Results 1 - 10 of 1566
Results 1 - 10 of 1566. Search took: 0.021 seconds
|Sort by: date | relevance|
[en] Ways of determining Langmuir constants are evaluated to improve the accuracy of calculating the parameters of hydrate processes. An indirect approach is used in the evaluation that consists of calculating the hydrate number using the Langmuir constants and comparing it to known values. The criterion of evaluation is the minimum deviation between these values. The selection of the best way of calculating the Langmuir constants is validated.
[en] Meta-analysis with high-quality studies can provide superior evidence. In this paper, we use meta-analysis to analyze the relationship between cadmium (Cd) content in semen and male infertility, and then objectively evaluate the effect of Cd on sperm quality. The objectives of this study were to update our understanding of infertility and to provide evidence to treat and prevent the infertility. We searched potentially relevant studies that were published from establishing database data to April 2018. Articles came from the databases of CNKI, Wanfang, VIP, PubMed, CMCI, and EMBASE. A total of 11 articles were included. We gathered the mean and variance of the infertility group and the control group to compare the Cd content in two groups. In total, the 11 studies include 1707 subjects, 1093 of which were in the infertility group and 614 of which were in the control group. We can get some information from this meta-analysis: SMD = 0.50 (95% Cl 0.39–0.61), Z = 8.92, P < 0.05; the funnel plot of the meta-analysis shows incomplete symmetry, which may have the publication bias. Therefore, the high content of Cd in semen is a causative factor of infertility. The Cd content in semen can be used as an indicator of sperm quality.
[en] The repeated breaking of a linear object, for example a stick, is a fundamental process which underlies numerous natural phenomena. Here we compare two distinct ensembles of stick-breaking: (i) a stick is broken with a certain rate over time; and (ii) a stick is broken a finite number of times. Both ensembles are deduced from appropriate integral equations and related to each other. The analyses performed here and the comparison of the two ensembles enables us to better understand the stick-breaking process by itself. (special issue in memory of vladimir rittenberg)
[en] Routine work in nuclear medicine requires the careful elution of radioactivity and its subsequent, storage and handling. Though all effort is maintained to prevent any “spill” of this radioactivity, accidents are bound to happen. The response to this spill is a methodically worked out a plan that is written and adopted as a “standard operating procedure.” This protocol is taught to all involved in the area of working as a mock drill/apprenticeship model. No formal evaluation of learning is in place except for the mock drills. The objectively structured assessment of technical skills (OSATS) is a variation on the Objective Structured Clinical Examination, which is a form of workplace based assessment. The OSATS is cited in the Accreditation Council of Graduate Medical Education evaluation toolbox on the website as the most desirable evaluation tool for the patient care topics. It is the objective of this paper is to introduce the “OSATS” for teaching, and assessment of the learning, of the protocol for the management of radioactive spill. As a review of the literature on the subject failed to reveal any such teaching protocol/material/document for this important technical skill, we hope that it may act as a landmark for the development of teaching and assessment of other technical skills also
[en] Pre- and post-selected (PPS) measurement, especially the weak PPS measurement, has been proved to be a useful tool for measuring extremely tiny physical parameters. However, it is difficult to retain both the attainable highest measurement sensitivity and precision with the increase of the parameter to be measured. Here, a modulated PPS measurement scheme based on coupling-strength-dependent modulation is presented with the highest sensitivity and precision retained for an arbitrary coupling strength. This idea is demonstrated by comparing the modulated PPS measurement scheme with the standard PPS measurement scheme in the case of unbalanced input meter. By using the Fisher information metric, we derive the optimal pre- and post-selected states, as well as the optimal coupling-strength-dependent modulation without any restriction on the coupling strength. We also give the specific strategy of performing the modulated PPS measurement scheme, which may promote practical application of this scheme in precision metrology. (paper)
[en] The mechanical properties of coal are important parameters for coalbed methane (CBM) extraction and gas outburst control. However, the effect of adsorbed gas on strength cannot be evaluated quantitatively yet. To better understand the weakening mechanisms of free and adsorbed gas on the strength of coal, normal coal, and deformed coal are chosen to test their mechanical properties of CH4-saturated and non-gas-saturated specimens under different conditions. Under the same effective stresses, the peaks of strength of CH4-saturated specimens with high-pressure gas are lower than those with low-pressure gas, implying that the adsorbed gas can also weaken the peak strength of coal. Then, a new model for the weakening values of strength induced by free and adsorbed gas was developed, and the effects of free gas and adsorbed gas on the strength of coal were assessed by our model. The results show that the free gas and adsorbed gas can weaken the strength of coal for different weakening mechanisms. The ratio of weakening value of strength due to free gas to that of adsorbed gas of the normal coal is 1.3–3.4, and that of the deformed coal is 8.4–19.8. These results can help us to better understand why the weakening effect of adsorbed CH4 in the laboratory is ignored in earlier studies.
[en] The evaluation of the electrical contact resistances of thermoelectric legs is important to predict the performance of thermoelectric modules. Thermoelectric modules can be divided into devices operating at high and low temperatures. In the former, the electrical contact resistance can change with temperature. However, many research groups have only analyzed the electrical contact resistance at mainly room temperature. In this study, an electrical contact resistance measurement system for thermoelectric legs of thermoelectric devices at high operating temperature (400 to 600 °C) is proposed, which provides a more accurate performance prediction. The measurement conditions are determined according to the amplitude and frequency of the current to minimize the measurement errors caused by the Peltier effect. Skutterudite thermoelectric legs with a Ti metallization layer are used to understand the specific contact resistance at high temperatures. Based on the obtained results, the thermoelectric module is analyzed through a simulation to investigate the power outputs with the specific contact resistances at both room and high operation temperatures.