GLUT4转运作用的研究

SSAO酶在脂肪细胞中的含量较多，位于细胞膜上的SSAO酶的活性和其蛋白质的免疫反应性都是最大的。对于体内葡萄糖的运输和葡萄糖转运蛋白的转运，此酶起到了一定的促进作用，当它与底物在膜上反应后会引起信号传导刺激细胞内葡萄糖转运蛋白(GLUT4)从内部囊泡转移到细胞表面程，从而促进葡萄糖的运输和细胞对葡萄糖的吸收。如果有SSAO酶抑制剂存在，如氨基脲，二溴乙胺等，这种对GLUT4转运的促进作用就会被削弱。本研究的目的在于建立一种新的定量方法-竞争ELISA法来测试脂肪细胞膜上GLUT4的含量，从而确定SSAO酶抑制剂对GLUT4转运的作用。实验结果说明当SSAO酶抑制剂和脂肪细胞预温育一段时间后，质膜上GLUT4的含量发生下降，钒盐使得这种下降的程度加大，证明GLUT4由细胞内囊泡向细胞质膜转运的易位过程受到了抑制。此种竞争性ELISA的测试方法优点在于只需要少量的细胞膜样品就可以确定GLUT4的含量，灵敏度较高。     

酶系对家畜机体的重要作用

所谓酶系即是集动物有机体内多种酶的总称。酶系存在于动植物界的每个组织细胞中，特别是动物的消化系统。酶系的生理生化作用对动物的生长发育及正常的生理机能起着十分重要的作用。本文就酶系的产生与生理生化功能作一浅析。以使今后对酶系的研究与探讨更加深化，同时更好的运用酶系在动物机体中的重要作用来实现动物的生态平衡与健康。     

基于YOLOv4的指针式仪表自动检测和读数方法研究

针对仪表自动检测读数时,由于仪表特征不明显、复杂背景环境等因素造成的仪表检测困难、提取速度慢的问题,提出了一种基于YOLOv4的指针式仪表自动检测和读数方法.首先,利用YOLOv4检测提取了仪表盘区域,采用霍夫变换裁剪了表盘区域;其次,在表盘区域查找了刻度线轮廓,利用最小二乘法拟合了刻度线轮廓直线,得到了指针回转中心;...     

磁场作用下的Fe3 O4磁流体承载能力的试验研究

通过对MS-800四球机油杯的改进,在测试区域内产生可调磁场,利用该改进后的油杯在四球机上对磁场作用下Fe3O4磁流体承载能力进行测定。试验结果表明,磁流体润滑膜在外加磁场作用下,综合承载能力得到了很大的提高,最大可提高至原来的1.3倍。结合Rosensweig理论模型,通过对磁场下磁流体粘度的测定,分析得出磁流体的粘度变化是引起综合承载能力发生变化的主要原因。     

喷丸对TC4钛合金材料叶片的影响研究

文章主要通过试验的方式,研究喷丸对钛合金材料(Ti-6Al-4V)长叶片的疲劳寿命、表面粗糙度、表面完整性、渗入Fe元素含量等的影响,为确定合理的钛合金材料长叶片喷丸方式提供一定的帮助.     

润滑条件对TC4钛合金切削加工影响的实验研究

为了研究冷却润滑条件及切削参数对TC4钛合金的切削力和表面粗糙度的影响,分别开展CMQL、冷风、浇注式冷却润滑条件的TC4钛合金高速切削实验、四种不同润滑环境的粗/半精/精加工实验以及CMQL条件下TC4钛合金正交切削试验,通过单因素分析和正交试验法研究冷却润滑条件及切削参数对切削加工性的影响。研究表明：CMQL冷却润滑条件可在TC4钛合金高速切削时有效降低切削阻力和改善表面粗糙度,并在高速精车削阶段体现出降低切削阻力的优势。考虑CMQL条件下高速精车TC4钛合金加工效率,最佳参数组合为较高的切削速度、较小的精加工余量和合适范围内较大的进给量。     

硬质合金高温性能对TC4钛合金高速铣削的影响研究

在高速铣削加工钛合金的过程中,硬质合金刀具承受较高的切削温度,导致刀具快速磨损和失效。通过添加TaC(NbC)难熔金属碳化物制备新型WC-Co基硬质合金,采用高温硬度计检测新型硬质合金的高温硬度和高温断裂韧性,均较传统WC-Co基硬质合金有提升。将添加TaC(NbC)的新型硬质合金材料制备成整体硬质合金立铣刀,并进行高速铣削钛合金TC4对比试验。结果表明:添加TaC(NbC)的硬质合金刀具,可以有效提高刀具的耐磨性,降低裂纹的出现和扩展,从而提高硬质合金刀具在高速铣削钛合金时的使用寿命。     

切削用量对车削Ti6Al4V切削力影响的研究

通过硬质合金刀具高速干切削Ti6Al4V钛合金的试验,分析了切削用量对切削力的影响.试验结果表明:在切削三要素中,切削深度和进给量对切削力的影响较大,切削速度对于切削力的影响较小.进给量对背向力的影响最大,切削深度对进给力的影响最大.刀尖圆弧半径对于进给力和背向力的变化规律有重要影响.     

基于AdvantEdge的钻尖结构对TC4钻削性能影响研究

钛合金作为一种典型的难加工材料,其弹性模量小、导热性差、比强度高,钻削时刀具极易磨损.针对该材料本文选取了四种不同钻尖结构的整体硬质合金麻花钻,基于AdvantEdge建立了有限元模型,分析了不同钻尖结构对切削力、切削温度及应力分布的影响,通过TC4钛合金钻削实验对比分析切削力、刀具磨损和钻头寿命,并验证仿真模型的可靠...     

放电参数对短电弧铣削TC4加工性能影响的研究

短电弧加工技术(SEAM)是一种实现难加工导电材料高效去除的新型放电加工方法。采用不同电极材料,开展钛合金TC4短电弧铣削加工试验,探究在不同放电参数(电压、频率和占空比)下对加工过程中材料去除率(MRR)、相对电极相对损耗率(RTWR)的影响规律;并进一步分析工件宏微观形貌、元素变化及硬度测定。试验表明：影响MRR和RTWR的因素为脉冲电压>脉冲占空比>脉冲频率;紫铜电极具有高的材料去除率和好的表面质量;加工后表面存在重铸层、熔滴和微孔等结构;其表面显微硬度由重铸层向基体逐渐降低,并在距离工件表面深度90μm处趋于稳定。由此证明,金属电极材料更适合SEAM加工钛合金材料,这为后续SEAM加工钛合金零部件提供了理论依据。     

SSAO酶活性的测定方法研究

SSAO(Semicarbazide-Sensitive Amine Oxidase 1.4.3.6)是对氨基脲敏感的一系列酶的统称,它在人体内广泛分布但生理功能尚不清楚.一些研究显示该酶可能与糖尿病并发症、心脏病以及一些神经系统疾病等有着一定的联系.SSAO的内源性底物包括甲胺和氨基丙酮等,它们通过酶催化氧化脱氨产生相应的醛、过氧化氢和氨.甲醛、丙酮醛和过氧化氢都是细胞毒性的物质.本研究我们用ABTS作为衍生过氧化氢的试剂,建立了一种操作简便、安全并且具有相当灵敏度的一种测定方法.实验结果显示该方法具有足够的灵敏度,能够满足SSAO酶活性测定的需要.该方法的建立为糖尿病和心脑血管疾病等疾病的病因学研究以及临床样品分析提供了一种适用的方法.     

The effect of temperature on gross slip fretting wear of cold-sprayed nickel coatings on Ti6Al4V interfaces

Fretting wear is an accumulation of damage that occurs at component interfaces that are subjected to high contact stresses coupled with low-amplitude oscillation. In metallic contacts, surface oxides, adhesion, and material transfer play a primary role in the initial stages of fretting wear degradation. Given these behaviors, the focus of this study was to determine the effect of temperature on inter-metallic fretting wear between Ti6Al4V (titanium, 6% aluminum, 4% vanadium) and cold-sprayed, commercially pure nickel coatings. The results presented herein show that increased temperature decreases friction through the formation of a uniform NiO layer, and by a reduction of Ni₂O₃ in contacts. In addition, it was found that a localized minimum friction coefficient is achieved at approximately 300 °C, above which friction increases slightly due to annealing of the cold-sprayed coatings.     

The effect of slip amplitude on fretting

The effect of slip amplitude on the mechanism of fretting was investigated. Measurements of wear volume, frictional coefficient and of electrical contact resistance were carried out to clarify the wear mechanism. X-ray microdiffraction was used to observe the difference of wear behaviour, and scanning electron microscopic observations were made.At small slip amplitudes wear damage was small compared with that at larger amplitudes the transition being in the region of 70 μ.At smaller slip amplitudes fretting oxidation, a mild type of wear occurs. At larger slip amplitudes, adhesion and abrasion together with oxidation cause fretting wear. At much larger slip amplitudes, wear similar to reciprocating sliding wear occurs.     

The effect of cryogenic treatment on tapping

This study was realized with two different types (flat and thread rolled) of coated (TiAlN), uncoated, and cryogenically treated taps (uncoated). The tapping processes were carried at four different cutting speeds (2, 3, 4, and 5 m/min) and 1.25 mm/rev feed rate under dry and wet cutting conditions on the Ti-6Al-4 V alloy. The measured cutting forces (cutting torque) were evaluated according to the cutting tool and cutting parameters. The best results in terms of cutting torque were obtained with straight flutes with spiral point taps. For the coated cutting tools, it was seen that the cutting torque was higher with respect to the other tools. The cutting fluid caused decreases in cutting forces for both of the cutters. Under dry cutting conditions, in the cryogenically treated tool, cutting torques came out to be lower with respect to the coated and uncoated tool.     

The effect of surface hardness on friction

The influence of bulk hardness, surface hardness and strain-hardening rate on the frictional behavior of Cu-Sn and Cu-Al alloys was investigated. Unlubricated specimens were subjected to severe relative sliding against tool steel (D2) and aluminum bronze (Ampco 25) anvils under constant interference conditions. A microindentation hardness survey, from the surface into the bulk, was carried out on sections of the specimens both before and after testing.The highest hardness was measured immediately below the wear surface; this hardness value was found to increase linearly with an increasing instantaneous strain-hardening rate. However, no correlation could be detected between the coefficient of friction and the bulk hardness, the strain-hardening rate or the surface hardness. There was a general trend for the coefficient of friction to increase with the greater increase in hardness produced during sliding against Ampco 25. Drawing on observations of metal transfer and surface damage made earlier, this increase could be attributed to the formation of junctions that were stronger than the parent material. There was no correlation with hardness increase when sliding against D2 and the coefficient of friction was often, but not always, lower. Thus a hardness increase during sliding led to increasing friction only with the metallurgically highly compatible pairs while differences in compatibility rather than hardness increase governed the magnitude of friction with less compatible pairs.     

The effect of strain-hardening on frictional behavior in tip test

In previous investigation of the tip test using aluminum alloy AL6061-O, it was found that the distance of radial tip from the external side surface of the workpiece deformed has a linear relationship with the maximum forming load measured at a certain punch stroke. In this study, further experiments with aluminum alloys AL2024-O, AL5083-O, AL6061-O, AL7075-O, annealed carbon steel AISI 1010 and pure copper C12100 were carried out to investigate the effect of material properties on frictional behavior by the tip test for the materials commonly used in bulk metal forming. To characterize the relationships among radial tip distance, maximum forming load and shear friction factor, finite element analyses were employed. It was observed that the linear relationships among these three were maintained for the various tested materials. Also, it was found that the friction condition at the punch was always higher than that at the lower die interface such that the ratio of shear friction factors at the die and punch interfaces should be less than one. By examining the material properties currently tested, it was determined that this ratio could be estimated from a logarithmic equation from the value of strain-hardening exponent, depending on the material used.     

The effect of water-cement ratio on acousto-ultrasonic characteristics in mortar

A self-improved and debugged acousto-ultrasonic system was used to investigate the effect of water cement ratio (w/c ratio) on ultrasonic pulse wave propagation and find more accurate and effective evaluation parameters than the traditional ultrasonic pulse velocity (UPV). An experimental study on the uniaxial compression test and acousto-ultrasonic test of mortar cylinder with different w/c ratios (0.4, 0.5, 0.6) was presented. The results showed that the increase of w/c ratios deteriorated the mortar mechanical properties with the compressive strength decreased and reduced the UPV. The high w/c ratio also leaded high attention of wave amplitude and energy. Through analysis of the ultrasonic pulse waveforms, the maximum peak amplitude (AE parameter) couldn’t reflect the real change of the waveforms. The parameter energy, which is mainly determined by the average amplitude, showed a higher sensitivity to the mortar w/c ratio and more accurate reflection of the changes of the waveforms with different w/c ratios. Compared with other parameters, the energy could be used to evaluate the cement based material properties changes caused by the changes of composition and external effect.