Urban Age HK Conference

http://urban-age.net/conferences/hongkong/

Hong Kong - Country history and economic development

http://www.nationsencyclopedia.com/economies/Asia-and-the-Pacific/Hong-Kong-COUNTRY-HISTORY-AND-ECONOMIC-DEVELOPMENT.html

1841. Hong Kong is seized by the British navy at the height of the first opium war (1839-42). The Chinese government is forced to accept Britain's sovereignty over the island by signing the Convention of Chuenpi.

1842. The British Royal Charter formally establishes Hong Kong as "a separate colony." The British government proclaims Hong Kong a free port, which encourages immigration from mainland China to Hong Kong. The United States government establishes the first foreign consulate in the colony.

1844. To control the Chinese population, the Hong Kong Legislative Council (Legco) passes a restrictive law which leads to a general strike, the return of many workers to China, and the paralysis of businesses. The Legco amends the law to restore normalcy.

1856. The Second Opium War (1856-58) begins. The Chinese workers of Hong Kong go on a strike and boycott British businesses.

1860. Britain expands its holdings in China by occupying Kowloon and Stonecutters Island. The Treaty of Beijing legalizes the occupation by leasing these lands to Britain in perpetuity.

1860s. Hong Kong's population grows significantly as a result of migration from mainland China. Its economy begins to flourish. Hong Kong's infrastructure emerges, including telegraph systems, street gas lighting, and secular schools.

1898. In the aftermath of the Sino-Japanese war (1894-95), the British government forces the weakened Chinese government to cede to Britain the New Territories and 235 islands in the proximity of Hong Kong on a 99-year lease to expire in June 1997.

1911. The Wuhan Uprising in Canton overthrows the Chinese Empire and makes its leader, Dr. Sun Yat-sen, the first president of China.

1920. Around 9,000 Hong Kong mechanics go on strike and leave for Canton. The subsequent paralysis of commerce leads to a wage increase and the settlement of the labor dispute.

1921. The Hong Kong government has to accept a wage increase for seamen similar to the one given to the mechanics in 1922 to end a general workers' strike.

1926. In October, the long general strike of Hong Kong's workers, in which 30 percent of the workforce participates, ends when the British Foreign Office agrees to change some of its unequal economic treaties with China.

1937. The Sino-Japanese War begins. The Japanese navy lands at Bias Bay in the New Territories.

1939. Japanese military forces occupy Hong Kong's Hainan Island.

1941. On 8 December, Japan invades Hong Kong. Governor Young accepts defeat and surrenders to the Japanese commander on 25 December.

1949. The Chinese Communist Party wins the civil war in China and declares the establishment of the People's Republic of China (PRC) on 1 October.

1950s. Hong Kong's population increases to 2.5 million as a result of the flight of hundreds of thousands of refugees from mainland China.

1961. Hong Kong's population increases to 3.1 million.

1970. Hong Kong's population grows to 4 million.

1979. As part of improving ties between China and Britain, China invites Hong Kong governor MacLehose for an official visit to discuss certain issues, especially the expiration of the New Territories lease in 1997.

1980. Hong Kong's population increases to 5.2 million. Hong Kong governor MacLehose announces the "Touch Base" policy to stop illegal immigration from China, which provides for the return of illegal immigrants to China.

1982. In September, British prime minister Margaret Thatcher visits Beijing to begin negotiations about the future status of Hong Kong.

1983. In July, the first official round of Sino-British talks over the future status of Hong Kong begins. In October, the Hong Kong dollar is pegged to the U.S. dollar at a rate of HK7.8 against US$1.

1984. The British and Chinese governments sign the Sino-British Joint Declaration regarding the peaceful hand-over of Hong Kong to China on 1 July 1997.

1985. In September, the Hong Kong government holds the first elections for Hong Kong's legislative body, the Legco.

1990. China's National People's Congress passes the Basic Law to serve as its mini-constitution based on the principle of "one country, two systems."

1991. In June, the Bill of Rights of Hong Kong is enacted with the power to override all other laws.

1994. Hong Kong holds its first fully democratic elections, and pro-democracy parties win a majority in the Legco. Selecting from among Hong Kong nationals, China appoints a 150-strong Preparatory Committee to lead Hong Kong's transfer to China. Over half of the committee are from Hong Kong's business elite.

1996. In December, China selects a Hong Kong ty-coon, Tung Chee-hwa, to be Hong Kong's first chief executive after the 1997 hand-over.

1997. On 1 July, the British government returns Hong Kong to China, which is renamed as the Hong Kong Special Administrative Region (SAR) of the People's Republic of China. Its Basic Law guarantees legal, judicial, and legislative systems independent from those of China and full economic autonomy.

1998. Hong Kong signs a treaty with China to eliminate double taxation of their respective businesses operating in each other's territory. In May, a Legco is formed by elections, which replaces the Provisional Legislative Council (PLC).

2000. In September, a new Legco is formed by elections.

Economic History of Hong Kong

http://eh.net/ENCYCLOPEDIA/ARTICLE/SCHENK.HONGKONG

Catherine R. Schenk, University of Glasgow

Hong Kong’s economic and political history has been primarily determined by its geographical location.  The territory of Hong Kong is comprised of two main islands (Hong Kong Island and Lantau Island) and a mainland hinterland. It thus forms a natural geographic port for Guangdong province in Southeast China. In a sense, there is considerable continuity in Hong Kong’s position in the international economy since its origins were as a commercial entrepot for China’s regional and global trade, and this is still a role it plays today.  From a relatively unpopulated territory at the beginning of the nineteenth century, Hong Kong grew to become one of the most important international financial centers in the world.  Hong Kong also underwent a rapid and successful process of industrialization from the 1950s that captured the imagination of economists and historians in the 1980s and 1990s. 

Hong Kong from 1842 to 1949

After being ceded by China to the British under the Treaty of Nanking in 1842, the colony of Hong Kong quickly became a regional center for financial and commercial services based particularly around the Hongkong and Shanghai Bank and merchant companies such as Jardine Matheson.  In 1841 there were only 7500 Chinese inhabitants of Hong Kong and a handful of foreigners, but by 1859 the Chinese community was over 85,000 supplemented by about 1600 foreigners. The economy was closely linked to commercial activity, dominated by shipping, banking and merchant companies. Gradually there was increasing diversification to services and retail outlets to meet the needs of the local population, and also shipbuilding and maintenance linked to the presence of the British naval and merchant shipping.  There was some industrial expansion in the nineteenth century; notably sugar refining, cement and ice factories among the foreign sector, alongside smaller-scale local workshop manufactures. The mainland territory of Hong Kong was ceded to British rule by two further treaties in this period; Kowloon in 1860 and the New Territories in 1898.

Hong Kong was profoundly affected by the disastrous events in Mainland China in the inter-war period. After overthrow of the dynastic system in 1911, the Kuomintang (KMT) took a decade to pull together a republican nation-state.  The Great Depression and fluctuations in the international price of silver then disrupted China’s economic relations with the rest of the world in the 1930s. From 1937, China descended into the Sino-Japanese War.  Two years after the end of World War II, the civil war between the KMT and Chinese Communist Party pushed China into a downward economic spiral.  During this period, Hong Kong suffered from the slowdown in world trade and in China’s trade in particular.  However, problems on the mainland also diverted business and entrepreneurs from Shanghai and other cities to the relative safety and stability of the British colonial port of Hong Kong. 

Post-War Industrialization

After the establishment of the People’s Republic of China (PRC) in 1949, the mainland began a process of isolation from the international economy, partly for ideological reasons and partly because of Cold War embargos on trade imposed first by the United States in 1949 and then by the United Nations in 1951.  Nevertheless, Hong Kong was vital to the international economic links that the PRC continued in order to pursue industrialization and support grain imports. Even during the period of self-sufficiency in the 1960s, Hong Kong’s imports of food and water from the PRC were a vital source of foreign exchange revenue that ensured Hong Kong’s usefulness to the mainland. In turn, cheap food helped to restrain rises in the cost of living in Hong Kong thus helping to keep wages low during the period of labor-intensive industrialization.

The industrialization of Hong Kong is usually dated from the embargoes of the 1950s.  Certainly, Hong Kong’s prosperity could no longer depend on the China trade in this decade.  However, as seen above, industry emerged in the nineteenth century and it began to expand in the interwar period. Nevertheless, industrialization accelerated after 1945 with the inflow of refugees, entrepreneurs and capital fleeing the civil war on the mainland. The most prominent example is immigrants from Shanghai who created the cotton spinning industry in the colony.  Hong Kong’s industry was founded in the textile sector in the 1950s before gradually diversifying in the 1960s to clothing, electronics, plastics and other labor-intensive production mainly for export.

The economic development of Hong Kong is unusual in a variety of respects.  First, industrialization was accompanied by increasing numbers of small and medium-sized enterprises (SME) rather than consolidation.  In 1955, 91 percent of manufacturing establishments employed fewer than one hundred workers, a proportion that increased to 96.5 percent by 1975. Factories employing fewer than one hundred workers accounted for 42 percent of Hong Kong’s domestic exports to the U.K. in 1968, amounting to HK$1.2 billion.  At the end of 2002, SMEs still amounted to 98 percent of enterprises, providing 60 percent of total private employment. 

Second, until the late 1960s, the government did not engage in active industrial planning. This was partly because the government was preoccupied with social spending on housing large flows of immigrants, and partly because of an ideological sympathy for free market forces.  This means that Hong Kong fits outside the usual models of Asian economic development based on state-led industrialization (Japan, South Korea, Singapore, Taiwan) or domination of foreign firms (Singapore) or large firms with close relations to the state (Japan, South Korea). Low taxes, lax employment laws, absence of government debt, and free trade are all pillars of the Hong Kong experience of economic development.

In fact, of course, the reality was very different from the myth of complete laissez-faire. The government’s programs of public housing, land reclamation, and infrastructure investment were ambitious. New industrial towns were built to house immigrants, provide employment and aid industry.  The government subsidized industry indirectly through this public housing, which restrained rises in the cost of living that would have threatened Hong Kong’s labor-cost advantage in manufacturing. The government also pursued an ambitious public education program, creating over 300,000 new primary school places between 1954 and 1961.  By 1966, 99.8% of school-age children were attending primary school, although free universal primary school was not provided until 1971. Secondary school provision was expanded in the 1970s, and from 1978 the government offered compulsory free education for all children up to the age of 15.  The hand of government was much lighter on international trade and finance. Exchange controls were limited to a few imposed by the U.K., and there were no controls on international flows of capital.  Government expenditure even fell from 7.5% of GDP in the 1960s to 6.5% in the 1970s.  In the same decades, British government spending as a percent of GDP rose from 17% to 20%.

From the mid-1950s Hong Kong’s rapid success as a textile and garment exporter generated trade friction that resulted in voluntary export restraints in a series of treaties with the U.K. beginning in 1959.  Despite these agreements, Hong Kong’s exporters continued to exploit their flexibility and adaptability to increase production and find new markets.  Indeed, exports increased from 54% of GDP in the 1960s to 64% in the 1970s.  Figure 1 shows the annual changes in the growth of real GDP per capita.  In the period from 1962 until the onset of the oil crisis in 1973, the average growth rate was 6.5% per year.  From 1976 to 1996 GDP grew at an average of 5.6% per year. There were negative shocks in 1967-68 as a result of local disturbances from the onset of the Cultural Revolution in the PRC, and again in 1973 to 1975 from the global oil crisis.  In the early 1980s there was another negative shock related to politics, as the terms of Hong Kong’s return to PRC control in 1997 were formalized.

Reintegration with China, 1978-1997

The Open Door Policy of the PRC announced by Deng Xiao-ping at the end of 1978 marked a new era for Hong Kong’s economy.  With the newly vigorous engagement of China in international trade and investment, Hong Kong’s integration with the mainland accelerated as it regained its traditional role as that country’s main provider of commercial and financial services. From 1978 to 1997, visible trade between Hong Kong and the PRC grew at an average rate of 28% per annum. At the same time, Hong Kong firms began to move their labor-intensive activities to the mainland to take advantage of cheaper labor.  The integration of Hong Kong with the Pearl River delta in Guangdong is the most striking aspect of these trade and investment links.  At the end of 1997, the cumulative value of Hong Kong's direct investment in Guangdong was estimated at US$48 billion, accounting for almost 80% of the total foreign direct investment there. Hong Kong companies and joint ventures in Guangdong province employed about five million people.  Most of these businesses were labor-intensive assembly for export, but from 1997 onward there has been increased investment in financial services, tourism and retail trade.

While manufacturing was moved out of the colony during the 1980s and 1990s, there was a surge in the service sector.  This transformation of the structure of Hong Kong’s economy from manufacturing to services was dramatic.  Most remarkably it was accomplished without faltering growth rates overall, and with an average unemployment rate of only 2.5% from 1982 to 1997.  Figure 2 shows that the value of manufacturing peaked in 1992 before beginning an absolute decline. In contrast, the value of commercial and financial services soared.  This is reflected in the contribution of services and manufacturing to GDP shown in Figure 3. Employment in the service sector rose from 52% to 80% of the labor force from 1981 to 2000 while manufacturing employment fell from 39% to 10% in the same period.

 

Asian Financial Crisis, 1997-2002

The terms for the return of Hong Kong to Chinese rule in July 1997 carefully protected the territory’s separate economic characteristics, which have been so beneficial to the Chinese economy.  Under the Basic Law, a "one country-two systems" policy was formulated which left Hong Kong monetarily and economically separate from the mainland with exchange and trade controls remaining in place as well as restrictions on the movement of people.  Hong Kong was hit hard by the Asian Financial Crisis that struck the region in mid-1997, just at the time of the handover of the colony back to Chinese administrative control. The crisis prompted a collapse in share prices and the property market that affected the ability of many borrowers to repay bank loans.  Unlike most Asian countries, Hong Kong Special Administrative Region and mainland China maintained their currencies’ exchange rates with the U.S. dollar rather than devaluing.  Along with the Sudden Acute Respiratory Syndrome (SARS) threat in 2002, the Asian Financial Crisis pushed Hong Kong into a new era of recession with a rise in unemployment (6% on average from 1998-2003) and absolute declines in output and prices.  The longer-term impact of the crisis has been to increase the intensity and importance of Hong Kong’s trade and investment links with the PRC. Since the PRC did not fare as badly from the regional crisis, the economic prospects for Hong Kong have been tied more closely to the increasingly prosperous mainland.

Suggestions for Further Reading

For a general history of Hong Kong from the nineteenth century, see S. Tsang, A Modern History of Hong Kong, London: IB Tauris, 2004.  For accounts of Hong Kong’s economic history see, D.R. Meyer, Hong Kong as a Global Metropolis, Cambridge: Cambridge University Press, 2000; C.R. Schenk, Hong Kong as an International Financial Centre: Emergence and Development, 1945-65, London: Routledge, 2001; and Y-P Ho, Trade, Industrial Restructuring and Development in Hong Kong, London: Macmillan, 1992. Useful statistics and summaries of recent developments are available on the website of the Hong Kong Monetary Authority www.info.gov.hk/hkma.

Citation: Schenk, Catherine. "Economic History of Hong Kong". EH.Net Encyclopedia, edited by Robert Whaples. March 16, 2008. URL http://eh.net/encyclopedia/article/schenk.HongKong

Janine Benyus: Biomimicry in action

Alsomitra macrocarpa - YouTube

Alsomitra macrocarpa - YouTube

Xiaoji Chen's Design Weblog » List

Xiaoji Chen's Design Weblog » List

URBAGRAM

URBAGRAM

A Week of Check-ins on the Path to One Billion

A Week of Check-ins on the Path to One Billion from foursquare on Vimeo.

Forward flight of swallowtail butterfly with simple flapping motion

Among the various types of flying insects, swallowtail butterflies have unique morphological features. Their wing area is very large relative to their body mass, and their flapping frequency is low. ...... Another feature of swallowtail butterflies is the small degree of freedom of the wing motion. The fore wing partly overlaps the hind wing and they flap as one large wing with little feathering. The feathering is structurally restricted by the wing connection. This means that the ability of butterflies to actively control the aerodynamic force of their wings is limited and the undulating body motion is produced passively by simple flapping.

........

To clarify the passive body motion in butterfly-type flapping flight, we fabricated a tailless ornithopter having the same mass and wing shape as an actual swallowtail butterfly. This ornithopter enabled us to observe the passive body motion caused by simple mechanical flapping in free flight. We also clarified the effect of the wing stiffness on the passive body motion by changing the wing venation of the ornithopter. Our experiments demonstrated that the forward flight of a swallowtail butterfly is realized by simple flapping without feedback control of the wing motion and that passive deformation of the wing significantly affects the passive body motion and resultant aerodynamic coefficients.

Simple flapping motion was achieved by means of a rubber-band-driven crank mechanism that made the wings flap vertically relative to the body at 10 Hz. 

A butterfly wing consists of thin membranes supported by wing veins extending from the wing base to the outer edge. The wing stiffness depends on the vein pattern(Wootton 1993).

To emulate the stiffness distribution of an actual wing, we fabricated the artificial wings with plastic veins mimicking those of an actual swallowtail butterfly (figure 2(a)). A mold for the veins was fabricated by plasma dry etching, and the veins were molded on a thin polymer film.
.........
The longitudinal position of the center of gravity was adjusted by changing the longitudinal position of a 0.04 g balance weight attached to the body of the ornithopter.....

The passive flight motion must depend on the design of the wings. In particular, the wing deformation determined by the wing stiffness presumably affects flight performance (Wootton

1993). A butterfly wing consists of thin membranes supported by wing veins extending from the wing base to the outer edge, and the wing stiffness depends on the vein pattern. 

4. Conclusion

Using the butterfly-type ornithopter, we demonstrated that the undulating body motion caused by simple flapping of swallowtail butterflies in forward flight has the effect of enhancing the lift coefficient during downstroke. The enhanced lift coefficient at the beginning of downstroke in

free flight exceeded 3.0, which is more than four times that in a steady flow. Though the drag coefficient also increased, the lift coefficient was large enough to keep the thrust coefficient

positive. This lift and drag enhancement was attributed to large angle of attack caused by the passive up-down body motion. The body motion was greatly affected by the wing deformation

depending on the wing stiffness and resultant aerodynamic coefficients in free flight. Wing veins are needed to prevent feathering deformation and produce a large up–down body motion.

Since butterfly-type flapping flight can be realized with simple flapping motion without feedback control, butterfly aerodynamics can be applied to future aerodynamic systems

Interview: Michael Pawlyn on Biomimicry

Why were you drawn to biomimicry?
As a teenager I was torn between studying architecture and biology and eventually chose the former. I was also quite politicized about environmental issues in my early teens after a relative gave me a copy of the Club of Rome’s “Blueprint for Survival”. When I joined Grimshaw to work on the Eden Project, I realized that there was a way to bring these strands together in pursuit of sustainable architecture inspired by nature.

You say we are entering the ecological age. What does that mean exactly?
As I see it, this is the age in which we have the knowledge, technology and imperative to formulate a truly sustainable way of living rather than pursuing approaches that simply mitigate negative impacts.

What are some of the most interesting examples, apart from the Eden Project, of existing architecture that uses biomimicry as its guiding principle?
Pier Luigi Nervi’s Palazzetto dello Sport, an indoor arena in Rome, is a masterpiece of efficiency inspired by giant Amazon water lilies. Many of Nervi’s projects were won in competitions and the secret to his success was his ability to produce the most cost-effective schemes. In a satisfying parallel with the refining process of evolution, the combination of ingenuity and biomimicry led to a remarkable efficiency of resources.

The Eastgate Centre in Harare, Zimbabwe by Mick Pearce, is based on termite mounds. It manages to create comfortable conditions for the people inside without air-conditioning in a tropical environment.

What species in nature are you most in awe of and why?
Camel’s nostrils are miracles of heat exchange and water recovery engineering. We are currently looking at cuttlebone(오징어 뼈) and bird skulls(두개골) to help design more efficient concrete structures for office buildings. The combustion(연소) chamber in the abdomen(하복부) of a bombardier beetle mixes two high explosives from fuel tanks with valves that open and close 200 times a second—it is being studied in order to develop needle-free medical injections, more efficient fuel injection systems and more effective fire extinguishers.

Not everything in nature is innocuous. Which are the species you would not want to “mimic”?
There are quite a few species that have been studied by defense industries in order to develop sophisticated weapons using parasites, natural toxins, germ warfare and the like. This is why some people make a distinction between “biomimicry” (which is specifically about developing sustainable solutions) and the more general term of “biomimetics”.

You have said that environmentally sustainable architecture tends to focus on mitigation, when it should be regenerative and restorative. How achievable is this?
Humans are accustomed to engineering things to maximize one goal, whereas ecosystems have evolved towards an optimized overall system. We are only slowly embracing the benefits of designing the kind of synergistic systems like the Cardboard to Caviar project (a closed-loop scheme which takes restaurant waste, turns it into horse bedding, feeds it to worms who in turn are fed to fish whose caviar eventually ends up back on the plates of the restaurant) and the Sahara Forest project.

It is also partly down to conventional economics, which externalizes issues such as pollution, liquidation of natural capital and so on. If we were to shift some taxation away from employment and towards the use of resources it would reward resource efficiency.

How would the construction industry have to change?
We need to get better at procuring the built environment in a way that delivers the maximum long-term value for the minimum long-term cost. At the moment, progress is hampered by short-term thinking, conventional economics and collaboration that do not lead to optimized results.

Why is getting something like the Sahara Forest project off the ground so slow? It seems like this is innovation with few downsides.
The powerful vested interests of oil and motor companies—both of which provide extensive funding to political parties—are a major impediment.

Short term ways of thinking also tend to favor solutions that produce quick profits at the expense of long-term loss. I think this occurred in the late ’80s and early ’90s when developers were fairly brazen about saying that they weren’t interested in anything with a payback period. We now need to create investment models that allow people to invest in longer term projects that deliver value far into the future.

What other projects are you working on at the moment?
I’m working on a concept study for a biomimetic office building—essentially using biomimicry to completely rethink the workplace with the aim of producing a scheme that is as far as possible self-heating, self-cooling and self-ventilating, entirely day-lit and a net producer of energy. Plants will also be incorporated to boost human productivity. A radical new approach to designing IT servers that delivers a factor-10 reduction in carbon emissions is possibly on the cards as well.

Via The Economist

butterfly flight

http://www.youtube.com/watch?v=TLnYQqnxEJw&feature=player_embedded

Japanese researchers are probing the mechanics of insect flight by creating artificial butterflies. The above video shows a wooden contraption gracefully flapping its wings in high-speed footage.

Hiroto Tanaka of Harvard University and Isao Shimoyama of the University of Tokyo made theornithopter out of balsa wood, polyurethane, and polymer film. It has the same mass and form as a swallowtail butterfly, including the planar shape of its wings.

The wings are powered by a crank mechanism. A rubber band is wound up to make the wings flap vertically at a frequency of 10Hz. It seems to fly for only a few seconds.

According to the study published in Bioinspiration & Biomimetics, the ornithopter flew like a swallowtail butterfly, even following an undulating course through the air. The researchers also found that plastic wings with veins generated a higher lift coefficient when flapping.

Shimoyama's lab has also created motor-driven insect ornithopters, pheromone-guided robots, and pneumatic hands.

Flight of a Samara_Alsomitra macrocarpa

The lift-to-drag ratio or the gliding ratio was about 3 ~ 4 and the rate of descent was 0.3 - 0.7 m/sec, which was smaller than those of other rotary seeds. The flight was so stable that samples were seen to take their optimal trimmed angle of attack with a value between the maximum gliding ratio and the minimum rate of descent. The aerodynamic function of the husk for the distribution of the seeds was also revealed by making wind tunnel tests of the husk.

If a horizontal wind, the speed of which is 10 m/sec, exists, then the horizontal
distance of flight is increased further by 10 m/sec x 24 sec = 240 m.

If wind is absent, the seed can get the highest distance by flying with a lift coefficient of CL = 0"27, at which the lift-to-drag ratio and thus the gliding ratio (the ratio of horizontal distance and the height loss) are maximum. However, if there is a wind, then the flight is strongly dependent on the time until the seed reaches the ground after the initiation of falling. This suggests that flight should occur at the lift coefficient giving the minimum rate of descent. Thus, it is an interesting fact that the actual lift coefficient of CL = 0.34 lies between two optimal lift coefficients,
the maximum lift-to-drag ratio (or the maximum gliding ratio) and the minimum rate of descent, but is closer to the former because the minimum rate of descent is almost constant beyond the selected value, CL > 0"34. Here, also, as seen in many other locomotions, the living creature acts to get the optimal performance.

Conclusion

The geometrical characteristics of the wing of Alsornitra macrocarpa, such as the slightly swept and twisted wing, the reflected trailing edge of the airfoil, the lightly loaded wing and adequately arranged CG position, are well fitted to assure the good performance and stability in gliding flight of the winged seed. The thin wing with a sharp leading edge and adequate aspect ratio (AR =3--4) produce the appropriate lift-to-drag ratio (L/D ~ 3- 4) for the flight in small Reynolds number (Re ~4 x 103). The low wing loading (mg/S ~ 0.5 N/m 2) also guarantees a smaller rate of descent (w=0.3-0,7 m/sec) than those of the rotary seeds. The flight is performed at a lift coefficient of CL =0.34, which not only gives the maximum gliding ratio but also guarantees approximately the minimum rate of descent. The above small lift coefficient is adopted because of the large drag coefficient at high angles of attack.
 By applying the local circulation method, the two-dimensional aerodynamic characteristics of the wing section is revealed. It is also made clear that the dispersal of the seeds is assisted by the wind surrounding the husk, and the resonant pendulum motion of the hung husk.

BBC_Earth News_Vine seeds become 'giant gliders'

http://news.bbc.co.uk/earth/hi/earth_news/newsid_8391000/8391345.stm

Remarkable footage has been captured of falling Alsomitra vine seeds, which use paper-thin wings to disperse like giant gliders.

The seeds, which are produced by a football-sized pod, can glide hundreds of metres across the forest.

That ensures that the seeds fall far from their parent, giving the next generation of vines a head start.

A BBC team captured the film of the gliding seeds for the natural history series Life.

The Alsomitra (Alsomitra macrocarpa) vine is a type of climbing gourd, and is also known as the Javan cucumber.

It grows in the forests of Java, Indonesia.

Each pod contains up to 400 individual seeds, each of which peels away from the parent tree in the wind.

Dispersing its seeds in this way is vital to the vine, which must avoid producing new plants that land close, competing for sunlight and soil nutrients.

The wings decay upon landing

The aerodynamics of the giant Alsomitra seeds were studied by two Japanese engineers, Akira Azuma and Yoshinori Okuno more than 20 years ago.

They found that design of the seed is so good that it achieves a descent angle of just 12 degrees, a property that has led to the seed's shape inspiring the design of aircraft.

That means it falls just 0.4m each second, compared to 1m per second for many winged seeds that rotate as they fall.

Once the seed has fallen to the ground, the wings decay, rotting away to leave the germinating seed.

A new vine then grows skyward toward the canopy and sunlight.

At up to 15cm across, and weighing around 300mg, they are among the largest winged seeds produced by any plant. Yet the seed's wings are less than 10 micrometres thick.

Generally, the seeds fall to the ground in broad circles up to 6m across.

However, compared to many other plant seeds, those of the Alsomitra vine can glide in a relatively straight line with a following wind, helping them fall further away from the parent plant.

"Gliding seeds" is broadcast within the Plants episode of the BBC series Life at 2100GMT on BBC One on Monday 7 December.