bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Temperature on the Optical and Morphological Properties of Zinc Oxide Thin Films Prepared by RF Magnetron Sputtering
Authors: Al-Bat’hi Souad A.M. , Othman Maizatulnisa
Published: July 2015

This investigation deals with the effect of temperature on the optical and morphological properties of Zinc Oxide thin films prepared by radio-Frequency (RF) magnetron sputtering technique. In the present work, zinc oxide (ZnO) thin films have been deposited on glass substrates from 50°C to 300°C by radio frequency magnetron sputtering. The effects of deposition temperature on the crystallization behaviour and optical properties of the films have been studied. The thin films were characterized using Ultraviolet Visible Spectroscopy (UV-VIS), Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction Analysis (XRD). From the UV-VIS testing, the average transmission percentage of the films is between 80-95% for all deposition temperatures meanwhile the energy gap of ZnO thin films varies from 3.26 eV to 3.35 eV which is not much different from the theoretical value. Also, the grain size is getting smaller from 3.886nm, 3.216nm, 3.119nm and 3.079nm with respect to the increasing deposition temperature 50°C, 100°C, 200°C and 300°C respectively whereas the average grain size per intercept value is increasing. The patterns of the peak were about the same for all deposition temperature where the thin films have polycrystalline hexagonal wurtzite structure with the orientation perpendicular (002) to the substrate surface (c-axis orientation) at 34.5(2θ).
Active Vehicle Suspension Control Using Full State-Feedback Controller
Authors: Bello Musa Mohammed , Akramin Shafie Amir , Khan Raisuddin
Published: July 2015

The main purpose of vehicle suspension system is to isolate the vehicle main body from any road geometrical irregularity in order to improve the passengers ride comfort and to maintain good handling stability. The present work aim at designing a control system for an active suspension system to be applied in today’s automotive industries. The design implementation involves construction of a state space model for quarter car with two degree of freedom and a development of full state-feedback controller. The performance of the active suspension system was assessed by comparing it response with that of the passive suspension system. Simulation using Matlab/Simulink environment shows that, even at resonant frequency the active suspension system produces a good dynamic response and a better ride comfort when compared to the passive suspension system.
Development of a Shape Memory Alloy (SMA) Based Assistive Hand
Authors: Hamid Alala M. Ba , Makhdoomi Mohatashem R. , Saleh Tanveer , Bhuiyan Moinul
Published: July 2015

In Malaysia, every year approximately 40000 people suffer from stroke and many of them become immobilized as an after effect. Rehabilitation robotics to assist disabled people has drawn significant attention by the researchers recently. This project also aims to contribute to this field. This paper presents a Shape Memory Alloy (SMA) actuated wearable assistive robotic hand for grasping. The proposed design is compact and sufficiently light to be used as an assistive hand. It is a joint less structure, has the potential because the human skeleton and joint replace the robot’s conventional structure. This design has been implemented on index and thumb fingers to enable grasping. Shape memory alloy springs and bias force mechanism are used for purpose of hand’s flexion and extension. This paper describes the mechatronic design of the wearable hand, experimental study of actuation unit and sensory system. Open loop experiments are conducted to understand the hand characterization and grip force provided by index finger. Current, temperature, extension and contraction of shape memory alloy springs are reported. This mechanism requires approximately 2A current for the SMA to actuate which provides maximum of 1.6N of gripping force. Conducted experiments show promising results that encourage further developments.
Simulation of Low Velocity Impact Test on Carbon/Epoxy Composite Plates
Authors: Buang Ziamah B. , Kashif S.M.
Published: July 2015

Composite materials that have low weight and high strength properties are currently one of the promising materials for a vehicle’s body. However, the effect of low velocity impact on composite may cause failure through matrix cracking, fibre breakage and delamination which may reduce the structure strength. Low velocity impact can be analysed either by experimentation or numerical simulation. Numerical simulation which is also known as finite element analysis can show the degradation of the composite structure properties after an impact loading condition without doing any experimentation. Thus, in this paper, LS-DYNA is the finite element analysis software that is used to simulate a low velocity impact on composite structures.
Transfer Function Prediction of a Lithium Iron Phosphate Battery with Nature-Inspired Approach
Authors: Toha Siti Fauziah
Published: July 2015

It is well known that the main constraint of electric vehicles (EVs) is the capabilities to supply efficient energy for driving-range that is comparable to petrol fueled vehicles. Moreover, a large number of batteries needed for EV contribute to heavy weight, poor durability and pricy total cost. In view of that, the need to prolong the battery lifetime, and use its full capacity, is of utmost importance. Therefore, an accurate battery model is a challenging first step to the overall problem soving chain. This paper presents a transfer function model prediction with nature-inspired approach for a Lithium iron phosphate battery. An Ant Colony Optimisation technique is used in search for accurate model with robust capability to adapt with different input current based on the New European Driving Cycle (NEDC) range. The model is further validated with autocorrelation and cross-correlation test and it is proven to give an error tolerance between the 95% confidence limit.
Design and Development of a Versatile Ice Clamping System
Authors: Bahar Rubina , Yahya Nur Adilah , Ariff Tasnim Firdaus
Published: July 2015

In manufacturing industries, workpiece clamping is one of the basic requirement prior to machining process as the clamping system is responsible to maintain the workpiece rigidity and withstand the cutting force generated from the machining process. Besides, Clamping device is one of the reasons which influence the surface integrity of a part. Clamping workpieces for machining can be challenging especially for intricate non-symmetric geometry and vulnerable parts. In this study, a new system has been designed and developed where the workpiece is submerged in a fluid and the fluid is completely frozen to form ice that holds the workpiece rigidly. This ice clamping system can hold any parts of the workpiece regardless of their geometry and fragility. To freeze the desired workpiece, the energy required for 942 cm3 of clamping fluid was 98.43 kJ. Total freezing time was 90 minutes. Further development on the system is required in terms of improving freezing time and de-freezing of the work-piece.
Effect of Lubrication Conditions to the Cutting Force Coefficients in Machining Process
Authors: Nowalid Wan Mohd Azlan , Shaharun Muhammad Adib , Yusoff Ahmad Razlan
Published: July 2015

The cutting force is the main important factor contributing the machined work piece surface and in determining the acceptable cutting parameters for high productivity in metal cutting industries. The prediction of cutting force coefficients of materials were calculated from the average cutting force model contributing to the constants of cutting force coefficients. In this study, experimental investigation is conducted to determine the cutting force coefficients in the average cutting force model, by identifying cutting force coefficients with different lubrication conditions such as dry, flood and minimal lubrication conditions and cutting speeds. A series of slot milling experiments are measured the milling forces by fixing the spindle speeds and radial/axial depths of cutting and linearly varying the feed per tooth. Using linearly fitting the experimental data, the tangential and radial milling force coefficients are then computed. The achieved results showed that the changing of spindle speed and different lubrication conditions affecting the milling force coefficient.
Investigation of Delamination at Exit of Drilled Carbon Fiber Reinforced Polymer (CFRP) Composite with Diamond Coated Ball Nose Drills
Authors: Konneh Mohamed , Abdullah Kassim A. , Izman Sudin , Jusoh Mohd Amirudin
Published: July 2015

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The investigation of the influence of machining parameters on delamination at exit of drilled holes after drilling into CFRP composite using 4 mm-diameter 2-fluted carbide drills coated diamond is present in this paper. The delamination at tool exit was analyzed in terms of delamination factor on the basis of analysis of variance (ANOVA) of Central Composite Design (CCD) of experiments. It is found that spindle speed is the most influential factor for the drilling of CFRP within the range of cutting parameters examined. The lowest delamination factor (1.003) was generated at rotational speed, 5063 rpm and feed rate, 180 mm/min; and the highest delamination factor (1.093) generated at rotational speed, 537 rpm and feed rate, 180 mm/min. A mathematical model has been predicted for the delamination at tool entry. The relationship between the machining variables and output variables is also established.
Electromagnetic Property of La0.7Sr0.3MnO3/Ag Composite at High Frequency
Authors: Yan Ke Lan , Fan Run Hua , Chen Min , Sun Kai , Wang Xu Ai , Hou Qing , Cheng Chuan Bing
Published: July 2015

The phase structure, and electrical and magnetic properties of La0.7Sr0.3MnO3 (LSMO)-x Ag (x is the mole ratio, x=0, 0.3, 0.5) composite were investigated. It is found that the sample with x=0 is single phase; the samples with x=0.3 and 0.5 present three phase composite structure of the manganese oxide and Ag. With the increasing of Ag content, the grain size of the samples increases and the grain boundaries transition from fully faceted to partially faceted. The permittivity of spectrum (10 MHz - 1 GHz) and the theoretical simulation reveal that the plasma frequency fp increase with Ag content, due to the increasing of free electron concentration, which is further supported by the enhancement of conductivity. While for the permeability (μr'), the μr' decrease with the increasing of Ag content at low frequency range (f < 20 MHz), while at the relative high frequency range (f > 300 MHz), the μr' increased with Ag content. Therefore, the introduction of elemental Ag resulted in a higher μr' at the relative high frequency range.
Molten Salt Synthesis of SnS2 Nanoparticles with Visible-Light Driven Photocatalytic Activity for the Degradation of Rhodamine B
Authors: Jia Tie Kun , Sun Guang , Cao Jian Liang , Zhang Zhan Ying
Published: July 2015

SnS2 nanoparticles with perfectly crystalline morphology were synthesized via a molten salt synthesis route at a relatively low temperature. The resulting SnS2 nanoparcticles were characterized by X-ray diffraction (XRD), field scanning electron microscopy (FESEM), and UV-vis diffuse reflectance spectra (UV-vis). The observations of FESEM images showed that the sample consists of a large number of aggregates assembled with numerous nanoparticles packed into compact texture. The photocatalytic activity of the as-prepared SnS2 samples was evaluated by the degradation of RhB aqueous solution. The effect of the molar ratio of thiourea to SnCl2 on the photocatalytic activity was also investigated, and the result showed that the as-prepared SnS2 sample has high photocatalytic activity efficiency in the degradation of RhB aqueous solution when the molar ratio of thiouea to SnCl2 was 3.
Synergistic Effect of K2O and Al2O3 on the Crystallization and Structure of Na2O-CaO-SiO2-MgO-Al2O3-ZnO of Glass-Ceramics
Authors: Cao Jian Wei , Wang Zhi
Published: July 2015

The Na2O-CaO-SiO2-MgO-Al2O3-ZnO glass-ceramics was prepared from the phosphorus slag as main primary raw materials by melt quenching technique. The effects of K2O and Al2O3 on crystallization behavior and structure of glass-ceramics were investigated by DSC, XRD and SEM. It is shown that the main crystalline phase is combeite (Na4Ca4(Si6O18)) in glass-ceramics. K2O and Al2O3 do not change the main crystalline phase of glass-ceramics, but K2O increases the crystallization temperature, Al2O3 increases the crystallization temperature, obviously decreases the grain size. The K2O isometric replaces Na2O at the same time the Al2O3 isometric to replace SiO2, reduced the grain size.
Processing of High-Quartz Porcelain Tile with Large Yellow Sand
Authors: Wen Xiao Qing , Gu Xing Yong , Luo Ting
Published: July 2015

In this study, the yellow sand waste with enormous reserves in the Inner Mongolia Tengger desert was taken as the main raw material mixed with the same regional clays for the infrared functional low-temperature porcelained tile. The mineral composition and granule feature of Tengri yellow sand as well as the micro-structure and infrared property of the fired body were discussed by the means of various testing such as the grain fineness distribution analysis, the XRD diffraction analysis, the SEM scanning electron microscope analysis, the coefficient of thermal expansion measure and the infrared performance detection. The results revealed that the natural mineral could be replaced by the yellow sand waste in large for preparing the environmental protection functional porcelained ceramics with favorable properties. The flexural strength of porcelained tiles sintered at 1140°C~1160°Ckeeps from 40 to 55Mpa when the high addition of yellow sand varies 75wt% to 90wt%. And the body is composed of high quartz as the main phase and little wollastonite phase which meets with the thermal shock resistant standard of the present architectural material .
In Situ Solidification Formation of the Architectural Ceramics Body with Full Barren Materials
Authors: Luo Ting , Gu Xing Yong , Wu Shao Ling , Wu Jun Ming
Published: July 2015

The traditional architectural ceramic body is mainly molded by compression forming process with dry power. The study introduced the starch into the body formula and the feasibility and correlate technological means of the situ solidification forming of fly ash architectural ceramics body with full barren materials were discussed. The body with full barren materials has a low green strength which is less than 1MPa by the traditional compression forming with dry power. But it could be improved greatly by optimizing the kind and amount of starch and the heat holding technologies in the forming process. The research showed that the body’s green strength is higher by introducing modified potato starch. The sintered body’s porosity and water absorption will be increased and lower flexural strength will be obtained by more starch. The body’s properties show the best when the amount of the starch reached 4wt% and the holding time for demoulding is 70min under the holding temperature what is 80°C. Under that molding condition, the green strength reached 3.61MPa, the flexural strength and water absorption of the sintered body reached 49.01MPa and 0.17% separately.
Preparation and Properties of Silicon Carbide Porous Ceramic Filter Membrane
Authors: Sun Guang Hao , Deng Xiang Yun , Sun Yang Shan , Huang Chuang Jun , Guan Xin
Published: July 2015

Spin coating method was adopted for preparation of two types of SiC filter membrane with different particles size. Sintering temperature was set at 1300°C. SEM was performed in order to characterize its micro-structure. For measuring the porosity of the membrane, we used Archimedes drainage method. The filter pressure testing system was used to character the membrane filter pressure drop. The experiment results indicated that, when the filter membrane was composed of average diameters 45μm and 23μm SiC particles, with their thickness reached about 300μm and 150μm respectively and the amount of ceramic binder was 10%, the porosity of the membrane achieved 43%, the surface of filtration membrane structure was uniform, and its filter pressure was smaller. On the premise of satisfying specific filtering accuracy and efficiency, larger size of silicon carbide particle could offer better performance of the membrane.
Microstructure and Properties of Hot-Pressing Sintered Tungsten Carbide Composites by Adding Cubic Boron Nitride
Authors: Li Kun , Chen Hai Yan , He Qiu Shuang , Dong Li Hua
Published: July 2015

(0, 5, 10, 15, 20) vol% CBN-WC/Co composites were consolidated by ball milling and the following hot-pressing sintering method. WC, Co and CBN powders were used as the starting materials. The effects of the CBN content on the density, microstructure and mechanical properties of CBN-WC/Co composites were investigated. The results showed that the CBN content had remarkable influence on the microstructure and mechanical properties of CBN-WC/Co Composites. With the increasing content of CBN, the density decrease, while Vickers hardness and flexural strength increased initially to the maximum values and then decreased at CBN 10 vol%. When 10 vol% CBN-WC/Co powders were hot-pressing sintered at 1350°C and 20MPa for 90 min, an excellent Vickers hardness of 19.8GPa was achieved, combining a flexural strength of 682MPa.
Sintering of Ti3SiC2 Ceramics by Hot Press from Commercial Powders
Authors: Zhu Yuan Yuan , Jia Jin , Zhou Ai Guo , Wang Li Bo , Zan Qing Feng
Published: July 2015

Layered ternary compounds Ti3SiC2 combines attractive properties of both ceramics and metals, and has been suggested for potential engineering applications. Near-fully dense Ti3SiC2 bulks were sintered from commercial Ti3SiC2 powders by hot press at 1350°C-1600°C for 60-120min under Ar atmosphere in this paper. The phase compositions and morphology of the as-prepared samples were evaluated by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). And the mechanical properties were measured by Three-Point bending method. It was found that the Ti3SiC2 had only a little of decomposition at sintering temperature above 1350°C. And effects of sintering temperature and holding time on the morphology of the bulk Ti3SiC2 are not obvious. Relative density of 98% and flexural strength of 480MPa were obtained for the Ti3SiC2 samples sintered at 30MPa and 1400°C for 90min.
Self-Excited Limit Cycle Yaw Oscillation Instability of External Sling Payloads with Dual-Point Suspension During Level Flight
Authors: Sommer III H. Joseph , Cimbala John M. , Miller David G.
Published: July 2015

This work developed and verified a computational model to predict self-excited limit cycle yaw oscillation (SELCYO) instability of external sling payloads carried under aircraft with dual-point suspension. Inverted-V and inverted-Y slings during steady-state level flight are discussed.
The primary goal was to provide a design tool for comparison of the onset of SELCYO between alternate sling geometries. The computational model incorporates steady-state aerodynamic loading during level flight based on scale-model wind tunnel testing. Scale-model sling tests of the onset of
SELCYO in the same wind tunnel were used for validation. Predictions of cargo hook load for a full-size HMMWV-M1025 payload carried by inverted-V slings are compared to V-22 Osprey flight-test data. Predictions of stability indicate that stiffer slings are generally more stable, and inverted-V
slings are significantly more stable than inverted-Y slings. Small differences between right and left front sling leg lengths caused by rigging error can significantly reduce stability.
Community Priority Index: Utility, Applicability and Validation for Priority Setting in Community-Based Participatory Research
Authors: Salihu Hamisu M. , Salinas-Miranda Abraham A. , Wang Wei , Turner DeAnne , Berry Estrellita Lo , Zoorob Roger
Published: July 2015

Background

Providing practitioners with an intuitive measure for priority setting that can be combined with diverse data collection methods is a necessary step to foster accountability of the decision-making process in community settings. Yet, there is a lack of easy-to-use, but methodologically robust measures, that can be feasibly implemented for reliable decision-making in community settings. To address this important gap in community based participatory research (CBPR), the purpose of this study was to demonstrate the utility, applicability, and validation of a community priority index in a community-based participatory research setting.

Design and Methods

Mixed-method study that combined focus groups findings, nominal group technique with six key informants, and the generation of a Community Priority Index (CPI) that integrated community importance, changeability, and target populations. Bootstrapping and simulation were performed for validation.

Results

For pregnant mothers, the top three highly important and highly changeable priorities were: stress (CPI=0.85; 95%CI: 0.70, 1.00), lack of affection (CPI=0.87; 95%CI: 0.69, 1.00), and nutritional issues (CPI=0.78; 95%CI: 0.48, 1.00). For non-pregnant women, top priorities were: low health literacy (CPI=0.87; 95%CI: 0.69, 1.00), low educational attainment (CPI=0.78; 95%CI: 0.48, 1.00), and lack of self-esteem (CPI=0.72; 95%CI: 0.44, 1.00). For children and adolescents, the top three priorities were: obesity (CPI=0.88; 95%CI: 0.69, 1.00), low self-esteem (CPI=0.81; 95%CI: 0.69, 0.94), and negative attitudes toward education (CPI=0.75; 95%CI: 0.50, 0.94).

Conclusions

This study demonstrates the applicability of the CPI as a simple and intuitive measure for priority setting in CBPR.
A Stakeholder-Based System Dynamics Model of Return-To-Work: A Research Protocol
Authors: Jetha Arif , Pransky Glenn , Fish Jon , Jeffries Susan , Hettinger Lawrence J.
Published: July 2015

Background

Returning to work following a job-related injury or illness can be a complex process, influenced by a range of interrelated personal, psychosocial, and organizational components. System dynamics modelling (SDM) takes a sociotechnical systems perspective to view return-to-work (RTW) as a system made up of multiple feedback relationships between influential components.

Design and Methods

To build the RTW SDM, a mixed-method approach will be used. The first stage, that has already been completed, involved creating a baseline model using key informant interviews. Second, in two manufacturing companies, stakeholder-based models will be developed through interviews and focus groups with senior management, frontline workers, and frontline supervisors. Participants will be asked about the RTW process in general and more targeted questions regarding influential components. Participants will also be led through a reference mode exercise where they will be asked to estimate the direction, shape and magnitude of relationships between influential components. Data will be entered into the software program Vensim that provides a platform for visualizing system-structure and simulating the effects of adapting components. Finally, preliminary model validity testing will be conducted to provide insights on model generalizability and sensitivity.

Expected Impact of the study for Public Health

The proposed methodology will create a SDM of the RTW process using feedback relationships of influential components. It will also provide an important simulation tool to understand system behaviour that underlies complex RTW cases, and examine anticipated and unanticipated consequences of disability management policies.
Barriers and Facilitators to Palliative Care of Patients with Chronic Heart Failure in Germany: A Study Protocol
Authors: Köberich Stefan , Ziehm Jeantte , Farin Erik , Becker Gerhild
Published: July 2015

Background

Despite its high prevalence, similar symptoms and symptom burden, people suffering from chronic heart failure receive less palliative care than patients with malignant diseases. Internationally, numerous barriers to palliative care of patients with chronic heart failure are known, however, there are no credible data regarding barriers and facilitators to palliative care of people suffering from chronic heart failure available for Germany.

Design and Methods

Tripartite study. First part of this study evaluates health care providers’ (physicians and nurses) perceived barriers and facilitators to palliative care of patients with chronic heart failure using a qualitative approach. At least 18 persons will be interviewed. In the second part, based on the results of part one, a questionnaire about barriers and facilitators to palliative care of patients with chronic heart failure will be designed and applied to at least 150 physicians and nurses. In the last part a classic Delphi method will be used to develop specific measures to improve the palliative care for chronic heart failure patients.

Expected Impact for Public Health

The results of this study will help to understand why patients with heart failure are seldom referred to palliative care and will provide solutions to overcome these barriers. Developed solutions will be the first step to improve palliative care in patients with heart failure in Germany. In addition, the results will help health care providers in other countries to take action to improve palliative care situations for heart failure patients.
Worship and the Lord’s Supper in Assemblies of God, and other selected Pentecostal churches in Nigeria
Authors: Mbamalu Williams O.
Published: July 2015

Pentecostals’ dominant liturgical principle has traditionally taken the pattern of unlimited expression of emotion and charismata, often formless and emphasising the subjective. The manifestations of the Spirit’s direct activity often interpreted as the reason for Pentecostals’ antiliturgical position, have in the past few years passed through a paradigm shift. The introduction of concrete rituals encompassing various significations, in a manner reminiscent of African traditions and culture by some churches, shows uncritical engagement with biblical theology of worship. Furthermore, the encouragement of individual appropriation of God’s promise in rites performance is a deviation from African traditional emphasis on community function. The researcher employed a participant observation methodology and engagement with pertinent literary works of pastors of the churches investigated. The article shows that the struggle of Pentecostals to be relevant is responsible for its juxtaposition of African traditions and culture with the Spirit in the performance of liturgical rites. The article concludes that in Nigeria Pentecostals’ practice of worship encourages the individual to appropriate the biblical promises of God at the expense of the community of Christ whose work in building character and guiding our lives is done through other Christians in the community.
Databases for stolen art: Progress, prospects and limitations
Authors: Roodt Christa , Benson Bernadine
Published: July 2015

Addressing the illicit trade in stolen works of art and other heritage items is notoriously difficult. Before thefts of heritage items can be recorded, the object in question must be identified as having special significance. The investigation of the circumstances in which such an object was acquired and the enforcement of legal and ethical standards of acquisition become unduly complicated in the absence of a comprehensive national inventory of museum holdings and of a database of stolen art and cultural objects. This article considers the development of inventories and databases in South Africa and elsewhere. We argue that cross-sectoral cooperation in sharing databases needs to improve significantly in order to boost compliance with due diligence standards. To help restore the credibility of the trade in art and cultural objects, the South African Heritage Resources Information System site must be endorsed as the centralised database for heritage crime. This would provide ready access to databases, helping art market participants, law enforcement officers and customs officials in the investigation of stolen art works.
Variation of the radiative properties during black carbon aging: theoretical and experimental intercomparison
Authors: He C. , Liou K.-N. , Takano Y. , Zhang R. , Zamora M. L. , Yang P. , Li Q. , Leung L. R.
Published: July 2015

Abstract. A theoretical black carbon (BC) aging model is developed to account for three typical evolution stages, namely, freshly emitted aggregates, coated BC by soluble material, and BC particles undergoing further hygroscopic growth. The geometric-optics surface-wave (GOS) approach is employed to compute the BC single-scattering properties at each aging stage, which are subsequently compared with laboratory measurements. Theoretical calculations are consistent with measurements in extinction and absorption cross sections for fresh BC aggregates, but overestimate the scattering cross sections for BC mobility diameters of 155, 245, and 320 nm, because of uncertainties associated with theoretical calculations for small particles as well as laboratory scattering measurements. The measured optical cross sections for coated BC by sulfuric acid and for those undergoing further hygroscopic growth are captured by theoretical calculations using a concentric core-shell structure, with differences of less than 20 %. This suggests that the core-shell shape represents the realistic BC coating morphology reasonably well in this case, which is consistent with the observed strong structure compaction during aging. We find that the absorption and scattering properties of fresh BC aggregates vary by up to 60 % due to uncertainty in the BC refractive index, which, however, is a factor of two smaller in the case of coated BC particles. Sensitivity analyses on the BC morphology show that the optical properties of fresh BC aggregates are more sensitive to fractal dimension than primary spherule size. The absorption and scattering cross sections of coated BC particles vary by more than a factor of two due to different coating structures. We find an increase of 20–250 % in absorption and a factor of 3–15 in scattering during aging, significantly depending on coating morphology and aging stages. Applying the aging model to CalNex 2010 field measurements, we show that the resulting BC direct radiative forcing (DRF) first increases from 1.5 to 1.7 W m-2 and subsequently decreases to 1.0 W m-2 during the transport from the Los Angeles Basin to downwind regions, as a result of the competition between absorption enhancement due to coating and dilution of BC concentration. The BC DRF can vary by up to a factor of two due to differences in BC coating morphology. Thus, an accurate estimate of BC DRF requires the incorporation of a dynamic BC aging process that accounts for realistic morphology in climate models, particularly for the regional analysis with high atmospheric heterogeneity.
Auroral ion acoustic wave enhancement observed with a radar interferometer system
Authors: Schlatter N. M. , Belyey V. , Gustavsson B. , Ivchenko N. , Whiter D. , Dahlgren H. , Tuttle S. , Grydeland T.
Published: July 2015

Abstract. Measurements of naturally enhanced ion acoustic line (NEIAL) echoes obtained with a five-antenna interferometric imaging radar system are presented. The observations were conducted with the European Incoherent SCATter (EISCAT) radar on Svalbard and the EISCAT Aperture Synthesis Imaging receivers (EASI) installed at the radar site. Four baselines of the interferometer are used in the analysis. Based on the coherence estimates derived from the measurements, we show that the enhanced backscattering region is of limited extent in the plane perpendicular to the geomagnetic field. Previously it has been argued that the enhanced backscatter region is limited in size; however, here the first unambiguous observations are presented. The size of the enhanced backscatter region is determined to be less than 900 × 500 m, and at times less than 160 m in the direction of the longest antenna separation, assuming the scattering region to have a Gaussian scattering cross section in the plane perpendicular to the geomagnetic field. Using aperture synthesis imaging methods volumetric images of the NEIAL echo are obtained showing the enhanced backscattering region to be aligned with the geomagnetic field. Although optical auroral emissions are observed outside the radar look direction, our observations are consistent with the NEIAL echo occurring on field lines with particle precipitation.
The role of watershed characteristics, permafrost thaw, and wildfire on dissolved organic carbon biodegradability and water chemistry in Arctic headwater streams
Authors: Larouche J. R. , Abbott B. W. , Bowden W. B. , Jones J. B.
Published: July 2015

Abstract. In the Alaskan Arctic, rapid climate change is increasing the frequency of disturbance including wildfire and permafrost collapse. These pulse disturbances may influence the delivery of dissolved organic carbon (DOC) to aquatic ecosystems, however the magnitude of these effects compared to the natural background variability of DOC at the watershed scale is not well known. We measured DOC quantity, composition, and biodegradability from 14 river and stream reaches (watershed sizes ranging from 1.5–167 km2) some of which were impacted by permafrost collapse (thermokarst) and fire. We found that region had a significant impact on quantity and biodegradability of DOC, likely driven by landscape and watershed characteristics such as lithology, soil and vegetation type, elevation, and glacial age. However, contrary to our hypothesis, we found that streams disturbed by thermokarst and fire did not contain significantly altered labile DOC fractions compared to adjacent reference waters, potentially due to rapid ecosystem recovery after fire and thermokarst as well as the limited spatial extent of thermokarst. Overall, biodegradable DOC ranged from 4 to 46 % and contrary to patterns of DOC biodegradability in large Arctic rivers, seasonal variation in DOC biodegradability showed no clear pattern between sites, potentially related to stream geomorphology and position along the river network. While thermokarst and fire can alter DOC quantity and biodegradability at the scale of the feature, we conclude that tundra ecosystems are resilient to these types of disturbance.
Low methane (CH4) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)
Authors: Deshmukh C. , Guérin F. , Pighini S. , Vongkhamsao A. , Guédant P. , Rode W. , Godon A. , Chanudet V. , Descloux S. , Serça D.
Published: July 2015

Abstract. Methane (CH4) emissions from hydroelectric reservoirs could represent a significant fraction of global CH4 emissions from inland waters and wetlands. Although CH4 emissions downstream of hydroelectric reservoirs are known to be potentially significant, these emissions are poorly documented in recent studies. We report the first quantification of emissions downstream of a subtropical monomictic reservoir. The Nam Theun 2 Reservoir (NT2R), located in Lao People's Democratic Republic, was flooded in 2008 and commissioned in April 2010. This reservoir is a trans-basin diversion reservoir which releases water to two downstream streams: the Nam Theun River below the dam and an artificial channel downstream of the powerhouse and a regulating pond that diverts the water from the Nam Theun watershed to the Xe Bangfai watershed. We quantified downstream emissions during the first four years after impoundment (2009–2012) on the basis of a high temporal (weekly to fortnightly) and spatial (23 stations) resolution of the monitoring of CH4 concentration. Before the commissioning of NT2R, downstream emissions were dominated by a very significant degassing at the dam site resulting from the occasional spillway discharge for controlling the water level in the reservoir. After the commissioning, downstream emissions were dominated by degassing which occurred mostly below the powerhouse. Overall, downstream emissions decreased from 10 Gg CH4 y−1 after the commissioning to 2 Gg CH4 y−1 four years after impoundment. The downstream emissions contributed only 10 to 30 % of total CH4 emissions from the reservoir during the study. Most of the downstream emissions (80 %) occurred within 2–4 months during the transition between the warm dry season (WD) and the warm wet season (WW) when the CH4 concentration in hypolimnic water is maximum (up to 1000 μmol L−1) and downstream emissions are negligible for the rest of the year. Emissions downstream of NT2R are also lower than expected because of the design of the water intake. A significant fraction of the CH4 that should have been transferred and emitted downstream of the powerhouse is emitted at the reservoir surface because of the artificial turbulence generated around the water intake. The positive counterpart of this artificial mixing is that it allows O2 diffusion down to the bottom of the water column enhancing aerobic methane oxidation and it subsequently lowering downstream emissions by at least 40 %.
Effect of sporadic destratification, seasonal overturn and artificial mixing on CH4 emissions at the surface of a subtropical hydroelectric reservoir (Nam Theun 2 Reservoir, Lao PDR)
Authors: Guérin F. , Deshmukh C. , Labat D. , Pighini S. , Vongkhamsao A. , Guédant P. , Rode W. , Godon A. , Chanudet V. , Descloux S. , Serça D.
Published: July 2015

Abstract. Inland waters in general and specifically freshwater reservoirs are recognized as source of CH4 to the atmosphere. Although the diffusion at the air–water interface is the most studied pathway, its spatial and temporal variations are poorly documented. We measured fortnightly CH4 concentrations and physico-chemical parameters at nine stations in a subtropical monomictic reservoir which was flooded in 2008 (Nam Theun 2 Reservoir, Lao PDR). Based on these results, we quantified CH4 storage in the water column and diffusive fluxes from June 2009 to December 2012. We also compared emissions with aerobic methane oxidation calculated from Deshmukh et al. (2015). In this monomictic reservoir, the seasonal variations of CH4 concentration and storage were highly dependant of the thermal stratification. Hypolimnic CH4 concentration and CH4 storage reached their maximum in the warm dry season (WD) when the reservoir was stratified. They decreased during the warm wet (WW) season and reached its minimum after the reservoir overturned in the cool dry season (CD). The sharp decreases of the CH4 storage were concomitant with sporadic extreme diffusive fluxes (up to 200 mmol m−2 d−1). These hot moments of emissions occurred mostly in the inflow region in the WW season and during the overturn in the CD season in the area of the reservoir that has the highest CH4 storage. Although they corresponded to less than 10 % of the observations, these CH4 extreme emissions (> 5 mmol m−2 d−1) contributed up to 50 % of total annual emissions by diffusion. Based on our fortnightly monitoring, we determined that accurate estimation of the emissions can be determined from measurements made at least at a monthly frequency. During the transition between the WD and WW seasons, a new hotspot of emissions was identified upstream of the water intake where diffusive fluxes peaked at 600 mmol m−2 d−1 in 2010 down to 200 mmol m−2 d−1 in 2012. In the CD season, diffusive fluxes from this area were the lowest observed at the reservoir surface. Emissions from this area contributed 15–25 % to total annual emissions although they occur on a surface area representative of less than 1 % of the total reservoir surface. We highly recommend measurements of diffusive fluxes around water intakes in order to evaluate if such results can be generalized.
Trend and climatic sensitivity of vegetation phenology in semiarid and arid ecosystems in the US Great Basin during 1982–2011
Authors: Tang G. , Arnone III J. A. , Verburg P. , Jasoni R. L.
Published: July 2015

Abstract. We quantified the temporal trend and climatic sensitivity of vegetation phenology in dryland ecosystems in the US Great Basin during 1982–2011. Our results indicated that vegetation greenness in the Great Basin increased significantly during the study period, and this positive trend occurred in autumn but not spring and summer. Spatially, increases in vegetation greenness were more apparent in the northwestern, southeastern, and eastern Great Basin but less apparent in the central and southwestern Great Basin. In addition, the start of growing season (SOS) was not advanced while the end of growing season (EOS) was delayed significantly at a rate of 3.0 days per decade during the study period. The significant delay in EOS and lack of earlier leaf onset caused growing season length (GSL) to increase at a rate of 3.0 days per decade during 1982–2011. Interestingly, we found that the variation of mean vegetation greenness in the period of March to November (SSA) was not significantly correlated with its mean surface air temperature but was strongly correlated with its total precipitation. Seasonally, the variation of mean vegetation greenness in spring, summer, and autumn was mainly attributable to changes in pre-season precipitation in winter and spring. Nevertheless, climate warming played a strong role in extending GSL that in turn resulted in the upward trend in mean vegetation greenness during 1982–2011. Overall, our results suggested that changes in wintertime and springtime precipitation played a stronger role than temperature in affecting the interannual variability of vegetation greenness while climate warming was mainly responsible for the 30-year upward trend in the magnitudes of mean vegetation greenness in the dryland ecosystems during 1982–2011.
Thermo-hydro-mechanical processes in fractured rock formations during a glacial advance
Authors: Selvadurai A. P. S. , Suvorov A. P. , Selvadurai P. A.
Published: July 2015

Abstract. The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-poroelasticity of the intact geological formation and the presence of a system of sessile but hydraulically interacting fractures (fracture zones). The modelling considers coupled thermo-hydro-mechanical effects in both the intact rock and the fracture zones due to contact normal stresses and fluid pressure at the base of the advancing glacier. Computational modelling provides an assessment of the role of fractures in modifying the pore pressure generation within the entire rock mass.
An approach for coupling higher and lower levels in marine ecosystem models and its application to the North Sea
Authors: Beecham J. A. , Bruggeman J. , Aldridge J. , Mackinson S.
Published: July 2015

Abstract. End to end modelling is an attractive and rapidly developing approach to solve developing strategies in marine systems science and management. However problems remain in the area of data matching and sub-model compatibility. A mechanism and novel interfacing system (Couplerlib) is presented whereby a physical/biogeochemical model (GOTM-ERSEM) that predicts dynamics of the lower trophic level (LTL) organisms in marine ecosystems is coupled to a dynamic ecosystem model (Ecosim) that predicts food-web interactions among higher trophic level (HTL) organisms. Coupling is achieved by means of a bespoke interface which handles the system incompatibilities between the models and a more generic Couplerlib library which uses metadata descriptions in extensible mark-up language (XML) to marshal data between groups, paying attention to functional group mappings and compatibility of units between models. In addition, within Couplerlib, models can be coupled across networks by means of socket mechanisms. As a demonstration of this approach, a food web model (Ecopath with Ecosim, EwE) and a physical/biogeochemical model (GOTM-ERSEM) representing the North Sea ecosystem were joined with Couplerlib. The output from GOTM-ERSEM varies between years dependent on oceanographic and meteorological conditions. Although inter-annual variability was clearly present, there was always the tendency for an annual cycle consisting of a peak of diatoms in spring, followed by (less nutritious) flagellates and dinoflagellates through the summer resulting in an early summer peak in the mesozooplankton biomass. Pelagic productivity, predicted by the LTL model, was highly seasonal with little winter food for the higher trophic levels. The Ecosim model was originally based on the assumption of constant annual inputs and, consequently, when coupled, pelagic species suffered population loss over the winter months. By contrast, benthic populations were more stable (although the benthic linkage modelled was purely at the detritus level). The coupled model was used to examine long term effects of environmental change, and showed the system to be nutrient limited, relatively unaffected by forecast climate change, especially in the benthos. The stability of an Ecosim formulation for large higher tropic level food webs is discussed and it is concluded that this kind of coupled model formulation is better for examining the effects of long term environmental change than short term perturbations.
Exploring the impact of forcing error characteristics on physically based snow simulations within a global sensitivity analysis framework
Authors: Raleigh M. S. , Lundquist J. D. , Clark M. P.
Published: July 2015

Abstract. Physically based models provide insights into key hydrologic processes but are associated with uncertainties due to deficiencies in forcing data, model parameters, and model structure. Forcing uncertainty is enhanced in snow-affected catchments, where weather stations are scarce and prone to measurement errors, and meteorological variables exhibit high variability. Hence, there is limited understanding of how forcing error characteristics affect simulations of cold region hydrology and which error characteristics are most important. Here we employ global sensitivity analysis to explore how (1) different error types (i.e., bias, random errors), (2) different error probability distributions, and (3) different error magnitudes influence physically based simulations of four snow variables (snow water equivalent, ablation rates, snow disappearance, and sublimation). We use the Sobol' global sensitivity analysis, which is typically used for model parameters but adapted here for testing model sensitivity to coexisting errors in all forcings. We quantify the Utah Energy Balance model's sensitivity to forcing errors with 1 840 000 Monte Carlo simulations across four sites and five different scenarios. Model outputs were (1) consistently more sensitive to forcing biases than random errors, (2) generally less sensitive to forcing error distributions, and (3) critically sensitive to different forcings depending on the relative magnitude of errors. For typical error magnitudes found in areas with drifting snow, precipitation bias was the most important factor for snow water equivalent, ablation rates, and snow disappearance timing, but other forcings had a more dominant impact when precipitation uncertainty was due solely to gauge undercatch. Additionally, the relative importance of forcing errors depended on the model output of interest. Sensitivity analysis can reveal which forcing error characteristics matter most for hydrologic modeling.