Device Modeling and Circuit Design of Neuromorphic Memory Structures

The downscaling of CMOS technology and the benefits gleaned thereof have made it the cornerstone of the semiconductor industry for many years. As the technology reaches its fundamental physical limits, however, CMOS is expected to run out of steam instigating the exploration of new nanoelectronic devices. Memristors have emerged as promising candidates for future computing paradigms, specifically, memory arrays and neuromorphic circuits. Towards this end, this dissertation will explore the use of two memristive devices, namely, Transition Metal Oxide (TMO) devices and Insulator Metal Transition (IMT) devices in constructing neuromorphic circuits. A compact model for TMO devices is first proposed and verified against experimental data. The proposed model, unlike most of the other models present in the literature, leverages the instantaneous resistance of the device as the state variable which facilitates parameter extraction. In addition, a model for the forming voltage of TMO devices is developed and verified against experimental data and Monte Carlo simulations. Impact of the device geometry and material characteristics of the TMO device on the forming voltage is investigated and techniques for reducing the forming voltage are proposed. The use of TMOs in syanptic arrays is then explored and a multi-driver write scheme is proposed that improves their performance. The proposed technique enhances voltage delivery across the selected cells via suppressing the effective line resistance and leakage current paths, thus, improving the performance of the crossbar array. An IMT compact model is also developed and verified against experiemntal data and electro-thermal device simulations. The proposed model describes the device as a memristive system with the temperature being the state variable, thus, capturing the temperature dependent resistive switching of the IMT device in a compact form suitable for SPICE implementation. An IMT based Integrate-And-Fire neuron is then proposed. The IMT neuron leverages the temperature dynamics of the device to deliver the functionality of the neuron. The proposed IMT neuron is more compact than its CMOS counterparts as it alleviates the need for complex CMOS circuitry. Impact of the IMT device parameters on the neuron\u27s performance is then studied and design considerations are provided

What, you care? : the effective use of aversive evoking content in viral videos for advocacy group advertising

Title from PDF of title page (University of Missouri--Columbia, viewed on March 6, 2013).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Thesis advisor: Dr. Paul BollsIncludes bibliographical references.M.A. University of Missouri--Columbia 2012."December 2012."The current research examined the use of aversive evoking content in advocacy viral videos and how the use of such content affected a person's intention to forward the message. In a 3 (Intensity) x 3 (Video) x 3 (Order) repeated measures design, participants watched nine viral video ads that varied in levels of aversive evoking content. The results of this research suggest that varying levels of aversive evoking content have significant effects on cognitive resources allocated to encoding, arousal, intention to forward, and persuasion. Implications for the construction of viral videos are discussed

Modeling and design of memristor-based fuzzy systems

The incessant down scaling of CMOS technology has been the main driving force for the semiconductor industry over the past decades. Yet, as process variations and leakage current continue to exhibit more pronounced effect with every technology node, this down scaling paradigm is expected to saturate in the few coming years. This prospect has led the research community to seek new technologies to surpass those challenges. Amongst the promising candidates is the memristor technology recently characterized by HP Labs. The miniaturized features and the peculiar behavior exhibited by the memsitor make it very well suited in some applications. For instance, memrsitors are used as memory cells in state-of-the-art memories known as Resistive RAMs in which the non-volatility of the memristor is exploited. The programmable nature of the memristor has made it a powerful candidate in neuromorphic and fuzzy systems that, in essence, go beyond the classical Von Neumann computing paradigm. In such systems, ideas from Artificial Intelligence, that for so long have been implemented on the software level, are implemented as electronic circuitry which renders benefits such as compact area and reduced power consumption. This work focuses on memrsitor-based Fuzzy applications. First, memristor-based Min-Max circuit used in the Fuzzy Inference engine is analyzed. It is proven that memrsitor-based Min-Max circuits can be extended to an arbitrary number of inputs ‘N’ under the proper design constraints. In addition, the effect of the memristor threshold is analyzed and a closed form expression is derived. It is shown that, for a given memristor with a specific OFF resistance and threshold current, there is a trade-off between the size and the resolution of the circuit. Then, a memrsitor-based Defuzzifier circuit is proposed. A major challenge in Defuzzifiers is their area occupancy due to the use of Multiplier and Divider circuits. In this design, the memrsitor analog programmability is leveraged to reduce the multiplication operation into simple Ohm’s Law which alleviates the need for dedicated hardware for multiplier circuit and, accordingly, reduces the area occupancy

Cooperation and Underlay Mode Selection in Cognitive Radio Network

In this research, we proposes a new method for cooperation and underlay mode selection in cognitive radio networks. We characterize the maximum achievable throughput of our proposed method of hybrid spectrum sharing. Hybrid spectrum sharing is assumed where the Secondary User (SU) can access the Primary User (PU) channel in two modes, underlay mode or cooperative mode with admission control. In addition to access the channel in the overlay mode, secondary user is allowed to occupy the channel currently occupied by the primary user but with small transmission power. Adding the underlay access modes attains more opportunities to the secondary user to transmit data. It is proposed that the secondary user can only exploits the underlay access when the channel of the primary user direct link is good or predicted to be in non-outage state. Therefore, the secondary user could switch between underlay spectrum sharing and cooperation with the primary user. Hybrid access is regulated through monitoring the state of the primary link. By observing the simulation results, the proposed model attains noticeable improvement in the system performance in terms of maximum secondary user throughput than the conventional cooperation and non-cooperation schemes

ETHNIC CONCENTRATION AREAS IN NEIGHBOURHOOD PERSPECTIVE IN ENSCHEDE, THE NETHERLANDS

Previous studies suggest that measuring ethnic segregation at a disaggregated level allows capturing variability of ethnic concentration areas within a city. However, many ignore the relative locations of each neighbourhood to identify ethnic concentration areas. It causes misidentification of ethnic concentration areas. Using the 2009 population data of Enschede, this study investigated the concentration areas at postcode level. The "scale of the neighbourhood" represents the extent of concentration influenced by population in neighbouring postcodes. Using composite population at different scales of neighbourhood, it was revealed that concentration areas at sub-city level are characterized by isolation and clustering dimensions. Few postcodes are Turkish or Moroccan concentration areas which are located outside the city center. Small number of cluster and isolated area indicates that the ethnic concentration in Enschede is relatively low. The study has advanced the hypothesis about segregation measurement, that spatial proximity to neighbouring areas has a large impact on variability of ethnic segregation. Banyak studi menyatakan bahwa pengukuran segregasi etnis pada tingkat rinci dapat menggambarkan variabilitas area konsentrasi dalam suatu kota. Namun, banyak studi mengesampingkan lokasi di lingkungan sekitar untuk mengidentifikasi area konsentrasi. Hal itu menyebabkan kesalahan dalam mengidentifikasi konsentrasi area. Studi ini bertujuan mengidentifikasi area konsentrasi pada tingkat area kodepos dengan menggunakan data populasi Kota Enschede tahun 2009. "Skala Lingkungan" digunakan untuk mewakili luasan konsentrasi yang terpengaruh akibat kumpulan populasi tertentu di sekitar areanya. Beberapa area kodepos yang terletak di luar pusat kota merupakan area konsentrasi keturunan Turki atau Moroko. Sedikitnya jumlah area terisolasi dan area klaster mengindikasikan bahwa konsentrasi etnis di Enschede adalah rendah. Studi ini telah memutakhirkan hipotesis mengenai pengukuran segregasi. dimana jarak menuju area sekitar mempunyai dampak besar pada variabilitas dari segregasi etnis

ETHNIC CONCENTRATION AREAS IN NEIGHBOURHOOD PERSPECTIVE IN ENSCHEDE, THE NETHERLANDS

Previous studies suggest that measuring ethnic segregation at a disaggregated level allows capturing variabilityof ethnic concentration areas within a city. However, many ignore the relative locations of each neighbourhoodto identify ethnic concentration areas. It causes misidentification of ethnic concentration areas. Using the 2009population data of Enschede, this study investigated the concentration areas at postcode level. The “scale of theneighbourhood” represents the extent of concentration influenced by population in neighbouring postcodes.Using composite population at different scales of neighbourhood, it was revealed that concentration areas atsub-city level are characterized by isolation and clustering dimensions. Few postcodes are Turkish or Moroccanconcentration areas which are located outside the city center. Small number of cluster and isolated areaindicates that the ethnic concentration in Enschede is relatively low. The study has advanced the hypothesisabout segregation measurement, that spatial proximity to neighbouring areas has a large impact on variabilityof ethnic segregation

Good things come in small packages: New trends in acquisition of remotely-sensed data

Not available

Evaluation of clinical outcome of laparoscopic hysterectomy versus open abdominal hysterectomy with pelvic lymphadenectomy in endometrial carcinoma early stage

Background: the aim of this study was to compare the operative, post-operative, and the oncological short-term outcomes of laparoscopic hysterectomy with lymphadenectomy and open abdominal hysterectomy with lymphadenectomy for early-stage endometrial cancer.Methods: 80 patients with clinical stage I endometrial cancer were enrolled in this trial; they were divided according to their selection of the method of intervention after counselling into two groups: total laparoscopic hysterectomy with pelvic lymphadenectomy group and total abdominal hysterectomy with pelvic lymphadenectomy group.Results: The mean operative time in the TLH group was 140.85± 10.033 minutes and was 118.45±12.713 minutes in the TAH group (p<0.001). The mean blood loss in the TLH group was 127.5±42.9 ml and 220.5± 84.82 ml in TAH group (p<0.001). The mean duration of postoperative ileus was 12.8±5.022 hours in the TLH group, and it was 22.3±5.573 hours in the TAH group (p<0.001). The mean time of hospital stay in the TLH group was 26.7±5.667 hours and in the TAH group was 116.4± 17.31 hours (p<0.001).Conclusions: Complete surgical staging of endometrial cancer can be performed using laparoscopy as an alternative to routine open method with similar efficacy about nodal retrieval and complication rate, and better operative and postoperative compliance in means of blood loss, ileus and hospital stay which may have an implication on cost saving in the medical service. Lymphadenectomy can be omitted in low-risk cases of endometrial cancer