Space-vector-modulated three-level inverters with a single Z-source network

The Z-source inverter is a relatively recent converter topology that exhibits both voltage-buck and voltage-boost capability. The Z-source concept can be applied to all dc-to-ac, ac-to-dc, ac-to-ac, and dc-to-dc power conversion whether two-level or multilevel. However, multilevel converters offer many benefits for higher power applications. Previous publications have shown the control of a Z-source neutral point clamped inverter using the carrier based modulation technique. This paper presents the control of a Z-source neutral point clamped inverter using the space vector modulation technique. This gives a number of benefits, both in terms of implementation and harmonic performance. The adopted approach enables the operation of the Z-source arrangement to be optimised and implemented digitally without introducing any extra commutations. The proposed techniques are demonstrated both in simulation and through experimental results from a prototype converter

Quasi Z-source NPC inverter for PV application

This paper presents the operating principles and modified space vector modulation strategy for a three-phase quasi Z-source neutral point clamped inverter for solar photovoltaic applications. This topology combines the advantages of the neutral point clamped and quasi Z-source inverters. These advantages include single-stage buck-boost power conversion, continuous input current, and low voltage stress of switches. Simulation results are presented to verify the presented concepts

A fuzzy-based evaluation of financial risks in build-own-operate-transfer water supply projects

The build–own–operate–transfer (BOOT) scheme is widely used for the provision of new bulk water supply. However, this scheme is complex and carries significant financial risks because of the characteristics of the water sector and the involvement of public-private stakeholders with new and extended responsibilities, large private capital, and long contract duration. Drawing on the Nungua Seawater Desalination Plant (NSDP) in Ghana, this study seeks to identify and assess the critical financial risks associated with BOOT water supply projects and evaluate the financial risk level of the NSDP project. The risks and their relative criticality on the NSDP project are investigated by using a questionnaire survey method. The questionnaire was formulated with a set of 18 risks derived from extant literature and project documentation. Perceived critical financial risks affecting the NSDP project were assessed by a team of experts who had direct involvement in the project. A fuzzy synthetic evaluation suggests that the project is financially risky and that all the risks are critical to the project. Bankruptcy of consortium members, unfavorable economy of the host country, uncertainty in tariff adjustment of water products, rate of return restrictions, and availability problem of private capital are the five most highly-ranked risks. The fuzzy technique is used to represent and model experiential knowledge of the survey participants and to address the fuzziness of their expert judgments. The study’s results facilitate prioritization of risks and a comprehensive risk management program during the lifecycle of the case project and future projects. The fuzzy technique is suitable for early phases of BOOT projects to prioritize the risks that require a detailed analysis and to predict the risk level of a project

Examining issues influencing green building technologies adoption : the United States green building experts' perspectives

Green building (GB) has been viewed as an effective means to implement environmental, economic, and social sustainability in the construction industry. For the adoption of GB technologies (GBTs) to continue to succeed and gain popularity, a better understanding of the key issues influencing its progress is crucial. While numerous studies have examined the issues influencing green innovations adoption in general, few have specifically done so in the context of GBTs. This study aims to investigate the underpinnings of GBTs adoption in the following areas: (1) the critical barriers inhibiting the adoption of GBTs, (2) major drivers for adopting GBTs, and (3) important strategies to promote GBTs adoption. To achieve these objectives, a questionnaire survey was carried out with 33 GB experts from the United States. Ranking analysis was used to identify the significant issues associated with GBTs adoption. Resistance to change, a lack of knowledge and awareness, and higher cost have been the most critical barriers. The major drivers for adopting GBTs are greater energy- and water-efficiency, and company image and reputation. The analysis results also indicate that the most important strategies to promote the adoption of GBTs are financial and further market-based incentives, availability of better information on cost and benefits of GBTs, and green labelling and information dissemination. The findings provide a valuable reference for industry practitioners and researchers to deepen their understanding of the major issues that influence GB decision-making, and for policy makers aiming at promoting the adoption of GBTs in the construction industry to develop suitable policies and incentives. This study contributes to expanding the body of knowledge about the influences that hinder and those that foster GBTs implementation

Novel current-limiting strategy for solid-state circuit breakers (SSCB) without additional impedance

Current-limiting strategies for solid-state circuit breaker (SSCB) without adding impedance is introduced in this paper. With the current limitation of novel phase-shifting method, the advantages are simple hardware structure, relatively low cost, no heat generation, low weight and small size. Current-limiting capability is exploited with qualities of good control accuracy and robustness. The principle and theoretical analysis of phase-shifting current-limiting method are detailed introduced together with simulation/experimental verifications

Emergence and Constraints of Enterprise Platform Silos for Online Interactions: A Case Study from Ghana Before and During Covid-19

The purpose of this study is to understand the emergence and constraints of enterprise platform silos for online interactions at the organizational level. Information systems (IS) research has focused more on external platforms without silos. As a result, not much is known about internal platforms and silos at the organizational level and how they constrain online interactions, especially in the developing economic context of Africa. This study follows an interpretive, qualitative case study methodology and the encounter-episode process model to investigate the case of using enterprise platform silos in an organization in Ghana, before and during Covid-19. The findings show how failure to modernize the installed-based platforms, integrate platform portfolios, use enterprise architecture, and build internal competence for platform integration leads to silos. Identified constraints include challenges with information sharing and transfer between platforms, manual intervention with delays and errors, and multiple sign-ins with different password formats per user

Semiconductor devices in solid-state/hybrid circuit breakers: current status and future trends

Circuit breakers (CBs) are the main protection devices for both alternating current (AC) and direct current (DC) power systems, ranging from tens of watts up to megawatts. This paper reviews the current status for solid-state circuit breakers (SSCBs) as well as hybrid circuit breakers (HCBs) with semiconductor power devices. A few novel SSCB and HCB concepts are described in this paper, including advantage and limitation discussions of wide-band-gap (WBG) devices in basic SSCB/HCB configuration by simulation and 360 V/150 A experimental verifications. Novel SSCB/HCB configurations combining ultra-fast switching and high efficiency at normal operation are proposed. Different types of power devices are installed in these circuit breakers to achieve adequate performance. Challenges and future trends of semiconductor power devices in SSCB/HCB with different voltage/power levels and special performance requirements are clarified

Slum or Sustainable Development? A Case Study of Sodom and Gomorrah in Accra, Ghana

The Accra Metropolitan Assembly (AMA) has been successful in demolishing a few slums in the City of Accra. However, Sodom and Gomorrah, also known to be a squatter and an illegal settlement in the City of Accra continues to prosper. This study examines the benefits and shortcomings of slums with specific reference to Sodom and Gomorrah and why it has avoided all demolition attempts by AMA. It also examines whether slums can be improved to promote sustainable urban development in Ghana. The researcher explored these issues with surveys which elicited the opinions and experiences of slum dwellers in Sodom and Gomorrah as well as neighboring high and middle income residents. The researcher also surveyed the views of opinion leaders who constituted the mouth piece of the squatters to further test for consistency of the responses of slum dwellers. City officials of the AMA and The Town and Country Planning Department (TCPD) were also interviewed regarding the surrounding government\u27s inability to demolish it, threats posed by the study area to city government, the benefits of the development and whether it should be demolished. As indicated, the need and relevance for this study emerges from the illegal status of the study area and its ability to escape all demolition attempts by city governments. Its flourishing nature and location in the urban hub of the capital city as well as proximity to the central business district compels further exploration regarding why Sodom and Gomorrah continues to prosper unabated

Artificial Intelligence Powered Chatbot for Business

Text has become an essential interaction manner between people. The use of chatbots improved quickly in business area including marketing, customer service and e-commerce. Users value chatbots because they are fast, intuitive and convenient. This paper discussed about the artificial intelligence technology that used to develop and implement chatbots which can the organization used to benefit in their businesses. A chatbot is a computer program that can interact with a human by using natural language. The main three areas in business that using chatbot the most are marketing, customer service and e-commerce fields. The roles of chatbot in mentioned areas has been discussed in this paper. AI powered chatbots transform business by reducing costs, increasing revenue and enhancing the customer experience. The benefits and limitation of chatbots have been also discussed in this paper

Assessing the applicability of student-based brand equity constructs in university institution preference in Ghana

With ad-hoc application of the traditional element of marketing failing to sustainably cushion institutions against growing competition, universities are frantically searching for ways to differentiate themselves in the long term. This study ascertains the applicability of five empirically established brand equity constructs to Ghana’s university industry. It is underpinned by a pragmatist philosophy - an objective-driven blend between the ontological and epistemological philosophical positions, and adopts a mixed-methods paradigm that combines qualitative and quantitative survey methods of data collection and analysis. For the qualitative part, 22 valid face-to-face in-depth interviews with undergraduate students selected from four universities were used while the quantitative study used 625 self-administered questionnaires from undergraduate students from twelve universities. Thematic analysis was used for the qualitative data while for the quantitative data, the structural equation modelling technique of partial least squares (PLS) was employed to ascertain relationships between the five independent student-based brand equity (SBBE) constructs on one hand, and students’ university brand preference (SUBP) as a dependent variable, on the other. Results of the analysis indicate a positive relationship between most of the SBBE constructs studied and university preference in Ghana. Four SBBE dimensions namely; university institutional reputation (UIR), university institutional image (UII), university graduate employability (UGE) and perceived institutional service quality (PISQ) recorded significant positive relationships with students’ university preference (SUP). Positive relationships were also obtained between university image and university reputation, university identity and university reputation, as well as between perceived institutional service quality and graduate employability. On the contrary, an insignificant relationship was obtained between university institutional identity (UI) and students’ university preference. The correlation analysis also indicates significant positive relationships among all the independent SBBE variables. Cumulatively, the results indicate that the SBBE concept is applicable to Ghana’s university context as the SBBE constructs and university preference are positively related. The prevalence of reputation, image, graduate employability and perceived institutional service quality in the research findings has implications for policy in the university sector. Also worthy of note is the significant positive relationship obtained between perceived institutional service quality and graduate employability; as well as between university institution identity, university institution image and university institution reputation. Much of the existing academic work on higher education branding has concentrated on brand equity’s antecedents and consequences. This study links empirically proven antecedents of university brand equity to university preference. Also, most of existing empirical research on brand equity in the university sector has focused on developed countries whose circumstances are fundamentally different from those of developing economies. This study is a novelty in the sub-Saharan African context where student-focused university branding is uncommon; and so comes as a significant contribution from Ghana, to the growing worldwide debate on university branding. While contributing a survey instrument that enhances SBBE research methodology, theoretically, the unique blend of SBBE constructs employed is unprecedented. Notwithstanding some limitations identified, this study presents an empirical model that stands to guide university management in judiciously dispensing scarce resources