Wave-Breaking Turbulence in the Ocean Surface Layer

AbstractObservations of winds, waves, and turbulence at the ocean surface are compared with several analytic formulations and a numerical model for the input of turbulent kinetic energy by wave breaking and the subsequent dissipation. The observations are generally consistent with all of the formulations, although some differences are notable at winds greater than 15 m s−1. The depth dependence of the turbulent dissipation rate beneath the waves is fit to a decay scale, which is sensitive to the choice of vertical reference frame. In the surface-following reference frame, the strongest turbulence is isolated within a shallow region of depths much less than one significant wave height. In a fixed reference frame, the strong turbulence penetrates to depths that are at least half of the significant wave height. This occurs because the turbulence of individual breakers persists longer than the dominant period of the waves and thus the strong surface turbulence is carried from crest to trough with the wave orbital motion.</jats:p

Semi-empirical dissipation source functions for ocean waves: Part I, definition, calibration and validation

New parameterizations for the spectra dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observation of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is non-zero only when a non-dimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short wave dissipation due to long wave breaking is introduced to represent the dissipation of short waves due to longer breaking waves. Several degrees of freedom are introduced in the wave breaking and the wind-wave generation term of Janssen (J. Phys. Oceanogr. 1991). These parameterizations are combined and calibrated with the Discrete Interaction Approximation of Hasselmann et al. (J. Phys. Oceangr. 1985) for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from gentle swells to major hurricanes, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but the parameterizations yield the best overall results to date. Perspectives for further improvement are also given.Comment: revised version for Journal of Physical Oceanograph

The Major Milestones for Development of Trade Unions in Tanzania: Is the Environment for the Operation Conducive?

Trade unions are legally recognized as official organizations representing and protecting workers rights and interests. They have to struggle to ensure the improvement of living standards of employees. This can be achieved through trade unions consciousness and participation in government’s labour policies, member’s commitment, and strong leadership. However, trade unions require favoring environment for their participation and rising voices, especially when governments and policies are silent about workers’ rights or when workers benefits are at stake. This paper, for that matter, explores the major milestones for the development of trade unions in Tanzania since independence to present. It also assesses the conduciveness of environment for the operation of trade unions in Tanzania today. It is however, the opinion of this paper that, the environment for the operation of trade unions is still a mixture and not much favorable for the operation of trade unions. Keywords: Environment, Milestones, Trade union

Assessment of Ocean Wave Model used to Analyze the Constellation Program (CxP) Orion Project Crew Module Water Landing Conditions

Mr. Christopher Johnson, NASA's Systems Manager for the Orion Project Crew Module (CM) Landing and Recovery at the Johnson Space Center (JSC), and Mr. James Corliss, Project Engineer for the Orion CM Landing System Advanced Development Project at the Langley Research Center (LaRC) requested an independent assessment of the wave model that was developed to analyze the CM water landing conditions. A NASA Engineering and Safety Center (NESC) initial evaluation was approved November 20, 2008. Mr. Bryan Smith, NESC Chief Engineer at the NASA Glenn Research Center (GRC), was selected to lead this assessment. The Assessment Plan was presented and approved by the NESC Review Board (NRB) on December 18, 2008. The Assessment Report was presented to the NRB on March 12, 2009. This document is the final Assessment Report

Examination of Performance Validity and the Relationship to Cognition and Symptoms in Schizophrenia Spectrum Disorders

Approximately one-in-five individuals with psychotic disorders (i.e., schizophrenia spectrum disorders [SSD]) fail performance validity indicators (PVIs) during neurocognitive testing. Ensuring the validity of neurocognitive test results is necessary if the test scores are to be of use for diagnostic consideration, intervention selection and planning, predicting outcomes, and following changes in cognition over time in response to intervention, spontaneous recovery, or disease progression. PVIs are designed to require only a minimum level of engagement with the evaluation, which means nearly everyone is expected to “pass,” even those with moderate to severe brain damage. Traditional interpretations of PVI failure suggest a noncredible response style is likely motivated by secondary gain. However, the reasons for the increased failure rate among individuals with SSD are unclear but may be due to factors unrelated to a noncredible response style. Recent research suggests negative symptoms and cognitive deficits are associated with increased PVI failure rates, both of which are typically experienced by individuals with SSD. If failure on PVIs is not due to lack of engagement, then the usefulness of PVIs as indicators of noncredible performance in schizophrenia spectrum disorders may be questionable. Therefore, the current study investigated the validity of an emerging PVI (i.e., Reliable Spatial Span [RSS]) created from a well-validated cognitive test, as well as attempted to disentangle the associations with cognitive and symptom measures to determine whether cognitive deficits or symptomatic burden (i.e., negative and depressive symptoms) are more strongly associated with increased PVI performance in individuals with SSD. The current study used two samples: a training sample of individuals with SSD (n = 60) and a no diagnosis healthy control group (ND; n = 28) and a testing sample of individuals with SSD (n = 86) and ND (n = 129). The training sample was used to validate the RSS, establish diagnostic utility, and elucidate cognitive and symptomatology factors related to RSS performance. The testing sample was used to cross-validate findings and assess whether patterns of performance and relationships with RSS performance matched in an independent sample. Results established RSS as an acceptable measure of performance credibility, with excellent overall discrimination and sensitivity and specificity in range with other established embedded PVIs. Analysis of relationships with neurocognition and symptom severity factors revealed general neurocognition was significantly related to RSS performance, more so than specific neurocognitive domains of processing speed and learning and memory. In contrast, general neurocognition exhibited only a marginally stronger association with RSS performance compared to estimated IQ. No significant general patterns or relationships were identified between RSS performance and symptom severity measures. The absence of a significant relationship between negative symptoms and PVI failure suggests that factors other than negative symptomatology alone play a more prominent role in influencing performance credibility captured by PVIs. Possible explanations for this discrepancy include the direct impact of cognitive deficits on PVI performance, the limitations of the measures employed to assess negative symptoms, and the interplay between cognitive deficits and negative symptoms

Relating Locke’s Idea of Social Contract Theory and Political Accountability in Tanzania

Locke opines that, a State is created through the medium of  a contract in which each individual agrees with each other to give up  to the community the natural right of enforcing the law of reason, in  order that life, liberty and property may be preserved. In modern States, such contract exists in their constitutions. The constitution grants power to citizens to hold the government accountable. The aspect as to whether the Locke’s idea of accountability works in Tanzania attracts an interesting debate. This article explores the mechanism (s) used in Tanzania by citizens to hold political leaders accountable basing on Locke’s idea of social contract using 2010 and 2015 general elections as case study. Data were collected through reviewing documents including the constitution of Tanzania and literatures on Locke’s social contract idea on political accountability. The study reveals that, it is through general elections citizens hold the government accountable hence, conforming to the said contract idea. The mechanism has its pros and cons in the country though debatably, the study opines that the cons seem to outweigh the pros. While the state moves on using the mechanism revealed, it can think of application of other mechanisms like referendum to better conform to Locke’s idea of accountability in Social Contract Theory. Keywords: Political accountability, Locke and Social Contract Theory DOI: 10.7176/JAAS/68-09 Publication date:September 30th 202