[en] Background: In the conceptual design of China Fusion Engineering Test Reactor (CFETR), two additional poloidal coils, with respect to International Thermonuclear Experimental Reactor (ITER), are used to generate snowflake divertor configuration proposed recently for the purpose of exploring effective way for reducing heat loads onto divertor targets. Heat flux onto divertor targets was dramatically reduced in detached regime, while the performance of impurity screening would also be reduced due to the decrease of divertor temperature. Purpose: This study aims to simulate the detachment operation of snowflake divertor for CFETR. Methods: The detachment operational status was investigated by numerical simulation based on the edge plasma simulation software SOLPS (Scrape-off Layer Plasma Simulation). A D₂ gas puffing in the main chamber was used to change plasma density. Results: When the gas puffing rate was sufficiently high, snowflake divertor of CFETR was completely detached, and the ion flux and heat loads onto the targets significantly decreased. However, the plasma temperature in the divertor region was too low and the impurities could easily pass through the X-point to core plasma, which implied a risk of radiation instability. Conclusion: Therefore, a proper operational status for the snowflake divertor in CFETR should be partial detachment. (authors)

[en] Fabric surface coating is deemed as the major route to fabricate functional fabrics, and interface stability is a critical factor affecting the performance of fabric. Here, electrophoretic deposition (EPD) is employed for fast and facile modification of hydrophobic polyamide fabric with graphene oxide (GO) nanosheets embedded in polymeric networks. For better grafting, polyethyleneimine is utilized to modify the surface of the fabric substrate, endowing more polar groups and resulting in reasonable interface properties of graphene oxide and fabric substrate. GO nanosheets are uniformly deposited on modified fabric via EPD method and then reduced by green hot-press processing. The modified fabric shows excellent electrical conductivity (electrical conductivity > 3.3 S/m), thermal conductivity (0.521 W/m·K), and UV protection performance (UPF > 500, UVA < 0.2%). Meanwhile, the contact angle test of fabric reveals that the addition of graphene significantly improved the hydrophobicity of the fabric.

[en] Shearography is an optical non-destructive testing (NDT) technique which is suitable for large area and fast inspections. However, it is difficult to detect cracks in metals by using conventional stress loading methods for shearography, including stress loadings by vacuum, thermal and vibrational excitations, due to the high rigidity and/or the high thermal conductivity of metals. In this work, we propose and demonstrate an acoustic shearography method for detection of cracks in metallic plates. Piezoelectric transducers bonded on the metallic structures are used to generate acoustic waves, which interact with crack defects and act as the stress loading for shearography testing. Systematic investigations on the wave-defect interaction based shearography indicate that the optimal testing frequencies are determined by the resonant frequencies of the piezoelectric transducers, which are independent of defect type and sample dimensions of the metallic plates. By using the optimal testing frequency, we successfully detected surface fatigue cracks as short as 3 mm and subsurface cracks at 10 mm depth in aluminum plates. We also demonstrate the feasibility of simultaneous detection of multiple notches in multiple fastener holes with one piezoelectric transducer. This wave-defect interaction based shearography developed here allows fast and effective detection of deep subsurface fatigue cracks, which is promising for practical NDT of defects in metallic structures. (paper)

[en] Crystal structures of both polymorphs of Li₄B₂O₅ were determined. The high temperature phase crystallized in a monoclinic space group I2/a with lattice constants a=10.2269(18) Å, b=4.6988(5) Å, c=8.7862(16) Å, and β=93.562(14)°, while the low temperature one crystallized in an orthorhombic space group Pca2₁ with lattice constants a=10.1497(8) Å, b=4.7365(5) Å, c=17.5880(14) Å. Though the lattice of the low temperature phase is of higher symmetry than that of the high temperature one, the structure itself loses symmetry elements when it transforms from the high temperature phase to the low temperature polymorph. The bond strain associated with the high temperature structure is supposed to be the reason for the phase transition. A slight increase in volume per formula unit was observed when Li₄B₂O₅ transforms from the high temperature polymorph to low temperature structure, which is quite unusual and has to be studied further. - Graphical abstract: The monoclinic high temperature polymorph of Li₄B₂O₅ loses symmetry elements when it transforms into the orthorhombic low temperature phase to relieve the bond strain. Highlights: ► Structures of two polymorphs of Li₄B₂O₅ are determined. ► The high and low temperature phases are monoclinic and orthorhombic, respectively. ► A slight larger molar volume was observed for the low temperature phase. ► Symmetry elements are lost in the phase transition from high to low temperature.

[en] Highlights: • The fully dense RGO/S136 composites via molecular-level mixing were firstly fabricated by selective laser melting. • EBSD patterns revealed the refined grain and tailored microstructure for SLM RGO/S136 composites. • SLM RGO/S136 composites with 0.1 wt% RGO exhibited maximum tensile properties and hardness. -- Abstract: In this work, a novel approach combining liquid deposition with selective laser melting (SLM) is used for fabricating reduced graphene oxide (RGO)/S136 metal matrix composites (MMCs). The grain sizes, crystallographic textures, phase compositions and mechanical properties can be tailored by controlling the RGO content in the RGO/S136 MMCs. The results show that the average grain size reaches its smallest size of 0.75 μm when 0.1 wt% RGO was added to the RGO/S136 MMCs. As the RGO content is increased from 0 wt% to 0.5 wt%, a continuous transition of the grains from the (001) orientation to the (101) and (111) orientations is observed. In addition, the cellular dendritic grains transform into equiaxed fine grains with increasing RGO content. The SLM-prepared RGO/S136 MMCs are dominated by high-angle grain boundaries (15°) and the martensite (bcc) phase. The hardness, ultimate tensile strength and yield strength of the SLM RGO/S136 MMCs exhibit trends that initially increase and then decrease, with maximum values of 580.6 HV, 535.3 MPa and 515.8 MPa, respectively. This paper highlights the possibility of controlling the RGO content to achieve the desired microstructural characteristics and mechanical properties of RGO/S136 MMCs fabricated by the SLM process.

[en] Mineralogical study showed that the Yuejin uranium ore is from a low grade, high carbonate and high pyrite sandstone type uranium deposit. Uranium leaching rate, uranium speciation of leachate, leaching kinetics and precipitation analysis were investigated under the conditions of different acidity, liquid-solid ratio and H₂O₂ concentration. The test results showed that the weak acid leaching process can be used to develop high carbonate type uranium deposits, however, because of the high content of pyrite, other oxidants except high concentration H₂O₂ need to be considered. (author)

[en] We examine the results of two measurements by the CLAS collaboration, one of which claimed evidence for a Θ⁺ pentaquark, whilst the other found no such evidence. The unique feature of these two experiments was that they were performed with the same experimental setup. Using a Bayesian analysis we find that the results of the two experiments are in fact compatible with each other, but that the first measurement did not contain sufficient information to determine unambiguously the existence of a Θ⁺. Further, we suggest a means by which the existence of a new candidate particle can be tested in a rigorous manner

[en] New cross sections for the reaction ep → e(prime)ηp are reported for total center of mass energy W=1.5--2.3 GeV and invariant squared momentum transfer Q²=0.13--3.3 GeV². This large kinematic range allows extraction of new information about response functions, photocouplings, and ηN coupling strengths of baryon resonances. A sharp structure is seen at W ∼ 1.7 GeV. The shape of the differential cross section is indicative of the presence of a P-wave resonance that persists to high Q². Improved values are derived for the photon coupling amplitude for the S₁₁(1535) resonance. The new data greatly expands the Q² range covered and an interpretation of all data with a consistent parameterization is provided

[en] The reaction γp → K⁺K^-p was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a Θ⁺⁺ pentaquark, a narrow doubly charged baryon state having strangeness S = +1 and isospin I = 1, in the pK⁺ invariant mass spectrum. No statistically significant evidence of a Θ⁺⁺ was found. Upper limits on the total and differential production cross section for the reaction γp → K^-Θ⁺⁺ were obtained in the mass range from 1.5 to 2.0 GeV/c², with an upper limit of about 0.15 nb, 95% C.L. for a narrow resonance with a mass M_#Theta#_#sup ++# = 1.54 GeV/c². This result places a very stringent upper limit on the Θ⁺⁺ width

[en] The cross section and decay angular distributions for the coherent φ meson photoproduction on the deuteron have been measured for the first time up to a squared four-momentum transfer t =(p_γ-p_φ)² = -2 GeV²/c², using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are compared with predictions from a re-scattering model. In a framework of vector meson dominance, the data are consistent with the total φ-N cross section σ_φN at about 10 mb. If vector meson dominance is violated, a larger σ_φN is possible by introducing larger t-slope for the φN → φN process than that for the γN → φN process. The decay angular distributions of the φ are consistent with helicity conservation