bluuebunny/crossref_metadata_2025 huggingface dataset:
CdSe Quantum Dot-Sensitized Solar Cell: Effect of Size and Attach Mode of Quantum Dot
Authors: Shao Fei Yan , Li Ming , Yang Jian Wen , Liu Yong Pin , Zhang Ling Zhi
Published: March 2015

Different size of colloidal CdSe quantum dot (QD) was synthesized through a simple solvothermal route and their structural, morphological and optical properties were characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), UV-visible absorption spectroscopy and fluorescence spectrometer. XRD and TEM measurement confirmed the formation of CdSe QDs. The red shift of absorption and fluorescence peaks indicated that the size of CdSe QDs increased with prolonging reaction time. The size of QDs varied from 2.2 nm to 3.4 nm by varying reaction time from 1 h to 7 h. The absorption spectra of CdSe/TiO2 electrodes proved that the loading of CdSe QDs on TiO2 can be greatly improved by MPA pretreatment. The effect of size of CdSe QDs on the performance of CdSe QDs sensitized solar cells was investigated. Due to the change of absorption range in the visible region and the conduction band shift for different size of CdSe, the photo-electric power conversion efficiency first increased and then decreased with increasing size of CdSe. The devices fabricated with 3.1 nm diameter CdSe nanoparticles exhibited the highest conversion efficiency of 0.70% under AM 1.5 G irradiation (100 mW cm−2).
Mechanical Properties of Epoxy Nanocomposites Using Alumina as Reinforcement - A Review
Authors: Pinto Deesy , Bernardo Luís , Amaro Ana , Lopes Sérgio
Published: March 2015

Polymers and their composites find use in many engineering applications as alternative products to metal-based ones and, nowadays, have wide technical applications. One of the most used composite materials is the epoxy resins (EP), which is a thermoset polymer matrix. After cure, this material displays some excellent mechanical, thermal, electrical and chemical properties. For these reasons, it has been widely used for a wide range of automotive and aerospace applications, as well as for shipbuilding or electronic devices. However, EP has poor resistance to crack propagation and is brittle. So, in recent years, a considerable amount of research has been carried out to improve the performance of the toughness of EP. The most common studied technique consist to reinforce the EP matrix with rigid nanoparticle fillers, such as alumina, silica, mica, talc, organoclays, nanoclays, carbon nanotubes, TiO2, among others. Among these nanofillers type, nanosize alumina particles has not been widely studied. However, recent studies have reported that the use of functionalized nanosize alumina particles as nanofiller can significantly improve the properties of the nanocomposite, even with low contents. These results, combined with the low cost of the alumina, show that the reinforcement of EP with alumina nanoparticles is a viable solution. In this paper, an attempt is made to review and highlight some recent findings and also some trends to show future directions and opportunities for the development of polymer nanocomposites reinforced with alumina nanoparticles.
Effect of Aging on the Performance of Glass Fiber Reinforced pCBT Resin
Authors: Liang Wen Yan , Fan Shao Hua , Yang Bin
Published: March 2015

In the present paper, pCBT casts and pCBT/E-glass fiber composites were prepared. In order to study the mechanical performance of the thermoplastic material in the aging environment, the specimens were exposed to salt spray, hygrothermal as well as immersion conditions. The hygroscopicity and mechanisation of the material were studied. From this research work, it is found that, in corrosion tests, the water absorb rate increases at the beginning of the test and decreases with the increase of time. Chloride ion concentrationb and a higher corrosion time have some influence on the moisture absorption kinetics. The results also show that the mechanical properties such as modulus and strength of pCBT and its glass fiber composites change with the trendency of moisture absorption curves.
Compression Performance of Repaired Composite Stiffened Panels: Bolted Repair and Scarfed Bonded Repair
Authors: Zhao Chuang , Guan Zhi Dong , Guo Xia
Published: March 2015

In this paper, compression performance of composite stiffened panels after bolted repair and scarfed bonded repair is presented. Several tests have been performed on the four kinds of stiffened panels. All the experiments show the influences of different damage actions, different repair methods for the mechanical properties of stiffened panels are different. Furthermore, numerical finite element models have been developed and solved using the software ABAQUS. In addition, stiffener-skin debonding was considered in the finite element models in order to ensure a better consistence with the fact. The comparison of simulation results and experiment shows that the finite element modeling method is effective. The result suggests that the failure load and the stiffness of the repaired stiffened panel are recovered close to the virgin ones’.
Optimal Configuration for Stiffened Plates under the Effect of Underwater Explosion
Authors: Elsayed Fathallah , Qi Hui , Tong Li Li , Helal Mahmoud
Published: March 2015

The dynamic response of a floating structure subjected to underwater explosion is greatly complicated by the explosion of a high explosive, propagation of shock wave, complex fluid–structure interaction phenomena, and the dynamic behavior of the floating structures. A numerical investigation has been carried out to examine the behavior of stiffened steel plates subjected to shock loads resulting from an Underwater Explosion (UNDEX). The aim of this work is to obtain the optimal configuration to resist underwater shock loading. A non-linear dynamic numerical analysis of the underwater explosion phenomena associated with different geometrical stiffened steel plates is performed using the ABAQUS/Explicit finite element program. Special emphasis is focused on the evolution of mid-point displacements. Further investigations have been performed to study the effect of including material damping and the rate-dependant material properties at different shock loads. The results indicate that stiffener configurations and shock loads affect greatly the overall performance of steel plates and sensitive to the material data.
Investigation of Tensile Strength of Composite Laminate under Diverse Environment Conditions
Authors: Seo Hyoung Seock , Jang Ho Yun , Chun Ho Hwan
Published: March 2015

To investigate ocean environmental effects of salt water and xenon light, salt water spray test and xenon test were performed on long immersion hours. CFRP (Carbon Fiber Reinforced Polymer) specimens were prepared for salt water spray experiment, xenon light exposure experiment and mechanical tensile tests. The composite specimens with total 15 layers were manufactured with diverse fiber orientations of [0°]15,[90°]15and [0°3/+45°2/-45°2/90°/-45°2/+45°2/0°3]. After applying environmental conditions, the tensile strength was compared with the tensile strength without environmental conditions. The influence of different fiber orientation was also investigated, respectively. Finally, the results showed that the tensile strength of composite specimens was affected by salt water and xenon light clearly.
Influence of Core Splice to the Mechanical Behavior of Sandwich Plate
Authors: Wang Wei , Yang Na Na , Yao Xiong Liang , Fang Dai Ning
Published: March 2015

The cores have to be spliced in the manufacturing process of sandwich plate due to the processing technology, the influence of core splice, compared with integrated core, on mechanical behavior of sandwich plate were investigated through two experiments. Two styles of specimens (B-style and C-style) were taken into experiments in sequence which included two kinds of plate with different cores.Firstly, it was found in stiffness experiment that stiffness and strength of sandwich plate with splicing core were obviously weaker than that with integrated core, which mean the former performed larger deformation under the same predetermined load with higher strain and behaved lower ultimate bearing capacity. Meanwhile the failure modes were mainly sheet crushing collapse and there was no evident difference in the failure mode of the two styles specimens with different cores. It concluded that the cores splice reduced the stiffness in location of two core splicing but the effect on the failure mode was slight.Secondly, it was found in stability experiment that the mechanical behaviour was approximately linear under the predetermined axial load and the predetermined out-of-plane load and similarly bulking strength of the sandwich plate with splicing core was about 10%~15% lower than that with integrated core. Basically, delamination between sheet and core kept accompany with bulking of the plate each time and two styles specimens with different cores didn’t show evident differences in failure mode as well. It demonstrated the conclusion and that core splice accounted to make the specimens produced geometric imperfections which resulted in stiffness reduction.Thirdly, based on experiments it was clear that the mechanical behaviour of sandwich plates with splicing cores suffered from more obvious discreteness compared with that with integrated cores, which indicated that manufacturing technology had greater influence on the former and core splice should be avoided in some important location of structure.Lastly, numerical simulation method based on progressive damage analysis was also studied and good correlation with experimental results was obtained, which could well predict the mechanical behaviour of the sandwich plates with splicing core and integrated core.
Electrical and Mechanical Properties of Short-Carbon-Fiber Reinforced Polymerized Cyclic Butylene Terephthalate Composites
Authors: Yang Bin , Zhang Ji Feng , Zhang Lu , Fan Shao Hua , Zhou Li Min
Published: March 2015

Polymerized cyclic butylene terephthalate (pCBT) resin casts filled with short carbon fibers were prepared by the melt-mixing approach. The electrical conductivity of short-carbon-fiber (SCF) reinforced thermoplastic pCBT resin casts were investigated with a special attention paid to the properties in the percolation threshold region and the mechanical properties of the composites were also studied. The percolation threshold value of the novel material system was determined which was also verified by SEM images and the thermoelectric behavior of the specimens. Even though the electrical properties of SCF/pCBT composites enhanced significantly, the material becomes more brittle than neat pCBT and all the specimens appear brittle fracture during the mechanical test. Moreover, fiber pull-out is the main damage form in three-point-bending test.
Parameter Study of Numerical Simulation for Tensile Properties of Multi-Layer SMATed Alloys
Authors: Wan Yun , Wang Xiao Qiang , Zhang Ji Feng , Lu Jian , Zhou Li Min
Published: March 2015

Strength and ductility are very important to marine engineering. Because of their remarkable mechanical properties, nanocrystalline metals have been the focus of much research in recent years. Based on surface mechanical attrition treatment (SMAT) and warm co-rolling technologies, the resulting material performances amazingly exhibit high strength and exceptional ductility. Therefore, this method is a promising avenue for advanced materials for marine engineering. Cohesive finite element method (CFEM) is employed to investigate the tensile performance of multi-layer SMATed alloys. With the results of simulation and experiment compared, simulation parameters have been studied . According to comparing different simulation results, the model parameters, normal direction strength and tangential direction strength in CFEM are studied.
An Efficient Analytical Failure Analysis Approach for Multilayered Composite Offshore Production Risers
Authors: Sun Xiu Shan , Tan Vincent B.C. , Chen Yu , Jaiman Rajeev K. , Tay Tong Earn
Published: March 2015

This paper proposes an efficient analytical failure analysis approach for multilayered composite risers used in the offshore oil industry. This approach is based on a layer-by-layer progressive damage model and a homogenization stress analysis method from which the discontinuous stresses through layers can be efficiently calculated. Different failure theories can be easily integrated into the approach to determine failure initiation in layers with different materials. Progressive failure analysis is based on layer-by-layer material degradation schemes, taking into consideration different failure modes such as yielding, fracture, matrix cracking, fiber broken, etc., in layers with different materials. In this approach, progressive failure information involving failed layers and their failure sequences as well as failure modes can be efficiently predicted for multilayered composite risers under given loading conditions. Failure envelopes of composite risers are generated for either initial failure or ultimate failure in different load spaces, and strengths of composite risers can be predicted under given load ratios. This analytical approach is efficient for failure analysis or strength prediction of composite risers with many layers because stress redistributions in all layers during failure progression can be easily and quickly calculated. A user-friendly interface based on Excel sheets is used to carry out this analytical failure analysis approach. Failure analyses of a 22-layer composite riser under several typical loading conditions are presented to demonstrate the application of the proposed approach. Initial and ultimate failure envelopes of the composite riser are shown in different force spaces. This failure analysis approach provides an efficient way for design of composite risers in the offshore oil and gas industry.
Interfacial Properties Improvement of Carbon Fiber Reinforced Epoxy Composites Modified with Carbon Nanotubes
Authors: Wu Zi Jian , Meng Ling Hui , Su Hai , Liu Li , Zhang Qing Bo , Jiang Da Wei , Chen Lei , Xing Li Xin , Wu Guang Shun , Huang Yu Dong
Published: March 2015

In order to improve the interfacial properties in carbon fiber (CF) reinforced epoxy (EP) composites, we directly introduced amidized carbon nanotubes (CNTs) dispersed in the fiber sizing onto the fiber surface. Morphology and surface energy of CFs were examined by scanning electron microscopy (SEM) and dynamic contact angle analysis test (DCAT). Tensile strength (TS) was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS and impact toughness were enhanced simultaneously.
Crack-Induced Stress Concentration Is Suppressed in Nacreous Composites
Authors: Yao Hai Min
Published: March 2015

Linear elastic fracture mechanics (LEFM) indicates that crack-like flaws tend to intensify stress in brittle materials with stress intensity proportional to the square root of the crack size. Under given loading, monolithic brittle materials can only endure cracks smaller than a critical size. In this paper, however, our exploration into the stress state of nacreous composites shows that the crack-induced stress intensification/concentration and its dependence on crack size can be suppressed in composites with ‘brick-and-mortar’ structure. This feature can be attributed to the unique ‘brick-and-mortar’ (B-and-M) structure and the complementary dissimilarity between ‘brick’ (e.g. minerals) and ‘mortar’ (e.g. proteins) phases in mechanical properties. Our findings provide a profound insight into the origin of high strength and high toughness in nacreous composites.
Design, Manufacturing and Testing of Filament Wound Composite Risers for Marine and Offshore Applications
Authors: Bhudolia S.K. , Fischer S. , He P.G. , Yue Chee Yoon , Joshi Sunil C. , Yang J.L.
Published: March 2015

The major challenge for producing and manufacturing risers for oil and gas production is to make them light weight so as to reduce the operational cost and improve the overall system requirements to make them an attractive option for marine and offshore industries. In the current research, the composite and metal-composite pipes (1) GFRP only (2) Al-GFRP and (3) PE-GFRP have been manufactured using filament winding machine operated using CADFIL and CADWIND CNC packages. The use of liners (Al and PE) has ensured the fluid tightness and collapse resistance of the pipe system. Small prototype pipes are manufactured based on optimized pipe design parameters for collapse under external pressure and burst under internal pressure using ANSYS 13 FEA analysis software. Experiments are conducted to verify the axial and hoop compressive strengths of the pipes with analytical results. The details of pipe manufacturing process using filament winding machine, simulation procedure to optimize the pipe parameters and validation of the simulation results with experimental results are the focal points of the current work.
Scarfing Repair Parameters Optimization for Composite Laminates
Authors: Tong Lei , Le Qun , Li Shi Qiu , Xiong Jun Jiang
Published: March 2015

Scarf repair parameters were optimized in this paper, to find the best repair parameter, and get better strength restoration effect. Composite laminates material was IM6/3501-6. Considering symmetry of structure, 1/4 repaired structure was taken as research object, to be built up finite element model and optimized for repair parameter. Element SOLID46 in software ANSYS was used to simulate main board and patch, element SOLID45 was used to simulate adhesive layer, to build up composite scarf repair finite element model. Because of small scarf repair angle and small ratio of adhesive layer thickness to composite laminate thickness, repair structure geometry was complex, to get exact calculation result, mesh was refined at place where stress is concentrated. There were 4488 element in the built up finite element model, with nodes number as 6263. Tsai-Wu rule and maximum shear stress was taken as failure criteria for composites laminate and adhesive layer respectively. With consideration on scarf ratio and adhesive layer thickness on repaired specimen strength, three dimension finite element models for scarf repair on composite laminates was constructed. Compared with experiment, it was found that finite element model agreed with experiment, thus validity of scarf repair model was proved. By Changing the value of each factor, finite element calculation of the repaired structure failure load showed that: the optimal value of scarf ratio is 1:20; influence of adhesive layer thickness of failure load of scarf repair structure is not obvious, generally 0.1mm meets the requirements; failure load increases when adhesive layer elastic modulus increases, but the rate of increase slows down gradually. Then the earliest failure site was analyzed according to finite element stress calculation result, failure process of adhesive layer was simulated, adhesive layer failure process was predicted, from 0 degrees to 45 degrees, and the adhesive layer top part first destroys, then spreads to 45 degrees to 90 degrees, and spreads to the adhesive layer lower end.
Uncertain-but-Nonrandom Dynamic Optimization of Composites Flexible Membrane Structure
Authors: Qiu He Chen , Qiu Zhi Ping
Published: March 2015

In the past few years, owing to the vital role in maritime safety monitoring and marine hazard warning, stratospheric airship has become a research hotspot around the world. The structure of stratospheric airship is a typical aerated flexible membrane one. It is geometrical nonlinear in essence and it bears a distinct mechanical nature of large deformation. Therefore it makes optimizing the structure more difficult. The current studies of air-supported flexible membrane structural optimization ignore the uncertainty influence which is resulted from the loading environments, material properties and structural parameters. According to the Lagrangian Coordinate method, the deformed configuration is used as a reference in order to build accurate strain/displacement geometry. The Equilibrium equation is created by using the principle of virtual work. Meanwhile, the accuracy and stability of the solution is ensured by using the Updated Lagrangian Formulation. The uncertain parameters which are introduced during the analysis and optimization of the aerated flexible membrane structure are portrayed by interval mathematical theory. With respect to engineering application, the factors of uncertainty are considered. Maximizing the structural fundamental frequency (or first-order natural frequency) is taken as the objective, while structural integrity is taken as the constraint. Then the dynamic optimization is carried out under interval uncertainty. In this way the reliability of the membrane structure in complex conditions is improved and the probability of failure is reduced.
Real-Time Impact Monitoring of Composites for Ship Applications
Authors: Lu Ming Yu , Yang Hai Nan , Qing Xin Lin , Su Zhong Qing , Zhou Li Min
Published: March 2015

Composites are getting more and more attention in the usage of major structures on ships owing to many advantages such as high specific strength and rigidity. However, composites are sensitive to impact, which indicates that the load-carrying capacity and stability of composite structures will decrease dramatically even for an invisible impact damage. Hence, a real-time impact monitoring system which has already been applied in aviation industry is important for reliability of ships, which inevitably encounter impacts during their lifetime due to different sources. This paper deals with the realization of an operational processing scheme to monitor the impact on composite structures, and estimate the impact location and load history by power distribution approach and system identification method. A PZT (piezoelectric lead zirconate titanate) sensor network was designed and employed to collect sensing signals for monitoring the impact. In the monitoring process, stress wave signals caused by impact were captured, and used to determine the impacted location and load history. Results demonstrate that the proposed method can be successfully applied in identifying the location and load history of impact on composite structures. The impact identification approach is of great significance for marine applications.
The Study on Chloride Transportation Mechanics in Marine Concrete under Coupling Action of Multi-Mechanistic
Authors: Liu Zong Min , Jia Hai Ming , Mao Ji Ze
Published: March 2015

For all the concrete structures in marine environment, the durability of concrete structures is focus of the concern for the serious corrosion of reinforcement in concrete caused by chloride penetration. The core issues of chloride penetration are chloride transportation mechanics in marine concrete. So it is important to study chloride transportation mechanics in marine concrete under coupling action of multi-mechanistic. The variational principle of coupling dynamics of chloride transportation is established by work and energy transfer principle and energy conservation law. Complete basic equations are obtained by deriving stationary value conditions of variational principle of coupling dynamics of chloride transportation. It is shown in this paper that it is a suitable way to study coupling dynamics of chloride transportation by variational principles.
Optimal Structure Design of Elliptical Deep-Submersible Pressure Hull
Authors: Elsayed Fathallah , Qi Hui , Tong Li Li , Helal Mahmoud
Published: March 2015

Geometric configurations such as hull shape, shell thickness, stiffener layout, and type of materials are the key factors influencing the structural performance of pressure hulls. The aim of this study is to maximize the structural efficiency of elliptical deep-submerged pressure hull under hydrostatic pressure. Minimize the buoyancy factor of a submarine pressure hull under hydrostatic pressure was proposed as an objective function for both composite and steel models. The thickness and the orientation angle of each layer, the radii of the ellipse and the operating depth are taken as design variables. Also, the shell buckling strength and the angle-ply laminated failure strength are considered in the case of composite model. In the other hand, the shell thickness, the radii of the ellipse, the stiffeners offsets, the stiffeners dimensions, and the operating depth, are selected as design variables for steel model with shell buckling and materials yielding constraints. The analysis is performed using commercial finite element analysis software ANSYS. Additionally, a sensitivity analysis is performed to study the influence of the design variables on the structural optimum design. Results of this study provide a valuable reference for designers of underwater vehicles.
Atti Sociali
Authors: Società Entomologica Italiana La
Published: March 2015

Atti Sociali
Due nuovi Orotrechus Müller del Vicentino (Veneto, Italia) e note sinonimiche (Coleoptera Carabidae trechinae)
Authors: Piva Erminio
Published: March 2015

Vengono qui descritti Orotrechus biancoi n. sp., di cavità del Bosco del tretto (Schio, Vicenza) (Gruppo del Carega - Piccole Dolomiti - Pasubio) e Orotrechus euganeus perettoi n. ssp., di ambiente sotterraneo superficiale e grotte dei Monti Berici (Arcugnano e Longare, Vicenza). Lo studio di abbondante materiale ha potuto dimostrare l’ampia variabilità delle sottospecie descritte di Orotrechus stephani, permettendo così di stabilire le due seguenti nuove sinonimie: Orotrechus stephani roboretanus Müller, 1933=Orotrechus stephani stephani (Müller, 1913) e Orotrechus stephani perinii tamanini, 1953=Orotrechus stephani stephani (Müller, 1913). Viene inoltre proposta una tabella dicotomica, opportunamente modificata, per il riconoscimento degli Orotrechus del gruppo stephani. Alcune note ecologiche, infine, vengono riportate per il nuovo taxon dei Monti Berici.
Relative Adrenal Insufficiency in Cirrhotic Patients
Authors: Anastasiadis Sotirios N. , Giouleme Olga I. , Germanidis Georgios S. , Vasiliadis Themistoklis G.
Published: March 2015

Relative adrenal insufficiency (RAI) was demonstrated in patients with cirrhosis and liver failure. A relationship appears to exist between the severity of the liver disease and the presence of RAI. Neither the mechanism nor the exact prevalence of RAI is fully understood. There is though a hypothesis that low high-density lipoprotein (HDL) levels in this group of patients may be responsible for the insufficiency of cortisol. Several questions also arise about the way and the kind of cortisol (total cortisol, free cortisol, or even salivary cortisol) that should be measured. The presence of RAI in patients with cirrhosis is unquestionable, but still several studies should come up in order to properly define it and fully understand it.
Смешанная задача для нагруженной системы уравнений с производными Римана-Лиувилля
Authors: Mamchuev Murat Osmanovich
Published: March 2015

Исследуется система двух уравнений с частными производными
Римана-Лиувилля с постоянными коэффициентами.
Доказана теорема существования и единственности решения
смешанной задачи и построена ее функция Грина.
Библиография: 7 названий.
О методе двустороннего продолжения решения интегрального уравнения свертки на конечном промежутке
Authors: Barseghyan Ani Garnikovna
Published: March 2015

Работа посвящена развитию метода двустороннего продолжения решения интегрального уравнения свертки
$$
S(x)=g(x)+\int _{0}^{r} K(x-t)S(t) dt,\qquad
0<x<r,\quad r< \infty,
$$
с четной ядерной функцией $K\in L_{1} (-r,r)$. Рассматриваются два
продолжения решения $S$: на $(-\infty, 0]$ и $ [r,\infty)$.
Используется факторизация типа Винера-Хопфа.
В условиях обратимости некоторых операторов задача сводится к
двум уравнениям с суммарными ядрами:
$$
H^{\pm } (x)=q_{0}^{\pm } (x)
\mp \int _{0}^{\infty } U(x+t+r)H^{\pm } (t) dt,\qquad
x>0,\quad U\in L^{+} .
$$
Обсуждаются прикладные аспекты реализации метода.
Библиография: 15 названий.
Специальность йордановых супералгебр, связанных с алгебрами Новикова-Пуассона
Authors: Zhelyabin Viktor Nikolaevich , Zakharov Anton Stanislavovich
Published: March 2015

В работе доказывается специальность йордановых супералгебр,
соответствующих алгебрам Новикова-Пуассона.
Библиография: 24 названий.
Новая верхняя оценка хроматического числа случайного подграфа дистанционного графа
Authors: Gusev Anton Sergeevich
Published: March 2015

Эта работа связана с классической проблемой Нельсона-Хадвигера
о нахождении хроматических чисел дистанционных графов
в ${\mathbb R}^n$. Мы рассматриваем класс графов
$G(n,2s+1,s)=(V(n,2s+1), E(n,2s+1,s))$,
определенных следующим образом:
\begin{align*}
V(n,2s+1)&=\{x=(x_1,x_2,…,x_n): x_i\in \{0,1\},
x_1+x_2+…+x_n=2s+1\},

E(n,2s+1,s)&=\{\{x,y\}:(x,y)=s\},
\end{align*}
где $(x,y)$ обозначает скалярное произведение. Мы
изучаем случайный граф ${\mathcal G}(G(n,2s+1,s),p)$,
каждое ребро которого независимо от других ребер берется
из множества $E(n,2s+1,s)$ с вероятностью $p$. В данной статье
мы докажем новую оценку для хроматического числа такого графа.
Библиография: 36 названий.
Оценки объема решений некоторых дифференциальных уравнений с производной Хукухары
Authors: Ocheretnyuk Evgenii Vladimirovich , Slyn'ko Vitalii Ivanovich
Published: March 2015

Для одного класса нелинейных дифференциальных уравнений
с производной Хукухары получены нижние оценки объема решений.
При этом используются классические неравенства А. Д. Александрова
для смешанных объемов в сочетании с методом сравнения.
Библиография: 9 названий.
О числе компонент фиксированного объема случайного $A$-отображения
Authors: Yakymiv Arsen Lubomirovich
Published: March 2015

Пусть $\mathfrak S_n$ - полугруппа отображений множества
из $n$ элементов в себя, $A$ - некоторое фиксированное
подмножество множества натуральных чисел $\mathbb N$,
$V_n(A)$ - множество отображений из $\mathfrak S_n$,
размеры контуров которых принадлежат множеству $A$.
Отображения из $V_n(A)$ принято называть $A$-отображениями.
Рассмотрим случайное отображение $\sigma_n$, равномерно
распределенное на $V_n(A)$. Предполагается, что множество $A$
имеет асимптотическую плотность $\varrho$, причем допускается,
что $\varrho=0$. Пусть $\xi_{in}$ - число компонент связности
случайного отображения $\sigma_n$ объема $i\in\mathbb N$.
В настоящей статье изучено асимптотическое поведение
совместного распределения случайных величин
$\xi_{1n},\xi_{2n},…,\xi_{bn}$ при $n\to\infty$
и фиксированном $b\in\mathbb N$. Показано, что это
распределение слабо сходится совместному распределению
независимых пуассоновских случайных величин
$\eta_1,\eta_2,…,\eta_b$ с некоторыми параметрами
$\lambda_i=\mathsf E\eta_{i}$, $i\in\mathbb N$.
Библиография: 32 названия.
Отображения с разделимой динамикой и спектральные свойства порожденных ими операторов
Authors: Antonevich Anatolij Borisovich , Ahmatova Anzhela A , Makowska Justyna
Published: March 2015

Отображение $\alpha $ пространства $X$ в себя порождает операторы взвешенного сдвига $B$, действующие в пространствах функций на $X$. Спектральные свойства таких операторов тесно связаны с динамикой отображения $\alpha$. Ранее было известно, что спектр оператора зависит только от множества инвариантных эргодических мер для отображения $\alpha$. В статье получены условия правосторонней обратимости операторов $B-\lambda I$ при спектральных значениях $\lambda$. Основной результат заключается в том, что
правосторонняя обратимость может иметь место только в случае существования нетривиального аттрактора.
Библиография: 29 названий.
О единственности стационарной меры для стохастической системы модели Лоренца бароклинной атмосферы
Authors: Klevtsova Yulia Yur'evna
Published: March 2015

Рассматривается одна нелинейная система дифференциальных уравнений в частных производных с параметрами. Эта система описывает двухслойную квазисоленоидальную модель Лоренца бароклинной атмосферы на вращающейся двумерной сфере. Правая часть системы возмущается белым шумом. Выводятся достаточные условия на параметры и правую часть для существования единственной стационарной меры.
Библиография: 40 названий.
THE INFLUENCE OF ABIOTIC FACTORS ON LITTER DEPOSITION IN A SEMIARID AREA, NORTHEASTERN BRAZIL
Authors: Diogo Ivan Jeferson Sampaio , Vieira Irlaine Rodrigues , Silveira Andréa Pereira , Araújo Francisca Soares de
Published: March 2015

The amount of deciduous material throughout the year is mostly related to climatic conditions in tropical areas. A large deposition of litterfall in the dry season is described for deciduous and semideciduous forests. We aimed to assess the monthly deposition rate of litterfall during one year and the climatic influence in a deciduous thorny woodland area. The study area had a permanent plot of one hectare. To collect litterfall, 50 plots were selected and a collector (0.5 x 0.5 m) was installed. Samples were collected monthly for twelve months and divided into fractions: leaves, branches, fruits and seeds, flowers and miscellaneous. We tested the correlation of four abiotic factors (rainfall, soil humidity, temperature and wind) and the litter deposition.The annual litterfall collected had a total value of 2,731.6 kg ha-1.The contribution fraction of leaves corresponded to 54.3%, branches (14.2%), fruits (12.6%), flowers (1.6%) and miscellaneous (17.2%). The wind was the abiotic factor most correlated with the total deposition of the litterfall, but other correlations were found. In this area, site-dependent climatic and edaphic variables have an important control on litterfall.
SOBREVIVÊNCIA DE Cyathea atrovirens (CYATHEACEAE; PTERIDOPHYTA) APÓS DESMATAMENTO
Authors: Tamaki Vívian , Nievola Catarina Carvalho , Medina Ivomar Aparecido , Lopes Elisabete Aparecida , Suzuki Rogério Mamoru
Published: March 2015

A adoção de medidas de mitigação é necessária para minimizar os impactos ambientais provocados pelo desmatamento para a construção de rodovias. Nesse contexto, a avaliação da adaptação de espécies vegetais que permaneceram na beira da estrada após o desmatamento, associada à realocação dos espécimes que foram retirados, pode favorecer a preservação destas espécies. O objetivo do trabalho foi avaliar a adaptação de exemplares de Cyathea atrovirens que permaneceram na beira de estrada após o desmatamento (Experimento-ABE) para construção do Trecho Sul do Rodoanel Mário Covas, em São Paulo e também avaliar a possibilidade de transplante dos indivíduos desta espécie que foram retirados por ocasião da supressão da mata (Experimento-AT), por até 43 meses. Os espécimes de ABE apresentaram 97% de sobrevivência e os de AT tiveram 80%. Foram observados novos báculos e frondes, bem como crescimento do cáudice em ambos os experimentos. Os resultados mostraram não haver necessidade de retirada e realocação dos exemplares de C. atrovirens que permaneceram nas bordas da mata após a supressão da vegetação e que houve adaptação dos exemplares transplantados, constituindo importante medida para a conservação de C. atrovirens, além de contribuir para o planejamento do desmatamento para a construção de rodovias, minimizando o impacto ambiental.
Dental Malocclusion among University Students and Its Effect on Self-esteem: A Cross-sectional Study
Authors: Sheikh Arsalan , Mathew Thomas , Siew Tan Bee
Published: March 2015

Introduction

Studies on prevalence of malocclusion and self-esteem among young adults are sparse in Malaysia. The objectives of this study were to highlight the type of Angle's malocclusion most commonly prevalent in young adults of International Medical University (IMU) of age 18 to 25 years as well as to assess the social impact of malocclusion in them. Another objective was to identify the young adults’ satisfaction level with the appearance of the teeth and self-perceived orthodontic treatment needs using a questionnaire and to correlate groups of malocclusion with self-esteem.

Materials and methods

All 142 subjects were randomly selected from the name list of different cohorts of students in IMU. Study information was provided to the subjects along with the consent form and two questionnaires about global self-esteem (GSE) and social impact of malocclusion. Intraoral clinical examination was performed using disposable mouth mirror, probe and metal ruler in presence of artificial illumination. Angle's molar relation and other occlusal characteristics were recorded.

Results

Angle's class I malocclusion was most prevalent (48.6%), followed by class III (26.8%), class II (16.2%) and normal occlusion (8.5%). Analysis of variance Anova test showed no significant association between Angle's malocclusion and GSE with mean self-esteem score of 14.1, 15.5 and 13.8 for class I, II and III malocclusion respectively.

Conclusion

The satisfaction with the teeth appearance (0.026) and social impact of malocclusion (0.004) had significant association.

How to cite this article

Sheikh A, Mathew T, Siew TB. Dental Malocclusion among University Students and Its Effect on Selfesteem: A Cross-sectional Study. World J Dent 2014;5(4):204-208.
Cigarette smoking and Awareness of Oral Health Problems of Tobacco use among Students at the University of Port Harcourt, South-South Nigeria
Authors: Bashiru Braimoh Omoigberai , Udo Umanah Ayamma
Published: March 2015

Objectives

Cigarette smoking is recognized as the most important environmental risk factor in periodontitis and also an important risk factor for oral cancer. The aim of this study was to determine the prevalence of cigarette smoking and awareness of oral health problems of tobacco use among university students in Port Harcourt, Nigeria.

Materials and methods

The study population consisted of 360 young adults: 188 (52.2%) males and 172 (47.8%) females. Participants answered questions regarding demography, smoking behavior, attitude and on oral effect of smoking. Data were analyzed using IBM SPSS (New York, USA) statistics version 20.0 and test of significance done using Chi-square.

Results

The overall prevalence of smoking was 78 (21.7%): 52 (27.7%) in males and 26 (15.1%) in females. Males significantly smoked more than females (p = 0.002). Fifty-one (65.4%) of the current smokers commenced smoking in secondary school, 39 (50%) had smoked for 6 to 10 years, 54 (69.2%) consumed one to five sticks of cigarettes per day and among those who quitted smoking, 39 (52%) stopped smoking for health reasons. While 262 (72.8%) were ignorant that smoking was harmful to oral health, 223 (61.9%) and 278 (77.2%) respectively could not identify smoking as a risk factor for oral cancers and gum disease.

Conclusion

Though majority of the students were aware of the negative impact of smoking on general health, most of them were ignorant of the effect on oral health. Therefore, shared risk approach should be employed to inform, guide and educate the public on the effects of tobacco and in the campaign against its use.

How to cite this article

Bashiru BO, Udo UA. Cigarette smoking and Awareness of Oral Health Problems of Tobacco use among Students at the University of Port Harcourt, South- South Nigeria. World J Dent 2014;5(4):209-212.
Action of the Salivary Microorganisms having Sorbitol as Substratum
Authors: Tonetto Mateus Rodrigues , de Andrade Marcelo Ferrarezi , Saad José Roberto Cury , Bhandi Shilpa H , Pinzan-Vercelino Célia Regina Maio , Amaral Fabrício Reskalla , Silva Monica Barros da , Assunção Elida Lucia Ferreira , Youssef Michel Nicolau
Published: March 2015

Microorganisms living in the saliva are able to ferment some sweetener types and to promote the fall of pH that has its critical point around 5.5; in this situation, they equal the input and the calcium output in the processes of remineralization and demineralization. For iteration of the three essential factors to the installation of the dental caries (microorganism, host and diet) suggested the accomplishment of a work that involved one of these factors. This work aims to study this issue, through the indication of substitute sweetener of the saccharose, whenever possible, it solved to evaluate pH of the saliva, exposed to sorbitol.

How to cite this article

Amaral FR, Tonetto MR, Pinzan- Vercelino CRM, da Silva MB, Assunção ELF, Bhandi SH, de Andrade MF, Youssef MN, Saad JRC. Action of the Salivary Microorganisms having Sorbitol as Substratum. World J Dent 2014;5(4):218-222.
Most Powerful Antioxidants to Prevent Cancers: Prevention is Better than Cure
Authors: Kumar Anand , Khanna Ruchika , Srivastava Ram K , Ali Iqbal , Wadhwani Puneet , Ali Mariyam Iqbal
Published: March 2015

Cancer is a state of disorders marked by out-of-control cell magnification. There are various types of cancer, and each is relegated by the type of cell that is initially concerned. Now a day's sundry treatment modalities for cancer is available, but at the last it is still a well verbally revealed that obviation is more preponderant than remedy. An anticancer nutritional therapy is an influential approach that one can use to subdue peril of cancer. Researches and numerous studies have significantly witnessed some of finest antioxidants which can be considered to obviate and even to remedy cancer at some extent. Researchers have shown that cancer is a deficiency disease provoked by lack of essential food compounds in modern's man diet. The intent of this is to explain that this human disaster can be stopped or impede existing on the basis of scientific knowledge.

How to cite this article

Kumar A, Khanna R, Srivastava RK, Ali I, Wadhwani P, Ali MI. Most Powerful Antioxidants to Prevent Cancers: Prevention is Better than Cure. World J Dent 2014;5(4):229-231.
Trends and drivers in global surface ocean pH over the past 3 decades
Authors: Lauvset S. K. , Gruber N. , Landschützer P. , Olsen A. , Tjiputra J.
Published: March 2015

Abstract. We report global long-term trends in surface ocean pH using a new pH data set computed by combining fCO2 observations from the Surface Ocean CO2 Atlas (SOCAT) version 2 with surface alkalinity estimates based on temperature and salinity. Trends were determined over the periods 1981–2011 and 1991–2011 for a set of 17 biomes using a weighted linear least squares method. We observe significant decreases in surface ocean pH in ~70% of all biomes and a mean rate of decrease of 0.0018 ± 0.0004 yr−1 for 1991–2011. We are not able to calculate a global trend for 1981–2011 because too few biomes have enough data for this. In half the biomes, the rate of change is commensurate with the trends expected based on the assumption that the surface ocean pH change is only driven by the surface ocean CO2 chemistry remaining in a transient equilibrium with the increase in atmospheric CO2. In the remaining biomes, deviations from such equilibrium may reflect that the trend of surface ocean fCO2 is not equal to that of the atmosphere, most notably in the equatorial Pacific Ocean, or may reflect changes in the oceanic buffer (Revelle) factor. We conclude that well-planned and long-term sustained observational networks are key to reliably document the ongoing and future changes in ocean carbon chemistry due to anthropogenic forcing.
Assessing the operation rules of a reservoir system based on a detailed modelling chain
Authors: Bruwier M. , Erpicum S. , Pirotton M. , Archambeau P. , Dewals B. J.
Published: March 2015

Abstract. According to available climate change scenarios for Belgium, drier summers and wetter winters are expected. In this study, we focus on two multi-purpose reservoirs located in the Vesdre catchment, which is part of the Meuse basin. The current operation rules of the reservoirs are first analysed. Next, the impacts of two climate change scenarios are assessed and enhanced operation rules are proposed to mitigate these impacts. For this purpose, an integrated model of the catchment was used. It includes a hydrological model, one-dimensional and two-dimensional hydraulic models of the river and its main tributaries, a model of the reservoir system and a flood damage model. Five performance indicators of the reservoir system have been defined, reflecting its ability to provide sufficient drinking water, to control floods, to produce hydropower and to reduce low-flow conditions. As shown by the results, enhanced operation rules may improve the drinking water potential and the low-flow augmentation while the existing operation rules are efficient for flood control and for hydropower production.
Brief Communication: A new testing field for debris flow warning systems and algorithms
Authors: Arattano M. , Coviello V. , Cavalli M. , Comiti F. , Macconi P. , Marchi L. , Theule J. , Crema S.
Published: March 2015

Abstract. Early warning systems (EWSs) are among the measures adopted for the mitigation of debris flow hazards. EWSs often employ algorithms that require careful and long testing to grant their effectiveness. A permanent installation has been so equipped in the Gadria basin (Eastern Italian Alps) for the systematic test of event-EWSs. The installation is conceived to produce didactic videos and host informative visits. The populace involvement and education is in fact an essential step in any hazard mitigation activity and it should envisaged in planning any research activity. The occurrence of a debris flow in the Gadria creek, in the summer of 2014, allowed a first test of the installation and the recording of an informative video on EWSs.
Models of Inter-Organizational Logistics Management in Slovenia
Authors: Murtič Sašo , Lisec Andrej
Published: March 2015

Throughout the history, the transportation of goods and related logistics have played an important role in human development and existence. This pertains to numerous interlinked processes, whose management is often linked to social system, international linkages, development of industry, market and market specifics. In modern times, the management of these processes is increasingly bound to globalization of production and market, moving of production to countries with cheaper labour force, environmental protection. The present Slovenian economy depends to a large extent on economies and corporate relations of the European Union and the world. Such inter-connectedness demands frequent transportation of semi-finished and finished goods. By providing timely delivery of goods, transportation consequently enables inter-organizational linkages and individual production, economic, market and other processes. Organizational and inter-organizational management of transport logistics demands profound understanding of transport flows, freight forwarding expertise and knowledge of transport, tax, environmental and other related regulations. Adequate knowledge and mastering of cultural, linguistic, national and other differences is important as well. The presented analysis and evaluation form the basis of the construction of inter-organizational model of logistics management in Slovenia.
Transportation Costs and Subsidy Distribution Model for Urban and Suburban Public Passenger Transport
Authors: Ševrović Marko , Brčić Davor , Kos Goran
Published: March 2015

Public transport (PT) subsidy provides the means to impose the optimal combination of fare and Level of Service (LoS) offered to passengers. In regions where one PT operator services multiple local communities on multiple lines it becomes hard to uniformly link the actual cost of a line and thus the LoS offered, to a particular local community. This leads to possible disproportions in the overall subsidy distribution that can result in being unfair to some local communities, mainly the ones that are sparsely populated or geographically isolated. In order to extricate this problem the appropriate level of PT subsidisation according to the average values in the European cities was investigated and the current subsidy policies in Croatia were investigated. Based on this research and the hypothesis that the offered LoS must be reflected in the subsidy amount a new subsidy distribution model was established that involves a series of analytical procedures and processes. This model introduces several factors used for the calculation of the actual share in costs. Thus, the amount of subsidies for individual lines in a region can be determined based on the actual service offered to the local community, The proposed model has been tested and successfully implemented in the Dubrovnik-Neretva County in the Republic of Croatia.