The spring controlled governor of the Wilson Hartnell type is shown in Fig. In this governor, the bell crank levers are pivoted at the ends of two arms which rotate with the spindle. The vertical arms of the bell crank lever support the balls and horizontal arms are attached to the sleeve through rollers. The
Wilson Hartnell Governor (Radial Spring Governor) Read More »
Figure shows a simplified overview of the database design process. The first step shown is requirements collection and analysis. During this step, the database designers interview prospective database users to understand and document their data requirements. The result of this step is a concisely written set of users’ requirements. These requirements should be specified in
Using High Level Conceptual Data Models for Database Design Read More »
In this section, we give an overview of the schema evolution commands available in SQL, which can be used to alter a schema by adding or dropping tables, attributes, constraints, and other schema elements. This can be done while the database is operational and does not require recompilation of the database schema. Certain checks must
Schema Change Statement in SQL Read More »
Governor Arrangement This is the most common type of governor. In the centrifugal type governors, rotation of the crank shaft is taken to a vertical spindle through suitable gears. It consists of two balls of equal mass, which are attached to the arms as shown in Fig. These balls are known as governor balls or
Centrifugal Governors – Principle of Working Read More »
Function of Governor The function of a governor is to automatically maintain the speed of an engine within specified limits whenever there is a variation of load. If the load on the engine increases, its speed decreases. So it becomes necessary to increase the fuel supply by opening the throttle valve. On the other hand,
Governor Vs Flywheel – Pedagogy Zone Read More »
In this section we introduce the concept of a view in SQL. We show how views are specified, and then we discuss the problem of updating views (Virtual Tables) and how views can be implemented by the DBMS. Concept of a View in SQL A view in SQL terminology is a single table that is
View (Virtual Tables) in SQL – Pedagogy Zone Read More »
So far, we have discussed the free vibrations of systems where a system once disturbed from its equilibrium position executes vibration indefinitely because of its elastic properties. In actual practice, this system will come to rest, sooner or later, depending upon the amount of damping present in the system. In case of forced vibrations, the
Forced Vibrations with Harmonic Excitation Read More »
Consider a uniform shaft of negligible mass rigidly fixed at its upper end and carrying a disc at its lower end, as shown in Fig. If the disc is given a twist about its vertical axis and then released, it will start twisting and untwisting about the axis, which is known as torsional vibrations. Let,
Natural Frequency of Free Torsional Vibrations Read More »
Critical or whirling or whipping speed is the speed at which the shaft tends to vibrate violently in the transverse direction. In other words, the speed at which resonance occurs are known as the critical speed. At critical speeds, the amplitude of vibration of rotors is excessively large and a large amount of force is
Whirling or Critical Speed of Shaft – Pedagogy Zone Read More »
In this section, we introduce two additional features of SQL: the CREATE ASSERTION statement and the CREATE TRIGGER statement. Before discusses CREATE ASSERTION, which can be used to specify additional types of constraints that are outside the scope of the built-in relational model constraints (primary and unique keys, entity integrity, and referential integrity) that we
Specifying Constraints as Assertions and Actions as Triggers Read More »