bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Mechanical Automation with Simulation of Wind Energy Conversion System Based on Sliding Mode Control
Authors: Tang San , Wang Wu
Published: August 2013

The exploitation of wind power will improve the energy structure and ease the power shortage, which is an effective approach to solving the world energy crisis. But the wind power generation system was a typical nonlinear system, which was hard to be controlled exactly by traditional controllers and the sliding mode control was proposed, the mathematical models of wind energy conversion system was created, which was combined with mechanical automation and electrical, the sliding mode control strategy was presented, the sliding surface was designed with equivalent controller and switching controller. The model and control strategy was established with MATLAB and the simulation result shows this control system with speed tracking performance, which can effectively implement maximum energy capture.
Study on the Preparation of Strontium-Doped Hydroxyapatite Whisker
Authors: Yan Ting Ting , Cui Yong Shun , Chen Qing Hua
Published: August 2013

Hydroxyapatite is well used as bone repair materials, due to its properties that can be combined with strontium to improve mechanical property and degradation property. In this article, hydroxyapatite whiskers with different amount of doped strontium were prepared with diammonium phosphate, calcium nitrate and strontium nitrate at 94 °C. Fourier transform infrared spectroscopy (FTIR) was used to identify the functional groups. X-ray diffraction (XRD) analysis was carried out to study the phase composition and crystallinity of the whisker. The morphology of the whiskers was characterized by scanning electron microscope (SEM). It was indicated that strontium can be doped in hydroxyapatite with proper process and then the strontium-doped hydroxyapatite whiskers were produced successfully.
Effect of Adding Micro Amount Rare Earth Element Er on Mechanical Property of Bi5Sb8Sn Solder Alloy
Authors: Li Shuai , Yan Yan Fu , Jiu Yong Tao , Wang Hong Na
Published: August 2013

A new Bi5Sb8SnRE quaternary alloy was formed by adding 0.25wt%-0.75wt% rare earth (RE)Er into Bi5Sb8Sn solder alloy to study the effect of its mechanical property.The results show that adding micro amount of Er could refine the microstructure.Meanwhile,more uniform microstructure,improvements of the mechanical properties were obtained with Er additon.Comparing with Bi5Sb8Sn matrix, the tensile strength and shear strength increased by 41.8% and 83.0% respectively when Er adds up to 0.5wt.%; However,the Microstructure coarsened and the mechanical properties were decreased when the addition of Er more than 0.5wt.%.
Porous Calcium Sulfate/Hydroxyapatite Whiskers Scaffold for Bone Tissue Engineering
Authors: Yan Ting Ting , Wu Xiao Pei , Cui Yong Shun , Chen Qing Hua , Yang Zhong Da
Published: August 2013

Porous calcium sulfate/hydroxyapatite whiskers composites scaffold is possible to be used in bone tissue engineering, for its biocompatibility, controllable degradation, and good mechanical properties. In this study, porous calcium sulfate/hydroxyapatite whisker composite scaffolds were fabricated by adding pore-forming agent and were characterized. The characteristics of the porous scaffolds were assessed by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and immersing testing techniques. It is shown that the scaffolds prepared in this article have the porous structure with the content of CaSO4 and HA. The scaffolds prepared in this article have been confirmed to be ideally used as biodegradable implants.
Biological Performances Investigation of KGM/SH Fiber Membranes
Authors: Li Yin , Wu Xiao Pei , Cui Yong Shun , Leng Chong Yan , Yan Ting Ting , Chen Qing Hua
Published: August 2013

Fiber woven membranes were prepared with konjac glucomannan (KGM) and sodium hyaluronate (SH). Glycerol was added as plasticizer and lactic acid as modifier. After treatment with microwave,wet spinning method and the programmable 2D mobile platform were used to prepare the KGM/SH fiber woven membranes. The in vitro degradability of the fiber membranes was tested by PBS immersion. The biological activity of the fiber woven membranes was observed by SBF mineralization experiments. The cytocompatibility was also investigated via co-culture of stem cells. It was revealed that the fiber woven membranes had good biological activity, degradation rate and cytocompatibility, which indicated that the membrane has a good prospect as a potential cartilage scaffold.
Effect of Konjac Glucomannan Content on the Structure and Properties of Sodium Hyaluronate/Chitosan/Konjac Glucomannan Composite Films
Authors: Zhu Wei Bo , Chen Jia , Yan Tin Ting , Zhu Wei Bo , Chen Qing Hua
Published: August 2013

Unsoluble composite films have been prepared by blending konjac glucomannan (KGM)/sodium hyaluronate (SH) aqueous solution with chitosan (CS) solution in acetate solution, filtering, deaerating, tape casting, drying at 55°C for 8h and crosslinking with the aid of sodium hydroxide solution for 2h. The effect of KGM content on the structure and properties of SH/CS/KGM composite films were investigated. It was indicated that the KGM can significantly improve the tensile strength (σb) and breaking elongation (εb) of the SH/CS composite films, and the tensile strength (σb) and breaking elongation (εb) increased with the increase of KGM content in composite films. It was revealed by IR and X-ray analysis that the crystallinity of composite films decreased with the increase of KGM content and the composite films was mainly amorphous. It was indicated via scanning electron microscopy (SEM) and bone marrow mesenchymal stem cell experiments that the films could support the growth of cells and were non-toxicity and good biocompatibility.
Surface Properties of the Ta and Ag Dual-Ion-Implanted Ti6Al4V Alloy
Authors: Leng Chong Yan , Zhou Rong , Zhang Xu
Published: August 2013

First, Ti6Al4V alloy samples were modified by tantalum ion implantation at a dose of 1.5×1017ions/cm2, and then silver ion at a dose of 1×1017ions/cm2. Glancing angle X-ray diffraction analysis was used to characterize the phase composition of un-implanted Ti6Al4V alloy and Ta+Ag dual-ion-implanted Ti6Al4V alloy samples. X-ray photoelectron spectroscopy analysis was used to investigate the chemical states of the elements on the Ta+Ag dual-ion-implanted Ti6Al4V alloy sample’s surface. The results show that small amounts of Ta and Ag were present in their elementary forms, along with TiO2, Ta2O5, and TaOx.
Study on the Environmental Materials with the Enzyme-Producing Conditions of a PCBs-Degrading Halophilic Bacterium
Authors: Zhao Zhe
Published: August 2013

Polychlorinated biphenyls (PCBs) are Persistent Organic Pollutants (POPs). This experiment screened a halophilic bacterium from the deep sea sediments, which could grow at the salinity of 15%, and designated as B2.6. The cells of this strain were rod shaped, Gram negative, motile, could grow in pH range of 5.0-9.0, and temperature range 10-37°C. Growth of this bacterium in the presence of PCBs, as the sole source of carbon and energy. The ions of IA, such as Na+ and K+ could enhance the activity of PCBs-degrading enzyme, while the transitional metal ions, such as Co2+, Mn2+, Cu2+, Fe2+ and Fe3+ may inhibit it in a certain degree. The optimal temperature, pH value and concentration of NaCl for the PCBs-degrading enzyme were 25-35°C, pH 6-8 and 50 g·L-1, respectively.
Wave Energy Conversion for Shoreline Protection
Authors: McCormick Michael E. , Murtha Robert C. , Steinmetz Jeffrey
Published: August 2013

AbstractThis paper is based on the premise that “wave energy conversion” is the conversion of the energy of ocean waves into other energy forms for the benefit of the environment. By taking advantage of the diffraction focusing phenomenon, commonly associated
with water wave energy conversion, a bimodal buoy called the Antenna Buoy has been developed to both attract and dissipate incident water wave energy. As a result, arrays of the buoy can be deployed to form an effective floating breakwater system. Results from a full-scale experimental study
show that an array of buoys, with each buoy pair separated by about 10 body widths, can dissipate up to 65% of the incident wave energy, where the value of the energy dissipation depends on the wave frequency. To arrive at this value, the full-scale test was conducted in a vertical-walled
tank, where wall reflections were from “virtual” units in an array. The full-scale model used in the study is based on the averaged wave climate in the central-to-northern waters of the Chesapeake Bay. In addition to being effective in its design operation, the bimodal buoy can
be repositioned or removed, as the site situation might require.
The Muskeget Channel Tidal Energy Project: A Unique Case Study in the Licensing and Permitting of a Tidal Energy Project in Massachusetts
Authors: Barrett Stephen B.
Published: August 2013

AbstractMarine hydrokinetic (MHK) energy projects, those generating power from the tides and waves, are subject to a comprehensive licensing and permitting process. In order to comply with federal, state, and local laws and regulations, project proponents must study the proposed
development site to fully understand existing conditions and disclose potential project impacts. The Muskeget Channel Tidal Energy Project proposed by the town of Edgartown in partnership with the University of Massachusetts presents an interesting case study of how an MHK project obtains
regulatory approvals. While other studies have reviewed the regulatory process of energy projects, the case of Muskeget is unique because (1) the applicant is a municipality, (2) it is proposing to obtain a license from the Federal Energy Regulatory Commission under its pilot license program,
(3) the project is being evaluated by Massachusetts’ agencies under the Massachusetts Ocean Plan, (4) it includes both a commercial energy generation project and a research test facility for the long-term testing of MHK technologies, and (5) the project is being led by a consortium of
public partners supported largely by the scientific institutions. The objective of this paper is to highlight the multidisciplinary character of this type of development and to illustrate the advanced level of complexity associated with the Muskeget Channel Project because of its ground-breaking
technology and oceanic location, which challenges the existing knowledge base in science, engineering, and law.
Consideration of a Variable Frequency Energy Conversion System for Marine and Onshore Wind Energy Extraction
Authors: Merz Clifford R.
Published: August 2013

AbstractWind energy is now well established as a viable means of generating electricity. It has good prospects of becoming increasingly competitive as volume production and improved technology further reduce capital costs and as its environmental advantages become more valued.
Conversion devices used to recover energy from the wind are typically referred to as wind turbines or wind machines. Examination of the literature finds numerous wind turbine designs in use, depending upon the intended size and application. This paper discusses the concept of a permanent magnet
synchronous generator (PMSG)-based variable frequency energy conversion system (VFECS) for wind and potentially water energy extraction operations.
Performance Modeling of Ducted Vertical Axis Turbine Using Computational Fluid Dynamics
Authors: Chatterjee Prasun , Laoulache Raymond N.
Published: August 2013

AbstractVertical axis turbines (VATs) excel over horizontal axis turbines in their independent flow direction. VATs that operate in an enclosure, e.g., a diffuser shroud, are reported to generate more power than unducted VATs. A diffuser-shrouded, high solidity of 36.67%,
three-blade VAT with NACA 633-018 airfoil section is modeled in 2-D using the commercial software ANSYS-FLUENT®. Incompressible, unsteady, segregated, implicit, and second order in time and space solver is implemented in association with the Spalart-Allmaras turbulent
model with a reasonable computational cost. The computational results are assessed against experimental data for unducted VAT at low tip speed ratios between 1 and 2 for further numerical analysis on diffuser models. Different diffuser designs are investigated using suitable nozzle size, area
ratio, length-to-diameter ratio and angles between the diffuser inner surfaces. The numerical model shows that, for a specific diffuser design, the ducted VAT performance coefficient can be augmented by almost 90% over its unducted counterpart.
The Impact of Tidal Stream Turbines on Circulation and Sediment Transport in Muskeget Channel, MA
Authors: Hakim Aradea R. , Cowles Geoffrey W. , Churchill James H.
Published: August 2013

AbstractThe Finite-Volume Community Ocean Model (FVCOM) is configured to evaluate the potential impact of the proposed Muskeget Tidal Energy Project on circulation and sediment transport in the surrounding region. The extraction of tidal kinetic energy from the water column
is modeled by augmenting the momentum equations with additional drag terms parameterized using local flow velocities and parameters specific to the installed turbine farm. Model-computed power output compares well with estimates based on velocities derived from a shipboard acoustic Doppler
current profiler (ADCP). Total extracted power from the proposed installations during a spring ebb tide represents roughly 9% of the natural power in the deep section of the channel and 30% of the natural tidal dissipation in the turbine installation region. Due to this low level of extraction,
turbine installations at the proposed transects result in relatively minor differences in the tidal current magnitude (2.5%), water level (0.8%), sediment flux (0.6%), and bed level (9%). Computations also indicate that the proposed installation generates minimal impacts to the tidal harmonics
(3.3% change in amplitude and 1-min delay in phase) and tide-induced depth-averaged residual currents (2.8%). Model-computed extraction at increased levels is associated with greater perturbations to the natural conditions.
Experimental Evaluation of a Mixer-Ejector Marine Hydrokinetic Turbine at Two Open-Water Tidal Energy Test Sites in NH and MA
Authors: Rowell Matthew , Wosnik Martin , Barnes Jason , King Jeffrey P.
Published: August 2013

AbstractFor marine hydrokinetic energy to become viable, it is essential to develop energy conversion devices that are able to extract energy with high efficiency from a wide range of flow conditions and to field test them in an environment similar to the one they are designed
to eventually operate in. FloDesign Inc. developed and built a mixer-ejector hydrokinetic turbine (MEHT) that encloses the turbine in a specially designed shroud that promotes wake mixing to enable increased mass flow through the turbine rotor. A scaled version of this turbine was evaluated
experimentally, deployed below a purpose-built floating test platform at two open-water tidal energy test sites in New Hampshire and Massachusetts and also in a large cross-section tow tank. State-of-the-art instrumentation was used to measure the tidal energy resource and turbine wake flow
velocities, turbine power extraction, test platform loadings, and platform motion induced by sea state. The MEHT was able to generate power from tidal currents over a wide range of conditions, with low-velocity start-up. The mean velocity deficit in the wake downstream of the turbine was found
to recover more quickly with increasing levels of free stream turbulence, which has implications for turbine spacing in arrays.
A Numerical Analysis of Bidirectional Ducted Tidal Turbines in Yawed Flow
Authors: Belloni Clarissa S.K. , Willden Richard H.J. , Houlsby Guy T.
Published: August 2013

AbstractThe paper presents a computational study of ducted bidirectional tidal turbines using three-dimensional Reynolds-averaged Navier-Stokes simulations. We model the outer duct as a solid body and use a porous disc to represent the turbine rotor, a simplification that
captures changes in linear momentum and thus the primary interaction of the turbine with the flow through and around the duct while greatly reducing computational complexity. The duct is modeled using linearly converging and diverging sections and a short straight pipe at the duct throat.We
investigate the performance of bare and ducted turbines and relate these to the flows through the devices. For the ducted turbine under investigation, we show a substantial decrease in power generated relative to a bare turbine of diameter equal to the external diameter of the duct. In the
case of ducted turbines with concave duct exteriors, we observe two external flow regimes with increasing turbine thrust: nozzle-contoured and separation dominated regimes. Maximum power occurs within the separation dominated flow regime due to the additional channel blockage created by the
external separation.The ducts of ducted tidal turbines have been argued to provide a flow straightening effect, allowing modest yaw angles to be readily accommodated. We present a comparison of bare and ducted turbine performance in yawed flow. We show that while bare turbine performance
decreases in yawed flow, ducted turbine performance increases. This is due to both a flow straightening effect and also an increase in effective blockage as ducts present greater projected frontal area when approached nonaxially.
Design of a Novel Vertical Axis Water Turbine With Retractable Arc-Type Blades
Authors: Wenlong Tian , Baowei Song , Zhaoyong Mao , Hao Ding
Published: August 2013

AbstractA drag-type vertical axis water turbine, like Savonius, experiences negative torque in the returning half cycle, which limits the power efficiency. A new drag-type turbine, which consists of several retractable blades that are mounted on a drum, is designed and analyzed
in this paper. The open angle of each blade is controlled to achieve a high output performance. Kinematics analysis demonstrated that the returning blades can fit to the drum and negative torques can then be considerably deduced. Two-dimensional computational fluid dynamics simulations were
performed to give detailed information about the output of the turbine. The simulation results show that the maximum averaged power coefficient is 0.2595, obtained at a flow coefficient of 0.4.
Modeling of the Efficiency of a Semisubmerged Ocean Wave Energy Converter
Authors: MacNicoll Michael T. , Thiagarajan Krish P. , Rohrer John
Published: August 2013

AbstractThe RTI G2 is a terminator-type wave energy converter (WEC) that converts energy through a power take-off (PTO) system located within an elongated, wave-front facing compressible air chamber. The compression and expansion of the chamber is driven by both kinetic and
potential energy due to the surge and heave wave forces acting on an actuator plate oriented parallel to oncoming waves. The RTI G2 converter is mounted on a stabilizing frame, which may float or be fixed to the seabed and allows the air chamber to be totally submerged below wave troughs during
severe seas. The present work examines the performance of the RTI G2 on a fixed frame. Model tests conducted on a 1:8 scale are reviewed, and a mathematical model to describe the performance of the RTI G2 is developed. The experimental results are used for calibration and validation of the
mathematical model. Several orientation angles of the compression chamber are modeled, with higher orientation angles yielding better efficiencies at higher wave frequencies. The RTI G2 is a novel WEC concept, and the present work provides the first analytical investigation into its behavior.
Velocity Deficit and Swirl in the Turbulent Wake of a Wind Turbine
Authors: Dufresne Nathaniel P. , Wosnik Martin
Published: August 2013

AbstractEnergy production data from several of the existing large offshore wind farms indicate that turbine arrays can suffer from a significant overall energy production shortfall, due to wakes generated by turbines upstream interacting with turbines downstream. An experimental
investigation of the axial and azimuthal (swirl) velocity field in the wake of a single three-bladed wind turbine with rotor diameter of 0.91 m was conducted. The turbine was positioned in the free stream, near the entrance of the 6 m×2.7 m cross section of the UNH Flow Physics Facility,
a 72-m-long boundary layer wind tunnel. The turbine model was tested at various rotor loading conditions with blade tip-speed ratios up to 2.8. A Pitot-static tube and constant temperature hot-wire anemometry with a multiwire sensor were used to obtain velocity field measurements in the wake
of the model turbine up to 20 diameters downstream. The results of an equilibrium similarity theory for the axisymmetric wake with rotation are presented. The measurements obtained were used to examine the validity of the derived scaling functions for streamwise and azimuthal velocity, wake
growth, and turbulence.
Theoretical Assessment of Ocean Current Energy Potential for the Gulf Stream System
Authors: Yang Xiufeng , Haas Kevin A. , Fritz Hermann M.
Published: August 2013

AbstractThe Gulf Stream system features some of the fastest and most persistent currents in the Atlantic Ocean and has long been identified as a promising target for renewable ocean current energy. This study investigates the theoretical energy potential of ocean currents
for the Gulf Stream system. A simplified analytical model is calibrated and utilized to represent the quasi-geostrophic balance in the North Atlantic subtropical circulation. The effect of turbines is included in the model as additional turbine drag force. The energy equation in the system
is derived and analyzed both locally and basin-wide. Basin-wide, energy production from surface wind stress is balanced by energy dissipation from natural friction and turbines. However, the pressure gradient is playing an important role in redistributing the energy in the local energy balance.
It is found that increasing turbine drag does not necessarily increase total energy dissipation from turbines. The maximum energy dissipation by turbines is estimated to be approximately 44 GW, although electrical power output will be significantly reduced due to various engineering and technological
constraints. The turbine drag has significant impact on the circulation system. The reduction of energy and volume fluxes in the circulation is featured for different levels of turbine drag. It is found that residual energy flux along the western boundary can be significantly reduced under
the peak energy dissipation by turbines, while reduction of volume flux is less extreme.
An Analysis of Florida’s Sea Water Cooling Resource
Authors: Porak Dustin N. , VanZwieten James H. , Wiles Benjamin
Published: August 2013

AbstractA study to assess the sea water cooling (SWC) feasibility in southeast Florida was conducted using simulated and measured sea water temperatures. These data were input into a representative SWC system model to quantify potential energy savings over conventional cooling
systems. The HYbrid Coordinate Ocean Model was used to characterize near-bottom temperatures statewide, predicting that minimum temperatures needed for effective SWC are closest to the shore off the coasts of Fort Lauderdale and Miami. Numerous in situ data sets recently collected near
Fort Lauderdale/Miami are presented alongside several historic data sets to further enhance temperature resource information. These data suggest that a cold water resource with a mean temperature of 8°C‐10°C is present off Fort Lauderdale in 160‐220 m of water and 7°C‐9°C
is present off Miami in 200‐300 m of water. Both cold water resources are located approximately 6 km from the shore. These temperatures vary significantly at frequencies between 2 days and 2 weeks, with cooler temperatures during the summer suggesting a seasonal variation. An SWC plant
model is presented that was used to predict the electric power needed to operate a generic 10-MW (2,857-ton) AC system, which is compared with a traditional unassisted AC system. The plant model, with 3 years of HYbrid Coordinate Ocean Model temperature data, predicted that, in South Miami,
an SWC system can operate using the least amount of average electrical power in the state. At this location, the chilling system is estimated to operate at an average power savings of 86.9%, and a total comfort cooling system is estimated to operate at an average power savings of 58%, when
compared with a traditional AC system.
The Use of Numerical Modeling to Optimize a New Wave Energy Converter Technology
Authors: Green Brandon E. , MacDonald Daniel G.
Published: August 2013

AbstractA numerical model of a new point-absorber wave energy converter (WEC) technology was designed for simulation purposes using Python. The governing equations were defined to take into account the relevant forces on the buoy in an ideal wave environment as well as any
opposing forces due to damping, the power take-off (PTO) mechanism, and alternator. These equations of motion were solved using a high-order iterative process to study the linear kinematics of the buoy, the behavior of the PTO, and the associated power output in an ideal ocean wave environment.
The model allows for the adjustment of relevant parameters to explore the behavior of the WEC and optimize system efficiency depending on the wave conditions. The numerical model was designed to run single simulations for a specified time interval; however, an optimization routine was implemented
to optimize the mechanical parameters that greatly affect power output. The optimization portion of the model was implemented to study the response of the virtual WEC to a variety of input conditions pertaining to the buoy, PTO, and wave dynamics. This paper explains the development of the
prototype WEC and the associated numerical model, in addition to evaluating the response of the WEC to a variety of input conditions. The output of the numerical model is discussed for the associated wave field used for simulation purposes. The design and implementation of the numerical model
provides insight into changes in design components to maximize system power output and efficiency. The results of the numerical model and examples of data output for specific input conditions are investigated.
Subsurface Mooring Stability in the Presence of Vertical Shear
Authors: Hanson Howard P.
Published: August 2013

AbstractObservations in the Florida Current reveal significant vertical shear that can occur on the scale of turbine rotors and that can reverse. Because ocean current turbines in the Florida Current will require anchored moorings, the dynamics of the moored systems in the presence of shear become a factor in design and operation. Here, a simple stability analysis shows that the case of negative shear (slow current near the surface) is dynamically unstable for moored turbine systems.
Geographical distribution and population structure of springbok Antidorcas marsupialis rumen protozoa in southern Africa
Authors: Wilkinson R. C. , Van Hoven W.
Published: August 2013

Springbok were sampled in Angola, South West Africa, Kalahari Gemsbok National Park, the Cape Province and Eastern Transvaal between July 1973 and July 1974. All the ciliates found in the 20 rumens investigated belonged to a single genus Entodinium (family Ophryoscolecidae) and they varied in number from 0,3 x 106 to 2,5 x 106 per cm3 of rumen fluid. The different species were found and a positive correlation is seen between total numbers and protein content of the feed. It has been concluded that the numbers of E. par-uum are closely related to the protein concentration of the feed.
Populasie-samestelling van die bontebok Damaliscus dorcas dorcas in die Bontebok Nasionale Park gedurende Januarie 1974
Authors: De Graaff G. , Van der Walt P. T. , Van Zyl L. J.
Published: August 2013

Population data for the bontebok Damaliscus dorcas dorcas in the Bontebok National Park are presented. The social structure of the species centres around several breeding herds and a ram herd. Information pertaining to reproduction for the period 1960-1973 is discussed.
Two new bird records for the Tsitsikama National Parks
Authors: Robinson G. A.
Published: August 2013

A comprehensive check-list of the birds that possibly could occur in the vicinity of the Parks was published by Skead and Liversidge (1967). They refer to 210 bird species but only record 205; three species were duplicated in Part 1 (forest habitats) and Part 2 (sea habitats). It would appear that two species were omitted from Part 1. However, one of the species recently recorded should be included in Part 1 while the other belongs to Part 2.
Lewensloop van 'n Kaapse buffelbevolking Syncerus caffer in die Bontebok Nasionale Park
Authors: Van der Walt P. T. , Van Zyl L. J. , De Graaff G.
Published: August 2013

The course of an experiment to re-introduce the Cape buffalo Syncerus coffer in the Bontebok National Park, near Swellendam, is described and illustrated.
Image-guided chemoport insertion by interventional radiologists: A single-center experience on periprocedural complications
Authors: Yaacob Yazmin , Nguyen Dang V , Mohamed Zahiah , Ralib A Razali A , Zakaria Rozman , Muda Sobri
Published: August 2013

Purpose: To report our early experience in image-guided chemoport insertions by interventional radiologists. Materials and Methods: This was a cross-sectional study conducted in a tertiary center with 161 chemoport insertions done from June 2008 to June 2010. The chemoports were inserted either at the angiography suite or at the mobile operation theater unit. Ninety percent of the chemoports had right internal jugular vein (IJV) as the entry site. Other entry sites included the left IJV, subclavian veins and the inferior vena cava. Immediate and early complications were recorded. All insertions were performed under image guidance with the aid of ultrasound and fluoroscopy. Results: The technical success rate was 99.4%. In terms of immediate complications, there were only two cases of arterial puncture that resolved with local compression. No pneumothorax or air embolism was documented. Twenty-six early complications were recorded. The most common early complication was catheter blockage (12/161; 7.4%), followed by catheter-related infection (9/161; 5.6%). Other complications were catheter malposition, venous thrombosis and catheter dislodgement or leak. A total of 11 (6.8%) chemoports had to be removed within 30 days; most of them were due to infections that failed to respond to systemic antibiotic therapy. In terms of place of procedure, there were no significant differences in complication rates between the angiography suite and the mobile operation theater unit. Conclusion: Image-guided chemoport insertion by interventional radiologist gives low periprocedural complication rates. Using right IJV as the entry site, the image guidance gives good success rate with least complication.
Article Commentary: Neuroscience and Learning: Implications for Teaching Practice
Authors: Guy Richard , Byrne Bruce
Published: August 2013

Although neuroscience studies have provided us with an increasingly detailed picture of the basis for learning and memory, very little of this information has been applied within the area of teaching practice. We suggest that a better understanding of neuroscience may offer significant advantages for educators. In this context, we have considered recent studies in the neuroscience of learning and memory, with particular emphasis on working and semantic memory, and also suggest that neuroscience research into self-referential networks may improve our understanding of the learning process. Finally, we propose that advances in understanding the neural basis for metacognition may encourage the development of new perspectives that may help us to motivate students to learn about their own learning processes.
Heart Surgery in End-Stage Renal Disease: Is Outcome Worse for African American Patients?
Authors: Nwiloh Jonathan O. , Obialo Chamberlain I.
Published: August 2013

General results of open heart surgery in end-stage renal disease patients (ESRD) have been well-documented. However, it is unknown if the African American subgroup with known decreased access to advanced healthcare services and a higher prevalence rate of ESRD have a worse long-term survival after heart surgery. Thirty of 150 African American patients who underwent open heart surgery by a single surgeon at an urban community hospital between 1996 and 2010 were identified to have ESRD and were on chronic maintenance hemodialysis prior to surgery. Clinical and outcome data from both groups were retrospectively analyzed. There were no significant differences in the baseline demographic characteristics of the patients, but the ESRD cohort showed a significantly higher prevalence of peripheral vascular and cardiovascular diseases [ P < 0.001]. Compared to the non-ESRD subjects, the predicted logistic EuroSCORE was 16.4% vs. 9.4%, [ P < 0.001], while the observed 30 days operative mortality was 16.6% vs. 4.2% [ P < 0.02], respectively. In isolated coronary artery bypass graft cases, operative mortality was 20.8% and 3.0%, respectively. The 5- and 10-year post-surgery survival was 40% and 25% vs. 72% and 57% [ P < 0.01], respectively, in the ESRD and non-ESRD groups. Operative mortality and survival was worse in ESRD patients compared to non-ESRD patients based on their preoperative risk scores. Although the operative mortality of our ESRD patients was high, long-term survival was comparable to reports from both the United States Renal Data System and a Japanese ESRD cohort.
Seasonal changes in photochemical properties of dissolved organic matter in small boreal streams
Authors: Porcal P. , Dillon P. J. , Molot L. A.
Published: August 2013

Abstract. The fate of dissolved organic matter (DOM) in lakes and streams is significantly affected by photochemical transformation of DOM. A series of laboratory photochemical experiments was conducted to describe seasonal changes in photochemical properties of DOM. The stream samples used in this study originated from three different catchments in the southernmost part of the Boreal ecozone near Dorset, Ontario, Canada. A first-order kinetics equation was used to model photochemical degradation of DOM and the kinetic rate constant, K, was used as an indicator of photochemical properties of DOM. Kinetic rate constants from all three catchments showed a sinusoidal pattern during the hydrological year. K increased steadily during autumn and winter and decreased during spring and summer with a more than 3-fold range in each stream. The highest values were observed during spring melt events when DOM was flushed from terrestrial sources by high flows. The minimum rate constants were found in summer when discharge was lowest. K was strongly correlated with pH and iron. DOM molecular weight and specific absorbance at 254 nm also exhibited annual cycles corresponding to the seasonal cycles of terrestrial organic matter, but the relationships between these properties and K differed between seasons and may have been affected by previous exposure to solar radiation during transit from the catchment.
Identifying sources and controlling factors of arsenic release in saline groundwater aquifers
Authors: Liu C.-W. , Lu K.-L. , Kao Y.-H. , Wang C.-J. , Maji S.-K. , Lee J.-F.
Published: August 2013

Abstract. An integrated hydrogeochemical study is carried out to realize the occurrence of arsenic (As) in a saline aquifer. Saline groundwater was mostly concentrated in the uppermost aquifer and non-saline water was in the lower aquifer in the study area. High As concentrations were found in both uppermost and lower aquifers. No correlation among salination, well depth and As concentration was observed. Both reducing and oxidizing forms of Fe oxyhydroxides were identified in the magnetic fractions, which were concentrated by high gradient magnetic separation (HGMS) technique, revealing that the redox cycling of Fe occurred in the subsurface. High levels of Fe, HCO3-, DOC and NH4+ concentrations accompanying alkaline pH in the As-rich groundwater were consistent with the mechanism triggered by the microbial-mediated reductive dissolution of Fe oxyhydroxides. A threshold value of 50 μg L−1. As concentration was used as an indicator for identification of active proceeding reductive dissolution of As-bearing Fe oxyhydroxides in the saline aquifer. Desorption behaviors of As were relevant to its valence in the sediments and the co-existence of anions. Experimental and numerical results showed that additions of Cl- and SO42-, which represented the main anions of saline water, had minor effect on leaching sedimentary As. Although bicarbonate addition resulted in less As desorption than that of phosphate on a molar basis, the contribution of bicarbonate to the total release of As was greater than phosphate due to the much higher concentration of bicarbonate in groundwater and the associated microbial mediation. Collectively, the chemical effect of saline water on the As-release to groundwater is mild in the coastal aquifer.
Energy fluxes and surface characteristics over a cultivated area in Benin: daily and seasonal dynamics
Authors: Mamadou O. , Cohard J. M. , Galle S. , Awanou C. N. , Diedhiou A. , Kounouhewa B. , Peugeot C.
Published: August 2013

Abstract. Latent and sensible heat fluxes are known as key factors in the West African monsoon dynamics. However, few long-term observations of these land surface fluxes are available to document their impact in the climate variability of this region. The present study took advantage of the Sudanian site of the AMMA-CATCH (African Monsoon Multidisciplinary Analysis – Coupling the Tropical Atmosphere and Hydrological Cycle) observatory where turbulent fluxes were measured using the eddy covariance technique. One full year of data of energy budget over a cultivated site located in northern Benin was examined. Four contrasted seasons were identified and detailed focusing on their corresponding daily cycles. The flux partitioning was investigated through the evaporative fraction (EF) and the Bowen ratio (β) at both seasonal and daily scales. Finally, the surface conductance (Gs) and the decoupling coefficient (Ω) were calculated and confronted with specific bare soil or canopy models to identify the main processes for each season. The results pointed out the contrasted seasonal variations of sensible and latent heat fluxes due to changing atmospheric and surface conditions. During the wet season, surface conditions barely affected EF, which remained in steady regime (EF = 0.75), while latent heat flux was dominant and β was about 0.4. During the transitional periods, both EF and β were highly variable. A low but significant evapotranspiration was measured in the dry season (EF = 0.08) attributed to few scattered bushes, distributed on a bare area, possibly fed by the water table. Nevertheless, sensible heat fluxes were largely dominant (β ~ 10) during dry season. Moreover, β revealed the ligneous vegetation flowering dynamics during the dry season. The results also showed a strong surface atmosphere coupling, which suggests a systematic mixing of the flow within the canopy with the atmospheric surface layer whatever the atmospheric conditions and vegetation height. Modeling approaches showed the good agreement of soil evaporation with the Sakaguchi bare soil model. Transpiration was also well reproduced with the Collatz stomata model. Finally, skin surface temperature had large seasonal and daily amplitude and played a major role for all surface processes. As a consequence, the modeling of surface temperature is crucial to represent correctly energy and water budget for this region.
Acting, predicting and intervening in a socio-hydrological world
Authors: Lane S. N.
Published: August 2013

Abstract. This paper asks a simple question: if humans and their actions co-evolve with hydrological systems (Sivapalan and Blöschl, 2012), what is the role of those humans who are simultaneously hydrological scientists, bound up within this system? To put it more directly, can we, as socio-hydrologists study the socio-hydrological world in isolation from that world in a way that mirrors the supposed separation between scientists and society? I answer this question, in the negative, from three linked perspectives. The first draws directly upon science-technology studies to make a case to the (socio-hydrological) community that we need to be sensitive to constructivist accounts of science in general and hydrology in particular. I review three positions taken by such accounts and apply them to hydrological science, supported with specific examples: (a) the philosophical critique of the claimed abstraction of scientists and scientific activity from the socio-hydrological world; (b) the way in which hydrological science is embedded in wider societal decision-making; and (c) the recognition that socio-hydrological knowledge is much more distributed than we as (socio-)hydrologists commonly recognise. For the second perspective, I consider predictive modelling as a socio-hydrological practice. I draw upon wider studies of the practice of modelling, coupled to empirical evidence for one element of hydrological modelling, roughness parameterisation, to consider how it is that socio-hydrological modellers come to believe in the predictive models that they use. This will show that if predictive modelling is to be more than analytical, that if it is to effect more sustainable socio-hydrological futures, then we need to rethink the basic tenets of how we practice predictive modelling. These first two perspectives are themselves, in combination, analytical, prone to the criticism that they cause us to degenerate into an "anything goes" relationship with the world around us. Thus, in a third perspective I explicitly challenge this degeneration by setting out a number of practices that might be valuable for doing prediction within a socio-hydrological system. These include: (1) working with conflict and controversy in hydrological science, rather than trying to eliminate them; (2) using hydrological events to avoid becoming paradigm-bound; (3) being empirical and experimental but in a socio-hydrological sense; and (4) co-producing socio-hydrological predictions. I will show how this might be done through a project that specifically developed predictive models for making interventions in river catchments to increase high river flow attenuation, in which I found myself becoming detached from my normal disciplinary networks and attached to the co-production of a predictive hydrological model with communities normally excluded from the practice of hydrological science.
Ensemble projections of future streamflow droughts in Europe
Authors: Forzieri G. , Feyen L. , Rojas R. , Flörke M. , Wimmer F. , Bianchi A.
Published: August 2013

Abstract. There is growing concern in Europe about the possible rise in the severity and frequency of extreme drought events as a manifestation of global change. In order to plan suitable adaptation strategies it is important for decision makers to know how drought conditions will develop at regional scales. This paper therefore addresses the issue of future developments in streamflow drought characteristics across Europe. Through off-line coupling of a hydrological model with an ensemble of bias-corrected climate simulations (IPCC SRES A1B) and a water use scenario (Economy First), long term (1961–2100) ensemble streamflow simulations are generated that account for changes in climate, and the uncertainty therein, and in water consumption. Using extreme value analysis we derive minimum flow and deficit indices and evaluate how the magnitude and severity of low flow conditions may evolve throughout the 21st century. This analysis shows that streamflow droughts will become more severe and persistent in many parts of Europe due to climate change, except for northern and northeastern parts of Europe. Especially southern regions will face strong reductions in low flows. Future water use will aggravate the situation by 10–30% in Southern Europe, whereas in some sub-regions in Western, Central and Eastern Europe a positive climate signal may be reversed due to intensive water use. The multi-model ensemble projections of more frequent and severe streamflow droughts in the south and decreasing drought hazard in the north are highly significant, while the projected changes are more dissonant in a transition zone in between.
QUANTITATIVE MEASUREMENT OF SOIL EROSION FROM TLS AND UAV DATA
Authors: Eltner A. , Mulsow C. , Maas H.-G.
Published: August 2013

Abstract. Soil erosion is a major issue concerning crop land degradation. Understanding these complex erosion processes is necessary for effective soil conservation. Herein, high resolution modelling of relief changes caused by run-off from precipitation events is an essential research matter. For non-invasive field measurements the combination of unmanned airborne vehicle (UAV) image data and terrestrial laser scanning (TLS) may be especially suitable. The study's objective is to measure high precision digital terrain models (DTM) of the soil surface at two selected research areas with the extent of at least 500 square meters. The used UAV is integrated with GPS and inertial measurement unit (IMU). Furthermore, an active stabilizing camera mount equipped with a customary compact camera is implemented. For multi-temporal comparison of measured soil surfaces and for aligning UAV and TLS data a stable local reference system consisting of signalized points is defined by total station measurements. Two different software packages are applied for DTM generation from UAV images and compared to the corresponding DTM captured by TLS. Differences between the point clouds are minimal six millimeters and generally within TLS accuracy range. First multi-temporal comparisons are made and illustrate interesting surface changes.
UAS-based automatic bird count of a common gull colony
Authors: Grenzdörffer G. J.
Published: August 2013

Abstract. The standard procedure to count birds is a manual one. However a manual bird count is a time consuming and cumbersome process, requiring several people going from nest to nest counting the birds and the clutches. High resolution imagery, generated with a UAS (Unmanned Aircraft System) offer an interesting alternative. Experiences and results of UAS surveys for automatic bird count of the last two years are presented for the bird reserve island Langenwerder. For 2011 1568 birds (± 5%) were detected on the image mosaic, based on multispectral image classification and GIS-based post processing. Based on the experiences of 2011 the results and the accuracy of the automatic bird count 2012 became more efficient. For 2012 1938 birds with an accuracy of approx. ± 3% were counted. Additionally a separation of breeding and non-breeding birds was performed with the assumption, that standing birds cause a visible shade. The final section of the paper is devoted to the analysis of the 3D-point cloud. Thereby the point cloud was used to determine the height of the vegetation and the extend and depth of closed sinks, which are unsuitable for breeding birds.