Minimum achievable height of a single-module LED low-beam projection headlamp.

Since the first full LED headlamp was introduced in 2007, technology has evolved townow provide enhanced performance, improved security, and memorable aesthetics. Further miniaturization has been continuously pursued to allow more advanced design options, but LED headlamp height has been stalled at around 40-60 mm for some years. Recently a total internal reflection-based low-beam module achieved an optical opening down to 20 mm. However, the small opening came with a housing envelope height that was larger than 40-60 mm. Conventional LED single modules are still more attractive in terms of cost and overall compactness, especially for low-cost, low-beam headlamps. A demanding question remains about the minimum achievable limit of a single-module LED low-beam projection headlamp consisting of an LED source, an elliptical reflector, a cutoff baffle, and a projection lens. Here, we answer that question using an analytical approach rather than attempt to base it on current applied design trials or parametric studies. First, we analytically investigated the baseline optical properties of an LED low-beam module in terms of geometrical optics and photometrical luminance transfer. During the analysis, we employed the ratio of the focal distances (m) of the elliptical reflectors as a design variable to efficiently consider geometrical similarities. Then we confirmed and extended the analytical results by numerical simulation, using ray-tracing software. Based on the results from the analytical and numerical analysis with low-beam regulations, we finally determined a suitable range of m (0.15-0.17), which satisfied the regulations, and found the best achievable height of a single module when m∼0.15 is 46 mm. The precise number will differ depending on the geometrical and ray-emitting properties of the LED applied, but our study provides a valid general framework for designing LED-based low-beam headlamps.

Clinical characteristics and treatment courses for cytomegalovirus-associated thrombocytopenia in immunocompetent children after neonatal period.

BACKGROUND: Cytomegalovirus (CMV) causes severe diseases in premature infants and immunocompromised hosts, and antiviral therapy is often required for disease control. However, the clinical manifestations and treatment courses for CMV-associated thrombocytopenia in immunocompetent children are unclear. METHODS: Medical records of the children who suffered from thrombocytopenia, and showed positive CMV polymerase chain reaction and CMV-like symptoms were retrospectively analyzed at three university hospitals in Daegu from January 2000 to March 2017. Patients suffering from leukemia, immunodeficiency, and other infections were excluded. RESULTS: Among 1,065 children with thrombocytopenia, 29 (2.7%) displayed CMV-associated thrombocytopenia. The median age at diagnosis was 15 months and the median platelet count was 26,000/µL. They were classified into the CMV-induced thrombocytopenia (23/29) and CMV-related secondary immune thrombocytopenia (ITP, 6/29) groups. Fourteen subjects had hepatic dysfunction, four had Evans syndrome, two had pneumonitis, and one had gastritis. IVIG was used for 21 patients, and six patients among them showed recurrence, for whom IVIG or antiviral therapy was used. All, except one, recurrent or chronic cases belonged to the CMV-induced thrombocytopenia group. Antiviral therapy was used more frequently for the CMV-induced thrombocytopenia group (8/23, 34.8%) than for the CMV-related secondary ITP group (0/6); however, the results were not statistically significant (P=0.148). CONCLUSION: CMV is a rare but unique etiology of thrombocytopenia, and observed even in healthy children after the neonatal period. About one-third patients need antiviral therapy for disease control. Further, CMV-induced thrombocytopenia is more complex than CMV-related secondary ITP.

Broadband optical parametric amplification at the communication band with periodically poled lithium niobate.

We report broadband optical parametric generation (OPG) in a single periodically poled lithium niobate crystal with a picosecond pump pulse at a fixed wavelength. We also demonstrate efficient optical parametric amplification of a broadband seed pulse within the quasi-phase-matched OPG band. The broad parametric gain band is attributed to group-velocity matching and degeneracy between the signal and idler, and the broad spectral width of the pumping source.