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Jørgensen Troels Højsgaard,Søndergaard Lars 대한심부전학회 2022 International Journal of Heart Failure Vol.4 No.1
Patients with heart failure with preserved ejection fraction (HFpEF) constitutes a considerable sized population like that of subjects with heart failure with reduced ejection fraction. The symptoms include exercise induced dyspnoea and fatigue besides an increased mortality rate when compared to the general population. There is limited evidence of benefit from pharmacological therapy. A main pathophysiological mechanism is a left ventricular filling pressure that might be near to normal during resting conditions but increases during exercise leading to pulmonary congestion. Based on observations like the apparent lesser symptomatology in patients with combined mitral valve stenosis and atrial septal defect (Lutembacher syndrome) when compared to patients with isolated mitral valve stenosis, several Inter-Atrial Shunt Devices (IASD) have been developed with the intent to unload the pressure in the left atrium by creating a shunt into the right atrium. Smaller studies have found that the IASDs reduce the left ventricular filling pressure during exercise and increase the functional status of patients both subjectively and objectively with reported low rates of complications. These devices are undergoing further investigations and might prove to be a new paradigm in the treatment of patients with HFpEF.
Jørgensen, Mathias,Lee, Young-Su,Bjerring, Morten,Jepsen, Lars H.,Akbey, Ü,mit,Cho, Young Whan,Jensen, Torben R. The Royal Society of Chemistry 2018 Dalton Transactions Vol.47 No.46
<P>The new compound Sr(BH4)2(NH3BH3)2 has been synthesized and characterized with <I>in situ</I> powder X-ray diffraction and fast (28 or 60 kHz) magic angle spinning <SUP>1</SUP>H, <SUP>11</SUP>B and <SUP>15</SUP>N NMR and structurally optimized with density functional theory calculations. This investigation reveals complex structural rearrangements for this compound as a function of temperature. A room temperature orthorhombic polymorph, α-Sr(BH4)2(NH3BH3)2, with the space group symmetry <I>Pbca</I>, has been determined with a layered structure of alternating ammonia borane and Sr(BH4)2, partially stabilized by dihydrogen bonding. Surprisingly the crystal symmetry is lowered upon heating, as evidenced both by <I>in situ</I> synchrotron powder X-ray diffraction and <SUP>11</SUP>B MAS NMR data, resulting in an intermediate polymorph, β′-Sr(BH4)2(NH3BH3)2, present from ∼65 to 115 °C. β-Sr(BH4)2(NH3BH3)2, a sub structure of the β′-polymorph showing higher symmetry with the space group symmetry <I>Aba</I>2, forms upon further heating. <I>Ab initio</I> molecular dynamics simulations show that the ammonia borane molecule can dynamically alternate between a bidentate and a tridentate coordination to Sr at finite temperature. The dynamic properties of the ammonia borane molecule in the solid state are suggested to cause the observed structural complexity. Based on simultaneous thermogravimetric analysis, differential scanning calorimetry and mass spectrometry, the decomposition of the compound was investigated showing a stabilization of ammonia borane in the structure relative to other metal borohydride ammonia boranes and neat ammonia borane.</P>
On the nonlinear structural analysis of wind turbine blades using reduced degree-of-freedom models
K. Holm-Jørgensen,J.W. Stærdahl,S.R.K. Nielsen 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.1
Wind turbine blades are increasing in magnitude without a proportional increase of stiffness for which reason geometrical and inertial nonlinearities become increasingly important. Often these effects are analysed using a nonlinear truncated expansion in undamped fixed base mode shapes of a blade, modelling geometrical and inertial nonlinear couplings in the fundamental flap and edge direction. The purpose of this article is to examine the applicability of such a reduced-degree-of-freedom model in predicting the nonlinear response and stability of a blade by comparison to a full model based on a nonlinear co-rotating FE formulation. By use of the reduced-degree-of-freedom model it is shown that under strong resonance excitation of the fundamental flap or edge modes, significant energy is transferred to higher modes due to parametric or nonlinear coupling terms, which influence the response and stability conditions. It is demonstrated that the response predicted by such models in some cases becomes instable or chaotic. However, as a consequence of the energy flow the stability is increased and the tendency of chaotic vibrations is reduced as the number of modes are increased. The FE model representing the case of infinitely many included modes, is shown to predict stable and ordered response for all considered parameters. Further, the analysis shows that the reduced-degree-of-freedom model of relatively low order overestimates the response near resonance peaks, which is a consequence of the small number of included modes. The qualitative erratic response and stability prediction of the reduced order models take place at frequencies slightly above normal operation. However, for normal operation of the wind turbine without resonance excitation 4 modes in the reduced-degree-of-freedom model perform acceptable.
Technical Barriers, Import Licenses and Tariffs as Means of Limiting Market Access
( Jan G. Jørgensen ),( Philipp J. H. Schroder ) 세종대학교 경제통합연구소 (구 세종대학교 국제경제연구소) 2006 Journal of Economic Integration Vol.21 No.1
Technical barriers (standards), import licenses and tariffs may be deployed as means of limiting the market access of foreign firms. The present paper examines these measures in a setting of monopolistic competition. We find that, if protection focuses predominantly on the number of foreign firms accessing the domestic market, a technical barrier (an import license) may dominate a tariff (tariff and a technical barrier) in terms of consumer welfare, even when tariff revenues are fully redistributed. However, if protection pays sucfficient focus on limiting the total import volume, then tariffs are the preferred means of protection. Within the model, reductions in technical barriers and tariffs, the removal of licensing schemes, and a harmonization of standards are all welfare-improving policies.
Multi-cell Operation of Class-PN at 6.78 MHz using GaN Devices for Industrial Dielectric Heating
Faheem Ahmad,Asger Bjørn Jørgensen,Stig Munk-Nielsen 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
Radio frequency (RF) dielectric heating is employed in industries like drying cross-laminated wood, baking food etc. Industries employ vacuum tube RF generators operating at 6.78 or 13.56 MHz to generate kVs range of RF output. High voltage at high frequency requirement is the reason for industry reliance on vacuum tubes, although they are only 60% efficient. Gallium nitride (GaN) devices have achieved multi-MHz operation, providing an opportunity to replace the inefficient vacuum tubes. However, the high voltage requirement is still a challenge as commercial GaN devices are only available at 650 V. This paper presents multi-cell operation of Class-PN to achieve the high voltage. Control design of Class-PN is provided. Three Class-PN cells are operated in multi-cell configuration to boost DC input of 185 V to peak-peak RF voltage of 1.1 kV at 6.78 MHz. Output power of 856 W at an efficiency of 80% from DC input to RF load is demonstrated.