• Title/Summary/Keyword: 적응형 기법

Search Result 672, Processing Time 0.02 seconds

Adaptive Data Hiding Techniques for Secure Communication of Images (영상 보안통신을 위한 적응적인 데이터 은닉 기술)

  • 서영호;김수민;김동욱
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.29 no.5C
    • /
    • pp.664-672
    • /
    • 2004
  • Widespread popularity of wireless data communication devices, coupled with the availability of higher bandwidths, has led to an increased user demand for content-rich media such as images and videos. Since such content often tends to be private, sensitive, or paid for, there exists a requirement for securing such communication. However, solutions that rely only on traditional compute-intensive security mechanisms are unsuitable for resource-constrained wireless and embedded devices. In this paper, we propose a selective partial image encryption scheme for image data hiding , which enables highly efficient secure communication of image data to and from resource constrained wireless devices. The encryption scheme is invoked during the image compression process, with the encryption being performed between the quantizer and the entropy coder stages. Three data selection schemes are proposed: subband selection, data bit selection and random selection. We show that these schemes make secure communication of images feasible for constrained embed-ded devices. In addition we demonstrate how these schemes can be dynamically configured to trade-off the amount of ded devices. In addition we demonstrate how these schemes can be dynamically configured to trade-off the amount of data hiding achieved with the computation requirements imposed on the wireless devices. Experiments conducted on over 500 test images reveal that, by using our techniques, the fraction of data to be encrypted with our scheme varies between 0.0244% and 0.39% of the original image size. The peak signal to noise ratios (PSNR) of the encrypted image were observed to vary between about 9.5㏈ to 7.5㏈. In addition, visual test indicate that our schemes are capable of providing a high degree of data hiding with much lower computational costs.

Application of Noninvasive Positive Pressure Ventilation in Patients with Respiratory Failure (호흡부전 환자에서 비침습적 양압환기법의 적용)

  • Seol, Young Mi;Park, Young Eun;Kim, Seo Rin;Lee, Jae Hyung;Lee, Su Jin;Kim, Ki Uk;Cho, Jin Hoon;Park, Hye Kyung;Kim, Yun Seong;Lee, Min Ki;Park, Soon Kew;Kim, Young Dae
    • Tuberculosis and Respiratory Diseases
    • /
    • v.61 no.1
    • /
    • pp.26-33
    • /
    • 2006
  • Background: Noninvasive positive pressure ventilation(NPPV) has been increasingly used over the past decade in the management of acute or chronic respiratory failure and weaning of mechanical ventilation. We performed this clinical study to evaluate the usefulness of NPPV in patients who developed acute respiratory failure or post-extubation respiratory failure. Methods: We analysed thirty four patients(sixteen males and eighteen females, mean ages 58 years) who applied NPPV(BIPAP S/T, Respironics co., USA) for respiratory failure or weaning difficulty at medical intensive care unit(MICU), emergency room and general ward of a tertiary hospital. We evaluated the underlying causes of respiratory failure, duration of treatment, the degree of adaptation, complication and predictive parameters of successful outcome. Results: The overall success rate of NPPV was seventy-one percent. The duration of NPPV applying time, baseline blood pressure, pulse rate, respiration rate, $PaO_2$, $PaCO_2$, $SaO_2$ were not different between success group and failure group. But, the baseline pH was higher in the success group. Predictors of success were higher baseline pH, patients with underlying disease of COPD, improvement of vital sign and arterial blood gas value after NPPV application. The success rate in patients with post-extubation respiratory failure was eighty percent. There were no serious complication on applying NPPV except minor complications such as facial skin erythema, abdominal distension & dry mouth. Conclusion: NPPV may be effective treatment in patients with acute respiratory failure or post-extubation respiratory failure in selected cases.