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Zhang, Lidong,Jeong, Young-Il,Zheng, Sudan,Suh, Hongsuk,Kang, Dae Hwan,Kim, Il American Chemical Society 2013 Langmuir Vol.29 No.1
<P>A series of oleamide derivatives, (C<SUB>18</SUB>H<SUB>34</SUB>NO)<SUB>2</SUB>(CH<SUB>2</SUB>)<SUB><I>n</I></SUB> [<I>n</I> = 2 (<B>1a</B>), 3 (<B>1b</B>), 4 (<B>1c</B>), or 6 (<B>1d</B>); C<SUB>18</SUB>H<SUB>34</SUB>NO = oleic amide fragment] and (C<SUB>18</SUB>H<SUB>34</SUB>NO)(CH<SUB>2</SUB>)<SUB>6</SUB>NH<SUB>2</SUB> (<B>2</B>), have been synthesized and their self-assembly is investigated in ethanol/water media. Self-assembly of <B>1a</B> and <B>1b</B> in ethanol/water (1/0.1 <I>v</I>/<I>v</I>) solution (5 mg mL<SUP>–1</SUP>) yields microspheres (MSs) with the average diameter ∼10 μm via a gradual temperature reduction and solvent volatilization process. Under the same self-assembly conditions, microrods (average diameter ∼6 μm and several tens of micrometers in length), micronecklace-like, and shape-irregular microparticles are formed from the self-assembly of <B>1c</B>, <B>1d</B>, and <B>2</B>, respectively. The kinetics of evolution for their self-assemblies by dynamic light scattering technique and in situ observation by optical microscopy reveals that the microstructures formation is from a well-behaved aggregation of nanoscale micelles induced by solvent volatilization. The FT–IR and temperature–dependent <SUP>1</SUP>H–NMR spectra demonstrate the hydrogen bonding force and π–π stacking, which drove the self-assembly of all oleamide derivatives in ethanol/water. Among the fabricated microstructures, the MSs from <B>1a</B> exhibit the best dispersity, which thus have been used as a scaffold for the in vitro release of doxorubicin. The results demonstrate a pH-sensitive release process, enhanced release specifically at low pH 5.2.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2013/langd5.2013.29.issue-1/la303634y/production/images/medium/la-2012-03634y_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la303634y'>ACS Electronic Supporting Info</A></P>
Yuhuan Zhang,Yu Dang,Yahan He,Xiao Ma,Lidong Wang 서울대학교 교육연구소 2021 Asia Pacific Education Review Vol.22 No.2
In general, private supplementary tutoring is considered an effective means of improving academic achievement by parents. However, previous studies have produced partial or inconclusive results regarding its effectiveness. Thus, the present study conducted a comprehensive analysis based on a specially designed longitudinal survey of private supplementary mathematics tutoring among middle school students in China. The hierarchical linear analysis did not show a considerably significant positive effect of regular private tutoring, even when such tutoring continued throughout the summer vacation and school semester. The data also allowed a deeper inquiry into the role of the quality, quantity, and applicability of private tutoring. In addition, the heterogeneous effect of private supplementary tutoring across students with different mathematics achievement levels was explored, with possible explanations including the different learning styles of students from different groups, the ceiling effect of the testing tool, and the different learning needs of different groups of students. These results suggest that parents should carefully select private tutoring for their children, and that the government should provide more comprehensive professional guidelines to regulate the industry.
Improved sliding mode control for mobile manipulators based on an adaptive neural network
Zhengnan Li,Lidong Ma,Zhijuan Meng,Jin Zhang,Yufeng Yin 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5
In this study, a wheeled mobile manipulator was modeled while considering the case of wheel-ground slippage. Considering the whole system, the number of states in the dynamic system equation was reduced by the kinematic solution, which facilitates the control of the system. For the system state equation, the improved sliding mode control method was applied, a flush continuous control term and a super-twisting algorithm were used to achieve the improved sliding mode control, and the gain of the super-twisting algorithm was adaptively controlled. The modeling error in the subsystem and the uncertain slippage were approximated by a neural network. The middle layer weights of the neural network were updated by the adaptive control law, and the stability of the system was demonstrated by a quadratic Lyapunov function. The simulation results show the superiority of the control method proposed in this paper by comparing them with results for the traditional sliding-mode control method and the improved sliding-mode control method.
Filled Skutterudites: from Single to Multiple Filling
Xi, Lili,Zhang, Wenqing,Chen, Lidong,Yang, Jihui The Korean Ceramic Society 2010 한국세라믹학회지 Vol.47 No.1
This paper shortly reviews our recent work on filled skutterudites, which are considered to be one of the most promising thermoelectric (TE) materials due to their excellent power factors and relatively low thermal conductivities. The filled skutterudite system also provides a platform for studying void filling physics/chemistry in compounds with intrinsic lattice voids. By using ab initio calculations and thermodynamic analysis, our group has made progresses in understanding the filling fraction limit (FFL) for single fillers in $CoSb_3$, and ultra-high FFLs in a few alkali-metal-filled $CoSb_3$ have been predicted and then been confirmed experimentally. FFLs in multiple-element-filled $CoSb_3$ are also investigated and anonymous filling behavior is found in a few specific systems. The calculated and measured FFLs, in both single and multiple-filled $CoSb_3$ systems, show good accordance so far. The thermal transport properties can be understood qualitatively by a phonon resonance scattering model, and it seems that a scaling rule may exist between the lattice thermal resistivity and the resonance frequency of filler atoms in filled system. Even though a few things become clear now, there are still many unsolved issues that call for further work.
A Network Security Scanning System for Mobile Internet Based on Android
Guanlin Chen,Lidong Zhang 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.11
Recently with the rapid development of smart phones and mobile Internet, network security is more and more important in people’s daily life. In this paper, a network security scanning system based on Android (wScan) is proposed, which aims to make sure users’ mobile terminals are in a secure network environment when they are using these devices. The system is composed of WiFi scanning, router tracking, port scanning, running service detection, virus killing and real-time communication functions, which integrates Java technology, Eclipse platform and SQLite database. Using Nmap toolkit in the system, the wScan can provide valuable information of running services and opening ports in mobile devices based on Android.
Zhengnan Li,Miaomiao Zhang,Bin Zheng,Lidong Ma 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.10
The on-line measurement of medium thickness steel plate length is an important part of the hot rolling production. In this paper, an easy calibration method and a visual measurement method of laser stripe center extraction algorithm based on structured light are proposed to achieve on-line measurement of medium thickness steel plate length. Firstly, an experimental platform is designed and built to fix the intersecting visual fields of each camera. Secondly, the actual detection size of each camera's visual field is calibrated by the calibration method, and a fixed digital image processing range is set according to the thickness of the steel plate. Then, an adaptive image processing range extraction algorithm is proposed to further reduce the redundant image scanning. Moreover, we improve the traditional gray center of gravity method to achieve higher accuracy of laser stripe center extraction. Finally, in the laboratory, three medium thickness steel plates with different lengths are measured by the laser stripe extraction algorithm proposed in this paper. Experimental results show that the measurement error is within ± 1.5 mm, which proves that the algorithm has the characteristics of higher extraction accuracy and has certain engineering application value.
Filled Skutterudites: from Single to Multiple Filling
Lili Xi,Wenqing Zhang,Lidong Chen,Jihui Yang 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.1
This paper shortly reviews our recent work on filled skutterudites, which are considered to be one of the most promising thermoelectric (TE) materials due to their excellent power factors and relatively low thermal conductivities. The filled skutterudite system also provides a platform for studying void filling physics/chemistry in compounds with intrinsic lattice voids. By using ab initio calculations and thermodynamic analysis, our group has made progresses in understanding the filling fraction limit (FFL) for single fillers in CoSb3, and ultra-high FFLs in a few alkali-metal-filled CoSb3 have been predicted and then been confirmed experimentally. FFLs in multiple-element-filled CoSb3 are also investigated and anonymous filling behavior is found in a few specific systems. The calculated and measured FFLs, in both single and multiple-filled CoSb3 systems, show good accordance so far. The thermal transport properties can be understood qualitatively by a phonon resonance scattering model, and it seems that a scaling rule may exist between the lattice thermal resistivity and the resonance frequency of filler atoms in filled system. Even though a few things become clear now, there are still many unsolved issues that call for further work.