ALBERT

Description: A very efficient boundary-element method for the calculation of the quasi-static port inductances of vertical interconnections within parallel-plate structures is developed. It requires only a one-dimensional discretization along the contour of the plate pair and can be applied to arbitrary geometries. The algorithm is validated by the exact analytical solution for the circular geometry. The low-frequency response of an arbitrary multiport structure can be directly analyzed by the coupled port-inductance network together with the plate capacitance. As examples a circular-shaped and two irregularly shaped plane pairs are considered. The comparison with exact analytical solutions and three-dimensional-full-wave field simulation shows a very good agreement.

Description: The leader progression model (LPM) is a tool for estimating the lightning performance of transmission lines. However, the large computation time remains a problem for the engineering application of this model. An analytical method is proposed in this paper to mitigate the aforementioned problem. First, nonlinear trajectory equations describing the movement of upward and downward leaders are obtained, starting with differential equations. Based on the trajectory equations, the average electric field between the upward and downward leader tips is represented with a comprehensive nonlinear equation. The final strike point is determined by solving the equations. Results show that the proposed method effectively mitigates the large computation time problem of traditional (numerical) LPM.

Description: Principal component analysis (PCA) and independent component analysis (ICA) for radiated emissions from printed circuits are critically intercompared, revealing similarities and differences of the extracted components between both methods. The input data in this analysis are measured wideband complex-valued magnetic radiated and evanescent fields with quasi-Gaussian spatial distributions. PCA and ICA lead to similar maps of their components when considered as spatial eigenmodes, but independent components exhibit simpler field structure than principal components.

Description: Closed-form expressions for the approximation of frequency variations of per-unit-length resistance and inductance of microstrip transmission lines are presented. The provided expressions guarantee causality of the time-domain response. They are valid from dc up to the highest frequencies for which the quasi-static analysis of microstrip transmission lines is applicable. Additionally, the expressions take into account the finite width of the ground plane and can deal with a broad range of dimensions of microstrip lines. The correctness of the formulas is experimentally verified.

Description: This paper investigates the convergence and error evaluation of the distributed analytical representation and iterative technique (DARIT-field) which is a new approach for the analysis of field coupling to multiconductor transmission lines. The DARIT-field method has the advantage of high computational efficiency over the other methods. In order to know the convergence speed and the error at each iteration step of DARIT-field, an analytic expression of iterative error is derived by combining the two telegrapher's equations into a matrix equation and using the euclidean norm to explore its upper bound. The expression shows that the convergence speed is mainly influenced by three parameters, namely coupling factor (CF), terminal loads, and the line length to excitation field wavelength ratio $(d/lambda)$ . The convergence speed is a function of CF, terminal loads, and the line length to excitation field wavelength ratio $(d/lambda)$ . These results allow the users to make a compromise between computational cost and accuracy by selecting the number of iterations.

Description: This paper presents an efficient evaluation method for multiconductor transmission lines with random translation over an infinite and perfectly conducting ground under a plane wave. Based on the assumption of small translation quantity, the equations for the estimation of average induced voltage, induced voltage variation, and the probability distribution of the voltage variation are derived. The average induced voltages and the probability distribution of the voltage variation estimated by the proposed method are in a good agreement with those via the Monte Carlo method but the proposed method is more efficient. The relative sensitivity of the induced voltage to the height approximately equals the inverse of the line height, which can be applied to evaluate the influence induced by the random translation of the line quickly, especially in the low frequency range.

Description: A passive and inherently stable multiport equivalent circuit for lossy transmission lines is presented. The convergence of the infinite modal representation is accelerated by appropriate inductances, for which an exact closed-form expression is developed. The order number of the truncated modal circuit is estimated by a simple relation, according to the required signal bandwidth. The coupling of arbitrary external electromagnetic fields is incorporated by a limited number of corresponding modal sources. The accuracy and versatility of the suggested SPICE-compatible equivalent circuit is demonstrated by examples in frequency and time-domain, including nonlinear terminations.

Description: Carson's, Pollaczek's, Wise's, and Sunde's earth-return impedances of an overhead line have been examined, and errors involved in the formulas are explained. Modified Pollaczek's and Carson's/Sunde's formulas are described. Wave propagation characteristics on a multiconductor in a high-frequency region are evaluated by adopting the modified earth-return impedance and Wise's earth-return admittance. Sommerfeld–Goubau propagation in a high-frequency region, which shows transition between transverse electromagnetic and transverse magnetic propagation, has been confirmed in the calculated results which agree with those predicted by Kikuchi for a single conductor. On a multiconductor system, it is found that the aerial mode also shows Sommerfeld–Goubau propagation when the separation between conductors is large and the earth resistivity is high.

Description: This paper deals with the electromagnetic interaction of a straight thin wire located inside a cylinder with the cylinder walls. The wire runs parallel to the cylinder axis and connects its two opposite caps. A lumped source is chosen, which feeds the terminated conductor. For this configuration, an exact analytical solution for the induced current on the conductor is presented. On the basis of a two-sum Green's function expressed in cylindrical coordinates, the current is derived from the boundary conditions for the total electrical field on the surface of the conductor and the Fourier expansion series for the unknown current and the (known) exciting electrical field. The obtained analytical results are compared to those obtained from a full-wave method and show excellent agreement. They clearly document that the electromagnetic interaction between the cylinder and wire can strongly influence the shape of the transmitted signal. In particular, at higher frequencies, more and more resonance frequencies of the cylinder occur in the current spectrum. Therefore, the application of classical transmission-line theory on conductors, which are housed in resonators, is not allowed in general.

Description: The aim of this paper is the definition of an equivalent two-port model of a transmission line that is able to take into account high frequency radiation effects. Such a model is particularly useful when one has to represent the line into a more complex power system, modeled in a lumped way. To reach this goal, it is necessary to produce a reliable and computationally effective solution to the problem of the high-frequency electromagnetic field coupling with a terminated transmission line. From a mathematical standpoint, this problem can be presented by means of an integral equation whose solution can be achieved with regularization procedures for linear inverse problems. In order to obtain a computationally efficient result, the unknown current is first developed in a Fourier series and then the Landweber iterative algorithm is applied to identify the series coefficients. The proposed method is then tested taking as reference the numerical results obtained using the Numerical Electromagnetics Code (NEC-2), reaching a good agreement.

Description: Mixed carbon nanotube bundles (MCBs) are considered to be highly potential interconnect solutions in the current nanoscale regime. Different MCBs with random and spatial arrangements are proposed based on the placements of single- and multiwalled carbon nanotubes (CNTs) (SWNTs and MWNTs) in a bundle. Propagation delay and dynamic crosstalk performances are analyzed using the modified equivalent single conductor model of proposed MCB topologies. Encouragingly, a significant reduction in propagation delay and crosstalk delay is observed for a spatial arrangement of an MCB wherein MWNTs are placed peripherally to the centrally located SWNTs. Typically, the average delay with and without crosstalk is improved by 82.8% and 80%, respectively, compared to the MCB having randomly distributed SWNTs and MWNTs.

Description: The continuous increase of the operating frequency and density of integrated circuits leads to consider single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs) as the most promising candidates for future interconnect technology because of their high current-carrying capacity and conductivity in the nanoscale, and immunity to electromigration. Several modeling methods for SWCNT and MWCNT interconnects have been based on the multiconductor transmission line (MTL) theory. These methods are limited to nanostructures with predefined values of electrical and geometrical parameters. Since process technology continues to scale downward and physical interconnect dimensions become smaller, the impact of design parameters (e.g., layout features) on the system behavior has to be carefully investigated for a successful design by performing design space exploration, optimization, and variability analysis. These design activities require multiple system simulations for different values of design parameters, and using MTL-based solvers is not an efficient choice. Parametric macromodels can be used to accurately and efficiently model these parameter effects, avoiding the brute-force use of MTL-based solvers.

Description: As the key devices of an HVDC transmission system, converter valves should bear different forms of overvoltage. Additionally, the wideband frequency electromagnetic noises caused by the switching of thyristor may impact the normal operation of the communication and control systems in an HVDC converter substation. Consequently, it is of great significance to build the model that is suitable for wide frequency range for the key components of converter valve system. Based on the elementary wideband model, the integrated wideband model is proposed and the estimation method for corresponding parameters is also addressed for different kinds of components in this paper. The theoretical analysis and simulation results show that the integrated wideband model has high accuracy and simplicity; it also can provide the results with rigorous passivity and specific physical meaning. As for the application, the proposed method is used to model the key components of an HVDC converter valve and proved to be correct and effective.

Description: The paper discusses the effect of frequency dependence of soil electrical parameters (also called soil dispersion) on lightning currents induced on the shield of buried cables. To this aim, a full-wave approach based on the finite element method is used in which soil dispersion is incorporated into the model using available analytical formulae obtained from experimental data. It is shown that the soil dispersion can affect the induced currents only for soils with very low conductivities ( $leq 0.003, {rm S/m}$ ). It is also shown that, depending on the burial depth of the cable, for poorly conducting soils with conductivities lower than 0.0005 S/m or so, the soil dispersion can result either in an increase or in a decrease of the induced current peak.

Description: Although catchment storage is an intrinsic control on the rainfall-runoff response of streams, direct measurement remains a major challenge. Coupled models that integrate long-term hydrometric and isotope tracer data are useful tools that can provide insights into the dynamics of catchment storage and the volumes of water involved. In this study, we use a tracer-aided hydrological model to characterize catchment storage as a dynamic control on system function related to streamflow generation, which also allows direct estimation of the non-stationarity of water ages. We show that in a wet Scottish upland catchment dominated by runoff generation from riparian peats (histosols) with high water storage, non-stationarity in water age distributions are only clearly detectable during more extreme wet and dry periods. This is explained by the frequency and longevity of hydrological connectivity and the associated relative importance of flow paths contributing younger or older waters to the stream. Generally, these saturated riparian soils represent large mixing zones that buffer the time variance of water age and integrate catchment-scale partial mixing processes. Although storage simulations depend on model performance, which is influenced by input variability and the degree of isotopic damping in the stream, a longer-term storage analysis of this model indicates a system which is only sensitive to more extreme hydroclimatic variability. This article is protected by copyright. All rights reserved.

Description: This study evaluates the immunity of a low-noise amplifier (LNA) using a transient voltage suppressor (TVS) diode under direct current injection high-power microwave (HPM) pulses. The ac behavior of the TVS diode is examined. Both experiments and analysis demonstrate that the injected HPM power to failure of the LNA is increased by a factor of about 6 through the introduction of a TVS diode, the power to failure of the LNA is also related to the proportion of the direct current injected into the TVS diode and LNA. This analysis is useful for further discussion regarding semiconductor protection under HPM pulses.

Description: Many studies were devoted to the analysis and the detection of electromagnetic attacks against critical electronic systems at the system or the component levels. Some attempts have been made to correlate effects scenarios with events logged by the kernel of the operating system (OS) of commercial-off-the-shelf computer running Windows. Due to the closed principle of the last OS, we decided to perform such an analysis on a computer running a Linux distribution in which a complete access to logs is available. It will be demonstrated that a computer running such an open OS allows detecting the perturbations induced by intentional electromagnetic interferences at different levels of the targeted computer.

Description: Technical Note: Reducing the spin-up time of integrated surface water–groundwater models Hydrology and Earth System Sciences, 18, 5169-5179, 2014 Author(s): H. Ajami, J. P. Evans, M. F. McCabe, and S. Stisen One of the main challenges in the application of coupled or integrated hydrologic models is specifying a catchment's initial conditions in terms of soil moisture and depth-to-water table (DTWT) distributions. One approach to reducing uncertainty in model initialization is to run the model recursively using either a single year or multiple years of forcing data until the system equilibrates with respect to state and diagnostic variables. However, such "spin-up" approaches often require many years of simulations, making them computationally intensive. In this study, a new hybrid approach was developed to reduce the computational burden of the spin-up procedure by using a combination of model simulations and an empirical DTWT function. The methodology is examined across two distinct catchments located in a temperate region of Denmark and a semi-arid region of Australia. Our results illustrate that the hybrid approach reduced the spin-up period required for an integrated groundwater–surface water–land surface model (ParFlow.CLM) by up to 50%. To generalize results to different climate and catchment conditions, we outline a methodology that is applicable to other coupled or integrated modeling frameworks when initialization from an equilibrium state is required.

Description: The December page is devoted to IEEE Communications Society Awards and the Awards Committee that receives the nominations and processes them to identify the recipients. ComSoc Awards are meant to honor colleagues who in some ways, either via scientific/technical contributions or exemplary services, have reached significant, widely recognized achievements in our telecommunications community. Owing to their high significance and value, they need to be awarded through a fair and transparent process, and this is the essential, yet difficult and heavy task of the Awards Committee. It is my pleasure to introduce Lajos Hanzo, the Chair of the IEEE Communications Society Awards Committee, who will describe the awards and the procedure followed by the Awards Committee.

Description: Presents the front cover for this issue of the publication.

Description: Extending periodic eddy covariance latent heat fluxes through tree sapflow measurements to estimate long-term total evaporation in a peat swamp forest Hydrology and Earth System Sciences Discussions, 11, 13607-13661, 2014 Author(s): A. D. Clulow, C. S. Everson, M. G. Mengistu, J. S. Price, A. Nickless, and G. P. W. Jewitt A combination of measurement and modelling was used to find a pragmatic solution to estimate the annual total evaporation (ET) from the rare and indigenous Nkazana Peat Swamp Forest (PSF) on the east coast of Southern Africa to improve the water balance estimates within the area. Total evaporation was measured during three window periods (between seven and nine days each) using an eddy covariance (EC) system on a telescopic mast above the forest canopy. Sapflow of an understory and an emergent tree was measured using a low maintenance heat pulse velocity system for an entire hydrological year (October 2009 to September 2010). An empirical model was derived, describing the relationship between the observed ET of the Nkazana PSF measured during two of the window periods ( R 2 = 0.92 and 0.90) which, overlapped with sapflow measurements, thereby providing hourly estimates of predicted ET of the Nkazana PSF for a year, totalling 1125 mm (while rainfall was 650 mm). In building the empirical model, it was found that including the understory tree sapflow provided no benefit to the model performance. In addition, the observed emergent tree sapflow relationship with observed ET between the two field campaigns was consistent and could be represented by a single empirical model ( R 2 = 0.90; RMSE = 0.08 mm). During the window periods of EC measurement, no single meteorological variable was found to describe the Nkazana PSF ET satisfactorily. However, in terms of evaporation models, the hourly FAO56 Penman–Monteith equation best described the observed ET from EC during the August 2009 ( R 2 = 0.75), November 2009 ( R 2 = 0.85) and March 2010 ( R 2 = 0.76) field campaigns, compared to the Priestley–Taylor model ( R 2 = 0.54, 0.74 and 0.62 during the respective field campaigns). From the empirical model of ET and the FAO56 Penman–Monteith equation, a monthly crop factor ( K c ) was derived for the Nkazana PSF providing a method of estimating long-term swamp forest ET from meteorological data. The monthly crop factor indicated two distinct periods. From February to May, it was between 1.2 and 1.4 compared with June to January, when the crop factor was 0.8 to 1.0. The derived monthly K c values were verified as accurate (to one significant digit) using historical data measured at the same site, also using EC, from a~previous study. The measurements provided insights into the microclimate within a subtropical peat swamp forest and the contrasting sapflow of emergent and understory trees. They showed that expensive, high maintenance equipment can be used during manageable window periods in conjunction with low maintenance systems, dedicated to individual trees, to derive a model to estimate long-term ET over remote heterogeneous forests. In addition, the contrast in ET and rainfall emphasises the reliance of the Nkazana PSF on groundwater.

Description: Cellular phone networks are often paralyzed after a disaster, as damage to fixed infrastructure, loss of power, and increased demand degrade coverage and quality of service. To ensure disaster victims and first responders have access to reliable local and global communication, we propose EmergeNet, a portable, rapidly deployable, small-scale cellular network. In this article, we describe EmergeNet, which addresses the challenges of emergency and disaster areas. EmergeNet provides free voice calling and text messaging within a disaster area, and enables users of unmodified GSM handsets to communicate with the outside world using the Skype VoIP network. We evaluate EmergeNet???s ability to provide robust service despite high load, limited bandwidth, and software or hardware failures. EmergeNet is uniquely well suited to providing reliable, fairly allocated voice and text communication in emergency and disaster scenarios.

Description: A wireless sensor network is liable to suffer faults for several reasons, which include faulty nodes or even the fact that nodes have been destroyed by a natural disaster, such as a flood. These faults can give rise to serious problems if WSNs do not have a reconfiguration mechanism at execution. It should be noted that many WSNs designed to detect natural disasters are deployed in inhospitable places and depend on multihop communication to allow the data to reach a sink node. As a result, a fault in a single node can leave a part of the system inoperable until the node recovers from this failure. In light of this, this article outlines a solution that entails employing unmanned aerial vehicles to reduce the problems arising from faults in a sensor network when monitoring natural disasters like floods and landslides. In the solution put forward, UAVs can be transported to the site of the disaster to mitigate problems caused by faults (e.g., by serving as routers or even acting as a data mule). Experiments conducted with real UAVs and with our WSN-based prototype for flood detection (already deployed in S??o Carlos, State of S??o Paulo, Brazil, have proven that this is a viable approach.

Description: The last 15 years have heralded many developments and advances in consumer communications, from early developments of device-specific challenges in interoperability and configuration that are well captured by the concept of plug and play to a more recent emphasis on mobility and service personalization. The one constant technical challenge, and to a great extent a business success, is home networking in its many forms. There is not a modern home without some variant of a set-top box. The three articles in this issue provide a good overview of current and topical requirements in consumer communications.

Description: With the ratification of the IEEE 802.11ad amendment to the 802.11 standard in December 2012, a major step has been taken to bring consumer wireless communication to the millimeter wave band. However, multi-gigabit-per-second throughput and small interference footprint come at the price of adverse signal propagation characteristics, and require a fundamental rethinking of Wi-Fi communication principles. This article describes the design assumptions taken into consideration for the IEEE 802.11ad standard and the novel techniques defined to overcome the challenges of mm-Wave communication. In particular, we study the transition from omnidirectional to highly directional communication and its impact on the design of IEEE 802.11ad.

Description: Although it performs an increasingly important role in our lives, the home network remains a bit of a mystery when end users wish to know what is ???happening on the inside.??? This article introduces Homenet3D, an open source project that allows users to view their home network???s state as objects in 3D space within a web browser window. Homenet3D maps quantitative state to the shape, size, spin, bounce, and/or color of selected objects to qualitatively communicate what is happening on the network. We describe our Homenet3D implementation for routers running OpenWRT, and discuss the potential for visualizing multirouter/ multi-subnet home networks.

Description: Millimeter-wave communication is one way to alleviate the spectrum gridlock at lower frequencies while simultaneously providing high-bandwidth communication channels. MmWave makes use of MIMO through large antenna arrays at both the base station and the mobile station to provide sufficient received signal power. This article explains how beamforming and precoding are different in MIMO mmWave systems than in their lower-frequency counterparts, due to different hardware constraints and channel characteristics. Two potential architectures are reviewed: hybrid analog/digital precoding/combining and combining with low-resolution analog- to-digital converters. The potential gains and design challenges for these strategies are discussed, and future research directions are highlighted.

Description: Virtual traffic lights (VTL) is a new technology that holds the promise of revolutionizing traffic control in urban areas. The original VTL idea was based on 100 percent penetration of VTL technology. In this article, contrary to conventional wisdom, it is shown that 100 percent penetration is not a necessary condition for deploying VTL technology as it can be implemented with partial or low levels of penetration. Furthermore, based on game-theoretic arguments, it is shown that the adoption of VTL technology can be accelerated by providing incentives to vehicles equipped with VTL technology.

Description: Cognitive radio technology allows the reuse of the underutilized frequency spectrum on an opportunistic and non-interfering basis by means of introducing, besides the legitimate primary users of the spectrum, a new kind of users called cognitive or secondary users. Thus, reliable spectrum sensing is critical to dynamically detect available licensed frequency bands and mitigate the primary signals, but it remains realistically difficult to carry out. In fact, although distributed collaborative sensing has turned out to be fruitful for the cognitive radio environment, its accuracy is often affected by the selfish and autonomous behavior of users. In this article, we model distributed spectrum sensing and channel allocation as a non-cooperative game, and apply the minority game to bring forth and study the cooperative behavior of users. The novelty brought by our study consists of alleviating the number of users contending for primary channels by giving them the opportunity to choose between the two, either sensing the channel or being inactive during the time slot. To address the trade-off faced by the SUs, we evaluate the performance of two secondary systems in a green communications context: energy consumption and transmission delay.

Description: In this 14th issue of the Automotive Networking and Applications Series, we are pleased to present three articles that address ??? Release 1 of the cooperative intelligent transport systems (C-ITS) standards in Europe ??? The implementation of a virtual traffic lights application with only partial market penetration ??? The usage of multihop wireless communications for intra-car sensor networking By timely information exchanges among vehicles, and between vehicles and roadway infrastructure, vehicles can transform from autonomous systems into cooperative systems, thereby enabling applications such as active road safety and traffic efficiency. Cooperative intelligent transport systems (C-ITS) standards are crucial to achieve interoperability among communications equipment made by different manufacturers for vehicles and roadway infrastructure. Release 1 of the C-ITS standards was completed in early 2014, and it covers base standards for ITS-G5 radio (also named wireless access in vehicular environment, or WAVE, in the United States), ad hoc networking and transport with GeoNetworking and Basic Transport Protocol (BTP), the facilities layer such as messaging protocols CAM and DENM, security, privacy and requirements for applications, among others. The first article, "Cooperative Intelligent Transport Systems Standards in Europe" by A. Festag, provides a comprehensive overview of release 1 of the C-ITS standards in Europe. The article first gives a brief overview of the C-ITS core standards set and compares it with the U.S. dedicated short-range communications (DSRC) standards in IEEE 1609 and SAE J2735. The author then provides more detailed overviews of the Release 1 C-ITS standards covering the access layer, the networking and transport layers, the facilities layer, and applications, security, and management in the subsequent sections of the article. The article concludes with a brief outlook on the expected C-ITS corridor pilots in Europe starting in 2015, as well- as future standardization directions.

Description: A review of a number of ongoing SDN standardization and open-source activities, this article also discusses the interactions both actual and potential in various standards bodies.

Description: I am honored to have been given the opportunity to initiate this supplement on Communications Standards. It is clear to me that standards enable the global market place to offer interoperable products and services at affordable cost. Standards Development Organizations (SDOs) bring together stake holders to develop consensus standards for use by a global industry. The importance of standards to the work and careers of communications practitioners motivated the creation of this publication on standards. This new quarterly publication will be incubated as a Communication Standards Supplement to IEEE Communications Magazine, which if successful, may transition into a new magazine. It is a platform for presenting and discussing standards-related topics in the areas of communications, networking, and related disciplines.

Description: As I serve the remaining days of my tenure as the president of the IEEE Standards Association (IEEE-SA), I ponder the future of technology: what's been achieved today and where would this amazing world be without standards?

Description: As Vice President of Standards Activities of the IEEE Communications Society, I want to welcome you to the first issue of the IEEE Communications Magazine supplement on Communications Standards. This supplement is the culmination of the efforts of many people to create a publication that serves the interests of the members of the global standards community who develop, use, or are otherwise interested in communications and networking standards. The aim of this publication is to cover a broad spectrum of communications and networking standards as well as standards-related disciplines, including innovation and standardization theory and methodologies, standards-related research, and standards regulations, as well as the intellectual property and socio-economic aspects of standards.

Description: The modal analysis is needed for the design of photonic waveguide devices to determine propagation constants of guided modes and their field pattern. Rigorous methods based on finite-difference or finite-element methods for the approximation of wave equations rely on the solution of eigenvalue problems. Imaginary-distance beam propagation methods require the solution of matrix equations of high order. The computation time needed for both approaches can be tedious. A modal analysis method based on a beam propagation scheme is proposed, which allows an efficient computation of field patterns and propagation constants, as the resulting algorithm is based on simple matrix vector multiplications. This allows the choice of a large number of discretization points and a dense discretization. The beam propagation operator is designed to include the eigenvalue spectrum of corresponding guided modes only. For this reason, the method can be interpreted as a subdomain propagation method. The concept will be validated by utilizing a single-mode and multimode rib waveguide.

Description: Self-Organizing Networks (SON) is a common term for mobile network automation, critical to the cost-efficient deployment, operation and maintenance of mobile networks. This article provides an overview of SON standardization in 3GPP, including both existing and planned functionalities. It also provides an operator perspective on the relevance and use of 3GPP SON functionalities at different stages of the network design-and-operations cycle. In the long-term it is envisaged that automation will become a natural component in network operations, although the success of SON will depend on automation???s benefits in relation to its cost.

Description: We have investigated the dependence of modal behavior on the structures of 2-D implant-defined coherently coupled vertical cavity surface-emitting laser (VCSEL) arrays experimentally and theoretically. 2-D VCSEL arrays with different interelement spacing have been designed and fabricated. Through the experimental analysis of near-field and far-field distribution, in-phase and out-of-phase mode are obtained from the arrays, depending on the interelement spacing. Considering the effect of thermal and carrier injection, the refractive index distribution of the arrays under operation is calculated. Then, FDTD Solutions software is employed to calculate the near-field distributions of the arrays through establishing a simplified refractive index model. The simulation results agree well with the experiments. Meanwhile, according to the phase characteristics of in-phase and out-of-phase mode, as observed from the near-field profiles, the far-field distributions are calculated, in an excellent agreement with the experiments.

Description: We present experimental investigations of the intensity noise properties of injection-locked midinfrared emitting quantum cascade lasers. Following the theoretical approach by Simos et al. , the injection locking is realized below and near the threshold of the free running slave laser, resulting in an efficient technique to achieve low-noise operation. We find that below the threshold, the locking characteristics as locking range, shape and bandwidth, are different in comparison with those above threshold. In addition, we also investigate injection locking into longitudinal side modes of the slave laser apart by several longitudinal mode hops, and observe similar characteristics, however, with the potential to achieve higher relative intensity noise suppression. The measurements are confirmed by additional numerical simulations with a new model, which considers the multimode spectrum of the slave laser and the spectral profile of the material gain. Under the actual experimental conditions, a reduction of the relative intensity noise of the slave laser of up to 10 dB (above threshold) and up to 20 dB (below threshold) in comparison to the free running slave laser noise level is achieved.

Description: The high accuracy of lasing wavelength spacing is one of the key requirements of a distributed feedback (DFB) semiconductor laser array. However, the nonuniformity of the wavelength spacing is increasingly deteriorating with the increase in the channel number in the laser array. In this paper, theoretical study was made to investigate the effects of sampling pattern deviation and seed grating, as well as waveguide dispersion on the wavelength-spacing uniformity for multiwavelength DFB semiconductor laser arrays (MLAs) fabricated using the reconstruction equivalent chirp (REC) technique. A simple measurement method of dispersion for DFB semiconductor lasers based on the REC technique is also proposed. With the dispersion compensation being included in the sampling period design and small deviation in the seed grating period being guaranteed, a high-channel-count (16-channel) DFB laser array with precise channel spacing of 0.7944 nm/channel (design value of 0.80 nm/channel) was achieved in our experiment. It shows excellent channel-spacing uniformity, and most wavelength residuals are within $pm$ 0.10 nm.

Description: An equivalent–asymmetric coupling coefficient (EACC) distributed feedback laser (DFB) semiconductor laser with equivalent-half apodization grating (EHAG) structure is proposed and experimentally demonstrated for the first time; the EHAG profile is equivalently realized by linearly changing the duty cycle of a sampled Bragg grating along the one half cavity, while that of the other half cavity is kept uniform. Compared with the equivalent–symmetric coupling coefficient DFB laser, the simulated intensity distribution of the EACC DFB laser shows that the light power is concentrated not only on near the phase-shift region and that the power at the front end is enlarged. Therefore, the longitudinal spatial hole burning may be reduced; the output efficiency and the single-mode stability may be improved. The experimental results show that the output power ratio between the front and rear facets is about 2.17 and the side-mode suppression ratios are over 50 dB when the injection current is in the range from 60 to 200 mA.

Description: A theoretical and experimental study of all-solid-state barium borate (BBO)-based optical parametric oscillator with wide tunability from visible to near-infrared by means of intracavity second-order cascaded nonlinear interaction has been demonstrated for simultaneous generation of multicolor radiation. Radiations in the wavelength range of 600–661 nm in the visible and 892–1322 nm in the near-infrared range are generated by a combination of optical parametric oscillation and simultaneous second harmonic generation in BBO crystal. The effective third-order susceptibility is measured to be 885.18 $mathrm{pm}^{2}$ / $mathrm{V}^{2}$ , which is greater than intrinsic third-order susceptibility by one order of magnitude.

Description: In finite-size high-contrast gratings (HCGs) guided modes with low $Q$ values can occur. On the one hand, this is a resonant mode with a $Q$ value of some hundreds only, on the other hand it can transform part of the finite-size incident wave into the in-plane direction. Such finite-size HCGs with guided modes are proposed here for optical sensors with an on-chip integrated p-i-n photodiode in the same HCG layer. The mode characteristics of the guided mode and the performance of the proposed integrated HCG-based optical sensors are investigated. The proposed integrated HCG-based optical sensors are compact, cost-effective, label-free, and highly sensitive, and can be extended to an array format increasing the throughput.

Description: This paper presents the fabrication, modeling, and characterization of a micromachined piezoelectric directional microphone. The microphone structure consists of a 20- $mu $ m-thick semirigid beam structure that rotates about torsional pivots in response to in-plane pressure gradients across the length of the beam. The motion of the beam structure is transduced by piezoelectric cantilevers, which deflect when the structure rotates. While the structure has been introduced in prior publications, this is the first paper summarizing rigorous acoustic characterization of first generation prototypes. An analytical model and multimode, multiport network model utilizing finite-element analysis for parameter extraction are presented and compared with acoustic sensitivity measurements. Directivity measurements are interpreted in terms of the multimode model. A noise model for the sensor and readout electronics is presented and compared with measurements.

Description: An increase in world population along with a significant aging portion is forcing rapid rises in healthcare costs. The healthcare system is going through a transformation in which continuous monitoring of inhabitants is possible even without hospitalization. The advancement of sensing technologies, embedded systems, wireless communication technologies, nano technologies, and miniaturization makes it possible to develop smart systems to monitor activities of human beings continuously. Wearable sensors detect abnormal and/or unforeseen situations by monitoring physiological parameters along with other symptoms. Therefore, necessary help can be provided in times of dire need. This paper reviews the latest reported systems on activity monitoring of humans based on wearable sensors and issues to be addressed to tackle the challenges.

Description: Three-dimensional ultrasound imaging is a promising medical imaging technology because of its ease of use and improved accuracy in diagnosis. However, its high computational complexity and resulting high power consumption has precluded its use in hand-held applications. In this paper, we present a separable beamforming method that greatly reduces computational complexity. Our method is based on decomposing the delay term in a way that minimizes the root-mean-square error caused by the decomposition. We analyze tradeoffs between the approximation error caused by the decomposition and computational complexity. Then, we present enhancements to the Sonic Millip3De hardware accelerator for ultrasound beamforming to implement separable beamforming. Using hardware synthesis targeting standard cells in 45 nm, we show that the proposed method allows us to boost the Sonic Millip3De frame rate from 1–2 Hz to 32 Hz while maintaining power consumption at 15 W. We validate image quality of our method using cyst phantom simulations in Field II. Our evaluation demonstrates that the proposed separable beamforming method can produce 3-D images with high quality that are comparable to those generated by non-separable beamforming.

Description: For MIMO systems, due to the deployment of multiple antennas at both the transmitter and the receiver, the design variables, e.g., precoders, equalizers, and training sequences, are usually matrices. It is well known that matrix operations are usually more complicated compared with their vector counterparts. In order to overcome the high complexity resulting from matrix variables, in this paper, we investigate a class of elegant multi-objective optimization problems, namely matrix-monotonic optimization problems (MMOPs). In our work, various representative MIMO optimization problems are unified into a framework of matrix-monotonic optimization, which includes linear transceiver design, nonlinear transceiver design, training sequence design, radar waveform optimization, the corresponding robust design and so on as its special cases. Then, exploiting the framework of matrix-monotonic optimization the optimal structures of the considered matrix variables can be derived first. Based on the optimal structure, the matrix-variate optimization problems can be greatly simplified into the ones with only vector variables. In particular, the dimension of the new vector variable is equal to the minimum number of columns and rows of the original matrix variable. Finally, we also extend our work to some more general cases with multiple matrix variables.

Description: This paper investigates the bias of the maximum likelihood target location estimate resulting from the Gaussian data measurement noise and sensor position errors. The bias components from them are interrelated, except when they are independent and identically distributed. The bias behaviors of time of arrival, time difference of arrival, and angle of arrival positionings are contrasted, and geometric conditions under which the location bias becomes zero are elaborated.We illustrate the developed results for bias compensation in improving the performance of target tracking.

Description: In a collaborative sensor network (CSN), the conventional target tracking algorithms employed are Kalman filtering (KF) or extended Kalman filtering (EKF). However, these techniques have a presumed probability distribution of the system noise and prediction noise. They also need some a priori information that may be unavailable in some circumstances. Therefore, the system is not flexible for a complicated scenario. With the help of a machine learning technique called expert prediction (EP), a novel target tracking approach for CSNs is developed. This scheme makes use of the aforementioned EP in parameter estimation course for the target of interest, instead of exploiting the filtering method as typically found in available literature. This idea is further unfolded with comparisons regarding the CSN using Kalman filters, extended Kalman filters, and decentralized sigma-point information filters (DSPIFs). The new tracking algorithm is investigated with both linear and nonlinear prediction methods. Simulation results demonstrate that this proposed measure will deliver forecasting output with more precision because of the built-in multimodel mode among different experts, the learning ability, and the self-perfection characteristic. Not only does this performance occur in a more robust way than those of the existing approaches – particularly in the presence of heavy clutter, highly maneuvering targets, and/or multiple targets – but it simultaneously requires the least a priori information and imposes the least limitation on the observation model.

Description: Hybrid aerial-terrestrial communication networks based on low-altitude platforms are expected to meet optimally the urgent communication needs of emergency relief and recovery operations for tackling large-scale natural disasters. The energy-efficient operation of such networks is important given that the entire network infrastructure, including the battery-operated ground terminals, exhibits requirements to operate under power-constrained situations. In this paper, we discuss the design and evaluation of an adaptive cooperative scheme intended to extend the survivability of the battery-operated aerial-terrestrial communication links. We propose and evaluate a real-time adaptive cooperative transmission strategy for dynamic selection between direct and cooperative links based on the channel conditions for improved energy efficiency. We show that the cooperation between mobile terrestrial terminals on the ground could improve energy efficiency in the uplink, depending on the temporal behavior of the terrestrial and aerial uplink channels. The corresponding delay in having cooperative (relay-based) communications with relay selection is also addressed. The simulation analysis corroborates that the adaptive transmission technique improves overall energy efficiency of the network whilst maintaining low latency, enabling real-time applications.

Description: In this paper, a reduced-rank scheme with joint iterative optimization is presented for direction of arrival estimation. A rank-reduction matrix and an auxiliary reduced-rank parameter vector are jointly optimized to calculate the output power with respect to each scanning angle. Subspace algorithms to estimate the rank-reduction matrix and the auxiliary vector are proposed. Simulations are performed to show that the proposed algorithms achieve enhanced performance over existing algorithms in the studied scenarios.

Description: Using the dynamic inversion philosophy, a nonlinear partial integrated guidance and control approach is presented in this paper for formation flying. It is based on the evolving philosophy of integrated guidance and control. However, it also retains the advantages of the conventional guidance then control philosophy by retaining the timescale separation between translational and rotational dynamics explicitly. Simulation studies demonstrate that the proposed technique is effective in bringing the vehicles into formation quickly and maintaining the formation.

Description: The use of ground-based transmitters (so-called pseudolites) for outdoor and indoor navigation has been under consideration since the origin of the Global Positioning System (GPS). However, one significant limitation of the use of code division multiple access (CDMA) was immediately obvious: one CDMA transmitter signal interferes with another CDMA transmitter signal. This is called the ""near-far problem."" Different methods have been studied in order to mitigate such jamming. This paper presents a new mitigation method based on a principle that can be summed up as follows: the signal and a delayed replica of the signal are broadcast by a ground transmitter antenna. At the receiver stage, the replica signal is used to eliminate the interference caused by the direct signal. This is called the double transmission technique (DTT), and it presents interesting performance features regarding interference mitigation. A signal processing technique corresponding to this method is presented in this paper, considering a GPS L1 C/A-code pseudolite. Performance simulations are also presented.

Description: This paper describes a novel framework to determine the relative pose and range of a solid-of-revolution-shaped spacecraft from a single image without any artificial beacons. The translation and the symmetry axis of the spacecraft can be estimated from the imaged cross sections of the spacecraft body. Then the pose and range of the spacecraft are fully determined by means of the images of its solar panels and asymmetric feature. Our method has been validated by both synthetic and real images.

Description: Data association, the problem of reasoning over correspondence between targets and measurements, is a fundamental problem in tracking. This paper presents a graphical model formulation of data association and applies an approximate inference method, belief propagation (BP), to obtain estimates of marginal association probabilities. We prove that BP is guaranteed to converge, and bound the number of iterations necessary. Experiments reveal a favourable comparison to prior methods in terms of accuracy and computational complexity.

Description: The objective of this paper is to present a methodology for identifying the current flow in the capacitors of a multiphase buck converter by synchronously measuring the capacitor currents. A multiphase buck converter uses multiple parallel buck converters with different switching times to source a large amount of current. Currents in the primary capacitors of a multiphase buck converter are drawn by all phases of the converter; however, the phases switch asynchronously. Synchronizing to the switching of a specific phase reveals how the current from that phase is distributed among the capacitors throughout a circuit board. The proposed measurement method is illustrated by comparing an initial printed circuit board design to a new design to show the effect of better capacitor placement and the addition of a ground plane. The new design confines the phase currents to the capacitors close to the field effect transistors of the specific phase.

Description: Research and development are currently being performed to transform the US's utility electric grid into a “smart grid [1] , [2] .” Smart meters are among the first intelligent metering devices used within the “smart grid” concept. They have been deployed in thousands of commercial and residential electrical installations around the US [3] , [4] . While the wide-scale deployment of these devices has initially proven very successful, there is still much that is unknown about how they will impact the long-term operation of a large utility grid or the electrical devices sourced by them [5] . One such device, whose operation appears to be impacted by the smart meter, under specific conditions, is a ground-fault circuit interrupter (GFCI). It has been reported that the RF transmissions from smart meters can induce false tripping events on GFCI outlets installed on temporary construction poles. In an effort to understand why this may happen, a research study, which is presented here, has been performed to understand the correlation between RF transmissions and GFCI tripping events on construction poles.

Description: A locating system based on an advanced time difference of arrival (TDOA) estimation method is developed to locate the position of a discharge source to avoid pulsed electromagnetic interference (PEMI) with the surrounding radio communication environment. In general, from the waveforms of PEMI waves received by an antenna array, the source position can be located or the direction of arrival (DOA) of the EM waves can be estimated by applying TDOA-based methods. However, owing to noises and multipath waves that occur at the metal surfaces of electric power equipment, the estimation accuracy of the TDOA may decrease, and the location accuracy will be degraded. To improve the accuracy of TDOA estimation, we propose a new TDOA estimation technique. In our developed locating system, PEMI waves are received by a four-antenna-square array and the DOA is estimated from the TDOA, which is estimated using the generalized cross-correlation phase transform method in combination with the proposed technique. A PEMI source is ultimately located by aiming a charge-coupled device camera, installed at the center of the antenna array, at the estimated DOA. The estimation accuracy of the locating system is evaluated through experimental measurements. The results show that the developed locating system can locate the position of a PEMI source existing within about 30 m from the system with high accuracy.

Description: High-frequency signals on interconnects can cause significant radiated electromagnetic emissions. An intermediate level modeling method aimed at providing a faster solution with less computing resources to allow designers to obtain rapid approximations is desirable. This paper presents a modeling technique to speed up the evaluation of radiated fields from interconnect cables. Based on the Hertzian dipole radiation theory and transmission-line frequency-dependant solutions, the radiating source is modeled by the sum of a large number of short dipoles. This model allows the contributions of line-end discontinuities to be included through a vector network analyzer measurement together with a monopole approximation. The proposed method is verified by open-line and RG 58 coaxial cable measurements.

Description: An efficient approach to achieve the shielding effectiveness (SE) by using a frequency-selective surface (FSS) is presented. This FSS, which consists of cross dipoles and rings printed on the opposite sides of a single-layer FR-4 substrate, exhibits a wide, 7.5-GHz stopband to provide simultaneous shielding in both X- and Ka-bands. Experimental results confirm SE of the prototype over an ultra-wide band with more than 20-dB measured attenuation. The design is compact and suitable to provide shielding against the radiation interference caused by license-free and other radio systems.

Description: The household appliances in buildings have increased rapidly in the recent years. However, the surge withstanding capability of these household appliances has not been increased. Therefore, it is necessary to install surge protection device (SPD) to prevent serious damage of household electrical appliances caused by the in-rushing surges. In order to avoid the oscillation phenomenon, the effective protection distance of SPDs should be addressed before installing SPDs in the buildings. This paper discussed the influence of a group of common household electrical appliances connected in parallel on the effective protection distance of an SPD to a household appliance. The surges impinging on the household appliances connected to a distribution system are analyzed using electromagnetic transient analysis software. It is found that the SPD's protection distance increases when multiple household appliances are connected in parallel. The SPD's effective protection distance for one specific household appliance, which is determined from the case in which only this household appliance is used, is a conservative value; even if other household appliances are connected with this appliance, the SPD still provides an effective protection to this specific appliance.

Description: Long-term variability of storm surge frequency in the Venice Lagoon: an update thanks to eighteenth century sea level observations Natural Hazards and Earth System Sciences Discussions, 2, 7465-7486, 2014 Author(s): F. Raicich Sea level observations made in the Venice Lagoon between 1751 and 1792 have been recovered, consisting of two time series of daily data on high and low waters at Venice and Chioggia. From comparisons with modern observations the quality of the 18th century data appears to be good enough to allow a useful analysis. A composite time series of daily mean sea level is obtained by merging the 18th century data and 1872–2004 observations at Venice Punta della Salute. The absence of reliable information on vertical references prevents the connection of the two 18th century time series with each other and with modern observations. However, daily sea level anomalies relative to the mean sea level enable to recognize storm surge events, that appear to occur more frequently in the second half of the 18th century than in the late 19th and 20th centuries, particularly during the 1751–1769 period. The record-breaking storm surge of 4 November 1966 turns out to be a remarkable event also in comparison with the events extracted from the 18th century time series. Further work is required to fill the gap between the old and modern observations.

Description: Ground-penetrating radar observations for estimating the vertical displacement of rotational landslides Natural Hazards and Earth System Sciences Discussions, 2, 7487-7506, 2014 Author(s): C. Lissak, O. Maquaire, J.-P. Malet, F. Lavigne, C. Virmoux, C. Gomez, and R. Davidson The objective of this paper is to demonstrate the applicability of Ground Penetrating Radar (GPR) for monitoring the displacement of slow-moving landslides. GPR data is used to estimate the vertical movement of rotational slides in combination with other surveying techniques. The experimental site is located along the Normandy coast (North East France) here several rotational landslides are continuously affected by a seasonal kinematic pattern (low displacement rates of 0.01 to 0.10 m yr −1 ) and periodically by major acceleration events (high displacement of 1.0 to 7.0 m per event).

Description: A smart monitoring system for superconducting cable test is proposed with an adaptive current control of a superconducting transformer secondary. The design, based on Fuzzy Gain Scheduling, allows the controller parameters to adapt continuously, and finely, to the working variations arising from transformer nonlinear dynamics. The control system is integrated in a fully digital control loop, with all the related benefits, i.e., high noise rejection, ease of implementation/modification, and so on. In particular, an accurate model of the system, controlled by a Fuzzy Gain Scheduler of the superconducting transformer, was achieved by an experimental campaign through the working domain at several current ramp rates. The model performance was characterized by simulation, under all the main operating conditions, in order to guide the controller design. Finally, the proposed monitoring system was experimentally validated at European Organization for Nuclear Research (CERN) in comparison to the state-of-the-art control system [P. Arpaia, L. Bottura, G. Montenero, and S. Le Naour, “Performance improvement of a measurement station for superconducting cable test,” Rev. Sci. Instrum.83, 095111 (2012)] of the Facility for the Research on Superconducting Cables, achieving a significant performance improvement: a reduction in the system overshoot by 50%, with a related attenuation of the corresponding dynamic residual error (both absolute and RMS) up to 52%.

Description: This paper presents a method which uses the characteristics of the etch pits induced in a polyallyl-diglycol-carbonate (PADC) detector of the CR-39/PM-355 type to estimate particle energy. This method is based on the data provided by a semiautomatic system that selects tracks according to two parameters, crater diameters, and mean gray level values. In this paper we used the results of the calibration measurements that were obtained in our laboratory in the period 2000–2014. Combining the information on the two parameters it is possible to determine unambiguously the incident projectile energy values. The paper presents the results of an attempt to estimate the energy resolution of the method when analyzing the tracks produced in the CR-39/PM-355 detector by energetic ions such as alpha particles, protons, and deuterons. We discuss the energy resolution of the measurement of light charged particle energy which is based on the parameters (crater diameter and mean gray level value) of tracks induced in solid state nuclear track detectors of the PADC type.

Description: In this work, an automated apparatus for driving single electrostatic probes and acquiring the plasma-related data has been designed and fabricated. The voltage range of the present system is ±110 V with an adjustable voltage step as low as 3 mV. Voltage and current measurements are carried out with high resolution and high accuracy circuits, both based on 16 bit analog-to-digital converters. The code embedded in a micro-controller, schedules the operation of the device and transfers the experimental data to a personal computer. The modular design of the system makes possible its modification and thus increases its adaptability to different plasma setups. Finally, the reliable operation of the entire device is confirmed by tests in Electron Cyclotron Resonance plasma.

Description: Continental Portuguese Territory Flood Susceptibility Index – contribution for a vulnerability index Natural Hazards and Earth System Sciences Discussions, 2, 7521-7552, 2014 Author(s): R. Jacinto, N. Grosso, E. Reis, L. Dias, F. D. Santos, and P. Garrett This work defines a national flood susceptibility index for the Portuguese continental territory, by proposing the aggregation of different variables which represent natural conditions for permeability, runoff and accumulation. This index is part of the national vulnerability index developed in the scope of Flood Maps in Climate Change Scenarios (CIRAC) project, supported by the Portuguese Association of Insurers (APS). This approach expands on previous works by trying to bridge the gap between different floods mechanisms (e.g. progressive and flash floods) occurring at different spatial scales in the Portuguese territory through: (a) selecting homogeneously processed datasets, (b) aggregating their values to better translate the spatially continuous and cumulative influence in floods at multiple spatial scales. Results show a good ability to capture, in the higher susceptibility classes, different flood types: progressive floods and flash floods. Lower values are usually related to: mountainous areas, low water accumulation potential and more permeable soils. Validation with independent flood datasets confirmed these index characteristics, although some overestimation can be seen in the southern region of Alentejo where, due to a dense hydrographic network and an overall low slope, floods are not as frequent as a result of lower precipitation mean values. Future work will focus on: (i) including extreme precipitation datasets to represent the triggering factor, (ii) improving representation of smaller and stepper basins, (iii) optimizing variable weight definition process, (iii) developing more robust independent flood validation datasets.

Description: Dye tracing for investigating flow and transport properties of hydrocarbon-polluted Rabots glaciär, Kebnekaise, Sweden Hydrology and Earth System Sciences Discussions, 11, 13711-13744, 2014 Author(s): C. C. Clason, C. Coch, J. Jarsjö, K. Brugger, P. Jansson, and G. Rosqvist Over 11 000 L of hydrocarbon pollution was deposited on the surface of Rabots glaciär on the Kebnekaise Massif, northern Sweden, following the crash of a Royal Norwegian Air Force aircraft in March 2012. An environmental monitoring programme was subsequently commissioned, including water, snow and ice sampling. The scientific programme further included a series of dye tracing experiments during the 2013 melt season, conducted to investigate flow pathways for pollutants through the glacier hydrological system, and to gain new insight to the internal hydrological system of Rabots glaciär. Results of dye tracing reveal a degree of homogeneity in the topology of the drainage system throughout July and August, with an increase in efficiency as the season progresses, as reflected by decreasing temporary storage and dispersivity. Early onset of melting likely led to formation of an efficient, discrete drainage system early in the melt season, subject to decreasing sinuosity and braiding as the season progressed. Analysis of turbidity-discharge hysteresis further supports the formation of discrete, efficient drainage, with clockwise diurnal hysteresis suggesting easy mobilisation of readily-available sediments in channels. Dye injection immediately downstream of the pollution source zone revealed prolonged storage of dye followed by fast, efficient release. Twinned with a low dye recovery, and supported by sporadic detection of hydrocarbons in the proglacial river, we suggest that meltwater, and thus pollutants in solution, may be released periodically from this zone of the glacier hydrological system. The here identified dynamics of dye storage, dispersion and breakthrough indicate that the ultimate fate and permanence of pollutants in the glacier system is likely to be governed by storage of pollutants in the firn layer and ice mass, or within the internal hydrological system, where it may refreeze. This shows that future studies on the fate of hydrocarbons in pristine, glaciated mountain environments should address the extent to which pollutants in solution act like water molecules or whether they are more susceptible to, for example, refreezing into the surrounding ice, becoming stuck in micro-fractures and pore spaces, or sorption onto subglacial sediments.

Description: A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μ s time window at a pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO 2 layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.

Description: ABSTRACT A reactive transport modeling framework is presented that allows simultaneous assessment of groundwater flow, water quality evolution including δ 13 C, and 14 C activity or “age”. Through application of this framework, simulated 14 C activities can be directly compared with measured 14 C activities. This bypasses the need for interpretation of a 14 C age prior to flow simulation through factoring out processes other than radioactive decay, which typically involves simplifying assumptions regarding spatial and temporal variability in reactions, flow, and mixing. The utility of the approach is demonstrated for an aquifer system with spatially variable carbonate mineral distribution, multiple organic carbon sources, and transient boundary conditions for 14 C activity in the recharge water. In this case the simulated 14 C age was shown to be relatively insensitive to isotopic fractionation during DOC oxidation and variations in assumed DOC degradation behaviour. We demonstrate that the model allows quantitative testing of hypotheses regarding controls on groundwater age and water quality evolution for all three carbon isotopes. The approach also facilitates incorporation of multiple environmental tracers and combination with parameter optimization techniques. This article is protected by copyright. All rights reserved.

Description: Water scarcity is likely to increase in the coming years, making improvements in irrigation efficiency increasingly important. An emerging technology that promises to increase irrigation efficiency substantially is a wireless irrigation sensor network that uploads sensor data into irrigation management software, creating an integrated system that allows real-time monitoring and control of moisture status that has been shown in experimental settings to reduce irrigation costs, lower plant loss rates, shorten production times, decrease pesticide application, and increase yield, quality, and profit. We use an original survey to investigate likely initial acceptance, ceiling adoption rates, and profitability of this new sensor network technology in the nursery and greenhouse industry. We find that adoption rates for a base system and demand for expansion components are decreasing in price, as expected. The price elasticity of the probability of adoption suggests that sensor networks are likely to diffuse at a rate somewhat greater than that of drip irrigation. Adoption rates for a base system and demand for expansion components are increasing in specialization in ornamental production: Growers earning greater shares of revenue from greenhouse and nursery operations are willing to pay more for a base system and are willing to purchase larger numbers of expansion components at any given price. We estimate that growers who are willing to purchase a sensor network expect investment in this technology to generate significant profit, consistent with findings from experimental studies. This article is protected by copyright. All rights reserved.

Description: Air temperature variability over three glaciers in the Ortles-Cevedale (Italian Alps): effects of glacier disintegration, intercomparison of calculation methods, and impacts on mass balance modeling The Cryosphere Discussions, 8, 6147-6192, 2014 Author(s): L. Carturan, F. Cazorzi, F. De Blasi, and G. Dalla Fontana Glacier mass balance models rely on accurate spatial calculation of input data, in particular air temperature. Lower temperatures (the so-called glacier cooling effect), and lower temperature variability (the so-called glacier damping effect) generally occur over glaciers, compared to ambient conditions. These effects, which depend on the geometric characteristics of glaciers and display a high spatial and temporal variability, have been mostly investigated on medium- to large-size glaciers so far, while observations on smaller ice bodies are scarce. Using a dataset from 8 on-glacier and 4 off-glacier weather stations, collected in summer 2010 and 2011, we analyzed the air temperature variability and wind regime over three different glaciers in the Ortles-Cevedale. The magnitude of the cooling effect and the occurrence of katabatic boundary layer (KBL) processes showed remarkable differences among the three ice bodies, suggesting the likely existence of important reinforcing mechanisms during glacier decay and disintegration. None of the methods proposed in the literature for calculating on-glacier temperature from off-glacier data fully reproduced our observations. Among them, the more physically-based procedure of Greuell and Böhm (1998) provided the best overall results where the KBL prevail, but it was not effective elsewhere (i.e. on smaller ice bodies and close to the glacier margins). The accuracy of air temperature estimations strongly impacted the results from a mass balance model which was applied to the three investigated glaciers. Most importantly, even small temperature deviations caused distortions in parameter calibration, thus compromising the model generalizability.

Description: Since 2007 a large decline in Arctic sea ice has been observed. The large-scale atmospheric circulation response to this decline is investigated in ERA-Interim reanalyses and HadGEM3 climate model experiments. In winter, post-2007 observed circulation anomalies over the Arctic, North Atlantic and Eurasia are small compared to interannual variability. In summer, the post-2007 observed circulation is dominated by an anticyclonic anomaly over Greenland which has a large signal-to-noise ratio. Climate model experiments driven by observed SST and sea ice anomalies are able to capture the summertime pattern of observed circulation anomalies, although the magnitude is a third of that observed. The experiments suggest warm SSTs and reduced sea ice in the Labrador Sea lead to warm temperature anomalies in lower troposphere which weaken the westerlies over North America through thermal wind balance. The experiments also capture cyclonic anomalies over north-western Europe, which are consistent with downstream Rossby wave propagation.

Description: Are seasonal calving dynamics forced by buttressing from ice mélange or undercutting by melting? Outcomes from full-Stokes simulations of Store Glacier, West Greenland The Cryosphere, 8, 2353-2365, 2014 Author(s): J. Todd and P. Christoffersen We use a full-Stokes 2-D model (Elmer/Ice) to investigate the flow and calving dynamics of Store Glacier, a fast-flowing outlet glacier in West Greenland. Based on a new, subgrid-scale implementation of the crevasse depth calving criterion, we perform two sets of simulations: one to identify the primary forcing mechanisms and another to constrain future stability. We find that the mixture of icebergs and sea ice, known as ice mélange or sikussak, is principally responsible for the observed seasonal advance of the ice front. On the other hand, the effect of submarine melting on the calving rate of Store Glacier appears to be limited. Sensitivity analysis demonstrates that the glacier's calving dynamics are sensitive to seasonal perturbation, but are stable on interannual timescales due to the strong topographic control on the flow regime. Our results shed light on the dynamics of calving glaciers and may help explain why neighbouring glaciers do not necessarily respond synchronously to changes in atmospheric and oceanic forcing.

Description: Deglaciation of the Caucasus Mountains, Russia/Georgia, in the 21st century observed with ASTER satellite imagery and aerial photography The Cryosphere, 8, 2367-2379, 2014 Author(s): M. Shahgedanova, G. Nosenko, S. Kutuzov, O. Rototaeva, and T. Khromova Changes in the map area of 498 glaciers located on the Main Caucasus ridge (MCR) and on Mt. Elbrus in the Greater Caucasus Mountains (Russia and Georgia) were assessed using multispectral ASTER and panchromatic Landsat imagery with 15 m spatial resolution in 1999/2001 and 2010/2012. Changes in recession rates of glacier snouts between 1987–2001 and 2001–2010 were investigated using aerial photography and ASTER imagery for a sub-sample of 44 glaciers. In total, glacier area decreased by 4.7 ± 2.1% or 19.2 ± 8.7 km 2 from 407.3 ± 5.4 km 2 to 388.1 ± 5.2 km 2 . Glaciers located in the central and western MCR lost 13.4 ± 7.3 km 2 (4.7 ± 2.5%) in total or 8.5 km 2 (5.0 ± 2.4%) and 4.9 km 2 (4.1 ± 2.7%) respectively. Glaciers on Mt. Elbrus, although located at higher elevations, lost 5.8 ± 1.4 km 2 (4.9 ± 1.2%) of their total area. The recession rates of valley glacier termini increased between 1987–2000/01 and 2000/01–2010 (2000 for the western MCR and 2001 for the central MCR and Mt.~Elbrus) from 3.8 ± 0.8, 3.2 ± 0.9 and 8.3 ± 0.8 m yr −1 to 11.9 ± 1.1, 8.7 ± 1.1 and 14.1 ± 1.1 m yr −1 in the central and western MCR and on Mt. Elbrus respectively. The highest rate of increase in glacier termini retreat was registered on the southern slope of the central MCR where it has tripled. A positive trend in summer temperatures forced glacier recession, and strong positive temperature anomalies in 1998, 2006, and 2010 contributed to the enhanced loss of ice. An increase in accumulation season precipitation observed in the northern MCR since the mid-1980s has not compensated for the effects of summer warming while the negative precipitation anomalies, observed on the southern slope of the central MCR in the 1990s, resulted in stronger glacier wastage.

Description: Inversion method for initial tsunami waveform reconstruction Natural Hazards and Earth System Sciences Discussions, 2, 7735-7772, 2014 Author(s): V. V. Voronin, T. A. Voronina, and V. A. Tcheverda This paper deals with the application of r-solution method to recover the initial tsunami waveform in a tsunami source area by remote water-level measurements. Wave propagation is considered within the scope of a linear shallow-water theory. An ill-posed inverse problem is regularized by means of least square inversion using a truncated SVD approach. The properties of obtained solution are determined to a large extent by the properties of an inverse operator, which were numerically investigated. The method presented allows one to control instability of the numerical solution and to obtain an acceptable result in spite of ill-posedness of the problem. It is shown that the accuracy of tsunami source reconstruction strongly depends on the signal-to-noise ratio, the azimuthal coverage of recording stations with respect to the source area and bathymetric features along the wave path. The numerical experiments were carried out with synthetic data and various computational domains including a real bathymetry. The method proposed allows us to make a preliminary prediction of the efficiency of the inversion with a given set of the recording stations and to find out the most informative part of the existing observation system. This essential property of the method can prove to be useful in designing a monitoring system for tsunamis.

Description: Stratospheric Sounding Units (SSU) on the NOAA polar orbiting satellites measured infrared radiances in the 15 micron CO 2 band between late 1978 and mid-2006. From these radiances a time series of layer mean stratospheric temperatures has been derived by several groups. Discrepancies in these temperature analyses have been highlighted recently and efforts are now underway to resolve the differences between them. This paper is the Met Office response summarising the issues to be resolved in creating a climate data record from the different SSUs, including corrections for radiometric, spectroscopic and tidal differences. Calibration issues identified include the SSU space view anomaly and radiometric anomalies in the NOAA-9 observations. The spectroscopic correction required for changing pressures in the pressure modulator cells is also outlined. The most important correction for the time series is for the solar diurnal and semi-diurnal tides as the satellite overpass local times change. Comparisons with other stratospheric temperature trend analyses are made and the reasons for the differences discussed. The time series presented here show sustained drops in stratospheric temperatures at all levels after the El Chichon and Pinatubo eruptions but only small trends to lower temperatures between eruptions.

Description: A high-order global shallow water model on Yin-Yang grid has been developed by using the multi-moment constrained finite volume (MCV) method. Different from the traditional finite volume method, more degrees of freedom (DOFs) which are the values at the solution points within each mesh element are defined and updated in time. The time evolution equations for these point values are derived from a set constraint conditions in terms of the so-called multi-moment quantities, such as the point value (PV), the volume-integrated average (VIA) and derivative (DV). Different moments use different forms of equations which are all consistent with the shallow water equations, among which the VIA moment is computed from a finite volume formulation of flux form that guarantees the rigorous numerical conservation. A fourth-order formulation is devised with the third-order reconstruction built over each element using the DOFs locally available. A simple and orthogonal overset grid, the Yin-Yang grid, is used to represent the spherical geometry with quasi-uniform grid spacing. The resulting global shallow water model is attractive in algorithmic simplicity and computational efficiency. The model has been validated by widely used benchmark tests. The numerical results of the present model are competitive to most existing advanced models.

Description: A major goal of nanotechnology is to develop the capability to arrange matter at will by placing individual atoms at desired locations in a predetermined configuration to build a nanostructure with specific properties or function. The scanning tunneling microscope has demonstrated the ability to arrange the basic building blocks of matter, single atoms, in two-dimensional configurations. An array of various nanostructures has been assembled, which display the quantum mechanics of quantum confined geometries. The level of human interaction needed to physically locate the atom and bring it to the desired location limits this atom assembly technology. Here we report the use of autonomous atom assembly via path planning technology; this allows atomically perfect nanostructures to be assembled without the need for human intervention, resulting in precise constructions in shorter times. We demonstrate autonomous assembly by assembling various quantum confinement geometries using atoms and molecules and describe the benefits of this approach.

Description: We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm 2 ) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of 〉10 7 cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrum of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on 57 Fe.

Description: We describe a nanosecond time-resolved fluorescence spectrometer that acquires fluorescence decay waveforms from each well of a 384-well microplate in 3 min with signal-to-noise exceeding 400 using direct waveform recording. The instrument combines high-energy pulsed laser sources (5–10 kHz repetition rate) with a photomultiplier and high-speed digitizer (1 GHz) to record a fluorescence decay waveform after each pulse. Waveforms acquired from rhodamine or 5-((2-aminoethyl)amino) naphthalene-1-sulfonic acid dyes in a 384-well plate gave lifetime measurements 5- to 25-fold more precise than the simultaneous intensity measurements. Lifetimes as short as 0.04 ns were acquired by interleaving with an effective sample rate of 5 GHz. Lifetime measurements resolved mixtures of single-exponential dyes with better than 1% accuracy. The fluorescence lifetime plate reader enables multiple-well fluorescence lifetime measurements with an acquisition time of 0.5 s per well, suitable for high-throughput fluorescence lifetime screening applications.

Description: Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.

Description: Glacier-like forms on Mars The Cryosphere, 8, 2047-2061, 2014 Author(s): B. Hubbard, C. Souness, and S. Brough More than 1300 glacier-like forms (GLFs) are located in Mars' mid-latitudes. These GLFs are predominantly composed of ice–dust mixtures and are visually similar to terrestrial valley glaciers, showing signs of downhill viscous deformation and an expanded former extent. However, several fundamental aspects of their behavior are virtually unknown, including temporal and spatial variations in mass balance, ice motion, landscape erosion and deposition, and hydrology. Here, we investigate the physical glaciology of martian GLFs. We use satellite images of specific examples and case studies to build on existing knowledge relating to (i) GLF current and former extent, exemplified via a GLF located in Phlegra Montes; (ii) indicators of GLF motion, focusing on the presence of surface crevasses on several GLFs; (iii) processes of GLF debris transfer, focusing on mapping and interpreting boulder trains on one GLF located in Protonilus Mensae, the analysis of which suggests a best-estimate mean GLF flow speed of 7.5 mm a −1 ; and (iv) GLF hydrology, focusing on supra-GLF gulley networks. On the basis of this information, we summarize the current state of knowledge of the glaciology of martian GLFs and identify future research avenues.

Description: Strategy of valid 14 C dates choice in syngenetic permafrost The Cryosphere Discussions, 8, 5589-5621, 2014 Author(s): Y. K. Vasil'chuk and A. C. Vasil'chuk The main problem of radiocarbon dating within permafrost is the uncertain reliability of the 14 C dates. Syngenetic sediments contain allochthonous organic deposit that originated at a distance from its present position. Due to the very good preservation of organic materials in permafrost conditions and numerous re-burials of the fossils from ancient deposits into younger ones the dates could be both younger and older than the true age of dated material. The strategy for the most authentic radiocarbon date selection for dating of syncryogenic sediments is considered taking into account the fluvial origin of the syngenetic sediments. The re-deposition of organic material is discussed in terms of cyclic syncryogenic sedimentation and also the possible re-deposition of organic material in subaerial-subaqueous conditions. The advantages and the complications of dating organic micro-inclusions from ice wedges by the accelerator mass spectrometry (AMS) method are discussed applying to true age of dated material search. Radiocarbon dates of different organic materials from the same samples are compared. The younger age of the yedoma from cross-sections of Duvanny Yar in Kolyma River and Mamontova Khayata in the mouth of Lena River is substantiated due to the principle of the choice of the youngest 14 C date from the set.

Description: Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams The Cryosphere, 8, 2007-2029, 2014 Author(s): J. Thompson, M. Simons, and V. C. Tsai Geodetic surveys suggest that ocean tides can modulate the motion of Antarctic ice streams, even at stations many tens of kilometers inland from the grounding line. These surveys suggest that ocean tidal stresses can perturb ice stream motion at distances about an order of magnitude farther inland than tidal flexure of the ice stream alone. Recent models exploring the role of tidal perturbations in basal shear stress are primarily one- or two-dimensional, with the impact of the ice stream margins either ignored or parameterized. Here, we use two- and three-dimensional finite-element modeling to investigate transmission of tidal stresses in ice streams and the impact of considering more realistic, three-dimensional ice stream geometries. Using Rutford Ice Stream as a real-world comparison, we demonstrate that the assumption that elastic tidal stresses in ice streams propagate large distances inland fails for channelized glaciers due to an intrinsic, exponential decay in the stress caused by resistance at the ice stream margins. This behavior is independent of basal conditions beneath the ice stream and cannot be fit to observations using either elastic or nonlinear viscoelastic rheologies without nearly complete decoupling of the ice stream from its lateral margins. Our results suggest that a mechanism external to the ice stream is necessary to explain the tidal modulation of stresses far upstream of the grounding line for narrow ice streams. We propose a hydrologic model based on time-dependent variability in till strength to explain transmission of tidal stresses inland of the grounding line. This conceptual model can reproduce observations from Rutford Ice Stream.

Description: Simulating the Antarctic ice sheet in the Late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project The Cryosphere Discussions, 8, 5539-5588, 2014 Author(s): B. de Boer, A. M. Dolan, J. Bernales, E. Gasson, H. Goelzer, N. R. Golledge, J. Sutter, P. Huybrechts, G. Lohmann, I. Rogozhina, A. Abe-Ouchi, F. Saito, and R. S. W. van de Wal In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The Late-Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions. Here, we present results from simulations of the Antarctic ice sheet by means of an international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP-ANT). For the experiments, ice-sheet models including the shallow ice and shelf approximations have been used to simulate the complete Antarctic domain (including grounded and floating ice). We compare the performance of six existing numerical ice-sheet models in simulating modern control and Pliocene ice sheets by a suite of four sensitivity experiments. Ice-sheet model forcing fields are taken from the HadCM3 atmosphere–ocean climate model runs for the pre-industrial and the Pliocene. We include an overview of the different ice-sheet models used and how specific model configurations influence the resulting Pliocene Antarctic ice sheet. The six ice-sheet models simulate a comparable present-day ice sheet, although the models are setup with their own parameter settings. For the Pliocene simulations using the Bedmap1 bedrock topography, some models show a small retreat of the East Antarctic ice sheet, which is thought to have happened during the Pliocene for the Wilkes and Aurora basins. This can be ascribed to either the surface mass balance, as the HadCM3 Pliocene climate shows a significant increase over the Wilkes and Aurora basin, or the initial bedrock topography. For the latter, our simulations with the recently published Bedmap2 bedrock topography indicate a significantly larger contribution to Pliocene sea-level rise from the East Antarctic ice sheet for all six models relative to the simulations with Bedmap1.

Description: Fluctuations of a Greenlandic tidewater glacier driven by changes in atmospheric forcing: observations and modelling of Kangiata Nunaata Sermia, 1859–present The Cryosphere, 8, 2031-2045, 2014 Author(s): J. M. Lea, D. W. F. Mair, F. M. Nick, B. R. Rea, D. van As, M. Morlighem, P. W. Nienow, and A. Weidick Many tidewater glaciers in Greenland are known to have undergone significant retreat during the last century following their Little Ice Age maxima. Where it is possible to reconstruct glacier change over this period, they provide excellent records for comparison to climate records, as well as calibration/validation for numerical models. These glacier change records therefore allow for tests of numerical models that seek to simulate tidewater glacier behaviour over multi-decadal to centennial timescales. Here we present a detailed record of behaviour from Kangiata Nunaata Sermia (KNS), SW Greenland, between 1859 and 2012, and compare it against available oceanographic and atmospheric temperature data between 1871 and 2012. We also use these records to evaluate the ability of a well-established one-dimensional flow-band model to replicate behaviour for the observation period. The record of terminus change demonstrates that KNS has advanced/retreated in phase with atmosphere and ocean climate anomalies averaged over multi-annual to decadal timescales. Results from an ensemble of model runs demonstrate that observed dynamics can be replicated. Model runs that provide a reasonable match to observations always require a significant atmospheric forcing component, but do not necessarily require an oceanic forcing component. Although the importance of oceanic forcing cannot be discounted, these results demonstrate that changes in atmospheric forcing are likely to be a primary driver of the terminus fluctuations of KNS from 1859 to 2012. We propose that the detail and length of the record presented makes KNS an ideal site for model validation exercises investigating links between climate, calving rates, and tidewater glacier dynamics.

Description: In this study we first present updated riverine total alkalinity (TA) loads to the various Baltic Sea sub-basins, based on monthly measurements in 82 of the major rivers that represent 85% of the total runoff. Simulations in the coupled physical-biogeochemical BALTSEM model show that these river loads together with North Sea water inflows are not sufficient to reproduce observed TA concentrations in the system, demonstrating the large influence from internal sources. Budget calculations indicate that the required internal TA generation must be similar to river loads in magnitude. The non-riverine source in the system amounts to about 2.4 mmol m -2 d -1 on average. We argue here that the majority of this source is related to denitrification together with unresolved sediment processes such as burial of reduced sulfur and/or silicate weathering. This hypothesis is supported by studies on sediment processes on a global scale, and also by data from sediment cores in the Baltic Sea. In a model simulation with all internal TA sources and sinks switched on, the net absorption of atmospheric CO 2 increased by 0.78 mol C m -2 y -1 compared to a simulation where TA was treated as a passive tracer. Our results clearly illustrate how pelagic TA sources together with anaerobic mineralization in coastal sediments generate a significant carbon sink along the aquatic continuum, mitigating CO 2 evasions from coastal and estuarine systems.

Description: Hydrogeology of an Alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow Hydrology and Earth System Sciences, 18, 4437-4452, 2014 Author(s): U. Lauber, P. Kotyla, D. Morche, and N. Goldscheider The frequency and intensity of extreme hydrological events in Alpine regions is projected to increase with climate change. The goal of this study is to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in Alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal (German Alps), where runoff from a karst spring infiltrates a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h −1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d −1 ) are low compared with other Alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h −1 . Downstream hydrographs revealed a delayed discharge response after 101 h and peaks damped by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in Alpine regions.

Description: Observed groundwater temperature response to recent climate change Hydrology and Earth System Sciences, 18, 4453-4466, 2014 Author(s): K. Menberg, P. Blum, B. L. Kurylyk, and P. Bayer Climate change is known to have a considerable influence on many components of the hydrological cycle. Yet, the implications for groundwater temperature, as an important driver for groundwater quality, thermal use and storage, are not yet comprehensively understood. Furthermore, few studies have examined the implications of climate-change-induced groundwater temperature rise for groundwater-dependent ecosystems. Here, we examine the coupling of atmospheric and groundwater warming by employing stochastic and deterministic models. Firstly, several decades of temperature time series are statistically analyzed with regard to climate regime shifts (CRSs) in the long-term mean. The observed increases in shallow groundwater temperatures can be associated with preceding positive shifts in regional surface air temperatures, which are in turn linked to global air temperature changes. The temperature data are also analyzed with an analytical solution to the conduction–advection heat transfer equation to investigate how subsurface heat transfer processes control the propagation of the surface temperature signals into the subsurface. In three of the four monitoring wells, the predicted groundwater temperature increases driven by the regime shifts at the surface boundary condition generally concur with the observed groundwater temperature trends. Due to complex interactions at the ground surface and the heat capacity of the unsaturated zone, the thermal signals from distinct changes in air temperature are damped and delayed in the subsurface, causing a more gradual increase in groundwater temperatures. These signals can have a significant impact on large-scale groundwater temperatures in shallow and economically important aquifers. These findings demonstrate that shallow groundwater temperatures have responded rapidly to recent climate change and thus provide insight into the vulnerability of aquifers and groundwater-dependent ecosystems to future climate change.

Description: μLaue diffraction with a polychromatic X-ray beam can be used to measure strain fields and crystal orientations of micro crystals. The hydrostatic strain tensor can be obtained once the energy profile of the reflections is measured. However, this remains a challenge both on the time scale and reproducibility of the beam position on the sample. In this review, we present a new approach to obtain the spatial and energy profiles of Laue spots by using a pn-junction charge-coupled device, an energy-dispersive area detector providing 3D resolution of incident X-rays. The morphology and energetic structure of various Bragg peaks from a single crystalline Cu micro-cantilever used as a test system were simultaneously acquired. The method facilitates the determination of the Laue spots’ energy spectra without filtering the white X-ray beam. The synchrotron experiment was performed at the BM32 beamline of ESRF using polychromatic X-rays in the energy range between 5 and 25 keV and a beam size of 0.5 μ m × 0.5 μ m. The feasibility test on the well known system demonstrates the capabilities of the approach and introduces the “3D detector method” as a promising tool for material investigations to separate bending and strain for technical materials.

Description: A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy and reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID B eff , it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within ±1 μ m. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R&D efforts by the APS toward APS Upgrade Project goals as well as the future generation of IDs for the Linac Coherent Light Source (LCLS).

Description: A description is given of an ultra-high vacuum surface-analysis chamber that incorporates an internal cell for performing atomic layer deposition at a pressure of up to ∼1 Torr. The apparatus permits the growth process to be interrupted in stages during which data can be obtained using infrared and x-ray photoemission spectroscopies together with other electron-based techniques. Demonstration results are given for the adsorption of H 2 O on Si (100) at a pressure of ∼0.3 Torr. The system described is generally applicable in the study of any surface reaction under non-high-vacuum conditions in which there is a need for both infrared and electron spectroscopies.

Description: We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane–propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an “electrical conductivity response phase diagrams” that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.

Description: In thermomechanical testing of hypersonic materials and structures, direct observation and quantitative strain measurement of the front surface of a test specimen directly exposed to severe aerodynamic heating has been considered as a very challenging task. In this work, a novel quartz infrared heating device with an observation window is designed to reproduce the transient thermal environment experienced by hypersonic vehicles. The specially designed experimental system allows the capture of test article's surface images at various temperatures using an optical system outfitted with a bandpass filter. The captured images are post-processed by digital image correlation to extract full-field thermal deformation. To verify the viability and accuracy of the established system, thermal strains of a chromiumnickel austenite stainless steel sample heated from room temperature up to 600 °C were determined. The preliminary results indicate that the air disturbance between the camera and the specimen due to heat haze induces apparent distortions in the recorded images and large errors in the measured strains, but the average values of the measured strains are accurate enough. Limitations and further improvements of the proposed technique are discussed.

Description: Snow mass decrease in the Northern Hemisphere (1979/80–2010/11) The Cryosphere Discussions, 8, 5623-5644, 2014 Author(s): Z. Li, J. Liu, L. Huang, N. Wang, B. Tian, J. Zhou, Q. Chen, and P. Zhang Snow cover has a key effect on climate change and hydrological cycling, as well as water supply to a sixth of the world's population across the Northern Hemisphere. However, reliable data on trends in snow cover in the Northern Hemisphere is lacking. Snow water equivalent (SWE) is a common measure of the amount of equivalent water of the snow pack. Here we verify the accuracy of three existing global SWE products and merge the most accurate aspects of them to generate a new SWE product covering the last 32 years (1979/80–2010/11). Using this new SWE product, we show that there has been a significant decreasing trend in the total mass of snow in the Northern Hemisphere. The most notable changes in total snow mass are −16.45 ± 6.68 and −13.55 ± 7.80 Gt year −1 in January and February, respectively. These are followed by March and December, which have trends of −12.58 ± 6.88 and −10.70 ± 5.62 Gt year −1 , respectively, from 1979/80 to 2010/11. During the same period, the temperature in the study area raised 0.17 °C decade −1 , which is thought to be the main reason of SWE decline.

Description: Factors controlling Slope Environmental Lapse Rate (SELR) of temperature in the monsoon and cold-arid glacio-hydrological regimes of the Himalaya The Cryosphere Discussions, 8, 5645-5686, 2014 Author(s): R. J. Thayyen and A. P. Dimri Moisture, temperature and precipitation interplay forced through the orographic processes sustains the Himalayan cryospheric system. However, factors controlling the Slope Environmental Lapse Rate (SELR) of temperature along the higher Himalayan mountain slopes across various glacio-hydrologic regimes remain as a key knowledge gap. Present study dwells on the orographic processes driving the moisture–temperature interplay in the monsoon and cold-arid glacio-hydrological regimes of the Himalaya. Systematic data collection at three altitudes between 2540 and 3763 m a.s.l. in the Garhwal Himalaya (hereafter called monsoon regime) and between 3500 and 5600 m a.s.l. in the Ladakh Himalaya (herefater called cold-arid regime) revealed moistrue control on temperature distribution at temporal and spatial scales. Observed daily SELR of temperature ranges between 9.0 to 1.9 °C km −1 and 17.0 to 2.8 °C km −1 in the monsoon and cold-arid regimes respectively highlighting strong regional variability. Moisture influx to the region, either from Indian summer monsoon (ISM) or from Indian winter monsoon (IWM) forced lowering of SELR. This phenophena of "monsoon lowering" of SELR is due to the release latent heat of condensation from orographically focred lifted air parcel. Seasonal response of SELR in the monsoon regime is found to be closly linked with the variations in the local lifting condensation levels (LCL). Contrary to this, cold-arid system is characterised by the extremely high values of daily SELR upto 17 °C km −1 signifying the extremely arid conditions prevailing in summer. Distinctly lower SELR devoid of monsoon lowering at higher altitude sections of monsoon and cold-arid regimes suggests sustained wetter high altitude regimes. We have proposed a SELR model for both glacio-hydrological regimes demostrating with two sections each using a derivative of the Clausius–Clapeyron relationship by deriving monthly SELR indices. It has been proposed that the manifestations of presence or absence of moisture is the single most important factor determining the temperature distribution along the higher Himalayan slopes driven by the orographic forcings. This work also suggests that the arbitary use of temperature lapse rate to extrapolate temperature to the higher Himalaya is extremely untenable.

Description: ABSTRACT In a review of the role of plants in river systems, Gurnell (2014) explains how living riparian vegetation can exert physical controls that enable it to modify and manipulate many fluvial processes. Those traits, in combination with their tendency to speed up the recovery of river systems between extreme flow events through their stabilising influence, imply that plants may act as ‘river system engineers’. In this sense, vegetation may be important in attenuating erosion during high flow and stabilising river features both during and after extreme flow conditions. This article is protected by copyright. All rights reserved.