Flow control characteristics of the digital and mechanical redundancy control electric modulation valve

The electrical modulation valve can provide proportional output valve element displacement,flow,or pressure according to a continuously changing input electrical signal.It is the core component of electro-hydraulic proportional control technology.To remove the influence of pressure difference changes on the output flow,the traditional scheme is to use a pressure compensation valve,which increases the difficulty of both manufacturing and maintaining the valve.To solve this problem,a method of digital and mechanical redundancy control flow is proposed.Pressure sensors are installed at the inlet and outlet of the valve,and the controller adjusts the displacement of the valve element according to the pressure difference between the valve ports to realize high-precision control of the flow.A pressure compensation valve is installed in front of the valve,and a three-way solenoid valve is used to control the working of the compensation valve.In the case of sensor failure,the valve is switched to the mechanical compensation differential pressure mode,to control the flow and to achieve redundancy control.The system security is thereby improved.The feasibility of this scheme is verified through simulation and tests.The results show that,both for digital compensation and mechanical compensation,the output flow can be kept constant when the pressure difference changes,and the system has good static and dynamic characteristics.The principle can be applied to the displacement-flow feedback type electrical modulation valve,and can realize accurate control of the flow of the pilot valve and,finally,accurate control of the flow in the main valve.

The Mechanism of Structural Control of Ore Formation and Geochemical Characteristics in the Massive Sulfide Deposits of the Wushan Copper Ore Field,Jiangxi

The ore-controlling mechanism of the bedding fault system in the massive sulfide deposits of the Wushancopper orefield may be generalized as the control of ore deposition by optimum surface in an ore-formingstructural trap. The mechanism has three major features: (1) timing of mineralization; (2) positioning of hostformation; and (3) dependence of ore-controlling structure on properties of rocks. The 'optimum surface' is adivisional structural plane which marks obvious difference in physical, chemical and mechanical properties andis favorable for mineralization. It is also a unity of structures. lithofacies and orebodies. The structural and geochemical characteristics of the ore deposits indicate the migration trend of the ma-jor characteristic clements in the ore-controlling fault belt: elements with a small radius (Si, Fe, Mg and Al)moved towards and concentrated at the center of the belt while large-radius ones (Ca, K and Na) were remotefrom the center.

Cutting Characteristics of Force Controllable Milling Head

In order to control cutting force and its direction i n milling operation, a new milling head was developed. The head has two milling cutters, which are connected by a pair of gears and rotate in opposite direction respectively. Both up-cut and down-cut can be carried out simultaneously by t hese milling cutters. The each depth of cut, the ratio of up/down cutting depth , by these cutters can be also selected. The cutting force characteristics were experimentally discussed by changing the ratio. The cutting force and its locus can be also changed by the selection of the ratio of up/down cutting depth. For practical usage of the head the analytical prediction method of the cutting forc e characteristics under selected cutting condition was proposed based on the ene rgy approach method proposed, in which both of cutting force characteristics of a single milling cutter and the combined milling cutter under a selected up/dow n cutting depth ratio were analytically estimated based on the two dimensional c utting data. It was experimentally shown that in NC milling machine the cutting force locus was controlled in pre-determined direction under various tool paths .

Rolling Control Characteristic Experimental Investigation of a Canard Missile with Free-Spinning Tail

To study the rolling control characteristics of a canard-controlled missile, a series of wind tunnel experiment is conducted. The experimental method, the structure features of wind tunnel model and the experimental results are introduced in this paper. The experimental data show that the canard is an inefficient rolling control device for canard-controlled missile with fixed tail fins; but for the free-spinning tail fin configuration, the canard can conduct rolling control of the missile, and even have higher controlling efficiency under larger canard deflection angle.

Harm,Reproduction,Invasion and Control of Spodoptera frugiperda

Spodoptera frugiperda is becoming more and more widely distributed in various regions of the world,and it does more and more harm to agriculture,which seriously affects the growth and development of crops.In this paper,focuses were laid on the harm,reproduction,invasion and control of Spodoptera frugiperda,with the aim to provide more scientific bases for agricultural departments to guide agricultural production and pest control.

Time-domain characteristics of overlying strata failure under condition of longwall ascending mining

Ascending mining is one of the most effective ways to solve problems of water inrush, gas outburst and rock burst in coal seams mining. In order to reveal the law of motion and spatiotemporal relationship of overlaying strata, field measurement has been done in a mine. Long distance drillings were constructed from 4# coal seam to 6# coal seam at several certain typical positions, and movement and failure law of overlying strata after mining was analyzed by drilling video and observing the fluid leakage. Besides, we also analyzed the spatiotemporal development law of overlying strata failure with different mining heights and time intervals in the lower coal seam. The results show that: ascending mining is significantly affected by time-domain characteristics of overlaying strata failure after the lower coal seam's mining, height equations of caving zone and fractured zone are given in this paper, and the feasibility of ascending mining was compartmentalized concretely according to the spatiotemporal relationship. Research methods and conclusions of this paper have certain referential significance for the study of ascending mining, mining under water, mining under building, mining under railway and stress-relief mining.

Analysis of Control Characteristic for the Drive System of Electric Transit Bus

The drive control system of the permanent magnetic direct current motor with the enhanced magnetism windings used in the electric transit bus is developed. The mathematics model of the drive control system for this motor is established. The new mode that the added exiting magnetism field could be weakened and the speed of the motor could be controlled automatically is proposed and realized. The method of root locus design is applied to analyze the acceleration control characteristic. The results of simulation show that the new drive motor control system has extraordinary response characteristic and adjustable performance. Experiments of vehicle running show that the drive control system's antijamming ability is strong and the adjustable performance is fast and smooth, it can meet the demand of power characteristic very well.

The Channel Characteristics Analysis of Two River Types in Lee's Ferry Area

Discovery showed that some of the rivers in Lee＇s Ferry area run on bedrocks while some are on the alluvium,based on geomorphology,the different kinds of channel characteristics can influence whether these rivers run on bed rock or alluvium. By analyzing the velocity,discharge,width and depth,hydraulic radius and comparing the different channel characteristics of rivers in other areas with Lee＇s Ferry,it is observed that the channel discharge,velocity and the hydraulic radius play an important role in controlling the transport-limited river and these factors can be inferred to be correct even for all the river channels in Arizona.

Direct Digital Frequency Control Based on the Phase Step Change Characteristic between Signals

We present a new digital phase lock technology to achieve the frequency control and transformation through high precision multi-cycle group synchronization between signals without the frequency transformation circuit. In the case of digital sampling, the passing zero point of the phase of the controlled signal has the phase step characteristic, the phase step of the passing zero point is monotonic continuous with high resolution in the phase lock process, and using the border effect of digital fuzzy area, the gate can synchronize with the two signals, the quantization error is reduced. This technique is quite different from the existing methods of frequency transformation and frequency synthesis, the phase change characteristic between the periodic signals with different nominal is used. The phase change has the periodic phenomenon, and it has the high resolution step value. With the application of the physical law, the noise is reduced because of simplifying frequency transformation circuits, and the phase is locked with high precision. The regular phase change between frequency signals is only used for frequency measurement, and the change has evident randomness, but this randomness is greatly reduced in frequency control, and the certainty of the process result is clear. The experiment shows that the short term frequency stability can reach 10-12/s orders of magnitude.

Simple PID Parameter Tuning Method Based on Outputs of the Closed Loop System

Most of the existing PID parameters tuning methods are only effective with pre-known accurate system models, which often require some strict identification experiments and thus infeasible for many complicated systems. Actually, in most practical engineering applications, it is desirable for the PID tuning scheme to be directly based on the input-output response of the closed-loop system. Thus, a new parameter tuning scheme for PID controllers without explicit mathematical model is developed in this paper. The paper begins with a new frequency domain properties analysis of the PID controller. After that, the definition of characteristic frequency for the PID controller is given in order to study the mathematical relationship between the PID parameters and the open-loop frequency properties of the controlled system. Then, the concepts of M-field and θ-field are introduced, which are then used to explain how the PID control parameters influence the closed-loop frequency-magnitude property and its time responses. Subsequently, the new PID parameter tuning scheme, i.e., a group of tuning rules, is proposed based on the preceding analysis. Finally, both simulations and experiments are conducted, and the results verify the feasibility and validity of the proposed methods. This research proposes a PID parameter tuning method based on outputs of the closed loop system.

Evaluation of Beauveria bassiana （Hyphomycetes） isolates as potential agents for control of Dendroctonus valens

The red turpentine beetle （RTB）, Dendroctonus valens LeConte, as a destructive invasive pest, has become one of the most economically important forest pest in China. Effective control measures are desperately needed. Entomopathogenic fungi, such as Beauveria bassiana, have shown great potential for the management of some bark beetle species. In this study, 12 isolates of B. bassiana from bark beetle were examined for biological characteristics and virulence, to assess their potential as biocontrol agents for RTB. There were significant differences （at P = 0.05） in colony growth rate, conidial yield, conidial germination, tolerance to UV light and extracellular proteases activity among the tested B. bassiana isolates. Isolates, including Bbl801, Bb1906, Bb789 and Bb773, exhibited the best characteristics, because they have faster hyphal growth rate, higher spore production and faster spore germination, higher UV tolerance and protease （Prl） production. The results of a pathogenicity test ofB. bassiana on RTB larvae showed that most isolates of B. bassiana have demonstrated high efficacy and the highest virulent isolate was Bb 1801, which killed 100% of the treated insects and had a median lethal time （LT50） of 4.60 days at a concentration of 1 ×107 conidia/mL. Therefore, isolate Bb1801 has a great potential for sustainable control of RTB in the forest. The correlation between biological characteristics and virulence of the fungal isolates is discussed and the possibility of combination of entomopathogenic fungi with semiochemicals, as one of the promising strategy for RTB control, is considered.

Parametric analyses on dynamic stall control of rotor airfoil via synthetic jet

The effects of synthetic jet control on unsteady dynamic stall over rotor airfoil are investigated numerically. A moving-embedded grid method and an Unsteady Reynolds Averaged Navier-Stokes（URANS） solver coupled with k-x Shear Stress Transport（SST） turbulence model are established for predicting the complex flowfields of oscillatory airfoil under jet control. Additionally, a velocity boundary condition modeled by sinusoidal function has been developed to fulfill the perturbation effect of periodic jet. The validity of present CFD method is evaluated by comparisons of the calculated results of baseline dynamic stall case for rotor airfoil and jet control case for VR-7 B airfoil with experimental data. Then, parametric analyses are conducted emphatically for an OA212 rotor airfoil to investigate the effects of jet control parameters（jet location, dimensionless frequency, momentum coefficient, jet angle, jet type and dual-jet） on dynamic stall characteristics of rotor airfoil. It is demonstrated by the calculated results that efficiency of jet control could be improved with specific momentum coefficient and jet angle when the jet is located near separation point of rotor airfoil. Furthermore, the dual-jet could improve control efficiency more obviously on dynamic stall of rotor airfoil with respect to the unique jet, and the influence laws of dual-jet＇s angles and momentum coefficients on control effects are similar to those of the unique jet. Finally,unsteady aerodynamic characteristics of rotor via synthetic jet which is located on the upper surface of rotor blade in forward flight are calculated, and as a result, the aerodynamic characteristics of rotor are improved compared with the baseline. The results indicate that synthetic jet has the capability in improving aerodynamic characteristics of rotor.

On the hydrodynamics of hydraulic machinery and flow control

Hydraulic machinery mainly includes turbine and pump, which is closely related to national economy and people＇s livelihood involving aerospace industry, marine engineering, hydropower engineering, petroleum industry, chemical industry, mining industry, biomedical engineering, environmental engineering, agricultural water-soil engineering, etc.. The internal flow of hydraulic machinery is extremely complex, and its characteristics can be summarized as high Reynolds number, multi-scales, inhomogeneous and vortex-dominant unsteady turbulence which interact with the rotating dynamic boundary（rotor blade）. Based on the analysis of the internal flow characteristics of hydraulic machinery, the author and his research team successively proposed a rotation correction model, a curvature corrected filter-based model, a scalable detached eddy simulation method, and a non-linear hybrid RANS/LES turbulence model to capture unsteady flow structures and then predict hydraulic performance and dynamic characteristics more accurately. According to the analysis on the internal flow, the corresponding flow control measures were put forward. It was verified by experiments that these methods could significantly improve the hydraulic performance, anti-cavitation performance and dynamic characteristics（pressure pulsation and vibration） of hydraulic machinery in a certain range of operating conditions. In addition, the mechanism how flow control measures influence internal flow was analyzed in depth, aiming at finding a feasible and effective way to improve hydraulic performance, anti-cavitation performance and dynamic characteristics of hydraulic machinery.

Mercury mass flow in iron and steel production process and its implications for mercury emission control

The iron and steel production process is one of the predominant anthropogenic sources of atmospheric mercury emissions worldwide. In this study, field tests were conducted to study mercury emission characteristics and mass flows at two iron and steel plants in China. It was found that low-sulfur flue gas from sintering machines could contribute up to41% of the total atmospheric mercury emissions, and desulfurization devices could remarkably help reduce the emissions. Coal gas burning accounted for 17%–49% of the total mercury emissions, and therefore the mercury control of coal gas burning, specifically for the power plant burning coal gas to generate electricity, was significantly important. The emissions from limestone and dolomite production and electric furnaces can contribute29.3% and 4.2% of the total mercury emissions from iron and steel production. More attention should be paid to mercury emissions from these two processes. Blast furnace dust accounted for 27%–36% of the total mercury output for the whole iron and steel production process. The recycling of blast furnace dust could greatly increase the atmospheric mercury emissions and should not be conducted. The mercury emission factors for the coke oven,sintering machine and blast furnace were 0.039–0.047 g Hg/ton steel, and for the electric furnace it was 0.021 g Hg/ton steel. The predominant emission species was oxidized mercury, accounting for 59%–73% of total mercury emissions to air.

A Design of the Quantizer of H.261 CODEC

This paper introduces two steps to design a quantizer of H. 261 CODEC: thefirst step is to implement the coarse quantizing through control algorithm for the buffer' soccupation ratio ; the second step is to finish the accurate uantizing through the control algorithmof visual characteristics . Moreover, satisfactory effects are got using these algorithms throughexperiment.