Browsing by Author "Li, Yan"

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    Anomalous Structural Transition and Electrical Transport Behaviors in Compressed Zn2SnO4: Effect of Interface
    (2015) Zhang, Haiwa; Ke, Feng; Li, Yan; Liu, Cailong; Zeng, Yi; Yao, Mingguang; Han, Yonghao; Ma, Yanzhang (TTU); Gao, Chunxiao
    The interface effect is one of the most important factors that strongly affect the structural transformations and the properties of nano-/submicro-crystals under pressure. However, characterization of the granular boundary changes in materials is always challenging. Here, using tetrakaidecahedral Zn2SnO4 microcrystals as an example, we employed alternating current impedance, X-ray diffraction methods and transmission electron microscopy to elucidate the effect of the interface on the structure and electrical transport behavior of the Zn2SnO4 material under pressure. We clearly show that grain refinement of the initial microcrystals into nanocrystals (approximately 5 nm) occurs at above 12.5 GPa and is characterized by an anomalous resistance variation without a structural phase transition. A new phase transition pathway from the cubic to hexagonal structure occurs at approximately 29.8 GPa in Zn2SnO4. The unexpected grain refinement may explain the new structural transition in Zn2SnO4, which is different from the previous theoretical prediction. Our results provide new insights into the link between the structural transition, interface changes and electrical transport properties of Zn2SnO4.
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    Evaluating the Impact of Improving Access on Consumption of Fruits and Vegetables in a Rural Community in Texas: A Modeling Study
    (2019) Katapodis, Nicole D.; Zhang, Donglan; Giabbanelli, Philippe J.; Li, Yan; Lyford, Conrad P. (TTU); Rajbhandari-Thapa, Janani
    Purpose: Most residents in rural regions of the United States consume fewer amounts of fruits and vegetables (FVs) compared with their urban counterparts. Difficulties in access to FVs often contribute to different consumption patterns in rural regions, aside from a lack of education or motivation for eating healthy foods. This article uses simulation methods to estimate the relationship between increasing food access and FV consumption levels in a targeted rural community. Methods: An agent-based model previously developed to predict individual dietary behaviors was used. We adapted it to a rural community in west Texas following a two-step process. First, we validated the model with observed data. Second, we simulated the impact of increasing access on FV consumption. We estimated model parameters from the 2010 census and other sources. Results: We found that decreasing the driving distance to FV outlets would increase FV consumption in the community. For example, a one-mile decrease in driving distance to the nearest FV store could lead to an 8.9% increase in FV consumption; a five-mile decrease in driving distance could lead to a 25% increase in FV consumption in the community. We found that the highest marginal increase in FV consumption was when the driving distance decreased from 3.5 miles to 3 miles. Conclusions: Analysis to inform policy alternatives is a challenge in rural settings due to lack of data. This study highlights the potential of simulation modeling to inform and analyze policy alternatives in settings with scarce data. The findings from modeling can be used to evaluate alternative policies in addressing chronic diseases through dietary interventions in rural regions.
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    Highly efficient and linear SiGe BiCMOS power amplifiers using envelope-tracking for mobile broadband wireless communications
    (2012-08) Li, Yan; Lie, Donald Y. C.; Bayne, Stephen B.; Giesselmann, Michael G.; Gale, Richard O.
    This dissertation presents the design insights towards the realization of a fully monolithic ratio frequency (RF) cascode silicon (Si) BiCMOS power amplifier (PA) using the integrated envelope tracking (ET) technique (i.e., an “ET-PA” system). The dissertation begins with the introduction of ET as an efficiency-linearity enhancement technique by demonstrate its operating principle with the RF/analog/digital system co-simulations in SPICE and analytic analysis. The bandwidth and timing mismatch sensitivities are compared between the ET and the envelope-elimination-and-restoration (EER) techniques. A discrete linear-assisted switching envelope modulator is designed to investigate the overall ET-PA system performances using a monolithic SiGe common-emitter PA for broadband 3G/4G cellular signals with high peak-to-average ratio (PAR). The design trade-off of the switching frequency and the bandwidth of the envelope modulator on the ET-PA will be studied carefully to improve the linearity without degrading the overall efficiency. After the design insights for the circuits and the ET-PA system are well-understood, a fully monolithic SiGe BiCMOS cascode ET-PA will be implemented and presented. The proper circuitry topology and envelope shaping method will be investigated to successfully apply the differential cascode SiGe/BiCMOS PA into the ET-PA system. The integrated CMOS envelope modulator is optimized specific to this cascode PA, where its finite bandwidth and switching frequency are considered for achieving a high efficiency with minimal distortion and low spurious noise. Such optimization of the monolithic envelope modulator design for a fully-integrated ET-PA system is novel and different from almost all the works previously published in the literature. Further improvements of the fully monolithic BiCMOS ET-PA will also be carried out by: (1) the combination of ET and transistor resizing techniques for additional efficiency enhancement at the low output power regions for power saving; (2) the integration of the ET technique with the power-combined SiGe PA with an on-chip transformer for higher linear output power; and (3) the design of the monolithic Bipolar-CMOS-DMOS (BCD) envelope modulator for higher voltage and higher power applications. Based on the literature surveys, all the above monolithic ET-PA designs achieved state-of-the-art world record efficiencies for Si-based RF PAs for broadband high PAR signals without needing any predisotortion technique. More work is underway to increase the maximum output linear power to enable this revolutionary silicon-based ET-PA technology into real products space for various handsets and wireless applications.
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    NIST interlaboratory study on glycosylation analysis of monoclonal antibodies: Comparison of results from diverse analytical methods
    (2020) De Leoz, Maria Lorna A.; Duewer, David L.; Fung, Adam; Liu, Lily; Yau, Hoi Kei; Potter, Oscar; Staples, Gregory O.; Furuki, Kenichiro; Frenkel, Ruth; Hu, Yunli; Sosic, Zoran; Zhang, Peiqing; Altmann, Friedrich; Grunwald-Grube, Clemens; Shao, Chun; Zaia, Joseph; Evers, Waltraud; Pengelley, Stuart; Suckau, Detlev; Wiechmann, Anja; Resemann, Anja; Jabs, Wolfgang; Beck, Alain; Froehlich, John W.; Huang, Chuncui; Li, Yan; Liu, Yaming; Sun, Shiwei; Wang, Yaojun; Seo, Youngsuk; An, Hyun Joo; Reichardt, Niels Christian; Ruiz, Juan Echevarria; Archer-Hartmann, Stephanie; Azadi, Parastoo; Bell, Len; Lakos, Zsuzsanna; An, Yanming; Cipollo, John F.; Pucic-Bakovic, Maja; Štambuk, Jerko; Lauc, Gordan; Li, Xu; Wang, Peng George; Bock, Andreas; Hennig, René; Rapp, Erdmann; Creskey, Marybeth; Cyr, Terry D.; Nakano, Miyako; Sugiyama, Taiki; Leung, Pui King Amy; Link-Lenczowski, Paweł; Jaworek, Jolanta; Yang, Shuang; Zhang, Hui; Kelly, Tim; Klapoetke, Song; Cao, Rui; Kim, Jin Young; Lee, Hyun Kyoung; Lee, Ju Yeon; Yoo, Jong Shin; Kim, Sa Rang; Suh, Soo Kyung; De Haan, Noortje; Falck, David; Lageveen-Kammeijer, Guinevere S.M.; Wuhrer, Manfred; Emery, Robert J.; Kozak, Radoslaw P.; Liew, Li Phing; Royle, Louise; Urbanowicz, Paulina A.; Packer, Nicolle H.; Song, Xiaomin; Everest-Dass, Arun; Lattová, Erika; Cajic, Samanta; Alagesan, Kathirvel; Kolarich, Daniel; Kasali, Toyin; Lindo, Viv; Chen, Yuetian; Goswami, Kudrat; Gau, Brian; Amunugama, Ravi; Jones, Richard; Stroop, Corné J.M.; Kato, Koichi; Yagi, Hirokazu; Kondo, Sachiko; Yuen, C. T.; Harazono, Akira; Shi, Xiaofeng; Magnelli, Paula E.; Kasper, Brian T.; Mahal, Lara; Harvey, David J.; O'Flaherty, Roisin; Rudd, Pauline M.; Saldova, Radka; Hecht, Elizabeth S.; Muddiman, David C.; Kang, Jichao; Bhoskar, Prachi; Menard, Daniele; Saati, Andrew; Merle, Christine; Mast, Steven; Tep, Sam; Truong, Jennie; Nishikaze, Takashi; Sekiya, Sadanori; Shafer, Aaron; Funaoka, Sohei; Toyoda, Masaaki; De Vreugd, Peter; Caron, Cassie; Pradhan, Pralima; Tan, Niclas Chiang; Mechref, Yehia (TTU); Patil, Sachin; Rohrer, Jeffrey S.; Chakrabarti, Ranjan; Dadke, Disha; Lahori, Mohammedazam; Zou, Chunxia; Cairo, Christopher; Reiz, Béla; Whittal, Randy M.; Lebrilla, Carlito B.; Wu, Lauren; Guttman, Andras; Szigeti, Marton; Kremkow, Benjamin G.; Lee, Kelvin H.; Sihlbom, Carina; Adamczyk, Barbara; Jin, Chunsheng; Karlsson, Niclas G.; Örnros, Jessica; Larson, Göran; Nilsson, Jonas; Meyer, Bernd; Wiegandt, Alena; Komatsu, Emy; Perreault, Helene; Bodnar, Edward D.; Said, Nassur; Francois, Yannis Nicolas; Leize-Wagner, Emmanuelle; Maier, Sandra; Zeck, Anne; Heck, Albert J.R.; Yang, Yang; Haselberg, Rob; Yu, Ying Qing; Alley, William; Leone, Joseph W.; Yuan, Hua; Stein, Stephen E.
    Glycosylation is a topic of intense current interest in the development of biopharmaceuticals because it is related to drug safety and efficacy. This work describes results of an interlaboratory study on the glycosylation of the Primary Sample (PS) of NISTmAb, a monoclonal antibody reference material. Seventy-six laboratories from industry, university, research, government, and hospital sectors in Europe, North America, Asia, and Australia submit-ted a total of 103 reports on glycan distributions. The principal objective of this study was to report and compare results for the full range of analytical methods presently used in the glycosylation analysis of mAbs. Therefore, participation was unrestricted, with laboratories choosing their own measurement techniques. Protein glycosylation was determined in various ways, including at the level of intact mAb, protein fragments, glycopeptides, or released glycans, using a wide variety of methods for derivatization, separation, identification, and quantification. Consequently, the diversity of results was enormous, with the number of glycan compositions identified by each laboratory ranging from 4 to 48. In total, one hundred sixteen glycan compositions were reported, of which 57 compositions could be assigned consensus abundance values. These consensus medians provide communityderived values for NISTmAb PS. Agreement with the consensus medians did not depend on the specific method or laboratory type. The study provides a view of the current state-of-the-art for biologic glycosylation measurement and suggests a clear need for harmonization of glycosylation analysis methods.
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    System and circuits investigation of wideband RF polar transmitters using envelope tracking for mobile WiMAX/WiBro applications
    (2009-08) Li, Yan; Lie, Donald Y. C.; Dallas, Timothy E. J.
    High efficiency radio frequency (RF) power amplifiers (PAs) are critical in portable battery-operated wireless communication systems because they can dominate the power consumption. Linear power amplifier is required for applications using non-constant envelope modulated signals (e.g., WiMAX) to minimize distortions. Traditionally, linear power amplifiers are implemented by “backing-off†the output power of PA. However, for a spectrally-efficient high peak-to-average (PAR) signal, the average PA efficiency is much lower than the peak efficiency, which is very undesirable. This thesis focuses on Envelope Elimination and Restoration (EER) and Envelope Tracking (ET) efficiency enhancement techniques to improve the PA average efficiency for high PAR signals. A modified bias-dependent Cann’s model has been developed to study the behavior of our monolithic class-E SiGe PAs. The time-mismatch sensitivity between the amplitude and RF paths is compared for ET vs. EER systems based on our modified model and with measurement data. Besides, RF+Analog+Digital system simulations were performed to study the static and group delays in ET/EER based polar TX systems. Both simulations and measurement show that an ET-based polar system has higher resilience against timing mismatches between the amplitude and the RF/phase paths. Our laboratory measurement also validates the bias dependence of our modified Cann’s model. A high efficiency wideband envelope amplifier is also designed for EER/ET based polar transmitters for WiBro/WiMAX applications. Several simulation and measurement results were discussed in terms of optimized efficiency and system linearity. Finally, detailed system co-design simulations including RF circuits and digital DSP blocks show that our class-E PA can be linearized by the open-loop ET technique, and the entire ET-based polar TX system meets the stringent 802.16e TX mask with ~33% overall average efficiency at output power of 18.5dBm.