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91.
Evaluation of the impact of fuel hydrocarbons and oxygenates on groundwater resources 总被引:2,自引:0,他引:2
The environmental behavior of fuel oxygenates (other than methyl tert-butyl ether [MTBE]) is poorly understood because few data have been systematically collected and analyzed. This study evaluated the potential for groundwater resource contamination by fuel hydrocarbons (FHCs) and oxygenates (e.g., tert-butyl alcohol [TBA], tertamyl methyl ether [TAME], diisopropyl ether [DIPE], ethyl tert-butyl ether [ETBE], and MTBE) by examining their occurrence, distribution, and spatial extent in groundwater beneath leaking underground fuel tank (LUFT) facilities, focusing on data collected from over 7200 monitoring wells in 868 LUFT sites from the greater Los Angeles, CA, region. Excluding the composite measure total petroleum hydrocarbons as gasoline (TPHG), TBA has the greatestsite maximum (geometric mean) groundwater concentration among the study analytes; therefore, its presence needs to be confirmed at LUFT sites so that specific cleanup strategies can be developed. The alternative ether oxygenates (DIPE, TAME, and ETBE) are less likely to be detected in groundwater beneath LUFT facilities in the area of California studied and when detected are present at lower dissolved concentrations than MTBE, benzene, or TBA. Groundwater plume length was used as an initial indicator of the threat of contamination to drinking water resources. Approximately 500 LUFT sites were randomly selected and analyzed. The results demonstrate MTBE to pose the greatest problem, followed by TBA and benzene. The alternative ether oxygenates were relatively localized and indicated lesser potential for groundwater resource contamination. However, all indications suggest the alternative ether oxygenates would pose groundwater contamination threats similar to MTBE if their scale of usage is expanded. Plume length data suggest that in the absence of a completely new design and construction of the underground storage tank (UST) system, an effective management strategy may involve placing greater emphasis on UST program for ensuring adequate enforcement and compliance with existing UST regulations. 相似文献
92.
Fu-Chien Chiu Wen-Chieh Shih Joseph Ya-min Lee Huey-Liang Hwang 《Microelectronics Reliability》2007,47(4-5):548
MOSFETs and MOSCs incorporating HfO2 gate dielectrics were fabricated. The IDS–VDS, IDS–VGS, gated-diode and C–V characteristics were investigated. The subthreshold swing and the interface trap density were obtained. The surface recombination velocity and the minority carrier lifetime in the field-induced depletion region measured from the gated diodes were about 2.73 × 103 cm/s and 1.63 × 10−6 s, respectively. The effective capture cross section of surface state was determined to be 1.6 × 10−15 cm2 using the gated-diode technique in comparison with the subthreshold swing measurement. A comparison with conventional MOSFETs using SiO2 gate oxide was also made. 相似文献
93.
Management by exceptions (MBE) is an effective management strategy in many domains. It suggests that managers focus on important jobs (e.g., planning and decision-making) without being involved in the tedious monitoring of exceptions (e.g., a critical item whose current status violates some regulations). Once an exception is detected, the managers are notified to respond to the exception promptly. Therefore, exception monitoring is the key to realize the idea of MBE. An exception monitoring system should detect exceptions in a timely manner for the managers. It should also control the extra loading it incurs to related information servers (e.g., database management systems) and the Intranet, which are fundamental backbones for information processing in businesses. In this paper, a multiagent paradigm Adaptive Agents for Management by Exceptions (AAMBE) is proposed for exception monitoring. The agents adapt to the environment by learning to work together to achieve timely detection of exceptions. An experiment to investigate the performance of AAMBE is conducted by simulating real-world operations of financial management in merchandising trades. Empirical and theoretical analyses show that AAMBE may detect more exceptions in a timelier manner by incurring less extra loading to the related information servers and the Intranet. 相似文献
94.
Fan C. Shih D.W. Hansen M.W. Esener S.C. Wieder H.H. 《Photonics Technology Letters, IEEE》1993,5(12):1383-1385
Electroabsorption modulation is achieved at or near a wavelength of 1.06 μm with InxAlyGa1-x-yAs/In xGa1-xAs multiple-quantum-well (MQW) structures grown on GaAs substrates. The lattice mismatch (close to 2%) between the MQW and the substrate is accommodated by a compositional-step-graded buffer array. A dislocation density of less than 107/cm2 is estimated for the MQW region. For 80-to-100 Å well widths, a maximum electroabsorption coefficient of 8000 cm-1 with an applied voltage of 15 V is obtained 相似文献
95.
A series of waterborne poly(urethane‐urea)s, WPUUs, based on using nonpolar hydroxyl‐terminated polybutadiene (HTPB) as the soft segment, were successfully synthesized in this article. The effects of the COOH group content and soft‐segment molecular weight (Mns) on the dispersion, morphology, and physical properties were investigated. Variations of the particle size, viscosity, and zeta potential were first governed by the hydrophilicity of the polymer chain, and then by the swelling derived from water. Fourier transfer infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) indicated that the degree of phase separation decreased as the COOH group content increased or as Mns decreased. However, the hydrogen bonding between the soft and hard segments and the two‐phase mixing could not occur in this nonpolar HTPB‐based WPUU system, indicating that the hard segments tended to form smaller domains and to pack more loosely. It was attributed to the fact that the presence of bulky ionic salt groups destroyed the ordered arrangement of the hard segments. In this case, the increases of the interface area between the soft and hard phases resulted in that the present behaviors were similar to the phase mixing. In tensile properties, HTPB‐based WPUUs exhibited higher tensile stress, elongation at break, and modulus as the COOH group content decreased or as Mns decreased. In thermal degradation, the introduction of HTPB polyol improved the thermal stability of WPUU. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
96.
Multimedia Tools and Applications - 相似文献
97.
Shih Yu Chang Hsiao-Chun Wu 《Wireless Communications, IEEE Transactions on》2009,8(6):2827-2830
In this paper, we design a novel computationallyefficient linear programming (LP) algorithm to maximize the throughput with respect to the minimum contention window size for the IEEE 802.11 Distributed Coordination Function (DCF) protocol. Based on our LP scheme, a new DCF protocol which can select the best access mode and the optimal size of the minimum contention window is proposed by considering the channel condition and the number of competing stations jointly. The numerical results demonstrate that our proposed DCF protocol significantly outperforms the conventional method. 相似文献
98.
Hsin-Hung Cho Chin-Feng Lai Timothy K. Shih Han-Chieh Chao 《Mobile Networks and Applications》2016,21(5):846-855
A mature cloud system needs a complete resource allocation policy which includes internal and external allocation. They not only enable users to have better experiences, but also allows the cloud provider to cut costs. In the other words, internal and external allocation are indispensable since a combination of them is only a total solution for whole cloud system. In this paper, we clearly explain the difference between internal allocation (IA) and external allocation (EA) as well as defining the explicit IA and EA problem for the follow up research. Although many researchers have proposed resource allocation methods, they are just based on subjective observations which lead to an imbalance of the overall cloud architecture, and cloud computing resources to operate se-quentially. In order to avoid an imbalanced situation, in previous work, we proposed Data Envelopment Analysis (DEA) to solve this problem; it considers all of a user’s demands to evaluate the overall cloud parameters. However, although DEA can provide a higher quality solution, it requires more time. So we use the Q-learning and Data Envelopment Analysis (DEA) to solve the imbalance problem and reduce computing time. As our simulation results show, the proposed DEA+Qlearning will provide almost best quality but too much calculating time. 相似文献
99.
Jiann‐Liang Chen Shih‐Wei Liu Szu‐Lin Wu Ming‐Chiao Chen 《International Journal of Communication Systems》2011,24(9):1150-1162
Owing to limited wireless network resources, network applications must provide an adaptive quality‐guaranteed service to satisfy user requirements. Different applications are associated with different quality of service (QoS) concerns, as well as different QoS control parameters. This work presents an adaptive QoS algorithm by discussing the QoS specifications of three wireless access technologies, i.e. 3G, WiMAX and WiFi. Based on cross‐layer and cognition concepts, these environmental parameters are integrated with the sensing of spectral and received signal strength from a cognitive radio paradigm. An adaptive QoS algorithm is then proposed to select the optimal access network for services. Simulation results indicate that the proposed adaptive QoS algorithm outperforms available ones in real‐time applications. Compared with traditional algorithms, the proposed algorithm reduces not only the average delay time and jitter for VoIP services to 0.16 s and 0.09 ms, respectively, but also the packet loss ratio for high‐definition video streaming by 3.4%. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
100.
Paul?FerkulEmail author Julie?Kleinhenz Hsin-Yi?Shih Richard?Pettegrew Kurt?Sacksteder James?T’ien 《Microgravity science and technology》2004,15(2):3-12
The conventional way of determining the flammability characteristics of a material involves a number of tedious single-sample
tests to distinguish flammable from non-flammable conditions. A novel test device and fuel configuration has been developed
that permits multiple successive tests for indefinite lengths of thin solid materials. In this device, a spreading flame can
be established and held at a fixed location in front of optimized diagnostics while continuous variations of test parameters
are made. This device is especially well-suited to conducting experiments in space (e.g. aboard the International Space Station)
where the limited resources of stowage, volume, and crew time pose major constraints. A prototype version of this device was
tested successfully in both a normal gravity laboratory and during low-gravity aircraft trials. As part of this ongoing study
of material flammability behavior, a numerical model of concurrent-flow flame spread is used to simulate the flame. Two and
three-dimensional steady-state forms of the compressible Navier-Stokes equations with chemical reactions and gas and solid
radiation are solved. The model is used to assist in the design of the test apparatus and to interpret the results of microgravity
experiments. This paper describes details of the fuel testing device and planned experiment diagnostics. A special fuel, developed
to optimize use of the special testing device, is described. Some results of the numerical flame spread model are presented
to explain the three-dimensional nature of flames spreading in concurrent flow and to show how the model is used as an experiment
design tool. 相似文献