Normal Pressure Conditions Research Articles

Isothermal and near-isothermal free evaporation of water from open tubes in air

The physics of air-water interface transport processes under very low mixing conditions is still poorly characterized. Consequently, correlations for mass transfer rates at very low Grashof numbers in weakly convective flows are not readily available, which often leads incorrect estimations of evaporation rates that are derived from simplified 1-D models. Here we investigate the evaporation from open tubes that results in complex massline patterns due to the interaction of the vertical walls with the buoyant flow in near isothermal conditions. Using numerical simulations validated by experimental data for typical Normal Conditions of Temperature and Pressure (NCTP), we analyze the water vapor transport dynamics for open tubes with aspect ratios ranging from 2 to 11 at the temperature of 290 K and 310 K, and relative humidity values from 0 to 99%, all at 1 atm. We show the dependence of the diffusion-driven and convection-driven processes as functions of the geometrical aspect ratio of the tubes. We propose a new Sherwood number correlations valid for both isothermal and near-isothermal processes in the range of Grashof numbers from 50 to 4,000. This correlation, which is optimized for air-water interfaces and is nearly invariant with temperatures near NCTP, expresses the Sherwood and Grashof numbers for varying aspect ratios. The proposed correlation estimates evaporation rates within 5% of values obtained from 3-D numerical simulations for the entire range of Grashof and Sherwood numbers under study.

Dissolution and precipitation behaviors of zircon under the atmospheric environment

The reactive behavior of zircon in three different solutions: 0.1 M HCl (aq), ultrapure water, and 0.1 M NaOH (aq) was examined under normal temperature and pressure conditions. Dissolved Si and Zr concentrations show that considerable Zr precipitated on the surface in all immersion cases. Bulk changes in the zircon were insignificant. However, the obvious surface change of the zircon immersed in 0.1 M NaOH (aq) was confirmed. Porous layer comprising an amorphous SiOx phase and needle crystals of ZrSiO4 around pores were detected on the near-surface area of the zircon immersed in 0.1 M NaOH (aq). Consequently, the reaction was limited when zircon was immersed in ultrapure water. Zr precipitated on the surface after the dissolution of ZrSiO4 in 0.1 M HCl (aq). Dissolved Zr and Si in 0.1 M NaOH (aq) precipitated on the surface, then the dissolution of ZrSiO4 formed a porous layer, and most dissolved Zr precipitated as zircon crystals.

Analysis of viable biogas production from anaerobic digestion of swine manure with the magnetite powder addition

The development of new technologies during the processes of Anaerobic Digestion (AD) has occurred through the use of new types of additives, to maximize the CH 4 production. Therefore, this study aimed to technically analyze the effect of magnetite powder in the AD process of the pigs’ litter in anaerobic reactors under mesophilic conditions. In this sense, the experiments were carried out in triplicate under two sequential processes to analyze the physicochemical characteristics and concentrations of trace elements (Fe, Zn, Mn, and Cu) before and after AD. The volume of biogas and yields of CH 4 were analyzed under normal conditions of temperature and pressure, to infer the role of magnetite in the digestion process. The results showed that the magnetite powder has a significant impact on yields of methane during the digestion process of pig slurry. The maximum methane generated were 3.82.10 −2 Nm 3 CH 4 /kg V S with the addition of 8 g of magnetite. The minimum methane produced was 2.18.10 −1 Nm 3 CH 4 /kg V S with the addition of 12 g of magnetite. The concentrations of trace elements were consistent with the literature data contributing to the smooth progress of the enzymatic activities of the methanogenic microorganisms. • The effect of magnetite in the anaerobic digestion process of the pigs’ litter in Brazilian meat sector was analyzed. • A sequential batch reactor in a small-scale promoted the highest organic reduction of 86.36%. • The maximum methane generated were 3.82 x 10 -2 Nm 3 CH 4 /kg VS. • The results displayed are based on the subtropical climate of dry winter (Cwa).

The effects of the pressure on the coccygeal skin on the perception of backward-leaning sitting positions in stroke patients

The present study investigated the effects of an additional pressure stimulus on coccygeal skin using an original tool to evaluate the perceptibility of sitting while leaning backward in 13 chronic stroke patients who were able to walk independently and 12 age-matched healthy subjects. Each participant’s perception of the trunk reference angle at which they felt the highest-pressure stimulation of the coccygeal skin while leaning backward from a quiet sitting position was evaluated based on the accuracy of each reproduction under both normal and additional pressure conditions. The absolute error under the pressure condition was significantly smaller than that under the normal condition in the control group, while no marked difference between conditions was found in the stroke group. The relationship between the absolute error under the normal condition and the pressure effect index showed a significant negative correlation in the stroke group. In stroke patients with a high trunk position perceptibility under the normal condition, the additional pressure information may have functioned as a disturbance and reduced the position perceptibility. In contrast, stroke patients with a low perceptibility in the normal condition may have been able to re-weight and prioritize the additional pressure information in the reference frame. In the control group, the added pressure information may have been re-weighted as prior position information in the reference frame.

Study on prediction model of thermal sensation under local draft in low pressure environment

Local draft experiments were conducted to establish the overall thermal sensation prediction model under low pressure environment. Head, chest, hand, and ankle were exposed to local airflow under three pressure environments: 1 atm, 0.87 atm, and 0.74 atm, respectively. The skin temperature was measured and the subjective questionnaires were collected. The results showed that in cooler environment, the mean skin temperature decreased with the decrease of pressure, and people maybe more sensitive. When the environmental pressure decreased, the overall thermal sensation decreased correspondingly. Compared with the normal pressure condition, as the pressure decreased, the weight of local thermal sensation on overall thermal sensation changed a little. The weight of chest decreased while the weight of hands increased. When exposed to local draft, the four body parts showed similar influence on the overall thermal sensation under lower pressure conditions. Based on influence of pressure, temperature, and local draft speed, the overall thermal sensation prediction model for each body part was established respectively. The results indicated that the predicted values were highly correlated with the measured values. The models could be used to predict thermal sensation of people who are exposed to local draft in low pressure environment.

Study on the Effect of Moisture Content and Dry Density on Shear Strength of Silty Clay Based on Direct Shear Test

Silty clay is a kind of clay with more powder group than sand group, and its shear strength is mainly influenced by moisture content, dry density, and particle gradation. In this study, the deformation characteristics of silty clay under different normal pressure conditions were investigated from the perspective of control variables through indoor direct shear experiments. The results of the study show that with the same guaranteed moisture content, it can be seen from the fitted curves that with the increase of dry density, the arrangement of soil particles becomes more compact, the cementation between soil particles is strengthened, the shear strength increases, the occlusal friction increases due to the change of arrangement between soil particles, and the angle of internal friction and cohesion are relatively larger; in addition, when the dry density is the same, with the increase of moisture content, the soil becomes softer, and the form of water in the soil particles changes. In addition, when the dry density is the same, as the moisture content increases, the soil becomes softer, the presence of water between the soil particles changes, resulting in the weakening of the occlusion between the soil particles, the shear strength decreases, and the cohesion and the angle of internal friction relatively decrease.

Introducing a Quasirandom Pattern in OPVs for Balancing the Transverse Magnetic and Electric Modes of Incident Light

To maximize solar energy utilization, this paper reports organic photovoltaics (OPVs) in which a 2D quasirandom pattern is fabricated and introduced in electron-transporting ZnO and photoactive layers in an easy and simple manner. The 2D quasirandom pattern is acquired from a digital versatile disc (DVD) where the data are recorded, and the nanostructure is introduced to OPVs under normal temperature and pressure conditions via soft-nanoimprinting lithography. The fabricated OPVs exhibit improved energy absorption/conversion characteristics in both transverse magnetic (TM) and transverse electric (TE) modes, with the mismatch between the two modes being within 1%. This value is approximately 3.5 times less than in conventional devices having a 1D grating pattern. The power conversion efficiency (PCE) of OPVs with a 2D quasirandom pattern introduced in ZnO and photoactive layers is improved to 9.2% through balanced TM/TE energy absorption, which corresponds to a 21% improvement compared to OPVs without the pattern.

Multi-Timescale Simulations of Temperature Elevation for Ultrasonic Welding of CFRP with Energy Director

Ultrasonic welding is an energy-efficient technology that enables quick bonding of thermoplastic composite materials under normal temperature and pressure conditions. Here, numerical multi-timescale simulation is proposed to understand the welding principle, using numerical simulations of ultrasonic welding. The simulation results are validated by comparing with temperature measurements in welding tests. In the multi-timescale simulations, microsecond-scale simulations are performed first. The ultrasonic wave is modeled as a vibration load, and the energy dissipation per vibration at 25, 75, 125, 175, 225, and 275∘C is analyzed. Then, the time derivative of the temperature rise is obtained. In the normal scale simulations, the ultrasonic wave and holding pressure are replaced by a constant load, and the entire process of ultrasonic welding is simulated. The slope of the temperature rise is fitted to the time derivative of the temperature rise obtained from the microsecond-scale simulations, using the material constant as a parameter. Explicit multi-timescale simulations were performed to investigate the relationship between stress concentration and temperature rise due to ED geometry. The result reveals similar temperature behavior to the experimental one, indicating the validity of the multi-timescale method. It suggests that viscoelastic energy dissipation and stress concentration are responsible for the temperature spike.

Comparative FE-studies of interface behavior of granular Cosserat materials under constant pressure and constant volume conditions

This article shows the outcomes of a systematic series of finite element (FE) calculations relevant to the shear behavior of a particulate-continuum interface system under different normal boundary conditions. In this respect, shearing of a thin and long granular Cosserat layer in the vicinity of a rigid moving wall with varied surface roughness values is analyzed under constant normal pressure and constant volume conditions. The material behavior is defined with a special elasto-plastic Cosserat model, taking into account micro-rotation, micro-curvature, couple stress, and mean particle size. The interaction between the layer of boundary particles and the surface roughness of the adjoining bottom wall is modeled by the rotation resistance of particles along the wall surface. Herein, the coupled effects of normal confining constraints imposed on the layer and the surface roughness of the bottom wall, are considered on the response of granular material under shearing. The influences of pressure level and initial void ratio are explored as well. Numerical results demonstrate that the dilatancy constraint prescribed to the interface plane in the normal direction, and the wall roughness have visible influences on the interface shear resistance as well as the deformation field formed within the layer. After large shearing, the width of the localized zone along the wall does not necessarily depend on the normal confining constraint and the applied pressure level. However, the localized zone characteristics and the interface shear response are mainly affected by the initial void ratio of the material. In addition to FE analyses, DEM-based simulations are also performed to investigate the micro-mechanical response of granular medium adjacent to a wall under shearing. FE predictions are qualitatively compared with DEM results, and reasonable agreement is observed.

Effect of types of resin cements on the bond strength of fiber post under simulated dives

Background: Changes in barometric pressure conditions that occur during flying and diving under hyperbaric oxygen conditions were found to influence the retention of dental restorations. Aim: This experimental laboratory study aimed to evaluate the bond strength of glass fiber posts after being cemented with self-adhesive resin cement (RelyX™ Unicem, 3M ESPE) and self-etch adhesive resin cement (RelyX™ Ultimate, 3M ESPE) under normal atmospheric pressure and hyperbaric pressure cycles that simulate diving conditions. Methods: A total of 40 extracted, single-rooted mandibular premolars were treated endodontically and randomly divided into two groups according to the cements used for fiber post cementation. Each group was further randomly divided into two equal subgroups that were subjected to normal atmospheric pressure conditions and a simulated hyperbaric condition in a hyperbaric chamber. The pull-out bond strength of fiber posts was tested using a universal testing machine. Data were analyzed using one-way analysis of variance with the Tukey post-hoc test (p<0.05). Results: At normal atmospheric pressure the mean value of the pull-out bond strength of RelyX Ultimate cement was significantly higher than that of RelyX Unicem cement. At hyperbaric pressure condition no significant difference was found between the mean values of the pull-out bond strength of RelyX Ultimate and RelyX Unicem cement. Conclusion: Hyperbaric pressure cycles demonstrated improved pull-out bond strength of glass fiber posts in RelyX Unicem cement but did not have significant effect on pull-out bond strength in RelyX Ultimate cement. Both resin cements have similar pull-out bond strength of glass fibers post after simulated dives.

Ultrasonic spray pyrolysis-induced growth of highly transparent and conductive F, Cl, Al, and Ga co-doped ZnO films

In this paper, the ultrasonic spray pyrolysis (USP) technology, under normal pressure conditions was adopts in this study to deposited ZnO films. The cheap zinc acetate, ammonium fluoride, and gallium chloride was used as Zn source, F source, Ga source and Cl source, respectively for deposited F, Cl, Al and Ga co-doped ZnO (FCAGZO) films. The influence of substrate temperature (Ts) on the morphology, structure, optical and electrical properties of ZnO thin films was studied. X-ray diffraction analysis shows that the Ts does not change the crystal structure of the ZnO film, and all films have a hexagonal wurtzite structure. With increase of Ts only the preferred orientation of the film changes from (100) to (002). X-ray photoelectron spectroscopy further confirmed the successful doping of ZnO by F, Cl, Al, and Ga, which accounts for the enhancement in carrier concentration in the FCAGZO films over that of pristine ZnO. As Ts increases, the resistivity first decreases, and then gradually increases. When the optimal substrate temperature Ts = 400 °C, the prepared FCAGZO film has a resistivity of 1.47 × 10-3 Ωcm when rapid heat treatment in N2 atmosphere at 750 °C, and the average transmittance exceeds 85% in the range of 400–1400 nm.

A computational fluid dynamic-based method for analyzing the nonlinear relationship between windage loss and pressure in a geotechnical centrifuge

Temperature control is an important limitation to further increase in geotechnical centrifuge power. Although vacuum pumps can reduce windage loss, they also negatively affect heat transfer performance. Therefore, in this study, we aim to accurately determine the rate at which windage loss decreases with pressure to help assess whether reducing pressure is beneficial to temperature control. A computational fluid dynamic method based on the multi-reference model and k–ω shear-stress transport turbulence model is used to simulate the ZJU400gt geotechnical centrifuge. The windage loss and temperature of ZJU400 at 0–150 gravity acceleration under normal pressure conditions are simulated. Compared with the experimental data, the error is < 20.7%, indicating simulation reliability. Furthermore, the simulation model is used to simulate the windage loss power under low-pressure conditions and predict the relationship between the windage loss power and pressure. Compared with current calculation methods, which yield a linear relationship between windage loss and operating pressure, the simulation results indicate a slightly nonlinear relationship. At 5,000 Pa, the simulated windage loss is 40% larger than the calculated value, severely affecting the temperature control design. Moreover, the velocity exhibits minimal variation with pressure, whereas the effective kinematic viscosity varies substantially. The nonlinear relationship between the windage loss and pressure can be attributed to increased turbulent kinetic energy and the size of the wake region caused by vacuum pumping. A formula for nonlinear windage loss with pressure is proposed, providing a basis for the future design of super-gravity geotechnical centrifuges.

Study on Reactor Core Physics Calculation of Marine Nuclear Power Platform

The marine nuclear power platform is an organic combination of small nuclear reactor and ship engineering technology. It has the characteristics of good manoeuvrability, long on-time charging operation cycle, high power density, low operating cost, energy saving and environmental protection. In this paper, The core geometry model is built based on the design of the marine nuclear power platform reactor core. The core reactivity and control rod worth are calculated by a Monte Carlo code MCNP for this core design at first cycle, initial loading, normal temperature, and normal pressure condition. The results of the calculation are compared with nuclear design values. It shows that MCNP code is suitable for marine nuclear power platform core design calculation, and can be verified with nuclear design values.

Applying surface-sensitive techniques to structural and chemical study of uncapped Sn-Sb-Te thin film. A density functional theory - based study

We present here a combined experimental and theoretical study of the structural and chemical properties of polycrystalline Sn-Sb-Te film with nominal composition SnSb2Te4 grown by pulsed laser deposition technique on mylar substrate. From the experimental side, surface-sensitive techniques as x-ray photoelectron spectroscopy (XPS), grazing incidence x-ray diffractometry (GIXRD) and 119mSn integral conversion electron Möβbauer spectroscopy (ICEMS) have been applied to the study of the film at room-temperature and under normal conditions of pressure. GIXRD showed that the Sn-Sb-Te film adopted a NaCl- type structure (Fm-3m), and in the detection limits, no other crystalline phase was revealed. ICEMS technique unambiguously indicated the coexistence of two different tin fractions: Sn(II), as expected for the SnSb2Te4 phase, and Sn(IV), suggesting oxidation of tin. Chemical in-depth profile obtained by means of XPS suggests the oxidation of all the constituent atoms at the topmost layers of the film and the progressive depletion of tin and antimony oxides going depth in the film. The in-depth atomic concentration profiles also reveals a notorious deficiency of Te in the sample. Theoretically, density functional theory-based calculations (assuming that the Sn-Sb-Te film adopts the Fm-3m structure) support the hypothesis that Te - vacancies sites are occupied by oxygen atoms during the natural oxidation process of Sn-Sb-Te film. Additionally, our calculations demonstrated that only the substitution of Te atoms by oxygen ones induces a semiconducting behavior of the otherwise metallic Sn-Sb-Te host.

All-silica fiber-optic temperature-depth-salinity sensor based on cascaded EFPIs and FBG for deep sea exploration.

Using fusion splicing and hydroxide catalysis bonding (HCB) technology, an all-silica inline fiber-optic sensor with high-pressure survivability, high-resolution salinity measurement capability, and corrosion resistance for deep sea explorations is proposed and experimentally demonstrated. Two extrinsic Fabry-Perot interferometers (EFPIs) and a fiber Bragg grating (FBG) are cascaded in one single-mode fiber (SMF), enabling structural integration of single lead-in fiber and versatility of the sensing probe for temperature, depth, and salinity monitoring. The HCB technology offers a polymer adhesive-free assembly of one open-cavity EFPI for refractive index (RI) (salinity) sensing under normal pressure and temperature (NPT) conditions, showing obvious advantages of strong bonding strength, reliable effectiveness, and no corrosive chemicals requirements. The other EFPI formed by a fused structure is designed for pressure (depth) measurement. The cascading of EFPIs, especially the open-cavity EFPI immersed in water, will result in large light transmission loss and bring challenges to signal interrogation. Graded-index fiber (GIF) micro-collimators and reflective films are added to prevent dramatic degradations of signal intensity and fringe visibility underwater. Thereby, a Fabry-Perot (FP) cavity of several hundreds of microns in length and an open cavity of a thousand microns can be cascaded for underwater applications, effectively enhancing sensitivities and underwater signal readout simultaneously. Results show that the proposed sensor can well operate in the deep-sea pressure range of 0∼2039.43 mH2O, RI range of 1.33239∼1.36885 RIU, and temperature range of 23∼80 °C, with resolutions of 0.033 MPa, 4.16×10-7 RIU, and 0.54 °C, respectively. With the multi-parameter measurement capability, all-silica construction, and inline compact structure, the proposed sensor could be a potential candidate for deep sea exploration.

Study of nitrazepam interaction with alcohol: an ultrasonic and physiochemical investigation

The intermolecular interaction between the constituent components of liquid mixtures can be revealed by ultrasonic analysis. In the present study, interaction of nitrazepam with methyl alcohol has been studied and presented using ultrasonic tools. The investigation involves calculation of ultrasonic velocity (υ), density (ρ), viscosity (η), and the associated derived parameters. The specific acoustic impedance (Z), isentropic compressibility (β), relaxation time (τ), intermolecular free length (Lf), and solvation number (Sn) are calculated to reveal the interaction information. The solvent–solvent and solute–solvent interaction between nitrazepam and alcohol molecules is considered. To see the impact of nitrazepam with alcohol in an ordinary day to day scenario, the investigation was carried out under normal temperature (303–313 K) and pressure conditions. The results indicate increased molecule association of nitrazepam in the presence of alcohol. This study suggests the presence of a synergistic depressants effect when nitrazepam is used with alcohol.

미생물의 방해석 석출 작용을 이용한 폐석고의 재활용에 관한 연구

In this study, to improve the characteristic that the waste gypsum reacts at the high temperature and high pressure when it is recycled, it was intended to develop the waste recycling method under the condition of room temperature and normal pressure. To do that, the calcium ion extraction test, and the mineralogical analysis and the structural analysis of the precipitation by the microbially induced calcite precipitation (MICP) were performed. The optimal calcium ion extraction condition was analyzed as solid-liquid ratio of 1:10, solvent type: HCl and HNO3. In addition, the air injection increased the activation of microorganism increasing the reduction of calcium ion by reaction time. Particularly, the precipitation was generated after MICP and it was confirmed that the precipitation was the calcium carbonate (CaCO3) through the mineralogical analysis and the structural analysis of the precipitation. Therefore, MICP can be utilized as a method to recycle the waste gypsum.

A Rapid Cu Enrichment Mechanism from Cu-Bearing Brine in Kuqa Basin, Xinjiang, China: Controlled by Crystallized Sequence of Saline Minerals

Sediment-hosted copper deposit is usually related to arid climate, ancient saline lake basin, and brine. The Kuqa Basin filled with giant-thickness evaporite units is located in the northern Tarim Basin, Xinjiang, China. It is famous for sandstone-hosted Cu deposits formed by synsedimentary processes. However, our recent studies reveal that Cu enrichment is closely related to brine on the surface of clastic rocks in the basin. It is shown that green Cu mineral coexisting with halite and gypsum occurred in the fractured fault belts of sandstones or was precipitated with halite on the surface of maroon clay in the scallops of sandstone. By SEM, EDS, and geochemical analysis methods on Cu-mineralized solid samples and brines, respectively, combined with previous geological evidence, our studies demonstrate that green Cu mineral is paratacamite, and it occurred with gypsum, halite, secondary glauberite, natural copper, and probably lead chloride on the fractured fault belts of sandstones or surface of clay. Meanwhile, the precipitation of paratacamite is controlled by a crystallized sequence of saline minerals accompanying with evaporated-concentrated course of brine in which gypsum, secondary glauberite, paratacamite, and halite are crystallized in turn. The Cu-bearing brine derived from meteoric waters and ancient seawater has a powerful capacity to leach metallic ions from its surrounding rocks and can be formed in a very short time (10 days is OK) in normal pressure and temperature conditions; also, the cycle of surface-Cu enrichment (mineralization) is only a few months (no more than 5). These indicate that a rapid Cu enrichment mechanism from Cu-bearing brine occurs on the earth’s surface of the evaporite basin. The mechanism might be supposed to make an enormous amount of metal mineralization in a short time if considered from a large-scale spatial viewpoint. By contrast with the lengthy geological period, the short evolutionary cycle of Cu enrichment (mineralization) is obviously different from the previous cognition.

Study of the Hemodynamics Effects of an Isolated Systolic Hypertension (ISH) Condition on Cerebral Aneurysms Models, Using FSI Simulations

Hemodynamics is recognized as a relevant factor in the development and rupture of cerebral aneurysms, so further studies related to different physiological conditions in human represent an advance in understanding the pathology and rupture risk. In this paper, Fluid-structure interaction simulations (FSI) were carried out in six models of cerebral aneurysms, in order to study the hemodynamics effects of an isolated systolic hypertension (ISH) condition and compare it to a normal or normotensive pressure condition and a higher hypertension condition. Interestingly, the ISH condition showed, in general, the greatest hemodynamics changes, evidenced in the Time-Averaged Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), and Relative Residence Time (RRT) parameters, with respect to a normal condition. These results could imply that a not high-pressure condition (ISH), characterized with a different shape and an abrupt change in its diastolic and systolic range may present more adverse hemodynamic changes compared to a higher-pressure condition (such as a hypertensive condition) and therefore have a greater incidence on the arterial wall remodeling and rupture risk.

In‐Situ Synthesis of MoS2/BiOBr Material via Mechanical Ball Milling for Boosted Photocatalytic Degradation Pollutants Performance

AbstractA novel visible‐light‐driven MoS2/BiOBr composite material is prepared in situ under normal temperature and pressure conditions through the efficient, green and energy‐saving ionic liquid‐assisted mechanical ball milling method. Under visible light irradiation, the MoS2/BiOBr composite exhibits enhanced photocatalytic degradation tetracycline (TC) activity than that of BiOBr monomer. Among them, 1.0 wt % MoS2/BiOBr exhibits the best photocatalytic degradation activity and can degrade 68 % of TC within 120 min, which is 30 % improvement in performance compared to BiOBr monomer. The introduction of MoS2 promotes the photocatalytic performance of the composite material, which is mainly attributed to the increased specific surface area, enhanced visible light absorption capacity and excellent photo‐generated carrier separation and transfer efficiency. Electron spin resonance, radical trapping experiments and XPS valence band spectroscopy confirmed that superoxide radicals and holes are the main active species in the photocatalytic process.