Bubble dissolution in horizontal turbulent bubbly flow in domestic central heating system

In a domestic central heating system, the phenomenon of microbubble nucleation and detachment on the surface of a boiler heat exchanger finds its origins in the high surface temperature of the wall and consequential localised super saturation conditions. If the surrounding bulk fluid is at under-saturated conditions, then after exiting the boiler, the occurrence is followed by bubbly flow and bubble dissolution. A comprehensive understanding of the fundamentals of bubble dissolution in such a domestic wet central heating system is essential for an enhanced deaeration technique that would consequently improve system performance. In this paper, the bubble dissolution rate along a horizontal pipe was investigated experimentally at different operating conditions in a purpose built test rig of a standard domestic central heating system. A high speed camera was used to measure the bubble size at different depths of focal plane using two square sectioned sight glasses at two stations, spaced 2.2 m apart. A dynamic model for bubble dissolution in horizontal bubbly flow has been developed and compared with experimental data. The effects of several important operating and structural parameters such as saturation ratio, velocity, temperature, pressure of the bulk liquid flow, initial bubble size and pipe inside diameter on the bubble dissolution were thus examined using the model. This model provides a useful tool for understanding bubble behaviours in central heating systems and optimising the system efficiency

Prediction of atherosclerotic plaque life – Perceptions from fatigue analysis

Cardiovascular diseases are the leading causes of morbidity and mortality globally. Heart disease and stroke contribute to most fatalities in which atherosclerotic plaque disruption is the underlying pathology. The pulsatile blood flow in the arteries generates mechanical stresses that affect the rupture of the atherosclerotic plaque. Fatigue failure being the accumulation of the damage due to repeated loading that occurs when the stresses are much lower than those needed to rupture the plaque with normal loading. Therefore, fracture mechanics concepts were used to investigate the impact of morphology and blood pressure on the plaque life. Incremental fatigue crack propagation simulations were performed on idealized geometries based on the maximum circumferential stress criteria by using a finite element solver. XFEM, which extends the standard finite element formulation by introducing additional enrichment functions was used to model the fatigue crack growth simulations. Paris’ Law was used to determine the fatigue crack growth rate. Cracks extended radially and fatigue crack growth rate increased with increase in pulse pressure. Further validation studies on the 3D printed arteries are necessary for better understanding the factors contributing to plaque rupture. The results could help in assessing the atherosclerotic plaque life under the fatigue environment of the cardiovascular system

A Balance of Lipid-Sensing Mechanisms in the Brain and Liver

Recent work has cast a spotlight on the brain as a nutrient-sensing organ that regulates the body's metabolic processes. Here we discuss the physiological and molecular mechanisms of brain lipid sensing and compare these mechanisms to liver lipid sensing. A direct comparison between the lipid-sensing mechanisms in the brain and liver reveals similar biochemical/molecular but opposing physiological mechanisms in operation. We propose that an imbalance between the lipid-sensing mechanisms in the brain and liver may contribute to obesity-associated type 2 diabetes

A Three-Dimensional Position Architecture Using Digital TDE Receiver and Cylindrical Array Antenna

AbstractThe robust three-dimensional position architecture is proposed in the paper, where the hybrid time difference of arrival (TDOA) and direction of arrival (DOA) position system was designed to backup the four-station TDOA position system. The digital time delay estimation (TDE) receiver is used for TDOA measurement and the cylindrical array antenna is used for DOA measurement. The general formula of linear phase compensation for cylindrical array antenna in horizontal plane is derived. The detection probability of the TDE receiver and the circular error probability (CEP) of the position systems over Rayleigh fading channel were numerically computed in three-dimensional space. Simulations indicate that the position accuracy of the four-station TDOA position system is degraded but the location function can be retained by the hybrid TDOA and DOA position system when any one of four-stations is out of work

Modeling on Stress Evolution of Step Part for Casting-heat Treatment Processes

AbstractHeat treatment usually follows the casting process to improve the physical properties of parts. Under the strong assumption that casting has no effect on the following heat treatment, the modeling of heat treatment process is currently based on ideal material conditions with zero residual stress and uniform properties. In this paper, residual stress generated by casting has been introduced as the initial conditions for a heat treated step part of 4140 steel. The results have been compared with that of no consideration about initial residual stresses of casting

Physiological characteristics of recent Canada western red spring wheat cultivars: nitrogen uptake and remobilization

Non-Peer ReviewedGenetic yield gains have been difficult to achieve within the CWRS wheat class because of stringent quality requirements, and a growing-season environment of low precipitation and high temperatures. Understanding the physiological basis of yield gains may provide breeders with better insight as to the selection of parents, or provide screening tools to identify desirable genotypes. The objective of the present study was to compare four new CWRS wheat cultivars, which averaged higher yields than Neepawa in three years of multi-location testing within registration trials, both as a group and individually while maintaining or even increasing protein content, with two older cultivars, Neepawa and Marquis, in terms of N uptake and N remobilization. Results indicated that new cultivars had higher N uptake and/or higher N remobilization than old cultivars. Low tissue N concentration at maturity could be a criterion for selecting high-yielding and high-protein cultivars.Grain protein concentration (GPC) is an important trait of major interest in breeding of bread wheat (T. aestivum L.), because it determines both baking and nutritional properties. Breeding for both high yield and high GPC is very difficult as a negative relationship between yield and GPC was found by many studies (Simmonds 1995; McNeal, et al., 1972; Whitehouse, 1973; Bhatia, 1975; Costa and Kronstad, 1994). Simmonds (1996), therefore, concluded that high yield and high GPC were unattainable simultaneously. However, Kibite and Evans (1984) indicated that the negative relationship between yield and GPC was not primarily driven by genetic factors, but mainly by environmental factors. Cox et al. (1985) found that negative correlations between yield and GPC for some wheat lines were low, although significant, which indicated that simultaneous increase in yield and GPC could be achieved by selection. This is supported by some studies (Davis et al., 1961; Terman et al. 1969; Johnson, 1978; McKendry et al. 1995). Jenner et al. (1991) indicated there is no fundamental conflict on physiological grounds in selecting cultivars for high carbohydrate yield at acceptable, even high, levels of GPC. GPC is determined by plant total nitrogen (N) uptake and N remobilization to the grain. Many studies found genetic differences in N uptake (Löffler, et al. 1985; Van Sanford and MacKown, 1986; Le et al. 2000; Desai and Bhatia, 1978; McKendry, et al. 1995), while Oscarson et al. (1995) did not find any major differences in NO3 uptake capacity among wheat grown hydroponically. A positive correlation between N uptake and GPC was found by Beninati and Busch (1992) and McKendry et al. (1995), but not by others (McNeal et al. 1966; Johnson et al. 1967; Desai and Bhatia 1978). Cultivar difference in N remobilization was also found by some authors (Seth et al. 1960; Johnson et al. 1968; Van Sanford and MacKown, 1987). However, the relationship between plant N metabolism and GPC was not clear. Some reported that N partitioning was associated with GPC (Johnson et al. 1968; Cox et al. 1986; McKendry et al. 1995), but others (McNeal et al. 1972; Woodruff 1972; Van Sanford and MacKown 1987; May et al. 1991) did not support this. Nitrogen harvest index was (grain N at maturity/maximum N uptake, %) used as a selection criterion by some authors (Desai and Bhatia 1978; Cregan and Berkum 1984; Löffler et al. 1985; Jenner et al. 1991; McKendry et al. 1995). Borghi et al. (1987) suggested that both higher biomass yield and efficiency of N remobilization are important traits to overcome the negative relationship between grain yield and GPC. Some studies suggested to use tissue N (Rostami and Giriaei 1998; Rostami and O'Brien 1996; Sylvester-Bradley 1990) or tissue protein concentrations (Noaman and Taylor 1990; Noaman et al. 1990) as selection criteria for increasing GPC because they were positively correlated with GPC. However, Jenner et al. (1991) indicated that from a physiological point of view, there is little logic in using grain protein percentage as a selection criterion. Delzer et al. (1995) also pointed that selection for grain protein only is questionable because the higher GPC is often associated with lower grain yield. Although there are not short of studies on N mechanisms, there are lack of consistencies in the results. Clarke et al. (1990) indicated that unless greater variation in N utilization parameters among cultivars can be demonstrated, there seems to be little justification for selection for parameters other than grain yield and protein concentration. Some recently developed bread wheat cultivars in western Canada have significantly increased yields, while maintaining or increasing percent protein content, relative to earlier cultivars (Wang et al. 2002). These cultivars can be used to study the physiological basis for these genetic improvements in N utilization. A better understanding of these improvements may allow breeders to design more efficient screening methods to develop future high yield and high GPC cultivars. This information may also assist agronomists and producers design soil and crop management practices that will permit full expression of these improved traits. The objective of this study was to estimate the characteristics of these new cultivars in N utilization in comparison with older cultivars and to identify potential criteria for selection of high yield and high GPC cultivars in the western Canadian semiarid prairie

Simulation of multi-deck medium temperature display cabinets with the integration of CFD and cooling coil models

This is the post-print version of the final paper published in Applied Energy. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.In this paper, the model for the multi-deck medium temperature display cabinets is developed with the integration of CFD and cooling coil sub-models. The distributed method is used to develop the cooling coil model with the airside inputs from the outputs of the CFD model. Inversely, the airside outputs from the cooling coil model are used to update the boundary conditions of the CFD model. To validate this cabinet model, a multi-deck medium temperature display cabinet refrigerated with a secondary refrigerant cooling coil was selected as a prototype and mounted in an air conditioned chamber. Extensive tests were conducted at constant space air temperature and varied relative humilities. The cabinet model has been validated by comparing with the test results for the parameters of air at different locations of the flow path, and temperatures of refrigerant and food product, etc. The validated model is therefore used to explore and analyse the cabinet performance and control strategies at various operating and design conditions.DEFR

Genotype difference in kernel discolorations in CWRS and CWAD wheats

Non-Peer ReviewedKernel discolorations of wheat, such as black point (including smudge and penetrated smudge), red smudge and Fusarium-damaged kernel (FDK), are important downgrading factors in western Canada. This study was undertaken to determine cultivar differences in incidences of these kernel discolorations and their downgrading effects in CWRS and CWAD wheats. Grain samples were taken at maturity from six CWRS and four CWAD cultivars in a four-year (1997-2000) field study at six sites: one in the Grey soil zone, two in the Brown soil zone and three in the Black soil zone in western Canada. For CWRS cultivars, Garnet tended to have lower incidences in black point, smudge and FDK and resulted in the least downgrading compared with other CWRS cultivars. For CWAD cultivars, Kyle tended to have lower incidence of black point, Plenty had less smudge caused downgrading effects, DT 369 had lower penetrated smudge incidence, but higher red smudge incidence, and Plenty tended to have severer FDK-caused downgrading effects compared with other CWAD cultivars. CWAD class had higher frequency of downgrading than CWRS class and it usually had higher incidences of all kernel discolorations (black point, smudge, penetrated smudge, red smudge and FDK) and greater downgrading effects than CWRS class

Duodenal ulcer is a multifactorial disorder the role of pepsinogen I

Serum pepsinogen I (PGI) levels were measured in 231 duodenal ulcer (DU) patients and 100 sex and age-comparable healthy controls. Significantly higher mean serum PGI levels were found in DU patients than in controls (124,7 ± 3,4 ng/ml v. 92,9 ± 2,3 ng/ml; P < 0,001) (mean ± SE). These levels were higher in male DU patients than in female DU patients (128,5 ± 3,9 ng/IDl v. 107,4 ± 6,4 ng/ml; P < 0,05). Smoking was associated with elevated serum PGI levels in DU patients (145,3 ± 5,1 ng/ml v. 109,0 ± 4,2 ngl/ml; P < 0,001). Healed DUs were associated with lower mean serum PGI levels than active ulcers (110,9 ± 7,6 ng/ml v. 129,4 ± 3,8 ng/ml, P < 0,05). Whether patients were positive or negative for Helicobacter pylori, infection did not affect mean serum PGI levels. All the risk factors for DU may not affect serum PGI levels and DU may therefore be considered a multifactorial disease