bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimize Formation Damage in Water-Sensitive Unconventional Reservoirs by Using Energized Fracturing Fluid
Authors: Kong Bing , Wang Shuhua , Chen Shengnan , Dong Kai
Published: January 2016

Slickwater has been widely used for hydraulic fracturing as it is inexpensive and able to carry proppants into the fracture. However, such fluid is unsuitable for water-sensitive formations, such as Montney. Water saturation around the fracture increases and clay swells when water leaks-off into matrix, both hindering natural gas flowing from matrix into fractures. N2 or CO2 energized water-based fracturing fluids have been widely used in water-sensitive formation as they can minimize fluid leak off during fracturing and achieve higher load fluid recovery during flow back.

In this paper, multi-phase numerical simulations are applied to study the formation damage mitigation in Montney tight reservoir by using energized fracturing fluid. A simulation model is built and history matched with flow back and early production data of a typical Montney tight gas well. The behavior of multi-phase fluid leak off and flow back is studied, and the sensitivity of foam quality of fracturing fluid on load fluid recovery and well after stimulation productivity is analyzed. Statistical analysis is conducted on the stimulation and production data of over 5000 Montney wells to study the performance of energized fracturing in water-sensitive Montney formation. It is found that multi-phase fracturing fluid has less dynamic fluid leak off than that of a single phase fracturing fluid (i.e., water), and the major fluid leak off occurs during the static leak off period between the end of the stimulation processes and start of the flow back. Gas phase penetrates deeper and faster into the reservoir matrix in comparison with the liquid phase, which greatly contributes to flow back of fracturing fluid. Formation damage caused by fracturing fluid leak off can affect both early and long term production. In addition, N2-foam leads to the highest load fluid recovery in Montney formation, which is 1.6 times of that of CO2-foam. This work provides critical insights into understanding the performance of using energized fracturing fluid to mitigate formation damage in tight formations.
Identifying the Source and Magnitude of Formation Damage from Pressure and Temperature Profiles
Authors: You Z. , Bedrikovetsky P.
Published: January 2016

Evaluation of flow rate profile along the wellbore is very important for reservoir characterization, because it indicates the contribution of each inflow point at different depth to the overall production rate. The temperature and pressure sensors in the wellbore are small and cheap, whereas flow meters are cumbersome and expensive, and affect the flow in the well. The method presented in the current paper shows its significance in predicting the gas rate from temperature and pressure data. A mathematical model for pressure and temperature distributions along gas well has been developed. Temperature and pressure profiles from nine well intervals in field C (Australia) have been matched with the mathematical model to determine the flow rates from different layers in the well. The present model considers the variables as functions of thermal properties at each depth, which is more accurate if compared to previous models. Results of tuning the mathematical model to field data show good agreement with the model prediction. Simple and explicit formulae are derived for effective evaluation of flow rate and thermal conductivity in gas wells. The proposed approach has been applied to the estimation of gas rates and formation thermal conductivities from the measured well pressure and temperature data in field C. It provides useful information for identifying the source and magnitude of formation damage and recommending well stimulation of the layers with low rates.
A New Phenomenon of Slow Fines Migration in Oil and Gas Fields (Laboratory and Mathematical Modelling)
Authors: Yang Y. , You Z. , Siqueira F. D. , Vaz A. , Bedrikovetsky P.
Published: January 2016

Fines migration causes significant permeability damage, due to mobilisation of particles at increased velocities, their migration in pores followed by straining at pore throats and attachment to pore walls. Numerous coreflooding tests with piecewise increasing rates are conducted. There are two main features of these tests: the first is long-term injection, which allows calculating permeability stabilisation time; the second is pressure measurement at intermediate points, allowing for evaluating the permeability profile along the core. The impedance data obtained from experiments are matched with the results from analytical model. It shows that the mobilised particles move with velocity much smaller than the carrier fluid, yielding long time for permeability stabilisation. It contradicts the classical filtration theory, which indicates the fines are transported with the carrier fluid velocity.
A New Method for Water Shut-Off Using Induced Formation Damage
Authors: Zeinijahromi Abbas , Bedrikovetsky Pavel
Published: January 2016

A common problem in aquifer water-drive reservoirs and water flooding projects is premature and excessive water production through natural fractures, faults or high permeable thief zones. The most common water shut-off methods today is polymer gel treatment; however, a large treatment volume is required to block the water influx that generally involves high operational, material and environmental costs.

It is well known that injection of low salinity water into a reservoir that contains movable clays can significantly decrease the rock permeability. This paper presents a new technique of applying induced formation damage for water shut-off in order to block the water influx from high permeable water producing layers. This study applies numerical simulation to investigate the effectiveness of the induced formation damage treatment for reducing water production. The results of the study show that injection of an small slug (~1% PVI) of low salinity water into the water producing well resulted in ~30% reduction in produced water cut and ~6% incremental recovery.
Delivering A More Consistent Estimation of Tight Rock Permeability
Authors: Ling Kegang , Feng Yin , Ghalambor Ali , Zhou Lijun , He Jun
Published: January 2016

Petroleum exploration and production from the tight reservoirs such as shale have gained great success in United States during last decade. Producing hydrocarbons from shale is challenging due to its low matrix permeability. It is therefore, crucial to investigate shale permeability to better understand the performance of unconventional resources wells. In addition, permeability is not only one of the key parameters in modeling fluids flow in matrix in reservoir simulation, but also a key parameter regulating production decline rate, which is critical to the stimulation process and to the economics of well. Since the inference of shale permeability is time consuming and expensive due to its low range of permeability, Gas Research Institute (GRI) method is applied as a shortcut. Unfortunately, many studies have pointed out that there is significant variation in the results reported by different laboratories using the GRI technique. It is difficult to identify that whether the differences are due to apparatus or the interpretation method, since GRI report did not provide a detailed description for interpreting the raw data. Furthermore, there is no available theoretical base in the literatures for the GRI technique. Due to the high uncertainty in the GRI method, it is worth to develop the theoretical basis for this technique. In this study, starting from the basic physics laws, we derived the governing equation for the fluid transient flow behavior in the GRI permeability measurement. The rigorous derivation provides a solid foundation for analyzing experimental data. The interpretation of test data can be more reliable through solving the governing equations either analytically or numerically. In this way, we can increase the agreement of the results from different laboratories using GRI technique. A case study is used to compare the developed mathematical model with literature data. The differences may be caused by the deviation from the assumptions in developing the theoretical model. Considering the non-spherical particles and non-uniform sizes of particles involved in the experiment, the multi-variable regression proposed in this study makes the analysis of GRI permeability data more practical and reasonable. In order to reduce the interpretation uncertainty, multiple reference cell pressures are used to measure the same crushed sample and generate corresponding pressure-decay curves. The proposed equation will allow engineers to interpret experimental data in a more practical and reasonable way.
Prediction of Formation Damage at Water Injectors Wells due to Channelization in Unconsolidated Formations
Authors: Bautista J. F. , Taleghani A. Dahi
Published: January 2016

Formation damage due to chemical reactions or physical failure of rock is a well-known issue in the oil and gas industry. In this paper, we look at the changes of injectivity at water injectors located in unconsolidated formations as a result of sand channelization. In these situations, sand particles migrate from the formation matrix toward the wellbore and consequently affect permeability of the formation and completion components like frac-packs or gravel-packs. To model this phenomenon, we propose a model that decomposes the sand matrix into two different phases by means of their volumetric fractions. The first phase consists of the immobile granular phase while the other is the fraction of grains that are detached from the matrix and carried away by the fluid. The ratio of these two phases evolves over time by means of erosion and deposition. A finite element code is developed for numerical implementation of this model for different reservoir properties. The results show how the porosity evolves over time around the wellbore by the formation of channels that enhance the flow, however, upon well shut-in, Flowback induced by the water hammer effect brings a large amount sand into the well and fill it up. A study of the effect of frac-packs which are typical completions for wells targeting soft formations is performed to demonstrate potential damage of repetitive shut-ins on injectivity in these wells. The presented model appears as a robust tool to predict sand production in different completion systems to achieve more sustainable injection treatments.
Sand Screen Design and Optimization for Horizontal Wells Using Reservoir Grain Size Distribution Mapping
Authors: Mahmoudi Mahdi , Roostaei Morteza , Ghalambor Ali
Published: January 2016

The primary goal of screen design for steam assisted gravity drainage (SAGD) operations is to prevent the entrance of the poorly or unconsolidated sand into the production flow stream, which could cause serious damages to the downhole/surface facilities. Current screen design approach fits one screen opening size for the entire length of the well, which leads to a conservative screen opening to avoid sand production along the well. This study introduces a new approach to design the screen opening, considering different opening sizes along the horizontal well.

The proposed workflow in designing the optimum screen opening relies on well logs and core analysis to map the grain size distribution within reservoir through a geostatistical approach. Considering the horizontal well path and the changes in liner length due to installation and thermal loads, we design the screen aperture size to optimize the screen selection based on sand facies present in different sections of the wellbore. This enables us to provide different screen opening for different sand facies along the horizontal well.

The new approach provides a more detailed design for screen opening for the horizontal well according to the sand size distribution within the reservoir instead of trying to fit one opening size for the entire horizontal section. It also considers the thermal expansion of the joints. This approach designs the screen opening for different sand facies along the horizontal well in a way which obtains the highest productivity and lowest produced sand.

This paper provides a novel workflow for the design and optimization of screen for horizontal wells, which could be used to optimize the design of different standalone screens such as slotted liner, precise punch screen (PPS) and wire wrapped screen (WWS).
Soil Moisture Differences between Terracette Benches and Risers on Semiarid Rangeland Hillslopes
Authors: Corrao Mark , Heinse Robert , Eitel Jan , Cosens Barbara , Link Tim
Published: January 2016

Core Ideas

Hoof impact on terracetted hillslopes affects bulk density and compaction between bench and riser.

Increased soil moisture is not plant available and doesn't increase forage production.

Greater water content on benches is due to shifts to smaller pore sizes with compaction.

Reduced vegetative cover due to root impedance results in greater water content.

Microtopographic features known asterracettesare found throughout semiarid rangelands. Their soil properties and hydrologic function, however, are virtually unknown. This research aimed to quantify whether or not terracetted hillslopes retain more soil water. The objectives of this research were to: (i) assess soil moisture measured at two terracetted field sites comparing bench and riser; (ii) identify to what extent microtopography, soil properties, and land use affect soil moisture; and (iii) quantify differences in soil moisture at the field scale between terracetted and control sites (grazed and ungrazed) in eastern Washington. We measured volumetric water content (θv), bulk density, soil texture, saturated hydraulic conductivity, and organic matter in addition to compaction, vegetative cover, and cattle density. Our results show significant θvdifferences between terracette benches and risers in the upper 10 cm, with benches exhibiting higher mean θvthan risers across all sites during both wet (+6.14%) and dry (+6.63%) seasons. Soil texture and organic matter did not vary between bench and riser features, and microtopography itself was not driving observed soil moisture differences. Soil moisture differences were attributed to land use (i.e., cattle) impact on soil bulk density and vegetative cover. Greater water content on terracette benches is partially attributed to shifts to smaller pore sizes with compaction and a reduction in transpiration resulting from lower vegetative cover due to root impedance. However, this increased water storage is not plant accessible and does not contribute to increased forage production. This work is intended to provide a mechanistic understanding of terracette hydrology for semiarid rangeland management.
One invariant of intrinsic shape
Authors: Shekutkovski Nikita , Velkoska Aneta
Published: January 2016

Based on the intrinsic definition of shape by functions continuous over a
covering and corresponding homotopy we will define proximate fundamental
group. We prove that proximate fundamental group is an invariant of pointed
intrinsic shape of a space.
Intrinsic shape - the proximate approach
Authors: Shekutkovski Nikita
Published: January 2016

In this paper we present the intrinsic approach to shape based on proximate
sequences and nets of functions, and establish equivalence of different
definitions. At the end are presented the results obtained recently, by use
of the intrinsic approach to shape.
Multiple orthogonality in the space of trigonometric polynomials of semi-integer degree
Authors: Stanic Marija , Tomovic Tatjana
Published: January 2016

In this paper we consider multiple orthogonal trigonometric polynomials of
semi-integer degree, which are necessary for constructing of an optimal set
of quadrature rules with an odd number of nodes for trigonometric polynomials
in Borges? sense [Numer. Math. 67 (1994) 271-288]. We prove that such
multiple orthogonal trigonometric polynomials satisfy certain recurrence
relations and present numerical method for their construction, as well as for
construction of mentioned optimal set of quadrature rules. Theoretical
results are illustrated by some numerical examples.
Conditions for the equivalence of power series and discrete power series methods of summability
Authors: Sezer Sefa , Çanak İbrahim
Published: January 2016

Discrete power series methods were introduced and their regularity results
were developed by Watson [Analysis (Munich), 18(1): 97-102, 1998]. It was
shown by Watson that discrete power series method (P?) strictly includes
corresponding power series method (P). In the present work we present
theorems showing when (P?) and (P) are equivalent methods and when two
discrete power series methods are equivalent.
On fixed point results for Matkowski type of mappings in G-metric spaces
Authors: Gajic Lj. , Stojakovic M.
Published: January 2016

The main result of this paper is a fixed point theorem for Matkowski type
mapping with contractive iterate at a point in a class of G-metric spaces.
Our result unifies, generalizes and complements some well known results in
metric and G-metric spaces.
Economic statistical design of X bar control chart for non-normal symmetric distribution of quality characteristic
Authors: Veljkovic Kristina , Elfaghihe Halima , Jevremovic Vesna
Published: January 2016

In economic statistical design of a control chart, the economic-loss function
is minimized subject to a constrained minimum value of power, maximum value
of probability of false alarms and average time to signal an expected shift.
This paper is concerned with the optimum economic statistical design of the X
bar chart when quality characteristic has non-normal symmetric distribution.
We considered three types of distributions: Student distribution, standard
Laplace distribution and logistic distribution. For each of these
distributions, we calculated theoretical distribution of standardized sample
mean (or its best approximation) and approximated it with normal, Pearson VII
and Johnson SU distributions. For considered example, constrained
minimization of expected loss function was done using genetic algorithm in
statistical software R. We compared results of economic statistical design of
X-bar chart for theoretical distribution of standardized sample mean with the
results for normal, Pearson and Johnson distributions. We found that, for all
chosen distributions of quality characteristic, Pearson VII distribution and
Johnson SU distribution give results very close to results based on
theoretical distribution of standardized sample mean, while normal
distribution gives much worse fit.
F-geodesics on manifolds
Authors: Bejan Cornelia-Livia , Druţǎ-Romaniuc Simona-Luiza
Published: January 2016

The notion of F-geodesic, which is slightly different from that of F-planar
curve (see [13], [17], and [18]), generalizes the magnetic curves, and
implicitly the geodesics, by using any (1,1)-tensor field on the manifold
(in particular the electro-magnetic field or the Lorentz force). We give
several examples of F-geodesics and the characterizations of the
F-geodesics w.r.t. Vranceanu connections on foliated manifolds and adapted
connections on almost contact manifolds. We generalize the classical
projective transformation, holomorphic-projective transformation and
C-projective transformation, by considering a pair of symmetric connections
which have the same F-geodesics. We deal with the transformations between
such two connections, namely F-planar diffeomorphisms ([18]). We obtain a
Weyl type tensor field, invariant under any F-planar diffeomorphism, on a
1-codimensional foliation.
On 3-triangulation of toroids
Authors: Stojanovic Milica
Published: January 2016

As toroid (polyhedral torus) could not be convex, it is questionable if it is
possible to 3-triangulate them (i.e. divide into tetrahedra with the original
vertices). Here, we will discuss some examples of toroids to show that for
each vertex number n ? 7, there exists a toroid for which triangulation is
possible. Also we will study the necessary number of tetrahedra for the
minimal triangulation.
On integrability conditions of derivation equations in a subspace of asymmetric affine connection space
Authors: Zlatanovic Milan , Mincic Svetislav , Velimirovic Ljubica
Published: January 2016

In a space LN of asymmetric affine connection by equations (1.1) a submanifold
XM ? LN is defined. On XM and on pseudonormal submanifold NXN-M asymmetric
induced connections are defined. Because of asymmetry of induced connection
it is possible to define four kinds of covariant derivative. In this work we
are considering integrability conditions of derivational equations [4]
obtained by help of the 1st and the 2nd kind of covariant derivative. The
corresponding Gauss-Codazzi equations are obtained too.
Pair of associated Schouten-van Kampen connections adapted to an almost contact B-metric structure
Authors: Manev Mancho
Published: January 2016

There are introduced and studied a pair of associated Schouten-van Kampen
affine connections adapted to the contact distribution and an almost contact
B-metric structure generated by the pair of associated B-metrics and their
Levi-Civita connections. By means of the constructed non-symmetric
connections, the basic classes of almost contact B-metric manifolds are
characterized. Curvature properties of the considered connections are
obtained.
Enhanced dynamic voltage clamping capability of Clustered IGBT at turn-off period
Authors: Long Hong , Sweet Mark , Narayanan Sankara
Published: January 2016

One of the critical requirements for high power devices is to have rugged and
reliable capability against hash operating conditions. In this paper, we
present the dynamic voltage clamping capability of 3.3kV Field Stop Clustered
IGBT devices under extreme inductive load condition. It shows that PMOS
trench gate CIGBT structure with outstanding performance of fast turn-off
time and low over-shoot voltage. Further optimization of current gain of
CIGBT structure is analyzed through numerical evaluation. A step further in
the safe operating area has been achieved for high voltage devices by CIGBT
technology.
MEMS design simplification with virtual prototyping
Authors: Sitte Renate
Published: January 2016

MEMS design requires a good understanding of interactions in complex
processes and highly specialized interdisciplinary skills. Traditional
prototyping is not easy or cheap due to typically needing very expensive
manufacturing facilities for its implementation. Progress towards faster,
cheaper prototyping has been achieved but, it cannot be applied to MEMS
fabrication in general. This paper analyzes the benefits of Virtual
Prototyping for a simplification and aid in MEMS design and proposes the
continuation of MEMS Animated Graphic Design Aid (MAGDA) project. Its purpose
is to simplify preliminary design stages and make MEMS design more accessible
to a wider audience.
Effects of pulsed negative bias temperature stressing in p-channel power VDMOSFETs
Authors: Manic Ivica , Dankovic Danijel , Davidovic Vojkan , Prijic Aneta , Djoric-Veljkovic Snezana , Golubovic Snezana , Prijic Zoran , Stojadinovic Ninoslav
Published: January 2016

Our recent research of the effects of pulsed bias NBT stressing in p-channel
power VDMOSFETs is reviewed in this paper. The reduced degradation normally
observed under the pulsed stress bias conditions is discussed in terms of the
dynamic recovery effects, which are further assessed by varying the duty
cycle ratio and frequency of the pulsed stress voltage. The results are
analyzed in terms of the effects on device lifetime as well. A tendency of
stress induced degradation to decrease with lowering the duty cycle and/or
increasing the frequency of the pulsed stress voltage, which leads to the
increase in device lifetime, is explained in terms of enhanced dynamic
recovery effects.
Comparison of classical CIC and a new class of stopband-improved CIC filters formed by cascading non-identical comb sections
Authors: Milic Dejan , Pavlovic Vlastimir
Published: January 2016

In this paper we propose a new class of selective CIC filters in recursive
and nonrecursive form. The filters use a modification of CIC concept, which
is achieved by applying a set of non-identical comb sections in cascade. We
illustrate examples of the proposed filter function and calculate integer
coefficients of filter impulse response. Detailed comparison between the
proposed selective filter class and classical CIC filters is given. The
results show that the stopband selectivity can be improved significantly in
comparison with classical CIC filters with the same filter complexity.
Inkjet printed resistive strain gages on flexible substrates
Authors: Zlebic Cedo , Zivanov Ljiljana , Menicanin Aleksandar , Blaz Nelu , Damnjanovic Mirjana
Published: January 2016

In this paper, resistive strain gages designed and fabricated in inkjet
printing technology with three different silver nanoparticle inks are
presented. Inks have different Ag content (15, 20 or 25 wt%) and solvents
(water type or organic type). Strain gages were printed on a 50 ?m thick
polyimide and 140 ?m thick PET-based substrate with different printer types
(professional and desktop). All printed sensors have the same size (17 mm ? 5
mm). To determine the change of resistance due to bending of the steel beam,
tensile tests were performed up to 1500 microstrains. Due to performed cycles
of loading and unloading of the steel beam, gauge factor and stability of the
response of the strain gages are measured. Resistance change was measured
with Keithley SourceMeter 2410. For acquisition of measured data, in-house
software tool was developed. Measured gauge factors of the sensors are in the
range between 1.07 and 2.03 (depending on a used ink, substrate and printer).
Results of this research indicate the strain gages with good GF can be
produced even with low-cost equipment, such as desktop printer EPSON C88+ and
PET-based substrate.
Application of infrared thermography to non-contact testing of AD/DC power supply
Authors: Galla Stanisław , Konczakowska Alicja
Published: January 2016

Testing of AC/DC power supplies using the thermography was carried out in
order to assess their assembly and operation correctness before launching
them on the market. The investigation was carried out for 17 AC/DC power
supplies which passed the standard tests (measurements of their basic
parameters and characteristics). The investigation consisted of two steps. In
the first step the dispersion of temperature on power supply boards was
measured after 20 minutes operating in nominal conditions. Three regions were
defined as potentially revealing a failure. In the second step the acceptable
temperature increments on the boards of tested power supplies were evaluated.
It was proposed to assess properties of power supplies on the basis of
temperature increments on their boards, registered by an infrared camera
either for 12 minutes or up to 20 minutes.
The application of the multivariate analysis method for some traits in wheat under drought stress
Authors: Mirtaheri Seyed , Paknejad Farzad , Behdad Marieh
Published: January 2016

In order to evaluate the relationship between yield and some relevant traits
and estimation of the most effective traits on grain yield, a split-plot
experiment based on completely randomized block design with four replications
was carried out in 2006-2007 in the research field of Islamic Azad University
of Karaj. The irrigation schemes scheduled as main plots included the
following: (T1) 40% moisture depletion throughout the growing season
(control); (T2) 60% moisture depletion throughout the growing season; (T3)
80% moisture depletion throughout the growing season; (T4) no irrigation
during the stem elongation stage and continuing with adequate irrigation to
the end of the growing season; (T5) no irrigation from the stem elongation
stage to the end of the growing season; (T6) no irrigation at flowering and
continuing with adequate irrigation to the end of the growing season; (T7) no
irrigation from flowering to the end of the growing season; and (T8) no
irrigation from the milk stage to the end of the growing season; and 2 wheat
cultivars [Marvdasht (V1), Chamran (V2)] as sub-plots. According to the
results of simple correlation, the grain yield exhibited the most positive
correlation with biomass (0.877), number of infertile spikelets (0.876) and
harvest index (0.855). The results of step-wise regression showed that, in
the absence of drought stress, biomass and harvest index had respectively the
most important effects on the grain yield but both exhibited different
results under drought stress. Path analysis results showed that the most
important effect on the grain yield in the total tested treatments was
related to the biomass, justifying a total of 87% of grain yield variations,
72% of which is the direct effect of this trait on grain yield.
Numerical analysis of Sakiadis flow problem considering Maxwell nanofluid
Authors: Mustafa Meraj , Khan Junaid
Published: January 2016

This article investigates the flow of Maxwell nanofluid over a moving plate in a calm fluid. Novel aspects of Brownian motion and thermophoresis are taken into consideration. Revised model for passive control of nanoparticle volume fraction at the plate is used in this study. The formulated differential system is solved numerically by employing shooting approach together with fourth-fifth-order-Runge-Kutta integration procedure and Newton?s method. The solutions are greatly influenced with the variation of embedded parameters which include the local Deborah number, the Brownian motion parameter, the thermophoresis parameter, the Prandtl number, and the Schmidt number. We found that the variation in velocity distribution with an increase in local Deborah number is non-monotonic. Moreover, the reduced Nusselt number has a linear and direct relationship with the local Deborah number.
Energy and exergy analysis of a combined refrigeration and waste heat driven organic Rankine cycle system
Authors: Cihan Ertugrul , Kavasogullari Barıs
Published: January 2016

Energy and exergy analysis of a combined refrigeration and waste heat driven organic Rankine cycle system were studied theoretically in this paper. In order to complete refrigeration process, the obtained kinetic energy was supplied to the compressor of the refrigeration cycle. Turbine, in power cycle, was driven by organic working fluid that exits boiler with high temperature and pressure. Theoretical performances of proposed system were evaluated employing five different organic fluids which are R123, R600, R245fa, R141b, and R600a. Moreover, the change of thermal and exergy efficiencies were examined by changing the boiling, condensing, and evaporating temperatures. As a result of energy and exergy analysis of the proposed system, most appropriate organic working fluid was determined as R141b.
The oil - paper insulation reliability estimation of 420 kV transformer concerning thermal stresses during exploitation conditions
Authors: Al-Musawi Safaa , Lazarevic Zoran , Radosavljevic Radovan , Bajramovic Zijad , Osmokrovic Predrag
Published: January 2016

The calculating of reached ageing based on the history of loading according
of International Electrotechnical Commission standard algorithm is the first
task. In order to verify the obtained results, measurements of
polymerization index were made on 28 paper samples taken directly from low
voltage terminals (winding ends) and bus connections of the transformer
under test rated 380 MVA, 2?15,75 kV/420 kV. The complete procedure of paper
sample locations and taking off is described, thereby providing a manner of
how this should be done, determined by specific conditions of the
transformer under test. Furthermore, the determination of limit viscosity
and using its relationship function with polymerization index are explained
together. Comparison is made with those of liquid chromatography of oil. The
results of particle sort and size analysis are shown. Finally, an estimation
of the transformer life remainder is made, which is of paramount importance
when defining the steps that have to be made either in revitalization
process or in transformer replacement planning.
Age at Menarche and Risk of Gestational Diabetes Mellitus: A Prospective Cohort Study Among 27,482 Women
Authors: Chen Liwei , Li Shanshan , He Chunyan , Zhu Yeyi , Buck Louis Germaine M. , Yeung Edwina , Hu Frank B. , Zhang Cuilin
Published: January 2016

OBJECTIVE

To examine the association between age at menarche and risk of gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

A prospective cohort study of 42,109 eligible pregnancies from 27,482 women in the Nurses’ Health Study II.

RESULTS

The adjusted risk ratios for GDM across the age at menarche categories (≤11, 12, 13, and ≥14 years) were 1.34 (95% CI 1.14–1.58), 1.13 (0.97–1.31), 1.11 (0.95–1.29), and 1.00 (referent; P for trend = 0.0005), respectively. Analysis of the mediating effect indicated that 42.1% (P = 0.0007) of the association was mediated through prepregnancy BMI.

CONCLUSIONS

These findings suggested that earlier menarche was significantly associated with an increased risk of GDM. This association was largely mediated through prepregnancy excessive body adiposity.
On the Classification of Simple Singularities in Positive Characteristic
Authors: Afzal Deeba , Binyamin Muhammad Ahsan , Janjua Faira Kanwal
Published: January 2016

The aim of the article is to describe the classification of simple isolated hypersurface sin- gularities over a field of positive characteristic by certain invariants without computing the normal form. We also give a description of the algorithms to compute the classification which we have implemented in the Singular libraries classifyCeq.lib and classifyReq.lib. 1 Int
On Characteristic Poset and Stanley Decomposition
Authors: Ahmad Sarfraz , Anwar Imran , Qureshi Ayesha Asloob
Published: January 2016

Let J ⊂ I be two monomial ideals such that I/J is Cohen Macaulay. By associating a finite posets

P

I
/
J

g

$P_{I/J}^g$

to I/J, we show that if I/J is a Stanley ideal then

I
/
J

˜

$\widetilde{I/J}$

is also a Stanley ideal, where

I
/
J

˜

$\widetilde{I/J}$

is the polarization of I/J. We also give relations between sdepth and fdepth of I/J and

I
/
J

˜

$\widetilde{I/J}$
A new proof of the bound for the first Dirichlet eigenvalue of the Laplacian operator
Authors: Li Chang-Jun , Gao Xiang
Published: January 2016

In this paper, we present a new proof of the upper and lower bound estimates for the first Dirichlet eigenvalue

λ
1
D

(

B

(

p
,
r

)

)

$\lambda _1^D \left({B\left({p,r} \right)} \right)$

of Laplacian operator for the manifold with Ricci curvature Rc ≥ −K, by using Li-Yau’s gradient estimate for the heat equation.
On the recovery of the doping profile in an time-dependent drift-diffusion model
Authors: Wu Bin , Wang Zewen
Published: January 2016

We consider an inverse problem arising from an time-dependent drift-diffusion model in semiconductor devices, which is formulated in terms of a system of parabolic equations for the electron and hole densities and the Poisson equation for the electric potential. This inverse problem aims to identify the doping profile from the final overdetermination data of the electric potential. By using the Schauder’s fixed point theorem in suitable Sobolev space, the existence of this inverse problem are obtained. Moreover by means of Gronwall inequality, we prove the uniqueness of this inverse problem for small measurement time. For this nonlinear inverse problem, our theoretical results guarantee the solvability for the proposed physical model.
Immediate Effect of Active Abdominal Contraction on Inter-recti Distance
Authors: Chiarello Cynthia M. , McAuley J. Adrienne , Hartigan Erin H.
Published: January 2016

Study Design

Controlled laboratory study.

Background

Inter-recti distance (IRD) is the measurement of the linear distance between the medial aspects of the rectus abdominis muscle. Inter-recti distance has been reported to decrease in postpartum women during a curl-up maneuver.

Objective

To determine if IRD decreases with active abdominal contraction in men and in nulliparous and parous women.

Methods

Fifty-six subjects (male, 11; nulliparous female, 22; parous female, 23) participated. Inter-recti distance was measured with the abdominal muscles at rest and during active contraction (curl-up), at 2 locations (above and below the umbilicus), using ultrasound imaging. A mixed-model, repeated-measures analysis of covariance was used for each of the 2 locations, to determine whether IRD differed between contraction states among the 3 groups, with age and umbilicus circumference as covariates. When significant differences were found, planned t test comparisons were made.

Results

The parous group's IRD significantly decreased from rest to contraction at both locations, whereas the nulliparous and male groups' IRD did not significantly change from rest to contraction. The nulliparous group's IRD was significantly narrower than the other groups at rest at both locations, and narrower than the parous group during active contraction.

Conclusion

Parous women had a narrower IRD in the curl-up condition than at rest, as hypothesized. However, an unexpected finding of a lack of significant within-group change in IRD in nulliparous women and men occurred. Findings suggest that the IRD in men may only differ from that of nulliparous women. J Orthop Sports Phys Ther 2016;46(3):177–183. Epub 26 Jan 2016. doi:10.2519/jospt.2016.6102
Synthesis of Several New 1-arylpyrazolo[3,4-d]Pyrimidines Containing an Amide Moiety
Authors: Liu Ju , Zhang Xin-Wei , Song Duan-Zheng , Cai Zhi-qiang , Zhou Yun-peng
Published: January 2016

A series of novel 1-arylpyrazolo[3,4-d]pyrimidine derivatives, containing an amide moiety, was synthesised by condensation of different acids with 1-(2,4-dichlorophenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine. This intermediate was prepared from 5-amino-1-(2,4-dichlorophenyl)-1H-pyrazole-4-carbonitrile by condensation with triethyl orthoformate and then cyclisation with ammonium hydroxide solution in tetrahydrofuran at room temperature. In addition, the molecular structure of a 1-arylpyrazolo[3,4-d]pyrimidine containing an amide moiety was determined by single crystal X-ray diffraction.
L'extension du malthusianisme dans le Sud-Ouest français
Authors: Pradel De Lamaze François
Published: January 2016

The progress of malthusianism in the south western part of France. As far as the demographic evolution and its trends are concerned, the SW part of France is generally considered as an illustration of malthusianism, since the local population's behaviour resulted in a systematic checking of the natural increase of population. The author stresses the fact that its effects were quite recently extended to the whole region and he suggests that the reasons for such an extent to the mountains and plateaux that had longer maintained their fecundity rate are related to social causes rather than to economic ones.
La question des unités spatiales de collecte de l'information en Aquitaine
Authors: Pailhé Joël
Published: January 2016

L'établissement de cartes découpant l'espace régional en ensembles homogènes mettant en valeur les phénomènes observés se heurte souvent aux contraintes du découpage des unités spatiales de collecte de l'information. Les cartes à fonds communal en surestimant les communes de vaste superficie risquent d'entraîner des erreurs d'interprétation, en raison du manque d'homogénéité de la trame communale, en Aquitaine plus encore que dans le reste de la France. Bien qu'a priori « artificiel », le découpage cantonal présente une incontestable cohérence, en raison de superficies présentant moins d'écarts à la moyenne que le découpage communal. Cela rend plus nécessaire, par contre, de distinguer au sein d'un canton les ensembles de communes rurales et les unités urbaines.
Cadres de vie urbains et activités physiques et sportives dans l'agglomération de Bordeaux
Authors: Augustin Jean-Pierre
Published: January 2016

La forte pratique sportive s'est d'abord développée dans la ville- centre par l'intermédiaire de grands clubs omnisports qui, selon leur lieu d'implantation et leur date de création, influaient différemment sur les secteurs résidentiels et sur les secteurs populaires. Les périphéries urbaines en développement rapide sont devenues le siège d'équipements sportifs nouveaux, de grande surface et très diversifiés. Certaines communes de banlieue (Mérignac par exemple) ne se sont pas contentées de financer des équipements, mais mènent une politique sportive active, aussi bien dans les milieux d'adultes que dans le milieu scolaire. Le cadre des activités sportives dépasse maintenant très largement les terrains aménagés dans l'agglomération même ; il s'étend aux espaces de week-end et de vacances avec lesquels l'agglomération a des relations privilégiées : Côte Aquitaine, Pyrénées, Parc naturel régional, secteurs plus diffus de loisirs en milieu rural.
CHEMICAL EVOLUTION OF THE INNER 2 DEGREES OF THE MILKY WAY BULGE: [α/Fe] TRENDS AND METALLICITY GRADIENTS
Authors: Ryde N. , Schultheis M. , Grieco V. , Matteucci F. , Rich R. M. , Uttenthaler S.
Published: January 2016

The structure, formation, and evolution of the Milky Way bulge is a matter of debate. Important diagnostics for discriminating between models of bulge formation and evolution include α-abundance trends with metallicity, and spatial abundance and metallicity gradients. Due to the severe optical extinction in the inner Bulge region, only a few detailed investigations of this region have been performed. Here we aim at investigating the inner 2 degrees of the Bulge (projected galactocentric distance of approximately 300 pc), rarely investigated before, by observing the [α/Fe] element trends versus metallicity, and by trying to derive the metallicity gradient in the b < 2° region. [α/Fe] and metallicities have been determined by spectral synthesis of 2 μm spectra of 28 M-giants in the Bulge, lying along the southern minor axis at (l, b) = (0, 0), (0, −1°), and (0, −2°). These were observed with the CRIRES spectrometer at the Very Large Telescope, (VLT) at high spectral resolution. Low-resolution K-band spectra, observed with the ISAAC spectrometer at the VLT, are used to determine the effective temperature of the stars. We present the first connection between the Galactic center (GC) and the Bulge using similar stars, high spectral resolution, and analysis techniques. The [α/Fe] trends in all our three fields show a large similarity among each other and with trends further out in the Bulge. All point to a rapid star formation episode in the Bulge. We find that there is a lack of an [α/Fe] gradient in the Bulge all the way into the center, suggesting a homogeneous Bulge when it comes to the enrichment process and star formation history. We find a large range of metallicities from −1.2 < [Fe/H] < +0.3, with a lower dispersion in the GC: −0.2 < [Fe/H] < +0.3. The derived metallicities of the stars in the three fields get, in the mean, progressively higher the closer to the Galactic plane they lie. We could interpret this as a continuation of the metallicity gradient established further out in the Bulge, but due to the low number of stars and possible selection effects, more data of the same sort as presented here is necessary to conclude on the inner metallicity gradient from our data alone. Our results firmly argue for the center being in the context of the Bulge rather than very distinct.
OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. V. TNG, KPNO, AND OAN OBSERVATIONS OF BLAZAR CANDIDATES OF UNCERTAIN TYPE IN THE NORTHERN HEMISPHERE
Authors: Álvarez Crespo N. , Masetti N. , Ricci F. , Landoni M. , Patiño-Álvarez V. , Massaro F. , D’Abrusco R. , Paggi A. , Chavushyan V. , Jiménez-Bailón E. , Torrealba J. , Latronico L. , La Franca F. , Smith Howard A. , Tosti G.
Published: January 2016

The extragalactic γ-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei. Many of the γ-ray sources included in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs) because there are no optical spectra available in the literature to confirm their nature. In 2013, we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the unidentified γ-ray sources to confirm their blazar nature. Whenever possible we also determine their redshifts. Here, we present the results of the observations carried out in the northern hemisphere in 2013 and 2014 at the Telescopio Nazionale Galileo, Kitt Peak National Observatory, and Observatorio Astronómico Nacional in San Pedro Mártir. In this paper, we describe the optical spectra of 25 sources. We confirmed that all of the 15 BCUs observed in our campaign and included in our sample are blazars and we estimated the redshifts for three of them. In addition, we present the spectra for three sources classified as BL Lacs in the literature but with no optical spectra available to date. We found that one of them is a quasar (QSO) at a redshift of z = 0.208 and the other two are BL Lacs. Moreover, we also present seven new spectra for known blazars listed in the Roma-BZCAT that have an uncertain redshift or are classified as BL Lac candidates. We found that one of them, 5BZB J0724+2621, is a “changing look” blazar. According to the spectrum available in the literature, it was classified as a BL Lac, but in our observation we clearly detected a broad emission line that led us to classify this source as a QSO at z = 1.17.
UBVRIz LIGHT CURVES OF 51 TYPE II SUPERNOVAE
Authors: Galbany Lluís , Hamuy Mario , Phillips Mark M. , Suntzeff Nicholas B. , Maza José , Jaeger Thomas de , Moraga Tania , González-Gaitán Santiago , Krisciunas Kevin , Morrell Nidia I. , Thomas-Osip Joanna , Krzeminski Wojtek , González Luis , Antezana Roberto , Wishnjewski Marina , McCarthy Patrick , Anderson Joseph P. , Gutiérrez Claudia P. , Stritzinger Maximilian , Folatelli Gastón , Anguita Claudio , Galaz Gaspar , Green Elisabeth M. , Impey Chris , Kim Yong-Cheol , Kirhakos Sofia , Malkan Mathew A. , Mulchaey John S. , Phillips Andrew C. , Pizzella Alessandro , Prosser Charles F. , Schmidt Brian P. , Schommer Robert A. , Sherry William , Strolger Louis-Gregory , Wells Lisa A. , Williger Gerard M.
Published: January 2016

We present a compilation of UBVRIz light curves of 51 type II supernovae discovered during the course of four different surveys during 1986–2003: the Cerro Tololo Supernova Survey, the Calán/Tololo Supernova Program (C&T), the Supernova Optical and Infrared Survey (SOIRS), and the Carnegie Type II Supernova Survey (CATS). The photometry is based on template-subtracted images to eliminate any potential host galaxy light contamination, and calibrated from foreground stars. This work presents these photometric data, studies the color evolution using different bands, and explores the relation between the magnitude at maximum brightness and the brightness decline parameter (s) from maximum light through the end of the recombination phase. This parameter is found to be shallower for redder bands and appears to have the best correlation in the B band. In addition, it also correlates with the plateau duration, being shorter (longer) for larger (smaller) s values.