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  • 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.
1

Environmental and Biogeochemical Changes in the Dapeng Bay over the Last Decade : Influence of Human Activities.

Huang, Wan-chen 12 December 2011 (has links)
Before January 2003, the Dapeng Bay lagoon was occupied by oyster culture racks and fish farming cages. Along with the development of the Dapeng Bay National Scenic Area Administration, the government has started taking actions on removing oyster culture racks, and has kept improving the quality of lagoon water. Nowadays, the government is implementing sediment dredging plan. As to discuss the change of biogeochemical processes, this study is divided by three parts, including the first stage, before the removal of oyster culture rafts; second stage, after the removal of oyster culture rafts, and the third stage, after implementation of sediment dredging. At the first stage, the annual mean of water exchange time at the Dapeng Bay was approximately 10 days. At the second and third stage, the annual mean of water exchange time were 6.2 days and 8.3 days, respectively. The difference is not significant between the second stage and third stage. The trend of water exchange time is similar to the seawater exchange rate. Distributions of chlorophyll a were controlled by temperature and solar radiation, rather than by nutrient concentration throughout three-stage periods. Although the change tendency between chlorophyll a, DIN, and DIP at the third stage is similar, chlorophyll a correlated positively with DIN and DIP only in fall. The net ecosystem production (NEP) was positive (p¡Ðr > 0) at all three stages, so the Dapeng Bay was always an autotrophic system throughout the study period. Before the removal of the oyster culture racks, the NEP was 5.64 mole C m-2 yr-1, after that, it increase to 11.64 mole C m-2 yr-1. During the sediment dredging period, the NEP was 14.31 mole C m-2 yr-1. The NEP increases 106 % from the first stage to the second stage, and increases 23% from the second stage to the third stage. The environmental remediation appears to produce significant influence on NEP. The concentration of DIN¡BDSi¡BDIP decreases by removing the oyster culture of racks. But the concentrations of particulate and dissolved organic carbon and nitrogen increase sharply after removing the oyster culture racks. Nevertheless, the concentration of dissolved organic carbon, nitrogen and the phosphorus decreases during the third stage, resulted mainly from the improvement of water quality. The system changed from the condition of phosphorus surplus (Si/N=1.8¡Ó1.2 and N/P=7.4¡Ó5.2) during the first and second stage to the condition of phosphorus limitation (Si/N=1.0¡Ó1.2 and N/P=22.2¡Ó18.7) during the third stage. The ratios of particulate organic carbon and nitrogen (POC/PN) are 7.7¡Ó1.1, 8.0¡Ó1.0, 6.5¡Ó1.3, respectively. The ratio at the third stage is very close to the Redfield ratio (C/N=6.6), which may result from the improvement of water quality. In terms of temporal and spatial variation of various parameters, DO variability was strong in the time scale than in the spatial scale, but nutrients and POC show a decrease of spatial variability from the first stage to the third stage. The removal of oyster culture racks, and the implementation of sediment dredging plan at the Dapeng Bay have significant influence on the improvement of lagoon environment for the past ten years.
2

Nepromlčitelnost práva na vyplnění blankosměnky / Exclusion of limitation of right to completion of a blank bill of exchange

Slavíček, Jan January 2022 (has links)
Exclusion of limitation of right to completion of a blank bill of exchange Abstract Blank bill of exchange is an intentionally incomplete instrument that is meant to be fulfilled in order to become a complete bill of exchange. The owner of the blank bill of exchange exercises his/her right to fulfill a blank bill of exchange by completing the prearranged requirements. The thesis focuses mainly on the time limitation of the right to fulfill a blank bill of exchange. The fulfillment of a blank bill of exchange is performed by the owner of a blank bill of exchange by exercising his right to fulfill a blank bill of exchange. This thesis focuses on the time limitation of the right to fulfill a blank bill of exchange. By exercising this right, the owner of a blank bill of exchange validates the bill of exchange. The absence of time limitation becomes especially significant when the maturity date of the bill of exchange is missing. In these circumstances, the owner of a blank bill of exchange has no time limitation for executing his right. According to the constant case-law of the Supreme Court of the Czech Republic, the right to fulfill a blank bill of exchange shall not be subject to the Statute of Limitations or any other time limitation. The presented thesis addresses the question as to whether the right to...
3

Local Fluctuations in the Relaxation Rate in Glassy Systems

Pandit, Rajib K. 11 June 2019 (has links)
No description available.
4

Dynamical Correlations in Glassforming Liquids: A Numerical Study

Aaron, Elise R. January 2022 (has links)
No description available.
5

Mathematical modelling of Degussa Furnace

Faraydoun Muhammed, Rans January 2021 (has links)
The energy demands in the world is rapidly increasing and with this,  a supply nuclear  power  is  of  much  interest.    Nuclear  fuel  is  relatively  efficient  when comparing to power sources like wind­ and hydropower plants. Pellets are used as fuel by many plants however, its main concern is to find maximize cost efficiency and  minimize  fuel­waste.   Studying  how  to  get  the  pellets  to  be  as  optimal  as possible is of massive importance and in huge focus in order to match the worlds power demand. These  pellets  are  sintered  in  a  furnace  type  known  as  ”pusher­type”  furnaces that functions continuously and is incredibly efficient when it comes to its heat transfer capacity and high­performance output.  In this sintering process, a gas­ flow from the opposite side from the pellets interacts with the solid pellets in order to get the desired reaction. However, the turbulence and the nature of the multi­ phase flow problem causes many unknown interactions and the main focus is do create a theoretical model based on the process parameters to understand what is happening in the furnace. In this study, a simplified model of the inside of the furnace chamber was created in order to observe where and when in the furnace a dissociation from CO2 to CO + O2 would occur. Data given by Westinghouse was put into a mathematical model created in MATLAB and parameters given by the thermodynamic model was in turn put in to ANSYS, a program based on Computational Fluid Dynamics for a simulation. The simulation was considered a success when the gas­mix goes from 3% CO2 to 0.4%. The CFD of the model estimates this to happen at 250 seconds, where as the thermodynamic model predicts the exchange time to be about 200 seconds.   This study is a major first step in understanding the dynamics of the furnace. / Energibehovet i världen ökar snabbt och då blir ett stadigt tillförsel av kärnenergi mycket intressant.  Kärnbränsle är relativt effektivt jämfört med kraftkällor som vind­  och  vattenkraftverk.    Pellets  används  som  bränsle  av många  kraftverk och då blir det ett upphov att hitta maximal kostnadseffektivitet och minimera bränsleavfall.  Att forska fram till hur man gör pellets så optimala som möjligt är av enorm betydelse och i stort fokus för att matcha världens energi behov. Dessa pellets sintras i en ugnstyp som kallas ”pusher­type” ugnar som fungerar kontinuerligt och är otroligt effektiva när det gäller dess värmeöverförings-kapacitet och högpresterande effekt.  I denna sintringsprocess startar ett gasflöde från motsatt sida från pelletsen med de fasta pelletsen för att få den önskade reaktionen.  Det blir ett flerfasigt flödesproblem och orsakar många okända interaktioner och huvudfokus är att skapa en teoretisk modell baserad på processparametrarna för att förstå vad som händer i ugnen. I  denna  studie  gjordes  en  förenklad  modell  av  ugnskammarens  insida för  att observera var och när i ugnen en dissociation från CO2 till CO + O2 skulle inträffa. Data från Westinghouse placerades i en matematisk modell skapad i MATLAB och  parametrar  som  gavs  av  den  termodynamiska modellen  lades  i  sin  tur  till ANSYS, ett program baserat på Computational Fluid Dynamics för en simulering. Simuleringen ansågs vara färdig när gasblandningen går från 3% CO2 till 0,4%. CFD:n  för  modellen  uppskattar att  detta  händer  vid  250  sekunder,  där  den termodynamiska modellen förutspår utbytestiden till cirka 200 sekunder. Denna studie är ett stort första steg för att förstå ugnens dynamik.

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