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Software-defined networking (SDN) has the ability to flexibly configure the network and is widely used in various scenarios. In SDN, different applications require the controller to deploy corresponding flow entries to maintain the effectiveness of network. However, the matching field range covered by entries of different applications may overlap, and when actions specified by these overlapping entries are inconsistent, conflicts may occur. Such conflicts may cause the flow to match the wrong entry, thereby affecting the correct expression of application functions. The scheme we proposed in this paper will be able to detect and resolve conflicts between flow entries. Firstly, we discussed the causes of conflicts, and then classified various conflict situations. This classification will help us to adopt different ways of resolving different types of conflicts and make the resolution of conflicts more targeted. Next, we propose a conflict detection algorithm based on B+ tree. This algorithm can detect different types of conflicts. According to theoretical proof, the use of B+ tree compared with other similar structures better in the performance of the time and space complexity. Finally, for the detected conflicting entries, we propose a conflict resolution scheme based on the failure degree of the flow entry according to the characteristics of SDN services tending to be more detailed. Through experimental evaluation, our scheme can effectively detect and resolve conflicts with lower overhead.

Cities with dense population are vulnerable to disasters as they may cause losses of human life and property. Mitigation is most effective for reducing the risks of communities as well as creating more resilient communities in cities. However, exploring the spatial prioritization for resources investment and evaluating the relative efficiency of different alternative risk reduction strategies are still challenges. In this study, we proposed an innovative methodology framework for exploring risk reduction strategies in large-scale urban areas. GIS spatial statistics technique is introduced to investigate global regional risk pattern as well as identify local risk hot spots in spatial scale, and scenario planning paradigm is used to explore the dynamically changing regional risk pattern and risk hot spots in temporal scale due to risk reduction. Moreover, scenario sets were developed to evaluate and analyze the effectiveness and cost of different alternative risk reduction strategies for trade-off. We then applied the methodology to a typical urban district of north China to demonstrate its utility. The results successfully obtained reveal the necessity of concerning dynamically changing nature of regional risk spatial pattern during the risk reduction process. The findings show that the methodology framework proposed in this study has potential to provide decision support for guiding future urban risk reduction and hazard mitigation planning. This work offers new perspectives and valuable demonstration on promoting urban risk management with the integration of emerging GIS spatial statistics and scenario planning technique.

An update high temperature superconducting Maglev measurement system (SCML-02) was successfully developed. The system includes liquid nitrogen vessel, cylinder permanent magnet (PM) or PM guideway (PMG), data collection and processing, mechanical drive and autocontrol. The liquid nitrogen vessel with high temperature superconductors (HTSCs) can be placed above or under the PM. This measurement system has other characteristics: high measurement precision, instant measurement at movement of the measured HTSCs specimen, synchronous measurement of levitation and guidance, measurement in three dimensions at one time, relaxation measurement of both levitation and guidance force, and so on. In order to calibrate measurement precision and to verify special function of SCML-02, two cylinder PMs are used, which have the same scale and technical specification. The Maglev properties of HTSCs YBCO bulk are measured on the basis of the calibration results of SCML-02. The levitation forces of single YBCO bulk and of seven YBCO bulks above PMG are measured by SCML-02. All functions are validated experimentally. The main specification of the measurement system is: position precision plusmn 0.05 mm; vertical force precision 2%c; horizontal force precision 1%c. The force measurement precision has achieved 0.02 N

The design consideration of the superhigh speed HTS Maglev vehicle system of 1000 m test line is presented on the basis of the experiment results of HTS Maglev vehicle in the years before last. The gross weight of NdFeB of test line guideway is 6750 kg. The low temperature rectangle-shape liquid nitrogen vessel on board has high mechanical strength at 77 K of the temperature. The vessel has 5 mm of bottom thickness and 12 hours of continuous working time. There are two seats in the HTS Maglev vehicle. The total load of the Maglev vehicle is 500 kg including 150 kg of weight of two passengers in the weight. The vehicle body is the quasiellipsoidal shape, and the outside outline size of the vehicle with shell is about 2.3 m of length 0.95 m of height, and 1.2 m of width. The vehicle is driven by a linear motor which is controlled by a ground controlling system. Drive acceleration is 5 g (about 49 m/s/sup 2/), and the acceleration section length is 300 m. The maximum speed of the vehicle is over 600 km/h when there is no onboard man, and the manned speed is still up to 100 km/h.

Since the first successful running of the people-carrying high temperature superconducting (HTS) Maglev test vehicle on 31 December 2000, about 27 000 people have taken it, and the accumulated running distance is about 400 km. The levitation force of the onboard HTS equipment is measured periodically, and new experimental results measured on 5 March 2003 show that the performance of the onboard HTS Maglev equipment is almost the same as that of two years ago. Experimental results indicate that the long-term stability of the HTS Maglev vehicle is good. This further proves the feasibility of the HTS Maglev vehicle for practical transportation. It is worth mentioning that all the results are measured at a low speed; however, investigations of the dynamic performance of the HTS Maglev vehicle at high speed are necessary for practical application. Research on the dynamic performance of the HTS Maglev vehicle is ongoing.

The first man-loading high-temperature superconducting (HTS) Maglev test vehicle in the world was successfully developed on Dec. 31, 2000 in the Applied Superconductivity Laboratory, Southwest Jiaotong University, China. Heretofore over 24 500 passengers took the vehicle, and it has been operating back and forth for about 400 km. The HTS Maglev vehicle provides inherent stability both in the vertical and lateral direction, so no control system is needed. The only control system is used for linear motor driving devices. The melt-textured YBaCuO bulk superconductors are fixed on the bottom of a liquid nitrogen vessel and cooled by liquid nitrogen. The bottom thickness of the rectangle liquid nitrogen vessel with its thin wall is only 3 mm. The onboard HTS Maglev module is placed over the guideway. The guideway consists of two parallel permanent magnetic tracks, whose concentrating magnetic field at 20 mm height above the surface is about 0.5 T. The levitation forces of 8 HTS Maglev modules were measured. The total levitation force of 8 onboard Maglev modules was 10431 N at the levitation gap of 10 mm, and 8486 N at the levitation gap of 15 mm, respectively. These results were measured on May 28, 2002.

The first man-loading high temperature superconducting Maglev test vehicle in the world is reported. This vehicle was first tested successfully on December 31, 2000 in the Applied Superconductivity Laboratory, Southwest Jiaotong University, China. Heretofore over 17,000 passengers took the vehicle, and it operates very well from beginning to now. The function of suspension is separated from one of propulsion. The high temperature superconducting Maglev provides inherent stable forces both in the levitation and in the guidance direction. The vehicle is 3.5 m long, 1.2 m wide, and 0.8 m high. When five people stand on vehicle and the total weight is 530 kg, the net levitation gap is more than 20 mm. The whole vehicle system includes three parts, vehicle body, guideway and controlling system. The high temperature superconducting Maglev equipment on board is the most important for the system. The onboard superconductors are melt-textured YBaCuO bulks. The superconductors are fixed on the bottom of liquid nitrogen vessels and cooled by liquid nitrogen. The guideway consists of two parallel permanent magnetic tracks, whose surface concentrating magnetic field is up to 1.2 T. The guideway is 15.5 m long.

When the velocity of the normal ground traffic transportation is higher than 350 km/h of the speed limit, not only the running noise of the ground traffic vehicle is higher, but also the 90% driving power is dissipated in the aerodynamic resistance. The high speed may be realized when a high temperature superconducting (HTS) Maglev vehicle runs in low-pressure tube or evacuated tube transport (ETT). Its speed is over 3000 km/h. As a new ground transportation system the HTS Maglev vehicle is presented after the experiment results of HTS Maglev vehicle are discussed in this paper.

Deep level defects in high temperature annealed semi-conducting InP have been studied by deep level transient spectroscopy (DLTS). There is obvious difference in the deep defects between as-grown InP, InP annealed in phosphorus ambient and iron phosphide ambient, as far as their quantity and concentration are concerned. Only two defects at 0.24 and 0.64 eV can be detected in InP annealed in iron phosphide ambient, while defects at 0.24, 0.42, 0.54 and 0.64 eV have been detected in InP annealed in phosphorus ambient, in contrast to two defects at 0.49 and 0.64 eV or one defect at 0.13 eV in as-grown InP. A defect suppression phenomenon related to iron diffusion process has been observed. The formation mechanism and the nature of the defects have been discussed.