Nowadays, wireless power transfer (WPT) has attracted great attention from researchers because it is a safe, convenient, and reliable way to recharge electric vehicles. Square and circular coils are ...most commonly used in WPT systems. However, there are few analyses of comparing these two geometry windings in detail. In this paper, two analytical models of both square and circular planar spiral coils between two semi-infinite substrates are developed based on Fourier-Bessel transformation and dual Fourier transformation. An analytical calculation of the selfand mutual inductance can be carried out with respect to the main parameters of the WPT systems such as the line spacing, the number of turns of the coils and the properties of the substrate. The analytical models can be used to investigate the different tendencies of selfand mutual inductance of square and circular coils, which is helpful for speeding up the design process. Finally, to compare the lateral misalignment tolerance between square and circular coils, a 600 mm × 600 mm with a nominal 200-mm-gap prototype has been built and tested.
Power transformer is widely used in the power system with the rapid development of the power converters connected to the grid. When a transformer operates under DC bias conditions, its iron core loss ...increases significantly, causing local overheating and threatening the proper operation of the transformer. However, there are persistent difficulties in accurately assessing the core loss when the induction waveform is influenced by a DC bias. This paper first proposes improvements to the J-A and Preisach models to evaluate the core loss of the iron core under DC bias. Additionally, we incorporate the hysteresis models into the finite element method (FEM) by modifying the fundamental constitutive equations in the FEM model in order to perform a precise core loss/distribution calculation. To verify the accuracy of prediction, a transformer prototype with a laminated core is developed. The improved J-A-FEM and Preisach-FEM models were directly compared in terms of calculation accuracy, numerical implementation, and computational burden.
In this paper, novel nano-enhanced phase change materials (NePCMs) were prepared by two step method. Nano-titania and erythritol were chosen as nano material and phase change material (PCM), ...respectively. Among many dispersants, triethanolamine (TEA) was proved the most effective one due to its low molecular weight and the carried hydroxide radical. The results showed that the heat capacity of NePCMs was enhanced by the doping of nano-titania. The enhancement was about 40% and 14% in solid and liquid state, respectively, when the volume fraction of nano-titania was only 0.2vol%. We argued that the increased fraction of atoms located in the metastable interfaces contributed to the increase of specific heat capacity in solid state. While in liquid state, the enhancement of heat capacity was due to the increased interfacial thermal resistance caused by high surface area of nanoparticles.
Direct generation of chirp-free solitons without external compression in normal-dispersion fiber lasers is a long-term challenge in ultrafast optics. We demonstrate near-chirp-free solitons with ...distinct spectral sidebands in normal-dispersion hybrid-structure fiber lasers containing a few meters of polarization-maintaining fiber. The bandwidth and duration of the typical mode-locked pulse are 0.74 nm and 1.95 ps, respectively, giving the time-bandwidth product of 0.41 and confirming the near-chirp-free property. Numerical results and theoretical analyses fully reproduce and interpret the experimental observations, and show that the fiber birefringence, normal-dispersion, and nonlinear effect follow a phase-matching principle, enabling the formation of the near-chirp-free soliton. Specifically, the phase-matching effect confines the spectrum broadened by self-phase modulation and the saturable absorption effect slims the pulse stretched by normal dispersion. Such pulse is termed as birefringence-managed soliton because its two orthogonal-polarized components propagate in an unsymmetrical "X" manner inside the polarization-maintaining fiber, partially compensating the group delay difference induced by the chromatic dispersion and resulting in the self-consistent evolution. The property and formation mechanism of birefringence-managed soliton fundamentally differ from other types of pulses in mode-locked fiber lasers, which will open new research branches in laser physics, soliton mathematics, and their related applications.
•Energy consumption patterns have long-term impacts on energy demand.•We explore determinants and structure of household energy consumption.•Tobit and OLS models are adopted to explore factors ...influencing energy expenditure.•Residential energy consumption in 2030 is evaluated using scenario analysis.
China’s growing energy demand is driven by urbanization. Facing the problem of energy scarcity, residential energy consumption is a crucial area of energy conservation and emissions reduction. Household energy consumption patterns, which are characterized by effects of “path lock-in”, have long-term impacts on China’s energy demand. Based on the survey data, this paper explores factors that influence household energy consumption and analyzes the structure of residential energy consumption in China. Based on the results of analysis of variance (ANOVA), this paper applies the Tobit and Ordinary Least Squares (OLS) models to investigate impacts of variables of “the tiered pricing for household electricity (TPHE)”, “solar energy usage”, “automobile ownership”, “rural or urban areas”, “household income” and “city scale” on the residential energy expenditure. In addition, household energy consumption is estimated under different scenarios including improving the utilization of solar energy, rise in energy prices and the increase in automobile ownership. Residential energy consumption in 2030 is evaluated by simulating different models for urban development. Policy recommendations are suggested for China’s urban development strategy, new energy development and household pathway selection of energy consumption.
Square and circular coils are two typical topologies for coupling coils and are applied to wireless charging. However, most of the research on coupling coils is based on the finite element model ...(FEM), which is a time-consuming process for 3-D structure coils. In this paper, on the basis of Fourier-Bessel transformation and Dual Fourier transformation, two theoretical models of square and circular coils between two multilayer media are proposed. With the proposed models, we consider several important parameters such as the size of the coils, thickness, and permeability of each layer. Thus, both the self-inductance and mutual inductance of two planar coils can be calculated without much computational time. Additionally, these theoretical models can help designers figure out the different trends of self-inductance and mutual inductance, which has plenty of benefits for the preliminary pad design. Lastly, a prototype with a size of 600 mm × 600 mm and a 200 mm air gap was built in order to verify the proposed models.
The development of pipeline steels with exceptional cryogenic toughness is deemed imperative for their applications in various engineering fields. In this work, API X65 steel with lamellar grain (LG) ...structure is constructed through warm deformation techniques. Comparative analysis with raw API X65 steel revealed notable enhancements in both yield strength (YS) and ultimate strength (UTS), exhibiting increments of 315 MPa and 164 MPa, respectively, while retaining substantial fracture toughness (KIc = 251.14 MPa m0.5). Remarkably, the LG steel exhibits a distinct absence of a ductile-brittle transition behavior over a wide temperature range, maintaining an exceptionally high impact energy from room temperature (RT) to liquid nitrogen temperature (LNT), and the Charpy impact energy exceeding 330 J at LNT, nearly 16 times higher than the raw API X65 steel. This performance can be primarily attributed to the superior plastic deformation capability, coupled with the delamination toughening mechanism. The resultant tortuous path of crack propagation effectively facilitates the absorption of substantial energy, decreases notch tip sensitivity depending on the temperature, stress triaxiality, and strain rate, thereby fostering excellent cryogenic toughness.
Pelvic ectopic kidney is a kind of congenital malformations of urinary system due to the failure of ascent from the pelvis to the abdomen during development.
A 39-year-old man was referred to the ...urology department of our hospital for abdominal pain for half a month. Radiographic studies revealed stones in pelvic ectopic left kidney. Laparoscopy-assisted ultrasound-guiding percutaneous nephrolithotomy (PCNL) was performed. Postoperative plain film revealed that the patient achieved a stone-free status.
Laparoscopy-assisted ultrasound-guiding PCNL is a safe alternative for the treatment of stones in pelvic ectopic kidney with a high stone-free clearance.
An LCC/SP self-tuning wireless charging system is proposed herein for use in a wireless charging test bench. With different dislocations in addition to changes in the coil self-inductance and mutual ...inductance caused by different secondary magnetic shielding materials, the system can ensure that the high power factor of the primary side remains unchanged without changing the circuit topology. Based on this normalized detuning LCC/SP circuit model, a switch-controlled capacitor (SCC) self-tuning method based on PI control is proposed. The control scheme employs only two MOSFETs and capacitors, without WIFI communication or parameter identification. A 2 kW experimental device was set up in the laboratory, and experimental verification was carried out with large-scale dislocations and different secondary magnetic shielding materials. The experimental results confirm that the system can maintain a high power factor (>0.9) under a system mutual inductance variation of 47.7% and secondary coil self-inductance variation of 12%, and that it can be applied in electric vehicle wireless chargers or high-power wireless charger test benches.
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