Tribological behavior of plasma spray coatings for marine diesel engine piston ring and cylinder liner

High-temperature wear characteristics between plasma spray coated piston rings and cylinder liners were investigated to find the optimum combination of coating materials using the disc-on-plate reciprocating wear test in dry conditions. The disc and plate represented the piston ring and the cylinder liner, respectively. Coating materials studied were Cr₂O₃-NiCr, Cr₂O₃-NiCr-Mo, and Cr₃C₂-NiCr-Mo. Plasma spray conditions for the coating materials were established adjusting stand-off distance to obtain a coating with a porosity content of ∼5%. It was found that a dissimilar coating combination of Cr₂O₃-NiCr-Mo and Cr₃C₂-NiCr-Mo provided the best antiwear performance. The addition of molybdenum was found to be beneficial to improve the wear resistance of the coating. Hardness differences between mating surfaces were also important factors in determining the wear characteristics, so that it should be controlled below 300 in Vickers hardness under dry conditions. Adhesive wear accompanying with metal transfer was a dominant wear mechanism for dry conditions.     

A comparison study of the capacitive behavior for sol-gel-derived and co-annealed ruthenium-tin oxide composites

The electrochemical behavior of mixed Ru-Sn oxides fabricated by a modified sol-gel process and a co-annealing method are systematically compared (using cyclic voltammetric and electrochemical impedance spectroscopic analyses), for the application of supercapacitors. Influences of annealing temperature and time on the specific capacitance and textural properties of oxides are also studied. Based on the quasi-linear dependence of voltammetric current density on the scan rate of CV (from 25 to 500 mV s⁻¹), the lowest proton diffusion resistance, and the high-frequency (∼426 Hz) capacitive responses of the co-annealed composite (RTOC_co) as well as its ease in composition control, co-annealing of hydrous RuO₂ and SnO₂ at 200 °C for 2 h is recommended as a promising and practical method for preparing mixed oxides in the supercapacitor application.     

Li-intercalation behaviour of vanadium oxide thin film prepared by thermal oxidation of vanadium metal

In order to produce thin films of crystalline V₂O₅, vanadium metal was thermally oxidised at 500 °C under oxygen pressures between 250 and 1000 mbar for 1-5 min. The oxide films were characterised by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). The lithium intercalation performance of the oxide films was investigated by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS). It was shown that the composition, the crystallinity and the related lithium intercalation properties of the thin oxide films were critically dependent on the oxidation conditions. The formation of crystalline V₂O₅ films was stimulated by higher oxygen pressure and longer oxidation time. Exposure for 5 min at 750 mbar O₂ at 500 °C resulted in a surface oxide film composed of V₂O_5, and consisting of crystallites up to 200 nm in lateral size. The thickness of the layer was about 100 nm. This V₂O₅ oxide film was found to have good cycling performance in a potential window between 3.8 and 2.8 V, with a stable capacity of 117 ± 10 mAh/g at an applied current density of 3.4 μA/cm². The diffusion coefficients corresponding to the two plateaus at 3.4 and 3.2 V were determined from the impedance measurements to (5.2 and 3.0) × 10⁻¹³ cm² s⁻¹, respectively. Beneath the V₂O₅ layer, lower oxides (mainly VO₂) were found close to the metal. At lower oxygen pressure and shorter exposure times, the oxide films were less crystalline and the amount of V⁴⁺ increased in the surface oxide film, as revealed by XPS. At intermediate oxygen pressures and exposure times a mixture of crystalline V₂O₅ and V₆O₁₃ was found in the oxide film.     

超高效液相色谱-串联质谱法测定鱼中孔雀石绿、结晶紫及其代谢物残留量

采用超高效液相色谱-串联质谱（UPLC-MS/MS）法测定鱼中孔雀石绿（MG）、隐色孔雀石绿(LMG)、结晶紫（CV）、隐色结晶紫(LCV)残留。样品加入内标,经乙腈涡旋提取、离心、中性氧化铝柱去除脂肪后,氮吹近干,V(乙腈)∶V(5 mmol/L醋酸铵)=50∶50的溶液定容,上机测定。MG、CV及其代谢物在4.0 μg/L质量浓度范围内有良好的线性关系,MG、LMG、CV的检出限为0.01 μg/kg,LCV的检出限为0.06 μg/kg。在空白样品中分别添加0.25、2.0 μg/kg混合标准溶液和2.0 μg/kg内标溶液进行回收率实验,平均回收率在81.4%~97.8%之间,相对标准偏差RSD（n=6）在5.9%~11.2%之间。对109批次实际鱼样进行检测,4种物质均有不同程度的检出。该方法能够灵敏、准确、可靠的测定鱼中MG、LMG、CV、LCV残留,为鱼类水产品养殖、流通及使用环节的市场监管提供参考依据。     

Gas-cooled reactor thermal hydraulic analyses with MELCOR

Pursuant to the Energy Policy Act of 2005, the High Temperature Gas-Cooled Reactor (HTGR) has been selected as the reference design for the Next Generation Nuclear Plant (NGNP). Stemming from a U.S. Nuclear Regulatory Commission (NRC) HTGR research initiative, a need was identified for validation of systems-level computer code modeling capabilities in anticipation of the eventual need to perform licensing analyses. Because the NRC has used MELCOR for light water reactors (LWR) in the past and because MELCOR was recently updated to include gas-cooled reactor (GCR) physics models, MELCOR is among the system codes of interest to the NRC. This paper describes MELCOR modeling of the General Atomics' Modular High Temperature Gas-Cooled Reactor (MHTGR). The MHGTR is a suitable design for demonstration of MELCOR GCR modeling competency for two reasons: 1) the MHTGR is a predecessor to the more advanced General Atomics’ Gas-Turbine Modular High Temperature Reactor (GTMHR), and 2) experimental data useful for benchmark calculations may soon become available. Using the most complete literature references available for the MHTGR design, researchers at Texas A&M University (TAMU) constructed a MELCOR input deck for the MHTGR to partially validate MELCOR GCR modeling capabilities. Normal and off-normal system operating conditions were modeled with appropriate boundary and initial conditions. MELCOR predictions of system response were obtained for steady-state, pressurized conduction cool-down (PCC), and depressurized conduction cool-down (DCC) scenarios. Code results were checked against nominal MHTGR design parameters, physical intuition, and anticipated GCR thermal hydraulic response. No inherent deficiencies in MELCOR modeling capability were observed, suggesting that the newly-implemented GCR models are adequate for systems-level analysis. If and when experimental benchmark data becomes available, further validation activities may proceed given the modeling efforts discussed herein.     

基于CV-SVM方法的手术时间估计

手术时间估计是进行科学手术排程的前提和依据,为了能够准确地估计手术时间从而为手术排程提供有效信息,采用交叉验证（CV）方法优化支持向量机(SVM)参数,构建基于交叉验证的支持向量机模型对手术时间进行估计。为了验证模型的性能,将CV SVM模型与径向基（RBF）神经网络模型相对比,通过某医院眼科角膜移植手术时间估计进行实例验证。结果表明,相比RBF模型,基于CV SVM模型的手术时间估计结果平均绝对百分误差在11%以内,相对误差在23%以内,验证了模型的有效性,为手术时间估计提供了一种有效的方法。     

基于Landsat的补连塔矿区植被时序特征分析

煤炭在我国能源结构中占有重要的地位。西北地区煤炭储量丰富,但是西北地区降水稀少、植被稀疏,生态环境脆弱。因此矿区植被时序分析对于西北矿区生态保护具有重要意义。本文基于神东矿区的补连塔煤矿为研究区,利用2000～2017年Landsat遥感影像,引入归一化植被指数(Normalized Difference Vegetation Index,NDVI),分析了补连塔煤矿在近15年以来矿区植被变化。结果表明:矿区植被出现明显增长趋势,分析原因是补连塔主要为井工矿,矿区开采对地表植被影响不明显,同时煤矿企业对区域生态建设投入大量资金。影像NDVI变异系数(Coefficient of Variation,CV)介于0. 2～0. 3之间,说明整个矿区NDVI离散性较小,整个矿区的植被覆盖比较平均。     

Uster条干仪试验中应注意的几个问题

介绍了采用Uster条干仪试验数据分析产品质量时应注意的几个问题。Uster统计值只是反映出当前阶段世界生产产品质量的平均水平，由于试样的容量小，用其平均值来反映产品的实际质量状况存在有局限性，为此作者提出了置信区间这一概念，同时指出了在试验中应注意的几个问题。     

Estimation of Relative SD

The relative SD is a measure that is now in common use in the pharmaceutical industry, for example, in pharmaceutical development and analytical chemistry, pharmacology, and quality control. This article comments on the usual point estimate of the true value; presents seven interval estimation methods, easily implemented on a desktop computer; and compares their individual merits and drawbacks. Finally, the question of determining an adequate sample size is addressed, and a possible solution is indicated.     

舰载光电跟踪设备的目标预测算法研究

舰载光电跟踪设备在跟踪百公里以上的目标时,由于受到障碍物干扰,目标有时可能从视场中丢失,需采用记忆跟踪算法对目标的未来时刻位置进行预测,重新找回目标。常规的CA、CV模型预测目标时忽略了残差,记忆跟踪时间短,从而造成预测目标不够精确。针对以上问题,提出了Kalman目标预测模型,延长记忆跟踪时间。首先,由船地坐标转换公式推导了甲板坐标系下船摇速度,前馈到伺服控制系统速度回路中,保证视轴自稳定,同时提高跟踪精度;其次,概述了CA、CV、Kalman目标预测模型;最后,重点论述了3种目标预测模型记忆跟踪和实时雷达引导二维位置信息之间的关系。试验结果表明,本文由于引入了Kalman目标预测模型,使得记忆跟踪时间比传统的CA、CV模型的预测目标时间提高了一个数量级。解决了工程中舰载光电跟踪设备受船摇影响时跟踪精度低和记忆跟踪时间短的问题。