Stability and Mechanical Properties of w1-X Mox b4.2 (X=0.0-1.0) From First Principles

Heavy transition-metal tetraborides (e.g., tungsten tetraboride, molybdenum tetraboride, and molybdenum-doped tungsten tetraboride) exhibit superior mechanical properties, but solving their complex crystal structures has been a long-standing challenge. Recent experimental x-ray and neutron diffraction measurements combined with first-principles structural searches have identified a complex structure model for tungsten tetraboride that contains a boron trimer as an unusual structural unit with a stoichiometry of 1:4.2. In this paper, we expand the study to binary MoB4.2 and ternary W1-xMoxB4.2 (x=0.0-1.0) compounds to assess their thermodynamic stability and mechanical properties using a tailor-designed crystal structure search method in conjunction with first-principles energetic calculations. Our results reveal that an orthorhombic MoB4.2 structure in Cmcm symmetry matches well the experimental x-ray diffraction patterns. For the synthesized ternary Mo-doped tungsten tetraborides, a series of W1-xMoxB4.2 structures are theoretically designed using a random substitution approach by replacing the W to Mo atoms in the Cmcm binary crystal structure. This approach leads to the discovery of several W1-xMoxB4.2 structures that are energetically superior and stable against decomposition into binary WB4.2 and MoB4.2. The structural and mechanical properties of these low-energy W1-xMoxB4.2 structures largely follow the Vegard\u27s law. Under changing composition parameter x=0.0-1.0, the superior mechanical properties of W1-xMoxB4.2 stay in a narrow range. This unusual phenomenon stems from the strong covalent network with directional bonding configurations formed by boron atoms to resist elastic deformation. The findings offer insights into the fundamental structural and physical properties of ternary W1-xMoxB4.2 in relation to the binary WB4.2/MoB4.2 compounds, which open a promising avenue for further rational optimization of the functional performance of transition-metal borides that can be synthesized under favorable experimental conditions for wide applications

Estimation of Evapotranspiration and Its Components across China Based on a Modified Priestley–Taylor Algorithm Using Monthly Multi-Layer Soil Moisture Data

Although soil moisture (SM) is an important constraint factor of evapotranspiration (ET), the majority of the satellite-driven ET models do not include SM observations, especially the SM at different depths, since its spatial and temporal distribution is difficult to obtain. Based on monthly three-layer SM data at a 0.25° spatial resolution determined from multi-sources, we updated the original Priestley Taylor–Jet Propulsion Laboratory (PT-JPL) algorithm to the Priestley Taylor–Soil Moisture Evapotranspiration (PT-SM ET) algorithm by incorporating SM control into soil evaporation (Es) and canopy transpiration (T). Both algorithms were evaluated using 17 eddy covariance towers across different biomes of China. The PT-SM ET model shows increased R2, NSE and reduced RMSE, Bias, with more improvements occurring in water-limited regions. SM incorporation into T enhanced ET estimates by increasing R2 and NSE by 4% and 18%, respectively, and RMSE and Bias were respectively reduced by 34% and 7 mm. Moreover, we applied the two ET algorithms to the whole of China and found larger increases in T and Es in the central, northeastern, and southern regions of China when using the PT-SM algorithm compared with the original algorithm. Additionally, the estimated mean annual ET increased from the northwest to the southeast. The SM constraint resulted in higher transpiration estimate and lower evaporation estimate. Es was greatest in the northwest arid region, interception was a large fraction in some rainforests, and T was dominant in most other regions. Further improvements in the estimation of ET components at high spatial and temporal resolution are likely to lead to a better understanding of the water movement through the soil–plant–atmosphere continuum

Testing Extensible Design Patterns in Object-Oriented Frameworks through Scenario Templates

Design patterns have been used in object-oriented frameworks such as the IBM San Francisco framework, Apple’s Rhaspody, OpenStep, and WebObjects, and DIWB. However, few guidelines are available on to effectively test the software developed with design patterns. This paper first discusses the issues in testing applications developed with design patterns using an object-oriented framework. Two kinds of design patterns are available, extensible and static patterns, and this paper focuses on testing applications using extensible design patterns. Applications developed using extensible design patterns are difficult to test due to dynamic typing, dynamic binding, extensibility, and communication complexity. This paper then presents a technique, Message Framework Sequence Specifications (MfSS), for generating scenario templates that can be used to generate test cases to test applications developed using extensible design patterns and an object-oriented framework. Various partition test cases and random test cases can be generated from a MfSS. Finally, this paper uses the MfSS technique to test a small bank framework. The test cases generated successfully detected numerous faults that were seeded in the program

Construction Progress and Aviation Flight Test of BDSBAS

As an important part of the BeiDou global navigation satellite system (BDS-3), the BeiDou satellite-based augmentation system (BDSBAS) aims to provide a high-integrity navigation service for users in China and its surrounding areas. At present, BDSBAS has completed the preliminary construction of the system and formed the single frequency (SF) augmentation service. The paper introduces the composition and working process of BDSBAS, and expounds the solution and performance evaluation methods of the BDSBAS SF service. Tests based on a general aviation aircraft were carried out at Caihu Airport in Shenyang, China, which simulated the aircraft’s take-off and landing operation during the approach phase and the transition flight operation during the en-route phase. On this basis, the BDSBAS SF service performance was analyzed and evaluated. The horizontal positioning errors of the three flight tests are 1.62, 1.27, and 1.49 m, respectively, and the vertical positioning errors are 4.38, 4.30, and 4.04 m, respectively. In the first two tests, the APV-I availability and continuity of the service reach 100%. In the last test, a receiver false alarm event occurred, resulting in an APV-I availability and continuity of 99.993% and 99.989%, respectively. The event was confirmed to be caused by some aviation environmental factors and was not related to the system service. No integrity events occurred during the tests. The test results show that the positioning accuracy, availability, and integrity of the BDSBAS SF service meet the APV-I level requirements of the ICAO standards, which preliminarily illustrates the ability of BDSBAS to be used in the field of civil aviation

High-speed multi-pass tunable diode laser absorption spectrometer based on frequency-modulation spectroscopy

We report a multi-pass tunable diode laser absorption spectrometer based on the frequency-modulation spectroscopy (FMS) technique. It has the advantage of high scan speed and is immune to the etalon effect. A multi-pass Herriott-type cell was used in the spectrometer to increase the effective optical length to 17.5 m and compact the physical dimensions of the spectrometer to 60x30x30 cm(3). Noise due to low-frequency fluctuation of the laser power and the I/f noise in the rapid detection are sufficiently reduced by FMS. Interference fringes are effectively suppressed when the modulation frequency equals to integer or half-integer times of their free spectral range (FSR). An absorption line of C2H2 around 1.51 mu m was recorded with the spectrometer to demonstrate its capabilities. The response frequency of the spectrometer is up to 100 kHz (10 mu s) thanks to the high modulation frequency of FMS. The detection sensitivity of the spectrometer is about 240 ppb (3 sigma) at 100 kHz measurement repetition rate. The amplitude of the absorption signal is highly linear to the C2H2 concentration in the range of 300 ppb - 100 ppm. Based on the Allan variation, the detection limit was determined to be 18 ppb with a detection time of 166 s. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Thermochemically driven crystal phase transfer via chlorination roasting toward the selective extraction of lithium from spent LiNi1/3Co1/3Mn1/3O2

The selective extraction of lithium from spent lithium-ion batteries (LIBs) is significant for combating potential lithium deficiencies and for providing environmental protection by enabling highly selective Li extraction through a short path. Herein, we demonstrate a thermochemically driven process for spent LiNi1/3Co1/3Mn1/3O2 (NCM) batteries by systematically understanding the conversion mechanisms and controlling the chlorination behavior during chlorinated roasting. First, software simulations based on thermochemical differences are introduced to select customized chloride salts for the thermal treatment of spent NCM materials. The thermal behavior characterization studies are combined with thermochemical calculations, showing that CaCl2 and its hydrates energetically favor the preferential destruction of the layered structure of lithium oxides and transform them into water-soluble chloride compounds. Based on this unique mechanism, the established lithium extraction system achieves outstanding selectivity and realizes the target of an acid-free method, greatly reducing its negative environmental impact. This work may shed new light on the mechanism of chlorination roasting for selective extraction and provide resources to develop promising technology for the green and selective extraction of lithium from spent NCM batteries

Statistical downscaling of reference evapotranspiration in Haihe River Basin: applicability assessment and application to future projection

<p>Future changes in reference evapotranspiration (ET₀) are of increasing importance in assessing the potential impacts on hydrology and water resources systems of more pronounced climate change. This study assesses the applicability of the Statistical Downscaling Model (SDSM) in projecting ET₀, and investigates the seasonal and spatial patterns of future ET₀ based on general circulation models (GCMs) across the Haihe River Basin. The results indicate that SDSM can downscale ET₀ well in term of different basin-averaged measures for the HadCM3 and CGCM3 GCMs. HadCM3 has a much superior capability in capturing inter-annual variability compared to CGCM3 and thus is chosen as the sole model to assess the changes in future ET₀. There are three homogeneous sub-regions of the Haihe River Basin: Northwest, Northeast and Southeast. Change points are detected at around 2050 and 2080 under the A2 and B2 scenarios, respectively. The Northwest is revealed to have a slight to strong increase in ET₀, while the Northeast and the Southeast tend to experience a pattern change from decrease to increase in ET₀.</p><p><b>EDITOR</b> M.C. Acreman</p><p><b>ASSOCIATE EDITOR</b> J. Thompson</p><p></p> <p><b>EDITOR</b> M.C. Acreman</p> <p><b>ASSOCIATE EDITOR</b> J. Thompson</p