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In this paper, a pulse-modulated Mach–Zehnder interferometer (MZI) is proposed for vibration location with high accuracy. In the system, the continuous wave light is modulated into periodic pulse sequences, and each pulse sequence is consisted of a certain number of narrow pulses. Then, the pulse modulated light is injected into the interferometric structure. The envelope of interference intensity is perturbed by the external vibration, which could offer the information of vibration position by means of locating the first affected interference pulse in a sequence. The experimental results demonstrate that the vibration location error is within the range of ± 9 m under 20 ns pulse width, which proves the effectiveness of the proposed method.

Riparian ecosystems associated with dam reservoirs, are subjected to a wide variety of stressors that alter their plant community composition and diversity patterns and affect riparian ecosystem services delivery. To enhance riverine and regional ecosystem management, the different influences of dam-induced environmental change and anthropogenic factors within and around the reservoir need to be understood across multiple scales. To elucidate the relative importance of these factors, this study examines riparian vegetation composition and structure along the Three Gorges Reservoir (China) and their responses to surrounding landscapes, habitat quality and reservoir management (three groups of influences). We recorded vegetation data in 5 × 1 m quadrats embedded in three stratified elevational zones 145–155 m, 155–165 m, and 165–175 m. Correspondence analyses were used to partition the contribution of various influences in explaining vegetation patterns at three organisational scales: site, community and individual species. Vascular plants totaled 150 species in 130 genera from 56 families. Overall, vegetation responses were idiosyncratic across the analysed scales. At the site-scale, landscape was most important in structuring communities. However, localised habitat and reservoir flooding influences have higher explanatory power at the community-scale, regardless of elevational divergence. Overall, there seem to be a general trend in the importance of variables across all analysed scales. Among the landscape factors, variables based on a landscape gradient model were much more influential than those based on the conventional patch mosaic model. Given the heavily inter-correlated nature of many variables at varying scales of human altered landscapes, the best way forward for reservoir riparian vegetation management strategies is to develop multi-scale, synthetic and location-specific approaches that may optimise conservation efforts.

Boolean chaos generated by autonomous Boolean networks has been successfully applied to random number generation, physical unclonable function, gene regulation and reservoir computing, because it can generate complex dynamics with very simple structure. Influences of noise on autonomous Boolean networks chaotic system in delay time parameter spaces are analyzed by simulation and experiments in this article. It is found that the influences of noise on Boolean chaotic system is two-sided. What is new is that noise may lead to chaos instability, i.e., the noise transforms the original chaotic outputs into periodic outputs, which means the Boolean chaos lacks robustness to noise. Then like other chaotic systems noise contributes to Boolean chaotic unpredictability. The physical origin of noise induced Boolean chaos instability is analyzed that noise may easily change delay time parameter no longer a chaotic parameter in discontinuous chaotic parameter spaces. In addition, simulation and experiments on FPGA show that the increase of the number of nonlinear elements of the chaotic system can improve the Boolean chaos robustness to noise. This research is significant to the design of autonomous Boolean networks.

Urban green spaces (UGS) are vital for developing and evolving natural elements in urban spaces. The UGS information of a megacity behemoth (Shanghai) from 1996, 2006, and 2016, and a small and medium-sized city (Xuchang) from 2010, 2015, and 2019 was used as the basic data. The UGS evolution spatiotemporal characteristics were analyzed using the area change index, spatial morphological dimension, and spatial aggregation dimension. The changes of greening policies for UGS evolution in the two cities were compared. The results indicated that: (1) the UGS in downtown Shanghai mainly developed southwards from 1996 to 2006, then northeastwards and northwestwards. The UGS in downtown Xuchang mainly developed northeastwards and northwards between 2010 and 2019; (2) the spatial morphological dimensions of UGS in downtown Shanghai gradually increased indicating the UGS had systematic coordination and stability. The spatial morphological dimensions of UGS in downtown Xuchang first increased then decreased, indicating that the UGS tended to be integrated and systematic; (3) the spatial aggregation dimensions of UGS in downtown Shanghai decreased first and then increased, and the focus of UGS construction shifted from the center to the suburbs. The spatial aggregation dimensions of UGS in downtown Xuchang gradually increased, and the spatial distribution of UGS tended to be multi-center clustered; and, (4) under the guidance of greening policies, UGS evolution in Shanghai was progressive with stronger self-organization ability, while that in Xuchang leaped forward with weaker self-organization ability. The research results can provide a reference for other similar sized cities in UGS planning and government decision-making.

The newly formed extensive flooded land associated with the Three Gorges Reservoir hold great potentials to provide ecosystem services (ESs) for surrounding cities and communities. Conflicting values and conventional management strategies may complicate and inhibit broad-scale decision-making for this novel ecosystem. Public attitudes are a crucial influence in the way this process plays out. This study was conducted to assess how the reservoir bank is perceived by the general public of Chongqing Municipality in terms of importance of riparian ESs, and preference for corresponding landscape design styles through photo-questionnaire interviewing. Although Chongqing citizens know little of the “ecosystem services” concept, they do recognise riparian environmental and ecological benefits especially the bank protection and pollution interception functions, while benefits of habitats for wildlife and flood attenuation were of less concern. Recreational values were least appreciated, which is inconsistent with other studies. This may be attributed to a wider, intensive environmental education in various social media in today’s China. But publicity has been dominated by toxic air, water and soil pollution control rather than the benefits of nature conservation and personal contact with nature. In line with recognition of ESs, there is quite strong preference for the forested design scenario and particularly vegetation components across the socio-demographic spectrum. Overall, socio-demographic variables have very low explanatory power for the perceptual responses. Our study also revealed misunderstandings around riparian functions and a gap between public expectations and special abiotic and biotic prerequisites in restoring novel ecosystems. Finally, we discuss the relevance of this research to urban novel ecosystems in general, and implications for raising public awareness, engaging appropriate public values in sustainable design and management of such ecosystems.

Co-urbanized areas around large cities in developing countries face the problem of spatial disconnection between supply and demand areas of ecosystem services (ES). To explore the reflection of human needs in the nonadjacent surrounding natural spaces and identify the response of the existing natural space system to the ES demand in terms of total amount and spatial distribution, a new method for ES demand mapping in co-urbanized areas was proposed. Based on the theory of the ES delivery chain, urban built-up areas are identified as service benefiting areas (SBAs) and the sources where demands are generated, natural spaces are regarded as service provision areas (SPAs) and the sinks and destinations where demands are satisfied, and ES spatial flow is considered as the delivery mechanism and ecological process that promotes the demand flow from sources to sinks. An indicator cluster composed of four multidimensional indicators, including flow quantity, flow boundary, flow direction and allocation mode along the distance, was used to characterize the spatial flow and represent the four key links in the technical path of allocating ES demand from built-up areas to natural spaces with spatial flow to intuitively reflect the spatial characteristics of human social demands projected in them. We quantified and mapped the distribution of three ES demands in built-up areas and surrounding natural spaces. In the former, the high-demand spaces are concentrated in the areas with high population density or high aging degree; while in the latter, the high-demand spaces are mainly adjacent to the built-up areas or the large-scale natural spaces. By controlling the flow quantity, expanding the flow area, increasing the flow directions and improving the ES supply capacity of SPAs within a given distance, the high ES demands in the above spaces can be effectively regulated.

Mitigating urban heat islands in neighborhoods is one of the most important issues in landscape planning. Identifying land-use patterns with cooling effect and applying them in practice is a way to reduce neighborhoods’ temperature. However, there are relatively few relevant theoretical and practical studies at present. A combination of factors influences the thermal environment of a neighborhood. With the increasing complexity of neighborhood land-uses, the cooling effect of these factors is difficult to measure individually and need to be considered from a holistic perspective. What kinds of hybrid land-use patterns (HLPs) in neighborhoods have the cooling effect and are prone to creating cold islands? This is a big question to environmental optimization and sustainable development, and there has little discussion about it. To address this, this paper proposed a technical framework for delineating and analyzing the cooling effect of HLPs at the neighborhood scale. Taking Jinan City as an example, four indicators were selected to describe the characteristics of HLPs, including building surface ratio (BSR), green-blue space surface ratio (GBSR), impervious surface ratio (ISR), and average building height (MAH). With the K-Medoids clustering algorithm, ten HLPs were delineated, and their marginal effects were analyzed by the Boosting Regression Trees (BRT) model. The study found that HLPs dominated by high-rise buildings and by green-blue spaces had the most pronounced cooling effect; low- and mid-rise dominated HLPs showed a weak cooling effect when the mean GBSR reached 34%, and the cooling effect of green-blue space and impervious surface dominated HLPs are more obvious when the mean GBSR reached 48%. The technical framework proposed in this paper provides a new perspective on thermal environment research and heat island mitigation at the neighborhood scale, which is applicable to cities with various climatic backgrounds and landscape characteristics and of generalization value.

The widespread use of current-use pesticides (CUPs) in modern agriculture has threatened the survival of aquatic organisms. Therefore, the residual levels, spatial distribution, and ecological risk assessment of 18 CUPs are investigated in an aquatic system of Shanghai. The aquatic system focused on a freshwater system that contains particles smaller than 0.45 μm in size, which are easily absorbed by aquatic organisms. The mean values of chlorpyrifos, napropamide, and atrazine were found to be the highest concentration CUPs, and propazine, mevinphos, ametryn, butylate, dichlorvos, ethoprop, and prometryn displayed the most significant positive correlations with each other. The concentration of the ∑18CUPs was higher in the southern areas of Shanghai (generally greater than 100 ng/L), but it was relatively low in the central areas (generally smaller than 75 ng/L). Six important CUPs were identified, and the differences in the concentration contribution rates and contribution amounts among different intensive land-use types were noticeable. The ecological risk in most areas of this aquatic system of Shanghai was high. Chlorpyrifos and butachlor produced the maximum toxic unit (mTU) for daphnid and green algae, respectively, and their toxic unit contribution rates to the entire mixture toxicity were both greater than 50%. This confirms that the mixture toxicity of the CUPs to aquatic organisms in this aquatic system of Shanghai primarily resulted from a few dominant toxic pesticides. However, for each sensitive organism, there will still be a risk contribution of approximately 5%–30% due to other CUPs.

This study investigated the effects of MnFe2O4-biochar on sludge anaerobic digestion performance, methane production and heavy metal stabilization. The highest cumulative methane yield was achieved when the MnFe2O4-biochar dose was 1.50 g, which was 55.86% higher than control. A suitable dose of MnFe2O4-biochar stimulated methanogenic activities and improved methane yield, whereas excessive addition shows an inhibitory effect on anaerobic digestion. MnFe2O4-biochar addition significantly enhanced the biodegradation of organic matter, as the average volatile fatty acids degradation rate increased by 35.44%, compared to the control. Chemical speciation analyses demonstrated that MnFe2O4-biochar addition was more helpful for immobilization and risk reduction of heavy metals in sewage sludge. Simultaneously, microbial community analysis indicated that MnFe2O4-biochar obviously enriched acetoclastic methanogens Methanosarcina that capable of participating in direct interspecies electron transfer, which could accelerate substrate decomposition and methane production. These findings supply useful information for the resource utilization of sewage sludge.

Urban architecture is an important contributor to urban heat island (UHI) effects. Yet thorough investigations into how three-dimensional (3D) architectural patterns influence urban thermal conditions collectively and individually are limited. This study bridges this gap by adopting a machine learning method, boosted regression tree (BRT), to analyze the relative influences and marginal effects of 3D urban architecture on land surface temperature (LST). Ten architectural metrics are incorporated to describe the composition and configuration of 3D architectural patterns at a neighborhood scale in the typical megacity of Shanghai. The results show that in summer, the building coverage ratio (BCR), mean architecture height (MAH), mean architecture height standard deviation (AHSD) and mean architecture projection area (MAPA) are the most influential factors, with relative contributions of 39.3%, 16.5%, 12.3% and 10.4%, respectively. The regulation amplitudes (ΔT) of the dominant metrics for the neighborhood average LST temperature are 2.7 °C, 0.9 °C, 0.6 °C, and 0.6 °C, respectively. Moreover, with the LST, the BCR exhibits a monotonic positive correlation, the MAH and AHSD show a stepwise negative correlation, and the MAPA shows a combination of positive and negative correlation. It is generally recommended to decrease the development intensity and architectural base area, while increase the building height and roughness to improve the urban thermal conditions at the neighborhood scale. The dominant contributors and related marginal effects are generally consistent across different seasons. These findings can provide quantitative insights for mitigating the LST effects via rational design and management of 3D architectural patterns. Given the distinctive insights provided, the BRT method is recommended for disentangling the relationship between LST and environmental variables in upcoming studies.

We numerically analyze the chaos complexity of a semiconductor laser with chirped fiber Bragg grating (CFBG) feedback by utilizing the permutation entropy (PE). Due to dispersion-induced nonlinearity of chirped grating, the time delay signature (TDS) can be suppressed or erased and the complexity enhancement is expected. The effects of laser parameters on PE as well as the TDS are studied in detail. The results show that for CFBG feedback, the TDS can be suppressed in the range of parameters where linewidth enhancement factor exceeds 3 and gain saturation coefficient is lower than 4 × 10−4 μ m3, and the complexity of chaotic signals is enhanced. As the feedback strength and bias current increase, the PE value under CFBG feedback increases linearly to a maximum of 0.994 and remains stable. Compared with mirror feedback, CFBG feedback can achieve increased complexity over a wider range of parameters. In addition, when the dispersion value of the chirped grating exceeds 2000 ps/nm, the frequency detuning range of -15 GHz to 10 GHz is beneficial to obtain chaotic signals with higher PE values.

The “one-city monopoly” is a controversial phenomenon. This paper proposed and adopted the “one-city monopoly index” (OMI) to dynamically measure its evolution characteristics. The relationship among the OMI, urban competitiveness and unbalanced provincial development was investigated. The results show that (1) the “one-city monopoly” is a complex and bewildering phenomenon that occurs during the processes of urbanization and regional development in the central and western regions of China, and it is still needed; (2) there is a dynamic relationship between the OMI and its urban comprehensive competitiveness (UCC); and (3) the fluctuations of the “one-city monopoly” phenomenon in the primate cities of the provinces are obviously correlated with the change in the intra-provincial development gap. Therefore, on the one hand, we cannot excessively restrain the growth of a primate city under the guise of “promoting balanced regional development”. On the other hand, we should not blindly pursue the ranking of urban competitiveness but give due consideration to the balanced development of cities or regions. Primate cities are also responsible for promoting the overall economic, social, cultural and ecological development of the provinces, and higher-quality regional coordinated development can be realized by further enhancing the spillover effects of primate cities.

Compared to non-spatial calculation of service values which is not intuitive, ecosystem services (ESs) mapping are more appealing to practitioners. However, applying these representations into ecological practice is still a challenge. Such research essentially embraces fundamental and applied characteristics, which have been exemplified by “Pasteur’s Quadrant” of use-inspired basic research. Based on this instructive quadrant model, we propose an analytical framework (Problem-Research-Practice) to review 76 SCI ESs mapping articles that purport to be relevant to ecological practice. Two questions led our investigation: (1) do these studies emulate (intentionally or otherwise) Pasteur’s Quadrant by establishing a clear pathway between research and practice (e.g. particular problems, issues or needs in the real world)? (2) what challenges-cum-opportunities for ESs mapping do we observe that may overcome resistance to practical purposes? Overall, substantial gaps exist in the research capacity to produce transformative and/or readily-usable knowledge; existing efforts to map ESs generally belie the conventions of practice systems. Given that ecological practice engages with real world problems at varying scales of human activity, we suggest some possible ways forward, such as developing participatory mapping techniques and alternative indicators directly targeting human needs that may accelerate uptake of ESs mapping outcomes by practitioners.

We experimentally demonstrate 10-Gb/s message transmission using an all-optical chaotic secure communication system. In this system, a semiconductor laser subject to mirror optical feedback, operating under a high bias current, is employed as the transmitter. Owing to the high bias current, the transmitter’s relaxation oscillation frequency is greatly increased, and consequently, the carrier bandwidth of the transmitted message is also enhanced. By injecting the bandwidth-enhanced signal into an open-loop receiver, we establish a chaos synchronization with a correlation coefficient of 0.94 between the transmitter and the receiver. Based on the high-quality chaos synchronization, a 10 Gb/s message is experimentally encrypted and decrypted with a bit error ratio (BER) below 3.8 × 1 0 − 3 , i.e., the hard decision forward error correction (HD-FEC) threshold. Bit error analysis indicates that the transceiver, using chaotic decryption, has a BER below the HD-FEC threshold over a wide parameter region. In this parameter region, it is difficult for an eavesdropper using direct decryption to obtain a message with a BER below the HD-FEC threshold.

We present a real time random bit generation scheme using broadband amplified spontaneous emission noise from a super-luminescent diode (SLD) as the physical entropy source. Utilizing latch comparators, and an exclusive-or gate, we eventually demonstrate a 3 Gbit/s true random bit sequence with real waveform that can be directly applied to the communication network obtained, and its randomness satisfies all of the NIST statistical tests. Moreover, our system has the scalability so that it can generate multiple channels of true random bits simultaneously. This feature further improves its bit rate to meet the needs of secure communication with higher rate.

A new scheme of all-optical random number generation based on the nonlinear effects in highly nonlinear fibers (HNLF) is proposed. The scheme is comprised of ultra-wide band chaotic entropy source, all-optical sampler, all-optical comparator and all-optical exclusive-or (XOR), which are mainly realized by four-wave mixing (FWM) and cross-phase modulation (XPM) in highly nonlinear fibers. And we achieve 10 Gbit/s random numbers through numerically simulating all the processes. The entire operations are completed in the all-optical domain, which may overcome the bottleneck problem of electronic devices, and apply directly in high-speed all-optical communication network.

A chaotic ultra-wideband (UWB) over fiber link is proposed and numerically demonstrated. The UWB signals with steerable and flatted power spectrum are generated in the optical domain based on the chaotic dynamics of an optically injected semiconductor laser with optical feedback. The 2.5 Gb/s on-off keying encoded chaotic UWB signals are error-free transmitted through a 25 km signal-mode (SMF) while the signal to noise ratio (SNR) of the wireless channel was fixed on 20 dB. Without utilizing any dispersion compensation module, the RF spectral of the chaotic UWB signals received by antenna fully comply with the spectral mask specified by the U.S. Federal Communications Commission (FCC), and the eye opening penalty (EOP) of the demodulated message are smaller than 3 dB. Moreover, we investigate the dependency of the decoded data EOP on the data bit rate, the fiber transmission distance, and SNR of the wireless channel.

We propose and experimentally demonstrate a frequency divider implemented by an optically injected Fabry–Perot laser diode (FP-LD) based on the nonlinear dynamical period-one oscillation. Injected by optical pulses, the FP-LD will oscillate in unstable dynamical period-one (P1) oscillation. Through changing the injected strength, emitting wavelength and bias current of the FP-LD, the oscillating frequencies of the P1 state can be varied. Once one of the harmonic frequencies is adjusted to match the repetition frequency of injected optical clock pulse, the P1 oscillation will be locked, and then a divided clock at the fundamental frequency of the P1 oscillation can be generated. By utilizing this divider, we can achieve the optical clock frequency division of divide-by-two, -three and -four in a wide input frequency range, for instance, of 9.0 to 20.0 GHz for divide-by-two. The influence of injected optical power on the timing jitter of the divided clock is also investigated. It is expected that this frequency divider can be applied to high frequency division exceeding 100 GHz due to its fast P1 oscillation.

We investigate the evolvement of the periodic intensity variations of the pulse-train in a fiber ring laser mode-locked by the nonlinear polarization rotation technique. It is found that the phenomenon of such intensity fluctuations is related to the orientation of the polarization controllers when the pump power is fixed. The numerical results show that the mechanism of the periodic intensity variations is caused by the interaction of the nonlinear polarization rotation and the passive polarizer in the cavity.

The message filtering characteristics of the receiver in closed-loop chaotic optical communication system are numerically studied based on laser rate equations. A pair of external cavity semiconductor lasers was employed as the chaotic carrier transmitter and the synchronized chaos receiver. We examined the filtering properties of the semiconductor laser receiver for message encoded with chaos masking. Our results demonstrate that, the lower the message frequency, the more easily the receiver filters out the message from chaotic carrier. We also analyzed the effects of each parameter mismatches between the transmitter and the receiver on the quality of the recovered message. Comparing the synchronization quality with the signal-to-noise ratio affected by parameter mismatches, we find that the quality of the recovered message depends not only on the synchronization quality but also on the filtering characteristics of the receiver. The filtering characteristics of receiver will be playing an important role on the quality of the recovered message in the case of large mismatches.

Semiconductor laser with optical feedback emitting chaotic optical signal can be treated as chaotic carrier transmitter. Based on laser rate equations, we numerically study the effect of external injection light on the bandwidth of chaotic carrier transmitter. Our numerical simulation shows that the bandwidth of the chaotic carrier transmitter can be enhanced significantly by external photons injection. Compared with the 2 GHz relaxation oscillation frequency of a solitary laser diode without optical injection, the bandwidth of a chaotic carrier transmitter is expanded to 14.5 GHz with injection parameter at k inj = 0.39. Simulation results also demonstrate that the enhanced bandwidth depends obviously on the frequency detuning between the external injection laser diode and the chaotic carrier transmitter. The maximum bandwidth of the chaotic transmitter can be obtained when the frequency of the injected light is higher than the central frequency of the carrier transmitter between 2 GHz and 4 GHz.