Hybrid approaches to estimating freeway travel times using point traffic detector data

The accurate and reliable estimation of travel time based on point detector data is needed to support Intelligent Transportation System (ITS) applications. It has been found that the quality of travel time estimation is a function of the method used in the estimation and varies for different traffic conditions. In this study, two hybrid on-line travel time estimation models, and their corresponding off-line methods, were developed to achieve better estimation performance under various traffic conditions, including recurrent congestion and incidents. The first model combines the Mid-Point method, which is a speed-based method, with a traffic flow-based method. The second model integrates two speed-based methods: the Mid-Point method and the Minimum Speed method. In both models, the switch between travel time estimation methods is based on the congestion level and queue status automatically identified by clustering analysis. During incident conditions with rapidly changing queue lengths, shock wave analysis-based refinements are applied for on-line estimation to capture the fast queue propagation and recovery. Travel time estimates obtained from existing speed-based methods, traffic flow-based methods, and the models developed were tested using both simulation and real-world data. The results indicate that all tested methods performed at an acceptable level during periods of low congestion. However, their performances vary with an increase in congestion. Comparisons with other estimation methods also show that the developed hybrid models perform well in all cases. Further comparisons between the on-line and off-line travel time estimation methods reveal that off-line methods perform significantly better only during fast-changing congested conditions, such as during incidents. The impacts of major influential factors on the performance of travel time estimation, including data preprocessing procedures, detector errors, detector spacing, frequency of travel time updates to traveler information devices, travel time link length, and posted travel time range, were investigated in this study. The results show that these factors have more significant impacts on the estimation accuracy and reliability under congested conditions than during uncongested conditions. For the incident conditions, the estimation quality improves with the use of a short rolling period for data smoothing, more accurate detector data, and frequent travel time updates.

Early morning in a short-hydroperiod Everglades marsh (south of TS/Ph-1b), Taylor Slough

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. This image is made available for non-commercial or educational use only.

Making chamber measurements of net ecosystem exchange in a short-hydroperiod Everglades marsh (at TS/Ph-1b), Taylor Slough

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. This image is made available for non-commercial or educational use only.

Ecosystem Structure and Function Still Altered Two Decades After Short-Term Fertilization of a Seagrass Meadow

An oligotrophic phosphorus (P) limited seagrass ecosystem in Florida Bay was experimentally fertilized in a unique way. Perches were installed to encourage seabirds to roost and deliver an external source of nutrients via defecation. Two treatments were examined: (1) a chronic 23-year fertilization and (2) an earlier 28-month fertilization that was discontinued when the chronic treatment was initiated. Because of the low mobility of P in carbonate sediments, we hypothesized long-term changes to ecosystem structure and function in both treatments. Structural changes in the chronic treatment included a shift in the dominant seagrass species from Thalassia testudinum to Halodule wrightii, large increases in epiphytic biomass and sediment chlorophyll-a, and a decline in species richness. Functional changes included increased benthic metabolism and quantum efficiency. Initial changes in the 28-month fertilization were similar, but after 23 years of nutrient depuration T. testudinum has reestablished itself as the dominant species. However, P remains elevated in the sediment and H. wrightii has maintained a presence. Functionally the discontinued treatment remains altered. Biomass exceeds that in the chronic treatment and indices of productivity, elevated relative to control, are not different from the chronic fertilization. Cessation of nutrient loading has resulted in a superficial return to the pre-disturbance character of the community, but due to the nature of P cycles functional changes persist.

Comparative study of periphyton community structure in long and short-hydroperiod Everglades marshes

The Florida Everglades is a mosaic of short and long-hydroperiod marshes that differ in the depth, duration, and timing of inundation. Algae are important primary producers in widespread Everglades’ periphyton mats, but relationships of algal production and community structure to hydrologic variability are poorly understood. We quantified differences in algal biomass and community structure between periphyton mats in 5 short and 6 long-hydroperiod marshes in Everglades National Park (ENP) in October 2000. We related differences to water depth and total phosphorus (TP) concentration in the water, periphyton and soils. Long and short-hydroperiod marshes differed in water depth (73 cm vs. 13 cm), periphyton TP concentrations (172μg g−1 vs. 107 μg g−1, respectively) and soil TP (284 μg g−1 vs. 145 μg g−1). Periphyton was abundant in both marshes, with short-hydroperiod sites having greater biomass than long-hydroperiod sites (2936 vs. 575 grams ash-free dry mass m−2). A total of 156 algal taxa were identified and separated into diatom (68 species from 21 genera) and “soft algae” (88 non-diatom species from 47 genera) categories for further analyses. Although diatom total abundance was greater in long-hydroperiod mats, diatom species richness was significantly greater in short- hydroperiod periphyton mats (62 vs. 47 diatom taxa). Soft algal species richness was greater in long-hydroperiod sites (81 vs. 67 soft algae taxa). Relative abundances of individual taxa were significantly different among the two site types, with soft algal distributions being driven by water depth, and diatom distributions by water depth and TP concentration in the water and periphyton. Periphyton communities differ between short and long-hydroperiod marshes, but because they share many taxa, alterations in hydroperiod could rapidly

The development of direct ultra-fast PCR for forensic genotyping using short channel microfluidic systems with enhanced sieving matrices

There are situations in which it is very important to quickly and positively identify an individual. Examples include suspects detained in the neighborhood of a bombing or terrorist incident, individuals detained attempting to enter or leave the country, and victims of mass disasters. Systems utilized for these purposes must be fast, portable, and easy to maintain. The goal of this project was to develop an ultra fast, direct PCR method for forensic genotyping of oral swabs. The procedure developed eliminates the need for cellular digestion and extraction of the sample by performing those steps in the PCR tube itself. Then, special high-speed polymerases are added which are capable of amplifying a newly developed 7 loci multiplex in under 16 minutes. Following the amplification, a postage stamp sized microfluidic device equipped with specially designed entangled polymer separation matrix, yields a complete genotype in 80 seconds. The entire process is rapid and reliable, reducing the time from sample to genotype from 1-2 days to under 20 minutes. Operation requires minimal equipment and can be easily performed with a small high-speed thermal-cycler, reagents, and a microfluidic device with a laptop. The system was optimized and validated using a number of test parameters and a small test population. The overall precision was better than 0.17 bp and provided a power of discrimination greater than 1 in 106. The small footprint, and ease of use will permit this system to be an effective tool to quickly screen and identify individuals detained at ports of entry, police stations and remote locations. The system is robust, portable and demonstrates to the forensic community a simple solution to the problem of rapid determination of genetic identity.

Short-term changes in phosphorus storage in an oligotrophic Everglades wetland ecosystem receiving experimental nutrient enrichment

Natural, unenriched Evergladeswetlands are known to be limited by phosphorus(P) and responsive to P enrichment. However,whole-ecosystem evaluations of experimental Padditions are rare in Everglades or otherwetlands. We tested the response of theEverglades wetland ecosystem to continuous,low-level additions of P (0, 5, 15, and30 μg L−1 above ambient) in replicate,100 m flow-through flumes located in unenrichedEverglades National Park. After the first sixmonths of dosing, the concentration andstanding stock of phosphorus increased in thesurface water, periphyton, and flocculentdetrital layer, but not in the soil or macrophytes. Of the ecosystem components measured, total P concentration increased the most in the floating periphyton mat (30 μg L−1: mean = 1916 μg P g−1, control: mean =149 μg P g−1), while the flocculentdetrital layer stored most of the accumulated P(30 μg L−1: mean = 1.732 g P m−2,control: mean = 0.769 g P m−2). Significant short-term responsesof P concentration and standing stock wereobserved primarily in the high dose (30 μgL−1 above ambient) treatment. Inaddition, the biomass and estimated P standingstock of aquatic consumers increased in the 30and 5 μg L−1 treatments. Alterationsin P concentration and standing stock occurredonly at the upstream ends of the flumes nearestto the point source of added nutrient. Thetotal amount of P stored by the ecosystemwithin the flume increased with P dosing,although the ecosystem in the flumes retainedonly a small proportion of the P added over thefirst six months. These results indicate thatoligotrophic Everglades wetlands respondrapidly to short-term, low-level P enrichment,and the initial response is most noticeable inthe periphyton and flocculent detrital layer.

Controls on Ecosystem Carbon Dioxide Exchange in Short- and Long-Hydroperiod Florida Everglades Freshwater Marshes

Although freshwater wetlands are among the most productive ecosystems on Earth, little is known of carbon dioxide (CO2) exchange in low latitude wetlands. The Everglades is an extensive, oligotrophic wetland in south Florida characterized by short- and long-hydroperiod marshes. Chamber-based CO2 exchange measurements were made to compare the marshes and examine the roles of primary producers, seasonality, and environmental drivers in determining exchange rates. Low rates of CO2 exchange were observed in both marshes with net ecosystem production reaching maxima of 3.77 and 4.28 μmol CO2 m−2 s−1 in short- and long-hydroperiod marshes, respectively. Fluxes of CO2 were affected by seasonality only in the short-hydroperiod marsh, where flux rates were significantly lower in the wet season than in the dry season. Emergent macrophytes dominated fluxes at both sites, though this was not the case for the short-hydroperiod marsh in the wet season. Water depth, a factor partly under human control, significantly affected gross ecosystem production at the short-hydroperiod marsh. As Everglades ecosystem restoration proceeds, leading to deeper water and longer hydroperiods, productivity in short-hydroperiod marshes will likely be more negatively affected than in long-hydroperiod marshes. The Everglades stand in contrast to many freshwater wetlands because of ecosystem-wide low productivity rates.

Seasonal differences in the CO2 exchange of a short-hydroperiod Florida Everglades marsh

Although wetlands are among the world's most productive ecosystems, little is known of long-term CO2 exchange in tropical and subtropical wetlands. The Everglades is a highly managed wetlands complex occupying >6000 km2 in south Florida. This ecosystem is oligotrophic, but extremely high rates of productivity have been previously reported. To evaluate CO2 exchange and its response to seasonality (dry vs. wet season) in the Everglades, an eddy covariance tower was established in a short-hydroperiod marl marsh. Rates of net ecosystem exchange and ecosystem respiration were small year-round and declined in the wet season relative to the dry season. Inundation reduced macrophyte CO2 uptake, substantially limiting gross ecosystem production. While light and air temperature exerted the primary controls on net ecosystem exchange and ecosystem respiration in the dry season, inundation weakened these relationships. The ecosystem shifted from a CO2 sink in the dry season to a CO2 source in the wet season; however, the marsh was a small carbon sink on an annual basis. Net ecosystem production, ecosystem respiration, and gross ecosystem production were −49.9, 446.1 and 496.0 g C m−2 year−1, respectively. Unexpectedly low CO2 flux rates and annual production distinguish the Everglades from many other wetlands. Nonetheless, impending changes in water management are likely to alter the CO2 balance of this wetland and may increase the source strength of these extensive short-hydroperiod wetlands.

Controls on sensible heat and latent energy fluxes from a short-hydroperiod Florida Everglades marsh

Little is known of energy balance in low latitude wetlands where there is a year-round growing season and a climate best defined by wet and dry seasons. The Florida Everglades is a highly managed and extensive subtropical wetland that exerts a substantial influence on the hydrology and climate of the south Florida region. However, the effects of seasonality and active water management on energy balance in the Everglades ecosystem are poorly understood. An eddy covariance and micrometeorological tower was established in a short-hydroperiod Everglades marsh to examine the dominant environmental controls on sensible heat (H) and latent energy (LE) fluxes, as well as the effects of seasonality on these parameters. Seasonality differentially affected H and LE fluxes in this marsh, such that H was principally dominant in the dry season and LE was strongly dominant in the wet season. The Bowen ratio was high for much of the dry season (1.5–2.4), but relatively low (H and LE fluxes across nearly all seasons and years (). However, the 2009 dry season LE data were not consistent with this relationship () because of low seasonal variation in LE following a prolonged end to the previous wet season. In addition to net radiation, H and LE fluxes were significantly related to soil volumetric water content (VWC), water depth, air temperature, and occasionally vapor pressure deficit. Given that VWC and water depth were determined in part by water management decisions, it is clear that human actions have the ability to influence the mode of energy dissipation from this ecosystem. Impending modifications to water management under the Comprehensive Everglades Restoration Plan may shift the dominant turbulent flux from this ecosystem further toward LE, and this change will likely affect local hydrology and climate.

Effects of shading on calcareous benthic periphyton in a short-hydroperiod oligotrophic wetland (Everglades, FL, USA)

The effects of shade on benthic calcareous periphyton were tested in a short-hydroperiod oligotrophic subtropical wetland (freshwater Everglades). The experiment was a split-plot design set in three sites with similar environmental characteristics. At each site, eight randomly selected 1-m2 areas were isolated individually in a shade house, which did not spectrally change the incident irradiance but reduced it quantitatively by 0, 30, 50, 60, 70, 80, 90 and 98%. Periphyton mat was sampled monthly under each shade house for a 5 month period while the wetland was flooded. Periphyton was analyzed for thickness, DW, AFDW, chlorophyll a (chl a) and incubated in light and dark BOD bottles at five different irradiances to assess its photosynthesis–irradiance (PI) curve and respiration. The PI curves parameters P max, I k and eventually the photoinhibition slope (β) were determined following non-linear regression analyses. Taxonomic composition and total algal biovolume were determined at the end of the experiment. The periphyton composition did not change with shade but the PI curves were significantly affected by it. I k increased linearly with increasing percent irradiance transmittance (%IT = 1−%shade). P max could be fitted with a PI curve equation as it increased with %IT and leveled off after 10%IT. For each shade level, the PI curve was used to integrate daily photosynthesis for a day of average irradiance. The daily photosynthesis followed a PI curve equation with the same characteristics as P max vs. %IT. Thus, periphyton exhibited a high irradiance plasticity under 0–80% shade but could not keep up the same photosynthetic level at higher shade, causing a decrease in daily GPP at 98% shade levels. The plasticity was linked to an increase in the chl a content per cell in the 60–80% shade, while this increase was not observed at lower shade likely because it was too demanding energetically. Thus, chl a is not a good metric for periphyton biomass assessment across variously shaded habitats. It is also hypothesized that irradiance plasticity is linked to photosynthetic coupling between differently comprised algal layers arranged vertically within periphyton mats that have different PI curves.

Cross-Cultural Cuisine: Long-Term Trend or Short-Lived Fad

Defining a consumer interest as a long-term trend or short-lived fad has significant implicatiosn for restauranteurs' management decisions. The terms "trend" and "fad" can be operationally defined for the food service industry. The authors examine today's popular cross-cultural cuisine to determine its trend or fad status and discuss the catalysts that promoted or hindered its trend/fad status, as well as implications for the food service industry.

The Study of Clustering of Taiwanese Tourists' Motivations to Hong Kong

Abstract Driven by the political and economic forces of cross-strait, Taiwan has become one of the major source markets for Hong Kong tourism industry since 1987. The major purposes of this study were to investigate the following factors (1) The influential factors of travel motivation, (2) The clusters of travel motivations, (3) The marketing segmentation of clusters of Taiwanese tourists to visit Hong Kong. Through ten travel agents, self-report surveys were distributed to collect data from 366 Taiwanese travelers. Hence, four push factors and six pull factors were identified as travel motivations through the factor analysis. Combined with the cluster analysis; five new groups were founded. Finally, five clusters which process unique profiles (location difference, visiting frequency, travel satisfaction, and destination loyalty) were addressed. The suggestions of developing effective market strategies to attract Taiwanese tourists to Hong Kong were also provided.

Effects of Simulated Drought on the Carbon Balance of Everglades Short-Hydroperiod Marsh

Hydrology drives the carbon balance of wetlands by controlling the uptake and release of CO2 and CH4. Longer dry periods in between heavier precipitation events predicted for the Everglades region, may alter the stability of large carbon pools in this wetland's ecosystems. To determine the effects of drought on CO2 fluxes and CH4 emissions, we simulated changes in hydroperiod with three scenarios that differed in the onset rate of drought (gradual, intermediate, and rapid transition into drought) on 18 freshwater wetland monoliths collected from an Everglades short-hydroperiod marsh. Simulated drought, regardless of the onset rate, resulted in higher net CO2 losses net ecosystem exchange (NEE) over the 22-week manipulation. Drought caused extensive vegetation dieback, increased ecosystem respiration (Reco), and reduced carbon uptake gross ecosystem exchange (GEE). Photosynthetic potential measured by reflective indices (photochemical reflectance index, water index, normalized phaeophytinization index, and the normalized difference vegetation index) indicated that water stress limited GEE and inhibited Reco. As a result of drought-induced dieback, NEE did not offset methane production during periods of inundation. The average ratio of net CH4 to NEE over the study period was 0.06, surpassing the 100-year greenhouse warming compensation point for CH4 (0.04). Drought-induced diebacks of sawgrass (C3) led to the establishment of the invasive species torpedograss (C4) when water was resupplied. These changes in the structure and function indicate that freshwater marsh ecosystems can become a net source of CO2 and CH4 to the atmosphere, even following an extended drought. Future changes in precipitation patterns and drought occurrence/duration can change the carbon storage capacity of freshwater marshes from sinks to sources of carbon to the atmosphere. Therefore, climate change will impact the carbon storage capacity of freshwater marshes by influencing water availability and the potential for positive feedbacks on radiative forcing.

Tree Island Response to Fire and Flooding in the Short-Hydroperiod Marl Prairie Grasslands of the Florida Everglades

Within the marl prairie grasslands of the Florida Everglades, USA, the combined effects of fire and flooding usually lead to very significant changes in tree island structure and composition. Depending on fire severity and post-fire hydroperiod, these effects vary spatially and temporally throughout the landscape, creating a patchy post-fire mosaic of tree islands with different successional states. Through the use of the Normalized Difference Vegetation Index (NDVI) and three predictor variables (marsh water table elevation at the time of fire, post-fire hydroperiod, and tree island size), along with logistic regression analysis, we examined the probability of tree island burning and recovering following the Mustang Corner Fire (May to June 2008) in Everglades National Park. Our data show that hydrologic conditions during and after fire, which are under varying degrees of management control, can lead to tree island contraction or loss. More specifically, the elevation of the marsh water table at the time of the fire appears to be the most important parameter determining the severity of fire in marl prairie tree islands. Furthermore, in the post-fire recovery phase, both tree island size and hydroperiod during the first year after the fire played important roles in determining the probability of tree island recovery, contraction, or loss.