Connecting political economies of energy in South Africa

The South African energy debate is and will remain a heated one. Given South Africa's history of racial inequality and contemporary concerns around sustainability, much of it rightly focuses on the links between energy, poverty and the environment. Yet, many contributions to the (mainstream) debate seem to have a somewhat one-sided focus that might hamper rather than stimulate the understanding of these links. They either display a strong technical, quantitative bias and/or lean towards rather simplistic ideas about policy processes and dynamics. The article argues that many of these analyses could benefit greatly from a critical focus on the political economy of energy: the political–economic power structures that influence both many energy policies and the issues of energy equality and sustainability. Two major global developments emphasise the importance of this focus: the recent financial crisis and South Africa's role in the increasingly tense geopolitics of energy in Africa. The article concludes with some suggestions on how currently disparate political economies of energy could be better connected.     

Low-Frequency Noise Phenomena in Switched MOSFETs

In small-area MOSFETs widely used in analog and RF circuit design, low-frequency (LF) noise behavior is increasingly dominated by single-electron effects. In this paper, the authors review the limitations of current compact noise models which do not model such single-electron effects. The authors present measurement results that illustrate typical LF noise behavior in small-area MOSFETs, and a model based on Shockley-Read-Hall statistics to explain the behavior. Finally, the authors treat practical examples that illustrate the relevance of these effects to analog circuit design. To the analog circuit designer, awareness of these single-electron noise phenomena is crucial if optimal circuits are to be designed, especially since the effects can aid in low-noise circuit design if used properly, while they may be detrimental to performance if inadvertently applied     

Developing semantic VR-shops for e-Commerce

Increased bandwidth, cheaper and faster hardware, dedicated technology and the success of e-commerce make VR-shops feasible. VR-shops are similar to the e-shops currently available on the Web, with the difference that the products are visualized as 3D objects in a virtual world. Although VR-shops do not require sophisticated VR technology, they should be very flexible: it should be easy to add, remove and rearrange products; and to add, change or remove functionality. Therefore, an appropriate approach that can be used by a non-VR expert and which provides a short development time and easy maintenance is necessary. Also usability is very important because this is crucial for the success of VR-shops. In this paper, we present an approach to develop VR-shops that meet these requirements. It allows specifying a VR-shop using high-level conceptual specifications and in terms of domain terminology; semantics are captured by ontologies; existing product information can be incorporated; and the actual code is generated.     

Dynamic simulation of human motion: numerically efficient inclusion of muscle physiology by convex optimization

Determining the muscle forces that underlie some experimentally observed human motion, is a challenging biomechanical problem, both from an experimental and a computational point of view. No non-invasive method is currently available for experimentally measuring muscle forces. The alternative of computing them from the observed motion is complicated by the inherent overactuation of the human body: it has many more muscles than strictly needed for driving all the degrees of freedom of the skeleton. As a result, the skeleton’s equations of motion do not suffice to determine the muscle forces unambiguously. Therefore, muscle force determination is often reformulated as a (large-scale) optimization problem. Generally, the optimization approaches are classified according to the formalism, inverse or forward, adopted for solving the skeleton’s equations of motion. Classical inverse approaches are fast but do not take into account the constraints imposed by muscle physiology. Classical forward approaches, on the other hand, do take the muscle physiology into account but are extremely costly from a computational point of view. The present paper makes a double contribution. First, it proposes a novel inverse approach that results from including muscle physiology (both activation and contraction dynamics) in the inverse dynamic formalism. Second, the efficiency with which the corresponding optimization problem is solved is increased by using convex optimization techniques. That is, an approximate convex program is formulated and solved in order to provide a hot-start for the exact nonconvex program. The key element in this approximation is a (global) linearization of muscle physiology based on techniques from experimental system identification. This approach is applied to the study of muscle forces during gait. Although the results for gait are promising, experimental study of faster motions is needed to demonstrate the full power and advantages of the proposed methodology, and therefore is the subject of subsequent research.     

Effectiveness of strategic environmental assessment in Canada under directive-based and informal practice

This article explores the diversity of strategic environmental assessment (SEA) practice in Canada and lessons for improving the effectiveness of SEA. There are multiple dimensions to effectiveness, but core to SEA effectiveness is its strategic nature. SEA under the Canadian federal Cabinet directive is approached largely as an impact assessment tool, and effectiveness evaluated based on compliance. Practice is entrenched in project-based assessment principles, but with no mandatory provision for public engagement, which limits the potential effectiveness of SEA. External to the Cabinet directive, across Canada’s provinces and territories, SEA and SEA-like practices are occurring in diverse forms and represent the more advanced and exemplary cases. A common challenge to SEA effectiveness, however, is that applications are often limited by their ad hoc nature and disconnected from any larger and formal system of participatory and integrated policy, planning and development decision making.     

The impact of the protein network on the pasting and cooking properties of dry pasta products

Durum wheat semolina gluten and starch as well as processing conditions determine pasta cooking quality. This study investigated whether, for good organoleptic properties, a permanent protein network needs to be formed during pasta drying or can still be formed during cooking. The cooking quality of 16 spaghetti samples was related to the levels of sodium dodecyl sulphate extractable protein (SDSEP), starch gelatinisation temperatures as well as to the swelling properties of milled dry spaghettis. SDSEP levels in dry and cooked products varied between 31% and 56%, and 12% to 21% of total protein contents, respectively. The highest quality spaghettis had relatively higher levels of SDSEP in the dry product, low starch gelatinisation temperatures and swelling powers, and rigid particles. The lowest quality spaghettis had lower levels of SDSEP and higher gelatinisation temperatures. This work implies that high pasta quality results from an optimal degree of protein polymerisation during drying and/or the subsequent cooking.     

Thermophilic biotrickling filtration of a mixture of isobutyraldehyde and 2‐pentanone

In this study, the possibility of the removal of isobutyraldehyde and 2‐pentanone was investigated in biotrickling filters (BTFs) at higher temperature (52–65 °C). First, the biodegradation of isobutyraldehyde and 2‐pentanone in activated sludge was proven by batch experiments at 52 and 62 °C. In batch experiments isobutyraldehyde was also degraded up to a temperature of 72 °C. Thereafter two bioreactors were operated in parallel, one at ambient temperature (BTF25), and one at 52 °C (BTF52). Maximum elimination capacities of 97 and 139 g m^?3 h^?1 were observed in BTF25 and BTF52, respectively, for isobutyraldehyde. Maximum elimination capacities of 53 and 63 g m^?3 h^?1 were obtained for 2‐pentanone in BTF25 and BTF52, respectively. A significant difference was observed in the operational stability of the two reactors. In the reactor at ambient temperature, operational problems such as foam formation, higher biomass accumulation and organic acid production were observed. In the thermophilic reactor these problems did not occur or were less severe. Copyright © 2007 Society of Chemical Industry     

Momentum Exchange in Straight Uniform Compound Channel Flow

Transverse exchange of momentum between the channel and the floodplain in straight uniform compound channel flow is considered in this paper. This process results in the so-called “kinematic effect,” a lowering of the total discharge capacity of a compound channel compared to the case where the channel and the floodplain are considered separately. The mechanisms responsible for the momentum exchange are considered. The transverse shear stress in the mixing region is modeled using a newly developed effective eddy viscosity concept, that contains: (1) the effects of horizontal coherent structures moving on an uneven bottom, taking compression and stretching of the vortices into account and (2) the effects of the three-dimensional bottom turbulence. The model gives a good prediction of the transverse profiles of the streamwise velocity and the transverse shear stress of the flood channel facility experiments. Characteristic features of the lateral profile of the eddy viscosity are also well predicted qualitatively, but in a quantitative sense there is room for improvement. Secondary circulations are shown to be of minor importance in straight uniform compound channel flows.     

Xylanase-mediated in situ production of arabinoxylan oligosaccharides with prebiotic potential in whole meal breads and breads enriched with arabinoxylan rich materials

Multiple studies have revealed the prebiotic activity of cereal derived arabinoxylan oligosaccharides (AXOS). This study investigated the in situ production of AXOS during bread making. In the first part, the AXOS producing capacity of different xylanases was compared in whole meal bread making. Three mesophilic xylanases originating from Bacillus subtilis, Aspergillus niger and Hypocrea jecorina, and one thermophilic xylanase from H. jecorina (HjXynA), were used in different dosages. At dosages that did not impair dough manageability, HjXynA solubilised and cleaved the arabinoxylan fraction to the largest extent, resulting in an AXOS content of 2.1% (dry basis) and an average degree of polymerisation (avDP) of 9. In the second part, the impact of HjXynA on the AXOS levels in dietary fibre enriched breads was studied. Rye or wheat bran fortified breads treated with HjXynA yielded good quality breads with AXOS levels above 2.0% with an avDP of 26 and 19, respectively.