Toy for Preschoolers with Deaf-Blindness

There are approximately 70,000-100,000 people living in America that are diagnosed as deaf-blind. Since children with deaf-blindness are an extreme minority in the US, research, toys and technological advancements for these children get overlooked. As a result, the developmental processes of children with deaf-blindness are delayed by several years, compared to normal children, due to the lack of resources available to encourage learning. According to Virginia’s Department of Education standards of learning for preschoolers, development physically, mathematically,of environmental awareness and of a sense of self are core requirements for Kindergarten. Therefore, there is a need for a toy that will provide stimulation to develop physical, social, and cognitive progression to keep children with deaf-blindness on a normal learning curve. Our design consists of components each of which stimulate one of the development goals. The first component is a chair that promotes proper posture. The second component is a colored and vibrating drum game to stimulate mathematical development through pattern recognition. The third component is a Braille exposure game to stimulate literacy development, by associating a Braille word with an object or concept. The fourth component is an apparatus that can be placed over the chair that contains dangling objects where the child can reach out to explore their surrounding environment. Under the supervision and interaction of a parent/guardian, the child will develop socially through human interaction and feedback suggested in the provided instruction manual. Our team has been conducting research online and consulting professionals that have worked, or are currently working, in the deaf-blind field; therefore we gathered information on how children with deaf-blindness typically react to certain stimuli and various developmental concerns, to aid with the design of the toy components. With this foundation, our group drafted a variety of design concepts. We weighed out the positives, negatives, and overall efficiency of each concept which lead us to produce our final design. Then we presented our final design to our faculty advisor, perfect our idea and move forward with materials selection. Our next step in the design process is to test the efficiency of different materials and methods that we selected for the stimulatory components through experimentation and computation of engineering principles behind the design. Unfortunately our group encountered a problem in the design process, we are behind in the construction of the chair components due to the amount of time it took to complete the machine shop class. Once our testing is completed, we will begin to construct and complete the full prototype of our product.https://scholarscompass.vcu.edu/capstone/1003/thumbnail.jp

250-MHz synchronously pumped optical parametric oscillator at 2.25-2.6 {\mu}m and 4.1-4.9 {\mu}m

A compact and versatile femtosecond mid-IR source is presented, based on an optical parametric oscillator (OPO) synchronously pumped by a commercial 250-MHz Er:fiber laser. The mid-IR spectrum can be tuned in the range 2.25-2.6 \mu m (signal) and 4.1-4.9 \mu m (idler), with average power from 20 to 60 mW. At 2.5 \mu m a minimum pulse duration of 110 fs and a power of 40 mW have been obtained. Active stabilization of the OPO cavity length has been achieved in the whole tuning range

Phase-stabilized, 1.5-W frequency comb at 2.8 to 4.8 micron

We present a high-power optical parametric oscillator-based frequency comb in the mid-infrared wavelength region using periodically poled lithium niobate. The system is synchronously pumped by a 10-W femtosecond Yb:fiber laser centered at 1.07 um and is singly resonant for the signal. The idler (signal) wavelength can be continuously tuned from 2.8 to 4.8 um (1.76 to 1.37 um) with a simultaneous bandwidth as high as 0.3 um and a maximum average idler output power of 1.50 W. We also demonstrate the performance of the stabilized comb by recording the heterodyne beat with a narrow-linewidth diode laser. This OPO is an ideal source for frequency comb spectroscopy in the mid-IR.Comment: 4 figure

Sub-harmonic resonant excitation of confined acoustic modes at GHz frequencies with a high-repetition-rate femtosecond laser

We propose sub-harmonic resonant optical excitation with femtosecond lasers as a new method for the characterization of phononic and nanomechanical systems in the gigahertz to terahertz frequency range. This method is applied for the investigation of confined acoustic modes in a free-standing semiconductor membrane. By tuning the repetition rate of a femtosecond laser through a sub-harmonic of a mechanical resonance we amplify the mechanical amplitude, directly measure the linewidth with megahertz resolution, infer the lifetime of the coherently excited vibrational states, accurately determine the system's quality factor, and determine the amplitude of the mechanical motion with femtometer resolution

Vergleichende Qualitätsuntersuchung zum Einfluss der Einführung einer Patienten-kontrollierten Epiduralen Analgesie (PCEA) zur Geburtserleichterung unter Berücksichtigung eines modernen geburtshilflichen Analgesiekonzeptes

Zielsetzung: Begleitende Qualitätsuntersuchung über Vor- und Nachteile eines neuen Schmerztherapieregimes mittels Patienten-kontrollierter Epiduralanalgesie (PCEA)-Technik im Vergleich zu traditionellem Bolusapplikation Epiduralanalgesie (TRAD) zur Geburtserleichterung bezüglich dem Einfluss auf die Sicherheit für Mutter und Kind und dem Komfort für die Schwangere und die beteiligten Berufsgruppen. Methode: Retrospektive Datenerhebung im Zeitraum 1.1.2006 - 31.12.2007 am Klinikum Memmingen in 2 Gruppen; Gruppe Traditionelle Bolusapplikation (TRAD; n = 36) und Gruppe Patienten-kontrollierte Epiduralanalgesie (PCEA; n = 33). Ergebnisse und Schlussfolgerung: Es konnte anhand der Analyse von standardisierten Patientinnen-Daten und einer zusätzlichen Begleitumfrage keine Unterlegenheit des neuen PCEA-Regimes gegenüber der traditionellen Bolusapplikation von Lokalanästhetika mittels Periduralkatheter festgestellt werden und keine Beeinflussung der Hämodynamik als Surrogat-Parameter zur Schmerzsymptomatik. Die Auswertungen der zusätzlich durchgeführten Befragungen ergaben mehrheitlich eine deutliche Zustimmung zum Organisationsablauf, der Durchführung der Epiduralanalgesie und dem nun eingesetzten PCEA-Verfahren. Dies betraf neben den beteiligten Fachdisziplinen auch die schwangeren Patientinnen, die sich mit einem hohen Anteil von 90 % wieder einer Epiduralanalgesie in PCEA-Technik unterziehen würden. Trotz einer initial bei uns zu beobachtenden nicht erklärbaren ph-Wert Verschlechterung der Neugeborenen unter PCEA mit Sufentanil konnte in den folgenden Untersuchungen des Neugeborenen durch die Pädiater kein substantieller negativer Effekt auf das Neugeborene festgestellt werden. In der vorgelegten Untersuchung konnte gezeigt werden, dass durch patientenkontrollierte Verfahren die Patientenzufriedenheit auf hohem Niveau gehalten wird, ohne dass es durch die mögliche Miteinbeziehung der Patientin in die Therapie zu einer Steigerung des Lokalanästhetikaverbrauches kommt

Protection of capacitor banks: Nuisance tripping of overcurrent relays; causes and possible remedies

The origin of this master thesis is Statnett having problems with nuisance tripping of capacitor banks. Their own measurements are said to indicate that harmonics are confusing the overcurrent relays. Disconnecting a large capacitor bank from the transmission system can have large consequences for the stability of the system. Consequently any nuisance tripping such as Statnett has experienced should not be allowed to happen again. Measures must be taken to increase the security of the protection system. The aim of this thesis is to investigate the overloading of capacitor banks and operation of numerical relays in harmonic rich environments. Investigate why Statnett have experienced nuisance tripping of overcurrent relays, and introduce possible mitigation measures. The definition of nuisance tripping has been broadened to also include correct tripping because of unwanted resonance. Initially a literature study was conducted to acquire information on the prevailing limits that dictate threshold in relays. Limits have been found in IEC60871-1, and IEEE Std 1036-2010, and IEEE Std. C37.99-2000. In addition a number of books, standards and other publications have been used to understand how capacitors, relays and the general protection systems are influenced by harmonics and possible remedies when overloading becomes an issue. Together with the limits found in standards and regulations measurements from PQSCADA was used as an overview of what can be considered normal operation.A model was created in ATPDraw based on the datasheet and a relay plan of a 420kV capacitor bank. The system is constructed for this simulation and does not represent one particular real life system. Further on it was used to test the difference between an unfiltered, single-tuned, and a c-type filtered capacitor bank. Simulations with both injection of harmonic current from the inductive load and simulations with a voltage source at the grid side dimensioned according to the regulation limits were conducted. It was shown that a system with multiple capacitive and inductive components will have multiple resonance frequencies. As the short-circuit power varies these will fluctuate and might occur at a characteristic harmonic. The consequent amplification of the current will in many instances be large enough to overload the capacitor bank. A single-tuned filter solution will lower the resonance frequency but it is dependent on the short-circuit impedance and will thus vary. Using a c-type filter is more complex than a single-tuned but it results in a filter that is independent of the short-circuit impedance. The amplification of currents at the resonance frequency is also smaller with the c-type filter.Aliasing of high harmonics can possibly cause nuisance tripping of the over current protection if they are not filtered out. It is therefore important to know what harmonics will be present and specify a relay that can handle such harmonics. Although applying a filter is normally intended to avoid actual overloading it can also be applied to lower the loading and making it easier for the relay to separate the particular situations where faults have occurred

Protection of capacitor banks: Nuisance tripping of overcurrent relays; causes and possible remedies

The origin of this master thesis is Statnett having problems with nuisance tripping of capacitor banks. Their own measurements are said to indicate that harmonics are confusing the overcurrent relays. Disconnecting a large capacitor bank from the transmission system can have large consequences for the stability of the system. Consequently any nuisance tripping such as Statnett has experienced should not be allowed to happen again. Measures must be taken to increase the security of the protection system. The aim of this thesis is to investigate the overloading of capacitor banks and operation of numerical relays in harmonic rich environments. Investigate why Statnett have experienced nuisance tripping of overcurrent relays, and introduce possible mitigation measures. The definition of nuisance tripping has been broadened to also include correct tripping because of unwanted resonance. Initially a literature study was conducted to acquire information on the prevailing limits that dictate threshold in relays. Limits have been found in IEC60871-1, and IEEE Std 1036-2010, and IEEE Std. C37.99-2000. In addition a number of books, standards and other publications have been used to understand how capacitors, relays and the general protection systems are influenced by harmonics and possible remedies when overloading becomes an issue. Together with the limits found in standards and regulations measurements from PQSCADA was used as an overview of what can be considered normal operation.A model was created in ATPDraw based on the datasheet and a relay plan of a 420kV capacitor bank. The system is constructed for this simulation and does not represent one particular real life system. Further on it was used to test the difference between an unfiltered, single-tuned, and a c-type filtered capacitor bank. Simulations with both injection of harmonic current from the inductive load and simulations with a voltage source at the grid side dimensioned according to the regulation limits were conducted. It was shown that a system with multiple capacitive and inductive components will have multiple resonance frequencies. As the short-circuit power varies these will fluctuate and might occur at a characteristic harmonic. The consequent amplification of the current will in many instances be large enough to overload the capacitor bank. A single-tuned filter solution will lower the resonance frequency but it is dependent on the short-circuit impedance and will thus vary. Using a c-type filter is more complex than a single-tuned but it results in a filter that is independent of the short-circuit impedance. The amplification of currents at the resonance frequency is also smaller with the c-type filter.Aliasing of high harmonics can possibly cause nuisance tripping of the over current protection if they are not filtered out. It is therefore important to know what harmonics will be present and specify a relay that can handle such harmonics. Although applying a filter is normally intended to avoid actual overloading it can also be applied to lower the loading and making it easier for the relay to separate the particular situations where faults have occurred

The economic impacts of digitalization through an extended input-output model: theory and application to Tunisia

The paper contributes to the existing literature related to the economics of technology adoption. It focuses on the impacts of digitalization on the economic growth through various channels, mainly via investment and total factor productivity. Firstly, we begin by extending the Input-Output (IO) model of Kratena (2019) to enable the simulations of the macroeconomic impacts of digitalization. Secondly, we apply the model to the Tunisian Economy. It is found that the three main priority sectors to digitalize in Tunisia are the public administration, the education, and the construction sectors. Their full digitalization costs 1.8% of the GDP over 2021-2026 and leads to the same gain in terms of GDP growth, and to the creation of about 23 000 jobs per year over the same period. Besides, from 2027 and beyond and under the (restrictive) assumption of no extensive growth of the digitalized sectors, the productivity gains leads to 0.4% additional GDP growth and to the destruction of jobs equivalent to 0.64% of the active population, yearly

High-speed asynchronous optical sampling with sub-50fs time resolution

We report an ultrafast time-domain spectroscopy system based on high-speed asynchronous optical sampling operating without mechanical scanner. The system uses two 1 GHz femtosecond oscillators that are offsetstabilized using high-bandwidth feedback electronics operating at the tenth repetition rate harmonics. Definition of the offset frequency, i.e. the timedelay scan rate, in the range of a few kilohertz is accomplished using directdigital-synthesis electronics for the first time. The time-resolution of the system over the full available 1 ns time-delay window is determined by the laser pulse duration and is 45 fs. This represents a three-fold improvement compared to previous approaches where timing jitter was the limiting factor. Two showcase experiments are presented to verify the high time-resolution and sensitivity of the system