The Performance of Traditional contract procurement on Housing projects in Nigeria.

The traditional contract procurement has been widely criticized as an ineffective procurement method because it often involves time and cost overrun on construction projects. Yet the method is still being widely used in Nigeria most especially for the procurement of housing projects. It is suspected that this procurement method may not be ineffective in all cost categories of housing projects. Therefore time and cost performances of the procurement method on 57 housing projects of varying cost categories initiated by the Nigerian government between 1993 and 1999 were studied. The category of one to five million naira (US$1.00 ≈ 92 Nigerian Naira in 1999) showed the least time overrun of 18.98% while the highest time overrun of 99.64 % was shown in the five to ten million naira. The over ten million naira category had the least cost overrun of 9.13% while the highest cost overrun of 34.55 % was shown in the less than one million naira. The one to five million naira cost category exhibited weak correlation between time and cost overruns but the five million naira and above categories showed strong correlation. It was concluded that one to five million naira cost category is quite suitable for traditional contract procurement on housing projects in Nigeria

Towards a time-domain modeling framework for small-signal analysis of unbalanced microgrids

Small-signal analysis is one of the most frequently used techniques to assess the operating conditions of power systems. Typically, this analysis is conducted by employing a phasor-based model of the power network derived under the assumption of balanced operating conditions. However, distribution networks and, amongst these, microgrids are often unbalanced. Hence, their analysis requires the development of tools and methods valid under such conditions. Motivated by this, we propose a modeling approach for generic nonlinear and unbalanced three-phase microgrids, which allows to derive a small-signal model in a standard fashion. The approach is based on a time-domain decomposition of the electrical waveforms in positive and negative synchronous reference frames. The efficacy of the approach is demonstrated via application to an exemplary unbalanced microgrid

An Improved Control Scheme for Grid-forming Inverters

In order to reduce the reliance of power grids on conventional (and often non-renewable) generation, reliable and dispatchable converter-interfaced distributed generators (DGs) are required. Instead of relying on large rotating machines for frequency and voltage regulation, it becomes crucial to develop improved control schemes for grid-forming inverters. In this paper we propose a simple and effective frequency and voltage control scheme that offers desirable dynamic response and power sharing. The proposed controller is compared to the conventional hierarchical control scheme via a stability analysis of the overall system dynamics and time-domain simulation results. It is shown that the transient performance and the stability properties are significantly improved.ERC starting grant 67977

Frequency and voltage control schemes for three-phase grid-forming inverters

Grid-forming inverters play an important role in supporting power systems with low rotational inertia. Their frequency and voltage control policies must guarantee a synchronised operation, accurate power sharing amongst inverters, and a good transient response. Simultaneously achieving the latter two requirements is in general a non-trivial problem and existing schemes in the literature often focus on one of these two aspects. In this paper, we propose a simple frequency controller that uses the inverter output current as feedback to adapt its frequency, and also propose controllers for the regulation of the DC and AC voltages. We show that the proposed control architectures achieve both power sharing without a communication link, and desirable passivity properties that can enhance the dynamic performance. Closed loop stability of the grid-forming inverter with a dynamic load is also proven and simulations on advanced models are carried out to validate the results.ERC starting grant 67977

Comparative Study of the Influence of the Home Background on Student\'s Achievement in Mathematics in Bensihangul Gumuz Regional State of Ethiopia.

The purpose of this study was finding out how the various home environments in which students live affect the development of their ability to continue with school academic success. It sought to establish if there was any relationship between the home front and the students' academic achievement. Within these environments, measurable characteristics would be the home background. Socioeconomic differences were conventionally indexed by such demographic variables as household income, parents' education, occupation, and the social status. The study was carried out X-post facto and the methods the researchers used were statistical correlation and ANOVA. Results showed that the home and its environment could predict academic achievement. The regression analyses showed no significant difference in the attitudes of students from different homes towards the learning of mathematics. The study made useful suggestions and recommendations for policy making. African Research Review Vol. 2 (1) 2008: pp. 94-10

Women’s accessibility to resources of agricultural productivity in Borno state, Nigeria

This study set out to investigate the extent of women’s accessibility to resources of agricultural productivity in Borno state, Nigeria. Data for the study were obtained from primary sources by the use of structured questionnaire. Multistage sampling technique was used to select 266 women farmers. The data obtained from the study was analyzed by the use of descriptive statistics. The results showed that the respondents had mean age of 39.5 years, mean farming experience of 17.2 years, while mean family size was 10 persons. Over 80% of the respondents were married. Furthermore, the findings showed that the respondents had the highest access to farm income, farm management decision making powers, farm land and off farm income. However, their access to extension services, education, cooperatives, production inputs and credit were limited. It was recommended among others that agricultural input distribution should be gender sensitive to afford women increased access to resources. Key Words: Women, Access, Productive resources, Productivit

Women’s Accessibility to Resources of Agricultural Productivity in Borno State, Nigeria

This study set out to investigate the extent of women’s accessibility to resources of agricultural productivity in Borno state, Nigeria. Data for the study were obtained from primary sources by the use of structured questionnaire. Multistage sampling technique was used to select 266 women farmers. The data obtained from the study was analyzed by the use of descriptive statistics. The results showed that the respondents had mean age of 39.5 years, mean farming experience of 17.2 years, while mean family size was 10 persons. Over 80% of the respondents were married. Furthermore, the findings showed that the respondents had the highest access to farm income, farm management decision making powers, farm land and off farm income. However, their access to extension services, education, cooperatives, production inputs and credit were limited. It was recommended among others that agricultural input distribution should be gender sensitive to afford women increased access to resources. Keywords: Women, Access, Productive resources, Productivity

A Scalable Control Design for Grid-Forming Inverters in Microgrids

Microgrids are increasingly recognized as a key technology for the integration of distributed energy resources into the power network, allowing local clusters of load and distributed energy resources to operate autonomously. However, microgrid operation brings new challenges, especially in islanded operation as frequency and voltage control are no longer provided by large rotating machines. Instead, the power converters in the microgrid must coordinate to regulate the frequency and voltage and ensure stability. We consider the problem of designing controllers to achieve these objectives. Using passivity theory to derive decentralized stability conditions for the microgrid, we propose a control design method for grid-forming inverters. For the analysis we use higher-order models for the inverters and also advanced dynamic models for the lines with an arbitrarily large number of states. By satisfying the decentralized condition formulated, plug-and-play operation can be achieved with guaranteed stability, and performance can also be improved by incorporating this condition as a constraint in corresponding optimization problems formulated. In addition, our control design can improve the power sharing properties of the microgrid compared to previous non-droop approaches. Finally, realistic simulations confirm that the controller design improves the stability and performance of the power network.ERC starting grant 67977

An Evaluation of Traditional Contract Method on Residential Building Projects

In order of priority of basic human needs, housing is recognized worldwide as second ·to food and comes before clothing. This high priority coupled with United Nations aggressive campaign for adequate shelter for all citizenry has forced governments of nations to embark on direct construction of housing units for their people. In Nigeria, government direct intervention in housing delivery to the masses took the form of traditional contract procurement. This paper reports the result of a survey carried out to know the performance of this procurement method in relation to time and cost overrun. Valid data from fifty-seven residential projects ranging from one million to one hundred million Naira in itiated by government between 1993 and 1999 couple with questionnaires administered on Clients, consultants and contractors were used for the analysis was to establish whether there is significant difference between the mean time overruns and the mean cost overruns of traditional contract on residential projects of different cost categories. The result showed that the traditional contract performs better in terms of time overruns (18.98%) when used to procure residential building projects of five million Naira and below. However the procurement method performs better in terms of cost overrun(9.13%) for projects above ten million Naira. Attempts were also made to know if a relationship exists between time and cost in each category