Covalently bonded two spin centers of paramagnetic metallofullerene dimer

Nano Research - Paramagnetic endohedral metallofullerenes with well protected unpaired spin have potential applications in molecular-scale qubit processing and magnetoreception system. In this...     

优化发动机生物柴油燃烧系统参数的试验研究

对ZS195柴油机燃烧生物柴油时,其燃烧系统参数对柴油机经济性能的影响进行了研究,通过试验确定了这些参数的最佳值。在这些参数最佳值范围内,ZS195柴油机最大额定转速功率可达到原机水平,燃烧效率可达到32%以上。     

Copper-doped flower-like molybdenum disulfide/bismuth sulfide photocatalysts for enhanced solar water splitting

A facile synthesis approach to fabricate Cu-doped MoS₂/Bi₂S₃ (Cu-MoS₂/Bi₂S₃) photocatalysts is reported. The photocatalyst samples with varying amounts of Cu are applied in the photocatalytic splitting of water to produce H₂ under the irradiation of simulated solar light. The Cu-MoS₂/Bi₂S₃ photocatalysts with an optimum Cu loading of 20 mol% exhibited high photocatalytic performance, achieving a total H₂ yield of 32.4 μmol/h after 6 h of reaction. The photoactivity of the Cu-doped sample was shown to have risen more than 40% than that of pure MoS₂/Bi₂S₃. The improved performance is attributed to the impurity states generated within Cu-doped MoS₂, which serve as trapping sites for photogenerated electrons. The effective charge transfer mechanism achieved was evidenced by photoelectrochemical measurements. Based on the experimental results obtained, a plausible mechanism for the photocatalytic process associated with Cu-MoS₂/Bi₂S₃ was proposed.     

Growth behavior comparison of Listeria monocytogenes between Type strains and beef isolates in raw beef

Food Science and Biotechnology - This study was conducted to compare the growth parameters of Listeria monocytogenes between beef isolates and Type strains in raw beef. Beef was artificially...     

Tunable Spectrum Selectivity for Multiphoton Absorption with Enhanced Visible Light Trapping in ZnO Nanorods

Observation of visible light trapping in zinc oxide (ZnO) nanorods (NRs) correlated to the optical and photoelectrochemical properties is reported. In this study, ZnO NR diameter and c‐axis length respond primarily at two different regions, UV and visible light, respectively. ZnO NR diameter exhibits UV absorption where large ZnO NR diameter area increases light absorption ability leading to high efficient electron–hole pair separation. On the other hand, ZnO NR c‐axis length has a dominant effect in visible light resulting from a multiphoton absorption mechanism due to light reflection and trapping behavior in the free space between adjacent ZnO NRs. Furthermore, oxygen vacancies and defects in ZnO NRs are associated with the broad visible emission band of different energy levels also highlighting the possibility of the multiphoton absorption mechanism. It is demonstrated that the minimum average of ZnO NR c‐axis length must satisfy the linear regression model of Z _p,min = 6.31d to initiate the multiphoton absorption mechanism under visible light. This work indicates the broadening of absorption spectrum from UV to visible light region by incorporating a controllable diameter and c‐axis length on vertically aligned ZnO NRs, which is important in optimizing the design and functionality of electronic devices based on light absorption mechanism.     

Assessing students' conceptual understanding using an online three‐tier diagnostic test

When solving a mathematical problem, students who do not have sufficient conceptual understanding may perform poorly and exhibit misconceptions. This study was aimed to examine students' conceptual understanding and significant misconceptions when solving number sense‐related problems. An online three‐tier diagnostic test was administered to 125 fifth‐grade students with varied socio‐economic backgrounds in Hong Kong. Only 14.40% of the students exhibited high performance with high confidence, indicating that these students had a profound conceptual understanding of number sense. In addition, the majority of the students (66.40%) did not demonstrate number sense; these students exhibited several significant misconceptions and could solve the questions only by using a rule‐based method or guessing. Accordingly, most students performed unsatisfactorily on number sense‐related problems. This study is imperative in identifying early predictors and provides information for further compatible interventions in the teaching and learning of number sense in Hong Kong in particular and worldwide in general.     

Lattice Boltzmann models for two-dimensional coupled Burgers’ equations

In this paper, two lattice Boltzmann models for two-dimensional coupled Burgers’ equations are proposed through treating the part or all of convection items as the source term, where the spatial gradient can be calculated by the distribution function. The models can exactly recover the Burgers’ equations without any assumptions. Some numerical tests are also performed to validate the present models. It is found that the proposed models are more accurate and efficient in solving two-dimensional coupled Burgers’ equations.     

碘在生物样品消解和灰化过程中的丢失研究

用＾１３１Ｉ示踪和中子活化法测定了碘在生物样品酸消解和灰化处理中回收率。结果表明：Ｄ 不同酸消化条件下碘的回收率差别很大。当ＨＮＯ３和ＣＨｌＯ４作消化液、用冷却水回流消解时，生物样品中碘的回收率可达９５％以上。用ＫＯＨ在６５０℃灰化时，回收率可达９０％以上。     

2001 survey of organochlorine pesticides in retail milk from Beijing, P R China.

A monitoring study was conducted in 2001 to determine the organochlorine pesticides and their metabolite residues in milk taken from supermarkets in Beijing, P. R. China. The average concentrations of total HCH and DDT were 0.038 and 0.046 mg x kg(-1), respectively, expressed on a fat basis. The aldrin residue was detected in nine milk samples, with a mean concentration of 0.035 mg x kg(-1). Heptachlor and its epoxides were not found in any milk samples. Of 72 milk samples analysed, three from South China contained the higher levels of DDT and HCH residues that exceeded the FAO/WHO accepted tolerance level. Although organochlorine pesticides such as DDT and HCH have been banned in China since 1983, the residues of such compounds still exist in the environment and cause food contamination, a fact likely attributed to the short prohibition period and illegal use for agricultural purposes at present.     

Compensation Scheme of Position Angle Errors of Permanent-Magnet Linear Motors

The position angle is very important in the current control of permanent-magnet linear motors (PMLMs), and its error affects the control precision of currents. However, the position angle is often not accurately detected because of faults in motor making, pulse loss of linear encoders, and so on. In order to precisely control the currents of PMLMs, a compensation scheme of position angle errors is proposed based on the mathematical relation between position angle errors and currents. In the scheme, a position angle error compensator is designed to compensate the position angles detected by linear encoders. Furthermore, a filter and a class of iteration learning algorithm are proposed to avoid the errors produced by detected phase currents and phase voltages. Simulation results show that position angle errors of PMLMs are fully compensated. Using the designed position angle error compensator, currents can be controlled in a more precise manner.