城市“热岛”效应对土体工程性质的影响及其关键科学问题

随着全球气候变暖、城市化进程加快,世界各地大城市的"热岛"效应及其带来的各种环境和生态问题越来越严重。本文从地质环境保护的角度,分析了城市"热岛"效应的成因、特点及其对地质环境的影响,重点讨论了城市"热岛"效应环境中土体工程性质的变化及其带来的各种灾害效应,在此基础上,凝练出了4个关键科学问题,即城市"热岛"效应环境中土体温度场变化规律、土体中水分迁移规律、土体工程性质变化规律以及土体地质灾害效应,并对它们的具体研究内容进行了详细的分析。论文的分析成果对于掌握城市"热岛"效应对土体工程性质的影响,保护城市地质环境和防灾减灾,实现城市的可持续发展具有重要的理论和现实意义。

血管的“热池”效应在氩氦刀靶向治疗肺癌过程中的临床研究

目的观察氩氦刀靶向治疗肺癌过程中冷冻对大血管的影响。方法 178例肺癌患者肿瘤均包绕于大血管及心脏,207次行氩氦刀靶向冷冻治疗患者。结果经氩氦刀靶向冷冻治疗后,侵犯主动脉、上腔静脉等大血管或心脏的肿瘤内有冰球形成,但无严重不良反应发生。结论因"热池"效应的存在氩氦刀靶向冷冻对大血管(包括主动脉、肺动脉、支气管动脉)及心脏无明显影响,对侵犯心脏和大血管的肺癌氩氦刀靶向治疗是可选择的治疗方法。

中国马拉松运动及其“热效应”的研究探讨

分析了国内外马拉松运动的发展历史,报告了我国马拉松运动近年来在发展中呈现出一种新的现状,表现为:马拉松运动与全民健身活动息息相关,成为构建和谐社会的重要载体,丰富城市文化和经济发展的新途径和新动力,论述了马拉松运动"热效应"背后的原因,对马拉松运动在发展过程中的产生的问题和解决办法进行了简要的研究和分析,提出了促进马拉松运动发展需在管理上更加制度化、规范化、科学化,同时应当充分发挥体育主管部门和当地政府积极性的建议。

位相调制产生“热像”效应理论研究

通过理论分析和数值模拟方法 ,研究了高功率激光系统中的非线性“热像”效应 .利用菲涅耳 基尔霍夫衍射积分和非线性近轴波动方程 ,在远场近似及光学薄近似条件下 ,得出了位相调制产生“热像”出现的位置及强度满足的解析关系 .结果表明 ,“热像”形成在非线性介质后与衍射物对称的位置 ,其强度可能比振幅调制产生“热像”的强度大几倍 .通过计算机模拟 ,并与理论预测结果进行比较 ,显示两者符合较好 .同时给“热像”的形成过程赋予了明确的物理意义 ,指出“热像”的形成类似于同轴位相夫琅禾费全息过程 .

MODAL FREQUENCY CHARACTERISTICS OF AXIALLY MOVING BEAM WITH SUPERSONIC/HYPERSONIC SPEED

The vibration characteristics of transverse oscillation of an axially moving beam with high velocity is in- vestigated. The vibration equation and boundary conditions of the free-free axially moving beam are derived using Hamilton＇s principle. Furthermore, the linearized equations are set up based on Galerkinl s method for the ap- proximation solution. Finally, three influencing factors on the vibration frequency of the beam are considered： （1） The axially moving speed. The first order natural frequency decreases as the axial velocity increases, so there is a critical velocity of the axially moving beam. （2） The mass loss. The changing of the mass density of some part of the beam increases the beam natural frequencies. （3） The thermal effect.＇ The temperature increase will decrease the beam elastic modulus and induce the vibration frequencies descending.

Drain and Source on Insulator MOSFETs Fabricated by Local SIMOX Technology

To overcome the floating-body effect and self-heating effect of SOI devices,the drain and source on insulator (DSOI) structure is fabricated and tested.The low dose developed recently and low energy local SIMOX technology combined with the conventional CMOS technology is used to fabricate this kind of devices.Using this method,DSOI,SOI,and bulk MOSFETs are successfully integrated on a single chip.Test results show that the drain induced barrier lowering effect is suppressed.The breakdown voltage drain-to-source is greatly increased for DSOI devices due to the elimination of the floating-body effect.And the self-heating effect is also reduced and thus the reliability increased.At the same time,the advantage of SOI devices in speed is maintained.The technology makes it possible to integrate low voltage,low power,low speed SOI devices or high voltage,high power,high speed DSOI devices on one chip and it offers option for developing system-on-chip technology.

Atomistic simulation of thermal effects and defect structures during nanomachining of copper

Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.

THERMOHYDRODYNAMIC LUBRICATION ANALYSIS ON EQUILIBRIUM POSITION AND DYNAMIC COEFFICIENT OF JOURNAL BEARING

The finite element method （FEM） is introduced to calculate the oil film pressure and temperature distribution of a journal bearing. The perturbation is performed directly on the finite element equation. Consequently, the Jacobian matrices of the oil film forces are concisely obtained. The equilibrium position of the bearing with a given static load is found by the Newton-Raphson method. As byproducts, dynamic coefficients are obtained simultaneously without any extra computing time. From the numerical results, it is concluded that the effects of film temperature on stiffness coefficients are bigger than those on damping coefficients. With the increase of rotational speed, the load capacity and the stiffness coefficients of the journal bearing are increased when the eccentricity is small, while decreased when the eccentricity is big.

A 1×4 Polymeric Digital Optical Switch Based on the Thermo-Optic Effect

We present a 1 × 4 Y-branch digital optical switch in which S-bend variable optical attenuators are integrated. The S-bend waveguides, which are always introduced to connect the switch and the standard fiber array, are made use of and designed as variable optical attenuators. A compact device with low crosstalk and larger branching-angle is obtained. The device is fabricated on the thermo-optic polymer materials,and the performance of the device is measured. With an applied driving power of less than 200mW, the device has a low crosstalk of less than - 35dB at a wavelength of 1.55 μm.

Magnetocaloric effect in Ni-Mn-In-Co microwires prepared by Taylor-Ulitovsky method

Ni-Mn-In-Co microwires with diameter of 30-100 μm are prepared by glass-coated metal filaments（Taylor–Ulitovsky） method. The effects of magnetic field on martensite transformation temperature in the as-prepared and annealed microwires are investigated using a physical property measurement system（PPMS）. Magnetocaloric effect（MCE） attributed to field-induced austenite transformation in the as-prepared and annealed microwires is analyzed indirectly from the isothermal magnetization（M-B） curves. The as-prepared microwire has a 7-layer modulated martensite structure（7M） at room temperature. The changes of austenite starting temperature induced by an external magnetic field（ΔAs/ΔB） in the as-prepared and annealed microwires are-1.6 and-4 K/T, respectively. Inverse martensite to austenite transformation exists in annealed microwires when an external magnetic field is applied at temperatures near As. The entropy change（ΔS） obtained in the annealed microwires is 3.0 J/（kg·K）, which is much larger than that in the as-prepared microwires 0.5 J/（kg·K）. The large entropy change and low price make Ni-Mn-In-Co microwires a potential working material in magnetic refrigeration.

太阳辐射对不同建筑群产生温升效果的探讨

介绍了建筑群温度变化的数学模型,并利用该模型模拟了济南某小区在四种不同工况下,太阳辐射作用引起的温升情况,对不同建筑密度、下垫面材料、自然通风风速的影响进行了比较。结果表明改变下垫面条件,加强自然通风可改善“城市热岛”效应。

A Novel LDMOS Structure in Thin Film Patterned-SOI Technology with a Silicon Window Beneath p Well

A novel patterned-SOI LDMOS structure with a silicon window beneath the p well is proposed.The performance is simulated numerically.In comparison to SOI counterpart,the off-state and the on-state breakdown voltage can increase by 57% and 70% respectively;transconductance is flatter;I-V curves take no sign of kink in the saturation region;the device temperature is much lower even at high input power;the floating body effect and the self-heating effect are distinctly suppressed.Furthermore,the advantage of low leakage current and low output capacitance in SOI structures does not degrade.The proposed structure will be a promising choice to improve the performance and reliability of SOI power device.

Numerical prediction of the long- term soil temperature variations around shallowsections of cross-river road tunnels

Considering the coupled heat transfer effect induced by parallel cross-river road tunnels, the long-term soil temperature variations of shallow sections of cross-river tunnels under the river beach are predicted using the finite difference method for numerical simulation. The boundary conditions and the initial values are determined by in situ observations and numerical iterations.The simulation results indicate that the ultimate calculated steady heat transfer time is 68 years, and most of the heat transfer is completed in 20 years.The initial constant temperature soil surrounding the tunnels is transformed to an annually variable one.An obvious temperature-varying region of the surrounding soil is discovered within 5 m from the tunnel exterior, as well as within the entire range of soil between the two tunnels.The maximum temperature increase value reaches 7.14 ℃ and the maximum peak-to-valley value of annual temperature increase reaches 10 ℃.The temperature variation of soils surrounding tunnels below 10 m is completely controlled by the heat transfer from the tunnels.The coupled heat transfer effect is confirmed because the ultimate steady temperature of soil between the two tunnels is higher than the ones along other positions.Moreover, the regression model comprising a series of univariate functions is proposed for the annual soil temperature fluctuation estimation for the locations varied distances around the tunnel.This investigation is beneficial to gain an insight into the long-term variation tendencies of local engineering geological conditions of the river beach above shallow sections of the cross-river road tunnels.

1.55μm Fabry-Perot Thermo-Optical Tunable Filter with Amorphous-Si as Cavity

A 1.55μm Fabry-Perot (F-P) thermo-optical t unable filter is fabricated.The cavity is made of amorphous silicon (a-Si) layer grown by electron-beam evaporation technique.Due to the excellent thermo-optical property of a-Si,the refractive index of the F-P cavity will be changed by heating;the transmittance resonant peak will therefore shift substantially.The measured tuning rang is 12nm, FWHM (full-width-at-half-maximum) of the transmissi on peak is 9nm,and heating efficiency is 0.1K/mW.The large FWHM is mainly due to th e non-ideal coating deposition and mirror undulation.Possible improvements to increase the efficiency of heating are suggested.

Temperature sensor based on polymer thin film optical waveguide

Based on attenuated total reflection （ATR） and thermo-optic effect, the polymeric thin film planar optical waveguide is used as the temperature sensor, and the factors influencing the sensitivity of the temperature sensor are comprehensively analyzed. Combined with theoretical analysis and experimental investigation, the sensitivity of the temperature sensor is related to the thicknesses of the upper cladding layer, the waveguide layer, the optical loss of the polymer material and the guided wave modes. The results show that the slope value about reflectivity and temperature, which stands for the sensitivity of the polymer thin film temperature sensor, is associated with the waveguide film thickness and the guided wave modes, and the slope value is the highest in the zero reflectance of a certain transverse electric （TE） mode. To improve the sensitivity of the temperature sensor, the sensor＇s working incident light exterior angle α should be chosen under a certain TE mode with the reflectivity to be zero. This temperature sensor is characterized by high sensitivity and simple structure and it is easily fabricated.

Proton Irradiation and Thermal Annealing of GaAs Solar Cells

The investigation on proton irradiation and thermal annealing of AlGaAs/GaAs solar cells has been reported.The energy of the proton irradiation is 325keV and the fluences are ranging from 5×10 10 to 1×10 13 cm -2 .It is demonstrated that the irradiation-induced degradation in the photovoltaic performance of the solar cells exists mainly in the short circuit current and the irradiation damage can be partly recovered by low temperature annealing at 200℃.In addition,it is found that the borosilicate cover glass has an obvious protection effect against the proton irradiation.

Gate breakdown of high-voltage P-LDMOS and improved methods

The failure experiments of the P-LDMOS （lateral double diffused metal oxide semiconductor） demonstrate that the high peak electrical fields in the channel region of high-voltage P-LDMOS will reinforce the hot-carrier effect, which can greatly reduce the reliability of the P-LDMOS. The electrical field distribution and two field peaks along the channel surface are proposed by Tsuprem-4 and Medici. The reason of resulting in the two electrical field peaks is also discussed. Two ways of reducing the two field peaks, which are to increase the channel length and to reduce the channel concentration, are also presented. The experimental results show that the methods presented can effectively improve the gate breakdown voltage and greatly improve the reliability of the P-LDMOS.

Channel Hot-Carrier-Induced Breakdown of PDSOI NMOSFET's

The hot-carrier-induced oxide breakdown i s systematically clarified for partially depleted SOI NMOSFET's fabricated on SI MOX wafer.The gate oxide properties are considered to analyze the channel hot-c arrier effects.Hot-carrier-induced device degradations are also analyzed by st ress experiments under three typical hot-carrier injection conditions.Based on these results,the influence of channel hot carriers on SOI NMOSFET's front-chan nel properties is investigated.A power time dependence extrapolation technique i s proposed to predict the device's lifetime.Experimental results show that the N MOSFET's degradation is caused by the hot-holes,which are injected into the gat e oxide from the drain and then trapped near the drain side.However,the electron s trapped in the gate oxide can accelerate the gate breakdown.The two simultaneo us breakages of Si-O bonds at a Si atom lead to the irreversible relaxation of the oxide network.A novel physical mechanism of channel hot-carrier-induced ga te oxide breakdown is also presented.

Oxide Thickness Effects on n-MOSFETs Under On-State Hot-Carrier Stress

Hot carrier induced (HCI) degradation of surface channel n MOSFETs with different oxide thicknesses is investigated under maximum substrate current condition.Results show that the key parameters m and n of Hu's lifetime prediction model have a close relationship with oxide thickness.Furthermore,a linear relationship is found between m and n .Based on this result,the lifetime prediction model can be expended to the device with thinner oxides.

1/f~γ Noise Characteristics of an n-MOSFET Under DC Hot Carrier Stress

The 1/fγ noise characteristic parameter Sfγ model in an n-MOSFET under DC hot carrier stress is studied. A method characterizing the MOSFET abilities of an anti-hot carrier with noise parameter Sfγ is presented. The hot carrier degradation effect of n-MOSFET in high-,mid-,and low gate stresses and its 1/fγ noise feature are studied. Experimental results agree well with the developed model.