Pre-Compensation of Thermal Error for Laser-Assisted Diamond Turning.

The laser-assisted diamond turning (LADT) method can effectively improve the machinability of hard and brittle materials based on the laser heating effect, resulting in prolonged diamond tool life and better surface integrity. However, due to the incomplete absorption of laser beam energy within the workpiece cutting zone, simultaneous heating of the tool holder occurs, resulting in a structural thermal expansion that affects the workpiece form accuracy. In this article, the form accuracy of a LADT-machined workpiece was systematically studied. Accurate calculations of the tool shank and tool holder thermal fields and thermal expansion were performed using thermodynamic coupled finite element analysis. In addition, the LADT tool path was precisely pre-compensated by taking into account the structure expansion. The experimental results demonstrate that the form accuracy can be significantly improved with a pre-compensated tool path, which provides crucial technical support for achieving a high-precision finish on optical elements using the LADT method.

Experimental Investigation on Laser Assisted Diamond Turning of Binderless Tungsten Carbide by In-Process Heating.

Binderless tungsten carbide (WC) finds widespread applications in precision glass molding (PGM). Grinding and polishing are the main processes to realize optical surface finish on binderless WC mold inserts. The laser assisted turning (LAT) by in-process heating is an efficient method to enhance the machinability of hard and brittle materials. In this paper, laser heating temperature was pre-calculated by the finite element analysis, and was utilized to facilitate laser power selection. The effects of rake angle, depth of cut, feed rate, and laser power are studied experimentally using the Taguchi method. The variance, range, and signal-to-noise ratio analysis methods are employed to evaluate the effects of the factors on the surface roughness. Based on the self-developed LAT system, binderless WC mold inserts with mirror finished surfaces are machined using the optimal parameters. PGM experiments of molding glass lenses for practical application are conducted to verify the machined mold inserts quality. The experiment results indicate that both the mold inserts and molded lenses with the required quality are achieved.

Tool path generation of turning optical freeform surfaces using arbitrary rake angle tools.

Slow tool servo diamond turning has widespread application in fabricating freeform optics. Previous studies are focused on the methods of the tool path generation and verification of zero-rake-angle tools. However, these methods are unsuitable for non-zero-rake tools that are used for machining hard-and-brittle materials. This paper presents a universal location-point-drive tool path generation method, which caters to arbitrary rake angle tools and the steady X movement feature, and the corresponding universal tool interference check method. Systematic analysis and ultra-precision machining experiments confirmed the feasibility of our methods and present better surface quality and form accuracy compared to the traditional method.

[Expression and significance of microRNA-125b in tongue squamous cell carcinoma].

OBJECTIVE: The expression of microRNA-125b in tongue squamous cell carcinoma (TSCC) was detected and analyzed for its relationship with the clinicopathological features of TSCC. METHODS: Real time fluorescence-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of microRNA-125b in 35 TSCC tissues and adjacent normal tissues from 35 TSCC cases. The relationship between the expression of microRNA-125b in TSCC tissues and the clinicopathological features of patients with TSCC was analyzed. In situ hybridization (ISH) was used to detect the expression level of microRNA-125b gene in the TSCC tissues and adjacent normal tissues. RESULTS: RT-qPCR results showed that the relative expression levels of microRNA-125b in the TSCC issues was 2.32±0.69, and that of normal tissues was 0.87±0.32. The statistical results showed that the expression level of microRNA-125b was significantly higher in the TSCC tissues than in the normal tissues (P<0.001). The expression level of microRNA-125b in the TSCC tissues was not significantly correlated with age, gender, pathological grade, and lymph node metastasis but was positively correlated with TNM stage. Patients with high TNM stage had high microRNA-125b expression levels (P<0.05). The ISH results showed that the expression levels of microRNA-125b in the TSCC tissues were 0.010±0.003, and that of normal tissues was 0.004±0.001. The expression levels of microRNA-125b in the 35 TSCC tissues were significantly higher than those in the normal tissues (P<0.05). CONCLUSIONS: MicroRNA-125b is highly expressed in TSCC and associated with TNM stage, suggesting that high microRNA-125b expression may be involved in the development of TSCC.

Off-spindle-axis spiral grinding of aspheric microlens array mold inserts.

A novel approach named off-spindle-axis (OSA) spiral grinding for fabricating aspheric microlens array (AMLA) mold inserts for precision glass molding (PGM) is presented. In OSA spiral grinding, three translational motions of the grinding wheel are synchronized with the rotation of the workpiece to form a local spiral wheel path for individual lens-lets. With this approach, the form accuracy of lens-lets can be compensated within sub-micrometer by means of the on-machine measurement. The determination of wheel path and form error compensation via on-machine measurement are systematically studied. A tungsten carbide mold insert with four convex aspheric lens-lets is fabricated to evaluate the grinding performance. PGM experiments are performed to produce glass AMLA using the ground insert. The experimental results indicate that both the ground and molded AMLA with homogeneous quality are achieved. The form accuracy and surface roughness of both the mold insert and the molded AMLA were less than 0.3 µm in PV and 10 nm in Sa, respectively.

Quality improvement of collimating lens produced by precision glass molding according to performance evaluation.

Precision glass molding technology is one of the most important approaches to produce optical glass lenses. However, the high fidelity and repeatability of optical performance be sometimes achieved even though the lenses meet the requirements of geometric assessments. The surface errorform errors transferred from mold surface with a complicated combination of components of different spatial-frequencies greatly influence the optical lenses performance. An optical model is built to investigate the impact of form errors with various frequencies on the optical performance of the lens. The mid-spatial frequency error is proved to be the factor that results in the most serious surrounding circle phenomenon. Based on the diffraction theory of the sinusoidal grating, numerical calculation is carried out to analyze their relationship. Experiments are conducted to validate the analysis and a mold polishing procedure is provided as a method to improve the quality of lenses according to performance evaluation.

[Teratomas on the palate and tongue with cleft palate: a case report].

Teratomas is a germ cell tumors, which is rare in the upper palatal and lingual. This article presents a patient with teratomas on the palate and tongue accompanied with cleft palate. The clinical manifestations and histopathological characteristics of teratomas are discussed according to relevant literatures.

[Establishment of animal model of rectus abdominis musculoperitoneal flap to reconstruct tongue defect].

OBJECTIVE: This study aims to investigate the feasibility of tongue reconstruction by a rectus abdominis musculoperitoneal flap with neurovascular pedicled in a canine model. METHODS: Twelve Beagle dogs were enrolled to the experiment. The animals were randomly divided into thee groups, two of which (group A and B) had nerve anastomosis. The left sides were experimental sides, whereas the right sides were control sides. Twelve weeks after operation, electrophysiological test was performed to detect hypoglossal nerve latency amplitude and conduction velocity as well as to evaluate the reinnervation of the rectus abdominis musculoperitoneal flap. RESULTS: Among the 12 Beagle dogs, nine animal tongue reconstruction models by rectus abdominis musculoperitoneal flap with neurovascular pedicled were successful, whereas one male Beagle dog died from ventral hemia 3 d after the operation, two female rectus peritoneal flaps were abandoned because their arterial anatomy differed from the male, which was not ideal. Hypoglossal nerve conduction velocity of group A and B were restored to the normal side of the 40%, 30%. CONCLUSION: Animal models of tongue reconstruction can be established by a rectus abdominis musculoperitoneal flap with neurovascular pedicled in Beagle dogs. Denervated rectus abdominis musculoperitoneal flap can regain hypoglossal nerve innervation. Hypoglossal nerve functions partly recover.

[Histological changes after the recontruction of tongue defect with rectus abdominis musculoperitoneal flap].

OBJECTIVE: To observe the cellular morphological and histological changes of the reconstructed tongue defect by rectus abdominis musculoperitoneal flap of dogs with or without nerve. METHODS: 12 Beagle dogs were randomly divided into two groups. Group A made rectus abdominis musculoperitoneal flap with the intercostal nerve while group B without the intercostal nerve. Nerve anastomosis was performed in Group A while not in Group B in the repairment. 12 weeks later, the length, width, surface area and cellular morphology and histological changes of the two transfer flaps were observed. RESULTS: The length, width, surface area of transplanted rectus abdominis musculoperitoneal flaps in group A were greater than those in Group B, and the differences were statistically significant at 12th week (P < 0.01). The microscope study found that the transplanted rectus abdominis musculoperitoneal flaps of group A had part of muscle fiber atrophy with some connective and adipose tissue, loose muscle fiber arrangement, while the transplanted rectus abdominis musculoperitoneal flaps of Group B had muscle cells atrophy with some adipocyte. The structure of muscle cells in Group A was basically normal, but it was disorder in Group B. The type II muscle fibers of Group B was atrophy and substituted by a lot of connective tissue. CONCLUSION: After tongue defect reconstructed by rectus abdominis musculoperitoneal flap with nerve, the changes of muscle fibers could be similar to tongue muscles, providing a basis for the dynamic recovery of the tongue.