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The connection between solar-induced fluorescence (SIF) and vegetation gross primary productivity is being widely investigated across spatial, temporal, and biological scales, including: a) studies at the leaf [1], [2], plant canopy [2]–[4] or satellite pixel scale [5], [6], b) temporally with studies spanning from diurnal [7] to seasonal scales [1], [3], [5], and b) biologically with studies covering various plant functional types (PFTs), e.g., crops [4], [7], deciduous [8] or evergreen forests [1], [3], in response to different sources of stress.

Gross primary production (GPP) from photosynthesis by terrestrial vegetation is the largest sink of atmospheric CO 2 . Sun-induced chlorophyll fluorescence (SIF) has been shown a powerful proxy for photosynthetic activity and used to estimate GPP. However, both non-physiological and functional factors controlling the emission of canopy SIF. The non-physiological factors, especially the sun-viewer geometry, impact the relationships between SIF and GPP. In this study, we did near-surface observations of both carbon flux and multi-view-angle spectra above a wheat canopy. The carbon flux was used to calculate GPP and the canopy spectra were used to retrieve SIF. SIF is significantly correlated with the angle between sun and viewer than SIF (R2=0.63). The relationships of SIF with GPP are also changing with different view azimuth angles. Generally, SIF observed at 180o (pointing north) are more correlated to GPP than that at the other two angles. A model recently developed by He et al. (2017) was used to normalize multi-angle SIF to the hotspot direction (SIF h ) and to compute the canopy-level total SIF (SIF t ), in order to reduce the effects of sun-viewer geometry on SIF. Compared to the correlation of GPP with the original observed SIF (SIF obs ), the coefficients of determination (R2) increase by ~0.1 and ~0.05 for those of GPP with SIF h and SIF t , respectively. These results would be helpful in estimating GPP of crops at large scales using remote sensing techniques.

Sun-induced fluorescence (SIF) is a novel remote sensing method, which can be potentially used as a direct indicator of photosynthetic activity. In this study, we present an approach for generating a consistent long-term global SIF product (2003–2015) by combining Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and the Global Ozone Monitoring Experiment -2 (GOME-2). The relationships between SCIAMACHY (2003–2011) and GOME-2 SIF (2007–2015) were established pixel by pixel using two data series during overlapped period (2007–2011). Then the SCIAMACHY SIF from 2012 to 2015 was estimated from GOME-2 SIF. With the consistent SIF product, the influence of extreme climate event such as high surface temperature to the vegetation of different terrestrial ecosystem will be studied. The vegetation phenological patterns will also be explored by SIF data.

Remote sensing of sun-induced chlorophyll fluorescence (SIF) is a novel optical tool for assessment of terrestrial photosynthesis or gross primary production (GPP). Along with the breakthroughs of global retrievals of SIF from space-borne sensors, exploitation of SIF in improving the representation of photosynthesis and its role in Earth System models became a very relevant and active field. Recent space-borne measurements of SIF can offer an observational constraint on photosynthesis simulations. Tailored to this special session, this presentation gives a discussion on recent advances in the retrievals of leaf biological traits from SIF, e.g., the maximum carboxylation rate (V cmax ), regarding the applications and problems.

Today's WLANs are struggling to provide desirable features like high efficiency, fairness and QoS because of the use of Distributed Coordination Function (DCF). In this paper we present OpenTDMF, an architecture to enable TDMA on commodity WLAN devices. Our hope is to provide the desirable features without entirely rebuilding the WLAN infrastructure. OpenTDMF is inspired by and architecturally similar to Software Defined Networking (SDN). Specifically, we leverage the backhaul of WLAN to coordinate all the stations for channel access. This fine-grained coordination is performed in a decoupled control plane which includes a central controller and programmable APs. To realize OpenTDMF on commodity WLAN devices, we develop several novel techniques to achieve μs-level time synchronization among all the APs. We also enable AP-triggered uplink transmission so that all the transmissions in the WLAN can be determined. We implemented a prototype of OpenTDMF based on commodity WLAN devices. Empirical results validate the OpenTDMF design and demonstrate its benefits.

Enabling flexible spectrum access (FSA) in existing wireless networks is challenging due to the limited spectrum programmability - the ability to change spectrum properties of a signal to match an arbitrary frequency allocation. This paper argues that spectrum programmability can be separated from general wireless physical layer (PHY) modulation. Therefore, we can support flexible spectrum programmability by inserting a new spectrum virtualization layer (SVL) directly below traditional wireless PHY, and enable FSA for wireless networks without changing their PHY designs. SVL provides a virtual baseband abstraction to wireless PHY, which is static, contiguous, with a desirable width defined by the PHY. At the sender side, SVL reshapes the modulated baseband signals into waveform that matches the dynamically allocated physical frequency bands - which can be of different width, or non-contiguous - while keeping the modulated information unchanged. At the receiver side, SVL performs the inverse reshaping operation that collects the waveform from each physical band, and reconstructs the original modulated signals for PHY. All these reshaping operations are performed at the signal level and therefore SVL is agnostic and transparent to upper PHY. We have implemented a prototype of SVL on a software radio platform, and tested it with various wireless PHYs. Our experiments show SVL is flexible and effective to support FSA in existing wireless networks.

Multicast benefits data center group communication in both saving network traffic and improving application throughput. The SLA (Service Level Agreement) of cloud service requires the computation correctness of distributed applications, translating to the requirement of reliable Multicast delivery. In this paper we present RDCM, a novel reliable Multicast approach for data center network. The key idea of RDCM is to minimize the impact of packet loss on the Multicast performance, by leveraging the rich link resource in data centers. A Multicast-tree-aware backup overlay is purposely built on group members for peer-to-peer packet repair. Riding on Unicast, packet repair not only achieves complete repair isolation, but also has high probability to bypass the pathological links in the Multicast tree where packet loss occurs. The backup overlay is organized in such a way that it causes little individual repair burden, control overhead, as well as overall repair traffic. We have implemented RDCM as a user-level library onWindows platform. The experiments on our test bed show that RDCM handles packet loss without obvious throughput degradation during high-speed data transmission.

Compressed-air jet cutting off soft formation was simulated by use of finite element explicit dynamic analysis program. The results of simulation experiments indicate that there are two inflections velocities during the jet penetration progress. Then the parameters including angle of arrival, traversing velocity, the number of jet bundle and diameter were simulated and the relations between various parameters and penetration efficiency were gained. Compact theory basis of designing bit was established in the pneumatic-injection reverse circulation drilling technology.

Cordyceps militaris, a kind of caterpillar fungus, has therapeutic effects including immunoregulative, anticancer, antibacterial and antifungal effects. Aqueous extraction and alkaline (NaOH) hydrolysis method were comparatively studied in polysaccharides extraction from submerged-cultured C. militaris mycelia. The results indicate that the polysaccharide content and the total extract rate from alkaline extraction method were obviously higher than those from the aqueous extraction method. The extraction process parameters of alkaline extraction were further optimized using response surface methodology (RSM), and a mathematical model was then developed to show the effect of each extraction condition and their interactions on the polysaccharide extraction. The model predicted the optimum alkaline concentration was 1.6 mol/L, extraction temperature 56.7 □, extraction time 1.94, and the extraction rate was 11.57%. Furthermore, verification of the calculated optimum of the model was done with a condition representing this maximum point and obtaining a extraction rate of 11.12 %. The good correlation between predicted and measured values of these experiments justifies the validity of the response model and the existence of an optimum point.

Candida glycerinogenes, an osmotolerant yeast, is currently used commercially in China for the production of glycerol. In this study, the osmotolerance of C. glycerinogenes 14-2, a partial glucose 6-phosphate dehydrogenase (G6PDH) deficiency mutant, to high glucose, NaCl or glycerol concentration was tested, and then the fermentation performance of the mutant was investigated. The mutant showed almost the same osmotolerance to glucose and NaCl as the wild type strain, but poor osmotolerance to glycerol. With low glucose (135 g/L), the mutant produced 34.0 g/L glycerol like its parent strain, while 27.7 % less than the control strain with high glucose (252 g/L). Under the both conditions, the specific glucose consumption rate and the specific glycerol formation rate of the mutant were much lower than those of the wild type strain, especially with high glucose. The partial deficiency of G6PDH resulted in declined tolerance to glycerol and poor performance of glycerol fermentation of C. glycerinogenes. The present study indicates that HMP plays important roles in osmoadaptation and glycerol biosynthesis of C. glycerinogenes. The research sheds new light on mechanism of osmoadaptation of yeast.

The goal of data center networking is to interconnect a large number of server machines with low equipment cost, high and balanced network capacity, and robustness to link/server faults. It is well understood that, the current practice where servers are connected by a tree hierarchy of network switches cannot meet these requirements (8), (9). In this paper, we explore a new server-interconnection struc- ture. We observe that the commodity server machines used in today's data centers usually come with two built-in Ethernet ports, one for network connection and the other left for backup purpose. We believe that, if both ports are actively used in network connections, we can build a low-cost interconnection structure without the expensive higher-level large switches. Our new network design, called FiConn, utilizes both ports and only the low-end commodity switches to form a scalable and highly effective structure. Although the server node degree is only two in this structure, we have proven that FiConn is highly scalable to encompass hundreds of thousands of servers with low diameter and high bisection width. The routing mechanism in FiConn balances different levels of links. We have further developed a low- overhead traffic-aware routing mechanism to improve effective link utilization based on dynamic traffic state. Simulation results have demonstrated that the routing mechanisms indeed achieve high networking throughput.

In this paper, we present Structon, a novel approach that uses Web mining together with inference and IP traceroute to geolocate IP addresses with significantly better accuracy than existing automated approaches. Structon is composed of three ideas which we realize in three corresponding steps. First, we extract geolocation information of Web server IP addresses from Web pages. Second, we devise heuristic algorithms to improve both the accuracy and the coverage of the IP geolocation database using these Web server IP addresses and their geolocations as input. Third, for those segments that are not covered in the first two steps, we use IP traceroute to identify the access routers of those segments. When the location of the access router is known, we can deduce the location of the associated segment since it is co-located together with the access router. By mining 500-million Web pages collected in China in 2006 (11 percent of the total Web pages in China at that time), we are able to identify the geolocations for 103 million IP addresses. This represents nearly 88 percent IP addresses allocated to China in March 2008. Structon is 87.4 percent accurate at city granularity and up to 93.5 percent accurate at province level. We also used 10 day Windows Live client log to evaluate our client IP addresses coverage: Structon identified geolocations of 98.9 percent of client IP addresses.

We propose a MAC layer handoff mechanism for IEEE 802.11 WLAN to give benefit to bandwidth-greedy applications at STAs. In order to find an optimal AP, we investigate a new measurement method called TFC (Transient Frame Capture) to estimate the achievable throughput from APs. Since TFC is employed under promiscuous mode, it avoids service degradation through the current associated AP. In addition, the mechanism is a client-only solution which does not require any modification on APs. We develop an analytic model for the throughput estimation and demonstrate it through experimental studies.

Rate adaptation is critical to the system performance of wireless networks. Typically, rate adaptation is considered as a MAC layer mechanism in IEEE 802.11. Most previous work relies only on frame losses to infer channel quality, but performs poorly if frame losses are mainly caused by interference. Recently SNR- based rate adaptation schemes have been proposed, but most of them have not been studied in a real environment. In this paper, we first conduct a systematic measurement-based study to confirm that in general SNR is a good prediction tool for channel quality, and identify two key challenges for this to be used in practice: (1) The SNR measures in hardware are often uncalibrated, and thus the SNR thresholds are hardware dependent. (2) The direct prediction from SNR to frame delivery ratio (FDR) is often over optimistic under interference conditions. Based on these observations, we present a novel practical SNR- Guided Rate Adaptation (SGRA) scheme. We implement and evaluate SGRA in a real test-bed and compare it with other three algorithms: ARF, RRAA and HRC. Our results show that SGRA outperforms the other three algorithms in all cases we have tested.

It has been a challenging problem to support VoIP-type delay sensitive applications in an 802.11 wireless LAN, because the standard handoff procedure implemented in many current 802.11 products occurs a delay deem unacceptable to VoIP users. To reduce this delay, we have developed a fast handoff scheme called Proactive Scan. It employs two new techniques. The first is to decouple the time-consuming channel scan from the actual handoff, and to eliminate channel scan delay by doing scan early and interleaving it with ongoing traffic in a non-intrusive way. The second technique is a smart trigger that takes into account both uplink and downlink quality and explicitly addresses the link asymmetry which has yet not been touched in previous work. Through implementation and experimentation study, we have shown that Proactive Scan does provide fast handoff and satisfactory performance to VoIP applications. Further, it is a software-only client-only solution that any mobile device can use in any existing 802.11 networks.

Developing and evaluating secure MANET (mobile adhoc networks) in real systems is a complex process that involves careful design of attack test cases and security countermeasures, as well as meaningful performance measurements to evaluate both the impact of attacks and the performance of security solutions. It is desirable to have a development and testing environment that can automate this process. In this paper, we propose a software framework for such an environment and describe a system implementation in the secure MANET routing domain. This environment includes the following three major features. First, the environment is built upon a wireless network emulation tool to support repeatable experimentation. Second, it adds an attack emulation layer with necessary API for easy development and execution of attack test cases. Third, the extensible attack library includes a full set of basic attacks at its core and a way to compose complex attacks from the atomic elements. To demonstrate the usefulness of this tool, we show the development of an Intrusion Detection System (IDS) as a case study. Our successful experience confirms that the platform can greatly facilitate the development of security solutions on MANET.

The explicit control protocol (XCP) has been proposed as a multi-level network feedback mechanism for congestion control of Internet transport protocols. Theoretical and simulation results have suggested that the protocol is stable and efficient over high bandwidth-delay product paths, while being more scalable to deploy than mechanisms that require per-flow state in routers. However, there is little operational experience with the approach. Since the deployment of XCP would require changes to both the end hosts and routers, it is important to study the implications of this new architecture before advocating such wide scale changes to Internets. This paper presents the results of an experimental study of XCP. We first implemented XCP in the Linux kernel and solved various systems issues. After validating previously reported simulation results, we studied the sensitivity of XCP's performance to various environmental factors, and discovered issues with TCP/IP configuration, capacity misestimation due to link sharing, handling of non-congestion losses, and the partial deployment of XCP queues in the network. These sensitivities can significantly reduce XCP's ability to control congestion and achieve fairness. Our contributions are twofold. First, through implementation we have revealed the challenges in platforms that lack large native data types or floating point arithmetic, and the need to keep fractions in the XCP protocol header. Second, through experiment and analysis we have identified several possibilities for XCP to enter into incorrect feedback control loops and adversely affect the performance. The challenges identified are deployment challenges intrinsic to the XCP design, and they suggest that the current proposal requires additional development and extension.

In today's heterogeneous Internet, bandwidth available to TCP flows is often variable. However, current TCP cannot perform optimally under such dynamically varying bandwidth conditions. This paper addresses this problem by introducing a new architecture to improve TCP performance with explicit bandwidth notification (EBN). It uses a normalized bandwidth feedback method to provide accurate and timely bandwidth estimations. Then, a new TCP control algorithm (TCP-EBN) is proposed to give a prompt response to any bandwidth changes. Our simulation results have shown that TCP-EBN performs much better than several other variations of TCP.

In heterogeneous networks such as today's Internet, TCP must be made to handle links and paths with vastly different characteristics, including longer delays and dynamically changing available bandwidth. In this research, we first analyze the performance of TCP under networks with TCP-unfriendly characteristics and introduce an architecture to tackle the performance problems in such networks.

Graceful performance degradation due to failures can be achieved by maintaining updated system reachability information. This can be accomplished through the early detection of site and communication failures and repairs. Surveillance protocols are responsible for gathering and updating this information which are known as views. The author present a simple, reliable surveillance protocol along with its application to distributed transaction processing systems. The authors examine the effect of surveillance on the performance of transaction processing during failures with and without surveillance. They show that while the cost of surveillance overhead is affordable through a fixed additional MIPS, the benefits of surveillance are indispensable. >