Pressure and solvent induced low-temperature synthesis of monodisperse superparamagnetic nanocrystals: The case of Fe3O4 in alkanols

The synthesis of nanoparticles via the decomposition of organometallic compounds has been studied extensively, but the effect of pressure has received little attention. Here we firstly focus on the pressure effect, and utilize it as well as the solvent and temperature effects to develop a “green” cheap low-temperature (140–200 °C) strategy via the decomposition of iron oleate in alcohol (or other alkanols) using oleic acid as the protecting reagent. The obtained monodisperse Fe₃O₄ nanocrystals (NCs) exhibit satisfying superparamagnetism. The mechanism of the process has been investigated and it was shown both high pressure and alkanol as the solvent can facilitate the formation of magnetite NCs. Furthermore, the solvent used in the preparation can control the shape, size and dispersion of NCs. In addition, the effects of reactant concentration, reaction time, temperature, and the mol ratio of oleic acid on the Fe₃O₄ NCs have also been discussed.     

A Method for Obtaining Three-dimensional Images with Visual Reality of Real Objects

A new method to remove the shadows in laser triangulation and a computer model for three-dimensional images with visual reality of three-dimensional diffuse objects are presented. The methods for acquiring color data in optical three-dimensional sensing are discussed. A method for obtaining three-dimensional images with visual reality of real objects is presented. The principles,the system structure and the experimental results are provided.     

付立叶变换轮廓术中参数的优化选择

利用等效波长的概念对ＦＴＰ测量方法中的参数θ与载频ｆ０进行优化选择，保证了付立叶频谱中各级谱的完全分离与系统测量精度，运用空间带宽积的概念，实现了对ＦＴＰ测量系统中若干参数的最高允许值进行选择与限制，计算机模拟的结果验证了理论上的推导。     

关于设计教学的一点思考

设计在我国已由学府研究、社会倡导阶段逐步走向市场，并产生一定的社会效益，从而推动设计的教学向更深层次发展。本文是关于设计教学的一点思考。     

Robust view selection in multiview stereo

A robust view selection algorithm for multiview stereo matching is presented. Different from the existent view selection algorithms which pick only the believable views for matching, this method assigns an adaptive weight to each target view based on the dissimilarity between it and the reference view. So it can utilize the information of all views more sufficiently. The algorithm has been evaluated with different real images to demonstrate its robustness.     

原子吸收光谱法测定过氧化氢-柠檬酸溶液中铁铬镍钴

研究了原子吸收光谱法测定压水堆主回路去污液过氧化氢-柠檬酸溶液中铁、铬、镍、钴的影响因素,选择了合适的测量条件,用合成样品进行了试验.结果表明.铁、钴、镍、铬含量在0.5～5mg·L~(-1)范围的回收率为100%±10%,相对标准偏差为6.0%～10%.     

Highly-Branched Palladium Nanodandelions: Simple,Fast, and Green Fabrication with Superior Oxygen Reduction Property

Controllable synthesis of highly-branched metallic structures is of great interest and broad significance for their unique properties of superior conductivity, high porosity, low density, etc., that promote the development of high-efficiency electrocatalysts. Herein, a simple, rapid and green method for the synthesis of highly-branched palladium nanodandelions with flexible ultrafine tentacles and bumpy superficial atomic steps is investigated, without the demand of elevated temperature, seed, template, prolonged reaction time and any organically toxic reducing agent from previously reported highly-branched nanostructures. For the first time, N,N′-methylenebisacrylamide (MBAA) serves as the only additive to simultaneously cover the functions of coordinating agent, reducing agent, and structure-directing agent, facilitating the strategy of intramolecular coordination and self-reduction. Derived from their plentiful ultrafine tentacles, porosity due to the highly-branched structure, and abundant surface atom steps, the Pd nanodandelions exhibit a more positive half-wave of 0.863 V (vs. RHE), optimized specific kinetic activity of 3.0 mA cm⁻² at 0.9 V, and better cycle stability with a maintenance of 77.8 % after 20000 s for the oxygen reduction reaction (ORR), when compared to commercial Pd black. The architectural design of highly-branched metallic structures, as well as the smart fabrication strategy, may hold great promise for exploring a variety of functional nanomaterials.     

Spontaneous Proton Chemistry Enables Ultralow-temperature and Long-life Aqueous Copper Metal Batteries

Aqueous copper metal batteries with acidic electrolytes are regarded as promising candidates for low-temperature energy storage, benefiting from fast kinetics of protons and acid resistance of copper. Here, a Cu(BF₄)₂ electrolyte that spontaneously generates protons is developed for ultralow-temperature copper metal batteries. Systematic studies demonstrate that the hydrolysis of BF₄⁻ generates more protons, rendering the Cu(BF₄)₂ among the most effective aqueous electrolyte capable of breaking hydrogen bonds in water molecules. This electrolyte endows a polyaniline/Cu battery to deliver a short charging time of 21 s and a charge/discharge capability of up to 10 A g⁻¹ at −30 °C, along with a high discharge specific capacity of 70 mAh g⁻¹ and a supercapacitor-comparable power density of 3000 W kg⁻¹. Furthermore, it can exhibit a long and stable cycling lifespan over 10 000 cycles at −50 °C and works well at −70 °C. This work provides an opportunity for intrinsically acidic electrolytes.     

多场耦合作用下氯离子分布场的数值模型

为了研究温度场、湿度场和CO2分布场对氯离子分布场的影响,基于Fick扩散定律和质量守恒定律,主要考虑氯离子扩散系数、湿度以及氯离子结合和释放4个敏感参数,推导了混凝土中氯离子三维分布场控制方程,给出了初始条件和边界条件.利用ANSYS内部集成的参数化程序设计语言APDL建立了数值分析框架.结合试验参数,进行了湿度场作用下混凝土中氯离子分布场的数值计算,并进行了模型参数敏感性分析.结果表明:该模型可以实现不同边界条件下二维和三维多场耦合的数值计算.湿度扩散系数、氯离子扩散系数、边界氯离子浓度以及氯离子结合等温线的取值对氯离子浓度分布影响显著.数值计算结果与实验结果吻合良好,数值模型具有足够的可靠性.     

冬春季节兰州市品蔬菜抗坏血酸含量的变化

研究了冬春季节中兰州９种市品蔬菜抗坏血酸含量的变化，对各种蔬菜在冬春不同时期的维生素Ｃ营养价值进行了评价，初步估计兰州居民在元月下旬至四月初期间的维生素Ｃ日供给量较低，约为４０～５５ｍｇ．