The drumlin problem : streamlined subglacial bedforms in southern Sweden

This thesis investigates stream-lined subglacial bedforms (often referred to as drumlins) in southern Sweden. The broad aim of this is to contribute to the solution of the ‘drumlin problem’. The term drumlin has come to be applied to a wide range of features whose internal architecture (core) and overall morphology are seen to vary greatly. This range in characteristics is in part responsible for the various competing theories of drumlin formation, each different type of core and morphology generating a new idea for how it came about. Here the new Swedish national height model, a high resolution LiDAR derived digital elevation model, in combination with detailed sedimentological work is used to characterise streamlined terrain in southern Sweden and investigate the formation processes associated with it. The findings of this are that drumlinoids in southern Sweden are predominantly rock cored. Soft cored features tend to be significantly longer than rock cored features. In general, drumlinoids in southern Sweden are located at the lower end of the size spectrum in terms of global streamlined sub-glacial features. Additionally it has been found that drumlinoids can form rapidly at glacial margins as well as within the main body of ice sheets. And finally, the most important contextual geological factor in drumlinoid parameter (morphology) formation appears to be drift depth/properties. The bedrock type beneath a feature and the hydrological system as recorded in eskers do play a role, but the exact nature of this is not certain and the correlations are difficult to analyse. In addition to these findings a generalised conceptual model of drumlinoid formation is proposed and a discussion of the possible ways in which physical processes influence said formation is offered. It is suggested that chaotic behaviour and the role of scale might be useful to consider and that whilst it is something of semantic point, the use of the term drumlinoid is deliberate and important. This is because due to equifinality there are many landforms that researchers can split into different categories, e.g. rock drumlins, clone drumlins, emergent drumlins, downwards emergent drumlins or obstacle drumlins. These are all valid divisions as there are different physical processes involved in their formation. However these processes and the final landforms that result from them are all part of the sub-glacial continuum and so at one level must be considered part of the same family

Can incentive-based spatial management work in the Eastern tuna and billfish fishery?

The Eastern tuna and billfish fishery (ETBF) is currently managed through an input quota system based on individual transferable effort units (the number of hooks) and a total allowable effort level (i.e. total number of hooks) A spatial management policy based on a series of differential hook-penalties has been proposed as a flexible tool to discourage vessels operating in certain areas (e.g. those with high bycatch potential) and encourage operating in other areas (e.g. with less bycatch potential). In this study, the importance of catch rates per hook to location choice is assessed through the estimation of a nested multinomial logit model. Other variables in the model include distance to the location, prices of the main species, fuel prices and vessel characteristics. The effects of increasing hook penalties in key areas on fishing effort in those areas and elsewhere are assessed. Implications for vessel economic performance are also assessed.Resource /Energy Economics and Policy,

Trade-Off between Collusion Resistance and User Life Cycle in Self-Healing Key Distributions with t-Revocation

We solve the problem of resisting the collusion attack in the one-way hash chain based self-healing key distributions introduced by Dutta et al., coupling it with the prearranged life cycle based approach of Tian et al. that uses the same self-healing mechanism introduced in Dutta et al. Highly efficient schemes are developed compared to the existing works with the trade-off in pre-arranged life cycles on users by the group manager and a slight increase in the storage overhead. For scalability of business it is often necessary to design more innovation and flexible business strategies in certain business models that allow contractual subscription or rental, such as subscription of mobile connection or TV channel for a pre-defined period. The subscribers are not allowed to revoke before their contract periods (life cycles) are over. Our schemes fit into such business environment. The proposed schemes are proven to be computationally secure and resist collusion between new joined users and revoked users together with forward and backward secrecy. The security proof is in an appropriate security model. Moreover, our schemes do not forbid revoked users from rejoining in later sessions unlike the existing self- healing key distribution schemes

Relating Static and Dynamic Measurements for the Java Virtual Machine Instruction Set

It has previously been noted that, for conventional machine code, there is a strong relationship between static and dynamic code measurements. One of the goals of this paper is to examine whether this same relationship is true of Java programs at the bytecode level. To this end, the hypothesis of a linear correlation between static and dynamic frequencies was investigated using Pearson’s correlation coefficient. Programs from the Java Grande and SPEC benchmarks suites were used in the analysis

Relating Static and Dynamic Measurements for the Java Virtual Machine Instruction Set

It has previously been noted that, for conventional machine code, there is a strong relationship between static and dynamic code measurements. One of the goals of this paper is to examine whether this same relationship is true of Java programs at the bytecode level. To this end, the hypothesis of a linear correlation between static and dynamic frequencies was investigated using Pearson’s correlation coefficient. Programs from the Java Grande and SPEC benchmarks suites were used in the analysis

Introducing secure modes of operation for optical encryption

We analyze optical encryption systems using the techniques of conventional cryptography. All conventional block encryption algorithms are vulnerable to attack, and often they employ secure modes of operation as one way to increase security. We introduce the concept of conventional secure modes to optical encryption and analyze the results in the context of known conventional and optical attacks. We consider only the optical system “double random phase encoding,” which forms the basis for a large number of optical encryption, watermarking, and multiplexing systems. We consider all attacks proposed to date in one particular scenario. We analyze only the mathematical algorithms themselves and do not consider the additional security that arises from employing these algorithms in physical optical systems

Selection for biparental inheritance of mitochondria under hybridization and mitonuclear fitness interactions

Uniparental inheritance (UPI) of mitochondria predominates over biparental inheritance (BPI) in most eukaryotes. However, examples of BPI of mitochondria, or paternal leakage, are becoming increasingly prevalent. Most reported cases of BPI occur in hybrids of distantly related sub-populations. It is thought that BPI in these cases is maladaptive; caused by a failure of female or zygotic autophagy machinery to recognize divergent male-mitochondrial DNA ‘tags’. Yet recent theory has put forward examples in which BPI can evolve under adaptive selection, and empirical studies across numerous metazoan taxa have demonstrated outbreeding depression in hybrids attributable to disruption of population-specific mitochondrial and nuclear genotypes (mitonuclear mismatch). Based on these developments, we hypothesize that BPI may be favoured by selection in hybridizing populations when fitness is shaped by mitonuclear interactions. We test this idea using a deterministic, simulation-based population genetic model and demonstrate that BPI is favoured over strict UPI under moderate levels of gene flow typical of hybridizing populations. Our model suggests that BPI may be stable, rather than a transient phenomenon, in hybridizing populations.publishedVersio

Production and preservation of the smallest drumlins

Few very small drumlins are typically mapped in previously glaciated landscapes, which might be an important signature of subglacial processes or an observational artefact. 143 newly emergent drumlins, recently sculpted by the Mulajokull glacier, have been mapped using high resolution LiDAR and aerial photographs in addition to field surveying. In this paper, these are used as evidence that few small drumlins (e.g. height H ≲ 4 m, width W ≲ 40 m, length L ≲ 100 m) are produced; at least, few survive to pass outside the ice margin in this actively forming drumlin field. Specifically, the lack of a multitude of small features seen in other landforms (e.g. volcanoes) is argued not to be due to i) Digital Elevation Model (DEM) resolution or quality, ii) mapper ability in complex (i.e. anthropogenically cluttered or vegetated) landscapes, or iii) post-glacial degradation at this site. So, whilst detection ability must still be at least acknowledged in drumlin mapping, and ideally corrected for in quantitative analyses, this observation can now be firmly taken as a constraint upon drumlin formation models (i.e. statistical, conceptual, or numerical ice flow). Our preferred explanation for the scarcity of small drumlins, at least at sites similar to Mulajokull (i.e. ice lobes with near-margin drumlin genesis), is that they form stochastically during multiple surge cycles, evolving from wide and gentle pre-existing undulations by increasing rapidly in amplitude before significant streamlining occurs

A Biometric Identity Based Signature Scheme

We describe an identity based signature scheme that uses biometric information to construct the public key. Such a scheme would be beneficial in a legal dispute over whether a contract had been signed or not by a user. A biometric reading provided by the alleged signer would be enough to verify the signature. We make use of Fuzzy extractors to generate a key string from a biometric measurement. We use this biometric based key string and an elliptic curve point embedding technique to create the public key and corresponding private key. We then make use of a pairing based signature scheme to perform signing and verification with these keys. We describe a possible attack on this system and suggest ways to combat it. Finally we describe how such a biometric signature scheme can be developed by reusing existing components in our Java Identity Based Encryption implementation. The design allows traditional as well as biometric identity based signatures

Innovating urban governance: a research agenda

Urban governance innovation is being framed as an imperative to address complex urban and global challenges, triggering the adoption of novel institutional forms, approaches and techniques. Urban political geographers are still some way off fully apprehending the dynamics of these innovations and their potential to reconfigure the composition and politics of urban governance. This paper suggests dialogue between urban political geography and public sector innovation literatures as a productive way forward. We build from this engagement to suggest a critical research agenda to drive systematic analysis of innovatory urban governance, its heterogeneous formation, politics and possibilities