Area of field of view formula
Magnets exert forces and torques on each other due to the rules of electromagnetism. The forces of attraction field of magnets are due to microscopic currents of electrically charged electrons orbiting nuclei and the intrinsic magnetism of fundamental particles such as electrons that make up the material. Both of these are modeled quite well as tiny loops of current called magnetic dipoles that produce their own magnetic field and are affected by external magnetic fields.
The most elementary force between magnetstherefore, is the magnetic dipole—dipole interaction. If all of the magnetic dipoles that make up two magnets are known then the net force on both magnets can be determined by summing up all these interactions between the dipoles of the first magnet and that of the second. It is often more convenient to model the force between two magnets as being due to forces between magnetic poles having magnetic charges 'smeared' over them.
Positive and negative magnetic charge is always connected by a string of magnetized material, and isolated magnetic charge does not exist. This model works quite well in predicting the forces between simple magnets where good models of how the 'magnetic charge' is distributed are available. The field of a magnet is the sum of fields from all magnetized volume elements, which consist of small magnetic dipoles on an atomic level.
The direct summation of all those dipole fields would require three-dimensional integration just to obtain the field of one magnet, which may be intricate. In case of a homogeneous magnetization, the problem can be simplified at least in two different ways, using Stokes' theorem. Upon integration along the direction of magnetization, all dipoles along the line of integration cancel each other, except at the magnet's end surface.
The field then emerges only from those mathematical magnetic charges spread over the magnet's end facets. This is called Gilbert model. On the contrary, when integrating over a magnetized area orthogonal to the direction of magnetization, the dipoles within this area cancel each otherexcept at the magnet's outer surface, where they mathematically sum up to a ring current. In both models, only two-dimensional distributions over the magnet's surface have to be considered, which is simpler than the original three-dimensional problem.
The net effect of these microscopic bound currents is to make the magnet behave as if there is a macroscopic electric current flowing in loops in the magnet with the magnetic field normal to the loops. The field due to such currents is then obtained through the Biot—Savart law. Gilbert model : In the Gilbert model, the pole surfaces of a permanent magnet are imagined to be covered with so-called magnetic chargenorth pole particles on the north pole and south pole particles' on the south pole, that are the source of the magnetic field lines.
The field due to magnetic charges is obtained through Coulomb's law with magnetic instead of electric charges. If the magnetic pole distribution is known, then the pole model gives the exact distribution of the magnetic field intensity H both inside and outside the magnet.
The surface charge distribution is uniform, if the magnet is homogeneously magnetized and has flat end facets such as a cylinder or prism. This pole model is also called the Gilbert model of a magnetic dipole. Far away from a magnet, its magnetic field is almost always described to a good approximation by a dipole field characterized by its total magnetic dipole momentm. This is true regardless of the shape of the magnet, so long as the magnetic moment is non-zero. One characteristic of a dipole field is that the strength of the field falls off inversely with the cube of the distance from the magnet's center.
The magnetic moment of a magnet is therefore a measure of its strength and orientation. A loop of electric currenta bar magnetan electrona moleculeand a planet all have magnetic moments. More precisely, the term magnetic moment normally refers to a system's magnetic dipole momentwhich produces the first term in the multipole expansion [note 1] of a general magnetic field.
Both the torque and force exerted on a magnet by an external magnetic field are proportional to that magnet's magnetic moment. The magnetic moment is a vector : it has both a magnitude and direction.The player efficiency rating PER is John Hollinger 's all-in-one basketball rating, which attempts to boil down all of a player's contributions into one number. Using a detailed formula, Hollinger developed a system that rates every player's statistical performance.
PER strives to measure a player's per-minute performance, while adjusting for pace. A league-average PER is always PER takes into account accomplishments, such as field goals, free throws, 3-pointers, assists, rebounds, blocks and steals, and negative results, such as missed shots, turnovers and personal fouls.
The formula adds positive stats and subtracts negative ones through a statistical point value system. The rating for each player is then adjusted to a per-minute basis so that, for example, substitutes can be compared with starters in playing time debates.
It is also adjusted for the team's pace. In the end, one number sums up the players' statistical accomplishments for that season. Hollinger's work has benefitted from the observations of sabermetric baseball analysts, such as Bill James.
One of the primary observations is that traditional counting statistics in baseball, like runs batted in and wins, are not reliable indicators of a player's value. For example, runs batted in is highly dependent upon opportunities created by a player's teammates.
PER extends this critique of counting statistics to basketball, noting that a player's opportunities to accumulate statistics are dependent upon the number of minutes played as well as the pace of the game. PER largely measures offensive performance. Hollinger freely admits that two of the defensive statistics it incorporates—blocks and steals which was not tracked as an official stat until —can produce a distorted picture of a player's value and that PER is not a reliable measure of a player's defensive acumen.
Bear in mind that this rating is not the final, once-and-for-all answer for a player's accomplishments during the season. This is especially true for players such as Bruce Bowen and Trenton Hassell who are defensive specialists but don't get many blocks or steals. Some have argued that PER gives undue weight to a player's contribution in limited minutes, or against a team's second unit, and it undervalues players who have enough diversity in their game to play starter's minutes.
PER has been said to reward inefficient shooting. Hollinger argues that each two point field goal made is worth about 1. A three point field goal made is worth 2. A missed field goal, though, costs a team 0. Given these values, with a bit of math we can show that a player will break even on his two point field goal attempts if he hits on On three pointers the break-even point is If a player exceeds these thresholds, and virtually every NBA player does so with respect to two-point shots, the more he shoots the higher his value in PERs.
So a player can be an inefficient scorer and simply inflate his value by taking a large number of shots. He made this assumption because he forgot that PER is calibrated against the rest of the league at the end of the formula.
Actually, if we took a player that was completely average in every other respect for the —07 season—rebounds, free throws, assists, turnovers, etc. As long-time PER fans know, that would make him considerably worse than nearly every player in the league. To end up with a league-average PER of Hollinger has set up PER so that the league average, every season, is Only 21 times has a player posted a season efficiency rating over As the metric is averaged over the length of a player's entire career a decrease in efficiency later in his career means a player can move down in the ranking.
For example, Jordan's PER took a big hit in the final two years of his career when he returned to the game with the Washington Wizardsposting Jordan's PER was At the conclusion of the —13 NBA season Miami Heat head coach, Erik Spoelstrastated that comparing players from different generations is the equivalent to comparing " apples and oranges.
The game is different now than when it was played in the s or even before that". Comparing players from different generations using PER presents several problems, this is primarily due to the rule changes and the changes in statistical data collected from different eras although many other factors could be taken into consideration, even down to the increased sample size as the NBA grew through incorporating more teams.
Some of the more important rule changes that should be considered include; some of the players on this list played before the three-point shot, blocks, and steals stats were officially recorded Wilt ChamberlainBill Russelletc.Field of View.
Posted by Dan Carr Jun 5, Tutorials.
Angle of View Vs. Field of View. Is There a Difference and Does it Even Matter?
Whilst researching some new tutorial content for this site, I stumbled upon a topic which seems to have a lot of people confused, and I have to be honest that when I began delving deeper into it, initially I just became more and more confused myself. Unfortunately it quickly contradicts itself in the very first line of the angle of view entry by citing a source that clearly states that people should not treat FOV and AOV the same.
That source, linked in the previous sentence, states that AOV is an angle, whilst FOV should be a measurement of linear distance.
That actually made a lot of sense to me, but other sources I trust explicitly on such matters, such as the excellent Photography Life websitecontradict that statement by saying that whilst AOV and FOV are different things, they are both measured as angles.
In their article it states that AOV is a property of the lens and does not change no matter what size of sensor is in the camera, whilst FOV is a function of the lens AND the sensor size. In other words, a full frame lens can have a particular AOV, but when used on a crop sensor camera the actual field of view FOV is going to be smaller. Once again, taken in a vacuum, this sounds like a perfectly excellent way to define both terms, but it does contradict other sources and I struggled to find anywhere else that suggested that particular pair of definitions.
I then started to look around to see how camera manufacturers were using the terminology and found that Canon, Nikon and Sony all cite angle of view in their lens specifications on their websites and appear to prefer this terminology over field of view. However, they also include the angle of view for both full frame lenses, and APS-C lenses see example belowwhich is contrary to the usually excellently researched content on Photography Life which says that AOV for a lens is constant, and only FOV changes based on sensor size.
Sample specification from Sony website. Canon and Nikon take much the same approach. In slightly more technical terms, it is the angular extent of the scene captured on the sensor, measured diagonally. Different lenses of equal focal length will always have the same angle of view when used with the same-size sensor.
The angle of view is the visible extent of the scene captured by the image sensor, stated as an angle. Wide angle of views capture greater areas, small angles smaller areas.
Changing the focal length changes the angle of view. The shorter the focal length e. The longer the focal length e. At this point I was thoroughly puzzled by all of this and all signs were pointing to the fact that the two terms are just so similar to each other that the internet has completely befuddled itself about them.
My definitions, as presented below, are the ones that make the most sense to me when I piece everything together.
So here is how I am going to define and use these terms on this site and in my future work unless someone can provide me with some well sourced information that contradicts this:. This is the formula that is most commonly cited for angle of view, and it agrees with the way in which lens specifications are presented by all the major camera manufacturers.
The angle of view is affected by both the focal length of the lens, and the size of the sensor in the camera. A long focal length delivers a very small angle of view. If you know the focal length, and the distance to subject, you can calculate the angle of view and then the field of view.
This would allow you to calculate the size of something within your frame, or, in reverse you could calculate your distance to the subject if you knew the size of it and what proportion of your frame it filled.Your users need to access and understand this data at-a-glance without doing a bunch of calculations in their heads.
Enter formula fields, the powerful tool that gives you control of how your data is displayed. Maybe you want to take two dates and calculate the number of days between them. All these things and more are possible using formula fields. You can create a simple formula field that automatically calculates that value. By adding the value to the Opportunity page layout, your users can quickly access this key information. You can also add this field to reports and list views for instant access.
You can create custom formula fields on any standard or custom object. Follow these steps to navigate to the formula editor:. Sometimes you need more! The next page lets you set field-level security.
For now, click Next so we can add our formula field to the page layout. For the time being, make sure that all the checkboxes are selected. Click Next and then click Save. Open the detail page for the Contact object you just created and find your new Account Number formula field. You can also use formula fields in reports to increase the visibility of important information. Say, for example, you wanted a report column that displays the number of days until an opportunity is closed.
First, create an Opportunity to test our formula. Select - Subtract from the Insert Operator menu. Find it in the Functions menu on the right side of the editor and click Insert Selected Function. From the Reports tab, click New Report. Then select Opportunities and click Create.
Your opportunity appears in the Preview panel. Search for Days to Close in the Fields menu on the left side of the page. This field is the formula field you just created. Drag it to the last column in your report.
The column populates automatically with the calculated value. Organizations often want to count the number of unique objects in a report with hundreds of records. Say, for example, you have a hundred opportunities listed in a report, but only a handful of users own all these opportunities.
How do you find the number of distinct users?I know enough people who handle all of these points (20. Why should the management of it be.Microscopes \u0026 Field of view (Part1)
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Supplier Selection Our Research Buyer's Guides, RFPs and Agency Top 100 to help you find a supplier. Advice If you're transforming your organisation's digital capabilities, skills and resources, talk to us. This service is currently undergoing maintenance. This post highlights how to do this with customers. Customers tend to fall into two camps: Those who don't want to review your product or hate it.
Those who can't review it or don't know how. Once you look at reviews in this way it'll become easier to identify opportunities. How to get customer reviews 1. Just ask me When you eat at a restaurant, the waiter will ask you whether you like the food. Email follow-ups Get customer email addresses at the point of purchase, even if you sell stock offline. Likewise Amazon email me every time I buy something to ask if I would like to leave feedback.
Make reviews count Another thing Amazon does well is to use my reviews to recommend other products that I may like in the future. Focus groups Before going to market with a product, bringing together a focus group is an essential step for gathering feedback.
Create a 'reviewographic' Collect data from customers and turn it into graphs and data sets to show on an Infographic. Here's an example of all the aggregated reviews on Yelp that you could do on a smaller scale: 6.
Create comparison charts Run a poll across your site to get customer feedback and then add this data into a comparison so people can see how you stack up against competitors. A good example is: Anti-Spyware Reviews 7.
Add reviews to your website An obvious step, but one that is missed a lot. Link to external reviews from your website I've written reviews before simply because I wanted to get either a tweet or a link from a major company to my own blog and I'm sure I can't be the first person to do this.
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Player efficiency rating
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Force between magnets
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