Pengajaran Matriks Dan Persamaan Linier Di Fakultas Teknik Universitas Tama Jagakarsa Jakarta

Matriks dan persamaan linier merupakan mata pelajaran tidak diminati oleh sebagian besar mahasiswa fakultas teknik. Operasional matriks dan persamaan linier agar mendapat kesan yang baik, hendaknya dimulai dengan menanamkan definisi dasar matriks, determinan dan perbedaannya. Bentuk-bentuk dan pemecahan persamaan linier seperti yang ada pada literatur biasanya hanya merupakan pemecahan persoalan tanpa menerangkan kegunaan permasalahan. Disamping itu tidak diterangkan metode mana yang paling mudah yang dapat dipergunakan oleh mahasiswa. Dosen hendaknya dapat membangun pengetahuan mahasiswa tentang kegunaan matriks dan persamaan linier, agar ada keinginan untuk mempelajarinya. Penyederhanaan pengajaran matriks dan persamaan linier merupakan upaya yang harus dikembangkan. Mahasiswa diberi kesempatan berkontribusi selama pembelajaran berlangsung. Dengan konstribusi ini proses pembelajaran menjadi bermakna karena mahasiswa bisa menyelesaikan masalah matematik oleh mereka sendiri. Dengan methode ini mahasiswa merasakan bahwa matematika menjadi alat dikenal untuk menolong memecahkan persoalan mereka, bukan menjadi masalah tambahan. Kata kunci : matriks, operasional matriks, dan persamaan linier

Solar coronal differential rotation from XBPs in Hinode/XRT and Yohkoh/SXT images

Our aim is to identify and trace the X-ray Bright Points (XBPs) over the disk and use them as tracers to determine the coronal rotation. This investigation will help to clarify and understand several issues: whether (i) the corona rotates differentially; (ii) the rotation depends on the sizes of the XBPs; and (iii) dependence on phases of the solar magnetic cycle. We analysed the daily full-disk soft X-ray images observed with (i) X-Ray Telescope (XRT) on-board the Hinode mission during January, March and April, 2007 and (ii) Soft X-ray Telescope (SXT) on-board the Yohkoh from 1992 to 2001 using SSW in IDL. We have used the tracer method to trace the passage of XBPs over the solar disk with the help of overlaying grids and derived the sidereal angular rotation velocity and the coordinates (latitude and longitude) of the XBPs. We have determined the position of a large number of XBPs both in Hinode/XRT and Yohkoh/SXT images and followed them over the solar disk as a function of time. We derived the coronal sidereal angular rotation velocity and compared it with heliocentric latitude and as a function of solar activity cycle. In addition, we measured the sizes of all the XBPs and related them with the coronal rotation. The important results derived from these investigations are: (i) the solar corona rotates differentially like the photosphere and chromosphere; (ii) the sidereal angular rotation velocity is independent of the sizes of the XBPs; (iii) the sidereal angular rotation velocity does not depend on phases of the solar magnetic cycle; and (iv) the differential rotation of the corona is present throughout the solar magnetic cycle.Comment: 9 pages, 4 figure

Sun's retrograde motion and violation of even-odd cycle rule in sunspot activity

The sum of sunspots number over an odd numbered 11 yr sunspot cycle exceeds that of its preceding even numbered cycle, and it is well known as Gnevyshev and Ohl rule (or G--O rule) after the names of the authors who discovered it in 1948. The G--O rule can be used to predict the sum of sunspot numbers of a forthcoming odd cycle from that of its preceding even cycle. But this is not always possible because occasionally the G--O rule is violated. So far no plausible reason is known either for the G--O rule or the violation of this rule. Here we showed the epochs of the violation of the G--O rule are close to the epochs of the Sun's retrograde orbital motion about the centre of mass of the solar system (i.e., the epochs at which the orbital angular momentum of the Sun is weakly negative). Using this result easy to predict the epochs of violation of the G--O rule well in advance. We also showed that the solar equatorial rotation rate determined from sunspot group data during the period 1879--2004 is correlated/anti-correlated to the Sun's orbital torque during before/after 1945. We have found the existence of a statistically significant $\sim$ 17 yr periodicity in the solar equatorial rotation rate. The implications of these findings for understanding the mechanism behind the solar cycle and the solar-terrestrial relationship are discussed.Comment: 13 pages, 4 figures, accepted by MNRA

A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun's Subsurface, Surface, Corona, and Sunspot Groups

Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985-2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the solar equatorial-rotation rates determined from the following data: i) the plasma rotation rates at 0.94Rsun, 0.95Rsun,...,1.0Rsun measured by Global Oscillation Network Group (GONG) during the period 1995-2010, ii) the data on the soft X-ray corona determined from Yohkoh/SXT full disk images for the years 1992-2001, iii) the data on small bright coronal structures (SBCS) which were traced in Solar and Heliospheric Observatory (SOHO)/EIT images during the period 1998-2006, and iv) the Mount Wilson Doppler-velocity measurements during the period 1986-2007. A large portion (up to approximate 30 deg latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94Rsun and 0.98Rsun.The variation in the yearly mean equatorial-rotation rate of the sunspot groups seems to be lagging that of the equatorial-rotation rate determined from the GONG measurements by one to two years.The amplitude of the latter is very small.The solar-cycle variation in the equatorial-rotation rate of the solar corona closely matches that determined from the sunspot-group data.The variation in the equatorial-rotation rate determined from the Mount Wilson Doppler-velocity data closely resembles the corresponding variation in the equatorial-rotation rate determined from the sunspot-group data that included the values of the abnormal angular motions (> 3 deg per day) of the sunspot groups. Implications of these results are pointed out.Comment: 22 pages, 10 figures, accepted by Solar Physic

Precis: “Social media social comparison and identity distress at the college transition: A dual-path model”

In Yang et al.’s study, researchers seek to identify how social comparison on social media influences individuals’ identity formation during the transition from high school to college. They do so through studying two processes that are related to social media use. First of all, individuals may competitively compare their abilities to others’ on social media in a judgmental way, namely comparing physical attractiveness, social likability, positive experiences, and other factors. This type of judgmental comparison was predicted to lead to rumination, or dwelling on repetitive, negative thoughts about the self. Secondly, individuals may compare their opinions with others’ on social media from a non-judgmental perspective. Using social media in this open, curious manner was predicted to lead to reflection, which allows individuals to analyze their own beliefs. By studying these two processes of social comparison, researchers were able to identify what role each process plays in the formation of these individuals’ identities.Human Development and Family Science

APLIKASI LEAST SQUARE UNTUK MENERANGKAN HUBUNGAN FISIS SUNSPOT DAN FLARE

Sunspot merupakan daerah atau bintik hitam yang merupakan perpotongan selubung garis gaya medan magnet matahari dengan permukaan matahari (fotosfer). Flare, adalah ledakan singkat di angkasa matahari, radiasinya diemisikan pada rentang spekrum elektromagnetik. Pada penelitian ini hanya ditinjau flare optik dan flare sinar X saja. Pada umumnya flare terjadi didahului oleh sunspot. Tetapi observasi juga menunjukan ada flare yang terjadi tanpa didahului oleh sunspot. Flare semacam ini disebut flare tanpa sunspot (spotless flare). Data harian bilangan sunspot dan frekuensi terjadinya flare selama 6 tahun dari 1999-2004 digunakan untuk menerangkan hubungan fisis sunspot dan flare dengan aplikasi least square

Prakiraan Umur Produktif Sunspot Kelas D, E, dan F Berdasarkan Frekuensi Aktivitas Flare

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Perbedaan Differensial Rotasi Matahari Yang Ditentukan Dengan Metode Doppler Dan Metode Tracing

Rotasi permukaan matahari yang ditentukan secara spektroskopi, yang ditentukan dari pelebaran garis-garis fraunhofer (metode Doppler) 7% lebih lambat dibandingkan dengan rotasi permukaan matahari yang ditentukan dari pergerakan bintik matahari harian (daily sunspots propermotion). Pergerakan bintik matahari harian ini disebut metode Tracing. Perbedaan ini mungkin disebabkan oleh berbedanya metode yang dipakai, tapi pada umumnya disebabkan karena perbedaan kondisi fisik antara fotosfer (plasma) yang bermedan magnet lemah dan sunspot yang bermedan magnet kuat. Bintik matahari pada waktu terbawa arus rotasi matahari masih berada di bawah pengaruh medan magnet yang berasal dari daerah konvektif. Daerah konvektif ini berada di bawah lapisan fotosfer, jadi rotasi bintik matahari tidak mencerminkan rotasi fotosfer sejati, seperti rotasi plasma yang menggunakan metode Doppler. Perbedaan kondisi fisik ini, diangkat sebagai permasalahan dalam program penelitian ini dengan menggunakan telaah momentum sudut total permukaan matahari yang ditentukan baik dari kurva rotasi yang ditentukan dengan metode Doppler maupun dari kurva rotasi yang ditentukan dengan metode Tracing.hlm. 1-