Three-level Hierarchical Structure Research Articles

Challenges in the design and analysis of a factorial-design cluster randomised trial

Optimising sedation quality in mechanically ventilated intensive care patients is important because excessive sedation is associated with increased hospital acquired infections, longer intensive care (ICU) and hospital stay, and possibly higher mortality. The Development and Evaluation of Strategies to Improve Sedation Quality in InTensive Care (DESIST) study aims to optimise sedation practice. Here we focus on the study design, statistical analysis plan, performing the analysis and issues that occurred. DESIST randomised eight ICUs in pairs to four different combinations of sedation-related quality improvement interventions. The primary outcome assessed optimum sedation within each 12 hour nursing shift (referred to as a DESIST care period). This resulted in a three-level hierarchical data structure: DESIST care periods within admissions, within ICU.

A Connectome Computation System for discovery science of brain

Much like genomics, brain connectomics has rapidly become a core component of most national brain projects around the world. Beyond the ambitious aims of these projects, a fundamental challenge is the need for an efficient, robust, reliable and easy-to-use pipeline to mine such large neuroscience datasets. Here, we introduce a computational pipeline—namely the Connectome Computation System (CCS)—for discovery science of human brain connectomes at the macroscale with multimodal magnetic resonance imaging technologies. The CCS is designed with a three-level hierarchical structure that includes data cleaning and preprocessing, individual connectome mapping and connectome mining, and knowledge discovery. Several functional modules are embedded into this hierarchy to implement quality control procedures, reliability analysis and connectome visualization. We demonstrate the utility of the CCS based upon a publicly available dataset, the NKI–Rockland Sample, to delineate the normative trajectories of well-known large-scale neural networks across the natural life span (6–85 years of age). The CCS has been made freely available to the public via GitHub (https://github.com/zuoxinian/CCS) and our laboratory’s Web site (http://lfcd.psych.ac.cn/ccs.html) to facilitate progress in discovery science in the field of human brain connectomics.

Using DEA and AHP for Multiplicative Aggregation of Hierarchical Indicators

The author [Pakkar, M.S. (2014) Using Data Envelopment Analysis and Analytic Hierarchy Process to Construct Composite Indicators. Journal of Applied Operational Research, 6(3), 174-187.] recently proposed a multiplicative approach using Data Envelopment Analysis (DEA) and Analytic Hierarchy Process (AHP) to reflect the priority weights of indicators in constructing composite indicators (CIs). Nonetheless, this approach is limited to the situations with a single level hierarchy which might not satisfy the needs of a multiple level hierarchy. Therefore, the current paper extends this approach to the situations in which the indicators of similar characteristics can be grouped into sub-categories and further linked into categories to form a three-level hierarchical structure. An illustrative example of road safety performance for a set of European countries highlights the usefulness of the proposed “extended approach”.

Structure of zirconium dioxide based porous glasses

This study is devoted to investigation of the micro- and mesostructure (including fractal properties) of porous zirconia glasses synthesized by precipitation from zirconium n-propoxide solutions in the presence of different hydrolyzing-agent (H2O) quantities at different temperatures. Analysis of small-angle neutron, ultra-small-angle neutron and X-ray scattering, scanning electron microscopy allows concluding that the synthesized glasses are complex systems with a three-level hierarchical fractal structure. It is revealed that both the temperature of synthesis and the H2O concentration in the initial solution significantly affect the structural characteristics of the glasses.

Hierarchy control of power quality for wind – battery energy storage system

Uncertainty of the wind results in a fluctuating power output of wind turbine generators, and consequently, causes adverse impacts on the stability of system frequency and voltage. To smooth such power fluctuation, this study proposes a power quality control strategy based on a three-level hierarchical structure for wind - battery energy storage hybrid power system, including grid demand calculating level, energy management level and voltage-source converters control level. The advantage of the control strategy is that the state of charge of a battery energy storage system is regulated within proper range and the voltage at the point of common coupling is kept stable while smoothing wind power. Effectiveness of the proposed method is validated by MATLAB/SIMULINK simulations and experiments.

Hierarchy of processing equipment configuration design problems for multiproduct chemical plants

A procedure for performing one stage of designing multiproduct chemical plant--definition of the processing equipment configuration is proposed. At this stage, a three-level hierarchical structure of problems is formed--at the upper level, the parameters of the operational mode of the chemical engineering system that ensures the desired output of each product are found; at the middle level, the size and number of equipment units and methods of product processing for all processing stages are chosen; at the lower level, technological and mechanical design of individual pieces of equipment (machines) are performed. The decomposition of the processing equipment design problem into three problems described above reduces the original mixed integer nonlinear programming problem to one nonlinear programming problem and a set of integer programming problems, where the number of integer programming problems is equal to the number of processing stages. The reduced problems can be solved using available optimization methods, which considerably reduces the solution time and improves the quality of design solutions. Basic information links between the problems of different hierarchical levels are determined, general problem statements and an algorithm for the simultaneous solution of the upper and middle level problems is proposed. By way of example, the problem of selection and design of a mechanical agitator for a vertical bulk-capacity storage is considered.

Impact of Subject Attrition on Sample Size Determinations for Longitudinal Cluster Randomized Clinical Trials

Subject attrition is a ubiquitous problem in any type of clinical trial and, thus, needs to be taken into consideration at the design stage particularly to secure adequate statistical power. Here, we focus on longitudinal cluster randomized clinical trials (cluster-RCT) that aim to test the hypothesis that an intervention has an effect on the rate of change in the outcome over time. In this setting, the cluster-RCT assumes a three-level hierarchical data structure in which subjects are nested within a higher level unit such as clinics and are evaluated for outcome repeatedly over the study period. Furthermore, the subject-specific slopes can be modeled in terms of fixed or random coefficients in a mixed-effects linear model. Closed-form sample size formulas for testing the preceding hypothesis have been developed under an assumption of no attrition. In this article, we propose closed-form approximate samples size determinations with anticipated attrition rates by modifying those existing sample size formulas. With extensive simulations, we examine performances of the modified formulas under three attrition mechanisms: attrition completely at random, attrition at random, and attrition not at random. In conclusion, the proposed modification is very effective under fixed-slope models but yields biased, perhaps substantially so, statistical power under random slope models.

Impact dynamics of water droplets on Cu films with three-level hierarchical structures

Three Cu films with different three-level hierarchical structures were fabricated using a one-step electric brush-plating technique. Impact dynamics of water droplets on three Cu films was investigated. In the absence of surface chemical modification, the Cu films showed static hydrophobicity and even superhydrophobicity. Under dynamic impact, the two hydrophobic Cu films were wetted partially, whereas the superhydrophobic Cu film exhibited considerably robust water-repellency in a wide range of Weber number. Analysis based on the pressure balance relation revealed that the considerably robust water-repellency of the superhydrophobic Cu film arises from the damping role of the varied height and shape of the micro-protrusions in lowering the water hammer pressure, the delaying role of the submicro-bumps on the side of the micro-protrusions in preventing the penetration process of the depinned water–air interface and the critical surface hydrophobization role of the nano-scale structure in changing the wetting property of the basal surface of the Cu film from hydrophilicity to hydrophobicity.

Cu surfaces with controlled structures: From intrinsically hydrophilic to apparently superhydrophobic

A series of Cu films with different surface structures were fabricated by an improved electric brush-plating technique. In the absence of surface chemical modification, the Cu films exhibited hydrophobic and even superhydrophobic behaviors due to their three-level hierarchical structures. Based on the classical Wenzel and Cassie models, the effects of two dimensionless geometrical parameters (the aspect ratio and the spacing factor of micro-scale structure) on the wetting behaviors of the Cu films were investigated. It was demonstrated that to obtain the stable Cassie superhydrophobic state, the aspect ratio and the water contact angle on the basal surface should be as large as possible and the spacing factor should be limited within a specific range for given aspect ratio and water contact angle on the basal surface.

Thermoresponsive transition of a PEO-b-PNIPAM copolymer: From hierarchical aggregates to well defined ellipsoidal vesicles

We analyze in detail the morphology transition of poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-b-PNIPAM) diblock copolymer in water with small angle neutron scattering. A three-level hierarchical structure is found below the critical solution temperature (LCST) of PNIPAM. The small-scale structure corresponds to the unperturbed PEO-b-PNIPAM chains. These coils assemble into intermediate-size aggregates which have a constant number density in solution, independently of the solution concentration, under the assumptions of a simple model based on the concentration dependence of the fitting parameters. Large clusters are also observed, which comprise the large-size structure. Above the LCST the system transforms into a well-defined geometry of monodisperse elliptical vesicles which does not depend on the solution concentration. The vesicles become less asymmetric with a higher aggregation number at the highest temperature.

Factors influencing container carriers’ use of coastal shipping

Coastal shipping is one of the most sustainable and economically competitive modes of transportation. This study employs the analytic hierarchy process (AHP) method to determine the importance of various factors influencing container carriers’ use of coastal shipping. A three-level hierarchical structure with the 17 attributes is proposed and tested. A previous AHP survey in Taiwan has indicated that port policy and infrastructure is the most critical factor influencing the coastal shipping by container carriers followed by operational cost, operational strategy and operational efficiency. Overall, the results indicate that the five most important attributes influencing the use of coastal shipping are simplified customs procedures; leasing a dedicated terminal; transhipment time; a favourable port charge system and efficient terminal operations.

An Adaptive Zone-Division-Based Automatic Voltage Control System With Applications in China

The power industry in China has grown significantly over the past decade, spurring the adoption of system-wide automatic voltage control (AVC) technology to meet stricter requirements for security and economical power system operation. To cope with the rapidly developing and frequently changing Chinese power grid, an AVC scheme based on adaptive zone division is introduced in this paper. Logically, this type of system has a three-level hierarchical structure, but, here, both secondary voltage control (SVC) and tertiary voltage control (TVC) are implemented via software at the same control center. The control zones are no longer fixed but are reconfigured online and updated in accordance with variations in the grid structure. The technical details of these procedures are presented here. The implementation of TVC (which is based on an online reactive optimal power flow) and SVC are also discussed, together with some technical details on improvements to their reliability and robustness. Some results obtained from field-site applications based on similar-days testing rather than simulations are employed to evaluate the performance and improvements of the AVC system. This system has been installed at over 20 control centers in China.

A Bayesian, Generalized Frailty Model for Comet Assays

This paper proposes a flexible modeling approach for so-called comet assay data regularly encountered in preclinical research. While such data consist of non-Gaussian outcomes in a multilevel hierarchical structure, traditional analyses typically completely or partly ignore this hierarchical nature by summarizing measurements within a cluster. Non-Gaussian outcomes are often modeled using exponential family models. This is true not only for binary and count data, but also for, example, time-to-event outcomes. Two important reasons for extending this family are for (1) the possible occurrence of overdispersion, meaning that the variability in the data may not be adequately described by the models, which often exhibit a prescribed mean–variance link, and (2) the accommodation of a hierarchical structure in the data, owing to clustering in the data. The first issue is dealt with through so-called overdispersion models. Clustering is often accommodated through the inclusion of random subject-specific effects. Though not always, one conventionally assumes such random effects to be normally distributed. In the case of time-to-event data, one encounters, for example, the gamma frailty model (Duchateau and Janssen, 2007). While both of these issues may occur simultaneously, models combining both are uncommon. Molenberghs et al. (2010) proposed a broad class of generalized linear models accommodating overdispersion and clustering through two separate sets of random effects. Here, we use this method to model data from a comet assay with a three-level hierarchical structure. Although a conjugate gamma random effect is used for the overdispersion random effect, both gamma and normal random effects are considered for the hierarchical random effect. Apart from model formulation, we place emphasis on Bayesian estimation. Our proposed method has an upper hand over the traditional analysis in that it (1) uses the appropriate distribution stipulated in the literature; (2) deals with the complete hierarchical nature; and (3) uses all information instead of summary measures. The fit of the model to the comet assay is compared against the background of more conventional model fits. Results indicate the toxicity of 1,2-dimethylhydrazine dihydrochloride at different dose levels (low, medium, and high).

감성의 이해를 통한 감성품질의 구조적 접근 방법에 관한 연구

Affective quality is considered one of the most influential factors for the competitive power of consumer products. Since the human affective response is very abstract and comprehensive, it is very difficult to understand and manipulate the Affective Quality in scientific method. This study suggested the three-level hierarchical structure of the human affection according to the human affective response process, and subdivided the Affective Quality into three subordinate concepts such as 'Organoleptic Quality', 'Affective Quality Factor' and 'Overall Affective Quality.' Also the categories of adjectives which used to express the human affections for the three levels of affective structure were suggested. The results of this study could be used as a frame of systematic approach method to the Affective Quality.

A Collusion-Resistant Conditional Access System for Flexible-Pay-Per-Channel Pay-TV Broadcasting

Pay-TV broadcasting system is an extensively deployed application that charges users based on their subscription. To ensure security for the Pay-TV broadcasting application, a conditional access system (CAS) is designed to control TV channel/program access to only the authorized subscribers. Several key management schemes with a four-level hierarchical key structure have been proposed. In this paper, we point out a severe security weakness of these schemes against collusion attacks. Then we propose a new CAS scheme with a three-level hierarchical key structure using ciphertext-policy attribute-set-based encryption (ASBE), an extension of ciphertext-policy attribute-based encryption (CP-ABE). Our scheme achieves scalable, flexible, fine-grained, and most importantly, collusion-resistant access control for Pay-TV broadcasting applications. The proposed scheme is designed to support all operations in Pay-TV applications. We then provide a detailed analysis on security and performance of our scheme. We also implement the scheme and it is showed to be both efficient and flexible for Pay-TV broadcasting applications.

Recognition of earthquake-prone nodes, a case study for North Vietnam (M ⩾ 5.0)

Morphostructural nodes in North Vietnam are delineated with the morphostructural zoning (MZ) method, and classified into seismogenic and non-seismogenic nodes. The compiled morphostructural map (scale 1: 1000000) shows a three-level hierarchical structure of blocks, boundary zones, and nodes. The identified nodes are classified with the pattern-recognition algorithm CORA-3 into those that are prone to generate M ⩾ 5.0 earthquakes and those that are not. Some of the earthquake-prone nodes coincide with epicenters of M ⩾ 5.0 earthquakes that have occurred; others may coincide with such events in the future.

Scene Aware Detection and Block Assignment Tracking in crowded scenes

How far can human detection and tracking go in real world crowded scenes? Many algorithms often fail in such scenes due to frequent and severe occlusions as well as viewpoint changes. In order to handle these difficulties, we propose Scene Aware Detection (SAD) and Block Assignment Tracking (BAT) that incorporate with some available scene models (e.g. background, layout, ground plane and camera models). The SAD is proposed for accurate detection through utilizing 1) camera model to deal with viewpoint changes by rectifying sub-images, 2) a structural filter approach to handle occlusions based on a feature sharing mechanism in which a three-level hierarchical structure is built for humans, and 3) foregrounds for pruning negative and false positive samples and merging intermediate detection results. Many detection or appearance based tracking systems are prone to errors in occluded scenes because of failures of detectors and interactions of multiple objects. Differently, the BAT formulates tracking as a block assignment process, where blocks with the same label form the appearance of one object. In the BAT, we model objects on two levels, one is the ensemble level to measure how it is like an object by discriminative models, and the other one is the block level to measure how it is like a target object by appearance and motion models. The main advantage of BAT is that it can track an object even when all the part detectors fail as long as the object has assigned blocks. Extensive experiments in many challenging real world scenes demonstrate the efficiency and effectiveness of our approach.

Self-efficacy beliefs of youth entering the labour market

Abstract This article presents the psychological meaning of school-to-work transition. Transition to taking up new social roles entails numerous difficulties, and that is why young people see it as a crisis point. According to researchers one of the predictors of effective transition to the labour market is self-efficacy. This article presents the two obtaining approaches to the psychology of self-efficacy beliefs. Both specific and generalized self-efficacy belief are good predictors of human behaviour, which has been repeatedly confirmed in the studies (main overview in this article). The authors of this compilation have integrated the two dominating approaches into one theoretical model, taking account of the three levels of generality proposed by Rosch. By doing that, a theoretical model has been created which allows for organising self-efficacy beliefs relating to life roles into a three-level hierarchical structure.

Fabrication and characterization of multi-level hierarchical surfaces

A nanostructured surface may exhibit low adhesion or high adhesion depending upon fibrillar density, and it presents the possibility of realizing eco-friendly surface structures with desirable adhesion by mimicking the mechanics of fibrillar adhesive surfaces of biological systems. The current research uses a patterning technique to fabricate smart adhesion surfaces: one-, two- and three-level hierarchical synthetic adhesive structure surfaces with various fibrillar densities and diameters. The contact angles and contact angle hysteresis were measured to characterize the wettability. A conventional and a glass ball attached to an atomic force microscope (AFM) tip were used to obtain the adhesive forces via force-distance curves and to study the buckling behavior of a single fiber on the hierarchical structures.

Control of surface acidity and catalytic activity of γ-Al 2O 3 by adjusting the nanocrystalline contact interface

Densification of 2–2.5 nm nanocrystals assemblies in the three-level hierarchical structure of γ-Al 2O 3 aerogel significantly increases the surface acidity, as determined using indicator titration, NH 3–TPD, and FTIR of adsorbed pyridine. Thermal treatment at 1073 K and insertion of additional alumina inside the aerogel pores eliminated the slit micropores with shrinkage of nanocrystals assemblies (N 2-adsorption, HRTEM, SEM) increasing the contact interface by a factor of 2. It caused a fivefold increase in alumina surface acidity and the strength of Lewis acid sites with no measurable dehydration (weight loss, TGA). This was attributed to the formation of additional low-coordinated aluminum ions with higher charge in the areas with atomic disorder of high-angle grain boundaries, detected by 27Al MAS NMR, HRTEM, XPS, and XRD. Densification of nanocrystalline alumina aerogel yielded a higher catalytic activity in dehydration of isopropanol; it was 10-fold more active compared with commercial γ-alumina on the catalyst weight basis.