4,062 research outputs found
How to teach the Pythagorean theorem: An analysis of lesson plans
This research was conducted among mathematics graduates who participated in a
pedagogical formation certificate program. Participants were asked to prepare a lesson
plan intended for use in teaching the Pythagorean theorem as part of a ninth grade
mathematics course. Eighteen out of 43 participants included a proof of the
Pythagorean theorem as a component of their lesson plan. These proofs were
classified in three categories: visual proofs (two participants), algebraic proofs (nine
participants), and proofs by using triangular similarities (seven participants). In
addition, the solved examples, homework, and evaluation questions included in the
lesson plans were classified according to TIMSS cognitive levels. Of the 233
questions prepared by 43 participants, 37% of the questions were at the knowledge
level, 60% were at the application level, and the remaining 3% were at the reasoning
level
Dynamic Vehicle Routing for Data Gathering in Wireless Networks
We consider a dynamic vehicle routing problem in wireless networks where
messages arriving randomly in time and space are collected by a mobile receiver
(vehicle or a collector). The collector is responsible for receiving these
messages via wireless communication by dynamically adjusting its position in
the network. Our goal is to utilize a combination of wireless transmission and
controlled mobility to improve the delay performance in such networks. We show
that the necessary and sufficient condition for the stability of such a system
(in the bounded average number of messages sense) is given by {\rho}<1 where
{\rho} is the average system load. We derive fundamental lower bounds for the
delay in the system and develop policies that are stable for all loads {\rho}<1
and that have asymptotically optimal delay scaling. Furthermore, we extend our
analysis to the case of multiple collectors in the network. We show that the
combination of mobility and wireless transmission results in a delay scaling of
{\Theta}(1/(1- {\rho})) with the system load {\rho} that is a factor of
{\Theta}(1/(1- {\rho})) smaller than the delay scaling in the corresponding
system where the collector visits each message location.Comment: 19 pages, 7 figure
Dynamic Server Allocation over Time Varying Channels with Switchover Delay
We consider a dynamic server allocation problem over parallel queues with
randomly varying connectivity and server switchover delay between the queues.
At each time slot the server decides either to stay with the current queue or
switch to another queue based on the current connectivity and the queue length
information. Switchover delay occurs in many telecommunications applications
and is a new modeling component of this problem that has not been previously
addressed. We show that the simultaneous presence of randomly varying
connectivity and switchover delay changes the system stability region and the
structure of optimal policies. In the first part of the paper, we consider a
system of two parallel queues, and develop a novel approach to explicitly
characterize the stability region of the system using state-action frequencies
which are stationary solutions to a Markov Decision Process (MDP) formulation.
We then develop a frame-based dynamic control (FBDC) policy, based on the
state-action frequencies, and show that it is throughput-optimal asymptotically
in the frame length. The FBDC policy is applicable to a broad class of network
control systems and provides a new framework for developing throughput-optimal
network control policies using state-action frequencies. Furthermore, we
develop simple Myopic policies that provably achieve more than 90% of the
stability region. In the second part of the paper, we extend our results to
systems with an arbitrary but finite number of queues.Comment: 38 Pages, 18 figures. arXiv admin note: substantial text overlap with
arXiv:1008.234
On the Quality of FFO Forecasts
This paper is the first attempt to provide an objective assessment of the quality of real estate funds from operations (FFO) forecasts. The work, which looks past the more primitive question concerning the appropriate measure for real estate earnings, quantifies and tests the quality of real estate investment trust (REIT) FFO forecasts relative to the net income forecasts of several comparison groups. The results show the high quality of REIT forecasts are remarkably robust and are not driven by the level of analyst attention. Investors in a post-Enron and Sarbanes-Oxley era may find the implications for high quality forecasts of real estate earning to be an appealing investment concept.
Financial Expertise of Directors
The composition and functioning of corporate boards is at the core of the academic and policy debate on optimal corporate governance. But does board composition matter for corporate decisions? In this paper, we analyze the role of financial experts on boards. In a novel panel data set on board composition, we find that financial experts significantly affect corporate decisions, though not necessarily in the interest of shareholders. First, when commercial bankers join boards, external funding increases and investment-cash flow sensitivity diminishes. But, the increased financing affects mostly firms with good credit and poor investment opportunities. Second, investment bankers on the board are associated with larger bond issues, but also worse acquisitions. Third, we find little evidence that financial expertise matters for compensation policy or for experts without affiliation to a financial institution. The results suggest a tradeoff between outside incentives (e.g. bank profits) and the incentive to maximize firm value. Requiring financial expertise on boards, as mandated by regulatory proposals, may not benefit shareholders if conflicting interests are neglected.
Topkapı Sarayı Müzesi ve ben
Taha Toros Arşivi, Dosya No: 120-Saraylarİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033
Emine Yılmaz, Narspi-Metin, Yazıçevrimi, Türkçe Çeviri, Sözlük-Dizin
[No Abstract Available
Reaction of central banks to federal reserve at zero lower bound
Bu çalışma; merkez bankalarının tepki fonksiyonlarında federal reserve e ne ağırlıkta yer verdiklerinin ve bu tepkinin 2008 finansal kriziyle ne ölçüde değiştiğini tespit etmeyi amaıyla 25 farklı ekonomi üzerinde yürütülmüştür.Federal funds rate in bağımsız değişken olarak eklendiği model 2000-2007 ve 2008-2014 dönemleri için ayrı ayrı sıradan en küçük karaler ekonometrik metoduyla test edilmiştir. Ampirik bulgulara göre ülkerin çoğu , dünyanın en büyük ekonomilerinin başında gelen ABD ekonomisine verilen tepki %5 anlamlılık düzeyinde istatistiki olarak anlamlı çıkmıştır. Ancak bu tepki kriz sonrası dönemde birçok ülke için devam etmekle beraber; ülke ülke incelediğinde her biri için önemli ölçüde değişikliğe uğramıştır. Ayrıca çalışmada; hem literatürden farklılaştırmak hem de sonuçları farklı bi yöntemle teyit etmek için zamanla değişen regression yöntemi de kullanılmıştır.Elde edilen sonuçlarla ilk bulgularla sağlamlaştırılmıştır. Anahtar Kelimeler: Para Politikası,Taylor Kuralı, Zamanla Değişen Regresyen, Sıfır Alt ÇizgisiThis study has been carried out on 25 different economies so as to determine how much central banks give place to federal reserve in reaction functions and to what extent this reaction changed with the effect of the financial crisis of 2008. The model to which federal funds rate was added as an independent variable was tested with OLS econometric method separately for 2000-2007 and 2008-2014 periods. According to the empirical evidence, the reaction of most of the countries to the US economy, which is the leading country of the world's biggest economies, turned out to be statistically 5% significant at the level of significance. However, together with this reaction's continuation for many countries after the crisis, it changed dramatically for each country when examined country-by-country. In addition, time varying regression method was used in this study so as to both differentiate it from literature and also to confirm the results with a different method. First findings were accordingly strengthened with the obtained results. Keywords: Monetary Policy, Taylor Rule, Time Varying Regression, Zero Lower Boun
Searching for the exit in a maze? Or setting sail for new Horizons? Metaphors by twelfth grade students for learning mathematics
This study examines and classifies the metaphors that twelfth grade students formulated to describe the concept of "learning mathematics". The sample of the study consists of 669 twelfth grade students (317 female, 352 male) of two Anatolian and two vocational high schools located in the city center of Denizli. The following questions guided this study: What metaphors do students use to describe the concept of "learning mathematics"? What conceptual categories can be derived from these metaphorical images? How these conceptual categories differ by high school type? How these conceptual categories differ by students' gender? The data were analyzed both qualitatively and quantitatively. According to the results, 76 valid metaphors and eight main conceptual categories were identified. These main conceptual categories are: discovering an unknown, learning a new skill, solving a puzzle, learning the rules and playing a game, using a tool, difficulties of learning mathematics, pleasure of learning mathematics, having a hardship. According to Pearson chi square calculations Anatolian high school students and girls produced more metaphors about enjoying mathematics than vocational high school students and boys. Also, vocational high school students and boys produced more metaphors about difficulties of learning mathematics and having a hardship than Anatolian high school students and girls. ©2013 Educational Consultancy and Research Center
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