Volatile compounds and descriptive odor attributes in umbu (Spondias tuberosa) fruits during maturation

The umbu fruit is appreciated in north and northeast region of Brazil mainly because of its refreshing and acidic flavor. The objective of this work was to determine the volatile compounds in half-ripe and ripe stages of umbu fruit and to identify important characteristic compounds which could contribute for its aroma by performing sniffing evaluation of volatile extracts. The principal volatile compounds identified in the ripe umbu fruit pulp were 4-methyl-3-penten-2-one, ethyl benzene, 1-penten-3-one, 2-acetyl thiazone, p-xylene, limonene, 2,2-dimethyl 4-octenal, 3-hexanol, 2-nonanol, 1-nonanol, 2-pentanol, 2-octanol, 3-methylethyl 2-butanoate, butyl benzoate, 3-allyl cyclohexene, 2-acetyl furan, 2-hexyl furan, ??-caryophyllene and methyl pyrazine. A total of 37 volatile compounds were diagnosed with characteristic aroma attributes. The principal volatile compounds which could be responsible for the characteristic aroma of ripe umbu fruit pulp were ??-(Z)-ocimene, methyl pyrazine, 2-butyl-thiophene, methyl octanoate, 2-hexyl furan, 2-octanol, (E)-2-cyclohexen-1-one, 3-bromo-cyclohexene, 1-heptanol, 2-nonanol and 1-octanol.     

网络监听实现与防范

网络监听技术是网络安全领域的一项重要而敏感的技术。文中对网络监听的实现和防范进行了深入分析。     

一种对IPKC的ESA攻击及对策*

首先介绍了PPKC和IPKC的概念,然后对比了几种典型攻击方法对PPKC和IPKC安全性的不同影响。利用IPKC的特殊性,提出了一种专门针对IPKC的攻击方法——错误探测攻击方法(Errors Sniffing Attacks, ESA);新型公钥密码方案NTRU是一种IPKC,因此必须研究其抵抗ESA攻击的能力;设计了一种利用NTRU解密错误发起的ESA攻击算法,该算法可以推测出私钥f部分甚至全部的信息。最后提出了增强NTRU抵抗ESA攻击的具体措施。     

谈网络攻击与解决方案

如今网络已成为主要的数据传输和信息交换平台．许多部门和企业在网上构建了关键的业务流程,网络安全是保障网上业务正常运行的关键。根据国际标准化组织提出的OSI模型,针对网络通信过程的各层次漏洞,可以研究出切实可行的防御方案。     

一种基于本地网络的DDOS攻击防御模型

介绍了DDOS的攻击原理、防御措施。从整个Internet的安全出发，提出了一种新的基于本地网络的防御DDOS攻击的模型ANTDD．该模型监控本地网络发送到Internet的数据包，阻止伪造源IP的DDOS攻击包的发送。并以一个小型本地网络为例,说明了ANTDD模型的实现方法。     

Odor Descriptors and Aromatic Series During the Oxidative Aging of Oloroso Sherry Wines

The aroma of Oloroso sherry wines obtained by industrial oxidative aging was studied by gas chromatography-olfactometry analysis. The aromagram exhibited five different odorant zones (OZ) separated by no-odor intervals of at least 6 min, in which no odor was detected. Based on the perceived aroma frequency the most distinctive series for OZ₁ was fruity. The OZ₂ and OZ₃ were mainly represented by chemical and fatty series, respectively, and the spicy and empyreumatic series were the most representative for the OZ₄ and OZ₅, although exhibiting few notes. Except for the vegetable, floral, and empyreumatic series, the remainder increased the number of odorant notes perceived during aging.     

谈网络攻击与解决方案

如今网络已成为主要的数据传输和信息交换平台,许多部门和企业在网上构建了关键的业务流程,网络安全是保障网上业务正常运行的关键。根据国际标准化组织提出的OSI模型,针对网络通信过程的各层次漏洞,可以研究出切实可行的防御方案。     

TCP／IP网络中的若干安全问题

讨论了ＴＣＰ／ＩＰ网络存在的若干安全上的问题，介绍了一些现存的攻击行为，并且以这些行为为例指出了存在安全问题的原因，最后进出一些保护网络安全的准则。     

Windows下网页信息实时监听程序的设计与实现

本文介绍了监听网页信息的程序设计方法和实现原理。利用WinPcap函数库捕获数据链路层的数据帧，由网络协议确定包含HTTP消息的TCP数据，最后根据HTTP报文格式和TCP连接原理截获网页信息。