Performance Improvement of a Solar-Powered Recompression Supercritical Carbon Dioxide Cycle by Introducing an Ammonia-Water Cooling-Power System

The wide utilization of solar energy is beneficial for the emission reduction of carbon dioxide. This paper proposes a novel power cycle system driven by solar energy, which consists of a recompression supercritical carbon dioxide cycle (RSCO2) and an ammonia-water cooling-power cycle (ACPC). The power system operates in a “self-production and self-sale” mode, which means that the refrigeration capacity produced by the ACPC is utilized to cool the main compressor inlet fluid of the RSCO2. The comprehensive energy and exergy analyses of the proposed novel system are presented. The effects of the six parameters on the system thermodynamic performance are evaluated, which are direct normal irradiation, the ammonia concentration of a basic solution, the pinch point temperature difference of an evaporator, the effectiveness of a recuperator, the pressure ratio of the RSCO2 and the molten salt outlet temperature. The results show that compared with the stand-alone RSCO2, the net power and energy efficiency of the proposed system are improved by 15.94 and 10.61%, respectively. In addition, the increasing ammonia concentration of the basic solution leads to the rise of the ACPC refrigeration output, and the inlet temperature of the main compressor can be declined to 32.97°C with the ammonia concentration of the basic solution of 0.88. Moreover, when the effectiveness of the recuperator in RSCO2 rises up to 0.98, the system energy and exergy efficiencies can reach their maximum value of 30.68 and 33.10%, respectively.

Selective Chelating Resin for Copper Removal and Recovery in Aqueous Acidic Solution Generated from Synthetic Copper-Citrate Complexes from Bioleaching of E-waste

This research focused on batch experiment using a new generation of chelating resins via an ion exchange process to describe the metabolic adsorption and desorption capacity onto iminodiacetic acid/Chelex 100, bis-pyridylmethyl amine/Dowex m4195, and aminomethyl phosphonic/Lewatit TP260 functional groups in bioleaching. The results showed that Dowex m4195 had the highest performance of adsorption capacity for copper removal in both H+-form and Na+-form. Results for Lewatit TP260 and Chelex 100 revealed lower adsorption performance than results for Dowex m4195. The investigation of desorption from chelating resins was carried out, and it was found that 2 M ammonium hydroxide concentration provided the best desorption capacity of about 64.86% for the H+-form Dowex m4195 followed by 52.55% with 2 M sulfuric acid. Lewatit with 2 M hydrochloric acid gave the best desorption performance in Na+-form while Chelex 100 using hydrochloric at 1 M and 2 M provided similar results in terms of the H+-form and Na+-form. As aspects of the selective chelating resins for copper (II) ions in aqueous acidic solution generated from synthetic copper-citrate complexes from bioleaching of e-waste were considered, H+-form Dowex m4195 was a good performer in adsorption using ammonium hydroxide for the desorption. However, chelating resins used were subsequently reused for more than five cycles with an acidic and basic solution. It can be concluded from these results that selective chelating resins could be used as an alternative for the treatment of copper (II) ions contained in e-waste or application to other divalent metals in wastewater for sustainable water and adsorbent reuse as circular economy.

Stabilization of Dicalcium Silicate-Zn Composite Approaching Layered Double Hydroxide Structure for Bioactive Cement Applications

Layered Double Hydroxide (LDH) is ionic clay that is characterized by the union of metal cations and OH- hydroxides. LDH composites exhibit considerably high releasing and recharging capacity and have applications as bioactive cements. They can be prepared by direct co-precipitation of metal salts at controlled pH. The preparation is carried out from an acid solution of Zn (NO3)2.6H2O, Al (NO3)3.9H2O and a basic solution of Na2CO3 and NaOH, with a Zn/Al ratio = 3, the pH is stabilized between 9 and 9.5 at a constant temperature of 45°C. The objective of this study is to incorporate Zinc and Aluminum elements at different percentages in dicalcium silicate phase to produce C2S phase incorporating LDH composite. The characterizations of the developed phases by XRD and SEM indicate the formation of stoichiometric LDH phases Zn6Al2(OH)16CO3.4H2O and non-stoichiometric Zn0.61Al0.39 (OH)2(CO3)0.195.xH2O, the incorporation of Zn in the belitic C2S phase and not Al. The obtained micrographs by SEM(EDAX) analysis show new morphology of the stabilized composite.

Enhanced Stability of Inactivated Foot-And-Mouth Disease Virus Vaccine With A Novel Solution Buffer.

Objectives: Stability is vital for potency of food-and-mouth disease virus vaccine preparation. However, the assembly of inactivated foot-and-mouth disease virus is poor stable and prone to dissociate into 12s under mild acidic or heating conditions, especially emulsified with oil-adjuvant. Thus, it is crucial to explore a suitable medium and condition to improve the stability and efficiency of inactivated FMDV vaccine. Results: In this study, the basic solution buffer and a serious of potential stabilizers, such as carbohydrate, amino acid, antioxidant, salt and antioxidant were screened for evaluating stable effect on FMDV antigen with aid of high performance size exclusion chromatography (HPSEC). On this basis, orthogonal experiment was performed to optimize and finally confirm the formulation. Anti-aging test were carried out to asses the efficiency of formulation on vaccine stability and the results showed that the vaccine was more stabler either stored at 37℃or 4℃. Moreover, physicochemical monitoring revealed that formulation had no influence on the properties of vaccine. The combined results suggested that the novel solution buffer would lower degradation and prolong shelf life of vaccine. In a word, the novel buffer is beneficial to make FMD vaccine more stable and effective, reducing the dependence on cold delivery and storage. This study also provides insight into the processes of optimization and inactivated vaccine development.

Settlement and Bearing Capacity of Rectangular Footing in Reliance on the Pre-Overburden Pressure of Soil Foundation

This article presents a solution for the quantitative evaluation of the stress–strain state (SSS) and the bearing capacity of rectangular foundations, factoring in the unit weight of the soil mass and different values of pre-overburden pressure (POP). In order to assess the SSS of the soil subgrade below a rigid rectangular footing under a uniformly distributed load, the authors applied the Boussinesq basic solution for an elastic half-space subjected to a vertical point load on its surface. As a result, the formulas for vertical stress, mean stress, shear strain, and volumetric strain for any point in Cartesian coordinates (x, y, z) and foundation settlement were determined. Additionally, the application of Hencky’s system of physical equations, with non-linear dependencies between mean stress and volumetric strain as well as deviator stress and shear strain, along with the experimental curves, depicts the relationships between bulk modulus and volume stress, and shear modulus and shear stress. The authors point out the non-linear behavior of the subgrade soil and propose a method for estimating the bearing capacity of a rigid rectangular foundation.

Solving Linear Programming Problems by Reducing to the Form with an Obvious Answer

The article considers a method for solving a linear programming problem (LPP), which requires finding the minimum or maximum of a linear functional on a set of non-negative solutions of a system of linear algebraic equations with the same unknowns. The method is obtained by improving the classical simplex method, which when involving geometric considerations, in fact, generalizes the Gauss complete exclusion method for solving systems of equations. The proposed method, as well as the method of complete exceptions, proceeds from purely algebraic considerations. It consists of converting the entire LPP, including the objective function, into an equivalent problem with an obvious answer. For the convenience of converting the target functional, the equations are written as linear functionals on the left side and zeros on the right one. From the coefficients of the mentioned functionals, a matrix is formed, which is called the LPP matrix. The zero row of the matrix is the coefficients of the target functional, $a_{00}$ is its free member. The algorithms are described and justified in terms of the transformation of this matrix. In calculations the matrix is a calculation table. The method under consideration by analogy with the simplex method consists of three stages. At the first stage the LPP matrix is reduced to a special 1-canonical form. With such matrices one of the basic solutions of the system is obvious, and the target functional on it is $ a_{00}$, which is very convenient. At the second stage the resulting matrix is transformed into a similar matrix with non-positive elements of the zero column (except $a_{00}$), which entails the non-negativity of the basic solution. At the third stage the matrix is transformed into a matrix that provides non-negativity and optimality of the basic solution. For the second stage the analog of which in the simplex method uses an artificial basis and is the most time-consuming, two variants without artificial variables are given. When describing the first of them, along the way, a very easy-to-understand and remember analogue of the famous Farkas lemma is obtained. The other option is quite simple to use, but its full justification is difficult and will be separately published.

Sustainability of material solutions of modern methods of construction

In the last decade, the construction industry has been going through a technological revolution known as Construction 4.0. This progress has brought digitization, automation, virtual reality, 3D printing and prefabrication to production. Prefabrication is the basic solution of most Modern Methods of Construction (MMC), thanks to which construction is faster, safer, better quality and with a lower impact on the environment. MMC design solutions can include volumetric, panel, hybrid systems, parts and components bat also on-site innovative technologies. From the point of the sustainability, material solutions of MMC are also very important and open the potential for their innovations. The aim of this article is to explore the possibilities of higher use of composite materials and mixtures, preferably with an emphasis on more environmentally friendly and recycled materials.

Multiple Slip Impact on the Darcy–Forchheimer Hybrid Nano Fluid Flow Due to Quadratic Convection Past an Inclined Plane

Nowadays, the problem of solar thermal absorption plays a vital role in energy storage in power plants, but within this phenomenon solar systems have a big challenge in storing and regulating energies at extreme temperatures. The solar energy absorber based on hybrid nanofluids tends to store thermal energy, and the hybrid nanofluids involve the stable scattering of different nano dimension particles in the conventional solvent at a suitable proportion to gain the desired thermophysical constraints. The authors focus on the behavior of the inclined plate absorber panel as the basic solution of water is replaced by a hybrid nanofluid, including Cu (Copper) and Al2O3 (Aluminum Oxide), and water is utilized as a base surfactant in the current investigation. The inclined panel is integrated into a porous surface with the presence of solar radiations, Joule heating, and heat absorption. The fundamental equations of the flow and energy model are addressed with the similarity transformations. The homotopy analysis method (HAM) via Mathematica software is used to explore the solution to this problem. Furthermore, the important physical characteristics of the rate of heat transfer, omission and absorption of solar radiation, and its impact on the solar plant are observed.

Constructing g-C3N4/Cd1−xZnxS-Based Heterostructures for Efficient Hydrogen Production under Visible Light

Two types of photocatalysts, 1%Pt/Cd1−xZnxS/g-C3N4 (x = 0.2–0.3) and Cd1−xZnxS/1%Pt/g-C3N4 (x = 0.2–0.3), were synthesized by varying the deposition order of platinum, and a solid solution of cadmium and zinc sulfides onto the surface of g-C3N4. The characterization of photocatalysts showed that, for 1%Pt/Cd1−xZnxS/g-C3N4, small platinum particles were deposited onto a solid solution of cadmium and zinc sulfides; in the case of Cd1−xZnxS/1%Pt/g-C3N4, enlarged platinum clusters were located on the surface of graphitic carbon nitride. Based on the structure of the photocatalysts, we assumed that, in the first case, type II heterojunctions and, in the latter case, S-scheme heterojunctions were realized. The activity of the synthesized samples was tested in hydrogen evolution from triethanolamine (TEOA) basic solution under visible light (λ = 450 nm). A remarkable increase in hydrogen evolution rate compared to single-phase platinized 1%Pt/Cd1−xZnxS photocatalysts was observed only in the case of ternary photocatalysts with platinum located on the g-C3N4 surface, Cd1−xZnxS/1%Pt/g-C3N4. Thus, we proved using kinetic experiments and characterization techniques that, for composite photocatalysts based on Cd1−xZnxS and g-C3N4, the formation of the S-scheme mechanism is more favorable than that for type II heterojunction. The highest activity, 2.5 mmol H2 g−1 h−1, with an apparent quantum efficiency equal to 6.0% at a wavelength of 450 nm was achieved by sample 20% Cd0.8Zn0.2S/1% Pt/g-C3N4.

Cassava Starch-Based Composite Reinforced with Coconut Mesocarpfibers: Analysis of Physicochemical Stability

In one of our previous articles, we developed a cassava starch material reinforced with coconut mesocarpfibers. Its properties have been evaluated. It appears that the behavior of the composite depends on the atmospheric conditions of exposure. The purpose of this work is to do a more in-depth physicochemical stability analysis. To do this, identical samples were exposed in different chemical environments: basic, saline, acidic and distilled water. The mass losses are measured after 75 days of immersion in the different solutions in three cases: films without addition of lime and fibers, film with the presence of lime and without reinforcements, and finally the composite with lime and fibers. We observe that, in all cases, the loss of mass decreases with the addition of lime and fibers. However, in the basic solution, this decrease is greater (53.4%) while it remains acceptable in a saline environment (1.1%). In short, this material can be used for several applications in the field of packaging such as the preservation of dry salty products.