LOCAL STUDIES OF ICE COVER EFFECTS ON DAM GATES

The experience of operation of surface emergency gates in ice-breaking conditions at a number of hydroelectric power plants has shown the insuffi cient eff ectiveness of the methods used to combat freezing of structures. The rules for technical operation of spillway dam gates in winter provide for heating of structures by slots, threshold and skin in conjunction with measures to maintain mines before construction. However, measures to heat gates and build mines are not always suffi ciently justifi ed and justifi ed. In order to obtain full-scale data and scientifi c information for the development of recommendations on operating and accounting modes during design, full-scale studies of stresses and defl ections in the load-bearing elements of the watershed gate of the hydroelectric power station were carried out. This article presents the results of fi eld studies in comparison with calculated values. As a result of the studies, information on the static operation of fl at gates in winter conditions is obtained, which is of theoretical and practical interest. The materials can be used to clarify technical operation rules and to clarify regulatory documents for the design of hydromechanical equipment at hydroelectric power stations.

A dynamically controlled anaerobic/aerobic granular sludge reactor efficiently treats brewery/bottling wastewater

This study investigated the application of a dynamic control strategy in an aerobic granular sludge (AGS) reactor treating real variable brewery/bottling wastewater. For 482 days, the anaerobic and aerobic reaction steps in a lab-scale AGS system were controlled dynamically. A pH-based control was used for the anaerobic step, and an oxygen uptake rate (OUR) based control for the aerobic step. Additionally, the effect of an elongated aerobic step, and the effect of the removal of the suspended solids from the influent, on AGS formation were also investigated. In comparison to a static operation, the dynamic operation resulted in similar reactor performance, related to effluent quality and the anaerobic dissolved organic carbon (DOC) uptake efficiency, while the organic loading rate was significantly higher. The removal of suspended solids from the influent by chemical coagulation with FeCl3 turned hybrid floccular-granular sludge into fully granular sludge. The granulation coincided with a significant increase in the abundance of the glycogen-accumulating Candidatus Competibacter and an increase in the content of gel-forming EPS to respectively around 14 and 30%. In conclusion, this study showed the successful application of a dynamic control strategy based on common and low-cost sensors for AGS treatment of industrial wastewater.

STABILITY OF THE METAL FRAME ELEMENTS WHEN WORKING IN CRAMPED CONDITIONS

The static operation of the building frame elements formed from thin-walled open profiles located in a monolithic foam concrete array is considered. This arrangement increases the overall stability and fire resistance of the floor beams.

IMPROVING THE STABILITY OF METAL FRAME ELEMENTS WHEN WORKING TOGETHER WITH FOAM CONCRETE

The static operation of building frame elements is considered. A comparison of the load-bearing capacity of floor beams made of rolled steel and beams made of thin-walled curved pro files is given

A simplified approach to the window gasket modeling for window strength calculation

Introduction. The study of the influence of window deformations on their performance characteristics is an urgent task. This problem is related to the issues of window elements static operation under the combined action of wind and temperature loads. It is proposed to use the capabilities of modern finite element modeling programs to analyze the window static operation. One of the problems is the modeling of an elastic window gaskets. Materials and methods. Computation of a gasket structural behavior in the direct formulation is associated with significant computational costs. In this article it is proposed a simplified method which allows taking into account the gasket mechanical work when creating window fine element model in the COMSOL Multiphysics software. For this purpose, the dependence of the gasket reaction force on the degree of its compression was obtained; this dependence was used to create a special boundary condition that imitates the force transfer from one window element to another through the gasket. Results. Two test computations were carried out with the same loads and grip conditions: in one, the gasket was modeled directly, in the other, it was replaced by the boundary condition described above. The results showed good agreement between the computations, moreover the second one needed much less time. Conclusions. Scientific foundations of window design should be based on modern research methods including computer modeling. Creating a computer model of the window static operation will allow us to consider in detail its deformed state and operational characteristics under various boundary conditions. The method proposed in this article for modeling the gasket structural behavior will be useful in achieving this aim.

A Time-Based Dynamic Operation Model for Webpage Steganography Methods

The webpage steganography technique has been used for a covert communication method for various purposes in which a sender embeds a secret message into a plain webpage file like an HTML file by using various steganography methods. With human eyes, it is very difficult to distinguish between the original webpage (cover webpage) and the modified webpage with the secret data (stego webpage) because both are displayed alike in a web browser. In this approach, when two communicating entities want to share a secret message, a sender uploads a stego webpage to a web server or modifies an existing webpage in the web server by using a webpage steganography method, and then a receiver accesses the stego webpage to download and extract the embedded secret data from it. Meanwhile, according to our extensive survey, we observed that most webpage steganography methods focused on proposing or improving steganography algorithms but did not well address how to operate a stego webpage as time passes. However, if a stego webpage is used in a static way such that the stego webpage does not change and is constantly exposed to web clients until the sender removes it, such a static operation approach will limit or badly affect the hiding capacity and undetectability of a webpage steganography method. By this motivation, in this paper, we proposed a time-based dynamic operation model (TDOM) that improves the performance of existing webpage steganography methods in terms of hiding capacity and undetectability by dynamically replacing the stego webpage with other stego webpages or the original webpage. In addition, we designed two time-based dynamic operation algorithms (TDOA-C and TDOA-U), which improve the hiding capacity of existing methods and TDOA-U for improving the undetectability of existing methods, respectively. To validate our model and show the performance of our proposed algorithms, we conducted extensive comparative experiments and numerical analysis by implementing two webpage steganography methods with our TDOM (CCL with TDOA-C and COA with TDOA-C) and tested them in the web environment. According to our experiments and analysis, our proposed algorithms could significantly improve the hiding capacity and undetectability of two existing webpage steganography methods.

Transient dynamic analysis of a pump-turbine with hysteresis effect

Hysteresis effect, which has a significant impact on transient characteristics of a pump-turbine, attracts more and more researchers’ attention and shows great potential. Influences of hysteresis on dynamic characteristics of a pump-turbine are investigated during the transient process in this paper. Transient trajectories of pump-turbines actually do not match their static operation trajectories, especially in the condition of turbine braking. In order to establish a transient model of a pump-turbine in different moving directions of dynamic trajectories, time delays among the relative parameters are introduced in this paper. Furthermore, effects of hysteresis on the dynamic characteristics of the pump-turbine are analyzed in detail by using numerical simulation. Based on the established transient model, influences of unit head on the dynamic characteristics of the pump-turbine are studied during the bidirectional transient process. The simulation results show the transient characteristic of the pump-turbine can be improved with the enhancement of hysteresis effect. While it gradually loses stability with the increase of hysteresis. The conclusions provide us a new approach for regulating the transient performance and stability of pump-turbines by using hysteresis effect during transient process.