Experiences with Problem-Based Learning: Virginia Initiative for Science Teaching and Achievement

The Virginia Initiative for Science Teaching and Achievement (VISTA) provides high-quality professional development for teachers and administrators to enhance the quality of their science instructional programs. One emphasis of this program is helping teachers learn to implement Problem-Based Learning in the elementary science classroom. Problem-Based Learning (PBL) has the potential to produce significant positive outcomes for students, such as increased student engagement, and opportunities for in-depth critical thinking [1]. Teachers find PBL challenging because it does take additional time for planning and material acquisition, but experience has shown that the benefits outweigh these challenges. Setting clear goals, identifying specific learning objectives, and developing big questions that tie these together help increase the success of the unit. Additionally, administrators can help teachers succeed in implementing a Problem-Based Learning unit by understanding the dynamic nature of the PBL environment, providing flexibility with unit pacing, and setting aside time for refining, reflection, and revision of the unit

EHD Lubrication Film Behaviour under Rapid Change of Velocity and Load

Tato disertační práce je zaměřena na experimentální studium chování mazacího filmu při náhlých změnách provozních parametrů. Ve většině reálných tribologických uzlů dochází v průběhu pracovního cyklu ke změně provozních podmínek jako jsou rychlost, zatížení a poloměry křivosti stýkacích se ploch. Změna provozních podmínek může představovat zvýšené riziko porušení mazacího filmu. Přímý dotyk kontaktních těles, v okamžiku porušení mazacího filmu, s sebou nese zvýšení tření a opotřebení. Pro sledování dynamických změn v kontaktu byla použita vysokorychlostní CMOS kamera. Z nasnímaných interferogramů, s pomocí metody optické interferometrie, byla provedena zpětná rekonstrukce mazacího filmu. Bylo potvrzeno, že provozní parametry mají zásadní vliv na utváření mazacího filmu a na jeho tloušťku a pro jistou kombinaci okrajových podmínek může dojít k porušení spojitosti vrstvy maziva.This dissertation is focused on experimental study of lubricant film behavior under transient conditions. For real machine parts such as gears, roller bearings and cam mechanism the operating conditions such as speed, load and radius of curvature of rubbing surfaces are vary during the working cycle. Change in operating conditions may pose an increased risk of the lubricating film breakdown. Direct contact of rubbing surfaces at the time of the lubricating film breakdown causes an increase in friction and wear. The high-speed CMOS camera was used to record the dynamic changes in lubricating film thickness during the experiment. The optical interferometry method has been used for reverse reconstruction of lubricating film thickness of the recorded interferograms. It was confirmed that the operating parameters have a major impact on the formation of lubricant film and its thickness and a certain combination of boundary conditions can cause lubricating film rupture. The obtained results showed, that modified topography of the rubbing surfaces can help to increase the lubrication film thickness especially in critical phases of working cycle.

FDTD-ANT User Manual

This manual explains the theory and operation of the finite-difference time domain code FDTD-ANT developed by Analex Corporation at the NASA Lewis Research Center in Cleveland, Ohio. This code can be used for solving electromagnetic problems that are electrically small or medium (on the order of 1 to 50 cubic wavelengths). Calculated parameters include transmission line impedance, relative effective permittivity, antenna input impedance, and far-field patterns in both the time and frequency domains. The maximum problem size may be adjusted according to the computer used. This code has been run on the DEC VAX and 486 PC's and on workstations such as the Sun Sparc and the IBM RS/6000

Designs for the ATDRSS tri-band reflector antenna

Two approaches to design a tri-band reflector antenna for the Advanced TDRSS are examined. Two reflector antenna configurations utilizing frequency selective surfaces for operation in three frequency bands, S, Ku, and Ka, are proposed. Far-field patterns and the antenna feed losses were computed for each configuration. An offset-fed single reflector antenna configuration was adapted for conceptual spacecraft design. CADAM drawings were completed and a 1/13th scale model of the spacecraft was constructed

Color Variation in the Caribbean Crab Platypodiella spectabilis (Herbst, 1794) (Decapoda, Brachyura, Xanthidae)

The use of color in brachyuran crab systematics, and in particular the use of subtle color differences to suggest or differentiate cryptic or morphologically similar species, is now well documented (e.g., see Campbell and Mahon 1974 for species of Leptograpsus, Williams and Felder 1989 for species of Menippe, Zimmerman and Felder 1991 for species of Sesarma). Less clearly understood is why color patterns and intensities can sometimes vary appreciably within a species, even within narrowly restricted geographic regions. An appreciation of color patterns is critical to correctly identifying species for conservation and resource management purposes, yet often color patterns and ranges are unreported, causing confusion and sometimes misidentifications. Here we document a wide range of color patterns in a small Caribbean xanthid crab based on specimens collected in essentially the same habitat at the same time of year

The Stomatopod Alachosquilla floridensis (Manning, 1962) (Crustacea, Stomatopoda, Nannosquillidae) Reported from Guana Island, British Virgin Islands, with Observations on Color

Although color pattern can vary among and within species of the Crustacea, it can also be a conservative feature that can be very helpful in field identifications. This is often the case in the Crustacea Decapoda, where sibling species can be detected by subtle differences in color (e.g., Williams and Felder 1989, Zimmerman and Felder 1991, Knowlton and Mills 1992). Stomatopods are among the most colorful crustaceans when living. Many species show a great deal of variability (Manning 1969, Camp 1973), and knowledge of this coloration is often key to their identification in the field and in the lab (Schotte and Manning 1993). As part of an ongoing survey of the marine invertebrate fauna of Guana Island, British Virgin Islands, we collected 2 large (45 mm and 48 mm TL) females, and one male specimen (30 mm TL) of the rarely reported stomatopod species Alachosquilla floridensis (Manning 1962). To our knowledge, the species has been reported previously in the literature only 4 times (see Schotte and Manning 1993). These reports are based on a total of 8 specimens. Previous distribution records for the species include Lake Worth Inlet, Florida; Virgin Gorda, US Virgin Islands; Isla Marguerita, Venezuela; Bahia, Brazil; and Saint Giles Island and London Bridge Rock, Tobago, West Indies (Manning 1969, Schotte and Manning 1993)

Artificial Reef Matrix Structures (Arms): An Inexpensive and Effective Method for Collecting Coral Reef-Associated Invertebrates

Collecting reef-associated invertebrates usually involves disturbance of the reef area, often damaging the habitat and sometimes damaging live corals. We introduce a nondestructive, inexpensive, and effective method for collecting coral reef-associated invertebrates using approximations of small coral heads constructed of concrete, PVC pipes, nylon cleaning pads, and other materials easily obtainable in most tropical (coral-rich) countries. An example showing the effectiveness of the method is presented based on fieldwork in the eastern Caribbean

An Object-Oriented Approach to Writing Computational Electromagnetics Codes

Presently, most computer software development in the Computational Electromagnetics (CEM) community employs the structured programming paradigm, particularly using the Fortran language. Other segments of the software community began switching to an Object-Oriented Programming (OOP) paradigm in recent years to help ease design and development of highly complex codes. This paper examines design of a time-domain numerical analysis CEM code using the OOP paradigm, comparing OOP code and structured programming code in terms of software maintenance, portability, flexibility, and speed

Bringing Transportation into a Cap-and-Trade Regime

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).The U.S. may at some point adopt a national cap-and-trade system for greenhouse gases, and if and when that happens the system of CAFE regulation of vehicle design very likely could still be in place. Imposed independently these two systems can lead to economic waste. One way to avoid the inefficiency is to integrate the two systems by allowing emissions trading between them. Two possible approaches to potential linkage are explored here, along with a discussion of ways to guard against violation under such a trading regime of vehicle standards that may be justified by non-climate objectives. At a minimum, implementation of a U.S. cap-and-trade system is several years in the future, so we also suggest intermediate measures that would gain some of the advantages of an integrated system and smooth the way to ultimate interconnection.This study received funding from the MIT Joint Program on the Science and Policy of Global Change, which is supported by a consortium of government, industry and foundation sponsors