Showing papers by "Virginia Tech published in 1973"

Response Surface Techniques for Dual Response Systems

Abstract: The purpose of this paper is to present the theory and develop an algorithm associated with the exploration of a dual response surface system. The approach is to find conditions on a set of independent or “design” variables which maximize (or minimize) a “primary response” function subject to the condition that a “constraint response” function takes on some specified or desirable value. A method is outlined whereby a user can generate simple two dimensional plots to determine the conditions of constrained maximum primary response regardless of the number of independent variables in the system. He thus is able to reduce to simple plotting the complex task of exploring the dual response system. The procedure that is used to generate the plots depends on the nature of the individual univariate response functions. In certain situations it becomes necessary to apply the additional constraint that the located operating conditions are a certain “distance” from the origin of the independent variables (or the cent...

Applying Probability Measures to Abstract Languages

Abstract: The problem of assigning a probability to each word of a language is considered. Two methods are discussed. One method assigns a probability to a word on the basis of particular measurable features of the language. The second method is applied to languages L(G) generated by a grammar G. A probability is associated with each production of G. These in turn define the word probabilities of each word in the language. The conditions for this assignment to be a probabilistic measure are derived.

Nonlinear coupling of pitch and roll modes in ship motions

Abstract: An analysis is presented for the nonlinear coupling of the pitch (heave) and roll modes of ship motions in regular seas when their frequencies are in the ratio of two to one. When the frequency of encounter (excitation frequency) is near the pitch frequency, the pitch mode is excited if the encountered wave amplitude (excitation amplitude) is small. As the excitation amplitude increases, the amplitude of the pitch mode increases until it reaches a critical small value. As the excitation amplitude increases further, the pitch amplitude does not change from the critical value (i.e., the pitch mode is saturated), and all of the extra energy is transferred to the roll mode. Thus, for large excitation amplitudes, the amplitude of the roll mode is very much larger than that of the pitch mode. When the excitation frequency is near the roll frequency, there is no saturation phenomenon and at close to perfect resonance, there is no steady state response in some cases. The present results indicate that large roll amplitudes are likely in this case also.

Sensitivity of Three Selected Bacterial Species to Ozone

Abstract: THE MINIMAL LETHAL CONCENTRATION OF OZONE IN WATER WAS DETERMINED FOR THREE BACTERIAL SPECIES: Escherichia coli, Bacillus cereus, and Bacillus megaterium. A contact period of 5 min was selected. The lethal threshold concentration for the cells of B. cereus was 0.12 mg/liter while that for E. coli and B. megaterium was 0.19 mg/liter. Low concentrations of ozone were ineffective when organic matter was present to interfere with the action of ozone on the bacterial cells. Also determined during the study was the sensitivity of spores of B. cereus and B. megaterium to ozone in water. The threshold concentration required to kill the spores of both species was 2.29 mg/liter. The cells and spores of these organisms exhibited the "all-or-none" die-away phenomenon normally associated with ozone treatment.

On Biased Estimation in Linear Models

Abstract: Hoer1 and Kennard introduced a class of biased estimators (ridge estimators) for the parameters in an ill-conditioned linear model. In this paper the ridge estimators are viewed as a subclass of the class of linear transforms of the least squares estimator. An alternative class of estimators, labeled shrunken estimators is considered. It is shown that these estimators satisfy the admissibility condition proposed by Hoer1 and Kennard. In addition, both the ridge estimators and shrunken estimators are derived as minimum norm estimators in the class of linear transforms of the least squares estimators. The former minimizes the Euclidean norm and the latter minimizes the design dependent norm. The class of estimators which are minimum variance linear transforms of the least squares estimator is obtained and the members of this class are shown to be stochastically shrunken estimators. An example is computed to show the behavior of the different estimators.

Economic Dispatch Using Quadratic Programming

Abstract: The economic dispatch problem is formulated as a quadratic programming problem and solved using Wolfe's algorithm. The method is capable of handling both equality and inequality constraints on p, q, and v and can solve the load flow as well as the economic dispatch problem. The quadratic programming algorithm does not require the use of penalty factors or the determination of gradient step size which can cause convergence difficulties. Convergence was obtained in three iterations for all test systems considered and solution time is small enough to allow the method to be used for on-line dispatching at practical time intervals. Results are presented for 5, 14, 30, 57, and 118 bus test systems.

Modified Broth-Disk Method for Testing the Antibiotic Susceptibility of Anaerobic Bacteria

Abstract: The most commonly used method for testing the antibiotic susceptibility of aerobic and facultative bacteria is the disk diffusion method. However, some anaerobic bacteria do not grow well enough in anaerobic jars for performance of disk diffusion tests. A modification of the broth-disk method of Schneierson allowed us to determine antibiotic susceptibility in a completely anaerobic environment. Commercial antibiotic disks were added anaerobically to tubes of prereduced brain heart infusion broth to achieve a concentration of each antibiotic approximating that attainable in blood. The tubes were then inoculated and incubated for 18 h. Resistance or susceptibility to each antibiotic was determined according to the amount of growth in each tube as compared with a control culture without the antibiotic. There was good correlation between results obtained by this broth-disk method and minimal inhibitory concentrations.

Cardiovascular and respiratory changes during heat stress in rainbow trout (Salmo gairdneri).

Abstract: 1. Trout were subjected to a steady increase in water temperature (1.5 °C/h) from 15 °C until death occurred, while several respiratory and cardiovascular parameters were monitored. 2. Oxygen consumption increased during the warming ( Q 10 = 2.35 between 16 and 20 °C). At the higher temperatures the increase was more marked ( Q 10 =4.96 between 20 and 26 °C). 3. Ventilatory frequency increased during the rising temperature with a general levelling off observed above 23 °C. The amplitude of the pressure changes in the buccal and opercular cavities increased more than did the ventilatory frequency. Further analysis of the differential pressure across the gills suggests that the adjustment of respiratory pumping to the increased oxygen demand is predominantly in the volume pumped per stroke (cycle). 4. Heart rate rose steadily with the increasing temperature until about 24-25 °C, when a bradycardia usually became evident. Synchrony between the heart beat and the respiratory pumps was observed in some preparations at the higher temperatures. 5. Blood pressure increases during the warming were more marked in the ventral aorta than in the dorsal aorta. At the highest temperatures, abnormal cardiac cycles were frequently observed. 6. Arterial oxygen content declined slightly during warming and venous oxygen content dropped to zero above 23 °C. 7. It is suggested that cardiovascular adjustments may be a limiting factor in this type of stress.

Optimizing Transportation Problems with Multiple Objectives

Abstract: Virtually all models developed for transportation problems have focused upon the optimization of a single objective criterion, namely the minimization of total transportation costs. They have generally neglected or often ignored the multiple conflicting objectives involved in the problem, the priority structure of these objectives, various environmental constraints, unique organizational values of the firm, and bureaucratic decision structures. However, in reality these are important factors which greatly influence the decision process of transportation problems. In this study the goal programming approach is utilized in order to allow for the optimization of multiple conflicting goals while permitting an explicit consideration of the existing decision environment.

Prompting a consumer behavior for pollution control.

Abstract: A field application of behavior modification studied the relative effectiveness of different prompting procedures for increasing the probability that customers entering a grocery store would select their soft drinks in returnable rather than nonreturnable containers. Six different 2-hr experimental conditions during which bottle purchases were recorded were (1) No Prompt (i.e., control), (2) one student gave incoming customers a handbill urging the purchase of soft drinks in returnable bottles, (3) distribution of the handbill by one student and public charting of each customer's bottle purchases by another student, (4) handbill distribution and charting by a five-member group, (5) handbills distributed and purchases charted by three females. The variant prompting techniques were equally effective, and in general increased the percentage of returnable-bottle customers by an average of 25%.

On Solving Multifacility Location Problems using a Hyperboloid Approximation Procedure

Abstract: An iterative solution method is presented for solving multifacility location problems involving rectilinear and/or Euclidean distances. The iterative procedure is based on the use of an approximating function involving hyperboloids, which in the limit approach the cones in the original objective function. Given that the hyperboloid approximation procedure converges, it is shown to converge to the optimum solution. Computational experience with the procedure is described.

Acoustic propagation in ducts with varying cross sections

Abstract: The method of multiple scales is used to derive the equations that describe the spatial and temporal variation of the amplitudes and phases of a wave packet propagating in slowly varying hard‐walled or lined ducts. The analysis is carried out for rectangular as well as circular ducts. These equations are statements of the conservation of energy. For large admittance or high‐frequency modes, an approximate expression is obtained for the attenuation. This expression shows that all possible acoustic modes are attenuating. The results also show that decreasing the cross‐sectional area can lead to elimination of some of the acoustic modes.

Response of Fresh‐Water Protozoan Artificial Communities to Metals*

Abstract: SYNOPSIS An artificial fresh-water protozoan community was subjected to different concentrations of Zn and Cu in a test system consisting of Plexiglas troughs through which pond water flowed continuously. Although the % survival of colonizing species exposed to Cu or Zn fluctuated greatly at each concentration, the range of toxicity for each compound allowed comparison of protozoa with other organisms with respect to resistance to heavy metal toxicity. Individual protozoan species also were exposed for 3 hr to Zn, Cu, Cr, phenol, Pb, Mn, Co, HNO3, acetic acid, Al, Sn, and HCl to derive time to death curves. Protozoa tested appeared to be more resistant than Daphnia to phenol, K2C2O7, and Cu; however, some species were more sensitive than Daphnia to Zn, nitric acid, and HCl. This suggests that the sensitivity of protozoa to toxicants may be either more or less than that of macroinvertebrates and that information does not suffice to predict sensitivity. Moreover, the relative sensitivity of protozoa to various toxicants will not always be the same, i.e. species X may be twice as tolerant to a toxicant as species Y but its relative sensitivity may be quite different for another toxicant.

Seismicity of the southeastern United States

Abstract: Review and analysis of the existing data base for southeastern United States earthquakes indicate that the spatial pattern of energy release can be interpreted to occur in zones both parallel (southern Appalachian seismic zone) and transverse (central Virginia and South Carolina-Georgia seismic zones) to the regional Appalachian structural trend. The temporal pattern, for events V ≦ Io ≦ VIII, can be expressed by the recursion relationship, log N = 3.01 − 0.59 Io. Felt areas are, in general, one order of magnitude greater than for similar west coast events. Their configuration is elliptical and aligned with regional structure, except in central Virginia and Alabama and in coastal South Carolina. These latter areas have circular or lobate felt areas that may be caused by differences in focal depths and/or focal mechanisms. A tentative local magnitude formula is developed that employs the vertical component of the short-period Lg phase. It appears that the regional attenuation characteristics of this phase are similar to those found by Nuttli (1973a) in the central United States.

The effects of inspection error on single sampling inspection plans

Abstract: SUMMARY Acceptance sampling plans are designed under the assumption of perfect inspection. However, inspection tasks are not, even under ideal inspection conditions, free of error. In this paper we consider the effects of inspection error on probability of acceptance, average outgoing quality, and average total inspection. These measures are examined under both replacement and non -replacement assumptions. Also, a method is presented whereby an acceptance sampling plan may be designed which explicitly considers inspection error.

Characterization of bicrystals using kikuchi patterns

Abstract: Three parameters, the misorientation angle, misorientation axis, and boundary normal, have been used to describe a general bicrystal,e.g., two adjacent grains, subgrains, or twins. An analysis developed to determine these parameters is presented. The angle and axis of misorientation are calculated from a misorientation matrix obtained from two Kikuchi patterns, one taken from each of the two crystals. To obtain the boundary normal, a specimen tilt is made inside the electron microscope. A rotation matrix specifying the actual specimen tilt is formulated from two Kikuchi patterns taken from the same crystal before and after tilt. With this rotation matrix and the change of projected boundary images before and after tilt, the boundary normal can be calculated. It is demonstrated that 1) for high-angle bicrystals, the misorientation angle may be determined to within ±0.2 deg, and the misorientation axis to within 0.1 deg; 2) for low-angle bicrystals, the misfit angle can be obtained to within ±0.1 deg, and the misfit axis to within 4 deg; and 3) the boundary normals so determined are generally accurate to 2 deg if suitable correction is made for the magnification change resulting from the specimen tilt.

Effect of the acoustic boundary layer on the wave propagation in ducts

Abstract: An analysis is presented for the wave propagation in two‐dimensional and circular lined ducts taking into account the effects of viscosity in both the mean and the acoustic problems. The method of composite expansions is used to express each acoustic flow quantity as the sum of an inviscid part and a boundary layer part insignificant outside a thin layer next to the wall. The problem is reduced to solving a second‐order ordinary differential equation for the pressure perturbation as in the inviscid acoustic case but with a modified specific wall admittance. An analytic expression is presented for the variation of the modified admittance with the wall and flow parameters, such as the acoustic boundary layer thickness, the mean velocity and temperature gradients at the wall, the frequency of oscillation, and the wavelength.

Ventilatory Responses of Teleost Fish to Exercise and Thermal Stress

Abstract: Exercise and thermal stress both markedly raise the oxygen demand of fish. The control of ventilation under these two conditions is apparently quite different and contrasts between species are noteworthy. Under both exercise and thermal stress, changes in respiratory pumping amplitude tend to be greater than changes in ventilatory frequency in most species. Respiratory pump uncoupling during thermal stress is frequently seen in trout but much less so in bullhead catfish or bluegills. In fish that actively ventilate the gills while swimming, the control for this probably depends on swimming muscle reflexes rather than blood humoral factors. This control mechanism may operate in a reverse fashion in fish that use ram-jet ventilation. During recovery from severe exercise and during thermal stress the control of gill ventilation is apparently humoral. Of the possible factors, blood oxygen and possibly also pH are considered to be the most important. Evidence is summarized that suggests the error detector is on the arterial side of the gas exchanger.

Spirochaetales, A Review

Abstract: (1973). Spirochaetales, A Review. CRC Critical Reviews in Microbiology: Vol. 2, No. 4, pp. 491-552.

The Structures of Monoclinic Potassium-Rich Feldspars

Abstract: The crystal structures of a low sanidine and an adularia (a -- 8.539(4), 8.545(2); b : 13.015(5)' 12.967(5);c :7.179G),2.201(3 )A; I :115.99(2),116.0 0(2)';2Yo:22o,65 0; space EtoupsC2/m) have been refined to R : 0.043 and 0.046, respectively. The mean T-O distances are (fl-O) = 1.650, 1.665A; (G-O) : 1.637,1.621A yielding by the linear model of Ribbe and Gibbs (1969) thefollowingaveragealuminumcontents: Alr,:O.29(2),O.aOQ);Aly,:g.21,0.l1.Thelowsanidine values agree well with a neutron diffraction site refinement of the same material by Brown et al. (1971): Alz, : 0.32(2); Al7" : 9.13. Multipie linear regression analysis of data from these two and three previous structure refinements of monoclinic K-rich feldspar indicates that the parameters influencing individual I-O bond length variations are, in order of importance: aluminum content of the ? site' -1lcos(T-O-?), >t1l(K-O)21 and the aluminum content of the bridging 7 site. Expressing aluminum content of the G and T, tetrahedra in terms of the cell-edge parameter (c - O.4b) and assuming average values of -l/cos(T-O-T) and >[l/(K-O)'?] for each of the oxygen atoms, eight equations of the form (7-O)o - pl + qt(c - O.4b) have been obtained which predict individual bond lengths that are in excellent agreement with those observed.

Beam-pointing errors of planar-phased arrays

Abstract: The beam-pointing error of an (M + 1) \times (N + 1) planar phased array is analyzed by the use of both analytical and Monte Carlo techniques. Simple formulas for the rms pointing error are obtained for uniform planar arrays with both uniform and Gaussian uncorrelated phase-error distributions and for any arbitrary scan angle.

The crystal structures of the humite minerals. IV. Clinohumite and titanoclinohumite

Abstract: The crystal structures of clinohumite [Mgs.rzFeo.ooMno.oeTio.ozCao.oor(SiOe)rFr.orHo.gaoo,osi a:4.jMt(2);b:10. 2501(5);c:t3.663 5(3)A; d:100.786(2)";P2 t/blandtitanocli nohumite [Mgz a:Fer orMno o;Tio rrcao oor(Sior)aoHr.oroo.goi a : 4.7451(8); b : 10.288(2); c : 13.709(3)A; a = 101.00(2).; P2tlblhave been refined by three-dimensional least-squares methods to R : 0.051 and R = 0.042, respectively. Their structures are based on a hexagonal close-packed array of anions and are similar to those of other minerals in the humite series and to the olivines. The serrated chain of edge-sharing octahedra in clinohumite consists of five unique octahedra; of these' M(l)c and M(Z)aarelike those in the olivines; M(l)N, M(2)6 and M(3) are like those in humite. One-half the octahedral sites and one-ninth the tetrahedral sites are filled. The distribution of transition metal ions in clinohumite is consistent with that in humite and chondrodite, Fe2+ being ordered into the more distorted MOo "olivine-like portion" of the structure. However. the distribution in titanoclinohumite is not consistent with any of the humite minerals previously studied. The distribution of Ti appears to be random and the M(3) site, with one (OH) iigand, appears to be slightly enriched in Fe, the balance of the Fe being randomly distributed amongst the octahedral sites.