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The nanocomposite of graphene oxide and silver nanoparticles with uniform particle distribution was successfully green synthesized for bioactive assessment and hydrogen peroxoide electro-sensing application.

In this study, selenium microparticles (SeMPs) were green-synthesized by utilizing the Terminalia catappa leaves extract as an effective reducing agent. SeMPs were then decorated onto graphene oxide (GO) with the assistance of ultrasound using the ex-situ technique to obtain the SeMPs-GO composite. SeMPs and SeMPs-GO were thoroughly characterized with modern analytical methods, whereas the antibacterial performance of the composites was evaluated via the optical density method. Particularly, SeMPs-GO held up an inhibition of 99 % against both Gram-positive and Gram-negative bacteria strains as well as restrained 50 % of fungal activity. SeMPs-GO was additionally incorporated onto chitosan (CTS) to collect the SeMPs-GO/CTS membrane which was characterized by similar advanced analysis methods. The antibacterial property of the membrane was determined by the inhibition zone diameter. Furthermore, the membrane exhibited good thermal and mechanical characteristics, showing no sign of degradation at a temperature below 260 °C, and a tensile strength of 38 N/mm

In this study, silver immobilizing onto graphene oxide (Ag/GO) was synthesized by the in-situ method. Subsequently, silver immobilizing reduced graphene oxide cotton fabric (Ag/rGO/cotton) was made by the dip-coating method in Ag/GO suspension followed by the chemical reduction with the presence of vitamin C as an environmentally friendly reducing agent. The characteristics of Ag/GO, Ag/GO/cotton, and Ag/rGO/cotton were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscope, and energy-dispersive X-ray spectroscopy. The results showed that AgNPs were uniformly distributed on the surface of GO sheets with an average size of 10–15 nm. Regarding Ag/rGO/cotton, the fiber surface was evenly covered by Ag/rGO materials. Besides, there was no significant difference between the two samples of Ag/GO/cotton and Ag/rGO/cotton, indicating the reduction reaction possessed no effect on the cotton structure. Moreover, the Ag/rGO/cotton also exhibited effective hydrophobicity with a wetting angle of 103.85 ± 0.75 o. The antibacterial performance of Ag/GO, Ag/GO/cotton, and Ag/rGO/cotton against the Gram-positive (Staphylococcus aureus-S. aureus) and Gram-negative (Pseudomonas aeruginosa-P. aeruginosa) bacteria were determined via the diameter zone of inhibition. The results indicated that the appropriate reducing agent is L-ascorbic acid-vitamin C (VC) with the conditions: the VC:Ag/GO mass ratio of 1:1, the reducing temperature of 140 oC, and the reducing time of 120 min showed the highest antibacterial effect against two types of bacteria. All results of the study confirmed that Ag/rGO/cotton possesses significant potential for several antibacterial applications such as protective equipment.

This work is concerned with a mathematical study of backward problem for time-space fractional diffusion equations associated with the observed data measured in Hilbert scales. Transforming the original problem into an operator equation, we investigate the existence, the uniqueness and the instability for the problem. In order to overcome the ill-posedness of the problem, we apply a modified version of quasi-boundary value method to construct stable approximation problem. Using a Holder-type smoothness assumption of the exact solution it is shown that estimates achieve optimal rates of convergence in Hilbert scales both for an a-priori and for an a-posteriori parameter choice strategies.

Khí permeate chủ yếu chứa CO2 (54%) và CH4 (43,6%), có nhiệt trị cao khoảng 16.625 KJ/Nm3 (bằng khoảng 47% nhiệt trị của khí tự nhiên mà Nhà máy Đạm Cà Mau đang sử dụng). Tại Nhà máy xử lý khí Cà Mau, khoảng 36% lượng khí permeate được tận dụng để đốt tại các thiết bị gia nhiệt (heater), còn lại (khoảng 70.000 Sm3/ngày) phải đốt tại đuốc, gây lãng phí lớn về mặt năng lượng. Bài báo đánh giá khả năng sử dụng khí permeate để làm nhiên liệu cho nồi hơi phụ trợ và lò đốt reforming sơ cấp tại Nhà máy Đạm Cà Mau; đề xuất các giải pháp khả thi về kỹ thuật và hiệu quả về kinh tế để thu hồi toàn bộ lượng khí permeate đang được đốt bỏ tại đuốc của Nhà máy xử lý khí Cà Mau.

This is a pre-registration of a scoping review based on the PRISMA Extension for Scoping Reviews (PRISMA-ScR). This scoping review identifies, classifies and examines active control strategies employed to reduce the transmission of airborne noise from heavy or auxiliary equipment used in the construction sector.

We investigate the linear but ill-posed inverse problem of determining a multi-dimensional space-dependent heat source in a time-fractional diffusion equation. We show that the problem is ill-posed in the Hilbert scale H r ( R n ) and establish global order optimal lower bound for the worst case error. Next, we use the Tikhonov regularization method to deal with this problem in the Hilbert scale H r ( R n ) . Locally optimal choices of parameters for the family of regularization operator in the Hilbert scales H r ( R n ) are analyzed by a-priori and a-posteriori methods. Numerical implementations are presented to illustrate our theoretical findings.

In this paper, we focus on the backward diffusion problem with the Caputo fractional derivative operator in time and a general spatial nonlocal operator. For T > 0 and s ∈ [ 0 , T ) , we consider the problem ( P s ) of recovering the distribution u ( x , s ) from a measure of the final data u ( x , T ) for the following non-homogeneous time–space fractional diffusion equation D t α u ( x , t ) + K β L γ u ( x , t ) = f ( x , t ) in R n × ( 0 , T ) subject to the final condition u ( x , T ) = u T ( x ) in R n . The derivative orders and the nonlocal operator are perturbed with noises. Firstly, for 0 s T , we prove the well-posedness of Problem ( P s ) by studying the unique existence and continuity with respect to the derivative orders, the source term as well as the final value of the solution. Secondly, for s = 0 , we verify the ill-posedness of Problem ( P 0 ) and use the method of modified iterated Lavrentiev to construct a regularization solution from inexact data and inexact derivative orders. We apply a modified form of the discrepancy principle to choose regularization parameter and establish new optimal convergence estimates between the exact solution and its regularized approximation.

We study an inverse problem of finding the source Q(x, t) for diffusion equation with space-fractional Laplacian u t ( x , t ) = − μ ( − Δ ) γ u ( x , t ) + Q ( x , t ) ( 0 γ ≤ 1 , μ > 0 , x ∈ R ) from the initial and the final data. Determining the unknown source is to identify the nature of diffusion process and that is one of the most important and well-studied problems in many branches of engineering sciences. This problem must be solved since its result will be used in scientific and technical applications. We limit the severely ill-posed problem to the one of finding Q ( x , t ) = Φ ( t ) S ( x ) with Φ being known. The cases that the variable x is in bounded domains of R n or the differential operator has the divergence form ( − ∇ · ( μ ∇ u ) ) γ with μ = μ ( x , t ) or μ = μ ( x , t , u ) are still not investigated in this paper. The uniqueness and the conditional stability for S are obtained. We apply the Fourier truncation method to construct stable approximation problem and we show the asymptotically optimal estimates for the worst case error of the method. This optimality cannot deduce directly from Tautenhaln’s results. We also establish a general method of a posteriori regularization parameter choice rule which has an error estimate independent of the smoothing parameter of S and, moreover, we prove that the choice rule gives in some cases the best error order ϵ. The μ-depended results show the incremental influent of the diffusivity μ on the optimal choice rules when μ is close to zero.

In this paper, we consider the backward diffusion problem for a space-fractional diffusion equation (SFDE) with a nonlinear source, that is, to determine the initial data from a noisy final data. Very recently, some papers propose new modified regularization solutions to solve this problem. To get a convergence estimate, they required some strongly smooth conditions on the exact solution. In this paper, we shall release the strongly smooth conditions and introduce a stepwise regularization method to solve the backward diffusion problem. A numerical example is presented to illustrate our theoretical result.

Objective:Cinnamic acid and its derivatives have a numerous potential applications in many different fields such as pharmacy, organic “building blocks”, and corrosion inhibitors.Method:It is well-known that Verley-Doebner modification is a high efficient method for the preparation of cinnamic acid derivaties, especially with the compounds containing electron-donating subtituents at para position in aromatic ring. In this paper, 4-ethoxy-cinnamic acid was synthesized according to Verley-Doebner reaction with the use of pyrine acting as catalyst and solvent. The effect of the β-alanine concentration on the conversion of the starting material of 4-ethoxy-benzaldehyde was thoroughly investigated using high performance liquid chromatography. The results showed that consuming of 8% of β-alanine would convert 100% of 4-ethoxy-benzaldehyde to 4-ethoxy-cinnamic acid.Result:The structure of the obtained 4-ethoxy-cinnamic acid was also confirmed using Fourier transform infrared spectroscopy, Raman spectroscopy, and Gas chromatography-Mass spectroscopy.Cinnamic acid and its derivatives have numerous potential applications in many different fields such as pharmacy, organic “building blocks”, and corrosion inhibitors. It is well-known that Verley-Doebner modification is a high efficient method for the preparation of cinnamic acid derivaties, especially with the compounds containing electron-donating subtituents at para position in aromatic ring. In this paper, 4-ethoxy-cinnamic acid was synthesized according to Verley-Doebner reaction with the use of pyrine acting as catalyst and solvent. The effect of the β-alanine concentration on the conversion of the starting material of 4-ethoxy-benzaldehyde was thoroughly investigated using high performance liquid chromatography. The results showed that consuming 8% of β-alanine would convert 100% of 4-ethoxy-benzaldehyde to 4-ethoxy-cinnamic acid. The structure of the obtained 4-ethoxy-cinnamic acid was also confirmed using Fourier transform infrared spectroscopy, Raman spectroscopy, and Gas chromatography-Mass spectroscopy.

In this paper, we deal with the backward problem for nonlinear parabolic equations involving a pseudo-differential operator in the \begin{document}$ n $\end{document}-dimensional space. We prove that the problem is ill-posed in the sense of Hadamard, i.e., the solution, if it exists, does not depend continuously on the data. To regularize the problem, we propose two modified versions of the so-called optimal filtering method of Seidman [T.I. Seidman, Optimal filtering for the backward heat equation, SIAM J. Numer. Anal., 33 (1996), 162–170]. According to different a priori assumptions on the regularity of the exact solution, we obtain some sharp optimal estimates of the Hölder-Logarithmic type in the Sobolev space \begin{document}$ H^q(\mathbb{R}^n) $\end{document}.

In this paper, we reconstruct the solution u(x,t) of the backward space-fractional diffusion problem with a locally Lipschitzian nonlinear source This problem is severely ill-posed in the Hadamard sense, hence, a regularization is in order. In the paper, we introduce one spectral regularization method and establish stability error estimates with optimal order under an a priori choice of regularization parameter. Finally, numerical implementations are given to show the effectiveness of the proposed regularization methods.