Microwave bandpass filters using re-entrant resonators.

Design techniques for microwave bandpass filters using re-entrant resonators are presented. The key feature is that each re-entrant resonator in the filter generates a passband resonance and a finite frequency transmission zero, above the passband. Thus an Nth degree filter can have N finite frequency transmission zeros with a simple physical realization. A physically symmetrical 5 pole re-entrant bandpass filter prototype with 5 transmission zeros above the passband was designed and fabricated. Measured results showed good correspondence with theories

Design of generalised Chebyshev lowpass filters using coupled line/stub sections

A new method for the design of distributed lowpass filters enables exact realisation of the series short circuited transmission lines which are normally approximated via unit elements in other filter realisations. The filters are based upon basic sections using a pair of coupled lines which are terminated at one end in open-circuited stubs. The approach enables realisation of transmission zeros at the quarter –wave frequency hence giving improved stopband performance. A complete design is presented and demonstrates performance in good agreement with theory

Transversal directional filters for channel combining

A new concept for the design of power combiners based on matched directional filters is presented. The directional filters consist of individual balanced sections composed of hybrids and single resonators. Each of the sections corresponds to a pole of an all-pass function composed of the sum of S11 and S12 of the desired filter transfer function. A simple synthesis method is presented. The filter combiner has the advantage of ease of tunability because each pole is associated with a single resonator. Furthermore, no cross couplings are required to realize finite frequency transmission zeros

Southern Africa Consortium for Research Excellence (SACORE): successes and challenges

Copyright © Mandala et al. Open access article distributed under the terms of CC BY.Published Online November 13, 2014 http://dx.doi.org/10.1016/S2214-109X(14)70321-

The epidemiology of gonorrhoea, chlamydial infection and syphilis in four African cities.

OBJECTIVES: To compare the epidemiology of gonorrhoea, chlamydial infection and syphilis in four cities in sub-Saharan Africa; two with a high prevalence of HIV infection (Kisumu, Kenya and Ndola, Zambia), and two with a relatively low HIV prevalence (Cotonou, Benin and Yaoundé, Cameroon). DESIGN: Cross-sectional study, using standardized methods, including a standardized questionnaire and standardized laboratory tests, in four cities in sub-Saharan Africa. METHODS: In each city, a random sample of about 2000 adults aged 15-49 years was taken. Consenting men and women were interviewed about their socio-demographic characteristics and their sexual behaviour, and were tested for HIV, syphilis, herpes simplex virus type 2 (HSV-2), gonorrhoea, chlamydial infection, and (women only) Trichomonas vaginalis infection. Risk factor analyses were carried out for chlamydial infection and syphilis seroreactivity. RESULTS: The prevalence of gonorrhoea ranged between 0% in men in Kisumu and 2.7% in women in Yaoundé. Men and women in Yaoundé had the highest prevalence of chlamydial infection (5.9 and 9.4%, respectively). In the other cities, the prevalence of chlamydial infection ranged between 1.3% in women in Cotonou and 4.5% in women in Kisumu. In Ndola, the prevalence of syphilis seroreactivity was over 10% in both men and women; it was around 6% in Yaoundé, 3-4% in Kisumu, and 1-2% in Cotonou. Chlamydial infection was associated with rate of partner change for both men and women, and with young age for women. At the population level, the prevalence of chlamydial infection correlated well with reported rates of partner change. Positive syphilis serology was associated with rate of partner change and with HSV-2 infection. The latter association could be due to biological interaction between syphilis and HSV-2 or to residual confounding by sexual behaviour. At the population level, there was no correlation between prevalence of syphilis seroreactivity and reported rates of partner change. CONCLUSION: Differences in prevalence of chlamydial infection could be explained by differences in reported sexual behaviour, but the variations in prevalence of syphilis seroreactivity remained unexplained. More research is needed to better understand the epidemiology of sexually transmitted infections in Africa

Maternity waiting homes as an intervention to increase facility delivery in rural Zambia

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150534/1/ijgo12864_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150534/2/ijgo12864.pd

Integrated Pest Management (IPM) Components for Control of Armored Bush Cricket on Pearl Millet and Sorghum in Farmers' Fields in Namibia and Zambia

Armored bush crickets (Acanthoplus spp.) are sporadic pests on cereals in southern Africa. The performance of different IPM components on pearl millet [Pennisetum glaucum] in Namibia and sorghum in Namibia and Zambia is reported, based on on-farm participatory trials

Investigation of Stored Energy Distribution in Filters Using K-Means Clustering Algorithm

The k-means clustering algorithm has been implemented to find patterns in the time-averaged stored energy distribution in various filter networks. A large data set comprising of numerous topologies for 50 different single band specifications has been investigated. By finding key characteristics within this data set, general guidelines for predicting the optimum topology for power handling have been established

Challenges and advocated solutions for environmental protection legislation for building infrastructure projects in developing countries: Evidence from Zambia

Environment protection legislation is often inadequate and poorly implemented in Africa even though literature shows that it is important for environmental protection. Furthermore, there is a paucity of studies which examine the catalytic role of legislation in the building infrastructure sustainability agenda. Therefore, to bridge that knowledge gap, this study examined the adequacy of environment protection legislation for building infrastructure projects in Zambia and their associated challenges and solutions. The study used an exploratory qualitative approach using semi-structured interviews with key stakeholders on environment protection. The study theorises that environment protection legislation in Zambia is fairly adequate but with inadequacies in its implementation, some with omitted content, and poor understanding of the importance of environment protection. Solutions include increasing the level of implementation of the legislation and championing awareness of the importance of protecting the environment. The findings have implications for sustainability transitioning in Africa

Challenges, drivers and incentives to private sector participation in public-private partnership projects in developing countries: evidence from Zambia

Purpose Governments in developing countries seeking to meet their infrastructure backlog are increasingly turning to public–private partnerships (PPP) due to a lack of public funds. However, while there are factors which drive the current uptake of projects, there are challenges with attracting private finance, and it is not clear what incentives can be used to attract more private participation, especially in sub-Saharan Africa (SSA). Therefore, this study aims to examine challenges, drivers and incentives that affect private participation in PPP projects in Zambia. Design/methodology/approach The study used a qualitative approach with semi-structured interviews with participants who had first-hand experience working on the administration of PPP projects. The participants were predominantly from the public sector, and so the results are largely a public sector perspective on the matter. Findings The findings show that bureaucracy and a poor business environment emanating from poor policies, long procedures and a poor economic environment are the main challenges affecting PPP projects. The current demand for the projects is being driven by a stable business and economic environment while incentives include enhancing the business environment by improving procedures and policies. Originality/value The study contributes to extant literature by proposing an overarching theory about the challenges affecting the implementation of PPP projects in Zambia, in particular, and in SSA, in general. The results show areas where governments and government agencies responsible for PPP projects can focus attention to promote private participation