Friday, May 11, 2007

Hongor - Jalam Har

Энэ видеог PMP-дээ татаж авах гэсэн FLV файл болохоор болохгүй юм. AVI болгодог хөрвүүлэгч татаж үзсэн боловч чадсангүй. Блогоороо л хааяа сонсож байя.


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Thursday, May 10, 2007

Өвөр Монголын эмэгтэй хөөмийчид

Өмнө нь эмэгтэйчүүд хөөмийлж байхыг сонсоогүй юм байна. Гэхдээ дажгүй ээ. хэхэ

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Хүнээс нуугдагч хүнлэг сэтгэлтэн

Хүн гэж сонин авиртай байх юм даа. Саяхан нэг блог гаргагч нөхөр Сонин.мн-ий нийтлэл бүрийн доор Хүнлэг сэтгэл гэсэн блог хаягаа тавиад байхаар нь орж үзтэл үнэхээр Монголын ядарсан хүүхдүүдэд туслая хэмээн дэмжүүштэй санаа гаргажээ. Тэр нь энэ хаягаар орсон хүмүүс Гүүгл зар сурталчилгаа руу хандсанаар түүний хувийн дансанд мөнгө орох юм байна. Тэгээд тэр мөнгөө Монголын хүүхдүүдэд бэлэг авч өгөе гэхээр нь (уг нь нэг эхээ эмчлүүлэх гэсэн ядарсан хүүд туслая гэж гарч ирсэн юм) өөрийн блогтоо линк хийж, дэмжиж буйгаа илэрхийллээ. Тэгээд өөрөө нуугдаад байх нь бусдад итгэл төрүүлэхгүй алхам юм биш үү, улам итгэлтэй болгохыг тулд ил гараач гэж зөвлөтөл и-мэйлээр дайрч доромжлоод, тэр блогтоо "сайн санаатнууд" гээд жагсаалтандаа оруулсан байсан миний нэрийг арилгачив. Хүн үнэхээр хүнд тус болоё гэсэн чин эрмэлзэлтэй байгаа бол өөрөө нуугдах шаардлагатай гэж үү ? Үгүй л байлтай. Гэхдээ яахав, нэг линк дээр дарснаар хэнээс ч юм хорогдохгүй. Харин үүний цаана хэн нуугдана вэ? Хэн нэгэн ашиг хонжоо хайгч биш байгаа гэсэн хардлага хэнд ч төрөхгүй гэж үү?

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Monday, May 07, 2007

Review of “Superconducting nanotransistor based digital logic gates”

By Bat-Otgon

Introduction

Currently Superconducting materials are being strongly studied for the future computational hardware designs, mainly for fabricating high speed switching devices. When the switching device’s size is reduced into the nanometric scale, conventional semiconductor devices will not function at all due to the quantum mechanical effects. This critical review examines the article about how the publishers successfully demonstrated the function and fabrication of logic gates based on a superconducting nanotransistor. Seung-Beck et al. have demonstrated and tested a NOT logic gate successfully and claim that other gates will be fabricated in this way, allowing low power consumption and improved levels of integration (Seung-Beck et al. p188).

Summary

In the introduction section of the article, the publishers propose that logic circuits based on a conventional Josephson junction is very difficult to produce. According to Seung-Beck Lee at al. the complex structure of a Josephson field effect transistor (JOFET) makes the circuit integration limited. Therefore they demonstrated a different type of superconducting nanotransistor (SNT) which uses an active load as a heater to insert “hot” phonons into the superconducting weak-link to switch the SNT on/off. In other words, the superconducting channel becomes non-superconducting when it is heated up. In this article they have explained briefly the function of an SNT and its fabrication method. The publishers used many reference materials for their research. The main point is this article was written based on their experimental data. Their proposed SNT has a layer structure. The layers are named from top down: the heater layer, the insulating layer and superconducting layer. The structure of a device and the fabrication process are illustrated in figure 2 of the article. In this figure we can see very narrow bridge between two big squares. In the superconducting layer (Nb) this narrow bridge makes the weak-link area; in top layer (NiCr) this narrow bridge will become a heater to produce “hot” phonons. When the bias voltage is applied to the heater, “hot” phonons will be produced and travel trough the insulating layer to the weak-link. When it reaches the link that superconducting current will stop to flow. In this article publishers described the circuit diagram of a NOT logic gate based on a single SNT (p190). The test result of a NOT gate is shown in figure 6 (p190). This result says that the circuit has voltage gain of 2. They claim that the power consumption of the NOT gate mentioned in this article was about ~50 nW which is much lower than the conventional Josephson junction.

Evaluation

In this detailed research work it has been achieved a very successful result. The publishers have proved by experimentation that their idea will work. Another important issue is that the fabrication of the device is much simpler than previously reported controllable superconducting transistors. Although they have mentioned the switching speed of the device and the factors that will affect the speed, they did not provide any experimental data on this issue. The importance of an SNT would have been clearly identified if they had run a test on the switching speed of an SNT and provide the result. Most important was their proof that device is a NOT logic gate which was mentioned in the results and discussion section. In figure 5, they showed how the logic gate became a member of the bigger integrated system (p190).
Publishers also described how to change the device in to a NOR logic gate by adding an additional heater section. This idea gives the sense that an SNT can be used for high speed digital computational hardware devices (p191).

Conclusion

Seung-Beck Lee et al. described the successful fabrication and digital logic operation of superconducting nanotransistors (Abstract, p188). Their demonstration proves that superconductor will be a key material for future computational devices. Beside the feature size of the switching device, low power consumption and higher switching speed are the most important issues in this field. Since they proved that an SNT can make either NOT or NOR logic gates, all other digital logic circuits can be implemented by using SNT’s.

The original article can be downloaded from:
http://ej.iop.org/links/rITI13MNv/Hi9NWJf82xGoVD2Uav5vpA/t30217.pdf

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THE SCIENCE OF STICKY FEET

The animal world has many surprising things from which scientists are finding a lot of new ideas. Most insects can stay attached to a surface which is facing downwards. Since their weight is so small, insects can stick to the wall or ceiling using many different ways. But some researchers (Dr. Autumn et al.) found that the Gecko (a type of reptile) has a unique way to stick on surfaces with their feet, eventhough they are much bigger and heavier than small insects. Recent studies revealed that it is the physical structure of the Gecko’s feet that allows them to stick to the wall.
The toes of the gecko have attracted a lot of attention, as they adhere to a wide variety of surfaces, without the use of liquids or surface tension. The skin of Gecko’s toes has print like structure and it is formed by almost 500,000 hairs on each foot. (http://en.wikipedia.org/ wiki/Gecko) This hairs are called setae; their width is 1/10 the diameter of human hair and the length is the diameter of two human hairs. The most amazing thing is how these hairs can stick to the surfaces using totally different way than small insects.
The setae is not just a hair, each setae can have 100 to 1000 microscopic branches, like a tree. These branches are called spatulae and every spatulae has a small pad on its tip. Due to being smaller than the wavelength of visible light, the pad must be studied with the electron microscope. Because pads can not be seen by normal optical microscope. Recently, researchers confirmed that the underlying attraction of the pads with a surface is the physics principle of van der Waals force and this process makes Geckos’ feet sticky.

If two molecules touch each other, they can attract each other, and start sharing their electrons. This phenomenon produces a weak attractive force which is called van der Waals force. This term is named after the Dutch physicist van der Waals (1837-1923, Amsterdam). Although the attraction strength of a single pad is relatively weak, when it is multiplied by a billion pads on a Gecko’s feet, the attraction becomes incredibly strong. Geckos may have 6.5 million foot hairs, if all hairs are stuck at the same time, this force can hang a man to the ceiling! When a Gecko steps, it spreads its toes, which are lined with hair. The foot is placed on the surface in a rolling fashion. Otherwise Geckos can’t take off the foot suddenly from the surface. This sticky feet structure has led to many new ideas for how to make sticky materials on hard surfaces like post-it and other type of stickers.

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