Tentative ventilation of torsional, axial and instraightforward groundwork retreat galaxy waves
The grease and mist strikeivity is single of the liberalst and the most globalized strikeivity in the cosmos-people. Petroleum products conceive plastics, fuels, ointments and abundant advance. With acceptions in cosmos-people population, decmethod and require of petroleum products own acceptiond. Primarily petroleum products are used as principle sources. With an acception in require, divergent, unconventional sources are substance explored. Instruction in itself is a complicated scheme attribuboard to the obscure curbmations in the sphere. A retreat is pierced in the sphere with a fragment, and tubulars are secure to it to stipulate axial vigor and series. The tubulars are indentation through which the instruction infiltratey is spreadd to take-quenched the avoid roll. Once the retreat is pierced, the fragment and tubulars are fascinated quenched, and a liberalr tubular is pushed down the retreat and cemented encircling the annulus to plug the retreat from caving in. The scheme is the correspondent as instruction a infiltrate polite bebehalf with great profoundness, influences, temperatures and complicatedities. Some of the grease and mist sources are besides recondite or besides complicated to be explored, bebehalf with novel technological product in instruction, sufficient penetrate, multiinstraightforward and downright polites, it is now likely to take-quenched unconventional grease and mist.
When an existence disturbs encircling its equilibrium aim, the existence is said to be in wave. In most of the circumstances waves are ordinary, as they suit damage to the scheme and waste principle. When vigor or principle is imparted to a scheme, waves appear. In omission of visible inducement, the waves are pur-poseated liberal waves. Schemes in recite of liberal waves disturb with eventual frequencies, which are contingent on the properties of scheme. With the intercourse of visible inducement, waves accustomed by the scheme are pur-poseated vigord waves. Waves behove increasingly liberal and are most detrimental when the inducement aburst is suspobject to single of the eventual frequencies. This inquisitiveness is pur-poseated resonance. When there is an principle colliquation from the scheme in provisos of excitement, investigate, attrition or any other regularity, the resulting waves are pur-poseated damped waves.
The ordinatestring galaxy is a very crave, thin scheme prsingle to unreasonable wave attribuboard to the multitudinous vigors strikeing on it. Primary vigors on the BHA are torque attribuboard to series and fragment roll interaction, axial vigors attribuboard to lugubriousness and instraightforward vigors attribuboard to cringing of the crave pipe and hitting the regards of the penetratehole.
Drillstring waves are categorized inveterate on the vigors strikeing on it, which are Torsional, Axial and Instraightforward vigors. These vigors fit to the three restrainms of wave: 1) Torsional waves, 2) Axial waves and 3) Instraightforward waves.
Torsional Waves: Ordinatestring is hangd from the demeanor to stipulate torque or shear vigor to avoid the roll.
A lab-lamina instruction rig was constrained curb the pur-pose of competing in Ordinatebotics International Student Race. OU Ordinatebotics team participated and won the race in 2015. The budattain restrictions scant the compatability and aburst of sensors bursted on the rig. The rig was upgraded in 2016 with the joined budget. The subjoined sections relate the rig establishedup and sensors grounded, dividing them inveterate on the schemes: (i) Rig Edifice, (ii) Elevateing Scheme, (iii) Rotary Scheme, (iv) Vogue Scheme, (v) Gaugement, Instrumentation and Curb Scheme and (vi) Ordinatestring Galaxy.
Rig Edifice consists of three main compatability: substructure, mast and roaming arrest.
In-issue built edifices own been fix to be speakingly cheaper than readymade edifices in the communicate. Advanceover, the primary-mentioned stipulates flexibility in the adoption of compatability, enjoin ratings and pur-pose styles. This subedifice was pur-poseed to by through doors, so the rig could be used curb curbthcoming educational pur-poses. The rig subedifice was constrained using 1Â½” balance-lusty tubing with aggravateperfect compatability of 84″ x 27″ x 36″. To afford rig restlessness, five markeboard gradation caster wheels were grounded, each with enjoin compatability of 1000 lbs. A 47″ x 27″ oblution made of Â¼” confused lusty fencing was external curb installation of vogue scheme and electrical smack. This left the rig with a illimitableness of 37″ x 27″ x 36″ to decide the roll scantling.
A mast of cantilever pur-pose was constrained quenched of Aluminium, as shown in Fig. 3.1.
Constructing the mast with aluminium stunted the ponderosity by 2.5 opportunitys to that made by steel. A 10-inch-wide C-Channel was attended by brace 90 discomposition seals. The base was secure to the board with hinges curb lying and manageable ecstasy of the rig.
The roaming arrest slides on a brace of straightforward conduct rails secure to the mast. Straightforward roller courses or pilbase arrests secure to the tail of the roaming arrest stipulate neighboring flatten excitement. Brace downright dishs were flyed on the upright dish. The remarkable dish strikeed as a burst curb the AC motor and inferior dish attended the swivel. A torque sensor was located in betwixt motor mass and swivel. The entirety ponderosity of the roaming arrest was gauged to be 77.72 lbs.
Hoisting scheme components conceive a inclose strikeing earnestness cylinder, pneumatic methods, a cockney of pneumatic convertors (Fig. A.1 and Fig. A.2) and a sheltered earnestness produce method. Regulated sheltered earnestness-method up to 130 psi was hooked up to the pneumatic convertors. Brace pneumatic methods from the convertors of climax compatability 120 psi curbled the earnestness stream and united to the entrance ports of the dual strikeing piston. Dual strikeing earnestness piston has a 1.125 inch penetrate and a 36-inch tickle elongation. The scheme has a compatability to elevate a enjoin of 119.28 lbs.
A extreme importune scheme was grounded with a 1 HP motor and a climax RPM of 1170 on the motor burst of the roaming arrest. The motor mass is united to the omega torque sensor via a burst coupling. The torque sensor has a rotating mass to mass conconstruction with an generous accelerate of 5000 RPM. The torque sensor is united to the swivel via another burst coupling. The swivel was pur-poseed and concocted in-issue with influence rating of 300 psi and impudence quencheder mass curb inrenewal opposition. The chrome dishd rod is wear-resistant to the peeling of the seals. Swivel rod is secure to an adapter at the base of the groundwork dish. A foul-mouthed fly flange bursted circle course nullifys any enjoin from substance catching to the rotary galaxy.
It is great to transport avoidtings from the retreat to ordinate advance afore. To terminate this, infiltrate, grease and explode inveterate instruction infiltrateys were fascinated into consequence. Infiltrate from the city method withquenched any additives was disjoinedd as instruction infiltratey aftercited portico require of a suspendd loop scheme curb revogue and require of additives and base infiltrateys into statement. It was as-well conjectured that the commodities of instruction infiltratey on ordinatestring waves was negligible.
A roller cross-examine with a influence rating of 300 psi was grounded to spread the infiltrate down the ordinatestring galaxy. A 1.5 HP 3-phase motor powers the cross-examine. The Omega digital flaunt stream meter, which was grounded aftercited the cross-examine, can mentor streamrate up to 15 GPM. Influence mentoring is dsingle by a influence transducer of rating 500 psi. Influence divergency of up to 50 psi was perceive-keepd attribuboard to intermittent stream granted by the roller cross-examine. A influence dampener was built with inabundant couplings and grounded upstream to the stream meter. This stipulated flatten and sboard stream. An analog influence probe was bursted aextreme the dampener to mentor divergency. Rubber hose with a influence rating of 300 psi connects the stream meter with the swivel. Instruction infiltratey from the swivel then streams into the ordinatestring and comes quenched of the fragment nozzles and quenched of the retreat through the annulus. As the instruction infiltratey is right infiltrate, it is byed down the sewer method acrave with the avoidtings and referable recirculated.
The Gaugement, Instrumentation and Curb scheme is the most great scheme in the automated rig. The sensors are bursted on the rig at multitudinous locates curb divergent functions. They stipulate analog deeds to the deeds merit module Omega DAQ-3001. An electrical smack is bursted at the groundwork oblution curb shielding the card and other distinguished provisoers from electrical interlocution. The deeds from the DAQ module transfers into the deskextreme computer, which is grounded on the rig edifice curb curb of the automated rig and storage and flaunt of deeds. Yield-inveterate VBA program is used curb the strikeion of the rig.
Subjoined are the sensors grounded on the rig to mentor deed of the rig and instruction scheme.
126.96.36.199 Misconstruction Laser Sensor
An aluminum dismantle is secure to the extreme of the roaming arrest with a impercipient tape heap on it. A Banner laser sensor is bursted abquenched 0.5 inches aggravatehead the roaming arrest on the mast. It can gauge climax misconstruction up to 3.93 inches with an achievement betwixt 0.019 inch to 0.039 inch.
188.8.131.52 Instraightforward Wave Laser Sensor
To gauge instraightforward waves of the ordinatestring, an xyz laser sensor is used. It can gauge interval from 1.57 inch to 6.29 inch with an achievement of short than 20 micrometer. The sensor was prior bursted on an aluminium dish secure to the roaming galaxy. Bebehalf the dismantle was crave and unreasonable waves attribuboard to fragment roll interrenewal suitd the dismantle to undulate at violent richness, providing illogical and false deeds. Hereafter the bursting edifice was made of a balance lusty tubing to surrender a sturdier edifice. The wave richness was then stunted and could be perceive-keepd singly at unreasonable waves attribuboard to violenter RPM and WOB.
184.108.40.206 Optical RPM Sensor
An LED-based, impercipient restrainm optical RPM sensor, which can gauge up to 15000 RPM, is bursted on the confine of swivel. Impercipient tape is heap on the burst coupling betwixt the swivel and torque sensor. The sensor is bursted at an discomposition so that the impercipient area acceptions curb meliorate gaugement.
220.127.116.11 Torque Sensor
It is conjectured that torque gauged by the torque sensor is the torque attribuboard to fragment-roll interaction. An Omega rotating mass to mass torque sensor has been bursted aggravatehead the swivel with a torque rating of 64 inch-pounds.
18.104.22.168 Axial Wave Sensor
An axial wave senor is grounded at the groundwork dish of the roaming arrest neighboring to the flange bursted circle course. The VBT-1 wave sensor has a micro-electro-mechanical scheme which despatchs a voltage proportional to the wave accelerate to the deeds merit module. It gauges wave accelerate from 0-25 mm/sec.
The ordinatestring galaxy comprises of 3 compatability, Aluminum pipe, fragment sub and fragment.
The pipe is made of Aluminum 6061 with an OD of 0.375 inch and a confusedness of 0.035 inch. Twain objects of the pipe own 3/8″ NPT courageous compression fittings secure on it. It is united on single object to 3/8″ NPT fecourageous impudence adapter which is united to the swivel rod and other object is united to 3/8″ NPT fecourageous fragmentsub.
The fragment sub is made quenched of colorshort steel curb inrenewal opposition. It has 3/8″ fecourageous NPT threads on twain objects. A roller sleeve with OD of 1.1 inch and ID of 0.9 inch is slide upon the fragment sub to strike as a stabilizer and stipulate flatten series. It has a despite penetrate to locate constriction of multitudinous sizes to substitute influence fperfect in the scheme.
The fragment is concocted in issue using colorshort steel rotund seal and machined to involve the baker huges fragment stipulated curb the race. The avoidters were bought from vendors and the OD of the avoidters suited was 0.5 inch. They are made quenched of carbide as opposed to the diamond avoidters stipulated and as-well wears down faster. The avoidters are screwed on the avoidter faces and are replaceable.
This passage relates the act of the trials done and the deeds composed. It as-well talks abquenched some assumptions, sensor calibration and deeds segregation.
The rig and perfect its components are powered on and the Yield program indoctrinated. The program has a disjoined fencing which takes the mutables of the tentative escape as an input. The singly mutables substituted curb the established of trials are RPM and WOB. Another mutable, which is the climax at which the string starts to hang was as-well been multiplied bebehalf it did referable own any commodities on the deeds.
A escort retreat of 1.25-inch crossing and 1-inch profoundness was pierced into the roll scantling using a coring fragment and hammer-chisel to infuse a conduct shoe in the retreat. The 6-inch crave conduct shoe strikeed as a penetrateretreat wperfect and nullifyed fragment walking. Using a flatten indicator, the roll scantling was adjusted to be downright.
The ordinatestring was the secure to the swivel adapter and rig was then slid aggravate the roll to align the ordinatestring and the conduct shoe. Using the flattening screws the rig was jacked up to be downright.
The entrance earnestness influence method and infiltrate method were opened up. Once perfect tentative mutables were established, the program was indoctrinated using the Start besideton. The primary plod of the program was to elevate the roaming arrest to the extrememost composition. At this aim a protection seal used to retain the roaming arrest elevateed was fascinated loose. The roaming arrest sloth inferiored down and once the fragment was within the conduct shoe, extreme-importune motor and cross-examine motor got strikeivated and string instituted to hang acrave with infiltrate pressurized within the pipe. The fragment spiritual touched the roll and instruction scheme began.
A suffering escape was carried quenched to brlazy if the schemes were launched uprightly and deeds was substance composed. A cockney of millimeters were pierced during the suffering escape so that the retreat got indoctrinated.
Aftercited a suffering escape, tentative escapes were carried quenched. Each trial was escape curb 6 min and plugped using the Plug besideton in the program. The cross-examine plugped cross-examineing infiltratey and ordinatestring plugped series. Roaming arrest was spiritual lifted up to the extrememost composition. Aftercited that strank tentative mutables were established and the next escape was carried quenched.
Experiments were done on 2 divergent roll scantlings. Primary established on a very arduous and compacted sandstsingle and the other on a very kind unconsolidated sandstone. UCS of the arduous sandstsingle rankd from 6000 to 9500 psi suitableness UCS curb the kind sandstsingle rankd from 2000 to 5000 psi.
Facts was unintermittently composed by Omega deeds merit scheme module and stored in an yield fencing. The deeds of attention were WOB, RPM, Torque, Axial Waves, Instraightforward Waves and ROP. Divergent conspires were generated despite mutables of attention to perceive-keep dependency and proceeding of the mutable inferior ventilation.
WOB is an incontingent mutable with regard to our ventilation. WOB was gauged using a enjoin cell secure to the tail roaming arrest connecting the piston. The calibration of WOB was carried quenched in the subjoined act. The rig was slid on a contemplation lamina. A established calculate of appraises were entered curb voltage sent to the groundwork pneumatic convertors. A perpetual voltage of 2 volts was sent to the extreme pneumatic convertor to stipulate a perpetual influence of 20 psi opcomposition despite shiftful brawny and to stipulate a perpetual attrition betwixt piston and cylinder regards in either inclination. Balbutiation on the contemplation lamina was recoded as WOB. Judiciously the WOB calibration was done in a static proviso. It was perceive-keepd that WOB balbutiation during the trial was divergent than the expected appraises inveterate on calibration. It was conjectured that the substitute of provisos from static to dynamic was the suit of dissimilitude. Hereafter to feign dynamic provisos suitableness calibration, rig was perpetually hammered down with a mallet to suit the rig to undulate and negate static attrition. The stabilized balbutiation on the lamina was used curb calibration. Bebehalf hammering peaceful did referable involve the waves happening during the instruction scheme and hereafter the WOB gaugement by the enjoin cell was divergent from expected inveterate on the calibration. Hereafter medium appraise of the WOB was adapted curb finished tentative escape and considered as the WOB which is substance exerted on the roll curb avoidting scheme.
The medium WOB perceive-keepd had a substitute of 19.9 % to -20.6 % from the expected input appraises. In strikeual instruction scheme, the WOB is never perpetual. As the instruction proceeds the WOB diminishs and ordinateer inferiors the ordinate string to acception and repress the established WOB. Hereafter a Â± 20 % substitute from the established aim is cheerful.
RPM deeds was gained from the optical RPM sensor which was calibrated using a handheld RPM sensor. At inferior RPM the fallacy was encircling 8 % and at violenter RPM it inferiored down to 0.5 %. So at inferior flattens the established aim was diminishd by 4 to liquidate curb the fallacy.
A rotating mass to mass torque sensor was located in betwixt the motor and swivel with a burst coupling on each object. Torque was calibrated using a torque strain. When escape at lazy provisos withquenched any instruction strikeion, torque balbutiation gained was conjectured to be attrition. That extra torque of 1.114 inch pounds was conjectured to be a behalf vigor or the attrition within the swivel and other rotating compatability such as the flange bursted circle course.
A laser misconstruction senor was secure to the mast to descry the concretion of instraightforward waves. It was aimed at the benevolence of the ordinatestring such the pipe was invariablely in rank of the laser. The laser sensor was kept 4 inches loose from the benevolence of pipe. NPT connections are inherently perception concentric and suits perception-alignment of pipe. The pipe wobbled attribuboard to perception-alignment and it disturbd remote and neighboring to the sensor. Hereafter there was a instraightforward and a explicit appraise curb misconstruction. The most instraightforward appraise of the misconstruction was used as a relation referablehing and finished deeds was shifted towards explicit with -0.24165 inch as a relation referablehing. Great the concretion, pipe travelled remotether loose from the sensor indicating violenter instraightforward waves.
An axial wave sensor was secure to the groundwork dish of the roaming arrest. It had micro-electro-mechanical scheme within to descry the wave accelerate and sobject a proportional voltage distinguished curb gaugement. The sensor came calibrated from the creator and it had a straightforward wave-accelerate to voltage correspondentity stipulated by the creator.
ROP was straightforwardly adapted by the program by dividing the profoundness pierced by the opportunity it besidesk to ordinate and stored in the Yield fencing. As the Arduous sandstsingle was arduous to ordinate the sensor could referable gauge any speaking substitute in pierced profoundness acrave with the waves of the galaxy and the fallacy in gaugement. Hereafter ROP deeds curb Arduous sandstsingle is referable fascinated into consequence. Kind sandstsingle deeds was composed and analyzed curb commodities of waves and other parameters.
Facts was composed from the aim where the fragment touches the roll to the aim when the program was plugped. Perfect trials were escape curb 6 minutes in which an medium of 100 deeds aims were composed in an yield fencing. An medium of those deeds was adapted and stored. Medium appraises of torque, axial waves and instraightforward waves were conspireted despite RPM and WOB disjoinedly. A trobject of deeds was analyzed inveterate on the conspires. With acception of RPM, substitute of torque, axial and instraightforward wave was perceive-keepd. Correspondent hapiece was carried quenched curb WOB. The conspires are shown in Appendix B.
Arduous Sandstone: Looking at the conspires (Fig. 5.1), with an acception in RPM at perpetual WOB, torque spiritual acceptions. At encircling 300 RPM, there is a rash acception in some circumstances which then diminishs. This proceeding is unforeseen and no misentry has been fix curb the conclude curb the abnormality. It can be conjectured that there would be some abnormally arduous lamina during instruction attribuboard to which such an acception is perceive-keepd as no such trobject was perceive-keepd in the conformable kind sandstone. Bebehalf open trobject is a sbase acception in torque with an acception of RPM at perpetual WOB. No wave of torque was perceive-keepd indicating omission of stick-slip.
At perpetual RPM, with acception in WOB there is a sbase acception in torque (Fig. 5.2). No restricted trobject curb RPM is perceive-keepd as some of the base RPM circumstances as-well own violenter torque than violent RPM circumstances.
Kind sandstone: Observing the conspire curb kind sandstsingle (Fig. 5.3), a sbase acception in torque was perceive-keepd with acception in ROM at perpetual WOB. No wave of torque was perceive-keepd indicating omission of stick-slip.
Figure 5.3: Torque vs. RPM conspire at perpetual WOB curb trials on kind sandstone
There is a open and plain trobject curb acception in torque with acception in WOB at perpetual RPM (Fig. 5.4).
Figure 5.4: Torque vs. WOB conspire at perpetual RPM curb trials on kind sandstone
Arduous Sandstone: Conspire (Fig. 5.5) shows that there is a sbase acception of torque with acception in RPM at perpetual WOB.
Figure 5.5: Instraightforward Waves vs. RPM conspire at perpetual WOB curb trials on arduous sandstone
No open trobject is perceive-keepd curb judicious base WOB trials (Fig. 5.6). With acception in WOB the instraightforward waves diminishd in base RPM circumstance and acceptiond in violent RPM circumstances.
Figure 5.6: Instraightforward Waves vs. WOB conspire at perpetual RPM curb trials on arduous sandstone
Kind sandstone: There is a open trobject of acception of instraightforward waves with acception in RPM (Fig. 5.7) bebehalf it is referable as speaking as in arduous sandstone.
Figure 5.7: Instraightforward Waves vs. RPM conspire at perpetual WOB curb trials on kind sandstone
The deeds is besides sparse to invent a open trobject curb commodities of WOB on instraightforward waves at perpetual RPM (Fig. 5.8). However, the trobject at violenter WOB shows a diminish in instraightforward waves. This can be attributed to the stiffening of the pipe attribuboard to violenter axial enjoin OR the pipe is turn and misaligned is making it bobject advance on the sensor behalf decreasing the swerving.
Figure 5.8: Instraightforward Waves vs. WOB conspire at perpetual RPM curb trials on kind sandstone
Arduous Sandstone: Axial waves folbase a correspondent trobject to torque (Fig. 5.9). With an acception in RPM, axial waves acceptiond. Correspondent to the trobject curb torque, some circumstances own abnormally violent wave concretion at 300 RPM which can be attributed to abnormally arduous lamina of curbmation.
Figure 5.9: Axial Waves vs. RPM conspire at perpetual WOB curb trials on arduous sandstone
Subjoined the open trobject axial waves acceptiond with an acception in WOB at perpetual RPM (Fig. 5.10).
Figure 5.10: Axial Waves vs. WOB conspire at perpetual RPM curb trials on arduous sandstone
Kind sandstone: With acception in RPM, axial waves acceptiond (Fig. 5.11). However curb kind sandstsingle the trobject do referable resemble the trobject in torque. In deed, it resembles advance to the trobject in ROP (Fig. B.10). There is a rash acception in axial waves at 700 rpm and then it diminishs spiritual.
Figure 5.11: Axial Waves vs. RPM conspire at perpetual WOB curb trials on kind sandstone
The deeds is besides sparse to invent a open trobject curb correspondentity betwixt WOB and axial waves (Fig. 5.12).
Figure 5.12: Axial Waves vs. WOB conspire at perpetual RPM curb trials on kind sandstone
Arduous Sandstone: No speaking deeds suited curb any segregation.
Kind sandstone: ROP acceptions with an acception in RPM at perpetual WOB (Fig. 5.13). It peaks at encircling 700 RPM and then it diminishs.
Figure 5.13: ROP vs. RPM conspire at perpetual WOB curb trials on kind sandstone
At violenter RPM, violenter WOB has an acceptiond commodities on ROP (Fig. 5.14). Bebehalf no belief of WOB can be seen at inferior appraises of RPM.
Figure 5.14: ROP vs. WOB conspire at perpetual RPM curb trials on kind sandstone
- At perpetual WOB, with acception in RPM, acception in instraightforward waves in arduous sandstsingle is violenter than in kind sandstsingle which indicates that instraightforward waves as-well depobject on restrainm of curbmation.
- Axial waves are violently contingent on torque. No subject what RPM, WOB or the curbmation restrainm is fascinated into statement if there a substitute in torque, fiting substitute accomplish be perceive-keepd in axial waves.
- WOB has short commodities on inducement of axial waves in kind rolls and advance commodities in arduous rolls. Hereafter the establishedaim WOB should be diminishd curb instruction into arduous rolls.
- RPM of 700 is the violentest RPM which can be used to gain violentest ROP withquenched portico the acceptiond waves into statement. Acception of RPM advance inferiors the ROP which can be attributed to such acceptiond waves and velocities that the fragment does referable attain plenty opportunity to contstrike and bring the roll demeanor.
Although the pur-pose of the rig was optimized, there is invariablely capability curb advancement. With an acception in budattain and scant pur-pose constraints, the rig can be constrained meliorate. Subjoined are the recommendations curb upgrading the rig.
- The kindware program used curb the curb algorithm can be upgraded to Labview or Dasylab which are advance user kindly curb programming the automation and curb architechture.
- Using Labview or Dasy lab accomplish afford to produce on a faster computer with a novel generous scheme which accomplish aid in faster deeds collation and storage.
- A vibrating atom can be secure to the roaming arrest when WOB calibration is done so that fallacy attribuboard to substitute in attrition appraises can be negated.
- The burst couplings secure to the torque can be upgraded with a violenter torque rating to nullify deficiency at violenter waves.
- A sboard living edifice curb the torque sensor and laser swerving sensor can be stipulated.
If the fragment can be gained or deceptive with diamond coated avoidters, then a established of trials can be pur-poseed where correspondentity could be examined betwixt RPM, WOB and the profoundness of avoid.
Forward and tailward spin-round characterization trials could be done with improved sensors curb descryion of spin-round rates.
Hammering strikeion can be conceived in the instruction strikeion and its commodities on ROP, instraightforward waves, torque and axial waves could be analyzed.
Braun, Simon G. Ewins, David J. Rao, Singiresu S.. (2002). Encyclopedia of Wave, Volumes 1-