Biomedical subjects

Xiang Peng

Publications and source records attributed to Xiang Peng.

10 recordsLinked to original sources

PubMed2006

Asymmetric cryptography based on wavefront sensing.

A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

Journal Article↗

PubMed2006

Chosen-plaintext attack on lensless double-random phase encoding in the Fresnel domain.

We demonstrate a method of chosen-plaintext attack on lensless double-random phase encoding (L-DRPE) in the Fresnel domain. With this attack an opponent can access two encryption keys with help of the impulse functions as chosen plaintexts. This shows that a lensless optical encryption scheme based on DRPE is vulnerable to chosen-plaintext attack. Cryptoanalysis also indicates that the security worry originates from the linearity of the encryption and decryption mechanism of the L-DRPE scheme. One of the interesting features of the proposed attack is that the decryption process is lossless. Numerical simulations show good agreement with theoretical analysis.

Journal Article↗

PubMed2006

Three-dimensional vision from a multisensing mechanism.

An approach for sensing a three-dimensional (3D) object surface with an arbitrary geometric shape is presented. Combining two different 3D sensing mechanisms, point-array encoding based on affine transformation and fringe encoding based on phase mapping, we construct a mathematic model for 3D vision in which the point-array encoding is initially applied to determine the fringe orders to create a control-vertex mesh with absolute coordinate values in 3D space. Then phase evaluation and phase unwrapping for fringe decoding is performed under the guidance of control-vertex mesh, leading to an absolute phase map and the corresponding range image of the test object. The computer simulations and experimental results are presented to demonstrate the theoretical prediction.

Journal Article↗

PubMed2006

Known-plaintext attack on optical encryption based on double random phase keys.

We demonstrate a new approach to known-plaintext attack on an optical encryption scheme based on double random phase keys. With this attack an opponent can access both random phase keys with the help of the phase retrieval technique. This demonstration shows that an optical encryption scheme based on double random encoding is vulnerable to known-plaintext attack.

Journal Article↗

PubMed2006

[The application of three-dimensional skull model in the treatment of craniofacial malformation].

OBJECTIVE: This study was to construct a geometric skull model with 3-dimension scanning and rapid-prototyping (RP) technology and also to evaluate the significance and further application of surgery simulation in the treatment of complex craniomaxillofacial malformation. METHODS: Twelve patients with complex craniomaxillofacial malformation were involved. The data obtained with CT scanning were transferred to a personal computer for surface rendering 3-dimension reconstruction. A geometric model was manufactured by selective laser sintering using rapid-prototyping device. Surgery simulation was performed both on the model and in the computer. Accordingly, a custom implant and an implant template, when needed, were constructed with the computer-aided design (CAD) and prefabricated with computer-aided manufacture (CAM) process. RESULTS: Surgery simulation made the operation shorter, the complications lower and the outcome better. CONCLUSIONS: Skull model provides great convenience in the treatment of cranio-maxillofacial malformation.

Adult↗

PubMed2005

Breaking the limit of maximum effective area for robust single-mode propagation in optical fibers.

We propose and demonstrate a novel approach in optical fiber design in which the optical waveguide is formed by a ring of large air holes surrounding a solid silica core. With an appropriate choice of the geometrical configuration, robust single-transverse-mode propagation with a record effective area of 1417 microm2, verified by various methods, was demonstrated. A breakthrough was made toward the development of practical ultra-high-power fiber lasers as we observed negligible loss of the fiber at bending diameters as small as 15 cm.

Journal Article↗

PubMed2005

Self-processing solgel material for one-step fabrication of micrometer-period sinusoidal phase gratings using the Lloyd's mirror scheme.

A novel self-processing silica-zirconia hybrid solgel material has been developed and employed in one-step fabrication of micrometer-period sinusoidal phase gratings. In the process, the gratings with a sinusoidal profile were corrugated on the surface of the solgel film by UV exposure using the Lloyd's mirror setup. No further development or etching step is needed to reveal the sinusoidal profile because the corrugation is formed due to the self-processing property of the solgel material, which is robust enough to be used as an end product. The period, amplitude, diffraction efficiency of the +/-1 order, and surface roughness of one of the fabricated gratings are 0.99 microm, 330 nm, 30.56%, and 1.27 nm, respectively. The new self-processing material is practical and promising for fabrication of micro-optical elements.

Journal Article↗

PubMed2005

Three-dimensional digital imaging based on shifted point-array encoding.

An approach to three-dimensional (3D) imaging based on shifted point-array encoding is presented. A kind of point-array structure light is projected sequentially onto the reference plane and onto the object surface to be tested and thus forms a pair of point-array images. A mathematical model is established to formulize the imaging process with the pair of point arrays. This formulation allows for a description of the relationship between the range image of the object surface and the lateral displacement of each point in the point-array image. Based on this model, one can reconstruct each 3D range image point by computing the lateral displacement of the corresponding point on the two point-array images. The encoded point array can be shifted digitally along both the lateral and the longitudinal directions step by step to achieve high spatial resolution. Experimental results show good agreement with the theoretical predictions. This method is applicable for implementing 3D imaging of object surfaces with complex topology or large height discontinuities.

Journal Article↗

PubMed2005

Three-dimensional vision with dual acousto-optic deflection encoding.

We report a new method of sensing a three-dimensional (3D) object surface with an arbitrary geometric shape. In this approach, the first-order beams diffracted from two acousto-optic deflectors (AODs) interfere with each other to form a spatial carrier that is used to encode the depth information from the 3D object surface. A direct digital synthesizer is utilized to control two AODs to generate sequentially spatial carriers with different spatial frequencies so that a modified temporal phase-unwrapping technique can be applied for decoding the shape information of the test surface. Preliminary experimental results are presented to demonstrate the effectiveness of this method.

Algorithms↗

PubMed2002

[Study of the function of leukocyte adhesion molecules in chronic respiratory diseases].

OBJECTIVE: To study the function of leukocyte adhesion molecules in the pathogenesis of Chronic Obstructive Pulmonary Diseases (COPD) and cor pulmonale, and to evaluate the effect of anti-leukocyte-adhesion therapy for cor pulmonale. METHODS: The positive expression rates of CD(11a), CD(11b), CD(18), CD(54) in peripheral blood were quantitatively analyzed by flow cytometry using monoclonal antibodies in 42 cases of COPD (stable stage), 41 cases of cor pulmonale (stable stage), 24 healthy controls as well as 20 cases of cor pulmonale who had taken huobahua. RESULTS: The expression rates of CD(11a), CD(11b), CD(18), CD(54) in monocytes and CD(11a) in lymphocytes from the COPD group were much higher than those in the control group (P < 0.05). CD(11a), CD(11b), CD(18), CD(54) in neutrophils and CD(11a), CD(18), CD(54) in monocytes, and CD(18) in lymphocytes in the cor pulmonale group were significantly stronger than those in the control group (P < 0.05); whereas the positive expression of CDs was greatly reduced in the cor pulmonale patients who had taken huobahua (P < 0.05). No differences were found in other groups. CONCLUSIONS: Upregulation of CD(11a)/CD(18), CD(11b)/CD(18), CD(54) in monocytes, CD(11a)/CD(18), CD(11b)/CD(18), CD(54) in neutrophils and CD(11a)/CD(18), CD(54) in monocytes in cor pulmonale may promote adhesion of leukocytes with endothelial cells, which may play an important role in the pathogenic process. Huobahua may prevent the development of cor pulmonale by down regulating the expression of CDs.

Aged↗