The Effect of Rapid Liquid-Phase Reactions on Injector Design and Combustion in Rocket Motors

Data are presented indicating the rates and magnitudes of energy released by the liquid-phase reactions of various propellant combinations. The data show that this energy release can contribute significantly to the rate of vaporization of the incoming propellants and thus aid the combustion process. Nevertheless, very low performances were obtained in rocket motors with conventional impinging-jet injectors when highly reactive systems such as N104-N2H4, were employed. A possible explanation for this low performance is that the initial reactions of such systems are so rapid that liquid-phase mixing is inhibited. Evidence for such an effect is presented in a series of color photographs of open flames using various injector elements. Based on these studies, some requirements are suggested for injector elements using highly reactive propellants. Experimental results are presented of motor tests using injector elements in which some of these requirements are met through the use of a set of concentric tubes. These tests, carried out at thrust levels of 40 to 800 lb per element, demonstrated combustion efficiencies of up to 98% based on equilibrium characteristic velocity values. Results are also presented for tests made with impinging-jet and splash-plate injectors for comparison

Environmental Management / Designing and Evaluating Bamboo Harvesting Methods for Local Needs: Integrating Local Ecological Knowledge and Science

Abstract in dt. Sprache nicht vorhandenDendrocalamus hamiltonii, a large, clump-forming bamboo, has great potential to contribute towards poverty alleviation efforts across its distributional range. Harvesting methods that maximize yield while they fulfill local objectives and ensure sustainability are a research priority. Documenting local ecological knowledge on the species and identifying local users\u2019 goals for its production, we defined three harvesting treatments (selective cut, horseshoe cut, clear cut) and experimentally compared them with a no-intervention control treatment in an action research framework. We implemented harvesting over three seasons and monitored annually and two years post-treatment. Even though the total number of culms positively influenced the number of shoots regenerated, a much stronger relationship was detected between the number of culms harvested and the number of shoots regenerated, indicating compensatory growth mechanisms to guide shoot regeneration. Shoot recruitment declined over time in all treatments as well as the control; however, there was no difference among harvest treatments. Culm recruitment declined with an increase in harvesting intensity. When univariately assessing the number of harvested culms and shoots, there were no differences among treatments. However, multivariate analyses simultaneously considering both variables showed that harvested output of shoots and culms was higher with clear cut and horseshoe cut as compared to selective cut. Given the ease of implementation and issues of work safety, users preferred the horseshoe cut, but the lack of sustainability of shoot production calls for investigating longer cutting cycles

Testing a silvicultural recommendation: Brazil nut responses 10 years after liana cutting.

1. Lianas or woody vines can be detrimental to the trees that support them. Research on liana cutting for tropical timber management has demonstrated positive yet costly benefits, but liana utting to enhance commercial outputs of nontimber forest products has not been examined. We implemented a controlled experiment to quantify the effects of cutting lianas on Brazil nut Bertholletia excelsa Bonpl. fecundity. 2. We conducted our 10-year experiment in a Brazilian extractive reserve where local harvesters collect fruits from this Amazonian canopy-emergent species as part of their forest-based livelihood system. We cut 454 lianas with a total basal area of 2 41 m 2 from 78 of 138 host trees ≥ 50 cm diameter at breast height. 3. Treated trees were significantly better producers 3 ½ years after liana cutting, and these differences increased dramatically in subsequent years, with consistent proportionally higher production in treated versus untreated individuals. 4. The number of lianas rooted within 5 m of the host tree significantly explained production levels, suggesting both above- and below-ground liana ? host tree competition. Once host crowns were liana-free, branch regrowth was highly visible, particularly in heavily infested trees, and crown reassessments suggested that liana cutting improved crown form. Additionally, liana cutting may induce some nonproducing trees to become producers and may circumvent mortality of trees heavily infested with lianas (> 75% crown covered). 5. Liana removal can be implemented easily when harvesting Brazil nut fruits. Only lianas associated with B. excelsa trees should be cut to conserve liana ecosystem functions. 6. Synthesis and applications. We quantified effects of liana cutting on Brazil nut host tree fecundity and provided estimates of increased commercial yields. Our long-term (10-year) study permits understanding of biological variation and informs related management decisions. Findings suggest that liana cutting reduces above- and below-ground competition with individual trees, ultimately allowing mature host crowns to recover such that 9 - 10 years after liana cutting, treated trees produced on average three times more fruits than untreated trees. Application of liana cutting to other tropical species would likely boost fruit and seed production, increase host tree fecundity and potentially enhance future recruitment

Sustainable forest use in Brazilian extractive reserves: natural regeneration of Brazil nut in exploited populations.

The emergence of Brazilian extractive reserves reinforced the notion that sustainable forest use could play a central role in conservation. Brazil nut is considered a model non-timber product for promoting conservation through use. Demographic studies, however, have demonstrated differential impacts of nut harvest on Brazil nut population structure. Comparing three populations with different forest use histories, degrees of road access, and recent levels of nut harvest, we asked: (1) Are they exhibiting regeneration failure? and (2) Are seedling/sapling densities explained by adult Brazil nut structure, fruit fate and/or overall forest structure? We installed four 9-ha plots in each site to census Brazil nut trees > 10 cm dbh, and within each plot, 36 subplots (25 × 25 m each) to quantify regeneration, overall forest structure, and open and closed fruit counts. Approximately 29-55% of fruits was unharvested, and more than 90% of these was opened by scatterhoarding dispersers. Population structure approximated a reverse-J size class distribution, with seedling densities varying from 3.2 to 5.8 individuals ha-1. We conclude that within the current harvest context, regeneration is sufficient for population persistence in our sites, at least over the medium term. The socioeconomics of sustainably managing Brazil nut is the greater challenge, involving interlinked competitive land uses, nut quality, and substantial increases in local income from harvest. Some of these challenges are being addressed in Brazil, Bolivia and Peru, providing hope that this cornerstone extractive species will continue to play a prominent role in the ecological and economic landscape of Amazonia

El Nino Southern Oscillation (ENSO) Enhances CO2 Exchange Rates in Freshwater Marsh Ecosystems in the Florida Everglades

This research examines the relationships between El Nino Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009-2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Nino and La Nina phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Nina phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (-11 to -110 g CO2 m(-2) yr(-1)) compared to El Nino and neutral years (-5 to -43.5 g CO2 m(-2) yr(-1)). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m(-2) yr(-1)) except in one exceptionally wet year that was associated with an El Nino phase (-16 g CO2 m(-2) yr(-1)). Considering that future climate predictions suggest a higher frequency and intensity in El Nino and La Nina phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades

Reliability Testing of Statistical Process Control Procedures for Manufacturing with Multiple Sources of Variation

Quality inconsistencies can be caused by processes with multiple sources of variation. Therefore, the development of control charts that perform properly for both producer's and consumer's risk can be very complex. This is particularly true for real-time SPC systems that collect a great deal of data through noncontact sensing. In this paper, we demonstrate the use of a Monte Carlo simulation procedure that can be used to test SPC charts for both consumer's and producer's risk, and an experimental design procedure to analyze the results. This procedure is shown to be especially useful where design factors interact to cause high variation in a quality characteristic of a product. The approach is illustrated for a practical problem taken from the lumber manufacturing industry and demonstrates that commonly used industrial practices to control product dimensions lead to erroneous conclusions. To that end, a new mathematical approach that yields the correct results is described. The Simulation / ANOVA procedure described in this paper may have applicability in the control of many other industrial processes

Statistical Considerations for Real-Time Size Control Systems in Wood Products Manufacturing

Currently, sawmill machinery companies are developing real-time size lumber size control systems using non-contact laser measuring systems. These systems rely on the application of industrial statistics to large quantities of lumber thickness and width data. Because of the sampling intensity and frequent decision making in real-time systems, there is an increased chance of committing Type I or Type II errors when drawing conclusions if statistical methods are incorrectly applied. There is confusion in the industry concerning the appropriate statistical model to use for lumber size control. This survey of the current literature discusses three distinct methods for calculating and partitioning sawing variation, and thereby calculating control limits for control charts. This paper reviews the statistical foundation and current understanding of industrial statistics for implementing real-time SPC systems and makes recommendations for improvement

SPC Methods for Detecting Simple Sawing Defects Using Real-Time Laser Range Sensor Data

Effective statistical process control (SPC) procedures can greatly enhance product value and yield in the lumber industry, ensuring accuracy and minimum waste. To this end, many mills are implementing automated real-time SPC with non-contact laser range sensors (LRS). These systems have, thus far, had only limited success because of frequent false alarms and have led to tolerances being set excessively wide and real problems being missed. Current SPC algorithms are based on manual sampling methods and, consequently, are not appropriate for the volume of data generated by real-time systems. The objective of this research was to establish a system for real-time LRS size control data for automated lumber manufacturing. An SPC system was developed that incorporated multi-sensor data, and new SPC charts were developed that went beyond traditional size control methods, simultaneously monitoring multiple surfaces and specifically targeting common sawing defects. In this paper, eleven candidate control charts were evaluated. Traditional X-bar and range charts are suggested, which were explicitly developed to take into account the components of variance in the model. Applying these methods will lead to process improvements for sawmills using automated quality control systems, so that machines producing defective material can be identified and prompt repairs made

An Effective Chemical Deterrent for Invasive Cuban Treefrogs

Introduced vertebrates have a variety of impacts on ecosystems and economies, and many cause problems for humans. One such problem is the loss of electrical power when invasive animals cause short circuits in power-transmission equipment. Cuban treefrogs (Osteopilus septentrionalis) are known to cause power outages and are a nuisance to humans when they invade homes and defecate on doors and windows. These large, slightly toxic treefrogs were introduced into Florida from the Caribbean. They now occur throughout the peninsula of Florida and are spreading to other states in the Southeast. We used refuge choice experiments to test the effectiveness of Sniff ’n’ StopTM animal deterrent to exclude Cuban treefrogs from enclosed spaces, such as utility switchgear boxes. We found that the deterrent was effective and showed potential as a low-cost means to prevent frog-related power outages and reduce conflicts with residents in the urbanized areas preferred by these invasive frog

Measurement of strain heat in shock-loaded 304 stainless steel: implications to powder consolidation; oral presentation of full paper

Over the past decades there have been numerous papers on the shock response of materials and more specifically towards metal powder compaction and consolidation. In general, the shock process for powdered materials has utilized the traditional pressure-volume shock relationships proportioned to the initial packing densities of the powders. However, this approach and its resulting data are in controversy due to the lack of knowledge of its associated particle strain and strain temperature uncertainties. This paper will describe the current understanding as well as the experimental technique used to obtain the shock response for distended materials. The above parameters are described within a pressure-strain-temperature interdependence. It was found that the experimentally measured strain heat was not only a function of initial packing density but also a function of powder size and distribution