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Fast frequency-domain equalization for single-carrier V-BLAST systems over multipath channel

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Science in China(Series F) 2009年第1期52卷 115-125页

作者： FENG ang YIN QinYe FAN JianCun School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710049 China

A low complex minimum mean-square error frequency-domain decision feedback （MMSE-FDDF） equalization algorithm is proposed in this paper for the single-carrier V-BLAST systems. Exploiting the factor that the discrete Fourier transform （DFT） is unitary, the proposed receiver can equalize the signals by the MMSE detecting to the spectrums in the frequency domain instead of the waveforms in the time domain. In order to obtain the right decisions, the detector must be able to equalize the overall spectrum with regard to each layer. This work can be performed very efficiently since the system matrix has been designed as a special block-circulant-block matrix. Similar to other V-BLAST-like systems, the detecting order has strong impact on the performance of MMSE-FDDF. Therefore, we further give a fast optimally sorting scheme for the MMSE-FDDF architecture. By using the newly constructed matrix, the coefficients computation and the sorting can be combined into one process, and then we employ the modified Gram-Schmidt （MGS） to simplify the process. The simulation results and the computational complexity analysis show that the proposed MMSE-FDDF has better tradeoff between the performance and the complexity than the existing algorithms. In addition, MMSE-FDDF can avoid the performance floor caused by the overlap-and-save technique in the severe dispersive channel.

关键词： single-carrier orthogonal frequency division multiplexing frequency domain equalization V-BLAST ordering Cholesky decomposition

Precise Large Deviations for Sums of Claim-size Vectors in a Two-dimensional Size-dependent Renewal Risk Model

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Acta Mathematicae Applicatae Sinica 2021年第3期37卷 539-547页

作者： Ke-ang FU Xin-mei SHEN Hui-jie LI Department of Statistics Zhejiang University City CollegeHangzhou 310015China School of Mathematical Sciences Dalian University of TechnologyDalian 116024China Shunfeng Express Shanghai 200120China

Consider a two-dimensional renewal risk model,in which the claim sizes{Xk;k≥1}form a sequence of *** of a non-negative random vector whose two components are *** that the claim sizes and inter-arrival times form a sequence of *** pairs,with each pair obeying a dependence structure via the conditional distribution of the inter-arrival time given the subsequent claim size being *** a precise large-deviation formula of the aggregate amount of claims is obtained.

关键词： consistent variation extended regular variation large deviations size-dependence two-dimensional risk model

Graphical password： prevent shoulder-surfing attack using digraph substitution rules

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Frontiers of Computer Science 2017年第6期11卷 1098-1108页

作者： Lip Yee POR Chin Soon KU Amanul ISLAM Tan Fong ang Department of Computer Science and Information Technology University of Malaya Kuala Lumpur 50603 Malaysia Department of Computer Science Universiti Tunku Abdul Rahman (Jalan Universiti) Kampar 31900 Malaysia

In this paper, a new scheme that uses digraph substitution rules to conceal the mechanism or activity re- quired to derive password-images is proposed. In the pro- posed method, a user is only required to click on one of the pass-image instead of both pass-images shown in each chal- lenge set for three consecutive sets. While this activity is sim- ple enough to reduce login time, the images clicked appear to be random and can only be obtained with complete knowl- edge of the registered password along with the activity rules. Thus, it becomes impossible for shoulder-surfing attackers to obtain the information about which password images and pass-images are used by the user. Although the attackers may know about the digraph substitution rules used in the pro- posed method, the scenario information used in each chal- lenge set remains. User study results reveal an average login process of less than half a minute. In addition, the proposed method is resistant to shoulder-surfing attacks.

关键词： graphical password authentication shoulder-surfing data and computer security digraph substitution rules

Giant piezoresponse and promising application of environmental friendly small-ion-doped znO

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Science China(Technological Sciences) 2012年第2期55卷 421-436页

作者： PAN Feng LUO JingTing ang YuChao Wang XuBo zENG Fei Key Laboratory of Advanced Materials Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

In recent years, with the growing concerns on environmental protection and human health, new materials, such as lead-free piezoelectric materials, have received increasing attention. So far, three types of lead-free piezoelectric systems have been widely researched, i.e., perovskites, bismuth layer-structured ferroelectrics, and tungsten-bronze type ferroelectrics. This article presents a new type of environmental friendly piezoelectric material with simple structure, the transition-metal（TM）-doped znO. Through substituting zn2＋ site with small size ion, we obtained a series of TM-doped znO with giant piezoresponse, such as zno.975Vo.o250 of 170 pC/N, zn0.94Cr0.06O of 120 pC/N, zn0.913Mn0.0870 of 86 pC/N and zn0.988Fe0.0120 of 127 pC/N. The tremendous piezoresponses are ascribed to the introduction of switchable spontaneous polarization and high permittivity in TM-doped znO, The microscopic origin of giant piezoresponse is also discussed. Substitution of TM ion with small ionic size for zn2＋ results in the easier rotation of noncollinear TM-O1 bonds along the c axis under the applied field, which produces large piezoelectric displacement and corresponding piezoresponse enhancement. Furthermore, it proposes a general rule to guide the design of new wurtzite semiconductors with enhanced piezoresponses. That is, TM-dopant with ionic size smaller than zn2＋ substitutes for zn2＋ site will increase the piezoresponse of znO significantly. Finally, we discuss the improved per- formances of some TM-doped znO based piezoelectric devices.

关键词： znO lead-free piezoelectric doping modification piezoresponse enhancement

Sound velocity in dense stellar matter with strangeness and compact stars

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Chinese Physics C 2021年第5期45卷 237-246页

作者： Chengjun Xia zhenyu zhu Xia zhou ang Li School of Information Science and Engineering Zhejiang University Ningbo Institute of Technology.Ningbo 315100 China Department of Astronomy Xiamen UniversityXiamen 361005China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China

The phase state of dense matter in the intermediate density range(~1-10 times the nuclear saturation density)is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron *** matter density increases in compact stars,the sound velocity is expected to approach the con-formal limit(cs/c=1/√3)at high densities and should also fulfill the causality limit(cs/c<1).However,its de-tailed behavior remains a prominent topic of *** was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition,where a particular shape might be expected for its density *** this work,we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark *** conditions are employed for the had-ron-quark phase transition with varying interface *** find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase,in addition to a deconfinement phase ***,it leads to a more compact star with a similar *** then propose a new class of quark star equation of states,which can be tested by future high-precision radius measurements of pulsar-like objects.

关键词： quark matter hadron-quark phase transition neutron star

Bound states in the continuum based on the total internal reflection of Bloch waves

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National Science Review 2023年第1期10卷 178-186页

作者： Peng Hu Chongwu Xie Qianju Song ang Chen Hong Xiang Dezhuan Han Jian zi College of Physics Chongqing University State Key Laboratory of Surface Physics Key Laboratory of Microand Nano-Photonic Structures (Ministry of Education) and Department of Physics Fudan University Chongqing Key Laboratory for Strongly Coupled Physics

A photonic-crystal slab can support bound states in the continuum(BICs) that have infinite lifetimes but are embedded into the continuous spectrum of optical modes in free *** formation of BICs re quires a total internal reflection(TIR) condition at both interfaces between the slab and the free ***,we show that the TIR of Bloch waves can be directly obtained based on the generalized Fresnel equations *** each of these Bloch waves picks up a phase with integer multiples of 2π for traveling a round trip,light can be perfectly guided in the slab,namely forming a BIC.A BIC solver with low computational complexity and fast convergence speed is developed,which can also work efficiently at high frequencies beyond the diffraction limit where multiple radiation channels *** examples of multi-channel BICs are shown and their topological nature in momentum space is also *** can be attributed to the coincidence of the topological charges of far-field radiations from different radiation *** concept of the generalized TIR and the TIR-based BIC solver developed offer highly effective approaches for explorations of BICs that could have many potential applications in guided-wave optics and enhanced light-matter interactions.

关键词： bound states in the continuum total internal reflection Bloch waves generalized Fresnel equations topological charges

Holocene Climate Cycles in Northwest Margin of Asian Monsoon

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Chinese Geographical Science 2012年第4期22卷 450-461页

作者： LI Yu Wang Nai'ang LI zhuolun zHOU Xuehua z.ang Chengqi College of Earth and Environmental Sciences Center for Hydrologic Cycle and Water Resources in Arid RegionLanzhou UniversityLanzhou 730000China

In the mid-latitude regions of the Asian continent, zhuye Lake is located in the northwest margin of the Asian monsoon, where the modem climate is affected by the Asian monsoon and Westerlies. In this study, we investi- gated the absolutely dated Holocene records in zhuye Lake for detecting the Holocene climate cycles. Totally, 14 14C dates and 6 optically simulated luminescence （OSL） dates are obtained from the QTH01 and QTH02 sections. The proxies of grain-size, total organic carbon content （TOC）, C/N and 813C are used for wavelet analysis, and the results show obvious -256, -512 and -1024-year climate cycles, which are consistent with the Holocene millennial and cen- tennial scale climate cycles in the typical Asian summer monsoon domain. In different parts of the zhuye Lake, the Holocene sediments show variable climate cycles that are affected by the lake basin topography. In the zhuye Lake, the Holocene climate cycles are mainly correlated with the solar-related Asian summer monsoon variability and the North Atlantic ice-rafting events.

关键词： Holocene climate cycle Asian monsoon wavelet analysis zhuye Lake

Quantile Regression for Thinning-based INAR(1)Models of Time Series of Counts

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Acta Mathematicae Applicatae Sinica 2021年第2期37卷 264-277页

作者： Dan-shu SHENG De-hui Wang Kai Yang zi-ang WU School of Mathematics Jilin UniversityChangchun 130012China School of Economics Liaoning UniversityShenyang 110036China School of Mathematics and Statistics Changchun University of TechnologyChangchun 130012China

In this paper,we develop the quantile regression(QR)estimation for the first-order integer-valued autoregressive(INAR(1))models by defining the smoothing INAR(1)*** method is used to derive the QR estimators for the autoregressive coefficient and the quantile of *** consistency and asymptotic normality of the proposed estimators are *** performances of the proposed estimation procedures are evaluated by Monte Carlo *** results show that the proposed procedures perform well for simulations and a real data application.

关键词： INAR(1)process quantile regression parameter estimation jittering

Stable isotope analysis of water sources for Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China

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Journal of Arid Land 2018年第6期10卷 821-832页

作者： z.ang Jinhu Wang Nai'ang NIU zhenmin SUN Jie DONG Chunyu z.ang LyuLyu College of Earth and Environmental Sciences Lanzhou University State Key Laboratory Breeding Base of Gansu Desertification and Aeolian Sand Disaster Combating Gansu Desert Control Research Institute Department of Geography University of California

The complex interactions in desert ecosystems between functional types and environmental conditions could be reflected by plant water use patterns. However, the mechanisms underlying the water use patterns as well as the water sources of Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China, remain unclear. This study investigated the water sources and water use patterns of T. laxa using the stable oxygen isotope method. The δ18O values of xylem water, soil water in different layers(0–200 cm), rainwater, snow water, lake water, atmospheric water vapor, condensate water, and groundwater were measured. The sources of water used by T. laxa were determined using the IsoSource model. The results indicate that T. laxa mainly relies on soil water. At the beginning of the growing season(in May), the species is primarily dependent on water from the middle soil layer(60–120 cm) and deep soil layer(120–200 cm). However, it mainly absorbs water from the shallow soil layer(0–60 cm) as the rainy season commences. In September, water use of T. laxa reverts to the deep soil layer(120–200 cm). The water use patterns of T. laxa are closely linked with heavy precipitation events and soil water content. These findings reveal the drought resistance mechanisms of T. laxa and are of significance for screening species for ecological restoration.

关键词： stable oxygen isotope water source water use pattern soil water stem water mega-dune Tamarix laxa