Potassium isotope fractionation between K-salts and saturated aqueous solutions at room temperature: Laboratory experiments and theoretical calculations

Li, Weiqiang,Kwon, Kideok D.,Li, Shilei,Beard, Brian L. Pergamon Press 2017 Geochimica et cosmochimica acta Vol.214 No.-

<P><B>Abstract</B></P> <P>Improvements in mass spectrometry have made it possible to identify naturally occurring K isotope (<SUP>39</SUP>K/<SUP>41</SUP>K) variability in terrestrial samples that can be used in a variety of geological and biological applications that involve cycling of K such as clay or evaporite formation. However, our ability to interpret K isotope variability is limited by a poor understanding of how K isotopes are fractionated at low temperatures. In this study, we conducted recrystallization experiments of eight K-salts in order to measure the K isotope fractionation factor between the salt and the saturated K solution (Δ<SUP>41</SUP>K<SUB>min-sol</SUB>). Measured Δ<SUP>41</SUP>K<SUB>min-sol</SUB> are +0.50‰ for K<SUB>2</SUB>CO<SUB>3</SUB>·1.5H<SUB>2</SUB>O, +0.32‰ for K<SUB>2</SUB>SO<SUB>4</SUB>, +0.23‰ for KHCO<SUB>3</SUB>, +0.06‰ for K<SUB>2</SUB>C<SUB>2</SUB>O<SUB>4</SUB>·H<SUB>2</SUB>O, +0.02‰ for KCl, −0.03‰ for K<SUB>2</SUB>CrO<SUB>4</SUB>, −0.15‰ for KBr, and −0.52‰ for KI. Overall the Δ<SUP>41</SUP>K<SUB>min-sol</SUB> decreases with increasing <I>r</I> for K in crystals, where <I>r</I> is the average distance between a K atom and its neighboring atoms of negative charge. Salts with monovalent anions and salts with divalent anion complexes define different linear trends with distinct slopes on a plot of Δ<SUP>41</SUP>K<SUB>min-sol</SUB> - <I>r</I>. We applied <I>ab initio</I> lattice dynamics and empirical crystal-chemistry models to calculation of K isotope fractionation factors between K salts; both methods showed that the calculated inter-mineral K isotope fractionation factors (Δ<SUP>41</SUP>K<SUB>min-KCl</SUB>) are highly consistent with experimentally derived Δ<SUP>41</SUP>K<SUB>min-KCl</SUB> under the assumption of consistent β factors for different saturated K solutions. Formulations for the crystal-chemistry model further indicate that both anion charge and bond length <I>r</I> are the principle controlling factors for K isotope fractionation, and the K isotope fractionation factors correlate with <I>r</I> following a 1/<I>r</I> <SUP>3</SUP> relationship. Our experiment and theoretical study confirms the existence of significant equilibrium K isotope fractionation at ambient conditions, and the K isotope fractionation factors for halides and sulfate obtained in this study provide a basis for future K isotope studies on evaporites.</P>

A High Step-up Modular Isolated DC-DC Converter for Large Capacity Photovoltaic Generation System integrated into MVDC Grids

Shilei Lu,Kai Sun,Guoen Cao,Yongdong Li,Jung-Ik Ha,Geon-Hong Min 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Nowadays, the research and design of the DCDC conversion system has become more and more popular in the application of photovoltaic generation into the medium voltage DC (MVDC) grids. A novel high power modular isolated DC-DC converter with high step-up ratio is proposed as a module of the DC-DC conversion system in this paper. Based on the input parallel and output series (IPOS) connections of the proposed modular converters, the system is easy to achieve high capacity and high voltage. A two-stage structure is employed in the proposed converter. The interleaved boost topology is applied to the front-stage, which realizes MPPT for PV arrays with low input current ripples. The full-bridge LLC topology is employed as the back-stage, which lowers power losses by the implementation of softswitching. The voltage gain of the proposed converter is derived in detail. The theoretical analysis and control strategy are studied in depth. Simulation and experiment verify the feasibility and effectiveness of the proposed converter.

Integrated Radial-axial Magnetic Bearing with Variable Permanent-Magnet Bias Flux In Situ

Xu Shilei,Li Jiajing,Wang Zhipeng,Sun Jinji,Ren Hongliang 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.4

Bias magnetic fl ux plays a crucial role in the performance of active magnetic bearings. However, the bias fl ux produced by NdFeB or SmCo materials in traditional permanent-magnet (PM) bias bearings cannot be adjusted, resulting in infl exible bearing performance. To improve the controllability of the PM bias fl ux in the integrated radial-axial magnetic bearing (RAMB), this article proposes a new design that uses a low coercivity AlNiCo magnet and equips a magnetization coil. By controlling the current of the magnetization coil, the magnetization state and bias fl ux of the AlNiCo magnet can be adjusted in situ, thereby improving the force characteristics and rotor iron losses of the PM-biased RAMB. The designed RAMB is analyzed and verifi ed by the 3D fi nite element method and the analytical model based on Preisach’s hysteresis theory and magnetic circuit method. The proposed design off ers a new idea for magnetic bearing structure and control.

Electrical properties and morphology of highly conductive composites based on polypropylene and hybrid fillers

Gu Zheming,Wang Gengchao,Zhang Ling,Cheng Qilin,Li Xiaohui,Wang Wendong,Jin Shilei,Li Chunzhong 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.1

Electrically conductive polypropylene/hybrid filler (PP/GO–MWNTs) and PP/MWNTs composite have been prepared via melt blending PP with the hybrid filler (multiwalled carbon nanotubes (MWNTs) and graphite oxide (GO)) and the single filler (MWNTs), respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to research the interior morphology of the GO–MWNTs hybrid filler, and the dispersion of the hybrid filler in the PP matrix is also observed by SEM. The results show that a clear reduction in electrical resistivity and percolation threshold of PP/GO–MWNTs composite can be ascribed to the corporation of GO. The electrical properties of PP composites were improved owing to the effective conductive networks formed by hybrid filler.

Characterization of clutch traits and egg production in six chicken breeds

Shi Lei,Li Yunlei,Isa Adam Mani,Ma Hui,Yuan Jingwei,Wang Panlin,Ge Pingzhuang,Gong Yanzhang,Chen Jilan,Sun Yanyan 아세아·태평양축산학회 2023 Animal Bioscience Vol.36 No.6

Objective: The better understanding of laying pattern of birds is crucial for developing breed-specific proper breeding scheme and management. Methods: Daily egg production until 50 wk of age of six chicken breeds including one layer (White Leghorn, WL), three dual-purpose (Rhode Island Red, RIR; Columbian Plymouth Rock, CR; and Barred Plymouth Rock, BR), one synthetic dwarf (DY), and one indigenous (Beijing-You Chicken, BYC) were used to characterize their clutch traits and egg production. The age at first egg, egg number, average and maximum clutch length, pause length, and number of clutches and pauses were calculated accordingly. Results: The egg number and average clutch length in WL, RIR, CR, and BR were higher than those in DY and BYC (p<0.01). The numbers of clutches and pauses, and pause length in WL, RIR, CR, and BR were lower than those in DY and BYC (p<0.01). The coefficient variations of clutch length in WL, RIR, CR, and BR (57.66%, 66.49%, 64.22%, and 55.35%, respectively) were higher than DY (41.84%) and BYC (36.29%), while the coefficient variations of egg number in WL, RIR, CR, and BR (9.10%, 9.97%, 10.82%, and 9.92%) were lower than DY (15.84%) and BYC (16.85%). The clutch length was positively correlated with egg number (r = 0.51 to 0.66; p<0.01), but not correlated with age at first egg in all breeds. Conclusion: The six breeds showed significant different clutch and egg production traits. Due to the selection history, the high and median productive layer breeds had higher clutch length than those of the less productive indigenous BYC. The clutch length is a proper selection criterion for further progress in egg production. The age at first egg, which is independent of clutch traits, is especially encouraged to be improved by selection in the BYC breed.