On the security of a provably secure, efficient, and flexible authentication scheme for ad hoc wireless sensor networks

In a recent paper, Chang and Le proposed an efficient smart card?based authenticated key exchange protocol (which is referred to as CL scheme) for heterogeneous ad hoc wireless sensor networks. However, we found that the CL scheme is subject to sensor capture attack which breaks the session key security of the CL scheme. An improved protocol is proposed to fix this problem.Peer reviewe

On Global Attractivity of a Class of Nonautonomous Difference Equations

We mainly investigate the global behavior to the family of higher-order nonautonomous recursive equations given by y n p ry n−s / q φ n y n−1 , y n−2 , . . . , y n−m y n−s , n ∈ N 0 , with p ≥ 0, r, q > 0, s, m ∈ N and positive initial values, and present some sufficient conditions for the parameters and maps φ n : R m → R , n ∈ N 0 , under which every positive solution to the equation converges to zero or a unique positive equilibrium. Our main result in the paper extends some related results from the work of Gibbons et al

Global Attractivity of a Family of Max-Type Difference Equations

We propose to study a generalized family of max-type difference equations and then prove the global attractivity of a particular case of it under some parameter conditions. Through some numerical results of other cases, we finally pose a generic conjecture

Fixation Probabilities on Complete Star and Bipartite Digraphs

This paper exactly formulates the kth-order fixation probabilities on complete star digraphs (CSDs), which extend the results from Broom and Rychtář (2008). By applying these probability formulae, some asymptotic properties on CBDs are analyzed, and certain CSDs are determined to be amplifiers of selection for arbitrary relative fitness larger than 1, while all the CSDs are proved to be amplifiers of selection for fixed relative fitness slightly larger than 1. A numerical method for fixed population structure (by solving a linear system) is developed to calculate the fixation probabilities on complete bipartite digraphs (CBDs), and some conjectures are finally given through simulations

Global Dynamics and Optimal Control of a Viral Infection Model with Generic Nonlinear Infection Rate

This paper is devoted to exploring the combined impact of a generic nonlinear infection rate and infected removable storage media on viral spread. For that purpose, a novel dynamical model with an external compartment is proposed, and the explanations of the main model assumptions (especially the generic nonlinear infection rate) are also examined. The existence and global stability of the unique equilibrium of the model are fully investigated, from which it can be seen that computer virus would persist. On this basis, a next-best approach to controlling the level of infected computers is suggested, and the theoretical analysis of optimal control of the model is also performed. Additionally, some numerical examples are given to illustrate the main results

TLTC, a T5 exonuclease–mediated low-temperature DNA cloning method

Molecular cloning is used in a wide variety of biological and medical research. Here, we developed a rapid and efficient DNA-assembling method for routine laboratory work. We discovered that the cleavage speed of T5 exonuclease is approximately 3 nt/min at 0°C and hence developed a T5 exonuclease–mediated low-temperature sequence- and ligation-independent cloning method (TLTC). Two homologous regions of 15 bp–25 bp compatible with the ends of the vector backbones were introduced into the inserts through PCR. Approximately 120 fmol of inserts and linear vectors was mixed at a molar ratio of approximately 3:1 and treated with 0.5 U of T5 exonuclease at 0°C for 5 min. Then, the mixture was transformed into Escherichia coli to generate recombinant plasmids. Single segment and multi-segments can be assembled efficiently using TLTC. For single segment, the overall cloning efficiency is above 95%. Moreover, extra nucleotides in the vectors can be removed during TLTC. In conclusion, an extremely simple and fast DNA cloning/assembling method was established in the present study. This method facilitates routine DNA cloning and synthesis of DNA fragments

Heat shock protein 90 promotes RNA helicase DDX5 accumulation and exacerbates hepatocellular carcinoma by inhibiting autophagy

Objective: Hepatocellular carcinoma (HCC), the main type of liver cancer, has a high morbidity and mortality, and a poor prognosis. RNA helicase DDX5, which acts as a transcriptional co-regulator, is overexpressed in most malignant tumors and promotes cancer cell growth. Heat shock protein 90 (HSP90) is an important molecular chaperone in the conformational maturation and stabilization of numerous proteins involved in cell growth or survival. Methods: DDX5 mRNA and protein expression in surgically resected HCC tissues from 24 Asian patients were detected by quantitative real-time PCR and Western blot, respectively. The interaction of DDX5-HSP90 was determined by molecular docking, immunoprecipitation, and laser scanning confocal microscopy. The autophagy signal was detected by Western blot. The cell functions and signaling pathways of DDX5 were determined in 2 HCC cell lines. Two different murine HCC xenograft models were used to determine the function of DDX5 and the therapeutic effect of an HSP90 inhibitor. Results: HSP90 interacted directly with DDX5 and inhibited DDX5 protein degradation in the AMPK/ULK1-regulated autophagy pathway. The subsequent accumulation of DDX5 protein induced the malignant phenotype of HCC by activating the β-catenin signaling pathway. The silencing of DDX5 or treatment with HSP90 inhibitor both blocked in vivo tumor growth in a murine HCC xenograft model. High levels of HSP90 and DDX5 protein were associated with poor prognoses. Conclusions: HSP90 interacted with DDX5 protein and subsequently protected DDX5 protein from AMPK/ULK1-regulated autophagic degradation. DDX5 and HSP90 are therefore potential therapeutic targets for HCC

Can one get fish and bears paws at the same time? Ethical dilemma of qualitative health research in Chinese culture

Ethical considerations of qualitative research are often likely to be ignored or downplayed. This article will follow bioethics principles to explore the dilemmas expressed in the Chinese proverb: One cannot get both fish and bear’s paws simultaneously. This succinct expression relates to so many phases of a research, based on the ethical characteristics of qualitative research. Four specific ethical dilemmas will be examined in this paper: the dilemmas between “building trust and rapport” and “informed consent,” finding the right balance between “providing benefit to participants” and “coercion through kindness,” the trade-off between “burning out researcher” and “ending research relationship,” and giving consideration to both “quoting comprehensive qualitative data” and “ensuring participant privacy.” Furthermore, the paper explores the different interpretations of autonomy between Chinese culture and Western individualism and their impact on the ethics aspects of qualitative research

어휘학습을 위한 SNS기반 협력학습 수업 설계 전략 개발

학위논문(석사)--서울대학교 대학원 :사범대학 교육학과(교육공학전공),2020. 2. 임철일.언어학습은 읽기, 말하기, 쓰기, 듣기 네가지 능력에 대한 학습으로 구성되어 있다. 언어학습에서 어휘는 중요한 역할을 맡고 있다. 어휘에 대한 지식은 학습자의 전반적인 언어 습득에 매우 필수적인 지표이다. 따라서 어휘학습은 언어학습에서 매우 중요한 것으로 강조되어 왔다. 어휘학습은 학습자가 높은 수준으로 참여함으로써 어휘에 대한 심도 깊은 학습을 유도하는 것을 목표로 요구하며, 성공적인 어휘학습을 위해서는 교수자의 계획적인 지도가 필요하다는 선행 연구 결과가 있다. 그러나 현재 언어교육 현장에서 교수자가 어휘지도를 중요하지 않게 생각하는 경우가 많고 어휘 학습이 암기 위주의 수동적인 학습 형태를 지니기 때문에 학습에 대한 흥미와 그 효과성 떨어뜨린다는 연구 결과가 있다. 따라서 효과적인 어휘 학습을 위해 학습자가 참여할 수 있으며 어휘 사용의 기회를 제공할 수 있고 흥미를 유발할 수 있는 수업의 설계전략 모색이 필요하다. 최근에는 어휘학습 수업에서 협력 학습 방법을 시도하고 있다. 연구 결과에 따르면 개별 학습활동과 비교했을 때 협력적 학습활동은 어휘학습에 효과적인 커뮤니케이션이 가능하도록 하여 학습자가 어휘를 지속적으로 사용할 수 있도록 한다. 이 과정에서 학습자의 어휘학습에 대한 참여도, 흥미도, 동기유발, 상호작용성에서 긍정적인 효과를 가 있는 것이 나타났다. 또한 그룹 학습활동에 참여한 학습자가 개별 학습활동에 참여한 학습자보다 언어적으로 더 정확한 문장을 만드는 경향이 있다는 결과가 나타났다. 따라서 이와 같은 연구 결과에 따라 어휘 학습에서 협력적 학습이 긍정적 영향을 미침을 확인하였다. 한편SNS는흥미성, 실천성, 어포던스, 세계적인 보급성, 상호작용성의 특성을 가지고 어휘학습의 동기 유발, 학습 태도에 긍정적인 영향을 미친다는 연구 결과가 있었다. 또한, SNS기반 협력학습은 학습자 중심의 학습을 가능하게 하여 협력적 환경에서 상호작용을 촉진할 수 있다는 연구 결과에 따라 학습자가 실재감을 가지고 능동적으로 참여하고 어휘학습에 긍정적인 영향을 미침을 확인하였다. 그러나 관련된 선행연구에서는 어휘학습을 위한 SNS기반 협력학습에 관한 연구가 주로 효과성 및 영향 요인에 초점을 두고 있으며 어휘학습에서 SNS를 활용한 협력학습의 구체적 수업 설계 전략이 부족하였다. 따라서 본 연구에서는 어휘학습을 촉진하는 SNS기반 협력학습 수업 설계 전략을 제시하였다. 본 연구의 연구 문제는 다음과 같다. 첫째, 어휘학습을 위한 SNS기반 협력학습의 수업 설계 전략은 무엇인가? 둘째, 어휘학습을 위한 SNS기반 협력학습 수업 설계 전략의 내적 타당성은 어떠한가? 셋째, SNS기반 협력학습을 활용해서 설계된 어휘학습 수업에서 학습자 및 교수자의 반응은 어떠한가? 이상의 연구문제를 해결하기 위해 설계·개발 연구방법론을 적용하여 크게 세 단계의 연구 절차를 거쳐 설계전략을 개발하였다. 우선 키워드를 바탕으로 선행 연구를 검색한 후, 관련된 주요 문헌 검토 결과를 바탕으로 초기 전략을 도출하고, 수업의 각 단계에 따른 상세 지침을 개발하였다. 그 다음 교육공학 전문가 4인을 대상으로 개발된 전략의 타당성에 대한 설문 및 심층면담을 실시하였다. 이후 개발된 전략을 적용한 수업을 실시하였다. 그리고 수업에 참여한 교수자 및 학습자의 반응을 수집하여 분석을 진행한 다음 최종 설계전략을 도출하였다. 최종 설계 전략은 8개 일반 설계 전략과 21개의 상세 지침으로 구성되었다. 설계 전략은 수업 단계에 따라서 수업 전, 수업 중, 수업 후 세 단계로 나누어서 구성하였다. 본 연구에서는 SNS 기반 협력학습이 어휘학습의 참여도, 흥미성, 효율성에 긍정적인 영향을 미칠 수 있음을 확인하였다. 본 연구의 연구결과는 어휘학습에서 SNS 기반 협력학습의 활용이 학습자의 어휘 사용에 더 많은 기회를 제공하여 어휘에 대한 학습자의 심도 깊은 이해를 지원하였다는 의의가 있으며 이를 어휘학습에 적용하는 데 구체적인 전략을 제시했다는 점에서 실천적인 의의가 있었다. 하지만 반복적인 현장 수업 적용 및 수정 보완을 통하여 교수 설계 전략이 개선될 필요가 있으며 학습 성과 분석에 대한 양적 연구를 통해 설계 전략 효과성 검증이 필요할 것이다. 향후 모바일 기기를 학습도구로 활용함으로써 학습자의 지속적인 흥미성을 유지하기 위한 전략 개발 연구를 모색할 수 있다.Vocabulary is the basis of constructing sentences and articles, an essential indicator to judge whether learners can master a language comprehensively, and a basic element for learners to achieve language output. Therefore, vocabulary learning plays an important role in language learning. Vocabulary learning aims at guiding learners' deep processing of vocabulary with their high participation. In this process, instructors' guidance helps learners to effectively learn vocabulary. In the actual language learning, learners often ignore the vocabulary instruction, and the dull and passive learning method makes learners lose their interest in learning, and finally leads to the poor instructional effect. Therefore, in order to make learners actively participate in vocabulary learning and make vocabulary learning more efficient, it is necessary to explore instructional strategies that can stimulate learners' interest and provide learners with opportunities to use vocabulary. Recently, people pay more and more attention to the application of collaborative learning in vocabulary learning. Compared with individual activities, collaborative learning can create more effective communication and interaction environment for vocabulary learning, enabling learners to create more vocabulary learning opportunities while using vocabulary continuously. In this process, learners' participation, interest, motivation and interaction are effectively affected. In addition, compared with individual learning, learners with group tend to produce correct language texts. In the other hand, SNS has the characteristics of interest, practice, context and interactivity, which can satisfy the motivation of vocabulary learning and stimulate learners' desire to participate actively, thus having a positive impact on vocabulary learning. However, vocabulary learning researches which in the SNS supported collaborative learning mainly focused on the effectiveness and influencing factors, lacking of specific instructional strategy. Therefore, this study developed the instructional strategies on SNS supported collaborative learning for vocabulary learning. The purpose of this study is to develop the instructional strategies that promote vocabulary in the SNS supported collaborative learning. The issues of this study are：1) What are the instructional strategies of SNS supported collaborative learning for vocabulary learning?; 2) Are the instructional strategies of SNS supported collaborative learning internally valid?; 3) What is the response of the learners and instructors towards the instructional strategies of SNS supported collaborative learning? In order to solve these three problems, this study is based on the Type 2 (Model Research) in Richey & Klein（2014）s Design and Development Research Method. The validity of the initial instructional strategy obtained was evaluated and revised to export the final instructional strategies. First of all, the initial strategies and specific guidelines were derived through a discussion of the advance researches. After that, four experts major in educational technology conducted a validity test on the initial strategies. These instructional strategies were then applied to actual classroom teaching at a university with 16 students. After the course, the responses of the instructor and learners participating in the course were analyzed to find out the external validity test results. The responses of the learner mainly focused on the incomplete of the supervision mechanism, while the instructor raised the point that the evaluation criteria were not clear enough. Finally, the strengths, weaknesses, and improvement points of the instructional strategies proposed by learners and instructor were synthesized to derive the final instructional strategy, which were divided into three stages according to the course process, consisting of 8 general strategies and 21 specific guidelines. The results show that the SNS supported collaborative learning outperformed the traditional learning in vocabulary gains. Furthermore, the learners positive response indicated that this new kind of instruction was interesting, helpful, and useful in increasing their motivation and engagement. This study suggests that SNS supported collaborative learning can be reasonably incorporate into the current curriculum to provide effective learning opportunities and to develop learners vocabulary learning.Chapter 1. INTRODUCTION 1 1.1 Problem Statement and Purpose 1 1.2 Research Questions 5 1.3 Definition of Terms 6 Chapter 2. REVIEW OF THE LITERATURE 7 2.1 Vocabulary Learning 7 2.1.1 Vocabulary Learning and Teaching 7 2.1.2 Vocabulary Learning in a Collaborative Learning Environment 11 2.1.3 SNS supported vocabulary learning 14 2.2 SNS supported Collaborative Learning 16 Chapter 3. METHODOLOGY 18 3.1 Participants 18 3.2 Research Procedure 19 3.3 Research Tool 21 3.4 Data Collection and Analysis 24 3.4.1 Literature Review 24 3.4.2 Internal Validation 25 3.4.3 External Validation 28 Chapter 4. RESULTS 36 4.1 The Initial Instructional Strategies 36 4.2 Internal Valid Result 41 4.2.1 The First Expert Evaluation 41 4.2.2 The Second Expert Evaluation 50 4.3 Response of the Learners and Instructors 57 4.3.1 Learners Response 57 4.3.2 Instructor Response 63 4.4 The Final Instructional Strategies 65 Chapter 5. DISCUSSION AND CONCLUSION 73 5.1 Discussion 73 5.1.1 The Effect of the Instructional Strategies 73 5.1.2 Suggestion 75 5.2 Conclusion 76 5.2.1 Summary and Conclusion 76 5.2.2 Implication 78 REFERENCES 79 APPENDIXES 91 국 문 초 록 128Maste