Coagu-Flocculation Mechanism of Flocculant and its Physical Model

On the basis of summarizing and analyzing the theory of coagu-flocculation and its practical application, this paper proposes a physical model for coagu-flocculation. The model defines the process of coagu-flocculation as three steps: mixing, coagulation and flocculation, though there is no strict distinction in the practical processes themselves. Through experiment, two facts are verified: (1) with organic flocculants mixing and flocculation occur substantially in the same step, and need strong mixing intensity; while with inorganic flocculants much weaker mixing intensity is needed; (2) so as to ensure big floccules are formed, weaker mixing for a certain period of time is required

Periodic Oscillations in a Chemostat Model with Two Discrete Delays

Periodic oscillations of solutions of a chemostat-type model in which a species feeds on a limiting nutrient are considered. The model incorporates two discrete delays representing the lag in nutrient recycling and nutrient conversion. Through the study of characteristic equation associated with the linearized system, a unique positive equilibrium is found and proved to be locally asymptotically stable under some conditions. Meanwhile, a Hopf bifurcation causing periodic solutions is also obtained. Numerical simulations illustrate the theoretical results

Atomistic modeling of resistivity evolution of copper nanoparticle in intense pulsed light sintering process

In this work, the intense pulsed light (IPL) sintering process of copper nanoparticle ink is simulated using molecular dynamics (MD) method. First, the neck size growth between the two copper nanoparticles during the IPL sintering process is computed. The resultant electrical resistivity is then calculated by substituting the neck size into the Reimann-Weber formula. Overall, a rapid decrease of electric resistivity is observed in the beginning of the sintering, which is caused by quick neck size growth, followed by a gradually decrease of resistivity. In addition, the correlation of the simulated temperature dependent resistivity is similar to that of the experimentally measured resistivity. The MD model is an effective tool for designers to optimize the IPL sintering process

Evaluating analytical quality in clinical biochemistry laboratory using Six Sigma

Introduction: In recent years, Six Sigma metrics has become the hotspot in all trades and professions, which contributes a general procedure to explain the performance on sigma scale. Nowadays, many large companies, such as General Healthcare, Siemens, etc., have applied Six Sigma to clinical medicine and achieved satisfactory results. In this paper, we aim to evaluate the process performance of our laboratory by using Sigma metrics, thereby choosing the correct analytical quality control approach for each parameter. Materials and methods: This study was conducted in the clinical chemistry laboratory of Shandong Provincial Hospital. The five-months data of internal quality control were harvested for the parameters: amylase (AMY), lactate dehydrogenase (LD), potassium, total bilirubin (TBIL), triglyceride, aspartate aminotransferase (AST), uric acid, high density lipoprotein-cholesterol (HDL-C), alanine aminotransferase (ALT), urea, sodium, chlorine, magnesium, alkaline phosphatase (ALP), creatinine (CRE), total protein, creatine kinase (CK), total cholesterol, glucose (GLU), albumin (ALB). Sigma metrics were calculated using total allowable error, precision and percent bias for the above-mentioned parameters. Results: Sigma values of urea and sodium were below 3. Sigma values of total protein, CK, total cholesterol, GLU and ALB were in the range of 3 to 6. Sigma values of AMY, uric acid, HDL-C, TBIL, ALT, triglyceride, AST, ALP and CRE were more than 6. Conclusion: Amylase was the best performer with a Sigma metrics value of 19.93, while sodium had the least average sigma values of 2.23. Actions should be taken to improve method performance for these parameters with sigma below 3

COVID-19 shock, financial flexibility, and hotels' performance nexus

[[abstract]]This study investigates the nexus of coronavirus disease 2019 (COVID-19) shock, financial flexibility (FF), and firm performance (FP) in Taiwan listed hotel firms. Quantile regression (QR) methods were used to analyze the data from Taiwan Stock Exchange listed hotel firms between 2020 Q1 and 2021 Q2. The results evidence that there is an inversed U-shaped linkage between FF and FP for the hotel industry. Additionally, FF has an inverted U-shaped effect on FP for the asset-light hotel firms for all quantiles except the 50th quantile. In addition, FF also has an inverted U-shaped impact on FP for the asset-heavy hotel firms in the 10th and 90th quantiles. A significant finding in this study is that there is a concave non-linear relationship between FF and FP, consistent with the law of diminishing marginal return. That is, with an increase in FF, the FP is on the rise; when FF exceeds the inflection point level, the FP begins to decline. Thus, a firm must ensure that the FF strategy it adopts must be the most efficient and effective, i.e., it must bring the trade-off between costs and benefits. The empirical results highlight the need for the hotel industry of Taiwan to take the rolling adjustment and optimization of FF after the COVID-19 pandemic for long-term sustainability.[[notice]]補正完

Nonlinear dynamics of full-range CNNs with time-varying delays and variable coefficients

In the article, the dynamical behaviours of the full-range cellular neural networks (FRCNNs) with variable coefficients and time-varying delays are considered. Firstly, the improved model of the FRCNNs is proposed, and the existence and uniqueness of the solution are studied by means of differential inclusions and set-valued analysis. Secondly, by using the Hardy inequality, the matrix analysis, and the Lyapunov functional method, we get some criteria for achieving the globally exponential stability (GES). Finally, some examples are provided to verify the correctness of the theoretical results

Tensile, Creep, and Fatigue Behaviors of 3D-Printed Acrylonitrile Butadiene Styrene

Acrylonitrile butadiene styrene (ABS) is a widely used thermoplastics in 3D printing. However, there is a lack of thorough investigation of the mechanical properties of 3D-printed ABS components, including orientation-dependent tensile strength and creep fatigue properties. In this work, a systematic characterization is conducted on the mechanical properties of 3D-printed ABS components. Specifically, the effect of printing orientation on the tensile and creep properties is investigated. The results show that, in tensile tests, the 0° printing orientation has the highest Young’s modulus of 1.81 GPa, and ultimate strength of 224 MPa. In the creep test, the 90° printing orientation has the lowest k value of 0.2 in the plastics creep model, suggesting 90° is the most creep resistant direction. In the fatigue test, the average cycle number under load of 30 N is 3796 cycles. The average cycle number decreases to 128 cycles when the load is 60 N. Using the Paris law, with an estimated crack size of 0.75 mm, and stress intensity factor is varied from 352 to 70

Study on the technology and properties of 3D bioprinting SF/GT/n-HA composite scaffolds

In this paper, three kinds of natural polymer materials, silk fibroin (SF), gelatin (GT), and nano-hydroxyapatite (n-HA), are mixed as 3D printing bioink to mimic protein polysaccharide and collagen fibers in natural articular cartilage. By changing the SF content, SF/GT/n-HA composite scaffolds with different ratios are prepared using 3D bioprinting technology. The microstructure and morphology, biological properties and mechanical properties of composite scaffolds are characterized. The results show that the printing precision of the bioink with 10% SF is best, and the composite scaffold with 10% SF also exhibits better mechanical properties, whose tensile elastic modulus is 10.60 ± 0.32 MPa and the compression elastic modulus is 1.22 ± 0.06 MPa. These studies are helpful to understand the interaction between SF, GT and n-HA, and provide a theoretical basis for the preparation of better silk fibroin-based composite scaffolds

Breaking the Property Trade-Offs by Using Entropic Conceptions

Entropic conception has been used as an effective strategy for developing materials to break the property recordings of current materials, for example, breaking the trade-off between the high-strength and low-ductility structural alloys. The performance of materials usually under a complex circumstance, a balance of multiple properties, for example, combined the high-strength, high ductility, high conductivity, high corrosion resistance, high irradiation resistance, etc., the strategy of high-entropy-alloy (HEA) will provide a materials design and development technology to realize the goal. Magnetic materials usually exhibit excellent magnetic properties but weak mechanical properties and corrosion resistance. The reported unique behaviors of HEAs, for example, self-healing effects may be the mechanism for the high irradiation resistance of the HEAs, and self-sharpening behaviors of the tungsten-based HEAs main closely be related to the serration behaviors