针对多用户并发操作环境中,多个用户程序同时存取同一数据,相互干扰导致丢失修改数据、不能重复读和读未提交的数据等问题,提出了解决并行操作下写/写和读/写数据库冲突的并发控制方法。该方法采取封锁机制,即某事务向系统发出请求,便...针对多用户并发操作环境中,多个用户程序同时存取同一数据,相互干扰导致丢失修改数据、不能重复读和读未提交的数据等问题,提出了解决并行操作下写/写和读/写数据库冲突的并发控制方法。该方法采取封锁机制,即某事务向系统发出请求,便将数据对象加锁并对锁以管理,实现其控制。在多用户环境下,Oracle8i数据库的后台并发控制与处理机制涉及事务隔离机制、封锁机制及强制锁释放等处理方法。PowerBuilder 7.0前端并发控制则可通过Key and Updatble Colums,并遵循抢先修改的事务设计原则。展开更多
Recently,virtualization technologies have been widely used in industry.In order to monitor the security of target systems in virtualization environments,conventional methods usually put the security monitoring mechani...Recently,virtualization technologies have been widely used in industry.In order to monitor the security of target systems in virtualization environments,conventional methods usually put the security monitoring mechanism into the normal functionality of the target systems.However,these methods are either prone to be tempered by attackers or introduce considerable performance overhead for target systems.To address these problems,in this paper,we present a concurrent security monitoring method which decouples traditional serial mechanisms,including security event collector and analyzer,into two concurrent components.On one hand,we utilize the SIM framework to deploy the event collector into the target virtual machine.On the other hand,we combine the virtualization technology and multi-core technology to put the event analyzer into a trusted execution environment.To address the synchronization problem between these two concurrent components,we make use of Lamport's ring buffer algorithm.Based on the Xen hypervisor,we have implemented a prototype system named COMO.The experimental results show that COMO can monitor the security of the target virtual machine concurrently within a little performance overhead.展开更多
Modeling and simulation of two different microturbine （MT） models to analyze load following performance as distributed energy resource （DER） have been presented in this paper. The first model consists of speed gov...Modeling and simulation of two different microturbine （MT） models to analyze load following performance as distributed energy resource （DER） have been presented in this paper. The first model consists of speed governor, acceleration control, and temperature control blocks while the other is GAST model. The system comprises a synchronous generator and a MT coupled to it. Simulations are carried out in islanded and grid-connected mode to observe the system response when supplying variable loads. The load following characteristics is observed and validated for this MT-synchronous generator model in Matlab-Simulink environment. This is applicable with combined heat power （CHP） generators both with general fuel as well as bio-fuels. The use of bio-fuels is very much promising for generating green power preventing green house gas emissions for fighting against global warming.展开更多
The Euphrates River is one of the major rivers in Iraq. When it reaches north of Hilla city, it will be divided in two branches. One of these braches flows toward Hilla city. On this branch, six locations were studied...The Euphrates River is one of the major rivers in Iraq. When it reaches north of Hilla city, it will be divided in two branches. One of these braches flows toward Hilla city. On this branch, six locations were studied for the water quality of the Euphrates water. The present paper is aimed to fill the gap of information of the presence of PAHs （poly aromatic hydrocarbons） in water and sediment of AI-Hilla River, as well as to determine the quality and quantity of some PAHs. The depth of the river ranges from 2 m to 6 m. The quality, quantity and the origin of PAHs were studied in the water and sediment of Al-Hilla River. In addition, some physical and chemical properties were studied at six sites along the studied area, for the period March, 2010 to February, 2011. Sixteen PAHs that are listed by USEPA （US Environmental Protection Agency） as priority pollutants （Nap （naphthalene）, Acpy （acenaphthylene）, Acp （acenaphthene）, Flu （fluorine）, Phen （phenanthrene）, Ant （anthracene）, Flur （fluoranthene）, Py （pyrene）, B（a）A （benzo（a）anthracene）, Chry （chrysene）, B（b）F （benzo（b）fluoranthene）, B（k）F （benzo（k）fluoranthene）, B（a）p （benzo（a）pyrene）, BbA （dibenzo（a,h）anthracene）, B（ghi）P （benzo（ghi）perylene） and Ind （indeno （1,2,3-cd） pyrene）） were detected in Al-Hilla river. High concentrations of PAHs were detected in the sediment relative to that within the water. The present study revealed that the origin of PAHs in water and sediment might be the pyrogenic origin.展开更多
文摘针对多用户并发操作环境中,多个用户程序同时存取同一数据,相互干扰导致丢失修改数据、不能重复读和读未提交的数据等问题,提出了解决并行操作下写/写和读/写数据库冲突的并发控制方法。该方法采取封锁机制,即某事务向系统发出请求,便将数据对象加锁并对锁以管理,实现其控制。在多用户环境下,Oracle8i数据库的后台并发控制与处理机制涉及事务隔离机制、封锁机制及强制锁释放等处理方法。PowerBuilder 7.0前端并发控制则可通过Key and Updatble Colums,并遵循抢先修改的事务设计原则。
基金supported in part by National Natural Science Foundation of China(NSFC)under Grant No.61100228 and 61202479the National High-tech R&D Program of China under Grant No.2012AA013101+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No.XDA06030601 and XDA06010701Open Found of Key Laboratory of IOT Application Technology of Universities in Yunnan Province Grant No.2015IOT03
文摘Recently,virtualization technologies have been widely used in industry.In order to monitor the security of target systems in virtualization environments,conventional methods usually put the security monitoring mechanism into the normal functionality of the target systems.However,these methods are either prone to be tempered by attackers or introduce considerable performance overhead for target systems.To address these problems,in this paper,we present a concurrent security monitoring method which decouples traditional serial mechanisms,including security event collector and analyzer,into two concurrent components.On one hand,we utilize the SIM framework to deploy the event collector into the target virtual machine.On the other hand,we combine the virtualization technology and multi-core technology to put the event analyzer into a trusted execution environment.To address the synchronization problem between these two concurrent components,we make use of Lamport's ring buffer algorithm.Based on the Xen hypervisor,we have implemented a prototype system named COMO.The experimental results show that COMO can monitor the security of the target virtual machine concurrently within a little performance overhead.
文摘Modeling and simulation of two different microturbine （MT） models to analyze load following performance as distributed energy resource （DER） have been presented in this paper. The first model consists of speed governor, acceleration control, and temperature control blocks while the other is GAST model. The system comprises a synchronous generator and a MT coupled to it. Simulations are carried out in islanded and grid-connected mode to observe the system response when supplying variable loads. The load following characteristics is observed and validated for this MT-synchronous generator model in Matlab-Simulink environment. This is applicable with combined heat power （CHP） generators both with general fuel as well as bio-fuels. The use of bio-fuels is very much promising for generating green power preventing green house gas emissions for fighting against global warming.
文摘The Euphrates River is one of the major rivers in Iraq. When it reaches north of Hilla city, it will be divided in two branches. One of these braches flows toward Hilla city. On this branch, six locations were studied for the water quality of the Euphrates water. The present paper is aimed to fill the gap of information of the presence of PAHs （poly aromatic hydrocarbons） in water and sediment of AI-Hilla River, as well as to determine the quality and quantity of some PAHs. The depth of the river ranges from 2 m to 6 m. The quality, quantity and the origin of PAHs were studied in the water and sediment of Al-Hilla River. In addition, some physical and chemical properties were studied at six sites along the studied area, for the period March, 2010 to February, 2011. Sixteen PAHs that are listed by USEPA （US Environmental Protection Agency） as priority pollutants （Nap （naphthalene）, Acpy （acenaphthylene）, Acp （acenaphthene）, Flu （fluorine）, Phen （phenanthrene）, Ant （anthracene）, Flur （fluoranthene）, Py （pyrene）, B（a）A （benzo（a）anthracene）, Chry （chrysene）, B（b）F （benzo（b）fluoranthene）, B（k）F （benzo（k）fluoranthene）, B（a）p （benzo（a）pyrene）, BbA （dibenzo（a,h）anthracene）, B（ghi）P （benzo（ghi）perylene） and Ind （indeno （1,2,3-cd） pyrene）） were detected in Al-Hilla river. High concentrations of PAHs were detected in the sediment relative to that within the water. The present study revealed that the origin of PAHs in water and sediment might be the pyrogenic origin.
