Twitter event networks and the Superstar model

Condensation phenomenon is often observed in social networks such as Twitter where one "superstar" vertex gains a positive fraction of the edges, while the remaining empirical degree distribution still exhibits a power law tail. We formulate a mathematically tractable model for this phenomenon that provides a better fit to empirical data than the standard preferential attachment model across an array of networks observed in Twitter. Using embeddings in an equivalent continuous time version of the process, and adapting techniques from the stable age-distribution theory of branching processes, we prove limit results for the proportion of edges that condense around the superstar, the degree distribution of the remaining vertices, maximal nonsuperstar degree asymptotics and height of these random trees in the large network limit.Comment: Published at http://dx.doi.org/10.1214/14-AAP1053 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

System overview on electromagnetic compensation for reflector antenna surface distortion

The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This paper addresses the system requirements for such a system and identify candidate technologies (analog and digital) for possible hardware implementation

Aplikasi Model Cooperative Script pada Pembelajaran IPS sebagai Upaya Meningkatkan Aktivitas Belajar Siswa di Kelas VI pada Semester Juli-Desember 2019UPT SDN 16 Lansat Kadap Kec. Rao Selatan Kab. Pasaman

Penelitian ini bertujuan untuk meningkatkan aktivitas belajar siswa melalui model Cooperative Script pada pembelajaran IPS Kelas VI UPT SDN 16 Lansat Kadap Kec. Rao Selatan Kab. Pasaman. Penelitian ini berlangsung selama dua siklus, setiap siklus terdiri dari tiga kali pertemuan. Disamping itu setiap satu siklus terdiri dari empat tahapan mulai dari perencanaan, tindakan, pengamatan dan refleksi. Tindakan dilakukan di Kelas VI UPT SDN 16 Lansat Kadap Kec. Rao Selatan Kab. Pasaman pada semester Juli-Desember TP 2019/2020 dimana siswa terdiri dari 20 orang. Data penelitian dianalisis dengan formula persentase untuk menggambarkan data sebagai mana adanya. Pada Siklus I rata-rata aktivitas belajar siswa dari keempat komponen yang diteliti diperoleh data sebesar 50,4% dan siklus II sebesar 77,5% dengan persentase peningkatan 27,1%. Dari hasil penelitian pada siklus I dan siklus II maka penelitian tidak dilanjutkan lagi karena telah mencapai target penelitian yakni 61%. Seiring dengan ini, maka hipotesis tindakan yang diajukan secara empiris terbukti dan dapat diterima

Array trade-off study using multilayer parasitic subarrays

The use of multilayer parasitic patch arrays in a microstrip phased array offers many potential advantages. An analytical study of microstrip arrays with high gain multilayer parasitic patch subarrays and conventional patch antennas is presented. It is indicated that a thinned array of half as many multilayer parasitic patch subarrays (per row and column) at twice the spacing will perform as well as the full array of ordinary patch antennas. The criterion for comparison was array gain, 3 dB beamwidth and sidelobe level. The attendant reduction in the required number of patch antennas and consequently, MMIC phase shifters is very significant in terms of array complexity, cost and power loss