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This paper investigated effects of slip length and hydraulic diameter on the hydraulic entrance length of laminar flow in superhydrophobic microchannels. Numerical investigations were performed for square microchannels with Re ranging between 0.1 and 1000. It is found that superhydrophobic microchannels have a longer hydraulic entrance length than that of conventional ones by nearly 26.62% at a low Re. The dimensionless hydraulic entrance length slightly increases with the increasing slip length at approximately Re

Reconstructing the Paleogene topography and climate of central Tibet informs understanding of collisional tectonic mechanisms and their links to climate and biodiversity. Radiometric dates of volcanic/sedimentary rocks and paleotemperatures based on clumped isotopes within ancient soil carbonate nodules from the Lunpola Basin, part of an east-west trending band of basins in central Tibet and now at 4.7 km, suggest that the basin rose from 4.0 km by 29 Ma. The height change is quantified using the rates at which wet-bulb temperatures ( T w ) decline at land surfaces as those surface rise. In this case, T w fell from ~8°C at ~38 Ma to ~1°C at 29 Ma, suggesting at least ~2.0 km of surface uplift in ~10 Ma under warm Eocene to Oligocene conditions. These results confirm that a Paleogene Central Tibetan Valley transformed to a plateau before the Neogene.

The accurate temperature measurement of high-power laser diode arrays is a considerable challenge due to their large temperature gradient and package structure. In this study, experiments based on the forward voltage method were set up to measure the transient temperature behavior of chips after the removal of heating load. A hybrid experimental/numerical method was developed to calculate multiple unknown interface thermal resistances and improve the prediction of the temperature distribution of high-power laser diode arrays by analyzing the transient temperature behavior of chips. The largest deviation between numerical and experimental results is 1.3 K. Based on the numerical results, thermal resistances for different layers and temperature distribution inside the chip were obtained and evaluated. Some suggestions for improving the thermal design of high-power laser diode arrays were derived.

High-power laser diode arrays (HPLDAs) have been widely used in pumps for solid-state lasers, medicine, optical data storage, and free-space optical communication due to their high efficiency, compact package, and long-term reliability. Similar to other high-power electronic chips, cooling is of great significance in maintaining the superior performance of HPLDAs including electro-optic conversion efficiency, beam quality, reliability, and long life span.

Considerable attention has recently been given to the new environment-friendly refrigerant of R1234ze(E) for applications such as heat pump and air-conditioning systems. In this study, an experiment was carried out to investigate two-phase flow patterns and flow transitions for R1234ze(E) in a smooth horizontal tube with an inner diameter of 6 mm. The experiments were performed at conditions covering saturation pressures from 0.215 to 0.415 MPa, mass fluxes from 130 to 258 kg/m2 s and heat fluxes from 10.6 to 74.8 kW/m2. The influences of saturation pressure, mass flux and heat flux on flow pattern transition were analyzed. Six well-known flow maps have been compared with the observed flow patterns of R1234ze(E). The results indicated that none of them can predict all the flow pattern transitions well. Thus, three dimensionless numbers K1, K2 and K3 which represent the ratio of the evaporation momentum force to the inertia force, the evaporation momentum force to the surface tension force, and the shear force to the gravity force respectively were introduced. Based on dimensionless numbers K1, K2, K3 and Xtt, a new flow pattern map for R1234ze(E) was proposed which could accurately predict the experimental data.

Land subsidence induced by excessive groundwater withdrawal has caused serious social, geological, and environmental problems in Beijing. Rapid increases in population and economic development have aggravated the situation. Monitoring and prediction of ground settlement is important to mitigate these hazards. In this study, we combined persistent-scatterer interferometric synthetic aperture radar with Grey system theory to monitor and predict land subsidence in the Beijing plain. Land subsidence during 2003–2014 was determined based on 39 ENVISAT advanced synthetic aperture radar (ASAR) images and 27 RadarSat-2 images. Results were consistent with global positioning system, leveling measurements at the point level and TerraSAR-X subsidence maps at the regional level. The average deformation rate in the line-of-sight was from −124 to 7 mm/year. To predict future subsidence, the time-series deformation was used to build a prediction model based on an improved Grey-Markov model (IGMM), which adapted the conv...

In this paper, the slamming pressure and load characteristics of a trimaran cross-section under various conditions were investigated by CFD (Computational Fluid Dynamics) simulations. The computation model was first validated against experimental results. After that, the simulation of different types of motion, i.e. free fall with different mass and entry velocity, entry with constant velocity and harmonic motion with different entry velocities were analysed. It was found that the characteristics of the dynamics during slamming strongly correlates to penetration depth, regardless of the types of entry. Distinguishing features during the wet-deck slam were observed for free fall motion under different conditions, including pressure drop under the main hull during wet-deck slam. The maximum acceleration would start to decrease after the mass has reached a certain value, and the second acceleration peak (corresponding to the wet-deck slam) would be smaller than the first one if the falling height is large enough.

In this paper, experimental tests and numerical studies were performed for better understanding the flow and heat transfer characteristics of the hybrid mini-channel and slot jet array heat sink. The average heat transfer coefficients were experimentally obtained and compared with independent mini-channel heat sink and slot jet array heat sink with a dimension of 10 mm × 10 mm at a flow rate from 0.1 L/min to 1.2 L/min, heat flux of 35.74 W/cm2 and 62.22 W/cm2. The results showed that the hybrid scheme has a better heat transfer performance than other two heat sinks at the same flow rate. Numerical simulations were conducted to further analyze thermal-hydraulic performance of the hybrid heat sink at an inlet Reynolds from 230 to 2760. Compared with k-e models, numerical results with transition SST flow model match better with the experimental results. According to the numerical results, we found vortexes in the channel of the hybrid heat sink and these vortexes are beneficial to the heat transfer. The influence of geometries on the overall thermal resistance and total pressure drop were discussed using numerical simulations. The results demonstrated that the base thickness, channel height, side wall to channel width ratio and channel number of the hybrid heat sink all have significant effect on the cooling performance and thermal resistance and pressure drop can be reduced obviously via geometry optimization.

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) systems have distinct advantages in the temperature range from 80 to 230 K. Tetrafluoromethane (R14) and ethane (R170) are essential components of mixed-refrigerants. In this paper, the adiabatic flow pattern map for R14/R170 mixtures was firstly developed based on previous flow pattern data. Then an experimental investigation on condensation two-phase flow patterns for R14/R170 mixtures (0.193/0.0.807, 0.437/0.563, 0.632/0.368 and 0.799/0.201 by mole) in a horizontal smooth tube with inner diameter of 4 mm was presented. Experiments were carried out at mass fluxes from 100 to 350 kg m−2s−1, saturation pressures from 1.5 to 2.5 MPa and heat fluxes from 8.4 to 42.2 kW m−2 over the entire range of vapor quality. The effects of mass flux, saturation pressure, heat flux and concentration on flow pattern evolutions were discussed and presented. Analysis results indicated that mass transfer resistance and heat flux account for the nonequilibrium effects of zeotropic mixture condensation, which leads to the different evolutionary trends between condensation and adiabatic two-phase flow. Finally, a new condensation flow pattern map was deduced by containing nonequilibrium effects into adiabatic flow pattern map.

Microchannels have an excellent thermal performance but they acquire a large pressure drop. Recent studies show that microchannels with superhydrophobic surfaces may provide an innovative approach to achieve a balance between thermal and hydraulic performances. In this work, the fluid flow and heat transfer in microtube with superhydrophobic surfaces are analyzed at fully developed laminar flow, and the formulas of fRe and Nu are obtained. Comparisons of thermal resistances on superhydrophobic and smooth microtubes are performed at identical flow rate, pressure drop and pumping power, respectively. At indentical flow rate, superhydrophobic surface can’t enhance the thermal-hydraulic performance. At identical pressure drop or pumping power, the critical pressure drop and pumping power exist respertively, which is the boundary point of the thermal-hydraulic performance between superhydrophobic and smooth microtubes. The critical parameters are deduced to help determining whether superhydrophobic surfaces enhance thermal-hydraulic performance.

This study examines the impact of culture on landscape-name perceptions of tourists from China, United States, and Europe utilizing both Hofstede's and Hall's cultural typologies. Data for this study were collected from visitors to two national parks in China. Culture is found to have a significant impact on both sub-dimensions of understanding (legibility and coherence) and involvement (mystery and diversity). Findings suggest that tourists from different cultures are likely to interpret landscape names differently. Those from cultures with a high power distance and low individualism would prefer landscape names that are mystical, dreamy, fictive, ingenious, original, and poetic, while those from cultures with a lower power distance and high individualism would prefer names that simply describe the landscape.

In this study, a hybrid microchannel and slot jet array heat sink is designed and fabricated to achieve a better thermal performance of the high-power laser diode arrays. A standard commercial laser bar with wavelength of 808 nm is packaged on the heat sink and experiments are performed to assess the cooling performance of the hybrid heat sink. In the experiments, the forward voltage method is used to measure the chip temperature and the structure function method is applied to obtain the thermal resistance of the heat sink. Using the deionized water as coolant, the heat sink deals with a heat flux of up to 506 W/cm2 and the thermal resistance of the heat sink is only 0.23 K/W when the flow rate is 0.8 L/min (The average jet velocity is 13.3 m/s). The optical power can be up to 135.5 W corresponding to the wall plug efficiency of 64.2%. Compared with the published solutions related to cooling similar laser chips, the thermal resistance reduces by over 15%, indicating that this hybrid heat sink is an interesting solution to improve the cooling of the high-power laser diode arrays.

Thermal design shows significant effects on energy conversion efficiency, lifespan and beam quality of high-power laser diode arrays (HPLDAs). In this study, a slot jet array heat sink (SJAHS) is designed to improve the cooling performance of HPLDAs, and numerical simulations were conducted to optimize the flow and heat transfer in the heat sink. Flow passages inside the heat sink ensured that the coolant is allocated to every jet uniformly. The jet geometry is optimized to enhance the heat transfer. When the working fluid is assumed as water at 293 K inlet temperature and at a flowrate of 800 mL/min, the heat sink is capable of removing 150 W heat over an area of 15 mm2 with a maximum temperature increase of 52.75 K from the coolant inlet to emitters. It means that the emitter-to-coolant thermal resistance is 0.35 K/W without considering the interface thermal resistance. The corresponding pressure drop is 361 kPa. Compared with the existing microchannel heat sink, the numerical results implied that this new heat sink possesses a better cooling performance.

Land subsidence is one of the important geological hazards in urban construction in Beijing, which has received the attention of academia and government departments. Ground settlement have caused damage of the buildings, railways, bridges and other infrastructure and have caused huge losses of economic, urban construction and people's lives. In this study, we monitor the temporal and spatial distribution of land subsidence evolution based on InSAR techniques, and the ground subsidence trend is estimated using gray-markov model. We obtain time-series surface subsidence information in Beijing plain by 39 ENVISAT ASAR data from 2003 to 2010 and 27 Radarsat-2 data from 2010 to 2014 using PS-InSAR technique. we analyzed the characteristics of land subsidence in the plain area of Beijing city, it is found that the land subsidence in this area is in a state of accelerated development, and the maximum sedimentation rate can reach 126mm/year in some areas. Based on the monitoring results, our study adopts gray-markov prediction model to predict land subsidence in some observation points in Beijing plain. The research results can provide a preliminary reference for urban planning, construction, and subsequent research.

BACKGROUND Endogenous nitric oxide and adenosine increase simultaneously to keep the balance of energy demand and supply when the oxygen supply is insufficient, which suggests that nitric oxide and adenosine might exert a synergistic myoprotection during tissue hypoxia. In this study, we tested this hypothesis utilizing a canine model of prolonged global myocardial ischaemic reperfusion injury. METHODS In this double blind, controlled study, the hearts of 24 anaesthetized mongrel dogs were arrested for 2 hours with aortic cross clamping and blood cardioplegia. The treatment groups were those supplemented with 2 mmol/L L-arginine (ARG), supplemented with 1 mmol/L adenosine (ADO), ARG + ADO supplemented with both, and no supplementation (control) (n = 6 in each group). Haemodynamics, biochemical indices, adenosine triphosphate (ATP) content and myeloperoxidase activities of myocardium were determined to evaluate myocardial injury. Statistical comparison was performed by two way ANOVA. RESULTS Although the requirements for inotropic supports were higher, the cardiac outputs were lower in control group than in ARG, ADO and the combination groups. Plasma cardiac troponin I levels were higher and the areas of hydropic changes were larger in control group than in ARG and ADO groups. Combination of arginine and adenosine provided further myoprotection with respect to better cardiac performance, lower release of cardiac troponin I, and smaller areas of hydropic changes compared with ARG and ADO groups. ATP content was higher, but myeloperoxidase activities of myocardium were significantly lower in the combination group than in control, ARG and ADO groups (P < 0.05). CONCLUSIONS Combination of L-arginine and adenosine provides synergistic myoprotection in a canine model of global myocardial ischaemia. Thus, the combination is recommended when the heart is exposed to a prolonged ischaemia during cardiac surgery.

Fiber nonlinearity of optical orthogonal frequency division multiplexed (OFDM) system restricts the capacity improvement of optical fiber transmission. In this paper, we propose a novel digital coherent superposition (DCS) scheme to improve the tolerance to fiber nonlinearity in a coherent optical orthogonal frequency division multiplexed system. In simulation, 71.53 Gbit/s orthogonal frequency division multiplexed signal per channel with Hermitian symmetry is transmitted over 400 km standard single mode fiber in a wave division multiplexed-polarization-division multiplexed-coherent optical orthogonal frequency division multiplexed system with five channels. The 4-quadrature amplitude modulation is used for symbol mapping. For the receiver, after the conventional OFDM signal processing, we conduct DCS for OFDM subcarrier pairs, which requires only conjugation and summation in the x, y polarization direction, respectively. Firstly, the channel spacing is 25 GHz, the maximum signal-to-noise ratio improvement is 9.05 dB or 6.02 dB with or without symmetric dispersion compensation compared with a conventional orthogonal frequency division multiplexed system. The optimum launch power is increased by 2 dB. Secondly, the channel spacing is changed to 50 GHz to investigate the nonlinearity tolerance at different channel spacings in the wave division multiplexed system, the maximum signal-to-noise ratio improvement is 8.75 dB or 4.9 dB with or without symmetric dispersion compensation, respectively. Theoretical and simulation analysis show that the proposed method in this paper can effectively mitigate the first-order nonlinear distortions and hence improve the tolerance of coherent optical orthogonal frequency division multiplexed system with different channel spacings to fiber nonlinear effects.

To elucidate the influence of the leukocyte depletion filter (LD-1) on leukocytes, IL-6, myeloperoxidase enzyme (MPO) and the pathological changes of myocardic tissues during cardiopulmonary bypass(CPB).Twelve dogs were used in this study. The LD-1, designed and made by ourselves, was fixed on the venous line in the trial group (n=6). It was used during the first 5 min after 2 min of CPB. LD-1 was not installed in the control group (n=6). Circulating leukocytes were counted before CPB, at 10 min, 40 min, 75 min during CPB, at the end of CPB, and 2 h after CPB. Plasma levels of IL-6 and MPO were also determined at the same time. The pathologic changes of left ventricular biopsies were observed before CPB, 5 min after protamine was given, and 2 h after CPB.The CPB 10 min WBC Count fell to 36% of that Before CPB in LD-1 group, which was lower than the WBC count in the control group synchronously (P0.01). But after CPB 2 h, both of them were close to the levels Before CPB in the two groups. In LD-1 group, IL-6 increased at CPB 40 min and reached to the top. But after wards it dropped continuously. The changes were of no significance in MPO and in the pathological examination of myocardic tissues (P0.05).The LD-1 on venous line was capable of decreasing WBC count effectively. As a result, the inflammation factors that leukocytes released were lower, so the program chain of inflammation by CPB was shorter. But LD-1 was not superior in myocardial preservation.