997 resultados para Dipole function


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The simulating wave nearshore (SWAN) wave model has been widely used in coastal areas, lakes and estuaries. However, we found a poor agreement between modeling results and measurements in analyzing the chosen four typical cases when we used the default parameters of the source function formulas of the SWAN to make wave simulation for the Bohai Sea. Also, it was found that at the same wind process the simulated results of two wind generation expressions (Komen, Janssen) demonstrated a large difference. Further study showed that the proportionality coefficient alpha in linear growth term of wave growth source function plays an unperceived role in the process of wave development. Based on experiments and analysis, we thought that the coefficient alpha should change rather than be a constant. Therefore, the coefficient alpha changing with the variation of friction velocity U (*) was introduced into the linear growth term of wave growth source function. Four weather processes were adopted to validate the improvement in the linear growth term. The results from the improved coefficient alpha agree much better with the measurements than those from the default constant coefficient alpha. Furthermore, the large differences of results between Komen wind generation expression and Janssen wind generation expression were eliminated. We also experimented with the four weather processes to test the new white-capping mechanisms based on the cumulative steepness method. It was found that the parameters of the new white-capping mechanisms are not suitable for the Bohai Sea, but Alkyon's white-capping mechanisms can be applicable to the Bohai Sea after amendments, demonstrating that this improvement of parameter alpha can improve the simulated results of the Bohai Sea.

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A fine-grid model (1/6degrees) covering the South China Sea (SCS), East China Sea and Japan/East Sea, which is embedded into a coarse-grid (3degrees) global model, was established to study the SCS circulation. In the present paper, we report the model-produced monthly and annual mean transport stream functions and sea surface heights(SSH) and their anomalies of the SCS. Comparison to the TOPEX/Poseidon data shows that the model-produced monthly sea surface height anomalies (SSHA) are in good agreement with altimeter measurements. Based on the results, the circulation of the SCS, especially the upper layer circulation, is discussed. In the surface layer, the western Philippine Sea water intrudes into the SCS through the Luzon Strait in autumn, winter and spring, but not in summer. However, as far as the whole water column is concerned, the water intrudes into the SCS through the Luzon Strait all the year round. This indicates that in summer the water still intrudes into the SCS in the subsurface and intermediate layers. The area near the northern continental slope of the SCS is dominated by a cyclonic circulation all the year round. The SCS Southern Anticyclonic Gyre, SE Vietnam Off-Shore Current in summertime and SCS Southern Cyclonic Gyre in wintertime are reproduced reasonably. The difference between the monthly averaged SSH and SSHA is significant, indicating the importance of the mean SSH in the SCS circulation.

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Under an external alternating current (ac) field, the effective ac dielectric response of graded composites consisting of the graded cylindrical inclusion having complex permittivity profiles has been investigated theoretically. A model that the dielectric function is assumed to be a constant while the conductivity has a power-law dependence on the radial variable r, namely epsilon(i)(r) = A + cr(k)/i omega. is studied and the local analytical potentials of the inclusion and the host regions are derived in terms of hyper-geometric function. In the dilute limit, the effective ac dielectric response is predicted. Meanwhile, we have given the exact proof of the differential effective dipole approximation (DEDA) method, which is suitable to arbitrary graded profiles. Furthermore, we have given the analytical potentials and the effective ac dielectric responses of coated graded cylindrical composites for two cases, case (a) graded core and case (b) graded coated layer, having the graded dielectric profiles, respectively. (c) 2005 Elsevier B.V. All rights reserved.

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利用ERA40逐日再分析资料、NCEP/NCAR2逐日再分析资料、中国740个测站日降水资料、上海台风研究所提供的西太平洋热带气旋资料、Kaplan等重建的月平均SSTA资料、NOAA逐日长波辐射(OLR)等资料,应用离散功率谱分析、带通滤波、EOF分析等统计方法,研究了东亚夏季风(EASM)的移动特征、东亚地区季节内振荡(ISO)的基本特征、季节内振荡对东亚夏季风活动的影响、季节内振荡对东亚夏季风异常活动的影响机理。主要结论如下: (1)综合动力和热力因素定义了可动态描述东亚夏季风移动和强度的指数,并利用该指数研究了东亚夏季风的爆发和移动的季节内变化及其年际和年代际变化特征。研究发现,气候平均东亚夏季风前沿分别在28候、33候、36候、38候、40候、44候出现了明显的跳跃。东亚夏季风活动具有显著的年际变率,主要由于季风前沿在某些区域异常停滞和突然跨越北跳或南撤引起,造成中国东部旱涝灾害频繁发生。东亚夏季风的活动具有明显的年代际变化,在1965年、1980年、1994年发生了突变,造成中国东部降水由“南旱北涝”向“南涝北旱”的转变。 (2)东亚季风区季节内变化具有10~25d和30~60d两个波段的季节内振荡周期,以30-60d为主。存在三个主要低频模态,第一模态主要表征了EASM在长江中下游和华北地区活动期间的低频形势;第二模态印度洋-菲律宾由低频气旋式环流控制,主要表现了ISO在EASM爆发期间的低频形势;第三模态主要出现在EASM在华南和淮河活动期间的低频形势。第一模态和第三模态是代表东亚夏季风活动异常的主要低频形势。 (3)热带和副热带地区ISO总是沿垂直切变风的垂直方向传播。因此,在南海-菲律宾东北风垂直切变和副热带西太平洋北风垂直切变下,大气热源激发菲律宾附近交替出现的低频气旋和低频反气旋不断向西北传播,副热带西太平洋ISO以向西传播为主。中高纬度地区,乌拉尔山附近ISO以向东、向南移动或局地振荡为主;北太平洋中部ISO在某些情况下向南、向西传播。 (4)季风爆发期,伴随着热带东印度洋到菲律宾一系列低频气旋和低频反气旋, 冷空气向南输送,10~25天和30~60天季节内振荡低频气旋同时传入南海加快了南海夏季风的爆发。在气候态下,ISO活动表现的欧亚- 太平洋(EAP)以及太平洋-北美(PNA)低频波列分布特征(本文提出的EAP和PNA低频波列与传统意义上的二维定点相关得到的波列不同)。这种低频分布形式使得欧亚和太平洋中高纬度的槽、脊及太平洋副热带高压稳定、加强,东亚地区的低频波列则成为热带和中高纬度ISO相互作用影响东亚夏季风活动的纽带。不同的阶段表现不同的低频模态,30~60d低频模态的转变加快了EASM推进过程中跳跃性;30-60d低频模态的维持使得EASM前沿相对停滞。 (5)30-60d滤波场,菲律宾海域交替出现的低频气旋和低频反气旋不断向西北传播到南海-西太平洋一带。当南海-西太平洋地区低频气旋活跃时,季风槽加强、东伸,季风槽内热带气旋(TC)频数增加;当南海-西太平洋低频反气旋活跃时,季风槽减弱、西退,TC处于间歇期,生成位置不集中。 (6)在El Nino态下,大气季节内振荡偏弱,北传特征不明显,但ISO由中高纬度北太平洋中部向南和副热带西太平洋向西的传播特征显著,东亚地区ISO活动以第三模态为主,EASM集中停滞在华南和淮河流域,常伴随着持续性区域暴雨的出现,易造成华南和江淮流域洪涝灾害,长江和华北持续干旱。在La Nina态下,大气季节内振荡活跃,且具有明显的向北传播特征,PNA低频波列显著,东亚地区ISO活动以第一模态单峰为主;EASM主要停滞在长江中下游和华北地区,这些地区出现异常持续强降水,华南和淮河流域多干旱;在El Nino态向La Nina态转换期,ISO活动以第一模态双峰为主,长江中下游常常出现二度梅。

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Apostichopus japonicus is a common sea cucumber that undergoes seasonal inactivity phases and ceases feeding during the summer months. We used this sea cucumber species as a model in which to examine phenotypic plasticity of the digestive tract in response to food deprivation. We measured the body mass, gross gut morphology and digestive enzyme activities of A. japonicus before, during, and after the period of inactivity to examine the effects of food deprivation on the gut structure and function of this animal. Individuals were sampled semi-monthly from June to November (10 sampling intervals over 178 days) across temperature changes of more than 18 degrees C. On 5 September, which represented the peak of inactivity and lack of feeding, A. japonicus decreased its body mass, gut mass and gut length by 50%, 85%, and 70%, respectively, in comparison to values for these parameters preceding the inactive period. The activities of amylase, cellulase and lipase decreased by 77%, 98%, and 35% respectively, in comparison to mean values for these enzymes in June, whereas pepsin activity increased two-fold (luring the inactive phase. Alginase and trypsin activities were variable and did not change significantly across the 178-day experiment. With the exception of amylase and cellulase, all body size indices and digestive enzyme activities recovered and even surpassed the mean values preceding the inactive phase during the latter part of the experiment (October-November). Principal Component Analysis (PCA) utilizing the digestive enzyme activity and body size index data divided the physiological state of this cucumber into four phases: an active stage, prophase of inactivity peak inactivity, and a reversion phase. These phases are all consistent with previously suggested life stages for this species, but our data provide more defined characteristics of each phase. A. japonicus clearly exhibits phenotypic plasticity (or life-cycle staging) of the digestive tract during its annual inactive period. (C) 2008 Elsevier Inc. All rights reserved.

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A frequency domain electromagnetic (conductivity) method for near surface soundings at low frequencies is discussed in this thesis. Its elementary principle is to detect the conductivity of the earth by the secondary magnetic fields induced by a current dipole on the earth. According to the EM induction theory, a coil with alternating current on the earth will generate a magnetic field in whole space which is referred to as the primary field Hp. The primary field would induce secondary currents in the earth which go down to depth like a batch of smoking rings. These currents further produce secondary magnetic field Hs .The primary and secondary magnetic fields are collected together by a receiver coil. Generally speaking,the secondary magnetic field is a complicated function of coil spacing, transmitting frequency and earth conductivity. But at low induction numbers, the secondary field is deduced to as a simple function of frequency, spacing and conductivity. Especially the ratio of secondary to primary field shares a linear proportion to the apparent conductivity. The earth conductivity can be interpreted by proper inversions with the apparent conductivity. The method is discussed at three steps: (1)Derivation of primary and secondary magnetic fields arising from vertical and horizontal magnetic dipoles on the earth based on the basic EM induction theory. (2)Field techniques and equipment developed for the method. (3)An interpretation technique was introduced using a cumulative and relative response function. Finally a test example is presented for examining the effectiveness of the method.

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To study the transport mechanism of hydrophobic organic chemicals (HOCs) and the energy change in soil/solvent system, a soil leaching column chromatographic (SLCC) experiment at an environmental temperature range of 20-40 degreesC was carried out, which utilized a reference soil (SP 14696) packed column and a methanol-water (1:4 by volume ratio) eluent. The transport process quickens with the increase of column temperature. The ratio of retention factors at 30 and 40 degreesC (k'(30)/k'(40)) ranged from 1.08 to 1.36. The lower enthalpy change of the solute transfer in SLCC (from eluent to soil) than in conventional reversed-phase liquid chromatography (e.g., from eluent to C-18) is consistent with the hypothesis that HOCs were dominantly and physically partitioned between solvent and soil. The results were also verified by the linear solvation energy relationships analysis. The chief factor controlling the retention was found to be the solute solvophobic partition, and the second important factor was the solute hydrogen-bond basicity, while the least important factors were the solute polarizability-dipolarity and hydrogen-bond acidity. With the increase of temperature, the contributions of the solute solvophobic partition and hydrogen-bond basicity gradually decrease, and the latter decreases faster than the former. (C) 2002 Elsevier Science Ltd. All rights reserved.

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Nonlinear multivariate statistical techniques on fast computers offer the potential to capture more of the dynamics of the high dimensional, noisy systems underlying financial markets than traditional models, while making fewer restrictive assumptions. This thesis presents a collection of practical techniques to address important estimation and confidence issues for Radial Basis Function networks arising from such a data driven approach, including efficient methods for parameter estimation and pruning, a pointwise prediction error estimator, and a methodology for controlling the "data mining'' problem. Novel applications in the finance area are described, including customized, adaptive option pricing and stock price prediction.

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We have investigated the relationship between the molecular configuration and dipole moment of some fluorinated liquid crystals (LCs). The aeornetries of the molecules were preliminarily optimized at empirical AM1 and then were further optimized at B3LYP/6-31G(d) level. The dipole moment has been calculated. It is strongly influenced by the position and number of fluorine substituents in the benzene ring of the molecule. The polarizability, mean polarizabilities, and anisotropic polarizability of the phenylbicyclohexane (PBC) fluorine substituents are also given and discussed. (c) 2004 Wiley Periodicals, Inc.

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Polycystic Ovary Syndrome (PCOS) is a complex disorder encompassing reproductive and metabolic dysfunction. Ovarian hyperandrogenism is an endocrine hallmark of human PCOS. In animal models, PCOS-like abnormalities can be recreated by in utero over-exposure to androgenic steroid hormones. This thesis investigated pancreatic and adrenal development and function in a unique model of PCOS. Fetal sheep were directly exposed (day 62 and day 82 of gestation) to steroidal excesses - androgen excess (testosterone propionate - TP), estrogen excess (diethylstilbestrol - DES) or glucocorticoid excess (dexamethasone - DEX). At d90 gestation there was elevated expression of genes involved in β- cell development and function: PDX-1 (P<0.001), and INS (P<0.05), INSR (P<0.05) driven by androgenic excess only in the female fetal pancreas. β- cell numbers (P<0.001) and in vitro insulin secretion (P<0.05) were also elevated in androgen exposed female fetuses. There was a significant increase in insulin secreting β-cell numbers (P<0.001) and in vivo insulin secretion (glucose stimulated) (P<0.01) in adult female offspring, specifically associated with prenatal androgen excess. At d90 gestation, female fetal adrenal gene expression was perturbed by fetal estrogenic exposure. Male fetal adrenal gene expression was altered more dramatically by fetal glucocorticoid exposure. In female adult offspring from androgen exposed pregnancies there was increased adrenal steroidogenic gene expression and in vivo testosterone secretion (P<0.01). This highlights that the adrenal glands may contribute towards excess androgen secretion in PCOS, but such effects might be secondary to other metabolic alterations driven by prenatal androgen exposure, such as excess insulin secretion Thus there may be dialogue between the pancreas and adrenal gland, programmed during early life, with implications for adult health Given both hyperinsulinaemia and hyperandrogenism are common features in PCOS, we suggest that their origins may be at least partially due to altered fetal steroidal environments, specifically excess androgenic stimulation

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This chapter examines the role of the advanced nurse practitioner (ANP) within the domains of practice identified by the Royal College of Nursing (2002) as the teaching and coaching function. (Note that this is referred to by the NMC as the education function. It approaches the analysis against the backdrop of three policy documents: The Expert Patient: a new approach to chronic disease management for the 21st century(DoH 2001), Choosing Health: making healthy choices easier (DoH 2004), Our health, our care, our say (DoH 2006). It draws into the frame the experiences of ANP students as they work with patients, clients and carers, with the intention of enabling health and managing illness. It uses examples from a range of everyday practice setting to illustrate the inherent challenges of the teaching and coaching function of the ANP, at the same time as recognising its significance if patients, clients and carers are to be enabled to make choices that might optimize their well-being. Before this, however, some statistics are presented to focus thinking on why education is an invaluable component of advanced nursing practice.

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The aim of this study was to analyze the effects of short-term resistance training on the body composition profile and muscle function in a group of Anorexia Nervosa restricting type (AN-R) patients. The sample consisted of AN-R female adolescents (12.8 ± 0.6 years) allocated into the control and intervention groups (n¼18 each). Body composition and relative strength were assessed at baseline, after 8 weeks and 4 weeks following the intervention. Body mass index (BMI) increased throughout the study (p = 0.011). Significant skeletal muscle mass (SMM) gains were found in the intervention group (p = 0.045, d = 0.6) that correlated to the change in BMI (r = 0.51, p < 0.031). Meanwhile, fat mass (FM) gains were significant in the control group (p = 0.047, d = 0.6) and correlated (r > 0.60) with change in BMI in both the groups. Significant relative strength increases (p < 0.001) were found in the intervention group and were sustained over time.

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King, R. D. and Wise, P. H. and Clare, A. (2004) Confirmation of Data Mining Based Predictions of Protein Function. Bioinformatics 20(7), 1110-1118

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Clare, A. and King R.D. (2003) Predicting gene function in Saccharomyces cerevisiae. 2nd European Conference on Computational Biology (ECCB '03). (published as a journal supplement in Bioinformatics 19: ii42-ii49)