bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the method of dynamic programming for solving the optimal unit commitment problem in distribution networks with local distributed generation
Authors: Dimishkovska Natasha , Iliev Atanas 
Published: July 2020

Abstract
The continuous growth of communities leads to an increase in electrical energy usage. Besides the technological advance of power systems, still, there are outages which lead to an interruption in the power supply. The implementation of distributed generation provides usage of the local renewable energy sources for satisfying local power needs which in good manner complexes the distribution networks. However, because the distributed energy resources depend on the weather conditions, the islanded work is not quite reliable. Grid-connected distributed energy resources have enhanced power supply reliability. In this paper, a dynamic programming model is used for the optimisation of power generation by the local distributed energy resources. Assuming the distributed energy resources have storage systems, the model takes into account the battery charge at the moment and the availability of the distributed energy resources depending on the weather conditions and whether is day or night. It is assumed that the distributed energy resources have equal power capacities. Case study reviews a low voltage distribution network with plenty of distributed energy resources from different renewable energy sources implemented and a cluster of household consumers.
On the use of blockchain technologies in smart home applications
Authors: Pazhev G , Spasov Gr , Shopov M , Petrova G 
Published: July 2020

Abstract
The paper presents an implementation of a smart home architecture with two gateways based on collaboration of blockchain technology and Internet of Things (IoT) Message oriented middleware (MOM) architecture for management of internal home appliances. A basic overview of IoT MOM, MQTT (Message Queue Telemetry Transfer) protocol and blockchain architectures is made and the key characteristics and consensus algorithms are presented. Some challenges and the Ethereum smart contracts concept of the blockchain technology are discussed.
Gamification of courses in the e-learning environment
Authors: Gachkova Mariya , Somova Elena , Gaftandzhieva Silvia 
Published: July 2020

Abstract
The paper presents a study in the field of gamification of learning, in particular – in structural gamification. The four-stages cyclic (Learning – Evaluation – Rewarding – Ranking) gamification learning model is proposed. The used gamified elements (level, story/history, challenge, team, time frame, game progress, status (avatar), bonus, badge, reward, hidden treasures, combo and leaderboard) with their impact to the learner’s motivation are explained. Two plug-ins are designed, developed and tested with real users. One of the plug-ins changes the design of the learning course in game-like view, while the other ranks the students in a leaderboard with their avatars, according to their course progress. The short explanation of the experiment with learners is done and part of the statistical results from the conducted survey in five areas (practical applicability; motivation; design and accessibility; interactivity and communication; and intelligibility) are shown.
Dynamical stresses in the high class wind turbine blades caused in nonhomogeneous nonstationary wind field. Part 1 Dynamical model
Authors: Kralov I , Genov J , Angelov I 
Published: July 2020

Abstract
The wind turbines of a high class are with considerable sizes. For this reason, the consideration of the fluid field as a homogeneous when performing the aerodynamic analysis is not quite correct. In addition, due to the gusts and horizontal turbulence, the wind field is also nonstationary. All this causes dynamic, time-varying loads and fatigue. The determination of these loads is a major aim of this publication. The turbine blades are considered as Euler-Bernoulli beams under the impact of the aerodynamic thrust and torque forces as well as from this of the centrifugal force. The finite element method is applied to solve the partial differential equations describing the model under consideration. Two-node elements with four degrees of freedom for each node and a cubic, polynomial approximation of modal shapes were used. The deformations are relatively small in the separated finite elements and this makes it possible to apply the superposition principle.
Application of multi-axis force/torque sensor system for experimental study of small unmanned aerial vehicles propulsion systems – Preliminary results
Authors: Serbezov V , Panayotov H , Todorov M , Penchev S 
Published: July 2020

Abstract
The experimental evaluation of the performance of small propellers plays important role in the process of multicopter UAV design perfection. This paper presents a small UAV propeller test stand, based on a multi-axis Force/Torque sensor system. The system makes possible to measure the thrust, torque and the pitching moment or lateral force (when in oblique flow) of the tested propeller. The data processing of the experimental results is discussed. Results for static, axial flow and oblique flow conditions are presented. Some conclusions about the measurement methodology are drawn. The results verify that the test bench has good accuracy and is easy for operation.
Aerodynamic testing of rotors and propellers for small unmanned aerial vehicles at Technical University - Sofia
Authors: Panayotov F , Serbezov V , Todorov M 
Published: July 2020

Abstract
The recent massive introduction of small unmanned aerial vehicles (UAVs) brought the problem of absence of reliable aerodynamic data and models for propulsion systems that work at low Reynolds numbers. At the same time the new capabilities of modern measuring equipment permit detailed experimental investigations of the aerodynamic characteristics of such systems. This paper presents the results of work in this direction, carried out at, or with serious contribution of the Department of Aeronautics at Technical University of Sofia. Two test benches are presented. The first one is for static testing of small helicopter rotors. It is designed also with provisions for installation in suitable wind tunnels. The second one is a test stand for evaluation of electric power plants for unmanned aircraft vehicles. It can be used statically, or may be installed on the roof of an automobile for mobile testing. As an illustration experimental results are given for a specific model helicopter rotor and a small airplane propeller.
Use of modern software solutions and systems for analysis and reconstruction of road accidents
Authors: Damyanov I S 
Published: July 2020

Abstract
This study examines the possibilities of investigating a road accident and provides initial data for the reconstruction of road accidents using photogrammetric techniques. Compared to the conventional practice of road accident reconstruction, photogrammetry saves time, money and is an effective method for investigating road accidents. The use of unmanned aerial vehicles - UAVs and mapping software enables the collection of collecting the data needed to investigate, analyze and reconstruct road accidents. The measurement results can be considered as initial information for a technique for repairing damage analysis. The study shows that photogrammetry has an increasing potential for application in the investigation and recovery of road accidents.
Crack propagation evaluation using virtual prototyping techniques
Authors: Kamberov K H , Ivanov Ts T , Zlatev B N 
Published: July 2020

Abstract
A methodology for crack propagation using virtual prototyping (VP) is demonstrated. It is based on a classical approach to assess crack propagation, improved with finite element analysis tools. It enables to examine in detail all aspects of crack formation and to evaluate the probability of its occurrence. Performed demonstration is based on Al2O3 substrate laser scribing process and its assessment in direction of possible crack occurrence. Presented study gives basic directions on application of virtual prototyping in crack initiation and propagation prediction. This approach gives the opportunity to monitor various parameters as stresses and to predict influence of various design changes over examined physical process output parameters.
Classification of parts used in mechatronic products and produced by permanent-mold casting methods
Authors: Zaharinov V , Malakov I , Nikolov S , Dimitrova R , Stambolov G 
Published: July 2020

Abstract
The paper presents the results from a research on parts used in mechatronic products and produced by the permanent-mold casting methods of gravity die casting and die casting. An overview and analysis of different definitions for mechatronic systems and examples of mechatronic products is made. As a result, a new definition for a mechatronic product is proposed. Various classifications of mechatronic products are analysed and deemed too general for the purposes of the current research. Permanent-mold casting methods are analysed and their advantages and disadvantages are pointed out. Arguments as to why these methods are suitable for producing mechatronic product parts are given. Based on the proposed definition for mechatronic product, the analysed classifications, and the overview of the permanent-mold casting methods a new classification is proposed. The classification is used for classifying permanent-mold cast parts used in mechatronic products. The parts are classified in six groups with regard to their application in the mechatronic product. In addition, the classification gives information regarding permanent-mold casting method used, material, and mechatronic product that includes the part.
Corrosion behaviour of aluminium alloys EN AW-6026 and EN AW-6082 in a sulphuric acid medium
Authors: Kamarska Kalina 
Published: July 2020

Abstract
The corrosion behaviour of aluminium alloys EN AW-6026 and EN AW-6082 in 0,1 M and 1 M sulphuric acid solutions at different temperatures has been investigated by using gravimetric techniques and a digital microscope. The study revealed that the corrosion rate increases with higher temperature and concentration of H2SO4. The surface attack increased with the increasing of the concentration of sulphuric acid and the temperature. Alloys EN AW-6026 and EN AW-6082 have a higher corrosion resistance at 25 °C.
Singularity formation for the fractional Euler-alignment system in 1D
Authors: Arnaiz Victor , Castro Ángel 
Published: July 2020

We study the formation of singularities for the Euler-alignment system with influence function

ψ
=

k
α

|

x

|

1
+
α

\psi =\frac {k_\alpha }{|x|^{1+\alpha }}

in 1D. As in [Commun. Math. Sci. 17 (2019), pp. 1779–1794] the problem is reduced to the analysis of a nonlocal 1D equation. We show the existence of singularities in finite time for any

α
\alpha

in the range

0
>
α
>
2

0>\alpha >2

in both the real line and the periodic case and with just a point of vacuum.
Torsion points of order 2𝑔+1 on odd degree hyperelliptic curves of genus 𝑔
Authors: Bekker Boris , Zarhin Yuri 
Published: July 2020

Let

K
K

be an algebraically closed field of characteristic different from

2
2

, let

g
g

be a positive integer, let

f
(
x
)
∈
K
[
x
]

f(x)\in K[x]

be a degree

2
g
+
1

2g+1

monic polynomial without multiple roots, let

C

f

:

y
2

=
f
(
x
)

\mathcal {C}_f: y^2=f(x)

be the corresponding genus

g
g

hyperelliptic curve over

K
K

, and let

J
J

be the Jacobian of

C

f

\mathcal {C}_f

. We identify

C

f

\mathcal {C}_f

with the image of its canonical embedding into

J
J

(the infinite point of

C

f

\mathcal {C}_f

goes to the zero of the group law on

J
J

). It is known [Izv. Math. 83 (2019), pp. 501–520] that if

g
≥
2

g\ge 2

, then

C

f

(
K
)

\mathcal {C}_f(K)

contains no points of orders lying between

3
3

and

2
g

2g

.

In this paper we study torsion points of order

2
g
+
1

2g+1

on

C

f

(
K
)

\mathcal {C}_f(K)

. Despite the striking difference between the cases of

g
=
1

g=1

and

g
≥
2

g\ge 2

, some of our results may be viewed as a generalization of well-known results about points of order

3
3

on elliptic curves. E.g., if

p
=
2
g
+
1

p=2g+1

is a prime that coincides with

char
⁡
(
K
)

\operatorname {char}(K)

, then every odd degree genus

g
g

hyperelliptic curve contains at most two points of order

p
p

. If

g
g

is odd and

f
(
x
)

f(x)

has real coefficients, then there are at most two real points of order

2
g
+
1

2g+1

on

C

f

\mathcal {C}_f

. If

f
(
x
)

f(x)

has rational coefficients and

g
≤
51

g\le 51

, then there are at most two rational points of order

2
g
+
1

2g+1

on

C

f

\mathcal {C}_f

. (However, there exist odd degree genus

52
52

hyperelliptic curves over

Q

\mathbb {Q}

that have at least four rational points of order 105.)
The first cohomology, derivations, and the reductivity of a (meromorphic open-string) vertex algebra
Authors: Huang Yi-Zhi , Qi Fei 
Published: July 2020

We give a criterion for the complete reducibility of modules satisfying a composability condition for a meromorphic open-string vertex algebraVVusing the first cohomology of the algebra. For aVV-bimoduleMM, letH^∞1(V,M)\hat {H}^{1}_{\infty }(V, M)be the first cohomology ofVVwith the coefficients inMM, which is canonically isomorphic to the quotient space of the space of derivations fromVVtoWWby the subspace of inner derivations. LetZ^∞1(V,M)\hat {Z}^{1}_{\infty }(V, M)be the subspace ofH^∞1(V,M)\hat {H}^{1}_{\infty }(V, M)canonically isomorphic to the space of derivations obtained from the zero mode of the right vertex operators of weight11elements such that the difference between the skew-symmetric opposite action of the left action and the right action on these elements are Laurent polynomials in the variable. IfH^∞1(V,M)=Z^∞1(V,M)\hat {H}^{1}_{\infty }(V, M)= \hat {Z}^{1}_{\infty }(V, M)for everyZ\mathbb {Z}-gradedVV-bimoduleMM, then every leftVV-module satisfying a composability condition is completely reducible. In particular, since a lower-boundedZ\mathbb {Z}-graded vertex algebraVVis a special meromorphic open-string vertex algebra and leftVV-modules are in fact what has been called generalizedVV-modules with lower-bounded weights (or lower-bounded generalizedVV-modules), this result provides a cohomological criterion for the complete reducibility of lower-bounded generalized modules for such a vertex algebra. We conjecture that the converse of the main theorem above is also true. We also prove that when a grading-restricted vertex algebraVVcontains a subalgebra satisfying some familiar conditions, the composability condition for grading-restricted generalizedVV-modules always holds and we needH^∞1(V,M)=Z^∞1(V,M)\hat {H}^{1}_{\infty }(V, M)= \hat {Z}^{1}_{\infty }(V, M)only for everyZ\mathbb {Z}-gradedVV-bimoduleMMgenerated by a grading-restricted subspace in our complete reducibility theorem.
Impact of Apoidea (Hymenoptera) on the World’s Food Production and Diets
Authors: Lorenzo-Felipe Israel , Blanco Carlos A , Corona Miguel 
Published: July 2020

AbstractBees and some wasp species of the superfamily Apoidea pollinate most of the crops used for food and feed, producing different impacts on agricultural production. Despite the considerable importance of Apoidea, the relevance of this group’s impact on global crop production and human diets is controversial. To measure the pollination effect of these insects on crop production, factors such as the myriad of agricultural practices, different crop varieties, fluctuating pollinators’ densities, constantly changing environmental conditions, and demands for food items in a diverse diets must be considered. An ‘Apoidea impact factor’ (AIF), a value calculated taking into consideration the effect of this superfamily on enhancing crop production through pollination, the diversity of crops in a given area, the area planted by specific crops, and agricultural output, was calculated for 176 agricultural crops. Consistently with previous estimations, our results show that Apoidea have a direct impact on 66% of the 128 most important agricultural crops consumed in the world. However, the analysis of the impact of Apoidea on global production and human consumption revealed a different perspective: Apoidea pollination affects only 16% of the total tonnage output, 14% of the cultivated area, and 9% of the kilocalories consumed. Because 25 of the most cultivated crops in the world do not require, or are slightly affected by Apoidea pollination, and these plants grow in 84% of the world’s cropland, constituting 50% of the world’s diet, and 89% of the kilocalories consumed by peoples around of the world, the AIF at the world level is reduced to 11% of food consumed, and 6% of the kilocalories. The AIF, when applied to a small geographical scale, for example, the municipality or county level rather than country or state level, becomes more useful identifying areas where bees and wasps have greater impact in agriculture. In this report, we update the widely popular quote ‘One out of every three bites of food we eat is a result of pollinators like honey bees’ to a more accurate one: ‘nearly 5% of the food we eat, and about 10% of the calories we burn have a direct relationship with Apoidea pollination’. This new estimate does not diminish the need for pollinators for many of the world’s most nutritious foods, but merely suggests that these foods do not provide an extensive part of the human diet. The AIF can be used to identify specific areas where these pollinators have greater impact and direct conservation efforts directly into them. This approach can serve as a better estimate of the role of these pollinators in our food, using data-driven arguments.
Discovery and Mediation Analysis of Cross-Phenotype Associations Between Asthma and Body Mass Index in 12q13.2
Authors: Salinas Yasmmyn D , Wang Zuoheng , DeWan Andrew T 
Published: July 2020

AbstractTwin studies suggest that shared genetics contributes to the comorbidity of asthma and obesity, but candidate-gene studies provide limited evidence of pleiotropy. We conducted genome-wide association analyses of asthma and body mass index (BMI; weight (kg)/height (m)2)) among 305,945 White British subjects recruited into the UK Biobank in 2006–2010. We searched for overlapping signals and conducted mediation analyses on genome-wide-significant cross-phenotype associations, assessing moderation by sex and age at asthma diagnosis, and adjusting for confounders of the asthma-BMI relationship. We identified a genome-wide-significant cross-phenotype association at rs705708 (asthma odds ratio = 1.05, 95% confidence interval: 1.03, 1.07; P = 7.20 × 10−9; and BMI β = −0.065, 95% confidence interval: −0.087, −0.042; P = 1.30 × 10−8). rs705708 resides on 12q13.2, which harbors 9 other asthma- and BMI-associated variants (all P &lt; 5 × 10−5 for asthma; all but one P &lt; 5 × 10−5 for BMI). Follow-up analyses of rs705708 show that most of the BMI association occurred independently of asthma, with consistent magnitude between men and women and persons with and without asthma, irrespective of age at diagnosis; the asthma association was stronger for childhood versus adult asthma; and both associations remained after confounder adjustment. This suggests that 12q13.2 displays pleiotropy for asthma and BMI. Upon further characterization, 12q13.2 might provide a target for interventions that simultaneously prevent or treat asthma and obesity.
Multiresolution Analyses of Neighborhood Correlates of Crime: Smaller Is Not Better
Authors: Mair Christina , Sumetsky Natalie , Gaidus Andrew , Gruenewald Paul J , Ponicki William R 
Published: July 2020

Abstract
Population analyses of the correlates of neighborhood crime implicitly assume that a single spatial unit can be used to assess neighborhood effects. However, no single spatial unit may be suitable for analyses of the many social determinants of crime. Instead, effects may appear at multiple spatial resolutions, with some determinants acting broadly, others locally, and still others as some function of both global and local conditions. We provide a multiresolution spatial analysis that simultaneously examines US Census block, block group, and tract effects of alcohol outlets and drug markets on violent crimes in Oakland, California, incorporating spatial lag effects at the 2 smaller spatial resolutions. Using call data from the Oakland Police Department from 2010–2015, we examine associations of assaults, burglaries, and robberies with multiple resolutions of alcohol outlet types and compare the performance of single (block-level) models with that of multiresolution models. Multiresolution models performed better than the block models, reflected in improved deviance and Watanabe-Akaike information criteria and well-supported multiresolution associations. By considering multiple spatial scales and spatial lags in a Bayesian framework, researchers can explore multiresolution processes, providing more detailed tests of expectations from theoretical models and leading the way to more effective intervention efforts.
Short-Term but not Long-Term Blood Pressure Variability Is a Predictor of Adverse Cardiovascular Outcomes in Young Untreated Hypertensives
Authors: Saladini Francesca , Fania Claudio , Mos Lucio , Vriz Olga , Mazzer Andrea , Spinella Paolo , Garavelli Guido , Ermolao Andrea , Rattazzi Marcello , Palatini Paolo 
Published: July 2020

Abstract

Background
Whether blood pressure variability (BPV) measured with ambulatory monitoring (short-term BPV) or computed from office visits (long-term BPV) are related to each other and carry similar prognostic information is not well known. We investigated the independent determinants of short-term and long-term BPVs and their predictive capacity for the development of major adverse cardiovascular and renal events (MACEs) in a cohort of young hypertensive participants.

Methods
Long-term BPV was calculated as visit-to-visit SD and average real variability from office blood pressure (BP) measured during 7 visits, within 1 year. Short-term BPV was calculated as weighted 24-hour SD and coefficient of variation. Hazard ratios (HRs) for risk of MACE were computed from multivariable Cox regressions.

Results
1,167 participants were examined; mean age was 33.1 ± 8.5 years. Variables independently associated with 24-hour systolic SD were 24-hour systolic BP, low physical activity, smoking, baseline office pulse pressure, systolic BP dipping, and diastolic white coat effect, while those associated with long-term BPV were mean systolic BP, age, female gender, and baseline office heart rate. During a median follow-up of 17.4 years 75 MACEs occurred. In Cox analysis only short-term BPV resulted a significant predictor of MACE (HR, 1.31 (1.07–1.59); P = 0.0086), while no index of long-term BPV was independently associated with outcome.

Conclusions
In young hypertensive subjects only short-term BPV resulted a significant predictor of MACE on top of traditional ambulatory BP monitoring parameters. Whether reduction of short-term BPV with therapy may reduce the cardiovascular risk independently from the effects on 24-hour BP is a matter for future research.