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Verifying Multi-Agent Systems by Model Checking Three-valued Abstractions
Get PDFABSTRACT We develop the theoretical foundations of a predicate abstraction methodology for the verification of multi-agent systems. We put forward a specification language based on epistemic logic and a weak variant of the logic ATL interpreted on a three-valued semantics. We show that the model checking problem for multi-agent systems in this setting is tractable by giving a provably correct procedure which admits a PTime bound. We give a constructive technique for generating abstract approximations of concrete multiagent systems models and show that the truth values are preserved between abstract and concrete models. We evaluate the effectiveness of the methodology on a variant of the bit-transmission problem
Looking Deathworthy Perceived Stereotypicality of Black Defendants Predicts Capital-Sentencing Outcomes
Get PDFABSTRACT-Researchers previously have investigated the role of race in capital sentencing, and in particular, whether the race of the defendant or victim influences the likelihood of a death sentence. In the present study, we examined whether the likelihood of being sentenced to death is influenced by the degree to which a Black defendant is perceived to have a stereotypically Black appearance. Controlling for a wide array of factors, we found that in cases involving a White victim, the more stereotypically Black a defendant is perceived to be, the more likely that person is to be sentenced to death. Race matters in capital punishment. Even when statistically controlling for a wide variety of nonracial factors that may influence sentencing, numerous researchers have found that murderers of White victims are more likely than murderers of Black victims to be sentenced to deat
Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection
Get PDFA compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4 epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36-6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context
Intracranial angioplasty with Gateway-Wingspan system for symptomatic atherosclerotic stenosis: preliminary results of 27 Chinese patients
Get PDFAbstract Background: We investigated the safety of treatment of symptomatic intracranial atherosclerotic stenoses with the Gateway-Wingspan system and its initial effect on prevention of ischemic events. Methods: Twenty-seven cases of symptomatic intracranial atherosclerotic stenoses were treated with angioplasty with a Wingspan stent. Location of stenoses, extent of stenoses before and after angioplasty, success rate of treatment, occurrence of procedural complications, and changes in recurrence of symptoms of ischemic events 30 days after treatment were recorded. Results: Twenty-nine angioplasties with the Wingspan system were successfully carried out in 29 stenoses in 27 patients. Of 29 stenoses, 17 were in the posterior circulation, and 12, in the anterior circulation. The degree of stenoses was reduced from baseline 71.8% (56%-87.8%) to 24.9% (0%-45%) after stenting. Complications were seen in four patients (14.8%), 3 of which were lesionrelated infarction of a perforated artery, and 1 was a non-lesion-related infarction. Two complications led to transient neurologic dysfunction, one led to defect of the visual field, and one led to hemiplegia. The prevalence of morbidity and serious morbidity were 7.4% and 3.7%, respectively, and no death occurred. No new ischemic events happened during 30 days after stenting. Conclusion: Angioplasty with the Wingspan system to treat symptomatic intracranial atherosclerotic stenoses appears to be safe. Its initial effect on prevention of ischemic events is acceptable. Crow
Tropical Cyclone Inner-Core Kinetic Energy Evolution
Get PDFAbstract Tropical cyclone (TC) destructive potential is highly dependent on the distribution of the surface wind-field. To gain a better understanding of wind structure evolution, TC 0-200 km wind-fields from aircraft reconnaissance flight-level data are used to calculate the low-level area-integrated kinetic energy (KE). The integrated KE depends on both the maximum winds and wind structure. To isolate the structure evolution, the average relationship between KE and intensity is first determined. Then the deviations of the KE from the mean intensity relationship are calculated. These KE deviations reveal cases of significant structural change, and, for convenience, are referred to as measurements of storm size (storms with greater (less) KE for their given intensity are considered large (small)). It is established that TCs generally either intensify and do not grow, or weaken or maintain intensity and grow. Statistical testing is used to identify conditions that are significantly different for growing versus non-growing storms in each intensification regime. Results suggest two primary types of growth processes: (1) secondary eyewall formation and eyewall replacement cycles, an internally dominated process; and (2) external forcing from the synoptic environment. One of the most significant environmental forcing is the vertical shear. Under light shear, TCs intensify but do not grow. Under moderate shear, they intensify less but grow more, and under very high shear they do not intensify or grow. As a supplement to this study, a new TC classification system based on KE and intensity is presented as a complement to the Saffir-Simpson hurricane scale.
Web-based Curricular Innovations with Diverse Learners: Stories from a University/School Partnership
Get PDFAs professional educators continue to work to improve student learning, partnerships within the school and the larger community are becoming a means to facilitate reformed-based changes in science education. In this article, we describe a partnership between a local university and a suburban school district that worked to implement technology-integrated classroom practices to promote learning within a diverse student environment. In this collaboration, two university faculty members, a science educator/researcher and a special education educator/researcher, partnered with a classroom biology teacher and a special education teacher who co-instructed in an inclusive ninth grade biology classroom. This collaborative endeavor followed a modified-partnership model presented in the Center for Education of the National Research Council report, Educating Teachers of Science, Mathematics, and Technology (2001). In this partnership model (see Need for the Partnership The classroom instructional partners co-teach a mix of lower-level learners and students identified with learning disabilities in an inclusive biology classroom setting. Prior to the 2 partnership, computer use by the biology teacher was limited and mainly consisted of information-seeking activities on the Internet by students. The special education teacher had used interactive educational software with her students and had prior experiences using Power Point presentations that contained links to available Web resources. Both teachers were aware that the World Wide Web provides various instructional resource types to enhance student science learning. These resources include: scientific visualizations, simulations, animations, video clips, and still images. The teachers believed that incorporating such instructional resources combined with effective instruction would assist student learning. However, the school team was frustrated in their attempts to incorporate technology within their instruction. Locating suitable instructional materials was a time consuming endeavor. In addition, they often experienced technical problems with their computers and network connections in the school computer lab. Despite this frustration, or because of it, the biology teacher accepted an invitation to participate in a National Science Foundation sponsored evaluation workshop of a new Webintegrated biology curriculum at a local university. This new curriculum was designed to promote biology literacy, consistent with the National Science Education Standards (National Research Council, 1996), using a learning cycle (engage, explore, explain, evaluate). The curricular materials consisted of a short concepts-oriented textbook, an extensive Website, and inquiry-based laboratory activities and experiments. The classroom teachers were interested in using the curricular materials with a goal to improve the integration of instructional technology within their instruction. The university educators/researchers interests included learning about contextual factors pertaining to the successful implementation of these materials in inclusive classroom settings. In addition, the educators/researchers were updating their knowledge in this area to better prepare the preservice science and special education teachers in their university methods courses. Therefore, a partnership was established to benefit the goals of both groups of educators. 3 Partnership Implementation During a period of six weeks, the university educator/researchers observed two inclusion biology classes as participant observers. During class and lab activities, the educator/researchers would question students individually and in small groups to determine how they were learning with the classroom activities. After class, the educator/researchers would recommend pedagogical changes that could be implemented in future lessons and activities. Many of the conversations among the partners included how to restructure the physical learning environment and how to customize the curricular materials to better accommodate the learning needs of their students. Additional guided prelab questions and activities were developed to provide learners with additional supports to help guide their thinking about the processes that would be occurring in the laboratory. Partnership discussions resulted in new sequencing of instruction and implementing new instructional practices that enhanced existing inclusive science classroom practices. Assessing Inquiry Skills Prior to the partnership, the teachers did not use inquiry-based laboratories with their inclusive classroom students. Often the laboratories that were used with these students were highly structured, material-centered verification type activities. During the partnership, students participated in a guided research laboratory. The inquiry-based activity was a weeklong laboratory, much longer than the usual laboratory implemented for the level of these students. This investigation was a two-part laboratory in which learners are provided with two questions to investigate: How fast does photosynthesis occur? How can an organism's photosynthesis be measured? In the first part of the investigation, students were provided with a detailed laboratory protocol and procedures for data collection and analysis. The "Conclusions" section of the laboratory prompted learners to formulate their own questions to be investigated in the second part of the laboratory. Learners then designed and implemented a new experiment based on the protocol of the initial laboratory. The results were presented in a laboratory report that was assessed through use of a rubric (see 4 Web-based animations in the online prelab materials illustrated how to utilize the tools for the laboratory. The integration of these visualizations in the prelab procedures provided students with additional confidence as they followed the written directions. Through a repetitive process of reviewing an experimental protocol, seeing the use of equipment in a Web-based visualization, and developing experimental protocols for their own investigations, the students became more confident in their use of laboratory equipment and investigative processes. Student assessment of inquiry processes included the use of the laboratory report rubric by the classroom teachers and informal student interviews conducted by the educator/researchers. The analysis of the laboratory report rubrics and interview data indicated that most of the students understood the investigative processes and the fundamentals of the content. In addition, the inclusion students were able to successfully complete an inquiry-based investigation. Technology Implementation The university educator/researchers provided specific technology implementation suggestions to the classroom teachers. They provided the teachers with vocabulary necessary to communicate properly with the school's technology office. One of the most important recommendations was to use an LCD projector in the teachers' classroom instead of having students use computers individually in a computer lab setting. The science teacher, who had limited experience with computers as a tool in the classroom, was encouraged by the educator/researchers to use an LCD projector in a one-computer classroom setting to deliver direct instruction. Upon implementation of this recommendation student attention and participation increased during the class. The educator/researchers noted an increase in the students' time on-task from 42% when working on individual computers in a computer lab to 88% when the teacher used the LCD projector in her own classroom. With the more frequent use of the one-computer setting, the teacher's confidence increased; thus, obtaining one of the goals of the partnership. During the partnership implementation, student content knowledge increased 5 significantly on biology content assessments. This improvement in test scores provided credible evidence for the classroom instructional team to petition their school district administration to purchase an LCD projector and interactive whiteboard for classroom use in the forthcoming school year. This research-supported evidence was a key factor to assist administrators in making technology-purchasing decisions. Inclusive Science Practice The educator/researchers provided validation for many of the techniques the teachers had developed during their careers. They noted the importance of assessing student background knowledge and prerequisite skills. Students in the inclusive biology classroom struggled with content and activities when they did not have sufficient background knowledge to complete a particular task The classroom teachers used explicit instruction to facilitate inquiry learning. Teachers directly modeled and demonstrated how to think about biology content and how to think through steps in laboratory experiments. Students were consistently involved in a variety of academic tasks: students took notes, completed guided-note sheets, engaged in conversations about biology content during small group activities with peers, used Web-based activities, and participated in laboratory experiments. The students demonstrated increased understanding of the content and became progressively more independent with inquiry-based applications as learnin
The governance of inter-organisational relationships during different supply chain maturity phases The governance of inter-organisational relationships during different supply chain maturity phases
No full textAbstract Supply chains and inter-organisational relationships have increased in popularity in recent years and supply chain management has received a vast amount of academic attention. The objective of this paper is to explore the implementation of supply chain management and, in particular, the changing phases of a supply chain as it moves towards maturity. We employ the minimal structure framework of van der Meer-Kooistra and Scapens ["The governance of lateral relations between and within organisations", Management Accounting Research, 2008] to analyse the governance of a supply chain as it moves through the various phases. Drawing on the findings from a case study in an aero-manufacturing company, we explore how the minimal structures emerge and evolve as the supply chain matures
Gamma Ray Bursts and the Cosmological Constant ' NOV 2 4 ~9S 1 Gamma Ray Bursts and the Cosmological Constant
No full textAbstract. It is generally considered that most long duration GRB come from Cosmological Distances. We show how the effects of a significant cosmological con stant and evolution can help provide an explanation to one of the puzzling effects of the Hardness vs Duration and intensity of the current BATSE 4B Catalogue. We also show that the Universe with f2A = 0.7andf2M = 0.3 behaves like an empty Universe for z < 3 and we show that InN vs InS distribution for GRB's is consistent with this behaViour if source evolution is included. This could imply f2A is not zero in a model of the Galactic Evolution
THE EFFECT OF TRHOUGHFLOW ON RAYLEIGH BERNARD CONVECTIVE ROLLS
No full textWe investigate Rayleigh-Benard convection in the presence of a horizontal Poiseuille flow transversal to the convective/ roll chain. Using a Id amplitude equation and a 2d numerical simulation of the basic field equations. we study how different boundary conditions at the inlet and outlet of the channel affect nonlinear convection. If convection is suppressed near the cell apertures. spatially localized traveling wave states appear with a uniquely selected bulk wavelength. For convectively unstable parameters the system becomes very sensitive to perturbations and noise driven convection occurs. Phase pinning boundary conditions lead to stationary roll patterns with a space dependent wavelength decreasing downstream. Strengthening the throughflow causes local Eckhaus instabilities which finally generate a transition to propagating rolls. I. INTRODUCTION From the theoretical point of view the properties of nonlinear convection in heated shear flows are hardly examined, so that the knowledge is mainly based on experiments l -7 and 2-&mensional numerical simulations8-13 of the hydrodynamic field equations. Convection in broad channels heated from below usually appears in the form of stationary rolls aligned parallel to the throughflow (longitudinal rolls). Traveling transversal rolls (axes perpendicular to the shear flow) have been detected in narrow channels, however, for small flow rates only. This is a result of two competing mechanisms: Perturbations in the form of longitudinal rolls are preferred by the throughflow, whereas traveling transversal disturbances are favoured by the influence of the lateral channel sidewalls 14.15. Luijkx et al. 4 reported transversal traveling roll patterns which did not fill the whole length of the channel. Such spatially localized structures have also been observed in numerical simulations U -13. Similar patterns also appear in the Taylor-Couette system with an axial throughflow 16 -18. Here we investigate transversal convective structures and in particular the question how the boundary conditions (b. c.) at the inlet and outlet of the channel affect the nonlinear convection structure. Our investigation is based on 2d computer simulations of the full field equations as well as a Id amplitude equation. A summary of the results has been published earlier 12