Increase In Number Of Stages Research Articles

The effect of flow modes on the capture of the energy between concentrated brine and seawater by reverse electrodialysis

The discharge of concentrated brine from the desalination unit waste amounts of salinity gradient energy, which could be harvested and converted to electric energy by reverse electrodialysis (RED). However, the poor power and restricted conversion efficiency obstacle its development. A suitable flow mode of feed solutions in a RED stack can improve energy conversion efficiency. Here, the influences of co– and counter-current flow modes on the performances of a single-stage RED stack and multi-stage stacks harvesting the energy are studied in the work. Based on this, the models of flow mode affecting the RED performances are built and experimentally verified. Results show that the counter-current in a single-stage stack is better than the co-current, and the advantage is more obvious with the concentration increase of the concentrated solution, the concentration decrease of the diluted solution, and the decrease of flow rate. Besides feed parameters, the stack sizes also influence the performances of the single-stage stack in both modes. The counter-current in the multi-stage stacks is also more excellent than the co-current. However, the difference decreases with the increase of stage number. This work provides some support for utilizing the salinity gradient energy between concentrated brine and seawater.

Parametric Study on the Influence of Pedestrians' Road Crossing Pattern on Safety

Objective: The present research concentrates on studying the road crossing time of pedestrians based on their pattern of the road crossing. The factors that influence the road occupancy time due to the irregular road crossing patterns of pedestrians have been studied. Methods: The research used a videographic survey of three midblock locations with different land-use types. The pedestrian variables from the video data are extracted to excel using a custom-made video player. The data set consists of 8718 pedestrian data, including all three sites, and the data is analysed using statistical methods. A binary logit analysis is performed to predict the variable influencing the crossing time High/Low. Results: According to the analysis, females making path changes and an increase in stage number show a higher road crossing time for pedestrians. Also, the absence of motor vehicles results in a higher road crossing time for pedestrians. The prediction accuracy of the model is 58.2%, and a variance of 6% shows a lesser degree of spread in the dataset. Conclusion: The inference from the study is that the crossing time of path-changing pedestrians is more than straight-moving pedestrians. Thus, an increase in road crossing time decreases the safety of pedestrians by increasing the exposure rate while crossing the road. So, the probability of safety risk is high when they practice irregular road crossing patterns.

An optical concentrator coupled multistage solar steam generation system for solar thermal-latent heat cascade utilization and water desalination: Performance and economic benefit analysis

Solar steam generation (SSG) for water treatment has attracted great interest for its convenience, accessibility and eco-friendliness. However, water production rate of traditional floating structure SSG system is relatively low. To further increase the water production rate, we develop a solar thermal-latent heat cascade utilization SSG system coupled with compound parabolic concentrator for desalination. A 2 × compound parabolic concentrator (CPC) was used in the outdoor experiment to improve the incident solar flux. Solar absorber of the SSG module has a high solar absorbance of 95 % which can effectively harvest solar energy and convert it into heat. A thin air gap above the solar absorber can restrain thermal loss through convection and radiation. Within the SSG module, seawater was supplied for the evaporation process driven by the capillary force in the capillary wick. Through the multi-stage design, solar thermal conversion and latent heat cascade recovery were achieved. As a result, the SSG module can achieve a gain to output ratio (GOR) of 185.09 % with a water flux of 2.82 kg∙m−2∙h−1 under one sun. Concentrating solar flux reached 1300 W∙m−2 in an early autumn day and a corresponding water flux of 3.5 kg∙m−2∙h−1 was achieved. Theoretical analysis showed that higher solar flux can increase the GOR. Optical concentration of 2 × can increase annual fresh water by 1.72 times while maintaining economic benefit. An insulation air gap above the solar absorber can reduce thermal loss from the solar absorber. Increasing stages can increase number of times the latent heat being reused and improve GOR, but economic benefit decreased with the increase of stage number. Considering the economic benefit and floor area, optical stage number of the system should be 4. Annual water production evaluation showed that a 1 m2 area system can annually generate 6321.29 kg fresh water with a water production cost of 7.03$/m3.

Thermodynamic analysis for a novel chemical precooling turbojet engine based on a multi-stage precooling-compression cycle

Precooling technology is an effective way to improve the flight Mach number for turbojet engine. To solve the problem of engine performance degradation caused by excessive fuel consumption, a multi-stage precooling-compression cycle is newly proposed, in which the secondary cooling capacity of fuel is reused by transfer the heat energy from fuel to the mechanical work. To evaluate the engine performance, several new performance parameters are defined and a thermodynamic model is established, in which the optimum distribution of pressure ratio for each stage of turbine/compressor and the performance limit of engine are derived in theory. By calculation, it is found that the heat absorption capacity of fuel and the engine performance could be improved with the increase of stage number. Further, the lower and upper performance boundaries of engine could be obtained when the stage number is set to one and infinity respectively. Moreover, considering the engineering application, the two-stage precooling-compression cycle will be regarded as the best design, and when the engine performance is improved by about 8.15%, the heat transfer area of pre-cooler will be increased by 88.19%, as well as the mass of compressor and turbine will be increased by 30.33% and 11.18% respectively.

Performance demonstration of cavity-free planar multi-stage bileg and unileg silicon-nanowire thermoelectric generators

The thermoelectric (TE) generator is expected to play an important role in the operation of tiny-watt capable wireless power supply devices, by converting waste heat energy into electrical energy. This work demonstrates planar cavity-free multi-stage n-type unileg- and bileg Si-nanowire (Si-NW) TE generators. The result shows that the output power of the multi-stage bileg-TE generator increases linearly with increasing the stage number, whereas the rate of increase of the multi-stage unileg-TE generator power output tends to decrease as the stage number increases. Although the power of the multi-stage bileg-TE generator fabricated in this work was smaller than that of the multi-stage unileg-TE generator, due to the large internal resistance of p-type elements, the improved linearity of the bileg-TE generator compared to the unileg-TE generator indicates the potential advantage of the multi-stage bileg-TE generator for large-scale integration.

Efficiency of Three Bacterial Strains Against Tetranychus urticae Koch (Acari: Tetranychidae) Under Laboratory Conditions

This study was conducted to evaluate the efficiency of three bacterial strains Pseudomonas aeruginosa, Bacillus subtilis and Lysinibacillus spaericus against adult females of Tetranychus urticae Koch using spraying and dipping techniques with concentrations (101, 103, 105, 107 cfu. ml-1). The mortality percentages were calculated and numbers of each stages resulting from the live treated females were recorded. The symptoms that appear on treated female's mites as a result of death under laboratory conditions were recorded and photographed. The results revealed that, P. aeruginosa caused the highest mortality percentage of adult females T. urticae 100% after 72h at concentration 107 cfu. ml-1 by spraying application. Whereas the mortality percentage which recorded by the dipping technique was 54.58±1.71. B. subtilis also, was recorded increased the average mortality percentage of female T. urticae as it reached 73.33±2.67 in spraying technique compared 41.25±2.08 in dipping technique. While in L. spaericus recorded 62.08±3.41 mortality (%) in spraying technique but at dipping technique the mortality was 27.50±1.61. A sharp decrease was shown in number of stages resulting from lived treated females of T. urticae with P. aeruginosa by four concentrations 101, 103, 105 and 107 by using spraying technique and the life cycle was stopped at the larval stage only at concentration 101 and were not changed into the nymphal stage. While with dipping technique a slight increase in the average number of stages resulting from the adult living females treated with the previously aforementioned concentrations of bacteria P. aeruginosa. The present study cleared that application of bacteria strains on T. urticae adult females either by spraying or dipping techniques lead to some deformations such as, swelling of the body, then fluids exit followed by complete dryness of the body and forward protrusion of the podosoma region and finally death of the adult females

Hydrogen decompression analysis by multi-stage Tesla valves for hydrogen fuel cell

Abstract Hydrogen fuel cell is an ideal power source for electric vehicles. For a hydrogen fuel cell electric vehicle, the hydrogen is reserved in a high pressure level to promote the recharge mileage while relatively low-pressure hydrogen is demanded for proper functioning of the fuel cell stack, so that decompression of hydrogen is needed before hydrogen flowing into the fuel cell. With a reverse flow through Tesla valves, there appears a large pressure drop between the inlet and outlet, which can be used for hydrogen decompression nicely. However, a single-stage Tesla valve cannot meet the pressure drop requirement, so multi-stage Tesla valves are utilized. In this paper, numerical simulations of reversed hydrogen flow through multi-stage Tesla valves are carried out. The stage number of multi-stage Tesla valves and the inlet/outlet pressure ratio are both studied, and the distributions of temperature, pressure, and velocity inside multi-stage Tesla valves are all investigated. Results show that as the stage number increases or the inlet/outlet pressure ratio decreases, the pressure and the velocity inside multi-stage Tesla valves decrease, and the less the stage number, the more possibility for the velocity higher than local acoustic speed. Besides, a power-law relationship between the flow rate, the stage number and pressure ratio is summarized.

Variation Aware Design of 50-Gbit/s, 5.027-fJ/bit Serializer Using Latency Combined Mux-Dual Latch for Inter-Chip Communication

The conventional MOS current mode logic (MCML)-based multiplexer needed for serializer application has various limitations, such as low voltage-swing, substantial power consumption, and large area overhead. In the circuit arrangement of a serializer using the MCML-based mux-tree concept, the output of one mux at any stage is used to feed another mux at the next stage through some latch circuits, which are basically used for timing synchronization giving away penalty in terms of delay and area. The increase in number of stages of the Serializer may lead to further reduction in output swing (if common mode is not properly set), thereby causing signal integrity issues and finally loss of data. To address the same, a latency combined current mode multiplexer incorporating pMOS-based dual cross-coupled latch circuit is unearthed in this paper to further outline an area and energy efficient high-speed serializer capable of maintaining uniform peak-to-peak swing and signal quality at differential outputs. The simulations of new serializer are performed for 90-nm CMOS in the Cadence Virtuoso platform, where the average power and delay are found to be $471.6~\mu \text{W}$ and 93.9 ps, respectively, to provide a power delay product of 43.8 fJ only at a power supply of 1 V. An improved output swing of 904 mV is also noticed along with a data rate of 50 Gb/s and a BER of <10−12. The entire design is proved to be a robust one after simulating it through Monte Carlo at five different process corners and also validated at lower process nodes such as 28-nm UMC.

INFLUENCING FACTORS OF SELF-PRIMING TIME OF MULTISTAGE SELF-PRIMING CENTRIFUGAL PUMP

Self-priming centrifugal pump are a type of drainage and irrigation equipment applied in crop irrigation, urban landscaping, dust prevention and cooling, and building water supply. At present, single-stage self-priming centrifugal pumps dominate the pump market. Hence, the market share for multistage self-priming pumps, which can provide high-pressure liquid, is barely adequate. Self-priming time is an important parameter that measures the self-priming performance of multistage self-priming centrifugal pumps. Although many studies have focused on the influences of a single factor on the self-priming time of single-stage self-priming centrifugal pumps, only a few have discussed the self-priming time of multistage self-priming pumps. In the current work, we conducted an experimental study that combined the orthogonal, grey correlation, and self-priming time tests to investigate the influencing factors of the self-priming time of a multistage self-priming centrifugal pump and shorten the corresponding self-priming time. The outlet width of the impeller blade, the radial gap between the impeller and the diffuser, the area of backflow hole, and the number of stages of the multistage self-priming centrifugal pump were selected as the influencing factors in the orthogonal test. The orthogonal analysis of the self-priming time of the multistage self-priming centrifugal pump was conducted, and the results were used as the basis in obtaining the order of importance of all influencing factors through the grey correlation test. Results demonstrate that self-priming time increases gradually with an increase in impeller blade outlet width but that it decreases continuously with an increase in stage number and area of backflow hole. As radial gap increases, self-priming time increases and then decreases. In summary, the area of backflow hole is the most important influencing factor of self-priming time of the multistage self-priming centrifugal pump, followed by impeller blade outlet width, radial gap, and stage number. These findings provide important references for shortening the self-priming time of multistage self-priming centrifugal pumps. Keywords: Multistage self-priming centrifugal pump, Grey correlation test, Orthogonal test; Self-priming time rrelation test, Bomba centrífuga autocebante multietapa, Ensayo de correlación Grey, Ensayo orthogonal, Ensayo de rrelación de tiempo autocebante

Finite Element Simulations Of Multi Stage Incremental Forming Process

The limitation over the maximum formable wall angle in single stage incremental forming can be overcome by adopting multi stage forming strategy. This paper focuses on some preliminary finite element studies on deformation behavior of EDD steel in multi stage incremental forming in terms of thickness distribution, strains and geometric accuracy. The study has been carried by forming a conical cup with 850wall angle in four stages. Thickness distribution results revels that the sine law cannot predict the thickness with increase in number of stages. The major and minor principal strain history shows that the material is under plane strain condition in stage#1 and is towards bi-axial stretching with increase in number of stages. The simulation results also captured the geometric inaccuracies due to the formation of residual cone in Multi Stage Incremental Forming (MSIF). The finite element simulations can be used successfully to decide the number of stages and geometric accuracy parts in MSIF.

Fractionation of bio-oil produced from hydrothermal liquefaction of microalgae by liquid-liquid extraction

Fractionation of bio-oil is in favor of upgrading bio-oil to transport fuel or chemicals. The microalgae Dunaliella tertiolecta was hydrothermally liquefied to form a bio-oil, which was split into two layers during cooling: the lower layer contained organics with relatively high molar mass from 78 to 389 g mol−1, while the super layer with relatively low molar mass from 44 to 121 g mol−1. The lower layer of hydrothermally liquefaction (HTL) bio-oil was further fractionated into ethanol phase (oil 1) and dichloromethane phase (oil 2), and the super layer yielded 1 or 3-4 fractions of extracts (oil 3) via single-stage or multistage liquid-liquid extraction respectively. The compositions of each fraction were analyzed by GC-MS in detail. Dichloromethane, chloroform, cyclohexane, benzene, toluene, iso-octanol, petroleum ether, carbon tetrachloride, 1,1,1-trichloroethane, ethyl acetate were compared in terms of their extraction capabilities to organics of bio-oil. The results indicated the chloroform and dichloromethane have the highest comprehensive extraction capabilities. In multistage extraction, when dichloromethane was used as extractant, the extraction distribution ratio (calculated using COD, chemical oxygen demand) was 0.66 in first-stage, then sharply dropped with an increase in stage number, 2nd∼3rd stage extractions achieved the maximum extraction percentage (approximately 53%). That the optimum combination of chloroform, benzene and 1,1,1-trichloroethane fractionated the super layer of HTL bio-oil can obtain very low oxygen content fraction: hydrocarbons (purity of hydrocarbons: relative content 97.9%) from the 2nd stage of multistage extraction.

Thermodynamic analysis and optimization of multistage latent heat storage unit under unsteady inlet temperature based on entransy theory

An optimization model for a multistage latent heat storage (LHS) unit with unsteady heat transfer fluid (HTF) inlet temperature was proposed. Thermodynamic analysis and optimization were performed based on the entransy theory. The expressions of the optimum phase change material (PCM) melting temperatures (Tm,opt) were derived. The effects of geometric parameters and unsteady HTF inlet temperature on the optimum phase change temperatures were investigated. The results indicate that with the increase of stage number (n), Tm1,opt increases and Tmn,opt decreases, which is beneficial to extend the selection range of PCM. For fixed entransy dissipation condition, increasing n will not change the fluctuation of the HTF outlet temperature; however a nearly uniform HTF outlet temperature can be obtained by increasing unit length (L). The unsteady HTF inlet temperature has great effects on the optimum phase change temperature. For a 3-stage LHS unit, the optimum phase change temperature of each stage increases by 14.9 K, 26.4 K and 38.0 K respectively with respect to the values obtained by steady method, which causes the heat storage capacity decreases by 6.1% and entransy dissipation decreases by 10.6%. The present work can provide guidance for the design of the multistage LHS unit with unsteady HTF inlet temperature.

Optimization of Multistage Latent Heat Storage Unit Under Unsteady Inlet Temperature Based on Entransy Theory

Thermodynamic analysis and optimization of a multistage latent heat storage (LHS) unit with unsteady heat transfer fluid (HTF) inlet temperature were performed based on the entransy theory. The expressions of the optimum phase change material (PCM) melting temperatures (Tm,opt) were derived. The results indicate that with the increase of stage number (n), Tm1,opt increases and Tmn,opt decreases, which extends the selection range of PCM. For fixed entransy dissipation condition, increasing n will not change the fluctuation of the HTF outlet temperature; however, a nearly uniform HTF outlet temperature can be obtained by increasing unit length (L). The unsteady HTF inlet temperature has great effects on the optimum phase change temperature. For a 3-stage LHS unit, the optimum phase change temperature of each stage increases by 14.9 K, 26.4 K and 38.0 K respectively with respect to the values obtained by steady method, which causes the heat storage capacity decreases by 6.1% and entransy dissipation decreases by 10.6%. The greater the temperature fluctuation is, the greater the effects will be. The present work can provide guidance for the design of the multistage LHS unit with unsteady HTF inlet temperature.

Thermal performance of cascaded thermal storage with phase-change materials (PCMs). Part II: Unsteady cases

Cascaded latent thermal storage can find its applications in renewable thermal energies with time-dependent temperatures. This paper presents thermal performance of cascaded heat storage with unsteady inlet temperature of heat transfer fluid (HTF). The optimization of temperatures of HTF and phase-change materials (PCMs) is performed based on exergy, entropy, and entransy. Corresponding analytical/numerical solutions with these concepts are obtained. The qualifications for existence of optimization solutions are proposed. The optimization result of unsteady case is compared with that of steady case. The fluctuation of HTF temperature is transferred along the HTF flow path. The HTF temperatures in different stages exhibit similar fluctuating trend, but the fluctuating amplitude is diminished along the HTF flow path. With an increase in stage number, the difference between temperatures of outlet HTF and environment is gradually decreased with obviously improved thermal performance. As NTU increases, thermal performance is gradually increased, but with decreased increasing amplitude. The optimization result with entransy is also compared with that of entropy. The optimal exergy efficiency based on entropy is greater than that based on entransy, while the optimal thermal efficiency based on entransy is superior to that based on entropy. The optimization can be applied to select PCMs for unsteady cascaded thermal storage.

Thermal performance of cascaded thermal storage with phase-change materials (PCMs). Part I: Steady cases

Cascaded latent thermal storage is an efficient technique for balancing the gap between demand and supply in renewable energy utilization. In this work, the steady cascaded thermal storage system with multiple phase-change materials (PCMs) of different phase-change temperatures is theoretically optimized from the viewpoint of thermodynamics. Analytical solutions for optimal temperatures of heat transfer fluid (HTF) and PCMs are obtained based on entropy and entransy concepts. The corresponding qualifications for optimization solutions are also discussed. With an increase in stage number or that in NTU, both thermal and exergy efficiencies increase. Compared with single-stage thermal storage, the cascaded thermal storage with multiple PCMs can not only improve the thermal performance, but also extend the application scope of thermal energy with multi-grade thermal energies provided. The temperature distribution for HTF and PCMs with entransy optimization is linear, while that with entropy optimization is geometric progression. The application situations of entropy and entransy in thermal energy utilization are identified by comparing optimal result based on entropy with that based on entransy. This optimization can not only be used to establish the steady cascaded thermal storage system, but also guide the filtration of PCMs used in such systems.

Performance investigation and exergy analysis of enthalpy recovery device using liquid desiccant

Enthalpy recovery device using liquid desiccant is regarded as an appropriate approach for energy saving in air-conditioning system. This kind of enthalpy recovery device with a cross-flow pattern is investigated in the present study and its simulation model is built. Exergy analysis is utilized as the theoretical tool for optimizing the handling process. Reasons leading to exergy destruction are clarified. In addition to solution mixing process, limited transfer ability and unmatched coefficient are two main factors accounting for exergy destruction. Recovery efficiencies varying with mass flow ratio between air and solution are analyzed and the optimal flow ratio is obtained. A multi-stage device is proposed as an improvement to reduce the negative influence due to the unmatched coefficient and solution mixing process. Both recovery efficiencies ηh (ηm) and exergy efficiency ηex improve with the increase of stage number, while exergy destruction caused by unmatched coefficient or solution mixing process decreases. The multi-stage process also helps to reduce the required NTU for a certain recovery efficiency. Efficiency of a 3-stage or 4-stage device is quite close to that with infinite stages. The present research is beneficial to design an optimized enthalpy recovery device using liquid desiccant.

Multistage aqueous two-phase extraction of a monoclonal antibody from cell supernatant.

This article presents results of continuous multistage aqueous two-phase extraction of an immunoglobulin G1 from cell supernatant in a mixer-settler unit. An aqueous two-phase system consisting of polyethylene glycol 2000, phosphate salt, and water was applied without and with sodium chloride (NaCl). Influences of different parameters such as throughput, phase ratio, and stage number on the extraction performance were analyzed. For systems without NaCl, the extraction was carried out as a washing step. An increase of stage number from one to five stages enabled to increase the immunoglobulin G1 purity from 11.8 to 32.6% at a yield of nearly 90%. Furthermore, a reduction of product phase volume due to a higher phase ratio led to an increase of purity from 20.8 to 29.6% in a three-stage countercurrent extraction. For experiments with NaCl moderate partitioning conditions were adjusted by adding 8 wt% NaCl. In that case, the extraction was carried out as a stripping step.

Influence of the number of stages on the heat source temperature of desiccant wheel dehumidification systems using exergy analysis

The influence of the number of stages on the heat source temperature (ths) of desiccant wheel dehumidification systems that adopt water or refrigerant as cooling/heating media is examined in this paper. Under the same working conditions, when the exergy provided by the hot water (Eh) or the power input of the compressor (P) are reduced, ths can also be reduced. To reduce Eh and P, the exergy destruction of the desiccant wheels and heat exchangers should be reduced. The influence of stage number on the exergy destruction of the desiccant wheels is not significant when Ar and Fr are equal to 1. However, stage number has a significant influence on the exergy destruction of the heat exchangers. For water-driven systems, as stage number increases, ths (inlet temperature of the hot water) does not always decrease. The optimal stage number varies according to the water's total mass flow rate. A (mccpw)/(macpa) value of around 4 and the number of stages being 2–4 are preferable, with ths being around 55 °C and tcs being higher than 18 °C. When refrigerant is used, as the number of stage increases, ths (condensing temperature) decreases. In this scenario, a 4-stage system with COP around 4.5 is preferable.

Synthesis Gas Production by Combined Reforming of CO2-Containing Natural Gas with Steam and Partial Oxidation in a Multistage Gliding Arc Discharge System

In this research, the effect of multistage gliding arc discharge system on the process performance of combined natural gas reforming with steam and partial oxidation has been investigated. The simulated natural gas used in this study contains 70% methane, 5% ethane, 5% propane, and 20% carbon dioxide. An increase in stage number of gliding arc reactors from 1 to 3, at a constant feed flow rate, enhances all reactant conversions and H2 yield with a substantial reduction of energy consumption. However, at a given residence time, an increase in stage number from 1 to 3 shows no effect on any hydrocarbon reactant conversions or the selectivities for H2 and CO but has a drastic reduction of energy consumption. For either the constant feed flow rate or the constant residence time, 3 stages are found to be an optimum stage number of gliding arc reactors for synthesis gas production from the reforming of CO2-containing natural gas with steam and partial oxidation, in terms of the lowest specific energy consumptio...

Retrospective analysis of results of treatment for nasopharyngeal carcinoma in Macao.

Nasopharyngeal carcinoma (NPC) is a common malignancy in Southeast Asia, however, a full consensus has not yet been reached as to the value of comprehensive treatment for NPC. This study was designed to evaluate the epidemiological characteristics of NPC and their prognostic value, as well as the long-term efficacy of NPC treatment. A total of 248 patients, with different stages of NPC, were included in this study. The 5-year overall survival (OS) rates for patients in stages I, II, III and IV were 90.48%, 76.71%, 76.89% and 33.87%, respectively (P=0.000), while the respective 5-year progression-free survival (PFS) rates were 85.15%, 72.36%, 63.88% and 26.26% (P=0.000). The respective 5-year OS rates, according to stage, for the group that received radiotherapy combined with chemotherapy and for the group that received radiotherapy only were as follows: stages I and II, 81.67% and 79.59% (P=0.753); stage III, 79.91% and 70.38% (P=0.143); stage IV, 35.22% and 0% (P=0.000). The respective 5-year PFS rates in these groups were as follows: stages I and II, 75.83% and 74.98% (P=0.814); stage III, 74.08% and 42.25% (P=0.027); stage IV, 27.31% and 0% (P=0.000). Clinical staging appears to be the most important prognostic factor for NPC. As the stage number increases, both the 5-year OS and PFS significantly decrease. Adding chemotherapy to radiotherapy was not advantageous for patients with stage I or II NPC, however the addition of chemotherapy to radiotherapy significantly improved OS and PFS in patients with stage IV NPC. The addition of chemotherapy improved PFS, but not OS in patients with stage III NPC.