The comparison of the Wnt signaling pathway inhibitor delivered electrospun nanoyarn fabricated with two methods for the application of urethroplasty

Urethral strictures were common disease caused by over-expression of extracellular matrix from fibroblast. In this study, we compare two nanoyarn scaffolds for improving fibroblasts infiltration without inhibition the over-expression of extracellular matrix. Collagen/poly(L-lactide-co-caprolactone) (Col/P(LLA-CL)) nanoyarn scaffolds were prepared by conjugated electrospinning and dynamic liquid electrospinning, respectively. In addition, co-axial electrospinning technique was combined with the nanoyarn fabrication process to produce nanoyarn scaffolds loading Wnt signaling pathway inhibitor. The mechanical properties of the scaffolds were examined and morphology was observed by SEM. Cell morphology, proliferation and infiltration on the scaffolds were investigated by SEM, MTT assay and H&E staining, respectively. The release profiles of different scaffolds were determined using HPLC. The results indicated that cells showed an organized morphology along the nanoyarns and considerable infiltration into the nanoyarn scaffolds prepared by dynamic liquid electrospinning (DLY). It was also observed that the DLY significantly facilitate cell proliferation. The D-DLY could facilitate the infiltration of the fibroblasts and could be a promising scaffold for the treatment of urethra stricture while it may inhibit the collagen production.     

Mould correction for sheet-metal multi-step incremental air-bending forming based on close-loop control and FEM simulation

There exist errors between the manufactured workpieces and the CAD models due to the springback of sheet-metal incremental air-bending forming. To reduce these errors, an off-line closed-loop control iterative algorithm, combined by fast Fourier and wavelet transform, is developed from the displacement adjustment method (DAM), smooth displacement adjustment method (SDAM) and deformation transfer function method (DTFM) for die surface. With this algorithm, the mould surface of sheet-metal incremental air-bending forming could be properly corrected, and the springback errors of the formed workpieces could be effectively reduced. In order to reduce mould cost and labor cost, the springback tests of workpieces forming, needed in the iterative process of closed-loop control system, are substituted by finite element model (FEM) simulation. The above correction algorithm was used in a semiellipse-shape workpiece incremental air-bending forming. Its average errors are +0.74/−0.39 mm. The results show that the mould correction algorithm with Fourier and wavelet transform is reasonable and the means of FEM simulation are effective. It can be taken as a new approach for sheet-metal multi-step incremental air-bending forming and mould design.     

JSM—T300扫描电镜物镜光阑加热线路维修一例

我单位自1985年购进日本电子公司JSM-T300型扫描电子显微镜,至今已工作23年,该仪器使用率很高,在我校的教学和科研中发挥了重要作用。在使用过程中,仪器先后发生了一些故障,大多由我室技术人员自行解决。现将最近出现的一次故障维修经验总结如下,以供拥有相同型号电镜用户参考。     

Effects of injection type on slot film cooling for a ramjet combustor

A slot film cooling technique has been used to protect a combustor liner from hot combustion gas. This method has been developed for gas turbine combustors. A ramjet combustor exposed to high temperature can be protected properly with a multi-slot film cooling method. An experimental study has been conducted to investigate the change of the first slot angle under recirculation flow and the influence of wiggle strip within a slot, which affects the film cooling effectiveness. The first slot angle has been changed to understand the effect of the injection angle on the film cooling effectiveness in a recirculation zone. The distribution of dimensionless temperature was obtained by a thermocouple rake to investigate the wiggle strip effect, and the adiabatic film cooling effectiveness on downstream wall was measured by a thermochromic liquid crystal (TLC) method. At the first slot position, the film cooling effectiveness decreases significantly because of the effects of recirculation flow. The lip angle of the first slot affects slightly on the film cooling effectiveness. The wiggle strip reinforces the structure of slot and keeps the uniform open area of slot. However, it induces three dimensional flows and enhances the flow mixing between the main flow and the injected slot flow. Therefore, the wiggle strip decreases slightly the overall film cooling effectiveness. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Kwanghoon Park received his M.S degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2007. He is currently working for an education of an officer as a drillmaster in Army Consolidated Logistics School. Kang Mo Yang joined the Republic of Korea Army in 2004. He is currently working towards the M.S. degree at the Department of Mechanical Engineering, Yonsei University. Keon Woo Lee received his M.S. degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2008. In 2008, he joined the Doosan heavy industries & Construction Co, LTD, where he is a member of the IGCC Business Team. Hyung Hee Cho received his PhD degree in Mechanical Engineering from University of Minnesota, Minneapolis, MN in 1992. In 1995, he joined the Department of Mechanical Engineering, Yonsei University, Seoul, Korea, where he is currently a full professor in the School of Mechanical Engineering. His research interests include heat transfer in turbomachineries, rocket/ramjet cooling as well as nanoscale heat transfer in thin films, and microfabricated thermal sensors. Hee Cheol Ham received his PhD degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2001. In 1984, he joined the Agency for Defense Development, Daejeon, Korea, where he is currently a Principal Researcher. Ki Young Hwang received his Ph.D. degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 1994. In 1979, he joined the Agency for Defense Development, Daejon, Korea, where he is currently a principal researcher in the Airbreathing Propulsion Directorate.     

PPy/graphene nanosheets/rare earth ions: A new composite electrode material for supercapacitor

Highly conductive PPy/graphene nanosheets/rare earth ions (PPy/GNS/RE³⁺) composites were prepared via in situ polymerization with p-toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The effects of GNS and RE³⁺ on the electrical conductivity of the composites were investigated. The results showed that the GNS as a filler had effect on the conductivity of PPy/GNS/RE³⁺ composites, which played an important role in forming a conducting network in PPy matrix. The microstructures of GNS and PPy/GNS/RE³⁺ were characterized by the SEM and TEM examinations. It was found that GNS and PPy nanospheres formed a uniform composite with the PPy nanospheres absorbed on the GNS surface and/or filled between the GNS. Such uniform structure together with the observed high conductivities afforded high specific capacitance when used as supercapacitor electrodes. A specific capacitance of as high as 238 F/g at a current density of 1 A/g was achieved over the PPy/GNS/Eu³⁺ composite.     

Investigation of the influence of temperature on threshold value and pulse duration of stimulated Brillouin scattering in liquid water

The threshold value and pulse duration of stimulated Brillouin scattering (SBS) have been measured over the temperature range 10–45°C in liquid water. Also, a theoretical analysis based on the temperature dependence of SBS has been carried out. The results show that the threshold value of SBS decreases with an increase of temperature, whereas the measured pulse duration increases with an increase of temperature.     

Structure and magnetic properties of Fe films with pyramid-like nanostructures deposited by oblique target direct current magnetron sputtering

Fe thin films were deposited by oblique target direct current magnetron sputtering on Si (100) and (111) substrates. The structure, surface morphology and magnetic properties of the thin films were characterized using X-ray diffraction, field emission scanning electron microscopy, and superconducting quantum interference device magnetometer, respectively. The results reveal that the structure of the as-deposited Fe thin films is body-centered cubic with the preferential [110] crystalline orientation. A pyramid-like nanostructure with sharp tip was formed on the surfaces of Fe thin films under appropriate sputtering power. Formation of the pyramid-like nanostructure is mainly owed to the enhancement of atomic mobility and the bombardment effect with increasing of sputtering power. Meanwhile, the crystalline orientation of Si substrate and the intrinsic stress in the films are expected to have little contribution to the formation of the pyramid-like nanostructure. The magnetic anisotropy was found in the as-deposited Fe thin films, and varies with the thickness of the Fe thin films. As the film thickness increases from 604 to 1,786 nm, the magnetic anisotropy field and the uniaxial anisotropy constant increase from 3.8 to 5.6 kOe, and from 0.4 × 10⁶ to 1.1 × 10⁶ erg/cm³, respectively, which indicates that besides magnetocrystalline anisotropy, stress induced anisotropy and shape anisotropy also exist in the as-deposited Fe thin films.     

Ni-P-PTFE化学复合镀层导热性能的研究

采用Ni-P-PTFE化学复合镀对铜管进行表面处理能有效减少污垢在换热表面上形成。然而,在实际应用上,复合镀层对铜管导热性能的影响是必须考虑的问题。实验利用热阻法对铜基Ni-P-PTFE复合镀层的导热系数进行测量,并利用Wilson plot方法处理数据最终得到Ni-P-PTFE复合镀层的导热系数。分析了镀层各组分镍(Ni),聚四氟乙烯(PTFE),碳(C),磷(P)的质量分数对其导热性能的影响规律。结果表明,Ni-P-PTFE复合镀层的导热系数随PTFE和P的质量分数增大而降低,随C的质量分数增加而增大。当PTFE,C以及P的质量分数w(PTFE)=1.76%,w(C)=3.82%和w(P)=10.81%时,最大值为23.12 W/(m.K)。尽管复合镀层的导热系数不高,但由于其厚度很小,镀层产生的热阻仅为9.91×10-5~1.6×10-4(m2.K)/W,所以复合镀层铜管仍保持很高的导热系数值314.88~357.55W/(m.K)。     

Rheology, fiber dispersion, and robust properties of Engineered Cementitious Composites

The capability of processing robust Engineered Cementitious Composites (ECC) materials with consistent mechanical properties is crucial for gaining acceptance of this new construction material in various structural applications. ECC’s tensile strain-hardening behavior and magnitude of tensile strain capacity are closely associated with fiber dispersion uniformity, which determines the fiber bridging strength, complementary energy, critical flaw size and degree of multiple-crack saturation. This study investigates the correlation between the rheological parameters of ECC mortar before adding PVA fibers, dispersion of PVA fibers, and ECC composite tensile properties. The correlation between Marsh cone flow rate and plastic viscosity was established for ECC mortar, justifying the use of the Marsh cone as a simple rheology measurement and control method before fibers are added. An optimal range of Marsh cone flow rate was found that led to improved fiber dispersion uniformity and more consistent tensile strain capacity in the composite. When coupled with the micromechanics based ingredient-tailoring methodology, this rheological control approach serves as an effective ECC fresh property design guide for achieving robust ECC composite hardening properties.     

Analysis of Infiltration,Solidification, and Remelting of a Pure Metal in Subcooled Porous Preform

The parts fabricated by selective laser sintering of metal powders are usually not fully densified and have porous structure. Fully densified parts can be obtained by infiltrating liquid metal into the porous structure and solidifying the liquid metal. When the liquid metal is infiltrated into the subcooled porous structure, the liquid metal can be partially solidified. Remelting of the partially solidified metal can also take place and a second moving interface can be present. Infiltration, solidification, and remelting of metal in a subcooled porous preform obtained by laser sintering of metal powders are analytically investigated in this article. The governing equations are nondimensionalized and the problem is described using six dimensionless parameters. The temperature distributions in the remelting and uninfiltrated regions were obtained by an exact solution and an integral approximate solution, respectively. The effects of porosity, Stefan number, subcooling parameter, and dimensionless infiltration pressure are investigated.