一起戊型肝炎暴发的血清流行病学调查

目的 了解一起戊型肝炎暴发的血清学特点。方法 对某单位在10 d内先后发病的5例急性黄疸性肝炎患者、在该单位食堂就餐的1 675人(暴发人群)及未就餐的邻近单位883人(对照人群)的血清在首发病例26 d后进行抗-HEV IgM和IgG检测,数据进行统计学分析。结果5例患者抗-HEV IgM和IgG均为阳性。暴发人群抗-HEV IgM和IgG的阳性率分别为8.7％和38.4％,而对照人群仅分别为0.1％和28.6％,差别均有非常显著意义。暴发人群145例抗-HEV IgM(+)中,ALT增高32例,明显高于IgM(-)及对照;而抗-HEV IgM(-)的ALT增高比例并不高于对照人群。4例患者系列血清检测见抗-HEV IgM逐渐下降,感染后4个月多数转阴,而IgG在感染后第2-3个月达高峰,随后缓慢下降。暴发人群中抗-HEV IgM(+)的IgG平均水平最高,IgM(-)而IgG(+)的IgC平均水平亦明显高于对照,提示暴发人群中既往感染者受到了免疫加强。暴发人群中抗-HEV IgM(+)者在性别及年龄组间差异无显著意义,但其中ALT增高男性的比例显著高于女性,而与年龄无关。结论 本次急性黄疸性肝炎的暴发由戊型肝炎病毒引起,与食源有关;抗-HEV IgM和IgG不仅可用于临床病例诊断,也可用于人群调查;感染危险性与年龄及性别无关,但男性ALT增高更常见

IASB和FASB之间的准则协调及其对我国准则制定的启示——以权益基础薪酬准则为例

虽然IASB和FASB已经加强了在准则制定方面的协调和合作 ,但两个准则制定机构在最近颁布的有关权益基础薪酬会计处理规定上仍存在一定差异。本文分析了出台权益基础薪酬规定的背景 ,并简要总结了两者之间的差异 ;以此为基础 ,探讨IASB和FASB就准则差异所做的处理 ,及其展开的协调。最后就IASB和FASB的协调方式 ,对我国的准则国际协调提出了几点启示

Study on the Anti-multipath Performance of Turbo Code over Shallow Water Acoustic Channels

针对复杂多变、强多途和大起伏的浅海水声信道,本文建立了包括时变衰落、多途和加性干扰在内的信道仿真模型及Turbo码编/译码结构.通过计算机仿真,研究了浅海水声信道中的Turbo码性能及Turbo码性能随多途效应、衰落率和信道交织器等的变化.结果表明:在水声通信可接受的信噪比范围内(10~20 dB),Turbo码具有良好的性能(误比特率小于10-4);浅海水声信道中,Turbo码性能随多途路径数的增加而下降;Turbo码性能随衰落率的减小而略有下降;浅海水声信道中,信道交织器可改善Turbo码性能,并弥补由于衰落率不同而造成的性能差异.Shallow water acoustic channels introduce long multipath spreads and rapid time variations that deteriorate the performance of digital communication systems.These characteristics of the channel limit the data rate of reliable communication systems and require sophisticated equalization and coding technique.In this paper,a channel model including time-varying fading,multipath and additive noise for the shallow water acoustic channels is built,and one of the turbo coder/decoder is introduced.Based on the channel model,the performance of the turbo code over shallow water acoustic channel is simulated,and the effects of multipath,fading velocity and channel interleaver on the decoding performance are studied.As the result,the following four conclusions can be given safely:SNR(signal noise rate) at the range of number accepted by underwater acoustic communication(10~20 dB),the performance of turbo code is excellent(Bit error rate less than);The performance of turbo code degrades with the increasing of the number of multipath;under the condition of 8 dB of SNR,the performance of turbo code degrades 20 dB or so with three multipath comparing with one path;The performance of turbo code degrades slowly with the decreasing of the fading velocity;Channel interleaver can improve the performance of turbo code,and make up its difference because of different fading velocity.国家自然科学基金(40476018)资

成年后找回“玩”的能力

风和日丽的午后，海边有三个小男孩在学着螃蟹的样子走路。他们边走边看着另外两个伙伴，咯咯地笑个不停。沙滩上留下了一排排小脚印。一个浪头涌上来，脚印没了。大一点的男孩说了一声&ldquo;冲啊&rdquo;，另外两个就一起跟着向海水里跑去。他们使劲踩着海水，溅起了一束柬浪花。也不知是谁踩起的浪花打在了自己的脸上，</p

Excitation and propagation of axisymmetric longitudinal guided waves in pipes immersed in infinite liquid media

利用声-结构耦合有限元法,分别对轴对称分布径的向及轴向外力作用在无限液体介质内未充液及充液管道内壁所激发导波进行了模拟,并进一步利用短时傅里叶变换技术对瞬态波形作时频分析,在此基础上,结合色散及衰减曲线,探讨了外力分布特征对导波激发的影响。研究表明,无限液体介质内未充液管中l(0,2)模式及充液管中l(0,3)~l(0,4)模式皆具有高群速度、弱色散且弱衰减频带,适宜用于缺陷探测,而通过控制轴对称分布外力的频率,并令其沿轴向作用于管内壁或外壁,可实现上述导波模式的高效激发。The transient elastodynamic responses of the vacuum and liquid-filled pipes surrounded by infinite liquid to axisymmetric external forces are simulated by the acoustic-structural coupled finite element method.The time-frequency distributions of the transients waveforms are obtained by the short-time Fourier transform(STFT).The influence of the distribution of the external forces on the excitation of the guided waves is analyzed based on the above results and dispersion and attenuation curves.The study shows that the L(0,2) mode in the vacuum pipe surrounded by the liquid is suitable to be employed for the pipe inspection because it is the fastest mode in a weakly dispersive and attenuative region of frequency.And it can be excited high efficiently in the above region of frequency if the axisymmetric external force is applied on the inner or outer surface of the pipe axially.Analogously,the L(0,3) and L(0,4) modes in the liquid-filled pipe surrounded by the liquid are suitable for the pipe inspection.国家自然科学基金(10704064;40776022);福建省自然科学基金(D0810027)资助项

Theoretical and numerical investigations of the acoustic field excited by submarine explosion

对固体基底浅海中声波传播的色散特性作了数值模拟与分析.利用液体及固体中声传播理论导出了固体基底内爆破源在浅海中所激发声场的解析解,在此基础上,通过数值计算,得出了浅海中不同空间点处的瞬态声压时域波形,并在瞬态声压时域波形的平滑伪Wigner-Ville分布基础上,对固体基底内爆破源在浅海中所激发瞬态声场的特性作了详细分析.This paper simulates and analyzes numerically the dispersion characteristics of the waves propagating in the shallow-ocean overlying a semi-infinite elastic solid. The analytical solution of the acoustic field in the shallow-ocean,excited by an explosive point source in the solid bottom,is derived by using the theories for sound propagation in liquid and solid. The time-domain waveforms of transient acoustic field are simulated with the above analytical solution. The dispersion characteristics of the transient acoustic field are analyzed by using the smoothed pseudo Wigner-Ville distribution.福建省自然科学基金(批准号:T0750014);; 中国科学院“声场声信息国家重点实验室”开放基金(2006)资助的课题~

The Study of Gibbs Sampling Algorithm for Three-parameter Normal Ogive Model

项目反应理论作为一种现代的教育和心理测量方法,凭借其强大的优势和先进性,在实际测量中应用越来越广泛.能否有效地估计模型中的参数是项目反应模型得以应用的前提.本文基于数据扩充技术给出了一种适用于三参数正态双卵模型的gIbbS抽样算法,有效的实现三参数正态双卵模型的贝叶斯分析.最后,通过计算机模拟研究和实例分析对该算法的有效性进行了验证.Item response theory as a kind of modern educational and psychological measurement method,with its strong advantage and progressiveness,is applied more and more widely in the actual measurement.Whether it can effectively estimate the parameters in the model is the premise of item response model application.In this paper,we propose the Gibbs sampling algorithm for three-parameter normal ogive based on the data expansion technique to effectively realize Bayesian analysis of three-parameter normal ogive model.Finally,the effectiveness of this algorithm is verified by computer simulation study.中央高校基本科研业务费专项资金(12SSXM006)和(10SSXT150)资