A Combined Forward Error Control and Multiple Access Protocol for Wireless Voice/Data Integration

Different strategies for error control are investigated, in conjunction with a MAC-level protocol, operating in a multimedia noisy cellular environment, where a base station co-ordinates mobile users within each cell. The channel multiplexing structure is based on Time Division (TDM), and the slots in each frame are dynamically assigned to the users and their service classes. The access rights are decided by an algorithm, namely, the Independent Stations Algorithm (ISA), at the cell base station, which broadcasts this information to the users. Each single mobile station is associated a bit error probability, which changes with time in a random fashion. Bit error probabilities are estimated and the protection level of the Forward Error Correction (FEC) code is dynamically adapted to the new conditions. The performance of the scheme is analyzed by simulation in the presence of mixed voice and data traffic, and with different error handling techniques (FEC and Automatic Retransmission Request (ARQ)).     

基于PIC单片机的自动喷料机设计

目前鉴于我国渔业养殖设备比较落后,介绍了在渔业养殖上广泛应用的自动喷料机的软、硬件设计.该设计具有可靠性高、能定时定量喷洒饲料、喷料均匀、喷料距离远、避免饲料浪费等特点.     

天线超方向性对PAF 射电望远镜视场影响研究

在基于相控阵馈源的抛物反射面的射电望远镜设计中,增加阵元间距可以扩大视场范围,但会降低 视场内灵敏度性能,不能有效提升巡天速度。超方向性天线单元可用于改善这一矛盾,文章将巡天速度指标(SSFoM)作为优化目标,以无限大理想导电平面上的方形口径模拟天线单元,结合解析公式和物理光学方法计算抛物反射面相控阵馈源(PAF)性能,讨论了抛物反射面在不同焦径比(f/D)情况下,天线单元超方向性同SSFoM值、灵敏度、口径效率以及系统噪声温度等性能之间的关系。仿真结果表明,超方向性在提升口径效率的同时,降低了系统噪声温度,提升灵敏度并扩展有效视场。f/D 为0.4、0.7 和1时,分别设置超方向性系数为1.69、1.37 和1.22,可获得最优的SSFoM 值,且该值相较于超方向性系数为1时分别提升53%、115%、71%,此时阵元间距分别可以达到0.65λ,0.8λ 和0.9λ。     

Determination of trace amounts of morpholine and its thermal degradation products in boiler water by HPLC

Summary Morpholine and its amine-type thermal degradation products present in boiler feed water and steam condensate were derivatised with N-succinimidyl-p-nitrophenylacetate. These pre-column derivatives were determined by high-performance liquid chromatography with UV detection at 280 nm. The analytical column was Supelco-sil-ODS with an isocratic mobile phase. Morpholine and its breakdown products were monitored in the range 0.01–10 g ml^–1 with a relative standard deviation of 0.4–3.0%. Chromatographic analysis of boiler feed water and steam condensate samples collected from a boiler servicing a petroleum refinery is described.     

Term structure extrapolation and asymptotic forward rates

We investigate different inter- and extrapolation methods for term structures under different constraints in order to generate market-consistent estimates which describe the asymptotic behavior of forward rates. Our starting point is the method proposed by Smith and Wilson, which is used by the European insurance supervisor EIOPA. We use the characterization of the Smith–Wilson class of interpolating functions as the solution to a functional optimization problem to extend their approach in such a way that forward rates will converge to a value which is an outcome of the optimization process. Precise conditions are stated which guarantee that the optimization problems involved are well-posed on appropriately chosen function spaces. As a result, a well-defined optimal asymptotic forward rate can be derived directly from prices and cashflows of traded instruments. This allows practitioners to use raw market data to extract information about long term forward rates, as we will show in a study which analyzes historical EURIBOR swap data.     

EFFINO

The program EFFINO (Environment For FItting Nuclear Optics) evaluates Mössbauer absorption and time spectra both in nuclear forward scattering and in grazing incidence reflection geometry. Timeintegral prompt and delayed angular scan spectra are also treated. The time spectra are calculated by Fourier transformation from frequency to time domain. The electric quadrupole and magnetic dipole fields at the nuclear sites are considered static at present. The specimen in both forward scattering and grazing incidence is assumed to be a multilayer, with individual thickness and interface roughness (the latter only for the grazing incidence case at present) and electronic index of refraction. Up to eight different layers plus eight repetition periods of those layers are treated. Each layer may contain zero to eight nuclear sites (zero in all layers being prompt Xray reflectivity), with their own effective thickness or (for grazing incidence) their own complex nuclear index of refraction. From the forward scattering amplitude, a differential 4 × 4 propagation matrix is constructed for each layer. Several experimental spectra of the same or different type(s) can be fitted simultaneously. Correlations between parameters of the same or of different spectra can be introduced.     

Increasing the Value of Hominy Feed as a Coproduct by Fermentation

Hominy feed is a low value ($83.7/metric ton) coproduct of the corn dry milling process that accounts for nearly 35% of the starting corn quantity. The average composition of hominy feed on a dry basis is 56.9% starch, 25.2% neutral detergent fiber, 11.1% protein, and 5.3% fat. Starch in hominy feed can be fermented to ethanol thus increasing its levels of protein and fat. The increase in protein and fat percentages may increase the market competitiveness and price of hominy feed. Hydrolysis and fermentation were performed on nine hominy feed samples collected from three corn dry milling plants in the USA. The original hominy feed samples and postfermentation solids were analyzed for starch, protein, fat, and fiber content. Compared to the original hominy feed, the percentage increase in protein, fat and fiber in postfermentation solids of nine samples ranged from 10.4 to 21.3, 6.78 to 10.6, and 12.6 to 28.7% (dry basis), respectively. Ethanol yields varied from 271.7 to 380.2 l/metric ton for the nine hominy feed samples. These results indicate that the value of hominy feed as an animal feedstock can potentially be increased with fermentation and can produce more profit per metric ton than currently being derived by its sale as a low protein feed ingredient.     

Influence of the Feed Gas Composition on the Fischer-Tropsch Synthesis in Commercial Operations

Key technical challenges relating to the Fischer-Tropsch(F-T)synthesis applied in the commer- cialization of coal/gas-to-liquids(CTL/GTL)technolo- gies have been reviewed.Based on the experiences ac- cumulated from pilot plant,semi-work test and lab re- searches,the influences of the H_2/CO ratio and the CO_2 in the feed gas on the F-T process as well as on CTL/GTL complex in terms of product yields,energy efficiency and carbon utilization efficiency have been studied.Being contrary to the current design schemes for F-T process using the coat derived syngas and the iron-based cata- lyst,it is suggested to feed the F-T synthesis unit with a syngas having a H_2/CO ratio of 0.5 and then adjusting to 1.4 via the recycling process.As a result,the carbon efficiency of the whole plant could be reached to as high as 50%.For the issue of CO_2 addition to the feed gas, it is proved that only a diluting role is played under the current commercial slurry phase F-T process.     

用进刀量补偿法减小细长轴车削加工误差

首先分析了细长轴车削加工时造成的位移,理论上分析了误差的大小与位移量的关系,然后运用材料力学公式得出切削点位移量与切削力的关系,又根据径向切削力经验公式获得切削力与进刀量的关系,推出了理论进刀量与实际进刀量的关系,提出了用进刀量补偿法减小细长轴车削加工误差的模型。最后通过试验验证了采用进刀量补偿方法,在不改变机床精度的前提下显著提高细长轴的加工精度。     

改造常规汽轮机电站联合循环系统的热力学分析

联合循环系统改造（Ｃｏｍｂｉｎｅｄ Ｃｙｃｌｅ－Ｒｅｐｏｗｅｒｉｎｇ）是常规燃煤电站更新最科学最有效的方法之一。本文对两种典型的联合循环系统（排气助燃型ＦＦ－Ｒｅｐｏｗｅｒｉｎｇ和给水加热型ＦＷＨ－Ｒｅｐｏｗｅｒｉｎｇ）进行了热力学系统模拟研究,得到了随燃机汽机功比变化排气助燃型系统效率单调变化以及给水加热型系统效率存在极值点的现象,并发现了一定燃机汽机功比下给水加热型效率大于排气助燃型的特殊规律。通过对联合循环系统改造各种因素的综合分析,揭示了上述特殊规律的热力学机理,澄清了有关研究的误区。该理论研究对采用联合循环系统技术改造常规电站具有指导意义。