Maximum Velocity Values Research Articles

Modeling shape deformation of ferrofluid ring section and secondary flow in ferrofluid seals with rectangular polar teeth using BEM and FVM

The focus of this study is on modeling the shape deformation of ferrofluid ring sections and secondary flows in ferrofluid seals with a rectangular polar tooth. These factors determine the sealing capability and homogenization of particles in ferrofluids. The model consists of governing equations for ferrofluid flows, the balance equation of normal stresses on ferrofluid free surfaces, the magnetic field equations and the ferrofluid volume equation. To solve the mathematical model, a method utilizing a combination of boundary element method and finite volume method is proposed. Discretizing the azimuthal velocity equation with boundary element method enables efficient determination of ferrofluid-ring section shape deformation. Furthermore, a discretely fitting method is proposed to solve the issue of lack of analytic expressions for the magnetic field distribution in sealing structures with rectangular polar teeth. Numerical tests of the magnetic field and azimuthal velocity distribution verify the validity and accuracy of the proposed solution method. Numerical experiments conducted on an actual ferrofluid sealing structure show that increasing the rotational speed of the shaft, in conjunction with effect of the centrifugal force, leads to deformation of the ferrofluid-ring section shape and reduces the contact area between the ferrofluid ring and shaft. This results in a decrease in pressure resistance. Typically, at a speed of 10 m/s, the pressure resistance falls by around 20%. The maximum value of secondary-flow velocity is significantly affected by the rotational speed of the shaft, although it does not exceed 0.8% of the linear velocity on the shaft surface in our study.

Effects of electric field and device size on the electron velocity in p-i-n GaAs semiconductor

This paper introduces the investigation of the influence of electric field and device size on the drift velocity of electrons in GaAs semiconductor using ensemble Monte Carlo simulation method under limited size conditions. We employed a GaAs diode device model with p-i-n structure, consisting of p-type and n-type semiconductor layers with uniform size of 20 nm, and a variable-sized intrinsic (i) semiconductor layer in between. We show that in the absence of external electric field, the damped velocity will diminish as the size of the (i) layer ranges from 100 nm to 800 nm. And the damped oscillation period of the electron velocity is a linear function of the device size. Additionally, by examining the maximum value of electron velocity under the influence of an external electric field, our observed results are consistent with those reported by Saraniti et al. (2002) [22] in low electric field below 50 kV/cm; while at higher electric fields, the maximum velocity gradually increased to a saturation value. Furthermore, the maximum velocity vmax is found to follow a simple logarithmic law as a function of i-layer size S as vmax=aln⁡(bS). The coefficients of this relation equation were derived using least-square approximation technique yielding a high determination coefficient R2 up to 0.998.

Identification and evaluation of CAZyme genes, along with functional characterization of a new GH46 chitosanase from Streptomyces sp. KCCM12257

The genomic analysis of Streptomyces sp. KCCM12257 presented 233 CAZyme genes with a predominant glycosyl hydrolase family. This contributes degradation of various polysaccharides including chitin and chitosan, and other promising candidates for the production of different oligosaccharides. We screened the strain providing different polysaccharides as a sole source of carbon and strain KCCM12257, showed higher activity towards colloidal chitosan. Further, we identified and characterized a new chitosanase (MDI5907146) of GH46 family. There was no activity towards chitin, carboxymethylcellulose, or even with chitosan powder. This enzyme acts on colloidal chitosan and hydrolyzes it down into monoacetyl chitobiose, which consists of two glucosamine units with an acetyl group attached to them. The maximum enzyme activity was observed at pH 6.5 and 40 °C using colloidal chitosan as a substrate. The Co2+ metal ions almost double the reaction as compared to other metal ions. The dissociation constant (Km) and of colloidal chitosan (≥90 % and ≥75%DD) were 3.03 mg/ml and 5.01 mg/ml respectively, while maximum velocity (Vmax) values were found to be 36 mg/ml, and 30 μM/μg/min, respectively. Similarly, catalytic efficiency (Kcat/Km) of colloidal chitosan with ≥90 %DD was 1.9 fold higher than colloidal chitosan with ≥75%DD.

Computational study of palladium percentage and oxygen ratio effects on air-methane catalytic combustion in a helical microchannel: A molecular dynamics approach

Combustion is an exothermic chemical process between an explosive substance and an oxidizing agent that is accompanied by heat generation and chemical change of raw materials. Catalysts are used in a combustion process for various reasons, including the speed at which the material reaches equilibrium. Catalysts are chemicals that increase the rate of reaction in chemical processes. The present research investigates the influence of palladium percentage and oxygen ratio on air-methane catalytic combustion in a helical microchannel. For this purpose, the atomic behavior and combustion performance of the simulated sample in the presence of excess oxygen and oxygen deficiency is reported by the molecular dynamics (MD) method. The potential functions used in this paper were Lennard-Jones, the embedded atom model (EAM), and Coulomb. It is concluded that increasing palladium percentage in limited ratios improves the atomic and combustion performance of the simulated structure, and this enhancement is greater in the presence of excess oxygen. In the presence of excess oxygen, the numerical value of maximum density, velocity and temperature converged from 0.138 atom/Å3, 0.33 Å/ps and 523 K to 0.144 atom/Å3, 0.36 Å/ps and 539 K, respectively with increasing palladium percentage from 1 % to 4 %. And by increasing the palladium ratio to 10 %, these numerical values decrease to 0.137 atom/Å3, 0.31 Å/ps and 530 K. Moreover, in the presence of oxygen deficiency, heat flux, thermal conductivity, and combustion efficiency of atomic samples reached 2049 W/m2, 1.23 W/m.K and 90 % after rising palladium to 4 %, and it decreased to 2035 W/m2, 1.19 W/m.K and 86 % by adding 10 % palladium. Therefore, the results indicate that the oxygen and the catalyst (palladium) ratios can benefit the combustion process. These results can optimize the atomic performance and combustion performance of structures essential for use in various industries.

Magnetic Resonance Imaging in the Diagnosis of Aortic Wall Elastic Properties Disorders and Its Hemodynamics

Background. Vascular stiffness is an important predictor of cardiovascular disease. The vascular wall biomechanical parameters change not only in patients with genetic disorders of the connective tissue. This means that, regardless of etiology, the early detection of a progressive loss of aortic elasticity is of great clinical importance in preventing the development of severe complications. Assessment of aortic biomechanical parameters using magnetic resonance imaging (MRI) is a new level of visualization for aortic diseases allowing to improve surgical tactics and prevent complications. A number of biomechanical parameters determined by aortic MRI demonstrates the process of its wall remodeling, so their analysis will allow to develope an algorithm for the early diagnosis of aneurysms and the threat of acute aortic syndrome.Objective: using aortic MRI data, to evaluate the aortic biomechanical parameters and hemodynamics at pre- and postoperative stages and their impact on the occurrence of complications and relapses in the long-term period.Material and methods. Between 2020 and 2023, in Petrovsky Russian Scientific Center of Surgery, aortic MRI was performed prospectively before and after surgery in 107 patients with diagnoses of ascending aortic aneurysm (55 patients: 48 (87%) males and 7 (13%) females, mean age 79.4±14.91 years) and DeBakey type I and III aortic dissection, chronic stage (52 patients: 44 (85%) males and 8 (15%) females, mean age 54.32±10.41 years).Results. The quantitative data analysis in the postoperative period showed a decrease in the aortic wall elastic properties in the form of extensibility (0.4 [0.34; 0.54] %/mm Hg in the aneurysm group; 0.5 [0.25; 0.55] %/mmHg in the dissection group) and an increase in stiffness in the form of Young’s modulus (0.6 [0.38; 0.68] MPa in the aneurysm group; 0.5 [0.39; 0.83] MPa in the dissection group). Hemodynamic changes in the dissection group after surgery demonstrated a significant increase in values of maximum velocity in the descending aorta (78.6 [66.24; 130.78] cm/sec) and pressure gradient at the celiac trunk level (2.10 [1.76; 6.84] mm Hg). When assessing the pulse wave velocity parameter in both groups, high values were noted with a tendency to increase after surgery (in the aneurysm group, 7.7 [5.7; 20.3] cm/s before surgery versus 8.7 [6.5; 10.65] cm/s after surgery; in the dissection group, 9.7 [6.8; 12.9] versus 12.7 [7.7; 15.7] cm/s, respectively).Conclusion. Monitoring general hemodynamics and blood flow patterns together with an assessment of the aortic wall elasticity will make it possible to identify patients with borderline aortic dilatation. At the same time, studies of the aortic prosthetic segment are of particular interest. The obtained data on hemodynamic changes occuring at the border of the prosthetic and native segments of the operated aorta can confirm and justify the development of a complication in the form of distal stent graft-induced new entry (dSINE).

Heterologous expression, purification, and characterization of thermo- and alkali-tolerant laccase-like multicopper oxidase from Bacillus mojavensis TH309 and determination of its antibiotic removal potential.

Laccases or laccase-like multicopper oxidases have great potential in bioremediation to oxidase phenolic or non-phenolic substrates. However, their inability to maintain stability in harsh environmental conditions and against non-substrate compounds is one of the main reasons for their limited use. The gene (mco) encoding multicopper oxidase from Bacillus mojavensis TH309 were cloned into pET14b( +), expressed in Escherichia coli, and purified as histidine tagged enzyme (BmLMCO). The molecular weight of the enzyme was about 60kDa. The enzyme exhibited laccase-like activity toward 2,6-dimethoxyphenol (2,6-DMP), syringaldazine (SGZ), and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The highest enzyme activity was recorded at 80°C and pH 8. BmLMCO showed a half-life of ~ 305, 99, 50, 46, 36, and 20min at 40, 50, 60, 70, 80, and 90°C, respectively. It retained more than 60% of its activity after pre-incubation in the range of pH 5-12 for 60min. The enzyme activity significantly increased in the presence of 1mM of Cu2+. Moreover, BmLMCO tolerated various chemicals and showed excellent compatibility with organic solvents. The Michaelis constant (Km) and the maximum velocity (Vmax) values of BmLMCO were 0.98mM and 93.45µmol/min, respectively, with 2,6-DMP as the substrate. BmLMCO reduced the antibacterial activity of cefprozil, gentamycin, and erythromycin by 72.3 ± 1.5%, 79.6 ± 6.4%, and 19.7 ± 4.1%, respectively. This is the first revealing shows the recombinant production of laccase-like multicopper oxidase from any B. mojavensis strains, its biochemical properties, and potential for use in bioremediation.

Design, fabrication, and experimental study of a full-scale compressed air ejection system based on missile acceleration limitation

In this paper, we study the interior ballistic characteristics of rockets or missiles with acceleration less than 10 g during the compressed air ejection process. First, we designed and fabricated a full-size compressed air ejection system, and utilizing different missile mass and initial pressure variables. Then, we established the mathematical model of the interior ballistics of the ejection system using the fourth-order Runge-Kutta scheme to estimate the ejection performance and results of the system. In addition, we independently built a full-scale compressed air ejection system test platform and conducted multi-condition live ejection tests. The results show that the effective travel distance of the missile is greater than 2.5 m and the acceleration is basically less than 10 g. With a certain missile mass, the acceleration peak, velocity peak and displacement of the missile are positively correlated with the initial pressure, and the opposite variable is negatively correlated. The maximum acceleration and velocity values are 10.11 g and 13.5 m/s, respectively, and the minimum values are about 3.5 g and 4 m/s. The variables are the same, the pressure peak at each measuring point in the ejection barrel is bottom > middle > upper, and the amplitude of the pressure drop between middle and bottom gradually decreases. Depending on the appearance time of the pressure point, the maximum pressure attenuation time in the ejection barrel is determined to be 0.838 s, and the minimum is 0.343 s. Comparing the pressure peak points at the bottom, middle and upper with the calculated pressure curve, the attenuation trend of the two is basically the same. Therefore, the research results show that the full-scale compressed air ejection system is effective and practical, and the test results provide data reference for related launches.

Laminar burning velocity measurements of C1-C4 alkane-air mixtures at elevated mixture temperatures

This study presents, the measurements of the laminar burning velocity (LBV) for C1-C4 alkane fuels with air at higher mixture temperatures, using an externally heated diverging channel (EHDC) method. The experimental results are shown for mixture conditions ranging from ϕ = 0.7 to 1.3, with a mixture temperature of 350–660 K at ambient pressure conditions. The temperature exponent (α) is obtained using the power-law correlation to explain the influence of LBV variation with the mixture temperature at different mixture equivalence ratios, ϕ. The maximum value of mixture burning velocity is recorded for marginally rich mixture conditions, (ϕ = 1.1) at different temperatures. The lowest value of temperature exponent (α) is observed at ϕ = 1.1. The data obtained from the current measurements are then compared with the literature results, and mechanism predictions are made using the kinetic models of USC Mech II, FFCM-1, Aramco Mech 2.0, Qin Mech, San Diego Mech, GRI Mech 3.0, and LLNL. The normalized sensitivity analysis for these straight chain C1-C4 alkane fuels reveals that the decomposition of formyl radical in reaction R163: HCO + M ↔ H + CO + M, which exhibits further major root of H atom, leading to enhancement of the LBV of these fuels at elevated mixture temperature conditions.

Enhancing catalytic performance of Fe and Mo co-doped dual single-atom catalysts with dual-enzyme activities for sensitive detection of hydrogen peroxide and uric acid

Single-atom catalysts (SACs) have attracted much attention due to their excellent catalytic activity, but the improvement of atomic loading which means that weight fraction (wt%) of metal atom was still facing great challenges. In this work, iron and molybdenum co-doped dual single-atom catalysts (Fe/Mo DSACs) was prepared for the first time by using the soft template sacrifice strategy, which improved significantly the atomic load and exhibited both the oxidase-like (OXD) activity and the dominant peroxidase-like (POD) activity. Further experiments reveal that Fe/Mo DSACs can not only catalyze O2 to generate O2•− and 1O2, but also catalyze H2O2 to generate a large number of •OH, which caused 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to be oxidized to oxTMB, accompanied by the color changing from colorless to blue. The steady-state kinetic test showed that Michaelis–Menten constant (Km) values and the maximum initial velocity values (Vmax) of the POD activity of Fe/Mo DSACs were 0.0018 mM and 12.6 × 10−8 M s−1, respectively. The corresponding catalytic efficiency was tens of times higher than Fe SACs and Mo SACs, which proves that the synergistic effect between Fe and Mo has significantly improved the catalytic ability. Based on the excellent POD activity of Fe/Mo DSACs, a colorimetric sensing platform combined with TMB was proposed to realize the sensitive detection of H2O2 and uric acid (UA) in a wide range, with limits of detection as low as 0.13 and 0.18 μM, respectively. Finally, accurate and reliable results were obtained in the detection of H2O2 in cells, and of UA in human serum and urine.

Analysis of the Sludge Settling Behavior of the Kibendera Waste Stabilization Ponds in Ruiru, Kenya

Waste Stabilization Ponds (WSP) provide both cost-effective and high-performance wastewater treatment benefits in the tropical regions. The 3-month sludge settling behavior in the Kibendera WSP in Ruiru, Kenya, was studied between July and September 2022. The study aimed at determining the sludge volume index (SVI) and hindered settling velocity during the dry weather flow regime. Based on these experimental data, Vesilind Model was used to characterize the settling behavior in the anaerobic and primary facultative ponds. Whereas Standard Methods for the examination of water and wastewater were used to determine the total suspended solids (TSS) concentrations in the ponds, batch column settling tests were used to generate the batch settling curves for each pond. Generally, good settling behavior characterized by SVI values of less than 150 mL/g was observed during the study period. Highest settling velocities of 1.16 m/hr and 1.22 m/hr were recorded in the anaerobic and primary facultative ponds respectively for TSS concentrations of 0.6 g/L and 0.416 g/L. Optimal maximum velocity (<i>V_max</i>) values of 3.42 m/hr and 1.78 m/hr were observed in the anaerobic and primary facultative ponds respectively. The corresponding optimal model parameters (n) describing the measured data accurately were 0.47 L/g and 0.51 L/g respectively. The model parameters so obtained may be useful in characterizing the sedimentation behavior in the WSP during the dry weather flow regimes.

Performance Analysis of Geometric Properties of Fuel Cell Components

Due to factors including low emission values, great energy efficiency, and reduced environmental contamination, fuel cells have gained popularity recently. Fuel cells using polymer electrolyte membranes can distribute reactant gases through gas flow channels and remove water that forms during the reaction from the fuel cell. This study looked at how different channel sizes and channel cross-section geometries (rectangular, triangular, and semicircular) affected the distribution of current density, oxygen concentration, velocity, and temperature parameters on the cathode catalyst in the flow channels of a single-channel PEM fuel cell at 0.75 V cell voltage. The model with the highest current density and consequently the best fuel cell performance was determined to be 9 x 10-5 A/cm2 in a channel with a height and breadth of 0.1 cm and A = 1 cm2, according to the data obtained. The flow channel length was assessed at 0.2 in the analysis results for all models because it did not alter with the oxygen concentration distribution. In varied channel designs with the same area, it has been found that the velocity distribution varies inversely with the current density. The maximum velocity value recorded at this location was 33.1 m/s in a semicircular canal with a R of 0.34 mm. It has been discovered that fuel cells from more places operate better as a result.

ОДНОМЕРНАЯ ДИНАМИКА ДОМЕННОЙ ГРАНИЦЫ В СЕМИСЛОЙНОЙ ФЕРРОМАГНИТНОЙ СТРУКТУРЕ

The dynamics of the domain boundary is considered using the example of a seven-layer ferromagnetic structure with three thin and four wide magnetic layers. The structure of the domain boundary is represented as a kink solution of the sine-Gordon equation. The equation of motion for magnetization was solved numerically using an explicit scheme. The discretization of the equation was carried out according to a standard five-point scheme of the "cross" type. The paper shows the features of the dynamics of the domain boundary in a multilayer magnetic system in the presence of thin magnetic layers with an increased value of the magnetic anisotropy constant. Thin layers with an increased value of the magnetic anisotropy constant compared to the homogeneous state represent potential barriers to the moving domain boundary. Thin layers with an increased magnitude of magnetic anisotropy compared to a homogeneous state represent potential barriers to a moving domain boundary. A diagram of possible scenarios of the dynamics of the domain boundary is constructed depending on the initial velocity of its movement and the distance between three thin magnetic layers. The maximum value of the kink velocity for reflection from all potential barriers, depending on their size, is obtained. With an increase in the height and width of the barrier, the value of such a threshold maximum reflection velocity of the domain boundary increases nonlinearly. With a sufficiently high barrier height, there is already an almost linear dependence on the width of this threshold velocity. With a slight increase in the speed of movement of the domain boundary, the kink can pass through the first barrier, but it is reflected from the second barrier. There is also a case of kink oscillation between the second and third potential barriers. Such fluctuations are clearly inharmonious. The dependence of the threshold velocity on the distance between the barriers is obtained. As the distance between the barriers increases, the threshold speed value tends to a value equal to the threshold speed for one barrier. In the work, the minimum value of the speed of the domain boundary of the passage of all layers, depending on the parameters of potential barriers, is obtained. It is also found that there is a critical distance separating the dynamics of the domain boundary into two regions with qualitatively different behavior of the system.

Technical safety of buildings around polish quarries against harmful seismic vibrations caused by rock blasting

This paper presents the results of measurements of the elliptical distribution of seismic vibrations generated during rock blasting.The technical safety of a building in the area of seismic vibrations is determined by the vibration velocity that does not exceed the line B included in zone II of the scale of dynamic influences [SWD]. The hypothesis proved in the paper is that for both elliptical and circular distributions of the vibration velocity in rock mining with blasting material [BM] there is a directionality of the horizontal radial component Vx and the tangential component Vy of the vibration velocity.The magnitude of the components Vx and Vy of the vibration velocity at the same distance from the vibration source depends on the directional angle "α" between the line of the blast holes and the line connecting the centre of the surface of the rock block being mined with [BM] and the place of measurement. The elliptical shapes of the graphs Vx and Vy obtained during the mining of the BM of the basalt deposit, which depend on the value of the directional angle, were compared with the shape of the circular velocity graphs Vx and Vy. New correlations are given that take into account the directional angle when calculating the maximum vibration velocity values needed to determine the damage caused to a bulding by the SWD.A dynamic impact scale [SWD] for the assessment of building damage as the vibration velocity acting on the building increases is given and discussed. Vibration velocity diagrams measured during the excavation of BM rock are presented for circular distributions in accordance with theoretical predictions. A vibration velocity diagram for an elliptical distribution, inconsistent with a circular distribution, measured during the excavation of BM rock is presented. It is shown that the directionality of the horizontal radial and tangential components of vibration velocity exists for both circular and elliptical distribution of vibration velocity in rock excavation with BM. In the conclusions, for the elliptical velocity field of the vibrations, the conditions to be observed in order to be able to direct the smallest vibrations towards the built up area are given.

The effect of external force and magnetic field on atomic behavior and pool boiling heat transfer of Fe3O4 /ammonia nanofluid: A molecular dynamics simulation

BackgroundIn this study, the pool boiling heat transfer of Fe3O4 /ammonia nanofluid in a copper (Cu) nanochannel is done using the molecular dynamics (MD) simulation. MethodsTo increase and improve the performance of heat transfer, the effect of external force, and external magnetic field frequency on the atomic and thermal performance of the simulated nanostructure was checked. The results show that the density increased with a positive slope when the external force was imposed on the nanostructure with a growing trend. The amount of velocity and temperature similarly increased. So, by increasing the external force from 0.001 to 0.005 eV/Å, the maximum values ​​of density, velocity, and temperature converge to the values ​​of 0.1441 atom/Å3, 13.939 Å/fs, and 794.61 K. Moreover, increasing the applied external force caused an increase in the heat flux and thermal conductivity in the nanostructure. Finally, studying the effect of external magnetic field on the nanofluid's atomic behavior shows that with the change in the frequency of external magnetic field, Poiseuille behavior was remained. The results of the increase in the frequency of external magnetic field show the increasing trend of velocity and temperature. Numerically, the maximum values of velocity and temperature increase from 7.133 to 11.476 Å/fs, and from 210.23 to 410.07 K, respectively. Furthermore, HF increases by increasing the frequency of external magnetic field. Significant findingsAs particles' movement increased, the structure's thermal resistance decreased. So, by increasing external force, the thermal resistance in the structure decreased.

Moisturizing at a molecular level - The basis of Corneocare.

This review covers the last 20 years of research we and our collaborators have conducted on ethnic differences in facial skin moisturization placed in historical context with previous research. We have focussed particularly on the biochemical and cellular gradients of the stratum corneum (SC) with the aim of discovering new skin moisturization and SC maturation mechanisms, identifying new technologies and/or providing conceptual innovations for ingredients that will improve our understanding and treatment of dry skin. Specifically, we discuss gradients for corneodesmosomes and proteases, corneocyte phenotype-inducing enzymes, filaggrin and natural moisturizing factor (NMF), and barrier lipids. These gradients are interdependent and influence greatly corneocyte maturation. The interrelationship between corneodesmolysis and the covalent attachment of ω-hydroxy ceramides and ω-hydroxy fatty acids to the corneocyte protein envelope forming the corneocyte lipid envelope is especially relevant in our new understanding of mechanisms leading to dry skin. This process is initiated by a linoleoyl-ω-acyl ceramide transforming enzyme cascade including 12R lipoxygenase (12R-LOX), epidermal lipoxygenase-3 (eLOX3), epoxide hydrolase 3 (EPHX3), short-chain dehydrogenase/reductase family 9C member 7 (SDR9C7), ceramidase and transglutaminase 1. Our research has opened the opportunity of using novel treatment systems for dry skin based on lipids, humectants, niacinamide and inhibitors of the plasminogen system. It is clear that skin moisturization is a more complex mechanism than simple skin hydration.

Biochemical and Kinetic Study for the Partial Purified Thioredoxin Reductase from Healthy Human Serum

The research included the separation of thioredoxin reductase (TrxR) from human blood serum using different biochemical techniques. Two proteinous peaks had been isolated by gel filtration using sephadex)G-50) and three proteinous peaks isolated from sephadex (G-100) that produced by ammonium sulphate precipitation (65%). The approximately molecular weight of the isolated protein as a source of enzyme using gel filtration chromatography (G-100) was (118059 + 925) Dalton.&#x0D; The results showed two peaks of enzyme when using ion exchange-type DEAE-cellulose and when using electrophoresis technique type SDS-PAGE indicated the presence of two bands from peak of separation column type sephadex G-100 and one band of each peak, resulting from the ion exchange process with molecular weights of 58231 +490 Dalton.&#x0D; The results showed that the optimum conditions of purified enzyme from human serum was at (200 µg/ml) of protein as a source of the enzyme using (0.4 mol/l) citric acid-Na2HPO4 buffer solution at pH (7) act for (25) minutes at (40°C). Using Line Weaver-Burk plot, the values of maximum velocity (Vmax) and Michaelis constant (Km) were found to be (0.182 µmol/ min) and (0.013 mol/l) respectively using 5,5-- dithio bis (2-nitrobenzoic acid) (DNTB) as a substrate. Finally, this was, also, involved the study of the effect of some chemicals and drugs on the enzyme activity. The results showed that gundinium - HCl is uncompetitive inhibitor, while bromoacetic acid is noncompetitive inhibitor and zinc sulphate is a competitive inhibitor for the enzyme at different concentrations of inhibitors, but dexathamazone was an activator to the enzyme.

Numerical Investigation of Water Inflow Characteristics in a Deep-Buried Tunnel Crossing Two Overlapped Intersecting Faults

Because fault core zones and damage zones overlap, when a tunnel crosses the intersecting faults the groundwater flow characteristics of the tunnel-surrounding rock will be different compared to that from a single fault. By using the theory of “Three-district zoning of faults”, an improved Darcy–Brinkman numerical model for a tunnel crossing the intersecting faults was established in this work. Based on the relative vertical positions between the tunnel axis and the intersection center of faults, the underground water seepage field was analyzed at steady-state by solving the improved Darcy–Brinkman equation for the host rock zone and the fault zone. The simulation results show that the flow field around the tunnel is almost unaffected by the relative positions but is mainly dependent on the relative heights. Specifically, the relative position variation of the fault intersection to the tunnel axis has little effect on the pore pressure. In terms of flow velocity, regardless of the relative positions of the fault intersection and the tunnel, the maximum value of flow velocity almost occurs near the bottom of the tunnel excavation face and consistently displays high values within a small distance ahead of the excavation face, and then decreases quickly as the distance increases. Furthermore, the flow velocity changes minimally in the host rock. It will likely encounter the maximum water inflow rate when the tunnel excavation face passes through the intersection. The numerical simulation results can provide a practical reference for predicting water inflow into deep-buried tunnels passing through overlapped intersecting faults.

Characteristics of the flow in channels with extended boundaries

Abstract In the flow in channels with extended boundaries, the channel sides are extended covering parts of the channel flow surface symmetrically or asymmetrically. The pressure on the top surface remains approximately atmospheric, while the distributions of both velocities and discharges in the flow cross-section are severely affected. In this study, cases with different asymmetric extension ratios and aspect ratios were experimentally examined. The effect of the roughness of both extensions and the flume bed was investigated. The velocity data were sampled using Acoustic Doppler Velocimeters. The resulting velocity iso-lines showed deformations due to asymmetricity and the maximum velocity distribution was shifted towards the sides of smaller extension ratios. Low-velocity zones were formed bounded by the extensions, the side boundaries, and the flume bed where the flow resembles that of a closed conduit with maximum velocity value near the middle, but with a major difference that the iso-lines are not closed due to the absence of the fourth boundary. In cases with a larger aspect ratio and roughness, high turbulence was noticed with severe cross-currents resulting in a low-flow velocity component. Results are demonstrated through figures and tables and the data were tested against well-known equations available in the literature.

Experimental assessment of velocity and bed shear stress in the main channel of a meandering compound channel with one-sided blocks in floodplain

Meandering rivers have an important role in transporting runoff from rainfall, especially during floods. With many cities and villages along rivers and the construction of water-management structures in floodplains, the flow pattern of the meandering rivers changes in time of floods. Here the flow behaviors in meandering compound channels with smooth floodplains and one-sided building floodplains are investigated using laboratory experiments. The experiments have been performed at three relative depths of 0.29, 0.39 and 0.49 and the corresponding discharges. The results show that the block density in a floodplain has a significant effect on flow behavior in the main channel. So that, with the increase of the relative depth, the ratios of main channel discharge compared to the total discharge (Qmc/Q) decreases in the bends with minimal extension of blocks floodplain, the crossover areas and the bends with maximal extension of blocks floodplain. For a given Dr, the significant increase in the Manning's n values as the density of the blocks increases (approximately 30%). With increasing the blocks density from zero to 23.7%, the maximum Darcy–Weisbach friction factor in sections CS1 and CS7 increases by 110% and 2%, respectively, which shows that increasing the density of blocks does not have a great effect on f in the section CS7. Under one-sided blocked floodplain conditions, the maximum longitudinal velocity in the main channel in the section with maximal extension of the blocks in the floodplain (CS7) is greater than the section with minimal extension of blocks in the floodplain (CS1). At the relative depth of 0.49, the maximum value of depth-averaged velocity in sections CS1-4 decreased by an average of 52% compared to the smooth floodplain. The maximum shear stress on the bed at the apex section for all channels occurs near the convex side and the bed shear stress at all sections decreases with decreasing relative depth and in the section with minimal extension of blocks floodplain (CS1) and cross-over sections. The maximum shear stress of the bed decreases with increasing the block density and these changes are more near the convex side than the concave side.

Assessment of Maximum Velocity: A Case Study of Pogon Szczecin Football Players in Polish Ekstraklasa

The aim of this study was to assess the maximum velocity achieved by professional soccer players. The study involved 20 professional football players. The analysis of the achieved velocities during the season was based on individual maximum velocity values obtained in a preseason period test using the GPS monitoring device Catapult Vector S7. The study covered 20 match units and 77 training units. A velocity equal to or greater than 100% of the maximum velocity was achieved 24 times - 21 times (accounting for 88%) during a competitive match (MD 0), 1 time (accounting for 4%) two days before (MD-2), and two times (accounting for 8%) three days before (MD-3). A velocity in the range of 90-99% of the maximum velocity was achieved 207 times. The results confirm that football players can achieve values equal to or greater than 100% of their maximum velocities; however, this occurrence is rare. Due to the low probability of high maximum velocity values during a training microcycle, it is recommended to incorporate specific training methods that allow for achieving high maximum velocities to reduce the risk of hamstring muscle injuries among players, especially among reserve players (who rarely participate in competitive matches).