Evaluasi Termal Vertical Greenery System Tipe Green Facade pada Dinding Bangunan

Increasing of ambient temperature due to global warming has a direct impact on increasing the room temperature. Heat from surrounding is transferred to building wall and room. By installing the Vertical Greenery System (VGS) on the building wall, it can be an alternative for heat absorber and eco-friendly indicator. The aims of this study are to determine the temperature that can be reduced by VGS type Green Façade (GF) and achieve the energy consumption reduction because of GF installation. GF is installed on the building wall, property of Mining Engineering Department, Sriwijaya University, to measure its temperature, then compare it with the temperature on control wall. The results showed that the GF can reduce the room temperature up to 1,2oC, compared to the control wall and the average is 0,3oC. The decrease in average temperature causes a decrease in energy consumption due to the use of air conditioners by 1.56-1.92%. Keywords: global warming, green facade, thermal evaluation, vertical greenery system

Effect of Viscoelasticity on Arterial-Like Pulsatile Flow Dynamics and Energy

Time-dependent arterial wall property is an important but difficult topic in vascular mechanics. Hysteresis, which appears during the measurement of arterial pressure–diameter relationship through a cardiac cycle, has been used to indicate time-dependent mechanics of arteries. However, the cause–effect relationship between viscoelastic (VE) properties of the arterial wall and hemodynamics, particularly the viscous contribution to hemodynamics, remains challenging. Herein, we show direct comparisons between elastic (E) (loss/storage < 0.1) and highly viscoelastic (loss/storage > 0.45) conduit structures with arterial-like compliance, in terms of their capability of altering pulsatile flow, wall shear, and energy level. Conduits were made from varying ratio of vinyl- and methyl-terminated poly(dimethylsiloxane) and were fit in a mimetic circulatory system measuring volumetric flow, pressure, and strain. Results indicated that when compared to elastic conduits, viscoelastic conduits attenuated lumen distension waveforms, producing an average of 11% greater cross-sectional area throughout a mimetic cardiac cycle. In response to such changes in lumen diameter strain, pressure and volumetric flow waves in viscoelastic conduits decreased by 3.9% and 6%, respectively, in the peak-to-peak amplitude. Importantly, the pulsatile waveforms for both diameter strain and volumetric flow demonstrated greater temporal alignment in viscoelastic conduits due to pulsation attenuation, resulting in 25% decrease in the oscillation of wall shear stress (WSS). We hope these findings may be used to further examine time-dependent arterial properties in disease prognosis and progression, as well as their use in vascular graft design.

Evaluation of Hemodynamics in a Prestressed and Compliant Tapered Femoral Artery Using an Optimization-Based Inverse Algorithm

The important factors that affect the arterial wall compliance are the tissue properties of the arterial wall, the in vivo pulsatile pressure, and the prestressed condition of the artery. It is necessary to obtain the load-free geometry for determining the physiological level of prestress in the arterial wall. The previously developed optimization-based inverse algorithm was improved to obtain the load-free geometry and the wall prestress of an idealized tapered femoral artery of a dog under varying arterial wall properties. The compliance of the artery was also evaluated over a range of systemic pressures (72.5–140.7 mmHg), associated blood flows, and artery wall properties using the prestressed arterial geometry. The results showed that the computed load-free outer diameter at the inlet of the tapered artery was 6.7%, 9.0%, and 12% smaller than the corresponding in vivo diameter for the 25% softer, baseline, and 25% stiffer arterial wall properties, respectively. In contrast, the variations in the prestressed geometry and circumferential wall prestress were less than 2% for variable arterial wall properties. The computed compliance at the inlet of the prestressed artery for the baseline arterial wall property was 0.34%, 0.19%, and 0.13% diameter change/mmHg for time-averaged pressures of 72.5, 104.1, and 140.7 mmHg, respectively. However, the variation in compliance due to the change in arterial wall property was less than 6%. The load-free and prestressed geometries of the idealized tapered femoral artery were accurately (error within 1.2% of the in vivo geometry) computed under variable arterial wall properties using the modified inverse algorithm. Based on the blood-arterial wall interaction results, the arterial wall compliance was influenced significantly by the change in average pressure. In contrast, the change in arterial wall property did not influence the arterial wall compliance.

Design of Sample Holders for Soil Experiments Using THz Spectroscopy

Terahertz spectroscopy (THz) is a brand-new radiation source with many unique advantages. It owns many potential applications in all area. An experiment was carried out on soil heavy metal detection using THz in Jun., 2010 at Oklahoma State University. Two types of sample holders (1.5mm thickness and 3 mm thickness) were designed based on specific requirements and applications in this paper. The optical material, size, thickness of the sample, thickness of the side-wall, property of samples for holding, adhesive materials, cost were discussed in detail; then, an integrated description were given and a 3-D model was established. Real holders were manufactured based on the former design and their THz characteristics were measured. At last, the holders were used in the current soil heavy metal detection experiment. The results showed that, the designed holders showed low absorption of THz and low reflection. Two thickness samples holders all performed well in the experiments, however, for the soil measurement, the sample information could not be completely collected before echo wave came. The 1.5mm thickness holder was selected in our experiment. The designed sample holders are feasible and this research provides a good solution for the difficulties we met in our experiment.