Combined Vacuum Research Articles

Effect of ultrasound pretreatment combined with different drying methods on the quality and bioactive compounds of broccoli stems

SummaryThe effects of ultrasound (US) pretreatment combined with drying process on storage quality maintenance and bioactive compound accumulation of broccoli stems were investigated. Results indicated that US pretreatment (λ = 8.5 mm) delayed the decline of L* value and ascorbic acid content but inhibited the increase of a* and b* values, browning index, and microbial counts of fresh‐cut broccoli stems. Furthermore, the US application enhanced total phenolics content by activating phenylalanine ammonia‐lyase, cinnamate‐4‐hydroxylase, and 4‐coumarate‐CoA ligase in phenylpropane metabolism. Meanwhile, it also promoted γ‐aminobutyric acid (GABA) accumulation by upregulating activities of diamine oxidase, polyamine oxidase, and aminoaldehyde dehydrogenase in GABA shunt and polyamine degradation pathway, respectively, which in turn, accelerated the biosynthesis of GABA from polyamines and glutamate. In addition, compared with other three drying methods, the combined vacuum freeze drying (VFD) could further retain the sensory attributes and bioactive compounds to a maximum extent in dehydrated broccoli stems. Hence, current findings illustrated that US pretreatment combined with VFD process is beneficial for commercial quality maintenance and nutritional value enhancement, thus providing new perspectives on the comprehensive utilisation of broccoli stems.

Numerical study of Tunis soft soil improved by combined vacuum consolidation and geodrains

Numerical study of Tunis soft soil improved by combined vacuum consolidation and geodrains

Investigation the effect of surface treatment on the mechanical properties of coating

AbstractThe study analyzed surface treatment's impact on mechanical properties of Fe-based amorphous coatings. Specimens underwent six-hour treatments at 670 and 770 °C using vacuum heat. Results revealed distinct mechanical features in the coating: Vickers hardness reached 755, scanning electron microscope images displayed glassy phases, showcasing good wear resistance and compressive residual stresses at around −55 MPa. A remarkable 122% increase in compressive residual stress was noted through combined vacuum heat treatment and sandblasting. Volume wear decreased from the initial 18 to 14 mm3 after treatment at 670 °C followed by sandblasting, indicating a 30% enhancement in wear resistance. Yet, using vacuum heat treatment at 770 °C negatively impacted the coating's properties.

American Ginseng Slice Drying and Optimization: Effect of Different Drying Methods on Drying Kinetics and Physicochemical Properties

This study compared four drying methods, namely hot-air and vacuum combined drying (HAVCD), hot-air drying (HAD), vacuum drying (VD), and vacuum freeze-drying (VFD), with the aim to select a high-quality and efficient drying method to dry American ginseng slices. Drying kinetics and various physicochemical properties, such as color, rehydration ratio, total ginsenoside content, total ginsenoside residual rate, hardness, and microstructure were explored. An improved multi-indicator test formula method was used to score the experimental results quantitatively. HAVCD resulted in comprehensive advantages, with the highest product score for the dried American ginseng slices. Therefore, HAVCD was subjected to a response surface methodology (RSM) analysis and process optimization. The interaction of hot-air temperature and vacuum temperature on the comprehensive score of American ginseng drying was highly significant (p < 0.01). The optimized and validated process parameters obtained were a hot-air temperature of 57 °C, a vacuum temperature of 54 °C, and a moisture content at the conversion point of 39% (wet basis). Under these conditions, the best drying time was 170 min; the total ginsenoside content was 2.3 mg/100 g; the L* value was 91.68; the rehydration ratio was 3.10; and the comprehensive score was 96.77. The findings of this work indicated HAVCD as a promising drying method for American ginseng slices, considering the drying time and dried-product quality attributes.

Consolidation behaviour of marine clay improvement by combined vacuum preloading with geotextile

ABSTRACT The traditional vacuum preloading method of prefabricated vertical drain (PVDs) has been widely used in practical engineering. However, the serious clogging effect around PVDs in the process of vacuum-preloading reinforcement can easily lead to a series of problems such as uneven settlement and large lateral displacement of soil after reinforcement, which seriously affects the application of PVDs in marine clay foundation treatment. In this paper, the effect of combined treatment of marine clay by geotextiles and PVDs on reducing the clogging effect around PVDs was studied by laboratory model experiment. The effects of geotextiles with different diameters and spacings on the surface settlement, excess pore water pressure and lateral displacement of the reinforced soil were analysed. The experimental results show that this method has obvious help on alleviating the above problems, thus providing a reference for the application of geotextile combined with vacuum preloading method to treat marine clay foundation in engineering practice.

Investigation and numerical simulation of two-phase ejectors for use in the water desalination cycle

This study investigates enhancing energy efficiency in desalination by introducing a novel combined ejector-solar vacuum tube collector cycle. The cycle utilizes a two-phase state and lower-temperature saturated steam generation to overcome the energy consumption hurdle, particularly by compressors. Water enters the ejector's primary nozzle in a liquid phase, while steam from the solar collector aids in separation, yielding desalinated water in a variable phase. Fluent software's computational fluid dynamics assesses the ejector's performance, considering primary and secondary inlet pressures' impact on hydrodynamic characteristics. TRNSYS software models the cycle transiently over a year in Tehran, exploring different pressures' effects on fluid behavior. Results indicate that increasing secondary nozzle pressure at constant primary pressure significantly boosts steam flow rate and inlet velocity. The investigation covers secondary inlet pressures ranging from 7000 Pa to 39,000 Pa and primary nozzle pressures between 200,000 Pa and 500,000 Pa, studying their impact on fluid behavior. Under Tehran's climatic conditions, the proposed cycle achieves a peak output rate of 1.35 kg/m2/h, a maximum daily yield of 8.47 kg/m2, and a total annual output of 767 kg/m2 for desalinated water. This innovative approach showcases promise for energy-efficient desalination, especially in regions with solar potential like Tehran.

Effect of vacuum UV and UV-C treatment on degradation and ecotoxicity of tire wear microrubber leachates.

Tire wear microrubber particles (TWMP) are a major source of environmental contamination. Degradation of TWMP is slow and leachates contain toxic constituents including heavy metals, polycyclic aromatic hydrocarbons (PAHs) and organic additives. Few studies have addressed methods to mitigate the potential ecotoxicity of TWMP leachates. This study investigated the effects of UV-C (254 nm) and combined UV-C and vacuum UV (185 nm) treatment (VUV-UV-C) of TWMP leachates on degradation and ecotoxicity. VUV-UV-C treatment mitigated dissolved zinc and degraded the TWMP constituents fluoranthene, pyrene and benzo(a)pyrene by up to 90%, and the additives benzothiazole and phthalates by up to 70%. The potential ecotoxicity and genotoxicity of TWMP constituents were examined before and after UV treatment in bioassays with Escherichia coli, the luminescent bacterium Aliivibrio fischeri, the microalga Raphidocelis subcapitata and the crustacean Daphia magna. VUV-UV-C treatment decreased the potential ecotoxicity up to five-fold as indicated by changes in median effective concentrations (EC50). This was likely due to the formation of less toxic and less bioavailable transformation products. The VUV-UV-C treatment did not require the addition of oxidants or catalysts, and the study indicated a potential of VUV-UV-C as an advanced oxidation process to mitigate toxic compounds in TWMP leachates from urban or industrial sources.

A Randomized, Split-Face, Comparative Study of a Combined Needle Radiofrequency/Intense Pulsed Light Device in Moderate-to-Severe Acne Patients.

Radiofrequency (RF) and intense pulsed light (IPL) have been reported as efficient adjuvant treatment modalities for acne vulgaris. We sought to evaluate the clinical efficacy and safety of a combined needle RF and vacuum IPL device for acne treatment without the use of other conventional topical or oral agents. This randomized, split-faced study was designed to include patients with moderate to severe acne vulgaris. Comedone extraction was performed on both parts of the face prior to laser treatment. One side of the face was treated with RF and IPL in 2-week intervals, while the other side was left untreated as a control. Two independent blinded investigators evaluated the patients for improvement using clinical photographs. We also assessed for possible adverse effects. The study included 44 patients with acne vulgaris (27 men and 17 women). Their ages ranged from 19-39 years (average, 23 years). At the final 12-week follow-up visit, the acne reduction rate was 34.80% (±33.45%; range, 30.92%-19.03%) on the treated side and 13.76% (±37.58%; range, 28.26%-23.27%) in the control group compared to baseline, constituting a significant difference. The difference in reduction rate between the treated and control sides was 21.03% (±25.09%), with the treated side experiencing more significant improvement (p<0.05). In the assessment of adverse events, one patient experienced mild surrounding erythema that spontaneously improved. Combined treatment of needle RF and IPL could improve acne lesions.

Effects of combined vacuum and heat pump drying on drying characteristics and physicochemical properties of pineapple

Vacuum drying (VD) and heat pump drying (HPD) are widely used in the food industry. However, their application is limited due to low drying efficiency and the resultant poor quality of dried products. Additionally, varying drying durations in combined drying can markedly impact the physical and chemical properties as well as the nutritional content of the dried product. To achieve the highest quality dried products, VD + HPD was initially compared and identified as the most suitable drying method. This paper investigates the impact of the first stage drying duration on the physical characteristics (color, microstructure, texture, volume shrinkage rate (VSR), rehydration rate (RR)) and bioactive components (total phenolic content (TPC), total flavonoid content (TFC), Polysaccharides) of pineapple. The results indicated that VD + HPD necessitated lower energy consumption and markedly enhanced the physical properties of dried products. The brightness, rehydration rate (RR), color difference, volume shrinkage rate (VSR), and surface microstructure of pineapple dried by VD 5h + HPD 5.5h were all optimal. In comparison with other tested drying methods, the textural properties (hardness, chewiness, viscosity) and bioactive components (TPC, Polysaccharides) exhibited significant improvement. Overall, these results indicate that VD5h + HPD5.5h can be viewed as a valuable technology for improving the quality of dried pineapples.

A combined MEMS thermal vacuum sensor with a wide pressure range

MEMS thermal vacuum sensors have been widely applied in many academic and industry fields, and pressure range is a key performance of MEMS thermal vacuum sensors. To extend the pressure range, a combined MEMS thermal vacuum sensor that consists of two diode-type MEMS thermal vacuum sensors in series is proposed in this work. The two diode-type sensors are designed to have different areas of sensitive region and distances between sensitive region and heat sink, and their responses to the pressure are from 3.0 × 10−3 to 3 × 104 Pa and from 1.7 × 10−2 to 4.4 × 105 Pa, respectively. By series-connecting them, the combined sensor achieves a pressure range of 1.3 × 10−3 to 6.9 × 105 Pa without any additional control circuit. In addition, it possesses a relatively small size of 400 × 300 μm2. These indicate that the combined MEMS thermal vacuum sensor has the characteristics of wide pressure range, high sensitivity and small size.

Ecotoxicity and rapid degradation of quaternary ammonium compounds (QACs) subjected to combined vacuum UV and UV-C treatment

Quaternary ammonium compounds (QACs) are active ingredients in a palette of commercially available disinfectants, sanitizers, and biocides. QACs are widely used because of their broad-spectrum antimicrobial properties but the ubiquitous uses have resulted in frequent detection in aquatic and terrestrial matrices including domestic wastewater, surface waters, urban soils and sediments. An increased domestic QACs consumption has increased the environmental occurrence, and investigation of mitigation methods and effects on non-target organisms are in demand. In this study, we examined the potential ecotoxicity of six QACs and investigated the effect of combined vacuum UV (185 nm) and UV-C (254 nm) irradiation (VUV/UVC) on degradation and mitigation of ecotoxicity of QACs. The study showed that combined VUV/UVC irradiation facilitated rapid degradation of benzalkonium chloride, benzethonium chloride, didecyldimethylammonium chloride, dodecyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride. The estimated half-lives varied between 2 and 7 min, and degradation was affected by the initial QAC concentrations, the UV fluence, and the water matrix. The potential ecotoxicity of QACs and VUV/UVC treated QACs was examined using a battery of test organisms that included the luminescent bacterium Aliivibrio fischeri, the gram-negative and gram-positive bacteria Escherichiacoli and Enterococcus faecalis, the freshwater microalga Raphidocelis subcapitata, and the crustacean Daphia magna. The potential for trophic transfer of QACs was investigated in a simplified aquatic food web. Test organisms from different trophic levels were included to assess adverse effects of bioactive compounds in VUV/UVC treated samples including transformation products. The study showed that several QACs were highly toxic to aquatic test organisms with EC50 and/or EC20 values < 1 μM. VUV/UVC treatment of QACs resulted in substantial photolysis of the parent compounds and comprehensive mitigation of the ecotoxicity potential. VUV/UVC represent an attractive oxidation technology for abatement QACs in contaminated water because the process does not require addition of catalysts or precursors.

Fabrication and high-temperature strength of 2.5D SiO2f /SiO2 composites prepared by a combined vacuum impregnation and sol-gel method

A combined vacuum impregnation and sol-gel method was used to prepare 2.5D SiO2f/SiO2 ceramic composites with good mechanical properties in both warp and weft direction in this study. Phase change and weight gain during forming process of the ceramic composites were measured to explain the forming process. The mechanical properties of materials along different direction at room temperature and high temperature were systematically analyzed, and the fracture mechanism in different service environments was elucidated. Results indicated that dense SiO2f/SiO2 ceramic composites could be prepared by impregnating the 2.5D woven fabric preforms in silica sol and sintering them at 800 °C for > 5 cycles. Flexural strength of the composite was directly affected by the arrangement density and straightening degree of the fibers in warp/weft direction. The composite prepared in this study showed a higher flexural strength (∼91.21 MPa) in the weft direction. With the increase of temperature, the quartz fibers inside the composites became brittle due to crystallization, resulting in the failure mechanism of the ceramic composite material changing from ductile fracture to brittle fracture.

Large-Strain Consolidation Analysis for Clayey Sludge Improved by Horizontal Drains

The use of prefabricated horizontal drains (PHDs) with combined surcharge and vacuum preloading is an effective improvement approach for dredged clayey slurries. However, there is no large-strain analysis method for PHD-induced consolidation of high-water-content sludge, even though it is a typical large-strain problem. This study develops a two-dimensional plane strain model based on Gibson’s large-strain theory, considering horizontal and vertical flows, nonlinear hydraulic conductivity, and compressibility during the consolidation process. The alternative direction implicit (ADI) difference method is used to solve the governing equation. The proposed model is verified by the data from an analytical one-dimensional (1D) large-strain model and from field measurements. Compared with the improved small-strain models, the proposed model produces a slower consolidation of sludge. Furthermore, the analyses incorporating geometrical and mechanical nonlinearities show that, in comparison with the external load and the horizontal permeability, the spacing of the PHDs (horizontal and vertical) and the vertical permeability are more crucial factors significantly impacting consolidation efficiency. Specifically, smaller PHD spacing and greater vertical permeability lead to a more efficient consolidation.

Efficient removal of electroneutral carbonyls by combined vacuum–UV oxidation and anion-exchange resin adsorption: mechanism, model simulation, and optimization

Electroneutral carbonyls (ENCs) with low molecular weights (e.g., aldehydes and ketones) are recalcitrant to single water treatment process to achieve ultralow concentration. Residual ENCs are present in reverse osmosis permeate and pose risks to human health during potable use or industrial application in manufacturing processes. Herein, a combined vacuum–UV (VUV) oxidation and anion-exchange resin (AER) adsorption method was developed to treat the ENCs and reduce total organic carbon (TOC) to an ultralow concentration (< 5 μg/L) with high efficiency and at low cost. VUV-AER was 2.1–2.4 times more efficient than VUV alone for the removal of TOC. VUV oxidized the ENCs to electronegative carboxylic acids, which were adsorbed by the AER through electrostatic interactions and hydrogen bonding. When the VUV fluence was lower than 643 mJ cm−2, the AER could not achieve ultralow TOC removal of ENCs. The treat capacity of 1500–2900 valid bed volume (BVs) was achieved after increasing the VUV fluence to 1929 mJ cm−2. The AER could more efficiently adsorb carboxylic acids that contained more carboxylic groups or shorter carbon chain. Acetate was identified as the primary breakthrough product at relatively low VUV fluence, and oxalate was the main byproduct at relatively high VUV fluence. A mathematical model to predict TOC breakthrough was developed considering the VUV–oxidation kinetics and the AER breakthrough curve. The model was used to optimize the method to maximize TOC removal and minimize energy consumption. These results imply that VUV-AER is technically feasible and economically applicable to eliminate recalcitrant ENCs to ultralow concentration for the production of water requires high quality (e.g., potable water or electronic-grade ultrapure water).

Tungsten separation behavior on preparation of high-purity cerium by combined vacuum gravity sedimentation–directional solidification

In light of the difficult removal of harmful impurity tungsten (W) in Ce metal, in this paper a combined vacuum gravity sedimentation‒directional solidification method was innovatively designed and the W separation behavior was investigated. By reducing the electron beam power instantly and gradually at reduction rates of 1, 3 and 5 kW/min, it is found that W is enriched at the bottom of ingots as the melt solidifies. The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases, attributed to the k0(W) ＞ 1 and ρ(W) ＞ ρ(Ce). Overall, the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot, and the purity of Ce increases from 99.932 wt% to 99.995 wt% by this combined method. Additionally, this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.

A review on photovoltaic combined vacuum glazing: Recent advancement and prospects

As a building envelope, glazing materials play a vital role in designing an energy-efficient building. Recently, PV combined vacuum glazing has become a popular research topic and attracted researchers to resolve the drawbacks of commonly used glazing products. In the last decade, researchers have conducted several studies combining PV glazing with vacuum glazing to develop an energy-efficient glazing product. In this review, we discussed the different constructions of PV combined vacuum glazing, recent advancements of this product, the influence of a few key design factors on thermal performance, as well as its prospects in designing an energy-efficient building.

Modified method for predicting lateral displacement of PVD-improved ground under combined vacuum and surcharge loading

A modified method is proposed to predict the lateral displacement (δ) of prefabricated vertical drains (PVDs) improved ground under combined vacuum and surcharge loads, which is derived based on a few modified triaxial tests and a series of finite element analyses of PVD unit cells. It is observed that reducing the surcharge load (ps) and loading rate (LR) and increasing the vacuum pressure (pv), pre-vacuum consolidation period (tv), and initial undrained shear strength (su0) could be effective in controlling the outward δ. Variations of the effective stress ratio (Ke) that controlling the δ with ps, pv, LR, tv, and su0 are then presented. A synthetic relationship between the normalized horizontal strain (εh) by a reference one-dimensional vertical strain (εv1) and the normalized Ke by the at-rest earth pressure coefficient (K0) is proposed for cases with and without tv. Further, a modified index parameter (β1) is introduced for quantitatively considering the effect of ps, pv, LR, tv, su0, and consolidation properties of the soil, a relationship between Ke and β1 is then established for evaluating the value of Ke. Combinations of the εh/εv1–Ke/K0 and Ke–β1 relationships enable modified predictions of the δ from basic preloading conditions and soil parameters.

Effect of ultrasound assisted vacuum osmotic dehydration on the mass transfer kinetics and qualities of orange slices

This research aimed to explore the effects of combined ultrasound and vacuum assisted osmotic dehydration on the mass transfer kinetics and qualities of fresh-cut orange slices. The experiments were carried out under four different conditions, i.e., osmotic dehydration (OD), vacuum osmotic dehydration (VOD), ultrasound assisted osmotic dehydration (UOD) and ultrasound assisted vacuum osmotic dehydration (UVOD). Aqueous solutions of the four osmotic agents – sucrose, xylitol, sorbitol, and maltitol at a concentration of 50°Brix were used in each condition. The results showed that UVOD had the highest (p < 0.05) water loss (WL) and solid gain (SG). The high regression coefficient (R2 > 0.99) and low χ2 and RMSE values revealed the applicability of Peleg model for fitting mass transfer of orange slice during osmotic dehydration. Low-field nuclear magnetic resonance (LF-NMR) spectra revealed the water distribution in orange cells. Electronic nose data indicated that osmotic dehydration did not significantly (p > 0.05) change the flavor of orange slices. Fourier transform infrared (FTIR) spectra indicated osmotic dehydration could preserve internal chemical composition of orange slice. Scanning electron microscope (SEM) images illustrated the mechanisms of VOD, UOD and UVOD. The results of mass transfer kinetics and qualities showed that sugar alcohols were good alternative osmotic agents to sucrose. Although UVOD led to the largest loss of vitamin C due to its highest WL, UVOD exhibited better hardness and could combine the advantages of VOD and UOD in water activity and color, respectively.

Лечение огнестрельных ран конечностей с использованием физических и ортобиологических методов

Currently, despite the wide possibilities in the treatment of wounds, patients with gunshot wounds of the extremities present a complex surgical task. The study included 60 patients with gunshot wounds of the extremities who underwent inpatient examination and treatment at the Center of Traumatology and Orthopedics of the Main Military Clinical Hospital named after academician N.N. Burdenko of Ministry of Defence of the Russian Federation. The patients were divided into groups. In group I, physical methods of treatment were used, such as vacuum therapy (35 people), of which 19 patients underwent combined vacuum therapy with laser irradiation of the wound (group IA), 16 patients underwent vacuum therapy in combination with high-intensity pulsed optical irradiation (group IB). Group II included patients in whom orthobiological techniques were used in the complex treatment of wounds (25 patients), including platelet-enriched fibrin glue — in 13 patients (group IIA) and a composition of heterogeneous implantable gel SpheroGEL® in the LONG version (hereinafter SpheroGEL®) — in 12 patients (group IIB). Results. Comparison of the results of the treatment revealed a significant improvement in the regenerative process according to the histological method in group IA: the maturation of mature granulation tissue was observed on the 9th day after the application of local treatment methods. Positive adhesive and wound healing effects were observed in group IIA. According to the "AnalyRan" program, there was a significant reduction in the time of wound healing in all groups under study. According to the results of the study, all techniques showed positive dynamics of wound healing and reduction of the inflammatory process.

Precise quantum measurement of vacuum with cold atoms.

We describe the cold-atom vacuum standards (CAVS) under development at the National Institute of Standards and Technology (NIST). The CAVS measures pressure in the ultra-high and extreme-high vacuum regimes by measuring the loss rate of sub-millikelvin sensor atoms from a magnetic trap. Ab initio quantum scattering calculations of cross sections and rate coefficients relate the density of background gas molecules or atoms to the loss rate of ultra-cold sensor atoms. The resulting measurement of pressure through the ideal gas law is traceable to the second and the kelvin, making it a primary realization of the pascal. At NIST, two versions of the CAVS have been constructed: a laboratory standard used to achieve the lowest possible uncertainties and pressures, and a portable version that is a potential replacement for the Bayard-Alpert ionization gauge. Both types of CAVSs are connected to a combined extreme-high vacuum flowmeter and dynamic expansion system to enable sensing of a known pressure of gas. In the near future, we anticipate being able to compare the laboratory scale CAVS, the portable CAVS, and the flowmeter/dynamic expansion system to validate the operation of the CAVS as both a standard and vacuum gauge.