Research on Nitrogen Reduction Processes in Fujian Mangrove Sediments Using Nitrogen Stable Isotope in China

近年来，由于人类活动频繁，导致大量营养盐输入水生系统中，造成严重的富营养化，威胁水生生物生长，污染饮用水，同时破坏水体的娱乐用途。当输入系统的氮不能通过生物地球化学作用被河流移除或滞留时，过量的氮大都带入海岸带河口，最终进入大陆架作为重要的氮汇途径，而这些过量氮素将会引起近岸海域富营养化及一系列环境问题。红树林是分布在热带和亚热带海岸河口地区潮间带开放的生态系统。其栖息地—海岸潮汐湿地—作为河口沉积区的重要组成，是全球碳、氮、磷的重要源、汇及转化器，因此成为了研究的热点。 本研究以我国东南沿海的不同区域红树林沉积物为主要研究对象，利用15N稳定同位素技术进行定位监测分析，通过室内培养测定红树...In recent years, a large number of nutrient discharge intothe aquatic system due to frequent human activities, causing serious eutrophication, threatening the growing of aquatic organisms, polluting drinking water, and destroying the recreational use of water at the same time.When the nitrogen discharging into system cannot be removed or stranded through the biogeochemical effects, excessive nitro...学位：理学硕士院系专业：环境与生态学院_环境管理学号：3312014115172

Preparation of Porous Silicon Materials as Anode for Lithium Ion Batteries

多孔硅具有大量孔洞,能有效缓解体积膨胀带来的压力,有望成为锂离子硅基负极材料的一个研究方向.采用光助电化学腐蚀、二次化学腐蚀制备高孔隙率n型多孔硅材料,通过优化后的光助电化学腐蚀,样品的孔径约为800~1 000nM,多孔层厚度(平均孔深)约为155μM,孔隙率约74%.二次腐蚀后,样品孔径增加到1.1μM,多孔层厚度减小到110μM,孔隙率增加到84%,表明二次腐蚀增加了样品的孔径和孔隙率.以二次腐蚀的多孔硅材料为负极的锂离子半电池在0.05C的恒流充放电循环测试下,循环20次后充放电比容量保持在188和198MAH/g,效率保持90%以上.实验结果表明,多孔硅锂电极比单晶硅锂电极具有更长的循环寿命,可有效提高锂电池的性能.Porous silicon can incorporate large amounts of Li and relieve the stress during lithiation with large superficial area and high porosity.N-porous silicon was produced by photoelectrochemical etching and chemical over-etching.The SEM images shows:the porous silicon materials produced by photoelectrochemical etching have 155 μm-long and 1 μm-wide macropores.After chemical over-etching carried out in porous silicon,the materials had 220 nm-wide walls and pores with diameter of 1.1 μm,respectively.The thickness of porous layer is 110 μm.Chemical over-etching enlarged diameters of holes,which increased poriness of the materials.At a rate of 0.05 C,the charged/discharge capacity of the cell with porous silicon materials as anode was 1 191,2 036 mAh/g in the first and dropped to 188,198 mAh/g after 20 cycles with the efficiency above 90%.The result shows that the porous silicon materials has longer cycle life than single-crystal silicon,which can improve lithium′s profermance.国家自然科学基金重点项目(61176050;61036003;61176092); 福建省自然科学基金项目(2012H0038

Dual heterogeneous structured medium-entropy alloys showing a superior strength-ductility synergy at cryogenic temperature

The tensile properties and the corresponding deformation mechanisms at both room and cryogenic temperatures for a CoCrNi-based medium entropy alloy with both a homogeneous structure and a dual heterogeneous structure have been studied and compared. The dual heterogeneous structure is found to be composed of both heterogeneous grain structure and coherent L1(2) nanoprecipitates. Both the homogeneous structure and the dual heterogeneous structure show a simultaneous improvement on yield strength and uniform elongation at cryogenic temperature as compared to those at room temperature, which can be attributed to higher hetero-deformation-induced hardening rate and higher density of geometrically necessary dislocations induced at cryogenic temperature. For the homogeneous structure, nano-spaced stacking faults along two slip systems with much smaller interspacing and higher density of Lomer-Cottrell locks should play the essential role in sustaining the strain hardening for better tensile ductility at cryogenic temperature. L1(2) nanoprecipitates are observed to be very effective on blocking dislocation slip and accumulation of dislocations around them. For the dual heterogeneous structure, more intense interactions between defects and L1(2) nanoprecipitates are observed after tensile deformation at cryogenic temperature, resulting in fragmentation and refinement of L1(2) nanoprecipitates for better tensile properties than at room temperature. (C) 2022 The Author(s). Published by Elsevier B.V

Deformation mechanisms for a new medium-Mn steel with 1.1 GPa yield strength and 50% uniform elongation

A new medium-Mn steel was designed to achieve unprecedented tensile properties, with a yield strength beyond 1.1 GPa and a uniform elongation over 50%. The tensile behavior shows a heterogeneous deforma-tion feature, which displays a yield drop followed by a large LAlders band strain and several Portevin-Le Chatelier bands. Multiple strain hardening mechanisms for excellent tensile properties were revealed. Firstly, non-uniform martensite transformation occurs only within a localized deformation band, and ini-tiation and propagation of every localized deformation band need only a small amount of martensite transformation, which can provide a persistent and complete transformation-induced-plasticity effect dur-ing a large strain range. Secondly, geometrically necessary dislocations induced from macroscopic strain gradient at the front of localized deformation band and microscopic strain gradient among various phases provide strong heter-deformation-induced hardening. Lastly, martensite formed by displacive shear trans-formation can inherently generate a high density of mobile screw dislocations, and interstitial C atoms segregated at phase boundaries and enriched in austenite play a vital role in the dislocation multipli-cation due to the dynamic strain aging effect, and these two effects provide a high density of mobile dislocations for strong strain hardening. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology

生物制药研究中的多维色谱

对全二维气相色谱(GC×GC)、全二维液相色谱(HPLC×HPLC)、多维毛细管电泳等多维分离技术在生物制药研究中的应用进行了综述，其中对作者所在研究组在全二维气相色谱应用于中药及固相萃取一液相色谱联用分析系统等方面的工作做了重点介绍。由所综述的生物制药研究得出结论：多维分离方法以其高分辨、快速、自动化等特点已经在生物制药领域显示出它的巨大优势，并将发挥更大的作用

Structure, Stress State and Piezoelectric Property of GaN Nanopyramid Arrays

GaN nanopyramid (NP) arrays have been fabricated by a convenient electrodeless photoelectrochemical etching method. Transmission electron microscopy measurement indicates that these NPs are composed of crystalline GaN surrounding a dislocation. High-resolution X-ray diffraction and the micro-Raman spectrum reveal a highly compressive stress relaxation in the NPs compared with compressed GaN subfilm. Additionally, negative piezoelectric current pluses are generated from the GaN NPs when the conductive atomic force microscope scans cross the arrays in the contact mode. The result demonstrates that the GaN NP arrays are a promising candidate for nanogenerators

A practical route towards fabricating GaN nanowire arrays

GaN nanowire (NW) arrays have been fabricated by the electrodeless photoelectrochemical (PEC) etching method for the first time. Under appropriate conditions, the etching process is just a dislocation-hunted process, in which the etching solution "digs down'' along the threading dislocations, resulting in the formation of GaN NWs by preferentially etching away the defective parts of GaN with dislocations and retaining the flawless parts. The NWs have a density of 1 similar to 2 x 10(7) cm(-2), diameters ranging from 150 nm to 500 nm, and corresponding lengths ranging from 10 mu m to 20 mu m. Transmission electron microscopy (TEM) indicates that these GaN NWs possess few dislocations. High resolution X-ray diffraction (HRXRD) and micro-Raman measurements show that these GaN NWs are stress-free. Room temperature cathodoluminescence (CL) measurements show a single near-band-edge emission at 367 nm with a full width at half maximum (FWHM) of 8 nm from the NWs, indicating a high optical quality. Additionally, negative piezoelectric current pluses are generated from the GaN NWs when the conductive atomic force microscope is scanned cross the arrays in contact mode. Such GaN NW arrays are promising building blocks for exploring nanodevices with excellent performance

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies