Stochastic Methods for Aircraft Design

The global stochastic optimization method, simulated annealing (SA), was adapted and applied to various problems in aircraft design. The research was aimed at overcoming the problem of finding an optimal design in a space with multiple minima and roughness ubiquitous to numerically generated nonlinear objective functions. SA was modified to reduce the number of objective function evaluations for an optimal design, historically the main criticism of stochastic methods. SA was applied to many CFD/MDO problems including: low sonic-boom bodies, minimum drag on supersonic fore-bodies, minimum drag on supersonic aeroelastic fore-bodies, minimum drag on HSCT aeroelastic wings, FLOPS preliminary design code, another preliminary aircraft design study with vortex lattice aerodynamics, HSR complete aircraft aerodynamics. In every case, SA provided a simple, robust and reliable optimization method which found optimal designs in order 100 objective function evaluations. Perhaps most importantly, from this academic/industrial project, technology has been successfully transferred; this method is the method of choice for optimization problems at Northrop Grumman

GENERIC BUSINESS STRATEGIES IN THE MICRO AND SMALL ENTERPRISE TYPOLOGY: AN EMPIRICAL INVESTIGATION AMONG NAIROBI MANUFACTURING MICRO AND SMALL ENTERPRISES

Micro and Small Enterprises (MSEs) play a significant role in Sub-Saharan Africa national economies, however, few transition to formal medium or large size enterprises due to a wide array of challenges faced. The MSE typology sought to provide an array of business strategies MSEs could use to overcome these challenges and improve their performance. A central foundation of the typology is the generic nature of the strategies, that is general applicability across industry, organization type or size. The general objective of this study, therefore, was to determine the extent to which the business strategies within the typology are indeed generic. The study evaluated the generalization across two sub-sectors (Furniture manufacturing and agro-food processing) as well as across gender (taken as male and female). From the study, and using binary logistic regression only two of the twenty-eight variables were statistically significant, albeit mild discriminant, therefore supporting generalizability across sub-sectors. In addition, none of the variables served as statistically significant discriminants between male or female owners. Though limited in scope the generic nature of the defined strategies was established, providing support for the MSE typology meeting the generic requirement from typology theory

EMPIRICAL VALIDATION OF AN MICRO AND SMALL ENTERPRISES TYPOLOGY: IMPACT OF PERFORMANCE ON MICRO AND SMALL ENTERPRISES IN NAIROBI

The Micro and Small Enterprises (SMEs) typology suggests competitive business strategies that MSEs can use to overcome the challenges they face and improve their performance. The typology combines strategic alliance (collaboration) and competency (differentiation and low cost) theories. The general objective of this study was the empirical determination of the extent to which the application of business strategies based on the MSE typology is associated with better performance. The study was carried out among Nairobi informal sector MSEs in the manufacturing sector. From the results, the ideal types captured in the typology were supported. In addition, there was partial support of better performance among four of the nine classes of strategies within the typology. These accounted for 64.8 percent of the sampled enterprises. None of the enterprises that did not fit into any of the classes, however, performed better than those that did

Y Chromosome Lineages in Men of West African Descent

The early African experience in the Americas is marked by the transatlantic slave trade from ∼1619 to 1850 and the rise of the plantation system. The origins of enslaved Africans were largely dependent on European preferences as well as the availability of potential laborers within Africa. Rice production was a key industry of many colonial South Carolina low country plantations. Accordingly, rice plantations owners within South Carolina often requested enslaved Africans from the so-called “Grain Coast” of western Africa (Senegal to Sierra Leone). Studies on the African origins of the enslaved within other regions of the Americas have been limited. To address the issue of origins of people of African descent within the Americas and understand more about the genetic heterogeneity present within Africa and the African Diaspora, we typed Y chromosome specific markers in 1,319 men consisting of 508 west and central Africans (from 12 populations), 188 Caribbeans (from 2 islands), 532 African Americans (AAs from Washington, DC and Columbia, SC), and 91 European Americans. Principal component and admixture analyses provide support for significant Grain Coast ancestry among African American men in South Carolina. AA men from DC and the Caribbean showed a closer affinity to populations from the Bight of Biafra. Furthermore, 30–40% of the paternal lineages in African descent populations in the Americas are of European ancestry. Diverse west African ancestries and sex-biased gene flow from EAs has contributed greatly to the genetic heterogeneity of African populations throughout the Americas and has significant implications for gene mapping efforts in these populations

Understanding interactions in face-to-face and remote undergraduate science laboratories

This paper reviews the ways in which interactions have been studied, and the findings of such studies, in science education in both face-to-face and remote laboratories. Guided by a systematic selection process, 27 directly relevant articles were analysed based on three categories: the instruments used for measuring interactions, the research findings on student interactions, and the theoretical frameworks used in the studies of student interactions. In face-to-face laboratories, instruments for measuring interactions and the characterisation of the nature of interactions were prominent. For remote laboratories, the analysis of direct interactions was found to be lacking. Instead, studies of remote laboratories were mainly concerned with their practical scope. In addition, it is found that only a limited number of theoretical frameworks have been developed and applied in the research design. Existent theories are summarised and possible theoretical frameworks that may be implemented in studies of interactions in undergraduate laboratories are proposed. Finally, future directions for research on the interrelationship between student interactions and laboratory learning are suggested