A research on the performance of down-flow hanging sponge (DHS) reactor treating domestic wastewater

The aim of this study was to evaluate the performance of a down-flow hanging sponge (DHS) system in treating domestic wastewater. A pilot-scale of DHS system with a capacity of 60 L was designed and fabricated from polyvinyl chloride (PVC). The dimensions of DHS system are 1.5 m in height and square surface with 0.2 m in width, consists of three identical segments connected vertically in series. Each segment was filled by polyurethane sphere containing sponge. The total area of sponge and polyurethane sphere was 3,300 m2 m-3, density at 150 kg m-3, void ratio at 90%. DHS system was operated at ambient temperature within 82 days and stepwise increased of organic f rate from 0.5 to 1 and 1.5 kg COD m-3 d-1. The results showed that, this system performed well throughout the operational period and achieve the maximum removal of COD, BOD5, NH4+-N, and TN as 80%, 83%, 65% and 60%. The effluent of wastewater from DHS system achieved the requirement for National technical regulation on domestic wastewater of Vietnam type B QCVN 14:2008/BTNMT. In conclusion, the performance of DHS system indicated a high potential for application in removing organic matter and converting nitrogen ammonia to nitrogen nitrate, however it did not perform well for the removal of total nitrogen, it is necessary to study further by providing an anoxic zone in the system to enhance the treatment of nutrient in wastewater

Thermoresistance of p-Type 4H–SiC Integrated MEMS Devices for High-Temperature Sensing

There is an increasing demand for the development and integration of multifunctional sensing modules into power electronic devices that can operate in high temperature environments. Here, the authors demonstrate the tunable thermoresistance of p‐type 4H–SiC for a wide temperature range from the room temperature to above 800 K with integrated flow sensing functionality into a single power electronic chip. The electrical resistance of p‐type 4H–SiC is found to exponentially decrease with increasing temperature to a threshold temperature of 536 K. The temperature coefficient of resistance (TCR) shows a large and negative value from −2100 to −7600 ppm K−1, corresponding to a thermal index of 625 K. From the threshold temperature of 536–846 K, the electrical resistance shows excellent linearity with a positive TCR value of 900 ppm K−1. The authors successfully demonstrate the integration of p–4H–SiC flow sensing functionality with a high sensitivity of 1.035 μA(m s−1)−0.5 mW−1. These insights in the electrical transport of p–4H–SiC aid to improve the performance of p–4H–SiC integrated temperature and flow sensing systems, as well as the design consideration and integration of thermal sensors into 4H–SiC power electronic systems operating at high temperatures of up to 846 K

MODIFICATION OF POLYSULFONE ULTRAFILTRATION MEMBRANES WITH PVA AND TiO2 FOR BETTER ANTIFOULING

The objective of this study was to investigate anti-fouling property of modified polysulfone ultrafiltration  (UF) membranes.  Polysulfone UF membranes were modified  by  coating  a  thin film of polyvinyl alcohol (PVA), or a mixture of polyvinyl alcohol and titanium dioxide (TiO2) on  surface.  Effects  of  curing  temperature  on  the  coated  membranes  were  also  studied.  The modified  membranes  were  tested  with  0.5  g/L  sodium  alginate  solution  and  industrial  dye wastewater.  Curing  temperature  influenced  remarkably  flux  and  fouling  property  of  the membranes. Among experiments studied, 85 oC was the best curing temperature. The PVA and PVA/TiO2-coated membranes reduced fouling significantly. Dispersion of TiO2 nanoparticles on membrane surface improved considerably bacteria removal of the membranes

OPTIMIZATION OF CONDITIONS FOR EXTRACTION OF COLLAGEN FROM THE SKINS OF BASA FISH (PANGASIUS HYPOPHTHALMUS) BY THE RESPONSE SURFACE METHOD

Collagen has been used widely in the production of pharmaceutical and cosmetic products. Fishbased collagen has still more advantages than other sources of collagen and becomes an object of interested researches recently. Extraction and some properties of collagens from the skin of Pangasius hypophthalmus fish were investigated. Pepsin enzyme and acetic-acid solution was used as an extracting solvent. The optimal conditions for collagen extraction were determined by response surface methodology. The effects of four independent variables (pepsin enzyme content, acetic-acid concentration, liquid/solid ratio, and temperature) on the extraction yield of collagen from Pangasius hypophthalmus skin were evaluated. The optimal conditions to obtain the highest yield were determinded as follows: a pepsin enzyme content of 0.25%, a acetic-acid concentration of 0.75 M, a liquid/solid ratio of 80, a temperature of 14oC. The predicted yield was 73% which was in agreement with the actual value (P0.05).  The molecular weights of α1, α2 and β chains in collagen were estimated to be 115 and 125 and 240 kDa, respectively. Keywords: fish collagen, extraction, pangasius hypophthalmu

Nano strain-amplifier: making ultra-sensitive piezoresistance in nanowires possible without the need of quantum and surface charge effects

This paper presents an innovative nano strain-amplifier employed to significantly enhance the sensitivity of piezoresistive strain sensors. Inspired from the dogbone structure, the nano strain-amplifier consists of a nano thin frame released from the substrate, where nanowires were formed at the centre of the frame. Analytical and numerical results indicated that a nano strain-amplifier significantly increases the strain induced into a free standing nanowire, resulting in a large change in their electrical conductance. The proposed structure was demonstrated in p-type cubic silicon carbide nanowires fabricated using a top down process. The experimental data showed that the nano strain-amplifier can enhance the sensitivity of SiC strain sensors at least 5.4 times larger than that of the conventional structures. This result indicates the potential of the proposed strain-amplifier for ultra-sensitive mechanical sensing applications.Comment: 4 pages, 5 figure

A rapid and cost-effective metallization technique for 3C-SiC MEMS using direct wire bonding

This paper presents a simple, rapid and cost-effective wire bonding technique for single crystalline silicon carbide (3C–SiC) MEMS devices. Utilizing direct ultrasonic wedge–wedge bonding, we have demonstrated for the first time the direct bonding of aluminum wires onto SiC films for the characterization of electronic devices without the requirement for any metal deposition and etching process. The bonded joints between the Al wires and the SiC surfaces showed a relatively strong adhesion force up to approximately 12.6–14.5 mN and excellent ohmic contact. The bonded wire can withstand high temperatures above 420 K, while maintaining a notable ohmic contact. As a proof of concept, a 3C–SiC strain sensor was demonstrated, where the sensing element was developed based on the piezoresistive effect in SiC and the electrical contact was formed by the proposed direct-bonding technique. The SiC strain sensor possesses high sensitivity to the applied mechanical strains, as well as exceptional repeatability. The work reported here indicates the potential of an extremely simple direct wire bonding method for SiC for MEMS and microelectronic applications