Auxiliary Reservoir Research Articles

AN EXPERIMENTAL STUDY OF THE EFFECT OF AN ADDITIONAL TANK ON THE DEFORMATION OF THE PNEUMATIC SPRING OF HIGH-SPEED RAILWAY ROLLING STOCK

The use of a pneumatic spring suspension system in the second stage of spring suspension of high-speed rolling stock is an integral component of ensuring its permissible dynamic indicators and traffic safety indicators. This work is aimed at researching the deformation characteristics of the rubber-cord shell of the pneumatic spring in the vertical and horizontal directions, taking into account manometric pressure, external load and an auxiliary reservoir. To achieve the goal, a methodology for experimental studies of pneumatic spring deformation was developed using a test rig with an assembled pneumatic spring suspension system, power and measuring equipment. Deformations of the rubber-cord sheath were measured by analog sensors of linear displacements using an analog-to-digital converter and special software. It was established that the effect of the auxiliary reservoir on the amount of vertical deformation of the lower part of the rubber-cord shell does not exceed 3.46 %, which allows us to conclude that the auxiliary reservoir of the pneumatic spring suspension system has a negligible effect on the vertical deformations of the lower part of the rubber-cord shell of the pneumatic spring. The dependences of the deformation of the rubber-cord shell of the pneumatic spring in the horizontal direction on the value of the manometric pressure when the auxiliary reservoir is connected and disconnected are obtained. It was established that in the range of manometric pressure changes of 1.0÷2.5 atm the presence or absence of an auxiliary reservoir has little effect on the amount of deformation of the rubber-cord sheath in the horizontal direction. However, at a pressure of more than 2.5 atm, closing the tap to the auxiliary reservoir leads to significantly greater deformation of the rubber cord shell compared to the deformation when the tap is open and the auxiliary reservoir is turned on. The obtained results regarding the deformation characteristics of the rubber-cord shell of the pneumatic spring will allow us to proceed to the study of the dynamic characteristics of the pneumatic spring, which are necessary when establishing safe conditions for the operation of modern high-speed rolling stock at the stage of its design.

Hydropeaking mitigation with re‐regulation reservoirs

AbstractThe role of hydropower as a renewable and balancing power source is expected to increase in a Net Zero Emissions by 2050 scenario. As a common phenomenon in hydropower plants, hydropeaking will become more prominent, resulting in additional stresses on the ecological status of rivers. Here we propose a novel approach to design and operate auxiliary reservoirs called re‐regulation reservoirs (RRR) that aim to mitigate the adverse impacts of hydropeaking on rivers. A re‐regulation reservoir aims at smoothing flow fluctuations caused by hydropeaking by diverting and retaining parts of high flows and returning them back to river corridors during low flows. Using actual data from a hydropeaking‐influenced river system, the operation and efficiency of potential reservoirs have been investigated. An open‐access algorithm was developed to analyze the influence of the reservoirs to mitigate hydropeaking, considering peak and minimum flow and up‐ and down‐ramping rates. The findings illustrate that, in most cases, the required reservoir volume increases as the flow thresholds become more stringent. Nonetheless, several exceptions were observed, where larger reservoir volumes were required compared with cases with more stringent thresholds. These findings highlight the importance of understanding the impact of flow adjustments, while carefully considering the river regime, sub‐daily flow patterns, and unique characteristics of the river's ecosystem. Our approach shows theoretical possibilities for regulating hydropeaking and provides a basis for optimizing re‐regulation reservoirs, contributing to practical and adaptable strategies for sustainable hydropower management without increasing the operational cost of power systems.

Hydrochemical stratigraphic analysis of the filling of the Meirama mine shaft I: monitoring and filling

The application of an old open-pit lignite mine as an auxiliary reservoir for the supply of the city of La Coruña has involved a detailed analysis of the chemical quality of the vertical profile. The study has shown that a stratified lake is formed where the shape of the filling (first with groundwater and later surface waters from the nearby rivers were added) has influenced the formation of the lake profile. The Meirama mine is an open-pit brown lignite mine located in NW Spain. Exploitation ended in March 2008, leaving a pit of approximately 146 hm3 with a maximum depth of 205 m. The rehabilitation of the pit consisted of the creation of a lake that will serve as an auxiliary water reservoir for the city of La Coruña. The filling process lasted approximately 8 years (March 2008–May 2016) with subterranean and surface contributions from the environment. The formation of an invariant chemocline and a seasonal thermocline was observed. Therefore, in this work, (the first of a series of two articles), an analysis of the evolution of various physicochemical parameters, elements, and compounds at certain heights (the surface, the first 2 m (2 mbs), at 59 masl, and at the bottom (2 masl)). In this first article, the physicochemical parameters of pH, dissolved oxygen, temperature, and some metallic elements (iron and manganese) are analysed. From the analyzed parameters it can be seen the creation of a surface thermocline and a chemocline at a depth of 59 masl with the beginning of the formation of anoxic conditions of the bottom of the pit through the consumption of oxygen.

Research on the air brake system of heavy haul trains based on neural network

To achieve precise prediction of the air pressure changes in the critical components of the air brake system, including brake pipes (BP), auxiliary reservoirs (AR), and brake cylinders (BC), this paper proposed a neural network-based air brake model developed from the brake application and release experimental data with different brake applications (50, 70, 100, and 150 kPa) conducted on a heavy haul train (HHT) test platform. The physical structures of the air brake system and the working mechanisms of a neural network are introduced, and the neural network-based air brake model scheme is presented by analysing the variation of air pressure within the air brake system under typical braking conditions (50 kPa). Besides, by comparing with other models, the superiority of the proposed model is verified, and the proposed model achieves higher computational efficiency, which increased by about 2900 times compared to the fluid dynamic model under the same conditions. Then, the model is applied to the calculation of the longitudinal dynamics of a 10,000-ton HHT, and the results demonstrate that the proposed model could serve as a promising tool for solving the braking excitation problem of longitudinal dynamics of trains and the study of intelligent braking control of trains.

Finding pythons in unexpected places

We argue that novel (highly nonclassical) quantum extremal surfaces (QESs) play a crucial role in reconstructing the black hole interior even for isolated, single-sided, non-evaporating black holes (i.e. with no auxiliary reservoir). Specifically, any code subspace where interior outgoing modes can be excited will have a QES in its maximally mixed state. We argue that as a result, reconstruction of interior outgoing modes is always exponentially complex. Our construction provides evidence in favor of a strong python’s lunch proposal: that nonminimal QESs are the exclusive source of exponential complexity in the holographic dictionary. We also comment on the relevance of these QESs to the geometrization of state dependence in the typicality arguments for firewalls.

Electro-Hydraulic Variable-Speed Drive Networks—Idea, Perspectives, and Energy Saving Potentials

Electro-hydraulic differential cylinder drives with variable-speed displacement units as their central transmission element are subject to an increasing focus in both industry and academia. A main reason is the potential for substantial efficiency increases due to avoidance of throttling of the main flows. Research contributions have mainly been focusing on appropriate compensation of volume asymmetry and the development of standalone self-contained and compact solutions, with all necessary functions onboard. However, as many hydraulic actuator systems encompass multiple cylinders, such approaches may not be the most feasible ones with respect to efficiency or commercial feasibility. This article presents the idea of multi-cylinder drives, characterized by electrically and hydraulically interconnected variable-speed displacement units essentially allowing for completely avoiding throttle elements, while allowing for hydraulic and electric power sharing as well as the sharing of auxiliary functions and fluid reservoir. With drive topologies taking offset in communication theory, the concept of electro-hydraulic variable-speed drive networks is introduced. Three different drive networks are designed for an example application, including component sizing and controls in order to demonstrate their potentials. It is found that such drive networks may provide simple physical designs with few building blocks and increased energy efficiencies compared to standalone drives, while exhibiting excellent dynamic properties and control performance.

DETERMINATION OF CHARACTERISTICS OF THROTTLING DEVICE FOR PNEUMATIC SPRING

Purpose. This paper focuses on determination of the dependence of the working medium flow on the capacity of the throttling device, its geometric features and the pressure difference in the pneumatic spring cylinder and in the auxiliary reservoir. Methodology. Calculation of the dependence of the working medium and pressure drop is performed in two ways: 1) by numerical simulation of a stationary gas flow through a throttling element; 2) its analytical calculation expression using empirical relationships (control calculation to evaluate the reliability of numerical simulation results). For the calculation, three models of throttling devices were chosen. Dependence of the flow rate of the working medium on the capacity of the throttling device and its geometric features was determined based on the approximation of the dependency graphs of the pressure drop against the mass flow rate of the working medium. Findings. We obtained graphical dependencies between the pressure drop and the mass flow rate of the working medium from the two calculation options. Based on the results of calculations performed with the help of a software package with visualization of the results, we calculated a proportionality coefficient that describes the dependence of the working medium flow on the throttling device capacity and its geometric features for each of the throttling elements considered, with three degrees of closure. The air flow values, obtained by numerical simulation, are greater than the flow rates obtained from semi-empirical formulas. At the same time, they are in good qualitative agreement, and the quantitative difference averages 25%, which can be regarded as confirmation of the reliability of the nu-merical model. Based on the calculation results, we plotted the proportionality coefficient graphs against the degree of closure of the throttling device. Originality. The work allows determining the degree of influence of the frictio-nal component on the variation of the pressure difference in the pneumatic cylinder and the auxiliary reservoir of the pneumatic suspension system. Also, the work proposes a method to determine the dependence of the working medium on the capacity of the throttling device and its geometric features. Practical value. The ability to predict the operating parameters of the pneumatic system depending on the pneumatic resistance of the throttling device will improve the car running characteristics, increase the comfort of passenger transport, and also reduce the wear of the rolling stock and track gauge due to vehicle-track interaction.

Development of a kw-class Stirling cryocooler for liquefaction of natural gas (NG)

Our research group has developed a kW-class Stirling cryocooler. The Stirling cryocooler adopts a ‘gamma-type’ configuration operated with a linear compressor. The cold-end of the Stirling cryocooler is equipped with heat exchangers that can accept and eventually liquefy natural gas (NG). The liquefied natural gas (LNG) is stored in an auxiliary reservoir. In this research paper, the experiments as a proof of concept has been carried out. The Stirling cryocooler has been independently tested prior to adopting the heat exchanger as the aforementioned above. It has been confirmed that the Stirling cryocooler can exert over 1 kW cooling capacity at 110 K cold-end temperature with 9 kW compressor input. This research paper mainly focuses on (1) relevant technical issues during the cooler development process and (2) demonstrating the liquefaction of argon gas (instead of using NG for the sake of safety regulation). The system presented in this paper, therefore, can be a good candidate for a small-scale liquefier does not require oil-involved maintenance.

Autonomous quantum state transfer by dissipation engineering

Quantum state transfer from an information-carrying qubit to a receiving qubit is ubiquitous for quantum information technology. In a closed quantum system, this task requires precisely-timed control of coherent qubit-qubit interactions that are intrinsically reciprocal. Here, breaking reciprocity by tailoring dissipation in an open system, we show that it is possible to autonomously transfer a quantum state between stationary qubits without time-dependent control. We present the general requirements for this directional transfer process, and show that the minimum system dimension for transferring one qubit of information is 3 $\times$ 2 (between one physical qutrit and one physical qubit), plus one auxiliary reservoir. We propose realistic implementations in present-day superconducting circuit QED experiments, and further propose schemes compatible with long-distance state transfer using impedance-matched dissipation engineering.

Analisa Gangguan Pada Hasil Perawatan Distributor Valve Kereta

Distributor valve adalah salah satu bagian dari sistem pengereman udara yang berfungsi sebagai pengatur tekanan antara brake cylinder, auxiliary reservoir dan brake pipe pada sistem pengereman yang memerlukan perawatan. Kenyataan di lapangan, pada saat dilakukan perawatan masih ditemukan gangguan pada distributor valve, sehingga hal tersebut dinilai menghambat efektifitas perawatan. Oleh sebab itu perlu dilakukan penelitian untuk mengetahui faktor apa saja penyebab sering terjadinya gangguan pada perawatan distributor valve. Pada penelitian ini dilakukan analisa menggunakan diagram pareto untuk mengetahui presentase gangguan yang sering terjadi pada hasil perawatan distributor valve. Setelah dilakukan analisa, hasilnya adalah 1) tekanan pada brake cylinder lebih dari 3.8 bar sebesar 37,7 %, 2) waktu release lebih dari 20s waktu (standar 15-20s) sebesar 26,6 %, 3) waktu application/brake lebih dari 5s (standar 3-5s) sebesar 20 % dan 4) kebocoran pada celah-celah distributor valve sebesar 15,5 %. Dari hasil penelitian dan pengamatan langsung di lapangan dapat diketahui bahwa faktor penyebab gangguan setelah dilakukan perawatan distributor valve pada kereta adalah ketidaksesuaian prosedur dan alat yang digunakan untuk merawat distributor valve.

Implementation of electronically controlled pneumatic brake formulation in longitudinal train dynamics algorithms

The main goal of this investigation is to integrate an electronically controlled pneumatic (ECP) brake model with efficient longitudinal train force algorithms based on the trajectory coordinate formulations. The ECP brake model, developed in this investigation consists of the train line (cable), locomotive automatic brake valve, air brake pipe, and ECP manifold. The train line, which covers the entire length of the train, allows the brake commands to be received by the car simultaneously. While pneumatic pressure is used to generate the braking forces, the brake pipe is no longer used to provide the brake level commands. Instead, the brake pipes are used to provide a continuous supply of compressed air stored in a reservoir mounted on each railcar. Using the ECP system to apply the brakes uniformly and instantaneously gives better train control, shortens the stopping distances, and leads to a lower risk of derailment. In this investigation, the fluid continuity and momentum equations are used to develop the governing air pressure flow equations. These partial differential equations are converted to a set of ordinary differential equations using the finite element method leading to an air brake force model that accounts for the effect of the air flow in long train pipes as well as the effect of leakage and branch pipe flows. The car brake forces are applied to the wheels using the ECP manifold located in each car. The ECP manifold used in this investigation has four valves: cut-off valve, vent valve, auxiliary valve, and emergency valve. The ECP manifold is connected to three main pneumatic components: the auxiliary reservoir, the emergency reservoir, and the brake cylinder. The reservoirs serve as the main storage of the pressurized air, while the brake cylinder and other mechanical components such as the rigging and the brake shoes transmit the brake force to the wheels. In this investigation, a mathematical model of the ECP manifold and its components is developed. The relationship between the main components of the ECP brake system and the train dynamics is discussed, and the final set of differential equations that integrates the ECP brake and train dynamics is presented. Different simulation scenarios are considered in this study in order to investigate the effect of the brake forces on the train longitudinal dynamics in the case of different braking scenarios. The performance of the developed ECP brake system is compared with the Association of American Railroads safety and operation standards, and with experimental results published in the literature.

Development of electronic diagnostic system for improving the diagnosis reliability of passenger car brakes

The mathematical model that allows determining the pressure in the brake cylinder, distributor chambers and auxiliary reservoir of the car depending on the absolute pressure changes in the air flow through the throttle openings for a scheduled time is developed in the paper for diagnosing the parameters of the brake system of the individual car or train. It is embedded in the hardware-software system algorithm. This allows simulating the operation of the serviceable brake equipment and provides a high accuracy of identifying the diagnostic features of the technical condition of pneumatic systems of passenger cars. The modern system of remote control of the passenger train brakes, which allows remote control of the brake equipment of the train and individual car during travel or at stops at the section and intermediate stations, is developed. The experimental data, recorded during the monitoring of basic parameters of the brake equipment by the electronic diagnostic system of car brakes are checked for the adequacy with the analytical data by the mathematical model. Their correlation is proved.

DEPENDENCE OF AIR SPRING PARAMETERS ON THROTTLE RESISTANCE

Purpose. In this paper it is necessary to conduct: 1) research and analyse the influence of throttle element pneumatic resistance on elastic and damping parameters of air spring; 2) to obtain the dependence of air spring parameters on throttle element pneumatic resistance value. Methodology. The work presents the elaborated model of the air spring as a dynamic system with three phase coordinates (cylinder pressure, auxiliary reservoir pressure, cylinder air mass). Stiffness and viscosity coefficients were determined on the basis of system response to harmonic kinematic disturbance. The data for the analysis are obtained by changing the capacity of the connecting element and the law of pressure variation between the reservoir and the cylinder. The viscosity coefficient is regarded as the viscosity ratio of the hydraulic damper, which for one oscillation cycle consumes the same energy as the air spring. The process of air condition change inside the cylinder (reservoir) is considered to be adiabatic; the mass air flow through the connecting element depends on the pressure difference. Findings. We obtained the curves for spring viscosity and stiffness coefficients dependence on the throttle resistance at three different laws, linking airflow through the cylinder with the pressure difference in cylinder and reservoir. At both maximum and minimum limiting resistance values the spring viscosity tends to zero, reaching its peak in the mean resistance values. Stiffness increases monotonically with increasing resistance, tends to the limit corresponding to the absence of an auxiliary reservoir (at high resistance) and the increase in cylinder volume by the reservoir volume (at low resistance). Originality.The designed scheme allows determining the optimal parameters of elastic and damping properties of the pneumatic system as function of the throttle element air resistance. Practical value.The ability to predict the parameters of elastic and damping properties of the pneumatic system as function of the throttle element air resistance will improve the running performance of carriages, the comfort of passenger transportation and reduce the wear of the rolling stock and the track caused by interaction of carriage and rails.

IMPROVING WATER PRODUCTIVITY THROUGH MICRO‐IRRIGATION IN ARID PUNJAB REGIONS

ABSTRACTInadequate water supply in a canal command area is a major limiting factor for sustainable crop production, as well as for adoption of crop diversification options. Shifting from conventional (surface) irrigation to micro‐irrigation in conjunction with an auxiliary reservoir is a possible alternative for managing irrigation water shortages. The auxiliary reservoir provides a reliable water supply for the micro‐irrigation system during the period when the canal system is not operational. To study the techno‐economic feasibility of a proposed technological package, an auxiliary reservoir of 1500 m3 capacity was constructed at the Research Farm of Central Institute of Post Harvest Engineering and Technology, Abohar, India, which received a canal supply from an outlet of the Panjawa minor of the Abohar distributory of the Sirhind canal system. Drip irrigation was used to irrigate kinnow (Citrus reticulata Blanco.), guava (Psidium guajava L.), pomegranate (Punica granatum L.), tomato (Lycopersicum esculentum L.) and capsicum (Capsicum annuum L.). Drip and micro‐sprinkler both were used for potato (Solanum tuberosum L.) and onion (Allium cepa L.). These crops were also grown with surface irrigation methods (border or furrow depending upon the crop) as control. Results of the study indicated that the interventions were able to save a substantial amount of irrigation water (3–46%) compared to surface methods, along with higher yields, a doubling of water productivity and more profits per mm of irrigation water. The study clearly showed that micro‐irrigation in conjunction with an auxiliary reservoir should be recommended in canal‐irrigated commands in order to improve water productivity and farmers' income in arid regions of Punjab. Copyright © 2013 John Wiley & Sons, Ltd.

A train air brake force model: Car control unit and numerical results

This and a companion paper focus on the integration of a model of a train’s air brake and a non-linear model of a train’s dynamics based on the use of trajectory coordinate formulations. The forces developed by the air brake depend on various system components, including the automatic brake valve, the brake pipe and the car control unit (CCU). The developed braking forces, which depend on the position of handle of the automatic brake valve, are applied to the wheels using the CCU located along the brake pipe and enter into the formulation of the non-linear dynamic equations for the train in addition to other external forces. In order to develop an efficient computational procedure, simplified valve models, with more straightforward operation modes, are considered in order to reduce the computational overhead. The CCU used in this research has a control valve connected to three main pneumatic components: the auxiliary reservoir, the emergency reservoir and the brake cylinder. The reservoirs are the main storage area of the pressurized air, while the brake cylinder transmits the brake force to the wheels using the mechanical components of the CCU, including the brake rigging and the brake shoes. The communications between different parts connected to the control valve are controlled by its slide valve that can be positioned in the brake application, brake release and lap positions. It is also assumed that the CCU modeled in this study has the emergency portion that enables it to apply emergency braking, including the effect of the CCU’s emergency vent valve. In this paper, a mathematical model for the CCU is developed, while the locomotive automatic brake valve and brake pipe models are developed in a companion paper. The relationship between the main components of the air brake system and the train dynamics is discussed, and the final set of differential equations that includes the two models is presented. Furthermore, different computer simulation scenarios are considered in this paper in order to investigate the effect of the air brake forces on the train’s longitudinal dynamics for cases of different braking modes. The numerical results, obtained in this study, are compared with experimental results published in the literature.

Model development and experimental research on an air spring with auxiliary reservoir

This paper focuses on the dynamic stiffness and overall equivalent damping of an air spring connected to an orifice and an auxiliary reservoir, with respect to the displacement excitation frequency, orifice area, and auxiliary reservoir volume. A theoretical model of this air spring with its auxiliary reservoir is derived by utilizing the energy conservation equation, gas state equation, and orifice flow rate equation. Simulation results from the presented model reveal that, when the air spring is subject to harmonic displacement excitation, its dynamic stiffness increases with an increase in excitation frequency and decrease in orifice area. Smaller orifice areas and lower excitation frequencies result in higher overall equivalent damping. A validation experiment is also implemented. When compared with experimental results, simulations show consistent varying trends of the dynamic stiffness and overall equivalent damping. The model developed here can correctly describe the behavior of the air spring with auxiliary reservoir, indicating that it is reasonable and feasible.

Proposed model for efficient water management at Razmgan irrigation project, a semi-arid region in Khorasan, Iran

Yield decrease caused by crop water deficit, especially in low scale farms and established orchards at semi-arid regions, results in a significant decrease in agricultural productivity. In this study an optimal water release of the reservoir based on prioritization in water allocation to the crop sensitive growth periods was linked to a non-linear optimization model in order to enhance the net income in a given cropping pattern. The proposed model by optimal water allocation for each growth stage of the crop reduced the impact of the imposed water stress in the dry season and increased the net income. The LINGO software has been used to evolve the optimal amounts of both water and land for the existing crops. The proposed model was applied for Razmgan area a semi-arid region which is located 10 km south of the Shirvan city, northern Khorasan province, Iran. Various scenarios of the water release from the existing auxiliary reservoir, to remove/reduce the imposed water-stress during the crop growth stages have been explored. Results show in the optimal case, whole of the existing water deficit is removed in months of July, August, September, October and November, only 13% of the deficit remains in month of May and in month of June the amount of deficit decreases to 42.16%. Also the proposed model is efficient and annual net income will increase to 26.21%, moreover, the total water consumption will decrease to 10.71% than the current status. Key words: Water deficit, agriculture income, sensitive growth stages, cropping pattern, optimal water release.

Simulation of a freight train brake system with 120 valves

A freight car air brake system simulation model that is based on air flow dynamics and function principle of the ‘120’ control valve is established. Functions of unsteady air flows in the air brake pipes, the boundary conditions used in the air brake system, and the calculation method for pressures in the brake pipe, brake cylinder, and auxiliary air reservoir are discussed. A comparison of the simulation results with the experiment test results is made to verify the validity of the simulation. The results of the simulations, including long and short train with large and small pressure reduction service brake application, release, and emergency brake application, show good consistence with the experiment results on pressure change and its timing in the brake pipe, brake cylinder, and auxiliary reservoir, with the exception of long train at small pressure reduction application. This indicates that the simulation model can correctly predict the pressure behaviour of the unsteady air flows in the air brake system and component movements in the ‘120’ control valve. The model can simulate braking characteristics of a freight train consisting of up to four locomotives. The simulation results can be used to successfully predict the braking distances and to assist longitudinal, dynamic, and impact force analyses of a train. The simulation is useful in the design, research, and development of brake systems and can provide insight into how components of the ‘120’ air brake control valve work.

Nonequilibrium Green’s function formalism and the problem of bound states

The non-equilibrium Green's function formalism for infinitely extended reservoirs coupled to a finite system can be derived by solving the equations of motion for a tight-binding Hamiltonian. While this approach gives the correct density for the continuum states, we find that it does not lead, in the absence of any additional mechanisms for equilibration, to a unique expression for the density matrix of any bound states which may be present. Introducing some auxiliary reservoirs which are very weakly coupled to the system leads to a density matrix which is unique in the equilibrium situation, but which depends on the details of the auxiliary reservoirs in the non-equilibrium case.

Air Suspension Dimensionless Analysis and Design Procedure

This article presents the dimensionless model and the design considerations of a pneumatic suspension with auxiliary reservoir. The dimensionless model provided makes it possible to fully understand the effect of the parameters which define the suspension and to select the spring type correctly. Without this selection, the suspension generates transmissibility curves with excessive amplification in the vicinity of the resonance, even after optimum definition of auxiliary volume and resistance. This aspect is the key point for defining effective applicable solutions. The design considerations provided at the end of the work constitute a useful résumé and a guide for designing suspensions of the type described.