Time-Based Factory Efficiency Analysis | I.C. Engine Assembly Line

Cold test stations are commonly arranged as sequential processes along a complete engine production line. The production line consists of several stations for engine building purposes, and before the engine exits the production line it passes through different validation and testing stations, such as leak testing stations, piston protrusion stations (known as torque to turn stations), and cold test stations. Each of these stations has a sequence of operation that is performed automatically or semi-automatic with the support of an operator. The waiting time until the engine finishes the operation in one station is called “cycle time”. The longer the cycle time the less efficient the production line. Cold testing stations are considered the most complicated and time-consuming, yet important test stations for engine and powertrain development. The lengthy cycle time affects the overall efficiency of the production line. This paper investigates the problem of the cycle time difference between consequent stations and its effect on the overall efficiency of the factory. New techniques and operations research methods are introduced aiming to recover from such a manufacturing obstacle. This research is investigating the limitations of a manufacturing operation standpoint. Each test station is treated as a block that simulates the actual station, and the overall factory workflow is described. Time-based equations governing block time, idling time, and utilization of the system are introduced, and the factory efficiencies are calculated and compared. After identifying the problem, a practical solution is explained.

An experimental test of the Mocikat-Herwig theory of local turbulent heat transfer measurements on cold objects

Experimental results are presented of a test of the theory of local turbulent heat transfer measurements proposed by Mocikat and Herwig in 2007. A miniaturized multi-layer heat transfer sensor was developed and employed in this study. The new heat transfer sensor was designed to work in air and liquids, and this capability enabled the simultaneous investigation of different Prandtl numbers. Two basic configurations, namely the flow past a blunt plate and the flow past an inclined square cylinder, were investigated in test sections of wind and water tunnels. Convective heat transfer coefficients were obtained through conventional testing (i.e., employing thoroughly heated test objects) and using the new miniaturized sensor approach (i.e., utilizing cold test objects without heating). The main prediction of the Mocikat-Herwig theory that a specific thermal adjustment coefficient of the employed actual miniaturized heat transfer sensor should exist in the fully turbulent flow regime was proven for developed two-dimensional flow. The observed effect of the Prandtl number on this coefficient was in good agreement with the prediction of the asymptotic expansion method. The square cylinder results indicated the inherent limits of the local turbulent heat transfer measurement approach, as suggested by Mocikat and Herwig.

Inverse Design of a Microstrip Meander Line Slow Wave Structure with XGBoost and Neural Network

We present a new machine learning (ML) deep learning (DL) synthesis algorithm for the design of a microstrip meander line (MML) slow wave structure (SWS). Exact numerical simulation data are used in the training of our network as a form of supervised learning. The learning results show that the training mean squared error is as low as 5.23 × 10−2 when using 900 sets of data. When the desired performance is reached, workable geometry parameters can be obtained by this algorithm. A D-band MML SWS with 20 GHz bandwidth at 160 GHz center frequency is then designed using the auto-design neural network (ADNN). A cold test shows that its phase velocity varies by 0.005c, and the transmission rate of a 50-period SWS is greater than -5 dB with the reflectivity below −15 dB when the frequency is from 150 to 170 GHz. Particle-in-cell (PIC) simulation also illustrates that a maximum power of 3.2 W is reached at 160 GHz with 34.66 dB gain and output power greater than 1 W from 152 to 168 GHz.

Flyers Tooth Squeeze - Current Concepts and Future Needs - A Review

BACKGROUND The flyers tooth or the tooth squeeze is the toothache during air travel, termed as Barodontalgia / Aerodontalgia by researchers. It was first identified as an in-flight physiologic and pathologic phenomenon at the start of the 20th century. With the introduction of the scuba in the 1940s, many in-flight manifestations caused by barometric variations were discovered to be synonymous with diving as well. Scuba diving is a type of underwater diving where the diver breathes underwater using equipment independent of the surface supply. It can be performed for fun or a living in various settings, including the scientific, army, and public security responsibilities. However, most commercial diving employs surface-supplied diving equipment wherever possible. Battle divers and assault swimmers are all terms for scuba divers who participate in clandestine military operations. Most cases of barodontalgia occur during ascent. The origin of the discomfort is also affected by the underlying pathology. In general, pain on the rise is associated with essential pulp disease, i.e., pulpitis and pain on descent with pulp necrosis. The pain subsides typically as the patient returns to the onset stage or the ground ambient level, although it can last longer if exacerbated by periapical infection. The Fédération dentaire internationale FDI advises that pilots, divers, and other professionals undergo yearly exams, as well as appropriate dental hygiene education from dentists, after a dental procedure that necessitates an anaesthetic or seven days after a dental procedure until travelling, teeth with pre-existing substantial restorations should have a cold-test examination or periapical radiographs taken to rule out occult pulp necrosis. It is appropriate to arrange outpatient dental appointments for a suitable period until the next scheduled flight. The possible treatment modalities vary from immediate relief to the control of infection and further subsequent treatment procedures. In recent years, the airline industry and scuba diving have grown in popularity, but little is known about the oral issues linked with high altitude. It is entirely the obligation of dental health experts to give the finest dental care to aviators as well as raise knowledge of the risks of dental treatments at higher altitudes. Dentists and flight crew members should both have appropriate awareness of barodontalgia and its role in its prevention. Particular attention should be given by the otolaryngologist and must be aware of the issues and hazards associated with scuba diving. KEY WORDS Aerodontalgia, Barodontalgia, Flyer's Tooth, Pulpitis; Scuba, Tooth Squeeze

Influence of Segmented Rolls on Homogeneity of Cooling in Continuous Casting

This paper deals with secondary cooling in a continuous caster. In particular, it deals with cooling inhomogeneity caused by spray arrangement and segmented rolls used for leading the strand. The cooling section is placed under the mold. Segmented rolls are supported by bearings in several places across the strand. Sprayed water can flow in the gaps between rolls where the bearing pocket is located. The main question that was experimentally studied is how this geometry with segmented rolls can influence homogeneity of cooling. Two experimental approaches developed for this study were applied, and both used full-scale geometrical configuration. The first one was a cold test where water flow and water distribution were observed using a transparent board with the studied surface structures (rollers and bearing pockets) and four spraying nozzles. The second one was a cooling test using a heated steel plate with rolls and bearing pockets. Cooling homogeneity was studied based on the temperature distribution on the rear side of the sample, which was recorded using an infrared camera. Homogeneity of cooling distribution was experimentally studied for three levels of cooling intensity that are used in typical cooling sections in plants. The hot tests showed that the bearing pockets do not provide significant cooling inhomogeneity despite the fact that a large amount of water flows through the gap between the rollers (which has been observed in cold tests).

Accuracy of the dental pulp sensibility test using cold spray for the diagnosis of pulp diseases: an observational clinical study

The dental pulp sensibility test is one of the main auxiliary resources for the diagnosis of pulp pathologies, and its accuracy is still debatable. This cross-sectional observational study evaluated the accuracy of the pulp sensibility test (PST) using cold spray (1,1,1,2-tetrafluoroethane) for the diagnosis of pulp diseases and determined the effect of individual and clinical variables on the reliability of this test. The paper was designed following the STROBE statement. Sixty patients with indications for primary endodontic treatment were selected and examined from August 2017 to July 2018. Data collection was performed through interviews, clinical/radiographic examinations and the PST. The results of the cold test, along with data on sex, age, the tooth type regarding the root number, and the presence of restorations and caries, as well as the recent consumption of analgesics, were recorded. The presence of bleeding within the pulp chamber was used as the gold standard to compare with the clinical diagnosis and to identify the true-positive, false-positive, true-negative, and false-negative responses. The accuracy of PST achieved in subgroups of individual and clinical variables was compared using the chi-square test with a significance level of 5% (p < 0.05). The PST with the use of cold spray showed a sensitivity of 0.88, a specificity of 1.00, a positive predictive value of 1.00, a negative predictive value of 0.86, and an accuracy of 0.93. The accuracy of the cold spray was not affected by individual or clinical variables. The PST with the use of cold spray is an accurate and reliable method for determining the diagnosis of pulp diseases, especially in cases of pulp vitality or irreversible pulpitis.

The ability of platelet-rich plasma to regenerate a non-vital immature permanent teeth

Objectives: To test the ability of platelet-rich plasma clinically and radiologically for pulp regeneration of immature teeth with apical periodontitis. Material and Methods: An experimental study was conducted From (March/2018-July/2020) 12 upper central immature incisors with acute apical periodontitis and necrotic pulp from six patients receiving regenerative endodontic treatment using concentrated platelets rich plasma were performed by the same endodontist at Mediclinic Middle East Hospitals. Informed consent, including explanation of risks and alternative treatments or no treatment were prepared and filled by the patient parents. The therapeutic protocol was involved accessing the pulp chamber; irrigation copiously with sodium hypochlorite; applying calcium hydroxide as intracanal medicament and a provisionally sealing it after 4 weeks. The canal was cleaned, dried and injected with concentrated platelets rich plasma which serve as a scaffold for pulp regeneration. MTA was used to seal the chamber before final filling with composite. Evaluations: All teeth were monitored clinically (mobility, palpation, percussion, and sensitivity cold test) and radiographically. Results: Twenty months follow-up all teeth showed resolution of periapical radiolucencies, continued root development with positive response to sensitivity cold test and no discoloration. Conclusion: The results of this study confirmed the previous finding that pulp regeneration can be gained by using cPRP successfully Keywords Immature teeth; Necrosis; cPRP; Regeneration.

Postanesthetic Cold Sensibility Test as an Indicator for the Efficacy of Inferior Alveolar Nerve Block in Patients with Symptomatic Irreversible Pulpitis of Mandibular Molars

Aim of the Work. The goal of the current study was to investigate the capability of the cold test to predict the profound pulpal anesthesia before starting the endodontic treatment of mandibular first molars with symptomatic irreversible pulpitis (SIP). Materials and Methods. This study was conducted on the mandibular first molars of 54 patients (35 males and 19 females) with signs and symptoms of SIP. To anesthetize the affected molars, all patients received a single carpule of 2% lidocaine with 1 : 100000 epinephrine using a standardized inferior alveolar nerve block (IANB) technique. The cold test was conducted before beginning the endodontic procedures and after gaining lip numbness, and the results were reported as either positive or negative response. The root canal preparation (RCP) was then initiated and the patients’ responses were documented (Gold standard test). True pulpal anesthetic failure was described as a pain perception during the access cavity and pulp tissue removal. True pulpal anesthesia was defined as no pain or discomfort during the access cavity and pulp extirpation. The qualitative variables frequencies and percentages of patients with true/false positive and negative responses were determined and then compared using the Chi-square test. The pain perception of male and female patients during the cold test and gold standard was compared using the Fisher exact test. The following diagnostic parameters were calculated using an online statistical calculator: sensitivity, specificity, predictive values, accuracy, and Youden index. In addition, a receiver operating characteristic curve (ROC) was constructed and the area under the curve (AUC) was calculated. Results. The overall percentage of actual failure of pupal anesthesia was 57%. The sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and Youden index for the cold test were 0.87, 0.91, 0.93, 0.84, 0.89, and 0.78, respectively. There was no statistically significant difference between male and female patients regarding their responses to cold testing and the gold standard test ( P > 0.05 ). Besides, the patients’ reactions to the cold test were significantly matched with their reactions to the gold standard test ( P < 0.05 ). The area under the ROC was mostly 0.9. Conclusion. The cold test could be a valuable and accurate method for predicting the potential pupal anesthesia before beginning the endodontic treatment of mandibular molars with symptomatic irreversible pulpitis, particularly after obtaining postanesthetic soft tissue numbness.