bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of ANN to Predict S.I. Engine Performance and Emission Characteristics Fuelled Bioethanol
Authors: Saravana Kannan T. , Saleh Ahmed Abu , Ani Farid Nasir
Published: June 2014

1024x768 The performance of artificial neural network (ANN) to predict spark ignition (S.I) engine performance such as torque, BSFC, exhaust temperature and emissions (CO and HC) for various compression ratios was investigated. For training and testing the ANN, experimental data from a single cylinder Hydra spark ignition engine powered by various bioethanol and gasoline blends (E0, E10, E20, E40 and E60) were used. ANN performance was measured by mean squared errors and correlation coefficient. The training function used was trainbr and the training algorithm used was feed-forward back propagation. The overall correlation coefficient obtained from the prediction was 0.98526 and the mean squared error obtained was very low (9.26 E-06). Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}
Optimization of Heavy Duty Truck Chassis Design by Considering Torsional Stiffness and Mass of the Structure
Authors: Kurdi Ojo , Rahman Roslan Abdul , Samin Pakharuddin Mohd
Published: June 2014

The torsional stiffness is one of the most important properties of chassis that significantly affect its dynamic characteristics such as handling and rollover. The torsional stiffness is desired to be as high as possible since low torsional stiffness may cause resonance or vibration. There are several types of heavy duty truck chassis that used in Malaysia and no information about the torsional stiffness magnitude of it. In this work, the torsional stiffness of several existing types of heavy duty truck chassis and some modified types, namely: arc model, block model, hole model, multi holes model and fully block model are determined using finite element method. The torsional stiffness of several chassis was compared together with the weight comparison in order to get the best design of chassis that has high torsional stiffness and low weight. Based on the simulation result, the multi holes model is the best design due to the highest of torsional stiffness and the lowest mass.
Optimizing the Ignition Timing of a Converted CNG Mono-Gas Engine
Authors: Fawzi Mas , Hashim Mohd Norfaiz , Zulkifli Fathul Hakim , Amirnordin Shahrin Hisham
Published: June 2014

Governmental policies on renewable energy and environmental act are aggressively being enforced to mitigate recent climate change. Natural gas is not renewable but it is the most abundant and has the lowest Lifecycle CO2emission among fossil fuel. Realizing such promising alternative, many logistics and transportation companies are converting their existing diesel-fueled vehicle to CNG-fueled. Researchers have shown that CNG engines offer advantages compared to diesel and gasoline engines such as high efficiency and low emissions. Prior to this work, a 4.3L 4-cylinder diesel engine was modified and retrofitted with a CNG mono gas system. However, it was observed that the engine, CNG-fueled combustion is not stable especially at idling speed. The purpose of this study is to optimize the ignition timing best suited for idling both in normal operating mode (700-850 rpm) and in cold start mode (1000-2000 rpm). The ignition timings tested were 20oBTDC and 25oBTDC. The measurements were made at engine speeds from 700 to 2500 rpm. Some irregularities were found in the result, but overall, the ignition timing 25oBTDC is better than 20oBTDC in terms of fuel consumption and exhaust gas emissions. For this particular system, the results recommend that the idling engine speed should be at 700-800 RPM and 1500 RPM during the normal mode and cold start mode respectively. The use of engine speed of 1000 to 1300 rpm should be minimized to reduce overall exhaust gas emissions.
Effect of Air Movement to Spray Development of Rapeseed Oil in Diesel Engine
Authors: Sapit Azwan , Azahari Mohd , Fawzi Mas , Khalid Amir , Manshoor Bukhari
Published: June 2014

Fuel-air mixing is important process in diesel combustion. Generally there a two air mixing strategy, which is slow fuel – fast air mixing and fast fuel – slow air mixing. Air movement inside the combustion chamber greatly affect the mixing process and made effective fuel air mixing possible. Biomass fuel needs great help of mixing to atomization because the fuel has high viscosity and high distillation temperature. This study investigates the effect of air movement to spray development and atomization characteristics of rapeseed oil (RO). Optical observation of RO spray was carried out using shadowgraph photography technique and also using high speed camera. The results show that fast air movement effectively promotes RO spray atomization, with the RO spray expand outward from the main body through the whole spray length, which suggests fuel dispersion due to fast air movement.
Heterogeneous Microwave Irradiation Biodiesel Processing of Jatropha Oil
Authors: Ani Farid Nasir , Bakheit Elhameed Ahmed
Published: June 2014

This paper investigated the three critical reaction parameters including catalyst concentration, microwave exit power and reaction time for the transesterification process of jatropha curcas oil using microwave irradiation. The work is an attempt to reduce the production cost of biodiesel. Similar quantities of methanol to oil molar ratio 6:1 and calcium oxide as a heterogeneous catalyst were used. The results showed that the best yield percentage 96% was obtained using 300W microwave exit power, 8 %wt CaO and 7 min. The methyl ester FAME obtained was within the standard of biodiesel fuel.
Modeling and Numerical Simulation for the Newly Designed Four Cavity Blades Vertical Axis Wind Turbine
Authors: Suffer Kadhim , Usubamatov Ryspek , Quadir Ghulam Abdul , Ismail Khairul Azwan
Published: June 2014

The last years have proved that Vertical Axis Wind Turbines (VAWTs) are more suitable for urban areas than Horizontal Axis Wind Turbines (HAWTs). To date, very little has been published in this area to assess good performance and lifetime of VAWTs either in open or urban areas. The main goal of this current research is to investigate numerically the aerodynamic performance of a newly designed cavity type vertical axis wind turbine having four blades. In the current new design the power generated depends on the drag force generated by the individual blades and interactions between them in a rotating configuration. For numerical investigation, commercially available computational fluid dynamic CFD software GAMBIT and FLUENT were used. In this numerical analysis the Shear Stress Transport (SST) k-ω turbulence model is used which is better than the other turbulence models available as suggested by some researchers. The computed results show good agreement with published experimental results.
Development of Computer-Aided EDM for Machining Micropits on Spherical Surface of Hip Implant
Authors: Kartiko Nugroho , Yahya Azli , Nor Liyana Safura Hashim , Syahrullail Samion , Razak M. Daud
Published: June 2014

This study aims to develop dedicated computer-aided workpiece positioning system for biomedical application. The application is for machining micropits on spherical surface of hip implant using electrical discharge machining (EDM). New spherical positioning system has been designed and realized for further development. A computer is used as a main control unit to control the positioning system and modular servo motors with tuneable PID controller are utilized by the system. This paper explains the configuration of the implemented system and tuning process to optimize the system performance.
Propeller Effect on 3D Flow at the Stern Hull of a LNG Carrier Using Finite Volume Method
Authors: Nakisa Mehdi , Malik Adi Maimun Abdul , Ahmed Yasser M. , Steen Sverre , Behrouzi Fatemeh , Hassanzadeh Reza , F. Sabki Ahmad
Published: June 2014

Numerical study and RANS simulations have been applied to investigate the incompressible free surface flow around the stern hull of Liquefied Natural Gas (LNG) ship affected by working propeller behind of her. Experimental works are carried out using LNG ship model in Marine Teknologi Center (MTC) of Univrsiti Teknologi Malaysia (UTM) to verify the computational fluid dynamic (CFD) results. Ansys-CFX 14.0 based on viscous flow finite volume code using the two-phase Eulerian–Eulerian fluid approach and shear stress transport (SST) turbulence model have been used in this study. A tetrahedral unstructured combined with prism grid were used with the viscous flow code for meshing the computational domain of water surface around it. CFD simulation has been verified using available experimental results. Finally, the flow structure, streamlines, velocity and pressure distribution around stern hull and propeller zone are discussed and analysed.
Partial Discharge Detection and Localization in Power Transformer Windings
Authors: Abdul-Malek Zulkurnain , Aziz Mohammed Abd Ali , Aziz Ali Saleh
Published: June 2014

The activity of partial discharge (PD) is one of the major causes of failure of high voltage transformers. Partial discharge detection is usually used as a preventive technique to avoid large-scale losses in the power system. Suitable and reliable methods to detect and localize PD in equipment winding insulation, such as in a transformer, are still widely researched. Among the methods used are based on the acoustic wave, on the electrical determination of the dominant capacitive region in frequency domain, and on the travelling wave method. After a brief review on current methods, a technique based on the frequency spectra of the measured signals showing the characteristic of the transfer functions is proposed. A Matlab simulation of the proposed technique is then presented. PD signals are injected at various points in a transformer winding to represent PD sources at different location within the winding. The main difficulties encountered in current methods, which is the noise and the limit in the detection frequency range, is overcome. In the frequency spectra of the proposed method, the crests and troughs could be used for locating the source of the discharge activity in a power transformer winding.
The Impacts of Hybrid Connection Pumped Storage Hydropower and Wind Power in Iranian Grid
Authors: Mohammad Fathi , Zulkurnain Abdul Malek
Published: June 2014

Many reasons such as increasing in price of fossil fuel and the decreasing sources of fuel as well as greenhouse gas problems cause the trend towards using renewable energy instead. One of the more popular renewable energy sources is wind power (WP). Beside of all the advantages and the fact that the wind farms (WFs) can connect to the grid, they have unstable production and the energy cannot be stored when the grid does not need power. The main concern of the increase number of WFs in Iran is the uncertainty of WP. Pumped storage hydropower (PSH) is a solution which helps WF operation to become more stable and reliable. Consequently, the ways of connections between grid, WP and PSH are important for this system. In this paper, an attempt is made to solve this problem by manipulating all available hybrid and individual connections between current grid, WF and PSH. This hybrid connection can help the grid to generate more reliable power. In addition, the amount of WP is shown to increase realistically. All possible connection types and their impacts were investigated.
Study on the Vertical Component of Lightning Electric Field during Monsoon Period in Malaysia
Authors: Salimi Behnam , Abdul-Malek Zulkurnain , Mehranzamir Kamyar , Ahmad Noor Azlinda
Published: June 2014

The most recognized and powerful demonstration of electrostatics in the natural world is a lightning discharge. The misoperation of several equipment and circuits would not only be caused by a direct contact with the lightning flash, but also by an indirect effect of a lightning channel. Appropriate information about lightning signature parameters can provide precise knowledge of lightning discharge that can be essential for the design of more improved detection and protective system. In this paper, the preliminary breakdown pulse train and the first return stroke of cloud to ground lightning discharge signatures observed in south of Malaysia are analyzed. Statistical analyses of the ratio between the maximum preliminary breakdown pulse trains amplitude and the first return stroke amplitude (BP/RS ratio), and the time duration between the high active part of the pulse train, and the return stroke (BP/RS separation) are presented. Observations on the statistical analyses show that about 94% of lightning signals have detectable breakdown pulses. The arithmetic means of BP/RS ratio and the BP/RS separation are 36.3% and 26.4ms, respectively.
Position Tracking Controllers for Two Wheeled Inverted Pendulum Robot
Authors: Bature Amir A. , Buyamin Salinda , Ahmad Mohamad Noh , Muhammad Mustapha
Published: June 2014

: This paper present comparison between model based controller and nonmodel based controller in position tracking of a two wheeled inverted pendulum (TWIP). A Linear Quadratic Controller (LQR) which is a state feedback linear controller and fuzzy logic controller (FLC) which is non-model based intelligent controller are designed and simulated and the performances of the two controllers are compared. The FLC shows better performance than the LQR controller.
Simulation of the Airflow Characteristics inside Hard Disk Drive
Authors: Tan Wee Choon , Lee Teck Wei , Lim Eng Aik
Published: June 2014

The flow pattern of the hard disk drive is correlated with the spinning speed produced of the disk, while spinning speed is the factor affecting the performance of the drive. The aim of this study was to investigate the airflow inside the hard disk drive. The simulation model is constructed based on the currently available 2.5-inches disk drive in the market, with 5400 rpm disk rotation speed. ANSYS Fluent is applied to analyze the airflow characteristic. Good agreement in normalized velocity magnitude and vectors plot shows the flowing of the air surrounded the drive region. In conclusion, it is found out that the results have close agreement with each other, with a range of percentage differences and errors between 2% to 5%.
A Verification and Validation Study of CFD Simulation of Wind-Induced Ventilation on Building with Single-Sided Opening
Authors: Kasim Nur Farhana Mohamad , Zaki Sheikh Ahmad , Mat Ali Mohamed Sukri , Mohammad Ahmad Faiz , Abd Razak Azli
Published: June 2014

Wind-induced ventilation is widely acknowledged as one of the best approaches for inducing natural ventilation. Computational fluid dynamics (CFD) technique is gaining popularity among researchers as an alternative for experimental methods to investigate the behavior of wind-driven ventilation in building. In this present paper, Reynolds averaged Navier-Stokes equation (RANS) k-ε model approach is considered to simulate the airflow on a simplified cubic building with an opening on a single façade. Preliminary simulation using models from previous experiment indicates the reliability of OpenFOAM, the open source software that will be used in this study. The results obtained in this study will better define options for our future study which aims to explore how different buildings arrays modify the airflow inside and around a naturally ventilated building.
Effect of Epoxidation Level in Silica Filled Epoxidized Natural Rubber Compound on Cure, Rheological, Mechanical and Dynamic Properties
Authors: Rohadi Afnan Aiman , Rahmat Abdul Razak , Kamal Mazlina Mustafa
Published: June 2014

Reinforcement of rubber by precipitated silica is adversely affected due to lack of strong polymer silica bonding. Functionalized polymers interact strongly with surface silanol groups of precipitated silica. In this work, effect of variation of epoxide content in silica filled Epoxidized Natural Rubber (ENR) compound was studied namely ENR 10, 25, 37.5 and 50mol%. Increasing in epoxide level of rubber has contributed to better rubber filler interaction and lead to better mechanical properties. Meanwhile, ENR’s with greater degree of polarity has contributed significantly to higher storage moduli at small deformation and also leads to increase in bound rubber content value. Fourier transform infrared spectroscopy studies showed that the silanol groups in silica interact with ENR through formation of Si-OH bond.
Survey on the Indirect Methods of Potential Flow Used for the Optimization of Airships Profile
Authors: Hassanzadeh Reza Abbasabadi , Shariatmadari Shahab , Chegeni Ali , Ghazanfari Seyed Alireza , Nakisa Mahdi
Published: June 2014

The present study aims to investigate the optimized profile of the body through minimizing the Drag coefficient in certain Reynolds regime. For this purpose, effective aerodynamic computations are required to find the Drag coefficient. Then, the computations should be coupled thorough an optimization process to obtain the optimized profile. The aerodynamic computations include calculating the surrounding potential flow field of an object, calculating the laminar and turbulent boundary layer close to the object, and calculating the Drag coefficient of the object’s body surface. To optimize the profile, indirect methods are used to calculate the potential flow since the object profile is initially amorphous. In addition to the indirect methods, the present study has also used axial singularity method which is more precise and efficient compared to other methods. In this method, the body profile is not optimized directly. Instead, a sink-and-source singularity distribution is used on the axis to model the body profile and calculate the relevant viscose flow field.
Songbird-transported tickIxodes minor(Ixodida: Ixodidae) discovered in Canada
Authors: Scott John D. , Durden Lance A.
Published: June 2014

Ticks are carried into Canada by millions of birds during spring migration, and some of these blood-sucking ectoparasites harbour tick-associated pathogens. During a pan-Canadian study of ticks on avian hosts, we identified an extralimital tick,Ixodes minorNeumann (Ixodida: Ixodidae) collected from a Common Yellowthroat,Geothlypis trichas(Linnaeus) (Passeriformes: Parulidae) at Toronto, Ontario, Canada. Although theI. minorlarva was not tested for any tick-borne pathogens, this tick species is considered a competent enzootic vector of the Lyme disease spirochete,Borrelia burgdorferiJohnson, Schmid, Hyde, Steigerwalt, and Brennersensu lato(s.l.). Epidemiologically, diverseB. burgdorferi s.l.genospecies have been detected in, or isolated fromI. minor, and this tick species potentially represents a public health risk not only in the southeastern United States of America, whereI. minoris indigenous, but also in Canada. This tick collection is the northernmost report ofI. minorin North America, and constitutes the first documentation of this tick species in Canada.
Transformative consumer research: Its origins and possible enrichment of the field of consumer research in South Africa
Authors: Ungerer Leona M.
Published: June 2014

Orientation: This article provides a rationale for considering transformative consumer research as a research approach for investigating the relationship between consumption and consumers’ well-being in South Africa.Research purpose: The purpose of this study is to explore the principles underlying transformative consumer research, including how it differs from traditional research methods and pointing out some established research areas in this field.Motivation for the study: Apart from pointing to a lack of literature, this article highlights the relevance of this approach for emerging countries by investigating the principles and practices embedded in transformative consumer research. It provides some indication of how an investigation of these areas may contribute to enhancing the relevance of consumer research to its various stakeholders.Research design, approach and method: The author used a literature review to conduct the study.Main findings: It appears that consumer research currently lacks external and internal relevance. A transformative consumer-research approach may address some of the fundamental problems in the way consumer psychologists plan and conduct their research, contributing to this lack of relevance.Practical/managerial implications: Most stages of the traditional research approach may need to be adapted for transformative research purposes. Some approaches appear particularly suited to transformative consumer research, including revelatory, incendiary, policy, participatory and coalition research. Contribution/value-add: This study’s primary contribution stems from suggesting a rather novel additional approach to enhance the relevance of consumer research in South Africa, pointing out some established practices in the field of transformative consumer research and suggesting how they may augment consumer research in South Africa.
Some thoughts on the relationship between Old Testament studies and systematic theology
Authors: Snyman S.D.
Published: June 2014

This article explores the relationship between Old Testament studies and systematic theology. After an overview of what Old Testament studies and systematic theology comprise, a historical overview of the problem is given. Two examples of the problem are provided (the USA and South Africa) before the author proceeds to his own views. The article argues that the two subjects have grown so far apart that it is doubtful whether the interaction between Old Testament studies and systematic theology will have any significant impact on the identity or content of either Old Testament studies or systematic theology. The identity of and the way in which the fields of study are practiced will not allow them to impact on one another. In an increasing way, theological disciplines will live side by side, each carrying on with what are perceived to be the cutting-edge questions within the respective fields of interest.
Observation of improved adherence with frequent urine drug testing in patients with pain
Authors: Yee, BS David A. , Hughes, BA Michelle M. , Guo, MS Alexander Y. , Barakat, BS Neveen H. , Tse, BS Stephanie A. , Ma, PharmD Joseph D. , Best, PharmD, MAS Brookie M. , Atayee, PharmD, BCPS Rabia S.
Published: June 2014

Objective: To determine the relationship between urine drug testing (UDT) frequency and patient adherence for prescribed buprenorphine, carisoprodol, fentanyl, hydrocodone, methadone, morphine, and oxycodone. Setting: Patients with pain routinely seen by private practitioners. Design: A retrospective analysis was conducted on urinary excretion data analyzed by Millennium Laboratories between March 2008 and May 2011.Patient participants: Patients in the United States with chronic pain who underwent routine UDT to confirm adherence for prescribed medications. Interventions: Adherence for the urine drug test was defined as the presence of parent drug and/or metabolite(s) greater than or equal to the lower limit of quantitation. The percent of adherence for prescribed medications was compared to the average percent of the same in subjects with five or more visits.Main outcomes: Correlation analyses were used to determine the relationship between adherence for prescribed medications and number of visits.Results: There were 255,168 specimens submitted for testing from 166,755 individuals. When monitoring with more frequent visits (>=5 visits) adherence was higher by 1 percent for buprenorphine (89 percent vs 88 percent); 8 percent for carisoprodol (77 percent vs 69 percent); 5 percent for fentanyl (95 percent vs 90 percent); 7 percent for hydrocodone (83 percent vs 76 percent); 3 percent for methadone (96 percent vs 93 percent); 5 percent for morphine (92 percent vs 87 percent); and 8 percent for oxycodone (90 percent vs 82 percent).Conclusions: Adherence for prescribed medications is higher with frequent urine monitoring. UDT can be used as tool that may help improve this in patients with chronic pain.
Preventing and managing aberrant drug-related behavior in primary care: Systematic review of outcomes evidence
Authors: Argoff, MD Charles E. , Kahan, MD Meldon , Sellers, MD Edward M.
Published: June 2014

Several strategies for preventing, identifying, and responding to aberrant opioid-related behaviors are recommended in pain management guidelines. This systematic review evaluated data supporting basic strategies for addressing aberrant opioid- related behaviors. Risk reduction strategies were identified via a review of available guidelines. Systematic literature searches of PubMed (May 1, 2007- January 18, 2013) identified articles with evidence relevant to nine basic strategies. Reference lists from relevant articles were reviewed for additional references of interest. Levels of evidence for articles identified were graded on a four-point scale (strongest evidence = level 1; weakest evidence = level 4) using Oxford Centre for Evidence-Based Medicine Levels of Evidence criteria. Weak to moderate evidence supports the value of thorough patient assessment, risk-screening tools, controlled substance agreements, careful dose titration, opioid dose ceilings, compliance monitoring, and adherence to practice guidelines. Moderate to strong evidence suggests that prescribing tamper-resistant opioids may help prevent misuse but may also have the unintended consequence of prompting a migration of users to other marketed opioids, heroin, or other substances. Similarly, preliminary evidence suggests that although recent regulatory and legal efforts may reduce misuse, they also impose barriers to the legitimate treatment of pain. Despite an absence of consistent, strong supporting evidence, clinicians are advised to use each of the available risk-mitigation strategies in combination in an attempt to minimize the risk of abuse in opioid treatment patients. Physicians must critically evaluate their opioid prescribing and not only increase their efforts to prevent substance
Uncertainties in future climate predictions due to convection parameterisations
Authors: Rybka H. , Tost H.
Published: June 2014

Abstract. In the last decades several convection parameterisations have been developed to consider the impact of small-scale unresolved processes in Earth System Models associated with convective clouds. Global model simulations, which have been performed under current climate conditions with different convection schemes, significantly differ among each other in the simulated transport of trace gases and precipitation patterns due to the parameterisation assumptions and formulations, e.g. the computation of convective rainfall rates, calculation of entrainment and detrainment rates etc. Here we address sensitivity studies comparing four different convection schemes under alternative climate conditions (with doubling of the CO2 concentrations) to identify uncertainties related to convective processes. The increase in surface temperature reveals regional differences up to 4 K dependent on the chosen convection parameterisation. These differences are statistically significant almost everywhere in the troposphere of the intertropical convergence zone. The increase in upper tropospheric temperature affects the amount of water vapour transported to the lower stratosphere, leading to enhanced water vapour contents between 40% and 60% at the cold point temperature in the Tropics. Furthermore, the change in transporting short-lived pollutants within the atmosphere is highly ambiguous for the lower and upper troposphere. These results reflect that different approaches to compute mass fluxes, detrainment levels or trigger functions determine the transport of short-lived trace gases from the planetary boundary layer to lower, middle or upper tropospheric levels. Finally, cloud radiative effects have been analysed, uncovering a shift in different cloud types in the Tropics, especially for cirrus and deep convective clouds. These cloud types induce a change in net cloud radiative forcing varying from 0.5 W m−2 to 2.0 W m−2.
Emission of iodine containing volatiles by selected microalgae species
Authors: Thorenz U. R. , Carpenter L. J. , Huang R.-J. , Kundel M. , Bosle J. , Hoffmann T.
Published: June 2014

Abstract. In this study we present the results of an incubation study of different phytoplankton samples in F/2 aqueous media treated with elevated ozone levels. Halocarbon measurements show that the samples tested released bromoform and different iodocarbons including iodomethane, iodochloromethane and diiodomethane. Iodide and iodate levels in the liquid phase were representative of concentrations of surface water in a natural environment. Measurement of volatile iodine (I2) emissions from two diatom samples (Mediopyxis helysia and Porosira glacialis) and the background sample (F/2-medium from locally seawater), showed that the quantity of I2 evolved depends on the ozone concentration in the air. This behaviour was assumed to be caused by the oxidation reaction mechanism of iodine with ozone. The I2 emission flux agrees with model calculations at different iodide concentrations. The I2 emission of a natural plankton concentrate sample was, however, very low compared to other samples and showed no dependence on ozone. The reason for this was shown to be the low iodide concentration in the algae suspension, which seems to be the limiting factor in the oxidative formation of I2.
Atmospheric black carbon and warming effects influenced by the source and absorption enhancement in Central Europe
Authors: Nordmann S. , Cheng Y. F. , Carmichael G. R. , Yu M. , Denier van der Gon H. A. C. , Zhang Q. , Saide P. E. , Pöschl U. , Su H. , Birmili W. , Wiedensohler A.
Published: June 2014

Abstract. Particles containing black carbon (BC), a strong absorbing substance, exert a rather uncertain direct and indirect radiative forcing in the atmosphere. To investigate the mass concentration and absorption properties of BC particles over Central Europe, the model WRF-Chem was used at a resolution of 12 km in conjunction with a high resolution BC emission inventory (EUCAARI 42-Pan-European Carbonaceous Aerosol Inventory; 1/8° × 1/16°). The model simulation was evaluated using measurements of equivalent soot carbon, absorption coefficients and particle number concentrations at 7 sites within the German Ultrafine Aerosol Network, PM10 mass concentrations from the dense measurement network of the German Federal Environmental Agency at 392 monitoring stations, and aerosol optical depth from MODIS and AERONET. A distinct time period (25 March to 10 April 2009) was chosen, during which the clean marine air mass prevailed in the first week and afterwards the polluted continental air mass mainly from south-east dominated with elevated daily average BC concentration up to 4 μg m−3. The simulated PM10 mass concentration, aerosol number concentration and optical depth were in a good agreement with the observations, while the modelled BC mass concentrations were found to be a factor of 2 lower than the observations. Together with backtrajectories, detailed model bias analyses suggested that the current BC emission in countries to the east and south of Germany might be underestimated by a factor of 5, at least for the simulation period. Running the model with upscaled BC emissions in these regions led to a smaller model bias and a better correlation between model and measurement. On the contrary, the particle absorption coefficient was positively biased by about 20% even when the BC mass concentration was underestimated by around 50%. This indicates that the internal mixture treatment of BC in the WRF-Chem optical calculation is unrealistic in our case, which over amplifies the light absorption by BC containing particles. By adjusting the modeled mass absorption cross-section towards the measured values, the simulation of particle light absorption of BC was improved as well. Finally, the positive direct radiative forcing of BC particles at top of the atmosphere was estimated to be in the range of 0 to +4 W m−2 over Germany for the model run with improved BC mass concentration and adjusted BC light absorption cross-section. This treatment lowered the positive forcing of BC by up to 70%, compared with the internal mixing treatment of BC in the model simulation.
Assessment of the sensitivity of core/shell parameters derived using the single-particle soot photometer to density and refractive index
Authors: Taylor J. W. , Allan J. D. , Liu D. , Flynn M. , Weber R. , Zhang X. , Lefer B. L. , Grossberg N. , Flynn J. , Coe H.
Published: June 2014

Abstract. Black carbon (BC) is the dominant absorbing aerosol in the atmosphere, and plays an important role in climate and human health. The optical properties and cloud condensation nuclei (CCN) activity of soot depend on the amounts (both relative and absolute) of BC and nonrefractory material in the particles. Mixing between these two components is often considered using a core/shell coated sphere morphology. The Single Particle Soot Photometer (SP2) is the premier instrument for reporting distributions of both core size and coating thickness. Most studies combine the SP2's incandescence and scattering data to report coating properties, but there is variation in the assumed density and refractive index of the core that are used in these calculations. In this study we explore the sensitivity of the reported coatings to these parameters. An assessment of the coating properties of freshly-emitted, thermodenuded ambient particles demonstrated that a core density of 1.8 g cm−3 and refractive index n = (2.26-1.26i) were the most appropriate to use with ambient soot in the Los Angeles area. Using these parameters generated a distribution of shell/core ratio of 1.04 ± 0.21, corresponding to an absolute coating thickness distribution of 1.7 ± 17.5 nm. This demonstrates that using this technique the SP2 can accurately determine the mixing state (externally or internally mixed) of ambient soot, but with limited precision. Using other core parameters resulted in an offset in the coating distribution, but similar precision. For comparison, using the core parameters that resulted in the thickest coatings (on the same particles as before) generated a distribution of shell/core ratio of 1.40 ± 0.19, corresponding to an absolute coating thickness distribution of 30.3 ± 14.9 nm. Relative changes in coatings associated with secondary aerosol condensation were captured regardless of the assumed core parameters. These results must be taken into account when comparing BC coatings measured using this technique, or if using these data for optical or CCN activity calculations.
An improved glyoxal retrieval from OMI measurements
Authors: Alvarado L. M. A. , Richter A. , Vrekoussis M. , Wittrock F. , Hilboll A. , Schreier S. F. , Burrows J. P.
Published: June 2014

Abstract. Satellite observations from the SCIAMACHY, GOME-2, and OMI spectrometers have been used to retrieve atmospheric columns of glyoxal (CHOCHO) with the DOAS method. High CHOCHO levels are found over regions with large biogenic and pyrogenic emissions, and hot-spots have been identified over areas of anthropogenic activities. This study focuses on the development of an improved retrieval for CHOCHO from measurements by the OMI instrument. From sensitivity tests, an optimal fitting window and polynomial degree are determined. Two different approaches to reduce the interference of liquid water absorption over oceanic regions are evaluated, achieving significant reduction of negative columns over clear water regions. Moreover, a high temperature absorption cross-section of nitrogen dioxide (NO2) is introduced in the DOAS retrieval to account for potential interferences of NO2 over regions with large anthropogenic emissions, leading to improved fit quality over these areas. A comparison with vertical CHOCHO columns retrieved from measurements of the GOME-2 and SCIAMACHY instruments over continental regions is performed, showing overall good consistency. Using the new OMI CHOCHO data set, the link between fires and glyoxal columns is investigated for two selected regions in Africa. In addition, mapped averages are computed for a fire event in the east of Moscow between mid-July and mid-August 2010. In both cases, enhanced CHOCHO levels are found in close spatial and temporal proximity to MODIS fire radiative power, demonstrating that pyrogenic emissions can be clearly identified in the OMI CHOCHO product.
Carbon and greenhouse gas balances in an age-sequence of temperate pine plantations
Authors: Peichl M. , Arain A. M. , Moore T. R. , Brodeur J. J. , Khomik M. , Ullah S. , Restrepo-Coupé N. , McLaren J. , Pejam M. R.
Published: June 2014

Abstract. This study investigated differences in the magnitude and partitioning of the carbon (C) and greenhouse gas (GHG) balances in an age-sequence of four white pine (Pinus strobus L.) afforestation stands (7, 20, 35 and 70 years old as of 2009) in southern Ontario, Canada. The 4 year (2004–2008) mean annual carbon dioxide (CO2) exchanges, based on biometric and eddy covariance data, were combined with the 2-year means of static chamber measurements of methane (CH4) and nitrous oxide (N2O) fluxes (2006–2007) and dissolved organic carbon (DOC) export below 1 m soil depth (2004–2005). The total ecosystem C pool increased with age from 9 to 160 t C ha−1 across the four stands. Rates of organic matter cycling (i.e. litter-fall and decomposition) were similar among the three older stands. In contrast, considerable differences related to stand age and site quality were observed in the magnitude and partitioning of individual CO2 fluxes showing a peak in production and respiration rates in the middle-age (20 year-old) stand growing on fertile post-agricultural soil. The DOC export accounted for 10% of net ecosystem production (NEP) at the 7 year old stand but < 2% at the three older stands. The GHG balance from the combined exchanges of CO2, CH4 and N2O fluxes was 2.6, 21.6, 13.5 and 4.8 t CO2 eq ha−1 yr−1 for the 7, 20, 35, and 70 year-old stands, respectively. The maximum annual contribution from the combined exchanges of CH4, N2O and DOC to the GHG balance was 8% and 15% in the 7 and 70 year-old stands, respectively, but < 1% in the two highly productive middle-age (20 and 35 year-old) stands. Averaged over the entire age-sequence, the CO2 exchange was the main driver of the GHG balance in these forests. The cumulative CO2 sequestration over the 70 years was estimated at 129 \\unit{t} C and 297 t C ha−1 yr−1 for stands growing on low and high productive sites, respectively. This study highlights the importance of accounting for age and site quality effects on forest C and GHG balances. It further demonstrates a large potential for C sequestration and climate benefits (i.e. cooling effect) gained through afforestation of marginal agricultural and fallow lands in temperate regions.
Pigments, elemental composition (C, N, P, Si) and stoichiometry of particulate matter, in the naturally iron fertilized region of Kerguelen in the Southern Ocean
Authors: Lasbleiz M. , Leblanc K. , Blain S. , Ras J. , Cornet-Barthaux V. , Hélias Nunige S. , Quéguiner B.
Published: June 2014

Abstract. The particulate matter distribution and phytoplankton community structure of the iron-fertilized Kerguelen region were investigated in early austral spring (October–November 2011) during the KEOPS2 cruise. The iron-fertilized region was characterized by a complex mesoscale circulation resulting in a patchy distribution of particulate matter. Integrated concentrations over 200 m ranged from 72.2 to 317.7 mg m−2 for chlorophyll a, 314 to 744 mmol m−2 for biogenic silica (BSi), 1106 to 2268 mmol m−2 for particulate organic carbon, 215 to 436 mmol m−2 for particulate organic nitrogen, and 29.3 to 39.0 mmol m−2 for particulate organic phosphorus. Three distinct high biomass areas were identified: the coastal waters of Kerguelen Islands, the easternmost part of the study area in the Polar Front Zone, and the southeastern Kerguelen Plateau. As expected from previous artificial and natural iron-fertilization experiments, the iron-fertilized areas were characterized by the development of large diatoms revealed by BSi size–fractionation and HPLC pigment signatures, whereas the iron-limited reference area was associated to a low biomass dominated by a mixed (nanoflagellates and diatoms) phytoplankton assemblage. A major difference from previous artificial iron fertilization studies was the observation of much higher Si : C, Si : N, and Si : P ratios (respectively 0.31 ± 0.16, 1.6 ± 0.7 and 20.5 ± 7.9) in the iron-fertilized areas compared to the iron-limited reference station (respectively 0.13, 1.1, 5.8). A second difference is the patchy response of the elemental composition of phytoplankton communities to large scale natural iron fertilization. Comparison to the previous KEOPS1 cruise also allowed to address the seasonal dynamics of phytoplankton bloom over the southeastern plateau. From POC, PON, and BSi evolutions, we showed that the elemental composition of the particulate matter also varies at the seasonal scale. This temporal evolution followed changes of the phytoplankton community structure as well as major changes in the nutrient stocks progressively leading to silicic acid exhaustion at the end of the productive season. Our observations suggest that the specific response of phytoplankton communities under natural iron fertilization is much more diverse than what has been regularly observed in artificial iron fertilization experiments and that the elemental composition of the bulk particulate matter reflects phytoplankton taxonomic structure rather than being a direct consequence of iron availability.
Impact of droughts on the C-cycle in European vegetation: a probabilistic risk analysis using six vegetation models
Authors: Van Oijen M. , Balkovič J. , Beer C. , Cameron D. , Ciais P. , Cramer W. , Kato T. , Kuhnert M. , Martin R. , Myneni R. , Rammig A. , Rolinski S. , Soussana J.-F. , Thonicke K. , Van der Velde M. , Xu L.
Published: June 2014

Abstract. We analyse how climate change may alter risks posed by droughts to carbon fluxes in European ecosystems. The approach follows a recently proposed framework for risk analysis based on probability theory. In this approach, risk is quantified as the product of hazard probability and ecosystem vulnerability. The probability of a drought hazard is calculated here from the Standardised Precipitation Evapotranspiration Index. Vulnerability is calculated from the response to drought simulated by process-based vegetation models. Here we use six different models: three for generic vegetation (JSBACH, LPJmL, ORCHIDEE) and three for specific ecosystems (Scots pine forests: BASFOR; winter wheat fields: EPIC; grasslands: PASIM). The periods 1971–2000 and 2071–2100 are compared. Climate data are based on observations and on output from the regional climate model REMO using the SRES A1B scenario. The risk analysis is carried out for ∼22 000 grid cells of 0.25° × 0.25° across Europe. For each grid cell, drought vulnerability and risk are quantified for five seasonal variables: net primary and ecosystem productivity (NPP, NEP), heterotrophic respiration (RH), soil water content and evapotranspiration. Climate change is expected to lead to increased drought risks to net primary productivity in the Mediterranean area: five of the models estimate that risk will exceed 15%. The risks will increase mainly because of greater drought probability; ecosystem vulnerability will increase to lesser extent. Because NPP will be affected more than RH, future C-sequestration (NEP) will also be at risk predominantly in southern Europe, with risks exceeding 0.25 g C m−2 d−1 according to most models, amounting to reductions in carbon sequestration of 20 to 80%.
Wind-induced upwelling in the Kerguelen Plateau Region
Authors: Gille S. T. , Carranza M. M. , Cambra R. , Morrow R.
Published: June 2014

Abstract. In contrast to most of the Southern Ocean, the Kerguelen Plateau supports an unusually strong spring chlorophyll (Chl a) bloom, likely because the euphotic zone in the region is supplied with higher iron concentrations. This study uses satellite wind, sea surface temperature (SST), and ocean color data to explore the impact of wind-driven processes on upwelling of cold (presumably iron-rich) water to the euphotic zone. High wind speeds typically correlate with cold sea surface temperatures, implying that wind-mixing leads to enhanced vertical mixing. Negative wind-stress curl also correlates with cold SSTs, implying that Ekman pumping can further enhance upwelling, and coupling between winds and SSTs associated with mesoscale eddies can locally modulate the wind-stress curl. Kerguelen has a significant wind shadow on its downwind side, which generates a wind-stress curl dipole that shifts location depending on wind direction. This leads to locally enhanced Ekman pumping on the downstream side of the Kerguelen Plateau, where Chl a blooms are observed most years.
Monitoring hillslope moisture dynamics with surface ERT and hydrometric point measurement: a case study from Ore Mountains, Germany
Authors: Hübner R. , Heller K. , Günther T. , Kleber A.
Published: June 2014

Abstract. Hillslopes are one of the basic units that mainly control water movement and flow pathways within catchments. The structure of their shallow subsurface affects water balance, e.g. infiltration, retention, and runoff. Nevertheless, there is still a gap of knowledge of the hydrological dynamics on hillslopes, notably due to the lack of generalization and transferability. To improve the knowledge of hydrological responses on hillslopes with periglacial cover beds, hydrometrical measurements have been carried out on a small spring catchment in the eastern Ore Mountains since November 2007. In addition, surface ERT measurements of several profiles were applied to enhance resolution of punctual hydrometric data. From May to December 2008 geoelectrical monitoring in nearly weekly intervals was implemented to trace seasonal moisture dynamics on the hillslope scale. To obtain the link between water content and resistivity, the parameters of Archie's law were determined using different core samples. To optimize inversion parameters and methods, the derived spatial and temporal water content distribution was compared to tensiometer data and resulting in remarkable coincidence. The measured resistivity shows a close correlation with precipitation. Depending on the amount and intensity of rain, different depths were affected by seepage water. Three different types of response to different amounts of precipitation (small, medium, high), could be differentiated. A period with a small amount causes a short interruption of the drying pattern at the surface in summer, whereas a medium amount induces a distinctive reaction at shallow depth (<0.9 m), and a high amount results in a strong response reaching down to 2 m.