Direct Analysis Method Research Articles

Robust decentralized optimal stabilizability of continuous time uncertain interconnected systems: Application to large scale power system

This article introduces a new design of a decentralized robust optimal feedback controller for a class of large-scale systems using the modified algebraic Riccati equations. The studied class of large-scale systems is characterized by structured uncertainties that are bounded. Our main contribution in this work is the use of the Lyapunov direct method for the stability analysis, associated with a quadratic function, in order to determine a new sufficient condition to guarantee the global asymptotic stability of the class of the studied uncertain interconnected systems. The proposed control approach is then implemented on a large-scale power systems composed of three interconnected generators. Simulation results show that the proposed robust optimal controller is quite effective and has an outstanding performance.

Direct convolution integration method for random vibration analysis of structures subjected to nonuniformly modulated nonstationary excitations

A comprehensive direct convolution integration method is presented in this study for the random vibration analysis of linear structures subjected to multiple nonuniformly modulated nonstationary excitations. The structural unit impulse responses with respect to each independent excitation are first identified and stored by a few time-history analyses. Then the structural response statistics are calculated by the direct convolution integration of unit impulse responses and excitation statistics. Further, two fast Fourier transform algorithms are presented to speed up the convolution integration. Because the convolution expressions are explicit, the presented method can be used to only calculate the responses at some specific degrees of freedom of interest in engineering. Furthermore, it can only calculate the responses at a small number of sparse moments in consideration of the time slow-varying property of nonstationary processes. Finally, the random vibration analysis of a frame structure excited by the fully coherent and incoherent nonstationary excitations is utilized to demonstrate its high accuracy and efficiency. Some suggestions of application are given.

Optimization Design and Injury Analysis of Driver’s Restraint System in Sedan Small Offset Collision

A combination of airbag, seatbelt, and other restraint systems greatly reduces injury to drivers in small offset collisions. However, the airbag causes accidental injury to the driver in the deployment process. To maximize the protection effect of the restraint system on the driver, this study proposes a pre-tensioned force-limiting seatbelt. A small offset collision accident with video information was simulated by using a Neon sedan and the THUMS (v.4.0.2) finite element model. The effectiveness of the accident model and the matching use of a pre-tensioned force-limiting seatbelt and airbag for driver protection were verified. To obtain the best parameter matching of protection effect, first, the seatbelt force-limiting A, pre-tensioned force B, pre-tensioned time C, airbag ignition time D, and mass flow coefficient E were selected as influencing factors, and orthogonal tests with different factor levels were designed. Then, the direct analysis method was applied to analyze the influence laws of each factor on driver dynamic response and injury. In addition, the radial basis function surrogate model was constructed by synthesizing each kind of critical injury value to the human body. Combined with NSGA-II multi-objective genetic algorithm, the structural performance parameters of the restraint system were optimized and matched. Results showed that the optimal protection matching parameters of the restraint system were 4933.5 N−2499.9 N−16 ms−15.3 ms−0.5 (A−B−C−D−E). Finally, the best matching parameters were input into the accident model for verification. After optimization, the WIC and Nij of drivers were reduced by 37.9% and 45.3%, respectively. The results show that the optimized restraint system can protect the driver the most.

Structural Stability Analysis of Steel Tubular Scaffold with Couplers Based on Direct Analysis Method

Structural Stability Analysis of Steel Tubular Scaffold with Couplers Based on Direct Analysis Method

Development of a derivatization RP-HPLC method for determination of sulfuryl chloride in chlorosulfonic acid for gefapixant citrate manufacture

Control of process impurities during manufacturing of drug substance is critical to ensure quality and process robustness. During commercial process development for the gefapixant citrate drug substance, several process impurities were found to derive from sulfuryl chloride, an impurity in the raw material, chlorosulfonic acid (CSA). This made controlling the CSA quality essential for commercial production of this drug substance. Various direct analysis methods were evaluated and found unsuitable because of the highly reactive nature and structural similarity of sulfuryl chloride and CSA. Therefore, a robust derivatization reversed-phase high performance liquid chromatography (RP-HPLC) method was developed and validated to accurately quantify sulfuryl chloride in CSA. The derivatization method was utilized to evaluate many CSA batches from different commercial suppliers and to establish a correlation between sulfuryl chloride levels in CSA and the levels of process impurities in downstream materials. The methodology described herein informed the development of setting the specification on sulfuryl chloride for CSA to ensure a robust process for manufacturing high-quality gefapixant citrate drug substance. The derivatization method was successfully validated and transferred to the commercial commodity supplier for release testing of CSA as a raw material for gefapixant citrate commercial campaigns.

Rapid Identification of 44 Steroids in Human Urine Samples using HPLCESI- QTOF-MS

Objective: Detailed analysis of un-processed and un-derivatized free and conjugated urinary steroids is useful to avoid miscalculations and to diagnose sports doping and adrenal problems, including abnormal steroidogenesis, congenital deficiency of related enzymes, cancer, and other disease conditions. Hence, the present study was conducted to develop a soft ionization method to identify the maximum number of urinary steroids using ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometer (HPLC–Q-TOF-MS). Material and Methods: HPLC–Q-TOF-MS was carried out for the qualitative detection of steroids and their conjugates in urine samples. The method provides high sensitivity and fast analysis of steroids and their glucuronides without hydrolysis or sample preparation or extraction of steroids. Results: Using the method, 44 steroids belonging to C-18, C-19, and C-21 classes and their conjugates were resolved and identified using positive and negative modes of ionizations by their characteristic ionization and collision energy induced dissociation behaviors. Conclusion: The method is time-saving and good to compare samples from different peoples with control or healthy ones as it does not require any kind of pre-treatment or sample processing. It provides a complete picture of steroids metabolism and catabolism. It can be good for doping control or to explore the effects of other drugs. However, in qualitative analysis, one may miss the significant information unless direct methods of steroids analysis to be employed.

Assessment of Cytotoxicity and Genotoxicity Potential of Effluents from Bahir Dar Tannery Using Allium cepa

Tannery effluent plays a significant role in increasing pollution in the environment; in particular, it contains toxic heavy metals which cause toxic effects on plant genetic materials. Among tannery effluent chemicals, chromium and lead have cytotoxicity and genotoxicity potentials on Allium cepa. This investigation was undertaken to assess the physicochemical properties of tannery wastewater and their effect on the genetic materials of A. cepa. Effluent’s physicochemical characteristics were investigated using digital instruments for direct measurement and standard methods of atomic absorption spectrophotometer colorimetric analysis. A series of six onion bulbs were grown in 0%, 20%, 40%, 60%, 80%, and 100% concentrations of wastewater (v/v) ratio, and root tips from each onion bulb were cut and processed for analysis by aceto-orcein squash technique. Most of effluent components were above the discharge limit standards set by Federal Environmental Protection Agency and Ethiopian Environmental Protection Authority. The cytotoxicity effect on the root growth showed a significant reduction at high concentration. Simple regression analysis showed that the results of mitotic index were statistically significant (P < 0.05) in different concentrations. A decrease in mitotic index with increasing concentration of the effluent was observed. The effluent had induced chromosomal abnormalities such as laggard, fragmentation, stickiness, bridge, micronucleus, and binucleated and morphologically changed nuclei in A. cepa root cells among others. The results showed that cytotoxicity, genotoxicity, and chromosomal aberrations were induced by the tannery effluent. Industries shall think of biological waste treatment methods.

Comparative Study of Direct Analysis Method and Effective Length Method on Structural Steel Piperack Using STAAD Pro V8i Software

Stability analysis is one of the most important aspects in the design of steel structures, including structural steel piperack. Based on AISC 360-16, there are two recommendation of stability analysis method, that is DM (Direct Analysis Method) and ELM (Effective Length Method). Since AISC 360-10, the DM method is used as the main method of structural stability analysis instead of the ELM method. The ELM method was not eliminated but was changed to an alternative method. The DM and ELM are two different stability analysis methods. The DM is a stability analysis based on second order elastic analysis, while ELM is a stability analysis based on elastic linear analysis. In this study, the two stability analysis methods will be compared to the structural design of the SPRK-22 (subpiperack-22) in the Jambaran-Tiung Biru project, Bojonegoro, East Java, Indonesia. The dimention of SPRK-22 is 54 m long and 6 m wide, and 12,75 m high. In addition, there is a loop structure with a length is 3 meters, a width is 6 m and a height is 9,75 m. The results of the analysis compared between the two methods are the ratio of structural members, beam deflection, column drift due to wind and column drift due to seismic. Based on the results of the analysis using the STAAD Pro V8i software, the DM produces a more conservative structure. The DM resulted in a ratio of 1,04% greater structural member, beam deflection 24,5% greater, column drift due to wind 9% greater and column drift due to seismic 26% greater than the ELM method.

Sustainability Performance of Green Building Rating Systems (GBRSs) in an Integration Model

In most countries, more than one green building rating system (GBRS) is available on the market. Because of their different approaches, it is difficult to confirm which system can respond to sustainability requirements better. A building considered to be “green” by one Green Building Council (GBC) may fail to satisfy the requirements set by another council. The aim of this study is to evaluate the sustainability performance of GBRSs and establish an integrated model of multi-certification for optimal sustainability. A direct content analysis method was utilized to evaluate GBRSs’ qualitative performance using the ISO sustainable building standards. In this study, seven purposively selected multi-certified buildings were evaluated, and an integrated model was proposed as a better mechanism for the multi-certification process. The proposed integrated model contributes to the achievement of sustainability indicators. The model was implemented on case study buildings, and the proposed combination shows better sustainability performance than existing practice. The developed model helps practitioners in their selection of GBRSs in the multi-certification process. In addition, the performance evaluation of GBRSs will support the future update of GBRSs. The qualitative performance evaluation was performed considering mandatory requirements and prerequisite and credit requirements of selected rating systems, making the work a stronger approach than previous studies.

Application of a Fourier Transform Infrared (FTIR) Principal Component Regression (PCR) Chemometric Method for the Quantification of Respirable Crystalline Silica (Quartz), Kaolinite, and Coal in Coal Mine Dusts from Australia, UK, and South Africa.

This article describes the approach used to assess the performance of a Fourier transform infrared (FTIR) and principal component regression (PCR) chemometric method when measuring respirable quartz, kaolinite, and coal in samples from a variety of mines from different countries; relative to target assigned values determined using X-ray diffraction (XRD). For comparison, FTIR results using the partial least squares regression (PLSR) method are also available. Bulk dusts from 10 Australian mines were scanned using XRD and grouped into three sets based on the levels of quartz, kaolinite, and feldspar within their crystalline mineral composition. Prediction samples were generated from 5 of these Australian mine dusts, Durrans coal dust, 2 mine dusts from the UK, and a single South African mine dust (71 samples in total) by collecting the aerosolized respirable dust onto 25-mm diameter polyvinylchloride filters using the Safety in Mines Personal Dust Sampler (SIMPEDS) operating at 2.2 l min-1. The predicted values from the FTIR chemometric methods were compared with assigned target values determined using a direct on-aerosol filter XRD analysis method described in Method for the Determination of Hazardous Substances (MDHS) 101. Limits of detection (LOD) and uncertainty values for each analyte were calculated from a linear regression between target and predicted values. The uncertainty was determined using the calibration uncertainty equation for an unweighted regression. FTIR results from PCR and PLSR are very similar. For the PCR method, the LOD for quartz, kaolinite, and coal were 5, 25, and 71 µg, respectively. For quartz, an LOD of 5 µg corresponds to an airborne quartz concentration of 10 µg m-3, assuming a 4-h sampling time and collection flow rate of 2.2 l min-1. The FTIR measurement met the expected performance criteria outlined in ISO 20581 when sampling quartz for more than 4 h using a flow rate of 2.2 l min-1 at a concentration of 0.1 mg m-3 (100 µg m-3), the current workplace exposure limit in Great Britain. This method met the same performance criteria when measuring exposures at the Australian Workplace Exposure Standard (WES) concentration of 0.05 mg m-3, although in this case a sampling period greater than 8 h was needed.

Gold in pyrites and sulfides by scintillation analysis

The method of scintillation atomic emission spectrometry (SAES) allows determination of the form of the element present in the sample and the size of inclusions in addition to the total content of the element in the direct analysis of powder samples. The aim of the work is to verify the expedience of using the direct method of analysis of individual gold particles in studying the possible forms of gold appearance in pyrites and sulfides, including the so-called «invisible» finely divided gold. The measurements were carried out both on individual pyrite single crystals, and on the samples of sulfide gold and brown coal deposits of Kazakhstan. The studies were carried out on a Grand-Potok complex (VMK Optoelektronika, Ltd.) equipped with a laser ablation system and a system for injection of aqueous solutions and aerosols samples. The samples of pyrite crystals of various sizes were analyzed to determine the content and speciation of gold in the samples. No dependence of the gold content on the crystal size was noted for all the studied pyrites. It is shown that gold and other precious metals are concentrated in the surface layers of pyrite crystals and in crystal lattice defects in the bulk of the crystal (according to SAES data during laser ablation of the sample in an arc discharge). The total content of gold in the bulk of pyrite crystals is about 2 g/ton, platinum and silver is less than 0.02 g/ton, while the content of Au, Ag, Pt on the surface ranges from 2 to 5 g/ton. The detection limit of gold determination by the SAES method is 0.01 g/ton. The SAES method can be used for determination of the gold speciation in pyrites and sulfides (finely dispersed, individual particles up to 1 μm or even less).

Robustness guarantees for structured model reduction of dynamical systems with applications to biomolecular models

AbstractModel reduction methods usually focus on the error performance analysis; however, in presence of uncertainties, it is important to analyze the robustness properties of the error in model reduction as well. This problem is particularly relevant for engineered biological systems that need to function in a largely unknown and uncertain environment. We give robustness guarantees for structured model reduction of linear and nonlinear dynamical systems under parametric uncertainties. We consider a model reduction problem where the states in the reduced model are a strict subset of the states of the full model, and the dynamics for all of the other states are collapsed to zero (similar to quasi‐steady‐state approximation). We show two approaches to compute a robustness guarantee metric for any such model reduction—a direct linear analysis method for linear dynamics and a sensitivity analysis based approach that also works for nonlinear dynamics. Using the robustness guarantees with an error metric and an input‐output mapping metric, we propose an automated model reduction method to determine the best possible reduced model for a given detailed system model. We apply our method for the (1) design space exploration of a gene expression system that leads to a new mathematical model that accounts for the limited resources in the system and (2) model reduction of a population control circuit in bacterial cells.

A stiffness reduction method for the in-plane design of stainless steel members and frames according with EN 1993-1-4

Current design standards for stainless steel such as ASCE 8-02 and EN 1993-1-4 prescribe provisions for the design of cross-sections and members that account for material nonlinearities and strain hardening, although these features are not considered in the global design of structures. Recent studies have highlighted the need of accounting for material nonlinearities in order to design efficient and safe stainless steel structures, and it is expected that the forthcoming versions of the standards will incorporate updated rules for the global design of these structures. To contribute to this field, this paper presents a Stiffness Reduction Method (SRM) for the in-plane design of stainless steel members and frames with stocky sections based on the prescriptions given in the next version of EN 1993-1-4. The proposed approach predicts the ultimate capacity and internal forces in stainless steel structures by performing a second-order elastic analysis in which the stiffnesses of the members are reduced by a set of factors defined in this paper to account for the effect of the spread of plasticity, residual stresses and member imperfections. The accuracy of the presented method is assessed for individual stainless steel structural members (columns, beams, and beam-columns) with different cross-sections and material properties, and for austenitic stainless steel portal frames, against numerical results obtained from nonlinear analyses conducted on finite element models. A comparison between the proposed approach and the Direct Analysis Method prescribed in the upcoming AISC 370 Specification is also provided, showing that the results are comparable in the two approaches.

Stability Design of Stainless Steel Structures

AbstractThe direct analysis method (DAM), featuring second-order elastic analysis with two stiffness reduction factors (τb and τg), is the primary means of stability design for steel structures in ...

Strontium isotopic analysis of environmental microsamples by inductively coupled plasma – tandem mass spectrometry

A method for direct (without chromatographic Rb/Sr separation) Sr isotopic analysis using tandem ICP-MS has been optimized for small-size environmental samples and applied to Antarctic PM10 and soil samples from South America and Australia as proof-of-concept.

Real Power Modulation Strategies for Transient Stability Control

Transient stability control of power systems is based on actions that are taken automatically following a disturbance to ensure that the system remains in synchronism. Examples of such measures include generator rejection and the insertion of dynamic braking resistors. Methods like these are designed to rapidly absorb excess energy or otherwise alter the generation-demand balance at key points in the system. While these methods are often effective, they lack the ability to inject real power to compensate for a deficit. Utility-scale inverter-based resources, particularly energy storage systems, enable bidirectional modulation of real power with the bandwidth necessary to provide synchronizing torque. These resources, and the control strategies they enable, have garnered substantial research interest. This paper provides a critical review of research on real power modulation strategies for transient stability control. The design of these control strategies is heavily informed by the methods used to assess changes in the transient stability margins. Rigorously assessing these changes is difficult because the dynamics of large-scale power systems are inherently nonlinear. The well-known equal-area criterion is physically intuitive, but conceptual extensions are necessary for multi-machine systems. So-called direct methods of transient stability analysis offer a more general alternative; however, these methods require many simplifying assumptions and have difficulty incorporating detailed system dynamics. In this paper, we discuss data-driven methods for offline stability assessment based on Koopman operator theory.

Comparison of non-destructive techniques and conventionally used spectrometric techniques for determination of elements in plant samples (coniferous leaves)

Conventionally used spectrometric techniques of inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma optical emission spectrometry (ICP-MS) usually involve time-consuming sample preparation procedure of a sample dissolution which requires the usage of aggressive and toxic chemicals. The need for suitable and sustainable analytical methods for direct multi-elemental analysis of plant samples has been increased in recent years. Spectrometric techniques for direct sample analysis, instrumental neutron activation analysis (INAA) and X-ray fluorescence (XRF) have been applied in environmental studies and various fields of screening tests. Nevertheless, these techniques are not commonly used for plant sample analysis and their performances need to be evaluated. This research aimed to assess how reliable non-destructive techniques are in the determination of elements in plants compared to conventionally used spectrometric techniques. A total of 49 plant samples of four conifer species (Pinus nigra, Abies alba, Taxus baccata and Larix decidua) were measured using two conventionally applied (ICP-MS, ICP-OES) and two non-destructive techniques (wavelength dispersive XRF (WD-XRF), INAA). The comparison was performed by investigation of relative ratios of concentrations and by correlation analysis. Moreover, precision of the techniques was examined and compared. The quality control included analysis of NIST pine needles certified reference material (1575a) using all examined techniques. Our results suggest that additional analytical and quality control steps are necessary for reaching the highest accuracy of multi-elemental analysis.

Impact of Patient Engagement on Healthcare Quality: A Scoping Review.

Patient engagement (PE) is a well-known strategy introduced and implemented by pharmaceutical and medical device companies for patient compliance and adherence to treatment protocols during clinical trials and care processes. This can affect a wider range of outcomes such as the quality of treatment decisions and quality of care outcomes. Few studies have paid attention to it. The involvement of patient is one of the crucial stakeholders of health care in their treatment that makes controversial opinions about the potential outcomes of their engagement in various aspects of healthcare. This scoping review was conducted in 2022 to collect the results of PE. The search was performed in the MEDLINE and Web of Sciences databases. The selected documents were categorized and reported by the direct content analysis method. Out of 3974 published documents, 17 articles were selected. Findings are categorized into 4 groups: (1) Health outcome, (2) patient compliance, (3) self-efficiency, and (4) return on investment. PE can improve both treatment outcomes and consequently patient satisfaction and health, as well as the productivity of the service provider. However, increasing self-care and patient adherence are among the positive effects of this engagement on the patient, and return on investment is still a challenge for PE.

Development of direct analysis method of conductivity by local electric field measurement

Recently, micro- and nanofluidics devices such as MEMS/NEMS and μ-TAS have attracted much attention. However, several unknowns have been remained in micro- and nanoscale transport phenomena unlike microscopic scale. In order to deepen understanding of such micro- and nanoscale phenomena, it is essential to develop a novel technique to measuer the small spaces. In this study, a localized and direct measurement method of electric fields is established by using a test section with a charcteristic length of 1 mm and a glass microelectrode. Using a KCl standard solution ranging from 0.56 to 100 mmol/L as a sample, the conductivity is successfully evaluated with a measurement error of less than 15%.

Using the Effect of Compression Stress in Fatigue Analysis of the Roller Bearing for Bimodal Stress Histories.

A new approach based on the direct spectral method for fatigue analysis of elements subjected to bimodal stress histories, including high compression effects, is proposed. A correction factor, taking into account the influence of the mean compressive stresses, is used in the proposed method. Equivalent amplitude is estimated, based on criteria proposed by Smith, Watson, and Tooper, and by Bergmann and Seeger. The method is presented with example of a thrust roller bearing. Two cases in which the rollers were subjected to constant force 206 N (where constant amplitude stresses occurred in the rollers) and cyclic force (where bimodal stresses with variable amplitudes occurred in the rollers) are studied. It is observed that multiaxial fatigue criteria (Crossland, Papadopoulos) do not include the influence of bimodal stresses and should not be used for such loading conditions. The proposed method includes both kinds of stress waveforms in the fatigue analysis and can be applied for the accurate identification of stress components and the determination of fatigue life. The damage rate calculated by the proposed approach for rollers subjected to a cyclic force (equivalent load equal to 151 N) was 0.86, which is in good agreement with the recommendations provided in the literature. The obtained accuracy of the proposed method is above 95%.