16 resultados para Spread spectrum communication

em Deakin Research Online - Australia


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Abstract— Audio watermarking is a promising technology for copyright protection of audio data. Built upon the concept of spread spectrum (SS), many SS-based audio watermarking method shave been developed, where a pseudonoise (PN) sequence is usually used to introduce security. A major drawback of the existing SS-based audio watermarking methods is their low embedding capacity. In this paper, we propose a new SS-based audio watermarking method which possesses much higher embedding capacity while ensuring satisfactory imperceptibility and robustness. The high embedding capacity is achieved through a set of mechanisms: embedding multiple watermark bits in one audio segment, reducing host signal interference on watermark extraction, and adaptively adjusting PN sequence amplitude in watermark embedding based on the property of audio segments. The effectiveness of the proposed audio watermarking method is demonstrated by simulation examples.

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This paper presents a novel rank-based method for image watermarking. In the watermark embedding process, the host image is divided into blocks, followed by the 2-D discrete cosine transform (DCT). For each image block, a secret key is employed to randomly select a set of DCT coefficients suitable for watermark embedding. Watermark bits are inserted into an image block by modifying the set of DCT coefficients using a rank-based embedding rule. In the watermark detection process, the corresponding detection matrices are formed from the received image using the secret key. Afterward, the watermark bits are extracted by checking the ranks of the detection matrices. Since the proposed watermarking method only uses two DCT coefficients to hide one watermark bit, it can achieve very high embedding capacity. Moreover, our method is free of host signal interference. This desired feature and the usage of an error buffer in watermark embedding result in high robustness against attacks. Theoretical analysis and experimental results demonstrate the effectiveness of the proposed method.

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This paper is the result of a "Rip Van Winkle" experience I had concerning the teaching of Business Communication. The paper focuses on the remarkable expansion in the curriculum of the traditional "Business Communication" or "Business Writing" course offered by many tertiary institutions around the world. Based on 25 years of personal observation and experience in a number of educational settings, the paper will trace the increasing sophistication and complexity of the study of business communication from one that covered little more than lessons in the design of hardcopy memos, letters, and reports to one that now covers a broad spectrum of topics such as "emotional intelligence," "intercultural communication," "effective public speaking," as well as the effects of purpose and audience on the design of a wide variety of business communications.

An example of an effective task that involves a number of on the job activities is provided in the form of a ready to use assignment that is applicable in a number of contexts.

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There is growing evidence that ultraviolet (UV) wavelengths play an important role in avian mate choice. One of the first experiments to support this idea showed that female zebra finches (Taeniopygia guttata) prefer UV-reflecting males to males whose ultraviolet reflection has been removed. The effect was very strong despite little or no UV reflection from several plumage areas. However, it is not clear how the importance of the UV waveband compares to other regions of the bird-visible spectrum. We tested whether the response of female zebra finches to the removal of male UV reflection is greater than to the removal of other wavebands. We presented females with a choice of males whose appearance was manipulated using coloured filters. The filters removed single blocks of the avian visible spectrum corresponding closely to the spectral sensitivities of each of the zebra finch's single cone classes. This resulted in males that effectively had no UV (UV-), no short-wave (SW-), no medium-wave (MW-) or no long-wave (LW-) plumage reflection. Females preferred UV- and SW- males. LW- and MW- males were least preferred, suggesting that female zebra finches show the greatest response to the removal of longer wavelengths. Quantal catches of the single cone types viewing body areas of the male zebra finch are presented for each treatment. Our study suggests it is important to consider the role of the UV waveband in avian mate choice in conjunction with the rest of the avian visible spectrum.

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Autism spectrum disorders (ASDs) are developmental conditions characterized by deficits in social interaction, verbal and nonverbal communication and obsessive/stereotyped patterns of behaviour. Although there is no reliable neurophysiological marker associated with ASDs, dysfunction of the parieto-frontal mirror neuron system has been suggested as a disturbance linked to the disorder. Mirror neurons (MNs) are visuomotor neurons which discharge both when performing and observing a goal directed action. Research suggests MNs may have a role in imitation, empathy, theory of mind and language. Although the research base is small, evidence from functional MRI, transcranial magnetic stimulation, and an electroencephalographic component called the mu rhythm suggests MNs are dysfunctional in subjects with ASD. These deficits are more pronounced when ASD subjects complete tasks with social relevance, or that are emotional in nature. Promising research has identified that interventions targeting MN related functions such as imitation can improve social functioning in ASDs. Boosting the function of MNs may improve the prognosis of ASDs, and contribute to diagnostic clarity.

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When new products and brands are introduced into other cultures, the speed and extent of the product's acceptance are important concerns for marketers. The spread of positive word of mouth (WOM) and the lack of negative WOM about the product or brand by early adopter groups are critical to the product's successful diffusion in a population. This is the first study to investigate the effects of consumers' cultural values on their WOM behavior. Data analysis from two samples indicates that the pattern, type, and target receivers of consumers' WOM activity depend on their cultural values. The authors use Hofstede's four cultural dimensions to test the effects of cultural values on WOM behavior to social in- and out-groups. They find that all four dimensions have significant effects on WOM engagement to those groups. Although the authors could not determine the causal nature of the relationships because of the sample design used, they argue that marketers should monitor the cultural values of their market to anticipate in- and out-group discussions and the choice of appropriate brand communication strategies in other countries.

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Objective: The attention profile of girls with autism spectrum disorder (ASD) is unclear compared with boys with ASD and typical children. This study aimed to investigate parent-reported ASD and ADHD symptoms in a large sample of boys and girls with and without ASD.

Method: A total of 124 normally intelligent children, half of them girls, 64 with autistic disorder or Asperger’s disorder, and 60 age- and gender-matched typically developing, aged 7 to 12 years, were recruited. Parents completed questionnaires regarding autistic and ADHD symptoms.

Results: No gender differences in social difficulties but more repetitive motor movements, communication difficulties, and inattention were reported in males, regardless of group. Younger boys with ASD had more elevated levels of hyperactivity-impulsivity than younger girls with ASD.

Conclusion: Gender differences in autistic symptoms and inattention in ASD reflected gender differences in typical children. More pronounced hyperactivity in younger boys with ASD could contribute to higher rates of clinical referral than girls.

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PURPOSE: The purpose of this study is to explore the use of virtual worlds by people with autism spectrum disorder (ASD), with a particular focus on the virtual world Second Life™. METHOD: Case study methodology was selected to explore the experiences of Wolf, a participant with ASD, in Second Life. Wolf participated in three in-depth interviews. The interviews were analyzed using a content analysis to identify themes and sub-themes. RESULTS: Analysis identified four main themes: social factors and communication, empowerment, virtual world versus physical world, and social cues and body language. CONCLUSION: Anecdotally Wolf's experiences suggest that people with ASD enjoy using a virtual world and may feel more comfortable communicating in the virtual world context than the physical world. Virtual worlds offer a venue for people with ASD to be a part of a virtual society, lowers communication barriers experienced in the physical world, and gives the participant a unique opportunity to create and maintain friendships. Virtual worlds offer an arena for people with ASD to meet their peers on equal terms, not being dependent on social cues, which in the physical world can be a barrier for communication for this group. Further research in this area is required. Implications for Rehabiliation People with autism spectrum disorder enjoy using a virtual world and may feel more comfortable communicating in the virtual world context than the physical world. Virtual worlds offer a venue for people with autism spectrum disorder to be a part of a virtual society. Virtual worlds offer an arena for people with autism spectrum disorder to meet their peers on equal terms, not being dependent on social cues, which in the physical world can be a barrier for this group.

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This study examined the prevalence of autism spectrum disorder (ASD) symptoms in a community-based sample of children with attention-deficit/hyperactivity disorder (ADHD) and non-ADHD controls. We also examined the relationship between ASD symptoms and ADHD subtype, ADHD symptom severity and child gender. Participants were 6-10-year-old children (164 ADHD; 198 non-ADHD control) attending 43 schools in Melbourne, Australia, who were participating in the Children's Attention Project. ADHD was assessed in two stages using the parent and teacher Conners' 3 ADHD index and the Diagnostic Interview Schedule for Children IV (DISC-IV). ASD symptoms were identified using the Social Communication Questionnaire (SCQ). Unadjusted and adjusted linear and logistic regression examined continuous and categorical outcomes, respectively. Children with ADHD had more ASD symptoms than non-ADHD controls (adjusted mean difference=4.0, 95% confidence interval (CI) 2.8; 5.3, p<0.001, effect size=0.7). Boys with ADHD had greater ASD symptom severity than girls with ADHD (adjusted mean difference=2.9, 95% CI 0.8; 5.2, p=0.01, effect size=0.4). Greater ADHD symptom severity was associated with greater ASD symptom severity (regression co-efficient=1.6, 95% CI 1.2; 2.0, p<0.001). No differences were observed by ADHD subtype. Greater hyperactive/impulsive symptoms were associated with greater ASD symptoms (regression coefficient=1.0; 95% CI 0.0; 2.0, p=0.04) however, this finding attenuated in adjusted analyses (p=0.45). ASD symptoms are common in children with ADHD. It is important for clinicians to assess for ASD symptoms to ensure appropriate intervention.

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Motor impairment is consistently reported in autism spectrum disorders (ASD) and may be an early risk factor for core ASD symptomatology. This chapter provides an overview of empirical motor studies in ASD and considers clinical, behavioral, neurophysiological, and neuroimaging studies of motor impairment in ASD. The association between motor impairment and core social communication disturbance is also explored, as well as the high comorbidity between ASD, motor impairment, and other neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD). Future research which aims to understand the specific motor pattern that may characterize ASD is suggested.

Alongside the core diagnostic features of autism, research has highlighted the significant and pervasive impact of motor dysfunction in autism spectrum disorders (ASD) (Fournier et al., J Autism Dev Disord 40(10):1227–40, 2010). Motor difficulties are commonly associated with ASD and potentially may be considered a “cardinal feature” (Fournier et al., J Autism Dev Disord 40(10):1227–40, 2010) of the disorder. Indeed, there has been an increase in the trajectory of motor research over the past decade, with greater understanding of the underlying neurobiological disruption that characterizes the disorder (Mostofsky et al., Brain 132:2413–25, 2009). This chapter will illustrate the importance of neuromotor assessment as a routine part of the diagnostic process and provide an overview of empirical research in the field.

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Autism Spectrum Disorder (ASD) is a behaviorally defined complex neurodevelopmental syndrome characterized by impairments in social communication, by the presence of restricted and repetitive behaviors, interests and activities, and by abnormalities in sensory reactivity. Transcranial magnetic stimulation (TMS) is a promising, emerging tool for the study and potential treatment of ASD. Recent studies suggest that TMS measures provide rapid and noninvasive pathophysiological ASD biomarkers. Furthermore, repetitive TMS (rTMS) may represent a novel treatment strategy for reducing some of the core and associated ASD symptoms. However, the available literature on the TMS use in ASD is preliminary, composed of studies with methodological limitations. Thus, off-label clinical rTMS use for therapeutic interventions in ASD without an investigational device exemption and outside of an IRB approved research trial is premature pending further, adequately powered and controlled trials. Leaders in this field have gathered annually for a two-day conference (prior to the 2014 and 2015 International Meeting for Autism Research, IMFAR) to share recent progress, promote collaboration across laboratories, and establish consensus on protocols. Here we review the literature in the use of TMS in ASD in the context of the unique challenges required for the study and exploration of treatment strategies in this population. We also suggest future directions for this field of investigations. While its true potential in ASD has yet to be delineated, TMS represents an innovative research tool and a novel, possibly transformative approach to the treatment of neurodevelopmental disorders. Autism Res 2015. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

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 This thesis investigated the link between ASD traits and relationship development and experience in both adults with ASD and their TD partners, through a series of online questionnaires. Firstly, for a large sample of female and male adults with ASD, we found that poor relationship development outcome was predicted by higher severity of social skills impairment. When males and females were considered separately, we found that higher severity of communication deficits predicted poor relationship development outcome for males only, and higher severity of social skills deficits predicted poor relationship development outcome for females only. We also found that higher severity of circumscribed interests predicted better relationship development outcomes for the whole sample. Next, in a comparison of relationship functioning across three partner groups (TD partners within a TD/TD dyad, ASD partners within an ASD/TD dyad and TD partners within an ASD/TD dyad), findings indicated that TD partners within an ASD/TD dyad had the poorest relationship outcome. Lastly, we investigated actor and partner effects of ASD traits on relationship outcome for a sample of ASD/TD dyads using an APIM. We found minimal evidence to suggest that ASD traits negatively impact relationship outcome of ASD/TD dyads. However, we consistently found that TD partner’s ASD trait severity positively influenced both ASD and TD partner’s relationship outcome, suggesting that mutual understanding between partners is protective against the challenges faced within ASD/TD relationships.

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This study examined relationships between executive functioning (EF) and ADHD/ASD symptoms in 339 6-8 year-old children to characterise EF profiles associated with ADHD and ADHD + ASD. ADHD status was assessed using screening surveys and diagnostic interviews. ASD symptoms were measured using the Social Communication Questionnaire, and children completed assessments of EF. We found the EF profile of children with ADHD + ASD did not differ from ADHD-alone and that lower-order cognitive skills contributed significantly to EF. Dimensionally, ASD and inattention symptoms were differentially associated with EF, whereas hyperactivity symptoms were unrelated to EF. Differences between categorical and dimensional findings suggest it is important to use both diagnostic and symptom based approaches in clinical settings when assessing these children's functional abilities.