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Records Added in April 2020
Records added in April 2020
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Showing records 76 to 86 of 86. [First] Page: 1 2 3 4 Last
An Online Contaminant Classification Method Based on MF-DCCA Using Conventional Water Quality Indicators
Yanni Zhu, Kexin Wang, Youxin Lin, Hang Yin, Dibo Hou, Jie Yu, Pingjie Huang, Guangxin Zhang
April 1, 2020 (v1)
Keywords: abnormal fluctuation analysis, cosine distance classification, D–S evidential theory, MF-DCCA, online contaminant classification
Emergent contamination warning systems are critical to ensure drinking water supply security. After detecting the existence of contaminants, identifying the types of contaminants is conducive to taking remediation measures. An online classification method for contaminants, which explored abnormal fluctuation information and the correlation between 12 water quality indicators adequately, is proposed to realize comprehensive and accurate discrimination of contaminants. Firstly, the paper utilized multi-fractal detrended fluctuation analysis (MF-DFA) to select indicators with abnormal fluctuation, used multi-fractal detrended cross-correlation analysis (MF-DCCA) to measure the cross-correlation between indicators. Subsequently, the algorithm fused the abnormal probability of each indicator and constructed the abnormal probability matrix to further judge the abnormal fluctuation of indicators using D−S evidence theory. Finally, the singularity index of the cross-correlation function and th... [more]
Review of the Numerical Modeling of Compression Molding of Sheet Molding Compound
Gustaf Alnersson, M. Waseem Tahir, Anna-Lena Ljung, T. Staffan Lundström
April 1, 2020 (v1)
Keywords: compression molding, numerical modeling, sheet molding compound
A review of the numerical modeling of the compression molding of the sheet molding compound (SMC) is presented. The focus of this review is the practical difficulties of modeling cases with high fiber content, an area in which there is relatively little documented work. In these cases, the prediction of the flows become intricate due to several reasons, mainly the complex rheology of the compound and large temperature gradients, but also the orientation of fibers and the micromechanics of the interactions between the fluid and the fibers play major roles. The details of this during moldings are discussed. Special attention is given to the impact on viscosity from the high fiber volume fraction, and the various models for this. One additional area of interest is the modeling of the fiber orientation.
The Demulsification Properties of Cationic Hyperbranched Polyamidoamines for Polymer Flooding Emulsions and Microemulsions
Yangang Bi, Zhi Tan, Liang Wang, Wusong Li, Congcong Liu, Zhantao Wang, Xiangchen Liu, Xinru Jia
April 1, 2020 (v1)
Subject: Other
Keywords: cationic hyperbranched polymers, demulsifiers, interfacial tension, microemulsion, polymer-flooding emulsion, turbidity
Polymer flooding emulsions and microemulsions caused by tertiary oil recovery technologies are harmful to the environment due to their excellent stability. Two cationic hyperbranched polyamidoamines (H-PAMAM), named as H-PAMAM-HA and H-PAMAM-ETA, were obtained by changing the terminal denotation agents to H-PAMAM, which was characterized by 1H NMR, FT-IR, and amine possession, thereby confirmed the modification. Samples (300 mg/L) were added to the polymer flooding emulsion (1500 mg/L oil concentration) at 30 °C for 30 min and the H-PAMAM-HA and H-PAMAM-ETA were shown to perform at 88% and 91% deoil efficiency. Additionally, the increased settling time and the raised temperature enhanced performance. For example, an oil removal ratio of 97.7% was observed after dealing with the emulsion for 30 min at 60 °C, while 98.5% deoil efficiency was obtained after 90 min at 45 °C for the 300 mg/L H-PAMAM-ETA. To determine the differences when dealing with the emulsion, the interfacial tension, ζ... [more]
Systematic Experimental Investigation of Segregation Direction and Layer Inversion in Binary Liquid-Fluidized Bed
Alberto Di Renzo, Giacomo Rito, Francesco P. Di Maio
April 1, 2020 (v1)
Keywords: expansion, layer inversion, liquid-fluidization, Mixing, multi-component beds, segregation
Multi-component liquid-fluidized beds are encountered in a variety of industrial processes. Often, segregation severely affects the performance of the process unit. Unfortunately, size-driven and density-driven separation processes may occur with a complex interplay, showing prevailing mechanisms that change with the operating conditions. For example, when the solids exhibit contrasting differences in size and density, even the direction of segregation can turn out hard to predict, giving rise for some systems to the so-called “layer inversion phenomenon”. A systematic experimental investigation is presented on 14 different binary beds composed of glass beads and ABS spheres with different size and density ratios and different bed composition. The analysis allows assessing the reliability of a model for predicting the segregation direction of fluidized binary beds (the Particle Segregation Model, PSM). By measurements of the solids’ concentration at the surface, expansion/segregation p... [more]
The Dependence of Effective Distribution Coefficient on Growth Rate and Mass Transfer Coefficient for P-Xylene in Solid-Layer Melt Crystallization
Lie-Ding Shiau
April 1, 2020 (v1)
Subject: Materials
Keywords: crystallization, growth rate, impurity, melt, para-xylene
The solid-layer growth kinetics and resulting crystal purity for a well-mixed p-xylene (PX) melt with impurity of o-xylene (OX) or ethylbenzene (EB) were studied in this work at various cooling temperatures. A correlation based on the energy balance was adopted to describe the dependence of growth rate on the temperature gradient between melt and cooling medium. An empirical equation based on the mass balance was proposed to relate the effective distribution coefficient with growth rate, mass transfer coefficient, and impurity mole fraction. By fitting the proposed empirical equation with the experimental effective distribution coefficients, the mass transfer coefficients for the PX/OX and PX/EB mixtures were retrieved respectively.
Utilization of Pyrolytic Carbon Black Waste for the Development of Sustainable Materials
Faizan Ali, Mishmal Ahmed Khan, Muhammad Ahmed Qurashi, Syyed Adnan Raheel Shah, Nasir Mahmood Khan, Zia Khursheed, Hafiz Shahzaib Rahim, Hunain Arshad, Muhammad Farhan, Muhammad Waseem
April 1, 2020 (v1)
Subject: Materials
Keywords: eco-friendly, materials, sustainable, waste management
The sustainable development of materials is one of the key targets in the modern era of engineering. These materials are developed by different waste products, following the concept of the circular economy. This study focuses on investigating the properties of concrete using carbon black as a partial replacement of natural fine aggregate at different percentages. Experiments were designed according to the British Standard (BS1881-Part-119) and American Standard (ASTM C-78) by including carbon black in concrete beams to perform as filler material to develop sustainable concrete. In this study, mechanical properties of concrete were targeted by developing beams using different percentages (0%, 25%, 50%, 75%, and 100%) as a replacement of fine aggregates. These beams were tested for flexural strength and, later on, the same beams were cut in the form of cubes, following the equivalent cube test mechanism for the compressive strength test. The waste carbon black lightweight concrete develo... [more]
Optimization of Microwave-Assisted Extraction Process of Callicarpa candicans (Burm. f.) Hochr Essential Oil and Its Inhibitory Properties against Some Bacteria and Cancer Cell Lines
Quoc Toan Tran, Thu Le Vu Thi, Tien Lam Do, Hong Minh Pham Thi, Bich Hoang Thi, Quang Truyen Chu, Phuong Thao Lai Phuong, Huu Nghi Do, Hoai Thu Hoang Than, Thu Thuy Ta Thi, Van Huyen Luu, Phuong Thi Mai Duong, Huong Thi Thu Phung
April 1, 2020 (v1)
Keywords: anti-proliferative activity, antimicrobial activities, Callicarpa candicans, essential oil, microwave-assisted extraction, Optimization, response surface methodology, the MAHD
Callicarpa candicans (Burm. f.) Hochr. (Callicarpa cana L.) is a medicinal plant that is distributed mainly in the tropics and subtropics of Asia and finds a wide range of uses in traditional medicine. In this study, we attempted and optimized the microwave-assisted hydro-distillation (MAHD) process to obtain essential oil from the leaves of C. candicans. In addition, the obtained oil was analyzed for volatile composition by gas chromatography−mass spectrometry (GC-MS) and assayed for bioactivity against several bacteria and cancer cell lines. To optimize the extraction process, response surface methodology (RSM) in combination with central composite design (CCD) was adopted. Experimental design and optimization were carried out with respect to three experimental factors including the ratio of water to raw material, extraction time, and microwave power. The optimal extraction conditions were obtained as follows: water to raw material ratio of 6/1 (v/w), extraction time 42 min, and micr... [more]
Evaluation of Thermal Effects on the Bioactivity of Curcumin Microencapsulated with Porous Starch-Based Wall Material Using Spray Drying
Chenwei Huang, Shengwen Wang, Huaiwen Yang
April 1, 2020 (v1)
Subject: Other
Keywords: color attribute, encapsulated curcumin, free radical scavenging activity, oven heating, spray drying
Curcumin was microencapsulated by porous starch using a spray dryer with a particle size between 1.5 and 2.0 µm and subjected to water bath (40−100 °C) and oven heating (150−200 °C) in comparison to non-encapsulated samples. The minimum possible encapsulation rate ranged from 26.75 to 52.23%. A reasonable thermal stability was observed after water bath heating with regard to 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging activity. On the other hand, the increase in oven heating temperature caused significant alterations compared with the control samples (p < 0.05). The encapsulated particles subjected to oven heating at 170 °C demonstrated serious collapse. The DPPH scavenging activity of non-encapsulated curcumin was significantly reduced (p < 0.05) from 48.94% ± 3.72% (control, 0 °C) to 40.42% ± 2.23% (oven heating, 160 °C); however, remained stable for the encapsulated samples (51.18% ± 4.86%−50.02% ± 1.79%) without significant difference (p < 0.05). The ABTS... [more]
Films of Bacterial Cellulose Prepared from Solutions in N-Methylmorpholine-N-Oxide: Structure and Properties
Igor S. Makarov, Gulbarshin K. Shambilova, Markel I. Vinogradov, Pavel V. Zatonskih, Tatyana I. Gromovykh, Sergey V. Lutsenko, Nаtalia A. Arkharova, Valery G. Kulichikhin
April 1, 2020 (v1)
Subject: Materials
Keywords: bacterial cellulose, cellulose solution, film formation, mechano-chemical activation, N-methylmorpholine-N-oxide, rheology, structure
In the present study, one of the possible methods of the bacterial cellulose processing is proposed via its dissolution in N-methylmorpholine-N-oxide using the stage of mechano-chemical activation of the solid polymer−solvent system. Preliminary solid-phase activation is apparently a decisive factor affecting the dissolution rate of bacterial cellulose in N-methylmorpholine-N-oxide. The effects of bacterial cellulose concentration, solvent nature, degree of polymerization and temperature on dissolution time were studied. The rheological behavior of the solutions does not change at 120 °C for at least half an hour that allowed us to process such solutions for films preparation. The films from these solutions by means of dry-wet jet spinning in aqueous coagulant were formed. The structure of the nascent cellulose and formed films was tested by the X-ray diffraction method and SEM. The thermal behavior of the films revealed an increase in the carbon yield for the formed films compared to... [more]
A Semi-Continuous PWA Model Based Optimal Control Method for Nonlinear Systems
Xinjian Zhu, Chunyue Song, Jun Zhao, Zuhua Xu
April 1, 2020 (v1)
Keywords: MPC, nonlinear system, optimal control, PWA model, semi-continuous
To alleviate the mode mismatch of multiple model methods for nonlinear systems when completely discrete dynamical equations are adopted, a semi-continuous piecewise affine (SCPWA) model based optimal control method is proposed. Firstly, a SCPWA model is constructed where modes evolve in continuous time and continuous states evolve in discrete time. Thanks to this model, a piecewise affine (PWA) system can switch at any time instant whereas mode switching only occurs at sample instants when a completely discrete PWA model is adopted, which improves the prediction accuracy of multi-models. Secondly, the switching condition is relaxed such that operating subspaces have overlaps and switching condition parameters are introduced. As a consequence, an optimal control problem with fixed mode switching sequence is established. Finally, a SCPWA model based model predictive control (MPC) policy is designed for nonlinear systems. The convergence of the MPC algorithm is proved. Compared with widel... [more]
Effect of Drying on Lettuce Leaves Using Indirect Solar Dryer Assisted with Photovoltaic Cells and Thermal Energy Storage
Pedro Cerezal Mezquita, Aldo Álvarez López, Waldo Bugueño Muñoz
April 1, 2020 (v1)
Keywords: lettuce leaves, mathematical modeling, solar drying, thin layer drying
The thin layer drying behavior of lettuce leaves was investigated using an indirect pilot solar dryer with thermal energy storage in water, equipped with solar collectors and photovoltaic cells. The drying procedure consisted of shredded lettuce leaves, temperature ≤ 52 °C, airspeed, 1.0 m∙s−1, and process time ~10.0 h. Fifteen drying models were adjusted to the experimental data obtained; three models with maximum values of coefficient of determination (R2)—Page, Midilli, and Kucuk, and Weibull Distribution, whose values of R2 ≥ 0.998, and other statistical parameters, χ2, SSE, and RMSE values closer to zero were chosen. The initial browning index BI = 120.5 ± 0.7 decreased compared to the dry sample BI = 78.99 ± 0.5, with chromatic coordinate degradations a* and b*; but not the luminosity L*; where ΔE = 8.26; whose meaning is that the dry sample is a “more opaque brownish color” due to the difference in the chroma ΔC = 6.65, and with a change from the yellow-green to yellow-red zone,... [more]
Showing records 76 to 86 of 86. [First] Page: 1 2 3 4 Last
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