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121.
冀敏 《数学的实践与认识》2013,43(10)
现代控制增稳飞机是高达几十阶的复杂系统,将其降阶为特定形式的低阶等效系统才能与已有飞行品质规范进行比较,进而预测和评价飞机飞行品质.从时域角度出发,提出了一种高阶控制增稳系统等效拟配参数在线辨识方法.分析了时域等效系统拟配的基本方法,提出了等效系统实时在线拟配的系统框架思路,基于Tustin变换法推导了由高阶系统时域响应获取四阶等效系统参数的数学公式,应用最小二乘法在MATLAB中实现了算法编程,并用试飞数据验证了所提方法的可行性.计算结果表明,所提方法可以快速准确地实现高阶控制增稳系统的等效系统参数辨识. 相似文献
122.
Firms often sell products in bundles to extract consumer surplus. While most bundling decisions studied in the literature are geared to integrated firms, we examine a decentralized supply chain where the suppliers retain decision rights. Using a generic distribution of customers’ reservation price we establish equilibrium solutions for three different bundling scenarios in a supply chain, and generate interesting insights for distributions with specific forms. We find that (i) in supply chain bundling the retailer’s margin equals the margin of each independent supplier, and it equals the combined margin when the suppliers are in a coalition, (ii) when the suppliers form a coalition to bundle their products the bundling gain in the supply chain is higher and retail price is lower than when the retailer bundles the products, (iii) the supply chain has more to gain from bundling relative to an integrated firm, (iv) the first-best supply chain bundling remains viable over a larger set of parameter values than those in the case of the integrated firm, (v) supplier led bundling is preferable to separate sales over a wider range of parameter values than if the retailer led the bundling, and (vi) if the reservation prices are uniformly distributed bundling can be profitable when the variable costs are low and valuations of the products are not significantly different from one another. For normally distributed reservation prices, we show that the bundling set is larger and the bundling gain is higher than that for a uniform distribution. 相似文献
123.
124.
A multifunctional integrated microfluidic biochip device was engineered to estimate the activity-toxicity and composition principle of medicine in a cell model in vitro. 相似文献
125.
Accurate measurement of low levels of testosterone is critical for diagnosis and treatment of androgen disorders. The very low concentrations of testosterone in children, females, and males with androgen suppression therapies necessitate the use of mass spectrometry‐based methods. We aimed to develop a liquid chromatography with tandem mass spectrometry method with simplified sample preparation and online solid‐phase extraction cleanup to achieve enhanced precision, accuracy, robustness, and cost‐effectiveness. The assay was linear from 10 to 20 000 pg/mL with an analytical recovery of 93–104%. The total coefficient of variation was 2.5, 1.9, and 1.7% at concentration levels of 348, 5432, and 10 848 pg/mL, respectively. No significant carryover was observed from samples with concentrations up to 20 000 pg/mL. No significant interference was observed from androstenedione, dehydroepiandrosterone, epi‐testosterone, and estriol. Comparison with CDC Hormone Standardization program (HoSt) reference samples with defined values (n = 40) showed a Deming regression slope of 0.963, intercept of 28.06 pg/mL, standard error of estimate was 66.9, a correlation coefficient of 0.9996, and a mean bias of ?0.6%. The method met the accuracy criteria by the CDC HoSt program. In addition, we achieved >12 000 injections on a single analytical column without significant performance deterioration due to the specific online solid‐phase extraction settings. 相似文献
126.
Chunying Li Min Sun Xiangping Ji Sen Han Xiuqin Wang Yu Tian Juanjuan Feng 《Journal of separation science》2019,42(12):2155-2162
Cotton fiber is an environmentally friendly and natural material with a certain extraction capacity, while its enrichment ability is poor. In order to improve the extraction efficiency of cotton fibers, it was carbonized to form a layer of amorphous carbon as the sorbent by a simple carbonization method. Carbonized cotton fibers were filled into a polyetheretherketone tube for in‐tube solid‐phase microextraction. The carbonization time was investigated to obtain high extraction efficiency. Coupled to high‐performance liquid chromatography, the extraction tube was evaluated with polycyclic aromatic hydrocarbons, estrogens and phthalates, and it exhibited best extraction efficiency for polycyclic aromatic hydrocarbons. Under the optimum conditions, an online analysis method for several polycyclic aromatic hydrocarbons was established with large linear ranges (0.016–0.20 μg/L), low limits of detection (0.005–0.020 μg/L), and high enrichment factors (948–2874). Analysis method was successfully applied to the detection of targets in the real samples and shown satisfactory durability and chemical stability. Moreover, the relative recoveries ranged from 82 to 119.2%, which demonstrated the applicability of carbonized cotton fibers in sample preparation. Compared with other reported methods, the proposed method provided shorter extraction time, higher enrichment factors, comparable limits of detection, and recoveries. 相似文献
127.
Xiangping Ji Min Sun Chunying Li Sen Han Xiuqin Wang Yu Tian Juanjuan Feng 《Journal of separation science》2019,42(14):2398-2406
Polypropylene hollow fibers as the adsorbent were directly filled into a polyetheretherketone tube for in‐tube solid‐phase microextraction. The surface properties of hollow fibers were characterized by a scanning electron microscope. Combined with high performance liquid chromatography, the extraction tube showed good extraction performance for five environmental estrogen hormones. To achieve high analytical sensitivity, four important factors containing sampling volume, sampling rate, content of organic solvent in sample, and desorption time were investigated. Under the optimum conditions, an online analysis method was established with wide linear range (0.03–20 µg/L), good correlation coefficients (≥0.9998), low limits of detection (0.01–0.05 µg/L), low limits of quantitation (0.03–0.16 µg/L), and high enrichment factors (1087–2738). Relative standard deviations (n = 3) for intraday (≤3.6%) and interday (≤5.1%) tests proved the stable extraction performance of the material. Durability and chemical stability of the extraction tube were also investigated, relative standard deviations of all analytes were less than 5.8% (n = 3), demonstrating the satisfactory stability. Finally, the method was successfully applied to detect estrogens in real samples. 相似文献
128.
Sen Han Juanjuan Feng Xiangping Ji Chunying Li Xiuqin Wang Yu Tian Min Sun 《Journal of separation science》2019,42(21):3363-3371
Nano‐molybdenum trioxide was prepared from nano‐molybdenum disulfide by simple firing in muffle furnace. Nano‐molybdenum trioxide was used as the extraction coating on the stainless steel wire. Four wires were filled in a polyetheretherketone tube to get an extraction tube. The tube was connected to the six‐port valve of a high performance liquid chromatograph, and the online analysis system was constructed. Extraction selectivity of the tube for different types of compounds, including polycyclic aromatic hydrocarbons, plasticizers, estrogens, anilines and neonicotinoids, was studied. Good enrichment ability for polycyclic aromatic hydrocarbons, but the extraction efficiency of others was not satisfactory. Using eight polycyclic aromatic hydrocarbons as the targets, an analytical method was established after optimizing main factors such as sampling volume, sampling rate, methanol content, and desorption time. The established method exhibited wide linear range to 0.016–20.00 μg/L and low limits of detection to 0.005 μg/L, and the enrichment factors can be up to 2443. The method was applied to the detection of trace polycyclic aromatic hydrocarbons in tap water and river water, and a good recovery was obtained. The tube showed good durability and chemical stability, and it still remained good extraction effect after more than 140 run. 相似文献
129.
The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy. 相似文献
130.