Determination of flow resistance coefficient for vegetation in open channel: laboratory study

This study focused on determination of flow resistances coefficient for grass in an open channel. Laboratory works were conducted to examine the effects of varying of roughness elements on the flume to determine flow resistance coefficient and also to determine the optimum flow resistance with five different flow rate, Q. Laboratory study with two type of vegetation which are Cow Grass and Pearl Grass were implementing to the bed of a flume. The roughness coefficient, n value is determine using Manning’s equation while Soil Conservation Services (SCS) method was used to determine the surface resistance. From the experiment, the flow resistance coefficient for Cow Grass in range 0.0008 - 0.0039 while Pearl Grass value for the flow resistance coefficient are in between 0.0013 - 0.0054. As a conclusion the vegetation roughness value in open channel are depends on density, distribution type of vegetation used and physical characteristic of the vegetation itsel

Temporal loudness weights are frequency specific

Previous work showed that the beginning of a sound is more important for the perception of loudness than later parts. When a short silent gap of sufficient duration is inserted into a sound, this primacy effect reoccurs in the second sound part after the gap. The present study investigates whether this temporal weighting occurs independently for different frequency bands. Sounds consisting of two bandpass noises were presented in four different conditions: (1) a simultaneous gap in both bands, (2) a gap in only the lower frequency band, (3) a gap in only the higher frequency band, or (4) no gap. In all conditions, the temporal loudness weights showed a primacy effect at sound onset. For the frequency bands without a gap, the temporal weights decreased gradually across time, regardless of whether the other frequency band did or did not contain a gap. When a frequency band contained a gap, the weight at the onset of this band after the gap was increased. This reoccurrence of the primacy effect following the gap was again largely independent of whether or not the other band contained a gap. Thus, the results indicate that the temporal loudness weights are frequency specific

Temporal weights in loudness : investigation of the effects of background noise and sound level

Previous research has consistently shown that for sounds varying in intensity over time, the beginning of the sound is of higher importance for the perception of loudness than later parts (primacy effect). However, in all previous studies, the target sounds were presented in quiet, and at a fixed average sound level. In the present study, temporal loudness weights for a time-varying narrowband noise were investigated in the presence of a continuous bandpass-filtered background noise and the average sound levels of the target stimuli were varied across a range of 60 dB. Pronounced primacy effects were observed in all conditions and there were no significant differences between the temporal weights observed in the conditions in quiet and in background noise. Within the conditions in background noise, there was a significant effect of the sound level on the pattern of weights, which was mainly caused by a slight trend for increased weights at the end of the sounds (“recency effect”) in the condition with lower average level. No such effect was observed for the in-quiet conditions. Taken together, the observed primacy effect is largely independent of masking as well as of sound level. Compatible with this conclusion, the observed primacy effects in quiet and in background noise can be well described by an exponential decay function using parameters based on previous studies. Simulations using a model for the partial loudness of time-varying sounds in background noise showed that the model does not predict the observed temporal loudness weights

Fish assemblage change following the structural restoration of a degraded stream

Decades of anthropogenic pressure have harmed riverscapes throughout North America by degrading habitats and water quality and can result in the extirpation of sensitive aquatic taxa. Local stream restoration projects have increased in frequency, but monitoring is still infrequent. In 2010, Kickapoo Creek in East Central Illinois was subjected to a stream restoration project that included implementation of artificial riffles, riprap, scouring keys, and riparian vegetation. We monitored the restoration efforts for 6years after the restoration through annual sampling efforts at restored and reference sites to determine changes in habitat and fish assemblage using standard habitat sampling and electrofishing techniques. We observed distinct temporal and spatial shifts in physico-chemical parameters along with changes in fish community structure. Although biotic integrity remained moderately low in reference assemblages, restored reaches showed 3-year delay in response to restoration, with biotic integrity positively linked to additional instream habitat and altered channel morphology. Larger substrate sizes, submerged terrestrial vegetation, and newly formed scour pools along with reduced siltation were found in the restored sites, in contrast to the reference sites. These changes resulted in increased species diversity, reduced number of opportunistic species and consequently an overall increase in health of fish communities. We also observed recruitment of habitat specialists and increase in species with reproductive strategies that rely on complex substrates. The results of this study highlight some of the complex dynamics driving reach-scale restoration projects. We demonstrate the usefulness of structural restoration as a management tool to increase biotic integrity through long-term alteration of critical habitat. The delay in the response of species to the restoration efforts emphasizes the need for long-term continuous temporal and spatial monitoring

Essays on river mechanics

CER94-95-PYJ-3.Presented by the Graduate Students in CE 717 - River Mechanics (Spring, 1995).Instructor: P.Y. Julien.Includes bibliographical references.April 1995

Evaluation of meniscal changes in two models of knee osteoarthritis: traumatic loading and modified transection

2013 Fall.Includes bibliographical references.Osteoarthritis (OA) is a debilitating joint disease characterized by the erosion of articular cartilage on the ends of long bones, causing painful bone on bone contact. OA can affect any joint but is commonly seen in the knee and is a major cause of disability. Normally thought of as a degenerative disease, the early onset of OA can be triggered by a number of factors including injury to the joint. With the number of younger athletes increasing as well as the incidence of knee injury increasing it is important to understand the development and progression of post traumatic OA (PTOA). Only then can measures be taken to prevent, or slow the progression. The most common method to study PTOA of the knee involves using an animal model where the anterior cruciate ligament is transected (ACLT). The ACLT model fails to account for a number of factors that are commonly seen in clinical cases. The compressive forces experienced by the joint as well as damage to other joint structures are not accounted for in the tradition ACLT model. Furthermore, despite the well documented role of the meniscus in joint stability and joint kinematics other tissues such as the articular cartilage and subchondral bone have received more attention. PTOA is a "whole organ" disease where damage to one structure influences other structures, and in order to fully understand the progression the entire joint must be studied. There is a lack of knowledge as to how the meniscus is both affected and influences the development of OA. To better understand its role there have been two PTOA models developed for this study. The first is a modified ACLT model (mACLT), where meniscal damage is surgically induced at the time of ACL transection. The second model is a traumatic tibiofemoral compressive impact model (ACLF) where the ACL is ruptured due to a blunt force trauma to the joint. The objective of this thesis was to monitor meniscal changes twelve weeks following impact for both the mACLT and ACLF model. Meniscal damage was monitored over time with the use of magnetic resonance imaging MRI. At dissection gross morphology was graded and compared to the acute and chronic MRI notes. Each meniscus was then sectioned into regions and mechanically tested. Indentation relaxation testing allowed for the instantaneous as well as equilibrium elastic moduli to be calculated. Following mechanical testing meniscal tissue was fixed and stained for glycosaminoglycan (GAG) content. Using semi qualitative analysis, the GAG intensity and coverage was analyzed. Acute and chronic damage, elastic moduli, and GAG content from the injured limbs was then compared to the contralateral controls