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By eliminating the influence of the substrate on parasitic thermal resistance, MEMS suspended structures become one of the accurate nanoscale thermoelectric performance evaluation devices. However, the process of MEMS suspended thermoelectric devices is complex, and its multilayer suspended structure is easy to fracture due to large stress. As a result, optimizing the design of suspended structures is critical in order to reduce manufacturing complexity and increase yield. In this study, finite element simulation is used to investigate the impacts of varying structures and sizes on the stress of MEMS suspended devices. The maximum stress and average stress of silicon nanomaterials are lowered by 90.89% and 92.35%, respectively, by optimizing the structure and size of the beams and nanobelt. Moreover, MEMS suspended devices of various structures are successfully manufactured. It not only increases the yield to more than 70% but also decreases the impact of strain on thermoelectric performance and can be used to create suspended devices with integrated silicon microstrips.

The demand for wearable sensors is vastly growing as it provides people the ability to monitor their daily activities, surrounding environment, and health conditions conveniently. The development of these sophisticated wearable sensors with specific- or multiple-function capacity largely depends on the innovation pace of fabrication technologies. This review focuses on the most recent development of micro/nanofiber fabrication technologies for fabricating wearable sensors, including drawing, spinning, coating, and printing. The basic working mechanisms are introduced, followed by some representative applications. Lastly, the perspectives of these advanced methods on the development of future wearable sensors are discussed. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Submitted/Accepted version This work was supported by the Fundamental Research Funds for the Central Universities (D5000220072), the National Key R&D Program of China (2021YFF0600905), the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2019-T2-2-127 and MOE-T2EP50120-0002), A∗STAR under AME IRG (A2083c0062), the Singapore Ministry of Education Academic Research Fund Tier 1 (MOE2019-T1- 001-103 (RG 73/19) and MOE2019-T1-001-111 (RG90/19)) and the Singapore National Research Foundation Competitive Research Program (NRF-CRP18-2017-02). This work was partly supported by the Schaeffler Hub for Advanced Research at NTU, under the ASTAR IAF-ICP Programme ICP1900093. This work was also supported by Nanyang Technological University.

With the continuous development and ceaselessly construction of power IoT system, a huge number of power terminal entities are connected to the power IoT system, which largely affect the performance of power IoT system. The lifecycle process analysis of power IoT terminal entity becomes more and more important. However, the traditional analysis methods often have some shortcomings such as complex process and huge workload. Therefore, it is urgently needed to find out some more effective method to analyze the state and behaviour of power IoT terminal entity. To overcome the shortcomings of traditional analysis methods, an OOPN-based power IoT terminal entity model is proposed by combining object-oriented idea with Petri net technology. The proposed model has the advantages of modularity design, object-oriented, simplified calculation and great flexibility, which is verified with a case study by selecting a transformer as an example of power IoT terminal entity and comparing the data.

With the comprehensive construction of the provincial metrology center, further digital management requirements are put forward for the daily operation and maintenance inspection work of the automated verification/testing area, the warehouse storage area, the material supporting turnover area and the temporary storage area, and the professional laboratory area. The article explains the UWB (ultra-wide band) technology and its principles and applies it to the smart supervision of the production area. It has developed functions such as basic information management, job attendance, positioning analysis, electronic fence, behavior monitoring, intelligent inspection and data analysis. The digital supervision plan has been verified in the actual production environment.

The internal anti-parallel Schottky barrier diode threshold voltage of SiC metal-oxide-semiconductor field-effect transistor (MOSFET) modules is less than that of their body diodes, which prevents the use of the body diode voltage drop to measure junction temperature. In this paper, a thermal resistance test of the SiC MOSFET module is proposed based on the onstate voltage drop as a temperature-sensitive electrical parameter. Measurements are performed with the method and its feasibility evaluated. The on-state voltage drop temperature sensitivity under different gate voltages and the repeatability of the on-state voltage drop parameters before and after electric power heating in the thermal resistance tests are studied. The on-state voltage drop is measured under a high gate voltage and the accuracy of junction temperature measurement improves when the grid voltage remains the same during heating and measurement.

Considering the problem of measuring the peak junction temperature of a double-chip module with temperature inhomogeneity, we use a double-chip parallel model to analyze peak junction temperature measurement error for the traditional electrical method. An improved test method is proposed that is based on the small current–voltage drop method—specifically the dual current test method employing an extended-dimension calibration curve library. This method realizes a match of the calibration current with the test current by expanding the dimension database, eliminates errors of temperature measurements, and finally obtains the peak junction temperature of the module. The measurement result is close to the set temperature of the model, thereby verifying its accuracy.

In this study, we grew CuO doped potassium tantalum niobate (Cu:KTN) crystals with a uniform superlattice structure by the off-center top-seeded solution growth (TSSG) method. The process of crystal superlattice structure formation was observed under a polarizing microscope at variable temperatures. It was found that the formation of the superlattice structure in the crystal was closely related to the formation process of the domain structure in the crystal. The 90° domain structure in the crystal promoted the formation of the superlattice structure in the crystal. The purpose of the formation of the superlattice structure is to enable the crystal to reach a more stable state. The clear diffraction effect of the crystal superlattice structure is similar to the x-ray diffraction phenomenon of low-temperature crystals, and it exists in the crystal in a three-dimensional structure.

Full static x-ray computed tomography (CT) technology has enabled higher precision and resolution imaging and has been applied in many applications such as diagnostic medical imaging, industrial inspection and security screening. In this technique, the x-ray source section is mainly composed of a thermionic cathode and electron beam scanning system. However, they have several shortcomings such as limited scanning angle, long response time and large volume. Distributed and programmable cold cathode (i.e. carbon nanotubes, ZnO nanowires (NWs)) field-emission x-ray sources are expected to solve these problems. However, there have been several long-standing challenges to the application of such cold field emitters for x-ray sources, such as the short lifetime and rigorous fabrication process, which have fundamentally prevented their widespread use. Here, we propose and demonstrate a cold field-emission x-ray source based on a graphene oxide (GO)-coated cuprous sulfide nanowire (Cu2S NW/GO) cathode. The proposed Cu2S NW/GO x-ray source provides stable emission (>18 h at a direct voltage of 2600 V) and has a low threshold (4.5 MV m−1 for obtaining a current density of 1 μA cm−2), benefiting from the demonstrated key features such as in situ epitaxy growth of Cu2S NWs on Cu, nanometer-scale sharp protrusions within GO and charge transfer between the Cu2S NWs and GO layer. Our research provides a simple and robust method to obtain a high-performance cold field emitter, leading to great potential for the next generation of x-ray source and CT.

Use of a homogeneous aquifer method to represent a heterogeneous aquifer for parameter estimation will inevitably result in uncertainties in the estimated parameter values. The objective of this paper is to evaluate the impacts of the reduced duration of the pumping test on the estimated hydraulic conductivity using the observations from pumping tests. Firstly, a heterogeneous hydraulic conductivity K field was generated using the Monte Carlo method. A MODFLOW groundwater flow model was then constructed to perform numerical pumping tests. The K value was estimated by the inverse method based on the Theis solution for an unconfined aquifer. The K fields were generated based on the hydraulic conductivity data sets collected for a karst aquifer in southwest of China. The effective hydraulic conductivity (Ke) was calculated to represent the hydraulic conductivity of a heterogeneous aquifer. For a single test in a heterogeneous aquifer, while the duration of the test is less than a critical value, the reduced duration will lead to the big uncertainty of the estimated hydraulic conductivity. However, Ke can achieve a relative stable value while the number of reduced duration tests is big enough to eliminate the impacts of the uncertainty of the separate K values.

The objective of this study was to address the deviation of electrical parameters, which is caused by the self-temperature rise effect of power devices in electrical testing processes. The pulse width and amplitude of the device test were considered as the research object. The three-dimensional variation of the power, junction temperature, and pulse width of semiconductor power devices were investigated using the principle of electrical temperature measurement, and the three-dimensional variation surfaces of the power, junction temperature, and pulse width were established. A method for selecting the pulse width and amplitude of the test to avoid the self-temperature rise of the power device is proposed. This method uses cutting projection to obtain the characteristic curve of the pulse width and power change, and selects an appropriate two-dimensional region of the pulse width and power to avoid the self-temperature rise of the power device. Moreover, the proposed method can be used as a reference when selecting a pulse test method.

To evaluate the reliability of endure high voltage when IGBT is turned off and eliminate the defective devices, HTRB (High Temperature Reverse Bias) test is one of the necessary tests for IGBT before it’s produced. According to the IEC standard, DUTs (Device Under Test) are usually blocked, and bear forward bias voltage, which is preferably 80% of VCESmax. During the HTRB test, DUT junction temperature should be set at maximum virtual junction temperature Tvj(max) which is usually between 125°C to 150°C. Due to high voltage, even though the leakage current is very low, high-power semiconductor devices generate dissipated power during HTRB test, which lead to junction temperature increase. And to access the reliability accurately, the rise of temperature cannot be neglected. To insure the test is carry out at standard temperature, this paper monitors DUTs junction temperature by using leakage current as a TSEP (Temperature Sensitive Electrical Parameter),. The experiment proofs that higher the junction temperature is, the more accurate the measure results will be, in the operating temperature range. In this paper, thermal resistance measurement is used to evaluate the validity of this method.

As optimization problems become more complex, the need of new algorithms becomes greater. In this paper, a new powerful algorithm based on nuclear reaction process, namely, nuclear reaction optimization, is proposed for numerical optimization. The NRO algorithm which includes nuclear fission and fusion phases mimics the fission and fusion processes. In the first phase, the Gaussian walk and differential evolution operators are used for modeling fission process. In the second phase, the variants of differential evolution operators are employed for modeling the ionization stage and fusion stage. Additionally, six benchmark functions and unconstrained engineering design problem are evaluated by NRO and other compared algorithms. The optimization results indicate that the NRO has presented feasibility and superiority performance.

The effect of an externally applied magnetic field on the ion acceleration by laser-driven collisionless shocks is examined by means of multi-dimensional particle-in-cell simulations. For the interaction of ultra-intense sub-picosecond laser pulses with the near-relativistic critical-density plasma, the longitudinal transport of the laser generated fast electrons are significantly inhibited by the kilo-Tesla (kT) level transverse magnetic field, resulting in a thermal pressure which significantly exceeds the laser radiation pressure in the hot electron accumulation region. As a result, the accumulated plasma expands into the vacuum and leads to acceleration of a supersonic plasma flow in the opposite direction through the rocket effect, which streams into the target and drives a supercritical magnetized collisionless shock. In comparison with the case without the external magnetic field, where an electrostatic collisionless shock can be driven, the energy flux of the shock accelerated quasi-monoenergetic ion beam is considerably increased by an order of magnitude due to the strength enhancement of the magnetized shock.

Advances in two-dimensional semiconducting thin films enable the realization of wearable electronic devices in the form factor of flexible substrate/thin films that can be seamlessly adapted in our daily lives. For wearable gas sensing, two-dimensional materials, such as SnSe2, are particularly favorable because of their high surface-to-volume ratio and strong adsorption of gas molecules. Chemical vapor deposition and liquid/mechanical exfoliation are the widely applied techniques to obtain SnSe2 thin films. However, these methods normally result in non-uniform and isolated flakes which cannot apply to the practical industrial-scale wearable electronic devices. Here, we demonstrate large-scale (10 cm × 10 cm), uniform, and self-standing SnSe2 nanoplate arrays by co-evaporation process on flexible polyimide substrates. Both structural and morphological properties of the resulting SnSe2 nanoplates are systematically investigated. Particularly, the single-crystalline SnSe2 nanoplates are achieved. Furthermore, we explore the application of the polyimide/SnSe2 nanoplate arrays as wearable gas sensors for detecting methane. The wearable gas sensors show high sensitivity, fast response and recovery, and good uniformity. Our approach not only provides an efficient technique to obtain large-area, uniform and high-quality single-crystalline SnSe2 nanoplates, but also impacts on the future developments of layered metal dichalcogenides-based wearable devices.

Based on the analysis of the historical data about oil spill accidents in the Bohai Sea, this paper discretizes oil spilled source into a limited number of spill points. According to the probability of oil spill risk, the demand for salvage forces at each oil spill point is evaluated. Aiming at the specific location of the rescue base around the Bohai Sea, a cost-benefit analysis is conducted to determine the total cost of disasters for each rescue base. Based on the relationship between the oil spill point and the rescue site, a multi-objective optimization location model for the oil spill rescue base in the Bohai Sea region is established. And the genetic algorithm is used to solve the optimization problem, and determine the emergency rescue base optimization program and emergency resources allocation ratio.

We discuss the feature of the magnetic field configuration arising from double counter oriented electric current-rings in the accretion disc around a Kerr black hole (BH). We discuss the relevant physical quantities corresponding to this configuration: (1) the power and torque transferred by the large-scale magnetic field, (2) the angular momentum and energy fluxes transferred from the BH to the inner disc, (3) the radiation flux from the disc. In addition, we discuss the possibility that the closed magnetic field anchored at the disc probably evolves to the open magnetic field, which is helpful to produce the jet from the disc.

Magnetic extraction of energy from a rotating black hole (BH) is discussed in the coexistence of the Blandford–Znajek (BZ) process and the magnetic coupling (MC) process by considering the effects of the screw instability of the magnetic field. It is shown that the screw instability affects the configuration of the magnetosphere and the evolution characteristics of the BH, augmenting the energy extracted in the BZ and MC processes. In addition, the observed energy and duration of several gamma-ray bursts can be fitted well by virtue of our model.