Reliability Parameter Interval Estimation of NC Machine Tools considering Working Conditions

Aiming at the problem that the parameter interval estimation of NC machine tool’s reliability model considering working conditions established by Hongzhou is difficult to implement, given that it has several independent variables, an improved interval estimation method based on Bootstrap is proposed. Firstly, the two-step estimation method was used to calculate the point estimation of NC machine tool’s reliability parameter in test field, based on which B resamplings are generated based on the point estimation. The reliability parameter’s point estimation of the resamplings was obtained by maximum likelihood estimation. Permutation of B point estimations was made in ascending order and the interval estimations were obtained by the α quantile of the permutation. Case study indicated that the location and length of the interval estimation of NC machine tools’ reliability parameter, under different levels of working condition covariates, vary obviously

Simulation of GSM/EGPRS employing SDMA and dynamic channel allocation

The development of GSM is currently focused on packet-switched services. The first solution to provide such services is known as General Packet Radio Service (GPRS), which has been deployed commercially. A further step comes with Enhanced General Packet Radio Service (EGPRS). To improve the capacity and achieve more efficient utilization of the frequency spectrum of cellular systems, the Space Division Multiple Access (SDMA) using smart antenna has drawn wide attention in recent years. However, its application, especially on GSM/EGPRS network, still needs further investigation. This work aims to evaluate the performance of the GSM/EGPRS cellular network employing SDMA, together with a complete Dynamic Channel Allocation (DCA) strategy, from various perspectives. Simulation results show that SDMA can greatly increase the system capacity, and that the data rate, the distribution of users, the propagation environments, the channel assignment schemes, the antenna sidelobe levels and the buffersize of users all have great influence on the performance of the EGPRS network with SDMA

The Estimation of the Probability of the Twin Crisis Occurrence

This paper calculates the probability of the twin crisis by empirical analysis with models of Logit and Probit. It selects some countries where twin crisis occurred in 1997 as samples, and forecasts within the samples. Then, it selects some countries where twin crisis occurred in 2008, and tests from outside samples. Results show that the model was well fitted and of high accuracy. The empirical results show that when economy growing too fast, a country should prevent the formation of the bubble economy; the excessive expansion of domestic credit will create bubble economy; variables of banking crisis tend to be as simultaneous or warning indicators for the occurrence of currency crisis. Structure of foreign debt must be suitable and the scale of foreign exchange reserves must be moderate. Key words: Banking crisis; Currency crisis; Twin crisis; Probability measuremen

Research on Simulation Inspection Detector

AbstractThe structure design problems of simulation inspection detector on ground are researched in this paper. The general design scheme is proposed based on the design task requirements of simulation inspection detector with a synthetic consideration on the requirements of the whole mass and the real grounded force. Detailed design for the concrete mechanical strcture has been carried out. The prototype of simulation inspection detector meets the test requirements, which can also provide important reference for the detector improvemen

Prediction of complex super-secondary structure βαβ motifs based on combined features

AbstractPrediction of a complex super-secondary structure is a key step in the study of tertiary structures of proteins. The strand-loop-helix-loop-strand (βαβ) motif is an important complex super-secondary structure in proteins. Many functional sites and active sites often occur in polypeptides of βαβ motifs. Therefore, the accurate prediction of βαβ motifs is very important to recognizing protein tertiary structure and the study of protein function. In this study, the βαβ motif dataset was first constructed using the DSSP package. A statistical analysis was then performed on βαβ motifs and non-βαβ motifs. The target motif was selected, and the length of the loop-α-loop varies from 10 to 26 amino acids. The ideal fixed-length pattern comprised 32 amino acids. A Support Vector Machine algorithm was developed for predicting βαβ motifs by using the sequence information, the predicted structure and function information to express the sequence feature. The overall predictive accuracy of 5-fold cross-validation and independent test was 81.7% and 76.7%, respectively. The Matthew’s correlation coefficient of the 5-fold cross-validation and independent test are 0.63 and 0.53, respectively. Results demonstrate that the proposed method is an effective approach for predicting βαβ motifs and can be used for structure and function studies of proteins

Metabolic engineering of the L-phenylalanine pathway in Escherichia coli for the production of S- or R-mandelic acid

<p>Abstract</p> <p>Background</p> <p>Mandelic acid (MA), an important component in pharmaceutical syntheses, is currently produced exclusively via petrochemical processes. Growing concerns over the environment and fossil energy costs have inspired a quest to develop alternative routes to MA using renewable resources. Herein we report the first direct route to optically pure MA from glucose via genetic modification of the L-phenylalanine pathway in <it>E. coli</it>.</p> <p>Results</p> <p>The introduction of hydroxymandelate synthase (HmaS) from <it>Amycolatopsis orientalis </it>into <it>E. coli </it>led to a yield of 0.092 g/L S-MA. By combined deletion of competing pathways, further optimization of S-MA production was achieved, and the yield reached 0.74 g/L within 24 h. To produce R-MA, hydroxymandelate oxidase (Hmo) from <it>Streptomyces coelicolor </it>and D-mandelate dehydrogenase (DMD) from <it>Rhodotorula graminis </it>were co-expressed in an S-MA-producing strain, and the resulting strain was capable of producing 0.68 g/L R-MA. Finally, phenylpyruvate feeding experiments suggest that HmaS is a potential bottleneck to further improvement in yields.</p> <p>Conclusions</p> <p>We have constructed <it>E. coli </it>strains that successfully accomplished the production of S- and R-MA directly from glucose. Our work provides the first example of the completely fermentative production of S- and R-MA from renewable feedstock.</p

Characteristics of multicystic biliary hamartoma: A case report

IntroductionMulticystic biliary hamartoma (MCBH) is a very rare hepatic benign neoplasm that manifests as a localized cystic-solid mass. Only 17 cases have been described in the literature to date. MCBH diagnosis is currently dependent on imaging and pathology following surgical resection and no precise standards are in place.Case PresentationThis case study involves a middle-aged male patient with a history of drinking but no other liver diseases. A routine ultrasound examination showed a 6.0 × 5.5 cm inhomogeneous echo mass in the right lobe of the liver. The patient experienced no discomfort or other symptoms, and blood tests were normal. Imaging revealed a localized cystic-solid neoplasm in segment 6 of the liver that did not have the features of a malignant tumor. Surgical resection was performed. Based on imaging, macroscopic examination, and histological results, a final diagnosis of MCBH was made.ConclusionThe imaging and pathological features of MCBH were summarized based on the published case reports to date. As a non-invasive examination, the imaging features will aid in the diagnosis of MCBH. Furthermore, these features, along with tumor size and patient symptoms, will facilitate clinicians in selecting surgical resection or follow-up for individual patients