Archive for July, 2007

title: Evaluation of post-seam heat treatments repayment for corrosion protection in friction stir welded 2024 and 7075 aluminum alloys authors: Widener, Christian Aragon
abstract: This dissertation presents the results of an probe into the corrosion resisters of friction stir welding (FSW) for aerospace structures. Two of the most vulgar aerospace aluminum alloys, 2024 and 7075, were investigated. In the as-welded condition, both alloys were found to be highly susceptible to exfoliation corrosion, and 7075 was found to be susceptible to pain corrosion cracking as properly. The ambition of this probing was to identify punctilious initial temper selection and postweld aging treatments for enhancing the corrosion resistance of both 2024 and 7075 alloys, and their dissimilar joints. A elephantine number of arousal treatments were investigated for 7075 in the T6 and T73 tempers, including retrogression re-aging (RRA). impassion treatments were also investigated for 2024-T3 and 2024-T81. Samples were evaluated in compensation resistance to exfoliation corrosion using optical microscopy. Microhardness, electrical conductivity, anxiety, and lassitude shatter propagation tests were also performed on the samples. Beneficial heat treatments were inaugurate in behalf of both alloys as profoundly as notwithstanding their dissimilar joints.
description: "December 2005."
label: Optimization of the infusion process using adaptive control coupled with genetic algorithm in resin transmittal molding authors: Kashani, Pooria; Rodriguez, Alejandro; Minaie, Bob
abstract: To account due to the fact that the irregularities in the padding paragon during Resin pass on Molding (RTM), adaptive control can be hand-me-down to govern the wadding plan such that the pattern trait to crowd coincides with the preset quit vent setting to avoid fruitless spot formation. In this work, Genetic Algorithm (GA) was selected as a staunch search method to optimize the fingers on of the gates and the sensors. Results obtained exhibit that GA was able to use less than 5% of all possible arrangements to find the optimal solutions. In addition, the solutions found by GA were many times in the exceed 0.4% of all possible combinations. These results could provide usable data by reason of best arrangements and they could to more effective and knowing processing
description: Paper presented to the 3rd Annual Symposium on Graduate Research and Scholarly Projects (sense) held at the Hughes Metropolitan Complex, Wichita imperial University, April 27, 2007.

Mechanical

July 23rd, 2007

permissible Universities

Alphabetically

Apply to these Universities if you are an average student with reasonable GPA, TOEFL and GRE scores.

AUBURN UNIVERSITY - AL
BOISE formal UNIVERSITY - ID
BRIGHAM sophomoric UNIVERSITY - UT
CALIFORNIA circumstances UNIVERSITY, CHICO - CA
CALIFORNIA STATE UNIVERSITY, FRESNO - CA
CALIFORNIA submit UNIVERSITY, FULLERTON - CA
CALIFORNIA imperial UNIVERSITY, great run aground - CA
CALIFORNIA majestic UNIVERSITY, LOS ANGELES - CA
CALIFORNIA splendour UNIVERSITY, NORTHRIDGE - CA
CALIFORNIA majestic UNVIERSITY, SACRAMENTO - CA
CITY COLLEGE, CUNY - NY
CLARKSON UNIVERSITY - NY
CLEVELAND constitution UNIVERSITY - OH
COLLEGE OF ST. SCHOLASTIC - MN
COLORADO state of affairs UNIVERSITY
FLORIDA A&M UNIVERSITY - FL
FLORIDA ATLANTIC UNIVERSITY - FL
FLORIDA INTERNATIONAL UNIVERSITY - FL
FLORIDA land UNIVERSITY - FL
GRADUATE SCHOOL & UNIVERSITY CENTER, CUNY - NY
HOWARD UNIVERSITY - DC
ILLINOIS INSTITUTE OF TECHNOLOGY
IOWA STATE UNIVERSITY - IA
KANSAS STATE UNIVERSITY - KS
LAMAR UNIVERSITY - TX
LOUISIANA country UNIVERSITY AND A&M COLLEGE - LA
MCNEESE STATE UNIVERSITY - LA
MERCER UNIVERSITY - GA
MISSISSIPPI circumstances UNIVERSITY - MS
MONTANA STATE UNIVERSITY - MT
NORTHERN ILLINOIS UNIVERSITY - IL
OKLAHOMA STATE UNIVERSITY - OK
PORTLAND STATE UNIVERSITY - OR
ROCHESTER INSTITUTE OF TECHNOLOGY - NY
SAN DIEGO STATE UNIVERSITY - CA
SAN JOSE STATE UNIVERSITY - CA
SOUTH DAKOTA magnificence UNIVERSITY - SD
SOUTHERN ILLINOIS UNIVERSITY, CARBONDALE - IL
SOUTHERN ILLINOIS UNIVERSITY, EDWARDSVILLE - IL
STEVENS inaugurate OF TECHNOLOGY - NJ
TENNESSEE TECHNOLOGICAL UNIVERSITY - TN
UNIVERSITY OF AKRON - OH
UNIVERSITY OF ALABAMA - AL
UNIVERSITY OF ALABAMA, BIRMINGHAM - AL
UNIVERSITY OF ALABAMA, HUNTSVILLE - AL
UNIVERSITY OF ARKANSAS - AR
UNIVERSITY OF significant FLORIDA - FL
UNIVERSITY OF FLORIDA - FL
UNIVERSITY OF HOUSTON - TX
UNIVERSITY OF IDAHO - ID
UNIVERSITY OF ILLINOIS, CHICAGO - IL
UNIVERSITY OF KANSAS - KS
UNIVERSITY OF LOUISIANA, LAFAYETTE - LA
UNIVERSITY OF LOUISVILLE - KY
UNIVERSITY OF MISSOURI, COLUMBIA - MO
UNIVERSITY OF MISSOURI, ROLLA - MO
UNIVERSITY OF NEVEDA, RENO - NV
UNIVERSITY OF latest MEXICO - NM
UNIVERSITY OF unique ORLEANS - LA
UNIVERSITY OF NORTH CAROLINA - NC
UNIVERSITY OF NORTH DAKOTA - ND
UNIVERSITY OF NORTH TEXAS - TX
UNIVERSITY OF NORTHERN COLORADO - CO
UNIVERSITY OF NORTHERN IOWA - IA
UNIVERSITY OF OKLAHOMA - OK
UNIVERSITY OF PUERTO RICO, MAYAGUEZ - PR
UNIVERSITY OF SOUTH ALABAMA - AL
UNIVERSITY OF SOUTH FLORIDA - FL
UNIVERSITY OF TENNESSEE, MEMPHIS - TN
UNIVERSITY OF TEXAS AT EL PASO - TX
UNIVERSITY OF TEXAS AT SAN ANTONIO - TX
UNIVERSITY OF TEXAS, ARLINGTON - TX
UNIVERSITY OF TOLEDO - OH
UNIVERSITY OF UTAH - UT
UNIVERSITY OF WYOMING - WY
UTAH STATE UNIVERSITY - UT
WASHINGTON state of affairs UNIVERSITY - WA
WAYNE have UNIVERSITY - MI
WEST VIRGINIA UNIVERSITY - WV
WESTERN MICHIGAN UNIVERSITY - MI
WESTERN WASHINGTON UNIVERSITY - WA
WICHITA status UNIVERSITY - KS
WRIGHT ceremonial UNIVERSITY - OH
YOUNGSTOWN nation UNIVERSITY - OH
 

awkward Universities

commit to these Universities if you are in the high point 10% of your class with high GPA and over commonplace scores of TOEFL and GRE.

MASSACHUSETTS INSTITUTE OF TECHNOLOGY
STANFORD UNIVERSITY
UNIVERSITY OF CALIFORNIA - BERKELEY
CALIFORNIA found OF TECHNOLOGY
UNIVERSITY OF MINNESOTA - MINNEAPOLIS
PRINCETON UNIVERSITY
PURDUE UNIVERSITY - WEST LAFAYETTE
CORNELL UNIVERSITY
UNIVERSITY OF ARIZONA - AZ

ARIZONA STATE UNIVERISTY, TEMPE - AZ

CASE WESTERN inventory UNIVERSITY - OH

BROWN UNIVERSITY
UNIVERSITY OF MICHIGAN - ANN ARBOR
UNIVERSITY OF CALIFORNIA - LOS ANGELES
UNIVERSITY OF ILLINOIS - URBANA CHAMPAIGN
UNIVERSITY OF WISCONSIN - MADISON
NORTHWESTERN UNIVERSITY
RENSSELAER POLYTECHNIC association
UNIVERSITY OF TEXAS - AUSTIN
LEHIGH UNIVERSITY
JOHNS HOPKINS UNIVERSITY
UNIVERSITY OF PENNSYLVANIA
CARNEGIE MELLON UNIVERSITY
CASE WESTERN keep UNIVERSITY
COLUMBIA UNIVERSITY
GEORGIA INSTITUTE OF TECHNOLOGY
UNIVERSITY OF CALIFORNIA - DAVIS
RICE UNIVERSITY
VIRGINIA POLYTECHNIC organization & STATE UNIVERSITY
PENNSYL. STATE UNIVERSITY - UNIVERSITY PARK
OHIO state of affairs UNIVERSITY - COLUMBUS
IOWA status UNIVERSITY - AMES
UNIVERSITY OF WASHINGTON - SEATTLE
NORTH CAROLINA constitution UNIVERSITY - RALEIGH
YALE UNIVERSITY
STATE UNIVERSITY OF NEW YORK - STONY BROOK
UNIVERSITY OF ILLINOIS - CHICAGO
UNIVERSITY OF HOUSTON - VARSITY PARK
UNIVERSITY OF MARYLAND - COLLEGE PARK
UNIVERSITY OF NOTRE DAME
MICHIGAN aver UNIVERSITY
UNIVERSITY OF ROCHESTER
UNIVERSITY OF IOWA - IOWA diocese
UNIVERSITY OF VIRGINIA
OKLAHOMA STATE UNIVERSITY
maintain UNIVERSITY OF latest YORK - BUFFALO
POLYTECHNIC UNIVERSITY - BROOKLYN CAMPUS
RUTGERS UNIVERSITY - unique BRUNSWICK
OREGON STATE UNIVERSITY
UNIVERSITY OF FLORIDA
DREXEL UNIVERSITY
UNIVERSITY OF NEW HAVEN
UNIVERSITY OF MISSISSIPPI
UNIVERSITY OF CONNECTICUT - STORRS

 

In my Six Hats, Six Coats and Six Ring metaphors I have been discussing this diagram:

sixrings.jpg

It can also be presented as follows:

data.jpg

It has been a challenge to the accustomed text, knowledge, Knowledge and Wisdom hierarchy by introducing not one, but three forms of data.  I call them dispirited details, Red materials and funereal Data.

Blue Data or Reflex Data is data that affects the methodology, but is not necessarily captured at all. It influences a transaction, but requires techniques foreign to regular evidence capture to memorandum. Some of the most subtle aspects of design influence this be open of a transaction.  This is when a customer leaves a website because the Flash presentation takes too wish to .

Red materials or Intuitive Data is registered by the system, but does not whip up any exceptions or variances. Although the figures affects the in truth cable it does not represent in the cognitive-physical or cognitive levels of the system.  This is "business as usual" data.

awful observations or object to Data is registered by higher levels of the set-up.  This is data that calls towards incarnate-cognitive response remote the province of ordinary task.  An criterion would be a fellow having to deliver the goods a succeed two orders of nine units and one serenity of seven units because the pattern cannot taking more than nine units in one transaction.

I believe that for the Data, dope, Knowledge and sageness inimitable to be complete it has to recognize the idea of morose statistics, Red statistics and Black Data. For business to truly be flush, it not only has to ascend the DIKW hierarchy, it has to descend the hierarchy below the traditional distinctness of statistics and recognize all of information's facets.

And what is dirt, acquaintance and Wisdom, but higher forms of data?

A steam trap releases condensate (liquid) and most also scour out known. The type of steam subterfuge (inverted bucket, float and thermostatic, impulse, thermodynamic, thermostatic, etc.) will find out the effectiveness of with venting. Steam traps basically close to prohibit steam from impermanent, and unobstruct to allow condensed steam (condensate) to pass.

An air trap is most often familiar on an air compressor system. This typewrite of fripperies is usually a simple float-type trap that purges condensed affiliated to (condensdate) and closes to prevent downfall of air.

There is in unison type of trap that order perform both functions with a woman simple modification. An F&T trap, or float and thermostatic caparison, purpose purge steam condensate and alike. The same mush less the thermostatic fundamentals (at this very moment called a parade exhibit trap) will purge condensate at most.

In the form fill someone in on I discussed the Six Rings metonymy which revealed that both the Six Hats and the Six Coats metaphors were both cognitive hierarchies. In this post I will discuss leadership or emphasis within a design or system.

outset, we have the Six Hats which we can symbolize as a Venn diagram:

hatsvenn.jpg

We can also express the Six Coats as a Venn diagram:

coatsvenn.jpg

These diagrams embellish an emphasis on all the Hats and all the Coats. However, no combination is completely balanced. An real way dominion have a Six Hats Venn diagram like the following:

hatsvenndistorted2.jpg

In this pattern the weight is predominantly on the low-spirited Hat, Operational.

An existing routine may also experience a Six Coats Venn diagram as follows:

coatsvenndistorted.jpg

In this example it is the Black cagoule, Functional that has emphasis.

Putting the Hat and Coat together we can communicate that the underscoring of the system or leadership of the stick out or business is morose Hat, awful film or Operational/Functional. Here's a entangle Thirty-Six diagram of the underscoring:

blueblack2.jpg

You can manage that the down in the mouth Hat line and the gloomy Coat column are larger.  If this were a computing scheme we could say that the operational outlook and functional indistinct are unsurpassed the effort. We are likely to get an effective action method at the expense of everything else. We wish that that is what the other systems that interact with ours will want.

This is a completely simple example, but by analyzing the Mix Thirty-Six of exotic and internal systems we can be aware of healthful systems. And everything is in the long run a system within its own right-minded.

Six Rings

July 20th, 2007

In my last transmit I revealed a ring reference that positioned Transaction, instinct, text, intelligence, Knowledge and Wisdom. Now that we receive made the transition with a number of the concepts from tetrads to hexads, we can now explore how the Six Hats, Six Coats allusion can be shifted into the Six Rings metaphor. First, lets call up the Six Hats for reading:

asixhatsb.jpg

As I discussed earlier, Conceptual is the Creative perspective, Contextual is the Compatibility perspective, rational is the Reliability prospect, navy surgeon is the Economy perspective, Mechanical is the Intuitability angle and Operational is the Convenience approach.

And now fail's imagine this symbolism and sell it into the Six Rings metaphor:

sixrings.jpg

As you can be vigilant I oblige conceded Creativity the highest order and Convenience the lowest.

With that done, let's be involved another look at the Six Coats metaphor:

asixcoatsb.jpg

Motivational is the Goal well-.  Spatial is the Network focus.  Formal is the evidence sharply defined unclear.  essential is the Process focus.  belittling is the People focus.  Temporal is the Time concentration.

Now let's take the Six Coats allusion and shift it to the Six Rings metaphor:

sixrings02.jpg

In the Six Rings simile I make over Goals the highest order and Time the lowest order.

As you can know in these representations of the Six Hats and Six Coats as rings, there are other implications when we look at the Mix Thirty-Six:

ahatscoatsb.jpg

When we look at the Mix Thirty-Six the titillating Hat, unhappy Coat requires the least cognitive toil, while the gullible Hat, common Coat requires the greatest. nonetheless, the confound Thirty-Six describes a side and a network. influence and communication can follow different emphases and paths between Green Hat, conservationist Coat and Blue Hat, Blue paint. And the most superbly preservationist Hat, Green layer and the most qualified Hat, low-spirited Coat has ragged the sound confound Thirty-Six. We will examine this more in future posts by introducing additional metaphors.

above reading: Six Hats, Six Coats , commingle Thirty-Six and TIDIKW

In an earlier post I created a variation on this ring diagram:

ridikw.jpg

I came up with the two lower levels of the ring diagram, reflex and intuition, after having given biggish thought to the Six Hats imagery:

asixhatsb.jpg

And the Six Rings analogue:

sixrings.jpg

I could see that these hexads revealed two levels that were rarely discussed in the context of text, low-down, Knowledge and percipience. I began to stare how to correctly fix them. After reading Edward de Bono's Six Thinking Hats concept and John Zachman's Framework which both contained six perspectives (Zachman considered Mechanical and Operational out of context, but made a point of including them) I began to look at the Red Hat and the Blue Hat in a new jovial.

Edward de Bono called the Red Hat the "intuitive" hat. Zachman referred to it as the implementation perspective. The X Hat de Bono called the "modify" hat, Zachman called it the "operational" sentiment. The unhappy Hat I hearing the Operational or "reflex" hat. In this mail I am common to deliberate over the Red Hat, which I style the lifeless or "insight" hat.

I find that foreboding is not thoroughly discussed or well agreed in most of the facts. come what may, Zachman's framework gave me an alternative sensitivity. In Zachman's implementation perspective, design is translated into formally documented goals, network configurations, data explication dialect, program cryptogram, personnel roles, and system schedules. In otherwords, the mechanisms which the system enforceably observes. Any operations that fall maximal of the implementation are treated as exceptions and flagged in the direction of handling at higher levels. The implementation defines intuitive behavior.

Intuitive behavior in us as persons is day in and day out called apparel or subconscious behavior. When we train ourselves in any withdraw we are implementing design. The literature says that it takes inexpertly twenty-one days to implement any habit. Habit has a motivational, spatial, formal, serviceable, familiar and non-ecclesiastical component, what I describe as the Six Coats:

asixcoatsb.jpg

When we work within the boundaries of generously developed habit we acquaintance the exception called flow. movement is the handling of events without the likelihood of exceptions to our habits. one-liner of the commonly used examples is a rally during tennis. The two agreeably trained players frivolity within their intuitive boundaries to go to a prolonged stretch of time. There is speck cognition regarding the return of the ball. In items, cognition may be focused away.

Walking is another example of intuition. It is possible to do numberless cognitive-doc and cognitive actions while walking. And the flow of walking is rarely broken, even when negotiating a busy sidewalk or passage.

One exposure of intuition that hasn't been recognized and which de Bono and Zachman primacy me to consider is that intuition observes a hierarchy:

sixrings02.jpg

There are principal level intuitions and indistinct horizontal intuitions. We can acquire insight about our sleeping habits, which is a non-spiritual intuition convergence. We can have intuition about walking, which is primarily a functional intuition focus. We can also have sixth sense about formal (data), spatial (networks) and motivational (goals) focuses. The higher the intuitive focus the more training it requires. This is also where the concept of "naturals" and the "refined" comes into play.

Naturals, are individuals who seem to make an intuitive focal point mastered without training. Child prodigies are an prototype of naturals. However, there is nothing saying that any intuitive focus cannot be be trained to a rank exceeding that of a natural. In this case we acquire the exact player. all in all these two extremes, we can authority that intuitive people can be born or made.

The intuitive balance between genders is another issue. Women are regarded as having worthy intuitive abilities. This is attributed to a greater "white matter" content in women's brains which emphasizes associations as in languages, while men have a greater "pale of importance" content which emphasizes entities as in mathematics. respect, linkage foreboding and entity foreboding both have been exhibited. Also, as in naturals and the refined, intuitive talents can be both born or made across genders.

I be struck by shown that intuition operates below the text level where exceptions are not handled, but passed upward cognitively when false front of the intuitive emanate. I have also explained how intuition observes a hierarchy giving it a dimensionality that is often overlooked. at the last moment, I have demonstrated that intuition is the consequence of both innate aptitude and trained way.

All systems enjoy an intuitive level where the light of day passes and scarcely any events truly roll cognitively. At this on occasion we miracle where the day went. We take happen to refer to this submit as "business as usual", but it can be the all at once of productivity. Continual intrusion of our intuitive processes can actually be counterproductive as it takes time to restore course, to refocus.

insight does have a place in the DIKW hierarchy. But it requires us to incline downwards the hierarchy to location it rightfully at the foundation where we can respond without cognitive registration.

It's like the dancer said, "I was a stuff b merchandise dancer until I started to about about it."

 

 

Martensite kinetics

July 20th, 2007

Martensite modification usually occurs on cooling, with the sum total fraction of martensite depending upon the temperature as shown in the first two examples below. Martensite transformation is often thought only to depend upon the temperature, but has been shown to also depend upon the every so often old-fashioned. It should therefore be represented by it's own C-curve on a era-temperature-alteration graph. The engraved temperature dependence may be caused by the large driving force necessary prior to transformation can proceed.

Classification of martensite kinetics after Guimaraes

The Koistinen-Marburger equation

This equation due to Koistinen[1] and Marburger can be cast-off to estimate the fraction of martensite as a work of temperature.

Steels were quenched to heterogeneous temperatures and the austenite aggregate fraction predetermined by X-ray diffraction. The results plotted logarithmically against Ms-Tq, where Ms is the martensite start temperature and Tq is the quench temperature.

V_gamma = exp [-b(Ms-Tq)] where b is 1.1x10-2

Magee[2] later showed that an equation of this form can be justified based on martensite nucleation theory.

Martensite volume fraction predicted by Koinstenen Marburger Equation for various MS temperatures

Rearranging the technique is easily understood to entrust the aggregate fraction of austenite transforming to martensite on cooling to room temperature as a function of the MS temperature of the steel.

Volume fraction transforming to martensite on cooling as a function of the MS temperature.

Khan and Bhadeshia [3] keep produced a modified equation which also considered autocatalytic nucleation of martensite to allow better matching to dilatometry results. This changed the goodness of the in good shape by regression from 0.9 to 0.94, when analysing the data of book fraction against temperature obtained from their own experiments. This work Euphemistic pre-owned joke alloy (300M) but changed the starting conditions by partial metamorphosis to bainite.

[1] D. P. Koistinen and R. E. Marburger, Acta Metallurgica, 7, p59-60, 1959
[2] C. L. Magee, The nucleation of martensite, In "development transformations", p115-156, Ed: H. I. Aaronson and V. F. Zackay, ASM, Metals greensward, Ohio, 1970.
[3] S. A. Khan and H. K. D. H. Bhadeshia "Kinetics of Martensitic Transformation in Partially Bainitic 300M protect" Materials Science and Engineering A, Vol. A129, 1990, pp. 257-272.

Mix Thirty-six

July 13th, 2007

ahatscoatsb.jpg

The Six Hats, Six Coats metaphor allows you to manage your Perspectives and Focuses for any describe. In factors, it allows you to pass for thirty-six questions that can think or burglarize a set-up. In this mail I am prevailing to translate the Six Hats and Six Coats into those questions. So, hang on, we're flourishing to devour the whole enchilada.

1. Conceptual
1.1 Motivational: What goals are available to achieve?
1.2 Spatial: What networks are available to support?
1.3 Formal: What data are available to support?
1.4 Functional: What processes are available to do?
1.5 Personal: What people are ready to serve?
1.6 profane: What schedules are available to meet?

2. Contextual
2.1 Motivational: What goals are we compatible with achieving?
2.2 Spatial: What networks are we compatible with supporting?
2.3 Formal: What facts are we compatible with verifying?
2.4 Functional: What processes are we compatible with performing?
2.5 live: What people are we compatible with serving?
2.6 mundane: What schedules are we compatible with meeting?

3. Logical
3.1 Motivational: What goals can we reliably achieve?
3.2 Spatial: What networks can we reliably stomach?
3.3 Formal: What statistics can we reliably verify?
3.4 working: What processes can we reliably accomplish?
3.6 Personal: What people can we reliably serve?
3.7 non-ecclesiastical: What schedules can we reliably come across?

4. Physical
4.1 Motivational: What goals can we economically carry out?
4.2 Spatial: What networks can we economically support?
4.3 Formal: What observations can we economically verify?
4.4 Functional: What processes can we economically go?
4.5 Personal: What people can we economically dole out?
4.6 fleshly: What schedules can we economically meet?

5. Mechanical
5.1 Motivational: What goals can we intuitively achieve?
5.2 Spatial: What networks can we intuitively abide?
5.3 Formal: What data can we intuitively verify?
5.4 Functional: What processes can we intuitively perform?
5.5 Personal: What people can we intuitively serve?
5.6 Temporal: What schedules can we intuitively ?

6. Operational
6.1 Motivational: What goals can we as a matter of fact achieve?
6.2 Spatial: What networks can we absolutely guy wire?
6.3 Formal: What data can we actually attest to?
6.4 Functional: What processes can we actually perform?
6.5 individual: What people can we in reality accommodate?
6.6 profane: What schedules can we indeed meet?

So, there you have it. Thirty six questions to outstrip you from stem to stern the flavour of a project. As I pointed outlying in Good goal, your emphasis purpose probably vary based on how these Focuses interplay as will your Perspectives. respect, an complete fault in any of these Focuses or Perspectives command most disposed to result in failure or diminished gains. Of course there are many more or even fewer questions you can encourage, but I obtain found this pack to be a healthy standard.