173,852 research outputs found
Modeling Building Block Interdependency
No full textThe Building-Block Hypothesis appeals to the notion of problem decomposition and the assembly of solutions from sub-solutions. Accordingly, there have been many varieties of GA test problems with a structure based on building-blocks. Many of these problems use deceptive fitness functions to model interdependency between the bits within a block. However, very few have any model of interdependency between building-blocks; those that do are not consistent in the type of interaction used intra-block and inter-block. This paper discusses the inadequacies of the various test problems in the literature and clarifies the concept of building-block interdependency. We formulate a principled model of hierarchical interdependency that can be applied through many levels in a consistent manner and introduce Hierarchical If-and-only-if (H-IFF) as a canonical example. We present some empirical results of GAs on H-IFF showing that if population diversity is maintained and linkage is tight then the GA is able to identify and manipulate building-blocks over many levels of assembly, as the Building-Block Hypothesis suggests
Price Impact of Block Trades and Price Behavior Surrounding Block Trades in Indian Capital Market
No full textWe analyze the permanent (information effect) and temporary (liquidity effect) impact of block trades transacted in the National Stock Exchange of India. Block trades are identified using multiple criteria based on trade value and trade volume. Overall, the permanent price impact is more for block purchases than for block sales indicating that block purchases are more informative than block sales, which may be motivated by liquidity need. Unlike in other markets, we observe that the temporary impact is greater than the permanent impact in case of block purchase. We classify the block trades as All-or-None (AON) and Not-AON trades depending on the number of transactions through which a block order is executed. As expected, the price impact is higher for Not-AON trades as compared to AON trades (which can be assumed to be pre-negotiated trades). Further, arrival of multiple block trades increases market confidence on the information. The permanent price impact is higher for days where there are more than one block trade of similar nature than for days with only one block trade. To analyze the speed of market response to the information associated with block trades, we have used the ‘transaction time event approach’, as used by Holthausen et al. (1990). We find that the prices start increasing (front running) 8 minutes before block purchases but not in case of block sales i.e. some information about the impending block purchase is factored in by the market when the block trade is for purchases. Further, in the case of block sales, prices revert quickly leaving very small permanent price impact.
On automorphism groups of block designs
No full textAbstractThis paper studies the relationship between the point orbits and block orbits for groups on automorphisms of balanced incomplete block designs. For a prime p and a group on a design with parameters v, b, r, k, λ, with t point orbits, of lengths v1, …, vt, and t′ block orbits, of lengths b1, …, bt′, the following main result is proved: ifp∤(r−λ)(r,b)(k,v)(resp.p∤r−λ)then there are t block orbits, of lengths bj1, …, bjt such that vi and bji are divisible by exactly the same powers of p for i=1, …, t (resp. of at least t−1 of the t indices i). A similar result is proved for constant-distance matrices (in particular for Hadamard matrices). Applications are given to permutation groups on a finite set Ω (about the orbits of k-element subsets of Ω) and to designs of configurations in other designs (e.g., about the flag orbits in a finite projective plane)
Teaching in the block: perceptions from an agricultural education classroom
No full textPlan BA relatively new initiative called block scheduling is being used in high schools all over the country. Several schools are investigating and adopting block schedules to replace traditional schedules. Block scheduling has several benefits to educators, for example, the larger blocks of class time allow for a variety of teaching methods and activities. The purpose of the study was to research the teachers' attitudes of the effectiveness of block scheduling design. The study focused on four questions (1) What are agricultural education teachers' perceptions of the overall effectiveness of block scheduling? (2) Have teaching methods in agricultural education changed in response to block scheduling? (3) Has enrollment in agriculture classes changed as a result of the block schedule? (4) What are important benefits and drawbacks of block scheduling specific to agricultural education classrooms? Surveys were distributed to Wisconsin Agricultural Education Instructors at the end of the 2002 school year. The survey consisted of demographic information, 30 Likert type items, and a comment section. A total of 48 surveys were mailed to participants and thirty-two (67%) were returned. Results show that many teachers feel overall that block scheduling is effective for their agricultural education programs. Many participants stated advantages to block scheduling such as hands-on and lab activities, more time for fieldtrips, and the opportunity to have more individualized contact with students. However, participants also mentioned disadvantages such as challenges with FFA recruitment and member involvement
Price impact of block trades in the Saudi stock market
No full textThis paper examines the price impact of block trades for the 124 companies that comprise all listed firms in the Saudi stock market (SSM). We use high frequency intraday data (one minute intervals) for the period 2005-2008 to provide out of sample evidence of the determinants of price impact. We find an asymmetric price impact of 0.5% for block purchases and -0.38% for block sales. We document a price continuation post block trades and a price reversal after block sales. Sellers of block trades in the Saudi market pay higher liquidity premiums than
buyers of block trades. However, on average, the price effect of a block trade is small and short-lived suggesting that resiliency is high in the market. Moreover, we find a direct relationship between the size of the trades and the level of information asymmetry in the market. Despite the structural differences of the SSM, the intraday pattern of price impacts is similar to patterns documented in other markets, namely an inverse J-shaped pattern. Finally,
sophisticated traders can gain abnormal profits in the SSM through “free riding”, a trader can benefit from the overreaction before the block trade and price reversal after the block trade
Teachers' perceptions of the block schedule
No full textPlan BThis study was developed to investigate Menomonie High School teachers’ perceptions of the block schedule regarding modifications to departmental courses and services, advantages and disadvantages of the block schedule, and suggestions for modifications to the current block schedule. A researcher-developed questionnaire was sent via school mailbox to 66 faculty, with 28 returning the questionnaire and participating in the study. The findings indicate that modifications made to departmental courses and services included: the compacting of curriculum, the addition of terms to some courses, the inclusion of additional grade levels in some courses, and the creation of new courses. The advantages that were indicated included: longer class time allowed for more in-depth discovery type learning, varied teaching practices and activities, integration of content areas such as U.S. history/U.S. literature and speech/composition, fewer teacher preparations, longer preparation time, fewer courses for students to manage, less stress for teachers and students, improved relationships between students and teachers, and the creation of new elective course offerings. The disadvantages indicated included: less developmental time for learning, an increase in class sizes, some curriculum lost due to compacting, some departments could not service all student requests, some departments dropped electives to accommodate more sections of required courses, no safety net for failing students, difficulty of placing transfer students in the schedule, class balances unequally distributed, some students had difficulty maintaining attention for the longer period of time, retention loss during gaps between related courses, curriculum watered down due to necessary review time, difficulties for substitute teachers, no study halls for remediation, and student absences are more detrimental. Suggestions for modifying the current block schedule included: going to a trimester schedule with twelve or thirteen week grading terms and five sixty to sixty-five minute periods, increasing staff, modifying the block with skinnies, implementing an A/B block schedule, adding electives in all areas, keeping students with the same teacher for all terms of a course, building in more one on one time for students who are failing, and having three terms for lower level courses
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Congenital heart block associated with Sjögren syndrome: case report
No full textBackground: Congenital heart block is a rare complication of pregnancy associated with Sjögren Syndrome that may result in the death of the foetus or infant, or the need for pacing in the newborn or at a later stage.Case report: The case is presented of a 64-year-old patient with primary Sjögren Syndrome and a history of having given birth to two sons with congenital heart block, both of whom required pacing several years later.Conclusion: The literature relating to this association is discussed including the suggested mechanism, long-term outcome of mothers of children with congenital heart block and preventive treatment strategies
Convex Cone Conditions on the Structure of Designs
No full textVarious known and original inequalities concerning the structure of combinatorial designs are established using polyhedral cones generated by incidence matrices. This work begins by giving definitions and elementary facts concerning t-designs. A connection with the incidence matrix W of t-subsets versus k-subsets of a finite set is mentioned. The opening chapter also discusses relevant facts about convex geometry (in particular, the Farkas Lemma) and presents an arsenal of binomial identities. The purpose of Chapter 2 is to study the cone generated by columns of W, viewed as an increasing union of cones with certain invariant automorphisms. The two subsequent chapters derive inequalities on block density and intersection patterns in t-designs. Chapter 5 outlines generalizations of W which correspond to hypergraph designs and poset designs. To conclude, an easy consequence of this theory for orthogonal arrays is used in a computing application which generalizes the method of two-point based samplin
A Novel Hexagonal Search Algorithm for Fast Block Matching Motion Estimation
No full textBased on real-world image sequence characteristics of center-biased motion vector distribution, a Hexagonal (HS) algorithm with center-biased checking point pattern for fast block motion estimation is proposed. The HS is compared with full search (FS), four-step search (4SS), new three-step search (NTSS), and recently proposed diamond search (DS) methods. Experimental results show that the proposed technique provides competitive performance with reduced computational complexity
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