Multi-objective group scheduling with learning effect in the cellular manufacturing system

Group scheduling problem in cellular manufacturing systems consists of two major steps. Sequence of parts in each part-family and the sequence of part-family to enter the cell to be processed. This paper presents a new method for group scheduling problems in flow shop systems where it minimizes makespan (Cmax) and total tardiness. In this paper, a position-based learning model in cellular manufacturing system is utilized where processing time for each part-family depends on the entrance sequence of that part. The problem of group scheduling is modeled by minimizing two objectives of position-based learning effect as well as the assumption of setup time depending on the sequence of parts-family. Since the proposed problem is NP-hard, two meta heuristic algorithms are presented based on genetic algorithm, namely: Non-dominated sorting genetic algorithm (NSGA-II) and non-dominated rank genetic algorithm (NRGA). The algorithms are tested using randomly generated problems. The results include a set of Pareto solutions and three different evaluation criteria are used to compare the results. The results indicate that the proposed algorithms are quite efficient to solve the problem in a short computational time

Patency rate and factors affecting the clinical outcome of patients with aortoiliac artery occlusion undergoing intra-arterial stenting

Background Occluding plaques are commonly found inthe infrarenal aorta and the iliac artery in patients with peripheralarterial disease (PAD). Aortoiliacocclusive disease(AIOD) occurs commonly in patients with PAD.Methods: This is a prospective study was carried out between2015 and 2017 in Sina hospital. Patients with occlusionin aortoiliac artery and its branches were included.Stent was placed for patients, if they had any obstructionor stenosis in aortoiliac artery in angiography. Patientswere examined in terms of clinical status and ABI calculationand underwent Color Doppler ultrasound of aortoiliacartery to determine patency rate at 1, 3, 12, and 24months after stent placement.Results: The mean age of patients was 64.60 (±10.41).The main symptoms of the patients were claudication(41.8%), ulcer (27.3%), pain at rest (20%), and gangrene(20%). The lesion was bilateral in 21 patients (38.2%).According to TASC stratification, lesions were of type A in26 patients (47.3%), type B in 4 patients (7.3%), type Cin 5 patients (9.1%), and type D in 20 patients (36.4%).The six-month, one-year, and two-year patency rates were89.1%, 83.6%, and 72.7%, respectively. The mean annualABI of patients was 0.79 (±0.11) and two year ABIwas 0.68 (±0.1).Conclusion: It seems that stenting and angioplasty areeffective in improving patients’ conditions and result in agood short and medium-term patency

Towards joint communication and sensing (Chapter 4)

Localization of user equipment (UE) in mobile communication networks has been supported from the early stages of 3rd generation partnership project (3GPP). With 5th Generation (5G) and its target use cases, localization is increasingly gaining importance. Integrated sensing and localization in 6th Generation (6G) networks promise the introduction of more efficient networks and compelling applications to be developed

Network optimization in RIS-assisted communications

Abstract This thesis presents new user association (UA) schemes that take cell interference into account for a multi-cell network aided with multiple reconfigurable intelligent surfaces (RISs). We formulate a network spectral efficiency maximization problem by jointly optimizing active beamforming at the base stations (BSs), passive beamforming at the RISs, and user-BS association with consideration to the impact of RISs. We then propose a computationally efficient iterative algorithm based on alternating optimization to resolve this intractable mixed-integer non-convex problem. A fractional programming technique is used to optimize active beamforming at the BSs and passive beamforming at the RISs, and a penalization method combined with successive convex programming is applied for UA optimization, which is shown to achieve an optimal solution. Additionally, we balance BS loads and maximize the network utility by optimizing the user association with a matching game in another scheme. Finally, a crucial aspect of 6G is that localization and sensing will not be a by-product of communications development but will instead be integrated into the system from the start, and thus is a main design target of 6G. Toward this, a vision for how location and sensing information can be used to support, enable, and enrich novel applications will be sketched. In addition, the potential benefits of location and sensing information for improving communications are investigated as use cases. Therefore, taking advantage of sensing with radio waves and localization, we propose a novel environment-aware joint active/passive beamforming approach for RIS-aided wireless communication based on the new concept of channel knowledge map (CKM). In the proposed scheme, the user equipment location information is combined with the radio environment information provided by CKM to achieve efficient beamforming without real-time training. Simulation results show the proposed scheme’s superior performance over training-based beamforming, which is also quite robust to errors related to the UE’s location in practice.Tiivistelmä Tässä väitöskirjassa esitellään uusia käyttäjäyhteys (user association, UA)- järjestelmiä, joissa otetaan huomioon solujen häiriöt monisoluverkossa, jossa on useita uudelleenkonfiguroitavia älykkäitä pintoja (reconfigurable intelligent surfaces, RIS). Muotoilemme verkon spektritehokkuuden maksimoinnin ongelman optimoimalla yhdessä aktiivisen keilanmuodostuksen tukiasemilla, passiivisen keilanmuodostuksen RIS-pinnoilla ja käyttäjän tukiasemayhteyden ottaen huomioon RIS-pintojen vaikutuksen. Tämän jälkeen ehdotamme laskennallisesti tehokasta iteratiivista algoritmia, joka perustuu vuorottelevaan optimointiin, jotta tämä hankala ei-konveksi sekakokonaislukuongelma saadaan ratkaistua. Tukiasemien aktiivisen keilanmuodostuksen ja RIS-pintojen passiivisen keilanmuodostuksen optimointiin käytetään fraktionaalista ohjelmointitekniikkaa, ja peräkkäiseen konveksiin ohjelmointiin yhdistettyä rangaistusmenetelmää sovelletaan käyttäjäyhteyden optimointiin. Sen avulla osoitetaan päästävän optimaaliseen ratkaisuun. Lisäksi tasapainotamme tukiasemien kuormia ja maksimoimme verkon käytön optimoimalla käyttäjäyhteyden vastaavalla pelillä toisessa järjestelmässä. 6G:n keskeinen näkökohta on, että paikantaminen ja tunnistaminen eivät ole viestinnän kehityksen sivutuotteita, vaan ne integroidaan järjestelmään alusta alkaen, ja ne ovat siten 6G:n suunnittelun päätavoitteita. Tätä varten hahmotellaan visio siitä, miten sijainti- ja tunnistamistietoja voidaan käyttää uusien sovellusten tukemiseen, mahdollistamiseen ja rikastamiseen. Lisäksi käyttötapauksina tutkitaan paikannus- ja tunnistamistietojen mahdollisia hyötyjä viestinnän parantamisessa. Tämän vuoksi ja radioaaltojen avulla tapahtuvaa tunnistamista ja paikannusta hyödyntämällä ehdotamme uutta ympäristötietoista yhdistettyä aktiivista/passiivista keilanmuodostusta RIS-avusteiseen langattomaan viestintään uuden kanavatietokartan konseptin perusteella. Ehdotetussa järjestelmässä käyttäjien laitteiden sijaintitiedot yhdistetään kanavatietokartan radioympäristötietoihin, jotta keilanmuodostus olisi tehokasta ilman reaaliaikaista koulutusta. Simulaatiotulokset osoittavat ehdotetun järjestelmän ylivertaisen suorituskyvyn verrattuna koulutukseen perustuvaan keilanmuodostukseen, ja se kestää myös erittäin hyvin käyttäjälaitteiden sijaintiin liittyviä virheitä käytännössä

A Two Step Secure Spectrum Sensing Algorithm Using Fuzzy Logic for Cognitive Radio Networks

In this paper, a two step secure spectrum sensing algorithm is proposed for cognitive radio networks. In this algorithm, the sensing results of secondary users are pre-filtered and applying fuzzy logic, so, the overall sensing performance of the network is improved. To determine pre-filter parameters, statistical parameters of the sensing results are used to remove those sensing results which are far from the majority sensing results. However, to obtain a better performance in the spectrum sensing, we propose a fuzzy logic to nullify the ef-fects of malicious users who transmit false sensing data to the fusion center. We further propose a Fuzzy Trust Level for each user as to weight the sensing result of the corresponding user before combining all sensing results in the fusion center. Simulation results demonstrate that our proposed algorithm yield signifi-cant improvement in the performance of the spectrum sensing and identifying malicious users

Centrifugal compressor performance assessment under different impeller tip clearance sizes from far to near stall conditions

Impeller tip clearance is a key parameter in design process of a centrifugal compressor which has influential effects on its aerodynamic and thermodynamic performances. Interaction of tip leakage flow with the main stream could be the major source for occurrence of stall phenomenon. In the present investigation, two impeller tip clearances of small and large sizes are investigated under different flow coefficients assigned to “design”, “low flow” and “high flow” conditions. Flow field is precisely simulated utilizing solution of the Reynolds-Averaged Navier-Stokes equations. Influence of the impeller stall on the volute flow field is studied. Structure of vortical flows within the impeller passages and volute are demonstrated in details. Numerical results showed that the flow within the volute becomes stall-prone while the flow within the impeller stalls. In contrast to the high flow case, the low flow condition was more prone for the stall occurrence. Performance tests were also conducted on Iran University of Science and Technology (IUST) centrifugal compressor test rig for validation of the numerical results