混合效应模型在研究接触—效应关系中的应用

目的用混合效应模型研究工人接苯水平与白细胞水平的关系及其影响因素,并确定最适接触剂量指标。方法在21个体检年度分别对每个研究对象的每次体检时估算区域浓度、8 h时间加权平均浓度(TWA8)、年度接触水平和累积接触水平。将接触水平定义为协变量,白细胞计数定义为效应变量,用混合效应模型分析剂量—效应关系。结果共观察接苯对象147名26 292人月,白细胞计数样本1 147份、对照组66名14 112人月白细胞计数样本396份。接触组、对照组白细胞计数平均水平分别为5.36×109,6.13×109/L。平均区域浓度、TWA8、年度接触水平和累积接触水平分别为5.10 mg/m3,4.69 mg/m3,72.90 mg/m3.月,783.70 mg/m3.月。4个混合效应模型均能收敛,其中以TWA8信息标准值最低。工人接苯水平增加、接触时间增长,白细胞水平下降。性别、吸烟与否对白细胞水平无明显影响。结论工人接苯水平和时间明显影响工人白细胞水平,TWA8可能是最适接触剂量指标。

Direct Tunneling Effect in Metal-Semiconductor Contacts Simulated with Monte Carlo Method

Considering the tunneling effect and the Schottky effect,the metal semiconductor contact is simulated by using self consistent ensemble Monte Carlo method.Under different biases or at different barrier heights,the investigation into the tunneling current indicates that the tunneling effect is of great importance under reverse biases.The Schottky barrier diode current due to Schottky effect is in agreement with the theoretical one.The barrier lowering is found a profound effect on the current transport at the metal semiconductor interface.

Simulation of a Novel Schottky Body-Contacted Structure Suppressing Floating Body Effect in Partially-Depleted SOI nMOSFET's

A novel Schottky body-contacted structure for partially depleted SOI nMOSFET's is presented.This structure can be realized by forming a shallow n +-p junction and two sidewall spacers in the source region,and then growing a thick silicide film,which can punch through the shallow junction and make a Schottky contact to the p-type silicon.Simulation results show that the anomalous subthreshold slope and kink effects are suppressed successfully and the drain breakdown voltage is improved considerably.This method has the same device area and is completely compatible with the bulk MOSFET process.

Stability analysis of the rotating tribological pair system on circular-disc end faces

In order to study the stability of friction and contact of the rotating tribological pair system,considering the influence of the changeable factors on the stability,the system dynamics analysis model based on the Lagrange equation is firstly established.The surface contact stiffness model is determined on the basis of the fractal theory.The model of the friction torque with velocities is created by using the Stribeck friction effect.The Lyapunov indirect method is employed to explore the eigenvalue problem of the system state equation.The effects of the applied load,the fractal dimension,the fractal scaling coefficient and the Stribeck coefficient on the system stability are investigated in detail.The numerical simulation results demonstrate that the tribological pair system is prone to causing system instability at low speed,and the system instability boundary value decreases when the Stribeck coefficient decreases.The fractal dimension and the fractal scaling coefficient impact the system stability slightly when fractal dimensions are large,and the system instability can be reduced by properly increasing the surface smoothness.Moreover,the system instability evidently increases with the increase in the applied load and the Stribeck coefficient.These achievements can provide a reference and theoretical support for the analysis of the dynamic performance of the tribological pair system.

EFFECT OF SHORT-TERM SOFT CONTACT LENS WEAR ON HUMAN OCULAR ABERRATIONS

Objective To evaluate the effect of short-term soft contact lens （SCLs） wearing on human ocular aberrations （ HOA ）. Methods This prospective study included 50 eyes of 50 young volunteers wearing SCLs for 1 month. The ocular aberrations were measured by Allegretto Wavefront Analyzer. The root-mean-square （RMS） values of the general （RMSG） , higher-order （RMSH） , first to sixth order （ RMS1 to RMS6） and aberration coefficients were analyzed. Results There were no significant differences in the mean values of RMSG, RMSH, RMS1 to RMS6 （ P 〉 0. 05 ） and changes of absolute values of aberration coefficients between baseline and various visits after SCLs discontinuation. However, at d I after the discontinuation of SCLs, changes in coefficient values of the third-order aberrations （ C6 to C9 ） were slightly higher than others, and C7 was the highest. The increase factors of RMS values were higher at 1 week and lower at the 2 week visit after SCLs discontinuation. The uniformity of dominating type in HOA and the corneal topography form was both about 60% after discontinuation of SCLs. The corneal thickness increased after SCLs wear and gradually decreased to baseline until 1 month discontinuation of SCLs. Conclusion The effect of short-term SCLs wear on human ocular aberrations is slight but profound. A month or more wait should be allowed before the short-term SCLs wearers are scheduled for wavefronted-guided LASIK.

Developments in the understanding of gas–solid contact efficiency in the circulating fluidized bed riser reactor:A review

In the last several decades, circulating fluidized bed reactors have been studied in many aspects including hydrodynamics, heat and mass transfer and gas–solid two phase contacting. However, despite the abundance of review papers on hydrodynamics, there is no summary paper on gas–solid contact efficiency to date, especially on high density circulating fluidized beds(CFBs). This paper gives an introduction to, and a review of the measurement of contact efficiency in circulating fluidized bed riser. Firstly, the popular testing method of contact efficiency including the method of heating transfer experiment and hot model reaction are discussed, then previous published papers are reviewed based on the discussed methods. Some key results of the experimental work are described and discussed. Gas–solid contact efficiency is affected by the operating conditions as well as the particle size distribution. The result of the contact efficiency shows that the CFB riser is far away from an ideal plug flow reactor due to the characteristics of hydrodynamics in the riser. Lacunae in the available literature have been delineated and recommendations have been made for further work.

排铅后再接铅生物指标的观测

目的 探讨排铅工人再接铅后 ,某些生物监测指标和卟啉代谢指标的动态变化。方法 110名冶炼厂工人经排铅治疗后 ,回生产岗位 2周、 7周、 2 4周 ,分别采样进行血铅 (PbB)、尿铅 (PbU)、尿氨基酮戊酸 (δ ALA)、血氨基酮戊酸脱水酶 (δ ALAD)、红细胞游离原卟啉 (FEP)、血红蛋白 (Hb)的监测 ,同时进行作业场所空气铅烟的监测。结果 低水平接触组以PbB变化较早和灵敏 ,其次为δ ALAD ,δ ALA和FEP的增高出现较晚 ;中等水平接触组以PbB ,PbU和δ ALAD变化出现最早和敏感 ,其后变化趋势变缓 ,但δ ALA、FEP持续增高 ;高水平接触组各项指标均出现明显的改变 ,以δ ALA变化幅度较大 ,其次为FEP、PbU、PbB ,而δ ALAD的变化与中等水平组相似 ,Hb仅在 2 4周出现降低。经相关和聚类分析 ,PbB、PbU、δ ALAD活性具有相似变化规律 ,而FEP与δ ALA具有相似的时间序列变化规律。结论 工人排铅后再接铅 ,在较短时间内出现铅的毒性效应 ,应加强一级预防 。

Effect of p-well contact on n-well potential modulation in a 90 nm bulk technology

The effect of p-well contact on the n-well potential modulation in a 90 nm bulk technology with P+ deep well is studied based on three-dimensional (3-D) TCAD device simulations. Simulation results illustrate that the p-well contact area has a great impact on the n-well potential modulation and the enhancement factor will level out as the p-well contact area increases, and that at the same time the increase of p-well doping concentration can also enhance the n-well potential modulation. However, the effect of p-well contact location on the n-well modulation is not obvious as the p-well contact distance increases. According to our simulation results, it is proposed that the p-well contact area should be cautiously designed to mitigate single event effect (SEE) in the P+ deep well technology.

锡矿工人接尘与矽肺危险度评价

目的探讨粉尘暴露与矽肺危险度之间的接触效应关系。方法选择广西４个锡矿１９６０～１９６５年间工作１年以上的３０１０名接尘工人进行队列研究。用生存分析法统计累积粉尘接触量和矽肺出现的关系。结果追访到１９９４年底，检出矽肺１０１５例（３３．７％）。矽肺平均潜伏期２１．３年。总粉尘浓度７．５ｍｇ／ｍ３（ＴＷＡ）。拟合生存分析模型表明：矽肺发病危险度与累积接尘量的关系适合Ｗｅｉｂｕｌ分布。累积总粉尘接触量低于１０ｍｇ·ｍ－３·ａ－１时，矽肺危险小于１％；累积总粉尘接触量超过２０ｍｇ·ｍ－３·ａ－１时，矽肺累积危险度升高加快；累积总粉尘接触量达１５０ｍｇ·ｍ－３·ａ－１时，矽肺危险超过６８％。接尘时间与接尘量和矽肺危险度呈正相关。结论矽肺危险度与累积接尘量之间存在接触效应关系。

Evidence for nematic superconductivity of topological surface states in PbTaSe2

Spontaneous symmetry breaking has been a paradigm to describe the phase transitions in condensed matter physics.In addition to the continuous electromagnetic gauge symmetry,an unconventional superconductor can break discrete symmetries simultaneously,such as time reversal and lattice rotational symmetry.In this work we report a characteristic in-plane 2-fold behaviour of the resistive upper critical field and point-contact spectra on the superconducting semimetal PbTaSe2 with topological nodal-rings,despite its hexagonal lattice symmetry(or D3 h in bulk while C3 v on surface,to be precise).The 2-fold behaviour persists up to its surface upper critical field Hc2R even though bulk superconductivity has been suppressed at its bulk upper critical field Hc2HC<<Hc2R,signaling its probable surface-only electronic nematicity.In addition,we do not observe any lattice rotational symmetry breaking signal from field-angle-dependent specific heat within the resolution.It is worth noting that such surface-only electronic nematicity is in sharp contrast to the observation in the topological superconductor candidate,CuxBi2Se3,where the nematicity occurs in various bulk measurements.In combination with theory,superconducting nematicity is likely to emerge from the topological surface states of PbTaSe2,rather than the proximity effect.The issue of time reversal symmetry breaking is also addressed.Thus,our results on PbTaSe2 shed new light on possible routes to realize nematic superconductivity with nontrivial topology.