[en] The discovery of efficient red-emitting-phosphor materials is critical to the next-generation white light-emitting diodes (white LEDs). In this work, we prepared a promising red-phosphor candidate: MgMoO₄:Eu³⁺,Bi³⁺,M (M=Li⁺, Na⁺, K⁺) with a standard solid-state reaction method. This material had high luminescence intensity upon ultraviolet light (UV), near ultraviolet light (near-UV), and blue excitation. We discovered that every four Mg sites formed a criss-cross unit site in the MgMoO₄ structure. These sites were used to remotely control the relative distance between Bi³⁺ and Eu³⁺ ions through changing the doping concentrations and charge compensation. A distinct new excitation band from the MgMoO₄:Eu³⁺,Bi³⁺,M (M=Li⁺, Na⁺, K⁺) phosphors coming from the ¹S₀→³P₁ transition of Bi³⁺ ions was clearly observed at about 352 nm. Moreover, the super energy transfer coming from Bi³⁺ to Eu³⁺ ions was designed and realized. Bi³⁺ and Eu³⁺ begin to sit in two adjacent Mg(1) sites when their total molar concentration is beyond 1/4. Thus, the new super energy-transfer emerges due to the adjacent Bi³⁺ and Eu³⁺ ions. The process and mechanism of the super energy transfer were further discussed. Our results indicated potential industrial applications of MgMoO₄:Eu³⁺,Bi³⁺,M in white LEDs.

[en] Graphical abstract: - Highlights: • BiOCl@Bi_2WO_6 composites were prepared via a controlled anion exchange method. • The shell of composites was composed of Bi_2WO_6 sheets with exposed (0 2 0) facets. • The BiOCl@Bi_2WO_6 composites showed efficient photocatalytic activity. • A possible photocatalytic degradation mechanism is proposed. - Abstract: Bi_2WO_6 photocatalysts has been extensively studied for its photocatalytic activity. However, few works have been conducted on hierarchical Bi_2WO_6 composite photocatalysts with specifically exposed facets. In this work, we report a facile method to synthesize BiOCl@Bi_2WO_6 hierarchical composite microspheres. Bi_2WO_6 nanosheets with specifically exposed (0 2 0) facet were directly formed on the surface of BiOCl precursor microspheres via a controlled anion exchange route between BiOCl and Na_2WO_4. The visible-light photocatalytic activity of the BiOCl@Bi_2WO_6 heterojunction with exposed (0 2 0) facets (denoted as BiOCl@Bi_2WO_6) was investigated by degradation of Rhodamine B (RhB) and ciprofloxacin (CIP) aqueous solution under visible light irradiation. The experimental results indicated that the BiOCl@Bi_2WO_6 composite microsphere with intimate interfacial contacts exhibited improved efficiency for RhB photodegradation in comparison with pure BiOCl and Bi_2WO_6. The BiOCl@Bi_2WO_6 composite microsphere also shows high photocatalytic activity for degradation of CIP under visible light irradiation. The enhanced photocatalytic performance of BiOCl@Bi_2WO_6-020 hierarchical microspheres can be ascribed to the improved visible light harvesting ability, high charge separation and transfer. This work will make significant contributions toward the exploration of novel heterostructures with high potential in photocatalytic applications.

[en] A novel Mn²⁺ doped Li₂CdSiO₄ phosphors were synthesized in 1100 °C without reducing atmosphere. Their structure, self-reduction mechanism and luminescence properties were evaluated. Oxygen vacancies were confirmed to exist in Li₂CdSiO₄ by electron spin-resonance spectroscopy and bond volume polarizability of Li₂CdSiO₄ was calculated to prove the lattice oxygen (O3) may easily form oxygen defect (${\mathrm{V}}_{\mathrm{o}}^{\mathrm{•}}$). After different valence Mn source (MnO₂ and MnCO₃) as raw materials were built into Li₂CdSiO₄, similar emission bands with a maximal value of 515 nm appeared under 226 nm excitation and it was ascribed that energy transfer occurred from host to Mn²⁺ ions. Meanwhile, it was demonstrated that a series of redox reactions does happen from MnCO₃ to Mn₃O₄ with increasing calcination temperature. Eventually, Mn₃⁺ (Mn₃O₄) ions were reduced to Mn²⁺ through electron transfer from ${\mathrm{V}}_{\mathrm{o}}^{\mathrm{•}}$ to Mn³⁺. Furthermore, interstitials oxygen (O_i) was detected in Li₂CdSiO₄:0.02Mn sample through X-ray photoelectron spectroscopy (XPS) and the special tunnel structure may provide a suitable position to stabilize O_i in air. Direct spectroscopic evidence and the assumed mechanism have been presented for explaining these processes. This research provides a new perspective for defects induced Mn²⁺ emission in designing broad band green phosphors. More importantly, the present work further deepens the understanding of the self-reduction mechanism of Mn²⁺.

[en] Highlights: • Thermal conductivity of n-dodecane and n-tetradecane was investigated. • Measurements cover a wide temperature and pressure region. • One polynomial were presented to calculate the thermal conductivity. • The comparison between literature data and the present data was carried out. With the key role of long-chain hydrocarbons in the wide applications in numerous industrial areas, such as working fluids, phase change materials, fuels, etc., the knowledge of the thermal conductivity of hydrocarbons is essential in the energy conversion process. Thus, it is of great significance to get reliable experimental data of hydrocarbons’ thermal conductivity for further accurately theoretical predictions and the potential applications. In this work, the thermal conductivities of two long-chain hydrocarbons of n-dodecane and n-tetradecane, are investigated experimentally. The transient hot-wire method was used for the measurement of the thermal conductivity under the conditions of 293–523 K and 0.1–15.0 MPa. By comparing the present work with literature results, the possible reasons for the deviations were analyzed. The results in this study provide accurately measured of the thermal conductivity of the two long-chain hydrocarbons at high temperature and pressure, which are expected to fill the gap in literature.

[en] Highlights: • Thermal conductivity of MeC4:0 and MeC6:0 was investigated. • Measurements cover a wide temperature and pressure region. • One polynomial were presented to calculate the thermal conductivity. • Predictive ability of three models is assessed using our data. Fatty acid methyl esters (FAMEs) are the main component of biodiesels. Before the industrial application of FAMEs, it is essential to investigate the thermophysical properties of FAMEs. Thermal conductivity of fuels is used in various processes, such as the design of the heat transfer system and the determination of the temperature distribution of engines. Thus, it is of great significance to acquire accurate experimental data and develop reliable models for obtaining accurate thermal conductivity data of FAMEs. In this work, thermal conductivities of two short-chain FAMEs, methyl butyrate (MeC4:0) and methyl caproate (MeC6:0) were studied experimentally and theoretically. The thermal conductivities of these two FAMEs were measured by the transient hot-wire method at T = 303 to 523 K and p = 0.1 MPa to 15 MPa, the data were correlated as a polynomial function of temperature and pressure, the AADs are 0.38% for MeC4:0 and 0.42% for MeC6:0, respectively. Moreover, the experimental thermal conductivities agree well with the available data from literature. In addition, three classical models (Latini model, Sastri model, Liu model) were used to represent the present experimental data and the results show that Liu model with re-fitted parameters performs better in the prediction of the thermal conductivity of FAMEs, with regard to accuracy.

[en] Variational quantum algorithms (VQAs) have been successfully applied to quantum approximate optimization algorithms, variational quantum compiling, and quantum machine learning models. The performance of VQAs is significantly influenced by the architecture of parameterized quantum circuits (PQCs). Quantum architecture search aims to automatically discover high-performance quantum circuits for specific VQA tasks. Quantum architecture search algorithms that utilize both SuperCircuit training and a parameter-sharing approach can save computational resources. If we directly follow the parameter-sharing approach, the SuperCircuit has to be trained to compensate for the worse search space. To address the challenges posed by the worse search space, we introduce an optimization strategy known as the efficient continuous evolutionary approach using Non-dominated Sorting Genetic Algorithm-II (NSGA-II). Then, we leverage prior information (symmetric property) designing Structure Symmetric Pruning for removing redundant gates of the searched ansatz. Experiments show that the efficient continuous evolutionary approach can search for more quantum architectures with better performance; the number of high-performance ansatzes obtained by our method is 10% higher than that in the literature (Du et al. in npj Quantum Inf. 8:62, 2022). The application of Structure Symmetric Pruning effectively reduces the number of parameters in quantum circuits without compromising their performance significantly. In binary classification tasks, the pruned quantum circuits exhibit an average accuracy reduction of 0.044 compared to their unpruned counterparts.

[en] Highlights: • A method is proposed for the evaluation of using an abandoned salt cavern for energy (natural gas) storage. • A feasibility analysis is given of China’s first UGS (Underground Gas Storage) facility using an abandoned salt cavern. • Numerical modeling has been used to investigate mechanical safety of a gas pressurized cavern. • Chinese abandoned salt caverns show good feasibility of being converted to UGSs. • China’s bedded rock salt can meet the requirements for UGS. - Abstract: Rock salt in China is primarily bedded salt, usually composed of many thin salt layers and interlayers (e.g. anhydrite, mudstone, and glauberite). Thus, the feasibility analysis of abandoned salt caverns located in salt beds to be used as Underground Gas Storage (UGS) facilities is full of challenges. In this paper, we introduce the feasibility analysis of China’s first salt cavern gas storage facility using an abandoned salt cavern. The cavern is located in Jintan city, Jiangsu province, China. The mechanical properties and permeability of the bedded salts are obtained by experiments. Based on the results of the analyses, it appears to be quite feasible to convert the abandoned salt caverns of Jintan city to UGS facilities. The stability of the cavern is evaluated by the 3D geomechanical numerical simulations, and the operating parameters are proposed accordingly. Results indicate that the maximum volume shrinkage of the cavern is less than 25% and the maximum deformations are less than 2% of the caverns’ maximum diameters after operating for 20 years. It is recommended that the weighted average internal gas pressure be maintained as 11 MPa to control the extent of the plastic zones to a safe level. Safety factors decrease with operating time, especially those of the interface between rock salt and mudstone layers decrease significantly. Effective strain is generally greater than 2%, and locally is greater than 3% after operating 20 years. The maximum pressure drop rate should be kept to less than 0.55 MPa/day. Based on above proposed parameters, China’s first salt cavern gas storage facilities were completed, and gas was first injected, in 2007. To check the status of the caverns after operating for 6 years, the volumes of the caverns were measured in 2013 by Sonar under working conditions. Measurement results show that the cavern shapes did not change much, and that volume shrinkages were less than 2%. Comprehensive results show that the feasibility analysis method proposed in this paper is reliable

[en] Highlights: • The stripping H₃PO₄ concentration didn't influence ammonia capture. • The water flux increased as the stripping H₃PO₄ concentration increased. • The liquid N-P fertilizer products were mixtures of (NH₄)₂HPO₄ and NH₄H₂PO_4. • Harvesting liquid N-P fertilizer from urine using HFMC made a profit of $7.809/L. In this study, we developed a submerged hollow fiber membrane contactor (HFMC) to recover ammonia from human urine to get compound N-P fertilizers. The ammonia capture performance, water vapor transmembrane performance, ion rejection performance and the liquid fertilizer components using 1–4 mol/L H₃PO₄ as the stripping solution was comprehensively investigated. Increasing H₃PO₄ concentration did not significantly affect the ammonia capture performance but the water vapor transfer and fertilizer components. The ammonia mass transfer coefficients were in a range of 1.95×10⁻⁶±4.77×10⁻⁸ to 2.28×10⁻⁶±6.71×10⁻⁸ m/s and the ammonia flux fluctuated between 17.80 and 20.80 g/m²·h. The water vapor flux increased with the increase of stripping solution concentration and the time elapsed. The N content (21.29–55.24 g/L) was in the range of the commercial products while the P₂O₅ content (99.41–281 g/L) was slightly higher, which can be used in the soils or plants with a high demand for phosphorus. The liquid fertilizers were all mixtures of (NH₄)₂HPO₄ and NH₄H₂PO_4, but the distribution ratio slightly changed with the different initial H₃PO₄ concentration. The economic assessment showed that harvesting liquid N-P fertilizer from human urine using HFMC can make a profit of $7.089/L.