Investigation on efficiency improvement of a Kalina cycle by sliding condensation pressure method

Conventional Kalina cycle-based geothermal power plants are designed with a fixed working point determined by the local maximum ambient temperature during the year. A previous study indicated that the plant’s annual average thermal efficiency would be improved if the ammonia mass fraction of the Kalina cycle could be tuned to adapt to the ambient conditions. In this paper, another sliding condensation pressure method is investigated. A theoretical model is set up and then a numerical program is developed to analyze the cycle performance. The condensation pressure adjustment in accordance to the changing ambient temperature has been numerically demonstrated under various ammonia-water mixture concentrations. The results indicate that the Kalina cycle using sliding condensation pressure method can achieve much better annual average thermal efficiency than a conventional Kalina cycle through matching the cycle with the changing ambient temperature via controlling condensation pressure. Furthermore, the sliding condensation pressure method is compared with the composition tuning method. The results show that the annual average efficiency improvement of the sliding condensation pressure method is higher than that of the composition tuning method

Service Deployment Model on Shared Virtual Network Functions With Flow Partition

Network operators can operate services in a flexible way with virtual network functions thanks to the network function virtualization technology. Flow partition allows aggregated traffic to be split into multiple parts, which increases the flexibility. This paper proposes a service deployment model with flow partition to minimize the service deployment cost with meeting service delay requirements. A virtual network function of a service is allowed to have several instances, each of which hosts a part of flows and can be shared among different services, to reduce the initial and proportional cost. We provide the mathematical formulation for the proposed model and transform it to a special case as a mixed integer second-order cone programming (MISOCP) problem. A heuristic algorithm, which is called a flow partition heuristic (FPH), is introduced to solve the original problem in practical time by decomposing it into several steps; each step handles a convex problem. We compare the performances of proposed model with flow partition and conventional model without flow partition. We consider the formulated MISOCP problem with adopting a strategy of even splitting to divide flows in a special case, which is called an even spitting heuristic (ESH). The performances of FPH and ESH are compared in a realistic scenario. We also consider the formulated MISOCP problem as an original problem and compare it to an FPH-based heuristic algorithm with the even-splitting strategy (FPH-ES), in both realistic and synthetic scenarios. The numerical results reveal that the proposed model saves the service deployment cost compared to the conventional one. It improves the maximum admissible traffic scale by 23% in average in our examined cases. We observe that FPH outperforms ESH and ESH outperforms FPH-ES in terms of the service deployment cost in their own focused problems, respectively

Organic Photovoltaic Cells Based on PbPc Nanocolumns Prepared by Glancing Angle Deposition

Organic small material lead phthalocyanine (PbPc) nanocolumns were prepared via glancing angle deposition (GLAD) on indium tin oxide (ITO) coated glass substrates. Organic electron acceptor materials fullerene (C60) was evaporated onto the nanocolumn PbPc thin films to prepare heterojunction structure ITO/PbPc/C60/Bphen/Al organic photovoltaic cells (OPVs). It is worthwhile to mention that C60 molecules firstly fill the voids between PbPc nanocolumns and then form impact C60 layer. The interpenetrating electron donor/acceptor structure effectively enhances interface between electron donor and electron acceptor, which is beneficial to exciton dissociation. The short circuit current density (Jsc) of organic photovoltaic devices (OPVs) based on PbPc nanocolumn was increased from 1.19 mA/cm2 to 1.74 mA/cm2, which should be attributed to the increase of interface between donor and acceptor. The effect of illumination intensity on the performance of OPVs was investigated by controlling the distance between light source and sample, and the Jsc of two kind of OPVs was increased along with the increase of illumination intensity

Performance Evaluation and Control Strategy Comparison of Supercapacitors for a Hybrid Electric Vehicle

Electrification of powertrain system is a great technical progress of traditional vehicle, leading to a significant reduction of fuel consumption and emission pollution. Energy storage system (ESS) normally consisting of batteries is a key component of an electric vehicle or hybrid electric vehicle. An ESS can recover braking energy during the regenerative braking process. Currently, lithium-ion batteries are the main energy storage device due to their high energy density. However, sometimes, a sudden large increase of operation current is required during acceleration or regenerative braking processes, which will jeopardize the operation life of batteries. A supercapacitor takes advantage of high power density and can tolerate large current in a short time. Application of supercapacitor in an ESS can reduce the peak current of batteries effectively, and the life time of batteries can be extended. Meanwhile, the braking energy can also be recovered sufficiently. Supercapacitors can be used solely in some hybrid electric vehicles. In this chapter, the application of supercapacitors in electric vehicles or hybrid electric vehicles is reviewed briefly. Then, the performance of a series hybrid transit bus, which uses a compressed natural gas engine and supercapacitors as power sources, is analyzed

Efficacy of some selected neo-adjuvant chemotherapy regimens in the treatment of advanced oral squamous cell carcinoma, and their effects on immune function

Purpose: To investigate the clinical efficacy of different neo-adjuvant chemotherapy (NACT) regimens in the treatment of advanced oral squamous cell carcinoma (OSCC), and their influence on immune function of the patients.Methods: Advanced OSCC patients (n = 94) who received NACT served as subjects in this study. They were assigned to 2 different treatment groups. Forty patients received docetaxel and fluorouracil regimen (DF group), while 54 patients received taxotere, cisplatin and fluorouracil regimen (TPF group). Surgery was performed after NACT. Changes in clinical efficacy and immune function were monitored in both groups. The clinical baseline data of patients were assessed prior to the treatments. Independent indicators of prognosis were determined using Cox regression analysis (CRA).Results: Clinical treatment efficacy was higher in TPF group than in DF group (p < 0.05). Objective remission rate (ORR) in DF group was lower than that in TPF group (p < 0.05). After chemotherapy, both groups had increased levels of CD4+ and CD4+/CD8+, and reduced level of CD8+, when compared with pre-chemotherapy values, with higher levels of CD4+ and CD4+/CD8+ ratio, and lower level of CD8+ in TPF group than in DF group (p < 0.05). Multivariate CRA revealed that the independent factors for prognosis of oral carcinoma (OC) were tumor node metastasis (TNM) stage and lymph node metastasis.Conclusion: These results indicate that TFP regimen improves clinical efficacy and immune function in patients with advanced OSCC

Modelling centrifugal membrane deployment of solar sails with the discrete element method

Spin-stabilized solar sails have been extensively studied in recent years. In this paper, a DEM-based approach is proposed for dynamic analysis of the centrifugal deployment of solar sails. In order to validate the proposed approach, the deployment of a small-scale solar sail similar to “IKAROS” is studied. The membrane is discretised into a number of particles, with no physical contact between them. Non-contact interaction is introduced to model in-plane stiffness of the membrane. In order to improve the accuracy, additional forces are applied to the mass particles to model buckling strength, crease stiffness, air drag and damping. The predicted results of the membrane deployment are compared with the experimental data and numerical results in the literature

Design of high frequency ultrasonic transducers with flexure decoupling flanges for thermosonic bonding

This paper presents the design of high frequency ultrasonic transducers for micro/nano device thermosonic bonding. The transducers are actuated by piezoelectric ceramics and decoupled with their connecting parts through novel flexure decoupling flanges. Firstly, the initial geometric dimensions of the transducers were calculated using electromechanical equivalent method, then dynamic optimization design was carried out based on 3D finite element method (FEM), and the geometric dimensions of the transducer were finally determined. Flexure decoupling flanges were presented, and the decoupling principle of the flanges was explained through compliance modeling using compliance matrix method and FEM. After that the dynamic characteristics of the transducers were analyzed through finite element analysis (FEA). The vibration frequencies and modes of the piezoelectric converter, concentrators and transducers were obtained through modal analysis, and the displacement nodes were determined. The longitudinal ultrasonic energy transmission was presented and the decoupling effects of the flexure flanges were compared. Finally, the transducers were manufactured and experimental tests were conducted to examine the transducer characteristics using an impedance analyzer. The experimental results match well with the FEA. The results show that the longitudinal vibration frequencies of the transducers with ring, prismatic beam and circular notched hinge based flanges are 126.6 kHz, 125.8 kHz and 125.52 kHz, respectively. The decoupling flange with circular notched hinges shows the best decoupling effect among the three types of flanges

Probe system design for three dimensional micro/nano scratching machine

This paper presents the design and testing methodologies for a probe system used in a tip-based three dimensional micro/nano scratching machine. The probe system is one of the most important components of the scratching machine, including an electromagnetic device and a probe suspension mechanism. The electromagnetic device is used to generate electromagnetic force to drive the probe suspension mechanism, and further scratch the sample. The probe suspension mechanism is utilized to support the diamond probe and form the capacitor plates with the aluminum film. Both analytical modeling and finite element analysis are conducted to improve the static and dynamic characteristics of the proposed scratching machine. A prototype has been developed to validate the established design methodologies. A number of experimental tests have been conducted to examine the prototype performance. From the experimental results, it is noted that the developed probe system has a force resolution of 78.4 μN, a displacement resolution of 60 nm, and the first natural frequency of 465 Hz. This indicates that it can be used for the development of the three dimensional submicron or even nano scratching

Design of a Piezoelectric-actuated microgripper with a three-stage flexure-based amplification

This paper presents a novel microgripper mechanism for micromanipulation and assembly. The microgripper is driven by a piezoelectric actuator, and a three-stage flexure-based amplification has been designed to achieve large jaw displacements. The kinematic, static and dynamic models of the microgripper have been established and optimized considering the crucial parameters that determine the characteristics of the microgripper. Finite element analysis was conducted to evaluate the characteristics of the microgripper, and wire electro discharge machining technique was utilized to fabricate the monolithic structure of the microgripper mechanism. Experimental tests were carried out to investigate the performance of the microgripper and the results show that the microgripper can grasp microobjects with the maximum jaw motion stroke of 190 μm corresponding to the 100-V applied voltage. It has an amplification ratio of 22.8 and working mode frequency of 953 Hz

Development of a piezo-driven 3-DOF stage with T-shape flexible hinge mechanism

This paper presents a 3-DOF (Degree of freedom) stage with T-shape flexible hinge mechanism for the applications in the precision measurement equipments and micro/nano manipulation systems. The stage is driven by three piezoelectric actuators (PEAs) and guided by a flexible hinge based mechanism with three symmetric T-shape hinges. The proposed T-shape flexible hinge mechanism can provide excellent planar motion capability with high stability, and thus guarantee the outstanding dynamics characteristics. The theoretical modeling of the stage was carried out and the stiffness and the dynamic resonance frequency have been obtained. The kinematic model of the 3-DOF stage was established and the workspace has been analyzed. The characteristics of the stage were investigated using finite element analysis (FEA). Experiments were conducted to examine the performance of the stage, through this stage, X-axis translational motion stroke of 6.9 µm, Y-axis translational motion stroke of 8.5 µm and rotational motion stroke along Z-axis of 289 µrad can be achieved. A hybrid feedforward/feedback control methodology has been proposed to eliminate the nonlinear hysteresis, the trajectory tracking performances and to reduce external disturbance of the 3-DOF stage