Dynamics of Flow in the Region of the Tsugaru Strait.

The Tsugaru Strait is one of four straits that connect the Sea of Japan to adjacent oceans. Flow dynamics in the Tsugaru Strait region are closely tied to the dynamics of the Tsushima Current, a branch of the Kuroshio that enters the Sea of Japan through the Korea Strait and exits through the Tsugaru and Soya Straits. This research concentrates on the dynamic interplay of the Tsushima Current and the Tsugaru Strait in three regions: the inflow region (Sea of Japan side), the strait itself, and the outflow region (North Pacific side). Dynamic calculations and steric sea leveling in the inflow region indicate that transport into the Tsugaru Strait is principally governed by the geostrophically balanced Tsushima Current. Setup generated south of the strait by the Tsushima Current cannot be maintained at the entrance to the strait; the resulting northward drop in coastal sea level is balanced by a net loss of transport into the strait. Within the strait, the flow is geostrophically balanced in the cross-stream direction. In the longstream direction, the barotropic pressure gradient is chiefly balanced by the longitudinal baroclinic pressure gradient and friction. Application of the Hansen-Rattray (1966) estuarine classification scheme to several straits shows that the Tsugaru Strait displays dynamics similar to that of a well-mixed estuary. The outflow jet emerging from the eastern mouth of the strait is governed by inertial-rotational dynamics; two distinct circulation modes, which behave in a manner consistent with the laboratory findings of Whitehead and Miller (1979), are seen

The implications of the shared genetics of psychiatric disorders

Recent genomic studies have revealed the highly polygenic nature of psychiatric disorders, including schizophrenia, bipolar disorder and major depressive disorder. Many of the individual genetic associations are shared across multiple disorders in a way that points to extensive biological pleiotropy and further challenges the biological validity of existing diagnostic approaches. Here we argue that the existence of risk alleles specific to a single diagnostic category is unlikely. We also highlight some of the important clinical repercussions of pleiotrop

Comparing the Economic Experiences of Rural and Urban University Students

This study examines the finances of students from rural and urban regions of Newfoundland and Labrador studying at Memorial University of Newfoundland. A sample of 722 senior full-time students was selected, and 439 of these students were interviewed by telephone. Statistical analysis of the data found that the two groups were significantly different in a number of respects. The results highlight the economic and financial disparities that exist between students from rural and urban regions of Newfoundland and Labrador. The policy implications are highlighted, and reform of current student financial assistance policies is encouraged to ease the financial difficulties encountered by university students from rural regions of the province.Cette recherche porte sur la situation financière d'étudiants provenant de régions rurales et urbaines de Terre-Neuve-et-Labrador inscrits à la l'Université Memorial de Terre-Neuve. D'un échantillon de 722 étudiants des cycles supérieurs et inscrits à temps plein, 439 ont été interviewés au téléphone. Une analyse statistique des données a révélé des différences significatives sur plusieurs plans entre les deux groupes. Les résultats font ressortir les disparités économiques et financières qui séparent les étudiants originaires de régions rurales et ceux des régions urbaines de Terre-Neuve-et-Labrador. On discute les incidences sur les politiques générales et propose des réformes visant les programmes d'aide financière aux étudiants et ayant comme but d'alléger les difficultés financières vécues par les étudiants d'université provenant des régions rurales de la province

PERFORMANCE OF A VARIABLE SPEED DOUBLE-FED INDUCTION GENERATOR WIND TURBINE DURING NETWORK VOLTAGE UNBALANCE CONDITIONS

The issues of the negative performance of DFIG’s due to supply network voltage unbalance are outlined in this paper. The paper shows the effects that voltage unbalance can have on a DFIG, using the power simulation program DigSilent. The results from simulations show that voltage unbalance affects the both the induction generator and the rotor converter, due to the high unbalanced currents generated. The ability to modify the control strategy of a DFIG to compensate for voltage unbalance is outlined and a proposal to build a test-rig suitable to implement such a system is suggested

ANALYSIS OF A VARIABLE SPEED DOUBLE-FED INDUCTION GENERATOR WIND TURBINE DURING NETWORK VOLTAGE UNBALANCE CONDITIONS.

The behaviour of Double-Fed Induction Generators to supply network voltage unbalance is investigated. The paper shows the effects that voltage unbalance can have on a DFIG, using Matlab/Simulink. The results from simulations show that voltage unbalance affects both the induction generator and the rotor converter, due to the high unbalanced currents generated. The ability to modify the control strategy of a DFIG to compensate for voltage unbalance is outlined and simulations show the improvements to the performance of the DFIG

Investigation into the local nature of rate of change of frequency in electrical power systems

In recent years power systems world-wide have seen large increases in wind power penetration and this trend is expected to continue. This is having the undesirable consequence of reducing the inertia of electrical power systems, especially at times of high wind generation. Reduced inertia makes a power system more susceptible to a larger rate of change of frequency (RoCoF) following a grid disturbance, such as the sudden disconnection of a load or generator. High RoCoF events could trigger generator protective devices or anti-islanding RoCoF relays, disconnecting generation from the grid, compounding the initial grid disturbance and in extreme cases result in the cascade tripping of generators and grid blackout. The objective of this research was to investigate how RoCoF varies with location in an electrical power system and determine if there is any significant difference between local RoCoF observed at individual buses and the system RoCoF seen across the entire power system. The results show that generators closest to the disturbance are impacted the most after the loss of a generator, and if this generator has relatively low inertia it could see a local RoCoF many times greater than the system RoCoF. It was also observed that when a large portion of the total power system inertia is concentrated at one machine, the mean of the local RoCoFs is significantly larger compared to when the power system inertia is equally distributed across all machines. It was observed that by measuring RoCoF using a rolling average window of 0.5 seconds, the magnitude of the measured RoCoF is significantly reduced and the effect that the distribution of inertia has on the mean of the local RoCoFs is eliminated. However, in some scenarios the local RoCof was still many times greater than the system RoCoF. The results demonstrate that local RoCoF could be an issue that needs to be considered when operating low inertia power systems, particularly as wind power continues to displace conventional generation

Estimating the Yield of Micro Wind Turbines in an Urban Environment: A Methodology

Micro wind turbines currently have the majority share of micro (electricity) generation installations in Ireland. These technologies are being installed predominantly in rural environments, and current applications to the Distribution Services Operator (DSO) for connection of all types of micro generator stand at less than 500. Poor market dissemination of information and research findings compounded with poor options for spill payment - as well as onerous planning restrictions do not –it appears - create a platform conducive to encouraging development in this market. This paper outlines the complexities associated with evaluating the wind resource within an urban environment and investigates the means to ‘estimate’ wind regimes in an urban environment based on an extrapolation of a reference wind speed from a rural environment into the urban area. Methodologies for estimating the wind speed in such circumstances are considered with modeled wind data – benchmarked against wind data acquired from a site in the city centre - being applied to a set of commercially available wind turbines