Investigation of 6S 1/2–8S 1/2 two-photon transition of cesium atoms by a single 822 nm laser

We experimentally investigate the 6S 1/2–8S 1/2 two-photon transition in cesium vapor by a single laser. A blue (455.5 and 459.3 nm) fluorescence signal is observed as a result of 822.5 nm laser beams illuminating the Cs vapor with a counter-propagating configuration. The dependences of the fluorescence intensity on the polarization combinations of the laser beams, laser power and vapor temperature are studied to obtain optimal experimental parameters. The frequency difference between the two hyperfine components of 4158 (7) MHz is measured with a Fabry–Perot interferometer as a frequency reference. Such a large spectral isolation and the insensitivity to the Earth’s magnetic field enable the 6S 1/2–8S 1/2 transition to be a stable frequency standard candidate for a frequency-doubled 1644 nm laser in the U-band window for quantum telecommunication.

Analisis Termodinamika Siklus Pembangkit Listrik Tenaga Uap Kapasitas 1500 kW

Pembangkit Listrik digunakan untuk membangkitkan listrik dari berbagai sumber energi seperti pembangkit listrik tenaga uap (PLTU). PLTU ini memiliki kapasitas 1500 kW dengan data data yang telah diperoleh tekanan dan temperatur berdasarkan tabel properties of saturated water (liquid–vapor) temperature maka dapat dilakukan perhitungan kualitas campuran pada kondensor dan efisiensi termal pada suatu siklus pembangkit listrik tersebut. Uap jenuh memasuki turbin pada siklus Rankine ideal pada tekanan 20 bar dan mengalami ekspansi pada turbin sampai pada tekanan kondensor 2,5 bar. Dalam penelitian ini dilakukan perhitungan efisiensi termal siklus pembangkit listrik tenaga uap tersebut, kemudian setelah dilakukan perhitungan didapatkan hasil efisiensi termal siklus tersebut adalah 19,3%. Efisiensi termal dapat ditingkatkan dengan melakukan penurunan suhu dan tekanan pada kondensor, meningkatkan tekanan pada boiler, dan meningkatkan suhu ketika fluida kerja dalam keadaan superheated.

Banking of AT-MSC and its Influence on Their Application to Clinical Procedures

Processing of MSCs to obtain a therapeutic product consists of two main steps: 1) the in vitro expansion of the cells until an appropriate number of them is obtained, and 2) freezing and storage of the expanded cells. The last step is critical and must be optimized so that after thawing the cells retain all their physiological properties including the secretory function. In this paper, we evaluated physiological parameters of AT-MSC’s after a full cycle of their processing, particularly freezing and storing at the liquid nitrogen vapor temperature. Based on the recovered proliferative and secretory capacities of the thawed cells, we have designed the optimal technique for processing of MSCs for clinical applications. In our work, we tried to select the best DMSO-based cryoprotectant mixture on the base of post thawing fully retain their properties. We have demonstrated the effectiveness of the use of DMSO in various configurations of the constituent cryoprotective fluids. We have also shown that AT-MSCs that show control levels in most standard tests (viability, shape, culture behaviour, and proliferative properties) after thawing, may show transient variations in some important physiological properties, such as the level of secreted growth factors. Obtained results let us to indicate how to optimize the AT-MSC preparation process for clinical applications. We suggest that before their clinical application the cells should be cultured for at least one passage to recover their physiological stability and thus assure their optimal therapeutic potential.

Mathematical modeling of dispersed media flows in the presence of nucleation, coagulation and phase transitions

A model of motion of a gas-dispersed medium in the presence of processes of nucleation, coagulation and phase transitions has been constructed. A homogeneous nucleation model is used to describe the nucleation process. It is believed that the process of cluster coagulation occurs due to their Brownian motion. The analysis of the solution of the coagulation equation in the particular case of monodisperse clusters in the presence of a source and sink of particles is carried out. To determine the rate of phase transitions the Hertz-KnudsenLangmuir formula is used. The calculations were carried out on the basis of a quasi-one-dimensional model within the equilibrium approximation (when the velocities and temperatures of the phases coincide). As a result of the study the main properties of the flow of a two-phase mixture in a channel in the presence of nucleation, coagulation, and phase transformations have been established. It is shown that the vapor temperature increases along the channel and reaches the saturation temperature at some distance from the channel entrance. Calculations have shown that the coagulation process has a rather strong effect on the distribution of cluster sizes along the channel.

Design, Construction and Experimental Study of a Solar Still for Brackish Water Purification under Djiboutian Climate

A single sloped solar still were designed and fabricated to operate under Djibouti city weather condition during the period April-May 2019. In this study, a single slope solar still has been constructed from materials available on the local market. Series of experiments were carried out on solar still using brackish water. Ambient temperature, water temperature in basin, absorber plate temperature, glass cover temperature and vapor temperature were measured along with the hourly water production. This study has revelead that the vapor temperature is always above that the others temperatures for all the four days of experiments. Then, the effect of water amount in the basin on productivity of solar still was investigated using different amount of water 6 L, 8 L, 10 L and 12 L. The experimental results show that the total accumulated distillate output for the single slope solar still is 2490 mL, 2390 mL, 2240 mL and 2015 mL, respectively. However, it is observed that with increase in basin water amount distillate water production decreases. On the other hand, the effect of wind speed on the daily productivity of solar still is evaluated. Experimental investigations show that the cumulative productivity increases when the wind speed average increase. Finally, water quality analyses were conducted before and after the experiments. The average analysis results obtained showed a removal efficiency of 98.16%, 98.42%, 97.43% and 95.39% for TDS, electrical conductivity, hardness water and chloride, respectively. It was also observed that data obtained of the product water were within the normal range prescribed by World Health Organization (WHO) standards.

A reel-down instrument system for profile measurements of water vapor, temperature, clouds, and aerosol beneath constant-altitude scientific balloons

The tropical tropopause layer (TTL; 14–18.5 km) is the gateway for most air entering the stratosphere, and therefore processes within this layer have an outsized influence in determining global stratospheric ozone and water vapor concentrations. Despite the importance of this layer there are few in situ measurements with the necessary detail to resolve the fine-scale processes within this region. Here, we introduce a novel platform for high-resolution in situ profiling that lowers and retracts a suspended instrument package beneath drifting long-duration balloons in the tropics. During a 100 d circumtropical flight, the instrument collected over a hundred 2 km profiles of temperature, water vapor, and aerosol at 1 m resolution, yielding unprecedented geographic sampling and vertical resolution. The instrument system integrates proven sensors for water vapor, temperature, pressure, and cloud and aerosol particles with an innovative mechanical reeling and control system. A technical evaluation of the system performance demonstrated the feasibility of this new measurement platform for future missions with minor modifications. Six instruments planned for two upcoming field campaigns are expected to provide over 4000 profiles through the TTL, quadrupling the number of high-resolution aircraft and balloon profiles collected to date. These and future measurements will provide the necessary resolution to diagnose the importance of competing mechanisms for the transport of water vapor across the TTL.

Numerical Analysis of Liquid–Liquid Heat Pipe Heat Exchanger Based on a Novel Model

Heat pipe heat exchangers (HPHEXs) are widely used in various industries. In this paper, a novel model of a liquid–liquid heat pipe heat exchanger in a countercurrent manner is established by considering the evaporation and condensation thermal resistances inside the heat pipes (HPs). The discrete method is added to the HPHEX model to determine the thermal resistances of the HPs and the temperature change trend of the heat transfer fluid in the HPHEX. The established model is verified by the HPHEX structure and experimental data in the existing literature and demonstrates numerical results that agree with the experimental data to within a 5% error. With the current model, the investigation compares the effectiveness and minimum vapor temperature of the HPHEX with three types of HP diameters, different mass flow rates, and different H* values. For HPs with a diameter of 36 mm, the effectiveness of each is improved by about 0.018 to 0.029 compared to HPs with a diameter of 28 mm. The results show that the current model can predict the temperature change trend of the HPHEX well; in addition, the effects of different structures on the effectiveness and minimum vapor temperature are obtained, which improve the performance of the HPHEX.

A Reel-Down Instrument System for Profile Measurements of Water Vapor, Temperature, Clouds and Aerosol Beneath Constant Altitude Scientific Balloons

The Tropical Tropopause Layer (14–18.5 km) is the gateway for most air entering the stratosphere, and therefore processes within this layer have an outsized influence in determining global stratospheric ozone and water vapor concentrations. Despite the importance of this layer there are few in situ measurements with the necessary detail to resolve the fine scale processes within this region. Here, we introduce a novel platform for high resolution in situ profiling that lowers and retracts a suspended instrument package beneath drifting long duration balloons in the tropics. During a 100-day circumtropical flight, the instrument collected over 100 two-kilometer profiles of temperature, water vapor and aerosol at one-meter resolution, yielding unprecedented geographic sampling and vertical resolution. The instrument system integrates proven sensors for water vapor, temperature, pressure and cloud and aerosol particles with an innovative mechanical reeling and control system. A technical evaluation of the system performance demonstrated the feasibility of this new measurement platform for future missions with minor modifications. Six instruments planned for two upcoming field campaigns are expected to provide over 4000 profiles through the TTL, quadrupling the number of high-resolution aircraft and balloon profiles collected to date. These and future measurements will provide the necessary resolution to diagnose the importance of competing mechanisms for the transport of water vapor across the TTL.

Energy Saving through Efficient BOG Prediction and Impact of Static Boil-off-Rate in Full Containment-Type LNG Storage Tank

Boil-off gas (BOG) from a liquefied natural gas (LNG) storage tank depends on the amount of heat leakage however, its assessment often relies on the static value of the boil-off rate (BOR) suggested by the LNG tank vendors that over/under predicts BOG generation. Thus, the impact of static BOR on BOG predictions is investigated and the results suggest that BOR is a strong function of liquid level in a tank. Total heat leakage in a tank practically remains constant, nonetheless the unequal distribution of heat in vapor and liquid gives variation in BOR. Assigning the total tank heat leak to the liquid is inappropriate since a part of heat increases vapor temperature. At the lower liquid level, BOG is under-predicted and at a higher level, it is over-predicted using static BOR. Simulation results show that BOR varies from 0.012 wt% per day for an 80% tank fill to 0.12 wt% per day at 10% tank fill.