A Simple Prediction Formula of Roll Damping of Conventional Cargo Ships on the Basis of Ikeda＇s Method and Its Limitation

Since the roll damping of ships has significant effects of viscosity, it is difficult to calculate it theoretically. Therefore, experimental results or some prediction methods are used to get the roll damping in design stage of ships. Among some prediction methods, Ikeda＇s one is widely used in many ship motion computer programs. Using the method, the roll damping of various ship hulls with various bilge keels can be calculated to investigate its characteristics. To calculate the roll damping of each ship, detailed data of the ship are needed to input. Therefore, a simpler prediction method is expected in primary design stage. Such a simple method must be useful to validate the results obtained by a computer code to predict it on the basis of Ikeda＇s method, too. On the basis of the predicted roll damping by Ikeda＇s method for various ships, a very simple prediction formula of the roll damping of ships is deduced in the present paper. Ship hull forms are systematically changed by changing length, beam, draft, mid-ship sectional coefficient and prismatic coefficient. It is found, however, that this simple formula can not be used for ships that have high position of the center of gravity. A modified method to improve accuracy for such ships is proposed.

On-treatment predictions of success in peg-interferon/ribavirin treatment using a novel formula

AIM:To predict treatment success using only simple clinical data from peg-interferon plus ribavirin therapy for chronic hepatitis C. METHODS:We analyzed the clinical data of 176 patients with chronic hepatitis and hepatitis C virus genotype 1 who received 48 wk standard therapy, derived a predictive formula to assess a sustained virological response of the individual patient using a logistic regression model and confirmed the validity of this formula.The formula was constructed using data from the first 100 patients enrolled and validated using data from the remaining 76 patients. RESULTS:Sustained virological response was obtained in 83(47.2%)of the patients and we derived formulae to predict sustained virological response at pretreatment and weeks 4,12 and 24.The likelihood of sustained virological response could be predicted effectively bythe formulae at weeks 4,12 and 24(the area under the curve of the receiver operating characteristic:0.821, 0.802,and 0.891,respectively),but not at baseline (0.570).The formula at week 48 was also constructed and validation by test data achieved good prediction with 0.871 of the area under the curve of the receiver operating characteristic.Prediction by this formula was always superior to that by viral kinetics. CONCLUSION:These results suggested that our formula combined with viral kinetics provides a clear direction of therapy for each patient and enables the best tailored treatment.

The Diagnostic Value of H Formula to Predict Mortality in Hospitalized Patients with Infectious Diseases

The ability to identify patients with risk of mortality in the initial stages allows us to introduce a more aggressive treatment in order to improve patients’ survival. In this study, we used systemic inflammatory response syndrome (SIRS) criteria, respiratory and heart rate per minute, and consciousness level [(Glasgow coma scale (GCS)] to develop a formula to predict death in patients admitted to the Infectious Diseases ward of Imam Reza hospital. Methods: This descriptive study was a cross sectional study done in the Infectious Diseases ward of Imam Reza hospital, Mashhad University of Medical Sciences, Iran. Alive and dead patients between the dates September 1, 2006 to September 1, 2007 were studied. In this study, data such as past medical history, prescribed drugs and their administration by nursing and medical staff was extracted from patients’ files. Also, the time of death, the first vital signs recorded in the hospital and the formula H = (PR + RR) - GCS (respiratory rate per minute plus heart rate per minute minus Glasgow coma scale (GCS)) was calculated for both alive and dead patients. Data was analyzed by SPSS software. Mann-Whitney test, Roc Curve, and logistic regression model were used for data analysis. Results: The total number of admitted patients was 1007 of whom 90 (10.82%) died. One patient was excluded from the study. Out of 90 dead patients, 51 (56.6%) were male and 39 (43.3%) were female. There was no significant difference between the two groups regarding the gender (P > 0.05). The mean age of the study group (deceased) was 59 ± 21 and the mean age of the control group (alive) was 58 ± 21. The Mann-Whitney test showed that the result of H Formula was significantly different between the two groups, (126 ± 26 for the study group and 111 ± 22 for the control group). The cutoff for H Formula was equal to 112.5. Negative and positive predictive values, specificity and sensitivity were 0.85, 0.35, 0.57, and 0.70 respectively. Logistic regression results show that the H index contents independently affected the mortality of infected patients. Conclusion: With regard to the importance of measuring vital signs in diagnosis and determining the mortality in patients with infectious disease, the H (Heydari) formula can be valuable for evaluation and determination of mortality risk and consequently, early intervention. Patients with severe tachycardia, severe tachypnea and altered mental status that cannot be properly and quickly improved within 2 hours after admission via hydration and other measures are at higher risk of mortality.

Prediction Method of Seismic Residual Deformation of Caisson Quay Wall in Liquefied Foundation

The multi-spring shear mechanism plastic model in this paper is defined in strain space to simulate pore pressure generation and development in sands under cyclic loading and undrained conditions, and the rotation of principal stresses can also be simulated by the model with cyclic behavior of anisotropic consolidated sands. Seismic residual deformations of typical caisson quay walls under different engineering situations are analyzed in detail by the plastic model, and then an index of liquefaction extent is applied to describe the regularity of seismic residual deformation of caisson quay wall top under different engineering situations. Some correlated prediction formulas are derived from the results of regression analysis between seismic residual deformation of quay wall top and extent of liquefaction in the relative safety backfill sand site. Finally, the rationality and the reliability of the prediction methods are validated by test results of a 120 g-centrifuge shaking table, and the comparisons show that some reliable seismic residual deformation of caisson quay can be predicted by appropriate prediction formulas and appropriate index of liquefaction extent.

Prediction of Symmetrical and Asymmetrical of Diurnal Global Solar Irradiance Distribution—New Approach

A simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis. It is expressed in terms of the length of the local day time td which is well defined in literatures on meteorological basis. The introduced distribution is also a function of the maximum value of the daily received irradiance qmax. which in turn is expressed in term of the solar constant. This renders the trial to be a closed system. Thus the obtained distribution is not a semi empirical one. Both cases of symmetrical and asymmetrical distributions for q(t) are considered. For its simplicity it can be easily integrated along the length of the day to get the daily totals of solar energy received by unit horizontal area. This is important for practical applications. Comparison between computed according to the present model and published experimental meteorological data in Barcelona (Spain), Hong Kong (China), Jeddah and Makkah (Saudi Arabia) is given as illustrative examples. Better fitting relative to the published trials for the same locations are obtained. The introduced model itself gives good fitting for the intermediate intervals points of the local day time which is the more effective region. The estimated relative error is 12% for Hong Kong, and it is 7% for Barcelona, Jeddah and Makah.

肾移植患者霉酚酸暴露量预测公式比较

目的比较目前已报道的12个基于有限采样策略的霉酚酸暴露量预测公式在我院肾移植患者霉酚酸暴露量中的预测效果。方法入组20例口服吗替麦考酚酯分散片的肾移植患者,采集不同时间的全血样本,使用二维液相色谱测定霉酚酸血药浓度。采用WinNonlin软件计算霉酚酸的药代动力学参数。运用12个预测公式预测霉酚酸AUC0~12h,计算预测值与实测值的相关系数(R2)值、预测AUC0~12h平均相对预测误差和理想预测AUC0~12h占比。结果公式8的预测AUC0~12h与MPA-AUC0~12h相关性较好,R2=0.923,平均预测误差绝对值最小(约为12.00),预测AUC0~12h在理想预测范围内的占比最高(80%)。结论预测公式8在估算我院肾移植患者霉酚酸暴露量中有良好的预测效果。

聚脲涂覆大型钢制储罐抗冲击性能数值仿真

为提高大型钢制储罐抗冲击性能,开展聚脲涂覆大型钢制储罐冲击响应的数值模拟和理论分析研究。基于前期工作已验证的数值模型,建立聚脲涂覆钢罐的有限元模型。数值模拟结果表明:将聚脲涂覆于罐体外表面能有效降低冲击载荷作用下局部塑性变形,在冲击体撞击角度为45°时能避免罐体穿孔破坏;聚脲涂层的主要防护机制为降速和垫层作用;提高喷聚脲涂厚度能增加罐体最大吸能值和面密度吸能值;当涂层厚度为15 mm时罐体不产生穿透破坏,满足英国储罐设计规范要求。根据罐体冲击响应特征和聚脲涂层作用机制,建立预测罐体断裂临界冲击速度的理论公式,能较精确预测涂覆罐的最大吸能值,可为聚脲涂覆钢制储罐抗冲击防护设计提供科学参考依据。

钦江河口盐水入侵距离预测模型研究

平陆运河工程是中国“西部陆海新通道”的重要水运基础设施,青年枢纽作为运河最下游的节点性控制枢纽,受钦江感潮河段的盐水上溯的影响,合理预测盐水入侵距离对认识青年船闸寿命与城市饮用水安全具有重要意义。利用钦江河口盐水上溯过程的实测数据,基于盐水上溯一维扩散稳态方程构建了考虑河口几何形状、潮汐作用及径流过程的高潮期盐水入侵长度预测模型,并通过径流与潮汐作用对钦江河口盐水入侵长度的影响分析,取得的主要结论为:当径流流量Q<100 m^(3)/s时,平陆运河工程后的高潮位期钦江河口盐水入侵长度L=10~27 km,较工程前增加了4.5 km;当径流流量Q<20 m^(3)/s时,钦江河口盐水将上溯至青年船闸闸下;枯水期,当河口潮差H 0>2.5 m时,青年枢纽减盐的最低泄流量须达到20 m^(3)/s。

Formation permeability evaluation and productivity prediction based on mobility from pressure measurement while drilling

Based on the measurement mechanism of mobility in pressure measurement while drilling, through analyzing a large number of mobility data, it is found that under the condition of water-based mud drilling, the product of mobility from pressure measurement while drilling and the viscosity of mud filtrate is infinitely close to the water phase permeability under the residual oil in relative permeability experiment. Based on this, a method converting the mobility from pressure measurement while drilling to core permeability is proposed, and the permeability based on Timur formula has been established. Application of this method in Penglai 19-9 oilfield of Bohai Sea shows:(1) Compared with the permeability calculated by the model of adjacent oilfields, the permeability calculated by this model is more consistent with the permeability calculated by core analysis.(2) Based on the new model, the correlation between the calculated mobility of well logging and the actual drilling specific productivity index bas been established. Compared with the relationship established by using the permeability model of an adjacent oilfield, the correlation of the new model is better.(3) Productivity of four directional wells was predicted, and the prediction results are in good agreement with the actual production after drilling.

基于运营数据的发动机压气机叶片裂纹扩展规律研究

为研究航空发动机实际服役中转子叶片在复杂载荷作用下的裂纹损伤扩展规律,基于航空发动机运营数据构建叶片的裂纹扩展寿命曲线,同时采用断裂力学理论建立裂纹扩展速率公式。以高压压气机叶片为实例,通过流固耦合方法构建压气机叶片结构的载荷模型,分别采用Paris、Walker、Newman裂纹扩展速率公式对压气机叶尖区域进行三维裂纹扩展分析。仿真结果表明,三种裂纹扩展速率公式在裂纹扩展前期预测结果与发动机运营数据裂纹扩展曲线具有一致性,可较好地描述叶片裂纹扩展规律;在裂纹稳定扩展阶段,Walker和Newman公式预测结果相对危险,Paris公式预测结果吻合度较高,并且能与厂家技术手册中关于其损伤发展控制要求相互印证。

非对称循环载荷下铝基复合材料的疲劳寿命预测

铝基复合材料由不同力学性能和疲劳行为的多种材料组成。在非对称循环载荷下,各组分间的相互作用和影响使其疲劳寿命预测变得复杂。为解决这一问题,研究一种非对称循环载荷下铝基复合材料疲劳寿命预测方法。用Na_(3)Al F_(6)和Ti O_(2)粉末强化铝合金基体,制备出复合材料样品。设计非对称循环载荷加载条件。用Walker裂纹扩展式结合Chaboche模型进行铝基复合材料疲劳寿命预测,Chaboche模型能较好地描述材料在循环加载下的非线性行为;通过引入应力比参数,Walker公式可更准确地预测裂纹在不同应力水平下的扩展行为。将两者结合能更全面地考虑材料在疲劳过程中的各种因素,从而提高疲劳寿命预测的准确性。结果表明:随着应力幅值的增加,试件裂缝长度随之上升,同时随着循环圈数的增加,试件应力随之上升,这使得铝基复合材料疲劳寿命下降,且该方法的预测结果与实测值更接近,说明预测结果可靠。

基于遗传算法的磨削力模型系数优化及验证

在磨削力模型求解问题中,目前大多使用分段计算法或列方程组直接计算各个待求系数,不仅计算量大且其精度也无法保证。另外,传统的回归模型容易陷入局部最优,难以描述非线性关系。为此,将遗传算法引入到非线性优化函数参数优化中,基于外圆横向磨削力模型、平面磨削力模型、外圆纵向磨削力模型等现有的模型数据,开展磨削力理论模型的系数优化方法研究。相关性分析结果表明:通过计算得到的3种模型磨削力的预测精度提高了14.69%~42.54%,且3种模型所预测的法向磨削力的平均误差分别为5.9%、9.13%、3.23%,切向力平均误差分别为6.78%、8.36%、3.69%。经对比知,优化后的模型拟合度较好,模型预测精度显著提高。遗传算法优化后的非线性优化函数GA-LSQ算法更适合磨削力模型的求解,可对磨削力的预测及实际加工生产中的参数优化提供参考。

食用菌预制菜的工艺配方研究及保质期预测

为丰富食用菌预制菜产品种类并解决预制菜储藏和运输的问题,通过运用高温反压式杀菌技术和加速破坏性试验(accelerated shelf-life testing,ASLT),开发出了一种复配型食用菌预制菜配方,并预测了其常温储藏保质期。采用3种食用菌为主要原料制作食用菌配方预制菜,加入猪五花肉、胡萝卜等配料,通过单因素和正交试验优化了其配方组成,获得了感官接受度较高的配方。配方组成为杏鲍菇200 g、香菇150 g、黑木耳50 g、猪五花肉70 g、胡萝卜30 g、香辣酱15 g、食盐1.2 g、蚝油1 g。该配方产品通过真空包装、高温反压式杀菌(121℃,20 min)和加速破坏性试验,预测在20℃下的保质期为195.4 d,满足常温储藏要求。通过对食用菌预制菜生产工艺的研究,证明了常温储藏食用菌预制菜的可行性。

基于机器学习的盾构隧道地表沉降曲线智能预测方法

联合机器学习模型和启发式智能优化算法,提出盾构隧道开挖地表沉降曲线智能预测方法。首先,建立盾构隧道开挖数值分析模型,在考虑等代层弹性模量、土体弹性模量、隧道半径、土体摩擦角、黏聚力影响的基础上,构建了1680组不同工况影响的地表沉降曲线数据库;然后,分析地层和衬砌力学参数、隧道几何参数对地表沉降曲线的影响规律,采用Peck函数对获得的地表沉降槽曲线进行拟合,获得对应工况下地表最大沉降和沉降槽宽度系数;最后,采用粒子群优化算法(particle swarm optimization,PSO)分别优化4种机器学习方法即多层感知机(multi-layer perceptron,MLP)、极限学习机(extreme learning machine,ELM)、随机森林(random forest,RF)和支持向量回归(support vector regression,SVR)的超参数或随机数,建立了4种盾构隧道开挖有限元模拟代理模型,预测了盾构隧道地表沉降曲线,并对模型的预测结果、预测误差和评价指标进行了对比分析,结果表明PSO-SVR模型在训练和测试过程中性能最佳。建立的盾构隧道地表沉降智能预测方法具有较高的计算精度及计算效率,能合理高效地预测地表沉降曲线分布规律。

隧道涌水量预测计算方法综述

预测隧道涌水量对于保障隧道施工安全、进度、洞室稳定和人身安全问题至关重要。国内外学者已提出多种预测方法,但是存在不同适用条件,根据隧道的水文地质条件选取恰当的方法能有效提高预测精度。对解析公式法、经验公式法、数值法、随机性数学模型预测法等多种涌水量预测方法进行了系统梳理和分析,通过对这些方法的基本原理及适用条件进行综合分析,讨论了当前涌水量预测方法存在的不足之处,并提出改进方向。结果表明:解析公式法应用简单,但结果偏差较大;经验公式法源于工程案例总结,适用于相似条件下隧道涌水量预测;数值法通过数学模型模拟,可以解决复杂水文地质条件下的涌水量预测,但对勘察设计阶段获取的水文地质参数提出更高的要求;随机性数学模型方法需要大量数据来保证结果的准确性;其他方法主要依赖于地理信息系统(GIS)技术、同位素分析法等手段,通过科学分析来识别并判断地下水量及其流动通道的地质特征,需要充分的数据支持和详尽的地下勘探结果作为依据。研究成果可为实际工程中选择合适的涌水量预测方法提供参考。

大断面浅埋隧道地表沉降Peck修正公式及其应用

针对经典Peck公式未考虑隧道断面形状、埋深对大断面浅埋隧道地表沉降影响的不足,考虑断面形状与隧道埋深修正系数改进Peck公式。利用白塔山隧道地表沉降实测数据对修正公式进行验证,两个监测断面预测值与实测值平均相对误差8.3%,最大相对误差18.4%。进而采用修正Peck公式对不同断面形状、不同埋深隧道开挖引起的地表沉降进行预测。结果表明:地表最大沉降与断面形状修正系数成正相关,地表最大沉降依次为矩形-1(Ⅰ)>马蹄形-1(Ⅱ)>圆形(Ⅴ)>矩形-2(Ⅲ)>马蹄形-2(Ⅳ);随着大断面浅埋隧道埋深增加,地表最大沉降减小而地表沉降槽宽度相应增大。地表沉降曲线形态由窄而深过渡到宽而浅,地表核心沉降区面积也逐渐减小。研究成果可为类似工程提供理论支持和技术参考。

塔筒安装条件下法兰盘受力变形分析研究

法兰盘是塔筒的重要部件,起到连接风机塔筒的作用。塔筒翻身吊装施工过程中,法兰盘及螺栓孔容易发生损伤变形,导致螺栓连接失效,严重影响塔筒的安全稳定性。因此,研究吊装条件下塔筒法兰盘的受力变形特征有着重要意义。采用有限元数值分析软件,对吊装条件下法兰盘及螺孔受力及变形特征进行分析研究,结果表明:塔筒吊装翻身过程中,当塔筒处于水平状态下法兰盘螺孔变形最大;法兰盘螺孔最大变形随法兰盘厚度增大而减小,随塔筒壁厚以及长度增大而增大。基于敏感性分析数据,提出了基于非线性拟合方法的法兰盘螺孔最大变形预测公式,平均误差仅为6.79%,可以为吊装条件下法兰盘螺孔最大变形预测提供有效的理论支持。

盾构下穿古城区地面沉降预测及现场监测分析

【目的】为了获取武汉市和平大道南延线盾构段地面的沉降数据,本研究通过Peck公式对现场沉降监测结果进行了拟合分析,并对Peck公式进行了修正。【方法】每30 m设置沿隧道上部对称分布的监测点进行现场地表沉降监测,选取其中4个最具代表性的断面沉降结果进行Peck公式拟合分析和验证,并根据实际沉降情况对Peck公式进行修正。【结果】研究结果表明,在隧道轴线上部存在异常沉降,因此通过对后续掘进段掘进参数进行调整,加强壁后同步注浆和监控测量控制沉降,并且将得到的沉降槽曲线与Peck公式进行拟合,得到4个断面的实测沉降数据与拟合曲线的拟合优度R2均高于0.85。【结结论论】盾构段沉降槽曲线与Peck公式计算结果高度拟合,可以用Peck公式对研究区沉降进行预测,选取地层体积损失率Vl为0.95%,沉降槽宽度系数k为0.55对Peck公式进行修正后,可以更加简单高效地预测后续沉降。

蜂窝夹层板面内剪切强度预测

蜂窝夹层板面内剪切强度是蜂窝夹层板结构设计中的重要参数之一。为了快速预测蜂窝夹层板面内剪切强度,基于拉丁超立方法抽样进行试验设计,构建了与仿真结果一致性良好的代理模型;利用代理模型基于Sobol法求解得到了影响蜂窝夹层板面内剪切强度各设计变量的灵敏度,确定了对蜂窝夹层板面内剪切强度有显著影响的参数;构建了蜂窝夹层板面内剪切强度预测公式,并对预测公式进行了验证。结果表明,蜂窝夹层板面内剪切强度预测值和实际值的相对误差最大不超过7%,平均相对误差不超过2%,满足工程应用精度要求。

New formula for predicting the plastic buckling pressure of steel torispherical heads under internal pressure

Thin-walled torispherical heads under internal pressure can fail by plastic buckling because of compressive circumferential stresses in the head knuckle.However,existing formulas still have limitations,such as complicated expressions and low accuracy,in determining buckling pressure.In this paper,we propose a new formula for calculating the buckling pressure of torispherical heads based on elastic-plastic analysis and experimental results.First,a finite element(FE)method based on the arc-length method is established to calculate the plastic buckling pressure of torispherical heads,considering the effects of material strain hardening and geometrical nonlinearity.The buckling pressure results calculated by the FE method in this paper have good consistency with those of BOSOR5,which is a program for calculating the elastic-plastic bifurcation buckling pressure based on the finite difference energy method.Second,the effects of geometric parameters,material parameters,and restraint form of head edge on buckling pressure are investigated.Third,a new formula for calculating plastic buckling pressure is developed by fitting the curve of FE results and introducing a reduction factor determined from experimental data.Finally,based on the experimental results,we compare the predictions of the new formula with those of existing formulas.It is shown that the new formula has a higher accuracy than the existing ones.