Optimum Environmental Load Design Criterion for Marine Structures Based on Investment and Benefit Analysis

Marine structures operating in natural ocean environment are subjected to various stochastic loads. For design of the marine structures, the most important task is to determine environmental load design criterion. This paper presents a method to determine the optimum environmental load design criterion for marine structures. This method is based on the investment and benefit analysis and it can reach the design purpose of decreasing total costs during the service life of the structures and increasing economic benefits.

Floating-roof steel tanks under harmonic settlement: FE parametric study and design criterion

Large vertical steel tanks for fluid storage are usually constructed on soft foundations, so it is not surprising that the tank wall will settle unevenly with the settlement of the foundation, thus inducing deformations and stresses in the tank. This work investigates the linear static behavior of floating-roof tanks under harmonic settlement through finite element (FE) analyses. The influences of the radius-to-thickness ratio, the height-to-radius ratio and the wind girder stiffness on the structural behavior are first analyzed. Comparisons between the circumferential stresses in the wind girder and the vertical stresses in the tank bottom are then made. The displacement and the stress along the tank height are also discussed, and the concept of tank division along its height is presented. Finally, a design approximation for the radial displacement at the tank top is developed based on FE results, and a settlement criterion based on the top radial displacement is proposed which can be used in practical design.

A new design criterion and construction method for space-time trellis codes based on classification of error events

The known design criterions of Space-Time Trellis Codes （STFC） on slow Rayleigh fading channel are rank, determinant and trace criterion. These criterions are not advantageous not onlv in operation but also in performance. With classifying the error events of STTC, a new criterion was presented on slow Rayleigh fading channels. Basod on the criterion, an effective and straighttbrward multi-step method is proposed to ennstruet codes with better performance. This method can reduce the computation of search to small enough. Simulation results show that the codes searched by computer have the same or even better performance than the repored codes.

Design Criterion for Interleaving and Magnetically Integrated Bidirectional DC/DC Converters

双向DC/DC变换器中大功率储能电感的设计是一件困难而具有挑战性的工作,提出研究双向DC/DC变换器的交错并联磁集成理论以克服这一困难。将三相Buck＋Boost双向DC/DC变换器的所有相电感集成为一个耦合电感,对磁集成后变换器运行在Buck模式下的稳态电流纹波和暂态响应速度进行深入研究,给出三相Buck＋Boost交错并联磁集成双向DC/DC变换器运行在Buck模式下的设计准则,即在设计这种变换器时,应根据占空比的大小及稳态相电流纹波和暂态总输出电流响应速度的技术要求,利用该文所给出的设计公式和设计区域选择磁集成耦合电感的反向耦合系数。仿真和实验验证了理论分析的正确性。

Discussion on uncertainties，attenuation of ground motion and aseismic design criterion

The usually calculated exceedance probability curves of ground motion are reduced as cumulative probability curves of normal distribution on some assumptions in this paper. These curves clearly displayed the variation of curve shape with the variance of attenuation relation and its physical implication. Similar investigation is also made on uncertainties of hypocenter locations and magnitudes of future earthquakes. The larger the uncertainty,the flatter the exceedance probability curve is. In a broad sense, the less people know future earthquakes, the flatter is the curve. Due to the rich or poor data sets available, the uncertainties of attenuation relation are different from region to region. The acceleration attenuation relations in these regions with no enough strong earthquake records can be obtained by conversion from other region, but with larger uncertainty. The uncertainty contains systematic difference between the two regions in addition to common stochastic error. A method to check and adjust the converted attenuation relation by using the local data is proposed in this paper. If the uncertainty of attenuation relation is too large, the result of seismic hazard assessment may be unaccepted sometimes.In order to realize that the structures do not collapse in large earthquakes, be repairable under moderate ones and without destruction in small earthquakes, this paper suggests that it may be reasonable to get the first and the third levels of aseismic design parameters by some empirical relation on the basis of the second level not by fixing the risk probability levels (63%, 10% and 3%). A particular aseismic design criterion is not only a balance between economic cost and seismic risk but also suited to the human's knowledge of nature.

Construction of Split-Plot Designs with General Minimum Lower Order Confounding

Fractional factorial split-plot design has been widely used in many fields due to its advantage of saving experimental cost. The general minimum lower order confounding criterion is usually used as one of the attractive design criterion for selecting fractional factorial split-plot design. In this paper, we are interested in the theoretical construction methods of the optimal fractional factorial split-plot designs under the general minimum lower order confounding criterion. We present the theoretical construction methods of optimal fractional factorial split-plot designs under general minimum lower order confounding criterion under several conditions.

一种提高镁合金零部件抗火焰蔓延性的尺寸设计类判据

基于能量守恒定律提出了一种用于预测棒状镁合金样品火焰蔓延时间的判据,该判据表明火焰蔓延时间主要受合金材料和样品尺寸影响。控制体的初始温度和起燃温度以及样品的S/l_c比值(样品横截面面积/横截面周长)是火焰蔓延时间的决定性因素。火焰蔓延时间正比于ΔH(将单位质量的样品从初始温度加热到起燃温度所需的能量)和S/l_c比值,这在Mg-8.5Al-0.5Zn-0.2Mn、Mg-2.7Nd-0.4Zn-0.6Zr和Mg-4.0Y-3.3Nd-0.5Zr镁合金中得到验证。对于尺寸相同的样品,Mg-8.5Al-0.5Zn-0.2Mn合金样品有着最大的ΔH以及最长的火焰蔓延时间;对于材质、长度和横截面面积相同的样品,圆形横截面样品的S/lc比值最大,其抗火焰蔓延性能也最佳。

基于FDS准则的响应曲面设计预测能力比较

预测能力是实际应用工作者评价设计优劣的重要准则之一,一般地,通过方差散布图可以对一个固定球面上的设计预测能力进行比较和选择,但无法获得对整个设计区域上的比较结果。文章介绍了基于正交表的响应曲面设计(OACD)以及基于极小极大准则的改进设计(OACM),并应用全区域预测方差占比准则——FDS准则对这两类中心组合设计进行预测能力的比较。结果表明,在一个较小方差范围内,OACD得到的FDS结果要优于OACM,而对于大部分给定方差值,OACM的FDS结果要优于OACD。

Cavity Flow Pattern Design for Supercaviting Torpedo

The flow pattern design of supercaviting torpedo,like the shape design of conventional bedewed torpedo,occupies an important position in torpedo system design.In this paper,the flow pattern design issues were studied systematically.A set of design criteria and main design requirements were proposed,and the design method and procedure were established.Moreover,the determination method of necessary parameters of cavitator and ventilated system for desired cavity flow pattern was given.Considered the speed and pressure disturbances in the torpedo navigation,a concept named margin design was proposed to solve the supercavitation deformation and instability caused by the disturbances.

拖挂载荷下复合材料水下防护结构损伤分析

通过对水下防护结构的材料开展海水劣化和材性试验,证明玻璃纤维和乙烯基酯树脂组成的复合材料在海水浸泡后仍具有很高的强度。根据海底管道终端的功能需求对水下防护罩展开结构设计和铺层设计。并基于Larc05损伤准则,借助ABAQUS对所设计的水下防护罩展开拖挂载荷下的损伤分析和研究。分别对有无帽型加强筋的两种防护罩上的4个不同拖挂位置进行加载、计算和分析,发现结构最容易发生的是基体损伤。无帽型加强筋的防护罩在位置3和4相对位置1和2更容易出现损伤。有帽型加强筋的防护罩相对无帽型防护罩,在位置2处的承载力下降了29.6%,发生纤维断裂损伤,剩余位置处承载力都有所提升。

Research on performance-based seismic design criteria

The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and economic development. A new performance-based seismic design criterion that is composed of three components is presented in this paper. It can not only effectively control the economic losses and casualty, but also ensure the building's function in proper operation during earthquakes. The three components are: classification of seismic design for buildings, determination of seismic design intensity and/or seismic design ground motion for controlling seismic economic losses and casualties, and determination of the importance factors in terms of service periods of buildings. For controlling the seismic human losses, the idea of socially acceptable casualty level is presented and the 'Optimal Economic Decision Model' and 'Optimal Safe Decision Model' are established. Finally, a new method is recommended for calculating the importance factors of structures by adjusting structures service period on the base of more important structure with longer service period than the conventional ones. Therefore, the more important structure with longer service periods will be designed for higher seismic loads, in case the exceedance probability of seismic hazard in different service period is same.

PRINCIPLES FOR OPTIMUM DESIGN OF OPEN PIT MINES

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Effects of time-delayed vibration absorber on bandwidth of beam for low broadband vibration suppression

The effects of time-delayed vibration absorber(TDVA) on the dynamic characteristics of a flexible beam are investigated. First, the vibration suppression effect of a single TDVA on a continuous beam is studied. The first optimization criterion is given,and the results show that the introduction of time-delayed feedback control(TDFC) is beneficial to improving the vibration suppression at the anti-resonance band. When a single TDVA is used, the anti-resonance is located at a specific frequency by the optimum design of TDFC parameters. Then, in order to obtain low-frequency and broad bands for vibration suppression, multiple TDVAs are uniformly distributed on a continuous beam,and the relationship between the dynamic responses and the TDFC parameters is investigated. The obtained relationship shows that the TDVA has a significant regulatory effect on the vibration behavior of the continuous beam. The effects of the number of TDVAs and the nonlinearity on the bandgap variation are discussed. As the multiple TDVAs are applied, according to the different requirements on the location and bandwidth of the effective vibration suppression band, the optimization criteria for the TDFC parameters are given, which provides guidance for the applications of TDVAs in practical projects such as bridge and aerospace.

船舶结构设计准则和衡准的研究进展

围绕船舶与海上设施设计准则和衡准,聚焦IACS、IMO、ISO/TC8五年来的最新研究进展,考虑了IACS各成员国的新规范、指南,以及地区海事结构安全规则的研发,讨论了数值孪生、营运数据、可靠性和风险评估、设计阶段中人为因素等对结构设计准则发展的影响等热点问题,给出了未来海事规则制定的总体方向的考虑。

Design of a(480,240)CMOS Analog Low-Density Parity-Check Decoder

Digital low-density parity-check(LDPC) decoders can hardly meet the power-limits brought by the new application scenarios. The analog LDPC decoder, which is an application of the analog computation technology, is considered to have the potential to address this issue to some extent. However, due to the lack of automation tools and analog stopping criteria, the analog LDPC decoders suffer from costly handcraft design and additional decoding delay, and are not feasible to practical applications. To address these issues, a decoder architecture using reusable building blocks is designed to lower the handcraft design, and a probability stopping criterion that is specially designed for analog decoder is further planned and implemented to reduce the decoding delay. Then, a(480,240) CMOS analog LDPC decoder is designed and fabricated in a 0.35-μm CMOS technology. Experimental results show that the decoder prototype can achieve 50 Mbps throughput when the power consumption is about 86.3m W, and the decoding delay can be reduced by at most 93% compared with using the preset maximum decoding delay in existing works.

Reliability-based design in rock engineering: Application of Bayesian regression methods to rock strength data

Reliability-based design (RBD) is being adopted by geotechnical design codes worldwide, and it is therefore necessary that rock engineering practice evolves to embrace RBD. This paper examines the Hoek-Brown (H-B) strength criterion within the RBD framework, and presents three distinct analyses using a Bayesian approach. Firstly, a compilation of intact compressive strength test data for six rock types is used to examine uncertainty and variability in the estimated H-B parameters m and σc, and corresponding predicted axial strength. The results suggest that within- and between-rock type variabilities are so large that these parameters need to be determined from rock testing campaigns, rather than reference values being used. The second analysis uses an extensive set of compressive and tensile (both direct and indirect) strength data for a granodiorite, together with a new Bayesian regression model, to develop joint probability distributions of m and σc suitable for use in RBD. This analysis also shows how compressive and indirect tensile strength data may be robustly used to fit an H-B criterion. The third analysis uses the granodiorite data to investigate the important matter of developing characteristic strength criteria. Using definitions from Eurocode 7, a formal Bayesian interpretation of characteristic strength is proposed and used to analyse strength data to generate a characteristic criterion. These criteria are presented in terms of characteristic parameters mk and σck, the values of which are shown to depend on the testing regime used to obtain the strength data. The paper confirms that careful use of appropriate Bayesian statistical analysis allows the H-B criterion to be brought within the framework of RBD. It also reveals that testing guidelines such as the International Society for Rock Mechanics and Rock Engineering (ISRM) suggested methods will require modification in order to support RBD. Importantly, the need to fully understand the implications of uncertainty in nonlinear strength criteria is identified.

Dimensioning of Punctiform Metal-Composite Joints: A Section-Force Related Failure Criterion

Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material-adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and fault-tolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.

CONSENSUS ANALYSIS AND DESIGN OF LINEAR INTERCONNECTED MULTI-AGENT SYSTEMS

We deal with the state consensus problem of a general Linear Interconnected Multi-Agent System （LIMAS） under a time-invariant and directed communication topology. Firstly, we propose a linear consensus protocol in a general form, which consists of state feedback of the agent itself and feedback form of the relative states between the agent and its neighbors. Secondly, a state-linear-transformation is applied to equivalently transform the state consensus problem into a partial stability problem. Based on the partial stability theory, we derive a sufficient and necessary criterion of consensus convergence, which is expressed via the Hurwitz stability of a real matrix constructed from the parameters of the agent models and the protocols, and present an analytical formula of the consensus function. Lastly, we propose a design procedure of the gain matrices in the protocol by solving a bilinear matrix inequality.

挤压油膜阻尼器高速永磁电机转子动力学分析及优化设计

为了抑制转子在高速旋转时的振动,研究了挤压油膜阻尼器对转子振动抑制的作用,分析了阻尼器转子不同参数下的临界转速、转子振幅以及支撑反力,采用多目标优化进行了参数设计。首先,分析了转子左右支撑等效刚度与阻尼对转子动力学特性的灵敏度。其次,在选定阻尼器内环半径后,分别研究了阻尼器间隙、阻尼器长度、滑油黏度、鼠笼支撑刚度与轴承刚度对转子动力学特性的影响。最后,选定了阻尼器间隙、鼠笼支撑刚度与轴承刚度作为优化变量,通过拉丁超立方采样使用四次多项式建立了转子临界转速、转子振幅和支撑反力的响应面模型,采用非支配排序遗传算法(NSGN-Ⅱ)得到优化方案,进行有限元仿真验证。优化后转子的临界转速得以提高,支撑反力和振动幅值都有所减小。

输氢海底管道强度设计准则研究

本文研究了输氢海底管道的强度设计、断裂韧度和氢致疲劳裂纹扩展速率模型准则,并对模型进行了敏感性研究。为输送氢气海底管道工程设计提供指导。