Some structural, equilibrium and kinetic studies of aromatic nitro-compounds with nucleophiles

The interactions of certain aromatic nitre compounds with nucleophiles in protic solvents and in protic dipolar aprotic solvent mixtures have been investigated using the techniques of proton magentic resonance and visible spectroscopy. Picrate ion reacts with concentrated aqueous sodium sulphite to give an unusual ion carrying five negative charges. This results from the covalent addition of two sulphite molecules to the picrate ion, at ring carbon carrying hydrogen. At low sulphite concentration a 1:1 adduct is produced. The equilibrium constants for the formation of these complexes have been determined. Solvent effects on the formation of 1:1 adduct were examined in water-dimethyl sulphoxide mixtures. With hydroxide ion in aqueous solutions, the major of the picrate ion is to give a 1:2 adduct.1,2,3,5-Tetranitrobenzene reacts with hydroxide ion or sulphite ion in water, or ethoxide ion in ethanol to form red complexes whose NMR spectra indicate covalent addition of the nucleophile at C(_4). The complexes are not stable and replacement of the nitro group at occurs quickly. The equilibrium and the rate constants for these processes have been measured. In contrast 1,2,4 ,5-tetranitrobenzene reacts with hydroxide ion to give 2,4,5-trinitrophenol without the production of colour. With ethoxide or sulphite ions coloured species are produced. l,3-Dimethoxy-4,6-dinitrobenzene reacts with methoxide ion in dimethyl sulphoxide-methanol mixtures to form an adduct whose NMR spectrum indicates methoxide addition at C(_2). The equilibrium constants in various solvent compositions have been determined. Solvent effects on the stability of Meisenheimer complexes formed from 1,3,5-trinitrobenzene and thiolate ions have been investigated in alcohol-water mixtures. The equilibrium constants for formation of the1:1 adducts are smaller in water than in alcohol but go through a maximum at about 80% alcohol. The equilibrium constants of the 1:2 adducts increase monotonically as the proportion of water is increased and are ca. 10(^3) greater in water than in pure alcohol. This greater stability is attributed partly to the good solvation by water of a localised negative charge on the nitro group between the positions of addition

A Novel Technique for Tuning PI -controller In Switched Reluctance Motor Drive for Transportation Systems

This paper presents, an optimal basic speed controller for switched reluctance motor (SRM) based on ant colony optimization (ACO) with the presence of good accuracies and performances. The control mechanism consists of proportional-integral (PI) speed controller in the outer loop and hysteresis current controller in the inner loop for the three phases, 6/4 switched reluctance motor. Because of nonlinear characteristics of a SRM, ACO algorithm is employed to tune coefficients of PI speed controller by minimizing the time domain objective function. Simulations of ACO based control of SRM are carried out using MATLAB /SIMULINK software. The behavior of the proposed ACO has been estimated with the classical Ziegler- Nichols (ZN) method in order to prove the proposed approach is able to improve the parameters of PI chosen by ZN method. Simulations results confirm the better behavior of the optimized PI controller based on ACO compared with optimized PI controller based on classical Ziegler-Nichols method

Procena potencijalnog rizika po zdravlje ljudi usled prisustva teških metala u zemljištu centralne zone Beograda

An investigation of the soil quality in the centre of Belgrade was performed to define how seriously the soil is polluted. On the basis of the heavy metal content (Zn, Cd, Pb, Co, Ni, Cu, Cr and Mn), the potential health risk assessment calculated for a lifetime of exposure (ingestion and inhalation), based on the USEPA model, was determined as the cumulative carcinogenic and non-carcinogenic risk for children and adults. The study proved that soil contamination in Belgrade is not insignificant; risk assessment indicated that the carcinogenic risk is completely insignificant but the cumulative non-carcinogenic risk tends to became significant, mainly for children, since it approaches unacceptable values. There is no particularly dangerous single heavy metal, but their cumulative effect, expressed as Child Soil Ingestion Hazardous Index, is for concern.Ispitivanje zemljišta centralne zone Beograda rađeno je sa ciljem da se odredi nivo njegove zagađenosti teškim metalima. Polazeći od sadržaja teških metala (Zn, Cd, Pb, Co, Ni, Cu, Cr i Mn) procenjen je kumulativni potencijalni kancerogeni i nekancerogeni zdravstveni rizik (za ingestiju i inhalaciju) za životni vek čoveka, dece i odraslih, polazeći od modela koji je razvila američka agencija za zaštitu životne sredine. Istraživanja pokazuju da zagađenje zemljišta u Beogradu nije zanemarljivo iako procena kancerogenog rizika ukazuje da je on zanemarljiv, ali da nekancerogeni rizik postaje značajan, posebno u slučaju dece. Za sada ne postoji određeni teški metal koji se može identifikovati kao opasan, ali kumulativni efekat svih ispitivanih metala iskazan kroz ingestioni hazardni indeks za decu postaje zabrinjavajući pošto se približava vrednostima koje se smatraju nepovoljnim

A Multiband, Low Power and Low Phase Noise CMOS Voltage-Controlled Oscillator with NMOS Varactor for UWB Applications

A multiband low power and low phase noise LC-tank Voltage Controlled Oscillator (VCO) is designed for low band channels of the standard IEEE 802.15.4a. The LC-VCO uses the structure of complementary cross-coupled differential negative resistance and tank circuit, which contains varactor arrays for frequency fine-tuning and a spiral inductor. A method that uses resistor tail biasing for reducing the phase noise and the power consumption has been adopted. The circuit is fully designed in TSMC’s 180 nm technology process. The oscillator output provides three center frequencies of 3.5, 4, 4.5 GHz with good phase noises of -113.784, -116.703 and -126.753 dBc/MHZ at 1 MHz offset, while it dissipates 9mW power energy. The proposed LC VCO not only set a good balance between low phase noise and low power consumption, but it is also a highly desired circuit for multiband wireless transceiver systems, which are the major contributions of this proposed design

A New Phase Current Profiling with FLC f or Torque Optimization of 12/8 SRM

The switched reluctance machine against its several merits such as simplicity, robustness, less cost manufacturing and large speed still suffers from its undesirable torque ripple and acoustic noise. Compared to different candidates of hybrid and electric vehicle engine, the frequency of use of SRM in traction drives is improved with the different optimizing torque oscillation solutions. Most of studies used the generic or specific model of switched reluctance machine in the Simulink library (6/4,8/6 and 10/8). Despite, a new non linear model simply implemented in Simulink tool usinga static finite element analysis a previous study is used in this work. Hence, a 12/8 non linear SRM drive system is simulated using MATLAB toolbox tested with an intelligent controller (FLC) in order to minimize the torque ripple of an oriented starter –alternator application of a hybrid vehicle

Chilling requirement affects plant response to hydrogen cyanamide in apple cultivars

Chilling requirements of 43 apple and 38 pear cultivars were estimated over a 2 year period by cutting shoots in the field at weekly intervals and forcing them in a warm greenhouse for 4 weeks. For apples, the mean values ranged from 490 Chill Units (CU) +- 1 for 'Dorsett Golden' to 1320.5 CU +- 8 for 'Cortland', 'Marshall Mclntosh' and 'Starking Delicious'. For pears, the mean values ranged from 749 CU +- 9 for 'Batjarka' to 1320.5 CU +- 8 for 'Poirier Fleurissant Tard'. Interval of sampling, coastal effect and involvment of other factors than CU accumulation in releasing plants from dormancy could be among the possible explanations for the variations in the year-to-year estimation of the chilling requirement. Budbreak and phytotoxicity (expressed as percent dead buds) induced by hydrogen cyanamide in apple cultivars depend on hydrogen cyanamide concentration, time of application and chilling requirements of the cultivars. 'Arlet' (811.5 CU), having the lowest chilling requirement, showed a different endodormancy pattern than 'Braeburn' (1141 CU), 'Golden Delicious' (1277 CU) and 'Starking Delicious' (1320.5 CU), resulting in a different response to the chemical. During early to deep dormancy, 'Braeburn', 'Golden Delicious' and 'Starking Delicious' exhibited a greater tolerance to hydrogen cyanamide, with an increase in budbreak and a reduction in phytotoxicity. In 'Arlet' however, the level of tolerance did not increase significantly during this period. Towards the end of endodormancy, the sensitivity to the chemical increased in all cultivars, but at a higher rate in 'Braeburn', 'Golden Delicious' and 'Starking Delicious' than in 'Arlet'. The sensitivity to hydrogen cyanamide was also dependent on bud and internode position in the shoot, with an increasing tolerance from the top to the base. This gradient disappeared after satisfaction of the chilling requirement of the buds, while it remained for the internodes, suggesting that other factors, unrelated to the dormant period, may be involved in determining the differential sensitivity of the stem along the shoot

Conservation de l'énergie sur des environnements de réseaux d'accès radio hétérogènes : vers des réseaux auto-organisants et verts

Since the last decades, environmental issues are becoming among the major concerns for most human activities, including the Information and Communication Technologies sector. This will surely influence upcoming networking technologies, architectures and usage practices. New approaches and methodologies are required in order to evaluate and to reduce the Carbon Footprint toward what is commonly denoted as Green Networks. Within the ICT sector, the main efforts are related to energy saving techniques. These efforts started in early stages within wireless technologies, mainly because of energy limitations on mobile devices such as mobile phones and wireless sensors. Additionally, because of health considerations, standardization bodies and government had set stringent policies and limits on electromagnetic radiation levels that can be emitted by radio stations. For these reasons, many academic and industrial research and development activities had led to a number of relatively energy efficient solutions. In this thesis, we consider energy efficiency in the context of Heterogeneous Wireless Access Networks. These are composed of multi-standards wireless network solutions, with non uniform topologies and cell sizes and Multi-Modal mobile terminals able to manage simultaneously different connections. The main contributions of our studies include the proposal of new optimization solutions regarding user association and scheduling techniques at both flow and packet levels for multi-homed mobile terminals. An overall context-based solution is also proposed in order to provide end-to-end energy efficient networking solutionsLa préservation de l’environnement et des ressources naturelles pour les prochaines générations est aujourd’hui considérée comme un des axes les plus prioritaires dans presque tous les secteurs économiques. Le secteur des Technologies de l’Information et de la Communication est loin d’être épargné de cette tendance écologique. Nous considérons dans cette thèse la problématique de la conservation d’énergie dans le contexte technologique actuel caractérisé par: •La coexistence d’une multitude de technologies d’accès sans fil offrant un environnement riche et dynamique • Des terminaux mobiles multimodaux • Limitations persistantes des sources d’énergie sur les terminaux mobiles. Dans ce contexte très riche, les possibilités offertes aux usagers sont à double tranchant. D’un côté, elles peuvent très bien améliorer la QoS en offrant toujours la meilleure connectivité en fonction du contexte de l’utilisateur. D’un autre côté, et sans une bonne optimisation de la consommation d’énergie sur le terminal, la disponibilité de celui-ci peut vite diminuer et donc faire baisser la QoE à cause de l’énergie nécessaire pour gérer plusieurs interfaces radio en parallèle. Nous considérons essentiellement les liens entre les stations de base (ou les point d’accès) et les terminaux mobiles. Notre objectif étant d’analyser la consommation d’énergie sur ces liens pour ensuite proposer des contributions permettant de mieux la maitriser. Nous focalisons essentiellement sur l’exploitation des multiples interfaces et du multi-flux pour étudier, analyser et proposer des solutions dynamiques et adaptatives d’ordonnancement, de sélection et de gestion d’interfaces minimisant la consommation d’énergi

Cigarette Smoking Effect on Microhardness and Flexural Properties of Denture Base Resins

Objective: To identify the tobacco effect on flexural properties and the microhardness of three acrylic resins. Material and Methods: Three resins were tested: two thermo-polymerizable acrylic resins (RMB 20 and BMS 014) and one autopolymerized acrylic resin. The 3-point bending and microhardness tests were carried out with a universal tensile-compression machine and a micro-Vickers hardness tester. The acrylic resin specimens have been exposed for 21 days to cigarette smoke in a smoking room. Their mechanical strength was compared to unexposed samples. Statistical analysis was performed using the data processing software SPSS Statistics 21.0. Results: The flexural properties of the resins were affected by cigarette smoke only in the case of Major Base 20® (drop in strength with p= 0.02; 0.6; 0.7 and in elastic modulus with p= 0.86; 0.74 and 0.85 for Major Base 20®, BMS 014® and Major Repair®). The cigarette smoke affected significantly microhardness for all groups (p<0.001). Conclusion: Cigarette smoking does not affect the flexural properties of the acrylic resin (BMS 014® and Major Repair® unlike Major Base 20®), but it does reduce the microhardness