Insert Configuration Research Articles

Augmented heat transfer and pressure drop of strip-type inserts in the small tubes

An experiment is carried out to investigate the characteristics of the augmentation of heat transfer and pressure drop by different strip-type inserts in small tube having an inside diameter of 2.0 mm. The effects of the imposed wall heat flux, mass flux, strip inserts with various configurations (heights, widths, pitches) on the measured augmentative heat transfer and pressure drop are examined in detail. In order to obtain insight into the fluid flow phenomena, flow visualization was also made to observe the detailed fluid flow characteristics of the present tubes inserted with strip-type inserts. In addition, comparisons are made with a plain tube having the same length, heat transfer area and experimental conditions. The measured heat transfer coefficients and pressure drops for this small pipe are also emphasized to compare with those for larger pipes. Furthermore, in order to compare results from the different configurations of strip-type inserts, several enhancement factors and performance ratios are defined to account for the effects of augmentation. Moreover, correlation equations for the heat transfer coefficient and pressure drop of the present study are proposed.

Concave versus posterior-stabilized tibial joint surface in total knee arthroplasty: Randomized evaluation of 47 knees

Forty-seven knees in 43 patients with severe deformities randomly received AMK total knee arthroplasty with concave (C, n = 25) or posterior-stabilized (PS, n = 22) polyethylene insert and with resection of the posterior cruciate ligament. Radiostereometric examinations were done postoperatively and after 3, 12, and 24 months. Two patients (1 C, 1 PS) underwent revision surgery. At the 2-year follow-up, the median absolute rotations of the tibial inserts ranged from 0.13° to 0.26° (C vs PS; P =.1-.7). The maximum total point motion was almost identical in the 2 groups (C, 0.38; PS, 0.39; P =.9). Maximum subsidence, lift-off, and Hospital for Special Surgery scores did not differ (P =.1-.6). Recipients of 20 of 24 knees with concave design and 14 of 19 knees with posterior-stabilized design reported that their knee could be regarded as normal or almost normal. Variations of the configuration of the polyethylene insert did not alter the outcome in the short term.

In vivo kinematics of total knee arthroplasty: flat compared with concave tibial joint surface.

This study evaluated the influence of the geometric configuration of the tibial joint area on the kinematics of the knee. Twenty-two patients with noninflammatory arthritis and minor preoperative deformity were studied. They each received an AMK total knee replacement with retention of the posterior cruciate ligament. Eleven patients without any knee abnormalities were used as controls. The patients were stratified to either the flat (terminology of the manufacturer: standard) or concave (terminology of the manufacturer: constrained) polyethylene insert (n = 11 in each group). Knee kinematics were assessed 1 year after the operation by having the patient ascend a platform corresponding to an extension of the knee from 50 to 70 degrees of flexion. During this motion, two film-exchangers simultaneously exposed six to 13 pairs of serial stereoradiographs. The concave geometric configuration of the tibial insert resulted paradoxically in increased anterior-posterior translations compared with the flat insert but no significant change of rotations and translations in the other directions. Compared with normal knees, the most obvious abnormality was increased anterior-posterior translations (p < 0.004). At 50 degrees of flexion, the implants with the flat tibial polyethylene insert had displaced 2 times and the concave ones had displaced 2.5 times more posteriorly than the normal knees (p < or = 0.001). Less internal tibial rotation was also recorded in the flexed positions for both types of inserts compared with the normal knees (p < 0.02). Four knees in four patients, who reported symptoms of instability and abnormal knee function, showed significantly increased proximal displacement of the center of the tibial plateau in the flexed position. The findings suggest that current prosthetic designs and surgical technique do not restore normal knee kinematics and indicate that design improvements should rely on in vivo kinematic studies.

Molecular Dynamics Study of Substance P Peptides Partitioned in a Sodium Dodecylsulfate Micelle

Two neuropeptides, substance P (SP) and SP-tyrosine-8 (SP-Y8), have been studied by molecular dynamics (MD) simulation in an explicit sodium dodecylsulfate (SDS) micelle. Initially, distance restraints derived from NMR nuclear Overhauser enhancements (NOE) were incorporated in the restrained MD (RMD) during the equilibration stage of the simulation. It was shown that when SP-Y8 was initially placed in an insertion (perpendicular) configuration, the peptide equilibrated to a surface-bound (parallel) configuration in ∼450 ps. After equilibration, the conformation and orientation of the peptides, the solvation of both the backbone and the side chain of the residues, hydrogen bonding, and the dynamics of the peptides were analyzed from trajectories obtained from the RMD or the subsequent free MD (where the NOE restraints were removed). These analyses showed that the peptide backbones of all residues are either solvated by water or are hydrogen-bonded. This is seen to be an important factor against the insertion mode of interaction. Most of the interactions come from the hydrophobic interaction between the side chains of Lys-3, Pro-4, Phe-7, Phe-8, Leu-10, and Met-11 for SP, from Lys-3, Phe-7, Leu-10, and Met-11 in SP-Y8, and the micellar interior. Significant interactions, electrostatic and hydrogen bonding, between the N-terminal residues, Arg-Pro-Lys, and the micellar headgroups were observed. These latter interactions served to affect both the structure and, especially, the flexibility, of the N-terminus. The results from simulation of the same peptides in a water/CCl 4 biphasic cell were compared with the results of the present study, and the validity of using the biphasic system as an approximation for peptide-micelle or peptide-bilayer systems is discussed.

RADIATIVE HEAT TRANSFER AUGMENTATION IN GAS-FIRED RADIANT TUBE BURNERS BY POROUS INSERTS: EFFECT OF INSERT GEOMETRY

This article presents the results of an experimental investigation of heat transfer augmentation by porous media in a natural gas-fired radiant tube burner. The results show that significant heat transfer augmentation is possible with the use of porous ceramic inserts in both premixed and nonpremixed gas-fired radiant tube burners. Furthermore, this work has shown that geometry variations in the porous insert configuration can appreciably alter both heat transfer rates and mixing and chemical reaction rates in these systems. In the case of nonpremixed flames, the effect of variation of insert geometry is more than simple heat transfer augmentation via gas enthalpy conversion to thermal radiation by the porous medium. There is also a significant alteration of the reactive gas mixing (and therefore chemical reaction and heat release) rates along the length of the tube. The basic mechanisms that control the mixing rate and heat release distribution in these systems are still unknown. Nevertheless, it appears...

An investigation on the configuration of inserts in tubular ultrafiltration module to control concentration polarization

The flux through a tubular ultrafiltration membrane has been improved using inserts with different configurations in the module. It is established that the introduction of inserts, irrespective of their configuration, leads to better flux in comparison with that in the empty tube. Inserts with variable cross-sectional area show better performances than do smooth cylindrical ones. The interruption of the formation of a gel layer by the inserts with variable cross-sectional area is attributed to the periodical change in the feed flow velocity and the tangential stress on the membrane surface.

Electroresistance of some semiconductors in the phase transition region at high pressure

Abstract In apparata of liquid type piston-cylinder up to 2GPa and toroid with solid anvil up to 25 GPa pressure (P) electrial resistance R(P) in sphere of phase transition (PT) CdSnAs2,SnTeInP,GaAs is investigated, and GaP at T = 300K, and also R(T,P) VTSP YB2Cu306+x in sphere of superconductive transition. In order to describe the substance behaviour in the vicinity of PT, that is, the region of gapped change of R the approximation geterophased structure is used - the effective environment (model GSEE) which checks different configuration of phases inserts and their dependence from P. In order to picture the solid substance behaviour in the vicinity of point PT at high pressure (HP) different methods are used [1–8].

The effect of reagent excitation on the dynamics of the reaction O(1D2)+H2→OH(X 2Π)+H

The effect of H2 translational, rotational, and vibrational excitation on the dynamics of the O(1D2)/H2 reaction are explored in a semiclassical trajectory study involving both of the energetically accessible potential energy surfaces of the system. Landau–Zener probabilities determine surface hopping. At low reagent excitation, the deep H2O potential minimum dominates the dynamics, causing the reagents to reorient towards a H–O–H (insertion) configuration and form the H2O intermediate, irrespective of the initial approach geometry. High vibrational excitation enhances the probability for transitions onto the excited state potential during the interaction. Reactions which sample the excited state potential have fundamentally different dynamics from those which remain on the lower state. For reactions involving H2(v=4), the OH product has a bimodal vibrational distribution, peaking in OH(v′=2) and OH(v′=9). The lower peak is due to reactions which access the excited state potential; the higher peak results from those which remain on the lower state for the entire interaction. High translational excitation shortens the interaction time and reduces the effect of the potential minimum to reorient the reagents. Rotational excitation also reduces the effect of the potential minimum by causing the system to rotate out of the insertion geometry before entering the potential minimum.

Fluid flow through lances with constant and variable pitch swirled inserts

Sirosmelt-type gas injection systems for submerged combustion in metallurgical baths use tubular lances with single or multistart-type helical vane swirlers in the annular region. These inserts not only promote heat transfer from the tube wall to the gas flowing through the tube but also increase pressure drop across the lance. The total pressure loss across such inserts is due to entrance effects and fully developed flow losses. These losses can be quite substantial depending upon the gas flow rate and configuration of inserts. In this paper, a comparison has been made between fixed and variable pitch inserts as far as pressure drop is concerned. A simple flow model has been proposed to describe the flow characteristics of both types of insert. An understanding of these flow characteristics forms a basis for improved lance designs.

A Cost-Effective Video Compressor

By limiting the endless variety of special effects to the most popular basic types and utilizing simple but efficient design approaches, a new cost-effective video compressor, called the “Squeezer,” has been developed. The unit produces four discrete compressed image sizes. Image position and crop size, shape, and placement are variable by joystick controls. Border width, hue, and saturation are adjustable. Four memory locations are available for storing four different sets of insert configurations. Images can be frozen or inverted horizontally. This article discusses the considerations that influenced the compressor's design and describes the resulting product.

A male-sterile insertion in the mouse.

Is(7;1)40H was found in the daughter of a male mouse given spermatozoal X-irradiation. It is a non-inverted insertion of about half of chromosome 7 into chromosome 1, generating a long somatic marker chromosome. Breakpoints are in bands 1B, 7B1, and 7F1; linkage tests show that these breakpoints are about midway between fz and In on the 1, and 0.2 units distal to ru-2 and 12 units proximal to fr on the 7. Female carriers had litters of about one-third normal size and showed some decline in length of reproductive life. Males were sterile, with testis weights only 30% of normal and with abrupt cessation of spermatogenesis in pachytene at stage IV of the seminiferous epithelial cycle. Positive sex-vesicle contact with the insertional configuration was found in only 40% of pachytene spermatocytes, which suggested that other factors may be involved in the spermatogonial breakdown. In oocytes at metaphase I 76% of insertion configurations were multivalent, because of one or more chiasmata in the inserted segment, as were 79% of synaptonemal complex configurations in male pachytenes. Karyotyping at 12.5 to 14.5 days of gestation showed that all embryos with duplications of the inserted segment were exencephalic, and the only example of a corresponding deficiency was retarded. Analysis of the consequences of heterozygosity for the insertion shows that the insertion length should be correlated with the frequency of unbalanced offspring and thus with the amount of F1 lethality. The genetic length of 36 cM estimated in this way from data on liveborn offspring is in reasonable agreement with estimates from cytological measurements and meiotic configurations but rather higher than that from linkage tests.