Ocean waves and turbulence as observed with an adaptive coherent multifrequency radar

An adaptive coherent multifrequency radar system is developed for several applications. The velocity distribution (Doppler spectrum) and spectral intensity of 15 different irregularity scales (waves and turbulence) can be measured simultaneously. Changing the azimuth angle of the antennas at regular intervals, the directivity of the wave/turbulence pattern on the sea surface can also be studied. A series of measurements for different air/sea conditions are carried out from a coast based platform. Experiments in the Atlantic are also performed with the same equipment making use of the NASA Electra aircraft. The multifrequency radar allows the measurement of the velocity distribution (""coherent and incoherent component'') associated with 15 different ocean irregularity scales simultaneously in a directional manner. It is possible to study the different air/sea mechanisms in some degree of detail

On dual Schur domain decomposition method for linear first-order transient problems

This paper addresses some numerical and theoretical aspects of dual Schur domain decomposition methods for linear first-order transient partial differential equations. In this work, we consider the trapezoidal family of schemes for integrating the ordinary differential equations (ODEs) for each subdomain and present four different coupling methods, corresponding to different algebraic constraints, for enforcing kinematic continuity on the interface between the subdomains. Method 1 (d-continuity) is based on the conventional approach using continuity of the primary variable and we show that this method is unstable for a lot of commonly used time integrators including the mid-point rule. To alleviate this difficulty, we propose a new Method 2 (Modified d-continuity) and prove its stability for coupling all time integrators in the trapezoidal family (except the forward Euler). Method 3 (v-continuity) is based on enforcing the continuity of the time derivative of the primary variable. However, this constraint introduces a drift in the primary variable on the interface. We present Method 4 (Baumgarte stabilized) which uses Baumgarte stabilization to limit this drift and we derive bounds for the stabilization parameter to ensure stability. Our stability analysis is based on the ``energy'' method, and one of the main contributions of this paper is the extension of the energy method (which was previously introduced in the context of numerical methods for ODEs) to assess the stability of numerical formulations for index-2 differential-algebraic equations (DAEs).Comment: 22 Figures, 49 pages (double spacing using amsart

Critical Illness Polyneuropathy, Complications

Background and Purpose: Critical Illness Polyneuropathy/Myopathy results from the presence of sepsis, multi-organ or respiratory failure, septic inflammatory response syndrome, or difficulty weaning from the ventilator. Decreased amplitudes of compound muscle and sensory action potentials, and widespread denervation potentials in muscle are the primary cause for the resultant muscle weakness. The purpose of this paper is to report on the rehabilitation progress in a woman who developed CIP following surgical complications. Case Description: A 63-year-old woman suffered from critical illness polyneuropathy following a complicated recovery following a sigmoidectomy secondary to diverticular disease. Multiple surgeries, inability to wean from the ventilator, and co-morbidities of obesity and smoking complicated her rehabilitation. Physical therapy rehabilitation included general strengthening, gait, balance and proprioceptive training, and activity modification education. Outcome: The patient returned home with assistance from family in three weeks. She was discharged with a single point cane and education on activity modification. Improvement, manifested in her AM-PAC and Tinetti functional outcome assessments, supported her discharge home. Discussion: Following three weeks of intensive physical therapy, the patient was ready for discharge and given the tools to further her rehabilitation to be functionally independent. She returned home with an assistive device and required minimal assistance from her family. Conclusion: Aggressive physical therapy that targets lower extremity and trunk strengthening, as well as balance and proprioception, and activity modification, is effective treatment for critical illness polyneuropathy

Endocortical bone loss in osteoporosis: The role of bone surface availability

Age-related bone loss and postmenopausal osteoporosis are disorders of bone remodelling, in which less bone is reformed than resorbed. Yet, this dysregulation of bone remodelling does not occur equally in all bone regions. Loss of bone is more pronounced near and at the endocortex, leading to cortical wall thinning and medullary cavity expansion, a process sometimes referred to as "trabecularisation" or "cancellisation". Cortical wall thinning is of primary concern in osteoporosis due to the strong deterioration of bone mechanical properties that it is associated with. In this paper, we examine the possibility that the non-uniformity of microscopic bone surface availability could explain the non-uniformity of bone loss in osteoporosis. We use a computational model of bone remodelling in which microscopic bone surface availability influences bone turnover rate and simulate the evolution of the bone volume fraction profile across the midshaft of a long bone. We find that bone loss is accelerated near the endocortical wall where the specific surface is highest. Over time, this leads to a substantial reduction of cortical wall thickness from the endosteum. The associated expansion of the medullary cavity can be made to match experimentally observed cross-sectional data from the Melbourne Femur Collection. Finally, we calculate the redistribution of the mechanical stresses in this evolving bone structure and show that mechanical load becomes critically transferred to the periosteal cortical bone.Comment: 13 pages, 3 figures. V2: minor stylistic improvements in text/figures; more accurately referenced subsection "Internal mechanical stress distribution"; some improved remarks in the Discussion sectio

Superintendent Selection in North Dakota: Practices and Criteria

The purpose of this study was to learn how North Dakota school board members who had recendy participated in the selection of a school superintendent perceived the relative importance of (a) hiring practices, (b) administrative skills, and (c) superintendent attributes. Analyses of individual items and clusters of items were conducted. In addition to the general purpose, analyses were conducted by gender, by duration of board incumbency, and by school enrollment size. Data for the study consisted of responses from 124 school board members from 39 school districts. (The universe of districts which had hired a superintendent during the 1990-1993 time frame was 55 districts.) Responses were gathered from a three-part questionnaire constructed by the writer. Administrative skills assessments dominated the selection process for new superintendents. Board members placed more importance on personal attributes of candidates than on hiring practices used. Female board members generally recorded higher importance assessments than male board members. Female board members also preferred greater education, experience, and management skill. Board incumbency seemed to be a negligible variable in the selection of a new superintendent. In the selection process, board members from smaller schools valued the advice of others less than did board members from larger schools. Board members from large schools were less concerned about age, appearance, and current job location than were board members from smaller schools

Valutakurser og de skandinaviske aksjemarkedene: En økonometrisk analyse 2009–2024

Denne masteroppgaven undersøker hvordan valutakursendringer påvirker aksjeavkastningen til børsnoterte selskaper i små, åpne økonomier, med særlig fokus på Norge, Sverige og Danmark. En flerfaktormodell anvendes på tre nivåer: hovedindekser, sektorindekser og enkeltaksjer. Analysen baserer seg på ukentlige data fra perioden 2009 til 2024, og modellen inkluderer både bilaterale valutapar og handelsvektede valutakursindekser. Resultatene viser at valutakurseksponeringen varierer betydelig mellom land, sektorer og selskaper. Eksponeringen er ofte både økonomisk og statistisk signifikant, og den amerikanske dollaren (USD) fremstår som den mest innflytelsesrike valutaen. I mange tilfeller gir handelsvektede indekser bedre forklaringskraft for aksjeavkastning enn enkeltvalutapar. Videre finner studien at valutarisiko er særlig uttalt blant internasjonalt orienterte selskaper, mens finansinstitusjoner har lavest eksponering. Funnene har viktige implikasjoner for risikostyring og porteføljeforvaltning i små, åpne økonomier, og understreker behovet for skreddersydde sikringsstrategier tilpasset den enkelte virksomhets inntekts- og kostnadsstruktur.This master’s thesis investigates how exchange rate fluctuations affect the stock returns of publicly listed companies in small, open economies, with a particular focus on Norway, Sweden, and Denmark. A multifactor model is applied at three levels of aggregation: market indices, sector indices, and individual stocks. The analysis is based on weekly data from the period 2009 to 2024. The model includes both bilateral exchange rates and trade-weighted currency indices. The results show that currency exposure varies significantly across countries, sectors, and firms. The exposure is often both economically and statistically significant, with the U.S. dollar (USD) emerging as the most influential currency. In many cases, trade-weighted indices offer greater explanatory power for stock returns than individual exchange rates. Furthermore, the study finds that currency risk is particularly pronounced among internationally oriented firms, while financial institutions exhibit the lowest sensitivity. These findings have important implications for risk management and portfolio allocation in small, open economies, highlighting the need for tailored hedging strategies aligned with each firm's revenue and cost structure