Internal Medium Research Articles

Study on the characteristics of microseismic wave field of complex medium model in coal mine

In order to provide an effective theoretical basis for the location of microseismic source, active seismic exploration technology, and internal medium structure inversion of coal mine in different areas, we analyze the propagation law of microseismic wave in different medium accurately and intuitively. In this paper, we first studied the finite difference method suitable for the analysis of wave field characteristics of coal and rock medium in a coal mine. Then, we established the typical models of coal-rock combination multi-layer medium, fault-bearing coal-rock medium, coal-rock dual-phase medium of water-bearing and gas-bearing and stochastic medium model, and random medium model. Finally, we obtained the wave field snapshot and single shot recording of different medium model. The research shows that the high-order finite difference method can accurately obtain P and S waves field characteristics under different media conditions. The wave field characteristics of different medium models are different. In the coal-rock combination multi-layer model, the transmitted wave, transmitted converted wave, reflected wave, and reflected converted wave are generated on the different medium interfaces. In the fault model, not only the transmitted wave, transmitted converted wave, reflected wave, and reflected converted wave but also the refracted and diffracted waves are produced at fault area. In the coal-rock dual-phase medium of water-bearing and gas-bearing model, three types of waves are excited by the source, which are fast longitudinal (P) waves, transverse (S) waves, and slow longitudinal (P) waves. However, the propagation of slow longitudinal wave is different in these models. Under the stochastic media model, there are very complex scattering waves. The snapshots at different time further describe the wave field’s dynamic characteristics vividly, which establish the theoretical basis of the analysis of microseismic waves. Based on the analysis of the wave field characteristics of coal and rock in the mine, it can provide theoretical support and basis for the active seismic exploration and internal medium structure inversion of coal mine in different areas. What’s more, a more practical wave velocity model can be established to provide an effective theoretical basis for the location of microseismic source. When there is a disaster in the coal mine, we can determine the exact location of the source as soon as possible and take corresponding measures.

Kinetic regularities of NO donation by binuclear dinitrosyl iron complexes with thiolate ligands based on thiophenol derivatives in the presence of red blood cells

The kinetics of nitrogen oxide release by binuclear dinitrosyl iron complexes (B-DNICs) with thiolate ligands based on thiophenol and its several oxy, amino, and nitro derivatives was studied using a suspension of red blood cells simulating the internal medium of a blood vessel. The NO donating ability of the complexes was estimated by the kinetic parameters of first-order equation, which described the formation of intra-erythrocytic methemoglobin. Three typical kinetic profiles of NO donation were distinguished: pseudosaturation donation and donation with prolonged and explosive profiles. In the case of first-type NO donation typical of complexes with thiophenol and its nitro derivatives, the curves display a fast coming to saturation long before the complete release of all NO groups contained in the structure of the starting complex into a solution. Such a type of donation is likely due to the formation of long-lived nitrosyl intermediates in the system. The prolonged type of NO donation shown by the complex with hydroxyphenyl ligand is characterized by virtually constant rate of NO release into a solution without pronounced transition to saturation during experiment (10–12 min). In the case of explosive-type donation characteristic of the complex with aminophenyl ligands, a considerable portion of NO was fast released into a solution within 1–3 min. All complexes under study caused hemolysis of a 0.2% suspension of red blood cells. The complex with aminophenyl ligands exhibited the highest hemolytic activity.

Antecedents and outcomes of the knowledge management process (KMP) in Malaysian SMEs

The purpose of this research was to identify and validate the antecedents and outcomes of the Knowledge Management Process (KMP) in the context of Malaysian SMEs. The antecedents (knowledge management (KM) enablers) in this study were internal collaboration, trust, small and medium enterprise (SME) network, transformational leadership, and information technology (IT) support. The outcomes were innovation speed and organizational performance. Data was collected from 242 SMEs through online surveys and personal visits and analyzed using partial least squares structural equation modeling (PLS-SEM).The salient findings were: (1) among the KM enablers, internal collaboration and IT support significantly influence the KMP; and (2) innovation speed mediates the relationship between the KMP and organizational performance. This study contributes to the literature by: (1) providing a comprehensive framework that links KM enablers, KMP, and performance for SMEs; and (2) establishing innovation speed as a mediator between the KMP and performance.

Discrete element simulation for evolution characteristics of multi-funnel mineral-rock force chain under flexible isolation layer

To further reveal the internal mechanism of the granular media flow process under the flexible isolation layer, numerical experiments on the evolution characteristics of bulk media flow force chain under the flexible isolation layer were carried out based on the discrete element software PFC. Based on a combination of contact mechanics and statistical mechanics, the evolution characteristics of the force chain length, quantity, strength, direction, and the collimation coefficient of the internal bulk medium system in the multifunnel ore drawing process were quantitatively studied. It is found that the proportions of the strong contact and the force chain contact is found to be relatively stable in the multi-funnel ore drawing process;the proportion of strong contact is stable at about 33%, that of the force chain contact is stable at about 16%, and the fluctuation amplitude is not more than 2%. The total number of force chains decreases with the increase in ore drawing times, and it is stable at 790 strips in the later stage of ore drawing. The probability distribution of the force chain length is almost the same under different ore drawing times, and it decreases exponentially with the increase in the force chain length. The probability distribution of the force chain strength first increases exponentially with the increase in the ore drawing times and then decreases exponentially;it reaches a peak value at 0.7■(■is the average contact force).In the initial ore drawing stage,the force chain is mainly distributed along the vertical direction, and the force chain direction distribution is similar to a peanut shape.After that, with the continuous release of ore particles, the phenomenon of local stress concentration in the granular media system becomes remarkable, and the main direction of the force chain distribution changes to become four(vertical direction, horizontal direction, and angles of ±60° to the horizontal). The force chain collimation coefficient increases exponentially with the increase in drawing times and gradually becomes stable.

Economic power control for offshore wind farms with loop connection cables

Abstract The Canadian developer and owner of green power facilities Northland Power Inc. owns two offshore wind farms (OWFs) in the German Bight, Deutsche Bucht and Nordsee One, operated by the subsidiary Northland Power Europe GmbH. The company supports and conducts research in the field of power flow optimization in wind farm networks. The work at hand represents the results of this effort to maximize the efficiency of the assets. The project was accomplished within a cooperation between the Nordsee One GmbH and the Institute of Electrical Power and Energy Technology at the Hamburg University of Technology. From an external point of view, an OWF represents an “en bloc” power plant connected to the onshore transmission grid via power export cables. Nevertheless, such a power plant comprises a complex, large-scale internal medium voltage network. In case of failure or cable outage, the network topology of an OWF may be modified and unintended overloading of inter-array cables (IACs) is possible. In order to address this issue, a new algorithm and software tool for economic power control in OWFs are introduced in the following which can be employed in wind farms with integrated loop connection cables (LCCs). This configuration particularly entails the risk of overloading cable segments depending on the present wind speed. The new algorithm provides the operator with adapted active power setpoints for each wind turbine generator (WTG) in a given network topology. The aim is to maximize OWF power generation and minimize internal power losses while secure network operation is guaranteed. Using load flow analysis based on WTG power output measurements, the load on each cable section is monitored and the cables can be utilized to their individual full capacity while overload is avoided. The practicability of the approach is demonstrated by means of simulation results.

Development of an apparatus with induced heat-and-mass transfer for drying and hydrothermal processing of moist materials

The need to solve the problems of efficient use of energy resources in processes of heat-and-mass transfer which are widely used in the food and processing industries and are very power-intensive was substantiated. The prospects of application of the induced processes such as the effect of induced heat-and-mass transfer characterized by high energy efficiency and environmental friendliness were noted. Drying and hydrothermal treatment of moist raw materials with gas-tight inserts in horizontal and vertical orientations were modeled. It was established that the nature of this effect in the presence of gas-tight inserts in the solid phase inside the thermostat does not differ from the nature of the effect of induced heat-and-mass transfer in absence of such inserts. It was proved that during the induced heat-and-mass transfer, features of the flow of any volume of internal thermostat medium affect the nature of this flow for other allocated volumes. It was noted that the feature of «artificiality» and controllability of this effect makes it possible to perform certain manufacturing operations in processing different raw materials in one device without their mixing. A technical solution of an apparatus using the effect of induced heat-and-mass transfer for drying and hydrothermal treatment of moist raw materials was proposed based on the obtained experimental results and established theoretical conclusions. The productivity of the developed apparatus in hydrothermal processing of cereals makes 18 kg/h and the energy consumption is 8.1·10 6 J/kg of dried product. The final product is a quick-recoverable porridge that does not require cooking. It was noted that the economic attractiveness of the developed device with the effect of induced heat-and-mass transfer for drying and hydrothermal treatment consists in the ability to reduce energy consumption for these manufacturing operations by 30 %

Cause Analysis of Leakage in 316L Stainless Steel Heat Exchanger

A large area of leakage occurred in plate heat exchanger of a power plant. The causes of leakage were analyzed by means of appearance analysis, chemical composition analysis, microstructure detection and energy spectrum analysis. The results show that Cl ion exists in the environment of the leaking heat exchanger, which has strong corrosiveness to austenitic stainless steel. At the same time, there are machining residual stress and internal stress produced by internal medium in the heat exchanger, which lead to stress corrosion and cracking.

Superhydrophilic ZSM-5 zeolite-coated membrane for enhancing water coalescence in water-in-oil emulsions

The filtration efficiency of coalescent filter elements used in gasoline and diesel oil dehydration in refineries is unsatisfactory and not sufficient to meet downstream water-content requirements. Thus, it was necessary to improve the internal filter medium of traditional oil-water coalescent filter elements. Zeolite membrane is a kind of material with superhydrophilicity and strong adsorption for and permeability to water. In this study, ZSM-5 zeolite membrane with superhydrophilic properties was successfully prepared by an in situ hydrothermal synthesis. Two experiments with zeolite membranes were performed, including membrane filtration and membrane coalescence tests. Membrane filtration tests showed that it possessed strong adsorption for and permeability to water and that the oil-water filtration efficiency for 32# turbine oil, kerosene, and corn oil were all >95 %. In the second part of this study, composite filtration was carried out using the membrane as well as hydrophilic glass fiber and hydrophobic polypropylene (PP) membranes. Membrane coalescence test demonstrated that, when the oil contained a phenol/water combination, the water rejection rate of the composite filtration with ABACBA (A, PP fiber; B, glass fiber; and C, molecular sieve membrane) was 90.8 %, with the downstream water content controlled within 100 mg/L and the quality factor increased from 0.18 to 0.23, relative to other systems. These experimental results showed potential for improving the current oil-water coalescent filters.

Characteristics of granulates used as core materials in the overmoulding process of hollow profiles

Abstract The hybridisation of structural components is an effective way to increase its functionality and lightweight potential. By combining different materials and semi-finished products, lightweight and load-adapted components can be achieved. An effective technology is the overmoulding of hollow profiles to realise additional stiffening and fastening elements. For this purpose, a consolidated and dimensionally stable hollow profile is positioned in the injection mould and is overmoulded. It is known, that hollow profiles have to be supported by an internal medium to prevent the structure from collapsing due to the high injection pressure. Previous studies have shown that granulates are well suited as inner support cores. This paper shows the load-bearing behaviour of support granulates consisting of mono-disperse particles. The structural and material properties of the particles are studied experimentally. Subsequently, the load-bearing behaviour of granulates depending on the filling height is investigated and associated with the particle properties. Based on this, numerical studies based on the DEM are carried out to derive the relationship between the particle properties and the load-bearing behaviour of the granular core. Here, a strong dependence between the interparticle-friction as well as the particle stiffness and the deformation of the granulate under compression loading has been observed.

Masonry chips aggregate as internal curing medium: A cost effective alternative to counteract improper curing conditions

Accompanied by high absorption and desorption capacity, Masonry Chips Aggregate (MCA) offers profound potential as a low-cost internal curing medium. This study overviews the previous studies conducted by research group of one of the authors to evaluate overall performance of concrete at various MCA replacement proportions. A considerable increase in Compressive Strength Ratio (CSR) and Tensile Strength Ratio (TSR) along with a decrease in Charge Ratio (CR) in chloride permeability tests has been observed for using MCA under improper curing conditions, particularly at 20% replacement proportion. Use of MCA has also increased Corrosion Initiation Time (CIT) values of concrete when subjected to at both improper curing conditions.

Gas circulation rate and medium exchange ratio as influential factors affecting ethanol production in carbon monoxide fermentation using a packed-bed reactor

A packed-bed reactor (PBR) which has recyclable internal gas and medium exchange functions for carbon monoxide (CO) fermentation was operated using an ethanol producing acetogen, Clostridium autoethanogenum DSM 10061.

Influence of Phase-Shifted Square Wave Modulation on Medium Frequency Transformer in a MMC Based SST

This article proposes an approach to identify intrinsic power losses of the medium frequency transformer that interfaces two modular multilevel converters (MMC) operated with phase-shifted square wave modulation (PS-SWM) to form a DC solid state transformer (DC SST) module. Cascaded MMC module based DC SST architecture is an excellent choice for HVDC to MVDC conversion for DC grid application as well as for renewable and distributed energy resource integration into the DC grid. Operation with PS-SWM allows reduced cell capacitor size and lower total semiconductor device ratings. However, this modulation generates a unique quasi-square waveform at the SST internal medium frequency (MF) AC interface, which differs from other known square-wave modulation types. This produces a similarly unique transformer flux density, resulting in a transformer core loss that cannot be predicted by existing methods which makes it challenging to identify. In the interest of presenting a useful and optimizable MF transformer design methodology, this article develops a tool to predict the loss of the MF transformer subjected to PS-SWM. The proposed loss estimation technique is validated through an experimental testbed operated in two different configurations and is demonstrated to provide a valid basis for the use of the proposed MF transformer design methodology. Furthermore, this article provides an analysis of the load-dependent MF transformer core loss, which demonstrates a secondary usefulness of the proposed loss prediction tool in identifying load-dependent converter losses

In-situ observation of high-temperature failure behavior of pipeline steel and investigation on burn-through mechanism during in-service welding

The risk of burn-through is a major concern when conducting in-service welding repair for oil-gas pipelines. The governing mechanism of burn-through has not hitherto been studied systematically. Here we perform a comprehensive analysis of the dynamic process of burn-through and the high-temperature failure behaviors of pipeline steel. Firstly, the in-service welding experiments were conducted to analyze the characteristics of burn-through. Influenced by the welding stress and especially the internal medium pressure, radial deformation of the pipe wall happens under the molten pool, thereby causing tensile stress. The pipeline metal under the molten pool contains the fusion zone and coarse grain zone. In order to study the crack initiation and propagation mechanism of the coarse grain zone and the fusion zone, the in-situ high-temperature tensile tests and in-situ high-temperature metallographic tests were carried out, respectively. The results indicate that during in-service welding process, the crack initiation mechanism of different microzones is different. For the fusion zone, the grain boundary melting leads to intergranular brittle fracture. While for the coarse grain zone, the stress concentration caused by grain boundary sliding makes the cracks appear easily at grain boundaries and triple junctions. Therefore, burn-through has intergranular cracking morphology. Microcracks originate from the fusion zone and penetrate along the weakened grain boundaries in the direction that perpendicular to the tensile stress and merge to form macroscopic cracks. Once the cracks penetrate to the inner wall, burn-through happens. We expect that these results would be valuable for clarifying the mechanism of burn-through and enriching the welding theories under severe conditions.

Burnt Clay Brick Aggregate for Internal Curing of Concrete under Adverse Curing Conditions

In this study, properties of concrete with brick aggregate as internal curing medium has been investigated under adverse curing conditions. Brick aggregates, commonly known as brick chips (BC), have high porosity and absorption capacity. Desorption tests of different sizes of BC revealed that BC could desorb about 90% of its absorbed water. It was also observed that smaller size BC had higher desorption capacity than that of larger ones. Moreover, higher internal relative humidity was observed for all internally cured (IC) samples as compared to control samples made with 100% rock aggregate particles commonly known as stone chips (SC). Internally cured samples with three different percent replacements (15%, 20% and 25%) of SC with BC were prepared and subjected to six simulated adverse curing conditions. The performance of internally cured concrete under different curing conditions was evaluated in terms of compressive strength, rapid chloride permeability test (RCPT) and linear shrinkage test. The internally cured samples exhibited higher strength and less permeability and shrinkage as compared to their control counterparts under all adverse curing conditions considered in the study. Based on the findings of the study, 20% partial replacement of SC with BC of 9.5 mm in size can be recommended as a guideline for producing internally cured concrete under adverse curing conditions.

SYSTEM OF METABOLISM OF DRINKING WATER AS A METHODOLOGICAL BASIS FOR THE ESTIMATION OF ITS MINERAL COMPOSITION

The physiological-hygienic system of drinking water metabolism is presented. Drinking water was shown to contain seven vital ions and eight organotrophic-obligate chemical elements as major integral components. Vital ions and water molecules are the main components of water-salt metabolism, are involved in all metabolic processes, including energy metabolism and thermoregulation of the body. Organotropic-obligate chemical elements can enter the composition of enzymes and selectively catalyze enzymatic processes. Circulation of water in the body is carried out both via transcorporal and intracorporal cycles, the adjustable by mechanisms of water-salt metabolism regulation. Transcorporal cycle has a direct relationship with the environment, and the intracorporal cycle is an internal medium. Vital ions and organotrophic-obligate chemical elements in drinking water have a range of hygienic norms that is demonstrated on the example of magnesium.

Delaying time to corrosion initiation in concrete using brick aggregate as internal curing medium under adverse curing conditions

Absence of proper curing results in weaker and permeable concrete and eventually, reduces the service life of reinforced concrete (RC) structures significantly, particularly in aggressive conditions like marine environment. One of the main causes for reduced service life under marine ambience is chloride induced corrosion resulting from ingress of chloride ion in concrete. The negative impacts caused by the lack of proper curing can be compensated by adapting the internal curing mechanism that ensures better hydration. Brick chip (BC) has the ability to absorb sufficient quantity of water during mixing and desorbs it afterwards and therefore, can be used to produce internally cured concrete. On the other hand, chloride ingress within concrete primarily depends on chloride diffusion coefficient of the concrete. As a result, internally cured concrete with appropriate proportion of BC is expected to linger the time of corrosion initiation in RC structure by producing robust and denser concrete. In this study, the delay in corrosion initiation time and consequent extension of the service life of internally cured concrete with BC under different unfavorable curing conditions was investigated. It was found that corrosion initiation time of internally cured concrete could be increased by several years as compared to conventional concrete depending on adversity of curing conditions and concrete cover. The study shows immense potential of internal curing using BC to enhance service life of concrete under adverse curing conditions and hinder premature repair work of concrete.

Development of temperature stabilization system for biological sample’s microscope

This paper deals with the development proposal of a heating system for maintaining a required temperature of a microscopic biological sample, which are located within the detection area of the microscope. The need for maintaining a specific temperature of a biological sample is given by the viability of the microorganism what is related to the temperature of their internal medium. Meeting the conditions for changing or maintaining the required temperature is especially necessary in cases such as monitoring the growth of microorganisms and within the temperature-dependent mutations. In this paper, several alternatives are presented, while the best possible design of the heating element is investigated through thermal simulation analysis. Consequently, the proposal for an appropriate control algorithm for the selected heating system and its arrangement is given together with its verification within the experimental sample of the microscope.

Numerical Experiments on Triaxial Compression Strength of Soil‐Rock Mixture

Soil‐rock mixture is a kind of unfavorable geologic material, and it is composed of low‐strength soil particles and high‐stiffness rock blocks. Mechanical properties of soil‐rock mixture were controlled by the internal mesoscopic medium, thus resulting in great difficulties of determination of mechanical parameters. In this paper, influences of rock content, mesoscopic features, and random distribution of mixture in soil‐rock mixture on its shear strength were discussed through discrete element numerical simulation of the laboratory triaxial test. Results demonstrated that, with the increase of rock content, the internal friction angle of soil‐rock mixture increased continuously, while the cohesion of soil‐rock mixture decreased firstly and then increased. The stress‐strain curve belonged to a nonlinear hardening type, which was close to soil characteristic. However, the shear strength was affected by mesoscopic medium of mixture particles significantly, resulting in the strong discreteness of strength, and only by large amounts of data statistics can we get a better regularity of strength. The research results can provide references to determine mechanical parameters of soil‐rock mixture.

Iron-Based Layered Double Hydroxide Implants: Potential Drug Delivery Carriers with Tissue Biointegration Promotion and Blood Microcirculation Preservation

This work explores the synthesis, physicochemical characterization, and in vivo biocompatibility of iron-based layered double hydroxides (LDHs) with molar ratio M2+/(Fe3+ + Al3+) equal to 2, Fe3+/Al3+ equal to 1, and chloride anions as charge-compensating ion (abbreviated Mg4FeAl-Cl and Zn4FeAl-Cl) prepared by the coprecipitation method. The higher structural organization of Zn4FeAl-Cl in comparison to Mg2+ analogous material was noticed by X-ray diffraction and scanning electron microscopy images. Biocompatibility of LDH was evaluated by intramuscular implantation in rats. Tablets of M4FeAl-Cl (M = Mg, Zn) were readily identified macroscopically after 7 and 28 days of implantation, denoting slow dissolution in the internal medium; adjacent to the tablets, blood flow was preserved without tortuosity or pathological dilatations, according to the Sidestream Dark Field Imaging technique. The histological analysis showed no inflammatory response and the presence of angiogenesis and tissue remodeling with the reconstruction of the extracellular matrix and cells around the tablets, besides the induction of collagen type-I formation. Prussian blue histochemical reaction suggested higher solubility of Mg4FeAl-Cl in the extracellular matrix compared to zinc LDH. Considering the positive biocompatibility results obtained for M4IIFeAl-LDH materials, experiments were conducted to intercalate the anti-inflammatory naproxen, as a model drug, into the iron-based LDHs (M4IIFeAl-NAP). The release profile of NAP in phosphate buffer showed 90% of the drug delivered after about 80 h. However, divalent metal leaching was verified mainly for Mg-LDH (around 50%) when compared to Zn2+ (around 1%). Iron-based LDHs have great potential for medical and technological applications as local drug delivery biomaterials exhibiting biocompatibility and biointegration properties.

Inhibition of Sodium-Hydrogen Antiport by Antibodies to NHA1 in Brush Border Membrane Vesicles from Whole Aedes aegypti Larvae.

The present research report describes Na+/H+ antiport by brush border membrane vesicles isolated from whole larvae of Aedes aegypti (AeBBMVw). Our hypothesis is that acid quenching of acridine orange by AeBBMVw is predominantly mediated by Na+/H+ antiport via the NHA1 component of the AeBBMVw in the absence of amino acids and ATP. AeNHA1 is a Na+/H+ antiporter that has been postulated to exchange Na+ and H+ across the apical plasma membrane in posterior midgut of A. aegypti larvae. Its principal function is to recycle the H+ and Na+ that are transported during amino acid uptake, e.g., phenylalanine. This uptake is mediated, in part, by a voltage-driven, Na+-coupled, nutrient amino acid transporter (AeNAT8). The voltage is generated by an H+ V-ATPase. All three components, V-ATPase, antiporter, and nutrient amino acid transporter (VAN), are present in brush border membrane vesicles isolated from whole larvae of A. aegypti. By omitting ATP and amino acids, Na+/H+ antiport was measured by fluorescence quenching of acridine orange (AO) caused by acidification of either the internal vesicle medium (Na+in > Na+out) or the external fluid-membrane interface (Na+in < Na+out). Vesicles with 100 micromolar Na+ inside and 10 micromolar Na+ outside or with 0.01 micromolar Na+ inside and 100 micromolar Na+ outside quenched fluorescence of AO by as much as 30%. Acidification did not occur in the absence of AeBBMVw. Preincubation of AeBBMVw with antibodies to NHA1 inhibit Na+/H+ antiport dependent fluorescence quenching, indicating that AeNHA1 has a significant role in Na+/H+ exchange.