Rotational failure analysis of spherical-cylindrical shell pressure controllers related to gas hydrate drilling investigations

In situ pressure-preserved coring(IPP-Coring)technology is considered one of the most efficient methods for assessing resources.However,seal failure caused by the rotation of pressure controllers greatly affects the success of pressure coring.In this paper,a novel spherical-cylindrical shell pressure controller was proposed.The finite element analysis model was used to analyze the stress distribution and deformation characteristics of the pressure controller at different rotation angles.The seal failure mechanism caused by the rotation of the pressure controller was discussed.The stress deviation rate was defined to quantitatively characterize the stress concentration.Based on the test equipment designed in this laboratory,the ultimate bearing strength of the pressure controller was tested.The results show that the rotation of the valve cover causes an increase in the deformation on its lower side.Furthermore,the specific sealing pressure in the weak zone is greatly reduced by a statistically significant amount,resulting in seal failure.When the valve cover rotates 5°around the major axis,the stress deviation rate is-92.6%.To prevent rotating failure of the pressure controller,it is necessary to control the rotation angle of the valve cover within 1°around the major axis.The results of this research can help engineers reduce failure-related accidents,provide countermeasures for pressure coring,and contribute to the exploration and evaluation of deep oil and gas resources.

Non-integer Order Control Scheme for Pressurized Water Reactor Core Power

Tracking load changes in a pressurized water reactor(PWR)with the help of an efficient core power control scheme in a nuclear power station is very important.The reason is that it is challenging to maintain a stable core power according to the reference value within an acceptable tolerance for the safety of PWR.To overcome the uncertainties,a non-integer-based fractional order control method is demonstrated to control the core power of PWR.The available dynamic model of the reactor core is used in this analysis.Core power is controlled using a modified state feedback approach with a non-integer integral scheme through two different approximations,CRONE(Commande Robuste d’Ordre Non Entier,meaning Non-integer orderRobust Control)and FOMCON(non-integer order modeling and control).Simulation results are produced using MATLAB■program.Both non-integer results are compared with an integer order PI(Proportional Integral)algorithm to justify the effectiveness of the proposed scheme.Sate-spacemodel Core power control Non-integer control Pressurized water reactor PI controller CRONE FOMCON.

Diffserv AQM algorithm for edge and core routers

The existing active queue management （AQM） algorithm acts on subscribers and edge routers only, it does not support differentiate-serve （Diffserv） quality of service （QoS）, while the existing diffserv QoS has not considered the link capacities between edge routers and connected core routers. When a core router in a two layers’ network experiences congestion, the connected edge routers have no ability to adjust their access data rates. Thus, it is difficult to achieve the congestion control for the large scale network with many edge routers and core routers. To solve these problems, two difffserve AQM algorithms are proposed for the congestion control of multilayer network. One diffserv AQM algorithm implements fair link capacities of edge routers, and the other one implements unequal link capacities of edge routers, but it requires the core routers to have multi-queues buffers and Diffserv AQM to support. The proposed algorithms achieve the network congestion control by operating AQM parameters on the conditions of proposed three theorems for core and edge routers. The dynamic simulation results demonstrate the proposed control algorithms for core and edge routers to be valid.

Factors controlling the nitrate in the DT-401 ice core in eastern Antarctica

Nitrate,an oxidized product of NO x preserved in the polar ice cores,has often been used to estimate past changes of the atmospheric nitrogen cycle.A 102.65 m ice core drilled at DT-401(79°01'S,77°00'E) in 1999 provides an opportunity to investigate the possible influencing factors for the nitrate budget in the eastern Antarctica.We studied the relationship between the δ18O(representing the temperature),accumulation rate,volcanic deposition and the astronomical factors(such as the solar activities,supernovae,etc.),and the nitrate variation along the whole duration(2680-year) of the ice core.Prominent impacts of the accumulation rate acting on the nitrate flux rather than the concentration were detected.However,no significant correlation was found between the δ18O and the nitrate deposition characteristics(concentration and the flux variations).Volcanic deposition can significantly affect the deposition of nitrate with a decreasing trend accompanied by the nss-SO42(volcanic signal) peak values.Impacts of the solar activities on the nitrate deposition can be detected at this site,and three prominent periodicities(16.6,24.0 and 102.0 yr) were found for the nitrate concentration variations.Six climatic events(Dalton Minimum,Maunder Minimum,Sporer Minimum,Wolf Minimum,Oort Minimum and Medieval Maximum) during the past 1150 years were observed with lower nitrate values for the foregoing five events and higher value for the last one.