摘要:
A method and apparatus for allocating subcarriers in an orthogonal frequency division multiple access (OFDMA) system is described. In one embodiment, the method comprises allocating at least one diversity cluster of subcarriers to a first subscriber and allocating at least one coherence cluster to a second subscriber.
摘要:
A diesel exhaust treatment system is disclosed that includes first and second diesel particulate reduction devices. The first diesel particulate reduction device is located upstream in the exhaust flow and contains an oxidation catalyst coating. The second particulate reduction device is located downstream from the first particulate reduction device and is generally non-catalyzed or lightly catalyzed. Each particulate reduction device comprises a flow-through fabric-type filtration media with substantial internal turbulence. As exhaust gas passes through the catalyzed upstream particulate reduction device, nitric oxide (NO) is oxidized to form nitrogen dioxide (NO2), a portion of which interacts with the particulate trapped within the upstream diesel particulate reduction device to regenerate the upstream device. A remaining portion of exhaust gas containing NO2 enters the downstream diesel particulate reduction device, where an additional portion interacts with the trapped particulate to regenerate the device. The relative volume weighted efficiency of the upstream particulate reduction device and of the downstream particulate reduction device are selected to optimize the overall system particle capture efficiency and backpressure, as well as to balance the amount of NO2 made with the amount of NO2 consumed so as to minimize NO2 emissions.
摘要翻译:公开了一种包括第一和第二柴油颗粒减少装置的柴油机排气处理系统。 第一柴油颗粒减少装置位于废气流的上游并且包含氧化催化剂涂层。 第二颗粒减少装置位于第一颗粒还原装置的下游,并且通常是非催化的或轻微的催化的。 每个颗粒还原装置包括具有实质内部湍流的流通织物型过滤介质。 当废气通过催化的上游颗粒还原装置时,一氧化氮(NO)被氧化以形成二氧化氮(NO 2 H 2),其一部分与捕获在上游柴油颗粒还原物内的颗粒相互作用 设备重新生成上游设备。 含有NO 2 N 2的排气的剩余部分进入下游柴油颗粒还原装置,其中附加部分与捕获的颗粒相互作用以再生装置。 选择上游颗粒还原装置和下游颗粒还原装置的相对体积加权效率以优化整个系统颗粒捕获效率和背压,以及平衡由下列颗粒还原装置制备的NO 2 2 / 消耗的NO 2量的量以使NO 2排放最小化。
摘要:
Techniques for fast cell search, selection and reselection for wireless communication systems such as OFDM or OFDMA communication systems. In various implementations of the described techniques, downlink subframes from base stations to mobile stations are designed to include information in form of preambles or post-ambles in one or more downlink subframes to facilitate cell search at receiving mobile stations at high speeds. The described preambles and post-ambles may also be used to improve the accuracy of signal synchronization in time and frequency.
摘要:
Mesoporous hexagonal, cubic or wormhole aluminosilicates derived from zeolite seeds using an ionic structure directing agent are described. The aluminum in the structures is stable so that the framework of the structures does not collapse when heated in the presence of water or water vapor (steam). The steam stable aluminosilicates can be used as acid catalysts for hydrocarbon conversions, including the fluidized bed catalytic cracking and the hydrocracking of petroleum oils, and other cracking of organic compounds.
摘要:
Mesoporous hexagonal, cubic or wormhole aluminosilicates derived from zeolite seeds using an ionic structure directing agent are described. The aluminum in the structures is stable so that the framework of the structures does not collapse when heated in the presence of water or water vapor (steam). The steam stable aluminosilicates can be used as acid catalysts for hydrocarbon conversions, including the fluidized bed catalytic cracking and the hydrocracking of petroleum oils, and other cracking of organic compounds.
摘要:
A neutral templating route to mesoporous molecular sieves based on H-bonding and self-assembly between neutral primary amine or diamine surfactants (S°) and neutral inorganic precursors (I°) has been used to prepare hexagonal and lamellar mesoporous silicas with site isolated transition metal centers. This templating approach allows for the preparation of hexagonal or hexagonal-like mesoporous oxidation catalysts with large framework wall thickness of at least about 17 Å, small elementary particle size (≦400 Å), and unique combinations of framework-confined mesopores and textural mesopores while at the same time providing for facile recovery of the neutral template by simple solvent extraction. The templating of neutral metallosilicate precursors (I°) with neutral diamine surfactants (S°—S°) affords thermally stable pillared lamellar metallosilicates exhibiting complementary framework-confined microporosity and textural mesoporosity while at the same time also providing for template recovery by solvent extraction. In addition, a hexagonal transition metal-substituted catalysts, analogous to MCM-41, have been prepared using the mediated S+X−I+ templating pathway (Pathway 3) and mild reaction conditions.
摘要:
Semi-crystalline alumina compositions with framework mesopores are disclosed. The compositions are assembled from inorganic aluminum precursors and nonionic polyethylene oxide surfactants. The new assembly pathway introduces several new concepts to alumina mesostructure synthesis. The application of low-cost, non-toxic and biodegradable surfactants and low cost aluminum reagents as alumina precursors which are inorganic and low solution reaction temperatures, introduces efficient and environmentally clean synthetic techniques to the formation of mesostructures. Recovery of the surfactant can be achieved through solvent extraction where the solvent may be water or ethanol or by calcination.
摘要:
A neutral templating route to mesoporous molecular sieves based on H-bonding and self-assembly between neutral primary amine or diamine surfactants (S.degree.) and neutral inorganic precursors (I.degree.) has been used to prepare hexagonal and lamellar mesoporous silicas with site isolated transition metal centers. This templating approach allows for the preparation of hexagonal or hexagonal-like mesoporous oxidation catalysts with large framework wall thickness of at least about 17 .ANG., small elementary particle size (.ltoreq.400 .ANG.), and unique combinations of framework-confined mesopores and textural mesopores while at the same time providing for facile recovery of the neutral template by simple solvent extraction. The templating of neutral metallosilicate precursors (I.degree.) with neutral diamine surfactants (S.degree.-S.degree.) affords thermally stable pillared lamellar metallosilicates exhibiting complementary framework-confined microporosity and textural mesoporosity while at the same time also providing for template recovery by solvent extraction. In addition, a hexagonal transition metal-substituted catalysts, analogous to MCM-41, have been prepared using the mediated S.sup.+ X.sup.- I.sup.+ templating pathway (Pathway 3) and mild reaction conditions.These new mesoporous metallosilicate molecular sieves exhibit exceptional catalytic activity for peroxide hydroxylation of benzene and oxidation of substituted aromatics with kinetic diameters that are too large (larger than 6 .ANG.) to access the pore structure of the conventional microporous transition metal-substituted molecular sieves such as titano- and vanadosilicates.
摘要:
A neutral templating route to mesoporous molecular sieves based on H-bonding and self-assembly between neutral primary amine or diamine surfactants (S.degree.) and neutral inorganic precursors (I.degree.) has been used to prepare hexagonal and lamellar mesoporous silicas with site isolated transition metal centers. This templating approach allows for the preparation of hexagonal or hexagonal-like mesoporous oxidation catalysts with large framework wall thickness of at least about 17 .ANG., small elementary particle size (.ltoreq.400 .ANG.), and unique combinations of framework-confined mesopores and textural mesopores while at the same time providing for facile recovery of the neutral template by simple solvent extraction. These new mesoporous metallosilicate molecular sieves exhibit exceptional catalytic activity for peroxide hydroxylation of benzene and oxidation of substituted aromatics with kinetic diameters that are too large (larger than 6 .ANG.) to access the pore structure of the conventional microporous transition metal-substituted molecular sieves such as titano- and vanadosilicates.
摘要:
A comparator used in a clock signal generation circuit compares two input signals and generates an output signal. The comparator has first and second input transistors coupled to the input signals. First and second hysteresis transistors are coupled between the input transistors and an output stage of the comparator, and apply hysteresis to a comparison of the input signals. First and second hysteresis control transistors are coupled between the input transistors and the hysteresis transistors to isolate the hysteresis transistors from the input transistors under control of a hysteresis enable signal. The comparator is operable in a first mode or a second mode based on a hysteresis enable signal. In the first mode the comparator applies hysteresis to the comparison of the input signals and in the second mode, compares the input signals without hysteresis.