二维趋化-流体系统的整体适定性

在无通量-Dirichlet-无滑移边界条件下考虑一类趋化-流体系统的二维初边值问题。通过正则化处理和一系列的先验估计证明该系统存在整体有界的经典解。

一体化预制泵站应用于市政道路地下通道案例分析及探讨

一体化预制泵站可工厂组装和预制,具有自身系统集成度高、施工工期短、运维成本低、易与周围环境融合等优点,是高效增益的给排水加压设备。结合南昌市东站北路下穿地下通道工程实例,阐述一体化预制泵站应用于市政道路地下通道雨水提升排放时,设计中各要素如汇水面积、降雨历时、径流系数等的计算或选定,采用“设计-校核”“公式-模型”双重验算的方式,计算校核设计雨水量,探索下穿通道一体化排水泵站方案并对其安全性进行讨论。

A Study of Human-Land Linking Policy Based on Urbanization Away from Home: A Case Study of Anhui Province

This paper analyzes the features and trends of urbanization away from home in Anhui Province,and believes that the cross-city floating population in the province shows a expanding scale,and dual cores of the province has obvious attractiveness. This paper also analyzes the relations between urban-rural construction land and urban-rural population transformation in the province,and expounds the possibility and necessity of carrying out human-land linking policy northern Anhui-Wanjiang. Based on the factors affecting human-land linking policy,this paper recommends that we should establish cross-regional trading policy system for land development rights in Anhui Province from four key links( urban entry,urban integration,rural exit,common urban-rural development),in order to effectively promote migrant workers' citizenization.

Survey on Germplasm Resources of Araliaceae Plants in Southeastern Tibet and Study on Their Landscape Application

In recent years,the Araliaceae plants have been widely used in the planning of urban garden and road green space. China is rich in Araliaceae plant resources and Araliaceae plants are outstanding in form,but their ornamental value is less studied. Through the statistical survey of the germplasm resources of Araliaceae plants in southeastern Tibet,and the research and analysis of their functions and ornamental characteristics,this paper concluded that the Araliaceae plants in southeastern Tibet have high ornamental value,and 12 varieties of Araliaceae plants can be used in gardens and have great research and development significance. Finally,it came up with recommendations for the collection and protection,introduction and breeding,and garden application of Araliaceae plant resources.

Investigation of Habitats and Causes of Population Decline of Euonymus sanguineus in Tibet

Tibet is one of the core distribution areas of the Chinese endemic plant Euonymus sanguineus,but the population decline is obvious. In order to protect and develop the plant resources in Tibet rationally,the ecological environment and growth conditions in Milin County,Nyingchi City,Tibet were investigated by means of sampling method in order to provide the theoretical basis for the protection,introduction,breeding and cultivation of E. sanguineus. The results were as follows:( i) The population quantity of E. sanguineus was too small and the survival area was too small,which seriously affected the interspecific mating,seed development and regeneration,and greatly reduced the genetic diversity within the population;( ii) The dry and hot river valley climate and human and animal activities inhibited the seed germination and seedling growth of E. sanguineus,resulting in very low survival rate of seedlings,and hindering the population expansion of E. sanguineus;( iii) The distribution area is located in the Yarlung Tsangpo river valley,and the natural habitat fragmentation has affected the interspecific gene exchange,resulting in the low seed bearing capacity and germination rate of E. sanguineus,which is the direct cause of the population decline of E. sanguineus;( iv) The litterfall of E. sanguineus had autotoxicity,which inhibited the growth of seedlings under the forest,caused slow natural regeneration of the population,and then caused the population of E. sanguineus to be unable to spread and develop.

Investigation of the Mechanism of Tangent Bifurcation in Current Mode Controlled Boost Converter

Tangent bifurcation is a special bifurcation in nonlinear dynamic systems. The investigation of the mechanism of the tangent bifurcation in current mode controlled boost converters operating in continuous conduction mode (CCM) is performed. The one-dimensional discrete iterative map of the boost converter is derived. Based on the tangent bifurcation theorem, the conditions of producing the tangent bifurcation in CCM boost converters are deduced mathematically. The mechanism of the tangent bifurcation in CCM boost is exposed from the viewpoint of nonlinear dynamic systems. The tangent bifurcation in the boost converter is verified by numerical simulations such as discrete iterative maps, bifurcation map and Lyapunov exponent. The simulation results are in agreement with the theoretical analysis, thus validating the correctness of the theory.

Effects of different types of biochar on the properties and reactivity of nano zero-valent iron in soil remediation

The addition of nano zero-valent iron(nZVI)is a promising technology for the in situ remediation of soil.Unfortunately,the mobility and,consequently,the reactivity of nZVI particles in contaminated areas decrease due to their rapid aggregation.In this study,we determined how nZVI particles can be stabilized using different types of biochar(BC)as a support(BC@nZVI).In addition,we investigated the transport behavior of the synthesized BC@nZVI particles in a column filled with porous media and their effectiveness in the removal of BDE209(decabromodiphenyl ether)from soil.The characterization results of N2 Brunauer-Emmett-Teller(BET)surface area analyses,scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)indicated that nZVI was successfully loaded into the BC.The sedimentation test results and the experimental breakthrough curves indicated that all of the BC@nZVI composites manifested better stability and mobility than did the bare-nZVI particles,and the transport capacity of the particles increased with increasing flow velocity and porous medium size.Furthermore,the maximum concentrations of the column effluent for bagasse-BC@nZVI(B-BC@nZVI)were 19%,37%and 48%higher than those for rice straw-BC@nZVI(R-BC@nZVI),wood chips-BC@nZVI(W-BC@nZVI)and corn stalks-BC@nZVI(C-BC@nZVI),respectively.A similar order was found for the removal and debromination efficiency of decabromodiphenyl ether(BDE209)by the aforementioned particles.Overall,the attachment of nZVI particles to BC significantly increased the reactivity,stability and mobility of B-BC@nZVI yielded,and nZVI the best performance.

Photothermal performance of MFe2O4 nanoparticles

Photothermal therapy(PTT) has emerged as one of the promising cancer therapy approaches.As a representative photothermal agent(PTA),magnetite possesses many advantages such as biodegradability and biocompatibility.However,photothermal instability hampers its further application.Herein,we systematically synthesized three kinds of ferrite nanoparticles and detailedly investigated their photothermal effect.Compared with Fe304 and MnFe2 O4 nanoparticles,ZnFe2 O4 nanoparticles exhibited a superior photothermal effect.After preservation for 70 days,the photothermal effect of Fe304 and MnFe2 O4 nanoparticles observably declined while ZnFe2 O4 nanoparticles showed slight decrease.Furthermore,in vitro experiment,ZnFe2 O4 nanoparticles showed little toxicity to cells and achieved outstanding effect in killing cancer cells under NIR laser irradiation.Overall,through synthesizing and studying three kinds of ferrite MFe2 O4 nanoparticles,we obtained ferrites as PTAs and learned about their changing trend in photothermal effect,expecting it can inspire further exploration of photothermal agents.

A novel 3780-point FFT processor scheme for the time domain synchronous OFDM system

The 3780-point FFT is a main component of the time domain synchronous OFDM （TDS-OFDM） system and the key technology in the Chinese Digital Multimedia/TV Broadcasting-Terrestrial （DMB-T） national standard. Sinc, e 3780 is not a power of 2, the classical radix-2 or radix-4 FFT algorithm cannot be applied directly. Hence, the Winograd Fourier transform algorithm （WFTA） and the Good-Thomas prime factor algorithm （PFA） are used to implement the 3780-point FFT processor. However, the structure based on WFTA and PFA has a large computational complexity and requires many DSPs in hardware implementation. In this paper, a novel 3780-point FFT processor scheme is proposed, in which a 60x63 iterative WFTA architecture with different mapping methods is imported to replace the PFA architecture, and an optimized CoOrdinate Rotation Digital Computer （CORDIC） module is used for the twiddle factor multiplications. Compared to the traditional scheme, our proposed 3780-point FFT processor scheme reduces the number of multiplications by 45% at the cost of 1% increase in the number of additions. All DSPs are replaced by the optimized CORDIC module and ROM. Simulation results show that the proposed 3780-point FFT processing scheme satisfies the requirement of the DMB-T standard, and is an efficient architecture for the TDS-OFDM system.

On detecting primary user emulation attack using channel impulse response in the cognitive radio network

Cognitive radio is an effective technology to alleviate the spectrum resource scarcity problem by opportunistically allocating the spare spectrum to unauthorized users. However, a serious denial-of-service(DoS) attack,named the ‘primary user emulation attack(PUEA)', exists in the network to deteriorate the system performance. In this paper, we propose a PUEA detection method that exploits the radio channel information to detect the PUEA in the cognitive radio network. In the proposed method, the uniqueness of the channel impulse response(CIR) between the secondary user(SU) and the signal source is used to determine whether the received signal is transmitted by the primary user(PU) or the primary user emulator(PUE). The closed-form expressions for the false-alarm probability and the detection probability of the proposed PUEA detection method are derived. In addition, a modified subspace-based blind channel estimation method is presented to estimate the CIR, in order for the proposed PUEA detection method to work in the scenario where the SU has no prior knowledge about the structure and content of the PU signal. Numerical results show that the proposed PUEA detection method performs well although the difference in channel characteristics between the PU and PUE is small.

Funneling media access control (MAC) protocol for underwater acoustic sensor networks

Due to the characteristics of the underwater acoustic channel, such as long propagation delay and low available bandwidth, the media access control (MAC) protocol designed for underwater acoustic sensor networks (UWASNs) is quite different from that for terrestrial wireless sensor networks. In this paper, we propose a MAC protocol for the UWASNs, named the funneling MAC (FMAC-U), which is a contention-based MAC protocol with a three-way handshake. The FMAC-U protocol uses an improved three-way handshake mechanism and code division multiple access (CDMA) based technology for request-to-send (RTS) signals transmitting to the sink in order that the sink can receive packets from multiple neighbors in a fixed order during each round of handshakes. The mechanism reduces the packet collisions and alleviates the funneling effect, especially alleviating the choke point of the UWASNs. Simulation results show that the proposed FMAC-U protocol achieves higher throughput, smaller packet drop ratio, lower end-to-end delay, and lower overhead of the control packet compared to the existing MAC protocols for UWASNs.

Retransmission in the network-coding-based packet network

In this paper, retransmission strategies of the network-coding-based packet network are investigated. We propose two retransmission strategies, the packet-loss-edge-based retransmission strategy (PLERT) and the minimum retransmission strategy (MRT), which focus on optimizing the retransmission efficiency without the constraint on the encoding field size. We compared the performances of the proposed retransmission strategies with the traditional automatic repeat-request (ARQ) strategy and the random retransmission strategy. Simulation results showed that the PLERT strategy works well when the packet loss rate is small. Among these retransmission strategies, the performance of the MRT strategy is the best at the cost of the high complexity that is still polynomial. Furthermore, neither of the proposed strategies is sensitive to the encoding field size.

A Dedicated MAC Protocol Package for Real-Time Ocean Current Field Estimation Using Distributed Underwater Acoustic Sensor Networks

Distributed underwater acoustic sensor networks(UASNs)are envisioned in real-time ocean current velocity estimation.However,UASNs at present are still dominated by post-processing partially due to the complexity of on-line detection for travel times and lack of dedicated medium access control(MAC)protocols.In this study,we propose a dedicated MAC protocol package for real-time ocean current velocity estimation using distributed UASNs.First,we introduce the process and requirements of ocean current velocity estimation.Then,we present a series of spatial reuse time division multiple access(TDMA)protocols for each phase of real-time ocean current field estimation using distributed UASNs,followed by numerical analysis.We divide UASNs into two categories according to their computing ability:feature-complete and feature-incomplete systems.The feature-complete systems that have abundant computing ability carry out the presented MAC protocol package in three phases,whereas the feature-incomplete ones do not have enough computing ability and the presented MAC protocol package is reduced to two phases plus an additional downloading phase.Numerical analysis shows that feature-complete systems using mini-slot TDMA have the best real-time performance,in comparison with feature-incomplete systems and other feature-complete counterparts.Feature-incomplete systems are more energy-saving than feature-complete ones,owing to the absence of in-network data exchange.

Design, fabrication, and characterization of a hydrostatic electroactive soft actuator for bio-inspired robots

In this paper,we design a hydrostatic electroactive soft actuator(HESA)inspired by octopus transverse musculature.We introduce the advantage of laser processing technology in HESA fabrication compared with existing similar actuators and discuss the effect of laser processing on the outer membrane of the actuator.In addition,a mathematical model is established for the single channel of the actuator,and the geometric parameters of the actuator are optimized by mathematical model simulation and experiments.We demonstrate the motion effect of the actuator.Our experiments show that the single piece of the actuator can achieve 32.2%strain in the axial direction and 7.8%strain in the radius direction.Furthermore,we stack three actuators together and describe their motion characteristics at different frequencies.The stacked actuators can realize axial elongation,radial shrinkage,and bend,which covers all the motion modes of the octopus biological transverse musculature.This study may lay a foundation for implementing the biomimetic soft actuator mimicking the octopus’s transverse musculature,which is one less discussed but crucial muscular composition in the octopus-inspired arm research.