[en] A novel dual-emitting Ca₈ZrMg(PO₄)₆(SiO₄): (Eu³⁺, Eu²⁺) phosphors with ultrahigh-sensitive optical temperature sensing are prepared by a conventional solid-state method. The Eu²⁺/Eu³⁺ co-activated Ca₈ZrMg(PO₄)₆(SiO₄) phosphors exhibit efficient dual-mode emissions with an intense, broad blue emission peaked at 414 nm and a relative bright red-emitting centered at 614 nm under 297 nm UV-light excitation, respectively. Furthermore, the fluorescence intensity ratio (FIR) technology is applied to analyse the optical temperature sensing performance of Ca₈ZrMg(PO₄)₆(SiO₄): (Eu³⁺, Eu²⁺) phosphors. Based on different thermal quenching behavior of Eu²⁺ and Eu³⁺ dual-emitting centers, linear temperature-dependent FIR between Eu²⁺ and Eu³⁺ is obtained. The maximal absolute sensitivity reaches as high as 5.94% K⁻¹, which is superior to that for the other luminescent temperature sensing materials reported previously. Analyses of the temperature-dependent photoluminescence spectra and configurational coordinate diagrams for Ca₈ZrMg(PO₄)₆(SiO₄): (Eu³⁺, Eu²⁺) phosphors indicate that the temperature-sensitive variation in FIR of Eu²⁺ to Eu³⁺ is originated from the difference in thermal quenching activation energy for 5d→4f transition of Eu²⁺ and ⁵D₀→⁷F_J (J = 1, 2, 4) transitions of Eu³⁺. These results reveal that the Ca₈ZrMg(PO₄)₆(SiO₄): (Eu³⁺, Eu²⁺) phosphors show glorious potential in high temperature optical thermometry.

[en] Highlights: • Inverse design of thermal boundary conditions. • Combined inverse and forward modeling. • Regularized matrix inversion for target indoor temperatures. • Model validation with a self-conducted experimental test. - Abstract: Thermal boundary conditions in commercial airliner cabins are crucial for creating a comfortable cabin environment. Cabin temperature distributions depend on the thermo-fluid boundary conditions of the boundary walls and the air supply. This paper proposed a combined inverse-forward model for designers to determine the total underfloor heating rates and the air-supply temperature in an aircraft cabin. The contribution ratio of indoor climate (CRI) is applied to describe the cause–effect relationship between the boundary wall convective heat release rates and the resulting temperature rise at certain points, which can be cast into a matrix. The solution contains three sub-models: (i) regularized inversion of the cause–effect matrix with the target cabin air temperatures as the known input, which solves the convective heat rates of the underfloor heaters and the air-supply temperature, (ii) solution of underfloor heater's surface temperatures based on Newton's law of cooling, and (iii) computation of the radiative heat rates. The above model was used to determine the total underfloor heating rates and air-supply temperature in a single-aisle aircraft cabin. The design targets are to create an average temperature of 24 °C near the upper human body and 26 °C at the ankle level. An experimental test was conducted in a simplified half section of an aircraft cabin for model validation. The results show that the proposed methodology is able to provide the total underfloor heating rates and air-supply temperature in good agreement with the measurement data and forward-simulation boundary conditions.

[en] Background: In nuclear plant vapor explosion analysis, fuel drop diameter is an important parameter which could significantly influence the evaluation of explosion pressure. Purpose: Decrease the uncertainty of vapor explosion calculation caused by fuel drop diameter. Methods: A simulation model of typical vapor explosion was built using MC3D to take sensitive analysis of fuel drop diameter. Results: The calculation relates to fuel drop energy, fuel drop fragmentation rate and vapor explosion pressure. The effect of fuel drop diameter in vapor explosion is analyzed based on theoretical analysis and the calculation. Conclusions: The results show that the vapor explosion pressure is very sensitive to fuel drop diameter, which is mainly caused by the fuel drop energy and the fuel drop fragmentation rate. (authors)

[en] Food irradiation uses electromagnetic radiation and is controlled by many identification methods according to the contents in foods. Currently there are ten methods used to identify the irradiated foods and electron spin resonance (ESR) spectroscopy is one of these methods to identify the irradiated food containing bone, cellulose and crystalline sugar. The present work was to detect the un-irradiated and irradiated wheat, rice and chickpea powder, study the ESR intensity with respect to the absorbed dose, and fading of ESR signal with time. As the radiation source, industrial type 5 MeV, 15 kW electron beam accelerator was applied and three grain flour was irradiated with the dose; 1, 1.5, 2.1, 2.6 and 3.2 kGy. The optical absorbance of B3 Windose film dosimeters was measured at 552 nm with GEX (Spectronic Genesys-20) spectrophotometer for absorbed dose measurement. ESR measurements were carried out using an ESR spectrometer (magnettech, MS 400). Free radicals generated by irradiation gave typical signal in the ESR spectrum for irradiation identification. In present study, irradiated samples showed strong ESR signals centered at g = 2.006, where un-irradiated samples had weak signals. And ESR intensity increased linearly with absorbed dose in most of the cases. The fading of ESR intensity of the samples stored at room temperature was studied over storage period of 4 weeks. Following one week after irradiation, ESR intensity decreased significantly with storage time. (author)

[en] Graphical abstract: Spin-polarized total and atomic DOS at S-(1 1 1) terminated slab and bulk in CsCl-type RbS. - Highlights: • The half metallic properties of CsCl-type RbS and KS have been studied. • The RbS's and KS's (1 1 1) slabs have been investigated. • Surface energy of RbS's and KS's (1 1 1) slabs are calculated. - Abstract: The electronic and magnetic properties of RbS and KS in CsCl structure have been investigated by using the full-potential local-orbital minimum-basis method. Calculating the relation between the total energies and lattice parameters for RbS and KS, we find out that the equilibrium lattice parameters are 4.02 Å and 3.84 Å for RbS and KS, respectively. According to our calculations in generalized gradient approximation approximation, both RbS and KS are half-metallic ferromagnets with the magnetic moments of 1 μ_B per formula unit, and band gap of 4.287 eV for RbS and 4.395 eV for KS. We also have studied the electronic and magnetic properties of (1 1 1) surfaces of RbS and KS, and have found out that the half-metallicity of their bulk is preserved in all of those surfaces. Finally, through the calculations of formation energy of RbS and KS, it is found that their thin films are stable in the equilibrium conditions, and the Rb-terminated (1 1 1) slab of RbS and the K-terminated (1 1 1) slab of KS are more stable than their S-terminated (1 1 1) slabs. All of the above properties lead the compounds of RbS and KS in CsCl structure to be promising candidates for spintronic applications

[en] The electronic structures and magnetic properties of a new series of quaternary Heusler alloys CoFeScZ (Z=P, As, Sb) are investigated through first-principle calculations. CoFeScP is found to have half-metallic ferromagnetism with a large half-metallic gap of 0.60 eV. The results show that both CoFeScAs and CoFeScSb are nearly half-metal under the equilibrium lattice constants. The change of the properties of CoFeScAs and CoFeScSb with pressure is investigated. - Highlights: • Investigate a new series of quaternary Heusler alloys CoFeScZ (Z=P, As, Sb). • The band gap of the half-metal CoFeScP is very large. • Study the magnetic properties and electronic structure of CoFeScP under the equilibrium lattice constant. • Investigate the influence of pressure on the magnetic properties and electronic structure of CoFeScAs and CoFeScSb

[en] Abstract Background: Passive containment cooling system (PCS) is part of the passive reactor safety design for cooling down the containment in accidents. Purpose: This study aims to analyze the key factors affecting the cooling capacity of PCS based on the containment safety verification via integral test (CERT). Methods: The calculating model of CERT was established using containment safety analysis program. The calculating results and the experiment results were compared to verify the model. The inner containment pressure response of double-ended cold leg guillotine (DECLG) break accident was calculated and the sensitive analysis of some parameters such as the cooling water flow, the outer shell cooling water coverage and the annulus wind speed were performed. Results: The result showed that the calculated pressure and temperature were similar to the experimental test results with a little bit higher than the latter. The maximum pressure of DECLG is 0.2661 MPa. The inner containment pressure increased significantly when the cooling water flow and the outer shell cooling water coverage decreased. The pressure decreased slightly when the annulus wind speed increased. Conclusion: The calculating model is applicable for CERT calculations, and the results are conservative. Inner containment pressure is sensitive to the cooling water flow and the outer shell cooling water coverage. (authors)

[en] We present evidence of halogen bond in iodine clusters formed in superfluid helium droplets based on results from electron diffraction. Iodine crystals are known to form layered structures with intralayer halogen bonds, with interatomic distances shorter than the sum of the van der Waals radii of the two neighboring atoms. The diffraction profile of dimer dominated clusters embedded in helium droplets reveals an interatomic distance of 3.65 Aa, much closer to the value of 3.5 Aa in iodine crystals than to the van der Waals distance of 4.3 Aa. The profile from larger iodine clusters deviates from a single layer structure; instead, a bi-layer structure qualitatively fits the experimental data. This work highlights the possibility of small halogen bonded iodine clusters, albeit in a perhaps limited environment of superfluid helium droplets. The role of superfluid helium in guiding the trapped molecules into local potential minima awaits further investigation. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] The ultrasmall Yb/Er: CaF₂ NCs are chosen as an example to certify the upconversion emission intensity can be greatly enhanced through combining various approaches together, including doping Na⁺ ions to promote the growth the particle size and tailor the crystal-field environment of the emitters, control shell thickness to lower the non-radiative decay and tune Yb³⁺ concentration in the shell to enhance the absorption of the excitation energy. In comparison with Na⁺-free 20Yb/2Er: CaF₂ NCs (~ 2 nm), the upconversion luminescence of 20Yb/2Er: CaF₂@10Yb: CaF₂ NCs (~ 9 nm) containing ~ 0.5 mmol Na⁺ ions in the core and 10% Yb³⁺ in the shell with 5 nm thickness intensifies for about 95 times. - Graphical abstract: Ultrasmall Yb/Er: CaF₂ NCs are chosen as an example to certify the UC emission intensity can be greatly enhanced through combining various approaches together, including Na⁺ ions doping, control shell thickness and tune Yb³⁺ concentration in the shell. In comparison with Na⁺-free 20Yb/2Er: CaF₂ NCs, the upconversion luminescence of 20Yb/2Er: CaF₂@10Yb: CaF₂ NCs containing Na⁺ ions in the core and 10% Yb³⁺ in the shell with 5 nm thickness intensifies for about 95 times.

[en] The Scram power level has significant influence on the steam rate and amount released from the break in main steam pipeline. In order to figure out the safety margin of the containment failure in accident conditions, it is necessary to research and analyze the effects of scram power level on the containment integrity. The thermal-hydraulic model of Passive Containment Cooling System has been built with passive containment analysis code in Large Power Passive Reactor. Based on the basis accident of Main Steam Line Break (MSLB), the containment responses to the different scram power level have been carried out. The analysis results show that: (1) the containment pressure is highest when scram power level is 30% of Fission Power (FP) under keeping the design water film coverage; (2) with decrease of water film coverage, the containment does not fail as a result of overpressure, although the pressure is highest on the scram power level 0%FP; (3) the containment failure could occur without cooling water outside the containment surface on the power level 0%FP. (authors)