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Experimental Study on Mixed Mode Fracture Behavior of Sandstone under Water⁻Rock Interactions
Wen Hua, Jianxiong Li, Shiming Dong, Xin Pan
May 16, 2019 (v1)
Subject: Other
Keywords: degradation mechanism, fracture criteria, mixed mode fracture resistance, T-stress, water–rock interaction
Water⁻rock interactions can significantly deteriorate the physical and mechanical properties of rocks, and it has been identified as one of the significant factors influencing the stability and safety of structures in rock⁻soil engineering. In this study, the fracture mechanical properties of sandstone under periodic water⁻rock interactions and long-term immersion have been studied with central cracked Brazilian disk specimens. The degradation mechanism of water⁻rock interactions was also studied using a scanning electron microscope (SEM). Finally, the generalized maximum tangential stress and generalized maximum tangential strain criteria were adopted to evaluate the experimental results. The results show that periodic water⁻rock interactions can remarkably affect the fracture resistance of sandstone. With the increase in the number of cycles, the pure mode I, pure mode II, and mixed mode fracture toughness decreases greatly, however, the values of KIf/KIC and KIIf/KIC decrease slight... [more]
A Hybrid Energy Feature Extraction Approach for Ship-Radiated Noise Based on CEEMDAN Combined with Energy Difference and Energy Entropy
Yuxing Li, Xiao Chen, Jing Yu
May 16, 2019 (v1)
Keywords: complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), energy difference (ED), energy entropy (EE), hybrid energy feature extraction, ship-radiated noise (S-RN)
Influenced by the complexity of ocean environmental noise and the time-varying of underwater acoustic channels, feature extraction of underwater acoustic signals has always been a difficult challenge. To solve this dilemma, this paper introduces a hybrid energy feature extraction approach for ship-radiated noise (S-RN) based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) combined with energy difference (ED) and energy entropy (EE). This approach, named CEEMDAN-ED-EE, has two main advantages: (i) compared with empirical mode decomposition (EMD) and ensemble EMD (EEMD), CEEMDAN has better decomposition performance by overcoming mode mixing, and the intrinsic mode function (IMF) obtained by CEEMDAN is beneficial to feature extraction; (ii) the classification performance of the single energy feature has some limitations, nevertheless, the proposed hybrid energy feature extraction approach has a better classification performance. In this paper, we first deco... [more]
Process Modeling and Evaluation of Plasma-Assisted Ethylene Production from Methane
Evangelos Delikonstantis, Marco Scapinello, Georgios D. Stefanidis
May 16, 2019 (v1)
Keywords: electrified process, Ethylene, non-oxidative methane coupling, non-thermal plasma, process modeling
The electrification of the petrochemical industry, imposed by the urgent need for decarbonization and driven by the incessant growth of renewable electricity share, necessitates electricity-driven technologies for efficient conversion of fossil fuels to chemicals. Non-thermal plasma reactor systems that successfully perform in lab scale are investigated for this purpose. However, the feasibility of such electrified processes at industrial scale is still questionable. In this context, two process alternatives for ethylene production via plasma-assisted non-oxidative methane coupling have conceptually been designed based on previous work of our group namely, a direct plasma-assisted methane-to-ethylene process (one-step process) and a hybrid plasma-catalytic methane-to-ethylene process (two-step process). Both processes are simulated in the Aspen Plus V10 process simulator and also consider the technical limitations of a real industrial environment. The economically favorable operating w... [more]
Advances in Mathematical Modeling of Gas-Phase Olefin Polymerization
Mohd Farid Atan, Mohd Azlan Hussain, Mohammad Reza Abbasi, Mohammad Jakir Hossain Khan, Muhamad Fazly Abdul Patah
May 16, 2019 (v1)
Keywords: gas phase, kinetics, Modelling, olefin
Mathematical modeling of olefin polymerization processes has advanced significantly, driven by factors such as the need for higher-quality end products and more environmentally-friendly processes. The modeling studies have had a wide scope, from reactant and catalyst characterization and polymer synthesis to model validation with plant data. This article reviews mathematical models developed for olefin polymerization processes. Coordination and free-radical mechanisms occurring in different types of reactors, such as fluidized bed reactor (FBR), horizontal-stirred-bed reactor (HSBR), vertical-stirred-bed reactor (VSBR), and tubular reactor are reviewed. A guideline for the development of mathematical models of gas-phase olefin polymerization processes is presented.
The Effects of Backfill Mining on Strata Movement Rule and Water Inrush: A Case Study
Jian Hao, Yongkui Shi, Jiahui Lin, Xin Wang, Hongchun Xia
May 16, 2019 (v1)
Subject: Other
Keywords: backfill mining, floor failure depth, ground pressure, strata movement, water inrush prevention
Backfill mining is widely used to control strata movement and improve the stress environment in China’s coal mines. In the present study, the effects of backfill mining on strata movement and water inrush were studied based on a case study conducted in Caozhuang Coal Mine. The in-situ investigation measured abutment pressure distribution (APD), roof floor displacement (RFD), and vertical stress in the backfill area. Results are as follows: (i) The range and peak of APD, RFD, and vertical stress in the backfill area are smaller than in traditional longwall mining with the caving method. (ii) Backfill mining could change the movement form and amplitude of overburden and improve the ground pressure environment. (iii) Floor failure depth (FFD) is much smaller in backfill mining. Backfill mining can be an effective method for floor water inrush prevention.
Comparison of Three Deoxidation Agents for Ozonated Broths Used in Anaerobic Biotechnological Processes
Ewelina Pawlikowska, Jaroslaw Domanski, Piotr Dziugan, Joanna Berlowska, Weronika Cieciura-Wloch, Krzysztof Smigielski, Dorota Kregiel
May 16, 2019 (v1)
Subject: Biosystems
Keywords: deoxidation, iron sulfate, Metschnikowia sp., ozonation, ultrasound
Anaerobic fermentation of organic compounds is used in many biotechnological processes and has been the subject of much research. A variety of process conditions and different growth media can be used to obtain microbial metabolites. The media must be free from contamination before fermentation. Sterilization is most often achieved by applying heat or other treatments, such as ozonation. Sterilization of liquid media using ozone can be very beneficial, but this method introduces high concentrations of residual oxygen, which inhibit anaerobic processes. Deoxidation is therefore necessary to remove the oxygen from ozonated broths. This study evaluates the effectiveness of three deoxidation agents for two kinds of fermentation media based on malt or molasses: ultrasound, iron(II) sulfate, and Metschnikowia sp. yeast. The time needed for deoxidation varied, depending on the kind of broth and the deoxidation agent. In general, the dynamics of oxygen removal were faster in malt broth. A comp... [more]
Integrated Hydrolysis of Mixed Agro-Waste for a Second Generation Biorefinery Using Nepenthes mirabilis Pod Digestive Fluids
Nkosikho Dlangamandla, Seteno Karabo Obed Ntwampe, Justine Oma Angadam, Elie Fereche Itoba-Tombo, Boredi Silas Chidi, Lukhanyo Mekuto
May 16, 2019 (v1)
Subject: Biosystems
Keywords: agro-waste, biorefinery, carboxylesterases, cellulases, Nepenthes mirabilis, total reducing sugars, xylanase, β-glucosidase
To sustainably operate a biorefinery with a low cost input in a commercial setting, the hydrolysis of lignocellulosic biomass must be undertaken in a manner which will impart environmental tolerance while reducing fermenter inhibitors from the delignification process. The challenge lies with the highly recalcitrant lignin structure, which limits the conversion of the holocelluloses to fermentable total reducing sugars (TRS). Due to these challenges, sustainable and innovative methods to pre-treat biomass must be developed for delignocellulolytic operations. Herein, Nepenthes mirabilis digestive fluids shown to have ligninolytic, cellulolytic and xylanolytic activities were used as an enzyme cocktail to hydrolyse mixed agro-waste constituted by Citrus sinensis (orange), Malus domestica (apple) peels, cobs from Zea mays (maize) and Quercus robur (oak) yard waste. The digestive fluids contained carboxylesterases (529.41 ± 30.50 U/L), β-glucosidases (251.94 ± 11.48 U/L) and xylanases (36.0... [more]
Smart Community Energy Cost Optimization Taking User Comfort Level and Renewable Energy Consumption Rate into Consideration
Kun Shi, Dezhi Li, Taorong Gong, Mingyu Dong, Feixiang Gong, Yajie Sun
May 16, 2019 (v1)
Keywords: renewable energy consumption rate, smart communities, user comfort levels
With the rapid development of smart community technologies, how to improve user comfort levels and make full use of renewable energy have become urgent problems. This paper proposes an optimization algorithm to minimize daily energy costs while considering user comfort level and renewable energy consumption rate. In this paper, the structure of a typical smart community and the output models of all components installed in the community are introduced first. Then, the characteristics of different types of loads are analyzed, followed by defining the coefficients of user comfort level. In this step, the influence of load-scheduling on user comfort level and the renewable energy consumption rate is emphasized. Finally, based on the time-of-use gas price, this paper optimizes the daily energy costs for an off-grid community under the constraints of the comfort level and renewable energy consumption rate. Results show that scheduling transferable loads and interruptible loads are not indepe... [more]
Investigation of Pore-Formers to Modify Extrusion-Spheronized CaO-Based Pellets for CO₂ Capture
Zonghao Zhang, Shuai Pi, Donglin He, Changlei Qin, Jingyu Ran
May 16, 2019 (v1)
Subject: Materials
Keywords: anti-attrition, calcium looping, Carbon Dioxide Capture, chemical sorption, pore-former particle size
The application of circulating fluidized bed technology in calcium looping (CaL) requires that CaO-based sorbents should be manufactured in the form of spherical pellets. However, the pelletization of powdered sorbents is always hampered by the problem that the mechanical strength of sorbents is improved at the cost of loss in CO₂ sorption performance. To promote both the CO₂ sorption and anti-attrition performance, in this work, four kinds of pore-forming materials were screened and utilized to prepare sorbent pellets via the extrusion-spheronization process. In addition, impacts of the additional content of pore-forming material and their particle sizes were also investigated comprehensively. It was found that the addition of 5 wt.% polyethylene possesses the highest CO₂ capture capacity (0.155 g-CO₂/g-sorbent in the 25th cycle) and mechanical performance of 4.0 N after high-temperature calcination, which were about 14% higher and 25% improved, compared to pure calcium hydrate pellet... [more]
Multiscale and Multi-Granularity Process Analytics: A Review
Marco S. Reis
May 16, 2019 (v1)
Keywords: data aggregation, industrial big data, multi-granularity methods, multiscale methods
As Industry 4.0 makes its course into the Chemical Processing Industry (CPI), new challenges emerge that require an adaptation of the Process Analytics toolkit. In particular, two recurring classes of problems arise, motivated by the growing complexity of systems on one hand, and increasing data throughput (i.e., the product of two well-known “V’s„ from Big Data: Volume × Velocity) on the other. More specifically, as enabling IT technologies (IoT, smart sensors, etc.) enlarge the focus of analysis from the unit level to the entire plant or even to the supply chain level, the existence of relevant dynamics at multiple scales becomes a common pattern; therefore, multiscale methods are called for and must be applied in order to avoid biased analysis towards a certain scale, compromising the benefits from the balanced exploitation of the information content at all scales. Also, these same enabling technologies currently collect large volumes of data at high-sampling rates, creating a flood... [more]
Effect of Supercritical Fluid Extraction Process on Chemical Composition of Polianthes tuberosa Flower Extracts
Javier C. Fragoso-Jiménez, Ernesto Tapia-Campos, Mirna Estarron-Espinosa, Rodrigo Barba-Gonzalez, Ma. Claudia Castañeda-Saucedo, Gustavo A. Castillo-Herrera
May 16, 2019 (v1)
Subject: Biosystems
Keywords: chemical composition, Polianthes tuberosa, supercritical fluid extraction
Supercritical fluid extracts from flowers of Polianthes tuberosa var. double were ob tained using carbon dioxide as a solvent. Yield extract obtained was 2.5%. The effects of the pressure process (18 MPa, 28 MPa, and 38 MPa) and temperature process (313 K, 323 K, and 333 K) on the volatile composition of tuberose flowers extracts were evaluated, and a significant variation in chemical composition was found. Characteristic compounds of tuberose as methyl isoeugenol, benzyl benzoate, methyl anthranilate, pentacosene, and heptacosene were obtained mainly at 18 MPa and 333 K process conditions, and could be used in the perfume or fragrance industry. Components such as geraniol, farnesol, and methyl eugenol were also obtained, these extracts could be used in the development of cosmeceutical products. This work allowed to identification of the chemical composition profile and evaluation of the changes in tuberose extracts due to the extraction process.
A Systems Engineering Approach to Performance-Based Maintenance Services Design
Maria Holgado
May 16, 2019 (v1)
Subject: Energy Policy
Keywords: IDEF0, industrial services, maintenance services, outcome-based services, performance-based services, systems engineering
Traditionally, industrial services have been mainly transaction-based, i.e., the equipment user pays the service provider for getting a job done or providing assistance and support for equipment operations. Recently, a trend has emerged of increasing the relational perspective of these services, which are becoming more oriented towards customer value and service performance levels. Among these emergent industrial services, performance-based services represent an opportunity for equipment manufacturers to transform their service offerings towards more relational and customer-oriented services. The purpose of this work is to study the design of a generic performance-based maintenance service under a novel perspective given by systems engineering. This paper is intended to serve as a starting point to fully understand this type of services and to develop a method that can support equipment manufacturers who wish to advance their service offerings.
Simulation Study on the Influence of Gas Mole Fraction and Aqueous Activity under Phase Equilibrium
Weilong Zhao, Hao Wu, Jing Wen, Xin Guo, Yongsheng Zhang, Ruirui Wang
May 16, 2019 (v1)
Keywords: activity, gas mole fraction, phase equilibrium, threshold value, UNIFAC
This work explored the influence of gas mole fraction and activity in aqueous phase while predicting phase equilibrium conditions. In pure gas systems, such as CH₄, CO₂, N₂ and O₂, the gas mole fraction in aqueous phase as one of phase equilibrium conditions was proposed, and a simplified correlation of the gas mole fraction was established. The gas mole fraction threshold maintaining three-phase equilibrium was obtained by phase equilibrium data regression. The UNIFAC model, the predictive Soave-Redlich-Kwong equation and the Chen-Guo model were used to calculate aqueous phase activity, the fugacity of gas and hydrate phase, respectively. It showed that the predicted phase equilibrium pressures are in good agreement with published phase equilibrium experiment data, and the percentage of Absolute Average Deviation Pressures are given. The water activity, gas mole fraction in aqueous phase and the fugacity coefficient in vapor phase are discussed.
Experimental Study on the Shear-Flow Coupled Behavior of Tension Fractures Under Constant Normal Stiffness Boundary Conditions
Changsheng Wang, Yujing Jiang, Hengjie Luan, Jiankang Liu, Satoshi Sugimoto
May 16, 2019 (v1)
Subject: Other
Keywords: constant normal stiffness conditions, hydraulic aperture, rock fracture, shear-flow coupled test, transmissivity
This study experimentally investigated the effects of fracture surface roughness, normal stiffness, and initial normal stress on the shear-flow behavior of rough-walled rock fractures. A series of shear-flow tests were performed on two rough fractures, under various constant normal stiffness (CNS) boundary conditions. The results showed that the CNS boundary conditions have a significant influence on the mechanical and hydraulic behaviors of fractures, during shearing. The peak shear stress shows an increasing trend with the increases in the initial normal stress and fracture roughness. The residual shear stress increases with increasing the surface roughness, normal stiffness, and initial normal stress. The dilation of fracture is restrained more significantly under high normal stiffness and initial normal stress conditions. The hydraulic tests show that the evolutions of transmissivity and hydraulic aperture exhibit a three-stage behavior, during the shear process—a slight decrease s... [more]
The Study on Extraction Process and Analysis of Components in Essential Oils of Black Pepper (Piper nigrum L.) Seeds Harvested in Gia Lai Province, Vietnam
Thien Hien Tran, Le Ke Ha, Duy Chinh Nguyen, Tan Phat Dao, Le Thi Hong Nhan, Dai Hai Nguyen, Trinh Duy Nguyen, Dai-Viet N. Vo, Quoc Toan Tran, Long Giang Bach
May 16, 2019 (v1)
Subject: Biosystems
Keywords: black pepper (Piper nigrum L.), essential oils, chemical composition analysis, GC-MS, hydrodistillation
Black pepper (Piper nigrum L.) is a tropical crop with extensive medicinal potential in ethnomedicine and nutraceutical applications. The essential oil of black pepper finds wide applications in inhabitation of respiratory infections and soothing of muscular pains due to its warming and energizing property. The pungent bioactive piperine is responsible for this function, and therefore, efficient technology is required for an optimal extraction process of this compound. In the present article, we have developed a procedure for extracting black pepper essential oil from Vietnam, optimizing conditions that affect the extraction process. The effect of process parameters, namely material size, preservation method, the concentration of sodium chloride, the concentration of soak time, the ratio of material to water, temperature extraction, time extraction on the extraction yield, and relative efficiency were investigated. Results demonstrated that 20 g of black pepper milled with a mesh size... [more]
Application of Data Mining in an Intelligent Early Warning System for Rock Bursts
Xuejun Zhu, Xiaona Jin, Dongdong Jia, Naiwei Sun, Pu Wang
May 16, 2019 (v1)
Keywords: clustering analysis, data mining, data warehouse, intelligent early warning, rock burst
In view of rock burst accidents frequently occurring, a basic framework for an intelligent early warning system for rock bursts (IEWSRB) is constructed based on several big data technologies in the computer industry, including data mining, databases and data warehouses. Then, a data warehouse is modeled with regard to monitoring the data of rock bursts, and the effective application of data mining technology in this system is discussed in detail. Furthermore, we focus on the K-means clustering algorithm, and a data visualization interface based on the Browser/Server (B/S) mode is developed, which is mainly based on the Java language, supplemented by Cascading Style Sheets (CSS), JavaScript and HyperText Markup Language (HTML), with Tomcat, as the server and Mysql as the JavaWeb project of the rock burst monitoring data warehouse. The application of data mining technology in IEWSRB can improve the existing rock burst monitoring system and enhance the prediction. It can also realize real... [more]
Pilot Plant Data Assessment in Anaerobic Digestion of Organic Fraction of Municipal Waste Solids
Massimo Migliori, Enrico Catizzone, Girolamo Giordano, Adolfo Le Pera, Miriam Sellaro, Alessandro Lista, Giuseppe Zanardi, Luciano Zoia
April 15, 2019 (v1)
Subject: Biosystems
Keywords: biogas, dry anaerobic digestion, municipal waste, wet anaerobic digestion
In this paper, a preliminary study of anaerobic digestion of organic fraction of municipal solid wastes (OFMSW) in presented with the aim to compare the performances of both wet- and dry-type reactors. The treatment of OFMSW via anaerobic digestion (AD) producing biogas is a process that is receiving a growing interest because two different needs can be coupled: the request of sustainable municipal waste treatments and increasing demand renewable energy. This paper aims to offer experimental results comparing batch test and continuous experimental reactors under different conditions of humidity and solid content. Results show that both the investigated configurations may be used for converting OFMSW into a high quality biogas and that the increase of dry matter in the continuous process still allows to achieve significant biogas production rates. A slight reduction of the methane content was observed (less than 5% relative) that can be also related to the change in the level of volatil... [more]
Analysis of Influencing Factors of Occupational Safety and Health in Coal Chemical Enterprises Based on the Analytic Network Process and System Dynamics
Kai Yu, Lujie Zhou, Chen Hu, Linlin Wang, Weiqiang Jin
April 15, 2019 (v1)
Subject: Energy Policy
Keywords: analytic network process, management and control measures, occupational safety and health, Simulation, system dynamics
In the production process of coal chemical enterprises, there are factors such as dust, poisons, as well as toxic and harmful gases, which seriously restrict the safety and health of employees. It is urgent to strengthen research on occupational safety and health (OSH) of coal chemical enterprises. Research on the influencing factors is very important to improve the level of OSH in coal chemical enterprises. Therefore, this paper analyzed the factors affecting OSH of coal chemical enterprises from four aspects: “human⁻machine⁻environment⁻management„. Then, an influencing factor indicator system was constructed. The weights of the indicator were analyzed using the Analytic Network Process (ANP). On this basis, the primary and secondary indicators of the influencing factors were ranked. Subsequently, the weights of ANP were taken as the influence coefficient between variables, and the System Dynamics (SD) model of OSH control measures was established and analyzed. According to the weight... [more]
Component Characterization in a Growth-Dependent Physiological Context: Optimal Experimental Design
Nathan Braniff, Matthew Scott, Brian Ingalls
April 15, 2019 (v1)
Keywords: cell physiology, characterization, host-context effects, model fitting, optimal control, optimal experimental design, synthetic biology
Synthetic biology design challenges have driven the use of mathematical models to characterize genetic components and to explore complex design spaces. Traditional approaches to characterization have largely ignored the effect of strain and growth conditions on the dynamics of synthetic genetic circuits, and have thus confounded intrinsic features of the circuit components with cell-level context effects. We present a model that distinguishes an activated gene’s intrinsic kinetics from its physiological context. We then demonstrate an optimal experimental design approach to identify dynamic induction experiments for efficient estimation of the component’s intrinsic parameters. Maximally informative experiments are chosen by formulating the design as an optimal control problem; direct multiple-shooting is used to identify the optimum. Our numerical results suggest that the intrinsic parameters of a genetic component can be more accurately estimated using optimal experimental designs, an... [more]
Approaches to Suppress CO₂-Induced Plasticization of Polyimide Membranes in Gas Separation Applications
Moli Zhang, Liming Deng, Dongxiao Xiang, Bing Cao, Seyed Saeid Hosseini, Pei Li
April 15, 2019 (v1)
Keywords: Carbon Dioxide, gas separation, membrane, plasticization, polyimide
Polyimides with excellent physicochemical properties have aroused a great deal of interest as gas separation membranes; however, the severe performance decay due to CO₂-induced plasticization remains a challenge. Fortunately, in recent years, advanced plasticization-resistant membranes of great commercial and environmental relevance have been developed. In this review, we investigate the mechanism of plasticization due to CO₂ permeation, introduce effective methods to suppress CO₂-induced plasticization, propose evaluation criteria to assess the reduced plasticization performance, and clarify typical methods used for designing anti-plasticization membranes.
Model-Based Cost Optimization of Double-Effect Water-Lithium Bromide Absorption Refrigeration Systems
Sergio F. Mussati, Seyed Soheil Mansouri, Krist V. Gernaey, Tatiana Morosuk, Miguel C. Mussati
April 15, 2019 (v1)
Keywords: absorption refrigeration, cost optimization, double-effect system, H2O-LiBr working pair, nonlinear mathematical programming
This work presents optimization results obtained for a double-effect H₂O-LiBr absorption refrigeration system considering the total cost as minimization criterion, for a wide range of cooling capacity values. As a model result, the sizes of the process units and the corresponding operating conditions are obtained simultaneously. In this paper, the effectiveness factor of each proposed heat exchanger is considered as a model optimization variable which allows (if beneficial, according to the objective function to be minimized) its deletion from the optimal solution, therefore, helping us to determine the optimal configuration. Several optimization cases considering different target levels of cooling capacity are solved. Among the major results, it was observed that the total cost is considerably reduced when the solution heat exchanger operating at low temperature is deleted compared to the configuration that includes it. Also, it was found that the effect of removing this heat exchange... [more]
Processes of Cracking and Crushing in Hybrid Fibre Reinforced High-Performance Concrete Slabs
Piotr Smarzewski
April 15, 2019 (v1)
Subject: Materials
Keywords: high-performance concrete, non-contact deformation measurements, polypropylene fibres, reinforcement, slab, steel fibres
This paper presents the experimental results obtained with the non-contact three-dimensional deformation measuring system⁻ARAMIS and finite element analysis performed using ANSYS of three slabs made of high-performance concrete (HPC) and hybrid (steel/ST and polypropylene/PP) fibre reinforced high-performance concrete (FRHPC). The research was performed on reinforced concrete (RC) slabs with a web mesh of ϕ8 mm bars. All the slabs had an identical amount of steel bars and differed by the fibre volume content. The main objective of the research was to determine the impact of adding polypropylene and steel fibres on the carrying capacity and ductility of HPC slabs. Analysis of the results was conducted based on load⁻deflection curves, crack distribution, vertical displacements and strains. The research findings indicate that fibres may improve peak strength. The presence of PP and ST hybrid fibres in HPC restricted the propagation of cracks. The energy absorption capacity as well as the... [more]
Employment of Emergency Advanced Nurses of Turkey: A Discrete-Event Simulation Application
Abdulkadir Atalan, Cem Cagri Donmez
April 15, 2019 (v1)
Keywords: advanced nurses, discrete event simulation, emergency service resources, emergency services
In the present study, problems in emergency services (ESs) were dealt with by analyzing the working system of ESs in Turkey. The purpose of this study was to reduce the waiting times spent in hospitals by employing advanced nurses (ANs) to treat patients who are not urgent, or who may be treated as outpatients in ESs. By applying discrete-event simulation on a 1/24 (daily) and 7/24 (weekly) basis, and by employing ANs, it was determined that the number of patients that were treated increased by 26.71% on a 1/24 basis, and by 15.13% on a 7/24 basis. The waiting time that was spent from the admission to the ES until the treatment time decreased by 38.67% on a 1/24 basis and 53.66% on a 24/7 basis. Similarly, the length of stay was reduced from 82.46 min to 53.97 min in the ES. Among the findings, it was observed that the efficiency rate of the resources was balanced by the employment of ANs, although it was not possible to obtain sufficient efficiency from the resources used in the ESs p... [more]
Study on the Preparation and Hydration Properties of a New Cementitious Material for Tailings Discharge
Yunbing Hou, Pengchu Ding, Dong Han, Xing Zhang, Shuxiong Cao
April 15, 2019 (v1)
Subject: Materials
Keywords: cement-based paste discharge, mechanical behaviors, MIP, new cementitious material, SEM, TG/DTG, XRD
Blast furnace slag (BFS) is often used as a cement-based raw material for underground filling and surface cemented paste discharge of tailings during mining processes. This paper studied a new cement-based material (NCM) with BFS to replace ordinary Portland cement (OPC). A uniaxial compressive strength (UCS) experiment was used to test the mechanical strength of samples; X-ray diffraction and thermal gravity experiments were used to test the crystalline phases and amount of hydration products by samples; a scanning electron microscope experiment was used to observe the influence of the hydration products morphology by samples; mercury intrusion porosimetry experiment was used to analyze the pore size distribution of samples. The samples with NCM had an optimum UCS; the crystalline phases of the hydration products were similar in OPC and NCM. However, the amount of product formed in OPC was less than that in NCM at the same curing time; more ettringite and calcium silicate hydrate were... [more]
Simulating the Filtration Effects of Cement-Grout in Fractured Porous Media with the 3D Unified Pipe-Network Method
Zizheng Sun, Xiao Yan, Weiqi Han, Guowei Ma, Yiming Zhang
April 15, 2019 (v1)
Subject: Other
Keywords: filtration effects, fractured porous medium, grout penetration, two-phase flow, unified pipe-network method
In grouting process, filtration is the retention and adsorption of cement-grout particles in a porous/fractured medium. Filtration partly/even completely blocks the transportation channels in the medium, greatly decreasing its permeability. Taking into account filtration effects is essential for accurately estimating the grout penetration region. In this paper, the 3D unified pipe-network method (UPM) is adopted for simulating 3D grout penetration process in a fractured porous medium, considering filtration effects. The grout is assumed to exhibit two-phase flow, and the filtration effects depend on not only the concentration and rheology of the grout but also the porosity and permeability of the fractured porous medium. By comparing the model with the experimental results, we firstly verify the proposed numerical model. Then sensitivity analysis is conducted, showing the influences of grout injection pressures, the water⁻cement ratios of grout (W/C) and the grout injection rates on fi... [more]
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