Mimics及ANSYS在跟距关节面静压力的有限元分析中的初步应用

目的:探讨Mimics及ANSYS在跟距关节面静压力的有限元分析中的初步应用。方法:对健康男性跟骨CT扫描,对图像用Mimics处理建模。用Ansys软件分析跟距关节面的生物力学特性。结果:在跟距关节面中央部位应力及形变最大。结论:Mimics可以高效的对CT数据建模,在此基础上ANSYS可以方便的进行各种力学分析。     

基于修正Drucker-Prager Cap模型的片剂粉末压缩有限元分析

采用修正Drucker-Prager Cap模型对乳糖的压缩过程进行了建模与有限元分析,系统研究了不同压缩速率和摩擦系数条件下的片剂特性.结果表明,压缩速率对片剂的上冲压力没有影响;压缩速度增大时,剪切应力增加,剪切应力带相应变大;当摩擦系数减小时,粉末流动性增强,片剂密度更加均匀;当摩擦系数增大时,粉末与冲模之间的摩擦力变大,靠近冲模壁的粉末位移变小.通过对药物粉末压缩过程的研究,能预测片剂的性能,为片剂的实际生产提供理论参考.     

Theory of Force Transducer Design Optimization for Die Wall Stress Measurement During Tablet Compaction: Optimization and Validation of Split-Web Die Using Finite Element Analysis

Purpose. 1) To illustrate how computer aided engineering stress analysis can be used to improve the transducer design process for tablet press instrumentation; 2) to use these optimal design procedures for the geometric optimization of a cylindrical, segmented, and a novel split-web die design. Discussion includes the selection of optimal die wall thickness, segment cutting angle, strain gage placement, Wheatstone bridge configuration, and the influence of tablet height and position within the die on signal output. Methods. Stress analysis was done with a finite element analysis (FEA) software package running on a personal computer. Results. For the segmented die, the admissible range of die wall thicknesses depends upon cutting angle; the signal output is non-linear because the stress distribution in the die wall is influenced by tablet height and position within the die. For the split-web die, the optimal configuration consists of a 1/8 in. sensing web with a strain gage located at the peak of the sensing-web arch. This prototype had a linear calibration curve (r² = 0.999) with no hysteresis. Radial versus axial stress transmission curves for: starch and sodium chloride were consistent with literature data. Conclusions. Finite element analysis (FEA) is a useful numerical tool for the systematic optimization of tablet press instrumentation. By enclosing the sensing web of a three layered die design in a cylinder, the split-web design can be directly mounted without modification of the die table.     

非线性粘弹性方程的EQrot1非协调有限元分析

针对非线性粘弹性方程,在半离散和全离散格式下给出EQrot1非协调有限元逼近.由于该单元的相容误差(O(h2)阶)比插值误差(O(h)阶)高一阶,可得到在H1模意义下的O(h2)阶超逼近结果,并利用插值后处理技术导出整体超收敛.进而,基于该单元的渐近展开式,构造新的插值后处理算子和外推格式,给出O(h4)阶的外推结果.最后,运用与以往文献不同的方法得到全离散逼近格式的最优误差估计.     

前牙PFM颈缘三维有限元受力分析

目的分析PFM在承受不同方向应力时颈缘及金瓷结合部上3个平面瓷体的应力变化。方法建立前牙烤瓷冠颈缘的三维有限元模型,分析其受力情况。结果唇侧颈缘应力最大,唇侧金瓷结合部无崩瓷现象;冠的切缘受唇向外力时,唇侧颈缘拉应力较大。结论受100N力时金瓷结合部无崩瓷现象,烤瓷冠受唇向外力易引起瓷面折裂。     

Progress in Intradermal and Transdermal Gene Therapy with Microneedles

Pharmaceutical Research - Gene therapy is one of the most widely studied treatments and has the potential to treat a variety of intractable diseases. The skin's limited permeability, as the...     

透室壁性心肌血运重建生物可降解支架的制备与优化

目的:制备心肌内生物可降解性支架,优化支架制备方式,评估其保持心肌孔道通畅的可行性.方法:以聚己内酯(PCL)为材料,聚乳酸-聚乙醇酸共聚物(PLGA)为药物载体,分别通过静电纺丝法、溶液浇注-溶剂挥发法和熔融挤出法制备成生物可降解性支架.采用万能材料测定仪测定支架的力学性能,制备猪慢性心肌局部缺血模型,在体评估该支架在透室壁性心肌血运重建术(TMR)后对心肌孔道的作用效果.结果:熔融挤出法制备的PCL支架具有较好的力学性能,支架压缩80%时承受的应力为1.7 MPa,在TMR后可保持心肌孔道通畅.结论:成功制备出了心肌内生物可降解性药物缓释支架,熔融挤出法制备出的支架能承受心肌压力,可维持TMR后的心肌孔道通畅.     

下颌骨颏部骨折坚强内固定三维有限元分析

目的：运用有限元法分析下颌骨颏部骨折坚强内固定的固定效果，为下颌骨骨折的治疗提供参考。方法：利用ANSYS软件建立下颌骨颏部骨折及坚强内固定的三维有限元模型。在模型上对颏部骨折不同固定方式在不同咬合情况下进行有限元法分析，比较各种情况下骨折断层的应力、骨折段位移，来评价内固定方法的固定效果。结果：正中咬合情况下，上缘单板和下缘单板固定时骨折段位移分别为0．156475mm，0．212586mm。双板固定为0.010963mm。结论：颏部正中骨折时，一块小型钛板固定存在隐患，应采用双板固定。     

Characterization of Microchannels Created by Metal Microneedles: Formation and Closure

Transdermal delivery of therapeutic agents for cosmetic therapy is limited to small and lipophilic molecules by the stratum corneum barrier. Microneedle technology overcomes this barrier and offers a minimally invasive and painless route of administration. DermaRoller^®, a commercially available handheld device, has metal microneedles embedded on its surface which offers a means of microporation. We have characterized the microneedles and the microchannels created by these microneedles in a hairless rat model, using models with 370 and 770 μm long microneedles. Scanning electron microscopy was employed to study the geometry and dimensions of the metal microneedles. Dye binding studies, histological sectioning, and confocal microscopy were performed to characterize the created microchannels. Recovery of skin barrier function after poration was studied via transepidermal water loss (TEWL) measurements, and direct observation of the pore closure process was investigated via calcein imaging. Characterization studies indicate that 770 μm long metal microneedles with an average base width of 140 μm and a sharp tip with a radius of 4 μm effectively created microchannels in the skin with an average depth of 152.5 ± 9.6 μm and a surface diameter of 70.7 ± 9.9 μm. TEWL measurements indicated that skin regains it barrier function around 4 to 5 h after poration, for both 370 and 770 μm microneedles. However, direct observation of pore closure, by calcein imaging, indicated that pores closed by 12 h for 370 μm microneedles and by 18 h for 770 μm microneedles. Pore closure can be further delayed significantly under occluded conditions.Key words: microneedles, microporation, pore closure, skin, transdermal delivery     

Finite Element Analysis of Extrinsic Parameters on the Onset of Tensile Strength in Powders

Most food, pharmaceutical, and chemical industries rely heavily on the supply of free-flowing powders that finds their application in raw materials, additives, and manufactured products. Improper storage conditions combined with environmental factors affect the free-flowing ability of powders. An undesirable transformation of these free-flowing powders into a coherent mass that resists flow is called caking. An important metric that can be used to measure the caking propensity of a material is the tensile strength, which is essentially the resistant stress needed to separate two layers of materials using an isostatic tensile strain. Even though several models have quantified the propensity of caking, the complex nature of interactions between the powder and its micro-environment makes the prediction of caking a challenging task. In the present work, the onset of tensile strength in isomalt with changes in temperature, relative humidity, and consolidation pressures using a shear cell was modeled using a finite element approach. The study found that at a consolidation pressure of 3 kPa and relative humidity of 85±0.1%, an increase in temperature by 5˚C increased the tensile strength of isomalt by a factor of 2. On the other hand, at a constant temperature of 25˚C, an increase in relative humidity from 85±0.1% to 86±0.1% registered an increase in tensile strength by 42.7%. This study also found that an increase in consolidation pressure from 3 kPa to 6 and 9 kPa increased the tensile strength by a factor of 1.79 and 2.54, respectively. The model had good agreement with the measurements and had an overall MAPE of 12.13%. This model can be applied to study the influence of extrinsic parameters on the propensity of caking during storage of bulk solids.     

微针的特点及其在黄褐斑治疗中的应用研究分析

黄褐斑是一种后天获得性色素沉着性疾病,困扰患者的工作和生活。外用经皮给药的主要挑战是药物透过角质层屏障的阻碍。微针作为物理促渗方法和新的递药系统,能够穿透角质层形成特定的药物输送通道,促进了药物的渗透,提高了药物的生物利用度。本文主要总结了微针的特点,并以黄褐斑为切入点,分析微针近年来在黄褐斑领域的应用研究,为后续黄褐斑微针产品的开发提供一定的参考。     

非线性粘弹性方程的EQ1rot非协调有限元分析

针对非线性粘弹性方程,在半离散和全离散格式下给出EQ1rot非协调有限元逼近.由于该单元的相容误差 (O(h2)阶)比插值误差 (O(h)阶)高一阶,可得到在H1模意义下的O(h2)阶超逼近结果,并利用插值后处理技术导出整体超收敛.进而,基于该单元的渐近展开式,构造新的插值后处理算子和外推格式,给出O(h4)阶的外推结果.最后,运用与以往文献不同的方法得到全离散逼近格式的最优误差估计.     

不同骨内段直径对支抗微种植体和颌骨表面影响的三维有限元分析

目的分析支抗微种植体骨内段直径变化对颌骨应力分布和微种植体位移的影响,为临床选择微种植体和种植体优化设计提供理论参照。方法利用Pro/E软件建立不同骨内段直径的微种植体和下颌骨三维有限元模型,并用Hypermesh对所建立模型进行网格划分,用ANSYS软件进行模拟计算,在种植体顶部中央位置施加1.96N与颌骨面平行的作用力,分析在上述载荷作用下种植体的位移和骨界面应力的变化。结果随着种植体骨内段直径的增加,骨界面应力峰值和微种植体位移都减小,应力峰值主要集中在颈部和尖部。骨内段直径为1.5mm时,微种植体z轴的Von-mises应力值最小,且曲线最为平缓。颌骨表面应力峰值的面积关系为1.7mm>1.6mm>1.4mm>1.5mm。结论支抗微种植体骨内段直径对微种植体应力分布有影响,在本实验条件下,微种植体骨内段为1.5mm时应力分布对颌骨损伤最小,微种植体位移最小。D2(mm)1.41.51.61.7Table1Theelementnumberandthenodenumberofmodels表1模型网格总数和节点总数网格总数5816631669057140节点总数22508247222764328230材料名称皮质骨松质骨微种植体Table2Mechanicalpropertiesoftheexperimentmaterial表2实验材料的力学参数弹性模量(MPa)137001370103400泊松比0.300.300.35Figure1Sketchforthemodelsofmicro-implantandmandible图1微种植体和颌骨的模型示意图(a)微种植体实体(b)微种植体模型(c)网格划分参考(图1a),建立包含微种植体支抗的下颌后牙区简化颌骨块模型,以下颌第一磨牙横断面作为基底面,直径为10mm,高为12mm,上部设置为3mm厚的皮质骨,其余为松质骨。微种植体骨外段直径为D1(2.0mm),骨内段直径为D2(1.4、1.5、1.6、1.7mm),颈部光滑区高度0.9mm,骨内段微种植体长度为6mm(图1b)。采用Hypermesh软件进行网格划分,图1c中O为原点坐标,坐标正方向如该图右上角所示。(2)建模操作。打开Pro/E软件,根据微种植体尺寸,通过"拉伸"和"旋转"操作建立除螺纹外的微种植体模型,通过"螺旋扫描"建立微种植体的螺纹模型,通过"旋转"完成颌骨模型的建立,模型最终都保存成ACIS格式。(3)网格划分操作。将颌骨模型和微种植体模型导入到Hypermesh中,通过"boolean"运算,切割出皮质骨和松质骨以及微种植体通道,并建立皮质骨和松质骨之间的共面关系,通过"tetramesh"操作对三部分模型分别进行网格划分,调节网格大小和最小角度来控制网格质量,最后定义网格属性,本文中所有网格到采用"solid45"网格类型。模型网格总数和节点总数见表1。1.2材料属性将微种植体颌骨模型导入Ansys10.0中,微种植体及颌骨均设置为线弹性、正交各向同性的均质连续材料,微种植体材料为钛,材料力学参数见表2。1.3边界条件及载荷条件微种植体和骨模型钉道之间建立非线性接触,骨模型底部节点设置为全位移约束。计算时,在微种植体模型顶部施加与颌骨面平行的正畸作用力1.96N,即Fz=1.96N,Fx=Fy=0(图1c)。2结果2.1微种植体-骨界面应力分布在压力侧和拉力侧骨界面上沿微种植体轴向,从颌骨表面开始,每隔0.7mm采集Von-mises应力值及位移值,得到微种植体植入深度和其Von-mises应力及位移折线图,见图2。皮质骨区域(y<3mm)是主要的应力区,其峰值出现在微种植体骨界面颈部下方2~3mm,松质骨区域(y>3mm)的应力值明显小于皮质骨,随D2D16mm3mm9mm10mm1.96NFigure2Thebroken-linegraphsofstress-locationanddisplacement-locationonthemicro-implant-boneinterface图2骨界面上的应力位移折线图微种植体植入深度(mm)1234560.050.040.030.020.010.00位移(mm)(d)拉力侧位移图中不同线型代表不同微种植体骨内段直径微种植体植入深度(mm)Von-mises应力(MPa)123456300250200150100500(a)压力侧Von-mises应力微种植体植入深度(mm)123456Von-mises应力(MPa)300250200150100500(b)拉力侧Von-mises应力微种植体植入深度(mm)1234560.050.040.030.020.010.00位移(mm)(c)压力侧位移     

Prediction of Tablet Characteristics from Residual Stress Distribution Estimated by the Finite Element Method

Tablet characteristics of tensile strength and disintegration time were predicted using residual stress distribution, simulated by the finite element method (FEM). The Drucker–Prager Cap (DPC) model was selected as the method for modeling the mechanical behavior of pharmaceutical powders composed of lactose (LAC), cornstarch (CS), and microcrystalline cellulose (MCC). The DPC model was calibrated using a direct shear test and analysis of the hardening law of the powder. The constructed DPC model was fed into the analysis using the FEM, and the mechanical behavior of pharmaceutical powders during compaction was analyzed using the FEM. The results revealed that the residual stress distribution of the tablets was uniform when the compression force increased. In particular, the residual stress distribution of tablets composed of equal amounts of LAC, CS, and MCC was more uniform than the tablets composed of 67% LAC and 33% CS, with no MCC. The tensile strength and disintegration time were predicted accurately from the residual stress distribution of tablets using multiple linear regression analysis and partial least squares regression analysis. This suggests that the residual stress distribution of tablets is related closely to the tensile strength and disintegration time.     

Finite Element Modeling of Powder Compaction: Mini-Tablets in Comparison with Conventionally Sized Tablets

Pharmaceutical Research - Mini-tablets are considered a promising solid dosage form in the pharmaceutical industry due to advantages such as dosing accuracy, efficiency as a drug delivery system,...     

Delivery of Methotrexate and Characterization of Skin Treated by Fabricated PLGA Microneedles and Fractional Ablative Laser

Purpose

This study investigated in vitro transdermal delivery of methotrexate through dermatomed porcine ear and cadaver human skin treated with poly (D,L-lactide-co-glycolide) acid microneedles or fractional ablative laser.

Methods

PLGA microneedles were fabricated and characterized using scanning electron microscopy and mechanical assessment techniques. The integrity of treated skin was evaluated by rheometer, transepidermal water loss, and skin electrical resistance measurements. Successful skin microporation was demonstrated by dye binding, histology, pore uniformity, confocal laser microscopy, and DermaScan studies. In vitro permeation experiment was performed on Franz diffusion cells to determine drug delivery into and across the skin.

Results

Both physical treatments resulted in a considerable decrease in skin resistance and an increase in transepidermal water loss value. The laser-created microchannels were significantly larger than those formed by microneedles (p?<?0.05). An effective force of 41.04?±?18.33 N was required to achieve 100% penetration efficiency of the microneedles. For both porcine ear and human skin, laser ablation provided a significantly higher methotrexate permeability into the receptor chamber and skin layers compared to microneedle poration and untreated skin (p?<?0.05).

Conclusions

Both fractional ablative laser and polymeric microneedles markedly enhanced in vitro transdermal delivery of methotrexate into and across skin.

Open image in new window

Graphical Abstract ?

     

Microneedles with Intrinsic Immunoadjuvant Properties: Microfabrication,Protein Stability,and Modulated Release

Purpose  

Intradermal immunization using microneedles requires compatible immunoadjuvant system. To address this challenge, we investigated microneedles coated with polyphosphazene polyelectrolyte, which served both as microfabrication material and an immunoadjuvant compound.     

上颌中切牙三维有限元模型的CT扫描建模

目的 研究在计算机上建立上颌中切牙的三维有限元数学模型.方法 利用牙齿的系列薄层CT截面影像、图像处理软件、计算机辅助设计软件、结合Ansys三维有限元专用软件程序,建立三维有限元模型.结果 建立了上颌中切牙的三维有限元模型.结论 探索了一种新的牙齿三维有限元模型建立的方法;建立的牙齿三维有限元模型具有高度的相似性.     

慢性肝病凝血酶原时间和血小板参数检测的临床意义

目的通过凝血酶原时间和血小板参数检测,探讨慢性肝病患者出凝血指标检测的临床意义.方法检测228慢性乙肝患者和40例健康者的凝血酶原时间和血小板参数,并对两组结果进行比较分析.结果慢性肝炎重度的凝血酶原时间(P＜0.05)、血小板计数(P＜0.01),慢性重症肝炎和肝硬化的凝血酶原时间、血小板计数、血小板平均体积(P＜0.01),与对照组比较有显著性差异.结论慢性肝病的出凝血状态随肝脏损害程度的加重而有明显改变,各测定值的异常与肝脏损害程度相一致.