@article{ding_zhao_sun_li_ma_lavernia_zhu_liu_2020, title={Alloying effects on the plasticity of magnesium: comprehensive analysis of influences of all five slip systems}, volume={32}, ISSN={["1361-648X"]}, DOI={10.1088/1361-648X/ab445d}, abstractNote={Low plasticity has been a major issue for the application of Mg alloys. Here, based on the generalized stacking fault energy curves and Arrhenius equation, we systematically study alloying effects on the stacking fault energies and the activation probability of basal and non-basal 〈a〉, and pyramidal 〈c  +  a〉 slip systems in twenty-one Mg alloys. Our results reveal that activation of 〈c  +  a〉 slip systems on pyramidal II plane can significantly improve the plasticity. For example, Ca is found to promote the activation probability of this slip system by one order of magnitude and dramatically improve the plasticity of Mg.}, number={1}, journal={JOURNAL OF PHYSICS-CONDENSED MATTER}, author={Ding, Zhigang and Zhao, Guangxuan and Sun, Hao and Li, Shuang and Ma, Fei and Lavernia, Enrique J. and Zhu, Yuntian and Liu, Wei}, year={2020}, month={Jan} }
 @article{liu_hu_zheng_zhang_ding_liu_zhu_sha_2020, title={Formation of solute nanostructures in an Al-Zn-Mg alloy during long-term natural aging}, volume={821}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2019.153572}, abstractNote={Nature aging (NA) is believed to produce solute nanostructures, including solute clusters and GPI zones in Al–Zn–Mg alloys. Here we report the first observation that GPII (GPη’) zones with an average Zn/Mg ratio near 1.3–1.4 formed in the Al–Zn–Mg alloys during long-term natural aging. High-angle-annular-dark-field scanning transmission electron microscopy and atom probe tomography were used to study the evolution of solute nanostructures during natural aging. Early clusters were found to have a wide spread of Zn/Mg ratios and their number density increased sharply with a dramatic hardening effect during the first month ageing. Further ageing up to 3 months made the Zn/Mg ratios of the solute clusters gradually converge to near 1.2 (GPI zones), but produced no change in the morphology, size distribution and volume fraction of the solute nanostructures, as well as hardness. At room temperature, GPII (GPη’ type) zones formed very slowly and provided stronger hardening effects than early clusters. Importantly, unlike solute-rich clusters, GPI and GPη’ zones are easy to transform into η′ during subsequent artificial ageing, avoiding hardness drop at the early stage of subsequent artificial aging at 120 °C.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Liu, Jizi and Hu, Rong and Zheng, Jialing and Zhang, Yidong and Ding, Zhigang and Liu, Wei and Zhu, Yuntian and Sha, Gang}, year={2020}, month={Apr} }
 @article{liu_huang_thorne_banzon_zhang_freeman_lawrimore_peterson_smith_woodruff_2015, title={Extended reconstructed sea surface temperature version 4 (ERSST.v4): Part II. Parametric and structural uncertainty estimations}, volume={28}, number={3}, journal={Journal of Climate}, author={Liu, W. and Huang, B. Y. and Thorne, P. W. and Banzon, V. F. and Zhang, H. M. and Freeman, E. and Lawrimore, J. and Peterson, T. C. and Smith, T. M. and Woodruff, S. D.}, year={2015}, pages={931–951} }
 @article{liu_liu_cheng_hu_2015, title={On the stability of the Atlantic meridional overturning circulation during the last deglaciation}, volume={44}, number={5-6}, journal={Climate Dynamics}, author={Liu, W. and Liu, Z. Y. and Cheng, J. and Hu, H. B.}, year={2015}, pages={1257–1275} }
 @article{liu_zhao_inoue_wang_bradford_kim_qiu_zhu_2012, title={Poly(vinyl alcohol) reinforced with large-diameter carbon nanotubes via spray winding}, volume={43}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2011.12.029}, abstractNote={For practical application of carbon nanotube (CNT)/polymer composites, it is critical to produce the composites at high speed and large scale. In this study, multi-walled carbon nanotubes (MWNTs) with large diameter (∼45 nm) and polyvinyl alcohol (PVA) were used to increase the processing speed of a recently developed spraying winding technique. The effect of the different winding speed and sprayed solution concentration to the performance of the composite films were investigated. The CNT/PVA composites exhibit tensile strength of up to 1 GPa, and modulus of up to 70 GPa, with a CNT weight fraction of 53%. In addition, an electrical conductivity of 747 S/cm was obtained for the CNT/PVA composites. The good mechanical and electrical properties are attributed to the uniform CNTs and PVA matrix integration and the high degree of tube alignment.}, number={4}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Liu, Wei and Zhao, Haibo and Inoue, Yoku and Wang, Xin and Bradford, Philip D. and Kim, Hyungsup and Qiu, Yiping and Zhu, Yuntian}, year={2012}, month={Apr}, pages={587–592} }
 @article{wang_bradford_liu_zhao_inoue_maria_li_yuan_zhu_2011, title={Mechanical and electrical property improvement in CNT/Nylon composites through drawing and stretching}, volume={71}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2011.07.023}, abstractNote={The excellent mechanical properties of carbon nanotubes (CNTs) make them the ideal reinforcements for high performance composites. The misalignment and waviness of CNTs within composites are two major issues that limit the reinforcing efficiency. We report an effective method to increase the strength and stiffness of high volume fraction, aligned CNT composites by reducing CNT waviness using a drawing and stretching approach. Stretching the composites after fabrication improved the ultimate strength by 50%, 150%, and 190% corresponding to stretch ratios of 2%, 4% and 7%, respectively. Improvement of the electrical conductivities exhibited a similar trend. These results demonstrate the importance of straightening and aligning CNTs in improving the composite strength and electrical conductivity.}, number={14}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Wang, Xin and Bradford, Philip D. and Liu, Wei and Zhao, Haibo and Inoue, Yoku and Maria, Jon-Paul and Li, Qingwen and Yuan, Fuh-Gwo and Zhu, Yuntian}, year={2011}, month={Sep}, pages={1677–1683} }
 @article{liu_zhang_xu_bradford_wang_zhao_zhang_jia_yuan_li_et al._2011, title={Producing superior composites by winding carbon nanotubes onto a mandrel under a poly(vinyl alcohol) spray}, volume={49}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2011.06.089}, abstractNote={A simple method for processing high-performance carbon nanotube (CNT)/poly(vinyl alcohol) (PVA) composites by coupling the spraying of a PVA solution with the continuous winding of CNT sheets from an array onto a rotating mandrel is reported. This method allows the CNT composites to have a high CNT volume fraction, while having a high degree of alignment, long CNTs, and good integration with the matrix, which are extremely difficult to realize simultaneously by other processes. As a result, the composites have a toughness, strength and electrical conductivity up to 100 J/g, 1.8 GPa and 780 S/cm, respectively. Such a one-step synthesis process is promising for industrial productions and also works for different types of polymers.}, number={14}, journal={CARBON}, author={Liu, Wei and Zhang, Xiaohua and Xu, Geng and Bradford, Philip D. and Wang, Xin and Zhao, Haibo and Zhang, Yingying and Jia, Quanxi and Yuan, Fuh-Gwo and Li, Qingwen and et al.}, year={2011}, month={Nov}, pages={4786–4791} }
 @article{zhao_bradford_wang_liu_luo_jia_zhu_yuan_2010, title={An intermetallic Fe-Zr catalyst used for growing long carbon nanotube arrays}, volume={64}, ISSN={["1873-4979"]}, DOI={10.1016/j.matlet.2010.05.045}, abstractNote={Metallic nanoparticles containing single and binary components have been known for their catalytic properties to grow carbon nanotube (CNT) arrays. In this paper, an intermetallic catalyst consisting of iron and zirconium was used to grow millimeter long, well aligned arrays. The Fe–Zr catalysts enabled the growth of 1.7 mm-long carbon nanotube arrays in 45 min. A comparison with pure iron catalyst indicated that adding Zr to iron can stabilize the Fe catalyst at the CNT growth temperature and moderate its reactivity. SEM images showed the different growth behaviors for Fe–Zr and Fe catalysts. The long, uniform CNT arrays grown here have potential applications in many advanced composites.}, number={18}, journal={MATERIALS LETTERS}, author={Zhao, Haibo and Bradford, Philip D. and Wang, Xin and Liu, Wei and Luo, Tzy Jiun Mark and Jia, Quanxi and Zhu, Yuntian and Yuan, Fuh-Gwo}, year={2010}, month={Sep}, pages={1947–1950} }
 @article{xu_liu_huang_2009, title={Two-Phase Interleaved Critical Mode PFC Boost Converter With Closed Loop Interleaving Strategy}, volume={24}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2009.2019824}, abstractNote={This paper presents a two-phase interleaved critical mode (CRM) power factor correction (PFC) boost converter with a novel closed loop interleaving technique. This new interleaving technique makes each phase work at ideally CRM. Natural current sharing and precise 180° phase shift are achieved. The scheme can be easily integrated into a PFC control chip. Full-order averaged model of CRM boost is derived to analyze the stability of the converter. The loop response and stability of the closed-phase regulation loop have been analyzed. A 400 W two-phase interleaved CRM PFC boost converter prototype is built. This proposed scheme is verified by simulation and experimental results.}, number={12}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Xu, Xiaojun and Liu, Wei and Huang, Alex Q.}, year={2009}, month={Dec}, pages={3003–3013} }
 @inbook{tuck_liu_torrellas_2007, title={CAP: criticality analysis for power-efficient speculative multithreading}, booktitle={2007 IEEE International Conference On Computer Design}, publisher={New York: IEEE}, author={Tuck, J. and Liu, W. and Torrellas, J.}, year={2007}, pages={409–416} }
 @article{barabash_ice_roder_budai_liu_figge_einfeldt_hommel_davis_2007, title={Characterization of growth defects in thin GaN layers with X-ray microbeam}, volume={244}, ISSN={["1521-3951"]}, DOI={10.1002/pssb.200675113}, abstractNote={Abstract}, number={5}, journal={PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS}, author={Barabash, R. I. and Ice, G. E. and Roder, C. and Budai, J. and Liu, W. and Figge, S. and Einfeldt, S. and Hommel, D. and Davis, R. F.}, year={2007}, month={May}, pages={1735–1742} }
 @article{barabash_ice_liu_einfeldt_hommel_roskowski_davis_2005, title={White X-ray microbeam analysis of strain and crystallographic tilt in GaN layers grown by maskless pendeoepitaxy}, volume={202}, number={5}, journal={Physica Status Solidi. A, Applications and Materials Science}, author={Barabash, R. I. and Ice, G. E. and Liu, W. and Einfeldt, S. and Hommel, D. and Roskowski, A. M. and Davis, R. F.}, year={2005}, pages={732–738} }
 @article{yang_wolden_liu_schlesser_davis_prater_sitar_1998, title={Coalesced oriented diamond films on nickel}, volume={13}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.1998.0157}, abstractNote={The growth of coalesced, highly oriented diamond films has been achieved on nickel substrates using a multistep process that consisted of (i) seeding the Ni surface with 0.5 μm diamond powder, (ii) annealing at 1100 °C in a hydrogen atmosphere, and (iii) growth at 900 °C in a mixture of hydrogen and 0.5% methane. Auger depth profile analysis of a sample quenched after the annealing stage showed the presence of significant amounts of carbon (6 at. %) close to the substrate surface and about 3 at.% deeper in the substrate. The loss of carbon into the substrate resulted in relatively low nucleation density. The addition of methane into the gas phase during the annealing stage proved very effective in compensating for the diffusion. An addition of 0.5% methane in the gas phase produced optimum results, as the nucleation density, orientation of diamond particles, and uniformity were substantially improved. Substrates nucleated under these conditions were grown out into coalesced, 30 μm thick films. Both (100) and (111) oriented films showed a high degree of orientation and Raman spectra obtained from these orientations showed intense and narrow diamond signature peaks with FWHM's of 5 and 8 cm-1, respectively.}, number={5}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Yang, PC and Wolden, CA and Liu, W and Schlesser, R and Davis, RF and Prater, JT and Sitar, Z}, year={1998}, month={May}, pages={1120–1123} }
 @article{sitar_liu_yang_wolden_schlesser_prater_1998, title={Heteroepitaxial nucleation of diamond on nickel}, volume={7}, ISSN={["0925-9635"]}, DOI={10.1016/S0925-9635(97)00244-6}, abstractNote={Highly oriented diamond has been grown on (100) nickel substrates by the hot filament chemical vapor deposition method. Epitaxial nuclei were obtained by a diamond powder seeding and high temperature annealing process. Since the timing of the process was crucial for the achievement of a high degree of orientation and high density of diamond nuclei, a real-time, in-situ laser reflectometry system was developed to monitor changes in surface morphology observed during the high temperature annealing stage. Characteristic features observed in the intensities of reflected and scattered light were interpreted by comparison with scanning electron micrographs of the samples quenched at sequential stages of the process. It was concluded that the scattered light signal can be effectively used as a process steering parameter. Using this technique, oriented nucleation and growth of diamond on Ni was reproducibly achieved. Auger spectroscopy showed that up to 6 at% of carbon was dissolved in the nickel surface layer. The investigation of interfacial microstructures and phases involved by transmission electron microscopy revealed the formation of Ni4C already in the early stages of nucleation. This phase was manifested as coherent precipitates and is believed to have been the precursor for diamond nucleation. Perfectly epitaxial diamond was grown by this process. The epitaxial relationship was determined by cross-sectional transmission electron microscopy and selected area diffraction analysis.}, number={2-5}, journal={DIAMOND AND RELATED MATERIALS}, author={Sitar, Z and Liu, W and Yang, PC and Wolden, CA and Schlesser, R and Prater, JT}, year={1998}, month={Feb}, pages={276–282} }
 @article{yang_liu_schlesser_wolden_davis_prater_sitar_1998, title={Surface melting in the heteroepitaxial nucleation of diamond on Ni}, volume={187}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(97)00854-3}, abstractNote={Surface melting associated with the heteroepitaxial nucleation of diamond on Ni was investigated. Scanning electron microscopy of quenched samples revealed flow patterns and a recrystallized surface morphology. A combination of techniques including in situ optical monitoring, differential thermal analysis, Auger depth profile analysis, and cross-section transmission electron microscopy (TEM) analysis were performed to identify the nature of the molten layer. Data obtained from different experiments were in good mutual agreement. All experimental results strongly indicated that a molten Ni–C–H surface layer was involved in the nucleation process. The presence of both carbon and atomic hydrogen played an important role in the depression of the melting point which was measured to be >300°C less than the melting point of pure Ni.}, number={1}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Yang, PC and Liu, W and Schlesser, R and Wolden, CA and Davis, RF and Prater, JT and Sitar, Z}, year={1998}, month={Apr}, pages={81–88} }
 @article{liu_yang_wolden_davis_prater_sitar_1998, title={Transmission electron microscopy analysis of the oriented diamond growth on nickel substrates}, volume={83}, ISSN={["0021-8979"]}, DOI={10.1063/1.367885}, abstractNote={Transmission electron microscopy (TEM) was used to investigate the interfacial microstructure and the phases that developed during the nucleation and growth of oriented diamond on Ni by a hot filament process. Oriented Ni4C nuclei were identified by plan-view TEM in a sample quenched during the nucleation stage. Likewise, the presence of the Ni4C phase between the diamond and the Ni substrate was observed by cross-section TEM in samples grown for several hours. The orientational relationship among the diamond, Ni4C, and Ni substrate was examined by selected area diffraction. Diamond and Ni4C interfacial phase had a good epitaxial relationship, while the interfacial Ni4C phase and the Ni substrate developed with a small misfit and rotation. Based on these experimental results, the nucleation mechanism of oriented diamond growth on Ni is proposed.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Liu, W and Yang, PC and Wolden, CA and Davis, RF and Prater, JT and Sitar, Z}, year={1998}, month={Jun}, pages={7658–7663} }