Vacuum Level Research Articles

The Existential Vacuum and Its Relationship to Pessimism and Optimism among Undergraduate Students

University students may confront an existential vacuum, characterized by a loss of life's meaning resulting from personal crises, socio-political shifts, and health transformations. These challenges, which some young individuals may struggle to adapt to, contribute to an existential vacuum, fostering feelings of pessimism and despair. The current study investigated the prevalence of existential vacuum, pessimism, and optimism among undergraduate students, assessing their interrelations and exploring potential differences based on gender. The research sample consisted of 466 students, both male and female, during the first semester of the 2021-2022 academic year. A correlational method was employed in this study. Utilizing validated scales to measure existential vacuum (α = .90, r = .87), pessimism, and optimism (α = .88), the findings indicated that while existential vacuum presented at low level (M= 2.44, SD= .96), optimism was high (M= 3.03, SD= .89), and pessimism was moderate (M=2.80, SD= .73). Gender-specific analyses revealed statistically significant differences; males showed higher levels of existential vacuum (F = 40.136, p<.00) and optimism (F = 196.548, p<.00), whereas females exhibited greater pessimism (F = 379.674, p<.05). Additionally, the study found a negative and statistically significant correlation between existential vacuum and optimism (r = -.09, P<.00), and a positive and statistically significant correlation between existential vacuum and pessimism (r = .19, P<.00). The study concluded that enhancing individuals' levels of optimism is crucial due to its role in providing meaning to life and reducing existential vacuum.

Experimental and theoretical thermal performance analysis of additively manufactured polymer vacuum insulation panels

Vacuum Insulation Panels (VIPs) are characterized by low thermal conductivity, which makes them attractive for applications in buildings, refrigerators, and cold chain logistics. The study of new technologies to manufacture VIPs has grown considerably in recent years. This work presents a feasibility analysis of additive manufacturing technique to manufacture polymer VIPs. The 3D printable multilayered VIPs, in which several interlayers are utilized to suppress gas conduction and thermal radiation, are designed and then manufactured using a commercial fused deposition modeling 3D printer. The effective thermal conductivity of the 3D printed VIPs is evaluated at various vacuum levels (1 atm, 10,000 Pa, 1000 Pa, 100 Pa and 10 Pa) using the standard test method (ASTM C518). Additionally, an analytical model and numerical simulation are performed to analyze heat transfer in these 3D printed VIPs and optimize the VIP design. The experimental results show that an effective thermal conductivity of 0.0155 W/m/K is achieved for the 3D printed VIP with 8 solid interlayers at 10 Pa, which is about 60 % of the thermal conductivity of air at 1 atm pressure. It is also found that there exists an optimal number of interlayers in the multilayered VIPs when its pressure is >1000 Pa. At lower pressures, the effective thermal conductivity of the multilayered VIPs decreases monotonically with increasing number of interlayers. This work is the first one to employ 3D printing techniques to manufacture polymer VIPs, and it is expected to offer a pathway for wider adoptions of VIPs due to its advantage low cost and high manufacturing flexibility.

Cooperation mechanism between the vacuum levels and interface dipole energy of triboelectric materials for real-time vibration recognition

Triboelectric Nanogenerator (TENG) device, acting as sensors of energy harvesting and material identification, are attracting intensive attention. Nevertheless, vibration wave recognition cannot be achieved by the developed devices owing to device structure and working mechanism limitations. Here, a cooperation mechanism between the vacuum level and interface dipole energy of triboelectric materials is proposed to explore triboelectric charge generation and migration. Hence, metallized cottons of high specific surface area encapsulated by polydimethylsiloxane (PDMS) of low elastic modulus are developed as TENG-based sensors to realize vibration recognition. The results indicate electrons flow from PDMS to metallized cotton with the generation of an extremely thin interfacial dipole barrier layer because the vacuum level of metallized cotton is higher than that of PDMS, resulting in the accumulation of triboelectric charges on the PDMS surface under vibration, further leading to generating distinct triboelectric signals that can be simply differentiated using signal amplitude or peak shape with 98.3 % recognition accuracy for vibration waveform. Besides, combined with the deep machine learning and triboelectric effect, a vibration perception system integrated with a TENG-based sensor, data processing and display modules is also developed for real-time vibration monitoring. This work contributes to further clarifying the theoretical mechanisms of triboelectric charge excitation under vibration.

Binding energy referencing in X-ray photoelectron spectroscopy: Expanded data set confirms that adventitious carbon aligns to the sample vacuum level

The correct referencing of the binding energy scale is essential for the accuracy of chemical analysis by X-ray photoelectron spectroscopy. The C 1s C–C/C–H peak from adventitious carbon (AdC), most commonly used for that purpose, was previously shown to shift by several eVs following changes in the sample work function ϕSA, thus indicating that AdC aligns to the sample vacuum level (VL). Here, results from a much larger sample set including 360 specimens comprising metals, nitrides, carbides, borides, oxides, carbonitrides, and oxynitrides are presented. Irrespective of the material system the C 1s peak of AdC is found to follow changes in ϕSA fully confirming previous results. Several observations exclude differential charging as plausible explanation for the C 1s peak shifts. All experimental evidence points instead to the VL alignment at the AdC/sample interface as the main reason. Should the C 1s peak of AdC be used for spectra referencing the measurement of sample work function is necessary, irrespective of whether samples are measured grounded or insulated from the spectrometer.

A holistic methodology for designing novel flat plate evacuated solar thermal collectors: Modelling and experimental assessment

This paper presents a comprehensive analysis of the design, implementation, experimentation, and optimization of a novel evacuated flat-plate solar thermal collector characterized by a vacuum level between the glass cover and the absorber plate. The paper addresses different research themes, primarily focusing on developing a low-cost evacuated solar thermal collector with a high innovation level. Additionally, it introduces a comprehensive approach for the conceptualization, design, fabrication, testing, and optimization of solar thermal collectors. Specifically, this study aims to highlight the characteristics of a vacuum-enhanced solar thermal collector and demonstrate a step-by-step process involved in its design, fabrication, testing, and optimization. The proposed methodology is based on the adoption of two software tools and an extensive experimental analysis: the commercial software ANSYS is utilized for structural analysis, while MatLab is employed to develop a suitable mathematical tool for assessing the energy performance of the system and optimizing it. The outcomes show the reliability of the methodology and the performance of the low-cost evacuated solar thermal collector under different vacuum levels, providing insights into energy, economic, and environmental aspects. This work innovates by presenting a thorough analysis covering all solar thermal collector production phases, from conceptualization to optimization. The conclusions highlight the production of a reliable approach, and proof-of-concept results demonstrate how increasing the vacuum level enhances the thermal efficiency of a solar collector.

Evaluasi Kinerja Steam Jet Ejector Tingkat Pertama Terhadap Kevakuman Kondensor

The steam jet ejector is a device for extracting NCG from the condenser. NCG can increase the pressure in the condenser until a vacuum condition is not reached. The diffuser pressure on the steam jet ejector has a normal operational limit of below 1 atm, meaning that the ejector performance will be optimal if it is operated at the operational limit under vacuum conditions. The expected objectives are to determine the effect of the steam jet ejector on condenser vacuum, calculate the performance of the first level steam jet ejector through pressure analysis in the diffuser section, calculate the performance of the steam jet ejector in actual conditions compared to the design data conditions and analyze actions that can be taken to improve the performance of the tool. Based on the results of calculations and analysis, it was found that the increase in steam jet ejector pressure had an effect on the increase in condenser pressure from the design pressure of 0.10 bar to 0.107-0.123 bar under actual conditions. The decrease in steam jet ejector performance results in the condenser vacuum level decreasing, but the equipment performance is within normal operational limit conditions, namely below 1 atm. The decrease in steam jet ejector performance is influenced by the motive steam mass flow rate, NCG mass flow towards suction, entrainment ratio value, NCG pressure and motive steam pressure which exceeds the design data.

Evidence for double resonant Raman decay from a Ag surface

We have investigated the electron pair emission from a Ag(100) surface upon photon absorption which leads to the emission of a 4p photoelectron. The subsequent Auger decay proceeds in a single-step process as shown previously. Key finding was the emergence of a diagonal intensity feature in a two-dimensional kinetic energy distribution of the electron pair whose width reveals a characteristic time of 30 as for the dynamics of the core-hole decay process. We utilize this observation as a tool to identify an unexpected pathway of electron pair emission. Once the photon energy is at the threshold of a double 4p core hole creation we notice a sizeable broadening of the energy sharing distribution. We associate this process to the excitation of two 4p electrons between the Fermi and vacuum level followed by radiation less double electron excitation. This feature is characterized by an energy sum of the pair which disperses linearly with the photon energy. Therefore, we regard it as a double resonant Raman decay. Published by the American Physical Society 2024

Ligand Driven Control and F‐Doping of Surface Characteristics in FASnI3 Lead‐Free Perovskites: Relation Between Molecular Dipoles, Surface Dipoles, Work Function Shifts, and Surface Strain

AbstractThe performance and operational stability of perovskite‐based devices heavily rely on the interfacial properties between the photoactive perovskite layer and charge transport layers. Understanding the theoretical relationship between surface/interface dipoles and surface energetics is crucial for scientific understanding and practical applications. In this study, a method is applied that bridges classical electromagnetism and modern atomistic approaches. The impact of dipolar ligand molecules functionalizing the FASnI3 perovskite surface is investigated, with inspection of the interplay between surface dipole, charge transfer, and local strain effect, and corresponding shifts in the valence level. The results reveal that the contribution of individual molecular entities to surface dipoles and electric susceptibilities follows an essentially additive behavior. The influence of F doping usually used to mitigate Sn oxidation in Sn‐based layer for photovoltaic applications, is also discussed. Furthermore, the findings are compared with predictions from classical approaches employing a capacitor model that links the induced vacuum level shift and the molecular dipole moment. The insights gained from the study provide theoretical guidelines for fine‐tuning the work functions of materials, thus enabling effective interfacial engineering in this class of semiconductors.

Flexible Substrate-Compatible and Efficiency-Improved Quantum-Dot Light-Emitting Diodes with Reduced Annealing Temperature of NiOx Hole-Injecting Layer

The growing demand for wearable and attachable displays has sparked significant interest in flexible quantum-dot light-emitting diodes (QLEDs). However, the challenges of fabricating and operating QLEDs on flexible substrates persist due to the lack of stable and low-temperature processable charge-injection/-transporting layers with aligned energy levels. In this study, we utilized NiOx nanoparticles that are compatible with flexible substrates as a hole-injection layer (HIL). To enhance the work function of the NiOx HIL, we introduced a self-assembled dipole modifier called 4-(trifluoromethyl)benzoic acid (4–CF3–BA) onto the surface of the NiOx nanoparticles. The incorporation of the dipole molecules through adsorption treatment has significantly changed the wettability and electronic characteristics of NiOx nanoparticles, resulting in the formation of NiO(OH) at the interface and a shift in vacuum level. The alteration of surface electronic states of the NiOx nanoparticles not only improves the carrier balance by reducing the hole injection barrier but also prevents exciton quenching by passivating defects in the film. Consequently, the NiOx-based red QLEDs with interfacial modification demonstrate a maximum current efficiency of 16.1 cd/A and a peak external quantum efficiency of 10.3%. This represents a nearly twofold efficiency enhancement compared to control devices. The mild fabrication requirements and low annealing temperatures suggest potential applications of dipole molecule-modified NiOx nanoparticles in flexible optoelectronic devices.

Quantum control and Berry phase of electron spins in rotating levitated diamonds in high vacuum

Levitated diamond particles in high vacuum with internal spin qubits have been proposed for exploring macroscopic quantum mechanics, quantum gravity, and precision measurements. The coupling between spins and particle rotation can be utilized to study quantum geometric phase, create gyroscopes and rotational matter-wave interferometers. However, previous efforts in levitated diamonds struggled with vacuum level or spin state readouts. To address these gaps, we fabricate an integrated surface ion trap with multiple stabilization electrodes. This facilitates on-chip levitation and, for the first time, optically detected magnetic resonance measurements of a nanodiamond levitated in high vacuum. The internal temperature of our levitated nanodiamond remains moderate at pressures below 10−5 Torr. We have driven a nanodiamond to rotate up to 20 MHz (1.2 × 109 rpm), surpassing typical nitrogen-vacancy (NV) center electron spin dephasing rates. Using these NV spins, we observe the effect of the Berry phase arising from particle rotation. In addition, we demonstrate quantum control of spins in a rotating nanodiamond. These results mark an important development in interfacing mechanical rotation with spin qubits, expanding our capacity to study quantum phenomena.

Tautomerism of herbicides metribuzin, diclosulam and clethodim: evaluation of different parameters for structure assignation

Pesticides are widely used in agriculture, and they can cause serious damage to human health and to the environment. In this work, three herbicides are studied regarding possible tautomeric equilibria: clethodim, diclosulam and metribuzin. Tautomerism is a key reaction that is directly related to action, disposition and toxicity of herbicides, and here lies the importance of this study. The specific aim of this work is to compare classical parameters (MAE and R2) with DP4+ method as a tool for obtaining relevant information about tautomeric equilibria in the three compounds, contrasting experimental NMR data with theoretical calculations carried out using DFT methods.1H and 13C NMR spectra of the three herbicides were recorded in DMSO‑d6. Additionally, HSQC and COSY spectra were obtained for clethodim. Theoretical calculations were carried out in order to obtain optimized geometries in vacuum (using B3LYP method at 6–31G(d,p) level of theory); and chemical shifts of nuclei corresponding to all possible tautomers of each herbicide were obtained by means of B3LYP-GIAO method using 6–311+G(2d,p) basis set.In the three cases, classical comparison parameters MAE and R2 fail in the assignation of tautomers since they gave doubtful or even inconsistent results. In the case of metribuzin, MAE values obtained from 1H and 13C point towards different structures. R2 and MAE values obtained from 1H and 13C are very close when comparing the two tautomers, and the assignation is not certain. The case of clethodim is more confusing, since the R2 and MAE values suggest that all signals correspond to the same structure. DP4+ method, on the other hand, gave more reliable results (within the set of proposed structures). It is important to remark that DP4+ method has been used before for tautomer assignation in only one case (to the best of our knowledge), and it has also proven successful in this context of use.We concluded that metribuzin and diclosulam exist in solution in one major tautomeric form (aminotriazinone and sulfonamide, respectively), while two tautomers of similar energy (E- and Z-ketoenolimine complexed with DMSO) are proposed for clethodim.

Quantifying squeeze film damping in four-leaf clover-coupled micro-resonators: A comprehensive study under variable vacuum degrees

The squeeze film effect has a significant impact on the performance of micro-resonators when utilizing the electrostatic excitation and capacitive detection technique, due to the narrow air gaps present. It becomes the most critical damping effect that needs to be addressed. However, when micro-resonators are encapsulated in vacuum or rarefied air, squeeze film damping analysis can become considerably complex due to high-quality factors. In this study, we systematically investigate the squeeze film damping of a widely-used four-leaf clover-coupled micro-resonator under different vacuum degrees. The characteristic frequencies of micro-resonators are determined by applying the principle of mode superposition. Subsequently, the energy transfer theory is utilized to derive the theoretical formula for the quality factor caused by squeeze film damping, for varying levels of vacuum. Finite element analysis is then conducted to simulate the characteristic behavior and squeeze film damping of the resonator, confirming the accuracy of the proposed theory. In the experiment, a novel four-leaf silicon micro-resonator is fabricated using bulk anisotropic wet etching and other micromachining technologies. An experimental platform is established to study the squeeze film damping of the micro-resonator under various vacuum degrees, where the micro-resonator is excited electrostatically and detected capacitively. The frequency response and quality factor of the resonator under different vacuum degrees are measured using a house-made modal test circuit board. The experimental results demonstrate excellent agreement with the theoretical and simulated results, indicating that the proposed method can be a reliable and precise guide for understanding the squeeze film damping effect in advance, once the primary model of a micro-resonator has been designed.

Study on the regeneration of activated carbon adsorbed with radon by using a deep depressurization method

ObjectiveTo develop a heating-free, rapid, and efficient method for the regeneration of activated carbon by introducing deep depressurization. MethodsA validation experimental setup was designed to systematically investigate the impacts of various desorption methods, durations, and conditions on the desorption effectiveness of activated carbon with adsorbed radon and water. Consecutive repetitive and expanded experiments were carried out. ResultsThe combination of continuous ventilation and deep depressurization was proved the most effective in the desorption of activated carbon. Considering factors such as overall energy consumption and time, the optimal desorption duration for activated carbon was determined at 2 ​h. Reducing the relative humidity of radon-laden air and increasing the desorption environmental temperature significantly enhanced the desorption rate. Under a temperature range of 24–25°C, a relative humidity range of 5%–15%, and a flow rate of 0.3 ​L/min, a desorption rate of 85% was achieved for 122.5 ​g of activated carbon after 2 ​h of desorption. Moreover, the desorption results remained stable throughout 10 repetitions. Further experiments on a kilogram-scale activated carbon bed demonstrate that under a vacuum level meeting the requirement for moisture evaporation and an appropriate flow rate, the desorption rate of the activated carbon reached that of a smaller activated carbon bed, independent of the shape of the activated carbon bed. ConclusionThe deep depressurization method shows great promise as a rapid and efficient online method for the regeneration of activated carbon with adsorbed radon and water.

Velocity Map Imaging Photoelectron Spectroscopy of Silver Iodide Aerosol Particles.

The valence band electronic structure of isolated silver iodide nanoparticles (AgI NP) was investigated by vacuum-ultraviolet aerosol photoelectron spectroscopy using the velocity map imaging technique (VUV VMI-PES). The VUV VMI-PES results were obtained for polydisperse aerosol produced by aggregation of hydrocolloid of silver iodide particles 8-15 nm in size. The ionization energy of the AgI particles was found to be 6.0±0.1 eV with respect to the vacuum level. The DFT calculations showed that the main contribution to the density of AgI electronic states in the valence region originates from I 5p orbitals. The dependence of the asymmetry parameter on the electron energy showed that the value of the characteristic energy loss of excited photoelectrons was 2.7 eV, which coincided with the band gap of the nanomaterial.

Multiscale experimental insights into vacuum drying of sludge for enhanced energy efficiency and emission control

This study provides a comprehensive analysis of the vacuum drying process for sludge drying, with a focus on optimizing energy efficiency and emission control. The study used both lab-scale static and pilot-scale vacuum drying systems to test various parameters like vacuum levels, heat source temperatures, and sludge thicknesses. The results indicated that optimal drying conditions were achieved at a vacuum level of −0.06 MPa, a heat temperature of 140 °C, and a sludge thickness of 3.4 mm, where the drying rate reaches 0.13278 g·g−1·min−1. The study underscores the significant influence of vacuum level, temperature, and sludge thickness on drying rates. The Page model was used to analyze drying kinetics, elucidating how changes in these parameters affect drying characteristics. Furthermore, the study also examined the pollutant emissions and energy efficiency at the pilot scale. It found that high vacuum environments could efficiently dry sludge using low-temperature heat source, leading to average energy consumption per unit evaporation of 3020.29 kJ/kg, which is lower compared to traditional methods. By harnessing low-grade industrial waste heat, this can be further reduced to 875.76 kJ/kg. This study offers valuable insights for sustainable sludge management systems, highlighting the environmental and economic benefits of vacuum drying technology. The detailed experimental approach and thorough analysis make a significant contribution to the field of the sludge drying.

New approach to the equilibrium of D-glucaric acid in water: DFT study of tetrahedral intermediates

The present study aims at investigating, for the first time, the formation of tetrahedral intermediates during the equilibrium mechanism of D-glucaric acid in water. In this work, carried out at B3LYP/6-31+G(d,p) computational level in vacuum and using the polarizable continuum model, two systems are proposed and simulated: the first describes an intramolecular proton transfer, and the second requires the intervention of solvent molecules for the proton transfer. The second system, simulated in vacuum, indicates greater ease in establishing this equilibrium due to a significant reduction in angular tensions. Also, the idea of a tetrahedral intermediate carrying two geminal diol groups constitutes a favorable hypothesis due to the low energy barriers calculated as well as a better structural flexibility generated following the equilibrium of the tetrahedral intermediates between them. Experimental confirmation of the presence of such a powerful tetrahedral intermediate would be a considerable advance in resolving the equilibrium mechanisms of D-glucaric acid.

Strong microwave squeezing above 1 Tesla and 1 Kelvin.

Squeezed states of light have been used extensively to increase the precision of measurements, from the detection of gravitational waves to the search for dark matter. In the optical domain, high levels of vacuum noise squeezing are possible due to the availability of low loss optical components and high-performance squeezers. At microwave frequencies, however, limitations of the squeezing devices and the high insertion loss of microwave components make squeezing vacuum noise an exceptionally difficult task. Here we demonstrate direct measurements of high levels of microwave squeezing. We use an ultra-low loss setup and weakly-nonlinear kinetic inductance parametric amplifiers to squeeze microwave noise 7.8(2) dB below the vacuum level. The amplifiers exhibit a resilience to magnetic fields and permit the demonstration of large squeezing levels inside fields of up to 2 T. Finally, we exploit the high critical temperature of our amplifiers to squeeze a warm thermal environment, achieving vacuum level noise at a temperature of 1.8 K. These results enable experiments that combine squeezing with magnetic fields and permit quantum-limited microwave measurements at elevated temperatures, significantly reducing the complexity and cost of the cryogenic systems required for such experiments.

Squeezed light from an oscillator measured at the rate of oscillation.

Sufficiently fast continuous measurements of the position of an oscillator approach measurements projective on position eigenstates. We evidence the transition into the projective regime for a spin oscillator within an ensemble of 2 × 1010 room-temperature atoms by observing correlations between the quadratures of the meter light field. These correlations squeeze the fluctuations of one light quadrature below the vacuum level. When the measurement is slower than the oscillation, we generate and detect of squeezing in a tunable band that is a fraction of the resonance frequency. When the measurement is as fast as the oscillation, we detect 4.7 dB of squeezing that spans more than one decade of frequencies below the resonance. Our results demonstrate a new regime of continuous quantum measurements on material oscillators, and set a new benchmark for the performance of a linear quantum sensor.

Vacuum Pump-Down of the Annular Insulation Space for Large Field-Erected Liquid Hydrogen Storage Tanks

Insulation systems are critical to liquid hydrogen storage tank performance. Tanks in the capacity range of 100 to 1,000 m3 are typically shop built and designed with high-vacuum (HV) multi-layer insulation (MLI), whereas storage vessels larger than 1,000 m3 are typically field-erected and supplied with bulk fill insulation working at moderate vacuum (MV) levels (1-100 millitorr). For large, field-erected vessels, two types of bulk fill insulation typically used: perlite and hollow glass microspheres (glass bubbles). Selection of either material is driven by a tradeoff between CAPEX and OPEX, such as the material and construction cost versus operating thermal performance and maintenance. In either case, the vacuum level needed to achieve optimum performance is likely to drive the field testing and commissioning portion of the construction schedule. A primary goal of this paper is to present practical experience and data for warm vacuum pressure (WVP) and cold vacuum pressure (CVP) levels. Recommended WVP levels needed prior to cooldown consider both perlite powder and glass bubbles. Pumping time expected to achieve target vacuum levels, considering a variety of factors, is also discussed. Recommendations for a standard practice in vacuum-insulated tank commissioning are based on historical NASA data, and those collected during recent projects.

Mechanical performances of continuous carbon fiber reinforced PEEK (polyether ether ketone) composites printed in a vacuum environment

Continuous fiber-reinforced thermoplastic (CFRTP) composites have attracted significant attention in various industries due to their exceptional mechanical properties and lightweight nature. Various methods have been applied to improve the mechanical properties of parts produced by fused deposition modeling (FDM), such as printing in a vacuum environment. Vacuum is utilized during printing to minimize heat transfer by convection, improve interfacial bonding, and reduce void formation. This study investigates the effects of vacuum and process parameters on the mechanical and microstructural properties of continuous fiber-reinforced thermoplastic composites. The goal was to investigate the effects of the printing parameters in a vacuum environment and therefore, enhance the mechanical properties. CFRTP test specimens were produced under various vacuum levels and processed at nozzle temperatures, heated bed temperatures, and printing speeds. Three-point bending tests were conducted to evaluate the flexural properties, and microstructural analysis was performed using optical microscopy. The results demonstrate the positive influence of vacuum on flexural performance and highlight the importance of controlling parameters, such as nozzle temperature and heated bed temperature for achieving enhanced mechanical properties. This study provides valuable insights into the production of higher mechanical properties of CFRTP composites and contributes to advancements in their manufacturing.