Digital twin technology has proven to be a transformative tool in the development of smart factories by providing real-time data-driven simulations and virtual representations of physical assets and systems. This paper explores the integration of digital twins in the context of Industry 4.0 and sustainability, highlighting their potential to increase operational efficiency, optimize material usage and minimize waste. To demonstrate these benefits, case studies are presented in which a digital twin of a real manufacturing system was implemented. The digital twin enabled us to run different “what-if” scenarios to evaluate the improvements in the manufacturing system, efficiency and reduction of raw material consumption and waste by incorporating quality control operations at all assembly stations. Based on the analyzed results of both case studies, we demonstrated that additional quality control operations had a significant impact on the efficiency of the manufacturing system and its sustainability, as waste was significantly reduced. The proposed approach has proven to be highly effective for different types and sizes of manufacturing systems, especially those with high waste generation.

Digital twin technology has proven to be a transformative enabler for sustainable manufacturing by providing real-time virtual representations of physical assets and supply chain processes. This paper explores the integration of digital twins with agile supply chain strategies to improve the sustainability of manufacturing systems. By leveraging real-time data and advanced simulations, digital twins facilitate dynamic decision making, optimize resource utilization and reduce environmental impact. A case study is presented in which a digital twin is implemented with the aim of improving the responsiveness of agile supply chains and suggesting appropriate times for the delivery of components and the shipment of the final product, with the goal of minimizing the time components spend in warehouses. The analysis shows how digital twins improve clarity, adaptability and predictive capabilities, leading to greater efficiency and sustainability. The results show that the combination of digital twin technology and agile supply chain frameworks contributes significantly to resource optimization, emissions reduction and overall operational resilience. The proposed approach proves to be highly effective for various manufacturing environments, especially those that strive to balance efficiency and sustainability goals.

Digital production in the digital factory is a modern approach to support the production process. It offers the possibility of achieving continuous progress at the logistical level of the production process in the company. This paper presents an innovative approach of a digital factory for use in SMEs with small volume production. The digital factory is created on this basis and on the real example of a tool shop. With simple settings, the simulation of the defined schedule can be performed quickly and the simulation results can be used to identify potential bottlenecks to create an optimal schedule. The built-in indicators that clearly characterize the state of the production process in the digital factory are also explained, and the progress of each operation on a time scale can be read from the visual printouts.

Virtual production in the virtual factory is a modern approach to support the production process and offers a possibility to achieve continuous progress at the logistical level of the organization of the production process. The first part of the paper presents an innovative approach of a virtual factory for use in SMEs with one off production. In the following, a virtual factory created on this basis and on real example of a tool shop is explained. With simple settings, the simulation of the defined production plans can be carried out quickly and the simulation results can be used to identify potential bottlenecks and thus to create an optimal production plan. In the third part, the built-in indicators are explained, which clearly characterized the state of the production process in the virtual factory. It is possible to identify the progress of each operation on a time axis. It is also possible to identify the expected utilization of production capacities depending on the various set of production parameters and the utilization of production processes by production capacity. And as the next option it is easy to determine the free production capacities for the selected period.

For many years, Poka-Yoke (PY) has been used as one of the means to overcome challenges that can affect errors and defects in process. It is a widely accepted concept-a way of thinking, which undoubtedly contributed to significant results in a struggle against the occurrence of errors in various work processes. However, although PY seems to be well understood in theory, there are a large number of scientific papers and books that still seek to clarify and redefine PY, in order to finally implement its application at full capacity. Many authors, as it seems, want to emphasize inconsistencies in current theoretical and practical experiences. This claim is supported by the fact that over 50 similar and different PY definitions have been found in literature. It seems that most researchers do not sufficiently perceive generally accepted attitudes in the field of PY, as well as differences and inconsistencies in some of them. Due to a sense of confusion during the process design stage, an effort to predict locations of possible sources of error is a direct consequence of the diffuse knowledge in the field, which imposes the need to change that state. This paper summarizes the latest studies and definitions in the field of PY applications, in order to propose a comprehensive and generally acceptable definition of PY. In order to find what is common to the most important attitudes in the field of PY, a systematic literature review has been undertaken, with the goal to identify the areas of disagreement, to recognize any gaps that exist and outline personal experiences and attitudes in the field. The novel approach to the types of PY presented in this paper should provide a solid foundation for the creation and development of PY model and a systematic approach to the application of PY in production and service systems. Finally, some conclusions and prospective future research directions are presented.

Nowadays the production process with as few as possible deadlocks is the most important goal of management in every company. An optimized production process can be reached with well-trained personnel and especially with well-trained schedule planners. In this contribution, a new strategy on how to train production planners for different types of production by using virtual factory is presented. Also, two specially developed parametric simulation models for typical make-to-order and large-scale types of production are presented. Every model describes the real production process in detail so that it enables the observation of responses to the different input data. In the first step, the strategy covers the training of personnel so that they learn how varied input data reflect in the output results. The second strategy step is supporting schedule planning by using virtual factory where variants of schedule plans are tested much earlier than the real production process is performed.

Three new approaches and models are developed for improvements related to manufacturing processes. The main focus is on planning in a digital environment before the actual manufacturing process is carried out. The first approach, which will be presented in this paper, is digital manufacturing, which gives us an opportunity for performing an entire manufacturing process in a virtual environment. In this way, engineers virtually define, plan, create, monitor, and control all production processes. The planning phase can be done simultaneously, while other manufacturing processes are already in place. In this way, processes can continue with no interruption. Various product lifecycle management tools have databases of various programs that are used for interfacing and communication with machinery, such as CNC machines and industrial robots. Ideally, after the manufacturing process has been verified in the digital environment, control data can be uploaded to numerically controlled machinery so that the production process can start. Two special models, presented in this study, have been developed for more detailed insight into special types of manufacturing processes. The second approach represents a model for the unique type of production that takes into account all resources as the most important factor in the manufacturing processes. The main variables that were included in this model are the availability and the presence of all required manufacturing resources needed for every single manufacturing operation. The third approach represents a model for large-scale production Proceedings of The 2014 IAJC/ISAM Joint International Conference ISBN 978-1-60643-379-9 that includes all significant parameters of a manufacturing process, as well as all required intermediate storages. The last two models, which will be shown in this paper, were developed as parametric, and the users in the training process can easily make tests for different types of input data.

This paper demonstrates a new methodology for designing a virtual factory model and model execution on the basis of a real schedule plan.The main characteristic of the developed method is that the inputs are regarded as one of the main parameters of the production process, and the main objective is to create a low-cost production process model.The methodology is adjusted for use in SMEs (Small and Medium-Sized Enterprises) with individual or unique type of production.For such companies, the method represents an ability to optimize existing production processes through detecting and eliminating possible errors and disturbances before the real production process is executed at an acceptable cost.The applicability and suitability of the developed method for virtual production performance has been proven with the verification process, where the input data for the simulation was obtained from a real company.The simulation results have shown that the presented methodology is a useful tool for the optimization of the production process.

In this paper, we present and propose the interactive push-pull lean game with a specific approach for training/testing of production processes. With our approach of combining the psychologically effective physical lean game and the simulation lean game for deeper analyses of the production process, we can successfully overcome the communication and motivation problems of production and management workers when new production strategies are being introduced into the company to raise the competitiveness. The game only takes two hours and it has been proven to be effective with leadership teams and shop floor workers alike in more than 50 real-case production environments. The game is played in two parts where each part is in sharp contrast to the other with respect to results. Once the participants of the game see the effects of both production strategies, they become extremely engaged and motivated, and it becomes much easier to manage organizational improvements. In the third chapter of the paper, we present the Virtual factory computer models of the game dynamic, showing the same results as obtained with groups. The two simulation models serve to test and verify the interactive game. The paper ends with the discussion and conclusions.

This paper presents a new approach for modelling and simulation of hydraulic spool valves by using the already known simple mathematical expressions for describing the sliding spool geometry. The main objective of the research is to divide the hydraulic sliding spool into functional elements which can be described analytically. Such models can be implemented as micro components into any hydraulic simulation tool's library. By using such an approach, hydraulic valves can be designed very flexibly, with different shapes of spool metering edges in combination with other functional elements. The user can quickly find the most appropriate spool construction for the desired hydraulic system performance. This can be done in advance, before designing the real system. The paper deals with and presents only one of the several different geometrical shapes of spool metering edges and the corresponding mathematical models of the volume flow characteristics that we have developed. Simulation results are verified and confirmed with experimental tests using a real valve geometry.

Enormous loss of production time in machining, handling and assembly operations is caused mainly by resources' unavailability. For this reason companies, both large and small, should optimize the production processes with the detection and elimination in advance of the majority of possible mistakes and disturbances that could cause deadlocks in the production process. The optimization tools which are available on the market are usually too expensive for smaller companies, which search for their competitive position in small quantity production. Therefore, a low cost simulation tool for the optimization of the resource present management is presented in this paper, where resources are treated as one of the main parameters in the production process and which could also enable smaller companies to optimize their production processes from the resource presence viewpoint.

V proizvodnih stroskih orodjarn pomenijo rezalna orodja, poleg samih obdelovalnih centrov, najvecji delež stroskov. Po vecini slabo urejeno skladiscenje ter slab pregled stanja rezalnih orodij se kaže v premajhni zasedenosti obdelovalnih centrov ter v relativno velikih stroskih za rezalna orodja. Z dobro organiziranimin racunalnisko podprtim upravljanjem obdelovalnih orodij je mogoce le stroske zmanjsati, vendar to se vedno ni dovolj za ucinkovito nacrtovanje proizvodnje. Zato je namen tega prispevka osvetliti to podrocje, prikazati koncept racunalniskega upravljanja z obdelovalnimi orodji, podprtega s simulacijo (RUOS) in predstaviti glavne znacilnosti sistema RUOS, ki je plod raziskovalno-razvojnega dela laboratorija LASIM v sodelovanju s slovensko orodjarno.

After machining centres, cutting tools are the most expensive item in the production costs of a tool-making company. Unorganised warehousing and poor reviewing of the condition of the cutting tools are still the characteristics of these companies, which results in under use of machining centres and high costs for cutting tools. By using computerized tool management of cutting tools it is possible to reduce costs, but for the efficient planning of production this is still not enough. Therefore, the purpose of this article is to throw light on these questions and to introduce the concept of Simulation-Based Tool Management (SBTM) and the main features of the SBTM system, which has been developed in cooperation with a tool-making company.

Background The role of postoperative radiotherapy in treatment of patients with completely resected non-small-cell lung cancer (NSCLC) remains unclear. We undertook a systematic review and meta-analysis of the available evidence from randomised trials.Methods Updated data were obtained on individual patients from all available randomised trials of postoperative radiotherapy versus surgery alone. Data on 2128 patients from nine randomised trials (published and unpublished) were analysed by intention to treat. There were 707 deaths among 1056 patients assigned postoperative radiotherapy and 661 among 1072 assigned surgery alone. Median follow-up was 3.9 years (2.3-9.8 for individual trials) for surviving patients.Findings The results show a significant adverse effect of postoperative radiotherapy on survival (hazard ratio 1.21 [95% CI 1.08-1.34]). This 21% relative increase in the risk of death is equivalent to an absolute detriment of 7% (3-11) at 2 years, reducing overall survival from 55% to 48%. Subgroup analyses suggest that this adverse effect was greatest for patients with stage I/II, N0-N1 disease, whereas for those with stage III, N2 disease there was no clear evidence of an adverse effect.Interpretation Postoperative radiotherapy is detrimental to patients with early-stage completely resected NSCLC and should not be used routinely for such patients. The role of postoperative radiotherapy in the treatment of N2 tumours is not clear and may warrant further research.

During the 14-year period under study, 48 patients with SST were treated al the Institute of Oncology in Ljubljana, Slovenia. There were 46 males and two females, aged 29-88 years (median, 60 years). Of 37 cytologically or histologically confirmed tumors, 12 were squamous, eight large-cell, one small-cell, eight adeno, and eight unclassified carcinomas. Performance status (Karnofsky) was assessed as > 90 in eight, 70-90 in 31 and < 70 in nine patients. The duration of symptoms before diagnosis ranged from 1 to 36 months (median, 5 months). All patients had pain, while six also had hemophthysis, 14 Horner's syndrome, and four Horner's syndrome and upper limb paresis. Before the first chest X-ray, 19 patients were treated for shoulder pain by different specialists. Apical tumor infiltration only on the chest X-ray was found in 13, destruction of the ribs in 31, and destruction of the ribs and vertebral bodies in four patients. Treatment was as follows: radiotherapy in 39 patients (22 with radical, 17 with palliative dose), a combination of surgery and radiotherapy in seven, radiotherapy and chemotherapy in one, and symptomatic therapy alone in one patient. One- and four-year survival of all treated patients was 27% and 11%, respectively. One of the seven patients operated on survived for 44 months, and 2/39 irradiated ones survived for 37 and 56 months, respectively, while others died within 24 months from diagnosis. In 81% of patients the pain was subdued after radiotherapy. The disease-specific survival of all patients included in the follow-up correlated with performance status and M stage, while that of those treated by irradiation alone correlated with tumor dose (P < 0.05). (C) 1997 Elsevier Science Ireland Ltd.

In the period 1988-1992, 74 consecutive radically resected patients with NSCLC were randomised to postoperative radiotherapy or surgery alone in order to evaluate the influence of postoperative radiotherapy on survival. There were 61 males and 13 females, aged 35-80 years, median 59 years. Their distribution by stage was as follows: pT1N2 = 19, pT2N2 = 54, pT3N2 = one patient; histology: 32 squamous, 32 adeno and 10 large cell carcinomas; surgery: atypical resection in six, lobectomy in 27, bilobectomy in ten, and pneumonectomy in 31 patients. In 27 patients, only one lymph node in a single mediastinal lymph node site was affected; in 31 patients more than one lymph node in one site; in 16 patients more sites were affected. In 35/74 patients radiotherapy of hilar and mediastinal sites with 3000 cGy in 2 weeks was performed. On December 31, 1994, 19 patients (26%) were still alive; 39/55 patients died of the following causes: locoregional failure-10(26%), distant metastases- 25 (64%), other tumor-unrelated causes-four patients (10%). Five-year survival rates did not show statistically significant differences between the irradiated and surgically treated patients only with respect to sex, pTNM stage, histology and frequency of locoregional failure. The number of metastatic mediastinal lymph nodes was the only significant prognostic factor (P < 0.005) in both randomised groups.

1. The higher relative molecular mass (M(r)) forms of larval honeybee haemolymph alpha-glucosidases are dissociated by dithiothreitol (DTT) into lower M(r) electrophoretic forms, without any important loss of activity. 2. The maximum velocity remains unchanged and the apparent dissociation constant is slightly increased, with Ki approximately equal to 247 mM and I50 approximately equal to 730 mM. 3. By contrast, the major changes affect the Hill coefficient which decreases from 1.0 in controls to 0.7 in presence of 600 mM DTT. 4. In the absence of both DTT and substrate, the major native enzyme form, isolated by gel filtration, spontaneously rearranges to give three additional minor forms, one of lower M(r) and two of higher M(r). 5. These data are consistent with the hypothesis of substrate-directed aggregation of enzyme protomers into functional complexes.