Effects of relaxation time on start-up time for starting flow of Maxwell fluid in a pipe

Although the analytical solution of the starting flow of Maxwell fluid in a pipe has been derived for a long time, the effect of relaxation time λ on start-up time ts of this flow is still not well understood. Especially, there exist a series of jumps on the ts-λ. curve. In this paper we introduce a normalized mechanical energy by mode decomposition and mathematical analogy to describe the start-up process. An improved definition of start-up time is presented based on the normalized mechanical energy. It is proved that the ts-λ. curve contains a series of jumps if λ is larger than a critical value. The exact positions of the jumps are determined and the physical reason of the jumps is discussed.

New Start-up Method for a Closed-Cycle Compression System with Gas Bearings and Its Characteristics

Gas bearings,which have the advantages of low frictional resistance and power loss,high rotational speed and high temperature operation,and long life,are more suitable than are traditional liquid lubricated bearings because of their high precision,high rotational speed,and special condition support.However,the problem of starting a closed-cycle compression system with gas bearings still needs to be solved for practical application.Thus,a new start-up method for a closed-cycle compression system with aerostatic gas bearings is proposed in this paper.Further,this paper presents a numerical simulation and experimental investigation of the method’s feasibility and characteristics during the start-up process when the gas tank’s initial pressure is fixed.The results show that the gas tank volume is approximately directly proportional to the start-up time allowable,and a gas tank volume sufficiently small,which not only ensures the feasibility of start-up,but also affects other components only slightly,can be obtained.A perfect combination of radial and axial loads also can be achieved to make the start-up time allowable as long as possible.R134a is a better choice for the working medium than is air,as the start-up time allowable is longer,which leads to a smaller gas tank.This research proposes a new start-up method for a closed-cycle compression system with aerostatic gas bearings which has sufficient load capacity to support system during the start-up method.

Application of high temperature heat pipe in hypersonic vehicles thermal protection

In order to develop further the application of high temperature heat pipe in hypersonic vehicles thermal protection, the principles and characteristics of high temperature heat pipe used in hypersonic vehicles thermal protection were introduced. The methods of numerical simulation, theory analysis and experiment research were utilized to analyze the frozen start-up and steady state characteristic of the heat pipe as well as the machining improvement for fabricating irregularly shaped heat pipe which is suitable for leading edge of hypersonic vehicles. The results indicate that the frozen start-up time of heat pipe is long （10 min） and there exists large temperature difference along the heat pipe （47 ℃/cm）, but the heat pipe can reduce the temperature in stagnation area of hypersonic vehicles from 1 926 to 982 ℃ and work normally during 1 000-1 200℃. How to improve the maximum heat transfer capability and reduce the time needed for start-up from frozen state of the heat pipe by optimizing thermostructure such as designing of a novel wick with high performance is the key point in hypersonic vehicles thermal protection of heat pipe.

A Quantitative Approach for Timing the Pedestrian Walk Interval

At a typical signalized intersection, the pedestrian phase consists of a walk interval and a change/clearance interval, during which pedestrians are given the right of way. The walk interval is intended to allow pedestrians to exit the curb ramp and enter the crosswalk. The clearance interval will enable them to cross entirely to the other side of the road. Unfortunately, the literature is quite vague on how long the walk interval should be and provides values ranging from 4 to 15 seconds based on qualitative pedestrian demand ranging from Negligible to High. To provide some quantitative guidance for walk interval selection, this paper reports on a study that collected 1,500 pedestrian movement data from 12 signalized intersections with varying pedestrian demand, pedestrian storage areas, and pedestrian push-button locations. The data was used to propose a quantitative model for designers to select the appropriate walk interval. Specifically, this paper seeks to add values to the Traffic Operations Handbook walk-interval guidelines as to how many pedestrians are considered “negligible volume” and can be accommodated by the 4 second minimum time, how many pedestrians are considered “typical volume” and require 7 to 10 seconds, and how many pedestrians are considered “high volume” and require 10 to 15 seconds, or perhaps longer. In addition to examining pedestrian demand, this paper looks at the impact of storage areas and pedestrian push-button location on pedestrian start-up time and, consequently, an appropriate walk interval.

100本最好的英语小说(六)

22.The Way We Live Now by Anthony Tr ollope（1875）安东尼·特罗洛普的《如今世道》Inspired by the author＇s fury at the corrupt state of England,and dismissed by critics at the time,The Way We Live Now is recognised as Trollope＇s masterpiece.23.The Adventures of Huckleberry Finn by Mar k Twain（1884/5）马克·吐温的《哈克贝利·费恩历险记》

The Principles of Causal Conspiracy

The human mind understands logical processes and causality and formulates theories based on logical descriptions of empirical evidence. The Principles of Causal Conspiracy is based on defining information as logical charges similar to electric charges. Such information charges can be modeled in the vacuum of a quantum probability firmament as symmetry of quantum charges with a zero net charge. Observation of a state lifts one of these charges in a M&oumlbius transformation from a multipolar field of possibilities that maximizes a local monopole field that is observable. In the first of several papers, I introduce new and profound principles, the Principles of Causal Conspiracy, to provide a consistent epistemology for quantum theory, relativity theory and all the known sciences.

Indication of Soil Microbial Activity by Electrical Signals of Microbial Fuel Cells with Re-Vegetated Red Soils

Electrical signals generated by microbial fuel cells(MFCs)may potentially indicate overall soil microbial activity.This study aimed to validate whether a significant correlation existed between soil microbial activity and electrical signals in different soils.Re-vegetated red soils with four vegetation types and unplanted eroded red soil were collected and packed into MFCs.The voltage of the MFCs was recorded during operation.Electrical signals including start-up time(ST),peak voltage,and coulomb quantity were extracted from the voltage curves.Soil dehydrogenase activity(DHA) was determined as a reference method to verify the reliability of the electrical signals.After MFC operation,the anodic bacterial community was analyzed by Illumina sequencing based on the 16S rRNA gene.The results indicated that ST was significantly correlated with DHA,along with soil organic carbon content.The linear regression model described the optimal relationships for ST and DHA.Clostridium and Acinetobacter constituted the dominant genera on the anode of the MFCs.The results demonstrated that ST may indicate soil microbial activity in re-vegetated red soils.

实施名牌战略促进企业发展

实施名牌战略促进企业发展王保佳，齐俊峰通过学习和大讨论，我们认识到，必须稳定和提高产品质量，才能在激烈的市场竞争中立不败之地。我厂把今年定为“９５质量年”，通过抓质量提高了原辅材料的供应质量，提高了设备有效利用率和科室服务质量，降低了消耗指标，也提高...

开发新产品项目贷款的调查分析

开发新产品项目贷款的调查分析张林斌近年来，随着改革的不断深入，根河市在开发新产品，引进新项目方面做了大量的工作。但终因经验不足，项目前期工作不够深入，可行性调查论证不充分等原因，给这项工作带来了很大的盲目性。在调查根河市自１９８５年以来的６４个开发引...

PMP模拟试题

1. One way to further team development is for the project manager to use a “personal touch” . Which of the following actions has proven effective toward this goal? A. Creating a team name B. Providing flexible work time C. issuing a project charter D. Celebrating special

一起唱歌学英语!

小朋友们，你看过《疯狂原始人》吗？这一期，QQ姐姐为大家带来的歌曲就是《疯狂原始人》的主题曲Shine Your Way。这首歌节奏轻快，歌曲励志。正如歌词“There＇s no time for us to waste.”所说的那样，我们应该珍惜时光，朝着前方勇敢奔跑，打造属于我们的灿烂未来！赶快去听听吧！