Optimal control of headway variation on transit routes

Headway control strategies have been proposed as methods for correcting transit service irregularities and thereby reducing passenger wait times at stops. This paper addresses a particular strategy which can be implemented on high frequency routes (headways under 10–12 minutes), in which buses are held at a control stop to a threshold headway. An algorithm is developed which yields the optimal control stop location and optimal threshold headway with respect to a system wait function. The specification of the wait function is based on the development of several empirical models, including a headway variation model and an average delay time model at control stops. A conclusion is reached that the headway variation does not increase linearly along a route, a common assumption made in many previous studies. Furthermore, the location of the optimal control stop and threshold value are sensitive to the passenger boarding profile, as expected. The algorithm itself appears to have practical application to conventional transit operations.     

传统氧传感器测试方法的局限性

采用以前认为可靠的测试方法诊断空燃比传感器或许会得出不可靠的结果,且所测数值有可能相反。实践证明,传统的氧传感器测试方法并不适合所有车型。     

GROWTH DIFFERENTIATION FACTOR-5 STIMULATES THE GROWTH AND ANABOLIC METABOLISM OF ARTICULAR CHONDROCYTES

Growthdifferentiationfactor5(GDF5),also knownascartilage derivedmorphogeneticprotein1(CDMP1),isamemberofthebonemorphogenet icprotein(BMP)familywhichbelongstothe transforminggrowthfactorβ(TGFβ)superfami ly[1].GDF5isarelativelynewmemberofthe BMPfamily.LikeotherBMPs,implantationofre combinantGDF5caninduceectopiccartilagefor mationinmusculartissues.Thephysiologicalrole ofGDF5hasbeenreportedincludingregulationof myogenesis,regulationofchondrogenesis,bone morphogenesis,andneurondifferen…     

重载轴承选型分析

介绍了重载轴承选型时应当考虑的影响因素,包括L10寿命、使用方式和维修方式等.     

马克的2008——2008年F1西班牙站

没有人怀疑法拉利将成为今年的主角,不过上天总喜欢和人开个小玩笑,因此在我的老家也就是今年的第一站澳大利亚上演了一点点小插曲。不过,真金不怕火炼,时间能证明一切,因此在马来西亚,巴林以及西班牙法拉利的实力得到了充分认可,     

Enhancing rail infra durability through freight bogie design

The extensive usage of railway infrastructure demands a high level of robustness, which can be achieved partly by considering (and managing) the track and rolling stock as one integral system with due attention to their interface. A growing number of infra managers consider, in this framework, the track-friendliness of vehicles that have access to their tracks as a key control parameter. The aim of this study is to provide further insight into potential contributions to track-friendliness, assessed in relation to track deterioration mechanisms and cost, understanding how potential benefits are best to be utilised. Six proposed freight bogie design measures are evaluated with respect to the improvement in curving behaviour, switch negotiation and related track degradation mechanisms. To this purpose a sensitivity analysis has been carried out by means of track–train simulations in the VAMPIRE® multi body simulation software. Additionally, the impact on track deterioration costs has been calculated for those track-friendly design modifications identified as most promising. Conclusions show that the standard Y25L freight bogie design displays rather a track-friendly behaviour. Tuning the primary yaw stiffness shows a high potential to further improve track-friendliness, significantly reducing track deterioration cost at narrow radius curves and switches (by, respectively, 30% and 60%). When calculating the overall deterioration cost for the travelled route, the calculation model should include a well-balanced representation of switches and narrow radius curves.     

EFFECT OF LOW SELENIUM ON CHONDROCYTE DIFFERENTIATION AND DIFFERENTIAL EXPRESSION OF COLLAGEN TYPES Ⅰ , Ⅱ AND X IN ARTICULAR CARTILAGE FROM MINI-PIGS

Objective According to the distribution of low selenium areas, low nutrition state of the residents and the affecting cartilage growth and articular cartilage of Kashin-Beck Disease(KBD),the chondrocyte differentia- tion and differential expression of collagen types Ⅰ , Ⅱ and Ⅹ in articular cartilage from Chinese mini-pigs treated with low selenium were investigated in order to gain insight into the effects of these conditions on chondrocyte differ- entiation in KBD cartilage. Mothods Eleven male juvenile mini-pigs, aged from 4 weeks to 6 weeks after birth, were divided into 3 groups. The Se content in the diet of the “low Se” group was 0. 035mg/kg diet, and 0. 175 mg/kg diet in the control. For Se-supplemented group 0. 390mg /kg diet was added. The content of Se in blood was assayed at the beginning and at the end of each experiment. Samples of articular cartilage were taken from the right femur condylus, and collagen types Ⅰ , Ⅱ and Ⅹ in articular cartilage were analyzed by immunohistochemistry and in situ hybridization. Results ①All cartilage samples from juvenile mini-pigs fed with low selenium diet revealed a re- duction in type Ⅹ collagen mRNA expression in the hypertrophic chondrocytes as shown by in situ hybridization, and reduced type Ⅹ collagen deposition in the lower hypertrophic zone as shown by immunohistochemistry. ②Addition of selenium to the diet restored the type Ⅹ collagen to normal level. ③Type Ⅱ collagen was evenly distributed over the entire articular cartilage in all experimental and control groups. Type Ⅱ collagen mRNA signals were most prominent in the upper articular layer as well as in the hypertrophic zone in all groups. Type Ⅱ collagen expression was restrict- ed to the zone of endochondral ossification in all experimental groups and the control. Conclusion Low selenium has an down-regulatory role on the synthesis and deposition of collagen type Ⅹ in hypertrophic chondrocytes in articular cartilage of mini-pigs. Supplement of the low Se diet with additional Se restored the signals of collagen type Ⅹ to nor- mal levels. These findings indicate that selenium deficiency may disturb chondrocyte differentiation to hypertrophic cells in the growth plate,and worthy to be investigated further.     

The congestion multiplier: Variations in motorists’ valuations of travel time with traffic conditions

The value of travel time savings in part depends upon the disutility of the travel time that is saved and partly on the use to which the time saved is put. It has long been recognised that the disutility of the time spent travelling also depends upon a wide range of factors such as the journey length or the effort, comfort and safety associated with travelling.Hence we might expect the value of motorists’ travel time to vary with the traffic conditions as represented by the degree of congestion, in part to reflect the more difficult driving environment when there are more vehicles, but also a higher sense of frustration, similar to that associated with waiting time and contributing to its premium valuation.In this context, and despite the predominance of car travel in developed countries, the empirical evidence specifically relating to car values of travel time tends to fail to distinguish between different types of time according to the degree of congestion. Thus we are often left unclear as to precisely what type of time has been valued. Moreover, when a distinction is made, it tends to be into a simple dichotomy of congested and uncongested traffic.This paper provides new evidence on the variation in the valuation of motorists’ travel time savings across a finer gradation of types of time than has been hitherto attempted. This is obtained from the same Stated Choice exercise conducted in the United Kingdom and the United States. The paper also provides an extensive account of previous research into how congestion impacts on motorists’ values of time.     

The evaluation of large cycling infrastructure investments in Glasgow using crowdsourced cycle data

Transportation - The benefits of cycling have been well established for several decades. It can improve public health and make cities more active and environmentally friendly. Due to the...     

Interpretation of cruise industry in a two-sided market context: An exploration on Japan

Two-sided markets are characterised by the presence of an intermediary and two groups of end-users. In the cruise market, cruise lines may play the role of intermediaries to connect the two end-users, viz. cruise passengers and cruise ports. Our research explored whether the cruise industry can be regarded as a two-sided market, starting with a theoretical modelling. The findings show that cruise lines might be hybrid intermediaries, selling their own ship-based products and services, while offering also a platform to enable the transaction between cruise passengers and cruise ports. This particular business model of a quasi-two-sided market is also reflected in the pricing scheme of cruise industry, whereby cruise ports charge an entry fee from cruise lines and port dues from cruise passengers. We illustrate an empirical analysis on the basis of the cruise market in Japan, and it provides a preliminary clue that the behaviours of cruise ports and cruise lines are consistent with our theoretical framework. The results are not convincingly significant due to data limitations, hence, the concept of a ‘two-sided market’ in the cruise industry call for further empirical research.