Project 5 Introduction Dot Plots: Fill & Download for Free

November 8, 2019: Corrected a minor error in Fig. 4.My postdoctoral stint involved stress relaxation of threaded fasteners. For that I specially strain gauged bolts, measured their preload loss over time and temperature, and applied a mathematical model to predict the extent of this preload reduction from bulk material creep properties. Vibration is probably the predominant reason for screw loosening, but my research involved ways bolts can lose preload in the absence of vibration. Thus this answer.First some essential background: To work, a fastener needs to be stretched. That induces a preload that keeps the members being bolted together tightly clamped. The desired preload (typically about 75% or greater of the proof load of the bolt) is most accurately attained by directly measuring the bolt stretch. Since this is impractical on a mass scale, torquing the bolt achieves nearly the same thing through a rough conversion between the torque and preload. Either way a preload is generated by straining the bolt.Now, if there were no friction between the surfaces of the threads and the clamped members, the inclination of the helix thread angle λ (Fig. 1 below) in and of itself would cause the bolt to back right out, which would relieve the preload. Torquing induces preload and hence friction on the contacting surfaces; more tightening provides more friction that opposes preload loss. Consequently, anything that reduces either this friction or the preload causes screw loosening.With that behind us, we can answer the question. One factor that reduces the contact friction is asperities. On a microscopic scale metal surfaces can be very rough. Figure 2 is a ridiculously exaggerated depiction of this for faying thread surfaces. At the asperity contact locations denoted by the dotted circles the local stresses upon torquing will be very high, likely beyond the yield point. Thus plastic deformation will occur there, which will decrease the initial tightening strain and thus the preload and accordingly lead to screw loosening.Another factor is misdimensioned screws. This can lead to the (greatly exaggerated) situation seen in Fig. 3, where it’s evident the reduced thread contact surfaces will create stresses higher than intended. Any ensuing plastic deformation will decrease bolt stretch and hence also preload and friction, leading once again to screw loosening.One other factor I’ll mention is creep of either the bolt material or the material being clamped. This particular area was the subject of my postdoctorate. In this scenario if the temperature is high enough or the materials composing either the screw or clamped members aren’t that robust, then high temperature creep—the slow deformation of solids under elevated temperature and stress—can generate diffusional mass flow that lessens bolt stretch. For this situation the role of creep properties in allowing for preload loss isn’t as amenable to visualization as with Figs. 1–3 but can be quantified mathematically[1] and the results plotted for ready analysis, as I’ll show now.To start with, in stress relaxation the strain [math]\epsilon_{tot}[/math] is constant for any time t and composed of both an elastic part, [math]\epsilon_{el}[/math], and a plastic (creep) component, [math]\epsilon_{cr}[/math]:[math]\displaystyle\text{(1)} \;\;\;\;\;\epsilon_{tot}=\epsilon_{el}+\epsilon_{cr}[/math]Per Hooke’s law,[math]\displaystyle\text{(2)} \;\;\;\;\;\epsilon_{el}=\frac{\sigma}{E}[/math]where E is elastic modulus.A simplistic textbook equation for power law creep at some high temperature gives the creep strain rate [math]\dot{\epsilon}_{cr}[/math] as[math]\displaystyle\text{(3)} \;\;\;\;\;\dot{\epsilon}_{cr}=B\sigma^n[/math]where B is a constant and n is the creep exponent. Now, since constant displacement is associated with stress relaxation, substituting Eq. (2) into Eq. (1), differentiating the resulting Eq. (1), and then substituting Eq. (3) gives[math]\displaystyle\text{(4)} \;\;\;\;\;\frac{1}{E}\frac{d\sigma}{dt}=-B\sigma^n[/math]To illustrate how Eq. (4) might be useful in design, say you want to know how long it would take for the preload stress to reduce to half its initial value [math]\sigma_i[/math] through stress relaxation creep processes. For that Eq. (4) can be integrated from [math]\sigma_i[/math] to [math]\sigma_i/2[/math] over times t = 0 to t. This yields the duration [math]t_{rel}[/math] for the preload to halve its initial value as[math]\displaystyle\text{(5)} \;\;\;\;\; t_{rel}=\frac{2^{n-1}-1}{(n-1)BE\sigma_i^{n-1}}[/math]Therefore, the creep parameters B and n in Eq. (3) for the bolt can be used to predict stress relaxation behavior. The resulting Eq. (5), moreover, lays out exactly how temperature and specific material constants influence this non-vibration preload-relaxation mechanism. To show furthermore what a representative stress relaxation curve looks like, I’ll invoke a stress relaxation calculation on a structural piece where I used a creep equation more complex than given by Eq. (3) but similar in principle. The ensuing behavior as described by its counterpart to Eq. (5) is presented below:Most of the preload loss occurs initially before tapering off. This is consistent with general stress relaxation trends.[2] Although Eq. (5) pertains to creep of the bolt, the same behavior as in Fig. 4 would occur if creep in the clamped material, rather than in the bolt, were the case. In my postdoctoral research my focus was in fact on creep of the clamped material while ignoring the bolt, and all the curves I obtained still looked exactly like the one in Fig. 4.I would be remiss not to recommend that anyone interested in this subject get Bickford’s book,[3] from which I adapted much of the above discussion. This was also my bible during my postdoctorate study. In my opinion it’s the most authoritative, complete reference on bolted joints. And finally, as an aside, all throughout my postdoctorate I kept thinking I’d never use bolted joint theory again. But I was wrong; it and the related stress relaxation theories have since come up many times in my career. So although at the time of it I didn’t appreciate what I was learning, today I’m very thankful for that project and years later e-mailed my primary faculty supervisor to let him know of that.Footnotes[1] Engineering Materials 1[2] Creep and Stress Relaxation in Metals: I. A. et al. Oding: Amazon.com: Books[3] An Introduction to the Design and Behavior of Bolted Joints, Revised and Expanded

Mainly by studying the redshift of light sources far away.First, we need to know what redshift, denoted [math] z [/math] is. As mentioned by Abhinav Bhatt's answer, the redshift is similar to the Doppler effect experienced in sound waves, for example.You analyse the spectrum of the light source (the light it emits in all wavelengths) and look for certain characteristic lines in a wavelength [math] \lambda_\text{ob} [/math] that you can compare to a known (laboratory, [math] \lambda_{\text{em}} [/math]) lines. Mathematically, we have that:[math]z \equiv \frac{\lambda_\text{ob} - \lambda_\text{em}}{\lambda_\text{em}}[/math]For example, in Supernovae II, you can look for hydrogen [math]\mathrm{H} \alpha[/math] lines (see [1]). This is mainly caused by the chemical composition of the star/galaxy you're studying. (Note: This is not the only way to measure a redshift, but it is the easiest to explain!)Historically, the first redshift evidence correlated to the expansion of the universe was found by Edwin Hubble, by analysing the redshifts and distance of nearly 20 galaxies. He derived the empirical formula now known as Hubble's Law:[math]z = \frac{H_0}{c} r[/math]Here, [math] c [/math] is the speed of light, [math] r [/math] is the distance to the galaxy and [math] H_0 [/math] is the Hubble constant.This image, copied from [2], is Hubble's original plot of redshift and distance.Eventually, a general relativity model for the whole universe was proposed by Friedmann, Robertson, Walker and Lemaître that could include an expansion of the universe:[math] \mathrm{d}s^2 = - c^2 \mathrm{d}t^2 + a(t)^2 \mathrm{d} \mathbf{r}^2 [/math]Here, [math] \mathrm{d}s^2[/math] is the space-time distance, [math] \mathrm{d}t^2 [/math] is the temporal distance, [math] \mathrm{d} \mathbf{r}^2[/math] is the spatial distance and [math] a(t)^2[/math] is the scale factor of the Universe, accounting for expansion or even contraction of the whole Universe.The scale factor is determined by the Friedmann equation:[math]H^2(t) \equiv \left( \frac{\dot{a}}{a} \right)^2 = H_0^2 \left( \sum_w \frac{\Omega_w}{a^{3(1+w)}} + \frac{1-\Omega_0}{a^2}\right)[/math]Here, [math] \Omega_w [/math] is the density parameter of a component with equation of state [math] p = w \epsilon [/math]. More references in [2] and [3].The evolution of universe models is a beautiful story, which you can read in the fantastic book [4].More recently, we have also used Supernovae Ia as standard candles to analyse their luminosity distance evolves with redshift. This is a bit more technical and can be seen in detail in [2].Supernovae observations have also lead to evidence for an accelerated expansion of the Universe, as seen first in [5] and [6], which have led to a Nobel prize in 2011 [7]!Recent data of SNe from the Union 2.1 compilation [8] offers strong evidence for an accelerated expansion:Image from [8], available in the Supernova Cosmology Project website.This is of course a quick glance of a long and detailed story. I suggest that you read the book [4] if you want more of it!References:[1] Optical Spectra of Supernovae, Alexei Filippenko (Annual Review of Astronomy and Astrophysics)[2] Barbara Ryden, Introduction to Cosmology (Introduction to Cosmology)[3] Pedro Henrique Bernardinelli's answer to What are the most interesting differential equations in science and mathematics? Why?[4] Lonely Hearts of the Cosmos - The Story of the Scientific Quest for the Secret of the Universe, Dennis Overbye (Lonely Hearts of the Cosmos)[5] Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant, Riess et al, 1998 ([astro-ph/9805201] Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant)[6] Measurements of Omega and Lambda from 42 High-Redshift Supernovae, Perlmutter et al., 1998 ([astro-ph/9812133] Measurements of Omega and Lambda from 42 High-Redshift Supernovae)[7] The 2011 Nobel Prize in Physics[8] The Hubble Space Telescope Cluster Supernova Survey: V. Improving the Dark Energy Constraints Above z>1 and Building an Early-Type-Hosted Supernova Sample, Suzuki et al., 2011 (V. Improving the Dark Energy Constraints Above z>1 and Building an Early-Type-Hosted Supernova Sample and Supernova Cosmology Project)

Bangalore in the early eighties?Sigh!Where should I begin?Okay, here you go. I am writing randomly whatever thoughts and memories flood my nostalgic mind.In the early eighties, I was a young man in my early thirties, a qualified structural design engineer, specialising in the design of steel structures in Industrial buildings, and working for a leading consultancy organisation in Bangalore.Transport in Bangalore:======================The excellent network of bus routes you see today, including Volvos etc, did not exist.You depended on the BTS buses (BMRTC buses were called BTS buses those days. BTS stood for Bangalore Transport Services)Japanese motorcyles were not available. They came during the nineties after the great economic liberalisation introduced by the Narasimha Rao/Man Mohan Singh Combination. Only Ambassadors and Premier Padminis (earlier called Fiats) dominated the roads. The 800cc Maruti came later. Autorickshaws were the only means for private transport but they were not allowed to seat more than two passengers. This was later relaxed to three. The ubiquitous horse drawn Jatkaas around city market, Malleswaram and Chamarajpet and Basavanagudi had just been withdrawn. No cycle rickshaws existed here as in Delhi.New Scooters were available only at a premium price. Vespa and Lambretta were popular. You had to wait for years to book and get a new one.So scooters had a fancy second hand price (More than the new one)Vijay scooter came later. Kinetic Honda made an appearance in the mid eighties and attracted a lot of attention due to the battery operated self starter and the gearless transmission.I used to ride a Yezdi motorcyle (250 cc two stroke engine) that gave me 29 to 30 kms per litre of petrol. I used to get a conveyance allowance of Rs 60 per month. Not bad! Petrol cost only Rs 3.11 per litre when I bought my motor cycle.Those who valued economy, chose the Rajdoot (175 cc, two stroke engine) that gave 40 kms per litre and started rather easily with just one light kick. The Yezdi wallas had to kick harder and more often to get it started. But the chaps say they loved the noise made by the Yezdi and had contempt for the sputter that Rajdoots produced. Most young motor cyclists had contempt for scooter riders and called them "effeminate". But most motorcyclists later switched over to scooters after getting married and having kids and becoming more mature in their thinking!I had bought a brand new Yezdi motor cycle from Haji and Sons at St Marks Road for Rs 6250/- (on the road price) in 1976 and sold it in 1984 for Rs 7000/-We envied the guys who went around on a Bullet. Other than Policemen and the house building contractors (also called "Bullet Maistries") very few ordinary young men rode a Bullet.It was expensive and the mileage was low.In 1983-84, I finally bought a second hand Bullet, just for prestige, not utility. I paid 8000/- and it was cheap because my brother who was emigrating, sold it to me at a discounted price under pressure from my mother. I sold it a year later for just Rs 10,000/- and it was a distress sale because I needed the money urgently. I inserted an ad in Deccan Herald and the day the ad appeared, right at 7 am in the morning, there stood a Bullet Maistry, outside my door with a thousand rupees in cash, and who offered it to me telling me not to sell it to anyone else and promising to bring the rest of the money before noon.The market price was at least 12000/- for a five year old Bullet that had already covered over 60,000 km.Real Estate:===========Banashankari, JP Nagar, and Indiranagar were developing localities. All these Hallis, Sandras, and Puras did not exist and they all remained villages, struggling to cope with modernisation. To be considered as living in a good locality, it needed to be some "Nagar" planned by the BDA.Multi-storied residential apartment complexes could be counted one one's fingers. The few that existed were all commercial. Unity Buildings at JC Road near the town hall was a prestigious landmark, till it was eclipsed by the Public Utility building on MG Road and later by the LIC building near the GPO.People never thought of buying an apartment. That was considered a Bombay life style. Malleswaram started the apartment boom sometime in the nineties. Large sites with owners dead and whose children had emigrated were sold to developers and a new trend started in the nineties and the old sprawling mansions with Mangalore tiled roofs were demolished to make way for Apartments.Till the eighties, people here liked to buy a small plot and build a house of their own. Most middle class homeowners bought a 30'x40' plot and built a small two bedroom, hall and kitchen house. Some put up a stair case outside the house, adjacent to the compound wall and built an upstairs portion usually for letting it out.Many of these houses did not have overhead tanks. Water pressure was sufficient to reach the first floor. BWSSB was doing a great job, supplying Kaveri Water to thirsty Bangalore when the Tippagondanahalli reservoir was found inadequate to meet the city's needs. The overhead tanks came later.Those with better resources opted for 60'x40' sites and built a larger house with a garage too.We had contempt for apartments. We could afford to do so. Plots were available and all locals (Kannadigas) and also outsiders who had lived here for 5 to 10 years were eligible to apply for and be granted a house site at greatly subsidized rates. Land acquisition problems did not exist. Farmers were glad to offer their lands to BDA and litigation was rare. They could see the city expanding towards their fields. They were growing old. Their children did not show interest in agriculture. They saw wisdom in selling when the prices were attractive and they could get in a lump sum much more than what agriculture yielded. Besides many were also given some plots of land after the development, as part of the deal, which they hatched for a few years and sold for much greater prices.In 1978, I had progressed sufficiently in my career to be able to afford to rent an independent house with a sit out, hall , two bedroom, kitchen, and single bathroom and toilet with an attached garage located on a 60'x40' plot in Jayanagar 7th block for Rs 450/- as monthly rent. The house could have fetched more if it had been better planned and if it had had a mosaic floor instead of the commonly used redoxide cement floor. A stair case from the sit out lead us to an open terrace.I lived happily there for 5 years and the rents increased from 450/- to 700/- when I finally vacated it. In 1984, I bought a site from the BDA at an auction in JP Nagar and built my own house. I spent Rs 5 lakhs totally(including the site value) on a two storied house with all modern amenities and finishings and with a built area of 1900 sq feet. HDFC financed a portion of it and the interest rate was 14 percent.Shopping:Malls did not exist. Most of us went to MG road and Commercial Street for fancy shopping and combined the shopping experience with an ice cream treat at Lake View or had our "tindi" at India Coffee house and watched a movie at Plaza, or Galaxy or Rex. You never needed to know Kannada in this part of Bangalore. The middle class locals went to shops around the Majestic area, Chickpet , Balepet. For daily needs the vegetable vendors brought them to our homes, pushing their carts and shouting out the prices of the individual vegetables. In South Bangalore where I have lived all along, those who had a fridge, went to Gandhi Bazaar for vegetables till the Jayanagar shopping complex was finally completed. Large families or groups of families who had cars would go directly to City Market and buy more at better prices and share the purchases.While Nandini Milk was popular, many families with elderly members, who were living with their adult children were not too happy with milk in plastic satchets and chose to get their milk from milkmen who brought the cow to their gates and milked it in their presence. You don't see that happening now.In 1974 when I landed in Bangalore the Jayanagar shopping complex was under construction. The Janata bazaar there (and also the one at Kempegowda Road) were the nearest we had that resembled a department store and it was a novelty for housewives with their kids when they could walk into a shop and explore the shelves, with a trolley and pick up what they wanted. But queues at the payment counter were long. They did not have modern methods of scanning bar codes and preparing and printing bills and of course no credit cards existed so the experience was not so pleasant. The vast majority still patronised the usual "Ganesha Stores" or "Manjunatha Stores" or "Raghavendra Stores" around street corners and each locality had at least one with these standard shop names. Their only competitors were the Muslim Malayalees from Kerala who set up their own chain (popularly called Kaaka shops) and you could identify them easily from the "secular" names displayed on the boards.Usually "National Stores", "Royal Stores" "Simla Stores" etc,Restaurants:None of today's Darhshinis, and Saagars existed. Eating houses were much lesser in numbers. The really famous ones had very modest interiors and were usually called "Bhavans" like Udupi Bhavan, Gopalkrishna Bhavan etc. The Kamaths, and Pais dominated and they monopolised the Grade II eating houses. Their only competition came from the chain of Janatha Hotels all over the city which served the same stuff at prices less than Kamat and Pai restaurants.Some modest and cramped eating houses had established reputations that they frankly did not quite deserve. I never understood why Vidyarthi Bhavan at Gandhi Bazaar and MTR near Lalbag north gate was hyped up so much. I have visited both and at MTR, after those experiences that taxed my patience, I swore never to visit them again. I had no grouse against quality. I admit the stuff they served was superlative and rich in "tuppa" (Ghee) and they served divine coffee in silver tumblers. The coffee might get cold but not the silver cups!But the waiting time to get a seat was killing. It would take more than half an hour sometimes to get a place to sit. What was more irritating was that as I sat enjoying my masala dosa with an appetite aggravated by the long wait, another customer would be waiting right behind my chair and also holding it with one hand as if to say, "This seat is reserved for me and I am going to sit on it as soon as this fellow gets up". While eating I could feel this waiting customer's glare on my back wondering how long I am going to continue sitting and why I was not hurrying up.Half the pleasure of eating out was lost due to these experiences.Theatres and entertainment.Multiplexes did not exist. We had superb movie theatres with great audio at Galaxy, Nartaki, Santosh, Rex, Lido etc and also cheap ones for desi films that did not need all the sophistication.I remember being greatly impressed by the Sound system in the movie McKenna's Gold which I saw at Galaxy.Majestic area had about 21 theatres, (I think) and most of them have been demolished.TV was introduced around 1980 in Bangalore, years after Delhi and Mumbai. There was just one channel in Black and white, and the programs started around 5 pm and the transmission was in Kannada till 8:30 pm. The Kannada news was read out at 7:30 pm. After 8:30 pm, all the regional centers around the country hooked up with Doordarshan Delhi and the programs were in Hindi and English. This caused considerable heartburn in Non Hindi speaking states.TV was free. We had a crude looking antenna on our roof tops that received the signals. DVDs, VCRs, and cable television did not exist. The Ramayana and Mahabharata were telecast by Doordarshan and the streets used to be empty during the telecast and the only other time this happened was when India and Pakistan were playing a cricket Match.Dr Rajkumar was a stalwart who dominated Kannada Cinema. Vishnu Vardhan and the Nag brothers (Late Shankar Nag and Anant Nag also had their own following. Lokesh and Srinath were not so popular. Puttana Kanagal,GV Iyer and others were legendary and Aarti was the leading actress if I remember right.Electronics:Personal computers, laptops, tablets, cell phones etc DID NOT EXIST!Having a landline phone on your table with a direct line, in the office and not having to go through the switch board and having an extension number was a prestigious perquisite for senior executives only. STD calls were rare and expensive. Bosses locked up their phones fearing "misuse" by their subordinates. Even these bosses were required to maintain a register logging all their STD calls and recording the date, time and duration. Imagine if you youngsters were required to do all this today!You will never realise the value of these blessings. Old timers like me have had the rare privilege of being productive professionals who managed to get a lot of work done without these aids and slowly adapted to these modern devices and gadgets and learned to use them. Heck, during the first few years I did all my design calculations using a slide rule. Calculators came later.I was better off than most of my colleagues. I was a computer literate fellow, having learned the new subject called Fortran Programming while doing my engineering studies and I was among the handful of engineers in my organisation who could write a few lines of code to solve simple programming problems. But minicomputers, PCs, did not exist and we used the IBM 360 mainframe computer at Indian Institute of Science. I used to ride my motor cycle all the way from KR Circle (where my office was located) to IISc campus and punch the cards there and submit my deck of cards for processing. I would come back next day to collect my output. Any mistake of even one byte, in the code or in the data would render our effort and trip fruitless and I would have re-punch those cards and resubmit, and return the next day. IISc maintained a queue system for jobs submitted by their customers. They rented out computer time to us. All jobs that could be processed in less than two minutes were called Quick. Those that took more than two minutes but less than 10 minutes were called "Express" jobs and those that took longer were called "Jumbo". Even longer jobs were scheduled during the night shift.Jobs that take a fraction of second today, to process, used to take 5 to 10 minutes those days and sometimes even half an hour.We punched our code and data on cards, and fed them into the card reader of the mainframe computer to get printed output. It was only later that the VDU terminal was invented in the early eighties and soon it rendered obsolete punched card or paper tape input. It also obviated the need for printing the output and we would print on fast line printers only if the output seen on the VDU terminal appeared okay. Terminals displayed in black and white only. Only text and numbers, not images. It was a novel thing those days and the highlight was the introduction of remote processing where the inputs would be received from VDUs and keyboards located at the customer's premises and the processing would be done at IISc's DEC System 10, using modems and telephone lines. The speeds were nothing to boast about but those days we had not known what "broad band" or any band was and any speed was impressive as it saved us a trip to IISc.Slowly minicomputers invaded Bangalore but they were primitive compared to today's laptops. We had 8" floppy disks, (360K capacity) followed by storage mediums for PCs viz 5 1/4" disks with 360 Kilo bytes capacity followed by 3 1/2" floppy disks with 1.44 Mb storage capacity.Just as cars and mobile phones are being advertised today, the eighties saw the advent of the first personal computers in Bangalore and the computer culture spread here faster than at other cities. HCL and Wipro were the main contenders for the top slot and Siva PCs made by Sterling Computers at Chennai (sorry, Madras as it was called those days) who sold the Siva brand of computers, Eiko, Uptron etc offered cheaper competition. The machines were shockingly primitive with barely 64 K to 128K core memory. Our office paid Rs 80,000/- for the first HCL PC we bought. It was "state of the art", a PC-AT (Advanced technology, as it was called) and had a 'whopping" 40 Mb as hard disk storage space and a crude low resolution colour monitor and the memory was an "astonishing" 512K! There was no mouse those days. We used the arrow keys on the keyboard to navigate and called up drop down menus using hot keys. Software developers boasted that their software was "user friendly" and "menu driven" in order to beat the competition.The One Mega barrier took some more years to breach and the Giga was simply not even known as a word! Project that price (Rs 80,000/- ) during the early eighties and see it's equivalent in today's prices and you will get an idea how special a computer was. No wonder these PCs were housed in special air conditioned rooms and in my company, the systems department would not allow any of us to enter the computer room with our shoes on. They were the high priests in charge of the machine and treated it as a deity kept in some sanctum sanctorum and would discourage us from using them thinking that we, the country bumpkins, would damage them. Most of us were computer illiterate any way and were easily bluffed into believing all the hype that they trotted out. With just basic knowledge of word processing, and spread-sheeting (using Word Star, and Lotus 123)and an ability to churn out a few lines of simple code in Basic, they posed as systems experts and impressed the top management with tables and reports neatly printed out on the noisy dot matrix printers in vogue then. Our office used these PCs more as glorified typewriters than as computing machines. Bosses were impressed by buzz words like Lotus, Dbase and Wordstar and I lost count of how many times I explained the difference between bit and byte to my boss. He never understood till his retirement!Needless to say, the Internet did not exist. I got introduced to it in the late nineties and my first internet connection at home used the telephone line and the download speed was 4k per second. It was useless for anything except for email without attachments.Other office equipment:The photo copying machine was still very primitive. Xerox was becoming famous. Just as any steel almirah was called a Godrej those days, any photo copy started to be called a Xerox copy. Before their advent, the copying technique had just been introduced and it used some kind of oil that smelt of a mixture of kerosene and machine oil. You had to expose the orginal several times once for each copy and keep the copy sandwiched between two glass sheets with micro fine carbon balls and allow the balls to roll over the sheet to produce a readable copy that smelt for a day of oil before the smell died out. It was a messy affair.More popular was the stencil that could be used instead of plain paper and mounted on the roller of a standard typewriter and then mounted on a "cyclostyling" machine (The Americans called this the mimeographing machine) to produce any number of copies.Telex was the mode of communication between offices for urgent messages. The messages were often received in garbled condition and important words and figures would be typed twice to ensure correct reading. Full stops and commas were written as (STOP) and (COMMA), Figures would be repeated in words and digits to avoid miscommunication.Most of the routine standard communication was in typed letters and posted using Snail mail. The common man used Telegrams for urgent communication. They paid by the word. So standard messages like "Reached safely", "Congratulations" "Best wishes for a happy married life" , "May heaven's choicest blessings be showered on the young couple" etc were given code numbers and these numbers could be quoted to save on expense.The fax machine came much later and create a sensation. Today emails make even faxes look primitive.Routine letters were typed on Manual typewriters (later on electric typewriters) using carbon paper for copies and sent by post or special company couriers for large companies. College Boys and girls during the admission season would be frantically going around looking for "gazzetted officers" who were important because they had the power to "attest" a copy of their mark lists and certificates which were painstakingly typed out. A batallion of typists sat under trees near the Passport office, Registrar's office and other Government departments, typing out documents for customers.Games and socialising:Children played games.They were physically active. Video games were unknown.We, adults, went out and met friends and relatives at their homes and entertained them during return visits. There was no "social media" like Twitter, or Facebook. We spread rumours and indulged in Gossip the old fashioned way using our tongues and hearing gossip with our ears. We laughed cried, joked and quarreled directly not using a computer screen and the internet! TV and internet that has now replaced all live human interaction did not exist. A movie was a special treat to be looked forward to and talked about for days afterwards. A visit to a circus or zoo was a super special treat for the children. Drama had a market and a willing audience.Classical music during Ramanavami was looked forward to.You had asked me about the area near Pallavi talkies, Banashankari and Cubbon park.The present Kempegowda tower there did not exist. The large dome built by L&T housing the indoor stadium did not exist.The direction of traffic movement was totally different. Nrupathunga Road was two way, and so was District office road.Banashankari induced fear! So far away! I thought it was a forest area before I saw it for the first time and felt charmed by the ups and downs and the views of the landscape. The Banashankari temple attracted crowds on certain days and the Kanakapura Road and Bannerghata road was used by us for driving our motorcyles at high speeds for continuous long stretches to recharge our batteries in the motorcycles! Hardly any traffic existed on these roads once you left Jayanagar and rode further south.I could reach Bannerghata National park in twenty minutes from my house in JP Nagar.Cubbon park had practically no encroachments. All roads were two way . None of the entrances was blocked. The Seshadri Memorial library was always full of readers. My kids enjoyed the toy train ride and we often visited Bal Bhavan for attending the programs there. I wonder if any modern kid goes there now.The above is just a limited list of topics that I have chosen to write about.The list of topics I have not written here is even larger but I know your patience is limited and before you run out of it let me stopI thank Chetan Achar who asked me to answer this question.Feel free to ask me anything else you are curious about in the comments section and I will do my best to answer.RegardsGV