Diaphragm Type Research Articles

Seismic performance of new detailing RCS connection with different axial compression ratio and FBP thickness

Reinforced Concrete column and Steel beam (RCS) structural system has been extensively studied due to the effective use of concrete and steel material and cost efficiency. Bearing failure and constructability were two main issues of RCS joint in practical engineering. To improve these two deficiencies, the authors proposed a whole-section diaphragm type RCS joint. This study aimed to examine the impact of axial compression ratio and face bearing plate (FBP) thickness on the seismic behavior of the proposed joint. In this research, six RCS joint specimens were designed to achieve joint failure and tested under cyclic loading. Shear failure was identified as the typical failure mode. The results revealed that higher axial, compression ratio could lead to higher cracking loads, with improved load-carrying capacity, stiffness, and energy dissipation capabilities. Additionally, the joint bearing distortion reduced as the axial compression ratio increased. All specimens displayed spindle-shaped hysteresis loops while the specimen without axial compression exhibited pinching effect. The presence of parallel FBPs significantly improved the shear capacity. However, as the thickness of the parallel FBPs increased from 6 mm to 10 mm, the load-carrying capacity showed limited enhancement. Moreover, a comparative analysis of current calculation methods was conducted. The results demonstrated that the AIJ and CECS347:2013 formulas showed acceptable accuracy in predicting the joint shear strength. These findings validated the applicability of the existing methods for proposed composite joints, while the effect of the axial compression ratio required further evaluation.

Investigative study of cost-effective ZrO2 nanoparticles/acrylic based diaphragm for alkaline electrolyzers

Energy is crucial to the cycle of existence in the universe and plays an important role in achieving sustainable growth. Considering the traits of the conventional approach and challenges dealing with conventional energy technologies, water electrolysis is reflected to be simple, sustainable, and green energy tool. Alkaline water electrolysis (AWE) process is mature technology of the last century for industrial hydrogen production. AWE uses asbestos as the separator medium. However, asbestos allows crossover of the produced gases therefore, low purity gas is obtained, and with limited stability. In the present study, a novel composite diaphragm separator has been synthesized using Zirconium oxide (ZrO2) with aqueous acrylic solution in different compositions and optimized for enhanced performance. The prepared composite is initially stabilized through sonication and applied on the medium with a uniform thickness using a doctor blade film applicator. The study aims to optimize the composite diaphragm to withstand the severe chemical and thermal conditions of the electrolyzer. Zirconium oxide-based diaphragms offer several advantages over other types of diaphragms, including excellent corrosion resistance, high chemical and thermal stability, and long service life. These coated separator diaphragms showed good electrolysis performance and stability in an alkaline medium.

Experimental study on seismic behavior of RC column-steel beam joints with whole column-section diaphragm

RC column–steel beam (RCS) frame is one of the most popular hybrid structural systems. Multiple types of RCS joints have been proposed in the last few decades. To avoid undesirable bearing failure, complicated strengthening details were required in RCS joints, which caused difficulties in construction. This study proposed a whole column-section diaphragm type RCS joint with simple details. Compared to most RCS joints, the steel web was cut off at the beam-column interface in the proposed joint, which facilitated the arrangement of stirrups and concrete casting. Moreover, the bearing failure could be avoided since the bearing area of concrete was enlarged and the local bearing stress decreased, requiring no additional strengthening details. To investigate the seismic performance of the proposed RCS joint and the impacts of strengthening configurations, four interior joint specimens were designed, fabricated, and tested under cyclic loading. In addition, joint strengths were calculated using the existing methods. The test results showed that joint shear failure occurred in all specimens. The concrete within the hole in the diaphragm has limited influence on joint behavior. The force in flanges could be fully transferred to concrete through the dowel action of longitudinal reinforcements and friction between the diaphragm and concrete. The ductility of joints was significantly improved due to the confinement provided by face bearing plates (FBPs). The orthogonal FBPs could greatly increase the shear resistance of the joint. The predictions for joint shear strengths following the current calculation methods were significantly conservative. It confirmed that adequate shear capacity could be obtained although the simplified details were used. The conclusions of this research can provide a reference for the engineering application of the RCS hybrid frame.

EXPERIMENTAL STUDY OF A VARIABLE BUOYANCY SYSTEM FOR LOW DEPTH OPERATION

Autonomous Underwater Vehicles (AUVs) are used for the underwater survey both in coastal areas and deep sea without any human intervention during their operations. However, high energy consumptions required by the thrusters of the AUV’s adversely affect their performance such as range and endurance, etc. Herein, we have presented a novel design and development of a standalone variable buoyancy system for autonomous underwater vehicle and investigated the numerical and experimental analysis of Variable Buoyancy System (VBS) in standalone mode. Design idea is based upon the ‘Pump Driven Variable Buoyancy System (PDVBS)’ using ‘Water Hydraulic Variable Buoyancy System (WHVBS)’ method to control the buoyancy using a diaphragm type positive displacement pump (PDP) with capacity of the maximum buoyancy change rate of 4.5 kg/min. Detail experimental and simulation performance of the developed VBS has been investigated. Developed VBS is tested for maximum depth of 5 m and compared the performance of the experimental and simulation results. Presented results demonstrate that designed VBS is effective in changing buoyancy and controlling heave velocities and that will result to achieve the higher range and endurance and better performance in rescue/attack operations.

Experimental and numerical investigation of vertical shock tube performance for blast load testing of geological media

In this paper, a new vertical shock tube test facility is described that has been designed and established for a research program aimed at studying the response of the geological media subjected to blast loading. In the present study, the vertical shock tube test facility is studied, and its performance is evaluated by characterizing generated blast waves considering two different diaphragm types; Aluminium and Lexan, and two driver gases; Nitrogen and Helium. The driver pressure in the vertical shock tube is varied by using Aluminium diaphragms of different thicknesses and groove depths and Lexan diaphragms of different thicknesses and numbers. The blast wave generated in the vertical shock tube is evaluated by studying its pressure loading profile, blast properties, Friedlander wave fit, trinitrotoluene equivalence, and by comparing it with idealized shock wave theory. The measured blast waves have properties that are a function of the driver pressure and driver gas. The positive-phase duration segment of the measured pressure wave is comparable to the blast waves in the actual free-field explosions. Based on the experimental results, the equations for the determination of driver pressure and peak-reflected overpressure considering Lexan diaphragms are also proposed. The profile of the measured pressure wave in the vertical shock tube demonstrated its capability in generating an air blast loading in controlled laboratory conditions. Finally, the three-dimensional finite element simulations are also performed, and results are validated with the experimental data.

The Use of Disk-Shaped Diaphragm of Vehicles in Double-Circuit Diaphragm Pumps

Introduction. The article concentrates on improving the efficiency of double-circuit diaphragm pumps, which can be successfully used in heat and water supply systems of industrial and agricultural facilities where there is excess head. It is advisable to equip double-circuit diaphragm pumps with disc-shaped diaphragms interconnected by a rod, for example, from motor vehicles, and to drive them from the available head of the hydraulic network. In order to increase the efficiency of their work and further use, it is necessary to predict the hydraulic characteristics according to the geometric parameters of the membranes and the cycle of their operation in dynamics. Aim of the Article. The article aims at obtaining adequate calculated dependencies of pumped liquid flow rate on speed of double-circuit diaphragm pumps. Materials and Methods. There were used the idealization method from differential geometry, physical experiment, and mathematical statistics to solve the tasks for identifying the relationship between the rod motion and the liquid flow rate for a poppet diaphragm with different geometric surfaces in dynamics. There have been obtained the dependences of pumped liquid volume on the movement of the point of attachment by the poppet diaphragm and the volume flow rate on the movement speed of the point of attachment by the poppet diaphragm with specific geometric parameters for the parabolic and chain line. An experimental testing of the dependence of displaced pumped liquid flow rate on the movement of the attachment point to the stem for the diaphragm type 30 was carried out. Results. Based on the obtained dependences of the volume flow rate on the speed of movement of the point of attachment by a poppet diaphragm with specific geometric parameters for a parabolic and chain line, there were constructed the graphs of dependences of the volume flow rate on the frequency of the working cycle. For practical implementation, there are proposed the dependencies for constructing the hydraulic characteristics of a two-circuit membrane (the dependence of the volume flow rate on the frequency of the working cycle) obtained on the basis of a parabolic interpretation. Discussion and Conclusion. The hydraulic characteristics of a two-circuit membrane pump are close to the equation of a straight line and are consistent with experimental dependencies within 4%.

Design of GH4169 diaphragm for combined improvements of yield strength and surface roughness

AbstractDiaphragm compressors have become the primary source of on-site hydrogen compression for hydrogen fuelling stations around the world. The most common hydrogen-compressor-failure mechanism has been identified as diaphragm fracture due to low tensile strength and poor surface properties. In this study, a new type of GH4169 diaphragm with high yield strength and low surface roughness was fabricated. Microstructures, tensile behaviours and surface properties of the specimens were characterized by using scanning electron microscopy, an electronic universal testing machine and atomic force microscopy, respectively. The evolution of the γ′′ and γ′ phases with temperature has been examined. Both γ′′ and γ′ phases were precipitant-strengthened phases for GH4169 and the volume and size of γ′′ and γ′ phases increase with ageing time. In addition, the γ′′ phase is the main strengthening phase and γ′ is the supportive strengthening phase. Tensile strength was increased due to the strengthening phases at the cost of ductility. The roughness of the diaphragm could reach an arithmetic average roughness (Ra) of 0.1 μ m by applying a cooling-assisted polishing process. This work improves the reliability and reduces the auxiliary steps and down-time for diaphragm compressors.

Mitochondrial creatine sensitivity is lost in the D2.mdx model of Duchenne muscular dystrophy and rescued by the mitochondrial-enhancing compound Olesoxime.

Duchenne muscular dystrophy (DMD) is associated with distinct mitochondrial stress responses. Here, we aimed to determine whether the prospective mitochondrial-enhancing compound Olesoxime, prevents early-stage mitochondrial stress in limb and respiratory muscle from D2.mdx mice using a proof-of-concept short-term regimen spanning 10-28 days of age. As mitochondrial-cytoplasmic energy transfer occurs via ATP- or phosphocreatine-dependent phosphate shuttling, we assessed bioenergetics with or without creatine in vitro. We observed that disruptions in Complex I-supported respiration and mH2O2 emission in D2.mdx quadriceps and diaphragm were amplified by creatine demonstrating mitochondrial creatine insensitivity manifests ubiquitously and early in this model. Olesoxime selectively rescued or maintained creatine sensitivity in both muscles, independent of the abundance of respiration-related mitochondrial proteins or mitochondrial creatine kinase cysteine oxidation in quadriceps. Mitochondrial calcium retention capacity and glutathione were altered in a muscle-specific manner in D2.mdx but were generally unchanged by Olesoxime. Treatment reduced serum creatine kinase (muscle damage) and preserved cage hang-time, microCT-based volumes of lean compartments including whole body, hindlimb and bone, recovery of diaphragm force after fatigue, and cross-sectional area of diaphragm type IIX fiber, but reduced type I fibers in quadriceps. Grip strength, voluntary wheel-running and fibrosis were unaltered by Olesoxime. In summary, locomotor and respiratory muscle mitochondrial creatine sensitivities are lost during early stages in D2.mdx mice but are preserved by short-term treatment with Olesoxime in association with specific indices of muscle quality suggesting early myopathy in this model is at least partially attributed to mitochondrial stress.

An Analysis of The Apartment's Tamansari Skylounge Halfslab Connection as a Diaphragm (Case Study : Padang Seismic Load)

Precast concrete is used in the Tamansari Skylounge Balikpapan Apartment's construction. The diaphragm is a slab that transmits lateral forces to the vertical element. This structure has a topped diaphragm as its diaphragm type. The goal of this analysis is to determine how seismic forces are distributed throughout a building using the seismic zone of Padang, to test the half-strength slab's during lifting, before and after a composite, to determine how deformation differs when a diaphragm is constrained, and to conduct research to strengthen the connection of the diaphragm's critical area to the building. The steps in data processing include analyzing the structure using SAP 2000, gravity load analysis based on PPIUG 1987, seismic load analysis based on SNI 1726:2012, connection diaphragm analysis based on NEHRP Seismic Design Technical Brief No. 3, normalizes and shear stress analysis on half slabs meeting between half slabs with topping based on Tension Material Analysis, and analysis of reinforced concrete structures based on SNI 2847: 2013. According to the analysis's findings, the 1B floor has the maximum seismic force at 19205269,17 N. The Half Slab reinforcement becomes ϕ10-150 with the added seismic load, and deformation with a diaphragm constraint is considerably less than without one. One piece of 12 mm diameter reinforcement with a shear connector is used for each square meter of the important diaphragm region.

Characterisation of the Operational Parameters of the Laboratory-Scale Membrane Alkaline Water Electrolysis Stack

Alkaline water electrolysis utilising porous diaphragm type separator of the electrode compartments represents industrially well-established technology of hydrogen production. This is due to the durable and stable operation utilizing abundant materials as iron, nickel, or stainless steel. However, many of the designs, construction solutions and approaches originate in the historical demands on the process (like mentioned durability rather than flexibility) and do not reflect up to date demands. Current demands on water electrolysis are given by the expected connection of water electrolysis technology with renewable sources of energy. The role of the water electrolysis is to use the surplus electrical energy in periods of the high output and/or low need for production of hydrogen. Hydrogen in such scheme represents an energy vector, which can be stored and used for electricity production in periods of the insufficient output of the renewable sources and/or high demand. Alternatively, hydrogen can be used as a fuel in fuel cell-based cars or as feedstock in industry. Due to connection with unpredictable renewable source, it is necessary for water electrolysis technologies to be flexible, highly efficient and be able to produce hydrogen of high purity. Current alkaline water electrolysis failed in several of these demands.Nowadays demands on water electrolysis are met by process utilizing proton exchange membrane (PEM) as separator of the electrode compartments. Unfortunately, PEM water electrolysis is limited by the need of the materials like titanium, platinum and iridium, which are rare, to be involved as electrodes, or catalysts of electrode reactions. The significant effort is paid to the possibility to combine advantages of both, alkaline and PEM processes by replacing porous diaphragm by dense anion-selective polymer membrane (ASM). Such change would allow to reduce the interelectrode distance to the thickness of the ASM used as separator of the electrode compartments, which would increase the performance of the membrane alkaline water electrolysis process. Utilisation of the ASM would also allow to decrease concentration of circulating electrolyte from commonly used 25 – 30 wt.% KOH to 1 – 5 wt.% KOH, increasing thus safety and flexibility. Another important beneficial impacts of ASM application are related to the improved current efficiency at low current densities and purity of the produced gasses, again especially at low current densities.Significant development was achieved in ASM synthesis in last decade and first promising materials are being commercially available. Despite the fact that many of the novel materials are tested in single cells under conditions of the membrane alkaline water electrolysis, the information on the stack behaviour are rare.In our work, we focused on the comparison of the porous diaphragm type and ASM separators in short stack comprising of 3 cells and geometrical area of the separator 78.5 cm2 under different operational conditions in terms of performance achieved. Besides the performance characterisation by mean of the load curve measurement, the complementary information on the gas purity, current efficiency and long-term stability were gathered for ASM separator.Zirfon Perl UTP 500 (Agfa, Belgium) was used as diaphragm type separator, meanwhile chloromethylated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene backbone functionalized by DABCO groups was used as ASM (TailorMem s.r.o., Czech Republic). Different concentrations of the liquid electrolyte represented by KOH solution were used in the range 1 – 15 wt.%. The temperature effect was verified at the same time by using the temperature of 25 and 40 °C. Load curves were measured galvanostically up to current density of 600 mA cm-2. The current efficiency was calculated based on the Faradays law by measuring the real oxygen production and comparing with theoretical value. The gas purity was measured for oxygen stream as the penetration of hydrogen into the oxygen stream is more important. Gas chromatography was used to measure the oxygen stream composition. The long-term stability was measured in 10 wt.% KOH solution at 40 °C at 240 mA cm-2.The results obtained indicate that at low KOH concentrations the performance of membrane alkaline water electrolysis is significantly better when compare to application of the diaphragm type separator. The differences in performance mitigated at increasing concentration. The characterisation of the membrane alkaline water electrolysis short-stack showed possibility to achieve high purity of the produced gasses and current efficiency even at low current densities. The long-term test showed excellent stability of the used ASM.Acknowledgement:This project has received funding from the European Union‘s Horizon 2020 Research and innovation action under grant agreement No 862509. Financial support by the Technology agency of the Czech Republic within the framework of the project No. TK02030103 is gratefully acknowledged.

Research of a new hot-rolled connector connection to composite walls

The composite members in steel residential buildings often possess small sections and have high restrictions on the indoor space extrusion of structural components, and then traditional diaphragm type and internal or exterior stiffener connections are hardly applied. A new hot-rolled connector connection was proposed, which used the flange-to-web arch transition of hot-rolled steel beams as the intermediate connector. The smooth section transition of the connector at the column face junction can reduce the stress concentrations and premature fracture potentials of connections between H-shaped beams and small-size composite walls or CFST columns in steel residential buildings. Four hot-rolled connector connections with different connector designs and beam sizes were tested under cyclic loads, and the seismic performances and working mechanisms were investigated. Refined finite element simulations were performed to indicate the load transfer path and load sharing mode in the connection. Results indicated that the proposed connection displayed plump hysteretic relations and satisfactory energy dissipation ability. The strengthened connectors succeeded in inducing the high plasticity away from the wall or column face. The bottom beam flange to connector butt weld was prone to fracture. The HTC connection with a long HTC connecting beam and the two bolt-row construction as the web connection was suggested.

Topology optimization of steel deck building diaphragms

This paper improves the roof diaphragm designs in steel buildings for lateral loads, such as those from wind and earthquakes, by maximizing the in-plane stiffness. The design of floors and roofs are typically dominated by gravity loads, however, the diaphragm's ability to transfer and resist in-plane shear forces is a key element in the structure's lateral force resisting system. The steel deck diaphragms are profiled steel sheet panels attached with fasteners and are typically placed with the same orientation throughout the entire diaphragm. Through variation of the layout of the steel profile and number of fasteners, the diaphragm's in-plane shear strength and stiffness cover a large range of values. In addition, the profiled nature of a steel panels results in different in-plane stiffnesses parallel and perpendicular to the deck profile. Through topology optimization, different roof diaphragm layouts are optimized for improved lateral stiffness by selecting a bare steel diaphragm type and orientation of the panel for each element. The optimized designs are complex and are interpreted into realizable steel diaphragm designs. Comparison of the designs finds that the optimized design is the stiffest followed by the realizable design. The traditionally designed diaphragms are much more flexible than both the realized and optimized designs. This work is part of a larger initiative (steeli.org) that aims to better understand and improve the role of diaphragms in the seismic response of steel buildings. Future work includes studying the non-linear behavior of optimized diaphragms and optimization that includes stress constraints to control initial yield.

Empirical Performance Levels of Strengthened Masonry Buildings Struck by the 2016 Central Italy Earthquake: Proposal of a New Taxonomy

ABSTRACT The complexity of the historical built environment may be reduced by discretizing buildings in types. At urban scale, typological classifications feed vulnerability models. Several literature procedures define types by the evaluation of constructive, geometrical, and structural features, but none seems to consider improving or upgrading interventions. These are the expected performance levels prescribed by seismic codes for strengthening existing masonry buildings. Notwithstanding, the 2016 Central Italy earthquake revealed the potentially detrimental role of interventions on the seismic behaviour of a building. A new performance-based taxonomy of masonry buildings is here proposed starting from the analysis of 2306 inspected dwellings struck by that event. Building features, i.e., masonry and diaphragm types, were matched to strengthening techniques, thus obtaining a preliminary description of that sample. The empirical evidence showed the performance levels of buildings with interventions, which were graded in four categories: upgrading and improvement, downgrading and worsening depending on their compliance with the box-like behaviour. Therefore, an expansion of the coded possible performance levels was found. Those levels entered the final taxonomy of the sample, yielding 15 robust performance-based types, which were cross-validated through the analysis of their most common damage mechanisms.

Application of Multiple Random Forest Algorithm in Image Segmentation of Nanoparticles

Because of its large specific surface area, small particle size, high surface energy, and unique nanoeffect, the morphological characteristics of nanoparticles are the key factors affecting the properties of materials. How to detect and evaluate the morphological characteristics of nanoparticles is the first problem to be solved in the preparation and application of nanomaterials. The main purpose of this paper is to use TEM to recognize the image features of nanoparticles and introduce the transmission electron microscope and image edge segmentation method and random forest algorithm. A method integrating the in situ characterization of modern electron microscopy and the measurement of the electrical properties of nanomonomers was developed. In this paper, a multielectrode TEM in situ electrical measurement platform is prepared, which improves the contact during the integration of nanomaterials and improves the electrical measurement accuracy of the TEM in situ electrical method. In this paper, based on the random forest algorithm, a multirandom forest algorithm is proposed. Due to the different gray levels of images referenced by the multirandom forest algorithm, the segmentation results are processed by FCM clustering algorithm. Experimental results show that in terms of image segmentation accuracy, the minimum Jaccard coefficient obtained by multiple random forest algorithm is 89% and 95%, respectively, which is obviously better than watershed segmentation method and maximum entropy threshold segmentation. In the aspect of automatic image segmentation of nanoparticles, the image segmentation accuracy is the highest when the sample block size and the number of sample blocks selected in the multiple random forest algorithm are 5∗5, 7500, and 35, respectively. Therefore, the multirandom forest algorithm has achieved high accuracy in image segmentation of nanoparticles, which provides valuable information for the preparation and application of nanomaterials. A new type of TEM dark‐field imaging diaphragm was prepared, which greatly improved the imaging quality of weak‐phase bulk materials represented by graphene and nonspiral biological samples represented by intracellular polyvesicles.

소듐냉각고속로를 위한 온도 영향 보정형 압력전송기 개념 개발

The sodium maintains the liquid phase in wide range of temperature and its heat transfer characteristics are excellent. It can be used as a coolant for heat transport system such as sodium-cooled fast reactors. However, the operating temperature is high and it must be isolated to prevent chemical reaction due to its high reactivity. The pressure is one of the key I&C factors to monitor and control the thermal-fluidic system and so the sensing technology for liquid sodium is very important. For the pressure sensor for liquid sodium, NaK-filled type pressure transmitter which uses NaK as a pressure transfer material has been developed and generally used. For the NaK-filled type, effect of temperature is required to be minimized and compensated since thermal expansion of inner pressure transfer material affects output signal at high temperature. In this study, a novel concept of diaphragm type pressure transmitter is proposed for compensating temperature effect. A temperature compensated concept for pressure transmitter is verified by experiments using a set-up which enables temperature and pressure control of a chamber.

Mitochondrial morphology and function varies across diaphragm muscle fiber types

In diaphragm muscle (DIAm), type I and IIa fibers are recruited to accomplish breathing, while type IIx/IIb fibers are recruited only during expulsive/straining behaviors. Thus, type I and IIa DIAm fibers are much more active (duty cycle of ∼40 %) than type IIx/IIb fibers (duty cycle of <1%), which we hypothesized underlies intrinsic differences in mitochondrial structure and function. MitoTracker Green labeled mitochondria were imaged in 3-D using confocal microscopy. Mitochondrial volume density (MVD, per muscle fiber volume) was higher, and mitochondria were more filamentous in type I and IIa DIAm compared to type IIx/IIb fibers. The maximum velocity of the succinate dehydrogenase reaction (SDHmax), measured using a quantitative histochemical technique was found to be higher in type I and IIa DIAm fibers compared to type IIx/IIb fibers with and without normalizing for MVD. These results are consistent with fiber type differences in the intrinsic structural and functional properties of DIAm fibers and closely match differences in energetic demands.

Regulation response of pilot-operated diaphragm type pressure-reducing valves: laboratory testing and impact on the performance of pressure control modes in water distribution systems

Pressure control is recognized as an efficient measure for reducing leaks from water distribution systems. We have evaluated the effectiveness of various pressure control modes by means of pilot-operated diaphragm type pressure-reducing valves (PRVs), taking into account the sensitivity of the valves to various settings. First, the response of a PRV to consecutive pressure settings variations was experimentally evaluated in the hydraulic simulation laboratory of National Institute for Scientific Research. These experiments revealed that the studied valve only reacts when variation in the pressure setting corresponds to at least a 1/6 turn of the pilot valve. Second, an actual case study from Quebec City, Canada, was simulated to evaluate the impact of the PRV response on three pressure control modes: fixed control, time-based control, and real-time control (RTC). The results show that RTC of pressure leads to reductions in leakage rate for the studied network but that the PRV operational constraints limit the expected performance of RTC.

(Invited) Development of Pulse-Heated Diaphragm Type MEMS Gas Sensors for Indoor Air Quality Measurement

IntroductionAmid growing concern about indoor air quality (IAQ), MOS type gas sensors for the detection of volatile organic compounds (VOC) are widely used in household appliances such as air purifiers for on-demand control of the appliances depending on VOC concentration in surrounding air. There are also potential demands for gas sensors to be used for mobile applications, with which people can monitor environmental conditions in dwelling or workplaces. However, detection accuracy, power consumption and cost of conventional MOS type gas sensors have not yet reached the level generally required for VOC concentration monitoring by mobile applications. To solve these issues, we have developed a new diaphragm type MEMS gas sensor, and studied their appropriate pulsed heating conditions. This optimized MEMS sensor chip was integrated with an ASIC with built-in temperature and humidity sensors in a SMD package, and its practical performance and mechanical durability were evaluated.Sensor structuresTwo types of MEMS structures were used for this study as shown in Fig.1. Air-bridge type MEMS structure [1] [2] which is being produced on a commercial basis has a square-shaped micro hot plate (MHP) with dimensions of 0.1 x 0.1 mm. Materials of the sensor electrodes and heater are Platinum, and the gas sensing material is Palladium doped Tin dioxide, which is turned into a paste using terpineol as a solvent. The gas sensing material was applied onto the MHP by micro dispenser, and then was calcined at 450°C for 3 hours in an electric furnace. The newly developed diaphragm type MEMS structure has a round shape MHP with 270m diameter which can avoid stress concentration of SiN/SiO2 membrane. Thickness of each layer stacked on the MHP was also optimized to achieve uniform dispersion of internal stress. The same sensing material as above mentioned was applied onto the MHP of the diaphragm type MEMS by screen printing method so that the gas sensing layers are formed in one printing pass on a wafer that produces 74K chips of MHP.MethodIn order to determine the appropriate pulsed heating conditions and thickness of the sensing material, sensor resistances in air (Ra) and in various concentrations of gases (Rg) were measured by using the air-bridge type MEMS sensor. The sensing material was intermittently heated for 100 msec. at several different temperature conditions in a range from 300 ~ 450 °C, and at different heating intervals ranging from 1 ~ 60 seconds. The thickness of gas sensing layer was varied in a range from 20 ~ 50 micro meters. For the diaphragm type MEMS sensor, the sensing material was heated at 430°C for 100 msec. at 1 second intervals.Results and ConclusionsSensing characteristics of the air-bridge type MEMS sensor to toluene and ethanol were investigated at different working temperature as shown in Fig. 2. Response to toluene increased as the working temperature decreased within the range between 350°C and 450°C, suggesting the capability for detecting low concentration toluene below 1 ppm. On the other hand, Response to ethanol within the same temperature range remained largely the same. Toluene and ethanol sensitivities both drastically dropped at 300°C. There were significant differences in toluene response depending on the heating intervals as shown in Fig.3. Response to toluene became smaller as the heating interval was longer. This result implies that a reaction of the gas sensing material with gas was inhibited by water vapor which had adsorbed on the surface of the sensing element during the heater OFF period. As for the effect of sensing material thickness on sensitivity, ethanol sensitivity was relatively more affected by the thickness than toluene. The sensor with the thinnest sensing layer showed the highest ethanol response, especially at a short heating interval.Taking these results into consideration, driving conditions of the diaphragm type MEMS sensor were determined as described above. Its sensing characteristics to various gases were examined as shown in Fig. 4. This sensor showed a particularly large response to m-xylene and hydrogen sulfide which are both among the major indoor air pollutants, and very small response to hydrogen and methane, both of which would work as an interference gas in IAQ measurement if present in ambient air. It was confirmed in parallel that the diaphragm type MEMS sensor with the determined driving conditions has a sufficient mechanical durability under the heater ON/OFF cycle test equivalent to 10 years operation, and the drop test which is required for mobile applications. The diaphragm type MEMS sensor produced by high-efficiency screen printing method was expected to have a capability as a practical solution for mobile IAQ monitoring. In addition, user-friendliness of the sensor was much improved by integrating with ASIC in comparison with conventional type single sensor.

Features and Structure of Diaphragm Type Vacuum Pump

The diaphragm type vacuum pump is a vacuum pump that exhausts gas using the reciprocating motion of the diaphragm. Especially, it is not contaminated by oil vapor. This pump is ideal for applications that require a clean atmosphere. With the recent rapid development of the semiconductor manufacturing industry and the electronics equipment industry, demand for the diaphragm type vacuum pump has also been increasing.

Numerical and Experimental Analyses of a Variable Buoyancy System for an Autonomous Underwater Vehicle

Autonomous Underwater Vehicles (AUVs) are widely used for marine survey, in both the coastal and deep sea areas and they are applicable to both civil and defense applications. They are pre-programmed and can operate without human intervention and this makes them attractive to many marine industries. A concern with AUVs is the high energy consumption required by their thrusters for depth control, buoyancy change and manoeuvrability and that adversely affects their performance and endurance. This paper presents the design and development of novel stand-alone variable buoyancy system for AUVs and investigates its performance through numerical and experimental investigations. The design idea is based upon the Pump Driven Variable Buoyancy System (PDVBS) and uses a hydraulic based method to control the buoyancy. The VBS is integrated into a medium sized AUV of 3 m length and the performance of the vehicle in vertical plane is investigated. The results are presented for a buoyancy change requirement of 5 kg and a diaphragm type positive displacement pump, with a buoyancy change rate of 5 kg/min, is utilized. Depth control performance of the AUV and its hovering capabilities, at a desired depth of 60 m using the Linear Quadratic Regulator (LQR) controller, are analysed in detail. Finally, the results indicate that the designed and developed VBS is effective in changing the buoyancy and controlling the heave velocity. These two features are expected to provide higher endurance and better performance in AUVs involved in rescue/attack operations.