Coastal Crisis: The Failure of Coastal Management in the Spanish Mediterranean Region

It is a fact that coastal zones in the Mediterranean are becoming progressively more seriously degraded. Instrumental to the phenomenon in Spain is the evident failure of the coastal management that the institutions have pursued for over three decades, both under the old, state-centralized model, and the new organizational model with the political division of land into autonomous regions. This failure can in part be explained not only by the inadequate tools the administration possesses to address the dynamism and complexity of the new economic activities that have sprung up along the coast, but also by incoherent sectoral policies. Finally, there has been no all-encompassing political strategy capable of dealing with coastal communities' demands for development and the need for the protection of ecosystems and their natural resources. All this has resulted not only in a deterioration of the area, but also in the discrediting of actions implemented by the institutions, and their plans and programs being perceived as an obstacle to economic development.     

Fuel burn and environmental implications of airline hub networks

Hubs act as switching points for interactions and so are places through which flows are concentrated. This research uses the interactions between a system of cities as an experimental context for understanding selected environmental costs and benefits of concentrated flow. Whether hub based networks create additional environmental costs has been debated in the literature. In this paper, fuel burn is used as an indicator of environmental cost. The essential ideas are: (1) to examine fuel costs associated with larger aircraft; (2) to determine implications of higher loads on dense routes; and (3) to model the resulting implications for hub and gateway location. Variants of these questions apply to passenger and freight flows, and the paper will initially concentrate on passenger models.The paper shows that by modeling fuel burn and introducing a fixed charge (like a set up cost), a multiple allocation hub and spoke model can be adjusted to direct more or less flow onto the inter-facility connector. In other words, usage of multiple connections and direct links can be controlled and modeled as a function of the fixed charge. The resulting networks are characterized by quite different levels of passenger miles, aggregate fuel burn and fixed charges. The preferred network in terms of minimal fuel burn is found by subtracting the fixed set up charge, thereby focusing attention on the modeled fuel burn. The lowest cost set up is a network with a high degree of connectivity, and a pure single assignment hub network has the highest fuel cost (as a result of larger passenger miles needed by connecting paths). The data also allow a tabulation of total passenger miles, which, not surprisingly, track very closely with the fuel burn. In an interesting application of the ideas, it is shown that a fuel efficient network may require a large number of smaller regional jets, and in the interests of avoiding noise and congestion from so many extra airport operations, the carriers may choose to substitute a smaller number of larger planes, thereby slightly increasing fuel needs. This paper also provides a key ingredient for models of an international network where it is impossible to serve many long distance market pairs without consolidation.     

An Alert System for Beach Hazard Management in the Balearic Islands

A real-time beach hazard level associated with nearshore hydrodynamics is presented in this article. The suitability of the discussed alert system is illustrated via its application to fifteen beaches in the Balearic Islands (Western Mediterranean Sea) providing nearshore safety conditions for beach safety manager. The system provides daily forecasts of nearshore wave conditions using the deep water wave forecasts. The shallow water wave data (wave height, period, and direction) together with the morphology of the site (presence of bars, capes, beach type, etc.) are used to define a hazard level (low, medium, and high) associated with local conditions. The resulting hazard level is transmitted via SMS to lifeguards and local authorities for real-time beach management. The low computational cost of this system after the initial implementation and subsequent calibration results in a very suitable approach for beach management in order to mitigate risks related to local hydrodynamics.     

Simulation of dynamic interaction between train and railway turnout

Dynamic train-track interaction is more complex in railway turnouts (switches and crossings) than that in ordinary tangent or curved tracks. Multiple contacts between wheel and rail are common, and severe impact loads with broad frequency contents are induced, when nominal wheel-rail contact conditions are disturbed because of the continuous variation in rail profiles and the discontinuities in the crossing panel. The absence of transition curves at the entry and exit of the turnout, and the cant deficiency, leads to large wheel-rail contact forces and passenger discomfort when the train is switching into the turnout track. Two alternative multibody system (MBS) models of dynamic interaction between train and a standard turnout design are developed. The first model is derived using a commercial MBS software. The second model is based on a multibody dynamics formulation, which may account for the structural flexibility of train and track components (based on finite element models and coordinate reduction methods). The variation in rail profile is accounted for by sampling the cross-section of each rail at several positions along the turnout. Contact between the back of the wheel flange and the check rail, when the wheelset is steered through the crossing, is considered. Good agreement in results from the two models is observed when the track model is taken as rigid.     

Computation of surface temperatures and energy dissipation in dry friction clutches for varying torque with time

This paper describes an investigation of the energy dissipated and the surface temperature at any instant of dry friction clutch assuming torque being a function of time during the slipping. The equations of the thermal loads, total energy dissipated and relative velocity between contact surfaces are presented. Two-dimensional axisymmetric heat conduction problem of dry friction clutch is modeled mathematically and solved numerically using the finite element method to determine the temperature distribution during a single engagement assuming uniform wear between the contact surfaces. The comparison is made between temperature field assuming the torque varying with time and when it’s constant with time. Moreover, the effects of slipping time and dimensionless thickness of the pressure plate λ are to be investigated as well.     

Brushless PM machine drive in electric and hybrid electric vehicles based on the space vector current control

This paper presents a space vector current controller for a brushless permanent magnet motor in electric and hybrid electric vehicles. The proposed current controller selects space vectors based on the sector selection under a three-level hysteresis comparator to decrease the current ripple. The proposed approach can improve the performance of a brushless PM drive such as the average switching frequency and the total harmonic distortion (THD) compared with the conventional hysteresis current control. The experiment is performed first to verify the proposed control. Then, the method is implemented in a hybrid electric vehicle simulation model with standard driving cycles based on the control strategy to evaluate the drive performance in the vehicle system. The experimental and simulation results indicate that the presented control can improve the performance of the brushless PM machine drive.     

高速铁路对都市区一体化的影响 ——以伦敦、马德里和巴黎为例

高速铁路建设的最初目的是连接相距400~600 km的都市区.但是近年,都市地区的郊区及城市出现了一些边缘位置的高铁车站,距都市中心的距离约100 km.重点研究位于马德里(瓜达拉哈拉、塞戈维亚和托莱多)、伦敦(斯特拉特福德、艾贝斯费特和阿什福德)和巴黎(鲁瓦西—戴高乐、马恩河谷—谢西和马西)附近的9座外围高铁车站,分析它们对都市区及当地的影响,并提取对加利福尼亚州高速铁路项目可借鉴之处.     

Effect of minor elements on the creep resistance of Mg-Zn-Mn-(Ca) alloy

Along with alumium, titanium and composite alloys, magnesium alloys have been given much attention by industry for applications such as lightweight automobiles and electronics because of their high strength, low specific density and good damping characteristics. In this paper, creep tests were done with magnesium alloys (Mg-3% Zn-1% Mn, Mg-1.2% Zn-1% Mn, and Mg-3% Zn-1% Mn-0.3% Ca) containing different amounts of Zn to investigate the effect of Zn and Ca on the deformation behavior and the rupture time for Mg alloy creep under elevated temperatures. The alloys were obtained as follows: (1) pure magnesium (9.7 kg) was melted at 720°C in an SF6 atmosphere; (2) the temperature was increased up to 800–820°C after adding 0.3 kg of pure Mn to make the Mg-1% Mn master alloy; (3) the minor element (Zn, Ca) was added to the master alloy; and (4) the magnesium alloy melts were cast into a metallic mold preheated to 150°C. The creep tests were executed under a constant load and temperature to measure the steady-state rate and rupture time of creep. Based on the experimental results, the creep behavior of the alloys seemed to be controlled by dislocation climb at around 0.5∼0.55T_m (T_m; melting temperature). In addition, the results showed that the addition of Ca was effective for increasing the creep resistance of a Mg alloy: the more Zn present in the alloy, the stronger the creep strength of the alloy.     

Rollover mitigation for a heavy commercial vehicle

A heavy commercial vehicle has a high probability of rollover because it is usually loaded heavily and thus has a high center of gravity. An anti-roll bar is efficient for rollover mitigation, but it can cause poor ride comfort when the roll stiffness is excessively high. Therefore, active roll control (ARC) systems have been developed to optimally control the roll state of a vehicle while maintaining ride comfort. Previously developed ARC systems have some disadvantages, such as cost, complexity, power consumption, and weight. In this study, an ARC-based rear air suspension for a heavy commercial vehicle, which does not require additional power for control, was designed and manufactured. The rollover index-based vehicle rollover mitigation control scheme was used for the ARC system. Multi-body dynamic models of the suspension subsystem and the full vehicle were used to design the rear air suspension and the ARC system. The reference rollover index was tuned through lab tests. Field tests, such as steady state cornering tests and step steer tests, demonstrated that the roll response characteristics in the steady state and transient state were improved.     

Independently Rotating Wheel Systems for Railway Vehicles-A State of the Art Review

This paper surveys the state-of-the-art in the field of Independently Rotating Wheel systems (IRW) for railway vehicles. Various methods that have been adopted to provide guidance capability to the system are discussed. Results of the stability and response characteristics of such systems obtained through both experimental and analytical efforts by various researchers are reviewed. Some critical research needs are identified.