Numerical simulations of coupled groundwater flow and heat transport incorporating freeze/thaw cycles and phase change in a continuous permafrost environment

Dans les régions nordiques, l’une des conséquences du réchauffement climatique est le dégel du pergélisol. En plus de favoriser la libération de quantités importantes de méthane et de dioxyde de carbone dans l’atmosphère, le dégel du pergélisol entraînera une modification des conditions hydrologiques locales et régionales, affectant ainsi les écosystèmes. Ce dégel pourra aussi conduire à un affaissement des sols et endommager ainsi les infrastructures routières. Dans le cadre de cette étude, des simulations numériques couplant l’écoulement des eaux souterraines et le transport de chaleur ont été réalisées dans le but de mieux appréhender les interactions entre l’écoulement des eaux souterraines et la dynamique thermique relative au dégel du pergélisol sur les pistes de l’Aéroport d’Iqaluit, Nunavut, Canada. Un modèle conceptuel du site est d’abord développé et le modèle numérique bidimensionnel correspondant est calé à partir des températures observées du sol. Les impacts futurs du réchauffement climatique sur le régime thermique et le système d’écoulement, aussi que le tassement dû au dégel, sont ensuite simulés sur la base des scénarios climatiques proposés par le Groupe Intergouvernemental sur l’Évolution du Climat (GIEC). Dans le cadre d’un réchauffement climatique, la couverture neigeuse de surface est identifiée comme le facteur principal affectant la dégradation du pergélisol, y compris par son rôle dans l’accroissement de la sensibilité de la dégradation du pergélisol aux changements de divers facteurs hydrogéologiques. Dans ce cas, le transfert de chaleur par advection joue un rôle relativement mineur, quoique non négligeable, vis-à-vis du transfert de chaleur par conduction, du fait de l’extension importante d’un sol de faible perméabilité à proximité de la surface. Le transfert de chaleur par convection, qui est fortement influencé par la couche de neige superficielle, contrôle la libération de l’eau non gelée et la profondeur de la couche active aussi bien que l’amplitude du tassement et du soulèvement par le dégel. L'effet de la zone non saturée sur le dégel du pergélisol est plus important dans les sols fins, recouverts de neige en surface. De plus, l’ampleur du tassement dû au dégel augmente considérablement en présence d’une couverture neigeuse. Enfin, les simulations ont montré que, le long de routes, les zones les plus vulnérables au tassement sont les accotements recouverts de neige ainsi que les zones de transition adjacentes au bloc de pergélisol. Les simulations numériques ont également montré l’importance d’utiliser les fonctions de gel appropriées pour les types de sols impliqués. En effet, la position du front de gel (couche active) varie en fonction des caractéristiques du sol. Les résultats des simulations ont également mis en évidence les effets d'une distribution stochastique de la conductivité hydraulique sur l’advection thermique. Les taux de dégel du pergélisol sont relativement plus élevés dans des zones de haute perméabilité, trouvées dans la structure du sol d'un système hétérogène, que dans le cas d’un sol homogène. Paradoxalement, les résultats ont montré que dans les zones de décharge, le transport de chaleur par advection a pour conséquence d'augmenter le plafond du pergélisol. En effet, l'eau froide s'écoulant dans ce secteur annule le gain de chaleur résultant du processus de conduction.At high northern latitudes, climate warming will induce permafrost degradation that will modify local and regional hydrogeological systems and ecosystem functionality, as well as increase the release of carbon and methane to the environment. Northern infrastructure, in particular roads and embankments, will also experience significant degradation. In this study, numerical simulations of coupled groundwater flow and heat transport have been developed to assess the effects of realistic combinations of hydrogeological parameters and surface conditions on the temporal and spatial evolution of permafrost degradation in a cold-region paved terrain, at the Iqaluit airport, Nunavut. A conceptual model is first developed for the site and a corresponding 2D numerical model is calibrated to the observed groundwater flow and thermal regime. Future climate warming impacts on the thermal regime and flow system, as well as thaw settlements are then simulated based on climate scenarios proposed by the IPCC (Intergovernmental Panel on Climate Change). Under climate warming, the surface snow cover is identified as the leading factor affecting permafrost degradation, and significantly contributes to positive feedback between the hydrogeological flow system and the frozen ground. In this case, advective heat transport plays a relatively minor, but non-negligible role compared to conductive heat transport, due to the significant extent of low-permeability soil close to surface. Conductive heat transport, which is strongly affected by the surface snow layer, controls the release of unfrozen water and the depth of the active layer as well as the magnitude of thaw settlement and frost heave. The effect of the unsaturated zone on permafrost thaw was most important in finer soil where overlain by snow. The magnitude of thaw settlement also significantly increases with a snow cover. The most vulnerable areas to permafrost thaw settlement along a road or taxiway embankment would be the snow-covered shoulders, as well as the transition zones at the adjacent margins of the permafrost block. The simulation results also showed the importance of selecting the appropriate freezing function based on the type of soil, when frequent freezing and thawing cycles occur in a permafrost setting. The thaw front simulated with a smooth (low slope) freezing function, was deeper compared to that for a steeper freezing function. The simulation results also highlighted the contributing effects of a stochastic hydraulic conductivity distribution on thermal advection. Permafrost thaw rates in high permeability zones, found in the soil structure of a heterogeneous system, are larger than rates for a homogeneous soil. Advective heat transport can paradoxically also increase the permafrost table in downgradient areas where the flowing cold water negates heat gain from conduction alone

Mazdak technique for PSNR estimation in audio steganography

A novel method to estimate PSNR of the resu lt of audio steganography before embedding is presented. Estimated PSNR by proposed linear interpolation formula was tested and the result was almost the same with the obtained PSNR in practical way

PSW statistical LSB image steganalysis

Steganography is the art and science of producing covert communications by concealing secret messages in apparently innocent media, while steganalysis is the art and science of detecting the existence of these. This manuscript proposes a novel blind statistical steganalysis technique to detect Least Significant Bit (LSB) flipping image steganography. It shows that the technique has a number of major advantages. First, a novel method of pixel color correlativity analysis in Pixel Similarity Weight (PSW). Second, filtering out image pixels according to their statistically detected suspiciousness, thereby excluding neutral pixels from the steganalysis process. Third, ranking suspicious pixels according to their statistically detected suspiciousness and determining the influence of such pixels based on the level of detected anomalies. Fourth, the capability to classify and analyze pixels in three pixel classes of flat, smooth and edgy, thereby enhancing the sensitivity of the steganalysis. Fifth, achieving an extremely high efficiency level of 98.049% in detecting 0.25bpp stego images with only a single dimension analysis

Effect of Blended Learning Classroom Environment on Student’s Satisfaction

This study investigates the impact of blended learning classroom environment on students’ satisfaction. The study was carried out in Farhangian University, College of Hazrate Fatemah, Khuzestan Iran, for undergraduate students who were studying in the field of primary education. To examine the level of students’ satisfaction, after undergoing blended learning, a questionnaire and interview form were prepared. The data obtained from students’ responses to the questionnaire and the interview form from different groups of blended learning environment, namely high technology dominant, balance technology and face to face, and face to face dominant. Descriptive statistic indices were used to describe the data. The results indicate that students’ satisfaction in the balance technology and face to face classroom environment was higher than that of the other two classroom environments. That is, students were more satisfied with balance technology and face to face than the other two classes. In addition, the students were preferred to take more courses in a balance technology and face to face classroom environment compared to other two classroom environments

Factor analysis of self-treatment in diabetes mellitus: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Self-treatment is a treatment of oneself without professional help, which may cause health-related consequences. This investigation examined the self-treatment behaviors in patients with diabetes mellitus in Iran/kashan.</p> <p>Methods</p> <p>The patients who referred to the clinic of diabetes and those who were admitted to the General hospital in the city of Kashan due to diabetes mellitus were asked to participate in this cross-sectional study. For data collection, The 25 item questionnaire of Likert scale type with four scales was used. Factor analysis was performed to define the patterns of self-treatment.</p> <p>Results</p> <p>398 patients participated in the study. The mean age of the study population was 54.9 ± 12.9 years. The majority (97%) had type 2 diabetes. 50% of patients reported self- treatment. The self-treatment score was 45.8 ± 8.8 (25-100). Female gender, lower education and co-morbid illnesses of hypertension, hyperlipidemia and cardiac disease had significant relationship with self-treatment. The factor analysis procedure revealed seven factors that explained the 43% of variation in the self-treatment. These seven factors were categorized as knowledge, deficiencies of formal treatments, available self-treatment methods, physician related factors, the tendency to use herbal remedies, underlying factors such as gender and factors related to diabetes.</p> <p>Conclusions</p> <p>There is a medium tendency for self-treatment in diabetic patients. The assessment of self-treatment practices must be an essential part of patients' management in diabetes care.</p

Interpretative key management framework (IKM)

Cryptography has been employed to establishing secure communication over insecure networks. Using symmetric keys to encipher and decipher data is one of common practices for achieving secrecy over networks. To employ symmetric key cryptography we require a secure and reliable key management framework for generating, distributing, and finally revoking keys. Many attacks endanger security of key management in each step and so need of secure key management frameworks now is felt more than ever. Proposed, Interpretative Key Management, framework reduces likelihood of attacks by eliminating key storage, reducing many times key distribution to just one time interpreter distribution, and increases security by means of using minutely, hourly, or daily key without need of key distribution. Also key revocation is automated process and IKM doesn’t require revocation call

Frequency and Side Effect of Episiotomy in Primiparous Women: A Three- Month Longitudinal Survey

&lt;p&gt;&lt;strong&gt;&lt;em&gt;Background and Objectives&lt;/em&gt;: &lt;/strong&gt;Episiotomy is one of the most commonly performed procedures in obstetrics; approximately 33%of women giving birth vaginally in 2000 had episiotomy, but the best technique of episiotomy and its clinical benefits remain largely unknown. The aim of this study was to determine episiotomy prevalence and its clinical complications in women with vaginal delivery in teaching hospitals in Tehran during 3 months after  child birth.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&lt;em&gt;Methods&lt;/em&gt;&lt;/strong&gt;: This descriptive study was conducted on 510 primiparous women in teaching hospitals in Tehran. The Data were collected using interviews 1, 10, 40 and 90 days after delivery and after recorded in special forms.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&lt;em&gt;Results&lt;/em&gt;: &lt;/strong&gt;Episiotomy was performed in 97.3 % of primiparous women who gave birth vaginally.32.3 % of women had midline episiotomy and 67.7 % had medio-&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;lateral episiotomy. Episiotomy complications included: perineal pain reported by 96.4 % at one, 63 % after 10 days , 25 % after 40days, and 12 % at three months after birth. Dyspareunia on 10, 40 the day and 3 months after delivery was reported to be 100 %, 66 %and 31.2 %, respectively.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&lt;em&gt;Conclusion&lt;/em&gt;: &lt;/strong&gt;The prevalence&lt;strong&gt; &lt;/strong&gt;of Episiotomy is higher here in Iran than that of any other country and prevalence of mediolatral episiotomy is higher than median episiotomy in Iran despite its difficulties. Therefore, it seems logical that the prevalence of its complications (preneal pain and dyspareunia) is also higher in Iranian women.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt