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Now showing items 1 - 16 of 18

  • Cooperative Network Coding Strategies for Wireless Relay Networks with Backhaul

    Jinfeng Du   Ming Xiao   Skoglund, M.  

    We investigate cooperative network coding strategies for relay-aided two-source two-destination wireless networks with a backhaul connection between the source nodes. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding schemes, namely, finite field and linear network coding, and lattice coding. To further exploit the backhaul connection, we also propose network coding based beamforming. We measure the performance in term of achievable rates over Gaussian channels, and observe significant gains over benchmark schemes. We derive the achievable rate regions for these schemes and find the cut-set bound for our system. We also show that the cut-set bound can be achieved by network coding based beamforming when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains.
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  • Research on Microstructure and Mechanical Property of S30432 Supreheater Pipe Aged at 700°C

    Jinfeng Du   Jun Liang   Huichuan Zhao and Biao Sun  

    The microstructure and performance of S30432 supreheater pipe were investigated before and after it is aged 3000 h at 700°C. A lot of twins disappeared after aging, M23C6 particles precipitated along the grain boundary and MX particles precipitated near the dislocation. After the endurance experiment of the aged pipe, M23C6 precipitations with the size of about 50 nm pinned dislocations and the cavity appeared on the grain boundary. The aged S30432 supreheater pipe showed the ductile fracture. Increasing temperature made the inter-granular fracture transfer the quasi-cleavage fracture and the equiaxed morphology change the parabola morphology. The strength of the untreated specimen decreased with the temperature increasing. The hardness and the impact energy of the aged specimen were larger than those of the untreated specimen. Tensile strength and elongation of untreated specimen were larger than that of aged specimen.
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  • Land pricing and its impact on land use efficiency in post-land-reform China: A case study of Beijing

    Jinfeng Du   Jean-Claude Thill   Richard B. Peiser  

    a r t i c l e i n f o Keywords: Land use efficiency Land use productivity Land pricing Beijing China This paper analyzes how the newly introduced land pricing system affects urban land productivity in China, taking post-land-reform Beijing as an example. China has been developing its urban land market by building an effective pricing system. This study indicates that the effects of such pricing system on urban land productivity have evolved with the progress of land reform. It is only since 2004, when land granting by negotiation was at last totally prohibited for profit-oriented developments, that the land pricing system has started to positively and significantly improve urban land productivity; the land pricing system also promotes more productive urban land usage by stimulating more intensive investment and better business management. Improving the efficient use of land is commonly recognized as of paramount importance in balancing the protection of farmland and the accommodation of socioeconomic development, especially for a country like China with intense human-land relationship and rapid urbanization (Choy, Lai, and Lok, 2013; Meng et al., 2008). During the planned economy era, land was free of charge for development in China. Land users tended to occupy more land than they actually needed, leading to massive loss of cultivated land in rural areas and inefficient land usage in urban areas. From 1956 to 1978, the area of cultivated land shrank 12.44 million ha nationwide and the annual loss amounted to 5652 km 2 (Li, 2000). An urban land reform based on the paid-to-use 1 principle was initiated in the late 1980s with the expectation that land pricing would improve the cost of land use. More accurate land use cost would compel land users to utilize land more economically, and therefore, help improve urban land use efficiency, 2 preserve cultivated land, and raise capital for development it remains unclear whether the market mechanism has helped improve land use efficiency as anticipated. With the expansion of urban land, land use efficiency can increase or decrease depending upon the relative rates of change between land consumption and socioeconomic output. Existing studies have looked critically at the massive magnitude of urban development by analyzing the dynamics of urban expansion and the institutional roots of " losing control " of urban sprawl in China (Zhou, 2006). However, incorporating more land to accommodate a growing population and to support urban economic growth is inherent …
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  • Classic OFDM Systems and Pulse Shaping OFDM/OQAM Systems

    Jinfeng Du   Svante Signell  

    In this report; we provide a comparative study of state-of-the-art in Orthogonal Frequency Division Multiplexing (OFDM) techniques with orthonormal analysis and synthesis basis. Two main categories; OFDM/QAM which adopts baseband Quadrature Amplitude Modulation (QAM) and rectangular pulse shape; and OFDM/OQAM which uses baseband offset QAM and various pulse shapes; are intensively reviewed. OFDM/QAM can provide high data rate communication and effectively remove intersymbol interference (ISI) by employing guard interval; which costs a loss of spectral efficiency and increases power consumption. Meanwhile it remains very sensitive to frequency offset which causes intercarrier interference (ICI). In order to achieve better spectral efficiency and reducing combined ISI/ICI; OFDM/OQAM using well designed pulses with proper Time Frequency Localization (TFL) is of great interest. Various prototype functions; such as rectangular; half cosine; Isotropic Orthogonal Transfer Algorithm (IOTA) function and Extended Gaussian Functions (EGF) are discussed and simulation results are provided to illustrate the TFL properties by the ambiguity function and the interference function.
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  • Cooperative Strategies in Multi-Terminal Wireless Relay Networks

    Jinfeng Du  

    Smart phones and tablet computers have greatly boosted the demand for services via wireless access points; keeping constant pressure on the network providers to deliver vast amounts of data over the wireless infrastructure. To enlarge coverage and enhance throughput; relaying has been adopted in the new generation of wireless communication systems; such as in the LongTerm Evolution Advanced standard; and will continue to play an important role in the next generation wireless infrastructure. Depending on functionality; relaying can be characterizing into three main categories: amplify-andforward (AF); compression-and-forward (CF); and decode-and-forward (DF). In this thesis; we investigate different cooperative strategies in wireless networks when relaying is in use. We first investigate the capacity outer and inner bounds for a wireless multicast relay network where two sources; connected by error-free backhaul; multicast to two destinations with the help of a full-duplex relay node. For high-rate backhaul scenarios; we find the exact cut-set bound of the capacity region by extending the proof of the converse for the Gaussian relay channel. For low-rate backhaul scenarios; we present two genie-aided outer bounds by extending the previous proof and introducing two lemmas on conditional (co)variance. Our inner bounds are derived from various cooperative strategies by combining DF/CF/AF relaying with network coding schemes. We also extend the noisy network coding scheme and the short-message noisy network coding approach to correlated sources. For low-rate backhaul; we propose a new coding scheme; partial-decode-and-forward based linear network coding. We derive the achievable rate regions for these schemes and measure the performance in term of achievable rates over Gaussian channels. By numerical investigation we observe significant gains over benchmark schemes and demonstrate that the gap between upper and lower bounds is in general not large. We also show that for high-rate backhaul; the cut-set bound can be achieved when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains. For wireless networks with independent noise; we propose a simple framework to get capacity outer and inner bounds based on the “one-shot” bounding models. We first extend the models for two-user broadcast channels to manyuser scenarios and then establish the gap between upper and lower bounding models. For networks with coupled links; we propose a channel decoupling method which can decompose the network into overlapping multiple-access channels and broadcast channels. We then apply the one-shot models and create an upper bounding network with only bit-pipe connections. When developing the lower bounding network; we propose a two-step update of these models for each coupled broadcast and multiple-access channels. We demonstrate by some examples that the resulting upper bound is in general very good and the gap between the upper and lower bounds is usually not large. For relay-aided downlink scenarios; we propose a cooperation scheme by cancelling interference at the transmitter. It is indeed a symbol-by-symbol approach to one-dimension dirty paper coding (DPC). For finite-alphabet
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  • The short-term efficacy and safety of treatment of HA280 immunoadsorption column in the polymyositis

    Shu Li;Haina Gan;Jinwei Chen;Suqing Xu;Jinfeng Du;Guanhui Ling;The Second Xiangya Hospital of Central South University;  

    Objective To evaluate the short-term efficacy and safety of treatment of HA280 immunoadsorption(IA) column in the polymyositis.Methods The clinical data of 72 patients with polymyositis admitted to the Department of Rheumatology of Xiangya No.2 Hospital of Central South University from January 2015 to march 2018 were analyzed. Of these patients, 22 patients were treated with HA280 immunoadsorption column for three times(immunoadsorption group) and 50 patients were treated with only drugs(control group). The changes of clinical symptoms and signs, autoimmune antibodies, myocardial enzyme spectrum, the inflammatory markers(ESR, CRP and ferritin), immunoglobulin, complement, other biochemical indexes and pulmonary imaging of the patients were detected and analyzed before and after the treatment.Results Compared with the control group, the symptoms and signs were obviously improved after treatment with HA280 immunoadsorption column(P<0.05). And the clearance of autoantibody, myocardial enzyme spectrum, the inflammatory markers(ESR, CRP) and immunoglobulin were more efficient in immunoadsorption group than the control group(P<0.05). Moreover, the lung CT scan showed that the immunoadsorption group could better improve the pulmonary lesions of the patients after 3 months follow-up(P<0.05). No serious adverse reactions occurred during the observation period.Conclusion HA280 immunoadsorption therapy can significantly clear the autoantibodies, muscle enzymes, inflammatory markers and immunoglobulin, improve the lung imaging of some patients in a short time. It shows safety in patients with polymyositis. HA280 immunoadsorption therapy could be an effective treatment for polymyositis.
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  • Comparison of CP-OFDM and OFDM/OQAM in Doubly Dispersive Channels

    S. Signell   Jinfeng Du  

    In this paper we compare the performance of cyclic prefix based OFDM (CP-OFDM) system and OFDM/offset QAM (OFDM/OQAM) system in doubly dispersive channels; by investigating the signal reconstruction perfectness; time and frequency dispersion robustness; and sensitivity to frequency offset. Both analysis and simulation results show that various parameter adaptations can be made with respect to the channel state information to improve the system performance.
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  • Unified Capacity Limit of Non-coherent Wideband Fading Channels

    Felipe Gómez-Cuba   Jinfeng Du   Muriel Médard   Elza Erkip  

    In non-coherent wideband fading channels where energy rather than spectrum is the limiting resource, peaky and non-peaky signaling schemes have long been considered species apart, as the first approaches asymptotically the capacity of a wideband AWGN channel with the same average SNR, whereas the second reaches a peak rate at some finite critical bandwidth and then falls to zero as bandwidth grows to infinity. In this paper it is shown that this distinction is in fact an artifact of the limited attention paid in the past to the product between the bandwidth and the fraction of time it is in use. This fundamental quantity, that is termed bandwidth occupancy, measures average bandwidth usage over time. As it turns out, a peaky signal that transmits in an infinite bandwidth but only for an infinitesimal fraction of the time may only have a small bandwidth occupancy, and so does a non-peaky scheme that limits itself to the critical bandwidth even though more spectrum is available, so as to not degrade rate. The two types of signaling in the literature are harmonized to show that, for all signaling schemes with the same bandwidth occupancy, rates converge to the wideband AWGN capacity with the same asymptotic behavior as the bandwidth occupancy approaches its critical value, and decrease to zero as the occupancy goes to infinity. This unified analysis not only recovers previous results on capacity bounds for (non-)peaky signaling schemes, but also reveals the fundamental tradeoff between precision and accuracy when characterizing the maximal achievable rate.
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  • Network-Coding-Aware Link Adaptation for Wireless Broadcast Transmission

    Jawad Manssour   Jinfeng Du  

    We present a network-coding-aware link adaptation scheme for wireless broadcast transmission; which can achieve significantly higher throughput compared to schemes which always ensure correct decoding by the weakest link receiver. We evaluate the performance for the broadcast phase of a twoway relay channel based on average SNR feedback. If dynamic switch between the bit-wise XOR network coding scheme and the generalized multiplicative network coding is allowed; a less than 1% throughput loss compared to ideal network coding can be achieved in most SNR regions; and a less than 6% throughput loss can be guaranteed regardless of link asymmetry.
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  • Cooperative Network Coding Strategies for Wireless Relay Networks with Backhaul

    Jinfeng Du   Ming Xiao   Mikael Skoglund  

    We investigate cooperative network coding strategies for relay-aided two-source two-destination wireless networks with a backhaul connection between the source nodes. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding schemes, namely, finite field and linear network coding, and lattice coding. To further exploit the backhaul connection, we also propose network coding based beamforming. We measure the performance in term of achievable rates over Gaussian channels, and observe significant gains over benchmark schemes. We derive the achievable rate regions for these schemes and find the cut-set bound for our system. We also show that the cut-set bound can be achieved by network coding based beamforming when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains.
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  • Clinical efficacy and safety comparison of HA280 and DNA230 immunoadsorption column in treating systemic lupus erythematosus

    Shu Li;Haina Gan;Jinwei Chen;Fen Li;Jinfeng Du;Guanhui Ling;The Second Xiangya Hospital of Central South University;  

    Objective: The aim of this study was to compare the efficacy and safety of HA280 and DNA230 immunoadsorption(IA) column in treating patients with systemic lupus erythematosus(SLE).Methods: We performed a one–center cohort retrospective analysis of seventy-three patients with moderate or severe SLE including 15 patients in the HA280 column group, 20 patients in the DNA230 column group and 38 patients in the drug control group.The clinical efficacy, adverse reactions and the costs of the three groups were compared.Results: There were no statistical difference in the baseline characteristics between the three groups. After IA treatment, the 24 h Upr, ESR, CRP, immunoglobulins level and SLEDAI score, anti-ANA titer, anti-ds-DNA titer decreased more significantly and C3 level increased more significantly than the drug control group(P <0.05); The efficiency in improving patients' symptoms, lowering ESR, CRP, 24 h Upr, IgG level, and SLEDAI score, ANA antibody titer and improve the C3 level simultaneously of two IA column groups were similar(P > 0.05). The efficiency in clearing anti-ds-DNA antibody of HA280 group were significantly less better than that of DNA230 group(P <0.05), while the hospitalization cost of HA280 group was significantly less than that of DNA230 group(P <0.05); the incidence of adverse events of two immunoadsorption groups was similar(P >0.05).Conclusions: Both HA280 column group and DNA230 column group have good clinical efficacy and safety in the treatment of moderate or severe SLE patients. However, the efficiency in clearing anti-ds-DNA autoantibody was more in DNA230 group than HA280 group, while the hospitalization cost of HA280 group was significantly less than that of DNA230 group. In clinical practice, we should choose individualized treatment plan and select the best IA methods according to disease severity and economic condition of patient.
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  • Pulse Shape Adaptation and Channel Estimation in Generalised Frequency Division Multiplexing Systems

    Jinfeng Du  

    Orthogonal Frequency Division Multiplexing (OFDM) is well known as an efficient technology for wireless communications and is widely used in many of the current and upcoming wireless and wireline communication standards. However; it has some intrinsic drawbacks; e.g.; sensitivity to the inter-carrier interference (ICI) and high peak-to-average power ratio (PAPR). Additionally; the cyclic prefix (CP) is not spectrum efficient and fails when the channel delay spread exceeds the length of CP; which will result in inter-symbol interference (ISI). In order to combat or alleviate these drawbacks various techniques have been proposed; which can be categorised into two main classes: techniques that keep the structure of OFDM and meanwhile increase the system robustness or re-organise the symbol streams on each sub-carrier; and techniques that increase the ISI/ICI immunity by adopting well designed pulse shapes and/or resorting to general system lattices. The latter class are coined as Generalised FDM (GFDM) throughout this thesis to distinguish with the former class. To enable seamless handover and efficient usage of spectrum and energy; GFDM is expected to dynamically adopt pulse shapes that are optimal in doubly (time and frequency) dispersive fading channels. This is however not an easy task as the method of optimal pulse shape adaptation is still unclear; let alone efficient implementation methods. Besides; performance of GFDM highly depends on the channel estimation quality; which is not straightforward in GFDM systems. This thesis addresses; among many other aspects of GFDM systems; measures of the time frequency localisation (TFL) property; pulse shape adaptation strategy; performance evaluation and channel estimation. We first provide a comparative study of state-of-the-art GFDM technologies and a brief overview of the TFL functions and parameters which will be used frequently in later analysis and discussion. A framework for GFDM pulse shape optimisation is formulated targeting at minimising the combined ISI/ICI over doubly dispersive channels. We also propose a practical adaptation strategy utilising the extended Gaussian functions (EGF) and discuss the trade-off between performance and complexity. One realisation under the umbrella of GFDM; namely OFDM/OQAM; is intensively studied and an efficient implementation method by direct discretisation of the continuous time model has been proposed. Besides; a theoretical framework for a novel preamble-based channel estimation method has been presented and a new preamble sequence with higher gain is identified. Under the framework; an optimal pulse shape dependent preamble structure together with a suboptimal but pulse shape independent preamble structure have been proposed and evaluated in the context of OFDM/OQAM.
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  • Urban land market and land-use changes in post-reform China: A case study of Beijing

    Jinfeng Du   Jean-Claude Thill   Richard B. Peiser   Changchun Feng  

    Highlights • Land use changed dramatically in post-reform Beijing from 1992 to 2008. • Cultivated land more than halved while two types of urban built land doubled. • Land price, cultivated land availability and location are significant dynamic factors. • Land reforms affected the spatial–temporal dynamics of land use changes. • Conformity of land price mechanism with reform goals depends on land use types. Abstract China launched an ambitious urban land-use reform to improve land-use efficiency, raise funds for infrastructure construction, and facilitate foreign investment in the late 1980s. Few studies have systematically evaluated the effects of the market mechanisms on land-use changes in Chinese cities. This paper takes the city of Beijing as a case study to quantify the magnitude of land-use changes and model it in relation to spatial and market drivers through time and across the metropolitan region. The analysis uses unique district-level land survey data from 1992, 1996, 2001, 2004 and 2008, as well as land granting records. Analysis reveals that, since the urban land market was established in 1992, the spatial pattern of land uses has changed dramatically in Beijing, land price has exerted a significantly influence on land-use conversion, and the municipal recognition of an open market for land assets has set the spatial–temporal pattern of land uses on a course that sharply differs from past trends in Beijing.
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  • Cross-layer design of network-coded transmission with a delay constraint

    Jinfeng Du   David C. Adams   Muriel Médard  

    We investigate the cross-layer design of wireless networks where end-to-end data transmission is subject to delay constraint and there is no end-to-end feedback. The transmission is coded by random linear network coding (RLNC) on packet level to recover from packet erasures and by forward error-correction coding (FEC) on bit level to combat channel distortions. Based on the two-layer model developed by Adams et al. where the end-to-end coded transmission is characterized by a throughput-reliability function, we formulate the cross-layer design as a goodput optimization problem relax the integrality constraint. We show that for single-hop transmissions there exists a globally optimal operating point for the relaxed problem. For multiple-hop transmissions, the goodput function is component-wise concave with respect to the physical layer data rate over each individual link.
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  • Novel Preamble-Based Channel Estimation for OFDM/OQAM Systems

    Jinfeng Du   Svante Signell  

    OFDM/OQAM has been considered as an attractive alternative to classic OFDM with cyclic prefix (CP) over doubly dispersive channels. By utilising well designed pulse shapes and removing CP; OFDM/OQAM has the advantage of reduced outof-band energy and a theoretically higher spectral efficiency. However; channel estimation over doubly dispersive channels has been a big problem for OFDM/OQAM due to the nonorthogonality between the real and imaginary parts of its modulated signals. Therefore conventional channel estimation (CE) methods used for OFDM cannot be directly applied to OFDM/OQAM. Recently a preamble-based CE method interference approximation method (IAM) has been proposed to ease this task. By treating the intrinsic interference from neighbour symbols as known information; two heuristic preamble sequences have been constructed based on tentative observations; which turn out to be suboptimal. In this paper; we present a general theoretical framework for IAM preamble design and apply it to identify the optimal IAM preamble sequence which results in a higher gain. Numerical results have verified the effectiveness of the theoretical framework and a gain of 2.4 dB against CPOFDM has been demonstrated with the new preamble in various doubly dispersive channels with a QPSK modulation.
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  • PAX3 inhibits β-Tubulin-III expression and neuronal differentiation of neural stem cell

    Sixian Cao   Jinfeng Du   Yan Lv   Hengrong Lin   Zuming Mao   Man Xu   Mei Liu   Yan Liu  

    Abstract PAX3 functions at the nodal point in neural stem cell maintenance and differentiation. Using bioinformatics methods, we identified PAX3 as a potential regulator of β-Tubulin-III (TUBB3) gene transcription, and the results indicated that PAX3 might be involved in neural stem cell (NSC) differentiation by orchestrating the expression of cytoskeletal proteins. In the present study, we reported that PAX3 could inhibit the differentiation of NSCs and the expression of TUBB3. Further, using luciferase and electrophoretic mobility shift assays, we demonstrated that PAX3 could bind to the promoter region of TUBB3 and inhibit TUBB3 transcription. Finally, we confirmed that PAX3 could bind to the promoter region of endogenous TUBB3 in the native chromatin of NSCs. These findings indicated that PAX3 is a pivotal factor targeting various molecules during differentiation of NSCs in vitro . Highlights • PAX3 expression is negatively correlated with the TUBB3 expression. • PAX3 inhibits the neuronal differentiation characterized with TUBB3 expression. • PAX3 binds the promoter region of TUBB3 gene and inhibit the TUBB3 transcription.
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