A 1.2 V,3.1%3σ-accuracy thermal sensor analog front-end circuit in 12 nm CMOS process

This paper presents a 1.2 V high accuracy thermal sensor analog front-end circuit with 7 probes placed around the microprocessor chip.This analog front-end consists of a BGR(bandgap reference),a DEM(dynamic element matching)control,and probes.The BGR generates the voltages linear changed with temperature,which are followed by the data read out circuits.The superior accuracy of the BGR’s output voltage is a key factor for sensors fabricated via the FinFET digital process.Here,a 4-stage folded current bias structure is proposed,to increase DC accuracy and confer immunity against FinFET process variation due to limited device length and low current bias.At the same time,DEM is also adopted,so as to filter out current branch mismatches.Having been fabricated via a 12 nm FinFET CMOS process,200 chips were tested.The measurement results demonstrate that these analog front-end circuits can work steadily below 1.2 V,and a less than 3.1%3σ-accuracy level is achieved.Temperature stability is 0.088 mV/℃across a range from-40 to 130℃.

Dynamic Stability and Fuzzy Reliability Analysis of Toppling Perilous Rock Under Seismic Excitation

To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under the action of bidirectional earthquakes is proposed.First,the mass viscoelasticity model is used to simulate two main control surfaces of toppling perilous rock,the seismic dynamic response model and motion equation of toppling perilous rock are established based on the D'Alembert principle,and the Newmark-β method is used to solve the dynamic motion equation.Then,the instability event of toppling perilous rock is considered a fuzzy event,the membership function expression of the stability coefficient of toppling perilous rock is determined based on the fuzzy failure criterion,the calculation equations of the toppling perilous rock dynamic stability coefficient and fuzzy reliability are established,and the fuzzy reliability evaluation method based on the probability distribution of reliability is proposed.Finally,the influence of different superposition modes of seismic excitation on the fuzzy reliability of toppling perilous rock is analyzed.The calculation results of toppling perilous rock in the engineering case show that the fuzzy reliability calculated after considering the fuzzy failure criterion is reduced by 10.73% to 25.66% compared with the classical reliability.Considering the bidirectional seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 5.46% to 14.89%.Compared with using the acceleration peak time encounter mode to superpose the seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 3.4% when the maximum action effect time encounter mode is adopted.

Enabling ultranarrow blue emission linewidths in colloidal alloy quantum dots by decreasing the exciton fine structure splitting and exciton–phonon coupling

The realization of colloidal alloy quantum dots(QDs)with narrow spectral linewidths requires minimization of the contributions of inhomogeneous and homogeneous broadening to the ensemble spectrum.Recently,there has been remarkable progress in eliminating the inhomogeneous contribution by controlling the size distribution of the QDs.However,considerable challenges remain in suppressing the homogeneous broadening,in terms of both intrinsic principles and rational synthetic routes.We find that ground-state exciton fine structure splitting and exciton-phonon coupling play a pivotal role in the homogeneous broadening mechanism.Here we demonstrate that the elimination of the lattice mismatch strain by using a coherent strain structure can decrease the light-heavy hole splitting,thus suppressing the asymmetric broadening of the emission on the high energy side.Besides,the improvement of the uniformity of the alloy by using a stepwise ion exchange strategy can weaken the exciton-longitudinal optical(LO)-phonon interactions,further minimizing the homogeneous broadening.As a result,the final alloy QD products exhibit a widely tunable blue emission wavelength(445-470 nm)with the narrowest ensemble photoluminescence full width at half maximum(FWHM)of 10.1-13.5 nm(or 58.4-75.3 meV).Our study provides a potential strategy for other semiconductor nanocrystals with ultranarrow spectral linewidths.

图上p-Laplace算子的特征值估计

设G(V,E)为满足CD_(P)^(√)(m,K)条件的连通有限图,其中p≥2,m> 0,K≤0.本文在G上考虑了方程△pu=-λ_(p)|u|^(p-2)u解的椭圆型梯度估计,其中△_(p)为p-Laplace算子.作为应用,导出了G上△_(p)的第一非零特征值的下界估计.

Microstructure and strength in ultrastrong cold-drawn medium carbon steel

Via traditional wire drawing,the medium carbon ferrite-pearlite(MCFP)steel wires can achieve the ultrahigh strength beyond 4 GPa normally for high-carbon pearlitic steel wires,but have a 30-60%lower production cost.The microstructural evolution and mechanical properties of medium carbon ferrite-pearlite steel wires have been investigated by means of scanning electron microscopy,transmission electron microscopy and tensile testing.The tensile strength of medium carbon ferrite-pearlite steel wires increases from 750 MPa up to 4120 MPa when the drawing strain increases up toε=6.4,which represents the highest strength reported so far-to our knowledge for a carbon steel with such low carbon content.At low and medium strains(ε≤1.95),the proeutectoid ferrite forms dense dislocation walls(DDWs)via dislocation activities,including sliding,accumulation,interaction,and tangling.With the drawing strain increase,the reorientation of DDWs to the drawing direction forms the coarse proeutectoid ferrite lamellae.Finally,the proeutectoid ferrite deformed to high strains is characterized by a lamellar morphology and the average lamellar spacing of proeutectoid ferrite is about 55 nm atε=6.4.The interlamellar spacing of pearlite and thickness of cementite decreases with the drawing strain increases.The dislocation density in ferrite lamellae increases with the drawing strain increases,and the dislocation density in ferrite lamellae is 7.8×10^(15)m^(2)atε=4.19.A higher dislocation density of 3.1×10^(16)m^(2)can be obtained atε=6.4 by means of extrapolation and TEM investigations.The stress contributions of proeutectoid ferrite and pearlite to the flow stress are estimated based on quantified structural parameters.Based on the assumption that the stress contributions from different strengthening mechanisms are linearly additive and the general rule of mixtures,a good agreement between the measured and estimated flow stresses has been found in a large range of flow stress.The good application of the general rule of mixture to the medium carbon ferrite-pearlite steel wires indicates the importance of quantitative characterization of microstructural evolution and parameters with the strain.

A 10 bit 200 MS/s pipeline ADC using loading-balanced architecture in 0.18 μm CMOS

A new loading-balanced architecture for high speed and low power consumption pipeline analog-todigital converter（ADC） is presented in this paper. The proposed ADC uses SHA-less, op-amp and capacitor-sharing technique, capacitor-scaling scheme to reduce the die area and power consumption. A new capacitor-sharing scheme was proposed to cancel the extra reset phase of the feedback capacitors. The non-standard inter-stage gain increases the feedback factor of the first stage and makes it equal to the second stage, by which, the load capacitor of op-amp shared by the first and second stages is balanced. As for the fourth stage, the capacitor and op-amp no longer scale down. From the system＇s point of view, all load capacitors of the shared OTAs are balanced by employing a loadingbalanced architecture. The die area and power consumption are optimized maximally. The ADC is implemented in a 0.18 μm 1P6M CMOS technology, and occupies a die area of 1.2×1.2 mm^2. The measurement results show a 55.58 dB signal-to-noise-and-distortion ratio（SNDR） and 62.97 dB spurious-free dynamic range（SFDR） with a 25 MHz input operating at a 200 MS/s sampling rate. The proposed ADC consumes 115 m W at 200 MS/s from a 1.8 V supply.

Rigid Properties of Quasi-almost-Einstein Metrics

In this paper,quasi-almost-Einstein metrics on complete manifolds are studied.Two examples are given and several formulas are established.With the help of these formulas,the author proves rigid results on compact or noncompact manifolds,in which some basic tools,such as the weighted volume comparison theorem and the weak maximum principle at infinity,are used.A lower bound estimate for the scalar curvature is also obtained.

Gap results for compact quasi-Einstein metrics

In this paper, we work on compact quasi-Einstein metrics and prove several gap results. In the first part, we get a gap estimate for the first nonzero eigenvalue of the weighted Laplacian, by establishing a comparison theorem for the weighted heat kernel. In the second part, we establish two gap results for the Ricci curvature and the scalar curvature, based on which some rigid properties can be derived.

Contact Electrification and Adhesion Between Carbon Nanotube and Graphene on Metal Surfaces: Insights from First-principles Study

The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,contact electrification and its relationship with adhesion are systematically studied using the first-principles calculation.Charge transfers from CNT or its special form,graphene,to the metal surface during the contact,and the transferred charge linearly correlates with the work function difference.Meanwhile,the adhesion energy is linearly related to the transferred charge for both CNT and graphene.More charge transfers from the flat graphene to metal surfaces than the curved CNT,leading to higher adhesion between graphene and metal surfaces.The curved structure of the CNT causes an irregular change of charge at the interface and hinders the charge transfer.Moreover,the curved structure induces electronic localization,which also decreases the interfacial charge transfer.The structure affects contact electrification,and hence adhesion is further demonstrated by the CNT with different deformation when contacting different surfaces.This study advances our understanding of contact electrification and its relationship with adhesion at the interface for bio-inspired carbon adhesive materials and sheds light on the control of them for engineering applications.