Study of sunless tanning formulas using molted snake skin as an alternative membrane model

Sunless tanning formulas have become increasingly popular in recent years for their ability to give people convincing tans without the dangers of skin cancer. Most sunless tanners currently on the market contain dihydroxyacetone (DHA), a keto sugar with three carbons. The temporary pigment provided by these formulasis designed to resemble a UV‐induced tan. This study evaluated the effectiveness of carbomer gels and cold process self emulsifying bases on skin pigmentation, using different concentrations of a chemical system composed of DHA and N‐acetyl tyrosine, which are found in moulted snake skins and their effectiveness was tested by Mexameter^® MX 18. Eight different sunless tanning formulas were developed, four of which were gels and four of which were emulsions (base, base plus 4.0%, 5.0% and 6.0% (w/w) of a system of DHA and N‐acetyl tyrosine). Tests to determine the extent of artificial tanning were done by applying 30 mg cm^?2 of each formula onto standard sizes of moulted snake skin (2.0 cm × 3.0 cm). A Mexameter^® MX 18 was used to evaluate the extent of coloration in the moulted snake skin at T₀ (before the application) and after 24, 48, 72, 168, 192 and 216 h. The moulted snake skins can be used as an alternative membrane model for in vitro sunless tanning efficacy tests due to their similarity to the human stratum corneum. The DHA concentration was found to influence the initiation of the pigmentation in both sunless tanning systems (emulsion and gel) as well as the time required to increases by a given amount on the tanning index. In the emulsion system, the DHA concentration also influenced the final value on the tanning index. The type of system (emulsion or gel) has no influence on the final value in the tanning index after 216 h for samples with the same DHA concentration.     

基于VB的线性电位器测试平台的设计

基于计算机平台的测试系统具有存储容量大、测试速度快等优点,因此基于VB的线性电位器关键参数的自动测试将成为一种新的研发趋势。本文提出一种基于VB技术的电位器测试平台的设计方案,使用户通过可视化界面操作测试系统,迅速获取阻值规律等关键测试值,并及时显示或者打印相应曲线。其中下位机主要由DS89C450、MX674A、SM202等元器件构成硬件电路,软件采用C语言和汇编语言混合编程;上位机采用VB编程,形成可视化界面,方便操作。本文给出一个应用实例,实验运行效果表明,该测试平台具有良好实时性和稳定性,具有实际应用与推广价值。     

实时操作系统uC/OS-II在ARM9上移植的实现

介绍了目前在嵌入式系统应用中非常流行的实时操作系统uC/OS-II和ARM微处理器,详细论述了uC/OS-II在基于ARM体系结构的Motorola 32-bit嵌入式微控制器MC9328MX1上移植的实现过程,指出了在uC/OS-II的移植过程中的重点和难点问题,得出了uC/OS-II在ARM上的移植的一般性方法。     

基于飞思卡尔i.MX31的Standalone开发平台设计

针对如何精确取得基于飞思卡尔i.MX31硬件平台下WMA（Windows Media Audio）Decoder的运行性能,提高其执行效率这一课题,搭建了Standalone开发平台。搭建该平台的关键是如何配置i.MX31中的MMU (Memory Management Unit) 。我们目前采用段存储块机制实现MMU。通过对在该平台下WMA Decoder实验数据的分析,已经精确地取得了项目的性能,而且运行效率也提高了29%。     

基于Flash MX实现计算机图形学经典算法仿真演示

计算机图形学算法的传统教学和学习方式抽象不直观,让学习者难以理解,因此成为学习上的难点。用Flash MX实现的算法仿真演示可以处理用户任意输入的图形,自动生成演示内容,同步显示算法执行的每一步中间过程和对输入图形的处理结果,并且还可以随意调节程序的执行速度及单步执行,形象直观,对学习者掌握算法提供了很大的帮助。该文阐述了仿真演示的原理、结构和实现方法。     

Liquid crystalline elastomer actuators with dynamic covalent bonding: Synthesis,alignment, reprogrammability,and self-healing

Liquid crystalline elastomers (LCEs) have demonstrated tremendous potential in applications such as soft robotics, biomedical materials, electronics, sensors, and biomimetic systems. The physical properties of LCEs are controlled by the degree of crosslinking, nature of the mesogens, and mesogen orientation in the LCE network structure. A wide range of dynamic covalent bonds (DCBs) capable of dynamic bond exchange reactions (DBERs) have been introduced into LCE structures to obtain intelligent materials in recent decades. In this review article, we discuss the molecular constitution, macrostructure, morphing mechanism, recent advances in LCEs with dynamic covalent bonds, the influence of DCBs on self-healing, reprogramming and reprocessing properties of LCE actuators, and challenges and opportunities in incorporating dynamic chemistry in the field of LCE actuators.     

SA517 Gr.B焊接工艺

采用E11018-G和E12018-G两种不同强度的焊材,对SA517Gr.B高强钢进行焊接工艺试验研究,进行拉伸试验、侧弯试验和冲击弯试验。结果表明,E11018-G和E12018-G焊接材料均能够满足SA517Gr.B钢材的焊接技术要求,采用E11018-G可有效降低接头焊接应力,降低焊缝裂纹敏感性,提高焊缝质量稳定性。