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1.
A star forest is a forest whose components are stars. The star arboricity of a graph G,denoted by sa( G),is the minimum number of star forests needed to decompose G. Let k be a positive integer. A k-star forest is a forest whose components are stars of order at most k + 1. The k-star arboricity of a graph G,denoted by sak( G),is the minimum number of k-star forests needed to decompose G. In this paper,it is proved that if any two vertices of degree 3 are nonadjacent in a subcubic graph G then sa2( G) ≤2.For general subcubic graphs G, a polynomial-time algorithm is described to decompose G into three 2-star forests. For a tree T and[Δ k, T)/k]t≤ sak( T) ≤[Δ( T)- 1/K]+1,where Δ( T) is the maximum degree of T.kMoreover,a linear-time algorithm is designed to determine whether sak( T) ≤m for any tree T and any positive integers m and k.  相似文献   

2.
This study is aimed to investigate and analyze the vegetation landscape around Rivers of Hou-lung, Fa-tz, Da-li, Ching-shuei and Gau- ping, and to select the suitable plant species that could be applied for the area of riverbank ecological engineering in Taiwan. Studying the vegetation established the key point and procedure of ecological engineering in the riverside and revetment, to compile and edit the dominant plants' types, life form, propagating method, root systems' characteristics and functions for soil conservation. This research choses three dominant plants for roots strength test. The fitting models of plants pulling resistance(Rp, kg) between plant height (H, cm), diameter near ground (Dn, mm), diameter above ground 100 mm (Da, mm), The research finished the relative abundant, types and cluster analysis of riverbank dominant plants that generalize vegetative distribution and ecological restoration for different river types to apply and manage in Taiwan.  相似文献   

3.
Numerous edge-chasing deadlock detection algonthms were developed lor the cycle detection in distributed systems, but their detections had the n steps speed limitation and n ( n- 1) overhead limitation to detect a cycle of size n under the one-resource request model. Since fast deadlock detection is critical, this paper proposed a new algorithm to speed up the detection process. In our algorithm, when the running of a transaction node is blocked, the being requested resource nodes reply it with the waiting or being waited message simultaneously, so the blocked node knows both its predecessors and successors, which helps it detecting a cycle of size 2 directly and locally. For the cycle of size n ( n 〉 2), a special probe is produced which has the predecessors information of its originator, so the being detected nodes know their indirect predecessors and direct successors, and can detect the cycle within n - 2 steps. The proposed algorithm is formally proved to be correct by the invariant verification method. Performance evaluation shows that the message overhead of our detection is ( n^2 - n - 2)/2, hence both the detection speed and message cost of the proposed algorithm are better than that of the existing al gorithms.  相似文献   

4.
Shengmaisan is a recipe of traditional Chinese medicine, which is composed of three herbs. The interaction among the components from the three herbs of Shengmaisan is investigated using FT-IR, Matrix Assistant Laser Desorption/Ionization Time of flight mass spectrometry (MALDI TOF MS) and TEM observation. Interactions among various components from different herbs cause enhancement of the solubility of some component and suppression of the solubility of others. Results from MALDI-TOF MS show that some components found in the decoction from a single herb disappear when different herbs are decocted together. On the other hand, new substances are produced when two and/or three herbs of Shengmaisan are decocted together. TEM showed that vacuoles formed in the decoction from two and/or three herbs of Shengmaisan but did not occur in any decoction from a single herb. This result provides us direct evidence that the solubilized structure is formed by the interaction among the components from different herbs. This knowledge helps us to understand the therapeutical effects of traditional Chinese medicine.  相似文献   

5.
In this paper, we analyze the bit error ratio (BER) of fast frequency hopping (FFH) system with binary phase shift keying (BPSK) in high-mobility wireless channels. By taking into account partial band noise jam- ming and channel estimation errors as Gaussian noise, both of maximal-ratio combining (MRC) and equal-gain com- bining (EGC) schemes are considered, and exact analytical BER expressions for MRC and EGC schemes are obtained. Especially, a closed-form BER expression for the MRC scheme is also presented in high signal-to-noise ratio region. Analytical and simulation results demonstrate that, the FFH/BPSK schemes suffer from performance degra- dation in the presence of channel estimation errors. The worst case jamming factor is shown to be inversely pro- portional to the signal to jamming ratio. With properly designed frequency hopping schemes and channel estima- tion schemes, the performance improvement is also observed as compared with the traditional noncoherent FFH/BFSK system.  相似文献   

6.
The ratio of Zirconium to Rubidium (Zr/Rb) is suggested to be a better proxy for the East Asian winter monsoon strength than the widely-used grain size distribution. The rationale for the Zr/Rb proxy relies on the following assumptions: (1) Grain size fractionating characteristics during eolian dust transport should be archived in the Zr/Rb ratio records and this assumption is based on the premise that Zr is preferentially enriched in coarser grain size fraction while Rb tend to be enriched in finer grain size fraction; and (2) post-depositional weathering does not change the Zr/Rb ratio due to the immobility of these two elements. To examine these two assumptions, three last interglacial paleosols (S1) from Dingxi, Tianshui and Lantian, along a NW-SE transect across the Chinese Loess Plateau, were geo- chemically investigated. Our results show that the Rb concentration exhibits an increasing trend along the NW-SE transect both in the paleosol (S1) and the measured portions of the loess units (L1 and L2), being supportive to the assumption that Rb is enriched in the fine particles. But we also found that Rb loss did occur to some extent in the three profiles, contradicting to the presumption of Rb immobility during pedogenic processes. The Zr concentration exhibits an expected decreasing trend in the measured portions of the loess units and an unexpected increasing trend in the paleosol along the NW-SE transect. Moreover, the ratios of Zirconium to Hafnium (Zr/Hf) show different variation patterns between interglacial and glacial, implying that Zr-bearing minerals and their resident grain size fractions are probably not identical during interglacial and glacial. Thus, the assumption that Zr is enriched in coarse grain size fraction can no longer hold. We conclude that the final Zr/Rb value is not only dependent on grain size sorting processes but also on post-depositional alteration and source prove- nance. Under enhanced chemical weathering, especially when chemical index of alterat  相似文献   

7.
Utilized here is the Carte Synoptique solar filament archive, namely the catalogue of solar filaments from March 1919 to December 1989, corresponding to solar rotation numbers 876 to 1823 to study latitudinal migration of solar activity at high latitudes. Except the well-known poleward migration of solar activity from middle latitudes to the poles, an equatorward migration is found from the solar poles toward middle latitudes (about 40°) within a normal cycle, which is neglected before, and the time interval for the former migration (4.4 years) is about 2.2 years shorter than that for the latter (6.6 years), indicating that the change from one migration to the other takes place around the maximum time of a normal cycle. In the future, a dynamo model should represent the migration from the poles toward middle latitudes of the Sun, besides the migration in "butterfly diagrams" and the "rush to the poles". The traditional extended activity cycle is actually a part of the period of the successive migration from the poles toward the solar equator.  相似文献   

8.
Paleoecological records of soil δ^13Corg from three regions in the middle latitudes of the Northern Hemisphere, including the Chinese Loess Plateau (CLP), the Great Plains and adjacent areas of North America and northwestern Europe, showed different variations since the Last Glacial period. An attempt was made to evaluate the causes for the difference in δ^13Corg on the basis of the modern climatic data collected in these regions and of the modern C3 and C4 plant distributions. The analysis indicates that temperature, especially the growing season temperature, has a dominant control on the growth of C4 plants. When the mean annual or growing season temperatures are below the "threshold value", the growth of C4 plants is limited. When the temperature is above the "threshold value", C4 plants can grow under a wide range of precipitation. However, when the precipitation is high enough to favor the growth of trees, the proportions of C4 plants in local biomass will decline. The implicit control factor recovered by sedimentary records is consistent with the control factor on modern C3/C4 distribution. Pure C3 plants have been dominating the local biomass since the Last Glacial period in European loess region, mainly owing to the low local temperature. The increases in C4 plants from the late Pleistocene to the Holocene in the Chinese Loess Plateau, the Great Plains and adjacent areas, mainly reflect the influence of increasing temperature.  相似文献   

9.
10.
Silicon has been regarded as one of the most promising anode materials for Li-ion batteries. Its theoretical capacity (4 000 mAh/g) is much higher than that of the commercialized graphite (372 mAh/g). However, the cycle performance of silicon is poor due to the severe volume expansion and shrinkage during Li^+ insertion/extraction which results in pulverization of Si particles, eventually losing its Li^+ storage ability. To solve this problem, nanosized Si particles were utilized and achieved a partial improvement by reducing the absolute volume change. Nevertheless, a new problem was encountered with nanosized material that small Si particles were aggregated to be larger one during Li^+ insertion/extraction, and then pulverized again. In this work, we have succeeded to improve the cycle performance of nanosized Si particles by synthesis of carbon coated silicon nanopartiele.  相似文献   

11.
介绍了空时扩展(STS)发送分集的MCDS—CDMA(Multicarrier Direct Sequence-code Division Multiple Access)系统的整个发送接收过程,并建立了该过程的离散模型。同时将其与MCDS-CDMA系统的最大比合并(MRC)接收分集相比较。通过仿真比较了单发单收、MRC接收分集与STS发送分集的MCDS-CDMA系统的误码率(BER)性能。仿真结果表明,采用最大比合并接收分集的MCDS-CDMA系统的性能最好,采用STS发送分集的MCDS-CDMA系统性能次之,且随着多址干扰(MAI)的增加,两者的性能差距随之减小。发送分集的优势在于把接收端的复杂度移到发送端的同时提高了系统的性能。  相似文献   

12.
为了更好地评价阅读理解模型的鲁棒性, 基于Dureader数据集, 通过自动抽取和人工标注的方法, 对过敏感、过稳定和泛化3个问题分别构建测试数据集。还提出基于答案抽取和掩码位置预测的多任务学习方法。实验结果表明, 所提方法能显著地提高阅读理解模型的鲁棒性, 所构建的测试集能够对模型的鲁棒性进行有效评估。  相似文献   

13.
4个小麦品种的抗白粉病遗传分析   总被引:4,自引:0,他引:4  
抗病品种郑315、CP87-26-12和91138-16-2-13-12,与感病品种豫麦49号杂交的F1代表现抗病,F2代抗、感单株的分离比例为31,表明这3个品种均携带1对显性抗病基因.N97189-2和豫麦18号的杂交F1代对白粉病表现高感,F2代抗、感单株的分离比例为13,由此推断N97189-2对白粉病的抗性由1对隐性基因控制.  相似文献   

14.
目的 :探索在我国不同程度慢性阻塞性肺疾病 (COPD)患者中应用 MRC分级的可能性。方法 :对 34例不同程度 COPD患者同时进行肺功能检测分级 (FEV1 % Pred)和 MRC分级 ,采用等级分组资料秩和检验、等级相关检验和同一对象两种实验的 χ2检验检测 MRC分级的可能性。结果 :MRC分级有显著统计学意义 (P<0 .0 1) ,肺功能分级和 MRC分级明显相关 ,两种分级无统计学差异 ,且重度 COPD中两种分级法有较好的一致性。结论 :MRC分级简单、实用 ,在基层医院或不具备肺功能检测的地方可单独使用。  相似文献   

15.
通过细胞增殖实验、单细胞凝胶电泳实验、细胞凋亡实验和细胞周期阻滞实验分别测定了3种氯代乙酰胺(CAcAms)的细胞毒性和遗传毒性,同时结合饮用水中CAcAms的实际浓度水平,分析了3种CAcAms在饮用水中的毒性风险.结果表明,一氯乙酰胺(MCAcAm)在饮用水厂中的浓度低于二氯乙酰胺(DCAcAm)和三氯乙酰胺(TCAcAm),但由于MCAcAm的毒性较大,其在饮用水厂中的毒性风险高于DCAcAm和TCAcAm.相对于氯消毒,氯胺消毒后的饮用水中CAcAms的浓度较高,从而CAcAms造成的细胞毒性和遗传毒性风险也较高.  相似文献   

16.
Deg5,deg8 and the double mutant,deg5deg8 of Arabidopsis thaliana were used to study the physiological role of the DEG proteases in the repair cycle of photosystem II (PSII) under heat stress. PSII activity in deg mutants showed increased sensitivity to heat stress, and the extent of this effect was greater in the double mutant, deg5deg8, than in the single mutants, deg5 and deg8. Degradation of the D1 protein was slower in the mutants than in the WT plants. Furthermore, the levels of other PSII reaction center proteins tested remained relatively stable in the mutant and WT plants following high-temperature treatment. Thus, our results indicate that DEG5 and DEG8 may have synergistic function in degradation of D1 protein under heat stress.  相似文献   

17.
如何抑制多址干扰 ,同时降低实现复杂度 ,是研究MC- DS/ CDMA系统的关键之一。论文在已有的联合最小均方误差 (MMSE)检测器的基础上 ,提出了两种基于单载波的MMSE检测器结构 ,即 MMSE- MRC结构和 MMSE- MMSE结构 ,比较了几种接收机的性能。仿真表明 :MMSE- MRC和 MMSE- EGC的性能与传统的解扩— MRC结构相近 ,不能有效地抑制多址干扰。当载波数较小或较大时 ,MMSE-MMSE的性能接近联合 MMSE检测器 ,而计算量只有O(N3/ M2 +M3) ,远小于联合 MMSE检测器的计算量 ,有利于工程实现。  相似文献   

18.
按容积最小化的蓄热器第一种优化设计原则未能充分考虑工业锅炉房的运行优化,而按照工业锅炉房实际运行效率最高的蓄热器第二种优化设计原则有可能导致其容积过分增大。按蓄热器寿命期内锅炉房总费用最小的优化设计,兼顾减小蓄热器容积和保证工业锅炉房的高运行效率,是第三种优化设计原则。这里提出这3种原则的模型,给出了程序结构。按照编制的包含这3种模型的蓄热器优化设计综合计算机程序,进行实例计算比较,分析了3种优化设计方法的适用性。  相似文献   

19.
流程参数对丙烷预冷混合制冷剂循环损失的影响   总被引:1,自引:0,他引:1  
在丙烷预冷的混合制冷剂循环液化流程热力分析的基础上,对流程进行分析,并分析了流程中天然气压力、丙烷预冷后天然气的温度、制冷剂进入压缩机时的温度和压力及制冷剂压缩机排气压力对流程各设备损失的影响.分析表明,压缩机的损失占整个流程损失的一半.提高天然气的压力、混合制冷剂压缩机进气温度、混合制冷剂压缩机进排气压力,降低预冷后天然气温度,均可降低整个流程的损失.  相似文献   

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