Imperfect Ones Research Articles

Multiple lubricated joints with long and short bearings in multibody mechanical systems - Modeling, simulation, and performance analysis

This study examines the effect of multiple lubricated imperfect long and short bearings on the performance of a multibody mechanical system. Unlike the typical assumption of a single perfect or imperfect lubricated joint due to modeling difficulties, this research considers the practical impacts of clearances in multiple joints. While unlubricated joints generally cause significant performance issues, lubricants reduce these effects, creating more localized peaks. The findings show that as the number of lubricated joints increases, both the magnitude and frequency of these peaks rise. In systems with multiple journal bearings, torque peaks become more noticeable due to the additional degrees of freedom introduced by the clearances. These degrees of freedom amplify acceleration, leading to higher lubricant reaction forces, which in turn require greater motor torque peaks to maintain the system's kinematics. Shorter lubricated joints exhibit more severe peaks than longer ones, mainly due to side leakage causing axial pressure variation and reduced damping capacity. The study highlights the need to replace idealized joints with imperfect ones for more accurate modeling of practical systems.

RIS-Aided Cell-Free MIMO System: Perfect and Imperfect CSI Design for Energy Efficiency

Thanks to the development of the 6th generation mobile network that makes it possible for us to move towards an intelligent ubiquitous information society, among which some novel technologies represented by cell-free network has also attracted widespread academic attention. Cell-free network has brought distinguished gains to the network capacity with its strong ability against inter-cell interference. Unfortunately, further improvement demands more base stations (BSs) to be settled, which incurs steep cost increase. To address this issue, reconfigurable intelligent surface (RIS) with low cost and power consumption is introduced in this paper to replace some of the trivial BSs in the system, then, a RIS-aided cell-free network paradigm is formulated. Our objective is to solve the weighted sumrate (WSR) maximization problem by jointly optimizing the beamforming design at BSs and the phase shift of RISs. Due to the non-convexity of the formulated problem, this paper investigates a joint optimizing scheme based on block coordinate descent (BCD) method. Subsequently, on account of the majority of the precious work reposed perfect channel state information (CSI) setup for the ultimate performance, this paper also extends the proposed algorithm to the case wherein CSI is imperfect by utilizing successive convex approximation (SCA). Finally, simulation results demonstrate that the proposed scheme shows great performance and robustness in perfect CSI scenario as well as the imperfect ones.

Is the system reliability profitable for retailing and consumer service of a dynamical system under cross-price elasticity of demand?

Retailing strategy is one of the most crucial factors for industries. A proper retailing strategy can help to enhance consumer service and increase the industry's profit. An improved approach to retailing is suggested in this research to deliver superior customer service while maximizing profits in a dynamic system. The study analyzes a retailing strategy for a demand with cross-price elasticity upon the retail price. A product's cross-price elasticity and the system reliability are critical factors in retailing. Understanding the cross-price elasticity of demand between products helps retailers to make pricing decisions that maximize profits by maintaining demand. Imperfect products are produced due to an imperfect production system. The imperfect ones must be adjusted with some costs to make them perfect for better retailing. The system failure rate is crucial for retailing under cross-price elasticity of demand patterns. Production system reliability, cross-price elasticity of demand, and consumer service are all essential factors that can impact a company's success in the market. The production rate is considered time- and system failure rate-dependent. Contradictory to the literature, a dynamical system is proposed for improved retail management, which is solved using the Euler-Lagrange theory. Finally, one can achieve the expected maximum profit for this retail system with optimum selling prices for different products by reducing the system failure rate. Some numerical illustrations with graphical representations are provided to validate the current study. Numerical examples show that applying cross-price elasticity of demand for more than two identical products provides 35% more profit for the retail industry than a single type of product.

An Inventory Model for Imperfect Quality Products with Rework, Distinct Holding Costs, and Nonlinear Demand Dependent on Price

Traditionally, the inventory models available in the literature assume that all articles in the purchased lot are perfect and the demand is constant. However, there are many causes that provoke the presence of defective goods and the demand is dependent on some factors. In this direction, this paper develops an economic order quantity (EOQ) inventory model for imperfect and perfect quality items, taking into account that the imperfect ones are sent as a single lot to a repair shop for reworking. After reparation, the items return to the inventory system and are inspected again. Depending on the moment at which the reworked lot arrives to the inventory system, two scenarios can occur: Case 1: The reworked lot enters when there still exists inventory; and Case 2: The reworked lot comes into when the inventory level is zero. Furthermore, it is considered that the holding costs of perfect and imperfect items are distinct. The demand of the products is nonlinear and dependent on price, which follows a polynomial function. The main goal is to optimize jointly the lot size and the selling price such that the expected total profit per unit of time is maximized. Some theoretic results are derived and algorithms are developed for determining the optimal solution for each modeled case. It is worth mentioning that the proposed inventory model is a general model due to the fact that this contains some published inventory models as particular cases. With the aim to illustrate the use of the proposed inventory model, some numerical examples are solved.

Il parto dell’orsa, un miope emendamento del Cuperus e il destino della poesia di Petronio

Starting from the examination of the lucky topos of the bear’s birth, which gives birth to small imperfect ones and licks them until she gives them a complete shape, we discuss an epigram by the Carthaginian poet Luxorius, dedicated to this topic. The identification of the imitation by Luxorius of an epigram attributed to Petronius (fr. 26 Bucheler = 26 Muller = AL 690 Riese2) allows us to introduce considerations regarding the diffusion of Petronian poetic florilegiums in late ancient North Africa, which soon migrated to the Spain of Isidorus of Seville and originated anthologies subsequently testified by IX century manuscripts such as the Vossianus Q. 86 and the deperditus Bellovacensis.

A Sustainable Inventory Model with Imperfect Products, Deterioration, and Controllable Emissions

Maintaining product quality and environmental performance are emerging concerns in modern competitive and transparent businesses. Many retailers separate perfect products from imperfect ones to ensure product quality and endeavor to achieve carbon dioxide (CO2) reduction through green technology investments and sustainable inventory planning. Product deterioration often badly hampers the retailing business; hence, suitable preservation technologies are used. In this study, we examined the optimization model of the selling price, investment, and replenishment planning to maximize the total profit. The proposed model considered the effect of a greater deterioration rate and discount price of imperfect products. Due to the high uncertainty in demand, a realistic holding cost was deliberated with a variable and constant part. Every time the retailer transports purchased items, greenhouse gases (GHGs), including CO2, are produced. Government regulations on CO2 minimization and customer awareness for greener products stimulate retailers to invest in energy-efficient green technology. This study simultaneously showed a harmonious relationship among the attributes of preservation technology, green technology investment, and discounts on defective items. Theoretical derivations were performed with numerical analysis.

A Better World in the Future

A Better World in the Future

Autonomation policy to control work-in-process inventory in a smart production system

The necessity of optimum safety stock is really essential for any smart production system. For this reason, the effect of autonomation policy makes a big difference with the basic traditional automation policy. Basically, for a long-run production system, a process may transfer to an ‘out-of-control’ state from an ‘in-control’ state due to labour problems, machinery problems, or any kind of energy problems. During this ‘out-of-control’ state, machines produced imperfect items instead of perfect items. As a result, an inspection is required to identify the imperfect ones. Until now, this inspection has been utilised by human beings through the traditional automation policy and inspection errors may occur. To perform an error-free inspection, an autonomation policy is examined in this model to detect imperfect items from the production process, which makes the process smarter. The defective rate is random and follows a certain distribution. A budget and a space constraints are adopted, which makes the model non-linear with a constraint problem. Contradictory to the existing literature, the demand is price- and quality-sensitive together in a smart production system. To solve this non-linear problem with an optimised value of backorders, number of delivery lots, safety factors, and collection rate, a non-linear optimisation technique (Khun–Tucker optimisation technique) is employed. A numerical example and sensitivity analysis are provided to illustrate the model. The result finds that the optimum autonomation policy can save work-in-process inventory at the optimum value of the decision variable in the proposed model.

Investigation on Dynamic Interaction of Multiple Clearance Joints for Flap Actuation System

A dynamic simulation model of the flap actuation system is developed in this paper to analyze the dynamic interaction behaviours of multiple clearance joints. The nonlinear contact force model and modified Coulomb friction model are adopted in the four clearance joints to capture their motion modes, including free flight mode, impact mode and continuous mode. The results show that there exists a strong dynamic interaction between different clearance joints and one impact motion mode in a joint will immediately affect other joints. And when the system reaches a stable state, the four clearance joints almost appears the similar tendency due to the rigid connection. Therefore, in order to accurately predict the dynamic responses of multibody system, it is essential for all joints to be modelled as imperfect ones.

Imperfect bifurcations in an initially curved plate loaded by incompressible axial airflow

This paper is concerned with the static bifurcations in a simply supported nonlinear curved plate subjected to a steady incompressible axial airflow. The fluid velocity potential of the flow is considered as the sum of two parts: One is due to the plate deformation, and the other is to the plate initial shape. The fluid force theoretically solved from the Bernoulli’s equation has been successfully verified through a wind tunnel experiment. The von Karman’s theory for large deflection of plates is used for the plate modeling. Results show that the plate loses symmetry and becomes imperfect due to its initial shape. The system has a fundamental and another two asymmetric bifurcated equilibrium solutions. Compared with the symmetric bifurcations in a flat plate, these bifurcations are called as the imperfect ones. The imperfect pitchfork-like bifurcation has a non-bifurcating branch and an additional imperfect bifurcation. The bifurcation regions and features are explored in detail in various parametric planes. There are two types of imperfect pitchfork-like bifurcations. The first type involves an additional saddle-node bifurcation and could be either supercritical or subcritical. However, the second type is associated with a transcritical-like bifurcation and represents the coexistence of both the supercritical and the subcritical bifurcations. The hysteresis in nature is due to the asymmetry of the system and can be restrained by increasing the tension and the fluid dynamic pressure.

Stability Landscape of Shell Buckling.

We measure the response of cylindrical shells to poking and identify a stability landscape, which fully characterizes the stability of perfect shells and imperfect ones in the case where a single defect dominates. We show that the landscape of stability is independent of the loading protocol and the poker geometry. Our results suggest that the complex stability of shells reduces to a low dimensional description. Tracking ridges and valleys of this landscape defines a natural phase-space coordinates for describing the stability of shells.

Simulating single photons with realistic photon sources

Quantum information processing provides remarkable advantages over its classical counterpart. Quantum optical systems are proved to be sufficient for realizing general quantum tasks, which however often rely on single photon sources. In practice, imperfect single photon sources, such as weak coherent state source, are used instead, which will inevitably limit the power in demonstrating quantum effects. For instance, with imperfect photon sources, the key rate of the BB84 quantum key distribution protocol will be very low, which fortunately can be resolved by utilizing the decoy state method. As a generalization, we investigate an efficient way to simulate single photons with imperfect ones to an arbitrary desired accuracy when the number of photonic inputs is small. Based on this simulator, we can thus replace the tasks that involve only a few single photon inputs with the ones that only make use of imperfect photon sources. In addition, our method also provides a quantum simulator to quantum computation based on quantum optics. In the main context, we take phase randomized coherent state as an example for analysis. A general photon source applies similarly and may provide some further advantages for certain tasks.

Beam-Column In-Plane Resistance Based on the Concept of Equivalent Geometric Imperfections

AbstractAssessment of the flexural buckling resistance of bisymmetrical I-section beam-columns using FEM is widely discussed in the paper with regard to their imperfect model. The concept of equivalent geometric imperfections is applied in compliance with the so-called Eurocode’s general method. Various imperfection profiles are considered. The global effect of imperfections on the real compression members behaviour is illustrated by the comparison of imperfect beam-columns resistance and the resistance of their perfect counterparts. Numerous FEM simulations with regard to the stability behaviour of laterally and torsionally restrained steel structural elements of hot-rolled wide flange HEB section subjected to both compression and bending about the major or minor principal axes were performed. Geometrically and materially nonlinear analyses, GMNA for perfect structural elements and GMNIA for imperfect ones, preceded by LBA for the initial curvature evaluation of imperfect member configuration prior to loading were carried out. Numerical modelling and simulations were conducted with use of ABAQUS/Standard program. FEM results are compared with those obtained using the Eurocode’s interaction criteria of Method 1 and 2. Concluding remarks with regard to a necessity of equivalent imperfection profiles inclusion in modelling of the in-plane resistance of compression members are presented.

Multi-item EPQ model with learning effect on imperfect production over fuzzy-random planning horizon

Uncertainty is certain in the world of uncertainty. This study revisits an economic production quantity (EPQ) model with shortages for stock-dependent demand of the items with reworking and disposing of the imperfect ones over a random planning horizon under the joint effect of inflation and time value of money, where the expected time length is imprecise in nature. Transmission of learning effect has been incorporated to reduce the defective production. The total expected profit over the random planning horizon is maximized subject to the imprecise space constraint. The possibility, necessity and credibility measures have been introduced to defuzzify the model. The simulation-based genetic algorithm is used to make decision for the above EPQ model in different measures of uncertainty. The model is illustrated through an example. Sensitivity analysis shows the impacts of different parameters on the objective function in the model.

Economic order quantity and sampling inspection plans for imperfect items

The creation of economic order quantity (EOQ) models that consider imperfect items is a step towards making these models even closer to real-world situations. The underlying assumption of these models, which is that conducting a full inspection to separate perfect items from imperfect ones, is a costly process and not always the best decision. In this paper, sampling inspection plans are designed on the basis of which a buyer would be able to make a decision regarding the next step. More precisely, we can find two cut-off points for the imperfect rate, and the best strategy is (i) not to conduct a full inspection when we expect to have imperfect rate below the first cut-off point; (ii) to conduct a full inspection when we expect to have an imperfect rate between the two cut-off points, and (iii) to reject the lot when the imperfect rate is expected to be higher than the second cut-off point. We formulate the problem, and derive the expected EOQ and optimal total profit of the problem. Numerical examples are used to illustrate the model. The numerical examples show that by considering the sampling inspection plans, the buyer gains more profit compared to the existing individual approaches (traditional EOQ, and EOQ models with full inspection).

Periarticular Hand Joint Limitation Syndromes in Diabetes

“Clear and precise definitions of disease, and the application of such names to them as are expressive of their true and real nature, are of more consequence than they are generally imagined to be: Untrue or imperfect ones occasion false ideas; and false ideas are generally followed by erroneous practice.” Percival Pott (1714-1788) The importance of accurate taxonomy for the under-standing of pathological processes, appropriate therapy, prognostication, and research data acquisition cannot be better stated after more than 200 years of medical progress. Despite this inarguable requirement, a plethora of terms have been used for complications of diabetes associated with finger joint contracture not involving the articular sur-face (1). Multiple designations have been used to denote the same condition, and widely disparate conditions have appeared under the same rubric. Stiff hand syndrome (2,3), diabetic hand syndrome (4,5), diabetic cheiroarthropathy (6), Rosenbloom syndrome (7-9), limited joint mobility (10), scleroderma-like syndrome (11), and digital sclerosis (12) have all been used to describe the unique limitation of hand and frequently other joints with associated thick tight waxy skin initially described in young patients with type 1 diabetes and later recognized to occur at all ages and with all forms of diabetes (1,10). The nonspecific nature of the terms stiff hand syndrome, diabetic hand syndrome, and limited joint mobility has contributed to their expan-sive use as an umbrella for several or all of the diabetes-related conditions resulting in finger joint limitation (5). Understanding the problems with the use or misuse of these terms in the literature is necessary to minimize the taxonomic confusion. In 1957, Lundbaek described “stiff hands in long-term diabetes” in 5 older adults with 40+ years duration of type 1 diabetes with contractures of all the fingers with pares-thesias, pain aggravated by movement, stiff hard skin over the palms, and arterial calcifications noted on radiography of the hands (2). Only a single case report of the syndrome has subsequently been published, suggesting that it may be an exceptional aggregation of diabetes complications affecting the hand (see Table 1), rather than a distinct entity. “Diabetic hand syndrome” was applied by Jung et al (4) to a group of adults having limitations involving all of the fingers with neuropathic pain and interosseous and palmar muscular atrophy. There was delayed nerve transmission in the forearm and in the median and ulnar nerves, with wide variability in severity. The condition may be confused with the carpal tunnel syndrome that results from entrap-ment of the median nerve within the carpal tunnel at the wrist, resulting in paresthesias of the thumb, index finger, and little finger, with pain that is often worse at night. Importantly, finger contractures do not occur with the car-pal tunnel syndrome. The involvement of both the ulnar and median nerve in the diabetic hand syndrome indicates intrinsic neuropathy, rather than entrapment, precluding anticipated improvement with carpal tunnel syndromesurgery (4). Although pain and muscle atrophy, as well as the exclusive adult distribution, distinguish the diabetic hand syndrome from the unique pediatric and adult limited joint mobility, diabetic hand syndrome has been considered synonymous with limited joint mobility (5). Also, “the diabetic hand” has been used as a general term to include any of the conditions affecting the hand in diabetes, such as Dupuytren disease, flexor tenosynovitis, shoulder-hand

Buckling Behaviors of Imperfect Single-Walled Carbon Nanotubes: A Molecular Dynamic Simulation

Carbon nanotube has attracted tremendous scientific and industrial interests due to its exceptional mechanical, electrical and thermal properties. In this paper, classic molecular dynamic simulations are carried out to investigate the buckling behaviors and mechanical properties of single-walled carbon nanotubes under axial compression, both for perfect and imperfect ones introducing atomic vacancies. The effect of chirality, diameter, quantity and position of vacancy are systematically studied. The simulation results reveal that their mechanical properties such as Young’s modulus, critical strain and stress suffering a significant decline as the increasing numbers of vacancies. It is also found that the critical stress and strain are sensitive to position of atomic vacancy. Carbon nanotubes with vacancies located at the center have lower critical strain and are easier to reach the failure stage than those with vacancies at both sides.

Generalizing Kant's Distinction between Perfect and Imperfect Duties to Trust in Different Situations

ABSTRACT Based on previous research that violations of perfect duties cause stronger correspondent inferences than violations of imperfect ones, the authors performed four experiments to generalize this effect to trust. In Experiment 1, abstract violations of perfect duties resulted in less trust than violations of imperfect ones for specific trust scenarios. In Experiments 2 and 3, the authors experimented with different levels of abstractness of the duty violations and obtained similar effects. Experiment 4 was concerned with generalizing further—from duty violations in one situation to trust in a different situation. Although mostly consistent with the findings from Experiments 1–3, the data also demonstrated partial generalization for violations of both perfect and imperfect duties.

Imperfect cross-correlation and amplitude balance effects on conventional multiuser decoder with turbo encoding

The present work aims to illustrate the improvement that turbo encoding/decoding algorithms can bring to a multiuser detection system, evaluated in terms of bit error rate (BER). Extended simulations have been performed for conventional multiuser detection algorithms and are still under study for other algorithms, like the optimal, the MMSE and the classical MMSE ones. Simulations have been performed in both optimal conditions and imperfect ones, like non-equal power of users and non-zero correlations between them and for different number of users. Several interesting conclusions have been highlighted with respect to parameters influence on overall system performances.

Divergent microsatellite evolution in the human and chimpanzee lineages

Comparison of the complete human genome sequence to one of its closest relatives, the chimpanzee genome, provides a unique opportunity for exploring recent evolutionary events affecting the microsatellites in these species. A simple assumption on microsatellite distribution is that the total length of perfect repeats is constant compared to that of imperfect ones regardless of the repeat sequence. In this paper, we show that this is valid for most of the chimpanzee genome but not for a number of human chromosomes. Our results suggest accelerated evolution of microsatellites in the human genome relative to the chimpanzee lineage.