Smoothness Index Research Articles

Perancangan Efisiensi Lintasan Produksi dengan Menggunakan Metode Helgeson-Birnie (Ranked Positional Weight) Untuk Meningkatkan Kapasitas Produksi (Studi Kasus Pada Unit Produksi I Shift I PT. SUMBETRI MEGAH)

The problem of line balancing in industry, assembling, and manufacturing often occurs. This is indicated by a relatively high bottleneck of work in process at several stations, resulting in non-optimal line efficiency and non-smooth process flow. This study aims to calculate line balancing and determine the division of work stations that can increase production capacity in the production unit I shift I pt. Magnificent resource. This study used the Helgeson-Birnie (Ranked Positional Weight) method. From this research, the design results were obtained with line efficiency (line efficiency) 89.16%, idle time 2730.85, balance delay 10.84%, smoothness index (smoothness index) 781.24, and the number of work stations 15. Based on the calculation, it can be seen that there is an increase in line efficiency from 74.46% to 89.35%, which is 14.89%.

Generalized Gini indices: Complementary sparsity measures to Box-Cox sparsity measures for machine condition monitoring

Sparsity measures that can quantify the sparsity of signals are often used as objective functions of signal processing and machine learning algorithms (e.g., sparse filtering, compressive sensing, blind deconvolution, and the fast Kurtogram, etc.). Classic sparsity measures include kurtosis, Gini index, negative entropy, the ratio of Lp norm to Lq norm, smoothness index, L1 norm, L0 norm, etc. To enrich the library of sparsity measures, this paper aims to generalize a classic Gini index to construct generalized Gini indices (GGIs). Firstly, inspired by the ratio of different quasi-arithmetic means, investigations on the GGIs showed that the GGIs satisfy all six properties of good sparsity measures. The GGIs only have one parameter a⩾0. When a=1, the GGIs are reduced to the classic Gini index. Secondly, investigations reveal that: (1) the GGIs can monotonically quantify the sparsity changes of Bernoulli coefficients. Sparsity quantification curves given by the GGIs are complementary to those generated by our recently proposed Box-Cox sparsity measures (BCSMs). Especially, when the unique parameters of the GGIs and the BCSMs are equal to zero, these sparsity quantification curves of the GGIs and BCSMs are reduced to that of negative entropy; (2) the GGIs are convergent with an increase of signal lengths; (3) when the squared envelope of white Gaussian noise is quantified by the GGIs, theoretical values of the GGIs are derived as a/(a+1), which can be used as baselines for machine abnormality detection. At last, two bearing run-to-failure datasets are used to validate the effectiveness of the GGIs for machine condition monitoring and their results showed that the GGIs are effective in detecting incipient faults and indicating informative frequency bands. In future, the proposed GGIs can be used in any algorithms that need sparsity measures.

Investigation into the effect of resin finish on the functional characteristics of plain fabrics using different curing methods

PurposeCellulosic fabric and plain weave are the most commonly used material in home textiles. The poor wrinkling, dimensional stability and pilling are some of the problems faced during usage. The textile industries apply resin finish to improve these characteristics. The purpose of this study is to improve pilling resistance, dimensional stability and smoothness appearance (SA) of rayon and rayon/cotton plain fabrics using different concentrations of dimethyloldihydroxyethylene urea (DMDHEU) and acrylic copolymer. The finish was fixed using two different fixation methods.Design/methodology/approachThree concentrations, 40, 100 and 150 g/l of Arkofix NF (DMDHE based) and Appretan N9211 (acrylic copolymer), were taken. The finish was applied at normal and shock cure. The effects of finish on pilling resistance, dimensional stability, smoothness, tear strength, light fastness, Berger whiteness and yellowness index of plain fabrics were investigated.FindingsThe changes in the characteristics of the finished fabrics were compared with unfinished fabrics. This study revealed that at 40 g/l of Arkofix NF and Appretan N9211 using a normal cure would improve the pilling resistance, dimensional stability and SA of the plain fabrics. Whereas, there was no adverse effect observed on tear strength, light fastness, Berger whiteness and yellowness index of plain fabrics at these conditions.Originality/valueUnlike the previous studies, this paper proposed the single finish formulation where the functional characteristics of the plain rayon and rayon cotton fabrics meet the general requirement of a customer.

Valorification of Ulva rigida Algae in Pulp and Paper Industry for Improved Paper Characteristics and Wastewater Heavy Metal Filtration

This paper presents preliminary results on the possibility of incorporating stranded macroalgae into the papermaking process; analyses of the physical-mechanical properties of filter paper, with the addition of stranded macrophytic marine algae from Ulva rigida species obtained previously; results of SEM–EDX analyses of filter paper samples; and results obtained from the filtration of a wastewater from the metallurgical industry, using the improved filter paper samples. In the filter paper recipe, stranded macrophytic seaweed of the species Ulva rigida was added at different percentages of 0.5%, 1%, 2%, 4% and 8%, and the addition was calculated in relation to the absolute dry material. The physicomechanical properties analyzed are grammage, thickness, density, moisture, ash content, breaking load, breaking length, tear resistance, bursting resistance, folding endurance, porosity, smoothness, water absorption and Cobb60 index. Additional information related to the homogeneity of the distribution of elements in the paper mass was obtained by scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDX). The addition of macroalgae to the paper mass improved the strength characteristics of the paper, such as breaking load, breaking length, tearing resistance, folding endurance and water absorption. Following industrial wastewater filtration using filter paper with added seaweed, positive results were obtained in terms of reduction of total Cr, Cu, total Fe and Zn concentrations.

Early Percutaneous Vertebroplasty Improves Bone-Cement Integration and Reduces Adjacent Fractures

Percutaneous vertebroplasty (PVP) is widely used for treatment of osteoporotic vertebral compression fractures (VCFs). However, the influence of PVP timing (early vs. late) on development of adjacent vertebral fractures has rarely been discussed. This retrospective cohort study aimed to evaluate bone-cement binding for thoracolumbar fractures (T8-L3) using a new assessment method to predict risk for adjacent vertebral fractures. Patients with a single-level T-score ≤-1.0 of lumbar bone mineral density and a primary osteoporotic VCF in the thoracolumbar region (T8-L3) who underwent PVP from October 2016 to February 2018 at our medical university-affiliated hospital were included. Patients were divided into refracture and non-refracture groups. All patients underwent computed tomography after vertebroplasty. Bone-cement distribution patterns were evaluated using standardized axial computed tomography images of each cemented vertebra by 4 independent observers with ImageJ software. The smoothness index was calculated as a percentage of smooth margins. Of 51 VCFs, 15 (29.4%) and 36 (70.6%) were refracture and non-refracture VCFs, respectively. The mean smoothness index (MSI) was higher in the refracture group than in the non-refracture group (P < 0.01), with an increased refracture risk that corresponded to increased MSI values (P= 0.004). Spearman correlation coefficient (0.375) showed a positive correlation between the fracture-vertebroplasty interval and MSI (P= 0.01). Axial computed tomography images were used to characterize bone-cement binding properties. Patients who underwent early PVP had a lower MSI, better bone-cement integration, and fewer adjacent fractures.

INCREASING UTILIZATION OF PRODUCTION MACHINERY THROUGH LINE BALANCING APPROACH (CASE STUDY ON PHARMACEUTICAL INDUSTRY)

The growth in sales volume of unbranded generic products (considering that drugs served by BPJS Kesehatan refer to the National Formulary and e-catalogs set by the government) has led to a decline in margins as price competition intensifies. The purpose of this research is to optimize the utilization and efficiency of the machine, increase productivity and balance the line. Improvements are made by following the ECRS (Eliminating, Combining, Rearranging, and Simplify) based line balancing concept. From the improvements that have been made to the granulation process, it was found that the time of the wet mixing process, wet sieving, drying, and dry sieving had decreased. Cycle time decreased, output increase, the total granulation process time “Product F” decreased. Line efficiency increased, balance delay decreased and smoothness index decreased. This shows that the granulation line is getting more balanced

Improved VMD-FRFT based on initial center frequency for early fault diagnosis of rolling element bearing

The extraction of weak fault signatures with periodic impulse characteristics is a crucial aspect of detecting an early fault of bearing. In order to suppress the interference of background noise to the weak fault signatures extraction by variational mode decomposition (VMD), some scholars recently proposed to use fractional Fourier transform (FRFT) to make the weak fault signatures concentrate more energy in the narrowband, which is called VMD-FRFT. Nevertheless, VMD-FRFT is more sensitive to the initial center frequency (ICF) than VMD according to our study, which will make it derive undesirable mode components due to unreasonable ICFs. Inspired by the resonant demodulation method to find the appropriate frequency band for demodulation, an improved VMD-FRFT with the guidance of ICF is proposed, which is to take the center frequencies corresponding to K selected frequency bands as the initial values of VMD-FRFT. Hence, the modal components hidden in multiple resonant frequency bands can be obtained in terms of performing iterative optimization. In this paper, a novel indicator named reciprocal of spectral autocorrelation smoothness index being sensitive to the periodic impulses is introduced to detect resonance frequency bands. Both simulated and experimental examples are used to verify the proposed method. The results show that the proposed method can effectively identify weak faults and detect bearing faults at an earlier time than other methods such as Infogram, reciprocal of spectral smoothness index and improved VMD.

Wrapping Deployment Simulation Analysis of Leaf-Inspired Membrane Structures

Deployable membrane structures have received wide attention in many engineering applications, such as the military, aerospace, and aviation. Their properties of light weight and high storage ratio meet the requirements for aerospace exactly. In this paper, the wrapping deployment of membrane structures inspired by leaves are simulation-analyzed for prospective improvement. Three leaf-inspired patterns are investigated and discussed from the corresponding paper-craft design principles and deployment process perspectives. The deployment performance evaluation system according to the factors effecting working performance including maximum stress, driving force, maximum strain energy, smoothness index, and maximum folding height is established based on the results of the simulation analysis. Then, a comparison between the three patterns is carried out based on the deployment performance evaluation system. Moreover, it is found that adding creases reduces the folded height but the development performance gets worse. There is a balance between the folding ratio and development performance when the additional creases are added. The results can provide useful suggestions for designing wrapping deployment structures.

Quasi-optimal Nonconforming Approximation of Elliptic PDEs with Contrasted Coefficients and $$H^{1+{r}}$$, $${r}&gt;0$$, Regularity

In this paper, we investigate the approximation of a diffusion model problem with contrasted diffusivity for various nonconforming approximation methods. The essential difficulty is that the Sobolev smoothness index of the exact solution may be just barely larger than 1. The lack of smoothness is handled by giving a weak meaning to the normal derivative of the exact solution at the mesh faces. We derive robust and quasi-optimal error estimates. Quasi-optimality means that the approximation error is bounded, up to a generic constant, by the best approximation error in the discrete trial space, and robustness means that the generic constant is independent of the diffusivity contrast. The error estimates use a mesh-dependent norm that is equivalent, at the discrete level, to the energy norm and that remains bounded as long as the exact solution has a Sobolev index strictly larger than 1. Finally, we briefly show how the analysis can be extended to the Maxwell’s equations.

Compilation method of CNC lathe cutting force spectrum based on kernel density estimation of G-SCE

The cutting force spectrum of the CNC lathe is the basic data for the reliability design, reliability test, and reliability evaluation of the CNC lathe and its components. Due to the complex and changeable turning conditions and different cutting processes, the cutting load presents multi-peak characteristics. At the same time, grouping the counted load cycles when parameter modeling will produce certain errors. As a result, the parameter distribution model cannot meet the modeling requirements. Thus, a compilation method based on kernel density estimation (KDE) of goodness-smoothness comprehensive evaluation (G-SCE) is proposed. The KDE is used to establish the dynamic cutting force distribution of the CNC lathe in which grouping the counted load cycles is not needed. For the bandwidth-determining methods, the rule of thumb method (ROT) and the least-squares cross-validation method (LCV) do not take into account the influence of different bandwidths on the goodness estimation and the smoothness of the estimated curve, and the G-CSE for KDE is proposed to determining the optimal bandwidth. It includes the estimation accuracy test method based on multiple goodness-of-fit tests and the smoothness test method based on the envelope curve, and the entropy method is used to comprehensively weights the estimated goodness index and the smoothness index to determine the optimal bandwidth. The results of the case analysis indicate that the method proposed can solve the problem of too large estimation error of parameter distribution for multimodal distribution. At the same time, it can better comprehensively evaluate the KDE under different bandwidths. In short, a new method of optimal bandwidth selection is proposed in the original method.

Twenty-four-hour and office blood pressure measurement in a comprehensive assessment of the effectiveness of 12-week therapy with a triple fixed-dose combination of amlodipine/indapamide/perindopril in hypertensive patients in actual clinical practice

Aim. To study the efficacy and safety of the triple fixed-dose combination (FDC) of amlodipine/indapamide/perindopril on blood pressure (BP) profile in patients with grade I-II hypertension (HTN) in actual clinical practice.Material and methods. Data from 54 patients with paired 24-hour ambulatory BP monitoring (ABPM) data were included in the TRICOLOR subanalysis (ClinicalTrials. gov study ID — NCT03722524). The mean 24-hour, daytime, and nighttime BP were calculated at baseline and after 12-week follow-up. We determined the proportion of patients with nocturnal HTN (≥120/70 mm Hg) and nocturnal hypotension (&lt;100/60 and &lt;90/50 mm Hg) initially and after 12 weeks of triple FDC therapy. Patients with nocturnal BP decrease included dippers (D; 10-20%), reduced dippers (RD; 0-10%) and extreme dippers (ED; &gt;20%), as well as those without nocturnal BP decrease (&gt;0%, non-dipper (ND)). The smoothness index (SI) was analyzed as the ratio of the mean hourly SBP fall to its mean standard deviation in paired ABPM. To assess the BP phenotypes, two methods were used with reference values of &lt;130/80 and &lt;140/90 mm Hg for ABPM and office BP, respectively. Controlled hypertension (CHT), uncontrolled hypertension (UHT), white coat hypertension (WHT) and masked ineffectiveness of antihypertensive therapy were distinguished.Results. Among 1247 participants of the TRICOLOR study, 54 patients with valid paired ABPM were selected (men, 46%; mean age, 57,7 [12,1] years; mean office BP, 150,4 [16,6]/93,3 [10,7] mm Hg; HTN duration, 8,3 [7,5] years). Initially, the mean 24-hour, daytime and nighttime BP was 141,1 [15,4]/85,9 [9,9], 144,2 [15,5]/88,8 [10,5] and 132,6 [18,0]/78,1 [9,9] mm Hg, respectively. After 12-week follow-up, the mean 24-hour, daytime and nighttime BP was 123,1 [10,5]/75,6 [8,5], 125,7 [10,9]/77,9 [8,7] and 115,4 [10,2]/68,6 [8,8] mm Hg, respectively (p&lt;0,001). After 12-week follow-up, the proportion of patients with nocturnal hypertension decreased from 64,8% to 25,0% (2,6 times) (p&lt;0,001). The proportion of NDs and EDs decreased from 16,7% and 7,4% to 5,8% and 0%, respectively (p=0,048); the proportion of patients with RD and D patterns increased from 42,6% and 33,3 to 57,7% and 36,5%, respectively (p=0,048). With triple FDC therapy, the SI during the day was higher than 0,73 in half of the cases. According to the two methods, the proportion of patients with UHT decreased from 81,6% to 4,4%, WHT from 12,2% to 0%. The prevalence of CHT increased from 4,1% to 57,8%, while masked ineffectiveness of antihypertensive therapy — from 2,0% to 37,8%.Conclusion. Twelve-week FDC therapy of amlodipine/indapamide/perindopril led to a significant fall in the mean 24-hour, daytime and nighttime BP values. Comprehensive analysis of two techniques (24-hour and office BP measurement) identified patients requiring further triple FGC titration.

Exact solution approaches for the workload smoothing in assembly lines

In this paper, the problem of minimizing the smoothness index for an assembly line given a fixed cycle time and the number of workstations is studied. This problem which is known as the workload smoothing line balancing problem (WSLBP) is a mixed-integer quadratic programming problem. Until recently, this problem has only been tackled using heuristic approaches. Recently, there have been some attempts to solve this problem exactly using mixed-integer linear programming (MILP). The MILP formulations, however, are not usually capable of solving large size problem instances. In this paper, the aim is to solve the WSLBP using mathematical programming formulations by using off-the-shelf solvers. Differently from the literature some non-MILP formulations are also considered for the problem. For this purpose, three MILP formulations, one from the literature, and two non-MILP formulations are compared. The two non-MILP formulations include a mixed-integer second order cone programming formulation and a constraint programming model. The superiority of the non-MILP formulations over the considered MILP formulations is experimentally shown.

Genetic variants of GRK4 influence circadian rhythm of blood pressure and response to candesartan in hypertensive patients

ABSTRACT Background: Genetic variants of coding genes related to blood pressure regulation participate in the pathogenesis of hypertension and determines the response to specific antihypertensive drugs. G protein-coupled receptor kinase 4 (GRK4) and its variants are of great importance in pathogenesis of hypertension. However, little is known about role of GRK4 variants in determine circadian rhythm of blood pressure and response to candesartan in hypertension. The aim of this study was to analyze the correlation of GRK4 variants and circadian rhythm of blood pressure, and to explore their effect on antihypertensive efficiency of candestartan. Methods: In this study, a total of 1239 cases were eligible, completed ambulatory blood pressure monitoring (ABPm) observation and exon sequencing of G protein-coupled receptor kinase 4 (GRK4). ABPm was obtained before and after 4-week treatment of candesartan. Diurnal variation of systolic blood pressure and antihypertensive effect of candesartan were then assessed. Results: Compared to GRK4 wild type (GRK4-WT), patients with GRK4 variants were more likely to be non-dippers (odds ratio (OR) 6.672, 95% confidence interval (CI) 5.124–8.688, P < .001), with GRK4 A142V (OR 5.888, 95% CI 4.332–8.003, P < .001), A486V (OR 7.102, 95% CI 5.334–9.455, P < .001) and GRK4 R65L (OR 3.273, 95% CI 2.271–4.718, P < .001), respectively. Correlation analysis revealed that non-dippers rhythm of blood pressure were associated with GRK4 variants (r = .420, P < .001), with GRK4 A142V (r = .416, P < .001), A486V (r = .465, P < .001) and GRK4 R65L (r = .266, P < .001), respectively. When given 4-week candesartan, patients with GRK4 variants showed better antihypertensive effect as to drop in blood pressure (24 h mSBP, 21.21 ± 4.99 vs 12.34 ± 4.78 mmHg, P < .001) and morning peak (MP-SBP, 16.54 ± 4.37 vs 11.52 ± 4.14 mmHg, P < .001), as well as greater increase in trough to peak ratio (SBP-T/P, .71 ± .07 vs .58 ± .07, P < .001) and smoothness index (SBP-SI, 1.44 ± .16 vs 1.17 ± .11, P < .001) than those with GRK4 WT. Conclusion: This study indicates that hypertensive patients with GRK4 variants are more likely to be non-dippers. What’s more, patients with GRK4 variants possess a significantly better antihypertensive response to candesartan than those with GRK4 WT.

Automated measurement of iris surface smoothness using anterior segment optical coherence tomography

Fuchs uveitis (FU) is a chronic and often unilateral ocular inflammation and characteristic iris atrophic changes, other than heterochromia, are common in FU and are key to the correct diagnosis in many cases. With the advent of anterior segment optical coherence tomography (AS-OCT), some investigators attempted to quantitatively study these atrophic changes; mostly by introducing various methods to measure iris thickness in AS-OCT images. We aimed to present an automated method in an observational case series to measure the smoothness index (SI) of the iris surface in AS-OCT images. The ratio of the length of the straight line connecting the most peripheral and central points of the anterior iris border (in nasal and temporal sides) to the actual length of this border on AS-OCT images, was defined as SI. In a uveitis referral center, twenty-two eyes of 11 patients with unilateral Fuchs uveitis (FU) (7 female) and 22 eyes of 11 healthy control subjects underwent AS-OCT imaging. Image J and a newly developed MATLAB algorithm were used for manual and automated SI measurements, respectively. Agreement between manual and automated measurements was evaluated with Bland–Altman analysis and interclass correlation coefficient. The inter-eye difference of SI was compared between the FU group and the control group. Automated mean overall SI was 0.868 ± 0.037 and 0.840 ± 0.039 in FU and healthy fellow eyes, respectively (estimated mean difference = − 0.028, 95% CI [− 0.038, − 0.018], p < 0.001). Bland- Altman plots showed good agreement between two methods in both healthy and FU eyes. The interclass correlation coefficient between the manual and automated measurements in the FU and healthy fellow eyes was 0.958 and 0.964, respectively. The inter-eye difference of overall SI was 0.029 ± 0.015 and 0.012 ± 0.008 in FU group and control group, respectively (p = 0.01). We concluded that the automated algorithm can rapidly and conveniently measure SI with results comparable to the manual method.

Dynamic Degradation Quantification of Wind Turbine High Speed Shaft Bearing Based on Oscillation Based Sparsity Indices

Wind turbine (WT) high speed shaft (HSS) bearing fault is important due to its significant number of failures. However, due to its non-stationary operation under varying speed condition, it is a challenging issue to quantify the degradation of WT-HSS bearing by conventional bearing indices. Aiming at the aforementioned issue, in this paper, tunable Q factor wavelet transform (TQWT) preprocessed sparsity indices are proposed to achieve the dynamic degradation quantification of WT-HSS bearing. Firstly, based on the ability of TQWT in dynamic extraction of fault component of a bearing signal under varying speed condition, low oscillatory transient signal component is separated from a noisy commercial WT-HSS bearing signal by continuously adjustable tunable Q factor wavelet transform (TQWT). Then, considering the suitability of sparsity indices in quantifying extracted fault component based on its energy concentration, four representative sparsity indices namely kurtosis, gini index, negative entropy and reciprocal smoothness index are used to quantify the separated low oscillatory signal component as a measure of WT-HSS bearing health. The proposed indices show a better performance than original sparsity indices and an improved version of sparsity indices based on adaptive weighted signal preprocessing in dynamic degradation quantification of a commercial WT-HSS bearing.

Distributed regularized least squares with flexible Gaussian kernels

We propose a distributed learning algorithm for least squares regression in reproducing kernel Hilbert spaces (RKHSs) generated by flexible Gaussian kernels, based on a divide-and-conquer strategy. Our study demonstrates that Gaussian kernels with flexible variances greatly improve the learning performance of distributed algorithms generated by a fixed Gaussian. Under some mild conditions, we establish sharp error bounds for the distributed algorithm with labeled data in which the variance of the Gaussian kernel serves as a tuning parameter. We show that with suitably chosen parameters our error rates can be almost mini-max optimal under the standard Sobolev smoothness condition on the target function. By utilizing additional information of unlabeled data for semi-supervised learning, we relax the restrictions on the number of data partition and the range of the Sobolev smoothness index.

SALSA: Combining branch-and-bound with dynamic programming to smoothen workloads in simple assembly line balancing

We consider a version of the well-known simple assembly line balancing problem (called SALBP-SX) where, given the cycle time and the number of stations, the workloads of the stations are to be leveled according to an adequately defined smoothness index SX. Our index SX involves for each station the quadratic deviation of its workload from the average (or ideal) workload and is therefore closely related to the variance, which is a common measure of dispersion in statistics. Contrary to the existing literature on workload smoothing in ALB, which often treats the optimization of a prespecified smoothness index as a secondary objective, we consider our SX-objective as the single one in order to account for the practical relevance of fair workload distributions and avoiding overloaded bottleneck stations.To optimally solve SALBP-SX, we develop a tailored branch-and-bound procedure. It contains a new station-oriented branching scheme, new lower bound arguments, logical tests and, in particular, a dynamic programming scheme for the pre-calculation of potential workloads, which accelerates the procedure greatly. In comprehensive computational experiments, we show that our method clearly outperforms a class of recently developed task-oriented branch-and-bound procedures and also the mathematical programming solver Gurobi.

Energy-Efficient Optimization of Two-Sided Disassembly Line Balance Considering Parallel Operation and Uncertain Using Multiobjective Flatworm Algorithm

The two-sided disassembly line is popular for its high-efficiency disassembly of large-volume end-of-life products. However, in the process of two-sided disassembly, some parts and components need to be disassembled in parallel, and the uncertainty of disassembly time lacks certain research. This paper constructs a fuzzy multiobjective two-sided disassembly line balance problem model based on parallel operation constraint, which aims to reduce the balance loss rate, smoothness index, and energy consumption of disassembly activities. A multiobjective flatworm algorithm based on the Pareto-dominance relationship is developed. To increase the diversity of feasible solutions in the evolution process and accelerate the convergence of Pareto-optimal solutions to prevent the random search of solution space, growth, splitting and regeneration mechanisms are embedded in the algorithm. The working mechanism and efficiency of the multiobjective flatworm algorithm are proved on a series of two-sided disassembly cases, and the excellent performance of the proposed model and algorithm are demonstrated by an actual automobile two-sided disassembly line.

Balancing time and physical effort in two-sided assembly lines

Abstract In assembly line balancing problems, time is balanced among workers. This does not necessarily balance their physical effort. The effort exerted by workers varies depending on the type of the job, and the size and weight of the component. In the two-sided assembly lines, commonly used for heavy industries, the variation in physical effort among workers is more emphasized. The unbalanced effort leads to fatigue, and may lower productivity and quality. This work aims at balancing the physical effort among workers in the two-sided assembly lines, while considering other conventional objectives. A genetic algorithm and a new decoding scheme are proposed. An effort smoothness index (ESI) is introduced to measure the variation in effort among workers. Results prove that balancing the physical effort is influential and can be achieved at no extra cost for most cases. Effort balancing is harder to achieve in difficult problems; of high order of strength.

A Comparison of Machine Health Indicators Based on the Impulsiveness of Vibration Signals

Vibration signals collected from machines can contain rich machine degradation information, such as impulsiveness and cyclo-stationarity. In the field of machine condition monitoring (MCM), quantification of impulsiveness has attracted many researchers’ interests because impulsiveness often indicates an occurrence of incipient faults. Impulsiveness-based health indicators (HIs) (e.g., Gini index, kurtosis, entropy, smoothness index, etc.) are some kinds of statistical parameters that can quantify the impulsiveness of vibration signals. Hence, they have been widely studied during recent years for MCM. However, a thorough comparitive study of those HIs is seldom reported. This paper aims to compare seven impulsiveness-based HIs including kurtosis, skewness, smoothness index, negative entropy, Gini index, Hoyer measure, and the ratio of L2 to L1 norm for MCM according to three properties including the robustness to the length of a signal, the gradient for sparsity or impulsiveness, and quantification of impulsiveness and cyclo-stationarity. Among the seven HIs, it was experimentally found that the Gini index is better than the other indicators to satisfy the three suggested properties for MCM.