A new model for heating of Solar North Polar Coronal Hole

This paper presents a new model of North Polar Coronal Hole (NPCH) to study dissipation/propagation of MHD waves. We investigate the effects of the isotropic viscosity and heat conduction on the propagation characteristics of the MHD waves in NPCH. We first model NPCH by considering the differences in radial as well as in the direction perpendicular to the line of sight (\textit{los}) in temperature, particle number density and non-thermal velocities between plumes and interplume lanes for the specific case of \ion{O}{VI} ions. This model includes parallel and perpendicular (to the magnetic field) heat conduction and viscous dissipation. Next, we derive the dispersion relations for the MHD waves in the case of absence and presence of parallel heat conduction. In the case of absence of parallel heat conduction, we find that MHD wave dissipation strongly depends on the viscosity for modified acoustic and Alfven waves. The energy flux density of acoustic waves varies between $10^{4.7}$ and $10^7 \,erg\,cm^{-2}\,s^{-1}$ while the energy flux density of Alfven waves turned out to be between $10^6-10^{8.6} \,erg\,cm^{-2}\,s^{-1}$. But, solutions of the magnetoacustic waves show that the parallel heat conduction introduce anomalous dispersion to the NPCH plasma wherein the group velocity of waves exceeds the speed of light in vacuum. Our results suggests all these waves may provide significant source for the observed preferential accelerating and heating of \ion{O}{VI} ions, in turn coronal plasma heating and an extra accelerating agent for fast solar wind in NPCH.Comment: 17 pages, 11 figures, Submitted to MNRA

Detecting Singleton Review Spammers Using Semantic Similarity

Online reviews have increasingly become a very important resource for consumers when making purchases. Though it is becoming more and more difficult for people to make well-informed buying decisions without being deceived by fake reviews. Prior works on the opinion spam problem mostly considered classifying fake reviews using behavioral user patterns. They focused on prolific users who write more than a couple of reviews, discarding one-time reviewers. The number of singleton reviewers however is expected to be high for many review websites. While behavioral patterns are effective when dealing with elite users, for one-time reviewers, the review text needs to be exploited. In this paper we tackle the problem of detecting fake reviews written by the same person using multiple names, posting each review under a different name. We propose two methods to detect similar reviews and show the results generally outperform the vectorial similarity measures used in prior works. The first method extends the semantic similarity between words to the reviews level. The second method is based on topic modeling and exploits the similarity of the reviews topic distributions using two models: bag-of-words and bag-of-opinion-phrases. The experiments were conducted on reviews from three different datasets: Yelp (57K reviews), Trustpilot (9K reviews) and Ott dataset (800 reviews).Comment: 6 pages, WWW 201

Essential oils as natural sources of fragrance compounds for cosmetics and cosmeceuticals products

Fragrance is an integral part of cosmetic products and is often regarded as an overriding factor in the selection of cosmetics among consumers. Fragrances also play a considerable role in masking undesirable smells arising from fatty acids, oils and surfactants that are commonly used in cosmetic formulations. Essential oils are vital assets in the cosmetic industry, as along with imparting pleasant aromas in different products, they are able to act as preservatives and active agents and, simultaneously, offer various benefits to the skin. Moreover, the stimulating demand for natural ingredients has contributed massively to a renewed interest in cosmetic and wellness industries in plant derivatives, especially essential oils. This has led popular cosmetic companies to endorse natural fragrances and opt for minimally processed natural ingredients, given the potentially adverse health risks associated with artificial fragrance chemicals, which are major elements of cosmetics. Among the high-valued essential oils used as fragrances are citrus, lavender, eucalyptus, tea tree and other floral oils, among others, while linalool, geraniol, limonene, citronellol, and citral are much-appreciated fragrance components used in different cosmetics. Thus, this review aimed to highlight the enormous versatility of essential oils as significant sources of natural fragrances in cosmetics and cosmeceuticals. Moreover, a special focus will be laid on the different aspects related to essential oils such as their sources, market demand, chemistry, fragrance classification, aroma profile, authenticity and safety

Analysis of the discontinuous PWM controlled D-STATCOM for reactive power compensation applications

U ovom se radu opisuju istraživanja diskontinuirane PWM (DPWM) kontrole Distribucijskog Statičkog Sinkroniziranog Kompenzatora (D-STATCOM). Različite su se DPWM metode uveliko koristile u pogonskom sistemu motora za kontrolu invertora i smanjenje gubitaka energije. S povećanim potrebama za energijom, energetska učinkovitost postala je pitanje od osnovne važnosti. Rezultat toga je sve češća upotreba D-STATCOM-a u distribucijskim sustavima. U ovom su radu DPWM metode primijenjene za unutarnju kontrolu D-STATCOM-a. Za vanjsku je kontrolu korištena kontrola faznog ugla te su PWM metode prilagođene tom kontrolnom algoritmu. Uz to, na D-STATCOM primijenjene su uobičajene kontinuirane PWM (CPWM) metode u svrhu komparacije. Sve su simulacije provedene u okruženju MATLAB-Simulink softvera. Gubitci snage značajno utječu na D-STATCOM te je stoga razvijen simulacijski model za izračunavanje gubitaka provođenja i prekidanja u svrhu ispitivanja učinkovitosti DPWM metoda u reduciranju gubitaka snage D-STATCOM-a. Rezultati su pokazali da je primjena raznih DPWM metoda na D-STATCOM-u prikladna za indekse visoke modulacije. To jasno pokazuje da se, u skladu s različitim DPWM metodama, može postići smanjenje gubitaka od 14 % do 50 % pri uključivanju/isključivanju D-STATCOMa. Nadalje, u ovom se radu predlažu primjene metoda CPWM i DPWM kod niskih i visokih indeksa modulacije, prema potrebama distribucijskog sustava.The scope of this paper covers the investigations of discontinuous PWM (DPWM) control of the Distribution Static Synchronous Compensator (D-STATCOM). Various DPWM methods have been widely used in motor drives for controlling the inverter and reducing power losses. With the rising demand for energy, energy efficiency has currently become an issue of vital importance. As a result, the use of the D-STATCOM in distribution systems is becoming increasingly common. In this study, DPWM methods were used for the D-STATCOM inner control. For the outer control, phase angle control was used and PWM methods were adapted to this control algorithm. In addition, conventional continuous PWM (CPWM) methods were applied to the D-STATCOM for comparison purposes. All simulations were performed in the MATLAB-Simulink software environment. Power losses have a significant impact on the D-STATCOM; therefore, a simulation model was developed to calculate the conduction and switching losses in order to investigate the effectiveness of DPWM methods in reducing the D-STATCOM power losses. Results showed that the utilization of different DPWM methods in the D-STATCOM was suitable for high modulation indexes. This clearly illustrates that, according to different DPWM methods, a reduction of from 14 % up to 50 % in D-STATCOM switching losses can be achieved. Furthermore, this study proposes the use of CPWM and DPWM methods in low and high modulation indexes, respectively, according to the requirements of the distribution system

Analysis of the discontinuous PWM controlled D-STATCOM for reactive power compensation applications

U ovom se radu opisuju istraživanja diskontinuirane PWM (DPWM) kontrole Distribucijskog Statičkog Sinkroniziranog Kompenzatora (D-STATCOM). Različite su se DPWM metode uveliko koristile u pogonskom sistemu motora za kontrolu invertora i smanjenje gubitaka energije. S povećanim potrebama za energijom, energetska učinkovitost postala je pitanje od osnovne važnosti. Rezultat toga je sve češća upotreba D-STATCOM-a u distribucijskim sustavima. U ovom su radu DPWM metode primijenjene za unutarnju kontrolu D-STATCOM-a. Za vanjsku je kontrolu korištena kontrola faznog ugla te su PWM metode prilagođene tom kontrolnom algoritmu. Uz to, na D-STATCOM primijenjene su uobičajene kontinuirane PWM (CPWM) metode u svrhu komparacije. Sve su simulacije provedene u okruženju MATLAB-Simulink softvera. Gubitci snage značajno utječu na D-STATCOM te je stoga razvijen simulacijski model za izračunavanje gubitaka provođenja i prekidanja u svrhu ispitivanja učinkovitosti DPWM metoda u reduciranju gubitaka snage D-STATCOM-a. Rezultati su pokazali da je primjena raznih DPWM metoda na D-STATCOM-u prikladna za indekse visoke modulacije. To jasno pokazuje da se, u skladu s različitim DPWM metodama, može postići smanjenje gubitaka od 14 % do 50 % pri uključivanju/isključivanju D-STATCOMa. Nadalje, u ovom se radu predlažu primjene metoda CPWM i DPWM kod niskih i visokih indeksa modulacije, prema potrebama distribucijskog sustava.The scope of this paper covers the investigations of discontinuous PWM (DPWM) control of the Distribution Static Synchronous Compensator (D-STATCOM). Various DPWM methods have been widely used in motor drives for controlling the inverter and reducing power losses. With the rising demand for energy, energy efficiency has currently become an issue of vital importance. As a result, the use of the D-STATCOM in distribution systems is becoming increasingly common. In this study, DPWM methods were used for the D-STATCOM inner control. For the outer control, phase angle control was used and PWM methods were adapted to this control algorithm. In addition, conventional continuous PWM (CPWM) methods were applied to the D-STATCOM for comparison purposes. All simulations were performed in the MATLAB-Simulink software environment. Power losses have a significant impact on the D-STATCOM; therefore, a simulation model was developed to calculate the conduction and switching losses in order to investigate the effectiveness of DPWM methods in reducing the D-STATCOM power losses. Results showed that the utilization of different DPWM methods in the D-STATCOM was suitable for high modulation indexes. This clearly illustrates that, according to different DPWM methods, a reduction of from 14 % up to 50 % in D-STATCOM switching losses can be achieved. Furthermore, this study proposes the use of CPWM and DPWM methods in low and high modulation indexes, respectively, according to the requirements of the distribution system

The Solvability of the Initial-Boundary Value Problems for a Nonlinear Schrödinger Equation with a Special Gradient Term

In this paper, the initial-boundary value problems for the two-dimensional nonlinear Schrödinger equation with a special gradient term with purely imaginary coefficients in the nonlinear part, when the coefficients of the equation are measurable bounded functions, are considered. The existence and uniqueness of solutions of the first and second initial-boundary value problems is proved almost everywhere.У статтi розглядаються початково-крайовi задачi для двовимiрного нелiнiйного рiвняння Шредiнгера iз спецiальним градiєнтним членом з чисто уявними коефiцiєнтами в нелiнiйнiй частинi, коли коефiцiєнти рiвняння є вимiрними обмеженими функцiями. Доведено iснування i єднiсть розв язкiв першо i друго початково-крайово задачi майже скрiзь

Relationship between subclinical hypothyroidism and serum homocysteine concentration in premenopausal women

Objective: In our study we aimed to examine serum homocysteinelevels of patients without thyroid dysfunctionswho have high serum anti thyroid peroxidase (anti-TPO)levels and patients with subclinical hypothyroidism whohave high serum thyroid stimulating hormone (TSH) andanti-TPO levels.Methods: One hundred and seven premenopause femaleoutpatients who referred to endocrine clinic of our hospitalwere included in our study. We generated 3 groups. Firstgroup (Control) consists of 53 (50%) patients between theages of 30-40 years. Second group (Euthyroid) consistsof 31 (29%) patients between the ages of 26-49. Thirdgroup (Subclinical Hypothyroidism) consists of 23 (21%)patients between the ages of 33-53 years. Serum totalcholesterol, triglycerides, high density lipoprotein (HDL)levels were measured by Olympus 2700 autoanalyzer.Serum TSH, free T4, anti-TPO and homocysteine levelswere measured by Siemens Immulite 2000 autoanalyzer.Results: In our study, total cholesterol, triglycerides, lowdensity lipoprotein (LDL) and very low density lipoprotein(VLDL) levels were not statistically significantly differentamong the groups. Although serum homocysteine levelsof the third group were higher than the other groups it wasnot statistically significantly different among the groups.Conclusion: Serum homocysteine and lipid levels of patientswith euthyroidism and subclinical hypothyroidismwho have positive anti-TPO levels may be inadequate inassessing the risk of cardiovascular diseases. J Clin ExpInvest 2013; 4 (3): 293-297Key words: Hypothyroidsm, homocysteine, premenopaus

Spatially Selective Assembly of Quantum Dot Light Emitters in an LED Using Engineered Peptides

Cataloged from PDF version of article.Semiconductor nanocrystal quantum dots are utilized in numerous applications in nano- and biotechnology. In device applications, where several different material components are involved, quantum dots typically need to be assembled at explicit locations for enhanced functionality. Conventional approaches cannot meet these requirements where assembly of nanocrystals is usually material-nonspecific, thereby limiting the control of their spatial distribution. Here we demonstrate directed self-assembly of quantum dot emitters at material-specific locations in a color-conversion LED containing several material components including a metal, a dielectric, and a semiconductor. We achieve a spatially selective immobilization of quantum dot emitters by using the unique material selectivity characteristics provided by the engineered solid-binding peptides as smart linkers. Peptide-decorated quantum dots exhibited several orders of magnitude higher photoluminescence compared to the control groups, thus, potentially opening up novel ways to advance these photonic platforms in applications ranging from chemical to biodetection. © 2011 American Chemical Society

A secured message transmission protocol for vehicular ad hoc networks

Vehicular Ad hoc Networks (VANETs) become a very crucial addition in the Intelligent Transportation System (ITS). It is challenging for a VANET system to provide security services and parallelly maintain high throughput by utilizing limited resources. To overcome these challenges, we propose a blockchain-based Secured Cluster-based MAC (SCB-MAC) protocol. The nearby vehicles heading towards the same direction will form a cluster and each of the clusters has its blockchain to store and distribute the safety messages. The message which contains emergency information and requires Strict Delay Requirement (SDR) for transmission are called safety messages (SM). Cluster Members (CMs) sign SMs with their private keys while sending them to the blockchain to confirm authentication, integrity, and confidentiality of the message. A Certificate Authority (CA) is responsible for physical verification, key generation, and privacy preservation of the vehicles. We implemented a test scenario as proof of concept and tested the safety message transmission (SMT) protocol in a real-world platform. Computational and storage overhead analysis shows that the proposed protocol for SMT implements security, authentication, integrity, robustness, non-repudiation, etc. while maintaining the SDR. Messages that are less important compared to the SMs are called non-safety messages (NSM) and vehicles use RTS/CTS mechanism for NSM transmission. Numerical studies show that the proposed NSM transmission method maintains 6 times more throughput, 2 times less delay and 125% less Packet Dropping Rate (PDR) than traditional MAC protocols. These results prove that the proposed protocol outperforms the traditionalMAC protocols

A blockchain-based authentication protocol for cooperative vehicular ad hoc network

The efficiency of cooperative communication protocols to increase the reliability and range of transmission for Vehicular Ad hoc Network (VANET) is proven, but identity verification and communication security are required to be ensured. Though it is difficult to maintain strong network connections between vehicles because of there high mobility, with the help of cooperative communication, it is possible to increase the communication efficiency, minimise delay, packet loss, and Packet Dropping Rate (PDR). However, cooperating with unknown or unauthorized vehicles could result in information theft, privacy leakage, vulnerable to different security attacks, etc. In this paper, a blockchain based secure and privacy preserving authentication protocol is proposed for the Internet of Vehicles (IoV). Blockchain is utilized to store and manage the authentication information in a distributed and decentralized environment and developed on the Ethereum platform that uses a digital signature algorithm to ensure confidentiality, non-repudiation, integrity, and preserving the privacy of the IoVs. For optimized communication, transmitted services are categorized into emergency and optional services. Similarly, to optimize the performance of the authentication process, IoVs are categorized as emergency and general IoVs. The proposed cooperative protocol is validated by numerical analyses which show that the protocol successfully increases the system throughput and decreases PDR and delay. On the other hand, the authentication protocol requires minimum storage as well as generates low computational overhead that is suitable for the IoVs with limited computer resources