Red Chips Research Articles

The Curious — and Crucial — Case of Mathematical Knowledge for Teaching

Good teachers know both content and how to get it across to their students. But specifying this knowledge has proven surprisingly difficult. A common approach is to require teachers to major in the fields they will teach and then add knowledge of how children learn and classroom experience. But some argue that the content knowledge that teachers need is different from that needed by mathematicians or physicists. Take the case of something as apparently simple as what knowledge is involved in teaching operations with integers. Most adults remember a for subtracting negative numbers--subtracting a negative is the same as adding a Is knowing this rule enough to teach this material? Note that this isn't the same as asking what students need to learn. Rather, we ask about the mathematical understanding needed to teach this topic. To focus the question, we drop in on Ms. Gonzalez, a 7th-grade mathematics teacher. She begins her lesson by using black chips to represent positive numbers and red chips for negative numbers. Adding one black and one red chip results in zero. Her students have been solving such problems as +4 + (-8) = x by as many black and red chips as possible, then counting the chips left over (in this case, four reds). The model seems to help her students solve addition problems. But the next problem in the text is different: Find the missing part for this chip problem. What would be a number sentence for this problem? Ms. Gonzalez begins by modeling -1 - (-3) on the overhead projector by combining two red chips and one black, or -2 + (+1), which is -1, and then subtracting three reds: The students struggle with this representation. A student ventures that the answer is -1; another proposes that the answer is 5; and a third argues for an answer of -2. Many more note that matching a black with red leaves four reds, or a result of -4. Ms. Gonzalez checks the answer in the teacher's edition; the answer it gives is 2. Unclear how to use the chips to show this, she abandons the model and demonstrates how to solve -1 - (-3) = 2 by showing that the minus sign in front of the 3 and the subtraction sign combine to make addition of a positive. What is the mathematical knowledge needed to teach this material and to interpret and use the text? Knowing the conventional procedure is clearly useful, and Ms. Gonzalez did know it. She is able to easily use it to solve problems involving subtraction of integers. But our analysis of the mathematical demands of teaching this lesson shows that more is involved. Modeling Mathematics in Teaching One of the most easily observable teaching tasks is constructing representations that are both mathematically accurate and helpful to learners. In this case, one of these representations involved using chips to solve subtraction problems. As the teacher and student confusion shows, this task is far from straightforward. The representation Ms. Gonzalez created--while mathematically correct--cannot be easily manipulated to arrive at the solution. A more promising way is to interpret subtraction as taking away (-3) from the initial quantity: However, only two red chips (-2) are present. How can (-3) be away? The solution, as briefly described by the textbook, would be to add another pair of black and red chips: The extra pair of black and red is equal to 0, so the total is still -1, but with this representation, three negative units can be taken away, showing the answer as +2. This representation is similar to what we do in multidigit subtraction when we rename the number (conventionally called regrouping or borrowing) to be able to subtract. Had Ms. Gonzalez seen this connection, she might have been better able to support students' use of the chip model. The lesson also requires facility with understanding and handling the mathematics that students say and do. …

Optimization of ECF bleaching of kraft pulp: II. Effects of acid prehydrolysis on hardwood pulp bleachability

Earlier studies [1] have shown that when a hardwood kraft pulp is bleached in the D0(EO)D1ED2 sequence, the brightness of the pulp emerging from the D2 stage can be accurately predicted from the brightness of the pulp entering that stage. The entering brightness, in turn, is a well-defined function of the ratio of the D1 stage ClO2 charge to the (EO) stage kappa number. In this study, we use the same model, together with the results of pulp-ing and bleaching experiments on southern U.S. red oak chips, to compare the bleachability characteristics of a conventional kappa number 15 pulp with that of an acid-prehydrolyzed pulp having, after 25% kappa number reduction by prehydrolysis, a similar kappa number. After the (EO) stage, the prehydrolyzed pulp had a lower extracted kappa number, but its brightness was lower than that of the control pulp. Both observations may be interpreted in terms of the relative amounts of residual lignin and hexenuronic acid present in the pulps. The full-sequence model described in our previous paper accurately described bleaching of the prehydrolyzed pulp. The model was used to evaluate the effects of the prehydrolysis on the optimized performance of the D1 and D2 stages. The brightness disadvantage of the prehydrolyzed pulp after the D0(EO) stages persisted over the lower range of D1 charge multiples but diminished as the multiple was increased, eventually disappearing. The prehydrolyzed pulp required slightly less ClO2 than the control pulp when bleaching to high brightness in five stages.

Temperature dependences of photoluminescence and electroluminescence spectra in light-emitting diodes

The temperature influence on the luminescence characteristics of light-emitting diodes (LEDs) is investigated to reveal the connection of photoluminescence (PL) with photon absorption and electroluminescence (EL) through current injection. By inspecting the PL and EL spectra at identical injection intensities, it has been found that the normalized spectra in PL and EL exhibit obvious similarities in shape and apparent differences in spectral characteristic values. Furthermore, the differences are found to originate from the junction temperatures in diverse injection modes. The observations are conducted on AlGaInP red LED chips.

Cover Picture: Phys. Status Solidi C 6/S2

AbstractLight‐emitting diodes (LED) with vertical stacking geometry were fabricated and characterized, as reported by K. N. Hui et al. on p. S902. Red, green and blue LED chips are stacked on top of each other to form a color‐adjustable light emitter. Color‐tunable and white‐light emission have been demonstrated. The emission of different colors, ranging from green‐blue over pink‐purple to yellow‐orange as well as white light emission have been achieved by adjusting the relative intensity of two or three individual emission bands, which in turn are controlled by adjusting the voltage supply (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Total valorisation of red cedar (Thuja Plicata) sawmills wastes. Isolation of extractives and production of activated carbon from the solid residue

Experiments were performed to evaluate a recent extraction process called the instantaneous controlled pressure drop process (briefly: DIC process: “Détente Instantanée Contrôlée”) for extracting some volatile compounds from red cedar wood. This process involves subjecting red cedar chips for a short time (30 s to 5 min) under a steam pressure (1 to 6 bars or from 100 to 165 °C). This first step is followed by a flash decompression toward vacuum (up to 50 mbar). This transition induces a fast evaporation of water and volatile compounds and a cooling effect. The effects of two processing parameters (steam pressure and heating time) on the total extraction yield and on yield of four volatile compounds were evaluated by response surface methodology. The results indicated that the processing pressure is the predominant parameter for global extraction yield of oil (E.O= Extracted Oil) and for yield of the four compounds investigated in this study. The processing time is also a significant parameter but less than processing pressure. Moreover, activated carbon produced from DIC-treated residue revealed larger pore sizes compared to untreated samples.

Optimization of ECF bleaching of kraft pulp: Part 1. Optimal bleaching of hardwood pulps made with different alkali charges

In an earlier modeling study, we showed that when a hardwood kraft pulp is bleached in the D0(EO)D1ED2 sequence with a D0 stage kappa factor of 0.20, the brightness of the pulp emerging from the D2 stage can be accurately predicted from the brightness of the pulp entering that stage. The entering brightness, in turn, is a well-defined function of the ratio of the D1 stage ClO2 charge to the (EO) stage kappa number. In the present study, we use the results of pulping and bleaching experiments on southern U.S. red oak chips to extend the model to account for the effect of changing the D0 kappa factor and use it to assess the effect of digester alkali charge on pulp bleachability. We also show how this approach can be used to minimize the total ClO2 requirement for any desired final brightness and to optimize the allocation of ClO2 to the three D stages of the D(EO)DED sequence or the two D stages of the D(EO)D sequence. Among the conclusions resulting from application of the model are that the combination of high effective alkali and high D0 kappa factor gives pulp with a higher final brightness ceiling than any other combination, but that for brightness targets of 91 or lower, the combination of low effective alkali and low kappa fac-tor is the most economical.

Thermal diffusion analysis for LED module

AbstractAn experimental investigation of the thermal characteristic of the LED chip and the sensitivity of illumination with thermal substrate is discussed in this study. An optimum thermal diffusion area to the heat flux of LED system is also conducted. Results show that a red LED chip has lower electrical resistance, and therefore has lower power consumption than that of green and blue LED chips. Given these three colors of lighting LEDs, the red LED chip is more sensitive to the thermal environment. A red LED's lighting illumination is decreased almost 12% when the substrate temperature difference is increased to 25°C. Under the same condition, an LED's illumination experiences only a 2 to 2.5% reduction for the green and blue LED chip. Copyright © 2004 Wiley Periodicals, Inc.Thermal diffusion area results show a close correlation between thermal diffusion ratio and LED substrate temperature. If the upper limit LED substrate temperature is set at 50°C and the thermal diffusion ratio approximates 72 cm2/w, for a 500 cm2 thermal diffusion area, it can sustain an optimum heat flux at 7 watts. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 449–458, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20182

A Context for Integer Computation

The National Research Council (2001) notes that a variety of metaphors have been used to introduce negative numbers in school, “including elevators, thermometers, debts and assets, losses and gains, hot air balloons, postman stories, pebbles in a bag, and directed arrows on a number line” (p. 245). In addition, standard textbooks have typically employed either a chip model, where positive integers are represented by black chips and negative integers by red chips; a charged-field model, showing +/−; or a number-line model. Some contexts or models are not really metaphors because, for example, negative numbers do occur in temperatures, in accounting, and in some sports scoring (e.g., scores under par in golf). However, these contexts become metaphorical when they are used to model arithmetical operations with integers. Each model or context must construct a scenario that makes it plausible to explain, for instance, why subtracting an integer is the same as adding its opposite or why a negative times a negative is a positive.

Contagion or Real Linkages? Some Evidence from China's Emerging Parallel Markets

AbstractThis paper empirically tests the existence of contagion using data on China's five parallel markets with different entry barriers for foreign capital. Taking the 1997 stock market crash as our experiment and using data on A, B and H shares, red chips and American depository receipts, the present paper tests whether these China‐backed market returns respond differently to foreign shocks during the pre‐1997 and post‐1997 crash period. Evidence suggests that the contagion effects are stronger in markets with fewer entry barriers. An important implication of our findings is that countries vulnerable to contagion could be justified to impose some limits on capital flows.

Implementation of Side Effects in Thermal Characterization of RGB Full-Color LEDs

This letter presents a useful thermal-characterization method for RGB full-color light-emitting diodes (LEDs). The superposition method was employed to calculate thermal resistances of a high-power RGB full-color LED package to implement the side effect. Independent driving of a single chip in the RGB package clearly exhibited a side effect on the other two chips. It was shown that driving a red chip at 350 mA, current induced 4.8degC temperature rise for the green and blue chips, which is about 30% of the temperature rise in the red chip itself. A thermal-resistance-coupling matrix was structured and used for the calculation of the junction temperatures of the chips. It was demonstrated that the superposition method can be employed for an accurate prediction of the junction temperature rises for the RGB full-color LED package.

Axial gas profiles in a bubbling fluidised bed biomass gasifier

A 200 mm laboratory-scale atmospheric bubbling fluidised bed reactor has been used to obtain experimental data for the air/steam gasification of eucalyptus red gum wood chips and commercial wood pellets. The unique feature of this gasifier is the ability to examine the variations to axial gas composition along the bed height. At present no such data is available in the literature for biomass gasification. Gasification tests were performed using beds of; silica sand, char or clay to determine the effect of bed type on the gas composition. The behaviour of the major gas species (CO, H2, CO2) were observed to be strongly influenced by the water–gas shift reaction within the freeboard of the gasifier resulting in the exit gas being relatively similar in composition as compared to the in-bed variations. These small differences in gas composition for all bed types tested are the result of the achievement of equilibrium in the water–gas shift reaction. The influence of bed type exerted the most impact on the C2–C3 emissions (tar proxy) with the char bed found to best aid in their breakdown and to limit the amount of hydrocarbons surviving into the freeboard. The reduction of iron oxide (Fe2O3) content in the clay to a more reactive form of magnetite Fe3O4 by CO and H2 in the product gas resulted in the clay bed to also exhibit a reduction in C2–C3 emissions compared to silica sand but less then char. The clay bed produced the highest calorific values for the producer gas. However, operation of the clay bed above 800 °C exhibits the potential for over reduction to form iron with subsequent agglomeration of the bed. Changing the fuel type to a biomass pellet resulted in higher emissions of C1–C3 hydrocarbons and in part its contribution is the result of primary particle fragmentation during screw feed conveying to the bed. Feeder location and bed design (conical or cylindrical) also exhibit an influence on hydrocarbon emissions.

A blue-violet enhanced BDJ photodetector and its applications in the probe chip measurements of the LEDs for solid-state lighting

A blue-violet enhanced buried double p–n junction (BDJ) photodetector with its characteristics is reported in this manuscript. It was fabricated on high resistivity float-zone silicon substrate by using ion implantation and exhibits low leakage currents. It can measure both the light intensity as a photometric detector and the wavelength of quasi-monochrome light as a wavelength sensor simultaneously. It was optimized to operate at wavelength from 380 nm to 780 nm in which the light emitting diodes (LEDs) for solid-state lighting is most interested. The resolution for the wavelength measurement of the photodetector is better than 1 nm. The probe chip tests of violet, blue, green and red LED chips have been demonstrated using the fabricated detector. This simple, fast and reliable method provides an alternative to low cost and fast examination technique for LED chips in vast production.

Using Top Ten Lists to Encourage Faith Integration Discussion in Economics Courses

This paper both documents and assesses the use of a role play simulation exercise that can easily be incorporated into the first week of the first course in accounting. The exercise actively involves students by having them assume roles and simulate transactions to start a business. In addition, the students also perform a record-keeping role. Both the medium of exchange and record-keeping are accomplished by using white, red and blue poker chips. A primary focus of the exercise is to learn how transactions affect the fundamental accounting equation (assets=liabilities+owners’ equity). In addition, several other fundamental accounting concepts are introduced. To assess if the exercise enhances student learning, other sections of the same accounting course learned identical subject matter with a lecture format. An assessment instrument was administered to both student groups. The results indicate that role play simulation enhances students’ transfer problem solving, but there is no evidence that it enhances conceptual recall beyond that which can be attained via a traditional lecture. In addition, there is evidence that the role play simulation exercise helps student better retain problem solving learning over a four week period.

Marking Time in Door County

Marking Time in Door County Sarah Gorham (bio) I'm sitting on the pier, first morning of our ten-day vacation. Green Bay is in party mode. Whitecaps collide and dance from crisscrossing wakes. Pontoon boats putter along, their riders squawking like chicks in aluminum baskets. I breathe in the odor of juniper, mown grass, beer, and, yes, alewives, a dozen of them, curled and bloated inside the marina. A storm's on its way, but sky-wise, there's only a distant smudge of cloud over Horseshoe Island. Inside the house the girls are waking up—Kristin humming in the shower, Laura at the fridge, Bonnie rummaging for her hairbrush. A fly finds its way to the honey at the bottom of my teacup. Ten thousand such mornings have passed since my grandparents purchased a house called Grey Logs, with lean-to kitchen and 150 feet of waterfront in Ephraim, Wisconsin. In 1947 the village held a few rustic hotels, an ice cream shop, and Anderson's dock with its graffiti-clogged barn. Native Americans, the French, and the Norwegians were among Ephraim's early visitors. We are the latest, one of 14 third- and fourth-generation families who now share this property with its Scandinavian log buildings, its hemlocks and swamp, its flocks of mallards and gulls. We come from all over the country—Washington, Kentucky, Idaho, California, and New York—to ground more constant and welcoming than the 14 places we call home. The approach from Highway 42 winds through Egg Harbor, Fish Creek, Ephraim, and finally Grey Logs, at the bottom of a deeply shadowed driveway. Then the sky opens out and water fills in the spaces. We can see Horseshoe Island, Eagle Bluff, and, remarkably, Three Sisters Islands, several miles away over swells and sails. No streetlights or lane markers here. And the trees are not the kind I worry about from my own backyard, yellowing and sparse. They are grand, gracious ladies in dark green dresses; they are here to soothe, to whisper reassurances. Stendhal defined beauty as "the [End Page 1] promise of happiness." I walk out onto the rickety pier and let the wind with its odor of grass and Green Bay hit me from all sides. I know that when this aphorism occurred to him, Stendhal was standing in just such a place. My grandparents are here too, invisible comfort, gentle ghosts. Gramps waving from the kitchen, Gagi still in bed with her tray of coffee and toast. They traveled the world but always returned, for there was no place they found lovelier than Grey Logs. My husband and I sleep in their room, shower in their once off-limits-to-kids bathroom. Though decades have passed since they died, it still feels like trespassing. The girls have staked out the upstairs. We make short shrift of unpacking, and with bathing suits under our shorts and water shoes in hand, the celebration begins. But no swimming for me, not just yet. Not even with the "Oh come on, Mom!" I have a ritual I must attend to on my 39th visit to Gray Logs. I say hello to the house by kissing the smooth gray banister, by shedding my shoes and running my toes over the flagstones, by opening the linen closet and counting the blue-and-white-striped towels. I'm expressing my thanks for safe arrival. Not just this one in 2002, but all my arrivals. Here on the braided living room rug, center of the house, where everything is stored, no whisper or footstep is excluded. I listen, breathe deeply, sniff for the raucous poker games on the folding card table, red and blue plastic chips careening about like rickety bicycles, Bicycle cards leaping when cousins John or Chuck or Nan slam an outrageously funny fist down. The sweep of Gramps' terrycloth robe, his tray of perfect over-easies and sausage. And my father vexing the floorboards with early morning stretches, leg lifts, sit-ups, creaking and moaning inside the body and out. I touch the maroon, slipcovered sofa. Down into the fibers I go like a medical detective uncovering wet towels, shed bathing suits, the crumpled wrappers...

Evaluation of Allelopathic Potential of Wood Chips for Weed Suppression in Horticultural Production Systems

Shredded and chipped wood mulches are used for weed suppression in perennial fruit crops, in urban landscapes, and occasionally in vegetable crops. Wood chip mulches with weed-suppressing allelochemicals may be more effective for weed control, especially under sustainable and organic production systems, than mulches without such properties. The objective of this study was to test for the presence of water-soluble allelochemicals in wood chips derived from tree species, often found in wood resource recovery operations in the southeastern US. Presence of allelochemicals in water eluates of woodchips and leaves was evaluated in a lettuce bioassay. Eluates of wood chips from red maple (Acer rubrum L.), swamp chestnut oak (Quercus michauxii Nutt.), red cedar (Juniperus silicicola L.H. Bailey), neem (Azadirachta indica A. Juss.), and magnolia (Magnolia grandiflora L.) highly inhibited germinating lettuce seeds, as assessed by inhibition of hypocotyl and radicle growth. The effects of wood chip eluates from these five species were more than that found for eluates from wood chips of black walnut (Juglans nigra L.,) a species previously identified to have weed-suppressing allelochemicals. Tests on red cedar, red maple, and neem showed that water-soluble allelochemicals were present not only in the wood but also in the leaves. In greenhouse trials, red cedar wood chip mulch significantly inhibited the growth of florida beggarweed (Desmodium tortuosum DC.), compared to the gravel-mulched and no-mulch controls.

Fungal degradation of wood: initial proteomic analysis of extracellular proteins of Phanerochaete chrysosporium grown on oak substrate

Two-dimensional (2-D) gel electrophoresis was used to separate the extracellular proteins produced by the white-rot fungus Phanerochaete chrysosporium. Solid-substrate cultures grown on red oak wood chips yielded extracellular protein preparations which were not suitable for 2-D gel analysis. However, pre-washing the wood chips with water helped decrease the amount of brown material which caused smearing on the acidic side of the isoelectric focusing gel. The 2-D gels from these wood-grown cultures revealed more than 45 protein spots. These spots were subjected to in-gel digestion with trypsin followed by either peptide fingerprint analysis by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS) or by liquid chromatography (LC)/MS/MS sequencing. Data from both methods were analyzed by Protein Prospector and the local P. chrysosporium annotated database. MALDI-TOF/MS only identified two proteins out of 25 analyzed. This was most likely due to problems associated with glycosylation. Protein sequencing by LC/MS/MS of the same 25 proteins resulted in identification of 16 proteins. Most of the proteins identified act on either cellulose or hemicellulose or their hydrolysis products. Thus far no lignin peroxidase, Mn peroxidase or laccases have been detected.

Corporate Governance and Firm Valuations: Evidence from Hong Kong

Do corporate governance standards affect firm value? Are shareholders in emerging markets willing to pay a premium for higher governance standards? We construct a corporate governance index to represent Hong Kong corporate governance standards and rank listed companies according to the index. Our model has 17 variables covering five governance mechanisms: board structure, executive compensation, ownership structure, executives' conflict of interest, and transparency standards. We compare and analyze the special characteristics of H Shares, Red Chips, and family controlled companies among listed companies. Our results indicate that these areas significantly impact firm value, and Hong Kong investors are willing to pay substantial premium for better governance standards. We find that firms with better rating in our CG model have higher firm value, which implies that firms can increase their valuations by restructuring their corporate governance standards according to our model.

Corporate Performance of Mixed Enterprises

We delineate Hong Kong listed corporations into three levels of privatization: the fully privatized blue chips, semi‐privatized red chips and the least privatized H shares. Both H shares and red chips are mixed enterprises that mimic private ownership with joint government and private stock ownership. We find that mixed enterprises are less profitable and lower valued than the fully privatized blue chips, but red chips are more efficient and perform better than blue chips when market confidence swings to their favor. Regression analysis suggests that increased stock ownership by the government and increased emolument incentives are counterproductive to profitability, especially in bad economic times of the 1997–98 Asian financial crisis.

Red Chips: Implications of the Semiconductor Industry's Relocation to China

Click to increase image sizeClick to decrease image size Additional informationNotes on contributorsMichael KlausMichael Klaus of Xavier University, is a former policy analyst at the US.-Taiwan Business Council.

Role of the state in Chinese enterprises listed in Hong Kong

Given the need to acquire portfolio equity flows on the one hand, but the absence of a developed domestic securities market on the other, China has resorted to listing state enterprises in Hong Kong. This has led to the emergence of two types of companies: H-share companies and red chips. The former are Chinese state-owned enterprises restructured for listing in Hong Kong, whereas the latter are Hong Kong-listed companies with major Chinese interest. This paper presents two case studies to show that, while listing enterprises in Hong Kong has helped China to raise a significant amount of foreign capital, it has contributed little to the improvement of the enterprises' economic performance. Rather, the residual role of the state in these enterprises has resulted in problems such as asset-stripping and submission to non-economic (social and political) factors. Contrary to neoclassical economic belief, privatization and internationalization of state enterprises do not necessarily lead to enhancement of economic efficiency.