水热法合成硼酸钙的场发射扫描电镜分析

以工业硼酸、硼砂和氧化钙为原料,通过改变反应温度和原料配比,用水热法合成了系列硼钙化合物。根据化学分析和XRD分析数据确定了各种合成产物的化学组成、物相名称,用场发射扫描电镜(FE-SEM)对六种硼酸钙的显微形貌、颗粒大小进行了表征,发现它们的显微形貌、颗粒大小有很大的不同。CaO.3B2O3.5H2O呈条板状,厚度在100~300 nm之间;2CaO.5B2O3.5H2O呈大纳米薄片,厚度在50~100 nm的居多;2CaO.3B2O3.H2O则是纳米细线,直径在100 nm左右;4CaO.5B2O3.7H2O呈小纳米薄片状,厚度在100 nm左右;2CaO.B2O3.H2O呈球粒状,大小在500 nm^1μm;CaO.B2O3呈粗针状,粗、细端直径在150~300 nm之间。

多转子极DSEG风力发电机的铁耗分析

风力发电机在低速高功率场合多采用多极对数的典型特征结构,电励磁双凸极风力发电机设计可以通过多转子极结构设计实现这种多极对数的典型特征结构。然而,转子极数的增加会明显的增加电机的铁耗。针对24-32极电励磁双凸极发电机分别分析了电机不同部分的磁通波形,并运用铁耗独立模型对铁耗进行了傅里叶分析和计算。通过分析和计算得到了电机在额定工作点的铁耗分布和不同负载下的铁耗。最后总结了不同负载下铁耗的变化规律,并通过分析对铁耗的变化规律进行了解释。

Non-steady FE analysis on porthole dies extrusion of aluminum harmonica-shaped tube

According to the rigid-viscoplasticity finite element method,the porthole die extrusion process of an aluminum harmonica-shaped tube was successfully simulated based on software Deform-3D. The distribution of stress field,effective strain field,velocity field and temperature field during the extrusion process were discussed and the metal flow in welding extrusion was analyzed. The simulation results show that the material flow velocities in the bearing exit are non-uniform with the originally designed die and the forepart of the profile is not neat or even. Aiming at solving this problem,the modification method of die structure was improved. The result shows that the uniform material flow velocities in the die exit and a perfect extruded are obtained by modification bearing length.

高速公路用防眩板在风荷载作用下的应力分析

高速公路用防眩板的抗风能力是其关键指标之一,对防眩板在风荷载作用时的应力分析具有重要意义。本文建立了防眩板在风荷载作用下的有限元模型,用相关试验数据对模型的有效性进行了验证,并利用有限元技术和力学抗风试验的结果比较,探讨了在风荷载作用下防眩板的破坏形式和应力集中点。结果表明,计算得到的防眩板的应力集中点和断裂位置与试验结果基本吻合,建立的模型可用于防眩板外形和结构设计研究。

猪颌面软硬复合组织破片伤有限元模型的建立与与有效性分析

目的:建立猪下颌复合组织破片伤三维有限元模型,并验证该数字化模型的有效性。方法:通过拍摄三维CT获取猪颌面部复合组织数字化信息,在Mimics 15.0中进行三维重建;设计直径与高度同为5.5 mm的圆柱体破片为致伤物,在有限元分析软件中加载加速度为831、1 120、1 536 m/s的破片撞击猪右侧下颌角区,模拟致伤过程和损伤的结果。同时采用二级轻气炮发射同形态30CrMnSi合金破片致伤离体猪头下颌角区,测量实际损态、面积和致伤时颌骨加速度,与数值模拟结果进行对比验证。结果:当破片速度分别为831、1 120、1 536 m/s时下颌骨损伤入口面积实验结果比数值模拟分别大13.4%、23.6%和22.3%,出口面积分别大18.7%、23.0%和26.5%,加速度峰值分别小16.7%、15.3%和14.6%。结论:成功建立了猪下颌复合组织破片伤数字化模型,其伤情数值模拟结果与动物实验结果吻合性较好,具有一定的有效性。

Determination of Fe and Zn contents and distributions in natural sphalerite/marmatite by various analysis methods

The contents of Fe and Zn in natural sphalerite samples were determined by chemical titration and spectroscopic techniques(portable X-ray fluorescence(P-XRF) spectrometry, electron probe microanalysis with energy dispersive spectroscopy(EPMA-EDS), electron probe microanalysis with wavelength dispersive spectroscopy(EPMA-WDS), and time-of-flight secondary ion mass spectrometry(To F-SIMS)). Besides, the distribution of Fe and Zn in sphalerite samples was analyzed by imaging EPMA-WDS and imaging To F-SIMS. The results show that Fe and Zn contents determined by each spectroscopic technique have good linearity with those determined by chemical titration(R^2>0.77), and the R^2 values of Fe are generally greater than those of Zn. The imaging analysis results revealed that Fe and Zn are not uniformly distributed in the sphalerite.

不同临床设计的ERA附着体义齿修复下颌牙列游离端缺损的三维有限元分析

目的:研究3种不同临床设计ERA附着体义齿修复下颌远中游离端缺损的应力及位移分布。方法:建立ERA附着体义齿修复下颌远中游离端缺损的三维有限元模型,根据临床设计分为基本组、支托组和跨弓组。应用有限元法研究在垂直及45°斜向2种载荷方向100 N的作用下,基牙及基托下黏膜的应力和位移以及基托的位移情况。结果:2种载荷下3组模型均在远中基牙远中邻面肩台出现应力集中,远中基牙预备体咬合面位移最大,支托组基牙位移最大,分别为14.91μm和63.09μ.m,其次为基本组(9.38μm和50.56μm),跨弓组最小(8.85μm和47.31μm)。结论:在本研究条件下,为远中游离端牙列缺损设计基本的ERA附着体义齿更趋于合理。

Thermodynamic analysis of Na−S−Fe−H_(2)O system for Bayer process

Thermodynamic diagrams of Na−S−Fe−H_(2)O system were constructed to analyze the behavior of sulfur and iron in the Bayer process.After digestion,iron mainly exists as Fe_(3)O_(4) and Fe_(2)O_(3) in red mud,and partial iron transfers into solution as Fe(OH)_(3)^(−),HFeO_(2)^(−),Fe(OH)_(4)^(−)and Fe(OH)_(4)^(2−).The dominant species of sulfur is S^(2−),followed by SO_(4)^(2−),and then SO_(3)^(2−)and S_(2)O_(3)^(2−).The thermodynamic analysis is consistent with the iron and sulfur species distribution in the solution obtained by experiments.When the temperature decreases,sulfur and iron can combine and precipitate.Controlling low potential and reducing temperature are beneficial to removing them from the solution.XRD patterns show that NaFeS_(2)·2H_(2)O,FeS and FeS_(2) widely appear in red mud and precipitates of pyrite and high-sulfur bauxite digestion solution.Thermodynamic analysis can be utilized to guide the simultaneous removal of sulfur and iron in the Bayer process.

颅骨生前骨折铁元素半定量分析

笔者用英制S250——MKⅢ型扫描电镜与美制wDx——2A型波谱仪、Q2000/S型能谱仪,先后检测了两例奸情杀人案被害人颅骨,一例死后经过时间为4年零5个月,另一例为9年零3个月,结果均获得成功。生前骨折Fe半定量计数值为死后骨折、无骨折部位的3～6倍;动物试验表明,生前骨折铁含量随伤后迁延时间而增高,与0.5％洗衣粉煮沸处理无关。笔者认为,在排除死后血淀坠积干扰的条件下,颅骨Fe半定量分析结果是认定生前骨折的可靠依据。

Dynamic analysis and experimental study of vibro-acoustic system with uncertainties at middle frequencies

To take into account the influence of uncetainties on the dynamic response of the vibro-acousitc structure, a hybrid modeling technique combining the finite element method（FE）and the statistic energy analysis（SEA） is proposed to analyze vibro-acoustics responses with uncertainties at middle frequencies. The mid-frequency dynamic response of the framework-plate structure with uncertainties is studied based on the hybrid FE-SEA method and the Monte Carlo（MC）simulation is performed so as to provide a benchmark comparison with the hybrid method. The energy response of the framework-plate structure matches well with the MC simulation results, which validates the effectiveness of the hybrid FE-SEA method considering both the complexity of the vibro-acoustic structure and the uncertainties in mid-frequency vibro-acousitc analysis. Based on the hybrid method, a vibroacoustic model of a construction machinery cab with random properties is established, and the excitations of the model are measured by experiments. The responses of the sound pressure level of the cab and the vibration power spectrum density of the front windscreen are calculated and compared with those of the experiment. At middle frequencies, the results have a good consistency with the tests and the prediction error is less than 3. 5dB.

Preparation and characterization of a composite membrane based on the asphaltene component of coal

Asphaltene-ceramic composite membranes were fabricated from ceramic supports and an asphaltene component, which was obtained from the separation of coal to give a kind of new carbonaceous precursor material. Using SEM and thermogravimetric analysis to measure the microstructure and properties of the asphaltene component allowed the porosity, permeability, and retention ratios to be determined. The results show that the asphaltene component can be regarded as a good carbon membrane precursor material because of its high carbon content and strong bonding capacity. When ceramic supports are impregnated with asphaltene colloid the asphaltene easily combines with the support surface and forms a good carbonaceous film after carbonization. Little of the asphaltene component permeates into the internal pores of the ceramic support. Although the number of coats applied to the substrate had little affect on the porosity of the asphaltene-ceramic composite membranes the permeability varied depend- ing upon the number of times the substrate was treated. The way bubbles escape from the film, and the phenomenon of coalescence, as affected by different film thicknesses also seem closely related to the number of coats. A composite membrane carbonized at a final temperature of 600℃ is relatively dense and the permeability of Fe（OH）3 colloid through it is very low. A membrane fired at 800℃ is porous and its permeability and retention of Fe（OH）3 colloid are 88 L/（m2 h MPa） and 85.3%, respectively when the trans-membrane pressure is 0.22 MPa.

End-effect of the permanent-magnet spherical motor and its influence on back-EMF characteristics

The permanent-magnet(PM) spherical motor has special configuration and complicated distribution of electromagnetic field.The spatial distribution of the effective flux density produced by permanent magnets is obtained,and the end-effect of the permanent magnets is analyzed.In the 3-dimensional(3-D) finite element(FE) analysis,the calculation of Back-EMF charac-teristics of the PM spherical motor needs to be conducted by steps,which leads to large computational burden.A novel ana-lyzing method to quantize the end-effect of the PM spherical motor is proposed,that is,the end-effect coefficient of the PM spherical motor is calculated to revise the back-EMF waveform obtained from the 2-D FE model.Under different outer radii of the stator coil and different pole arc coefficients of the PM spherical motor,the revised 2-D results are validated by the results obtained from the 3-D FE model and the experimental results.With this method,the special structural feature of the PM spherical motor is fully considered;the pure 3-D calculation of electromagnetic field is conducted only once;higher precision and less computational burden can be achieved.The method provides a new approach to investigating the back-EMF charac-teristic of the PM spherical motor.

Synthesis of Large-Area, Few-Layer Graphene on Iron Foil by Chemical Vapor Deposition

We demonstrate a simple and controllable way to synthesize large-area, few-layer graphene on iron substrates by an optimized chemical vapor deposition （CVD） method using a mixture of methane and hydrogen. Based on an analysis of the Fe-C phase diagram, a suitable procedure for the successful synthesis of graphene on Fe surfaces was designed. An appropriate temperature and cooling process were found to be very important in the synthesis of highly crystalline few-layer graphene. Graphene-based field-effect transistor （FET） devices were fabricated using the resulting few-layer graphene, and showed good quality with extracted mobilities of 300-1150 cm2/（V.s）.