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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Protograph-Based Generalized LDPC Codes: Enumerators, Design, and Applications

Abu-Surra, Shadi Ali January 2009 (has links)
Among the recent advances in the area of low-density parity-check (LDPC) codes, protograph-based LDPC codes have the advantages of a simple design procedure and highly structured encoders and decoders. These advantages can also be exploited in the design of protograph-based generalized LDPC (G-LDPC) codes. In this dissertation we provide analytical tools which aid the design of protograph-based LDPC and G-LDPC codes. Specifically, we propose a method for computing the codeword-weight enumerators for finite-length protograph-based G-LDPC code ensembles, and then we consider the asymptotic case when the block-length goes to infinity. These results help the designer identify good ensembles of protograph-based G-LDPC codes in the minimum distance sense (i.e., ensembles which have minimum distances grow linearly with code length). Furthermore, good code ensembles can be characterized by good stopping set, trapping set, or pseudocodeword properties, which assist in the design of G-LDPC codes with low floors. We leverage our method for computing codeword-weight enumerators to compute stopping-set, and pseudocodeword enumerators for the finite-length and the asymptotic ensembles of protograph-based G-LDPC codes. Moreover, we introduce a method for computing trapping set enumerators for finite-length (and asymptotic) protograph-based LDPC code ensembles. Trapping set enumerators for G-LDPC codes represents a more complex problem which we do not consider here. Inspired by our method for computing trapping set enumerators for protograph-based LDPC code ensembles, we developed an algorithm for estimating the trapping set enumerators for a specific LDPC code given its parity-check matrix. We used this algorithm to enumerate trapping sets for several LDPC codes from communication standards. Finally, we study coded-modulation schemes with LDPC codes and pulse position modulation (LDPC-PPM) over the free-space optical channel. We present three different decoding schemes and compare their performances. In addition, we developed a new density evolution tool for use in the design of LDPC codes with good performances over this channel.
122

Capacity estimation and code design principles for continuous phase modulation (CPM)

Ganesan, Aravind 30 September 2004 (has links)
Continuous Phase Modulation is a popular digital modulation scheme for systems which have tight spectral efficiency and Peak-to-Average ratio (PAR) constraints. In this thesis we propose a method of estimating the capacity for a Continuous Phase Modulation (CPM) system and also describe techniques for design of codes for this system. We note that the CPM modulator can be decomposed into a trellis code followed by a memoryless modulator. This decomposition enables us to perform iterative demodulation of the signal and improve the performance of the system. Thus we have the option of either performing iterative demodulation, where the channel decoder and the demodulator are invoked in an iterative fashion, or a non-iterative demodulation, where the demodulation is performed only once followed by the decoding of the message. We highlight the recent results in the estimation of capacity for channels with memory and apply it to a CPM system. We estimate two different types of capacity of the CPM system over an Additive White Gaussian Noise (AWGN). The first capacity assumes that optimum demodulation and decoding is done, and the second one assumes that the demodulation is done only once. Having obtained the capacity of the system we try to approach this capacity by designing outer codes matched to the CPM system. We utilized LDPC codes, since they can be designed to perform very close to capacity limit of the system. The design complexity for LDPC codes can be reduced by assuming that the input to the decoder is Gaussian distributed. We explore three different ways of approximating the CPM demodulator output to a Gaussian distribution and use it to design LDPC codes for a Bit Interleaved Coded Modulation (BICM) system. Finally we describe the design of Multi Level Codes (MLC) for CPM systems using the capacity matching rule.
123

Lietuvos ginčytinų profesinių ligų atvejų 2005-2009 metais charakteristikos bei jų sąsajos su profilaktiniais sveikatos tikrinimais / Lithuanian controversial cases of occupational diseases in the years 2005-2009: characteristics and their associations with annual health check ups

Erapart, Evelina 11 June 2012 (has links)
Įvadas. Žmonės didelę laiko dalį leidžia dirbdami, daugelis jų yra veikiami profesinių rizikos veiksnių, lemiančių profesinės ligos atsiradimą. Pastaruoju metu profesinės ligos bei jų keliama našta tapo ypač aktualia problema įvairiose šalyse. Siekiant nustatyti veiksnius, kurie sukelia ginčus, būtina analizuoti ginčytinus profesinių ligų atvejus. Profilaktiniai sveikatos tikrinimai padeda nustatyti profesines ligas ankstyvose stadijose, darbo medicinos gydytojams suteikia svarbią, papildomą informaciją apie pacientą, profesinės ligos nustatymo metu. Todėl nagrinėjant ginčytinus profesinių ligų atvejus svarbu įvertinti profilaktinių sveikatos tikrinimų įtaką. Darbo tikslas. Išanalizuoti Lietuvos ginčytinų profesinių ligų atvejų (GPLA) 2005–2009 m. charakteristikas bei jų sąsajas su profilaktiniais sveikatos tikrinimais. Uždaviniai. Įvertinti ginčytinų profesinių ligų atvejų pasiskirstymą pagal charakteristikas (diagnozę (pirminę, galutinę), priežastis, profesiją, ekonominę veiklos rūšį, kenksmingus darbo aplinkos veiksnius, amžių, darbo stažą, lytį, gyvenamąją vietą). Įvertinti ginčytinų profesinių ligų atvejų pasiskirstymą pagal pirminės ir galutinės diagnozės sutapimą. Įvertinti ginčytinų profesinių ligų atvejų pasiskirstymą pagal profilaktinių sveikatos tikrinimų rezultatus. Įvertinti profilaktinių sveikatos tikrinimų ir ginčytinų profesinių ligų atvejų charakteristikų sąsajas. Tyrimo metodika. Darbe naudoti aprašomosios statistikos ir kiekybiniai tyrimo metodai. Duomenys... [toliau žr. visą tekstą] / Intoduction. A lot of people spend their days at work; high proportion is influenced different risk factors causing occupational diseases. Nowadays the burden occupational diseases is discussed very often all around the world. To identify problems causing disputes about occupational disease diagnosis it is necessary to analyze the controversial cases of occupational diseases. Annual health check ups provide important additional information for occupational doctors, who are determining the diagnosis of occupational disease, also helps to identify diseases in early stages. Since the efectivness of annual health check ups is discussed it is necessary to evaluate how annaul health check ups influence changes in the controversial cases of occupational diseases (CCOD). Aim. To analyze the controversial cases of occupational diseases in Lithuania during years 2005-2009, characteristics of cases and their relation to health annual (mandatory) health check ups. Tasks. To evaluate the distribution of CCOD by characteristics (age, gender, place of residence, seniority, cause of dispute, occupation, economic activity, employment, harmful environmental factors, diagnosis (primary and final). To evaluate distribution of CCOD by congruence of primary and final diagnosis. To evaluate distribution of CCOD by the results of annual health check ups. To evaluate associations with characteristics of contraversial cases of occupational diseases. Methodology. The CCOD registered and analysed by... [to full text]
124

Pacientų, kuriems taikoma trečiojo lygio neuroreabilitacija, mitybos būklės pokyčių ir su jais susijusių veiksnių vertinimas / Third level neurorehabilitation patiens nutritional status changes and related factors assesment

Žemaitienė, Lilija 11 July 2014 (has links)
Lilija Žemaitienė. Pacientų, kuriems taikoma trečiojo lygio neuroreabilitacija, mitybos būklės pokyčių ir su jais susijusių veiksnių vertinimas, magistro baigiamasis darbas/mokslinė vadovė doc. dr. O. Riklikienė; Lietuvos sveikatos mokslų universitetas, Medicinos akademija, Slaugos fakultetas, Slaugos ir rūpybos katedra; konsultantė doc. dr. G. Damulevičienė; Lietuvos sveikatos mokslų universitetas, Medicinos akademija, Geriatrijos klinika. ‒Kaunas, 2014‒85 p. / Lilija Žemaitienė. Third level neurorehabilitation patiens nutritional status changes and related factors assesment / supervisor Ph. d. O. Riklikienė ; Lithuanian University of Health Sciences; Faculty of Nursing, Department or Nursing and Care; consultant Ph. d. G. Damulevičienė; Lithuanian University of Health Sciences, Clinic Geriatric, Kaunas, 2014, – s. 85.
125

Modern coding schemes for unequal error protection

Deetzen, Neele von January 2009 (has links)
Zugl.: Bremen, Univ., Diss., 2009
126

Iterative Codierungs- und Entzerrungsverfahren für die optische Nachrichtenübertragung

Schorr, Torsten January 2006 (has links)
Zugl.: Kaiserslautern, Techn. Univ., Diss., 2006
127

Optimized belief propagation decoding for low delay applications in digital communications /

Hehn, Thorsten. January 2009 (has links)
Zugl.: Erlangen, Nürnberg, University, Diss., 2009.
128

Code generation and simulation of an automatic, flexible QC-LDPC hardware decoder

Von Leipzig, Mirko 03 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Iterative error correcting codes such as LDPC codes have become prominent in modern forward error correction systems. A particular subclass of LDPC codes known as quasicyclic LDPC codes has been incorporated in numerous high speed wireless communication and video broadcasting standards. These standards feature multiple codes with varying codeword lengths and code rates and require a high throughput. Flexible hardware that is capable of decoding multiple quasi-cyclic LDPC codes is therefore desirable. This thesis investigates binary quasi-cyclic LDPC codes and designs a generic, flexible VHDL decoder. The decoder is further enhanced to automatically select the most likely decoder based on the initial a posterior probability of the parity-check equation syndromes. A software system is developed that generates hardware code for such a decoder based on a small user specification. The system is extended to provide performance simulations for this generated decoder. / AFRIKAANSE OPSOMMING: Iteratiewe foutkorreksiekodes soos LDPC-kodes word wyd gebruik in moderne voorwaartse foutkorreksiestelsels. ’n Subklas van LDPC-kodes, bekend as kwasisikliese LDPC-kodes, word in verskeie hoëspoed-kommunikasie- en video-uitsaaistelselstandaarde gebruik. Hierdie standaarde inkorporeer verskeie kodes van wisselende lengtes en kodetempos, en vereis hoë deurset. Buigsame apparatuur, wat die vermoë het om ’n verskeidenheid kwasisikliese LDPC-kodes te dekodeer, is gevolglik van belang. Hierdie tesis ondersoek binêre kwasisikliese LDPC-kodes, en ontwerp ’n generiese, buigsame VHDL-dekodeerder. Die dekodeerder word verder verbeter om outomaties die mees waarskynlike dekodeerder te selekteer, gebaseer op die aanvanklike a posteriori-waarskynlikheid van die pariteitstoetsvergelykings se sindrome. ’n Programmatuurstelsel word ontwikkel wat die fermware-kode vir so ’n dekodeerder genereer, gebaseer op ’n beknopte gebruikerspesifikasie. Die stelsel word uitgebrei om werksverrigting te simuleer vir die gegenereerde dekodeerder.
129

Combined CTLA-4 and PD-1 inhibition a single institute in-depth analysis of toxicity and efficacy in patients treated at the Dana-Farber Cancer Institute

Munivenkata Swamy, Preethi 02 November 2017 (has links)
PURPOSE: The purpose of this study was to compare the rate of grade 3-4 immune related adverse events (irAEs) in patients with advanced metastatic melanoma treated with the combined anti-CTLA-4 and anti-PD-immune-therapy at the Dana Farber Cancer Institute(DFCI), to that of the published rate of grade 3-4 irAEs among patients treated with the same combination of check-point therapy in the pivotal phase II and phase III trials that led to the FDA approval of the combination regimen. This study also measures the tumor response with the Ipi-Nivo combination therapy and overall-survival of patients in the study cohort at DFCI. METHODS/PROCEDURES: This is a retrospective cohort study conducted at DFCI during 2014 to 2016 among stage III/IV melanoma patients treated outside of the clinical trials with the Ipi-Nivo combination therapy. Chart review of the electronic medical record(EMR) was conducted to abstract the data for this study. irAEs were graded and classified as per the NCI-CTCAE v.4.0 guidelines. The comparison of the rate of grade 3 4 toxicity in the clinical settings at DFCI and the clinical trials was performed using a one sample proportion hypothesis test. For efficacy assessment of tumor response, RECIST1.1 criterion was used to ascertain the best clinical response. RESULTS: During an overall follow-up period of 600 days, 52 patients were treated on expanded access protocol (EAP) and commercial Ipi-Nivo combination therapy at DFCI. The rate of grade 3-4 immune mediated toxicity for this cohort of patients treated outside of clinical trials was 32.6%. The average rate of grade 3-4 irAEs reported in phase II/III clinical trials was approximately 55%. The results from the one-proportion hypothesis test [(P-value: 0.002) (95% C.I: 19.14-46.23)], prove that patients in the “real world” clinical settings have a different safety profile than patients treated in the clinical trials. The rate of grade 3-4 irAEs was found to be lower (19.14% to 46.23%) in the population treated with Ipi/Nivo combination therapy at the DFCI, compared to the check-mate clinical trials (approximately 55%) CONCLUSION: The results from the study indicate a lower rate of grade 3-4 irAEs in patients treated at DFCI, in comparison with the patients treated in the clinical trials for the Ipi-Nivo combination group. The results support the need for preemptive safety signal detection of symptoms of irAEs to improve patient’s safety. However, larger database studies are required for the generalizability of this results to a wider patient population treated outside of DFCI.
130

Parent experiences of a family-centered intervention: Examining ethnocultural group differences

Bustos, Cristina E., 1979- 03 1900 (has links)
xiii, 101 p. / Ensuring that psychological interventions are well received and effective among ethnically and culturally diverse groups is at the forefront of psychological research. This study is a nonexperimental, posttest evaluation of differences between European American and ethnocultural group parents' perceptions of the Family Check-Up (FCU), a family-centered, ecologically and community-based intervention that provides family assessment, support, and motivation to change for families coming to counseling. Research has demonstrated the effectiveness of the FCU but has yet to evaluate parent perceptions of the FCU. This study examines features of intervention implementation that lead to treatment satisfaction and adherence by evaluating parent perceptions of (a) the FCU intervention, (b) therapist interpersonal qualities, and (c) therapist multicultural competence. Both parent and observational coder ratings of the intervention were assessed along these dimensions. In the first year of a longitudinal study of the FCU, data were collected from parents of children who attended three public middle schools in a metropolitan area of the Pacific Northwest. Within-subjects analyses were conducted to assure measurement validation and treatment fidelity. A between-subjects multivariate analysis of variance was utilized to examine ethnocultural group differences. Results revealed that all measures demonstrated high internal consistency reliability, high interscale correlations, and good construct validity. Results revealed high interrater agreement between parent ratings of treatment receipt and coder ratings of treatment delivery, indicating treatment fidelity. Results revealed no statistically significant differences in parent perceptions of the FCU intervention, regardless of parent ethnocultural group. Additional analyses demonstrated that observational coders rated family consultants who worked with ethnocultural group parents higher in multicultural competence than those who worked with European American parents. In summary, study results suggest (a) that the measures developed and adapted for this investigation were reliable and valid, and (b) that we found no evidence of perceived differences in the FCU intervention across ethnocultural group and European American parents. The FCU continues to be an intervention that can be successfully implemented among ethnically and culturally diverse families. / Committee in charge: Dr. Benedict McWhirter, Chair; Dr. Elizabeth Stormshak, Member; Dr. Joseph Stevens, Member; Dr. Thomas Dishion, Outside Member

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