Publications

We present an SoC testing approach that integrates test data compression, TAM/test wrapper design, and test scheduling. An improved LFSR reseeding technique is used as the compression engine. All cores on the SoC share a single on-chip LFSR. At any clock cycle, one or more cores can simultaneously receive data from the LFSR. Seeds for the LFSR are computed from the care bits from the test cubes for multiple cores. We also propose a scan-slice-based scheduling algorithm that tries to maximize the number of care bits the LFSR can produce at each clock cycle, such that the overall test application time is minimized. Experimental results for both ISCAS circuits and industrial circuits show that optimal test application time, which is determined by the largest core, can be achieved. The proposed approach has small hardware overhead and is easy to deploy. Only one LFSR, one phase shifter, and a few counters should be added to the SoC. The scheduling algorithm is also scalable for large industrial circuits. The CPU time for a large industrial design ranges from 1 to 30 minutes.

Abstract The tribovoltaic effect is the direct‐current (DC) output that results from sliding a p‐type semiconductor on top of an n‐type semiconductor, and it is caused by the electron–hole pairs generated However, the rigid structure of traditional semiconductor limits its potential application in wearable fields. Here, p–type and n–type fabric with semiconductor properties are prepared by doping small organic molecules of cetyltrimethylammonium bromide and sodium dodecylbenzene sulfonate on the carbon atoms of single–wall carbon nanotubes (SWCNTs), and three all‐fabric direct‐current triboelectric nanogenerators based on the tribovoltaic effect (AFDC‐TENG) are developed , which exhibit high flexibility, satisfactory comfort, and stable DC output. In addition, the effects of structural parameters and environmental factors on the electrical output of AFDC‐TENG are systematically discussed. The output voltage, current, and power density of p‐type AFDC‐TENG can reach 0.2 V, 0.29 µA, and 45.5 mV m −2 at a maximum speed of 0.2 m s −1 and a sliding frequency of 1 Hz, respectively. This work proposes a simple and scalable design form for all‐fabric DC power supply devices, which has potential applications in the future micro/nano energy or self‐powered flexible sensors.

Abstract A quantum‐mechanical microscopic model of the piezoelectric effect in 2D materials is developed. The piezoelectric coefficient requires the calculation of an internal atomic displacement and an effective piezoelectric charge. The internal displacement is obtained from minimizing the strain energy given by a Keating‐like model, while the effective charge takes into account the atomic displacements and also a redistribution of the electronic charge; a bond‐orbital model is used to compute the latter. The final theory only requires atomic energies and the elasticity constants of the materials as input parameters. The piezoelectric coefficients of a number of II‐VI, III‐V and IV‐IV materials that could stably form in the planar hexagonal structure are computed; results for the IV‐IV materials are obtained for the first time.

This paper provides a comprehensive review on the methodological development and technical applications of in situ microscopy, including transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), developed in the last decade for investigating the structure-mechanical-property relationship of a single one-dimensional nanomaterial, such as nanotube, nanowire and nanobelt. The paper covers both the fundamental methods and detailed applications, including AFM-based static elastic and plastic measurements of a carbon nanotube, external field-induced resonance dynamic measurement of elastic modulus of a nanotube/nanowire, nano-indentation, and in situ plastic deformation process of a nanowire. Details are presented on the elastic property measurements and direct imaging of plastic to superplastic behavior of semiconductor nanowires at atomic resolution, providing quantitative information on the mechanical behavior of nanomaterials. The studies on the Si and SiC nanowires clearly demonstrated their distinct, "unexpected" and superior plastic mechanical properties. Finally, a perspective is given on the future of nanomechanics.

A method is presented for efficiency calculation and coincidence-summing correction of high-purity germanium (HPGe) detector spectra by using Monte Carlo N-particle transport (MCNP) code. This technique will be used in the efficiency calibration of HPGe detectors to reduce the number of standard sources to be prepared. Modeling of the detector geometry is described in detail, and differences between the simulated and measured spectra are discussed. Standard point sources traceable to the National Institute for Science and Technology were used to measure the full-energy peak and total efficiencies. The simulated full-energy peak efficiency for noncoincidence /sup 137/Cs gamma rays agreed with the measured value to within 2%, but the simulated total efficiency is about 8% lower than the measured value for 662 keV. A /sup 60/Co point source was placed in five positions above along the center line of the detector from 0.6 to 14.2 cm. For the 1173- and 1332-keV gamma rays from /sup 60/Co, their spectra were simulated using MCNP separately. Subsequently, these spectra were combined according to their coincidence relationship to form the simulated /sup 60/Co spectrum. The calculated coincidence summing factors for 1173 and 1332 keV are about 3% lower than the measured values at the closest geometry for a point source due to the underestimation of the total efficiency.