Structural Performance of Thin-Walled Twisted Box-Section Structure

The light weight and high strength-to-mass ratio of thin-walled boxed sections have incited interest in their widespread use in the construction of domes. However, the installation of these sections in forming the dome geometry has induced initial twists and curving features, to which their mechanical response has rarely been explored. Therefore, the structural performance of a structure with thin-walled twisted box sections is numerically studied in this paper, employing ANSYS, the verification of which is carried out through a comparison with experimental results. Additional components examined include the longitudinal stiffening rib, diaphragm, and web. The effects of variations in the thicknesses of these member plates on the mechanical behaviors are investigated. In general, the ultimate capacity of the structure is improved by increasing the thickness of the longitudinal stiffening rib, diaphragm, and web, but the strengthening effect of the stiffener is limited by a certain thickness enhancement. The common failure mode of the initial model is found to be an overall elastic-plastic buckling. A reduction in the thickness of the stiffener or web creates a curving deformation zone in the lower arch at the ultimate capacity, whereas the diaphragm thickness has little effect on the failure mode of the model.

Topological optimisation technology of gravity dam section structure based on ANSYS partial differential equation operation

This paper uses the finite element method to explain the specific nature of numerical instability such as network dependence in the topology optimisation of engineering structures from the perspective of partial differential equations. Gaussian function filtering method reduces the global impact of local extremum on topology optimisation. Finally, the method is introduced into the topology optimisation of concrete gravity dams in hydraulic engineering, and the topology optimisation program is developed in conjunction with ANSYS software language to achieve the topology optimisation of building structures in hydraulic engineering from a technical perspective.

Theoretical study on photoemission of double-layer AlxGa1−xAs/GaAs nanocone array photocathode

In the design of photocathode, the internal electric field could be formed due to the graded Al compositional [Formula: see text] nanostructure, which can improve the top surface emission probability of carriers. In this paper, [Formula: see text] nanostructure array photocathode composed of two sub-layers is presented. Based on the finite element method, the influence of graded geometrical parameters on their optoelectronic characteristics is investigated. The results show that when the thickness of the sublayer is equal, the difference of the Al composition between the two sublayers of nanostructure is larger, the sub-layers are less, and the quantum efficiency is higher. The light capture ability of the photocathode can be enhanced by increasing the thickness and the array spacing of the first sublayer. Compared with the hexagonal cross-section structure, the light trapping effect and spectral response of the circular cross-section structure are better.

Barrier Properties and Hydrophobicity of Biodegradable Poly(lactic acid) Composites Reinforced with Recycled Chinese Spirits Distiller’s Grains

Adding natural biomass to poly(lactic acid) (PLA) as a reinforcing filler is a way to change the properties of PLA. This paper is about preparing PLA/biomass composites by physically melting and blending Chinese Spirits distiller’s grains (CSDG) biomass and PLA to optimize the composite performance. Composites of modified PLA (MPLA) with varying amounts of CSDG were also prepared by the melt-mixing method, and unmodified PLA/CSDG composites were used as a control group for comparative analysis. The functional groups of MPLA enhanced the compatibility between the polymer substrate and CSDG. The composite water vapor/oxygen barrier and mechanical properties were studied. It was found that the barrier and mechanical properties of MPLA/CSDG composites were significantly improved. SEM was adopted to examine the tensile section structure of the composites, and the compatibility between the filler and the matrix was analyzed. An appropriate amount of CSDG had a better dispersibility in the matrix, and it further improved the interfacial bonding force, which in turn improved the composite mechanical properties. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were conducted to determine the crystalline properties and to analyze the stability of the composites. It was found that the CSDG content had a significant effect on the crystallinity. Barrier and biodegradation mechanisms were also discussed.

Influence of Polymer Solvents on the Properties of Halloysite-Modified Polyethersulfone Membranes Prepared by Wet Phase Inversion

Ultrafiltration polyethersulfone (PES) membranes were prepared by wet phase inversion. Commercial halloysite nanotubes (HNTs) in the quantities of 0.5 wt% vs. PES (15 wt%) were introduced into the casting solution containing the polymer and different solvents: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), or 1-methyl-2-pyrrolidinone (NMP). The type of solvent influenced the membranes’ morphology and topography, as well as permeability, separation characteristics, and antifouling and antibacterial properties. The membranes prepared using DMA exhibited the loosest cross-section structure with the thinnest skin and the roughest surface, while the densest and smoothest were the DMF-based membranes. The advanced contact angles were visibly lower in the case of the membranes prepared using DMF compared to the other solvents. The highest water permeability was observed for the DMA-based membranes, however, the most significant effect of the modification with HNTs was found for the NMP-based series. Regardless of the solvent, the introduction of HNTs resulted in an improvement of the separation properties of membranes. A noticeable enhancement of antifouling performance upon application of HNTs was found only in the case of DMF-based membranes. The study of the antibacterial properties showed that the increase in surface roughness had a positive effect on the inhibition of E. coli growth.

Technology and specificity of surface seismic in the Upper Kama Potash Salt Deposit

Exploration surveys at the Upper Kama Potash Salt Deposit widely use the surface seismic method by the common reflection point at depth. Based on the implemented research, a technology is developed for shallow seismic using an explosion source of elastic vibrations for the purposes of geological exploration. The research involved the comparative analysis of the main elastic wave sources used in the shallow seismic. It is highlighted that it is important to consider carefully the near-surface section structure and the surface relief. The accuracy of the velocity analysis procedure in the high-velocity section of salt strata is analyzed. The specificity of acquisition in the shallow seismic with an explosion source is discussed. The actual test data show a considerable increment in the energy of reflections from the roof and floor of the salt strata, which, in the absence of a priori geological information and geophysical logging data (acoustic logging and vertical seismic profiling), affects the velocity analysis precision and, as a consequence, the accuracy of reflection identification at depth. It is found that the explosion source has a much higher signal/noise ratio as against a pulse cartridge, which greatly improves neutrality of interpretation results. The use of a pulse cartridge in the surveys in the depth interval of 200–400 m is only justified when the surface conditions are perfect and the low velocity layer is not thick.

Impact of the conjugation construction of the apron section structure with the tailrace on water flow kinematics

Purpose: to determine the impact of the conjugation construction of the apron section structure with the downstream on the water flow kinematics with the use of the performed field and laboratory studies data and their processing. The relevance of this issue lies in the fact that in case of unsatisfactory conjugation of the apron with the discharge canal slopes, negative phenomena are formed in it in the form of faulty currents, whirlpools at the canal slopes, etc., affecting the stability of the apron conjugation, creating a threat to the stability of the structure itself. Materials and Methods: the materials were the data of field studies carried out on a number of hydraulic structures of irrigation systems in Stavropol Territory, as well as on models in laboratory conditions with the identification of the impact of conjugation structures of the apron with the discharge canal slopes on the water flow distribution in tailrace. The measurement of velocities in natural conditions was carried out by observing the integrating floats movement in the discharge canals. On the model, the velocities were measured using a miniflowmeter, and the trajectories were traced using luminous floats. Results: graphs of the dependence of the sought factors on the known parameters were built on the basis of the information obtained, and using the methods of mathematical statistics, the coefficient of the conjugation of the apron structure with the canal slopes in tailrace was obtained. The result of the research was an empirical dependence for determining the flow velocity along its dynamic axis, which is the scientific novelty of the research performed. Conclusions: the type of conjugation of the apron of the structure with the distribution canal slopes has a great influence on the hydraulic flow regime on the apron and in the discharge canal. Each type of conjugation creates a sudden expansion of the flow on the apron, which affects the value of the average flow velocity along the dynamic axis, on which the deformation of the discharge canal depends.

STRATEGI PERCEPATAN PROYEK MENGGUNAKAN METODE CRASH PROGRAM (Studi Kasus : Program Kerja Masa Pengeringan Proyek Rehabilitasi Saluran Induk Klambu Kiri Tahun 2017)

Based on the initial plan from the contract of the Rehabilitation Klambu Kiri’s Project, main channel's work was carried out continously by an open and closed system using the kistdam method. However by the time of execution work, the stakeholders wanted the work in the main channel to be carried out based on cropping pattern, where there a drying period and a drainage period. In this case, flow area and bottom structure of the channel can only be worked during the drying period lasting three months. To be able to determine the impact of these change, a duration calculation is carried out from project's data which are internal's BQ, initial plan's resources, and the relations between activities using Microsoft Project on the flow section structure which be worked in drying period of 2017. The normal duration obtained from analysis is 203 days. It was exceeded time of drying period and possibly could have an impact on the overall project completion schedule resulting in delays, defaults and even termination of contracts. Therefore, it is necessary to have an accelerate strategy of the work on the flow section structure to be completed within a predetermined time. In this study, the acceleration strategy was carried out using crashing analysis in the critical activities from normal duration using Microsoft Project. The crashing method was carried out in stages from the crashing simulation of 30 days, 60 days, to 120 days so that obtained the duration of acceleration was 83 days. The cost component of acceleration is calculated by choosing the lowest cost from the alternatives of increasing work hours (overtime) or by adding resources. From the simulation results, the crash cost to complete the acceleration work is Rp. 1.298.307.591,- or about 2,05% of direct cost, so the efficiency is Rp. 9.692.409,- from normal duration

Characterization and antioxidant capacity of anchovy by-product protein films enriched with rosemary and laurel essential oils

In this study, characterization and antioxidant capacity of anchovy by-product protein (ABP) films with 0.5, 1.0 and 1.5% rosemary (REO) and laurel essential oils (LEO) were investigated. The films with REO and LEO showed higher elongation at break and water vapor permeability (WVP), but lower elastic modulus, transparency, and tensile strength. L* and b* values decreased as a function of essential oil (EO) amount and films became darker and slightly yellowish. The solubility of films with REO and LEO decreased by 10.00-16.05% and 13.84-18.20%, respectively. Intermolecular interaction and molecular organization in the polymer matrix were changed by EO incorporation. Films with EOs showed a nonhomogeneous surface and comparatively smooth cross-section structure providing easy permeation. The antioxidant properties of films were enriched by addition EO and the highest antioxidant capacity was determined in 1.5% LEO film. As a result, although ABP films enriched with EOs have a high WVP, they can be used as packaging material for food products that are susceptible to lipid oxidation.