THE TOP DOWN APPROACH
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Thetop-down approach to deploying once identity management is providedto help someone choose the best option to assimilate identitymanagement competencies into the environment. It is a tacticalapproach which is limited in coverage. It also has a lower impact onthe overall organization. This approach has several advantages thatare discussed in the next paragraph. A simple design for the top-downapproach is shown below.
Anotherillustration of top-down approach is shown below.
Advantagesof using Top Down approach
Thetop-down approach helps the organization in realizing a focused useof resources from the individually managed application. In doing so,it helps in solving engineering problems that may be the lack ofenough resources. The approach enables the engineers to maximise theavailable resources thus, saving on cost. Another advantage of usinga top-down budgeting is that you do not have to rely on lower levelmanagers to come up with budgeting information. Your business canallow the lower level managers to focus on their department and whatthey do best (Peristeras V. 2002. 48). Using this kind of approachsaves engineers time thus a lot of work can be done within a shorttime. The top-down approach is also important before the phases arecompleted for the managed application, you would have implemented adeeper, more mature implementation of the identity managementsolution (Harken H. 2004. 34). The operation and maintenanceresources are not initially impacted as severely as with thebottom-up approach. These advantages are very useful in dealing withthe engineering problems. Some of the engineering problems mayinclude poor management, less skilled personnel and also inadequatelabour or engineers. the diagram below shows comparison of top-downand bottom-up.
Ballscrew linear actuator
Alinear actuator is a mechanical device that converts energy to createmotion in a straight line. It can also be used to apply force. Alllinear actuator depends on an external force, non-linear force todrive some piston back and forth. A piston usually consists of ashort cylinder fitting within a cylindrical vessel along which itmoves back and forth. There are several options regarding the linearactuator driving force. Manual Mechanical methods include the leadscrew systems of vises and clamps and levels found manual juicers orcan crushers.
Thedense roller screw linear actuator sequence was developed to offer astrong, long-lasting and precise linear actuator for great endapplications. It provides the many benefits of the Ball Screw withadditional benefits for certain actuators. As an alternative tohydraulic actuators, it eliminates many of the associated concerns.Such as heat, noise, controllability, leakage and squat stiffness,while handling significant loads at high speeds and maintaining therough and long-lasting steel construction characteristic ofhydraulics. It has been applied in high loads, high extremedurability. High load and speed provide precision motion while fullyenclosed, thus, eliminating contamination related failures. A steelslot provides anti-rotation and counters the tangential forcescreated during high speed, high load operation, and high frequency.This is illustrated below.
Theheavy duty linear actuator with roller screw is designed to suitvirtually any gear box, motor, or gear-head chosen by the customer touse. Comparable, as well as inline offset conformations, are standardwith 2:1 and 1:1 synchronous gear belt. Merge switch tracks offer asimple way of placing and adjusting switches for over travelprotection, as well as home detection.
Ballscrew linear actuator is constructed by providing steel balls inbetween the screw shaft and the nut. Then the balls roll in thegrooves. That is, change to rolling contact from sliding contact toreduce friction. This is illustrated bellow
Aball screw drive comprises of a ball nut and a ball screw withrecirculating ball demeanours. The boundary between the nut and thescrew is made by ball demeanours that roll in the corresponding formsin the ball nut and ball screw (Schrader D. 1958). The weight of theball screw is spread over a huge number of ball demeanours so thateach ball is exposed to a moderately small load. Due to its rollingelements, the ball screwdriver has a very low coefficient of frictionthat equates to high to high mechanical efficiency. This isillustrated below.
Asimple illustration of a hydraulic cylinder is shown below
Advantagesof Ball screw linear actuator
Ballscrews are the greatest type of screws utilised in industrialmachinery and meticulousness machines. Their primary function is toconvert rotary torque or motion to shove, and vice versa, with thetopographies of high accuracy, efficiency and reversibility. Thecombination of the state of the art machining technology,manufacturing experiences, and engineering expertise make usershigh-tech winners. These screws use a precise procedure to generateexact groove outlines, either by precision rolling or by grinding.Accurate heat management is also used to guarantee the hardness ofthe ball screws.
Theball screw used in an actuator to replace the traditional hydraulicor pneumatic actuator has many advantages. They include no filtering,no leakage, good repeatability and energy saving. They also haveseveral benefits when used over the pneumatic and the hydrauliccylinders. These include high efficiency and reversibility, backlashelimination, high stiffness, and high lead accuracy among othersHarris. A ball screw adds balls between the nut and spindle. Thesliding friction of the conventional screw is, therefore, replaced bythe rolling motion of the balls. The diagram below shows themodification of a ball screw linear actuator.
Ballscrew can reach efficiency as high as 90% because of the rollingcontact between the screw and the nut. Therefore, the torque neededis approximately one-third of that of conventional screws (Laskey D.2000. 58). Ball screws have Super surface finish in the ball tracksthat reduce the contact friction between the balls and the balltracks. However, computer numerical control machine requires ballscrews with zero axial backlash and minimal elastic deformation. Inorder to achieve high stiffness and repeatable positioning in CNCmachines, preloading of the ball screws is commonly used (Harris A.2011. 145). Excessive preload increases the friction torque inoperation. The special design and fabrication process provide ballscrews with no backlash and less heat loss.
Inapplications where high accuracy is needed, the ball screw permitsachievements of the international standards and specific customerrequirements. Unlike other conventional screws, governed by the wearon the contact surfaces, ball screws can be used to metal fatigue. Bycautious attention to the quality of materials, design, heattreatment and production, ball screws have attested to be troublefree and reliable during the time of anticipated service life.
Ballscrews have rolling ball contact makes them require only a smallstarting force to overcome their starting friction
Theorigin of PLC is in the motor manufacturing industries. Manufacturing processes were partly automated by the use of stiffcontrol circuits, hydraulic, electrical and pneumatic. It was notedthat whenever an alteration had to be done, the scheme had to bereconfigured or rewired. With the development of computers, it wasrealised that if they could switch things on and off and riposte toan array of inputs, then the variations could be done byreprogramming the computer. Thus, the PLC started. There are stillnumerous applications of automated organizations with perpetualconnections to execute a single control action. Frequently the systemuses logic mechanisms to produce the exact action. The PLC mimicsthis process by performing the logical operations with the programmerather than with real components. In this way, cost saving areproduced as fewer components are required, and more elasticity ispresented as programmes can be altered more easily than rearranging ahardware system. A simple illustration of a PLC programme is shownbelow.
TheMotor Control Circuit to PLC Ladder is illustrated below.
AProgrammable Logic Controller is a mini computer specificallydesigned for industrial and other applications. Examples includehydraulic machines, pneumatic machines, robots, production process,traffic lights and signalling systems and refining processes. The PLCtriggers its output stations in order to switch stuffs on and off.The decision to actuate an output is centred on the position of thesystem`s response sensors and these are linked to the input stationsof the PLC (Cong-ling Z. 2008. 87). The resolution is based on thelogic programmes kept in the ROM and RAM memory. They have a centralprocessing unit, address bus and data bus.
ThePLC has certain diagnostic, monitoring and testing facilities withinthe software. Light emitting diodes shows the status of the input andoutputs. It is programmed with local commands.
Ballscrew linear actuators have a lot of advantages over the pneumaticand hydraulic methods. They are more advanced and improvised toreduce friction that may cause wear and tear. The Top-down approachis mostly applied to save time. Unlike bottom up approach, operationand resources are not initially impacted. Programmable LogicController is a program that is essential for a designer of PLC tounderstand the use of registers for inputs, outputs and internalprogramme component.
Cong-ling,Z. Z. X. W., & Yu-rong, W. U. (2008). Design of candy packingmachine control system based on PLC [J]. Food& Machinery, 2,026
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Harris,A. (2011). System improvement through collective capacitybuilding.Journalof Educational Administration, 49(6),624-636.
Laskey,D. R. (2000). U.S.Patent No. 6,101,889.Washington, DC: U.S. Patent and Trademark Office.
Peristeras,V., & Tarabanis, K. (2000). Towards an enterprise architecturefor public administration using a top-down approach. EuropeanJournal of Information Systems, 9(4),252-260.
Schrader,D. L. (1958). U.S.Patent No. 2,860,266.Washington, DC: U.S. Patent and Trademark Office.
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