pH-Responsive Carboxymethylcellulose-g-Poly(sodium acrylate)/Polyvinylpyrrolidone Semi-IPN Hydrogels with Enhanced Responsive and Swelling Properties

Wenbo Wang,Qin Wang,Aiqin Wang 한국고분자학회 2011 Macromolecular Research Vol.19 No.1

Novel pH-responsive semi-interpenetrated polymer network (semi-IPN) superabsorbent hydrogels were prepared by the radical graft polymerization of carboxymethylcellulose (CMC) and partially neutralized acrylic acid (NaA) in the presence of a crosslinker, N,N’-methylene-bis-acrylamide (MBA), and linear polyvinylpyrrolidone (PVP). FTIR spectroscopy showed that NaA was grafted onto the CMC backbone and PVP combined with CMCg-PNaA network by hydrogen-bonding interaction. SEM showed that the formation of a semi-IPN structure improved the surface structure of the hydrogels. The reaction variables, including the mass ratio of acrylic acid (AA)to CMC, MBA concentration and PVP content were optimized, and the crosslinking density of the hydrogels was determined. In addition, the pH-response, swelling behavior of the hydrogel in various saline solutions and aqueous cetyltrimethylammonium bromide (CTAB) solutions were investigated. The results showed that the introduction of CMC and PVP clearly enhanced the swelling capability and rate, and improved the pH-responsive and On-Off switching swelling abilities, salt-resistance, and intriguing time-dependent swelling characteristics.

Distributed Power and Rate Control for Cognitive Radio Networks

Wang, Wei,Wang, Wenbo,Zhu, Yajun,Peng, Tao The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.2

In this paper, a distributed power and end-to-end rate control algorithm is proposed in the presence of licensed users. By Lagrangian duality theory, the optimal power and rate control solution is given for the unlicensed users while satisfying the interference temperature limits to licensed users. It is obtained that transmitting with either 0 or the maximum node power is the optimal scheme. The synchronous and asynchronous distributed algorithms are proposed to be implemented at the nodes and links. The convergence of the proposed algorithms are proved. Finally, further discussion on the utility-based fairness is provided for the proposed algorithms. Numerical results show that the proposed algorithm can limit the interference to licensed user under a predefined threshold.

Stackelberg Game for Distributed Time Scheduling in RF-Powered Backscatter Cognitive Radio Networks

Wang, Wenbo,Hoang, Dinh Thai,Niyato, Dusit,Wang, Ping,Kim, Dong In IEEE 2018 IEEE Transactions on Wireless Communications Vol.17 No.8

<P>In this paper, we study the transmission strategy adaptation problem in an RF-powered cognitive radio network, in which hybrid secondary users are able to switch between the harvest-then-transmit mode and the ambient backscatter mode for their communication with the secondary gateway. In the network, a monetary incentive is introduced for managing the interference caused by the secondary transmission with imperfect channel sensing. The sensing-pricing-transmitting process of the secondary gateway and the transmitters is modeled as a single-leader-multi-follower Stackelberg game. Furthermore, the follower sub-game among the secondary transmitters is modeled as a generalized Nash equilibrium problem with shared constraints. Based on our theoretical discoveries regarding the properties of equilibria in the follower sub-game and the Stackelberg game, we propose a distributed, iterative strategy searching scheme that guarantees the convergence to the Stackelberg equilibrium. The numerical simulations show that the proposed hybrid transmission scheme always outperforms the schemes with fixed transmission modes. Furthermore, the simulations reveal that the adopted hybrid scheme is able to achieve a higher throughput than the sum of the throughput obtained from the schemes with fixed transmission modes.</P>

A novel flexible micro-ratchet/ZnO nano-rods surface with rapid recovery icephobic performance

Wang, Manxiang,Yu, Wenbo,Zhang, Yupei,Woo, Jae-Young,Chen, Yu,Wang, Bo,Yun, Yanbin,Liu, Guicheng,Lee, Joong Kee,Wang, Lei Elsevier 2018 Journal of industrial and engineering chemistry Vol.62 No.-

<P><B>Abstract</B></P> <P>In this communication, we present a significant method to fabricate a robust icephobic surface on a flexible polymer substrate. The flexible functional surface is obtained by integrating both soft-lithography and crystal growth methods. Modified by the materials with low surface free energy, the composite surface exhibits a robust superhydrophobicity at not only room temperature but also low temperature. After freezing test, the surface can recover to its original function quickly, which has achieved the level for industrial application, and also performed significant role for enhancing the icephobic theories.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ZnO nano-rods are uniformly planted on the flexible PDMS surface. </LI> <LI> Fabrication of the surface integrates both crystal growth and physical vapor deposition methods. </LI> <LI> The superhydrophobic surface successfully realizes fast-recovery from freezing state. </LI> <LI> In freezing process, the nanorods can hardly cracked due to the flexible basement. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The liquid droplet can recover to sphere state (Cassie's state) after melting from low temperature (for example, 20°C). ▪</P> <P>[DISPLAY OMISSION]</P>

Optimal Utilization of Low Voltage GaN HEMT in High Frequency Boost Converter

Wenbo Wang,Frans Pansier,Jelena Popovic,J.A. Ferreira 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper, investigations on optimal topology and operation mode for low voltage GaN HEMT are performed. Analytical loss model of GaN HEMT, in which influences of circuit and package parasitics are accounted for, is developed as a tool to analyze losses in GaN HEMT in different switching conditions. Analysis results shows that when applied in both Vout〈2Vin and Vout〉2Vin situations in Boundary Conduction Mode with Valley Switching(BCM-VS) in a boost converter, where GaN HEMT is switched on when voltage across it is lowered, switching loss can be greatly reduced. Switching loss reduction results not only from the exemption of discharging the large output capacitance of GaN HEMT at high voltage, but also from the fact that parasitic inductance has much less effects on switching loss in GaN HEMT in BCM-VS than in Continuous Conduction Mode (CCM). Limitations and design tradeoffs when GaN HEMT is applied in BCM-VS are also revealed. Forward voltage of GaN HEMT in reverse conduction is high and its conduction should be prevented when Vout〉 to achieve conduction loss reduction. This further loss reduction can be realized by switching on transistor before valley point. Besides, in BCM-VS, overvoltage on GaN HEMT is larger and oscillatory energy dissipation in circuit is higher than in CCM due to higher turn off current. Paralleling external capacitor to the transistor helps to ease voltage stress; however turn on loss will be increased. This loss increase is more severe in the case of Vout〈2Vin than Vout〉2Vin. Trade-offs on the selection of proper external capacitor value exists between increased switching loss and reduced voltage stress. Experimental setup is built to verify and demonstrate the analysis.

Robust Image Watermarking via Perceptual Structural Regularity-based JND Model

( Chunxing Wang ),( Meiling Xu ),( Wenbo Wan ),( Jian Wang ),( Lili Meng ),( Jing Li ),( Jiande Sun ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.2

A better tradeoff between robustness and invisibility will be realized by using the just noticeable (JND) model into the quantization-based watermarking scheme. The JND model is usually used to describe the perception characteristics of human visual systems (HVS). According to the research of cognitive science, HVS can adaptively extract the structure features of an image. However, the existing JND models in the watermarking scheme do not consider the structure features. Therefore, a novel JND model is proposed , which includes three aspects: contrast sensitivity function, luminance adaptation, and contrast masking (CM). In this model, the CM effect is modeled by analyzing the direction features and texture complexity, which meets the human visual perception characteristics and matches well with the spread transform dither modulation (STDM) watermarking framework by employing a new method to measure edge intensity. Compared with the other existing JND models, the proposed JND model based on structural regularity is more efficient and applicable in the STDM watermarking scheme. In terms of the experimental results, the proposed scheme performs better than the other watermarking scheme based on the existing JND models.

Experimental research on pressure fluctuation and vibration in a mixed flow pump

Kai Wang,Houlin Liu,Xiaohua Zhou,Wenbo Wang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1

To study the pressure fluctuation and vibration in mixed flow pumps, we chose a mixed flow pump with specific speed of 436.1 tomeasure. The time domains and frequency domain at each monitoring point on diffuser and outlet elbow were analyzed, as well as thevibration frequency domain characteristics at the impeller outlet and near the motor. The results show that the peak value of pressurefluctuation peak decreased gradually with the increase of flow rate. The pressure fluctuation of each monitoring point had periodicity,and the frequency domain dominated by blade passing frequency and multiple shaft frequency. The vibration frequency of each monitoringpoint occurred at shaft frequency and its multiple shaft frequency. The dominant frequency and the second frequency were distributedin shaft frequency and double shaft frequency.

Effect of CBN surface coating on properties of abrasive and vitrified CBN composites

Xuezhi Wang,Minghai Wang,Jingqiang Zhang,Wenbo Fan,Tianbiao Yu 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.1

The advantages of CBN abrasive and vitrified bonds allow the wide use of vitrified CBN grinding tools. However, theirproperties can be affected by various factors such as vitrification itself and binding between vitrified bond and abrasive grains. In view of this, the current work aims to improve the binding characteristics of vitrified bond and abrasive grains byelucidating the effect of CBN surface coating. In particular, the thermal properties of typical nickel and titanium coatedabrasive grains were compared with those of ordinary abrasive grains. Furthermore, the strength, microstructure and phasecomposition of vitrified CBN composites were studied as well. According to the results, the thermal stability of abrasive grainsdecreased after coating processing. However, applying the vitrified CBN composite material and sintering, if appropriable, wasshown to ensure protection of the abrasive grains. Moreover, as an intermediate transition layer, the bonding properties ofvitrified bond and abrasive grains can be improved to some extent. Finally, the vitrified Ti-coated CBN composite was foundto possess the best performance.

Functional analysis of the HD-Zip I gene ZmHDZ1 in ABA-mediated salt tolerance in rice

Qianqian Wang,Kangyong Zha,Wenbo Chai, Yu Wang,Bin Liu,Haiyang Jiang,Beijiu Cheng,Yang Zhao 한국식물학회 2017 Journal of Plant Biology Vol.60 No.2

The homeodomain-leucine zipper I (HD-Zip I) transcription factors play crucial roles in the regulation of abiotic stress responses, whereas, up to now, most of them are still functionally unknown. In present study, we identified a maize HD-Zip I gene, designing as ZmHDZ1, and investigated its potential roles in salt stress response. The qRT-PCR results showed that expression of ZmHDZ1 was induced by ABA and salt stress. Transactivation assay and transient expression analyses indicated that ZmHDZ1 protein was located in the nucleus in tobacco leaf cells and had the transactivation activity in yeast. Over-expression of ZmHDZ1 in rice reduced tolerance to salt stress, thus, led to greater accumulation of malondialdehyde (MDA) as well as higher level of relative electrolyte leakage (REL) compared to WT plants. In addition, the transgenic seedlings also increased sensitivity to exogenous ABA. Furthermore, the expression levels of four salt responsive genes were different between transgenic and WT rice under normal or NaCl treatment. These results suggested that ZmHDZ1 function as a negative regulator in response to salt stress through the ABAmediated signal transduction pathways.

Distributed Power and Rate Control for Cognitive Radio Networks

Wei Wang,Wenbo Wang,Tao Peng,Yajun Zhu 한국통신학회 2009 Journal of communications and networks Vol.11 No.2

In this paper, a distributed power and end-to-end rate control algorithm is proposed in the presence of licensed users. By Lagrangian duality theory, the optimal power and rate control solution is given for the unlicensed users while satisfying the interference temperature limits to licensed users. It is obtained that transmitting with either 0 or the maximum node power is the optimal scheme. The synchronous and asynchronous distributed algorithms are proposed to be implemented at the nodes and links. The convergence of the proposed algorithms are proved. Finally, further discussion on the utility-based fairness is provided for the proposed algorithms. Numerical results show that the proposed algorithm can limit the interference to licensed user under a predefined threshold.