Piezoresistive effect of p-type single crystalline 3C-SiC on (111) plane

This paper presents for the first time the effect of strain on the electrical conductivity of p-type single crystalline 3C-SiC grown on a Si (111) substrate. 3C-SiC thin film was epitaxially formed on a Si (111) substrate using the low pressure chemical vapor deposition process. The piezoresistive effect of the grown film was investigated using the bending beam method. The average longitudinal gauge factor of the p-type single crystalline 3C-SiC was found to be around 11 and isotropic in the (111) plane. This gauge factor is 3 times smaller than that in a p-type 3C-SiC (100) plane. This reduction of the gauge factor was attributed to the high density of defects in the grown 3C-SiC (111) film. Nevertheless, the gauge factor of the p-type 3C-SiC (111) film is still approximately 5 times higher than that in most metals, indicating its potential for niche mechanical sensing applications

Impact of electronic word of mouth to the purchase intention - the case of Instagram

This research aims to discover and confirm the factors of e-WOM that influence users' shopping intentions on Instagram. The data was collected from 700 customers who belong to Gen Y and Gen Z from 18 to 39 years old who live and work in Vietnam. The research model and the scales were built from the empirical research of e-WOM from Lim (2016); Park et al. (2007); Prendergast et al. (2010). Quantitative methods were performed by Cronbach's Alpha reliability testing, EFA discovery factor analysis, regression, and ANOVA test. The research results showed that the fourth factor of e-WOM positively impacts users' purchase intent on Instagram with decreasing levels as Information Provider's Expertise, the quantity of e-WOM, and the Source credibility of e-WOM, and the quality of e-WOM, respectively. Also, users' purchase intention on Instagram under the impact of e-WOM varies by gender, but there is no difference by age and income

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

Reservoir optimization with differential evolution

Reservoir optimization, is one of recent problems, which has been researched by several methods such as Linear Programming (LP), Non-linear Programming (NLP), Genetic Algorithm (GA), and Dynamic Programming (DP). Differential Evolution (DE), a method in GA group, is recently applied in many fields, especially water management. This method is an improved variant of GA to converge and reach to the optimal solution faster than the traditional GA. It is also capable to apply for a wide range space, to a problem with complex, discontinuous, undifferential optimal function. Furthermore, this method does not requirethe gradient information of the space but easily find the global solution by asimple algorithm. In this paper, we introduce DE, compare to LP which was considered mathematically decades ago to prove DE's accuracy, then apply DE to Pleikrong, a reservoir in Vietnam, then discuss about the results

STUDY ON CAUSE-EFFECT RELATIONS AND OPTIMIZATION OF TABLETS CONTAINING AQUILARIA CRASSNA SPRAY-DRIED EXTRACT

Objective: The aim of this study was to develop and optimize the formulation of tablets containing Aquilaria crassna extract using the direct compression method.Methods: D-optimal design based on three independent variables was applied to evaluate the cause-effect relations and optimize the A. crassna tablet formulation. The weight variation (Y1), disintegration time (Y2), hardness (Y3) and friability (Y4) were investigated with respect to three independent variables including % dicalcium phosphate anhydrous (DCPA) in filler (X1), % filler (X2) and % croscarmellose sodium (CCNa) (X3). The dissolution study of the optimized A. crassna tablets were investigated in simulated gastric fluid (SGF) (pH 1.2) using a validated high-performance liquid chromatography (HPLC) method for mangiferin analysis.Results: All investigation factors were found to have significant effects on the physical properties of A. crassna tablet. The tablet hardness and the disintegration time increased in positive relations with the ratios of DCPA. The results exhibited the negative relations between disintegration time and the percentages of CCNa. The optimized A. crassna tablet formulation which included 35 % (w/w) DCPA in filler, 60 % (w/w) filler and 7% (w/w) CCNa possessed the weight variation of 1.38 % (w/w), the disintegration time of 6.29 min, the hardness of 85.63 N and the friability of 0.41 % (w/w). The optimized A. crassna tablet formulation was experimentally examined which demonstrated a good agreement between the experimental and predicted values. Mangiferin was found to release completely from the optimized A. crassna tablets within 30 min.Conclusion: The cause-effect relations and optimization of A. crassna tablet formulation were investigated and reported for the first time. The A. crassna spray-dried extract could be formulated into tablet by direct compression method with good mechanical properties and acceptable release profile

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

Factors affecting the creativity of high school students

Creativity is a vital personality quality of each individual. Each person has their potential for creativity, and it can be nurtured and developed in an appropriate and safe environment. The purpose of the study was to find out which factors from schools and students themselves affect creativity as well as the association between creativity and age, gender and giftedness of students, which then a basis to adjust and establish appropriate methods from schools, families, and students themselves to develop elements and their creativity. The study was conducted on 108 high school students in three grades from giftedness and non-giftedness schools. The data was collected through a survey method using a self-constructed questionnaire and drawing creativity test TCT-DP to determine students' creativity levels and personal information. The study's finding, which uses mathematical methods and one-way analysis of variance, reveals that factors affecting elements and creativity level are objective factors including education environment from school; behavior of teachers, and subjective factors including interests, perspectives, and thoughts of students. It was also found that there were no significant differences in the components of creativity and creativity among students in different grades, gender, and groups of giftedness schools

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

The relationship between brand equity and intention to buy: the case of convenience stores

The research aims to identify the components of brand equity that affect consumer purchasing intentions and measure the effect of brand equity components on the intention of consumer purchases at the convenience stores in Ho Chi Minh City. The authors conduct the group discussions, expert discussion, and then analyze data from 200 valid questionnaires with four components of brand equity, namely perceived quality, brand loyalty, brand association, brand awareness. The results of Exploratory Factor Analysis (EFA) show that all four elements have a positive effect on the customer' intention to purchase in the convenience store of Ho Chi Minh City. In particular, the brand association factor has the strongest influence, followed by perceived quality, brand awareness, and brand loyalty. This research contributes that the results confirm the theory of Aaker (1991), Brown and Stayman (1992), Cobb-Walgren et al. (1995), MacKenzie (1986) in the new context of convenience stores in Ho Chi Minh City, Vietnam. Besides, the study gives some recommendations to help convenience stores improve the elements of brand equity and it, to enhance attraction for consumers

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 °