Harmonics Analysis Due to Connecting an Electrical Traction to A 3-phase Power Supply System Through V/V Transformer

The wide application and usage of electrical traction system presents utilities with planning and operation challenges. Electric railways impose several power quality problems to the utility grid. Such as generated large negative sequence components (NSCs), undesirable harmonics, cause system voltage and current unbalance. Harmonics and unbalanced voltage also may cause negative effects on the components of the power system such as: overheating the transformers and the transmission lines, vibration and cause torque reduction of rotating machines, additional losses of lines and transformers, interference with communication systems, malfunctions of protection relays, measuring instrument error. All these problems have become more and more significant. This paper is an attempt to quantify and assess the impact of electrical traction on the grid side through a V/V transformer. Firstly in this paper, the typical utility power grid and traction power supply system model are designed. Then, the traction system is integrated with the power supply system through a V/V transformer. Two cases of the connection are considered. The first case, when the traction system is connected to one side of transformer. The second case, when there is a balance traction load on the both transformer side. Finally, PSCAD simulation is used to analyze the power system quality and to estimate the harmonics that are generated in the traction and power supply system sides due to this integration. The simulation results show that, in the both cases, high levels of voltage and current harmonics are generated in the traction side. These harmonics are generated only on the phases that the traction is connected to them, while the other phase will not be affected. Also, it is observed that, the generated harmonics at the traction load side have also been transferred to the power supply system side though the transformer

Bis (benzothiazolyl) benzene and Bis (benzothiazolyl)-4-methyl benzene) Transition Metal Complexes as Catalysts for Ethylene Polymerization: Synthesis, Characterization and Polymerization Activity

A series of 16 complexes of 1,2-bis(benzothiazolyl) benzene and 1,2-bis(benzothiazolyl)-4-methyl benzene compounds with Ti(IV), Zr(IV), V(III), Fe(III), Fe(II), Co(II), Ni(II) and Cu(II) were synthesized and characterized. After activation with methylalumoxane (MAO), these complexes showed variable activities towards ethylene polymerization. The polymerization activities of the catalyst system 3, 5, 7 and 15 /MAO were investigated under different polymerization conditions. The highest activity 625 [Kg PE / mol Cat. H] is obtained by the catalyst system 5/MAO at 50 °C and cocatalyst concentration of 1000 equivalents. The produced resins showed high molecular weights associated with broad or even bimodal molecular weight distributions for all catalysts systems except the polymers produced with nickel catalysts 9 and 17/MAO. DOI: http://dx.doi.org/10.17807/orbital.v9i1.94

Polymerization of Ethylene Catalyzed by Vanadium(III) Complexes

Thirty five  complexes of 1,2- bis(benzimidazole, benzothiazole and benzoxazole)benzene,  1,2-bis(benzimidazole, benzothiazole and benzoxazole)-4-methyl-benzene, 1,2-bis  (benzimidazole, benzothiazole and benzoxazole)4-bromobenzene, 1, 2-bis(benzimidazole, benzothiazole and benzoxazole) 4- chlorobenzene,  and 2, 6-bis(benzimidazole, benzothiazole and benzoxazole) pyridine compounds with V (III) metal centers were synthesized, characterized, activated with methylalumoxane (MAO) and then tested for catalytic ethylene polymerization. The catalysts generally show moderate to good activities compared to the benchmark catalyst Cp2ZrCl2. The activities of the various catalysts were found to be function of the hetero atoms in the ligand frameworks and also strongly influenced by the bridging unit of the ligand. The highest activity was obtained with 36 / MAO (442 kg PE / mol cat. h). The produced polyethylenes showed high molecular weights (up to 2.7 × 106 g/mol) and broad molecular weight distributions (PD = 1.4 - 16.6). Thermal analysis of polyethylenes produced with vanadium complexes revealed that the catalyst systems were capable to produce high density polyethylenes with melting temperatures > 135 °C and crystallization temperatures range from 117-120 °C with high degree of crystallinity. DOI: http://dx.doi.org/10.17807/orbital.v9i3.98

Harnessing Agricultural Services Centers for Agricultural Extension Services: A case Study Gezira state-Wad Medani Great Locality, Sudan

Agricultural Services Centers expect to plays an important role in facilitate marketing of most agricultural commodities such as seeds, feed, fertilizers and pesticides. This paper attempts to realize the Importance of agricultural services centers in supporting agricultural extension services in the study area. The study based on two sources of data, primary and secondary, the primary quantitative and qualitative data were collected from field survey using structured questionnaire (in-depth and repeated interview) which designed and pre-tested. Fifty seven respondents (members ASCs) were randomly selected to represent the study population. Statistical Package for Social Sciences (SPSS) software was used for data analysis (Descriptive Statistic) in addition to correlation and regression analysis to test significant level of variables. The findings indicated that 98% of the respondents were explained that the link with farmers was direct link, 53% stated that the farmers they visits them to get information. 90% of the respondents reported that they provided farmers with input and information, 98% of them explained that their source of inputs was imported companies, and 91% explained that their method to present the information to the farmers was personal explanation. The results of correlation and regression analysis showed Education level had high significant correlation with link with extension (.001) the value (.430), High significant correlation also with the link with extension and Components that you consider more useful in giving information sig (.000) value (.772) and the available components in case of problem sig (.000) value (.774). Imported companies had significant regression value (.457 beta) (.042) in information exchange other partners had no significant. Conclusion: Agricultural Services Centers enhance the role of agricultural extension through marketing of most agricultural commodities. The paper recommends that the service centers workers should look after the recommended information and follow up their inputs after sailing process to the farmers, the extension view should be more than the trading view

The legality of non-forcible counter-measures in international law

The object of this thesis is to examine the legality of nonforcible counter-measures in bilateral contexts. The major questions addressed are as follows: (i) do counter-measures constitute an autonomous category of justification for wrongful conduct? (ii) if so, what are the conditions of the legality of that category? (iii) what are the more significant collateral constraints on the legality of countermeasures? and (iv) what is the extent to which policy considerations contribute towards the determination of the legality of counter-measures? The study begins with an Introduction which indicates the scope and the outline of the thesis, the terminology employed, and the approach adopted. Chapters One and Two deal with the historical development of the law of reprisals with special reference to non-forcible counter-measures. Chapter Three is entitled "The status of non-forcible counter-measures in customary international law since 1945: a preliminary sketch". Chapters Four, Five,and Six are devoted to examining the conditions of the legality of non-forcible counter-measures, viz., (i) breach, (ii) prior demand for reparation; and (iii) proportionality. Chapter Seven examines some of the more significant collateral constraints on the legality of counter-measures. In Chapter Eight an attempt will initially be made to examine the circumstances in which the performance of obligations under a treaty may be withheld as a counter-measure. The conclusions reached will then be compared and contrasted with the regime established by the Vienna Convention on the Law of Treaties. Chapter Nine considers the legality of counter-measures in the context of a commitment to peaceful settlement. Chapter Ten is concerned with the legality of economic coercion, and also with whether the legality of that concept has a bearing on the question of lawful counter-measures. The final Chapter summarises the major characteristics of the existing legal regime of counter-measures.</p