The relationship between microscales and wind-wave spectral development

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution October, 1971The objective of this study was to describe the mechanics of wind wave generation and spectral development. Intermittency, high frequency microstructure in wind and wave fields, and strong nonlinear coupling involving a wide range of scales are shown to be crucial elements in the transfer of momentum to, from, and within the wave field. None of these elements are included in available theories. Measurements of wave height and of the turbulent atmospheric and subsurface boundary layers were made, from a small surface following platform and from a stable 38.5m spar buoy. The structure of moving gust patterns (cat's paws) is described and related to the generation of surface waves. Results from this and other background studies are then applied to a discussion of spectral growth during a two day period of active wave generation. Cat's paws contain 'bursts' of intense turbulent stress and buoyancy fluctuations separated by quiescent 'intervals'. There is a difference of over three orders of magnitude in fluctuation strength between these features. Rapid growth rate generation of high frequency surface waves and atmospheric turbulence occurs during the bursts. The resultant microscale components aid the growth of lower frequency instabilities by strong nonlinear coupling between scales of motion and by acting as drag or roughness elements. Evidence of strong coupling between frequency bands and of weakly resonant capillary-gravity wave interactions is presented. Thermal stratification has a strong influence on fluctuation magnitude and can delay the onset of surface wave generation. Major spectral growth is highly unsteady. Much of the momentum flux from air to sea occurs during intermittent events that are similar in nature to cat's paws, and goes directly into high frequency waves. The bursts occur predominantly over large groups of surface waves and involve strong nonlinear interactions between media and frequency bands. The long-term equilibrium balance between wind and water is disrupted by variations in surface currents. There are 'critical' wind speeds characterized by anomalous relationships between parameters of the predominantly logarithmic velocity profile

Methods and software for cosmic ray scintillation studies

The principal instrument used in cosmic ray scintillation studies is the spectra constructed from intensive observation. This method has its drawbacks in that the statistical characteristics of the process undergo essential reconstruction, i.e., the process becomes nonstationary from the viewpoint of such phenomena as Forbush decrease and during solar flares. The software used to process the above includes the direct Fourier transform and its modifications, autoregressive processes, and instantaneous spectrum methods. Used in various combinations, they prove helpful in handling the time series

The effects of protective clothing and its properties on energy consumption during different activities

There are many situations where workers are required to wear personal protective clothing (PPC), to protect against a primary hazard, such as heat or chemicals. But the PPC can also create ergonomic problems and there are important side effects which typically increase with rising protection requirements. The most extensively studied side effect is that of increased heat strain due to reduced heat and vapour transfer from the skin. Less studied is the extra weight, bulk and stiffness of PPC garments which is likely to increase the energy requirements of the worker, reduce the range of movement and lead to impaired performance. Current heat and cold stress standards assume workers are wearing light, vapour permeable clothing. By failing to consider the metabolic effects of actual PPC garments, the standards will underestimate heat production and therefore current standards cannot be accurately applied to workers wearing PPC. Information on the effect of the clothing on the wearer and the interactions between PPC, wearer and environment is limited. Data was collected to quantify the effect of PPC on metabolic load based on the properties of the PPC for the EU THERMPROTECT project (GERD-CT-2002-00846). The main objective of the project was to provide data to allow heat and cold stress assessment standards to be updated so that they need no longer exclude specialised protective clothing. The aim of this thesis was to investigate the effect of PPC and its properties on energy consumption during work. For this purpose, the effects of a range of PPC garments (Chapter 3), weight (Chapter 4), number of layers and material friction (Chapter 5) and wet layers (Chapter 6) on energy consumption whilst walking, stepping and completing an obstacle course were studied. The impact of PPC on range of movement in the lower limbs was also investigated (Chapter 7). The main findings were; a) Increased metabolic cost of 2.4 - 20.9% when walking, stepping and completing an obstacle course in PPC compared to a control condition. b) An average metabolic rate increase of 2.7% per kg increase in clothing weight, with greater increases with clothing that is heavier on the limbs and in work requiring greater ranges of movement. c) 4.5 to 7.9% increase in metabolic cost of walking and completing an obstacle course wearing 4 layers compared to a single layer control condition of the same weight. d) Changes in range of movement in PPC due to individual behavioural adaptations. e) Garment torso bulk is the strongest correlate of an increased metabolic rate when working in PPC (r=0.828, p<0.001). f) Garment leg bulk (r=0.615), lower sleeve weight (r=0.655) and weight of the garment around the crotch (r=0.638) are also all positively correlated with an increased metabolic rate. Total clothing weight and clothing insulation had r values of 0.5 and 0.35 respectively. This thesis has confirmed the major effect of clothing on metabolic rate, and the importance of including this effect in standards and models

Diversity of Nitrogen-Fixing Symbionts of Chamaecrista fasciculata (Partridge Pea) Across Variable Soils

We evaluated whether geographic distance and soil characteristics influence genetic structure of nitrogen-fixing bacterial symbionts associated with the host plant Chamaecrista fasciculata (Partridge Pea). We tested phylogeographic clustering and associations between genetic distance, geographic distance, and soil variables using sequences of 2 bacterial genes and soil chemistry across 23 sites in Mississippi. We identified rhizobia isolated from Partridge Pea as Bradyrhizobium. We detected significant genetic structure at a regional level, and determined that rhizobia within each region were more phylogenetically related than expected. Significant correlation between genetic distance and distances based on soil chemistry suggests environmental influences on rhizobia diversity. High levels of diversity among rhizobia over small spatial scales suggest that symbionts respond to local factors. Understanding geographic diversity in natural assemblages of rhizobia aids in predicting how hosts and symbionts respond to environmental perturbations

Cosmic ray modulation by high-speed solar wind fluxes

Cosmic ray intensity variations connected with recurrent high-speed fluxes (HSF) of solar wind are investigated. The increase of intensity before the Earth gets into a HSF, north-south anisotropy and diurnal variation of cosmic rays inside a HSF as well as the characteristics of Forbush decreases are considered

The effects of protective clothing on metabolic rate

There are many industrial sectors where workers are required to wear personal protective clothing and equipment (PPC/PPE). Although this PPC may provide protection from the primary hazard, for example heat or chemicals, it can also create ergonomic problems. The growing concern regarding health and safety of workers has generated regulations and standards, as well as research and development in the area of PPC/PPE (1). Although these have helped to improve the quality of the PPC and increase the safety of the workers, information on the effect of the clothing on the wearer and the interactions between PPC, wearer and environment are limited. Most PPC is designed for optimal protection against the hazard present, however the protection in itself can be a hazard. There are important side effects to protective clothing and typically with increasing protection requirements, the ergonomic problems increase. The problems of protective clothing can be split into thermal and metabolic issues. By creating a barrier between the wearer and the environment, clothing interferes with the process of thermoregulation, particularly reducing dry heat loss and sweat evaporation. Protective clothing also increases the metabolic cost of performing a task by adding weight and by otherwise restricting movement. The binding or hobbling effect of bulky, stiff or multilayered clothing adds measurably to work (2) . Current heat and cold stress standards consider the balance of heat production and loss but focus on environmental conditions, clothing insulation and work rate metabolism. They also assume workers are wearing light, vapour permeable clothing. By failing to consider the metabolic effects of actual protective clothing, the standards can underestimate heat stress or overestimate cold stress; therefore current standards cannot be accurately applied to workers wearing PPC. The effects of protective clothing on workers has been studied across a number of industries but studies have emphasized the thermal effects of clothing, such as heart rate, core temperature responses to different garments and performance decrements in the heat. Very few studies have considered the metabolic effects. Multilayered clothing ensembles have been reported to increase oxygen uptake by an amount significantly in excess of that which can be accounted for by the increases in the clothed weight of the subjects. Teitlebaum and Goldman (1972) walked subjects on a treadmill either wearing an additional 5 layers of arctic clothing over their standard fatigues or carrying the 11.19kg weight of the five layers as a lead-filled belt. In conclusion, the authors suggest the significant increase on average of approximately 16% in the metabolic cost of working in the clothing compared to the belt can most probably be attributed to ‘friction drag’ between the layers and/or a ‘hobbling effect’ of the clothing (3). Duggan (1988) investigated the effect using a bench stepping task in military chemical protective clothing, with long underwear and quilted thermal jackets/trousers as extra layers. When corrected for clothing weight, VO2 was greater by an average of 9% (4). In order to obtain data on a wider range of PPC and further investigate this possible ‘hobbling effect’ an experiment was performed on an extensive set of protective clothing ensembles with a focus on the metabolic effects

Investigating the effect of clothing layers and their frictional properties on metabolic rate

The effects of protective clothing (PPC) on metabolic rate were investigated in the first study of this thesis. Significant increases in the metabolic cost of work were found wearing a range of PPC and a number of suggestions put forward, following observations from the study and the literature, as to the possible factors that might be contributing to this increase. Subsequently weight and its distribution on the waist and limbs was studied, with results suggesting that the weight of the protective garments would have had an effect on the metabolic rate. However the results from the weight study could not account for all of the metabolic rate increases recorded in the PPC garments, unless it would be assumed all weight was located at the wrists and ankles, which seems rather unrealistic. Another concept suggested by a number of authors who also found similar increases in energy cost / oxygen consumption in PPC is that of a friction drag between layers, frictional resistance as one layer slides over another during movement. Despite being mentioned in the discussion and conclusions of a number of papers only one study has been found on the contribution of clothing friction and its effects on performance. However the study predominantly looked at task performance measures rather than energy cost / metabolic rate

The effects of protective clothing and its properties on energy consumption during different activities: literature review

There are many industrial situations where workers are required to wear personal protective clothing and equipment (PPC), for example, firefighters, chemical workers, cold store workers, army personnel and those working in the steel and forestry industries. Although this protective clothing may provide protection from the primary hazard, for example heat or chemicals, it can also create ergonomic problems. In recent years many PPC product standards have been introduced, these have helped to improve the quality of the protective clothing and so increased the safety of the workers. However, information on the effect of the clothing on the wearer and the interactions between PPC, wearer and environment are limited. Most PPC is designed for optimal protection against the hazard present, but this protection in itself can be a hazard. There are important side effects to protective clothing and typically with increasing protection requirements, the ergonomic problems increase. Often the main problem is the added load on the body in terms of weight. Also reduced mobility due to garment stiffness reduces the freedom of movement and may increase the risk of falls or getting caught in machinery. Even worse, the extra load and discomfort due to the protective clothing may tempt workers not to wear it when the primary hazard risk is low, leaving them unprotected if the hazard unexpectedly reappears or increases in strength. The problems of protective clothing can be seen as thermal, metabolic and performance issues. By creating a barrier between the wearer and the environment, clothing interferes with the process of thermoregulation, particularly reducing dry heat loss and sweat evaporation. The main metabolic effects come from the added weight of the clothing and the ‘hobbling effect’ due to garment bulk and stiffness, both of which increase metabolic cost so the worker has to expend more energy when carrying out tasks. Loss of freedom of movement and range of motion due to PPC can also lead to reduced performance. Current heat and cold stress standards consider the balance of heat production and loss but focus on environmental conditions and work rate metabolism. They also assume workers are wearing light, vapour permeable clothing. By failing to consider the metabolic effects of actual protective clothing, the standards underestimate heat production and therefore current standards cannot be accurately applied to workers wearing PPC. The effects of protective clothing on workers have been studied across a number of industries but studies have mainly concentrated on the thermal effects of clothing, such as heart rate, core temperature responses to different garments and on performance decrements caused by wearing PPC. Very few studies have considered the metabolic effects. Quantifying the effect of PPC on metabolic load based on the properties of the PPC was one of the objectives of the European Union THERMPROTECT project and the work undertaken for this thesis made up work package 4 of the EU project. The main objectives of the project were to provide data and models which allow the heat and cold stress assessment standards to be updated so that they need no longer exclude specialised protective clothing

Effects of simulated clothing weight distribution on metabolic rate

Protective clothing is worn in many industrial and military situations. Although worn for protection from one or more hazards, the clothing can have secondary effects which may limit the ability of the worker to perform the tasks required of the job. As demonstrated in the previous chapter, increases in energy consumption of 10 to 20 % are not uncommon. A small number of other results in this range have been reported in the literature along with suggestions that the additional clothing weight of the protective garments may be contributing to the observed increases. However, despite these proposals little investigation has been undertaken. In the previous chapter a plot of the percentage increases in metabolic rate in relation to the garment weight, fitted with a linear regression line resulted in a 2.7 % increase in metabolic rate per kg of clothing weight, which is considerably higher than would be predicted for carrying load

Modelling the effects of personal protective clothing properties on the increase of metabolic rate

Many of the PPC garments studied in this thesis are heavy, bulky and made up of multiple layers and stiff fabric as evident from the previous chapters. However it has proved hard to isolate completely the effect of a single garment property on the overall increased energy cost when wearing the actual PPC. An alternative approach to studying the individual contributors to metabolic effects of PPC is by studying them combined. In this chapter, data on a number of PPC properties will be collected and analysed using Pearson’s r and multiple regression, to determine the relative importance of these properties on recorded metabolic rate increases. This technique has been used to study other complex interactions before (Havenith et al. 1995). For this purpose, relevant predictive parameters of the clothing tested in Chapter 3 will be determined (weight distribution, insulation, bulk, stiffness) and the previously observed increases in metabolic rate analysed in relation to these predictors. Attempts will be made to use simple and non-destructive methods to determine the parameters, in order that tests could be repeated by others and would be usable in the workplace