ERP系统实施风险的模糊综合评判

充分考虑了ERP系统实施的风险性,建立了一套用模糊综合评判法评判ERP系统实施风险的指标,并通过实例说明了ERP系统实施风险的模糊综合评判方法.     

高新技术企业R&D绩效测度系统的开发

九十年代以来 ,就如何测度R&D绩效 ,已有许多学者提出一些具体的测度系统 (方法 ) ,但这些系统本身还存在某些不足 ,另外 ,学者们没有对测度系统的实施和更新进行研究。针对这种情况 ,本文从设计、实施、更新的角度对高新技术企业R&D绩效测度系统进行了有效的开发。     

Noise characteristics of tractors and health effect on farmers

An investigation was conducted to determine the noise propagation (under stationary condition) and noise at operator’s ear level of popular 18.7 and 26.1 kW tractors and 4.6 and 6.7 kW hand tractors during field operations with various implements. It was observed that both tractors produced the noise of 92 dB(A) L_eq in the working zone of operator. The sound pressure level (SPL) of the hand tractor was about 2 dB(A) L_eq higher than that of the tractor. The SPL during field operations at operator’s ear level increased with increase in engine speed and forward speed. Furthermore, the SPL was higher for field operations corresponding to the implement requiring higher draft. It was observed that the SPLs of the tractors and hand tractors were more than the exposure limit of noise for 8-h workday recommended by ISO and OSHA. This may cause health problems to the farmers in the long run.     

高精度硅微谐振加速度计工程化设计与实现

硅微谐振加速度计因具有小体积优势和高精度潜力,成为硅微惯性传感器研制的热点之一。工程化设计是硅微谐振加速度计从原理样机向成熟产品转化过程中的关键步骤之一。在分析硅微谐振加速度计工作机理的基础上,从工程实用化设计角度出发,提出了一种高精度硅微谐振加速度计工程化设计方法。分别从系统设计、结构设计、控制电路设计和测试与补偿技术等方面进行了分析和对比,讨论了误差来源与改进方法。测试表明,设计的高精度硅微谐振加速度计质量块基频大于3 k Hz,谐振音叉中心频率约18 k Hz,标度因数大于100 Hz/g,量程±40 g,死区小于0.67 mg,带宽大于200 Hz,振动整流误差0.344 mg,零位一次通电稳定性优于50μg,测试结果基本满足工程化应用指标。     

Modeling and validation of hitch loading effects on tractor yaw dynamics

This paper develops a yaw dynamic model for a farm tractor with a hitched implement, which can be used to understand the effect of tractor handling characteristics for design applications and for new automated steering control systems. Dynamic equations which use a tire-like model to capture the characteristics of the implement are found to adequately describe the tractor implement yaw dynamics. This model is termed the “3-wheeled” Bicycle Model since it uses an additional wheel (from the traditional bicycle model used to capture lateral dynamics of passenger vehicles) to account for the implement forces. The model only includes effects of lateral forces as it neglects differential longitudinal or draft forces between inner and outer sides of the vehicle. Experiments are taken to verify the hitch model using a three-dimensional force dynamometer. This data shows the implement forces are indeed proportional to lateral velocity and that differential draft forces can be neglected as derived in the “3-wheeled” Bicycle Model. Steady state and dynamic steering data are used for implements at varying depths and speeds to quantify the variation in the hitch loading. The dynamic data is used to form empirical transfer function estimates (ETFEs) of the implements and depths in order to determine the coefficients used in the “3-wheeled” Bicycle Model. Changes in a single parameter, called the hitch cornering stiffness, can capture the various implement configurations. Finally, a model that includes front wheel drive forces is derived. Experiments are taken which provide a preliminary look into the effect of four-wheel drive traction forces, and show a difference with two-wheel versus four-wheel drive, on the yaw dynamics of a tractor with the hitched implement.     

The shearing edge of tracked vehicle – Soil interactions in path clearing applications utilizing Multi-Body Dynamics modeling & simulation

Tracked vehicle – soil interactions were modeled and analyzed to compare the mobility of two notional path clearing implements pushed by a tracked vehicle. This exploration assesses the capabilities and limitations of the state-of-the-art in tracked vehicle dynamics modeling and simulation over soft-soil terrain. Unique modeling and simulation methods to stretch the capability of the current state-of-the-art contribute to the overall discussion. One path clearing implement was a roller and rake combination. The other was a quickly rotating flail system that cleared a definitive path by impacting and flinging the soil away. Geotechnical forcing functions implemented Coulomb’s lateral earth pressure theory and Terzaghi passive soil failure models to compute the forces at the soft-soil – implement interfaces. Coulomb theory was reimagined to account for anomalies present when modeling the flail, mainly its arced motion and non-semi-infinite soil resistance zone. The path-clearing implements were simulated over discrete events and compared by means of load and acceleration time histories. The discrete events include side-slopes, grades, half-rounds, potholes, cross country terrain, and ‘V’ shaped ditches (V-ditch). Overall, the flail system experienced lower peak loads at the interface brackets and lower peak accelerations at the vehicle’s center of gravity than the roller-rake system.     

城市旅游规划的实施困境与实施要则

分析了城市旅游规划蓬勃发展过程中面临的实施问题,针对这些具体问题,从规划层面,法律层面,管理层面,技术层面提出四方面的实施要则,以期能够更好地解决城市旅游规划的具体实施问题.