To decrease the cost of lithium‐ion cathode materials, cobalt‐free Li‐Fe‐Ni‐Mn‐O (FeAl000) was synthesized by a facile sol–gel method by using citric acid as the chelating agent. To enhance the electrochemical performance of FeAl000, low‐costing and environmentally friendly aluminum was added as a dopant. The Al‐doped Li‐Fe‐Al‐Ni‐Mn‐O (FeAl015) material exhibited excellent electrochemical performance. The charge/discharge capacity and corresponding differential capacity curves suggested that Al‐doping activated the transformation of Mn4+ into Mn3+, and the activated Mn3+/Mn4+ redox/oxide couple contributed to an increase in the discharge capacity. X‐ray photoelectron spectroscopy analyses demonstrated the transformation of Mn4+ into Mn3+/2+. The Nyquist and Bode curves obtained by electrochemical impedance spectroscopy indicated that Al doping enhanced electron transfer and somewhat hampered formation of the solid–electrolyte‐interphase layer during cycling.
A humanoid robot is an advanced representation of robot techniques. It can move like a human and possesses the ability to use human tools. Sensing and intelligent control technologies have increased the intelligence of humanoid robots. However, the dexterity of a humanoid robot is still far from that of a human. Herein, a bending sensor is introduced to detect human motion, which can thus be digitized to enable a humanoid robot to learn to be more dexterous. This bending sensor is fabricated of carbon fiber with a cascade structure, resulting in excellent characteristics, including a quantitative detection capability, high gauge factor, low hysteresis, long‐term durability, and high‐frequency response. Thus, the bending sensor can recognize both the large‐scale motion of joint bending and subtle motion of muscle contraction. Fourteen bending sensors corresponding to the 14 knuckles of the human hand can accurately recognize and digitize hand gestures. These multichannel sensors are combined with nine additional bending sensors to comprehensively digitize the grasping process of the upper limb and recognize the grasping of objects with different sizes and weights. These successful applications demonstrate that the bending sensor can open a path toward learning human behavior for a humanoid robot.
The agglomerated and sheet Li1.2Ni0.3Mn0.6Al0.1O2.2 materials were synthesized by hydrothermal method (HT‐NMA) and sol‐gel method (SG‐NMA) respectively. Compared with sheet particles, agglomerated particles had better mutual contact. The specific surface area calculated by Brunauer–Emmett–Teller (BET) method was 8.92 m2/g for HT‐NMA and 5.90 m2/g for SG‐NMA. Larger specific surface area achieved better connections between cathode material and conductive agent. Better electron transitivity contributed to better electrochemical performance of HT‐NMA, at the potential range of 2.0 V–4.8 V, the retention of capacity was 86 % at the current density of 20 mA/g after 31 cycles and the discharge capacity was 108mAh/g at the current density of 1000 mA/g. Both Nyquist and Bode plots were used to deeply investigate the reason for better performance of HT‐NMA, the results showed that agglomerated particles had better electron migration capacity both before and after cycle.
In this paper we study a class of singularly perturbed interface boundary value problems with discontinuous source terms. We first establish a lemma of lower-upper solutions by using the Schauder fixed point theorem. By the method of boundary functions and the lemma of lower-upper solutions we obtain the existence, asymptotic estimates, and uniqueness of the solution with boundary and interior layers for the proposed problem.
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