A Study of Tower Shadow Effect on Fixed-Speed Wind Turbines

This paper studies the impact of tower shadow effect on the power output of a fixed-speed wind farm. A data acquisition unit was placed at a wind farm in Northern Ireland which consists of ten fixed-speed wind turbines. The recording equipment logged the wind farmpsilas electrical data, which was time stamped using the global positioning network. Video footage of the wind farm was recorded and from it the blade angle of each turbine was determined with respect to time. Using the blade angle data and the wind farmpsilas power output, studies where performed to ascertain the extent of tower shadow effect on power fluctuation. This paper presents evidence that suggests that tower shadow effect has a significant impact on power fluctuation and that this effect is increased due to the synchronising of turbine blades around the tower region.

Modelling and Control of a Variable-Speed Switched Reluctance Generator based Wind Turbine

This paper studies the system modelling and control aspects of switched reluctance generator (SRG) based variable speed wind turbines. A control system is implemented to provide proper operation of the SRG as well as power tracking capabilities for varying wind speeds. The control system for the grid side inverter that will allow the SRG to properly generate power to the system is also presented. Studies are presented of both the SRG and inverter control systems capabilities during a balanced three-phase fault. The paper will demonstrate that the SRG based wind turbine presents a feasible variable wind speed solution with good fault response capabilities.

Effect of impeller speed on mechanical and dissolution properties of high-shear granules

Impeller speed is one of the most crucial process variables that affect the properties of the granules produced in a high-shear granulator. Several reports can be found in literature that discuss the influence of impeller speed on the granules size. For instance some researchers like Knight report an increase of granule size with impeller speed [1] and [2], while others (Scheaefer et al. and Ramaker et al.) observed a decrease of granules size with increasing impeller speed [3] and [4]. However there is limited work reported in literature on the effect of the impeller speed on the mechanical properties of granules. Mechanical properties are important as they affect the performance of the granules on the other downstream process such as transportation and handling. The work reported here serves to address the missing in knowledge gap regarding the influence of impeller speed on mechanical properties granules. How the granulation system responds to the changes in the impeller speeds depends on binder that is used in the process. For this reason the two extreme cases, of a low viscosity binder system and high viscosity binder system are considered in this research. For low viscosity binder system it was observed that the granule size decreased with increasing impeller speed whilst for the high viscosity binder system the opposite was observed by Knight [1]. The granule strength, the Young's modulus and yield strength of the high viscosity granules increased with increasing impeller speed where as the opposite trends were observed for the low viscosity binder granules.

K-Contagion: Sound, Space and Speed in Psy's 'Gangnam Style'

Park Jae-Sang’s (otherwise known as PSY) bewilderingly successful pop contagion ‘Gangnam Style’ needs no introduction. As of January 2013, it has become the most watched video in YouTube’s history and has garnered over 1.23 billion hits since. ‘Gangnam Style’ has also become a rapid global pop phenomenon with multiple parodic reproductions, imitations and adaptations; Rapper PSY himself has become an international name and styled as the ‘anti-hero’ of the glamour-driven K-pop scene. His fame has transcended the social sphere and permeated the political stratosphere with politicians such as Barrack Obama and David Cameron being among the many whom PSY has exchanged pleasantries with. Apart from breaking ground and creating social and media history in many ways, ‘Gangnam Style’ has even been purported by UN Secretary-General Ban Ki Moon to be a “force for world peace” – cultural barriers are demolished as the world dances. Underlying this sentiment is the video’s almost universal appeal that assumes a supracultural yet equally paradoxical translatability: Korea’s neoteric ‘K-Wave’ phenomenon is at once local yet global, and where the latter is predicated on the former quality. The paper’s concern is thus two-fold. It will consider the dromological aspects of this musical contagion as it exemplifies and performs quite literally Paul Virilio’s thesis that the modern condition is driven by speed yet arrested to a dictatorship of movement. While many theories have been put forward for this astounding pop peculiarity, this paper would also examine the intercultural currents that advocate such a global (pop) cultural response. Through an analysis of sonic qualities – digital techno-beat rhythms, synth-based musicality, cyclical lyrics, horse-galloping movements – and acoustic receptions, it will consider the simultaneous and dichotomous currents of glocalisation and globalisation as it relates to the ways in which sonic ‘hyper-links’ establish new concepts of global-cultural identities even as these seem to be interrogated in the borderless worlds of hyper-mediatised realities and cultural technologies.

Speed of processing in the primary motor cortex: A continuous theta burst stimulation study

‘Temporally urgent’ reactions are extremely rapid, spatially precise movements that are evoked following discrete stimuli. The involvement of primary motor cortex (M1) and its relationship to stimulus intensity in such reactions is not well understood. Continuous theta burst stimulation (cTBS) suppresses focal regions of the cortex and can assess the involvement of motor cortex in speed of processing. The primary objective of this study was to explore the involvement of M1 in speed of processing with respect to stimulus intensity. Thirteen healthy young adults participated in this experiment. Behavioral testing consisted of a simple button press using the index finger following median nerve stimulation of the opposite limb, at either high or low stimulus intensity. Reaction time was measured by the onset of electromyographic activity from the first dorsal interosseous (FDI) muscle of each limb. Participants completed a 30 min bout of behavioral testing prior to, and 15 min following, the delivery of cTBS to the motor cortical representation of the right FDI. The effect of cTBS on motor cortex was measured by recording the average of 30 motor evoked potentials (MEPs) just prior to, and 5 min following, cTBS. Paired t-tests revealed that, of thirteen participants, five demonstrated a significant attenuation, three demonstrated a significant facilitation and five demonstrated no significant change in MEP amplitude following cTBS. Of the group that demonstrated attenuated MEPs, there was a biologically significant interaction between stimulus intensity and effect of cTBS on reaction time and amplitude of muscle activation. This study demonstrates the variability of potential outcomes associated with the use of cTBS and further study on the mechanisms that underscore the methodology is required. Importantly, changes in motor cortical excitability may be an important determinant of speed of processing following high intensity stimulation.

Voltage scalable high-speed robust hybrid arithmetic units using adaptive clocking

In this paper, we explore various arithmetic units for possible use in high-speed, high-yield ALUs operated at scaled supply voltage with adaptive clock stretching. We demonstrate that careful logic optimization of the existing arithmetic units (to create hybrid units) indeed make them further amenable to supply voltage scaling. Such hybrid units result from mixing right amount of fast arithmetic into the slower ones. Simulations on different hybrid adder and multipliers in BPTM 70 nm technology show 18%-50% improvements in power compared to standard adders with only 2%-8% increase in die-area at iso-yield. These optimized datapath units can be used to construct voltage scalable robust ALUs that can operate at high clock frequency with minimal performance degradation due to occasional clock stretching. © 2009 IEEE.

High-Speed Fully Homomorphic Encryption Over the Integers

A fully homomorphic encryption (FHE) scheme is envisioned as a key cryptographic tool in building a secure and reliable cloud computing environment, as it allows arbitrary evaluation of a ciphertext without revealing the plaintext. However, existing FHE implementations remain impractical due to very high time and resource costs. To the authors’ knowledge, this paper presents the first hardware implementation of a full encryption primitive for FHE over the integers using FPGA technology. A large-integer multiplier architecture utilising Integer-FFT multiplication is proposed, and a large-integer Barrett modular reduction module is designed incorporating the proposed multiplier. The encryption primitive used in the integer-based FHE scheme is designed employing the proposed multiplier and modular reduction modules. The designs are verified using the Xilinx Virtex-7 FPGA platform. Experimental results show that a speed improvement factor of up to 44 is achievable for the hardware implementation of the FHE encryption scheme when compared to its corresponding software implementation. Moreover, performance analysis shows further speed improvements of the integer-based FHE encryption primitives may still be possible, for example through further optimisations or by targeting an ASIC platform.

High-speed conversion of xylose to l-lactate by electrodialysis bioprocess

Conversion of xylose to l-lactate was carried out by Lactococcus lactis IO-1 using an electrodialysis bioprocess (ED-BP). At 50 g l -1 xylose, the ED-BP was already complete in half the time (32 h) taken by the control culture without electrodialysis (>60 h). At 80 g l -1 xylose, the control culture was unable to consume >50 g l -1 xylose, whereas the ED-BP consumed 75 g l -1 xylose in 45 h. Thus, the simultaneous removal of lactate and acetate by ED-BP was associated with high-speed l-lactate production, increased xylose consumption and an increased l-lactate production. Copyright (C) 1998 Elsevier Science B.V.

Very high speed 17 Gbps SHACAL encryption architecture

Very high speed and low area hardware architectures of the SHACAL-1 encryption algorithm are presented in this paper. The SHACAL algorithm was a submission to the New European Schemes for Signatures, Integrity and Encryption (NESSIE) project and it is based on the SHA-1 hash algorithm. To date, there have been no performance metrics published on hardware implementations of this algorithm. A fully pipelined SHACAL-1 encryption architecture is described in this paper and when implemented on a Virtex-II X2V4000 FPGA device, it runs at a throughput of 17 Gbps. A fully pipelined decryption architecture achieves a speed of 13 Gbps when implemented on the same device. In addition, iterative architectures of the algorithm are presented. The SHACAL-1 decryption algorithm is derived and also presented in this paper, since it was not provided in the submission to NESSIE. © Springer-Verlag Berlin Heidelberg 2003.

Investigations Into the Performance of a Turbogenerated Biogas Engine During Speed Transients

Turbogenerating is a form of turbocompounding whereby a Turbogenerator is placed in the exhaust stream of an internal combustion engine. The Turbogenerator converts a portion of the expelled energy in the exhaust gas into electricity which can then be used to supplement the crankshaft power. Previous investigations have shown how the addition of a Turbogenerator can increase the system efficiency by up to 9%. However, these investigations pertain to the engine system operating at one fixed engine speed. The purpose of this paper is to investigate how the system and in particular the Turbogenerator operate during engine speed transients. On turbocharged engines, turbocharger lag is an issue. With the addition of a Turbogenerator, these issues can be somewhat alleviated. This is done by altering the speed at which the Turbogenerator operates during the engine’s speed transient. During the transients, the Turbogenerator can be thought to act in a similar manner to a variable geometry turbine where its speed can cause a change in the turbocharger turbine’s pressure ratio. This paper shows that by adding a Turbogenerator to a turbocharged engine the transient performance can be enhanced. This enhancement is shown by comparing the turbogenerated engine to a similar turbocharged engine. When comparing the two engines, it can be seen that the addition of a Turbogenerator can reduce the time taken to reach full power by up to 7% whilst at the same time, improve overall efficiency by 7.1% during the engine speed transient.