Normal Vacuum Research Articles

Study on the microstructure of recycled aggregate concrete strengthened by the nano-SiO2 soaking method

Herein, the study investigates the microstructure of recycled aggregates concrete (RAC) prepared by nano-silica strengthened recycled aggregates (RAs). Five concentrations (0 %,1.0 %,1.5 %,2%, 2.5 %) of nano-silica solutions in two different conditions (normal pressure and vacuum pressuring of 1ba) are selected to soak RAs. After the soaking process, the chemical composition, the porosity and pore structure, and micrographs of nano-silica strengthened RAs and RA-based concrete are investigated. Results show that the 2 % concentration alone with the vacuum pressing is optimal. It reduces CH content by more than 40 %, decreases porosity, narrows the average pore size, and increases the volume fraction of pores that are less harmful (less than 50 nm). These results, verified by ESEM, are attributed to the conversion mechanism of secondary hydration and the filling effect of nanoparticles. The research at a microscopic level explains the strengthening effect of nano-silica upon recycled aggregate concrete and lays a theoretical foundation for upcycling construction and demolition wastes.

Development of a data-driven subsurface thermal probing technique for lunar exploration

Conducting in-situ measurements of planetary environments is a key scientific goal in the geoscience field for the extraterrestrial exploration, such as the Moon or Mars. Among these measurements, determining the thermal properties of regolith is particularly challenging due to the material’s inhomogeneities. In this paper, an active thermal probing technique is proposed, utilizing a transient hot-wire technique with a needle-like probe structure integrated with temperature sensors and a heater. It is capable of measuring in-situ temperature variations and inner heat flux without disturbing the surrounding regolith. In addition, a machine-learning-based method is proposed for inverting in-situ thermophysical properties, including density, thermal conductivity, and heat capacity. An embedded artificial neural network model has been developed and trained with data sets from both finite element simulations and experiments. This machine learning model is capable of efficiently predicting temperature responses for different lunar regolith simulants. For total 12 parameters, the errors of ten cases are less than 10%, and other two cases are 12.23% and 13.17%. Finally, the proposed method is verified by heat measurement experiments under normal pressure and vacuum, and the variation of thermal properties with different compactness is obtained. The proposed probing technique provides novel ideas to measure the in-situ thermal properties of extraterrestrial regolith.

Surface Plasmon Polaritions via Squeezed Vacuum States

This paper investigates a dielectric under a squeezed vacuum state, a thermal field and a normal vacuum state. The dielectric atoms are considered in a three-level lambda type configuration, where a weak probe field induces and generates surface plasmon polaritons (SPPs) at the silver and dielectric interface. Therefore, to get deeper insights into the dispersion and absorption spectra, the propagation length and the skin depth, we investigate the system’s coherence. Hence, we demonstrate that the strong laser used to couple the intermediate level to the upper excited state drastically affects the generated SPPs wavelength at the interface. Additionally, the system properties are fully controlled by the average photon number, the thermal field, the normal vacuum and the squeezed vacuum state. Finally, in an attempt to elaborate a straightforward technique that manipulates the Lsp ( surface plasmon length ) distance we control the system by simultaneously tuning the phase and the control field in a particular detuning region. Our results might be of great interest to the engineering of miniature nano-photonic devices and circuits requiring sub-wavelength property.

Rapid detection of the vacuum failure of logging tools based on the variation in equivalent thermal conductivity

The logging tool is the key downhole facility used for oil and gas exploration. A vacuum flask is indispensable for protecting the inside electronics of the logging tool from extreme working environments. During transport, assembly, or working processes, vacuum flask failure can lead to the destruction of the logging tool. The existing test methods are unable to detect vacuum failure quickly and accurately. To solve this problem, a rapid test method based on the variation in equivalent thermal conductivity before and after vacuum failure was proposed. First, the principle of this method was illustrated in detail, and a simplified 1D heat transfer model was calculated by the finite difference method. We found that the temperature rise ratio between the insulator and heat source (defined as P) can be used as the testing indicator with a 1 h testing time. Subsequently, a rapid test device was designed, and numerical simulations were performed to determine the critical values of the testing indicator for actual vacuum flasks. The simulated results showed that independent of the heating power and initial temperature, the P values for vacuum flasks in normal and abnormal states are 0.391 and 0.299, respectively, with a critical value of 0.351. Finally, experimental tests were conducted to test the effectiveness of the rapid test method and testing indicator. The experimental results showed that the measured P values of normal and abnormal vacuum flasks were above or below the critical value (Pe) under different test conditions, respectively, indicating that the proposed rapid test method can quickly and accurately detect vacuum failure. The maximum error between the simulated and experimental results was only 8.7%.

Quality assessment of rose tea with different drying methods based on physicochemical properties, HS-SPME-GC-MS, and GC-IMS.

The purpose of this study is to compare the physicochemical properties and volatile flavor compounds of rose tea obtained by the methods of normal temperature drying, hot-air drying (HAD), and vacuum freeze-drying (VFD) and to evaluate the quality of rose tea. The physicochemical results showed that the content of ascorbic acid (VC) and the pH value was the highest in rose tea obtained by HAD. The contents of anthocyanin, proanthocyanidins, and total phenols were highest in rose tea obtained by VFD. However, there was no significant difference in total flavonoids between drying methods. The volatile organic compounds (VOCs) in rose tea with different drying methods were analyzed by headspace solid-phase microextraction-gas chromatography-mass spectroscopy (HS-SPME-GC-MS) and HS GC-ion mobility spectroscopy (HS-GC-IMS), and the flavor fingerprint of rose tea was established by principal component analysis (PCA). The concentration of VOCs in rose tea varied greatly with different drying methods. The main flavor compounds of rose tea were alcohols, esters, aldehydes, and terpenoids. HS-GC-IMS was used for the identification of volatile flavor compounds of rose tea, thereby helping to assess the quality of rose tea. In addition, the rose tea samples with different drying methods were well distinguished by PCA. This study deepens the understanding of the physicochemical properties and volatile flavor compounds of rose tea with different drying methods and provides a reference for the identification of rose tea with different drying methods. PRACTICAL APPLICATION: This study deepens the understanding of the physicochemical properties and volatile flavor compounds of rose tea with different drying methods and provides a reference for the identification of rose tea with different drying methods. It also provides an effective theoretical basis for consumers to buy rose tea.

The effect of FSP on the friction and wear behaviour of Al5083 under normal atmosphere and vacuum conditions

In current technology, there are a lot of machines that work under vacuum conditions such as in space and aviation. For this reason, friction and wear properties of especially light metals, such as aluminium and magnesium alloys, which are candidates to be used in such areas should be examined under vacuum conditions. In this study, the effect of friction stir processing parameters such as traverse speed and pass number on the microstructure, hardness and wear properties of the Al 5083 alloy were investigated. During the friction stir processing, three traverse speeds and from 1 to 4 passes were applied to the surface of the samples. The wear behaviour of the processed and unprocessed samples was investigated by using the ball-on disc tribometer under air and 5 × 10−3 mbar vacuum conditions. After friction and wear experiments, all FSPed samples showed lesser wear amount under vacuum conditions compared with air conditions.

Effect of pre-saturated lightweight sand on material properties of eco-friendly lightweight cementitious composites

In this study, eco-friendly lightweight high-strength engineered cementitious composites (ELHECC) were developed using lightweight sand fines (LSF) and fly ash cenospheres. The effects of LSF content and pretreatment methods on mechanical properties, shrinkage and micro-mechanism of ELHECCs were investigated. Two pretreatment methods—normal pressure immersion and vacuum saturation—were employed. The internal curing effects of treated and untreated LSF were compared. The results showed that increasing the content of LSF slightly reduced compressive strength but improved the tensile properties and ductility of ELHECCs. Vacuum-saturated LSF improved the mechanical properties of ELHECCs more than normal pressure-immersed LSF. In addition, increasing the substitution amount of LSF increased the corresponding internal relative humidity, extended the duration of saturated humidity, and subsequently reduced the autogenous shrinkage of ELHECC. The reduction effect of autogenous shrinkage and drying shrinkage after LSF pre-saturation was much greater than without saturation. Moreover, LSF significantly delayed the hydration process and reduced the hydration heat rate and hydration heat, and the content of Ca(OH)2 in ELHECCs decreased with increased LSF substitution rate. The effect of vacuum saturation for LSF in reducing the porosity of ELHECC was greater than that of normal pressure saturation. Furthermore, LSF had superior bonding with the ELHECC matrix, forming a well-integrated sand–matrix interface. The experimental results provide inspiration for green applications in bridge bearing structure, building structure reinforcement and repair in terms of impressive tensile properties, low shrinkage, light weight, and waste utilization.

The steady-state of probe susceptibility in a four-level N-type atomic system with a squeezed vacuum field

The gain, absorption and dispersion properties of a probe field for a four level N-type atomic system with a normal vacuum and a squeezed vacuum fields is studied. Under such conditions that normal and squeezed vacuum-induced interference among decay channels is significant. Our study also reveals that the quantum interference will produce a remarkable effect on the absorption and dispersion properties of the system. A single squeezed vacuum is coupled to three transitions. Numerically the effect of the squeezing vacuum field parameters and the relative phases between the squeezed vacuum and the probe (strong) fields on the index of refraction is analyzed.

Experience of using the NALCO 1392 scale inhibitor in the circulating water supply system of the Novovoronezh NPP

Power facilities use large amounts of water to cool steam in the steam turbine condensers, and lubricating oils, gas and air in turbine sets. The key requirement for the quality of cooling water is to ensure normal vacuum in condensers. Cooling water must not form mineral and biological deposits and corrosion products in the system. Deposits of mineral salts in the condenser tube system, as well as in auxiliary cooling systems, lead to deterioration in heat exchange and a major decrease in the cost effectiveness of the power equipment operation, and require the heat-exchange equipment to be periodically cleaned. The source water used for cooling is normally taken from nearby water bodies (large rivers or lakes). Circulating water supply systems are used most commonly: these systems use repeatedly the same water inventory for cooling, and require only small amounts of water added to make up for evaporation losses. Coolers, in this case, are cooling towers, spray pools and evaporation ponds. The water chemistry should ensure the operation of equipment without any damage to its components or the loss of efficiency caused by the corrosion of the internal surfaces as well as without scale and sludge formation. It is exactly when using circulating water supply that a stabilizing treatment program is the most practicable way to ensure a cost-effective and environmentally friendly mode of operation. To inhibit scaling processes on the heat-exchange surfaces of the turbine condenser tubes at the Novovoronezh NPP’s unit 5, the cooling water was treated with the NALCO 1392 inhibitor. The results of the NALCO 1392 inhibitor pilot tests in the circulating water supply system (with a cooling pool) are presented.

Effects of vacuum on gas content, oxide inclusions and mechanical properties of Ni-based superalloy using electron beam button and synchrotron diffraction

The effects of vacuum induction melting (VIM) vacuum (<1 Pa–100 Pa) on gas content, oxide inclusions and mechanical properties of Ni-based superalloy K4648 has been investigated by electron beam (EB) button experiment under high vacuum (10-3 Pa) and high resolution synchrotron X-ray powder diffraction (SXPD). The results indicated that VIM remelting vacuum drop has obvious effect on the existing form of trace oxygen. The total amount of oxygen did not increase significantly but a dramatic increase in the amount of oxide inclusions by 1–2 orders of magnitude was found. The inclusions are mainly oxides including Al2O3, Cr2O3, NiAl2O4 and complex oxides or sulfides. Remelting under 100–110 Pa has no significant effect on mechanical properties such as stress rupture life and tensile strength but decreased ductility obviously. In comparison to the normal vacuum counterpart, the tensile elongation and impact ductility of the alloy remelted under lower vacuum level decreased by 67% and 39%, respectively. This study reveals the relationship between the vacuum level and mechanical properties of superalloys and highlights the trace amount of oxide inclusions which should be considered as one of the key issues for the cleanliness of virgin or revert superalloys apart from the typical measurement of the gas content only.

The Dirac Sea, T and C Symmetry Breaking, and the Spinor Vacuum of the Universe

We have developed a quantum field theory of spinors based on the algebra of canonical anticommutation relations (CAR algebra) of Grassmann densities in the momentum space. We have proven the existence of two spinor vacua. Operators C and T transform the normal vacuum into an alternative one, which leads to the breaking of the C and T symmetries. The CPT is the real structure operator; it preserves the normal vacuum. We have proven that, in the theory of the Dirac Sea, the formula for the charge conjugation operator must contain an additional generalized Dirac conjugation operator.

Vacuum current and polarization induced by magnetic flux in a higher-dimensional cosmic string in the presence of a flat boundary

In this present paper, we investigate the vacuum bosonic current and polarization induced by a magnetic flux running along a higher-dimensional cosmic string in the presence of a flat boundary orthogonal to the string. In our analysis, we assume that the quantum field obeys Dirichlet or Neunmann conditions on the flat boundary. To develop this analysis we calculate the corresponding positive frequency Wightman function. As consequence of the boundary condition, the Wightamn function is expressed in term of two contributions: The first one corresponds to the Wightman function in cosmic string spacetime in the absence of boundary, while the second one is induced by the presence of the boundary. Due to the fact that the analysis of induced bosonic current and polarization effects in the pure cosmic string spacetime have been developed by many authors, the main objective of this paper is to study the effects induced by the boundary. Regarding to the induced current, we show that, depending on the condition adopted, the boundary-induced azimuthal current can cancel or intensifies the total induced azimuthal current on the boundary; moreover, the boundary-induced azimuthal current is a periodic odd function of the magnetic flux. As to the vacuum expectation values of the field squared and the energy-momentum tensor, the boundary-induced contributions are even functions of magnetic flux. In particular, we consider some special cases of the boundary-induced part of the energy density and evaluate the normal vacuum force on the boundary.

Synthesis of cis-syn-cis and cis-anti-cis linear triquinanes via photo-thermal metathesis

Diverse cis-syn-cis and cis-anti-cis triquinane frameworks have been assembled by a simple synthetic protocol starting with substituted cage diones under microwave irradiation conditions. Thermal fragmentation of the cyclobutane ring play a key role in this process and milder reaction conditions have been employed in contrast to normal flash vacuum pyrolysis conditions. Here, thermal isomerization of the double bond has also been realized under the microwave irradiation conditions to afford the isomeric triquinanes at low temperature. These triquinane units are considered to be useful for the total synthesis of natural products and non-natural products containing fused cyclopentane rings.

Quantum atmosphere of Reissner-Nordström black holes

Hawking radiation originates from a "quantum atmosphere" around black holes, not necessarily from the vicinity of the horizon. We examine and discuss the properties of quantum atmospheres of asymptotically flat Reissner-Nordstr\"om black holes, which extends further and further away from the black hole as extremality is approached, though arguably it becomes indistinguishable from normal vacuum fluctuation at spatial infinity. In addition, following our previous findings on re-writing the Hawking temperature of a Kerr black hole in terms of a "spring constant", we generalize the same notion to the Reissner-Nordstr\"om case, which allows us to put a minimum size on the location where Hawking particles can be emitted near a black hole, which agrees with the stretched horizon.

RETRACTED: Restorations of fresh surfaces for topological materials by de-capping Te

Abstract The topological categorization originates from a depiction of the sequencing of bands around the band gap of the material in comparison to the normal vacuum type band ordering. The structure can either be normal or inverted, and thus topologically trivial or non-trivial. An odd number of Dirac fermions on the surface occurs in this type of material. Time-reversal symmetry is responsible to preserve the surface bands. On the other hand, topological crystalline insulator is protected by mirror symmetry; this system has an even number of Dirac surface state per BZ. Capping layer of Te or Se is necessary due to the high sensitivity of films surfaces to atmospheric pressure. The capping layer works as a protection from oxidation. In Bi2Te3 samples, the bonds between Bi and Te are covalent bonds while the bonds between Te-Te at a certain position are van der Waals bonds. Thereby, the bonds between amorphous Te cap and sample surface is weaker than van der Waals bonds within the sample structure. However, the top boost cleaving method was successful. But, for Pb1-xSnxTe samples the top boost cleaving method unsuccessfully results. The bonds between the metallic Pb1-xSnxTe sample surface and amorphous Te cap are stronger than van der Waals bonds in BaF2 substrate, i.e. F-F van der Waals bonds. In this paper, we present different techniques to recover fresh surfaces, from classical methods (such as sputtering and annealing) working for all types of films and top boost methods, which could be less used due to the strong bonds in some films. Moreover, we were able to recover the immaculate surfaces for non-capped samples. We present here in a systematic study by low energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS), and angle-resolved photoemission spectroscopy (ARPES).

Correlation of Normal Labor and Vacuum Extraction with Postlabor Stress Urinary Incontinence

Objective: To determine the correlation between normal delivery methods and vacuum extraction with postpartum stress urinary incontinence in West Sumatra.Methods: This study used cross-sectional study design in the Obstetrics and Gynecology Department of the RSUP Dr. M. Djamil Padang, network hospital and Puskesmas in Padang City from October 2018-February 2019. The sampling technique was consecutive sampling. Urinary stress incontinence were assessed using a questionnaire for urinary incontinence diagnosis (QUID).Results: There was a correlation between normal delivery and vacuum extraction with stress urinary incontinence after delivery in the province of West Sumatra (p &lt;0.05).Conclusion: There is a correlation between normal labour and vacuum extraction with stress urinary incontinence after delivery in the province of West Sumatra.Keywords: normal labour, stress urinary incontinence, vacuum extraction&#x0D; &#x0D; Abstrak&#x0D; Tujuan: Mengetahui hubungan cara persalinan normal dan vakum ekstraksi dengan stress inkontinensia urin pascasalin di Provinsi Sumatera Barat.Metode: Penelitian ini menggunakan desain potong lintang di Poliklinik Bagian Obstetri dan Ginekologi RSUP Dr. M Djamil Padang, RS jejaring dan Puskesmas di Kota Padang sejak bulan Oktober 2018-Februari 2019, Teknik pengambilan sampel dengan consecutive sampling. Penilaian stress inkontinensia urin dengan menggunakan questionnaire for urinary incontinence diagnosis (QUID).Hasil :Terdapat hubungan persalinan normal dan vakum ekstraksi dengan stress inkontinensia urin pascasalin di provinsi Sumatera Barat (p&lt;0,05).Kesimpulan : Penelitian menyimpulkan terdapat hubungan persalinan normal dan vakumekstraksi dengan stressinkontinensia urin pascasalin di provinsi Sumatera Barat.Kata kunci: persalinan normal, stres inkontinensia urin, vakum ekstraksi

Heat coupling effect on photothermal detection with a moving Gaussian excitation beam.

A strong photothermal response is beneficial to the measurement of optical and thermal properties of optical materials using the laser-induced thermal mirror method. A highly sensitive asymmetrical thermal mirror method was recently proposed by employing a moving Gaussian excitation beam [Appl. Phys. Lett.114, 131902 (2019)APPLAB0003-695110.1063/1.5080163]. However, the heat transfer across the interface between the thermodynamic system and the surroundings is ignored, which will lead to an error in the absolute measurement of the material properties. To address the problem, we present a theoretical and experimental study of heat transfer within the heated sample and out to the air coupling fluid in the photothermal detection with a Gaussian excitation beam moving at a constant velocity. We analyze the dynamic temperature fields inside the sample and in the surrounding air, and the phase shifts induced by the thermoelastic displacement of the sample (thermal mirror) and the refractive index gradient of air (thermal lens), as well as the diffracted intensity profiles of the probe beam in the detection plane. The experiments are implemented under normal pressure and vacuum, respectively, for a fused silica glass-air heat coupling system to verify the theoretical model. The experimental results show that the thermal lens, due to the heat coupling effect, introduces a signal deviation approximately 4.2% of the total photothermal signal, which is close to the theoretical result of 5%.

A prospective study on effectiveness of drotaverine in acceleration of labor

Background: Labor is a naturally occurring physiological process associated with uterine contractions, effacement, dilatation of cervix and descent of presenting part. Drotaverine hydrochloride is a non-anticholinergic isoquinoline derivative which acts by elevating intracellular cyclic Adenosine Mono Phosphate (cAMP) and cyclic Guanosine Mono Phosphate (cGMP) promoting smooth muscle relaxation.&#x0D; Materials and Method: This was a hospital based prospective study on effectiveness of Drotaverine Hydrochloride on enhancing dilatation of cervix and acceleration of active phase of labor. The sample size was 100. Fifty cases of women in active phase of labor received injection drotaverine hydrochloride 40 mg (group i) and fifty cases of women did not receive any drug (group ii) among those at term with singleton pregnancy and vertex presentation. Variables like maternal age, interval between administration of drug and delivery, mode of delivery, apgar score at 5 minutes, NCU (Neonatal Care Unit) admission and neonatal outcomes were recorded. Data analysis was done with the help of SPSS program.&#x0D; Results: The mean interval between drug administration to delivery in primipara and multipara in group i was 3.05 hours and 2.31 hours while in group ii was 4.5 hours and 3.75 hours respectively. The mean interval between drug administration and delivery was shorter in both groups of multipara. In group i, 96% had normal delivery and 4 % had vacuum delivery and in group ii 90% and 10% had normal delivery and vacuum delivery respectively. None of the participants had caeserian section. There were no perinatal mortalities.&#x0D; Conclusion: The administration of drug Drotaverine Hydrochloride is effective in shortening duration of labor with favorable feto-maternal outcome.

Unruh acceleration radiation revisited

When ground-state atoms are accelerated and the field with which they interact is in its normal vacuum state, the atoms detect Unruh radiation. We show that atoms falling into a black hole emit acceleration radiation which, under appropriate initial conditions (Boulware vacuum), has an energy spectrum which looks much like Hawking radiation. This analysis also provides insight into the Einstein principle of equivalence between acceleration and gravity. The Unruh temperature can also be obtained by using the Kubo–Martin–Schwinger (KMS) periodicity of the two-point thermal correlation function, for a system undergoing uniform acceleration; as with much of the material in this paper, this known result is obtained with a twist.

Realization of Photo‐Thermal Metathesis Under Microwave Irradiation Conditions: An Entry to Triquinane Frameworks

AbstractWe report a simple and convenient synthetic route to cis,syn,cis triquinane frameworks under microwave irradiation conditions starting with cage diones. This is feasible because of the substituents present in the precursors, which facilitate the metathesis under milder reaction conditions as compared to normal flash vacuum pyrolysis conditions (∼600 °C). Isomerization of the double bond was realized under microwave irradiation to deliver the other triquinanes, which are useful precursors for natural product synthesis.