Monthly and Diurnal Variability of Rain Rate and Rain Attenuation during the Monsoon Period in Malaysia

Rain is the major source of attenuation for microwave propagation above 10 GHz. In tropical and equatorial regions where the rain intensity is higher, designing a terrestrial and earth-to-satellite microwave links is very critical and challenging at these frequencies. This paper presents the preliminary results of rain effects in a 23 GHz terrestrial point-to-point communication link 1.3km long. The experimental test bed had been set up at Skudai, Johor Bahru, Malaysia. In this area, a monsoon equatorial climate prevails and the rainfall rate can reach values well above 100mm/h with significant monthly and diurnal variability. Hence, it is necessary to implement a mitigation technique for maintaining an adequate radio link performance for the action of very heavy rain. Since we now know that the ULPC (Up Link Power Control) cannot guarantee the desired performance, a solution based on frequency band diversity is proposed in this paper. Here, a secondary radio link operating in a frequency not affected by rain (C band for instance) is placed parallel with the main link. Under no rain or light rain conditions, the secondary link carries without priority radio signals. When there is an outage of the main link due to rain, the secondary link assumes the priority traffic. The outcome of the research shows a solution for higher operating frequencies during rainy events

Hard hexagon partition function for complex fugacity

We study the analyticity of the partition function of the hard hexagon model in the complex fugacity plane by computing zeros and transfer matrix eigenvalues for large finite size systems. We find that the partition function per site computed by Baxter in the thermodynamic limit for positive real values of the fugacity is not sufficient to describe the analyticity in the full complex fugacity plane. We also obtain a new algebraic equation for the low density partition function per site.Comment: 49 pages, IoP styles files, lots of figures (png mostly) so using PDFLaTeX. Some minor changes added to version 2 in response to referee report

Integrability vs non-integrability: Hard hexagons and hard squares compared

In this paper we compare the integrable hard hexagon model with the non-integrable hard squares model by means of partition function roots and transfer matrix eigenvalues. We consider partition functions for toroidal, cylindrical, and free-free boundary conditions up to sizes $40\times40$ and transfer matrices up to 30 sites. For all boundary conditions the hard squares roots are seen to lie in a bounded area of the complex fugacity plane along with the universal hard core line segment on the negative real fugacity axis. The density of roots on this line segment matches the derivative of the phase difference between the eigenvalues of largest (and equal) moduli and exhibits much greater structure than the corresponding density of hard hexagons. We also study the special point $z=-1$ of hard squares where all eigenvalues have unit modulus, and we give several conjectures for the value at $z=-1$ of the partition functions.Comment: 46 page

Social inequalities in utilization of a feminist telehealth abortion service in Brazil : A multilevel analysis

The disruption caused by the COVID-19 pandemic on health services around the world boosted interest over telehealth models of care. In Brazil, where abortion is heavily restricted, abortion seekers have long relied on international telehealth services to access abortion pills. We conducted a cross-sectional multilevel study to assess the effect of individual and contextual social factors on utilization of one such service. For the individual-level, we analyzed data from the records of abortion seekers contacting this feminist international telehealth organization during 2019 (n = 25,920). Individual-level variables were age, race, education level and pregnancy length. Contextual-level units were states, for which we used data from the national Demographic Census and Household Surveys. Contextual-level variables were household income per capita, adjusted net school attendance rate, percentage of racialized women and income Gini Index. We fitted five multilevel Poisson Mixed-effects models with robust variance to estimate prevalence ratios (PR) of service utilization, which was defined as receiving abortion pills through the service. We found that only 8.2% of requesters got abortion pills through the service. Utilization was higher among women who were older, white, more educated and 5-8-weeks pregnant. Independently of this, service utilization was higher in states with higher income and education access, with lower proportions of racialized women, and located in the South, Southeast and Central-West regions. We concluded that while feminist telehealth abortion initiatives provide a life-saving service for some abortion seekers, they are not fully equipped to overcome entrenched social inequalities in their utilization, both at individual and contextual levels

CODIGESTÃO ANAERÓBIA DE ESGOTO SANITÁRIO E LODO ALGÁCEO EM UM REATOR UASB

Essa pesquisa objetivou estudar os efeitos da codigestão anaeróbia de esgoto sanitário e lodo algáceo em um reator UASB, analisando o desempenho do reator antes (Etapa 1) e durante no processo de codigestão anaeróbia (Etapa 2). O reator UASB utilizado possui 3,78 m³ de volume útil de 4,8 metros de altura e foi monitorado por 410 dias. No processo de codigestão foi utilizado lodo algáceo físico-químico sem pré-tratamento. Após o período de partida que durou 138 dias, o reator manteve desempenho satisfatório no tratamento anaeróbio do esgoto sanitário na etapa 1 (164 dias) e etapa 2 (108 dias). O efluente apresentou concentração média de 160 mg/L de DQO e 49 mg/L de SST (etapa 1) e 125 mg/L de DQO e 41 mg/L de SST (etapa 2). O TDH e COV do reator foi de 8,8h e 1,14 kgDQO.m-3 .d-1 (etapa 1) e 9,5h e 0,98 kgDQO.m-3 .d-1 (etapa 2). A idade do lodo decresceu da etapa 1 (108 dias) para a etapa 2 (98 dias), como consequência do aumento da produção de sólidos de 0,48 kgST.d1 (etapa 1) para 0,57 kgST.d-1 (etapa 2). Tal fato implica em uma maior frequência de descarte do lodo de excesso do UASB. O aporte contínuo de lodo algáceo na etapa 2 tornou o lodo significativamente menos estabilizado na região de manta, provavelmente devido ao carreamento das microalgas da região de leito para a manta de lodo do UASB. A produção de biogás foi de 10 L/hab.d (Etapa 1) e 6 L/hab.d (Etapa 2). A produção estimada de metano foi 6 L/hab.d (Etapa 1) e 4 L/hab.d (Etapa 2). Como consequência, a potência disponível do biogás efetivamente capturado foi de 0,18 kW (0,0024 kW/hab) e 0,11kW (0,0015 kW/hab) nas etapas 1 e 2, respectivamente. Atribui-se à diminuição da COV aplicada e Temperatura à queda na produção de metano na etapa 2. O resultado do balanço de massa de DQO sugere que o processo de codigestão anaeróbia contribuiu para o aumento da DQO convertida em lodo anaeróbio. Esse aumento relativo da produção de lodo pode estar relacionado com a não digestão das microalgas, as quais são capturadas pelo lodo do reator, mas não são totalmente digeridas por ele. A DQO das microalgas pouco contribuiu para a produção de metano no UASB neste estudo. Por fim, concluiu-se que para aumentar a conversão do material orgânico no reator deve-se operar o UASB à máxima idade do lodo e pré-tratar o lodo algáceo antes do processo de codigestão anaeróbia

The brachistochrone problem in open quantum systems

Recently, the quantum brachistochrone problem is discussed in the literature by using non-Hermitian Hamilton operators of different type. Here, it is demonstrated that the passage time is tunable in realistic open quantum systems due to the biorthogonality of the eigenfunctions of the non-Hermitian Hamilton operator. As an example, the numerical results obtained by Bulgakov et al. for the transmission through microwave cavities of different shape are analyzed from the point of view of the brachistochrone problem. The passage time is shortened in the crossover from the weak-coupling to the strong-coupling regime where the resonance states overlap and many branch points (exceptional points) in the complex plane exist. The effect can {\it not} be described in the framework of standard quantum mechanics with Hermitian Hamilton operator and consideration of $S$ matrix poles.Comment: 18 page

Standstill Electric Charge Generates Magnetostatic Field Under Born-Infeld Electrodynamics

The Abelian Born-Infeld classical non-linear electrodynamic has been used to investigate the electric and magnetostatic fields generated by a point-like electrical charge at rest in an inertial frame. The results show a rich internal structure for the charge. Analytical solutions have also been found. Such findings have been interpreted in terms of vacuum polarization and magnetic-like charges produced by the very high strengths of the electric field considered. Apparently non-linearity is to be accounted for the emergence of an anomalous magnetostatic field suggesting a possible connection to that created by a magnetic dipole composed of two mognetic charges with opposite signals. Consistently in situations where the Born-Infeld field strength parameter is free to become infinite, Maxwell`s regime takes over, the magnetic sector vanishes and the electric field assumes a Coulomb behavior with no trace of a magnetic component. The connection to other monopole solutions, like Dirac`s, t' Hooft`s or Poliakov`s types, are also discussed. Finally some speculative remarks are presented in an attempt to explain such fields.Comment: 11 pages, 3 figures. In this version is update a permanent address of the author L.P.G. De Assis and information on submission publication. Submetted to International Journal of Theoretical Physic