Introduction: power after peace

The chapter provides a substantive conceptual introduction to the volume, examining what is meant by the concept of "political economy of statebuilding", and what the implications for the study of statebuilding are

Commodity futures prices: more evidence on forecast power, risk premia and the theory of storage

In this paper, we examine the temporal stability of the evidence for two commodity futures pricing theories. We investigate whether the forecast power of commodity futures can be attributed to the extent to which they exhibit seasonality and we also consider whether there are time varying parameters or structural breaks in these pricing relationships. Compared to previous studies, we find stronger evidence of seasonality in the basis, which supports the theory of storage. The power of the basis to forecast subsequent price changes is also strengthened, while results on the presence of a risk premium are inconclusive. In addition, we show that the forecasting power of commodity futures cannot be attributed to the extent to which they exhibit seasonality. We find that in most cases where structural breaks occur, only changes in the intercepts and not the slopes are detected, illustrating that the forecast power of the basis is stable over different economic environments.

Britain as a global power in the twentieth century

This chapter examines the extent to which Britain's status as a global power in the twentieth century was underpinned by the existence of its empire. It suggests that, in a military sense, empire represented an uncertain resource. While the mobilization of the empire in the two world wars was ultimately crucial to British victory, its latent power in the years leading to those conflicts was poorly appreciated, not least by UK policy‐makers themselves. As such, it had limited value as a deterrent to Britain's enemies. Furthermore, the process of mobilizing the empire for war placed an almost intolerable strain on the fragile structures of imperial control. Britain's continuing aspirations to play the role of a global power following post‐war decolonization reflect the extent to which its overseas interests had always transcended the formal boundaries of empire. Meanwhile the Anglo‐American alliance provided Britain with a degree of security that its empire had never offered.

A contribution to the wireless transmission of power

A resonant transmitter–receiver system is described for the wireless transmission of energy at a useful distance for grid-coordinate power and information. Experimental results are given showing delivery of power of an unmodified Tesla resonator contrasted with a modified version achieving improved efficiency over a 4 m range. A theoretical basis is provided to back up the experimental results obtained and to link the study with previous research in the field. A number of potential routes are suggested for further investigations and some possible applications of the technology are considered.

The power of purchase: addressing sustainability through public procurement

This article focuses on sustainable development and public procurement and reflects on the significance of questioning the goals sustainable public procurement seeks to achieve. While it is recognised that developing appropriate legal frameworks and regulatory tools for environmental, social and economic quality assurance is important, achieving sustainable procurement nevertheless remains political. With the forthcoming adoption of new European Union Public Procurement Directives, the article provides a timely reminder that for sustainability to be integral to good procurement, the power of purchase must capture a paradigmatic shift from doing things better to doing better things.

Power allocation strategies for distributed space-time codes in two-way relay networks

We study a two-way relay network (TWRN), where distributed space-time codes are constructed across multiple relay terminals in an amplify-and-forward mode. Each relay transmits a scaled linear combination of its received symbols and their conjugates,with the scaling factor chosen based on automatic gain control. We consider equal power allocation (EPA) across the relays, as well as the optimal power allocation (OPA) strategy given access to instantaneous channel state information (CSI). For EPA, we derive an upper bound on the pairwise-error-probability (PEP), from which we prove that full diversity is achieved in TWRNs. This result is in contrast to one-way relay networks, in which case a maximum diversity order of only unity can be obtained. When instantaneous CSI is available at the relays, we show that the OPA which minimizes the conditional PEP of the worse link can be cast as a generalized linear fractional program, which can be solved efficiently using the Dinkelback-type procedure.We also prove that, if the sum-power of the relay terminals is constrained, then the OPA will activate at most two relays.

Efficient wireless power delivery for biomedical implants

Power delivery for biomedical implants is a major consideration in their design for both measurement and stimulation. When performed by a wireless technique, transmission efficiency is critically important not only because of the costs associated with any losses but also because of the nature of those losses, for example, excessive heat can be uncomfortable for the individual involved. In this study, a method and means of wireless power transmission suitable for biomedical implants are both discussed and experimentally evaluated. The procedure initiated is comparable in size and simplicity to those methods already employed; however, some of Tesla’s fundamental ideas have been incorporated in order to obtain a significant improvement in efficiency. This study contains a theoretical basis for the approach taken; however, the emphasis here is on practical experimental analysis

Choosing the most suitable analogue redesign method for forward-type digital power converters

This work proposes a method to objectively determine the most suitable analogue redesign method for forward type converters under digital voltage mode control. Particular emphasis is placed on determining the method which allows the highest phase margin at the particular switching and crossover frequencies chosen by the designer. It is shown that at high crossover frequencies with respect to switching frequency, controllers designed using backward integration have the largest phase margin; whereas at low crossover frequencies with respect to switching frequency, controllers designed using bilinear integration have the largest phase margins. An accurate model of the power stage is used for simulation, and experimental results from a Buck converter are collected. The performance of the digital controllers is compared to that of the equivalent analogue controller both in simulation and experiment. Excellent correlation between the simulation and experimental results is presented. This work will allow designers to confidently choose the analogue redesign method which yields the greater phase margin for their application.

Sharing power? Prospects for a U.S. concert-balance strategy

The Pax Americana and the grand strategy of hegemony (or “Primacy”) that underpins it may be becoming unsustainable. Particularly in the wake of exhausting wars, the Global Financial Crisis, and the shift of wealth from West to East, it may no longer be possible or prudent for the United States to act as the unipolar sheriff or guardian of a world order. But how viable are the alternatives, and what difficulties will these alternatives entail in their design and execution? This analysis offers a sympathetic but critical analysis of alternative U.S. National Security Strategies of “retrenchment” that critics of American diplomacy offer. In these strategies, the United States would anticipate the coming of a more multipolar world and organize its behavior around the dual principles of “concert” and “balance,” seeking a collaborative relationship with other great powers, while being prepared to counterbalance any hostile aggressor that threatens world order. The proponents of such strategies argue that by scaling back its global military presence and its commitments, the United States can trade prestige for security, shift burdens, and attain a more free hand. To support this theory, they often look to the 19th-century concert of Europe as a model of a successful security regime and to general theories about the natural balancing behavior of states. This monograph examines this precedent and measures its usefulness for contemporary statecraft to identify how great power concerts are sustained and how they break down. The project also applies competing theories to how states might behave if world politics are in transition: Will they balance, bandwagon, or hedge? This demonstrates the multiple possible futures that could shape and be shaped by a new strategy. viii A new strategy based on an acceptance of multipolarity and the limits of power is prudent. There is scope for such a shift. The convergence of several trends—including transnational problems needing collaborative efforts, the military advantages of defenders, the reluctance of states to engage in unbridled competition, and hegemony fatigue among the American people—means that an opportunity exists internationally and at home for a shift to a new strategy. But a Concert-Balance strategy will still need to deal with several potential dilemmas. These include the difficulty of reconciling competitive balancing with cooperative concerts, the limits of balancing without a forward-reaching onshore military capability, possible unanticipated consequences such as a rise in regional power competition or the emergence of blocs (such as a Chinese East Asia or an Iranian Gulf), and the challenge of sustaining domestic political support for a strategy that voluntarily abdicates world leadership. These difficulties can be mitigated, but they must be met with pragmatic and gradual implementation as well as elegant theorizing and the need to avoid swapping one ironclad, doctrinaire grand strategy for another.

Constructing the frequency and wave normal distribution of whistler-mode wave power

We introduce a new methodology that allows the construction of wave frequency distributions due to growing incoherent whistler-mode waves in the magnetosphere. The technique combines the equations of geometric optics (i.e. raytracing) with the equation of transfer of radiation in an anisotropic lossy medium to obtain spectral energy density as a function of frequency and wavenormal angle. We describe the method in detail, and then demonstrate how it could be used in an idealised magnetosphere during quiet geomagnetic conditions. For a specific set of plasma conditions, we predict that the wave power peaks off the equator at ~15 degrees magnetic latitude. The new calculations predict that wave power as a function of frequency can be adequately described using a Gaussian function, but as a function of wavenormal angle, it more closely resembles a skew normal distribution. The technique described in this paper is the first known estimate of the parallel and oblique incoherent wave spectrum as a result of growing whistler-mode waves, and provides a means to incorporate self-consistent wave-particle interactions in a kinetic model of the magnetosphere over a large volume.

On the nature of ULF wave power during nightside auroral activations and substorms: 2. temporal evolution

We present a statistical analysis of the time evolution of ground magnetic fluctuations in three (12–48 s, 24–96 s and 48–192 s) period bands during nightside auroral activations. We use an independently derived auroral activation list composed of both substorms and pseudo-breakups to provide an estimate of the activation times of nightside aurora during periods with comprehensive ground magnetometer coverage. One hundred eighty-one events in total are studied to demonstrate the statistical nature of the time evolution of magnetic wave power during the ∼30 min surrounding auroral activations. We find that the magnetic wave power is approximately constant before an auroral activation, starts to grow up to 90 s prior to the optical onset time, maximizes a few minutes after the auroral activation, then decays slightly to a new, and higher, constant level. Importantly, magnetic ULF wave power always remains elevated after an auroral activation, whether it is a substorm or a pseudo-breakup. We subsequently divide the auroral activation list into events that formed part of ongoing auroral activity and events that had little preceding geomagnetic activity. We find that the evolution of wave power in the ∼10–200 s period band essentially behaves in the same manner through auroral onset, regardless of event type. The absolute power across ULF wave bands, however, displays a power law-like dependency throughout a 30 min period centered on auroral onset time. We also find evidence of a secondary maximum in wave power at high latitudes ∼10 min following isolated substorm activations. Most significantly, we demonstrate that magnetic wave power levels persist after auroral activations for ∼10 min, which is consistent with recent findings of wave-driven auroral precipitation during substorms. This suggests that magnetic wave power and auroral particle precipitation are intimately linked and key components of the substorm onset process.

Do magnetospheric shear Alfvén waves generate sufficient electron energy flux to power the aurora?

Using a self-consistent drift-kinetic simulation code, we investigate whether electron acceleration owing to shear Alfvén waves in the plasma sheet boundary layer is sufficient to cause auroral brightening in the ionosphere. The free parameters used in the simulation code are guided by in situ observations of wave and plasma parameters in the magnetosphere at distances >4 RE from the Earth. For the perpendicular wavelength used in the study, which maps to ∼4 km at 110 km altitude, there is a clear amplitude threshold which determines whether magnetospheric shear Alfvén waves above the classical auroral acceleration region can excite sufficient electrons to create the aurora. Previous studies reported wave amplitudes that easily exceed this threshold; hence, the results reported in this paper demonstrate that auroral acceleration owing to shear Alfvén waves can occur in the magnetosphere at distances >4 RE from the Earth.

Electron trapping in shear Alfvén waves that power the aurora

Results from 1D Vlasov drift-kinetic plasma simulations reveal how and where auroral electrons are accelerated along Earth’s geomagnetic field. In the warm plasma sheet, electrons become trapped in shear Alfven waves, preventing immediate wave damping. As waves move to regions with larger vTe=vA, their parallel electric field decreases, and the trapped electrons escape their influence. The resulting electron distribution functions compare favorably with in situ observations, demonstrating for the first time a self-consistent link between Alfven waves and electrons that form aurora.