Using recycled coarse aggregate (RCA) to replace natural pebbles and using lithium slag (LS) from industrial waste to replace cement in order to improve the mechanical properties of concrete and ...solve environmental problems. In this study, the effects of different substitution rates of RCA (0, 30%, 50%, and 70%) and different LS contents (0, 10%, 15%, 20%, and 25%) on the mechanical properties of concrete were investigated. The main results indicate that when the substitution rate of RCA is 30% and the LS content is 20%, optimal cube compressive strength, axial compressive strength, and elastic modulus can be achieved, with an increase of 9.90%, 48.22%, and 9.94% respectively; when the substitution rate of RCA is 70% and the LS content is 20%, the splitting tensile strength and flexural strength can be improved by 9.90% and 48.22%, respectively. The morphology of RCA concrete specimens with LS was observed with a scanning electron microscope (SEM). Moreover, corrections were made to improve the relevant formula according to the differences between the measured intensity index and data converted from current specifications.
Due to intermediate hydrophobicity of methyl methacrylate (MMA) monomer in water, it is difficult to prepare its stable water in oil high internal phase emulsion (HIPE). Moreover, the addition of ...fully hydrophilic co-monomer such as 2-hydroxyethyl methacrylate (HEMA) in MMA monomer makes it further troublesome to stabilize these emulsions. This paper addresses the preparation of such type of difficult to prepare emulsions via addition of an amphiphilic fluorinated di-block copolymer (FDB), poly(2-dimethylamino)ethylmethacrylate-b-poly(trifluoroethyl methacrylate) (PDMAEMA-b-PTFEMA) as stabilizer. Interestingly, HEMA and/or HFBA (hexa fluorobutyl acrylate) as co-monomers were successfully added to impart some special properties such as thermodynamic stability, desired amphiphilicity to the final polyHIPEs. Fluorinated blocks in FDB anchored well at oil/water interface of HIPE, offering enough hydrophobicity to the comparatively hydrophilic monomers and in turn providing resistance against coalescence. MMA polyHIPEs were found to be fully hydrophobic just by replacing HEMA co-monomer with HFBA. Due to superb inherent hydrophobic nature of fluorine atoms, MMA-HFBA polyHIPEs showed remarkable water contact angle of 139°. Furthermore, the addition of fluorinated co-monomer in MMA based HIPEs significantly improved thermal stabilities of these materials with improvement in degradation temperature from 305 °C to 360 °C.
Display omitted
•The circular structure could be related to the emplacement of a concealed intrusion.•Propose a new structural model for the deep and concealed orebodies at Dongping.•Recent ...exploration drilling based on our new model has successfully intersected additional concealed ore-bodies.
The Dongping gold deposit is the largest gold deposit in the Hebei province, China, with proven gold reserves of more than 100 tons. After the main gold ore-bodies were mined out, the Dongping gold deposit faced a shortage in gold reserves with an uncertain future. As a result, we conducted systematic studies on the ore-controlling structures at the Dongping gold deposit, with the aim of finding additional concealed ore-bodies, should these be present. Gold mineralization at Dongping is controlled by two stages of maximum principal compressional stress (σ1): NW-trending stress that produced the NE- to NW-trending structures, and sub-vertical stress that produced the circular structure, respectively. The sub-vertical compressional stress may have resulted from the emplacement of a concealed intrusive body, which also led to horizontal extensional stress, generating structures surrounding the intrusion. Development of such structures potentially increased the permeability of the local crust, facilitating the mobilisation of gold-bearing hydrothermal fluids that subsequently precipitated along the structures, forming the gold ore-bodies. We propose that the deep part of the Dongping gold deposit at the lithological contact with the concealed intrusive bodies is prospective for the exploration of additional reserves, which is supported by our subsequent drilling and the discovery of concealed gold ore-bodies beneath the deposit.
Branch-guide energy couplers can be used in the terahertz relativistic sheet electron beam traveling wave tubes (THz-RSBTWT) for high and high frequency microwave radiations. To analyze this type of ...coupler, a new method based on the phase superposition principle was put forward in this paper. A physical model was developed, which is applicable no matter the coupler width is large or small. The general distance relationship between the branches was derived and a rapid design formula was obtained, which can help design energy coupler with arbitrary coupling coefficient.
This manuscript presents a new extended linear system for integral equation based techniques for solving boundary value problems on locally perturbed geometries. The new extended linear system is ...similar to a previously presented technique for which the authors have constructed a fast direct solver. The key features of the work presented in this paper are that the fast direct solver is more efficient for the new extended linear system and that problems involving specialized quadrature for weakly singular kernels can be easily handled. Numerical results illustrate the improved performance of the fast direct solver for the new extended system when compared to the fast direct solver for the original extended system.
•A locally perturbed geometry differs from the original in local portion of the boundary.•Local refinement in boundary discretization is also regarded as local perturbation.•Extended systems allow for linearly scaling direct solvers for the perturbed problem.•The solver built for the original problem is reused to solve the perturbed one.
During the course of ionospheric heating experiments, researchers at the European Incoherent Scatter Scientific Association (EISCAT) observed an apparent electron density enhancement. The enhancement ...extended over a wide range of altitudes, above the reflection altitude of the high-frequency pump wave. However, whether this enhancement actually corresponds to a true enhancement in electron density remains an open question. When the dispersion relation of ion acoustic waves is followed, the frequency ratio of the enhanced ion line to the background ion line suggests that the profile of the effective ion mass may have remained unchanged. Furthermore, the solar radio flux and ion drift velocity indicate no significant changes in the ion species and their densities. In conclusion, the electron density enhancement observed at EISCAT should not, in fact, be considered a true enhancement.
Using the characteristic that the distance apart between the emitting fiber and receiving fiber only shifts the angular-power curve, a differential reflective fiber-optic sensor for angular ...displacement measurement is presented through subtraction of two power signals from two receiving fibers placed on both sides of one emitting fiber. A theoretical model is established to characterize the performance of the differential reflective fiber-optic angular displacement sensor. The measurements made indicate that the general behavior of the experimental results agrees with that of the theoretical results, and the sensor can improve sensitivity by about 120%, resulting in the significant improvement of anti-interference capability, which will be more suitable for high accuracy bipolar absolute angular displacement measurement. Design guidelines are also suggested to achieve desired sensor performances.
•A differential reflective fiber-optic sensor is proposed to measure angular displacement.•A theoretical model verified by the experimental measurements was established to characterize the sensor׳s performance.•The sensor can improve sensitivity and anti-interference capability.•The sensor is more suitable for bipolar absolute angular displacement measurement.
Aims
The aim of this study was to investigate the incidence of alexithymia in intensive care unit nurses and determine the associated factors.
Design
A multi‐center, cross‐sectional study.
Methods
In ...total, 485 nurses in intensive care unit were recruited from 53 hospitals in China. Data collection tools used in the study included demographic characteristics, the Social Support Rating Scale (SSRS), Emotional Intelligence Scale (EIS), and the 20‐item Toronto Alexithymia Scale (TAS‐20). SPSS 25.0 software (Corp., Armonk, NY, USA) was used to preform data analysis.
Results
About 43.7% of intensive care unit nurses were classified as alexithymia in the whole sample (males: 50%, females: 43%). The median TAS‐20 score was 60 (interquartile range = 9). The study found that alexithymia was significantly associated with marital status, whether living alone, working years, and social support (Adjusted R Squared = 0.194, F = 6.466, p < 0.01), while emotional intelligence was not statistically significant with alexithymia.
Conclusions
Alexithymia is a psychological problem with high incidence in intensive care unit nurses. In this study, being unmarried or divorced, living alone, and having fewer years of work (≤5 years) were associated with a higher risk of alexithymia. Interventions that strengthen social support may also help improve the mental health of ICU nurses.
The Au-20Sn solder is widely used in the packaging of high-end electronic products, and the requirement on the reliability of the solder joints is more and more strict with a continuous increase in ...the performance of the package products. As the oxygen content in the Au-Sn solder is a key factor dominating the quality of fluxless packaging, in this study, the wettability and spreading performance of the Au-20Sn solder with different oxygen contents and the interfacial microstructure, mechanical properties, gas tightness and ratio of soldering area of the Au-Sn/Cu solder joints prepared using these solders were comprehensively investigated to clarify the effects of trace oxygen content. The results reveal that the wetting and spreading performances of the solder decrease sharply with increasing oxygen content. When the oxygen content increased from 18 to 77 ppm, the spreading area of the solder on the Cu substrate decreased from 92.8 to 49.2 mm2, reducing by 47%. Meanwhile, pores and microcracks appear in the solder joint with relatively high oxygen content, making the shear strength decrease from 56.6 to 31.7 MPa. The oxygen also greatly affects the gas tightness and ratio of soldering area. For the optical window packaged using Au-Sn solder containing 40 ppm of oxygen, the leakage rate was higher than 5 × 10−11 mbar·m−3·s−1 and cannot fulfill the requirements. With increasing oxygen content in the Au-Sn solder, the cleanliness of the chip packaged with these solders deteriorated, and the solder surface was obviously oxidized. When the oxygen content was 18 ppm, the ratio of soldering area was 92%, but decreased sharply to 53% when the oxygen content increased to 77 ppm. It is demonstrated that an oxygen content lower than 27 ppm is required for the Au-20Sn solder used in fluxless packaging.
PDF
