Categories: General
      Date: Aug  6, 2010
     Title: Question for the month

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Question for October 2017

Why does friction produce a heat?

Question for September 2017

What is a functionable system type?

Question for August 2017

What is a Post-Maintenance Flight Test ?

Question for July 2017

How to estimate Total Packinging Cost?

Question for June 2017

An O-ring is made from an elastomer with equimolar portions of vinylidene fluoride and hexafluoropropylene. Calculate the weight fraction of each polymer.

Question May 2017

Estimate the particle size of a wear fragment produced by the adhesive wear of two 1040 steel surfaces under a load of 50 kg with a sliding distance of 5 mm. (Assume the particle to be a hemisphere of diameter d.)  

Question for April 2017

Electromagnetic radiation with photon energies greater than 15 eV can damage semiconductors that are used in a communications satellite. Could visible light be a source of this damage?

Question for March 2017:

What are the mechanisms of the Electrical Insulation Failures?

Question for February 2017

An extremely dis-organised organization operates n different systems numbered from 1 to n, in n different locations. Once a year these systems must be replaced. A central operator obtains a set of new systems and must transfer them to the appropriate locations. The central operator sends the spare systems in a random manner so that each system may find itself in any location. What is the probability that at least one system will be send to the correct address?

Question for January 2017

Consider a fleet containing m identical systems. In each system there are k identical modules. It is known that n units are failed in the fleet. What is the probability that exactly r   k units are failed in the first system?

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Question for December 2016

What is Solar Storm ?

Question for November 2016

What are the effects of thermal shock environments on maintainable systems? 

Question for October 2016:

Does ocean tides generate magnetic fields?

Question for September 2016:

Does environmental temperature impact reliability of UK's Type 45 Destroyer?

Question for August 2016

What is the 2nd Law of Mirce Science ?

Question for July 2016

What is the 1st Law of Mirce Science?

Question for June 2016

What is fourth Axiom of Mirce Science?

Question for May 2016

What is the thirds Axiom of Mirce Science?

Question for April 2016

What is the second axiom of Mirce Science?

Question for March 2016:

What is the first axiom of Mirce Science?

Question for February 2016:

An automated guided missile hits the target if booster rocket, guidance system and detonator functions properly.  The probability of failure of booster rocket, guidance system and detonator is 0.1, 0.3 and 0.2 respectively. 
1) Probability of failure of the missile,
2) If the missile fails what is the probability that it failed due to guidance system

Question for January 2016:

What are fundamental physical differences between particles and waves?

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Question for December 2015

In the jargon of maintenance professionals expression “Easter Egging” is frequently used. What does it mean?

Question for November 2015

Assume that it is known that the number of parts produced in a specific factory during a week is a random variable with mean of 50.

a) What is the probability that the next week the number of parts produced will exceed 50?
b) If the variance of weekly production is 25, what is the probability that the next week production will be between 40 and 60?

Question for October 2015

What is Economic Redundancy?

Question for September 2015

What is the difference between Correlation and Coincidence?

Question for August 2015

What is the Nature of Probability Theory?

Question for July 2015

What is Aerotoxic Syndrome?

Question for June 2015

What is frangibillity?

Question for May 2015

What is a Discrete Random variable?

Question for April 2015

Is weather and climate the same?

Question for March 2015

What is Anti-core Icing ?

Question for February 2015

What is Impact of Electromagnetic Phenomena on Aircraft Functionabnility ?

Question for January 2015

The module under consideration consists of two items, A and B whose relevant functionability measures are given in Table 1,

Table 1. RMS Data of Modules Considered
Item    Distribution    Scale [hrs]  Shape [hrs]    MTTR [hrs]    MLDT [Day]
A        Exponential     1000            N/a                   6                       7
B        Normal             800             300                  12                      1

 where, MTTR stands for the mean time to restore and MLDT for mean logistic delay time.

 For the initial period of operation of 3000 hours, determine:
1.    The expected number of negative functionability events, NNE, for each item;
2.    The expected number of  NNE  for the module, bearing in mind that the consisting items are connected in series from the point of view of reliability;
3.    The expected number of maintenance man-hours for the module.
4.    The expected logistic delay time for the module if one-for-one spare policy is applied for the consisting items.

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Question for December 2014

What are the main advantages of building a model of a system, process or activity under consideration?

Question for November 2014:

A European producer is to export a packaging machine to a customer in Brazil. The machine is packaged in wooden box of the following internal dimensions: length=7.00 m, width=2.75 m and height=3.00 m.Calculate a required number of desiccant units that should be used in order to for the machine to arrive to Brazil in the functionable state.

Question for October 2014

The majority of plastic component failures occur in the mid to long term.  Even, in normally tough, ductile plastic materials failures are invariable brittle in nature and result in a short service life.  What are the most common causes of such brittle failures?

Question for September 2014

What are mechanisms for formation of plastics?

Question for August 2014

What are Non Destructive Methods for Corrosion Monitoring?

Question for July 2014

What is corrosion?

Question for June 2014

What are the processes of heat transfer?

Question fro May 2014

What is Infrared Thermography?

Question for April 2014

What are the main differences between inspection and examination as condition monitoring activities?

Question for March 2014

For a continuously operating machine, does the increase in the number of spare engines: 

  1. Increases the number of failures of the gearbox? 
  2. Has no impact on the number of failures of the gearbox?
  3. Decreases the number of failures of the gearbox?

 Question for February 2014

What are the differences between linear and dynamic programming?

Question for January 2014

Under what conditions are the two random variables X and Y independent?

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Question for December 2013

Suppose that there is a piece of test equipment that could be provided to each base that would enable the base to repair more first-indenture items. The cost of the test equipment has to be weighed against the benefit. Consider the cost as fixed and determine whether the benefit of the test equipment at bases increases or decreases with each of the following:

1. higher target availabilities;
2. projected longer repair times
3. longer order-and-ship times;
4. more years of operation;
5. reduction in unit cost:
6. increase in demand rates;
7. no increase in demand rates but an increase in variability;
8. more failures in the test equipment itself;
9. higher skill requirements for operators;
10. more false positives and negatives in the equipment diagnoses 

 Question for November 2013

Functionality and Functionability of machines are:
a) The same properties, just different names?
b) Not the same, but very similar properties?
c) Fundamentally different properties?

 Question for October 2013

Air Transit, a manufacturer of freight aircraft is evaluating the potential benefit of a process improvement programme that should change the applicable learning curve percentage from 85% to 80%. The aircraft on which this programme is to be implemented requires 996 person-years for its first unit (where a person year is defined as work of 52 weeks with 40 hours in each week).

a) Given the following data, approximate the potential cost saving for the 20th aircraft unit manufactured.

Direct labour cost:  $25/hr
Direct material cost:  $46.7m per unit
Overhead:          100% on direct labour

b) Given the data above, approximate the potential reduction in cost saving for the 20th aircraft unit manufactured if the actual learning curve percentage after programme implementation is 82% rather than 80%.
c) Discuss factors that might influence the extent and rate of time reduction as a consequence of the learning process in manufacturing.

Question for September 2013

As in all chemical reactions, corrosion reactions occur through an exchange of electrons. In electrochemical reactions, the electrons are produced by a chemical reaction in one area, the anode, travel through a metallic path and are consumed through a different chemical reaction in another area, the cathode. In some cases, such as the common dry cell battery, electrochemical reactions can be used to supply useful amounts of electrical current.

What is the generic chemical formula for the corrosion of metals?

Question for August 2013

Which of the following failure mechanisms the most frequently causes failure of polymers?

 Question for July 2013:

For continuously operating machine, exposed to corrective maintenance policy, the increase in spare parts will:

1. Increase the Number of Failures
2. Decrease the Number of Failure
3. Not affect the Number of Failures.

Question for June 2013:

Is the law of conservation of energy true for phenomena related to:

1. Living world?
2. Non-living world?
3. Both worlds? 

Question for May 2013

Are expressions “complicated system” and “complex system”

a) Two ways to describe the same entity?
b) Two different entities?
c) Irrelevant question?

Question for April 2013:

Bahrain Grand Prix is scheduled for 19-21 April 2013. Due to its closeness to the desert Sakhir, Bahrain International Circuit, during last few years recorded only 5 rainy days per year. However, current weather forecast predicts the rain on the racing Sunday. When it actually rains, the weather forecast is accurate 90% of the time. When it doesn't rain, the incorrect forecasts for rain are 10% of the time. What is the probability that it will rain on the 2013 Grand Prix day?

Question for March 2013

Among some reliability experts the following statement is commonly accepted “To double reliability you just need to double the Mean Time To Failure.” Is this statement:

a) Correct?
b) Incorrect?
c) Meaningless?

Question for February 2013:

A company has decided to develop a new control processor for a North Sea installation of a wind turbine. The processor will be based on equipment the company already has field reliability data for. It is envisaged that it will consist of the following three elements:

1. Fan, vaneaxial, whose Time to First Failure is defined by W(5000,5)
2. Data processor, whose Time to First Failure is defined by W(10000,1)
3. Mounting tray, whose Time to First Failure is defined by W(10000,7)

The three components are connected in series, from reliability point of view, and no maintenance activities are planned till the first failure of the control processor takes place.

The Solution Requirements
a) What is the Reliability Function of the Control Processor?
b) What is the Mean Time to First Failure of the Control Processor?
c) What is the probability of fault free operation for the first 6 months of continuous operation?
d) Given the difficulty in maintaining off-shore wind turbines, how much of an improvement in the intrinsic Mean Time to First Failure could be expected if another data Processor is added in a parallel configuration?

Question for January 2013:

When asked to define the length of time a customer is going to wait for spare parts for a new type of equipment, the logistics support manager (who has spent seventeen years supporting similar equipment, made the following judgement:

a) Making use of the above data, determine the probability that a potential customer will receive the necessary parts within 3 hours of placing an order.
b) Also determine the proportion of customers whose demand for needed spares will be met within two weeks from the placing the order.

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