotational discontinuities (RDs, identified by > 0.4, Δ∣ B ∣/∣ B ∣ < 0.2) is proved to be a major and inherent defect of MVAB, which can occur even when λ 2/λ 3 is large. Such a misidentification process is revealed to be related to a special discontinuity geometry. It also explains the false RD predominance reported by previous studies based on MVAB. Finally, we provide advice for the application of MVAB and discuss the possibility of obtaining the real statistical properties of interplanetary discontinuities by using MVAB.

Construction &amp; Validation of Civic Sense Scale (CSS) in Urdu Language for Pakistani Secondary School Students

Civic sense plays a crucial role in human life. It determines the success and usefulness of a citizen in a society. The civic sense consists of both civic knowledge and civic practices. The students’ civic knowledge or self-perception of civic sense improves their civic practices in the community. This paper describes constructing and validating the Civic Sense Scale (CSS). This scale is prepared to measure students’ civic knowledge and civic practices. Generalized Structural Component Analysis (GSCA) technique is applied in this study. This scale was administered to 1200 Federal Government Educational Institutions students studying in 10th grade in Pakistan. A total of 1196 students out of 1200 students responded to the questionnaire. The data was collected from students through a stratified sampling technique. Both self-perception and civic practices on civic sense consisted of 45 items. There were 23 and 22 items on Civic Sense Scale on self-perception and civic practices, respectively. The reliability indicator Cronbach’s alpha and Rho were observed to be more than 0.7. Likewise, the construct validity, convergent and discriminant validity measures were in acceptable ranges. These show that Civic Sense Scale (CSS) is highly recommended to measure civic sense and its practices in the educational setting. Initially, this study was limited to secondary school students in Federal Government Educational Institutions of Pakistan.

In-droplet hydrogen-deuterium exchange to examine protein/peptide solution conformer heterogeneity.

Many different structure analysis techniques are not capable of probing the heterogeneity of solution conformations. Here, we examine the ability of in-droplet hydrogen-deuterium exchange (HDX) to directly probe solution conformer heterogeneity of a protein with mass spectrometry (MS) detection. Two vibrating capillary vibrating sharp-edge spray ionization (cVSSI) devices have been arranged such that they generate microdroplet plumes of the analyte and D2 O reagent, which coalesce to form reaction droplets where HDX takes place in the solution environment. The native HDX-MS setup has been first explored for two model peptides that have distinct structural compositions in solution. The effectiveness of the multidevice cVSSI-HDX in illustrating structural details has been further exploited to investigate coexisting solution-phase conformations of the protein ubiquitin. In-droplet HDX reveals decreased backbone exchange for a model peptide that has a greater helix-forming propensity. Differences in intrinsic rates of the alanine and serine residues may account for much of the observed protection. The data allow the first estimates of backbone exchange rates for peptides undergoing in-droplet HDX. That said, the approach may hold greater potential for investigating the tertiary structure and structural transitions of proteins. For ubiquitin protein, HDX reactivity differences suggest that multiple conformers are present in native solutions. The addition of methanol to buffered aqueous solutions of ubiquitin results in increased populations of solution conformers of higher reactivity. Data analysis suggests that partially folded conformers such as the A-state of ubiquitin increase with methanol content; the native state may be preserved to a limited degree even under stronger denaturation conditions. The deuterium uptake after in-droplet HDX has been observed to correspond to some degree with peptide backbone hydrogen protection based on differences in intrinsic rates of exchange. The presence of coexisting protein solution structures under native and denaturing solution conditions has been distinguished by the isotopic distributions of deuterated ubiquitin ions.

Association of embryo aneuploidy and sperm DNA damage in unexplained recurrent implantation failure patients under NGS-based PGT-A cycles.

Recurrent implantation failure (RIF) is one of the most common conditions affecting In Vitro Fertilization (IVF)/Intracytoplasmic sperm injection (ICSI) outcomes. Aneuploidy embryos, one of the main types of embryos-related factors, was reported to be a major contributor to RIF. The present study aimed to examine the association between sperm DNA fragmentation index (DFI) and outcomes of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidy (PGT-A) in unexplained RIF patients. This study analyzed 119 couples with unexplained RIF who underwent 119 PGT-A cycles between January, 2017 and March, 2022. The 119 males were divided into 3 groups according to their sperm DFI levels: Group1 (low, DFI ≤ 15%, n = 50), Group2 (medium, 15% < DFI < 30%, n = 41) and Group3 (high, DFI ≥ 30%, n = 28). Sperm DFI was measured by sperm chromatin structure analysis (SCSA) technique. Trophectoderm biopsy on day 5 or 6 were performed with NGS technique. The following outcomes of PGT-A were analyzed and compared: fertilization, good-quality embryos, aneuploidy rate, miscarriage, live birth and newborn defects. The component of aneuploidy embryos was significantly higher in high DFI group (42.71%) than that of medium group (28.39%) and low group (27.80%). The miscarriage rate of high DFI group (27.27%) and medium group (14.29%) is significantly higher than that of low group (0.00%). No significant differences were found regarding fertility, good-quality embryo rate, pregnancy rate, live birth rate or newborn defects among three groups. The sperm DNA damage is associated with blastocyst aneuploidy and miscarriage rate in unexplained RIF cases. Embryo selection by PGT-A and efforts to decrease sperm DFI before IVF/ICSI treatments should be considered for those male patients with high DFI.

Structural transformation and magnetic properties of Co(II) coordination polymers with pyrazole-3,5-dicarboxylate and pyrazine

A two-dimensional (2D) Co(II) coordination polymer with rectangular channel, namely {[Co2(Hpzdc)2(pyz)(CH3OH)(H2O)2]⋅3H2O}n (1) was synthesized under the solvothermal condition (Hpzdc = pyrazole-3,5-dicarboxylate and pyz = pyrazine). Both Co(II) centers exhibit octahedral geometry. The coordinated methanol and all water molecules in 1 can be removed by heating to give rise to the amorphous phase of desolvated 1 (1a). After 1a was immersed in the mixture of water and methanol, a new isostructural {[Co2(Hpzdc)2(pyz)(H2O)3]⋅3H2O}n (2) was obtained. The replacement of water for methanol in 1 leads to an alteration in the intermolecular packing, which gives rise to the color variations. The single-crystal to amorphous to single-crystal transformations accompanied by the color changes were confirmed by single crystal X-ray structure analysis, XRPD, TGA, elemental analysis, and spectroscopic techniques. The magnetic properties of 1 and 2 exhibit the antiferromagnetic interaction and spin–orbit coupling of octahedral high-spin Co(II) ion.

The Perceptions of Elementary School Children toward Problem-Solving Abilities

The objective of this study is to assess the correlation between various factors influencing the problem-solving skills of elementary school students. To achieve this, eight hypotheses were formulated and examined using the General Structural Component Analysis (GSCA) technique. We collected questionnaire responses from 240 elementary school students from diverse locations. Google Forms is used for question creation and administration. The experimental findings validated seven assumptions among the eight anticipated correlations between factors. That is, the teacher's actions affect the learning environment; teachers' actions affect learning motivation; learning motivation affects both learning attitudes and metacognition; learning attitude, metacognition and learning environment all directly affect problem solving abilities. The remaining hypothesis was rejected; metacognition had no effect on problem-solving abilities. Overall, the model explains 59.6% of the variance in the data. The impact of this study has been demonstrated through theoretical and practical implications

Capillary electrophoresis-mass spectrometry for protein analyses under native conditions: Current progress and perspectives.

Native mass spectrometry is a rapidly emerging technique for fast and sensitive structural analysis of protein constructs, maintaining the protein higher order structure. The coupling with electromigration separation techniques under native conditions enables the characterization of proteoforms and highly complex protein mixtures. In this review, we present an overview of current native CE-MS technology. First, the status of native separation conditions is described for capillary zone electrophoresis (CZE), affinity capillary electrophoresis (ACE), and capillary isoelectric focusing (CIEF), as well as their chip-based formats, including essential parameters such as electrolyte composition and capillary coatings. Further, conditions required for native ESI-MS of (large) protein constructs, including instrumental parameters of QTOF and Orbitrap systems, as well as requirements for native CE-MS interfacing are presented. On this basis, methods and applications of the different modes of native CE-MS are summarized and discussed in the context of biological, medical, and biopharmaceutical questions. Finally, key achievements are highlighted and concluded, while remaining challenges are pointed out.

Defining the structure of the epic &lt;em&gt;Khan Kharangui&lt;/em&gt;

The article analyzes the syntagmatic and paradigmatic structure of “Khan Kharangui” as the origin of Mongolian epics. In doing so, through syntagmatic and paradigmatic analysis each meaningful narrative in the epic is traced on the sentence level and consolidated in a chart grouping all these narratives. The theoretical and methodological significance of this study is to demonstrate how to apply the techniques of structural and syntagmatic analysis while studying epic poetry.&#x0D; The manuscripts of “Khan Kharangui” from Okin (Buryatia, Russia) and Kyzyl (Tuva, Russia) as well as “Rinchen” (published in Hungary) and “Tod Üseg” (St. Petersburg, Russia) are known to researchers. It was concluded that all the manuscripts of “Khan Kharangui” are originated from one source, namely from the source written in ancient script tod üseg. Since that source was substantially damaged, the other sources are used in this study. The Okin and the Rinchen manuscripts match almost word for word while the Kyzyl manuscript is more literary both in stylistic and orthographic aspects, but some episodes are rendered in a somewhat more shortened form compared to the former manuscripts. There are slight differences in their size, but they are same in terms of substantive functions and structures.&#x0D; When analyzing the syntagmatic structure of the epic by means of the functions described in Vladimir Propp’s “Morphology of the Folktale”, the following functions are not identified in the epic about Khan Kharangui: branding (J), unrecognized arrival (O), unfounded claims (L), difficult task (M), solution (N), recognition (Q) and exposure (Ex).&#x0D; As for the paradigmatic structure of the epic, it could be analyzed by the method proposed in “The Structural Study of Myth” by Claude Lévi-Strauss. A particular feature in the paradigmatic structure of the epic is that it legitimizes how one ripostes and what the ultimate results will be when the established relationships and attitudes are violated. That is why each column on the left constitutes a premise or condition for the column on the right, and each column on the right becomes a consequence or implication for the left one with respect to the two columns on the right and left in the illustrated chart.

Development of Quantitative Structural Analysis for Crystalline/Amorphous Phase Mixtures by Synchrotron X-ray Total Scattering

A technique for the structural analysis of crystalline and amorphous phase mixtures using X-ray total scattering measurement is developed. The technique extracts the pair distribution function of the amorphous phase by subtracting of that of the crystalline phase from the observed scattering. Li2VO2F, a high-capacity cathode material in lithium-ion batteries, partially forms an amorphous phase upon charging. Applying the technique to the Li2VO2F material, the contribution of the hidden amorphous phase is obtained. Analysis of the pair distribution function of the amorphous phase allows the three-dimensional atomic configurations associated with the material function to be visualized. The structural analysis technique is expected to provide an understanding of the material properties from the viewpoint of the microscopic structure in the amorphous phase, not only of the battery materials but also of any mixtures of crystalline and amorphous phases.

Investigation on nonlinear buckling performance of the optimized wing structure under the realistic flight cases

The nonlinear finite element simulation is a standard technique for structural stability analysis, whereas it still has disadvantages of highly computational cost and poor convergence, especially for the large and complex wing structure. In this paper, nonlinear buckling analysis of a wing structure is performed and focused on the local region that is prone to instability, the boundary conditions of which are determined using the sub-modeling technique and realistic flight conditions of an aircraft. Firstly, the flight envelope is calculated based on the preliminary parameters of a large aircraft. Three typically flight cases of the aircraft are selected and the corresponding aerodynamic loads are achieved. Then, an optimization problem with strength and deformation constraints is defined to minimize the weight of the wing structure under the design limit load. A significant reduction in structural weight is achieved by considering three typically flight cases in the optimization process. Next, linear structural analyses come to a conclusion that the upper skin of the wing butt box located between the inner and outer wings is easy to lose stability. The sub-modeling technique is used to extract the local model of the wing butt box from the global model of the wing structure. A nonlinear buckling analysis is performed on the local model by applying the realistic boundary conditions solved from the global model. The skin depressions produced by buckling are carefully studied. Finally, the wing upper skin is reinforced by assigning the stringers to increase the buckling resistance of the structure. The appearance of the skin depressions is significantly postponed, meanwhile the depth is largely reduced.

PROBLEMS OF COMPUTER STRUCTURAL ANALYSIS AND REINFORCEMENT CALCULATION TECHNIQUES OF REINFORCED CONCRETE RIBBED SLABS

This paper proposes an overview of computer structural analysis and reinforcement calculation techniques of reinforced concrete ribbed slabs that are used in Ukraine. It considers the fundamental hypotheses and assumptions of these techniques and analyzes the possibility of implementation of the building codes’ requirements into automated calculations. Numerical experiments confirm the existence of a relationship between the normal stress distribution pattern in the rib’s cross section and the width of the slab zone, which participates in the rib’s bending. We conclude the need to develop a generalizing methodology of FEM structural analysis for such structures, which could be implemented in modern FEM-analysis packages implementing building information modelling technology (BIM).Design forces in the elements of monolithic ribbed floors are determined taking into account plastic deformations. This approach is based on the assumption of the formation with increasing load in statically indeterminate systems of plastic hinges, each of which leads to a decrease in the static indeterminacy of the system by one degree. The appearance of plastic hinges leads to a redistribution of bending moments, which is calculated using a static or kinematic method. In the general case, the sum of the span moment and half of the support moments for the span of a single-span beam is always equal to the span moment in a similar single-span beam. That is, the ratio of support and span moments does not affect the bearing capacity of the statically indeterminate system as a whole, but only determines the order of formation of plastic hinges.