lecture 12 (DD At The Rigsite)

DD at the Rigsite 

About this chapter
The DD has other rig-site responsibilities not directly related to drilling. These include
keeping an accurate inventory of the DD tools. The logistics involved in getting
equipment to and from the rig-site varies, depending on the location. it is vital that the
DD keep the various reports up to date. This information is needed by the location
manager and, often, the unit technical manager.
Finally, knowing the rig-site politics and abiding by the rules makes the DD job run
much more smoothly than otherwise. The degree to which the DD is "his own boss"
often depends as much on himself as it does on the client. This chapter highlights the
above.
Objectives of this Chapter
On completing this chapter the directional driller should be able to do the following
exercises:
1. Acquaint himself with the safety procedures of politics.
2. Produce timely and accurate reports.
3. Professionally handle rig-site any location.
4. Control rig-site tool inventory.

12.1 On Arrival at the Rig


On arrival at the rig, the following is a recommended routine.
1. Familiarize yourself with the safety procedures on board (life raft, life boat
assignments, frequency of fire drills and abandon ship drills etc.).
2. Meet the company representative. Discuss briefly the well program. Be aware of the
present operation on the rig. Confirm that there is at least one directional plot on
board (if you’re going to do a blind sidetrack, obviously this does not apply). Put up a
copy of the plot on the wall of the company rep’s office. The anti-collision map
("Spider Plot"), if applicable, is usually updated after each well and shows the
relative positions of the wells drilled to date.
3. Meet the toolpusher. Check that there are sufficient drill collars and HWDP on board
the rig.
4. Meet the driller on tour. If there’s any instructions to be given to him, do it now. For
instance, if he’s drilling down to the kickoff point, he will need to be informed if a
multishot survey will be taken prior to POOH, the composition of the next BHA etc.
5. Attend safety meeting with the other Anadrill cell members, if applicable.
6. Do a complete inventory of the directional tools. It is advisable to caliper everything
as you check them. The serial numbers of every tool must be recorded. While it takes
a few hours to caliper everything properly, a lot of the tools (apart from those that
will be re-cut and new tools that arrive) will only need to be calipered once in the
course of a project. Thus, it’s important to do it properly the first time.

7. Use a check-list. If there’s any tool obviously missing, check that it has been ordered.
Call the Anadrill office if necessary. Also check for damaged threads and shoulders.
Check the D+C hours already on the mud motors, if a different Anadrill DD was on
the rig most recently.
8. On a new job (e.g. multiwell platform) which is expected to last several months or
more, it is advisable to get a rack fabricated by the welder to hold all the subs,
stabilizers and, possibly, short collars. This minimizes the space occupied by the DD
tools. It also helps protect the tools, makes them easy to find and easy to pick up/lay
down.

  Note

Permission must be gotten from the toolpusher before the tool rack is made. He will
normally coordinate the fabrication of the rack with the welder. The DD can make
design suggestions. To store stabilizer sleeves, an area should be found which is big
enough to allow gauging of the sleeves as required. The remaining tools (e.g. mud
motors, NMDCs, EQ Jars and possibly short collars) are normally kept in the drill collar
bay.


9. Fill out a DD inventory sheet. Give a copy to the company representative. Post one
copy in the doghouse to facilitate the driller’s BHA paperwork.
10. Check all the survey instrument kits systematically (gyro and/or magnetic, singleshot
and/or multishot). Run a check shot for confirmation. Take a short multishot test
film, if applicable. Order any necessary missing equipment from the base. If you will
be using the rig floor power supply (e.g. in case of gyro), ensure that the voltages are
compatible.
11. Check all the survey running gear. Make up the complete mule shoe orienting barrel
assembly. Make up the bottom-landing shock absorber assembly also. If it’s a hot
hole, ensure that the long protective barrel is at the rig-site.
12. The running gear which might be needed during the course of the well is normally
stored on a rack behind the drawworks. Ensure the storage place is dry and clean.
13. Excess running gear should be stored in the steel box in which it arrived on the rig.
14. Check the rig equipment. Ensure the slick line unit is in good condition and that
there is sufficient line on the drum. Watch out for “kinks" in the slick line. It is
recommended to get the driller/assistant driller to cut off some slick line before
attaching the upper part of the single-shot running gear.
15. Familiarize yourself with the driller's console. Check that there are adequate sensors
operational and that there is nothing obviously wrong with the drill-floor equipment
from a DD viewpoint.
16. Run the GEOMAG program, in conjunction with the MWD engineer. Otherwise, use
Zone maps to determine the number of NMDCs needed in the BHAs in this well.
17. If on a multiwell platform, or close to other wells, ensure that the surface coordinates
of the well to be drilled (referenced to the fixed origin) are entered in the Advisor
and/or Macintosh so that the anti- collision program can be run later.

18. Set up survey files on the Advisor and/or Macintosh for the well to be drilled. If any
TOTCO surveys have already been taken, they should be entered in the file(s). Prior
to running a multishot survey in a nominally- vertical hole, TOTCO survey data
allows the DD to choose the appropriate compass/angle unit.


12.2 General DD duties as the well progresses


1. Ensure that the drilling supervisor is kept up to date on the progress of the well from
a DD standpoint. He must be informed of your intentions to change the BHA If a
correction run is required, the DD should explain why. He should also make
recommendations as to when the correction should be done. Sometimes a target
extension is the better option. That decision is made by the client.
2. Ensure that the driller and assistant driller is given a copy of the next BHA in good
time. Mark all the tools to be picked up. Ensure no unnecessary lost rig time occurs
because of confusion over BHA components.
3. Have good communication with the drillers. Drilling parameters usually have to be
changed regularly.
4. Surveys should be taken as necessary. Give the updated survey calculation sheet to
the drilling supervisor promptly.
5. During a kickoff, it is not always easy to have time to plot all the surveys. A good
DD will know how the kickoff is progressing without having to plot every survey.
The desired hole direction is known. It is very easy to calculate whether or not the
build-up rate achieved is "keeping up with the program".
6. Even during the kickoff, each survey should be calculated promptly and given to the
company representative. Where Anadrill’s MWD tool is in use, this is usually taken
care of by the MWD engineer on the Advisor. If there is a Macintosh on board,
MacDD Survey file should be updated by the DD as time allows.
7. When the kickoff is almost finished, it s necessary to plot a few surveys. After the
kickoff, plot the latest survey position on the DD plot promptly. Project ahead. use
BHA history from previous wells in the area to help in decision-making.
8. Keep all DD paperwork up to date. Consumables, run charges, personnel charges
(where applicable) should be noted on the Anadrill Daily Drilling Report. All other
relevant forms - Mud Motor Report, Survey Calculations & Analysis, BHA Analysis,
Steerable Report, DD Tool Inventory etc. should be comprehensively filled out.
9. Perform basic maintenance on UBHO subs, Roller Reamers, stabilizer sleeves etc.
10. Underreamers and Hole Openers should be stored in an oil bath (usually a length of
casing which is filled with oil) when not in use.
11. Survey instrument kit should be kept in the quarters (in cases where MWD tools are
in use) or in the driller’s dog-house (provided it’s clean and secure).
12. The DD should be on the drill floor when EQ Jars or Shock Guard is being picked up
or laid down. Ensure the Jack Nut (if applicable) is screwed down torqued to correct
value before RIH.
13. It’s advisable to be on the drill floor when the driller’s change tour. Don’t rely on the
driller to relay your instructions to his relief.

14. Ensure that the company representative has up-to-date survey information on his
desk at report time. He shouldn’t have to come looking for survey calculation data!
15. Grading of the bits is often a joint effort between the DD and the driller
.


12.3 Location Politics

The DD has a responsible and rewarding job at the rig-site. However, there are some
minefields which, if not avoided, can lead to major problems for the DD. Some advice
and guidelines are listed below.
1. Anadrill is a service company. We work to please the client. The service quality
which we provide will make us a major force in directional drilling.
2. Drilling of a directional well is a joint effort between the client and the DD
company. From the preplanning stage to the actual drilling of a directional well, the
plan may be changed several times. However, once the final plan is agreed, it is up to
the people on the rig to make their contribution to a successful well.
3. The amount of authority that the DD actually has at the wellsite depends on several
factors:
·  The level of experience and competence of the DD.
·  The level of confidence the client has in the particular DD. This is often based
on the previous performance of the DD.
·  The amount of experience the client has in drilling directional wells.
·  The amount of control the drilling superintendent wishes to have over BHA
selection etc.
·  Whether or not the company representative is a former DD or at least has a good
knowledge of DD techniques.
4. Some DDs like to make all the decisions involved in drilling a directional well -
amount of lead angle, BHA composition, deciding on when to do a correction run,
choosing drilling parameters, possibly specifying bits. This is fine, provided the
client is happy with this arrangement. However, a situation should never arise where
the DD oversteps his authority. There are many clients who make all the major DD
decisions for the DD. In such a case, the DD is merely someone who makes up
BHAs, steers a mud motor, calculates surveys and keeps the DD plot up to date. Lots
of DDs are happy with this arrangement. Some are not. They would be better suited
to a DD job where they had more autonomy. Ideally, the DD and the client together
should make a lot of the decisions.
5. It is important to keep the Anadrill manager/supervisor informed of the progress of
the well.
6. If there is a disagreement between the DD and the company representative over a
decision related to DD (e.g. BHA composition) it may be necessary to
(confidentially) call the Anadrill manager/supervisor and inform him of the situation.
Try not to be made a scapegoat for something you never did!

7. The DD should ensure that he is not "caught in the middle” between the geologist
and the drilling supervisor. Unless told otherwise, the DD always should follow
instructions from the drilling supervisor only. Any internal disagreement between the
drilling supervisor and the geologist is no concern of the DD.
8. If possible, it is advisable to be present when the drilling supervisor makes his
morning phone report to the drilling superintendent. Some input may be needed from
the DD, e.g. When is the next BHA change planned ? Is a correction run likely ? Is a
request for a target extension imminent?
9. As mentioned earlier in this manual, if a mud pump needs repair while ROP is high
(particularly in larger hole sizes at shallow depths), the DD should recommend that
drilling cease until the pump is back on line. This may not suit the toolpusher, as it
increases the rig down-time. However, drilling with insufficient annular velocity can
lead to serious hole problems later.
10. On returning to base after the job, the DD would be well advised to visit the drilling
superintendent and thus "close the loop". A short discussion on the well just drilled
might lead to a slightly different approach to drilling the next well. This will,
hopefully, lead to increased drilling efficiency.

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APPROVED DRUG PRODUCTS free download





CONTENTS

PREFACE TO THIRTY SECOND EDITION………… ………… …………
..…................
iv
2
HOW TO USE THE DRUG PRODUCTS LISTS
..............................................................
2-1
2.1
Key Sections for Using the Drug Product Lists …………………….….………………
......
2-1
2.2
Drug Product Illustration ……………………………………………
..….…………….……..
2-3
2.3
Therapeutic Equivalence Evaluations Illustration ………………….….…………..………2-4 DRUG PRODUCT LISTS
Prescription Drug Product List ……………………………………….…………….………………
...
3-1
OTC Drug Product List ……………………………………………….…………….…………………4-1
Drug Products with Approval under Section 505 of the Act Administered
Drug Products Which Must Demonstrate in vivo Bioavailability
by the Center for Biologics Evaluation and Research List
...……….…….………………...
5-1
Discontinued Drug Product List .…………………………………………….…….………………
....
6-1
Orphan Products Designations and Approvals List …………….………….…….………………
..
7-1
Only if Product Fails to Achieve Adequate Dissolution …………………
..………………………..
8-1
APPENDICES
A.
Product Name Index ……….…...………………………….………..……………………A-1 B. Product Name Index Listed by Applicant ………………….……
..……………………..
B-1
C.
Uniform Terms …………………………………………….………
..…………...………...
C-1
PATENT AND EXCLUSIVITY INFORMATION ADDENDUM ……….……..………………..........AD1
A.
Patent and Exclusivity Lists …………………………….…
..……..……………..……ADA1
B.
Patent and Exclusivity Terms
...……………………….….………...…………………ADB1

Freezing

Freezing is the unit operation in which the temperature of a food is reduced below its
freezing point and a proportion of the water undergoes a change in state to form ice
crystals. The immobilisation of water to ice and the resulting concentration of dissolved
solutes in unfrozen water lower the water activity (aw) of the food (aw is described in
Chapter 1). Preservation is achieved by a combination of low temperatures, reduced
water activity and, in some foods, pre-treatment by blanching. There are only small
changes to nutritional or sensory qualities of foods when correct freezing and storage
procedures are followed.
The major groups of commercially frozen foods are as follows:
• fruits (strawberries, oranges, raspberries, blackcurrants) either whole or pure´ed, or as
juice concentrates
• vegetables (peas, green beans, sweetcorn, spinach, sprouts and potatoes)
• fish fillets and seafoods (cod, plaice, shrimps and crab meat) including fish fingers,
fish cakes or prepared dishes with an accompanying sauce
• meats (beef, lamb, poultry) as carcasses, boxed joints or cubes, and meat products
(sausages, beefburgers, reformed steaks)
• baked goods (bread, cakes, fruit and meat pies)
• prepared foods (pizzas, desserts, ice cream, complete meals and cook–freeze dishes).
Rapid increases in sales of frozen foods in recent years are closely associated with
increased ownership of domestic freezers and microwave ovens. Frozen foods and chilled
foods (Chapter 19) have an image of high quality and ‘freshness’ and, particularly in
meat, fruit and vegetable sectors, outsell canned or dried products.
Distribution of frozen foods has a relatively high cost, due to the need to maintain a
constant low temperature. Distribution logistics are discussed further in Chapter 19 in
relation to chilled foods and in Chapter 26. A recent advance in distribution of chilled
and frozen foods is described by Jennings (1999), in which carbon dioxide ‘snow’
(Section 21.2.4) is added to sealed containers of food, which are then loaded into
normal distribution vehicles. The time that a product can be held at the required chilled
or frozen storage temperature can be varied from four to 24 hours by adjusting the
amount of added snow. Other advantages of the system include greater flexibility in
being able to carry mixed loads at different temperatures in the same vehicle, greater
control over storage temperature and greater flexibility in use, compared to standard
refrigerated vehicles.
21.1 Theory
During freezing, sensible heat is first removed to lower the temperature of a food to the
freezing point. In fresh foods, heat produced by respiration is also removed (Chapter 19).
This is termed the heat load, and is important in determining the correct size of freezing
equipment for a particular production rate. Most foods contain a large proportion of water
(Table 21.1), which has a high specific heat (4200 J kg 1 K 1) and a high latent heat of
crystallisation (335 kJ kg 1). A substantial amount of energy is therefore needed to
remove latent heat, form ice crystals and hence to freeze foods. The latent heat of other
components of the food (for example fats) must also be removed before they can solidify
but in most foods these other components are present in smaller amounts and removal of
a relatively small amount of heat is needed for crystallisation to take place. Energy for
freezing is supplied as electrical energy, which is used to compress gases (refrigerants) in
mechanical freezing equipment (Sections 21.2.1–3) or to compress and cool cryogens
(Section 21.2.4).
If the temperature is monitored at the thermal centre of a food (the point that cools
most slowly) as heat is removed, a characteristic curve is obtained (Fig. 21.1).
The six components of the curve are as follows.


AS        The food is cooled to below its freezing point f which, with the exception of
pure water, is always below 0ºC (Table 21.1). At point S the water remains
liquid, although the temperature is below the freezing point. This phenomenon is
known as supercooling and may be as much as 10ºC below the freezing point.


SB         The temperature rises rapidly to the freezing point as ice crystals begin to form
and latent heat of crystallisation is released.


BC           Heat is removed from the food at the same rate as before, but it is latent heat
being removed as ice forms and the temperature therefore remains almost
constant. The freezing point is gradually depressed by the increase in solute
concentration in the unfrozen liquor, and the temperature therefore falls slightly.
It is during this stage that the major part of the ice is formed (Fig. 21.2).


CD      One of the solutes becomes supersaturated and crystallises out. The latent heat
of crystallisation is released and the temperature rises to the eutectic temperature
for that solute (Section 21.1.2).


















DE        Crystallisation of water and solutes continues. The total time tf taken (the
freezing plateau) is determined by the rate at which heat is removed.
EF         The temperature of the ice–water mixture falls to the temperature of the freezer.
A proportion of the water remains unfrozen at the temperatures used in
commercial freezing; the amount depends on the type and composition of the
food and the temperature of storage. For example at a storage temperature of
20ºC the percentage of water frozen is 88% in lamb, 91% in fish and 93% in
egg albumin.

Food Processing Technology Principles and Practice 2nd Edition (P. Fellows) free download









Contents


Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
List of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxvii
List of acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxx
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The food industry today . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
About this book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Note on the second edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
PART I BASIC PRINCIPLES 7
1 Properties of foods and processing theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.1 Properties of liquids, solids and gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.1.1 Density and specific gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.1.2 Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.1.3 Surface activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.1.4 Rheology and texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.2 Material transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.3 Fluid flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.3.1 Fluid flow through fluidised beds . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.4 Heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.4.1 Energy balances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1.4.2 Mechanisms of heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1.4.3 Sources of heat and methods of application to foods . . . . . . . 37
1.4.4 Energy conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.4.5 Effect of heat on micro-organisms . . . . . . . . . . . . . . . . . . . . . . . . . 40
1.4.6 Effect of heat on nutritional and sensory characteristics . . . . 43
1.5 Water activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
1.5.1 Effect of aw on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
1.6 Effects of processing on sensory characteristics of foods . . . . . . . . . . . 48

1.6.1 Texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
1.6.2 Taste, flavour and aroma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
1.6.3 Colour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
1.7 Effects of processing on nutritional properties . . . . . . . . . . . . . . . . . . . . . . 50
1.8 Food safety, good manufacturing practice and quality assurance . . . 52
1.8.1 HACCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
1.8.2 Hurdle technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
1.9 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
1.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2 Process control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.1 Automatic control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.1.1 Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
2.1.2 Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
2.2 Computer-based systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
2.2.1 Programmable logic controllers (PLCs) . . . . . . . . . . . . . . . . . . . . 72
2.2.2 Types of control systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
2.2.3 Software developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
2.2.4 Neural networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
2.3 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
PART II AMBIENT-TEMPERATURE PROCESSING 81
3 Raw material preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.1 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.1.1 Wet cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.1.2 Dry cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
3.1.3 Removing contaminants and foreign bodies . . . . . . . . . . . . . . . . 85
3.2 Sorting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.2.1 Shape and size sorting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
3.2.2 Colour sorting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.2.3 Weight sorting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
3.3 Grading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.4 Peeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.4.1 Flash steam peeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.4.2 Knife peeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.4.3 Abrasion peeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.4.4 Caustic peeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.4.5 Flame peeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
4 Size reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4.1 Size reduction of solid foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.1.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.1.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
4.1.3 Effect on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
4.2 Size reduction in liquid foods (emulsification and homogenisation) 110
4.2.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
4.2.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
4.2.3 Effect on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
4.3 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5 Mixing and forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
5.1 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
5.1.1 Theory of solids mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
5.1.2 Theory of liquids mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.1.3 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.1.4 Effect on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5.2 Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5.2.1 Bread moulders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.2.2 Pie and biscuit formers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.2.3 Confectionery moulders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
5.3 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
5.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6 Separation and concentration of food components . . . . . . . . . . . . . . . . . . . . 140
6.1 Centrifugation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
6.1.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
6.1.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
6.2 Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
6.2.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
6.2.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.3 Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
6.3.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
6.3.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
6.4 Extraction using solvents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
6.4.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
6.4.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
6.5 Membrane concentration (hyperfiltration and ultrafiltration) . . . . . . . . 157
6.5.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
6.5.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.6 Effect on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
6.7 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
6.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
7 Fermentation and enzyme technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
7.1 Fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
7.1.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
7.1.2 Types of food fermentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
7.1.3 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
7.1.4 Effect on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
7.2 Enzyme technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
7.2.1 Enzyme production from micro-organisms . . . . . . . . . . . . . . . . . 186
7.2.2 Application of enzymes in food processing . . . . . . . . . . . . . . . . . 187
7.3 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
7.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8 Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
8.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
8.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
8.2.1 Measurement of radiation dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
8.2.2 Dose distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
8.3 Effect on micro-organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
8.4 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
8.4.1 Sterilisation (or ‘radappertisation’) . . . . . . . . . . . . . . . . . . . . . . . . . 202
8.4.2 Reduction of pathogens (or ‘radicidation’) . . . . . . . . . . . . . . . . . 202
8.4.3 Prolonging shelf life (or ‘radurisation’) . . . . . . . . . . . . . . . . . . . . 202
8.4.4 Control of ripening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.4.5 Disinfestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.4.6 Inhibition of sprouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.5 Effect on foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.5.1 Induced radioactivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.5.2 Radiolytic products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
8.5.3 Nutritional and sensory value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
8.6 Effect on packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
8.7 Detection of irradiated foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
8.7.1 Physical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
8.7.2 Chemical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
8.7.3 Biological methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
8.8 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
8.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
9 Processing using electric fields, high hydrostatic pressure, light or
ultrasound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
9.1 Pulsed electric field processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
9.1.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
9.1.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
9.2 High pressure processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
9.2.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
9.2.2 Processing and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
9.2.3 Effect on micro-organisms, enzymes and food components 221
9.3 Processing using pulsed light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
9.3.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
9.3.2 Equipment and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
9.3.3 Effect on micro-organisms and foods . . . . . . . . . . . . . . . . . . . . . . 223
9.4 Processing using ultrasound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
9.4.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
9.4.2 Application to processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
9.5 Other methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
9.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226




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shale sandstone conglomerate sp and gamma ray log interpertation




well control .pdf

 





Kicks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-2
Controlling a kick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3
Shut-in procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3
Kill methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3
Wait-and-weight method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3
Driller's method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-4
Concurrent method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-4
Kick control problems

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Differential sticking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2
ENVIRO-SPOT spotting fluid . . . . . . . . . . . . . . . . . . . . . . . . 12-4
DUAL PHASE spotting fluid . . . . . . . . . . . . . . . . . . . . . . . . . 12-5
Determining depth to stuck zone . . . . . . . . . . . . . . . . . . . . . . . 12-9
Packing off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-9
Undergauge hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11
Plastic flowing formations . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11
Wall-cake buildup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11
Keyseating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-12
Freeing stuck pipe

Baroid Mud Handbook (well cementig .pdf free download )



Overview
The main cementing materials used in oilfield
applications are:
C Portland cement, API Classes A, C, H, and G
C Blast furnace slag (BFS)
C Pozzolans (fly ash), ASTM Types C and F
Portland cement is the name used for all cementitious
material composed largely of calcium, silica, and
aluminum oxides. Blast furnace slag (BFS) is a byproduct
obtained in the manufacture of pig-iron in a
blast furnace. Pozzolans are silica or silica/alumina
materials that react with calcium hydroxide (lime) and
water to form a stable cement. Pozzolans can be natural
or synthetic.
Cementing materials are used in drilling operations to:
C Isolate zones
C Support casing in the borehole
C Protect the casing from collapse, corrosion, and
drilling shock
C Plug non-producing wells for abandonment
C Plug a portion of a well for sidetracking
This chapter explains the use of additives to control
cementing slurry properties and provides the ideal
operational guidelines for each type of additive. Slurry
design and applications are provided for lead, tail, and
squeeze slurries. Plug design, spacer guidelines, and
spacer-volume calculations are also provided.












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Cementing additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3
Accelerators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3
Retarders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-5
Fluid-loss control additives . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-6
Extenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7
Free-water control additives . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7
Weighting materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-8
Slag activators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-8
Dispersants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-9
Strength retrogression preventers . . . . . . . . . . . . . . . . . . . . . . . 17-9
Slurry design and applications . . . . . . . . . . . . . . . . . . . . . . . . . 17-10
Lead slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-10
Tail slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-10
Squeeze slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
Plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
Spacers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
Spacer volume calculations . .

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Drilling Oil wells in Algeria










Drilling Oil wells  in Algeria "Petroleum (Industry)" platform and it's types workover petroleum

ADVANCES IN COMPUTER SCIENCE AND ENGINEERING free download





Edited by Matt hias Schmidt

Contents


Part 1

Applied Computing Techniques 1
Next Generation Self-learning Style
in Pervasive Computing Environments 3
Kaoru Ota, Mianxiong Dong,
Long Zheng, Jun Ma, Li Li,
Daqiang Zhang and Minyi Guo
Automatic Generation of Programs 17
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fundamentals of electricity free download




fundamentals of electricity

A review of basic principles of electricity & physics lec (4)

Complex Representation of Signals

Most generally, we can use complex or imaginary values for s (and/or A for that matter)
in equation 9, where s is known as the “complex frequency.” In electrical engineering it
is common practice to use the convention that
j = (-1)^.5 in order to avoid confusion with
the use of i to represent current; we will use that convention for the remainder of this
section. When s is purely imaginary, with the value s = jω and A is real, we can take
advantage of Euler’s relation, that:
We can apply a sinusoidally varying voltage at the frequency ω, V= cos(ωt), across the
capacitor. Note that the V is the real part of Aejωt = Re(Aest).
Substituting into equation 8:

We are interested only the real part of the current, of course, so equation 11 simplifies to
iC = –ωCAsin(ωt), the result of equation 6 above. Looking again at equation 9, when
s = jω the ratio of the voltage to the current is 1/ jω C.
Generalization of Ohm’s law
The ratio of a complex voltage, V, to a complex current, I, is represented by the
impedance, Z. Because sinusoidally varying signals are conveniently represented by
complex numbers (and, as we will see when we discuss the Fourier transform in a
separate section, this can be a generalized representation of most any signal we
encounter), this is an exceptionally powerful formalization. For complex signals, Ohm’s
law states simply that:

The magnitude of the impedance is given in units of Ohms, like resistance, but in
general also incorporates a phase shift. For capacitors, as noted above, the impedance is
1/jωC. Applying Voltage as a cosine wave results in a current that is an inverted sine
wave – a 90° phase shift. In general, multiplication by j represents a 90° phase shift.
As we noted above, the voltage and current relationships for most electrical circuits
(specifically, linear electrical circuits), can be found through the application of Ohm’s
law coupled with KVL and KCL. The Laplace transform solution, as in equation 9, allows
this to be generalized readily to the analysis of devices like capacitors, which store
energy.
One should be a little bit careful here concerning the values of ω, which are in units of
radians/second or angular frequency. In common use we generally speak of frequencies
in cycles/second or “Hertz”. As one cycle is 2π radians, ω=2πf, where the letter f denotes
the frequency in cycles/second. When the input voltage is a sinusoid with frequency, f,
equation 9 may be written as:

A review of basic principles of electricity & physics lec (3)

Energy Storage Devices

Though hundreds of different devices exist, we will consider just three other circuit
elements: batteries, capacitors and inductors.
A battery is a familiar device that is an approximation to an ideal Voltage source.
Physically, batteries produce voltage difference through the chemical separation of
charges. As current is allowed to flow from one pole of the battery to the other, charges
move back together releasing energy, generally into the circuit that connects the poles of
the battery. In the circuit of A1.003 (a), a wire connects the positive and negative pole of
a battery. If the wire were “ideal”, having zero resistance, we would expect that all of the
charge would flow instantaneously from the positive to the negative pole of the battery,
such that the current, dQ/dt, would be infinite. Of course this doesn’t actually happen.
Instead, it turns out that all real batteries show some resistance to current flow, which
limits the current. The circuit of A1.003 (b) shows a practical and realistic model of the
battery as an ideal Voltage source in series with a resistor. (This combination is known
as the Thévenin equivalent). Many of the electrical properties of neurons and other
excitable cells may be accurately modeled in this manner.

Capacitors
When two conductors are separated from one another by an insulator, and a source of
current is applied (Figure A1.004), positive charge will accumulate on one side of the
insulator and negative charge on the other, resulting in a buildup of Voltage. As long as
the charge keeps flowing the Voltage will increase steadily, and without limit.
Analogously, if a Voltage source is applied across the separated conductors, charge will
build (immediately, in the case of ideal conductors) of such a magnitude that the
potential energy difference is equal to the Voltage of the source. When the sources are
removed, however, the charge difference, and therefore the Voltage difference, is
retained across the insulating boundary, thus storing potential energy. A device made of
conductors – typically in the form of thin films – separated by an insulating layer is
known as a capacitor. However, capacitance will exist between any conductors
separated by an insulating layer or material. Unlike resistors, capacitors store energy,
rather than dissipate it.





The capacitance, C, is measured as the ratio of the charge across the capacitor to the
applied Voltage:
Q = CV.

The circuit symbol for a capacitor is shown in figure A1.005, and represents two
separated conductive plates.


The unit of capacitance is the Farad. A large capacitance, achieved by having a very
small insulating gap, means that a relatively small charge results in a large Voltage
potential difference, chiefly because the attractive forces between positive and negative
charge are very large over short distances. Taking the first derivative of equation 1, we
see that the current is proportional to the Voltage change over time.


In a sense, this appears similar to Ohm’s law, except that now the current is
proportional to the rate of change of the Voltage, rather than the Voltage alone, as it is in
a resistor. The capacitor, in this case, takes the place of the resistor, but one whose
resistance depends on the rate of change of the Voltage. Rather then resistance, the term
impedance, measured still in Ohms, is used to describe this behavior. In effect, this
means that while an insulating layer does not pass constant current, time-varying
currents may be passed. The units of Farads are defined such that a Voltage that
changes by 1 V/s, when applied across a 1 Farad capacitor, will result in the flow of 1
ampere (a very large amount) of current. Most often, capacitors used in electronic
circuits have capacitance of a few microfarads (μF).
Specifically, consider applying a sinusoidally varying voltage across the capacitor:



that is, a sinusoidal current with a 90° (=π/4) phase lead with respect to the Voltage.
The term, ω, is the frequency, and this frequency-dependent resistance, measured in
Ohms, is given the term impedance. Specifically, the impedance goes down as the
frequency goes up. Capacitors pass greater current at the same Voltage when the
frequency is higher. They are like resistors whose resistance decreases with frequency.
Unlike resistors however, which dissipate energy as heat, the capacitor only stores
energy, by converting between potential energy in the form of Voltage, and kinetic
energy in the form of current.

Ohms law tells us that the magnitude of this proportionality is the resistance, which we
now see is proportional to s. The exponential term, est, simply drops out of the equation.
No assumptions were made about A or s, however, except that they are constant with
respect to t. This solution form to the differential equation 4 is known as the Laplace
transform, and is an important solution method in all forms of linear systems.