Optical wireless communication based indoor positioning algorithms: performance optimisation and mathematical modelling

In this paper, the performance of the optimal beam radius indoor positioning (OBRIP) and two-receiver indoor positioning (TRIP) algorithms are analysed by varying system parameters in the presence of an indoor optical wireless channel modelled in line of sight configuration. From all the conducted simulations, the minimum average error value obtained for TRIP is 0.61 m against 0.81 m obtained for OBRIP for room dimensions of 10 m × 10 m × 3 m. In addition, for each simulated condition, TRIP, which uses two receivers, outperforms OBRIP and reduces position estimation error up to 30%. To get a better understanding of error in position estimation for different combinations of beam radius and separation between light emitting diodes, the 90th percentile error is determined using a cumulative distribution frequency (CDF) plot, which gives an error value of 0.94 m for TRIP as compared to 1.20 m obtained for OBRIP. Both algorithms also prove to be robust towards change in receiver tilting angle, thus providing flexibility in the selection of the parameters to adapt to any indoor environment. In addition, in this paper, a mathematical model based on the concept of raw moments is used to confirm the findings of the simulation results for the proposed algorithms. Using this mathematical model, closed-form expressions are derived for standard deviation of uniformly distributed points in an optical wireless communication based indoor positioning system with circular and rectangular beam shapes

Computing by everyone for everyone

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The viewpoint draws upon a wide variety of experiences and observations in order to reassess the status of information ethics action. Some empirical examples are used to demonstrate the need to refocus action in the information ethics field. The traditional view of focusing ethical action on professionals is challenged and a new action paradigm is proposed

Poetical potentials: the value of poems in social impact education

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.For the technologist it is easy to remain in safe technological enclaves with a bespoke language, a community of like minds and a familiar knowledge base. However, progress requires pushing the boundaries, thinking beyond the traditional and the ordinary, and questioning accepted norms. It requires opening of minds. It may surprise the reader that poetry can offer the key to unlock the closed mind. This potential is explored through a variety of poems dealing, in a novel manner, with the social impact of technology

No. 03: International Migration, Immigrant Entrepreneurs and South Africa’s Small Enterprise Economy

Since 1990 there has been a growing movement of foreign migrants and refugees to South Africa. The migrants have come primarily from South Africa’s traditional supply areas, including many Southern African Development Community (SADC) countries. An increasing number, however, are from elsewhere in Africa and further afield. South Africa’s new migration regime has generated considerable controversy within the country. The policy debate focuses on the implications of migration for the national labour market and for the development of new national immigration policy. The best-documented form of migration by temporary workers is from surrounding African countries in such sectors as mining and agriculture. Less well-known are the migrants and new immigrants who have established themselves in the informal and small enterprise economy. This report examines and analyses the role of new foreign migrants working in the small, medium and micro enterprise (SMME) sector of South Africa’s major city, Johannesburg, is of particular interest because it is the focal point for much of the current international migratory flow into South Africa. The study is based on a detailed survey of 70 immigrant entrepreneurs who have established small businesses in Johannesburg. These entrepreneurs operate their businesses in the inner-city of Johannesburg, an area which has experienced dramatic changes in its organisation, residential complexion and business make-up over the last decade. Large parts of the inner-city have, in fact, been taken over by foreign migrants. Foreign-owned SMMEs are now a particularly significant element of the changing economy and landscape of inner-city Johannesburg. Several general conclusions can be drawn about foreign migrant involvement in the SMME sector: The kinds of businesses established by immigrant entrepreneurs fall within a relatively narrow band of activities. Most SMMEs are in retail or service rather than production activities. In our sample, business activities included selling curios, retailing ethnic clothes and foods, motor-car repairs/panelbeating and hairdressing salons. Other activities included the operation of restaurants, nightclubs, cafés, a music shop, several import-export businesses and one traditional healer. Among the group of production SMMEs, many are clustered in the clothing sector. Activities include making traditional African clothes, wedding dresses, and general tailoring. Distinct clusters emerged in the kinds of businesses operated by migrants from particular countries. Malawian immigrants tend to be involved in clothes production or curio selling; Zimbabweans and Mozambicans in motor-car repair or curio selling; and West Africans in ethnic businesses related to clothes, food retailing and the operation of restaurants. Typically, these new immigrant businesses are run by single, young, male entrepreneurs who work long hours. On average the entrepreneurs work a 64-hour week. Employees work similar hours. The entrepreneurs often endure considerable hostility towards both themselves and their businesses as a result of xenophobic sentiment and actions. Despite a sometimes difficult local climate in which to operate, most immigrant entrepreneurs express optimism and look to the possibilities of expanding their existing business in South Africa. Despite Johannesburg’s tarnished popular image of crime and violence, the entrepreneurs interviewed preferred to run their businesses there. Proximity to home (for SADC citizens), strong market potential and networks of family and friends are all important reasons. Among these immigrants, Johannesburg enjoys a far more positive image than might be expected. The study allows us to distinguish two distinct groups of migrant-entrepreneurs, namely migrants from SADC countries and non-SADC migrants. The research points to a number of marked differences between SMMEs operated by SADC and non-SADC migrants. Many of the businesses operated by migrants are integrated into and supported by wider international (non-SADC migrants) and regional (SADC migrants) networks. Overall, some 65% of the sample operated like businesses in their countries of origin. Non- SADC entrepreneurs have wide international family and business connectivity including links to West Africa, Canada, the United States of America and Europe. Most SADC entrepreneurs acquired their start-up capital from previous jobs in South Africa. Most non-SADC entrepreneurs financed their businesses with funds brought in from outside South Africa. Businesses run by SADC immigrants are smaller and seemingly less well-capitalised than those of their non- SADC counterparts. Part of the diversity and strength of the non-SADC run businesses derives from their exploitation of income niches as “ethnic businesses” and of Francophone culture in general. Immigrant entrepreneurs from non-SADC countries are better educated than those from SADC countries and have wider horizons in their business development strategies. Some 50% of non-SADC entrepreneurs had some university-level education. Three had masters degrees and one was a qualified dentist. The majority of SADC entrepreneurs had a secondary school education. The entrepreneurs face a number of problems operating their businesses. Most frequently cited were (a) access to finance and credit including difficulties opening bank accounts; (b) problems associated with acquiring visas and permits and dealing with customs (with SADC migrants experiencing greater problems); (c) harassment by police and local officials; and (d) being targeted by criminals and gangs. The most important set of policy-relevant findings in this study relate to the role of foreign-owned SMMEs in job creation: The SMME’s in the study had created a total of 227 job opportunities (or 3,33 jobs per business). Non-SADC businesses created more jobs on average (4,06 per enterprise) than SADC businesses (2,65), but both groups clearly created employment. Within SADC enterprises, some 53% of employees are from the home country. The figure for non-SADC enterprises is much lower (at 27%). Non-SADC enterprises, particularly Francophone-owned, tend to employ non-home country migrants as well, but some 50% of employees are South Africans. Most entrepreneurs begin by employing relatives or fellow immigrants from the home country. After a period of consolidation and growth, they begin to employ more South Africans. These small immigrant-run businesses are thus clearly contributing directly towards local job creation in Johannesburg for South Africans. Once the business is well-established, the major beneficiaries in job creation are South Africans. In the long-term, given the continuing prosperity and growth of these enterprises, an ever-increasing proportion of South African workers will be absorbed into these small businesses. In combating the xenophobia that surrounds foreign-owned business, it is essential that national and local policy-makers appreciate and openly acknowledge the positive role - both existing and potential - of these businesses. In particular, this issue will be crucial in the context of future job creation and local economic development planning for Johannesburg. In fact, given the concentration of businesses and entrepreneurs’ residences in the inner-city areas of Johannesburg, city planners and policy-makers should not overlook the potential contribution of these SMMEs towards the economic and social regeneration of inner-city Johannesburg. The same could be true of other South African cities

The employment of nations — a primer

This paper examines low-frequency movements in employment in a cross-section of industrialized countries for the period 1960–95, using both aggregate and disaggregated data. It documents nine stylized facts about cross-country variations in employment.Employment (Economic theory)

Taxation and Market Work: Is Scandinavia an Outlier?

This paper argues that it is essential to explicitly consider how the government spends tax revenues when assessing the effects of tax rates on aggregate hours of market work. Different forms of government spending imply different elasticities of hours of work with regard to tax rates. I illustrate the empirical importance of this point by addressing the issue of hours worked and tax rates in three sets of economies: the US, Continental Europe and Scandinavia. While tax rates are highest in Scandinavia, hours worked in Scandinavia are significantly higher than they are in Continental Europe. I argue that differences in the form of government spending can potentially account for this pattern.

Anti-symmetric motion of a pre-stressed incompressible elastic layer near shear resonance

A two-dimensional model is derived for anti-symmetric motion in the vicinity of the shear resonance frequencies in a pre-stressed incompressible elastic plate. The method of asymptotic integration is used and a second-order solution, for infinitesimal displacement components and incremental pressure, is obtained in terms of the long-wave amplitude. The leading-order hyperbolic governing equation for the long-wave amplitude is observed to be not wave-like for certain pre-stressed states, with time and one of the in-plane spatial variables swapping roles. This phenomenon is shown to be intimately related to the possible existence of negative group velocity at low wave number, i.e. in the vicinity of shear resonance frequencies

A two-dimensional model for extensional motion of a pre-stressed incompressible elastic layer near cut-of frequencies

A two-dimensional model for extensional motion of a pre-stressed incompressible elastic layer near its cut-off frequencies is derived. Leading-order solutions for displacement and pressure are obtained in terms of the long wave amplitude by direct asymptotic integration. A governing equation, together with corrections for displacement and pressure, is derived from the second-order problem. A novel feature of this (two-dimensional) hyperbolic governing equation is that, for certain pre-stressed states, time and one of the two (in-plane) spatial variables can change roles. Although whenever this phenomenon occurs the equation still remains hyperbolic, it is clearly not wave-like. The second-order solution is completed by deriving a refined governing equation from the third-order problem. Asymptotic consistency, in the sense that the dispersion relation associated with the two-dimensional model concurs with the appropriate order expansion of the three-dimensional relation at each order, is verified. The model has particular application to stationary thickness vibration of, or transient response to high frequency shock loading in, thin walled bodies