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

ASSESSING CONSUMER BEHAVIOR TOWARDS FISH SAUCE PRODUCTS BY USING FOOD CHOICE QUESTIONNAIRE

This study aims to assess Vietnamese consumer behavior towards fish sauce product. It consists of two experiments. In the first experiment, consumer concept was explored using word association method. It was performed on 300 Vietnamese consumers with the prompt word as “fish sauce”. The data were analyzed by a triangulation method. The results evoke six factors associated with fish sauce as Sensory Appeal, Health, Price, Convenience, Traditional Value, Quality and Safety. These findings were the starting point for a modification of food choice questionnaire (FCQ) adapted to fish sauce product. In the second experiment, the modified FCQ with 18 items was used to assess the consumer behavior. The survey was performed on 300 Vietnamese consumers. The data were analyzed by using Exploratory Factor Analysis and Confirmatory Factor Analysis. The obtained model with five factors was adapted to fish sauce for Vietnamese consumers ( = 1.67, GFI = 0.93, CFI = 0.92, RSME = 0.47). In this, Sensory Appeal is the most important factor which might affect consumer food choice motivations. We expect that these results will be useful for the local manufacturers who want to develop traditional food products and/or enlarge national market

Vehicle classification by estimation of the direction angle in a mixed traffic flow

The application of Intelligent Transportation System (ITS) is very important in developing societies nowadays. Vehicle monitoring is one of the primary tasks of ITS, where vehicles are classified by lanes for traffic management, especially in case of a mixed flow of motorcycles and other automobiles in the transport system of Vietnam. This paper proposes a new approach in vehicle classification, which is based on evaluation of the direction angle of the first primary axis of each coming vehicle detected in the captured video sequence and map into the predetermined database to mark it as motorcycle or automobiles instead of consideration of vehicle size. The experimental results show that the classification performance is promising, especially for motorcycles and cars, and therefore is applicable in detection of vehicle penalties moving in wrong lanes

Isolation and identification of indole acetic acid producing bacteria from the coasts of Ben Tre and Tra Vinh Provinces

Beneficial plant-growth-promoting bacteria (PGPB) have been reasonably applied to rescue crucial issue for agriculture by salinity soil. Observed most of PGPB was found in endophyte, rhizosphere and soil. Indole acetic acid (IAA)-producing bacteria could naturally stimulate and facilitate plant growth. The knowledge of IAA production and content of bacteria resident in the marine environment has been typically insufficient and limited to date. In recent years, unwarrantable intrusions of sea water have been enlarged in the Mekong River Delta of Vietnam, threatening productive rice fields, local fruits, and cash crops. Therefore, finding PGPB in the coastal regions in the Mekong River Delta as a creative resource for sustainable agriculture is necessary and is a prompt challenge. In this study, IAA-producing bacteria from coastal regions of Ben Tre and Tra Vinh Provinces were isolated and adequately identified. Out of 202 bacterial isolates, 10 isolates showed the possible ability to produce IAA from L-tryptophan. These 10 isolates were objectively evaluated the capacity to produce IAA under 5% (w/v) NaCl in King B and marine broths. The results revealed that IAA production decreased in 5% NaCl, even though bacterial growth increased. These 10 IAA-producing bacteria were classified at the species level, Marinobacter hydrocarbonoclasticus, M. pelagius, M. daepoensis, and Mameliella phaeodactyli by 16S rRNA gene analysis. The most IAA producer in King’s B broth, the isolate C7, was investigated in more detail. The isolate C7 produced the maximum IAA amount (192.2 ± 1.14 µg/ml) under the presence of 20 g/l yeast extract, 2 g/l of L-tryptophan and 1% NaCl. The isolate C7 was able to grow at 1–17% (w/v) NaCl (optimum, 4%), but not in the absence of NaCl, indicating it is a moderate halophilic bacteria. This study highlighted the considerable ability to produce IAA of marine bacteria, which could be thoughtfully considered to use naturally as biofertilizers to promote plant growth in saline intrusion lands.

A hot-film air flow sensor for elevated temperatures

We report a novel packaging and experimental technique for characterizing thermal flow sensors at high temperatures. This paper first reports the fabrication of 3C-SiC (silicon carbide) on a glass substrate via anodic bonding, followed by the investigation of thermoresistive and Joule heating effects in the 3C-SiC nano-thin film heater. The high thermal coefficient of resistance of approximately −20 720 ppm/K at ambient temperature and −9287 ppm/K at 200 °C suggests the potential use of silicon carbide for thermal sensing applications in harsh environments. During the Joule heating test, a high-temperature epoxy and a brass metal sheet were utilized to establish the electric conduction between the metal electrodes and SiC heater inside a temperature oven. In addition, the metal wires from the sensor to the external circuitry were protected by a fiberglass insulating sheath to avoid short circuit. The Joule heating test ensured the stability of mechanical and Ohmic contacts at elevated temperatures. Using a hot-wire anemometer as a reference flow sensor, calibration tests were performed at 25 °C, 35 °C, and 45 °C. Then, the SiC hot-film sensor was characterized for a range of low air flow velocity, indicating a sensitivity of 5 mm−1 s. The air flow was established by driving a metal propeller connected to a DC motor and controlled by a microcontroller. The materials, metallization, and interconnects used in our flow sensor were robust and survived temperatures of around 200 °

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

Electrically stable carbon nanotube yarn under tensile strain

We report a highly stable electrical conductance of a compact and well-oriented carbon nanotube yarn under tensile strain. The gauge factor of the yarn was found to be extremely small of approximately 0.15 thanks to the improvements in the dry spinning process, includingmultiweb spinning and heat treatment. The threshold strain εs, below which the yarn retains its electrical conductance stability, has also been determined to be approximately 15 × 103 ppm. Owing to its highly stable resistance under mechanical strain, the yarn has a good potential as a wiring material for niche applications,where lightweight and resistance stability are required

CONTAMINATION BY PERSISTENT ORGANIC POLLUTANTS AND ENDOCRINE DISRUPTING CHEMICALS IN VIETNAM : PATTERNS, BEHAVIOR, TRENDS AND TOXIC POTENTIAL

Joint Research on Environmental Science and Technology for the Eart

Advances in Rational Design and Materials of High Performance Stretchable Electromechanical Sensors

Stretchable and wearable sensor technology has attracted significant interests and created high technological impact on portable healthcare and smart human–machine interfaces. Wearable electromechanical systems are an important part of this technology that has recently witnessed tremendous progress toward high‐performance devices for commercialization. Over the past few years, great attention has been paid to simultaneously enhance the sensitivity and stretchability of the electromechanical sensors toward high sensitivity, ultra‐stretchability, low power consumption or self‐power functionalities, miniaturisation as well as simplicity in design and fabrication. This work presents state‐of‐the‐art advanced materials and rational designs of electromechanical sensors for wearable applications. Advances in various sensing concepts and structural designs for intrinsic stretchable conductive materials as well as advanced rational platforms are discussed. In addition, the practical applications and challenges in the development of stretchable electromechanical sensors are briefly mentioned and highlighted