Problem For Several Years Research Articles

Sound Plans Help Thwart Identity Theft

Sound Plans Help Thwart Identity Theft

The Approximability of Three-valued MAX CSP

In the maximum constraint satisfaction problem (MAX CSP), one is given a finite collection of (possibly weighted) constraints on overlapping sets of variables, and the goal is to assign values from a given domain to the variables so as to maximize the number (or the total weight, for the weighted case) of satisfied constraints. This problem is NP-hard in general, and, therefore, it is natural to study how restricting the allowed types of constraints affects the approximability of the problem. It is known that every Boolean (that is, two-valued) MAX CSP with a finite set of allowed constraint types is either solvable exactly in polynomial time or else APX-complete (and hence can have no polynomial-time approximation scheme unless P=NP). It has been an open problem for several years whether this result can be extended to non-Boolean MAX CSP, which is much more difficult to analyze than the Boolean case. In this paper, we make the first step in this direction by establishing this result for MAX CSP over a three-element domain. Moreover, we present a simple description of all polynomial-time solvable cases of our problem. This description uses the well-known algebraic combinatorial property of supermodularity. We also show that every hard three-valued MAX CSP contains, in a certain specified sense, one of the two basic hard MAX CSPs which are the Maximum k-Colorable Subgraph problems for k=2,3.

An adaptive scheme for fault-tolerant scheduling of soft real-time tasks in multiprocessor systems

The scheduling of real-time tasks with primary-backup-based fault-tolerant requirements has been an important problem for several years. Most of the known scheduling schemes are non-adaptive in nature meaning that they do not adapt to the dynamics of faults and task's parameters in the system. In this paper, we propose an adaptive fault-tolerant scheduling scheme that has a mechanism to control the overlap interval between the primary and backup versions of tasks such that the overall performance of the system is improved. The overlap interval is determined based on the observed fault rate and task's soft laxity. We also propose a new performance index, called SR index, that integrates schedulability ( S) and reliability ( R) into a single metric. To evaluate the proposed scheme, we have conducted analytical and simulation studies under different fault and deadline scenarios, and found that the proposed adaptive scheme adapts to system dynamics and offers better SR index than that of the non-adaptive schemes.

OS6-02 実機配管に対する多機能超音波非破壊検査装置の開発(OS6 設備診断・運用保全技術)

Cracks in welded piping in fossil and nuclear power plants have been a potential problem for several years. Ultrasonic examination is one technique that helps detect cracking at stages early enough to implement corrective measures. We have developed the development of an ultrasonic inspection system and the applicability of the TOFD and phase array techniques to the detection and sizing of cracking. This report discusses the validation of the system by inspecting pipe-shaped welded specimens with internal crack-like defects simulating type IV cracks due to creep damage and stress corrosion cracks.

Financial Problems in University Libraries: the Turkish Case

The scarcity of financial resources is the main obstacle to improve university library services in both developed and developing countries. Examples from different countries show that lack of financial resources is an international problem. It is clear that the worldwide crisis in the economy in the 1970s negatively affected the universities and their libraries of both developed and developing countries. Librarians have therefore struggled to overcome the finance problem for several years. Today, university libraries in different countries, either developed or developing, are still complaining about the lack of financial resources for their services. But, their problems are not identical. It is seen that the universities of developed countries have found alternative income resources and have transferred some of them to their libraries. When looking at university libraries in developing countries, in addition to scarcity of financial resources, the lack of library policy regarding fiscal resources is an another barrier. Turkish university libraries are also suffering from similar problems. In this paper, the current trends related to financial resources of university libraries in a global context are described and then the situation in Turkey more specifically is discussed.

When Is 100% Inspection Not Enough? An Analysis of Three Pickup Truck Front Wheel Assembly Failures

The loss of a cotter pin in the front wheel assembly of cars and trucks has been a problem for several years. This is shown by the fact that the automobile manufacturers have been committed to a 100% inspection of the process for installing them on cars and trucks. In this paper, three accident cases are presented, along with a method by which the forensic engineer can determine if a cotter pin has ever been installed on the front wheel assembly. Testing was done to show what the spindle would look like if the cotter pin had been installed properly and forcibly removed. Photographs show both the accident and test spindle for comparison.

Dislocation distributions in ion implanted optical waveguides

The origin of anomalous refractive index values in ion implanted optical waveguides in some crystalline materials has been an outstanding problem for several years. By use of complementary X-ray edge-topography and Raman microprobe imaging we have found evidence that changes in the dislocation density after implantation correlate with changes in the dynamic response of the lattice to light. This implies that the effects of reduced dislocation density may be related to the origin of the refractive index anomalies, possibly as a result of strain relief. Further support for this hypothesis comes from the fact that the original bulk dislocation density is recovered throughout the crystal by annealing to the temperature at which the refractive index anomalies are lost.

Hot gas environment around STOVL aircraft in ground proximity. II - Numerical study

Ingestion of hot exhaust gases by the engines of STOVL aircraft has been an important research problem for several years. The hot gas environment around STOVL aircraft is three-dimensional and turbulent. In this study, the Navier-Stokes equations governing the hot gas ingestion flowfield are solved by an efficient finite-difference calculation procedure. The complete geometry including the head wind and the fuselage is simulated. Four demonstration calculations with variations in the height of the fuselage and the head wind velocity are presented. It is shown that the calculation procedure efficiently provides a solution to the governing equations and produces realistic descriptions of the flow and temperature fields.

Mandibular Advancement Using the Bilateral Sagittal Osteotomy Past, Present, and Future

SUMMARY Although the group of articles studying the sagittal split osteotomy is large and varied, it is possible to draw several conclusions regarding the present state of knowledge. First, several variables have been shown not to cause relapse within the limits of the patients studied. These variables include age, preoperative orthodontics, and mandibular plane angle. Likewise, several factors decidedly do have an influence on relapse. As various investigators have shown,26'30'56 the magnitude of advancement is positively correlated with relapse, presumably secondary to stretch of muscles and other paramandibular soft tissues. Condylar displacement has also been shown by many authors15,17, 25, 28-30, 34, 39, 45, 59 to lead to relapse, along with a more general variable of proximal fragment position. In addition, as Schendel and Epker45 reported (and the variability of relapse figures demonstrates), “different surgeons had predictably good or unacceptable results”— i.e., some unspecified technical variables are apparently at work. Although identifying some of the factors responsible for relapse is an important step, it is only a first step. The next step is to find ways of preventing relapse by manipulating these factors. Skeletal fixation has been conclusively shown to reduce the amount of horizontal relapse and anterior facial height increase after sagittal osteotomies.11,35 It is less clear what effect the devices used intraoperatively to position the proximal segment might have on relapse. Several investigators reported on such devices15,22,31,41 and recommended their use, but only Raveh and coworkers41 had data to support such a recommendation. Rigid internal fixation was regarded as a panacea for the relapse problem for several years, but recent studies have shown that the role of this technique in the stability of the advanced mandible is not so clearcut. The present understanding is that when the amount of advancement exceeds 6 to 7 mm, there is a significant decrease in stability. It should be realized that with the different screws (self-tapping, nonself-tapping) and the different configurations of screws and plates used, rigid fixation cannot be considered a single technique. Finally, some potential influences on stability have not yet been ruled in or out. The suprahyoid myotomy is a prime example. Indeed, clinicians and researchers have postulated for 20 years that “muscle pull” is one of the primary causes of mandibular relapse.16,20,21,36,38, 49 The extent of the contribution of muscle pull to instability, and the specific role played by the suprahyoid muscle group and its myotomy, is one of the prime questions left for the future. Another factor whose role is as yet unclear is the articular cartilage and its response, both short and long term, to increased loading such as is found after mandibular advancement. Huang and Ross23 examined the amount of advancement and its influence on mandibular relapse in growing individuals. They found in all patients that growth ceased for 1 year, during which time neuromuscular adaptation presumably occurred. However, growth then resumed in 6 of the 11 patients having less than 10 mm of advancement. Those patients with greater than 10 mm of advancement showed no growth, with three of ten patients even showing continued decrease in mandibular length. This suggests that the articular cartilage was loaded with concomitant remodeling changes, and in the group with larger advancements, the loading was above the level that permitted mandibular growth. Copray and colleagues6 also investigated the influence of compressive forces on condylar cartilage, using rat embryonic cartilage in culture. They found that although continuous and intermittent compressive forces up to 3 g and 8 g, respectively, not only allowed but stimulated growth, forces above these levels caused deformation and necrotic shrinkage of the condyles. What does the future hold for the bilateral sagittal osteotomy? It seems clear that the procedure will continue to be the main technique for surgical mandibular advancement. The principal advances that need to be made lie in the areas of determining the role of muscle stretch and adaptation and the response of the articular cartilage. Once these two factors are well understood, the bilateral sagittal osteotomy will be much more predictable.

Distorted Flow Field in Compressor Inlet Channels

Solving the complex inlet-distortion related problems in turbojets or turbofans has become crucial to the successful development of new-generation engines. In order to curtail costs, reliable prediction methods, both analytical and numerical, must be developed and implemented. ONERA has been studying this problem for several years now. This paper reports on the preliminary numerical investigations of the three-dimensional flow field in the annular duct extending in front of a compressor with distorted inflow. The computational approach is a fully unsteady time-splitting, finite difference method solving the inviscid flow equations with nonuniform steady boundary conditions. Some analytical examples are presented and discussed. Matching of this three-dimensional computer code with models representing rotating or fixed blade rows is under way and will be reported on in a future contribution.

Phylogenetic Patterns and Hybridization

Hybridization is an important part of the evolutionary history of flowering plants. If hybridization has occurred among the species of a taxon under cladistic analysis the results are varied but always present additional difficulties. Hybridization results in incongruent intersecting data that obscure the underlying hierarchy. Guidelines and methods are examined for their usefulness in identifying possible hybrids in a cladistic study. Seven genera are analyzed cladistically and the resulting cladograms examined for possible hybrids. These hypotheses of hybridization are then compared to other data, such as distribution and cytology, to see if the hypotheses of hybridization are supported or rejected. The more hybrids an analysis contains and the more complex the interactions, the more difficult it becomes to identify possible hybrids and their parents. It is difficult to overemphasize the importance of hybridization and polyploidy in evolution because they are outstanding features of many plant groups. According to some authorities 30-80% of the species of angiosperms are polyploids (Goldblatt, 1979; Lewis, 1979; Stebbins, 1974), which allows for the possibility of a tremendous amount of hybridization. Of course, these figures do not include diploid hybrids. Despite its importance, hybridization has been virtually ignored by those who have dominated the discussion of evolutionary theory. This is a result, no doubt, of evolutionary theory being largely in the hands of scientists who work on groups in which such phenomena as polyploidy and hybridization have a strong relationship with unisexuality and are not considered important in evolution. There are different types of hybridization. Figure 1 summarizes some of the possibilities (a more detailed explanation is found in Funk, 1981) but does not include introgression. For the purpose of this paper it is important to note that many hybrids are sexually reproducing individuals and are morphologically distinct and in some manner reproductively isolated from both parents. Thus, they behave as species no matter whose definition you chose to adopt. THE STUDY OF HYBRIDIZATION The basic concept of phylogenetic systematics (sensu Hennig, 1966) is an ever branching pattern or hierarchy. The method of cladistics (phylogenetic systematics) seeks to discover these patterns by grouping together taxa that share apomorphies (evolutionarily novel, unique, or derived characters). Hybridization, or reticulate evolution, is inconsistent with a method designed to depict hierarchies. Hybridization is, therefore, a cause of incongruent, intersecting data that obscure phylogenetic information. Cladists have been concerned with this problem for several years. Most realize that any method that seeks to identify patterns of relationship must be able to accommodate hybridization because of its frequency. Workers in the problems of hybridization and phylogenetic systematics include Bremer (1983), Bremer and Wanntorp (1977), Clark (1982), Funk (1981), Humphries (1983), Humphries and Funk (1984), Nelson (1983), Nelson and Platnick (1980), Rosen (1979), Wagner (1969, 1983), Wanntorp (1983), and Wiley and Brooks (1982). One favorite method of botanists in estimating the closeness of relationships among taxa is the percentage of hybridization in crossing studies. An important point about such hybridization studies was made by Rosen (1979: 277): reproductive compatibility is a primitive attribute for the members of a lineage and has, therefore, no power to specify relationships within a genealogical framework. We cannot use the ability of two or more species to hybridize as an indication of close relationship because the ability is relaI A number of people, who do not necessarily agree with everything that I have said, have kindly provided me with data and comments on various drafts of the manuscript and this paper would not have been possible without their assistance. They include: R. Jansen, J. Semple, C. Clark, R. Sanders, C. Humphries, H.-E. Wanntorp, K. Bremer, G. Nelson, N. Platnick, D. Rosen, and P. Weston. I appreciate the assistance of B. Kahn in helping prepare the illustrations. 2 Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560. ANN. MISSOURI BOT. GARD. 72: 681-715. 1985. This content downloaded from 207.46.13.148 on Sun, 11 Sep 2016 04:15:12 UTC All use subject to http://about.jstor.org/terms 682 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 72

Similarity and stability of the laminar boundary layer in a streamwise corner

The study of laminar viscous flow along the line of intersection of two solid surfaces at right angles is examined in its present state, and out­standing differences between various experimental and theoretical results are analysed. New experimental results are presented in which the stability of the corner boundary layer is examined in terms of the degree of streamwise similarity of its velocity profiles. Conclusive evidence is found that the layer does not exist in stable laminar form when the streamwise pressure gradient is zero and the Reynolds number much above about 10 4 . The new results also help to explain the differences between various experimental results, and between theory and experi­ment, which have characterized the corner boundary layer problem for several years. By extrapolation, an approximate prediction is obtained of what the velocity profile of the corner boundary layer would be in the limiting case of zero pressure gradient, if the layer were stable in that state. The predicted profile is compared with the results of current theories.

'En attendant Debye...' ('Until Debye': the specific heat of solids)

The problem of the specific heat of solids and its behaviour at low temperatures played an important role in the evolution of basic ideas in physics at the turn of the century. It was finally solved by Debye, but why did Einstein, who showed a keen interest in that problem for several years, fail to propose the Debye model? The article recalls a few facts and presents a few suggestions.

Surgical manpower. A symposium.

Dr. Chase: To keep up with the times we have, by consensus, renamed this symposium "Surgical Personpower." It is evident that surgeons have been interested in this most critical health care problem for several years and once again we hope we are demonstrating ourselves to be in the vanguard. You have an outstanding panel today and I am not going to waste your time with lengthy introductions but, as you know, we are faced with some critical problems in the health care industry in this country. A few examples are (1) uncertainty as to the optimum number of physicians, (2) maldistribution among specialties and geographic areas, (3) changing ratio of foreign medical graduates to US graduates (particularly in view of the fact that in this current year only one in five premedical graduates will get into an American medical school), (4) federal reimbursement for doctors of osteopathy in our residency

Spectral approximants of normal operators

For each non-empty subset Λ of the complex plane, let (Λ) be the set of all those operators (on a fixed Hilbert space H) whose spectrum is included in Λ. The problem of spectral approximation is to determine how closely each operator on H can be approximated (in the norm) by operators in (Λ). The problem appears to be connected with the stability theory of certain differential equations. (Consider the case in which Λ is the right half plane.) In its general form the problem is extraordinarily difficult. Thus, for instance, even when Λ is the singleton {0}, so that (Λ) is the set of quasinilpotent operators, the determination of the closure of (Λ) has been an open problem for several years (3, Problem 7).

Fire and high buildings

The time necessary to evacuate today’s high-rise buildings in a fire emergency is unsatisfactory from the standpoint of the development of untenable smoke conditions. The Division of Building Research has been working on the problem for several years and suggests several approaches to controlling smoke movement in buildings.

SIMPLE KIDNEY-STORAGE TECHNIQUE.

Several years ago we did not seriously consider removing kidneys from healthy living people and transplanting them to uraemic patients. The obvious plan was to store kidneys for subsequent transplantation. The problems involved in storage were not underestimated. It was pointed out : If the immunological problems and other problems involved in procuring a normal functioning organ were solved our difficulties would be by no means over. There would still remain the problem of storage of organs. This presents many difficulties. While there is no difficulty in preserving skin and blood-vessels in the frozen state, other organs, such as kidney, would require more delicate handling. It is possible that an organ-perfusion apparatus may turn out to be the only safe method of preserving delicate organs ready for homotransplantation at any given (Dempster, 1951). However, the results of transplanting cadaveric kidneys were disappointing because of a high rate of immediate anuria or oliguria, although occasionally function was resumed several days later (Hume et al., 1955). The pioneering effort of Oeconomos et al. (1953), using a fresh kidney, impressed us and influenced our attitude to the donor problem for several years. A scientific contraindication, we think, to continuing with live donors at this juncture is the high incidence of a curious complication of obliterative and other vascular lesions involving kidneys some time after homotransplantation and leading inevitably to anuria and death of the patient. A blood-perfusion machine presents many difficulties, and unless oxygenated blood is used perfusion can be definitely harmful because the perfused organ becomes oedematous (Nizet and Cuypers, 1962). Even when oxygenated blood is used vasoconstrictor substances are liberated and damage to the isolated kidney consistently develops after a period of about three hours. Perfusion of the whole cadaver would overcome many problems involving vasoconstrictor substances. There would appear to be better prospects for this method of perfusion than for perfusing the isolated kidney. However, both methods involve teams of workers who must be prepared at any moment to go into action. This may not be practicable in some hospitals and hence our attempt to reassess cooling. Simple methods, such as storage in a refrigerator at 4? C, have often been employed, but the results have been inconsistent (Kiser et al., 1961). Several years ago we were unable to confirm the results of Lefebvre (1951), who used refrigerator storage. Lefebvre and Nizet (1952) reported and illustrated very well the total medullary damage which we found consistently and which they encountered in some of their experiments (see Fig.). Lapchinsky (1960) reported that autotransplanted kidneys can be perfused in a blood-flow circuit within a refrigerator. However, his technique was not successful for homotransplanted kidneys, which is our main concern at the moment.

Preventing Corrosion in Gas-condensate Wells

Abstract This paper discusses the most dangerous form of corrosion encountered incondensate well oil production, the discovery of the agent causing thiscorrosion and the remedial chemical treatment proved effective by field use.The injection of ammonium hydroxide, even as little as one quart per day, hasproved effective in preventing gas-condensate well corrosion. The injection of"Bone oil" is applied to wells producing brines containing calcium andmagnesium salts. Introduction The severe corrosion of equipment in high pressure gas condensate wells hasbeen a problem for several years and numerous papers have been presented on thesubject. The term ?gas condensate? or ?distillate well? is applied to a distinctvarieties of hydrocarbon producing well, the characteristics of these wellsbeing high bottom-hole (formation) pressures and temperatures and high gasproduction. These wells usually produce about 40 gal of water per million cubicfeet of gas and the gas contains from 0.1 pct to 2 pct carbon dioxide. In theoperation of this type of well, the operators soon noted severe internalcorrosion of the pipe carrying the production. In some instances the welltubing has been found to be corroded to perforation in eight months. The highwell head pressure of 2500 to 8000 psi makes any weakening of the wellequipment by corrosion extremely hazardous. Bursting of the wells equipmentresults in very expensive repair operations and may result in the loss of thecostly well, or even loss of life. In November 1944, a gas-condensate well in a Gulf Coast field producing from9500'Ft showed a tubing leak. The well was ?killed? by filling it with mudthrough the tubing, and then the tubing was pulled. Corrosion was found to havecaused several perforations in the tubing, Fig. 1. While the mud was beingcirculated to kill the well, a high pressure jet from the corroded hole in thetubing perforated the casing and damaged the well to the extent that the costof repairs amounted to $75,000. In November 1944, another gas-condensate well in a Gulf Coast field producingfrom 11,400'Ft. showed tubing failure. This well had been producing an averageof 2,500,000 cu ft of gas daily for two years. In the workover of this well, itwas found that a hole one inch in diameter had corroded though the tubing andthat corrosion had reduced the wall of the tubing to less than half thestandard thickness over large areas of the interior of the tubing. It was foundthat corrosion had also caused two leaks in the casing. After four months spentin an attempted workover failed to make the well safe for further production, the well was plugged and abandoned at a total low or $300,000.00. T.P. 2229

The Use of Oil Spray on Citrus Trees

In recent years the red and black scales of citrus trees in California have, in certain districts, been developing increasing immunity to cyanide gas fumigation. One of the outgrowths has been the widespread use of sprays; those having an oil base have been the most successful. The California Fruit Growers Exchange, which handles three-fourths of the State's citrus crop, has been investigating this particular scale problem for several years. The observations of its Pest Control Department during the past season, which have covered the insect problems in all districts, might be summarized for oil sprays in part as follows: 1. The so-called quick breaking emulsions of white oil type, characterized by high viscosity and low volatility, and which leave an oil film on the tree for many weeks, has been the most effective type of spray against both armored and unarmored scales and the red spider where used in sufficient concentration. The concentration which assures dependable results appears to be not less than 1 1/2 per cent actual oil in the case of scale insects. 2. Heavy applications of the white oil type of spray at concentrations approximating 1 1/2 per cent actual oil appeared in many instances to produce certain undesirable effects on the plant itself, the extent of which was modified particularly by the environment of the plant, by the season of year, the variety of fruit and time of its maturity. Some of these effects were retarded coloration of fruit, reduced quality, lessened crop, drop of immature fruit and of tree ripe fruit, increase of aphis and possibly increased difficulty in controlling mealybug through the utilization of beneficial insects. At concentrations much lower than lY:l' per cent actual oil these troubles largely disappeared in most districts. Scale kill, however, at lower concentrations was irregular. 3. In the case of the California red scale these white oil types of sprays give decidedly better scale kill on cutinized surfaces such as fruit and new wood than on the old wood which more readily absorbs the oil. The residual oil prevents the settling of larval scale for a considerable period on fruit and new wood. 4. The application of certain oil sprays to red scale followed within one or two weeks by a furmigation has been the most effective method of controlling the most resistant type of scale. 5. Some brands of oil emulsions are safely used with sulphur compounds under normal weather conditions whereas others are non-compatible with sulphur. The mixture of lime sulphur with certain oil sprays in the presence of calcium caseinate results in a spray which leaves little or no oily coating on the foliage, does not retard frui coloration, nor affect the set. Such combination sprays are among the most effective against immature unarmored scale but are of little value against the armored scales of citrus trees.