Adaptive antenna arrays for satellite communications: Design and testing

When two separate antennas are used with each feedback loop to decorrelate noise, the antennas should be located such that the phase of the interfering signal in the two antennas is the same while the noise in them is uncorrelated. Thus, the antenna patterns and spatial distribution of the auxiliary antennas are quite important and should be carefully selected. The selection and spatial distribution of auxiliary elements is discussed when the main antenna is a center fed reflector antenna. It is shown that offset feeds of the reflector antenna can be used as auxiliary elements of an adaptive array to suppress weak interfering signals. An experimental system is designed to verify the theoretical analysis. The details of the experimental systems are presented

Dynamics and Non-Gaussianity in the Weak-Dissipative Warm Inflation Scenario

We calculate the general solutions for a warm inflationary scenario with weak dissipation, reviewing the dissipative dynamics of the two-fluid system, and calculate the bispectrum of the gravitational field fluctuations generated in the case where dissipation of the vacuum potential during inflation is the mechanism for structure formation, but is the sub-dominant effect in the dynamics of the scalar field during slow-roll. The bispectrum is non-zero because of the self-interaction of the scalar field. We compare the predictions with both those of standard, or `supercooled', inflationary models, and warm inflation models with strong dissipation and consider the detectability of these levels of non-Gaussianity in the bispectrum of the cosmic microwave background. We find that the levels of non--Gaussianity for warm and supercooled inflation are an order of magnitude different.Comment: Replaced with version accepted for publication in Phys. Rev. D., minor changes; 7 pages, Late

Bilateral superficial ulnar artery with high origin from the axillary artery: its anatomy and clinical significance

The superficial ulnar artery (SUA) is a rare anatomical variant that usually arises either in the axilla or the arm and runs a superficial course in the forearm, enters the hand, and participates in the formation of superficial palmar arch. During the routine dissection of cadavers in the department of anatomy, whilst preparing the specimen for medical students, an unusual bilateral branch of the axillary artery was found in one of the cadavers: a rare variant of the artery known as SUA, which originates from the 2nd part of the axillary arteries of both sides. The SUA is a known anatomical variant, but the bilateral high origin from the 2nd part of the axillary artery is extremely unusual. Its occurrence is of great clinical importance to the surgical and radiological departments

RF and IF mixer optimum matching impedances extracted by large-signal vectorial measurements

This paper introduces a new technique that allows us to measure the admittance conversion matrix of a two-port device,using a Nonlinear Vector Network Analyzer.This method is applied to extract the conversion matrix of a 0.2 µµµµm pHEMT,driven by a 4.8 GHz pump signal,at different power levels,using an intermediate frequency of 600 MHz.The issue on data inconsistency due to phase randomization among different measurements is discussed and a proper pre- processing algorithm is proposed to fix the problem. The output of this work consists of a comprehensive experimental evaluation of up-and down-conversion maximum gain,stability,and optimal RF and IF impedances

Effect of Fibonacci Modulation On Superconductivity

We have studied finite-sized single band models with short range pairing interactions between electrons in presence of diagonal Fibonacci modulation in one dimension. Two models, namely the attractive Hubbard model and the Penson-Kolb model, have been investigated at half-filling at zero temperature by solving the Bogoliubov-de Gennes equations in real space within a mean field approximation. The competition between ``disorder'' and the pairing interaction leads to a suppression of superconductivity (of usual pairs with zero centre-of-mass momenta) in the strong-coupling limit while an enhancement of the pairing correlation is observed in the weak-coupling regime for both the models. However, the dissimilarity of the pairing mechanisms in these two models brings about notable difference in the results. The extent to which the bond ordered wave and the $\eta$-paired (of pairs with centre-of-mass momenta = $\pi$) phases of the Penson-Kolb model are affected by the disorder has also been studied in the present calculation. Some finite size effects are also identified.Comment: 14 pages, 13 figure

Constraining H0 from Chandra Observations of Q0957+561

We report the detection of the lens cluster of the gravitational lens (GL) system Q0957+561 from a deep observation with the Advanced CCD Imaging Spectrometer on-board the Chandra X-ray Observatory. Intracluster X-ray emission is found to be centered 4.3 +/- 1.3 arcsec east and 3.5(-0.6,+1.3) arcsec north of image B, nearer than previous estimates. Its spectrum can be modeled well with a thermal plasma model consistent with the emission originating from a cluster at a redshift of 0.36. Our best-fit estimates of the cluster temperature of T_e = 2.09(-0.54,+0.83) keV (90 percent confidence) and mass distribution of the cluster are used to derive the convergence parameter kappa, the ratio of the cluster surface mass density to the critical density required for lensing. We estimate the convergence parameter at the location of the lensed images A and B to be kappa_A = 0.22(+0.14,-0.07) and kappa_B = 0.21(+0.12,-0.07), respectively (90 percent confidence levels). The observed cluster center, mass distribution and convergence parameter kappa provide additional constraints to lens models of this system. Our new results break a mass-sheet degeneracy in GL models of this system and provide better constraints of ~ 29 percent (90 percent confidence levels) on the Hubble constant. We also present results from the detection of the most distant X-ray jet (z = 1.41) detected to date. The jet extends approximately 8 arcsec NE of image A and three knots are resolved along the X-ray jet with flux densities decreasing with distance from the core. The observed radio and optical flux densities of the knots are fitted well with a synchrotron model and the X-ray emission is modeled well with inverse Compton scattering of Cosmic Microwave Background photons by synchrotron-emitting electrons in the jet.Comment: 18 pages, includes 7 figures, Accepted for publication in Ap

Strengthening Food Security Policy: Reforms on Hybrid Maize Seeds Delivery Mechanism

From 2009 to 2017, Indonesia produced an average of 18.8 million tons of maize per year. This failed to meet the domestic demand by an average of 2.4 million tons per year during the same period. Since imports have been severely restricted in recent years, domestic maize prices have become much higher than international prices and also caused domestic price increases for other food commodities. Since 2015, the government’s UPSUS program addresses the shortage by attempting to increase domestic maize production. Farmers are being provided with hybrid maize seeds free of charge. To improve the overall effectiveness of the UPSUS hybrid maize seed subsidies, local maize markets need to be categorized by their particular strength. Thin maize markets produce little maize because farmers opt for other crops such as vegetables and fruits as their primary source of income; in semi-strong maize markets most farmers plant traditional types of maize and there are two to four private seed companies plus one off-taker; in strong maize markets all farmers plant hybrid maize, with five or more private seed companies and at least two off-takers. Moreover, the maize market types also differ by the dominance of maize and dry land agriculture in the local markets, as well as the local adoption of Good Agricultural Practices (GAP). The UPSUS hybrid seed subsidy program is most effective in areas with semi-strong maize markets because here it supports the transition from traditional to hybrid maize types with positive effects on production levels. Since absorption rates of UPSUS seeds in thin and strong maize markets are lower, distributing seeds in these markets appears to contribute to the emergence of black-markets where farmers illegally sell their UPSUS seeds to finance other needs. The current quota system of the 2018 Technical Implementation Guideline of Maize Cultivation mandates that 65% of all UPSUS seeds must come from the Research and Development Agency of the Ministry of Agriculture (Balitbangtan) and licensed domestic producers. Since these seeds are of lower quality than the 35% of seeds that originate from the private sector, this quota system hinders the farmers from receiving the quality best suited to increase production levels. We propose three policy reforms for the UPSUS seed subsidy program to improve its effectiveness: Firstly, Ministry of Agriculture (MOA) regulation 03/2015 section III(B) must add a classification matrix to assess the strength of local maize markets and then reduce the distribution of UPSUS seeds to mainly districts with semi-strong markets. The development of local maize markets should be periodically assessed and the distribution of seeds should be terminated if markets have become strong enough to end the subsidy in favor of market mechanisms. Intensive capacity-building programs should facilitate this development of markets. Local governments need to create partnerships with the private sector and develop functioning seed markets for a sustainable agriculture once the UPSUS program has ended in their district. Secondly, the current quota of 65% maize seeds from Balitbangtan and other licensed producers as stipulated in the 2018 Technical Implementation Guideline of Maize Cultivation should be abolished. Farmers should receive seeds of the quality they request

Time-Dependent Synchrotron and Compton Spectra from Jets of Microquasars

Jet models for the high-energy emission of Galactic X-ray binary sources have regained significant interest with detailed spectral and timing studies of the X-ray emission from microquasars, the recent detection by the HESS collaboration of very-high-energy gamma-rays from the microquasar LS~5039, and the earlier suggestion of jet models for ultraluminous X-ray sources observed in many nearby galaxies. Here we study the synchrotron and Compton signatures of time-dependent electron injection and acceleration, adiabatic and radiative cooling, and different jet geometries in the jets of Galactic microquasars. Synchrotron, synchrotron-self-Compton, and external-Compton radiation processes with soft photons provided by the companion star and the accretion disk are treated. An analytical solution is presented to the electron kinetic equation for general power-law geometries of the jets for Compton scattering in the Thomson regime. We pay particular attention to predictions concerning the rapid flux and spectral variability signatures expected in a variety of scenarios, making specific predictions concerning possible spectral hysteresis, similar to what has been observed in several TeV blazars. Such predictions should be testable with dedicated monitoring observations of Galactic microquasars and ultraluminous X-ray sources using Chandra and/or XMM-Newton.Comment: Accepted for publication in ApJ; 37 manuscript pages, including 10 eps figures; uses AASTeX macro

New way to achieve chaotic synchronization in spatially extended systems

We study the spatio-temporal behavior of simple coupled map lattices with periodic boundary conditions. The local dynamics is governed by two maps, namely, the sine circle map and the logistic map respectively. It is found that even though the spatial behavior is irregular for the regularly coupled (nearest neighbor coupling) system, the spatially synchronized (chaotic synchronization) as well as periodic solution may be obtained by the introduction of three long range couplings at the cost of three nearest neighbor couplings.Comment: 5 pages (revtex), 7 figures (eps, included

Reforming Trade Policy to Lower Maize Prices in Indonesia

In the first half of 2018, the consumption of maize for animal feed reached 8.60 million tonnes, more than 70% of total Indonesian maize consumption in that period. From 2009 to 2018, maize consumption for animal feed grew every year by 477,780 tonnes. Despite the implementation of a free hybrid maize seeds program, known as UPSUS (Upaya Khusus / Special Effort), domestic maize production only increased by 294,440 tonnes per year. These circumstances contributed to high maize prices in Indonesia, which reached more than twice the international market price in August 2018. High maize prices impact animal feed producers because they use maize as a raw material. High prices also impact land animal farmers who must pay a high price to feed their animals. In turn, high maize prices also contribute to increases in the price of chicken eggs, chicken meat, and beef, which affects the 21 million farming and 35 million non-farming households that are net maize consumers. The implementation of ministerial regulations MOA 57/2015 and MOT 21/2018 has aggravated the problem as they contradict each other when specifying who is authorized to import maize and what documents are required by legal importers. Both regulations impose long procedure for obtaining import license, which can take up to 53 working days to complete. As the result, imports are unable to lower maize prices in Indonesia