Littérature scientifique sur le sujet « Blockiness »

This research examines changes to the functional (solubility, emulsifying and foaming) properties of pea protein isolate when complexed with commercial citrus pectin of different structural attributes. Specifically, a high methoxy (P90; degree of esterification: 90.0%; degree of blockiness: 64.5%; galacturonic acid content 11.4%) and low methoxy (P29; degree of esterification: 28.6%; degree of blockiness: 31.1%; galacturonic acid: 70%) pectin at their optimum mixing ratios with pea protein isolate (4:1 pea protein isolate to P90; 10:1 pea protein isolate to P29) were assessed at the pHs associated with critical structure forming events during the complexation process (soluble complexation (pHc), pH 6.7 and 6.1; insoluble complex formation (pHϕ1), pH 4.0 and 5.0; maximum complexation (pHopt), pH 3.5 and 3.8; dissolution of complexes, pH 2.4 and 2.1; for admixtures of pea protein isolate–P90 and pea protein isolate–P29, respectively). Pea protein isolate solubility was improved from 41 to 73% by the presence of P90 at pH 6.0 and was also moderately increased at pH 4.0 and pH 5.0 by P90 and P29, respectively. The emulsion stability of both pea protein isolate–pectin complexes was higher than the homogeneous pea protein isolate at all critical pHs except pHopt as well as pHc for pea protein isolate–P29 only. P90, with the higher level blockiness and esterification, displayed better foaming properties at the maximal complexation pH when complexed with pea protein isolate than pea protein isolate–P29 or pea protein isolate alone. However at pHϕ2, pea protein isolate–P29 admixtures produced foams with 100% stability, increasing pea protein isolate foam stability by 85%. The enhanced functionality of pea protein isolate–pectin complexes based on the type of pectin used at critical pHs indicates they may be useful biopolymer ingredients in plant protein applications.

Purpose is to determine a function of the reduced expenditures connected with drilling-and-blasting operations, loading and hauling operations, and rock fragmentation depending upon the cost of machine-shift of the applied facility, its operation modes, hardness of rock being blasted, cost of the used explosive, and rock fragmentation quality based upon the developed optimization mathematical model. Methods. Method of statistical evaluation of natural blockiness structure of the rock as well as quality of its fragmentation by means of explosive energy has been applied. Statistical studies have been carried out concerning the basic indices of rock fragmentation depending upon its largeness and block hardness. Purposely-designed experimental equipment has been applied for sampling analysis of the rock fracturing in the process of its drilling by means of rotary drilling rig. The abovementioned supported representativeness of the sampling. Findings. Statistical distributions of the rock blockiness structure in terms of each bar length involving its place within the drilling assembly as well as in terms of the well depth have been compiled. Visual comparison of experimental data and theoretical data has helped determine that the statistical distributions of natural blockiness structure of the rock have the closest correlation with gamma distribution which differential function has two positive parameters. Statistical dependence has been defined between drilling-and-blasting results and the total expenditures connected with hard rock mining. Originality. A concept of oversize crushing coefficient has been introduced; its statistical dependence upon the mined rock hardness and specific consumption of the applied explosive has been derived. An alternative has been proposed concerning changes in parameters of the differential function of the assumed gamma distribution relative to the predicted granulometric composition of rock mass. Practical implications. Economic and mathematical model has been developed involving a target function of the total expenditures connected with the listed operations as well as a set of constraints avoiding incorrect decisions. The optimization method makes it possible to control drilling-and-blasting parameters at each stage of hard rock mining.

Rapid growth of wired and wireless multi-media data challenges the researchers to develop an efficient objective assessment meter to estimate their quality. This research is focused to design objective quality assessment meters for images and video sequences. In this work, we proposed blockiness and blurriness distortion meters using full, reduced and no reference approaches. Both blockiness and blurriness distortions are calculated using frequency domain analysis. Since blockiness is an abrupt luminance change at DCT block boundaries which is also periodic therefore it generates harmonics in frequency domain, we used the strength of harmonics to estimate blockiness distortion. The more severe the blockiness is, the stronger will be the strength of harmonics in frequency domain. While blurriness removes the sharpness of the image by removing the high frequency components therefore we studied the loss of high frequency coefficients to measure blurriness artefact. We also aimed to design a multi-artefact distortion meter which can estimate the distortion without prior knowledge of distortion type. We developed the combined distortion meter for full, reduced and no reference approaches to estimate both blockiness and blurriness artefacts. We also studied the impact of spatial masking in image quality estimation. Due to the non linear behaviour of human visual system which perceives different amount of distortions at different spatial frequencies, we applied the masking process which weights the visibility of distortion according to the local spatial activity of the image. We investigated the importance of spatial masking in FR, RR and NR modes. Finally for video sequences, the quality metric of each frame is calculated and then we explored the methods to integrate these scores into a single value. Then the temporal masking is applied to mask the motion by using motion vectors and their standard deviations. The results are compared with the subjective scores provided by LIVE image and video database.

This thesis focuses on No Reference (NR) methods for Image Quality Assessment (IQA). A review of the IQA field is presented in Chapter 2; where the different IQA methods are described and classified. In particular, the application of IQA methods within a workflow chain is discussed. In Chapter 3 we focus on NR metrics for JPEG-blockiness and noise artifacts. It is in general assumed that subjective methods produce an actual estimate of the perceived quality while objective methods produce values that should be correlated with human perceptions as best as possible. From the analysis of the regression curves that correlate objective and subjective data we have found that in some cases the metric's predictions are not in correspondence with the subjective scores. After reviewing the available databases, we realize that the distortion ranges considered are not in general representative of real case applications. Therefore, in Chapter 4 the Imaging and Vision Lab (IVL) database is introduced. It was generated with the aim of assessing the quality of images corrupted by JPEG and noise. In Chapter 5 we approach the NR-IQA field by focusing on a classification problem. A framework based on machine learning classification is proposed that let us evaluate how images can be classified within different groups or classes, according to their quality. NR metrics are considered as features and the assigned classes are obtained from the psychovisual data. For the JPEG distortion case, the feature space of the classifiers is built using each NR metric as single feature and also a pool of eleven NR metrics. Classification within five and three classes was addressed. In the former case, the five classes are in correspondence to the five categories recommended by the ITU (excellent, good, fair, poor, and bad) when designing image quality experiments. In the latter case we were interested in classifying images as high, medium or low quality ones. The classifiers are trained and tested on different databases. The classifier obtained using the pool of metrics outperforms each single metric classifier. Better performance is obtained in the case of three classes. Considering an image as the combining of two signals, content and distortion, we note that the crosstalk between both signals influences both subjective and objective quality assessment. We address this problem in Chapter 6 where our working hypothesis is that regression can be improved if performed within a group of images that present similar contents in terms of low level features. The criteria chosen to divide the images in different groups is the image complexity. The proposed strategy consists on two steps: the images (of a given database) are first classified in three groups of low, medium and high complexity. In a second step, regression is performed within each of these groups separately. The strategy is tested for different NR metrics for JPEG-blockiness and noise artifacts, different databases are considered. Correlation coefficients are computed and statistical significance tests are applied. The gain in performance depends on the metric and distortion considered. Summarizing, the two main proposals of this research work, i.e. the classification approach that combines several NR metrics and the grouping strategy, are able to outperform the correlation between subjective and objective data for the case of JPEG-blockiness. Both strategies can be extended to consider other type of distortions.

This dissertation demonstrates the preparation of blocky brominated syndiotactic polystyrene (sPS-co-sPS-Br) copolymers with tailored chain sequences using a simple, post-polymerization functionalization method conducted in the heterogeneous gel state, and investigates the effect of sPS reaction state and sPS/solvent gel morphology on the copolymer microstructure and thermal properties. Gel-state (Blocky) brominated copolymers were prepared from a 10 w/v% sPS/carbon tetrachloride (CCl4) gel and a 10 w/v% sPS/chloroform (CHCl3) gel in a matched set containing 6−32 mol% p-bromostyrene (Br-Sty) units. For comparison, a matched set of randomly brominated copolymers was prepared using a homogeneous solution-state (Random) reaction method and a set of brominated copolymers was prepared using a heterogenous powder-state (Powder) reaction method. The degree of bromination was evaluated using 1H nuclear magnetic resonance (NMR) spectroscopy. Powder-state bromination produced copolymers with a limited degree of functionalization of up to 12 mol% Br and required a threefold longer reaction time than the gel-state method conducted on the sPS/CHCl3 gel, demonstrating that the powder-state method is time-consuming and the dense sPS powder is incapable of producing copolymers with high Br-content. Microstructural characterization provided by 13C NMR spectroscopy, showed that bromination of sPS produces multiple peaks in the quaternary carbon region of the NMR spectrum, signifying through-bond communication between neighboring styrene and Br-Sty monomers. This work provides the first high-resolution comonomer sequencing of brominated sPS copolymers. Characterization of the quaternary carbon spectrum, assisted by band selective gradient heteronuclear multiple bond correlation (bsgHMBC) spectroscopy, electronic structure calculations, and simulated statistically random copolymer chains, revealed that each resonance peak could be assigned to a styrene or Br-Sty unit that exists in the center of a unique sequence of five monomers (i.e., a pentad) along the copolymer chain (e.g., ssssb where s = styrene and b = brominated styrene). Our comonomer sequencing method demonstrated that the Blocky and Powder copolymers have block-like character. Remarkably, the Blocky copolymers exhibit notably higher degrees of blockiness and larger fractions of sssss and bbbbb pentads at low Br contents (i.e., 32 mol% Br), relative to the Powder copolymers, confirming their blocky microstructure. Quenched films of the Blocky copolymers, analyzed using ultra-small-angle (USAXS) and small-angle X ray scattering (SAXS), show micro-phase separated morphologies that are reminiscent of conventional block copolymer phase behavior, supporting that the Blocky copolymers contain distinct segments of pure sPS and segments of randomly brominated sPS. Crystallization behavior of the copolymers, examined using differential scanning calorimetry (DSC), demonstrates that the Blocky copolymers are more crystallizable and crystallize faster at lower supercooling compared to their Random analogs. Simulations of blocky copolymers were developed based on the semicrystalline gel morphology to rationalize the effect of gel-state functionalization on copolymer microstructure and crystallization behavior. The simulations confirm that restricting the accessibility of the brominating reagent to monomers well removed from the crystalline fraction of the gel network produces copolymers with a greater prevalence of long runs of pure sPS that is advantageous for preserving desired crystallizability of the resulting blocky copolymers. To investigate the effect of sPS/solvent gel morphology on copolymer microstructure and crystallization behavior, the sPS/CCl4 and sPS/CHCl3 copolymers were compared directly. Characterization of the sPS/solvent gels using USAXS/SAXS, revealed that the gels exhibit different morphologies and average lamella thicknesses. Microstructural analysis showed that the sPS/CHCl3 copolymers contain larger fractions of sssss pentad and a greater degree of blockiness. The sPS/CHCl3 copolymers contain larger phase domains, supporting that these copolymers contain longer distinct segments of pure sPS and randomly brominated sPS in a multiblock-like microstructure. In addition, the sPS/CHCl3 copolymers are more crystallizable during conditions of rapid cooling and crystallize faster at low supercooling relative to their sPS/CCl4 analogs. Simulated average chains of the Blocky copolymers, generated from the empirical pentad sequence distributions, provide strong evidence that the runs of pure sPS in the Blocky copolymers originate from the crystalline stems within the crystalline lamellae. Thus, the simulations support that semicrystalline blocky brominated copolymers with tailored chain sequences, phase behavior, and crystallization properties and can be prepared simply by changing the gelation solvent.
Doctor of Philosophy
Block copolymers are a class of large molecules (polymers) that are made up of two or more chains (blocks) of different smaller units (monomers) linked together at one of each of the chain ends. When the monomers that make up each block have distinctly different chemical properties, the blocks may be capable of self-assembling into well-ordered physical structures, which give the block copolymer unique material properties that are different, and often better than the properties of the individual blocks alone (homopolymers). Block cop olymers have thus received tremendous attention with respect to controlled preparation, tailored structure development, and customized physical properties, for their potential use in self-assembled, nanostructured materials. Nevertheless, the generally difficult procedures and conditions required to make (polymerize) block copolymers with controlled sequences limits the scope of their commercial application. As an alternative to conventional polymerization methods, this dissertation demonstrates a comparatively simple physical method to make copolymers that contain significantly non-random (blocky) monomer sequences, starting with a homopolymer and using a reagent to modify units along the polymer chain. This post-polymerization method is conducted in the homopolymer’s gel state, in which segments of the homopolymer chains are effectively shielded from the reagent. The homopolymer, syndiotactic polystyrene (sPS), was used as a model to conduct a fundamentical investigation into the effects of the polymer reaction state, i.e., gel, solution, or powder, and the gel structure (morphology) on the copolymer structure and properties. The gel-state was found to produce copolymers with a high degree of modification and a greater degree of blockiness than the solution-state and powder-state. Copolymers prepared from the gel state exhibited properties that are characteristic of conventional block copolymers. Furthermore, using the gel-state method, blocky copolymers with tailored chain sequences and properties were prepared by simply changing the gel morphology. Thus, reaction in the gel-state is demonstrated as a simple physical approach to polymer design and synthesis that will be useful in the development of next-generation functionalized materials through the modification of lowcost commodity polymers. As an advancement to the manner in which nanostructured materials are created, these tailored materials will greatly enhance the convenience of block copolymers for a wide variety of applications including structural and biomechanical materials, and polymeric membranes for energy conversion and water purification systems.

Images are playing a more and more important role in sharing, expressing, mining and exchanging information in our daily lives. Now we can all easily capture and share images anywhere and anytime. Since digital images are subject to a wide variety of distortions during acquisition, processing, compression, storage, transmission and reproduction; it becomes necessary to assess the Image Quality. In this thesis, starting from an organized overview of available Image Quality Assessment methods, some original contributions in the framework of No-reference image quality metrics are described.

2010/2011
This work presents original algorithms for the measurement of artefacts impairing the quality of digital video sequences. The intended use of these algorithms is the control of the restoration processes performed on the video in advanced monitors for costumer applications. The problem of the artefact measurement at this stage of the processing chain di ffer from the assessment of quality performed in other applications. Quality assessment aimed to the improvement of the encoding operation, for example, can be done using the original sequence for comparison, and based on the pixel-by-pixel di erences with it. Quality measurements in intermediate stages of the transmission chain of the video, where the sequence is available in compressed form, can employ useful information contained in the bitstream, such as the frequency distribution of the frame content, the bitrate, the quantisation step and the error rate, all factors related to the global quality. In the proposed application, i. e. at the monitor, the measurements of the frame degradation must instead take place on the decoded numerical values of the pixels of the sole altered sequence. In addition, these measurement should require a low computational cost, so that they can be used in real time. In the rst part of this work some of the existing methods for Quality Assessment are briefly overviewed and classi ed based on the chosen approach to the problems. In this overview three main classes of methods are identi ed, namely the methods based on the measurement of speci c frame and video artefacts, the methods measuring the discrepancies between some statistical properties of the pixel distribution or the sequence parameters and ideal models, and the methods processing highly generic measures with trained classi ers. The rst strategy is deemed the most promising in the intended application, due to the good achieved results with relatively little computation and the possibility to avoid a long and complex training phase. The proposed algorithms are therefore based on the measurement of speci c video artefacts. A second part of the work is devoted to the identi cation of the main potential degradation factors in one of the most recent encoding standard, namely H264. The main aspects of frame degradation, namely blockiness in smooth areas and texture, edge degradation, and blurriness, are identi ed, and their relationship to the encoding options is briefly examined. Based on this brief inspection, two of the most common artefacts of the transmitted video, namely blurriness and blockiness, are chosen for measurements estimating the picture quality degradation. The devised algorithms integrate measures of the inter-pixel relationships determined by the artefacts with models of human vision to quantify their subjective appearance. For the blurriness measurement two methods are proposed, the fi rst acting selectively on object edges, the second uniformly on the frame surface. In the measurement of the edge blurriness the hierarchical role of each edge is estimated, distinguishing between the marginal edges of the detail and the edges of the main objects of the frame. The former have reduced contrast and short length compared to the edges of the surrounding shapes, and have little e ect on the overall blurriness impression. Conversely, the state of the latter is the main responsible of the frame quality aspect. The edge blurriness measure is based on the edge width and steepness, corrected with the edge length and the activity of the surrounding scene. This measure of edge blurriness is further corrected with a measure of the local scene clutter, accounting for the fact that in cluttered scenes the perception of the artefact is reduced. The resulting method yields blurriness measurements in local frame parts. The correlation of this measurements with subjective impression is evaluated in experimental tests. The two metrics acting uniformly on the frame measure the decrement in perceived contrast and the lack of detail, respectively. Used together, they are e ective in identifying special types of blurriness resulting in the generation of large areas with few edges and little contrast. These forms of blurriness generally cause a milder degradation of the perceived quality compared to the blurriness caused by encoding. The ability to distinguish among blurriness types and corresponding quality ranges is veri ed in experimental tests. Also the artefacts resulting from block based compression are analysed with a method acting on the sole edges and another applied to the whole frame. The edge degradation, consisting in an unnatural geometric alteration of the main objects, was measured from the frequency and length of straight edge fractions and the incidence of square corners. A correction procedure is introduced in order to avoid false alarms caused by natural polygonal objects and by the intrinsic nature of digital pictures. The measure of the blocking artefact on the frame surface, which appears altered by an unnatural grid, is performed with an original solution especially devised for video frames, and aimed to detect the displacement of the synthetic block edges caused by the motion compensation performed in video encoding. On this purpose very sensitive local blockiness indicators are devised, and corrected with models of the human perception of discontinuities in luminance in order to avoid false alarms. Vision models are further integrated in the computation of a global frame blockiness measure consisting in a weighted sum of local measures on detection points. The metric is tested with respect to its constance on subsequent frames, robusteness to upscaling and correlation with the quality ratings produced in experiments by a group of human observers.
Questo lavoro presenta algoritmi originali per la misura di artefatti che causano un degrado della qualità di sequenze video digitali. L'uso previsto per questi algoritmi è il controllo dei processi di restauro compiuti sul video in monitor avanzati di uso domestico. Il problema della misura di artefatti a questo stadio della catena di elaborazione si differenzia dalla stima di qualità compiuta in altre applicazioni. La stima di qualità volta al miglioramento dell'operazione di codifica, per esempio, può fare uso della sequenza originale per confronto, ed essere basato sulle differenze rispetto ad essa, calcolate pixel per pixel. Misure di qualità compiute in stadi intermedi della catena di trasmissione del video, dove la sequenza è disponibile in forma compressa, possono sfruttare utili informazioni contenute nel flusso di bit compresso, come la distribuzione in frequenza del contenuto del fotogramma, il tasso di compressione, l'intervallo di quantizzazione ed il tasso di errore, tutti fattori legati alla qualità globale del video. Nell'applicazione prevista, cioè al monitor, la misura del degrado dei fotogrammi deve invece avvenire usando solo i valori decodificati dei pixel della sequenza corrotta. Inoltre questa misura dovrebbe richiedere un basso costo computazionale, per poter avvenire in tempo reale. Nella prima parte di questo lavoro alcuni dei metodi esistenti per la stima di qualità sono brevemente esaminati e classificati in base al modo in cui affrontano il problema. I metodi sono divisi in tre categorie principali, cioè i metodi fondati sulla misura di specifici artefatti del fotogramma video, i metodi che misurano l'allontanamento di alcune proprietà statistiche della distribuzione dei pixel o dei parametri della sequenza da particolari modelli ideali, ed i metodi che fanno un'elaborazione di misure molto generiche con classificatori addestrati. La prima strategia è ritenuta la più promettente nell'applicazione considerata, per i buoni risultati ottenuti con una complessità di calcolo relativamente ridotta e la possibilità di evitare una lunga e complessa fase di addestramento. Gli algoritmi proposti si fondano perciò sulla misura di specifici artefatti del video. Una seconda parte del lavoro è dedicata all'identificazione dei principali fattori di degrado insiti nella codifica secondo uno dei più recenti standard, H264. Sono identificati i principali aspetti del degrado del fotogramma, cioè la blocchettatura in aree piane e tessitura, degrado dei bordi, e sfocatura, ed è brevemente esaminato il loro rapporto con le impostazioni di codifica. Sulla base di questo breve esame, due degli artefatti più comuni nel video trasmesso, cioè la sfocatura e la blocchettatura, sono scelti come oggetto di misure per stimare il degrado della qualità dell'immagine. Gli algoritmi progettati integrano misure delle relazioni fra pixel causate dagli artefatti con modelli della percezione umana che determinano la visibilità di tali artefatti. Per la misura di sfocatura sono presentati due metodi, il primo applicato selettivamente ai bordi degli oggetti, il secondo uniformemente sulla superficie del fotogramma. Nella misura della sfocatura dei bordi è stimato il ruolo gerarchico di ciascun bordo, distinguendo tra bordi secondari del dettaglio e bordi degli oggetti principali dell'immagine. I primi hanno contrasto ridotto e sono corti rispetto ai bordi degli oggetti nei dintorni, e hanno poco effetto sull'impressione di sfocatura complessiva. I secondi invece sono determinanti per la qualità del fotogramma. La misura di qualità dei bordi si fonda sulla loro larghezza e ripidità, corretta con la lunghezza e con l'attività della scena circostante. Questa misura di sfocatura dei bordi è ulteriormente corretta con una misura della densità della scena, misura che tiene conto del fatto che in scene affollate la percezione del difetto è ridotta. Il metodo complessivo fornisce misure di sfocatura in aree locali dell'immagine. La correlazione di queste misure con l'impressione soggettiva è valutata in test sperimentali. Le due misure di sfocatura che agiscono uniformemente sull'immagine misurano rispettivamente la diminuzione del contrasto percepito e la mancanza di dettaglio. Il loro uso congiunto permette di identificare specifici tipi di sfocatura che generano grandi aree con pochi bordi e basso contrasto. Queste forme di sfocatura generalmente causano un degrado di qualità percepita più lieve rispetto alla sfocatura dovuta alla codifica. La capacità di distinguere fra i tipi di sfocatura e fra i corrispondenti intervalli di qualità è verificata in prove sperimentali. Anche gli artefatti dovuti alla compressione a blocchi sono analizzati con un metodo che agisce sui soli bordi ed un altro applicato sull'intera superficie del fotogramma. Il degrado dei bordi, che consiste in un'innaturale alterazione geometrica degli oggetti principali, è stimata in base alla frequenza e alla lunghezza delle parti di bordi diritte ed alla frequenza degli angoli retti. Una correzione è introdotta per evitare falsi allarmi causati da oggetti di forma naturalmente poligonale e dalla natura intrinseca delle immagini digitali. La misura dell'artefatto di blocchettatura sulla superficie del fotogramma, che appare alterato da una griglia artificiale, è compiuta con un metodo originale specificamente studiato per fotogrammi video, e volto a rilevare lo spostamento dei bordi artificiali dei blocchi causato dalla compensazione del movimento compiuta nella codifica video. A questo scopo sono adottati indicatori di blocchettatura locale molto sensibili, corretti con modelli della percezione delle discontinuità di luminanza per evitare falsi allarmi. Modelli della percezione umana sono anche integrati nel calcolo di una misura globale della blocchettatura del frame, calcolata come somma pesata di misure locali sull'insieme dei punti di rilevamento. L'indice di blocchettatura è valutato in base alla sua uniformità in fotogrammi consecutivi, alla resistenza al riscalaggio e alla correlazione con i giudizi di qualità espressi da un gruppo di osservatori umani nelle prove sperimentali.
XXIII Ciclo
1981

Syfte och frågeställningar

Syftet med studien är att undersöka förekomst, hantering och upplevda orsaker till mentala blockeringar inom kvinnlig truppgymnastik på nationell ungdoms- och juniornivå.

• Vilken typ av övning är den vanligaste mentala blockeringen inom kvinnlig truppgymnastik?

• Hur visar sig blockeringarna enligt gymnasterna och tränarna?

• Vilka orsaker till uppkomsten av mentala blockeringar kan utläsas utifrån gymnasterna och tränarnas berättelser?

• På vilka sätt har gymnaster och tränare försökt hantera mentala blockeringar?

Metod

Studien inleddes med en litteratursökning för att finna tidigare forskning. Därefter utformades en enkät i två versioner (för tränare och gymnaster) och dessa delades ut till gymnaster och tränare på nationell ungdoms- och juniornivå i sex olika föreningar. Gymnasterna valdes efter tränings- och tävlingsnivå och har en medelålder på 14 år.

Resultat

Resultatet visade att mentala blockeringar är ett mycket vanligt fenomen inom truppgymnastiken och något som majoriteten av gymnasterna någon gång drabbats av. Blockeringarna visar sig ofta genom att gymnasten vägrar eller helt utesluter övningen ur sin träning och blockeringarna är vanligast i grenen tumbling. Dock visade studien att de flesta gymnaster upplever blockeringar i mer än ett redskap. Volter som roterar baklänges tenderade att vara den typ av övning som flest gymnaster har blockeringar för. Detta ansågs främst bero på att gymnasterna i fråga inte tror att de kommer att lyckas med övningen följt av orsaker som tidigare skador och mental omognad. De allra flesta gymnaster och tränare har på något sätt försökt behandla problemet, främst genom fysiska åtgärder och har i situationer med mentala blockeringar känt sig rädda, frustrerade och misslyckade.

Slutsats

Problematiken kring mentala blockeringar är stor och få gymnaster och tränare vet hur de kan hantera dessa. Behovet av fortsatt forskning inom området samt större fokus på mental träning inom förbundets utbildningar är stort.

Aim and Questions

The aim of this study is to examine the incidence, handling and experienced causes of mental blockings in female teamgym at national youth and junior level.

• Which type of exercise is the most common mental blocking in female teamgym?

• How does the blockings show according to the gymnasts and coaches?

• Which possible causes to origin of mental blockings can be understood on the basis of the stories of the gymnasts and coaches?

• In which ways have gymnasts and coaches tried to handle mental blockings?

Method

The study started out with a literature search for previous research. Thereafter a questionnaire was formed in two versions (for gymnasts and coaches) and these were sent to gymnasts and coaches at national youth and junior level in six different clubs. The gymnasts were chosen by their level of training and competition.

Results

The study showed that mental blockings is a very common phenomenon in teamgym and is something that the majority of the gymnasts at some point have been affected by. The blockings are often revealed by the gymnasts refusing or totally excluding the exercise from training and the blockings are most frequently occurring in the apparatus called tumbling. Yet, the study shows that most gymnasts experience mental blockings in more then one apparatus. Vaults that rotate backwards tend to bee the type of exercise that most gymnasts have blockings for. This was believed to mainly depend on the gymnasts thinking they will fail to succeed with the exercise followed by causes like previous injuries and mental immatureness. Most gymnasts and coaches have in some way tried to solve the problem, mainly by physical measures and have in situations of mental blockings felt afraid, frustrated and like failure.

Conclusions

Mental blockings is a big problem and few gymnasts and coaches know how to handle them. The need of more research in the area and focus on mental training in the gymnastics association is big.

碩士
國立臺灣科技大學
電機工程技術研究所
85
The interaction of congestion control and prioritized statistical multiplexing for real-time services (e.g., voice and video) in cell-based networks (e.g., B-ISDN based on ATM) with call blockings is studied. Focus on a bufferless mu-ltiplexer supporting real-time ON-OFF sources. Real-time source information is divided into two streams, low- and high-priority streams, in accordance with importance. Favored transport is given to high-priority stream resulting in s-ignificantly better QoS than unprioritized system. Two prioritization schemes are considered. In the first approach, independent channels of different QoS are used to transport low- and high-priority streams. In the second approach, a single channel is used in conjunction with a selective packet discarding pr-ocedure which means to limit packet loss to low-pritority stream. The effect of packet loss on quality is quantified by relating low- and high-priority pa-cket loss to signal-to-reconstruction-noise ratio (SNR). Both static and dyna-mic scenarios are studied. In the static scenario, the number of calls are fi-xed; while in the dynamic case, the number of calls are varying due to call r-andom arrivals and terminations. Firstly, the optimal allocation of source in-formation and channel capacity in the static scenario is found. Secondly, the dynamic allocation of source information and channel capacity are compared to the fixed allocation, and it is shown that the dynamic allocation could achie-ve much better SNR than the fixed allocation in many cases.

Tese de doutoramento, Ciências Geofísicas e da Geoinformação (Meteorologia), Universidade de Lisboa, Faculdade de Ciências, 2017
Blocking high pressure systems are large-scale atmospheric circulation patterns with meteorological impacts that vary across regions and seasons, depending on the blocking location, spatial characteristics and temporal length. While blocking episodes are an important component of intra-seasonal and inter-annual variability at mid-latitudes, particularly in Europe, previous studies have mostly focused on characterizing European blocking impacts on either winter or summer seasons. In this thesis, a thorough characterization of Euro-Atlantic blocking occurrence within different longitudinal sectors (Atlantic, European and Russian) was performed, followed by a comprehensive analysis of their seasonal impacts on temperature and on the precipitation regimes of the European continent and specific sub-regions, with particular emphasis on Iberia, and on extreme events. In order to distinguish high-latitude blocking from other common high pressure systems affecting Europe, namely sub-tropical ridges, a novel ridge detection scheme was developed. Ridges do not require a wave-breaking occurrence as blockings do, although they are frequent precursors of wave-breaking, which may lead to blocking. Thus, as an additional novelty, this thesis also characterizes the distinctive seasonal impacts associated with sub-tropical ridges occurring at different longitudinal sectors of the Euro-Atlantic region. Finally, an assessment of the involved mechanisms behind the temperature and precipitation responses to blocking is also carried out. This included for precipitation the role of cyclonic activity (storm-tracks and cut-off lows), moisture transport, and large-scale atmospheric instability, while for temperature the focus was on the role played by horizontal advection, subsidence and imbalances in various radiation budgets. This distinction clarifies that most extreme heat episodes in southern Europe and Mediterranean areas should not be attributed to blockings, but rather to ridges. In central and northern areas of the continent, both regimes are responsible for warm conditions in summer, due to enhanced radiative heating and increased subsidence. During winter, blocking and ridges lead to opposite temperature responses. Blocking reinforces cold northerly advection in its eastern flank, thus promoting European cold winter spells, especially those located in the eastern Atlantic and western Europe, while mild Atlantic flows associated to ridge patterns result in warmer conditions. Regarding the impacts on precipitation, blocking and ridges are associated with a marked northsouth dipole for the three considered longitudinal sectors of occurrence. While blocking patterns force a split of the storm-track, ridges are associated with a stronger zonal flow at higher latitudes. Thus, negative (positive) precipitation anomalies during blocks occur at higher (lower) latitudes. Enhanced atmospheric instability and cyclonic activity south of blocking centers relate very well with increased rainfall in southern Europe, including Iberia, where torrential regimes are more relevant in the precipitation totals. This dipole is reversed during ridges, which lead to dry conditions in southern Europe. The seasonal analysis further reveals that winters characterized by high frequencies of blocking (ridge) occurrence present above (below) average snow covered soils. Blocking/ridge impacts on temperature and precipitation have also additional effects on meteorological and climate extreme events with large socio economic impacts. Thus, the results show a blocking/ridge role at different time-scales in controlling a significant part of wildfire inter annual variability in Mediterranean areas. Meteorological pre-conditioning raises vegetation stress during dry winters, while increased ridge and blocking occurrence in summer fosters meteorological conditions which are prone to fire ignition and spread. Finally, outputs from state-of-the-art General Circulation Models raise the challenge to develop further these automated schemes for blocking/ridges detection, as their representation in climate models is crucial to understand impacts towards the later decades of the 21st century. Summing up, the main novelties and achievements of this thesis are: 1) the clear disentanglement between blocks and ridges; 2) the seasonal analyses of specific regional impacts resulting from different locations of blocking/ridge structures; 3) the detailed analysis of dynamical/physical forcing mechanisms associated to each considered weather pattern.
Apesar de não existir uma definição unanimemente aceite para o conceito de bloqueio atmosférico, este pode ser descrito como uma supressão do fluxo zonal devido à presença de um sistema de alta pressão. Esta circulação anticiclónica, normalmente localizada nas latitudes onde se observa a corrente de jato polar, apresenta uma dimensão espacial de larga-escala, é geralmente quase-estacionária, e tem um tempo de vida útil entre vários dias a várias semanas. Os sectores orientais dos oceanos Atlântico e Pacífico são geralmente as regiões de ocorrência preferencial de bloqueios no Hemisfério Norte. A ocorrência de bloqueios atmosféricos está diretamente associada a condições prolongadas de tempo seco e estável nas regiões diretamente localizadas sob o sistema de altas pressões. O seu posicionamento geralmente origina uma divisão em dois ramos da corrente de jato. Esta perturbação do habitual padrão zonal resulta em alterações significativas das condições meteorológicas a outras latitudes (tanto meridional como setentrional) distintas da zona diretamente afetada pela posição central do bloqueio. Torna-se necessária assim uma compreensão mais detalhada da climatologia associada aos bloqueios atmosféricos centrados no setor Euro-Atlântico, com especial ênfase aos impactos específicos associados às diferentes localizações que os seus centros de ação possam ter. Apesar de serem um fenómeno que ocorre à escala sinóptica, os bloqueios podem implicar impactos climáticos muito distintos à escala regional, ou mesmo local. Desta forma, um dos principais objetivos desta tese centra-se na elaboração de uma climatologia completa da sua ocorrência, e na respetiva caracterização dos impactos climáticos regionais resultantes da ocorrência de bloqueios em diferentes sectores longitudinais: Atlântico (ATL; 30W-0W), Europeu (EUR; 0E-30E) e Russo (RUS; 30E-60E). Tendo-se verificado na literatura uma certa confusão entre bloqueio de alta latitude e outros sistemas comuns de alta pressão que afetam a Europa, nomeadamente as cristas sub-tropicais, foi considerado prioritário obter um novo catálogo de cristas de alta pressão para o setor Euro-Atlântico. Desta forma, um segundo objetivo central da tese foi o do desenvolvimento de um novo algoritmo automático de deteção de cristas sub-tropicais, que permita assim realizar uma clara distinção fenomenológica e dos impactos destes dois padrões atmosféricos (bloqueios versus cristas). Assim, a compreensão das condições sinópticas e dos mecanismos físicos envolvidos em cada um destes padrões é também tema central desta tese. No caso da precipitação, esta análise de mecanismos incluiu o papel da atividade ciclónica (storm-tracks e cut-off lows), do transporte de humidade e da instabilidade atmosférica em larga escala. Para avaliar os impactos na temperatura analisou-se a contribuição da advecção horizontal, da subsidência e das alterações nos vários balanços radiativos. A desagregação bloqueios-cristas permite distinguir fenomenologias por vezes confundidas na literatura, nomeadamente aquando da análise de episódios de calor extremo no sul da Europa. Verifica-se dos resultados obtidos que, devido a uma clara distinção no posicionamento latitudinal dos centros de ação entre bloqueios e cristas, as respostas na temperatura associadas a cada padrão são também bem distintas, sendo estas diferenças particularmente notáveis no inverno. De uma forma geral, nesta estação, os bloqueios (essencialmente os centrados nos sectores ATL e EUR) resultam em valores das temperaturas do ar bastante abaixo da média, provocadas pela advecção de ar frio de latitudes mais elevadas ao longo do flanco este dos anticiclones. Em oposição, as cristas originam anomalias positivas na temperatura na maior parte do continente europeu, essencialmente como resultado do transporte de massas de ar de origem Atlântica, e de uma redução do arrefecimento radiativo, associado ao aumento da nebulosidade. Durante o verão, ambos os padrões atmosféricos estão associados a temperaturas acima da média em vastas áreas da Europa central e do norte. Em contrapartida, nas regiões mais a sul, e em particular na área da bacia do Mediterrâneo, as cristas controlam a ocorrência de dias extremamente quentes (usualmente identificados como ondas de calor). No verão é também de salientar o papel dominante do aquecimento radiativo solar (sob condições de céu limpo) como principal impulsionador destas anomalias positivas de temperatura em dias de ocorrência de bloqueio/crista, particularmente para os sistemas localizados sobre áreas continentais. Relativamente aos impactos nos regimes de precipitação, existe um claro dipolo norte-sul ao analisar as anomalias associadas a dias de bloqueio/crista. A ocorrência de bloqueios leva a uma redução da precipitação na metade norte do continente Europeu (em algumas áreas superior a 50%) devido ao bloqueio dos sistemas depressionários de médias-latitudes (e do correspondente transporte de humidade) provenientes do Atlântico. No entanto, esta configuração sinóptica leva a um aumento da precipitação (relativamente à média) nas zonas mais a sul, fundamentalmente relacionado com o desvio do storm-track nesta direção, e a um consequente aumento da instabilidade atmosférica e da convecção. Este padrão resulta numa clara mudança nas distribuições de regimes de precipitação nos países do sul da Europa, e demonstra também a ligação entre bloqueios atmosféricos e os regimes de precipitação torrencial na área do Mediterrâneo. Em padrões de fluxo zonal intenso as anomalias da precipitação são no geral opostas às encontradas durante bloqueios, originando um deficit de precipitação no sul da Europa. No contexto dos vários regimes possíveis de fluxo zonal forte, as cristas sub-tropicais estão associadas a condições particularmente secas nos países do sul da Europa. Isto naturalmente também se aplica à Península Ibérica, onde os totais anuais de precipitação dependem largamente da atividade frontal de origem Atlântica (em particular nos meses de inverno), sendo esta afastada da região durante a ocorrência de cristas nos sectores ATL e EUR. Neste contexto, mostra-se crucial o recurso a bases de dados de alta-resolução com uma densidade de estações muito mais elevada, permitindo uma análise regional mais detalhada para o domínio da Península Ibérica. Os bloqueios centrados em latitudes elevadas, em particular os que ocorrem no sector ATL, são responsáveis por invernos com maior cobertura de neve no continente Europeu (até cerca de 50% mais dias com a superfície coberta de neve na Europa central), devido a uma maior frequência de dias frios sob os fluxos de norte associados à circulação anticiclónica. Por outro lado, a ocorrência de cristas nos sectores ATL e EUR (que estão associadas a dias de inverno bastante amenos) impõe uma frequência muito mais baixa de dias com neve no solo. Foi também concluído que os padrões de bloqueio/crista exercem um efeito regulador importante na variabilidade inter-anual de incêndios florestais. Mostra-se que o feedback existente entre a ocorrência destes padrões atmosféricos, a ocorrência de secas, e os incêndios florestais, acontece a diferentes escalas temporais. Nos meses antecedentes à época de incêndios, uma frequência superior ao normal de cristas (bloqueios) é responsável por valores de precipitação abaixo (acima) da média no sul da Europa, aumentando a vulnerabilidade da vegetação. Durante a própria época de incêndios, este padrão atmosférico está associado a condições anomalamente quentes e secas que promovem a ignição e fácil propagação do fogo. Finalmente, no contexto das alterações climáticas, verificou-se que nas últimas décadas a frequência de cristas sub-tropicais aumentou bastante no sul da Europa. As projeções futuras dos Modelos de Circulação Geral sugerem uma expansão para norte das altas pressões subtropicais (associadas à expansão da célula de Hadley). Por outro lado, não existem sinais dinâmicos de alterações muito significativas na frequência e localização dos bloqueios de alta latitude no sector Euro-Atlântico, exceto uma ligeira tendência de deslocamento para nordeste na sua região preferencial de ocorrência. Pretende-se como trabalho futuro utilizar também uma abordagem dinâmica (não apenas baseada em campos de anomalia) para o algoritmo de deteção de cristas, que permitirá uma maior confiança na extrapolação para cenários futuros.

Image acquisition systems usually acquire images with distortions due to various factors associated with digitization processes. Poisson is one of the common types of noises present in the image, and it distorts the fine features. Hence, it is necessary to denoise the noisy image by smoothing it to extract the features with fine details. Among the denoising methods, anisotropic diffusion method provides more adequate results. In this chapter, the authors dealt with existing models such as Perona-Malik (PM), total variation, Tsai, Chao, Chao TFT, difference eigen value PM, adaptive PM, modified PM, and Maiseli models. The performances of the models were tested on synthetic image added with the Poisson noise. Quality metrics are used to quantify and to ensure the smoothness of the resultant images. However, in order to ensure the completeness of the denoising effect, the qualitative attributes such as sharpness, blurriness, blockiness, edge quality, and false contouring are considered on smoothened images. The analysis results are shown the completeness of the denoising effect of the models.

Parfit proposed blocking the Continuum Argument for the Repugnant Conclusion by letting incommensurabilities (“imprecise equalities” in his terminology) intervene at some points in the argument’s population sequence. It is an attractive option. But the relevant incommensurabilities need to be very thoroughgoing if the argument is to be blocked: they must persist even if the next population in the sequence is improved by making it arbitrarily larger. While such persistency might well seem problematic (not just in this case but also when it comes to blockings other spectrum arguments), this article suggests how it can be explained and defended if incommensurability is interpreted on the lines of the fitting-attitudes analysis of value relations. On that analysis, two items are incommensurable if divergent preferential attitudes towards them are permissible (i.e., not unfitting); for example, if it is permissible to prefer one item to the other but also permissible to have the opposite preference. It is shown how to provide a modeling of this kind for persistent incommensurability and how to account for this persistency. However, even if Parfit’s main suggestion can in this way be defended, one of his substantive value assumptions—the Simple View regarding the marginal value of added lives—should be given up, to avoid implausible implications.