A study of user experience in Tsinghua Wireless and Mobile Digital Library System(TWIMS)

Tsinghua University Library recently launched Tsinghua Wireless and Mobile Digital Library System(TWIMS) to meet users’ need for wireless access to library services.A survey of user experience about TWIMS was carried out for the purpose of studying its users’ behavior and their level of satisfaction about the system design and its various performance indicators. Based on our research findings, we concluded our research paper with a set of evaluative comments and suggestions. Those remarks are aimed at furthering the TWIMS’ functionality and reconstructing a more sensible questionnaire survey appertaining to the system users’ experience as well in the next phase of our extended research.

Peak-to-Average Power Ratio Performance Analysis for Orthogonal Chirp Division Multiplexing Multicarrier Systems Based on Discrete Fractional Cosine Transform

In doubly selective fading channels, the orthogonal frequency division multiplexing (OFDM) multicarrier system may fail. Chirp like basis (fractional Fourier transform-fractional cosine transform) may be used instead of complex exponential basis in this case to improve the system performance. However, in multicarrier transmission, the high peak to average power ratio (PAPR) of the transmitted signal is one of the difficult problems that face both the chirp and the exponential basis. In this paper, an evaluation for the PAPR performance of a multicarrier system based on the fractional cosine transform (FrCT) is introduced and then compared with DFrFT and FFT. Moreover, applying the SLAM technique over these systems is provided to understand the behaviour of these systems when applying SLAM. Simulations verify that this system obtains a better PAPR performance. Moreover, further PAPR reduction can be gained using the well-known PAPR reduction methods. Moreover, applying SLAM technique improves the performance of (dB) by 4 dB to 5 dB and all systems become as competitive to each other when SLAM is applied. Finally, BER performance comparison among OFDM, Discrete Cosine Transform MCM (DCT- MCM), Discrete Hartley Transform MCM (DHT-MCM), DFrFT-OCDM and DFrCT- OCDM MCM systems was done by means of simulation over 100,000 multicarrier blocks for each one and showed that our proposed scenario gave the best performance.

Research on the Accurate Location of the 2007 M_S6.4 Ning'er, Yunnan Earthquake

Five mobile digital seismic stations were set up by the Earthquake Administration of Yunnan Province near the epicenter of the main shock after the Ning＇er M6. 4 earthquake on June 3, 2007. In this paper, the aftershock sequence of the Ning＇er M6. 4 earthquake is relocated by using the double difference earthquake location method. The data is from the 5 mobile digital seismic stations and the permanent Simao seismic station. The results show that the length of the aftershock sequence is 40kin and the width is 30km, concentrated obviously at the lateral displacement area between the Pu＇er fault and the NNE-trending faults, with the majority occurring on the Pu＇er fault around the main shock. The depths of aftershocks are from 2kin to 12km, and the predominant distribution is in the depth of 8 ~ 10km. The mean depth is 7. 9kin. The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence, which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang fault in the earthquake area. There are more earthquakes concentrated in the northwest segment than in the southeast segment, which is perhaps related to the underground medium and faults. The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu＇er fault and the seismic faults dip to the southwest, consistent with the dip of the west branch of the Pu＇er fault. In all, the fault strike revealed by earthquake relocations matches well with the strike in the focal mechanism solutions. The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed, showing that faulting was complete in both the NE and SW directions.

Digital rights management independent of terminals in mobile applications

At present, most mobile terminals do not have any functions of fights management, and the cryptology-based method cannot resolve all the copyright problems in the mobile digital distribution service. With the urgent demand of digital rights management in digital distribution service, a scheme independent of terminals is proposed in this article. It integrates the watermark and signature techniques. In this article the scheme theory, architecture, service process, and performance are mainly discussed. In the end, the functional relationship between the proposed digital rights management （DRM） and the cryptology-based open mobile alliance digital rights management （OMA-DRM） is given. The analysis shows that the scheme is feasible and secure.

A stream-based Parasitic Model for implementing Mobile Digital Earth

A Parasitic Model is proposed in this study for Digital Earth running on mobile phones through a mobile network.Because of mobile phones’limited capabilities in high-performance computing,rendering,storing,and networking(CRSN),these functions are accomplished by a superior host computer in this model.Rendered virtual scenes are compressed in a time-series as a data stream and are sent to the mobile phone through a mobile network,thus allowing Digital Earth to be operated on a mobile phone.This study examines a prototype and shows that a Mobile Digital Earth based on a Parasitic Model can achieve functionality beyond the mobile phone’s actual hardware capabilities and can reduce network traffic.These results demonstrate quasi-real-time interactions,but with bandwidth increases in next-generation mobile networks such as 4G and 5G,there is potential for real-time interactions in the near future.

Design and Implementation of Spatial Data Watermarking Service System

Nowadays, more and more digitalized spatial data are sold and transmitted on the Internet. Thus, there arises an important issue about copyright protection of the digital data. To solve this problem, this paper has designed and implemented a spatial data watermarking service (SDWS) system which can provide a secure framework for data transaction and transfer via the Internet and protect the rights of both copyright owners and consumers at the same time.