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<jats:p>The properties of urea under high pressure and high temperature (HPHT) are studied using a China-type large volume cubic high-presentation apparatus (CHPA) (SPD-6 × 600). The samples are characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and Raman spectroscopy. By directly observing the macroscopic morphology of urea with SEM, it is confirmed that the melting point of urea rises with the increase of pressure. The XRD patterns of urea residues derived under different pressures show that the thermal stability of urea also increases with the increase of pressure. The XRD pattern of the urea residue confirms the presence of C<jats:sub>3</jats:sub>H<jats:sub>5</jats:sub>N<jats:sub>5</jats:sub>O (ammeline) in the residue. A new peak emerges at 21.80°, which is different from any peak of all urea pyrolysis products under normal pressure. A more pronounced peak appears at 708 cm<jats:sup>−1</jats:sup> in the Raman spectrum, which is produced by C–H off-plane bending. It is determined that the urea will produce a new substance with a C–H bond under HPHT, and the assessment of this substance requires further experiments.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Interdigitated back contact silicon hetero-junction (IBC-SHJ) solar cells exhibit excellent performance owing to the IBC and SHJ structures. The front surface field (FSF) layer composed of electric field passivation and chemical passivation has been proved to play an important role in IBC-SHJ solar cells. The electric field passivated layer n<jats:sup>+</jats:sup>-a-Si: H, an n-type Si alloy with carbon or oxygen in amorphous phase, is simulated in this study to investigate its effect on IBC-SHJ. It is indicated that the n<jats:sup>+</jats:sup>-a-Si: H layer with wider band gap can reduce the light absorption on the front side efficaciously, which hinders the surface recombination of photo-generated carriers and thus contributes to the improvement of the short circuit current density <jats:italic>J</jats:italic> <jats:sub>sc</jats:sub>. The highly doped n<jats:sup>+</jats:sup>-a-Si: H can result in the remakable energy band bending, which makes it outstanding in the field passivation, while it makes little contribution to the chemical passivation. It is noteworthy that when the electric field intensity exceeds 1.3 × 10<jats:sup>5</jats:sup> V/cm, the efficiency decrease caused by the inferior chemical passivation is only 0.16%. In this study, the IBC-SHJ solar cell with a front n<jats:sup>+</jats:sup>-a-Si: H field passivation layer is simulated, which shows the high efficiency of 26% in spite of the inferior chemical passivation on the front surface.</jats:p>

<jats:p>Based on the energy transfer model (ETM) proposed by Bao <jats:italic>et al</jats:italic>. and the Monte Carlo (MC) model proposed by Hutcherson and Ye, this paper proposes an efficient molecular model (MC-S) for squeeze-film damping (SQFD) in rarefied air by releasing the assumption of constant molecular velocity in the gap. Compared with the experiment data, the MC-S model is more efficient than the MC model and more accurate than ETM. Besides, by using the MC-S model, the feasibility of the empirical model proposed by Sumali for SQFD of different plate sizes is discussed. It is proved that, for various plate sizes, the accuracy of the empirical model is relatively high. At last, the SQFD of various vibration frequencies is discussed, and it shows that, for low vibration frequency, the MC-S model is reduced to ETM.</jats:p>

<jats:p>Based on the thermal network of the two-dimensional heterojunction bipolar transistors (HBTs) array, the thermal resistance matrix is presented, including the self-heating thermal resistance and thermal coupling resistance to describe the self-heating and thermal coupling effects, respectively. For HBT cells along the emitter length direction, the thermal coupling resistance is far smaller than the self-heating thermal resistance, and the peak junction temperature is mainly determined by the self-heating thermal resistance. However, the thermal coupling resistance is in the same order with the self-heating thermal resistance for HBT cells along the emitter width direction. Furthermore, the dependence of the thermal resistance matrix on cell spacing along the emitter length direction and cell spacing along the emitter width direction is also investigated, respectively. It is shown that the moderate increase of cell spacings along the emitter length direction and the emitter width direction could effectively lower the self-heating thermal resistance and thermal coupling resistance, and hence the peak junction temperature is decreased, which sheds light on adopting a two-dimensional non-uniform cell spacing layout to improve the uneven temperature distribution. By taking a 2 × 6 HBTs array for example, a two-dimensional non-uniform cell spacing layout is designed, which can effectively lower the peak junction temperature and reduce the non-uniformity of the dissipated power. For the HBTs array with optimized layout, the high power-handling capability and thermal dissipation capability are kept when the bias voltage increases.</jats:p>

<jats:p>Four 4H-SiC p–i–n ultraviolet (UV) avalanche photodiode (APD) samples PIN-0.1, PIN-0.35, PIN-0.5, and PIN-1.0 with different intrinsic layer thicknesses (<jats:inline-formula> <jats:tex-math><?CDATA $0.1\,{\rm{\mu }}{\rm{m}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.1</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_098503_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA $0.35\,{\rm{\mu }}{\rm{m}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.35</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_098503_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA $0.5\,{\rm{\mu }}{\rm{m}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.5</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_098503_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math><?CDATA $1.0\,{\rm{\mu }}{\rm{m}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1.0</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_098503_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, respectively) are designed and fabricated. Single photon detection efficiency (SPDE) performance becomes better as the intrinsic layer thickness increases, which is attributed to the inhibitation of tunneling. Dark count origin is also investigated, an activation energy as small as 0.22 eV of the dark count rate (DCR) confirms that the trap-assisted tunneling (TAT) process is the main source of DCR. The temperature coefficient ranges from −2.6 mV/°C to 18.3 mV/°C, demonstrating that the TAT process is dominant in APDs with thinner intrinsic layers. Additionally, the room temperature maximum quantum efficiency at 280 nm differs from 48% to 65% for PIN-0.35, PIN-0.5, and PIN-1.0 under 0 V bias, and UV/visible rejection ratios higher than 10<jats:sup>4</jats:sup> are obtained.</jats:p>

<jats:p>The intrinsic transverse relaxation mechanisms of polarized alkali atoms enclosed in the radio-frequency magnetometer cell are investigated. The intrinsic transverse relaxation rate of cesium atoms as a function of cell temperature is obtained. The absorption of alkali atoms by the glass wall and the reservoir effect are the main error factors which contribute to the disagreements between theory and experiments. A modified relaxation model is presented, in which both the absorption of alkali atoms by the glass wall and the reservoir effect are included. This study provides a more accurate description of the intrinsic transverse relaxation mechanisms of polarized alkali atoms, and enlightens the optimization of the cell design.</jats:p>

<jats:p>A supersymmetric version of the Ito equation is proposed by extending the independent and dependent variables for the classic Ito equation. To investigate the integrability of the <jats:italic>N</jats:italic> = 1 supersymmetric Ito (sIto) equation, a singularity structure analysis for this system is carried out. Through a detailed analysis in two cases by using Kruskal’s simplified method, the sIto system is found to pass the Painlevé test, and thus is Painlevé integrable.</jats:p>

<jats:p>The unconditional security of quantum key distribution (QKD) can be guaranteed by the nature of quantum physics. Compared with the traditional two-dimensional BB84 QKD protocol, high-dimensional quantum key distribution (HD-QKD) can be applied to generate much more secret key. Nonetheless, practical imperfections in realistic systems can be exploited by the third party to eavesdrop the secret key. The practical beam splitter has a correlation with wavelength, where different wavelengths have different coupling ratios. Using this property, we propose a wavelength-dependent attack towards time-bin high-dimensional QKD system. What is more, we demonstrate that this attacking protocol can be applied to arbitrary <jats:italic>d</jats:italic>-dimensional QKD system, and higher-dimensional QKD system is more vulnerable to this attacking strategy.</jats:p>

<jats:p>Using the thermal-entangled state representation and the operator-ordering method, we investigate Wigner function (WF) for the squeezed negative binomial state (SNBS) and the analytical evolution law of density operator in the amplitude decay channel. The results show that the analytical WF is related to the square of the module of single-variable Hermite polynomials, which leads to a new two-variable special function and its generating function, and the parameters <jats:italic>s</jats:italic> and <jats:italic>γ</jats:italic> play opposite roles in the WF distributions. Besides, after undergoing this channel, the initial pure SNBS evolves into a new mixed state related to two operator Hermite polynomials within normal ordering, and fully loses its nonclassicality and decays to vacuum at long decay time.</jats:p>

<jats:p>Preserving non-Markovianity and quantum entanglement from decoherence effect is of theoretical and practical significance in the quantum information processing technologies. In this context, we study a system <jats:italic>S</jats:italic> that is initially correlated with an ancilla <jats:italic>A</jats:italic>, which interacts with the environment <jats:italic>E</jats:italic> via an amplitude damping channel. We also consider dipole-dipole interactions (DDIs) between the system and ancilla, which are responsible for strong correlations. We investigate the impact of DDIs and detuning on the non-Markovianity and information exchange in different environments. We show that DDIs are not only better than detuning at protecting the information (without destroying the memory effect) but also induce memory by causing a transition from Markovian to non-Markovian dynamics. In contrast, although detuning also protects the information, it causes a transition from non-Markovian to the Markovian dynamics. In addition, we demonstrate that the non-Markovianity grows with increasing DDI strength and diminishes with increasing detuning. We also show that the effects of negative detuning and DDIs can cancel out each other, causing a certain loss of coherence and information.</jats:p>