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101.
This paper presents the results of a study dealing with the risk for heavy vehicles in ramps. Two approaches are used. On one hand, statistics are applied on several accidents databases to detect if ramps are more risky for heavy vehicles and to define a critical value for longitudinal slope. χ2 test confirmed the risk in ramps and statistical analysis proved that a longitudinal slope superior to 3.2% represents a higher risk for heavy vehicles. On another hand, numerical simulations allow defining the speed profile in ramps for two types of heavy vehicles (tractor semi-trailer and 2-axles rigid body) and different loads. The simulations showed that heavy vehicles must drive more than 1000 m on ramps to reach their minimum speed. Moreover, when the slope is superior to 3.2%, tractor semi-trailer presents a strong decrease of their speed until 50 km/h. This situation represents a high risk of collision with other road users which drive at 80–90 km/h. Thus, both methods led to the determination of a risky configuration for heavy vehicles: ramps with a length superior to 1000 m and a slope superior to 3.2%. An application of this research work concerns design methods and guidelines. Indeed, this study provides threshold values than can be used by engineers to make mandatory specific planning like a lane for slow vehicles. 相似文献
102.
103.
随着第五代移动通信(5G)时代的到来,高频、大带宽的谐振器成为通信行业的迫切需求。该文设计制备了一款可实现高频超大带宽的横向激发体声波谐振器(XBAR)。该谐振器A1模式的谐振频率为5.81 GHz,机电耦合系数可达39.6%,Q-3 dB为248;A3模式的谐振频率高达17.04 GHz,机电耦合系数为7.0%。该谐振器A1和A3模式的频率温度漂移系数(TCF)分别为-72.6×10-6/℃和-38.5×10-6/℃。此外,该文还提出了一种新型叉指电极(IDT)结构,该结构可以抑制寄生模式,提升谐振器性能。 相似文献
104.
105.
《Signal processing》1987,13(3):287-299
Median filters (MF) are used both to filter ‘salt and pepper’ noise from signals and images and in other signal processing applications. In this paper, an extension of the MF, the vector median filter (VMF), is introduced. As opposed to the MF, the VMF outputs for each window location a number of data elements. By adjusting the VMF parameters, the MF is obtained as a VMF special case. Just like the MF, the VMF filters impulses while simultaneously preserving step changes in a signal. The VMF's principal advantage is that it reduces the total stored data signal computation time while it produces visual outputs comparable to that of an MF. Deterministic and statistical properties of the VMF are examined. Computer-generated experimental results are also presented. 相似文献
106.
《Energy and Buildings》1988,12(3):207-218
This paper describes a nomograph that can be used as a design tool for estimating annual cooling and heating coil loads in interior zones of office buildings. Based on simplified relationships between the heat load on an air-conditioning system, internal heat generation and outdoor air intake rate, the equations for normalized anuual cooling and heating coil loads in interior zones of office buildings are derived as a function of outdoor air enthalpy, two variables related to the intensity of internal cooling load, and the minimum and maximum outdoor air intake rates. Normalization of heat load on an ari-conditioning system made it possible to construct a design nomograph which can be used to calculate the energy-saving effects of an economizer cycle (passive cooling with ventilation air) and an exhaust air heat recovery unit on annual cooling and heating coil loads at the schematic design stage.Example calculations using the nomographs for three locations in Japan show that the energy-sacing effects of economizer cycle and exhaust air heat recovery units are heavily dependent on the profiles of regional weather conditions. A validation study showed that annual cooling and heating coil loads estimated from the nomographs were in good agreement with those from a detailed computer-based calculation. 相似文献
107.
提出一种改进YOLOv7的纸张表面缺陷一步式检测算法。首先将注意力机制模块CBAM融合到主干和特征提取网络结构,从空间和通道2个维度提取信息,提升小目标纸病特征提取准确性和算法稳定性;将ASPP空洞卷积加入主干网络SPP中,ASPP可以进一步扩大感受野,使较小目标的特征信息在网络传递时得到保留,解决了小目标信息量不足的问题,进而提高小目标纸病识别的性能。通过自制纸病数据集检测实验,与YOLOv7相比,精确率、召回率及平均精确率均值mAP 0.5分别提升了1.5、2.3和2.1个百分点。 相似文献
108.
为了解决多余力矩对电动负载模拟器强干扰,影响加载指令跟踪精度的问题,论文将基于蚁群优化的PID控制方法用于加载电机控制器的设计.首先在分析加载电机结构以及工作原理的基础上建立了电动加载系统的数学模型,并利用结构不变性原理进行前馈补偿推导;其次针对常规PID控制器无法通过变参数来应对复杂的非线性环境的问题,提出了一种基于... 相似文献
109.
《Artificial Intelligence in Engineering》1987,2(1):11-22
The true potential of a CIM system cannot as yet be fully realised. A further requirement is for a device which can extract manufacturing information from the outset. The main aim of the research described in this paper is to develop a knowledge-base system for extracting such information and to promote a coming together of design and manufacture. The major goal must be to enable industry to manufacture without manual intervention. A prototype knowledge-base system called HOLDEX described in this paper is an implementation that relies on combining the advantages of existing technology such as AI, CAD representation schemes, advanced manufacturing systems, man-machine interface and most importantly the encapsulated knowledge of a manufacturing engineer. The aim of the prototype system is to encourage a workpiece designer towards manufacturing standards and to assist him in the use of a general purpose CAD package. One benefit to be obtained from providing such assistance is to facilitate the ease of extracting manufacturing information. The scope of the extracted information includes the detailed specification of a set of cutting tools, the recognition of a list of required activities prior to a machining operation, the recommendation of the appropriate machine tool and the automated design of fixtures. 相似文献
110.