رایانش ابری الگویی کم هزینه با کارایی بالا، برای عرضه ی خدمات رایانشی در پاسخ به نیازهای استفاده کنندگان خدمات نوین حوزه فناوری اطلاعات است. مسائل امنیتی موجود در رایانش ابری دلیل عدم تمایل برخی کاربران و سازمان ها به استفاده از زیرساخت ابری است باوجود اقدامات پیشگیرانه و واکنشی که در شبکه ها بکار گرفته می شوند، انجام پی جویی و پیگرد مجرمین پس از وقوع جرائم و حملات سایبری لازم و ضروری است؛ اما معماری کنونی رایانش ابری، پاسخگوی نیازهای پزشکی قانونی ابری نیست؛ بنابراین روند تحقیقات پزشکی قانونی در این زمینه با چالش های بسیاری روبروست. با توجه به مزیت های استفاده از رایانش ابری نمی توان به دلیل مسائل امنیتی آن را نادیده گرفت. پژوهشگران راه حل های مختلفی برای حل چالش های امنیتی رایانش ابری با در نظر گرفتن ماهیت پویای رایانش ابری و مسائل قانونی ارائه داده اند. در این مقاله مروری ابتدا ضمن بررسی اهمیت گذار از سرویس سنتی به خدمات ابری، مشکلات امنیتی استفاده از این خدمات را در قالب پزشکی قانونی ابری موردمطالعه قرار می دهیم و چالش ها و موضوعات باز تحقیقاتی در این حوزه را طبقه بندی می نماییم.

this study examines the effetivenss of task-based activities in helping students learn english language structures for a better communication. initially, a michigan test was administered to the two groups of 52 students majoring in english at the allameh ghotb -e- ravandi university to ensure their homogeneity. the students scores on the grammar part of this test were also regarded as their pretest scores. having ensured the homogeneity of the two groups, the two different teaching techniques were applied to the subjects. the students in the control group were intstructed through structural techniques and the subjects in the experimental group throught task-based ones. after 10 sessions of instruction, the same michigan test was administered to the two groups. their scores on the grammar part were considered as their posttest scores. regarding ho 1, the performance of the two groups on the posttest were compared and analyzed applying the t-test formula. the t-observed the t-critical value at both 0.05 and 0.01 levels of significance (3.10>2.02, 3.10>2.7). therefore, the first null hypothesis is refuted. in case of ho2: the performance of the control group on their present and posttest were analyzed using t-test formula. the results showed that the t-observed was less than the t-critical value at both levels of significance (1.16<2.02. 1.16<2.70). thus the second null hypothesis is maintained. considering ho3, the performance of the experimental group on their present and posstest were analyzed. in this case, the t-observed exceeded the t-critical value again at both 0.05 and 0.01 levels of significance (4.39>2.02, 4.39>2.70). hence, the third null hypothesis is rejected, too. taking above discussions into consideration, it can be concluded that the tought efl students learn english language structures better when they are taught task-based techniques than through structural techniques. therfore, language teachers are invited to furnish their teaching with the task-based techniques and activities. if they wish to educate more proficient language learners. (implications of this study for teaching and for further research are also discussed in chapter v).