• ETRI Journal
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• 제43권6호
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• pp.1004-1012
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• 2021

The collaboration productively interacting between multi-agents has become an emerging issue in real-world applications. In reinforcement learning, multi-agent environments present challenges beyond tractable issues in single-agent settings. This collaborative environment has the following highly complex attributes: sparse rewards for task completion, limited communications between each other, and only partial observations. In particular, adjustments in an agent's action policy result in a nonstationary environment from the other agent's perspective, which causes high variance in the learned policies and prevents the direct use of reinforcement learning approaches. Unexpected social loafing caused by high dispersion makes it difficult for all agents to succeed in collaborative tasks. Therefore, we address a paradox caused by the social loafing to significantly reduce total returns after a certain timestep of multi-agent reinforcement learning. We further demonstrate that the collaborative paradox in multi-agent environments can be avoided by our proposed effective early stop method leveraging a metric for social loafing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.483-503
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• 2014

In this paper, human action recognition using pyramid histograms of oriented gradients and collaborative multi-task learning is proposed. First, we accumulate global activities and construct motion history image (MHI) for both RGB and depth channels respectively to encode the dynamics of one action in different modalities, and then different action descriptors are extracted from depth and RGB MHI to represent global textual and structural characteristics of these actions. Specially, average value in hierarchical block, GIST and pyramid histograms of oriented gradients descriptors are employed to represent human motion. To demonstrate the superiority of the proposed method, we evaluate them by KNN, SVM with linear and RBF kernels, SRC and CRC models on DHA dataset, the well-known dataset for human action recognition. Large scale experimental results show our descriptors are robust, stable and efficient, and outperform the state-of-the-art methods. In addition, we investigate the performance of our descriptors further by combining these descriptors on DHA dataset, and observe that the performances of combined descriptors are much better than just using only sole descriptor. With multimodal features, we also propose a collaborative multi-task learning method for model learning and inference based on transfer learning theory. The main contributions lie in four aspects: 1) the proposed encoding the scheme can filter the stationary part of human body and reduce noise interference; 2) different kind of features and models are assessed, and the neighbor gradients information and pyramid layers are very helpful for representing these actions; 3) The proposed model can fuse the features from different modalities regardless of the sensor types, the ranges of the value, and the dimensions of different features; 4) The latent common knowledge among different modalities can be discovered by transfer learning to boost the performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권3호
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• pp.861-880
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• 2023

Semantic segmentation of road scene is the key technology of autonomous driving, and the improvement of convolutional neural network architecture promotes the improvement of model segmentation performance. The existing convolutional neural network has the simplification of learning knowledge and the complexity of the model. To address this issue, we proposed a road scene semantic segmentation algorithm based on multi-task collaborative learning. Firstly, a depthwise separable convolution atrous spatial pyramid pooling is proposed to reduce model complexity. Secondly, a collaborative learning framework is proposed involved with saliency detection, and the joint loss function is defined using homoscedastic uncertainty to meet the new learning model. Experiments are conducted on the road and nature scenes datasets. The proposed method achieves 70.94% and 64.90% mIoU on Cityscapes and PASCAL VOC 2012 datasets, respectively. Qualitatively, Compared to methods with excellent performance, the method proposed in this paper has significant advantages in the segmentation of fine targets and boundaries.

• 영어어문교육
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• 제11권4호
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• pp.365-389
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• 2005

The purpose of this study is to present the task model that is the most effective in English language methodology based on the investigation of task-based performance in Korean EFL classroom practice. The subjects were 538 high school students and 126 high school teachers, each of whom had common experiences using the materials of task-based activities for more than one year. To analyze the data, the program SPSS WIN 11.0 including frequency distribution and chi-square analysis was used. The results of the questionnaire analysis showed that both teachers and students had a comparatively high level of satisfaction in task rationale, but that they had some mixed responses in the fields of input data, settings, and activity types. To conclude, a few suggestions are made to provide some meaningful considerations for the EFL teachers and material developers: a) task goals and rationale that encourage the learner's positive motivation; b) authenticity of input data based on the real-world context; c) collaborative learning environment that enhances communicative interaction; d) proportional representation of the creative problem-solving activities related to discussions and decision-making processes; e) systematic introduction of integrated language skills. It also suggests that the multi-lateral task model, which has some positive assets compared to previous task models, be newly introduced and applied to the second language learning classrooms.

• 전자공학회논문지CI
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• 제48권3호
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• pp.36-45
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• 2011

소셜러닝의 대표적 학습인 협력학습에서의 에이전트란 학습자에게 현황이든, 환경이든, 과제이든 설명해 줄 수 있거나, 보편적이고 일반적인 방법으로 독립적인 기능을 수행할 수 있는 것이다, 이를 위해서는 에이전트 사이에서의 의사소통에 관한 정보기술 표준화 방법이 요구된다. 본 연구는 협력학습에서 사용되는 각종 에이전트들의 의사소통에 관한 데이터 모델에 관한 기술을 제시한다. 따라서 이러닝 협력학습 환경을 지원하는 많은 에이전트들의 유형을 파악하고, 이 에이전트들 간의 상호 의사소통에 관한 규칙을 갖는 데이터 모델을 설계하여 그 요소들을 정의하고자 한다. 이렇게 제시된 표준화된 데이터 모델을 기반으로 하는 다중 에이전트 시스템은 여러 응용 에이전트가 독립된 프로세스로 활동할 수 있도록 정의된 통신 데이터모델에 의해 메시지 상호 교환이 가능해진다. 본 연구는 소셜러닝에서 주를 이루는 학습방법인 협력학습 중에서 다양한 에이전트를 활용하는 경우 이를 지원하는 에이전트간의 통신에 관한 의사소통 모델 응용을 통해 원활한 협력학습이 구현되도록 기여할 것으로 기대한다.

• 한국비블리아학회지
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• 제23권4호
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• pp.93-108
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• 2012

본 연구는 문헌정보학과 학생들의 조별활동의 성과를 높이기 위해 위키를 활용한 교육을 진행할 때 발생하는 문제점을 발견하고 이를 개선함으로써 학생들의 학습능력을 향상시키기 위한 방안을 마련하기 위해 수행되었다. 학생들이 수업을 위해 사용한 위키 사이트에서의 활동은 물론, 수강 학생들 중 12명을 대상으로 인터뷰를 진행하였다. 연구결과, 학생들이 수강하는 수업에서 조별활동은 보편적인 것으로 나타났고 개별적으로 과제를 하는 것보다 조별로 하는 과제로부터 더 많은 학습을 하는 것으로 나타났다. 그러나 학습의 과정에서 위키사용경험이 없다는 점과 학점을 중시하게 됨으로써 관계보다는 과제중심의 조별활동이 이루어지는 문제점이 발견되었다. 또한, 새로운 개념의 도구가 제안되었다 할지라도 과거의 방식에 따라 조별활동을 진행하는 것으로 나타났다. 따라서 학생들에게 위키사용 방법을 교육함과 동시에 협업을 통한 학습의 교육적 효과를 경험해보는 것이 중요하다. 또한 관계중심의 조별활동이 이루어진다면 그 교육적 효과가 커질 것으로 기대된다.