The effects of die shapes and additives on the physical and biodegradable properties of biodegradable cushioning extruded foams

In this study, efforts were focused on the effects of the operating parameters, i.e. die shapes (DS), PVA ratio (PR), additives (AT) on the physical and biodegradable properties of the corn/PVA extrudates. We also evaluated the extrudates as cushioning materials. The process variables were the operating, conditions, die shapes (○, ∞, ? and O ), PVA ratio (40%, 50%, 60%) and additives [sodium bicarbonate (NaHCO₃), calcium carbonate (CaCO₃) and calcium hydroxide (Ca(OH)₂)]. The experiment is a 4 × 3 × 3 factorial design. Samples of each treatment were collected and the physical, mechanical and chemical properties were measured and analysed using the PROC ANOVA and PROC CORR of the SAS 6.0 software package. 35 The experimental results indicated that: (a) The change of die shapes (DS) had a significant effect on the longitudinal expansion, bulk density, compressibility and biodegradability properties of the extrudates; (b) the change of PVA ratio (PR) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the biodegradability properties of the extrudates; and (c) the change of additives (AT) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the spring index of the extrudates. Copyright © 2003 John Wiley & Sons, Ltd.     

Untersuchungen über das Strangpressen kubisch-flächenzentrierter Metalle. Teil II: Kraftbedarf und Kraftverteilung

Investigation of the extrudability of face-centred cubic metals Part II: During continuous extrusion at certain intervals dry oxides are discharged. This is explained with the aid of rheological investigations. If a shearing device according to DIN standard is used the results may show errors in a range of 70% and more. A new device is described which avoids this source of error. The shear strength of high purity aluminium was determined at various temperatures and rates of deformation. Investigations were conducted under similar conditions on the extrusion of aluminium and a relationship between shear strength and power requirement was established. On this basis the power requirement to extrude new alloys may be predicted by comparing the shear strength of this alloy with the shear strength of an alloy whose extrudability is known. Direct extrusion experiments under isothermal conditions were conducted in the reduction range R = 1.2–300. The linear relationship in double logarithmic scale exists only in the range of R = 4–40. Indirect extrusion experiments also showed a linear relationship below the reduction rate R = 4 in a logarithmic scale. It was found that during indirect extrusion a dead metal zone is also formed and this explains the divergence of the found pressure distribution from the theoretical values. The normal pressure of the container was measured at a number of points at various temperatures and reduction rates. In the range of 150°–170°C peculiar unsteadiness occured. Normal pressure on the change of the velocity of extrusion was investigated with the aid of a stepped-down die and a strong dependence was found. A device was developed to compare the plasticity of cubic face centered metals, and it was found that the maximum plasticity is reached at 90% of the melting point in degrees absolute. Efficiency investigations during extrusion showed that the power consumption required to overcome the radial shear in continuous extrusion is 60% to 77%, whereas the power required to overcome the total shear in extrusion in a piston driven press is 94% to 87%. Extrusions inside a calorimeter showed, on the basis of mechanothermodynamic conversion, that 85% to 94% of the power was used for the deformation of the metal.     

99mTc-MIBI used for diagnosis of portal hypertension: an experimental study

The authors investigated the relationship between portal-systemic shunting and portal pressure in 16 CCl4-induced cirrhotic wistar rats by 99mTc-MIBI photography of heart and liver. Based on radio-counts taken at 30 minutes after 99mTc-MIBI was given per rectum 8 rats or medial clonic vein 8 rats, heart radio-counts/liver radio-counts (H/L) and portal-systemic shunting index (SI) were recorded. It was shown that 1. H/L and SI of the two cirrhotic groups were greater than those of normals (P < 0.001); 2. H/L in cirrhotic rats by rectum 99mTc-MIBI administration was more closely related to free portal pressure (FPP, r = 0.83, P < 0.01) than in those by venous route (r = 0.74, P < 0.05) and its regressive formation FPP (kPa) = 0. 24 + 4.06 (H/L) was deduced and used to calculate portal pressure of cirrhotic rats. The very good relationship between the calculated and measured portal venous pressure was shown in a group of 12 cirrhotic rats (r = 0.85, P < 0.01). These findings suggested that the rectum administration of 99mTc-MIBI may be a useful method in calculating portal pressure and portal-systemic shunting in portal hypertensive patients.     

The software engineering of a microcomputer application system

A system development methodology is outlined before describing its application to the development of a microcomputer system. Structured analysis techniques were used for determining the information flow through the system. The system was then structured into modules using structured design and information hiding techniques. The detailed design of the system was described in pseudocode. The system was coded in assembler supplemented by a set of structured programming macros. A systematic bottom-up testing procedure was adopted for system integration.     

Studies on the solvent exchange technique for making dry cellulose acetate membranes for the separation of gaseous mixtures

The effect of the pore size on the surface of the water-wet reverse osmosis membrane and the solvents used in the solvent exchange process on the pore size of the resulting dry cellulose acetate membrane was studied with respect to the separation of a CO₂/CH₄ mixture. It has been found that there is a critical pore size on the surface of wet membrane that results in the smallest pore size on the dry membrane and, consequently, in the highest separation factor. Such critical pore sizes become greater when the boiling point of the second solvent is increased.     

Measurement of intermodulation products generated by structuralcomponents

A computer-controlled measurement system is described, developed to investigate intermodulation products generated by nonlinear junctions in antenna towers, mast support and mounting components. Results are presented which suggest that certain mechanical features, commonly encountered in some components, should be regarded as more likely to be associated with this cause of interference     

Relationship between age and clinical characteristics of patients with gastric cancer

The relationship between the prognosis and age of patients with gastric cancer is controversial. To evaluate whether there is a biological characteristic specific to the age of patients, we examined the clinical characteristics of patients with gastric cancer with special reference to their age. Based on a prospective database, a retrospective study of 419 patients who underwent radical gastrectomy for cure in the past 6 years was conducted. Clinical characteristics including gender, gross appearance of the tumour (Borrmann's classification, tumour location), histopathology (depth of tumour invasion, lymph node status, Lauren's classification and degree of tumour cell differentiation) and TNM tumour stage were analysed in six different age groups (< 39, 40-49, 50-59, 60-69, 70-79, > 80 years). The mean age of the 419 patients was 64.6 years (range from 26-91) and the peak age incidence of gastric cancer (46.3%) was in the 60-69 year old age group. The male: female ratio was 4.6:1 on the whole and male gender predominated at ages > 60. The proportion of diffuse type tumours (68.4%) by Lauren's criteria in the young age group (< 39 yrs) decreased with age (25% in the > 80 years group; P < 0.001). Similarly, the proportion of poorly-differentiated tumours (89.5%) in the young age group (< 39 yrs) decreased with advancing age (P < 0.001). These findings suggest that both diffuse type and poorly-differentiated tumours predominate in younger patients and, without considering the factor of delay in diagnosis, may explain the poorer prognosis demonstrated in younger patients.     

The Design Trade-Offs of BitTorrent-Like File Sharing Protocols

The BitTorrent (BT) file sharing protocol is very popular due to its scalability property and the built-in incentive mechanism to reduce free-riding. However, in designing such P2P file sharing protocols, there is a fundamental trade-off between keeping fairness and providing good performance. In particular, the system can either keep peers (especially those resourceful ones) in the system for as long as possible so as to help the system to achieve better performance, or allow more resourceful peers to finish their download as quickly as possible so as to achieve fairness. The current BT protocol represents only one possible implementation in this whole design space. The objective of this paper is to characterize the design space of BT-like protocols. The rationale for considering fairness in the P2P file sharing context is to use it as a measure of willingness to provide service. We show that there is a wide range of design choices, ranging from optimizing the performance of file download time, to optimizing the overall fairness measure. More importantly, we show that there is a simple and easily implementable design knob so that the system can operate at a particular point in the design space. We also discuss different algorithms, ranging from centralized to distributed, in realizing the design knob. Performance evaluations are carried out, both via simulation and network measurement, to quantify the merits and properties of the BT-like file sharing protocols.