According to Wikipedia, the relation between the shear stress and the strain rate is linear for a Newtonian fluid. The constant of proportionality being the coefficient of viscosity. On the other hand, the relation between the shear stress and the strain rate is nonlinear for a non-Newtonian fluid, and can even be time-dependent. Therefore a constant coefficient of viscosity cannot be defined.

The following video clip illustrates the idea. A person moving quickly and applying sufficient force with their feet can literally walk across such a non-Newtonia liquid. In this video, a mixture of cornstarch and water was prepared in a tank. It becomes a non-Newtonian fluid. When stress is applied to the cornstarch mixture, it exhibits properties of a solid.

A test is carry out to see which internet browser needs the least memory. Other function such as user-friendliness, pop up window disable, bookmarking are not consider. Here is a direct comparison among the free available internet browsers for their memory efficiency. Which browser consumes the least memory while freeing up space for you to do word processing or gaming?

The test conditions are: Open 3 separate tabs for ‘google news’, ‘hotmail’ and ‘reading a pdf document in Applied Physics Letter’. The task manager is invoked and the memory consumption is displayed. Here are the result:

MS Internet Explorer 7

Mozilla Firefox 2.00.17

Safari 3.0.4

Google Chrome 2.0.172.43

From the Task managers above, Chrome (~250k) consumes the most memory by far and IE7 (~9k) consumes the least !

But most people are likely to be a die-hard Firefox or Chrome fans and will never consider changing back to IE. Many reasons include safety feature, user-friendliness, fast loading etc.

So this is good news for RAM manufacturers, the ever growing need  for larger and larger memory space for the programs we are running.

01 Sep 2009

Have you ever wonder how car engine transfers its energy to the four wheels or rear wheels? This transfer mechanism comes a long way. The most basic most of the readers can think of is just connecting the roller beam to the engine.

Let’s share a case study on planets surrounding a central core or sun in a circular orbit. If all planets move at the same speed, yellow planet is going to finish the cycle earlier. If all of them want to finish the cycle earlier, outer ones (black) has to move a lot more  faster than inner one. Imagine two spheres (outermost and innermost) are being connected like the wheels connected in a roller beam of a car which is driving around a corner, one of the wheels has to slip on the floor if it wants to keep the same speed with the other one. This is exactly happened to a car if we have such a simple beam-connected wheels.

The following video will show you how engineer has come a long way to achieve differential mechanism. It was an old-school video, we found it interesting to share with the readers here.

Credits given to Chevrolet Motor Division of General Motor Sales Corporation.

However I have not seen any significant progress recently, until I came across an article by Xueshen Wang et al. from Tsinghua University in Nano Letters (no volume number given yet). Unlike previously “super” long carbon nanotube, typically has length in range of milimeters. The article reported a method to grow a ultra long carbon nanotube up to 18 cm long with diameter of 6 nm.

How can they create such a lenghty nanotubes ? The trick is using a process called chemical vapour deposition (CVD). Seed of carbon nanotube are placed inside an oven that can be heated up to 900 degree Celcius. Along with that a iron-molybenum catalyst used to stimulate the growth. At the same time, ethanol or methane gas is flown to the chamber. CNT reported to grow at the rate of 40 micron per second. Furthermore the produced long CNT are straight and parallel each other.

The article also reported that they are able to produce hundreds or more identitcal field effect transistor (FET) along the single strand of CNT. This is confirming the uniform electrical properties along the CNT length.

All in all, being able to grow such a long CNT is an achievment by itself. Furthermore to be able to orderly possitioning the tubes gives hope for the first CNT integrated circuits. At least, long CNT alone presents another step further to have a stronger and lighter materials than steel.

Aug 14, 2009

Written by Koffee999

Bundanoon, a southern city in Australia, had became the first city on earth to ban the sale of bottled water recently. Environmentalist applauded the move. This unprecedented green act could catalyze similar move around the world. In Singapore, there have been calls for consumers to reduce the consumption of bottled water, thus the demand of the plastic wares. Plastic bottled waters sold in Singapore include mineral water, distilled water, underground water, newwater and other soft drinks. Letters from the local newspaper’s forum have attracted supportive voices, most advocated drinking directing from the taps and there is no added benefit of bottled drink, apart from the taste. In Singapore, we are fortunate that we have clean portable water from the taps. In countries where I have visited and lived in, tap water is not safe and people have been loading gallons and gallons of water from stores as a way of life.

Plastic bottles are made of polyethylene or polypropene, which are thermoplastic and popularly utilized to produce containers through injection or blow injection. They can be recycled readily. If the consumers duly carry out proper disposal of recyclable materials the authority should have not considered the unpopular ban. Most of the plastic ends up in the landfill and these material probably take a century to decompose. As population increases, demand for plastic increases, the limited landfill space is never able to catch up on the disposal of rubbish. Alternative includes incineration, but the problem is then shifted to filling the earth atmosphere with more greenhouse gases.

The environmentalists have probably given enough of green calls over this matter, let’s look at this plastic bottle at another angle.

What has gone into the production, distribution, disposal and recycling of a plastic bottle or any consumers’ item? Energy. Energy is fed into the extraction of raw material and processing of a bottle at a factory. In addition, energy is fed into the transportation of a bottle from the factory into your next door convenience shore. Energy is fed into the cold storage so that we can have a nice cold drink. Finally, energy is fed into the burning or dumping the bottle into the landfill. So energy is involved in so many aspect of a new bottle’s life, so probably we can convince everyone that drinking straight from the tap is better, as water pipe has been installed and the only energy consumed is just turning the tap. The key for illustrating the above picture is due to the fact of the shortage of earth’s resources.

Oil supply will be depleted in about 80 years (depending on which reports you read). So are natural gases and coal, however they can support human’s consumption relatively longer. While we are enjoying power at the convenience of flicking a wall switch, fire at a cooking stove, automobile power at the fuel filling station, we should spare a thought that our next few generations might not able to enjoy the conveniences. In our daily lives, we might have taken for granted the very little energy that is used at every stages in a plastic bottle for example. This does not apply in 50 years later, where energy used in all stages of human activities will be scrutinized and maybe governed for use at the maximum efficiency.

What else are the earth shortages? The list is long. For example, drinking water, clean air, and even sunlight if your region is plagued with burning forest or volcano activity. What about the precious metal? Indium and platinum supplies are dwindling fast in the earth crust. Indium is used in compound semiconductor and LCD’s transparent conducting glass screen. Platinum is used in the automobile cleaning exhaust system and fuel cells. The next fact is telling us that there will be a rise in demand for indium and platinum as the demand for LCD and cleaner exhaust system growing exponentially. You may want to re-think about new technologies that are still using these scarce materials or you may want to get involve in a research career to look for replacement of these scarce materials. Another problem adding towards worsening shortage: The extraction of indium and platinum need a lot more energy than these materials would be producing in the future, especially serving as part of the solar cells. So it would not be commercially viable or energetically sensible, so the mining is abandoned. Shortage, yet no one wants to extract them from the earth crust.

Hence the next time you want to discard something, remember to slot them in the correct recycle bins. Earth resources are not infinite, we should use sparingly and give back to our earth and to our children.

Written by koffee999

It was a refreshing experience. In his keynote speech, he guided the history of nanotechnology with the audience, listed several prominent research works, and applications that could impact on people’s life. He pointed out the enthusiasm of researchers getting into the nano act and highlighted billion of dollars invested on nano research. So after 10 years or so of nano era, what would be the fruit of labour to be reaped ?

Disappointingly low. He stopped short of calling nanotechnology a hype.

The problem Tim pointed out that almost all existing nano research works are push technologies. Beautiful packaged laboratory results looked very promising and they were presented to investors. They were pushed to the market place in the hope that this is another Viagra success story. Often, much effort were done to bridge the gap between lab and mass production. Sadly, in introspect, they are not well received. We need to re-think about this entrepreneurship model. The answer could be in the reverse approach: finding customers, understanding their problems, matchmaking for existing solution, researching for improved solution, customizing and finally presenting the final solution.

The author is a research student on fabricating nanostructured materials. He is hopeful for the future as hope keeps spirit alive.

We would like to express our utmost gratitude to Professor Michael Graetzel for his valuable and kind sharing of knowledge and technical advice to our solar research.

Special Thanks to Swissnex Singapore for the wonderful experience brought to Singapore research community.

Nissan Leaf, a 100% electric zero-emission automobile

Aug 3, 2009
Written by Koffee999

Last weekend, Nissan announced a 100% electric zero-emission automobile called Leaf. It is powered by a lithium ion batteries and can be charged to full capacity using a home wall plug within 8 hours. Further, Nissan forecasts there will be dedicated power charging stations, at key locations along motor highway, shopping areas or offices, to provide quick charging to 80% capacity as short as in half an hour.

So much for the convenience of topping up ‘energy’, then what does Leaf offers in term of specification? This electric vehicle will give out 80 kilowatts of power, boasting a performance equivalent to an automobile running on fossil fuel. The Leaf will have a maximum range of over 140 kilometers on one full charge. This is a pretty impressive range as it would potentially satisfy most consumers’ requirement of daily home-office commuting.

Leaf has a clean sporting look, it is a 5-door hatchback with sophisticated dashboard monitoring display. The price of Leaf is not release yet. It is widely expected that Nissan will price Leaf competitively at the same level of a regular 5-door hatchback class, minus the battery pack. Thus it will be price-sensitive to the lithium ion batteries.

Lithium battery has come a long road from powering smaller device such as mobile phones to larger device such as laptop. Initial version of lithium battery had an inherent problem: it is not stable and could be explosive during operation. Thus, it is prohibited from powering larger electronic device. In the recent research breakthrough, lithium battery can be made stable and larger without the danger of exploding. As a result, lithium battery found application in powering electric vehicle besides offering high energy density, light weight and high recharge cycles.

Electric vehicle is nothing new. Years ago, electric vehicles were found in golf courses, running nickel metal hydride or lead-acid batteries. So, can Leaf bring forth a revolutionary change in transportation? Yes, it has far more commutable range than its predecessor and provide a higher energy return on energy invested (EROEI). The lithium battery packs more energy per kg and offers longer life-span (recharging cycles). The spotlight is on the ‘environmental friendliness’ of Leaf. It has zero emission which the ever warming earth could get some timely relief no matter how small the green act is.

Leaf is a plugged-in electric vehicle and energy needs to come from somewhere. Renewable energy such as wind, solar, hydro and tidal energies should be pushed more to account for a larger share in feeding electricity into the grid. Taking a leaf out of Leaf, going green is the way for promoting a healthier planet which all of us live in.

On 28 July 2009, I attended a lecture by Prof Boediono in Shangri-La hotel Singapore. He was the invited speaker by NTU-RSIS.

The lecture was mainly on economics and political issue between Indonessia and Singapore. Since this blog is about nature, science and technology, I believe in the fact that Economic is one of the science branches, i.e social science.

Prof Boediono first started the lecture by presenting his analysis of the current economic crisis. According to him, the first factor is the over spending of the big GIANT like US. As the results, debts are accumulating on one sides, while wealth is accumulating on the other side like China. This gap was getting worse as the spending fueled by one’s over confidence of taking ever greater market risk.

According to him, Indonesian had been significantly affected by the crisis as a result of decceleration of export rate. The worst was third quarter of 2008, where lots of investment were withdrawn from Indonesia. Fortunately, there are two factors that protected Indonesia from financial downfall. He attributed the first factor to the nature, that Indonesia had enjoyed a good agricultural harvest in 2008, thus assuring the sufficient of food supplies, particularly paddy rice. Then he honoured the second factor to Indonesia’s large population which makes  her the largest domestic market in South East Asia. Large markert acts as a safety net in the global financial market. Although Indonesian export rate have been tumbling, domestic market is virtually unaffected, and somehow showing the sign of growing. Furthermore, how Indonesia responded to the world crisis was also important. Her government has been improving transparency in finance and birocracy, providing liquidity support for financial institution, increasing government spending, and the most importantly safeguarding the social safety net for the poor and low-income citizen, e.g price stability.

As the results, statistically in this crisis Indonesia is achieving economic growth of 4% annually. Furthermore, rupiah is pretty stable right now, with tendency being appreciated. However appreciated rupiah will make me slightly poorer as I am on a payroll in Singapore. In short, I am having lesser purchasing power in Indonesia, i.e less rupiah for a dollar. If only I had an investment in Indonesia, probably I would slightly less poor by now.

Prof Boediono then further elaborated on the how Indonesian economic policy will be made. The first priority will be in improving physical infrastructure in Indonesia, particularlly the inter-island transport and trade route. He commented that domestic trade have to be higher than international trade in order to survive in this crisis. The second priority is to have the national cohesion which must be maintained and improved. One of the steps is to bring down the unemployment rate, even the poorest could survive. The third and the last policy is to achieve a good and clean government, i.e transparency and corruption eradication.

In conclusion, local market is extremely important as a buffer zone for global economic crisis. Indonesia had survived the financial crisis due to it’s strong domestic market.

Tears of wine is a phenomenon identified by physicist James Thompsonn in 1855. This effect was later name after an Italian Physicist Carlo Marangoni, who studied this phenomenon in his thesis.

This effect refers to the mass transfer along an interface due to the gradient of surface tension and the tears of wine refers to ring of clear liquid, near the top of a glass wine, from which droplets form and flow back into the wine. (See figure 1 & 2) In layman term, some called it wine legs, curtains or church windows.

Figure 1: From top view of a glass

Figure 2: Side view of a glass of wine

It is mostly observed in wine of high alcohol content. It had also been used in ancient time to judge the quality of a wine. However we do not intend to have a long discussion on the quality of wine or beverage here, not even teaching  the skills of judging here (though the best way is to taste it), we are indeed impressed by the science behind this Marangoni effect.

As a researcher working in colloidal science and assembly, I came across this interesting paper [1] depicting the forgotten effect of Maragoni on Coffee-Ring deposition. The science of Marangoni flow was long forgotten due to common use of water-based colloids in daily life. This effect was found to have significant effect on the mass transfer of particles along the free surface of liquid, provided no surface-active agent present [2].

Conventional understanding of coffee-ring deposition occurs at which particles tends to deposits at the edge of water droplet where the evaporation rate is the fastest. The author Hu brought us a new insight that alkane-based colloids without surfactant tends to be different. Deposition occurred at the center of the droplet instead of the edge, despite higher evaporation at the edge. The question here is: “Does the directional convective flow towards the edge stop?”

The answer is definitely no. He revealed a recirculatory flow of particles, which started from the convective flow of particles to the side, and then followed by surface-tension driven flow along the free liquid surface, from edge towards the center top of the droplet. This flow was driven by the gradient of surface tension caused by the temperature difference along the liquid surface. The particles then sinked down to the bottom and continued with the convective flow to the edge. As drying time is short, particles tends to adhere to the center of the substrate, resulting in the deposition at the center of the droplet.

The following shows the flow field of liquid droplet (Marangoni Flow) as depicted by Hu et al.

The curved line shows the flow field over the free liquid surface. Read more in full-text mode

Things to know: Surface-active agent

Supporting Video by Hu et al on “Marangoni Effect Reverses Coffee-Ring Depositions”

http://pubs.acs.org/doi/suppl/10.1021/jp0609232/suppl_file/jp0609232si20060213_090622.avi

References:

1. Hua Hu and Ronald G. Larson, “Marangoni Effect Reverses Coffee-Ring Depositions,” The Journal of Physical Chemistry B 110, no. 14 (April 1, 2006): 7090-7094, doi:10.1021/jp0609232.
2. Savino et al, “Buoyancy and Marangoni Effects in an Evaporating Drop,” Journal of Thermophysics and Heat Transfer 60, no. 4, (Oct-Dec 2002): 562-574.