An optimal sliding mode congestion controller for connection-oriented communication networks with lossy links

A new discrete-time sliding-mode congestion controller for connection-oriented networks is proposed. Packet losses which may occur during the transmission process are explicitly taken into account. Two control laws are presented, each obtained by minimizing a different cost functional. The first one concentrates on the output variable, whereas in the second one the whole state vector is considered. Weighting factors for adjusting the influence of the control signal and appropriate (state or output) errors are incorporated in both the functionals. The asymptotic stability of the closed-loop system is proved, and the conditions for 100% bottleneck node bandwidth utilization are derived. The performance of the proposed algorithm is verified by computer simulations

Sliding mode approach to congestion control in connection-oriented communication networks

In this paper, a novel sliding mode flow controller design for the connection-oriented communication networks is proposed. The networks are modeled as discrete time systems with the available bandwidth acting as disturbance. The proposed controller is designed in such a way that the closed-loop system stability and fast, finite time error convergence are ensured. In order to avoid the problem of excessive control signal magnitude, a sliding mode controller with saturation is proposed. When this controller is applied no bottleneck link buffer overflow and full utilization of its available bandwidth are guaranteed. Furthermore, transmission rates generated by the controller are always upper bounded and nonnegative

Flow control in connection-oriented networks: a time-varying sampling period system case study

summary:In this paper congestion control problem in connection-oriented communication network with multiple data sources is addressed. In the considered network the feedback necessary for the flow regulation is provided by means of management units, which are sent by each source once every M data packets. The management units, carrying the information about the current network state, return to their origin round trip time RTT after they were sent. Since the source rate is adjusted only at the instant of the control units arrival, the period between the transfer speed modifications depends on the flow rate RTT earlier, and consequently varies with time. A new, nonlinear algorithm combining the Smith principle with the proportional controller with saturation is proposed. Conditions for data loss elimination and full resource utilisation are formulated and strictly proved with explicit consideration of irregularities in the feedback information availability. Subsequently, the algorithm robustness with respect to imprecise propagation time estimation is demonstrated. Finally, a modified strategy implementing the feed-forward compensation is proposed. The strategy not only eliminates packet loss and guarantees the maximum resource utilisation, but also decreases the influence of the available bandwidth on the queue length. In this way the data transfer delay jitter is reduced, which helps to obtain the desirable Quality of Service (QoS) in the network

Discrete‐Time Sliding Mode Control with Outputs of Relative Degree More than One

This work deals with sliding mode control of discrete‐time systems where the outputs are defined or chosen to be of relative degrees more than one. The analysis brings forward important advancements in the direction of discrete‐time sliding mode control, such as improved robustness and performance of the system. It is proved that the ultimate band about the sliding surface could be greatly reduced by the choice of higher relative degree outputs, thus increasing the robustness of the system. Moreover, finite‐time stability in absence of uncertainties is proved for such a choice of higher relative degree output. In presence of uncertainties, the system states become finite time ultimately bounded in nature. The work presents in some detail the case with relative degree two outputs, deducing switching and non‐switching reaching laws for the same, while for arbitrary relative degree outputs, it shows a general formalisation of a control structure specific for a certain type of linear systems

Zespolenie nerwu twarzowego z połową nerwu podjęzykowego w leczeniu porażenia nerwu twarzowego

Background and purpose Commonly used classic hypoglossal (CN XII) to facial nerve (CN VII) anastomosis has the disadvantage of tongue hemiatrophy. Thus, various attempts have been made to modify this method to reduce the tongue damage. The aim of this report was to present the results of hemihypoglossal-facial nerve anastomosis (HHFA) technique in relation to facial muscles reanimation and hemitongue atrophy. Material and methods The first 7 consecutive patients who underwent CN VII anastomosis with half of the CNXII, for which the follow-up period exceeded 12 months, were analysed. During the procedure, CN VII was transected as proximally as possible after drilling the mastoid process. CN XII was separated longitudinally into two parts at a short distance to allow suture of the stumps without any tension. One half of CN XII was transected and sutured to the distal stump of CN VII. Recovery from facial palsy was quantified with the House-Brackmann grading system (HB). Tongue function was assessed according to the scale proposed by Martins. Results Features of initial reinnervation of facial muscles were visible after 6 months in all 7 patients. All patients achieved satisfactory outcome of CN VII regeneration (HB grade III) until the last control examination (12-27 months after surgery, mean 16). No or minimal tongue atrophy without deviation (grades I-II according to the Martins scale) was found in 4 patients. Mild hemiatrophy with tongue deviation < 30 degrees (grade III) was visible in 3 patients. Conclusions In our experience, HHFA is effective treatment of facial palsy and gives a chance to reduce damage of the tongue.Wstęp i cel pracy W leczeniu porażenia nerwu twarzowego często stosuje się zespolenie z nerwem podjęzykowym. Wadą tej metody jest połowiczy zanik języka, dlatego od wielu lat podejmuje się próby jej modyfikacji, aby zmniejszyć uszkodzenia języka. Celem pracy jest ocena wyników zespolenia nerwu twarzowego z połową nerwu podjęzykowego w kontekście reanimacji mięśni twarzy oraz następowego uszkodzenia języka. Materiał i metody Analizowano wyniki leczenia 7 pierwszych, kolejnych chorych, u których wykonano zespolenie nerwu twarzowego z połową nerwu podjęzykowego, u których czas obserwacji przekraczał 12 miesięcy. W czasie zabiegu wypreparowywano pień nerwu twarzowego z wyrostka sutko-watego oraz jego zewnątrzczaszkowy odcinek aż do jego podziału. Wypreparowywano nerw podjęzykowy, rozdzielano go podłużnie na dwie części na krótkim odcinku, aby uzyskać zespolenie bez żadnego napięcia. Jedną połowę nerwu pod-językowego zeszywano z kikutem dystalnym nerwu twarzowego. Wyniki reinerwacji mięśni twarzy oceniano wg skali House'a-Brackmanna (HB), natomiast nasilenie zbaczania i jednostronnego zaniku języka oceniano za pomocą skali zaproponowanej przez Martinsa. Wyniki Po upływie 6 miesięcy u wszystkich 7 chorych stwierdzono początkowe cechy reinerwacji mięśni twarzy. Do czasu ostatniej kontroli (12–27 miesięcy po zabiegu, średnio 16 miesięcy) u wszystkich chorych uzyskano satysfakcjonujący wynik regeneracji nerwu twarzowego (III stopień HB). Brak lub minimalny jednostronny zanik mięśni bez zbaczania języka (stopnie I–II wg Martinsa) stwierdzono u 4 pacjentów, a średniego stopnia zanik połowiczy ze zbaczaniem języka < 30 stopni (III stopień) u 3 pacjentów. Wnioski Zespolenie nerwu twarzowego z połową nerwu pod-językowego umożliwia w naszym doświadczeniu satysfakcjonującą reanimację mięśni twarzy i daje szanse na zmniejszenie uszkodzenia funkcji języka

LQ Optimal Sliding Mode Control of Periodic Review Perishable Inventories with Transportation Losses

In this work we apply the control-theoretic approach to design a new replenishment strategy for inventory systems with perishable stock. Such systems are supposed to effectively satisfy an unknown and permanently time-varying consumers' demand. The main obstacle of achieving this goal is the need of obtaining supplies from a distant source. During the supply process goods are inevitably lost due to various causes. Furthermore, those goods which successfully arrive at the distribution center still deteriorate while stored in its warehouse. We explicitly take into account both of these factors in designing our control strategy. We propose a sliding mode strategy and choose its parameters to minimize a quadratic quality criterion. This approach allows us to ameliorate the bullwhip effect (the amplification of the demand variations when going up in the supply chain). The control strategy proposed in this work ensures bounded orders, guarantees full consumers' demand satisfaction, and eliminates the risk of exceeding the warehouse capacity. These properties are stated in three theorems and proved in the paper

Rola markerów metabolizmu kostnego w kwalifikacji do leczenia osteoporozy. Wyniki programu POMOST

Introduction: Increased bone turnover markers (BTM) level is consider as independent risk factor of bone fracture. However, it was not used in 10-year probability of bone fracture method (FRAX) proposed by WHO, which helps in qualification of patients for pharmacological treatment of osteoporosis. The aim of the study was to evaluate the usefulness of BTM in qualification for pharmacological treatment of osteoporosis. Material and methods: The study was performed in 152 subjects (20 men and 132 women) referred to Krajowe Centrum Osteoporozy. One-hundred thirty two of them were qualified for pharmacological treatment and 20 for prophylaxis on the basis of qualitative method. The following BTM were examined in all patients: of bone formation - N-terminal propeptide of procolagen type I (PINP) and N-mid osteocalcin (OC) and of bone resorption - C-terminal cross-linked telopeptide of collagen type I (CTx). Results: The values over that considered as independent fracture risk (in women only, no data for men) were found in 39 women with PINP, 39 with OC and 41 with CTx. Part of women had decreased serum BTM (10 women 3 BTM and 35 with 1 at least). There were not significant differences in serum BTM depending on the presence of clinical fracture risk factors: osteoporotic fracture in past, osteoporotic hip fracture in parents, chronic treatment with glucocorticosteroids and qualification for pharmacological treatment on the basis of qualitative and FRAX method. There was no significant difference in the presence of fracture risk factors depending on increased or decreased serum BTM. Conclusions: Results of the study did not show the practical use of BTM in qualification for pharmacological treatment of osteoporosis.Wstęp: Za niezależny czynnik ryzyka złamania kości uważa się podwyższenie stężenia markerów metabolizmu kostnego (BTM, bone turnover markers). Nie uwzględniono tego jednak w metodzie oceny 10-letniego ryzyka złamania kości (FRAX) zaproponowanej przez Światową Organizację Zdrowia (WHO, World Health Organization), która ma ułatwiać decyzję o farmakologicznym leczeniu osteoporozy. Celem niniejszej pracy była ocena przydatności oznaczania stężenia markerów metabolizmu kostnego w kwalifikacji do leczenia farmakologicznego osteoporozy. Materiał i metody: Badania wykonano u 152 osób (20 mężczyzn i 132 kobiet), skierowanych do Krajowego Centrum Osteoporozy (KCO), spośród których 132 były zakwalifikowane do leczenia, a 20 do profilaktyki osteoporozy na podstawie metody jakościowej stosowanej w KCO. U wszystkich pacjentów oznaczono stężenie w surowicy markerów tworzenia kości: N-końcowy propeptyd prokolagenu typu I (PINP) i N-końcowy fragment osteokalcyny (OC) oraz resorpcji kości: C-końcowy usieciowany telopeptyd kolagenu typu I (CTx). Wyniki: Wartości powyżej progu uznanego za niezależny czynnik ryzyka złamania kości stwierdzono u 39 kobiet w przypadku PINP, 39 - OC i 41 - CTx (brak progowych wartości dla mężczyzn). Część chorych miała obniżone stężenie markerów w surowicy (10 kobiet 3 markery, 35 co najmniej 1). Nie stwierdzono istotnej różnicy stężeń markerów w zależności od obecności poszczególnych czynników ryzyka złamania kości (przebytego złamania osteoporotycznego kości, złamania biodra u rodziców i przewlekłego leczenia glikokortykoidami) oraz od kwalifikacji do leczenia osteoporozy na podstawie metody jakościowej i metody FRAX. Nie było istotnej różnicy w częstości występowania czynników ryzyka złamania kości w zależności od obniżenia czy podwyższenia stężeń (BTM). Wnioski: Nie wykazano praktycznego zastosowania oznaczania stężenia markerów metabolizmu kostnego przy podejmowaniu decyzji o konieczności leczenia farmakologicznego osteoporozy