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Optical Fiber Code-Division Multiple-Access Networks Using Concatenated Codes
Lam, Pham-Manh,Minh, Do-Quang The Korea Institute of Information and Commucation 2002 Journal of communications and networks Vol.4 No.3
An optical fiber code-division multiple-access (CDMA) network is proposed in which encoding is based on the use of concatenated sequences of relatively large weight. The first short component sequence in the concatenated sequence permits realistic electronic encoding of each data bit. The chips of this sequence are then all-optically encoded at substantially higher rate. In spite of the relatively large weight of the sequence the all-optical encoder is practical by virtue of the shortness of the component sequences. The use of Gold and Lempel sequences as component sequences for generating the concatenated sequences is studied and the bit-error rate (BER) performance of the proposed system is presented as a function of the received optical power with the number of simultaneous users as parameter.
Lam H Pham,Linh T Pham,DongQuy Hoang,김진환 한국고분자학회 2019 Macromolecular Research Vol.27 No.12
By adding diammonium phosphate (DAP) or aluminum diethyl phosphinate (OP) as flame retardants, flame retardancy of composites based on polypropylene and wood flour (PP-WF) improved significantly. A loading of 25 wt% DAP achieved a UL-94 V-0 rating as well as LOI value of 29%, which increased by 52.6% compared with that of the PP-WF composite alone. A 30 wt% OP loading provided a rating of UL-94 HB standard, and achieved LOI value of 28%. Meanwhile, the PPWF composite without flame retardant, completely burned to the sample holder clamp with low LOI value (19%). Thermal properties of the PP-WF composite with and without DAP and OP flame retardants, were investigated using TGA and DSC. Flame retardant performance was also studied, through the morphology and chemical structure of residual char by TGA, FTIR, SEM, and XPS analyses. There was interaction between DAP and the composite, which played a key role in maintaining mechanical properties of the material.
Lam H Pham,Hai D Nguyen,김진환,DongQuy Hoang 한국섬유공학회 2019 Fibers and polymers Vol.20 No.11
Thermal properties and the flame retardancy of polypropylene/wood flour (PP-WF) composite were improved byadding aluminum hydrogen phosphonate (AHP) and triphenyl phosphate (TPP) flame retardants. PP-WF compositescontaining 30 wt% of AHP and 30 wt% of TPP achieved UL-94 HB standard with the horizontal burning rate of 20.8 mm/min and of 11.5 mm/min, respectively. Thermal properties of PP-WF composite with and without flame retardant, as well asthe interaction between PP-WF and flame retardant were investigated through TGA analysis. The flame retardant mechanismis mainly in condensed phase for AHP and in gas phase for TPP. The residual char after the decomposition of PP-WF/AHPcomposite was analyzed by FTIR to understand how the formation of char affected on the flame retardancy and thermalstability PP-WF composite.
( Dinh-lam Pham ),( Hyun Ahn ),( Kwanghoon Pio Kim ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.8
Workflow process mining is becoming a more and more valuable activity in workflow-supported enterprises, and through which it is possible to achieve the high levels of qualitative business goals in terms of improving the effectiveness and efficiency of the workflow-supported information systems, increasing their operational performances, reducing their completion times with minimizing redundancy times, and saving their managerial costs. One of the critical challenges in the workflow process mining activity is to devise a reasonable approach to discover and recognize the bottleneck points of workflow process models from their enactment event histories. We have intuitively realized the fact that the iterative process pattern of redo-activities ought to have the high possibility of becoming a bottleneck point of a workflow process model. Hence, we, in this paper, propose an algorithmic approach and its implementation to discover the redo-activities and their performers’ involvements patterns from workflow process enactment event logs. Additionally, we carry out a series of experimental analyses by applying the implemented algorithm to four datasets of workflow process enactment event logs released from the BPI Challenges. Finally, those discovered redo-activities and their performers’ involvements patterns are visualized in a graphical form of information control nets as well as a tabular form of the involvement percentages, respectively.
Discovering Temporal Work Transference Networks from Workflow Execution Logs
Dinh-Lam Pham,안현,김광훈 한국인터넷정보학회 2019 인터넷정보학회논문지 Vol.20 No.2
Workflow management systems (WfMSs) automate and manage workflows, which are implementations of organizational processes operated in process-centric organizations. In this paper, wepropose an algorithm to discover temporal work transference networks from workflow execution logs. The temporal work transference network is a special type of enterprise social networks that consists of workflow performers, and relationships among them that are formed by work transferences between performers who are responsible in performing precedent and succeeding activities in a workflow process. In terms of analysis, the temporal work transference network is an analytical property that has significant value to be analyzed to discover organizational knowledge for human resource management and related decision-making steps for process-centric organizations. Also, the beginning point of implementinga human-centered workflow intelligence framework dealing with work transference networks is to develop an algorithm for discovering temporal work transference cases on workflow execution logs. To this end, we first formalize a concept of temporal work transference network, and next, we present a discovery algorithm which is for the construction of temporal work transference network from workflow execution logs. Then, as a verification of the proposed algorithm, we apply the algorithm to an XES-formatted log dataset that was released by the process mining research group and finally summarize the discovery result.