In this study, we aim to examine the effect of company and auditor characteristics on the issuance of going-concern opinions. The study population encompasses all financially distressed manufacturing ...companies listed on the Vietnam Stock Exchange during 2010-2019. The results indicate that the financial condition, incurring loss, audit report delay, and frequency of the board of director meetings significantly influence the issuance of auditors' going-concern opinions. Company size, auditor size, and other financial ratios such as return on asset, leverage, and liquidity have no significant impact on the going-concern audit opinions. This study contributes to the limited research on going-concern audit opinions in the context of Vietnam. The results also provide a basis for recommendations to both auditors and audit clients on the determinants of going-concern audit opinions.
This paper’s primary goal is to examine the influence of a firm’s capital structures on practices of accrual-based earnings management by doing empirical research covering 51 non-financial Vietnamese ...listed companies during a period from 2013 to 2022. To estimate accrual-based earnings management practices, the modified Dechow and Dichev (2002) model was mobilized. Then, a regression between earnings management estimated values based on accruals and a group of capital structure variables and control variables that are hypothesized to influence earnings management practices is performed. The feasible generalized least square model is used to address econometric issues. Empirical results reveal that activities for managing accrual-based earnings indicate a considerable adverse influence from institutional ownership. However, other hypothesized variables that are management ownership, ownership concentration, foreign ownership, and leverage do not have a determinant sign as expected. ROA, one of five control factors, has a favorable impact on accrual-based earnings management practices, whereas company size has a negative impact. The study provides useful information to investors and stakeholders for their making investment decisions in Vietnam. The empirical findings are also based for recommendations to control earnings management practices at Vietnamese listed enterprises to enhance accounting information quality, thus contributing to the sustainable development of the Vietnam Stock Exchange.
In this study, ZnO‐doped carbon aerogel is synthesized from cellulose in coconut peat with sodium alginate as a binder via both freeze‐drying and pyrolysis processes. Of those, zinc nitrate is used ...as not only a crosslinking agent to form gel but also a precursor source to dope ZnO in the carbon aerogel matrix. The effect of precursor ratios on the characterization and energy storage capacity of composite aerogel is investigated. As a result, it is indicated that the formed ZnO‐doped carbon aerogel possesses a highly porous structure which is typical for aerogel structure shown by SEM images, density, and porosity. Besides, via the XRD patterns, the confirmation of the ZnO crystal structure is found within the carbon aerogel lattice. In terms of energy storage, based on the specific capacitance results, the ZCA‐4 sample with a sodium alginate and cellulose weight ratio of 1:20 shows the best energy storage with a specific capacitance of 105 F/g in the voltage range of 0–0.5 V and scan‐rate speed of 0.005 V. Therewithal, the ZCA‐4 also performs high durability, high scanning speed tolerance, and stable storage performance with efficiency reaching more than 99% after 500 consecutive scan cycles. These results demonstrate that the ZnO‐doped carbon aerogel has potential applications as electrode materials in supercapacitors.
Adsorption characteristics of the antibiotic meropenem on a novel magnetic material synthesized by surface coating cobalt iron oxide (CFO) with gold nanoparticles (AuNPs) were systematically ...investigated. The AuNPs can enhance material adsorption capacity by having high affinity towards the thioether and amine groups in the meropenem structure. Au coverage on the CFO surface decreased the saturation magnetization from 55.8 emu/g to 48.8 emu/g, still allowing synthesized CFO@Au nanomaterials to be magnetically recoverable. The CFO@Au nanomaterials showed enhanced adsorption capacity of 25.5 mg/g at optimum conditions of pH 4.0 adsorption time 120 min, and adsorbent mass 0.05 g. Adsorption equilibrium was in accordance with a monolayer Langmuir isotherm, while the adsorption kinetics followed pseudo-first-order kinetics and intraparticle diffusion models. This work provides a simple method to prepare a magnetic composite material with high adsorption efficiency for meropenem and probably other thioether-containing substances.
In this study, Cu-doped ZnO nanomaterials were fabricated by the sol–gel method using the extract of
Piper chaudocanum
L. leaves and the mixture of Zn (II) and Cu (II) salts. The Cu-doped ZnO ...nanomaterials changed from the Zn
1−x
Cu
x
O solid solution into the ZnO/CuO nanocomposites with increasing Cu content from 1 to 10%. The monodisperse particles agglomerate into a block; the pyramidal blocks tent to form a longer and narrower in width at high Cu content with increasing porosity and adsorption sites. The pH
pzc
of ZSCu10 was about 8.8. The Cu (II) adsorption increased with increasing the Cu content while the optimum conditions were found to be pH 7; adsorption time 120 min and adsorption efficiency at 1.0 g/l ZSCu10 or 10 ppm Cu (II) reached about 99%. The adsorption isotherms were fitted well with the Langmuir model while adsorption kinetics followed pseudo-second-order.
To analyze hard turning performance characteristics, a new mathematical model was developed for the hard turning process, and cutting force (CF), another important response for cutting machining, was ...also studied in the present work. The analysis of the mathematical model and experimental results revealed that thrust force (Fy) was the largest, followed by tangential force (Fz) and feed force (Fx). The resultant CF was most influenced by inclination angle (IA) with 25.02%, followed by rake angle (RA) (14.26%) and cutting edge angle (CEA) (10.04%). Increasing CEA changed the position of cutting on the tool-nose radius and increased local negative RA and correspondingly local clearance angle (CA). Meanwhile, increasing negative RA and IA resulted in larger local negative RA and CA. Moreover, local RA and local CA were the main geometric factors affecting surface roughness (SR), tool wear (TW), and CF. Increasing local negative RA resulted in higher SR and CF. In contrast, increasing local CA resulted in lower SR, TW, and CF. Under specific conditions, the positive effects of the local CA overcame the negative effects of the local negative RA, leading to a simultaneous decrease in SR and TW. The proposed novel mathematical model can be further applied to calculate local CF, cutting temperature, and TW for each cutting-edge element, to analyze and optimize the hard turning process.
The study proposes a framework combining machine learning (ML) models into a logical hierarchical system which evaluates the stability of the sheet wall before other predictions. The study uses the ...hardening soil (HS) model to develop a 200-sample finite element analysis (FEA) database, to develop the ML models. Consequently, a system containing three trained ML models is proposed to first predict the stability status (random forest classification, RFC) followed by 1) the cantilever top horizontal displacement of sheet wall (artificial neural network regression models, RANN1) and 2) vertical settlement of soil (RANN2). The uncertainty of this data-driven system is partially investigated by developing 1000 RFC models, based on the application of random sampling technique in the data splitting process. Investigation on the distribution of the evaluation metrics reveals negative skewed data toward the 1.0000 value. This implies a high performance of RFC on the database with medians of accuracy, precision, and recall, on test set are 1.0000, 1.0000, and 0.92857, respectively. The regression ANN models have coefficient of determinations on test set, as high as 0.9521 for RANN1, and 0.9988 for RANN2, respectively. The parametric study for these regressions is also provided to evaluate the relative insight influence of inputs to output.
The main purpose of this study is to investigate the influence of tool geometry (cutting edge angle, rake angle, and inclination angle) and to optimize tool wear and surface roughness in hard turning ...of AISI 1055 (52HRC) hardened steel by using TiN coated mixed ceramic inserts. The results show that the inclination angle is the major factor affecting the tool wear and the surface roughness in hard turning. With the increase in negative rake and inclination angles, the tool wear decreases, and the surface roughness increases. However, the surface roughness will decrease when the inclination angle increases to overpass a certain limit. This is a new and significant point in the research of the hard turning process. From this result, the large negative inclination angle (λ = −10°) should be applied to reduce the surface roughness and the tool wear simultaneously. With the optimal cutting tool angles in the research, the hard machining process is improved remarkably with decreases of surface roughness and tool wear 8.3% and 41.3%, respectively in comparison with the standard tool angles. And the proposed tool-post design approach brings an effective method to change the tool insert angles using standard tool-holders to improve hard or other difficult-to-cut materials turning quality.
•High stability of PDADMAC-AuNPs solutions with time, pH, high salt concentrations.•Spherical structure of AuNPs with particle size ranging from 8 to 15 nm.•Linear increase of maximum absorption at ...520 nm with cysteine concentration.•Wide linear range from 5.0 × 10-7 to 1.5 × 10-4 M, very low LOD of 8.8 × 10-8 M.•Selective towards different cations, anions, acid amines and vitamins.•Successfully applied for the determination of cysteine in real drugs samples.
Positively charged and stable gold nanoparticles (AuNPs) with particle size of 8–15 nm were successfully synthesized from HAuCl4 solution via reduction by sodium borohydride (NaBH4) using a strong polycation, polydiallyldimethylammonium chloride (PDADMAC), as stabilizing agent. The stability of AuNPs was greatly enhanced by the capping of polymer; solutions were stable for at least 2 months and hardly affected by environmental factors such as pH, presence of strong electrolytes such as NaCl, and inorganic ions. A simple colorimetric method for detecting cysteine was developed, based on the strong interaction of the thiol groups of Cys with gold surfaces. In the presence of cysteine, the PDADMAC-AuNPs solution gave a linear increase of the maximum absorption at 520 nm with cysteine concentration. Under optimum conditions of pH 4, incubation time 7 min, 10-2 M NaCl and 10-4 M Cu2+, the method achieved a wide linear range from 5 × 10-7 to 1.5 × 10-4 M, a low limit of detection (LOD) of 8.8 × 10-8 M, and high precision (RSD less than 5%). High selectivity for cysteine over glutathione, some vitamins and other amino acids is demonstrated. The method was successfully applied for the determination of cysteine in real pharmaceutical samples.
The term of audit expectation gap (AEG) was created nearly 50 years ago and has received the attention of many researchers. Despite a lot of research on AEG, the method of measuring AEG remains ...controversial. The number of studies which propose the method of measuring AEG is limited and there are many problems when applying these methods in empirical studies. Inherited from previous studies, this paper aims to develop a new method of measuring AEG and proves it by the results from the application of this method in empirical research in Vietnam. The article achieves two important results: (1) Proposing a new method of measuring AEG based on the Porter’s definition and structure of AEG; and (2) Proving the results from the application of the new method for measuring AEG by conducting empirical research in Vietnam.
PDF
