College education and the poor in China: documenting the hurdles to educational attainment and college matriculation

Xiaobing Wang,Chengfang Liu,Linxiu Zhang,Renfu Luo,Thomas Glauben,Yaojiang Shi,Scott Rozelle,Brian Sharbono 서울대학교 교육연구소 2011 Asia Pacific Education Review Vol.12 No.4

Although universities have expanded in size, it is unclear whether the poor have benefited. If there are high returns to college education, then increasing access of the poor to college has important welfare implications. The objective of this paper is to document the rates of enrollment into college of the poor and to identify the hurdles to doing so. Relying on several sets of data, including a survey of college students from universities in three poor provinces in China, we have found that the college matriculation rate of the poor is substantially lower than students from non-poor families; the same is true for rural women and minorities. Clearly, there are barriers that are keeping the rural poor out. The paper also demonstrates that the real hurdles are not during the years of secondary schooling or at the time of admissions to college. The real impediments keeping the rural poor from pursuing a college education arise long before high school-as early as preschool and elementary school years-and are present throughout the entire schooling system.

Effects of the costoclavicular block versus interscalene block in patients undergoing arthroscopic shoulder surgery under monitored anesthesia care: a randomized, prospective, non-inferiority study

Luo Quehua,Zheng Junyi,Yang Caiqi,Wei Wei,Wang Kejia,Xiang Xiaobing,Yao Weifeng 대한마취통증의학회 2023 Korean Journal of Anesthesiology Vol.76 No.5

Background: Recent studies have reported that costoclavicular blocks (CCBs) can consistently block almost all branches of the brachial plexus while sparing the phrenic nerve and provide effective analgesia after shoulder surgery. We aimed to compare the efficacy of the CCB with that of the interscalene block (ISB) as the sole blocking technique for shoulder surgery.Methods: A total of 212 patients undergoing elective arthroscopic shoulder surgery were randomized to receive an ISB or CCB based on a non-inferiority design. All patients received titration sedation with propofol under monitored anesthesia during surgery. The primary outcomes were the proportion of patients with complete motor blockade of the suprascapular nerve (SSN) and incidence of hemidiaphragmatic paralysis (HDP). The secondary outcomes included block-related variables, complications, and postoperative pain scores. Results: The proportion of patients with complete motor blockade of the SSN at 20 min between the CCB and ISB groups (53% vs. 66%) exceeded the predefined non-inferiority margin of −5%, but was comparable at 30 min (87% vs. 91%). The CCB resulted in a significantly lower incidence of HDP (7.55% vs. 92.45%), Horner’s syndrome (0% vs. 18.87%), and dyspnea (0% vs. 10.38%) than the ISB. None of the patients experienced failed blocks or required conversion to general anesthesia. Pain scores were comparable between the groups.Conclusions: Ultrasound-guided CCBs may be comparable to ISBs, with fewer unfavorable complications in patients with impaired lung function undergoing arthroscopic shoulder surgery.

Elastic Properties of Lead-free (Na1/2Bi1/2)TiO3-BaTiO3 Single Crystals near the Morphotropic Phase Boundary as Studied by Using Brillouin Spectroscopy

이병완,고재현,Xiaobing Li,Haosu Luo 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9

The elastic properties of lead-free (Na1/2Bi1/2)TiO3-BaTiO3 single crystals near the morphotropic phase boundary were investigated by using Brillouin spectroscopy at room temperature. The measured longitudinal elastic constants of unpoled single crystals with a BaTiO3 content of 5% exhibited large changes depending on the scattering geometry, indicating that a substantial acoustic dispersion effect exists in this system. This was attributed to the relaxor nature due to inherent disorder in the A-site of the perovskite structure.

Influence Mechanism and Effect of Rotary Shell Speed on Roto-Jet Pump Performance

Huang Qi,Luo Wencui,Wang Xiaobing,Shen Jiancheng 한국유체기계학회 2024 International journal of fluid machinery and syste Vol.17 No.1

The roto-jet pump mainly features the synchronous rotation of the impeller and the rotary shell as the structure, which is beneficial to reduce the friction loss of the disc and improve the pump efficiency. The synchronous rotation state of the impeller and the rotary shell, however, does not represent the optimal operating condition of the roto-jet pump. In order to examine the mechanism and the effect of the rotary shell speed on the performance of the roto-jet pump, an experimental research was carried out under two states, namely, rotating and fixed rotary shell, using the open test bench of the roto-jet pump as the research object. A simulation test was performed at rotating shell speed ratio i = 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6. The results show a relatively high entropy production and dissipation at the inlet of the collecting pipe and the outlet of the impeller at each operating point, and a large energy loss. In addition, the energy loss in the wall area of the rotary shell is basically proportional to the rotational speed of the rotary shell. The collecting pipe has a significant influence on the vortex structure inside the rotary shell, and the surrounding vortices are mainly generated on the upstream surface and the wake area of the collecting pipe. At constant impeller speed, the radial pressure gradient of the liquid in the rotary shell can be increased by increasing the rotary shell speed. The liquid pressure in the area of relative radius s < 1 corresponds inversely to the rotary shell speed, while the liquid pressure in the area of s > 1 corresponds proportionally to the rotary shell rotating speed. The minimum value of the total disc friction loss for this pump occurs at position i = 0.8. At this point, the friction loss of the impeller disc is 83.8% of the total loss. The friction loss of the rotary shell disc is 16.2%, and the pump efficiency has the highest value, 1.3% higher than that of the rotary shell synchronous rotation operating point. The optimum rotating speed ratio between the rotating shell and the impeller is 0.8, and the research results can be a reference for the differential operation of the impeller and rotary shell of the roto-jet pump

An Engineering Method to Estimate the Junction Temperatures of Light-Emitting Diodes in Multiple LED Application

Xing Fu,Run Hu,Xiaobing Luo 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.2

Acquiring the junction temperature of light emitting diode (LED) is essential for performanceevaluation. But it is hard to get in the multipleLED applications. In this paper, an engineeringmethod is presented to estimate the junction temperatures of LEDs in multiple LED applications. This method is mainly based on an analytical model, and it can be easily applied with some simplemeasurements. Simulations and experiments were conducted to prove the feasibility of the method,and the deviations among the results obtained by the present method with those by simulationas well as experiments are less than 2% and 3%, respectively. In the final part of this study, theengineering method was used to analyze the thermal resistances of a street lamp. The materialof leadframe was found to affect the system thermal resistance mostly, and the choice of soldermaterial strongly depended on the material of the leadframe.

Acoustic anomalies and relaxation dynamics of relaxor ferroelectric Na1/2Bi1/2TiO3 single crystals studied by using Brillouin spectroscopy

오수한,고재현,Li Xiaobing,Luo Haosu 한국물리학회 2020 Current Applied Physics Vol.20 No.7

Acoustic anomalies of relaxor ferroelectric Na1/2Bi1/2TiO3 single crystals were investigated over a wide temperature range from −196 °C to 900 °C by using Brillouin spectroscopy. The longitudinal sound velocity, the acoustic absorption coefficient and the elastic constant C11 were determined for the acoustic phonon mode propagating in the [100] direction. Two acoustic anomalies, weaker ones at the cubic-tetragonal phase transition temperature of ~540 °C and more pronounced ones at temperatures near 315 °C near the dielectric maximum temperature, were investigated and discussed in relation with the relevant order parameters coupled to the acoustic waves. The relaxation dynamics in the cubic phase were studied based on the flattening of the mode frequency and the half width, which was observed for the first time, and a modified Arrhenius law.

Effect of Mn doping on the acoustic and vibrational behaviors of lead-free piezoelectric (Na1/2Bi1/2)TiO3-xBaTiO3 single crystals

오수한,이병완,장문규,고재현,Xiaobing Li,Haosu Luo 한국물리학회 2019 Current Applied Physics Vol.19 No.11

The acoustic and vibrational properties of Mn-doped (Na1/2Bi1/2)TiO3-xBaTiO3 with x=0.05 were investigated by using Brillouin and Raman spectroscopies and compared with those of undoped crystals. The mode frequency and the half width of the Brillouin doublet of the longitudinal acoustic mode showed more drastic changes near the dielectric maximum temperature compared to the broad and diffused changes of the undoped crystals, which indicates that Mn-doping induces polar domains larger than the typical polar nanoregions formed in undoped counterpart. The acoustic anomalies were most pronounced along the<100>direction suggesting that the polarization fluctuations are anisotropic and largest along this direction. Temperature dependence of Raman spectra showed that there are two characteristics temperatures where mode splitting occurs due to local symmetry changes. The high-temperature anomaly was associated with the changes in the acoustic properties, while the low-temperature mode splitting was related to the dielectric anomaly near depolarization temperature.