Investigation of unconventional reconstruction and electronic properties on the Na2IrO3 surface

Na2IrO3 is an intriguing material for which spin-orbit coupling plays a key role. Theoretical predictions, so far unverified, have been made that the surface of Na2IrO3 should exhibit a clear signature of the quantum spin Hall effect. We studied the surface of Na2IrO3 using scanning tunneling microscopy and density-functional theory calculations. We observed atomic level resolution of the surface and two types of terminations with different surface periodicity and Na content. By comparing bias-dependent experimental topographic images to simulated images, we determined the detailed atomistic structure of both observed surfaces. One of these reveals a strong relaxation to the surface of Na atoms from the subsurface region two atomic layers below. Such dramatic structural changes at the surface cast doubt on any prediction of surface properties based on bulk electronic structure. Indeed, using spatially resolved tunneling spectroscopy we found no indication of the predicted quantum spin Hall behavior

Gauge Theories on Deformed Spaces

The aim of this review is to present an overview over available models and approaches to non-commutative gauge theory. Our main focus thereby is on gauge models formulated on flat Groenewold-Moyal spaces and renormalizability, but we will also review other deformations and try to point out common features. This review will by no means be complete and cover all approaches, it rather reflects a highly biased selection.Comment: v2 references added; v3 published versio

Harapan Dan Persepsi Konsumen Terhadap Kualitas Layanan Di Kantin Di Universitas Kristen Petra

Penelitian ini dilakukan untuk menganalisa harapan dan persepsi konsumen terhadap kualitas layanan yang dilihat dari lima dimensi (reliability, responsiveness, assurance, empathy, dan tangibles) di kantin Universitas Kristen Petra. Serta untuk melihat gap antara harapan dan persepsi konsumen terhadap kualitas layanan. Teknik analisa yang dilakukan adalah deskriptif kuantitatif. Hasil penelitian menunjukkan adanya gap negatif antara harapan dan persepsi konsumen kantin Universitas Kristen Petra, yang berarti harapan konsumen lebih tinggi dari persepsi konsumen terhadap lima dimensi kualitas layanan di kantin Universitas Kristen Petra. This study was conducted to analyze the expectations and perceptions of consumers towards service quality views on five dimension (reliability, responsiveness, assurance, empathy, and tangibles) on canteen Petra Christian University. As well as seeing the gap between the expectation and perceptions of consumers towards service quality. The analysis technique used is quantitative descriptive. The results showed the gap between the expectations and perceptions of consumers of canteen Petra Christian University, overall the results obtained there are negative gap between the expectation and perception of consumers toward five dimension of service quality on canteen Petra Christian University

Triple Bars and Complex Central Structures in Disk Galaxies

We present an analysis of ground-based and HST images of three early-type barred galaxies. The first, NGC 2681, may be the clearest example yet of a galaxy with three concentric bars. The two other galaxies were previously suggested as triple-barred. Our analysis shows that while NGC 3945 is probably double-barred, NGC 4371 has only one bar; but both have intriguing central structures. NGC 3945 has a large, extremely bright disk inside its primary bar, with patchy dust lanes, a faint nuclear ring or pseudo-ring within the disk, and an apparent secondary bar crossing the ring. NGC 4371 has a bright nuclear ring only marginally bluer than the surrounding bulge and bar. There is no evidence for significant dust or star formation in either of these nuclear rings. The presence of stellar nuclear rings suggests that the centers of these galaxies are dynamically cool and disklike.Comment: LaTeX: 6 pages, 3 figures, uses emulateapj.sty. Accepted by Astrophysical Journal Letters. Version with full-resolution figures available at: http://www.astro.wisc.edu/~erwin/research

Perancangan Sistem Monitoring Pengolahan Limbah Cair Pada IPAL

Pengolahan limbah cair dikerjakan dalam IPAL (Instalasi Pengolah Air Limbah). Dalam pengoperasion IPAL diperlukan data parameter yang ada dalam proses pengolahan limbah cair tersebut yaitu pH, suhu, oksigen terlarut (dissolved oxygen/DO), daya hantar listrik, TOC (Total Organic Carbon), BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), dll. Untuk dapat mengetahui nilai parameter diatas perlu dipasang sensor-sensor. Apabila operator tidak dapat memonitor IPAL secara kontinyu, maka dipastikan kinerja IPAL akan tidak efektif dan efisien. Masalah ini bisa diatasi dengan pemasangan sistem otomatis yang mampu melakukan monitoring dan pengendalian proses. Namun sistem seperti ini sangat mahal, perlu biaya operasional dan perawatan yang besar pula. Untuk menekan biaya maka cukup dipasang sistem monitoring secara remote saja, pengendalian proses tetap dikerjakan operator. Dalam sistem ini sensor-sensor yang terpasang akan mengambil nilai data parameter, selanjutnya melalui RTU (Remote Terminal Unit) data-data ini dikirimkan ke kantor operator. Hasil monitoring ini ditampilkan melalui komputer menggunakan perangkat lunak Human Machine Interface (HMI). Dari data hasil monitoring ini operator dapat menentukan tindakan apa yang akan dilakukan untuk pengendalian proses di IPAL. Pada makalah ini dibuat rancangan sistem monitoring pengolahan limbah cair. Rancangan bersifat universal sehingga dapat diterapkan untuk segala jenis IPAL