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31.
Xiaowei Li Dr. Bao Li Long Chen Jinchuan Hu Chengdanyang Wen Prof. Qingdong Zheng Prof. Lixin Wu Dr. Huaqiang Zeng Prof. Bing Gong Prof. Lihua Yuan 《Angewandte Chemie (International ed. in English)》2015,54(38):11147-11152
Producing macrocyclic mesogens that are responsive to guest encapsulation presents a significant challenge. Cyclo[6]aramides, a type of macrocycle with a hydrogen‐bond‐constrained backbone, exhibit thermotropic lamellar, discotic nematic, hexagonal, and rectangular columnar mesophases over a considerably wide temperature range, including at room temperature. Additionally, cyclo[6]aramides show unusual mesophase transitions from lamellar to hexagonal columnar phase mediated by macrocyclic host–guest (H–G) interactions between the macrocycles and alkylammonium salts. The phase transition, triggered by an organic guest engaging in H–G interactions with a macrocyclic cavity, provides a novel strategy for manipulating the properties of liquid‐crystalline materials. The crystal structure of a homologous cyclo[6]aramide reveals a disk‐shaped, near‐planar molecular backbone that facilitates intermolecular π–π stacking and leads to columnar assembly. 相似文献
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超声导波是近年来桥梁拉索无损检测研究的重要方法之一。针对弹性波在高强钢丝介质中传播的多模态频散问题,采用单点时域波形的小波时频变换进行混叠信号的模态识别分离。通过数值求解Pochhammer频率超越方程,计算得到0~1.5 MHz范围内纵向导波模态理论频散曲线;采用有限元模拟半波正弦脉冲激励导波在钢丝中传播过程,由小波时-频变换得到导波模态分布,并进行了不同腐蚀程度钢丝实验对比分析。结果表明,经小波时-频变换得到的第1、2、3阶纵向导波模态与理论值对应吻合,单点时域波形的小波时-频变换结果能够有效识别高强钢丝中的导波模态;钢丝在无腐蚀状态下,一阶纵向导波模态能量占比达57.74%,随腐蚀程度增加,能量更为集中到一阶纵波模态,二阶模态能量逐渐减小。 相似文献
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Jinchuan Liu Xiaotian Ji Hanying Zhao 《Journal of polymer science. Part A, Polymer chemistry》2017,55(12):2047-2052
This research provides an efficient method for the fabrication of hybrid micelles with enzyme molecules at the interfaces. Amphiphilic block copolymer is synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and thiol‐modified porcine pancreatic lipase (PPL‐SH) is obtained by treatment of native PPL with Traut's reagent. PPL‐SH is conjugated to the block copolymer chains by thiol‐disulfide exchange reaction. In phosphate buffered saline, the bioconjugate self‐assembles into micelles with enzyme molecules at the interfaces between hydrophobic cores and hydrophilic coronae. The bioactivity of the enzyme molecules on the micelles are compared with the native enzyme. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2047–2052 相似文献
36.
Haiyan Yu Haochun Zhang Jinchuan Zhao Jing Liu Xinlin Xia Xiaohu Wu 《Frontiers of Physics》2022,17(2):23202
Micro/nano-porous polymeric material is considered a unique industrial material due to its extremely low thermal conductivity, low density, and high surface area. Therefore, it is necessary to establish an accurate thermal conductivity prediction model suiting their applicable conditions and provide a theoretical basis for expanding their applications. In this work, the development of the calculation model of equivalent thermal conductivity of micro/nano-porous polymeric materials in recent years is summarized. Firstly, it reviews the process of establishing the overall equivalent thermal conductivity calculation model for micro/nanoporous polymers. Then, the predicted calculation models of thermal conductivity are introduced separately according to the conductive and radiative thermal conductivity models. In addition, the thermal conduction part is divided into the gaseous thermal conductivity model, solid thermal conductivity model and gas–solid coupling model. Finally, it is concluded that, compared with other porous materials, there are few studies on heat transfer of micro/ nanoporous polymers, especially on the particular heat transfer mechanisms such as scale effects at the micro/nanoscale. In particular, the following aspects of porous polymers still need to be further studied: micro scaled thermal radiation, heat transfer characteristics of particular morphologies at the nanoscales, heat transfer mechanism and impact factors of micro/nanoporous polymers. Such studies would provide a more accurate prediction of thermal conductivity and a broader application in energy conversion and storage systems. 相似文献
37.
LIU Shuman;ZHANG Jinchuan;YE Xiaoling;LIU Junqi;WANG Lijun;ZHUO Ning;ZHAI Shenqiang;LI Yuan;LIU Fengqi 《光子学报》2023,52(10):30-49
Interband Cascade Laser （ICL） and Quantum Cascade Laser （QCL） are currently the mainstream mid-infrared semiconductor coherent light sources. Among them, QCL has the advantage of watt-level high power in the spectral band above 4 μm, and the power consumption is usually high. ICLs are characterized by low power consumption and operate in the 3~5 μm spectral band. This band contains a wealth of molecular fundamental modes, such as alkane molecules, which are important in the petrochemical industry, SO2 and formaldehyde, which are closely related to environmental pollution, as well as NO and H2S, which are biomarkers in the medical and health fields. At present, most of the high-sensitivity optical sensing systems based on mid-infrared laser absorption spectroscopy technology ranging from 10-6 to 10-9 use single-mode ICLs with low power consumption as the coherent light sources.It is known that one-dimensional Distributed Feedback （DFB） gratings buried near the active region are most commonly used in mode selection for InP-based semiconductor lasers thanks to the mature InP regrowth technology. However, it is hard to regrow the antimonide superlattice waveguide structure of an ICL on a grating layer, which makes the buried grating structure impossible for a DFB ICL. Even for the simplest surface gratings, since an ICL epitaxial structure is usually capped with a thin lattice mismatched InAs layer, the surface grating can only be etched in the InAs/AlSb superlattice waveguide layer. The etching rate of InAs and AlSb is different, resulting in non-smooth grating side walls. As a result, several grating schemes have been reported so far. For example, a high refractive index Ge layer was deposited on the surface of the ICL structure to avoid etching the grating in the superlattice waveguide, where a 1st DFB grating was fabricated by electron-beam lithography and lift-off. In such a process, it should be noted that the Ge layer is relatively easy to fall off. In contrast to the non-crystalline Ge layer, another surface DFB grating ICL was reported recently, in which a 200-nm-thick epitaxial GaSb top layer was used as the grating layer. Etching the grating in the GaSb layer avoids the problem of non-uniform etching rates of InAs and AlSb, which can improve the grating quality.So far, the highest room temperature continuous wave power of 55 mW was achieved by the fourth-order DFB ICLs, in which the gratings were fabricated by dry etch on both side walls of the laser ridge. The process of etching the grating with a high aspect ratio is a great challenge. In addition, the Side-Mode Suppression Ratios （SMSRs） of single-mode emission are low. Recently, DFB ICLs with two sets of gratings were reported, in which a top 1st sampling grating realized single-mode emission and high-order side-wall gratings suppressed the high-order horizontal mode. The laser exhibited a high output power and high SMSRs. From the point of view of processing, the yield of lateral metal gratings placed on both sides of the laser ridge is relatively high. Nanoplus offers lateral metal grating DFB ICLs emitting at a wide wavelength range with low threshold currents and low output power of several milliwatts.In this review we compare and analyze the performance of several DFB ICLs with different grating configurations, and discuss the dominant loss mechanisms and the improvement routes. In addition, vertical cavity surface emission and photonic crystal ICLs are also introduced. Their performances are compared to the DFB ICLs. Although the performance of these two kinds of single-mode ICLs is not satisfactory and cannot be used as a practical single-mode light source at present, their research is still in its infancy, and it is expected that more in-depth research can improve the device's performance in the future. 相似文献
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Let A be a unital algebra and M be a unital A-bimodule. A linear map δ : A →M is said to be Jordan derivable at a nontrivial idempotent P ∈ A if δ(A) ? B + A ? δ(B) =δ(A ? B) for any A, B ∈ A with A ? B = P, here A ? B = AB + BA is the usual Jordan product. In this article, we show that if A = Alg N is a Hilbert space nest algebra and M = B(H), or A = M = B(X), then, a linear map δ : A → M is Jordan derivable at a nontrivial projection P ∈ N or an arbitrary but fixed nontrivial idempotent P ∈ B(X) if and only if it is a derivation. New equivalent characterization of derivations on these operator algebras was obtained. 相似文献
39.
为了解决百ns级可见光条纹相机时空非线性标定需求,提出了通过构建一个时空二维分布的等间距标准光场快速标定条纹相机二维非线性的设想。通过序列脉冲光构造技术获得时间维度间距相等的参考点;通过光场空间调制技术获得空间维度间距相等的参考点。分析了序列脉冲光和光学系统的设计准则,基于该准则研制了一套可见光条纹相机二维非线性快速标定系统。该系统的时间分辨可达0.1 ns、空间分辨小于90 μm。基于该系统,通过单次扫描成像高效标定了国产某型条纹相机的扫描非线性、时间弥散、时间畸变和几何像差等非线性信息。此外,利用该系统对不同电路的扫描非线性进行了分析验证。该标定系统快速验证了双边扫描电路有利于优化扫描非线性。分析验证结果表明,该标定技术通过单次扫描即可对条纹相机的非线性参数进行标定。 相似文献
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