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متن کامل


اطلاعات دوره: 
  • سال: 

    2018
  • دوره: 

    4
تعامل: 
  • بازدید: 

    142
  • دانلود: 

    0
چکیده: 

IN RECENT YEARS, SOCIAL NETWORKS HAVE BECOME POPULAR AMONG INTERNET USERS, AND VARIOUS STUDIES HAVE BEEN PERFORMED ON ANALYSIS OF SUCH NETWORKS. ONE OF THE IMPORTANT ISSUES IN ANALYZING SOCIAL NETWORKS IS INFORMATION DIFFUSION ANALYSIS. IN THIS CONTEXT, USERS' BEHAVIOR IS ASSUMED TO BE INFLUENCED BY OTHER SOCIAL NETWORK USERS. SEVERAL MODELS HAVE BEEN DESIGNED TO SIMULATE AND ANALYZE HOW INFORMATION IS DISSEMINATED IN SOCIAL NETWORKS. IN THIS PAPER, WE STUDY THE PROBLEM OF LEARNING THE DIFFUSION PROBABILITIES FOR THE Independent Cascade MODEL. WE FIRST OUTLINE THE IMPORTANCE OF THE SUBJECT, AND THEN WE PROPOSE A METHOD TO ESTIMATE DIFFUSION PROBABILITIES. IN THIS METHOD, WE ASSIGN A WEIGHT TO EACH INDIVIDUAL DIFFUSION SAMPLE OF EACH LINK IN THE NETWORK BASED ON ITS PARAMETERS. WE PROPOSE TWO WEIGHTING SCHEMES TO CONSIDER THE DIFFERENT EFFECTS OF DIFFUSION SAMPLES. THEN, WE EVALUATE OUR METHOD FOR LEARNING DIFFUSION PROBABILITIES WITH THE HELP OF SEVERAL DATASETS AND PRESENT THE RESULTS. ALSO, THE METHOD PRESENTED IN THIS PAPER IS COMPARED WITH OTHER METHODS IN TERMS OF MEAN ABSOLUTE ERROR AND TRAINING TIME.

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نویسندگان: 

VARDASBI ALI | Heshaam Faili | Asadpour Masoud

اطلاعات دوره: 
  • سال: 

    2018
  • دوره: 

    10
  • شماره: 

    4
  • صفحات: 

    11-21
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    206
  • دانلود: 

    0
چکیده: 

Influence maximization serves as the main goal of a variety of social network activities such as viral marketing. The Independent Cascade model for the influence spread assumes a one-time chance for each activated node to influence its neighbors. On the other hand, the manually activated seed set nodes can be reselected without violating the model parameters or assumptions. This view divides the influence maximization process into two cases: the simple case where the reselection of the nodes is not considered and the reselection case. In this study we will analyze real world networks in the reselection case. First we will show that the difference between the simple and the reselection cases constitutes a wide spectrum of networks ranging from the reselection-free to the reselection-friendly ones. Then we will experimentally show a significant entanglement between this and influence spread dynamics as well as other structural parameters of the network. Specifically, we show that under a realistic condition, the reselection gain of a network has a correlation of 0. 73 to a newly introduced influence spread dynamic. Furthermore, we propose a measure for detecting star-like networks and experimentally show a significant correlation between our proposed measure and the reselection gain in real world networks with different edge weight models.

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اطلاعات دوره: 
  • سال: 

    1397
  • دوره: 

    10
  • شماره: 

    37-38
  • صفحات: 

    85-100
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    402
  • دانلود: 

    155
چکیده: 

در مسیله حداکثر سازی نفوذ حداقل نودی را پیدا می کنیم که بیشترین انتشار و نفوذ را در جامعه داشته باشند. مطالعات راجع به حداکثرسازی نفوذ و انتشار به صورت گسترده ای درحال گسترش است. در سال های اخیر الگوریتم های زیادی در زمینه مسیله حداکثر سازی نفوذ در شبکه های اجتماعی ارایه شده است. این مطالعات شامل بازار یابی ویروسی، گسترش شایعات، اتخاذ نوآوری و شیوع بیماری های همه گیر و. . . است. در این مقاله روشی جدید برای حل مسیله حداکثرسازی نفوذ باعنوان ICIM-GREEDY را ارایه کرده ایم. در الگوریتم ICIM-GREEDY دو معیار مهم که در کارهای انجام شده قبلی در نظر گرفته نشده اند را در نظر می گیریم، یکی قدرت نفوذ و دیگری حساسیت به نفوذ. این دو معیار همیشه در زندگی اجتماعی انسانها وجود دارد. روش پیشنهادی روی دیتاست های استاندارد مورد ارزیابی قرار گرفته شده است. نتایج به دست آمده نشان می دهد که روش مذکور نسبت به دیگر الگوریتم های مقایسه شده از کیفیت بهتری درپیدا کردن نودهای بانفوذ در 50 نود seed برخوردار می باشد. همچنین روش ICIM-GREEDY در اکثر مواقع از لحاظ زمانی نیز نسبت به الگوریتم های مقایسه شده به لحاظ همگرایی نسبتا سریع، بهتر عمل می کند.

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مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
نویسندگان: 

KIMBER S.J. | SPANSWICK C.

اطلاعات دوره: 
  • سال: 

    2000
  • دوره: 

    11
  • شماره: 

    2
  • صفحات: 

    77-92
تعامل: 
  • استنادات: 

    1
  • بازدید: 

    155
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

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بازدید 155

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اطلاعات دوره: 
  • سال: 

    1395
  • دوره: 

    5
  • شماره: 

    17
  • صفحات: 

    79-86
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    1222
  • دانلود: 

    672
چکیده: 

در سال های اخیر، هزینه های فعالیتهای فن آوری اطلاعات در نتیجه پیچیده سازی تکنولوژیکی و استراتژی های بازارمحورتر به سرعت در حال افزایش است که زنجیره های ارزش شرکت ها را پیچیده تر می سازد. بسیاری از این هزینه ها به کالاها مربوط نبوده بلکه به مشتریان، بخشهای بازار و کانال های توزیع مرتبط می باشند. این مقاله نشان می دهد که شرکتها به دنبال تعیین قیمت تمام شده کالاها و خدمات خود هستند. به همین دلیل روش های مدیریت هزینه بازارمحور و مشتری محور محبوبیت فزاینده ای یافته اند. این تحقیق از جمله تحقیقات کاربردی است و هدف مقاله حاضر تشریح روش هزینه یابی بر مبنای فعالیت به عنوان یک فرآیند و ابزار حسابداری مدیریت راهبردی است. بدین منظور مدل جدیدی از هزینه یابی با عنوان هزینه یابی آبشاری معرفی می گردد که از طریق آن مشتری محوری براساس روش هزینه یابی برمبنای فعالیت به فرآیندهای مدیریت هزینه اضافه می کنیم. در تحقیق حاضر مطالعه موردی در بخش فن آوری اطلاعات یکی از بانکهای کشور امارات متحده عربی که از مدل توسعه یافته هزینه یابی بر مبنای فعالیت استفاده می نماید، انجام می پذیرد. نحوه پیشرفت مدل هزینه یابی برمبانی فعالیت به سمت فرآیندی که عملکردهای مشتریان مختلف را با یکدیگر مقایسه میکند، به عبارتی "هزینه یابی بر مبنای فعالیت مبتنی بر مشتری "را تشریح خواهیم کرد. نهایتاً به این نتیجه دست رسیدیم که به منظور محاسبات دقیقتر سود بهتر است از روشهای توسعه یافته هزینه یابی برمبنای فعالیت نسبت به روشهای سنتی استفاده نمود. همچنین برای سهولت انجام کار میتوان استفاده از روش هزینه یابی آبشاری را مدنظر قرار داد.

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نویسندگان: 

GHOLAMI AIDA | RASOOLY HASSAN

اطلاعات دوره: 
  • سال: 

    2013
  • دوره: 

    2
  • شماره: 

    6
  • صفحات: 

    26-32
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    351
  • دانلود: 

    0
چکیده: 

A simple semi-phenomenological model, which accurately predicts the dependence of threshold current for temperature of Resonant-phonon three well quantum Cascade laser based on vertical transitions is offered. We found that, the longitude optical phonon scattering of thermally excited electrons is the most important limiting factor for thermal performance of high frequency THz QCLs. In low frequency region, parasitic current increases the threshold current. Based on our model the use of materials with higher longitude optical phonon energy such as InGaAs/GaAsSb and decreasing the lower laser level lifetime can increase the maximum performance temperature. Our observations may can be used to understand the notion of the effects of thermal electrons on reduction of laser performance.

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بازدید 351

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مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
نویسندگان: 

AMANIFARD NIMA

اطلاعات دوره: 
  • سال: 

    2005
  • دوره: 

    18
  • شماره: 

    1 (TRANSACTIONS A: BASICS)
  • صفحات: 

    9-16
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    357
  • دانلود: 

    0
چکیده: 

The unstable flow with rotating-stall-like (RS) effects in a rotor-Cascade of an axial compressor was numerically investigated. The RS was captured with the reduction in mass flow rate and increasing of exit static pressure with respect to design operating condition of the single rotor. The oscillatory velocity traces during the stall propagation showed that the RS vortices repeat periodically, and the mass flow rate was highly affected by the blockage areas made by stall vortices. The results also showed that large scale vortices highly affects on the generation and growth of the new vortices. An unsteady two-dimensional finite-volume solver was employed for the numerical study which was developed based on Van Leer’s flux splitting algorithm in conjunction with TVD limiters and the κ-ε turbulence model was also employed. The good agreement of the computed mass flow rate with the experimental results validates the numerical study.

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بازدید 357

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اطلاعات دوره: 
  • سال: 

    2009
  • دوره: 

    6
تعامل: 
  • بازدید: 

    130
  • دانلود: 

    0
چکیده: 

PROVISION OF FRESH WATER IS A MAJOR PROBLEM IN REMOTE AREAS AND ARID ZONES. PASSIVE SOLAR STILL IS ONE OF THE MANY APPARATUS THAT CAN BE WIDELY USED FOR WATER PURIFICATION IN MENTIONED AREAS WHEN THE CLIMATIC CONDITIONS IS FAIR AND THE DEMAND IS NOT TOO LARGE. PASSIVE SOLAR STILLS ARE BROADLY DIVIDED INTO BASIN AND INCLINED TYPES. IN THIS PAPER, TWO Cascade SOLAR STILLS WERE CONSTRUCTED WITH AND WITHOUT LATENT HEAT THERMAL ENERGY STORAGE SYSTEM (LHTESS). PARAFFIN WAX IS SELECTED AS PHASE CHANGE MATERIAL (PCM) THAT ACTS AS A LHTESS. USING WEIR ON EACH STEP OF STILLS LEADS TO FORCED FLOW OF INLET WATER AND INCREASES IN ITS RESIDENCE TIME IN THE STILLS. FURTHERMORE, A THIN LAYER OF WATER COVERS COMPLETELY THE EVAPORATION SURFACE AND PREVENTS TO SPOTS DRY UPON IT. THERMAL PERFORMANCES OF STILLS WERE COMPARED IN TYPICAL SUNNY AND PARTIALLY CLOUDY DAYS. THE RESULTS SHOWED THAT NEARLY THE SAME VALUES OF TOTAL PRODUCTIVITY ARE OBTAINED FOR STILLS WITH AND WITHOUT LHTESS IN SUNNY DAY.ON THE OTHER HAND, A SIGNIFICANT DIFFERENCE WAS OBSERVED IN TOTAL PRODUCTIVITY WHEN THE STILLS OPERATED IN PARTIALLY CLOUDY DAY. HENCE, STILL WITHOUT LHTESS IS PREFERRED FOR SUNNY AREAS BECAUSE OF ITS SIMPLICITY AND LOW CONSTRUCTION COST. STILL WITH LHTESS IS PROPOSED FOR PARTIALLY CLOUDY AREAS DUE TO THE HIGHER PRODUCTIVITY. IN ADDITION, THE EFFECT OF VARIOUS FLOW RATES ON TOTAL PRODUCTIVITY OF THE STILLS WERE INVESTIGATED DURING FIVE SUNNY CONSECUTIVE DAYS AND FOUND THAT THE MAXIMUM PRODUCTIVITY IS OBTAINED IN LOWEST POSSIBLE FLOW RATE.

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اطلاعات دوره: 
  • سال: 

    2024
  • دوره: 

    12
  • شماره: 

    2
  • صفحات: 

    373-386
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    6
  • دانلود: 

    0
چکیده: 

Background and Objectives: One of the important topics in oncology treatment and prevention is the identification of genes that initiate cancer in cells. These genes are known as cancer driver genes (CDGs). Identification of the CDGs is important both for a basic understanding of cancer and to help find new therapeutic or biomarker goals. Several computational methods to find the genes responsible for cancer have been developed based on genome data. However, many of these methods find key mutations in genomic data to predict which genes are responsible for cancer. These methods depend on the mutation and genome data and often show a high rate of false positives in the results. In this study, we proposed an influence maximization-based approach, CinfuMax, which can detect the genes responsible for cancer without needing information on mutations.Methods: In this method, the concept of influence maximization and the Independent Cascade model are employed. Firstly, the gene regulatory network for breast, lung and colon cancers was built using regulatory interactions and gene expression data. Next, we implemented an Independent Cascade diffusion algorithm on the networks to compute each gene's coverage. Finally, the genes with the highest coverage were classified as driver.Results: The results of the proposed method were compared to 19 other computational and network-based methods based on the F-measure and the number of detected driver genes. The results demonstrated that the proposed method produces better results than other methods. Also, CinfuMax is able to detect 18, 19 and 22 individual driver genes in three breast, lung and colon cancers, respectively, which have not been identified in any of the previous methods.Conclusion: The results show that Independent cascading methods to identify driver genes perform better than linear threshold methods. Driver genes are also classified in terms of influence speed and have identified the genes with the highest diffusion rate in each type of cancer. Identification of these genes can be useful for molecular therapies and drug purposes.

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اطلاعات دوره: 
  • سال: 

    2023
  • دوره: 

    9
تعامل: 
  • بازدید: 

    42
  • دانلود: 

    0
چکیده: 

Influence maximization techniques emphasize selecting a set of influential nodes in order to maximize influence. Because the algorithms presented in this field ignore the topology of cliques for diffusion, there are two major challenges in influence maximization algorithms: optimal diffusion and computational overhead reduction. As a result, the CDP algorithm is presented in this article to address these issues. This algorithm first selects suitable cliques for diffusion based on their position and strategy in social networks. Furthermore, for each clique, a score is calculated based on the topological criteria of the clique, and suitable cliques are selected for diffusion by applying a threshold limit. The seed nodes are chosen from the cliques in the second step. To avoid the rich club phenomenon, only a few nodes from each clique are chosen as seed candidate nodes. Finally, the seed nodes are chosen based on the node's topology and the strength of the node's level one neighbor. In the experiment section, the CDP algorithm significantly outperforms the best algorithms presented in recent years in terms of influence spread rate and execution time.

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