Opini ini terinspirasi dari Dosen favorit saya, Ibu Endang Sih Prapti, Dosen Senior pada Fakultas Ekonomi Gadjah Mada.

Kalau ada yang berdemonstrasi di depan kedutaan besar Amerika serikat, mereka melakukan kesalahan besar. Membakar bendera Amerika dan meneriakkan slogan slogan anti amerika, meneriakkan yel yel, Boikot Produk Amerika adalah fatal. Mengapa fatal? Mereka tidak tahu bahwasanya selama ini kita hidup, makan, bekerja dan tidur di bawah bantuan Amerika. Contoh contoh berikut merupakan kenistaan kita bagi bangsa Indonesia yang hidup di bawah bayang bayang bangsa Asing. Semua barang dan jasa yang kita konsumsi merupakan buatan luar negeri

• Di pagi hari, ketika bangun tidur, menyantap hidangan pagi, mereka tidak tahu kalau beras, tempe, indomie (sebagian besar inputnya) diimpor  dari Amerika. Ketika menggosok gigi, Pasta dan sikat gigi juga inputnya dimpor dari Amerika.
• Berangkat Kerja? Naik bis ataupun Mobil pribadi buatan luar negeri (sebagian besar diimpor dari Amerika. Bahan Bakar pun Import.
• Be-SMS ria, Teknologi dan sebagian besar produk juga dari Amerika.
• Berpakaian, sukanya merk Amerika dan luar negeri.
• Di tempat kerja? Ruangan Ber-AC, Komputer, Lampu, Alat alat tulis, sebagian besar produk luar negeri.
• Pulang kerja dan sebelum tidur, nonton TV, buatan luar negeri.

Banyak contoh lain yang menggambarkan bahwa kehidupan kita adalah pemberian Luar Negeri. Oleh karena itu bila kita konsisten (khususnya para demonstran penentang Amerika) harusnya mereka tidak sekedar meneriakkan yel yel anti Amerika. Harus ada tindakan nyata dari mereka. Kalau menurut saya, kalau mereka konsisten, mungkin mereka semua sudah mati dan hidup tanpa busana karena apa yang mereka konsumsi adalah produk luar negeri.

Setiap tahun, ketika kongres Amerika melakukan sidang untuk menentukan Anggrannya (semacam sidang pembahasan APBN), semua negara miskin hadir dan main petak umpat di sekitar lokasi berlangsungnya sidang. Mengapa? Untuk mengemis. Amerika setiap tahunnya mengalokasikan Anggarannya untuk membantu negara negara miskin dunia. Rupanya Indonesia juga masuk di sana. Mereka melobi dan meminta anggota kongres agar bantuan untuk negaranya masing masing, kalau perlu lebih besar bantuannya. Itulah kenyataannya.

Kembali ke Fokus?

Jadilah Indonesia Sejati…..

sebuah pertanyaan simple, Terus apa produk atau buatan asli Indonesia?

Contoh menarik dapat kita temui pada iklan beberapa produk yang menggunakan slogan, Gunakan Produk Indonesia atau Pakailah Produk Indonesia. Benar kalau itu adalah produk Indonesia, tetapi cobalah bertanya pada Produsennya, apakah local contentnya mutlak Indonesia? Tidak!

Kita juga memproduksi beras, kedelai, beras, pakaian dan lain lain, tetapi tidak cukup untuk memberi makan pada seluruh rakyat Indonesia. Negara kita sangat kaya, lebih kaya dibandingkan dengan Amerika. Cobalah bertanya kepada pemerintah, Apakah Indonesia akan bangkrut kalau hidup tanpa bantuan asing?

Kita harusnya merefleksikan diri mengenai hidup ini. Kita hanya tidak bangga menggunakan produk kita sendiri dan mengembangkannya menjadi produk nasional. contoh;

Ketika jumlah penduduk Amerika bertambah, Konsumsi gandum meningkat. Mereka bingung karena persediaan dan produksi gandum yang terbatas dan oleh karenanya mereka harus mengimpor. Tapi mereka tidaklah Bodoh. Bangsa Amerika tidaklah bodoh. Mengurangi konsumsi Gandum tetapi tidak menggangu perut Rakyatnya. CEREAL adalah inovasi terhebat. Bahannya dari jagung dan mereka berhasil. Mereka bangga makan jagung (yang sudah diolah, sehingga menjadi kenikmatan sendiri). Di Indonesia, terkenal dengan semboyan, kalau belum makan nasi, belum kenyang walaupun sudah makan jagung ataupun cemilan lainnya.

Benarkah kalau kita tidak bangga makan jagung dan Ubi yang merupakan produk asli?

Perut kita sepertinya sudah kerasan dengan nasi (beras) dan sangat sulit untuk mengubahnya. Sedemikian sulitnya kah?

Pemerintah perlu untuk mengubah kebiasaan perut kita dan kebiasaan kita. Kitapun demikian, harus mengubah ketergantungan kita kepada beras. Bayangkan Jagung diekspor tetapi beras diimpor! Aneh..!

Kalau Bung Karno pernah bilang, Go to hell with your Aid!, apa kita masih berani mengatakannya di saat ini?

Tanya saja sama pemerintah!!!!!!!!!!

Pada menit pertama saya berhasil mengidentifikasi permasalahannya, yaitu Utilisasi CPU yang terlalu tinggi mencapai 99%”. Hal ini saya ketahui melalui monitoring tool yang saya gunakan, jadi saya gak perlu repot2 login ke router karena dengan kondisi seperti sekarang sangat sulit untuk bisa masuk ke router. Setelah tau penyebabnya maka sekarang saya harus mencari penyebab “High CPU Utilization”. Berikut hal-hal yang dapat anda lakukan apabila mengalami problem yang sama.

Identifikasi Masalah

SHOW PROCESS CPU NOTIFICATIONS (if any)

Router#show process cpu sorted

Dengan command ini anda akan mendapatkan informasi tetang CPU utilisasi, process-process yang menggunakan CPU, dan interrupt percentages. Informasi tersebut bisa anda dapatkan pada baris pertama dari output show.

router#sh proc cpu sort

CPU utilization for five sec: 99%/54%; one minute: 99%; five minutes: 99%
PID ntime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
77 11697800 822858 14216 38.52% 37.51% 37.71% 0 IP Input
128 702920 714062 984 2.47% 2.57% 2.50% 0 Tag Input

Keterangan:

CPU utilization for five seconds: x%/y%; one minute: a%; five minutes: b%

Total CPU Utilization: x%

Process Utilization: (x - y)%

Interrupt Utilization: y%

Process Utilization is the difference between the Total and Interrupt (x and y). The one and five minute utilizations are exponentially decayed averages (rather than an arithmetic average), therefore recent values have more influence on the

calculated average.

SHOW LOG

Lakukan “show logging” untuk mendapatkan informasi log router, barangkali ada informasi berguna yang dapat membantu untuk melakukan identifikasi masalah dan menemukan akar permasalahannya.

Dampak dari High CPU Utilization

- Input queue drops

- Slow performance

- Slow response int Telnet or unable to Telnet router

- Slow response on the console

- Slow or no response to ping

- Router doesn’t send routing updates

Kemungkinan Penyebab High CPU Utilization

Berdasarkan hasil “show process cpu” saya mendapatkan informasi bahwa IP Input menggunakan resource CPU cukup besar. Maka ada kemungkinan penyebabnya adalah seputar IP Input. Tetapi meskipun demikian, saya tidak menutup mata akan adanya penyebab yang lain. Hal-hal yang mungkin menyebabkan High CPU Utilization antara lain:

Hardware failure

Perkiraan saya untuk hardware failure yang dapat menyebabkan High CPU Utilization adalah RSP failure dan/atau VIP failure.

Configuration

Berdasarkan hasil “show process cpu” kemungkinan permasalahan berhubungan dengan IP Input, jadi bisa saja karena konfigurasi fast switching, TCP intercept, penggunaan IP NAT, dll. Atau bisa juga karena ada yang melakukan DoS.

Langkah-langkah Penanganan

Hardware failure

a. RSP Failure

Jika yang bermasalah RSP ya diganti aja . Tetapi sekedar saran mungkin opsi ini dijadkan pilihan terakhir saja, karena untuk menggangti RSP router harus dimatikan. Total estimasi downtime yang dibutuhkan kurang lebih 15 menit. Waktu yang dibutuhkan router 7600 untuk booting kira2 10-15, itu termasuk update routing, dll.

b. VIP Failure

Untuk memastikan apakah yang bermasalah VIP atau bukan, maka anda bisa melakukan:

Router#sh controllers vip all proc cpu | i utilization

CPU utilization for five seconds: 1%/1%; one minute: 1%; five minutes: 1%

CPU utilization for five seconds: 5%/5%; one minute: 5%; five minutes: 5%

CPU utilization for five seconds: 21%/21%; one minute: 21%; five minutes: 21%

CPU utilization for five seconds: 19%/19%; one minute: 20%; five minutes: 19%

Jika anda ingin melihat detil prosesnya maka lakukan perintah “sh controllers vip vip_number proc cpu “.

Configuration

TRY THIS: If IP Input is consuming the CPU, one of the following might be the cause:

– Fast switching is disabled on an interface (or interfaces) that has a lot of outgoing traffic. Examine the output of the ‘show interfaces switching’ command to see which interface is burdened with traffic. Re-enable fast switching on that interface.

- TCP Intercept is enabled. TCP Intercept requires process switching for all packets during session set-up.

- Fast switching is disabled on an interface which supports more than one network and is routing traffic between them. This can occur when an interface has one or more secondary network addresses configured.

INFO: The router will process switch all packets sourced from the interface and destined to host(s) off the same interface which is a CPU-intensive task. Use the ‘ip route-cache same-interface’ interface configuration command to allow packets to be fast switched on the same interface.

- Traffic that can’t be fast switched is arriving. This could be any of the following types of traffic:

* Packet for which there is no entry yet in the switching cache.

INFO: If there is a device in the network which is generating lots of packets at an extremely high rate for devices reachable through the router and is using different source or destination ip addresses, there won’t be a match for these packets in the switching cache, so they will be processed by the IP Input process. This source device can be a malfunctioning device or a device attempting a Denial-of-Service (DOS) attack.

* Packets destined for the router (ie. Routing Updates or a Spoof Attack)

* IP packets with options

* Packets that require protocol translation

* Multilink PPP

* Packets that require policy routing.

INFO: IOS versions 11.3 and higher allow policy-routed packets to be fast switched. Usee the ‘ip route-cache policy’ interface configuration command to allow policy-routed packets to be fast switched.

* Packets going through serial interfaces with X.25 encapsulation. In the X.25 protocol suite, flow control is implemented in layer 2 of the OSI model.

* Compressed traffic. If there’s no Compression Service Adapter (CSA) in the router, compressed packets must be process-switched.

* Encrypted traffic. If there’s no Encryption Service Adapter (ESA) in the router, encrypted packets must be process-switched.

- A lot of packets, arriving at an extremely high rate, for a destination in a directly attached subnet, for which there is no entry in the ARP table. This shouldn’t happen with TCP traffic, because of the windowing mechanism, but it can happen with UDP traffic.

- A lot of multicast traffic going through the router. Unfortunately, there’s no easy way to examine the amount of multicast traffic. If you’ve configured multicast routing on the router, you can enable fast switching of multicast packets using the ‘ip mroute-cache’ interface configuration command (fast switching of multicast packets is off by default).

- A lot of broadcast traffic. Check the number of broadcast packets in the ‘show interfaces’ command output.

- Too much traffic is passing through the router. If the router is over-used and is incapable of handling this amount of traffic, try distributing the load among other routers or consider purchasing a high-end router.

- IP NAT is configured on the router and there are lots of DNS packets going through the router. UDP or TCP packets with source and/or destination port 53 (DNS) are always punted to process level by NAT.

- Check who’s logged on to the router and what they are doing. If someone is logged on and is issuing commands that produce long output, the high CPU utilization by the IP input process will be followed by a much higher CPU utilization by the virtual EXEC process.

- Make sure all debugging commands in your router are turned off by issuing the undebug all or no debug all command.

- Check for a possible security issue. Commonly, high CPU utilization is caused by a security issue, such as a worm or virus operating in your network. Usually, a configuration change, such as adding additional lines to your access lists can mitigate the effects of this problem. Check the Cisco Product Security Advisories and Notices for information on the most likely causes and specific workarounds.

Ada yang mengganjal dalam diri ini.

Jika saya menulis dalam bahasa Indonesia, jumlah pembaca hanya sekitar 100 juta orang Indonesia ( yang mempunyai akses internet) plus sejumlah kecil wong londo yang bisa berbahasa Indonesia. Lain hal kalau saya menulis dalam bahasa Inggris, jumlah pembaca potential saya hampir mencapai 1 milliar. bayangkan!

Apa yang mengganjal?

Saya mengakui dan dengan rendah hati mengatakan kalau saya juga tidak fasih bahasa Inggris. Jadi bila saya menggunakan dalam bahasa Inggris, Ide saya mungkin ( hampir benar) tidak dapat diterjemahkan dengan baik karena kendala vocabularies. tetapi keuntungan yang saya peroleh adalah 1 milliar potential reader dapat membaca dan mengetahui isi gagasan dan opini saya.

So pake bahasa yang mana ya?

Kalau bohoso Jowo, jumlahnya pembaca menurun tajam, apa lagi bahasa kampungku, Lamaholot, lebih parah lagi cuma 5000 orang yang mempunyai akses internet.

Kacau, pake bahasa tubuh lebih gawat lagi…..

Saya mempunyai sebuah anekdot ringan mengenai Indonesia, tapi sebelumnya, jangan bilang-bilang ya sama pemerintah; nanti ditangkap dan transmigrasi di Nusakambangan dan opini mengenai Indonesia mandek sampai di sini. hehehe

Indonesia itu bagaikan seorang pemuda yang minum minuman keras. Hobinya adalah Ropi Miring. Temannya bernama Prancis juga suka minuman keras, yakni Wine. Nah sekarang perbedaan terletak pada perilaku mabuknya. Temannya si Perancis ini setelah menghabiskan sebotol wine, tidak mabuk tetapi pikirannya tenang, rilex, tidak muntah, badannya mulai hangat. Sedangkan si Indonesia, setelah menghabiskan sebotol topi miring, wah jadi kacau perilakunya, muntah muntah, perut bergoncang, mulai kacau dan bawaannya bikin onar, tidak dapat berpikir jelas, wah pokoknya 75-25 ( cape deh).

well well well

Apa maksudnya? Indonesia danPerancis, sama sama membuat kebijakan mengenai masa depan negaranya dan menganut pola yang kurang lebih sama. Mungkin Indonesia lebih bagus karena punya Pancasila. Kebijakan dan seluruh program yang tercermin dalam APBN adalah ibarat minuman keras dan beralkohol tadi…

Namun apa boleh buat, kebijakan yang kita minum ternyata membuat kita muntah muntah, kacau, menghasilkan tindakan anarkis…

Lantas, kebijakan seperti apa? (minuman alkohol seperti apa yang harus Indonesia minum agar hasilnya seperti yang dirasakan orang Perancis tadi? Mudahkan menjawabnya? Ganti Topi Miring dengan Wine. Tapi sayang, Wine terlampau keras karena kadar alkohol yang terlalu tinggi. Berarti jawabannya sulit dong! Tidak juga..

In my opinion, sebaiknya Indonesia minum susu saja.

Ulasan Bank Dunia (World Bank) ‘ Quality of Growth’ terbit tahun 2002 benar. Sebagai negara berkembang, kita menganut pola pembangunan dengan moto bangun dulu baru atur, sehingga untuk mengenyangkan perut 250 juta penduduk Indonesia, pemerintah melalui kebijakannya yang bersifat sesaat (diskrit).

Seperti apakah pola itu? Mari kita melihatnya bersama. Pola pembanguan sektor pertanian dengan sektor industri sebagai penopang menuju ke pola industrialisasi dengan sektor pertanian sebagai pendukungnya pada era Presiden Soeharto; di satu sisi peut kita memang telah dikenyangkan (tidak semua ya) namun di sisi lain, dampak yang ditimbulkan begitu dashyat yang kita nikmati sekarang ini.

Sektor Pertanian; Dalam rangka mencapai swasembada pangan tahun 1980-an, pola ekstensifikasi lahar pertanian dilakukan dengan pembukaan lahan baru (melalui transmigrasi) telah mengakibatkan jutaan hektar hutan dibabat. Yang penting makan dulu, Banjir masalah belakangan. jadi kita melihat bahwa program reboisasi dan penghijauan yang dilakukan waktu itu tidak berjalan dengan baik ( hanya formalitas karena tekanan dari negara donor).

Untuk yang sama dapat kita lakukan pada sektor sektor yang lain misalkan sektor kehutanan di mana penebangan hutan dilakukan hanya untuk kepentingan sesaat. Polusi akibat industrialisasi dan sektor sektor yang lain juga menganut pola pembanguan bangun dulu baru atur.

Yang menjadi pertanyaan kita saat ini, apakah moto semacam ini masih dianut atau sudah ditinggalkan oleh pemerintahan saat ini. Implementasi yang kita lihat mungkin belum berjalan karena investasi semacam ini adalah jangka panjang, namun kita dapat melihat apakah ada rencana semacam ini atau tidak dalam program pemerintah.

Sebagai penutup untuk opinion diatas, apakah ada jawaban rasional untuk pertanyaan

Mengapa Bencana selalu menimpa bumi Indonesia? haruskah kita menjawab TAKDIR seperti jawaban seorang ketika ditanya mengapa Pattimura ditangkap?

How’s Optimizing Keywords Done?

Before any other things, you need to select your keywords carefully and smartly. Keywords aren’t the words or phrases that you invent. You have to discover what searchers are typing to find what they want. Then, you choose the closest to the content you want to write and write with those keywords in your mind.

Use a Variety of them

To distinguish individual pages of your site from each other, optimizing keywords for search engines can help. Every webpage on your website should have its own keywords or key phrases. Search engines, then, realize your pages are different from each other. Also, they see what the difference is.

On the other hand, in optimizing keywords for search engines, it will be very useful if the keywords of various pages on your site are similar and/or relevant. This, of course, will be the best SEO tactic in terms of optimizing keywords and will enhance the content relevancy on your site.

Optimizing Keywords or Key Phrases?

Today only the known brands or very successful websites use keywords successfully. Does it sound disappointing? Don’t worry! What I mean is that one single word (common name) can hardly bring you targeted audience unless you’re well-known or famous for that single work.

So, what’s the solution? You have to get involved in optimizing keywords for search engines in a precise way.

Use a string of words, a key phrase. The longer a key phrase, the more targeted your site visitors. Of course, there’s some limit to it! These days, three-word key phrase or even four-word key phrase is the best to have.

For example, “affordable search engine optimization India” brings more targeted customer to your site than “seo India” or “seo packages” if you’re an SEO company in India trying to sell lower-priced search engine services in your country.

Where to Use them!

You’ve carefully been optimizing keywords for search engines by now. The outcome should now be used at your title tags, alt tags, first two headings, beginning and end of pages, middle of pages, menu links, inbound links, etc.

This doesn’t mean that you stuff the above positions with your keywords. Of course, the more inbound links with your keywords in them, the more benefit you get, specially from quality web pages outside your website.

How to Use them!

Once you’ve decide what key phrases to use and where and completed optimizing keywords, stick to them as they are. Never split them up by adding a word in the middle of such strings or words.

Key phrases should have appropriate weight, frequency and density on your web pages, not more not less than necessary. Otherwise, they will be seen as inefficient or spam!

Therefore, you should be extremely careful about how to use keywords or key phrases at your web pages.

How to Use Keywords Appropriately!

After you’ve completely done optimizing keywords for search engines, you should use them sufficiently and efficiently. This is something that search engines will find out easily. You also need to use good softwares or hire SEO experts to adjust this crucial point at your website.

While you’ve put all the above tactics into action, in your web pages, you could expect more targeted visitors. Obviously, this ends in having more customers who find you and buy what you’ve got to offer.

About The Author

Rahman Mehraby is mainly focused on Website Assessment as an initial step before taking any SEO Packages. He writes articles to help webmasters gain higher organic search engine placement. Visit his website at: http://www.site-booster.com.

Berikut ini merupakan gambar pinout dari S-Video to RCA

Anda dapat membeli connector tersebut di toko-toko elektronik. Sedikit informasi tamnahan saya sudah pernah mencoba mencari di Carrefour, Acehardware, dan electronic city tetapi tidak ada.

The traditional role of routers in DHCP has been simply to act as a proxy device, forwarding information between the client and server. Since IOS level 12.0(1)T, Cisco routers also have DHCP server and client features. But the DHCP proxy function is still the most common for routers.

Because the initial DHCP request comes from a client that typically doesn’t have an IP address, it must find the server using a Layer 2 broadcast. So, if the router was not able to function as a proxy for these broadcasts, it would be necessary to put a DHCP server on every network segment.

IP Helper Configuration Example:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#interface Ethernet0
Router1(config-if)#ip helper-address 172.25.1.1
Router1(config-if)#ip helper-address 172.25.10.7
Router1(config-if)#exit
Router1(config)#end
Router1#

NB: 172.25.1.1 and 172.25.10.7 is DHCP server IP Address

The DHCP server needs two critical pieces of information before it can allocate an IP address to the client. It must know the subnet that the client is connected to, and it needs the client device’s MAC address. The subnet information is needed to ensure that the address that the server allocates will actually work on client’s network segment. And the MAC address is necessary so that the server can find any information that is unique to this workstation. This is particularly true if you need to ensure that the end device always gets the same IP address every time it connects to the network.

So the DHCP proxy, which is the router itself, must convert the local broadcast from the client to a unicast packet and forward it to the server. This is what the ip helper-address command does.

When the DHCP client sends the DHCP request packet, it doesn’t have an IP address. So it uses the all-zeroes address, 0.0.0.0, as the IP source address. And it doesn’t know how to reach the DHCP server, so it uses a general broadcast address, 255.255.255.255, for the destination.

So the router must replace the source address with its own IP address, for the interface that received the request. And it replaces the destination address with the address specified in the ip helper-address command. The client device’s MAC address is included in the payload of the original DHCP request packet, so the router doesn’t need to do anything to ensure that the server receives this information.

The DHCP server now has enough information to assign an address from the correct address pool, since it now knows what the originating subnet was for the DHCP request. The server then sends a unicast response back to the proxy router, which in turn sends the request back to the correct MAC address.

The example shows two ip helper-address commands. You should include one of these commands for each of your DHCP servers. The router will forward the DHCP broadcasts to all of these addresses. Most organizations use at least two DHCP servers because although the utilization is light, the functionality is critical. In the very likely event that the client device receives several responses to a DHCP request, it will usually just select the one it received first.

It is important to note that the ip helper-address command does not just forward DHCP requests. In fact, although you can configure it to forward any UDP broadcast you want, by default it will forward UDP broadcast packets for several different UDP ports to the specified address. In some cases, this unwanted traffic can cause problems on the network or DHCP server.

The show ip interface command includes information about the helper addresses configured on an interface:

Router1#show ip interface Ethernet0
Ethernet0 is up, line protocol is up
  Internet address is 192.168.30.1/24
  Broadcast address is 255.255.255.255
  Address determined by setup command
  MTU is 1500 bytes
  Helper addresses are 172.25.1.3
                       172.25.1.1
  Directed broadcast forwarding is disabled
  <removed for brevity>
Router1#

Limiting the Impact of IP Helper Addresses

The ip helper-address command implicitly enables forwarding several different kinds of UDP broadcasts. You can prevent the router from forwarding the unwanted types of broadcasts with the no ip forward-protocol udp configuration command:

Router1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#no ip forward-protocol udp tftp
Router1(config)#no ip forward-protocol udp nameserver
Router1(config)#no ip forward-protocol udp domain
Router1(config)#no ip forward-protocol udp time
Router1(config)#no ip forward-protocol udp netbios-ns
Router1(config)#no ip forward-protocol udp netbios-dgm
Router1(config)#no ip forward-protocol udp tacacs
Router1(config)#end
Router1#

MIT team experimentally demonstrates wireless power transfer, potentially useful for powering laptops, cell phones without cords

Franklin Hadley, Institute for Soldier Nanotechnologies
June 7, 2007

Imagine a future in which wireless power transfer is feasible: cell phones, household robots, mp3 players, laptop computers and other portable electronics capable of charging themselves without ever being plugged in, freeing us from that final, ubiquitous power wire. Some of these devices might not even need their bulky batteries to operate.

A team from MIT’s Department of Physics, Department of Electrical Engineering and Computer Science, and Institute for Soldier Nanotechnologies (ISN) has experimentally demonstrated an important step toward accomplishing this vision of the future.

The team members are Andre Kurs, Aristeidis Karalis, Robert Moffatt, Prof. Peter Fisher, and Prof. John Joannopoulos (Francis Wright Davis Chair and director of ISN), led by Prof. Marin Soljacic.

Realizing their recent theoretical prediction, they were able to light a 60W light bulb from a power source seven feet (more than two meters) away; there was no physical connection between the source and the appliance. The MIT team refers to its concept as “WiTricity” (as in wireless electricity). The work will be reported in the June 7 issue of Science Express, the advance online publication of the journal Science.

Late-night beeps

The story starts one late night a few years ago, with Soljacic (pronounced Soul-ya-cheech) standing in his pajamas, staring at his cell phone on the kitchen counter. “It was probably the sixth time that month that I was awakened by my cell phone beeping to let me know that I had forgotten to charge it. It occurred to me that it would be so great if the thing took care of its own charging.” To make this possible, one would have to have a way to transmit power wirelessly, so Soljacic started thinking about which physical phenomena could help make this wish a reality.

Radiation methods

Various methods of transmitting power wirelessly have been known for centuries. Perhaps the best known example is electromagnetic radiation, such as radio waves. While such radiation is excellent for wireless transmission of information, it is not feasible to use it for power transmission. Since radiation spreads in all directions, a vast majority of power would end up being wasted into free space.

One can envision using directed electromagnetic radiation, such as lasers, but this is not very practical and can even be dangerous. It requires an uninterrupted line of sight between the source and the device, as well as a sophisticated tracking mechanism when the device is mobile.

The key: Magnetically coupled resonance

In contrast, WiTricity is based on using coupled resonant objects. Two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly with extraneous off-resonant objects. A child on a swing is a good example of this. A swing is a type of mechanical resonance, so only when the child pumps her legs at the natural frequency of the swing is she able to impart substantial energy.

Another example involves acoustic resonances: Imagine a room with 100 identical wine glasses, each filled with wine up to a different level, so they all have different resonant frequencies. If an opera singer sings a sufficiently loud single note inside the room, a glass of the corresponding frequency might accumulate sufficient energy to even explode, while not influencing the other glasses. In any system of coupled resonators there often exists a so-called “strongly coupled” regime of operation. If one ensures to operate in that regime in a given system, the energy transfer can be very efficient.

While these considerations are universal, applying to all kinds of resonances (e.g., acoustic, mechanical, electromagnetic, etc.), the MIT team focused on one particular type: magnetically coupled resonators. The team explored a system of two electromagnetic resonators coupled mostly through their magnetic fields; they were able to identify the strongly coupled regime in this system, even when the distance between them was several times larger than the sizes of the resonant objects. This way, efficient power transfer was enabled.

Magnetic coupling is particularly suitable for everyday applications because most common materials interact only very weakly with magnetic fields, so interactions with extraneous environmental objects are suppressed even further. “The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations,” Kurs, a graduate student in physics, points out.

The investigated design consists of two copper coils, each a self-resonant system. One of the coils, attached to the power source, is the sending unit. Instead of irradiating the environment with electromagnetic waves, it fills the space around it with a non-radiative magnetic field oscillating at MHz frequencies. The non-radiative field mediates the power exchange with the other coil (the receiving unit), which is specially designed to resonate with the field. The resonant nature of the process ensures the strong interaction between the sending unit and the receiving unit, while the interaction with the rest of the environment is weak.

Moffatt, an MIT undergraduate in physics, explains: “The crucial advantage of using the non-radiative field lies in the fact that most of the power not picked up by the receiving coil remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost.” With such a design, power transfer has a limited range, and the range would be shorter for smaller-size receivers.

Still, for laptop-sized coils, power levels more than sufficient to run a laptop can be transferred over room-sized distances nearly omni-directionally and efficiently, irrespective of the geometry of the surrounding space, even when environmental objects completely obstruct the line-of-sight between the two coils. Fisher points out: “As long as the laptop is in a room equipped with a source of such wireless power, it would charge automatically, without having to be plugged in. In fact, it would not even need a battery to operate inside of such a room.” In the long run, this could reduce our society’s dependence on batteries, which are currently heavy and expensive.

At first glance, such a power transfer is reminiscent of relatively commonplace magnetic induction, such as is used in power transformers, which contain coils that transmit power to each other over very short distances. An electric current running in a sending coil induces another current in a receiving coil. The two coils are very close, but they do not touch. However, this behavior changes dramatically when the distance between the coils is increased. As Karalis, a graduate student in electrical engineering and computer science, points out, “Here is where the magic of the resonant coupling comes about. The usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system.”

Old physics, new demand

WiTricity is rooted in such well-known laws of physics that it makes one wonder why no one thought of it before. “In the past, there was no great demand for such a system, so people did not have a strong motivation to look into it,” points out Joannopoulos, adding, “Over the past several years, portable electronic devices, such as laptops, cell phones, iPods and even household robots have become widespread, all of which require batteries that need to be recharged often.”

As for what the future holds, Soljacic adds, “Once, when my son was about three years old, we visited his grandparents’ house. They had a 20-year-old phone and my son picked up the handset, asking, ‘Dad, why is this phone attached with a cord to the wall?’ That is the mindset of a child growing up in a wireless world. My best response was, ‘It is strange and awkward, isn’t it? Hopefully, we will be getting rid of some more wires, and also batteries, soon.’”

This work was funded by the Army Research Office (Institute for Soldier Nanotechnologies), National Science Foundation (Center for Materials Science and Engineering), and the Department of Energy.