87 research outputs found
Oil shale pyrolysis in indirectly heated fixed bed with metallic plates of heating enhancement
No full textThis study is devoted to improving the heating to oil shale particles and in turn the yield and quality of shale oil in fixed bed reactors indirectly heated through use of internals. Metallic heating plates were vertically welded on the reactor wall as heating enhancement internals to provide extra heating surfaces inside the oil shale bed and to increase the high-temperature heating surface area by 35% to 210%. Comparison of heating rate to particles and shale oil yield was made between the reactors without and with the plate internals. Utilizing internals evidently enhanced the heating to oil shale particles and shortened pyrolysis time by 30% to 50%. The shale oil yield increased by 7% to reach 90% of the Fischer Assay oil yield (8.98 wt.%, dry base) when the heating surface area was increased by 70-110%. With increased heating surface area above 110%, the shale oil yield manifested conversely a slight decrease. Nonetheless, the fraction of light oil (boiling point <350 degrees C by analysis in simulation GC) was increased to about 66 wt.% from 60.94 wt.% for the reactor without any heating plate. Characterizing the char samples at different lateral positions of the oil shale bed justified that the flow of gaseous pyrolysis product in the reactor was guided to the vicinity of heat transfer plates to speed up gas exhaust and selective cracking. Consequently, adding heat transfer plates into an indirectly heated reactor would obviously intensify the heating to the oil shale bed and also elevate the pyrolysis oil yield and quality. (C) 2015 Elsevier Ltd. All rights reserved
Detection in distributed sensor networks
No full textThis thesis describes detection and communication algorithms for distributed sensor networks.In the first part of the thesis, we investigate a new architecture for distributed binary hypothesis detection by employing a Collision Resolution Algorithm (CRA), where all local sensors share a common channel to communicate with the decision fusion center. This architecture is important in the design of sensor fields, where a large number of distributed sensors share a single "emergency" channel.In the second part of the thesis, we discuss an industrial application of such a distributed detection system, namely, the LonWorks control network. We concentrate on the predictive p-persistent CSMA protocol implemented in the MAC layer of LonWorks protocol, which was proposed by the Echelon Corporation in the 1980s. In order to model this algorithm, we expand the CRA model developed in the first part to analyze variable-length messages. Predictions of the model are compared to an OPNET simulator of LonWorks, and to resultsfrom a physical network.Finally, we propose a direction-of-arrival (DOA) algorithm for sensor networks. It employs an improved polynomial rooting method using unitary transformations.Ph.D., Electrical Engineering -- Drexel University, 200
Place construction and public space: Cantonese opera as leisure in the urban parks of Guangzhou, China
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Modeling and performance evaluation of collision resolution algorithms for lonworks control networks
No full textRaman spectroscopic study of cyclohexane at pressures below 1000 MPa
No full textAt present, the room temperature freezing pressure of cyclohexane is still uncertain, and the phase transition pressure of solid I - solid III is not reliable at ambient temperature. In this work, we have performed a Raman spectroscopic study of cyclohexane in a Moissanite anvil cell at pressures below 1000 MPa at 25 degrees C, and analyzed the characteristic of Raman brands v(s)(CH2), v(as)(CH2) and v(b)(Ring). Two phase transition pressures 80 MPa and 550 MPa were determined by a quartz pressure gauge, and they are the room temperature freezing pressure of cyclohexane and the phase transition pressure of solid I to solid III, respectively. Furthermore, from the phase diagram of cyclohexane, it is inferred that pressure plays an important role on the stability of cyclohexane as the main constituent of oil, and it can be beneficial to understanding the formation, migration and preservation of petroleum in subterranean rock strata. (C) 2017 Elsevier B.V. All rights reserved.Fundamental Research Fund for Institute of Geomechanics of the Chinese Academy of Geological Sciences [DZLXJK201004]; National Natural Science Foundation of China [10299040, 40173019]SCI(E)ARTICLE52-5418
Compositional dependence of physical and structural properties in (Ge1−xGax)S2 chalcogenide glasses
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