The formation of the coarse columnar crystal structure of Ti-6Al-4V alloy in the process of additive manufacturing greatly reduces the mechanical performance of the additive manufactured parts, which ...hinders the applications of additive manufacturing techniques in the engineering fields. In order to refine the microstructure of the materials using the high intensity ultrasonic via the acoustic cavitation and acoustic flow effect in the process of metal solidification, an ultrasonic vibration technique was developed to a synchronous couple in the process of Laser and Wire Additive Manufacturing (LWAM) in this work. It is found that the introduction of high-intensity ultrasound effectively interrupts the epitaxial growth tendency of prior-β crystal and weakens the texture strength of prior-β crystal. The microstructure of Ti-6Al-4V alloy converts to fine columnar crystals from typical coarse columnar crystals. The simulation results confirm that the acoustic cavitation effect applied to the molten pool created by the high-intensity ultrasound is the key factor that affects the crystal characteristics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper proposes a closed-loop compensation method to remove oscillations caused by control valve stiction. With the control loop operating at the auto mode, the proposed method adds a short-time ...rectangular wave to the reference to introduce two movements for the control valve to arrive at a desired position. A systematic way to design the parameters of the short-time rectangular wave is developed. The proposed method is robust against modeling errors and measurement noises. The effectiveness of the proposed method is illustrated by laboratory and simulation examples.
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IJS, KILJ, NUK, PNG, UL, UM
Polyurethane coatings containing nanopools of a grafted lubricating liquid ingredient for dewetting enablement (NP-GLIDE) are prepared by curing a commercial polyol P0, a hexamethylene diisocyanate ...trimer, and P1-g-PDMS, which is a graft copolymer consisting of a polyol backbone P1 bearing poly(dimethylsiloxane) (PDMS) side chains. These materials are known as NP-GLIDE because most test liquids have no problem to cleanly glide off them and because segregated nanopools of the grafted lubricating ingredient (PDMS) for dewetting enablement are dispersed throughout the coating matrix. To optimize the dewetting performance of the NP-GLIDE coatings, the molecular weights of the PDMS side chains in the P1-g-PDMS samples were increased from 1.0 kDa (1k) to 5.0 kDa (5k) and 10.0 kDa (10k). A comparative study of the coatings containing three different P1-g-PDMS samples at a constant PDMS mass fraction of either 6.0 or 2.00% (m/m) showed that P1-g-PDMS5k-based coatings exhibited the best dewetting properties. These properties included the lowest sliding angles for test liquids that were incompatible with PDMS and the fastest and most effective contraction of marker ink traces and a paint. Coatings containing 0.50 and 1.00% (m/m) of PDMS5k were also prepared from P1-g-PDMS5k and compared with those containing 2.00 and 6.0% (m/m) of PDMS5k. The coatings were shown to retain their dewetting properties with the PDMS contents as low as 1.00% (m/m). Although the results of this study provided valuable insight into the design of future practical NP-GLIDE coatings, a model has also been proposed for the surface structure of the coatings to justify our observations.
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IJS, KILJ, NUK, PNG, UL, UM
It is generally believed that cracks in metal matrix composites (MMC) parts manufacturing are crucial to the reliable material properties, especially for the reinforcement particles with high volume ...fraction. In this paper, WC particles (WCp) reinforced Fe-based metal matrix composites (WCp/Fe) were manufactured by laser melting deposition (LMD) technology to investigate the characteristics of cracks formation. The section morphology of composites were analyzed by optical microscope (OM), and microstructure of WCp, matrix and interface were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), in order to study the crack initiation and propagation behavior under different laser process conditions. The temperature of materials during the laser melting deposition was detected by the infrared thermometer. The results showed that the cracks often appeared after five layers laser deposition in this experiment. The cracks crossed through WC particles rather than the interface, so the strength of interface obtained by the LMD was relatively large. When the thermal stress induced by high temperature gradient during LMD and the coefficient of thermal expansion mismatch between WC and matrix was larger than yield strength of WC, the cracks would initiate inside WC particle. Cracks mostly propagated along the eutectic phases whose brittleness was very large. The obtained thin interface was beneficial to transmitting the stress from particle to matrix. The influence of volume fraction of particles, laser power and scanning speed on cracks were investigated. This paper investigated the influence of WC particles size on cracks systematically, and the smallest size of cracked WC in different laser processing parameters was also researched.
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•Cracks cross through WC particles rather than the interface.•Cracks initiate inside WC particle and propagate along the eutectic phases.•Interface layer between WC particle and Fe matrix generated during laser melting deposition is very thin.•The influence of WC particles size and volume fraction on cracks is investigated.•Smallest sizes of cracked WC particles are related to laser processing parameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A detailed investigation on bond performance of non-uniform corrosion in concrete.•A new impressed current method was used to induced non-uniform corrosion of rebar.•The effects of longitudinal rib ...of rebar on corrosion and bon degradation are discussed.
In this work, the bond degradation of non-uniformly corroded steel rebars embedded in concrete was studied. A total of 105 concrete specimens with accelerated corrosion of steel rebar were evaluated using the pull-out test. The influences of corrosion mode, corrosion level, orientation of the longitudinal rib, and the position of steel rebar on the bond degradation were analyzed. The cracking patterns of corrosion-induced cracks, bond failure modes, and bond stress-slip relations were discussed. The results showed that the orientation of longitudinal rib and the thickness of concrete cover play a vital role in determining the cracking patterns of corrosion-induced cracks. In comparison to the uniformly corroded specimens, the bond performance of specimens with non-uniform corrosion of steel rebar degraded more significantly, and this phenomenon became even more pronounced as the corrosion level increased. Moreover, the beneficial improvements caused by the expansive rust on the bond performance were greatly dependent on the degrees of concrete constraint and corrosion level.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this article, properties of solitons in a parity-time periodical lattices with a single-sited defect are investigated. Both of the negative and positive defects are considered. Linear stability ...analyses show that, when the defect is positive, in the semi-infinite gap, the solitons are always stable, while in the first gap, the solitons are unstable in most of their existence region except for those near the edge of the second band; when the defect is negative, in the semi-infinite gap, other than those near the edge of the first band, most solitons are stable, but in the first gap, all solitons are unstable. Such stability analyses are corroborated by numerical simulations.
New methods for preparation of tailor-made fluorine-containing compounds are in extremely high demand in nearly every sector of chemical industry. The asymmetric construction of quaternary C–F ...stereogenic centers is the most synthetically challenging and, consequently, the least developed area of research. As a reflection of this apparent methodological deficit, pharmaceutical drugs featuring C–F stereogenic centers constitute less than 1% of all fluorine-containing medicines currently on the market or in clinical development. Here we provide a comprehensive review of current research activity in this area, including such general directions as asymmetric electrophilic fluorination via organocatalytic and transition-metal catalyzed reactions, asymmetric elaboration of fluorine-containing substrates via alkylations, Mannich, Michael, and aldol additions, cross-coupling reactions, and biocatalytic approaches.
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IJS, KILJ, NUK, PNG, UL, UM
Rheological behavior of paste in metal mines Wu, Aixiang; Ruan, Zhuen; Wang, Jiandong
International journal of minerals, metallurgy and materials,
04/2022, Volume:
29, Issue:
4
Journal Article
Peer reviewed
Cemented paste backfill (CPB) has been one of the best practical approaches for tailings management and underground goaf treatment. Paste rheology is a science to study the flow and deformation ...behaviors of paste or filling body under the effects of stress, strain, temperature, and time during the CPB process. The goal of studying paste rheology is to solve the engineering problems existing in four key processes; that is, paste rheology should meet the engineering demands of thickening, mixing, transportation, and backfilling. However, paste rheology is extremely complicated due to its high concentration, materials complexity, and engineering characteristics of non-stratification, non-segregation, and non-bleeding. The rheological behavior of full tailings in deep thickening, rheological behavior of paste in mixing and pipeline transportation, and rheological behavior of filling body are introduced and discussed: (1) gel point, compressive yield stress, and the hindered settling function are adopted to characterize the rheological properties of full tailings in deep thickening. Combination of Coe-Clevenger theory and Buscall-White theory can also analyze the thickening performance in the whole area of deep cone thickener; (2) yield stress and viscosity are consistent with the evolution trend of the relative structure coefficient of paste in mixing; (3) coupling effect of wall slip and time-temperature dependency has a significant influence on the rheological properties and pipeline transportation; (4) damage variable is introduced to the Burgers model to describe the creep damage of the filling body. However, in-depth and systematic studies were still needed to establish a complete theoretical system of paste rheology in metal mines.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
China is one of the regions with highest PM2.5 concentration in the world. In this study, we review the spatio-temporal distribution of PM2.5 mass concentration and components in China and the effect ...of control measures on PM2.5 concentrations. Annual averaged PM2.5 concentrations in Central-Eastern China reached over 100μgm−3, in some regions even over 150μgm−3. In 2013, only 4.1% of the cities attained the annual average standard of 35μgm−3. Aitken mode particles tend to dominate the total particle number concentration. Depending on the location and time of the year, new particle formation (NPF) has been observed to take place between about 10 and 60% of the days. In most locations, NPF was less frequent at high PM mass loadings. The secondary inorganic particles (i.e., sulfate, nitrate and ammonium) ranked the highest fraction among the PM2.5 species, followed by organic matters (OM), crustal species and element carbon (EC), which accounted for 6–50%, 15–51%, 5–41% and 2–12% of PM2.5, respectively. In response to serious particulate matter pollution, China has taken aggressive steps to improve air quality in the last decade. As a result, the national emissions of primary PM2.5, sulfur dioxide (SO2), and nitrogen oxides (NOX) have been decreasing since 2005, 2006, and 2011, respectively. The emission control policies implemented in the last decade could result in noticeable reduction in PM2.5 concentrations, contributing to the decreasing PM2.5 trends observed in Beijing, Shanghai, and Guangzhou. However, the control policies issued before 2010 are insufficient to improve PM2.5 air quality notably in future. An optimal mix of energy-saving and end-of-pipe control measures should be implemented, more ambitious control policies for NMVOC and NH3 should be enforced, and special control measures in winter should be applied. 40–70% emissions should be cut off to attain PM2.5 standard.
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•In 2013, only 4.1% of the Chinese cities attained the annual average PM2.5 standard.•Secondary inorganic aerosol ranked the highest fraction among PM2.5 species.•National emissions of primary PM2.5 and SO2 have been decreasing since 2005/2006, so as NOX since 2011.•Emission controls make important contributions to decreasing trends in PM2.5 concentrations in megacities.•40–70% emission reduction in the future is needed to attain the PM2.5 standard.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Gallbladder cancer is the most common biliary tract malignancy and not sensitive to chemotherapy. Autophagy is an important factor prolonging the survival of cancer cells under chemotherapeutic ...stress. We aimed to investigate the role of long non-coding RNAs (lncRNAs) in autophagy and chemoresistance of gallbladder cancer cells.
We established doxorubicin (Dox)-resistant gallbladder cancer cells and used microarray analysis to compare the expression profiles of lncRNAs in Dox-resistant gallbladder cancer cells and their parental cells. Knockdown or exogenous expression of lncRNA combined with in vitro and in vivo assays were performed to prove the functional significance of lncRNA. The effects of lncRNA on autophagy were assessed by stubRFP-sensGFP-LC3 and western blot. We used RNA pull-down and mass spectrometry analysis to identify the target proteins of lncRNA.
The drug-resistant property of gallbladder cancer cells is related to their enhanced autophagic activity. And we found a lncRNA ENST00000425894 termed gallbladder cancer drug resistance-associated lncRNA1 (GBCDRlnc1) that serves as a critical regulator in gallbladder cancer chemoresistance. Furthermore, we discovered that GBCDRlnc1 is upregulated in gallbladder cancer tissues. Knockdown of GBCDRlnc1, via inhibiting autophagy at initial stage, enhanced the sensitivity of Dox-resistant gallbladder cancer cells to Dox in vitro and in vivo. Mechanically, we identified that GBCDRlnc1 interacts with phosphoglycerate kinase 1 and inhibits its ubiquitination in Dox-resistant gallbladder cancer cells, which leads to the down-regulation of autophagy initiator ATG5-ATG12 conjugate.
Our findings established that the chemoresistant driver GBCDRlnc1 might be a candidate therapeutic target for the treatment of advanced gallbladder cancer.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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