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Background: The overflow valve, as an essential pressure control element, is widely applied in various hydraulic transmission systems because of its characteristics of constant pressure overflow, stable pressure, system unloading and safety protection. The research on the structure and working principle of the overflow valve are beneficial to improve the working efficiency and operating stability of pressure control of the hydraulic transmission. Therefore, the development trend of the overflow valve for pressure control has been paid more and more attention. Objective: To meet the growing demands for the working efficiency and operating stability of hydraulic transmission, the structure of the overflow valve for pressure control such as direct-acting overflow valve and pilot-operated overflow valve is being improved continuously. Methods: This paper retraces various current representative patents relative to the structural device of direct-acting overflow valve and pilot-operated overflow valve for pressure control. Results: Through investigating a large number of patents on the overflow valve for pressure control, the main current existing problems such as low working efficiency and poor operating stability are summarized and analyzed. Moreover, the development tendency of the overflow valve for pressure control in the future is also discussed. Conclusion: The optimization of the structure of the overflow valve for pressure control is conducive to improve working efficiency and operating stability. More correlative patents will be invented in the future.

Background: Electrical Discharge Machining (EDM) has been widely applied in manufacturing high strength and high hardness of mental material due to no mechanical forces in the EDM process. The discharge state, an important process parameter of EDM, directly affects the machining quality and machining efficiency. So, it is necessary to detect the real-time discharge state of EDM. Therefore, discharge state detection of EDM at present has been paid more and more attention. Objective: To meet the increasing requirement of machining quality and machining efficiency in the EDM process, the methods for discharge state detection of EDM are being improved continuously. Methods: This paper reviews various representative patents related to the methods for discharge state detection of EDM. Results: By summarizing numerous patents about the methods for discharge state detection of EDM, the main problems such as low detection accuracy and long delay time of discharge state detection of EDM are summarized and analyzed. In addition, the further development of discharge state detection method of EDM is discussed. Conclusion: The optimization of methods for discharge state detection is conducive to improving machining quality and machining efficiency in the EDM process. Moreover, more relevant patents will be invented in the future.

A climate event at 7.5–7.0 cal ka BP (thousand calibrated years before present) has been recognized. This event is important for foreseeing the possible response of the climate system to global warming and for interpreting considerable societal change, but it has heretofore lacked a systematic review. Here, we summarize previously published paleoclimate records spanning this event from 47 sites around the world. The proxy evidence from a variety of paleo-archives, including lake sediments, speleothems, marine sediments, and ice cores, provides a clear picture of this climate change. The synthesis results show a weaker Asian summer monsoon, in contrast to a stronger South American summer monsoon during the event. The event also involves dramatic cooling and wetter conditions in north-central Europe and in western North America, widespread aridity across Africa, contrasting patterns of precipitation variability throughout the Mediterranean, and notable cooling over the polar region, suggesting that it is a worldwide climate event. Comparison of paleoclimate records with climate-forcing time series gives likely climate controls for the event. The close correspondence in time of solar irradiance minima, strong volcanic eruptions, the meltwater flux into the North Atlantic, an orbitally induced decrease in solar insolation, and climate changes indicated by proxy data suggest possible linkages. More quantitative reconstructions and higher resolution climate records are needed to fully capture the magnitude, timing, duration, and nature of this event, which will be of considerable relevance to modeling.

A lot of algae fossils were found in Cenozoic lake sediments, especially Pediastrum fossil sedimentary deposits in some places of China and also in some nearby seacoasts. For imitating Pediastrum mine ralization in lake sediments, several species of Pediastrum are cultured using BBM medium and sea water with 18% salt. By optical and electronic microscope observation and photosyntheic pigment analysis, we found that Pediastrum boryanum, P.duplex var clathratum and P.tetras , etc. cannot grow well in sea water. If cultured in saline medium, the specimen will die in a short period of time. We consider that probably the Pediastrum fossil that appeared in marine sediments were transported to the sea by river. In order to prove the mineralization condition of in living organism and fossils of Pediastrum, the following analysis is made. The fat soluble substances are high and they contain a small amount of alkane, alkene fatty acid and a great deal of plant pigments. Pediastrum has high H/C and low O/C (atom number ratio) value. Therefore, it is a good resource of oil formation. The products of oxidative degradation of the insoluble cell wall of Pediastrum are similar to the production obtained by kerogen, which is known to be of algal origin. So, the insolable materials of cell wall are probably a source of kerogen during the deposition.

This paper presents an intelligent alarm processing system based respectively on network configuration model and Petri nets model. By analyzing breaker tripping messages, this alarm processing system can identify fault component or possible fault area, and by considering both relay actuating and breaker tripping messages, it can identify the determined fault component, and if needed, the malfunctioning breaker or malfunctioning relay. This alarm processing system will be implemented on East China Power System to serve as an assistant tool for the operators to take correct and swift actions during emergency conditions.

In this paper, an approach for assisting operators to prevent power system blackouts during emergency conditions is presented. It is based on expert system and fuzzy logic techniques to summarize the operating experience of power system dispatchers. The Fault Diagnosis and Restoration Control (FDARC) program has been developed using the C++ language and object-oriented programming technology, on a PC-486 which is integrated with a VAX computer via a serial link. It has been implemented in the East China Power System Control Center for trial operation since March 1998.