Experimental study on a hybrid-driven servo press using iterative learning control

Servo presses provide flexible punch motions, which satisfy different production needs. To achieve this merit, the control system must maintain the punch motion accurately despite versatile desired trajectories or varied loadings. Against this backdrop, the current paper proposes an iterative learning control (ILC) scheme for a hybrid-driven servo press. A proportional derivative (PD) type ILC controller that contains a closed-loop feedback controller is adopted. The sensitivity Jacobian is introduced into the controlling algorithm as the proportional gain in order to smoothen and increase the error convergence rate. The proposed ILC controller is then developed and verified on a servo press prototype. Experimental validations of a cup-shaped drawing are also carried out. The results show that the proposed ILC scheme effectively made the punch position root-mean-square (RMS) errors converge to less than 0.2 mm within five iterations. The precision was also improved to less than 50 μm that was equivalent to 35–40% of the original level without the ILC.     

Intestinal lipid absorption in the nephrotic rat

Phage display technology represents a powerful tool for the identification of peptides reacting with disease-related antibodies present in human sera. The application of this technology to type 1 diabetes could provide a set of novel reagents for diabetes prediction and could also lead to the identification of novel autoantigens or even of environmental factors possibly causing the disease. In the present study, sera of prediabetic and high risk individuals were used to select candidate peptides from phage-displayed random peptide libraries. Diabetes specific phage clones were then identified from these through screening and counter screening, using sera from diabetic and non-diabetic individuals. The results presented in this paper demonstrate the feasibility of this methodology to identify peptides reacting preferentially with antibodies present in the serum of diabetic patients.     

A comparison of hot-gas by-pass and suction modulation method for partial load control in refrigerated shipping containers

Simulation studies using a mathematical model are made to compare the performance of the hot-gas by-pass control and the suction modulation control in refrigerated shipping containers. Key factors such as compressor power draw, coefficient of performance and the sensible heat factor of evaporator coil against variations in container load, set-point and ambient temperatures are examined. Results show that the suction modulation control strategy is the more energy efficient of the two. The evaporator performance is found to be largely unaffected by either strategy. The analysis indicates the possibility of controlling relative humidity in the cargo space by variation of the superheat level.     

A case study of the structural responses of a tall building in Singapore subjected to close‐in detonations

The response of tall buildings has been a major concern in metropolitan cities, especially with the recent surge in extreme activities targeted at structures with viable commercial values. This paper discusses a study carried out on the structural behaviour of a 2D frame, modelled to represent a tall building with ABAQUS. The model frame was subjected to a charge of the equivalent weight of 1 ton of TNT but placed at two varying cases of 5 and 10‐m standoff distances. Plane‐strain elements that incorporate the feature of material nonlinearity were utilized to model the structural components of the building and the simulated blast overpressures were obtained from the CONWEP software. The effects of large deformations of beams and columns corresponding to the short time loading duration depicted by the explosions were analysed from a local perspective. The extent of the damage is based on a local index defined as the ratio of curvatures. These local indices are consequently used to determine the possibility of disproportionate collapse of the frame from a global perspective. Finally, the provision of more ductile structural detailing is recommended to enhance the structural integrity of the building, increasing its resilience against blast attacks. Copyright © 2009 John Wiley & Sons, Ltd.     

A Conceptual Approach to Integrate Design and Control for the Epoxy Dispensing Process

Performance improvement of manufacturing systems in the semiconductor industry involves interdisciplinary expertise, such as physical modeling, mechanical design, electrical control, and even material science. Integration of these different disciplines is a challenging problem in the semiconductor industry. The paper presents a conceptual approach to integrate design and control methodology for complex processes with specific application to an epoxy-dispensing control system – a critical equipment in the semiconductor packaging process. This methodology includes three hierarchical levels: process design (system-level and component-level), multivariable control and the statistics-based supervision. This paper deals with conceptual design at system-level by integrating an approximate model with an axiomatic approach, and briefly introduces approaches at other levels. In the conceptual design at system level, the primitive model of the system is sufficient to show some basic properties of the process, by which the axiomatic design can be easily integrated to evaluate the system design and suggest an optimal system configuration with invariant properties to internal variations. Under minimal internal variation, the multivariable control that is intended to suppress external variations can be approximately constructed by a set of independent controllers. Statistics-based supervision will provide suitable setpoints for the multivariable control so as to maintain good performance in the dynamic environment.     

The optimal diamond wheels for grinding diamond tools

Grinding is the most suitable process for manufacturing good quality diamond tools. In this paper, diamond wheels have been studied. From the grinding of polycrystalline diamond (PCD) insets, the effects of certain factors such as the bonding material, the grit size and structure of a diamond wheel have been investigated. It is concluded that vitrified bond diamond wheels are the most suitable for grinding PCDs and the recommended grit size is mesh number 1000, which can get a good surface quality within an appropriate time. The wheel structure is another important factor. Rougher wheels (mesh #800, #1000) with the softer grade scale P yield a higher material removal rate (MRR) than scale Q. However, a finer wheel (mesh #1200) needs a tougher structure to promote its grinding ability and to have a higher MRR.     

Modeling a solar-powered double bed novel composite adsorbent (silica activated carbon/CaCl2)-water adsorption chiller

During the past few decades, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Adsorption cooling system is one of the technologies which could be powered by renewable energy. This study aims to improve the performance of a solar-powered adsorption chiller by applying a novel composite adsorbent, a mixture of activated carbon, silica gel and calcium chloride. Modeling is established to investigate the cooling performance of a composite adsorbent based adsorption chiller driven by flat-type solar collectors with three different configurations of glaze: (1) single glazed cover; (2) double glazed cover and (3) transparent insulation material (TIM) cover. The simulation results show that the coefficient of performance (COP) and the specific cooling power (SCP) of the adsorption chiller depend hugely on the solar collector temperature. It is found that a double glazed cover shows the best cooling performance and 30 m² is the most optimized solar collector area. Two to three hours of pre-heating time is required to initiate the desorption process of the adsorber in a day of operation. This newly developed silica activated carbon/CaCl₂ composite material as adsorbent used in the adsorption chiller could achieve a high mean COP_sc of 0.48. Its satisfactory performance suggests that this novel composite material has a potential to be used in the adsorption chiller system even if it is powered by unstable solar energy.     

Silk stealing by Argyrodes lanyuensis (Araneae: Theridiidae): a unique form of kleptoparasitism

Serpulina pilosicoli was isolated from 8 of 43 (19%) faecal specimens obtained from feral waterbirds sampled around a small lake at Perth Zoological Gardens, Western Australia, and from 3 of 7 (43%) samples of the lake water. The organism was only isolated from 1 of 204 (0.5%) samples from captive birds and animals in the zoological collection. Multilocus enzyme electrophoresis analysis of the isolates showed that they were genetically diverse, and none had identical electrophoretic profiles as those previously obtained from human beings, dogs, pigs and other avian species. To determine the survival time of S. pilosicoli in water, cells of strain 1648 were seeded into lake and tap water, and incubated at 4, 25 and 37 degrees C. The organism could be recultured from lake water for up to 66 days at 4 degrees C, and for 4 days at 25 degrees C. A healthy human volunteer who drank water seeded with S. pilosicoli strain Wes B became colonized, and developed abdominal discomfort and headaches. Contamination of water by faeces may represent a source of S. pilosicoli infection for both humans and animals.     

Dynamic behavior of a direct expansion evaporator under frosting condition. Part II. Field investigation on a shipping container

A field investigation is performed on the frost formation at an evaporator of a commercial full-scale refrigerated container that uses R-12 as the working refrigerant. Results when compared with those from a numerical model presented earlier show that the model is capable of predicting the dynamic behavior of a direct expansion evaporator under both non-frosting and frosting conditions. The air outlet and energy transferred compare well between experiment and model, and within 20% for the air pressure drop. The frost occurrence and propagation agree well generally, with the frost formation first occurring at the first row where the refrigerant enters the evaporator.     

Dynamic behavior of a direct expansion evaporator under frosting condition. Part I. Distributed model

A general distributed model with two-phase flow for refrigerant coupled with a frost model is developed for studying the dynamic behavior of an evaporator. The equations are derived in non-steady-state manner for the refrigerant and a quasi-steady state model with permeation for the frost. The complex flow and geometry of the finned tube evaporator lead to uneven wall and air temperature distributions, which in turn affect the rate of frost growth and densification along the coil depth. Results include frost accumulation and its effect on energy transfer, air off-coil temperature, refrigerant liquid dry-out position and propagation of frost formation along the coil.