Force response characteristics and mechanical properties of friction stir welded AA2024 sheets

Process force and tensile properties in friction stir welding of AA2024 sheets were studied. Results show that the forces present a periodic variation with the same periodicity which is nearly equal to the time of one tool rotation, and thus it only depends on rotation speed. With increasing welding speed the forces increase gradually, while with increasing rotation speed the forces first decrease and then increase. Joints with superior strength-ductility synergy are produced at 900?rev?min^?1–300?mm?min^?1 and 1000?rev?min^?1–350?mm?min^?1. These joints experience nearly the same peak temperature and axial force. As heat input increases the failure initiates from the interface between nugget zone (NZ) and thermo-mechanically affected zone to heat-affected zone continuing to NZ.     

FMEA在低压铸造铝合金轮毂设计中的应用

通过失效模式影响分析(FailureModeEffectAnalysis,简称FMEA)不但能够提高产品设计可靠性,缩短设计周期,而且可以降低产品研制成本。FMEA技术的科学性和有效性越来越为设计人员所重视。     

酸析-氨化法处理腐殖酸生产硫基复合肥技术

传统的氨化造粒硫基复合肥中不含有机质,因此肥效相对较低。在氨化造粒硫基复合肥生产过程中,分两步加入腐殖酸并使其得到酸析-氨化处理,从而使所生产的硫基复合肥富含有机质。该产品不仅可改良土壤、提高肥料利用率,而且能刺激作物生长,适用于大田及经济作物,尤其适用于忌氯作物。该技术利用原有氨化造粒硫基复合肥生产装置,无需增加设备和改造投资,调整工艺即可生产,简单易行。     

浅谈如何加强制药企业GMP认证后的设备维护保养

从4个方面简要地概述了药品生产企业取得GMP认证后,如何加强设备维护保养,从而保障药品的生产质量。     

AZ31镁合金型材宽展挤压工艺参数研究

在某镁业有限公司的挤压车间进行了AZ31镁合金型材宽展挤压温度、挤压速度和变形程度等工艺参数的研究,在某铝业有限公司进行了AZ31镁合金型材宽展挤压。通过对挤压温度、挤压速度和变形程度进行控制,有效地提高了出品速度和成品率,对于镁合金型材宽展挤压技术具有实践意义。     

艺术设计专业Photoshop教学的改革与实践

本文针对艺术设计专业在Photoshop教学中存在的问题,提出了包括课程设置、教学内容设计、教学方法、考评机制等方面的教学改革方案。教学实践表明,该方案具有良好的教学效果。     

活塞曲柄机构的运动仿真

对于多个构件协调运动的复杂机构来说,要通过仿真准确表达出构件间的运动关系,实现的方法不多。同时,传统的仿真方法在网络应用方面也存在不足。针对这些情况,一种应用VRML仿真机构运动的方法被提出。采用AutoCAD建模,通过3dsMax转化为VRML文件,并利用构件坐标和角度的变化实现了构件的运动仿真。坐标变化通过Transform节点嵌套实现,角度变化根据矢量方程解析法分析出的构件转角相对于原动件转角的关系由VRMLScript脚本语言编程实现。最后实现了活塞曲柄机构三维运动仿真,并总结了仿真流程。为同类机构的仿真演示提供了一种实现方法。     

紫外分光光度法测定氟苯尼考可溶性粉的含量

采用紫外分光光度法测定氟苯尼考可溶性粉的含量。结果表明,氟苯尼考的最大吸收波长为267nm,在此波长处,氟苯尼考在20.0～160.0μg/mL浓度范围内,其吸光度与浓度呈现良好的线性关系:A=0.0011x+0.0240,r2=0.9999(n=8)。该方法操作简单、快速,结果准确,可用于氟苯尼考可溶性粉的含量测定。     

Influence of Various Cooking Methods on the Concentrations of Volatile N‐Nitrosamines and Biogenic Amines in Dry‐Cured Sausages

Abstract: N‐nitrosamines, biogenic amines, and residual nitrites are harmful substances and are often present in cured meats. The effects of different cooking methods (boiling, pan‐frying, deep‐frying, and microwave) were investigated on their contents in dry‐cured sausage. The various N‐nitrosamines were isolated by a steam distillation method and analyzed by gas chromatography mass spectrometry (GC‐MS). The biogenic amines were determined after extraction with perchloric acid as dansyl derivatives by high‐performance liquid chromatography (HPLC) method. The results showed that initial dry‐cured raw sausage contained 5.31 μg/kg of total N‐nitrosamines. Cooking by deep‐frying or pan‐frying resulted in products having the highest (P < 0.05) contents, compared with boiling or microwave treatments, which were not different from the raw. Although frying increased the content of N‐nitrosodimethylamine (NDMA), N‐nitrosodiethylamine (NDEA), and N‐nitrosopyrrolidine (NPYR), it decreased the contents of histamine and cadaverine. Boiling and microwave treatments decreased the total biogenic amines significantly (P < 0.05). Residual nitrite was significantly reduced by cooking treatments. The results suggest that boiling and microwave treatments were more suitable methods for cured meat. Practical Application: N‐nitrosamines and biogenic amines are considered potentially harmful substances to humans and often present in dry‐cured sausage. Different cooking methods may effect the content of these harmful substances. However, little information exists on the different cooking methods on dry‐cured meats.     

Multi-Factor Password-Authenticated Key Exchange via Pythia PRF Service

Multi-factor authentication (MFA) was proposed by Pointcheval et al. [Pointcheval and Zimmer (2008)] to improve the security of single-factor (and two-factor) authentication. As the backbone of multi-factor authentication, biometric data are widely observed. Especially, how to keep the privacy of biometric at the password database without impairing efficiency is still an open question. Using the vulnerability of encryption (or hash) algorithms, the attacker can still launch offline brute-force attacks on encrypted (or hashed) biometric data. To address the potential risk of biometric disclosure at the password database, in this paper, we propose a novel efficient and secure MFA key exchange (later denoted as MFAKE) protocol leveraging the Pythia PRF service and password-to-random (or PTR) protocol. Armed with the PTR protocol, a master password pwd can be translated by the user into independent pseudorandom passwords (or rwd) for each user account with the help of device (e.g., smart phone). Meanwhile, using the Pythia PRF service, the password database can avoid leakage of the local user’s password and biometric data. This is the first paper to achieve the password and biometric harden service simultaneously using the PTR protocol and Pythia PRF.