Enclosure Dimensions Research Articles

Inexpensive precision temperature control for microculture

The design and construction of an inexpensive precision temperature control system used successfully for microculture applications is described. It is easily assembled from a homemade, precise, solid-state, proportional thermoregulator, resistive heating element, and insulated enclosure. The basic system easily adapts and can be customized for a variety of microculture applications with changes in enclosure dimensions or design. Control temperature accuracy, range and span can be varied by changing the components and design of the thermoregulator and enclosure. A series of such systems placed in a refrigerated or air-conditioned area accomodates multiple, parallel temperature treatments for experiments.

Increased aggression after rapid eye movement sleep deprivation in Wistar rats is not influenced by reduction of dimensions of enclosure

Twelve female and twelve male Wistar rats were assigned to home groups, platform-control groups, and rapid eye movement sleep deprivation groups. The deprivation was performed with the cuff-pedestal method. Rats were tested in pairs in a shrinking chamber to increase proximity of the rats and to provoke interaction between them. An increase in boxing behavior was noted in the sleep-deprived groups. The result confirms that deprivation of rapid eye movement sleep increases aggressive behavior in the rat. However, this behavior is not influenced by the area of the testing arena. The sleep-deprived females explored each other more than the controls; the males' behavior did not differ in this respect. The amount of genital exploration decreased with diminishing area of enclosure, whereas boxing was not area dependent.

A guide to the literature on aggressive behavior

A guide to the literature on aggressive behavior

Effects of source separation and phasing on acoustic power in a semireverberant space with application to active noise control

The acoustic response of a semireverberant enclosure with two interacting, velocity prescribed source distributions was analyzed using standard modal analysis techniques with a view towards a better understanding of active noise control. Different source and enclosure dimensions, source separations, and single wall admittances were studied over representative bandwidths of 10 Hz, and between 40 and 300 Hz, with source relative phase as a parameter. Results indicate that power radiated into the enclosure correlates with the spatial average of the mean‐square pressure even though the reverberant field is nondiffuse. Power reductions can therefore be used to estimate global noise reduction in a nondiffuse semireverberant environment. Parametric studies indicate that maximum power reductions of up to 25 dB can be achieved when secondary and primary sources are compact and closely spaced, as might be expected. Although there is less reduction with increasing frequency and source separation or size, significant reductions of up to 8 dB still occur over 1‐ or 2‐Hz bandwidths.

Strength analysis of the frozen-ground enclosure of a low-temperature storage reservoir for liquefied gases

The geometrical dimensions of a frozen-ground enclosure for a low-temperature storage reservoir are determined from a static designstorage reservoir are determined from a static design on the assumption of a safe excavation of ground in digging the trench. Neglecting the combined work of the enclosure and surrounding thawing rock mass, the problem is reduced to the design of the frozen-ground shell, stressed along its outer contour by the thawing ground pressure. To estimate the tension of the wall of an enclosure it is sufficient to use the solution of the problem of a thick-walled tube subjected to ambient pressure. It is difficult to find a sufficiently simple analogue for the problem of the bottom. The solution of the plate-bending problem locates the neutral line in the middle of the section when there are equal tensile and compressive stresses at the inner and the outer contour. If the combined work of the bottom of the section and the wall is taken into account, the neutral line shifts from the centre of the bottom to the inner contour of the enclosure, i.e., the compressive stresses exceed the tensile ones, which is of particular importance for materials with different resistance to compression and tension.

Radiation from smoke layers

This paper develops a model for calculating radiant heat transfer from smoke layers in fires within enclosures. Nongray, nonhomogeneous, and nonisothermal effects are quantified in a well defined model. Input parameters for the model are the vertical distributions of temperature, product species and enclosure dimensions. A convenient new instrument for accurate measurements of soot concentrations in hostile environments is described. Local mean absorption coefficients for the smoke are calculated by accounting for molecular band effects and an assumed, 1/λ dependence for the spectral absorption coefficient for soot. Calculations are in good agreement with measurements of mean absorption coefficient. Vertical distributions of soot and gaseous species concentrations are found by relating the degree of air entrainment to the measured temperature profile. Simple numerical and analytic approximations are provided which permit an evaluation of the radiative flux by means of an equivalent homogeneous smoke layer model. These approximations allow considerably simplified calculations with little loss in accuracy. The radiance and radiative flux calculations are in good agreement with experimental measurements in a variety of enclosure fires.

Intraspecific aggression in rats and dimensions of enclosure.

Irritable fighting of rats exposed to noxious stimuli is negatively correlated with size of enclosure. Experimental territorial aggression, however, is independent of cage-size. Although atypically large cages have been used to investigate residents' attack upon intruders, standard pan-type plastic cages may also give comparable results. The relative influence of dimensions of enclosure emphasizes the distinction between two unique forms of conspecific aggression.

Resonant Frequency Calculations for Microstrip Cavities (Correspondence)

Microstrip circuits in metal enclosures frequently exhibit loss spikes. These spikes are sometimes shown to be related to cavity resonances whose frequency can be calculated from enclosure dimensions using known theory. These calculations are presented graphically so that resonant frequencies may be determined for a particular structure or resonances within a band avoided through judicious choice of enclosure dimensions. Comparison of experimental and calculated results are tabulated.

Low-Frequency Shielding Effectiveness of Nonuniform Enclosures

This paper presents a quasi-static approximate solution to the magnetic shielding of several nonuniform enclosures using the integral form of Maxwell's equations and insight gained from other approaches. The solution is called quasi-static as the assumptions made are from physical arguments based on low-frequency cases where the enclosure size is much less than a wavelength. The integral form of Maxwell's equations is used to obtain a first order correction to the static solution to obtain induced currents in the time-varying case. A cylindrical shell immersed in an axial magnetic field is used to illustrate the method, which is then extended to derive a formula for a similarly excited rectangular enclosure. These shields are seen to behave like a low-pass filter. Although the enclosure dimensions are small compared to the wavelength, the skin depth effects in the walls cannot be neglected even for relatively thin material as usually encountered in an enclosure. These skin effects are included in the analysis and experimental checks performed on a variety of enclosure sizes and materials, excited by a Helmholtz coil show agreement within two decibels over the 4-octave frequency range examined. No one can say whether this method offers a better solution to the shielding problem, as all solutions are approximate, but the author attempts to present an alternative formulation that aids in understanding the physical processes involved in the shielding effectiveness of an enclosure and fills some of the gaps between the plane-wave analysis and circuit approaches presently used.

Noise Reduction by Partial Enclosures

Noise exposure in factories is often a serious problem only for workers close to noisy machines. Partial enclosure of a machine will often provide a reduction of 10 to 20 db in the near field and, with good design, a significant reduction can also be obtained in the far field. These reductions are, of course, for frequencies having wavelengths considerably smaller than the enclosure dimensions. Enclosure design parameters were obtained by measurements of noise reduction in the model factory described in the previous paper. Enclosures with 2, 3, and 4 sides were tested to obtain noise reduction in octave bands as a function of enclosure size. For practical sizes, reductions in the near field were 6 to 10 db for enclosures without a top and up to 25 db with a top. Acoustical lining of the ceiling above an enclosure increased the reduction and was particularly effective in the far field, where 12 db could be obtained even with fairly “open” enclosures. [This work was supported in part by the National Gypsum Company.]