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381.
For bulk carriers in hogging, the most critical situation is the alternate hold loading (AHL) condition with odd numbered
holds loaded with high density cargoes and even numbered holds empty. The effect of the local lateral pressure loads should
be considered in the assessment of ultimate hull girder strength in the hogging and AHL conditions. In the present paper the
ultimate strength of a Capesize bulk carrier hull girder under combined global and local loads in the hogging and AHL condition
is extensively and systematically investigated using nonlinear finite element (FE) analysis with ABAQUS software. Since the
bulk carrier used as a reference vessel in this study is an old design we also studied the effect of modified scantlings by
multiplying the plate thickness in the bottom structure by a design modification factor (DMF). In particular, it should be
noted that a DMF of 1.4 gives a design in accordance with the new CSR rules. Based on the results obtained by nonlinear FE
analyses, a practical interaction equation is established between global hogging bending capacity and average external sea
pressure over the bottom. 相似文献
382.
383.
This paper focuses on the mechanisms of combustion noise during the accelerating operation of multi-cylinder diesel engines
using testing technology for the transient conditions of IC engines. Based on impact factors, such as the gas dynamic load
and cylinder pressure oscillations, tests and analysis of the combustion noise during transient and steady-state conditions
for different loads are made on four-cylinder naturally aspirated engines, turbocharged engines, EGR-introduced engines, and
high pressure common rail engines. The laws of combustion noise difference for the same engine speed and load are researched
during transient and steady-state conditions. It is found that during transient conditions, the maximum pressure rise rate
and the high frequency oscillation amplitude of the cylinder pressure are all higher than those observed during steadystate
conditions for the same engine speed and load. With their joint action, the combustion noise during transient conditions is
greater than that during steady-state conditions. Turbocharging is useful in reducing the combustion noise during transient
conditions. Turbocharging has a better effect on the control over the combustion noise during transient conditions with a
constant engine speed and an increasing torque than in conditions with a constant torque and an increasing engine speed. One
of the main reasons for different control effects on the combustion noise is that turbocharging causes different wall temperatures
inside combustion chambers. The introduction of the appropriate EGR is helpful in the reduction of the combustion noise during
transient conditions. The key to the control of combustion noise with EGR during transient conditions is whether a real-time
adjustment to the EGR rate can be made to achieve the optimization of the EGR rates for different transient conditions. By
means of analyzing the differences in the combustion noise between the transient and steady-state conditions for different
pilot injection controls, we obtain a strategy for controlling the combustion noise during transient conditions with a pilot
injection. Compared with the steady-state conditions, a larger pilot injection quantity and a longer interval between the
main injection and pilot injection should be selected for transient conditions, and this is verified through tests. 相似文献
384.
385.
该文针对数字地面模型(DTM)的拼接问题提出了基于拼接线对三角网进行裁减的算法,并对其基本原理及主要过程进行了详细介绍。运用该算法编制的程序实现了数模之间的良好衔接,使数模满足构建线路三维模型的要求。 相似文献
386.
387.
哑铃型钢纤维粉煤灰混凝土基本力学性能及抗弯韧性 总被引:12,自引:0,他引:12
为了研究哑铃型钢纤维对混凝土力学性能的效用,试验研究了新拌纤维混凝土的坍落度和密度,测定了纤维混凝土的抗压强度、弹性模量、抗劈裂强度;基于美国ASTM及日本JCI方法,用四点弯曲梁测得了抗弯初裂强度、抗弯拉强度和抗弯韧性等。试验证明:哑铃型纤维能够均匀地分散在混凝土中,纤维无结团现象;该纤维对混凝土具有良好的增强和增韧双重效应,对抗弯初裂强度、抗弯拉强度和抗弯韧性等力学指标都有明显的提高。 相似文献
388.
本文建立了速比i=2.0、i=0.5两种工况下的金属带式无级变速传动系统的实体和有限元模型,针对其复杂的结构,提出了节点-节点离散杆单元模型,简化并建立了系统的结构动态模型。运用灵敏度 Lanczos迭代法求解系统的振动模态。在车辆传动实验台上采集了运行过程中传动系统的加速响应信号。在此基础上运用环境激励的模态分析方法识别了系统的固有特性参数,并与理论计算值进行了比较。结果证明本文提出模型的正确合理性。该研究所用的方法及计算的结果有助于提高无级变速器传动系统的运行平稳性,为降低系统在运行过程中产生的噪声提供理论参考。 相似文献
389.
运动图像处理在车型识别中的应用 总被引:6,自引:0,他引:6
本文介绍了多品种混流机器人喷漆自动线的汽车车型识别系统的一种方法,提出了基于运动序列图像的自适应阈值判别法,利用特征匹配法解决了同种车型的图像在结构上产生局部变化的识别问题。 相似文献
390.