A design for a novel tubular high-precision direct-drive brushless linear motor has been developed. The novelty of the design lies in the orientation of the magnets in the mover. In conventional linear motors the magnets of the armature are arranged such that the attractive poles are adjacent throughout, in an NS-NS-NS orientation, where N denotes the north pole and S denotes the south pole of the magnet. In the new design, the magnets in the moving part are oriented in an NS-NS-SN-SN orientation. This change in orientation yields greater magnetic field intensity near the like-pole region. The magnets of the mover are encased within a brass tube, which slides through a three-phase array of current-carrying coils. As the coils are powered, they induce a force on the permanent magnets according to the Lorentz force equation. The primary advantages of the motor are its compact nature, fast, precise positioning due to its low-mass moving part, direct actuation, extended travel range, and ability to extend beyond its base. The linear motor is used in conjunction with a position sensor, power amplifiers, and a controller to form a complete solution for positioning and actuation requirements. Controllers were developed for two applications, with a lead-lag as the backbone of each. For the first application, the principal requirements are for fast rise and settling times. For the second application, the primary requirement is for near-zero overshoot. With the controller for application 1, the motor has a rise time of 55 ms, a settling time of 600 ms, and 65% overshoot. With the controller for application 2 implemented, the motor has a rise time of 1 s, a settling time of 2.5 s, and 0.2% overshoot. The maximum force capability of the motor is measured to be 26.4 N. The positioning resolution is 35 ?m. This thesis discusses the motors physical design, construction, implementation, testing, and tuning. It includes specifications of the components of the motor and other necessary equipment, desired and actual motor performance, and the primary limitations on the precision of the system.
Anahtar Kelimeler :
actuator, linear motor, brushless, robotic, mechatronic
A new design AMTEC converter model was developed, and its effectiveness as a design tool was evaluated. To develop the model, requirements of the model were defined, several new design models were successively developed, and finally an optimal new design model was developed. The model was created within Sinda/Fluint, with its graphical interface, Thermal Desktop, a software package that can be used to conduct complex thermal and fluid analyses. Performance predictions were then correlated and compared with actual performance data from the Road Runner II AMTEC converter. Predicted performance results were within 10% of actual performance data for all operating conditions analyzed. This accuracy tended to increase within operating ranges that would be more likely encountered in AMTEC applications. Performance predictions and parametric design studies were then performed on a proposed new design converter model with a variety of annular condenser heights and with potassium as a working fluid to evaluate the effects of various design modifications. Results clearly indicated the effects of the converter design modifications on the converters power and efficiency, thus simplifying the design optimization process. With the close correlation to actual data and the design information obtained from parametric studies, it was determined that the model could serve as an effective tool for the design of AMTEC converters.
A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel chain-wire mooring lines is extended to allow for the large elongation in a mooring line, the dependence of the modulus on tension, and energy dissipation of a polyester rope under mean and cyclic loads. The modified CABLE3D is then integrated into a numerical package, known as COUPLE6D, for computing the interaction between a floating structure and its hybrid polyester mooring system. The Deepstar Spar is chosen in this study to represent the floating structure. By considering large elongation in polyester ropes in numerical simulation, the static offset curve of a polyester mooring system is softer than that calculated under the assumption of small elongation. That is, about 10% reduction in restoring force at the mean offset position of the Spar under the impact of 100-year hurricane storm. The effects of the mean loads on the modulus of polyester ropes are much greater than those of the dynamic loads. Hence, the former is more important in the simulation of the response of floating structures. The energy dissipation in polyester ropes under cyclic loading does not play significant roles in the responses of the Spar and tensions in a polyester mooring system. The above findings, although observed based on the numerical simulation of a particular floating structure, namely Spar, may have implications to other floating offshore structures moored by a polyester mooring system. Two systems are simulated in two different met-ocean conditions: hurricane and loop current condition. To study the properties of polyester, numerical simulation were conducted in three ways. Those are related to the modulus based on mean load, mean and dynamic loads, and structural damping respectively. Through the simulation, statistics of motions of the hull and tension in the mooring lines are compared with those of a conventional steel mooring system.
The internet revolution has led to the demand for high speed, low cost solutions for providing high bandwidth to the consumers. Cable and DSL systems address these requirements through sophisticated analog and digital signal processing schemes. A key element of the analog front end of such systems is the line driver which interfaces with the transmission medium such as co-axial cable or twisted pair. The line driver is an amplifier that provides the necessary output current to drive the low impedance of the line. The main requirements for design are high output swing, high linearity, matched impedance to the line and power efficiency. These requirements are addressed by a class AB amplifier whose output impedance can be controlled through feedback. The property of this topology is that when the gain is unity, the output resistance of the driver is matched to the line resistance. Unity gain is achieved for varying line conditions through a tuning loop consisting of peak-to-peak detectors and differential difference amplifier. The design is fabricated in 0.5 micron AMI CMOS process technology. For line variations from 65 to 170 ohms, the gain is unity with an error of 3 % and the impedance matching error is 20 % at the worst-case. The linearity is better than 50 dB for a 1.2 V peak-to-peak signal over the signal bandwidth from 10 kHz to 5 MHz and the line resitance range from 65 to 160 ohms.
Anahtar Kelimeler :
Analog design, CMOS line driver, High speed amplifier, Adaptive line termination, online tuning
Soluble polymers as supports are gaining more attention now. Developing new polymers, new reagents and catalysts, new separation systems are thus of great interest as these sorts of materials applications in synthesis and catalysis increase. The work described in the succeeding chapters describes my efforts to synthesize new catalysts that can be attached to polymer supports, to study their catalytic activity and to study separation efficiency. Most of the work focus is on polyacrylamide polymers. Both organometallic catalysts and organic catalysts have been studied. Liquid/liquid separation was the technique mainly investigated. In addition, a new separation scheme called latent biphasic system which is a new liquid/liquid separation method is described. Finally, studies with the Cremer group where the LCST behavior of polyacrylamides was studied using dark field methods are also discussed.
Epigenetic regulation is a mechanism by which heritable changes in gene expression are controlled by chromatin status rather than primary DNA sequence. Changes in chromatin structure affect accessibility of DNA elements to the transcriptional machinery and thus affect transcription activity of the gene. A key event in this process is reversible modification of core histones, which is catalyzed by histone acetyltransferases (HATs) and histone deacetylases (HDs, HDAs, or HDACs). In general, histone deacetylation is related to transcriptional gene silencing, whereas acetylation is associated with gene activation.To study the role of histone deacetylase in plant gene regulation and development, we generated constitutive antisense histone deacetylase 1 (CASH) transgenic plants. AtHD1 is a homolog of RPD3 protein, a global transcriptional regulator in yeast. Expression of the antisense AtHD1 caused dramatic reduction in endogenous AtHD1 transcription, resulting in accumulation of acetylated histones. Down-regulation of histone deacetylation caused a variety of growth and developmental abnormalities and ectopic expression of tissue-specific genes. However, changes in genomic DNA methylation were not detected in repetitive DNA sequences in the transgenic plants.We also identified a T-DNA insertion line in exon 2 of AtHD1 gene (athd1-t1), resulting in a null allele at the locus. The complete inhibition of the AtHD1 expression induced growth and developmental defects similar to those of CASH transgenic plants. The phenotypic abnormalities were heritable across the generations in the mutants. When the athd1-t1/athd1-t1 plants were crossed to wild-type plants, the mutant phenotype was corrected in the F1 hybrids, which correlated with the AtHD1 expression and reduction of histone H4 Lys12 acetylation. Microarray analysis was applied to determine genome-wide changes in transcriptional profiles in the athd1-t1 mutant. Approximately 6.7% (1,753) of the genes were differentially expressed in leaves between the wild-type (Ws) and the athd1-t1 mutant, whereas 4.8% (1,263) of the genes were up- or down-regulated in flower buds of the mutant. These affected genes were randomly distributed across five chromosomes of Arabidopsis and represented a wide range of biological functions. Chromatin immunoprecipitation assays indicated that the activation for a subset of genes was directly associated with changes in acetylation profiles.
The United States acted unilaterally to terminate the Bretton Woods monetary system in August 1971, and international exchange rate management went from a regime of fixed to floating parities, much to the displeasure of the membership of the European Community. The Nixon, Ford, and Carter administrations adopted policies that heavily benefited U.S. reform objectives and domestic economic goals, which frequently clashed with allied concerns, and damaged American monetary relations with France and West Germany. Yet, the inability of France and the Federal Republic of Germany to form cohesive economic and monetary policies throughout international negotiations or within the European Community (EC), allowed American desires to dictate the path and pace of European integration. France and Germany attempted, with limited success, to influence U.S. monetary policy through bilateral diplomacy during years of exchange rate fluctuations, dollar devaluations, oil shocks, and payments deficits. Finally, President Valery Giscard dEstaing and Chancellor Helmut Schmidt created the European Monetary System (EMS) in 1979, reversing the trend of half-hearted attempts at European integration so relevant the decade before. The EMS detached the ECs currencies from the dollars control, was compatible with the reformed international monetary system, advanced a more independent European monetary identity, and formed the base for future monetary integration. As a result, the EMS, as the birthplace of the Euro, the single European currency launched in 2002, may soon rival the dollars position as the primary reserve currency. American monetary policies designed to improve the health of the dollar during the 1970s were a catalyst for European integration. However, as the European Union deepens its economic integration and the Euro grows in strength, it seems that U.S. policies created a regime and a currency that will challenge its dominant position in international monetary affairs.
Anahtar Kelimeler :
monetary, foreign relations, Bretton Woods, European Monetary System
The Rodessa Formation is one of the major oil and gas reservoirs in the East Texas Basin. In Van Field, the upper Rodessa Formation consists of interbedded biotic and abiotic mudstones to grainstones. The lower Rodessa is composed of interbedded sandstones, shales, and limestones called the Carlisle Member. Based on core and well log interpretation, the Rodessa Formation was deposited on a broad, restricted, shallow marine platform interpreted to be lagoonal, subtidal, and intertidal. Both Rodessa limestone and sandstone have been altered significantly by diagenetic processes that include micritization, cementation, dissolution, neomorphism and compaction. Dissolution is the main factor that resulted in enhanced porosity and permeability while cementation adversely affected porosity. Diagenesis is interpreted to have begun in the marine phreatic environment and continued through the freshwater phreatic and shallow burial environments. Two reservoir units have been identified from core and well log interpretations. The potential reservoir within the Rodessa Formation occurs in the Carlisle Member which is composed mainly of medium to coarse grained sandstone with porosities and permeabilities in ranges of 8 to 11 percent and 46 to 896 millidarcies, respectively. The water saturation analysis has also shown the reservoir to be hydrocarbon bearing, having water saturation below 46 percent.
The HPr proteins were characterized as folding by a two-state folding mechanism. Here, we present a comparison of the equilibrium and kinetic folding for the HPr protein from Bacillus subtilis, E coli and a key variant from these proteins. For the wild-type protein we find that GHX is greater than GUDC, suggesting that the HPr does not fold by a simple two-state mechanism. This discrepancy is revealed by testing the two-state nature of the folding reaction of HPr with mutation. We show that removing a single charge side chain (Asp 69) converts the HPr protein back to a simple two-state mechanism. Ribonuclease Sa and two charge-reversal variants can be converted into amyloidin vitro by the addition of 2,2,2-triflouroethanol (TFE). We report here amyloid fibril formation for these proteins as a function of pH. The pH at maximal fibril formation correlates with the pH dependence of protein solubility, but not with stability, for these variants. Additionally, we show that the pH at maximal fibril formation for a number of ivwell-characterized proteins is near the pI, where the protein is expected to be the least soluble. This suggests that protein solubility is an important determinant of fibril formation.
The trade mechanisms joining the Mycenaean Aegean to the greater Levant have intrigued and eluded Bronze Age scholarship since the earliest discoveries of foreign objects in Mycenaean burials. In the past decade, topics of interregional trade in the eastern Mediterranean have enjoyed renewed discussions, inspired in no small part by the excavation of the Uluburun shipwreck. Data generated from the shipwreck is amounting to an extraordinary body of evidence for contact between the Aegean and the Near East. The proposed Mycenaean presence on board the Uluburun ship requires that the sum of evidence and hypotheses for trade between the two regions be re-examined. By attempting to demonstrate the role the Mycenaeans had performed on the last journey of the Uluburun ship, an important mechanism of trade may be revealed between the Aegean and Semitic worlds.
The theory of interpolation and approximation of solutions to differential and integral equations on spheres has attracted considerable interest in recent years; it has also been applied fruitfully in fields such as physical geodesy, potential theory, oceanography, and meteorology. In this dissertation we study the approximation of linear partial differential equations on spheres, namely a class of elliptic partial differential equations and the heat equation on the unit sphere. The shifts of a spherical basis function are used to construct the approximate solution. In the elliptic case, both the finite element method and the collocation method are discussed. In the heat equation, only the collocation method is considered. Error estimates in the supremum norms and the Sobolev norms are obtained when certain regularity conditions are imposed on the spherical basis functions.
Color stability and cooked muscle color were evaluated in relation to myoglobin content, oxygen consumption rate, pH, lipid oxidation, oxygen penetration depth, metmyoglobin reductase activity, Hunter L*- a*- b*- values, discoloration, and degree of doneness for the M. Infraspinatus (IF), M. Triceps brachii (TB), M. Teres major (TM), M. Rectus femoris (RF), M. Vastus lateralis (VL), M. Semimembranosus (SM), M. Biceps femoris (BF), M. Semitendinosus (ST), M. Gluteus medius (GM), as well as the M. Psoas major (PM), and M. Longissimus lumborum (LL). Steaks from these muscles were segmented into a low oxygen dark, low oxygen light, high oxygen, and PVC overwrap packaging environment for six days of retail display. There were no major differences in pH, oxygen consumption rate, or myoglobin reductase acitivity between shelf-life days and packaging environments for the muscles used in the study. The VL, TB, ST, SM, and the GM had higher levels of lipid oxidation in the later days of shelf-life storage and were higher (P < 0.05) in high oxygen packaging compared to the other three treatments. Oxygen penetration depth was greater (P < 0.05) over all storage days for the high oxygen treatment in the TB and LL as compared to the other treatments. Hunter CIE a* and b* values significantly decreased across all muscles for the high oxygen and PVC treatments. Discoloration increased significantly as storage days increased in the high oxygen and PVC treatments for the TB, SM, VL, BF, IF, GM, PM, and TM. Degree of doneness was higher (P < 0.05) for the PM, TB, and SM muscles in a high oxygen atmosphere as compared to the low oxygen light and low oxygen dark treatments. Aerobic reducing ability tended to decrease as retail shelf-life day increased. A high oxygen environment increased rancidity, oxygen penetration depth, redness values, and degree of doneness (P < 0.05) when compared to a low oxygen light and low oxygen dark modified atmosphere package.
Anahtar Kelimeler :
beef, MAP, color, degree of doneness
The heritability of microfibril angle (MFA) in loblolly pine, Pinus taeda L., and its genetic relationships with height, diameter, volume and specific gravity were examined in two progeny tests with known pedigrees. Significant general combining ability (GCA), specific combining ability (SCA), and SCA x block effects indicated that there are both additive and non-additive genetic influences on MFA. Individual-tree narrow-sense heritability estimates were variable, ranging from 0.17 for earlywood (ring) 4 MFA to 0.51 for earlywood (ring) 20 MFA. Genetic correlations between MFA, specific gravity and the growth traits were non-significant due to large estimated standard errors. Multiple-trait selection and breeding in a mainline and elite population tree improvement program were simulated using Excel and Simetar (Richardson 2001). The effects of four selection indices were examined in the mainline population and the effects of seven selection indices and four breeding strategies were examined in the elite population. In the mainline population, selection for increased growth caused decreased wood quality over time. However, it was possible to maintain the overall population mean MFA and mean specific gravity at levels present in the base population by implementing restricted selection indices. Likewise, selection for improved wood quality in the elite population resulted in decreased growth unless restricted selection indices or pulp indices derived from those of Lowe et al. (1999) were used. Correlated phenotypic responses to selection on indices using economic weights and heritabilities were dependent on breeding strategy. When a circular mating system (with parents randomly assigned to controlled-crosses) was used, the index trait with a higher economic weight was more influential in determining correlated responses in non-index traits than the index trait with a lower economic weight. However, when positive assortative mating was used, the index trait with a greater variance was more influential in determining correlated responses in non-index traits than the index trait with a lower variance regardless of economic weight.
This study analyzes the economic and demographic patterns of at-home pork consumption for representative individuals over 18 years of age in the United States. Three data sets purchased by the National Pork Board (NPB) are mined for this purpose: (1) National Eating Trends (NET) data from National Panel Diary (NPD) on individuals intake and their demographic characteristics; (2) weekly retail prices for fresh meats and fresh pork cuts from FreshLook; and (3) weekly retail prices for processed pork products from A.C. Nielsen. Heckman sample selection models are used to find demographic, health, and attitudinal/lifestyle patterns of consumption of twelve fresh and processed pork products as well as beef, chicken, and seafood. In the fall, individuals have a higher probability of eating beef, chicken, pork tenderloin, and bacon, but a lower probability of eating fresh seafood, canned ham, and smoked ham relative to the spring. The New England region has the highest likelihood of eating fresh pork, beef, chicken, seafood, pork roasts, pork tenderloin, and pork hotdogs. Blacks, on average, eat more fresh and processed pork, chicken, pork sausage, bacon, and canned ham, but less beef relative to whites. Concern about serving food with fat is negatively related with the likelihood of eating processed pork, lunchmeat, ham, and bacon, but it is positively related with the likelihood of eating pork hotdogs. A three-stage selectivity-adjusted censored LA/AIDS model is developed and estimated to find demand-price relationships for: (1) fresh meats (pork, beef, chicken, and seafood) and (2) nine fresh and processed pork cuts. However, aggregate fresh meats are substitutes for each other in at-home market, but there are substantial complementarities between pork cuts. Pork sausage is the major competitor for the processed products, pork roasts and pork tenderloin, but a major complement for pork ribs. There is relatively week substitutability between pork and beef, and relatively strong substitutability between pork and chicken and between beef and chicken. This could suggest opportunities for some joint marketing efforts between pork and beef commodity interests. This information can be used as a guide for marketing strategists for targeting and promotion as well as for category management of the disaggregated pork products.
Anahtar Kelimeler :
Pork, Data Mining, Three-Stage, LA/AIDS, Heckman, NPD
This study focussed on the reduced platen compression (RPC) testing of the cancellous bone of the proximal tibia. The objective of this study was to improve the current testing methods with an emphasis on the location of the RPC specimens, and to correlate the mechanical properties of the rodent cancellous bone with the various density measures. Analytical studies were made to assess the effect of the size and shape of the platen based on the values from mechanical testing of the cancellous bone. RPC specimens are made from transverse slices of the proximal tibia metaphysis. Specimen location was determined using planar radiograph method at a distance of 1.75 mm distal to the growth plate. The distance from the top of the proximal tibia to the line at 1.75 mm distal to the growth plate was measured and this distance is termed as the first cut distance. Specimen thickness of 2 mm was then cut for the RPC test. Endocortical method was followed to determine the platen sizing for RPC testing. The cancellous bone was then tested in compression to failure. Correlations were performed between the mechanical properties of the cancellous bone and the density measures from pQCT and radiographic techniques. SigmaStat and TableCurve 2D were used to perform the correlations and estimate the P value for the correlation. Linear and power law fits were made for all the correlations. Based on this study, several improvements to the reduced platen compression test were recommended. An improved specimen location method was developed. However, it requires a corrective distance to account for the tissue that cannot be identified in the radiographic analysis. A new method for estimating the density of the cancellous bone that is directly tested by the platen was developed. Correlations between the density of the cancellous bone and the mechanical properties show that, there is a strong correlation between ultimate stress and aluminum layer intensity. Elastic modulus correlates best with the last batch tested in this study. Recommendations for future study include advanced technology like finite element analysis and custom shaped platens to enhance RPC testing.
The issue of substation integration is recognized as a very important one ever since the process of technological development brought a multitude of new computer-based devices and functions into substation operation. During the relatively short time period after the first microprocessors were invented, a myriad of computer-based devices found their application in power engineering. Those devices had a variety of input and output data formats, which hampered exchange of data among different devices. Recent initiatives for standardization of substation data formats and communication protocols have progressed to facilitate production of devices with standardized data formats and data exchange capabilities. Central substation computers now have an opportunity to collect and process data from such computer-based devices. An advanced data collecting and processing solution is developed and implemented as Integrated Substation Software in an effort to enhance substation integration. This report describes a solution that comprises data generation using a substation model, data collecting from modeled apparatus and instruments and finally application of data processing and consistency checking algorithms for creating outputs. The process of data collecting and processing is automated and repeated in equidistant time intervals. Results of processing and related reports are concisely displayed on the user interface screen and exported through data files. The Substation Integration Software was tested through the set of scenarios where each scenario is used to test one of the processing and consistency checking algorithms. The results show that measurements are improved and applicable for usage by other substation and system-wide applications.
Anahtar Kelimeler :
Power Engineering, Substation Integration, Data Collecting, Measurement Processing
Peptide mass fingerprinting (PMF) of protein digests is a widely-accepted method for protein identification in MS-based proteomic studies. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) is the technique of choice in PMF experiments. The success of protein identification in a PMF experiment is directly related to the amount of amino acid sequence coverage. In an effort to increase the amount of sequence information obtained in a MALDI PMF experiment, performic acid oxidation is performed on tryptic digests of known proteins. Performic acid was chosen as the chemical oxidant due to the ease of use and to the selective oxidation of cysteine, methionine, and tryptophan residues. In experiments performed in our laboratory, performic acid oxidation either increased or did not affect protein sequence coverage in PMF experiments when oxidized tryptic digests were analyzed by MALDI. Negative mode MALDI data were acquired, as well as positive mode MALDI data, due to the enhanced ionization of cysteic acid-containing peptides in negative mode. Furthermore, the confidence in a protein match is increased by observation of mass shifts indicative of cysteine, methionine, and/or tryptophan in oxidized peptide ion signals when comparing MALDI spectra prior to performic acid oxidation and after oxidation due to the low abundance of these residues in the majority of all known and hypothetical proteins.
Anahtar Kelimeler :
peptide mass fingerprint, tryptic peptides, chemical oxidation, MALDI-MS, percent sequence coverage
Density, species diversity, species richness, and evenness of bivalve mollusks were measured in the deep (0.2km to 3.7km) northern Gulf of Mexico to describe the community structure of benthic bivalve mollusks. Density decreased gradually from shallow continental slope depths, with remarkably high values in the Mississippi canyon, to the deepest sites. Diversity of bivalve mollusks increased from shallow continental slope depths, with low values in the Mississippi canyon, to a maximum at intermediate depths (1-2km), followed by a decrease down to the deepest locations (3.7km). Nine distinct groups were formed on the basis of the similarity in species composition. The pattern varied more abruptly on the slope compared to the deeper depths, possibly due to steeper gradients in physical variables. ANOVA indicated that the density of bivalve mollusks was not significantly different at different depths, was not significantly different on different transects, was not significantly different between basin and non-basin, but was significantly different in canyon and non-canyon locations. Similar distinctions were observed in diversity, except that basins were lower than non-basins. The patterns observed reflect the intense elevated input of terrigenous sediments accompanied by high surface-water plankton production from the Mississippi River to the north central gulf.
Anahtar Kelimeler :
community structure, deep-sea, bivalve, mollusks, Gulf of Mexico
We study the ∂-Neumann operator and the Kobayashi metric. We observe that under certain conditions, a higher-dimensional domain fibered over Ω can inherit noncompactness of the d-bar-Neumann operator from the base domain Ω. Thus we have a domain which has noncompact d-bar-Neumann operator but does not necessarily have the standard conditions which usually are satisfied with noncompact d-bar-Neumann operator. We define the property K which is related to the Kobayashi metric and gives information about holomorphic structure of fat subdomains. We find an equivalence between compactness of the d-bar-Neumann operator and the property K in any convex domain. We also find a local property of the Kobayashi metric [Theorem IV.1], in which the domain is not necessary pseudoconvex. We find a more general condition than finite type for the local regularity of the d-bar-Neumann operator with the vector-field method. By this generalization, it is possible for an analytic disk to be on the part of boundary where we have local regularity of the d-bar-Neumann operator. By Theorem V.2, we show that an isolated infinite-type point in the boundary of the domain is not an obstruction for the local regularity of the d-bar-Neumann operator.
Diamond interchanges and their associated ramps are where the surface street arterial system and the freeway system interface. Historically, these two elements of the system have been operated with little or no coordination between the two. Therefore, there is a lack of both analysis tools and operational strategies for considering them as an integrated system. One drawback of operating the ramp-metering system and the diamond interchange system in isolation is that traffic from the ramp, particularly if it is metered, can spill back into the diamond interchange, causing both congestion and safety concerns at the diamond interchange. While flushing the ramp queues by temporarily suspending ramp metering has been the primary strategy for preventing queue spillback, it can result in freeway system breakdown, which would affect the entire systems efficiency. The aim of this research was to develop operational strategies for managing an integrated diamond interchange ramp-metering system (IDIRMS). Enhanced modeling methodologies were developed for an IDIRMS. A computer model named DRIVE (Diamond Interchange and Ramp Metering Integration Via Evaluation) was developed, which was characterized as a mesoscopic simulation and analysis model. DRIVE incorporated the enhanced modeling methodologies developed in this study and could be used to perform system analysis for an IDIRMS given a set of system input parameters and variables. DRIVE was validated against a VISSIM microscopic simulation model, and general agreement was found between the two models. System operational characteristics were investigated using DRIVE to gain a better understanding of the system features. Integrated control strategies (ICS) were developed based on the two commonly used diamond interchange phasing schemes, basic three-phase and TTI four-phase. The ICS were evaluated using VISSIM microscopic simulation under three general traffic demand scenarios: low, medium, and high, as characterized by the volume-to-capacity ratios at the metered ramps. The results of the evaluation indicate that the integrated operations through an adaptive signal control system were most effective under the medium traffic demand scenario by preventing or delaying the onset of ramp-metering queue flush, thereby minimizing freeway breakdown and system delays.
All-fiber multireflector spectral filters which have potential application in optical communications have been investigated experimentally. These multireflector etalons were produced by aligning equal-length fiber sections with TiO2/SiO2 dielectric mirrors deposited on the end in a silicon v-groove. Fiber sections 1.33mm in length were produced by polishing, with the fibers held in a silicon wafer polishing jig. The fibers were aligned inside the polishing jig using a precision micro positioner. Then four polishing steps with increasingly finer grit were applied to produce high-quality polished end surfaces on each fiber section. Finally, a dielectric mirror was deposited on one end of each fiber section by magnetron sputtering. After characterizing the optical loss, length, and mirror reflectance for each of the fiber sections, sections which were well-matched in length were chosen for assembly of the four-mirror etalon, which had nominal reflectance values of 10%, 50%, 50%, and 10% for the dielectric mirrors. Measured transmittance spectra for a mutireflector spectral filter were compared with calculated spectra. Thermal tuning of the multireflector etalon was also investigated. A 0.34 nm wavelength shift was observed for a 23° C temperature change, in agreement with prediction. increasingly finer grit were applied to produce high-quality polished end surfaces on each fiber section. Finally, a dielectric mirror was deposited on one end of each fiber section by magnetron sputtering. After characterizing the optical loss, length, and mirror reflectance for each of the fiber sections, sections which were well-matched in length were chosen for assembly of the four-mirror etalon, which had nominal reflectance values of 10%, 50%, 50%, and 10% for the dielectric mirrors. Measured transmittance spectra for a mutireflector spectral filter were compared with calculated spectra. Thermal tuning of the multireflector etalon was also investigated. A 0.34 nm wavelength shift was observed for a 23° C temperature change, in agreement with prediction.
Anahtar Kelimeler :
Fabry-Perot, Band pass filter, optical filter, multi-reflector
This research expands on previous work and provides further validation of the Multidimensional Work Ethic Profile (MWEP) by exploring the relationships among the MWEP dimensions and other common work-related attitude variables: job involvement, job satisfaction, and organizational commitment. Furthermore, this study investigates the extent to which the MWEP dimensions explained variance in the above mentioned variables over and beyond that which could be explained by conscientiousness and need for achievement. Although the MWEP dimensions correlated with the other work-related variables, the MWEP allowed for the evaluation of unique patterns of relationships among these variables and the work ethic dimensions. The results indicated that the MWEP dimensions were significantly related to conscientiousness yet accounted for significant variance in job involvement, organizational commitment, and job satisfaction above and beyond that explained by conscientiousness. Contrary to what was expected, need for achievement was not significantly related to the MWEP dimensions. Implications and suggestions for future research are discussed.
In order to achieve the stated goal of reducing the final closing procedure time cycle for construction projects at the Texas Department of Transportation (TxDOT) Odessa District, several standard operating procedures (SOPs) for project construction control and management had to be revised. Seemingly unrelated tasks created posterior chains of events that resulted in bottlenecks in the process and delayed final project closing. Four specific SOPs were identified and analyzed to determine which tasks required modification and what was expected from these modifications. A mission for each specified SOP was conceived and written to give a clear view of the intent of the procedure. Afterwards, district policies were drafted to provide the means to fulfill the intent. The procedural changes, compatible with TxDOT statewide procedures, allowed the time spent in the processes to remain the same but redistributed it to reduce the end-loading of the control process. The new SOPs require an even time distribution cyclically throughout the project. Control procedures are done only once, shortening the final closing procedure for projects by doing one-time, short, cyclical, consecutive control tasks of the same procedure throughout the life of the project, rather than doing some of them once cyclically and then again at the closing procedure and others just at the closing procedure. These changes resulted in a shorter end-cycle time, which substantially reduced the final closing procedure time for each project, without affecting the integrity and safeguards of the project. The changes resulted in more efficient and timely financial, managerial, and engineering control of projects. The procedures revised were (1) Review and Approval of Change Orders; (2) Review and Approval of Monthly Progress Estimates; (3) Review and Approval of Interim and Final Audits and Final Estimate; and (4) Storm Water Pollution Prevention Plans (SW3P) Records Management and Auditing Procedures.
Anahtar Kelimeler :
construction contract, contract administration, standard operating procedures