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We present a microfluidic technique that shrinks lipidstabilized microbubbles from O(100) to O(1) µm in diameter–the size that is desirable in applications as ultrasound contrast agents. We achieve microbubble shrinkage by utilizing vacuum channels that are adjacent to the microfluidic flow channels to extract air from the microbubbles. We tune a single parameter, the vacuum pressure, to accurately control the final microbubble size. Finally, we demonstrate that the resulting O(1) µm diameter microbubbles have similar stability to microfluidics generated microbubbles that are not exposed to vacuum shrinkage. We anticipate that, with additional scale-up, this simple approach to shrink microbubbles generated microfluidically will be desirable in ultrasound imaging and therapeutics applications.

Coal-based H2 generation has abruptly increased in recent years. The PSA-VPSA-SC process is the matured and standard framework for H2 purification and CO2 capture in many existing plants, including normal and vacuum pressure swing adsorption units in series (PSA-VPSA), and shallow condensation unit (SC). However, this standard process is frequently subjected to low H2 recovery ratio and high purification cost. In this work, H2-selective and CO2-selective membrane units, i.e., HM and CO2M, are attempted to support the standard process and ameliorate constraints. In the beginning, HM unit is arranged after VPSA to enhance H2 recovery from the decarbonized stream, i.e., the PSA-VPSA-SC/HM process. As a result, H2 recovery ratio can be enhanced significantly from 83% to 98%. In the following, VPSA is replaced with CO2M unit to reduce investment and operation cost, i.e., the PSA-CO2M-SC/HM process. Accordingly, the specific purification cost is diminished from 33.46 to 32.02 USD·(103 m3 H2)−1, saved by 4.3%, meanwhile the construction cost is falling back and just a little higher than that for the standard process. In the end, another CO2M unit is launched before PSA, i.e., the CO2M-PSA-CO2M-SC/HM process, which could unbundle CO2 enrichment partially from H2 purification, and then save more investment and operation cost. In comparison with the standard process, this ultimate retrofitted process can be superior in all the three crucial indices, i.e., recovery ratio, investment, and specific purification cost. On the whole, coal-based H2 generation can be ameliorated significantly through high efficient H2-selective and CO2-selective membrane units.

The research purpose was to develop the basics for silage preparation by vacuuming with the use of flexible polymer containers and estimating silage quality. The analysis of modern systems used for silage preparation and storage showed that the main disadvantages include the high storage and preparation costs, and losses of silage weight and nutrients by 3–25% after opening of storage facilities. To eliminate these disadvantages, the basics for preparing the silage by vacuuming in flexible polymer containers that can be transported and stored with optimum volume have been studied and developed. The study pursuits its goals by observing the changes in density and degree of silage compaction caused by the vacuum pressure and deadweight. A comparative estimation of silage quality indices was conducted by means of chemical analysis of silage specimens. The results show graphical dependencies of changes in silage volume and density at vacuum pressure up to 60 kPa. Moreover, a comparative assessment of quality indices of silage specimens prepared by vacuuming in soft containers, and traditional method using trenches was conducted. The reliability of results for silage storing quality in a vacuum container was achieved by fivefold test repetition within 2 years. Comparison of silage quality indices obtained using vacuum technology and traditional method showed improvement in favour of the proposed method: dry matter by 2.05%; protein by a factor of 1.47; nitrogenous substances by 1.37; starch by 1.56; calcium by 1.83; phosphorus by 2; digestible protein by 1.24; feed unit by 1.31; exchange energy by 1.16, which was achieved thanks to the elimination of succus leakage.

This paper aims to establish an analytical model on vacuum consolidation of dredged slurry treated by PVD with special considerations on the clogging effects. A series of laboratory tests have been conducted to characterize the temporal/spatial variations of the clogging zone and the vacuum pressure in soil. Based on the nonlinear relationship between the compressibility, the permeability and the void ratio (e-p and e-k curves), an analytical model incorporating the clogging zone was proposed and solved considering the nonlinear attenuation of the vacuum pressure. The solution was verified and validated by comparing with published data and field test results, respectively. Parametric studies reveal that the clogging significantly slows down the consolidation rate, and thus reduces the final degree of consolidation of the dredged slurry.

Prefabricated horizontal drain (PHD) assisted by vacuum pressure has been used in practice to accelerate the consolidation process of dredged soft mud. However, very few studies have investigated t...

Herbal industries are facing challenges while processing the herbal leaves. Herbal leaves are processed using various methods such as convection drying, chemical drying, vacuum drying, microwave drying, etc. The common issues encountered during the time of drying the herbal leaves are lost in phytochemicals, nutrients and colour. Heat pump drying is an important method by which the drying can be made without influencing of environmental condition and by controlling the drying properties without loss in phytochemicals, nutrients and colour. In this proposed work the experimental device, namely closed-loop heat pump dryer is designed and developed for conducting experiments. For this study, Moringa leaves were considered as herbal leaves. The vacuum is introduced in the heat pump dryer and the Moisture Removal Rate (MRR) is calculated under this condition. The experiments were conducted with vacuum pressures of 0.9 & 0.8 bar and the air velocities of 1.1 m/s & 1.4 m/s respectively. In this study, the experiments were conducted under the above-said conditions for several periods with temperature transients. Based on the experimental study it is observed that the moisture removal rate is increased significantly under low pressure with high temperature and velocity.

Vacuum preloading is one of the popular methods improving the engineering properties of slurry ground with high water content. Commonly, the efficiency of vacuum preloading gradually decreased due to the clogging of prefabricated vertical drains (PVDs) and the low-vacuum transmission rate inside slurry. Thus, the calcium-based flocculants were used to accelerate the dewater capacity and enhance the soil strength during vacuum preloading. This paper performed a series of model tests to investigate the effect of calcium-based flocculants on the efficiency of vacuum preloading. It is found that the vacuum transmission rate was significantly improved by flocculants in comparison with raw slurry. Accordingly, the after-treatment undrained shear strength increased with the vacuum pressure, while the after-treatment water showed a decrease trend. This suggests that the increase of vacuum transmission rate inside the slurry due to the calcium-based flocculants was the main reason for the improvement of efficiency of vacuum preloading. In addition, there existed an optimal flocculants amount, where the vacuum pressure increased with flocculants’ amount up to this threshold value, followed by a decrease in vacuum pressure. This means that, at lower flocculants amount, the increase in soil flocs due to flocculation effect tended to refine the net-frame structure and water flow path, leading to an increase in the efficiency of vacuum preloading. When exceeding the optimal amount, overdosage of flocculants resulted in the clogging of PVDs due to large cemented soil particles, reducing the vacuum transmission rate inside the slurry. Hence, the after-treatment soil strength decreased with flocculants’ amount when it is higher than the optimal value.

In this study, a new design of photovoltaic thermal (PV/T) collector is proposed. This design uses a vacuum layer above the silicon wafer and not exists in the traditional PV/T collector. This layer is used to decrease the heat loss from the top surface of the PV/T collector. The analysis is conducted using a 3D thermal modeling. The new collector design with the vacuum layer achieved a 26.6% increase in the thermal power while keeping the electrical the same at Reynolds number of 50 and solar radiation of 1000 W/m2. In addition, the degradation of the vacuum pressure slightly influence the thermal performance while increasing the vacuum pressure from 0.01 Pa to 10 Pa. While further increase in the vacuum pressure from 10 Pa to 1.013×105 Pa substantially decreases the gained thermal power with insignificant increase in the electrical power.

This paper presents a case study on the improvement of thick marine deposits. A new method that combines vacuum pressure and surcharge load with no need for a sand cushion is proposed and evaluated...

International audience; Gas separation by adsorption processes such as pressure swing adsorption (PSA) presents an attractive alternative for upgrading biogas to biomethane. A new vacuum pressure swing adsorption (VPSA) cycle is proposed for a unit designed to purify pre-cleaned biogas (40% CO 2 and 60% CH 4) in industrial conditions (feed flow rate more than 500Nm 3 /h and large-volume equipment). The process simulations performed to optimize the VPSA unit consider the kinetic separation of the feed components by using an appropriate carbon molecular sieve (CMS) adsorbent having a high kinetic separation selectivity for CO 2 with respect to CH 4. The designed VPSA unit is composed of five columns that perform three equalization steps. Minimizing methane losses during the regeneration steps necessitates injecting part of the off-gas rich in CO 2 at the bottom of the column during the production step to push the CH 4 forward. The produced biomethane meets the specification (97% CH 4) of grid injection purity. The developed cycle allows a CH 4 recovery of 92% to be obtained with a specific energy consumption of 0.35kWh/Nm 3 , thus meeting the initial requirements for industrial exploitation of VPSA technology for biomethane purification from biogas sources.

Palladium (Pd) membranes for industrial applications have gained much interest as of late. The purification of hydrogen through Pd membranes has therefore been proposed as a viable solution to traditional separation methods. Hydrogen permeation can be enhanced when coupled with a vacuum at the permeate side. In this study, the effect of different degrees of vacuum pressures on H2 permeation through a high-permselectivity Pd membrane in different binary gas mixtures was investigated and compared to those without vacuum. Three feed gases containing H2 concentrations of 90, 70, and 50 vol% were used. Hydrogen permeation rates were studied at 320, 350, and 380 °C under vacuum pressures ranging between 0 and −60 kPa. An increase in vacuum degree intensified H2 permeation. However, best performance improvements were observed at lower H2 concentrations, lower temperatures, and also at lower vacuum pressures for all gas mixtures. The highest performance improvement of 88.83% was with the gas mixture containing 50% H2 at 320 °C with a −15 kPa vacuum pressure. Hence, from an efficiency point of view, lower temperatures and vacuum pressures were preferred for all the gas mixtures. Activation Energies were also relatively lower for conditions with a vacuum for all gas mixtures.

Thermal management of Al composites is a crucial issue to keep the promising performance and excellent reliability of the devices. We revealed a novel method to enhance the surface property of graphite flakes (GF) with Cu and Ni coatings by chemical plating way. Taking advantage of Cu and Ni co-doped GF and silicon powders, the GF@Cu@Ni/Si/Al composites were fabricated by vacuum pressure infiltration method. The GF@Cu-30@Ni-10 composites revealed about 2 times larger TC (474.4 W/m·K) and lower CTE 6.22 ppm/K than neat Al. Our strategy for highly TC offers not only the advanced process for dispersing reinforcements but also an extremely simple way for the anisotropic composites with high TC and low CTE.

Horizontal spacing of horizontal extraction gas wells can be designed to achieve a 90% pumping rate of the total generated landfill gas (LFG) from given waste properties (viz: gas permeability, landfill gas generation and non-homogeneity with depth), cover characteristics and vacuum pressure. However, cover characteristics and vacuum pressure are also important design parameters and different combinations of them result in different distributions of gas pressure in the waste, some of which would induce problematic air intrusion while others might pose threat to cover stability. This paper uses the maximum gas pressure directly below cover to distinguish these combinations, and provides the first study of the effects of the above parameters on potential outcomes. The ability of the overlying cover to resist LFG emission from the landfilled waste is suggested not to exceed a critical value, otherwise the maximum gas pressure below it would become at least 1 kPa larger than atmospheric pressure. A design formula for this critical value is proposed with respect to typical values of waste properties, vacuum pressure and the buried depth of horizontal wells in wide ranges. Together with consideration of recovery efficiency, the proposed method can be used to design a horizontal extraction gas collection system and a cover system in better working condition, and to evaluate the maximum gas pressure below cover. These applications are illustrated by a worked example.

A process to upgrade a biogas product to biomethane has been investigated. Recycling of an absorbent is important for low-cost upgrading of biogas by chemical absorption. This study investigated the alkaline recovery of absorbent solution by thermal decomposition at various temperatures (75, 85 and 95 °C) and various vacuum levels (0.2, 0.4 and 0.6 bar). During heating, CO2 and H2S were released from the absorbent solution, which increased the pH. The highest pH 10.58 was reached for NaHCO3 solution from initial pH 8.86 when treated at 95 °C and 0.6 bar vacuum level (gauge pressure). The mass fraction of CO32− in the solution increased from 0.06 to 0.78. Experiments on H2S removal from NaHS solution gave the highest pH 10.38 at 95 °C and 0.6 bar vacuum pressure. Moreover, the performance of the recovered alkaline solution was tested in biogas absorption. The results show that CO2 and H2S removal efficiencies of alkaline solution before and after recovery were similar, at 80 and 99 % respectively. This study demonstrated that thermal decomposition has high potential for recovering the alkaline used absorbent, for recirculation back into the absorption process.

Conventional landslide drainage methods always seem to lack a long-term and efficient drainage capacity. Thus, it is necessary to develop a new drainage method that does not have these disadvantage...

The performance of vertical pumping wells in municipal solid waste (MSW) landfills can be effectively enhanced if vacuum pressure is applied to the well. In this study, a dual-porosity model for coupled leachate and gas flow to vertical wells in MSW landfills has been established. The proposed model divides waste into fracture and matrix domains; the leachate and gas in these two domains flow horizontally and vertically into a vertical well together, and mass exchange occurs between them. The hydraulic conductivity of the fracture domain is much higher than that of the matrix domain. The model is solved using the finite-difference method to obtain numerical solutions of the leachate pumping rate Qw and leachate level drawdown S. Numerical simulations indicate that Qw and S decrease with the increasing hydraulic conductivity ratio of the fracture and matrix domains, kirf/kirm. As the proportion of the fracture domain in the total domain wf increases, additional large pores are available for leachate flow, and Qw and S gradually increase. Qw and S estimated by the single-porosity model are 1·5–3·0 times as large as those obtained using the dual-porosity model. Qw and S increase with the increasing vacuum pressure applied at the pumping well. A field vacuum well pumping test was carried out at Tianziling landfill to verify the proposed model. When the vacuum pressure at the well increased from 0 kPa to −30 kPa, Qw increased from 33 m3/day to 45 m3/day at t = 36 h and S increased from 2·7 m to 5·6 m at a radial distance from the pumping well r = 10 m. The dual-porosity model performed better than the single-porosity model when simulating the pumping test.

In this paper, we assess the performance of vacuum pressure swing adsorption (VPSA) for co-purification of H2 and CO2 through modelling and process optimization. VPSA allows for the integration of ...

In this study, a novel osmotic membrane was developed by polyamide (PA) coating on the tubular electrospun nanofiber (TuEN) support membrane. Water and reverse salt flux properties of the obtained membrane were investigated by applying pressure in addition to the osmotic forces. Surface characterization of the membrane was carried out by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analyses and flux performance tests were performed in both cross flow and submerged membrane setups. Applying pressure from the feed to the concentrate side had significant effects on the water and salt fluxes. Higher pressure differences between the feed and concentrate sides resulted in unexpected high water fluxes up to 500 Lm(-2)h(-1) (LMH). Besides, the pressure helps to transfer the salt content of feed water into the concentrate side, differently from the osmotic process preventing the salinity build-up at the feed side. PA coated TuEN membrane operated under pressure will exhibit a favorable solution in water/wastewater treatment applications, especially for membrane bioreactors (MBR) in terms of preventing salt accumulation in the bioreactor, decreasing the membrane fouling, increasing the volume of product water, and enabling the concentrate management.

A series of modified triaxial tests was conducted to investigate the deformation characteristics of mini-prefabricated vertical drain (PVD) unit cells. The factors considered are the (1) magnitudes of surcharge load (ps) and vacuum pressure (pvac); (2) pre-vacuum consolidation period (tva) before applying surcharge load; (3) surcharge loading rate (SLR); and (4) initial effective stress state in the specimens. Based on the test results, relationships between the coefficient of earth pressure (Kes) at the end of surcharge load application and the normalized horizontal and vertical specimen strains are established. Further, a method is proposed for estimating the value of Kes, and therefore the horizontal and vertical strains of the PVD improved soil layer subjected to combined vacuum pressure and surcharge load using loading conditions and basic soil properties. Finally, the proposed method was applied to a case history reported in the literature and good agreement between the field-measured and calculated lateral displacement and settlement was obtained, which suggesting that the proposed method can be a useful tool for designing preloading projects involving combined vacuum and surcharge loads.

Composite scaffolds are made by various methods, such as copolymerization, freeze gelation, and thermally induced phase separation, which can compound materials with different properties using solvents and heat. However, it is difficult to compound solvents and heat-sensitive materials such as natural polymers. In this study, we investigated a vacuum pressure impregnation (VPI) method for creating a composite of natural polymers. A collagen solution could not be introduced into a poly (l-lactide) (PLA) porous material using an immersing treatment, but it is possible using the VPI method. The resulting PLA-collagen composite scaffold had greater water adsorption and degradation than a PLA scaffold. These results indicate that VPI may be a promising method for creating composites of natural materials. Impact Statement This is the development of a method for introducing cells into a completed porous material in a short time. This technology is expected to be applied to tissue regeneration and 3D culture.

The deformation characteristics of soil among prefabricated vertical drains (PVDs) subjected to vacuum pressure are investigated using a model test conducted on dredged slurry. Red iron particles are used to indirectly indicate the lateral displacement of soil under vacuum preloading. Test results showed that, in addition to the settlement of soil between two PVDs, there was also lateral displacement that varied with consolidation time and lateral distance from the PVD because of lateral vacuum suction. The lateral displacement arose successively with the increasing lateral distance. And it increased from zero on the PVD surface and dropped back to zero again at the midpoint between the two PVDs. There should have been a maximum value of the lateral displacement at a point near the PVD. The combined vertical and lateral displacement formed a soil pile around the PVD and showed a ‘V’ shaped soil surface.

Vacuum consolidation of soils is a technology that, to date, has not been implemented in the Valley of Mexico, where clays are highly compressible and have very low shear resistance and low permeability. This paper describes the experience of a test embankment, in which the drain-to-drain vacuum preloading was assessed. The evaluation includes the description of the subsoil conditions, characteristics of the embankment, construction process and instrumentation that was installed. The test lasted approximately one year with a vacuum applied for six months. The monitoring results showed that the vacuum distributed along the vertical drains and on the surface soil layers accelerated the consolidation, reduced the lateral displacements toward the outside of the platform and increased the effective stress of the soil to a depth similar to the length of the drains. However, there were vacuum pressure losses of approximately 30% between the pumps and end of the horizontal flexible pipes that distribute the vacuum. These losses of vacuum pressure affected the soil consolidation process.

Clogging will inevitably occur while using vacuum preloading method to process super-soft soils with high water content. How to quantitatively evaluate the effect of clogging on the consolidation behavior is a key issue to be solved. Based on NALSC (negative axisymmetric large-strain consolidation) model, considering the “internal clogging” and the “external clogging”, a calculation method by using parameter “clogging rate” to reflect clogging problem is proposed for single-well consolidation theory. Effects of clogging rate and clogging occurred time on Us (degree of consolidation defined by strain) and Up (degree of consolidation defined by stress) are investigated. Differences of the effect of clogging on consolidation degree are determined between large-strain and small-strain consolidation theory. The results show that, the larger the clogging rate, the smaller the degree of consolidation of the soil at the same consolidation time. Effect of clogging on Up is greater than Us. The earlier the clogging occurs, the smaller the degree of consolidation at the same clogging rate. Influences on the degree of consolidation for large-strain and small-strain theory are the same. Consolidation rate of soil is determined to a certain extent by the “generalized clogging parameter μ”. The “external clogging” has a greater influence on the degree of consolidation than the “internal clogging” at the same clogging rate.

In the present study, 3D needle-punched Cf/SiC–Al composites were prepared by precursor infiltration and pyrolysis (PIP) and vacuum pressure infiltration processes. The microstructure and mechanical properties of the as-prepared 3D needle-punched Cf/SiC–Al composites were investigated in comparison to the porous 3D needle-punched Cf/SiC composites and the dense 3D needle-punched Cf/SiC composites with the same carbon fiber fabric. The results showed that the open porosity of 3D needle-punched Cf/SiC–Al composites was 4.63%, while the open porosity of the porous 3D needle-punched Cf/SiC composites and the dense 3D needle-punched Cf/SiC composites was 27.23% and 11.68%, respectively. Furthermore, the compressive strength of 3D needle-punched Cf/SiC–Al composites was significantly improved compared to the porous 3D needle-punched Cf/SiC composites, increasing from 168 ± 17 MPa to 445 ± 15 MPa, which was approached that of the dense 3D needle-punched Cf/SiC composites (451 ± 32 MPa). The microstructural investigations revealed that most of the pores were filled with Al alloy, improving the bearing capacity of the matrix of 3D needle-punched Cf/SiC composites.

The properties of a composite are depending on the manufacturing process, fiber and its configuration, epoxy used etc. The present research deals with the tensile and wear behaviour of the composites manufactured using Hand Layup (HL) and Vacuum Infusion Process (VIP) with structural and non-structural epoxy combination. 4-layerd (all the layers are oriented in the longitudinal direction) unidirectional CFRP was manufactured using VIP and those results were compared with the HL made samples. The addition of structural epoxy in the resin mixer have shown a significant effect on its fiber volume fraction, tensile and erosion properties. The effect of vacuum pressure in mould cavity on the tensile strength of the CFRP composite was also studied. The morphologies of the CFRP composites made with VIP and HL were studied with the help of the scanning electron microscopy (SEM). The CFRP composites manufactured through VIP have shown a greater tensile strength but it was poor in wear resistance. The addition of structural adhesive to the resin system enhanced the wear resistance. Hence it made the VIP a recommended process for composite manufacturing where both tensile and wear properties are required.

Jabon (Anthocephalus cadamba Miq.) is a fast-growing species that exhibits a lower natural resistance than that exhibited by the timber sourced from natural forests. Jabon’s resistance to termite attack can be improved by impregnating its wood structure with poisonous organic materials. This study examined jabon’s resistance to termite attack when impregnated with wood vinegar and an animal adhesive. The wood specimens were impregnated using sengon wood vinegar and an animal adhesive (8% and 10%, respectively) using a vacuum pressure machine. The specimens were tested for their resistance to subterranean and dry-wood termites according to Indonesian National Standard (SNI 7207-2014). The results denoted that jabon impregnated with wood vinegar and an animal adhesive concentration of at least 8% with the addition of 4% borate was effective to resist termite attacks. The impregnated jabon exhibited a lower weight loss and higher termite mortality when compared with those exhibited by the control specimens. Thus, the resistance class improved from class IV to class I.

Based on the principle of Chiu et al., this work proposes a phase-sensitive total-internal-reflection (TIR) sensing system for measuring vacuum pressure. In the system, linearly polarized light propagates through a specially-designed phase-sensitive TIR apparatus composed of a wave-plate type phase shifter, an isosceles right-angle prism combined with a vacuum cavity, and an analyzer. Under the suitable axis azimuth of the wave plates and the analyzer, it can raise the phase difference of the s- and p- polarization states of the totally-reflected light beam from the TIR apparatus. The raised phase difference is related to the vacuum pressure; therefore the pressure is easily and accurately determinable with measuring the phase difference variation using the heterodyne phase-detection technique. The experimental results demonstrated the feasibility of this method. Measurement resolution and sensitivity levels superior to 0.4 torr and 0.02°/torr were respectively attainable in measurement region of 10 torr to 760 torr.

Stabilising soft marine clay and estuarine soils via vacuum preloading has become very popular in Australasia over the past decades because it is a cost-effective and time-efficient approach. In recent times, new land on areas outside but adjacent to existing port amenities, the Fisherman Islands at the Port of Brisbane (POB), was reclaimed to cater for an increase in trade activities. A vacuum preloading method combined with surcharge to stabilise the deep layers of soil was used to enhance the application of prefabricated vertical drains (PVDs). This paper describes the performance of this combined surcharge fill and vacuum system under the embankment and also compares it with a surcharge loading system to demonstrate the benefits of vacuum pressure over conventional fill. The performance of this embankment is also presented in terms of field monitoring data, and the relative performance of the vacuum together with non-vacuum systems is evaluated. An analytical solution to radial consolidation with time-dependent surcharge loading and vacuum pressure is also presented in order to predict the settlement and associated excess pore water pressure (EPWP) of deposits of thick soft clay. Keywords: Soft clay, Prefabricated vertical drains (PVDs), Vacuum consolidation, Membrane-less system, Membrane system

A six-step, two-bed dual-reflux pressure swing adsorption process for air separation using LiLSX zeolite was first developed and studied systematically. Then two original integrated vacuum pressure...

The results from three laboratory model tests performed under various vacuum and surcharge loads with PVDs are reported. Different SLRs were adopted to investigate the effect on the consolidation of dredged soil. To measure the lateral displacement, a refitted inclinometer was developed and tested. In the tests, the settlement, lateral displacement, and vane shear strength were measured, and the degree of consolidation (DOC), horizontal coefficient of consolidation (Ch), and bearing capacity were calculated. The results indicate that larger SLR values promote consolidation. The largest vane shear strength, settlement, and Ch values were all obtained under the highest SLR, and the bearing capacity under this SLR was more than double that under the lowest SLR. The DOC was found to increase with the growth of the SLR. However, considering the vacuum pressure was higher in Case-III, the influence of SLR on reinforcement effect may not be so significant.

In this study, an efficient PID control system has been designed for a vacuum pressure swing adsorption (VPSA) process which used silica gel to capture CO2 from dry flue gas. Changes of CO2 composition in feed gas are set as disturbances and vary from 12.0 to 15.0% to make simulation work more closely to reality. Meanwhile, adsorption step time duration was set to change consistently according to the feedback of CO2 purity in product. PID control strategy built in software gPROMS is employed in this paper. The competence of the control system is firstly analyzed by a transient impulse of CO2 content in feed gas (15.0% dropped to 12.0%). Then random pulse is added to test the ability of the control system to reject the unknown disturbances and track the set point. Detailed changes in bed under open and closed-loop are listed and made comparisons. Results demonstrate that the model shows an enhanced performance in the presence of random disturbances under closed-loop control compared with the open-loop operation. And this proves that closed-loop feedback PID control can be used to improve the CO2 capture of VPSA process operations.

Vacuum preloading is an effective ground improvement technique for treating soft soils. Most previous research focused on the soil’s consolidation within the treatment depth of the prefabricated vertical drains (PVDs). Researches on the soil consolidation and the vacuum pressure distribution below the PVDs are very limited. Another debatable issue is the distribution of vacuum pressure within the treatment depth. Some researchers suggested that vacuum pressure decreases rapidly with depth, so there exists an effective treatment depth. Other researchers suggested that vacuum pressure does not change significantly with depth. Based on the massive monitoring data from the Shanghai Theme Park ground improvement project, it was found that all of the final surface settlements were greater than the target settlements with an average increase of 13%, and the settlement under PVDs contributed 8–18% to the final settlement. Therefore, for a project with thick soft soils under PVDs, the substratum settlement cannot be ignored. Meanwhile, the vacuum pressure below the PVDs was significant to an influence depth of up to 10 m, and the back-calculated coefficient of consolidation was 4 times higher than that determined from laboratory tests. In addition, the measured vacuum pressures were almost constant along the depth up to 20.5 m. This result indicates that the decrease of vacuum pressure with depth may not be an issue if a good sealing system is used.

A study was performed for hydrogen purification of multicomponent mixture (N2/CO/CO2/CH4/H2=0.007/0.012/0.17/ 0.021/0.79) by one-column VPSA with AC5-KS. The performance of the one-column VPSA process can be predicted by a heat and mass transfer model with porous media adsorption. The simulation results agreed well with experimental data. The model was employed to assess the effects of P/F ratio and adsorption time in VPSA unit. The result showed, an increase in P/F ratio and a decrease in feeding time led to an increase in purity of hydrogen and a decrease in recovery. The Sequential Quadratic Programming method was applied to optimize the cycle. The result showed when pressure was set at 5 bar, feed rate was set at 5×10-5 m3/s and P/F ratio was set at 0.3, hydrogen was obtained with a purity of 99.17% and recovery of 58.94% after purification in N2/CO/CO2/CH4/H2 mixture.

The system of vacuum pressure combined with vertical drains to accelerate soil consolidation is one of the most effective ground improvement methods. The consolidation theories of soft soil improved by vertical drains including void ratio–dependent compressibility and permeability have been widely applied in practice to predict the consolidation behavior. In this paper, analytical solutions of the consolidation of vertical drains are derived incorporating the loss and propagating stage of vacuum pressure. In addition, special solutions are obtained for the cases of instantaneous surcharge loading and staged surcharge loading, based on the general solution. The solution is verified by ignoring the propagating stage of vacuum pressure formation and comparing it with an existing solution. The effects of vacuum pressure loss and propagating stage combined with other parameters are investigated through the ratio between excess pore water pressure and surcharge loading.\ud \ud

The 8YSZ-C/MoS2 composite coating was fabricated to improve its tribological properties by introducing a novel and simple method. The C/MoS2 composite lubricants were synthesized in defects of 8YSZ coating via hydrothermal reaction connect with vacuum pressure impregnation. Results indicate that the porous C/MoS2 flower-like microsphere powders consist of interconnected ultrathin nanoflakes. The C and MoS2 are uniformly attached to the defects of 8YSZ coating and unable to assemble into microspheres due to the limitation of the size of pores and cracks. The tribological behaviors of the composite coating are significantly improved, which are devoted to the formation of the lubricating film. This preparation technique provides a novel approach to establish self-lubricating ceramic composite coatings with temperature-sensitive solid lubricants.

In recent years, reconstituted small samples have often been used to assess the performance of radial consolidation due to prefabricated vertical drains (PVDs), but the permeability and compressibility of samples of undisturbed soil often differ from those of the remoulded ones. The problem seems more complex in marine environment due to the presence of random coarse particles including gravels, shells and natural partings. Performing small-scale laboratory experiment with reconstituted samples, especially in marine environment, cannot predict the exact soil behaviour in the field. This paper describes an experimental programme that measures radial consolidation using a conventional Rowe cell and a large-scale consolidometer, where the samples of undisturbed soil obtained from a site along the Pacific Highway (north of Sydney) were compared using measured settlements and excess pore pressures. Moreover, this paper highlights the implications of the smear effect and sample size influence, which are imperative in translating the laboratory testing practices to actual real-life behaviour. The effect of vacuum pressure on the coefficient of radial consolidation of a large-scale undisturbed test specimen is also discussed. The paper demonstrates that the extent of smear zone in the field can be very similar to the large-scale laboratory consolidation test using a scaled-down drain and mandrel, but considerably different from the data obtained for small laboratory specimens. Keywords: Consolidation, Soft soil, Vertical drain, Undisturbed clay

Microwave-assisted synthesis is known to accelerate the transesterification process and address the issues associated with the conventional thermal process, such as the processing time and the energy input requirement. Herein, the effect of microwave irradiation on the transesterification of palm oil methyl ester (PME) with trimethylolpropane (TMP) was evaluated. The reaction system was investigated through five process parameters, which were reaction temperature, catalyst, time, molar ratio of TMP to PME and vacuum pressure. The yield of TMP triester at 66.9 wt.% and undesirable fatty soap at 17.4% were obtained at 130 °C, 10 mbar, sodium methoxide solution at 0.6 wt.%, 10 min reaction time and molar ratio of TMP to PME at 1:4. The transesterification of palm oil-based methyl ester to trimethylolpropane ester was 3.1 folds faster in the presence of microwave irradiation. The total energy requirement was markedly reduced as compared to the conventional heating method. The findings indicate that microwave-assisted transesterification could probably be an answer to the quest for a cheaper biodegradable biolubricant.

Automatic draping of carbon-fiber prepreg plies for the aerospace industry is a promising technique for lowering the manufacturing costs and to this end, a thorough in-process quality control is crucial. In this paper, out-of-plane defects in the layup are investigated. After draping, air pockets are occasionally encountered. The question is, if such apparent defects can be mitigated sufficiently during vacuum debulking. The 3D topology is measured by means of a structured-light 3D scanner and air pockets are segmented. An approximate mass-spring ply model is used to study the behavior of the air pockets during application of vacuum pressure. The model is computationally fast and will indicate online whether the air pocket will be removed or manual intervention is required. Upon comparing the model predictions with experimental data, it is shown that the system is capable of correctly predicting 13 out of 14 air pockets in a test layup., Accepted manuscript

Elevated vacuum (EV) is suggested to improve suspension and limb volume management for lower limb prosthesis users. However, few guidelines have been established to facilitate configuration of EV sockets to ensure their safe and proper function. A benchtop model of an EV socket was created to study how prosthetic liner tensile elasticity, socket fit, and socket vacuum pressure affect liner displacement and subsequent pressure on the residual limb. A domed carbon fiber layup was used to represent an EV socket. Inserts were used to simulate various air gaps between the socket and liner. Various prosthetic liner samples were placed under the carbon fiber layup. Liner displacement and the corresponding pressure change underneath the liner were measured as vacuum was applied between the liner sample and socket wall. Tissue vacuum pressure increased linearly with socket vacuum pressure until the liner contacted the socket wall. Predicted tissue vacuum pressure matched well with experimental results. Findings suggest that the effect of vacuum pressure on the residual limb is primarily determined by air gap distance. The developed model may be used to assess effects of EV on residual limb tissues based on an individual's socket fit, liner characteristics, and applied vacuum. Understanding the physiological effects of EV on the residual limb could help practitioners avoid blister formation and improve EV implementation.

The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat treatment. Impregnation of wood with a 400-ppm silver nanosuspension was carried out under an initial vacuum pressure of 0.07 MPa, followed by a pressure of 0.25 MPa for thirty minutes, before heat treatment. Heat treatment was carried out under hot air at three relatively mild temperatures, 145, 165, and 185 &deg, C. Results showed improvement of some properties in heat-treated wood at 145 &deg, C. This was indicative of the improving impact caused by hornification and irreversible hydrogen bonding in the course of water movements due to heat treatment, significant fluctuations in the intensities of FTIR spectra bands at 1750&ndash, 1500 cm&minus, 1 were corroborating evidence of chemical alterations in hemicellulose polymer. The high mass loss at temperature 185 &deg, C, and the extreme thermal degradation thereof, overcame the improving effects of hornification and formation of irreversible hydrogen bonds, consequently mechanical properties decreased significantly. Interaction of different elements involved made it hard to predict properties in specimens modified at 165 &deg, C. Impregnation of specimens with nanosilver suspension resulted in significant increase of mass loss in specimens heat-treated at 185 &deg, C, and significant fluctuations in properties of specimens heat-treated at 145 &deg, C.

Specific gas permeability of beech wood was determined and compared with values obtained after nanosilver-impregnation and heat-treatment in three mediums of air, water, and water steam at 150 &deg, C for four durations of 1, 2, 3, and 4 hours. Separate sets of specimens for each group were prepared and impregnated with a 400 ppm aqueous nanosilver suspension. The results revealed that the effect of heat treatment in hot-air depended on the duration of treatment. Hydrothermal treatment generally increased gas permeability, this was attributed to the dissolving of extractives in the hot water medium, although lower duration of one hour did not significantly change permeability. Hygrothermal treatment increased gas permeability at all four durations, revealing its effectiveness as a pre-treatment to improve penetration of preservatives and fire-retardants into wood texture in wood preservation industry. High thermal conductivity of silver nanoparticles intensified the effects of heat treatment in all mediums.

In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 ℃, vacuum heating curing at &ndash, 0.05 MPa + 30 min + 80 ℃, and hot-press curing at 0.7 MPa + 5 min + 50 ℃, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.

In this work, date juices were concentrated at low temperature by Vacuum Membrane Distillation (VMD). Tests were conducted at fixed operating conditions (feed flowrate, 28 L/h; feed temperature, 28 °C; vacuum pressure, 4 mbar) on two commercial flat polypropylene membranes, different in pore size and thickness. Date concentrates (70 °Bx) were obtained starting from juices at 18 °Bx, and pure permeates (0 °Bx) were collected. The water vapour trans-membrane flux depended on membrane properties until a concentration of ~50 °Bx was reached; then, the resistance at the feed side controlled the process.

Dredging slurry is treated by a combination of lime treatment and vacuum preloading. However, the mechanical characteristics and consolidation mechanics of lime-treated slurry under vacuum loading is not fully understood, making it difficult to predict slurry settlement. In this study, we develop a laboratory model of lime-treated slurry and subject it to vacuum preloading to investigate the compression and consolidation behaviors. The results demonstrate the reduction of the risk of clogging around the prefabricated vertical drains, the increase in soil permeability, and the improvement of vacuum preloading upon lime treatment. log (1 + e)-log p curves for soils with different percentages of lime content are obtained through a series of modified oedometer tests. Based on these curves, an analytical solution for lime-treated slurry settlement under vacuum preloading was derived and validated through laboratory tests. The solution can be used to predict lime-treated slurry settlement under vacuum pressure effectively.

This paper presents a novel pneumatic artificial muscle (PAM) that is able to generate a high payload and buckling pressure. The proposed actuator exploits open-cell foam, and 0.8 mm thick rigid rings to reinforce structure stiffness, and to implement stable contraction under depressurization. All components are embedded in a sealing elastomeric skin. The actuator can support 6.8 N of external load, which is 34.5 times greater than its own weight (20g). When depressurized, the actuator deforms stably, without buckling. The results of the preliminary experimental analysis show that it is able to contract up to 51.8% upon -80kPa, with a 5.6% hysteresis for pressure vs. contraction ratio. Moreover, a quasi-static model is proposed to estimate the actuator blocking force, of which the measured maximum value is 32.7 N at -80kPa vacuum. The presented actuator shows repeatable and reliable performance, providing a promising soft material solution for pneumatic driven movement.

The application of vacuum pressure to a treated area not only induces vertical settlement and inward lateral displacement but also causes the formation of tension cracks near the ground surface. In general, the strain method is applied to calculate the lateral displacement at the boundary of a treated area; however, the influence scope of lateral displacement has not yet been presented. Based on thein situdata of soft clayey soil foundation treated by vacuum consolidation, lateral displacement was estimated in the influence scope in this study. To calculate the influence scope of lateral displacement induced by vacuum pressure, the ratio of the lateral displacement within the influence scope to the ground surface settlement under the centre of the treated area is defined as the maximum value of the lateral displacement (ELD) within the influence scope. This paper proposes a direct relationship between ELD and the distance from the treated area boundary (Lx), considering the length of the prefabricated vertical drain. In addition, the FEA (finite-element analysis) is used to simulate the process of vacuum preloading to reinforce soft soil foundation. The influence scope simulated is almost close to the calculated valueLx. Accordingly, the safety distance between the boundary of the treated area and the surrounding building can be estimated when the soft soil foundation is consolidated by using a vacuum preloading method.

This paper deals with a solar still for distilled water, using the heat of the sun to evaporate, cool and then collect the water. They are used in areas where drinking water is unavailable, so that...

The present paper aims to introduce a novel and environment-friendly sludge dewatering method based on the osmotic technique, and to examine the efficiency of this method from macro- and micro-points of view. Intact sample, taken from the primary settler of a local wastewater treatment plant in Guangzhou (China), was firstly dewatered by mechanical methods (i.e. vacuum filtration and centrifugation), then by the osmotic technique. Macroscopic experimental results show that: the vacuum filtration and centrifugation can only dewater the sludge from 94.5 to 78.3% and to 78.8%, respectively, whereas, using the osmotic technique, water content of the sludge can be decreased to 44.2% in 12 h and to 35.9% in about two days. The micro-structure, obtained by scanning electron microscope (SEM), shows that: the sludge samples after vacuum filtration and centrifugation have a porous structure and water can be drained either through the cracks that have been developed under the vacuum pressure or by the micro-...

A two-bed, six-step vacuum pressure swing adsorption (VPSA) process using LiLSX zeolite for industrial-scale 80% oxygen production with rapid cycling was investigated by numerical simulation and optimization. keeping the structural parameters of the VPSA devices unchanged and ensuring the purity of oxygen never be lower than 80%, the operating variables were optimized to achieve the target of minimum power consumption and maximum yield, which can maximize the devices’ potential performance for various production requirements. In the case of minimum power consumption, after optimization, the minimum power consumption was reduced from 0.313 to 0.289 kWh Nm−3 O2, meanwhile, the productivity fell from 106.42 to 93.75 Nm3 h−1 ton−1. In the maximum productivity case, a high productivity of O2 was achieved (117.87 Nm3 h−1 ton−1) but the power consumption rose to 0.324 kWh Nm−3 O2. A subsequent detailed analysis was carried out to provide insights into these observations and compare the impact of the decision variables on the process performance.

A vacuum pressure tracking system with high-speed on-off valves is a discontinuous system due to the discrete nature of high-speed on-off valves. Chamber pressure changes in the system are determined by the mass flow rates during the processes of charging and discharging. Here, a sliding mode controller with an asymmetric compensator based on average mass flow rate is designed for accurate vacuum pressure tracking. The controller output signal is converted into the duty cycles of the high-speed on-off valves via a pulse width modulation pulsing scheme. Owing to the extreme asymmetry of the processes, an asymmetric structure comprising one high-speed on-off valve in the charging unit and three high-speed on-off valves in the discharging unit is applied to weaken the impact of asymmetry. In addition, an asymmetric compensator is also designed to modify the pulse width modulation pulsing scheme to further eliminate the asymmetry. Experimental results indicate that the proposed controller achieves better performance in pressure tracking with the asymmetric compensator overcoming process asymmetry and enhancing system robustness.