基于改进G-O模型的软件可靠性测试方法

为克服传统G-O(Goel-Okumoto)软件可靠性模型中缺陷发现率过于简化处理的局限性,提出了一种以更精准的方式描述缺陷发现率随时间实际变化的模型。改进模型不同于常规假设将其视为恒定或单调的函数,并考虑了测试人员的学习和排错能力的进步,以及软件固有的缺陷发现率随时间递减的趋势,从而假设缺陷发现率呈现先上升后下降的动态变化趋势。通过在两组公开的软件缺陷检测数据集上的应用,并与多种经典的模型进行了对比验证,验证了模型的有效性。实验结果表明,改进后的G-O模型在拟合能力和预测能力方面都显示出优异的性能,证明其在软件可靠性评估中的适用性和优越性。

A Process-based Model of N_2O Emission from a Rice-Winter Wheat Rotation Agro-Ecosystem:Structure,Validation and Sensitivity

In order to numerically simulate daily nitrous oxide （N2O） emission from a rice-winter wheat rotation cropping system, a process-based site model was developed （referred to as IAP-N-GAS） to track the movement and transformation of several forms of nitrogen in the agro-eeosystem, which is affected by climate, soil, crop growth and management practices. The simulation of daily N2O fluxes, along with key daily environmental variables, was validated with three-year observations conducted in East China. The validation demonstrated that the model simulated well daily solar radiation, soil temperature and moisture, and also captured the dynamics and magnitude of accumulated rice aboveground biomass and mineral nitrogen in the soil. The simulated daily N2O emissions over all three years investigated were generally in good agreement with field observations. Particularly well simulated were the peak N2O emissions induced by fertilizations, rainfall events or mid-season drainages. The model simulation also represented closely the inter-annuM variation in N2O emission. These validations imply that the model has the capability to capture the general characteristics of N2O emission from a typical rice-wheat rotation agro-ecosystem. Sensitivity analyses revealed that the simulated N2O emission is most sensitive to the fertilizer application rate and the soil organic matter content, but it is much less sensitive to variations in soil pH and texture, temperature, precipitation and crop residue incorporation rate under local conditions.

Collusion detector based on G-N algorithm for trust model

In the open network environment, malicious attacks to the trust model have become increasingly serious. Compared with single node attacks, collusion attacks do more harm to the trust model. To solve this problem, a collusion detector based on the GN algorithm for the trust evaluation model is proposed in the open Internet environment. By analyzing the behavioral characteristics of collusion groups, the concept of flatting is defined and the G-N community mining algorithm is used to divide suspicious communities. On this basis, a collusion community detector method is proposed based on the breaking strength of suspicious communities. Simulation results show that the model has high recognition accuracy in identifying collusion nodes, so as to effectively defend against malicious attacks of collusion nodes.

洗心汤对散发性老年性痴呆大鼠脑内tau蛋白O-GlcNAc糖基化修饰的影响

目的研究洗心汤(人参、半夏、茯神、附子、菖蒲)对散发性老年性痴呆模型大鼠脑组织tau蛋白O位N-乙酰葡萄糖胺(O-GlcNAc)糖基化修饰水平的影响。方法 SPF级健康雄性SD大鼠侧脑室注射链脲佐菌素(ICV-STZ),随机分为模型组、多奈哌齐对照组、洗心汤小、中、大剂量组并设假手术组作为对照。治疗结束及行为学测试之后,以免疫组化及蛋白印迹方法检测大鼠脑组织tau蛋白O-GlcNAc糖基化修饰水平。结果洗心汤能明显提高散发性老年性痴呆大鼠海马组织以琥珀酸化凝集素富集的O-GlcNAc糖基化蛋白质以及用RL2、CTD110.6检测的O-GlcNAc糖基化tau蛋白表达,组间差异有统计学意义(P<0.05,P<0.01)。多奈哌齐对照组与散发性老年性痴呆模型组相比则无显著性差异(P>0.05)。结论洗心汤能够明显提高散发性老年性痴呆大鼠海马组织tau蛋白O-GlcNAc糖基化修饰水平,从而可能起到抑制tau蛋白在重要位点的过度磷酸化及其tau毒性,防止散发性老年性痴呆病理进展的作用。

g-C_(3)N_(4)/Ag_(2)O复合光催化剂的制备及其近红外光催化性能

通过简易化学合成法制备了g-C_(3)N_(4)/Ag_(2)O_(p-n)异质结复合光催化剂,利用XRD、XPS、SEM、TEM、DRS等对所制复合材料的物相结构、微观形貌及光学性质进行表征,借助近红外光下催化降解罗丹明B(RhB)试验评价其光催化活性,重点探讨了g-C_(3)N_(4)/Ag_(2)O_(p-n)异质结复合材料的光催化降解机理。结果表明,当g-C_(3)N_(4)、Ag_(2)O质量比为1∶16时,所制g-C_(3)N_(4)/Ag_(2)O复合光催化剂具有最佳的近红外光催化性能且活性稳定;h+和·O-2活性自由基在近红外光催化降解过程中发挥了主要作用。

Poisson冲击下的k/n(G)系统的可靠性分析

本文研究了一类Poisson冲击下的k/n(G)系统(即k-out-of-n:G系统).假定冲击的到达数形成一个参数为λ的Poisson过程,且冲击的量服从某一分布.当每次冲击到达时,对系统中工作的部件独立地产生影响.进而假定每一部件以一定的概率故障,概率值是冲击量的函数.且各次冲击独立地对系统造成损失,直到工作部件数少于k系统故障为止.在这些假定下,我们获得了系统的可靠度函数和系统的平均工作时间.进一步,假定系统是可修的,系统中有一个维修工,并根据"先坏先修"的维修规则对故障部件进行维修.在维修时间服从指数分布的假设下,系统状态转移服从Markov过程.对该系统我们建立了状态转移方程,并求得了系统可用度、稳态下的平均工作时间、平均停工时间和系统失效频率等可靠性指标.最后,我们还给出了一个简单例子来演示讨论的模型.

改进的G-N迭代法在Logistic模型参数估计中的应用

研究了Logistic模型的参数估计,给出了两种迭代算法:G-N迭代法和改进的G-N迭代法,指出G-N迭代法虽然是应用较为广泛的计算方法,但得到的结果可能会不收敛,而改进的G-N迭代法可避免这一问题.通过实例验证了此法的有效性.

V_(2)O_(5)/g⁃C_(3)N_(4)催化剂的制备及其模拟油中硫化物的脱除

以三聚氰胺、偏钒酸铵、硼酸为前驱体,通过煅烧法制备V_(2)O_(5)/g⁃C_(3)N_(4)催化剂。采用XRD、FT⁃IR、XPS、SEM和BET等技术对催化剂的结构与形貌进行表征。以V_(2)O_(5)/g⁃C_(3)N_(4)为催化剂,乙腈为萃取剂,H_(2)O_(2)为氧化剂对模拟油中二苯并噻吩(DBT)的脱除进行考察。探究了反应温度、催化剂质量、萃取剂体积、n(H_(2)O_(2))/n(S)以及不同硫化物等因素对脱硫效果的影响。在模拟油体积为5.0 mL、萃取剂乙腈体积为3.0 mL、n(H_(2)O_(2))/n(S)=8、催化剂质量为0.02 g、反应温度为30℃和反应时间为60 min的最佳条件下,DBT的脱除率达到91.9%,经过5次催化剂再生后脱硫率仍可以达到85.7%。

Nitrous oxide emissions following seasonal freeze-thaw events from arable soils in Northeast China

Seasonal soil freeze-thaw events may enhance soil nitrogen transformation and thus stimulate nitrous oxide （N2O） emissions in cold regions. However, the mechanisms of soil N2O emission during the freeze-thaw cycling in the field remain unclear. We evaluated N2O emissions and soil biotic and abiotic factors in maize and paddy fields over 20 months in Northeast China, and the structural equation model （SEM） was used to determine which factors affected N2O production during non-growing season. Our results verified that the seasonal freeze-thaw cycles mitigated the available soil nitrogen and carbon limitation during spring thawing period, but simultaneously increased the gaseous N2O-N losses at the annual time scale under field condition. The N2O-N cumulative losses during the non-growing season amounted to 0.71 and 0.55 kg N ha 1 for the paddy and maize fields, respectively, and contributed to 66 and 18% of the annual total. The highest emission rates （199.2- 257.4 μg m-2 h-1） were observed during soil thawing for both fields, but we did not observe an emission peak during soil freezing in early winter. Although the pulses of N2O emission in spring were short-lived （18 d）, it resulted in approximately 80% of the non-growing season N2O-N loss. The N2O burst during the spring thawing was triggered by the combined impact of high soil moisture, flush available nitrogen and carbon, and rapid recovery of microbial biomass. SEM analysis indicated that the soil moisture, available substrates including NH4＋ and dissolved organic carbon （DOC）, and microbial biomass nitrogen （MBN） explained 32, 36, 16 and 51% of the N2O flux variation, respectively, during the non-growing season. Our results suggested that N2O emission during the spring thawing make a vital contribution of the annual nitrogen budget, and the vast seasonally frozen and snow-covered croplands will have high potential to exert a positive feedback on climate change considering the sensitive response of nitrogen biogeochemical cycling to the freeze-thaw disturbance.

Numerical Experiments on the Impact of Spring North Pacific SSTA on NPO and Unusually Cool Summers in Northeast China

A set of numerical experiments designed to analyze the oceanic forcing in spring show that the combined forcing of cold （warm） El Ni（n）o （La Ni（n）a） phases in the Ni（n）o4 region and sea surface temperature anomalies （SSTA） in the westerly drifts region would result in abnormally enhanced NorthEast Cold Vortex （NECV） activities in early summer.In spring,the central equatorial Pacific El Ni（n）o phase and westerly drift SSTA forcing would lead to the retreat of non-adiabatic waves,inducing elliptic low-frequency anomalies of tropical air flows.This would enhance the anomalous cyclone-anticyclonecyclone-anticyclone low-frequency wave train that propagates from the tropics to the extratropics and further to the mid-high latitudes,constituting a major physical mechanism that contributes to the early summer circulation anomalies in the subtropics and in the North Pacific mid-high latitudes.The central equatorial Pacific La Ni（n）a forcing in the spring would,on the one hand,induce teleconnection anomalies of high pressure from the Sea of Okhotsk to the Sea of Japan in early summer,and on the other hand indirectly trigger a positive low-frequency East Asia-Pacific teleconnection （EAP） wave train in the lower troposphere.

Fast electron transfer and enhanced visible light photocatalytic activity by using poly-o-phenylenediamine modified AgCl/g-C_3N_4 nanosheets

Exfoliation of bulk graphitic carbon nitride(g‐C3N4)into two‐dimensional(2D)nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g‐C3N4 nanosheets(CN)have larger specific surface areas and more reaction sites.In addition,poly‐o‐phenylenediamine(PoPD)can improve the electrical conductivity and photocatalytic activity of semiconductor materials.Here,the novel efficient composite PoPD/AgCl/g‐C3N4 nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach.The obtained photocatalysts have larger specific surface areas and could achieve better visible‐light response.However,silver chloride(AgCl)is susceptible to agglomeration and photocorrosion.The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density,which is three times that of CN.Obviously enhanced photocatalytic activities of PoPD/AgCl/g‐C3N4 are revealed through the photodegradation of tetracycline.The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly.Furthermore,.O2^-and h+are the main active species,which are confirmed through a trapping experiment and ESR spin‐trap technique.Therefore,the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst,in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles.This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues.

Monte Carlo study of the universal area distribution of clusters in the honeycomb O(n) loop model

We investigate the area distribution of clusters （loops） in the honeycomb O（n） loop model by means of the worm algorithm with n = 0.5, 1, 1.5, and 2. At the critical point, the number of clusters, whose enclosed area is greater than A, is proportional to A-1 with a proportionality constant C. We confirm numerically that C is universal, and its value agrees well with the predictions based on the Coulomb gas method.

Enhanced Fenton,photo-Fenton and peroxidase-like activity and stability over Fe_3O_4/g-C_3N_4 nanocomposites

We prepared the Fe3O4/g‐C3N4nanoparticles(NPs)through a simple electrostatic self‐assembly method with a3:97weight ratio to investigate their Fenton,photo‐Fenton and oxidative functionalities besides photocatalytic functionality.We observed an improvement of the Fenton and photo‐Fenton activities of the Fe3O4/g‐C3N4nanocomposites.This improvement was attributed to efficient charge transfer between Fe3O4and g‐C3N4at the heterojunctions,inhibition of electron‐hole recombination,a high surface area,and stabilization of Fe3O4against leaching by the hydrophobic g‐C3N4.The obtained NPs showed a higher degradation potential for rhodamine B(RhB)dye than those of Fe3O4and g‐C3N4.As compared to photocatalysis,the efficiency of RhB degradation in the Fenton and photo‐Fenton reactions was increased by20%and90%,respectively.Additionally,the horseradish peroxidase(HRP)activity of the prepared nanomaterials was studied with3,3,5,5‐tetramethylbenzidinedihydrochloride(TMB)as a substrate.Dopamine oxidation was also examined.Results indicate that Fe3O4/g‐C3N4nanocomposites offers more efficient degradation of RhB dye in a photo‐Fenton system compared with regular photocatalytic degradation,which requires a long time.Our study also confirmed that Fe3O4/g‐C3N4nanocomposites can be used as a potential material for mimicking HRP owing to its high affinity for TMB.These findings suggest good potential for applications in biosensing and as a catalyst in oxidation reactions.

TACE联合索拉菲尼治疗晚期肝癌患者的疗效及对血清VEGF、CTGF、HIF-1α及OPN水平的影响

目的 探讨经肝动脉灌注化疗栓塞术（transcatheter arterial chemoembolization,TACE）联合索拉菲尼对晚期肝癌（hepatocellular carcinoma,HCC）患者的临床疗效及对血清血管内皮生长因子（vascular endothelial growth factor,VEGF）、结缔组织生长因子（connective tissue growth factor,CTGF）、缺氧诱导因子1α（hypoxia inducible factor 1α,HIF-1α）及骨桥蛋白（osteopontin,OPN）水平的影响。方法 选取2013年9月~2014年12月台州市肿瘤医院收治的HCC患者113例,按照随机数字法分为对照组（n=56）和试验组（n=57）,对照组采用TACE治疗,试验组采用TACE联合索拉菲尼治疗。分别于术前及术后1、3、7 d采用间接酶联免疫吸附测定法检测并比较2组患者血清VEGF、CTGF、HIF-1α及OPN水平,并进行Spearman相关性分析;统计2组远期临床疗效及不良反应发生情况。结果 术后1 d 2组患者血清VEGF、CTGF、HIF-1α及OPN水平较术前显著升高（P〈0.01）;术后1 d至7 d 2组患者血清各因子水平均呈下降趋势（P〈0.05）,且2组间差异有统计学意义（P〈0.05）;HIF-1α水平与VEGF、CTGF及OPN水平均呈显著正相关（r=0.951,r=0.954,r=0.929,P〈0.05）;试验组中位生存时间及1年生存率较对照组显著增加（P〈0.01）;试验组手足反应、脱发及腹泻发生率显著高于对照组（P〈0.05）,2组间其他各项不良反应发生率差异无统计学意义。结论 TCAE联合索拉菲尼较单独TACE可显著降低HCC患者VEGF、CTGF、HIF-1α、OPN水平,延长患者生存期,且不增加不良反应。

压强影响2NO2（g）N2O4（g）平衡的实验设计

为让学生能直观地体验新的化学平衡建立的标志和时间节点,运用DIS数字传感器,对“压强影响2NO2（g）=N2O4（g）平衡的实验”进行了探究.介绍了实验设计思路、实验内容和实验数据,并对实验结果进行了讨论.该实验教学旨在提升学生运用现代化实验手段分析问题、解决问题的意识和能力.

Damage and fracture mechanism of 6063 aluminum alloy under three kinds of stress states

To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value（equivalent plastic fracture strain）,the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.

DFT Study on Two C_4N_(12)O_4 Isomers with Pagodane- and Isopagodane-like Structures

Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.

Simulation of Capacitively Coupled Dual-Frequency N_2,O_2,N_2/O_2 Discharges:Effects of External Parameters on Plasma Characteristics

A one-dimensional fluid model is adopted to simulate the characteristics of N2, O2, and N2/O2 dual-frequency （DF） capacitively coupled plasmas （CCPs） under typical conditions in PECVD technologies. Not only the ground, the excited states but also the vibration levels of the main species are considered. The study focuses on the influence of external parameters such as matching of the high-frequency （HF） and low-frequency （LF）, HF and LF of the voltage sources, as well as discharge pressures, on physical characteristics of discharges. The results show that the decoupling of the two sources is possible by increasing the applied HF, the electron density and ion flux are determined only by the HF of the voltage source, whereas the LF has a little influence on the plasma characteristics. In addition, the matching of frequency affects the characteristics of discharges to some extent. Fhrthermore, the pressure is a main external parameter affecting the characteristics of discharges, and a small amount of oxygen in N2 plasma can efficiently increase N＋ ion flux incident onto the electrode and the density of N atom.

Phase Transitions of a Dilute O（n） Model

We investigate tricritical behavior of the O(n) model in two dimensions by means of transfer-matrix and finite-size scaling methods. For this purpose we consider an O(n) symmetric spin model on the honeycomb lattice with vacancies; the tricritical behavior is associated with the percolation threshold of the vacancies. The vacancies are represented by face variables on the elementary hexagons of thelattice. We apply a mapping of the spin degrees of freedom model on a non-intersecting-loop model, in which the number n of spin components assumes the role of a continuously variable parameter. This loop model serves as a suitable basis for the construction of the transfer matrix.Our results reveal the existence of a tricritical line, parametrized by n, which connects the known universality classes of the tricritical Ising model and the theta point describing the collapse of a polymer. On the other side of theIsing point,the tricritical line extends to the n = 2 point describing a tricritical O(2) model.

Middle-High Latitude N_2O Distributions Related to the Arctic Vortex Breakup

The relationship of N2O distributions with the Arctic vortex breakup is first analyzed with a probability distribution function （PDF） analysis. The N2O concentration shows different distributions between the early and late vortex breakup years. In the early breakup years, the N2O concentration shows low values and large dispersions after the vortex breakup, which is related to the inhomogeneity in the vertical advection in the middle and high latitude lower stratosphere. The horizontal diffusion coefficient （Kyy） shows a larger value accordingly. In the late breakup years, the N2O concentration shows high values and more uniform distributions than in the early years after the vortex breakup, with a smaller vertical advection and Kyy after the vortex breakup. It is found that the N2O distributions are largely affected by the Arctic vortex breakup time but the dynamically defined vortex breakup time is not the only factor.