Comparative study of MCe0.75Zr0.25Oy (M = Cu, Mn, Fe) catalysts for selective reduction of NO by CO: Activity and reaction pathways

Basic oxygen furnace steelmaking leads to the production of CO-rich off-gas. When CO and NO are combined in off-gas, selective catalytic reduction by CO (CO-SCR) effectively achieves the synergistic removal of both pollutants. In this paper, CuCe 0.75Zr 0.25O y, MnCe 0.75Zr 0.25O y, and FeCe 0.75Zr 0.25O y catalysts are prepared and evaluated for their CO-SCR activity, and the results show that the reaction system needs to be anaerobic; thus, the CO-SCR reaction can be dominant. The T 90 values of CuCe 0.75Zr 0.25O y and FeCe 0.75Zr 0.25O y are 200 °C and 223 °C, respectively. The activities of these two catalysts are higher than that of MnCe 0.75Zr 0.25O y (T 90 = 375 °C). Linear nitrate and bridged bidentate nitrate are the main intermediate species involved in NO conversion on the catalyst surface, and bidentate CO 3 2− coordination is the main intermediate species involved in CO conversion on the catalyst surface. CuCe 0.75Zr 0.25O y has high lattice oxygen mobility and is more likely to react with NO and CO. In the presence of oxygen, most CO is oxidized by O 2, which increases continuously to 100%, 100%, and 98% for CuCe 0.75Zr 0.25O y, FeCe 0.75Zr 0.25O y, and MnCe 0.75Zr 0.25O y, respectively; additionally, CO is oxidized by O 2, and the CO-SCR reaction cannot be carried out

3D-printed integrative probeheads for magnetic resonance

射频探头前端作为核磁共振设备的核心部件之一，极大程度的决定着系统实验性能的优劣。探头前端通常由射频线圈、射频电路及样品检测管道等部分组成。现有的射频线圈制作技术主要是通过手工或机械手段按照所需的线圈形状进行绕制。但是，当线圈结构较为复杂、不规则，或体积尺寸较小时，常规绕制方法便难以满足结构设计和制造的精度需求，因此造成线圈性能的劣化，增大检测区域的射频场不均匀性，对核磁共振检测产生负面影响。本研究中，利用3D打印熔融沉积制造或光敏树脂选择性固化技术精确加工出一体化磁共振探头前端，使用常温液态金属填充线圈模型管路形成射频线圈，搭建出稳定的一体化磁共振射频探头。利用高精度3D打印和液态金属灌注技术制备出包含有射频线圈和定制化样品管道结构在内的一体化磁共振射频探头前端，克服了传统磁共振三维微型线圈成型困难、与样品腔匹配程度差等问题，提高了探头的信噪比，为定制化的磁共振检测提供了新思路。 该工作由厦门大学电子科学与技术学院陈忠教授、游学秋副研究员和孙惠军高级工程师共同指导完成，博士研究生谢君尧为论文第一作者。厦门大学电子科学与技术学院黄玉清高级工程师、王忻昌副教授、倪祖荣助理教授、硕士研究生张德超，化学化工学院杨朝勇教授、博士研究生李星锐，萨本栋微米纳米科学技术研究院陈宏教授为合作作者。【Abstract】Magnetic resonance (MR) technology has been widely employed in scientific research, clinical diagnosis and geological survey. However, the fabrication of MR radio frequency probeheads still face difficulties in integration, customization and miniaturization. Here, we utilized 3D printing and liquid metal filling techniques to fabricate integrative radio frequency probeheads for MR experiments. The 3D-printed probehead with micrometer precision generally consists of liquid metal coils, customized sample chambers and radio frequency circuit interfaces. We screened different 3D printing materials and optimized the liquid metals by incorporating metal microparticles. The 3D-printed probeheads are capable of performing both routine and nonconventional MR experiments, including in situ electrochemical analysis, in situ reaction monitoring with continues-flow paramagnetic particles and ions separation, and small-sample MR imaging. Due to the flexibility and accuracy of 3D printing techniques, we can accurately obtain complicated coil geometries at the micrometer scale, shortening the fabrication timescale and extending the application scenarios.The work is supported by the National Natural Science Foundation of China (Grants U1632274, 11761141010, U1805261, 11475142, 22073078, and 61801411), and China Postdoctoral Science Foundation (2017M622075).研究工作得到国家自然科学基金、中国博士后科学基金等项目支持

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Investigation of Adhesion Properties of Tire—Asphalt Pavement Interface Considering Hydrodynamic Lubrication Action of Water Film on Road Surface

To obtain the tire–pavement peak adhesion coefficient under different road states, a field measurement and FE simulation were combined to analyze the tire–pavement adhesion characteristics in this study. According to the identified texture information, the power spectral distribution of the road surface was obtained using the MATLAB Program, and a novel tire hydroplaning FE model coupled with a textured pavement model was established in ABAQUS. Experimental results show that here exists an “anti-skid noncontribution area” for the insulation and lubrication of the water film. Driving at the limit speed of 120 km/h, the critical water film thickness for the three typical asphalt pavements during hydroplaning was as follows: AC pavement, 0.56 mm; SMA pavement, 0.76 mm; OGFC pavement, 1.5 mm. The road state could be divided into four parts dry state, wet sate, lubricated state, and ponding state. Under the dry road state, when the slip rate was around 15%, the adhesion coefficient reached the peak value, i.e., around 11.5% for the wet road state. The peak adhesion coefficient for the different asphalt pavements was in the order OGFC > SMA > AC. This study can provide a theoretical reference for explaining the tire–pavement interactions and improving vehicle brake system performance

Design of a Redundant Manipulator for Playing Table Tennis towards Human-Like Stroke Patterns

This study investigates the design of a 7-DOF humanoid manipulator capable of playing table tennis with human-like stroke patterns. The manipulator system includes a redundant arm, real-time stereo vision system, and a distributed motion control system. First, the size, weight, workspace, and motion capability of the designed arm are similar to those of a human's arm. The forward and inverse kinematics, and the Jacobian matrix of the redundant manipulator are formulated. Next, a distributed motion control system is designed. The ball trajectory prediction method is proposed. Then, a human-inspired optimization method based on Jacobian pseudoinverse and the comfort of the arm posture for stroke pattern trajectory is proposed to achieve human-like stroke patterns and decrease the counterforce exerted on the manipulator. Finally, the validity of the proposed system and methods is demonstrated via human-like stroke pattern experiments

Unio: A Unified I/O System Framework For Hybrid Scientific Workflow

Recent years have seen an increasing number of Hybrid Scientific Applications. They often consist of one HPC simulation program along with its corresponding data analytics programs. Unfortunately, current computing platform settings do not accommodate this emerging workflow very well. This is mainly because HPC simulation programs store output data into a dedicated storage cluster equipped with Parallel File System (PFS). To perform analytics on data generated by simulation, data has to be migrated from storage cluster to compute cluster. This data migration could introduce severe delay which is especially true given an ever-increasing data size. While the scale-up supercomputers equipped with dedicated PFS storage cluster still represent the mainstream HPC, ever increasing scale- out small-medium sized HPC clusters have been supplied to facilitate hybrid scientific workflow applications in fast-growing cloud computing infrastructures such as Amazon cluster compute instances. Different from traditional supercomputer setting, the limited network bandwidth in scale-out HPC clusters makes the data migration prohibitively expensive. To attack the problem, we develop a Unified I/O System Framework (UNIO) to avoid such migration overhead for scale-out small-medium sized HPC clusters. Our main idea is to enable both HPC simulation programs and analytics programs to run atop one unified file system, e.g. data-intensive file system (DIFS in brief). In UNIO, an I/O middle-ware component allows original HPC simulation programs to execute direct I/O operations over DIFS without any porting effort, while an I/O scheduler dynamically smoothes out both disk write and read traffic for both simulation and analysis programs. By experimenting with a real-world scientific workflow over a 46-node UNIO prototype, we found that UNIO is able to achieve comparable read/write I/O performance in small-medium sized HPC clusters equipped with parallel file system. More importantly, since UNIO completely avoids the most expensive data movement overhead, it achieves up to 3x speedups for hybrid scientific workflow applications compared with current solutions

Calculation of and Key Influencing Factors Analysis on Equivalent Resilient Modulus of a Submerged Subgrade

To calculate and analyze the equivalent resilient modulus of a submerged subgrade, a constitutive model considering the effect of saturation and matrix suction was introduced using ABAQUS’s user-defined material (UMAT)subroutine. The pavement response under falling weight deflectometer (FWD) load was simulated at various water levels based on the derived distribution of the resilient modulus within the subgrade. The equivalent resilient modulus of the subgrade was then calculated using the equivalent iteration and weighted average methods. Based on this, the influence of the material and structural parameters of the subgrade was analyzed. The results indicate that the effect of water level rise on the tensile strain at the bottom of the asphalt layer and the compressive strain at the top of the subgrade is obvious, and its trend is similar to an exponential change. The equivalent resilient modulus of the subgrade basically decreases linearly with the rise in the water level, and there is high consistency between the equivalent iteration and weighted average methods. The saturated permeability coefficient and subgrade height have the most significant effect on the resilient modulus of the subgrade, which should be emphasized in the design of submerged subgrades, and the suggested values of the resilient modulus of the subgrade should be proposed according to the relevant construction conditions

A Comprehensive Method to Evaluate Ride Comfort of Autonomous Vehicles under Typical Braking Scenarios: Testing, Simulation and Analysis

To highlight the advantages of autonomous vehicles (AVs) in modern traffic, it is necessary to investigate the sensing requirement parameters of the road environment during the vehicle braking process. Based on the texture information obtained using a field measurement, the braking model of an AV was built in Simulink and the ride comfort under typical braking scenarios was analyzed using CarSim/Simulink co-simulation. The results showed that the proposed brake system for the AV displayed a better performance than the traditional ABS when considering pavement adhesion characteristics. The braking pressure should be controlled to within the range of 4 MPa~6 MPa on a dry road, while in wet road conditions, the pressure should be within 3 MPa~4 MPa. When steering braking in dry road conditions, the duration of the “curve balance state” increased by about 57.14% compared with wet road conditions and the recommended curve radius was about 100 m. The slope gradient had a significant effect on the initial braking speed and comfort level. Overall, the ride comfort evaluation method was proposed to provide theoretical guidance for AV braking strategies, which can help to complement existing practices for road condition assessment