bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenge-based Learning: The Case of Sustainable Development Engineering at the Tecnologico de Monterrey, Mexico City Campus
Authors: Membrillo-Hernández Jorge , Ramírez-Cadena Miguel de Jesús , Caballero-Valdés Carlos , Ganem-Corvera Ricardo , Bustamante-Bello Rogelio , Benjamín-Ordoñez José Antonio , Elizalde-Siller Hugo
Published: May 2018

Recently, The Tecnologico de Monterrey (ITESM) in Mexico has launched the Tec21 Educational Model. It is a flexible model in its curriculum that promotes student participation in challenging and interactive learning experiences. At the undergraduate level, one of the central scopes of this model is addressing challenges by the student, to develop disciplinary and cross-disciplinary skills. Two institutional strategies have been implemented to reach the ultimate goal of the ITESM, to work in all careers under the Challenge Based Learning (CBL) system: the innovation week (i-week) and the innovation semester (i-semester). Here we report on the results of four i-week and one i-semester models implemented in 2016. The i-semester was carried out in conjunction with a training partner, the worldwide leader Pharmaceutical Company Boehringer Ingelheim. Thirteen Sustainable Development Engineering career students were immersed for a 14 week period into the strategies to solve real-life challenges in order to develop the contents of four different courses. Six teachers of the academic institution and four engineers from the Boehringer plant served as mentors. Continuous evaluations were carried out throughout the abilities examination and partial and final examinations were performed by both experts, from the company and from the University.
Dual Education: The Win-Win Model of Collaboration between Universities and Industry
Authors: Pogatsnik Monika
Published: May 2018

The purpose of this paper is to describe the new experiences of the dual training model in engineering education in Hungary. This new model has been introduced recently in the higher education and has become a focus of interest. This is a fa-vorable program for the students to experience the real industry environment pri-or to graduation and it is a good tool to motivate them to study harder. The dual education students study in the institutional academic period together with the regular full-time students at their higher education institute, and parallel to their academic education they participate in the practical training. It gives the students an opportunity to join a specific training program at an enterprise. Being involved in specific "operational" practical tasks and project-oriented work enhances inde-pendent work, learning soft skills and experiencing the culture of work. Our ob-jectives are to analyze the benefits of the dual training for all three parties: the stu-dent, the company and university. The study confirms earlier results from prior studies which show, for example, that students who choose the dual option achieve better program outcomes.
Trial for E-Learning System on Information Security Incorporate with Learning Style and Consciousness Factors
Authors: Nagata Kiyoshi , Kigawa Yutaka , Aoki Tomoko
Published: May 2018

In Japanese higher educational institutions as in universities, many studies and practices on e-learning have been reported, but the state of trial and errors are still continuing. Thus, we propose the construction of an e-learning system incorporating not only with learner's consciousness but also with their learning style. Our proposing system is consistent of three individual parts and one integration phase. The first part is composed of tools, methods, and facilities used to provide the e-learning environment. The second part is composed of theoretical or practical works on learning styles. The third part is composed of learner’s consciousness factors on information security which we have studied so far. In the integration phase, the components of e-learning discussed in the first part are evaluated from learning style related psychological aspects. In the paper, we propose a trial version of e-learning system which includes several types of content with proper links to information security factors and to learning styles.
"A Generator": A Mini Hydroelectric Apparatus as Renewable Source of Energy
Authors: Satir Secil , Kestane Yildirim B. , Dogru Sertan
Published: May 2018

Abstract--The matter is considered in the scope of sustainability and initially the basis and content of the term is defined. Based on this definition, the qualities of water and water energy are inspected as water is one of the most important type of clean energy source. Water energy is a time-honored renewable energy whose use dates back to earliest periods in history. The subject titled “A Generator” is a small but significant support to environmental protection as it defines a patented object which generates energy from water with a mini apparatus.

Protection of future lives of creatures and keeping them in infinite existence necessitate taking measures in advance. Concepts such as environment protection, sustainability, green energy, green economy etc. have also been under consideration by the UN since the 1970s. The subject is very comprehensive. This paper inspects as required hydroelectric power plants which produce clean energy and date back to ancient times. Water, as main source of hydroelectric power plants, is collected in proper basins and thus provided with potential energy. Water is then dropped from heights to trigger its kinetic energy and canalized to turbine wheels, moving which it turns kinetic/mechanical energy into electric power. This basic characteristic of water is evaluated in a mini apparatus this time. And an apparatus of unaccustomed size is obtained, which could support electricity production in household wet areas.
Extending STEM Education to Engineering Programs at the Undergraduate College Level
Authors: Zaher Ashraf A. , Damaj Issam W
Published: May 2018

Science, technology, engineering, and mathematics (STEM) education is gaining wide attention. STEM education assimilates rigorous disciplines and requires diverse skills. Effort to promote and integrate STEM education in schools has been significant during the recent years. This paper investigates promoting students interest in STEM beyond the K-12 levels outside the US. The investigation targets the American University of Kuwait, where the educational community in general, and the students in particular, are faced with different challenges. Comprehensive proposals are suggested to extend STEM education to be part of the Engineering programs at the undergraduate level, with focus on Electrical, Computer, and Systems Engineering. Remedies for overcoming the weak background in mathematics and sciences, for many students, are explored. In addition, parallel laboratory-based educational components are applied, for selected courses, to enhance the technological aspects via providing deep hands-on experience and exposure to real-life scenarios. Incorporating STEM education in courses/labs, academic activities, extracurricular activities, capstone design projects, internships, and satisfying accreditation requirements are addressed. A thorough discussion is presented to include analysis of best practices, evaluations, examples, and case studies from the local and regional institutions.
Variation of stream metabolism along a tropical environmental gradient
Authors: Saltarelli Wesley A. , Dodds Walter K. , Tromboni Flavia , Calijuri Maria do Carmo , Neres-Lima Vinicius , Jordão Carlos E. , Palhares Julio C.P. , Cunha Davi G.F.
Published: May 2018

Stream metabolism is affected by both natural and human-induced processes. While metabolism has multiple implications for ecological processes, relatively little is known about how metabolic rates are influenced by land use in tropical streams. In this study, we assessed the metabolic characteristics and related environmental factors of six streams located in a transition area from Cerrado to Atlantic Forest (São Carlos/Brazil). Three streams were relatively preserved, while three were flowing through more agriculturally and/or urban impacted watersheds. Surface water samples were analyzed for biological and physico-chemical parameters as well as discharge and percentage of canopy cover. Metabolism was determined through the single-station method to estimate gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) with BAyesian Single-station Estimation (BASE). Nutrient concentrations tended to be higher in impacted versus preserved streams (e.g., average total phosphorus between 0.028-0.042 mg L-1 and 0.009-0.038 mg L-1, respectively). Average canopy cover varied between 58 and 77%, with no significant spatial or seasonal variation. All streams were net heterotrophic (ER exceeded GPP) in all sampling periods. GPP rates were always lower than 0.7 gO2 m-2 d-1 in all streams and ER varied from 0.6 to 42.1 gO2 m-2 d-1.  Linear Mixed-Effect models showed that depth, discharge, velocity and total phosphorus are the most important predictors for GPP. For ER, depth, velocity and canopy cover are significant potential predictors. Canopy cover was the main light limiting factor and influenced stream metabolism. Our findings reinforced the concepts that shifts in the shading effect provided by vegetation (e.g., through deforestation) or changes in discharge (e.g., through land use conversion or water abstractions) can impact freshwater metabolism. Our study suggests that human activities in low latitude areas can alter tropical streams’ water quality, ecosystem function, and the degree of riparian influence. Our data showed that tropical streams can be especially responsive to increases of organic matter inputs leading to high respiration rates and net heterotrophy, and this should be considered to support management and restoration efforts.
Mediastinal silicone lymphadenopathy revealed after thymectomy for autoimmune myasthenia gravis
Authors: Moraitis Sotirios D. , Agrafiotis Apostolos C. , Kapranou Amalia , Kanakakis Konstantinos
Published: May 2018

Breast reconstruction is a very popular surgical intervention performed either for cosmetic reasons or after oncological resections. Even though silicone is considered to be an inert material, there are side effects that have been reported, such as silicone lymphadenopathy. In the case reported herein, a silicone lymphadenopathy of the internal mammary and the anterior mediastinal lymph nodes were revealed after a thymectomy for autoimmune myasthenia gravis. Silicone lymphadenopathy should always be part of the differential diagnosis of enlarged lymph nodes, in patients with previous cosmetic or oncoplastic surgery with the use of silicone gel breast implants. Special attention should be paid in case of previous breast cancer in order to rule out metastasis.
The effect of positive psychotherapy in test anxiety among Zahedan students with hemophilia
Authors: Ghavidel Heydari Mahbobe , Shirazi Mahmoud , Sanagouyemoharer Gholam Reza
Published: May 2018

Hemophilia is a chronic disease which due to several reasons, including frequent absences from school and reduced motivation, leads to the incident of test anxiety among patients. This study was conducted with the aim of evaluating the effectiveness of positive psychotherapy in test anxiety among students with hemophilia. The current study followed a pretest, posttest, and two-month followup quasi-experimental design with an experimental group and a control group. This study had a statistical population including all senior elementary and junior high school students with hemophilia who had medical records in Zahedan Hemophilia Society. After screening them, 60 students were selected and randomly assigned to two 30-person groups of experimental and control. Since some patients refused to continue taking part in this study, the sample decreased to 57 people. Measurement tool used in this study was Sarason Test Anxiety Scale. Positive psychotherapy was held in 8 sessions (two 120-minute sessions per week) and a follow-up was conducted two months after completing the psychotherapy. Data were analyzed using a repeated measure analysis of variance. Results showed that positive psychotherapy significantly reduced test anxiety among the students with hemophilia. Moreover, the stability of the effects of this therapy in the follow-up was confirmed. The obtained results indicated that policymakers should pay a lot of attention to this new positive psychological training and its effects on reducing test anxiety.
aPaRT: A Fast Meta-Heuristic Algorithm using Path-Relinking and Tabu Search for Allocating Machines to Operations in FJSP Problem
Authors: Jazayeriy Hamid , Bakhtar Sahar , Valinataj Mojtaba
Published: May 2018

This paper proposes a multi-start local search algorithm that solves the flexible job-shop scheduling (FJSP) problem to minimize makespan. The proposed algorithm uses a path-relinking method to generate near optimal solutions. A heuristic parameter, $\alpha$, is used to assign machines to operations.Also, a tabu list is applied to avoid getting stuck at local optimums.The proposed algorithm is tested on two sets of benchmark problems (BRdata and Kacem) to make a comparison with the variable neighborhood search.The experimental results show that the proposed algorithm can produce promising solution in a shorter amount of time.
On the variance of the error term in the hyperbolic circle problem
Authors: Cherubini Giacomo , Risager Morten S.
Published: May 2018

Let

e(s)

be the error term of the hyperbolic circle problem, and denote by

e_\alpha(s)

the fractional integral to order

\alpha

of

e(s)

. We prove that for any small

\alpha>0

the asymptotic variance of

e_\alpha(s)

is finite, and given by an explicit expression. Moreover, we prove that

e_\alpha(s)

has a limiting distribution.
Parabolic Harnack inequality on fractal-type metric measure Dirichlet spaces
Authors: Lierl Janna
Published: May 2018

This paper proves the strong parabolic Harnack inequality for local weak solutions to the heat equation associated with time-dependent (nonsymmetric) bilinear forms. The underlying metric measure Dirichlet space is assumed to satisfy the volume doubling condition, the strong Poincaré inequality, and a cutoff Sobolev inequality. The metric is not required to be geodesic. Further results include a weighted Poincaré inequality, as well as upper and lower bounds for non-symmetric heat kernels.
On the variation of maximal operators of convolution type II
Authors: Carneiro Emanuel , Finder Renan , Sousa Mateus
Published: May 2018

In this paper we establish that several maximal operators of convolution type, associated to elliptic and parabolic equations, are variation-diminishing. Our study considers maximal operators on the Euclidean space

\mathbb R^d

, on the torus

\mathbb T^d

and on the sphere

\mathbb S^d

. The crucial regularity property that these maximal functions share is that they are subharmonic in the corresponding detachment sets.
The Dirichlet boundary problem for second order parabolic operators satisfying a Carleson condition
Authors: Dindoš Martin , Hwang Sukjung
Published: May 2018

We establish

L^p

,

2\le p\le\infty

, solvability of the Dirichlet boundary value problem for a parabolic equation

u_t- \mathrm {div}(A\nabla u) - \boldsymbol{B}\cdot\nabla u =0

on time-varying domains with coefficient matrices

A=[a_{ij}]

and

\boldsymbol{B} = [b_{i}]

that satisfy a small Carleson condition. The results are sharp in the following sense. For a given value of

1 < p < \infty

there exists operators that satisfy Carleson condition but fail to have

L^p

solvability of the Dirichlet problem. Thus the assumption of
smallness
is
sharp
. Our results complements results of Hofmann, Lewis and Rivera-Noriega, where solvability of parabolic

L^p

(for some large

p

) Dirichlet boundary value problem for coefficients that satisfy large Carleson condition was established. We also give a new (substantially shorter) proof of these results.
Smooth torus actions are described by a single vector field
Authors: Turiel Francisco Javier , Viruel Antonio
Published: May 2018

Consider a smooth effective action of a torus

\mathbb T^n

on a connected

C^{\infty}

-manifold

M

. Assume that

M

is not a torus endowed with the natural action. Then we prove that there exists a complete vector field

X

on

M

such that the automorphism group of

X

equals

\mathbb T^n \times \mathbb R

, where the factor

\mathbb R

comes from the flow of

X

and

\mathbb T^n

is regarded as a subgroup of Diff

(M)

. Thus one may reconstruct the whole action of

\mathbb T^n

from a single vector field.
On a paper of Berestycki–Hamel–Rossi and its relations to the weak maximum principle at infinity, with applications
Authors: Magliaro Marco , Mari Luciano , Rigoli Marco
Published: May 2018

The aim of this paper is to study a new equivalent form of the weak maximum principle for a large class of differential operators on Riemannian manifolds. This new form has been inspired by the work of Berestycki, Hamel and Rossi for trace operators, and allows us to shed new light on it and to introduce a new sufficient bounded Khas’minskii type condition for its validity. We show its effectiveness by applying it to obtain some uniqueness results in a geometric setting.
The Loewner equation and Lipschitz graphs
Authors: Rohde Steffen , Tran Huy , Zinsmeister Michel
Published: May 2018

The proofs of continuity of Loewner traces in the stochastic and in the deterministic settings employ different techniques. In the former setting of the Schramm–Loewner evolution SLE, H¨older continuity of the conformal maps is shown by estimating the derivatives, whereas the latter setting uses the theory of quasiconformal maps. In this note, we adopt the former method to the deterministic setting and obtain a new and elementary proof that Hölder-1/2 driving functions with norm less than 4 generate simple arcs. We also give a sufficient condition for driving functions to generate curves that are graphs of Lipschitz functions.
Isoperimetric profiles and random walks on some permutation wreath products
Authors: Saloff-Coste Laurent , Zheng Tianyi
Published: May 2018

We study the isoperimetric profiles of certain families of finitely generated groups defined via marked Schreier graphs and permutation wreath products. The groups we study are among the “simplest” examples within a much larger class of groups, all defined via marked Schreier graphs and/or action on rooted trees, which includes such examples as the long range group, Grigorchuck group and the basillica group. The highly nonlinear structure of these groups make them both interesting and difficult to study. Because of the relative simplicity of the Schreier graphs that define the groups we study here (the key fact is that they contained very large regions that are “one dimensional”), we are able to obtain sharp explicit bounds on the L1 and L2 isoperimetric profiles of these groups. As usual, these sharp isoperimetric profile estimates provide sharp bounds on the probability of return of simple random walk. Nevertheless, within each of the families of groups we study there are also many cases for which the existing techniques appear inadequate and this leads to a variety of open problems.
Solid hulls of weighted Banach spaces of entire functions
Authors: Bonet José , Taskinen Jari
Published: May 2018

Given a continuous, radial, rapidly decreasing weight

v

on the complex plane, we study the solid hull of its associated weighted space

H_v^\infty(\mathbb C)

of all the entire functions

f

such that

v|f|

is bounded. The solid hull is found for a large class of weights satisfying the condition (B) of Lusky. Precise formulations are obtained for weights of the form

v(r)=

exp

(-ar^p), a > 0, p > 0

. Applications to spaces of multipliers are included.
Some remarks on the comparison principle in Kirchhoff equations
Authors: Figueiredo Giovany M. , Suárez Antonio
Published: May 2018

In this paper we study the validity of the comparison principle and the sub-supersolution method for Kirchhoff type equations. We show that these principles do not work when the Kirchhoff function is increasing, contradicting some previous results. We give an alternative sub-supersolution method and apply it to some models.
Spectral permanence in a space with two norms
Authors: Kang Hyeonbae , Putinar Mihai
Published: May 2018

A generalization of a classical argument of Mark G. Krein leads us to the conclusion that the Neumann–Poincar´e operator associated to the Lamé system of linear elastostatics equations in two dimensions has the same spectrum on the Lebesgue space of the boundary as the more natural energy space. A similar result for the Neumann–Poincaré operator associated to the Laplace equation was stated by Poincaré and was proved rigorously a century ago by means of a symmetrization principle for non-selfadjoint operators. We develop the necessary theoretical framework underlying the spectral analysis of the Neumann–Poincaré operator, including also a discussion of spectral asymptotics of a Galerkin type approximation. Several examples from function theory of a complex variable and harmonic analysis are included.
The approximation property for spaces of Lipschitz functions with the bounded weak* topology
Authors: Jiménez-Vargas Antonio
Published: May 2018

Let

X

be a pointed metric space and let Lip

_0(X)

be the space of all scalar-valued Lipschitz functions on

X

which vanish at the base point. We prove that Lip

_0(X)

with the bounded weak* topology

\tau_{bw^*}

has the approximation property if and only if the Lipschitz-free Banach space

\mathcal F(X)

has the approximation property if and only if, for each Banach space

F

, each Lipschitz operator from

X

into

F

can be approximated by Lipschitz finite-rank operators within the unique locally convex topology

\gamma\tau_\gamma

on Lip

_0(X,F)

such that the Lipschitz transpose mapping

f\mapsto f^t

is a topological isomorphism from Lip

_0(X,F),\gamma\tau_\gamma)

to (Lip

_0(X),\tau_{bw^*})\epsilon F

.
О сложности схем и формул ограниченной глубины над базисом из многовходовых элементов
Authors: Sergeev Igor Sergeevich
Published: May 2018

Получены оценки сложности реализации булевых функций $n$ переменных схемами и формулами, использующими многовходовые функциональные элементы конъюнкции и дизъюнкции и либо элементы отрицания, либо отрицания переменных в качестве входов. Дополнительно накладываются ограничения на глубину схем или формул. В ряде случаев полученные оценки оказываются асимптотически точными. В частности, для сложности схем с переменными и их отрицаниями на входах получена асимптотика функции Шеннона $2\cdot2^{n/2}$, которая достигается на схемах глубины 3.
Формулы для одной характеристики сфер и шаров в двоичных пространствах большой размерности
Authors: Mikhailov Vladimir Gavrilovich
Published: May 2018

Изучается специальная функция $\rho(H)$ множества $H$ векторов $n$-мерного линейного пространства над полем $K$, используемая в оценках точности пуассоновской аппроксимации для распределения числа решений систем случайных уравнений и систем случайных включений над $K$. В случае, когда $K=GF(2)$, а множество $H$ является сферой или шаром (в метрике Хемминга) в $\{0,1\}^n$, получены явные и приближенные формулы для $\rho(H)$, выполненные при достаточно больших значениях параметра $n$.
Оценки среднего размера образа подмножества при композиции случайных отображений
Authors: Zubkov Andrei Mikhailovich , Serov Aleksandr Aleksandrovich
Published: May 2018

Пусть $\mathcal{X}_N$ - множество из $N$ элементов и $F_1,F_2,\ldots$ - последовательность случайных независимых равновероятных отображений $\mathcal{X}_N\to\mathcal{X}_N$. Для подмножества $S_0\subset \mathcal{X}_N$, $|S_0|=m$, рассматривается последовательность его образов $S_t=F_t(\ldots F_2(F_1(S_0))\ldots)$, $t=1,2\ldots$ Описан рекуррентный способ точного вычисления распределения $|S_t|$. Получены двусторонние неравенства для $\mathbf{M}\{|S_t| | |S_0|=m\}$, в которых разность между верхней и нижней оценками имеет порядок $o(m)$, если $m,t,N\to\infty, mt=o(N)$. Результаты представляют интерес для анализа алгоритмов балансировки времени и памяти.
Conséquences de l’incorporation en excès de déchets de poisson dans la ration de porcs à l’engrais
Authors: Drieux Henri , Labie C. , Castric M.
Published: May 2018

Des porcs à l’engrais, recevant une ration trop riche en déchets de poisson ont présenté une odeur et une couleur jaune-brun anormales qui les ont rendus impropres à la consommation. Ces défauts sont dus à la présence, dans le tissu adipeux de ceroïdes, formes peroxydées de lipides à forte teneur en acides gras hautement non-saturés. Ces chromolipoïdes s’accumulent dans certaines cellules seulement du tissu adipeux qui sont vraisemblablement dérivées des histiocytes du tissu conjonctif. Il convient de faire preuve de prudence dans l’alimentation des porcs à l’aide de déchets de poisson. L’administration de vitamine E semble être indiquée comme mesure de précaution complémentaire.
The economic effects of refugee return
Authors: Dadush Uri
Published: May 2018

The recent surge in the number of forcibly displaced persons who cross international borders in search of protection has prompted interest in evaluating policies that achieve the possible “end points” of the phenomenon. These are the integration of the forcibly displaced persons in the country of destination, relocation in a third country, and return to the country of origin. The focus of this paper is on the third aspect, and more specifically on the appropriateness of return policy viewed from an economic perspective. Although the vast majority of forcibly displaced people is found in developing countries, the object of this paper are the return policies of advanced countries.
Evaluating Algae as an Alternative Fuel for Chemical Looping Combustion
Authors: Williams Catherine , Bentley Sam , Peramatukorn Chris , Rafi Hamza
Published: May 2018

Chemical Looping Combustion (CLC) and Chemical Looping with Oxygen Uncoupling (CLOU) are low-pollution energy generation techniques conventionally utilizing natural gas or synthetic gas as fuel. Using a redox reaction of metal oxides in dual fluidised beds, CO2 can be captured and prevented from entering the atmosphere at efficiencies up to 80% [4,8]. Algae is a sustainable source of biofuel with the additional benefit of carbon capture through photosynthesis [7]. This Meta-Study attempts to determine the viability of algae as CLC/CLOU reactor fuel for long term sustainable energy generation by identifying trends in different fuels and reactants to see if algae fuel can produce an acceptable output and identify areas of weakness. Energy balance calculations were performed as well as thermal energy output, processing energy and enthalpy values. Graciliara sp. and Chlorella Vulgaris made the most effective fuels for CLC and CLOU respectively due to the low amount of algae required to produce fuel. For CLC, 3.57kg Graciliara sp. produced 1kg fuel. For CLOU, 1.7kg Chlorella Vulgaris produced 1kg fuel. CLOU was the most mass efficient with an energy/mass efficiency ratio of 11600kJ/kg compared to CLC’s 15.7kJ/kg. The energy balance ratio analysis of the production of algal fuel also identified Chlorella Vulgaris as the best fuel, with an EBR of -0.4 in CLOU. In terms of evaluating output, CLOU's energy/mass efficiency ratio surpassed a modern coal plant [45], whose value was 2840 kJ/kg. The defining factor was the enthalpy of reaction.
A comparative analysis on the impact of salinity on the heat generation of OTEC plants to determine the most plausible geographical location
Authors: Lynn Bradley , Medved Alexander , Griggs Timothy
Published: May 2018

This meta-study aims to analyse how the salinity and temperature gradient of the ocean influences the efficiency of ocean-based power plants utilising Ocean Thermal Energy Conversion (OTEC) systems to recommend optimal geographical locations. A comparative analysis of relevant and up to date literature was conducted with pooled data collected by other researchers and utilised such that reasonable conclusions were drawn on how the factors above impact the efficiency of the system. Through the comparisons of the different outputs of the various operational OTEC facilities, it was concluded that seawater with a higher salinity has a negative impact on the heat generated by the OTEC system. By decreasing the salinity by 10% the heat generated increased by up to 0.4%. This information conveys that ideal locations for OTEC power generation lie within the tropics, in regions with lower sea-water salinity. These findings could positively impact the power output of future OTEC plants and highlight the potential for new sources of renewable energies for coastal regions.
Quantification of methane sources in the Athabasca Oil Sands Region of Alberta by aircraft mass balance
Authors: Baray Sabour , Darlington Andrea , Gordon Mark , Hayden Katherine L. , Leithead Amy , Li Shao-Meng , Liu Peter S. K. , Mittermeier Richard L. , Moussa Samar G. , O'Brien Jason , Staebler Ralph , Wolde Mengistu , Worthy Doug , McLaren Robert
Published: May 2018

Abstract. Aircraft-based measurements of methane (CH4) and other air pollutants in
the Athabasca Oil Sands Region (AOSR) were made during a summer intensive
field campaign between 13 August and 7 September 2013 in support of the
Joint Canada–Alberta Implementation Plan for Oil Sands Monitoring. Chemical
signatures were used to identify CH4 sources from tailings ponds (BTEX
VOCs), open pit surface mines (NOy and rBC) and elevated plumes from
bitumen upgrading facilities (SO2 and NOy). Emission rates of
CH4 were determined for the five primary surface mining facilities in
the region using two mass-balance methods. Emission rates from source
categories within each facility were estimated when plumes from the sources
were spatially separable. Tailings ponds accounted for 45 % of total
CH4 emissions measured from the major surface mining facilities in the
region, while emissions from operations in the open pit mines accounted for
∼ 50 %. The average open pit surface mining emission rates
ranged from 1.2 to 2.8 t of CH4 h−1 for different facilities
in the AOSR. Amongst the 19 tailings ponds, Mildred Lake Settling Basin, the
oldest pond in the region, was found to be responsible for the majority of
tailings ponds emissions of CH4 (> 70 %). The sum of
measured emission rates of CH4 from the five major facilities,
19.2 ± 1.1 t CH4 h−1, was similar to a single mass-balance
determination of CH4 from all major sources in the AOSR determined from
a single flight downwind of the facilities, 23.7 ± 3.7 t CH4 h−1.
The measured hourly CH4 emission rate from all facilities in
the AOSR is 48 ± 8 % higher than that extracted for 2013 from the
Canadian Greenhouse Gas Reporting Program, a legislated facility-reported
emissions inventory, converted to hourly units. The measured emissions
correspond to an emissions rate of 0.17 ± 0.01 Tg CH4 yr−1 if
the emissions are assumed as temporally constant, which is an uncertain assumption. The
emission rates reported here are relevant for the summer season. In the future,
effort should be devoted to measurements in different seasons to further our
understanding of the seasonal parameters impacting fugitive emissions of CH4
and to allow for better estimates of annual emissions and year-to-year
variability.
Identification of secondary aerosol precursors emitted by an aircraft turbofan
Authors: Kılıç Doğuşhan , El Haddad Imad , Brem Benjamin T. , Bruns Emily , Bozetti Carlo , Corbin Joel , Durdina Lukas , Huang Ru-Jin , Jiang Jianhui , Klein Felix , Lavi Avi , Pieber Simone M. , Rindlisbacher Theo , Rudich Yinon , Slowik Jay G. , Wang Jing , Baltensperger Urs , Prévôt Andre S. H.
Published: May 2018

Abstract. Oxidative processing of aircraft turbine-engine exhausts was studied using a
potential aerosol mass (PAM) chamber at different engine loads corresponding
to typical flight operations. Measurements were conducted at an engine test
cell. Organic gases (OGs) and particle emissions pre- and post-PAM
were measured. A suite of
instruments, including a proton-transfer-reaction mass spectrometer (PTR-MS)
for OGs, a multigas analyzer for
CO, CO2, NOx, and an aerosol mass spectrometer (AMS) for
nonrefractory particulate matter (NR-PM1) were used. Total aerosol mass
was dominated by secondary aerosol formation, which was approximately
2 orders of magnitude higher than the primary aerosol. The chemical
composition of both gaseous and particle emissions were also monitored at
different engine loads and were thrust-dependent. At idling load (thrust
2.5–7 %), more than 90 % of the secondary particle mass was organic
and could mostly be explained by the
oxidation of gaseous aromatic species, e.g., benzene; toluene; xylenes; tri-, tetra-, and
pentamethyl-benzene; and naphthalene. The oxygenated-aromatics, e.g., phenol,
furans, were also included in this aromatic fraction and their oxidation
could alone explain up to 25 % of the secondary organic particle mass at
idling loads. The organic fraction decreased with thrust level, while the
inorganic fraction increased. At an approximated cruise load sulfates
comprised 85 % of the total secondary particle mass.
Fine-particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models
Authors: Song Shaojie , Gao Meng , Xu Weiqi , Shao Jingyuan , Shi Guoliang , Wang Shuxiao , Wang Yuxuan , Sun Yele , McElroy Michael B.
Published: May 2018

Abstract. pH is an important property of aerosol particles but is difficult to measure directly. Several studies have estimated the pH values for fine particles in northern China winter haze using thermodynamic models (i.e., E-AIM and ISORROPIA) and ambient measurements. The reported pH values differ widely, ranging from close to 0 (highly acidic) to as high as 7 (neutral). In order to understand the reason for this discrepancy, we calculated pH values using these models with different assumptions with regard to model inputs and particle phase states. We find that the large discrepancy is due primarily to differences in the model assumptions adopted in previous studies. Calculations using only aerosol-phase composition as inputs (i.e., reverse mode) are sensitive to the measurement errors of ionic species, and inferred pH values exhibit a bimodal distribution, with peaks between −2 and 2 and between 7 and 10, depending on whether anions or cations are in excess. Calculations using total (gas plus aerosol phase) measurements as inputs (i.e., forward mode) are affected much less by these measurement errors. In future studies, the reverse mode should be avoided whereas the forward mode should be used. Forward-mode calculations in this and previous studies collectively indicate a moderately acidic condition (pH from about 4 to about 5) for fine particles in northern China winter haze, indicating further that ammonia plays an important role in determining this property. The assumed particle phase state, either stable (solid plus liquid) or metastable (only liquid), does not significantly impact pH predictions. The unrealistic pH values of about 7 in a few previous studies (using the standard ISORROPIA model and stable state assumption) resulted from coding errors in the model, which have been identified and fixed in this study.
Diurnal variation of aerosol optical depth and PM2.5 in South Korea: a synthesis from AERONET, satellite (GOCI), KORUS-AQ observation, and WRF-Chem model
Authors: Lennartson Elizabeth , Wang Jun , Castro Garcia Lorena , Ge Cui , Carmichael Gregory , Gao Meng , Kim Jhoon , Janz Scott
Published: May 2018

Abstract. Spatial distribution of diurnal variations of aerosol properties in South Korea, both long term and short term, is studied by using 9 AERONET sites from 1999 to 2017 and an additional 10 sites during the KORUS-AQ field campaign in May and June of 2016. The extent to which WRF-Chem model and the GOCI satellite retrieval can describe these variations is also analyzed. In daily average, Aerosol Optical Depth (AOD) at 550 nm is 0.386 and shows a diurnal variation of 20 to −30 % in inland sites, respectively larger than the counterparts of 0.308 and ±20 % in coastal sites. For all the inland and coastal sites, AERONET, GOCI, WRF-Chem, and observed PM2.5 data consistently show dual peaks for both AOD and PM2.5, one at ∼10 KST and another ∼14 KST. In contrast, Angstrom exponent values in all sites are between 1.2 and 1.4 with the exception of the inland rural sites having smaller values near 1.0 during the early morning hours. All inland sites experience a pronounced increase of Angström Exponent from morning to evening, reflecting overall decrease of particle size in daytime. To statistically obtain the climatology of diurnal variation of AOD, a minimum of requirement of ∼2 years of observation is needed in coastal rural sites, twice more than the urban sites, which suggests that diurnal variation of AOD in urban setting is more distinct and persistent. While Korean GOCI satellite retrievals are able to consistently capture the diurnal variation of AOD, WRF-Chem clearly has the deficiency to describe the relatively change of peaks and variations between the morning and afternoon, suggesting further studies for the diurnal profile of emissions. Furthermore, the ratio between PM2.5 and AOD in WRF-Chem is persistently larger than the observed counterparts by 30–50 % in different sites, but no consistent diurnal variation pattern of this ratio can be found. Overall, the relative small diurnal variation of PM2.5 is in high contrast with large AOD diurnal variation, which suggests the large diurnal variation of AOD-PM2.5 relationships, and therefore, the need to use AOD from geostationary satellites for constrain either modeling or analysis of surface PM2.5 for air quality application.
Size Resolved Online Chemical Analysis of Nano Aerosol Particles: A Thermal Desorption Differential Mobility Analyzer Coupled to a Chemical Ionization Time Of Flight Mass Spectrometer
Authors: Wagner Andrea C. , Bergen Anton , Brilke Sophia , Fuchs Claudia , Ernst Markus , Hoker Jesica , Heinritzi Martin , Simon Mario , Bühner Bertram , Curtius Joachim , Kürten Andreas
Published: May 2018

Abstract. A new method for size resolved chemical analysis of nucleation mode aerosol particles (size range from ~ 10 to ~ 30 nm) is presented. The Thermal Desorption Differential Mobility Analyzer (TD-DMA) uses an online, discontinuous principle. The particles are charged, a specific size is selected by differential mobility analysis and they are collected on a filament by electrostatic precipitation. Subsequently, the sampled mass is evaporated in a clean carrier gas and analyzed by a chemical ionization mass spectrometer. Gas phase measurements are performed with the same mass spectrometer during the sampling of particles. The characterization shows reproducible results, with a particle size resolution of 1.19 and the transmission efficiency for 15 nm particles being slightly above 50 %. The signal from the evaporation of a test substance can be detected starting from 0.01 ng and shows a linear response in the mass spectrometer. Instrument operation in the range of pg/m3 is demonstrated by an example measurement of 15 nm particles produced by nucleation from dimethylamine, sulfuric acid and water.
Development and field-testing of an online instrument for measuring the real-time oxidative potential of ambient particulate matter based on dithiothreitol assay
Authors: Puthussery Joseph V. , Zhang Chen , Verma Vishal
Published: May 2018

Abstract. We developed an online instrument for measuring the oxidative potential (OP) of ambient particulate matter (PM) using dithiothreitol (DTT) assay. The instrument uses a mist chamber (MC) to continuously collect the ambient PM2.5 in water, followed by its DTT activity determination using an automated syringe pump system. The instrument was deployed at an urban site in the University of Illinois campus, and its field performance was evaluated by comparing the results with the offline DTT activity measurements of simultaneously collected PM-laden filters. The online DTT activity measurements correlated well with the offline measurements but were higher than both methanol (slope = 0.86, R2 = 0.93) and Milli-Q water (slope = 0.52, R2 = 0.86) extracts of the PM filters, indicating a better efficiency of MC for collecting the water-insoluble fraction of PM. The hourly measurements of ambient PM2.5 OP were obtained by running the online instrument intermittently for 50 days with minimal manual assistance. The daytime DTT activity levels were generally higher than at night. However, a four-fold increase in the hourly averaged activity was observed on the night of July 04 (Independence Day fireworks display). Diurnal profile of the hourly averaged OP during weekdays showed a bimodal trend, with a sharp peak in the morning (around 7:00 AM), followed by a broader afternoon peak, which plateaus around 2:00 PM, and starts subsiding at night (around 7:00 PM). To investigate the association of the diurnal profile of DTT activity with the emission sources at the site, we collected time-segregated composite PM filter samples in four different time periods of the day [morning (7:00 AM–10:00 AM), afternoon (10:00 AM–3:00 PM), evening (3:00 PM–7:00 PM) and night (7:00 PM–7:00 AM)] and determined the diurnal variations in the redox active components [i.e. water soluble Cu, Fe, Mn, organic carbon, elemental carbon and water soluble organic carbon]. Based on this comparison, we attributed the daytime OP of ambient PM2.5 to the water-soluble Cu from both exhaust and non-exhaust emissions, whereas secondary particles formed by the photochemical transformation of primary emissions appear to enhance the OP of PM during the afternoon and evening period.
Inputs and processes affecting the distribution of particulate iron in the North Atlantic along the GEOVIDE (GEOTRACES GA01) section
Authors: Gourain Arthur , Planquette Hélène , Cheize Marie , Lemaitre Nolwenn , Menzel Barraqueta Jan-Lukas , Shelley Rachel , Lherminier Pascale , Sarthou Géraldine
Published: May 2018

Abstract. The GEOVIDE cruise (May–June 2014, R/V Pourquoi Pas?) aimed to provide a better understanding on trace metal biogeochemical cycles in the North Atlantic. As particles play a key role in the global biogeochemical cycle of trace elements in the ocean, we discuss the distribution of particulate iron (PFe), in light of particulate aluminium (PAl), manganese (PMn) and phosphorus (PP) distributions. Overall, 32 full vertical profiles were collected for trace metal analyses, representing more than 500 samples. This resolution provides a solid basis for assessing concentration distributions, elemental ratios, size-fractionation, or adsorptive scavenging processes in key areas of the thermohaline circulation. Total particulate iron (PFe) concentrations ranged from as low as 9 pmol L−1 in surface Labrador Sea waters to 304 nmol L−1 near the Iberian margin, while median PFe concentrations of 1.15 nmol L−1 were measured over the sub-euphotic ocean interior. At most stations over the Western, the relative concentrations of total PFe and aluminium (PAl) showed the near-ubiquitous influence of crustal particles in the water column. Overall, the lithogenic component explained more than 87 % of PFe variance along the section. Within the Irminger and Labrador basins, the formation of biogenic particles led to an increase of the PFe / PAl ratio (up to 0.7 mol mol−1) compared to the continental crust ratio (0.21 mol mol−1), Margins provide important quantities of particulate trace elements (up to 10 nmol L−1 of PFe) to the open ocean, and in the case of the Iberian margin, advection of PFe was visible more than 250 km away from the margin. Additionally, several benthic nepheloid layers spreading over 200m above the seafloor were encountered along the transect, especially in the Icelandic, Irminger and Labrador basins, delivering particles with high PFe content, up to 89 nmol L−1 of PFe. Finally, remineralisation processes are also discussed, and showed different patterns among basins and elements.
Feasibility of three-dimensional density tomography using dozens of muon radiographies and Filtered BackProjection for volcano
Authors: Nagahara Shogo , Miyamoto Seigo
Published: May 2018

Abstract. This study is the first trial to apply the method of filtered backprojection (FBP) method to reconstruct three-dimensional (3D) bulk density images via cosmic-ray muons, We also simulated three-dimensional reconstruction image with dozens of muon radiographies using FBP method for a volcano and evaluated its practicality. FBP method is widely used in X-ray and CT image reconstruction but has not been used in the field of muon radiography. One of the merits to use FBP method instead of ordinary inversion method is that it doesn't require an initial model, while ordinary inversion analysis need an initial model. We also added new approximation factors by using data on mountain topography into existing formulas to successfully reduce systematic reconstruction errors. From a volcanic perspective, airborne radar is commonly used to measure and analyze mountain topography. We tested the performance and applicability to the model of Omuroyama, a monogenetic scoria cone located in Shizuoka, Japan. As a result, it was revealed that the density difference between the original and reconstructed images depended on the number of observation points and the accidental error caused by muon statistics depended on the multiplication of total effective area and exposure period. Combining above all things, we established how to evaluate an observation plan for volcano using dozens of muon radiographies.