Design and Experimental Analysis of Charge Recovery for Piezoelectric Fan

The piezoelectric (PE) fan is widely adopted in the field of microelectronics cooling due to its advantages of high reliability and good heat dissipation characteristics. However, PE fans driven by conventional circuits suffer from plenty of energy loss. To save energy, we propose an inductor-based charge recovery method and apply it to the driving circuit for the PE fan. Two inductor-based driving circuits, a single inductor-based driving (SID) circuit and a double inductor-based driving (DID) circuit are compared. The SID circuit has a simple structure and a slightly higher energy-saving rate, while the DID circuit introduces no additional oscillations and is more stable. The experimental results show that when the supply voltage changes, both circuits have a relatively stable energy-saving rate, which is about 30% for the SID circuit and 28% for the DID circuit. Moreover, the proposed circuits enjoy the same driving capacity as the conventional circuit, and the driven fan has the same cooling performance.

Experimental Evaluation of the Blackbody Radiation Shift in the Cesium Atomic Fountain Clock

The cesium atomic fountain clock is the world’s most accurate microwave atomic clock. The uncertainty of blackbody radiation (BBR) shift accounts for an increasingly large percentage of the uncertainty associated with fountain clocks and has become a key factor in the performance of fountain clocks. The uncertainty of BBR shift can be reduced by improving the system environment temperature. This study examined the mechanism by which the BBR shift of the transition frequency between the two hyperfine energy levels of the 133Cs ground state is generated and the calculation method for the BBR shift in the atomic fountain. Methods used to reduce the uncertainty of BBR shift were also examined. A fountain system structure with uniform temperature and good heat preservation was designed, and related technologies, such as that for measuring the temperature of the cesium fountain system, were studied. The results of 20 days of measurements, in combination with computer simulation results, showed that the temperature uncertainty of the atomic action zone is 0.12 °C and that the resulting uncertainty of BBR shift is 2.4 × 10−17.

A Multi-Objective Design Optimization for a Permanent Magnet Synchronous Machine with Hairpin Winding Intended for Transport Applications

Nowadays, interest in electric propulsion is increasing due to the need to decarbonize society. Electric drives and their components play a key role in this electrification trend. The electrical machine, in particular, is seeing an ever-increasing development and extensive research is currently being dedicated to the improvement of its efficiency and torque/power density. Among the winding methods, hairpin technologies are gaining extensive attention due to their inherently high slot fill factor, good heat dissipation, strong rigidity, and short end-winding length. These features make hairpin windings a potential candidate for some traction applications which require high power and/or torque densities. However, they also have some drawbacks, such as high losses at high frequency operations due to skin and proximity effects. In this paper, a multi-objective design optimization is proposed aiming to provide a fast and useful tool to enhance the exploitation of the hairpin technology in electrical machines. Efficiency and volume power density are considered as main design objectives. Analytical and finite element evaluations are performed to support the proposed methodology.

Rice flour as a heat insulator for learning media for students with special needs

The objective of this study was to determine the use of rice flour as a heat insulator for learning media for students with special needs. Experiments were done method by testing rice flour placed on the wall that heat radiated by bulb lamp with various intensities (i.e. 8, 10, and 12 W). The results showed that rice flour is a good heat insulator. This is confirmed by the test results using thermocouple tools showing a decrease in temperature of the insulator testing toolbox. The rice flour caused the heat from the lamp inside the box to be restrained from spreading out completely. The concept of heat radiation and the change of heat adsorbed by rice flour was explained, which can be further developed for learning media for students with special needs. The results of this study are expected to facilitate teachers in providing understanding to students in understanding the occurrence of heat insulators, especially for students with special needs.

Tapioca flour as a heat insulator for learning media for students with hearing impairments

The objective of this study was to determine the use of tapioca flour as a heat insulator for learning media for students with hearing impairments. Experiments were done method by testing tapioca flour placed on the wall that heat radiated by bulb lamp with various intensities (i.e. 8, 10, and 12 W). The results showed that tapioca flour is a good heat insulator. This is confirmed by the test results using thermocouple tools showing a decrease in temperature of the insulator testing toolbox. The tapioca flour caused the heat from the lamp inside the box to be restrained from spreading out completely. The concept of heat radiation and the change of heat adsorbed by tapioca flour was explained, which can be further developed for learning media for students with hearing impairment. The results of this study are expected to facilitate teachers in providing understanding to students in understanding the occurrence of heat insulators, especially for students with hearing impairments.

Modelling of Jatropha Oil Hydrocracking in a Trickle-Bed Reactor to Produce Green Fuel

Trickle-bed reactor (TBR) modelling to produce green fuel via hydrocracking of jatropha oil using silica-alumina-supported Ni-W catalysts was performed in this research. The objectives of this study are to obtain a TBR with good heat transfer and the optimum condition for high purities of products. A two-dimensional axisymmetric model with a diameter of 0.1 m and a length of 10 m was used as a representative of the actual TBR system. Heterogeneous phenomenological models were developed considering mass, energy, and momentum transfers. The optimisation was conducted to obtain the highest green fuel purity by varying catalyst particle diameter, inlet gas velocity, feed molar ratio, and inlet temperature. The simulation shows that a TBR with an aspect ratio of 100 has achieved a good heat transfer. The diesel purity reaches 44.22% at 420°C, kerosene purity reaches 21.39% at 500°C, and naphtha purity reaches 25.30% at 500°C. The optimum condition is reached at the catalyst diameter of 1 mm, the inlet gas velocity of 1 cm/s, the feed molar ratio of 105.5, and the inlet temperature at 500°C with the green fuel purity of 69.4%.

Effect of graphite microstructure on their physical parameters and wettability properties

To produce castings of titanium, nickel, zinc, copper and many other metal alloys, graphite molds can be used. Using graphite molds has many advantages which are no lubricate or coating layers are needed, high cooling rate, easy of production of complicated shapes. However, for good quality of castings there is needed a good quality of graphite with high mechanical properties and good heat transfer coefficient. Because of no room for manipulating of chemical composite of graphite molds, the most important factor influencing the properties of the molds is their production process. Thus, in the present study mechanical properties of two different type of graphite were investigated. There was graphite produced by different technological processes. One of the processes was a typical graphite production process from the isotropic coke, the second process was an electrolytic method production. Investigations included mechanical tests as well as the structure observations by scanning electron microscope. Chemical analysis was determined by Energy Dispersive X-ray Spectroscopy method additionally, phase analysis using the XRD method was performed. Mechanical properties were obtained by compression tests and three points banding tests at room temperature. It was found that the porosity of a graphite is the key parameter for good its mechanical properties. In addition, it was found that the mechanical anisotropy of graphite is the effect of the production method where the size and distribution of pores play an important role. Ill. 7. Ref. 9.

Effects of Black Scoria on Mechanical Properties and Thermal Insulation Properties of Building Materials

The effect of fine black scoria on the mechanical properties and thermal conductivity of building materials was investigated in this study. Black scoria was used to replace cement in concrete with various percentages. Four concrete samples containing 0%, 10%, 20%, and 30% black scoria were prepared. Characterization black scoria was performed via X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry analysis. Then, the compressive strength of the samples was investigated after 14, 21, 28, and 91 days of curing at room temperature. Finally, the thermal conductivities of the samples were measured after 28 days. Based on the experimental results, the highest compressive strength among the samples was 45.3 MPa, obtained from the mixture containing 10% black scoria after 91 days of curing. It was also observed that the average thermal conductivity of the concrete samples decreased with an increase in the fine black scoria content from 1.8 to 0.193 W m−1 K−1. Thus, black scoria is an appropriate substitute for commercial admixtures in cement composites in thermally insulating building materials due to its low density, excellent compressive strength, and good heat insulation properties.

The Effect of Mold Conditions on Heat Resistance of Injection-Molded Stereocomplex Polylactide-b-polyethylene Glycol-b-Polylactide Bioplastic

The effect of mold conditions was investigated in terms of mold temperature (30oC and 90oC) and cooling time (30 s and 60 s) on the heat resistance of injection-molded bars for stereocomplex polylactide-b-polyethylene glycol-b-polylactide (scPLA-PEG-PLA). Comparative study was performed for poly(L-lactide) (PLLA) and PLLA-b-PEG-b-PLLA (PLLA-PEG-PLLA). scPLA-PEG-PLA was 90/10 (w/w) PLLA-PEG-PLLA/poly(D-lactide) blend. scPLA-PEG-PLA exhibited the easiest crystallization upon cooling scan as shown by differential scanning calorimetry (DSC). Higher mold-temperature and longer cooling-time induced higher degree of crystallinity as assessed by X-ray diffractometry (XRD) except for PLLA bars. The heat resistance of both PLLA-PEG-PLLA and scPLA-PEG-PLA bars was improved with increased mold-temperature and cooling-time as shown by dynamic mechanical analysis (DMA), vicat softening temperature (VST) and heat distortion-resistance tests except for PLLA bars. In conclusion, the heat resistance of injection-molded bars prepared at 90˚C mold temperature was in the order scPLA-PEG-PLA ] PLLA-PEG-PLLA ] PLLA. The results suggested that flexible PLLA-PEG-PLLA and scPLA-PEG-PLA with high degrees of crystallinity were successfully obtained by injection molding for use as good heat-resistant bioplastic products.