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In this paper, a new repairable k-out-of-n system model is proposed, in which the deviation cost of the system is taken into account. Firstly, the standard k-out-of-n system is replaced at planned time or at the failure time. Next, replacement policies are studied at planned time or periodic time when k is a constant. Thirdly, replacement policies are studied at planned time or periodic time when k is a random number, respectively. Finally, replacement policies are planned at the completion of random working time. The expected cost rate functions and its optimum replacement policies are derived analytically for each model. Meanwhile, optimum number of units is designed. The analytical solution of replacement policies for each model is discussed. Numerical examples are given to demonstrate our results. [ABSTRACT FROM AUTHOR]

For a 24/7 database system, backups should be implemented right after a large volume of data has been updated, putting their backup windows in non-busy states with user's convenience.From this viewpoint, this paper studies periodic and random incremental backup policies, in which, incremental backup is implemented right after data update and full backup is performed at periodic times KT , or at a number N of data updates, respectively. We firstly describe the stochastic processes of data update and database failure, and then model the expected cost rates for data backup and data restoration.Respective K ∗ , N ∗ , K f ∗ , and N f ∗ are obtained to minimize their expected cost rates in analytical ways, respectively. Finally, numerical examples are given to illustrate the optimum policies. [ABSTRACT FROM AUTHOR]

Identifying purchase intention by analyzing the Query and the Document of the product description (Q &D) text is one of the most important means of promoting Purchase Rate (PR). In view of that customers sometimes cannot describe their purchasing intention in queries, this paper aims to identify purchase intention from implicit queries by computing semantic similarity between Q &D and proposes a novel model based on Word2Vec algorithm, Long Short-term Memory (LSTM) and Deep Structured Semantic Model (DSSM). Besides, an empirical analysis is conducted through the Keras framework and based on the factual retrieval data of the Home Depot, an E-commerce website selling building materials in America. The results show that the proposed model has achieved improving F1-score on test dataset compared with other existing models. The novel model combines Word2Vec and LSTM to extract text features and applies DSSM to further fetch high-dimension representations by maximizing semantic similarity between the user query and the description of the correct merchandise. Our proposed model can be used to remove or minimize subjective factors in extracting features, improves the performance of purchasing intention identification, and also improves the customer experience of online shopping. [ABSTRACT FROM AUTHOR]

To distinguish between the kinetic and chemical contributions in the impact of PTFE/Al, this study explores the feasibility of introducing an inert substitute for PTFE/Al by substituting aluminum (Al) with inert materials. Three specimens were fabricated through a process involving mixing, compression, and sintering of raw materials The mechanical properties of these specimens were assessed. Dynamic fragmentation tests of PTFE/Al and PTFE/LiF specimens were performed. These results further substantiate the potential of PTFE/LiF as an inert alternative to PTFE/Al, the two materials exhibit comparable fragmentation distribution characteristics. A preliminary exploration of the energy release in both materials was conducted via vented chamber calorimetry tests. The findings reveal that, at an impact velocity of roughly 650 m/s, only 66.9 % of the materials were deposited into the chamber, with a mere 17.8 % being initiated, about 88.9 % of the total deposited energy results from the chemical reaction energy within the PTFE/Al materials. Importantly, this method demonstrates promise for further application in energy release analysis experiments for various PTFE/Al‐based reactive materials. These findings are beneficial for evaluating the energy release characteristics of reactive fragments on typical targets and lay the foundation for refining energy release models of such materials in future research. [ABSTRACT FROM AUTHOR]

The wheel–rail adhesion is one of the key factors limiting the traction performance of railway vehicles. To meet the adhesion optimization needs and rapidly obtain wheel–rail creep characteristics under specific operating conditions, an engineering identification method for wheel–rail adhesion characteristics based on a nonlinear model is proposed. The proposed method, built upon the traditional Teaching-Learning-Based Optimization (TLBO) algorithm, has been adapted to the specific nature of nonlinear wheel–rail adhesion model parameters identification, enhancing both the search speed in the early stages and the search accuracy in the later stages of the algorithm. The proposed identification algorithm is validated using experimental data from the South African 22E dual-flow locomotive. The validation results demonstrate that the proposed identification algorithm can obtain a nonlinear wheel–rail adhesion characteristics model with an average adhesion coefficient error of around 0.01 within 50 iteration steps. These validation results indicate promising prospects for the engineering practice of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Retinal pigment epithelium (RPE) dysfunction, manifested as drusen formation and RPE mottling, is a characteristic lesion of aging. The mechanism of RPE dysfunction remains unknown. Previous animal studies have proven that the activation of NLRP3 inflammasome in RPE leads to apoptosis and pyroptosis, which may play a very important role in the development of age-related macular degeneration (AMD). However, there is a lack of clinical evidence to support the above hypothesis. Herein, we report a 38-year-old Chinese Han woman who had NLRP3-associated autoinflammatory disease (NLRP3-AID) with widely scattered drusen at the posterior pole in both eyes. NLRP3-AID is a rare disease caused by mutations of the NLRP3 gene, leading to NLRP3 inflammasome activation. This report of early-onset drusen provides clinical evidence that the NLRP3 inflammasome might contribute to the occurrence of RPE dysfunction and is a potential cause of age-related macular degeneration (AMD). [ABSTRACT FROM AUTHOR]

Under neoclassical assumptions, this paper develops a model to illustrate the effects of government use of carbon allowances for carbon emission control. We find that control using the instrument of issuing long-term carbon allowances does not produce the same good results in the Decentralised Equilibrium as in the Planning Problem. Thus, while Coase's Theorem ensures that the Pareto optimum is maintained in an economy with multiple agents, it does not align the social development with the economic optimum of the planner. We believe this is due to the that the price of carbon allowances is determined by asset profiles of investors rather than externalities. The steady-state under the special pathway shows that consumption is determined by the rate of technological progress, the total amount of carbon dioxide at steady-state, the level of technology at which steady-state is reached and the total amount of carbon allowances remaining. The comparison with the optimal tax path reveals that the price of carbon allowances has increased too quickly, leading to excessive consumption of fossil fuels in the early stages. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether the rare NLRP3-Associated Autoinflammatory Disease (NLRP3-AID) is associated with retinal changes and to assess the ocular involvement. Methods: A retrospective cohort study of 20 patients(40 eyes) diagnosed with rare NLRP3-AID at Peking Union Medical College Hospital, from April 2015 to August 2022. Patients underwent a comprehensive ophthalmological examination, including visual acuity, intraocular pressure examination, slit-lamp examination, fundus photography, optical coherence tomography(OCT), and fluorescence angiography (FA). Some patients also underwent optical coherence tomography angiography (OCTA). Results: This study analyzed 40 eyes of 20 patients (11 [55.0%] male; median age, 25.0 years [range, 12–52 years]) and 13 patients (26 eyes, 65%) demonstrated ocular involvement. The most common ophthalmologic manifestation was conjunctivitis (22 eyes, 84.6%), followed by papilledema (14 eyes, 53.8%), retinopathy (10 eyes, 38.5%), optic atrophy (6 eyes, 23.1%), uveitis (4 eyes, 15.4%), reduced pupil light reflex (3 eyes, 11.5%) and cataracts (2 eyes, 7.7%). Ocular involvement was bilateral in 11 patients (55.0%). Five kinds of retinal lesions were seen in 5 patients (10 eyes, 25%) with NLRP3-AID, including peripheral retinal vascular leakage, microaneurysms, macular ischemia, macular epiretinal membrane formation and drusen. Conclusions: Peripheral retinal vascular leakage, macular ischemia, microaneurysms and drusen are newly identified retinal findings in patients with NLRP3-AID, which suggests the importance of detailed retinal examination in these patients. [ABSTRACT FROM AUTHOR]

Rotor-bearing systems play a vital role in machine tools, aero engines, and wind turbines. Generally, worn-induced degradation quantities and manufacturing errors of components are the main error sources that influence the precision reliability of rotor-bearing systems. The current precision reliability evaluation models are focusing on several error sources in only a few key components without agreeable results. Therefore, a precision reliability evaluation model is proposed considering all time-variant error sources and random error sources. Firstly, time-variant wear models for commonly occurred degradation types in a rotor-bearing system are developed. Secondly, the constructed time-variant wear models are inserted into the precision model with all moving components in the rotor-bearing system using meta-action structural decomposition method. Finally, the time-variant stochastic process discretization method is employed to establish the precision reliability evaluation model, and solve the precision reliability of the rotor-bearing systems. Case investigations are carried out to verify the performance of the present model, which provides a more accurate precision reliability evaluation model to estimate the conditions of rotor-bearing systems during the service period. [ABSTRACT FROM AUTHOR]

This article revisits the optimization problems of age-based replacement models for exponential failure distributions. First, we show the steps how an age replacement time goes to an infinite value when the lifetime of a unit has an exponential distribution, and then, we give two discussions of possible replacement times, by introducing a new concept of cost named as deviation cost per unit of time between replacement and failure. Second, similar discussion is given for a random replacement model when the age replacement time is a random variable with a uniform distribution. Third, the models of age-based replacement first and last with deviation costs are discussed when a random replacement is taken into account for an age replacement model. Numerical examples are illustrated to show the results of the analytical discussions. Finally, necessary proofs are provided in the Appendixes. [ABSTRACT FROM AUTHOR]

This paper takes up managerial maintenance policies during different phases for mission executions. When a mission execution is divided into two phases and three phases respectively, replacement, minimal repair and keeping failure status become alternatives for managerial maintenance policies. Further, we give approximations of the above managerial maintenance policies to make the computations simple. In this paper, keeping failure status is considered as the last choice for the last phase of mission executions. We aim to minimize the expected maintenance costs for the total mission executions. All of the discussions are made analytically and their numerical examples are given. [ABSTRACT FROM AUTHOR]

Background. The study analyzed gut microflora's composition and investigated the associations between the associations between gut dysbiosis and inflammatory indicators in pediatric patients with acute appendicitis. Methods. High-throughput sequencing and bioinformatics analysis were used to investigate the composition and diversity of gut microflora in 20 pediatric patients with acute appendicitis and 11 healthy children. Endpoints measured were operational taxonomic units (OTU) of gut microflora. The OTU and its abundance analysis, sample diversity analysis, principal component analysis of samples, differential analysis, and analysis of biomarkers were performed. Results. Overall fecal microbial richness and diversity were similar in patients and controls. Yet richness within the group of Bilophila, Eggerthella, Clostridium, Parvimonas, Megasphaera, Atopobium, Phascolarctobacterium, Adlercreutzia, Barnesiella, Klebsiella, Enterococcus, and Prevotella genera was higher in patients. Adlercreutzia was significantly positively correlated with IL-10, while the three other genera, comprising Klebsiella, Adlercreutzia, and Prevotella, were positively correlated with B cells level. Conclusion. Gut microbiome components are significantly different in pediatric patients with acute appendicitis and healthy children. The differential abundance of some genera is correlated with the production of inflammatory markers in appendicitis. [ABSTRACT FROM AUTHOR]

When a unit should provide reliability at mission time, the mission success probability or failure probability becomes an important constraint to plan inspection policies. From this viewpoint, this paper considers the optimization problems of periodic and sequential inspection policies with mission failure probabilities. In this paper, a mission time is considered as a renewal point for inspection polices, but the failure cost occurred at mission time is higher than the total cost of inspection and failure detection. We give an upper limit of the failure probability at mission time, that is, mission failure probability, to minimize the total expected costs and the expected cost rates of inspection policies. In addition, the extended models of inspection policies for an interval mission, possible random times, and operating interval are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we propose a computing algorithm to obtain optimal checking times which minimize the expected cost rate of sequential inspection models. This algorithm is applied to two modified inspection models with finite intervals such that the unit is checked at times T k (k = 1 , 2 , ... , N) for given N and given S ≡ T N . The modified algorithms are proposed and optimal checking times to minimize the expected cost rates are obtained. Numerical examples of each model are given to show how to use the algorithm. This method would be applied to other sequential inspection models by its suitable modifications. [ABSTRACT FROM AUTHOR]

In order to balance the deviation time between replacement and failure, a new notion of cost named as deviation cost is taken into account for planning replacement policies. We firstly take up a standard parallel system with n identical units and model replacement policies that are done at planned time and at periodic times. Next, we model again the above replacement policies when the number of units is a random variable that has a Poisson distribution. Thirdly, replacement policies are planned preventively at the completion of random working times. Optimum number of units is scheduled for a total working interval that is constantly and randomly given. Finally, we give reliability functions of k-out-of-n systems for extensions of parallel systems. We give analytical discussions for the above replacement policies and illustrate numerical examples when the failure time of each unit has an exponential distribution. [ABSTRACT FROM AUTHOR]

In this paper, in order to improve microhardness and wear resistance of grinding layers for metal-bonded laser cladding grinding tools, the integrity of CBN grits during laser cladding process is protected and bonding quality between metal matrix and CBN grits is improved. 0%, 1.25%, 2.5%, 3.75%, and 5% of B4C as additive for CBN/CuSnTi laser cladding layers were conducted. The surface morphology of these laser cladding layers was observed. The elements distribution and species of phases in cross section of these laser cladding layers were analyzed by scanning electron microscopy (SEM)/energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD), and reaction mechanism was analyzed by Gibbs free energy theory. The microhardness and wear resistance of these laser cladding layers were tested. Then, grinding tests with 0%, 2.5%, and 5% B4C added CBN/CuSnTi LCGTs were conducted. The results show that no cracks and intact CBN cutting edges were on laser cladding layer when 5% B4C was added. The mechanical quality involved microhardness and wear resistance of 5% B4C added laser cladding layer were better than that of other B4C contents of laser cladding layers. The surface roughness of 5% added LCGT is the best. 5% B4C can be the additive for CBN/CuSnTi LCGT. [ABSTRACT FROM AUTHOR]

It has been proposed that if replacement time is planned too early prior to failure, a waste of operation cost, i.e., excess costs, would incur because the system might run for an additional period of time to complete critical operations, and if replacement time is too late after failure, a great failure cost, i.e., shortage cost, is incurred due to the delay in time of the carelessly scheduled replacement. In order to make the preventive replacement policies perform in a more general way, the above two variable types of costs are taken into considerations for periodic replacement policies in this paper. We firstly take up a standard model in which the unit is replaced preventively at periodic times. Secondly, the modeling approaches of whichever occurs first and last are applied into periodic and random models, and replacement first and last policies are discussed to find optimum periodic replacement times for a random working time. Furthermore, optimum working numbers are obtained for the extended models. We give analytical discussions of the above replacement policies, and finally, numerical examples are illustrated. [ABSTRACT FROM AUTHOR]

Nowadays selecting the most suitable robot is a difficult task for manufacturing firms due to increase in production demands and availability of various robot models. Robot evaluation and selection can be regarded as a multiple criteria decision-making (MCDM) problem and three key issues are the assessment of robots, the determination of criteria weights and the prioritisation of alternatives. This paper aims to propose an integrated model based on hesitant 2-tuple linguistic term sets and an extended QUALIFLEX approach for handling robot selection problems with incomplete weight information. The new model can not only manage uncertain and imprecise assessment information of decision-makers with the aid of hesitant 2-tuple linguistic term sets, but also derive the important weights of criteria objectively when the weight information is incompletely known. Moreover, based on the extended QUALIFLEX algorithm, the priority orders of robots can be clearly determined and a more reasonable and credible solution can be yielded in a particular industrial application. Finally, a robot selection case study is carried out, and comparative experiments indicate the practicality and effectiveness of the proposed integrated linguistic MCDM approach. [ABSTRACT FROM PUBLISHER]

Background: To evaluate the efficacy and safety of topical β-blockers in the treatment of superficial infantile hemangiomas (SIH) and mixed infantile hemangiomas (MIH), respectively, and compare the efficacy and safety of topical β-blockers with other interventions.Methods: The PRISMA guidelines were adhered to. We searched for randomized controlled trials in databases from 2010 to 2018 comparing topical β-blockers with other interventions for infantile hemangiomas. The outcomes evaluated were efficacy and adverse effects. Data analyses were performed using RevMan 5.3. Publication bias was assessed to account for bias in patient selection.Results: Eleven studies, involving 1,235 patients, were subjected to this meta-analysis. Six studies compared topical β-blockers with other interventions (propranolol, placebo, corticosteroids or pulsed dye laser) in treating SIH, and 5 studies evaluated the efficacy and safety of a topical β-blocker when it was combined with another intervention in treating MIH. A topical β-blocker was discovered to be as effective as oral propranolol in treating SIH (risk ratio, RR, 0.96, 95% confidence interval, CI, 0.91-1.02, p = 0.20, I2 = 0%), and topical β-blockers were more beneficial than placebo, corticosteroids or pulsed dye laser in treating SIH (RR 2.25, 95% CI 1.66-3.05, p < 0.00001, I2 = 0%). Topical β-blockers combined with another intervention gave rise to a better clinical response in the treatment of MIH than intervention alone (RR 1.99, 95% CI 1.10-3.60, p = 0.02, I2 = 55%) (standard mean difference 0.80, 95% CI 0.28-1.31, p = 0.002, I2 = 0%). Compared with oral propranolol, topical β-blockers were associated with fewer incidences of adverse effects (RR 0.05, 95% CI 0.01-0.39, p = 0.004, I2 = 0%). No significant difference in adverse effects was found when a topical β-blocker was combined with another intervention in treating MIH (RR 1.01, 95% CI 0.58-1.74, p = 0.98, I2 = 0%).Conclusions: This meta-analysis provided evidence that topical β-blockers may replace oral propranolol as first-line therapy for SIH and that they are of additive value in treating MIH. [ABSTRACT FROM AUTHOR]

This paper discusses preventive replacement policies for an independent damage process, in which successive shocks occur at random times, and the independent damages caused by shocks are random variables. It is assumed that a unit fails when the damage has exceeded a prespecified level K. We consider three models: Model 1: the unit is replaced at the M th shock for damage Z , at damage K , or at time T , whichever occurs first. Model 2: the unit is replaced at the M th shock for damage Z , at damage K or at shock N , whichever occurs first. Model 3: the unit is replaced at the M th shock for damage Z , at damage K , at shock N or at time T , whichever occurs first. We obtain the expected cost rates for each model and discuss analytical optimal T ∗ and N ∗ to minimize their expected cost rates. Numerical examples are given when the damage has an exponential distribution and shocks occur at a gamma distribution. [ABSTRACT FROM AUTHOR]

When we consider the improvement of the functional performances that are released by the new updates of the products, it is an interesting problem to revisit the existing replacement policies. For such a viewpoint, four replacement models with product update announcements, i.e., PUA for abbreviation, are given in this paper: Model 1, the unit is replaced at time T or at PUA over time T. Model 2, the unit is replaced at the Kth failure or at PUA over the Kth failure. By considering both time T and failure K, Models 3 and 4 are obtained based on the approaches of replacement first and last. We obtain the expected cost rates for four models and discuss analytically their optimal replacement policies Further, numerical examples are given when the time for PUA has an exponential distribution. [ABSTRACT FROM AUTHOR]

It is always difficult to discuss the analytical formulas, in which optimum solutions of replacement policies satisfy, due to the mathematical complexity. This paper proposes several approximate calculations for age-based random replacement policies, such that the unit is replaced at time T, at random time Y j (j = 1 , 2 , ...) over time T, and at random time YN for Y j (j = 1 , 2 , ... , N). We use the inequality properties of the formulas and the bounds of the extended failure rate functions to find the approximate calculations of replacement times in analytical ways. It is shown from numerical examples that these approximate calculations would become useful references for the optimum age-based random replacement times. [ABSTRACT FROM AUTHOR]

In this investigation, in order to improve bonding strength between superabrasive/metal matrix/grinding substrate, life span of grinding wheel, and grinding using small grits in continuous grinding simultaneously to fit for high speed and high precision machining in industry, coaxial powder feeding laser cladding method with CAD/CAM technology is introduced to manufacture textured CBN/CuSnTi–grinding wheels. The morphology of CBN grit on laser-cladding layer under optimized laser-cladding parameters and a pit created by fallen-off CBN on laser-cladding layer with lower laser–cladding energy density are observed by scanning electron microscope (SEM). The element distributions of interfaces of CBN/CuSnTi/AISI 1045 are analyzed by SEM and energy disperse spectroscope (EDS). The morphology and elements distribution of residual resultants on the surface of CBN grits etched by nitric acid are analyzed by SEM and EDS. Comparative-grinding process between laser cladding–grinding wheel (LCGW) and customized electroplated grinding wheel (EGW) is analyzed with grinding forces and temperature aspects respectively. The wear morphology of CBN grits on LCGW after grinding is observed by SEM. The results show that CBN grit with integrate cutting edges can protrude 50% height of its diameter on laser-cladding layer under optimized laser–cladding parameters. Fe, N, Ti, and B segregates attached to the interfaces of CBN/CuSnTi/AISI 1045 with Cu and Sn distributed uniformly in the laser-cladding layer. Residual resultants on CBN can be divided into two parts based on the distances from the surface of CBN grits. The grinding forces (Fz and Fy) and grinding temperature from LCGW are lower than those from EGW. The wear conditions of CBN on laser cladding are three parts: microfracture, cleavage plane, and wear-out. [ABSTRACT FROM AUTHOR]

The random age replacement policies discussed in literatures are helpful to complete the nonstopping works with random working cycles, however, maintenance policies are more easily performed at periodic times in real applications. For such a viewpoint, this paper proposes that age replacement policies are planned at periodic times while considering the random working cycles. Using the modeling approaches of replacement first and last policies, we discuss two models such that the unit is replaced at periodic times K T and working cycles N , whichever occurs first and whichever occurs last. The expected cost rate models are obtained and their optimal solutions for K and N are discussed. The comparisons between the policies of K and N , and replacement first and last are made from the point of cost. Numerical examples are illustrated when the failure time has a Weibull distribution. [ABSTRACT FROM AUTHOR]

It would be of interest to formulate the general replacement models, combing the constant and random policies to satisfy the commonly planned and randomly needed replacement times. This paper takes up age and periodic replacement models again to formulate their general models when replacement actions are also conducted at random times Y i (i = 1 , 2 , ... , n) . The classic approach of whichever occurs first and the newly proposed approach of whichever occurs last are used for such general models, whose models are named as replacement first, modified replacement first, replacement last and modified replacement last, respectively. We compare all of the replacement models analytically and numerically to find which policy should be selected from the viewpoint of cost. It is shown that the modified replacement policies with combined approaches of whichever occurs first and last are more economical than others. In addition, the replacement models with different replacement costs are extended for further studies. [ABSTRACT FROM AUTHOR]

In order to ensure the data security, plans of incremental and differential backups are usually set up to save the costs which suffer from full backups. In this paper, we suppose that failures occur at data updating times and backups are implemented only at the end of data updates, and full backups are done at time T , over time T and update N to balance the costs of data backup and failure recovery. Using the theory of renewal process, we obtain the expected costs of backup and recovery and the expected cost rates for full backups. Optimum solutions of T and N to minimize the expected cost rates are obtained, and their comparisons are discussed from the optimizations of the integrated models in analytical ways. [ABSTRACT FROM AUTHOR]

Preventive replacement policy conducted at a routine time T ∗ has been surveyed extensively in literatures. Another two random replacement times Y 1 and Y 2 for time T ∗ are jointly considered in this paper. We formulate the models of replacement first, replacement last and replacement middle, which are based on the respective assumptions of whichever occurs first, whichever occurs last and whichever occurs middle. Next, we modify replacement first and replacement last by using whichever occurs first and last jointly. Furthermore, we give the model of replacement overtime when the assumptions of whichever occurs first, whichever occurs last and replacing the unit over time T are simultaneously considered. Comparisons among these replacement models are made to find which policy is more economical than the other. [ABSTRACT FROM AUTHOR]

It has been proposed in recent literatures that if replacement time is planned too early prior to failure time, a waste of operation cost, i.e., excess costs, would incur because the system might run for an additional period of time to complete critical operations; and if the replacement time is too late after failure, a great failure cost, i.e., shortage cost, is incurred due to the delay in time of the carelessly scheduled replacement. The above notion of shortage and excess costs are taken into consideration for the replacement first, replacement last and replacement overtime models in this paper. We obtain the expected cost rates and their optimum replacement times. Comparisons among these optimum times are made analytically and numerically. [ABSTRACT FROM AUTHOR]

Zhao, X.; Yu, T.; Zhao, Y.; Zhang, Y.; Sun, X.; Ma, Z.; Li, M., and Zhang, T., 2018. The investigation of the morphology and failure types of pre-placed CBN on Cu-Ni-Sn-Ti bonded to steel by laser process. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 486–489. Coconut Creek (Florida), ISSN 0749-0208. Pre-placed CBN on Cu-Ni-Sn-Ti was bonded to AISI 1045 steel with various process parameters by laser in the present paper. The wettability and the oxidization condition of the CBN in laser bead were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) respectively. The failure types of the CBN in laser bead were observed by optical microscopy (OM). The results show that the wettability of the CBN and Cu-Ni-Sn-Ti mixed powder is pronounced because of active element Ti regardless the CBN size and laser processing parameters. Oxidization is serious after laser process even though the protected gas argon being added during the laser process. The failure types can be identified into two types, mechanical press process failure and laser process failure. [ABSTRACT FROM AUTHOR]

Zhao, X.; Yu, T.; Zhao, Y.; Zhang, Y.; Yang, L.; Jiang, S., and Wang, W., 2018. Laser cladding Ti coated CBN/CuSnTi alloy on steel for grinding tools of ocean ship. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 571–578. Coconut Creek (Florida), ISSN 0749-0208. In this study, laser cladding CBN/CuSnTi alloy mixed powder on the AISI 1045 steel substrate for grinding tools of ocean ship was investigated. Various laser cladding processing parameters were conducted to find the appropriate laser cladding parameters to fabricate grinding tools of ocean ship in the continuous fiber laser beam with coaxial powder nozzle. The morphology of the laser cladding layer was analyzed by laser scanning confocal microscopy (LSCM) and the CBN grits with specific laser process parameters was observed by scanning electron microscopy (SEM). The interface conditions among the CBN grit/alloy matrix/substrate were detected by SEM and EDS to analyze the elements distribution and the morphology qualities of the bonding interface. The scratching test for the laser cladding layer with a simulated grinding force was operated to testify the bonding strength of the CBN grits embedded in the laser cladding layer for satisfying the grinding process in the industrial operation. The results showed that the cross-section and the surface of the laser cladding layer exerted by the laser process parameters of laser power of 205 W, laser scanning speed of 5 mm/s, defocus distance of 4 mm, powder feed rate of 0.8 rad/min were free of microcracks and porosities. On the other hand, the integrity and uniformity of CBN remain. Element Ti in the CuSnTi alloy matrix played a significant role in the experiment not only of the interface between matrix and CBN but also matrix and substrate. The diffusion and segregation of element Ti to the interface of CBN and substrate formed Ti-B, Ti-N, Ti-Fe compounds respectively, which caused the metallic bonding of the interfaces. During the scratching test, the phenomenon of the pull-out of the CBN embedded in the laser cladding layer was not found. CBN grits were fixed steadily with the fractured cleavage plane. It was concluded that the uniformity, integrity and metallic bonding with metal matrix of the CBN in the laser cladding layer can be carried out, which is fundamental for the laser cladding abrasive grinding tools of ocean ship produced in the industry. [ABSTRACT FROM AUTHOR]

It has been modeled for several replacement policies in literatures that the whole life cycle or operating interval of an operating unit should be finite rather than infinite as is done with the traditional method. However, it is more natural to consider the case in which the finite life cycle is a fluctuated parameter that could be used to estimate replacement times, which will be taken up in this article. For this, we first formulate a general model in which the unit is replaced at random ageU, random timeYfor the first working number, random life cycleS, or at failureX, whichever occurs first. The following models included in the general model, such that replacement done at ageTwhen variableUis a degenerate distribution, and replacement done at working numbersNsummed by numberNof variableY, are optimized. We obtain the total expected cost until replacement and the expected replacement cost rate for each model. Optimal ageT, working numberN, and a pair of (T,N) are discussed analytically and computed numerically. [ABSTRACT FROM AUTHOR]

A new periodic damage model is proposed in this paper, where the damage produced by shocks is only measured at periodic times, without considering the stochastic shocks and the cumulative process of damage in discrete times. We model five replacement policies for the periodic damage models using three approaches of whichever triggering event occurs first, whichever triggering event occurs last, and replacing over a planned measure, which are named as replacement first, replacement last, over-damage replacement, over-damage replacement first, and over-damage replacement last, respectively. In analytical ways, we obtain their optimum replacement policies to minimize the expected cost rates and compare them to find which model is more economical. Finally, numerical examples are given to illustrate the validity of the presented models. [ABSTRACT FROM AUTHOR]

It has been commonly known in a Database Management System that constant plans of incremental/differential backup schemes are set up and their full backups should be done to balance the costs of data backup and failure recovery. In this paper, we consider a database system that is running for 24/7 and has several random busy states of updates, and we suppose that incremental/differential backups are implemented after each update and full backups are triggered at constant time and random updates . That is, models with decision variables of and for full backups with random incremental/differential backups are considered. We obtain the expected costs of data backup and failure recovery and the expected cost rates for full backups. Optimum solutions to minimize the expected cost rates are discussed in analytical ways. Furthermore, full backups that are made at time and updates are considered as constant and random modes respectively and compared analytically. For the discussions, numerical examples in exponential cases are given. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to propose several new maintenance policies that can be performed at suitable middle times for trivariate preventive maintenance scenarios. Firstly, characteristics and limitations for the approaches of whichever occurs first and whichever occurs last are analyzed, and their respective maintenance models, which are called first maintenance and last maintenance, are given directly. Secondly, a combined approach of first and last is employed and middle maintenance is proposed. Thirdly, the aforementioned policy is modified to be performed at discrete working cycles, using the method of overtime maintenance. Finally, a new approach of whichever occurs middle is proposed for modelings. We give the analyses of how to formulate the middle maintenances and obtain their expected maintenance cost rates, using the technique of cumulative damage models. Numerical examples are given to compare the optimal policies among first, last, and middle maintenances. Finally, a potential application of middle maintenance is provided for future studies. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

When a unit is running successive works with cycle times, it would be uneconomical or impractical to do maintenances during any working cycle. This paper firstly reviews two replacement models proposed in literatures as follows: (1) replacement is done over a planned time $$T$$ at the completion of the working cycle, which is called over-time replacement, and (2) replacement is done over damage level $$Z$$ at the completion of the forthcoming working cycle, which is called over-level replacement. From the viewpoint of replacement cost savings, we secondly focus on comparisons of over-time replacement and its standard age-based policy, over-level replacement and its standard condition-based policy. Furthermore, modified over-time and over-level replacement costs are obtained to specify critical points at which these new replacements, rather than their standard polices, would save more replacement costs. Discussions in this paper are given analytically and computed numerically. [ABSTRACT FROM AUTHOR]

To make effective use of a running system, this paper proposes that, when replacement times could be scheduled at a planned time T of operation, and at a number N of minimal repairs, the newly proposed approach of whichever occurs last should be employed into optimizations for policy consideration. The replacement policy with the classical approach of whichever occurs first is also used to make comparison with the approach of whichever occurs last. Further, using the overtime technique, a replacement scheduled at time T in this paper is modified to be done at the first failure after T has arrived, to avoid probable interruptions for running jobs. That is, the system is replaced at failure N before time T, or at the first failure after T has arrived, whichever occurs first, and last, respectively. The policies acting on the approaches of first and last with minimal repairs are analyzed in detail, and their expected cost rates are formulated. Optimal solutions for separate and bivariate T and N are obtained and compared analytically. [ABSTRACT FROM PUBLISHER]

The tribopairs of water hydraulic plunger pumps are usually operated under severe conditions, due to the poor lubrication of water and silt suspended in natural water. It is essential to identify the desired engineering materials and material combinations for designing water pumps. As the candidate materials of tribopairs, the tribological characteristics of different Al2O3-TiO2 coatings combined with Si3N4 ceramics under silt-laden water and tap water lubrication were investigated. The Al2O3-TiO2 coatings with different weight percentages of TiO2 in a wide range from 3 to 100% were tested. The tribological characteristics of the various couple pairs were researched using a ring-on-ring test rig. The microstructures of the contact surfaces were analyzed with a scanning electron microscope before and after the test to study the wear mechanism. The experimental results indicate that the friction coefficient of the Al2O3-TiO2/Si3N4 tribopairs increases with an increase in the percentage of TiO2 content in the Al2O3-TiO2 coating. However, the TiO2 content does not present a clear relationship with the wear rate. Considering the friction and wear properties, Al2O3-13%TiO2 is the preferred coating to use in water hydraulic pumps when sliding against Si3N4. [ABSTRACT FROM AUTHOR]