High-Frequency Modeling and Optimization of E/O Response and Reflection Characteristics of 40 Gb/s EML Module for Optical Transmitters

Chengzhi Xu,Y.Z. Xu,Yanli Zhao,Kunzhong Lu,Weihua Liu,Shibing Fan,Hui Zou,Wen Liu 한국전자통신연구원 2012 ETRI Journal Vol.34 No.3

A complete high-frequency small-signal circuit model of a 40 Gb/s butterfly electroabsorption modulator integrated laser module is presented for the first time to analyze and optimize its electro-optic (E/O) response and reflection characteristics. An agreement between measured and simulated results demonstrates the accuracy and validity of the procedures. By optimizing the bonding wire length and the impedance of the coplanar waveguide transmission lines, the E/O response increases approximately 5% to 15% from 20 GHz to 33 GHz, while the signal injection efficiency increases from approximately 15% to 25% over 18 GHz to 35 GHz.

Facile, Efficient Liquid Exfoliated Cyanoethylated Cellulose Nanofibrils and Their Application

Weihua Zhang,Mingjie Li,Chunlin Xu,Chaoxu Li 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2

Traditionally, cellulose nanofibers are difficult to disperse in organic solvent and redisperse after drying, and thereby limit their practical applications. Herein, we develop a new, convenient, scalable and energy efficient method for producing cyanoethylated cellulose nanofibers. Through the synergy of mechanical and chemical reaction processes, the produced cyanoethylated cellulose nanofibers are ca. 3 nm wide and several hundred to 1000 nanometers long. Particularly, compared with common TEMPO oxidized cellulose nanofibrils, they show improved hydrophobicity and redispersibility in different organic solvent. In addition, these dispersed CCNFs also exhibit greater potential to construct high-performance structural materials, e.g., transparent ductile nanopapers with large elongation up to 18% and toughness as high as 16.5 MJ/m³.

Antitumor Activities and Immunomodulatory Effects of Ginseng Neutral Polysaccharides in Combination with 5-Fluorouracil

Weihua Ni,Xu Zhang,Bo Wang,Yan Chen,Han Han,Yuying Fan,Yifa Zhou,Guihua Tai 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.2

A neutral polysaccharide fraction (WGPN) prepared from Panax ginseng C.A. Meyer by hot water extraction and DEAE-cellulose chromatography was tested for its anticancer activity alone and in combination with 5-fluorouracil (5-FU) in Sarcoma-180 (S180) tumor-bearing mice by intragastric administration. WGPN alone inhibited S180 tumor growth in a bell-shaped dose–response curve, and the combination with 5-FU showed a synergistic effect. Studies of various immunological activities in S180-bearing mice revealed that WGPN stimulated the proliferation of lymphocytes, increased natural killer cell cytotoxicity, enhanced the phagocytosis and nitric oxide production by macrophages, and increased the level of tumor necrosis factor-α in serum. In combination with 5-FU, WGPN mitigated damage to the immune system caused by 5-FU in S180-bearing mice. These results suggest that WGPN might be a potential adjuvant for chemotherapeutic drugs.

Estimation of Lipoprotein-lipase Activity (LPL) and Other Biochemical Changes in Two Breeds of Overfeeding Geese

Xu, Hengyong,Wang, Yan,Han, Chunchun,Jiang, Li,Zhuo, Weihua,Ye, Jianqiang,Wang, Jiwen Asian Australasian Association of Animal Productio 2010 Animal Bioscience Vol.23 No.9

This study aimed to examine the effect of overfeeding on biochemical parameters and lipoprotein-lipase (LPL) mRNA expression in different tissues associated with hepatic lipogenesis in Sichuan white and Landes geese. Fifty healthy male Sichuan white geese and fifty male Landes geese (Cygnus atratus) were hatched on the same day under the same feeding conditions and were selected as experimental animals. After overfeeding for 14 days (from 14 weeks to 16 weeks) and then slaughtering, the biochemical changes of hepatic lipogenesis were evaluated. Results showed that i) in Landes geese, the plasma concentration of glucose was higher (p<0.001), while plasma concentrations of insulin and VLDL were both lower (p<0.01); ii) the LPL mRNA level in pectoralis muscle and leg muscle of the overfed groups in both breeds was higher (p<0.05) than in the control groups; iii) in Sichuan white geese, the proportion of fatty liver weight was positively correlated with plasma triacylglycerols (TG)(p<0.05) and VLDL concentrations (p<0.05), while these correlations were not significant in Landes geese; and iv) the activity of LPL had significant positive correlation with the proportions of lipids in subcutaneous adipose tissue and abdominal adipose tissue in Sichuan white geese, while in Landes geese the correlation was negative (p<0.05) with proportions of lipids in the liver, LPL activity had a significant positive correlation with the proportions of lipids in subcutaneous adipose tissue. These results suggest that the Landes geese have a better ability to use the massive amount of ingested food and to store lipids preferentially in the liver, but the Sichuan white geese have a relatively lower ability to use energetic nutrients and lipid storage is more efficient in the adipose tissues.

Driver Preview Model with Dual Far-near Points for Autonomous Vehicles

Rongrong Xu,Zezheng Huang,Weihua Li,Jianfeng Wang,Dianbo Ren,Xuewen Geng 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.11

This paper proposes a driver preview-based path-following controller to control both the lateral and longitudinal movements of a vehicle. First, a lateral tracking controller with two preview points is established by considering the displacement and heading errors of the two preview points: the far point, determined by the vehicle speed and fixed preview time, and the near point located at the center of the front axle. Depending on different parameters of the road input, the steering wheel angle is calculated, and different weights are assigned to the steering wheel angles corresponding to different road inputs. Next, a longitudinal tracking controller is established, which controls the vehicle velocity based on the road information of the far point. The control objects are the brake and accelerator pedals. Subsequently, the coupling of the lateral and longitudinal motion of the vehicle is analyzed, and an integrated longitudinal and lateral tracking controller is established. To verify the performance of the controller, the controller and vehicle model are established in Simulink and CarSim, respectively, to enable joint simulation. It is observed that the coupling is solved, and the near-point control makes the tracking error converge to zero and enhances the control effect. It demonstrates high adaptability and control accuracy of the proposed controller.

Low-Temperature Scanning Near-Field Optical Microscope and Spectroscopy: Application in Quantum Well Device

Gengzhao XU,Xing ZHU,Hu Liang,Kay May Lau,Weihua ZHANG,Yun-Dong Qi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1

We have constructed a versatile low-temperature scanning near-field optical microscope (LTSNOM) with the capability of near-field imaging and spectroscopy, operating at liquid nitrogen (LN) temperature. A sample is illuminated either electronically or optically by introducing a laser beam through specially designed coaxial double lenses and an optical fiber. The detected optical signal is transmitted via a fiber tip to a photoelectric multiplier tube (PMT) or a spectrometer. Shear-force detection by using a tuning-fork technique is applied to maintain the tip-sample distance. A shearforce topographic image, an optical image and a local spectrum can be obtained simultaneously. The whole scanning head is enclosed inside a container which is immersed in liquid nitrogen in a storage Dewar during the measurement. We have used this LT-SNOM to study the electroluminescence (EL) properties of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs), at both room temperature and liquid nitrogen temperature. Low-temperature experiments with the LT-SNOM show the stability of our construction and stable image acquisition at LN temperature. The results show that at room temperature the EL intensity distribution is quite inhomogeneous with islands like bright spots, and at LN temperature the EL intensity increased dramatically and the inhomogeneity reduced greatly. Furthermore, the near-field spectra show a peak at a higher photon energy at around 2.95 eV at low temperature, in addition to the 2.7 eV peak observed by far field at room temperature. The results indicate that the self-organized In rich regions play a key role in the EL properties of these LEDs, which act as radiation recombination centers. In conjunction with nearfield spectroscopy, the possible mechanism of this phenomenon is explained in terms of irradiative recombination in the MQWs, as well as the quantum-confined Starks effect.

Joint Space-time Coding and Power Domain Non-orthogonal Multiple Access for Future Wireless System

( Jin Xu ),( Hanqing Ding ),( Zeqi Yu ),( Zhe Zhang ),( Weihua Liu ),( Xueyan Chen ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.1

According to information theory, non-orthogonal transmission can achieve the multiple-user channel capacity with an onion-peeling like successive interference cancellation (SIC) based detection followed by a capacity approaching channel code. However, in multiple antenna system, due to the unideal characteristic of the SIC detector, the residual interference propagated to the next detection stage will significantly degrade the detection performance of spatial data layers. To overcome this problem, we proposed a modified power-domain non-orthogonal multiple access (P-NOMA) scheme joint designed with space-time coding for multiple input multiple output (MIMO) NOMA system. First, with proper power allocation for each user, inter-user signals can be separated from each other for NOMA detection. Second, a well-designed quasi-orthogonal space-time block code (QO-STBC) was employed to facilitate the SIC-based MIMO detection of spatial data layers within each user. Last, we proposed an optimization algorithm to assign channel coding rates to balance the bit error rate (BER) performance of those spatial data layers for each user. Link-level performance simulation results demonstrate that the proposed time-space-power domain joint transmission scheme performs better than the traditional P-NOMA scheme. Furthermore, the proposed algorithm is of low complexity and easy to implement.

Diagnosing axle box bearings’ fault using a refined phase difference correction method

Qing Xiong,Weihua Zhang,Yanhai Xu,Yiqiang Peng,Pengyi Deng 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

The wheelset treads and axle box bearings of railway vehicles often suffer from fatigue failures. Their regular maintenance highly depends on manual off-line inspection with low working efficiency and poor precision for early failure detection. This study proposes a fault diagnosis method by band-pass filtering and by enveloping the accelerations collected from the axle box bearing on the underfloor wheelset lathe to improve the maintenance efficiency. This process is followed by the refined phase difference correction using the fourterm third derivative Nuttall-windowed fast Fourier transform (RPNWF) to extract accurate amplitudes of the fault characteristic frequency and its harmonics. The integration scheme, work flow, and application examples of the fault diagnosis system are presented. Simulation analysis and results show that the developed method can achieve effective diagnosis of the fault and fault degree of axle box bearings as well as yield better correction accuracy than the commonly used discrete spectrum correction methods.

Interactive Effects of Ultraviolet Radiation and Dissolved Organic Carbon on Phytoplankton Growth and Photosynthesis in Sanya Bay, Northern South China Sea

Jianzu Liao,Weihua Zhou,Jie Xu,Xiangcheng Yuan,Yuxian Liang,Yajuan Guo,Hui Huang,Sheng Liu,Aimin Long 한국해양과학기술원 2019 Ocean science journal Vol.54 No.4

The effects of a simulated climate change scenario, i.e., increased ultraviolet radiation (UVR) and dissolved organic carbon (DOC), on the growth and photosynthesis of tropical coastal phytoplankton were evaluated in Sanya Bay, northern South China Sea, in summer. Microcosm experiments were conducted at two contrasting stations (Stns S1 and S2) with three different UVR treatments and two DOC addition treatments. Our results showed that natural sunlight UVR or increased UV-B did not affect phytoplankton biomass and primary production. However, increased UV-B significantly decreased the proportion of picophytoplankton and the efficiency of carbon fixation at Stn S2. DOC enhancement caused negative effects on primary production under natural sunlight UVR only at Stn S1. Interactive effects of UVR and DOC addition on phytoplankton biomass and primary production were detected at Stn S1, due to the negative effects of DOC being eliminated under the increased UV-B condition. The lack of interactive effects at Stn S2 were likely due to the differences with Stn S1 in terms of light acclimation and biological interaction. In summary, this future climate change scenario will probably not affect the photosynthetic CO2 fixation and biomass of natural phytoplankton in Sanya Bay.

Rapid Separation of Gossypol from Cottonseeds by a Solid-Phase Synthetic Method

Wu, Hankui,Xu, Zhiyong,Ma, Ya,Qi, He,Cao, Jinxia,Li, Gang,Chen, Yong,Yang, Weihua Korean Chemical Society 2016 대한화학회지 Vol.60 No.3