硅尖阵列的制备及其在真空微电子加速度计中的应用(英文)

针对微电子器件,提出了一种简单、低成本、便于批量加工的硅尖阵列制备方法。分析了各向异性和各向同性湿法腐蚀的特点,研究了不同腐蚀液中硅尖的形成机理和腐蚀速率,采用扫描电子显微镜(SEM)观测硅尖形貌。结果表明:在质量分数40%KOH腐蚀液中添加I2和KI,显著减小了削角速率,得到了呈"火箭尖"的硅尖阵列。各向同性腐蚀采用HNA腐蚀液,腐蚀的硅尖呈埃菲尔铁塔形。通过调整腐蚀液配比,氧化锐化后,硅尖尖端曲率半径小于15nm。该硅尖阵列已成功应用于真空微电子加速度计之中。

利用汽轮机真空系统严密性试验获取更多信息的研究

通过对汽轮机真空系统严密性试验过程中真空下降速度的分析 ,指出真空下降速度并不是漏入真空系统空气量的单值函数 ,其还受到凝汽器运行参数及汽轮机排汽量的影响 ,为了使真空系统严密性试验结果具有可比性 ,应该将试验结果进行修正。同时 ,为了利用真空系统严密性试验得到更多的信息 ,指出了真空系统严密性试验在凝汽器水侧脏污与汽侧空气量故障的分离。

余热汽轮机真空严密性不合格原因分析及应对

介绍了中天合创化工分公司余热汽轮机的设备情况及蒸汽流程,认为余热汽轮机在正常运行过程中出现的真空度上升问题是由于真空严密性不合格所致。排除了真空破坏门、排汽缸结合面及爆破片、机组多级水封、凝汽器汽侧其他设备、机组轴端等泄漏原因后,考虑到余热机组汽源的特殊性,认为机组来汽中混入大量含CO、H_(2)S的不凝结气体是导致汽轮机真空严密性不合格的原因,并提出了应对措施。

Vacuum assisted high-pressure die casting of AZ91D magnesium alloy at different slow shot speeds

The effects of vacuum assistance on the microstructure and mechanical properties of high-pressure die cast AZ91 D alloy at different slow shot speeds were evaluated. Plate-shaped castings of AZ91 D alloy were carried out on a TOYO BD-350V5 cold chamber die casting machine incorporated with a self-improved TOYO vacuum system. It was found that the vacuum pressure in the die cavity at the beginning of mold filling increases with the increase of slow shot speed, following a cubic polynomial curve, resulting in a decline in the porosity-reduction ability of vacuum assistance with the increase of slow shot speed. The externally solidified crystal（ESC） contents in conventional and vacuum die castings behave similar against the slow shot speed. The tensile properties of vacuum die castings were strongly influenced by the ESC content at relative low slow shot speeds. With the increase of slow shot speed, the influence of the gas porosity level in vacuum die castings would get prominent.

Effect of multi-step slow shot speed on microstructure of vacuum die cast AZ91D magnesium alloy

Two multi-step （two-step and three-step） slow shot speeds were used in the vacuum die casting process of AZ91D magnesium alloy. The vacuum pressure variation in the die cavity before mold filling was monitored by using a pressure sensor. The microstructures of the produced castings were analyzed with optical microscope and image analysis software. The experimental results demonstrate that, the vacuum pressure in the die cavity at the beginning of mold filling is significantly reduced by using three-step slow shot speed, resulting in a low gas porosity level in the produced castings. At an appropriate multi-step slow shot speed, the dwell time of the liquid metal in the shot sleeve before mold filling can be reduced and the flow of the liquid metal in the shot sleeve at the later stage of the slow shot process can be restrained, which cause a low externally solidified crystal content in the produced castings.

Characterization of A390 aluminum alloy produced at different slow shot speeds using vacuum assisted high pressure die casting

The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390alloy at different slow shot speeds were evaluated.Plate-shaped specimens of hypereutectic A390aluminum alloy were produced on a TOYO BD?350V5cold chamber die casting machine incorporated with a self-improved TOYO vacuum system.According to the results,the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling.Meanwhile,tensile properties of vacuum die castings were deteriorated by the porosity content.In addition,the average primary silicon size decreased from23to14μm when the slow shot speed increased from0.05to0.2m/s,which has a binary functional relationship with the slow shot speed.After heat treatment,microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved intoα(Al)matrix.Furthermore,the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment.

Propagation of Smooth Pulses in Anomalously Dispersive Media

In the present letters we study the propagation of smooth pulses in anomalously dispersive media. We prove that non-analytical but smooth points in a pulse still propagate with the vacuum speed of light, c. It gives an upper limit for signal velocity as well as the non-continuous points of the envelop of a pulse or its derivatives of arbitrary order do.

Schemes for Producing 1.8 He Ⅱ and the Prediction of the Pumping Speed for the Method of Vacuum-Pumping

Cryogenic ground supporting equipment (CGSE) developed for international cooperation scientific experimental item AMS-02 is the ground supporting and cooling system, which will complete the cooling process of the superconductor of AMS-02 from ambient temperature to 1.8 K. Obtaining 1.8 K He Ⅱ by vacuum-pumping is discussed in detail and compared with the other three schemes. The results show that the scheme of vacuum-pumping not only could meet the requirement of the project much better but also has higher reliability compared with other schemes. To select the vacuum pump, the energy conservation model is presented according to the experimental system of CGSE. Therefore, the pumping speed is also determined.

Vacuum Ultraviolet Photodissociation Dynamics of OCS via the F Rydberg State:theS(^(3)P_(J=2,1,0))Product Channels

Vacuum ultraviolet(VUV)photodissociation dynamics of carbonyl sulfide was investigated experimentally by using a tunable photolysis light source and the timesliced velocity map ion imaging technique.Ion images of S(^(3)P_(J=2,1,0))dissociation products were measured at five photolysis wavelengths from 133.26 nm to 139.96 nm,corresponding to the F Rydberg state of OCS.Two dissociation channels:S(^(3)P_(J))+CO(X^(1)Σ+)and S(^(3)P_(J))+CO(A^(3)Π)were observed with the former being dominant.The vibrational states of CO co-products were partially resolved in the ion images.The product total kinetic energy releases,anisotropy parameters(β),and the branching ratios of high-lying CO vibrational states were determined for the S(^(3)P_(J))+CO(X^(1)Σ^(+))channel.We found that the anisotropy parameters suddenly changed from negative to positive when OCS was excited to the higher vibrational levels of the F state.Furthermore,the anisotropy parameters for S(^(3)P_(J))products of J=2,1,0 were even different.These anomalous phenomena may result from the simultaneous existence of both parallel and perpendicular dissociation mechanisms,suggesting the involvement of other electronic states with different symmetry in the initially-excited energy region.This work provides a further understanding of the nonadiabatic couplings in the VUV photodissociation process of OCS.

Photodissociation Dynamics of OCS Near 128 nm:S(3PJ=2,1,0),S(1D2)and S(1S0)Channels

Here we report the study of the photodissociation dynamics of carbonyl sulfide in the vacuum ultraviolet region using the time-sliced velocity map ion imaging technique.Images of S(^3PJ=2,1,0),S(^1D2)and S(^1S0)products were measured at four photolysis wave-lengths of 129.32,128.14,126.99,and 126.08 nm,respectively.Four main dissociation channels:S(^3PJ=2,1,0)+CO(X^1Σ^+),S(^3PJ=2,1,0)+CO(A^3π),S(^1D2)+CO(X^1Σ^+)and S(^1S0)+CO(X^1Σ^+)channels,have been clearly observed and identified.Vibrational states of the CO co-products were partially resolved in the experimental images.From these images,the product total kinetic energy releases,the branching ratios and angular distributions of products have been derived.While the S(^3PJ=2,1,0)+CO(A^3π)product channel is formed through the adiabatic dissociation process after the excitation to the(3^1Σ^+)excited state,the results suggest that strong nonadiabatic coupling plays an important role in the formation of other three channels.

Rarefied planar jets into vacuum

This paper presents a fundamental gaskinetic study on high speed rarefied jets expanding into vacuum from a cluster of planar exits.Based on the corresponding exact expressions for one planar jet,this paper straightforwardly derives the combined multiple jet flowfield solutions of density and velocity components,however,for the combined temperature and pressure solutions,extra attention shall be practiced.Several direct simulation Monte Carlo simulation results are provided and they validate these analytical solutions of rarefied planar jet flows.

凝汽器漏入空气量的定量计算

本文从泄漏的根本原理出发进行分析,证明了少为人知、应用较少的HEI推荐公式,同时对主要影响因素进行了扩展分析和修正计算,使漏入空气量与专业人员惯用的、易于获取的真空下降速率建立直接数学关系,并适用于机组变工况。

Quantum State-to-State Vacuum Ultraviolet Photodissociation Dynamics of Small Molecules

The present review focused on selected, recent experimental progress of photodissociation dynamics of small molecules covering the vacuum ultraviolet (VUV) range from 6 eV to 20 eV. These advancements come about due to the available laser based VUV light sources along with the developments of advanced experimental techniques, including the velocitymap imaging (VMI), H-atom Rydberg tagging time-of-flight (HRTOF) techniques, as well as the two-color tunable VUV-VUV laser pump-probe detection method. The applications of these experimental techniques have allowed VUV photodissociation studies of many diatomic and triatomic molecules to quantum state-to-state in detail. To highlight the recent accomplishments, we have summarized the results on several important molecular species, including H2 (D2, HD), CO, N2, NO, O2, H2O (D2O, HOD), CO2, and N2O. The detailed VUV photodissociation studies of these molecules are of astrochemical and atmospheric relevance. Since molecular photodissociation initiated by VUV excitation is complex and is often governed by multiple electronic potential energy surfaces, the unraveling of the complex dissociation dynamics requires state-to-state cross section measurements. The newly constructed Dalian Coherent Light Source (DCLS), which is capable of generating coherent VUV radiation with unprecedented brightness in the range of 50-150 nm, promises to propel the photodissociation experiment to the next level.

浅析硫化碱列管蒸发系统带液现象

本文针对当前硫化碱行业蒸发系统存在的蒸发带液问题，通过对蒸发器蒸发室尺寸、除沫器形式、进料口位置、循环管出口位置等蒸发器结构分析，以及对蒸发系统真空度、进料速度、蒸发底液、蒸发浓度等控制的讨论，提出了解决硫化碱行业蒸发系统带液现象的具体措施。

Gauss-Bonnet as Effective Cosmological Constant

It is known that Gauss-Bonnet terms in higher dimensional gravity can produce an effective cosmological constant.We add extra examples to this picture by presenting explicitly two branches of accelerating vacuum solutions to the Einstein-Gauss-Bonnet gravities with a bare cosmological constant in 5 and 6 dimensions.Both branches of solutions are of constant curvature and the effective cosmological constants are independent of the acceleration parameter.One branch(the "-" branch) of the solutions is well defined in the limit when the Gauss-Bonnet parameter approaches zero,in which case the effective cosmological constant becomes identical with the bare value,while the other(i.e.the "+") branch is singular in the same limit,and beyond this singular limit,the effective cosmological constant is inversely proportional to the Gauss-Bonnet parameter with a negative constant of proportionality when the bare value vanishes.