WANG LEI
Email Address
dbswale@nus.edu.sg
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Publication Amine-catalyzed [3+2] Huisgen cycloaddition strategy for the efficient assembly of highly substituted 1,2,3-triazoles(2012-05-07) Wang, L.; Peng, S.; Danence, L.J.T.; Gao, Y.; Wang, J.; PHYSICS; CHEMISTRYAn enamine-catalyzed strategy has been utilized to fully promote the Huisgen [3+2] cycloaddition with a broad spectrum of carbonyl compounds and azides, thereby permitting the efficient assembly of a vast pool of highly substituted 1,2,3-triazoles. In particular, the employment of commonly used and commercially available carbonyl compounds has resulted in the introduction of a diverse set of functional groups, such as alkyl, aryl, nitrile, ester, and ketone groups, at the 1-, 4-, or 5-positions of the 1,2,3-triazole scaffold. This approach might be manipulated to access more useful and sophisticated heterocyclic compounds. Most significantly, the reaction process exhibits complete regioselectivity, with the formation of only one regioisomer. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Publication 3-5 GHz 4-channel UWB beamforming transmitter with 1° scanning resolution through calibrated vernier delay line in 0.13-μm CMOS(2012) Wang, L.; Lian, Y.; Heng, C.-H.; ELECTRICAL & COMPUTER ENGINEERING; PHYSICSA 3-5 GHz 4-channel UWB beamforming transmitter with 1° scanning resolution and 135° scanning range is presented in this paper. The fine resolution is attained through Vernier delay lines capable of fine resolution down to 10 ps. Accurate path delay across channels as well as UWB pulse center frequency are achieved through the proposed Δσ DLL calibration technique, which speeds up the calibration by 48 times compared with a counter-based approach. A novel power spectral density calibration circuit is included to adjust the UWB pulse shape for meeting the FCC mask. Fabricated in 0.13-μm CMOS, the proposed transmitter occupies only 7.2 μm. The power consumption is 9.6 mW while transmitting at 80 Mbps, with each transmitter achieving 10 pJ/bit and transmitter efficiency of 7.5%. This is about ten times better than those existing UWB beamforming transmitters. © 2012 IEEE.Publication Thermal rectification and negative differential thermal resistance in lattices with mass gradient(2007-07-24) Yang, N.; Li, N.; Wang, L.; Li, B.; PHYSICSWe study thermal properties of one-dimensional (1D) harmonic and anharmonic lattices with a mass gradient. It is found that a temperature gradient can be built up in the 1D harmonic lattice with a mass gradient due to the existence of gradons. The heat flow is asymmetric in anharmonic lattices with a mass gradient. Moreover, in a certain temperature region, negative differential thermal resistance is observed. Possible applications in constructing thermal rectifiers and thermal transistors by using the graded material are discussed. © 2007 The American Physical Society.Publication Anomalous heat conduction and anomalous diffusion in nonlinear lattices, single walled nanotubes, and billiard gas channels(2005) Li, B.; Wang, J.; Wang, L.; Zhang, G.; TEMASEK LABORATORIES; PHYSICSWe study anomalous heat conduction and anomalous diffusion in low-dimensional systems ranging from nonlinear lattices, single walled carbon nanotubes, to billiard gas channels. We find that in all discussed systems, the anomalous heat conductivity can be connected with the anomalous diffusion, namely, if energy diffusion is o 2(t)=2Dt α (0 < α ≤ 2), then the thermal conductivity can be expressed in terms of the system size L as K=cL β with β=2-2/α. This result predicts that a normal diffusion (a=l) implies a normal heat conduction obeying the Fourier law (β=0), a superdiffusion (α > 1) implies an anomalous heat conduction with a divergent thermal conductivity (β>0), and more interestingly, a subdiffusion (α < 1) implies an anomalous heat conduction with a convergent thermal conductivity (β < 0), consequently, the system is a thermal insulator in the thermodynamic limit. Existing numerical data support our theoretical prediction. © 2005 American Institute of Physics.Publication Nonequilibrium properties of the one-dimensional hard-point gas system(2006) Casati, G.; Prosen, T.; Wang, L.; Li, B.; PHYSICSWe discuss the stability properties of a one-dimensional hard-point gas. We study the decay of the Loschmidt echo which describes the stability of the motion under system perturbations. We show a universal behavior in the echo decay which is intimately connected to the linear dynamical instability of the motion. In particular, in spite of such a weak instability, the asymptotic decay follows a simple exponential law. © 2006 The American Physical Society.Publication Thermal logic gates: Computation with phonons(2007-10-24) Wang, L.; Li, B.; PHYSICSLogic gates are basic digital elements for computers. We build up thermal logic gates that can perform similar operations as their electronic counterparts. The thermal logic gates are based on nonlinear lattices, which exhibit very intriguing phenomena due to their temperature dependent power spectra. We demonstrate that phonons, the heat carriers, can also be used to carry information and processed accordingly. The possibility of nanoscale experiments is discussed. © 2007 The American Physical Society.Publication A miniaturized heterogeneous wireless sensor node in 3DIC(2011) Liu, X.; Wang, L.; Jayakrishnan, M.; Lan, J.; Li, H.; Choong, C.S.; Raja, M.K.-S.; Guo, Y.; Goh, W.L.; He, J.; Gao, S.; Je, M.; ELECTRICAL & COMPUTER ENGINEERING; PHYSICSIn this paper, an innovative design of a miniaturized heterogeneous 3DIC-based wireless sensor node (WSN) is proposed. The design contains stacks of radio frequency (RF) die, mixed-signal die, digital die, and integrated antenna die using the through silicon via (TSV) technology. Significant enhancements to the existing 2D design and verification flow are developed to solve the critical concerns of heterogeneous 3DIC integration, including the block-level partitioning, TSV macro design, the TSV-related modeling and characterization, and physical verification. Solutions are proposed to minimize the electromagnetic interference (EMI) effects between the IC and the antenna. The size of the proposed 3DIC is only 66% as compared to a similar 2D implementation, permitting miniaturization of the complete WSN system. © 2011 IEEE.Publication Interface thermal resistance between Frenkel-Kontorova and Fermi-Pasta-Ulam lattices(2007-09-30) Lan, J.; Wang, L.; Li, B.; PHYSICSBy connecting two dissimilar anharmonic lattices exemplified by Fermi-Pasta-Ulam (FPU) model and Frenkel-kontorova (FK) model, we successfully build up one dimensional thermal diode. We find the rectifying effect is closely related to asymmetric interface thermal resistance ( Kapitza resistance). And the asymmetric thermal resistance depends on how the temperature gradient is applied. Moreover, a quatitative relationship between the thermal rectification and the phonon spectra is propsoed. © World Scientific Publishing Company.Publication A flexible modified dipole antenna printed on PET film(2012) Wang, L.; Guo, Y.-X.; Salam, B.; Lu, C.W.A.; ELECTRICAL & COMPUTER ENGINEERING; PHYSICSA flexible transparent modify dipole antenna printed on PET film is presented in this paper. The proposed antenna was designed to operate at 2.4GHz for ISM applications. The impedance characteristic and the radiation characteristic were simulated and measured. The proposed antenna has good performance. It can be easily mounted on conformal shape, because it is fabricated on PET film having the flexible characteristic. © 2012 IEEE.Publication Highly efficient assembly of 3-hydroxy oxindole scaffold via a catalytic decarboxylative [1,2]-addition strategy(2012-12-07) Ren, Q.; Huang, J.; Wang, L.; Li, W.; Liu, H.; Jiang, X.; Wang, J.; PHYSICS; CHEMISTRYThe 3-hydroxy-2-oxindole scaffold is being continuously discovered to be at the core of a diverse set of natural products. Herein, we document a highly efficient catalytic decarboxylative [1,2]-addition strategy to quickly assemble this scaffold, using a catalytic amount of weak base. © 2012 American Chemical Society.