Frame time-hopping patterns in multirate optical CDMA networks using conventional and multicode schemes

A class of generalized optical orthogonal codes (OOCs), namely, frame time-hopping (FTH) patterns with an extremely large cardinality, are studied for implementing multirate and multiservice (MR/MS) optical CDMA (OCDMA) networks. Conventional MR/MS methods, namely variable spreading rate and parallel mapping, are considered. Using FTH patterns, the problem of low OOC code cardinality in conventional MR/MS schemes is removed. Moreover, several new multicode methods, using subcode concatenation scheme, are proposed for MR/MS OCDMA. The proposed multicode schemes present flexibility for supporting MR/MS applications such as lower implementation complexity and cost, less need for service synchronization, and finally lower link power budget. Multiple-access performances of the systems are evaluated using saddle-point approximation methods considering photodetector shot-noise, dark current, and circuit thermal noise. The results show that the conventional parallel mapping outperforms the other schemes in high received powers, and the proposed multicode method, using Walsh subcode along with difference modulation, presents the best performance in low received powers for the cases considered.     

Application of convolutional error correcting codes in ultrawideband M-ary PPM signaling

The interference issues related to ultrawideband (UWB) radio pose tight restrictions on the maximum data rate of UWB radio telecommunication systems. A possible solution is to reduce the required signal to interference ratio (SIR) that gives satisfactory performance to the UWB system. In this letter, we propose coded M-ary UWB radio communication systems. Two classes of convolutional codes, namely, low-rate superorthogonal codes and high-rate punctured codes are considered for this purpose. Simulation results on the bit error rate of the proposed system indicates that the system is capable to work in lower SIR's and therefore supports higher data transmission rates in a real interference environment compared to the previously proposed UWB communication systems.     

The effect of cold rolling regime on microstructure and mechanical properties of AISI 304L stainless steel

In this paper, the effect of different thickness reductions by cold rolling on the microstructure and mechanical properties of AISI 304L austenitic stainless steel were investigated. The hot rolled steel strips were subjected to cold rolling at 0 °C from 10 to 90% thickness reduction. Microstructures, strain-induced martensitic transformation and mechanical properties of the cold-rolled specimens were characterized by X-ray diffraction, Feritscope measurements, optical metallography, hardness and tensile tests. The resulting transformation curve showed a sigmoidal shape with the saturation value of strain-induced martensite of approximately 100%. A good agreement was found between the experimental results and the Olsen–Cohen model. The results indicated that formation of strain-induced martensite clearly resulted in a significant strengthening of the steel.     

Voltammetric and Scanning Electrochemical Microscopic Studies of the Adsorption Kinetics and Self-Assembly of n-Alkanethiol Monolayers on Gold

The adsorption kinetics and self-assembly of hexadecyl mercaptan on gold have been investigated by scanning electrochemical microscopy (SECM), chronoamperometry, and cyclic voltammetry. The developed methodology allows one to evaluate the surface coverage and the average size of the defects in the monolayer film from the effective rate constant of electron transfer. Two kinetic regimes of self-assembly were identified: a rapid initial adsorption of hexadecyl mercaptan onto a clean gold surface from 5 mM solution (more than 90% coverage obtained in 1 to 5 min), and a slower subsequent annealing of a thiol monolayer resulting in a more compact film. Typically, a long-chain-length thiol-treated gold surface acts as an electronically insulating surface after about 1 h. The SECM images of partially covered gold surfaces were always featureless, suggesting that the defects in the film were smaller than 0.5 μm for any exposure time ≥ 1 min.     

Perspective: A Standards-Based System for Manufacturing Information Integration

This paper presents an infrastructure and a prototype system for a manufacturing information system, which is distributed its nature and is able to store, index, manage, retrieve and present business data, inventory data, and manufacturing processes data. The system works with all kinds of information, such as continuous (i.e., stream oriented) data, production (e.g., decision support) data, legacy data, and multimedia data (say, drawings, pictures, audio signals, voice annotations, and video streams). A key criterion is support for content-based information retrieval across all application areas. The main objective is to provide support for automated information transactions. The prototype of our architecture uses JAVA, STEP (ISO 10303) standard, the Internet, and CORBA. A fully functional system, called Perspective, for retrieval of part and manufacturing process has been designed and implemented in a distributed environment. Among other capabilities, the system can retrieve a set of parts or manufacturing processes based on similarity to some desired criteria.     

Recension des écrits sur l'impact des contacts sexuels précoces sur les hommes.

A review of the literature on the impact of sexual contacts between adults and boys reveals the existence of two principal outcomes: 1) some participants develop various disorders once in adulthood, such as behavioural problems, sexual disorders, or personality problems; 2) some participants do not present with any major disorders in the long run. These different outcomes may be associated with several moderating variables related to the sexual contacts, such as the level of coercion at the time of these contacts, the bond between the child and the adult, or the context of the sexual relation. However, the conclusions relating to the relations between early sexual contacts with adults and subsequent problems of adaptation in adulthood are difficult to determine. This is because of various methodological problems associated with relevant studies (i.e., definition of these contacts, nature of the sample, method evaluation, statistical analyses). In this article, we propose certain avenues of research that may help clarify this problem. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postcesarean endometritis. Clinical risk factors predictive of positive blood cultures

OBJECTIVE: To identify peripartum risk factors that are predictive of positive blood cultures in patients with postcesarean endometritis. STUDY DESIGN: A retrospective review of 179 patients diagnosed with postcesarean endometritis was conducted. Patients with positive and negative blood cultures obtained at the time of diagnosis were compared. Patient's charts were reviewed for intrapartum, intraoperative and postpartum factors. Chi-square and nonpaired Student's tests were used when appropriate, with P < .05 considered significant. RESULTS: During this period, 179 (20%) postcesarean patients developed endometritis. One hundred sixty-eight (94%) of those patients had blood cultures. Eleven (6.5%) were positive; however, one of these grew a skin contaminant and was disregarded. When patients with positive blood cultures were compared to those with negative blood cultures, length of labor, number of vaginal examinations, postoperative day when the diagnosis was established, estimated blood loss at the time of cesarean delivery, presence of intrapartum chorioamnionitis, number of hours of ruptured membranes, white blood cell count at the time of diagnosis, use of prophylactic antibiotics, development of wound infection or other infectious etiologies were not shown to be predictive. There were no positive blood cultures among patients with a temperature < 38.5 degrees C. At a temperature < 38.8 degrees C, 1/126 (0.79%) had a positive blood culture. At a temperature > or = 38.8 degrees C, 9/42 (21.4%) had a positive blood culture (P < .001). Approximately $5,890 was spent on obtaining positive blood cultures in patients with temperatures < 38.8 degrees C. In contrast, $218 was spent per positive blood culture obtained from patients with a temperature > or = 38.8 degrees C. CONCLUSION: The traditional practice of obtaining blood cultures at a temperature > or = 38.0 degrees C is not justified but elevating the threshold to 38.8 degrees C is equally effective and less costly.     

Three-dimensional FE analysis of ring rolling by employing thermal spokes method

This paper investigates the performance of the “Thermal Spokes Method” in modeling the effect of the guide rolls on the ring rolling process. If the guide rolls are not included FE, simulation encounters problems such as tilting of the ring and process instability. Thermal spokes are introduced to withstand any unwanted moment of the resultant rolling forces at the roll gap and to maintain the ring in a centralized location in the mill. By employing the thermal spokes method, much closer predictions for the lateral spread and flow patterns are calculated. This method is able to predict the tilting of the ring with respect to the stiffness of the elements of the adjustment mechanism. It is also possible by this method to predict the point at which the ring changes its support from one guide roll to another one and to study the deformation mechanism outside the roll gap. To verify the validity of the proposed method, the predicted results from this method are compared with some available references. Since the proposed method considers the effect of the guide rolls and consequently offers much closer predictions, it is a very suitable method for ring rolling simulations.