Envelope Construction Research Articles

Density-based phase envelope construction

A new density-based phase envelope construction procedure is proposed. The equations for two-phase saturation molar density and temperature computations are established by equating to zero the tangent plane distance (TPD) function in terms of component molar densities and temperature to find a non-trivial set of component molar densities at various specifications: mixture molar density, temperature and the modified equilibrium constants. The latter are defined as the ratios of feed to incipient phase component molar density. The nonlinear system of equations is solved by the full Newton method. The sequence of calculations is started at some conditions where convergence is easily obtained and an extrapolation procedure provides high quality initial guesses for subsequent calculations. The phase envelope is traced in the molar density-temperature plane, where a unique saturation temperature exists at specified mixture molar density; the representation in the pressure-temperature plane is obtained by calculating explicitly the pressure from the equation of state at given temperature and component molar densities on the saturation curve. The equation of state (EoS) must not be solved for volume and the elements of the Jacobian matrix have simpler expressions than their conventional (pressure-based) counterparts. The proposed method is successfully tested for a variety of mixtures, ranging from binary and ternary mixtures to reservoir fluids, exhibiting usual (closed) and unusual phase envelopes, such as open-shaped envelopes characterized by a bubble point branch extending to infinity, branches with negative pressures constructed in a single run (unlike in the conventional case), several branches, double retrograde behavior and swallowtail pattern corresponding to liquid demixing at low temperatures. The proposed method is not dependent of the thermodynamic model and any pressure-explicit equation of state can be used, provided the required partial derivatives of fugacity and pressure with respect to mole numbers, temperature and volume are available.

From Monge\u2013Amp\xe8re equations to envelopes and geodesic rays in the zero temperature limit

Let (X,theta ) be a compact complex manifold X equipped with a smooth (but not necessarily positive) closed (1, 1)-form theta . By a well-known envelope construction this data determines, in the case when the cohomology class [theta ] is pseudoeffective, a canonical theta -psh function u_{theta }. When the class [theta ] is Kähler we introduce a family u_{beta } of regularizations of u_{theta }, parametrized by a large positive number beta , where u_{beta } is defined as the unique smooth solution of a complex Monge–Ampère equation of Aubin–Yau type. It is shown that, as beta rightarrow infty , the functions u_{beta } converge to the envelope u_{theta } uniformly on X in the Hölder space C^{1,alpha }(X) for any alpha in ]0,1[ (which is optimal in terms of Hölder exponents). A generalization of this result to the case of a nef and big cohomology class is also obtained and a weaker version of the result is obtained for big cohomology classes. The proofs of the convergence results do not assume any a priori regularity of u_{theta }. Applications to the regularization of omega -psh functions and geodesic rays in the closure of the space of Kähler metrics are given. As briefly explained there is a statistical mechanical motivation for this regularization procedure, where beta appears as the inverse temperature. This point of view also leads to an interpretation of u_{beta } as a “transcendental” Bergman metric.

Experimental Analysis of MOC Composite with a Waste-Expanded Polypropylene-Based Aggregate.

Polypropylene (PP) is one of the most widely produced types of plastic worldwide, but its recycling is limited. This work presents a study of the utilization of expanded polypropylene (EPP) waste in a magnesium oxychloride cement (MOC) composite usable in the building industry. MOC is formed by mixing magnesium oxide powder and a concentrated solution of magnesium chloride and is characterized by excellent bonding ability to large quantities of different types of aggregates. A developed air-cured MOC composite, where an EPP-based aggregate was used for the full replacement of natural aggregate, was investigated in terms of its basic physical, mechanical, thermal and water resistance properties. The results demonstrate that incorporation of EPP waste greatly improved the thermal insulation properties, while the mechanical resistance was reduced to an acceptable level. The developed MOC composite containing EPP waste can be considered as an alternative thermal insulation material applicable for the construction of floor or envelope construction systems.

Automatic Detection of Aortic Valve Opening Using Seismocardiography in Healthy Individuals.

Accurate detection of fiducial points in a seismocardiogram (SCG) is a challenging research problem for its clinical application. In this paper, an automated method for detecting aortic valve opening (AO) instants using the dorso-ventral component of the SCG signal is proposed. This method does not require electrocardiogram (ECG) as a reference signal. After preprocessing the SCG, multiscale wavelet decomposition is carried out to get signal components in different wavelet subbands. The subbands having possible AO peaks are selected by a newly proposed dominant-multiscale-kurtosis- and dominant-multiscale-central-frequency-based criterion. The signal is reconstructed using selected subbands, and it is emphasized using the weights derived from the proposed relative squared dominant multiscale kurtosis. The Shannon energy followed by autocorrelation coefficients is computed for systole envelope construction. Finally, AO peaks are detected by a Gaussian-derivative-filtering-based scheme. The robustness of the proposed method is tested using clean and noisy SCG signals from the combined measurement of ECG, breathing, and SCG database. Evaluation results show that the method can achieve an average sensitivity of 94%, a prediction rate of 90%, and a detection accuracy of 86% approximately over 4585 analyzed beats.

A global envelope test to detect non‐random bursts of trait evolution

AbstractThe joint analysis of species’ evolutionary relatedness and their morphological evolution has offered much promise in understanding the processes that underpin the generation of biological diversity.Disparity through time (DTT) is a popular method that estimates the relative trait disparity within and between subclades, and compares this to the null hypothesis that trait values follow Brownian evolution along the time‐calibrated phylogenetic tree. To visualise the differences a confidence envelope is normally created by calculating, at every time point, the 97.5% minimum and 97.5% maximum disparity values from multiple simulations of the null model. The null hypothesis is rejected whenever the empirical DTT curve falls outside of this envelope, and these time periods may then be linked to events that may have sparked non‐random trait evolution.Here, simulated data are used to show this pointwise (ranking at each time point) method of envelope construction suffers from multiple testing and a poor, uncontrolled, false‐positive rate. As a consequence it cannot be recommended. Instead, each DTT curve can be given a single rank based upon their most extreme disparity value, relative to all other curves, and across all time points. Ordering curves this way leads to a test that avoids multiple testing, but still allows construction of a confidence envelope. The null hypothesis is rejected if the empirical DTT curve is ranked within the most extreme 5% ranked curves from the null model. Comparison of the rank envelope curve to the Morphological Disparity Index and Node Height tests shows it to have generally higher power to detect non‐Brownian trait evolution. An extension to allow simultaneous testing over multiple traits is also detailed.Overall the results suggest the new rank envelope test should be used in null model testing for DTT analyses. The rank envelope method can easily be adapted into recently developed posterior predictive simulation methods used in model selection analyses. More generally, the rank envelope test should be adopted whenever a null model produces a vector of correlated values and the user wants to determine where the empirical data are different to the null model.

A compound interpolation envelope local mean decomposition and its application for fault diagnosis of reciprocating compressors

Abstract Local mean decomposition (LMD) is a self-adaptive analysis method which can decompose a signal into a set of product function (PF) components, and the construction of envelope function plays an important role in the accuracy of its PF components. According to the local nonstationary characteristics of vibration signals, a compound interpolation envelope (CIE) LMD was proposed through a novel envelope construction method. By defining an nonstationary coefficient to evaluate the local nonstationary characteristics of vibration signals, an compound envelope construction method which use Monotonic Piecewise Cubic Hermite Interpolation (MPCHI) for nonstationary part and Cubic spline interpolation (CSI) for smooth part was proposed, and an CIE LMD algorithm was give based on the novel envelope construction method. A numerical example simulation was conducted to verify the performance of CIE LMD, results indicated that CIE LMD outperforms three other methods. The CIE LMD was employed to diagnose the oversized bearing clearance fault in reciprocating compressor, and the envelope frequency spectrum of PF component gives a more significant peak of fault frequency than that of original signal, which further indicates that this proposed method is competent for the diagnosis of reciprocating compressor oversized bearing clearance fault.

The anomalous yield behavior of fused silica glass

We develop a critical-state model of fused silica plasticity on the basis of data mined from molecular dynamics (MD) calculations. The MD data is suggestive of an irreversible densification transition in volumetric compression resulting in permanent, or plastic, densification upon unloading. The MD data also reveals an evolution towards a critical state of constant volume under pressure-shear deformation. The trend towards constant volume is from above, when the glass is overconsolidated, or from below, when it is underconsolidated. We show that these characteristic behaviors are well-captured by a critical state model of plasticity, where the densification law for glass takes the place of the classical consolidation law of granular media and the locus of constant-volume states defines the critical-state line. A salient feature of the critical-state line of fused silica, as identified from the MD data, that renders its yield behavior anomalous is that it is strongly non-convex, owing to the existence of two well-differentiated phases at low and high pressures. We argue that this strong non-convexity of yield explains the patterning that is observed in molecular dynamics calculations of amorphous solids deforming in shear. We employ an explicit and exact rank-2 envelope construction to upscale the microscopic critical-state model to the macroscale. Remarkably, owing to the equilibrium constraint the resulting effective macroscopic behavior is still characterized by a non-convex critical-state line. Despite this lack of convexity, the effective macroscopic model is stable against microstructure formation and defines well-posed boundary-value problems.

Lightweight composite timber façade wall with improved thermal response

For the construction of modern energy-efficient buildings, lightweight construction is becoming very popular among designers. EU legislation encourages such design, especially if wood, as a sustainable material, is used. However, lightweight building envelope construction, in general, exhibits poor dynamic thermal properties, which are particularly pronounced in prefabricated metal walls and thin wooden or composite building panels, such as door fillers or opaque parts (parapets) of prefabricated walls with the glazing of the skeleton-built buildings. The aim of this research was the development of a composite timber façade wall, which will not exceed the thickness of building elements, such as doors and windows, and will meet the requirements of energy efficiency and have improved dynamic thermal properties. The composite timber building element with a thickness of 68 mm, which includes two layers of advanced technologies: vacuum insulation panel (VIP) and phase change material (PCM), was developed and optimized. The optimization included a parametric study on VIP and PCM panels’ position in the thin, lightweight building wall. The research has shown that dynamic thermal properties comparable to the heavyweight building envelope constructions (time lag of the heat wave up to 12 h) can be achieved; moreover, the thermal transmittance is considerably reduced.

Sustainability of multi-skin facades

The paper considers the issues of buildings multi-skin envelope construction. Such a constructions is often used for buildings with wet inside air and for buildings with low energy consumption. A number of factors effect on the durability, sustainability and other properties of facade during the whole lifecycle of a building.

Thermal Inertia Performance Evaluation of Light-Weighted Construction Space Envelopes Using Phase Change Materials in Mexico City’s Climate

The present study’s main objective was to determine the applicability of organic phase change materials (PCMs) in a building’s envelope construction system for the passive provision of comfortable indoor thermal conditions over one year based on thermal inertia in Mexico City. Research on PCMs relate mainly to their use in building envelope construction systems to reduce energy consumption for mechanical indoor thermal conditioning—not in passive systems. Computer simulation results of mean indoor temperature variations are presented with the objective of evaluating these construction systems’ thermal inertia properties. In the present study, dynamic thermal simulations (DTS), using EnergyPlus software, of ten 1 m3 test units with envelope construction systems combining organic PCMs of different fusion temperatures with conventional materials were performed. Based on the results, it is concluded that the implementation of organic PCMs with a fusion temperature around 25 °C in combination with aerated concrete in a space envelope results in the highest number of hours the indoor temperatures remain within the comfort range throughout a typical year, due to the decrement of indoor temperature oscillations and, to a large extent, to thermal lag.

Urban Farming Construction Model on the Vertical Building Envelope to Support the Green Buildings Development in Sleman, Indonesia

The purpose of this paper is to analyze the construction model of urban farming on vertical building envelopes to support the green building development in Sleman Regency, Special District Yogyakarta Province, Indonesia. The construction of vertical buildings in Sleman district is growing rapidly together with the increasing demand for the provision of housing and public facilities. The rapid physical development in Sleman has caused the reduction of green land such as green open space (RTH), agricultural land and rice fields. These developments potentially threaten food security in Sleman district. Urban farming is a method of agricultural activities to reduce the problems of agricultural land limitation in urban areas, like Sleman district. The construction design model of urban farming on the vertical building envelope is one aspect of green building that will support the efforts in vertical farming processes. This showed that the method did not require any horizontally ground space but effectively used the vertical space on the building envelope, including wall and building roof features and construction. In fact, the urban farming construction method will not only contribute to productive agricultural activities, but also support the greening of the urban area as well as reduce the crisis of agricultural land issues. The urban farming construction model of the vertical building facade includes the urban farming construction on the roof, wall, and balcony.

Experimental Research on Thermal Performance Differences of Building Envelopes in Multiple Heating Operation Conditions

The thermal performance of building envelopes, including heat insulation performance and dynamic property in multiple heating operation conditions, was concentrated on this paper. The north wall of the experimental building has four kinds of envelope constructions, and thereby marked as the external insulation wall, internal insulation wall, intermediate insulation wall and solid brick wall, the lengths of which are all 650 mm in square. Results shown that the external insulation wall had the highest inner surface temperature and achieved the best indoor thermal comfort in the process of continuous heating, while the internal insulation wall had the fastest inner surface temperature change and obtained the best indoor thermal comfort during intermittent heating condition. Moreover, the closer to indoor low energy storage materials, the better thermal performance and energy efficiency of the envelope construction would achieve.

Vacuum insulation panels (VIPS) in building envelope constructions: An overview

Driven by updated building energy codes and green building initiatives across the world, vacuum insulation panel, also known as VIP, has become a desired insulation product for building envelope constructions. VIP has initial center-of-panel thermal conductivity of 0.004 W/mK or lower, and integration of VIP in building envelopes can reduce CO2 emissions and contribute towards ‘net-zero’ or ‘near-net-zero’ building constructions. Although VIPs have been applied in real-world constructions across the world, primarily in Asia, Europe and North America, it is still a novel building product under investigation. This overview paper is a summary of fundamentals, constituents, constructions and performances of VIPs. The paper shows there exists many advantages and challenges associated with the integration of VIPs in building envelope constructions. The speed at which VIPs will be integrated in building envelope construction in the coming years remains unclear; nevertheless, it is evident that vacuum technology is the promising way forward for sustainable building envelope constructions in the 21st century.

Energy Performance and Thermal Comfort of Double-Skin and Single-Skin Facades in Warm-Climate Offices

The energy performance and thermal comfort of an office building with single and double skin facades, in a warm climate was studied using TAS software. A double-skin facade is an envelope construction that consists of two transparent surfaces separated by a cavity. The extra skin can reduce cooling demand in summer and heating demand in winter. It is concluded that in a warm climate office, a double skin facade can perform better than a single skin facade. In a warm climate a double skin facade fully provides heating and thermal comfort in winter. In a warm climate however its benefit in summer is limited. Further studies are needed to increase the performance of double skin facades in summer.

Multi-criterion optimization of building envelope in the function of indoor illumination quality towards overall energy performance improvement

This paper elaborates the formulation and application of an integral methodology for overall energy performance improvement of office buildings and demonstrates its application. The developed multi-objective methodology is demonstrated on a reference office building located in a temperate climate zone with high annual temperature variations. The idea is to formulate a research based proposition in building science with a formulation of a general/integral methodology which could be applied widely in energy performance refurbishment of existing office buildings and help architects and engineers in the early-design stages of new projects. The goal was to formulate an optimized building envelope model using multi-criterion optimization methodology in order to determine efficient window to wall ratio (WWR) and window geometry (WG) in the function of indoor illumination quality, followed by the assessment of glazing parameters influence on the annual energy demand. The integral methodology for overall energy performance improvement of office buildings utilizes multi-criterion optimization method and highly detailed Building Information Modeling (BIM) programs and dynamic energy simulation engines. The developed coupled-integral methodology links together both building envelope construction optimization and user comfort. The methodology is both flexible and adaptable for application in various climatic conditions and for different construction types.

Multiobjective optimization design of green building envelope material using a non-dominated sorting genetic algorithm

To realize the goal of environmental sustainability, improving energy efficiency in buildings is a major priority worldwide. However, the practical design of green building envelopes for energy conservation is a highly complex optimization problem, and architects must make multiobjective decisions. In practice, methods such as multicriteria analyses that entail capitalizing on possibly many (but in nearly any case limited) alternatives are commonly employed. This study investigated the feasibility of applying a multiobjective optimal model on building envelope design (MOPBEM), which involved integrating a building envelope energy performance model with a multiobjective optimizer. The MOPBEM was established to provide a reference for green designs. A nondominated sorting genetic algorithm-II (NSGA-II) was used to achieve a tradeoff design set between three conflicting objectives, namely minimizing the envelope construction cost (ENVCOST), minimizing the envelope energy performance (ENVLOAD), and maximizing the window opening rate (WOPR). A real office building case was designed using the MOPBEM to identify the potential strengths and weaknesses of the proposed MOPBEM. The results showed that a high ENVCOST was expended in simultaneously satisfying the low ENVLOAD and high WOPR. Various designs exhibited obvious cost reductions compared with the original architects' manual design, demonstrating the practicability of the MOPBEM.

Thermal Bridges Impact on Energy Need for Heating in Low Energy Wooden House

Energy need for heating is depend on the heat loss of the builing. It is essential to minimize heat losses when designing and building energy efficient buildings. For an energy-efficient building in a cold climate, a large part of the space heating demand is caused by transmission losses through the building envelope. The low-energy buildings are enevelope construction with high thermal resistance. The impact of thermal bridges was studied by comparative calculations for a case study building with different amounts of insulation. In the low-energy buildings are envelope construction with high thermal resistance. When more insulation is used the relative impact of thermal bridges increases. In these buildings is necessary to specify each thermal bridges. This thesis deals with the influence of thermal bridges on energy need for heating in low energy wooden houses.

Acoustic Analysis of Double Transparent Facades in Bratislava

Implementation of double transparent facades (DTF) into architectural concept of modern intelligent buildings is a well established trend of modern administrative building design. The Positive influence on acoustic comfort of a working place caused by this type of envelope construction is evident. DTF allow building designing in high noise exposure urban areas. Comparison of eight DTF from structural and acoustic properties point of view is presented in this paper. Results from acoustic measurements of buildings situated in Bratislava were analyzed.

Risk Assessment of Airtightness of Building Envelope

The paper deals with risk analysis of insufficient airtightness of the envelope construction. The risk analysis is a systematic and structured data processing to identify potential hazards. The main aim of paper is to qualified risks which arise from the danger, i.e. insufficiently airtight of the building envelope. The quality of airtight building envelope except for low energy consumption also minimizes the risk of damage to the structure associated with the spread of the heat, water vapor in the structure and fungal growth. The qualification of risks consists of choice of method and determinative indicators, input data and simulation of model with drawing results.

Moisture management performance of wood-frame in-fill wall in Shanghai, China

This paper discusses the results of a research project which aimed at determining the hygrothermal (i.e. thermal and moisture) performance of the Canadian wood-frame building envelope construction in the city of Shanghai in China. The performance assessments of the wood-frame walls were conducted using the two-dimensional hygrothermal simulation tool called hygIRC-2D. In this study an in-fill type wall was considered and hygrothermal simulations were carried out for the weather conditions of Shanghai. Investigations were conducted to determine the influence of the vapour barrier, exterior stucco cladding material and different types of sheathing boards on the moisture performance of in-fill walls. Additional simulations were carried out to determine the influence of air leakage on the moisture performance of in-fill walls. The outputs from the simulations were analysed with the help of a hygrothermal response indicator called RHT index. It was concluded that the design of the in-fill wall including a rain screen but omitting a vapour barrier is expected to lead to the maximum reduction in hygrothermal loading when exposed to the weather conditions of Shanghai, China.