Search results for "PD"
showing 10 items of 1971 documents
Singular quasilinear elliptic systems involving gradient terms
2019
Abstract In this paper we establish the existence of at least one smooth positive solution for a singular quasilinear elliptic system involving gradient terms. The approach combines the sub-supersolutions method and Schauder’s fixed point theorem.
Isotropic p-harmonic systems in 2D Jacobian estimates and univalent solutions
2016
The core result of this paper is an inequality (rather tricky) for the Jacobian determinant of solutions of nonlinear elliptic systems in the plane. The model case is the isotropic (rotationally invariant) p-harmonic system ...
Pulmonary hypertension in COPD and lung transplantation: Timing and procedures
2014
The prevalence of pulmonary hypertension (PH) in the general chronic obstructive pulmonary disease (COPD) population is undefined because stable COPD patients do not routinely undergo screening echocardiogram and right heart catheterization. Most studies published on this topic are focused on a highly selected group of patients with moderate to severe disease awaiting lung transplantation, since hemodynamic data from cardiac catheterization are part of the standard transplant evaluation. In a very recent article, Hurdman et al. studied the characteristics and outcomes, with a particular focus on mortality, of extensively phenotyped, consecutive patients with PH-COPD over a 9-year period. Th…
Radiating and non-radiating sources in elasticity
2018
In this work, we study the inverse source problem of a fixed frequency for the Navier's equation. We investigate that nonradiating external forces. If the support of such a force has a convex or non-convex corner or edge on their boundary, the force must be vanishing there. The vanishing property at corners and edges holds also for sufficiently smooth transmission eigenfunctions in elasticity. The idea originates from the enclosure method: The energy identity and new type exponential solutions for the Navier's equation.
Overcoming synchronization issues in wireless technology Partial Discharge measurement
2016
In this paper, several aspects of the fundamentals of wireless Partial Discharge (PD) measurements are first discussed. Then, the relevance of the problem of voltage synchronization in PD wireless diagnosis is outlined. When portable instruments are used for PD detection, the main issue is the voltage measurement at the site where the PD detection is carried out. When such analysis is carried out over shielded cables, the AC (50/60 Hz) voltage reference signal is not easily detectable, while one of the basic parameters for PD diagnosis, the displacement of the inception voltage of the PD as compared to the reference voltage, is not available. Even if highperformance sensors are readily avai…
Analysis of Thermal Comfort Conditions and Actual Energy Efficiency for Different Heating Systems in Test Buildings
2015
The aim of this study is detailed analysis of long-term monitoring data on thermal comfort conditions and energy efficiency in small test buildings equipped with different heating systems. Calculations of PPD index and local thermal discomfort factors, as well as actual energy efficiency ratios for different heat pump systems are provided for the test buildings during three weeks of the heating season. It is shown that the type of heating system has an influence not only on heating energy needs, but also on thermal comfort conditions in the room.
Automated Kick Control Procedure for an Influx in Managed Pressure Drilling Operations
2016
Within drilling of oil and gas wells, the Managed Pressure Drilling (MPD) method with active control of wellbore pressure during drilling has partly evolved from conventional well control procedures. However, for MPD operations the instrumentation is typically more extensive compared to conventional drilling. Despite this, any influx of formation fluids (commonly known as a kick) during MPD operations is typically handled by conventional well control methods, at least if the kick is estimated to be larger than a threshold value. Conventional well control procedures rely on manual control of the blow out preventer, pumps, and choke valves and do not capitalize on the benefits from the instru…
Partial discharges on IGBT modules: Are sinusoidal waveforms sufficient to evaluate behavior?
2014
In recent years, the increasing use of AC-DC converters, especially in the field of renewable energy sources has led to the implementation of new modulation techniques, in particular the ones based on the pulse width modulation. The purpose of the present work is to verify the different behavior that is obtained when the components are subjected to the partial discharge test carried out with a sinusoidal waveform, and when they are subjected to PWM stress-type, similar to the actual signal generated by this type of electronic components. By considering equal rms value of the fundamental sine wave, the comparison has shown different partial discharges patterns.
Experimental Research of Thermal Comfort Conditions in Small Test Buildings with Different Types of Heating
2015
Abstract The aim of this study is detailed analysis of long-term monitoring data of thermal comfort conditions and energy efficiency in small test buildings equipped with different heating systems. Calculations of PPD index and local thermal discomfort factors are provided for the test buildings during three weeks of heating season. It is shown that the type of heating system has influence not only on heating energy need, but also on thermal comfort conditions in the room.
Apdzīvojuma attīstība un sociālekonomiskie procesi Engurē
2015
Apdzīvojuma attīstība ir nozīmīgs cilvēka ģeogrāfijas pētījumu objekts. To labi var savienot ar sociālekonomiskajiem procesiem, jo šie procesi lielā mērā var ietekmēt un ietekmē apdzīvojumu un nosaka tā pārmaiņu tendences. Bakalaura darbā tiek apskatīta apdzīvojuma attīstība un pārmaiņas, kā arī sociālekonomiskie procesi laikposmā no 1970. gada līdz mūsdienām Engures novada, Engures pagasta Engurē. Bakalaura darba mērķis ir raksturot apdzīvojuma attīstību un sociālekonomiskos procesus Engurē. Darbā izmantoti dažāda veida avoti, tai skaitā arhīvu materiāli un statistikas dati, ka arī autora izveidots kartogrāfiskais materiāls. Darba pirmajā nodaļā definēts apdzīvojuma jēdziens, kā arī apskat…