Dissertations / Theses on the topic 'On-off current'

Zum ersten Mal konnte die kohärente Erzeugung von ultrakurzen Pulsen mit Feld stärken im MV/cm Bereich mit einem Spektralbereich von 0.1-30 THz im organischen Kristall DSTMS. Kohärente mehrdimensionale Terahertzspektroskopie (CMTS) hat sich zu einer wichtigen Methode zur Untersuchung der niederenergetischen Anregungen von Halbleitern and deren kohärenter Dynamik entwickelt. Eine neuartige CMTS Methode mit drei phasenstarren, zueinander zeitverzögerten Terahertzpulsen wurde entwickelt. Sie beruht auf der kollinearen Wechselwirkung der Pulse mit der Probe, sodass verschiedene Ordnungen des nichtlinearen Signals in gleicher Richtung emittiert werden und deshalb gleichzeitig gemessen werden können. Amplitude und Phase des nichtlinearen Signals können durch elektro-optisches Abtasten vermessen werden, wodurch die zeitliche Entwicklung der kohärenten Wechselwirkungen in Echtzeit untersucht werden kann. CMTS erlaubt zusätzlich die eindeutige Zerlegung des nichtlinearen Signals in die verschiedenen nichtlinearen Ordnungen in der jeweiligen mehrdimensionalen Frequenzdomäne. Die nichtlineare, nicht-resonante Antwort zweier undotierter Halbleiter, des Ferroelektrikums Lithiumniobat (LiNbO3) und Indiumantimonids (InSb) kann mit dieser neuartigen Methode untersucht werden. In LiNbO3 wird das nichtlineare Signal durch einen Femtosekunden nichtlinearen Verschiebestrom (SC) hervorgerufen. SC wird durch die gebrochene Inversionssymmetrie des Kristalls in Verbindung mit einer ultraschnellen Dephasierung der feldinduzierten, kohärenten interband-Polarisation hervorgerufen. Die Dephasierung der interband-Polarisation erlaubt das Tunneln von Elektronen vom Valenzband in das Leitungsband. In InSb wird das kohärente Signal durch sowohl zwei-Phonen als auch zwei-Photonen interband-Anregungen erzeugt. Die impulsive Anregung einer kohärenten zwei-Phononen Polarisation wird durch das große Übergangsdipolmoment von InSb verstärkt, was zu deutlich größeren Amplituden der Polarisation als im linearem Regime führt.<br>For the first time, the coherent generation of ultrashort MV/cm field pulses with a spectrum covering the frequency range 0.1-30 THz is demonstrated in the organic crystal DSTMS. Coherent multidimensional terahertz spectroscopy (CMTS) has become a prominent technique for, e.g., driving low-energy excitations in semiconductors and monitoring their coherent dynamics. A novel CMTS technique using three phase-locked inter-delayed THz pulses is implemented. It relies on a collinear interaction of the pulses with a sample, so that different contributions to the nonlinear signal are emitted in the same direction, and thus can be measured all at once. Phase-resolved detection by electro-optic sampling allows for measuring amplitude and absolute phase of the nonlinear signal, thereby enabling to investigate the evolution of coherent interactions between quantum excitations in real time. In CMTS, the nonlinear signal is dissected into the distinct nonlinear contributions in the corresponding multidimensional frequency domain. This novel technique is applied to study the nonlinear off-resonant response of two undoped bulk semiconductors, the wide-bandgap ferroelectric lithium niobate (LiNbO3) and the narrow-bandgap indium antimonide (InSb). In LiNbO3, the nonlinear signal is generated by a femtosecond nonlinear shift current (SC), a distinctive characteristic of the bulk photovoltaic effect. The SC stems from the lack of inversion symmetry and the ultrafast dephasing of the field-induced interband coherent polarization due to a sufficiently high decoherence rate, which enables tunneling of electrons from the valence to the conduction band. In InSb, the nonlinear signal is caused by the coherent response on both the two-phonon and two-photon interband excitations. The impulsive generation of the two-phonon coherent polarization is enhanced by the large interband transition dipole of InSb, resulting in much larger polarization amplitudes than in the regime of linear response.

Philosophiae Doctor - PhD<br>Although jellyfish are recognised recently as key components that can influence ecosystem functioning and trophic flows in the northern Benguela upwelling ecosystem, the number of published studies on their abundance, seasonality, life history and ecological roles off Namibia is strictly limited. Chrysaora fulgida is one of the most common and conspicuous medusae in the plankton off Namibia, and has flourished in the region, following the decline of the pilchard fishery at the end of the 1960s. It is said that their biomass (together with Aequorea forskalea) exceed that of the commercially important fish stocks off Namibia. In addition, this species is also capable of forming large swarms in northern Benguela where they are a nuisance to fisheries operations. The objective of this study is to try and fill gaps regarding our knowledge of the biology and ecology of Chrysaora fulgida off Namibia, with a view to improve our understanding of its success in the northern Benguela ecosystem. In the Chapter 1, a general overview on the current knowledge and population dynamics of jellyish blooms and their ecology is compiled. Other key topics of the thesis such as jellyfish life cycles and their reproduction are also introduced. Chapter 2 investigates the temporal changes in the jellyfish community in Walvis Bay over a 23-month period from biweekly plankton samples. All twelve of the recovered taxa were characteristically neritic, and included meroplanktonic Hydrozoa and Scyphozoa, as well as cydippid ctenophores and shallow water siphonophores. Whilst, ephyrae of Chrysaora fulgida were dominant overall, and peaked in abundance during mid-spring (Year 2012: 168 933 ind. 100 m-3) and late winter (Year 2013: 23 389 ind. 100 m-3), they were not present all year round, being replaced (in part) by Obelia in summer and autumn, Bougainvillia in spring and summer, and Muggiaea atlantica in summer. Seasonal changes in the composition and structure of the community were driven primarily by bottom water temperature and day length (explaining 24% of the variability in community structure), with wind speed and moon illumination playing a secondary role. The recruitment of ephyrae of C. fulgida to the plankton off Walvis Bay is confirmed not to be continuous throughout the year. Chapter 3 present the first detailed investigation on the identification, morphological development and growth of wild caught ―ephyrae‖ of the scyphozoan Chrysaora fulgida and Chrysaora africana in Walvis Bay, off Namibia. Concrete morphological dissimilarities are documented to distinguish C. africana from C. fulgida, despite the limited sample size of C. africana: coloration differences and the presence/absence of branched canals on the periphery of velar and rhopalial canal tips. In the case of C. fulgida the morphological development from an ephyra (Stage 0) to a juvenile medusa could be described successfully in six stages, whilst missing stages were noted for C. africana. In general, the development of ephyrae described here agrees with patterns described for other species in the genus from elsewhere. The ephyrae stages of C. fulgida illustrated a low overall growth rate (4.33 and 3.45% d-1, respectively) and longer ontogenic development (~164 days), respectively, than most other jellyfish species. Through the histological examination of medusa gonads, Chapter 4 investigates the sexual reproduction and maturation of both Chrysaora species, collected off Walvis Bay, Namibia. Both species were non-brooding, gonochoristic, displayed a 1:1 sex ratio and exhibited no clear sexual dimorphism features. Gametogenesis in both species was similar to that displayed by other Discomedusae, whilst some differences in gonad maturity were evident between them – Chrysaora fulgida displayed aseasonal, reproductive heterogeneity (maturing at ~300 mm diameter) and individuals were semelparous, whilst C. africana appeared strongly seasonal but iteroparous. Through stable isotope analysis (𝛿13C, 𝛿15N and C:N ratios), Chapter 5 examines the presence of tissue, ontogenetic, seasonal, spatial and interspecific variability in medusae of Chrysaora fulgida and Chrysaora africana off Walvis Bay, in the northern Benguela, Namibia. This study did not only illustrate size-associated shifts in trophic ecology, but also revealed spatial, inter-species and some tissue differences in the northern Benguela upwelling system. Size would appear to be the over-riding factor that influences the isotope signatures of Chrysaora fulgida; size being linked in turn to space. A clear negative relationship is illustratred between 𝛿15N and individual size for two scyphozoans (C. fulgida and C. africana) off central Namibia, indicating that larger jellyfish feed lower down the food chain than smaller ones in both species. This is explained by the need and ability of ephyrae and small medusae to access the microbial food web which consists of many trophic steps and hence numerous opportunities for enrichment of nitrogen isotopes, resulting in higher 𝛿15N values of smaller individuals. Chapter 6 provides a synthesis of the main findings of the thesis, and makes recommendations on ways that the research can be carried forward.<br>2020-08-31

Thesis (M.S. in Applied Mathematics)--Naval Postgraduate School, December 2007.<br>Thesis Advisor(s): Giraldo, Francis ; Paduan, Jeffrey. "December 2007." Description based on title screen as viewed on January 18, 2008. Includes bibliographical references (p. 69). Also available in print.

[Truncated abstract] The role of marine microzooplankton in aquatic food webs has been studied in most regions of the world’s oceans, with the exception of the subtropical/temperate eastern Indian Ocean. This thesis addresses this gap in knowledge by investigating microzooplankton from five stations on a cross continental shelf transect and in two mesoscale features ∼300 km offshore of south west Western Australia. My primary focus was to measure and evaluate microzooplankton community change over space and time and their impact on phytoplankton on a cross shelf transect, sampling five stations from February 2002 December 2004 as part of a large multidisciplinary investigation into the pelagic ecosystem on the shelf (Chapter 2). This transect was named the Two Rocks transect. I also investigated an eddy pair (Chapter 5), which had originated from water in the vicinity of the Two Rocks transect, also undertaken as part of a larger study, investigating biophysical coupling within mesoscale eddies off south west Western Australia . . . The distribution of mixotrophic cells differed across the transect. Those mixotrophs that use photosynthesis as their primarily energy source exploited nutrient limited conditions inshore consuming particles, while mixotrophs that are primarily heterotrophic survived low prey conditions offshore by photosynthesizing. In the eddies, the grazing behaviour of microzooplankton was dependent on the specific phytoplankton assemblage in each eddy. The warm core eddy had a resident population of diatoms that were consumed by heterotrophic dinoflagellates present in high numbers. The cold core eddy had a warm cap which prevented upwelled water reaching the surface, resulting in stratification and a very active microbial food web, particularly in the surface.

Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>A complete study of a topology resulting from a combination of two Forward structures, attached to the same magnetic core of a transformer and operating as a Full-Bridge converter is presented. In order to reduce the switching losses and the electromagnetic interference, a soft commutation cell that provides ZCS commutation of all the switches is implemented. This converter limits the current on the main switches at the load current because diverts the sinusoidal half cycle to a auxiliary switch. This way, a new Double Forward On-Off ZCS was developed.<br>Um estudo completo de uma topologia, resultante de uma combinação entre duas estruturas Forward, acopladas ao mesmo núcleo magnético de um transformador, e operando como um conversor Full-Bridge, é apresentado. Com o objetivo de reduzir as perdas por chaveamento e a interferência eletromagnética, uma célula de comutação não dissipativa, que fornece uma comutação ZCS para todas as chaves do conversor é implementada. Este conversor limita a corrente nas chaves principais ao valor da corrente nominal, pois desvia o semiciclo senoidal da corrente ressonante para uma chave auxiliar. Deste modo, um novo conversor Duplo Forward On-Off ZCS é obtido.<br>Mestre em Ciências

Multi functional health monitoring wearable devices are quite prominent these days. Usually these devices are battery-operated and consequently are limited by their battery life (from few hours to a few weeks depending on the application). Of late, it was realized that these devices, which are currently being operated at fixed voltage and frequency, are capable of operating at multiple voltages and frequencies. By switching these voltages and frequencies to lower values based upon power requirements, these devices can achieve tremendous benefits in the form of energy savings. Dynamic Voltage and Frequency Scaling (DVFS) techniques have proven to be handy in this situation for an efficient trade-off between energy and timely behavior. Within imec, wearable devices make use of the indigenously developed MUSEIC v2 (Multi Sensor Integrated circuit version 2.0). This system is optimized for efficient and accurate collection, processing, and transfer of data from multiple (health) sensors. MUSEIC v2 has limited means in controlling the voltage and frequency dynamically. In this thesis we explore how traditional DVFS techniques can be applied to the MUSEIC v2. Experiments were conducted to find out the optimum power modes to efficiently operate and also to scale up-down the supply voltage and frequency. Considering the overhead caused when switching voltage and frequency, transition analysis was also done. Real-time and non real-time benchmarks were implemented based on these techniques and their performance results were obtained and analyzed. In this process, several state of the art scheduling algorithms and scaling techniques were reviewed in identifying a suitable technique. Using our proposed scaling technique implementation, we have achieved 86.95% power reduction in average, in contrast to the conventional way of the MUSEIC v2 chip’s processor operating at a fixed voltage and frequency. Techniques that include light sleep and deep sleep mode were also studied and implemented, which tested the system’s capability in accommodating Dynamic Power Management (DPM) techniques that can achieve greater benefits. A novel approach for implementing the deep sleep mechanism was also proposed and found that it can obtain up to 71.54% power savings, when compared to a traditional way of executing deep sleep mode.<br>Nuförtiden så har multifunktionella bärbara hälsoenheter fått en betydande roll. Dessa enheter drivs vanligtvis av batterier och är därför begränsade av batteritiden (från ett par timmar till ett par veckor beroende på tillämpningen). På senaste tiden har det framkommit att dessa enheter som används vid en fast spänning och frekvens kan användas vid flera spänningar och frekvenser. Genom att byta till lägre spänning och frekvens på grund av effektbehov så kan enheterna få enorma fördelar när det kommer till energibesparing. Dynamisk skalning av spänning och frekvens-tekniker (såkallad Dynamic Voltage and Frequency Scaling, DVFS) har visat sig vara användbara i detta sammanhang för en effektiv avvägning mellan energi och beteende. Hos Imec så använder sig bärbara enheter av den internt utvecklade MUSEIC v2 (Multi Sensor Integrated circuit version 2.0). Systemet är optimerat för effektiv och korrekt insamling, bearbetning och överföring av data från flera (hälso) sensorer. MUSEIC v2 har begränsad möjlighet att styra spänningen och frekvensen dynamiskt. I detta examensarbete undersöker vi hur traditionella DVFS-tekniker kan appliceras på MUSEIC v2. Experiment utfördes för att ta reda på de optimala effektlägena och för att effektivt kunna styra och även skala upp matningsspänningen och frekvensen. Eftersom att ”overhead” skapades vid växling av spänning och frekvens gjordes också en övergångsanalys. Realtidsoch icke-realtidskalkyler genomfördes baserat på dessa tekniker och resultaten sammanställdes och analyserades. I denna process granskades flera toppmoderna schemaläggningsalgoritmer och skalningstekniker för att hitta en lämplig teknik. Genom att använda vår föreslagna skalningsteknikimplementering har vi uppnått 86,95% effektreduktion i jämförelse med det konventionella sättet att MUSEIC v2-chipets processor arbetar med en fast spänning och frekvens. Tekniker som inkluderar lätt sömn och djupt sömnläge studerades och implementerades, vilket testade systemets förmåga att tillgodose DPM-tekniker (Dynamic Power Management) som kan uppnå ännu större fördelar. En ny metod för att genomföra den djupa sömnmekanismen föreslogs också och enligt erhållna resultat så kan den ge upp till 71,54% lägre energiförbrukning jämfört med det traditionella sättet att implementera djupt sömnläge.

碩士<br>國立交通大學<br>顯示科技研究所<br>98<br>High performance OTFT has been studied for many years. The most important issue is low cost, high performance, and stability. By the mature process of MOSFET, OTFT has been improved a lot, but unfortunately most of them are fabricated on silicon base or thermal oxide, this is expensive and not suit for low cost requirement. For future application, we fabricated a vertical organic transistor, which is similar to vacuum tube. We achieved a comparable performance of on/off ratio, and lower driving voltage, increasing output current compared to the FET made by same P3HT materials. Here we purposed three kinds of SCLT devices. First is bottom injection SCLT, which owns highest on/off ratio. And then we discussed the impact of grid position in the SCLT space. The second is top injection which is good for new ambient material, because we won’t be limit by ITO work function. Third is simplified from the first structure, we use SAM to replace insulator layer, and use in solvent annealing SCLT devices, which has great output current but higher grid leakage current. By using SAMs treatment, we get higher current gain. Here we discussed a lot of information and process about SCLT, it’s useful for future developing.

碩士<br>長庚大學<br>光電工程研究所<br>95<br>More researches are investigated on organic thin film transistor (OTFT) due to the development of flexible electronics. The polymer thin film transistor has the advantage of its simple process. However, it has some drawbacks such as higher threshold voltage and lower on/off current ratio. These disadvantages limit its applications on circuit. In order to improve the electrical performance, we focus our attentions on the three components of device such as dielectrics, electrodes, and active materials. First, we use Al2O3 and HfO2 as dielectrics. Devices with the dielectric layer of higher dielectric constant lead to lower threshold voltage. Devices with the dielectric of HfO2 have threshold voltage lower than 3V. Next, we try to limit the gate leakage current and to enhance the carrier injection current by using different metals as electrodes in device. We use Al and Al/Au as gate and contact electrodes, respectively. The gate leakage current will be controlled less than 10-8A and the performance of carrier injection current will also be improved. Finally, we choose rr-P3HT dissolved in various solvents, p-xylene, chloroform, and 1,2,4-trichlorobenzene as active materials. We used spin coating system to deposit the rr-P3HT films. The results show that chloroform devices have a lower gate leakage current and the threshold voltage of ~2V, mobility of 3 10-3 cm2/V-s, driving current of 1uA, and the on/off current ratio of 186 can be extracted from measurements.

碩士<br>國立中央大學<br>電機工程學系<br>104<br>Since the channel current of MOSFETs is governed by the drift-diffusion mechanism, their subthreshold swing is limited to 60 mV/decade or higher at room temperature. Whereas, tunnel field-effect transistors (TFETs), whose current conduction is based on quantum mechanical band-to-band tunneling mechanism that gives a sub-60 mV/decade subthreshold slope, have been considered a promising energy-efficient device for low voltage and low power circuits. Since the inception of this proposal, TFETs based on Si/Ge material system have been demonstrated by a few groups. However, the devices are limited by either a low on-current or a high off-current due to the unfavored bandgap and band alignment of Si/Ge. Attention is then switched to narrow bandgap III-V compounds as the aforementioned issues could be solved by band gap engineering. This study is focused on III-V TFETs, aiming at the design and analysis of a normally-off TFET with high-on current. It covers the setup of a physical model in the TCAD tool, the effects of band alignments, gate position, and doping concentration on the electrical properties of the type-II band lineup GaAsxSb1-x/InyGa1-yAs heterojunction TFETs. Our simulation indicate that although GaAsxSb1-x/InyGa1-yAs TFETs could be designed to have a small Ebeff at the hetero-interface for high-on current, their high off-state current manifest themselves unacceptable for practical use. To solve this issue, a GaAs0.51Sb0.49/InAs/In0.53Ga0.47As TFET with an InAs quantum well (QW) is proposed to reduce the Ebeff from 0.5 eV to 0.1 eV at the source/channel interface, leading to an on-state current increasing from 27 A/m to 89 A/m at VGS=VDS=0.5 V, while the IOFF still maintains on the order of 10-7 μA/μm at VGS=0 V, simultaneously. To improve the device performance further and increase noise immunity at the gate, a graded InGaAs QW is designed to replace the InAs QW in the GaAs0.51Sb0.49/In0.53Ga0.47As TFET above. On this design, a normally-off TFET with high on-state current and threshold voltage greater than 50 mV has been achieved.

碩士<br>國立中正大學<br>勞工關係學系碩士在職專班<br>106<br>The changes in labor’s right have great impacts on labors in Taiwan. The amended Labor Standard Act on “one fixed day off and one flexible rest day” regulations have impacts on the catering industry which is normally very labor intensive with low wages and long working hours. This change has caused an increase in resting days, inflexibility of work schedules and which, in turn, increases in labor cost, additional overtime pay and increases in sales prices. It is evident that this change did not bring any benefits to all three parties, namely, the labors, the employers and the government. In 2018, the government revised a new version of “one fixed day off and one flexible rest day” again with regards to a flexible arrangement on overtime, job schedules, work shifts, special resting days, and resting days real calculation of overtime work. It is yet to know if this new version will bring a satisfactory outcome to protect labor’s right. It was mentioned that this revised regulation will address the need for Taiwan to go global and an increasing awareness in labor’s rights. But there was a very little study on the impact of the revised regulations on the employer and labor’s rights. Therefore, this study analyzes the impact on the catering industry after implementing the “one fixed day off and one flexible rest day” regulation. This study uses the qualitative method in analyzing the subjects. It uses a systematic analysis on the existing literature for international labor law, Taiwan Labor Act, regulations on working hours and historical background of labor disputes. After the consolidation of related literature, in-depth semi-structured interviews with employer, labors, and practitioners are conducted to summarize the key findings of this study. Through the key findings, this study hopes to understand the situations of existing implementation on the revised labor law and to find the corresponding solutions so as to be used for practice management and for future research. Keywords: one fixed day off, one flexible rest day, working hour regulation, flexible working hours, Taiwan Labor Act, food industry

碩士<br>國立中興大學<br>光電工程研究所<br>107<br>In recent years, many studies on junctionless transistors (JLT) have been published. Among these papers, the gate all around (GAA) structure showed a superior performance. The L-typed double gated device structure is fabricated. There are two parts in this thesis. First, the L-type double gated device structure is fabricated and the basic electrical characteristics are measured and compared with one another. The dielectric layer of top gate is SiO2, and the one of bottom gate is Si3N4. The top gate is heavily doped with phosphorus. The bottom gate is heavily doped with phosphorus or boron. Both top-gate and bottom-gate are connected and measured, which is similar to gate-all-around structure. The L-type double gated device structure has a good performance in electrical characteristic, and the performance shows the subthreshold swing (S.S.)less than 200 mV/dec. and the ION/IOFF current ratio larger than 106. The different doped Poly-Si bottom gate materials induce different work function differences, which leads to a threshold voltage of -0.793 V in the N+ type device, and a 0.611 V in the P+ type device. Due to the work function of the P+ type is larger, so that the threshold voltage shows a more positive offset. The second part is to discuss the negative drain current of the thin-film transistors operated in the off-state. By measurement techniques and simulating the hole densities in the channel by TCAD, a new leakage current mechanism is proposed, which is different from conventional gate induced drain leakage current (GIDL) mechanism. The mechanism of the negative drain current in the off-state is described as follow: In the sweeping of gate voltage from -5 V to +8 V, when the electric field in the channel decreases, the hole densities decrease and the change value is large, which leads to a transient negative drain current. When the transient negative current is greater than the GIDL, the region of the negative drain current will be measured. In the sweeping of gate voltage from +8 V to -5 V, the transient positive current will happen due to the increase of the hole densities in the channel. Therefore, no negative drain current region can be measured. These measurement data reconfirms that the proposed mechanism is correct.

University of Technology Sydney. Faculty of Business.<br>This thesis provides evidence on two research questions regarding the independent influence of CFOs on firms’ financial reporting. Chapter 2 examines the effect of relative CFO power on financial reporting integrity and Chapter 3 investigates changes in financial reporting integrity surrounding routine versus non-routine CFO turnover. The primary proxy for financial reporting integrity is the recognition of non-current asset impairments in response to indicators of impairment which remains a key focus area of regulatory scrutiny and inquiry. Based on a sample of 1,781 Australian firm-years over the period 2007 to 2015, the evidence in Chapter 2 illustrates that firms record less timely non-current asset impairments (in the presence of adverse economic circumstances and worsening financial performance) as the degree of relative CFO power increases. 463 Australian CFO changes between 1 July 2007 and 30 June 2015 are examined in Chapter 3 which finds that new CFOs use asset write-offs as a vehicle to engage in ‘big bath’ accounting in the year of a non-routine appointment. The results in Chapter 3 also indicate that (irrespective of the nature of the CFO change) CFOs bias earnings upward in the period prior to their departure. The results are consistent with respect to a number of sensitivity tests and alternative proxies for financial reporting integrity. While CFOs, therefore, have the capacity to exert independent influence over firms’ reported results the balance of findings suggest that CFOs act in self-interest. In other words, CFOs’ financial reporting decisions are opportunistically motivated by their own compensation and career incentives and the personal costs they face. The evidence in this thesis is, therefore, contrary to the view that CEO pressure is a primary driver of CFOs’ involvement in earnings manipulation.