Superfluidity of Dense 4^4He in Vycor

We calculate properties of a model of $^4$He in Vycor using the Path Integral Monte Carlo method. We find that $^4$He forms a distinct layered structure with a highly localized first layer, a disordered second layer with some atoms delocalized and able to give rise to the observed superfluid response, and higher layers nearly perfect crystals. The addition of a single $^3$He atom was enough to bring down the total superfluidity by blocking the exchange in the second layer. Our results are consistent with the persistent liquid layer model to explain the observations. Such a model may be relevant to the experiments on bulk solid $^4$He, if there is a fine network of grain boundaries in those systems.Comment: 4 pages, 4 figure

Površinska obrada polimera u tinjavom argonskom izboju

Surface treatment of polymer material (thin polyester samples) was performed in the DC glow discharge, using Ar gas. The effect of the experimental parameters of the glow discharge (the gas pressure and the sample treatment time) on the wettability of the samples was studied. The wettability was characterized by the water repellency (water spray test). In the present work, it was shown that at a constant gas pressure (270 or 670 Pa), the wettability of the polyester sample was decreased by increasing the exposure time of the sample in the glow discharge. At constant exposure times (2, 5, 10 or 15 min) the wettability of the polyester sample was increased by increasing the gas pressure. This is due to the formation of hydrophilic groups, which increased by increasing the density of electrons and/or metastables.Površinski smo obrađivali polimerni materijal (tanke uzorke poliestera) u istosmjernom tinjavom argonskom izboju. Proučavali smo učinke eksperimentalnih parametara izboja (tlaka plina i vremena izlaganja u izboju) na močivost uzoraka. Močivost smo određivali mjerenjem odbojnosti vode (metoda prskanjem vode). U ovom se radu pokazuje da se na stalnom tlaku plina (270 ili 670 Pa), močivost uzoraka poliestera smanjuje za dulja vremena izlaganja u izboju. Za određena vremena izlaganja (2, 5, 10 ili 15 min), močivost uzoraka je porasla pri povećanom tlaku argona. Razlog tome je stvaranje hidrofilnih grupa koje su bile brojnije pri povećanoj gustoći elektrona i/ili metastabila

Površinska obrada polimera u tinjavom argonskom izboju

Surface treatment of polymer material (thin polyester samples) was performed in the DC glow discharge, using Ar gas. The effect of the experimental parameters of the glow discharge (the gas pressure and the sample treatment time) on the wettability of the samples was studied. The wettability was characterized by the water repellency (water spray test). In the present work, it was shown that at a constant gas pressure (270 or 670 Pa), the wettability of the polyester sample was decreased by increasing the exposure time of the sample in the glow discharge. At constant exposure times (2, 5, 10 or 15 min) the wettability of the polyester sample was increased by increasing the gas pressure. This is due to the formation of hydrophilic groups, which increased by increasing the density of electrons and/or metastables.Površinski smo obrađivali polimerni materijal (tanke uzorke poliestera) u istosmjernom tinjavom argonskom izboju. Proučavali smo učinke eksperimentalnih parametara izboja (tlaka plina i vremena izlaganja u izboju) na močivost uzoraka. Močivost smo određivali mjerenjem odbojnosti vode (metoda prskanjem vode). U ovom se radu pokazuje da se na stalnom tlaku plina (270 ili 670 Pa), močivost uzoraka poliestera smanjuje za dulja vremena izlaganja u izboju. Za određena vremena izlaganja (2, 5, 10 ili 15 min), močivost uzoraka je porasla pri povećanom tlaku argona. Razlog tome je stvaranje hidrofilnih grupa koje su bile brojnije pri povećanoj gustoći elektrona i/ili metastabila

Criterion for polynomial solutions to a class of linear differential equation of second order

We consider the differential equations y''=\lambda_0(x)y'+s_0(x)y, where \lambda_0(x), s_0(x) are C^{\infty}-functions. We prove (i) if the differential equation, has a polynomial solution of degree n >0, then \delta_n=\lambda_n s_{n-1}-\lambda_{n-1}s_n=0, where \lambda_{n}= \lambda_{n-1}^\prime+s_{n-1}+\lambda_0\lambda_{n-1}\hbox{and}\quad s_{n}=s_{n-1}^\prime+s_0\lambda_{k-1},\quad n=1,2,.... Conversely (ii) if \lambda_n\lambda_{n-1}\ne 0 and \delta_n=0, then the differential equation has a polynomial solution of degree at most n. We show that the classical differential equations of Laguerre, Hermite, Legendre, Jacobi, Chebyshev (first and second kind), Gegenbauer, and the Hypergeometric type, etc, obey this criterion. Further, we find the polynomial solutions for the generalized Hermite, Laguerre, Legendre and Chebyshev differential equations.Comment: 12 page

Multi-Channel Preemptive Priority Model for Spectrum Mobility in Cognitive Radio Networks

Cognitive Radio techniques have been proposed for improving utilization of the spectrum by exploiting the unoccupied bands of the licensed spectrum. This paper proposes a preemptive multi-channel access model for prioritized cognitive radio networks using an iterative method of queuing theory to solve the spectrum scarcity problem. The proposed model formulates accurate closed form of an expected waiting time in the queue, an expected number of users in the queue, an expected waiting time in the system, and an expected number of users in the system. The results compared to the basic model (without preemptive priority) show that, the waiting time in queue and the waiting time in the system compared to the basic model will be improved by 92.99% and 33.15% respectively for class one secondary user. The results also show that, the waiting time in queue and the waiting time in the system will be improved by 43.25% and 15.42% respectively for class two secondary users. The proposed model investigates the desirable schedules of primary and secondary users

Identifikasi Bakteri pada Sputum Pasien Penyakit Paru Obstruktif Kronis Eksaserbasi Akut di RSUD Arifin Achmad Provinsi Riau

Chronic Obstructive Pulmonary Disease is characterized by persistent airflow limitation, progressive, associated with chronic inflammatory response caused by noxious particles and gases. The severity of COPD depends on its exacerbations and comorbidities of each individual. One of the most factors cause exacerbation of COPD is bacterial infection. The purpose of this study was to know the percentage of bacterial infection cause the exacerbation and the pattern of its etiologic bacteria. The samples were sputum of hospitalized patients with exacerbation of COPD in the Lung room RSUD Arifin Achmad Riau Province. The sputum specimen was collected using sterile containers and subjected to Gram's stain, culture and biochemical reactions. This study obtained 100% of sputum cultur for pathogenic bacteria was possitive in all 23 cases. The most etiologic bacteria were gram negative 83% which is Klebsiella sp. as the leading bacteria 48%, followed by Acinetobacter sp. 22% and Enterobacter sp. 13%. Gram possitive Staphylococcus aureus were found about 17% in exacerbation of COPD

Smart integration of a DC microgrid: Enhancing the power quality management of the neighborhood low-voltage distribution network

The fast development of the residential sector regarding the additional integration of renewable distributed energy sources and the modern expansion usage of essential DC electrical equipment may cause severe power quality problems. For example, the integration of rooftop photovoltaic (PV) may cause unbalance, and voltage fluctuation, which can add constraints for further PV integrations to the network, and the deployment of DC native loads with their nonlinear behavior adds harmonics to the network. This paper demonstrates the smart integration of a DC microgrid to the neighborhood low-voltage distribution network (NLVDN). The DC microgrid is connected to the NLVDN through a three-phase voltage source inverter (VSI), in which the VSI works as a distribution static compensator (DSTATCOM). Unlike previous STATCOM work in the literature, the proposed controller of the VSI of the DC smart building allows for many functions: (a) it enables bidirectional active/reactive power flow between the DC building and the AC grid at point of common coupling (PCC); (b) it compensates for the legacy unbalance in the distribution network, providing harmonics elimination and power factor correction capability at PCC; and (c) it provides voltage support at PCC. The proposed controller was validated by Matlab/Simulink and by experimental implementation at the lab

Physical applications of second-order linear differential equations that admit polynomial solutions

Conditions are given for the second-order linear differential equation P3 y" + P2 y'- P1 y = 0 to have polynomial solutions, where Pn is a polynomial of degree n. Several application of these results to Schroedinger's equation are discussed. Conditions under which the confluent, biconfluent, and the general Heun equation yield polynomial solutions are explicitly given. Some new classes of exactly solvable differential equation are also discussed. The results of this work are expressed in such way as to allow direct use, without preliminary analysis.Comment: 13 pages, no figure