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Abstract

B a c k g r o u n d: Near Infrared Spectroscopy (NIRS) is considered a reliable assessment method of a balance between cerebral oxygen demand and supply. One of forms of anaesthesia applied during extensive abdominal surgical procedures is the epidural anaesthesia. Its application in addition to the general anaesthesia is a commonly accepted form of anaesthesia in patients undergoing abdominal surgery. The aim of this study was to verify the hypothesis that epidural blocks may have eff ects on cerebral saturation in patients undergoing abdominal surgery under general anaesthesia.

M e t h o d s: Cerebral saturation was monitored intrasurgically. Reduction of cerebral oxymetry by over 25% in relation to the baseline, or cerebral oxymetry value below 50% was considered clinically significant.

R e s u l t s: One hundred and one (101) subsequent and non-randomised patients, age between 35 and 84 years (mean 64 ± 10) qualifi ed for major abdominal surgeries were enrolled. In 14 (13.9%) patients of 101 enrolled a clinically signifi cant reduction of cerebral saturation was observed. In 50 (49.5%) of the enrolled patients, the epidural anaesthesia was applied along the general anaesthesia. A clinically signifi cant reduction of cerebral saturation was observed in 9 of them. No statistically significant association was found between the application of epidural anaesthesia and development of cerebral desaturation.

C o n c l u s i o n: The application of epidural anaesthesia caused no clinically significant reduction of cerebral saturation during the general anaesthesia in course of major abdominal surgical procedures.

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Authors and Affiliations

Tomasz Składzień
Janusz Andres
Artur Pasternak
Jerzy Wordliczek
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Abstract

This paper proposes a self-excited induction generator model with saturation effect for power generating mode in a remote site. The model is led through the space vector mathematical formalism and allows one to analyze the steady and dynamic states. It is developed for a squirrel cage induction machine. This model provides magnetizing inductance variation able to influence the build-up and the stabilization of voltage generation when the load changes. The final result is a realistic approach model which takes into con- sideration the dependency of the magnetizing inductance versus magnetizing current. This novel model is validated through experimental measurements to demonstrate its validity and practicability.

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Authors and Affiliations

Ezzeddine Touti
Habib Kraim
Remus Pusca
Raphael Romary
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Abstract

In this paper, the influence of impact damage to the induction motors on the zero-sequence voltage and its spectrum is presented. The signals detecting the damages result from a detailed analysis of the formula describing this voltage component which is induced in the stator windings due to core magnetic saturation and the discrete displacement of windings. Its course is affected by the operation of both the stator and the rotor. Other fault detection methods, are known and widely applied by analysing the spectrum of stator currents. The presented method may be a complement to other methods because of the ease of measurements of the zero voltage for star connected motors. Additionally, for converter fed motors the zero sequence voltage eliminates higher time harmonics displaced by 120 degrees. The results of the method application are presented through measurements and explained by the use of a mathematical model of the slip-ring induction motor.
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Authors and Affiliations

Piotr Drozdowski
Arkadiusz Duda
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Abstract

Groundwater resources are typically affected by both global climate factors and anthropogenic activities. This influence is most apparent in arid and semi-arid climates of the Saharan desert. With rising temperatures and minimal precipitation, climate variability in these regions has a particularly significant and systemic impact on the chemical composition of shallow aquifer water. In this regard, our study aims to evaluate the climatic effects on groundwater in Saharan environments, using the Ouargla basin as a prime example. Water samples taken from 45 observation piezometers in our selected study area in February and June 2021 were used to assess the overall impact of inter-annual climate variations on salinity within this shallow groundwater basin. The obtained results show that groundwater located in the first three meters of shallow aquifer depth is directly influenced by surface climate. This pattern holds true for both observed seasonal periods. Stratification indices within the saturated zone were found to be positive, indicating an increase in groundwater salinity at lower depths and negative in shallower depths. This suggests a direct climate influence on this groundwater. These findings can be used to enhance sustainable development strategies in such environments, notably by quantifying salt accumulation and efficiently managing salinity exchange between saturated and vadose horizons.
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Bibliography

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Authors and Affiliations

Medjani Fethi
1
ORCID: ORCID
Zahi Faouzi
2
ORCID: ORCID
Djidel Mohamed
1
ORCID: ORCID
Labar Sofiane
3
ORCID: ORCID
Hamilton Cynthia Mei-Ling
4
ORCID: ORCID

  1. Laboratory of Geology of the Sahara, University Kasdi Merbah Ouargla, Algeria
  2. Laboratory of Geological Engineering, University of Jijel, Algeria
  3. Department of Geography and Territorial Planning, Houari Boumediene University of Science and Technology, Algeria
  4. Environmental Geochemist & Educator., Bakersfield, CA United States
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Abstract

The ways of the improvement of the method for the determination of steel losses in the electrical devices of basic types are substantiated. The method is refined by taking into account the magnetic system properties at high saturation. The presence of the interrelation between the special features of the domain structure movement and the shape of the hysteresis loop is proved for laminated cores. It enabled the explanation of the causes for the abnormally high values of the losses in the steel and the atypical shapes of the hysteresis loops at its high saturation. The empiric dependence for the determination of steel losses is obtained. It provides for the high convergence of the calculated and experimental data at the actual degree of saturation and can be used in the direct-current operation of the analyzed devices.

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Authors and Affiliations

Mykhaylo Zagirnyak
Viacheslav Prus
Dmitro Rodkin
Yurii Zachepa
Volodymyr Chenchevoi
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Abstract

The pattern of pore water pressure dissipation from the one-dimensional consolidation test significantly affects the calculated value of the coefficient of consolidation. This paper discusses the interpretation methodology for laboratory dissipation data from the oedometer test with the pore water pressure measurements or Rowe cell test. In the analysis, the gradient-based algorithm for finding the optimal value of the coefficient of consolidation is used against experimental results, obtained for various fine-grained soils. The appropriate value of coefficient of consolidation is considered as one with the lowest associated error function, which evaluates fitness between the experimental and theoretical dissipation curves. Based on the experimental results, two different patterns of the pore water pressure dissipation are identified, and the saturation of the specimen was found to be the key factor in describing the change in the patterns. For the monotonically decreasing dissipation curve, an inflection point is identified. The values of degree of dissipation at the inflection point are close to the theoretical value of 53.4%.
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Authors and Affiliations

Bartłomiej Szczepan Olek
1
ORCID: ORCID

  1. Krakow University of Technology, Faculty of Civil Engineering, Warszawska 24, 31-155 Kraków, Poland
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Abstract

The paper presents a detailed description of one of the newest methods of vacuum saturation of reinforcing preforms in gypsum molds. As an appropriate selection of the infiltration time is a crucial problem during realization of this process, aim of the analysis shown in the paper is to present methods of selection of subatmospheric pressure application time, a sequence of lowering and increasing pressure, as well as examining influence of structure of reinforcing preforms on efficiency of this process. To realize the aim, studies on infiltration of reinforcing preforms made of a corundum sinter of various granulation of sintered particles with a model alloy were conducted. The infiltration process analysis was carried out in two stages. The first stage consisted in investigation of influence of lengthening of sucking off air from the reinforcing preforms on efficiency of this process. In the second stage, an analysis of influence of a two-staged infiltration process on saturation of the studied materials was conducted. Because the studied preforms were of similar porosity, the obtained differences of the saturation level of particular preforms have shown, that the saturation process is influenced mostly by size of pores present in the reinforcement. Because of these differences, each reinforcement type requires individual selection of time and sequence of the saturation process. For reinforcements of higher pore diameter, it is sufficient to simply increase air sucking off time to improve the saturation, while for reinforcement of smaller pore diameter, it is a better solution to apply the two-staged process of sucking off air. Application of the proposed analysis method allows not only obtaining composite castings of higher quality, but also economical optimization of the whole process.

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Authors and Affiliations

K. Gawdzińska
D. Nagolska
P. Szymański
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Abstract

This paper presents a predictive torque and flux control algorithm for the synchronous reluctance machine. The algorithm performs a voltage space phasor pre-selection, followed by the computation of the switching instants for the optimum switching space phasors, with the advantages of inherently constant switching frequency and time equidistant implementation on a DSP based system. The criteria used to choose the appropriate voltage space phasor depend on the state of the machine and the deviations of torque and flux at the end of the cycle. The model of the machine has been developed on a d-q frame of coordinates attached to the rotor and takes into account the magnetic saturation in both d-q axes and the cross saturation phenomenon between both axes. Therefore, a very good approximation of this effect is achieved and the performance of the machine is improved. Several simulations and experimental results using a DSP and a commercially available machine show the validity of the proposed control scheme.

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Authors and Affiliations

R. Morales
M. Pacas
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Abstract

In this study, the compressive deformation of crushed sandstone was tested using a crushed rock deformation-seepage test system, and the effects of various factors, including crushed rock grade, grade combination, water saturation status, and stress loading method (i.e., continuous loading or cyclic loading and unloading), on the compressive deformation of crushed sandstone was analyzed from four perspectives including stress-strain, bulking coefficient, deformation mechanism and energy dissipation. The results indicate that the stress-strain relations of crushed sandstone are closely associated with all factors considered, and are well represented by exponential functions. The strain observed for a given applied stress increased with increasing crushed rock grade throughout the loading period. Crushed sandstone grades were combined according to a grading index (n), where the proportion of large-grade rocks in the sample increased with increasing n. The bearing capacity of a water-saturated crushed sandstone sample with n = 0.2 was less than that of an equivalent dry sample for a given applied stress. The stress-strain curve of a water-saturated crushed sandstone sample with n = 0.2 under cyclic loading and unloading was similar to that obtained under continuous loading. Observation and discovery, the deformation mechanism of crushed sandstone was mainly divided into four stages, including crushing, rupture, corner detachment and corner wear. And 20% of the work done by testing machine is used for friction between the crushed sandstone with the inner wall of the test chamber, and 80% is used for the closing of the void between the crushed sandstone, friction sliding, crushing damage.

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Authors and Affiliations

Yanan Sun
Peisen Zhang
ORCID: ORCID
Wei Yan
ORCID: ORCID
Fenqian Yan
Junda Wu
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Abstract

We demonstrated a tunable Q-switched ytterbium-doped fiber laser (YDFL) using MoWS2/rGO nanocomposite as passive saturable absorber. Further, the Mo1−xWxS2/rGO nanosheets, with x proportion of 0.2, are synthesized using hydrothermal exfoliation technique. The proposed nanocomposite-PVA based thin film is fabricated by mixing the MoWS2/rGO nanosheets with polyvinyl alcohol (PVA). The fabricated thin film is sandwiched between two fiber ferrules to realize the proposed saturable absorber (SA). Further, the proposed MoWS2/rGO-PVA based thin film SA exhibits a fast relaxation time and a high damage threshold which are suitable to realize a Q-switched pulsed laser with a tunable wavelength range of 10  nm that extends from 1028 nm to 1038 nm. For the highest pump power of 267.4 mW, the generated Q-switched pulses exhibit a narrow pulse width of 1.22 μs, the pulse repetition rate of 90.4 kHz, the highest pulse energy of 2.13  nJ and its corresponding average power of 0.193 mW. To the best of author’s knowledge, this is the first realization of a tunable Q-switching fiber laser in a 1 μm wavelength using MoWS2/rGO nanocomposite saturable absorber.

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Authors and Affiliations

J. Mohanraja
V. Velmuruganb
S. Sivabalanc
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Abstract

Artificial intelligence operated with machine learning was performed to optimize the amount of metalloid elements (Si, B, and P) subjected to be added to a Fe-based amorphous alloy for enhancement of soft magnetic properties. The effect of metalloid elements on magnetic properties was investigated through correlation analysis. Si and P were investigated as elements that affect saturation magnetization while B was investigated as an element that affect coercivity. The coefficient of determination R2 (coefficient of determination) obtained from regression analysis by learning with the Random Forest Algorithm (RFR) was 0.95 In particular, the R2 value measured after including phase information of the Fe-Si-B-P ribbon increased to 0.98. The optimal range of metalloid addition was predicted through correlation analysis method and machine learning.
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Authors and Affiliations

Min-Woo Lee
1
ORCID: ORCID
Young-Sin Choi
1
ORCID: ORCID
Do-Hun Kwon
1
ORCID: ORCID
Eun-Ji Cha
1
ORCID: ORCID
Hee-Bok Kang
2
ORCID: ORCID
Jae-In Jeong
2
ORCID: ORCID
Seok-Jae Lee
3
ORCID: ORCID
Hwi-Jun Kim
1
ORCID: ORCID

  1. Smart Liquid Processing R&D Department of Korea Institute of Industrial Technology, Incheon 21999, Korea
  2. R&D Center of Youngin Electronic, Youngin 1033, Korea
  3. Jeonbuk National University, Division of Advanced Materials Engineering, Jeonju 54896, Korea
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Abstract

This paper concerns the analytical investigation of the axisymmetric and steady flow of incompressible couple stress fluid through a rigid sphere embedded in a porous medium. In the porous region, the flow field is governed by Brinkman's equation. Here we consider uniform flow at a distance from the sphere. The boundary conditions applied on the surface of the sphere are the slip condition and zero couple stress. Analytical solution of the problem in the terms of stream function is presented by modified Bessel functions. The drag experienced by an incompressible couple stress fluid on the sphere within the porous medium is calculated. The effects of the slip parameter, the couple stress parameter, and permeability on the drag are represented graphically. Special cases of viscous flow through a sphere are obtained and the results are compared with earlier published results.
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Authors and Affiliations

Krishna Prasad Madasu
1
ORCID: ORCID
Priya Sarkar
1
ORCID: ORCID

  1. Department of Mathematics, National Institute of Technology, Raipur-492010, Chhattisgarh, India
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Abstract

In this study some of the experimental results of water shut-off treatments in oil and gas production wells were presented. The effect of water saturation of Miocene rocks of the Carpathian Foredeep on the relative permeability to gas was analyzed. Also, wide review of the worldwide publications from the point of view of the results obtained in water shut-off treatments in oil and gas formation was presented. Based on experimental results efficiency of relative permeability modification of sandstone from Szydłowiec to brine and nitrogen by four selected chemicals polymers and microgels was evaluated. Experimental results indicated that trend changes of permeability modification strongly depends on the fluid used in the RPM treatment. Moreover, efficiency of permeability modification to brine depends on flow rate of brine through the core - the lower brine flow rate the higher efficiency of the RPM treatment. RPM product number 1 caused significant loss of permeability to brine ca. 60% and slight permeability modification to gas ca. 18%. This permeability change to brine and gas was obtained by modification of formation wettability what affects well productivity. In the case of product number 2 which is based on microgels technology, also significant modification of selective permeability to brine was observed. Loss of permeability to brine was in the range of 65 to 90% while to gas ca. 50%.

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Authors and Affiliations

Sławomir Falkowicz
Stanisław Dubiel
Renata Cicha-Szot

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