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61.
Understanding the Chena Hot Springs,Alaska, geothermal system using temperature and pressure data from exploration boreholes 总被引:1,自引:0,他引:1
Chena Hot Springs is a small, moderate temperature, deep circulating geothermal system, apparently typical of those associated to hot springs of interior Alaska. Multi-stage drilling was used in some exploration boreholes and was found to be useful for understanding subsurface flow characteristics and developing a conceptual model of the system. The results illustrate how temperature profiles illuminate varying pressure versus depth characteristics and can be used alone in cases where staged drilling is not practical. The extensive exploration activities helped define optimal fluid production and injection areas, and showed that the system could provide sufficient hot fluids (∼57 °C) to run a 400-kWe binary power plant, which came on line in 2006. 相似文献
62.
Walter A. Wohlmuth Bill Davenport Tyler Bowman Pat Hamilton Robert Hallgren Frederick S. Pool Andy Turudic 《Solid-state electronics》2005,49(12):1978
GaAs MESFETs with novel lowly-doped drain structures have been developed utilizing molecular implants of silicon trifluoride. Short-channel effects in the 1/4 μm enhancement- and depletion-mode transistors have been suppressed with drain-induced barrier height lowering of less than 70 mV/V and pinch-off voltage shifts of less than 220 mV as the gate length was scaled from 1.0 to 1/4 μm. The 3-terminal breakdown, the transconductance to output conductance ratio, and the unity current gain, cut-off frequency were simultaneously optimized. The E-mode device possessed breakdown of >10 V, Gm · Rds > 9.5, Ft > 55 GHz, and nominal on-resistance of 2.1 Ω mm while the D-mode device had breakdown >10 V, Gm · Rds > 6.0, Ft > 45 GHz, and nominal on-resistance of 1.9 Ω mm. These optimized transistors enabled the realization of a variety of low-power digital and high-power mixed signal circuits, using 3-level source-coupled transistor and common-mode logic, such as laser and electro-optic drivers, highly integrated transceivers, multiplexers, demultiplexers, and clock data recover circuits. 相似文献
63.
Jungho Kim Kondratko P.K. Shun Lien Chuang Walter G. Holonyak N. Jr. Heller R.D. Jr. Zhang X.B. Dupuis R.D. 《Quantum Electronics, IEEE Journal of》2005,41(11):1369-1379
A theoretical and experimental study of a particular transverse-electric (TE) mode lasing mechanism of a tunneling injection InP quantum-dot (QD) laser is reported. In the experiment, the TE mode lasing action takes place at the first excited state of InP biaxially compressively strained QDs. This QD state is coupled to the ground state of two tensile-strained InGaP quantum wells (QWs) although the tensile-strained QW structure favors the transverse-magnetic (TM) polarization light emission. The measured TE and TM modal gain spectra show a typical QW gain evolution behavior at low injection currents, which can be theoretically modeled by the quasi-equilibrium of carrier distribution. When the injection current is increased near threshold, a TE gain narrowing and a simultaneous TM gain pinning are observed in the measured modal gain spectra, which cannot be explained via the quasi-equilibrium model. We propose a polarization-dependent photon-mediated carrier redistribution in the QD-coupled-QW structure to explain this TE and TM gain evolution behavior. When the injection current is just below threshold, the strong carrier depletion via stimulated emission due to coupling between the InP QD and InGaP QW states plays an important role in carrier redistribution, which depends on the optical transition energy and polarization. This concept of the polarization-dependent photon-mediated carrier redistribution explains the TE gain narrowing and TM gain pinning behavior. In addition, a coupled rate equation model is established, and the calculated polarization power ratio based on the coupled rate equations explains the experimental observation. 相似文献
64.
Prochazka T. Fischer M. Gruber B. Manner R. Matz R. Walter S. 《Components and Packaging Technologies, IEEE Transactions on》2003,26(3):591-597
Design and technology of microwave conductor lines embedded in low-temperature cofired ceramic (LTCC) multilayer substrates are summarized with a focus on achieving the highest possible quality (Q) factor for a given line inductance. The work was initiated to test the integrability of base station voltage-controlled oscillators (VCOs) in ceramic multilayer substrates. This approach leads to a miniaturization of current versions by a factor of 2 to 4. However, base station specifications for phase noise and hence resonator Q are extremely demanding. Therefore, both the design and the processing technology were optimized. By choosing a twin-line design with two parallel lines vertically separated by a single LTCC layer, Q factors of 90 and 180 have been achieved for integrated 5.5 nH inductors at frequencies of 640 MHz and 1650 MHz, respectively. Application of this result to VCO modules in standard LTCC technology already yields low phase noise levels, e.g., -136 dBc/Hz at 100 kHz offset, which is suitable for base station applications. However, further noise reduction is expected from a dedicated high Q fabrication process that uses conventional via punching and filling steps to replace the ceramic material between the two lines by conductive silver paste. This raises the Q to 120 and 200, respectively, at the two frequencies and adds extra degrees of freedom to LTCC design for low-loss wireless solutions. 相似文献
65.
Arun Chandrasekhar Steven Brebels Serguei Stoukatch Eric Beyne Walter De Raedt Bart Nauwelaers 《Microelectronics Reliability》2003,43(3):351-357
At frequencies beyond 1 GHz, every component of the IC package contributes to the RF performance, whether required or not. In this work, we study the effects of packaging materials namely, the substrate and the globtop/underfill material on RF performance. We have measured interconnects on two area-array CSPs, the ball grid array and the polymer stud grid array using IMEC’s MCM-D technology. The measurements on the package interconnect show that the losses in the package substrate material account for about 50% of the total losses at 1.8 GHz and this drops to less than 20% at 5.2 GHz. The losses due to impedance mismatch dominate the losses especially below 10 GHz and considerable improvement in performance cannot be obtained by using an improved/expensive substrate. The other study is about the influence of globtop/underfill materials on wirebonds (through 3D EM simulations) as well as on standard 50 Ω MCM-D transmission lines (through experiments). While a higher value of dielectric constant of the globtop/underfill material is better on wirebonds, the influence of loss tangent is felt only above values of 0.1. The influence of seven different globtop/undefill materials on 50 Ω transmission lines has been used to extract their dielectric constant and loss tangent values at 30 GHz. These results are very valuable since one can hardly find the properties of globtop/underfill materials beyond 1 GHz. 相似文献
66.
Providing reliable group communication is an ever recurring topic in distributed settings. In mobile ad hoc networks, this problem is even more significant since all nodes act as peers, while it becomes more challenging due to highly dynamic and unpredictable topology changes. In order to overcome these difficulties, we deviate from the conventional point of view, i.e., we "fight fire with fire," by exploiting the nondeterministic nature of ad hoc networks. Inspired by the principles of gossip mechanisms and probabilistic quorum systems, we present in this paper PILOT (probabilistic lightweight group communication system) for ad hoc networks, a two-layer system consisting of a set of protocols for reliable multicasting and data sharing in mobile ad hoc networks. The performance of PILOT is predictable and controllable in terms of both reliability (fault tolerance) and efficiency (overhead). We present an analysis of PILOT's performance, which is used to fine-tune protocol parameters to obtain the desired trade off between reliability and efficiency. We confirm the predictability and tunability of PILOT through simulations with ns-2. 相似文献
67.
The photoelectric properties of thin-film ZnO/CdS/Cu(In,Ga)Se2 solar cells were studied by polarization photoactive absorption spectroscopy. It was shown that the thin-film solar cells
have a high efficiency relative to the intensity of unpolarized radiation in the photon energy range from 1.2 to 2.5 eV. The
induced photopleochroism coefficient P
I
increases with the angle of incidence of the incident radiation as P
I
∼θ
2
and at 70° it reaches 17–20% with photon energy 1.3 eV. Oscillations of the photopleochroism were also observed. These results
are discussed taking into account the antireflection effect. The results obtained by us make it possible to use such solar
cells as wide-band photosensors for linearly polarized radiation and for monitoring the production of high-efficiency, thin-film
solar cells based on ternary semiconductors.
Fiz. Tekh. Poluprovodn. 31, 806–810 (July 1997) 相似文献
68.
Heme-dependent and heme-independent nitrite reduction by lactic acid bacteria results in different N-containing products 总被引:1,自引:0,他引:1
Gudrun Wolf Elke K. Arendt Ute Pfhler Walter P. Hammes 《International journal of food microbiology》1990,10(3-4):323-329
Seventy strains of lactic acid bacteria were investigated for nitrite reductase activity. Two types of this activity were detected. Type I was found in Lactobacillus plantarum, L. pentosus and Pediococcus pentosaceus. This activity is heme-dependent with ammonia as the sole product. Type II mechanism is heme-independent and reduces nitrite to NO and N2O. 相似文献
69.
The secondary diamine 1,3,5,7-tetrahydro[1,2c:4,5c'] benzodipyrrole (3) and 1,2,4,5-tetrabromomethylbenzene (1) form a polymeric ionene with spirane structure through a repetitive alkylation reaction. The structure of the product could be proven by13C-NMR spectroscopy by comparison with suitable reference compounds. Solutions in aqueous methanol exhibit a typical polyelectrolyte effect. Variation of the counterions produces sufficient solubility in organic solvents. From the crystal structure of a similar model compound one can conclude that the synthesized polymer has a rod-like shape. 相似文献
70.
Walter Gsele Wolfgang Egel-Hess Klaus Wintermantel Friedrich Richard Faulhaber Alfons Mersmann 《化学,工程师,技术》1990,62(7):544-552
Formation of solids by crystallization and precipitation. Formation of solids from solutions can take place by crystallization or precipitation. The principal factor is the relationship between solubility and supersaturation. In crystallization, the solubility of the crystallising substance is so high that the formation of solids occurs largely in the metastable zone in the immediate vicinity of the solubility limits. Crystal growth and nucleation are functions of supersaturation. If a high supersaturation is required at low substance-specific growth rates for an adequate crystal growth, high nucleation rates and hence small crystals will result. On this basis, the authors present information for the specific design of crystallization processes. In contrast, the solubility of the precipitated product must be very low for precipitation. Direct crystal formation is possible only for substance systems of high solubility. As a rule, however, the precipitated substance is so insoluble that solids are formed via amorphous intermediates. The results of a large number of experiments show the influence of various parameters of the precipitation process on the filtrability of the precipitated product. 相似文献