2,3,4,5-四氟苯甲酸的合成工艺进展与展望

介绍了合成2,3,4,5-四氟苯甲酸的8条工艺路线,按采用主要原料来分,它包括:四氯苯酐法,四氟苯甲醇法,邻苯二腈法,四氟苯法,八氯萘法,N-苯基四氯邻苯二甲酰亚胺法等.对其中四氯苯酐法和N-苯基四氯邻苯二甲酰亚胺法,由于原料易得,操作条件适宜,容易工业化等原因作了重点叙述.合成步骤一般采用缩合、氟化、开环、脱羧和水解等反应合成2,3,4,5-四氟苯甲酸.2,3,4,5-四氟苯甲酸是一种重要的医药中间体,尤其是合成第3、4代喹诺酮抗菌药物的重要原料或中间体,如合成:洛美沙星、司氟沙星、氟罗沙星、氧氟沙星、左氧氟沙星和芦氟沙星等.从发展趋势看,世界抗菌药物市场正在由头孢菌素向喹诺酮药物转移,所以,开发2,3,4,5-四氟苯甲酸具有璀璨的前景.     

Prejudice and gender differentials in the US labor market in the last twenty years

Earnings differentials between men and women have experienced a stable convergence during the 1980s, following a process started in the late 1970s. However, in the 1990s the convergence has almost stopped. The first objective of the paper is to evaluate if discrimination, defined as explicit prejudice, may have a role in explaining this slowdown in the convergence. The second objective is to assess whether the prediction of a decrease in the proportion of prejudiced employers implied by the Becker’s model of taste discrimination is taking place and if so at what speed. These objectives are achieved by developing and estimating a search model of the labor market with matching, bargaining, employer’s prejudice and worker’s participation decisions. The results show that the proportion of prejudiced employers is estimated to be decreasing at an increasing speed, going from about 69% in 1985 to about 32% in 2005. Therefore prejudice is not estimated to be a relevant factor in explaining the slower convergence between male and female earnings in the 1990s. The results are consistent with the Becker’s model of taste discrimination if one is willing to assume a very slow adjustment process.     

一热轧硅钢加热炉燃控系统的研制与开发

加热炉燃控系统主要是提高加热炉的自动化程度,增强系统的稳定性、安全性、可靠性,提高炉子的热效率,保证钢坯在炉内加热的质量和温度控制精度。系统选用了西门子的PCS7V7．0来进行设计,采用（C／S）的网络构架模式,分布式I／OET200M构架通过光纤传输进行数据交换。燃控系统引入了双交叉限幅作为主要控制方式,能有效地抑制空气、煤气的大幅波动,实现了炉内气氛的严格可调,并且在问拔阀上做了重新的设计,优化了系统,大大提高了控制精度和系统稳定性。     

西门子S7—200替换S5序列PLC在鼓风机改造中的应用

福州祥坂污水处理厂有4台鼓风机,采用的是西门子的S5-101U序列PLC。由于SS序列PLC当前已处于淘汰状态,备件难以获得,并且价格昂贵,所以需要对鼓风机系统进行升级。考虑到相同品牌的兼容性,所以采用了主流的S7～200序列PLC进行改造。改造完成后,鼓风机达到了原系统的所有功能,并且在原基础上增加了远程监控和操作功能。使鼓风机子系统和全厂自动化得到了整合。     

浅谈基于iSCSI的Windows7无盘工作站架设

随着iSCSI存储技术的日益成熟,微软在Windows7企业版内置了iSCSI无盘网络启动功能,使基于iSCSI的无盘网络应用也越来越广泛。本文首先对基于iSCSI的Windows7无盘网络实现方式进行分析,然后通过实例讲解实现的方法。     

Decision-making in competitive framings—Strategic behavior of chess players in mini-ultimatum game chess puzzles

We introduce a competitive framing in the mini-ultimatum game utilizing chess puzzles. Therein, our chess playing participants accept low offers significantly more often compared to a neutral framing. We conclude that in familiar competitive surroundings egoistic behavior is more acceptable.     

Natural resource extraction and civil conflict

Based on evidence linking natural resources to civil conflict, this paper studies two armed groups fighting to control a resource and possibly a second prize. Labor is used in the agricultural, resource extraction and conflict sectors, and the groups also buy a capital input to conflict subject to the constraint that capital spending cannot exceed resource earnings. I find that exogenous shocks can have different effects on conflict intensity depending on whether the credit constraint binds. In particular, international policies to ban natural resource exports from conflict zones (e.g. ‘blood diamonds’), raise agricultural productivity or limit the import of weapons will limit conflict intensity if the credit constraint binds. However, if the credit constraint does not bind, then the first two policies promote conflict, and so could even the third policy. The results therefore suggest some caution in international policymaking.     

Central bank design with heterogeneous agents

We study alternative institutional arrangements for the determination of monetary policy in a general equilibrium model with heterogeneous agents, where monetary policy has redistributive effects. Inflation is determined by a policy board using either simple-majority voting, supermajority voting, or bargaining. We compare the equilibrium inflation rates to the first-best allocation.     

通过7SJ62实现PT断线闭锁低电压

文章着重介绍了西门子7SJ62的CFC逻辑编程功能实现PT断线闭锁低电压功能。该装置可以通过CFC编程采集分析输入的开关量和测量量,自动判断是否满足动作条件,并发出动作指令。