Cement Wall Research Articles

A New People

IF ONE is going to build a wall, it is best to ask first what is being walled in and what is being walled out. I borrow this thought from Robert Frost, but I was prompted to bring it up by those in Congress who want to build a wall along the Rio Grande and the school principal in Kansas who suspended a child for speaking Spanish in the hallway. These people have a lot in common. Dismiss the idea that a wall will keep out terrorists or that suspending one Hispanic kid with the effrontery to speak his native language will protect American values. Fear makes us do strange things. Instead of spending a pile on the false security of a cement wall, why not instead provide guest-worker permits that would free up immigration officials to focus on border crossers who are seeking more than just a job? And if politicians object to hearing Spanish on the street, why do they cut funds for adult literacy classes that have waiting lists of English-language learners? For educators who don't know or don't want to know how to deal with and respect another culture, I have a piece of advice: get a grip. To quote a recent report by the Metropolitan Center for Urban Education at New York University on the challenges ahead, this nation is becoming a new people. The demographics are not something that can be walled out or suspended, and the sooner educators and policy makers acknowledge what is happening in this country, the quicker we can move forward. Behind the rhetoric about our growing diversity are some startling statistics that should inspire much more than fear. For example, who will make up our future work force--from those who clean buildings to those who design them? Analyzing census data, the National Center for Public Policy and Higher Education concludes that in a decade and a half the white working-age population will have declined to 63% (from 82% in 1980). This is happening because larger numbers of younger workers are members of ethnic minorities, and larger numbers of white workers are retiring. The largest increase among young workers will be among Hispanics. Because the fastest-growing populations are ethnic minorities, the work force that will propel our economy and shape our society--and also provide the Social Security check of almost everyone reading this--could have a lower level of personal income than current workers. Unless something is done to close the education gap, according to the study, the most highly educated generation in the history of the U.S. could be replaced by a generation with far lower levels of (as measured by high school and college completion rates). While ethnic minorities reside in all states, 90% of Hispanics live in 16 states, and 90% of blacks live in 21 states. This means that inequalities in terms of and income will exist between the states as well as within them. Another study, by the Pew Hispanic Center, presents equally dramatic data. The Hispanic population is growing faster in the South than anywhere else in the country. Among the six states studied, the increase in the percentage of Hispanics ranged from 204% to 394%. In some counties, the growth rate exceeded 1,000%. Between 1990 and 2000, the school-age population of Hispanic children in these states grew by 322%, and the rate of growth was even faster in the preschool population. During the same time span, the number of students with limited proficiency in English climbed from 18,000 to 64,000. By next year, Hispanics will make up at least 10% of the population of these states. The Pew study points out that the current impact of Hispanics in the states is only beginning to be felt because most of those who have recently arrived are young men. But as these men bring families into the country, the schools will experience an even larger surge in the number of Hispanic students (the black population in these states increased by 18% as well). …

Indians, Oil, and Politics: A Recent History of Ecuador

Indians, Oil, and Politics: A Recent History of Ecuador

Flexural capacity of thin wall fibre reinforced cement

A method of calculating the flexural strength (cracking) of fibre reinforced cement floor and wall systems is presented. The method for flexural strength is based on non-linear stress-strain relationship at failure tension and corresponding stress distribution in section at cracking and subsequent failure. The method is verified in tests of full-scale ‘V’ and ‘U’ shaped panels made of asbestos-cement which were tested as simply supported beams designed for the construction of low cost housing and wall facades. Additional tests were performed on small sized samples to verify the mechanical properties of material used.

Advances in Total Hip Arthroplasty

Detailed, long-term studies of cemented total hip arthroplasties clearly show that failure of fixation of the acetabular component is a major problem, with a rising incidence and an unusual complexity. By finite element analysis the stress distribution in the human acetabulum before and after total hip arthroplasty was analyzed by three different groups of investigators. Data from all three studies are in agreement that the introduction of cemented acetabular components of high-density polyethylene results in major disturbances of stress distribution, with peak stresses after total hip arthroplasty occurring in the cement, trabecular bone, and medial wall of the acetabulum. The most effective way to reduce these peak stresses in these three critical areas is to use an acetabular component with a metal backing. Long-term follow-up studies of 51 patients who underwent total hip arthroplasty performed by the author during the period from 1971 to 1975 using metal-backed acetabular components confirm the improved fixation that results from use of this design. Both the analytic data of stress distribution and clinical follow-up studies strongly support the use of metal-backed acetabular components in cemented total hip arthroplasty.

Fire testing flat roofs and wall linings with point fire sources

AbstractIn the spring of 1977 seven real scale fire tests on flat roofs and wall linings were carried out with relatively small fire loads to simulate the early stages of a fire. Tests with large fire loads had already been performed. Five tests were carried out on insulated corrugated steel roof decks with a fire‐retardant EPS (expanded polystyrene) foam insulation of reduced flammability and one test with a non‐combustible mineral‐wool insulation. A seventh test was run to study the fire behaviour of corrugated asbestos cement roofs and wall linings with EPS foam insulations and fire loads of the same kind (wood cribs up to 200 kg) as before. The tests demonstrated both the advantages and the disadvantages of the different insulations for corrugated steel roof decks in case of fires before Flash‐over.

KAJI EKSPERIMENTAL PENGARUH KONDENSAT UNTUK MENDINGINKAN LIQUID LINE PADA CHEST TYPE MINI COOLER DENGAN METODE RADIANT COOLING

Pendinginan liquid line dengan kondensat yang dihasilkan pada dinding chest type mini cooler adalah salah satu cara untuk menambah subcool sehingga kapasitas refrigerasi yang dihasilkan akan lebih besar dan dengan demikian akan dihasilkan penghematan energi. Kondensat yang dihasilkan pada chest type mini cooler ini memiliki temperatur yang lebih rendah dari temperatur lingkungan sehingga akan menurunkan temperatur liquid line, dimana kondensat tersebut dialirkan ke tabung tube in tube sepanjang 30 cm dengan diameter 1 inci untuk mendinginkan liquid line. Radiant cooling didapat dengan menanam koil evaporator ke sekeliling dinding kabin yang terbuat dari semen dimana alat ekspansi menggunakan TXV dengan R22 sebagai refrigeran dengan kapasitas kompresor 1 pk. Kabin dengan dimensi 50cm x 50cm x 50cm dikondisikan pada suhu 5 oC untuk mendinginkan tomat seberat 1 kg. Dari penelitian ini didapat bahwa Chilling Time dengan menggunakan HX kondensat sebesar 35 menit sedangkan tanpa HX kondensat sebesar 38 menit. Subcool rata-rata dengan menggunakan HX kondensat sebesar 3,320C sedangkan tanpa HX kondensat sebesar 0,030C. COPaktual rata-rata dengan HX kondensat sebesar 4,49 sedangkan tanpa HX kondensat sebesar 4,55. Nilai Efisiensi sistem rata-rata dengan HX kondensat sebesar 82,26 sedangkan tanpa HX kondensat sebesar 80,66. Konsumsi energy dengan HX kondensat sebesar 0,635 kWh sedangkan tanpa HX kondensat sebesar 0,701 kWh.
 
 Kata kunci: radiant cooling, kondensat, liquid line sub-cooler

Relative Productivity of Perforated Casing - II

Abstract The effect of depth of formation penetration by casing perforations has beenstudied by means of an electrolytic model. It is found that the relativeproductivity of perforated casing is profoundly affected by the depth to whichthe formation is penetrated. The first in. of penetration is of especialimportance. A scaling equation which was shown to agree with experimentalresults at zero penetration is used to calculate the relative productivity of ascaled down casing with scaled down perforations. Introduction In an earlier paper the authors showed that the point sink representation ofcasing perforations is inadequate. It was pointed out at that time that whilethe electrolytic model results were a marked improvement over point-sinkcalculations, they still left a great deal to be desired in that theelectrolytic model represented a case not realizable in practice, namely, aclean hole through the casing but undisturbed formation on the other side ofthe casing. Obviously, to be effective, the perforation must penetrate a finitedistance into the producing formation. It was the purpose of the presentinvestigation to find how the relative productivity of perforated casing varieswith depth of penetration. The term "depth of penetration" as used in this paper refers to thedistance which the perforation penetrates the producing formation. The amountof casing and cement penetrated is not taken into account, a fact which isdiscussed more fully later. The "casing radius," therefore, is to beinterpreted as the radius of the boundary between cement and formation wall, incases where the casing is not in contact with the formation wall. Apparatus The electrolytic model experimental setup was identical with that describedin the previous paper except that the platinum electrodes were now allowed toproject from the lucite cylinder by varying amounts. When fewer than eightelectrodes were used, the unused ones were covered with a coat of insulatingmaterial to minimize disturbances to the current flow-lines. T.P. 2933