Low-pressure Compression Research Articles

Improved Electromagnetic Interference Shielding Efficiency of PVDF/rGO/AgNW Composites via Low-Pressure Compression Molding and AgNW-Backfilling Strategy.

Silver nanowires (AgNWs) have excellent electrical conductivity and nano-sized effects and have been widely used as a high-performance electromagnetic shielding material. However, silver nanowires have poor mechanical properties and are prone to fracture during the preparation of composite materials. In this study, PVDF/rGO/AgNW composites with a segregated structure were prepared using low-pressure compression molding and the AgNW-backfilling process. The low-pressure compression of the composite significantly improves its electromagnetic shielding performance because the low-pressure process can maintain the AgNWs' integrity. The backfilled AgNWs played a vital role in increasing the path of electromagnetic wave propagation and the absorption of electromagnetic waves. The backfilled amount of AgNWs was only 1 wt%, which increased the composite material's conductivity by one order of magnitude. The total electromagnetic interference shielding (SET) of the composite materials increased by 23.3% from 24.88 dB to 30.67 dB. The absorption contribution (SEA/SET) increased from 84.2% to 92.8%, significantly improving the electromagnetic interference shielding and the absorption contribution of the AgNWs in the composites. This was attributed to the backfilling of the porous structure by the AgNWs, which promoted multiple reflections and enhanced the absorption contribution.

CELLULOSE NANOCRYSTAL-INCORPORATED CO-PROCESSED EXCIPIENT IN TABLET FORMULATION

The objective of the current work is to develop a new co-processed excipient based on cellulose nanocrystals and investigate its pharmaceutical excipient properties. Cellulose nanocrystals were isolated from the pseudostem of Musa balbisiana, following TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-mediated oxidation, and then co-processed with potato starch by the wet granulation method. Physicochemical properties, including the flow property, consolidation characteristics and rate of consolidation, were investigated, and a Kawakita plot was also generated. The compressibility, compactibility and tabletability of the novel excipient were determined. The equivalent circle diameter of the excipient particle was calculated as 4.09±0.90 μm, exhibiting a fair to passable flow property. The mean yield pressure from the Heckel plot was found to be 82.64 MPa, indicating its ability to undergo plastic deformation at relatively lower compression pressures. When compared to sodium starch glycolate, a standard tablet disintegrant, the cellulose nanocrystal-based co-processed excipient produced better dissolution of the model drug paracetamol.

Hydrogen refueling station synergistically driven by liquid hydrogen pump and thermal compression

The energy consumption of conventional 70-MPa hydrogen refueling stations (HRS) with liquid hydrogen (LH2) pumps remains at a high level due to the low efficiency of LH2 pumps working at extremely high pressures, up to nearly 90 MPa. This paper presents a novel HRS with significantly lower energy consumption, based on a step-by-step compression strategy enabled by a highly-efficient 50-MPa LH2 pump for low-pressure compression and a subsequent thermal compression module for high-pressure compression driven by thermal energy. The performance of the cryogenic pressure vessels in the HRS process is analyzed via a numerical model, and then several improvements to the HRS process are proposed for large-scale refueling requirements. Finally, the techno-economic performance of the HRS is compared with the conventional HRSs and the HRS with pure thermal compression. Compared to the conventional HRSs with 90-MPa LH2 pumps, the capital cost of the proposed 400-kg/day HRS is reduced to $1.52M from $1.80M, while its energy consumption is reduced to 0.3 kWh/kgH2 from 1.3 kWh/kgH2. This work provides a new solution for low-energy-consumption hydrogen refueling which would be beneficial for reducing the overall cost of the hydrogen supply chain.

Impedance Study of the Effect of Cell Compression on PEMFC Under Various Oxygen Supply Conditions

Cell compression impacts the performance of polymer electrolyte membrane fuel cells (PEMFCs). A previous study has reported a trade-off between mass transport and contact resistances from cell compression [1]. Our study focuses on how the compression pressure affects polarization resistance under various oxygen partial pressure conditions. Without hot pressing the gas diffusion layers, a membrane electrode assembly with an electrode area of 1 cm2 was set in a housing in which the compression pressure could be adjusted [2]. Impedance spectra were measured at 0.7 A/cm2 under various oxygen partial pressure conditions. Figure 1 shows that polarization resistance decreases with increasing compression pressure under low compression pressure conditions, and conversely increases under high compression pressure conditions. The change in polarization resistance is more pronounced under low oxygen partial pressure conditions. In this contribution, the effect of cell compression on the different polarization processes will be discussed, considering the impact of compression pressure on catalyst layer thickness and porosity.

Marine diesel engine turbocharger fouling phenomenon risk assessment application by using fuzzy FMEA method

Turbocharger fouling phenomenon was analyzed from the risk assessment perspective in this study. The research employed exhaust system and turbocharger equipment of commercial ship that equipped with a Doosan-MAN B&W 6S50 MC-C diesel engine was used as the main research materials, and utilized the fuzzy Failure Mode and Effects Analysis (FMEA) based on the expert system as a methodical approach. The experts revealed different types of turbocharger fouling failure modes (FMs), along with their respective causes and subsequent consequences. Following that, the specialists allocated an O, S, and D score to each FM. Within the framework of fuzzy logic, the process entails the establishment of input and output membership functions, as well as the construction of a fuzzy model incorporating an inference mechanism and a rule base. Based on the analysis findings, the three primary factors are as follows: low cylinder compression pressure with a Fuzzy Risk Priority Number (FRPN) score of 6.95, high main engine fuel oil consumption with a score of 6.92, and high CO, CO2, SOx emissions with a 6.45. The phenomenon of turbocharger fouling, being an inherent occurrence, has significant ramifications on the main engine, the vessel as a whole, and the ecological surroundings. The quantitative results presented in this study provide valuable insights into the risks associated with maritime endeavors. The data generated from this research can be used by stakeholders in the maritime industry to better understand this situation and take proactive measures to mitigate potential risks in the future. Furthermore, the findings of the research provide corroboration for the implementation of predictive maintenance procedures.

Conversion of Polypropylene (PP) Foams into Auxetic Metamaterials

In this work, a simple and environmentally friendly process combining low pressure (vacuum) and mechanical compression is proposed to convert recycled polypropylene (PP) foams (28 kg/m3) into low density foams (90–131 kg/m3) having negative tensile and compressive Poisson’s ratios (NPR). The main objective of the work was to determine the effect of processing conditions (vacuum time, temperature and mechanical pressure). Based on the optimized conditions, the tensile Poisson’s ratio of the resulting auxetic foams reached −1.50, while the minimum compressive Poisson’s ratio was −0.32 for the same sample. The foam structure was characterized via morphological analysis (SEM) to determine any changes related to the treatment applied. Finally, the tensile and compressive properties (Young’s modulus, strain energy, energy dissipation and damping capacity) are also presented and discussed. It was observed that the mechanical properties of the resulting auxetic foams were improved compared to the original PP foam (PP-O) for all tensile properties in terms of modulus (19.9 to 59.8 kPa), strength (0.298 to 1.43 kPa) elongation at break (28 to 77%), energy dissipation (14.4 to 56.3 mJ/cm3) and damping capacity (12 to 19%). Nevertheless, improvements were also observed under compression in terms of the energy dissipation (1.6 to 3.6 mJ/cm3) and the damping capacity (13 to 19%). These auxetic foams can find applications in sport and military protective equipment, as well as any energy mitigation system.

Природа эволюции магматизма в истории Земли

Numerous evidences of hot heterogeneous accretion of the Earth have been obtained. According to these data, the Early Precambrian crystalline complexes and acidic crust were resulted from emerging residual melts formed by low-pressure compression fractionation of the bottom parts of the early magmatic ocean. The rise of residual melts from various layers of the magmatic ocean, crystallized from top to bottom, caused the evolution of magmatism of ancient platforms from acidic to basic, then to alkaline-ultrabasic and kimberlite. The warming of the mantle by the initially hot core led to the appearance of a direct geothermal gradient in it at the end of the Neoproterozoic and to the beginning of the rise of mantle plumes. Under their influence, oceanic and subduction environments were formed. Magmas in them are formed as a result of frictional and decompression melting of the differentiates of the magmatic ocean.

Conversion of polystyrene foams into auxetic metamaterials

AbstractAuxetic foams have gained popularity within the research community because of their enhanced properties, such as low density combined with high relative stiffness, toughness, and damping properties. Low density polystyrene (PS) foams are commonly used in the packaging industry, but have a short service life and generate a high volume of waste (white pollution). This is why their recycling and valorizing is necessary and imperative. The objective of this work is to present a simple and environmentally friendly process combining low pressure (vacuum) and mechanical compression to convert recycled PS foams (15 kg/m3) into low density foams (50–63 kg/m3) having negative tensile and compressive Poisson's ratios (NPR). The effect of processing conditions (vacuum level, temperature, mechanical pressure, and time) were studied. Based on the optimized conditions, the tensile Poisson's ratio of the resulting auxetic foams reached −0.65 for the Y direction (width) and −0.74 for the Z direction (thickness) when stretching in the X direction (length). On the other hand, the minimum compressive Poisson's ratios were −0.32 for the Y direction and −0.28 for the Z direction. The foam structure was characterized via morphological analysis to determine the changes after treatment. Finally, tensile and compressive properties (Young's modulus, strain energy, energy dissipation, and damping capacity) are also discussed. It was observed that the mechanical properties of the resulting auxetic foams were improved compared to the original PS foam (PS‐O) in terms of resilience and strength. For example, the elongation at break of auxetic foams (31%–62%) were much higher compared to PS‐O (7%). These auxetic foams can be used in several applications, such as sports and military protective equipment.

A Simple Method to Convert Cellular Polymers into Auxetic Metamaterials

The objective of this study was to present a simple and environmentally friendly process combining low pressure (vacuum) and mechanical compression to convert low-density polyethylene (LDPE) foams into low-density foams (76–125 kg/m3) with negative tensile and compressive Poisson’s ratios (NPR). As a first step, four series of recycled LDPE foams (electronics packaging) with starting densities of 16, 21, 30 and 36 kg/m3 were used to determine the effect of different processing conditions including temperature and pressure. Based on the optimized conditions, the tensile and compressive Poisson ratios of the resulting auxetic foams reached −2.89 and −0.66, while the tensile and compressive modulus of the auxetic foams reached 40 kPa and 2.55 kPa, respectively. The foam structure of the samples was characterized via morphological analysis and was related to the mechanical properties before and after the treatment (i.e., foams with positive and negative Poisson’s ratios). The tensile and compressive properties (Young’s modulus, strain energy, energy dissipation and damping capacity) for these auxetic foams were also discussed and were shown to be highly improved. These auxetic foams can be applied in sports and military protective equipment. To the best of our knowledge, there is only one report on vacuum being used for the production of auxetic foams.

(Digital Presentation) Effect of Compression Pressure on Water Removal and Power Generation Performance of PEFC with Modified Electrode/Channel Structure

Water flooding in cathode electrodes of polymer electrolyte fuel cells (PEFCs) is a critical issue that must be solved for achieving high efficiency and high power density operations. To alleviate this problem, it is necessary to design the optimum electrode/channel structure for actively removing liquid water from the porous media to the flow channel. In the previous studies, Okuhata et al. [1] revealed that the introduction of penetration holes to gas diffusion electrodes (GDEs) effectively promotes the water discharge and improves the limiting current density. Nishida et al. [2] investigated the effect of channel hydrophilization on the water behavior in the cathode of an operating cell using the cross-sectional visualization technique. It was found that the hydrophilization of cathode channels encourages the water suction from the gas diffusion layer (GDL) to the channel and enhances the oxygen diffusibility to the catalyst layer (CL). Our research group has proposed a novel hybrid electrode/channel structure combining the electrode perforation and channel hydrophilization and has investigated its effect on the improvements of water drainage and cell performance. In this study, we directly visualized the liquid water distribution in the cathode GDL of a customized PEFC with the hybrid electrode/channel structure using X-ray imaging and evaluated the transient response of cell voltage under the constant-current operations. Furthermore, the influence of compression pressure on the water behavior in the perforated GDL and the performance characteristics of the customized cell was also examined.For the X-ray investigation, we fabricated a specialized miniature fuel cell with the effective electrode area of 2.88 cm2. The membrane electrode assembly (MEA) was sandwiched between two carbon separators with a single-serpentine flow field (number of channels: 7, channel width: 1.0 mm, depth: 1.0 mm, total length: 88.5 mm). Fig. 1 shows a schematic cross-sectional view on the cathode side of the experimental cell. Since the cathode GDL is irradiated with X-ray beam in the in-plane direction, the through-plane distributions of water can be observed in the GDL under the 4th channel and under the land between the 3rd and 4th channel. To promote the water discharge from the fine porous media, a penetration groove (width: 300 μm, length: 11 mm) was installed into the GDL, MPL and CL and positioned along the right sidewall of the 4th channel. The channel walls on the cathode side were coated with the silica-based hydrophilic solvent. The contact angle of water on the hydrophilized channel is 9.8o. In the hybrid electrode/channel structure, liquid water accumulated in the CL and MPL is firstly discharged into the large groove in the in-plane direction. Subsequently, water droplets gathered in the groove are grown up and attached to the hydrophilized channel walls. The droplets are spread out on the hydrophilic sidewalls and the liquid films are moved upward. Fig. 2 presents the distributions of water saturation in the perforated GDL of the customized cell assembled under two different compression pressures of 0.5 and 1.0 MPa. The current density was increased stepwise from 0.14 to 1.02 A/cm2 for 8 min under the room temperature and non-humidification condition. All images were captured at t=8 min after starting the operation. Dry hydrogen (stoichiometry: 1.5@2.0A/cm2) and oxygen (stoichiometry: 3.0@2.0A/cm2) were supplied to the anode and cathode in the counter-flow arrangement. It was found that the introduction of the hybrid structure effectively decreases the water saturation around the groove due to the in-plane water discharge. The reduction of saturation under the land is much less than under the channel because the strong mechanical compression crushes the pore structure under the land regions and suppresses the water transport. In addition, the low-saturation region of 28% or less around the groove is enlarged with a decrease in compression pressure. The low compression pressure maintains the relatively large porosities in diffusion media and facilitates the water removal.

Aerodynamic Analyses of an Integrated Low-Pressure Compression System for Adaptive-Cycle Micro Turbofan Type Jet Engine

Unmanned Aerial Vehicles (UAVs) are commonly propeller-driven and low-speed. The concept of cost-efficient, much higher speed and longer range applications of micro jet engines was previously addressed such that an existing basic turbojet engine was converted into a single spool turbofan without using additional components of booster and low pressure turbine. Normally, this situation emerges matching problems since two spools are required to adjust the fan speed independently. A simple solution was to use a Continuously Variable Transmission (CVT) gearbox to adjust optimal speed for the fan. As a result, missing of the positive functionality of the booster would lump into the fan root to form a unified low pressure compression system (unified-LPC). Such a unified-LPC demands unique characteristics of having an extreme twist, very high pressure ratio and mass flux at the root section than at the tip section, despite the exact opposite is being enforced due to the wheel speed rise with radius. In light of these challenges, this work aims to investigate detailed aerodynamics of an existing design previously made and reported by the authors. It is shown that, despite the aerodynamic loading contrast throughout the span, the unified-LPC can still have a wide operating range and acceptable off-design aerodynamics. Complementing the previous design-oriented work, this paper aims to provide guidelines for such unified compression systems.

Negative porosity issue in the Heckel analysis: A possible solution

A parameterization of compaction simulator generated dynamic compression profile with a few grams of powder provides important information about the material deformation and compact elasticity. The Heckel equation is by far the most popular choice among pharmaceutical scientists for such parametrization. A general approach of Heckel analysis uses pycnometric powder density (ρP0) for relative density calculation. However, as ‘in-die’ tablet bulk density at applied compression pressure (ρBP) becomes greater than or equal to the measured ρP0, the general approach typically poses a negative porosity challenge at high compression pressure regions. It is only theoretically possible to have a tablet with zero or negative porosity. Negative porosity may be detected during ‘in-die’ compression analysis, but it will not exist after ejection of the tablet in practical aspect. Thus, the present work proposes a new approach to using pycnometric tablet density (ρPP) in the relative density calculations of Heckel analysis. This ρPP may be a better representation of actual tablet particle volume, as it is composed of non-accessible intra-particulate pores, which are broken under applied compression pressure. A new approach showed its immunity for Heckel high-pressure negative porosity. It enables the utilization of the compression and decompression phases of dynamic compression profiles to evaluate macroscopic compaction performance. The proposed approach was validated with a reported modified Heckel approach. The Heckel parameters computed with both methodologies for microcrystalline cellulose and lactose were not statistically different. However, a modified Heckel approach was unable to compute Heckel parameters of poorly compacting starch unlike the new approach. A modified Heckel approach became invalid during starch compaction at low compression pressures (below 400 MPa), where starch was forming weaker but still intact tablets. Certainly, a complete Heckel profiling with a new approach could save time and costs in an early development stage for designing and screening scientifically based lead prototype formulations.

Діагностика паливної апаратури, приводу клапанів газорозподілу та форсунок змащення циліндрів сучасних двотактних двигунів

The application of a vibration sensor with an in-cylinder pressure sensor extends the capabilities of internal combustion engines and compressor diagnostics for various types of plants and installations, such as marine diesel engines, refrigeration piston compressors, aircraft engines. The fuel injection equipment malfunctions as valve as valve train system malfunctions could be detected from the experimental indicated diagrams P(V), P(deg) of the engine cylinder operating process as it is known. The main indicators are the following: the shape of the diagram and the parameters of working cycle – the maximum combustion pressure Pmax, the compression pressure Pcomp, mean indicated pressure IMEP, etc. However, it should be considered that different types of malfunctions could have the same reflection on the indicated diagram. For instance, the late fuel injection and the fuel-injection equipment wear could have almost similar effects on the indicated diagram and main diagnostic parameters. Another example is the low compression pressure Pcomp, which could be caused by the cylinder or compression rings wear and by the exhaust valves wrong timing or valve leakage. It should also be mentioned that many types of malfunctions at their early stages are very difficult to detect and clarify based solely on the indicated diagrams analysis. The detection of such malfunctions usually requires the direct measurements of the fuel injection pressure and injector’s needle lift diagrams with accurate valve timing measurements. However, mentioned measurements could be performed under laboratory conditions and are difficult to apply under engine operating conditions. The vibration sensor application could be a reasonable alternative to the direct measurements, as it allows the determination of the injector’s needle lift-off and landing timing, high-pressure fuel pump cut-off and discharge timing, the preheated heavy fuel circulation start/stop timing as well as gas-distribution valves opening and closing timing, the oscillation frequency, and amplitude from the refrigeration system piston compressor valve operation and the cylinder oil injector timing. The vibration sensor has a magnetic basement that allows its easy mounting on the engine parts. All this information could be directly measured during engines and compressor trials by the vibration sensor applied in the advanced diagnostic systems.

Development of a Novel Transcription Molding Process to Fabricate Sophisticated Polymer Products with Precise Microstructure and High Transparency Applicable to Display Devices and Bio-chips

Abstract In this study, we developed a novel transcription-molding process and experimentally discussed its validity for fabricating polymer products having the precise microstructure on the surface. The process was named “Melt-Transcription Process” which consists of two characteristic stages; coating and compression. In the coating stage, a molten polymer is coated on the surface of a metal mold having the precise microstructure by a coating device specially designed in this study. The thickness of the coated polymer melt is typically 100 μm or more. Immediately after coating, the coated polymer is compressed against the mold surface so as to make the polymer flow into the microstructure cavities engraved on the mold, and to fabricate the 3-dimensional structure of polymer products. The pressure required for compression is quite lower than that in conventional nano-imprinting process, because the molten polymer of high temperature is distributed in advance over the mold surface in the coating stage. The “Melt-Transcription Process” was applied to fabricate polymer products with the size of 150 mm in length, 150 mm in width and 1 mm in thickness, having the microstructure of tens micrometers on their surface. Cyclo-olefin polymer (COP) and Polymethyl methacrylate (PMMA) were used as the polymer materials, and the dimensions and transcription ratios (the ratio of the height of the transcribed microstructure to the depth of the microstructure on the mold) of the molded microstructure were experimentally evaluated. As a result, by the Melt-Transcription Process, the microstructure was sufficiently transcribed on a very thin substrate of large surface area with high transcription ratios, typically 95% or more, under relatively low compression pressure of less than 10 MPa. The process was also applied for fabricating products with a range of thicknesses and we could experimentally verify that products composed of a membrane of 80 μm thickness and a surrounding frame with 1.95 mm thickness were successfully molded. Furthermore, we fabricated a micro-lens array product by using film grade PMMA with relatively higher viscosity in a product having 125 μm in thickness and a size of 102 mm × 102 mm.

Technical feasibility of producing binder-free water hyacinth briquettes for domestic energy use

Production of biomass briquettes of good strength and combustion characteristics usually requires the addition of a binder material to the feedstock. This study was aimed at developing a methodology for producing briquettes from water hyacinth at low compression pressures without using a binder material. Fresh water hyacinth was chopped to a maximum length of 3 cm, sun-dried to a moisture content of about 10%, mixed with shredded waste office paper in four water hyacinth to paper proportions on weight basis (100:0, 90:10, 80:20 and 70:30). The mixtures were soaked in water for three days and briquetted using a 6-cylinder screw briquetting machine. The resulting briquettes were subjected to standard strength and combustion tests. A Completely Randomized Design with four treatments replicated five times was used as the experimental design. Results from the study indicate no significant differences in compressed density, relaxed density, relaxation ratio and calorific value between the briquettes. The results further indicate that briquettes made without a binder material have significantly low but adequate shatter resistance, low ignition time, high burning rate and take a longer time to bring water to boil. It can be concluded that good quality water hyacinth briquettes can be produced at low compression pressures without using a binder material. This methodology can potentially increase adoption of water hyacinth briquettes in areas with poor access to binder materials. The originality of the research is the development of a water hyacinth briquetting methodology that does not use binder materials.

BaTiO3@PVDF-TrFE nanocomposites with efficient orientation prepared via phase separation nano-coating method for piezoelectric performance improvement and application to 3D-PENG

Piezoelectric organic–inorganic hybrid nanocomposites utilize the advantages of high piezoelectricity of piezoelectric ceramics as well as the dielectric properties and flexibility of polymers. BaTiO3 particles that are nano-coated using the phase separation nano-coating method have effective orientation due to interaction with the PVDF-TrFE polymer chain. After mixing the piezoelectric BaTiO3 nanoparticles with the PVDF-TrFE matrix, an organic–inorganic hybrid nanocomposite film with enhanced efficiency characteristics of inorganic piezoelectric particles, and the flexibility and processability of the polymer was fabricated. The piezoelectric organic–inorganic hybrid nanocomposite film, in which the BaTiO3 coated with a polymer layer of about 5 nm or less, was dispersed and produced an output voltage of 59.5 V and an output current of 6.52 μA at a relatively low compression pressure of 100 N and frequency of 2.5 Hz. The result was about 4.8 times and 2 times higher than that of pure PVDF-TrFE and BaTiO3 nanocomposite dispersed films, respectively. The output power was measured against the external load resistance. On the other hand, the maximum output power value was measured to be 165.8 μW. In addition, by using the excellent processability of the uniformly dispersed BaTiO3@PVDF-TrFE nanocomposite solution, the piezoelectric nano-generator was implemented in a new form, in which the existing form factor was changed by coating on a three-dimensional shape as well as a two-dimensional flat film.

A concise and systematic study of the hydrothermal synthesis of Si-MCM-48: Structural aspects and mechanical stability

The structural collapse of mesoporous molecular sieve Si-MCM-48 by mechanical compression was investigated. Samples were synthesized by modifying temperature and time of a hydrothermal synthesis, according to a 32 experiment design. In this way, flexibility of the synthesis method was evaluated. Structural and textural characteristics were investigated using X-ray diffraction, nitrogen physisorption, and scanning and transmission electronic microscopies. As a consequence of the increase in applied pressure, different behavior was observed in the average wall thickness of samples related to the porous organization of the solid. The collapse of interparticular macropores caused a greater increase in thickness at low compression pressures, while the intraparticular mesopores, supported by the silica walls, supported greater compression. The macropores collapsed by mechanical compression at pressures as low as 60 MPa, while mesoporous ones exhibited reasonable resistance up to 200 MPa. Samples synthesized with high temperatures and long reaction times presented better mechanical resistance due to the favorable kinetics of silica condensation on the walls and, thus, are more interesting for applications in catalysis or adsorption.

Effects of diosmin-hesperidin and low pressure compression stocking combination in superficial venous insufficiency

Aim: The main aim of the study is to investigate the efficacy and patient tolerance of Daflon 1000mg/day and low-pressure compression stocking combination in the treatment of superficial venous insufficiency. Materials and Methods: This prospective study included 112 patients diagnosed with superficial venous insufficiency and reflux in saphenofemoral junction during March 2018 and 2019 at our center. All the patients received 1000 mg micronized purified flavonoid fractions containing 90% diosmin-10% hesperidin and low-pressure venous compression stockings (15-20 mmHg) throughout the study. Patients superficial, perforator, and deep venous systems were evaluated by Doppler US at the beginning and average of 5.3 ± 3.7 months after treatment. Results: A total of 99 (88.4%) patients out of 112 eligible patients completed the investigation. The mean age was 41±12.6, the female was 66 (58.9%), the mean follow-up was 5.3±3.7 months. Pre-treatment and post-treatment diameters of SFJ were 6.27±2.9 and 5.68±1.8 mm, respectively, this was statistically significant (P=0.033). All of the patients have SFJ reflux initially, after the treatment, patients with SFJ reflux were decreased to 44 (44.4%), this was also statistically significant (P0.001, OR:0.004, 95% CI: 0.0002-0.07). We also found significant improvement in grade III and grade IV reflux (P0.05) after treatment. The symptomatic patients decreased from 63 to 16 after treatment, this was statistically severely significant (P0.001, OR:0.11, 95% CI: 0.056-0.216). During the follow-up period, 6 (5.4%) patients were worsened and underwent surgical intervention, this was not statistically significant (P=0.076). Conclusion: Daflon 1000mg/day with a combination of low- pressure CS well tolerates by venous insufficiency patients. Six months of continuous application may reduce the reflux of SFJ and VSM, and causes marked symptomatic relief.

Pore Size Distribution Characteristics of High Rank Coal with Various Grain Sizes.

Particle void filling effects (Pf) under low pressure and coal matrix compressibility effects (Pc) at high pressure should not be ignored when using mercury intrusion porosimetry (MIP) to study the pore size distribution of coal. In this study, two coal samples (FX and HF) collected from western Guizhou were crushed into three different grain sizes; then, the subsamples were analyzed by MIP and low-pressure nitrogen adsorption to study the pore size distribution characteristics. The micro- and transition pore volumes contribute to the total pore volume of the FX and HF subsamples. With decreasing subsample grain sizes, the macropore volume of FX subsamples tends to increase, while mesopore volume decreases; the volumes of micropores and transition pores first increase and then decrease. In regard to the HF subsamples, the volumes of macropores and mesopores do not reveal any distinctive changes, while the 40–60 mesh subsample contains the greatest volume of micropores and transition pores. Fractal theory was introduced to determine Pf and Pc. Pf barely changed as grain size decreased; it ranged from 0.1 to 0.15 MPa. However, Pc increased with reduced coal grain sizes. The coal matrix compressibility coefficients of the subsamples were calculated from the cumulative mercury volume curve, and the true pore volume was also modified. The modified volume of macropores does not change markedly, while the volumes of mesopores and transition pores decrease significantly, clearly indicating the coal matrix compressibility under high mercury injection pressure. The modified pore volume shows that the pore (<10,000 nm) still harbors fractal characteristics.

Influence on the Electrical Efficiency of a Hybrid MGT-SOFC-System by μ-fogging in a-Two-Staged Compressor System

Hybrid combinations of solid oxide fuel cell and recuperated micro gas turbines can convert the chemical energy of hydrocarbon-based fuels in electrical energy with high electrical efficiency. With an integrated and improved cycle management, more than 70% of the energy content of the fuel could be converted. Therefore, the systems are highly suitable for the Power-To-Gas conversion. In particular, a pressure charging of the SOFC fuel cell leads to an increase in stack performance. By a downstream turbo set, after residual fuels are intentionally oxidized with an afterburner, additional electrical energy can be gained from the expansion of the hot exhaust gas stream and the overall efficiency can be increased. In order to increase the electrical efficiency of the system, it is proposed, to ensure the required compression of the process air in particular by a-two-staged turbo compressor with an intermediate cooling system. By thus achievable reduction of the dissipation of the compressor and by targeted condensation of finest drops in front of the second compressor stage affected by intermediate cooling, an increase in efficiency of the system is possible. This is achieved by targeted cooling of the process air behind a low pressure compression, so that it is saturated over 100% relative air humidity. As a result, a slightly supersaturated airflow is available for the second compressor stage, which enters the compressor after heat removal via an intermediate cooling having a small number of microdroplets. Therefore, the condensed water evaporates again by the heat of compression in the second stage and the compressed flow ultimately enters the recuperation at a lower temperature than during normal compression. Thus, more heat can be recovered within the recuperation system. Therefore, the electrical energy of the system can be produced having higher efficiency, because the heat dissipation of the overall system decreases. In this article it is presented, how such a process is thermodynamically modelled and how a technical realization can be built after optimization by simulations. Finally, in this study, the process-influencing factors are analyzed to show the highest possible electrical yield of such a system.