Viser treff 573-592 av 919

    • On geometric construction of some power means 

      Høibakk, Ralph; Lukkassen, Dag; Persson, Lars Erik; Meidell, Annette (Journal article; Peer reviewed, 2018-11-27)
      In the homogenization theory, there are many examples where the effective conductivities of composite structures are power means of the local conductivities. The main aim of this paper is to initiate research concerning geometric construction of some power means of three or more variables. We contribute by giving methods for the geometric construction of the harmonic mean $ P_{-1} $ and the arithmetic ...
    • On heat conduction in domains containing noncoaxial cylinders 

      Lukkassen, Dag; Meidell, Annette (Journal article; Peer reviewed; Tidsskriftartikkel, 2012)
      We consider heat conduction in domains containing noncoaxial cylinders. In particular, we present some regularity results for the solution and consider criteria which ensure the single valueness of the corresponding complex potential. Examples are discussed. In addition, we present some classes of cases where the parameters describing the solution are rational. Alternative ways of calculating the ...
    • On operator estimates in homogenization of nonlocal operators of convolution type 

      Piatnitski, Andrei; Sloushch, Vladimir; Suslina, Tatiana; Zhizhina, Elena (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-11)
    • On Some Power Means and Their Geometric Constructions 

      Høibakk, Ralph; Lukkassen, Dag; Meidell, Annette; Persson, Lars Erik (Journal article; Peer reviewed; Tidsskriftartikkel, 2018)
      The main aim of this paper is to further develop the recently initiatedresearch concerning geometric construction of some power means wherethe variables are appearing as line segments. It will be demonstratedthat the arithmetic mean, the harmonic mean and the quadratic meancan be constructed for any number of variables and that all power meanswhere the number of variables are n = 2m, m 1 2 N for all ...
    • On the boundedness of subsequences of Vilenkin-Fejér means on the martingale Hardy spaces 

      Persson, Lars Erik; Tephnadze, George; Tutberidze, Giorgi (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03)
      In this paper we characterize subsequences of Fejér means with respect to Vilenkin systems, which are bounded from the Hardy space <i>H<sub>p</sub></i> to the Lebesgue space <i>L<sub>p</sub></i>, for all 0 < p < 1/2. The result is in a sense sharp.
    • On the Heat and Wave Equations with the Sturm-Liouville Operator in Quantum Calculus 

      Shaimardan, Serikbol; Persson, Lars-Erik; Tokmagambetov, Nariman (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-19)
      In this paper, we explore a generalised solution of the Cauchy problems for the q-heat and q-wave equations which are generated by Jackson’s and the q-Sturm-Liouville operators with respect to t and x, respectively. For this, we use a new method, where a crucial tool is used to represent functions in the Fourier series expansions in a Hilbert space on quantum calculus. We show that these solutions ...
    • On Weighted Fourier InequalitieS –– Some New Scales of Equivalent Conditions 

      Kufner, Alois; Persson, Lars-Erik; Samko, Natasha G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06)
      For Lebesgue spaces on R<sup>n</sup>, we study two-weight p → q-inequalities for Fourier transform. Some sufficient conditions on weights for such inequalities are known for special ranges of parameters p and q. In the same ranges of parameters we show, that in every case each of those conditions can be replaced by infinitely many conditions, even by continuous scales of conditions. We also ...
    • Onshore and Offshore Coordination of Logistics Services at Seaports 

      Adu-Gyamfi Appiah, Bright (Master thesis; Mastergradsoppgave, 2019-06-28)
      As global trade increases, sizes of vessels and cargo throughputs have also experienced a sudden rise thereby putting excess pressure on ship berths and ports. This is shifting most ports to much smarter technological solutions with the aim of optimizing operations, increasing efficiency and reducing logistics cost without the need for huge infrastructural and equipment investments. Developing the ...
    • Optical water types of the Nordic Seas and adjacent areas 

      Aas, Eyvind; Højerslev, Niels Kristian; Høkedal, Jo; Sørensen, Kai (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-05-20)
      A new map of Jerlov's optical water types in the Nordic Seas and adjacent waters at 139 locations, as well as a table with statistical and geographical properties of the vertical attenuation coefficient of downward irradiance at 475 nm, are presented. The data analysis is based on 715 recordings at different stations, at latitudes between 54° and 82°N, and longitudes between 31°W and 49°E, obtained ...
    • Optimal bruk av reaktive ressurser 

      Arnesen, Jan Tore (Master thesis; Mastergradsoppgave, 2021-05-18)
      God kontroll av reaktiv effekt er en helt nødvendig del av et velfungerende kraftsystem. Reaktiv effekt er funksjon av spenning og lastvinkel, men er i størst grad påvirket av spenningen under normale forhold. Det finnes mange forskjellige reaktive ressurser i kraftsystemet, og de har forskjellige egenskaper og karakteristikker. Statiske reaktive ressurser er kondensatorbatterier, reaktorer og ...
    • Optimal placement of PMUs considering logical topology of communication medium power system observability 

      Nikumbh, Bhushan Madan (Master thesis; Mastergradsoppgave, 2016-11-07)
      A phasor measurement unit (PMU) has a unique ability of providing synchronized phasor measurements of voltage and currents. This ability distinguishes it from all other metering devices. It has been perceived that PMUs hold the capability of revolutionizing the way of power system monitoring and control. However, high per unit cost and challenges related to its communication system has made ...
    • Optimal power flow based coordinated reactive and active power control to mitigate voltage violations in smart inverter enriched distribution network 

      Wagle, Raju; Sharma, Pawan; Charu, Sharma; Amin, Mohammad (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-30)
      Voltage violations are the main problem faced in distribution networks (DN) with a higher penetration of inverter-based generations (IBG). Active and reactive power control from smart inverters (SI) can mitigate such violations. Optimal power flow (OPF)-based control provides more accurate operating set points for the coordinated operation of SIs. Therefore, this paper presents a three-phase OPF-based ...
    • Optimal routing and charging procedures for electric buses 

      Masliakova, Kseniia (Master thesis; Mastergradsoppgave, 2016-04-06)
      The goal of the project is to use Ant Colony Optimization techniques with Genetic Algorithm to design and analyse routes and recharging schedules for electric buses. One system so-called “en route” charging was analysed where the bus applies a kind of pantograph at bus stops to recharge the bus batteries. This implies more frequent, but short recharging intervals. The program offers diff t variants ...
    • Optimal Solutions for Underwater Capacitive Power Transfer 

      Al-Sallami, Hussein; Hoff, Bjarte; Østrem, Trond (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-09)
      Capacitive power transfer (CPT) has attracted attention for on-road electric vehicles, autonomous underwater vehicles, and electric ships charging applications. High power transfer capability and high efficiency are the main requirements of a CPT system. This paper proposes three possible solutions to achieve maximum efficiency, maximum power, or conjugate-matching. Each solution expresses the ...
    • Optimal Volt Var control in Smart Distribution Networks 

      Shamraiz, Shamraiz (Master thesis; Mastergradsoppgave, 2021-05-24)
      Both the generation and transmission power networks are facing new threats and opportunities as the number of distributed energy resources (DERs) grows. Because of the high solar PV penetration, voltage rise and voltage volatility are becoming major problems in the distribution network. Voltage regulating devices (VRDs), such as on load tap changers (OLTCs), phase voltage regulators (SVRs), and ...
    • Optimization models and methods for sustainable reverse logistics network design 

      Yu, Hao (Doctoral thesis; Doktorgradsavhandling, 2018-11-29)
      With the increased focus on sustainable development and circular economy, as never before, the value recovery and re-creation from the End-of-Use and End-of-Life products has been paid considerable attention by the whole society. Reverse logistics is believed as one of the most effective and promising means for the value recovery of the End-of-Use and End-of-Life products, which is the process for ...
    • Optimization of a mixed refrigerant based H2 liquefaction pre-cooling process and estimate of liquefaction performance with varying ambient temperature 

      Jackson, Steven; Brodal, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-24)
      Hydrogen used as an energy carrier can provide an important route to the decarbonization of energy supplies, but realizing this opportunity will require both significantly increased production and transportation capacity. One route to increased transportation capacity is the shipping of liquid hydrogen, but this requires an energy-intensive liquefaction step. Recent study work has shown that the ...
    • Optimization of ground icing protection for aircraft: Snow endurance tests, rheological analysis and thermography of anti-icing fluids 

      Benaissa, Sanae; Momen, Gelareh; Harvey, Derek; Taghavi, Seyed Mohammad; Khawaja, Hassan Abbas (Conference object; Konferansebidrag, 2023-10-11)
    • Optimization of industrial power grid of Narvik 

      Khan, Md Nafis Ul Hoq (Master thesis; Mastergradsoppgave, 2023-05-22)
      The objective of this study is to review a comprehensive plan for optimization framework for the industrial power grid. Few factors considered such as power generation, transmission, distribution, energy storage solutions, cost development. The aim targets an overview of planning and optimization for a hydrogen production plant in Narvik region. It will improve the overall efficiency, stability, ...
    • Optimization of long-term performance of municipal solid waste management system: A bi-objective mathematical model 

      Yu, Hao; Solvang, Wei Deng; Li, Shiyun (Peer reviewed; Journal article; Tidsskriftsartikkel, 2015)
      Management of municipal solid waste has becoming an extremely important topic for any urban authorities in recent years due to the rapidly increasing solid waste quantity and potential environmental pollution. In this paper, a bi-objective dynamic linear programming model is developed for decision making and supporting in the long-term operation of municipal solid waste management system. The proposed ...