飞机容冰技术的研究进展

回顾了国内外在飞机结冰方面的研究情况。在此基础上,介绍了近年来国外在飞机容冰技术研究中的最新设想——智能防冰系统(SIS),对SIS研究中涉及的结冰气动模型进行了探讨,从飞行安全角度出发,给出了SIS中结冰飞行包线保护系统的基本原理及实现方法。

基于容冰概念的民机结冰保护系统设计方法研究综述

结冰是威胁民机飞行安全的重要致灾因素,也是适航审查方关注的重大安全问题。基于容冰概念开展结冰保护系统设计,最大程度降低结冰对飞机气动特性的影响,充分发挥飞行性能潜力,是当前民用飞机结冰防护研究的前沿方向。针对民机飞行安全性设计和适航认证需求,从飞机本体容冰设计和主动控制容冰设计两方面出发,对基于容冰概念的民机结冰保护系统设计方法进行分析。针对结冰损失,提炼了考虑结冰损失的机翼气动优化设计策略,形成了基于飞行控制律重构的容冰保护控制系统设计思路,将“被动结冰飞行安全”向“主动结冰安全设计”转变,能够有效提升民机在结冰气象条件下的生存力和安全性。

结冰翼型前缘下垂变弯度容冰特性改善机制

传统容冰气动力优化设计方法难以完全兼顾常规飞行和结冰状态对翼型几何特征的矛盾需求。依据前缘下垂变弯度的思路创新性地提出了一种能有效协调和解耦翼型气动/容冰特性的解决方案。针对GLC305-944结冰翼型典型过失速状态开展了基于IDDES(Improved Delayed Detached Eddy Simulation)方法的前缘下垂前后容冰特性对比分析,表明前缘下垂后结冰翼型失速特性显著改善,前缘吸力以压力平台形式恢复,分离泡形态由大尺度全局回流退化到冰角后方的局部流动结构,湍流脉动影响范围约束于前缘近壁面有限区域内。由于前缘下垂后冰角与当地壁面组成类凹腔结构,剪切层涡系经短暂发展后能迅速在壁面附近触发掺混融合-动量输运效应,有效促进再附过程,导致时均再附点提前、混合层厚度降低、分离泡几何尺度减缩,这是容冰特性改善的主要机制。

飞机结冰特性及防除冰技术研究

了解结冰对飞行的危害、预测结冰的特性和发展防除冰方法,对于保证飞行安全极为重要。阐述结冰的形成及其严重程度度量方法,分析结冰对飞机气动、操稳及起降特性的影响,总结现有的飞机防冰与除冰技术,并对飞机防冰试验进行综述。考虑到带冰飞行是不可避免的,强调容冰技术对于保障安全飞行的重要性,并给出结冰条件下的操纵建议。研究表明,影响飞机结冰的因素不同导致结冰严重程度上存在差异,结冰对飞机特性影响较大,导致飞行性能下降,而防除冰技术的使用及容冰能力的提高对于确保结冰条件下的飞行安全意义重大。

Minimally invasive video-assisted thyroidectomy for thyroid adenoma

Objective： The aim of the study was to investigate the value of minimally invasive video-assisted thyroidectomy for thyroid benign adenoma. Methods： From June 2003 to June 2007, 128 cases of thyroid tumors, including 123 cases of adenoma and 5 cases of carcinoma, were performed by Miccoli＇s endoscopic thyroidectomy. The surgical techniques and the clinical outcomes with respect to pathologic results, duration of operation, postoperative drainage, pain, cosmetic results and complications of endoscopic thyroid surgery via the neck approach were retrospectively summarized. Results： NI the patients underwent minimally invasive endoscope-assisted thyroidectomy successfully. Five cases of carcinoma revealed by frozen section. In which, 3 papillary carcinoma cases underwent subtotal thyroidectomy of disease-side in video-assisting, whereas the other 2 cases with follicular and medullary carcinoma underwent conventional total thyroidectomy of disease-side combined with subtotal thyroidectomy of the opposite-side. The transient hoarseness occurred in one patient and recovered well one week later, and the other patients recovered successfully without any complications. Conclusion： Minimally invasive video-assisted thyroidectomy for thyroid adenoma is safe and reliable. This procedure offers a shorter incision, less invasion and better cosmetic results as compared with conventional thyroidectomy.

A Simulation-Based Probabilistic Design Method for Arctic Sea Transport Systems

When designing an arctic cargo ship, it is necessary to consider multiple stochastic factors. This paper evaluates the merits of a simulation-based probabilistic design method specifically developed to deal with this challenge. The outcome of the paper indicates that the incorporation of simulations and probabilistic design parameters into the design process enables more informed design decisions. For instance, it enables the assessment of the stochastic transport capacity of an arctic ship, as well as of its long-term ice exposure that can be used to determine an appropriate level of ice-strengthening. The outcome of the paper also indicates that significant gains in transport system cost-efficiency can be obtained by extending the boundaries of the design task beyond the individual vessel. In the case of industrial shipping, this allows for instance the consideration of port-based cargo storage facilities allowing for temporary shortages in transport capacity and thus a reduction in the required fleet size / ship capacity.

Integrated reliability of travel time and capacity of urban road network under ice and snowfall conditions

In order to evaluate and integrate travel time reliability and capacity reliability of a road network subjected to ice and snowfall conditions,the conceptions of travel time reliability and capacity reliability were defined under special conditions.The link travel time model(ice and snowfall based-bureau public road,ISB-BPR) and the path choice decision model(elastic demand user equilibrium,EDUE) were proposed.The integrated reliability was defined and the model was set up.Monte Carlo simulation was used to calculate the model and a numerical example was provided to demonstrate the application of the model and efficiency of the solution algorithm.The results show that the intensity of ice and snowfall,the traffic demand and supply,and the requirements for level of service(LOS) have great influence on the reliability of a road network.For example,the reliability drops from 65% to 5% when the traffic demand increases by 30%.The comprehensive performance index may be used for network planning,design and maintenance.

Parameter identification for volumetric heat capacity and thermal conductivity in a quasi-linear thermodynamic system of sea ice

This paper is intended to determine physical parameters describing volumetric heat capacity and thermal conductivity of sea ice in u quasi-linear thermodynamic system using field observations. The quasi-linear thermodynamic system of sea ice with unknown physical parameters is described, and the existence and uniqueness of its solution is proved. Then the physical parameters are taken as control variable, temperature devi- ations as objective function, and a parameter identification model is established. The existence of its optimal solution is discussed. To solve the identification model, a new algorithm containing genetic algorithm, Hooke- Jeeves algorithm and semi-implicit finite difference scheme is constructed. The physical parameters are calculated using the obser- vations measured at Nella Fjord around Zhongshan Station, Antarctic in CHINARE 2006. For comparability and consistency with other works, a new internationM standard named TEOS-10 is used. To examine the validity of the identified results, another sim- ulation for temperature profiles in different measurement period is operated. Numerical results show that better simulations of temperature distribution are possible with the identified parameters than EC1993. Therefore not only the identified parameters can be applied in sea ice modeling, but also this study can enrich and supplement observations of sea ice.