• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2171
  • 521
  • 361
  • 294
  • 238
  • 165
  • 102
  • 66
  • 52
  • 51
  • 47
  • 46
  • 42
  • 28
  • 18
  • Tagged with
  • 4853
  • 2547
  • 620
  • 402
  • 354
  • 342
  • 325
  • 271
  • 266
  • 264
  • 249
  • 248
  • 241
  • 238
  • 224
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
471

Emissions of volatile organic compounds in the Hsuehshan tunnel

Chang, Po-Jui 04 July 2008 (has links)
Hsuehshan tunnel which included two bore and three ventilation shaft systems is the longest (12.9 km) freeway tunnel in Taiwan. 56 species volatile organic compounds (VOCs) were sampled in two different locations each bore and three emitted shafts to determine the emission factors (EFs). Each sampling day has three sampling period: morning (8:00-10:00), Noon (12:00-14:00) and afternoon 16:00-18:00). C2 species were analyzed by GC/FID and C3 − C12 species were analyzed by GC/MS. The composition in southern bore was expressed by alkanes (36.69% − 39.20%), aromatics (34.14% − 36.33%), alkenes (20.27% − 21.95%), Alkynes (3.35% − 4.11%) and Naphthenes (1.06% − 1.35%). Northern bore had the similar profile. Ethylene (4.93 ¡Ó 2.21 mg/veh-km), Isopropane (4.85 ¡Ó 2.75 mg/veh-km), toluene (4.55 ¡Ó 1.31 mg/veh-km), m,p-xylene (2.98 ¡Ó 0.90 mg/veh-km) and propylene (2.70 ¡Ó 0.88 mg/veh-km) are the top five abundant VOCs in southern bore ; Isopropane (6.78 ¡Ó 3.33 mg/veh-km), ethylene (5.44 ¡Ó 2.63 mg/veh-km), toluene (5.32 ¡Ó 2.39 mg/veh-km), propylene (3.55 ¡Ó 1.67 mg/veh-km) and m,p-xylene (3.36 ¡Ó 1.45 mg/veh-km) are the top five abundant VOCs in northern bore. The EFs were smaller than other freeway tunnel investigated. Shaft emitted the partial mass of VOCs result in concentration gradient dropped off. The total VOCs EF of shafts during holidays was in the range of 72.24 mg/s − 180.60 mg/s higher than on weekdays in the range of 53.40 mg/s − 82.74 mg/s. The EF of shafts had effected by air-extracting apparatus, so standard deviations (S.D.) varied widely. Combining the EF of shaft with EF of tunnel we obtained the overall vehicle EF which was close to other freeway tunnel results. The proportion of Ozone formation potential (OFP) in both bore were alkenes (47.5% − 48.5%), aromatics (40.2% − 42.3%) and alkanes (9.8% − 10.1%). Note that sum of alkenes and aromatics exceeded 90%.
472

Measurements of Air Pollutants in the Hsuehshan Tunnel

Chen, Yi-chuan 30 June 2009 (has links)
The purpose of this study is the distribution, the emission factors, and the emission rates of the ventilation shafts of air pollutant concentration in the Hsuehshan tunnel, and analyze the correlation. The study, in the inside of Hsuehshan tunnel (the southern and the northern) and the three ventilation shafts, the real-world measure air pollutants(CO, NOx, NO, THC, NMHC and SO2) at the same time, and to analyze the concentration of air pollutants in the tunnel that is distribution of the time and spatial. In this study, the ventilation system is natural ventilation in the Hsuehshan tunnel, and the proportion of heavy vehicles in the period are less than 8%. The concentration of air pollutants in the tunnel, showing the exit higher than the entrance, the northern tunnel higher than the southern tunnel and the holidays higher than on weekdays concentration of distribution trends. The emissions and the concentration of air pollutants at the ventilation shaft No. 2 are the highest with the three shafts. All the ventilation shafts on holidays higher than weekdays were displayed on the trend of concentration distribution. The concentration of air pollutants in the tunnel are CO (12.04¡Ó1.85 ppm), THC (4.08¡Ó0.48 ppm), NMHC (2.21¡Ó0.46 ppm), NOx (1.58¡Ó0.23 ppm), NO (1.44¡Ó0.20 ppm) and SO2 (6.33¡Ó0.83 ppb). The results show that the emission factors of air pollutants in northern tunnel are higher than in southern tunnel by influence of slope. The emissions of ventilation shaft a sequence were CO, THC, and NOx. The concentrations(r¡×0.55 − 0.93) and the emission factors(r¡×0.60 − 0.96) of air pollutants are much related with traffic situation, and it shows that the air pollutants change with traffic condition. Comparison the emission factors between this study and past research in the Hsuehshan tunnel show that the air quality are becoming badly.
473

Effects of Automoblie Tailpipe Emissions in the Hsuehshan Tunnel on the Air Quality of Neighboring Areas Using ADMS Model

Wang, Chen-wen 30 June 2009 (has links)
The Hsuehshan tunnel, whose length is about 12.9 kilometers, is the longest tunnel in Taiwan and Southeast Asia. Since the tunnel is used, it reduces the traveling time from Taipei to Ilan and brings the convenience of transportation; but the vehicles and pollution sources are added. Furthermore, the concentrations of pollutants are increased by accumulation in the long tunnel. This study estimates the effects of automobile tailpipe emissions in the Hsuehshan tunnel on the air quality of neighboring areas by using Atmospheric Dispersion Modelling System for Roads (ADMS-Roads). This work simulates carbon monoxide (CO), nitrous oxides (NOx) and sulfur dioxide (SO2) at two sites (Pin-Ling and Tou-Cheng management centers) in northern Taiwan in winter of 2008. The average concentrations of CO, NOx and SO2 at Pin-Ling (Tou-Cheng) management centers respectively are 0.49 (0.55) ppm, 10.60 (14.83) ppb and 4.80 (7.47) ppb on non-holiday and 0.66 (0.64) ppm, 16.88 (15.12) ppb and 4.70 (4.20) ppb on holiday. It shows that the concentrations of pollutants on holiday are higher than on non-holiday by increasing vehicles. Simulated results show that effects of traffic exhaust in the tunnel on the air quality of neighboring areas are less. Estimations using the ADMS-Roads suggest that the emissions are not the predominant contributors at two sites. The effect is the highest with northern (northeastern) winds at the southern (northern) area of the Hsuehshan tunnel. Comparisons between simulations and measurements at both sites are satisfactory. Simulated values are generally in agreement with measured values, with a correlation coefficient of R = 0.37 ¡V 0.81, the index of agreement (IOA) = 0.58 ¡V 0.77, and the normalized mean square error (NMSE) = 0.03 ¡V 0.25. The ADMS-Roads will be applied to assess the environmental impact while the tunnel will be allowed more types of vehicles to drive in the future.
474

Studies on N-Heterocyclic Compounds

Armugam, S 03 1900 (has links)
The thesis entitled "Studies on N-Hetero cyclic Compounds: (a) Reaction of 5,6,7,8-Tetrahydroisoquinolines with Vilsmeier Reagent and (b) Amide Induced in situ Alkylation of 5,6-Dihydroisoquinolines" is presented in two parts. Part I involves a study of the Vilsmeier reaction of 4-cyano-1,3-dihydroxy-5,6,7,8 tetrahydroisoquinoline derivatives, while Part II concerns the in situ alkylation of l-alkyl-4-cyano-3-methoxy-5,6- dihydroisoquinolines in presence of KNH2/liq.NH3.
475

A VLBI study of OH masers in a proto-planetary nebula OH 0.9+1.3. /

McAlpine, Kim. January 1900 (has links)
Thesis (M.Sc. (Physics & Electronics)) - Rhodes University, 2008.
476

Contracten voor Suriname : arbeidsmigratie vanuit Brits-Indië onder het indentured-labourstelsel 1873-1916 /

Bhagwanbali, Radjinder, January 1996 (has links)
Proefschrift--Nijmegen--Katolieke Universiteit, 1996. / Textes en néerlandais, résumé en anglais.
477

Implication des mécanismes d'activation, d'intégration et de construction sur la nature d'une trace mnésique étude des effets de fréquence sur l'amorçage de répétition /

Nevers, Brigitte. Bougeant, Jean-Claude. Versace, Rémy January 2000 (has links)
Thèse de doctorat : Psychologie cognitive : Lyon 2 : 2000. / Titre provenant de l'écran-titre. Bibliogr.
478

Le Disease Management de l'origine à l'application par l'industrie pharmaceutique /

Quinio, Sophie Truchaud, Alain. January 2008 (has links)
Reproduction de : Thèse d'exercice : Pharmacie : Nantes : 2008. / Bibliogr.
479

L'amorçage négatif : influence du mismatch et remise en cause du modèle de l'inhibition sélective

Allain, Gaël. Versace, Rémy January 2002 (has links)
Reproduction de : Thèse de doctorat : Psychologie cognitive : Lyon 2 : 2002. / Titre provenant de l'écran-titre.
480

Revue de pertinence des journées d'hospitalisation en soins de suite et de réadaptation

Guilé, Romain Moret-Majoube, Leïla. January 2008 (has links)
Reproduction de : Thèse d'exercice : Médecine. Santé publique et médecine sociale : Nantes : 2008. / Bibliogr.

Page generated in 0.0468 seconds