Metastable states of a ferromagnet on random thin graphs

We calculate the mean number of metastable states of an Ising ferromagnet on random thin graphs of fixed connectivity c. We find, as for mean field spin glasses that this mean increases exponentially with the number of sites, and is the same as that calculated for the +/- J spin glass on the same graphs. An annealed calculation of the number <N_{MS}(E)> of metastable states of energy E is carried out. For small c, an analytic result is obtained. The result is compared with the one obtained for spin glasses in order to discuss the role played by loops on thin graphs and hence the effect of real frustration on the distribution of metastable states.Comment: 15 pages, 3 figure

Self-consistent approach for the quantum confined Stark effect in shallow quantum wells

A computationally efficient, self-consistent complex scaling approach to calculating characteristics of excitons in an external electric field in quantum wells is introduced. The method allows one to extract the resonance position as well as the field-induced broadening for the exciton resonance. For the case of strong confinement the trial function is represented in factorized form. The corresponding coupled self-consistent equations, which include the effective complex potentials, are obtained. The method is applied to the shallow quantum well. It is shown that in this case the real part of the effective exciton potential is insensitive to changes of external electric field up to the ionization threshold, while the imaginary part has non-analytical field dependence and small for moderate electric fields. This allows one to express the exciton quasi-energy at some field through the renormalized expression for the zero-field bound state.Comment: 13 pages, RevTeX4, 6 figure

Konstribusi Mobilitas Siswa Sman Favorit Terhadap Kinerja Ruas Jalan Di Kota Bandung

The volume of traffic on the road sections leading to the center of the City of Bandung is influenced by the number of vehicles used by students of favorite school located in the center of Bandung. This study was carried out on the trips made by the students of the state favorite schools in Bandung and the impact of the trips on the performance of the road. The results indicate that if there were not any journey undertaken by students heading to favorite schools, the degree of saturation of road or the potential traffic congestion on the road could have been reduced

Penyempurnaan Teknik Penyadapan Resin Pinus Dengan Metode Kuakan

Penyadapan resin pinus yang berlebihan berupa ukuran kuakan yang terlalu lebar dan dalam serta menggunakan stimulansia anorganik menyebabkan pohon menjadi rusak dan mudah tumbang. Salah satu cara untuk mengurangi kerusakan pohon dan meningkatkan produksi resin pinus adalah dengan memodifikasi teknik penyadapan. Modifikasi teknik penyadapan dilakukan dengan mempertimbangkan aspek ekonomi, ekologi, sosial dan teknis. Tujuan penelitian adalah untuk mendapatkan informasi lebar dan jumlah kuakan per pohon yang paling optimal, jenis stimulansia organik yang tepat, serta menganalisis biaya dari modifikasi teknik penyadapan. Hasil penelitian menunjukkan bahwa teknik penyadapan berupa perbedaan jumlah kuakan per pohon dan lebar sadapan memberikan pengaruh yang berbeda nyata terhadap produksi resin. Akan tetapi, perbedaan jenis stimulansia organik dan interaksinya dengan jumlah serta ukuran kuakan tidak memberikan pengaruh yang nyata terhadap produksi resin yang dihasilkan. Selain itu, modifikasi teknik penyadapan dan stimulansia berpengaruh terhadap biaya dan pendapatan dari pihak pengelola

Efisiensi Penggunaan Pupuk Majemuk Terhadap Pertumbuhan dan Produksi Baby Kailan (Brassica oleracea L.) dengan Hidroponik Sistem Sumbu

Teknik hidroponik sistem sumbu sangat cocok dikembangkan dan diusahakan terutama di kota-kota besar. Penelitian ini bertujuan untuk mempelajari pengaruh aplikasi jenis pupuk majemuk dan konsentrasi electrical conductivity (EC) terhadap pertumbuhan dan produksi baby kailan varietas Nova dengan hidroponik sistem sumbu. Percobaan ini dilaksanakan di greenhouse Kebun Percobaan Cikabayan dan Laboratorium Pascapanen Departemen Agronomi dan Hortikultura, Institut Pertanian Bogor, Dramaga, Bogor, pada bulan Agustus 2017 sampai Oktober 2017. Rancangan percobaan yang digunakan adalah Rancangan Kelompok Lengkap Teracak (RKLT) dua faktor yang disusun secara faktorial. Faktor pertama yaitu jenis pupuk majemuk (AB Mix, Growmore, dan Gandasil D) dan faktor kedua yaitu konsentrasi EC (1.5 mS cm-1; 2.0 mS cm-1; dan 2.5 mS cm-1). Setiap perlakuan diulang tiga kali sehingga terdapat 27 satuan percobaan. Kombinasi pupuk AB Mix dengan konsentrasi EC 1.5 mS cm-1 pada budidaya baby kailan dengan hidroponik sistem sumbu menghasilkan tinggi tanaman pada 3 MST, jumlah daun pada 3 MST, panjang tangkai daun pada 2 dan 3 MST, dan panjang daun pada 1 MST yang nyata lebih tinggi dibandingkan kombinasi lainnya. Pupuk AB Mix dan konsentrasi EC 1.5 mS cm-1 merupakan perlakuan terbaik untuk budidaya baby kailan dengan hidroponik sistem sumbu. &nbsp; Kata kunci: baby kailan, electrical conductivity, hidroponik sistem sumbu, pupuk majemu

Quasiparticle dynamics and phonon softening in FeSe superconductors

Quasiparticle dynamics of FeSe single crystals revealed by dual-color transient reflectivity measurements ({\Delta}R/R) provides unprecedented information on Fe-based superconductors. The amplitude of fast component in {\Delta}R/R clearly tells a competing scenario between spin fluctuations and superconductivity. Together with the transport measurements, the relaxation time analysis further exhibits anomalous changes at 90 K and 230 K. The former manifests a structure phase transition as well as the associated phonon softening. The latter suggests a previously overlooked phase transition or crossover in FeSe. The electron-phonon coupling constant {\lambda} is found to be 0.16, identical to the value of theoretical calculations. Such a small {\lambda} demonstrates an unconventional origin of superconductivity in FeSe.Comment: Final published version; 5 pages; 4 figure

Studies of InGaN∕GaN multiquantum-well green-light-emitting diodes grown by metalorganic chemical vapor deposition

InGaN(3nm)∕GaN(5nm) three period multiquantum green-light-emitting diodes(LEDs) grown by the metalorganic chemical vapor deposition technique have been studied using high-resolution transmission electron microscopy (HRTEM), double crystal high resolution x-ray diffraction (HRXRD) and low temperature photoluminescence. HRTEM analysis showed that the defect density gradually decreased in the growth direction with increasing thickness. Self-assembled quantum dot-likestructures in the wells and black lumps between the well and barrier due to In segregation and strain contrast were observed, respectively. The HRXRD spectrum of the green LEDstructure was simulated using the kinematical theory method to obtain the composition and thickness of the well and barrier. The quantum-well (QW) green emission peak 2.557eV at 10K showed “S” shaped shift like a red–blue–red shift with variation of the temperature in the photoluminescence spectra due to potential fluctuations caused by inhomogeneous alloy distribution in the wells. The activation energy of 49meVobtained from the QW green emission line indicated deepening of the localization of the carriers