Analyses of activity design in geometry in the light of student actions

Abstract

The goal of this study is to show that inquiry activities in a dynamic geometry environment, intentionally designed to confront students with contradictions and uncertainties, push them towards explanations that include deductive elements. Three different but dependent aspects of the activities are characterized and analysed: The epistemological, which includes all possible inquiry paths; the didactic, which involves only those paths that reflect the intention of the designer; and the cognitive, which accounts for actual student actions (conjectures and explanations) and their analyses. The research conclusions are based on the interplay among these three aspects. The analysis of students’ investigations and the analysis of their explanations fulfil, to a broad extent, the design goals.     

Source-synchronization and timing vernier techniques for 1.2-GB/sSLDRAM interface

This paper describes a validation system for an SLDRAM interface. The SLDRAM system utilizes two techniques to achieve a high data-transfer rate with a conventional module mounting style. The first technique is a source-synchronization scheme. Since the chip that transmits data also supplies the data clock, the clock and data are completely synchronous. The second is the timing vernier technique. A wait time for output data is programmable in each SLDRAM. Therefore, the time at which data arrive at the controller from any SLDRAM can be set by the controller with a 200-ps step size. The validation chip is designed to emulate these operations. The chip is fabricated using a 0.35-μm CMOS process technology and packaged in a conventional 0.65-mm pitch thin small out-line package, mounted on a single-chip module, and put into an eight-module system. A stub series terminated logic (SSTL)-like interface is adopted for high-speed signals. From system-level measurements, the data eye width of 600 ps is obtained at a data rate of 600 Mbps. Errorless data transmission is observed in both read and write operations in a bit-error rate testing. The validation system has successfully demonstrated a data-transmission rate of 1.2 GB/s (600 Mbit/s/pin) using source-synchronization and timing vernier techniques at the supply voltage of 2.5 V     

Compound interest [President's Column]

The IEEE is celebrating its 125th anniversary this year. This is certainly a noteworthy event to acknowledge the history of the world's largest professional technical association. Yes, the IEEE is the world's leading professional association for the advancement of technology. It all began with the formation of the American Institute of Electrical Engineers (AIEE) in 1884. This was followed by the formation of the Institute of Radio Engineers (IRE) in 1912. In 1963, the AIEE and IRE merged to form the Institute of Electrical and Electronic Engineers, the IEEE. Today, the organization's scope of interest has expanded into so many related fields that it is simply referred to by the letters I-E-E-E ("Eye-triple-E"). It is a global organization with almost 400,000 Members in over 160 countries. IEEE Members have access to the industry's most essential technical information, networking opportunities, career development tools, and many other exclusive benefits. And the IEEE Microwave Theory and Techniques Society (MTT-S) is proud to be part of that heritage.     

Symposium review: Milk fat globule size: Practical implications and metabolic regulation

Milk fat globule (MFG) size ranges over 3 orders of magnitude, from less than 200 nm to over 15 µm. The significance of MFG size derives from its tight association with its lipidome and proteome. More specifically, small MFG have relatively higher content of membrane compared with large globules, and this membrane exerts diverse positive health effects, as reported in human and animal studies. In addition, MFG size has industrial significance, as it affects the physicochemical and sensory characteristics of dairy products. Studies on the size regulation of MFG are scarce, mainly because various confounders indirectly affect MFG size. Because MFG size is determined before and during its secretion from mammary epithelial cells, studies on the size regulation of its precursors, the intracellular lipid droplets (LD), have been used as a proxy for understanding the mechanisms controlling MFG size. In this review, we provide evidence for 2 distinct mechanisms regulating LD size in mammary epithelial cells: co-regulation of fat content and triglyceride-synthesis capacity of the cells, and fusion between LD. The latter is controlled by the membrane's polar lipid composition and involves mitochondrial enzymes. Accordingly, this review also discusses MFG size regulation in the in vivo metabolic context, as MFG morphometric features are often modulated under conditions that involve animals' altered energy status.     

The Synthesis of Vicinal Diacylamines via Bamberger Ring Cleavage of Substituted Imidazoles. 1,2,4-Triacylaminobutanes Bearing Different Acyl Groups

Bamberger ring cleavage acylation of N-p-toluenesulfonyl (tosyl) histamine followed by hydrogenation yields 3,4-diacylaminobutanetosylamine, a triamine containing groups with different chemical reactivities.     

Adaptive Median Filtering for Impulse Noise Elimination in Real-Time TV Signals

A two-dimensional (3 × 3) median filter with controlled turn-on is employed in an adaptive fashion for selective removal of impulse noise interference in real-time television signals. Various filters and threshold conditions are selected from programmed PROM's as a function of impulse noise detected and counted during a vertical interval window period. The adaptive median filter is used in conjunction with a satellite FM communication downlink system and can effectively improve the onset of threshold performance by about 3 dB carrier-to-noise ratio. The particular FM system discussed employs a multiplexed analog component, MAC, formatted TV signal. Use of the filter for standard NTSC composite signals is indicated.     

连接工业--连接器依靠其节省劳力的设计使工人能安全、快速装配,取得了成本效益

为使连接器保持竞争力,工程人员们都在努力提高其使用简易程度和成本效益以及工效学.连接器仅在气密和阻漏方面优越是不够的.在今天市场上,作为连接器工业还必须具其它卓越性能.     

Behavioral and Physiological Measures in the Detection of Concealed Information.

The authors examined the incremental validity of the reaction time (RT) measure beyond that of skin conductance response (SCR) in the detection of concealed information. Participants performed a Stroop-like task in which they named the color of critical and neutral words. Results show that the SCR highly differentiated between the relevant and neutral words. However, the RT demonstrated a significant differentiation only when the critical words denoted personally significant items (e.g., one's own name) and not when they denoted crime-relevant items related to a simulated crime. In both cases, combining the 2 measures yielded no advantage over the use of SCR alone. Thus, although behavioral measures may differentiate between relevant and neutral information in some cases, their practical use is questionable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relative importance of informational units and their role in long-term recall by closed-head-injured patients and control groups.

Applied qualitative analysis to the information recalled by control Ss and closed-head-injured (CHI) patients. The Logical Memory subtest of the Wechsler Memory Scale (WMS) was administered to 40 CHI and 40 control Ss. Recall was tested immediately after administration, 40 min later, and 24 hrs later. The analysis took into account the importance of recalled information as determined by a prior rating according to 3 levels of importance. Results suggest that CHI patients have difficulty selectively retrieving the most important information after a long delay. (PsycINFO Database Record (c) 2010 APA, all rights reserved)