Senin, 28 Desember 2009

Fisikawan Urang Sunda

Villa Isola - Wikipedia bahasa Indonesia, ensiklopedia bebas

Berbeda dengan gedung rektorat perguruan tinggi lainnya di Bandung, Gedung Rektorat Universitasi Pendidikan Indonesia (UPI) yang berada di Jalan Setiabudi, cukup unik. Tak hanya dari bentuknya, namanya pun cukup mengundang rasa penasaran. Vila Isola, terpahat jelas di salah satu bagian bangunan.

Vila Isola merupakan salah satu karya dari arsitektur terkenal C.P. Wolff Schoemaker. Proses pembuatan vila ini termasuk cepat, hanya memakan waktu 8 bulan. Dimulai pada Agustus 1933 dan selesai pada April 1934.

Kata Isola pada Vila Isola diambil dari kata Isolo yang berarti terpencil. D.W Berreti pemilik vila menginginkan dibuatkan vila yang jauh dari keramaian. Terlihat dari falsafah Berreti saat membangun vila ini yang berbunyi 'M Isolo E Vivo' yang berarti 'saya mengasingkan diri dan bertahan hidup dalam kesendirian'.

Walaupun terpencil, Vila Isola merupakan bangunan yang tercanggih di jamannya. Dengan memadukan unsur modernitas dan tradisional, karya C.P. Wolff Schoemaker ini mendapatkan banyak pujian. Bahkan salah satu arsitektur terkenal pada saat itu JP Coen mengatakan bahwa Vila Isola adalah salah satu mahkota dunia. Vila Isola adalah bangunan tercanggih pada jamannya dan masih terlihat kemegahannya sampai saat ini.

Unsur modern dilihat dari gaya art deco yang memang sedang berkembang di Eropa. Sedangkan unsur tradisional dilihat dari penggunaan kosmik Jawa, yang menggunakan sumbu pintu selatan dan utara.

Vila Isola pada awalnya memang dibuat untuk rumah tinggal untuk D.W. Berreti dan keluarganya. Sayangnya, D.W Berreti hanya sempat menempati Vila Isola setahun karena meninggal dunia akibat kecelakaan pesawat.

Beberapa tahun setelah kematian D.W Berreti, Vila Isola pun dibeli oleh Hotel Savoy Homan dan menjadi bagian dari hotel tersebut. Pada masa penjajahan Jepang, vila ini juga sempat menjadi tempat menginap para tentara Jepang sebelum menjelang diselenggarakannya perjanjian Kalijati.

Tentara Indonesia kemudian berhasil merebut Vila Isola. Semenjak itulah nama Vila Isola berubah menjadi Bumi Siliwangi yang mengandung arti rumah pribumi. Saat itu keadaan Vila Isola atau Bumi Siliwangi berupa puing-puing bangunan yang telah hancur di beberapa bagian.

Pada tahun 1954 Vila Isola pun dibeli pemerintah Indonesia seharga Rp 1.500.000. Vila Isola atau Bumi Siliwangi itu pun kemudian dijadikan gedung Perguruan Tinggi Pendidikan Guru (PTPG). PTPG ini merupakan cikal bakal dari IKIP atau UPI Bandung saat ini.

Semenjak tahun 1954 Vila Isola menjadi kantor rektorat dan juga ruang kelas sekaligus. Tahun 1963 PTPG pun berubah menjadi IKIP Bandung. Sampai saat ini Rektor, Pembantu Rektor dan Sekretariat Universitas masih menempati Vila Isola.

Koordinator Public Relation Universitas Pendidikan Indonesia (UPI) Bandung, Andika Dutha Bachari, mengakui memang banyak versi cerita yang ada di masyarakat seputar Vila Isola. Baik segi sejarah, filosofi, bangunan, ataupun misteri dibalik Vila Isola. "Coba saja search di google, pasti ada banyak cerita," kata Andika.

UPI merasa bangga dan beruntung memiliki salah satu karya heritage yang begitu terkenal. "Kita dititipi warisan dunia yang begitu berharga, walaupun biaya pengurusannya memang tidak sedikit," kata Andika.

UPI berencana akan merevitalisasi kawasan Vila Isola sebagai bagian dari kampus UPI. Isola Heritage akan jadi kawasan cagar budaya yang dapat dinikmati seluruh kalangan sebagai bagian dari wisata pendidikan. "Tapi bangunan Vila isola tidak akan diubah sedikitpun karena yang dipugar hanya taman dan daerah sekitarnya," kata Andika.

Lebih lanjut Andika menuturkan, masih ada karya C.P. Wolff Schoemaker selain Vila Isola di kawasan Kampus UPI, yaitu 12 rumah yang berada di sebelah barat Vila Isola.

"Dalam revitalisasi nanti rencananya 12 rumah tersebut akan dijadikan questhouse yang dapat disewakan untuk siapa saja yang akan menginap. Dan pendapatan dari situ dapat dialokasikan untuk perawatan Vila Isola itu sendiri," katanya.

Dengan konsep bact to original alias mengembalikan Vila Isola ke fungsi awal, UPI telah melakukan berbagai upaya seperti membentuk tim perencanaan dan pengumpulan data. Hal tersebut dilakukan agar hasil akhir Isola Heritage ini tidak akan mengecewakan. Revitalisasi ini akan dibuat sesuai dengan bentuk dan fungsi Vila Isola dari catatan sejarah dan dokumen yang ada, untuk itu perlu dikonsultasikan dengan berbagai pihak supaya tidak salah kaprah.

"UPI tidak akan bertindak gegabah, dengan senang hati kami terbuka untuk semua saran dan kritik yang diberikan seputar Vila Isola," kata Andika.

"Kami tidak merasa Vila Isola itu milik UPI saja tapi juga milik warga Bandung, Indonesia juga," sambungnya.

Physics (Greek: physis – φύσις meaning "nature") is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its motion. More broadly, it is the general analysis of nature, conducted in order to understand how the world and universe behave. Note that the term 'universe' is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term 'universe' may also be used in slightly different contextual senses, denoting concepts such as the cosmos, the philosophical world, and nature.

Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics had been considered synonymous with philosophy, chemistry, and certain branches of mathematics and biology, but during the Scientific Revolution in the 16th century, it emerged to become a unique modern science in its own right. However, in some subject areas such as in mathematical physics and quantum chemistry, the boundaries and the borderlines of physics remain difficult to distinguish.

Physics is both significant and influential, in part because advances in its understanding have often translated into new technologies, but also because new ideas in physics often resonate with the other sciences, mathematics and philosophy. For example, advances in the understanding of electromagnetism led directly to the development of new products which have dramatically transformed modern-day society (e.g., television, computers, and domestic appliances); advances in thermodynamics led to the development of motorized transport; and advances in mechanics inspired the development of the calculus.

Senin, 30 November 2009

Oleh-oleh dari Universitas California, Berkeley

"Limit (mendekati nol) itu tidak pernah menghasilkan nol, sekecil apapun pasti akan ada nilainya.
Kebaikan sekecil apapun, sekalipun niat, itu ada nilanya.
sekalipun gagal tetap akan ada nilainya dan bukan nol.
Hidup nol jika tidak ada nilai
Kita tidak ada nilai jika kita tidak ada karya
Karya tidak akan ada jika kita tidak ...ada usaha
sedangkan usaha akan nol jika tidak ada perpindahan (Pola pikir, Jasad/kerja)
Jika nilai kita nol, apa bedanya dengan yang ada di alam kubur?
Selama Tuhan masih memberikan waktu kepada kita untuk hidup."
Kita masih ada HARAPAN
~Power Ranger, B. Ach~
Selamat Berkarya

U.C. Berkeley Physics Lecture Demonstrations

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Selasa, 10 November 2009

Termodinamika

6.4 Brayton Cycle in - Coordinates

The Brayton cycle has two reversible adiabatic (i.e., isentropic) legs and two reversible, constant pressure heat exchange legs. The former are vertical, but we need to define the shape of the latter. For an ideal gas, changes in specific enthalpy are related to changes in temperature by , so the shape of the cycle in an - plane is the same as in a - plane, with a scale factor of between the two. This suggests that a place to start is with the combined first and second law, which relates changes in enthalpy, entropy, and pressure:

$\displaystyle dh = Tds + \frac{dP}{\rho}.$

On constant pressure curves

and

. The quantity desired is the derivative of temperature,

, with respect to entropy,

, at constant pressure: $(\partial T /\partial s )_p$ . From the combined first and second law, and the relation between

and

, this is

$\displaystyle \left(\frac{\partial T}{\partial s}\right)_p = \frac{T}{c_p}.$

(6..2)

The derivative is the slope of the constant pressure legs of the Brayton cycle on a - plane. For a given ideal gas (specific ) the slope is positive and increases as .

We can also plot the Brayton cycle in an - plane. This has advantages because changes in enthalpy directly show the work of the compressor and turbine and the heat added and rejected. The slope of the constant pressure legs in the - plane is $(\partial h/\partial s)_p=T$ .

Note that the similarity in the shapes of the cycles in - and - planes is true for ideal gases only. As we will see when we examine two-phase cycles, the shapes look quite different in these two planes when the medium is not an ideal gas.

**Figure 6.4:** Ideal Brayton cycle as composed of many elementary Carnot cycles [Kerrebrock]

Plotting the cycle in - coordinates also allows another way to address the evaluation of the Brayton cycle efficiency which gives insight into the relations between Carnot cycle efficiency and efficiency of other cycles. As shown in Figure 6.4, we can break up the Brayton cycle into many small Carnot cycles. The `` $i^\textrm{th}$ '' Carnot cycle has an efficiency of

$\displaystyle \eta_{Ci} =1-\left(\frac{T_\textrm{low,i}}{T_\textrm{high,i}}\right),$

where the indicated lower temperature is the heat rejection temperature for that elementary cycle and the higher temperature is the heat absorption temperature for that cycle. The upper and lower curves of the Brayton cycle, however, have constant pressure. All of the elementary Carnot cycles therefore have the same pressure ratio:

$\displaystyle \frac{P(T_\textrm{high})}{P(T_\textrm{low})}=PR=\textrm{constant (the same for all cycles)}.$

From the isentropic relations for an ideal gas, we know that pressure ratio,

, and temperature ratio,

, are related by: $PR^{(\gamma-1)/\gamma} = TR$ .

The temperature ratios $(T_\textrm{low,i}/T_\textrm{high,i})$ of any elementary cycle ``i'' are therefore the same and each of the elementary cycles has the same thermal efficiency. We only need to find the temperature ratio across any one of the cycles to find what the efficiency is. We know that the temperature ratio of the first elementary cycle is the ratio of compressor exit temperature to engine entry (atmospheric for an aircraft engine) temperature, in Figure 6.4. If the efficiency of all the elementary cycles has this value, the efficiency of the overall Brayton cycle (which is composed of the elementary cycles) must also have this value. Thus, as previously,

$\displaystyle \eta_\textrm{Brayton}=1- \frac{T_\textrm{inlet}}{T_\textrm{compressor exit}}.$

**Figure 6.5:** Arbitrary cycle operating between $T_\textrm {min}$ , $T_\textrm {max}$

A benefit of this view of efficiency is that it allows us a way to comment on the efficiency of any thermodynamic cycle. Consider the cycle shown in Figure 6.5, which operates between some maximum and minimum temperatures. We can break it up into small Carnot cycles and evaluate the efficiency of each. It can be seen that the efficiency of any of the small cycles drawn will be less than the efficiency of a Carnot cycle between $T_\textrm {max}$ and $T_\textrm {min}$ . This graphical argument shows that the efficiency of any other thermodynamic cycle operating between these maximum and minimum temperatures has an efficiency less than that of a Carnot cycle.

Muddy Points

If there is an ideal efficiency for all cycles, is there a maximum work or maximum power for all cycles? (MP 6.7)

6.4.1 Net work per unit mass flow in a Brayton cycle

In Section 3.7.1 we found the net work of a Brayton cycle in terms of heat transfer. Now that we have defined entropy, we can reexamine the net work using an enthalpy-entropy (

) diagram, Figure 6.6. The net mechanical work of the cycle is given by:

$\displaystyle \textrm{Net mechanical work/unit mass} =w_\textrm{turbine} -w_\textrm{compressor},$

where, by the first law,

$\displaystyle w_\textrm{compressor}$	$\displaystyle = -\Delta h_{03} = \Delta h_\textrm{comp}$
$\displaystyle w_\textrm{turbine}$	$\displaystyle = \Delta h_{45} = -\Delta h_\textrm{turb}.$